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Search Results: 1 - 10 of 144373 matches for " B. Courty "
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Gas and Metal Distributions within Simulated Disk Galaxies
B. K. Gibson,S. Courty,D. Cunnama,M. Molla
Physics , 2012,
Abstract: We highlight two research strands related to our ongoing chemodynamical Galactic Archaeology efforts: (i) the spatio-temporal infall rate of gas onto the disk, drawing analogies with the infall behaviour imposed by classical galactic chemical evolution models of inside-out disk growth; (ii) the radial age gradient predicted by spectrophometric models of disk galaxies. In relation to (i), at low-redshift, we find that half of the infall onto the disk is gas associated with the corona, while half can be associated with cooler gas streams; we also find that gas enters the disk preferentially orthogonal to the system, rather than in-plane. In relation to (ii), we recover age gradient troughs/inflections consistent with those observed in nature, without recourse to radial migrations.
Two-dimensional shear modulus of a Langmuir foam
S. Courty,B. Dollet,F. Elias,P. Heinig,F. Graner
Physics , 2003, DOI: 10.1209/epl/i2003-00283-5
Abstract: We deform a two-dimensional (2D) foam, created in a Langmuir monolayer, by applying a mechanical perturbation, and simultaneously image it by Brewster angle microscopy. We determine the foam stress tensor (through a determination of the 2D gas-liquid line tension, 2.35 $\pm$ 0.4 pJ$\cdot$m$^{-1}$) and the statistical strain tensor, by analyzing the images of the deformed structure. We deduce the 2D shear modulus of the foam, $\mu= 38 \pm 3 \mathrm{nN}\cdot \mathrm{m}^{-1}$. The foam effective rigidity is predicted to be $ 35 \pm 3 \mathrm {nN}\cdot \mathrm {m}^{- 1}$, which agrees with the value $37.5 \pm 0.8 \mathrm {nN}\cdot \mathrm {m}^{-1}$ obtained in an independent mechanical measurement.
Testing gravity law in the solar system
B. Lamine,J. -M. Courty,S. Reynaud,M. -T. Jaekel
Physics , 2011,
Abstract: The predictions of General relativity (GR) are in good agreement with observations in the solar system. Nevertheless, unexpected anomalies appeared during the last decades, along with the increasing precision of measurements. Those anomalies are present in spacecraft tracking data (Pioneer and flyby anomalies) as well as ephemerides. In addition, the whole theory is challenged at galactic and cosmic scales with the dark matter and dark energy issues. Finally, the unification in the framework of quantum field theories remains an open question, whose solution will certainly lead to modifications of the theory, even at large distances. As long as those "dark sides" of the universe have no universally accepted interpretation nor are they observed through other means than the gravitational anomalies they have been designed to cure, these anomalies may as well be interpreted as deviations from GR. In this context, there is a strong motivation for improved and more systematic tests of GR inside the solar system, with the aim to bridge the gap between gravity experiments in the solar system and observations at much larger scales. We review a family of metric extensions of GR which preserve the equivalence principle but modify the coupling between energy and curvature and provide a phenomenological framework which generalizes the PPN framework and "fifth force" extensions of GR. We briefly discuss some possible observational consequences in connection with highly accurate ephemerides.
Pioneer 10 Doppler data analysis: disentangling periodic and secular anomalies
A. Levy,B. Christophe,P. Berio,G. Metris,J-M. Courty,S. Reynaud
Physics , 2008, DOI: 10.1016/j.asr.2009.01.003
Abstract: This paper reports the results of an analysis of the Doppler tracking data of Pioneer probes which did show an anomalous behaviour. A software has been developed for the sake of performing a data analysis as independent as possible from that of J. Anderson et al. \citep{anderson}, using the same data set. A first output of this new analysis is a confirmation of the existence of a secular anomaly with an amplitude about 0.8 nms$^{-2}$ compatible with that reported by Anderson et al. A second output is the study of periodic variations of the anomaly, which we characterize as functions of the azimuthal angle $\varphi$ defined by the directions Sun-Earth Antenna and Sun-Pioneer. An improved fit is obtained with periodic variations written as the sum of a secular acceleration and two sinusoids of the angles $\varphi$ and $2\varphi$. The tests which have been performed for assessing the robustness of these results are presented.
Chemodynamics of a Simulated Disc Galaxy: Initial Mass Functions and SNIa Progenitors
C. G. Few,S. Courty,B. K. Gibson,L. Michel-Dansac,F. Calura
Physics , 2014, DOI: 10.1093/mnras/stu1709
Abstract: We trace the formation and advection of several elements within a cosmological adaptive mesh refinement simulation of an L* galaxy. We use nine realisations of the same initial conditions with different stellar Initial Mass Functions (IMFs), mass limits for type-II and type-Ia supernovae (SNII, SNIa) and stellar lifetimes to constrain these sub-grid phenomena. Our code includes self-gravity, hydrodynamics, star formation, radiative cooling and feedback from multiple sources within a cosmological framework. Under our assumptions of nucleosynthesis we find that SNII with progenitor masses of up to 100 Msun are required to match low metallicity gas oxygen abundances. Tardy SNIa are necessary to reproduce the classical chemical evolution knee in [O/Fe]-[Fe/H]: more prompt SNIa delayed time distributions do not reproduce this feature. Within our framework of hydrodynamical mixing of metals and galaxy mergers we find that chemical evolution is sensitive to the shape of the IMF and that there exists a degeneracy with the mass range of SNII. We look at the abundance plane and present the properties of different regions of the plot, noting the distinct chemical properties of satellites and a series of nested discs that have greater velocity dispersions, are more alpha-rich and metal poor with age.
Properties of simulated Milky Way-mass galaxies in loose group and field environments
C. G. Few,B. K. Gibson,S. Courty,L. Michel-Dansac,C. B. Brook,G. S. Stinson
Physics , 2012, DOI: 10.1051/0004-6361/201219649
Abstract: We test the validity of comparing simulated field disk galaxies with the empirical properties of systems situated within environments more comparable to loose groups, including the Milky Way's Local Group. Cosmological simulations of Milky Way-mass galaxies have been realised in two different environment samples: in the field and in environments with similar properties to the Local Group. Apart from the environments of the galaxies, the samples are kept as homogeneous as possible with equivalent ranges in last major merger time, halo mass and halo spin. Comparison of these two samples allow for systematic differences in the simulations to be identified. Metallicity gradients, disk scale lengths, colours, magnitudes and age-velocity dispersion relations are studied for each galaxy in the suite and the strength of the link between these and environment of the galaxies is studied. The bulge-to-disk ratio of the galaxies show that these galaxies are less spheroid dominated than many other simulated galaxies in literature with the majority of both samples being disk dominated. We find that secular evolution and mergers dominate the spread of morphologies and metallicity gradients with no visible differences between the two environment samples. In contrast with this consistency in the two samples there is tentative evidence for a systematic difference in the velocity dispersion-age relations of galaxies in the different environments. Loose group galaxies appear to have more discrete steps in their velocity dispersion-age relations. We conclude that at the current resolution of cosmological galaxy simulations field environment galaxies are sufficiently similar to those in loose groups to be acceptable proxies for comparison with the Milky Way provided that a similar assembly history is considered.
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.
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