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FEM-BEM coupling methods for tokamak plasma axisymmetric free-boundary equilibrium computations in unbounded domains
No full textIncorporating boundary conditions at infinity into simulations on bounded computational domains is a repeatedly occurring problem in scientific computing. The combination of finite element methods (FEM) and boundary element methods (BEM) is the obvious instrument, and we adapt here for the first time the two standard FEM-BEM coupling approaches to the free-boundary equilibrium problem: the Johnson-Nédélec coupling and the Bielak-MacCamy coupling. We recall also the classical approach for fusion applications, dubbed according to its first appearance von-Hagenow-Lackner coupling and present the less used alternative introduced in [AlbaneseEtAL1986]. These methods are compared through numerical experiments. We show that the von-Hagenow-Lackner coupling suffers from non-optimal approximations properties, and, moreover, that such coupling methods require Newton-like iteration schemes, for solving the corresponding non-linear discrete algebraic systems.La prise en compte des conditions aux limites à l’ infini dans les simulations sur des domaines de calcul bornes est un problème récurrent en calcul scientifique. Pour ce faire le couplage de la méthode des éléments finis (FEM) avec celle des éléments de frontière (BEM) est l’outil naturel. Nous adaptons ici pour la première fois les deux approches standards de couplage FEM-BEM pour le problème de l’équilibre du plasma: le couplage de Johnson-Nedelec et celui de Bielak-MacCamy. Nous rappelons également l’approche classique dans les codes de fusion, baptisée selon sa première apparition couplage de von-Hagenow-Lackner et présentons l’alternative moins utilisée introduite dans [AlbaneseEtAL1986]. Ces m´méthodes sont comparées au travers d’expériences numériques. Nous montrons que le couplage von-Hagenow-Lackner souffre d’une convergence non-optimale et, en outre, que de telles méthodes de couplage nécessitent l’utilisation de schémas itératifs de type Newton, pour résoudre les systèmes algébriques discrets non linéaires correspondants
La politique de concurrence comme levier de la politique industrielle dans la France de l’après-guerre
No full textInternational audienceThe establishment of the cartels technical commission in 1953, seems to prefigure theGerman competition law and the Treaty of Rome four years later. However some differences haveto be put into relief. First, it does not participate to a defence of competition law based order asthe German ordo-liberals promoted at that time. Second, the collusive practices targeted mainlyconcerned bid-rigging practices in public procurement in the reconstruction and modernisationplans. If this competition policy contrasts with war experiences and the interwar period argumentsfor a regulated competition, sanctioning horizontal collusion makes sense within an industrial policymodel based on a close co-operation between Government and some national championsAvec la création en 1953 de la Commission technique des ententes, lapolitique de concurrence française précède la loi sur la concurrence allemande et letraité de Rome. Cependant, la principale préoccupation ne tenait pas, à l’inverse decelle des ordo-libéraux allemands, dans la préservation d’un ordre concurrentiel maisaux défis posés par des comportements collusifs horizontaux, notamment dans lesmarchés publics liés au plan de reconstruction et d’équipement. Si cette politiquecontrastait avec les traditions dirigistes héritées des expériences des économies deguerre ou avec les approches planistes, favorables aux ententes entre firmes au nomde l’efficience productive, elle était motivée par une conception d’une politique industriellefondée sur une étroite coopération entre les administrations et les futurs championsnationau
A Discontinuous Galerkin Time Domain Method for Plasmonics with a Nonlocal Dispersion Model
No full textInternational audience— We present recent advances of the development on Discontinuous Galerkin Time Domain (DGTD) solvers for computational nanophotonics, focusing on metallic nanostructures irradiated by laser pulses. By this means, we firstly discuss an analytical nonlocal dispersion model for the electron gas which is necessary in order to account for spatial dispersion for structures of the size of 2 nm to 25 nm. Subsequently, we deal with the numerical modeling of this nonlocal model when coupled to 3D Maxwell's equations in time domain. We conclude by assessing our implementation with analytical solutions and provide selected numerical examples
The Multiscale Hybrid Mixed method for time dependent propagation of electromagnetic waves
No full textInternational audienc
Robustness in spatial analysis: the example of the generalized center optimal location
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As palavras, o texto, os corpora e arquivo: o historiador face à linguística. Logometria e análise do discurso
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Note sous l’arrêt de la 1ère chambre civile de la Cour de cassation du 1er février 2017
No full textNote d'arrêt (caractère solidaire de l’obligation au paiement des frais et honoraires des arbitres
On the Progenitor of Binary Neutron Star Merger GW170817
No full textInternational audienceOn 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy’s center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy’s star formation history, provided the stellar populations are older than 1 Gyr
Relativistic Localizing Processes Bespeak an Inevitable Projective Geometry of Spacetime
No full textInternational audienceSurprisingly, the issue of events localization in spacetime is poorly understood and a fortiori realized even in the context of Einstein’s relativity. Accordingly, a comparison between observational data and theoretical expectations might then be strongly compromised. In the present paper, we give the principles of relativistic localizing systems so as to bypass this issue. Such systems will allow locating users endowed with receivers and, in addition, localizing any spacetime event. These localizing systems are made up of relativistic autolocating positioning subsystems supplemented by an extra satellite. They indicate that spacetime must be supplied everywhere with an unexpected local four-dimensional projective structure besides the well-known three-dimensional relativistic projective one. As a result, the spacetime manifold can be seen as a generalized Cartan space modeled on a four-dimensional real projective space, that is, a spacetime with both a local four-dimensional projective structure and a compatible (pseudo-)Riemannian structure. Localization protocols are presented in detail, while possible applications to astrophysics are also considered
