936 research outputs found
Mauersegler weiter Wege. Mathias Enard: Kompass
No full textAnalysis of the peculiar scientific narrative in the novel of the Prix-Goncourt winning author Mathias Enard
Les commissions électorales en Afrique de l'Ouest
No full text[author: Mathias Hounkpe ; Ismaila Madior Fall]Electronic ed.: Abuja ; Bonn : FES, 201
Higher order space-time finite element methods on evolving and fixed domains: applied to the Navier-Stokes equations and wave problems
No full textIn this work, various aspects of space-time finite element discretizations for the Navier-Stokes equations and wave problems are investigated.
First, an overview of the current state of the science is given in Chapter 1 and the notation is introduced in Chapter 2.
Then, in Chapter 3, flow problems on time-dependent domains are studied.
These play a major role in engineering practice, for example in the simulation of fluid-structure interaction problems, such as the interaction of a fluid with a rotor.
In this work, rigid bodies moving in a viscous fluid described by the time-dependent Navier-Stokes equations are considered as an example problem for this purpose.
This means that the flow area changes depending on the position of the rigid body.
A classical way to simulate such problems is the Arbitrary-Lagrangian-Eulerian method (ALE method), which is based on the transformation of the flow domain to a reference mesh.
This transformation has the disadvantage that it is computationally intensive, can induce nonlinearities, and also, for larger deformations of the flow domain, an update of the underlying computational grid is inevitable.
Further, such a remeshing is again computationally expensive and usually means that all matrices and vectors of the underlying simulation have to be rebuilt.
In this work, a method is presented in which all computations are performed on a fixed background grid that can be arbitrarily cut by the rigid body.
This method is called the Cut Finite Elmenent Method (CutFEM).
A prerequisite for an implementation is to be able to integrate functions over arbitrarily cut cells in order to be able to assemble the underlying system matrices and vectors.
To accomplish this, a flexible method was developed, based on the iterated application of 1d integrals.
In the case of cells that become very small, if they are cut by the rigid body, unphysical steep gradients of the solution arise in these cells.
These result in poor conditioning of the system matrix and numerical instabilities.
To circumvent the problem, a so-called "ghost penalty" stabilization was implemented, which constrains the gradients and makes the method robust.
Furthermore, the stabilization operator implicitly propagates the flow solution into the entire rigid-body domain.
This allows all calculations to be performed on a fixed, time-independent background grid.
All aspects mentioned so far have been verified in numerical convergence tests and simulations.
Then, in Chapter 4, a geometric multigrid method for higher order finite element space-time discretizations of the Navier-Stokes equations is then implemented for time-independent domains.
The method is based on a Vanka smoother, which dampens high-frequency error components over all space-time degrees of freedom in each time step.
All major parts of our code are implemented in parallel using the Message Passing Interface (MPI).
The multigrid method, used in this work, is verified by simulating the 3d DFG benchmark "flow around a cylinder", with more than 96 million space-time degrees of freedom per time step.
Adapting the method to problems with time-dependent domains in conjunction with CutFEM results in increased iteration counts, depending on the size of the rigid body.
The causes of this are analyzed and investigated numerically in this work.
In Chapter 5 classical continuous finite element methods for time discretization are combined with collocation methods to obtain efficient higher order methods in time, which also result in a discrete solution of higher regularity.
Such Galerkin-Collocation methods are developed and applied first for the wave equation and then for the Navier-Stokes equations.
Compared to traditional continuous finite element time discretizations, we could significantly increase the time step size with these methods, while maintaining the same quality of the solution.
Especially in coupled problems, methods of this type could be advantageous if coefficients of the derivative of one problem are included in the problem description of the other problem.N
Paul Bourget, écrivain engagé
No full textPaul Bourget, A committed writer, Yehoshua Mathias.
In the France of the early twentieth century, Paul Bourget's figure is that of a successful novelist who became gradually a «committed author». A monarchist, deeply conservative, passionate defender of religion and the family as the vital bases of the social order, he thus became the bard of the bourgeois ethic faced with the destabilization of modernity.Mathias Yehoshua. Paul Bourget, écrivain engagé. In: Vingtième Siècle, revue d'histoire, n°45, janvier-mars 1995. pp. 14-29
„Nature must be felt“ – Alexander von Humboldt, pioneer of an ecological worldview and protagonist of „transversal reason“
No full textDer Text erinnert zum 250sten Geburtsjahr an Alexander von Humboldt, ein Vordenker für eine ökologische Sicht der Welt und ein früher Protagonist „transversaler Vernunft“. Er ist als Ideengeber für die „neuen Naturtherapien“, für die Integrative Therapie und für eine ökologische Sicht in der Psychotherapie eine unverzichtbare Quelle. Einige aus dieser Perspektive wichtige Aspekte seines Denkens und Werkes werden aufgezeigt. Er ist ein Referenzautor für transversales und integratives Konzeptualisieren in unserer Zeit.The text commemorates the 250th year of birth of Alexander von Humboldt, a thought leader for an ecological view of the world and an early protagonist of „transversal reason“. He is an indispensable source of ideas for the „new nature therapies“, for integrative therapy and for an ecological viewpoint in psychotherapy. Some important aspects of his thinking and work are shown from this perspective. He is a reference author for transversal and integrative conceptualization in our time.https://www.fpi-publikation.de/gruene-texte/17-2019-petzold-h-g-mathias-wiedemann-u-natur-muss-gefuehlt-werden-alexander-v-humboldt/peerReviewedpublishedVersio
„Natur muss gefühlt werden“ – Alexander von Humboldt, Vordenker einer ökologischen Weltsicht und Protagonist „transversaler Vernunft“
No full textDer Text erinnert zum 250sten Geburtsjahr an Alexander von Humboldt, ein Vordenker für eine ökologische Sicht der Welt und ein früher Protagonist „transversaler Vernunft“. Er ist als Ideengeber für die „neuen Naturtherapien“, für die Integrative Therapie und für eine ökologische Sicht in der Psychotherapie eine unverzichtbare Quelle. Einige aus dieser Perspektive wichtige Aspekte seines Denkens und Werkes werden aufgezeigt. Er ist ein Referenzautor für transversales und integratives Konzeptualisieren in unserer Zeit.The text commemorates the 250th year of birth of Alexander von Humboldt, a thought leader for an ecological view of the world and an early protagonist of „transversal reason“. He is an indispensable source of ideas for the „new nature therapies“, for integrative therapy and for an ecological viewpoint in psychotherapy. Some important aspects of his thinking and work are shown from this perspective. He is a reference author for transversal and integrative conceptualization in our time.https://www.fpi-publikation.de/polyloge/25-2019-petzold-h-g-mathias-wiedemann-u-natur-muss-gefuehlt-werden-alexander-v-humboldt/peerReviewedpublishedVersio
The reality of fiction: the ECO by Mathias Goeritz
No full textAbstract
This article covers the full biography of a building, the Experimental Museum El Eco, designed by Germanborn and Mexican émigré artist and architect Mathias Goeritz. It provides an approach intersecting the biography of the author, the history of the building, and prominent individuals of the two cultural traditions, German and Mexican, who participated in the creation of a very special and unique building: El Eco. On the one hand, the ethics of Expressionism, the interest in non-European art, the cult of primitivism and the aesthetic system of the pair of concepts abstraction-empathy, all stemming from German culture. On the other, the pantheistic religiosity of landscape, zoomorphism and anthropomorphism, the interest in masks, and the aesthetics of monumental scale, stemming from pre-Cortesian Mexican culture. Taking the stance of intertwining Mathias Goeritz parcours with those of individuals and issues from his German past and his Mexican future – highlighting the figures of Wilhelm Worringer, Paul Westheim, Luis Barragán, Edmundo O'Gorman, and Ida Rodríguez Prampolini – this article proposes a return trip from fiction to reality, following in the footsteps of the author and comparing them with the pathway of the very building El Eco
Efficiency of local Vanka smoother geometric multigrid preconditioning for space-time finite element methods to the Navier-Stokes equations
No full textThis article is licensed under the terms of the Creative Commons Attribution-NonCommercial License (https://creativecommons.org/licenses/by-nc/4.0/).Vo
Oswald Mathias Ungers and Sol LeWitt: Variations
No full textOne of the fundamentals of Oswald Mathias Ungers work is the definition of a new unity between art and architecture. What this investigation is focused on is the identification of the intersection point between art and architecture, considering the project for the Entrance to the Kaiserthermen in Trier (20032007) as case study, revealing the system of theoretical, methodological and compositional correspondences. Plastic art is Ungers' main interlocutor: one of the author's most important references is Sol LeWitt (1928-2007), an artist he admired and collected. Setting the work of Oswald Mathias Unger and Sol LeWitt side by side, offers the opportunity to underline the shared interpretation that the two authors have of the world of forms postulated by Henri Focillon (1881-1943) in Life of Forms, according to which form, autonomous with respect to time and place, has its own universe, governed by its own laws, space and matter. According to these premises, we propose to read Trier's building through the instruments of art, following the hypothesis that in this project art embodies a creative and positive component in the definition of architecture, a cultural stimulus that guides the author in the design process
CutFEM and ghost stabilization techniques for higher order space-time discretizations of the Navier-Stokes equations
No full textWe propose and analyze computationally a new fictitious domain method, based
on higher order space-time finite element discretizations, for the simulation
of the nonstationary, incompressible Navier-Stokes equations on evolving
domains. The physical domain is embedded into a fixed computational mesh such
that arbitrary intersections of the moving domain's boundaries with the
background mesh occur. The potential of such cut finite element techniques for
higher order space-time finite element methods has rarely been studied in the
literature so far and deserves further elucidation. The key ingredients of the
approach are the weak formulation of Dirichlet boundary conditions by Nitsche's
method, the flexible and efficient integration over all types of intersections
of cells by moving boundaries and the spatial extension of the discrete
physical quantities to the entire computational background mesh including
fictitious (ghost) subdomains of fluid flow. Thereby, an expensive remeshing
and adaptation of the sparse matrix data structure are avoided and the
computations are accelerated. To prevent spurious oscillations caused by
irregular intersections of mesh cells, a penalization, defining also implicitly
the extension to ghost domains, is added. These techniques are embedded in an
arbitrary order, discontinuous Galerkin discretization of the time variable and
an inf-sup stable discretization of the spatial variables. The parallel
implementation of the matrix assembly is described. The optimal order
convergence properties of the algorithm are illustrated in a numerical
experiment for an evolving domain. The well-known 2d benchmark of flow around a
cylinder as well as flow around moving obstacles with arising cut cells and
fictitious domains are considered further
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