Le Journal De Physique Colloques 

About: Le Journal De Physique Colloques is an academic journal. The journal publishes majorly in the area(s): Amorphous solid & Grain boundary. Over the lifetime, 8177 publications have been published receiving 38539 citations.

The mechanism of the long spark formation

Abstract: The aim of this paper is to present the state of the art of the research on the physics of long sparks. The reference configuration is a non uniform long gap subjected to positive impulse voltages, which is the laboratory schematization of the most critical conditions occurring in the design of EHV apparatus. Under these conditions, the spark formation develops through different subsequent phases : the inception of the first ionization phenomena, the development of corona streamers, the formation of the corona stem and of the leader channel, the leader propagation, the time-evolution of the leader characteristics, the appearance of channel reilluminations, the final jump and the transition to the highly conductive spark channel. Each phase is governed by a complex interaction of electromagnetic, hydrodynamic and thermodynamic elementary processes. Each chapter of the paper presents both the experimental results and the theoretical models which have been obtained for each single phase. In recent years a number of sophisticated measuring systems have been used to study the local conditions of the different discharge phases (space charge distribution, electric field, electron energy, gas temperature and density, etc...) : the first part of each chapter presents a summary of these experimental results, in order to define the physical conditions under which the discharge develops, and to select the elementary phenomena which appear to be dominant. The second part of each chapter presents the different theoretical models, which have been obtained by simplifying the basic electromagnetic, hydrodynamic and thermodynamic equations, according to the dominant phenomena. The good agreement between computed and experimental results, over a large variety of test conditions, certify the large steps forward, which have been taken in the last years by the research on the physics of long sparks. The final objective, i.e. the formulation of a complete breakdown model, able to predict the discharge features in all the possible practical configurations, starting from the physics of the elementary phenomena, is not yet realized, but it appears as a realistic possibility of the further development of the research in this area.

Techniques de renormalisation de la théorie des champs et dynamique des phénomènes critiques

Abstract: La dynamique des phenomenes critiques telle qu'elle est decrite par les equations stochastiques de type Ginzburg-Landau dependant du temps, avec ou sans loi de conservation, est etudiee par les techniques de renormalisation de la theorie des champs. Le cas des systemes comportant un couplage mode-mode est brievement aborde.

Bertlmann's socks and the nature of reality

Abstract: The Einstein-Podolsky-Rosen correlations are very like many ordinary occurrences of everyday life. So it is a little difficult for the man in the street to understand immediately why there has been so much fuss about them. It must be recalled that the founding fathers of quantum mechanics had convinced themselves that it was necessary to abandon the idea of an objective reality at the microphysical level. But the correlations in question, together with the idea of local causality, were a formidable argument for such a reality. The founding fathers offered counter-arguments (neither very clear nor very convincing in my opinion) and each side held to its position. Since then it has been possible to push the analysis a little further, considering especially situations just a little different from those considered before. Then correlations appear, according to quantum mechanics, which are not at all like those of everyday life. As a result it is not now easy to believe, with Einstein, that quantum mechanical predictions are reconcilable with the notion of a Lorentz invariant objectively real microphysical world.

Un attracteur étrange (?) du type attracteur de hénon

Abstract: ), par iteration de cette application, soit diverge soit converge vers un attracteur etrange, qui apparait etre le produit d'une variete a une dimension par un ensemble de Cantor. Nous proposons une autre application pour laquelle l'attrac-teur obtenu parait plus simple, en ce sens qu'il semble etre le produit de segments de droites par un ensemble de Cantor. Abstract. — In [1] M. Henon and Y. Pomeau have defined a map from the plane to itself. The sequence of points obtained by iteration of the mapping either diverges or converges towards a strange attractor, which appears to be the product of a one-dimensional manifold by a Cantor set. We propose an other mapping for which the attractor seems to be more simple in that sense that it seems to be the product of parts of straight lines by a Cantor set.