Solving the stationary Liouville equation via a boundary element method

Intensity distributions of linear wave fields are, in the high frequency limit, often approximated in terms of flow or transport equations in phase space. Common techniques for solving the flow equations for both time dependent and stationary problems are ray tracing or level set methods. In the context of predicting the vibro-acoustic response of complex engineering structures, reduced ray tracing methods such as Statistical Energy Analysis or variants thereof have found widespread applications. Starting directly from the stationary Liouville equation, we develop a boundary element method for solving the transport equations for complex multi-component structures. The method, which is an improved version of the Dynamical Energy Analysis technique introduced recently by the authors, interpolates between standard statistical energy analysis and full ray tracing, containing both of these methods as limiting cases. We demonstrate that the method can be used to efficiently deal with complex large scale problems giving good approximations of the energy distribution when compared to exact solutions of the underlying wave equation

Une innovation en contentieux administratif français: la protection des libertés fondamentales par la procédure du référé-liberté

Une innovation en contentieux administratif français: la protection des libertés fondamentales par la procédure du référé-libert

América latina: el estado de las ciencias sociales.

En esta ponencia se introducen temas que son relevantes a la sociología especialmente aplicada en América Latina. También se observa un auge de temas culturales, unas mutaciones de violencia en sus diferentes formas, un gran desarrollo de flujos y redes tradicionales. Además el autor trata de enfatizar en los diferentes movimientos como: la globalización, identidad en América latina, migraciones transnacionales, socialismo del siglo XXI (con Chávez) y por último el movimiento de los Latinos en EE.UU

The Right of access to the courts under the State of emergency in France

International audienceThe measures taken under the State of emergency regime generate important effects for individuals and can create significant limitations of fundamental rights. Therefore, the rule of law implies the intervention of a judge to exercise a control. This issue has two dimensions: one the one hand, the right to a constitutional judge and, on the other hand, the right to an ordinary judge

Geometrical theory of diffraction for sound radiation and structural response

International audienceThis study focuses on geometrical theory of diffraction (GTD) applied to vibroacoustics with a particular emphasis to fluid-structure interaction. Six types of hybrid rays are identified travelling either from structure-to-fluid (sound radiation) or from fluid-to-structure (structural response). Three rays correspond to sound radiation by the surface, edge, or corner of a structure while the three others are the reciprocal paths corresponding to sound-to-vibration conversion by the surface, edge, or corner. We present the calculation of geometrical properties of wavefronts (principal directions and curvatures) and their laws of transformation during an interaction process. Furthermore, some simple explicit relationships for diffraction coefficients are given under the light fluid assumption. Finally, two examples are discussed to illustrate the concepts. The first one is a pure radiation problem while the second one involves transmission through walls, structural response and sound radiation

The Right of access to the courts under the State of emergency in France

International audienceThe measures taken under the State of emergency regime generate important effects for individuals and can create significant limitations of fundamental rights. Therefore, the rule of law implies the intervention of a judge to exercise a control. This issue has two dimensions: one the one hand, the right to a constitutional judge and, on the other hand, the right to an ordinary judge

Relaxation Tribometry: A Generic Method to Identify the Nature of Contact Forces

Recent years have witnessed the development of so-called relaxation tribometers, the free oscillation of which is altered by the presence of frictional stresses within the contact. So far, analysis of such oscillations has been restricted to the shape of their decaying envelope, to identify in particular solid or viscous friction components. Here, we present a more general expression of the forces possibly acting within the contact , and retain six possible, physically relevant terms. Two of them, which had never been proposed in the context of relaxation tribometry, only affect the oscillation frequency, not the amplitude of the signal. We demonstrate that each of those six terms has a unique signature in the time-evolution of the oscillation, which allows efficient identification of their respective weights in any experimental signal. We illustrate our methodology on a PDMS sphere/glass plate torsional contact

Dynamical energy analysis on mesh grids: a new tool for describing the vibro-acoustic response of complex mechanical structures

We present a new approach for modelling noise and vibration in complex mechanical structures in the mid-to-high frequency regime. It is based on a dynamical energy analysis (DEA) formulation which extends standard techniques such as statistical energy analysis (SEA) towards non-diffusive wave fields. DEA takes into account the full directionality of the wave field and makes sub-structuring obsolete. It can thus be implemented on mesh grids commonly used, for example, in the finite element method (FEM). The resulting mesh based formulation of DEA can be implemented very efficiently using discrete flow mapping (DFM) as detailed in [1] and described here for applications in vibro-acoustics

Du social au territorial, du territorial au social : l'Etat, l'industrie de la chaussure et les districts en France au XXème siècle.

Communication présentée au XVème Congrès International d'Histoire Economique à Utrecht (Pays-Bas) le 5 août 2009.La problématique des districts industriels (expression prise ici au sens large) a surgi au cœur des sciences humaines et sociales lorsque la crise économique des années 1970, et les décennies de dépression consécutives, ont fait vaciller le modèle du gigantisme industriel fordien. Les pouvoirs publics des pays développés et, pour ce qui nous intéresse, les français, ont cherché des alternatives et des remèdes à travers un intérêt renouvelé porté aux PME et aux territoires industrialisés dédiés à des productions spécifiques. Dans la longue durée, cette dimension n'est pas nouvelle, puisqu'elle vient s'inscrire dans l'histoire du rôle mobilisateur auquel s'astreint l'Etat durant le XXe siècle en matière économique et sociale. La question posée ici est celle des voies suivies par l'action publique en matière de mobilisation des ressources ; l'approche se fera à travers l'exemple d'une industrie, celle de la chaussure, qui a connu de manière plus ou moins parallèle ou successive, c'est selon, le développement de deux types de configurations : des concentrations géographiques de PME (Fougères, Romans, Limoges, Cholet, etc.), des concentrations usinières et en groupes (les Chaussures André, etc.). Nous montrerons que l'Etat dans sa recherche d'institutions partenaires, pour assurer sa prise sur l'économie, s'avère dans l'obligation impérative de prendre en compte les reconfigurations du système productif, sans forcément y réussir

Direct numerical simulation of the dynamics of sliding rough surfaces

The noise generated by the friction of two rough surfaces under weak contact pressure is usually called roughness noise. The underlying vibration which produces the noise stems from numerous instantaneous shocks (in the microsecond range) between surface micro-asperities. The numerical simulation of this problem using classical mechanics requires a fine discretization in both space and time. This is why the finite element method takes much CPU time. In this study, we propose an alternative numerical approach which is based on a truncated modal decomposition of the vibration, a central difference integration scheme and two algorithms for contact: The penalty algorithm and the Lagrange multiplier algorithm. Not only does it reproduce the empirical laws of vibration level versus roughness and sliding speed found experimentally but it also provides the statistical properties of local events which are not accessible by experiment. The CPU time reduction is typically a factor of 10.Comment: 16 pages, 16 figures, accepted versio