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Vincent M.,Schneider Electric | Vincent M.,CEA Grenoble | Rowe S.W.,Schneider Electric | Poulain C.,CEA Grenoble | And 4 more authors.
Applied Physics Letters | Year: 2010

Material transfer from one electrical contact part to the other has already been reported in microswitches operating under hot switching conditions. By using an atomic force microscope with a conductive cantilever, we highlighted that electrons are emitted from the cathode when electrode separation becomes less than a few tens of nanometers. This electronic emission proves to follow Fowler-Nordheim theory and leads to the damage of the opposite contact member (anode) by impact heating. Anode material evaporates under this extreme heating and deposits on the opposite contact member (cathode), leading to a material transfer from anode to cathode. © 2010 American Institute of Physics. Source

Juillard J.,CNRS Electrical Engineering Laboratory of Paris
Journal of Sound and Vibration | Year: 2015

Abstract In this paper, the equations governing the pull-in of electrostatic (micro-electromechanical systems MEMS) oscillators are established and analyzed. This phenomenon defines the maximal oscillation amplitude that can be obtained without incurring instability and, hence, an upper limit to the performance of a given device. The proposed approach makes it possible to accurately predict pull-in behavior from the purely resonant case, in which the electrostatic bias is very small, to the static case. The method is first exposed in the case of a parallel-plate resonator and the influence of the excitation waveform on the resonant pull-in characteristics is assessed. It is then extended to the more complex case of clamped-clamped and cantilever beams. The results are validated by comparison with transient simulations. © 2015 Elsevier Ltd. Source

Hubert O.,Ecole Normale Superieure de Cachan | Daniel L.,CNRS Electrical Engineering Laboratory of Paris
Journal of Magnetism and Magnetic Materials | Year: 2011

A main limitation of most models describing the effect of stress on the magnetic behavior is that they are restricted to uniaxial tensile or compressive stress. Nevertheless, stress is multiaxial in most of industrial applications. An idea to overcome the strong limitation of models is to define a fictive uniaxial stress, the equivalent stress, that would change the magnetic behavior in a similar manner than a multiaxial stress. A first definition of equivalent stress, called the deviatoric equivalent stress, is proposed. It is based on an equivalence in magneto-elastic energy. This formulation is first derived for isotropic materials under specific assumptions. An extension to orthotropic media under disoriented magneto-mechanical loading is made. A new equivalent stress expression, called generalized equivalent stress, is then proposed. It is based on an equivalence in magnetization. Inverse identification of equivalent stress is made possible thanks to a strong simplification of the description of the material seen as an assembly of elementary magnetic domains. It is shown that this second proposal is a generalization of the deviatoric expression. Equivalent stress proposals are compared to former proposals and validated using experimental results carried out on an ironcobalt sheet submitted to biaxial mechanical loading. These results are compared to the predictions obtained thanks to the equivalent stress formulations. The generalized equivalent stress is shown to be a tool able to foresee the magnetic behavior of a large panel of materials submitted to multiaxial stress. © 2011 Elsevier B.V. All rights reserved. Source

Cho J.,Ecole Polytechnique - Palaiseau | Cho J.,KCC Corporation | O'Donnell B.,Ecole Polytechnique - Palaiseau | O'Donnell B.,Total S.A. | And 5 more authors.
Progress in Photovoltaics: Research and Applications | Year: 2013

We present a single pump-down process to texture hydrogenated amorphous silicon solar cells. Mats of p-type crystalline silicon nanowires were grown to lengths of 1 μm on glass covered with flat ZnO using a plasma-assisted Sn-catalyzed vapor-liquid-solid process. The nanowires were covered with conformal layers of intrinsic and n-type hydrogenated amorphous silicon and a sputtered layer of indium tin oxide. Each cell connects in excess of 10 7 radial junctions over areas of 0.126 cmÂ. Devices reach open-circuit voltages of 0.8 V and short-circuit current densities of 12.4 mA cm-2, matching those of hydrogenated amorphous silicon cells deposited on textured substrates. Copyright © 2012 John Wiley & Sons, Ltd. Source

Satiramatekul T.,Kasetsart University | Bouillault F.,CNRS Electrical Engineering Laboratory of Paris
IEEE Transactions on Magnetics | Year: 2010

This paper deals with two-dimensional modeling of a multifilamentary wire composed of two superconducting filaments in a conducting matrix. In order to avoid three-dimensional problem solving, a novel technique is proposed to solve the coupled problem in two dimensions. For that, it is enough to divide the filaments in several sections in the direction of the length of the wire and to impose a relation between the currents crossing the matrix and the electric fields in the different sections of the filaments. The numerical simulation results show the distributions of the current density in the modeled domain. The influence of the wire length on the total magnetization is also considered. © 2006 IEEE. Source

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