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Aubert A.,CNRS Systems and Applications of Information Technologies and Energy Laboratory | Loyau V.,CNRS Systems and Applications of Information Technologies and Energy Laboratory | Mazaleyrat F.,CNRS Systems and Applications of Information Technologies and Energy Laboratory | LoBue M.,CNRS Systems and Applications of Information Technologies and Energy Laboratory
Journal of the European Ceramic Society | Year: 2017

In this study, we have compared magnetic and magnetostrictive properties of polycrystalline CoFe2O4 pellets, produced by three different methods, focusing on the use of Spark Plasma Sintering (SPS). This technique allows a very short heat treatment stage while a uniaxial pressure is applied. SPS was utilized to sinter cobalt ferrite but also to make the reaction and the sintering (reactive sintering) of the same ceramic composition. Magnetic and magnetostrictive measurements show that the reactive sintering with SPS induces a uniaxial anisotropy, while it is not the case with a simple sintering process. The induced anisotropy is then expected to be a consequence of the reaction under uniaxial pressure. This anisotropy enhanced the magnetostrictive properties of the sample, where a maximum longitudinal magnetostriction of -229ppm is obtained. This process can be a promising alternative to the magnetic-annealing because of the short processing time required (22min). © 2017 Elsevier Ltd.

Guo S.-S.,Wuhan University | Francais O.,CNRS Systems and Applications of Information Technologies and Energy Laboratory
Analytical Chemistry | Year: 2011

Electrochemical techniques based on ultramicroelectrodes (UMEs) play a significant role in real-time monitoring of chemical messengers' release from single cells. Conversely, precise monitoring of cells in vitro strongly depends on the adequate construction of cellular physiological microenvironment. In this paper, we developed a multilayer microdevice which integrated high aspect ratio poly(dimethylsiloxane) (PDMS) microfluidic device for long-term automated perfusion culture of cells without shear stress and an independently addressable microelectrodes array (IAMEA) for electrochemical monitoring of the cultured cells in real time. Novel design using high aspect ratio between circular "moat" and ring-shaped micropillar array surrounding cell culture chamber combined with automated "circular-centre" and "bottom-up" perfusion model successfully provided continuous fresh medium and a stable and uniform microenvironment for cells. Two weeks automated culture of human umbilical endothelial cell line (ECV304) and neuronal differentiation of rat pheochromocytoma (PC12) cells have been realized using this device. Furthermore, the quantal release of dopamine from individual PC12 cells during their culture or propagation process was amperometrically monitored in real time. The multifunctional microdevice developed in this paper integrated cellular microenvironment construction and real-time monitoring of cells during their physiological process, and would possibly provide a versatile platform for cell-based biomedical analysis. © 2011 American Chemical Society.

Amara Y.,CNRS Research Group of Electrotechnics and Automatics of Le Havre | Hlioui S.,Ecole Normale Superieure de Cachan | Hlioui S.,French National Conservatory of Arts and Crafts | Belfkira R.,Laboratoire Of Genie Electrique Of Paris Lgep | And 2 more authors.
IEEE Transactions on Vehicular Technology | Year: 2011

Double excitation synchronous machines combine permanent-magnet (PM) excitation with wound field excitation. The goal behind the principle of double excitation is to combine the advantages of PM-excited machines and wound field synchronous machines. These machines can constitute an energy-efficient solution for vehicle propulsion. This paper presents a comparison of the open circuit flux control capability of two structures of double excitation synchronous machines. First, a review of the state of the art of double excitation machines is presented. Then, the structures of these two machines are presented: one is a series double excitation synchronous machine and the other is a parallel double excitation synchronous machine. Finally, the open circuit flux control capabilities of both structures are compared. © 2011 IEEE.

El Korso M.N.,CNRS Systems and Applications of Information Technologies and Energy Laboratory | Renaux A.,University Paris - Sud | Boyer R.,University Paris - Sud | Marcos S.,University Paris - Sud
IEEE Transactions on Signal Processing | Year: 2013

This correspondence investigates lower bounds on estimator's mean square error applied to the passive near field source localization. More precisely, we focus on the so-called threshold prediction for which these bounds are known to be useful. We give closed form expressions of the McAulay-Seidman, the Hammersley-Chapman-Robbins, the McAulay-Hofstetter bounds and also, a recently proposed bound, the so-called Todros-Tabrikian bound, for the deterministic observation model (i.e., parameterized mean) and the stochastic observation model (i.e., parameterized covariance matrix). Finally, numerical simulations are given to assess the efficiency of these lower bounds to approximate the estimator's mean square error and to predict the threshold effect. © 2012 IEEE.

Moulin J.,University Paris - Sud | Mazaleyrat F.,CNRS Systems and Applications of Information Technologies and Energy Laboratory | Mendez A.,University Paris - Sud | Dufour-Gergam E.,University Paris - Sud
Journal of Magnetism and Magnetic Materials | Year: 2010

Thin films of Finemet-type alloy with thickness varying from 50 to 1000 nm have been deposited by RF sputtering and annealed at temperature ranging from 150 to 450 °C. Their magnetic and structural properties have been characterized using alternating gradient field magnetometry and X-ray diffraction. In addition, the stress in the films has been measured as a function of temperature from the curvature of the wafers using a laser scanning technique. The coercive field of the films first decreases with annealing temperature due to stress relaxation, and then increases again when crystallisation begins. The optimal annealing conditions comprises between the glass transition and the crystallisation temperature. Its is observed that the coercivity of the as-deposited material is continuously decreasing as the thickness increases, following an inverse square root dependence, in relation with the stress-induced magneto-elastic contribution to the total anisotropy. By opposition, it has been found that the coercive field of devitrified and totally relaxed films is inversely proportional to film thickness. In order to explain this evolution, a model is proposed, based on random anisotropy considerations applied to thin films in which the anisotropy was considered localised in the dimension of thickness. © 2009 Elsevier B.V. All rights reserved.

Joubert P.-Y.,University Paris - Sud | Le Diraison Y.,CNRS Systems and Applications of Information Technologies and Energy Laboratory
Proceedings of IEEE Sensors | Year: 2014

In this paper, an original pulsed eddy current (EC) imaging system dedicated to the enhanced non-destructive evaluation (NDE) of aeronautical riveted is presented. The system aims to combine the advantages of the pulsed eddy current (PEC) sensors with those of EC imaging devices. The system is based on the combination of a PEC inducer, and a magneto-optical (MO) set-up used to measure the magnetic twodimensional impulse response of the part under evaluation. The obtained data are in the form of a temporal succession of high resolution EC images, enabling both the spatial and temporal EC characterization of the part. The system is implemented here on aluminum riveted assemblies featuring calibrated defects placed next to rivets. The study demonstrates the relevance of the PEC imager to separate defects signature from rivets and to characterize the detected defects thanks to the extraction of space-time features from the provided data. © 2014 IEEE.

Idoughi L.,University Paris - Sud | Mininger X.,University Paris - Sud | Bouillault F.,University Paris - Sud | Bernard L.,University Paris - Sud | Hoang E.,CNRS Systems and Applications of Information Technologies and Energy Laboratory
IEEE Transactions on Magnetics | Year: 2011

The aim of the method detailed in this paper is to get an equivalent thermal model of a stator slot, in order to simplify the calculation of desired temperatures in an electrical machine winding. This study is divided in two steps: First, the equivalent thermal conductivity is deduced from a homogenization of the winding, and next, a discretization is achieved using the finite integration technique considering transient analysis. In order to evaluate the method, results from the equivalent model are compared with finite element simulations considering two slot geometries. © 2011 IEEE.

Loumaigne M.,University Paris - Sud | Praho R.,CNRS Systems and Applications of Information Technologies and Energy Laboratory | Nutarelli D.,University Paris - Sud | Werts M.H.V.,CNRS Systems and Applications of Information Technologies and Energy Laboratory | Debarre A.,University Paris - Sud
Physical Chemistry Chemical Physics | Year: 2010

Colloidal gold particles functionalised with oligoethylene-glycolated disulfide ligands and fluorescent moieties derived from fluorescein isothiocyanate (FITC) have been prepared and studied in aqueous suspension using fluorescence correlation spectroscopy (FCS). FCS probes the dynamics of the particles at the single object level, and reveals the desorption of fluorescent ligands which subsequently aggregate into larger (slower diffusing) objects. Cross-correlation spectroscopy of the FITC fluorescence and the Rayleigh-Mie scattering (RM-FCCS) of the gold cores shows that the only detectable fluorescent objects are free ligands and aggregates not associated with a gold particle. The fluorescence of bound fluorophores is quenched making their fluorescence too weak to be detected. FCS and RM-FCCS are useful tools for characterising functionalised noble metal particles in solution, under conditions similar to those used in optical bio-imaging. Desorption of thiolates from gold nanoparticles needs to be taken into account when working with these materials at low concentration. © 2010 the Owner Societies.

Bestaoui Y.,French National Center for Scientific Research | Kuhlmann H.,CNRS Systems and Applications of Information Technologies and Energy Laboratory
48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition | Year: 2010

The objective of this paper is to present the preliminary results of a model of a quadrotor airship, taking into account wind effect as well as the varying mass effects, using Newton formulation. Euler angles are used for kinematics. For dynamics, a mathematical description of a dirigible flight must contain the necessary information about aerodynamic, structural and other internal dynamic effects (engine, actuation) that influence the response of the airship to the controls. Copyright © 2010 by Bestaoui.

Navarro J.R.G.,CNRS Systems and Applications of Information Technologies and Energy Laboratory | Werts M.H.V.,CNRS Systems and Applications of Information Technologies and Energy Laboratory
Analyst | Year: 2013

Dark field resonant light scattering by gold and silver nanoparticles enables the detection and spectroscopy of such particles with high sensitivity, down to the single-particle level, and can be used to implement miniaturised optical detection schemes for chemical and biological analysis. Here, we present a straightforward optical spectroscopic methodology for the quantitative spectrometric study of resonant light scattering (RLS) by nanoparticles. RLS spectroscopy is complementary to UV-visible absorbance measurements, and we apply it to the characterisation and comparison of different types of gold, silver and gold-silver alloy nanoparticles. The potential of gold and silver particles as alternatives for fluorescent probes in certain applications is discussed. RLS spectroscopy is shown to be useful for studying analyte-induced gold nanoparticle assembly and nanoparticle chemistry, which can induce radical changes in the plasmonic resonances responsible for the strong light scattering. Furthermore, the feasibility of dark field RLS detection and quantitation of metal nanoparticles in microfluidic volumes is demonstrated, opening interesting possibilities for the further development of microfluidic detection schemes. © 2013 The Royal Society of Chemistry.

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