A formal specification of the Fractal component model in Alloy

This report contains a formal specification of the Fractal component model using the Alloy specification language. The report covers all the elements of the (informal) reference specification of the Fractal model. It provides a truly language-independent specification of the Fractal model, and lifts the ambiguities of the reference specification

An Eulerian finite volume solver for multi-material fluid flows with cylindrical symmetry.

International audienceIn this paper, we adapt a pre-existing 2D cartesian cell centered finite volume solver to treat the compressible 3D Euler equations with cylindrical symmetry. We then extend it to multi-material flows. Assuming cylindrical symmetry with respect to the z axis (i.e. all the functions do not depend explicitly on the angular variable $\theta$), we obtain a set of five conservation laws with source terms that can be decoupled in two systems solved on a 2D orthogonal mesh in which a cell as a torus geometry. A specific upwinding treatment of the source term is required and implemented for the stationary case. Test cases will be presented for vanishing and non-vanishing azimuthal velocity $u_{\theta}$

Using Premia and Nsp for Constructing a Risk Management Benchmark for Testing Parallel Architecture

International audienceFinancial institutions have massive computations to carry out overnight which are very demanding in terms of the consumed CPU. The challenge is to price many different products on a cluster-like architecture. We have used the Premia software to valuate the financial derivatives. In this work, we explain how Premia can be embedded into Nsp, a scientific software like Matlab, to provide a powerful tool to valuate a whole portfolio. Finally, we have integrated an MPI toolbox into Nsp to enable to use Premia to solve a bunch of pricing problems on a cluster. This unified framework can then be used to test different parallel architectures

Temperature effect on microalgae: a crucial factor for outdoor production

International audienceHigh rate outdoor production units of microalgae can undergo temperature fluctuations. Seasonal temperature variations as well as more rapid daily fluctuations are liable to modify the growth conditions of microalgae and hence affect production efficiency. The effect of elevated temperatures, above optimal growth temperatures, on growth is seldom reported in literature, but often described as more deleterious than low temperatures. Depending on the species, different strategies are deployed to counteract the effect of above optimal temperatures such as energy re-balancing and cell shrinking. Moreover, long term adaptation of certain species over generation cycles has also been proven efficient to increase optimal temperatures. Physical models coupled to biological kinetics are able to predict the evolution of temperature in the growth media and its effect on the growth rate, highlighting the downstream drastic economic and environmental impacts. Regarding the relative elasticity of microalgae towards temperature issues, cell mortality can depend on species or adapted species and in certain cases can be attenuated. These elements can complement existing models and help visualize the effective impacts of temperature on outdoor cultures

Une typologie multi-dimensionnelle des structures énumératives pour l'identification des relations termino-ontologiques

International audienceCe travail s'inscrit dans le cadre de la construction de ressources termino-ontologiques. Il vise à améliorer l'extraction des relations sémantiques en exploitant les structures énumératives contenues dans les textes. Nous proposons ici une typologie multi-dimensionnelle de ces structures énumératives, selon les axes visuel, rhétorique, intentionnel et sémantique. Cette typologie intervient dans le cadre d'une campagne d'annotation outillée par LARAt (Logiciel d'Acquisition de Relations par l'Annotation de textes), pour l'identification de relations par apprentissage supervisé

Combining Finite Element Method and L-Systems Using Natural Information Flow Propagation to Simulate Growing Dynamical Systems

International audienceThis paper shows how to solve a system of di↵erential equa-tions controlling the development of a dynamical system based on finite element method and L-Systems. Our methods leads to solve a linear system of equations by propagating the flow of information throughout the structure of the developing system in a natural way. The method is illustrated on the growth of a branching system whose axes bend under their own weight

Bemisia tabaci sur cotonnier au Sénégal : analyse de la situtation et recommandations

Au Sénégal, l'aleurode Bemisia tabaci (Gennadius) est depuis longtemps connu comme un ravageur du cotonnier et des cultures maraîchères, mais ses infestations sont d'importance variable d'une année à l'autre. En 1998, elles ont été très fortes, suscitant l'inquiétude des milieux agricoles et de la filière cotonnière. A partir de l'analyse des pratiques culturales, phytosanitaires en particulier, des recommandations peuvent être formulées dans le sens d'une gestion raisonnée des populations de ce ravageur. (Résumé d'auteur