COBRA : Une plate-forme de RàPC basée sur des ontologies

International audienceCet article présente un projet en cours qui a pour objectif de développer une plate-forme de RàPC pour le diagnostic basée sur des ontologies, appelée COBRA. Cette plate-forme est constituée de deux parties principales : les modèles de connaissances décrits par des ontologies, et les processus de raisonnement. Nous travaillons actuellement sur la défaillance des barrières de sécurité installées sur des sites industriels. Cependant, notre objectif est de rendre la plate-forme générique et indépendante du domaine d'application. Nous affirmons que, pour mieux exploiter les avantages des ontologies dans les systèmes de RàPC, il est important de pouvoir utiliser n'importe quel concept dans la description des cas. Ainsi, COBRA permet de définir les attributs de chaque cas dynamiquement au moment de l'exécution, ce qui conduit à une base de cas hétérogène. Dans cet article, nous présentons l'architecture de la plate-forme, les modèles de connaissances, les processus principaux, ainsi que les problèmes rencontrés en travaillant avec des cas hétérogènes

Breathing mode for systems of interacting particles

We study the breathing mode in systems of trapped interacting particles. Our approach, based on a dynamical ansatz in the first equation of the Bogolyubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy allows us to tackle at once a wide range of power law interactions and interaction strengths, at linear and non linear levels. This both puts in a common framework various results scattered in the literature, and by widely generalizing these, emphasizes universal characters of this breathing mode. Our findings are supported by direct numerical simulations.Comment: 4 pages, 4 figure

Looking for bimodal distributions in multi-fragmentation reactions

The presence of a phase transition in a finite system can be deduced, together with its order, from the shape of the distribution of the order parameter. This issue has been extensively studied in multifragmentation experiments, with results that do not appear fully consistent. In this paper we discuss the effect of the statistical ensemble or sorting conditions on the shape of fragment distributions, and propose a new method, which can be easily implemented experimentally, to discriminate between different fragmentation scenarii. This method, based on a reweighting of the measured distribution to account for the experimental constraints linked to the energy deposit, is tested on different simple models, and appears to provide a powerful discrimination.Comment: 11 pages, 7 figure

Examine the species and beam-energy dependence of particle spectra using Tsallis Statistics

Tsallis Statistics was used to investigate the non-Boltzmann distribution of particle spectra and their dependence on particle species and beam energy in the relativistic heavy-ion collisions at SPS and RHIC. Produced particles are assumed to acquire radial flow and be of non-extensive statistics at freeze-out. J/psi and the particles containing strangeness were examined separately to study their radial flow and freeze-out. We found that the strange hadrons approach equilibrium quickly from peripheral to central A+A collisions and they tend to decouple earlier from the system than the light hadrons but with the same final radial flow. These results provide an alternative picture of freeze-outs: a thermalized system is produced at partonic phase; the hadronic scattering at later stage is not enough to maintain the system in equilibrium and does not increase the radial flow of the copiously produced light hadrons. The J/psi in Pb+Pb collisions at SPS is consistent with early decoupling and obtains little radial flow. The J/psi spectra at RHIC are also inconsistent with the bulk flow profile.Comment: 12 pages, 4 figures, added several references and some clarifications et

GALICS III: Predicted properties for Lyman Break Galaxies at redshift 3

This paper illustrates how mock observational samples of high-redshift galaxies with sophisticated selection criteria can be extracted from the predictions of GALICS, a hybrid model of hierarchical galaxy formation that couples the outputs of large cosmological simulations and semi-analytic recipes to describe dark matter collapse and the physics of baryons respectively. As an example of this method, we focus on the properties of Lyman Break Galaxies at redshift 3. With the MOMAF software package described in a companion paper, we generate a mock observational sample with selection criteria as similar as possible to those implied in the actual observations of z = 3 LBGs by Steidel et al.(1995). Our model predictions are in good agreement with the observed number density and 2D correlation function. We investigate the optical/IR luminosity budget as well as several other physical properties of LBGs and find them to be in general agreement with observed values. Looking into the future of these LBGs we predict that 75% of them end up as massive ellipticals today, even though only 35% of all our local ellipticals are predicted to have a LBG progenitor. In spite of some shortcomings, this new 'mock observation' method clearly represents a necessary first step toward a more accurate comparison between hierarchical models of galaxy formation and real observational surveys.Comment: 19 pages, 15 figures, submitted to MNRAS. Full resolution figures at http://galics.iap.fr

FOREDUNE GUIDED REMOBILIZATION EXPERIMENTS ALONG THE SOUTHWEST COAST OF FRANCE

This contribution presents the response of experimental management methods implemented along 2 km stretch of the southwest coast of France with the objective to restore aeolian dynamics and foredune mobility to promote quasi alongshore-uniform landward foredune migration. The analysis based on eight airborne LiDAR campaigns and several morphometric indicators shows that the alongshore and temporal variability of foredune evolution depends on natural dynamics and contrasted managed strategies. These experiments offer new perspectives and guidelines for coastal dune managers in areas where chronic erosion threatens fixed dune systems

MoMaF : The Mock Map Facility

We present the Mock Map Facility, a powerful tool to generate mock catalogues or images from semi-analytically post-processed snapshots of cosmological N-body simulations. The paper describes in detail an efficient technique to create such mocks from the GALICS semi-analytic model, providing the reader with an accurate quantification of the artifacts it introduces at every step. We show that replication effects introduce a negative bias on the clustering signal -- typically peaking at less than 10 percent around the correlation length. We also thoroughly discuss how the clustering signal is affected by finite volume effects, and show that it vanishes at scales larger than about a tenth of the simulation box size. For the purpose of analysing our method, we show that number counts and redshift distributions obtained with GALICS and MOMAF compare well to K-band observations and to the 2dFGRS. Given finite volume effects, we also show that the model can reproduce the APM angular correlation function. The MOMAF results discussed here are made publicly available to the astronomical community through a public database. Moreover, a user-friendly Web interface (http://galics.iap.fr) allows any user to recover her/his own favourite galaxy samples through simple SQL queries. The flexibility of this tool should permit a variety of uses ranging from extensive comparisons between real observations and those predicted by hierarchical models of galaxy formation, to the preparation of observing strategies for deep surveys and tests of data processing pipelines.Comment: 19 pages, 15 Figs, significantly modified version now accepted for publication in MNRAS. High-resolution version available at http://galics.cosmologie.fr/papers/momaf.ps.g

Enhancement and Inhibition of Spontaneous Photon Emission by Resonant Silicon Nanoantennas

Substituting noble metals for high-index dielectrics has recently been proposed as an alternative strategy in nanophotonics to design broadband optical resonators and circumvent the Ohmic losses of plasmonic materials. In this paper, we demonstrate that subwavelength silicon nanoantennas can manipulate the photon emission dynamics of fluorescent molecules. In practice, we show that dielectric nanoantennas can both increase and decrease the local density of optical states at room temperature, a process that is inaccessible with noble metals at the nanoscale. Using scanning probe microscopy, we analyze quantitatively, in three dimensions, the near-field interaction between a 100-nm fluorescent nanosphere and silicon nanoantennas with diameters ranging between 170 and 250 nm. Associated with numerical simulations, these measurements indicate increased or decreased total spontaneous decay rates by up to 15% and a gain in the collection efficiency of emitted photons by up to 85%. Our study demonstrates the potential of silicon-based nanoantennas for the low-loss manipulation of solid-state emitters at the nanoscale and at room temperature