Philippe JEAN-PIERRE

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• Type de publi. :
• Date de publi. : 15/09/2004
• Auteurs : Jacques J. RangerJ-D. NzilaBernhard ZellerJean-Paul LaclauJean-Pierre BouilletPhilippe DeleporteJudicaël MoukoumiJ-H. JussyJ-N. Marien
• Organismes : Unité de recherche Biogéochimie des Ecosystèmes Forestiers Unité de recherche Biogéochimie des Ecosystèmes Forestiers UMR INRA / ENSAM : Rhizosphère et Symbiose UMR INRA / ENSAM : Rhizosphère et Symbiose

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• Type de publi. : Article dans une revue
• Date de publi. : 11/09/2004
• Auteurs : Eric ChassefièreJean-Loup BertauxJean-Jacques BerthelierMichel CabaneValérie CiarlettiGeorges DurryFrançois ForgetMichel HamelinFrançois LeblancMichel MenvielleM. GerasimovOleg KorablevS. LinkinG. ManagadzeA. JambonG. ManhèsPhilippe LognonnéP. AgrinierPierre CartignyD. GiardiniT. PikeW. KofmanA. HeriquePatrice CollA. PersonF. M. CostardPhilippe SardaPhilippe PaillouM. ChaussidonBernard MartyFlorent RobertS. MauriceM. BlancC. d'UstonJ.-Ch. SabrouxJ.-F. PineauPierre Rochette
• Organismes : Service d'aéronomie Service d'aéronomie Centre d'étude des environnements terrestre et planétaires Service d'aéronomie Service d'aéronomie Service d'aéronomie Service d'aéronomie Service d'aéronomie Service d'aéronomie Service d'aéronomie Space Research Institute of the Russian Academy of Sciences Space Research Institute of the Russian Academy of Sciences Space Research Institute of the Russian Academy of Sciences Space Research Institute of the Russian Academy of Sciences Institut de Physique du Globe de Paris Institut de Physique du Globe de Paris Institut de Physique du Globe de Paris Institut de Physique du Globe de Paris Institut de Physique du Globe de Paris Institut für Informationssysteme Imperial College London Laboratoire de Planétologie de Grenoble Laboratoire de Planétologie de Grenoble Laboratoire Interuniversitaire des Systèmes Atmosphériques Université Pierre et Marie Curie - Paris 6 Université Paris-Sud, Université Paris-Sud, Observatoire aquitain des sciences de l'univers Centre de Recherches Pétrographiques et Géochimiques Centre de Recherches Pétrographiques et Géochimiques Laboratoire de minéralogie Observatoire Midi-Pyrénées Observatoire Midi-Pyrénées Observatoire Midi-Pyrénées Institut de Radioprotection et de Sûreté Nucléaire Institut de Radioprotection et de Sûreté Nucléaire Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement
• Publié dans Advances in Space Research le 26/10/2020

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Résumé : In view to prepare Mars human exploration, it is necessary to promote and lead, at the international level, a highly interdisciplinary program, involving specialists of geochemistry, geophysics, atmospheric science, space weather, and biology. The goal of this program will be to elaborate concepts of individual instruments, then of integrated instrumental packages, able to collect exhaustive data sets of environmental parameters from future landers and rovers of Mars, and to favour the conditions of their implementation. Such a program is one of the most urgent need for preparing human exploration, in order to develop mitigation strategies aimed at ensuring the safety of human explorers, and minimizing risk for surface operations. A few main areas of investigation may be listed: particle and radiation environment, chemical composition of atmosphere, meteorology, chemical composition of dust, surface and subsurface material, water in the subsurface, physical properties of the soil, search for an hypothesized microbial activity, characterization of radio-electric properties of the Martian ionosphere. Scientists at the origin of the present paper, already involved at a high degree of responsibility in several Mars missions, and actively preparing in situ instrumentation for future landed platforms (Netlander - now cancelled, MSL-09), express their readiness to participate in both ESA/AURORA and NASA programs of Mars human exploration. They think that the formation of a Mars Environment working group at ESA, in the course of the AURORA definition phase, could act positively in favour of the program, by increasing its scientific cross-section and making it still more focused on human exploration. © 2004 Published by Elsevier Ltd on behalf of COSPAR.

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• Type de publi. : Communication dans un congrès
• Date de publi. : 07/09/2004
• Auteurs : Pierre-Alain GuidaultO. AllixLaurent ChampaneyJean-Philippe Navarro
• Organismes : Laboratoire de Mécanique et Technologie Laboratoire de Mécanique et Technologie Laboratoire d'Etudes Mécaniques des Assemblages Dassault Aviation

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Résumé : Today, structural analysis involving cracking is being reconsidered in the light of emerging new methods, such as the Strong Discontinuity Approach (SDA) introduced by Simo, Oliver and Armero. Other approaches, such as the eXtended Finite Element Method (XFEM) and the Generalized Finite Element Method (GFEM), make use of the Partition of Unity Method (PUM) first introduced by Melenk and Babuška in 1996. By enabling one to enrich the kinematics of continuous media, these techniques allow the introduction of discontinuities into the displacement field using only a relatively small number of degrees of freedom. One of the main advantages in this case is that the mesh does not have to conform to the crack's geometry. These techniques greatly simplify the meshing and remeshing processes which, despite the improvement of meshing tools, remain tedious tasks for engineers confronted with crack propagation situations. However, these techniques do not completely incorporate the multiscale aspect induced by the localization of strains in the cracked zone. Generally, they require further remeshing around the crack: thus, the remeshing problem is only partially resolved. Moreover, conditioning difficulties remain because of the treatment of multiscale phenomena without separation. To overcome these two difficulties, the strategy we developed in cooperation with Dassault Aviation is based on a two-scale approach in which the enrichment is introduced on the microscale. The process involved is a combination of two techniques. The first technique stems from work done at LMT-Cachan, which has been developing computational strategies with a strong mechanical meaning which makes them efficient. More precisely, this technique consists in applying the recently developed micro-macro approach based on a homogenization technique. The microscale is associated with local phenomena which occur around the crack. This is a much smaller scale than the macroscale, which corresponds to the whole structure. This multiscale approach ensures a correct global-local interaction between the macroscale and the microscale. The second technique, known as the PUM, is used to define a proper representation of the local solution (in terms of discontinuity and solution at the crack's tip) on the microscale. The integration of enrichment functions is obtained by the XFEM. With this scale separation, the macroproblem keeps the same structure throughout the calculation while the whole numerical effort is directed towards the microlevel. In the micro-macro approach, the fact that a crack affects both the local level and the global level raises the question of the kinematics and the description of forces on the two scales. The simplest solution consists in keeping the "usual" macroscopic description. Some examples showing the feasibility, but also the disadvantages, of such a method are presented. Consequently, different means of enriching the macroscale to improve the description of the macrokinematics are studied and illustrated. The integration of the PUM on the microlevel will be the subject of a subsequent paper.

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• Type de publi. : Article dans une revue
• Date de publi. : 02/09/2004
• Auteurs : Nicolas BrunelVincent HakimPhilippe IsopeJean-Pierre NadalBoris Barbour
• Organismes : Neurophysique et physiologie du système moteur Laboratoire de Physique Statistique de l'ENS Laboratoire de Neurobiologie (UMR 8544) Laboratoire de Physique Statistique de l'ENS Laboratoire de Neurobiologie (UMR 8544)
• Publié dans Neuron le 01/11/2020

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Résumé : It is widely believed that synaptic modifications underlie learning and memory. However, few studies have examined what can be deduced about the learning process from the distribution of synaptic weights. We analyze the perceptron, a prototypical feedforward neural network, and obtain the optimal synaptic weight distribution for a perceptron with excitatory synapses. It contains more than 50% silent synapses, and this fraction increases with storage reliability: silent synapses are therefore a necessary byproduct of optimizing learning and reliability. Exploiting the classical analogy between the perceptron and the cerebellar Purkinje cell, we fitted the optimal weight distribution to that measured for granule cell-Purkinje cell synapses. The two distributions agreed well, suggesting that the Purkinje cell can learn up to 5 kilobytes of information, in the form of 40,000 input-output associations.

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• Type de publi. : Article dans une revue
• Date de publi. : 01/09/2004
• Auteurs : Aude SimonWilliam JonesJean-Michel OrtegaPierre BoisselJoël LemairePhilippe Maıtre
• Organismes : Laboratoire de Chimie Physique D'Orsay Laboratoire de Chimie Physique D'Orsay Laboratoire pour l'utilisation du rayonnement électromagnétique Laboratoire de Chimie Physique D'Orsay Laboratoire de Chimie Physique D'Orsay Laboratoire de Chimie Physique D'Orsay
• Publié dans Journal of the American Chemical Society le 30/10/2020

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• Type de publi. : Article dans une revue
• Date de publi. : 01/09/2004
• Auteurs : Jean-Philippe DeguinePierre Ferron
• Organismes : Centre de Coopération Internationale en Recherche Agronomique pour le Développement Chercheur indépendant
• Publié dans Le Courrier de l'environnement de l'INRA le 30/10/2020

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Résumé : L’importance des dégâts occasionnés aux cultures et aux denrées stockées par divers organismes nuisibles ou concurrents, encore dénommés bio-agresseurs (ravageurs, micro-organismes et virus, mauvaises herbes), contraint l’agriculteur à recourir à des mesures de protection. Parmi celles-ci, la lutte chimique à l’aide de pesticides de synthèse a longtemps été considérée comme la solution la plus efficace et la plus facile à mettre en œuvre, dans des conditions économiques supportables, du moins par une agriculture de type productiviste. Cependant ses effets secondaires sur l’environnement et la santé ne s’avèrent pas compatibles avec une exploitation durable des agro-écosystèmes. Des solutions alternatives sont donc recherchées, une prévention accrue des risques étant considérée aujourd’hui comme un préalable nécessaire. On est ainsi conduit à concevoir une stratégie phytosanitaire nouvelle, reposant d’abord sur la gestion agro-écologique des populations et des peuplements. Cette stratégie remet en cause les pratiques courantes, implique une adaptation des systèmes de culture et une prise en considération rationnelle à l’échelle du paysage, comme une sensibilisation des praticiens aux problèmes environnementaux. Pour permettre un retour à une situation d’équilibre, elle demande non seulement un raisonnement à court terme, cher aux praticiens, mais également une réflexion à long terme telle que celle recommandée par les écologistes. Une illustration en culture cotonnière paysanne en est donnée.

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• Type de publi. : Article dans une revue
• Date de publi. : 01/09/2004
• Auteurs : Valérie-Gaëlle RoullinMartine MegeLaurent LemaireJean-Pierre CueyssacM.-C. Venier-JuliennePhilippe MeneiErik GamelinJean-Pierre Benoit
• Organismes : Micro et Nanomédecines Translationnelles Micro et Nanomédecines Translationnelles Micro et Nanomédecines Translationnelles Service de neurochirurgie [CHU Angers] Micro et Nanomédecines Translationnelles
• Publié dans Pharmaceutical Research le 02/11/2020

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Résumé : To determine (i) the efficiency of radiosensitizing 5-FU-loaded microspheres and (ii) the impact of microparticle formulation on response to treatment.

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• Type de publi. : Article dans une revue
• Date de publi. : 01/09/2004
• Auteurs : Pierre-Philippe CombesThierry MagnacJean-Marc Robin
• Organismes : Groupement de Recherche en Économie Quantitative d'Aix-Marseille Equipe Universitaire de Recherche en Economie Quantitative Centre de Recherche en Économie et Statistique
• Publié dans Journal of Urban Economics le 31/10/2020

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Résumé : We study the impact of local economic structure on employment dynamics. Local employment is decomposed into the product of the average plant size and the number of plants in the area and industry. We estimate the dynamics of both components simultaneously using French yearly data on 36 industries and 341 areas between 1984 and 1993. The careful specification of short-run dynamics and the control for fixed effects and endogeneity are shown to be critical in the empirical model. First, static externalities are prevalent compared to dynamic ones. Moreover, whereas area-and-industry effects explain most of the spatial variation of plant size, the local number of plants is mainly driven by the current local economic structure. Policies targeted towards plant creation should thus be more efficient. For instance, large areas endowed with a small number of even size industries have both more and larger plants. A large number of plants heterogeneous in size also increases the average plant size, but the number of plants is higher when plants have similar size.

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• Type de publi. : Communication dans un congrès
• Date de publi. : 31/08/2004
• Auteurs : Philippe DessusEric Allègre
• Organismes : Laboratoire des Sciences de l'Éducation (Grenoble) Centre de Recherches en Education Formation et Insertion de Toulouse

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Fichiers liés : aecse04.PDF

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• Type de publi. : Communication dans un congrès
• Date de publi. : 14/08/2004
• Auteurs : Dominique PlansonDominique TournierJean-Pierre ChantePascal BevilacquaChristophe RaynaudPhilippe GodignonJ MillanX JordaJ-F de Palma
• Organismes : Centre de génie électrique de Lyon Institut National des Sciences Appliquées de Lyon Centre de génie électrique de Lyon Centro Nacional de Microelectronica [Spain] Institut National des Sciences Appliquées de Lyon Centre de génie électrique de Lyon Institut National des Sciences Appliquées de Lyon Centre de génie électrique de Lyon Institut National des Sciences Appliquées de Lyon Centre de génie électrique de Lyon Institut National des Sciences Appliquées de Lyon Centro Nacional de Microelectronica [Spain] Centro Nacional de Microelectronica [Spain] Centro Nacional de Microelectronica [Spain] Ferraz-Shawmut

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Résumé : The expansion of electricity networks (distribution of energy, telecommunication), strongly contributed to increase the risks of appearance of defects, such as surge or overload. This multiplicity and complexity of electric networks, the need to have reliable systems favoured the development of serial protection devices. Fuse solution allows an efficient and total protection but requires to replace an element in case of failure. Therefore, other solutions have been investigated. Complex systems have been developed, all based on serial compensation, such as supra-conductor material, GTO MOV combination ... Indeed, because of the strong energy appearance during a short circuit, it is necessary to limit and to dissipate the energy of the short circuit, under high bias. This constraint leads to a feasibility study of a current limiter in 4H silicon carbide (4H-SiC). A VJFET structure was retained focusing on a nominal current of IN = 1 A and a nominal voltage of VN = 690 V. The device was optimised, taking into account SiC excellent physical properties. The VJFET was designed checking the trade-off between a low on-resistance value, high voltage capability and the highest gate transconductance value. A first batch of component was made, validating the bi-directional limitation function in both current and voltage mode, (VMAX = 970 V). The efficiency of the protection was validated, demonstrating the capacity of a component to react very quickly (t < 1 µs). Using such a device is very suitable in several applications (protection against short circuit, transient over current…) as it will allow to reduce transient phenomena and thus increase the efficiency and lifetime of the whole system.

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Fichiers liés : paper_ipemc2004.pdf

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