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Montauban, France

Riou J.,ONERA | Garnier E.,ONERA | Basdevant C.,University of Paris 13 | Basdevant C.,Institute Galilee
AIAA Journal

A numerical study of a control strategy based on pitching oscillations that aims at limiting the separated flow over a stalled missile fin was conducted. The angle of attack is equal to 25°, and the Mach and Reynolds numbers, respectively, equal 0.7 and 5:8 × 106. The frequency of the sinusoidal motion of the fin has been set equal to F+ = 1.5. The analysis of the time-averaged flows has shown that the separated flow is deeply altered by the pitching motion of the fin. Indeed, for the two forced cases, the size of the reverse flow region decreases. In the current investigation, the sinusoidal pitching motion of the missile fin is ensured using the arbitrary Lagrangian-Eulerian formulation. Such a control strategy then seems to be a good candidate to enhance the performance of missile fins without any additional control system. Source

Osmani A.,Institute Galilee | Roze L.,IRISA
European Control Conference, ECC 1999 - Conference Proceedings

Detection and isolation of failures in large and complex systems, as telecommunication networks, are crucial and challenging tasks. We propose in this article a model-based diagnosis system for telecommunication network breakdown based on two steps: Off-line step: the telecommunication management network is, first, modeled by temporal and communicating finite state machines. Then, a set of breakdown situations is simulated in the model. The simulation task generates for each simulated situation a set of all possible sequences of alarms received by the supervisor. And a learning database is built associating breakdown situations to different sequences of alarms. Finally, a learning module computes discrimination between all simulated breakdown situations; On-line step: results of off-line step are used to recognize on-fly breakdown situations from the stream of alarms arriving at the supervisor. © 1999 EUCA. Source

Beilvert A.,French National Institute for Agricultural Research | Faure F.,Departement dOrl et Chirurgie Cervico Maxillo Faciale | Faure F.,European Sialendoscopy Training Center | Meddahi-Pelle A.,University of Paris 13 | And 7 more authors.

Objectives/Hypothesis In sialendoscopy, stents are often used to keep the salivary duct open after surgery. These stents need to be removed. Recently, our group developed a new starch-based shape-memory material that is a widespread degradable polymer. Such a device could be manufactured into a deployable resorbable stent to keep the salivary duct open before in situ degradation. An experimental test was performed to establish a methodology and to evaluate the feasibility of the starch stent implantation in an animal model with clinical equipment. Study Design Evaluation of different formulations - potato and high amylose content maize starch without and with plasticizer - with laboratory bench-top testing and in vivo evaluation in a large-animal model. Methods Starch-based stents were manufactured. They were evaluated for their shape-memory properties (water, 37°C) and their degradability in simulated saliva in both static and flow conditions mimicking salivary flow in the submandibular duct. A pilot study of stent implantation was then performed in vivo in a large-animal model to assess that the stent dimensions were consistent for implantation in the submandibular duct. Results Stents made from plasticized starch had the required shape-memory properties to be used as self-deploying stents. However, starch-based stents were rapidly hydrolyzed in simulated saliva. Stents could be directly inserted in the dilated salivary duct in a pig model without harming the epithelium. Conclusions Shape-memory stents with suitable geometry for sialendoscopic surgical procedure can be fabricated and inserted in the submandibular duct. Starch-based stents can be used in other pathologies with less α-amylase content in the surrounding medium. Level of Evidence NA. Laryngoscope, 124:875-881, 2014 © 2013 The American Laryngological, Rhinological and Otological Society, Inc. Source

Tingaud D.,Institute Galilee | Besson R.,CNRS Material Physics Group

We present a detailed investigation of the influence of atomic vibrations on the point defect and diffusion properties of ordered metallic alloys, by means of ab initio calculations with density-functional theory. Considering the case of Ni2Al3 which provides a rich panel of defect-related properties, our study reveals that the behaviour of this compound is largely monitored by self-interstitials, whereas such defects are usually ignored in metallic compounds. The vibration free energies are obtained for the full set of point defects of Ni2Al3, showing that these quantities are strongly defect-dependent, and significantly modify the free energy of the compound in an intricate composition-dependent manner. The second key-issue is the first ab initio full analysis of attempt frequencies, via the coupling of vibration analysis and saddle-point search for significant atomic jumps. This analysis indicates that attempt frequencies range over several orders of magnitude and exponentially increase with migration energies. We show the importance of these factors in reaching realistic composition-dependent diffusion coefficients. © 2013 Elsevier Ltd. All rights reserved. Source

Riou J.,ONERA | Garnier E.,ONERA | Basdevant C.,University of Paris 13 | Basdevant C.,Institute Galilee
AIAA Journal

An experiment conducted to examine control of the flow over a delta wing in the transonic regime is presented. Suction effects on the vortical flow over a 65 deg sweep delta wing in the transonic regime have been investigated. The suction slot is located at the leading edge of the wing and the momentum coefficient has been set equal to 2%. The leading-edge vortex is stabilized, as testified by the single peak in the PDF of its lateral location. However, it should be noted here that this peak is less acute than that observed in the PDF of the location of the shock, since the vortex is still influenced by the small-scale vortices embedded in the shear layer emanating from the leading edge. This shock interacts with the boundary layer, inducing its separation. In the controlled case, this crossflow shock is no longer present and is substituted by an oblique shock sitting on the suction slot. Source

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