Variational Formulation and Upper Bounds for Degenerate Scales in Plane Elasticity

International audienceDegenerate scales appear when certain plane boundary value problems solved using Boundary Integral Equations do not have a unique solution. The main contribution of this paper is to prove four inequalities that constrain the degenerate scales for plane elasticity. These results are based on a new variational formulation. It is shown that the degenerate scales depend only on Poisson’s ratio. The bounds on the degenerate scales for plane elasticity in a given boundary are obtained mainly from the degenerate scales obtained from the Laplace equation for the same boundary, which are well documented

A Gurson-type model accounting for void size effects

AbstractIn this paper we present an extension of the Gurson model of cavity growth which includes the void size effect. To this end, we perform the limit analysis of a hollow sphere made up of a Fleck and Hutchinson’s strain gradient plasticity material. Based on the trial velocity field of Gurson, we derive an approximate closed form expression of the macroscopic criterion. The latter incorporates the void size dependency through a non dimensional parameter defined as the ratio of the cavity radius and the intrinsic length of the plastic solid. The accuracy of this approximate criterion is demonstrated by its comparison with numerical data. In the last part of the paper we present a complete plasticity model involving the damage rate and a power-law strain hardening of the matrix. It is shown that the cavity size effect has a strong dependency on damage growth as well as on the stress strain response

The Notion of the “Matrix”: New Perspectives in Group Psychotherapy for Psychotic Patients

International audienceFollowing on from the work of Foulkes (1964), we propose in thisarticle to take up the concept of ‘group matrix’. We set out to providenew clinical–theoretical perspectives via the notion of group as‘envelope’ elaborated by Anzieu (1975). This formulation will provideus with a canvas within which to apprehend the organizational andstructural evolution of a therapeutic group for chronic psychoticpatients. We will suggest models of the networks forming the matrixand the texture of the psychic envelope of the group. The aim is tobring out the peculiarities of the matrix in this type of group as wellas its impact on the psychic positioning of the therapist and on his/her therapeutic work within the group

Mise en groupe, psychose et porosité des enveloppes psychiques

International audienceNous proposons d’étudier les processus psychiques du thérapeute durant la période de mise en groupe dans le cadre d’un groupe psychanalytique de paroles mené dans un service d’ergo-sociothérapie avec des patients psychotiques adultes. Le but est de montrer que les premiers temps d’un groupe thérapeutique ont pour effet de modifier la texture des enveloppes psychiques du clinicien, qui vont tendre vers une plus grande porosité. Après avoir défini ce que nous entendons par « porosité des enveloppes psychiques », nous présenterons la façon dont nous envisageons la position psychique du thérapeute en situation de groupe, puis nous reviendrons sur les deux premières séances du groupe psychanalytique de paroles. Les résultats de notre recherche nous permettront d’aller plus loin dans la définition du positionnement psychique du thérapeute en situation de groupe, de son cadre interne et de sa position dite « méta »

The psychotic transference in groups

International audienceWe wish to present a study of psychotic transference in groups, following on from the work of W.R. Bion and Foulkes. We put forward the hypothesis that in the early stages of such a therapeutic group, group psychotic transference oscillates between expansive movements and restrictive movements. This will be expressed by a tendency of the patients to withdraw, either exclude himself, or engage in an undifferentiated way. To illustrate our premise, we will rely on the analysis of the early stages of a psychoanalytic psychodrama session conducted in a hospital unit. The results will enable us to rethink the therapeutic stakes for this type of treatment

Green functions and associated sources in infinite and stratified poroelastic media

International audienceThe purpose of this paper is to study Green functions for porous saturated media and to present an example of numerical simulation using these Green functions. In the first part the equations of the porous media are recalled and the principal results concerning the features of the waves are given. The second part is devoted to the determination of sources and Green functions. We give the analytical solution, then we study some of its properties. In the third part we focus on the construction of synthetic seismograms. We show examples of bi-dimensional computation in a semi-infinite stratified porous medium, for a double dipole or a fluid injection

Multi-scale acoustics of partially open cell poroelastic foams

International audienceThe present paper reports on the modeling of linear elastic properties of acoustically insulating foams with unit cells containing solid films or membranes at the junction between interconnected pores from a numerical homogenization technique. It combines fluid-flow induced microstructure identification with simulations of the effective Young's modulus and Poisson ratio from a mixture of routinely available laboratory measurements (porosity, permeability, cell size) and finite element calculations when the boundary conditions of the periodic unit cell take particular symmetric forms. This combination results in microstructural determination of the macroscopic coefficients entering into the Biot-Allard theory of wave propagation and dissipation through porous media. Precise control over pore morphology and mechanical properties of the base material renders this multi-scale approach particularly suitable for various advanced applications

A non-parametric probabilistic model for soil-structure interaction

International audienceThe paper investigates the effect of soil-structure interaction on the dynamic response of structures. A non-parametric probabilistic formulation for the modelling of an uncertain soil impedance is used to account for the usual lack of information on soil properties. Such a probabilistic model introduces the physical coupling stemming from the soil heterogeneity around the foundation. Considering this effect, even a symmetrical building displays a torsional motion when submitted to earthquake loading. The study focuses on a multi-story building modeled by using equivalent Timoshenko beam models which have different mass distributions. The probability density functions of the maximal internal forces and moments in a given building are estimated by Monte Carlo simulations. Some results on the stochastic modal analysis of the structure are also given

Sollicitations sismiques dues aux exploitations minières : amplification des ondes en surface (et vibrations des structures)

National audienceL'objectif de ce travail est d'analyser l'impact des secousses induites par les exploitations minières sur les structures situées en surface. Du fait des conditions géologiques locales, le mouvement créé par les secousses peut parfois être amplifié de façon importante en surface (effet de site). A partir d'une modélisation numérique du problème, l'amplification du mouvement est analysée pour différentes formes de remplissages sédimentaires et des contrastes de propriétés entre couches variables. Les valeurs de fréquences fondamentales (i.e amplification maximale) sont comparées à des résultats antérieurs

Patrick Charaudeau, La conquête du pouvoir. Opinion, persuasions, valeur. Les discours d’une nouvelle donne politique

Relevant institutionnellement des sciences du langage, les recherches de Patrick Charaudeau sont bien identifiées dans le champ des sciences de l’information et de la communication. Analyste du discours, ce dernier s’est de longue date et résolument engagé dans les voies d’une interdisciplinarité « focalisée » (Questions de communication, 17, 2010, pp. 195-222), suscitant dans cet espace de nombreux échos et ce, tant au plan théorique que via des travaux analytiques plus spécialisés. Le disco..