Self-similar perturbation near a corner: matching versus multiscale expansions for a model problem

International audienc

High-frequency homogenization for periodic dispersive media

High-frequency homogenization is used to study dispersive media, containing inclusions placed periodically, for which the properties of the material depend on the frequency (Lorentz or Drude model with damping, for example). Effective properties are obtained near a given point of the dispersion diagram in frequency-wavenumber space. The asymptotic approximations of the dispersion diagrams, and the wavefields, so obtained are then cross-validated via detailed comparison with finite element method simulations in both one and two dimensions

Comparaison des techniques de raccordements de développements asymptotiques et de développements multiéchelles

National audienceOn considère le problème de Laplace–Dirichlet dans un domaine polygonal qui présente une perturbation de taille ε en l'un de ses sommets. Cette perturbation est supposée auto-similaire, i.e. provient d'un motif fixe dilaté à l'échelle ε. Sur ce problème modèle, nous mettons en oeuvre deux méthodes : développements asymptotiques raccordés et développement multi-échelle. Nous mettons en évidence les particularités de chaque approche et montrons comment passer d'un développement à l'autre

Load allocation problem for optimal design of aircraft electrical power system

More and more electric systems are embedded in today aircraft. As a result, the complexity of electrical power system design is increasing and the need of generic and efficient design methods is today required. Among numerous design tasks, the allocation of electric systems on the busbars of the electrical power system is considered as an important one since it has a direct impact on the aircraft mass. But due to the high number of possible allocations and regarding the large diversity of potential sizing cases for the equipments, finding the optimal allocation of electric loads is a hard task. In this paper, the problem is formalized mathematically. Then, four stochastic optimization methods are assessed on complex load allocation problems. Based on this assessment, a genetic algorithm using niching method is considered as the most appropriate algorithm for solving this aircraft design proble

Modeling the Radiative Signatures of Turbulent Heating in Coronal Loops

The statistical properties of the radiative signature of a coronal loop subject to turbulent heating obtained from a three-dimensional (3D) magnetohydrodynamics (MHD) model are studied. The heating and cooling of a multistrand loop is modeled and synthetic spectra for Fe XII 195.12, Fe XV 284.163, and Fe XIX 1118.06 ? are calculated, covering a wide temperature range. The results show that the statistical properties of the thermal and radiative energies partially reflect those of the heating function in that power-law distributions are transmitted, but with very significant changes in the power-law indices. There is a strong dependence on the subloop geometry. Only high-temperature radiation (?107 K) preserves reasonably precise information on the heating function

Gratings: Theory and Numeric Applications

International audienceThe book containes 11 chapters written by an international team of specialist in electromagnetic theory, numerical methods for modelling of light diffraction by periodic structures having one-, two-, or three-dimensional periodicity, and aiming numerous applications in many classical domains like optical engineering, spectroscopy, and optical telecommunications, together with newly born fields such as photonics, plasmonics, photovoltaics, metamaterials studies, cloaking, negative refraction, and super-lensing. Each chapter presents in detail a specific theoretical method aiming to a direct numerical application by university and industrial researchers and engineers

Nucleoside triphosphate diphosphohydrolase-1 ectonucleotidase is required for normal vas deferens contraction and male fertility through maintaining P2X1 receptor function

In this work, we report that Entpd1(-/-) mice, deficient for the ectonucleotidase nucleoside triphosphate diphosphohydrolase-1 (NTPDase1), produce smaller litters (27% reduction) compared with wild-type C57BL6 animals. This deficit is linked to reduced in vivo oocyte fertilization by Entpd1(-/-) males (61 ± 11% versus 88 ± 7% for Entpd1(+/+)). Normal epididymal sperm count, spermatozoa morphology, capacitation, and motility and reduced ejaculated sperm number (2.4 ± 0.5 versus 3.7 ± 0.4 million for Entpd1(+/+)) pointed to vas deferens dysfunction. NTPDase1 was localized by immunofluorescence in the tunica muscularis of the vas deferens. Its absence resulted in a major ATP hydrolysis deficiency, as observed in situ by histochemistry and in primary smooth muscle cell cultures. In vitro, Entpd1(-/-) vas deferens displayed an exacerbated contraction to ATP, a diminished response to its non-hydrolysable analog αβMeATP, and a reduced contraction to electrical field stimulation, suggesting altered P2X1 receptor function with a propensity to desensitize. This functional alteration was accompanied by a 3-fold decrease in P2X1 protein expression in Entpd1(-/-) vas deferens with no variation in mRNA levels. Accordingly, exogenous nucleotidase activity was required to fully preserve P2X1 receptor activation by ATP in vitro. Our study demonstrates that NTPDase1 is required to maintain normal P2X1 receptor functionality in the vas deferens and that its absence leads to impaired peristalsis, reduced spermatozoa concentration in the semen, and, eventually, reduced fertility. This suggests that alteration of NTPDase1 activity affects ejaculation efficacy and male fertility. This work may contribute to unveil a cause of infertility and open new therapeutic potentials

Le projet GazePlay : des jeux ouverts, gratuits et une communauté pour les personnes en situation de polyhandicap

International audienceIn order to develop and enhance an augmentative and alternative communication (AAC), gaze is often considered as one of the most natural way and one of the easiest to set up in order to support individuals with multiple disabilities to interact with their environment. For children who start naturally from scratch, who have in addition such difficulties, it is a strong challenge even to acquire or to support the required basic knowledge. Games are often considered a good way to learn. Games designed for eye-trackers, i.e. electronic devices able to compute the position of the gaze, allow children to discover the power of their eyes and the consequences of the actions triggered by their gazes. Video games can be a good way to improve basic requirements as gaze fixation and gaze pursuit as well as conventions like rewards or dwell interactions often used in AAC tools. In this article, we present the GazePlay project which main contribution is a free and open-source software which gathers several mini-games playable with all eye-trackers including low cost ones.Afin de développer et d'améliorer une communication Augmentée et alternative (CAA), le regard est souvent considéré comme l'un des moyens les plus naturels et les plus faciles à mettre en place pour permettre aux personnes en situation de polyhandicap d'interagir avec leur environnement. Bien entendu, pour des enfants qui partent par nature de zéro, qui de plus ont de telles difficultés, c'est déjà un grand défi d'acquérir et de soutenir les connaissances de base que cette communication requiert. Les jeux sont souvent considérés comme un bon moyen d'apprendre. Les jeux destinés à être utilisés avec des oculomètres (eye-trackers), c'est-à-dire des dispositifs électroniques capables d'estimer la position du regard, peuvent être un bon moyen d'améliorer les compétences requises comme la fixation et la poursuite oculaire, ainsi que des conventions comme les récompenses ou les interactions de fixation (dwell interaction) souvent utilisées dans les outils de CAA. Dans cet article, nous présentons le projet GazePlay dont la principale contribution est un logiciel libre et gratuit qui rassemble plusieurs mini-jeux compatibles avec tous les oculomètres, y compris les moins chers