220 research outputs found
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 magnétomÚtres 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 magnétomÚtres 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 âbridgesâ 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
La conversion analogique numérique des récepteurs à l'étirement de la patte métathoracique du criquet Schistocerca gregaria
Development of the self-healing concept for high temperature sealing of electrochemical cells
Un des points clĂ©s pour lâutilisation sur le long terme des SOEF et SOFC est lâĂ©tanchĂ©itĂ©. Les solutions de scellement les plus rĂ©pandues sont des matĂ©riaux rigides de type vitreux. Ils prĂ©sentent lâinconvĂ©nient de se fissurer lorsquâils sont soumis Ă des cycles thermiques. Ceci est dĂ» aux diffĂ©rences de CET entre les composants mĂ©talliques ou cĂ©ramiques et les matĂ©riaux vitreux. Lâautocicatrisation est une solution prometteuse pour pallier ce problĂšme, deux mĂ©canismes existent : intrinsĂšque et extrinsĂšque. Lâautocicatrisation intrinsĂšque de matĂ©riaux vitreux est basĂ©e sur leur ramollissement. Nous avons dĂ©veloppĂ© une formulation de joints vitreux «pĂąteux» qui prĂ©sente des propriĂ©tĂ©s autocicatrisantes, donc moins sensible aux diffĂ©rences de CET. La viscositĂ© de ces verres a Ă©tĂ© estimĂ©e par microscopie de chauffage et leur stabilitĂ© a Ă©tĂ© caractĂ©risĂ©e par DRX et microsonde de Castaing. Lâautocicatrisation extrinsĂšque ne nĂ©cessite pas dâintervention extĂ©rieure. Elle est obtenue par ajout de particules cicatrisantes Ă la matrice vitreuse. Lors de lâapparition de fissures, les particules sâoxydent au contact de lâatmosphĂšre pour former des oxydes qui donne in situ de nouveaux verres. Ces oxydes, fluides Ă la tempĂ©rature de fonctionnement, sâĂ©coulent dans la fissure, formant localement, par rĂ©action, un nouveau verre. Des tests rĂ©alisĂ©s in situ par MEBE-HT ont permis de mettre en Ă©vidence le processus dâautocicatrisation. La formation de phases cicatrisantes a Ă©tĂ© caractĂ©risĂ©e par microsonde de Castaing et par RMN. Un ensemble de caractĂ©risations a Ă©tĂ© effectuĂ© afin de valider lâapplicabilitĂ© de lâautocicatrisation extrinsĂšque 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
CaractĂ©risations numĂ©rique et expĂ©rimentale du comportement thermo-aĂ©raulique dâune double-fenĂȘtre 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-fenĂȘtre est une solution de rĂ©novation qui rĂ©pond aux problĂ©matiques Ă©nergĂ©tique et architecturale de prĂ©servation des façades du bĂąti ancien. Elle constitue un systĂšme basĂ© sur la pose de deux fenĂȘtres, lâune derriĂšre lâautre, la nouvelle fenĂȘtre Ă©tant le plus souvent, posĂ©e du cĂŽtĂ© intĂ©rieur de lâhabitat ancien. Ce systĂšme se diffĂ©rencie des doubles vitrages puisquâici il sâagit dâajouter une fenĂȘtre entiĂšre (dormant et ouvrant). LâĂ©tude approfondie de la littĂ©rature scientifique a mis en avant quâaucune considĂ©ration nâa Ă©tĂ© apportĂ©e Ă lâapplication de ce dispositif Ă des bĂątiments historiques alors que cela modifie fortement sa conception et son fonctionnement. Le systĂšme Ă©tudiĂ© dans ce travail de thĂšse est une double-fenĂȘtre par lâintĂ©rieur, adaptĂ©e aux bĂątis historiques du XIXe siĂšcle, ventilĂ©e mĂ©caniquement en insufflation rendant cet Ă©lĂ©ment de façade actif. Il sâagit dâun dispositif innovant que ce soit par son domaine dâapplication ou par ses propriĂ©tĂ©s techniques dont il nâexiste Ă lâheure actuelle, ni de caractĂ©risation ni dâoutil pour caractĂ©riser la double-fenĂȘtre innovante Ă©tudiĂ©e dans cette thĂšse. Par consĂ©quent, ce travail de thĂšse vise Ă caractĂ©riser son comportement et ses performances thermiques et Ă dĂ©gager des recommandations quant Ă sa conception et son utilisation. Pour atteindre ces objectifs, deux approches ont Ă©tĂ© mises en place. La premiĂšre, expĂ©rimentale, a consistĂ© en lâĂ©laboration et lâutilisation de prototypes multi-Ă©chelle. Deux types de dispositifs expĂ©rimentaux ont Ă©tĂ© mis au point, afin de mener des tests en conditions contrĂŽlĂ©es et in situ. Plusieurs campagnes de mesures ont Ă©tĂ© effectuĂ©es et ont fourni une base de donnĂ©es expĂ©rimentale consĂ©quente. GrĂące Ă ce travail expĂ©rimental, nous avons pu dĂ©crire le comportement thermo-aĂ©raulique de la double-fenĂȘtre en diverses situations de fonctionnement et montrer le caractĂšre dynamique de ses performances. En revanche, il sâest avĂ©rĂ© que la caractĂ©risation du comportement thermique de ce dispositif nâa pu ĂȘtre complĂšte. Par consĂ©quent, nous avons dĂ©cidĂ© dâutiliser une seconde approche, numĂ©rique. Celle-ci a constituĂ©, dans un premier temps, en lâĂ©laboration dâun modĂšle numĂ©rique dynamique et rapide dâutilisation. Lâoutil numĂ©rique crĂ©Ă© a Ă©tĂ© validĂ© Ă lâaide des donnĂ©es expĂ©rimentales et dâune mĂ©thode originale et critique de validation. Dans un second temps, lâapproche numĂ©rique sâest portĂ©e sur la caractĂ©risation paramĂ©trique de la double-fenĂȘtre ventilĂ©e afin dâappuyer et complĂ©ter les observations expĂ©rimentales. Cette approche paramĂ©trique a Ă©galement permis de fournir une mĂ©thode de dĂ©termination dynamique des performances thermiques
- âŠ