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Champs-sur-Marne, France

Dobson M.,CERMICS ENPC | Luskin M.,University of Minnesota | Ortner C.,Mathematical Institute
Computer Methods in Applied Mechanics and Engineering

Force-based atomistic-continuum hybrid methods are the only known pointwise consistent methods for coupling a general atomistic model to a finite-element continuum model. For this reason, and due to their algorithmic simplicity, force-based coupling methods have become a popular class of atomistic-continuum hybrid models as well as other types of multiphysics models. However, the recently discovered unusual stability properties of the linearized force-based quasicontinuum (QCF) approximation, especially its indefiniteness, present a challenge to the development of efficient and reliable iterative methods.We present analytic and computational results for the generalized minimal residual (GMRES) solution of the linearized QCF equilibrium equations. We show that the GMRES method accurately reproduces the stability of the force-based approximation and conclude that an appropriately preconditioned GMRES method results in a reliable and efficient solution method. © 2010 Elsevier B.V. Source

Al Haj M.,CERMICS ENPC | Forcadel N.,University of Paris Dauphine | Monneau R.,CERMICS ENPC
Archive for Rational Mechanics and Analysis

In this article, we study the existence and the uniqueness of traveling waves for a discrete reaction-diffusion equation with bistable nonlinearity, namely a generalization of the fully overdamped Frenkel-Kontorova model. This model consists of a system of ODEs which describes the dynamics of crystal defects in lattice solids. Under very weak assumptions, we prove the existence of a traveling wave solution and the uniqueness of the velocity of propagation of this traveling wave. The question of the uniqueness of the profile is also studied by proving Strong Maximum Principle or some weak asymptotics on the profile at infinity. © 2013 Springer-Verlag Berlin Heidelberg. Source

Noumir Y.,Ecole Normale Superieure de Cachan | Le Guilcher A.,CERMICS ENPC | Lardjane N.,CEA DAM Ile-de-France | Monneau R.,CERMICS ENPC | Sarrazin A.,CERMICS ENPC
Journal of Computational Physics

We develop a new algorithm for the computation of the Geometrical Shock Dynamics (GSD) model. The method relies on the fast-marching paradigm and enables the discrete evaluation of the first arrival time of a shock wave and its local velocity on a Cartesian grid. The proposed algorithm is based on a first order upwind finite difference scheme and reduces to a local nonlinear system of two equations solved by an iterative procedure. Reference solutions are built for a smooth radial configuration and for the 2D Riemann problem. The link between the GSD model and p-systems is given. Numerical experiments demonstrate the efficiency of the scheme and its ability to handle singularities. © 2014 Elsevier Inc.. Source

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