1,721,195 research outputs found
A conversation with Volker Mehrmann
No full textVolker Mehrmann is a complete mathematician excelling in all areas: research, teaching, knowledge transfer, and management. He is a specialist in numerical linear algebra, algebraic-differential equations, and control theory, and he enjoys conducting research motivated by real-world problems and developing fundamental mathematics that has a significant impact on science and technology. With a striking personality, Mehrmann leaves a remarkable legacy as former president of GAMM (International Association for Applied Mathematics and Mechanics), MATHEON (Mathematical Research Center for Key Technologies), ECMath (Einstein Center for Mathematics in Berlin), and EMS (European Mathematical Society). He is attentive to how mathematics is communicated to fellow mathematicians and to the general public, and he takes care of the working environment of his students.The three of us (Sílvia Barbeiro, Ana Isabel Mendes and Martin Raussen) held a videoconference meeting with Volker Mehrmann last October. We listened eagerly to his answers to all our questions. At the end, we discovered his secret: mathematics brings happiness
Uma Conversa com Volker Mehrmann: A Matemática traz Felicidade:Matemáticos na primeira pessoa
No full textVolker Mehrmann er en komplet matematiker og overrasker i alle aspekter: forskning, undervisning, videnoverførsel og administrative stillinger. Specialist inden for områderne numerisk lineær algebra, algebraiske differentialligninger og kontrolteori, nyder han at lave forskning motiveret af reelle problemer og udvikle virkningsfuld grundlæggende matematik inden for videnskab og teknologi.<br/
A generalized structured doubling algorithm for the numerical solution of linear quadratic optimal control problems
No full textNumerical algebra, matrix theory, differential-algebraic equations and control theory: festschrift in honor of Volker Mehrmann
No full textThis edited volume highlights the scientific contributions of Volker Mehrmann, a leading expert in the area of numerical (linear) algebra, matrix theory, differential-algebraic equations and control theory. These mathematical research areas are strongly related and often occur in the same real-world applications. The main areas where such applications emerge are computational engineering and sciences, but increasingly also social sciences and economics. This book also reflects some of Volker Mehrmann's major career stages. Starting out working in the areas of numerical linear algebra (his first full professorship at TU Chemnitz was in "Numerical Algebra," hence the title of the book) and matrix theory, Volker Mehrmann has made significant contributions to these areas ever since. The highlights of these are discussed in Parts I and II of the present book. Often the development of new algorithms in numerical linear algebra is motivated by problems in system and control theory. These and his later major work on differential-algebraic equations, to which he together with Peter Kunkel made many groundbreaking contributions, are the topic of the chapters in Part III. Besides providing a scientific discussion of Volker Mehrmann's work and its impact on the development of several areas of applied mathematics, the individual chapters stand on their own as reference works for selected topics in the fields of numerical (linear) algebra, matrix theory, differential-algebraic equations and control theory
Numerical methods in control, from pole assignment via linear quadratic to H infinity control
No full textWe study classical control problems like pole assignment, stabilization, linear quadratic control and H1 control from a numerical analysis point of view. We present several examples that show the difficulties with classical approaches and suggest reformulations of the problems in a more general framework. We also discuss some new algorithmic approaches. AMS subject classification. 65F15, 93B40, 93B36, 93C60. Authors: Volker Mehrmann and Hongguo Xu Fakultat fur Mathematik, TU Chemnitz, D-09107 Chemnitz, FRG. Supported by Deutsche Forschungsgemeinschaft, within Sonderforschungsbereich SFB393, `Numerische Simulation auf massiv parallelen Rechnern'. 1 Introduction In the last 40 years linear systems theory (control theory) has evolved into a mature field that has found a stable position on the borderline between applied mathematics, engineering and computer science. The major success is not only due to the fact that beautiful mathematical theories (like linear algebra, ring theory, rep..
Doubling Algorithms with Permuted Lagrangian Graph Bases
No full textWe present an approach to the determination of the stabilizing solution of Lur'e matrix equations. We show that the knowledge of a certain deflating subspace of an even matrix pencil may lead to Lur'e equations which are defined on some subspace, the so-called "projected Lur'e equations." These projected Lur'e equations are shown to be equivalent to projected Riccati equations, if the deflating subspace contains the subspace corresponding to infinite eigenvalues. This result leads to a novel numerical algorithm that basically consists of two steps. First we determine the deflating subspace corresponding to infinite eigenvalues using an algorithm based on the so-called "neutral Wong sequences," which requires a moderate number of kernel computations; then we solve the resulting projected Riccati equations. Altogether this method can deliver solutions in low-rank factored form, it is applicable for large-scale Lur'e equations and exploits possible sparsity of the matrix coefficients. © 2012 Society for Industrial and Applied Mathematics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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