30,422 research outputs found
Stabilization of low-order cross-grid <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="mml43" display="inline" overflow="scroll" altimg="si43.gif"><mml:msub><mml:mrow><mml:mi>P</mml:mi></mml:mrow><mml:mrow><mml:mi>k</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>Q</mml:mi></mml:mrow><mml:mrow><mml:mi>l</mml:mi></mml:mrow></mml:msub></mml:math> mixed finite elements
No full textIn this paper we analyze a low-order family of mixed finite element methods for the numerical solution of the Stokes problem and a second order elliptic problem, in two space dimensions. In these schemes, the pressure is interpolated on a mesh of rectangular elements, while the velocity is approximated on a triangular mesh obtained by dividing each rectangle into four triangles by its diagonals. For the lowest order P1Q0, a global spurious pressure mode is shown to exist and so this element, as P1Q1 case analyzed in Armentano and Blasco (2010), is unstable. However, following the ideas given in Bochev et al. (2006), a simple stabilization procedure can be applied, when we approximate the solution of the Stokes problem, such that the new P1Q0 and P1Q1 methods are unconditionally stable, and achieve optimal accuracy with respect to solution regularity with simple and straightforward implementations. Moreover, we analyze the application of our P1Q1 element to the mixed formulation of the elliptic problem. In this case, by introducing the modified mixed weak form proposed in Brezzi et al. (1993), optimal order of accuracy can be obtained with our stabilized P1Q1 elements. Numerical results are also presented, which confirm the existence of the spurious pressure mode for the P1Q0 element and the excellent stability and accuracy of the new stabilized methods.Fil: Armentano, Maria Gabriela. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentin
Interpolation in Jacobi-weighted spaces and its application to a posteriori error estimations of the p-version of the finite element method
No full textThe goal of this work is to introduce a local and a global interpolator in Jacobi-weighted spaces, with optimal order of approximation in the context of the p-version of finite element methods. Then, an a posteriori error indicator of the residual type is proposed for a model problem in two dimensions and, in the mathematical framework of the Jacobi-weighted spaces, the equivalence between the estimator and the error is obtained on appropriate weighted norm.Fil: Armentano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Moreno, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentin
Maria Bersani
No full textLa voce illustra la biografia e l'apporto letterario dato da Maria Bersani alla letteratura per l'infanziaThe headword explains the biography and the contribution of the author Maria Bersani to the children's literatur
Interpolación en espacios de Jacobi con pesos y su aplicación a estimaciones de error a posteriori para la versión p del método de elementos finitos
No full textEn este trabajo introducimos un interpolador local y global en espacios de Jacobi-Sobolev con pesos, con orden de aproximación óptimo en el contexto de la versión p del método de elementos finitos. Luego, para un problema modelo en dos dimensiones, proponemos un estimador a posteriori del error y mostramos la equivalencia entre el estimador y el error en una norma con pesos adecuada.Fil: Armentano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Moreno, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaV Congreso de Matemática Aplicada, Computacional e IndustrialTandilArgentinaAsociación Argentina de Matemática Aplicada, Computacional e Industria
Plasma surface modification of porous PLLA films: Analysis of surface properties and in vitro hydrolytic degradation
No full textThe aim of this research was to investigate the effects of plasma treatment on the surface and on the in vitro degradation behavior of poly(L-lactide) (PLLA) films. Polymer films were prepared by solvent casting, and their surface was modified by radiofrequency plasma treatments by using oxygen and tetrafluorocarbon gas. Pristine and treated PLLA films were characterized by field emission and atomic force microscopy and by contact angle measurements. In vitro hydrolytic degradation studies were conducted by measurements of weight loss, water absorption, visual inspection, and thermal transitions as a function of the incubation time. As-deposited PLLA films show a uniform distribution of ring-like porous structures on the surface due to solvent evaporation. Plasma treatments produce a mass reduction following the etching of the polymer surface. Moreover, the morphology of the porous polymer is modified by the plasma, which induces different micro/nanometric topographic reliefs as a function of the different selected plasma processing parameters. The results indicate PLLA surface become hydrophilic and the surface roughness increased with treatment time in the case of oxygen, whereas a hydrophobic behavior was induced with tetrafluorocarbon plasma treatment. However, in vitro degradation studies show that plasma treatments do not affect the PLLA bulk and the hydrolytic degradation properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 201
DIACOM-fr - Banca dati terminologica
No full textDIACOM-fr est une banque de données terminologiques de type diachronique consacrée à la terminologie du commerce. Elle vise la description des multiples propriétés diachroniques, sémantiques, syntaxiques, etc. des termes, par le biais d’une représentation de type réseau terminologique
Approximations by mini mixed finite element for the Stokes-Darcy coupled problem on curved domains
No full textIn this work we solve a Stokes-Darcy coupled problem in a plane curved domain using curved elements. We approximate the velocity-pressure pair by applying the MINI-element method, for the whole coupled problem. We show that, under appropriate assumptions about the curved domain, the proposed method has optimal accuracy, with respect to solution regularity, and has a simple implementation. We also present numerical tests which show the good performance of the proposed method.Fil: Armentano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; ArgentinaFil: Stockdale, María Lorena. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Variations on the Author
No full text“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
A posteriori error estimates of stabilized low-order mixed finite elements for the Stokes eigenvalue problem
No full textIn this paper we obtain a priori and a posteriori error estimates for stabilized low-order mixed finite element methods for the Stokes eigenvalue problem. We prove the convergence of the method and a priori error estimates for the eigenfunctions and the eigenvalues. We define an error estimator of the residual type which can be computed locally from the approximate eigenpair and we prove that, up to higher order terms, the estimator is equivalent to the energy norm of the error. We also present some numerical tests which show the performance of the adaptive scheme.Fil: Armentano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Moreno, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentin
Finite element approximations in a non-lipschitz domain: part II
No full textIn a paper by R. Dur ́ an, A. Lombardi, and the authors (2007) the finite element method was applied to a non-homogeneous Neumann problem on a cuspidal domain Ω ⊂ R 2 , and quasi-optimal order error estimates in the energy norm were obtained for certain graded meshes. In this paper, we study the error in the L 2 norm obtaining similar resul ts by using graded meshes of the type considered in that paper. Since many classical results in the theory Sobolev spaces do not apply to the domain under consideration, our estimates require a particular duality treatment working on appropriate weighted spaces. On the other hand, since the discrete domain Ω h verifies Ω ⊂ Ω h ,inthe above-mentioned paper the source term of the Poisson problem was taken equal to 0 outside Ω in the variational discrete formulation. In this article we also consider the case in which this condition does not hold and obtain more general estimates, which can be useful in different problems, for instance in the study of the effect of numerical integration, or in eigenvalue approximations.Fil: Acosta, Gabriel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; ArgentinaFil: Armentano, Maria Gabriela. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentin
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