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MULTISCALE HOMOGENIZATION OF NONLINEAR HYPERBOLIC EQUATIONS WITH SEVERAL TIME SCALES

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Acta Mathematica Scientia 2011年第3期31卷 843-856页

作者： jean Louis Woukeng david Dongo Department of Mathematics and Computer Science Faculty of Science University of Dschang

We study the multiscale homogenization of a nonlinear hyperbolic equation in a periodic *** obtain an accurate homogenization *** also show that as the nonlinear term depends on the microscopic time variable,the global homogenized problem thus obtained is a system consisting of two hyperbolic *** is also shown that in spite of the presence of several time scales,the global homogenized problem is not a reiterated one.

关键词： hyperbolic multiscale nonlinear

Characterization of Particle Emissions of Turbocharged Direct Injection Gasoline Engine in Transients and Hot Start Conditions

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Journal of Thermal Science 2021年第6期30卷 2056-2070页

作者： Vincent BERTHOME david CHALET jean-François HETET Ecole Centrale de Nantes LHEEA Lab.(ECN/CNRS)Nantes 44300France

Reducing pollutant emissions,particularly soot particles emitted by internal combustion engines,is a major challenge for car *** this paper,the experimental setup is a turbocharged three-cylinders gasoline direct injection engine installed on a HORIBA dynamic test driven by a HORIBA STARS *** particle-measuring device is a Pegasor Particles Sensor that measures the current carried by previously electrically charged *** hot engine stabilized tests,with lambda parameter lower or equal to one,have very low emission levels,unlike dynamic *** a consequence,the present paper deals with experiments in transient *** diesel engine,cycle tests show that particulate emissions vary *** understand the phenomenon,a simple transient was created and reproduced a hundred times in order to obtain enough data to analyze and compare these different *** transient starts from idle to reach the speed of 2000 r/min and 60 N·m in 5 *** reach this point,it is necessary to stay in full load for about 3 *** maximum deviations of particles reaches 85%with the standard deviationσ=18%.The cylinder pressure sensor shows significant variations at the very beginning of each transient,i.e.,during the first 500 *** kind of result was observed for Worldwide harmonized Light vehicles Test Cycles(WLTC)with a maximum deviations of particles reaching 75%withσ=30%,on Real Drive Emissions Cycle(RDE)with a maximum deviations of particles reaching 45%withσ=22%and for a 300 s Mini-Cycle with a maximum deviations of particles reaching 70%withσ=17%.The Mini-cycle is made up of the five largest accelerations of the WLTP cycle.A complete analysis highlights the importance of filling the first engine *** depends on the opening speed of the throttle,the position of the crankshaft at the beginning of the transient,and the acceleration of the first ***,the NO_(x) sensor shows very slight variations between each *** a consequence,i

关键词： particles gasoline engine cycle-to-cycle variations transients oil consumption

On the relevance of analytical film thickness EHD equations for isothermal point contacts: Qualitative or quantitative predictions?

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Friction 2016年第4期4卷 369-379页

作者： jean-david WHEELER Philippe VERGNE Nicolas FILLOT david PHILIPPON Univ Lyon INSA Lyon CNRS LaMCoS-UMR5259 Villeurbanne F-69621 France

Thin film and elastohydrodynamic lubrication regimes are rather young domains of tribology and they are still facing unresolved *** they rely upon a full separation of the moving surfaces by a thin (or very thin) fluid film,the knowledge of its thickness is of paramount importance,as for instance to developing lubricated mechanisms with long lasting and efficient *** a consequence,a large collection of formulae for point contacts have been proposed in the last 40 ***,their accuracy and validity have rarely been *** purpose of this paper is to offer an evaluation of the most widespread analytical formulae and to define whether they can be used as qualitative or quantitative *** methodology is based on comparisons with a numerical model for two configurations,circular and elliptical,considering both central and minimum film thicknesses.

关键词： thin film lubrication elastohydrodynamic lubrication (EHL) film thickness prediction EHD analytical equation central film thickness minimum film thickness circular contacts elliptical contacts

Oil Strategies Benefits over Different Driving Cycles using Numerical Simulation

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Journal of Thermal Science 2017年第4期26卷 371-377页

作者： Hanna SARA david CHALET Mickael CORMERAIS jean-Francois HETET Ecole Centrale de Nantes LHEEA lab.(ECN/CNRS)NantesFrance MANN+HUMMEL France LavalFrance

95 g/kin is the allowed quantity of CO2 emission normalized to NEDC to be set in 2020. In addition, NEDC will be replaced by more severe driving cycles and will be united worldwide. To respond to those criteria, automotive industries are working on every possible field. Thermal management has been proved to be effective in reducing fuel consumption. Cold start is a primordial reason of ovcrconsumption, as the engine highest efficiency is at its optimal temperature. At cold start, the engine＇s oil is at its lowest temperature and thus its higher viscosity level. A high viscosity oil generates more friction, which is one of the most important heat losses in the engine. In th/s paper, hot oil storage is studied. Numerical simulations on GT-suite model were done. The model consists of a 4-cylinder turbocharged Diesel engine using a storage volume of 1 liter of hot oil. Ambient temperature vari- ation were taken into consideration as well as different driving cycles. Furthermore, different configurations of the thermal strategy （multifunction oil sump） were proposed and evaluated. Lubricant temperature and viscosity profiles are presented in the article as well as fuel consumption savings for different configurations, driving cycles and ambient temperatures.

关键词： Thermal management Hot oil storage Oil sump Oil viscosity Fuel consumption

Covalent functionalization/polycarboxylation of tungsten disulfide inorganic nanotubes （INTs-WS2）

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Nano Research 2015年第5期8卷 1454-1463页

作者： Daniel Raichman david A. Strawser jean-Paul Lellouche Department of Chemistry Nanomaterials Research Center Institute of Nanotechnology & Advanced Materials Bar-Ilan University Ramat-Gan 5290002 Israel

Inorganic nanotubes of tungsten disulfide （INTs-WS2） are insoluble in common solvents and practically inert, hindering their usefulness in both research and commercial applications. The covalent attachment of functional species onto the surface of INT-WS2 is a critical first step in realizing the potential that INT-WS2 offer for high-performance materials and products. Although a few attempts have been reported regarding preparing modified nanotubes, only a limited range of surface functionalities is possible with these methods. We have developed a versatile method, based on a modified, highly electrophilic acidic Vilsmeier- Haack reagent, to produce covalently bonded, polycarboxylated functional WS2 nanotubes that are dispersible in polar liquids, including water. The surface polycarboxylated shell provides a means for additional derivatization, enabling matching compatibility of derivatized nanotubes to both hydrophobic and hydrophilic materials. Nanocomposites incorporating derivatized INT-WS2 are expected to show improved properties as a result of enhanced interfacial compatibility, made possible by the large number of classes of functionalization available through the initial polycarboxylation step.

关键词： tungsten disulfide nanotubes inorganic nanotube of tungsten disulfide(INT-WS2) Vilsmeier-Haack reagents polycarboxylation inorganic nanotube functionalization

Modelling of Electrical Conductivity of a Silver Plasma at Low Temperature

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Plasma Science and Technology 2016年第8期18卷 812-820页

作者： Pascal ANDRE William BUSSIERE Alain COULBOIS jean-Louis GELET david ROCHETTE Université Clermont Auvergne LAEPT MERSEN 15 rue Jacques de Vaucanson

During the working of electrical fuses, inside the fuse element the silver ribbon first begins to melt, to vaporize and then a fuse arc appears between the two separated parts of the element. Second, the electrodes are struck and the burn-back phenomenon takes place. Usually, the silver ribbon is enclosed inside a cavity filled with silica sand. During the vaporization of the fuse element, one can consider that the volume is fixed so that the pressure increase appears to reach pressures higher than atmospheric pressure. Thus, in this paper two pressures, 1 atm and 10 atm, are considered. The electrical field inside the plasma can reach high values since the distance between the cathode surface and the anode surface varies with time. That is to say from zero cm to one cm order. So we consider various electrical fields： 102 V/m, 103 V/m, 5×103 V/m, 104 V/m at atmospheric pressure and 105 V/m at a pressure of 10 atm. This study is made in heavy species temperature range from 2,400 K to 10,000 K. To study the plasma created inside the electric fuse, we first need to determine some characteristics in order to justify some hypotheses. That is to say： are the classical approximations of the thermal plasmas physics justified？ In other words： plasma frequency, the ideality of the plasma, the Debye-Hückel approximation and the drift velocity versus thermal velocity. These characteristics and assumptions are discussed and commented on in this paper. Then, an evaluation of non-thermal equilibrium versus considered electrical fields is given. Finally, considering the high mobility of electrons, we evaluate the electrical conductivities.

关键词： electrical conductivity silver fuses non-ideal plasma Debye-Hiickelapproximation drift velocity thermal velocity thermal non-equilibrium electrical fields

Mitochondrial recruitment in myelin:an anchor for myelin dynamics and plasticity?

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Neural Regeneration Research 2024年第7期19卷 1401-1402页

作者： jean-david M.Gothié Timothy E.Kennedy Department of Neurology and Neurosurgery Montreal Neurological InstituteMcGill UniversityMontrealQCCanada

Optimal propagation of neuronal electrical impulses depends on the insulation of axons by myelin,produced in the central nervous system by *** is an extension of the oligodendrocyte plasma membrane,which wraps around an axon to form a compact multi-layered *** is composed of a substantially higher proportion of lipids compared to other biological membranes and enriched in a small number of specialized proteins.

关键词： plasticity insulation dynamics

Migration of bone marrow progenitor cells in the adult brain of rats and rabbits

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World Journal of Stem Cells 2016年第4期8卷 136-157页

作者： Donnahue Dennie jean-Pierre Louboutin david S Strayer Section of Anatomy Department of Basic Medical SciencesUniversity of the West IndiesMona Campus Department of Cell Biology Anatomy and PathologyThomas Jefferson University

Neurogenesis takes place in the adult mammalian brain in three areas:Subgranular zone of the dentate gyrus(DG);subventricular zone of the lateral ventricle;olfactory *** molecular markers can be used to characterizethe cells involved in adult *** has been recently suggested that a population of bone marrow(BM)progenitor cells may migrate to the brain and differentiate into neuronal *** explore this hypothesis,we injected recombinant SV40-derived vectors into the BM and followed the potential migration of the transduced ***-term BM-directed gene transfer using recombinant SV40-derived vectors leads to expression of the genes delivered to the BM firstly in circulating cells,then after several months in mature neurons and microglial cells,and thus without central nervous system(CNS)*** of transgene-expressing cells expressed NeuN,a marker of mature ***,BM-derived cells may function as progenitors of CNS cells in adult *** mechanism by which the cells from the BM come to be neurons remains to be *** the observed gradual increase in transgene-expressing neurons over 16mo suggests that the pathway involved differentiation of BM-resident cells into neurons,cell fusion as the principal route cannot be totally ruled *** studies using similar viral vectors showed that BM-derived progenitor cells migrating in the CNS express markers of neuronal precursors or immature ***-positive cells were found in the subgranular zone of the DG of the hippocampus 16 mo after intramarrow injection of the *** addition to cells expressing markers of mature neurons,transgene-positive cells were also positive for nestin and doublecortin,molecules expressed by developing neuronal *** cells were actively proliferating,as shown by short term BrdU incorporation *** seizures by using kainic acid increased the number of BM progenitor cells transduced by SV40vectors migrating

关键词： Stem cells Bone marrow Hippocampus Cell therapy SV40 Brain Nestin Doublecortin Neurons Development Epilepsy Seizures

Rectifying jet breakup by electric forcing

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Droplet 2023年第2期2卷 85-93页

作者： david Van Assche Thomas Beneyton jean-Christophe Baret CRPP UMR5031CNRSUniversitéde BordeauxPessacFrance Institut Universitaire de France ParisFrance

The high-throughput production of monodisperse droplets is paramount in most of the applications in droplet *** a flow-focusing junction,a straightforward way to increase droplet production rate is to increase the flow ***,at a critical flow velocity,the droplet monodispersity breaks down due to a transition from the dripping to the jetting *** a result,a much more polydisperse droplet population is *** change from monodisperse to polydisperse droplet production emerges from the intrinsic properties of the instabilities of *** the jetting regime,droplet pinch-off is governed by a convective instability which amplifies random noise when traveling down the jet leading to an irregular *** show that with the use of an amplitude-modulated electric signal,we select the breakup frequency of the *** the perturbation frequency close to the natural breakup frequency of the jet,we increase the monodispersity of the droplet *** method is applicable to droplet production at a high throughput,that is,beyond the dripping to jetting threshold,including an active control since the frequency,and hence droplet sizes,are determined by the forcing frequency.

关键词： disperse regime hence