Heidelberg Graduate School HGS MathComp

HGS MathComp Events

WS 12/13SS 13WS 13/14SS 14WS 14/15SS 15WS 15/16SS 16WS 16/17SS 17WS 17/18
Workshops
info  Numerical simulations of Fluid Structure Interaction problems via Immersed Methods: a variational implementation Prof. Luca Heltai Mar. 7, 2013, 14:15 ECTS-Points: not yet determined
Abstract, registration & information:
Several methods exist in the literature that allow the numerical treatment of FSI problems via two independent grids, one Eulerian, where the independent variable (x) denotes a fixed point in space, and one Lagrangian, \"immersed\" in the first grid, where the independent variable (s) denotes a material particle in a reference domain. The coupling between the two grids can be achieved in several ways, depending on the underlying discretisation techniques.

The original method was first introduced by Peskin (Immersed Boundary Method - IBM) in the late seventies, to simulate the interaction between blood flow and heart valves. In that method, the coupling is obtain via approximations of Dirac-delta distributions, which allowed a clever interpolation between a finite difference grid and a collection of fibers, used to simulate the immersed body. Another type of Dirac-delta approximation (Reproducing Kernel Particle Method - RKPM) was used instead in the first formulation of the Immersed Finite Element Method (IFEM).

By contrast, a truly variational formulation of immersed methods does not require the use of Dirac-delta distributions, either formally or practically. This was shown in the Finite Element Immersed Boundary Method (FEIBM), where the variational structure of the problem is exploited to avoid Dirac-delta distributions at both the continuous and the discrete level.

In this talk, I will present a generalisation of the FEIBM to the case where an incompressible Newtonian fluid interacts with a general hyperelastic solid. Specifically, we allow (i) the mass density to be different in the solid and the fluid, (ii) the solid to be either viscoelastic of differential type or purely elastic, and (iii) the solid to be and either compressible or incompressible. At the continuous level, our variational formulation combines the natural stability estimates of the fluid and elasticity problems.
In immersed methods, such stability estimates do not transfer to the discrete level automatically due to the non-matching nature of the finite dimensional spaces involved in the discretization. After presenting our general mathematical framework for the solution of FSI problems, I will focus in detail on the construction of natural interpolation operators between the fluid and the solid discrete spaces, which guarantee semi-discrete stability estimates and strong consistency of our spatial discretization.
Location:
INF 368, Room 432
Time:
14:15
ECTS-Points:
not yet determined
info  Workshop on Discrete Graphical Models and Combinatorial Optimization Dr. Jörg Kappes Nov. 8-9, 2012 ECTS-Points: 1
Link for more information Location:
HCI, Speyerer Straße 6, 69115 Heidelberg
Time:
13:00
ECTS-Points:
1
Events
info  Von Dunkler Materie bis Alpha Centauri Prof. Dr. Harald Lesch Mar. 4, 2013 ECTS-Points: 0
Abstract (PDF)
Location:
Hörsaal 1, INF 306
Time:
18:00
ECTS-Points:
0
info  Eolian 2: Universidad de Chile`s Solar Car Enrique Guerrero M. Feb. 07, 2013, 11:15, IWR room 432 ECTS-Points: 0
Abstract, registration & information:
Solar car races are events that take place regularly in different
countries (Australia, Chile, Japan, South Africa, United States), posing
the challenge to cross long distances in vehicles powered only by solar
energy, raising thus very interesting optimization problems with
perturbations, stochasticity, nonlinearities and unknown parameters. The
talk will explain basic concepts about solar cars, solar car races and
the problems that arise, giving special emphasis in the cooperation
windows that could exist in which the IWR tools or others could be
applied.
Location:
IWR, room 432
Time:
11:15
ECTS-Points:
0
info  Mathematical and Computational Modelling of Tissue Engineered Bone in a Hydrostatic Bioreactor Katie Leonard Jan. 15, 2013 ECTS-Points: 0
Abstract, registration & information:
The use of tissue engineered implants could facilitate unions in situations where there is loss of bone or non-union, thereby increasing healing time, reducing the risk of infections and hence reducing morbidity. Currently engineered bone tissue is not of sufficient quality to be used in widespread clinical practice. In order to improve experimental design, and thereby the quality of the tissue-constructs, the underlying biological processes involved need to be better understood.

In conjunction with experimentalists, we consider the effect hydrodynamic pressure has on the development and regulation of bone, in a bioreactor designed specifically for this purpose.

To answer the experimentalists’ specific questions, we have developed a time-dependent mathematical model describing the development of the bone-producing cells and mineralised collagen. Two separate hypothesis of the mineralised extracellular matrix deposition rate are considered.

In order to represent experimental results, it is demonstrated that in incluing a decay rate to account for length of loading above a pressure threshold is needed. The mathematical model is then used to computationally screen for operating parameters in order to determine the optimal experimental strategy.
Location:
BIOQUANT SR 043.
Time:
15:15
ECTS-Points:
0
info  The model of closed-loop control by thermostats: applications, properties and optimization. Grzegorz Dudziuk Institute of Mathematics, room 214, INF 294, 14:15 ECTS-Points: 0
Location:
Institute of Mathematics, room 214, INF 294
Time:
14:15
ECTS-Points:
0
info  Asymptotically correct discontinuous Galerkin methods for radiative transfer problems Prof. Guido Kanschat 14:15, IWR room 432 ECTS-Points: 0
Abstract, registration & information:
While discontinuous Galerkin (DG) methods had been developed and analyzed in the 1970s and 80s
with applications in radiative transfer and neutron transport in mind, it was pointed out later in the
nuclear engineering community, that the upwind DG discretization by Reed and Hill may fail to produce
physically relevant approximations, if the scattering mean free path length is smaller than the mesh size. Mathematical analysis reveals, that in this case, convergence is only achieved in a continuous subspace of the finite element space. Furthermore, if boundary conditions are not chosen isotropically, convergence can only be expected in relatively weak topology. While the latter result is a property of the transport model, asymptotic analysis reveals, that the forcing into a continuous subspace can be avoided. By choosing a weighted upwinding, the conditions on the diffusion limit can be weakened. It has been known for long time, that the so called diffusion limit of radiative transfer is the solution to a diffusion equation; it turns out, that by choosing the stabilization carefully, the DG method can yield either the LDG method or the method by Ern and
Guermond in its diffusion limit. Finally, we will discuss an efficient and robust multigrid method for the resulting discrete problems.
Location:
14:15, IWR room 432
Time:
14:15
ECTS-Points:
0
info  Locomotion of Multibody Systems: Dynamics and Optimization Prof. Felix L. Chernousko Nov. 30, 2012, 16:15 ECTS-Points: 0
Abstract, registration & information:
Several principles of locomotion for multibody mechanical systems are discussed. Locomotion is based on the change of the system configuration and is possible in the presence of the resistive medium. Snake-like multilink systems, fish-like and frog-like systems, and also systems containing internal moving masses are considered. Various resistance forces including linear and quadratic forces depending on the velocity as well as dry friction forces, both isotropic and anisotropic, are taken into account. Dynamics and control of locomotion are analyzed. Optimal values of the system parameters as well as optimal controls are found that correspond to the maximal speed of locomotion. Experimental results are presented, and possible applications to robotic systems, especially to mini-robots, are discussed. The talk is based on the results obtained in the Institute for Problems in Mechanics of the Rus-sian Academy of Sciences.
Location:
IWR, Im Neuenheimer Feld 368, 4th Floor Room 432
Time:
16:15
ECTS-Points:
0
info  Dynamical properties of billiards and flows on surfaces Dr. Corinna Ulcigrai INF 288, HS 2, 17:00 ECTS-Points: 0
Abstract, registration & information:
In a mathematical billiard a particle moves without friction in a planar domain bouncing elastically at the boundary. Billiards inside rational polygons and area preserving flows on surfaces are two examples of dynamical systems which can be studied using Teichmueller dynamics, a topical and exciting fields of research. We will give a brief introduction to the study of mathematical billiards and present some recent results on billiards in regular polygons (joint work with J. Smillie) and chaotic properties of area preserving flows on surfaces.
Link for more information
Location:
INF 288, HS 2
Time:
17:00
ECTS-Points:
0
info  Evidence synthesis for estimating burden of infectious diseases Dr. Anne Presanis BIOQUANT, room 042, 14:15 ECTS-Points: 0
Abstract, registration & information:
Estimation of key characteristics of infectious disease, such as prevalence, incidence or severity, is challenging, as these quantities are typically not easy to measure directly. However, they may be estimated potentially from a network of information from multiple and varied sources, combining these data using evidence synthesis methods. The available data sources relevant to the disease under study may include, for example, surveillance systems, observational studies, registries and community surveys. Such data may be incomplete and/or biased, therefore only indirectly informing the quantities to be estimated. To synthesise such diverse and challenging data usually implies the formulation of complex probabilistic models, often in a Bayesian framework. In the context of such complexity, critical model assessment, including the detection of conflicting evidence, is essential. We illustrate these concepts through examples such as the estimation of HIV prevalence and modelling influenza severity.
Link for more information
Location:
BIOQUANT, room 042
Time:
14:15
ECTS-Points:
0
info  Optimizing Counter-Terror Operations Prof. Dr. Gustav Feichtinger Wed, Nov. 14, 10:00 (sharp!) ECTS-Points: 0
Abstract, registration & information:
Considering the aftermaths of September 11th, it is needless to say that the impact of terror and counter-terror measures poses many complex challenges to decision makers such as governments, security and military organizations. The purpose of the present contribution is to illustrate how methods of optimal control and dynamic games may be applied to
terror related problems to provide insights into questions of how to effectively fight terror. The state variable of such an intertemporal conflict situation, x, corresponds to the number of terrorists (or,
more generally, the power of this organization). In the resulting two-player differential game both opponents have to select the intensity of attacks and counter-attacks both reducing the strength x. Both
opponents have to take into consideration the trade-off between the utility and the costs of their measures. Two versions of a one-state non-zero sum dynamic game are presented. In the first case the terrorists are interested both in becoming powerful (by increasing x) as well as maximizing their attacks, while the target country intends to eliminate as many terrorists as possible. Focusing
our analysis to open-loop Nash equilibria, we are able to derive a stable limit cycle for the long-run behavior. Note that the government´s efforts follow essentially the periodic strength of the terrorists,
whereas the terrorists behave anti-cyclically.

In another version, the target country tries to minimize the strength of the terrorists as well as the intensity of their attacks, while the terrorists_ political objectives induce excessive counter-attacks as an
indirect way of stirring up sentiments against the target country. Moreover, the systems dynamics includes the (undesirable indirect) effect in increasing the recruitment rate of terrorists due to collateral damages induced by the target country´s counter-terror measures. Confining to the interior solutions, we are able to calculate stationary Nash equilibria. Due to the state-separability of this dynamic game, its open-loop Nash equilibrium qualifies as Markovian (feedback) solution. The state-control separability allows to determine also stationary Stackelberg solutions. The explicit calculations allow a comparative static analysis delivering valuable insights into the design of optimal counter-terror strategies.
Location:
IWR, INF 368, r 432
Time:
10:00
ECTS-Points:
0
info  Weltbilder der Informatik Prof. Dr. Britta Schinzel Oct. 24, 2012, 19:15 ECTS-Points: 0
Abstract, registration & information:
In diesem Vortrag werden Absichten und Ergebnisse unseres zweiteiligen DFG-Projekts „Weltbilder der Informatik“ vorgestellt und im Anschluss notwendige Schlussfolgerungen für Unterricht und Studium der Informatik diskutiert.

Das Projekt ging davon aus, dass Weltbilder nicht nur die Ziele der Informatik, sowie die soziale Situation in Studium und Informatikberufen beeinflussen, sondern auch die Art, Nutzbarkeit und Qualität ihrer Produkte.

Im ersten Teil des o.g. Projekts wurden die Weltbilder der Informatikstudierenden hinsichtlich der sieben Schwerpunkte: Technikbild, Wirklichkeitsauffassung, Relation Realität – informatische Rekonstruktion derselben, Menschenbild, Relation Mensch-Maschine, Relation EntwicklerInnen – NutzerInnen, sowie Berufsbild Informatik untersucht. Herausragende Ergebnisse waren dabei u.a. die mangelnde Diversität im Studium der Informatik, sowohl personell als auch hinsichtlich der Inhalte, Foci und Lehrmethoden und ihre Ursachen, die durchs Studium beeinflusste Verantwortungsfrage und das Geschlechterwissen der Studierenden.

In einer folgenden Analyse wurden die gewonnenen Daten ein zweites mal hinsichtlich der Fragestellungen: Bild der Informatik in der Öffentlichkeit, Eigenbild der Informatik und die Situation der Studierenden ausgewertet. Die Ergebnisse können als empirische Basis für die aktuelle Diskussion in den Berufsverbänden und für eine Aktualisierung der Curricula dienen.
Link for more information
Location:
Mathematisches Institut HS2
Time:
19:15
ECTS-Points:
0
info  Dataflow Computing for Scientific Applications Dr. Vitali Averbukh and Dr. Oscar Mencer Oct. 18, 2012, 16:00 ECTS-Points: 0
Abstract, registration & information:
Since the introduction of computers into routine scientific work in the middle of the last century,
their role in the scientific endeavour has changed dramatically from mere auxiliary tools of
numerical computation into an essential element of scientific discovery. The progress in computer
technology has been leading the tremendous advances in the application of numerical techniques in
science. The available computational power and computer memory resources define the scope of
the scientific problems that can be presently addressed, as well as the achievable accuracy level of
theoretical modeling and thus also the reliability of the scientific prediction. Modern science strives
to address more and more challenging problems on a larger and larger scale using accurate
theoretical models. The present scientific objectives of computational quantum chemistry, for
example, include the study of electronic structure of molecular systems relevant to biological and
energy production processes using not only the density functional theory (DFT) techniques, but
also at the more demanding first-principles, or ab initio level. Achieving such challenging goals in
the coming years will require development of principally new powerful computational
technology. Dataflow computing is a new, very promising approach to scientific computation that
has already been proved extremely efficient for a wide range of applications both in academic
science and in the industry. Based on the more than decade-long scientific and technological
development at Stanford, Bell Labs and Imperial College London, dataflow computing equipment
is being now produced on the industrial scale by Maxeler Technologies (London, Palo Alto) and is
provided to academic users through the Maxeler University Programme. Dataflow computers show
acceleration rates of the order of 20x-40x, within the same space and power constraints, for such
diverse applications as Monte Carlo simulations, numerical solutions of ordinary and partial
differential equations, numerical integration methods, finite difference and finite elements methods,
operations with sparce matrices, and have a strong potential to do still better in future. Moreover,
when deployed on the industrial scale, dataflow computing model has led to orders-of-magnitude
lower power consumption and dramatically lower data centre space requirements. The key reason
for the success of the dataflow model is the “vertical” multidisciplinary approach to scientific
computation whereby instead of optimizing algorithms to standard microprocessors, the dataflow
computer is designed to match the given computational problem. This presentation will discuss the
general principle and the implementation details of dataflow computer operation and give an
overview of the applications of dataflow technology. We shall also present the unique user-friendly
dataflow programming environment that makes the exciting opportunities of the dataflow systems
available to the wide community of researchers interested in scientific computing.
Location:
IWR, Im Neuenheimer Feld 368, 4th Floor Room 432
Time:
16:00
ECTS-Points:
0