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  • Open Access
    Authors: 
    Theisen, Lambert;
    Publisher: figshare

    All P3 basis functions and an attached WolframScript to generate the same plots for arbitrary Pm elements.

  • Publication . Preprint . Article . 2020
    Open Access
    Authors: 
    Lambert Theisen; Manuel Torrilhon;
    Publisher: Association for Computing Machinery (ACM)

    We present a mixed finite element solver for the linearized R13 equations of non-equilibrium gas dynamics. The Python implementation builds upon the software tools provided by the FEniCS computing platform. We describe a new tensorial approach utilizing the extension capabilities of FEniCS's Unified Form Language (UFL) to define required differential operators for tensors above second degree. The presented solver serves as an example for implementing tensorial variational formulations in FEniCS, for which the documentation and literature seem to be very sparse. Using the software abstraction levels provided by the UFL allows an almost one-to-one correspondence between the underlying mathematics and the resulting source code. Test cases support the correctness of the proposed method using validation with exact solutions. To justify the usage of extended gas flow models, we discuss typical application cases involving rarefaction effects. We provide the documented and validated solver publicly. Comment: 29 pages, 13 figures, 8 listings, 3 table. Submitted to ACM Transactions on Mathematical Software (TOMS)

  • Open Access
    Authors: 
    Theisen, Lambert; Stamm, Benjamin;
    Publisher: Zenodo

    ddEigenLab.jl: Domain-Decomposition Eigenvalue Problem Lab

  • Open Access
    Authors: 
    Lambert Theisen; Benjamin Stamm;
    Publisher: Society for Industrial & Applied Mathematics (SIAM)

    This paper provides a provably quasi-optimal preconditioning strategy of the linear Schr\"odinger eigenvalue problem with periodic potentials for a possibly non-uniform spatial expansion of the domain. The quasi-optimality is achieved by having the iterative eigenvalue algorithms converge in a constant number of iterations for different domain sizes. In the analysis, we derive an analytic factorization of the spectrum and asymptotically describe it using concepts from the homogenization theory. This decomposition allows us to express the eigenpair as an easy-to-calculate cell problem solution combined with an asymptotically vanishing remainder. We then prove that the easy-to-calculate limit eigenvalue can be used in a shift-and-invert preconditioning strategy to bound the number of eigensolver iterations uniformly. Several numerical examples illustrate the effectiveness of this quasi-optimal preconditioning strategy. Comment: 29 pages, 9 figures, 2 tables

  • Open Access English
    Authors: 
    Theisen, Lambert; Torrilhon, Manuel;
    Publisher: Zenodo

    fenicsR13: A Tensorial Mixed Finite Element Solver for the Linear R13 Equations Using the FEniCS Computing Platform The project can be accessed at https://git.rwth-aachen.de/lamBOO/fenicsR13

  • Open Access
    Authors: 
    Theisen, Lambert; Stamm, Benjamin;
    Publisher: Zenodo

    This work was supported by the German Research Foundation (DFG) under project 411724963. ddEigenLab.jl: Domain-Decomposition Eigenvalue Problem Lab

  • Open Access
    Authors: 
    Theisen, Lambert; Stamm, Benjamin;
    Publisher: Zenodo

    ddEigenLab.jl: Domain-Decomposition Eigenvalue Problem Lab

  • Publication . Book . 2021
    Open Access French
    Authors: 
    Balsells, M. Àngeles; Biehal, Nina; Chapon, Nathalie; Chervaz Dramé, Mireille; Coum, Daniel; Demierre, Nathalie; Fuentes-Peláez, Nuria; Lambert, Marie-France; Milani, Paola; Pastor, Crescencia; +7 more
    Publisher: Presses universitaires de Provence

    À partir de la question centrale de la parentalité d’accueil, nous avons souhaité comprendre, confronter, comparer les approches dans les différents pays européens en matière de protection de l’enfance et plus particulièrement en accueil familial. Comment en Europe se déclinent les dispositifs de prise en charge en protection de l’enfance et de la famille ? Quels sont les choix retenus et favorisés ? Quelles sont les politiques familiales et les mesures choisies pour les familles et les enfants ? Nous verrons que l’Europe est riche d’une variété de choix politiques en protection de l’enfance, de mesures de prise en charge allant du placement en institution à celui en famille d’accueil ou en famille élargie, ou d’un statut professionnel à celui de bénévole. Le croisement européen ouvre le dialogue permettant une meilleure compréhension des choix politiques, institutionnels et des pratiques dans les différents pays. L’accueil familial est une réponse possible qui se décline en différentes versions selon les 9 pays étudiés (France, Luxembourg, Suisse, Allemagne, Espagne, Italie, Belgique (Wallonie-Bruxelles et Flandre, Pays-Pas, Angleterre).

Advanced search in
Research products
arrow_drop_down
Searching FieldsTerms
Author
arrow_drop_down
includes
arrow_drop_down
Include:
8 Research products, page 1 of 1
  • Open Access
    Authors: 
    Theisen, Lambert;
    Publisher: figshare

    All P3 basis functions and an attached WolframScript to generate the same plots for arbitrary Pm elements.

  • Publication . Preprint . Article . 2020
    Open Access
    Authors: 
    Lambert Theisen; Manuel Torrilhon;
    Publisher: Association for Computing Machinery (ACM)

    We present a mixed finite element solver for the linearized R13 equations of non-equilibrium gas dynamics. The Python implementation builds upon the software tools provided by the FEniCS computing platform. We describe a new tensorial approach utilizing the extension capabilities of FEniCS's Unified Form Language (UFL) to define required differential operators for tensors above second degree. The presented solver serves as an example for implementing tensorial variational formulations in FEniCS, for which the documentation and literature seem to be very sparse. Using the software abstraction levels provided by the UFL allows an almost one-to-one correspondence between the underlying mathematics and the resulting source code. Test cases support the correctness of the proposed method using validation with exact solutions. To justify the usage of extended gas flow models, we discuss typical application cases involving rarefaction effects. We provide the documented and validated solver publicly. Comment: 29 pages, 13 figures, 8 listings, 3 table. Submitted to ACM Transactions on Mathematical Software (TOMS)

  • Open Access
    Authors: 
    Theisen, Lambert; Stamm, Benjamin;
    Publisher: Zenodo

    ddEigenLab.jl: Domain-Decomposition Eigenvalue Problem Lab

  • Open Access
    Authors: 
    Lambert Theisen; Benjamin Stamm;
    Publisher: Society for Industrial & Applied Mathematics (SIAM)

    This paper provides a provably quasi-optimal preconditioning strategy of the linear Schr\"odinger eigenvalue problem with periodic potentials for a possibly non-uniform spatial expansion of the domain. The quasi-optimality is achieved by having the iterative eigenvalue algorithms converge in a constant number of iterations for different domain sizes. In the analysis, we derive an analytic factorization of the spectrum and asymptotically describe it using concepts from the homogenization theory. This decomposition allows us to express the eigenpair as an easy-to-calculate cell problem solution combined with an asymptotically vanishing remainder. We then prove that the easy-to-calculate limit eigenvalue can be used in a shift-and-invert preconditioning strategy to bound the number of eigensolver iterations uniformly. Several numerical examples illustrate the effectiveness of this quasi-optimal preconditioning strategy. Comment: 29 pages, 9 figures, 2 tables

  • Open Access English
    Authors: 
    Theisen, Lambert; Torrilhon, Manuel;
    Publisher: Zenodo

    fenicsR13: A Tensorial Mixed Finite Element Solver for the Linear R13 Equations Using the FEniCS Computing Platform The project can be accessed at https://git.rwth-aachen.de/lamBOO/fenicsR13

  • Open Access
    Authors: 
    Theisen, Lambert; Stamm, Benjamin;
    Publisher: Zenodo

    This work was supported by the German Research Foundation (DFG) under project 411724963. ddEigenLab.jl: Domain-Decomposition Eigenvalue Problem Lab

  • Open Access
    Authors: 
    Theisen, Lambert; Stamm, Benjamin;
    Publisher: Zenodo

    ddEigenLab.jl: Domain-Decomposition Eigenvalue Problem Lab

  • Publication . Book . 2021
    Open Access French
    Authors: 
    Balsells, M. Àngeles; Biehal, Nina; Chapon, Nathalie; Chervaz Dramé, Mireille; Coum, Daniel; Demierre, Nathalie; Fuentes-Peláez, Nuria; Lambert, Marie-France; Milani, Paola; Pastor, Crescencia; +7 more
    Publisher: Presses universitaires de Provence

    À partir de la question centrale de la parentalité d’accueil, nous avons souhaité comprendre, confronter, comparer les approches dans les différents pays européens en matière de protection de l’enfance et plus particulièrement en accueil familial. Comment en Europe se déclinent les dispositifs de prise en charge en protection de l’enfance et de la famille ? Quels sont les choix retenus et favorisés ? Quelles sont les politiques familiales et les mesures choisies pour les familles et les enfants ? Nous verrons que l’Europe est riche d’une variété de choix politiques en protection de l’enfance, de mesures de prise en charge allant du placement en institution à celui en famille d’accueil ou en famille élargie, ou d’un statut professionnel à celui de bénévole. Le croisement européen ouvre le dialogue permettant une meilleure compréhension des choix politiques, institutionnels et des pratiques dans les différents pays. L’accueil familial est une réponse possible qui se décline en différentes versions selon les 9 pays étudiés (France, Luxembourg, Suisse, Allemagne, Espagne, Italie, Belgique (Wallonie-Bruxelles et Flandre, Pays-Pas, Angleterre).

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