L'article propose, pour l'étude des chauffages industriels mettant en jeu plusieurs gradateurs triphasés, une méthode de caractérisation de l'onde de la puissance instantanée triphasée. Dans le cas d'un fonctionnement en trains d'onde à période minimale (commande discrète dite syncopée) et afin de rendre compte du comportement global d'un ensemble comportant plusieurs gradateurs, différentes modélisations de l'onde triphasée sont envisagées. Une fois établi le concept de la modélisation, et à partir de signaux de commande élaborés logiciellement, une procédure de reconstruction de l'onde de puissance associée à chaque gradateur permet de simuler et de caractériser les performances de ces systèmes de chauffage industriel. Les résultats de simulation validés par des essais expérimentaux permettent d'envisager la mise au point de stratégies globales minimisant les fluctuations de la puissance triphasée instantanée.

We present an iterative method for the determination of the potential map of the conducting skin coating on the surface of cast resin electrical devices. The efficiency of the procedure is shown on an exactly solvable case (bus bar). For complex devices, it is shown that the original 3D problem often degenerates into two standard 2D resolutions and one iteration. This point is illustrated with a one-phase Cast Resin Transformer.

Le but de cette étude est de mettre en évidence le comportement non linéaire des générateurs électrochimiques secondaires soumis à des sollicitations impulsionnelles de charge ou de décharge de grande amplitude. L'influence de la création de composés gazeux sur l'impédance de la batterie est examinée. En second lieu, cette non-linéarité au niveau de la réponse à l'impulsion est exploitée pour détecter l'état de charge de la batterie. Les informations issues de la réponse à diverses sollicitations impulsionnelles en courant (différentes durées, différentes amplitudes, en charge ou en décharge) sont fusionnées, afin de détecter l'état de charge de l'accumulateur. Une méthodologie pour prendre en compte le régime de décharge est exposée dans l'article (cas des accumulateurs plomb-acide). Une réalisation expérimentale permettant la détection de l'état de charge d'un accumulateur au plomb est présentée.

Transport critical current measurements were performed at 77 K on bulk silver-less (Bi, Pb)2Sr2Ca2Cu3O10+x ceramics textured by slow sinter-forging process. The influences of the 85 K superconductive 2212 phase and non-superconductive secondary phases (SrxCa1−x)2PbO4, (Sr,Ca)14Cu24Oy and (SrxCa1−x)2CuO3, are discussed in terms of their amounts, their grain sizes and shapes and their distribution among the 2223 matrix. The importance of the temperature profile and the atmosphere the annealing that follows the sinter-forging process is clearly demonstrated.

For the first time, the influence of an electron beam irradiation on InAs with native oxides was investigated. An irradiation modifies the chemical and physical properties of the surface oxides. The latent image can later be revealed by in situ exposure to Cl2 gas at 190 °C. The etching rate by Cl2 of the irradiated native oxides depends on the experimental conditions; it can be either increased or decreased. In consequence, differently irradiated zones of a sample surface later exposed to Cl2 are more or less etched than the non irradiated areas. The effect depends not only on the dose, but also on the electron energy: an irradiation is more effective at low energy. A stationary beam exposure at 30 keV reveals the contribution of the backscattered electrons, their geometrical and energetic spreading and the effect of a gradual variation of the dose. This experiment is compared to the spatial distribution of the backscattered electrons obtained by means of a Monte-Carlo type calculation.

The losses of an inverter supplying an induction motor are compared for different vector control and pulse width modulation strategies. The study is carried out in simulation. As a conclusion, an optimal control in terms of losses is determined.

The characteristic features of a dc discharge generated between parallel plate electrodes and especially the discharge stabilization by the GaAs semiconducting cathode in such a system are studied. The cathode was irradiated on the back-side with IR light in a particular wavelength range that was used to control the photoconductivity of the material. The semiconductor material was found to stabilize the discharge. The current-voltage and radiation-voltage characteristics of the gas discharge cell with a semiconducting cathode were obtained experimentally. An investigation of the effect of the voltage amplitude on the dynamics of transient processes in the plane semiconductor-discharge gap structure was made for explanation of the light intensity and current decay. Expressions are obtained for the photoelectric gain.

A $\rm (\bar{1}11)NiSi_2 //(1\bar{1}5)Si$ heterotwin interface has been observed by high resolution electron microscopy (HREM) along the common direction $\rm [\bar{1}\bar{1}0]NiSi_2 //[\bar{1}\bar{1}0]Si$ to identify the long period atomic structural units (ASU's). Coexistence of two different structural doMayns has been found with ASU's corresponding to two different cycles of five-, six-, and seven-atom rings. A dislocation/ledge (DL) has been particularly studied because its separates these two unusual cycles of ASU's. The elastic displacement field u of the atom columns around the DL has been calculated using both crystallographic and anisotropic elasticity properties of the crystals, assuming a two-dimensional u field. From a comparison between the positions of the atom columns as derived from elasticity calculations and as deduced from the HREM image, it is concluded that the DL is a mixed dislocation with the Burgers vector $\rm (-1/4)[111]NiSi_2 + (1/2)[1\bar{1}0]Si= (1/12)[515]Si$, a result also in agreement with the imperceptible ledge height associated with the DL core. Such a Burgers vector underlines the role of the Si matrix dislocations for producing such structural doMayns.

Le stockage d'énergie à l'aide de bobines supraconductrices soulève généralement le problème de la pollution électromagnétique par des champs de fuite extérieurs au dispositif. Différentes configurations ont été classiquement étudiées : le solénoïde, le tore, ainsi que les solénoïdes à axes parallèles non concentriques bobinés tête-bêche, en "fagot". Nous étudions ici une nouvelle configuration de stockage qui n'engendre qu'une pollution extérieure minimale. Le système théorique de base est constitué par l'association de deux distributions sphériques de courant concentriques. L'étude analytique que nous présentons s'appuie sur la résolution de l'équation de Laplace. L'étude de ce système couvre les données suivantes : l'énergie, l'induction ainsi que les données géométriques. On étudie aussi une configuration approchée de la configuration sphérique, constituée par des bobines circulaires. Une comparaison de ce système avec les solutions connues sera apportée en conclusion.

The current-voltage characteristics of a gas discharge system in parallel-plane geometry are studied. The gas discharge system with a photosensitive semiconductor cathode have been studied in a wide range of the gas pressures p (21.3−1013 hPa), inter-electrode distances d (10μm−5mm), and conductivities of the semiconductor. Gallium arsenide $(10^7 -10^8\, \Omegarm\ {\rm cm})$ has been used as the semiconducting cathode. The cathode was irradiated on the back-side with light in a particular wavelength range that was used to control the photoconductivity of the material. The semiconductor material was found to "stabilize" the discharge. When the current is increased above the stable limit, breakdown or small current oscillations begin. The filamentation was primary due to the formation of a space charge of positive ions in the discharge gap which changed the discharge from the Townsend to the glow type.

The uniaxial chiral medium, which is a modification of the well-studied reciprocal chiral material, can be created by embedding microscopic metal helices in an isotropic host medium in such a way that the axes of all helices are oriented parallel to a fixed direction but distributed in random locations. In the present investigation, based on the concept of cylindrical vector wave functions in this class of medium, electromagnetic scattering by a uniaxial chiral circular cylinder in the proximity of a PEC plane is rigorously formulated by eigenfunction expansion approach. Formulation of this problem is greatly facilitated by using the image theory of bianisotropic object in the presence of a PEC plane to replace the PEC by an image object with constitutive parameters of image forms. Numerical results indicate the phenomena of backscattering enhancement and polarization transformation phenomenon would occur, simultaneously.

The solar cell metallic contacts are decisive elements to get high and stable photovoltaic performance. On the other hand, the necessary cost reduction leads to the replacement of monocrystalline semiconductor by a multicrystalline one, and the evaporated contact by the screen printing technique; this last has the advantage of being inexpensive and easy to use. In this work, we have developed a methodology to characterize the screen printed contacts on multicrystalline silicon solar cells. These contact parameters are given by the TLM (Transmission Line Model) technique. This study constitutes in extending this model for multicrystalline silicon by the use of an average method. It is experimentally and analytically compared to a standard average technique. In this paper, we show that TLM measurements can be adapted, with a good accuracy, to characterize the screen printed contacts on multicrystalline silicon solar cells; thirty six TLM patterns are sufficient to get this.

We compare high resolution roughness measurements on fractured granite, basalt and sandstone samples. For granite and basalt, the fractures display over the full experimental length scale range a self-affine geometry with a characteristic Hurst exponent consistent with the value 0.8 suggested to be universal by several authors. For sandstone, the rugosity spectrum reMayns independent on the fracturation velocity but displays self-affine characteristics only for characteristic length scales roughly larger than the grain size: furthermore, the corresponding Hurst exponent takes a value 0.47 ± 0.05 distinctly smaller than the previous one. At characteristic length scales below the grain size, a clear cutoff is observed in the spectrum. This cut-off is shown through numerical simulations to be largely explainable by the faceted shape of the sand grains and to a minor degree by the finite size of the profilometer sensor tip. None of these factors seems to influence the low frequency part of the spectrum from which Hurst's exponent is determined. The differences between the values of Hurst's exponent may reflect the intergranular nature of fracture in the sandstone samples while no effect of structural heterogeneities on fracture propagation is observed in granite.

This paper presents a contribution to the numerical simulation of the left ventricle taking into account simultaneously the fluid flow inside the cavity and the motion of the cardiac wall. One describes mathematical tools which are useful for such a problem of fluid-structure interaction. After having written the continuous mathematical problem and noted the difficulties which exist to solve such a problem, one makes two important simplifying assumptions: on the one hand, one builds a new problem which, on the mathematical viewpoint, can be distinguished from the continuous problem but which, on the physical and physiological viewpoints, can be considered as acceptable. One builds then a software which has to be considered just as a numerical investigation tool. It can be noted that it is necessary to impose, for the shape of the cardiac wall, a time-evolution. Such a bi-dimensional framework is sufficient to study the numerical aspect of this interaction, but is not sufficient to investigate the effects of major parameters governing the behavior of the left ventricle.

Un modèle original a été adopté pour analyser l'hydrodynamique de la phase fondue pour la technique de la zone flottante, en croissance cristalline. En particulier, une petite échelle capillaire, située près des fronts de fusion, est prise en considération. Son extension se révèle influencer significativement la structure des écoulements. L'existence de solutions multiples est, pour la première fois, mise en évidence en gravité zéro.

A qualitative description of the plasma jet flow in field reversal configuration confinement scheme has been presented taking into account the conductivity and anisotropic temperature effects which were not included previously following the "free-streaming fluid model".

The structural model discussed in Part I of the present work is applied to "true" behavior – i.e. shear thinning followed by shear thickening (sometimes followed by shear thinning) – very often observed in complex fluids as the applied shear is increased. This model states that the viscosity η of these fluids – described as concentrated dispersions of several classes of Structural Units (SUs) – is a unique function of a flow-dependent effective volume fraction, φeff. The latter is expressed in terms of Si = fraction of "aggregated" particles contained in all the SUis (as SUs of i-class) and Ci = (ϕi−1−1)= "compactness factor", directly related to the mean compactness ϕi of SUis. Shear induced flocculation (SIF) is the more obvious process capable to explain the shear thickening behavior of partially flocculated suspensions (obviously, another process should be required for stabilized dispersions). After progressive reduction of SUs submitted to shear forces (i.e. leading to a decrease of Si), such a behavior should be observed if SIF occurs beyond a critical shear rate ${\dot {\gamma}_{\rm C}}$, then resulting in re-increase of Si, thus of φeff and η. The simplest "SIF-model" will introduce only one class of SUs, with only one variable S governed by a kinetic equation in which the kinetic rate for SU-formation increases with shear, thus giving the expected shear-thickening behavior if ${\dot {\gamma}}>{\dot {\gamma}_{\rm C}}$. However, at high shear rates, SIF is limited by a (Smoluchowski-like) shear decreasing sticking probability. Effects of varying model parameters on predictions of the resulting SIF-model are discussed. Finally, this model is tested by comparison with observed rheological behavior, namely viscosity change vs. pH in aqueous styrene-ethylacrylate dispersions, from Laun's data [2].

This paper is aimed at providing some data on the detonability of methane mixtures at a high initial pressure. The relevant work that has been performed so far was based on a conventional source of ignition, i.e., a blasting cap. Following these initiation experiments at the French German Research Institute (ISL), two sets of experiments were performed in CH4/Air mixtures, at initial pressures in the range of 0.1 to 3.7 MPa, at the University of Washington (UW): (1) using a piston that directly enters the test section in the velocity range of 1100–1800 ms−1 and (2) the piston impacts an intermediate section of CH4/O2. An additional series of experiments was performed using an initiator stage of stoichiometric CH4/O2 ignited by a 150 J conventional fuse cap.

An analysis of inertia effects in controlled stress rheometry is presented. For Newtonian fluids, this study takes exact account of both the instrumental inertia and the discontinuous stress change in this type of rheometer. In fact, supposedly smooth stress ramps are always approximated by a series of stress steps. The significance of this limitation, which is sometimes critical, is pointed out for the first time. The error induced by assuming that the stress ramps are smooth in Krieger's method for inertia correction [1], is quantitatively evaluated. An improved calculation for non-Newtonian, inelastic fluids is described.