Publications

2000

• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Homogenization of a spectral problem in neutronic multigroup diffusion
  
  • Allaire Grégoire
  • Capdeboscq Yves
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2000, 187 (1-2), pp.91--117. This paper is concerned with the homogenization of an eigenvalue problem in a periodic heterogeneous domain for the multigroup neutron diffusion system. Such a model is used for studying the criticality of nuclear reactor cores. We prove that the first eigenvector of the multigroup system in the periodicity cell controls the oscillatory behaviour of the solutions, whereas the global trend is asymptotically given by a homogenized diffusion eigenvalue problem. The neutron flux, corresponding to the first eigenvector of the multigroup system, tends to the product of the first periodic and homogenized eigenvectors. This result justifies and improves the engineering procedure used in practice for nuclear reactor core computation. (10.1016/S0045-7825(99)00112-7)
  DOI : 10.1016/S0045-7825(99)00112-7
• Polar IFS + Parisian GP = Efficient IFS inverse problem solving
  
  • Collet Pierre
  • Lutton Evelyne
  • Raynal Frédéric
  • Schoenauer Marc
  Genetic Programming and Evolvable Machines, Springer Verlag, 2000, 1 (4), pp.339-361. The inverse problem for Iterated Functions Systems (finding an IFS whose attractor is a target 2D shape) with non-affine IFS is a very complex task. Successful approaches have been made using Genetic Programming, but there is still room for improvement in both the IFS and the GP parts. This paper introduces Polar IFS: a specific representation of IFS functions which shrinks the search space to mostly contractive functions and gives direct access to the fixed points of the functions. On the evolutionary side, the ``Parisian'' approach is presented. It is similar to the ``Michigan'' approach of Classifier Systems: each individual of the population only represents a part of the global solution. The solution to the inverse problem for IFS is then built from a set of individuals. Both improvements show a drastic cut-down on CPU-time: good results are obtained with small populations in few generations.
• Convergence Analysis of a Schwarz Type Domain Decomposition Method for the Solution of the Euler Equations
  
  • Dolean V.
  • Lanteri Stephane
  • Nataf Frédéric
  , 2000, pp.45. we report on a preliminary convergence analysis of a domain decomposition method for solving the Euler equations for compressible flows. This method was previously described in Dolean and Lanteri. It relies on the formulati- on of an additive Schwarz type algorithm on a non-overlapping decomposition of the computational domain. According to the hyperbolic nature of the Euler equations, the transmission conditions that are set at subdomain interfaces, express the conservation of the normal flux. In [3], this method is assessed experimentally in the context of a flow solver which is based on a mixed finite volume/finite element formulation on unstructured triangular meshes. Here, we study the convergence of the proposed method in the two- and three-dimensional cases, and for a two-subdomain decomposition, by considering the linearized equations and applying a Fourier analysis. In doing so, we observe that in spite of the fact that we use simple transmission conditions, the method converges and demonstates, for particular flow conditions, an optimal convergence rate. Various numerical experiments allow to exhibit at least qualitatively, the convergence behavior obtained analytically.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.
• Images du Virtuel
  
  • Colonna Jean-François
  , 2000. Images calculees lors d'experiences virtuelles a partir de modeles mathematiques de systemes physiques.