Development and validation of a numerical tool for the simulation of the temperature field and infrared radiance rendering in an urban scene

International audienceWe present a numerical tool aimed at simulating infrared images of an urban environment, by solving the direct heat transfer problem, and then computing the radiance rendering at the sensor level. SOLENE (Cerma, Nantes) was coupled with two software packages developed at ONERA: SUSHI (Simulation in Urban Scene of Heat dIffusion) and MOHICANS (MOdélisation Hyperspectrale d'Images en entrée Capteur pour l'ANalyse et l'inversion du Signal) for realizing this task. SUSHI is also used for computing the surface temperatures: either a 1D model or a 2D model is used. We present the whole software chain, its validation by software and experimental analysis

RECONSTRUCTION OF SKY ILLUMINATION DOMES FROM GROUND-BASED PANORAMAS

The knowledge of the sky illumination is important for radiometric corrections and for computer graphics applications such as relighting or augmented reality. We propose an approach to compute environment maps, representing the sky radiance, from a set of ground-based images acquired by a panoramic acquisition system, for instance a mobile-mapping system. These images can be affected by important radiometric artifacts, such as bloom or overexposure. A Perez radiance model is estimated with the blue sky pixels of the images, and used to compute additive corrections in order to reduce these radiometric artifacts. The sky pixels are then aggregated in an environment map, which still suffers from discontinuities on stitching edges. The influence of the quality of estimated sky radiance on the simulated light signal is measured quantitatively on a simple synthetic urban scene; in our case, the maximal error for the total sensor radiance is about 10%

Recommendations on X80 steel for the design of hydrogen gas transmission pipelines

International audienceBy limiting the pipes thickness necessary to sustain high pressure, high-strength steels could prove economically relevant for transmitting large gas quantities in pipelines on long distance. Up to now, the existing hydrogen pipelines have used lower-strength steels to avoid any hydrogen embrittlement. The CATHY-GDF project, funded by the French National Agency for Research, explored the ability of an industrial X80 grade for the transmission of pressurized hydrogen gas in large diameter pipelines. This project has developed experimental facilities to test the material under hydrogen gas pressure. Indeed, tensile, toughness, crack propagation and disc rupture tests have been performed. From these results, the effect of hydrogen pressure on the size of some critical defects has been analyzed allowing proposing some recommendations on the design of X80 pipe for hydrogen transport. Cost of hydrogen transport could be several times higher than natural gas one for a given energy amount. Moreover, building hydrogen pipeline using high grade steels could induce a 10 to 40% cost benefit instead of using low grade steels, despite their lower hydrogen susceptibility

Active learning on large hyperspectral datasets: a preprocessing method

International audienceMachine learning algorithms demonstrated promising results for hyperspectral semantic segmentation. However, they strongly rely on the quality of training datasets. As far as the annotation of hyperspectral images is often expensive and time-consuming, only a few thousand pixels can be labeled. In this context, active learning algorithms select the most informative pixels to be labeled. In the machine learning community, recent active learning methods have overcome the performance of conventional algorithms but do not always scale to large remote sensing images. Therefore, we introduce in this paper a preprocessing method that allows the use of computationally intensive active learning algorithms without significant impacts on their effectiveness

Damage mechanisms at a microscopic scale of PM Ti-6Al-4V at 20 K

The microscopic damage mechanisms at cryogenic temperature of an extra low interstitial Ti-6Al-4V obtained by powder metallurgy (PM) are investigated. Through SEM observations and EBSD mapping, it is attempted to identify the microstructural features that control the damage. Damage nucleation as well as texture evolution with strain are particularly analyzed. It is shown that both features are closely related to twinning

Ability of X80 steel for hydrogen gas transmission pipelines CATHY-GDF project

By limiting the pipes thickness necessary to sustain high pressure, high-strength steels could prove economically relevant for transmitting large gas quantities in pipelines. Up to now, the existing hydrogen pipelines have used lower-strength steels to avoid any hydrogen embrittlement. The CATHY-GDF project, funded by the French National Agency for Research, explores the ability of an industrial X80 grade for the transmission of pressurised hydrogen gas in large diameter pipelines. This project has developed experimental facilities to test the material under hydrogen gas pressure. Then, tensile, toughness, fatigue and disc tests are performed on the base material and on the welds. Moreover, an apparatus has been designed to simulate the hydrogen gas impact on a damaged pipe section. Hydrogen gas influence has been evaluated by FEM coupling H diffusion and mechanical fields. The results stress the necessity to improve the guidelines, updating the safety margins, for high-strength hydrogen transmission pipelines

Ability of X80 steel for hydrogen gas transmission pipelines CATHY-GDF project

By limiting the pipes thickness necessary to sustain high pressure, high-strength steels could prove economically relevant for transmitting large gas quantities in pipelines. Up to now, the existing hydrogen pipelines have used lower-strength steels to avoid any hydrogen embrittlement. The CATHY-GDF project, funded by the French National Agency for Research, explores the ability of an industrial X80 grade for the transmission of pressurised hydrogen gas in large diameter pipelines. This project has developed experimental facilities to test the material under hydrogen gas pressure. Then, tensile, toughness, fatigue and disc tests are performed on the base material and on the welds. Moreover, an apparatus has been designed to simulate the hydrogen gas impact on a damaged pipe section. Hydrogen gas influence has been evaluated by FEM coupling H diffusion and mechanical fields. The results stress the necessity to improve the guidelines, updating the safety margins, for high-strength hydrogen transmission pipelines