Performances of a Newly High Sensitive Trilayer F/Cu/F GMI Sensor

We have selected stress-annealed nanocrystalline Fe-based ribbons for ferromagnetic/copper/ferromagnetic sensors exhibiting high magneto-impedance ratio. Longitudinal magneto-impedance reaches 400% at 60 kHz and longitudinal magneto-resistance increases up to 1300% around 200 kHz.Comment: 4 pages, 6 figures, Sensors and Actuators A (in review

Induction Magnetometers Principle, Modeling and Ways of Improvement

International audienceThis book provides an introductory overview of the research done in recent years in the area of magnetic sensors. The topics presented in this book range from fundamental theories and properties of magnets and their sensing applications in areas such as biomedicine, microelectromechanical systems, nano-satellites and pedestrian tracking. Written for the readers who wished to obtain a basic understanding of the research area as well as to explore other potential areas of applications for magnetic sensors, this book presents exciting developments in the field in a highly readable manner

Capteurs et dispositifs électroniques des magnétomètres dédiés à l'étude des ondes dans les plasmas spatiaux.

Sensors and electronic conditioning of magnetometers dedicated to waves study in space plasma.Capteurs et dispositifs électroniques des magnétomètres dédiés à l'étude des ondes dans les plasmas spatiaux

The Search Coil Magnetometer for THEMIS

International audienceTHEMIS instruments incorporate a tri-axial Search Coil Magnetometer (SCM) designed to measure the magnetic components of waves associated with substorm breakup and expansion. The three search coil antennas cover the same frequency bandwidth, from 0.1 Hz to 4 kHz, in the ULF/ELF frequency range. They extend, with appropriate Noise Equivalent Magnetic Induction (NEMI) and sufficient overlap, the measurements of the fluxgate magnetometers. The NEMI of the searchcoil antennas and associated pre-amplifiers is smaller than 0.76 pT/ p Hz at 10 Hz.The analog signals produced by the searchcoils and associated preamplifiers are digitized and processed inside the IDPU, together with data from the EFI instrument. Searchcoil telemetry includes waveform transmission, FFT processed data, and data from a filter bank. The frequency range covered in waveform depends on the available telemetry. The searchcoils and their three axis structures have been precisely calibrated in a quiet site, and the calibration of the transfer function is checked on board usually once per orbit. The tri-axial searchcoils implemented on the five THEMIS spacecraft are working nominally

Periodic solutions and refractory periods in the soliton theory for nerves and the locust femoral nerve

Close to melting transitions it is possible to propagate solitary electromechanical pulses which reflect many of the experimental features of the nerve pulse including mechanical dislocations and reversible heat production. Here we show that one also obtains the possibility of periodic pulse generation when the boundary condition for the nerve is the conservation of the overall length of the nerve. This condition generates an undershoot beneath the baseline (`hyperpolarization') and a `refractory period', i.e., a minimum distance between pulses. In this paper, we outline the theory for periodic solutions to the wave equation and compare these results to action potentials from the femoral nerve of the locust (locusta migratoria). In particular, we describe the frequently occurring minimum-distance doublet pulses seen in these neurons and compare them to the periodic pulse solutions.Comment: 10 pages, 6 Figure

Effect of electric load and dual atmosphere on the properties of an alkali containing diopside-based glass sealant for solid oxide cells

© 2019 Elsevier B.V. All rights reserved.A new alkali-containing diopside based glass-ceramic sealant for solid oxide cells was synthesized, characterized and tested. The composition was designed to match the coefficient of thermal expansion (CTE) of Crofer22APU interconnect. The sealant has a glass transition temperature of 600°C, a crystallization peak temperature of 850°C and a maximum shrinkage temperature of 700°C, thus suggesting effective densification prior to crystallization. The CTE of the glass-ceramic is 11.5 10-6 K-1, a value which is compatible with the CTE for Crofer22APU stainless steel. Crofer22APU/glass-ceramic/Crofer22APU joined samples were tested in simulated real-life operating conditions at 800°C in dual atmosphere under an applied voltage, monitoring the electrical resistivity. The effect of two different applied voltages (0.7V and 1.3V) was evaluated. A voltage of 1.3V led to a rapid decrease in the electrical resistivity during the test;such a drop was due to the formation of Cr2O3 “bridges” that connected the two Crofer22APU plates separated by the sealant. There was no decrease in the resistivity when a voltage of 0.7V was applied. Instead,resistivity value remained stable at around 105 Ω cm for the 100h test duration. The degradation mechanisms, due to both the alkali content and the applied voltage, are investigated and discussed.Peer reviewe

Development of the self-healing concept for high temperature sealing of electrochemical cells

Un des points clés pour l’utilisation sur le long terme des SOEF et SOFC est l’étanchéité. Les solutions de scellement les plus répandues sont des matériaux rigides de type vitreux. Ils présentent l’inconvénient de se fissurer lorsqu’ils sont soumis à des cycles thermiques. Ceci est dû aux différences de CET entre les composants métalliques ou céramiques et les matériaux vitreux. L’autocicatrisation est une solution prometteuse pour pallier ce problème, deux mécanismes existent : intrinsèque et extrinsèque. L’autocicatrisation intrinsèque de matériaux vitreux est basée sur leur ramollissement. Nous avons développé une formulation de joints vitreux «pâteux» qui présente des propriétés autocicatrisantes, donc moins sensible aux différences de CET. La viscosité de ces verres a été estimée par microscopie de chauffage et leur stabilité a été caractérisée par DRX et microsonde de Castaing. L’autocicatrisation extrinsèque ne nécessite pas d’intervention extérieure. Elle est obtenue par ajout de particules cicatrisantes à la matrice vitreuse. Lors de l’apparition de fissures, les particules s’oxydent au contact de l’atmosphère pour former des oxydes qui donne in situ de nouveaux verres. Ces oxydes, fluides à la température de fonctionnement, s’écoulent dans la fissure, formant localement, par réaction, un nouveau verre. Des tests réalisés in situ par MEBE-HT ont permis de mettre en évidence le processus d’autocicatrisation. La formation de phases cicatrisantes a été caractérisée par microsonde de Castaing et par RMN. Un ensemble de caractérisations a été effectué afin de valider l’applicabilité de l’autocicatrisation extrinsèque aux joints de scellement vitreux.A key point for using SOEC and SOFC in the long-term is the sealant. The most sealing solutions commonly used are rigid materials, particularly glassy seals. However, they have the disadvantage of cracking in operation when subjected to thermal cycles. This is mainly due to TEC differences between metal and ceramic components and glass materials. The self-healing is a promising solution to overcome this problem. Two mechanisms exist: intrinsic and extrinsic. The intrinsic self-healing of glassy materials is based on their softening at high temperature. We developed a formulation of viscous glass seal that exhibits self-healing properties at the operating temperature systems SOEC/SOFC. They are less sensitive to differences of TEC. The glass viscosity was estimated by hot stage microscopy and their stability under use condition has been characterized by XRD and Castaing microprobe. In contrast, the extrinsic self-healing requires no external intervention. It is obtained by the addition of healing particles in the glassy matrix. When cracks occur, the particles oxidize with atmosphere contact to form oxides and in-situ new glasses. We developed this extrinsic method from particles generating B2O3 and V2O5. These oxides, fluid at operating temperature 700-900°C, flow in the crack and form a new locally glass by reaction with glassy matrix. An in-situ test by HT-ESEM highlights the self-healing process. The formation of glass and crystal phases is characterized by Castaing microprobe and solid state NMR. A set of physico-chemical characterization was performed to validate extrinsic self-healing applicability in the SOEC/SOFC glassy seal

Caractérisations numérique et expérimentale du comportement thermo-aéraulique d’une double-fenêtre active

Double windows appear as a relevant renovation solution to both energy and architectural questions of historic buildings preservation. The device consists in the addition of a second window behind an original one, the new one being mainly installed on the interior side of the historic facade. Double windows differ from double glazings since it is a question of adding an entire window, not just a glazed surface. The scientific literature investigation highlighted the lack of knowledge concerning historic buildings integration of double windows although it alters their design and their working. The device studied in this PhD thesis is an interior double window, adapted to historic features of XIXth century buildings, mechanically ventilated making this façade element active and innovative. There is no characterization or characterization tool of this kind of device yet. Thus, this PhD work aims to characterize the thermo-aeraulic behaviour and performances and to extract some design or use recommendations. With this in mind, two approaches were set up. The first one, the experimental approach, consisted in the design and the use of multi-scale prototypes. Two kind of prototype were elaborated in order to perform both controlled conditions and in situ tests. Several experimental campaigns were led et and provided a strong experimental database. This work allowed us to describe the thermo-aeraulic behaviour of the active double window in many functional configurations and to highlight the dynamic characteristics of its energy performances. However, it appeared that the characterization remained incomplete so we decided to set up a second approach. This latter, which is numerical, consisted in the precise and dynamic modelling of the active double window. The numerical model was experimentally validated thanks to the measurements database and to an original and critical validation method. Finally, the numerical approach focused on the parametrical characterization of the active double window in order to back up and complete the experimental previous observations. This parametrical approach also highlighted a dynamic determining method of the thermal performances.La double-fenêtre est une solution de rénovation qui répond aux problématiques énergétique et architecturale de préservation des façades du bâti ancien. Elle constitue un système basé sur la pose de deux fenêtres, l’une derrière l’autre, la nouvelle fenêtre étant le plus souvent, posée du côté intérieur de l’habitat ancien. Ce système se différencie des doubles vitrages puisqu’ici il s’agit d’ajouter une fenêtre entière (dormant et ouvrant). L’étude approfondie de la littérature scientifique a mis en avant qu’aucune considération n’a été apportée à l’application de ce dispositif à des bâtiments historiques alors que cela modifie fortement sa conception et son fonctionnement. Le système étudié dans ce travail de thèse est une double-fenêtre par l’intérieur, adaptée aux bâtis historiques du XIXe siècle, ventilée mécaniquement en insufflation rendant cet élément de façade actif. Il s’agit d’un dispositif innovant que ce soit par son domaine d’application ou par ses propriétés techniques dont il n’existe à l’heure actuelle, ni de caractérisation ni d’outil pour caractériser la double-fenêtre innovante étudiée dans cette thèse. Par conséquent, ce travail de thèse vise à caractériser son comportement et ses performances thermiques et à dégager des recommandations quant à sa conception et son utilisation. Pour atteindre ces objectifs, deux approches ont été mises en place. La première, expérimentale, a consisté en l’élaboration et l’utilisation de prototypes multi-échelle. Deux types de dispositifs expérimentaux ont été mis au point, afin de mener des tests en conditions contrôlées et in situ. Plusieurs campagnes de mesures ont été effectuées et ont fourni une base de données expérimentale conséquente. Grâce à ce travail expérimental, nous avons pu décrire le comportement thermo-aéraulique de la double-fenêtre en diverses situations de fonctionnement et montrer le caractère dynamique de ses performances. En revanche, il s’est avéré que la caractérisation du comportement thermique de ce dispositif n’a pu être complète. Par conséquent, nous avons décidé d’utiliser une seconde approche, numérique. Celle-ci a constitué, dans un premier temps, en l’élaboration d’un modèle numérique dynamique et rapide d’utilisation. L’outil numérique créé a été validé à l’aide des données expérimentales et d’une méthode originale et critique de validation. Dans un second temps, l’approche numérique s’est portée sur la caractérisation paramétrique de la double-fenêtre ventilée afin d’appuyer et compléter les observations expérimentales. Cette approche paramétrique a également permis de fournir une méthode de détermination dynamique des performances thermiques