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LTI
Saint-Sauveur-en-Rue, France

Bennacer R.,Ecole Normale Superieure de Cachan | Rahli O.,University of Science and Technology Houari Boumediene | Hammed H.B.,LTI
Computational Thermal Sciences | Year: 2012

The present document covers fundamental, academic, and practical topics. Indeed, the mixed convection in channels heated and cooled differentially has been studied in relation to several practical applications. Most interest in these flows are encountered in several domains to explain certain geological phenomena and atmospheric flows, and intervene in many industrial applications such as cooling of electronic appliances, plastics manufacturing, building sciences, moisture transfer, or in the chemical vapor deposition and other crystal growth techniques. It either permits simulation of pollution problems or storage of different fluid mixtures either in natural storage (traps structures) or in industrial tanks. Being bound by any such applications, the subject is currently open for exploration in order to enrich our knowledge of this complicated problem. We consider three-dimensional thermosolutal mixed convection with flow confined between two parallel and horizontal planes where the lower and upper surfaces are hot and cold, respectively. Such a configuration of convective flows is referred to as Poiseuille-Rayleigh-Benard, (PRB) which is based on the famous Rayleigh-Benard problem. In such a PRB configuration, the flow results from the superposition of two convective sources; i.e., the horizontal pressure gradient that causes the main flow within the duct and a vertical temperature and/or concentration gradient, which are the cause of thermo convective structure formations. The stability diagram and the effect of the entrance domain on the exchanges are presented. We classify the different behaviors and we complete the classical stability analysis by linear stability on a bounded domain. The numerical results demonstrate explicitly the important effect of the entrance domain on the obtained solution and also on the resulting exchange (heat and mass). © 2012 by Begell House, Inc. Source


Hrarti M.,University of Poitiers | Hrarti M.,Mohammed V University | Saadane H.,University of Poitiers | Larabi M.-C.,University of Poitiers | And 2 more authors.
3rd European Workshop on Visual Information Processing, EUVIP 2011 - Final Program | Year: 2011

In the frame-level rate control algorithm of H.264/AVC baseline profile, the Quantization Parameter (QP) is determined according to a target bit-rate estimated by the bit allocation process and a frame complexity measure. The target bits calculation process assumes similar characteristics for all frames and for a single frame on the whole set; the Mean Average Difference (MAD) is used as complexity measure. As a result, inappropriate QP values are selected leading to inefficient bit allocation. To overcome this limitation, we propose a new frame level QP adjustment. The proposed algorithm exploits a saliency map to allocate more bits to more salient frames. The saliency map is produced simulating the human visual attention by a bottom-up (signal-dependent) approach. Experimental simulations conducted at low bit-rates show that the proposed approach reduces bit-rates up to 26% without visual quality loss when compared to H.264/AVC JM15.0 reference software. © 2011 IEEE. Source


Khattab K.,DRIVE | Brunet P.,DRIVE | Zamilpa C.,DRIVE | Jaafari A.,LTI
SAE Technical Papers | Year: 2011

This article focuses on the wireless transfer of energy. It describes the operation of a transformer without magnetic circuit associated with a resonant inverter to meet the constraints imposed by mobile sources (catenaries with magnetic induction to power electric vehicles). The receiving and transmitting units consist of an air-gap transformer and a generator who feeds the transformer. In this article, we show how to determine the transformer's parameters and configuration needed for this transfer to be efficient. The transformer is fed by a half-bridge converter for serial resonant load. The primary winding of the transformer is fixed on the ground. The secondary winding can move horizontally in a parallel plane of that of the primary. This application targets mainly the transfer of static electricity for the charging of batteries and super capacitors in electric cars and trams. Copyright © 2011 SAE International. Source


Grant
Agency: National Science Foundation | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2005

This Small Business Innovation (SBIR) Phase I project will investigate the feasibility of the design, manufacture, and marketing of an apparatus that will demonstrate the phenomena of rotating fluid systems that parallel those in weather and ocean systems. With such a device and supporting materials for educators and students, underlying physical principles can be taught that help to satisfy the NRC Standards and AAAS Benchmarks. When coupled with suitable simulation software, such information-based technology can be used to encourage interactive and inquiry-based activities. Such a system will help promote interdisciplinary studies, use the latest space-based imagery, and aid in teaching the content of the national standards, especially earth science at the middle and high school level. The project seeks to take the results of experimental techniques used to hone the physical intuitions of scientists and their university students and make them accessible to lower academic levels and to the general public. Without employing the sophisticated mathematical models needed to understand the physics of rotating fluids, novices will be able to comprehend the connection between global processes and the weather they observe daily. On a broader scale, the project will result in a deeper understanding among school children and the general public of the global nature of weather systems and the methods by which scientists come to understand their underlying driving forces.


Gueye A.K.,ESP | Janicot S.,University Pierre and Marie Curie | Niang A.,LTI | Sawadogo S.,LTI | And 3 more authors.
Climate Dynamics | Year: 2011

The aim of this work is to define over the period 1979-2002 the main synoptic weather regimes relevant for understanding the daily variability of rainfall during the summer monsoon season over Senegal. "Pure" synoptic weather regimes are defined by removing the influence of seasonal and interannual time scales, in order to highlight the day by day variability of the atmospheric circulation. The Self-Organizing Maps (SOM) approach, a clustering methodology based on non-linear artificial neural network, is combined with a Hierarchical Ascendant Classification to compute these regimes. Nine weather regimes are identified using the mean sea level pressure and 850 hPa wind field as variables, and gathered into three classes. Two of these weather regimes represent the classical 3-5-day African easterly waves with a mean wavelength of about 3,000 km. Three others are characterized by a modulation of the semi-permanent trough located along the western coast of West Africa and might be interpreted in terms of the 6-9-day easterly waves. The last four weather regimes are characterized by a more or less strong north-south dipole of circulation. They can be interpreted as a northward/southward displacement of the Saharan Heat Low for two of them, and a filling/deepening of this depression for the other two. The circulation patterns of all these nine weather regimes are very consistent with the associated anomaly patterns of precipitable water, mid-troposphere vertical velocity, outgoing longwave radiation, and finally rainfall. Rainfall distribution is also highlighted over the southwestern area of Senegal. © 2010 Springer-Verlag. Source

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