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Sagot B.,Ecole Superieure des Techniques Aeronautiques et de Construction Automobile
Journal of Aerosol Science | Year: 2013

Prediction of thermophoretic migration of particles suspended in a fluid is of practical importance for many industrial applications including gas cleaning applications. The design of particle-laden fluid systems requires an estimation of the thermophoretical deposition rate, which depends on the temperature gradient and also on the evaluation of a thermophoretic diffusion coefficient Kth, for which various theoretical models are available, such as the ones proposed by Talbot et al. (1980), or Beresnev and Chernyak (1995). A recent study by Sagot et al. (2009) has shown that although widely used, Talbot's model always provides Kth values higher than their measurements, in the transition regime. In the literature, the experimental determinations of Kth are usually based on one of the three techniques: measurement of forces, deposition efficiencies, or thermophoretic velocities. These techniques lead to different types of results: in an electrodynamical balance (Li & Davis 1995a, 1995b), the thermophoretical force can be measured directly, and a drag force model must be provided to build an experimental value of Kth. When using a velocity measurement technique, the determination of the thermophoretic velocity is based on the particle trajectories deviation measurements, in a jet flow within a temperature gradient (Prodi et al., 2002), and this result can be directly used to get a Kth value. Due to these differences in the measurement techniques and corresponding results, the confrontation of available data is difficult.The aim of this work is to propose a unified presentation of currently available data and models from the literature, and to establish that the model proposed by Beresnev and Chernyak (1995) is currently the most relevant one for the evaluation of Kth for spherical particles. Particularly, it is shown that this model is currently the only one to predict correctly the influence of the accommodation coefficient on the evaluation of the thermophoretic diffusion coefficient. © 2013 Elsevier Ltd. Source


Guerich M.,Ecole Superieure dIngenieurs Leonard de Vinci | Assaf S.,Ecole Superieure des Techniques Aeronautiques et de Construction Automobile
Journal of Vibration and Acoustics, Transactions of the ASME | Year: 2013

An optimization methodology to increase the noise transmission loss (TL) of damped sandwich structures is presented. The prediction of the TL uses a numerical tool based on a finite element formulation for the sandwich plate coupled to a boundary element method for the acoustic medium. This tool can be used for arbitrarily shaped three-layer sandwich plates with various boundary conditions and it is well adapted to parametric and optimization studies. First, a parametric study was conducted to choose the objective function, the constraints, and the pertinent design variables to use in the optimization problem which consist in reducing the sound power transmitted by a viscoelastically damped sandwich plate. Next, by constraining the acoustical behavior of the sandwich panel, the surface mass of the sandwich structure was minimized. It is shown that a significant reduction in the transmitted sound power can be achieved by selecting the appropriate geometric configuration and damping layer material. Copyright © 2013 by ASME. Source


Rizoug N.,Ecole Superieure des Techniques Aeronautiques et de Construction Automobile | Bartholomeus P.,Ecole Centrale Lille | Le Moigne P.,Ecole Centrale Lille
IEEE Transactions on Industrial Electronics | Year: 2010

In this paper, different modeling approaches representing the behavior of supercapacitors are presented. A hybrid modeling approach is developed to improve the characterization of classical supercapacitor models proposed in the literature. This approach uses various representations (frequency and temporal results) of the same cycling test to extract easily and with a good precision the parameters of the models. Then, it is applied for studying the ageing of this component, which mainly depends on the temperature and cycling process. © 2010 IEEE. Source


Assaf S.,Ecole Superieure des Techniques Aeronautiques et de Construction Automobile
International Journal of Acoustics and Vibrations | Year: 2011

In this study, a finite element model for the vibration analysis of cross-ply laminated sandwich beams is presented. This formulation is an extension of our previous work on predicting the acoustic and vibration responses of sandwich beams and plates with homogeneous elastic faces and a viscoelastic core. The formulation is based on a layerwise linear axial displacement through the beam thickness. The formulation assumes the classical lamination theory for the faces and Timoshenko theory for the core. The governing equations of motion are obtained using Hamilton's principle. A finite element method and a beam element are further developed to predict the natural frequencies and modal loss factors. In order to validate the proposed model, several free vibration analyses of composite sandwich beams with different boundary conditions, length-to-thickness ratios and face laminations are presented. The results are then compared with solutions available in the literature and with those obtained by the PATRAN/NASTRAN finite element software package. These results show the validity of the present formulation. Finally, the effects of ply-stacking sequence, core-to-face stiffness ratio and core-to-face thickness ratio upon the natural frequencies and modal damping are investigated. Source


Rizoug N.,Ecole Superieure des Techniques Aeronautiques et de Construction Automobile | Bartholomeus P.,Ecole Centrale Lille | Le Moigne P.,Ecole Centrale Lille
IEEE Transactions on Energy Conversion | Year: 2012

In this paper, a study of the supercapacitors ageing process is presented. The originality of this paper is that the tests are made under conditions similar to those of an industrial application. A continuous cycling is applied in order to obtain these test conditions. The measurement is done, thanks to a test bench developed in our laboratory. More than 560,000 cycles have already been done, which corresponds to 325 cumulated days of continuous cycling. These tests allow to understand the ageing process of supercapacitors and to follow the evolution of theirs characteristics during their lifetime. The aim of this paper is to study the behavior of the cells, which compose the supercapacitors module (48V/112F). © 2012 IEEE. Source

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