MESURE DES COEFFICIENTS D'ABSORPTION DE DIVERS GAZ MOLÉCULAIRES DANS L'ULTRAVIOLET EXTRÊME (400-100 Å). ANALYSE DES COURBES DE PHOTOIONISATION DANS LE DOMAINE DES ÉNERGIES NOTABLEMENT SUPÉRIEURES A CELLE DU SEUIL

Après une brève description du dispositif expérimental, on donne les courbes d'absorption pour O2, CO, N2, NO, CO2, N2O, H2O, NH3, CH4, CH3OH, C2H5OH, C3H7OH entre 400 et 100 Å (250-1 000 kK). Pour ces énergies de photons les processus de photoionisation simple semblent prépondérants et l'absorption moléculaire suit des lois très voisines de celles applicables dans le domaine des rayons X.After a short description of the experimental set-up, the authors give the absorption curves of O2, CO, N2, NO, CO2, N2O, H2O, NH3, CH4, CH3OH, C2H5OH, C3H7OH between 400 and 100 Å (250-1 000 kK). At these photon energies, the photoionization processes seem prevailing and the molecular absorption follows a law very similar to that for the X-ray region

Generation of Large Angle Bimodal Sea States using a Single Segmented Wavemaker

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Improved transient water waves technique for the experimental estimation of ship responses.

National audienceWe consider the transient water waves technique for the experimental determination of Response Amplitude Operators (RAO) of a floating structure. The main advantage of this technique which consists in generating a wave focused near the model and analyzing the resulting motions, is that a single test is required to accurately estimate the RAO in a wide frequency range. The focused wave however may involve non-linear effects. We thus propose an improved method in which the response is linearized by means of crest and trough focusing. The method is applied to a model barge and compared to other classical methods such as regular, random and transient waves. Based on criteria like accuracy, time required and ease of use, focused waves technique appears to provide many advantages to determine RAOs

Génération de Houle Directionnelle Complexes dans le bassin de Centrale Nantes

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Reproduction Déterministe de Paquets de Vagues Focalisés en Bassin Physique et Numérique

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Numerical and Physical Experiments of Wave Focusing in Short-Crested Seas

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A Hardware Projector/Backprojector Pair for 3D PET Reconstruction

International audienceForward and Backward projections are two computational costly steps in tomography image reconstruction such as Positron Emission Tomography (PET). To speed-up reconstruction time, a hardware projection/backprojection pair has been built following algorithm architecture adequacy principles. Thanks to an original memory access strategy based on an 3D adaptive and predictive memory cache, the external memory wall has been overcome. Thus, for both projector architectures several units run efficiently. Each unit reaches a computational throughput close to 1 operation per cycle. In this paper, we present how from our hardware projection/backprojection pair, an analytic (3D-RP) and an iterative (3D-EM) reconstruction algorithms can be implemented on a System on Programmable Chip (SoPC). First, an hardware/software partitioning is done based on the different steps of each algorithm. Then the reconstruction system is composed of two hardware configurations of the programmable logic resources (FPGA). Each one corresponds mainly to the projection and backprojection step. Our projector/backprojector has been validated with a software 3D-RP and 3D-EM reconstruction on simulated PET-SORTEO data. A reconstruction time evaluation of these reconstruction systems are done based on the measured performances of our projectors IPs and the estimated performances of the additional simple hardware IPs. The expected reconstruction time is compared with the software tomography distribution STIR. A speed-up of 7 can be expected for the 3D-RP algorithm and a speed-up of 3.5 for the 3D-EM algorithm. For both algorithms, the architecture cycle efficiency expected is largely greater than the software implementation : 120 times for 3D-RP and 60 times for 3D-EM

Higher Order Spectral Numerical Modeling of a 3D Wave Basin Compared to Experiments

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