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Past School Seminars by Reverse Date

 


All School Seminars (Historical)

On coherence-incoherence transition in dynamical networks: spatial chaos and chimera states
Yuri Maistrenko (Potsdam)
19 Jul 2011Harrison 170 Tuesday 10amApplied Mathematics
We discuss the breakdown of spatial coherence in networks of coupled oscillators with nonlocal interaction. By systematically analyzing the dependence of the spatiotemporal dynamics on the range and strength of coupling, we uncover a dynamical bifurcation scenario for the coherence-incoherence transition which starts with the appearance of narrow layers of incoherence occupying eventually the whole space. Our findings for coupled chaotic and periodic maps as well as for time-continuous Ro¨ssler systems reveal that intermediate, partially coherent states represent characteristic spatiotemporal patterns at the transition from coherence to incoherence.

 

The phase-amplitude description of neural oscillators.
Kyle Wedgewood (University of Nottingham)
11 Jul 2011Harrison 170 Monday 2pmApplied Mathematics
It is quite common to describe neural oscillators with a phase variable, thus reducing the model description to that of dynamics on a circle. However, if a limit cycle is not strongly attracting then this reduction may poorly characterise behaviour of the original system. Here we consider a coordinate transformation to a phase- amplitude framework that allows one to track the evolution of distance from the cycle as well as phase on cycle. A number of common models in computational neuroscience (primarily the Morris-Lecar model) are revisited in this framework and their response to pulsatile current forcing is investigated. We highlight the differences between phase and phase-amplitude descriptions, and show that the former can miss some substantial features of neuronal response. Finally, we discuss extensions of this work to consider the effects of off-cycle dynamics contributing to shear-induced chaos.

 

Spatio-temporal GIS
Prof. Christophe Claramunt (Naval Academy Research Institute, Brest, France)
4 Jul 2011Harrison 170 Monday 3pmComputer Science
TBA

 

Decentralized spatial computing for geosensor networks, especially in movement analysis
Dr Patrick Laube (Department of Geography, University of Zurich)
4 Jul 2011Harrison 170 Monday 4pmComputer Science
TBA

 

Weather, climate and renewable energy
David Brayshaw (University of Reading)
23 Jun 2011Harrison 209 Thursday 2pmApplied Mathematics
Securing a reliable electricity supply that is sufficient to meet demand is a vital concern for any modern economy. With the growth of renewable energy generation (particularly wind), it is important to understand the impacts of weather and climate variability on both supply and demand at national and international scales. At the day-to-day level, discussion in the UK often focuses on the issue of wind-supply during peak demand conditions – that is, the estimation of the minimum contribution that wind-power will make during extreme demand periods. Recorded power system data alone is insufficient to robustly estimate this wind “capacity value”, leading to the emergence of a rather confused picture in both the energy systems literature and the wider public debate. Weather-classification tools are proposed here as a means to address this problem. By identifying the relevant meteorological patterns associated with low-winds and peak-demand, it is demonstrated that the prevailing view of an anti-cyclonic "low-wind cold-snap" does not adequately describe peak-demand conditions. At longer timescales, large-scale low-frequency variability in the climate system can also have a marked impact on renewable generation, a fact that is often ignored during resource assessment and wind integration studies. A simple example is the North Atlantic Oscillation (NAO), variations in which are capable of yielding a difference in mean wind-power generation at UK sites of up to 10%. The NAO also correlates strongly with large-scale variations in seasonal-mean surface temperature and precipitation patterns, potentially affecting the demand for electricity and the availability of hydro-power, as well as wind generation. Such large-scale co-variability is likely to become increasingly important as cross-border transports within the European energy system increase. This talk presents ongoing research which seeks to better explore the links between weather, climate and energy. It will highlight some of the areas where meteorological information can be used to inform decision making in the UK and European electricity systems.

 

Why is the Arctic warming so fast?
James Screen (University of Melbourne)
21 Jun 2011Harrison 102 Tuesday 2pmApplied Mathematics
Recent climate change has been especially pronounced in the Arctic region, with surface temperatures rising two to four times faster than the global average and an accompanying rapid decline of sea ice. Both the Arctic warming and the sea ice loss are unprecedented over at least the last few thousand years. A multitude of climate feedbacks have been proposed that amplify the Arctic surface temperature response to climate forcing. This talk will discuss some of these, and explore whether they are already active and contributing to recent Arctic change. It will present evidence that strong ice-temperature feedbacks have emerged and that the decline in sea ice is playing a central role in Arctic temperature amplification. Both the sea ice loss and the warming have significant impacts on the Arctic moisture budget. These will be discussed in the context of changes in atmospheric water vapour content and in the phase of summer precipitation. There is evidence of humidity increases and a transition towards less snow and more rain. The causes, impacts, and feedbacks associated with these hydrological changes will be considered.

 

TBA
TBA
16 Jun 2011Harrison LT04 Thursday 2pmApplied Mathematics

 

Title: New Computational techniques for modeling Acoustic Fluids and Wave Propagation
Professor S Gopalakrishnan (Department of Aerospace Engineering, Indian Institute of Science, Bangalore)
9 Jun 2011Harrison H170 (3D Visualisation Suite) Thursday 2pmAdvanced Technologies RI
In this talk, new computational models for studying dynamics of acoustic fluids will be presented. The talk will cover two different computational models, namely the conventional finite elements and the frequency domain based spectral finite elements. Two different fluid finite element formulations based on Lagrangian frame of reference, one based on h-type formulation and the second based on Legendre's time domain spectral elements will be presented in this talk. One of the problems associated with h-type Lagrangian FEM is that they suffer from mesh locking problems due to fluid incompressibility. In addition to mesh locking problems, these elements exhibit a numerous zero energy eigen modes due to fluid circulation. To circumvent these zero energy modes, the fluid is made irrotational, which will further stiffen the formulated fluid element. Hence the formulated h-type will suffer from two different constraints, one due to fluid incompressibility and the second due to fluid irrotationality. The main objective of the first part of the talk is to formulate Lagrangian h-type FEM that is free from mesh locking due to twin constraints. In this work, formulation of both 2-D and 3-D elements will be presented. In the second part of the talk, Lagrangian FEM based on Lengendre's basis functions is presented. Here, it will be seen that the choice of different integration scheme for the volumetric stiffness and rotational stiffness will not only eliminate mesh locking, but also exhibit superior convergence property. The last part of the talk will address the formulation of Spectral FEM, especially for studying wave propagation in acoustic fluids. The talk will cover a number of examples that show the computational superiority of Spectral Fem over conventional FEM. The use of the formulated elements for fluid-structure interaction problems will be addressed in this talk.

 

TBA
TBA
9 Jun 2011Harrison LT04 Thursday 2pmApplied Mathematics

 

** postponed to 23rd June **
David Brayshaw (University of Reading)
2 Jun 2011Harrison LT04 Thursday 2pmApplied Mathematics
** postponed to 23rd June **

 

[symposium] Rotating Flow and Dynamo
Taylor and Francis sponsored symposium
2 Jun 2011Harrison 215 Thursday from 11amApplied Mathematics
Thursday, 2 June, 2011 at Room 215 Harrison Building 11:00--12:30 Tea/Coffee/Biscuits, Room 215 Harrison Building 12:30-2:00, Lunch at Xfi Building 2:00-2:30, Andrew Soward (Exeter) The onset of strongly localised thermal convection in rotating spherical shells. 2:30-3:00, Radostin Simitev (Glasgow), Effects of shell thickness and velocity boundary conditions on convective dynamos in rotating spherical shells. 3:00-3:30, Jun Zou (Hong Kong), Inverse Electromagnetic Obstacle Scattering. 3:30-4:30, Tea/Coffee/Biscuits, Room 215 Harrison Building; 4:30-5:00, Phil Livermore (Leeds) Dynamics of the tangent cylinder in rapidly-rotating inviscid flows, 5:00-5:30, Yannick Ponty (France) Large scale and small scale dynamos 5:30-6:00 Emilie Neveu (France) Multigrids for data assimilation on geophysics models 6:30--9:00 Conference dinner (the location to be confirmed) Friday, 3 June, 2011, at Room 215 Harrison Building 9:00-9:30 Steve Tobias (Leeds), Direct Statistical Simulation of Jet Formation 9:30-10:00 Emmanuel Dormy (France), Weak and Strong Field Dynamos 10:00-10:30 Paul Bushby (Newcastle), Dynamo action in rotating compressible convection 10:30-11:00 Tea/Coffee/Biscuits, Room 215 Harrison Building; 11:00--11:30 Keke Zhang (Exeter), Asymptotic solution for resonant flow in a spheroidal cavity driven by latitudinal libration. 11:30-12:00 Michael Chan (Hong Kong), Fluid motion and dynamos in a triaxial cavity driven by libration 12:00-13:30, Lunch at Xfi Building (THE END)

 

-- no seminar --
-- no seminar --
26 May 2011Harrison LT04 Thursday 2pmApplied Mathematics

 

Connecting mesoscale and macroscale models of cellular migration
Ruth Baker (University of Oxford)
19 May 2011Harrison LT04 Thursday 2pmApplied Mathematics
Continuum, partial differential equation (PDE) descriptions of cell movement are often employed in modelling studies because of their analytical tractability, and the wealth of numerical methods available for their solution. Derived from, for example, conservation of mass approaches these models describe how cell density changes with time due to random movements of cells, different types of taxes/kineses and cell proliferation/death. In the main, these processes are represented in the model equations in a phenomenological manner, providing gross descriptions not necessarily derived from the underlying cell behaviour. In this talk I will consider effects such as cell shape and volume exclusion, discussing how such phenomena may be modelled at the mesoscale, and how population-level macroscale models may be derived from these descriptions.

 

Title: Damage Tolerance Optimization of Tapered Composite Laminates
Giuliano Allegri (Department of Aerospace Engineering, University of Bristol)
12 May 2011Harrison H170 (3D Visualisation Suite) Thursday 2pmAdvanced Technologies RI
Tapering structural element is necessary in order to optimize specific stiffness and strength. Tapered metallic parts can be manufactured by casting or machining, whilst for fibre reinforced composites tapering always requires terminating, i.e. dropping-off, plies. Ply drop-offs act as stress raisers since they represent discontinuities for the laminate geometrical arrangement and elastic properties. Therefore ply terminations promote delamination and thus compromise the laminate strength and damage tolerance performance. An analytical solution for the calculation of the energy release rates associated with delaminations emanated from ply drop-offs has been developed and employed to optimize the termination sequences in tapered laminates for maximum damage tolerance performance under given geometric constraints. This optimization task has been proved to be analogous to the classical "travel salesman" problem, provided than a suitable fracture energy metric is introduced. Different optimization techniques have been employed, including genetic algorithms and simulated annealing with stochastic tunnelling. The optimization results can be synthesised in a set of "robust" design principles which have been implemented in a fuzzy logic framework in order to provide optimized configurations at limited computational costs.

 

== COLLOQUIUM == Collective behaviour of swimming micro-organisms
Professor Tim Pedley (University of Cambridge)
12 May 2011Harrison LT04 Thursday 2pmApplied Mathematics
Suspensions of swimming micro-organisms exhibit a rich variety of collective behaviour, such as the bioconvection patterns seen for suspensions of upswimming cells that are denser than their surroundings, or the time-varying coherent structures seen in dense suspensions of swimming bacteria. Here we investigate the fluid dynamic mechanisms underlying these patterns, by means of (1) a continuum model for dilute suspensions, (2) hydrodynamic interactions between pairs of model micro-organisms, and (3) simulations and models for non-dilute suspensions. The talk will conclude with recent observations of ‘dancing’ algae.

 

Discrete Variational Derivative Methods for PDES
Chris Budd
9 May 2011Harrison 203 Monday 2pmApplied Mathematics

 

Title: Developing a Strategic Framework for the Successful Implementation of Additive Manufacturing Technologies
Stephen Mellor (Engineering, CEMPS, University of Exeter)
5 May 2011Harrison H170 (3D Visualisation Suite) Thursday 1pmAdvanced Technologies RI (Internal)
It has long been understood that innovation in production technology can be used strategically as a powerful competitive weapon, enabling a manufacturing organisation to produce products that are better, cheaper and made faster than the competition. However, the wrong technology, or even the right technology poorly implemented, can be disastrous. Additive Manufacturing (AM) technologies have played an important role in product development (Rapid Prototyping) for many years, and we are beginning to see their use in production applications, albeit on a limited scale. This research proposes that the only similarity between using these technologies for prototyping and production is the process itself. Secondly, that there remains a significant gap in our knowledge of when and how to implement AM, and that this knowledge is key to increasing the adoption and diffusion of these technologies. This research project investigates the process of AM implementation over its life-cycle, identifying and developing an understanding of the factors influencing its success and failure. Beginning with a framework developed from the process technology implementation literature and existing AM implementation studies, exploratory case studies are used to test this framework and develop implementation roadmaps.

 

Time-stepping errors in weather and climate simulations
Paul Williams (University of Reading)
5 May 2011Harrison LT04 Thursday 2pmApplied Mathematics
Comprehensive assessments of uncertainty in weather and climate prediction models should in principle consider contributions from the discretised numerical schemes, as well as from the parameterised physics and other sources. The numerical contributions are often assumed to be negligible, however. This talk reviews the evidence for uncertainty arising from time-stepping schemes. Most contemporary weather and climate models still use the simple centred-difference (leapfrog) time-stepping scheme, in concert with the Robert-Asselin filter to stabilise the computational mode. This talk proposes a new alternative filter, known as the RAW filter, which substantially reduces the numerical errors and improves the formal accuracy. Examples are shown in which the new filter yields more skilful weather forecasts and reduces biases in climate models.

 

Title: Pressure response analysis in head injury
Christopher Pearce (Engineering, CEMPS, University of Exeter)
7 Apr 2011Harrison H170 (3D Visualisation Suite) Thursday 1pmAdvanced Technologies RI (Internal)
Head injury is a significant cause of death and disability in society. Recent advances in Finite Element (FE) modelling techniques can provide insight and aid understanding of the trauma mechanisms of head injury. A new approach to generating bio-fidelic numerical models is presented based on a technique adapted from the marching cubes approach. This approach automates the generation of meshes based on 3D scan data and allows for a number of different structures (e.g. skull, scalp, brain) to be meshed simultaneously. The numerical models were used to validate an analytical model developed by one of the authors and good agreement was observed. Under certain impact conditions low mass impactors were found to produce large transient peaks of positive and negative pressure in the brain. A sensitivity study was conducted to investigate the robustness of this effect across a wide range of impact conditions. Numerical models of increased bio-fidelity were then analyzed and the transient pressure amplification behaviour for certain impact conditions was again observed; this provides confidence that the behaviour holds true as the model becomes more realistic. Beyond its significance in the area of head impact biomechanics, the study has demonstrated that numerical models generated from 3D medical data can be used effectively to simulate physical processes. This is particularly useful when considering the risks, difficulties and ethical issues involved when using cadavers.

 

Calibrating computer simulators using ABC
Richard Wilkinson (University of Nottingham)
28 Mar 2011Harrison 209 Monday 3pmApplied Mathematics
Computer simulators are now used in nearly all scientific disciplines. Comparing simulators with observations of reality (in order to estimate parameters, quantify errors etc) is major challenge for statistics. In this talk I'll introduce a relatively new class of methods that can be used to calibrate simulators called Approximate Bayesian Computation (ABC) algorithms. I'll illustrate these methods on a problem from evolutionary biology.

 

Review of the Euler singularity problem (and our small contribution).
Andrew Gilbert (with Walter Pauls, University of Bielefeld).
23 Mar 2011Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

TBA
*no seminar - no room available*
21 Mar 2011Harrison 170 Monday 2pmApplied Mathematics

 

Title: On the Use of Open-Source Software for Complex CFD Modeling: from Blood Damage in Cardiovascular Devices to Interaction of Wind Turbines with the Atmospheric Boundary Layer
Professor Eric Paterson (Computational Mechanics Division, Applied Research Laboratory, The Pennsylvania State University)
17 Mar 2011Harrison 215 Thursday 2pmAdvanced Technologies RI
Over the past 5 years, the computational fluid dynamics (CFD) community has witnessed the emergence of the first significant open-source software package (OpenFOAM) that rivals the capabilities of commercial software tools. Cost savings of "free" software is attractive to organizations which incur large software licensing fees, however, these cost savings are often offset by the need for resident expertise in molding the open-source tools to local needs. The real benefits of using open-source tools is the gain in local expertise and "ownership" (i.e., it is no longer a black box), and the access to source code and a flexible architecture, both of which are significant enablers for new and complex-physics modeling. The focus of this presentation will be on the use of OpenFOAM at Penn State University in modeling a number of complex fluid dynamics problems, including: blood damage in heart-assist devices; conjugate mass transfer and canine olfaction; compressible multiphase flow associated with underwater explosions; fluid-structure interaction of flexible turbomachinery; adjoint-based optimization for hydropower; and wind-turbines operating in a turbulent atmospheric boundary layer. An overview and key results for each problem will be presented, along with a discussion of how OpenFOAM enabled successful modeling of these complex problems.

 

Chaotic mixing in a helix-like pipe with periodic variations in curvature and torsion
Mitsuaki Funakoshi (Kyoto University)
17 Mar 2011Harrison 170 Thursday 2pmApplied Mathematics
Chaotic motion of fluid particles by a steady viscous flow in a helix-like circular pipe caused by an axial pressure gradient, and mixing efficiency of this flow are numerically examined. This pipe is wound around a circular or elliptic cylinder with a constant pitch so that the curvature kappa and torsion tau of centerline of this pipe vary continuously and periodically. If both kappa and tau are small and slowly-varying, the cross-sectional motion of fluid particles is expected to be approximately governed by the sum of Dean's flow and the flow of rigid rotation. From Poincare sections and the values of an index of the extent of mixing, it is found that there is an intermediate range of Reynolds number Re of flow within which chaotic regions in Poincare sections are large and mixing efficiency in a short time is high. Moreover, larger chaotic regions and higher mixing efficiency are observed for pipes wound around a circular cylinder of smaller radius, and for pipes wound around a thinner elliptic cylinder. These results can be explained by the variation in characteristic ratio 12 tau / (kappa Re) in one period.

 

Unfolding of homoclinic and heteroclinic behaviour in a multiply-symmetric strut buckling problem.
Dr Khurram Wadee
16 Mar 2011Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Localized buckling in infinitely long structures has been at the forefront of furthering our understanding of homoclinic solutions in a class of reversible fourth-order systems. At criticality, the system encounters a sub-critical Hamiltonian-Hopf bifurcation from which emanate homoclinic (localized) solutions. These are unstable in the physical sense but the presence of higher order nonlinearity can act to stabilize the solutions. When appropriate stabilization is present, the homoclinic solution transforms into a heteroclinic solution with the propogation of a front. Careful analysis of the boundary layer between the zero solution and constant finite amplitude solution is the key to understanding how this transformation occurs. These predictions are then tested against numerical solutions of the governing equations.

 

Latent Force Models
Prof. Neil Lawrence (Department of Computer Science, University of Sheffield)
16 Mar 2011Harrison 215 Wednesday 2pmComputer Science
Physics based approaches to data modeling involve constructing anaccurate mechanistic model of data, often based on differentialequations. Machine learning approaches are typically datadriven-perhaps through regularized function approximation.These two approaches to data modeling are often seen as polaropposites, but in reality they are two different ends to a spectrum ofapproaches we might take.In this talk we introduce latent force models. Latent force models area new approach to data representation that model data through unknownforcing functions that drive differential equation models. Bytreating the unknown forcing functions with Gaussian process priors wecan create probabilistic models that exhibit particular physicalcharacteristics of interest, for example, in dynamical systemsresonance and inertia. This allows us to perform a synthesis of thedata driven and physical modeling paradigms. We will show applications of these models in systems biology and (given time) modelling of human motion capture data.

 

Differential Geometric MCMC Methods
Prof. Mark Girolami (Department of Statistical Science, University College London)
15 Mar 2011Harrison 209 Tuesday 3pmComputer Science
In recent years a reliance on MCMC methods has been developing as the “last resort” to perform inference over increasingly sophisticated statistical models used to describe complex phenomena. This presents a major challenge as issues surrounding correct and efficient MCMC-based statistical inference over such models are of growing importance. This talk will argue that differential geometry provides the tools required to develop MCMC sampling methods suitable for challenging statistical models. By defining appropriate Riemannian metric tensors and corresponding Levi-Civita manifold connections MCMC methods based on Langevin diffusions across the model manifold are developed. Furthermore proposal mechanisms which follow geodesic flows across the manifold will be presented. The optimality of these methods in terms of mixing time shall be discussed and the strengths (and weaknesses) of such methods will be experimentally assessed on a range of statistical models such as Log-Gaussian Cox Point Process models and Mixture Models. This talk is based on work that was presented as a Discussion Paper to the Royal Statistical Society and a dedicated website with Matlab codes is available at http://www.ucl.ac.uk/statistics/research/rmhmc

 

Title: Memristive Devices and Applications
Dr Themis Prodromakis (Imperial College)
10 Mar 2011Harrison H170 (3D Visualisation Suite) Thursday 2pmAdvanced Technologies RI
As CMOS technology approaches the nano-scale floor, electron devices attain comparable dimensions to their constituting atoms, imposing significant challenges on the performance, reliability and eventually the manufacturability of analogue and digital circuits. Yet, in 1959 R. Feynman proposed that there is plenty of room at the bottom and he predicted that the operation of emerging devices would rely on the manipulation of just a few atoms; the memristor is nowadays considered as an exemplar device. Memristive devices are not something new; we have been experiencing similar dynamics well before Leon Chua established the theoretical grounds of the field. Yet, such behaviours were, until recently, attributed to random hysteretic effects, since the ionic mechanics were not fully appreciated. Nowadays though, we are able to reliably reproduce memristive elements and utilise their unique properties in novel applications. During this talk, I will present the state-of-the-art developments in the field while it will be demonstrated how memristive dynamics could be exploited in practical applications, with particular emphasis in the areas of analogue IC design and neurobiology.

 

Detecting the Interior Profile of Jupiter’s Differential Rotation by Gravity Science Techniques.
Dali Kong
9 Mar 2011Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
NASA’s JUNO Jupiter probe is going to be launched soon. One of its primary scientific goals is to determine the interior structure, and the deep atmosphere of Jupiter, by making detailed measurements of its complete gravity field from orbit tracking. The observations may help unveil the mechanism producing one of the most fascinating Jovian features, the persistent zonal jets and belts structure on Jupiter’s visible surface. In this work, for the first time, an up bound is given upon how much Jovian gravity field can be distorted, if a deep differential rotation model is assumed. The problem is discussed based on perturbed Maclaurin spheroid theory but is ready to be generalized to a more realistic physical state. It is suggested that the largest field expansion coefficient J_2 of Jupiter may be subject to a 10^{-3} relative change owing to the current observed zonal jet speed.

 

TBA
TBA
7 Mar 2011Harrison 209 Monday 3pmApplied Mathematics

 

Title: Multi-objective Optimisation in Additive Layer Manufacturing processes
Giovanni Strano (Engineering, CEMPS, University of Exeter)
3 Mar 2011Harrison H170 (3D Visualisation Suite) Thursday 1pmAdvanced Technologies RI (Internal)
Selective Laser Sintering (SLS), as one of the most widely used additive manufacturing technologies, represents a valuable manufacturing process in the aerospace, automotive and medical industries. Due to the preheating requirement for the SLS of polymer materials, one of the main challenges is to reduce the energy required for the part building process and at the same time maintain the surface quality of the parts, represented by surface roughness, as this has aesthetic and functional importance for industrial applications. These objectives are competing criteria and are significantly influenced by the build orientation of the parts in the SLS process. This study investigates a computational methodology for the simultaneous minimization of surface roughness and energy consumption in the SLS process, to locate the optimal trade-off set between these objectives, known as Pareto set; thus, it provides with a consistent decision support system for the identification of optimal build orientations for Selective Laser Sintering. The methodology and the mathematical approach presented are generally applicable to powder bed based ALM platforms such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM). The multi-objective approach, in addition to the studied objectives, can be employed for the optimisation of more targets, for example by including the minimisation of anisotropy in mechanical proprieties of part produced by any ALM platforms.

 

Metric Learning with Eigenvalue Optimization
Dr. Yiming Ying (Department of Computer Science, University of Exeter)
1 Mar 2011Harrison 209 Tuesday 3pmComputer Science (Internal)
In this talk I will mainly present a novel eigenvalue optimization framework for learning a Mahalnobis metric from data. Within this context, we introduce a novel metric learning approach called DML-Eigen which is shown to be equivalent to a well-known eigenvalue optimization problem called minimizing the maximal eigenvalue of a symmetric matrix. Moreover, we show that similar ideas can be extended to large margin nearest classifiers (LMNN) and maximum-margin matrix factorisation for collaborative filtering. This novel framework not only provides new insights into metric learning but also opens new avenues to the design of efficient metric learning algorithms. Indeed, first-order algorithms scalable to large datasets are developed and their convergence analysis will be discussed in detail. At last we show the competitiveness of our methods by various experiments on benchmark datasets. In particular, we report an encouraging result on a challenging face verification dataset called Labeled Faces in the Wild (LFW).

 

On the applied Mathematics of Ocean Waves
Peter Janssen (ECMWF)
28 Feb 2011Harrison 170 Monday 2pmApplied Mathematics
For the (applied) Mathematician the subject of ocean waves, or to be more precise, surface gravity waves is an interesting problem because on the one hand it is a relatively simple and attractive while on the other hand the subject is very relevant for society. Nevertheless, due to its nonlinear character the problem has still not been solved, despite the fact that it received considerable attention for at least two centuries. Presently there is a renewed interest in the subject because of attempts to try to understand the generation of "freak" waves. After a brief historical account of the subject I will introduce the hamiltonian formulation of surface gravity waves. For weak nonlinearity there is a natural distinction between free and bound gravity waves. This distinction allows the introduction of a relatively simple evolution equation, which is called the Zakharov equation. From this evolution equation a number of interesting properties of weakly nonlinear water waves may be derived. In this talk I will concentrate on only one property, namely the instability of a uniform wave train which is an example of a four-wave interaction process. In fluid Mechanics this instability is called the Benjamin-Feir instability. It turns out that this instability, because it is a four-wave interaction, is also found in other fields. Examples are nonlinear Optics and Plasma Physics. In its most simple form the Benjamin-Feir Instability leads to the generation of envelope solitons which provides a possible explanation for the generation of "freak" waves. Because these extreme events are rare, forecasting of freak waves is difficult. Nevertheless, the probability of these extreme events can be estimated and at ECMWF probablistic forecasting of "freak" waves was introduced a number of years ago. This is the 32nd Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics".

 

Discrete Mereotopology in automated histological image analysis
Dr. David A. Randell (Medical Imaging Research Group, College of Medical and Dental Sciences, University of Birmingham)
22 Feb 2011Harrison 209 Tuesday 3pmComputer Science
This cross-disciplinary talk covers the integration of qualitative spatial reasoning (QSR) with quantitative histological image processing methods using digitised images of stained tissue sections and other preparations examined under the microscope. The talk will show how the QSR spatial logic Discrete Mereotopology can be used to model and exploit topological properties of segmented images of cells and their parts and general tissue architecture. Relation sets and other mathematical structures extracted from the theory are factored out and used to complement and guide algorithmic-based segmentation methods. The net result is a change of emphasis away from classical pixel-based segmentation algorithms to one where the primary ontological primitives are regions and their spatial relationships each to the other. The work forms part of that done by the Medical Imaging Group with a long-standing interest in: image segmentation in histopathology, quantitative measures of tissue architecture and complex data characterisation and visualisation.

 

**POSTPONED** Time-stepping errors in weather and climate simulations
**POSTPONED** Paul Williams (**POSTPONED** University of Reading)
21 Feb 2011Harrison 170 Monday 2pmApplied Mathematics
Comprehensive assessments of uncertainty in weather and climate prediction models should in principle consider contributions from the discretised numerical schemes, as well as from the parameterised physics and other sources. The numerical contributions are often assumed to be negligible, however. This talk reviews the evidence for uncertainty arising from time-stepping schemes. Most contemporary weather and climate models still use the simple centred-difference (leapfrog) time-stepping scheme, in concert with the Robert-Asselin filter to stabilise the computational mode. This talk proposes a new alternative filter, known as the RAW filter, which substantially reduces the numerical errors and improves the formal accuracy. Examples are shown in which the new filter yields more skilful weather forecasts and reduces biases in climate models.

 

Accelerating chaos control: how waiting can speed things up
Chris Bick (Max Planck Institute for Dynamics and Self-Organization, Goettingen)
15 Feb 2011Harrison 254 Tuesday 2pmApplied Mathematics

 

Huabing Yin
Microengineering biointerfaces for sensing and cell response (University of Glasgow)
14 Feb 2011Harrison 170 Monday 2pmApplied Mathematics
In the body, a cell senses and responds to its surrounding microenvironment. Increasingly, it has been demonstrated that this behavior is associated with important processes like stem cell differentiation, cancer cell invasion and wound healing. However, the natural habitat of a cell, the extracellular matrix (ECM), consists of interconnected physical, chemical and biological cues. Understanding the influence of these arrangements on cell function will have a profound impact in developing biomaterials that induce desired cellular responses. However, it remains an ongoing challenge. In this context, we have been developing microenvironments in vitro with the aim to closely mimic the multiplex cues found in vivo. Our work combines microfabrication, microfluidics and new surface chemistry to create functional biointerfaces, where multiple cues (both biological and physical) are spatially arranged on a length scale of nano- and micrometers. This interdisciplinary approach has enabled a flexible platform for a number of applications, ranging from high throughput drug screening for pharmaceutical development to the emerging fields of stem cell research. For example, discrete or gradient patterns of single or multiple biomolecules (e.g peptide and carbohydrates) have been reliably generated on a surface to investigate their collective roles in regulating cell migration, differentiation and elasticity (via AFM indentation). In this talk, I will discuss the rationales behind the design of these biointerfaces, their advantages and the challenges with our recent work in these areas.

 

TBA
TBA
7 Feb 2011Harrison 170 Monday 2pmApplied Mathematics

 

Title: On the mechanism of displacive phase transformations
Professor Bob Pond (University of Exeter)
3 Feb 2011Harrison H170 (3D Visualisation Suite) Thursday 1pmAdvanced Technologies RI (Internal)
Phase transformations are key processes in the manufacture and application of engineering materials. In displacive transformations, the transforming material undergoes a change of shape, primarily by shear. This feature underlies key properties such as the hardenability of steel and the toughening of ceramics. It is also responsible for the widely exploited properties of shape-memory and super-elastic alloys. It is important to develop a comprehensive understanding of the processes of nucleation and growth of a new phase. Recent research on growth mechanisms and the factors governing transformation kinetics will be outlined in this talk. The techniques employed are principally transmission electron microscopy and atomic-scale computer simulation.

 

TBA
TBA
31 Jan 2011Harrison 170 Monday 2pmApplied Mathematics

 

Automating the Heuristic Design Process
Dr. Matthew Hyde (ASAP Group, University of Nottingham)
26 Jan 2011Harrison 170 Wednesday 2pmComputer Science
The current state of the art in the development of search methodologies is focused around the design of bespoke systems, which are specifically tailored to a particular situation or organisation. Such bespoke systems are necessarily created by human experts, and so they are relatively expensive. Some of our research at Nottingham is concerned with how to build intelligent systems which are capable of automatically building new systems. In other words to automate some of the creative process, to make it less expensive by being less reliant on human expertise. In this talk, I will present some work we have recently published on the automatic design of heuristics for two dimensional stock cutting problems. The research shows that genetic programming can be used to evolve novel heuristics which are at least as good as human designed heuristics for this problem. Research into the automatic design of heuristics could represent a change in the role of the human expert, from designing a heuristic methodology, to designing a search space within which a good heuristic methodology is likely to exist. The computer then takes on the more tedious task of searching that space, while we can focus on the creative aspect of designing it.

 

Implicit hydrodynamic simulations of stellar convection
Maxime Viallet (Physics Dept, University of Exeter)
24 Jan 2011Harrison 170 Monday 2pmApplied Mathematics

 

Many Objective Optimisation of Engineering Problems
Dr. Evan J. Hughes (Department of Informatics and Sensors, University of Cranfield)
19 Jan 2011Harrison 170 Wednesday 3pmComputer Science
Most real engineering problems are characterised by having many criteria that are to be optimised simultaneously. Unfortunately the criteria are often conflicting and so have to be considered as a many-objective optimisation process in order to derive a trade-off surface of the available optima solutions. Although a plethora of algorithms have been developed for optimising two-objective problems, many of them do not work well as the number of objectives increase. The talk introduces some of the new algorithms that have been developed for investigating many-objective problems and describes how the methods have been used to advance the design of airborne fire-control and surveillance radars.

 

Order vs. chaos when the space is discrete.
Franco Vivaldi (Queen Mary)
17 Jan 2011Harrison 170 Monday 2pmApplied Mathematics

 

Title: Quality in Supply Chains - Good Relationships Needed for Successful Engineering Business
Pinar Baban (Engineering, CEMPS, University of Exeter)
13 Jan 2011Harrison H170 (3D Visualisation Suite) Thursday 2pmAdvanced Technologies RI (Internal)
This research focuses on improving the performance of supply chains with regard to quality. Recent examples from industry such as Toyota gas pedal failure and global banking crisis as an outcome of the lack of common rules over the national and international financial regulatory norms show that supply chains, operating in both manufacturing and service, are still experiencing problems. Supply chain structure along with relationship factors proposes a potential for a successful integration in a supply chain for which supply chain quality can be defined. As supply chain quality is considered as a relatively unexplored area, a contribution to the literature would be possible by developing a conceptual framework in which formulation, centralisation, communication and relationship factors are simultaneously adapted in constructing the conceptual model. Main purpose of the research is to transcend the quality concept of an organisation to the supply chain level with reference to this model. The case study method is used to test the conceptual model. Data collected is to be analysed in order to verify the model so that practical implications and guidelines for firms operating in various fields ranging from manufacturing to service sectors could be formulated.

 

Accounting for the limitations of quantitative models
Jonty Rougier (University of Bristol)
10 Jan 2011Harrison 171 Monday 2pmApplied Mathematics
There is a wide spectrum of modelling approaches for complex systems. However, in an area such as environmental science, even the most 'realistic' models tend to result in substantial system uncertainty. These realistic models are usually too unwieldy to be embedded within a statistical framework, necessary for performing the standard tasks of model criticism, model calibration, and system prediction. Instead, we consider whether it is possible to use much simpler 'phenomenological' models. The principles and practice are illustrated using a model for glacial cycles developed by Michel Crucifix as part of the ITOP project. The practice uses the very latest techniques from statistical computing, namely Particle Markov chain Monte Carlo (P-MCMC).

 

Passive scalar decay in chaotic flows with boundaries
Fatma Zaggout
14 Dec 2010Harrison 101 Tuesday 9amApplied Mathematics (Internal)
We study the decay rate of a passive scalar in two-dimensional chaotic flows, with a focus on the effect of boundary conditions for kinematically prescribed velocity fields with random or time periodic time-dependence. The boundary conditions on the scalar and flow in a subdomain are imposed by restricting to a subclass invariant under certain symmetry transformations. At late times the decay of the variance of a passive scalar, for example temperature, is exponential in time with rate $\gamma$. For a variety of different cases scaling laws of the form $\gamma(\kappa) \simeq C \kappa^\alpha$ are obtained with exponents $\alpha$ that depend on the boundary conditions mentioned before.

 

Dynamics of differential-delay equations with single, multiple and time--varying lags
Gabor Kiss (University of Bristol)
13 Dec 2010Harrison 170 Monday 2pmApplied Mathematics
We compare the stability properties of some families of delay differential equations with one delay to associated families of equations with distributed delays. With the aid of some examples, we indicate some differences between the non--linear oscillations of equations with one and distributed delays. Furthermore, we report on the existence of pullback attractors of multiple delayed equations.

 

Title: The impact and blast resistance of lightweight structures
Professor Wesley Cantwell (Centre for Materials and Structures, University of Liverpool)
9 Dec 2010Harrison H170 (3D Visualisation Suite) Thursday 2pmAdvanced Technologies RI
This talk will focus on current and recent research investigating the response of lightweight materials and structures to impact and blast loads. The presentation will initially outline a number of projects on topics such as high rate Mode III interlaminar fracture, scaling effects, smart materials based on shape memory alloys and embedded optical fibres and new lightweight core materials for sandwich structures. Attention will then focus on the impact and blast response of both thermoplastic-matrix compositemetal hybrid systems (fibre metal laminates) and lattice structures manufactured using the selective laser melting technique. Attempts are made to model the dynamic behaviour of the FMLs and lattice structures using finite element techniques.

 

Dispersion of Pollution by Transitional Atmospheric Boundary Layers
Alex Taylor
7 Dec 2010Harrison 101 Tuesday 9amApplied Mathematics (Internal)
We consider the dispersion of passive tracer particles within the atmospheric boundary layer through the development of two different methods, Lagrangian stochastic modelling and large-eddy simulation. Initially we focus on obtaining agreement with previous studies and observations for the case of a steady convective boundary layer, moving on to address the case of a typical evening 'decaying' convective boundary layer and investigating the role of residual convective turbulence on dispersion.

 

To snake or not to snake in the planar Swift-Hohenberg equation
Daniele Avitabile (University of Surrey)
6 Dec 2010Harrison 170 Monday 2pmApplied Mathematics
Localised stationary structures play an important role in many biological, chemical and physical processes. Such structures have been observed in a variety of experiments ranging from vertically-vibrated granular materials, liquid crystals, binary-fluid convection, autocatalytic chemical reactions, electrochemical systems to nonlinear optical devices. We investigate the bifurcation structure of stationary localised patterns in a prototypical model, the two- dimensional Swift-Hohenberg equation, on an infinitely long cylinder and on the plane. On cylinders, we find localised roll, square and stripe patches that exhibit snaking and non-snaking behaviour on the same bifurcation branch. Some of these patterns snake between four saddle-node limits: recent analytical results predict then the existence of a rich bifurcation structure to asymmetric solutions, and we trace out these branches and the PDE spectra along these branches. On the plane, we study the bifurcation structure of fully localised roll structures, which are often referred to as worms. We also show preliminary numerical results on oscillons, that is, time-periodic spatially-localised structures.

 

Title: Carbon Based Memories: Understanding the observed switching behaviour at the nanoscale
Peiman Hosseini (Engineering, CEMPS, University of Exeter)
2 Dec 2010Harrison H170 (3D Visualisation Suite) Thursday 1pmAdvanced Technologies RI (Internal)
The ever increasing demand for data storage capacity has pushed the current dominating technologies to their respective limits. Research groups around the world are investing enormous effort and resources to develop the next generation of memory devices that target 100 billion $ market currently shared between HD, DRAM and FLASH. Following the discovery of fullerenes Carbon continues to receive great scientific attention thanks to its extraordinary chemical and physical properties. Given the right environmental conditions carbon can exist as stable graphite or metastable Diamond, these allotropes have completely different electrical conductivity making them appealing for memory systems. The aim of our research project is to induce change in nano-scale regions of thin carbon films and to characterize and understand the nature of the observed switching effect that results.

 

Various Formulations for Learning the Kernel and Structured Sparsity
Prof. Massimilino Pontil (Department of Computer Science, UCL)
1 Dec 2010Harrison 170 Wednesday 2pmComputer Science
The problem of learning a Mercer kernel is of central importance in the context of kernel-based methods, such as support vector machines, regularized least squares and many more. In this talk, I will review an approach to learning the kernel, which consists in minimizing a convex objective function over a prescribed set of kernel matrices. I will establish some important properties of this problem and present a reformulation of it from a feature space perspective. A well studied example covered by this setting is multiple kernel learning, in which the set of kernels is the convex hull of a finite set of basic kernels. I will discuss extensions of this setting to more complex kernel families, which involve additional constraints and a continuous parametrization. Some of these examples are motivated by multi-task learning and structured sparsity, which I will describe in some detail during the talk.

 

Uncertainty in Climate Projections.
Mat Collins
30 Nov 2010Harrison 101 Tuesday 9amApplied Mathematics (Internal)
We are not certain about how severe future climate change will be. Climate models that are used to make projections of the future are known to be inadequate at simulating past climate and climate change because of limitations in computing resources and because of limitations in our understanding of the climate system. Although models are constantly improved, inadequacies persist and policy makers are beginning to require quantitative information to plan for the future. This talk will discuss techniques for dealing with uncertainties using physical, mathematical and statistical approaches. A particular example will be future climate projections made for the UK under the UKCP09 project (http://ukcp09.defra.gov.uk/).

 

Convergence of fast-slow ODEs to stochastic differential equations
Ian Melbourne (University of Surrey)
29 Nov 2010Harrison 254 Monday 10amApplied Mathematics
A project started recently with Andrew Stuart investigates the convergence of certain deterministic systems to a stochastic differential equation. For (presently over-simplified) fast-slow systems, we prove, under very mild conditions on the fast variables (including the case where the fast equation is the Lorenz attractor), that the slow-variable solutions converge to solutions of a stochastic differential equation. A major difference between our approach and related projects is that we do not rely on decay of correlations for the fast variables (decay of correlations for flows is a notoriously difficult and poorly understood problem). Instead we use invariance principles (a generalisation of the central limit theorem giving convergence to Brownian motion) and large deviation estimates which have been derived for a very large class of systems in collaboration with Matthew Nicol.

 

Adaptive Mesh Modelling of the Global Atmosphere
Hilary Weller (University of Reading)
29 Nov 2010Harrison 170 Monday 2pmApplied Mathematics
The next generation of models for weather and climate prediction may look very different from the current, well optimised generation: Future models may use different grids which avoid the pole problem and use unstructured or adaptive meshes. During this talk I will demonstrate some advantages and disadvantages of a lat-lon grid, a cubed sphere and triangular and hexagonal icosahedral grids both with and without local refinement. I will then describe and demonstrate a mesh refinement criteria which anticipates mesh requirements many time steps into the future.

 

Robustness of funnel control in the gap metric.
Markus Mueller
23 Nov 2010Harrison 101 Tuesday 9amApplied Mathematics (Internal)
For m-input, m-output, finite-dimensional, linear systems satisfying the assumptions (i) minimum phase, (ii) relative degree one and (iii) positive high-frequency gain), the funnel controller achieves output regulation in the following sense: all states of the closed-loop system are bounded and, most importantly, transient behaviour of the tracking error is ensured such that its evolution remains in a performance funnel with prespecified boundary. As opposed to classical adaptive high-gain output feedback, system identification or internal model is not invoked and the gain is not monotone. Invoking the conceptual framework of the nonlinear gap metric we show that the funnel controller is robust in the following sense: the funnel controller copes with bounded input and output disturbances and, more importantly, it may even be applied to a system not satisfying any of the classical conditions (i)–(iii) as long as the initial conditions and the disturbances are “small” and the system is “close” (in terms of a “small” gap) to a system satisfying (i)–(iii).

 

Scaling properties of the spectrum for DDEs with large delay
Matthias Wolfrum (Weierstrass Institute for Applied Analysis and Stochastics, Berlin)
22 Nov 2010Harrison 170 Monday 2pmApplied Mathematics
Delay-differential equations play an important role in many applied problems including e.g. economy, neuroscience, and optoelectronics. For the dynamics of semiconductor lasers with optical feedback or coupling in many cases the delay caused by the finite speed of light has to be considered as large compared to the internal time scales of the laser being in the range of picoseconds. For a laser with optical feedback the classical Lang-Kobayashi model shows a large variety of dynamical behavior related to the large delay, including the coexistence of many periodic solutions with different stability properties, high dimensional chaos and other. Starting from these phenomena, we investigate typical phenomena in delay-differential equations (DDEs) where the delay time tends to infinity. We show that the spectrum of linear delay differential equations with large delay splits into two different parts. One part, called the strong spectrum, converges to isolated points when the delay parameter tends to infinity. The other part, called the pseudo-continuous spectrum, accumulates near criticality and converges after rescaling to a set of spectral curves, called the asymptotic continuous spectrum. We show that the spectral curves and strong spectral points provide a complete description of the spectrum for sufficiently large delay and can be comparatively easily calculated by approximating expressions. The abstract results will be illustrated by by some examples.

 

Zero dynamics and funnel control of linear differential-algebraic systems
Thomas Berger (Ilmenau University of Technology, Germany)
17 Nov 2010Harrison 101 Monday 2pmApplied Mathematics
We consider linear differential-algebraic equations of the form E\dot{x}_(t) = Ax(t) + Bu(t) y(t) = Cx(t) ; (1) for E,A \in R^{n \times n}, B,C^{T} \in R^{n \times m} and regular matrix pencil sE-A \in R[s]^{n \times n}, i.e. det(sE-A) \in R[s]\{0}. Furthermore we assume that the transfer function G(s) = C(sE-A)^{-1}B has proper inverse, i.e. G^{-1}(s) exists and lim _{s \rightarrow \infty} G^{-1}(s) = D for some D \in R^{m \times m}. For this class of systems a so called `zero dynamics form' which is a simple ("almost" a normal) form of the DAE is derived; it is a pendant to the well-known Byrnes-Isidori form for ODE systems. The `zero dynamics form' is exploited to characterize the zero dynamics of (1) by (A,E,B)-invariant subspaces; structural properties such as stable zero dynamics, minimum phase, and high-gain stabilizability are also characterized. Finally, the zero dynamics form is the main mathematical tool to show that the `funnel controller', that is a time-varying proportional output error feedback u(t) = -k(t)e(t), achieves for all DAE systems (1) with stable zero dynamics that the output signal y(\dot) tracks a reference signal y_{ref}(\dot) with respect to pre-specified transient behaviour.

 

Initialising Decadal Prediction in HadCM3 with RAPID Array Observations
Leon Hermanson (University of Reading/Met Office)
16 Nov 2010Harrison 101 Tuesday 3pmApplied Mathematics
The RAPID array consists of several moorings at about 26°N in the Atlantic that measure temperature and salinity from which the meridional overturning circulation (MOC) and its components at this latitude can be determined. The main aim of the VALue Of the RAPID array (VALOR) project is to assess the value of the RAPID array observations for predictions of the Atlantic MOC and its impact on climate. In addition, the project will explore a range of issues concerning the design of a potentional MOC prediction system. One of the models used in this work is the Hadley Centre HadCM3 model. In this work we have investigated the issues that arise when trying to initialise the HadCM3 model with the RAPID observations. This has initially been investigated in an idealised setting where pseudo-observations from the same model are used to reconstruct a known transport. Leon is a Research Fellow at University of Reading, but is currently seconded to the Met Office, where he is working in the Decadal Climate Prediction group. He is visiting the College for the entire week 15-9 Nov to work with Tom Fricker and Chris Ferro, so will be available to talk to about any aspect of his seminar, or his wider work, during that time.

 

Probabilistic transient envelope: Characterizing Disturbances and Perturbations.
Iakovos Matsikis
16 Nov 2010Harrison 101 Tuesday 9amApplied Mathematics (Internal)
We study the transient effect of deterministic or stochastic distrubances on a system that is perturbed deterministically or stochastically by constructing a transient envelope. The envelope is constructed with intensive simulation and it allows us to calculate the initial structures that cause amplification and attenuation over all time steps of interest, the biggest and smallest values the system might assume and the probability that the output belongs in certain bounded intervals. For application we use population projection matrices.

 

Fine-scale structure formation in Saturn's rings
Henrik Latter (University of Cambridge)
15 Nov 2010Harrison 170 Monday 2pmApplied Mathematics
Recent radio and UV occultation experiments carried out by the Cassini spacecraft have revealed that swathes of Saturn's A and B-ring support fine-scale axisymmetric patterns. This 'microstructure' is surprisingly regular, possessing wavelengths between 150 and 250 metres, and is probably driven by a pulsational instability of viscous origin. Using a simple hydrodynamical model, I show how this fine-scale quasiperiodic structure is related to nonlinear wave trains associated with the instability. I will also examine how variations and `defects' in the waves' phase and amplitude may relate to irregular features on larger-scales. This is the 31st Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics".

 

Title: Proper Use of Unit Cells in Micromechanical Finite Element Analyses of Materials with Periodic Microstructures
Professor Shuguang Li (Faculty of Engineering, University of Nottingham)
11 Nov 2010Harrison 170 (3D Visulisation Suite) Thursday 2pmAdvanced Technologies RI
Unit cells have been increasingly employed in various analyses, in particular, for micromechanical analyses of composite materials where periodicities feature the microstructure, often in conjunction of the use of finite elements. The formulation of a unit cell could start as if it was a trivial exercise, at least as often perceived. However, it soon becomes overwhelming to such an extent that most attempts have gone either futile or incorrect, as is often observed in open literature, including research papers from reputable academic journals. Some typical examples of this kind will be cited to set the scene for the discussion. The lecture is intended to draw some clear guidelines for proper formulation of unit cells in a systematic manner, which rests firmly on the concept of symmetries and their physical properties. Significant implications of properly formulated unit cells on the pre-processing (meshing) and post-processing (e.g. derivation of effective properties) will be discussed.

 

Analysis, synthesis and applications of gene regulatory network models
Prof. Yaochu Jin (Department of Computing, University of Surrey)
10 Nov 2010Harrison 107 Wednesday 2pmComputer Science
This talk starts with a brief introduction to computational models of gene regulatory networks (GRN), followed by a description of our recent results on analyzing and synthesizing gene regulatory motifs, particularly from the robustness and evolvability perspective. We show that in a feedforward Boolean network, the trade-off between robustness and evolvability cannot be resolved. In contrast, how that this trade-off can be resolved in an ODE-based GRN model for cellular growth based on a quantitative evolvability measure. In addition, we demonstrate that robust GRN motifs can emerge from in silico evolution without an explicit selection pressure on robustness. Our results also suggest that evolvability is evolvable without explicit selection.

 

The climate and habitability of planets orbiting red dwarf stars
Manoj Joshi (NCAS Climate, Reading)
8 Nov 2010Harrison 170 Monday 2pmApplied Mathematics
The concept of the habitable zone, or the region in which a planet can support liquid water at its surface, is almost ubiquitous in studies of "astrobiology", or the study of life in the universe. The habitable zone becomes especially interesting when considering red dwarf stars, or those stars with a mass between 0.1 and 0.5 times that of the Sun. On the one hand, red dwarfs are far more common than sun-like stars, and are thought to maintain their mean luminosity for much longer; on the other hand a red dwarf's habitable zone is so close to the star that phenomena such as tidal locking and stellar flares might be important in determining whether or not a planet can support an atmosphere (or even life). In this talk I'll review research on the habitable zone, especially with regard to red dwarf stars; work which shows that while the tidal locking of planets orbiting red dwarfs is not a barrier to habitability, stellar activity might be; and finally how all this is relevant to present and future planet-finding space missions.

 

Title: Fullerene-Like WS2 Nanoparticles and Nanocomposites: Processing, Characterisation and Applications
Dr Hong Chang (Engineering, CEMPS, University of Exeter)
4 Nov 2010Harrison H170 (3D Visualisation Suite) Thursday 1pmAdvanced Technologies RI (Internal)
A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Following the discovery of carbon fullerenes and nanotubes, closed-cage non-carbon fullerene-like nanoparticles or nanotubes were discovered and they were given the name of inorganic fullerene-like materials (abbreviated as IFs). This research is focused on the processing and characterisation of WS2 IFs and their nanocomposites. The presentation will begin with a review on the extraordinary properties and potential applications of WS2 IFs, followed by the research motivation, periodic research progresses and plans for future work.

 

Buoyant plumes: simple models and large-eddy simulation
Ben Devenish (Met Office)
3 Nov 2010Harrison 106 Wednesday 2pmApplied Mathematics
NOTE - THIS IS THE SEMINAR POSTPONED FROM 27th OCTOBER. Examples of buoyant plumes abound in both natural and man-made situations: the recent eruption of Eyjafjallajokull in Iceland and the plume generated by the fire at the Buncefield oil depot in December 2005 are just two well-known examples. The ability to predict the dispersion of any resulting hazardous material was demonstrated with dramatic effect earlier this year and provides a clear motivation for the study of buoyant plumes. Despite their obvious complexity, buoyant plumes have been successfully described by relatively simple models. In this talk I will review these models and then consider what further insight can be gained from large-eddy simulations. I will also present results on more complicated but realistic scenarios such as the effect on the plume of a crosswind.

 

An Ontology of Information and Information Bearers.
Dr. Antony Galton (Computer Science)
3 Nov 2010Harrison 170 Wednesday 2pmComputer Science (Internal)
In many areas, such as emergency management, coordinated action can be hampered by lack of suitable informatic support for integrating diverse types of information, in different formats, from a variety of sources, all of which may be relevant to the problem at hand. To create software that is able to handle such a diversity of information types in a unified framework it is necessary to understand what types of information there are, what forms they can take, and how they are related to each other and to other entities of concern. To this end, I am currently developing a formal ontology of information entities to serve as a reference point for subsequent system development activities. In this talk I will discuss some of the issues that I have had to address in developing the ontology.

 

The role of global manifolds in the transition to chaos in the Lorenz system
Bernd Krauskopf (University of Bristol)
1 Nov 2010Harrison 170 Monday 2pmApplied Mathematics
joint work with Hinke Osinga (University of Bristol) and Eusebius Doedel (Concordia University). The Lorenz system still fascinates many people because of the simplicity of the equations that generate such complicated dynamics on the famous butterfly attractor. This talk addresses the role of two-dimensional stable manifolds of the origin and of saddle periodic orbits in organising the overall dynamics. These global objects need to be computed numerically with specialized algorithms. We present an approach that is based on the continuation of orbit segments, defined as solutions of suitable boundary value problems. In this way, we are able to study bifurcations of global manifolds as the Rayleigh parameter of the Lorenz system is changed. We show how the entire phase space of the Lorenz system is organised and how the manifolds change dramatically during the transition to chaotic dynamics. The delicate structure of global manifolds that we find also demonstrates the accuracy of the computations.

 

***** SEMINAR POSTPONED TO 3rd NOVEMBER *****
Ben Devenish (***** SEMINAR POSTPONED TO 3rd NOVEMBER *****)
27 Oct 2010Harrison 101 Wednesday 2pmApplied Mathematics
***** SEMINAR POSTPONED TO 3rd NOVEMBER *****

 

Novel Machine Learning Methods for Data Integration
Dr. Colin Campbell (Intelligent System Lab, University of Bristol)
27 Oct 2010Harrison 170 Wednesday 2pmComputer Science
Substantial quantities of data are being generated within the biomedical sciences and the successful integration of different types of data remains an important challenge. We begin the talk with an overview of our motivation for our investigations in this context. We begin by briefly reviewing work on the joint unsupervised modeling of several types of data believed functionally linked such as microRNA and gene expression array data from the same cancer patient. Next we consider supervised learning and outline several approaches to multi-kernel learning which can handle disparate types of input data. We conclude with a discussion of future avenues for investigation in this context.

 

On Finite Element Methods for Fully Nonlinear Elliptic Equations of Second Order
Klaus Boehmer (University of Marburg)
25 Oct 2010Harrison 170 Monday 2pmApplied Mathematics
For the first time, we present for the general case of fully nonlin- ear elliptic differential equations of second order a nonstandard C1 finite element method (FEM). We consider, throughout the paper, two cases in parallel: For convex, bounded, polyhedral domains in Rn, or for C2 bounded domains in R2, we prove stability and convergence for the corresponding conforming or nonconforming C1 FEM, resp. The classical theory of discretization methods is applied to the differential operator or the combined differential and the boundary operator. The consistency error for satisfied or violated boundary conditions on polyhedral or curved domains has to be estimated. The stability has to be proved in an unusual way. This is the hard core of the paper. Essential tools are linearization, a compactness argument, the interplay between the weak and strong form of the linearized operator and a new regularity result for solutions of finite element equations. An essential basis for our proofs are Davydov’s results for C1 FEs on polyhedral domains in Rn or of local degree 5 for C2 domains in R2. Our proof for the second case in Rn, includes the first essentially as special case. The method applies to quasilinear elliptic problems not in divergence form as well. A discrete Newton methods converges locally quadratically, essentially independently of the actual grid size by the mesh independence principle.

 

Rubberband Algorithms - A General Strategy for Efficient Solutions of Euclidean Shortest Path Problems
Prof. Reinhard Klette (University of Auckland, New Zealand)
20 Oct 2010Harrison 170 Wednesday 2pmComputer Science
Algorithms for solving shortest path problems in 2D or 3D Euclidean space are typically either solvable in linear time, or of higher order time complexities, often even NP-hard. Rubberband algorithms follow a general design strategy which is relatively simple to implement assuming a step set has been identified which contains the vertices of shortest paths, and is easily calculable itself. The talk informs about solutions to selected shortest path problems using rubberband algorithms.

 

Flows on real networks
David Arrowsmith (Queen Mary)
18 Oct 2010Harrison 170 Monday 2pmApplied Mathematics

 

Title: Mechanical Properties as a function of Nano-Architecture
Dr Dean C. Sayle (Department of Engineering and Applied Science, Cranfield University)
14 Oct 2010Harrison H170 (3D Visualisation Suite) Thursday 2pmAdvanced Technologies RI
If we build an arch not out of stone bricks, but using NanoBuilding Blocks will it have unprecedented load carrying capacity? Here, we formulate ‘Engineering Rules at the Nanoscale’ using HPC. Specifically, we use atomistic computer simulation to generate models of nanomaterials and calculate their mechanical properties. In particular, nanoparticle building blocks are positioned at crystallographic positions to facilitate a particular (nano)architecture and the mechanical strength calculated using molecular dynamics simulation.

 

Kent's talk: A hyper-heuristic approach to generating mutation operators with tailored distributions.

Richard's talk: A Bayesian Framework for Active Learning
Kent McClymont and Richard Fredlund (Computer Science)
13 Oct 2010Harrison 107 Wednesday 2pmComputer Science (Internal)
Kent's talk: Discussion on a method for generating new probability distributions tailored to specific problem classes for use in optimisation mutation operators. A range of bespoke operators with varying behaviours are created by evolving multi-modal Gaussian mixture model distributions. These automatically constructed operators are found to match the performance of a single tuned Gaussian distribution when compared using a (1+1) Evolution Strategy. In this study, the generated heuristics are shown to display a range of desirable characteristics for the DTLZ and WFG test problems; such as speed of convergence.

Richard's talk: We describe a Bayesian framework for active learning for non-separable data, which incorporates a query density to explicitly model how new data is to be sampled. The model makes no assumption of independence between queried data-points; rather it updates model parameters on the basis of both observations and how those observations were sampled. A "hypothetical" look-ahead is employed to evaluate expected cost in the next time-step. We show the efficacy of this algorithm on the probabilistic high-low game which is a non-separable generalisation of the separable high-low game introduced by Seung et al. (1993). Our results indicate that the active Bayes algorithm performs significantly better than passive learning even when the overlap region is wide, covering over 30% of the feature space.

 

Evolution of magnetic helicity with the solar cycle: observations and dynamo theory
Kirill Kuzanyan ((1) IZMIRAN, Russian Academy of Sciences, Moscow (2) National Astronomical Observatories of China, B)
12 Oct 2010Harrison 101 Tuesday 9amApplied Mathematics
We review the long term systematic observation of solar vector magnetic fields at several observatories in the USA, China and Japan. The data sample at Huairou Solar Observing station of Chinese Academy of Sciences (Beijing) cover the whole period 1988-2005 which is the longest available systematic dataset of three-component magnetic field in solar active regions over the two consecutive solar cycles 22 and 23. We can apply to this sample a self-consistent averaging procedure which is the observational proxy to the averaging over the ensemble of turbulent pulsations. Thus we have obtained large-scale coherent structures resembling the mean magnetic field. It obeys Hale’s polarity rule for sunspots and magnetic fields in quiet photosphere, in accord with other observational results. We also use the data sample to compute current helicity and twist. They are important observational proxies of magnetic helicity which is the invariant in MHD flows. These helical parameters demonstrate hemispheric sign rule: in the northern/southern hemispheres their signs are predominantly negative/positive. However, based on the data sample covering almost overall 22 year magnetic solar cycle we have established specific areas in latitude and time when they are regularly inverted, mainly in the beginning at the end of the sunspot butterfly wings. In solar dynamo models helicity can be used as an important nonlinear drive controlling growth of the solar cycle, and at the same time it is a proxy of the alpha-effect which is a measure of regeneration of the poloidal field from the toroidal one. We discuss possible implications of our observational findings in the light of the solar dynamo. 30th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics".

 

Bifurcations in generalization of Kuramoto-Skaguchi model of coupled phase oscillators
Oleksandr Burylko (National Academy of Sciences of Ukraine)
11 Oct 2010Harrison 170 Monday 2pmApplied Mathematics
We consider the extension of popular Kuramoto (Kuramoto-Sakaguchi) model of globally coupled phase oscillators with the phase shift in coupling function that depends nonlinearly on the order parameter. This system was proposed by A.Pikovsky and M.Rosenblum (Phys. Rev. Lett. (2007), Physica D (2009). We discuss bifurcations of transition from full synchronization to desyncronization through different clustering states. We show that the typical way of this transition passes through different heteroclinic bifurcations. The obtained results are mostly based on the lemma about localization of equilibria that was proved. Also, we describe the multistability that occurs in the system.

 

Crystal inspired beam networks with negative elastic properties
Tom Hughes (Engineering, CEMPS, University of Exeter)
7 Oct 2010Harrison H170 (3D Visualisation Suite) Thursday 1pmAdvanced Technologies RI (Internal)
An astonishing result was published in 1998: far from being the rare property it was then thought to be, negative Poisson's ratio behaviour in metals is actually quite common [1]. Of the 32 cubic metals investigated, around 69% were found to exhibit auxetic behaviour when strained in the [110] direction however, this paper only proposed inconclusive explanations and a limited mechanism. Since then, no study has revisited the issue, and no one has answered the really puzzling question, which is "why are one third of cubic metals NOT auxetic?". In this work we first study the elastic properties of cubic metals using atomistic modelling, and then of beam frameworks inspired by cubic metals using finite element analysis To determine the elastic constants for a range of 24 body-centred and face-centred metallic crystals, we use two-body and many-body classical potentials. The elastic constants can then be used to calculate the Poisson's ratio of the crystals for a strain in any direction. The simpler two-body potentials obey the Cauchy relation, and consequently always predict a negative Poisson's ratio. Many-Body potentials, such as Finnis-Sinclair, are able to more accurately predict the elastic constants of the crystals and Poisson's ratios are generally found to be in agreement with experimental data published in the literature. The deformation mechanisms for both positive and negative Poisson's ratio in body-centred and face-centred cubic structures are also determined. The bond network in cubic metals is also used as inspiration for truss structures composed of bending beams. By modelling the first, second and third nearest neighbour bonds in a cubic crystal as beams of varying stiffness, it has been possible to show (using the finite element method) how the Poisson's ratio of the structure changes from negative to positive according to the relative stiffness of the three classes of beams. This paradigm is then extended to investigate structures of lower symmetry, in a bid to find novel engineering structures with negative Poisson's ratio. [1] Baughman et al. Negative Poisson's ratios as a common feature of cubic metals. Nature 392, 362-365 (1998)

 

Librationally driven flow in triaxial ellipsoids.
Keke Zhang
5 Oct 2010Harrison 101 Tuesday 9amApplied Mathematics (Internal)

 

The oscillations of rotating fluids and their applications to stars and planets
Michel Rieutord (Laboratoire Astrophysique de Toulouse)
4 Oct 2010Harrison 170 Monday 2pmApplied Mathematics
Stars and planets are all rotating. Due to the conservation of angular momentum, this leads to specific oscillations known as inertial oscillations. These oscillations modify the low-frequency oscillation spectrum of these bodies and introduce new phenomena which I shall try to describe in a simple manner. I'll present, for instance, some of the peculiarities of these oscillations (like singularities) and the role they play in the dynamics of tidally interacting bodies like stars harbouring a hot Jupiter. 29th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics".

 

California Hottest and Coldest Days: Their Large-scale Weather Patterns, Extreme Statistics, Downscaling, and Further Questions
Richard Grotjahn (Atmospheric Science Program, Univ. of California, Davis, U.S.A.)
19 Jul 2010Harrison 170 Monday 2pmApplied Mathematics
Extreme hot days as defined for the California central valley (CV) have a characteristic large scale structure that affects much of the west coast of North America as well. Extreme cold air outbreaks affect much of the southwestern United States. The patterns for both types of extreme events (EEs) will be briefly summarized, including statistically highly significant regions far from California. Simple statistics (boostrap resampling and simple tail tests) for assigning significance to parts of the EE patterns in both cases will be summarized. The EE patterns for the hottest 1% of summer days have been compared to daily weather maps in a simple calculation of a daily anomaly 'HDA index' to hindcast (and forecast) hottest days in daily anomaly values. The 'HDA index' captures ~1/2 of the hottest 1% days from a 25 year period using a peaks over a threshold test to find the highest 1% of HDA index and CV observed temperature. Perhaps unexpectedly, the HDA index has high correlation with maximum temperatures on near-normal and below-normal dates as well (overall correlation between daily maximum temperature at central valley stations and HDA index: 0.84). Remaining questions include how the large scale patterns develop dynamically and improved extreme statistics.

 

Title: Infra-red imaging in experimental mechanics
Professor Janice Barton (School of Engineering Sciences, University of Southampton)
1 Jul 2010Harrison H170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI
Infra-red imaging is usually associated with fairly the crude temperature measurements made to assess the condition of structures and for thermal based non-destructive evaluations. Highly sensitive infra-red detectors are now available that allow high spatial resolutions along with temperature resolutions of about 20 mK. If lock-in processing is used the temperature resolution can be improved to 2 mK. A technique that takes advantage of the high spatial and temperature resolution of modern IR detectors is TSA (thermoelastic stress analysis). Here the infra-red (IR) detector is used to 'measure' the small reversible temperature change associated with the thermoelastic effect from a component subjected to cyclic load. The detector output signal is related to the changes in the sum of the principal stresses on the surface of the material. Therefore the 'thermal image' provides full-field data that is a function of the surfaces stresses. For orthotropic materials, such as laminated composite structures, the small temperature change is related to the changes in the stresses in the principal material directions on the surface of the material. The data is recorded and processed in a matter of seconds enabling practically real-time studies and hence providing clear benefit in damage evaluations. In the presentation the background theory underpinning the application of TSA is provided. The focus of the presentation is application of infra-red imaging to polymer composites, sandwich structures and foam core materials. Examples of applications as well as some more fundamental physical issues will be presented.

 

Demand Management - Good or Bad?
David Evans (Water Resource Consultant)
29 Jun 2010Harrison 170 Tuesday 2pmInformatics RI
The UK’s population is predicted to rise by 20 million in coming decades, while the climate is expected to become wetter in winter and drier in summer. Much emphasis is therefore being put on demand management (or ‘water efficiency’) - but is this the right approach? Our climate is highly seasonal. In summer, evaporation exceeds rainfall and the incoming water resource is negative. But winter resources are large, and summer needs are met by storing winter surplus either naturally in the soil and as groundwater, or artificially in reservoirs. Wetter winters would increase that surplus (though perhaps offset by greater storminess). Groundwaters are fully committed, but water supply for the additional population can come from whatever is the best combination of demand management and surface water development. However, with climate change the predicted combination of less summer rain and higher evaporation spells summer desiccation. It is far from clear if there will be enough water to grow our food or to sustain our green environment. This could be a much bigger issue than water supply and the presentation explores it quantitatively. Fortunately water supply is non-consumptive – it almost all comes back, either as effluent or as leakage, and can be reused, for example for irrigation. Even coastal effluents are water resources available to reclaim when needed. The more the water supply, the more the returns. Conversely, demand management reduces the amount of water that the water companies store in winter and return in summer. The presentation will show how the multiple benefits of water storage greatly exceed those of too much demand management. The future is alarming for our food and green environment. Reservoirs will help; demand management won’t.

 

Flood frequency estimation in urban catchments
Dr Thomas Kjeldsen (Centre for Ecology & Hydrology, Wallingford)
22 Jun 2010Harrison 170 Tuesday 2pmInformatics RI
The presentation will introduce the industry-standard for flood frequency estimation in the UK, the Flood Estimation Handbook (FEH), and review ongoing activities in quantifying the impact of urbanisation on catchment flood response and flood frequency relationships. Catchment-scale effects of urbanisation are shown to be complex, and the study will highlight future data requirements needed to improve modelling capabilities in catchments where urban areas interact with the terrestrial water cycle.

 

Simple statistical methods for complex ecological dynamics
Simon Wood (University of Bath)
21 Jun 2010Harrison 215 Monday 2pmApplied Mathematics

 

Mathematical analysis of circadian systems.
Ozgur Akman
15 Jun 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Circadian oscillations are universal, controlling 24-hour rhythms of metabolism, physiology and behaviour in organisms ranging from humans to cyanobacteria. The regulatory gene networks underlying these oscillations have proved to be useful systems for quantifying the relationship between the structures of biochemical systems and their higher order properties. By constructing mathematical models of key circadian organisms and analysing the models using techniques derived from nonlinear dynamics, insights can be obtained into the reasons why circadian networks have considerably more complex architectures than the minimal negative feedback loop required for entrainable oscillations. Recent results obtained from modelling a range of circadian species suggest that one of the possible benefits of the high feedback loop complexity characteristic clock networks is the increased functional flexibility that such architectures confer. Moreover, the techniques developed to construct and analyse the models have potential applicability to a broader range of signalling pathways, particularly with respect to parameter-fitting and sensitivity analysis.

 

Mathematical modelling of the active process of hearing in insects and mammals
Alan Champneys (University of Bristol)
14 Jun 2010Harrison 106 Monday 2pmApplied Mathematics
Hearing organs in mammals are remarkable in that a passive signal is electro-mechanically amplified over several orders of magnitude within the cochlear itself before any neural processing has taken place. In the insect world, the male mosquito also has a highly developed active hearing process, whose function is crucial to the mating process. It has recently been proposed, based on data from the bull frog, that the conceptual model of a Hopf bifurcation normal form captures all the features of the cochlear amplifier and that this might be a universal model across many species. The aim of this talk is to challenge this assertion and to show that there is no substitute for ab initio mathematical modelling that on the one hand attempts to capture the true physics and on the other hand is sufficiently simple to be amenable to qualitative as well as quantitative understanding. In particular I shall present recent work with Avitable and Homer based on the experiments in the lab of Robert in Bristol on a new mathematical model for the mosquito hearing organ. The organ is far more primitive than the mammalian cochlear and at bottom level can be described by a see-saw like lever arm that is attached to many threads that can provide mechanical stimulus in the form of a "twitch". The model is shown to capture the amplification of low-level sound, quenching of high input hysteresis and self-oscillation that is observed in live insects. I shall also present ongoing work with Szalai, Homer, O'Maoileidigh and Jülicher together with experimental teams in Bristol and Keele on mathematical models for the outer-hair cells that are thought to cause the active process within mammalian hearing. We show that this model displays a periodically forced cusp bifurcation, an unfolding of which is also able to show the characteristic 1/3-growth law that a Hopf bifurcation normal form displays. We also show how the dominant features of this model produce a very different kind of simple model, this is able to match experimental data in showing regions of active amplification with different amplitude-dependent exponents.

 

Evolution 1 - ID 0: One more case of biological complexity resolved.
Orkun Soyer
8 Jun 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
The molecular basis of chemotaxis in the model organism Escherichia coli requires 7 signalling proteins, interacting in specific ways. The resulting dynamical system has non-trivial features including high sensitivity and precise adaptation. It remains unknown, how such a relatively complex system could have evolved and through which intermediary systems. This results in bacterial chemotaxis and the underlying signalling networks to be presented as an evolutionary puzzle. The lack of evolutionary understanding also limits our ability to extend the findings from E. coli to other species, which show remarkable differences to E. coli both in response dynamics and network structure. Using a mathematical approach we explore the potential evolutionary paths in chemotaxis. In particular, we reduce potential chemotaxis strategies to a simple formalism containing few key parameters that correspond to biological implementation of such strategies. We then compare the performance of such strategies under different parameter regimes. This yields a plausible evolutionary path from simple networks with straightforward dynamics to networks with adaptive dynamics. Interestingly, while the evolutionary transition can be driven only by selection for increased chemotaxis performance, the optimal performance can be achieved by different strategies under different parameter regimes (i.e. biological implementations).

 

The use of acoustic methods for sewer network management
Mr Richard Long (Richard Long Associates)
8 Jun 2010Harrison 170 Tuesday 2pmInformatics RI
The sewer system in the UK is ageing and is being put under increasing strain by climate change and ongoing development. To replace the systems would cost in excess of ?100billion and would be hugely disruptive, so careful management by the sewerage undertakers is vital. Yet they have only very limited information about the condition of their assets and how they are deteriorating over time. This need has been recognised by government and the companies themselves. Sewerage undertakers in the UK need more information, but existing CCTV technology is slow and it would be unaffordable to survey the whole sewer system on a regular basis this way. Anticipating a demand for new low-cost techniques, a team led by Bradford University has been collaborating to develop acoustic techniques to meet this need. By providing inexpensive, quick, accurate, digital output SewerBatt has the potential to allow the water industry and other industries with extensive drainage assets to meet the increasingly demanding requirements of government, regulators, customers and shareholders. The presentation will examine the need for new technology and describe the project undertaken. Examples of the output from the system will be provided and how it could be incorporated into sewerage management practice will be discussed.

 

Dynamical Systems and Complex Networks: Are such Theories Useful for Neuroscience and Earth Sciences?
Juergen Kurths (PIK, Potsdam)
7 Jun 2010Harrison 170 Monday 2pmApplied Mathematics
Complex networks were firstly studied by Leonhard Euler in 1736 when he solved the Königsberger Brückenproblem. Recent research has revealed a rich and complicated network topology in various model systems as well as in several fields of applications, such as transportation and social networks, or the WWW. It will be discussed whether this approach can lead to useful new insights into rather large complex systems or whether it is fashionable only to interpret various phenomena from this viewpoint and publish papers on that. A challenging task is to understand the implications of complex network structures on the functional organization of the brain activities. We investigate synchronization dynamics on the cortico-cortical network of the cat and find that the network displays clustered synchronization behaviour and the dynamical clusters coincide with the topological community structures observed in the anatomical network. Next we consider an inverse problem: Is there a backbone-like structure underlying the climate system? For this we reconstruct a global climate network from temperature data. Parameters of this network, as betweenness centrality, uncover relations to global circulation patterns in oceans and atmosphere. We especially study the role of hubs in the flows of energy and matter in the climate system. This new approach seems to be promising for understanding the dynamics of changing climate and its impacts.

 

Statistical Attractors and the Convergence of Time Averages
Ozkan Karabacak
1 Jun 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
There are various notions of attractor in the literature, including the ideas of measure (Milnor) attractors and statistical (Ilyashenko) attractors. We relate the notion of statistical attractor to that of the essential omega-limit set and prove some elementary results about these. In addition, we consider the convergence of time averages along trajectories. Ergodicity implies the convergence of time averages along almost all trajectories for all continuous observables. For non-ergodic systems, time averages may not exist even for almost all trajectories. However, averages of some observables may converge; we characterize conditions on observables that ensure convergence of time averages even in non-ergodic systems.

 

Spectacle cycles and modular forms
Dr Jens Funke (Durham university)
27 May 2010Harrison 203 Thursday 3pmPure Mathematics
The classical Shintani lift is the adjoint of the Shimura correspondence. It realizes periods of even weight cusp forms as Fourier coefficients of a half-integral modular form. In this talk we revisit the Shintani lift from a (co)homological perspective. In particular, we extend the lift to Eisenstein series and give a geometric interpretation of this extension. This is joint work with John Millson.

 

Excitability in ramped systems: The compost bomb instability.
Sebastian Wieczorek
25 May 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
About one year ago, Catherine Luke and Peter Cox reported (in one of our internal seminars) on the "combost-bomb instability" which represents a potential tipping point in the response of the climate system to anthropogenic forcing. In this strongly nonlinear phenomenon, biochemical heat release destabilizes peatland above some critical rate of global warming, leading to a catastrophic release of soil carbon into the atmosphere. This talk explains the "compost-bomb instability" as a novel type of excitability where a stable quiescent state exists for different fixed settings of a system's parameter but enormous excitable bursts appear when the parameter is increased gradually (ramped) from one setting to another. We show that an excitable system with a ramped parameter forms a singularly perturbed problem with at least two slow variables and focus on the case with locally folded critical manifold. Analysis of the desingularised flow identifies an excitability threshold as a canard trajectory through a folded singularity and leads to the analytical formula for the critical rate of global warming.

 

Many Criteria Decision Making in Control and Systems Design
Prof. Peter Fleming (University of Sheffield)
25 May 2010Harrison 170 Tuesday 2pmInformatics RI
Design problems arising in control and systems can often be conveniently formulated as multi-criteria decision-making problems. However, these often comprise a relatively large number of criteria. Through close association with designers in industry a range of machine learning tools and associated techniques have been devised to address the special requirements of many-criteria decision-making. These include visualisation and analysis tools to aid the identification of features such as “hot-spots” and non-competing criteria, preference articulation techniques to assist in interrogating the search region of interest and methods to address the special computational demands (for example, convergence and diversity management) of these problems. Test problems and real design exercises will demonstrate these approaches.

 

Normalized coprime representations for time-varying linear systems
Markus Mueller
18 May 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
By considering the behaviour of stabilizable and detectable, linear time-varying state-space models over doublyinfinite continuous time, we establish the existence of so-called normalized coprime representations for the system graphs; that is, stable and stably left (resp. right) invertible, image (resp. kernel) representations that are normalized with respect to the inner product on L2(−oo,oo). The approach is constructive, involving the solution of timevarying differential Riccati equations with single-point boundary conditions at either +oo or −oo.

 

CANCELLED Interfacial instabilities in a two-layer system with vertical electric current
Sergei Molokov (University of Coventry)
17 May 2010cancelled cancelled cancelled cancelledApplied Mathematics
CANCELLED 28th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics". abstract TBA

 

Title: Processing and applications of nanotubes and graphene
Dr Ian Kinloch (School of Materials, University of Manchester)
13 May 2010Harrison 170 (3D Vis Suite) Thursday 2pmAdvanced Technologies RI

 

Evidence for Rotational Parametric Instability in Earth's Core from Analysing Relative Paleointensity Data
Keith Aldridge (York University, Canada)
11 May 2010Harrison 170 Tuesday 12noonApplied Mathematics
29th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics" Evidence for Rotational Parametric Instability in Earth's Core from Analysing Relative Paleointensity Data Abstract We have developed an algorithm to search records of relative paleointensity for evidence of a parametric instability in Earth's core. Under the assumption that the spectrum of magnetic field intensity is a proxy for that of fluid velocity, the presence in Earth's core of a parametric instability will be seen in records of the magnetic field intensity. As long as the strain rate produced by either precessional or tidal forces exceeds the dissipation rate, a parametric instability will grow and subsequently decay repeatedly as observed in laboratory experiments. In the event that the externally imposed strain rate is close to the dissipation rate, a balance will result in what we call a steady state. Our algorithm has searched records of relative paleointensity from sedimentary cores from the past 2 million years. We smooth the data and set a threshold of significant change in the field which is segmented into intervals of growth, decay or steady state. According to our model of parametric instability, adjacent decays and growths recovered by our algorithm can be combined to give the magnitude of the external strain rate. Application of this algorithm to the SINT2000 data reveals distinct maxima that correspond to all the reversals of the field in the interval studied. Thus our model for parametric instability in Earth's core is consistent with the occurrence of magnetic field reversals at times when the external straining is largest.

 

What can convection teach us about the nature of turbulence?
Fritz Busse (University of Bayreuth)
11 May 2010Harrison 170 Tuesday 11amApplied Mathematics
27th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics". abstract: TBA

 

Info-Gap Theory for Strategic Planning Under Severe Uncertainty: Applications to Pollution Control Policy
Prof. Yakov Ben-Haim (Technion - Israel Institute of Technology)
11 May 2010Harrison LT04 Tuesday 2pmInformatics RI
Info-gap theory is a method for analysis, planning, decision and design under uncertainty. The future may di®er from the past, so our models may err in ways we cannot know. Our data may lack evidence about surprises: catastrophes or windfalls. Our scienti¯c and technical understanding may be incomplete. These are info-gaps: incomplete understanding of the system being managed. Info-gap theory provides decision-support tools for modelling and managing severe uncertainty. After outlining the info-gap methodology, we explore applications to public policy for pollution control. Given uncertainty in the marginal costs and bene¯ts of pollution emission, is it better to impose a tax on pollution or to establish legal limits to pollution? Given uncertainty in the costs of abatement, how should a public regulator allocate auditing and enforcement resources?

 

Self-consistent nonlinear MHD
David Hughes (University of Leeds)
10 May 2010Harrison 170 Monday 2pmApplied Mathematics
26th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics". The majority of astrophysical dynamo modelling is performed using mean field MHD, an elegant theory of MHD turbulence in which small-scale interactions are captured by various transport coefficients, most notably the alpha-effect. Here I shall extend the standard mean field approach from a kinematic one - treating the instability of a magnetic field to a purely hydrodynamic basic state - so as to consider fully MHD basic states (with both flow and field). It is then vital to treat the momentum and induction equations on the same footing. This leads to a description of any resulting instability in terms of four tensors, two familiar and two new.

 

Industrial Experiences and Applications of Artificial Intelligence (AI) in Real-Time Strategy Computer Games
Ingimar Gudmundsson (Creative Assembly)
7 May 2010Harrison 170 Friday 1pmInformatics RI
TBA

 

CANCELLED
Fares Al Essa
6 May 2010Harrison 170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI (Internal)
CANCELLED

 

Control Engineering Approaches to Systems Biology Research
Declan Bates (University of Exeter)
4 May 2010Harrison 170 Monday 4pmApplied Mathematics

 

Constraints on the relaxation of magnetic fields.
Antonia Wilmot-Smith (University of Dundee)
4 May 2010Harrison 170 Tuesday 2pmApplied Mathematics
23rd Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics" full abstract: TBA

 

Decision making under risk: the optimization of storm sewer network design
Sun Si'Ao (University of Exeter)
4 May 2010Harrison 215 Tuesday 2pmInformatics RI
It is widely recognised that flood risk needs to be taken into account when designing a storm sewer network. Due to the stochastic character of the flood risk, comparisons between candidate networks are not straightforward. This study aims to explore the decision making in flood risk based storm sewer network design. It is viewed as an optimisation problem with the decision criterion determined by a subject judgement of the decision maker. Several decision criteria are introduced and applied to select an optimal design after a multi-objective optimisation. Different decisions are made according to different criteria as a result of different concerns represented by the criteria. Moreover, the problem can be formed as a single-objective optimisation if the decision criterion is provided a priori. The design using a single-objective optimisation is also studied, with the flood risk being evaluated under design storms or via sampling.

 

Deciphering the Swine-flu pandemics of 1918 and 2009
Richard Goldstein ((NIMR, Mill Hill))
30 Apr 2010Harrison 170 (visualisation suite) Friday 2pmApplied Mathematics
The devastating ‘Spanish flu’ of 1918 killed an estimated 50 million people worldwide, ranking it as the deadliest pandemic in recorded human history. It is generally believed that the virus transferred from birds directly to humans shortly before the start of the pandemic, subsequently jumping from humans to swine. By modelling how the viral sequences changes in human, avian, and swine hosts, we find it likely that the Spanish flu of 1918, like the current 2009 pandemic, was a 'swine-origin' influenza virus. Now that we are faced with a new pandemic, can we understand how influenza is able to change hosts? Again by modelling the evolutionary process, we can identify locations that seem to be under different selective constraints in humans and avian hosts, identifying changes that may have facilitated the establishment of the 2009 swine-origin flu in humans.

 

Hertfordshire Surface Water Management Plan
Mr Nathan Muggeridge (Mouchel)
13 Apr 2010Harrison 170 Tuesday 2pmInformatics RI
Defra awarded £9.7 million in October 2009 to allow 77 Councils to develop Surface Water Management Plans (SWMPs). One of these councils was Hertfordshire County Council and this presentation will provide an insight to the Strategy developed for the SWMP, tasks already completed and what is planned to be delivered. Presentation will cover risk, pluvial modelling, data collection and communication plan.

 

Rules and Tools for Directed Evolution
Florian Hollfelder (University of Cambridge)
9 Apr 2010Harrison 170 Friday 2pmApplied Mathematics
I will address approaches leading up to directed evolution of functional proteins. First the observation of catalytic promiscuity is used to define functional relationships in enzyme superfamilies as a basis for phylogentic relationships for catalysis. Promiscuous activities could be remnants from the evolutionary ancestor that has been gene duplicated and adapted to fullfill a new function. Alternatively the observation of promiscuity could indicate that an enzyme is ‘pregnant’ with another activity, i.e. has the potential to be mutated or evolved into a new catalyst Specifically we demonstrate this principle with observations of strong promiscuous activities with rate accelerations between 109 and 1016 in a class of hydrolytic enzymes that share an unusual formylglycine active site nucleophile. Promiscuity in these enzymes is not limited to a single activity, but allows the same active site to catalyse up to six activities efficiently in addition to its native activity.. Evolution experiments should ideally analysed by high-throughput approaches, but require the development of special technologies. The quantitative assessment of large numbers of experiments is possible in water-in-oil emulsion droplets that act as discrete picolitre reactors. These droplets, originally introduced by Dan Tawfik and Andrew Griffiths, are so small that high-throughput experiments on the order of > 108 become possible. Recent experiments to this end - in vitro expression, cell-based assays and continuous PCR reactions – will be discussed. See: http://www.bio.cam.ac.uk/~fhlab/index.html

 

A Taxonomy of Agility Strategies in UK Companies
Rundong Wang (Engineering, CEMPS, University of Exeter)
1 Apr 2010Harrison 170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI (Internal)
In the past decade, significant changes have taken place in manufacturing industry. The changes are characterized by the increased intensity of global outsourcing and global marketing, the rising energy and material costs and problems associated with the quality and security of the supply networks. Under this circumstance, firms have been forced to adjust their strategic manufacturing emphases and seek more effective strategies to survive from the dynamic and rapidly changing marketplace. Agility, that aims to provide firms with competitive capabilities to prosper from dynamic and continuous changes in the business environment, has been widely accepted as a prevailing strategy. Whilst most previous work has considered agility as a holistic concept, this study applies a taxonomical approach to identify if there are clear patterns in companies' needs for agility and in their emphases of agility capabilities. Furthermore, the most significant differences between agility strategies with respect to supply chain design and management practices are examined. In the presentation, the initial identification of existing patterns of agility strategies will be described. Typical cases will be briefly depicted with explanations of strategies and practices they adopted.

 

Validation of mesospheric analyses
David Long
1 Apr 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
The Met office produce analyses of the middle atmosphere on a daily basis. The project is concerned with validating these analyses against observational satellite data, namely profiles obtained from the EOS MLS and SABER experiments. Systematic baises in the dataset will be presented and concluesions drawn. Particular attention will be made to the operational gravity wave paramterisation scheme used at the Met Office and it's contribution to the accurate representation of the middle atmospheric circulation and temperature fields. The design of experiments with the aim of reducing the described systematic baises will be presented, with particular attention to the impact of including turbulent heating (due to gravity wave dissipation) in the operational parameterisation scheme.

 

1D, 2D and 3D modelling of urban flooding
Prof. Slobodan Djordjevic (University of Exeter)
30 Mar 2010Harrison 170 Tuesday 2pmInformatics RI
Within the dual drainage framework, flooding can be modelled either as flow in a network of 1D (one-dimensional) open channels and ponds, or as a 2D flow with depth-averaged velocities, or as a 3D computational domain. Each of these approaches has its advantages and drawbacks, thus there is no single “best” choice of the dimensionality of surface flow. In addition, every model – be it 1D, 2D or 3D – involves specific problems related to: spatial resolution and generation of computational mesh, treatment of buildings and terrain features, sub-surface/surface interactions, how the rainfall variability and surface run-off are introduced, possibilities for model calibration and how the uncertainties in model parameters are handled, communication of results etc. Therefore we can only talk about an adequate approach because it very much depends on the extent of the area, quality of available data, purpose and type of the analysis i.e. the required number of off-line or real-time runs and other factors. The talk will address these issues through experiences from several ongoing urban flooding projects and by outlining some unresolved research questions and practical problems.

 

Flux Rope Instabilities in Coronal Mass Ejections
Bernhard Kliem (Potsdam)
29 Mar 2010Harrison 170 Monday 2pmApplied Mathematics
25th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics" Images of erupting prominences typically suggest the magnetic structure of a single line-tied flux rope. Many prominence eruptions and coronal mass ejections (CMEs) begin with an approximately exponential rise, suggesting an instability. I will present numerical simulations of two relevant flux rope instabilities, the well-known helical kink instability and the torus instability, using the force-free line-tied flux rope equilibrium by Titov and Demoulin as initial condition. The properties of these instabilities indicate which parameters of the initial configuration control whether the eruption stays confined or becomes ejective, evolves into a fast or a slow CME, shows strong or weak writhing. Exponential as well as power-law rise profiles can be modelled. Supporting quantitative comparison of the simulations with several well observed eruptions will be included.

 

Averaging, passages through resonances, and captures into resonance in dynamics of charged particles
Anatoly Neishtadt (Loughborough University)
26 Mar 2010Harrison 170 (visualisation suite) Friday 3pmApplied Mathematics
A study of motion of charged particles in the field of an electromagnetic or electrostatic wave propagating in plasma in the presence of a uniform stationary background magnetic field is a classical problem in plasma physics. Under different relations between parameters of this problem completely different dynamical phenomena take place. In this talk I am planning to describe phenomena of capture into resonance and scattering on resonance that occur in the case of slow high frequency waves and a weak background magnetic field. Capture into resonance may lead to unlimited particle acceleration along the front of the wave (so called surfatron acceleration).

 

Extracting materials mechanical constitutive parameters from full-field deformation measurements: the Virtual Fields Method
Professor Fabrice Pierron (Laboratoire de Mécanique et Procédés de Fabrication)
25 Mar 2010Harrison 170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI
The fast development and diffusion of full-field deformation measurement techniques (such as digital image correlation, speckle interferometry etc.) has opened new prospects in the identification of the mechanical behaviour of materials. The research group led by Professor Fabrice Pierron has been active in this area for more than 15 years. In particular, an original identification method dedicated to full-field measurements has been in the centre of most of the developments in the group. This technique is called the Virtual Fields Method (VFM, www.camfit.fr). The presentation will provide an overview of a vast range of applications of this methodology (static, vibrations, high strain rate) on different types of materials (composites, damaged materials, metals, welds, polymers, wood, foams etc...) to enhance the capabilities of the VFM and provide tracks for the future.

 

Population Modelling of Montastraea annularis
Heather Burgess
25 Mar 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
We are studying the reef-building coral Montastraea annularis. Previously we have modelled a population of coral patches using Population Projection Matrices. This involves the discretization of size. This discretization is restrictive because there is not enough data to accurately assign transition rates between some of these discretized size classes. Therefore we are now aiming to build an Integral Projection Model for this population which assumes continuous size classes. Some initial results are presented together with a comparison to our PPM approach.

 

Applying real options and evolutionary optimisation methods to evaluate flood risk intervention strategies
Ms Michelle Woodward (University of Exeter / HR Wallingford)
23 Mar 2010Harrison 170 Tuesday 2pmInformatics RI
A framework has been developed to analyse optimum flood risk intervention strategies. Real Options Analysis is recognised as an appropriate technique for valuing flexibility in investment decisions and is now promoted by the treasury as being appropriate for flood and coastal erosion risk management. In particular, the ability of Real Options Analysis to assist in developing climate change adaptation strategies is well recognised. Moreover, the application of Real Options combined with evolutionary optimisation methods, and in particular multiobjective optimisation, provides the ability to generate long term flood risk intervention strategies. A computational framework will be described which assesses the most appropriate set of interventions to make in a flood system and the opportune time to make these interventions, given the future uncertainties. This framework captures the concepts of real options and employs an optimised decision framework to evaluate potential flood risk management opportunities across a range of future climate change and socio economic scenarios.

 

Geomagnetic reversals from low order dynamo models
Graham Sarson (Newcastle University)
22 Mar 2010Harrison 170 Monday 2pmApplied Mathematics
24th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics" TBA

 

CANCELLED
Ozgur Akman
18 Mar 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

TBA
Professor Frances Kirwan (University Oxford)
18 Mar 2010Harrison 106 Thursday 3pmPure Mathematics

 

Rainfall-Runoff Simulation and Groundwater Recharge in Arid Regions
Prof. Moshen Sherif (College of Engineering, UAE University)
17 Mar 2010Harrison 203 Wednesday 3pmInformatics RI
In arid and semi-arid regions, rainfall events are limited and random. Extreme events are more frequent and, hence, detention and retention dams are usually built across the main wadis to intercept surface water runoff and recharge the groundwater systems. In this presentation, the focus is devoted to the simulation of surface water runoff and groundwater recharge due to water storage in the lakes of dams. HEC-HMS model is used to simulate the surface water runoff and water storage in the lakes of three main dams due to rainfall events in the northern area of the United Arab Emirates. Within the calibration process of HEC-HMS, the simulated water flow and storage in the dams were compared with the observed data for several storm events. Using the calibrated model, a family of rainfall-runoff/storage curves was developed based on the duration and intensity of rainfall events. These curves can be used for prediction of surface water runoff in the three wadis and water storage in the dams in response to different rainfall events. The groundwater recharge was simulated using MODFLOW. The model was calibrated and verified using different data sets and the results of groundwater levels were found to be in good agreement with the observed data. The model was also used to assess the increase of groundwater recharge due to the construction of dams. Significant amounts of the infiltrated water are retained in the unsaturated zone.

 

A Simulation-Optimisation Model to Study the Control of Saltwater Intrusion into Coastal aquifers
Mr Hany F. Abd-Elhamid (University oif Exeter)
16 Mar 2010Harrison 170 Tuesday 2pmInformatics RI
Seawater intrusion is one of the most serious environmental problems in many coastal regions all over the world. It is one of the processes that degrade water-quality by raising salinity to levels exceeding acceptable drinking water standards. Mixing a small quantity of seawater with groundwater makes it unsuitable for use and can result in abandonment of aquifers. Therefore, seawater intrusion should be prevented or at least controlled to protect groundwater resources. This work presents development and application of a simulation-optimization model to control seawater intrusion in coastal aquifers using different management models. The model is based on the integration of a genetic algorithm optimization technique and a coupled transient density-dependent finite element model, which has been developed for simulation of seawater intrusion. The management scenarios considered include abstraction of brackish water, recharge of fresh water and combination of abstraction and recharge. The objectives of these management scenarios include minimizing the total costs for construction and operation, minimizing salt concentrations in the aquifer and determining the optimal depth, location and abstraction/recharge rates for the wells. Also, a new methodology is presented to control seawater intrusion in coastal aquifers. In the proposed methodology ADR (abstraction, desalination and recharge), seawater intrusion is controlled by abstracting brackish water, desalinating it using small scale reverse osmosis plant and recharging to the aquifer. The developed model is applied to a number of case studies. The efficiencies of three different scenarios are examined and compared. The results show that all the three scenarios could be effective in controlling sea intrusion but using ADR methodology, results in the lowest cost and salt concentration in aquifers and maximum movement of the transition zone towards the sea. The application of ADR methodology appears to be more efficient and more practical, since it is a cost-effective method to control seawater intrusion in coastal aquifers. The developed model is an effective tool to control seawater intrusion in coastal aquifers and can be applied in areas where there is a risk of seawater intrusion. Finally, the developed simulation model is applied to study the effects of likely climate change and sea level rise on saltwater intrusion in coastal aquifers.

 

High-Frequency Self-Excited Oscillations in 3D Collapsible Tube Flows
Robert Whittaker (University of Oxford)
15 Mar 2010Harrison 170 Monday 2pmApplied Mathematics
Experiments show that steady flow along an elastic-walled tube can become unstable to large-amplitude oscillations involving both the tube wall and the fluid. We consider a 'Starling resistor' setup - a finite length elastic tube attached to rigid end sections, through which an axial flow is driven by either a steady flux at the downstream end or a steady pressure drop between the ends. I shall describe a theoretical analysis of small-amplitude high-frequency long-wavelength oscillations. We first consider the fluid mechanics (prescribed oscillations) and then the solid mechanics (to derive an appropriate tube law) in isolation. The two strands of work are then combined to investigate the full fluid--structure interaction problem for self-excited oscillations. We determine the form of the normal modes and obtain expressions for the growth rate and frequency of the oscillations. The predictions from our modelling show good agreement with numerical simulations performed using the oomph-lib C++ library.

 

Title: The Role of Particle Cavitation in the Toughening of Rubber-modified Epoxy Adhesives
Professor Felicity Guild (Department of Mechanical Engineering, Imperial College London)
11 Mar 2010Harrison 170 (3D Vis Suite) Thursday 2pmAdvanced Technologies RI
Many investigations into the source of toughness in rubber toughened adhesives have associated enhanced toughness with the process of rubber particle cavitation. Our model for rubber particle cavitation has now been established using an energy balance approach. This model used a combination of finite element simulations and experimental results. Predictions for rubber particle cavitation in both uniaxial loading conditions and the triaxial loading conditions ahead of a crack and the dependence on particle size will be presented and compared with experimental results. The energy contributions arising from the different energy sources can be evaluated. These predictions for particle cavitation allow the role of this process in the overall toughness of these materials to be assessed.

 

Dynamics of microscale swimmers
Andrew Gilbert (with Feodor Ogrin, Peter Petrov and Peter Winlove)
11 Mar 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
The problem of swimming on small scales, for example microorganisms, has a long and rich history. On such scales fluid may be thought of as very viscous (i.e. low Reynolds number) and one has to imagine swimming in treacle. It turns out that motions that are not time-reversible need to be adopted to have persistent motion in one direction, the so-called 'scallop theorem'. Such swimmers need to break the symmetry, and biological organisms have evolved a variety of ways of achieving this. With interest now in micromachines and microscale processing of chemical and biological materials - the idea of the lab-on-a-chip - there is interest in developing tiny scale pumps, valves, gels, and machines that can swim, perhaps to deliver a drug very precisely. Recently a microscale swimming device has been developed here in Physics by the Biomedical Physics Group, consisting of elastically coupled magnetic beads whose motion is driven by an external magnetic field. The seminar will discuss the mathematical modelling of such swimmers, regimes, parameters and mechanisms.

 

irreducible $\Qp$-representations of compact $p$-adic analytic groups
Dr Konstantin Ardakov (Nottingham university)
11 Mar 2010Harrison 106 Thursday 3pmPure Mathematics

 

Molecular Programming
Luca Cardelli (Microsoft Research)
10 Mar 2010Harrison 215 Wednesday 2pmApplied Mathematics
Nucleic acids (DNA/RNA) encode information digitally, and are currently the only truly 'user-programmable' entities at the molecular scale. They can be used to manufacture nano-scale structures, produce physical forces, act as sensors and actuators, and do computation in between. Eventually we will be able to interface then with biological machinery to detect and cure diseases at the cellular level under program control. The technology to create and manipulate them has existed for many years, but the imagination necessary to exploit them has been evolving slowly. Recently, some very simple computational schemes have been developed that are autonomous (run on their own once started) and involve only short (easily synthesizable) DNA strands with no other complex molecules. We need programming abstractions and tools that are suitable for molecular programming. Low-level molecular design is required to produce molecules that interact in the desired controllable ways. On that basis one can then design various kinds of 'logic gates' and 'computational architectures', which is where much of the imagination is currently needed. Then one needs programming languages both at the level of gate implementation (Andrew Phillips at Microsoft Research Cambridge has built a strand-level DNA language and simulator), and at the level of circuit implementation (I will describe a Strand Algebra for implementing e.g. automata and Petri nets). Since DNA computation is massively concurrent, some tricky and yet familiar issues arise: the need to formally verify gate designs to avoid subtle deadlocks and race conditions, and the need to design high-level languages that exploit concurrency and stochasticity.

 

Community Resilience to Extreme Weather (CREW)
Dr Albert Chen (University of Exeter)
9 Mar 2010Harrison 170 Tuesday 2pmInformatics RI
'Community Resilience to Extreme Weather' (CREW) is an EPSRC-funded research project, established to develop a set of tools for improving the capacity for resilience of local communities to the impacts of future extreme weather events. CREW focuses on understanding the probability of current and future extreme weather events and their likely socio-economic impacts. Initiatives, such as the Stern Review, provide high-level socio-economic impacts but do not provide the sub-regional or local estimates pertinent at the community and individual scale. Therefore, the CREW consortium is investigating impacts at the local level (on householders, SMEs and local policy/decision makers). The research is also investigating the opportunities and limitations for local communities' adaptive capacity. CREW, using five South East London boroughs as case studies, is considering the decision making processes across communities including impediments and drivers of change. A web-based portal will provide a facility for presenting probable extreme weather events for a range of scenarios, and for presenting and evaluating coping mechanisms. Dr Slobodan Djordjevic and Dr Albert Chen at the CWS are involving with the Programme Package SWERVE (Severe Weather Events Risk and Vulnerability Estimators) of CREW for urban pluvial flood modelling. Albert Chen is going to introduce the CREW project and explain the details of modelling that accounts for the impact of future climate scenarios.

 

Micro-chaos in switched control systems with digital sampling
Piotr Kowalczyk (University of Manchester)
8 Mar 2010Harrison 170 Monday 2pmApplied Mathematics
TBA

 

Giant Magnetoresistive and Multiferroic Thin Film Development Using a New Sputtering Technique
Denh Tran (College of Engineering, Mathematics and Physical Sciences, University of Exeter)
4 Mar 2010Harrison 170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI (Internal)
A new sputter deposition technique will be described. This technology, developed at Plasma Quest Ltd., is designed for high rate sputtering and uniform erosion of the target. This gives the name of the technique 'High Target Utilsation Sputtering' (HiTUS). Other key advantages of this technology will be highlighted. This seminar will also review the use of HiTUS for Giant Magnetoresistive thin films and the interesting new area of multiferroics.

 

Stability Analysis of Three Linearly Coupled Laser Oscillators
Nicholas Blackbeard
4 Mar 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Coupled nonlinear oscillators exhibit rich and complex dynamics. Semiconductor lasers are particularly interesting and technologically relevant examples of nonlinear oscillators that feature an intrinsic amplitude-phase coupling, quantified by the alpha-parameter. This characteristic nonlinearity causes different dynamics that can be utilised for a wide variety of applications. Many of these require the use of laser arrays - where the desired behaviour ranges from a high power coherent radiation to that of robust chaos. We study a system of three lasers with nearest neighbour coupling as a first step towards understanding the complexity of larger arrays.

 

P-adic interpolation of automorphic forms
Dr David Loeffler (University Warwick)
4 Mar 2010Harrison 106 Thursday 3pmPure Mathematics
Coleman’s work on overconvergent p-adic modular forms shows that finite slope modular eigenforms can be interpolated p-adically, forming rigid-analytic families of eigenforms parametrised by their weights. This has been generalised by Emerton to cohomological automor- phic representations of a wide range of reductive groups, where the local factor at p is principal series. I shall give an exposition of Emerton’s construction, and of recent joint work with Richard Hill and myself in which we have extended this to certain non-principal-series cases

 

Neptune: Risk-Based Decision Support for Water Distribution System Incident Management
Mr Josef Bicik and Dr Mark Morley (University of Exeter)
2 Mar 2010Harrison 170 Tuesday 2pmInformatics RI
Project Neptune aims to develop an integrated, risk-based Decision Support System (DSS) to facilitate tactical (near real-time) and strategic decision making. This system should inform network operators and permit the rapid investigation, evaluation rectification of network failure events. In so doing, the Neptune DSS seeks to reduce the impact on customers, assist water companies in meeting regulatory requirements and to minimize the environmental and economic impact of incidents. This talk describes some of the work undertaken within the Centre for Water Systems on developing the risk-based methodologies and software components that make up the Neptune DSS. It concludes with a live demonstration of the Decision Support System on a number of case studies.

 

Double Diffusive Magnetic Buoyancy Instability
Lara Silvers (City University)
1 Mar 2010Harrison 170 Monday 2pmApplied Mathematics
The generation of magnetic field by velocity shear and the field’s subsequent evolution are of great importance to an understanding of the operation of the solar dynamo. While the current dynamo paradigm contains many complex interacting components, an integral part of all current large-scale solar dynamo models is the creation of strong toroidal magnetic structures in the tachocline. Strong toroidal magnetic field is thought to be induced by the stretching action of the differential rotation on any background poloidal field. Subsequently, magnetic buoyancy instabilities of the generated field are invoked as the mechanism for the creation of distinct magnetic structures and their subsequent rise toward eventual emergence at the solar surface as active regions. In this talk I will focus on double diffusive magnetic buoyancy instabilities. I will discuss the criterion for this form of the instability to exist and show the first images from numerical simulations of this instability. This is the 22nd Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics"

 

For Whom the Bell Tolls -The mute (silent) bell in Cologne cathedral as a dynamical system
Tassilo Kuepper (University of Cologne)
25 Feb 2010Harrison 170 (vis suite) Thursday 2pmApplied Mathematics
The “Kaiserglocke” in the cathedral of Cologne is known as a spectacular example of a bell withstanding to ring since the clapper remained in the center of the bell, hence showing synchronous oscillations with the bell. Based on a mathematical model describing the motion of clapper and bell as two connected pendula Veltmann has shown that such synchronous oscillation may exist if only 4 characteristic parameters (“length” and mass of clapper and bell) satisfy a specific relation, which turned out to hold in the case of the “Kaiserglocke”. To prove, though, that under such constellation it is never possible for a bell to ring requires more advanced mathematical tools which had not yet been developed a 100 years ago. In this talk we will supplement Veltmann's argument with regard to stability considerations. The system of clapper and bell can serve as a nice illustration for modern mathematical investigations. Since Veltmann has only be interested to derive reasons for non-ringing of bells, he only needed to consider motions without contact between clapper and bell. True ringing relies on that contact. Mathematically that requires an extension from the classical system of differential equations used by Veltmann by “impacts”. This leads to the class of non-smooth dynamical systems, an area of present research. Our analysis shows how the interaction between bell and clapper influences the motion; for example we also show how various forms of ringing may result from a change of the coupling between clapper and bell.

 

Optimisation on emergency scheduling of the raw water supply system in Zhuhai
Qi Wang (Tsinghua University, China)
23 Feb 2010Harrison 170 Tuesday 2pmInformatics RI
For a water supply system near river estuary, the time length of taking river water is affected by the saline tide period. Therefore, in order to increase the security and reliability of the water supply system, it is necessary to make reasonable scheduling, which aims to ensure reservoirs volume within the system to meet the water demand during the saline intrusion period. In this research, a mathematical model on the water supply system with multi-source near the estuary was established. A genetic algorithm was conducted to calculate the water level control lines of reservoirs, in which both the power consumption and system security were considered in the objective function. Compared with historical operating data, it shows that an optimal hydrograph obtained using the proposed method can significantly improve the security of water supply system and reduce the operation energy cost.

 

p-adic L-functions of modular forms at supersingular primes
Dr Antonio Lei (Cambridge university)
22 Feb 2010Harrison 171 Monday 2pmPure Mathematics

 

The Theory of Configuration of Rapidly Rotating Giant Planets
Da-Li Kong
18 Feb 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
The classical homogeneous Maclaurin ellipsoid model for rapidly rotating planets is extended to a more realistic two-layer configuration by making use of a minimized energy principle combined with the hydrostatic free surface condition. By adopting oblate spheroidal coordinates, a universal semi-analytical method is derived. The details about coordinate system, spheroidal harmonics, physical principles and special numerical integration techniques are intensively investigated.

 

On volumes of arithmetic hyperbolic n-orbifolds.
Dr Mikhail Belolipetsky (Durham University)
15 Feb 2010Harrison 106 Monday 2pmPure Mathematics
The main topic of my talk is the search for the minimal volume quotients of the hyperbolic n-space. In dimension 2 the problem was solved by Siegel who also asked about the general case. Since then a considerable progress has been made for the so-called arithmetic quotients and the only case which was still open is when the dimension n is odd and >3. After a brief introduction I will focus on the solution to this problem which we obtained in a recent joint work with Vincent Emery.

 

Recurrence and extreme behaviour in dynamical systems
Mark Holland
11 Feb 2010Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
We explore the statistical properties of chaotic dynamical systems, including case studies of the Lorenz and Henon attractors. We examine questions such as the long term distribution of typical solution trajectories and how frequently they visit a prescribed region of the space. We also discuss the issue of asymptotic (in)dependence: how long do we have to wait until the system settles down to some equilibrium and does this equilibrium dependent on the initial conditions?

 

Weiestrass Points and Automorphisms of Curves
Dr Kay Magaard (University of Birmingham)
11 Feb 2010Harrison 106 Thursday 3pmPure Mathematics
Let $X$ be a compact connected Riemann surface of genus $g \geq 2$. A point of $p \in X$ is Weierstrass if there exists a non-constant meromorphic function on $X$ that has a pole of order $\leq g$ at $p$ and is holomorphic on $X \setminus p$. A lemma of Sch\"oneberg asserts that if an automorphism $\alpha$ of $X$ fixes five or more points of $X$, then every one of them is a Weierstrass point. In the talk we will discuss the impact of Sch\"oneberg's lemma has on the structure of the automorphism group of $X$.

 

Non-residually finite extension of arithmetic groups.
Dr Richard Hill (University College London)
8 Feb 2010Harrison 106 Monday 2pmPure Mathematics
Let Gamma be an arithmetic group with the congruence subgroup property, and with an associated Shimura variety. A theorem of Deligne states that there is a central extension of Gamma by a cyclic group which is not residually finite. This result was used by Toledo to give examples of complex projective varieties for which the topological fundamental group does not embed in the algebraic fundamental group. In the talk I'll generalize Deligne's result to the case that Gamma has no associated Shimura variety, so for example my result holds for congruence subgroups of SL(n,Z) with n at least 3.

 

A study of scanning probe phase change memory
Dr Lei Wang
4 Feb 2010Harrison 170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI (Internal)
Data storage roadmaps are looking towards density targets of around 1Tbit/in2 by 2010 and to 10Tbit/in2 and beyond thereafter. It is well known that conventional storage devices are challenged by some formidable barriers (the superparamagnetic limit for magnetic storage disks, the diffraction limit for optical storage disks, and device scaling limits in flash storage) as they strive to reach ultra-high storage densities. It is hence timely for new, emerging memory technologies to enter the storage field. One possible new technology is scanning probe-based phase change memories, due to their potentially ultra-high-capacity, non-volatility, low-power consumption, low-cost, and write-once/re-writable capability. Therefore, various research groups worldwide have been putting their efforts in to developing scanning probe phase change memories technologies experimentally. In this circumstance, theoretical models are also required in order to understand the physical processes involved, and thus to help spur further experimental developments. Thus, this presenation looks at a theoretical framework and associated computational model for write, read, and erase processes in electrical probe storage on phase change materials (Ge2Sb2Te5).

 

Condensation and metastability in stochastic particle systems
Stefan Grosskinsky (University of Warwick)
1 Feb 2010Harrison 170 Monday 2pmApplied Mathematics
The zero-range process is a recently well studied stochastic particle system that exhibits a condensation transition. When the total density exceeds a critical value, a finite fraction of all particles condenses on a single lattice site, which can be characterized mathematically by the equivalence of ensembles via convergence in specific relative entropy. Although the transition is continuous, finite systems exhibit interesting metastable behaviour and phase coexistence. We establish a law of large numbers for the excess mass fraction in the maximum, which turns out to jump from 0 to a positive value at the critical point. The metastable states can be characterized heuristically as fixed points of a simple effective dynamical system.

 

Congruences in noncommutative Iwasawa theory
Dr Mahesh Kakde (University College London)
28 Jan 2010Harrison 106 Thursday 3pmPure Mathematics

 

The confidence to build - Some thoughts on engineering software
Prof. Bill Harvey
26 Jan 2010Harrison 170 Tuesday 2pmInformatics RI
Engineering software began about 1950 with some of the earliest available digital computers. It became possible to analyse complex structures. Since then, the poawer of computers has grown at an almost frightening rate. Endless bells and whistles have been added to analytical software. In recent years ther have been attempts to couple CAD programs to analysis and call the package design. But engineering design is not about deciding on a geometry then asking the computer where the forces go. Real design is about deciding where you want the forces to flow and then arranging the geometry to make that happen. The same thing is true in CFD but that is not where I work. It is long past time that we realised and released the power of computers to help with design insteead of merely providing analytical results. That will involve fundamental changes in our vision of what we want to do. Bill's work is chiefly in structural assessment and in this field, surprisingly, the problem is greater. When designing a new building, if the analysis says this bit is too weak, a stroke of a pen (or mouse) is enough to make it stronger. If the structure is already there we often need to know where the forces might really go rather than where they could go if they need to. The seminar will cover some of the issues described above in the light of the sort of exploratory analysis Bill uses for his assessment work.

 

Integrated Water Management – Experience from Australia and GHD’s Innovative IWM Toolkit
Mr Mike Jones (Head of Water, UK, GHD)
19 Jan 2010Harrison 170 Tuesday 2pmInformatics RI
Integrated Water Management (IWM) is a strategy that draws together all facets of the water cycle including water supply, sewage and stormwater management to achieve beneficial social, environmental and economic outcomes. While the application of IWM principles to the UK water industry is in its infancy, a wide range of IWM strategies have been used successfully in communities throughout Australia. We will present an overview of IWM in Australia. A number of case studies will be discussed that demonstrate the range of IWM strategies being developed in Australia along with some lessons learnt from the Australian experience. GHD’s IWM Toolkit will also be presented. The IWM Toolkit is an innovative water balance modelling software tool that simulates complex integrated water servicing scenarios to assist water system planners in identifying the preferred water servicing strategy from a range of options.

 

Amplified stochastic oscillations
Alan McKane (University of Manchester)
18 Jan 2010Harrison 170 Monday 2pmApplied Mathematics
I discuss a systematic approach to the modelling of various biological systems which starts from individual-based models, and then goes on to derive from these the corresponding deterministic equations (which are valid when the size of the system is large) and the leading order stochastic correction to them. The individual-based models are formulated as master equations, which allows use to be made of well-established methods from the theory of these equations to analyse their behaviours. In many cases large and well-defined stochastic cycles arise, even though the corresponding deterministic equations predict the system will approach a fixed point. Application of these ideas to predator-prey dynamics, epidemiology, cellular systems and autocatalytic reactions, amongst others, will be discussed.

 

On Optimisation of Internal Micro-Architectures Using Finite Element Modelling
David Raymont
7 Jan 2010Harrison 170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI (Internal)
Internal micro-architectures have many uses ranging from light-weight support structures to bone substitutes, or scaffolds as well as aiding bone-implant integration. Designing such structures using traditional CAD software is non-trivial. This presentation focuses on the generation of porous internal micro-architectures principally for use in medical applications, but also extended to internal structures for CAD components. An image-based approach is developed using triply periodic level-set functions to define unit cell topology. Methods for generating both functionally graded and large inhomogeneous micro-architectures will be presented. When addressing the issue of optimisation the limiting factor for such structures is often the finite element analysis (FEA) required for a fitness function. The complexity of these structures demands fine meshing, resulting in computationally expensive simulations. Combined with the need to evaluate the structure's performance hundreds or possibly thousands of times, the optimisation problem soon becomes intractable. To overcome this a homogenisation-like technique has been developed allowing approximate FEA models to be produced. Methods for optimising the generated micro-architectures will be discussed.

 

Generalized stochastic resonance models for abrupt climate changes
Istvan Daruka (Eotvos University, Budapest)
14 Dec 2009Harrison 170 (3D vis suite) Monday 9.30amApplied Mathematics
The glacial-interglacial changes observed in Paleoclimatic temperature data of the middle to late Pleistocene epochs are analyzed in terms of two generalized stochastic resonance models including memory effects. The simple models account for the asymmetric, saw-tooth shaped temperature oscillations occurring both at Milankovitch (100kyr) and millennial time scales.

 

RUAM: Ready-to-Use Additive Layer Manufacture
Dr Jorn Mehnen (Manufacturing Department, Cranfield University, Cranfield, Bedfordshire MK43 0AL, United Kingdom)
10 Dec 2009Harrison 170 (3D Vis Suite) Thursday 2pmAdvanced Technologies RI
RUAM (Ready-to-Use Additive Layer Manufacturing) is an innovative concept for building ready-to-use large metal parts. Additive Layer Manufacturing parts are built in a layer-by-layer fashion using advanced arc welding processes. The RUAM machine is a hybrid concept that integrates welding and finishing in one single machine. The deposition process is controlled by a robot that follows a tool path that is directly created from CAD drawings. The robot paths are determined by design rules that take the complex behaviour of the arc welding process into account. FEM is used to predict temperature and stress distributions to minimise part distortions. The design for RUAM has to take many aspects into account which depend on e.g. the actual geometry and manufacturability of the parts. Best welding parameters as well as best welding techniques (e.g. CMT (Cold metal transfer) and Interpulse welding, high deposition rates) have been investigated for building efficiently ready-to-use RUAM parts. The first prototype of an integrated machine has been introduced. The RUAM machine is designed for building large structures in steel, aluminium and titanium.

 

Long-term behavior of linear, stochastic, discrete time systems: Asymptotic amplification and attenuation in covariance
Iakovos Matsikis
10 Dec 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Lyapunov exponents are the tool widely used in studying the long-term dynamics of systems under the influence of randomness. They do not, however, take into account the effect of initial conditions and in general are difficult to compute. In this talk we will employ second mean analysis and ideas from linear algebra and will present the new notions of asymptotic amplification and attenuation in covariance. These new mathematical tools are depended on initial conditions, are easily computed and together with the second mean exponent they provide a framework of study for linear stochastic systems. Specifically they can be used in the construction of envelopes that capture the system's dynamics and make visible its asymptotic properties. We will finally apply our results to a population dynamics model.

 

On the existence of quasipattern solutions of the Swift-Hohenberg equation.
Alastair Rucklidge ( University of Leeds)
9 Dec 2009Harrison HAR170 Wednesday 10amApplied Mathematics

 

Coupled water environmental model and system dynamics (SYDWEM) of integrated population-economy-water-river system in a rapidly urbanising catchment
Dr Hua-Peng Qin (University of Exeter)
8 Dec 2009Harrison 170 Tuesday 2pmInformatics RI
The rapidly urbanizing catchments in developing countries are usually faced with water quantity shortage and quality deterioration because water infrastructure development lags behind the demand of rapid population and economic growth. Although the existing environmental models can individually describe socioeconomic, water infrastructure and natural water systems, they cannot effectively capture the interactions among them. Taking rapidly urbanizing Shenzhen river catchment in China as an example, we developed a system dynamic based approach (SYDWEM) to couple water environmental models of population-economic, water infrastructure and river system in the catchment. The approach was verified to have the ability to simulate relationship between social, economic, water resource and effluent discharge issues as well as pollutant behaviour in the river. The approach was further applied to predict GDP and population growth, water balance and water quality variation in the catchment scale under proposed socio-economic policies (e.g. industrial structure regulation, water conservation) and engineering measures (e.g. wastewater treatment and reuse). By comparing the effects and sensitivities of proposed polices and measures, integrated management strategy was proposed to harmonize the socio-economy and eco-environment development in the catchment. The results indicated that SYDWEM provides a flexible decision making tool for integrated water management in urbanizing catchments.

 

Assimilating data into ocean models
Chris Jones (University of Warwick)
7 Dec 2009Harrison 170 Monday 2pmApplied Mathematics
Abstract: The technology-enabled increase in data acquisition is well matched by that coming from computational modeling. The subject of Data Assimilation (DA) addresses the issue of making optimal use of both sides of this equation. Bayes’ Theorem provides a framework for DA, but this is only the beginning of what is interesting mathematically. I have come at this subject from the perspective of Lagrangian DA, which aims at assimilating data from ocean instruments that "go with the flow". I will argue that Lagrangian DA is both exciting and promising exactly because the Lagrangian flow can be very complicated (highly nonlinear, chaotic etc) even though the fluid flow field may be tame. I will suggest that this leads to a guiding principle for DA as a whole.

 

Additive Layer Manufacturing of Aluminium Aerospace Components
Peter Jerrard
3 Dec 2009Harrison 170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI (Internal)
Additive Layer Manufacturing (ALM) has now been around for 25 years and can be considered a process that has a place aside more conventional manufacturing methods. Due to some of the advantages that ALM offers many sectors, including the aerospace industry, have vested interest. Unfortunately, like other processes, ALM is far from perfect and is still considered a ‘novel’ process by many. This is due to such issues as limited material choice and mechanical properties, which can be poor when compared to other manufacturing techniques. In particular, the aerospace industry has particular interest in aluminium alloys, the current material of choice for aircraft. One ALM technology, Selective Laser Melting (SLM), allows the processing of a select range of metals. It is only in the last year or so that a few aluminium alloys have become officially available to SLM, which has drawn the attention of the aerospace industry. These alloys are conventional alloys that lend themselves to the SLM process. However, the processing nature of SLM may mean that conventional aluminium alloys may not be the best choice for producing parts. Instead, it may be that new or unconventional alloys may have to be tried. This presentation looks at the potential and current aerospace use of ALM, of the comparison to other manufacturing processes and of the research path the author has chosen to follow in the SLM of aluminium alloys.

 

Palaeoclimate and dynamical systems : challenges and promises
Michel Crucifix (Université Catholique de Louvain)
3 Dec 2009Harrison 170 (3D suite) Thursday 2pmApplied Mathematics
Palaeoclimate data present important challenges to the climate modeller : sparse data, dating uncertainties, high non-stationarities, and unknown physical constraints at these time scales. On which basis may one formulate tractable problems in such difficult conditions ? First, palaeoclimate do indeed show spatio-temporal structures owing to the effect of orbital elements, and phenomena of bifurcation may be visualised with continuous wavelet transforms. These offer opportunities of empirical model validation and selection, in spite of dating uncertainties. Other methods of identification, for example clustering methods to determine the number of regimes, show promise but will not be adressed here. Second, we do have a physical knowledge of the climate system, but often the physical models employed nowadays lack the dynamical range required to tackle palaeoclimate time scales. Consider this : building a 3000-m-thik ice sheet over 80,000 years imply a yearly mass imbalance of 37 cm/year : arguably below the precision of current models. Furthermore, physical mechanisms proper to palaeoclimate time scales, such as ice sheet instability, have received little attention in current models. The strategy is therefore to reduce empirically general circulation models, and build on this basis parameterisations that may be used and calibrated at more ambitious time scales. Several challenges, especially regarding stochastic parameterisations and carbon cycling remain unmet. Third, statisticians have been creative at developing parameter estimation methods suitable for dynamical systems. Here we show examples based on an implementation of the particle filter with auxiliary sampling, adapted for the parameter estimation problem. Such algorithm provide a basis to formulate the model calibration and selection problem on a sound statistical basis, making use of prior information obtained with more sophisticated models. The lecture will be articulated around these three themes, with examples based on Pleistocene palaeoclimate time series, simulations with the LOVECLIM earth system model of intermediate complexity, and particle filtering of simple dynamical systems.

 

Towards the sustainable city? Principles and practice
Prof. David Butler (University of Exeter)
1 Dec 2009Harrison 170 Tuesday 2pmInformatics RI
The presentaton asks the question 'what is a sustainable city' and 'would we know it when we saw it'? The aim of the presentation is not to headline gold standard exemplars, but to evaluate the reality of what sustainability means on the ground for large-scale housing projects. It describes and discusses the attempts of the government of England and Wales to take the principles embedded at policy level and to begin to roll out new ‘sustainable’ developments in practice, with specific reference to water management. It concludes with another question 'Is the journey towards sustainability more important than the goal'?

 

New nonlinear mechanisms of midlatitude atmospheric low-frequency variability
Alef Sterk (University of Groningen)
30 Nov 2009Harrison 170 Monday 2pmApplied Mathematics
In this talk we will discuss the dynamical mechanisms potentially involved in the so-called atmospheric low-frequency variability, occurring at midlatitudes in the Northern Hemisphere. This phenomenon is characterised by recurrent non-propagating and temporally persistent flow patterns, with typical spatial and temporal scales of 6000-10000 km and 10-50 days, respectively. We study a low-order model derived from the 2-layer shallow water equations on a $\beta$-plane with bottom topography, which is forced by relaxation to an imposed westerly wind. The low-order model is obtained by a Galerkin projection retaining only the Fourier modes with wavenumbers 0, 3 (zonal) and 0, 1, 2 (meridional). The amplitude of the bottom topography and magnitude of zonal wind forcing are used as control parameters to study bifurcations of equilibria and periodic orbits. In the low-order model equilibria destabilise through Hopf bifurcations, which can be interpreted in terms of mixed barotropic/baroclinic instabilities. These Hopf bifurcations give birth to two families of periodic orbits with different spatio-temporal characteristics. In turn, the periodic orbits bifurcate into strange attractors via the following codimension-1 routes to chaos: period-doublings, break-down of 2-tori, and intermittency. The dynamics on these strange attractors are associated with low-frequency variability: the vorticity fields show weakening and amplification of non-propagating planetary waves on time scales of 10-200 days. These spatio-temporal characteristics are ``inherited'' (by intermittency) from the two families of periodic orbits and are detected in a relatively large region of the parameter plane. This scenario differs fundamentally from those proposed in the literature so far, which mainly rely on theories involving multiple equilibria. This is joint work with Renato Vitolo (Exeter), Henk Broer (Groningen), Carles Simo (Barcelona), and Henk Dijkstra (Utrecht)

 

Vertical Discretisations for Coupling the Atmospheric Boundary Layer with the Large Scale Dynamics
Dan Holdaway
26 Nov 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
It is now well understood that for modelling the equations describing the large scale atmosphere the Charney-Phillips grid is preferable to the Lorenz grid. Not only does the Lorenz grid give a poorer representation of the dispersion relation, it also supports a single zero frequency computational mode. For modeling the atmospheric boundary layer it is preferable to use a Lorenz grid, otherwise an averaging is required in order to compute the Richardson number. We show, through linearisation and comparison of transients, that vertical configurations can be systematically compared for the boundary layer type problem. This can then be used in order to compare configurations of the complete coupled system and thus to aid in understanding the affect that the boundary layer has on both the computational mode and the overall dispersion relation.

 

Talking Heads: Creating Realistic 2D & 3D Facial Animations
Dr Paul Rosin (Cardiff University)
24 Nov 2009Harrison 170 Tuesday 2pmInformatics RI
This talk will describe ongoing work at Cardiff University for building photo-realistic models of faces using active appearance models (AAMs) applied to both 2D image data and textured 3D mesh data. We have applied these models in a variety of contexts: 1/ speech driven animation, in which a combined audio and image model is built and new unseen audio is used to synthesise appropriate an image sequence, 2/ performance-driven animation, in which the animation parameters analysed from a video performance of one person are used to animate the facial model of another person, 3/ production of stimuli for psychological experiments to determine the human perception and judgement of the facial dynamics of smiles, and 4/ biometrics, in which people are identified based on their facial dynamics captured during an utterance.

 

Numerical experiments for $L_1$-norm regularisation in variational data assimilation.
Melina Freitag (University of Bath)
23 Nov 2009Harrison 170 Monday 2pmApplied Mathematics
In this talk we give a brief introduction to data assimilation and we show that data assimilation using 4DVar (4D Variation) can be interpreted as some form of Tikhonov regularisation, a very familiar method for solving ill-posed inverse problems. It is known from image restoration problems that $L_1$-norm penalty regularisation recovers sharp edges in the image better than the $L_2$-norm penalty regularisation. We apply this idea to 4DVar for problems where shocks are present and give some examples where the $L_1$-norm penalty approach performs much better than the standard $L_2$-norm regularisation in 4DVar.

 

Evolution of biological system dynamics
Orkun Soyer
19 Nov 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Systems biology aims to understand the structure and dynamics of biological networks that underlie physiological responses, while synthetic biology ultimately aims to implement such networks. A fundamental question at the crossroads of these two fields is; what is the repertoire of biological networks that can underlie a given response dynamics? Answering this question could allow us to understand how networks underlying a given response would differ in different species and whether there are minimal networks, more amenable for synthetic biology implementations. In this talk, I will illustrate how evolutionary and mathematical approaches can be employed towards reaching such an understanding.

 

SUPR Models : Models for the Study of the Uncertainty in PalaeoClimate Reconstruction.
John Haslett (Trinity College, Dublin)
18 Nov 2009Harrison LT04 Wednesday 3pmApplied Mathematics
We present some modelling challenges that have arisen in the context of our work on palaeoclimate reconstruction. The simplest version of the the problem is as follows. A 10m core of lake sediment contains pollen deposited over the past several millennia. Samples ($n =150$) from along the core are examined under a microscope; each sample is rendered as a multivariate count vector $y^a_i$ of `ancient' pollen. Such vectors describe the composition of the ancient `pollen rain'. As such they provide information on the surrounding vegetation at times in the past; that is, ancient pollen is a `proxy' for ancient climate, for we know from modern data that vegetation composition reflects the climate $c$. Models built on such data, $D^m$, provide information on the probability distribution $\pi[y|c, D^m]$. This in turn permits inference $\pi[c|y^a_i,D^m]$ on the ancient climates corresponding to the samples. Variations on this are applied to other proxies (eg diatoms) in other archives (eg ocean sediment). At its simplest, palaeoclimate reconstruction returns `best climates' $\hat c^a_i$ corresponding to each $y^a_i$. Our concern in this paper lies with the underlying uncertainties and with the statistical models that we have found to be useful. For example there are many cores, and sample counts thus have spatial and temporal location $(s_i, t_i)$. Individually each $\pi[c|y^a_i,D^m]$ is a statement of uncertainty concerning an aspect of a common latent space-time process $C(s,t)$. How can we formalise the joint statistical inference? Our approach has been Bayesian, and has rested on stochastic process models including: Gaussian (Markov) Random Fields; a novel monotone stochastic process with continuous sample paths, based on a bivariate renewal process; and long tailed random walks with Normal Inverse Gaussian increments. The talk will illustrate their use in this joint inference, and some of the many remaining challenges. There are of course several scientific challenges to the underlying methodology, for example: To what extent can we rely on modern data to tell us about ancient climate-vegetation relationships? Is climate-change the only driver of vegetation change. We look forward to some of the statistical challenges that these questions pose. This work has involved collaboration with, and stimulation from, many including Brian Huntley, Andrew Parnell, Mike Salter-Townshend, Havard Rue, Alan Gelfand and Caitlin Buck. It has been supported by several grants from Science Foundation Ireland and by a welcome sojourn with Durham University's Institute of Advanced Study.

 

Codimension two bifurcations arising in a system of phase coupled oscillators
Ann-Katrin Becher (Cologne University, Germany)
17 Nov 2009Harrison 170 Tuesday 2pmApplied Mathematics
A model of phase coupled oscillators is introduced describing a network with both excitatory and inhibitory interactions. The phase dynamics are modelled by a Kuramoto-like system but without symmetries with regard to coupling. The coexistence of inhibitory and excitatory interactions and the asymmetry of coupling give rise to several different scenarios of synchronization. We study the model from the standpoint of bifurcation theory of low-dimensional dynamical systems. Therefore we focus on different configurations of coupling which lead to various bifurcation phenomenons with codimension >1.

 

Chimera states in heterogeneous Kuramoto networks
Carlo Laing (Massey University)
16 Nov 2009Harrison 170 Monday 2pmApplied Mathematics
Since 2002 several groups have studied "chimera states" in networks of identical phase oscillators, in which some oscillators synchronise while the remainder are incoherent. However only in the simplest case did the authors study the stability of such states. I show how to greatly generalise these results to other networks, deriving time-evolution PDEs with as many spatial dimensions as the network. The results emphasise the commonality of the dynamics of different networks, and provide stability information that was previously inferred.

 

Amorphous structures of rapid phase-change memory materials
Dr Konstantin Borisenko (Department of Materials, University of Oxford)
12 Nov 2009Harrison 170 (3D Vis Suite) Thursday 2pmAdvanced Technologies RI
Accurate reduced density functions (RDF), which are closely related to the radial distribution functions, can now be routinely obtained from small areas of thin film materials using electron diffraction. The technique provides unique information about distribution of interatomic distances in the material, on the basis of which atomistic models can be built and refined, and then related to the observed properties of the films. This technique has been applied to various materials ranging from metallic glasses to amorphous magnetic films. In this presentation applications of the technique to studies of amorphous phases of rapid phase-change memory materials for information storage are described.

 

Visualising probabilistic forecasts
Tim Jupp
12 Nov 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
We consider the problem of creating maps of ternary probabilistic forecasts. As in traditional (binary) methods, continuous forecast distributions are projected onto discrete ternary forecasts, in which probabilities are assigned to three categories defined by quantiles of the current climatology. Our innovation is to think geometrically and consider each ternary forecast as a point in the triangle of barycentric coordinates (i.e. a 2-simplex). This allows us to assign a unique colour to each forecast from a continuum of colours defined on the triangle. We show that a single easy-to-interpret map can convey full information from a ternary forecast in addition to a measure of the past skill of the forecasting system. Specifically, the forecast at each location is expressed by a circle whose colour encodes the ternary forecast and whose radius encodes past skill. We use the natural symmetries in the problem to assign colours to forecasts using the hue-saturation-value colour system. We derive mathematical measures of subjective certainty H, dominant category theta and misfit R. These measures are used to assign strong colours to forecasts that differ greatly from the climatology, and large circles to regions of high skill. Finally, we show how the concepts of uncertainty, reliability, resolution and calibration (which are usually taken to apply to binary forecasts) can be extended to ternary forecasts. Methods for interpreting these quantities geometrically are proposed. These ideas are illustrated with probabilistic precipitation forecast data from climate model runs, processed using "R" and displayed using "Google Earth".

 

Environmental implications of water efficiency measures in buildings
Abdi Fidar (University of Exeter)
10 Nov 2009Harrison 170 Tuesday 2pmInformatics RI
To encourage the efficient and sustainable use of resources (e.g. energy, water, construction materials) in England and Northern Ireland, the government has introduced ‘Code for Sustainable Homes’. The code requires reduction in per capita water consumption in households, and accordingly provides a rating scheme. Water efficiency related targets can be met using a range of water efficient microcomponents. However, very little is known about their environmental and energy related implications. This paper describes the development of a strategy to quantify the water and energy use of microcomponents and evaluate the environmental performance of composite strategies (comprising different combinations of water efficient microcomponents). A multi-objective optimisation based simulation tool has been developed to investigate the impacts of the composite strategies. Preliminary findings indicate that, depending on the objective (i.e whether to reduce water consumption or greenhouse gas emissions), a trade off is required. For example the analysis of results suggests that (a) energy use and the associated greenhouse gas emissions are largely dependent on how a given volume of water is contributed by the different microcomponents (b) the influence of dishwashers on water consumption reduces significantly when water efficient kitchen taps are present (c) baths do not necessarily use more water than showers (d) in most cases, for a given water consumption, the energy use and the greenhouse gas emissions are inversely proportional to the toilet flush volume.

 

Using model reduction methods from control theory within variational data assimilation
Caroline Boess (University of Reading)
9 Nov 2009Harrison 170 Monday 2pmApplied Mathematics
In this talk the use of model order reduction methods from control theory within variational data assimilation is discussed. The focus is on four-dimensional variational assimilation – a method which requires the minimization of a series of simplified cost functions. These simplified functions are usually derived from a spatial or spectral truncation of the full system being approximated. In this talk a new method for deriving these simplified problems is proposed, based on control theoretic model reduction methods. Moreover, a new model reduction approach for unstable systems is considered. It is shown that this performs well within the state estimation problem occurring in data assimilation.

 

Reduction of the energy consumption of a highly energy intensive manufacturing process
Richard de Salis
5 Nov 2009Harrison 170 (3D Vis Suite) Thursday 1pmAdvanced Technologies RI (Internal)
The manufacturing industry is currently undergoing a number of changes to attempt to reduce the energy consumption of their production processes, due to the cost of energy in the current market conditions, and the environmental pressure being placed on them through legislation and consumer opinion. The Ceramic Tile industry is an example of a highly energy intensive sector and as such offers great potential for reduction and the savings this can provide. In this project, work has been carried out with a manufacturer analysing their energy usage, and from this investigating methods which could be used to reduce it. A number of technologies were considered, which will be overviewed, with the conclusion being that in this case the use of energy consumption as an optimisation criterion in their production scheduling will offer the best potential for improvement with their current installed equipment.

 

What really matters in data assimilation?
Dan Cornford (Aston University)
5 Nov 2009Harrison 101 Thursday 2pmApplied Mathematics
In this talk I will consider the state of the art in data assimilation theory, focussing on our recent variational Bayesian approaches, but also discussing path sampling, particle filtering, 4DVAR and ensemble Kalman filters. I will then consider the question of what really matters in data assimilation - in particular I will consider the formulation of the data assimilation problem from a statistical perspective, and try to relate this to the real world application of data assimilation methods in operational settings.

 

Unsaturated Soil Mechanics: Expansive Soils & Soil Treatment
Prof Farimah Masrouri and Dr Olivier Cuisinier (LAEGO-ENSG-INPL, France)
5 Nov 2009Harrison 170 Thursday 2pmInformatics RI
Part I: Expansive Soils Shrinkage and swelling of clayey soils are responsible for a large amount of building damages and give rise to number of questions. This presentation is focused on 3 different points of a research project carried out to contribute to the comprehension of physical mechanisms of this natural hazard and its consequences on lightly-loaded structures. Part II: Stabilisation with lime Quicklime addition is a common technique to improve the physical properties of fine soils and is also known to significantly reduce the swelling ability of expansive soils. One of the main concerns with this practice is the permanence of the stabilization effects brought by the lime addition. This part of the presentation will be focused on a research project that intends to asses the impact of water circulation on the long term behaviour of lime-stabilised soils.

 

Dynamics and geometry near resonant bifurcations
Sijbo Holtman (University of Groningen, NL)
29 Oct 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
In this talk we focus on non-linear parameter dependent dynamical systems exhibiting resonance. This phenomenon occurs if oscillatory subsystems interact, while the corresponding frequencies are rationally related. Such a situation appears in many real-world scenarios, e.g., coupled pendula, the moon-earth system, and electric circuits. The main goal is to explain the parameter dependence of the qualitative behavior of the dynamics. In particular, we consider the geometry of parameter values for which resonance occurs. It turns out that in the non-degenerate case the geometry is given by the well-known 2-dimensional Arnol'd resonance tongue. A mildly degenerate case corresponds to a more complicated 4-dimensional geometry, which we describe in detail. We also present so-called recognition conditions determining to which of these two cases a given resonant family of dynamical systems belongs.

 

Local Water Symbiosis Approach to More Sustainable Urban Water Management
Dr Sara Moslemi Zadeh (University of Birmingham)
27 Oct 2009Harrison 170 Tuesday 2pmInformatics RI
In 21st century, stress on water resources is reaching critical levels due to population growth, rapid urbanization, economic development, climate change, and an ageing infrastructure. An Integrated Water Resources Management approach is urgently needed to secure the equitable and more sustainable management of freshwater to meet environmental, economic and social needs. Greywater treatment and its subsequent use for toilet flushing have been explored as more sustainable water resources management options. However, the infrastructure needs and the disinfectant required for greywater systems make it very difficult to see these systems as environmentally friendly and cost effect (unsustainable), especially for individual households. This is the reason for low uptake of greywater recycling system, particularly in UK. The aim of this project is to test the hypothesis that transferring the concept of industrial symbiosis from industries to urban areas may improve the sustainability of urban water management. The research focuses on greywater reuse among users in residential and office buildings in a local area. The local symbiosis is designed in 3 stages: first, calculating a potential water balance through water reuse and recycling options, including greywater generation; second, identifying or estimating sharing potentials in the area by considering the qualities of the water available for reuse; and finally calculating the optimal scale and mix of users as well as identifying any barriers to implementation. By minimizing the potable water usage, the environmental effect and the cost of the system are reduced.

 

Compressible Hartmann and mixed Ekman-Hartmann boundary layers.
Krzysztof Mizerski (University of Leeds)
26 Oct 2009Harrison 170 Monday 2pmApplied Mathematics
21st Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics" We consider the effect of compressibility in mixed Ekman-Hartmann boundary layers on an infinite plane ($z=0$), in the presence of an external magnetic field oblique to the boundary. The aim is to investigate the influence of the magnetic pressure on the fluid density, and hence, via mass conservation, on the mass flow into or out of the boundary layer. We find that if the $z$-component of vorticity in the main flow, immediately above the boundary layer, is negative, then there is a competition between Ekman suction and the magnetic pressure effect. Indeed, as the magnetic field strength is increased, the magnetic pumping may overcome the Ekman suction produced by anti-cyclonic main flow vortices. Such competition may play a role in the solar tachocline, the region of strong shear at the base of the convective zone and a plausible site for the solar dynamo. Here field must be confined until it becomes sufficiently strong that, on escaping, it can rise to the solar surface relatively unscathed, thus giving rise to active regions. The Ekman-Hartmann boundary layer is the simplest model of a thin region with large shear and a magnetic field; our simplified model may therefore describe some of the important physics of the tachocline.

 

A model for physics-dynamics coupling
Bob Beare
22 Oct 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Formulations of numerical weather prediction and climate models divide conveniently into the resolved dynamical core and the sub-grid physical parametrizations. Improving these components is an ongoing area of research and development. Arguably less examined, however, is the coupling between these components. More research on the physics-dynamics coupling might therefore lead to significant improvements in future model performance. Here, we demonstrate a new approach to physics-dynamics coupling. We compare a full dynamics model with a model explicitly constrained to balance the large scale dynamics and the boundary layer parametrization.

 

Diagnostic Assessment of Search Controls and Failure Modes in Many-objective Evolutionary Optimisation
Prof. Patrick Reed (Penn State University, USA)
20 Oct 2009Harrison 170 Tuesday 2pmInformatics RI
The growing popularity of multiobjective evolutionary algorithms (MOEAs) for solving many-objective real world problems, where search failures can have actual economic costs, warrants the careful investigation of their search controls and failure modes. This study contributes a detailed statistical assessment of the search controls and failure modes for a broad range of MOEAs as well as a novel measure of controllability. The comparative analysis applies ten state-of-the-art MOEAs on the DTLZ scalable test problems for 2-7 objectives. From these results, we quantitatively compare the effectiveness and controllability of the algorithms. The study concludes by providing guidance on the top performing algorithms' non-separable, multiparameter controls when performing many-objective search.

 

Using constraint-based optimization to model multilayer buckling phenomena
Rorie Edmunds (University of Bath)
19 Oct 2009Harrison 004 Monday 2pmApplied Mathematics
A constraint-based methodology will be presented which has successfully been applied to a solid, elastic, frictional model for parallel folding. Conceived from investigations of the engineering design process, the constraint-based methodology has helped design engineers identify and understand the initial constraints and limitations placed on a system. Written as a set of algebraic expressions the design objectives and constraints can be formulated and optimal solutions found using numerical optimization techniques. A bespoke Constraint Modeller has been created to embrace the methodology. This is able to resolve large systems comprising of over 100 degrees-of-freedom using a variety of optimization routines. Parallel folding is representative of multilayer geological systems undergoing buckling deformation and modelling the evolution of folds poses a significant problem. Simplifying down to a two layer formulation, the behaviour of the central interface is modelled using a number of points whose movement is constrained. Looking for least energy solutions, the small-deflection model closely matches the sequential nature seen in experiments. Using the full large-deflection energy formulation, further phenomena are found which match experimental evidence. Additionally, by altering some of the parameters, the parallel folding model can admit solutions that are kink band-like in structure. Thus insight is given into the transition between the different folding-types seen in nature.

 

Geoengineering the climate: unthinkable last resort or optimal solution?
Peter Cox
15 Oct 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

A Framework for Supporting Rainwater Harvesting in the UK: addressing system design and implementation deficits
Sarah Ward (University of Exeter)
13 Oct 2009Harrison 170 Tuesday 2pmInformatics RI
A broad range of recent policy vehicles, such as the Code for Sustainable Homes, Future Water and the Draft Flood and Water Management Bill, are placing increased emphasis on the incorporation of sustainable urban drainage systems (SUDS) within new developments (and, to a lesser extent at present, retrofitting to existing developments). This is in response to both potable water demand reduction and surface runoff source control drivers. Rainwater harvesting (RWH) is one such SUDS technique that can both supplement mains water and attenuate stormwater flows. Putting aside debates on the cost-benefit and life-cycle analysis of such systems, the UK is significantly behind other countries, such as Germany and Australia, in implementing RWH. Although the previously mentioned policies promote the use of RWH, there is at present limited enabling of stakeholders (householders, businesses, schools) to implement RWH. This presentation outlines research that has utilised an interdisciplinary approach, undertaking both ‘hard’ and ‘soft’ scientific methods, to establish technical and stakeholder evidence bases related to RWH. Analysis of these evidence bases has resulted in the identification of a number of technical and social ‘implementation deficits’, which hinder the increased uptake of RWH in the UK. Key messages from the evidence bases are derived, resulting in recommendations for restructuring current support mechanisms, having implications for both policy makers and technical innovators.

 

The liquid top: precession and tides in planetary cores
Andreas Tilgner (University of Goettingen, Germany)
5 Oct 2009Harrison 004 Monday 2pmApplied Mathematics
20th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics"

 

Heat transfer in turbomachinery predictions with an open source CFD code
Cosimo Bianchini (Faculty of Engineering, University of Florence)
1 Oct 2009Harrison 170 Thursday 1pmAdvanced Technologies RI (Internal)
Due to the continuously growing need of power and efficiency for turbo engines, combustion chamber temperature has far overcome the metal critical temperature indeed more and more loading the combustor liner and first stages cooling devices. These often critical thermal conditions require a detailed knowledge of the aero-thermal behavior of real engine components in order to proceed with improved design. The use of CFD is thus becoming more and more popular among turbine producers also for at design stage of the secondary air system. Dealing with complex geometries, non-aerodynamic bodies, strong temperature and velocity gradients and unsteady phenomena, and ranging the reference Mach from the incompressible limit of the coolant to the transonic regime in the first vanes, it is often very challenging to obtain reliable results and specific tools should be used in order to improve the quality of predictions. The path to make OpenFOAM libraries a reliable tool for heat transfer prediction in turbomachinery is hence illustrated, together with details of the implemented algorithms and models. A wide set of applications of the code to both internal (ribbed and pinned internal channel, impingements) and external (film and effusion holes) cooling are also shown ranging from simple validation test cases to real engine components studied experimentally with Thermo Liquid Crystals.

 

New type of soil reinforcements
Prof. Meng Xi (Shanghai University)
1 Oct 2009Harrison 170 Tuesday 2pmInformatics RI
tba

 

Computation facilitating insight: from autonomous observation to artificial intelligence
David Lary (NASA, Goddard Space Flight Center, USA)
11 Aug 2009Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

"Why the Beauty of your Neighbour's Garden may Belong to You" or "How should we Pay for Urban Water"
Jim Robinson (University of Waterloo, Canada)
6 Aug 2009Harrison 170 Thursday 2pmInformatics RI
Many water utilities experience peak summer demands which are very expensive to satisfy, and providing for them can only be achieved at a cost many times per liter what is being charged currently for water. Some utilities are quite interested in using tariff structures, partly because they improve equity by better reflecting real costs of providing for peak demands. Some modelling has shown that 65-85% of customers would end up with lower water bills if summer use rates were implemented. However, utility staff feel such rate structures are a lot of work to implement just to improve equity and would be much more interested if there were strong evidence that peak demands will in fact be lowered, and this utility capital spending could be averted. Many utilities would like evidence about effects of peak demand rates to be gathered but would prefer someone else do it. Part of this is nervousness over the public relations issues associated with rate changes. A few brave water companies in the UK have started to collect that evidence, some using innovative experimental techniques. In one 5000 household trial in the UK, a brand new customer or a change of name on an account leads to installation of an automated meter and data logger collecting meter readings every 30 minutes, and assignment to one of five charging regimes all of which are revenue neutral to an average customer. Other utilities have suggested compensating trial participants up front to be more certain that no customer is disadvantaged. The foci of this presentation are to show ways that peak demand pricing trials have been and can be implemented, and to discuss some tentative results and their implications.

 

Post-buckling response of thin-walled auxetic tubes
Edward Hirons (SECaM)
7 Jul 2009Harrison 107 Tuesday 13:00Advanced Technologies RI (Internal)
The project involves examination of the pre- and post-buckling response of thin walled tubes loaded under flexure, and comparison to various elastic analytical buckling models. The results of experimental data show that the models are inadequate to predict the limit moment reached by the tubes, due largely to the fact that plasticity is not yet modeled. Work is ongoing to incorporate plasticity and potentialy extend the models' application to similar but distinct geometries, i.e. sandwich panels.

 

Binocular rivalry - a new model
Peter Ashwin
2 Jul 2009Harrison 106 Wednesday 3.30pmApplied Mathematics (Internal)
The effect of binocular rivalry is a well-known phenomenon in the psychology of perception, where the brain will move between recognition of two conflicting images presented to each eye. It is particularly interesting as a system where the brain constantly "changes its mind" in the absence of any change to the input. This talk will discuss a newly developed model of the author and A Lavric, based on heteroclinic switching.

 

Top-down versus bottom-up
Daithi Stone (Climate Systems Analysis Group, University of Cape Town, South Africa)
30 Jun 2009Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

Anomalous diffusion of migrating biological cells
Rainer Klages (Queen Mary, University of London)
29 Jun 2009Harrison 101 Monday 2pmApplied Mathematics

 

Ground-based GPS measurements of water vapor: climatology and applications
Junhong Wang (NCAR, Boulder, CO, USA)
24 Jun 2009Green Island 2 Wednesday 11amMet Office/Hadley Centre

 

Harper operators, equations and maps: a laboratory for strange nonchaotic attractors
Joaquim Puig (Universitat Politecnica de Catalunya, Barcelona, Spain)
15 Jun 2009Harrison 101 Monday 2pmApplied Mathematics
This talk is part of the workshop "Global Dynamics and Applications" held on 15/16 June 2009 in SECaM, University of Exeter. (http://secamlocal.ex.ac.uk/people/staff/rv211/woglodyn09.html)

 

Phase transitions in statistical physics models
Barrie Cooper
11 Jun 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
From a physical point of view, macroscopic properties of a material such as its temperature, structure and magnetisation are determined by the properties and interactions of its constituent microscopic particles. A primary aim of statistical physics is to study these emergent properties of complex systems. Of particular importance are phase transitions, whereupon there is a qualitative change in the macroscopic properties of a system, such as the spontaneous demagnetisation of a ferromagnet at the Curie point. I will describe a family of statistical physics models exhibiting phase transitions and explore how representation theory and the algebraic properties of the operators in such models can help drastically reduce the complexity of the numerical calculations required to detect such a phase transition.

 

Boundary layer dynamics in extra-tropical cyclones
Ian Boutle (University of Reading)
8 Jun 2009Harrison 101 Monday 2pmApplied Mathematics
19th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal "Geophysical and Astrophysical Fluid Dynamics"

 

Wave propagation on adapting, inhomogeneous and unstructured grids
John Thuburn
4 Jun 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Reinforcement of weak soils: Are we utilising the reinforcement to get the best outcomes?
Dr Mostafa Mohamed (University of Bradford)
2 Jun 2009Harrison 170 Tuesday 2pmInformatics RI
In recent years, there has been growing usage of geosynthetic materials for fulfilment of a wide range of functions including improvement of the shear strength of weak soils in order for civil engineering projects to be constructed without the fear of long-term serviceability problems. Reinforcement of surface soils is also used to overcome potential negative consequences for construction in areas that are featured by the inclusion of pockets of soft soils. In general, the behaviour of the reinforced ground relies on the frictional resistance between the reinforcement and surrounding soils. In most of the cases there has been over use of reinforcing layers that never utilises the tensile strength of the reinforcing elements to their utmost. Furthermore, to speed up the construction process, reinforcement is often arranged in a simple manner. The presentation will review the current practice for soil reinforcement highlighting various failure mechanisms. Then it will focus in presenting a new approach to reinforcing the surface soils in which a nominal amount of soil is wrapped around with a layer of geotextile in order to create a wrapped cushion underneath the surface footing. The proposed reinforcement approach shows that significant improvements could be achieved. The presentation will show that the new reinforcement arrangement has the potential to improve the bearing capacity of surface footing several times and to reduce associated settlement. The improvements achieved by the proposed approach are greater than what it could be obtained by the conventional soil reinforcement. Cases in which pockets of soft soils exist will be discussed. Finally, an outline will be given of recent geotechnical engineering research undertaken at the University of Bradford.

 

Model prediction of component quality in Additive Layer Manufacturing
Gilian Hatwell
1 Jun 2009Harrison 209 Thursday 13:00Advanced Technologies RI (Internal)
Additive Layer Manufacturing (ALM) is the generic term applied to a range of high technology processes that are capable of producing net-shape or near net-shape objects from a variety of input materials. ALM covers a broad range of techniques, but methods utilising lasers to process metallic or polymeric powders are of particular interest to high-end engineering manufacturers. The benefits that ALM can provide may have a wide application across many manufacturing sectors. However, this is limited due to concerns about component quality and system repeatability. Previous work has concluded that small variations in the build chamber leads to unacceptable variations in component qualities, particularly mechanical strength. Thermal control systems are already present within ALM processes, and are vital for successful operation, but these are limited and typically only concerned with the corresponding build stage. This seminar looks at the three stages of the PhD; analytical, experimental and computational to build up a generic model predicting the component quality, based on the build conditions (both laser and material parameters) of a polymeric Selective Laser Sintering (SLS) process.

 

Solitons, homoclinic orbits and exponentially small phenomena in reversible systems
Tomas Lazaro (Universitat Politecnica de Catalunya, Barcelona, Spain)
1 Jun 2009Harrison 101 Monday 2pmApplied Mathematics

 

Asymmetric Desynchronization and Ratcheting in Networks of Coupled Oscillators
Ozkan Karabacak
28 May 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
We analyze an example system of four coupled phase oscillators and discover a novel phenomenon that we call “heteroclinic ratchet”; a particular type of robust heteroclinic network on torus where connections wind in only one direction. We show that, for coupled phase oscillators, this type of heteroclinic network can exist as an attractor in phase space resulting in asymmetric desynchronization of certain pairs of oscillators. In other words, oscillators with natural frequencies w1 and w2 break synchrony for w1-w2>0 but not for w1-w2<0. Similarly, when w1=w2, arbitrary small noise results in a break of synchrony such that after the desynchronization the observed frequencies W1 and W2 satisfy W1>W2.

 

Eliassen-Palm, Charney-Drazin, and the development of wave, mean-flow interaction theories in atmospheric dynamics
David Andrews (Department of Physics, University of Oxford)
21 May 2009Green Island 2 Thursday 2pmMet Office/Hadley Centre

 

Satellite observed variability and trends in the global sea-ice cover
Josefino C. Comiso (NASA, Goddard Space Flight Center, USA)
21 May 2009Green Island 1 Thursday 3pmMet Office/Hadley Centre

 

Is the water vapor feedback the same in nature and models?
Aiguo Dai (NCAR, Boulder, CO, USA)
20 May 2009Green Island 1 Wednesday 11amMet Office/Hadley Centre

 

Variability of surface temperature in the polar regions as inferred from satellite infrared data
Josefino C. Comiso (NASA, Goddard Space Flight Center, USA)
19 May 2009Green Island 1 Tuesday 2pmMet Office/Hadley Centre

 

The effect of mechanical forcing on buoyancy-driven flows
Remi Tailleux (University of Reading)
18 May 2009Harrison 101 Monday 2pmApplied Mathematics

 

L-functions and Arithmetic
Professor John Coates (Cambridge university)
14 May 2009Harrison 101 Thursday 3pmPure Mathematics

 

Reconnection in braided magnetic fields
Gunnar Hornig (University of Dundee)
11 May 2009Harrison 101 Monday 2pmApplied Mathematics

 

The higher Hilbert symbol via (phi,G)-modules
Dr Sarah Zerbes (Exeter university)
7 May 2009Harrison 101 Thursday 3pmPure Mathematics

 

A SCM modeling by using Multi-Agent System (MAS)
Naihui He (XMEC)
5 May 2009Harrison 103 Tuesday 13:00Advanced Technologies RI (Internal)
The supply chain is a worldwide network which involves all of those stages from raw material to completed products; while the Supply Chain Management (SCM) is then described as "the integration of all activities" occurring along the supply chain through improved supply chain relationships in order to achieve a suitable competitive advantage. Due to the interior complexity of SCM, SCM modeling has provided a convenient method and become a popular way for scholars to solve emerging problems in a supply chain, such as collaboration and coordination method, and etc. In particular among those modeling approaches, the agent-based technique of Multi-Agent System (MAS) that is a branch of Distributed Artificial Intelligence (DAI) encompasses multiple agents with specific roles each of which interacts with others for achieving its local responsibilities and the overall targets, and thereby is able to address the complexity and dynamics of SCM. This seminar will present a simulation-based SCM modeling system by applying the technique of MAS, which involves the specification of the framework of the modeling and its validation processes.

 

Metals at the tap – how did we get it so wrong and what next?
Dr Colin Hayes (School of Engineering, Swansea University)
5 May 2009Harrison 170 Tuesday 2pmInformatics RI
The metals at the tap of greatest concern are lead, copper and nickel, all of which have health concerns (particularly lead). These metals mainly arise from pipes and fittings in the domestic water supply system. Despite apparent EU requirements to mitigate such issues, sampling problems have conspired to substantially diminish corrective action, the big exception being the UK , where 95% of public water supplies are dosed with ortho-phosphate to suppress plumbosolvency. As sampling deficiencies are rectified, the true scale of problems will emerge. An initial assessment is that 25% of the EU population could be at risk from lead in drinking water. Copper problems appear to be insignificant, whereas nickel problems may also be significant, subject to any future changes in the health based standard. International research networking has potentially influenced the revision of the EU Drinking Water Directive and the implementation of the WHO/UN Protocol on Water and Health. Metals at the tap appear set to climb the international policy agenda. A zonal lead emission model has been developed at Swansea University that can predict compliance with lead standards across an entire City or Town. This is based on a Monte Carlo probabilistic framework and has been validated successfully in numerous case studies. It has been used to optimise phosphate dosing and is currently being used to investigate health risks.

 

Parity of the rank of an elliptic curve: results
Dr Tim Dokchitser (Cambridge university)
30 Apr 2009Harrison 101 Thursday 4pmPure Mathematics

 

Parity of the rank of an elliptic curve: phenomena
Dr Valadimir Dokchitser (Cambridge university)
30 Apr 2009Harrison 101 Thursday 3pmPure Mathematics

 

A catalogue of singularities
Jens Eggers (University of Bristol)
27 Apr 2009Harrison 101 Monday 2pmApplied Mathematics

 

Atmospheric freshwater transport in three generations of the Hadley Centre model
Jose Rodriguez (Met Office, Exeter)
7 Apr 2009Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

A Semantic Theory of the Interpretation of a Vague Language
Dr Brandon Bennett (University of Leeds)
26 Mar 2009Harrison 170 Tuesday 3pmInformatics RI
I present a semantics for the interpretation of a language that includes vague predicates, based on a refinement and extension of the "supervaluation" approach. The proposed theory provides a formal characterisation of the space of possible precise interpretations (precisifications) of the language, in terms of parameters that specify the applicability of vague concepts by means of thresholds on the values of observable measurements. These observables also determine a set of possible states of the world. Thus the truth of a proposition depends on both the possible world and the precisification with respect to which it is evaluated. On the basis of this semantics, the acceptability of a proposition to an agent is characterised in terms of the agent's beliefs about the world and attitude to admissible interpretations of vague predicates. The theory is applied to analysing certain aspects of the cognitive evaluation of vague information --- in particular the sorites paradox. A further extension, in which probability spaces are defined over the sets of possible worlds and precisifications, is used to give a statistical measure of the acceptability of a proposition to an agent.

 

Sha and Degree 4 del Pezzo Surfaces.
Prof. Victor Flynn (Oxford University)
20 Mar 2009Harrison LT04 Friday 2pmPure Mathematics

 

Topology Optimisation: Challenges and Applications
Dr H Alicia Kim (Department of Mechanical Engineering, University of Bath)
19 Mar 2009Harrison 171 Thursday 2pmAdvanced Technologies RI
Topology optimisation is considered the most generalised form of structural optimisation. This seminar will discuss two of the most popular methods: SIMP (Solid Isotropic Material with Penalisation) and ESO (Evolutionary Structural Optimisation). Our recent research showed both of the methods are prone to numerical instabilities, due to the use of regular mesh and piecewise constant design variables. This finding supports the recent development of the boundary based approaches such as level-set function methods. Research at Bath has been developing the efficient and convergent optimisation methods and the current research activities will be presented. The seminar will also show two application areas: traditional engineering design and study of bone remodelling.

 

Skew Power Series Rings
Prof. Otmar Venjakob (Heidelberg University)
19 Mar 2009Harrison 101 Thursday 3pmPure Mathematics

 

Systematic decision analysis for flood risk management
Hamish Harvey (Newcastle University)
17 Mar 2009Harrison 170 Tuesday 3pmInformatics RI
Continuing rapid growth in the availability of data and the plummeting cost of computation represents both a great opportunity and a challenge. How can this abundance be utilised to improve the quality of decision making in water management? This opportunity has been grasped in the use of risk analysis in strategic decision making for flood risk management. Risk analysis represents only the first step in a process of development, however, the logical conclusion of which is systematic, quantitative decision analysis. Decision analysis techniques allow the merits of sets of management options to be examined, according to a variety of performance metrics and under a range of possible future conditions. I will outline a conceptual framework for such analyses and discuss the initial design of a software tool that implements it. Our focus is strategic decision making, in which option performance must be assessed over long time horizons. This introduces the need to represent processes of change, for example in demographics or climate, which may be highly uncertain. Early applications of risk analysis have demonstrated some of the opportunity of computational experiments in informing decisions. They have also exposed some aspects of the challenge: the results of these analyses are often opaque and difficult to trust. Properly managed and with the use of appropriate tools, however, the process of setting up and running a decision analysis can lead not only to greater insight but also to improved transparency. Our work sets out to bridge this gap between present reality and future potential.

 

TBC
Andrew Gilbert (University of Exeter)
12 Mar 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Multi-layered approach to generalising Digital Terrain Models for 2D Flood Modelling
Mr Barry Evans (University of Exeter)
10 Mar 2009Harrison 170 Tuesday 3pmInformatics RI
In surface flow path flood modelling, 2D models are the preferred choices as they can simulate surface flow more accurately than 1D models, they are however more computationally demanding and thereby require greater simulation time. One approach that can be used to reduce the computational time required in 2D modelling is to utilise coarser resolution of data by down-sampling the original data-set. Yu and Lane (2006a) showed however that even relatively small changes in model resolution have considerable effects on the predicted inundation extent and the timing of flooding. One of the key causes of changes in the coarse resolution in an urban environment is that of the spreading of buildings into their surroundings and subsequent loss key details such alleyways. This seminar will outline the potential of utilising a multi-layered approach for the representation of buildings within a generalised terrain model and the automata processes involved in converting Digital Terrain Model data into a multiple layer generalised grid.

 

Simulating the stratosphere with HadGEM
Steven Hardiman (Met Office, Exeter)
10 Mar 2009Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

TBA
Chris Jones (University of Leeds)
9 Mar 2009Harrison 101 Monday 2pmApplied Mathematics

 

Period Domains Modular Forms and Lattices
Dr Gregory Sankaran (Bath University)
5 Mar 2009Harrison 101 Thursday 3pmPure Mathematics

 

Adapting the strategic management of water systems to climate (and other) change - the need for new methods for analysing uncertainty and making robust risk-based decisions
Peter von Lany (Principal Consultant, Halcrow Group Ltd)
3 Mar 2009Harrison 170 Tuesday 3pmInformatics RI
Much attention is focused on mitigating factors that contribute to climate change. Mitigation needs to be integrated with actions to adapt to climate (and other) change in ways which do not exacerbate the causes or effects of climate change nor limit the ability of other sectors to adapt. Decision making processes such as the UKCIP Adaptation Wizard (see www.ukcip.org.uk) signal the need for risk-based decision making techniques and methods for analysing uncertainty to help: o determine aspects of water system(s) that are vulnerable to the effects of climate (and other) change o assess the potential risks to the system(s) and the opportunities arising from climate (and other) changes, and their implied costs and benefits o develop adaptive responses to these risks and opportunities to maintain or enhance in a sustainable manner aspects of the system that are most valued. The seminar will outline some recent work that the presenter has been involved in, in the strategic planning of flood risk management and water resources. It will consider the need for new techniques for risk-based decision making and dealing with uncertainty, and identify, for discussion, some of the challenges faced and possible ways forward to dealing with these issues.

 

Anisotropic elastic properties
Arnaud Marmier (SECaM)
2 Mar 2009Harrison 209 Thursday 13:00Advanced Technologies RI (Internal)
Elastic Properties have received a resurgence of interest in the last decades, triggered by the discovery of “negative” properties (Poisson’s ratio –PR– and Linear Compressibility –LC–). The fact that these properties are negative is usually described as anomalous, but more and more materials are discovered that posses a negative Poisson’s ratio, usually in a direction without special symmetry. One of the reasons that negative elastic properties still appear unusual is that the formalism of elastic theory, while conceptually simple, does not lend itself well to the representation of properties, especially off-axis. And at present, there are no easily available, convenient to use, method of calculating elastic properties in any direction. In this seminar I will first describe the theory of elasticity in anisotropic media through the tensor formalism. I will then discuss the ElAM computer code (Elastic Anisotropy Measures), which can represent a variety of elastic properties in any direction. Finally, I will present case studies: direction of extrema in cubic crystals, extreme PR and LC, data mining.

 

A Hamiltonian approach to variational data assimilation
Ian Roulstone (University of Surrey)
2 Mar 2009Harrison 101 Monday 2pmApplied Mathematics

 

The performance of the Hadley Centre Earth System model (HadGEM2)
Bill Collins (Met Office, Exeter)
2 Mar 2009Green Island ? Monday ?Met Office/Hadley Centre

 

Air quality forecasting in the UM
Nick Savage, Carlos Ordonez and Paul Agnew (Met Office, Exeter)
27 Feb 2009Green Island 1 Friday 11amMet Office/Hadley Centre

 

Extending semi-geostrophic theory to include boundary layer diffusion
Bob Beare (University of Exeter)
26 Feb 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Since the seminal work of Hoskins (1975), the semi-geostrophic model has proved invaluable in describing the dynamics of meteorological fronts and cyclone formation. The model has also been a focus for the mathematically inclined as, for example, the equations can be proved to be well-posed and can be interpreted in terms of variational principles. However, a weakness of the semi-geostrophic model as an interpretive framework for climate models is that it contains no inclusion of the sub-grid physical processes such as boundary layer diffusion. In this talk, I will review some of the existing approaches to including boundary layer diffusion in semi-geostrophic theory and propose a more accurate formulation.

 

A Hybrid Generative/Discriminative Framework to Train a Semantic Parser from an Un-annotated Corpus
Dr Yulan He (University of Exeter)
24 Feb 2009Harrison 170 Tuesday 3pmInformatics RI
We propose a hybrid generative/discriminative framework for semantic parsing which combines the hidden vector state (HVS) model and the hidden Markov support vector machines (HM-SVMs). The HVS model is an extension of the basic discrete Markov model in which context is encoded as a stack-oriented state vector. The HM-SVMs combine the advantages of the hidden Markov models and the support vector machines. By employing a modified K-means clustering method, a small set of most representative sentences can be automatically selected from an un-annotated corpus. These sentences together with their abstract annotations are used to train a HVS model which could be subsequently applied on the whole corpus to generate semantic parsing results. A filtering method is then used to select the most confident semantic parsing results to generate a fully-annotated corpus which is used to train the HM-SVMs. The proposed framework has been tested on the DARPA Communicator Data. Experimental results show that an improvement over the baseline HVS parser has been observed using the hybrid framework. When compared with the HM-SVMs trained from the fullyannotated corpus, the hybrid framework gave a comparable performance with only a small set of lightly annotated sentences.

 

Localised pattern formation
Jonathan Dawes (University of Bath)
23 Feb 2009Harrison 101 Monday 2pmApplied Mathematics

 

TBC
Svitlana Popovych (University of Cologne)
19 Feb 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Manin-Mumford and Andre-Oort conjectures : a unified approach.
Dr Andrei Yafaev (UCL)
19 Feb 2009Harrison 101 Thursday 3pmPure Mathematics

 

Manin-Mumford and Andre-Oort conjectures : a unified approach.
Dr Andrei Yafaev (UCL)
19 Feb 2009Harrison 101 Thursday 3pmPure Mathematics

 

Statistical challenges within the water industry
Dr Tim Watson (MWH - Business Solutions)
17 Feb 2009Harrison 170 Tuesday 3pmInformatics RI
The use of statistics is becoming more important within the water industry as a means of developing models that aim to improve the understanding of both the present performance of assets as well as forecasting the future performance of assets. These models, and related forecasts, are typically used to determine short and long-term investment requirements by use of some form of constrained optimization. The accurate estimation of the deterioration and performance of assets over time should be seen as a critical step in the efficient and sustainable allocation of investment spend and ongoing profitability. The modelling process, and the models themselves, therefore need to contain a large helping of statistical rigor and be fit for purpose, to ensure investment plans are robust and as accurate as the data supports. In this presentation, we will present some of the challenges that the water industry face to achieve the above with the constraints of ‘real world’ problems. These challenges are diverse in nature and relate to three key areas, resources, data, and statistical rigor.

 

Climate change, cities, and the urban heat island
Mark McCarthy (Met Office, Exeter)
17 Feb 2009Green Island 3+4 Tuesday 11amMet Office/Hadley Centre

 

Dynamical networks and graph theory
Markus Kirkilionis (University of Warwick)
16 Feb 2009Harrison 101 Monday 2pmApplied Mathematics
Non-linearities like mass-action kinetics describe events created by collisions of molecules in a well-mixed environment giving them locally the same probability to meet each other. Moreover this probability is only dependent on the concentration of the mutual partners. In a deterministic approximation the dynamical system describing the evolution of molecular concentrations over time can be interpreted as defining a dynamical network, for example linking species together by the ability to be transformed into each other. Different feedback loops encoded in the non-linearities will determine the qualitative behaviour of the system. In this talk we are looking at dynamical networks and ask a fundamental but unfortunately hard mathematical question which is currently discussed in many branches of complex systems theory and systems biology: What is the relationship between network topology and qualitative behaviour of such a dynamical network? The answer to this question will depend on what kind of information can be retrieved from different graphs associated to the dynamical system. In this talk I will discuss several such graphs that have been constructed for reaction systems which here will serve as a basic example of a dynamical network in general.

 

A revised land hydrology in the ECMWF model: a step towards water fluxes prediction in a fully-closed water cycle
Gianpaolo Balsamo (ECMWF, Reading)
13 Feb 2009Green Island 1 Friday 11amMet Office/Hadley Centre

 

Design of a 5-Axis Ultraprecision Micro Milling Machine (UltraMill) and its application to micro/nano manufacturing
Prof. Kai Cheng (University of Brunel)
12 Feb 2009Harrison 171 Thursday 2pmAdvanced Technologies RI
Ultraprecision micro manufacturing is emerging as the key enabling technology for engaging high value manufacturing. Although conventional ultraprecision machines have been used as a major means to manufacture high precision components/products for a few decades, it still remains a big issue in machining high precision 3D miniature/micro components, microstructures and products in terms of predictability, producibility and productivity. Therefore, it is essential and much needed to develop ultraprecision micro machines which are industrially feasible for undertaking micro manufacturing, e.g. having the features of small footprint, high precision, low cost and easy to run, etc. This seminar will present the development of a novel 5-axis bench-top micro milling machine - UltraMill. The design considerations and specifications of the machine are discussed against the delicate industrial application requirements. An integrated machine design and analysis approach is described, covering the dynamics of the machine structure, moving components, control system and the machining process, and used to analyze and optimize the entire machine performance at the early design stage. Three prioritized design issues of motion accuracy, dynamic stiffness and thermal stability formulate the holistic design for UltraMill. Furthermore, the approach has been applied to the development of key machine components and their integration so as to enable the machine to achieve high accuracy and fine surface finish. Micro machining trials have been successfully conducted on the machine to produce miniature components and microstructure in a variety of engineering materials. The results have not only verified that the machine renders sub-micron accuracy and nanometer-level surface finish, but also demonstrated that bench-top ultraprecision machines would lead to the trend in design of next/future generation of ultraprecision machines. The seminar will conclude with a further discussion on the potentials and applications of the machine in micro/nano manufacturing in particular.

 

Smoothing geometric maps and applications to KAM theory.
Alejandra Gonzalez-Enriquez (University of Exeter)
12 Feb 2009Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
We show that finitely differentiable diffeomorphisms which are either symplectic, volume-preserving, or contact can be approximated with analytic diffeomorphisms that are, respectively, symplectic, volume-preserving or contact. We prove that the approximating functions are uniformly bounded on some complex domains and that the rate of convergence, in $C^{r}$-norms, of the approximation can be estimated in terms of the size of such complex domains and the order of differentiability of the approximated function. As an application to this result, we give a proof of the existence, the local uniqueness and the bootstrap of regularity of KAM tori for finitely differentiable symplectic maps.

 

On the theory relating changes in area-average and pan evaporation
W. James Shuttleworth (University of Arizona, Tucson, USA)
11 Feb 2009Green Island 2 Wednesday 2pmMet Office/Hadley Centre

 

System Dynamics Modelling for the simulation of complex hydrological/ water management systems
Dr Lydia Vamvakeridou-Lyroudia (University of Exeter)
10 Feb 2009Harrison 170 Tuesday 3pmInformatics RI
System Dynamics Modelling is a methodology for studying and managing complex feedback systems, typically used when formal analytical models do not exist, but system simulation can be developed by linking a number of feedback mechanisms. They are particularly useful for building, understanding and presenting models to non-engineers. This seminar presents the procedure for developing conceptual and System Dynamic Modelling in participatory interdisciplinary context, for a complex hydrological/water management system, the Merguellil valley catchment in Tunisia. The model is being used for studying various water management scenarios for 35 small and one large dam in the Merguellil valley, and their impact to aquifer recharge, under different climatic conditions.

 

Impact of stratospheric resolution on seasonal forecast skill for Europe
Andrew Marshall (Met Office, Exeter)
10 Feb 2009Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

A benchmark for initial perturbations used in ensemble prediction
Martin Leutbecher (ECMWF, Reading)
6 Feb 2009Green Island 1 Friday 11amMet Office/Hadley Centre

 

Numerical Methods For Weather and Climate Models
James Kent (University of Exeter)
5 Feb 2009Harrison 101 Thursday 2pmApplied Mathematics (Internal)
Numerical models for weather and climate have finite resolution in space and time; the governing equations are solved on the resolved scales while important processes occurring on smaller scales must be represented by sub-grid models. The numerical schemes used to solve the resolved scales are not perfect; they suffer from truncation errors. A controversial issue is whether the truncation errors, by accident or by design, can be interpreted as representing some sub-grid processes.

 

Professor
Professor Nigel Boston (Dublin)
5 Feb 2009Harrison 101 Thursday 3pmPure Mathematics
Arboreal representations, factoring iterates, and p-extensions

 

Collaboration resulting from operational use of the UM
George Pankiewicz (Met Office, Exeter)
4 Feb 2009Green Island 1 Wednesday 2pmMet Office/Hadley Centre

 

A hidden semi-Markov model for recurrent events
Theo Economou (University of Exeter)
3 Feb 2009Harrison 170 Tuesday 3pmInformatics RI
There is a large and rich literature on statistical modelling recurrent events found mainly in the survival and reliability context. Typically the way in which this is done is by assuming a counting process such as the non-homogeneous Poisson process (NHPP) with a time dependent intensity function (occurrence rate). Sometimes it may be appropriate to use a hidden Markov process formulation to account for the fact that in longitudinal data such as recurrent events data, the subjects in the study undergo changes in time which could possibly depend on the events themselves. In addition it is more appropriate to assume a hidden semi-Markov instead of a Markov process since the latter assumes that the times between each state are geometrically distributed and we believe that this is an unrealistic assumption. The semi-Markov process allows the incorporation of a temporal structure thus increasing flexibility. The hidden semi-Markov model is implemented using MCMC on some illustrative data sets including river floods and water pipe bursts.

 

Cancelled
David Raymont (SECaM)
2 Feb 2009Harrison 170 Thursday NoneAdvanced Technologies RI (Internal)
Cancelled

 

Computer assisted rigorous hyperbolicity estimates in one-dimensional dynamics
Stefano Luzzatto (Imperial College)
2 Feb 2009Harrison 101 Monday 2pmApplied Mathematics

 

An evaluation of the MetUM over the central Arctic Ocean using in-situ observations
Cathryn Birch (University of Leeds)
30 Jan 2009? ? Friday ?Met Office/Hadley Centre

 

Linear growth of rational points on Chatelet surfaces
Dr Tim Browning (Bristol university)
29 Jan 2009Harrison 101 Thursday 3pmPure Mathematics

 

Does climate change mean it is not worth reducing deforestation in Amazonia?
Richard Betts (Met Office, Exeter)
28 Jan 2009Green Island 1 Wednesday 11amMet Office/Hadley Centre

 

Water Resources Management: The Myth, The Wicked, & The Future
Prof. Patrick M. Reed (The Pennsylvania State University, USA)
27 Jan 2009Harrison 170 Tuesday 2pmInformatics RI
There is a growing recognition that we must better account for a broader range of process couplings as well as their associated uncertainties to manage the evolving human-natural systems that shape our water resources. These challenges are confounded by and potentially conflict with increasing expectations that engineers facilitate public participation in infrastructure design decisions. Water resources management has long considered these types of challenges. Many valuable historical perspectives have been somewhat lost in the recent water resources management literature. In this talk, I will argue that we are neglecting two key historical lessons as engineers: (1) least-cost optimality in complex human-natural systems is a myth and (2) that water resources management is reflective of a class of wicked social value problems where uncertainties, diverse perspectives, and couplings require collaborative formulation and evaluation of a broad range of design aspirations. Future water resources systems management paradigms must acknowledge wealth—risk tradeoffs, their associated uncertainties, and the potential consequences of limitations in our knowledge of the “chains of causality” operating in complex water systems (will A cause B?). Simultaneous consideration of these factors motivates the need for new frameworks for “constructive” decision-aiding. Decision-aiding can be viewed as a process of collaborative learning and negotiation that can exploit many objective analysis to identify alternatives that capture a broad suite of system behaviors relevant to both modeled and unmodeled objectives, helping decision makers to discover system dependencies and/or tradeoffs and exploit this information in the negotiated management of complex water resources systems. An example of constructive many-objective decision aiding will be provided for an urban water supply portfolio planning case study for the Lower Rio Grande Valley located in Texas, USA.

 

Damped wave equations with supercritical nonlinearities
Sergey Zelik (University of Surrey)
26 Jan 2009Harrison 101 Monday 2pmApplied Mathematics

 

Orographic precipitation in the tropics: large-eddy simulations and theory
Dan Kirshbaum (University of Reading)
22 Jan 2009Green Island 2 Thursday 2pmMet Office/Hadley Centre

 

Autumn 2008 Climate Brief
Andrew Marshall, Paul James and Tim Legg (Met Office, Exeter)
21 Jan 2009Green Island ? Wednesday ?Met Office/Hadley Centre

 

Hemispheric transport of air pollution
Michael Sanderson (Met Office, Exeter)
20 Jan 2009Green Island 3+4 Tuesday 3pmMet Office/Hadley Centre

 

The Open Hole Tensile Test – A Challenge For Virtual Testing of Composites
Stephen Hallett (University of Bristol)
15 Jan 2009Harrison 107 Thursday 2pmAdvanced Technologies RI
The open hole tension strength is an important parameter for composite structures since it is can be a limiting factor in design. It is also difficult to characterise and predict through analytical or numerical methods since there exists a wide variation in experimental results depending on testing configuration. Here a range of such variations are presented and the behaviour explained in terms of the development of sub-critical damage in the form of intra-ply splits and inter-ply delaminations and their interaction with each other and also with fibre failure. A finite element based numerical analysis technique has been developed and applied to each case in turn, successfully predicting the failure modes, trends and strengths. This is sufficiently robust to form the basis for a virtual testing framework for the open hole tensile strength of composite materials.

 

On Geometry of Hilbert Modular Varieties and Applications to Canonical Subgroups
Dr Payman Kassaei (King's College London)
15 Jan 2009Harrison 101 Thursday 3pmPure Mathematics

 

Using Interaction information for clustering variables in causal Bayesian networks
Michael Barclay (University of Exeter)
13 Jan 2009Harrison 170 Tuesday 2pmInformatics RI
Mutual information and conditional mutual information functions have been used to learn the structure of variants of naive Bayesian classifiers for several years. Related combinations of these functions have also been used to select relevant but not redundant feature sets. In the case of a causal Bayesian classifier, where the classification variable is not a common parent of the relevant features and where as a consequence hidden variables are often needed, the interaction information function can be shown to be a required, but not sufficient, method for appropriate clustering of variables into parent sets. Several unresolved problems in constructing a final network from the variable clusters are presented for discussion.

 

Blending in situ and satellite data for monitoring extreme temperatures over land
Elizabeth Good (Met Office, Exeter)
12 Jan 2009Green Island 3+4 Monday 2pmMet Office/Hadley Centre

 

Fibrous materials – Hemp, aramid and few others in-between
Dr Michael Sloan (X-AT)
6 Jan 2009Harrison 209 Tuesday 13:00Advanced Technologies RI (Internal)
Fibrous materials play an important role in a number of research projects currently running in SECaM and Exeter Advanced Technologies (X-AT). This presentation will introduce the fibres and their applications in composite materials. Mike Sloan is an associate research fellow in X-AT and has recently completed his PhD titled Eco-efficient friction materials. This work will form the first part of the presentation. The aim of his research was to evaluate the performance of aramid fibres in automotive brake pads and suggest environmentally sustainable replacement fibres such as hemp or flax. The presentation will discuss the analysis of aramid fibres throughout the life of a brake pad from virgin raw material, through to the friction and wear performance of a composite friction material. The effect of substituting natural fibres in a friction material formulation will also be discussed. The second part of the presentation will introduce the Blast curtains project. In this work Helical Auxetic Yarns are being developed and analysed for energy absorbing applications such as blast protection. The construction of a helical auxetic yarn will be shown and the experimental techniques used to evaluate their performance introduced.

 

Software development practices for climate models: what we've learned
Steve Easterbrook (University of Toronto, Canada)
6 Jan 2009Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

The Atmospheric Circulation Reconstructions over the Earth (ACRE) initiative
Rob Allan and Philip Brohan (Met Office, Exeter)
16 Dec 2008Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

Atomistic simulation of phase-change memory materials
Dr. Jozsef Hegedus (University of Cambridge)
11 Dec 2008Harrison 107 Thursday 2pmAdvanced Technologies RI
GeSbTe materials are used in optical DVDs and non-volatile electronic memories (phase-change random-access memory). In both, data storage is effected by fast, reversible phase changes between crystalline and amorphous states. Despite much experimental and theoretical effort to understand the phase-change mechanism, the detailed atomistic changes involved are still unknown. In our work we describe how the entire write/erase cycle for the Ge2Sb2Te5 composition can be reproduced using ab initio molecular-dynamics simulations. Deep insight is gained into the phase-change process; very high densities of connected square rings, characteristic of the metastable rocksalt structure, form during melt cooling and are also quenched into the amorphous phase. Their presence strongly facilitates the homogeneous crystal nucleation of Ge2Sb2Te5. As this simulation procedure is general, the microscopic insight provided on crystal nucleation should open up new ways to develop superior phase-change memory materials, for example, faster nucleation, different compositions, doping levels and so on.

 

Warm rain and climate: VOCALS, CloudSat, models
Rob Wood (University of Washington, USA)
11 Dec 2008? ? Thursday ?Met Office/Hadley Centre

 

Bifurcation analysis of heteroclinic chains involving periodic orbits
Thorsten Riess
10 Dec 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
The bifurcation analysis of heteroclinic chains is important for many applications; such chains arise for example in biological models (cells) or physical models (lasers), and their existence is often connected with a rich variety of nearby dynamics. Recently, some of the theoretical and computational tools for the analysis of heteroclinic chains connecting hyperbolic equilibria have been extended to chains connecting hyperbolic equilibria and hyperbolic periodic orbits. The analytical results obtained via an extension of Lin's method can readily be applied to an equilibrium-to-periodic-orbit cycle (EtoP cycle), giving rise to bifurcation equations for homoclinic orbits near the EtoP cycle. These analytical results are confirmed by numerical evidence for a concrete example, which is obtained by a computational method to find and continue EtoP connections in parameters. This numerical method is also based on the theoretical framework of Lin's method.

 

Integrating Genetic Algorithms (GA) with a water system simulator for the multiobjective optimisation of reservoir operation
Lydia Vamvakeridou-Lyroudia
9 Dec 2008Harrison 170 Tuesday 2pmInformatics RI
AQUATOR® is a commercial software for developing and running simulation models of natural rivers, water resources and water supply systems, using different operational rules, constraints and priorities. Developed by Oxford Scientific Software, it is being used by several water companies in the UK. The Centre for Water Systems has undertaken the task of linking AQUATOR to a GA optimisation module. Initially GANetXL, an add-in for Microsoft Excel®, developed by the Centre for Water Systems, was linked to AQUATOR, for the multiobjective optimisation of reservoir operation. However due to the excessive computational time required, AQUATOR-GA, a new GA application was developed, using distributed computing, which has been integrated within the AQUATOR environment. This seminar presents a comprehensive overview of the project comprising the mathematical approach and structure of the multiobjective optimisation problem, the development of a prototype as an Excel add-in, and the distributed AQUATOR-GA module that followed.

 

The mean field approach to the transport of magnetic field
Alice Courvoisier (University of Leeds)
8 Dec 2008Harrison 101 Monday 2pmApplied Mathematics
18th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal 'Geophysical and Astrophysical Fluid Dynamics'

 

p-adic semistable representations and generalization of the Shafarevich Conjecture
Professor Victor Abrashkin (Durham University)
3 Dec 2008Harrison 101 Thursday 3pmPure Mathematics
Breuil’s theory of semistable p-adic representations is applied to prove the following property: if X is a projective variety over Q with semistable reduction modulo 3 and good reduction at all other primes then its Hodge number h^{2,0} = 0

 

Perpendicular magnetic recording and a development of contact recording system.
Komkrit Chooruang (SECaM)
2 Dec 2008Harrison 209 Tuesday 13:00Advanced Technologies RI (Internal)
Perpendicular magnetic recording (PMR) is one of the suggested technologies that could postpone the onset of superparamagnetic effects. As the increasing of areal density of the PMR implies that the bit size and head/disk flying heights will have to be decreased in nanometre scales and new media must be developed with improved characteristics. These requirements create a need for instrumentation which can be used to characterise the ultimate performance of heads and media at high recording densities. Therefore, we have developed a contact magnetic recording test system that can help researchers to carry out recording test on different media in order to investigate its performance.

 

Multiobjective Neural Network Ensembles based on Regularized Negative Correlation Learning
Huanhuan Chen (University of Birmingham)
2 Dec 2008Harrison 170 Tuesday 2pmInformatics RI
Negative Correlation Learning (NCL) is a neural network ensemble learning algorithm which introduces a correlation penalty term into the cost function of each individual network so that each neural network minimizes its mean-square-error (MSE) together with the correlation. This paper analyzes NCL in depth and observes that the NCL corresponds to training the entire ensemble as a single learning machine that only minimizes the MSE error without regularization. This insight explains that NCL is prone to overfitting the noise in the training set. The paper analyzes this problem and proposes the multiobjective regularized negative correlation learning (MRNCL) algorithm which incorporates an additional regularization term for the ensemble and uses the evolutionary multiobjective algorithm to design ensembles. In MRNCL, we define the crossover and mutation operators and adopt nondominated sorting algorithm with fitness sharing and linear rank-based fitness assignment. The experiments on synthetic data as well as real-world data sets demonstrate that MRNCL achieves better performance than NCL, especially when the noise level is non-trivial in the data set. In the experimental discussion, we give three reasons why the performance of our algorithm outperforms others.

 

An anthropogenic influence on El Nino
Mat Collins (Met Office, Exeter)
2 Dec 2008Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

Stochastic approximation of fast chaotic Hamiltonian degrees of freedom
Wolfram Just (Queen Mary, University of London)
1 Dec 2008Harrison 101 Monday 2pmApplied Mathematics
We restate the problem whether the Hamiltonian dynamics of slow variables coupled to a small number of fast chaotic degrees of freedom can be modelled by an effective stochastic differential equation. Formal perturbation expansions, involving a Markov approximation, yield a Fokker-Planck equation in the slow subspace which respects conservation of energy. A detailed numerical and analytical analysis of suitable model systems demonstrates the feasibility of obtaining drift and diffusion terms and the accuracy of the stochastic approximation on all time scales.

 

Limits of normal functions and Abel Jacobi maps
Matthew Kerr (Durham University)
27 Nov 2008Harrison 101 Thursday 3pmPure Mathematics

 

TBC
Renato Vitolo (University of Exeter)
26 Nov 2008Harrison 215 Wednesday 10amApplied Mathematics (Internal)

 

Tearfund’s Impact on MDG 7
Frank Greaves (Programme Development Adviser for Water & Sanitation at Tearfund)
25 Nov 2008Harrison 209 Tuesday 2pmInformatics RI
Tearfund is a Christian relief and development organisation, working in 40 countries worldwide through a network of some 350 partners, and through its own operational arm (the Disaster Management Team). Tearfund’s vision is to empower the local church to bring about transformational change to poor communities. It views the need for water & sanitation as a fundamental cornerstone in development, and acknowledges the effect that access to safe and sufficient water and sanitation has on livelihoods, economic well-being, health, and education. In terms of Watsan, Tearfund aspires to work with the church in making the greatest impact possible on achieving Millennium Development Goal 7, Target 10 (“By 2015, to reduce by half the proportion of people without sustainable access to safe drinking water and sanitation”). Our campaign for next year (2009) is that 6 million people will benefit from hygiene education through Tearfund programmes, and of these, by 2015, 3 million people will have improved access to safe water and sanitation facilities (ideally within 500 metres of a water source and 50m of sanitation). We also aspire to see a Global Action Plan for water and sanitation, agreed by world leaders in 2010, and fully implemented globally. This presentation will explore the distinctive Tearfund brings to relief & development in water & sanitation, and will consider: - Applying core development values of sustainability, replicability, empowerment, community-participation, holistic (whole-person) transformation. - Case studies of Watsan programmes which both exemplify and struggle with realising these values: What typifies our successes? and, What typifies our struggles? - Key approaches and concerns: - Sanitation, especially “demand-led” approaches, as opposed to “supply-driven”. - Environmental sustainability - Building partner capacity - Mainstreaming gender - Engaging in effective advocacy in Watsan.

 

Some processes relevant to sulphur-based geoengineering in the lower stratosphere
Adrian Tuck (Imperial College, London)
25 Nov 2008Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

Applications of delay differential equations in science and engineering
Thomas Erneux (Universite Libre de Bruxelles, Belgium)
24 Nov 2008Harrison 101 Monday 2pmApplied Mathematics

 

Can the stratosphere determine the extratropical circulation response to surface forcing?
Chris Fletcher (University of Toronto, Canada)
24 Nov 2008Green Island 1 Monday 11amMet Office/Hadley Centre

 

The Holm Navier-Stokes-alpha equation
Andrew Soward (University of Exeter)
19 Nov 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Multi-agent modelling and applications to robotics and cognition
Dr Aladdin Aayesh
19 Nov 2008Harrison 203 Wedensday 2pmInformatics RI
The link between emotion, cognition and behavior is well investigated in psychological and social studies. In recent years, system developers started to explore, mostly as part of agent technology and the concept of agency, cognition and its potential models that suitable for algorithmic representation, i.e. translation into programs that can work interactively in distributed environment. Emotion modeling has evolved as part of cognitive systems and been recognized as an important aspect of these systems which affects greatly reasoning on its both fronts: representation and inference. This interest in emotions and cognitive agents is helped by advances in games, simulations, and architectures for domestic devices (i.e. robots). Whilst cognitive science is applied into developing cognitive agents, cognitive agents are often used to simulate and test cognitive models and their impact on human perception and responses. The social simulation in particular (e.g. crowd simulation in games) depends on agent technology that utilize some aspect of cognition and behaviorism. Some new studies started to incorporate aspects of emotions to influence agent behavior in a group evolving into an artificial society with emergent social and collective properties, e.g. panic.

 

The Anglian Water Alliance – Modelling Experiences from AMP4 and future challenges for AMP5
James Lau (Black & Veatch)
18 Nov 2008Harrison 170 Tuesday 2pmInformatics RI
The Anglian Water Alliance is a virtual company setup to deliver the AMP4 Capital Delivery program for Anglian Water Plc. The partnership of consultants, contractors and client has formed an effective delivery vehicle focussed on delivering value and innovation. Computational modelling has played a key role in delivering appropriate and cost effective solutions for schemes with varying complexities and problems. This presentation focuses on a number of schemes where novel and innovative approaches have been used. Challenges for AMP5 will also be discussed.

 

Geoengineering stratocumulus clouds to control global warming: are the side-effects worse than the cure?
Jim Haywood (Met Office, Exeter)
18 Nov 2008Green Island 1 Tuesday 11amMet Office/Hadley Centre

 

Multifractal analysis for non-uniformly hyperbolic dynamical systems
Thomas Jordan (University of Bristol)
17 Nov 2008Harrison 101 Monday 2pmApplied Mathematics

 

Personalised Footwear: From Elite to High Street using Rapid Manufacturing
Dr Candice Majewski (Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University)
13 Nov 2008Harrison 107 Thursday 2pmAdvanced Technologies RI
Rapid Manufacturing encompasses a group of additive technologies used to fabricate end-use parts. A major advantage of this approach is the elimination of the requirement for tooling, thereby allowing production runs of N=1 whilst incurring no cost penalties. This, combined with the geometric freedom achievable with these processes, makes true personalisation of consumer products a viable option. The ~£1 million IMCRC-funded integrated project ‘Personalised Sports Footwear: From Elite to High Street’ is investigating the use of Rapid Manufacturing to produce personalised sports shoes, with the aim of enhancing performance, reducing injury, and providing improved functionality. Initially focussing on footwear for elite athletes, the ultimate goal of the project is to allow the general public to purchase fully personalised footwear at an affordable price, by replacing injection moulded outsoles with rapid manufactured alternatives.

 

Determinant functors for triangulated categories
Dr Manuel Breuning (Kings College)
13 Nov 2008Harrison 101 Thursday 3pmPure Mathematics

 

Modelling and Dynamics of coupled laser
Hartmut Erzgraber (University of Exeter)
12 Nov 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Structural similarities and differences in climate responses to CO2 increase between two perturbed physics ensembles
Tokuta Yokohata (Met Office, Exeter)
12 Nov 2008Green Island 1 Wednesday 2pmMet Office/Hadley Centre

 

Linking AHP and Social Choice Methods in Group Decision-Making
Bojan Srdjevic (University of Novi Sad, Serbia)
11 Nov 2008Harrison 170 Tuesday 2pmInformatics RI
The social choice (SC) theory is in close relation with multicriteria decision-making (MCDM), especially in group decision contexts. SC theory includes various voting systems while MCDM is represented by utility and outranking methods; among utility models, the analytic hierarchy process (AHP) is probably the most popular in group decision support. Two possible contexts in modeling decentralized decision problems in water management will be investigated. The first is based on AHP only and two group aggregation techniques. The second one assumes the AHP application in subgroups, while at a group level, aggregation is performed by the SC voting procedures. Comparative analyses show good agreement of the results when two methodologies are applied as the decision support to the water committee of given river basin. The second methodology is called AHP+SC and is considered more promising for implementation in real-decision situations in water management.

 

Heteroclinic structures in small motifs of Hodgkin-Huxley neurons? Indication from a numerical study
Thomas Nowotny (University of Sussex)
10 Nov 2008Harrison 101 Monday 2pmApplied Mathematics

 

Out of sight - out of mind - travels of a water engineer
Jo Parker
10 Nov 2008Harrison 102 Monday 1pmInformatics RI
Presenter's experiences in Afghanistan, Bosnia, Jamaica, Philippines, Indonesia and Iran focussing on buried assets, leakage detection and water quality/hygiene.

 

On the Iwasawa theory of abelian varieties over function fields
Dr Fabian Trihan (Nottingham university)
6 Nov 2008Harrison 101 Thursday 3pmPure Mathematics

 

Evidential Reasoning in Water Distribution System Operations
Josef Bicik (University of Exeter)
4 Nov 2008Harrison 170 Tuesday 2pmInformatics RI
Due to aging infrastructure, incidents (e.g. pipe bursts) in water distribution systems (WDS) occur on a daily basis and can lead to significant losses of potable water and interruption of service to customers. A method to support decision making of WDS operators in failure situations, based on information fusion using Dempster-Shafer theory of evidence, will be presented. Information coming from several sources (e.g. telemetry systems, historical records and customer contacts) is combined together to provide the operator with a better insight into the most likely location of a failure in a WDS. The method is placed within the context of a decision support system for near real-time WDS operation and its requirements and potential further developments are identified and discussed.

 

Is old better than new? - The benefits of remanufactured products to the consumer and society
M. Errington (X-MEC)
3 Nov 2008Harrison 106 Thursday 13:00Advanced Technologies RI (Internal)

 

Comparing deterministic and stochastic models for cell motility and domain growth
Ruth Baker (University of Oxford)
3 Nov 2008Harrison 101 Monday 2pmApplied Mathematics

 

Probing the temporal power-law characteristics of the global atmospheric circulation
Dmitry Vyushin (University of Toronto, Canada)
30 Oct 2008Harrison 103 Thursday 2pmApplied Mathematics
Climate variability on timescales longer than a year is often characterized by temporal scaling ("power law") behaviour for which spectral power builds up at low frequencies in contrast to red-noise behaviour for which spectral power saturates at low frequencies. We estimate temporal power-law exponents ("Hurst exponents") for the global atmospheric circulation of pre-industrial control and 20th century simulations for the troposphere and stratosphere. We consider 17 most established climate models from the CMIP3 archive. We show that current-generation climate models generally simulate the spatial distribution of the Hurst exponents well. We also use simulations of an atmospheric GCM with different climate forcings to explain the Hurst exponent distribution and to account for discrepancies in scaling behaviour between different observational products. Our analysis demonstrates that at the surface regions of large power law exponents coincide with the regions of strong decadal variability, namely northern North Atlantic, northern and tropical Pacific, and the Southern Ocean. In the free atmosphere these regions are confined to the tropical and subtropical troposphere and stratosphere. The spectral steepness in the former is explained by its strong coupling to the surface and in the later by its sensitivity to the volcanic aerosols. We conclude that this analysis of how climate models capture the falloff of spectral power with frequency provides valuable physical insight into climate variability.

 

The Manin constant of elliptic curves over function fields
Dr Ambrus Pal (Imperial College)
30 Oct 2008Harrison 101 Thursday 3pmPure Mathematics
We study the p-adic valuation of the values of normalized Hecke eigenforms attached to non-isotrivial elliptic curves defined over function fields of transcendence degree one over finite fields of characteristic p. Under certain assumptions we compute on the smallest attained valuation in terms of the minimal discriminant. As a consequence we show that the former can be arbitrarily small. We also use our results to prove for the first time the analogue of the degree conjecture unconditionally for infinite families of strong Weil curves defined over rational function fields

 

Cointegration: an econometric time-series tool applied to the carbon cycle
Tim Jupp (University of Exeter)
29 Oct 2008Harrison 101 Wednesday 10amApplied Mathematics (Internal)

 

Multi-objective league tables
Richard Everson (University of Exeter)
28 Oct 2008Harrison 170 Tuesday 2pmInformatics RI
As multi-objective optimisation methods are extended to many-objective problems, there is a need to visualise the mutually non-dominating sets produced. We present a new way of using barycentric coordinates to map a non-dominating set onto the plane for visualisation. The fidelity of the mapping is optimised by minimising the graph Laplacian of the nearest neighbour distances graph. League tables ranking, for example, universities are commonly produced by combining making a weighted sum of several measures into a score. Recognising this as a multi-objective problem, we show how to divide the universities into a series of mutually non-dominating sets -- Pareto shells -- and thus provide an unambiguous division into tiers. There are 5 shells for the scores that yield the THES 2008 university league table. We visualise the shells and examine various ways of ranking within a Pareto shell. The effect on the ranking of measurement noise in the scores is evaluated.

 

Almost Koszul algebras from quantum subgroups
Dr Barrie Cooper (Exeter University)
23 Oct 2008Harrison 101 Thursday 3pmPure Mathematics

 

Designing the dynamics of coupled oscillators
Peter Ashwin (University of Exeter)
22 Oct 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Pareto-Optimality of Cognitively Preferred Polygonal Hulls for Dot Patterns
Antony Galton (University of Exeter)
21 Oct 2008Harrison 170 Tuesday 2pmInformatics RI
In several areas of research one encounters the problem of generating an outline that is in some way representative of the spatial distribution of a pattern of dots. Several different algorithms have been published which can generate such outlines, but the detailed evaluation of such algorithms has mostly concentrated on their computational and mathematical properties, while the adequacy of the resulting outlines themselves has been left as a matter of informal human judgment. In this paper it is proposed to investigate the perceptual acceptability of outlines independently of any particular algorithm for generating them, in order to determine objective criteria for evaluating outlines from the full range of possibilities in a way that is conformable to human intuitive assessments. For the sake of definiteness it is assumed that the outline to be produced is a simple closed polygon whose vertices are elements of the given dot pattern, all remaining elements of the dot pattern being in the interior of the polygon. It is hypothesised that to produce a cognitively acceptable outline one should seek simultaneously to minimise both the area and perimeter of the polygon, and that therefore the points in area-perimeter space corresponding to cognitively optimal outlines will lie on or close to the Pareto front. A small pilot study was conducted, the results of which lend strong support to the hypothesis. The paper concludes with some suggestions for further more detailed investigations.

 

Vortices, waves and numerical schemes for mesoscale atmospheric dynamics
Peter Bartello (McGill University, Montreal, Canada)
20 Oct 2008Harrison 101 Monday 2pmApplied Mathematics
An overview of recent research on the wave/vortex dynamics of the mesoscale range of the atmospheric energy spectrum will be presented. The presence or absence of these dynamics in a variety of "realistic" models will also be discussed. A few of these reproduce the correct spectrum while most do not. It is argued that this may be attributed to their numerics and/or parameterisation schemes.

 

Flood rich periods and flood poor periods in the UK's hydrological record - a new way of thinking through 21st century flood risk?
Stuart Lane (University of Durham)
20 Oct 2008Harrison 106 Monday 2pmApplied Mathematics

 

Multiple materials patterning using novel a dry powder printer
Dr. Shoufeng Yang (Queen Mary, University of London)
16 Oct 2008Harrison 107 Thursday 2pmAdvanced Technologies RI
The creation of three dimensional functional gradients by powder processing methods requires the capability to arrange a sequence of two dimensional colour images that can be presented to a solid freeforming device. Planar stacking methods can only achieve a one dimensional gradient. We describe the acoustic control of powder metering and dispensing valves in which the flow rate and switching of powders from a capillary can be controlled using the frequency and amplitude of acoustic vibration from a computer sound card. An orchestra of such valves can be used to pattern layers of powder on the building platform which forms part of a 3-axis table.

 

Algebraic surfaces and hyperbolic geometry
Prof. Burt Totaro (Cambridge university)
16 Oct 2008Harrison 101 Thursday 3pmPure Mathematics
The intersection form among curves on a complex algebraic surface always has signature (1,n) for some n. So the automorphism group of an algebraic surface always acts on hyperbolic (n-1)-space. For a class of surfaces including K3 surfaces and many rational surfaces, there is a close connection between the properties of the variety and the corresponding group acting on hyperbolic space

 

Small Gain Theorems and Feedback Loops - Can They Really Be Relevant in Modelling Endangered Plants?
Stuart Townley (University of Exeter)
15 Oct 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Urban Water Optioneering Tool
Evangelos Rozos (University of Exeter)
14 Oct 2008Harrison 209 Tuesday 2pmInformatics RI
UWOT is a decision support tool that simulates the urban water cycle by modelling individual units (e.g. toilets, washing machines, treatment units, tanks, reservoirs) and assessing their combined effects at the development scale. UWOT simulates not only the standard urban water flows (potable water, wastewater and runoff) but also the water flows (greywater, treated greywater or greenwater – including harvested rainwater) introduced by the advanced water saving and recycling schemes. A hierarchical structure is adopted for the representation of the development water features. The local appliances are at the bottom level of the hierarchy, on a higher level is the household type and at the top level is the development. UWOT is linked with a database that contains information over the major characteristics of each technological category. The selection of technologies for a given urban water cycle configuration may be done manually by the user or may be done automatically by an optimisation algorithm.

 

Agent-based modelling and optimisation
Dr O.M. Akanle
13 Oct 2008Harrison 107 Thursday 13:00Advanced Technologies RI (Internal)

 

A lattice Boltzmann formulation for magnetohydrodynamics with current-dependent resistivity
Paul Dellar (University of Oxford)
13 Oct 2008Harrison 101 Monday 2pmApplied Mathematics

 

Rational points of definable sets and diophantine problems
Dr. Jonhatan Pila (Bristol University)
9 Oct 2008Harrison 101 Thursday 3pmPure Mathematics
I will discuss problems and results concerning the distribution of rational points on algebraic and, mainly, certain non-algebraic sets in $\RR^n$. More specifically, definable sets in o-minimal structures. I will describe a result, joint with Wilkie, that such a set $X$ can have only ``few'' rational points, in a density sense, that do not lie on some positive dimensional connected semi-algebraic subset of $X$.I will give some applications to problems of Andre-Oort-Manin-Mumford type, including a new proof, joint with Zannier, of the Manin-Mumford conjecture, and some variant special cases of results of Andre-Oort and mixed Andre-Oort-Manin-Mumford type.

 

Rational points of definable sets and diophantine problems
Dr. Jonhatan Pila (Bristol University)
9 Oct 2008Harrison 101 Thursday 3pmPure Mathematics
I will discuss problems and results concerning the distribution of rational points on algebraic and, mainly, certain non-algebraic sets in $\RR^n$. More specifically, definable sets in o-minimal structures. I will describe a result, joint with Wilkie, that such a set $X$ can have only ``few'' rational points, in a density sense, that do not lie on some positive dimensional connected semi-algebraic subset of $X$.I will give some applications to problems of Andre-Oort-Manin-Mumford type, including a new proof, joint with Zannier, of the Manin-Mumford conjecture, and some variant special cases of results of Andre-Oort and mixed Andre-Oort-Manin-Mumford type.

 

Astrophysical applications of self-similar flows
Yu-Qing Lou (Tsinghua University, China)
6 Oct 2008Harrison 101 Monday 2pmApplied Mathematics
17th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal 'Geophysical and Astrophysical Fluid Dynamics' *** Astrophysical research activities at Tsinghua University China are briefly described. We present new results on self-similar hydrodynamics and magnetohydrodynamics under self-gravity. Astrophysical applications include star formation, planetary nebulae, stellar collapses, rebound shocks of supernovae, galactic bulge evolution and so forth. We also describe astrophysical voids in self-similar expansion.

 

The Severn Barrage and Other Options - the Environmental Impact
Prof Roger Falconer (Cardiff University)
3 Jul 2008Harrison 171 Thursday 4pmInformatics RI
In recent years there has been growing international public concern about climate change, global warming, reducing the carbon footprint, increasing oil prices and the rapid depletion of oil reserves. These issues, as well as others, have led to renewed enthusiasm to consider proceeding with the Severn Barrage, either in the original location proposed by the Severn Tidal Power Group, or at a smaller scale such as the Shoots Barrage. In particular, the Sustainable Development Commission concluded in its 2007 report on ‘Turning the Tide: Tidal Power in the U.K.’ that ‘Electricity from a barrage would displace output from fossil-fuelled power stations, making a significant contribution to the UK’s renewable energy targets’. As well as the Severn Barrage there is considerable scope for various forms of tidal renewable energy along the Severn Estuary, as well as the North Wales coast and much of Scotland. The presentation will review the current main Severn Barrage proposals, as originally promoted by the Severn Tidal Power Group, together with giving a brief overview of alternative options such as the Shoots Barrage and Offshore Tidal Impoundments. In particular, emphasis will focus on assessing the potential hydro-environmental impact of a barrage, including the implications for geomorphological and flood risk changes. Finally, an outline will be given of recent research undertaken by the Hydro-environmental Research Centre, at Cardiff University, on bacterial-sediment interactions and the application of computational hydro-environmental models to predict the impacts of a Severn Barrage on the tidal currents, sediment transport concentrations and the background bacterial and water quality levels. The presentation will show that the Barrage has the potential to reduce the tidal currents in a highly dynamic estuary. This will lead to reduced suspended sediment loads (particularly upstream of the barrage), increased light penetration within the water column and, potentially, an increase in the benthic bio-diversity and the level of aquatic life in the estuary.

 

Reconciling an emissions model with a climate change model
Peter Cox and Owen Kellie-Smith (University of Exeter)
13 Jun 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Some climate models take (as inputs or control variables) scenarios of future greenhouse gas emissions and output measures of climate change. The altered climate does not necessarily feed back into the emission scenarios. This work-in-progress aims to identify the space of feasible emission scenarios, via a highly simplified economic model in which emissions are fed back as a model output.

 

Singapore Membrane Technology Centre, NTU UNESCO Centre for Membrane Science & Technology, UNSW
Tony Fane (University of Oxford)
12 Jun 2008Harrison 171 Thursday 4pmInformatics RI
Membrane technologies are now key processes in the water industry. This presentation briefly introduces the various membrane technologies and their historical development as well as trends in costs and energy usage. The potential benefits of membranes are discussed and their roles in water supply, desalination, water reclamation and wastewater treatment are described in terms of state-of-the-art, and emerging novel concepts. Singapore provides an interesting case study of how membrane technology can be used in the water cycle. The application of membranes to decentralization is also attractive. Finally the challenges facing membrane technology, including product water quality issues, energy usage and GHG emissions, are discussed.

 

Low Impact Urban Design and Development
Jeremy Gabe (Landcare Research)
10 Jun 2008Harrison 107 Tuesday 12pmInformatics RI
The talk is about the results of current research in New Zealand, mostly on issues related to sustainable urban development (low impact urban design and development).

 

TBA
M.L. Wears (SECaM)
9 Jun 2008Harrison 209 Thursday 13:00Advanced Technologies RI (Internal)
TBA

 

Determining Convergence Rates: Order of Accuracy vs Function Continuity.
Dan Holdaway (University of Exeter)
30 May 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
The relation between order of accuracy and convergence rate for simple linear finite difference schemes for differentiation and advection is examined theoretically and empirically. When a function is sufficiently smooth convergence will be given by the order of accuracy of the scheme. For less smooth functions convergence rate for differentiation can be determined from the function's spectral slope. Convergence for advection of a non smooth function involves an interaction between order of accuracy and spectral slope.

 

Dynamics of aircraft on the ground
Bernd Krauskopf (University of Bristol)
29 May 2008Harrison 170 Thursday 2pmApplied Mathematics

 

Systematic strategies for stochastic modelling of climate variability
Christian Franzke (British Antarctic Survey, Cambridge)
19 May 2008Harrison 203 Monday 2pmApplied Mathematics
The climate system has a wide range of time scales for important physical processes, ranging from organized synoptic scale weather systems on a daily time scale, extra-tropical low-frequency variability on a time scale of 10 days to months, to decadal time scales of the coupled atmosphere-ocean system. An understanding of the processes acting on these different time scales is important since all these processes interact with each other due to the nonlinearities in the governing equations. The spatial structure of extra-tropical variability can be described by only a few teleconnection patterns. The two most prominent examples are the North Atlantic Oscillation (NAO) and the Pacific-North American (PNA) pattern. These teleconnection patterns explain a large amount of the total variability, have a strong impact on surface climate and are related to climate change. In atmosphere-ocean science, slowly evolving large-scale structures like the NAO and PNA, and their statistical behavior, are often of the most interest, and yet the computational power of complex climate models is spent on resolving the smallest and fastest variables in the system. Reduced models for only the most important teleconnection patterns provide computationally feasible alternatives for calculating the statistical behavior of the climatologically relevant slow variables. These reduced models give also insight into the dynamics of the slow variables and their interaction with the unresolved variables. In these reduced models the fast variables are systematically represented by stochastic processes. In my presentation I will discuss systematic strategies to extract reduced stochastic models from data of complex atmospheric circulation models. The stochastic mode reduction strategy accounts systematically for the effect of the unresolved degrees of freedom and predicts the functional form of the effective reduced equations. These procedures extend beyond simple Langevin equations with additive noise by predicting nonlinear effective equations with both additive and multiplicative (state-dependent) noises. The stochastic mode reduction strategy predicts rigorously closed form stochastic models for the slow variables in the limit of infinite separation of time-scales. Even though there is only a very moderate time-scale separation in the atmospheric flows the reduced stochastic models reproduce well the statistics of the complex circulation models. The reduced models have about 10 or less degress of freedom while the complex atmospheirc models have about 1000 degress of freedom.

 

Cancelled
Professor Miranda (Plymouth University)
15 May 2008Harrison 170 Cancelled 2pmInformatics RI
Cancelled

 

The phase relation between poloidal and toroidal magnetic fields in latitude and longitude observed in the cycles 22-23
Valentina Zharkova (University of Bradford)
12 May 2008Harrison 203 Monday 2pmApplied Mathematics

 

Numerical wave propagation on the Hexagonal C-Grid
John Thuburn (University of Exeter)
9 May 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Additive Layer Manufacturing of Aerospace Components
Danel Johns (UK Airbus Ltd)
8 May 2008Harrison 209 Thursady 2PMAdvanced Technologies RI

 

TBA
Ingo Fischer (Heriot-Watt University, Edinburgh)
8 May 2008Harrison 170 Thursday 2pmApplied Mathematics

 

Treating Uncertainties in the Real-world Scheduling
Prof. Sanja Petrovic's (University of Nottingham)
8 May 2008Harrison 171 Thursday 4pmInformatics RI
Scheduling represents a major issue in modern production planning and control. Ever since the first results of deterministic scheduling theory appeared around 50 years ago, scheduling research has attracted a lot of attention from both academia and industry. Consequently, the scheduling literature is very rich. However, majority of scheduling models and algorithms assume that all parameters are well-known and precisely defined. However, this is rarely the case in real-world problems where activities are often fraught with uncertainties. This often prevents the results of deterministic scheduling theory from being applied in practice. This talk will introduce a number of real-world scheduling problems and uncertainties that they face. Three ways of using fuzzy sets in scheduling problems will be discussed: (a) in modelling of uncertain scheduling parameters and constraints, (b) in multicriteria decision making in which satisfaction grades of each of the criteria defined to evaluate the quality of the schedules are introduced, and (c) in the rules that schedulers use to draw conclusions based on imprecise premises. Some new directions in raising the level of generality of scheduling algorithms that work well over a range of scheduling problems will be discussed.

 

Eigenvarieties and p-adic Banach spaces
Richard Hill (University College, London)
8 May 2008Harrison 106 Thursday 3pmPure Mathematics

 

Rheological characterisation of a commercial glass poly(vinylphosphonate) cement
P. Brookbanks (SECaM)
7 May 2008Harrison 170 Wednesday 13:00Advanced Technologies RI (Internal)
: It has been shown that the working and setting properties of traditional glass ionomer cements (GICs) are affected by the cement mixing time. The aim of this study was to explore the effects of mixing time on the working and setting time of a commercially-available glass poly(vinylphosphonate) cement which differs from traditional GICs in that it is based on a co-polymer of vinyl phosphonic acid and polyacrylic acid. The working and initial setting time of GICs when using an oscillating rheometer have previously been defined by Wilson and Nicholson. Working time is defined as the time taken for the displacement to reach 95% of the initial displacement value and the initial setting time is when the displacement reaches <5% of the initial displacement value.

 

Industrial practices and research potential for reverse logistics systems
Dr Qu Tang (Department of Management and Engineering, Linkoping University, Sweden)
1 May 2008Harrison 209 Thursady 1pmAdvanced Technologies RI

 

Integral Points on Curves of Higher Genus
Samir Siksek (Warwick)
1 May 2008Harrison 106 Thursday 3pmPure Mathematics
For many curves of higher genus, Baker's Theory provides (astronomical) bounds for the size of integral points. I explain how to combine Baker's bounds with the Mordell-Weil sieve to compute all the integral points on some curves of higher genus. This is based on joint work with Bugeaud, Mignotte, Stoll and Tengely.

 

Using the past to predict the future: what can we learn from 20th century and last millennium temperature changes?
Gabi Hegerl (University of Edinburgh)
28 Apr 2008Harrison 203 Monday 2pmApplied Mathematics
16th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal 'Geophysical and Astrophysical Fluid Dynamics'

 

An Approach to Machine Musicianship
Marcelo Gimenes (Plymouth University)
24 Apr 2008Harrison 171 Thursday 4pmInformatics RI
Marcelo Gimenes investigates the genesis and development of musical styles in artificial worlds. He developed a real-time computer musical system, iMe (Interactive Musical Environments) with which it is possible to observe a number of processes regarding musical perception and cognition and to evaluate how musical influence can lead to particular musical world views. The system has successfully been used in a real performance of a two piano improvisation piece, one of which played by an artificial agent. This experiment allowed the observation of a unique musical experience, connecting the human previous musical background to the complexities of an enhanced human/ machine dialogue

 

Urban Drainage Modelling in Thames Water
Andrew Hagger (Thames Water)
17 Apr 2008Harrison 171 Thursday 4pmInformatics RI
TBA

 

Image based simulation of large strain deformation of open celled foams.
B. Notarberardino (SECaM)
1 Apr 2008Harrison 170 Tuesday 13:00Advanced Technologies RI (Internal)
Open celled foams are used in industrial applications, (e.g. seating, helmets, space vehicles) as well as commonly found in natural structures (e.g. bone, plant stalks, corals). Analytical models and experimental tests have been carried out by a number of material scientists to gain an understanding of the influence the complex relationship between the parent material properties and the architecture of the foam has on the resultant effective physical properties. Computational modelling offers the prospect of providing a deeper understanding than experimental tests of the mechanisms at work during deformation and more realistic model results than can be achieved via analytical approaches. However the difficulty of meshing the complex topologies of foam micro-architectures has proved, until recently, a barrier to effectively using the most popular of physics based simulation techniques for mechanical characterisation: the finite element method. In the present study, for the first time, a new image based meshing approach ScanFE is used to obtain geometrically and topologically accurate finite element meshes of open celled foams based on 3D imaging data. The finite element models were used in an explicit code, LS-DYNA®, to characterise the quasi-static through to dynamic stress-strain behaviour of the materials for various compression velocities and for both linear elastic and elasto-plastic material properties from small strains right through to strains well into the compaction regime. Both end-plate contacts and general foam to foam contact of the cell walls with sliding were modelled.

 

Multi-objective Ant Colony Optimisation: A Meta-heuristic Approach to Supply Chain Design
L. Moncayo (SECaM)
17 Mar 2008Harrison 203 Thursday 13:00Advanced Technologies RI (Internal)
This paper proposes a new approach to determining the supply chain (SC) design for a product mix comprising complex hierarchies of subassemblies and components. For the supply chains considered, there may be multiple suppliers that could supply the same components as well as optional manufacturing plants that could assemble the subassemblies and the products. Each of these options is differentiated by its lead time and cost. Given all the possible options the supply chain design problem is to select the options that minimise the total cost while keeping the total lead time within required delivery due dates. This work introduces Pareto Ant Colony Optimisation as an especially effective meta-heuristic for solving the problem of SC Design. A number of ant colonies generate a Pareto Optimal Set of SC Designs in which only the non dominated SC designs allow ants to deposit pheromones over the time and cost pheromone matrices. An experimental example is used to test the algorithm and show the benefits of utilising two pheromone matrices and multiple ant colonies in SC optimisation problem.

 

Modelling the atmospheric boundary layer
Bob Beare (University of Exeter)
14 Mar 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

The atmospheric boundary layer is the turbulent layer above the Earth's surface with a thickness between 100m and 2km. It is responsible for exchange of momentum, heat and moisture between the surface and the free atmosphere, so is an important component of the climate system.

This talk describes simulations of the atmospheric boundary layer as it changes from it's weak turbulence state at night to its strong turbulence in the day. The mixed phase state between the night and day time turbulence is defined more precisely than before and is shown to scale strongly with wind shear.

 

KALYPSO – An Open Source Software Tool for Flood Studies in Rivers
Professor Erik Pasche (Hamburg University of Technology)
13 Mar 2008Harrison 171 Thursday 4pmInformatics RI
As a result of climate change, urbanization and land-use changes, floods are becoming more frequent and causing increased loss and damage to property and life. The EU water policy reacted with a paradigm change in its water policy from blocking off flood prone areas (with dikes and walls) to give water more space and live with the flood. The consequence is the need to expand the relationship between the city, space and water and to improve stake-holders’ capacity to adapt to flood risk. These new guidelines for flood management require a good understanding about the impact of river morphology and anthropogenic changes on the flow regime in rivers and on the probability of inundation. Research Activities in the last dec-ades have considerably improved this understanding leading to sophisticated mathematical fluvial flow models. They range from 1-dimensional unsteady flow models to 2- and 3-dimensional hydrodynamic models, which make use of refined roughness concepts and turbu-lence approaches and accomplish a high resolution of the topography. The engineering world should have access to theses instruments in a most flexible and effi-cient way being able to combine 1- and 2-dimensional models (hybrid modeling), to select refined roughness concepts for vegetated flood plains (physically based roughness modeling) and to compare different turbulence approaches. Also the enormous amount of geographical data calls for an efficient and versatile data management and visualization tool. Thus present research concentrates more on model integration and data mining than model generation. Since two years a team of researchers at the Institute of River & Coastal Engineering at TUHH/Hamburg together with engineers from Björnsen Consulting Engineers Koblenz have developed such an integration shell for fluvial flow modelling called KALYPSO (www.kalypso.wb.tu-harburg.de). This Open Source software system for flood risk modelling is based on OGC-standards (www.opengeospaial.org) and provides an Open GIS user inter-face for map-based data access and input. A Web Map Service (WMS) based on an imple-mentation of the Open Source software deegree (www.deegree.org) provides access to GIS-data via Internet. With a work flow browser the user is guided through the tasks of flood modelling in a logical order including various tools for grid generation and boundary data management (pre-processing), for defining and starting the simulation cases (processing) and for analysing and visualization of the simulation results in inundation maps, flood damage maps and flood risk maps (post-processing). For the modelling of fluvial flow hybrid model-ling technique is available integrating 1- and 2-dimensional discretization elements and St. Venant and Shallow Water Equations. This new modelling shell for fluvial floods will be presented and its theoretical concept illus-trated. The hybrid modelling technology, the data mining functionality and the open GIS-based GUI will be explained and its application demonstrated at real cases of fluvial floods

 

Modular forms and Galois representations over imaginary quadratic fields
Tobias Berger (Cambridge)
13 Mar 2008Harrison 106 Thursday 3pmPure Mathematics
In joint work with Gergely Harcos I strengthened a result of Taylor on associating Galois representations to cuspforms over imaginary quadratic fields. I further present a result (joint with Kris Klosin) on the modularity of ordinary, residually reducible Galois representations of imaginary quadratic fields.

 

Stability of rolls in rotating magnetoconvection with physically realistic boundary conditions
Olga Podvigina (Russian Academy of Sciences, Moscow, Russia)
12 Mar 2008Harrison 173 Wednesday 11amApplied Mathematics
15th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal 'Geophysical and Astrophysical Fluid Dynamics' *** We consider small amplitude Boussinesq convection in a horizontal layer rotating about a vertical axis with an imposed vertical magnetic field. Rigid electrically insulating no slip horizontal boundaries held at constant temperature are assumed. Depending on parameter values, convection at the onset can be steady or oscillatory. For the steady onset of convection rolls can emerge in a supercritical or subcritical bifurcation of the trivial steady state, and they can be unstable with respect to the same rolls flow rotated by an arbitrary angle. We study, for which parameter values convection at the onset is steady or oscillatory, and how stability of small amplitude rolls depends on the parameters.

 

My Evil Determinant Problem
Robin Chapman (University of Exeter)
11 Mar 2008Harrison 103 Tuesday 9amPure Mathematics (Internal)

 

Optimization of ergodic averages
Oliver Jenkinson (Queen Mary, University of London)
10 Mar 2008Harrison 209 Monday 2pmApplied Mathematics

 

Mean-field equations for weakly non-linear two-scale perturbations of forced hydromagnetic convection in a rotating layer
Vladislav Zheligovsky (Russian Academy of Sciences, Moscow, Russia)
10 Mar 2008Harrison 203 Monday 11amApplied Mathematics
14th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal 'Geophysical and Astrophysical Fluid Dynamics' *** We consider stability of regimes of hydromagnetic thermal convection in a rotating horizontal layer with free electrically conducting boundaries, to perturbations involving large spatial and temporal scales. Equations governing the evolution of weakly non-linear mean perturbations are derived under the assumption that the alpha-effect is insignificant in the leading order (e.g., due to a symmetry of the system). The mean-field equations generalise the standard equations of hydromagnetic convection: New terms emerge - a second-order linear operator representing the combined eddy diffusivity, and quadratic terms associated with the eddy advection. If the perturbed CHM regime is non-steady and insignificance of the alpha-effect in the system does not rely on the presence of a spatial symmetry, the combined eddy diffusivity operator also involves a non-local pseudodifferential operator. If the perturbed CHM state is almost symmetric, alpha-effect terms appear in the mean-field equations as well. Near a point of a symmetry-breaking bifurcation, cubic nonlinearity emerges. All the new terms are in general anisotropic.

 

Convection in rotating cylinders: asymptotic theory and numerical simulations
Keke Zhang (University of Exeter)
7 Mar 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Forecasting complex systems: it's about dynamics, it's not about statistics
Kevin Judd (University of Western Australia, Perth, Australia)
6 Mar 2008Laver 320 Thursday 12.00Applied Mathematics
In 1963 Edward Lorenz published a paper that changed the way scientists think about the prediction of geophysical systems. Two years earlier, Rudolf Kalman had published a paper that changed the way engineers thought about prediction of electronic and mechanical systems. In recent years geophysicists have become increasingly interested in Kalman filters, where as engineers have become increasingly interested in chaos. I will argue that prediction of complex systems like the weather has more to do with nonlinear dynamics than it has to do with linear statistics. A position with which I think both Lorenz and Kalman would likely agree. I will attempt to show why attractors, shadowing trajectories, nonlinear filters, optimal control, and other concepts from nonlinear dynamics are important in weather prediction, by first illustrating the ideas with Lorenz's 1963 example of a chaotic system, then confirming these results by experiments with an operational weather forecasting model.

 

Fundamental groups of hyperbolic curves and the principle of Birch and Swinnerton-Dyer
Minhyong Kim (University College, London)
6 Mar 2008Harrison 106 Thursday 3pmPure Mathematics

 

period domains, modular forms and lattices
Dr Gregory Sankaran (Bath University)
5 Mar 2008Harrison 101 Thursday 3pmPure Mathematics

 

Hopf-Galois Module Structure of Tame Extensions of Prime Power Degree
Paul Truman (University of Exeter)
4 Mar 2008Harrison 103 Tuesday 9amPure Mathematics (Internal)
A major result in local Galois module theory is Noether's Theorem, that given a finite Galois extension of local fields L/K, the ring of integers OL is free over the integral group ring OK[G] if and only L/K is at most tamely ramified. In Hopf-Galois module theory, the Galois group is replaced by a (possibly non-unique) Hopf algebra, giving a so-called Hopf-Galois structure on the extension, and the behaviour of OL in this Hopf-Galois structure is studied. We present a generalisation of Noether's Thereom to this setting for Galois extensions of prime power degree.

 

Revealing the ghost in the machine: noise and population dynamics
Tim Benton (University of Leeds)
3 Mar 2008Harrison 101 Monday 2pmApplied Mathematics

 

A dwell-time approach to the stability of switched linear systems
Özkan Karabacak (University of Exeter)
29 Feb 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Switched linear systems arise as examples or generalizations of hybrid systems, especially in control engineering. A switched system consists of a family of different subsytems and a set of signals that controls the switching between these subsystems. In this talk switched linear systems and its stability problems will be introduced in general. One of these, namely, finding a sufficient condition on the minimum dwell time of the switching signal that guarantees the stability of switched linear systems will be considered and a new approach to this problem will be presented. The proposed method interprets the stability of switched linear systems through the distance between the eigenvector sets of subsystem matrices. Thus, an explicit relation in view of stability is obtained between the family of the involved subsytems and the set of admissible switching signals.

 

Zeeman's nerve impulse model
Martin Krupa (New Mexico State University, Las Cruces, NM, USA)
28 Feb 2008Newman D Thursday 2pmApplied Mathematics
In early 1970's E.C. Zeeman proposed a three dimensional model of the dynamics of a neuron. The model is a slow/fast ODE with one fast variable and two slow ones and is a caricature of the Hodgking-Huxley equation. In this talk we analyze the model of Zeeman using methods of geometric singular perturbation theory and blow-up, veryfying the numerical predictions of the dynamics of the model. As a part of the analysis we discuss the dynamics near a singularly perturbed cusp.

 

Water Distribution System Modelling and Calibration
Daniel Kozelj (University of Ljubljana)
28 Feb 2008Harrison 171 Thursday 4pmInformatics RI
The seminar will present the Slovenian experience on water distribution system modelling together with the fields of calibration, sampling design and optimisation. An overview will be given on the aforementioned issues and project results will be presented. The projects presented will include: (1) Calibration of a WDS model by Genetic Algorithms (part of Ljubljana WDS – 35,000 inhabitants), (2) Sampling Design for Calibration of WDS by GA (Sezana – 11,000 inhabitants), (3) Rehabilitation of a WDS by GA (Logatec – 11,000 inhabitants) and (5) Experiences of modelling WDS and macrocalibration (Skofja Loka – 22,000 inhabitants and Celje – 65,000 inhabitants). Finally, the role of the tools in facilitating these processes will be discussed based on the findings of the real life applications.

 

Arithmetic properties for partitions with non-repeating odd parts
James Sellers (Pennsylvania State)
28 Feb 2008Harrison 106 Thursday 3pmPure Mathematics

 

Some examples of local Galois module structure in characteristic 0 and characteristic $p$.
Nigel Byott (University of Exeter)
26 Feb 2008Harrison 103 Tuesday 9amPure Mathematics (Internal)
Let $L/K$ be a totally ramified abelian extension of local fields, with Galois group $G$. A basic question in Galois module structure is to determine when the valuation ring $S$ of $L$ is a free module over its associated order in the group algebra $K[G]$. When $K$ is a finite extension of $\mathbb{Q}_p$ (the characteristic $0$ case), Y.~Miyata has given a freeness criterion for a large family of {\em cyclic} extensions of degree $p^n$. In this talk, I will give an alternative formulation of Miyata's criterion, and will present work in progress (joint with Griff Elder), where the same freeness criterion arises for {\em elementary abelian} extensions of the field $K=\mathbb{F}_q((T))$ of formal Laurent series over a finite field (the characteristic $p$ case).

 

Magneto-seismology of the solar atmosphere: does really wag the tail the dog?
Robert Erdelyi (University of Sheffield)
25 Feb 2008Harrison 209 Monday 2pmApplied Mathematics

 

Magnetic fields in star formation
Daniel Price (University of Exeter)
22 Feb 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Magnetic fields are observed in sufficient strengths to be important at every stage of the star formation process, from the dynamics of the interstellar medium in galaxies, in turbulent molecular clouds and in individual star forming cores. I will discuss our attempts to incorporate magnetic fields into numerical simulations of the fragmentation of dense cores and of star cluster formation from turbulent initial conditions using a Smoothed Particle Magnetohydrodynamics algorithm.

 

Growth in linear algebraic groups: an approach through incidence
Harald Helfgott (Bristol)
21 Feb 2008Harrison 106 Thursday 3pmPure Mathematics
Let K be R, C or a Z/pZ. Let G = SL_2(K). Not long ago, I proved the following theorem: for every subset A of G that is not contained in a proper subgroup, the set A\cdot A\cdot A is much larger than A. A generalisation to groups of higher rank was desired by many, but seemed hard to obtain. I shall now present a proof somewhat different from the first one. The role of both linearity and the group structure of G should now be clearer. A few ideas towards a generalisation will be discussed, with a focus on the case of SL_3(Z/pZ).

 

WDS Pressure Management for Water Loss Reduction: State of the Art
Julian Thornton (Thornton International Ltd.)
19 Feb 2008Harrison 215 Tuesday 4pmInformatics RI
Water distribution system pressure management encompasses several approaches and has a number of important benefits; it has been referred to as “the preventative method par excellence” of water loss management. Changes in leak flow rates and some components of consumption are now reasonably predictable however there has been little published data as to how improved management of excess pressures and surges can influence new break frequency of mains and services. This discussion will encompass the types of pressure management utilized in the industry today, how to assess potential volume benefits from pressure management and the challenge which lies ahead to improve the industry understanding of how to assess pressure break frequency relationships. Several case studies will be cited during the discussion.

 

On The Rank of Classgroups of Quadratic Function Fields
Andreas Schwiezer (University of Exeter)
19 Feb 2008Harrison 103 Tuesday 9amPure Mathematics (Internal)

 

Estimation of the correlation decay rate for chaotic intermittency maps
David Natsios (University of Liverpool)
18 Feb 2008Harrison 203 Monday 11amApplied Mathematics
Chaotic intermittency maps give a non-linear, non-Gaussian method of generating long memory time series. In particular we study the symmetric cusp map, the asymmetric cusp map, polynomial maps and logarithmic maps. In previous studies by Bhansali and Holland, it has been shown that these maps can simulate stationary time series with a full range of values for the long memory parameter, including d = 0.5 which is usually considered non-stationary, d = 0 which is usually considered short memory and d < 0 which is usually intermediate memory. This gives us the opportunity to carry out a simulation study to investigate the robustness of various long memory estimation techniques in extreme cases and when the assumptions of linearity and Gaussian distribution no longer hold. We show that standard methods can give large bias and we introduce an extended dual parameter long memory model, which includes the standard one-parameter fractional difference model as a special case and also accommodates a boundary behaviour of the type not admissible in the standard model. We also consider extensions of the chaotic intermittency maps, including stochastic versions and a bivariate version of the polynomial map. Our dual parameter methods of long memory parameter estimation are once again compared to standard methods and methods of distinguishing between the stochastic maps are introduced.

 

Machine learning in astronomy: time delay estimation in gravitational lensing
Peter Tino (University of Birmingham)
18 Feb 2008Harrison 209 Monday 2pmApplied Mathematics
A ray of light (or any other form of electromagnetic radiation, e.g. radio or x-rays) travels along a geodesic, which could be locally curved due to the gravitational effect of clumps of matter like stars or galaxies. This is known as gravitational lensing. Gravitational lensing, caused by intervening matter along the line of sight, can give rise to interesting cosmic illusions like magnified and seriously distorted images of distant sources, sometimes splitting into multiple images. Since the distortion of the images depends on the distribution of matter in the lensing object, this is the most direct method of measuring matter (which is often dark) in the Universe. Quasar Q0957+561, an ultra-bright galaxy with a super massive central black hole was the first lensed source to be discovered and it is the most studied so far. Gravitational lens creates two distinct images of Q0957+561. We attempt to recover the phase shift in the 2 lensed images of Q0957+561 using a model based approach formulated within the framework of kernel regression. In a set of controlled experiments emulating presence of realistic observational gaps, irregular observation times and noisy observations, we compare our method with other state-of-art statistical methods currently used in astrophysics. We then apply the method to actual observations doubly imaged quasar Q0957+561 at several radio and optical frequencies.

 

Nanoflares in the solar corona
Mitchell Berger (University of Exeter)
15 Feb 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

Solar flares are magnetic storms in the sun's atmosphere. The distribution of flare energies is a power law over several orders of magnitude. The smallest flares (nanoflares) may be responsible for heating the coronal plasma to over a million degrees. The nature of nanoflares is unknown, as they are below observational resolution. In the 1980s Parker suggested that nanoflares occur when braided magnetic flux tubes reconnect. This talk gives a model of flux tube braiding and reconnection similar to self-organized forest fire models, with a power law energy distribution.

 

Can Metallurgy Have a New Life?
Professor Z Fan (BCAST (Brunel Centre for Advanced Solidification Technology))
14 Feb 2008Harrison 215 Thursday 2pmAdvanced Technologies RI
Metallurgy, as a black art, has made marks on every single step of human civilization. Today, metallic materials have become the backbone of any nation’s economy. The global metals production is over 2 billion tonnes per annual. However, metallurgy as a research subject appears to be saturated, no major or exiting development; metallurgy as an industry is regarded as “sun-setting”; metallurgy as an educational subject cannot attract enough interests for young kids to sign in as metallurgical students. The overall picture for metallurgy is indeed very gloomy. In this presentation, I will take snap shots in the metallurgical history to examine critically the causes of the current problems. Possible solutions to such problems will then be presented in terms of new research directions, industrial reorganisation and new strategies for sustainable exploitation of natural resources. Some examples will be drawn from our own research to illustrate such new directions and new strategies.

 

Water & Sewerage Capital Maintenance Risk Modelling
Nathan Muggeridge, and Mark Randall-Smith (Mouchel Parkman)
14 Feb 2008Harrison 170 Tuesday 4pmInformatics RI
The Water Companies are required to prepare Asset Management Plans (AMP) every 5 year and these determine the level of charges for water and sewerage services. The Asset Management Plan for the period between 2010 and 2015 is currently being prepared and OFWAT, the water industry Regulator, requires the capital maintenance elements of the plans to adopt a risk-based approach. This presentation provides an insight into the preparation of an Asset Management Plan for water and sewerage infrastructure, and demonstrates the role of research in the development of the plans. It will also highlight some of the current problems with implementing a risk-based approach to capital maintenance.

 

Semi-stable models of modular curves
Adam Joyce (Bristol)
14 Feb 2008Harrison 106 Thursday 3pmPure Mathematics

 

Bayesian learning from the last glacial maximum on climate sensitivity
Hermann Held (Potsdam Institute for Climate Impact Research, Potsdam, Germany)
11 Feb 2008Harrison 209 Monday 2pmApplied Mathematics
13th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal 'Geophysical and Astrophysical Fluid Dynamics'

 

The Impenetrable Hedge – some thoughts on propriety, equitability and consistency
Ian Jolliffe (University of Exeter)
8 Feb 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

In weather and climate forecasting, hedging is said to occur whenever a forecaster’s judgment and forecast differ, and it is usually taken as evident that hedging is undesirable. Forecasts are often judged by computing a verification measure or score. A number of different scores are available in most circumstances, and to choose between them, various desirable properties of scores have been defined.

Three ‘desirable’ properties of scores are linked to the idea that hedging should be avoided, namely propriety, equitability and consistency. It is fair to say that none of these properties is fully understood.

This talk will provide some clarification and new insights, as well as some historical background. Nearly as many questions are raised as are answered.

 

Low Energy and Sustainable Cooling of Underground Railway Systems
Jolyon Thompson (Research Engineer - Cooling the Tube Programme)
7 Feb 2008Harrison 170 Tuesday 4pmInformatics RI
Underground railway system usage is growing throughout the developing world and in many cities the underground railway is the most commonly used form of public transport. The intense service provided on these systems generates substantial quantities of rejected heat energy. This energy can significantly increase air temperatures within the trains and tunnels. When coupled to high ambient temperatures this can lead to passenger discomfort and health issues. Conventional air conditioning systems have been used in some modern underground railway installations but their operation has had limitations and leads to highly energy intensive solutions. Conventional air conditioning often cannot be included in older systems through heat rejection and spatial problems. Sustainable cooling systems could reduce the overall system energy usage and provide an acceptable environment for passengers. These could include energy management methods such as reduced train velocity, low weight carriages as well as sustainable cooling technologies that have been introduced from modern building services engineering such as Groundwater and geothermal cooling. However due to the increased complexity of the air flow paths, the increased heat density and the transient nature of the situation the problem provides many unique and difficult engineering challenges. Most low energy and sustainable systems that could be used on underground railways have been developed and used in more conventional building services applications. Ventilating an underground railway environment, in which there is to be heavy traffic of electrically-propelled rapid-transit trains, differs from those normally encountered in conventional building-services applications. The heat generated by the train motors and electric lighting, together with body heat from passengers, is so great that excessive temperatures would prevail in summer when limited cooling is available. During this seminar the drivers behind the low energy and sustainable cooling will be briefly looked at and some possible methods will be briefly discussed. The seminar will then provide detailed discussion of groundwater cooling, evaporative cooling and geothermal cooling. The seminar will finally conclude with some general remarks about the objectives and strategies of introducing sustainable and low energy cooling to an operating underground railway.

 

The anabelian geometry of Grothendieck
Mohamed Saidi (University Of Exeter)
5 Feb 2008Harrison 103 Tuesday 9amPure Mathematics (Internal)
I will explain what the Grothendieck anabelian conjectures are and how did Grothendieck come to them. I will give an overview on the state of these conjectures and my contribution to the subject.

 

Physical Properties of Palladium Thin Films in a an Hydrogen Atmosphere
R. Matelon (SECaM)
4 Feb 2008Harrrison 215 Monday 13:00Advanced Technologies RI (Internal)
TBA

 

Control of beams and plates: a mathematical perspective
Mark Opmeer (University of Bath)
4 Feb 2008Harrison 209 Monday 2pmApplied Mathematics

 

The dynamics of wheel shimmy or good memory causes trouble
Gabor Orosz (University of Exeter)
1 Feb 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

The lateral vibration of towed wheels, called shimmy, may appear on airplane landing gears, motorcycle wheels, caravans, rear wheels of semi-trailers and articulated buses, and it usually presents a safety hazard. The dynamics of wheel shimmy is studied when the vibrations are related to the elasticity of the tyre. In the corresponding stretched-string tyre model, the non-holonomic rolling constraint is described by a partial differential equation (PDE) that is coupled to an integro-differential equation (IDE) governing the lateralwheel motion. The coupled PDE-IDE system can be transformed to a delay differential equation (DDE) by assuming travelling wave solutions along the contact patch. Investigating the stability of the stationary rolling motion reveals intricate stability charts where instabilities lead to periodic and quasi-periodic vibrations. These vibrations are found by numerical simulation and verified by experiments.

 

Evolving the Water Industry to the Next Generation (With a Satistical Bent) - Lessons We Can Learn from Other Industries
Tim Watson (MWH UK Ltd)
31 Jan 2008Harrison 170 Tuesday 4pmInformatics RI
The recent drive within the water industry has been towards ‘whole of life’ costing, necessitating the need for robust and quantifiable forecasting of asset performance. However, it is generally accepted that data is sparse, unreliable, and of poor quality. Therefore, constructing robust statistical forecasting models remains a challenge. In this talk, we will highlight the above problem with two examples. Firstly, we believe that the current OFWAT directive of ‘business as usual’ – embedding a decision support system within the assets themselves – is an excellent first step to begin to populate the necessary data sets. Secondly, as a comparison to the water industry, we will provide examples from other industries where such a ‘business as usual’ undertaking has been achieved over the past 10 years, resulting in an environment that is data rich and therefore able to produce robust forecasts of future investment.

 

The relative kernel group of an order and SK_1
Steve Wilson (Bristol)
31 Jan 2008Harrison 106 Thursday 3pmPure Mathematics

 

Aerosol modelling in the Unified Model and their importance in global weather and climate
Duncan Ackerley (University of Reading)
28 Jan 2008Harrison 209 Monday 2pmApplied Mathematics

 

Second mean analysis of stochastically perturbed population dynamics
Iakovos Matsikis (University of Exeter)
25 Jan 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

Population Projection Matrices (PPM's) are mathematical models that describe the evolution of age- or stage-classified populations. These models usually are stochastically perturbed, due to environmental reasons and their asymptotic dynamics are governed by the resulting spectra (Lyapunov exponents). This mean asymptotic analysis however, do not give satisfactory answers regarding the PPM's transient behavior.

In this talk we study stochastically perturbed PPM's using second mean techniques. We plot pseudospectra and variance envelopes which capture the transient dynamics and discuss non-normality of matrices and its implications in the population's transient evolution.

 

On the efficient use of uncertainty when performing expensive ROC optimisation
Dr Jonathan Fieldsend (UoE)
24 Jan 2008Harrison 171 Thursday 3pmInformatics RI
When optimising receiver operating characteristic (ROC) curves there is an inherent degree of uncertainty associated with the operating point evaluation of a model parameterisation x. This is due to the finite amount of training data used to evaluate the true and false positive rates of x. The uncertainty associated with any particular x can be reduced, but only at the computation cost of evaluating more data. Here we explicitly represent this uncertainty through the use of probabilistically non-dominated archives, and show how expensive ROC optimisation problems may be tackled by only evaluating a small subset of the available data at each generation of an optimisation algorithm. Illustrative results are given on data sets from the well known UCI machine learning repository.

 

The acoustics and stability of swirling flow
Nigel Peake (University of Cambridge)
21 Jan 2008Harrison 209 Monday 2pmApplied Mathematics

 

Designing objects from the inside-out
Dr. Siavash H. Mahdavi (Complex Matters)
17 Jan 2008Harrison 106 Thurday 2PMAdvanced Technologies RI
Currently, when choosing a material to be used for a particular product, the best fit material for the task is found from a predefined set of materials (wood, steel, plastic…). Often, it is necessary to modify the original design of the product due to material constraints. At Complex Matters our approach is different. We think that it is better to look at the application first and then design a material, with the use of 3D imaging and rapid manufacturing, from the ground up, essentially designing our own microstructure. This results in a lighter, better suited product that can also exhibit material properties that were previously unattainable.

 

Rectilinearity Measure for Detecting Buildings on Satellite Images
Dr Jovisa Zunic (UoE)
17 Jan 2008Harrison 171 Thursday 3pmInformatics RI
Rectilinear structures often correspond to human-made structure, and are therefore justified as attentional cues for further processing. For instance, in aerial image processing and reconstruction, where building footprints are often rectilinear on the local ground plane, building structures, once recognized as rectilinear can be matched to corresponding shapes in other views for stereo reconstruction. Perceptual grouping algorithms may seek to complete shapes based on the assumption that the object is question is rectilinear. Using the proposed measure, such systems can verify this assumption.

 

Chiral Smart Honeycombs
W. Miller (SECaM)
14 Jan 2008Harrison 203 Thursday 13:00Advanced Technologies RI (Internal)
TBA

 

Towards the seamless prediction of weather and climate
Tim Palmer (ECMWF, Reading)
14 Jan 2008Harrison 203 Monday 2pmApplied Mathematics

 

Bursting dynamics in the neuronal systems
Abul Kalam Al-Azad (University of Exeter)
11 Jan 2008Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

Bursting is a relatively slow rhythmic alternation between an active phase of rapid spiking and a quiescent phase. It is exhibited by a wide range of nerve and endocrine cells, including pancreatic beta-cells, respiratory pacemaker neurons, dopaminergic neurons of the mammalian midbrain, thalamic relay cells, and pyramidal neurons of the neocortex.

One of the major challeges in the theoretical neuroscience is to understand the dynamical and computational properties of bursters, and their underlying physiological mechanism both in the single cell and network levels.

We examine synchronization phenomena in varying parameter regime for the bursting neuronal systems governed by standard minimal models, and emergence of clustering in the ensuing dynamics. We also present a method to compute the stability of the subspace formed by partial synchronous clusters.

 

TBA
Dr Richard Everson (UoE)
10 Jan 2008Harrison 170 Tuesday 2pmInformatics RI
TBA

 

Convection and magnetic stability of the planetary cores
Sergey Starchenko (IZMIRAN, Troitsk, Russia)
7 Jan 2008Harrison 209 Monday 2pmApplied Mathematics

 

Invasion Dynamics: Resilient vs. Vulnerable Populations
Stuart Townley (University of Exeter)
7 Dec 2007Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
In this talk we consider two interacting populations - a resident and an invader.

From uncertain models of each population we want to determine if the invader, initiated with negligible density, can dislodge the resident from steady state carrying capacity. Adopting robustness tools from control engineering, we show that resilience (robustness of non invasion) and vulnerability (non robustness and transient interactions) can be captured from pseudospectrum plots of linearised invasion matrices.

 

Research Performed at the Aerospace Structures Laboratory Faculty of Aerospace Engineering
Prof. Haim Abraovich (Aerospace Structures Laboratory Faculty of Aerospace Engineering, Technion, I.I.T, Haifa, Israel)
6 Dec 2007Harrison 106 Thursady 2PMAdvanced Technologies RI
The research performed at the Aerospace Structures Laboratory Faculty of Aerospace Engineering, Technion,I.I.T, Haifa, Israel. consists on two main topics: stability and dynamics of thin walled laminated composite structures and smart structures applications. An overview will be given on both topics.

 

Sewer Infrastructure Capital Maintenance - Theory and Practice
Alec Erskine (MWH UK Ltd)
6 Dec 2007Harrison 170 Tuesday 2pmInformatics RI
A discussion of the impact of the Common Framework on asset management in the water industry particularly the sewerage infrastructure. Attempts to apply risk theory and cost benefit analysis to the CCTV inspection of sewers prior to intervention. What actually happens in practice at selected water companies.

 

Vinogradov's three primes revisited
Andrew Booker (Bristol)
5 Dec 2007Harrison 106 Thursday 3pmPure Mathematics

 

Real Life MCDM Applications in Water Resources Management: Case Studies – Serbia and Brazil
Prof. Bojan Srdjević (University of Novi Sad)
4 Dec 2007Harrison 209 Tuesday 4pmInformatics RI
An overview of two real life applications will be presented: (1) Serbian Case Study - Participative decision-making at regional hydro system level based on AHP methodology (Nadela system in Vojvodina Province); and (2) Brazilian Case Study - Assessment of water allocation scenarios in a reservoir system by combined use of river basin simulation models and MCDM methods (Tandem reservoirs França and São Jose de Jacuípe in Paraguacu river basin, Bahia). The AHP multicriteria method will be presented in brief as well.

 

The Fluid Dynamics of Lymphatic Vessels
A. McDonald (SECaM)
3 Dec 2007Harrison 209 Thursday 13:00Advanced Technologies RI (Internal)
TBA

 

Palaeomagnetic field and palaeoclimatic changes: observations from China
Yongxin Pan / Rixiang Zhu (Chinese Academy of Sciences, Beijing, China)
3 Dec 2007Harrison 209 Monday 2pmApplied Mathematics
12th Taylor & Francis sponsored seminar -- Taylor & Francis are publishers of the journal 'Geophysical and Astrophysical Fluid Dynamics'

 

A model for the pure bending of isotropic tubes: beyond the Brazier effect
Khurram Wadee (University of Exeter)
30 Nov 2007Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
Tubular structures are common in engineering and biological settings. They provide an efficient way of carrying load but are also susceptible to elastic instabilities. Under conditions of pure bending, thin tubes are known to ovalize; the basic theory was formulated exactly 80 years ago but assumed that the ovalization occurs uniformly along the length of the tube. In this talk a novel treatment will be presented which identifies other routes to instability that provide a better approximation to the real behaviour of tubes. Furthermore, this new formulation is applicable to tubes made of auxetic or orthotropic materials.

 

System Dynamics Modelling (SDM) for the Simulation of Complex Water Systems
Lydia S. Vamvakeridou-Lyroudia (University of Exeter)
29 Nov 2007Harrison 170 Tuesday 2pmInformatics RI
System Dynamics Modelling (SDM) is a methodology for studying and managing complex feedback systems, typically used when formal analytical models do not exist, but system simulation can be developed by linking a number of feedback mechanisms. They are particularly useful for building, understanding and presenting models to non-engineers. Moreover they are useful for developing models in participatory interdisciplinary context, as is the case for most European Commission (EC) projects. This seminar presents the procedure for developing SDM for complex water systems within the EC FP6 project AQUASTRESS, followed by two specific application case studies.

 

Self-points on elliptic curves
Christian Wuthrich (Nottingham)
29 Nov 2007Harrison 106 Thursday 3pmPure Mathematics

 

Asymptotics of large bound states of localised structures
Jon Chapman (University of Oxford)
26 Nov 2007Harrison 209 Monday 2pmApplied Mathematics

 

Cat's eyes and Landau poles
Matt Turner (University of Exeter)
23 Nov 2007Harrison 254 Friday 10 amApplied Mathematics (Internal)

The relaxation of a smooth two–dimensional vortex to axisymmetry is examined, after an instantaneous, weak external strain field is applied. In this limit the disturbance decays exponentially in time at a rate that is linked to a pole of the associated linear inviscid problem (known as a Landau pole). As a model of a typical vortex distribution that can give rise to cat’s eyes, here distributions are considered that have a basic Gaussian shape but whose profiles have been artificially flattened about some radius rc . A numerical study of the Landau poles for this family of vortices shows that as the location rc is varied, so the decay rate of the disturbance moves smoothly between poles as the decay rates of two Landau poles cross.

Cat’s eyes which occur in the nonlinear evolution of a vortex lead to an axisymmetric azimuthally averaged profile with an annulus of approximately uniform vorticity, rather like the artificially flattened profiles investigated. It is found that finite thickness cat’s eyes can persist (i.e. the mean profile has a neutral mode) at two distinct radii, and in the limit of a thin flattened region the result that vanishingly thin cat’s eyes only persist at a single radius is recovered. The decay of non–axisymmetric perturbations to these flattened profiles for larger times is investigated and a comparison with the result for a Gaussian profile is made.

 

Physical Modelling of Venford Dam Spillway
Professor Godfrey Walters (University of Exeter)
22 Nov 2007Harrison 170 Tuesday 2pmInformatics RI
Following a request from South West Water, a physical model of the spillway structure and toe works of Venford Dam on Dartmoor was built at a 1:20 scale in the Fluids Laboratory. This talk outlines the background to the study, the theoretical and practical details of constructing the model, and the outcomes of a series of tests on the existing structure and proposed amendments.

 

Siegel modular forms and representation numbers of quadratic forms
Lynne Walling (Bristol)
22 Nov 2007Harrison 106 Thursday 3pmPure Mathematics
Number theorists love to count things, especially integral objects. An example is to count the number of ways an integral quadratic form represents each integer, where the variables of the quadratic form are only allowed to assume integral values. More generally, we can ask to count the number of ways a quadratic form represents a lower dimensional quadratic form. These representation numbers are encoded in the Fourier coefficients of generalized theta series, which are examples of modular forms. When counting representation numbers of integers, the associated theta series is a function of one complex variable, whereas to count representation numbers of rank n quadratic forms, the associated theta series is a function of an n by n symmetric complex matrix. We will discuss these theta series, with particular attention given to the Hecke operators and the information they provide regarding representation numbers.

 

Maximum-entropy velocity profiles and boundary layer theory in turbulent flow
Robert Niven (University of New South Wales, Canberra, Australia)
21 Nov 2007Harrison 107 Wednesday 2pmApplied Mathematics
The maximum entropy method of Jaynes (1957) is used to determine the "most probable" steady-state velocity profile u(y) in several "classical" fluid flow systems, including axial flow in a cylindrical pipe (Poiseuille flow) and flow between parallel plates. In each case, the analysis yields an analytical solution for the velocity profile over the complete spectrum of laminar to turbulent flow, as a function of the maximum velocity u_{max} and a momentum parameter M. In each case, the predicted profile reduces to the well-known laminar solution at M = 0, whilst for M > 0 it gives an equation which supersedes the semi-empirical correlations commonly used for turbulent flow profiles. The main steps of the analysis and the predicted profiles are presented here. The analysis is then used to derive a new maximum-entropy laminar-turbulent boundary layer theory, for the velocity profile in steady flow along a flat plate. For M = 0, this reduces to the laminar boundary layer theory given in some texts, which approximates the Prandtl-Blasius solution to the Navier-Stokes equation. For turbulent flow, it yields a previously unreported set of solutions.

 

Solitary surface waves on fluids in electric fields
Paul Hammerton (University of East Anglia)
19 Nov 2007Harrison 209 Monday 2pmApplied Mathematics

 

Maximum Entropy Production in planetary atmospheres
Tim Jupp (University of Exeter)
16 Nov 2007Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

Atmospheric motions constitute a heat engine. As energy flows down temperature gradients from the tropics to the poles, so entropy is produced. Observations, and numerical simulations, suggest that the terrestrial atmosphere produces entropy at the "maximum possible rate". The currently developing theory of Maximum Entropy Production (MEP) provides a framework for interpreting these observations.

In this talk I shall give an overview of MEP theory and its application to planetary atmospheres. In particular, the influence of surface drag on atmospheric entropy production is examined. A simple dynamical model is used to give insight into previous numerical results. The dependence of the MEP state on parameters such as planetary radius and rotation rate is then used to extrapolate the results to other planets.

Link to talk

Link to MEP reference material

 

Crystalline representation and F-crystals
Fabien Trihan (Nottingham)
16 Nov 2007Harrison 171 Friday 3pmPure Mathematics
Let K be a complete discrete valuation field of mixed characteristics. Assume its residue field has a finite p-basis. Then there exists an equivalence of category between the category of crystalline representations of the absolute Galois group of K, with Hodge-Tate weights in {0,1} and the Barsotti-Tate groups over the ring oif integers of K.

 

Lessons from BedZED
Chris Shirley Smith (Director of Water Works UK Ltd)
15 Nov 2007Harrison 170 Tuesday 2pmInformatics RI
The lecture will cover the development of BedZED as planned, the construction period and the water management plan. Things did not go entirely as planned and the lessons which can be drawn from the project are opened for viewing and subsequent discussion.

 

Magnetic Recording & Hard Disk Drive Technology
B.C. Choo (SECaM)
14 Nov 2007Harrison 215 Wednesday 13:00Advanced Technologies RI (Internal)
TBA

 

Invariant polygons in systems with grazing-sliding
Robert Szalai (University of Bristol)
12 Nov 2007Harrison 209 Monday 2pmApplied Mathematics

 

Relaxation Oscillations arising in the Thermal Convection of Rapidly Rotating Spherical Systems
Ed Blockley (University of Exeter)
9 Nov 2007Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
This work will make up the final chapter of my thesis and is concerned with studying the behaviour of the following PDE system:
which has been modified from the complex Ginzburg-Landau equation (CGLE) studied in previous work by the addition of a temperature gradient and thermal diffusion time-scale .
Starting from the limit (for which we recover the CGLE featured in Blockley et. al.) we reduce and observe how the behaviour of the system changes becoming quasi-periodic before breaking down to chaos.

 

Atomistic Simulation of Oxide/Oxide Interface
Andrada Maicaneanu (Babes-Bolyai University, Department of Chemical Technology, Romania)
8 Nov 2007Harrison 209 Thursady 2PMAdvanced Technologies RI
When supported, thin films demonstrate remarkable structural transformations, with important implications for catalysis, sensors, electrochemistry, semiconductors or superconductors. At present, the tools available to characterize solid-solid systems cannot provide atomic level resolution of, for example mixed screw-edge dislocations. Therefore atomistic simulation can provide an invaluable complement to experiment. In this work atomistic simulation was employed to generate models of oxide thin films. First an atom deposition methodology was used to create an SrO thin film on a BaO(001) support. The evolution of the thin film from small clusters (submonolayer coverage), to five atomic layers, which includes cracks in its structure, was studied. Specifically, information related to growth and nucleation processes can be explored using this methodology. Secondly an amorphisation and recrystallisation methodology was developed to explore the more complex system, that of ceria deposited on zirconia and yttrium stabilized zirconia. Simulated amorphisation and recrystallisation involves forcing the thin film to undergo a transformation into an amorphous state prior to recrystallising and therefore the recrystallisation process rather than the (perhaps artificial) initial structure will dictate the final structure. The recrystallisation process enables the evolution of all the important structural modifications as the thin film evolves structurally in response to the support. These include dislocations (pure edge and mixed screw-edge), dislocation networks, grain-boundaries and defects (interstitials, vacancies and substitutionals, including complex defect association) all within a single simulation cell.

 

Recent Advances in Data Assimilation in Large Scale Hydrodynamic and Hydrological Forecasting Models
Henrik Madsen (DHI (Danish Hydraulic Institute))
8 Nov 2007Harrison 170 Tuesday 2pmInformatics RI
The use of data assimilation in hydrodynamic and hydrological forecasting systems has advanced considerably in recent years. This talk gives a review of the developments, considering the data assimilation problem within a general filtering framework. This framework incorporates updating of different modelling components in the forecast system, including model forcing, model state, and model parameters. It includes as a special case the classical Kalman filter. Various extensions of the filter especially tailored towards operational applications are reviewed. These include (i) approximate Kalman filter schemes that utilize cost-effective approximations of the error modelling, (ii) combination of filtering and forecasting of model prediction errors, (iii) filtering with coloured or biased model errors, and (iv) application of regularization techniques.

 

Pattern transformation induced by an elastic instability
Tom Mullin (University of Manchester)
5 Nov 2007Harrison 209 Monday 2pmApplied Mathematics

 

A Review of Mantle Convection
Francisco Pla (Depto. de Matematicas, Facultad de Ciencias Quimicas and IMACI, Universidad de Castilla-La Mancha)
2 Nov 2007Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

The formation of the rocks indicates that viscosity in the interior of the Earth and planets strongly depends on temperature, and this influence is the fundament for understanding the mantle convection and subduction motions. This is the goal for which a convection problem with temperature-dependent viscosity in the Navier-Stokes equations is studied. The dimensionless hydrodynamics equations are considered in which the viscosity is an exponential function of the temperature ν(T ) = ν0 · exp(−γT ).

This work studies the time-dependent solutions in codim-2 zones for different aspect-ratios, Rayleigh numbers, exponential rate γ and other parameters.

A bifurcation study with the stability results for constant viscosity and variable viscosity are also exposed.

This work is by Francisco Pla and Henar Herrero, Depto. de Matematicas, Facultad de Ciencias Quimicas and IMACI, Universidad de Castilla-La Mancha and Ana Maria Mancho, Instituto de Matematicas y Fisica Fundamental, Consejo Superior de Investigaciones Cientificas.

 

Water Distribution Network System Modelling in China: Opportunities and Challenges
Professor Hongbin Zhao, Director, Water and Wastewater Systems Research Center (Harbin Institute of Technology, China)
1 Nov 2007Harrison 170 Tuesday 2pmInformatics RI
There is a large demand in modelling water distribution networks and systems in China, and with that, a huge potential market for modellers and model developers. However, the modelling community in China is still relatively small in size compared to Western countries, and research and development in still relatively slow. This talk will attempt to: (i) discuss and summarise various hurdles currently faced by modellers and model developers in China; (ii) discuss some of the problems in using hydraulic models to simulate water distribution networks; and (iii) propose some new directions in water distribution research.

 

Computing the Brauer-Manin obstruction
Martin Bright (Bristol)
1 Nov 2007Harrison 106 Thursday 3pmPure Mathematics

 

Delay dynamics in semiconductor laser systems
Vicky Crockett and Hartmut Erzgräber (University of Exeter)
26 Oct 2007Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

Vicky Crockett

Lasers with optical feedback can exhibit a wide range of complicated dynamics which can be useful or problematic depending on the desired application. In either case we need to know how to understand laser instabilities to achieve and control the desired type of dynamics.

Much work has been done on a laser with little light reflected back in from a distant external mirror, modeled with delay differential equations. For a laser with a nearby external mirror and a large amount of reflected light, the composite cavity model is more appropriate. In such an approach, the system is modeled by ordinary differential equations coupled to a set of algebraic equations for the modes. The mode equations are dependent on the coupling mirror transmission, , and optical length difference between the laser and external cavity, dLo. Bifurcation analysis is used to find regions of stable and chaotic dynamics on the plane of (T,dL).

Hartmut Erzgräber

Mathematical modeling and understanding the dynamics of coupled laser devices is of importance for many modern laser applications and holds various interesting problems for fundamental research. In the weak coupling approach a laser coupled to a filter can be modeled by delay-differential equation, which has an infinite dimensional phase space. We will present a comprehensive bifurcation analysis with respect to the relevant parameters. This reveals several codimension-two points as organizing centers. The calculated bifurcation diagrams show qualitative agreement with experiments.

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New Approaches to Adaptive Water Management Under Uncertainty (NeWater)
Raziyeh Farmani (University of Exeter)
25 Oct 2007Harrison 170 Tuesday 2pmInformatics RI
In this talk an introduction will be given to the NeWater project as an Integrated Project (IP) funded by European Commission (EC) under sixth Framework Programme (FP6). This will be followed by introduction to adaptive water resources management. The need for transition from prevailing water management regimes towards adaptive regimes of water facing climate, global and socio-economic boundary conditions changes will be highlighted. Finally, the role of the tools in facilitating these processes will be discussed and some real applications will be presented.

 

Hodge structures on homotopy groups
Jonathan Pridham (Cambridge)
25 Oct 2007Harrison 106 Thursday 3pmPure Mathematics

 

The persistence of disease in an SIR model with self-regulation and seasonal birth rate
Ben Mestel (Open University)
22 Oct 2007Harrison 209 Monday 2pmApplied Mathematics

 

Modelling the Atmosphere
Dan Holdaway and James Kent (University of Exeter)
19 Oct 2007Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

This seminar will consist of two twenty minute talks on numerically modelling the atmosphere.

Numerical solutions to the Governing Equations cannot resolve all relevant scales. Processes that are larger than the grid length can be included in the model, however there are many processes that occur on a subgrid level. These subgrid process can interact with the resolved scale processes and affect the large scale flow. The large scale quantities can be solved by the numerical method, while the small subgrid scale processes need to be parametrized.

Numerical Methods for Weather and Climate Models. Subgrid Models (SGM) can be added to the numerical scheme to act as the effect of the subgrid processes. All numerical schemes contain errors. If these errors equal the effect of the subgrid processes then there is no need for an explicit SGM. The numerical errors associated with the numerical scheme solving the resolved scale equations could provide an implicit subgrid model for the unresolved scales.

Physics Dynamics Coupling. Proper coupling between the SGMs and the resolvable dynamics is key in obtaining accurate weather and climate forecasts. By examining the normal modes of the solutions, the spatial aspects of the coupled system are examined. Questions of particular interest are, what choice of thermodynamic variable works best? What choice of vertical staggering works best? What are the effects of nonuniform grid spacing?

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Water Resources Modelling Tools - The ODYSSEUS Project
Evangelos Rozos (University of Exeter)
18 Oct 2007Harrison 170 Tuesday 2pmInformatics RI
The subject of the “ODYSSEUS” project was the development of an integrated system of computing tools, which, in combination with a parallel framework of methodologies and technical specifications, provided an infrastructure suitable for a rational and sustainable management of water resource systems at a variety of scales. The research teams that participated to the project implementation derived from the academic field, the private field and the local authorities. The project was funded by the European Development Fund (EDF), the European Social Fund (ESF), the Greek State and Greek private organisations, in the framework of the Operational Project “Competitiveness” of the Third Community Cohesion Fund. The project duration was three years, and begun at July 2003.

 

A Jacquet-Langlands correspondence in weight 1
Lloyd Kilford (Bristol)
18 Oct 2007Harrison 106 Thursday 3pmPure Mathematics
We will give a brief introduction to quaternionic modular forms, and present the results of explicit computations relating quaternionic and classical modular forms of weight 1 (using a form of the Jacquet-Langlands correspondence). This is joint work with Kevin Buzzard

 

The transition to turbulence in confined shear flows
Ashley Willis (University of Bristol)
15 Oct 2007Harrison 209 Monday 2pmApplied Mathematics

 

Spatio-temporal code generation with globally coupled oscillators
John Wordsworth (University of Exeter)
12 Oct 2007Harrison 106 Wednesday 3pmApplied Mathematics (Internal)
For systems of globally coupled phase oscillators it is possible to find attractors that form symmetrical and robust heteroclinic networks. By detuning the natural frequencies of the oscillators it is then possible to break the symmetry of these networks. These dynamics can then be used to generate a spatio-temporal code from the input that has been fed into the system by means of detuning and this code can be used to classify the input accordingly.

 

Tailoring composite material structures at different length-scales
Hua-Xin Peng (University of Bristol)
11 Oct 2007Harrison 209 Thursday 2pmAdvanced Technologies RI
The conventional approach to the development of discontinuous composites is to pursue a homogeneous distribution of the micro-sized reinforcements in the form of particles, whiskers or short fibres in the matrix. This has enabled some advantages of composites over unreinforced monolithic materials to be realised to a limited extent by altering volume fraction, size and aspect ratio of the reinforcing phases. However, our recent analysis shows that a homogeneously discrete distribution of the reinforcement inevitably results in a property close to the lower bound of the optimal Hashin-Shtrikeman (HS) lower and upper bounds. Importantly, in principle, there exists a range of material structures that attain all the properties encapsulated by the HS lower and upper bounds. In other words, every point within this encapsulated region corresponds to at least one material structure or geometry. Unfortunately, most of such structures are not known. To identify these material structures required innovative thinking and is of major scientific importance. Two new approaches are proposed to achieve this, namely, (1) tailoring the phase contiguity at the Micro-scale, and (2) tailoring the phase spatial distribution at the Meso-scale. This is based on the fact that both our preliminary experimental results and the recently derived contiguity model have shown that a material structure with varying degree of continuity of the reinforcing phase will be more effective for property improvement. We have also shown that composites with a controlled inhomogeneous reinforcement distribution can result in significant property improvement and such composites effectively have a structure with two-hierarchies: the meso-composite contains a reinforcing phase which itself is a conventional micro-composite.

 

Asset Deterioration, Multi-Utility Data and Multi-Objective Data Mining
Dragan Savic (University of Exeter)
11 Oct 2007Harrison 170 Tuesday 2pmInformatics RI
Physically-based models derive from first principles (e.g. physical laws) and rely on known variables and parameters. Because these have physical meaning, they also explain the underlying relationships of the system and are thus usually transportable from one system to another as a structural entity, while only the model parameters have to be updated. Data-driven or regressive techniques involve data mining for modelling and one of the major drawbacks of this is that the functional form describing relationships between variables and the numerical parameters is not transportable to other physical systems as is the case with their classical physically-based counterparts. Aimed at striking a balance, Evolutionary Polynomial Regression (EPR) offers a way to model multi-utility data of asset deterioration in order to render model structures transportable across physical systems. EPR is a recently developed hybrid regression method providing symbolic expressions for models and works with formulae based on true or pseudo-polynomial expressions, usually in a multi-objective scenario where the best Pareto optimal models (parsimony vs. accuracy) are selected from data in a single case study. This article discusses the improvement of EPR for dealing with multi-utility data (multi-case study) advances data-driven modelling while achieving a general model structure for asset deterioration prediction across different water and wastewater systems.

 

Controlling neurons
Jeffrey Moehlis (University of California, Santa Barbara, USA)
8 Oct 2007Harrison 209 Monday 2pmApplied Mathematics
The phase response curve (PRC) for a nonlinear oscillator describes the phase-shift of the oscillation due to an impulsive perturbation as a function of the phase at which the perturbation occurs. We consider how knowledge of the PRC for a neuron can be used to determine external currents which control the time at which the neuron fires. We first use variational methods to determine the optimal currents that elicit spikes at a desired time, showing that there is a unique current that minimizes a square-integral measure of its amplitude. For intrinsically oscillatory models, we further demonstrate that the form and scaling of this current is determined by the model's PRC. We then propose a novel feedback control mechanism which allows one to control the phase of an oscillation, assuming only that the PRC is known and that a once-per-period marker event, such as the time at which a neuron fires, can be detected. This work represents a first step toward feedback-based treatment of ailments such as Parkinson's disease by using electrical deep brain stimulation, in which current is injected into the appropriate brain region to try to desynchronize pathologically synchronized neurons.

 

Two Stochastic Approaches for Benchmarking Urban Water Systems
Michael Möderl (University of Innsbruck)
4 Oct 2007Harrison 170 Tuesday 2pmInformatics RI
A traditional procedure for performance evaluation of systems is to test approaches and methodologies on one or more case studies. However, it is well known that the investigation of real case studies is a tedious task. Moreover, due to the limited amount of case studies available it is not certain that all aspects of a problem can be covered in such procedure. With increasing computer power an alternative methodology has emerged, that is the investigation of a multitude of virtual case studies by means of a stochastic consideration of the overall performance. Within the frame of this approach we develop here a Modular Design System for water distribution systems and we will develop and Case Study Generator for urban drainage systems. With the algorithmic application of such tools it is possible to create a variety of different virtual case studies. Additionally the benchmark of the virtual case studies is shown by an application example, where 2,280 different water distribution systems are evaluated.

 

The dynamics of the North Atlantic Oscillation and Annular Modes
Edwin Gerber (Columbia University, USA)
24 Sep 2007Harrison 209 Monday 2pmApplied Mathematics
The North Atlantic Oscillation (NAO) and Annular Modes are the dominant patterns of intraseasonal variability in the extratropical atmosphere. The NAO in particular characterizes a significant fraction of the wintertime variability in Eastern North America and Europe, and has been recognized in some form since the eighteenth century. I'll begin with a simple model based on random walks to explain why these patterns of variability always dominate statistical analyses of the extratropical circulation. I'll then move to a more realistic model, a dry general circulation model of the atmosphere, to probe the dynamics of the variability. Annular Mode and NAO-like patterns are created with the addition of idealized topography and heating anomalies approximating land-sea contrast. We find that the NAO arises from the confluence of topographic and thermal forcing, and is best understood in terms of the eddy life cycle. We also find a parameter sensitive coupling between eddies and the large-scale flow that extends the persistence of the variability on timescales of 10-100 days. The feedback loop, however, is very sensitive to zonal asymmetries. This sensitivity is explored with a coupled oscillator model to illustrate the impact of standing waves on the eddy-mean flow feedback.

 

THE A-METRICS STORY, sub Angstrom distance measurement
Peter Armitage (SECaM)
17 Sep 2007Harrison 170 Thursday NoneAdvanced Technologies RI (Internal)
The story of an emerging new technology is presented. Starting from the initial invention of a sub-angstrom distance measuring device built in a persons living room, to its evaluation and testing at Exeter University and at the National Physical Laboratory in London, together with its subsequent exploitation in the USA. In addition to the technology, the presentation includes the human and business factors and obstacles faced by Inventors that develop revolutionary new technology. The presentation ends with a discussion about possible applications for the device, such as in Metrology (indentation creep), Meteorology (micro air pressure measurements), Geophysics (Earth tide and seismic sensors) and Astrophysics (Quantum gravity wave detection).

 

Development of Scaffolds and Bioreactors for Tissue Engineering and Stem Cell Bioprocessing
Julian Chaudhuri (University of Bath)
13 Sep 2007Harrison X-AT Conference Room (121) Thursday 2pmAdvanced Technologies RI
Mass transfer limitations of tissue engineering scaffolds are currently hindering the development of three-dimensional, clinically viable, tissue engineered constructs. In our laboratory we are investigating routes to improve the formation of viable tissue constructs. This presentation will describe our interests in developing both novel scaffolds and bioreactors, to support cell culture and improve nutrient transport to the proliferating cells. We are also using similar approaches to improve the handling and bioprocessing of stem cell populations.

 

Global transient behaviour: basins of attraction in experimental nonlinear dynamics
Lawrie Virgin (Duke University, USA)
13 Sep 2007Harrison 170 Thursday 2pmApplied Mathematics

 

Periodicity and recurrence in a map with two half-planes
Arek Goetz (San Francisco State University)
7 Aug 2007Harrison 004 Tuesday 2pmApplied Mathematics

 

Bridging the Gap - Skeletal Regneration using mesenchymal populations - an interdisciplinary approach
Prof. Richard O C Oreffo (University of Southampton)
26 Jul 2007Harrison 107 Thursday 2:30Advanced Technologies RI
Given the demographic challenges of an ageing population combined with rising patient expectation and the growing emphasis placed on cost containment by healthcare providers, economic regenerative medicine approaches for skeletal regeneration is a major clinical and socio-economic need. Mesenchymal stem cells or human bone marrow stromal stem cells are defined as multipotent progenitor cells with the ability to generate cartilage, bone, muscle, tendon, ligament and fat. These primitive progenitors exist postnatally and exhibit stem cell characteristics, namely low incidence and extensive renewal potential. These properties in combination with their developmental plasticity have generated tremendous interest in the potential use of mesenchymal stem cells to replace damaged tissues. To date, relatively little is known concerning the phenotypic characteristics, whether from a morphological or biochemical standpoint whilst direct in vivo confirmation of the lineage potential and plasticity or interconversion potential that exists of mesenchymal stem cells and osteogenic progenitor cells remains Nevertheless, strategies harnessing tissue engineering approaches offer much promise for skeletal regeneration using mesenchymal populations. Upon isolation of an appropriate progenitor population, repair and reconstruction of bone defects present additional challenges to the orthopaedic, reconstructive and maxillo-facial surgeon including an ability to generate a functional microvascular network within engineered constructs to provide oxygen and nutrients that facilitates growth, differentiation, and tissue. The development of a functional vasculature is critical in respect to bone defects which can be extensive. To achieve this goal of skeletal regeneration, it will be necessary to harness the skills set from a variety of disciplines and there will be a need for close interactions between modelers, physical scientists, tissue engineers and clinicians.

 

A Changing Climate for Prediction
Peter Cox (University of Exeter)
20 Jul 2007Harrison 254 Friday 12 noonApplied Mathematics (Internal)
Standard climate model projections, which have shown the significance of global warming, must be redesigned to inform climate change adaptation and mitigation policy. In this seminar, Peter Cox explains the modelling that informed his & David Stephenson's paper in "Science" of 13.7.07, and invites discussion on climate prediction as an initial value problem.

 

Laser Assisted Manufacturing
Prof. Lin Li (University of Manchester)
12 Jul 2007Harrison 209 Thursday 2pmAdvanced Technologies RI
This presentation outlines some of the research work carried out by staff and students in the Laser Processing Research Centre, The University of Manchester. A focus of the presentation is on the innovative approaches for industrial problems, by “thinking outside the box”. The presentation includes subjects on new developments in laser cutting, laser drilling, laser assisted surface engineering, laser micro/nano manufacturing and hybrid laser-non-laser manufacturing technology development. It is hope the that presentation will inspire young engineers and researchers to innovative approaches for practical problems and an interest in high power laser engineering.

 

Engineering Civilisation from the Shadows
ICE - Institute of Civil Engineers - South West (6th Brunel International Lecture)
11 Jul 2007Royal Clarence Hotel - Wednesday 6pmInformatics RI

This lecture will examine world poverty and climate change in the 21st century, focusing on the role of engineering in addressing these challenges in relation to the Millennium Development Goals.

The lecture is free to attend but it is necessary to register attendance.

** Places are limited, so register early to avoid disappointment **

Contact Barbara Davey, Regional Administrator:
t +44 (0)1626 879 836
e barbara.davey@ice.org.uk
w ice-southwest.org.uk

ICE South West
10 Newton Road, Bishppsteignton
Teignmouth, Devon TQ14 9PN

 

The seasonal cycle of gravity wave drag in the middle atmosphere estimated by an assimilation technique
Manuel Pulido (UNNE, Corrientes, Argentina)
26 Jun 2007Harrison 209 Tuesday 2pmApplied Mathematics
11th TAYLOR AND FRANCIS sponsored lecture. T&F are publishers of the Journal Geophysical and Astrophysical Fluid Dynamics// A novel technique to estimate gravity wave drag from global scale analyses will be presented. It is based on the principles of four-dimensional variational data assimilation using a dynamical model of the middle atmosphere and its adjoint. The control variables are solely the horizontal components of gravity wave drag so that the minimum of the cost function that measures the differences between model states and observations gives the optimum gravity wave drag.// The assimilation technique is applied to estimate gravity wave drag using Met Office analyses as the initial conditions and the observations for the year 2002. The seasonal variations of the one-year gravity wave drag estimation will be presented and analysed. Vertical variations in the sign and pattern of the estimated drag suggest filtering of the gravity wave spectrum by the background flow.

 

Wild ramification in extra-special extensions
Griff Elder (Virginia Tech / University of Nebraska at Omaha)
21 Jun 2007Harrison 106 Thursday 2pmPure Mathematics
It was observed, with J. Hooper, that sharp lower bounds for the largest ramification break number in quaternion extensions of dyadic local number fields depend upon the refined ramification filtration, as defined with N. Byott. Moreover, quaternion counter-examples to the conclusion of Hasse-Arf require that this refined filtration be extreme in two different ways. In this talk, we will extend these results to a more general class of non-abelian extensions that includes extra-special extensions. To keep complications to a minimum, we will work over characteristic $p$ local fields.

 

Introduction to the new Nature Geosciences Journal
Heike Langenberg (Editor of Nature Geosciences)
19 Jun 2007Harrison 209 Tuesday 12pmApplied Mathematics

 

Wealth without money
Dr. Adrian Bowyer (Bath Univeristy)
14 Jun 2007Harrison 209 Thursday 2pmAdvanced Technologies RI
Look at your computer setup. Imagine if you hooked up a 3D printer. Instead of printing on bits of paper this 3D printer makes real, robust, mechanical parts. To give you an idea of how robust these parts are think of Lego bricks and you're in the right area. You could make lots of useful stuff, but interestingly you could also make most of the parts to make another 3D printer. That would be a machine that could copy itself. This talk will be abut RepRap - the Replicating Rapid-prototyper. This 3D printer will make components using FDM Rapid Prototyping, which builds the component up in layers of plastic. This technology already exists, but the cheapest commercial machine would set you back £15,000. And it isn't even designed so that it can make itself. So what the RepRap team are doing is to develop and to give away the designs for a much cheaper machine with the novel capability of being able to self-copy (material costs will be about £300). We are distributing the RepRap machine entirely free to everyone using open-source - so, if you have one, you can make another and give it to a friend...

 

Forecast verification of extremes: Use of Extreme Value Theory
Rick Katz (NCAR, Boulder, Colorado, USA)
11 Jun 2007Harrison 107 Monday 4pmApplied Mathematics
Evaluating the ability of a weather forecasting system to predict extremes should be an important consideration in forecast verification, particularly given the well known societal impacts of extreme events. Yet statistical methods devised for extreme values have only rarely been applied. // I adopt a distributions-oriented approach to forecast verification, making use of the calibration-refinement factorization of the joint distribution of forecasts and observations. The exceedance of a high (or falling below a low) threshold by the weather variable is modeled by a conditional Poisson distribution, whose rate parameter is expanded as a function of the forecast. Likewise, the excess over a high (or deficit below a low) threshold of the weather variable is modeled by a conditional generalized Pareto distribution, whose scale parameter depends on the forecast. In this way, whether or not there is any skill (or how much skill exists) in forecasting weather extremes corresponds to determining whether or not (or to what extent) using the forecast as a covariate improves the fit (e.g., via a likelihood ratio test). // The proposed method is applied to a set of specialized NWS minimum temperature forecasts and observations at Yakima, WA, USA. Because of the risk of damage to fruit buds from freezing during their development, these forecasts were made available to orchardists each spring.

 

Unfolding of codimension-two grazing-sliding bifurcations
Piotr Kowalczyk (University of Exeter)
5 Jun 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

A new global analysis of precipitation
Mathew Sapiano (University of Maryland, USA)
31 May 2007Harrison 171 Monday 2pmApplied Mathematics
Many merged multi-source global analyses of precipitation exist, including the Global Precipitation Climatology Project (GPCP) analysis and the CPC Merged Analysis of Precipitation (CMAP). The multi-source nature of these datasets allows them to use the best data available to produce the most accurate estimate of precipitation for any given place and time. However, this strength can lead to weaknesses in the form of discontinuities in the longer record, which raise questions regarding their suitability for trend analysis. Additionally, high latitude precipitation is poorly determined in these datasets since the available estimates originate from either gauges (which suffer from problems related to under-catch of solid precipitation) or satellite data (which exhibit large errors at high latitudes due to ice-contamination issues). We aim to produce a new global analysis of precipitation using Optimum Interpolation (OI) that will overcome both of these issues by using the relatively long consistent precipitation record (~20 years) from the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) and forecast precipitation from the ERA-40 reanalysis. An additional advantage of the OI methodology is its facility in the calculation of errors associated with the analysis, which are needed for most applications. I will start by showing results from an inter-comparison of the several commonly used precipitation algorithms for SSM/I. Next I will discuss issues associated with the OI and show some early results from our analysis. Finally, I will describe our plans to extend the analysis back in time by using proxy records tied to the reanalysis precipitation and calibrated by the SSM/I data. Our goal is that this extended record of precipitation will be suitable for the assessment of changes in global precipitation in the latter part of the 20th Century at all latitudes.

 

Stability of patterns for the complex Ginzburg-Landau equation
Jorge Diosdado (CIMAT, Guanajuato, Mexico)
29 May 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

The Design and Rehabilitation of Water Distribution Systems Using the Hierarchical Bayesian Optimisation Algorithm
Ralph Olsson (UoE)
25 May 2007Harrison 209 Friday 12noonInformatics RI
The design and rehabilitation of water distribution systems is considered here as a constrained least cost optimisation problem. In the design and rehabilitation of water distribution systems the solution space tends to be vast. This paper uses the hierarchical Bayesian Optimisation Algorithm (hBOA) (Pelikan and Goldberg, 2000) to search the solution space with the aim of decreasing the number of fitness evaluations required for convergence. hBOA is a probabilistic model building genetic algorithm which uses a Bayesian network to model the set of promising solutions in each generation. This network is in turn sampled to generate the offspring to be incorporated into the next generation. hBOA has been shown to solve a number of challenging problems in sub-quadratic time, that is the number of fitness evaluations required for convergence is of order less than the square of the number of design variables. Since a fitness evaluation requires the solution of a set of hydraulic equations there are significant time benefits to be had by reducing the number of evaluations. hBOA is applied to two sample networks as deterministic, single objective problems; the New York Tunnels problem and the 'Anytown' network. Initial results show hBOA to compare favourably with other evolutionary computation techniques in the literature, both in terms of the proportion of runs in which the best known solution is found and in terms of the number of fitness evaluations required.

 

Statistics of elliptic curves over finite fields
Ernst-Ulrich Gekeler (University of Saarbruecken)
24 May 2007Harrison 106 Thursday 3pmPure Mathematics

 

Aspects of feedbacks and forcing in stochastic dynamics
Stuart Townley (University of Exeter)
22 May 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

On the dynamics and adjustment of the Atlantic thermohaline circulation
David Marshall (University of Oxford)
21 May 2007Harrison 107 Monday 2pmApplied Mathematics

 

Imprecise probabilities of climate change: aggregation of fuzzy scenarios and model uncertainties
Dr. Guangtao Fu (UoE)
18 May 2007Harrison 209 Fri 12noonInformatics RI
Whilst the majority of the climate research community is now set upon the objective of generating probabilistic predictions of climate change, disconcerting reservations persist. Attempts to construct probability distributions over socio-economic scenarios are doggedly resisted. Variation between published probability distributions of climate sensitivity attests to incomplete knowledge of the prior distributions of critical parameters in climate models. This presentation addresses these concerns by adopting an imprecise probability approach. We think of socio-economic scenarios as fuzzy linguistic constructs. Any precise emissions trajectory can be thought of as having a degree of membership in a fuzzy scenario. Rather than attempting to distribute an additive probability measure across scenarios a weaker assumption is adopted in monotonic (but non-additive) measures. It is demonstrated how fuzzy scenarios can be propagated through a low-dimensional climate model, MAGICC. Fuzzy scenario uncertainties and imprecise probabilistic representation of climate model uncertainties are combined using random set theory to generate lower and upper cumulative probability distributions for Global Mean Temperature. Further, application of this method in a decision-making context is demonstrated through flood risk analysis in Thames defence system.

 

Which overconvergent Hilbert modular forms are classical?
Shu Sasaki (Imperial College London)
17 May 2007Harrison 106 Thursday 3pmPure Mathematics

 

What controls the rate of mixing of passive scalars in smooth flows?
Peter Haynes (DAMTP, University of Cambridge)
14 May 2007Harrison 107 Monday 2pmApplied Mathematics

 

Bayesian modelling of time aggregated water pipe bursts with a zero-inflated, non-homogeneous Poisson process.
Theodoros Economou (UoE)
11 May 2007Harrison 209 Fri 12noonInformatics RI
A commonly used approach to modelling recurrent failures is based on a non-homogeneous Poisson process (NHPP) and requires data on actual failure times. Modelling and predicting bursts in underground water pipes is vital to water companies from both an economic and conservation perspective, but often does not allow for use of a conventional NHPP for two reasons. Firstly, because data is commonly only recorded on numbers of failures over a (relatively long) time period and not on exact failure times. Secondly, because failures are usually only observed in a very small proportion of pipes in the network. This paper proposes a model derived from the conventional NHPP which only makes use of numbers of failures in an observed time period and the age of each pipe at the end of this period, but is still able to capture the age deterioration phase of the reliability curve. The model is then further extended to account for censoring and truncation in the data as well as an excess of zeros. Application of this `aggregated' model and its zero-inflated extension are illustrated on a data set involving a network of 532 cement water pipes in Manukau City, Auckland, New Zealand.

 

BLEEDING COMPOSITES - Autonomic Self-Healing
Dr. Ian P. Bond (University of Bristol)
10 May 2007Harrison 107 Thursday 2pmAdvanced Technologies RI
Self-healing is receiving an increasing amount of interest worldwide as a method to autonomously address damage in materials. In particular, for advanced fibre reinforced polymer composite materials it offers an alternative to applying conservative damage tolerant design and potentially could remove the need to perform temporary repairs to damaged structures. The concept of an autonomic self-healing composite material, where initiation of repair is integral to the material, is now being considered for many engineering applications. This bio-inspired concept offers the designer an ability to incorporate secondary functional materials capable of counteracting service degradation whilst still achieving the primary, usually structural, requirement. Most materials in nature are themselves self-healing composite materials. This seminar reviews the various self-healing technologies currently being developed for fibre reinforced polymeric composite materials, most of which are bioinspired. The most recent self-healing work has attempted to mimic natural healing using more detailed study of natural processes. The presentation will also discuss work at Bristol to develop self-healing fibre reinforced composites incorporating resin filled hollow fibres and vascular networks. A perspective on current and future self-healing approaches will be offered.

 

On canonical subgroups of abelian varieties
Payman Kassaei (Kings College London)
10 May 2007Harrison 106 Thursday 3pmPure Mathematics

 

Networks that draw networks or honeybees on scent
Gabor Orosz (University of Exeter)
8 May 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

Evolutionary computation-based meta-modelling - a way forward to run thousands of large simulation?
Dr Soon-Thiam Khu (UoE)
4 May 2007Harrison 209 Fri 1pmInformatics RI
Evolutionary algorithms such as genetic algorithms (and other population-based search algorithms) are increasing used to solve many engineering optimisation problems.Although these algorithms have the distinct advantage of able to find near-global solutions relatively fast, the bottleneck of using evolutionary algorithms for real-world optimisation is due to the computational intensive running of the engineering simulation model. The talk will attampt to examine various ways of resolving such a problem while proposing a relatively new method known as evolutionary computation-based meta-modelling. This talk should be of interests to all modellers (like myself) being fustrated with long simulation times using GA optimisation. It will also be a great opportunity for computer scientist to share their experience in resolving such problems.

 

Witt-groups of constructible derived categories
Jonathan Woolf (Liverpool)
3 May 2007Harrison 106 Thursday 3pmPure Mathematics

 

A new asymptotic solution for stellar dynamo
Dmitry Sokoloff (Moscow State University, Russia)
30 Apr 2007Harrison 107 Monday 2pmApplied Mathematics
10th TAYLOR AND FRANCIS sponsored lecture. T&F are publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

On the continuous part of codimension 2 algebraic cycles on certain threefolds
Volodya Guletskii (University of Liverpool)
26 Apr 2007Harrison 106 Thursday 3pmPure Mathematics

 

Compressible convection in rapidly rotating spherical shells
Kirill Kuzanyan (University of Leeds)
24 Apr 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

The dynamics of the Antarctic slope front
Peter Baines (Quantifying Earth Systems, QUEST, Earth Sciences, University of Bristol)
23 Apr 2007Harrison 107 Monday 2pmApplied Mathematics

 

Lean Implementation: Challenges, and Future Research Direction
Dr Kim Hua Tan (Univeristy of Nottingham)
19 Apr 2007Harrison 209 Thursday 2pmAdvanced Technologies RI
A series of case studies have been, and are being, performed, that look at challenges in Lean Implementation. The focus is on understanding current issues to identifying future research direction. Results are presented from four recent studies.

 

Challenges in the development of "non-powered, no moving part" technologies for urban water management
Dr Mike Faram (Hydro International plc)
5 Apr 2007Harrison 107 Thursday 2pmInformatics RI
Founded in 1980, Hydro International has developed a reputation as being an innovative and forward thinking party within the water management "equipment supply" sector. The company ranks among the top 800 UK R&D spenders overall and among the top 50 "industrial engineering" spenders. The presentation, by the group's Technical Manager, will provide an introduction to the company, focusing in particular on its technologies, many of which make clever use of fluid-dynamic or hydraulic principles in their operation. The challenges faced in developing such "simple in form" yet "complex in operation" systems will be discussed. This will consider the use of experimental methods and numerical techniques (including Computational Fluid Dynamics (CFD)) in product development, and the challenges faced in converting the outputs into practical performance prediction and design selection models.

 

Integrated wastewater asset management for small catchments
Guo, Yufeng (South West Water)
30 Mar 2007Harrison 102 Friday 1pmInformatics RI
Advanced asset management of wastewater systems has recently gained increasing support within industry and research. This project presents a decision support tool (DST) to address integrated management of wastewater assets in South West Water, including wastewater treatment works, sewers and wastewater pumping stations. In the DST, a catchment ranking system based on key performance indicators is set up to identify critical catchments. Proactive interventions are suggested with their potential impacts on cost, performance and failure trends. In the end, cost-effective maintenance strategies are accommodated, which can be employed into the industry capital maintenance plan and utilised as a part of "business as usual" operational management.

 

TBA
Shaun Stevens (East-Anglia)
29 Mar 2007Harrison 106 Thursday 3pmPure Mathematics

 

The precession-driven dynamo in a plane layer
Paul Roberts (IGPP, UCLA, USA)
23 Mar 2007Harrison 107 Friday 2pmApplied Mathematics
9th TAYLOR AND FRANCIS sponsored lecture. T&F are publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

Flood Risk Management
Dr Slobodan Djordjevic (University of Exeter)
16 Mar 2007Harrison 102 Friday 1pmInformatics RI
Flood Risk Management Research Consortium (FRMRC) is the ongoing research project involving about thirty UK institutions, with total budget in excess of £6m. Following an overview of the Consortium and the background of the CWS involvement, outputs from Work Package 6.1 Urban Flooding to date will be presented. Various problems in development of modelling approaches will be discussed and the examples from case studies will be shown. The following topics will be covered: – GIS-based tools to support integrated modelling of urban flooding – Interactions between below-ground and above-ground systems – Coupled 1D/1D and 1D/2D simulation of urban flooding – Sensitivity-based flood risk attribution Research themes envisaged for the second phase of the Consortium (FRMRC2, which is currently being negotiated with EPSRC and other funders) will be addressed, as well as some other projects that will result from this research in the near future.

 

Interpolation by vector-valued analytic functions, with applications to the controllability of linear systems
Jonathan Partington (University of Leeds)
15 Mar 2007Harrison 215 Monday 2pmApplied Mathematics

 

TBA
Ahmed Abbes (Paris)
15 Mar 2007Harrison 106 Thursday 3pmPure Mathematics

 

Parametric instability of the helical dynamo
Marine Peyrot (LEGI, Grenoble)
13 Mar 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

Efficient data assimilation for spatially extended systems: a local ensemble transform Kalman filter
Brian Hunt (University of Maryland, USA)
12 Mar 2007Harrison 107 Monday 4pmApplied Mathematics
8th TAYLOR AND FRANCIS sponsored lecture. T&F are publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

Spatial survival modelling and the 2001 UK foot-and-mouth disease epidemic
Professor Trevor Bailey (UoE)
9 Mar 2007Harrison 102 Fri 1pmInformatics RI
The potentially large economic impacts of animal disease epidemics have been highlighted in recent years through outbreaks such as foot-and-mouth disease (FMD) in the UK during 2001. This talk reports work from a project with the Veterinary Laboratories Agency (VLA), Weybridge, UK which is concerned with use of survival modelling to develop dynamic space-time predictions of survivor and hazard functions for individual farm premises as an animal disease epidemic progresses. Such survival analyses could provide powerful insights into the patterns of infection, and assist in optimising various aspects of the operational response activities, such as targeting of `at-risk' premises. The talk will discuss and compare various possible Bayesian model formulations using both real and simulated epidemics and then go on to illustrate how model predictions may be used to refine epidemic control policies

 

Cohomology of locally analytic representations
Jan Kohlhaase (Muenster)
9 Mar 2007Harrison TBA Friday TBAPure Mathematics

 

Innovative phase-change pigging of difficult topologies
Professor Joe Quarini (University of Bristol)
8 Mar 2007Harrison 107 Thursday 2pmAdvanced Technologies RI
The brief presentation will introduce the concept of using phase changing slurries to act as pigs. The aims of these pigs are to hydraulically clean ducts and equipment as well as product recover and product separate material within complex processing plant. In its simplest form, this technology uses water with a freezing point depressant to produce a pumpable ice slurry with the attractive rheological property of behaving like a fluid when under dramatic shear gradients and looking more like a solid when shear is reduced. This means that the ‘ice pig’ is able to pass through orifice plates and then expand out to remove debris on the downstream side of the contraction! The ice pig can be used to clean very complicated geometries, including plate heat exchangers. It can be used as a separator between fluid streams as well as to recover fluid in ducts and equipment. Typically, it requires 100 to 1000 volumes of water to achieve the same level of ‘clean’ as one volume of the ice pig. What makes it really attractive is that it can never ever get stuck….it simply melts away. Further, it is environmentally very friendly, as it reduces waste, ameliorates the need for effluent treatment and reduces the amount and potency of harsh cleaning chemicals currently used. The potential beneficiaries include the food manufacturing sector, fine chemical producers, the medical/pharmaceutical industry and the utilities including water and power.

 

Exactly solvable problems for excitons in two dimensions
Misha Portnoi (University of Exeter)
6 Mar 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

The dynamics of deep convection and large-scale tropical wave motion
Glenn Shutts (Met office)
5 Mar 2007Harrison 107 Monday 2pmApplied Mathematics

 

Managing Distribution Retention Time to Improve Water Quality
Malcolm Brandt (Black and Veatch Ltd)
1 Mar 2007Harrison 107 Thursday 2pmInformatics RI
When water leaves a treatment works and travels through a distribution system, its quality, with respect to many chemical and biological parameters, will degrade. The quality of the delivered water will be largely influenced by: The quality of treated water supplied into the network; The condition of distribution assets within the network; The retention time within the network. The water industry has focused predominantly on the quality of treated water and the physical condition of distribution assets when improving the quality of water at the customer’s tap. However the quality of the water delivered is also affected by the time the water is retained in the different elements of the distribution network. Retention time is controlled both by the physical characteristics of the system and the operational regime. Physical characteristics such as pipe roughness may change throughout the life of the asset or be modified by rehabilitation. The aim of this research is to demonstrate that water quality within distribution networks can be managed effectively by controlling retention time and to develop practical and pragmatic methodologies for doing so.

 

On the p-adic elliptic polylogarithm and the two-variable p-adic L-function for an CM-elliptic curve
Kenichi Bannai (Nagoya/Paris)
1 Mar 2007Harrison 106 Thursday 3pmPure Mathematics

 

Transient dynamics - are they just a passing trend or ... ?
Stuart Townley (University of Exeter)
27 Feb 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

Are the fractal skeletons the explanation for the plankton paradox and the in-stent restenosis?
Celso Grebogi (University of Aberdeen)
26 Feb 2007Harrison 107 Monday 2pmApplied Mathematics
Nature is permeated by phenomena in which active processes, such as chemical reactions and biological interactions, take place in environmental flows. They include the dynamics of growing populations of plankton in the oceans and the evolving distribution of ozone in the polar stratosphere. I will show that if the dynamics of active particles in flows is chaotic, then necessarily the concentration of particles have the observed fractal filamentary structures. These structures, in turn, are the skeletons and the dynamic catalysts of active processes, yielding an unusual singularly enhanced productivity. I will argue that this singular productivity could be the hydrodynamic explanation for the plankton paradox, in which an extremely large number of species are able to coexist, negating the competitive exclusion principle that asserts the survival of only the most perfectly adapted to each limiting resource. I will then suggest that the presence of such fractal skeletons in arterial flow could be the explanation for the eventual restenosis of arteries after a stent-assisted angioplasty.

 

Evolutionary Optimisation for Microsoft Excel
Josef Bicik (UoE)
23 Feb 2007Harrison 102 Fri 1pmInformatics RI
The aim of this seminar is to introduce a new tool allowing the use of single and multiple-objective optimisations using genetic algorithms from within Microsoft Excel. The presentation will show the features of the tool and demonstrate them on several optimisation problems. Special attention will be paid to use of the tool in the optimisation of water systems, however it will be shown that it can be integrated with various other simulation packages.

 

Potentially crystalline representaions and p-adic representations of GL_2.
Matthias Strauch (Cambridge)
23 Feb 2007Harrison TBA Friday TBAPure Mathematics

 

Simulations of nonlinear pore-water convection in spherical shells
Zhifeng Dai (University of Exeter)
20 Feb 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

Quaternions and particle dynamics in the Euler equations
John Gibbon (Imperial College London)
19 Feb 2007Harrison 107 Monday 2pmApplied Mathematics

 

Practical bifurcation analysis of piecewise smooth systems
Daniel Pagano (University of Bristol)
15 Feb 2007Harrison 107 Thursday 2pmApplied Mathematics
The lack of smoothness in these systems precludes the application of local analysis tools (so useful in differentiable dynamics) and then, as a consequence, the separation between local and global issues has a fuzzy character, if it actually exists. Therefore, the bifurcation analysis in this context turns out to be cumbersome and specific for each concrete case. We will show how to proceed in order to obtain bifurcation sets in representative families of planar Filippov systems, and comment the difficulties to overcome in non-solved cases.

 

On the continuous part of codimension two algebraic cycles on certain threefolds over a field
Volodya Guletskii (University Of Liverpool)
15 Feb 2007Harrison 106 Thursday 3pmPure Mathematics
Let X be a non-singular projective threefold over a field with resolution of singularities, and let A^2(X) be the group of algebraically trivial codimension 2 algebraic cycles on X modulo rational equivalence with coefficients in Q. Assume X is birationally equivalent to another threefold X' admitting a fibration over a curve whose generic fiber F satisfies the following three conditions: (i) the motive M(F) is finite-dimensional, (ii) for l-adic etale cohomology H^1(F)=0 and (iii) H^2(F) is spanned by divisors on F. We prove that, provided these three assumptions, the group A^2(X) is weakly representable: there exists a curve Y and a correspondence z from Y to X, such that z induces an epimorphism A^1(Y) --> A^2(X), where A^1(Y) is isomorphic to Pic^0(Y) tensored with Q. In particular, the result holds for threefolds birational to three-dimensional Del Pezzo fibrations over a curve.

 

Marginal stability of planetary convection and magnetism
Sergey Starchenko (IZMIRAN, Troitsk, Russia)
13 Feb 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

Numerical methods for solving electromagnetic problems
Jun Zou (The Chinese University of Hong Kong)
12 Feb 2007Harrison 107 Monday 2pmApplied Mathematics
7th TAYLOR AND FRANCIS sponsored lecture. T&F are publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

An Operational Framework for Trading Water Abstraction Permits in England and Wales
Ana Maria Millan (University of Exeter)
9 Feb 2007Harrison 102 Fri 1pmInformatics RI
This study aims to show how the use of market forces to allocate water resources can improve the allocation of water resources in England and Wales. At present, there are growing concerns about the availability of water resources in England and Wales to satisfy increasing demands. These derive mainly from traditional consumers, from the requirements of the Water Framework Directive to protect the water-dependent environment, and from the effects of climate change on flow variability and drought frequency. These conditions show the vulnerabilities of the existing allocation system, which in turn, create an opportunity to propose changes.

 

Development of a Performance Measurement System for JIT Enabled Manufacturing Environment
Dr Chike Oduoza (Univeristy of Wolverhampton)
8 Feb 2007Harrison 107 Thursday 2pmAdvanced Technologies RI
The quest for performance measurement and improvement in the manufacturing industry has been an important agenda over the last few decades. It forms an integral part of management control systems and it is used to gauge the performance of business enterprises. Performance Measurement Systems (PMS) are most successful when they are integrated with the company mission, vision, values and strategy. Under intensive global competitive pressure, most companies around the world have applied innovative thinking to management and begun to examine technology that can lead to improved manufacturing flexibility. Just-in-time manufacturing (JIT), and lean manufacturing are thought to be some of the most important performance enhancing management innovations during the last two decades. However, to date, relatively little research has determined what PMS is consistent with the adoption of lean manufacturing systems such as JIT. Empirical research involving the study of JIT consists primarily of case studies of specific organizations, which have implemented JIT philosophy, however there is no methodology for the measurement of success or failure of this technique or the effect of relevant parameters on its successful implementation The aim of this study is to present a methodology for performance measurement in a JIT enabled manufacturing environment and will identify JIT drivers that are key to influencing performance in a typical production environment. Dynamic simulation and modelling, and a variety of management tools will be applied to determine the impact of typical variables such as TQM, line balancing, set up time etc on enterprise productivity and efficiency. The outcome is a model that would serve as a guide to researchers and industry practitioners on the approach to effective JIT implementation.

 

Dynamo action in a helical pipe
Leszek Zabielski (Warsaw University of Technology)
5 Feb 2007Harrison 107 Monday 2pmApplied Mathematics

 

Modelling Pollutant Adsorption: The atomistic view
Arnaud Marmier (UoE)
2 Feb 2007Harrison 102 Fri 1pmInformatics RI
Halogenated chemicals have been used as pesticides and generated as by products of industrial, commercial or social activities. Crucial information needed in order to assist stakeholders in developing remediation strategies for land contaminated by these pollutants includes data on how the pollutants move through a contaminated environment and how the pollutants change and degrade with time. Experiments to answer these questions are difficult to perform and require a significant investment of time. Consequently, such experiments are generally limited studies of a few specific molecules interacting with a small number of soil types. Atomic scale computational models provide a method complementary to experiment. They can produce additional information that aids our understanding of the fundamental processes that lead to pollutant mobility. In this communication, I focus on the adsorption of polychloro-dibenzo-p-dioxins (PCDDs) and polychloro-biphenyls (PCBs). In order to better understand how these pollutants move through soils I performed calculations at the atomic scale to resolve how they bind to the components of typical soils. The surface chosen is the (001) face of the di-octahedral 2:1 sheet silicate pyrophillite, Al4Si8O20(OH)4. This is a particularly simple example of the family of clay minerals that form a significant fraction of many soil and rock types. I will also discuss the possibilities offered by some eScience tools for high-throughput modelling of this sort.

 

HANDLING UNCERTAINTY IN REAL-TIME FLOOD FORECASTING SYSTEMS
Professor Ian Cluckie (University of Bristol)
1 Feb 2007Harrison 107 Thursday 2pmInformatics RI
The seminar will focus on the problems of handling uncertainty in complex real-time flood forecasting systems. This will inevitably introduce the use of closely coupled high-resolution mesoscale atmospheric models at one end of the scale and quantitative weather radar at the other. Some of the features of coupled models and systems will be introduced in relation to both urban and rural flood forecasting. The seminar will seek to provide an overall briefing on the area with an introduction to some of the exciting developments which are currently underway. This is particularly so in terms of the current efforts to utilise dual-polarisation weather radar technology for operational purposes in the United Kingdom.

 

Upper triangular technology and the Arf-Kervaire invariant
Victor Snaith (University Of Sheffield)
1 Feb 2007Harrison 106 Thursday 3pmPure Mathematics
This is a talk about an old topology problem in the theory of the homotopy groups of spheres. I will do my best to make it entertaining for non-specialists with emphasis on (i) mathematical history and (ii) the simple algebra which Upper Triangular Technology transforms the topology in.

 

Reduced atmospheric models using dynamically motivated basis functions
Frank Kwasniok (University of Exeter)
30 Jan 2007Harrison 209 Wednesday 2pmApplied Mathematics (Internal)

 

Overcoming essential instabilities induced by coupling delay
Jan Sieber (University of Aberdeen)
29 Jan 2007Harrison 107 Monday 2pmApplied Mathematics
Realistic tests in mechanical engineering often involve bidirectional real-time coupling between computer simulations and mechanical experiments. If this coupling occurs at a fixed joint then arbitrarily small delays in the coupling can result in an essential instability, that is, the linearization has infinitely many unstable eigenvalues. A general theorem (see, for example, the textbook of Hale/Verduyn-Lunel) implies that this kind of instability is impossible to compensate. We discuss an approach that is potentially able to overcome this difficulty. This is joint work with Yuliya Kyrychko (Bristol).

 

Nonlinear dynamics of lasers
Sebastian Wieczorek (University of Exeter)
23 Jan 2007Harrison 203 Wednesday 1pmApplied Mathematics (Internal)

 

Solitons in photonic crystal fibers
Dmitry Skryabin (University of Bath)
22 Jan 2007Harrison 107 Monday 2pmApplied Mathematics

 

Modelling atmospheres
Beccy Mitchell, Dan Holdaway and James Kent
19 Jan 2007Harrison 107 Wednesday 3pmApplied Mathematics (Internal)

 

Data inversion in solar radio spectroscopy: application to the flares
Gregory Fleishman (Ioffe Physico-Technical Institute, St. Petersburg, Russia)
16 Jan 2007Harrison 107 Wednesday 1pmApplied Mathematics (Internal)

 

Design of parametrically forced patterns
Alastair Rucklidge (University of Leeds)
15 Jan 2007Harrison 170 Monday 2pmApplied Mathematics

 

Some dynamical systems without ergodicity
Peter Ashwin (University of Exeter)
9 Jan 2007Harrison 107 Wednesday 1pmApplied Mathematics (Internal)

 

Equation-free modeling of inelastic collapse
Mark Muldoon (University of Manchester)
8 Jan 2007Harrison 107 Monday 2pmApplied Mathematics
A hard sphere gas whose particles collide inelastically lacks a straightforward hydrodynamic limit and its evolution is poorly described by PDEs. Such gasses undergo a so-called "inelastic collapse", after which most particles are confined to slow-moving, high-density clusters. Here we apply the recent, "equation-free" methods of Kevrekides and collaborators---which combine short bursts of stochastic simulation with Euler-like time stepping---to a prototypical example of inelastic collapse, a one-dimensional gas originally studied by Du, Li and Kadanoff.

 

Modelling of contaminant transport in soils
Mohammed Al-Najjar (University of Exeter)
15 Dec 2006Harrison 102 Friday 1pmInformatics RI
The movement of contaminants through soils to the groundwater is a major cause of degradation of water resources. In many cases, serious human and stock health implications are associated with this form of pollution. In this presentation, the development and validation of a numerical model for simulation of the flow of water and air, heat transfer and contaminant transport through unsaturated soils will be presented. All the major mechanisms and phenomena controlling transport of contaminants in soils (including advection, dispersion, diffusion, adsorption (under equilibrium and non-equilibrium conditions), chemical reactions and the effect of mobile and immobile domains on transport of contaminants in the soil) have been considered in the model. The mathematical framework and the numerical implementation of the model will be presented and described. The validation of the model will be presented by application to several experiments on contaminant transport in soils from the literature. The application of the model to some case studies will then be presented and discussed.

 

Simulated annealing and greedy search for multi-objective optimisation
Dr Richard Everson (University of Exeter)
8 Dec 2006Harrison 209 Friday 1pmInformatics RI
Evolutionary optimisation algorithms can be broadly categorised by the search techniques used. One such categorisation can be made upon the acceptance criteria for solutions within the algorithm; two popular criteria are to allow only greedy searching (to discard solutions which are not an improvement over previous solutions) and to retain new solutions by Metropolis-Hastings sampling (as used in simulated annealing). Another categorisation can be made comparing algorithms which sequentially optimise a single solution and those which consider a set of solutions for optimisation. In this seminar we introduce a new multi-objective simulated nnealing technique and illustrate the effect upon convergence of combinations of greedy searching, searching with an annealing schedule, sequential optimisation of a single solution and optimisation of a set of solutions. Apparently greedy strategies are found to be remarkably effective for many problems and we discuss the types of multi-objective problem that will prevent convergence of greedy optimisers.

 

Solar differential rotation: a new proposal for the tachocline
Michael McIntyre (DAMTP, University of Cambridge)
4 Dec 2006Harrison 107 Monday 2pmApplied Mathematics

 

On McRae's Invariant
Prof Peter Vamos (University Of Exeter)
4 Dec 2006Harrison 209 Monday 3pmPure Mathematics (Internal)

 

Fuzzy multiobjective optimisation for WDS
Dr Lydia Vamvakeridou-Lyroudia (University of Exeter)
1 Dec 2006Harrison 102 Fri 1pmInformatics RI
This seminar presents the application of fuzzy reasoning, combined with hierarchical multiobjective optimisation for the design of water distribution networks, using genetic algorithms. The problem has been formally structured as a Multilevel Multicriteria Decision Making (MCDM) process with two objectives: cost minimisation and benefits maximisation, resulting in a Pareto trade-off curve of non dominated solutions. A number of criteria are introduced, individually assessed by fuzzy reasoning. The overall benefits function is a combination (aggregation) of criteria, according to their relative importance and their individual fuzzy assessment. It is obtained through an analytic hierarchy process (AHP), applied directly within the genetic algorithm, using an original mathematical approach. The decision maker enters data and preferences using exclusively linguistic “engineer friendly” definitions and parameters. In this way, the whole design algorithm moves away from strict numerical functions, and acts as a Decision Support System (DSS) for water network design optimisation. The model has been applied to “Anytown”, a well-known benchmark network, for which results are presented and discussed.

 

Multi-objective Optimization on Operation of Water Distribution Systems in China
Professor Liu (Tongji University, China)
30 Nov 2006Harrison 107 Thursday 2Informatics RI
Traditional research and application of optimal operation of water distribution systems was mostly based on functions of least cost in construction and energy consumption. With the fast urban development and the ageing pipe networks in the world, new targets and tasks have been arising out for water supply companies to deal with, e.g. water pressure satisfaction, water quality uncertainty, water leakage and bursts, environment requirements, etc. In the presentation, extended period simulation models and computer software on optimal operation of water distribution systems were introduced for assessment and forecasting of the hydraulic movements, water quality changes and towards to real time optimal operation and control, based on multiple objectives. The software was applied in several cities in China with valuable results for improving the further planning and operation techniques in water distribution systems. In addition, definitions of optimal diameters and economic leakage in the pipe network will be discussed.

 

Sediment transport above rippled beds
Vanesa Magar (University of Plymouth)
28 Nov 2006Harrison 107 Wednesday 1pmApplied Mathematics (Internal)

 

Quadratic differential forms and (some of) their applications
Paolo Rapisarda (University of Southampton)
27 Nov 2006Harrison 107 Monday 2pmApplied Mathematics
Often when dealing with dynamical systems it is important to describe and analyze the interplay of dynamics and functionals of the variables of the system and their derivatives; for example, in the case of linear systems, quadratic functionals are of paramount importance in filtering, estimation, optimal control, etc. Recently, the formalization of these functionals using two-variable polynomial matrices has been proposed by Willems and Trentelman in a framework in which there is no need to use first-order (i.e. state) representations of a dynamical system as it is customary to do, and one can work with descriptions of the dynamics in terms of systems of higher-order differential equations. In this talk the basic features and some applications of the calculus of these so-called quadratic differential forms are presented.

 

Discolouration of water distribution networks
Dr Jan Vreeburg (KIWA (Netherlands))
24 Nov 2006Harrison 102 Fri 1pmInformatics RI
Discolouration is the single most important reason for customers to complain at their water company about the water quality. Traditionally discoloured water is assumed to be the result of corrosion of unlined cast iron pipes. In the Netherlands (and also elsewhere) however the problem also exists in completely plastic or cementitious pipes so the corrosion cannot be the single cause. In the last decade a lot of research has been done to the nature and cause of discoloured water that resulted in new knowledge and new approaches. Managing discoloured water in a network demands a multi-angle approach. In the Netherlands a three stage approach has been developed based on an understanding of the theory of particles in the network. Remedial actions are aimed at hydraulically controlling the accumulation of particles. The results of this approach are comprehensive guidelines for cleaning networks and designing of self cleansing networks. Continuing research in the Netherlands is now concentrating on the challenge of improving the water quality at the treatment to prevent to loading of the network and in that way try to get a proactive solution instead of the reactive measures as cleaning the network. The aim of the lecture is to demonstrate the new knowledge and analysis techniques and try to translate this into practical guidelines and new additional research challenges for the typical UK situation.

 

High Productivity Welding for the Trans Alaska Gas Pipeline
Professor Stewart Williams (Cranfield University)
23 Nov 2006Harrison 215 Thursday 2pmAdvanced Technologies RI
Installation of new pipelines is predicted to grow at a rapid rate over the next twenty years, due in part to the increase use worldwide of combined cycle power generation plant using natural gas as fuel. The need to construct large diameter pipelines over long distances has led to an increased demand to improve the productivity of pipeline girth welding. The Welding Engineering Research Centre (WERC) at Cranfield University has been researching into to this application for several with the work split into three phases:  Phase 1 – High efficiency automated dual tandem GMA (CAPS) for improved productivity in the fill passes (4 instead of 16)  Phase 2 – Application to very high strength steel to reduce the pipe wall thickness from 25mm to 20mm (and therefore material costs (500,00 tonnes less))  Phase 3 – Fibre laser or hybrid fibre laser welding of the root pass – higher speeds. The talk will describe how gas pipelines are manufactured, provide a brief history of pipeline welding, and describe how the first two phases have implemented along with the current research into phase three. The talk will be preceded by a brief introduction to Cranfield University and the current research programme of the WERC.

 

The effect of mantle conductivity on the super-rotating jets near the liquid core surface
Konrad Bajer (Warsaw University, Poland)
23 Nov 2006Harrison 107 Thursday 2pmApplied Mathematics

 

Arithmetic conjectures on algebraic cycles
Prof Andreas Langer (University Of Exeter)
20 Nov 2006Harrison 209 Monday 3pmPure Mathematics (Internal)

 

Translating conjunctive water management from concept to practice in mature irrigation systems
Imogen Fullagar (CSIRO, Australia)
17 Nov 2006Harrison 102 Fri 1pmInformatics RI
Environmental and production demand for water are increasing interest in realising system efficiencies of groundwater and surface water. This is difficult in mature irrigation systems because management regimes tend to separate groundwater and surface water responsibilities and accounting. Ms Fullagar's research has been to design scoping processes to identifying system efficiency opportunities, and deliver these through local (socio-economic and management) circumstances. The development of these processes has been based primarily on qualitative data from Coleambally, a rice-growing irrigation area in New South Wales, Australia. Feedback and comment on processes and research method is welcome.

 

Rapid mixing and other statistical properties of Lorenz attractors
Mark Holland (University of Exeter)
14 Nov 2006Harrison 107 Wednesday 1pmApplied Mathematics (Internal)
I will survey the statistical properties of Lorenz maps and Lorenz flows and in particular give details about the mixing properties of the classical Lorenz attractor (work in progress).

 

Vortex multipoles and vortex quasimodes: the parallels and differences between coherent structures of fluids and plasmas
Lorena Barba (University of Bristol)
13 Nov 2006Harrison 107 Monday 2pmApplied Mathematics
A column of electrons surrounded by a conducting wall and confined by a strong magnetic field is an excellent manifestation of two-dimensional vortices in an inviscid fluid. The equations governing the drift motion of a magnetized electron column are isomorphic to the Euler equations for incompressible, 2D flow. This isomorphism implies, for example, that surface charge perturbations on the electron column (called diocotron modes) are equivalent to surface waves on vortex columns (called Kelvin waves). In the plasma literature, a quasimode is a vorticity perturbation which is weakly damped, and behaves like it was a single azimuthally propagating wave on the vortex edge. In fluids, a multipole is an arrangement of two or more peaks of vorticity which is compact, coherent and long-lived. The topology of quasimodes and multipoles can appear quite similar. But, is there any inherent physical relationship between the core quasimodes, basically explained by wave phenomena, and the hydrodynamic multipoles, which are more readily explained by the nonlinear interaction of vorticity?

 

Realizable Galois Module Classes for some Nonabelian Extensions
Dr Nigel Byott (University Of Exeter)
13 Nov 2006Harrison 209 Monday 3pmPure Mathematics (Internal)

 

Data-driven Approach to Asset Deterioration Modelling.
Prof Dragan Savic (University of Exeter)
10 Nov 2006Harrison 102 Fri 1pmInformatics RI

 

Piezoelectric composites: Properties and applications
Chris Bowen (University of Bath)
9 Nov 2006Harrison 107 Thursday 2pmAdvanced Technologies RI
This presentation will provide an overview of the properties and applications of piezoelectric composites. Porous piezoelectrics ceramics with '3-3' connectivity will be described for hydrophone applications and the mechanism by which porosity increases the performance of the material for SONAR applications will be discussed. These porous piezoelectrics will also be infiltrated with a conductive phase to create model conductor-dielectric composites in an attempt to understand the origins of the 'universal dielectric response'; a property observed in many materials. Both modelling and experimental results will be presented.

 

Bringing mathematical insights to the climate change problem
Peter Cox (University of Exeter)
7 Nov 2006Harrison 106 Wednesday 1pmApplied Mathematics (Internal)

 

Analytic invariants associated with a parabolic fixed point in C^2
Vincent Naudot (University of Warwick)
6 Nov 2006Harrison 107 Monday 2pmApplied Mathematics
Near a parabolic fixed point 0 in R^2, a real analytic diffeomorhism can be embedded in a smooth autonomous flow. We show that in the complex-analytic case the situation is completely different. We construct 2 analytic invariants with respect to local analytic changes of coordinates. One invariant vanishes for time-1 maps of analytic flows but generically not equal to 0.

 

Hopf-Galois Module Structure Of Tame Biqaudratic Extensions
Paul Truman (University Of Exeter)
6 Nov 2006Harrison 102 Monday 3pmPure Mathematics (Internal)

 

Multi-Objective Optimisation in the Presence of Uncertainty
Jonathan Fieldsend (University of Exeter)
3 Nov 2006Harrison 102 Friday 1pmInformatics RI
There has been only limited discussion on the effect of uncertainty and noise in multi-objective optimisation problems and how to deal with it. Here this problem is addressed by assessing the probability of dominance and maintaining an archive of solutions which are, with some known probability, mutually nondominating. Methods are examined for estimating the probability of dominance. These depend crucially on estimating the effective noise variance and a novel method for learning the variance during optimisation is discussed as part of this. Probabilistic domination contours are presented as a method for conveying the confidence that may be placed in objectives that are optimised in the presence of uncertainty.

 

An efficient phase-field model for polycrystaline grain growth
Prasad Patnaik (University of Exeter)
31 Oct 2006Harrison 106 Wednesday 1pmApplied Mathematics (Internal)

 

TBA
Francesco Di-Pierro (University of Exeter)
27 Oct 2006Harrison 102 Friday 1pmInformatics RI
TBA

 

Slow flow between concentric cones
Oskar Hall (University of Exeter)
24 Oct 2006Harrison 106 Wednesday 1pmApplied Mathematics (Internal)

 

The helicity conservation in delta-Omega and alpha-delta-Omega and its impact to eleven year solar torsional oscillations
Valery Pipin (Institute Solar-Terrestrial Physics, Irkutsk, Russia)
23 Oct 2006Harrison 107 Monday 2pmApplied Mathematics
This is the 5th TAYLOR AND FRANCIS sponsored lecture. Taylor and Francis are the publishers of the Journal Geophysical and Astrophysical Fluid Dynamics.

 

Discolouration in potable water distribution systems
Dr Joby Boxall (Pennine Water Group)
20 Oct 2006Harrison 102 Friday 1pmInformatics RI
Discolouration is one of the single biggest causes of water quality related customer complaints received by water supply companies. Hence, water companies wish to be able to predict the occurrence of discolouration events and implement appropriate operational and maintenance strategies to reduce such complaints. However there is a large degree of uncertainty around the processes that lead to discolouration events. This talk will present the development of a modelling approach towards predicting the occurrence of discolouration events and the results of field and laboratory studies undertaken to elucidate discolouration processes and mechanisms. For further background information, see the project web page www.PODDS.co.uk

 

Improved Methods for the Optimum Design and Operations of Water Distribution Systems
Prof. Graeme Dandy (University of Adelaide)
19 Oct 2006Harrison 170 Tuesday 2pmInformatics RI
A water distribution system (WDS) is a very complicated system of reservoirs, tanks, pipes, pumps and valves that supplies water to the population of a city. If the system is working properly, it will provide water on demand at adequate pressures and of a suitable quality. A great deal of research has been carried out into the optimum design and operations of WDS. Evolutionary techniques such as genetic algorithms (GAs) have proven to be extremely useful in solving these large non-linear optimisation problems. However, GAs have the disadvantage that they may require very long run times to identify near-optimal solutions. This presentation will provide some background on the development and application of genetic algorithms for optimising the planning, design and operations of WDS. The emphasis will be on the practical applications of this set of techniques to real water supply systems. There will be a discussion of recent developments aimed at producing significant speed up of GAs using meta-modeling. Meta-modelling works by combining the GA with a simplified (statistical or neural network) model of the system. Excellent results have been achieved at run times that are 100 to 1000 times faster than the GA alone. There will also be a discussion of recent research into the optimisation of water quality in WDS and the consideration of sustainability objectives in WDS.

 

Asymptotic receptivity and the Parabolized Stability Equation: a combined approach to boundary layer transition
Matthew Turner (University of Exeter)
17 Oct 2006Harrison 106 Wednesday 1pmApplied Mathematics (Internal)

 

Spatio-temporal epidemic modelling for public health protection
Ian Hall (Health Protection Agency: Porton Down)
16 Oct 2006Harrison 107 Monday 2pmApplied Mathematics

 

Multiobjective optimization of water reuse systems
Darko Joksimovic (University of Exeter)
13 Oct 2006Harrison 102 Friday 1pmInformatics RI
This presentation will deal with the recently completed research project - AQUAREC, in which the role of the CWS was to derive design principles for integrated water reuse systems. This was achieved by first developing a simulation and optimisation methodology, incorporating it in a DSS named WTRNet, and applying the developed software on several case studies. Following a brief introduction into the concept of integrated water reuse planning, the DSS methodology will be presented with particular focus on its optimisation component. The presentation will conclude with a discussion of WTRNet application results and possible future work.

 

TBA
TBA
12 Oct 2006Harrison None Thursday 2pmAdvanced Technologies RI

 

Regulation of primary photosynthetic processes and problems of ecological monitoring
Andrei Rubin (Moscow State University)
10 Oct 2006Harrison 106 Wednesday 1pmApplied Mathematics (Internal)

 

Connections between discrete control theory and numerical methods for ODEs
Adrian Hill (University of Bath)
9 Oct 2006Harrison 107 Monday 2pmApplied Mathematics
We write a general linear method for the numerical integration of ODEs as a discrete control system. The positive real lemma, the Z-transform and perturbation methods are used to explore the stability of such numerical methods.

 

The Battle of the Water Sensor Networks: Multiobjective Cross-Entropy Approach
Gianluca Dorini and Philip Jonkerguow (University of Exeter)
6 Oct 2006Harrison 102 Friday 1pmInformatics RI

 

What is the Region Occupied by a Set of Points?
Dr Anthony Galton (University of Exeter)
5 Oct 2006Harrison 170 Tuesday 2pmInformatics RI
There are many situations in GIScience where it would be useful to be able to assign a region to characterize the space occupied by a set of points. Such a region should represent the location or configuration of the points as an aggregate, abstracting away from the individual points themselves. In this paper, such a region will be called a 'footprint' for the points. We investigate and compare a number of methods for producing such footprints, with respect to nine general criteria. The discussion identifies a number of potential choices and avenues for further research. Finally, we contrast the related research already conducted in this area, highlighting differences between these existing constructs and our 'footprints'.

 

Numerical Rossby wave propagation on the C-grid
John Thuburn (University of Exeter)
3 Oct 2006Harrison 106 Wednesday 1pmApplied Mathematics (Internal)

 

Decay of correlations for Lorentz gases
Ian Melbourne (University of Surrey)
2 Oct 2006Harrison 107 Monday 2pmApplied Mathematics

 

Verifying deterministic forecasts of extreme events
Chris Ferro (Department of Meteorology, University of Reading)
25 Sep 2006Harrison 254 Monday 2pmApplied Mathematics
Forecast verification, the practice of assessing forecast quality, is difficult for at least two reasons when the event being forecasted is rare. First, sampling variability of quality measures may be high if only a small number of events has been observed. Second, many quality measures necessarily degenerate to trivial values as events become rarer. These problems will be mitigated by means of a statistical model based on extreme-value theory that quantifies the relationship between observations and forecasts. The model's two parameters can be interpreted as measures of forecast quality that do not degenerate with event rarity. The model also predicts the values of standard quality measures as event rarity increases. These model estimates are more efficient than evaluating the measures directly and show that different standard measures can indicate opposing changes in forecast quality as rarity increases. The model will be used to assess forecast quality for some extreme weather events.

 

The dynamo bifurcation in rotating spheres
Emmanuel Dormy (Ecole Normale Superieure, Paris)
22 Sep 2006Harrison 170 Friday 2pmApplied Mathematics
This is the 4th TAYLOR AND FRANCIS sponsored lecture. Taylor and Francis are the publishers of the Journal Geophysical and Astrophysical Fluid Dynamics.

 

TBA
TBA
14 Sep 2006Harrison None Thursday 2pmAdvanced Technologies RI

 

TBA
TBA
10 Aug 2006Harrison None Thursday 2pmAdvanced Technologies RI

 

TBA
TBA
13 Jul 2006Harrison None Thursday 2pmAdvanced Technologies RI

 

Feel sick? Follow the money!
Dr. Dirk Brockmann (Max-Planck-Institute for Dynamics and Self-Organization)
22 Jun 2006Harrison B74 Thursday 2pmApplied Mathematics
In the light of increasing international trade, intensified human mobility and an imminent influenza A epidemic the knowledge of dynamical and statistical properties of human travel is of fundamental importance. A quantitative assessment of these properties on geographical scales still remains elusive and the assumption that humans disperse diffusively still prevails in models.
In 1998 Hank Eskin invented the internet game wheresgeorge.com, an online bill tracking system.
The idea behind the game is simple. Users can register at the website, mark individual dollar bills, report them to the website, reenter them into circulation and subsequently monitor their geographic dispersal as other users make reports to the website. We have analysed the wheresgeorge.com dataset and used the dispersal of nearly half a million dollar bills as a proxy for human travel. We were thus able to assess the statistical properties of human travel with a high spatio-temporal precision. We found that dispersal is anomalous in two ways. First, the distribution of travelling distances decays as a power law, indicating that trajectories of bank notes are reminiscent of scale free random walks known as Lévy flights. Secondly, the probability of remaining in a small, spatially confined region for a time T is dominated by algebraic tails which attenuate the superdiffusive spread. We were able to show that human travel can be described mathematically on many spatiotemporal scales by a two parameter continuous time random walk model to a surprising accuracy and conclude that human travel on geographical scales is an ambivalent effectively superdiffusive process.

 

Periodicity in a system of two rotations (joint work with Anthony Quas)
Prof Arek Goetz (San Francisco State University)
13 Jun 2006Harrison 170 Tuesday 12 noonApplied Mathematics

 

Piezoelectric composites: Properties and applications
Dr Chris Bowen (Materials Research Centre, Department of Mechanical Engineering, University of Bath)
8 Jun 2006Harrison None Thursday 2pmAdvanced Technologies RI
This presentation will provide an overview of the properties and applications of piezoelectric composites. Porous piezoelectrics ceramics with '3-3' connectivity will be described for hydrophone applications and the mechanism by which porosity increases the performance of the material for SONAR applications will be discussed. These porous piezoelectrics will also be infiltrated with a conductive phase to create model conductor-dielectric composites in an attempt to understand the origins of the 'universal dielectric response'; a property observed in many materials. Both modelling and experimental results will be presented.

 

An overview of the research activities at IIT Kanpur: Hydrological Modelling
Dr. Ashu Jain (ITT Kanpur, India)
1 Jun 2006Harrison 170 Tuesday 2pmInformatics RI
"In this talk I plan to first give a very brief background of the Indian Institutes of Technology (IITs), IIT Kanpur, and the department of civil engineering at IIT Kanpur. The research activities of the Hydraulics and Water Resources Engineering (HWRE) group at IIT Kanpur will be presented. The focus will be on hydrological modelling. Some case studies on water demand modelling and hydrological modelling will be presented. The methods employed include data-driven techniques of Artificial Neural Networks (ANNs) and Genetic Algorithms (GAs). Special issues such as difficulties in ANN training, integration of conceptual and data-driven approaches, etc. will be discussed and the results presented. If the time permits, a case study on the exploration of physical significance in trained ANN hydrologic models will also be presented."

 

Syntomic cohomology and explicit reciprocity laws
Hannu Harkonen (University of Cambridge)
25 May 2006Harrison 106 Thursday 5pmPure Mathematics

 

Serre's conjectures over totally real fields
Frazer Jarvis (Sheffield)
25 May 2006Harrison 106 Thursday 3pmPure Mathematics

 

Relating forced climate change to natural variability
Owen Kellie-Smith
23 May 2006Harrison 106 Wednesday 12 noonApplied Mathematics (Internal)
Link to slides

 

Research in the Computer Graphics and Interactive Systems Laboratory at the Technical University of Cluj-Napoca in Romania
Professor Dorian Gorgan (Technical University of Cluj-Napoca)
23 May 2006Harrison 170 Tuesday 2pmInformatics RI
- Satellite image processing on the Grid structures (MEDIOGRID project) - Location based services - Graphical modelling and simulation of 3D textile surfaces - Pen based annotation in 2D and 3D graphical applications

 

Counting Hopf-Galois Structures
Nigel Byott (University Of Exeter)
22 May 2006Harrison 103 Tuesday NonePure Mathematics (Internal)

 

A conjectural relative fixed point formula
Damian Roessler (Paris)
18 May 2006Harrison 106 Thursday 3pmPure Mathematics

 

The validity of Boussinesq and anelastic equation sets in convecting atmospheres: A normal mode analysis
Rebecca Mitchell (Exeter)
16 May 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

The sheaf of overconvergent Witt Vectors
Prof Andreas Langer (University Of Exeter)
15 May 2006Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Near Infrared Optical Tomography for the detection of breast cancer
Dr Hamid Dehghani (School of Physics)
11 May 2006Harrison None Thursday 2pmAdvanced Technologies RI

 

Rigid syntomic cohomology with coefficients and applications
Kenichi Bannai (Paris)
11 May 2006Harrison 106 Thursday 3pmPure Mathematics

 

Delay induced dynamics of a nonlinear transmission line oscillator model
David Barton (Bristol Centre for Applied Nonlinear Mathematics, University of Bristol)
9 May 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

On the torsion of elliptic curves over sufficiently general function fields
Andreas Schweizer (University Of Exeter)
8 May 2006Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Generalized Coleman power series in K2
Sarah Zerbes (Paris)
4 May 2006Harrison 106 Thursday 3pmPure Mathematics

 

Pseudospectra
Dominic Mc-Carthy (UIniversity of Exeter)
2 May 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

Dynamos in flows with cat's eyes
Andrew D Gilbert (Exeter)
25 Apr 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

Multilevel Classifier Systems - Issues, Motivations and Challenges
Dr Bogdan Gabrys (Bounemouth University)
6 Apr 2006Harrison 170 Tuesday 2pmInformatics RI
The talk will be concerned with pattern classification problems and in particular the motivations and challenges behind using and designing multiple classifier systems. Starting with an attempt to answer the question of why would one like to combine classifiers we will move to an overview of how to combine them. This will be followed by discussing the issues of majority voting limits and an illustration of the potential enhancement for theoretical error limits when using hierarchical multistage organisations for majority vote based combination systems. The talk will also cover the issues of classifier diversity, classifier selection and will finish with discussions of various practical evolutionary algorithm based implementations of multistage, multilevel and multidimensional selection-fusion models.

 

Multistability in the Kuramoto model with synaptic plasticity
Yuri Maistrenko (Institute of Medicin and Virtual Institute of Neuromodulation, Research Centre Jülich)
28 Mar 2006Harrison 106 Wednesday 11amApplied Mathematics (Internal)

 

A high order WENO finite difference scheme for incompressible fluids and magnetohydrodynamics
Paul Roberts (IGPP, UCLA, USA)
27 Mar 2006Harrison 170 Monday 2pmApplied Mathematics
Sponsored by TAYLOR AND FRANCIS, publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

Computed eigenmodes of planar regions
Nick Trefethen (University of Oxford)
16 Mar 2006Harrison 170 Thursday 2pmApplied Mathematics
Recently developed numerical methods make possible the high-accuracy computation of eigenmodes of the Laplacian for a variety of "drums" in two dimensions, or as some physicists prefer to call them, problems of "quantum billiards". A number of computed examples will be presented together with a discussion of their implications concerning bound and continuum states, symmetry and degeneracy, eigenvalue avoidance, resonance, localization, eigenvalue optimization, perturbation of eigenvalues and eigenvectors, and the problem of "can one hear the shape of a drum?".

 

Equivariant vector-bundles on p-adic symmetric spaces
Elmar Grosse-Kloenne (Muenster)
16 Mar 2006Harrison 106 Thursday 3pmPure Mathematics

 

Dependence of magnetic field generation by convective flows in a plane layer on the kinematic Prandtl number
Olga Podvigina (International Institute of Earthquake Prediction Theory and Mathematical Geophysics, Russian Ac.Sci.)
14 Mar 2006Harrison LT6 Tuesday 12pmApplied Mathematics
Sponsored by TAYLOR AND FRANCIS, publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

Dependence of magnetic field generation by convective flows in a plane layer on the kinematic Prandtl number
Olga Podvigina (International Institute of Earthquake Prediction Theory and Mathematical Geophysics, Russian Ac.Sci.)
14 Mar 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)
Sponsored by TAYLOR AND FRANCIS, publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

P-D Structures
Prof Andreas Langer (University Of Exeter)
13 Mar 2006Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Weakly nonlinear stability of convective hydromagnetic systems with insignificant alpha-effect in a plane rotating layer to perturbations involving large scales
Vlad Zheligovsky (International Institute of Earthquake Prediction Theory and Mathematical Geophysics, Russian Ac.Sci.)
7 Mar 2006Harrison LT6 Tuesday 12pmApplied Mathematics
Sponsored by TAYLOR AND FRANCIS, publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

Weakly nonlinear stability of convective hydromagnetic systems with insignificant alpha-effect in a plane rotating layer to perturbations involving large scales
Vlad Zheligovsky (International Institute of Earthquake Prediction Theory and Mathematical Geophysics, Russian Ac.Sci.)
7 Mar 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)
Sponsored by TAYLOR AND FRANCIS, publishers of the Journal Geophysical and Astrophysical Fluid Dynamics

 

Prehistoric demography and the spread of the Neolithic: Models based on radiocarbon dates
Anvar Shukurov (University of Newcastle upon Tyne)
6 Mar 2006Harrison 170 Monday 2pmApplied Mathematics

 

The Ring Of Witt-Vectors
Prof Andreas Langer (Universty of Exeter)
6 Mar 2006Harrison 103 Tuesday NonePure Mathematics (Internal)

 

The dynamincs of coupled phase oscillators
John Wordsworth (Exeter)
28 Feb 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

Bifurcation and non-uniqueness of exact Navier-Stokes solutions: Is it consistent to neglect far-field boundaries?
Rich Hewitt (University of Manchester)
27 Feb 2006Harrison 170 Monday 2pmApplied Mathematics

 

The onset of almost adiabatic planetary convection
Sergey Starchenko (Rybinsk State Avian-Technical Academy)
23 Feb 2006Harrison 170 Thursday 2pmApplied Mathematics

 

Galois-module structure of a cyclic extension: on a result of Miyata
Nigel Byott (University of Exeter)
23 Feb 2006Harrison 106 Thursday 3pmPure Mathematics

 

Galois-module structure of a cyclic extension: on a result of Miyata
Nigel Byott (University Of Exeter)
23 Feb 2006Laver B74 Thursday 3pmPure Mathematics (Internal)

 

Jeffery-Hamel flow between two cones
Oscar Hall (Exeter)
21 Feb 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

Transport of momentum and particle in hydrodynamic and magnetohydrodynamic turbulence
Eun-jin Kim (University of Sheffield)
20 Feb 2006Harrison 170 Monday 2pmApplied Mathematics

 

Synchronization of globally coupled chaotic maps: clusters and quasi-clusters
Anastasiya Panchuk (NAS of Ukraine, Kiev)
16 Feb 2006Harrison 170 Thursday 2pmApplied Mathematics

 

On the power of linear dependences
Imre Barany (London)
16 Feb 2006Harrison 106 Thursday 3pmPure Mathematics

 

What on earth is a Normalized Bi-Conjugate Minimum Residual Gradient Method? - A brief introduction to Krylov subspace methods"
John Thuburn (Exeter)
14 Feb 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

Describing and modeling biofilm mechanics
Isaac Klapper (Montana State University)
9 Feb 2006Harrison 170 Thursday 2pmApplied Mathematics

 

Remote Magnetic Sensing of People (Advanced Technologies Research Institute (ATRI) research seminar)
Professor Des Mapps (Centre of Expertise in Electromagnetic Sensors, University of Plymouth)
9 Feb 2006Harrison 203 Thursday 2pmEngineering

 

Real K3 surfaces
V. Nikulin (Liverpool)
9 Feb 2006Harrison 106 Thursday 3pmPure Mathematics
Up to deformation, there are three real types of elliptic curves which depend on the number of real ovals: 0, 1 or 2. All elliptic curves are hyper-elliptic, and their real forms can be obtained by the double covering of P^1/R ramified in four points, some of them conjugate. This gives equations of real elliptic curves.
K3 surfaces give a 2-dimensional generalization of elliptic curves. What about similar results for them? This will be the subject of the talk.

 

Wave Train Solutions in Spherical Couette Flow
Ed Blockley (Exeter)
7 Feb 2006Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

Hopf-Galois Module Structure of Tame Biquadratic Fields
Paul Truman (University Of Exeter)
6 Feb 2006Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Congruence kernels in arithmetic lattices
Alec Mason (Glasgow)
2 Feb 2006Harrison 106 Thursday 3pmPure Mathematics

 

Finite-dimensional attractors of randomly-forced PDEs
David Broomhead (University of Manchester)
30 Jan 2006Harrison 170 Monday 2pmApplied Mathematics

 

Nonlinear dynamics of warped accretion discs
Gordon Ogilvie (University of Cambridge)
23 Jan 2006Harrison 170 Monday 2pmApplied Mathematics

 

Approximate iterative methods for variational data assimilation
Amos Lawless (University of Reading)
16 Jan 2006Harrison 170 Monday 2pmApplied Mathematics

 

Green Ceramic Machining: A Top-down Approach to Rapid Prototyping of Ceramics
Dr Bo Su (Department of Oral and Dental Science, University of Bristol)
12 Jan 2006Harrison 203 Thursday 2pmEngineering

 

Nucleation of localised 2D patterns
David Lloyd (University of Surrey)
9 Jan 2006Harrison 170 Monday 2pmApplied Mathematics
Localised patterns have been observed in a variety of physical experiments from vibrated granular materials to nonlinear optics. We present the results of Umbanhowar et al. Nature 382 (1996) for the vibrated granular material problem and propose a new process for pattern formation and selection in 2-dimensions. We demonstrate this new process by taking a toy model, namely the Swift-Hohenberg equation. Taking our guidance from known 1D results, we develop analytical and numerical techniques to explore the nucleation of localised patterns in 2D. Finally, I present results showing the rich bifurcation structure of these patterns and suggest avenues for on going research.

 

Understanding turbulence through the sequence-of-bifurcation approach
Fritz Busse (University of Bayreuth)
8 Dec 2005Harrison 170 Thursday 2pmApplied Mathematics

 

Raster-based models for flood inundation: Simple solutions to a complex problem?
Dr Neil Hunter (School of Geographical Sciences, University of Bristol)
1 Dec 2005Harrison 203 Thursday 2pmEngineering

 

Polynomial invariants of links, graphs, and matroids
S Huggett (Plymouth)
1 Dec 2005Harrison 106 Thursday 3pmPure Mathematics
We review the relationships between links, graphs, and matroids. In particular, given a planar graph there are two well-established methods of generating an alternating link diagram. Switching from one of these methods to the other corresponds in knot theory to tangle insertion in the link diagrams, and in combinatorics to the tensor product of the cycle matroids of the graphs. We show how the Jones and Tutte polynomials behave under these operations.

 

Heuristic Algorithms in Group Theory
M. Craven (Exeter)
24 Nov 2005Harrison 106 Thursday 3pmPure Mathematics

 

Bifurcations and heteroclinic-like oscillations in highway traffic models with reaction-time delay
Gabor Orosz (University of Exeter)
22 Nov 2005Harrison LT6 Tuesday 12 noonApplied Mathematics (Internal)

 

Coupled systems: Theory and examples
Marty Golubitsky (University of Houston)
21 Nov 2005Harrison 170 Monday 2pmApplied Mathematics
A coupled cell system is a collection of interacting dynamical systems. Coupled cell models assume that the output from each cell is important and that signals from two or more cells can be compared so that patterns of synchrony can emerge. We ask: How much of the qualitative dynamics observed in coupled cells is the product of network architecture and how much depends on the specific equations? The ideas will be illustrated through a series of examples and theorems. One theorem classifies spatio-temporal symmetries of periodic solutions and a second gives necessary and sufficient conditions for synchrony in terms of network architecture.

 

Convectons
Edgar Knobloch (University of California, Berkeley)
17 Nov 2005Harrison 170 Thursday 2pmApplied Mathematics
Recent simulations of binary fluid convection reveal the presence of multiple numerically stable spatially localized steady states we have called 'convectons'. These states consist of a finite number of rolls embedded in a nonconvecting background and are present at supercritical Rayleigh numbers. The convecton length decreases with decreasing Rayleigh number; below a critical Rayleigh number the convectons are replaced by relaxation oscillations in which the steady state is gradually eroded until no rolls are present (the slow phase), whereupon a new steady state regrows from small amplitude (the fast phase) and the process repeats. The Swift-Hohenberg equation, both variational and nonvariational) provides much insight into this behaviour. This equation contains several classes of localized steady states whose length grows in a characteristic 'snaking' fashion as they approach spatially periodic states, and the associated dynamics resemble the binary fluid simulations. The origin of the snaking and the stability properties of the associated states will be elucidated, and the results used to shed light on the remarkable complexity of these simple systems.

 

Climate Sensitivities via a Fokker-Planck Adjoint Approach
John Thuburn (University of Exeter)
15 Nov 2005Harrison LT6 Tuesday 12 noonApplied Mathematics (Internal)

 

Stability of magnetic flux tubes subject to external flows
Antonio Ferriz Mas (Universidad de Vigo, Spain)
14 Nov 2005Harrison 170 Monday 2pmApplied Mathematics

 

Stark units, Hilbert symbols and Stickelberger-like ideals at s=1
D. Salomon (Kings College London)
10 Nov 2005Harrison 106 Thursday 3pmPure Mathematics

 

Uncertain Matrix Systems: From Pseudospectra to Kharitonov Theorems.
Stuart Townley (Universty of Exeter)
8 Nov 2005Harrison LT6 Tuesday 12 noonApplied Mathematics (Internal)

 

Metric approximations in global weather forecasting
Andy White (Met. Office)
7 Nov 2005Harrison 170 Monday 2pmApplied Mathematics
Weather forecasting by national meteorological centres such as the Met Office is guided by the output of numerical models of the atmosphere's motion and thermodynamics. Most centres use models based on the so-called hydrostatic primitive equations, which in a global context make an assumption of shallowness that involves neglect of part of the Coriolis force. Met Office models have been based on more accurate underlying equations since 1992, and on non-hydrostatic equations since 2002. Recent work has identified a hierarchy of consistent approximated equation sets that are at least as accurate as the hydrostatic primitive equations. The hierarchy includes the hydrostatic primitive equations themselves, the Met Office's equation sets, and a non-hydrostatic formulation used by the Canadian Environment Service. An equation set is said to be consistent if it possesses good conservation properties (for energy, angular momentum and potential vorticity) and if it can be directly derived from Lagrange's equations of motion. Four consistent formulations arise as two approximations are made or not made: (a) an assemblage of approximations known collectively as the shallow atmosphere approximation; (b) neglect of the time derivative in the vertical component of the momentum equation. These may be concisely regarded in terms of approximations of metrics - in one case, of metric factors that describe the assumed geometry, in the other case, of the velocity metric that appears in the definition of kinetic energy.

 

Hydroinformatics Technologies for Urban Water Systems Planning and Management
Dr Zoran Vojinovic (UNESCO-IHE Institute for Water Education (IHE-Delft))
3 Nov 2005Harrison 203 Thursday 2pmEngineering

 

Euler-characteristics of nearly perfect complexes
B. Koeck (Southampton)
3 Nov 2005Harrison 106 Thursday 3pmPure Mathematics

 

Uncertainty Intervals, Stability and Kharitonov’s Theorem
Dominic McCarthy (University of Exeter)
2 Nov 2005Harrison LT6 Wednesday 12 noonApplied Mathematics (Internal)

 

Spatiotemporal chaos in Rayleigh-Benard convection
Mike Cross (Caltech)
31 Oct 2005Harrison 170 Monday 2pmApplied Mathematics

 

Solving conics over function fields
J. Cremona (Nottingham)
27 Oct 2005Harrison 106 Thursday 3pmPure Mathematics

 

Uncertain Matrix Systems: From Pseudospectra to Kharitonov Theorems
Stuart Townley (University of Exeter)
25 Oct 2005Harrison LT6 Tuesday 12 noonApplied Mathematics (Internal)

 

Two-dimensional flows in slowly deforming domains
Jacques Vanneste (University of Edinburgh)
24 Oct 2005Harrison 170 Monday 2pmApplied Mathematics

 

Modelling of nucleation kinetics
Lindsay Greer (University of Cambridge)
20 Oct 2005Harrison 170 Thursday 2pmApplied Mathematics
Most phase transitions proceed by growth from particular nucleation sites, which either appear sporadically or are pre-determined. In recent decades great progress has been made in the quantitative analysis of growth kinetics, but nucleation remains notoriously difficult to model quantitatively. Yet nucleation is important in so many ways: not only in materials (casting of metals, transparency of polymers), but in medicine (CJD, kidney stones), environment (meteorology, crop damage). This presentation will introduce some of the issues in the mechanisms of nucleation, the consequences for how it is modelled and for mathematical techniques. There are, for example, nucleation phenomena that are in general understood, but where the complexity as yet precludes prediction of nucleation rates. Different forms of analysis may be needed at different length scales. Despite the difficulties, recent work shows that there are cases in which sound quantification and prediction are possible. Nucleation is often regarded as an intrinsically stochastic process, yet the recent work focuses on deterministic behaviour.

 

Shared values of meromorphic functions on compact Riemann surfaces
A.Schweizer (Exeter)
13 Oct 2005Harrison 106 Thursday 3pmPure Mathematics

 

Timestepping methods for linearly stiff systems
Paul Matthews (University of Nottingham)
10 Oct 2005Harrison 170 Monday 2pmApplied Mathematics

 

On Tsuzuki's approach to the Crew-conjecture
M.Lederer (Innsbruck)
6 Oct 2005Harrison 106 Thursday 3pmPure Mathematics

 

The linked twist map approach to fluid mixing
Rob Sturman (University of Bristol)
3 Oct 2005Harrison 170 Monday 2pmApplied Mathematics

 

The analytic structure of Euler flow
Uriel Frisch (Observatoire de Nice)
19 Sep 2005Harrison 170 Monday 2pmApplied Mathematics

 

Probabilistic aspects of recurrence in dynamical systems
Sandro Vaienti (Luminy, Marseille)
16 Sep 2005Harrison B74 Friday 2pmApplied Mathematics

 

Where Strategic and Evolutionary Stability Depart - A Study of Minimal Diversity Games
Dieter Balkenborg (Exeter (Economics))
28 Jun 2005Harrison 170 Tuesday 3.40pmApplied Mathematics
The paper is concerned with the connection between two different approaches to game theory: evolutionary game theory and equilibrium refinement. The literature on learning and evolution studies the evolution of simple forms of adaptive behaviour. It asks, for instance, under which conditions evolutionary selection or learning will in the long run lead to rational behaviour and Nash equilibrium.

In contrast, the literature on refinement presupposes highly rational individuals. Its starting point is the observation that many interesting games have Nash equilibria that are unconvincing as solutions to a game and that additional criteria are needed to refine among them. The most developed notion of equilibrium refinement is the concept of strategically stable sets of Nash equilibria as introduced by Kohlberg and Mertens and as further developed by Mertens.

A number of papers indicate a strong connection between evolutionary and strategic stability. Recently De Michelis and Ritzberger have shown for a very general class of dynamics that model evolutionary or learning processes between different populations that an asymptotically stable Nash equilibrium component must contain a strategically stable set if its Euler characteristic is not zero.

We ask whether, conversely, a strict equilibrium set containing a Mertens stable set must have non-zero Euler characteristic.

We address this question for a special class of games that we call minimal diversity games. In a minimal diversity game each member of a team of I players must independently and simultaneously choose one of the numbers k=1,...,K. Each player gets payoff -1 if all players name the same number and payoff 0 otherwise.

Minimal diversity games have two equilibrium components. One consists of an isolated mixed strategy Nash equilibrium where each player takes each choice with equal probability. The other consists of the set of efficient Nash equilibria where at least two players choose different pure strategies. The mixed strategy Nash equilibrium is strategically stable, but not evolutionary stable. The efficient component is shown to be a topological sphere of dimension (I-1)*(K-1)-1. It has hence zero Euler characteristic iff it is odd dimensional, i.e. if I or K is odd. Therefore it contains a strategically stable set if it is an even dimensional sphere. For the cases I=2 and K odd we show that it does not contain a strategically stable set.

Closely related (and proved with the same construction) is the fact that for nearby payoff perturbations of the game generically no trajectory of an evolutionary dynamic converges. It is not yet known whether the finding extend to other minimum diversity games with three of more players.

 

Master equation approach to the study of phase change processes in data storage media
Konstantin Blyuss (Exeter)
28 Jun 2005Harrison 170 Tuesday 4.30pmApplied Mathematics
The dynamics of crystallization in phase-change materials is investigated using a master equation approach. We develop a novel model using the thermodynamics of the processes involved. Some partial analytical results are obtained for the isothermal case and for large cluster sizes, but principally numerical simulations are used to investigate the model.

 

Real-time dynamic substructuring: stability and Hopf bifurcation in a neutral delay differential system
Yuliya Kyrychko (Bristol)
28 Jun 2005Harrison 170 Tuesday 1.30pmApplied Mathematics
Real-time dynamic substructuring is a powerful testing method which brings together analytical, numerical and experimental tools for the study of complex structures. It consists of replacing one part of the experimental structure with a numerical model, connected by a transfer system. In order to provide reliable results, the hybrid system has to remain stable during the whole test. One of the problems with the method is the presence of delay due to several technical factors. This delay can lead to destabilization and failure. In this talk we consider a hybrid system, consisting of a pendulum attached to a mass-spring-damper. The latter is replaced by a numerical model and the transfer system is an actuator. The model we use is a system of two coupled second order neutral delay differential equations. We carry out a stability analysis of the system and identify possible regions of instability and the number of stability switches depending on parameters and delay time. Using the parameters from a real experiment, we perform numerical simulations which confirm our analytical findings, and show regions of periodic and quasi-periodic behaviour.

 

Robustness tools in ecology
Stuart Townley (Exeter)
28 Jun 2005Harrison 170 Tuesday 2.20pmApplied Mathematics

 

Classification of defect Artin-Schreier extensions
Franz-Viktor Kuhlmann (Saskatchewan & Newton Inst)
28 Jun 2005Harrison 106 Tuesday 10amPure Mathematics

 

Classification of defect Artin-Schreier extensions
Franz-Viktor Kuhlmann (Saskatchewan & Newton Inst)
28 Jun 2005Harrison 106 Tuesday 10amPure Mathematics

 

Ramification and Galois structure in 1-dimensional elementary abelian local extensions
Griff Elder (University of Nebraska at Omaha)
24 Jun 2005Harrison B93 Friday 3pmPure Mathematics

 

TBA
Professor Mario Alexandre Teles de Figueiredo
2 Jun 2005Harrison 254 Tuesday 3pmComputer Science

 

THIS SEMINAR HAS BEEN CANCELLED 'Automated feature detection and classification in Solar Feature Catalogues'.
Dr Valentina Zharkova
26 May 2005Harrison 254 Tuesday 3pmComputer Science
The searchable Solar Feature Catalogues (SFC) developed using automated pattern recognition techniques from digitized solar images are presented. The techniques were applied for detection of sunspots, active regions,filaments and line-on-sight magnetic neutral lines in the automatically standardized full disk solar images in Ca II K1, Ca II K3 and Ha taken at the Meudon Observatory and white light images and magnetograms from SOHO/MDI. The results of automated recognition were verified with the manual synoptic maps and available statistical data that revealed good detection accuracy. Based on the recognized parameters a structured database of the Solar Feature Catalogues was built on a mysql server for every feature and published with various pre-designed search pages on the Bradford University web site http://www.cyber.brad.ac.uk/egso/. The SFCs with a coverage of 10 years (1996-2005) are to be used for the solar feature classification and activity forecast, the first classification attempts will be discussed.

 

Faltings's strict modules: a characteristic p analogue of classical finite flat group schemes
Victor Abrashkin (Durham)
20 May 2005Harrison 106 Friday 5pmPure Mathematics

 

A conservation of fragility law and its consequences for biochemical network dynamics
Jorge Gonçalves (Cambridge University)
19 May 2005Harrison 170 Thursday 2pmApplied Mathematics
Robustness is a defining feature of successful complex systems. In this talk I will describe a fundamental limit on the robustness of complex systems achievable through feedback control. Based on a generic formulation of the control problem, we define /fragility/ in terms of the sensitivity of an output to a disturbance and derive an integral constraint (lower-bound) on the net fragility of a system. Put simply, reducing the sensitivity to disturbances at one range of frequencies by feedback control will necessarily amplify disturbances at other frequencies. For the special case of linear feedback systems, this result reduces to Bode's integral formula. We illustrate the implications of this robustness tradeoff for biological systems, and identify feedforward control and buffering as strategies for ameliorating the tradeoff. Finally, the theory provides an alternate interpretation of Shannon's channel capacity theorem for nonlinear control systems.

 

Computation without representation, and other mysteries
Derek Partridge (Department of Computer Science)
13 May 2005Harrison 171 Friday 4pmComputer Science (Internal)
The talk will cover the necessity for software that is not, and cannot be, faultless, but is, nevertheless, optimal. In particular, the need for inductive software technologies and why it may be impossible to track down known bugs. Then we move on to computations that know when they're wrong (to cope with the inevitable erroneous outputs), and a final generalization into the philosophical notion of accurately approximate computation as an alternative to precisely correct/incorrect computation.

 

Inaugural Lecture: The mathematical basis for numerical weather and climate models: past successes; future challenges
John Thuburn (University of Exeter)
9 May 2005XFI centre - Monday 6pmApplied Mathematics

 

THIS SEMINAR HAS BEEN CANCELLED
Using perceptual models to improve fidelity and provide invariance to valumetric scaling for quantization index modulation watermarking
Professor Ingemar Cox
5 May 2005Harrison 254 Tuesday 3pmComputer Science
Quanitization index modulation (QIM) is a computationally efficient method of watermarking with side information. This paper proposes two improvements to the original algorithm.
First, the fixed quantization step size is replaced with an adaptive step size that is determined using Watson's perceptual model. Experimental results on a database of 1000 images illustrate significant improvements in both fidelity and robustness to additive white Gaussian noise.
Second, modifying the Watson model such that it scales linearly with valumetric (amplitude) scaling, results in a QIM algorithm that is invariant to valumetric scaling. Experimental results compare this algorithm with both the original QIM and an adaptive QIM and demonstrate superior performance.

 

URBAN WATER MANAGEMENT IN DEVELOPING COUNTRIES - RESEARCH@WEDC
Dr V. Vairavamoorthy (Loughborough)
5 May 2005Harrison 203 Thursday 2pmEngineering
The presentation will cover research currently being undertaken in the area of Hydroinformatics at WEDC, Department of Civil and Building Engineering, Loughborough University. Research is currently being undertaken to develop decision support systems for low and middle income countries in the areas of: water supply management; risk and reliability of water supply systems; watershed models for optimal plans of spatial allocation of water and land resources; hydraulic simulation of irrigation systems using open source technologies like Java and MySQL. The presentation will provide a brief description of two example research projects that attempt to support the United Nations Millennium Development Goals (MDG’S). The MDG’s have set clear targets for reducing poverty, hunger, illiteracy, disease, discrimination against women and environmental degradation by 2015. Progress towards the key MDGs will be accelerated through improved environmental health conditions, in particular access to water and sanitation and environmental sustainability. The two example research projects contribute in a small way to the Target 10 of the MDGs as the first is in relation to improving access to water (quantity) and the second is in relation to improving access to improved water quality. Both research projects involve: development of appropriate technology for the particular problem in the developing country; involve a strong software component; involve a capacity building element. The two example research projects that will be presented will be: Guidelines for “Design of water supply systems operating under water scarcity conditions” –In many countries the availability of water is either inadequate or restricted due to difficulties such as power cuts. An alternative approach to design of these systems has been developed which employs a modified network analysis procedure and utilises formal optimisation techniques to ensure the maximum uniformity in supply. Guidelines for “Water quality risk assessment & management in piped water” - This concerns the risk of contaminant intrusion into water distribution systems (WDS) under extreme conditions (e.g. pipe break, low etc.) which is one of the main reasons for water quality degradation. The presentation will describe the development of IRA-WDS, a new and innovative GIS based tool for managing water quality in urban distribution systems in developing countries. The outputs from IRS-WDS are a series of risk maps that indicate the risk of contaminant intrusion in the various parts of the water distribution system.

 

Counting orbits on colourings, flows, and codewords
Peter Cameron (Queen Mary)
5 May 2005Harrison 106 Thursday 3pmPure Mathematics

 

A unifying explanation of the transition to seizure states via a model of Human EEG
John Terry (Loughborough)
28 Apr 2005Harrison 209 Thursday 4pmApplied Mathematics

 

Inaugural Lecture - The World of Primes since Fermat
Professor Andreas Langer (University of Exeter)
28 Apr 2005Harrison LT3 Thursday 2pmPure Mathematics

 

Terascale simulation using byte-size pieces
Lee Margetts (University of Manchester)
25 Apr 2005Harrison 170 Monday 2pmApplied Mathematics

 

Design Optimization and Stochastic Analysis: Issues of Commercial Software Development
Professor Vassili Toropov (Altair Engineering Ltd.)
15 Apr 2005Harrison H203 Friday 14.00Engineering
This talk will be on design optimization and stochastic analysis as seen by Altair Engineering, an international commercial software developer, vendor and consulting company. Examples from its customers will demonstrate how such software tools are used in product development in automotive, aerospace, consumer goods, medical, offshore and other sectors.

 

Future issues in urban drainage modelling: urban flooding and integrated approaches
Prof. Theo Schmitt (Technical University of Kaiserslautern)
24 Mar 2005Harrison 203 Thursday 2pmEngineering
After a short introduction of my group at Kaiserslautern University, I would briefly outline the development of urban drainage modelling and then focus on two specific issues: (1) Modelling of urban flooding has become an important issue elated to the European Standard EN 752 and the flooding frequencies ecommended for urban drainage systems. A detailed approach coupling hydraulic models for surface and sewer flow will be presented. (2) Integrated modelling of the urban wastewater system has been pushed during the last decade to consider all wastewater related sources of pollution load discharged to receiving waters. Aspects of integrated modelling will be illustrated by linking a detailed pollution load model (drainage system) and IWA's Activated Sludge Model (wastewater treatment plant).

 

The Soft Machines: Computing with the Code of Life
Martyn Amos (Department of Computer Science)
18 Mar 2005Harrison 171 Friday 4pmComputer Science (Internal)
Cellular computing is a new, rapidly expanding field of research at the intersection of biology and computer science. It is becoming clear that, in the 21st century, biology will be characterized more often as an information science. The flood of data generated first by the various genome projects, and now by large-throughput gene expression, has led to increasingly fruitful collaborations between biologists, mathematicians and computer scientists. However, until recently, these collaborations have been largely one-way, with biologists taking mathematical expertise and applying it in their own domain. With the onset of molecular and cellular computing, though, flow of information been growing in the reverse direction. Computer scientists are now taking biological systems and modifying them to obtain computing devices. Cells are being re-engineered to act as microbial processors, smart sensors, drug delivery systems and many other classes of device. This talk traces the brief history of cellular computing and suggests where its future may lie.

 

Arithmetic progressions of primes
Ben Green (Bristol)
17 Mar 2005Harrison 106 Thursday 3pmPure Mathematics
Green and Tao recently announced a proof of the existence of arbitrarily long finite arithmetic progressions consisting entirely of primes. This is one of the biggest results in number theory in recent years. Ben Green will be talking about this work today.

 

On phase transitions in coupled map lattices
Wolfram Just (Queen Mary University of London)
14 Mar 2005Harrison 170 Monday 2pmApplied Mathematics
Coupled map lattices are a paradigm for studying fundamental questions in spatially extended dynamical systems. Within this tutorial we focus on qualitative changes of the motion which are intimately related with the limit of large system size. Similar to equilibrium phase transitions, such qualitative changes are an ubiquitous feature of dynamical systems with a large number of degrees of freedom. Within the first part we present an overview and some phenomenological facts of phase transitions in coupled map lattices. The following two parts describe in some details analytical tools which are useful for understanding phase transition behaviour in dynamical systems beyond plain numerical simulations. We explain how coupled map lattices are linked with the canonical equilibrium physics of spin systems when techniques of symbolic dynamics are applied. Using a simple model we explain how coupled map lattices are linked with phase transitions in equilibrium spin models. In the last part we describe an alternative approach in terms of kinetic spin models linking the dynamics of coupled map lattices with equilibrium and nonequilibrium statistical mechanics.

 

A model for the pure bending of isotropic tubes: localized buckling and the Brazier effect
Khurram Wadee (University of Exeter)
14 Mar 2005Harrison 106 Monday 10amApplied Mathematics (Internal)

 

Effect of heat release on the dissipation of scalar fluctuations in turbulent premixed flames
Dr N. Swaminathan (University of Cambridge)
10 Mar 2005Harrison 203 Thursday 2pmEngineering
The scalar dissipation rate signifies the local mixing rate and thus plays a vital role in the modelling of reaction rate in turbulent flames. The local mixing rate is influenced by the turbulence, the chemical and the molecular diffusion processes which are strongly coupled in turbulent premixed flames. Thus, the model for the mean scalar dissipation rate, thus the mean reaction rate, should include the contributions of these processes. Earlier models for the scalar dissipation rate includes only a turbulence time scale. In this study, we derive exact transport equations for the instantaneous and the mean scalar dissipation rates. Using these equations, a simple algebraic model for the mean scalar dissipation rate is obtained. This model includes a chemical as well as a turbulence time scale and its prediction compares well with direct numerical simulation results. Reynolds--Averaged--Navier--Stokes calculations of a test flame using the model obtained here show that the contribution of dilatation to local turbulent mixing rate is important to predict the propagation phenomenon in turbulent premixed flames.

 

Euler characteristics in relative algebraic K-groups
Manuel Breuning (Nottingham)
10 Mar 2005Harrison 106 Thursday 3pmPure Mathematics

 

The fundamental group scheme in characteristic p and the conjectures of Nori
Vikram Mehta (Tata Institute, Mumbai)
10 Mar 2005Harrison LT321 Thursday 10amPure Mathematics

 

RSS Local Group Meeting
Bayesian spatial partition modelling in epidemiological case-control studies
Carmen Fernández (Lancaster University)
10 Mar 2005Exeter University Laver, 321 Thurs 2pmStatistics & Operational Research
The talk considers developments in the modelling of case-control data where each sample individual is associated with a geographical location. A logistic regression framework is used and residual spatial variation is flexibly accommodated via the use of Voronoi tessellations with unknown numbers and locations of tiles. Modifications for matched case-control studies are also discussed.

 

Using a dynamical systems approach to study the dyanmics of model reference adaptive control systems
David Wagg (University of Bristol)
7 Mar 2005Harrison 170 Monday 2pmApplied Mathematics

 

Nonlinear dynamo action in hydrodynamic instabilities driven by shear
Pu Zhang (University of Exeter)
7 Mar 2005Harrison 106 Monday 10amApplied Mathematics (Internal)

 

How computer science can reveal problems with the standard model of cancer and can identify new models of cancer
Ajit Narayanan (Department of Computer Science)
4 Mar 2005Harrison 171 Friday 4pmComputer Science (Internal)
The dominant paradigm of cancer development is that mutations to a small number of genes transform a healthy cell into a cancerous cell by blocking normal pathways or making other pathways hyperactive. Specific molecular pathways ('subway lines') are claimed to be responsible for programming these behaviours. My work on cancer gene expression data does not support this view.

While my own research aim is also to come up with networks and maps of cancer, what distinguishes my approach from the dominant paradigm and its alternatives is that, in my approach, a specific pathway may be normal or cancerous depending on the expression values of genes making up the pathway. We do not need to assume that a cancer pathway is like a tube-train taking a different and unscheduled route from normal. Instead we can assume that the same route may be used in both normal and cancer cells. What differs is the number of trains passing through each station. It may not even matter that some of these trains are not fully formed trains (i.e. are mutated). What matters is the volume of traffic along the route: a route that is normal one day can become cancerous another day if the volume of traffic along the route changes significantly. If this is right, this will lead to a new view of cancer development and progression that has immediate and very different implications for possible therapeutic intervention and prevention.

No knowledge of biology is assumed. The talk will introduce the dominant paradigm of cancer and present some of our work on the alternative, leaving room for discussion and speculation.

 

Towards an Evolutionary Computation Approach to the Origins of Music
Dr Eduardo Reck Miranda
3 Mar 2005Harrison 254 Tuesday 3pmComputer Science
Evolutionary Computation (EC) may have varied applications in Music. This paper introduces three approaches to using EC in Music (namely, engineering,creative and musicological approaches) and discusses examples of representative systems that have been developed within the last decade, with emphasis on more recent and innovative works. We begin by reviewing engineering applications of EC in Music Technology such as Genetic Algorithms and Cellular Automata sound synthesis, followed by an introduction to applications where EC has been used to generate musical compositions. Next, we introduce ongoing research into EC models to study the origins and evolution of music and detail our own research work on modelling the evolution of musical systems in virtual worlds.

 

The fundamental group of curves in positive characteristic
Mohamed Saidi (University of Exeter)
3 Mar 2005Harrison LT321 Thursday 10amPure Mathematics

 

A simple model of the dynamics of sudden stratospheric warmings
Gavin Esler (University College London)
28 Feb 2005Harrison 170 Monday 2pmApplied Mathematics

 

How to compute using globally coupled oscillators
Jon Borresen (University of Exeter)
28 Feb 2005Harrison 106 Monday 10amApplied Mathematics (Internal)

 

Bayesian Averaging over Decision Trees
Vitaly Schetinin (Department of Computer Science)
25 Feb 2005Harrison 171 Friday 4pmComputer Science (Internal)
Bayesian averaging (BA) over classification models allows analysts to estimate the uncertainty of classification outcomes within prior knowledge. By averaging over ensemble of classification models, the class posterior distribution, e.g. its shape and parameters, can be estimated and used by analysts to judge on the confident intervals. However the standard Bayesian methodology has to average all possible classification models that makes this methodology computationally infeasible for real-world applications.

The feasible way of implementing the BA is the use Markov Chain Monte Carlo (MCMC) technique of random sampling from the posterior distribution. Within the MCMC technique the parameters of classification model are drawn from the given priors. The proposed models are accepted or rejected accordingly to a Bayes rule. When the class posterior distribution becomes stable, the classification models are collected and their classification outcomes are averaged.

Regarding to Decision Tree (DT) classification models which provide a trade-off between the classification accuracy and interpretability, there are three questions which still remain open. The first is the condition under which the Markov Chain can make reversible moves and guarantee that the MCMC can explore DTs with different parameters within the given priors. The second question is how to avoid local minima during the MCMC search. The final third question is how to select a single DT from the DT ensemble which could be used for interpretation. All these three problems will be discussed and the experimental results obtained on some real world data (e. g. the UCI Machine Learning Repository, StatLog, the Trauma data etc) will be presented.

 

On the p-adic regulator of varieties over p-adic fields
Dr Noriyuki Otsubo (Paris)
24 Feb 2005Harrison 106 Thursday 3pmPure Mathematics

 

Purity for p-divisible groups
Prof Thomas Zink (Bielefeld)
24 Feb 2005Harrison 106 Thursday 5pmPure Mathematics

 

Postgraduate Seminar
Some investigations in discriminant analysis with mixed variables
Nor Idayu Mahat (University of Exeter)
24 Feb 2005Exeter University Laver, 321 Thurs. 2pmStatistics & Operational Research
The location model has been developed for the treatment of mixed categorical and continuous variables in discriminant analysis. In its recent development, Asparoukhov and Krzanowski (2000) suggested estimating the parameters of the location model by using non-parametric smoothing procedures. This approach overcomes some deficiencies in Maximum Likelihood Estimation and Linear Model Estimation. However, the choice of smoothing parameters by maximising the leave-one-out pseudo-likelihood function suggested in this approach depends on distributional assumptions This talk will describe how the smoothing parameters can instead be chosen by optimising either the error rate or the Brier score, neither of which make distributional assumptions. Some investigations on other possible smoothing procedures also will be discussed.

 

Slumping of granular media
Rich Kerswell (University of Bristol)
21 Feb 2005Harrison 170 Monday 2pmApplied Mathematics

 

Mixing of passive scalars in Baker's maps
Andrew Gilbert (University of Exeter)
21 Feb 2005Harrison 106 Monday 10amApplied Mathematics (Internal)

 

A Dominance-Based Mapping from Multi-Objective Space for Single Objective Optimisers
Kevin Smith (Department of Computer Science)
18 Feb 2005Harrison 171 Friday 4pmComputer Science (Internal)
Traditional optimisation research has concentrated on the single-objective case, where one measure of the quality of the system is optimised exclusively. Most real-world problems, however, are constructed from multiple, often competing, objectives which prevent the use of single-objective optimisers. Here a generic mapping to a single objective function is proposed for multi-objective problems, allowing single-objective optimisers to be used for the optimisation of multi-objective problems. A simulated annealer using this method is proposed which uses this technique and is shown to perform well on both test and commercial problems.

 

A conservation of fragility law and its consequences for biochemical network dynamics (POSTPONED until 19 May)
Jorge Gonçalves (Cambridge University)
17 Feb 2005Laver LT321 Thursday 2pmApplied Mathematics
Robustness is a defining feature of successful complex systems. In this talk I will describe a fundamental limit on the robustness of complex systems achievable through feedback control. Based on a generic formulation of the control problem, we define /fragility/ in terms of the sensitivity of an output to a disturbance and derive an integral constraint (lower-bound) on the net fragility of a system. Put simply, reducing the sensitivity to disturbances at one range of frequencies by feedback control will necessarily amplify disturbances at other frequencies. For the special case of linear feedback systems, this result reduces to Bode's integral formula. We illustrate the implications of this robustness tradeoff for biological systems, and identify feedforward control and buffering as strategies for ameliorating the tradeoff. Finally, the theory provides an alternate interpretation of Shannon's channel capacity theorem for nonlinear control systems.

 

Topological invariants of singular spaces
Burt Totaro (Cambridge)
17 Feb 2005Harrison 106 Thursday 3pmPure Mathematics

 

Synchronization in Kuramoto-like model of globally coupled oscillators
Alexander Burilko (Kiev)
14 Feb 2005Harrison 106 Monday 10amApplied Mathematics (Internal)

 

Identifying Familiarity and Dialogue Type in Transcribed Texts
Andrew Lee (Department of Computer Science)
11 Feb 2005Harrison 171 Friday 4pmComputer Science (Internal)
In a spoken dialogue, there is a lot of information that is not explicitly stated but can be identified through non-linguistic features, such as tone of voice or a change in speaker. However, this information is not always available when the conversation is transcribed into a written text.

In this talk, I'll be describing methods for measuring two aspects of dialogues that can be lost when transcribed: the familiarity between participants and the type of dialogue.

In the case of familiarity, Dialogue Moves are counted for conversational transcripts from the Map Task corpus. The differences in Dialogue Move pair distributions are compared between transcripts where participants are either familiar or unfamiliar with each other to explore whether a measure of familiarity can be based on this approach.

To identify the type of dialogue, the frequency distribution of Verbal Response Modes in a transcribed text are counted for number of different dialogues, including interviews, presentations and speeches. Profiles generated from the frequency distributions are then be used as a basis for comparison to identify the closest matching dialogue type.

 

Interactions between vortices, boundaries and bottom topography
Ted Johnson (University College London)
7 Feb 2005Harrison 170 Monday 2pmApplied Mathematics

 

Eddy scaling for poleward heat transport in Earth's atmosphere
John Thuburn (UIniversity of Exeter)
7 Feb 2005Harrison 106 Monday 10amApplied Mathematics (Internal)

 

ROC Optimisation of Safety Related Systems
Jonathan Fieldsend (Department of Computer Science)
4 Feb 2005Harrison 171 Friday 4pmComputer Science (Internal)
In this talk the tuning of critical systems is cast as a multi-objective optimisation problem. It is shown how a region of the optimal receiver operating characteristic (ROC) curve may be obtained, permitting the system operators to select the operating point. This methodology is applied to the STCA system, showing that the current hand-tuned operating point can be improved upon, as well as providing the salient ROC curve describing the true-positive versus false-positive trade-off. In addition, through bootstrapping the data we can also look at the effect of data uncertainty on individuals parameterisations, and the ROC curve as a whole.

 

Ultrasound Image Segmentation
Professor Alison Noble (University of Oxford)
3 Feb 2005Harrison 254 Tuesday 3pmComputer Science
Ultrasound image segmentation is considered a challenging area of medical image analysis as clinical images vary in quality and image formation is nonlinear. Most classicial approaches to segmentation do not work well on this data.
In this talk, I will provide an overview of research we have done in this area, using what I call weak physics based approaches, specifically looking at the tasks of displacement estimation, and segmentation of tissue regions and perfusion uptake.

 

Picard groups of some module categories
Peter Vamos (University of Exeter)
3 Feb 2005Harrison 106 Thursday 3pmPure Mathematics

 

Hilbert's 16th problem - some analytic and algebraic aspects
Colin Christopher (University of Plymouth)
31 Jan 2005Harrison 170 Monday 2pmApplied Mathematics
The second part of Hilbert's 16th problem deals with the number of limit cycles of polynomial vector fields in the plane. It remains one of the few of the original 23 problems that have not been substantially solved over the past century. However, over the past twenty years or so, insights from the theory of foliations and algebraic geometry as well as improved analytic techniques have brought many new advances to our understanding of this old problem. My aim in the talk is to give a brief survey of some of these recent advances as well as the many open questions which surround the study of polynomial vector fields in the plane.

 

Quasi-geostrophic approximation revisited
Keke Zhang (University of Exeter)
31 Jan 2005Harrison 106 Monday 10amApplied Mathematics (Internal)

 

Random preorders
Dudley Stark (Queen Mary)
27 Jan 2005Harrison 106 Thursday 3pmPure Mathematics

 

High-dimensional chaos in the Kuramoto model
Yuri Maistrenko (Kiev)
24 Jan 2005Harrison 106 Monday 10amApplied Mathematics (Internal)

 

Adopting Open Source tools in a production environment: are we locked in?
Brian Lings (Department of Computer Science)
21 Jan 2005Harrison 171 Friday 4pmComputer Science (Internal)
Many companies are using model-based techniques to offer a competitive advantage in an increasingly globalised systems development industry. Central to model-based development is the concept of models as the basis from which systems are generated, tested and maintained. The availability of high-quality tools, and the ability to adopt and adapt them to the company practice, are therefore important qualities. Model interchange between tools becomes a major issue. Without it, there is significantly reduced flexibility, and a danger of tool lock-in. In this talk I report on a case study in which a systems development company, SAAB Combitech, has explored the possibility of complementing their current proprietary tools by exporting models in XMI to open source products for supporting their model-based development activities. We found that problems still exist with interchange, and that the technology needs to mature before industrial-strength model interchange becomes a reality.

 

TBA
Dr Sunil Vadera
20 Jan 2005Harrison 209 Tuesday 3pmComputer Science

Much of our daily reasoning appears to be based on stereotypes, exemplars and anecdotes. Yet, basic statistics informs us that decisions based only limited data are, at best, likely to be inaccurate, if not badly wrong. However, exemplars and stereotypes are not arbitrary data points, they are based on experience and represent prototypical situations. The ability to predict the behaviour of a consumer, observe that two people are related, diagnose an illness, and even how an MP might vote on a particular issue, all depend on a person's past experience - that is the exemplars and stereotypes a person learns.

If this hypothesis, namely that we can form and reason well with exemplars is true, we should be able to identify exemplars from data. To achieve this, we need to answer the following questions: (a) What is an exemplar and how can it be represented? (b) How do we learn good exemplars incrementally? (c) How can exemplars be used?

This seminar presents an approach to these questions that involves the use of the notion of family resemblance to learn exemplars and Bayesian networks to represent and utilise exemplars. Empirical results of applying the model will be presented and relationships with other models of machine learning also discussed.

 

Corner eddies: new variations on an old theme
Keith Moffatt (Cambridge University)
17 Jan 2005Harrison 170 Monday 2pmApplied Mathematics

 

MODELLING THROUGH: The growing role of decision analytic models in Health Technology Assessment
Martin Pitt (Department of Computer Science)
14 Jan 2005Harrison 171 Friday 4pmComputer Science (Internal)
In recent years, analytic modelling has been widely used to support decision making within the National Health Service (NHS) for a range of applications and with varying levels of success.

A recent development has been the adoption of mathematical and computer based models as a central element if the process of Health Technology Assessment (HTA). HTA is concerned with the evaluation of alternative healthcare interventions (eg alternative drug therapies) in order to directly inform decision making. It is now at the forefront of health research in the UK representing the largest single strand of NHS funded research activity. HTA outputs form a key element in the process by which the National Institute for Clinical Excellent determine general guidelines for UK prescription and clinical practice.

This presentation will take an informal look at the rapidly developing field of decision analytic modelling in field HTA. It will outline the range of alternative mathematical and computer based approaches adopted with reference to case study examples, and illustrate how model outputs feed into the decision making process. Key challenges within this field, such as how data uncertainty is handled, will be examined in relation to current areas of active development.

 

Dynamics of delayed relay systems
Jan Sieber (University of Bristol)
10 Jan 2005Harrison 170 Monday 2pmApplied Mathematics

 

***Jonas Gamalielsson - Developing a Method for Assessing the Interestingness of Rules Induced from Microarray Gene Expression Data ***Zelmina Lubovac - Revealing modular organization of the protein interactome by combining its topological and functional properties ***Simon Lundell - Modelling the Heamatopoietic Stem Cell System.
Jonas Gamalielsson, Simon Lundell and Zelmina Lubovac
17 Dec 2004Harrison 209 Wednesday 3pmComputer Science
***Jonas Gamalielsson - Abstract :The aim and contribution of this work is to develop a method for assessing the interestingness of rules induced from microarray gene expression data using a combination of objective and domain specific measures, which will assist biologists in finding the most interesting hypotheses to test after mining for rules in microarray gene expression data and also generate more accurate models than if objective measures alone were used. More specifically, a method is being developed for assessing the biological plausibility of hypothetic regulatory relations generated by data mining algorithms applied to gene expression data. The idea is to use an information fusion approach where knowledge is used about the Gene Ontology functional classification of gene products and the topology of known regulatory pathways with the purpose of generating templates representing general knowledge of regulation in pathways. Templates show what kind of gene products with respect to molecular function that have been found to participate in different types of regulatory relations in pathways. A training set of regulatory relations is used to derive the templates. A test set of hypothetic regulatory relations is used to assess how well the templates can distinguish between hypothetic relations showing a high and low level of biological plausibility with respect to the set of training relations. ***Zelmina Lubovac- Abstract :Understanding the structure of the protein interaction network is useful as a first step towards revealing the underlying principles of the large-scale organisation of the cell. In this project, we analyse a topological characterisation of the yeast (/Saccharomyces cerevisiea/) protein-protein interaction network, and relate it to functional annotations from Gene Ontology (GO). We aim to develop a biologically informed measure to reveal modular formations in an interactome. A semantic similarity measure has been used to assess the role of hubs in a network in terms of functional annotation from GO. The existing graph theoretic notion of the module has been used in previous work to perform a modular decomposition of the protein network, i.e. to break down sub-graphs into a hierarchy of nested modules or units that groups proteins with common functional roles. Our attempt is to complement the existing graph theoretic approach with semantic similarity based on proteins? ontological terms to achieve more biologically plausible descriptions of modular decomposition. ***Simon Lundell -Abstract :During life of higher animals the heamatopoietic system produces blood, with a composition of various cell types, e.g. lymphocytes, erythrocytes and platelets. This system has to adopt to the animals growth and for changes such as stress conditions, e.g. infection and blood loss. If the animal is infected then a new composition of blood cells is needed as well as a compensation for the cells lost in the battle against the intruder. The heamatopoietic system is a highly adaptable and has stem cells that are dormant in long periods of time. The dormant cells can,when needed, be proliferated, and may then give rise to millions of new cells. The regulation of the number of heamatopoietic cells is crucial to animals; the heamatopoietic system must avoid depletion of stem cells as well as excess production of cells, both instances are life threatening conditions. A mouse produces 60% of its body weight in blood cells in its lifetime and a human produces 10 times its body weight. Although the large production of blood cells only a few stem cells has been stated as necessary to recreate hematopoietic system. Using an object based model of this system we were able to reproduce experimental data, and were able to find out which types of feedback regulations are active during stem cell transplantation. The systems intricate organisation, dynamic structure and the need to compare the simulations to a large number of experimental setups, opts for a new way of organising these models.

 

Wiggly Outlines: The Ins and Outs of Non-convex Hulls
Antony Galton (Department of Computer Science)
17 Dec 2004Harrison 171 Friday 4pmComputer Science (Internal)
Given a set of objects located in space, how can we represent the region occupied by those objects at different granularities? At a very fine granularity, the region simply consists of all the points occupied by the objects themselves, whereas at a very coarse granularity it might be given by the convex hull of those points. In many cases, neither of these representations is very useful: what we want is some kind of non-convex hull to convey the overall 'shape' of the region. But whereas the convex hull of a set of points is uniquely defined, there are any number of candidates for their non-convex hull. In this talk I shall introduce and explore some of the properties of a family of non-convex hulls generated by a generalisation of a simple convex-hull algorithm.

 

TBA
Achim Ilchmann (Ilmenau, Germany)
10 Dec 2004Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

A personal view of computer assisted formal reasoning
Matthew Fairtlough (University of Sheffield)
10 Dec 2004Harrison 171 Friday 4pmComputer Science (Internal)
I will survey my work of the last 13 years in the field of logic and formal reasoning; in particular I will discuss the methods, logics, implementations, tools and applications involved. The most striking development has been a new modal logic called Lax Logic, so my talk will focus on this. I will give a flavour of the logic itself and of its application to formal reasoning across (multiple) abstraction boundaries, where inevitably constraints arise whose values may not be precisely known in advance. I will end by presenting some recent work using Mathematica to analyse and animate a dynamic 3-dimensional lattice.

 

Ultrasound attenuation as a quantitative measure of fracture healing
Dr Sabina Gheduzzi (University of Bristol)
9 Dec 2004Harrison 203 Thursday 2pmEngineering
The monitoring of fracture healing still relies upon the judgement of callus formation and on the manual assessment of the stiffness of the fracture. A diagnostic tool capable of quantitatively measuring healing progression of a fracture would allow the fine-tuning of the treatment regime. Ultrasound attenuation measurements were adopted as a possible method of assessing the healing process in human long bones. The method involves exciting ultrasonic waves at 200 kHz in the bone and measuring the re-radiation along the bone and across the fracture zone. Seven cadaveric femora were tested in-vitro in intact form and after creating a transverse fracture by sawing through the cortex. The effects of five different fracture types were investigated. A partial fracture, corresponding to a 50% cut through the cortex, a closed fracture and fractures of widths varying between 1, 2 and 4 mm were investigated. The introduction of a fracture was found to produce a dramatic effect on the amplitude of the signal. Ultrasound attenuation was found to be sensitive to the presence of a fracture, even when the fracture was well reduced. It would therefore appear feasible to adopt attenuation across a fracture as a quantitative measurement of fracture healing.

 

On the Andre-Oort conjecture
Andrei Yafaev (University College, London)
9 Dec 2004Harrison 106 Thursday 3pmPure Mathematics
The Andre-Oort conjecture asserts that the Zariski closure of a set of special points in a Shimura variety is a subvariety of Hodge type. In this talk I will present recent results on this conjecture and an application to the transcendence theory of hypergeometric functions.

 

A numerical scheme for stochastics PDEs
Gabriel Lord (Heriot-Watt University)
6 Dec 2004Harrison 170 Monday 2pmApplied Mathematics

 

New Effects in Mean-Field Magnetic Dynamos
Igor Rogachevskii (Ben-Gurion University, Beer-Sheva, Israel)
3 Dec 2004Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Seeing where the other guy is coming from: A survival guide for young researchers working in multi-disciplinary subjects.
James Hood (Department of Computer Science)
3 Dec 2004Harrison 171 Friday 4pmComputer Science (Internal)
Part of the confidence I have gained recently in my own work is the result of trying to see where different disciplinary groups in my general field of research are coming from -- what they are trying to gain in doing what they are doing. This action, which has led to a better understanding of my own research goals, was not possible until I situated my own research against that of a greater research community. The upshot of this exercise was my very own 'research map', on which, as the product of generalisation of people and groups, I felt I had a better idea of not only where the different groups where coming from, but also where I was going to. In this talk I want to present to you my research map and my experiences of and the lessons I have learned from creating it. Bridge building in multi-disciplinary research is now so important that all of us could benefit from doing a little map making every now and then. I hope therefore that this talk will be of some interest.

 

Iwasawa theory for elliptic curves at supersingular primes
Shinuchi Kobayashi (University of Paris)
2 Dec 2004Harrison 106 Thursday 3pmPure Mathematics

 

Postgraduate Seminar
Spatial Survival Analysis and the FMD epidemic in Devon
Trevelyan McKinley (University of Exeter)
2 Dec 2004Exeter University Laver, 321 Thurs 2pmStatistics & Operational Research
The magnitude of the potential economic impacts of epidemic animal disease events have been highlighted in recent years through outbreaks such as the foot-and-mouth disease epidemic in the United Kingdom during 2001. This talk reports some initial work from a project in conjunction with the Veterinary Laboratory Agency, Weybridge, which is looking at the feasibility of using survival modelling to develop dynamic space-time predictions of survivor and hazard functions for individual farm premises as an animal disease epidemic progresses. Survival analysis used in a spatial context is a potentially useful approach to quantifying the risk of infection of susceptible premises within future time periods given the characteristics of these premises and their geographical location relative to potential sources of infection. Results from such analyses could provide powerful insights into the patterns of infection, such as regional differences in the dynamics of the epidemic, and can assist in optimising various aspects of the operational response activities, such as targeting of at-risk farms. We consider various possible model formulations and apply a range of these to data from Devon for the 2001 UK FMD epidemic.

 

Rates of mixing in hyperbolic flows
Mike Field (University of Houston, USA)
29 Nov 2004Harrison 170 Monday 2pmApplied Mathematics

 

TBA
Paolo Rapisarda (University of Southampton)
27 Nov 2004Harrison 254 Monday 2pmApplied Mathematics

 

Stellar differential rotation
Guenther Rudiger (Potsdam, Germany)
26 Nov 2004Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

This seminar has been cancelled owing to illness
 

 

Isotropy of quadratic forms in finite and infinite dimension
Detlev Hoffmann (University of Nottingham)
25 Nov 2004Harrison 106 Thursday 3pmPure Mathematics

 

Unpredictability in population dynamics
Josef Hofbauer (University College London)
22 Nov 2004Harrison 170 Monday 2pmApplied Mathematics

 

Quasi-geostrophic approximation revisited
Keke Zhang (Mathematical Sciences)
19 Nov 2004Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

This seminar has been postponed until early in the new year - date to be advised
 

 

Explanatory Shifts and structures for knowledge
Donald Bligh (Department of Computer Science)
19 Nov 2004Harrison 171 Friday 4pmComputer Science (Internal)
Explanations involve fitting what is to be explained into a context that has already formed in the minds or brains of he who explains and he who tries to understand. But how did they come to understand that preformed context? By fitting it into an earlier preformed context and so on ad infinitum?

Well no, not quite. Eventually you reach fundamental elements of preformed contexts of which there are at least ten: sameness, difference, change, direction, force, awareness, like/dislike, obligation and intention. Just as items of knowledge are built upon previous knowledge, so their preformed contexts build upon each other. The elements build upon each other in ever more complex ways, a bit like complex molecular structure built of simple elements.

When asked to justify an explanation the reverse process of occurs – analysis or deconstruction of the explanation. If so the justification is in a different context from the explanation being justified. That is what I call an explanatory shift.

 

Semisymmetric cubic graphs
Chris Parker (University of Birmingham)
18 Nov 2004Harrison 106 Thursday 3pmPure Mathematics

 

RSS Local Group Meeting:
Competing Risks: a brief introduction
Martin Crowder (Imperial College)
18 Nov 2004Exeter University Laver, 321 Thurs 2pmStatistics & Operational Research
The origins of Competing Risks date back to Bernoulli's attempt in 1760 to disentangle the risk of dying from smallpox from other risks. Much subsequent work has been demographic and actuarial in nature and although obviously of potential relevance in Reliability and Survival Analysis, applications to those fields are quite recent. The talk will cover some of the basic ideas and application of the subject.

 

Different limiting mechanisms for nonlinear dynamos
Dave Galloway (University of Sydney, Australia)
15 Nov 2004Harrison 170 Monday 2pmApplied Mathematics

 

Piecewise Isometric Disk Packings and the Arbelos
Marcello Trovati (Mathematical Sciences)
12 Nov 2004Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Theory of Molecular Computing. Splicing and Membrane systems
Pier Frisco (Department of Computer Science)
12 Nov 2004Harrison 171 Friday 4pmComputer Science (Internal)
Molecular Computing is a new and fast growing field of research at the interface of computer science and molecular biology driven by the idea that molecular processes can be used for implementing computations or can be regarded as computations. This research area has emerged in recent years not only as a novel technology for information processing, but also as a catalyst for knowledge transfer between the fields of information processing, nanotechnology and biology. Molecular Computing (together with research areas such as Quantum Computing, Evolutionary Algorithms and Neural Networks) belongs to Natural Computing which is concerned with computing taking place in nature and computing inspired by nature. In this talk I will give an overview of my research in the theoretical aspects of Molecular Computing. In particular I will talk about two theoretical models of computation: splicing systems and membrane systems.

 

Additive decompositions of the primes
Christian Elsholtz (Royal Holloway, University of London)
12 Nov 2004Harrison LT6 Friday 3pmPure Mathematics

 

Statistics Seminar
Limited and full information estimation and goodness-of-fit testing in 2^n contingency tables: A unified framework
Albert Maydeu-Olivares (Faculty of Psychology, University of Barcelona)
12 Nov 2004Exeter University Laver B74 Friday 4pmStatistics & Operational Research
High-dimensional contingency tables tend to be sparse and standard goodness-of-fit statistics such as chi-square cannot be used without pooling categories. As an improvement on arbitrary pooling, for goodness-of-fit of large 2^n contingency tables, we propose classes of quadratic form statistics based on the residuals of margins or multivariate moments up to order r. These classes of test statistics are asymptotically chi-square. Further, the marginal residuals are useful for diagnosing lack of fit of parametric models. We show that when r is small (r = 2,3) the proposed statistics have better small sample properties and are asymptotically more powerful than chi-square for some useful multivariate binary models. Related to these test statistics is a class of limited information estimators based on low-dimensional margins. We show that these estimators have high efficiency for one commonly used latent trait model for binary data (the two parameter logistic IRT model)

 

Fractals and Image Processing
Professor Revathy
11 Nov 2004Harrison 209 Tuesday 3pmComputer Science

 

Corings and Galois theory
Tomasz Brzezinski (Swansea, University of Wales)
11 Nov 2004Harrison 106 Thursday 3pmPure Mathematics

 

Cycling cycles: Dynamics near a heteroclinic network
Claire Postlethwaite (Cambridge University)
8 Nov 2004Harrison 170 Monday 2pmApplied Mathematics

 

The role of inertia in the evolution of spherical dynamos
Binod Sreenivasan (Mathematical Sciences)
5 Nov 2004Harrison LT3 Wednesday 2pmApplied Mathematics (Internal)

 

A Painless Introduction to Mereogeometry
Dr Ian Pratt-Hartmann (University of Manchester)
4 Nov 2004Harrison 209 Tuesday 3pmComputer Science
One of the many achievements of coordinate geometry has been to provide a conceptually elegant and unifying account of spatial entities. According to this account, the primitive constituents of space are points, and all other spatial entities---lines curves, surfaces and bodies---are nothing other than the sets of those points which lie on them. The success of this reduction is so great that the identification of all spatial objects with sets of points has come to seem almost axiomatic. For most of the previous century, however, a small but tenacious band of authors has suggested that more parsimonious and conceptually satisfying representations of space are obtained if we adopt an ontology in which regions, not points, are the primitive spatial entities. These, and other, considerations have prompted the development of formal languages whose variables range over certain subsets (not points) of specified classes of geometrical structures. We call the study of such languages `mereogeometry'. In the past decade, the Computer Science community in particular has produced a steady flow of new technical results in mereogeometry, especially concerning the computational complexity of region-based topological formalisms with limited expressive power. The purpose of this talk is to survey this work in general and (largely) non-technical terms. In particular, we aim to locate the various recent mathematical results in mereogeometry within a general mathematical framework. The result will be an inventory of stock and a list of open problems.

 

Companion forms
Toby Gee (Imperial College, London)
4 Nov 2004Harrison 106 Thursday 3pmPure Mathematics

 

How long can left and right handed life forms coexist?
Axel Brandenburg (NORDITA, Copenhagen, Denmark)
1 Nov 2004Harrison 170 Monday 2pmApplied Mathematics

 

Dynamics, Damping and Defects in Thin Ferromagnetic Films
Robert D. McMichael (US National Institute of Standards and Technology)
29 Oct 2004Newman E Friday 11amEngineering
Modern disk drives can read and write bits every two nanoseconds, a time scale very similar to the magnetic damping time of the ferromagnetic metals used in the heads. The damping characteristics are also important for thermally-driven magnetic noise in sensors. Furthermore, it seems likely that damping will limit data rates in magnetic random access memory, since the magnetization in a memory cell must be allowed to settle between switching events. For all of these applications, measurements of damping are important, and these measurements are most commonly made by ferromagnetic resonance linewidth. The two problems that complicate measurements of damping by ferromagnetic resonance are: 1) defects contribute to the linewidth, so that the linewidth is the combined effect of defects and damping, and 2) the form of the damping itself is the subject of some debate.

 

$p$-groups and semistable reduction of curves
Mohamed Saidi (University of Exeter)
28 Oct 2004Harrison 106 Thursday 3pmPure Mathematics

 

Introduction to de Rham-Witt cohomology
Andreas Langer (University of Exeter)
26 Oct 2004Harrison B93 Tuesday 3pmPure Mathematics

 

Zonal flows and magnetic fields in laboratory plasmas
Pat Diamond (University of California, San Diego, USA)
25 Oct 2004Harrison 170 Monday 2pmApplied Mathematics

 

Beilinson's conjecure for $K_2$ of certain (hyper)elliptic curves
Rob de Jeu (University of Durham)
21 Oct 2004Harrison 106 Thursday 3pmPure Mathematics

 

A mechanism of solar variability influence on climate
Alexander Ruzmaikin (JPL, Pasadina, USA)
18 Oct 2004Harrison 170 Monday 2pmApplied Mathematics

 

Investigation and monitoring of tunnelling works at Lewes, incorporating the ABI Code of Practice for Tunnelling.
Dr Robert Hodgson (Black & Veatch)
14 Oct 2004Harrison 203 Thursday 2pmEngineering

 

Matrix functions: Theory and algorithms
Nick Higham (University of Manchester)
11 Oct 2004Harrison 170 Monday 2pmApplied Mathematics

 

The slow-fast myth in geophysical fluid dynamics
David Dritschel (University of St Andrews)
4 Oct 2004Harrison 170 Monday 2pmApplied Mathematics

 

A model of cross-contamination by wind in genetically modified oilseed rape
Martin Hoyle (Biological Sciences)
24 Sep 2004Harrison L40 Wednesday 11amApplied Mathematics (Internal)

 

TBA
Professor Peter Cowling (Bradford University)
10 Jun 2004Harrison 209 Tuesday 3pmComputer Science

 

Machine Consciousness
Dr Owen Holland (University of Exeter)
3 Jun 2004Harrison 209 Tuesday 3pmComputer Science

 

The work at the Hadley Centre for Climate Prediction and Research, Met Office
Dr Vicky Pope (The Met Office)
26 May 2004Harrison 209 Tuesday 3pmComputer Science

 

Quantification of the effect of flow on the initial processes of bacterial attachment.
Mr John Boyle
20 May 2004Harrison 203 Thursday 2pmEngineering

 

Agents and affect: why embodied agents need affective systems.
Professor Ruth Aylett (Salford University)
13 May 2004Harrison 209 Tuesday 3pmComputer Science

 

Modulling the Micromechanics of Auxetics (Stealing ideas from granular mechanics)
Dr Neil Gaspar
13 May 2004Harrison 203 Thursday 2pmEngineering

 

Logic-based visual perception for a humanoid robot
Dr Murray Shanaham (Imperial College)
6 May 2004Harrison 209 Tuesday 3pmComputer Science

 

The aerodynamics of airborne pollen: how do pines pollinate? (Or, is nature really that stupid?)
Dr James Cresswell and Dr Gavin Tabor
6 May 2004Harrison 203 Thursday 2pmEngineering

 

Future Floods - the Foresight flood and coastal defence project.
Professor Richard Ashley
5 May 2004Harrison 203 Thursday 9.15amEngineering

 

Imprecise methods for analysing uncertainty in climate projections and impacts.
Dr Jim W Hall
29 Apr 2004Harrison 203 Thursday 2pmEngineering

 

Asymptotic structure of biological excitability equations
Vadim Biktashev (University of Liverpool)
8 Dec 2003Harrison 170 Monday 2pmApplied Mathematics

 

Nonlinear Schroedinger equations as models of superfluidity
Natalia Berloff (Cambridge University)
1 Dec 2003Harrison 170 Monday 2pmApplied Mathematics

 

To be announced
Adam Epstein (Warwick)
27 Nov 2003Harrison 106 Thursday 3pmPure Mathematics

 

To be announced
Adam Epstein (Warwick)
27 Nov 2003Harrison 106 Thursday 3pmPure Mathematics

 

Magnetic fields in numerical simulations of the interstellar medium
Graeme Sarson (University of Newcastle)
24 Nov 2003Harrison 170 Monday 2pmApplied Mathematics

 

Stability of Hamiltonian relative equilibria and applications to underwater vehicles
Claudia Wulff (University of Surrey)
17 Nov 2003Harrison 170 Monday 2pmApplied Mathematics

 

To be announced
Daniel Delbourgo (Nottingham)
13 Nov 2003Harrison 106 Thursday 3pmPure Mathematics

 

To be announced
Daniel Delbourgo (Nottingham)
13 Nov 2003Harrison 106 Thursday 3pmPure Mathematics

 

Qualitative behaviour of thin liquid metal layers at low magnetic Reynolds number
Paul Dellar (Oxford University)
10 Nov 2003Harrison 170 Monday 2pmApplied Mathematics

 

To be announced
Alan Camina (UEA)
6 Nov 2003Harrison 106 Thursday 3pmPure Mathematics

 

To be announced
Alan Camina (UEA)
6 Nov 2003Harrison 106 Thursday 3pmPure Mathematics

 

Robust control of 2D and 3D channel flow with CFD validation
Eric Rogers (University of Southampton)
3 Nov 2003Harrison 170 Monday 2pmApplied Mathematics

 

To be announced
Victor Flynn (Liverpool)
30 Oct 2003Harrison 106 Thursday 3pmPure Mathematics

 

To be announced
Victor Flynn (Liverpool)
30 Oct 2003Harrison 106 Thursday 3pmPure Mathematics

 

Renormalization in interval translation maps
Henk Bruin (University of Surrey)
27 Oct 2003Harrison 170 Monday 2pmApplied Mathematics

 

To be announced
Sophie Huczysnka (Edinburgh)
23 Oct 2003Harrison 106 Thursday 3pmPure Mathematics

 

To be announced
Sophie Huczysnka (Edinburgh)
23 Oct 2003Harrison 106 Thursday 3pmPure Mathematics

 

Formation of vortices and jets in rotating convection on a beta-plane: Jupiter's belts and zones in the laboratory
Peter Read (Oxford University)
20 Oct 2003Harrison 170 Monday 2pmApplied Mathematics

 

To be announced
Tom Korner (Cambridge)
16 Oct 2003Harrison 106 Thursday 3pmPure Mathematics

 

To be announced
Tom Korner (Cambridge)
16 Oct 2003Harrison 106 Thursday 3pmPure Mathematics

 

Two MHD problems: Helical dynamos and the pulsar magnetosphere
Jonathan Mestel (Imperial College)
13 Oct 2003Harrison 170 Monday 2pmApplied Mathematics

 

Dynamics of impacting systems: Theory and experiments
Marian Wiercigroch (Aberdeen University)
6 Oct 2003Harrison 170 Monday 2pmApplied Mathematics

 

Strange attractors and their basins
Yongluo Cao (Suzhou University)
18 Sep 2003Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Quasipatterns in surface waves
Alastair Rucklidge (Leeds University)
10 Sep 2003Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Shape optimization for induction hardening
Jan Sokolowski ('Henrie Poincare University, Nancy')
11 Jul 2003Harrison 170 Monday 2pmApplied Mathematics

 

Dynamos and convection: mean flow generation
Jon Rotvig (University of Exeter)
13 Jun 2003Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

RSS Local Group Meeting:
Measurement error, power and sample size in gene-environment interaction studies
Jian'an Luan (University of Cambridge)
11 Jun 2003Laver None NoneStatistics & Operational Research
See here for abstract

 

Partial stability and stabilization. Part 2
Reza Rokni Lamooki (University of Exeter)
6 Jun 2003Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Partial stability and stabilization. Part 1: an introduction
Reza Rokni Lamooki (University of Exeter)
30 May 2003Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

RSS Local Group Meeting:
Machine Learning Techniques for Bioinformatics
Colin Campbell (University of Bristol)
29 May 2003Laver None NoneStatistics & Operational Research
See here for abstract

 

Operational Research Seminar:
A cash flow criterion for controlling a base stock inventory system
Roger Hill (University of Exeter)
22 May 2003Laver None NoneStatistics & Operational Research
It is common practice to control certain inventory systems using a 'base stock' policy and the standard approach is then to associate time-weighted costs with holding stock and with having unsatisfied demand and to determine the base stock which minimises the long run average total cost per unit time. This approach ignores the impact of the control policy on the timing of the cash flows associated with payments made to suppliers and revenues received from customers. The approach made here is to concentrate on cash flows and determine the control policy which optimises an appropriate cash flow measure. The impact of the control system is measured in two ways. Firstly, if a customer order is met immediately from stock then we determine for how long that unit has been held in stock and compute the corresponding compound loss of interest resulting from having paid the supplier for it early. Secondly, if a customer order is not met from stock then we determine the delay in meeting that demand and the consequent loss of interest which could have been earned on the customer payment if it had not been delayed. The objective is to minimise the total expected cash flow impact per unit time. A solution procedure is given and a comparison is made between this approach and other ways of controlling this system.

 

The AKS algorithm
Robin Chapman (University of Exeter)
21 May 2003Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Integrability of Hamiltonian systems: from Poincare to Ziglin.
Alexei Tsygvinstev (University of Exeter)
19 May 2003Harrison 170 Monday 2pmApplied Mathematics

 

To be announced
Rahman Bahmani Sangsari (University of Exeter)
14 May 2003Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Pinching without branch points: new mechanism for absolute instability
Jonathan Healey (Keele University)
12 May 2003Harrison 170 Monday 2pmApplied Mathematics

 

Statistics Seminar:
Bootstrapping SIR for Dimension Assessment in a General Regression Problem
Santiago Velilla (Universidad Carlos III de Madrid)
8 May 2003Laver None NoneStatistics & Operational Research
A bootstrap method is constructed for assessing the dimension of a general regression problem. A resampled version of the matrix used in the SIR method of Li (1991) is obtained, and the bootstrap distributions of the statistics of interest characterized. The proposed methodology incorporates both formal and graphical inference procedures and can be considered as an alternative to the permutation test of Cook and Yin (2001).

 

To be announced
Julie Fowler (University of Exeter)
7 May 2003Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Cuntz and Leavitt algebras
Peter Vámos (University of Exeter)
30 Apr 2003Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Chaotic mixing and eigenfunctions
Jean-Luc Thiffeault (Imperial College)
28 Apr 2003Harrison 170 Monday 2pmApplied Mathematics

 

Infinite Designs
Bridget Webb (Open University)
20 Mar 2003Harrison 106 Thursday 3pmPure Mathematics
Infinite designs are quite rare in the literature--most books on design theory have no mention of them at all. In this talk I will present a brief history of infinite designs, give a precise definition, and compare some properties of finite and infinite designs.

 

Cuntz and Leavitt algebras - (POSTPONED)
Peter Vámos (University of Exeter)
19 Mar 2003Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Characterization of a family of two-roll mill flows
Jonathan Kobine (University of Dundee)
17 Mar 2003Harrison 170 Monday 2pmApplied Mathematics

 

Convergence groups and Hausdorff dimension
James Anderson (Southampton)
13 Mar 2003Harrison 106 Thursday 3pmPure Mathematics

 

Statistics Seminar:
Nonparametric classification exploiting separation of populations
Adolfo Hernandez (University of Exeter)
13 Mar 2003Laver None NoneStatistics & Operational Research
Kernel discriminant analyisis is greatly affected by the well-known phenomenon often referred to as the 'curse of dimensionality'. This causes bad behaviour of the rules because of the amount of data required as the dimension of the problem increases. In this seminar two dimension reduction methods are proposed, based on the concept of separation of populations. The basic idea is firstly to obtain a dimension reduction subspace through the maximization of certain functionals which can be seen as indexes of separation, and, secondly, to evaluate a reduced kernel discriminant rule in that subspace. The good behaviour of these methods is justified both theoretically and also through application to data sets where comparisons with other methods proposed in the literature can be established.

 

Asymptotics of class numbers
Anton Deitmar (University of Exeter)
12 Mar 2003Harrison 103 Tuesday NonePure Mathematics (Internal)

 

The structure of periodic causal operators on L2
George Weiss (Imperial College London)
10 Mar 2003Harrison 170 Monday 2pmApplied Mathematics

 

The McKay correspondence in dimension 3
Alistair King (Bath)
6 Mar 2003Harrison 106 Thursday 3pmPure Mathematics

 

Hermitian structures on lattices
Robin Chapman (University of Exeter)
5 Mar 2003Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Energy, helicity and crossing number relations for complex flows
Renzo Ricca (University College London)
3 Mar 2003Harrison 170 Monday 2pmApplied Mathematics

 

The Arithmetic of Quadratic Recurrence Sequences
Graham Everest (East Anglia)
27 Feb 2003Harrison 106 Thursday 3pmPure Mathematics

 

RSS Local Group Meeting:
Markov Chain Monte Carlo exact inference for binomial and multinomial logistic regression models
John MacDonald (University of Southampton)
27 Feb 2003Laver None NoneStatistics & Operational Research
See here for abstract

 

Nonlinear waves in diverging flows
Rich Kerswell (University of Bristol)
24 Feb 2003Harrison 170 Monday 2pmApplied Mathematics

 

Generalized blocks for symmetric groups
Geoffrey Robinson (Birmingham)
20 Feb 2003Harrison 106 Thursday 3pmPure Mathematics

 

Statistics Seminar:
Spatial modelling of childhood malaria in the Gambia
Rana Moyeed (University of Plymouth)
20 Feb 2003Laver None NoneStatistics & Operational Research
A spatial generalized linear mixed model is developed to describe the variation in malarial prevalence amongst a sample of village resident children in the Gambia. The response from each child is a binary indicator of the presence of malarial parasites in a blood-sample. The model includes terms for the effects of child-level covariates, village-level covariates and separate components for residual spatial and non-spatial extra-binomial variation. The results show that the extra-binomial variation is spatially structured, suggesting an environmental effect rather than variation in familial susceptibility. The method of inference was Bayesian using vague priors and a Markov chain Monte Carlo implementation.

 

Parametrisation of attractors and Takens embedding thereom
James Robinson (University of Warwick)
17 Feb 2003Harrison 170 Monday 2pmApplied Mathematics

 

Paths in the cube
Imre Leader (Cambridge)
13 Feb 2003Harrison 106 Thursday 3pmPure Mathematics

 

The application of the method of matched asymptotic expansions to problems arising in reaction-diffusion theory
John Leach (University of Reading)
10 Feb 2003Harrison 170 Monday 2pmApplied Mathematics

 

RSS Local Group Meeting:
The Forward Search and the Analysis of Multivariate Data
Anthony Atkinson (London School of Economics)
6 Feb 2003Laver None NoneStatistics & Operational Research
See here for abstract

 

Revisiting scaling laws for the magnetic and velocity fields
Glenn Ierley (University of California San Diego)
31 Jan 2003Harrison 170 Monday 2pmApplied Mathematics

 

Mapping class groups and Teichmuller spaces
William Harvey (King's College)
30 Jan 2003Harrison 106 Thursday 3pmPure Mathematics

 

Marangoni-Benard convection in square and almost square containers
Edgar Knobloch (University of Leeds)
27 Jan 2003Harrison 170 Monday 2pmApplied Mathematics

 

Symmetric squares of elliptic curves: evidence for the Bloch-Kato Conjecture
Neil Dummigan (Sheffield)
23 Jan 2003Harrison 106 Thursday 3pmPure Mathematics

 

Instabilities of the Stewartson layer
Rainer Hollerbach (University of Glasgow)
20 Jan 2003Harrison 170 Monday 2pmApplied Mathematics

 

Free Lie algebras as modules for finite groups
Ralph Stohr (UMIST)
16 Jan 2003Harrison 106 Thursday 3pmPure Mathematics

 

Operational Research Seminar:
An Overview of OR in Sport
Chris Potts (University of Southampton)
16 Jan 2003Laver None NoneStatistics & Operational Research
This talk reviews some contributions that operational research (OR) has made in sport. The contributions roughly fall within the areas of planning and strategy, scheduling, ranking and performance measurement, and prediction. In planning and strategy, we discuss the use of dynamic programming for optimising batting strategies in one-day cricket, and describe how pit stop strategies are determined in formula one motor racing. For scheduling sports fixtures, we indicate how OR has been used in county cricket. Different sports use different methods for measuring the performance of players/teams. We comment briefly on the need for more robust systems. Finally, prediction is important for bookmakers and is of interest to sports enthusiasts. The modelling of the results of soccer games is discussed.

 

Transient vortex events in turbulence
Bob Kerr (University of Warwick)
13 Jan 2003Harrison 170 Monday 2pmApplied Mathematics

 

Zonal flows on Jupiter
Chris Jones (University of Exeter)
13 Dec 2002Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Postgraduate Seminar:
Clustering Gene Expression Data
Heather Turner (University of Exeter)
12 Dec 2002Laver None NoneStatistics & Operational Research
Gene expression data, resulting from the relatively new microarray technology, has many features which make it difficult to analyse. Many traditional techniques fail due to the size of the data sets or the lack of conformity to common assumptions, such as normality or independence.Clustering has proven to be a useful method of discovering functional grouping of genes, one of the main objectives of microarray experiments. A number of clustering algorithms have been specifically developed for gene expression data, designed to be more efficient and more flexible than standard algorithms. Tne of these algorithms is the plaid model, a two-way overlapping clustering method proposed by Lazzeroni and Owen (2002). This talk introduces the plaid model and proposes an alternative optimisation algorithm that may improve its efficiency. Possible extensions of the model will also be discussed.

 

New observational constraints on the geodynamo
Richard Holme (University of Liverpool)
9 Dec 2002Harrison 170 Monday 2pmApplied Mathematics

 

Geometric approach to the distribution of n**2 alpha mod 1
Jens Marklof (Bristol)
5 Dec 2002Harrison 106 Thursday 3pmPure Mathematics

 

Functorial aspects of the unit sum number of rings
Nahid Ashrafi (University of Exeter)
4 Dec 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

RSS Local Group Meeting:
Predicting Reliability for Orthopaedic Hip Replacements
Simon Wilson (Trinity College Dublin & Carlos III University Madrid)
4 Dec 2002Laver None NoneStatistics & Operational Research
See here for abstract

 

Nature of torsional oscillations in the solar convection zone
Reza Tavakol ('Queen Mary, University of London')
2 Dec 2002Harrison 170 Monday 2pmApplied Mathematics

 

Topological invariants for quasicrystals
John Hunton (Leicester)
28 Nov 2002Harrison 106 Thursday 3pmPure Mathematics

 

Totally and weakly ramified extensions
Lee Jackson (University of Exeter)
27 Nov 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Some bifurcation results for differential-algebraic equations
Robert Beardmore (Imperial College)
25 Nov 2002Harrison 170 Monday 2pmApplied Mathematics

 

Iwasawa algebras and arithmetic
John Coates (Cambridge)
21 Nov 2002Harrison 106 Thursday 3pmPure Mathematics

 

RSS Local Group Meeting:
Challenges in Bioinformatics for Statisticians
Wally Gilks ('MRC Biostatistics Unit, Cambridge')
21 Nov 2002Laver None NoneStatistics & Operational Research
See here for abstract

 

A new proof of the uniqueness of elastic surface waves
Yibin Fu (University of Keele)
18 Nov 2002Harrison 170 Monday 2pmApplied Mathematics

 

Non-Abelian Iwasawa Theory and Elliptic Curves, Theory and Examples
Susan Howson (Oxford)
14 Nov 2002Harrison 106 Thursday 3pmPure Mathematics

 

Simple groups and Hopf-Galois structures
Nigel Byott (University of Exeter)
13 Nov 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Validity of various approximations of the fully-compressible atmospheric equation as inferred from normal-mode analysis
'Andrew Staniforth, Terry Davies and Nigel Wood' (Met Office)
11 Nov 2002Harrison 170 Monday 2pmApplied Mathematics

 

Topological Hochschild cohomology of noncommutative ring spectra
Andrey Lazarev (Bristol)
7 Nov 2002Harrison 106 Thursday 3pmPure Mathematics

 

Statistics Seminar:
Denoising real data using complex wavelets
Stuart Barber (University of Bristol)
7 Nov 2002Laver None NoneStatistics & Operational Research
Wavelet shrinkage is an effective nonparametric regression technique when the underlying curve has irregular features such as spikes or discontinuities. The basic idea is simple: take the discrete wavelet transform (DWT) of data consisting of a signal corrupted by noise; shrink the wavelet coefficients to remove the noise; and then invert the DWT to form an estimate of the true underlying curve. Various authors have proposed methods of doing this using real-valued wavelets. Complex-valued versions of some wavelets exist, but are rarely used. We propose two shrinkage techniques which use complex wavelets. Simulation results show that both methods give smaller errors than using state of the art shrinkage rules with real-valued wavelets.

 

Magnetic fields in barred galaxies
David Moss (University of Manchester)
4 Nov 2002Harrison 170 Monday 2pmApplied Mathematics

 

Magnetic damping of surface gravity waves
Binod Sreenivasan (University of Exeter)
1 Nov 2002Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Starks conjecture and new Stickelberger phenomena
Vic Snaith (Southampton)
31 Oct 2002Harrison 106 Thursday 3pmPure Mathematics

 

Commuting superline maps
Ben Mestel (University of Exeter)
30 Oct 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Statistics Seminar:
Bayesian rule based classification
Chris Holmes (Imperial College London)
30 Oct 2002Laver None NoneStatistics & Operational Research
We describe a new method for statistical pattern recognition that is based on probabilistic rule sets. The model constructs a set of first-order rules of the form IF A THEN B where the antecedent A relates to conditions on a set of predictor measurements x and the consequence B relates to changes in the odds function of the conditional probability p(y/x) for a category label y. Rule-set models are highly expressive and interpretable and a key feature of the method is the ease by which expert domain knowledge can be incorporated into the classifier system. A Bayesian framework is used which places a prior distribution over the state space of all probabilistic rule sets. Inference proceeds using stochastic simulation via tailored Markov chain Monte Carlo algorithms. The methodology is illustrated using examples taken from the machine learning literature where typically we have tens or hundreds of predictors and hundreds or thousands of observations.

 

Virial functional in fluid mechanics
Vladimir Vladimirov (Univeristy of Hull)
28 Oct 2002Harrison 170 Monday 2pmApplied Mathematics

 

Random matrix theory and L-functions
Jon Keating (Bristol)
24 Oct 2002Harrison 106 Thursday 3pmPure Mathematics

 

Operational Research Seminar:
Inventory - too much , too little, or right on?
Geoff Relph (Manchester Business School)
24 Oct 2002Laver None NoneStatistics & Operational Research
Inventory has a major impact on business performance. How do you achieve that elusive balance - customer satisfaction and lower inventory? This talk examines some of the issues involved in better inventory planning. The concept of 'overage inventory' is defined and developed. Case research on inventory management in a manufacturing company is discussed. Options for evaluating and estimating the value of overage and determining simple prioritisation techniques for the desired corrective action needed to reduce the overage are examined. The pragmatic balance between purist academic views of inventory management and the instinctive approach often used in a small business are considered.

 

Impulse differential inclusions: Towards a viability theory of hybrid systems
John Lygeros (University of Cambridge)
21 Oct 2002Harrison 170 Monday 2pmApplied Mathematics

 

A new test for chaos in deterministic nonlinear dynamical systems
Ian Melbourne (University of Surrey)
14 Oct 2002Harrison 170 Monday 2pmApplied Mathematics

 

Mixing and Diophantine problems
Tom Ward (UEA)
10 Oct 2002Harrison 106 Thursday 3pmPure Mathematics

 

Fractal asymptotics
Carl Dettmann (University of Bristol)
7 Oct 2002Harrison 170 Monday 2pmApplied Mathematics

 

Counting subgroups in nilpotent groups and points on elliptic curves
Marcus du Sautoy (Oxford)
18 Jun 2002Harrison 106 Thursday 3pmPure Mathematics

 

Complex and p-adic Stark Conjectures at s=1
David Solomon (Kings College)
13 Jun 2002Harrison 106 Thursday 3pmPure Mathematics

 

On the relationship between the discrete and continuous Painleve equations
Peter Clarkson (University of Kent)
10 Jun 2002Harrison 170 Monday 2pmApplied Mathematics

 

'Invariant extension of automorphic functions, differential intertwining operators and Jacobi polynomials'
Andreas Juhl (Stockholm)
6 Jun 2002Harrison 106 Thursday 3pmPure Mathematics

 

Conformal geometry and Clifford algebras
Fran Burstall (Bath)
30 May 2002Harrison 106 Thursday 3pmPure Mathematics

 

Explicitly time-dependent alpha-quenching
Axel Brandenburgh (NORDITA)
27 May 2002Harrison 170 Monday 2pmApplied Mathematics

 

The Hasse principle for Diophantine equations
Alexei Skorobogatov (Imperial)
23 May 2002Harrison 106 Thursday 3pmPure Mathematics

 

RSS Local Group Meeting:
Does the weather God play dice?
David Stephenson (University of Reading)
23 May 2002Laver None NoneStatistics & Operational Research
See here for abstract

 

Higher power residue codes and unimodular lattices
Mehrdad Ahmadzadeh-Raji (University of Exeter)
21 May 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Galois covers of degree p and semi-stable reduction of curves
Mohamed Saïdi (Durham)
16 May 2002Harrison 106 Thursday 3pmPure Mathematics

 

RSS Local Group Meeting & AGM:
Something in the air? Multivariate analysis and atmospheric science
Ian Jolliffe (University of Aberdeen)
16 May 2002Laver None NoneStatistics & Operational Research
See here for abstract

 

Stochastic population dynamics
Xuerong Mao (University of Strathclyde)
13 May 2002Harrison 170 Monday 2pmApplied Mathematics

 

New quadratic iterations to Pi
Heng Huat Chan (National U Singapore)
9 May 2002Harrison 106 Thursday 3pmPure Mathematics

 

Constructing Hopf orders to act on valuation rings
Julie Fowler (University of Exeter)
7 May 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Pisot numbers and Coxeter graphs
Chris Smyth (Edinburgh)
2 May 2002Harrison 106 Thursday 3pmPure Mathematics

 

Operational Research Seminar:
Base stock inventory policies
Mundappa Pakkala (University of Mangalore)
2 May 2002Laver None NoneStatistics & Operational Research
We consider an inventory model in continuous time. Demand follows a Poisson process and demand during a stockout is backordered. The stock level is controlled by means of a base stock policy in which the balance of physical stock plus stock on order less backorders is maintained at the base stock level. Therefore if a demand occurs then an order for replacement stock is placed immediately. The time for a replacement order to arrive is the lead time - this may be fixed or it may vary. We consider here two variants on this basic policy. First, multi-item demand processes. Second, modelling the cash flows. In each case we discuss the context of the problem, its mathematical formulation and a procedure for finding the optimal solution.

 

Quantum monodromy
Holger Dullin (Loughborough University)
29 Apr 2002Harrison 170 Monday 2pmApplied Mathematics

 

The Kubota symbol on SL_n
Richard Hill (UCL)
25 Apr 2002Harrison 106 Thursday 3pmPure Mathematics

 

Composition convection due to the decrease of the rapidly rotating shell
Serguey Starchenko (GFO Borok)
22 Apr 2002Harrison 170 Monday 2pmApplied Mathematics

 

'Paperfolding, automata, and rational functions'
Alf van der Poorten (Sydney)
14 Mar 2002Harrison 106 Thursday 3pmPure Mathematics

 

Operational Research Seminar:
Locating ambulances in Riyadh: theoretical developments and practical application
Graham Rand (University of Lancaster)
14 Mar 2002Laver None NoneStatistics & Operational Research
The location of Emegency Medical Services (EMS) is an important problem. Good locations, enabling rapid response, can save lives. Typical OR modelling for these problems tries to improve coverage which is defined as the ability to travel from a service station to a demand point in a pre-specified time. A model was developed to evaluate locations for the Saudi Arabian Red Crescent Society (SARCS), Riyadh City, Saudi Arabia. In this model the usual 0-1 coverage definition (i.e. the demand is covered or not) is replaced by the probability of covering a demand within the target time. Second, once the locations are determined, the minimum number of vehicles at each location that satisfies the required performance levels is determined. Thus, the problem of identifying the optimal locations of a pre-specified number of emergency medical service (EMS) stations is addressed by goal programming. The first goal is to locate these stations so the maximum expected demand can be reached within a pre-specified target time. Then, the second goal is to ensure that any demand arising located within the service area of the station will find at least one vehicle, such as an ambulance, available. Erlang's loss formula is used to identify the arrival rates when it is necessary to add an ambulance in order to maintain the performance level for the availability of ambulances. The use of the model for the Riyadh EMS will be described. This work was undertaken jointly with Othman Alsalloum

 

Determining matroid representability over the reals
Rosemary Baines (University of Exeter)
12 Mar 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Shear and magnetic buoyancy instabilities in the solar tachocline
Steve Tobias (University of Leeds)
11 Mar 2002Harrison 170 Monday 2pmApplied Mathematics

 

Beyond Borel-Cantelli
Maurice Dodson (York)
7 Mar 2002Harrison 106 Thursday 3pmPure Mathematics

 

On the matrix type of a ring
Rahman BahmaniSangesari (University of Exeter)
5 Mar 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Vortex equilibria of the Euler equations
Darren Crowdy (Imperial College)
4 Mar 2002Harrison 170 Monday 2pmApplied Mathematics

 

RSS Local Group Meeting:
Inference in fMRI experiments using spectral domain methods
Jonathan Marchini (University of Oxford)
28 Feb 2002Laver None NoneStatistics & Operational Research
See here for abstract

 

Torsion theory and co-Cohen-Macaulay modules
Mohammad Bijan-Zadeh (University of Tehran)
26 Feb 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Thin layer theories
Richard Craster (Imperial College)
25 Feb 2002Harrison 170 Monday 2pmApplied Mathematics

 

Polylogarithms and special values of L-functions
Guido Kings (Regensburg)
21 Feb 2002Harrison 106 Thursday 3pmPure Mathematics

 

Postgraduate Seminar:
Lot sizing policies in an advance ordering environment
Lynette Frick (University of Exeter)
21 Feb 2002Laver None NoneStatistics & Operational Research
In most classic inventory models customer demand is either assumed to be deterministic or stochastic. In some multi-period applications, future demand is only

 

Localisation of patterns in convection
Stephen Cox (University of Nottingham)
18 Feb 2002Harrison 170 Monday 2pmApplied Mathematics

 

Homology decompositions of classifying spaces
Dietrich Notbohm (Leicester)
14 Feb 2002Harrison 106 Thursday 3pmPure Mathematics

 

Statistics Seminar:
Disease mapping of stage-specific cancer incidence data
Leo Knorr-Held (University of Lancaster)
14 Feb 2002Laver None NoneStatistics & Operational Research
We propose two approaches for the spatial analysis of cancer incidence data with additional information on the stage of the disease at time of diagnosis. The two formulations are extensions of commonly used models for multicategorical response data on an ordinal scale. We include spatial and age group effects in both formulations, which we estimate in a nonparametric smooth way. More specifically, we adopt a fully Bayesian approach based on Gaussian pairwise difference priors where additional smoothing parameters are treated as unknown as well. We argue that the proposed methods are useful in monitoring the effectiveness of mass cancer screening and illustrate this through an application to data on cervical cancer in the former German Democratic Republic. The results suggest that there are large spatial differences in the stage-proportions, which indicates spatial variability with respect to the introduction and effectiveness of pap smear screening programs. This is joint work with G Rasser, University of Munich and N Becker, German Cancer Research Center Heidelberg.

 

Pattern selection and symmetry in rotating Rayleigh-Benard convection
Jon Dawes (University of Cambridge)
11 Feb 2002Harrison 170 Monday 2pmApplied Mathematics

 

Local analogue of the Grothendieck Conjecture
Victor Abrashkin (Durham)
7 Feb 2002Harrison 106 Thursday 3pmPure Mathematics

 

Statistics Seminar:
Cross-validation in additive main effect and multiplicative interaction (AMMI) models
Carlos Tadeu dos Santos Dias (University of Sao Paulo/ESALQ)
7 Feb 2002Laver None NoneStatistics & Operational Research
The additive main effects and multiplicative interaction (AMMI) model has been proposed for the analysis of genotype/environmental data. For plant breeding, the recovery of pattern might be considered to be the principal objective of analysis. However, some problems still remain with the analysis, notably in selecting the number of multiplicative components in the model. Methods based on distributional assumptions do not have sound methodological basis, while existing data-based approaches do not optimise the cross-validation process. This talk will first summarise the AMMI model and outline the available methodology for selecting the number of multiplicative components to include in it. Then two new methods will be described that are based on a full leave-one-out procedure optimising the cross-validation process. Both methods will be illustrated and compared on some unstructured multivariate data. Finally, their application to analysis of GxE interaction will be demonstrated on experimental grain yield data.

 

Realisable classes of wild extensions
Lee Jackson (University of Exeter)
5 Feb 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

The role of the heating mode of the mantle in intermittent reorganisation of plate velocities
Julian Lowman (University of Leeds)
4 Feb 2002Harrison 170 Monday 2pmApplied Mathematics

 

Rings generated by Eulerian derivatives
David Jordan (Sheffield)
31 Jan 2002Harrison 106 Thursday 3pmPure Mathematics

 

On globally periodic solutions of the difference equation $x_{n+1} = f(x_n)/x_{n-1}$
Ben Mestel (University of Exeter)
29 Jan 2002Harrison 103 Tuesday NonePure Mathematics (Internal)

 

MHD in metallurgical processes
Peter Davidson (University of Cambridge)
28 Jan 2002Harrison 170 Monday 2pmApplied Mathematics

 

'Ergodic averages, exponential sums and combinatorial number theory'
Kit Nair (Liverpool)
24 Jan 2002Harrison 106 Thursday 3pmPure Mathematics

 

RSS Local Group Meeting:
Anticipating catastrophes through extereme value modelling
Stuart Coles (University of Bristol)
24 Jan 2002Laver None NoneStatistics & Operational Research
See here for abstract

 

Fast dynamo problem
Oleg Kozlovski (University of Warwick)
21 Jan 2002Harrison 170 Monday 2pmApplied Mathematics

 

The Fermat equation over real quadratic fields
Frazer Jarvis (Sheffield)
17 Jan 2002Harrison 106 Thursday 3pmPure Mathematics

 

Statistics Seminar:
Geostatistical models and applications
Paulo Ribeiro (University of Lancaster)
17 Jan 2002Laver None NoneStatistics & Operational Research
The term 'geostatistics' identifies the part of spatial statistics which is concerned with continuous spatial variation. The term 'model-based geostatistics' was coined by Diggle, Tawn and Moyeed (1998) to mean the application of explicit parametric, stochastic models and formal, likelihood-based, methods of inference to geostatistical problems. Geostatistical methods are currently applied in a wide range of subjects and model-based methods provide further options to tackle challenging pratical problems. Motivated by some pratical applications, this talk discusses model-based geostatistical methods and their computational implementation.

 

Jets, waves and vortices in the Jovian atmosphere
POSTPONED
Yasuhiro Yamazaki (University of Oxford)
14 Jan 2002Harrison 170 Monday 2pmApplied Mathematics

 

Operational Research Seminar:
A bounding problem in inventory modelling
Roger Hill (University of Exeter)
10 Jan 2002Laver None NoneStatistics & Operational Research
A fundamental inventory model is the stochastic demand, periodic or continuous review, backorder model with linear holding, shortage and ordering costs and a general lead time on replenishment. It is well-established that the optimal control policy for this model is an (s,S) policy and efficient procedures exist for deriving this optimal policy. An important feature of most practical systems is that packaging and handling considerations require that replenishments must be in multiples of some unit of stock transfer q. This talk describes, in outline, the fundamental model and shows how the analysis can be adapted to allow for a general unit of stock transfer q. It finally raises some, as yet unresolved, issues on developing procedures for finding the optimal policy for this modified model.

 

Deterministic and random products of Euclidean transformations
CANCELLED
Ian Melbourne (University of Surrey)
7 Jan 2002Harrison 170 Monday 2pmApplied Mathematics

 

Global bifurcation to travelling waves in spherical Couette flow
Andrew Soward (University of Exeter)
7 Dec 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Goldbach's conjecture and powers of 2
Roger Heath-Brown (Oxford)
6 Dec 2001Harrison 106 Thursday 3pmPure Mathematics

 

A golden mean functional recurrence
Ben Mestel (University of Exeter)
4 Dec 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Adaptive controllers and the gap metric
Mark French (University of Southampton)
3 Dec 2001Harrison 170 Monday 2pmApplied Mathematics

 

A new generation of geodynamo models
Keke Zhang (University of Exeter)
30 Nov 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Lower and Upper Bounds in Discrepancy Theory
William Chen ('Macquarie University, Sydney')
29 Nov 2001Harrison 106 Thursday 3pmPure Mathematics

 

Analysis of transplant survival rates
Dave Collett (University of Reading)
28 Nov 2001Laver None NoneStatistics & Operational Research

 

Realisable classes for tame non-abelian extensions of degree 8
Nigel Byott (University of Exeter)
27 Nov 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Oscillations in small aspect ratio magnetoconvection
Mike Proctor (University of Cambridge)
26 Nov 2001Harrison 170 Monday 2pmApplied Mathematics

 

Nonlinear models of rotating spherical convection
Steve Cole (University of Exeter)
23 Nov 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Schur Weyl duality and tilting theory
Steffen Koenig (Leicester)
22 Nov 2001Harrison 106 Thursday 3pmPure Mathematics

 

Should small firms be more cautious than large ones? - Dynamic programming models of operations management decisions in small firms.
Lyn Thomas (University of Southampton)
22 Nov 2001Laver None NoneStatistics & Operational Research
Operations management models, like inventory control and production levels have proved very successful in the operations of firms. However they all take as their objective the maximisation of profit or the minimisation of cost. For small firms it could be argued that maximising the probability of survival of the firm is the principal objective. This talk looks at how one can model the operations management decisions under this criterion using dynamic programming and compares the survival probability maximising decisions with the profit maximising ones. It suggests that small firms should be more cautious ( but not too cautious) than large firms.

 

A family of equivariant Fredholm modules
Stuart Horswell (University of Exeter)
20 Nov 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Galactic magnetic fields
Steven Cowley (Imperial College)
19 Nov 2001Harrison 170 Monday 2pmApplied Mathematics

 

Hopf bifurcation with the symmetry of the cube
Pete Ashwin (University of Exeter)
16 Nov 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Do we really live in a Riemannian world?
Dmitri Vassiliev (Bath)
15 Nov 2001Harrison 106 Thursday 3pmPure Mathematics

 

Postgraduate Seminar: Statistical modelling of performance indicators
Paul Hewson (University of Exeter)
15 Nov 2001Laver None NoneStatistics & Operational Research
Performance Indicators are amongst the most widely published official statistics in the UK. It has been suggested that the UK central government has set over 5,000 targets against these statistics. In contrast to the wealth of numerical data available, less effort has been applied to the statistical analysis of the data. Most work performed to date has been in the educational and health fields, although considerable money has been spent evaluating data envelopment analysis for the Home Office to develop targets for police performance. Using two sets of Performance Indicators, relating to Housing Benefit Administration and Road Safety (reflecting output and outcome indicators), various methods for analysis will be reviewed, particularly approaches based upon generalised linear mixed models. Work in progress to account for the multivariate nature of the data in such models will also be described.

 

A probabilistic proof of the Andrews-Gordon identities
Robin Chapman (University of Exeter)
13 Nov 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Particles in a random field
Andrew Stuart (University of Warick)
12 Nov 2001Harrison 170 Monday 2pmApplied Mathematics

 

Some issues in stochastic control
Stuart Townley (University of Exeter)
9 Nov 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Transversals in Latin Squares
Ian Wanless (Oxford)
8 Nov 2001Harrison 106 Thursday 3pmPure Mathematics

 

RSS Meeting: Modelling spatial-temporal processes for hydrology and climate
Valerie Isham (University College London)
7 Nov 2001Laver None NoneStatistics & Operational Research
A review will be given of some of the spatial-temporal models developed by an interdisciplinary team from University College and Imperial College for use in the context of hydrological design. Approaches using both point-process-based stochastic models and statistical, generalised linear, models (GLMs) will be described. A strength of the former models is their ability to represent high space-time resolution, while the latter more easily enable spatial and temporal nonstationarities to be incorporated. These models are also being used to investigate other climatological processes, such as temperature and wind speed, where there is a particular focus on questions of the influence of long-range effects (e.g., El Nino), and climate change.

 

Endomorphisms of free modules of infinite rank
Peter V'{a}mos (University of Exeter)
6 Nov 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Shear propagation into the solar radiative zone
Pascale Garaud (University of Cambridge)
5 Nov 2001Harrison 170 Monday 2pmApplied Mathematics

 

Energy fluxes and dissipation in planetary cores
Chris Jones (University of Exeter)
2 Nov 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Statistics, symmetry and skew products
Mike Field (University of Houston)
29 Oct 2001Harrison 170 Monday 2pmApplied Mathematics

 

Vorticity, mixing and motion
Andrew Gilbert (University of Exeter)
26 Oct 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Probability and learning
Igor Rivin (Manchester)
25 Oct 2001Harrison 106 Thursday 3pmPure Mathematics

 

RSS Meeting: Bayes 'n' drugs 'n' sporting role
Phil Brown (University of Kent)
25 Oct 2001Laver None NoneStatistics & Operational Research
A joint EU/IOC international project centered on St. Thomas's Hospital London has been looking at detection of growth hormone abuse in sport. We describe approaches to modelling multivariate markers of GH intake through time to discriminate between those that were treated with growth hormone and those on placebo in a double-blind study.

 

Mellin transforms of Whittaker functions
Anton Deitmar (University of Exeter)
23 Oct 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Kinematic dynamos at high magnetic Reynolds number
Graeme Sarson (University of Newcastle upon Tyne)
22 Oct 2001Harrison 170 Monday 2pmApplied Mathematics

 

Scaling properties of spatial and temporal spectra of the geomagnetic field
Roberta Tozzi (Rome)
19 Oct 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Rings of injective dimension 1
Arthur Chatters (Bristol)
18 Oct 2001Harrison 106 Thursday 3pmPure Mathematics

 

Estimating abundance from data containing many zeros
Alan Welsh (University of Southampton)
18 Oct 2001Laver None NoneStatistics & Operational Research
North East Herald Cay is a small but ecologically significant coral cay in the Coral Sea, about 350 km off the coast of Queensland, Australia. As part of the development of a monitoring program, we consider the problem of estimating the number of nests of different species of seabirds on North East Herald Cay based on surveys of 10mx10m quadrats along transects across the Cay. We consider three approaches based on different plausible models. Our main findings are that an approach based on a conditional negative binomial model which allows for additional zeros in the data works well and that a transform-both-sides regression approach produces badly biased estimates and should not be used. We discuss our experience of collecting the data, applying the methodology to the available data and discuss the implications for monitoring nesting on North East Herald Cay.

 

Saturating Mordell-Weil groups
John Cremona (Nottingham)
11 Oct 2001Harrison 106 Thursday 3pmPure Mathematics

 

Statistics in sport and games
Frank Duckworth ('Editor, RSS News')
10 Oct 2001Laver None NoneStatistics & Operational Research

 

Weak disjointness in topological dynamics
Xiangdong Ye (University of Science and Technology of China)
25 Sep 2001Harrison 170 Monday 2pmApplied Mathematics

 

Are there any (interesting) non-commutative Hopf orders?
Nigel Byott (University of Exeter)
26 Jun 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

From matroids to equations and back
Peter Vamos (University of Exeter)
19 Jun 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Numerical modelling of star formation
Matthew Bate (University of Exeter (Physics))
15 Jun 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Families of modular forms
Kevin Buzzard (Imperial College)
14 Jun 2001Harrison 106 Thursday 3pmPure Mathematics

 

Packing properties of invariant disks for some planar piecewise isometries
Xin-Chu Fu (University of Exeter)
8 Jun 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Generalizing the analytic class number formula
Annette Huber-Klawitter (Leipzig)
7 Jun 2001Harrison 106 Thursday 3pmPure Mathematics

 

Quantum turbulence in superfluid helium
Tomasz Lipniacki (University of Warsaw)
1 Jun 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Quantisations of Kleinian Singularities and Beyond
Dmitriy Rumynin (Warwick)
31 May 2001Harrison 106 Thursday 3pmPure Mathematics

 

Special RSS Meeting and AGM at Plymouth University (Robbins Seminar Room 2): A Heretic's View of Placebos and Ethics in Clinical Trials
Stephen Senn ('University College, London')
31 May 2001Laver None NoneStatistics & Operational Research

 

Evolution of sharp edged planar vortices
Ian Hall (University of Exeter)
25 May 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Refined class number formulas for abelian L-functions
David Burns (King's College)
24 May 2001Harrison 106 Thursday 3pmPure Mathematics

 

Postgraduate Seminar: Using State Space models to investigate the effect of vitamin A supplement on diarrhoea
Valeska Andreozzi (University of Exeter)
24 May 2001Laver None NoneStatistics & Operational Research

 

Postgraduate Seminar: A Score Test for Zero-inflated Negative Binomial Models
Naratip Jansakul (University of Exeter)
24 May 2001Laver None NoneStatistics & Operational Research

 

Lefschetz formulae for dynamical systems
Anton Deitmar (University of Exeter)
22 May 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Routes to chaos, channel capacity and the representation of numbers in non-integer bases'
Paul Glendinning (UMIST)
21 May 2001Harrison 170 Monday 2pmApplied Mathematics

 

Instabilities induced by the differentially rotating inner core and mantle
Pu Zhang (University of Exeter)
18 May 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Principal homogeneous spaces for some Hopf orders
Silvia Sommaro (University of Exeter)
15 May 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Chaotic Dynamics in Semiconductor Lasers
Pieter Collins (University of Liverpool)
14 May 2001Harrison 170 Monday 2pmApplied Mathematics

 

Fourier series on spheres
Paul Earnshaw (University of Exeter)
11 May 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Bending Kleinian Groups
Caroline Series (Warwick)
10 May 2001Harrison 106 Thursday 3pmPure Mathematics

 

Invariant distributions on limit sets
Martin Olbrich (Goettingen)
3 May 2001Harrison 106 Thursday 3pmPure Mathematics

 

Bizarre q-series identities
Robin Chapman (University of Exeter)
1 May 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

One hundred years of normal numbers
Glyn Harman (Royal Holloway)
26 Apr 2001Harrison 106 Thursday 3pmPure Mathematics

 

'Numerical exterior algebra, with applications in hydrodynamic stability and dynamical systems'
Tom Bridges (University of Surrey)
23 Apr 2001Harrison 170 Monday 2pmApplied Mathematics

 

The size of orders from customers, characterisation, forecasting and implications
Roy Johnston (Warwick University)
18 Apr 2001Laver None NoneStatistics & Operational Research

 

Dynamics of a Sigma-Delta modulator as a piecewise isometry
Jonathan Deane (University of Surrey)
30 Mar 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

The 200th proof of quadratic reciprocity?
Robin Chapman (University of Exeter)
20 Mar 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Using the Randomisation in Specifying the Mixed Models and ANOVA tables
Chris Brien (University of South Australia)
16 Mar 2001Laver None NoneStatistics & Operational Research

 

Symmetric powers of Galois modules
Bernhard Koeck (University of Southampton)
15 Mar 2001Harrison 106 Thursday 3pmPure Mathematics

 

'Typical magneto-convection values in the interiors of Jupiter, Saturn and the Earth'
Sergey Starchenko ('GFO Barok, Russia')
13 Mar 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Galois Module Structure of some non-normal extensions (of p-adic fields)
Julie Fowler (University of Exeter)
13 Mar 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Modulating pulse solutions for a class of nonlinear wave equations
Mark Groves (University of Loughborough)
12 Mar 2001Harrison 170 Monday 2pmApplied Mathematics

 

MHD shear layers in spherical Couette flow
Andrew Soward (University of Exeter)
9 Mar 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Rings having finite unit sum number
Nahid Ashrafi (University of Exeter)
8 Mar 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Postgraduate Seminar: Analysis of Multivariate Process Control Data
Julie Badcock (University of Exeter)
8 Mar 2001Laver None NoneStatistics & Operational Research

 

Postgraduate Seminar:The Evolution of Trees: Application of Genetic Algorithms to Network Optimisation
Evan Thompson (University of Exeter)
8 Mar 2001Laver None NoneStatistics & Operational Research

 

Derangements and (0,1) matrices with line sum 2
Douglas Rogers
6 Mar 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Stochastic bifurcation: concepts and examples
Ludwig Arnold ('Universitat Bremen')
5 Mar 2001Harrison 170 Monday 2pmApplied Mathematics
Part of the %http://www.maths.ex.ac.uk/Research/applDSC/events/ndc.html%Southern Bifurcation Meeting%

 

Quasi-invariant sets in Piecewise Isometries
Miguel Mendes (University of Surrey)
2 Mar 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Characteristic classes of surface bundles
Ulrike Tillmann (University of Oxford)
1 Mar 2001Harrison 106 Thursday 3pmPure Mathematics

 

Use of discrete event simulation in the evaluation of screening for Helicobacter pylori for the prevention of peptic ulcers and gastric cancer.
Ruth Davis (University of Southampton)
1 Mar 2001Laver None NoneStatistics & Operational Research

 

Higher power residue codes and the Leech lattice
Mehrdad Ahmadzadeh-Raji (University of Exeter)
27 Feb 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Neutral Rayleigh waves in Hagen-Poiseuille flow
Andrew Walton (Imperial College)
26 Feb 2001Harrison 170 Monday 2pmApplied Mathematics

 

Non-orientable manifolds in three-dimensional vector fields
Hinke Osinga (University of Exeter)
23 Feb 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Prehomogeneous vector spaces and the trace formula
Werner Hoffman (University of Berlin)
22 Feb 2001Harrison 106 Thursday 3pmPure Mathematics

 

Almost Unique Factorisation Domains
Peter V'{a}mos (University of Exeter)
20 Feb 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Receptivity of boundary layers to free-stream disturbances
Paul Hammerton (University of East Anglia)
19 Feb 2001Harrison 170 Monday 2pmApplied Mathematics

 

Convection in a semi-infinite layer above a flat plate
Andrew Bassom (University of Exeter)
16 Feb 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Probabilistic structures in Dynamics
Stefano Luzatto (Imperial College)
15 Feb 2001Harrison 106 Thursday 3pmPure Mathematics

 

RSS meeting: Estimating Mixtures of Regressions
Merrilee Hurn (University of Bath)
15 Feb 2001Laver None NoneStatistics & Operational Research

 

Crystallographic groups and Milnor's conjecture
Dietrich Burde (Dusseldorf)
13 Feb 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

'Dynamo action in the stretch, fold, shear model'
Andrew Gilbert (University of Exeter)
9 Feb 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Cyclic homology and the Baum-Connes conjecture
Michael Puschnigg (University of Munster)
8 Feb 2001Harrison 106 Thursday 3pmPure Mathematics

 

Krull-Schmidt theorem, Goldie dimensions and uniserial modules
Alberto Facchini (University of Padua)
6 Feb 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

The magneto-rotational instability in a Couette-type flow
Wolfgang Dobler (University of Newcastle upon Tyne)
5 Feb 2001Harrison 170 Monday 2pmApplied Mathematics

 

The anatomy of some non-holonomic oscillators
Ciprian Coman (University of Exeter)
2 Feb 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

The matrix group recognition project
Charles Leedham-Green (QMW)
1 Feb 2001Harrison 106 Thursday 3pmPure Mathematics

 

Class numbers of cubic orders
Anton Deitmar (University of Exeter)
30 Jan 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Rotational instabilities of contained fluids; laboratory experiments and applications to the Earth's core
Keith Aldridge (York University, Canada)
29 Jan 2001Harrison 170 Monday 2pmApplied Mathematics

 

Rational Points Close to Curves
Martin Huxley (University of Cardiff)
25 Jan 2001Harrison 106 Thursday 3pmPure Mathematics

 

RSS meeting: Independent component analysis: flexible sources and non-stationary mixing
Richard Everson (University of Exeter (Computer Science))
25 Jan 2001Laver None NoneStatistics & Operational Research

 

A contraction mapping proof of Schroeder's theorem
Ben Mestel (University of Exeter)
23 Jan 2001Harrison 103 Tuesday NonePure Mathematics (Internal)

 

Using constrained variational techniques to improve numerical weather prediction
Ian Roulstone (University of Reading)
22 Jan 2001Harrison 170 Monday 2pmApplied Mathematics

 

Bifurcations in nonlinear dynamos driven by ABC forcing
Olga Podvigina (University of Moscow)
19 Jan 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Symmetric group representations
Gordon James (Imperial College)
18 Jan 2001Harrison 106 Thursday 3pmPure Mathematics

 

%http://www.maths.ex.ac.uk/~PAshwin/workshop_15_1_01.html%Dynamics and Intermittency%
(WORKSHOP)
15 Jan 2001Harrison 170 Monday 2pmApplied Mathematics

 

Multi-scale space-periodic kinematic dynamos
Vlad Zheligovsky (University of Moscow)
12 Jan 2001Harrison 106 Wednesday 3pmApplied Mathematics (Internal)

 

Integration on non-locally compact spaces and local L-functions of arithmetic schemes
Ivan Fesenko (University of Nottingham)
11 Jan 2001Harrison 106 Thursday 3pmPure Mathematics

 

Is intermittency that nonlinear?
Sergei Nazarenko (University of Warwick)
8 Jan 2001Harrison 170 Monday 2pmApplied Mathematics