Motion tubes for the representation of images sequences

International audienceIn this paper, we introduce a novel way to represent an image sequence, which naturally exhibits the temporal persistence of the textures. Standardized representations have been thoroughly optimized, and getting significant improvements has become more and more difficult. As an alternative, Analysis-Synthesis (AS) coders have focused on the use of texture within a video coder. We introduce here a new AS representation of image sequences that remains close to the classic block-based representation. By tracking textures throughout the sequence, we propose to reconstruct it from a set of moving textures which we call motion tubes. A new motion model is then proposed, which allows for motion field continuities and discontinuities, by hybridizing Block Matching and a low-computational mesh-based representation. Finally, we propose a bi-predictional framework for motion tubes management

Microstructure and Thermal Conductivity of Mo-TiC processed by hot isostatic pressing . Accepté pour publication dans Le Flem M. , Allemand A., Urvoy S., Cédat D., Rey C..-

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Fabrication and characterization of 15Cr-15Ni austenitic steel cladding tubes for sodium fast reactors

International audienceTwo fabrication routes requiring industrial facilities are being conducted to produce several hundred 15Cr-15Ni claddingtubes. The processing methods involve varying degrees of cold work and different heat treatment conditions. In order to ensure that the specifications are fulfilled, both batches of tubes are fully characterized regarding several aspects. The microstructure isobserved using optical and electron microscopy. A refinement of the grain size is detected in the inner diameter of one batch, which is caused by a nitrogen contamination revealed by glow discharge mass spectrometry analysis. The precipitates are also carefully analyzed. Selective dissolutions are performed on both batches to determine their mass fractions. The precipitates (TiC, TiN and Ti$_2$CS) are identified using X-ray diffraction. The titanium content in solid solution is measured and the resulting values are analyzed to assess the quality of the last solution annealing. The tensile properties measured at room temperature comply with those expected for this steel grade. On the basis of our results and considering past experience with cladding irradiated in Phenix reactor a good behavior in pile can be foreseen for these tubes

Quorum Sensing Regulates the Hydrolytic Enzyme Production and Community Composition of Heterotrophic Bacteria in Coastal Waters

Heterotrophic microbial communities play a central role in biogeochemical cycles in the ocean by degrading organic matter through the synthesis of extracellular hydrolytic enzymes. Their hydrolysis rates result from the community’s genomic potential and the differential expression of this genomic potential. Cell-cell communication pathways such as quorum sensing (QS) could impact both aspects and, consequently, structure marine ecosystem functioning. However, the role of QS communications in complex natural assemblages remains largely unknown. In this study, we investigated whether N-acylhomoserine lactones (AHLs), a type of QS signal, could regulate both hydrolytic activities and the bacterial community composition (BCC) of marine planktonic assemblages. To this extent, we carried out two microcosm experiments, adding five different AHLs to bacterial communities sampled in coastal waters (during early and peak bloom) and monitoring their impact on enzymatic activities and diversity over 48 h. Several specific enzymatic activities were impacted during both experiments, as early as 6 h after the AHL amendments. The BCC was also significantly impacted by the treatments after 48 h, and correlated with the expression of the hydrolytic activities, suggesting that changes in hydrolytic intensities may drive changes in BCC. Overall, our results suggest that QS communication could participate in structuring both the function and diversity of marine bacterial communities

Correlation between quenching rate, mechanical properties and microstructure in thick sections of Al Mg Si( Cu) alloys

International audienceThermal treatment is key for the mechanical behavior of 6000 series aluminum alloys. Numerous studies have therefore been devoted to the impact of aging treatment parameters like time and temperature. However the influence of quenching rate is rather poorly documented while it could be of primary interest for applications requiring thick sections. Using a series of AleMgeSi(eCu) specimens quenched in various fluids, we propose to monitor and describe the quench properly and study the impact of the quenching rate on the microstructure and mechanical properties obtained after aging. Acknowledging the critical quench rate to be about 10°C s −1 , quenching was performed in various quenching fluids (water, air and oil) on 10 cm side 6061 alloy cubes. The quench rate was evaluated by thermocouples placed at several locations and by numerical modeling. For each temper, the microstructure and mechanical behavior has been studied at local and macro scales to highlight some correlations. The combination of transmission electron microscopy imaging and related image analysis, chemical and crystallographic mapping, microhardness maps and tensile tests has pointed out many micro-structural differences at nanoscale and inhomogeneous mechanical behavior we strived to explain and correlate

Rapidly synthesis of nanocrystalline MgIn2O4 spinel using combustion and solid state chemistry.

International audienceNanometric/submicronic powders of magnesium indate spinel MgIn2O4 were prepared with a two-steps process. First, nano-oxides of In2O3 and MgO were obtained by combustion of aqueous solutions of metal nitrates (as an oxidizer) and different fuels (glycine/urea/citric acid). Then, the as-prepared combustion ashes were converted into pure spinels after calcinations at elevated temperature. The as-prepared powders spinels have nanometric or submicronic grain size. This process allows preparing the MgIn2O4 spinel compound in 1 day whilst 10 days were necessary when the classical solid state chemistry is used. In this paper, we compare these two ways and study the effect of different reaction parameters, such as the nature of fuels or the fuel/oxidiser ratio. Crystallites sizes of the synthesized compounds were investigated by powder X-ray diffraction and Scanning Electron Microscopy

Quorum sensing disruption regulates hydrolytic enzyme and biofilm production in estuarine bacteria

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Comparison of 15Cr-15Ni austenitic steel cladding tubes obtained by HPTR cold pilgering or by cold drawing

International audienceDue to their high void swelling resistance, work-hardened titanium stabilized austenitic steels have been chosen as cladding material for sodium cooled fast reactor. In this study, HPTR cold pilgering process is compared to cold drawing at the last shaping step of the tube processing. The effects of the cold work accumulation and heat treatments are studied in connection with the microstructure (grain size), the hardness and the texture. The following results were found:-As larger amount of cold work can be applied by HPTR cold pilgering, a lower number of intermediate heat treatments are required. In addition, the bending of the tube is significantly reduced after each pass for this process allowing for a limitation of the straightening operations.-For both processes, optical micrographs show micrometric titanium carbide precipitates and the presence of deformation twins on a few grains on the final tube. A significant grain size refinement from $\approx$45 \mu^m to $\approx$17 \mu^m can be obtained by reducing annealing temperature from 1403K down to 1353K. For the latter, the precipitated mass fraction measured by selective dissolution of the alloy matrix is the largest, revealing a possible negative impact on swelling under irradiation.-Through-wall Vickers hardness profiles show an increase of the hardness at the outer diameter for HPTR cold pilgering whereas the hardness profile remains continuous for cold drawing. It is found that the Q-factor has an influence on these wall-thickness hardness profiles.-For each process, neutron diffraction measurements on finished tubes reveal two main fiber texture components and parallel to the tube axis with differences in their relative intensities

Effect of chromium grain size and morphology on the HT oxidation behavior of chromium coated Zr based alloys

International audienceOne of the hypothetical accidents studied in the field of the safety studies of Pressurized light Water Reactors (PWR) is the Loss-Of-Coolant Accident (LOCA). In this scenario, zirconium alloy fuel claddings could undergo a high level of oxidation at high temperature in a steam environment. Cladding tubes constitute the first confinement barrier of radioelements and then it is essential that they keep a certain level of ductility after quenching to ensure their integrity. These properties are directly related to the growth kinetics of both the oxide and the sub-oxide αZr(O) layers and especially to the oxygen diffusion profiles in the residual prior-β layer after HT oxidation and final water quenching. This study was focused on the influence of a pre-annealing thermal treatment performed on first generation of 6-8 µm thick Cr-coated zirconium based specimens and on their further HT oxidation behavior. The effect of pre-annealing temperature on the structure and morphology of the Chromium coating microstructure was investigated using scanning electron microscopy. During the annealing treatment, the chromium coating experienced recrystallisation and the initial columnar grains morphology became more equiaxed. After oxidation at HT, the weight gains of pre-annealed Cr-coated specimen were generally lower than the non-annealed ones. Glow discharge mass spectrometry, Electron Probe Micro Analysis and Raman spectroscopy measurements have confirmed that the thickness of ZrO2 and αZr(O) phases were significantly reduced for some of the pre-annealed samples, indicating that the grain size and morphological evolutions of the chromium coating upon the pre-annealing thermal treatment may influence its further HT oxidation behavior