CNRS Electrical Engineering Laboratory of Paris
CNRS Electrical Engineering Laboratory of Paris
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.
Cozza A.,CNRS Electrical Engineering Laboratory of Paris |
Monsef F.,CNRS Electrical Engineering Laboratory of Paris
IEEE Antennas and Wireless Propagation Letters | Year: 2017
The problem of predicting the performance of time-reversal transmissions (TRT) in a time-varying complex medium is addressed in this letter. The loss of coherence in the propagation medium and its nominal energy contrast are proven sufficient to predict the average loss of quality in received signals. In particular, it is shown how a perturbation in the medium affects in a different way coherent focusing and background fluctuations. In the extreme case of a diffusive medium (e.g., Rayleigh channels), the fluctuations intensity is unaltered. The predictions of the proposed theoretical models are validated against experimental results measured in a reverberation chamber, where a mechanical paddle (stirrer) acts as the source of perturbation in the medium. It is confirmed that, depending on the medium statistics, perturbations can have a varying impact on TRT performance. © 2002-2011 IEEE.
Zemmour H.,University Paris Est Creteil |
Baudoin G.,University Paris Est Creteil |
Diet A.,CNRS Electrical Engineering Laboratory of Paris
IEEE Antennas and Wireless Propagation Letters | Year: 2017
Wireless underground sensor networks (WUSNs) is an emerging area of research. They are used in many applications from intelligent irrigation to security and assisted navigation. WUSNs mainly use narrowband systems working in the frequency range below 1 GHz and, therefore, suffer from a poor localization capability and large-sized antennas. The use of impulse radio ultrawideband (UWB) technique allows alleviating these drawbacks. In this letter, the impact of soil on UWB underground-To-Aboveground communication link is studied experimentally. More specifically, the effects of the orientation of the buried antenna and burial depth and soil moisture are investigated. The experimental results show that, at 7 GHz, additional attenuations of 10, 34, and 40 dB are noted for depointing the underground antenna by 90°, increasing the depth from 0 to 30 cm and raising the soil moisture from 0% to 20%, respectively. Burial depth lower than 30 cm or soil moisture lower than 20% allow getting acceptable received signal strength (superior to-100 dBm) for communication and localization, particularly in the UWB low band (3.1-5 GHz). The obtained results bring out the feasibility of UWB WUSN. © 2002-2011 IEEE.
Dai J.,CNRS Electrical Engineering Laboratory of Paris |
Guillaud X.,École Centrale Lille
IEEE Transactions on Power Delivery | Year: 2017
The Modular Multilevel Converters (MMCs) have emerged as the most suitable converter technology for HVDC application. Besides the recognized advantages over conventional VSCs, one of the remarkable features of the MMC is its ability to store energy in the distributed sub-module capacitors. This important feature can be used to mitigate the fluctuations of the DC voltage, which is inherently volatile against power disturbances compared to the frequency of conventional AC systems. This paper proposes a novel control strategy, named Virtual Capacitor Control, which enables to utilize the energy storage capability of the MMC to attenuate voltage fluctuations of HVDC systems. With the proposed control, the MMC behaves as if there were a physical capacitor whose size is adjustable and can be even bigger than the physical capacitor embedded in the converter. This control allows the system operator to optionally adjust this virtual capacitor of each MMC station, and thus it provides an additional degree of freedom to the HVDC system operation. The EMT simulations of a 401-level MMC-based HVDC link system show the effectiveness of the proposed control to improve DC voltage transient dynamics. IEEE
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.
Longeaud C.,CNRS Electrical Engineering Laboratory of Paris |
Journal of Non-Crystalline Solids | Year: 2012
In this paper we review some of the techniques based on the photoconductivity property of hydrogenated amorphous silicon (a-Si:H) from which it is possible to extract transport parameters as well as density of states (DOS) spectroscopies. We also present a new experiment based on the steady state photocarrier grating technique. We show that combined with simple steady state photoconductivity it gives information on the DOS. The comparison of these results with those of other techniques used for DOS measurements theoretically allows determination of transport parameters in a-Si:H. © 2011 Elsevier B.V.
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.
Longeaud C.,CNRS Electrical Engineering Laboratory of Paris
Review of Scientific Instruments | Year: 2013
The design of an automated steady state photocarrier grating (SSPG) experiment is presented that matches most of the requirements of an industrial environment. We first briefly recall the bases of the SSPG technique and that the minority carrier diffusion length deduced from this experiment is a key parameter in the fabrication of thin film solar devices. We then underline the main drawbacks of the use of the classical SSPG technique as an industrial and systematic characterization technique mostly that all the adjustments have to be done manually. We show that this issue can be overcome to end with a compact (90 × 60 cm2), fast, reliable, and easy-to-use system that could become a routine characterization technique for research laboratories and thin film solar industry. We illustrate the possibilities of this new system by showing some of the results obtained with it on very different thin films. © 2013 AIP Publishing LLC.
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.
Serhir M.,CNRS Electrical Engineering Laboratory of Paris
Progress In Electromagnetics Research B | Year: 2015
This paper studies the effect of three important parameters in planar time-domain (TD) near-field (NF) to far-field (FF) transformation. These parameters are the NF spatial sampling, NF measurement distance and scan surface truncation. The effect of these parameters over the TD FF accuracy are difficult to predict for Ultra Wide Band antennas. In this paper we aim to choose the optimum NF measurement parameters guaranteeing accurate calculation of the time-domain far-field. This allows the optimization of the computation time and memory requirements. Computations using analytic array of elementary dipoles radiation pattern are used to study the impact of each parameter in time-domain near-field antenna measurement. The comparison of the far-field results are presented in time and frequency domains. In particular, it is shown that the choice of the measurement distance and the size of the scan surface decide predominantly on the frequency band of accurate FF calculation. The used formalism in this paper for the NF to FF transformation is based on the Green's function.