Ulrich Langer – författare

Finite element methods are the most popular methods for solving partial differential equations numerically, and despite having a history of more than 50 years, there is still active research on their analysis, application and extension. This book features overview papers and original research articles from participants of the 30th Chemnitz Finite Element Symposium, which itself has a 40-year history. Covering topics including numerical methods for equations with fractional partial derivatives; isogeometric analysis and other novel discretization methods, like space-time finite elements and boundary elements; analysis of a posteriori error estimates and adaptive methods; enhancement of efficient solvers of the resulting systems of equations, discretization methods for partial differential equations on surfaces; and methods adapted to applications in solid and fluid mechanics, it offers readers insights into the latest results.

These are the proceedings of the 27th International Conference on Domain Decomposition Methods in Science and Engineering, which was held in Prague, Czech Republic, in July 2022.

Domain decomposition methods are iterative methods for solving the often very large systems of equations that arise when engineering problems are discretized, frequently using finite elements or other modern techniques. These methods are specifically designed to make effective use of massively parallel, high-performance computing systems.

The book presents both theoretical and computational advances in this domain, reflecting the state of art in 2022.

This book is the third volume of three volume series recording the "Radon Special Semester 2011 on Multiscale Simulation & Analysis in Energy and the Environment" taking place in Linz, Austria, October 3-7, 2011. This book surveys recent developments in the analysis of wave propagation problems. The topics covered include aspects of the forward problem and problems in inverse problems, as well as applications in the earth sciences.

Wave propagation problems are ubiquitous in environmental applications such as seismic analysis, acoustic and electromagnetic scattering. The design of efficient numerical methods for the forward problem, in which the scattered field is computed from known geometric configurations is very challenging due to the multiscale nature of the problems. Even more challenging are inverse problems where material parameters and configurations have to be determined from measurements in conjunction with the forward problem. This book contains review articles covering several state-of-the-art numerical methods for both forward and inverse problems.

This collection of survey articles focusses on the efficient computation of wave propagation and scattering is a core problem in numerical mathematics, which is currently of great research interest and is central to many applications in energy and the environment. Two generic applications which resonate strongly with the central aims of the Radon Special Semester 2011 are forward wave propagation in heterogeneous media and seismic inversion for subsurface imaging. As an example of the first application, modelling of absorption and scattering of radiation by clouds, aerosol and precipitation is used as a tool for interpretation of (e.g.) solar, infrared and radar measurements, and as a component in larger weather/climate prediction models in numerical weather forecasting. As an example of the second application, inverse problems in wave propagation in heterogeneous media arise in the problem of imaging the subsurface below land or marine deposits.

The book records the achievements of Workshop 3 "Wave Propagation and Scattering, Inverse Problems and Applications in Energy and the Environment". It brings together key numerical mathematicians whose interest is in the analysis and computation of wave propagation and scattering problems, and in inverse problems, together with practitioners from engineering and industry whose interest is in the applications of these core problems.

This volume collects longer articles on the analysis and numerics of Maxwell’s equations. The topics include functional analytic and Hilbert space methods, compact embeddings, solution theories and asymptotics, electromagnetostatics, time-harmonic Maxwell’s equations, time-dependent Maxwell’s equations, eddy current approximations, scattering and radiation problems, inverse problems, finite element methods, boundary element methods, and isogeometric analysis.

This volume collects longer articles on the analysis and numerics of Maxwell’s equations. The topics include functional analytic and Hilbert space methods, compact embeddings, solution theories and asymptotics, electromagnetostatics, time-harmonic Maxwell’s equations, time-dependent Maxwell’s equations, eddy current approximations, scattering and radiation problems, inverse problems, finite element methods, boundary element methods, and isogeometric analysis.

This volume provides an introduction to modern space-time discretization methods such as finite and boundary elements and isogeometric analysis for time-dependent initial-boundary value problems of parabolic and hyperbolic type. Particular focus is given on stable formulations, error estimates, adaptivity in space and time, efficient solution algorithms, parallelization of the solution pipeline, and applications in science and engineering.

This collection of selected papers presented at the 11th International Conference on Scientific Computing in Electrical Engineering (SCEE), held in St. Wolfgang, Austria, in 2016, showcases the state of the art in SCEE. 

The aim of the SCEE 2016 conference was to bring together scientists from academia and industry, mathematicians, electrical engineers, computer scientists, and physicists, and to promote intensive discussions on industrially relevant mathematical problems, with an emphasis on the modeling and numerical simulation of electronic circuits and devices, electromagnetic fields, and coupled problems. The focus in methodology was on model order reduction and uncertainty quantification. 

This extensive reference work is divided into six parts: Computational Electromagnetics, Circuit and Device Modeling and Simulation, Coupled Problems and Multi‐Scale Approaches in Space and Time, Mathematical and Computational Methods Including Uncertainty Quantification, Model Order Reduction, and Industrial Applications. Each part starts with a general introduction, followed by the respective contributions. 

This book will appeal to mathematicians and electrical engineers. Further, it introduces algorithm and program developers to recent advances in the other fields, while industry experts will be introduced to new programming tools and mathematical methods.

This book constitutes the thoroughly refereed post-proceedings of the Second International Conference on Symbolic and Numerical Scientific Computation, SNSC 2001, held in Hagenberg, Austria, in September 2001.

The 19 revised full papers presented were carefully selected during two rounds of reviewing and improvement. The papers are organized in topical sections on symbolics and numerics of differential equations, symbolics and numerics in algebra and geometry, and applications in physics and engineering.

This volume contains eight state of the art contributions on mathematical aspects and applications of fast boundary element methods in engineering and industry. This covers the analysis and numerics of boundary integral equations by using differential forms, preconditioning of hp boundary element methods, the application of fast boundary element methods for solving challenging problems in magnetostatics, the simulation of micro electro mechanical systems, and for contact problems in solid mechanics. Other contributions are on recent results on boundary element methods for the solution of transient problems.

This book is addressed to researchers, graduate students and practitioners working on and using boundary element methods. All contributions also show the great achievements of interdisciplinary research between mathematicians and engineers, with direct applications in engineering and industry.

Dieses Lehrbuch ist als Einführung in die numerische Lösung partieller Differentialgleichungen mittels der Finite-Elemente-Methode (FEM) und in das dazu notwendige Handwerkszeug aus der numerischen linearen Algebra konzipiert. Für verschiedene physikalisch-technische Probleme wie Wärmeleitprobleme sowie Probleme aus der Festkörpermechanik und der Elektrotechnik wird deren Modellierung mittels partieller Differentialgleichungen diskutiert. Die Grundideen der FEM, der wohl am häufigsten genutzten Rechenmethode für diese Modelle, und Lösungstechniken für die bei der FEM-Diskretisierung entstehenden (nicht)linearen Gleichungssysteme bzw. Systeme gewöhnlicher Differentialgleichungen werden anwendungsorientiert vermittelt.

Die zweite Auflage dieses Buches stellt auch eine gründliche Überarbeitung und Erweiterung der ersten Auflage dar.

Im Kapitel 1 wurde vor allem den Abschnitt 1.3 überarbeitet. Die Beschreibung von elektrischen und magnetischen Feldern sowie entsprechende Rechenbeispiele werden jetzt in einem Unterabschnitt zusammengeführt und aus den vollen Maxwellschen Gleichungen hergeleitet. Neu im Kapitel 2 ist neben der Modellierung typischer stationärer und instationärer Wärmeleitprobleme die mathematische Modellierung charakteristischer Probleme aus der linearen Elastostatik und Elastodynamik.

Das Kapitel 4 zur FEM für mehrdimensionale Randwertprobleme wurde wesentlich überarbeitet und erweitert.

Der Beschreibung von direkten und iterativen Lösungsverfahren für lineare Gleichungssysteme im Kapitel 5 ist jetzt ein Abschnitt vorangestellt, in welchem Grundbegriffe aus der linearen Algebra zusammengestellt sind, die später bei der Diskussion der Eigenschaften der Lösungsverfahren benötigt werden. Außerdem werden Eigenschaften der FE-Gleichungssysteme diskutiert.

Der Abschnitt zu den direkten Lösungsverfahren wurde wesentlich erweitert. Neu in diesem Kapitel ist auch die Beschreibung vonProfilminimierungsalgorithmen wie des Cuthill-McKee-Algorithmus und des Minimalgrad-Algorithmus. Bezüglich der iterativen Lösung linearer Gleichungssysteme wurden im Abschnitt 5.3.4 eine Motivation für die Idee von Mehrgitterverfahren hinzugefügt.

Neu sind auch die Abschnitte 8.2.5 und 8.3. Im Abschnitt 8.2.5 werden praktische Hinweise zu einfachen Zeitschrittsteuerungen, die auf Schätzungen des lokalen Fehlers beruhen, gegeben.