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  1. Article

    Open Access

    A space–time variational method for optimal control problems: well-posedness, stability and numerical solution

    We consider an optimal control problem constrained by a parabolic partial differential equation with Robin boundary conditions. We use a space–time variational formulation in Lebesgue–Bochner spaces yielding a...

    Nina Beranek, Martin Alexander Reinhold in Computational Optimization and Applications (2023)

  2. No Access

    Chapter

    Maple , or why computers can sometimes help

    Maple is a program developed and distributed by the company Maplesoft (also in cooperation with universities and research institutes). It is a compute...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    Modeling, or where do differential equations come from

    Partial differential equations describe numerous phenomena in nature, technology, medicine, economics, ... In this first chapter we shall describe the derivation of the partial differential equations associate...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    Elementary methods

    In this chapter we will derive explicit solutions for a number of partial differential equations. The equations we will be considering here represent a number of important models such as those of the vibrating...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    Sobolev spaces and boundary value problems in dimension one

    Sobolev spaces on an interval have special appeal: they consist of functions which can be written as indefinite integrals of integrable functions. Numerous properties and rules of calculation, such as the inte...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    Neumann and Robin boundary conditions

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    The Reduced Basis Method in Space and Time: Challenges, Limits and Perspectives

    The simulation and optimization of several real-world industrial problems involve parameters, e.g. unknown constants, design parameters, controls etc. In many cases, these parameters are subject to uncertainties....

    Karsten Urban in Model Order Reduction and Applications (2023)

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    Chapter

    Numerical methods

    Thus far we have met and modeled a number of partial differential equations, considered elementary solution methods for them and finally developed mathematical theories to handle them. Everything up until now ...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    Classification and characteristics

    In the preceding chapter we encountered a whole series of partial differential equations arising from natural processes as well as economic models. Given the huge variety of such equations, it should not be su...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    Hilbert spaces

    The goal of this chapter is to give an elementary but comprehensive introduction to the theory of Hilbert spaces, where we wish to highlight the many-faceted interplay of their geometric and analytic propertie...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    Hilbert space methods for elliptic equations

    We started by introducing Sobolev spaces in dimension one only, or more precisely for functions defined on an open interval in ℝ ...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Chapter

    Spectral decomposition and evolution equations

    The spectral decomposition of the Laplacian with suitable boundary conditions gives us precise information about the solvability of the equation ...

    Wolfgang Arendt, Karsten Urban in Partial Differential Equations (2023)

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    Book

    Partial Differential Equations

    An Introduction to Analytical and Numerical Methods

    Wolfgang Arendt, Karsten Urban in Graduate Texts in Mathematics (2023)

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    Book

  15. Article

    Open Access

    Linear/Ridge expansions: enhancing linear approximations by ridge functions

    We consider approximations formed by the sum of a linear combination of given functions enhanced by ridge functions—a Linear/Ridge expansion. For an explicitly or implicitly given objective function, we reform...

    Constantin Greif, Philipp Junk, Karsten Urban in Advances in Computational Mathematics (2022)

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    Chapter

    Multiskalenprobleme in der Numerik–Lehre – Ein Erfahrungsbericht

    Der Bologna–Prozess hat u. a. bewirkt, dass Lehrveranstaltungen von Studierenden mit vermehrt heterogenen Eingangskompetenzen besucht werden. Bei gleichen angestrebten Ausgangskompetenzen stellt dies die Lehre...

    Laura Burr, Stefan Hain, Klaus Stolle in Unterstützungsmaßnahmen in mathematikbezog… (2022)

  17. No Access

    Chapter and Conference Paper

    A Variational Formulation for LTI-Systems and Model Reduction

    We consider a variational formulation of Linear Time-Invariant (LTI)-systems and derive a model reduction in dimension and time inspired by space-time variational reduced basis (RB) methods for parabolic probl...

    Moritz Feuerle, Karsten Urban in Numerical Mathematics and Advanced Applica… (2021)

  18. No Access

    Chapter and Conference Paper

    Matrix Oriented Reduction of Space-Time Petrov-Galerkin Variational Problems

    Variational formulations of time-dependent PDEs in space and time yield (d + 1)-dimensional problems to be solved numerically. This increases the number of unknowns as well as the storage amount. On the other han...

    Julian Henning, Davide Palitta in Numerical Mathematics and Advanced Applica… (2021)

  19. No Access

    Article

    HT-AWGM: a hierarchical Tucker–adaptive wavelet Galerkin method for high-dimensional elliptic problems

    This paper is concerned with the construction, analysis, and realization of a numerical method to approximate the solution of high-dimensional elliptic partial differential equations. We propose a new combinat...

    Mazen Ali, Karsten Urban in Advances in Computational Mathematics (2020)

  20. Article

    Open Access

    Intraday renewable electricity trading: advanced modeling and numerical optimal control

    As an extension of (Progress in industrial mathematics at ECMI 2018, pp. 469–475, 2019), this paper is concerned with a new mathematical model for intraday electricity trading involving both renewable and convent...

    Silke Glas, Rüdiger Kiesel, Sven Kolkmann in Journal of Mathematics in Industry (2020)

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