Introduction

C’est dans les échafaudages tubulaires de l’église de Saint-Nectaire qu’est née, le 14 mars 2002, ma collaboration scientifique avec Bruno Phalip. Nos stimulants échanges autour des problématiques d’érosion-conservation-restauration des monuments historiques n’ont cessé depuis lors, sur des terrains divers, de l’abbatiale de Manglieu dans le Puy-de-Dôme au temple de Ta Keo à Angkor en passant par l’enceinte chypriote de Famagouste. Ces échanges scientifiques ont souvent débordé le cadre acad..

Enrichissement du profil utilisateur à partir de son réseau social dans un contexte dynamique : application d'une méthode de pondération temporelle

International audienceLe profil de l’utilisateur est un élément central dans les systèmes d’adaptation de l’information. Les réseaux sociaux numériques représentent une source d'informations très riche sur l’utilisateur. Nous nous intéressons au processus d’enrichissement du profil utilisateur à partir de son réseau social. Ce processus extrait les intérêts de l’utilisateur à partir des individus dans son réseau égocentrique afin de construire la dimension sociale du profil de l'utilisateur. Afin de prendre en compte le caractère dynamique des réseaux sociaux, nous proposons, dans ce travail, de construire cette dimension sociale en intégrant un critère temporel afin de pondérer les intérêts de l’utilisateur. Ce poids "temporel", qui reflète la pertinence d’un intérêt, est calculé, d’une part, à partir de la pertinence des individus du réseau égocentrique de l’utilisateur en prenant en compte la fraicheur de leurs liens avec l’utilisateur et, d’autre part, à partir de la pertinence des informations qu’ils partagent en prenant en compte la fraicheur de ces informations. Les expérimentations sur les réseaux de publicationsscientifiques DBLP et Mendeley ont permis de montrer montrer que notre proposition fournit des résultats plus satisfaisants que ceux du processus existant

Time-aware Egocentric network-based User Profiling

International audienceImproving the egocentric network-based user's profile building process by taking into account the dynamic characteristics of social networks can be relevant in many applications. To achieve this aim, we propose to apply a time-aware method into an existing egocentric-based user profiling process, based on previous contributions of our team. The aim of this strategy is to weight user's interests according to their relevance and freshness. The time awareness weight of an interest is computed by combining the relevance of individuals in the user's egocentric network (computed by taking into account the freshness of their ties) with the information relevance (computed by taking into account its freshness). The experiments on scientific publications networks (DBLP/Mendeley) allow us to demonstrate the effectiveness of our proposition compared to the existing time-agnostic egocentric network-based user profiling process

Regards croisés du géographe et de l’archéologue du bâti sur l’état de santé du patrimoine médiéval du Massif central

Le présent article constitue la première pierre posée à un édifice qui prend forme dans le cadre du programme de recherche pluridisciplinaire sur la durabilité des matériaux du patrimoine roman en grès, conduit sur un territoire allant du Bourbonnais à la Limagne de Brioude. Certains monuments présentent des signes inquiétants de dégradation qu’il convient d’interpréter dans un dialogue étroit entre le géographe spécialiste de l’érosion des matériaux rocheux et l’archéologue du bâti qui est en mesure de décrypter et de dater les étapes successives de la vie d’un bâtiment. Seront évoqués ici les formes et les causes naturelles ou anthropiques de la détérioration de la pierre, ainsi que les effets pervers de certaines restaurations des Monuments Historiques qui ont assez paradoxalement accéléré la dégradation du patrimoine médiéval roman du Massif central.This paper is the first stone laid on a building that is taking shape as part of the multidisciplinary research program on the Romanesque sandstone heritage materials sustainability, led on a territory spreading-out from the Bourbonnais to the Brioude Limagne plain. Some monuments show worrying signs of degradation that should be interpreted in a close dialogue between the geographer specializing in the erosion of rock materials and the building archaeologist who is able to decipher and date the successive stages of a building life. The forms and natural or anthropogenic causes of stone deterioration will be discussed here, as well as the perverse effects of several Historical built Heritage restorations that have paradoxically accelerated the degradation of the medieval Romanesque heritage in the Massif Central

Chronique polaire

Depuis 1954, les lecteurs fidèles de Norois ont régulièrement rendez-vous avec la chronique des hautes latitudes arctiques initiée et alimentée pendant dix ans par Charles-Pierre Péguy, Jean Corbel et Pierre Biays. À leur suite, Alice Saunier-Picard publiera une douzaine de chroniques de 1966 à 1973. Annick Moign et Jean-Claude Bodéré lui succéderont jusqu’en 1984, épaulés à partir de 1982 par François Carré et Thierry Simon. Pendant plus de dix ans, après la disparition tragique d’Annick Moi..

DISCUSSION ON THE COMPOSITION AND TRANSPORT COEFFICIENTS CALCULATION MADE IN PLASMA OUT OF EQUILIBRIUM

International audienceIn this paper, the composition calculation in plasma out of thermal equilibrium is discussed and we test the viscosity formulations of Wilke, Gupta et al, Chapman Enskog and Sutherland in air plasma out of thermal equilibrium. Finally we applied the formulations to Fire II reentry

Comparative Study between kinetic and thermodynamic calculation of composition in SF6 Plasmas

For an SF6 plasma at atmospheric pressure the compositions calculated in chemical equilibrium, in the multi-temperature model and using kinetics (33 reactions involving 18 species) are compared. The ratio of the electron temperature Te to that of heavy species Th was calculated as a function of electron density and an intermediate temperature T* between Te and Th was introduced to cope with the relationship kf(T*) / kr(T*) = Kx(T*) where kf and kr are the reaction rate coefficients (forward and reverse) and Kx the equilibrium constant. The main difference between equilibrium and kinetic calculations lies in the densities of S+, S2+, SF+, F- and S- species between 2000 and 6000 K. The multi-temperature method gives results very different from those of the kinetic calculations even when neglecting the charge loss reactions. This is in contrast to what happens with H2 or N2

Calculation of combined diffusion coefficients from the simplified theory of transport properties

The aim of this study is to check if it is possible to use the combined diffusion coefficients introduced by Murphy at equilibrium in a two-temperature model (electron temperature Te different from that of heavy species Th) such as that denned by Devoto or Bonnefoi for transport properties. Murphy's coefficients describe the diffusive mixing of two non reactive ionized gases while the Devoto's or Bonnefoi's simplified theories allow the calculation of transport coefficients (except diffusion) out of thermal equilibrium. It has to be noticed that in the latter case when Te tends towards Th, the results are those obtained with an equilibrium calculation. The two-temperature (2-T) theory of transport properties was established by separating electrons and other species because of their mass difference. First, the exact combined diffusion coefficients of Murphy are calculated for an Ar-N2 (50wt%) mixture at atmospheric pressure. Then, expressions of combined diffusion coefficients are obtained using the simplified theory of Bonnefoi. The results of the calculation of combined diffusion coefficients from the simplified theory of transport properties, assuming equilibrium is achieved (Te=Th), is compared with those of Murphy at equilibrium. It is shown that large discrepancies occur when ionization is important. These results prove that the simplified 2-T theory cannot be used for the treatment of diffusion. Thus, a new theory of transport coefficients has to be developed taking into account the coupling of electrons and heavy species and work is in progress

New method to derive transport properties including diffusion in a two-temperature plasma

A new derivation of transport properties in a two-temperature plasma has been performed. The electron kinetic temperature Te is supposed to be different from that of heavy species Th. The resolution of the Boltzmann's equation, thanks to the Chapman-Enskog method, is used to calculate transport coefficients and it allows to the generalisation ofbracket integrals out of thermal equilibrium. Two-temperature diffusion coefficients are defined and the obtained results are presented for an atmospheric two-temperature argon plasma

Transport Coefficients in non equilibrium argon-hydrogen thermal plasmas

Transport coefficients in non-equmbrium argon-hydrogen thermal plasmas, where the kinetic temperature of electrons Te is different from that of heavy species Th, are calculated at atmospheric pressure from a recent theoretical approach of Rat et al. The latter consists in deriving transport properties in thermal plasmas from the solution of the Boltzmann's equation according to the Chapmann Enskog method keeping the coupling between electrons and heavy species. Plasma composition is obtained from a non equilibrium constant method and a stationnary kinetic calculation. First, electrical and translational thermal conductivities are compared with those evaluated with the simplified theory of transport properties of Devoto and Bonnefoi. Non-neglible discrepancies occur reaching more than 30% and 40% respectively for the electrical and electron thermal conductivities at Te= 15000 K for theta = 2. Second, the dependence with Te of electrical and total thermal conductivities (including translational, internal and reactional contributions) and viscosity is examined as a function of the method of calculation of plasma composition and the non-equilibrium parameter theta= Te /Th . It is emphasized that non-equilibrium transport coefficients are strongly dependent on the method of plasma composition