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Search Results: 1 - 10 of 2112 matches for " Courty Ph. "
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Procédés de mise en forme des catalyseurs Catalyst Forming Process
Courty Ph.,Duhaut P.
Oil & Gas Science and Technology , 2006, DOI: 10.2516/ogst:1974036
Abstract: Cet article vise à rassembler et à donner une vue d'ensemble des principaux rocédés de mise en forme des catalyseurs et des techniques élémentaires que ces procédés utilisent. The aim of this article is ta gather and give on overview of the leading catalyst orming processes and the elementary techniques used by these processes.
Méthodes générales de synthèse des catalyseurs à base d'oxydes General Synthesis Methods for Mixed Oxide Catalysts
Courty Ph.,Marcilly C.
Oil & Gas Science and Technology , 2006, DOI: 10.2516/ogst:1978005
Abstract: De nombreux procédés industriels (industrie céramique, électronique, nucléaire catalyse hétérogène) utilisent des matériaux constitués d'oxydes mixtes. Les études fondamentales réalisées en catalyse et leurs applications industrielles montrent qu'au-delà des diverses interprétations fines de l'activité catalytique des oxydes mixtes, une notion plus générale se dégage, celle de l'homogénéité de la phase active, donc du premier intermédiaire de fabrication du catalyseur (le précurseur). Les différentes méthodes de synthèse des oxydes mixtes, puis des catalyseurs, sont alors exposées. Pour chacune d'entre elles, il est montré comment l'obtention d'un précurseur homogène peut être favorisée et maintenue. Un exemple illustre le cas de l'oxyde mixte déposé sur support. Finalement, l'étape de mise en forme de l'oxyde mixte est évoquée, l'aspect économique de la fabrication du catalyseur conclut ce texte. A great mony industrial processes (ceramics, electronics, nuclear energy, hererogeneous catalysis) use materials made up of mixed oxides. Fundamental research on catalysis and its industrial applications has shown that, over and beyond the various subtle interpretations of the catalytic activity of mixed oxides, a more general concept emerges, i. e. that of the homogeneity of the active phase, hence of the first catalyst-manufacturing intermediate (the precursor). Different synthesis methods for mixed oxides, and then for cotalysts, are described. The demonstration is made for each of them how the production of a homogeneous precursor con be enhanced and maintained. An example illustrotes the case of a mixed oxide deposited on a carrier. To conclude, the shaping of the mixed oxide is described, followed by the economic aspect of catalyst manufacturing.
Bases scientifiques de la préparation des catalyseurs constitués d'oxydes mixtes massiques Scientific Bases for the Preparation of Bulk Mixed Oxide Catalysts
Courty P.,Marcilly C.
Oil & Gas Science and Technology , 2006, DOI: 10.2516/ogst:1984026
Abstract: Cette étude de la préparation des oxydes mixtes massiques et de leur mise en régime dans le milieu réactionnel concerne les différentes méthodes de synthèse utilisées et précise quelles sont les lois générales qui régissent chaque étape unitaire de la préparation (séparation d'un précurseur hydraté, lavage, transformations hydrothermiques, séchage, activation thermique, addition d'autres éléments, mise en forme). De nombreux exemples révèlent la diversité des transformations observées. L'oxyde mixte activé thermiquement est lui-même le précurseur d'autres oxydes mixtes, de métaux ou d'alliages divisés, de sulfures, de nitrures ou de carbures simples ou mixtes. Ces composés se forment lors de la stabilisation du catalyseur dans le milieu réactionnel, au cours d'une transformation complexe et spécifique du type de réaction envisagé. Divers exemples (oxydation ménagée, déshydrogénation, synthèse d'alcools) sont donnés. Une caractérisation systématique et rigoureuse de chaque intermédiaire réactionnel est finalement nécessaire pour préciser les lois plus ou moins empiriques qui régissent l'évolution des propriétés superficielles et massiques de texture, de structure et de composition, au cours des transformations successives du solide ; le procédé de préparation et de mise en régime optimisé qui en résulte doit enfin satisfaire aux impératifs techniques et économiques du procédé catalytique correspondant. This study of the preparation of bulk mixed oxides and of their stabilization into the reaction medium deals with the different synthesis methods used and gives some general laws governing each specific type of preparation (separation of a hydrated precursor, washing, hydrothermal transformations, drying, thermal activation, addition of other elements, shaping). Numerous examples reveal the diversity of the transformations observed. The thermally activated mixed oxide becomes itself the precursor of other mixed oxides, divided metals or alloys, sulfides, nitrides or simple or mixed carbides. These compounds are formed when the catalyst is stabilized in the reaction medium during a complex transformation which is often specific to the type of reaction considered. Various examples (mild oxidation, dehydrogenation, synthesis of alcohols) are given. Finally, a systematic and strict characterisation of each reaction intermediate is required for specifying the more or less empirical laws governing the evolution of the superficial and bulk properties of texture, structure and composition during the successive transformations of the solid. The resulting optimized
Transverse-mode coupling in a Kerr medium
J. M. Courty,A. Lambrecht
Physics , 1998, DOI: 10.1103/PhysRevA.54.5243
Abstract: We analyze nonlinear transverse mode coupling in a Kerr medium placed in an optical cavity and its influence on bistability and different kinds of quantum noise reduction. Even for an input beam that is perfectly matched to a cavity mode, the nonlinear coupling produces an excess noise in the fluctuations of the output beam. Intensity squeezing seems to be particularly robust with respect to mode coupling, while quadrature squeezing is more sensitive. However, it is possible to find a mode the quadrature squeezing of which is not affected by the coupling.
Synthetic Or Reformulated Fuels: a Challenge for Catalysis Carburants de synthèse ou reformulés : un défi pour la catalyse
Courty P.,Chaumette P.,Raimbault C.
Oil & Gas Science and Technology , 2006, DOI: 10.2516/ogst:1999032
Abstract: Despite comparative figures for wordwide crude oil and natural gas proven reserves, present time contribution of syngas chemistry to motorfuels remains marginal when the refining industry is faced to main constraints: market demand evolution, stringent specifications and environmental issues. Actually natural gas upgrading via syngas chemistry yields key products (e. g. methanol) among which clean motorfuels (ethers, FT products) should develop despite the huge investments required, mostly for syngas production. Main challenges and corresponding issues for catalysts and related technologies are identified for Fischer-Tropsch synthesis and motorfuels long-term reformulation. Among other, mastering the chain-growth (FT synthesis) improving the FCC products: gasoline, and LCO for Diesel pool. All these issues need significant progresses in catalyst and technology to be solved. Lastly, our economical study, focused on Diesel-fuel production, shows up that clean diesel (from SR-LCO mixtures) and FT Diesel reach similar production costs when cheap NG is available. In the future, FT middle distillates should amount to a few percent (5-150 Mt) of the 1700-2000 Mt of transport middle distillates expected from oil refining. However they should more and more be a compulsory part of diesel pool if the level of investment for an FT process continues to decrease significantly. Malgré des réserves prouvées en pétrole et en gaz du même ordre de grandeur, la contribution de la chimie du gaz de synthèse à la production de carburants reste marginale, alors que l'industrie du raffinage est confrontée à des contraintes majeures : évolution de la demande, durcissement des spécifications des produits et contraintes environnementales. Cependant, la conversion chimique du gaz, via la chimie du gaz de synthèse, fournit des produits stratégiques (e. g. méthanol) parmi lesquels les carburants propres (éthers, produits Fischer-Tropsch) devraient se développer, bien que les investissements requis soient lourds, notamment pour la production du gaz de synthèse. Les principaux défis, et les voies de progrès correspondantes concernant les catalyseurs et les technologies, sont présentés pour la synthèse Fischer-Tropsch et la reformulation à long terme des carburants. Parmi d'autres, le contr le de la croissance de cha ne (synthèse Fischer-Tropsch), l'amélioration des produits du FCC : essence et LCO pour le pool Diesel, constituent des défis majeurs pour lesquels des progrès importants en matière de catalyseur et de technologie sont attendus. Enfin, une étude économique ciblée sur la pro
The circum-galactic gas around cosmologically simulated disks
Stephanie Courty,Brad K. Gibson,Romain Teyssier
Physics , 2010, DOI: 10.1063/1.3458467
Abstract: We analyze the physical properties and infall rates of the circum-galactic gas around disks obtained in multi-resolved, cosmological, AMR simulations. At intermediate and low redshifts, disks are embedded into an extended, hot, tenuous corona that contributes largely in fueling the disk with non-enriched gas whereas the accretion of enriched gas from tidal streams occurs throughout episodic events. We derive an infall rate close to the disk of the same value as the one of the star formation rate in the disk and its temporal evolution as a function of galacto-centric radius nicely shows that the growth of galactic disks proceeds according to an inside-out formation scenario.
Back-action cancellation in interferometers by quantum locking
J. -M. Courty,A. Heidmann,M. Pinard
Physics , 2003, DOI: 10.1209/epl/i2003-00527-x
Abstract: We show that back-action noise in interferometric measurements such as gravitational-waves detectors can be completely suppressed by a local control of mirrors motion. An optomechanical sensor with an optimized measurement strategy is used to monitor mirror displacements. A feedback loop then eliminates radiation-pressure effects without adding noise. This very efficient technique leads to an increased sensitivity for the interferometric measurement, which becomes only limited by phase noise. Back-action cancellation is furthermore insensitive to losses in the interferometer.
Quantum fluctuations for drag free geodesic motion
Jean-Michel Courty,Serge Reynaud
Physics , 1999, DOI: 10.1088/1464-4266/2/2/304
Abstract: The drag free technique is used to force a proof mass to follow a geodesic motion. The mass is protected from perturbations by a cage, and the motion of the latter is actively controlled to follow the motion of the proof mass. We present a theoretical analysis of the effects of quantum fluctuations for this technique. We show that a perfect drag free operation is in principle possible at the quantum level, in spite of the back action exerted on the mass by the position sensor.
Optical nonlinear dynamics with cold atoms in a cavity
A. Lambrecht,E. Giacobino,J. M. Courty
Physics , 1998, DOI: 10.1016/0030-4018(94)00493-E
Abstract: This paper presents the nonlinear dynamics of laser cooled and trapped cesium atoms placed inside an optical cavity and interacting with a probe light beam slightly detuned from the 6S1/2(F=4) to 6P3/2(F=5) transition. The system exhibits very strong bistability and instabilities. The origin of the latter is found to be a competition between optical pumping and non-linearities due to saturation of the optical transition.
Transverse effects on squeezing with atoms
A. Lambrecht,J. M. Courty,S. Reynaud
Physics , 1998,
Abstract: We evaluate the squeezing of a probe beam with a transverse Gaussian profile interacting with an ensemble of two-level atoms in a cavity. We use the linear input-output formalism where the effect of atoms is described by susceptibility and noise functions. The transverse structure is accounted for by averaging atomic functions over the intensity profile. The results of the plane-wave and Gaussian-wave theories are compared. When large squeezing is predicted we find the prediction of the plane-wave model not to be reliable outside the Kerr domain. We give an estimate of the squeezing degradation due to the Gaussian transverse structure.
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