Together with the Computational Engineering Research Center of the TU Darmstadt a joint seminar with interesting talks in the field of CE is organized in every semester. If you are interested in these seminars and would like to receive invitations please subscribe for the corresponding mailing list.
20190917
20190917
We consider PDEconstrained optimization problems, where the partial differential equation has uncertain coefficients modelled by means of random variables or random fields. The goal of the optimization is to determine an optimum that is satisfactory in a broad parameter range, and as insensitive as possible to parameter uncertainties. First, an overview is ... [more] »
20190917
Due to the continuously increasing use of electromagnetic services for communications and sensor functionalities, the accurate and reliable characterization of antennas by measurements becomes increasingly important. Traditionally, antenna measurements have been performed in very specialized measurement chambers, which are very expensive and not very ... [more] »
20190826
An improved understanding of the divergencefree constraint for the incompressible NavierStokes equations leads to the observation that a seminorm and corresponding equivalence classes of forces are fundamental for their nonlinear dynamics. The recent concept of pressurerobustness allows to distinguish between space discretisations that discretise these ... [more] »
20190604
This talk will present interdisciplinary research that entails the applicability of computer science tools and techniques on realworld scientific applications spanning nuclear physics, molecular dynamics, nextgeneration sequencing and magnetohydrodynamics (the study of the Sun). As architectures evolve, it is only becoming increasingly challenging for ... [more] »
20190401
With the capability to locally control the material composition of a structure, multimaterial and multimethod 3D printing technologies provide a new level of design freedom beyond the sole realization of complex topologies. However, the precise design and optimization of spatially varying material compositions within a structure is beyond the capabilities ... [more] »
20190603
Amdahl’s law states that parallel processing gain will diminish quickly if problem size does not increase with the computing power. Memorywall problem clams that data access is the performance bottleneck for data intensive applications; whereas big data applications are all datacentric applications. Data access becomes THE performance concern of ... [more] »
20190503
In a joint project with DLR, we recently demonstrated that the size of a slum is independent of city, country and culture. The question arises as to why this is so. Natural borders such as coastlines, mountains, rivers or motorways do not serve as reasons. Size must be inherent in migration dynamics. We see migration as a reaction diffusion system by ... [more] »
20190412
Everybody is familiar with the concept of eigenvalues of an n times n matrix. In this talk, we consider the nonlinear eigenvalue problem. These are problems for which the eigenvalue parameter appears in a nonlinear way in the equation. The last decade, the number of applications is increasing. In physics, the ... [more] »
20190412
In my presentation I will discuss some results from the European Industrial Doctorate project "MIMESIS – Mathematics and Materials Science for steel production and manufacturing”. The last fifteen years have seen the development of ever more refined highstrength and multiphase steels with purpose designed chemical compositions allowing for ... [more] »
20190412
Fluidstructure interaction problems, interface problems, and partial differential equations with interfaces and/or defects often require the solution of coupled bulkinterface problems. In this talk, I will discuss and analyse some of the techniques that can be used to tackle this class of problems, combining Finite Element Methods, Boundary Element ... [more] »
20190322
The estimation of large sparse inverse covariance matrices is an ubiquitous statistical problem in many application areas such as mathematical finance or geology or many others. Numerical approaches typically rely on the maximum likelihood estimation or its negative loglikelihood function. When the Gaussian mean random field is expected to be sparse, ... [more] »
20190322
Many application problems that lead to solving linear systems make use of preconditioned Krylov subspace solvers to compute their solution. Among the most popular preconditioning approaches are incomplete factorization methods either as singlelevel approaches or within a multilevel framework. We will present a block incomplete triangular factorization that ... [more] »
20180726
Interaction between structures and the flow around them requires a correct treatment of both of them. If the computational requirements are high, the methods need to be efficient on modern supercomputers that offer a high number of compute nodes and cores. In structural mechanics, often Finite Element (FE) methods are used, while fluid dynamics (especially ... [more] »
20181030
Particle methods like vortex methods or smoothed particle hydrodynamics are numerical schemes that are ideally suited for convection dominated flow problems. Unlike other meshbased flow solvers, these methods do not suffer from numerical diffusion and have excellent conservation properties. One of the reasons why particle methods are so rarely used in ... [more] »
20181017
The numerical simulation of physical phenomena is very well understood given that the input data are given exactly. However, in practice, the collection of these data is usually subjected to measurement errors. The goal of uncertainty quantification is to assess those errors and their possible impact on simulation results. In this talk, we address different ... [more] »
20181219
Abstract: I will provide an introduction to the general concepts of quantum computation and a brief discussion of its strengths and weaknesses from a highperformance computing perspective. The talk is tailored to a computer science audience with basic (popularscience) or no background in quantum mechanics and will focus on the computational aspects. I ... [more] »
20180927
Differential Algebraic Equations (DAEs) combine Ordinary Differential Equations (ODEs) with algebraic constraints. Hence, even for linear systems both the initial condition and the control input cannot be arbitrarily chosen. We present a framework for linear regular systems, which allows to characterise the space of consistent initial conditions and the set ... [more] »
20181023
Abstract: Concerns about energyefficiency and cost are forcing our community to reexamine system architectures, and, specifically, the memory and storage hierarchy. While memory and storage technologies have remained relatively stable for nearly two decades, new architectural features, such as deep memory hierarchies, nonvolatile memory (NVM), and ... [more] »
20180927
Decades ago, the author obsessed with articulating why topological aspects of 3D finite element (FE) meshes could be deceptively unintuitive, while 2D was so obvious. For EEs, this dichotomy didn’t originate with FE meshes, but is implicit in how nonplanar electronic circuits are communicated. In FE for electromagnetics, the ease with which homology ... [more] »
20180724
This talk discusses entropy structures for partial differential equations, and how they can be used for efficient HPC computations, and uncertainty quantification. Especially, we recall the entropyentropy flux structure of hyperbolic conservation laws describing macroscopic flows, and how this structure is inherited from underlying mesoscopic models for ... [more] »
20181008
We analyze autonomous differential algebraic equations (DAEs) with the following particular structure: \[\begin{aligned} x'_1 & = \frac{\text{d}}{\text{d}t} f_1 (y_1) + g_1 (y_1) + r_1,\\ y'_2 & = \frac{\text{d}}{\text{d}t} f_2 (x_2) + g_2 (x_2) + r_2,\\ x_1 & = A_1^\top z,\\ x_2 & = A_2^\top z,\\ 0 & = A_1 y_1 + A_2 y_2, \end{aligned}\] where (\(A_1\), ... [more] »
20180821
We consider Galerkin boundary element methods for the approximation of different kinds of electromagnetic resonance problems. Examples are the cavity resonance problem, the scattering resonance problem and the plasmonic resonance problem. An analysis of the used boundary integral formulations and their numerical approximations ispresented in the framework ... [more] »
20180718
Solving Maxwell's equations in time domain efficiently is a nontrivial task and represents a fascinating research area. This talk will consist of two parts. In the first part a brief introduction to time integration methods for Maxwell's equations will be given. In particular, we will discuss (1) why the celebrated Yee scheme (often used in Finite ... [more] »
20180618
Hemodynamic models of blood flow in the left ventricle (LV) and aorta are important tools for analyzing the mechanistic links between myocardial deformation and flow patterns in human hearts. Typically, computational fluid dynamics (CFD) models driven by imagebased kinematic models are employed aiming to predict the acute response to an intervention. While ... [more] »
20180129
QuasiNewton methods are used in many fields to solve nonlinear equations without explicitly known derivatives. This is the case, e.g., in coupled multiphysics applications such as fluidstructure interactions where we combine several independent solvers in a partitioned approach coupled simulation environment. To do so, we have to solve a (in general ... [more] »
20180413
In nanoplasmonics, most metal devices are sub wavelength. This leads to geometrical sizes comparable to the skindepth of electromagnetic waves at optical frequencies. Appropriate material models of the metallic bulk are hence indispensable. Additionally, if the effective wavelength of the plasmon (a wave that relies on oscillations of the free electrons ... [more] »
20180604
Mixed integer programming (MIP) problem is a general form to model combinatorial optimization problems and has many industrial applications. The performance of MIP solvers, software packages to solve MIPs, has improved tremendously in the last two decades and these solvers have been used to solve many realword problems. However, against the backdrop of ... [more] »
20180413
Powerconservation is a fundamental property of mathematical models describing physical phenomena. The modeling consistency can be ensured if each subsystem fulfills this requirement. Next step in modeling is to ensure, that the combination of these subsystems still maintains this property. To this end, we employ bond graph and portHamiltonian modeling. ... [more] »
20180129
In finite dimensions abslinearization of a function defined by smooth elementals and abs, min, and max yields a piecewise linear continuous approximation function at a given development point. The error between this local model and the underlying piecewise smooth function is uniformly of second order in the distance to the development ... [more] »
20180511
In this talk the linear elastic rod (1D) model and linear elastic shell (2D) model will be shown. Since numerical solving of 3D linear elasticity PDE on thin domains is challenging and gives incorrect results due to using dense meshes, lowdimensional models show great advantage. After that, we will show applications of those concepts in modelling ... [more] »
20180413
We present a framework for the design, analysis and application of computational multiscale methods for slowfast highdimensional stochastic processes. We call these processes "microscopic'', and assume existence of an approximate "macroscopic'' model that captures the slow behaviour of a selected set of macroscopic state variables. The ... [more] »
20180413
Because of quadratic memory requirements classical boundary element realisations are applicable only for a rather moderate number N of boundary elements. A possible solution to this problem is to take advantage of the good approximation properties of the boundary element matrices. One established approximation scheme is called the adaptive cross ... [more] »
20180413
We will consider the acoustic wave propagation in a channel separated from a chamber by a thin periodic layer. This model stand for microperforated absorbers which are used to supress reflections from walls. Due to the smallness of the periodicity a direct numerical simulation, e.g. with the finite element method (FEM), is only possible for very large ... [more] »
20180413
Parallel programming for HPC systems is a challenging task, and will remain so. Although we have found that certain programming models and development approaches are more productive than others, there is no single best tool for the job. In this talk, I will present our performance analysis and engineering workflow and and our findings on the programming ... [more] »
20180309
We present a novel method to compute approximations of integrals over implicitly defined hypersurfaces. Control applications for thermonuclear fusion reactors, such as the upcoming ITER tokamak, are the initial motivation of this research work. The new method is based on a weak formulation that uses the coarea formula to circumvent an explicit integration ... [more] »
20180115
Quasistatic electromagnetic field models are considered for situations, where the shortest wave length of a problem exceeds the spatial dimensions of the problem by at least one order of magnitude. A taxonomy of such quasistatic field models distinguishes between the electroquasistatic, the magnetoquasistic and the socalled Darwin field models. These ... [more] »
20171215
We study sparse solutions of optimal control problems governed by elliptic PDEs with uncertain coefficients. Sparsity of controls is achieved by incorporating the \(L^1\)norm of the mean of the pointwise squared controls in the objective. Two optimal control formulations are proposed, one where the solution is a deterministic control that optimizes ... [more] »
20171204
While waveform relaxation methods converge for coupled ODE systems, they may suffer from instabilities for coupled differentialalgebraic equations (DAEs). Whereas several convergence criteria are known for index1 DAEs, we present here a convergence criterion for quasilinear index2 DAEs for the first time. It applies to systems of coupled ODE/circuit ... [more] »
20171018
Since 2011 the EU MontBlanc project pushes the development of ARMbased compute platforms, following the vision of leveraging the fast growing market of mobile technology for performing scientific computation. The process started almost 5 years ago with the development of prototypes based on Android devkits and is now evolving beyond the research project, ... [more] »
20170926
20170906
The Linac Coherent Light Source is a linacbased, Xray free electron laser (FEL) at the SLAC National Accelerator Laboratory. It accelerates single bunches up to 413 GeV before sending them to the undulator for lasing. A project is underway to run the LCLS bunches in trains, with up to initially four and later eight bunches in a train. Bunch trains will ... [more] »
20170221
For more than thirty years it was thought that the efficient construction of pressurerobust mixed methods for the incompressible NavierStokes equations, whose velocity error is pressureindependent, was practically impossible. However, a novel, quite universal construction approach shows that it is indeed rather easy to construct pressurerobust mixed ... [more] »
20170510
The presentation summarizes progress made over the past few years in the calculation of spectral bounds of interval Hessian matrices. Spectral bounds of this type play an important role in global optimization algorithms. They can be used, for example, to detect if a given optimization problem is convex, or to generate a convex relaxation in case it is not. ... [more] »
20170621
The numerical computation of small probabilities of failure for a system is a notoriously difficult problem, and the Subset Simulation algorithm of Au & Beck (Prob. Eng . Mech., 2001) has become one of the most popular method to solve it. Subset simulation has been shown to provide significant savings in the number of evaluations of the performance ... [more] »
20170403
Parallel programming for large scale computer architectures is a complex and errorprone task. Automatic tools can assist application developers in the detection and removal of such errors. This talk will present the scalable runtime tool MUST, the methods behind the tool (graph analysis, push down automaton) and the limitations that ... [more] »
20170508
We investigate methods of topology and shape optimization for an optimal design problem from electrical engineering which is constrained by the quasilinear PDE of twodimensional magnetostatics. We derive the topological derivative of the objective function, i.e., its sensitivity with respect to a topological perturbation of the domain, and compare it to ... [more] »
20170616
In this talk, we will give an introduction to Integer Programming (IP) and show how we used IP in recent research projects. The projects range from problem formulations in visualization to urban modeling. The talk will focus mainly on the modeling side of integer programming, i.e. how to formulate a given problem as integer ... [more] »
20170522
Cyberphysical systems (CPS) combine cyber aspects such as communication and computer control with physical aspects such as movement in space, which arise frequently in many safetycritical application domains, including aviation, automotive, railway, and robotics. But how can we ensure that these systems are guaranteed to meet their design goals, e.g., ... [more] »
20170508
The basic idea of model order reduction utilizing proper orthogonal decomposition (PODMOR) consists in replacing a highdimensional problem by a lowdimensional POD approximation with the aim to save computational times and storage capacity while preserving a good approximation quality. Following the idea of Sirovich (1987), the POD surrogate models are ... [more] »
20170403
Protection and sustainable management of water resources is one of the key problems in environmental engineering. In this aspect, accurate modeling and simulating coupled ground and surface water flows is a necessity. Chemically reactive components such as dissolved minerals, colloids, or contaminants are transported by advection and diffusion over long ... [more] »
20170523
Since the beginning of "highperformance" parallel computing, observing and analyzing performance for purposes of finding bottlenecks and identifying opportunities for improvement has been at the heart of delivering the performance potential of nextgeneration scalable systems. Interestingly, it is the everchanging parallel computing landscape ... [more] »
20170509
Nanohelices with pitch and diameter as characteristic dimensions of the order of 100 nm are formidable systems to investigate optical and electronic properties of matter on the nanoscale. Their unique helical structure on the nanoscale is the source of a range of unconventional properties. In the present work, first the production process of the ... [more] »
20170223
To date, there is a large literature on nonoverlapping domain decomposition (DD) methods for acoustic and electromagnetic wave problems. For some of these methods, the domain decomposition is tightly coupled to the formulation and makes it difficult to understand. In this talk (based on joint work with Timo Euler, CST AG), we develop a unified DD ... [more] »
20170105
We present some attempts at improving the accuracy and efficiency of the reference numerical methods presently employed to model charged particle motion in magnetic quadrupoles. We first introduce the standard technique used to reconstruct the quadrupole magnetic vector potential, based on general solutions of the Laplace equation in cylindric coordinates. ... [more] »
20170123
High performance computing (HPC) systems are nowadays large, consist of diverse components, and exhibit massive parallelism. Exploiting the available hardware parallelism is notoriously challenging, in part due to difficulty in exposing and expressing parallelism in the computational applications. Loops are considered the main source of parallelism in most ... [more] »
20170112
Parallel file systems (PFS) have been developed to support typical HPC applications, where most file system operations include reading or writing huge chunks of data, which can be easily striped over the storage backend. New dataintensive applications will change these patterns and small random I/Os will occur more frequently in HPC, missing the sweetspot ... [more] »
20170105
For timedependent partial differential equations, parallelintime integration using the "parallel full approximation scheme in space and time" (PFASST) is a promising way to accelerate existing spaceparallel approaches beyond their scaling limits. Inspired by the classical Parareal method and nonlinear multigrid ideas, PFASST allows to integrate ... [more] »
20161115
The aerodynamics of flying insects is a field of research currently receiving much attention from a broad, interdisciplinary community of researchers. Their motivation ranges from the design of bioinspired robots to fundamental questions in biology and fluid mechanics. Insects are known to produce a surprising amount of force, using comparatively small ... [more] »
20161020
We consider linear and timeinvariant partial differentialalgebraic equations and show that these can be represented as differentialalgebraic equations on infinitedimensional Banach spaces. We will discuss solution theory, decoupling and control by means of several examples in flow and electric circuit theory. [more] »
20160926
We will discuss the modelling and simulation of generalized Stefan problems to describe phasechange processes in water ice. An idealized mathematical system for the classical Stefan problem consists of two freeboundary secondorder partial differential equations for both the solid, and the liquid phase. The system is closed by assuming local energy ... [more] »
20160825
Although dataparallelism is ubiquitous in highperformance computing (HPC) algorithms, many algorithms in other areas such as graph analytics, machine learning, and VLSI placement and routing exhibit a more complex kind of parallelism that called "amorphous dataparallelism." In this talk, I describe a simple programming model called the ... [more] »
20160926
Abstract: An experimental study is presented that uses a corrugated structure as a passive “dechirper”— i.e. as a device for removing energy chirp — in a high energy (4.4 ‐ 13.3 GeV) electron beam at the Linac Coherent Light Source (LCLS) at SLAC. Time‐resolved measurements of both longitudinal and transverse wakefields of the device are presented and ... [more] »
20160711
Electrical machines commonly consist of moving and stationary parts, e.g., an electric motor features a rotor and a stator. If volume based numerical schemes such as the Finite Element Method (FEM) are applied the electromagnetic simulation of such devices is a challenging task since the variation of the geometrical configuration needs to be incorporated ... [more] »
20160613
Measuring and reporting performance of parallel computers constitutes the basis for scientific advancement of highperformance computing (HPC). Most scientific reports show performance improvements of new techniques and are thus obliged to ensure reproducibility or at least interpretability. Our investigation of a stratified sample of 120 papers across ... [more] »
20160407
Nondestructive testing and evaluation (NDT&E) by ultrasonic (or electromagnetic) waves is important for the identification of material parameters, for quality assurance and lifetime control. Many NDT&E techniques and procedures are available, but generally rely on a considerable amount of a priori knowledge and expertise which are often expensive ... [more] »
20160621
The MMPDE moving mesh method is a dynamic mesh adaptation method for use in the numerical solution of partial differential equations. It employs a partial differential equation (MMPDE) to move the mesh nodes continuously in time and orderly in space while adapting to evolving features in the solution of the underlying problem. The MMPDE is formulated as the ... [more] »
20160203
The goal of an a posteriori error analysis for an approximate PDE solution is to establish the equivalence of error and a posteriori estimator. Unfortunately, this equivalence is often only up to so called oscillation terms. In this talk we shall clarify the reasons for the presence of oscillation and point out shortcomings of common oscillation terms. ... [more] »
20160613
ACE3P is a 3D massively parallel electromagnetic simulation suite that has been developed at SLAC National Accelerator Laboratory for the past decades. This set of codes is based on the finiteelement method so that geometries of complex structures can be represented with high fidelity through conformal grids, and high solution accuracies can be obtained ... [more] »
20160407
The project nanoCOPS is a collaborative research project within the FP7ICT research program funded by the European Union. The consortium comprises experts in mathematics and electrical engineering from six universities (BU Wuppertal, HU Berlin, Brno UT, TU Darmstadt, FH Oberösterreich Hagenberg im Mühlkreis, EMAU Greifswald), a research institute ... [more] »
20160530
Even though supercomputers are typically described in terms of their floating point performance, science applications also need significant I/O performance for all parts of the science workflow. This ranges from reading input data, to writing simulation output, to conducting analysis across years of simulation data. This talk presents recent data on the use ... [more] »
20160407
In the development of numerical methods to solve boundary value problems the requirement of flexible mesh handling gains more and more importance. The BEMbased finite element method [1] is one of the new promising strategies which yield conforming approximations on polygonal and polyhedral meshes, respectively. This flexibility is obtained by special ... [more] »
20160407
We consider the scattering of acoustic or electromagnetic waves at a penetrable object composed of different homogeneous materials, that is, the material coefficients are supposed to be piecewise constant in subdomains. This makes possible to recast the problem into boundary integral equations posed on the interfaces. Those can be discretized by means of ... [more] »
20160407
Absorbing boundary conditions and perfectly matched layers are not only useful for the truncation of computational domains, they can also be very effectively used to obtain preconditioners. This was first realized in the context of Schwarz methods about 20 years ago, in the research group around Frederic Nataf and Laurence Halpern, and led to the class of ... [more] »
20160310
The subsurface holds numerous resources ranging from groundwater and minerals to energy (e.g., geothermal, hydrocarbons), but it can also act as storage site for CO_{2} and nuclear waste. Any optimal and safe utilization of the deep subsurface requires a thorough ... [more] »
20160404
Many incompressible flows of engineering interest involve fluids that are governed by complex constitutive relations. For viscoelastic fluids in particular, the advective nature of the constitutive equation requires numerical stabilization. Moreover, the use of three distinct variable fields means that two separate compatibility conditions must be ... [more] »
20160407
20160222
The Oneshot method for design optimization problems has been successfully implemented for various physical applications. To this end, a slowly convergent primal fixedpoint iteration of the underlying state equation is augmented by an adjoint iteration and a corresponding preconditioned design update. Besides a suitable choice for the ... [more] »
20160129
Modern parallel architectures have a complex memory hierarchy, which consists of several cache levels and multiple memory controllers per system. In such architectures, the performance of memory accesses from a thread depends highly on which core the thread is executing and on which cache/memory controller the data is located. Therefore, ... [more] »
20160108
We present an asynchronous method for the explicit integration of multiscale partial differential equations with a particular focus on microwaveplasma interactions. This method is restricted by a local CFL condition rather than the traditional global CFL condition. Moreover, contrary to other local timestepping (LTS) methods, the asynchronous algorithm ... [more] »
20160208
The efficient numerical solution of eddy current problems, whether formulated with differential or integral techniques, requires some topological preprocessing. Kotiuga, in his pioneering papers in the eighties, showed that computational topology is something that one should get familiar with when bumps into problems related with the design of ... [more] »
20151208
PDE constrained optimal control problems with pointwise state constraints are known to cause certain theoretical and numerical difficulties. In this talk, we are concerned with an elliptic Dirichlet boundary control problem with low regularity of the state variable. After discussing first order optimality conditions in KKTform, we will focus on presenting ... [more] »
20151021
Fast chemical reactions in combustion take place in thin layers, which are usually called flamelets. The flamelet regime is the most prominent one in technical applications. Thus, flameletbased models have been used very successfully and are actively developed for the simulation of turbulent combustion by the scientific community. ... [more] »
20151119
Der Vortrag behandelt die schnelle numerische Lösung elliptischer Randwertprobleme mittels hierarchischer Matrizen. Im ersten Teil des Vortrags werden nichtlokale Operatoren, die beispielsweise durch Diskretisierung von Integraloperatoren entstehen, untersucht. Die auftretenden Systemmatrizen sind vollbesetzt, so dass bereits ihre Generierung eine ... [more] »
20151002
For efficient detailed aerodynamic or aeroacoustic designs as well as optimal active flow control, the use of adjoint approaches is an essential ingredient. Using adjoint methods, one is able to compute the gradients needed for sensitivitybased optimization and control methods, with a numerical effort independent from the number of ... [more] »
20151022
The finiteelement timedomain simulation of nonlinear systems requires the iterative solution of a large, sparse system of equations at every timestep. Modelorder reduction is a powerful tool for reducing the computational effort for this task. Stateoftheart methods compute an affine approximation to the nonlinearity. In contrast, the ... [more] »
20150619
Abstract With rising system and application complexity, performance analysis is more important, but also more difficult than ever. Traditional performance are capable of measuring large volumes of performance data that can help with this process, but the interpretation of this data is becoming more and more the bottleneck. Simply comparing ... [more] »
20150706
Traditionally in the geodynamics community, staggered grid finite difference schemes and mixed Finite Elements (FE) have been utilised to discretize the variable viscosity Stokes problem. While these methods are considered to be sufficiently robust and accurate for a wide range of variable viscosity problems they tend to have infsup constants which are ... [more] »
20150709
Abstract Supercomputers help to analyze huge data sets and to simulate complex theories in different science domains. Today, the results of these analyses and simulations are visualized using GPUs in workstations or small, dedicated visualization clusters. However, visualization on GPUs becomes harder and harder due to the ever increasing data size ... [more] »
20150526
The Virtual Element Method (VEM) is a generalisation of the finite element method recently introduced by Beirao da Veiga, Brezzi, Cangiani, Manzini, Marini and Russo in 2013, which takes inspiration from modern mimetic finite difference schemes, and allows to use very general polygonal/polyhedral meshes. This talk is concerned with a new method based ... [more] »
20150323
In this talk we will give an overview of the High Performance Scientific Computing activities that are currently taking place at the Computer Science and Engineering of the University Politehnica of Bucharest, Romania. In particular, we will present applications from the areas of: meteorology, aerospace, ... [more] »
20150622
In this talk we will present efficient numerical schemes for two classes of complex flows: i) FluidStructure interaction problems with application in hemodynamics and ii) Singular limit flows with application in meteorology. We derive problemsuited finite volume and/or Discontinous Galerkin approximations and analyse the scheme with respect to ... [more] »
20150323
In this talk we discuss the current design and implementation of ADiJaC, an automatic differentiation tool for Java classfiles. ADiJaC uses source code transformation to generate derivative codes in both the forward and the reverse modes of automatic differentiation. We describe the overall architecture of the tool, and ... [more] »
20150415
After a brief introduction to the boundary element method and Hmatrices we consider the efficient solution of strongly elliptic potential problems with stochastic Dirichlet data. The computation of the solution’s twopoint correlation is well understood if the twopoint correlation of the Dirichlet data is known and sufficiently smooth. Unfortunately, the ... [more] »
20150327
We consider AllenCahn and CahnHilliard equations as phase field models with constant and variable mobility. Both equations are discretized in space using symmetric interior penalty discontinuous Galerkin (SIPG) finite elements. Time discretization is performed by the energy stable average vector field (AVF) method for gradient systems like AllenCahn ... [more] »
20150209
The boundary element method is a widely used technique for solving problems governed by elliptic PDEs. On the other hand, the application of integral equation methods to time dependent problems is much less developed and a topic of current research. Time dependence is reflected in the fact that boundary integral operators involve integrals over time in ... [more] »
20150127
Two important influences on the accuracy of simulation results are the approximation properties of the numerical scheme with respect to, on the one hand, the unknown solution, and on the other hand, the geometry representation. The latter aspect poses a particular challenge in the context of deforming computational domains. These deformations can either be ... [more] »
20141215
In this talk we give an overview of the FHO activities in the fp7 research projects ICESTARS, nanoCOPS, the ENIAC project ARTEMOS, and the Austrian basic research project "Spline/wavelet based methods in circuit simulation". In Radio Frequency (RF) circuits one observes slowly varying envelope or baseband signals modulated by a carrier signal at ... [more] »
20141127
High dimensional data exhibit distinct properties compared to its low dimensional counterpart; this causes a common performance decrease and a formidable computational cost increase of traditional approaches. Novel methodologies are therefore needed to characterize data in high dimensional spaces. Considering the parsimonious degrees of freedom of ... [more] »
20141016
Physical phenomena in most engineering fields and applications are inherently nonlinear. Yet, most established engineering design tools have been developed for idealised linear systems. In particular, structural nonlinearity in engineering design has been traditionally associated with problems and loss of functionality, often at the expense of overdesign ... [more] »
20141002
Electrostatic discharge (ESD) is a serious design concern in microelectronic device fabrication and usage. Current spikes of the order of amperes active over a time lap of a nanosec need to be screened off from the core circuits by ESD protection devices. Onchip silicon controlled rectifiers are used for this purpose. The fast transient effect lead to ... [more] »
20140912
The powerful properties of formulations enriched with discontinuous or singular functions like XFEM, GFEM and SDA is the ability to represent features independently of the mesh structure. However, a problematic point in their practical implementation is given by the quadrature to compute the element stiffness. In fact, especially in 3D, the element are ... [more] »
20140623
Derivatives of mathematical functions are needed in various areas of computational engineering. Examples include the solution of nonlinear systems of equations and inverse problems. When the function is given in the form of a computer program, automatic differentiation (AD) enters the picture. In this set of powerful techniques, ... [more] »
20140729
Simulations of realistic Earth science problems are characterised by massive scale and coupled sets of equations. In the case of problems such as subduction zones, geometric effects are central. These features demand numerical methods and software libraries that are flexible and high performance, and the deployment of scalable linear solvers. In working ... [more] »
20140815
We consider parameterized mathematical programs with constraints governed by the generalized nonlinear complementarity problem and with additional nonequilibrial constraints. We study a local behavior of stationarity maps that assign the respective C or Mstationarity points of the problem to the parameter. We provide criteria for the isolated calmness ... [more] »
20140429
In this presentation we will address different aspects concerning Reduced Basis (RB) methods for parametric partial differential equations (PDEs). This class of model reduction techniques enables rapid solution of parametric problems in the realtime or manyquery context and has gained quite some interest and wide development over the last decade After ... [more] »
20140429
We introduce a relativistic splitting structure as a means to map fields and equations of electromagnetism from curved fourdimensional spacetime to threedimensional observer's space. We focus on a minimal set of mathematical structures that are directly motivated by the language of the physical theory. Spacetime, worldlines, time translation, space ... [more] »
20140623
For numerous applications the exploitation of structure and/or parallelism is indispensable for the efficient computation of derivatives and also for the design of new solution approaches. We discuss recent developments integrated in the software package ADOLC for the algorithmic differentiation of C and C++ codes to utilize ... [more] »
20140429
20140429
Particle accelerators are among the most complicated contemporary devices and consist of a large number of components, each with a specific function. All components need to be tuned with respect to each other to achieve the prescribed particle beam characteristics. Seemingly small deviations from an individual component's design specifications may induce ... [more] »
20140630
In mathematical physics and engineering, Trefftz approximations by definition involve functions that satisfy the underlying differential equation of the problem (as well as the interface boundary conditions). Examples include harmonic polynomials for the Laplace equation; plane waves, cylindrical or spherical harmonics for wave problems; exponential ... [more] »
20140509
An optimal control problem governed by an elliptic variational inequality is considered. We focus on the optimal control of the obstacle problem, which is a prototypical example of variational inequalities of the first kind. A robust multigrid strategy for solving obstacle problems will be presented. This algorithm is then extended in order to apply ... [more] »
20140604
Simulation of flow and transport processes in porous media provides a formidable challenge and application field for highperformance computing. Relevant continuumscale models include partial differential equations of elliptic, parabolic and hyperbolic type which are coupled through highly nonlinear coefficient functions. The multiscale character and ... [more] »
20140206
In industrial product development, design decisions are mostly based on intensive parameter studies combined with expert knowledge, where in case of complex technical systems like aero engines typically several experts from different departments have to be involved. However, typically each department uses its own analysis programs with its own data ... [more] »
20140509
Wavy plies or wrinkles in carbon fiber reinforced plastic (CFRP) composite structures can result in performance knockdowns. The performance impact of the ply distortion can depend on many factors, but two commonly desired parameters are the wrinkle height and width. An ultrasonic Bscan of the wrinkle can reveal the ply distortion; however, visual ... [more] »
20140429
20140424
The coupling and finite and boundary element methods has been attractive for the numerical solution of boundary value problems of second order partial differential equations for decades. In particular, socalled nonsymmetric formulations have been very popular in applications for a long time. Originally, the results on the stability of related ... [more] »
20140221
Magnetostrictive materials belong to the large class of Smart Materials, which change their mechanical behavior and properties in response to the application of an external field, such as temperatur or magnetic field. Particularly magnetostrictive elastomers, composites consisting of ferrous particles dispersed in an elastomeric matrix, can exhibit large ... [more] »
20140424
This talk will focus on issues arising in the context of the generation of a discrete adjoint version of OpenFOAM using algorithmic differentiation (AD). The existing discrete adjoint version of OpenFOAM is based on our AD tool dco/c++ (derivate code by overloading in C++). It uses the adjoint MPI (AMPI) library for adjoint message passing. Prototyped at ... [more] »
20140204
In this talk he will discuss the source analysis tool PBound, that estimates the upper performance bounds of C and Fortran applications. Built on the ROSE compiler framework, PBound generates parametrized expressions for different types of memory accesses and integer and floatingpoint computations. Additionally, PBound uses application reuse distance ... [more] »
20140117
Deep brain stimulation (DBS) has evolved as a widely employed procedure to treat the symptoms of motor skill disorders such as Parkinson’s disease, essential tremor and dystonia. Although successfully employed across various clinical fields, the fundamental mechanisms of action of DBS remain uncertain. Starting in the last decade, many computational models ... [more] »
20140120
Computing discrete adjoints by algorithmic differentiation (AD) enables gradientbased optimization for highdimensional problems. First, I introduce AD principles and implementation options (i.e. operator overloading) relevant to models written in C++ and parallelized with MPI. Then I present our ongoing work with the Ice Sheet System Model (ISSM), ... [more] »
20130920
In electrical engineering, the input data (dimensions, material properties, external inputs, etc.) of models are often assumed to be known exactly. The models as well as their outputs are then deterministic. However, in the real world, the input data are often stochastic. The dimensions of any device are known within a given uncertainty (tolerance) due to ... [more] »
20130920
Simulation of microturbulence in magnetic fusion plasmas either in stellarators or in tokamaks can be realised efficiently with Particle In Cell methods (PIC) provided some efficient noise reduction is achieved so that noise levels are well below signal levels. This can be achieved using a control variate method using a stochastic process associated with ... [more] »
20131212
We consider a PDE constrained optimization problem governed by a free boundary problem. The state system is based on coupling the Laplace equation in the bulk with a YoungLaplace equation on the free boundary to account for surface tension, as proposed by P. Saavedra and L.R. Scott. This amounts to solving a second order system both in the bulk and on the ... [more] »
20131126
Many parallel applications suffer from latent performance limitations that may prevent them from scaling to larger machine sizes. Often, such scalability bugs manifest themselves only when an attempt to scale the code is actually being made  a point where remediation can be difficult. However, creating analytical performance models that would allow such ... [more] »
20131126
In today's economic climate, time to market, or more generally time to solution, is critical. At the same time, mainstream hardware does not only become massively parallel, it also becomes much more diverse: Graphics Processors (GPUs), large vector machines such as Intel's XeonPhi, and even programmable hardware in the form of FPGAs find an increasing ... [more] »
20131126
Parallel Programming has long closely been tied to high performance computing. Today's ubiquity of multicore chip architectures radically changes this: parallel programming moves from a niche market into the main stream of computing. At the same time, hardware becomes more and more diverse: varying numbers of cores with complex cache hierarchies, ... [more] »
20130920
20131106
“More bang for the buck” is the promise of deploying accelerators attached to commodity host processors for technical computing. Since NVIDIA introduced the CUDA programming model in 2006, more and more programmers started using graphics processors for technical computing. Amazing success stories reported high speedup rates of applications accelerated by ... [more] »
20130920
The concept of Isogeometric Analysis (IGA) was introduced by Hughes with the aim of bridging the gap between computer aided design (CAD) and the finite element method. This aim is pursued by adopting the same Non Uniform Rational BSpline (NURBS) basis functions to construct both trial and test spaces in the discrete variational formulation of differential ... [more] »
20131029
Pushing back the frontiers of simulation technology in science and engineering becomes ever more complex. Better simulations of more realistic systems require greater complexity in both equations and numerics, while the shift from increasing processor speed to massive finescale parallelism radically increases the complexity of the software implementation. ... [more] »
20131004
Understanding the properties and consequences of friction under light normal loads is fundamental to further advancing areas such as tactile sensing, haptic systems used in robotic gripping of sensitive objects, and characterization of products that range from the softness of fabrics to effects of surfactants, such as lotions, on skin. In tactile sensing, ... [more] »
20130930
An analyticalnumerical model based on first principles for representation of the motions of a submarine in the horizontal and in the vertical plane is presented. The model is implemented through computational algebra, being its parameters expressed as function of the main dimensions and form coefficients of the hull and its appendices, ... [more] »
20130920
The sustainable environmental tendencies lead to a highly optimized design of majority of consumer products. In Materials Engineering, this is mirrored by a race towards miniaturization and top product performance. A potential success is seen in a detailed understanding and incorporation of characteristic physical processes taking place at materials ... [more] »
20130918
We describe our efforts in performance modeling in the context of automatic performance tuning. We consider analytic models constructed through source code analysis, semianalytic models constructed with a combination of source code analysis and empirical measurement, and fully empirical models. We describe several uses ... [more] »
20130829
In this talk we show a new approach to the numerical simulation of Bingham fluids, based on semismooth Newton methods. From pipe flow to thermally convective flow, we present the challenges and the modeling and numerical tools to overcome such issues. [more] »
20130603
The past, present and future scalability of the Uintah Software framework is considered with the intention of describing a successful approach to large scale parallelism. Uintah allows the solution of large scale fluidstructure interaction problems through the use of fluid flow solvers coupled with particlefinite element based solid methods. In addition ... [more] »
20130702
In this work, we present a computationally efficient finite element (FE) model for statics, dynamics and vibration control of smart composite and sandwich shallow shells integrated with piezoelectric sensors and actuators, considering their nonlinear characteristics under strong electric field. The nonlinearity is modeled using the rotationally invariant ... [more] »
20130708
In this talk, I will present our recent work on robustly tracking objects that deform due to an external applied force. The geometry of the object is reconstructed over time based on noisy observations from a single viewpoint. A template mesh of the object in its reststate is fit to observations in a nonlinear optimization. We use a redundant ... [more] »
20130214
Hybrid parallel programming with the message passing interface (MPI) for internode communication in conjunction with a sharedmemory programming model to manage intranode parallelism has become a dominant approach to scalable parallel programming. While this model provides a great deal of flexibility and performance potential, it saddles programmers with ... [more] »
20130603
Penalization approaches are nowadays commonly employed to solve boundary or initialboundary value problems. They consist in embedding the original, possibly complex spatial domain inside a bigger domain having a simpler geometry, for example a torus, while keeping the boundary conditions approximately enforced thanks to new terms that are added to the ... [more] »
20130430
The simulation of turbulent flows by the Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS) approaches requires extremely low numerical dispersion and dissipation. Finite Elementlike highorder methods such as the discontinuous Galerkin (DGM), spectral difference (SDM) and spectral element methods (SEM), ... have attracted considerable ... [more] »
20130619
In this seminar, we will discuss a number of recent advances in visual pattern recognition and image classification. In particular, we will present three applications of visual pattern recognition: to emotion recognition, 3D vision for assistive navigation, and human activity monitoring using Doppler radar. One of the challenges of visual pattern ... [more] »
20130419
Many engineering problems such as chemical reaction processes, population dynamics, ground water contamination are governed by coupled diffusionconvectionreaction partial differential equations (PDEs) with nonlinear source or sink terms. Nonlinear transport systems are typically convection and/or reaction dominated with characteristic solutions possessing ... [more] »
20130212
This talk is provided together with the department of mathematics. [more] »
20130607
Shielding sheets are commonly used in the protection of electronic devices. With their large aspect ratios they become a serious issue for the direct application of the finite element method, as many small cells are required to resolve the sheets, as well as the direct application of the boundary element method (BEM) due to the occuring almost singular ... [more] »
20130321
Compressed Sensing is a novel research area, which was introduced in 2006, and since then has already become a key concept in various areas of applied mathematics. It predicts that highdimensional signals, which allow a sparse representation by a suitable basis/frame, can be recovered from highly incomplete linear measurements by using efficient ... [more] »
20130521
A broad class of structures in electronics and highfrequency engineering exhibits linear timeinvariant system properties. It ranges from antennas and filters through wiring structures of integrated circuits to the cavities of linear accelerators and the elementary cells of metamaterials. Such structures constitute distributedparameter systems of high ... [more] »
20130221
The multicore trend has brought forth a variety of computer architectures suitable for numerical simulation. Nowadays there is no longer a single driving force for numerical performance. To make efficient use of the hardware the programmer must address multiple architectural features at the same time – otherwise he will face a performance ... [more] »
20130313
First, an overview about the research done at the institute will be given to set the framework why we are interested in the computationally so demanding particle methods. These methods have recently emerged as engineering tools that can be widely used in many different disciplines. Due to their meshless nature, they are especially well suited for problems ... [more] »
20130408
National power grids are currently evolving from static entities, producing mainly a unidirectional ﬂow from generation to loads, to more dynamic and decentralized structures. These emerging power systems should accommodate the local generation by renewable sources and peak demands of electrical vehicle charging. The crossborder interconnection of power ... [more] »
20121217
Suppression of brake squeal has received a lot of attention by engineering researchers in the past. It is widely accepted in the scientific community that the selfexcited vibrations induced by the frictional contact between brake disc and brake pad are the main cause of brake squeal. Presently, a variety of methods are being discussed to avoid squealing, ... [more] »
20121119
We study the fluidstructure interaction encountered in hydraulic fracturing, a technique used by the oil and gas industry. Simulating this process needs to take into account the interaction between a fracturing solid and the fluid flow in the crack. In particular, with the possible presence of a fluid lag, the evolving fluid front inside the crack and the ... [more] »
20121109
This talk is concerned with the derivation of computable and guaranteed upper and lower bounds of the dierence between the exact and the approximate solution of boundary value problems for static Maxwell type equations. Our analysis is based upon purely functional argumentation and does not attract specic properties of an approximation method. Therefore, ... [more] »
20121109
Multidomain and multiphysics problems with moving interfaces and parameter studies with changing geometric domains can be severely limited by the use of conforming meshes when complex geometries in three spatial dimensions are involved. To overcome these limitations, several fixedgrid methods based on XFEM, Nitsche's method and related approaches have ... [more] »
20121101
Software development in academia is subject to a set of special circumstances that make the development of sustainable, maintainable, and highquality software particularly difficult. In this talk I address these problems, explain why academia might be facing substantials problems in years to come, but also why the creation of ... [more] »
20120828
Consistently replacing prototypes or physical experiments by computations has been pursued within the Engineering and Applied Science community in the last decades, to a large extent due to the impressive computer power available nowadays. But the use of computer simulations as an effective tool still faces conceptual and technical challenges. Chief among ... [more] »
20120723
A threedimensional nonlinear timemarching method and numerical analysis for aeroelastic behaviour of oscillating blade row has been presented. The approach is based on the solution of the coupled fluidstructure problem in which the aerodynamic and structural equations are integrated simultaneously in time. Thus providing the correct formulation of ... [more] »
20120806
20120529
The multicore era has led to a renaissance for shared memory parallel programming models. Moreover, the introduction of Tasklevel parallelization raises the level of abstraction compared to threadcentric expression of parallelism. However, shared memory parallel applications may exhibit poor performance on NUMA systems if ... [more] »
20120529
We will discuss recent advances in the Portable, Extensible Toolkit for Scientific computing (PETSc) that enable application scientists to develop composable linear, nonlinear, and timestepping solvers for multiphysics and multilevel methods on emerging extremescale architectures. Examples of usage include lithosphere dynamics, ... [more] »
20120529
We describe recent and ongoing work in the area of automatic performance tuning. By employing specialization, we can develop tuned variants for the most common usage scenarios in a given application. By posing the empirical search problem as a mathematical optimization problem, we can draw upon the large body of research in derivative free optimization ... [more] »
20120309
At GSI a new data center is being built, which sets new standards in energy efficiency and cost. The computer racks are cooled directly with heat exchangers and mounted on a steel structure much like a high rack warehouse. This architecture enables power densities exceeding 20 kW/m² and floor or 100 kW/m². The entire data center will support computers up to ... [more] »
20120508
Substrate integrated waveguide (SIW) technology has been largely explored as a lowcost lowprofile transmission line in passive microwave and millimeter circuits and devices. Yet,little research has been done to assess SIW performance in integration with active elements, e.g. Power Amplifier (PA) and Low Noise Amplifier (LNA). The ... [more] »
20120119
In many engineering applications, the way natural fluid flows behave leaves some room for improvement. While geometric optimizations, such as streamlined shapes, require no additional energy input, they might not always be possible, feasible, or sufficient.
Another option is active flow control, where a suitable actuator more or less ... [more] »
20120322
The FLAME project has yielded modern alternatives to LAPACK and related efforts. An attractive feature of this work is the complete vertical integration of the entire software stack, starting with low level kernels that support the BLAS and finishing with a new distributed memory library, Elemental. In between are layers that target a single core, ... [more] »
20120113
Nowadays, a variety of modeling strategies exist for the computer simulation of electromagnetic wave propagation in the time domain. Despite a lot of advances on numerical methods able to deal accurately and in a flexible way with complex geometries through the use of unstructured (nonuniform) discretization meshes, the FDTD (Finite Difference Time Domain) ... [more] »
20120120
Proteins are biological nanomachines. Virtually every function in the cell is carried out by proteins  ranging from protein synthesis, ATP synthesis, molecular binding and recognition, selective transport, sensor functions, mechanical stability, and many more. The combined interdisciplinary efforts of the past years have revealed how many of these ... [more] »
20111012
20111009
20111014
20111007
20111007
In the first part of the talk, and in order to set the stage, we will offer a multiscale and averaging strategy to compute the solution of a singularly perturbed system when the fast dynamics oscillates rapidly; namely, the fast dynamics forms cyclelike limits which advance along with the slow dy namics. We describe the limit as a Young measure with ... [more] »
20110704
Trotz zunehmend komplexer werdender elektromagnetischer Probleme machen heute neue Rechnerarchitekturen die numerische Simulation großer gekoppelter Probleme möglich. Die einzelnen Teilprobleme sind oft differentialalgebraische Gleichungen, die aus der Ortsdiskretisierung partieller Differentialgleichungen (PDGLn) stammen. In diesem Vortrag werden ... [more] »
20110701
Die Diskretisierung linearer zeitinvarianter Systeme mittels finiter Elemente (FE) führt auf große, dünnbesetzte lineare Gleichungssysteme, deren Dimension typischerweise in der Größenordnung von Hunderttausend bis einigen Millionen liegt. Während ihre Lösung für eine einzelne Frequenz beim heutigen Stand der Technik kein Problem mehr bereitet, stellt die ... [more] »
20101110
20110614
This talk is about the advancement of gridbased simulation algorithms for modelling electromagnetic wave propagation in photonics. For this purpose, existing algorithms for problems arising from the microwave range are extended for the analysis and the design of linear passive nanostructures at optical frequencies. The focus is put on the calculation of ... [more] »
20110614
Elektromagnetische Felder, die durch die zu beschleunigenden Ladungsträger im Teilchenbeschleuniger hinterlassen werden, stellen eine wesentliche Limitierung für im Bau befindliche und zukünftige Teilbeschleunigerprojekte dar. Zur Dämpfung dieser als Wakefelder bezeichneten elektromagnetischen Felder werden spezielle Kopplerstrukturen eingesetzt, die den ... [more] »
20110526
Several examples of a curious interplay between analytical and numerical methods will be presented. First, accurate local (semi)analytical Trefftz approximations lead to highorder difference schemes and to singularityfree boundarydifference methods. Second, Whitneylike interpolation, well established in finite element analysis, is now put to a new use ... [more] »
20101217
This talk will discuss the recently introduced class of isogeometric finite elements, which generalize the isoparametric concept to Bsplines and NURBS (NonUniform Rational BSplines). The latter are one of the standard descriptions for free form surfaces and various typical engineering shapes in Computer Aided Design (CAD) software. Besides explaining the ... [more] »
20110418
The influence of walls on the Lagrangian transport and mixing of passive scalars in turbulent twodimensional flows is investigated. Two distinct geometries are considered by means of direct numerical simulation: a biperiodic domain and a circular domain with noslip boundary conditions for velocity and zero flux for the scalar. A penalization method allows ... [more] »
20101129
Flows with interfaces exhibit interactions on a large range of scales, resulting in large demands on compute power for simulations. Singlephase flows already can exhibit a large range of strongly coupled scales whose efficient computational modeling poses a challenge by itself. Immersed interfaces add smallscale transport phenomena and can dominate the ... [more] »
20100930
We describe computations performed using the Gerris code, an opensource software implementing finite volume solvers on an octree adaptive grid together with a piecewise linear volume of fluid interface tracking method. The parallelisation of Gerris is achieved by domain decomposition into a large number of grains (a "forest of tree" approach) ... [more] »
20101104
20110113
Bei der Lösung von Optimierungsaufgaben bei partiellen Differentialgleichungen und von Parameteridentifikationsaufgaben werden häufig sehr ähnlich mathematische Probleme untersucht. Dabei haben die mathematischen Gebiete Inverse Probleme und Optimale Steuerung sehr unterschiedliche Herangehensweisen. Ausgehend von der Korrektheitsdefinition von Hadamard ... [more] »
20110113
Adaptive Finite Elemente Verfahren werden seit den 1970er Jahren erfolgreich zur effizienten numerischen Lösung partieller Differenzialgleichungen verwendet. Das übliche adaptive Verfahren ist eine Iteration der Form SOLVE → ESTIMATE → MARK → REFINE. Die meisten Arbeiten zu adaptiven Finiten Elementen befassen sich mit dem Modul ESTIMATE, ... [more] »
20101201
In this talk, we consider a stateconstrained optimal control problem of Maxwell's equations based on a 'vector potential ansatz' for the control. The pointwise state constraints here play an important role to prevent singularities or to achieve certain $L^p$regularity of the optimal state. Due to the lack of regularity of the controltostate ... [more] »
20101126
20101006
Robotics is rapidly expanding into the human environment and vigorously staying engaged in its emerging challenges. From a largely dominant industrial focus, robotics has undergone, by the turn of the new millennium, a major transformation in scope and dimensions. This expansion has been brought about by the maturity of the field and the advances in its ... [more] »
20101103
Multicomponent AMFM models, also known as McAulayQuatieri models in audio and speech processing, are highly parametric representations of non stationary signals that are able to effectively represent a large class of real phenomena with no limitations in terms of signal kind, applicative domain, and so on. During recent decades, the elegant formulation of ... [more] »
20100928
Since 2004, the driving behavior of more than five hundred drivers has been collected while subjects drove in real traffic, by researchers at Nagoya University in Japan. The main purpose of this data collection is to build corpora (large bodies of representative data) for a new research challenge  human behavior signal processing. Environmental and ... [more] »
20100429
20100429
This talk is provided together with the Center of Smart Interfaces (CSI). [more] »
20100722
Driven by the impressive growth of the communication industry, we see a rapid convergence of digital computing and analog wireless technology. This has become possible due to the progress of, semiconductor technology into the nanometer regime which is going to continue for the next ten to fifteen years. Highlevel integration with unprecedented ... [more] »
20100630
20100611
In this presentation I will briefly introduce my research group and its goals. I will explain why we are interested in adaptive finite element methods based on computational, as opposed to mathematical/analytical error estimates. Main principles of adaptive higherorder finite elementi methods (hpFEM) will be explained and demonstrated via live ... [more] »
20100428
When building a mathematical model to describe the behavior of a physical system, one has often to face a certain level of uncertainty in the proper characterization of the model parameters and input data. An example is given by the study of groundwater flow, where the subsurface permeability is largely unknown and often reconstructed from few available ... [more] »
20100506
One of the challenges of visual pattern recognition is robustness to photometric and geometric distortions that occur in uncontrolled natural environments. To this end, we have proposed recently a new paradigm for visual pattern recognition which combines feature extraction and classification in one hierarchical image classification architecture. The ... [more] »
20100324
Traditional finitedifference methods are typically based on Taylor expansions of the differential operator. The generalized finitedifference calculus of Flexible Local Approximation MEthods (FLAME) often dramatically improves the accuracy by replacing these Taylor expansions with Trefftz functions – local solutions of the underlying differential ... [more] »
20100421
This talk is provided together with the Center of Smart Interfaces (CSI). [more] »
20100505
Es wird eine kurze Übersicht über die DFGProjekte im DFG Schwerpunktprogramm SPP 1395 (InKoMBio) gegeben. Nach einer kurzen Einführung in die elementaren informationstheoretischen Begriffe wird auf die Analyse binärer polynomialer Systeme mittels der Fourier Analyse eingegangen. (Vorstellung des DFGProjektes: Die Evolutive Anpassung der transkriptionellen ... [more] »
20100422
Die dynamische Simulation ist ein aktueller Forschungsbereich mit vielen Anwendungsgebieten. Dieser Bereich umfasst u.a. die Simulation von Starrkörpern, Textilien und Weichkörpern. Dynamische Simulation ist heutzutage ein wichtiger Bestandteil im Entwicklungsprozess von komplexen Maschinen (wie z.B. in der Robotik), im Forschungsbereich der Medizin, in der ... [more] »
20100412
Die variationelle MehrskalenMethode wurde vor ca. 15 Jahren zum ersten Mal der Fachwelt als theoretisches Rahmenwerk für die Entwicklung numerischer Methoden für Probleme mit sehr breiten Skalenspektren vorgestellt. Als Beispiele für solche MehrskalenProbleme kann man u.a. viele Problemstellungen der Materialmodellierung, aber auch z.B. turbulente ... [more] »
20100121
20100412
20100415
20100415
20100203
Part 1: Singularity type functions, such as the Dirac delta, are usually defined assuming that they operate on well defined functions  usually called ‘good functions’. The results that hold for singular ity functions, and for the good function case, do not hold, in general, for the usual case where non good functions are to be considered and this has led ... [more] »
20100125
Rieselfilme (d.h. dünne durch Gravitation getriebene flüssige Filme) spielen in einer Vielzahl technischer Prozesse in der Energie und Verfahrenstechnik eine Rolle. In Kühltürmen wird z.B. Wasser auf sogenannte Rieseleinbauten gesprüht, wodurch sich ein verdunstender Film ausbildet. Rieselfilme aus flüssigem Lithium werden in der Kernfusionsforschung zur ... [more] »
20100113
Although Boundary Element Method (BEM) requires us heavy calculation cost and large required memory, it givs us some remarkable advantages due to property of surface mesh such as in open bounary problems, moving boundary problems, optimized shape design problems, inverse problems, coupling problems with moving charged particles, and so on. This means that ... [more] »
20091211
Airborne vehicle or and its payload are extremely expensive and their loss as a result of a nearby lightning strike is highly undesirable. Even though one could launch only under ideal weather conditions, the cost involved with long launch delays could be very high. So in this age of all weather usage of airborne launch vehicles, it has become necessary to ... [more] »
20091117
Hearing impaired people suffer from significant problems of understanding speech in noisy environments. The damage of the outer hair cells in the cochlear causes a reduced frequency resolution or higher frequency masking of the auditory perception, respectively. The only possibility to compensate for this effect is to offer people a signal with reduced ... [more] »
20091016
According to textbook wisdom, flow down a pipe becomes turbulent near a Reynolds number of about 2000. This simple statement misses many subtleties of the transition: the absence of a linear stability of the laminar flow, the sensitive dependence on perturbations that sometimes succed and sometimes fail to induce turbulence and the unexpected observation ... [more] »
20090820
When we speak of cognition, we usually think of the human brain: A powerful and highly complex informationprocessing system. So, I set the stage for my lecture by describing the ActionPerception Cycle that is an inherent characteristic of the brain. With the ActionPerception Cycle as the focus of attention throughout the lecture, I will then describe ... [more] »
20090907
Urban Search And Rescue (USAR) is a time critical task since survivors have to be rescued within the first "golden" 72 hours. One goal in Rescue Robotics is to support emergency response by mixedinitiative teams consisting of humans and robots. Their task is to explore the disaster area rapidly while reporting victim locations and hazardous areas ... [more] »
20090907
Latente Variablen haben eine langjährige Geschichte in der Modellierung komplexer statistischer Zusammenhänge. Indem sie versteckte Strukturen in Daten selbständig aufgreifen und repräsentieren können, ermöglichen sie es, erstaunlich elegante und einfache Modelle einer Vielzahl komplexer Phänomene zu generieren. Klassische Beispiele für Verfahren, die auf ... [more] »
20090624
The advances in hardware functionality and programmability of graphics processors (GPUs) have greatly increased their appeal as addon coprocessors for scientific computing. However, for largescale computations a desktop with a single GPU is not sufficient and parallel workstations or even clusters with multiple GPUs must be considered. This talk will ... [more] »
20090610
Flow fields play an important role in a wide range of scientific, engineering, and medical disciplines. Due to the advancements in computing technologies and computational fluid dynamics (CFD), recently we have seen a large number of flow datasets with ever increasing size and complexity from numerical fluid simulations. In order to obtain valuable ... [more] »
20090528
Am 15. Januar 2009 gelang dem Piloten einer Maschine vom Typ A320 der US Airways nach dem Ausfall beider Triebwerke eine Notwasserung auf dem Hudson River in New York. Alle 155 Insassen überstanden die Notwasserung nahezu unverletzt. Der Vortrag behandelt einen randständigen Bereich des Flugzeugbaus, der sich mit der Notwasserung und Schwimmfähigkeit von ... [more] »
20090511
We exploit ideas from model predictive control to construct nonlinear distributed and boundary controllers for flow governed by the instationary Navier Stokes equations or the Boussinesq approximation. We numerically test the performance of the controllers considering as example control of the wake of the circular cylinder in the laminar flow regime, and ... [more] »
20090608
20090526
Existing wireless networks are designed for coexistance, i.e. essentially for interference avoidance. In contrast cooperative wireless communication intentionally accepts interference to optimize network performance. In this talk we start out with a brief introduction to cooperative wireless communication and in particular wireless relaying. Subsequently ... [more] »
20090514
A systematic framework for implicit LES modeling will be presented. Unlike previous approaches to ILES, where given nonlinearly stable discretizations are employed without a priori analysis of the effect of the truncation error, with the proposed framework ALDM (adaptive local deconvolution model) physically consistent modeling is introduced to ILES. With ... [more] »
20090428
Spektralelementmethoden (SEM) kombinieren die Genauigkeit von Spektralmethoden mit der Flexibilität von FiniteElementeVerfahren. Dieser Anspruch lässt sich In der Praxis nicht immer leicht verwirklichen.
Dieser Vortrag startet mit einigen Erfolgsbeispielen aus dem SFB 609 an der TU Dresden.
Der zweite Teil widmet sich der implementierung von ... [more] »
20090306
Every optimization technique has inherent strengths and weaknesses. Moreover, some optimization algorithms contain characteristics which make them better suited to solve particular kinds of problems. Hybridization, or the combining of two or more complementary, but distinct methods, allows the user to take advantage of the beneficial elements of multiple ... [more] »
20090324
Optimization problems with partial differential equations constraints are computationally challenging problems that appear in a wide range of engineering applications. Spacemapping techniques allow to speed their solution procedure by extracting information from approximate models such as for instance analytical and lumped parameter approximations. Early ... [more] »
20090330
The Finite Difference Time Domain (FDTD) algorithm, originally proposed by K. S. Yee, is one of the most common algorithm for the timedomain simulation of electromagnetic problems. This is essentially due to the fact that the FDTD algorithm is explicit, so that its computationally complexity and memory requirement are low, and to the fact that the limit ... [more] »
20090302
We combine the classical theories of discrete computation (Turing computability and complexity classes like NP) and real number computation (Recursive Analysis and BSS model) with Theoretical Physics in order to
1. investigate physical foundations of computing (ChurchTuring Hypothesis) and
2. devise a complexity theory of computer simulation ... [more] »
20090205
Anisotropic mesh adaptation has proven to be a useful tool for enhancing accuracy and efficacy in the numerical solution of partial differential equations, especially those exhibiting anisotropic features in their solutions and/or structures. On the other hand, the mathematical characterization of anisotropic meshes has not been well understood. In ... [more] »
20081107
The simulation of electromagnetic phenomena using field solvers for semiconductor structures demands the use of potentials and vector potentials because the local energy, more than the local force, determines the electron and hole distributions. The ideas underlying the finiteintegration method are applied to the potential fields leading to a discretization ... [more] »
20081027
Electromagnetic modelling for photonics shares many common problems with other applications. These include the requirement for: multiscale modelling, requiring an accurate description of small features that can have significant influence on the performance of a significantly larger system; addressing multiphysics problems operating on timescales; highly ... [more] »
20081219
Der Vortrag gibt eine Übersicht über die Entwicklung von DiscontinuousGalerkinVerfahren für instationäre Probleme. Durch ihre Flexibilität und die Qualität der Näherungslösungen werden diese Verfahren als eine künftige Möglichkeit gesehen, numerische Simulationen in komplexen Geometrien effizienter zu machen. Das DGVerfahren kann als eine Kombination von ... [more] »
20081114
Modern graphics cards are not only powerful rendering systems but can also be used as massively parallel compute devices. Applications that are well suited for the cards' SIMD architecture can achieve speed ups of more than two orders of magnitude compared to single CPU implementations. In this talk, I will give an introduction to NVIDIA's CUDA ... [more] »
20081210
20081105
The multilevel fast multipole algorithm (MLFMA) is a powerful method for the fast and efficient solution of scattering and radiation problems in electromagnetics. Reallife problems formulated with surface integral equations can be solved iteratively, where the required matrixvector multiplications are performed efficiently by MLFMA. However, many ... [more] »
20081027
20081027
20081007
Elektromechanische Systeme werden durch die Maxwellschen Gleichungen in Verbindung mit der Newtonschen Bewegungsgleichung beschrieben. Die physikalischen Gesetze liegen dabei in Form (partieller) Differentialgleichungen vor, die durch Anwendung numerischer Verfahren schrittweise in lineare Gleichungssysteme überführt und auf dem Rechner gelöst werden. ... [more] »
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