Dissertations / Theses on the topic 'Mesure du champ magnétique'
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Le, Ny Mathieu. "Diagnostic non invasif de piles à combustible par mesure du champ magnétique proche." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00844407.
Frachon, Didier. "Développement de bancs de mesure magnétique pour ondulateurs et wigglers." Grenoble 1, 1992. http://www.theses.fr/1992GRE10040.
Latorre, Laurent. "Evaluation des techniques microélectroniques contribuant à la réalisation de microsystèmes : application à la mesure du champ magnétique." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 1999. http://tel.archives-ouvertes.fr/tel-00397734.
L'objectif des travaux présentés dans cette thèse est le développement de méthodologies qui conduisent à la caractérisation de la technologie FSBM et à la conception de microsystèmes électromécaniques.
L'étude expérimentale d'une structure de test appelée "cantilever U-Shape" est présentée. Cette étude permet l'extraction des paramètres mécaniques qui ne sont pas caractérisés dans la cadre d'une utilisation traditionnelle de la technologie en microélectronique.
Afin de proposer aux concepteurs de MEMS des outils de simulation, le cantilever FSBM fait l'objet d'une modélisation qui s'appuie sur une étude théorique de poutres composites. Le codage de ces modèles dans le langage VHDL Analogique montre alors comment il est possible d'intégrer les composants mécaniques dans le flot de conception microélectronique.
L'utilisation conjointe des résultats de caractérisation et des modèles théoriques conduit finalement à l'évaluation de la structure "U-Shape" excitée par la force de Laplace en tant que capteur de champ magnétique.
En perspective à ces travaux, des solutions alternatives pour la mesure du champ magnétique à l'aide de microstructures sont proposées.
Chanet, Nicolas. "Imagerie par résonance magnétique à champ cyclé in vivo." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS574/document.
Fast Field Cycling Magnetic Resonance Imaging (FFC-MRI) has the ability to separate two key processes that both depends on the main field intensity B0. On one hand, signal acquisition and localization and on the other hand NMR relaxation, basis of MRI contrast. The equipment thus combines a standard MR scanner with a secondary system to rapidly switch the magnetic field B0 as compared to relaxation times. FFC enables to measure the evolution of NMR relaxation as a function of magnetic field B0, namely the NMR dispersion (NMRD) profile. Combining it with MRI the NMRD profile can be localized in vivo, together with the usual characterization at fixed B0. The NMRD profile of water carries information on molecular mobility in the surrounding biological tissues, and is thus another source of contrast. The objective of this PhD project was to further develop and evaluate the potential of FFC-MRI between 1 T and 2 T in a cancer model. This work required original instrumental and methodological developments to integrate FFC in MRI. First a precise measurement of magnetic field time profile was developed, as well as the compensation of eddy currents and of irreproducible transients in the secondary system. Moreover acquisition sequences with better signal to noise efficiency and applicable for longitudinal as well as transverse relaxation were implemented. Finally a kidney tumor mouse model was explored with FFC MRI
Magued, Michael. "Virtualisation de la mesure d’exposition du public général au champ magnétique basse fréquence dans le domaine de l’automobile." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC015/document.
Exposure to electromagnetic fields is a major issue in society that affects the automotive domain. The development of electric and hybrid vehicles technology requires the consideration of the issue of exposure since the conception stage.The work presented in this paper is mainly concerned with exposure to low-frequency (LF) magnetic fields distinguished with non-thermal electric stimulation effects. In this frequency range, the main sources of exposure risks are the powertrain elements often located close to the passengers.The main objective of this thesis is to virtualize the measurement assessing exposure to LF magnetic fields, hitherto performed by a commercial exposure level tester, to be able to minimize exposure risks, a priori, without incurring additional costs to the manufacturer. This is realized by virtualizing the measuring instrument.We focus first on understanding the exposure evaluation measurement and on the operation of the ELT-400 Narda field meter used at our automobile manufacturer to measure the exposure index. Thus, we show the different definitions and methods of calculating exposure index of the general public to LF magnetic fields. Finally, we present applications of the use of the field meter on measuring cases in statistic and dynamic states.The second part of the study is consecrated to the construction of the virtual prototype to model the measurement of the exposure index to LF magnetic fields performed by Narda field meter ELT-400. To do this, first we develop and optimize the model of the field meter’s triaxial probe in FEKO to position and orient the probe as selected by the user. Then the magnetic field radiated by the virtual probe is processed to obtain a virtual measurement of the magnetic induction detected by the probe and of the exposure index.The third part of the study deals with the validation of the whole model on real cases of measurements done over manual spot welding clamps by comparing the virtual prototype results with those measured. The model validation is performed in three different case studies corresponding to different field profiles, different frequencies in LF domain and different forms of signal.In the last part of our study, a stochastic simulation approach is proposed by applying the Monte-Carlo Method based on a large number of random draws. This method allows studying the dispersion of results due to the plausible imprecise positioning and orientation committed by the operator of the probe. This method is applied at different distances from elementary radiating sources. The main results of this part focus on the link between the field homogeneity at the investigated point and the variability of the virtual measurement around this point due to the inaccuracy committed
Legris, Michel. "Identification de l'état magnétique d'un système ferromagnétique à partir de mesures du champ proche." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0170.
Legris, Michel. "Identification de l'état magnétique d'un système ferromagnétique à partir de mesures du champ proche." Phd thesis, Grenoble INPG, 1996. http://tel.archives-ouvertes.fr/tel-00869936.
Pinaud, Olivier. "Caractérisation, modélisation et identification de sources de champ magnétique dans un véhicule électrique." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT070/document.
Electric vehicles have a lot of electrical devices onboard. All of them may generate electromagnetic field inside the car: a quite small space containing the passengers. A complete modeling of the vehicle can hardly be done because of the parameters number. The magnetic field measurement everywhere inside the car is also impossible. We first measure the magnetic field inside the car to study its characteristics. Then we propose to merge together a priori modeling with measurements into a Bayesian approach of the inverse problem. Based on spherical harmonic decomposition of the magnetic field, a priori information helps the resolution and gives the identified parameters with a very few measurements
Phua, Chee Teck. "Développement d’une nouvelle méthode de mesure du rythme cardiaque et du débit sanguin fondée sur les perturbations localisées d’un champ magnétique." Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1099/document.
Continuous pulse rate, blood pressure and blood flow monitoring are important for the assessment of physiological vital signs as these are able to provide continuous feedback on the health condition of an individual. Existing commercial, medical and research methods to continuously acquire such these physiological vital signs require good electrical or optical contact. During this research, a magnetic based sensing method, at room temperature, for blood pulse, flow and pressure is developed to achieve data acquisition through fabric, environmental contaminants and body-fluids. This method is named Modulated Magnetic Signature of Blood (MMSB) and physical measurements were conducted on multiple subjects, mathematically modelled and simulated in a multi-physics environment with verification through use of measurement data. Measurement results, using MMSB, for blood pressure and blood flow were compared, and found to be well correlated, with lifestyle device and medical research instruments respectively. In addition, two devices are developed, and are in the midst of commercialization, to support lifestyle applications
Phua, Chee Teck. "Développement d'une nouvelle méthode de mesure du rythme cardiaque et du débit sanguin fondée sur les perturbations localisées d'un champ magnétique." Phd thesis, Université Paris-Est, 2012. http://tel.archives-ouvertes.fr/tel-00794495.
Ifrek, Lyes. "Identification des défauts d'une pile à combustible par la mesure du champ magnétique externe : vers la détermination de défauts locaux." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT076/document.
A noninvasive technique for identifying the current distribution in a fuel cell from the external magnetic field is developed. The magnetic field measurements are carried out on a set of points chosen in order to detect only the variations of the magnetic field in a case of a faulty fuel cell. Two components of the magnetic field are used because they are sensitive to current heterogeneities. The exploitable measurement of the magnetic field is the difference between a healthy mode and a faulty mode.An ill-posed inverse problem is modeled by investigating several parametrization approaches of the current distribution. The ill-posed property of the problem conducts to a non-uniqueness of the solution and a high sensitivity to the noise. A regularization method is used in order to get a stable solution. The developed tool allows identifying the current distribution independently of the size of the fault within the sensitivity limit. A validation is done on a fuel cell simulator and on a GENEPAC fuel cell in a laboratory conditions
Mangeant, Christophe. "Génération de fortes pressions magnétiques et mesure des densités de courant associées." Paris 6, 2002. http://www.theses.fr/2002PA066241.
Kammerer, Jean-Baptiste. "Capteurs intégrés pour la mesure à haute résolution de champs magnétiques." Université Louis Pasteur (Strasbourg) (1971-2008), 2004. http://www.theses.fr/2004STR13064.
Integrated technologies allow to develop magnetic measurement systems on chip. Since they can be integrated using any standard manufacturing process, Hall effect sensors are particularly attractive for low cost magnetometers design. Thus, the first part of this thesis is focused on the improvement of this type of sensors using electronic circuits. We demonstrate that the association of a specific circuit and a Hall effect sensor of a particular shape allows to reach any absolute sensitivity. We also propose a new method for canceling the piezo-resistance effect which is responsible for a parasitic cross-sensitivity. The developed Hall effect sensors are particularly useful for low voltage technologies and for measurement systems subjected to vibrations. Thanks to the rise of nanotechnologies, thin film ferromagnetic based devices and more particularly magnetic tunnel junctions should be part of the standard components of microelectronics industry very soon. Thus, in the second part of this thesis, we studied the potentialities of this new device and we propose a new measurement technique based on the fluxgate principle generalized to two dimensions and applied to the magnetic tunnel junction. The realized magnetometer allows to measure simultaneously and in a very localized way, two components of a magnetic field with a very high sensitivity. All the realized systems tends to benefit from a sensitive element using specific electronic circuits
Delmas, Antoine. "Définition, validation et mise en place d’un suivi de l’exposition au champ magnétique statique des travailleurs en IRM." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0074/document.
The Magnetic Resonance Imaging (MRI) is a medical imaging modality using electromagnetic fields (EMF) in order to perform human body tomodensitometric images. Even if these fields are Non-Ionizing Radiations (NIR), some transitory effects can be felt by the staff working in the vicinity of the MRI. Such workers are qualified as “exposed” to EMF, even if all expert comities agree to say that no accumulative or long term effects have been identified yet. Short term effects are known and identified, from metallic taste in the mouth, nerve and muscle stimulation, to biologic tissue heating, which can be troublesome or dangerous. The main exposure concern comes from the MRI permanent static magnetic field (ranging from 1.5 T to 7 T). An expert comity, mandated by the World Health Organization (WHO), has therefore defined the evaluation of the exposure of the MRI workers to the static magnetic field as a priority. This was the focus of this PhD thesis. A light and autonomous static magnetic field monitor (called "exposimeter") has been developed. It allows the recording of the three-dimensional magnetic fields as well as workers’ movements. Its magnetic induction measurement accuracy has been ensured by a specific calibration, which takes into account non-linearity and non-orthogonality of the magnetic sensors. Based on exposimeter data, a magnetic induction extrapolation method has then been developed. This method allows the estimation of the EMF exposure at the head with sensors placed on the torso. Finally, a practical validation of the device has been performed in multiple MRI clinical and research centers, included clinical MRIs (1.5 T and 3 T), an interventional MRI (1.5 T) and an ultra-high field MRI (7 T). Metrics have been defined in order to precisely analyze and compare workers exposure. All the works presented in this PhD thesis open new perspectives such as long term static magnetic field exposure follow-up. Moreover, industrial transfer of the device has been performed and is currently being validated
Valtier, Michel. "Mise en oeuvre de gradients de champ radiofréquence intenses et applications aux mesures de diffusion translationnelle et à l'imagerie par résonance magnétique nucléaire." Nancy 1, 1998. http://www.theses.fr/1998NAN10220.
Maffei, Pablo Fabian. "Développements en microscopie RMN par gradients de champ radiofréquence." Nancy 1, 1993. http://www.theses.fr/1993NAN10017.
Woelfflé, Angélique. "Étude et modélisation du transport de plasma dans la magnétosphère interne." Toulouse, ISAE, 2010. http://www.theses.fr/2010ESAE0013.
Pascal, Joris. "Système intégré pour la mesure tridimensionnelle de champ magnétique dans un environnement d'imagerie médicale IRM : application à la correction de signaux ECG perturbés." Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/public/theses_doctorat/2008/PASCAL_Joris_2008.pdf.
The measurement of the electrocardiogram signal ECG during a medical MRI imaging sequence exhibits artefacts that make the measured signal unreadable. These artefacts can be removed by using a signal processing algorithm that features the perturbed ECG signal as well as the value of the perturbing magnetic field as input data. A so called SmartMRECG system for smart ECG sensor dedicated to magnetic resonant imaging sequence has to be integrated in a low cost 0. 35 µm CMOS technology. This system will implement an instrumental chain dedicated to ECG signal amplification, as well as a magnetometer and a signal processing unit. The contribution of this thesis to the SmartMRECG system design is the integration of the magnetometer. We have designed the first monolithic three-dimensional (3D) Hall magnetometer in standard 0. 35 µm CMOS technology. This magnetometer features three Hall plates dedicated to the measurement along the three dimensions of space: one conventional horizontal Hall plate is integrated along with two innovative vertical ones. The signals delivered by these three sensing elements are amplified by three analog instrumental chains integrated within the same substrate. The resulting 3D Hall probe exhibits a resolution that is equivalent to the one of the commercially available probes integrated in high voltage CMOS technology. These results fit the requirements for the measurement of magnetic fields within a MRI environment and open the way to the industrialization of the SmartMRECG system
Bardet, Benoît. "Lévitation électromagnétique : expériences terrestres et simulations numériques." Grenoble INPG, 2006. https://tel.archives-ouvertes.fr/tel-00141231.
The thesis carried out is at the same time an experimental and numerical work. An electromagnetic experiment of levitation was implemented. A specific image processing was developed. Thus videos obtained were used as a basis to have geometrical and electric data in order to confront the results of various programs with controlled experiments and in order to highlight the effect of the helicity of the inductor on the form of the free surface of the drop and to control the behaviour of a drop under modulated magnetic field, in particular for frequencies of modulations close to the frequency of natural resonance of the load. Numerical work leads to the validation of axisymmetrical programs for the description of electromagnetism, the average form of the free surface, the movements of surface and inside the drop. A criterion of destabilization based on the initial deformation and the viscosity of the drop was proposed. This criterion takes into account internal electromagnetic stirring
Bui, Viet Phuong. "Diagnostic des machines électriques par l'analyse du champ magnétique de fuite : application à l'identification de défauts rotoriques d'un alternateur à vide." Phd thesis, Grenoble INPG, 2007. http://www.theses.fr/2007INPG0110.
Adiagnosis method of the electrical machines based on the magnetic flux leakage and on the inverse approach is proposed. We developped a direct modelling tool allowing to compute the 3D magnetic flux leakage of the machine. Several numerical methods were studied (finite elements, magnetic moment, boundary integral. . . ). A precise, light and original model was developed. The inverse approach consisted of finding the distribution of flux in the machine airgap according to the measurements of the field outside. We have showed that this approach allows the discrimination, the localization and the quantification of the relevant faults. Finally, our approach was experimentally, validated thanks to the instrumentation of a model of synchronous machine (30k VA, 4 poles) associated with a system of magnetic field sensors Fluxgate
Bui, Viet Phuong. "Diagnostic des machines électriques par l'analyse du champ magnétique de fuite : application à l'identification de défauts rotoriques d'un alternateur à vide." Phd thesis, Grenoble INPG, 2007. http://tel.archives-ouvertes.fr/tel-00187238.
Gostan, Thierry. "Diversification des champs d'application de la mesure de diffusion par RMN." Montpellier 1, 2004. http://www.theses.fr/2004MON13521.
Plays, Thibault. "Influence d’un champ magnétique sur la séparabilité d’un mélange de molécules paramagnétiques et diamagnétiques." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM045.
The purpose of my thesis is to evaluate the impact of a magnetic field on the separation process of a mixture of paramagnetic and diamagnetic molecules. More precisely, the system of interest is the air. Oxygen, nitrogen and argon have quite similar chemicophysical properties, so the energy and the economical cost to separate those molecules are pretty high. However, the magnetic properties of those three molecules are different : the oxygen is paramagnetic whereas the nitrogen and the argon are diamagnetic. The internal energy of oxygen increases when a magnetic field is applied to the molecule, and a force attracts the oxygen towards the area with the higher magnetic field. The objective was to explore different ways to apply a magnetic field to our system in order to observe an impact on the possibility to separate the molecules. Literature reveals three major axes of study. The first one is the thermodynamic study of liquid-vapor equilibrium under a magnetic field. The second one is about the impact of a magnetic field on the hydrodynamic flow of gaseous air. And the le last one, concerns the magnetic membranes composed of a membrane doped with magnetic particles. Those three axes have been studied. A theoretical analysis and several experiments have been conducted to observe an impact of the magnetic field. The strategy was to explore many approaches with a multitude of prototype in order to find the most valuable solution for a separation process. For the magnetic membranes, we had neither the knowledge to synthesis one nor the time to acquire one. However, we tried to reproduce the concept to evaluate the potential of magnetic nanoparticles in a separation process. The interaction between nanoparticles and oxygen has been evaluated. A campaign of measure on the solubility of oxygen in a ferrofluide (solvent containing magnetic nanoparticles) has been conducted. We prove that the impact of the magnetic field on the liquid/vapor equilibrium is too weak to use it in an industrial separation process. The lead of a kinetic process is more encouraging. The experiments with hydrodynamic flows seem to be impact by a magnetic field, even if this impact is pretty moderate. In this work, the complexity of the simulation of the phenomenon in order to establish the best geometry and conditions for the process was described. However, the lead of nanoparticles is promising. Even if my study did not reveal any influence of the magnetic field on the solubility in a ferrofluid nor on the interaction between oxygen and the nanoparticles, literature shows impressive results for systems using magnetic membranes
Chadebec, Olivier. "Modélisation du champ magnétique induit par des tôles - identification de l'aimantation - Application à l'immunisation en boucle fermée d'une coque ferromagnétique." Phd thesis, Grenoble INPG, 2001. http://tel.archives-ouvertes.fr/tel-00010342.
Ferraris-Bouchez, Laura. "Mesure du moment dipolaire électrique du neutron : correction de l'effet systématique du champ fantôme." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALY018.
The search for a permanent electric dipole moment for simple systems such as the neutron is one of the most promising leads to discover CP violation beyond the Standard Model of particle physics.The discovery of such CP violation sources and the identification of new models beyond the Standard Model could lead to an explanation of the baryon asymmetry of the Universe.Therefore, there are several experiments aiming to measure a non-zero EDM for various systems (neutron, electron, atoms...).The Paul Scherrer Institute (PSI) nEDM experiment is one of them.The nEDM collaboration has collected data during two years (2015 and 2016) and published the most recent limit for the neutron EDM in April 2020.Precision measurements such as that experiment require an optimal control of the systematic effects.In this thesis, we present how to control the effects of the magnetic field inhomogeneities, which arise from the use of a mercury co-magnetometer in the PSI nEDM experiment.The co-magnetometer allows us to monitor the stability of the magnetic field and is essential to optimize the statistical sensibility.In order to correct the systematic effects of the magnetic field inhomogeneities, we perform an offline characterization of the field : the mapping.We present in this thesis the mapping measurement method, its analysis and the resulting corrections of the main systematic effect of the neutron EDM measurement.Once those corrections are taken into account, the last step of the analysis of nEDM data can be achieved, in order to extract the neutron EDM value which was published by the collaboration.The application of that step and its results are also presented in this thesis
Colinas, Jérôme. "Étude et amélioration des performances d'une méthode de mesure en champ proche, la méthode des courants magnétiques équivalents." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ65569.pdf.
Mischler, Éric. "Système informatique pour la génération de séquences RMN : application aux mesures d'auto-diffusion translationnelle par gradients de champ radiofréquence." Nancy 1, 1996. http://www.theses.fr/1996NAN10318.
Hamaz, Tahar. "Outils de caractérisation et de diagnostic d'une pile à combustible de type PEM par mesure du champ électromagnétique externe." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT074/document.
Proton exchange membrane fuel cell (PEMFC) is a potential alternative energy conversion device for stationary and automotive applications. Wide commercialization of PEMFC depends on progress that can be achieved to enhance its reliability and durability. The PEM fuel cell is subject to several types of complex and not fully mastered degradations which vary with operating conditions. It is desirable to operate the PEMFC at uniform current distribution because non uniform current distribution over the MEA could result in poor reactant and catalyst utilization, overall cell performance degradation as well as corrosion processes inside the PEM fuel cell. Therefore, new diagnostic strategies must be proposed, including choice of information gathered on the system and the fuel cell operation representation. My research is to develop a new diagnostic tool based on a measure of the external electromagnetic field (non-invasive) radiated by the fuel cell. The magnetic field has the advantage of being correlated to the local distribution of the current flowing inside the fuel cell (a physical indicator to obtain information on local performance of a fuel cell); it is linked to the local operating conditions: relative humidity level, temperature etc. It is then possible, from a magnetic signature to trace local information. Baselines (vectors) which contain the magnetic fields data generated by specific current distribution are built to characterize the magnetic field generated by the undesirable operation of the fuel cell. Baselines constitute a representation space of abnormal system behavior. Two methods have been developed to enable: (i) to extract the relevant parameters on the distribution of the current density resulting from PEM fuel cell stack local performance, (ii) to classify different types of undesirables operations. The first method is to generate vector residuals by comparing the actual behavior of the system (characterized by a measurement vector) with the baselines generated. Qualitative variables were created to classify the undesirable modes of PEM fuel cell stack operation. The second method is to extract parameters from the projection of the vector in the direction of measurement baselines. The classification is performed in 2D space. Validation from experimental measurements of the two proposed methods has been carried out on a commercial scale PEMFC (GENEPAC stack of 40 cells built by the CEA and PSA). The relevance of the extracted parameters was verified based on current density distributions measured directly. The undesirable predefined operating modes were used to locate the operating conditions parameters that led to the evolution of the current density distribution. The tools are made easily transferable to other PEMFC stack
Cury, Luiz Alberto. "Propriétés électroniques de structures semiconductrices III-V à effet tunnel résonnant sous pression hydrostatique et sous fort champ magnétique." Toulouse, INSA, 1992. http://www.theses.fr/1992ISAT0004.
Nencib, Nadim. "Conception et validation d'un dispositif de caractérisation magnétique sous excitation bidimensionnelle : comportement des toles FeSi en champ tournant." Grenoble INPG, 1994. http://www.theses.fr/1994INPG0109.
Malinowski, Grégory. "Transport dépendant du spin et couplage d'échange : de la jonction tunnel au capteur magnétique intégré." Phd thesis, Université Henri Poincaré - Nancy I, 2004. http://tel.archives-ouvertes.fr/tel-00008797.
Manseur, Megdouda. "Contribution à l’étude d’un système de biotélémesure intracorporelle par gélule ingérable." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14430/document.
This thesis is a contribution to study of intracorporeal measure of ingestible capsule. It concerns more specifically the problems of wireless transmission of energy and information between the capsule and ingestible extracorporeal control and monitoring system. Thus we first set of design methods and theoretical characterization of the experimental system of wireless remote power up capsules. A second part was dedicated to wireless transmission of energy and information design through magnetic induction, it led to the creation of an original system of tuning by synchronous switched capacitor. The problem of miniature antennas characterization has been a third party in which we have proposed innovative solutions based on techniques for measuring parameters Sij in differential (or transmission). Finally, we presented in the last part the design and characterization of a magnetic field probe designed to validate the simulation results
Bourgeois, Olivier. "Mesures de transport sur des jonctions supraconducteur/composé magnétique." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10155.
Nabias, Julie. "Capteur de courant à Magnéto-Impédance Géante (GMI) souple et portatif." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAT013/document.
The GMI effect displays several advantages, such as high sensitivity, high detection resolution and bandwidth, and mechanical flexibility. These advantages predispose this technology to the implementation of flexible contactless current sensors measuring both DC and AC currents.This thesis work aims at exploring the feasibility of a flexible GMI current sensor. A particular attention to the impact of influence parameters which largely condition the design solutions of the sensor has been paid.The effects of temperature and mechanical constraints such as bending and torsion, which apply in a real measuring environment, are characterized by taking into account the intrinsic features which are necessary to the design of the sensor. The impact of the general measuring configuration and electronics are also studied. The effects of magnetic disturbances and of the position of the current-carrying conductor in the measuring loop are quantified and an adequate shielding method is proposed. Finally, the sensor prototype obtained at the end of this work is described with its performances and the possible optimization and enhancement ways
Hébrard, Elodie. "Magnétométrie stellaire et imagerie Zeeman-Doppler appliquées à la recherche d'exoplanètes par mesures vélocimétriques." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30215/document.
Forthcoming instruments dedicated to exoplanets detection through the radial velocity method are numerous, and increasingly more accurate. However this method is indirect: orbiting planets are detected and characterised from variations on the spectrum of the host star. We are therefore sensitive to all activity phenomena impacting the spectrum and producing a radial velocity signal (pulsation, granulation, spots, magnetic cycle...). The detection of rocky Earth-like planets around main-sequence stars, and of hot Jupiters into young systems, are currently limited by the intrinsic magnetic activity of the host stars. The radial velocity fluctuations caused by activity (activity jitter) can easily mimic and hide signals from such planets, whose amplitude is of a few m/s and hundreds of m/s, respectively. As a result, the detection threshold of exoplanets is largely set by the stellar activity level. Currently, efforts are invested to overcome this intrinsic limitation. During my PhD, I studied how to take advantage of imaging tomographic techniques (Zeeman-Doppler imaging, ZDI) to characterize stellar activity and magnetic field topologies, ultimately allowing us to filter out the activity jitter. My work is based on spectropolarimetric observations of a sample of weakly-active M-dwarfs, and young active T Tauri stars. Using a modified version of ZDI, we are able to reconstruct the distribution of active regions, and then model the induced stellar signal allowing us to clean RV curves from the activity jitter. First tests demonstrate that this technique can be efficient enough to recover the planet signal, especially for the more active ones
Barbut, Jean-Marc. "Texturation d'YBa2Cu3O(7-[delta]) par fusion de zone sous champ magnétique : détermination par mesure de courant critique de son diagramme de phase dans le plan [H,[THETA]] à 77 K : mise en évidence par mesures résistives de l'existence en champ nul d'une transition du 1er ordre dans l'état supraconducteur." Grenoble 1, 1994. http://www.theses.fr/1994GRE10049.
Andretzko, Jean-Paul. "Contribution à l'optimisation et à la modélisation d'un banc de mesure CEM - Application à la caractérisation de l'immunité des stimulateurs cardiaques." Phd thesis, Université Henri Poincaré - Nancy I, 2007. http://tel.archives-ouvertes.fr/tel-00405118.
Zidi, Manel. "Utilisation de la Magnéto-Impédance Géante pour la réalisation d'un capteur de courant." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT096/document.
A GMI current sensor was designed. This study was devoted to the investigation of the electronic conditioning of the sensor. An accurate, stable and high frequency digital oscillator was developed. A voltage-to-current converter based on the Howland source was associated to this oscillator. An innovative and promising technology for precise measurements was proposed: the RMS-DC detector. This detector was conditioned for demodulating AC signals. Also an original approach of an amplitude detector using a limiting amplifier was developed. These technologies have been successfully integrated into a GMI current sensor
Marchand, Dominique. "Calcul des corrections radiatives à la diffusion compton virtuelle. Mesure absolue de l'énergie du faisceau d'électrons de Jefferson Lab. (Hall A) par une méthode magnétique : projet ARC." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 1998. http://tel.archives-ouvertes.fr/tel-00298382.
Les expériences de diffusion Compton virtuelle nous permettent d'accéder à de nouvelles observables du proton : les polarisabilités généralisées. L'extraction de ces polarisabilités s'effectuant par comparaison des sections efficaces expérimentale et théorique, il est indispensable de contrôler avec une grande précision les erreurs systématiques et les effets radiatifs liés à l'expérience. Un calcul complet des corrections radiatives internes a donc été mené dans le cadre de l'électrodynamique quantique. Ce calcul inédit tient compte de tous les graphes contribuant à l'ordre alpha^4 au niveau de la section efficace à l'exception de ceux mettant en jeu l'échange de deux photons entre les bras leptonique et hadronique ainsi que ceux relatifs au rayonnement du proton. La méthode de régularisation dimensionnelle a été employée pour le traitement des divergences ultraviolettes et infrarouges. Après utilisation d'une procédure d'addition-soustraction, la compensation infrarouge est vérifiée. Nous avons privilégié le calcul analytique pour les intégrales les plus internes et avons eu ensuite recours à un traitement numérique spécifique. Les résultats présentés correspondent aux différentes cinématiques de l'expérience VCS qui s'est déroulée à TJNAF en 1998.
La méthode de mesure absolue d'énergie que nous avons développée s'appuie sur la déviation magnétique, constituée de huit dipôles identiques, conduisant le faisceau de l'accélérateur au hall A expérimental. L'énergie est déterminée à partir de la mesure absolue de l'angle de déviation du faisceau dans le plan horizontal et de la mesure absolue de l'intégrale de champ magnétique le long de la déviation magnétique. La mesure de l'angle de déviation se décompose en une mesure ponctuelle d'un angle de référence (par une méthode optique d'autocollimation) et en une mesure « en ligne » des déviations angulaires du faisceau par rapport à cet angle de référence (utilisation de quatre profileurs à fil : une paire en amont et une paire en aval de l'arc). L'intégrale de champ absolue le long de la déviation résulte, elle, de la mesure ponctuelle de la somme des intégrales de champ relatives des huit dipôles de l'arc par rapport à un aimant de référence et de la mesure « en ligne » de l'intégrale de champ de cet aimant de référence alimenté en série avec les huit autres de l'arc.
Raulet, Renaud. "Conception et réalisation d'un système original de gestion d'un spectromètre RMN : application à des mesures de relaxation croisée hétéronucléaire et à des expériences d'imagerie par gradients de champ radiofréquence." Nancy 1, 1996. http://www.theses.fr/1996NAN10270.
Sarno, Thomas. "Caractérisation sécuritaire des mémoires magnétiques MRAM." Thesis, Saint-Etienne, EMSE, 2015. http://www.theses.fr/2015EMSE0796.
MRAM (magnetoresistive RAM) is an emergent non-volatile memory technology; it has the particularity to store data in magnetic moments orientations. It has very interesting characteristics that overwhelm mature technologies on several points. Crocus Technology is developing a new MRAM technology called TAS-MRAM (for Thermally Assisted Switching). During write operations, this new MRAM technology uses a current to heat the memory cell. This reduces the power consumption and makes scalability easier. TAS-MRAM are developed for secure or critical applications but this technology relies on spintronic, a field of physics not much studied for electronics security.This work aims to evaluate potential security weaknesses of this technology. More specifically the memory capacity to guarantee data confidentiality was studied. This work was divided in two parts; one part is dedicated to the analysis of MRAM resistance against physical perturbations, with a special focus on magnetic fields (both static and pulsed) effects on read and write operations as well as their effects on data retention. Various methods to reduce these effects were tested and compared. The effect of high temperature was also studied.The second part focuses on the analysis of electromagnetic emissions of the MRAM components during its operations. Methods to retrieve the Hamming weight of data written in the memory are exposed and compared
Mansour, Malik. "Étude et mise en oeuvre de magnétorésistances anisotropes et à effet tunnel pour la mesure des champs magnétiques faibles dans les plasmas spatiaux." Palaiseau, Ecole polytechnique, 2012. https://pastel.hal.science/pastel-00835740.
In situ study of Sun-Earth relations and ionized environments of our solar system needs for the measurement of waves propagated in magnetized plasma. Aboard space observatories, wave's magnetic components are measured by inductive magnetometers. High frequencies measurement (a few Hz up to a few 100 kHz) is made by Searchcoil magnetometers whereas low frequencies (a few Hz down to a few 10 mHz) and dc field measurement are leaved to Fluxgate magnetometers. In this thesis we deal with the design of a broadband magnetometer able to measure magnetic fields from dc to a few kiloHertz. We present an innovative instrumental concept based on the implementation, in a unique instrument, of both an inductive and a magnetoresistive measurement of the magnetic field. We address both the design and the study of anisotropic (AMR) and tunneling (TMR) magnetoresistive sensors whose magnetic properties are controlled by exchange anisotropy. We show how those sensors can be associated to a Searchcoil magnetometer whose ferromagnetic rode is used to achieve an efficient magnetic concentrator. We then detail the design of a hybrid Searchcoil/Magnetoresistor magnetometer meeting the environmental constraints associated to space experiments as well as an original optimization tool based on finite element modeling and a genetic algorithm. We finally prove the feasibility of the concept making a fist prototype of a hybrid tri-axes Searchcoil/PHE sensor magnetometer and its low noise conditioning electronics. This prototype reaching a detectivity around 200 fT/sqrt (Hz) at 1 kHz and 400 pT/sqrt (Hz) at 1 Hz has been tested in real conditions during a scientific rocket experimen
Pardanaud, Cédric. "Etude de la conversion de spin nucléaire de l'eau en matrices de gaz rares : mesures, modélisation de l'influence des interactions spin-spin intermoléculaires et contexte astrophysique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2007. http://tel.archives-ouvertes.fr/tel-00259961.
Dans les atmosphères cométaires, la mesure du rapport d'abondance de ces isomères pour les molécules de H2O, NH3, CH4, et plus récemment de CH3OH, montre un écart à l'équilibre thermodynamique. Sa signification physique est à ce jour au cœur d'un débat : est- ce un indicateur de la température qui régnait dans l'environnement primordial au sein duquel se sont formées ces molécules ?
Ce travail expérimental alliant techniques de vide et de cryogénie, vise à identifier, en amont d'une étude dans les glaces cométaires, certains paramètres impliqués dans la conversion de spin nucléaire de H2O isolée dans des environnements plus simples : les matrices de gaz rare. Dans un tel environnement, un enrichissement en isomère de spin ortho ou para est produit par un changement brutal de température (entre 4,2 et 30 K). La détermination du temps de retour à l'équilibre thermodynamique se fait à partir de l'enregistrement dans le temps des spectres infrarouges ro-vibrationnels des modes Ν2 (déformation angulaire) et Ν3 (élongation antisymétrique), au moyen d'un spectromètre commercial IR par transformée de Fourier.
L'étude systématique en fonction de la concentration que nous avons réalisée à 4,2 K en matrice d'argon, montre qu'il existe deux régimes de conversion qui sont en compétition. Pour des dilutions [Ar/H2O] supérieures à 1000, les temps de conversion (~670 minutes) sont indépendants de la concentration et atteignent un plateau. Cette conversion qui n'est pas imputable à des effets parasites (impuretés moléculaires, exposition au rayonnement IR du spectromètre, influence du support, ...) est sans doute due à un processus d'origine intramoléculaire, accéléré par la matrice. Par contre, en dessous du 1000ème, une accélération très nette de la conversion avec l'augmentation de la concentration est observée (~180 minutes au 50ème), indiquant clairement une origine intermoléculaire. Nous avons, dans ce cadre, développé un modèle faisant intervenir des interactions magnétiques entre les spins nucléaires des protons appartenant à des molécules d'eau différentes, et des échanges d'énergie avec les phonons de la matrice. Ce modèle, qui ne dépend que de l'écart en énergie entre les niveaux de rotation et du taux de relaxation collisionnelle de la molécule isolée en matrice, autorise la conversion d'origine intermoléculaire à 4,2 K en ouvrant un canal de conversion couplant le premier niveau de rotation de chacun des isomères de spin. L'existence d'un deuxième canal, plus efficace d'un ordre de grandeur à 25 K, dû à un effet de population, explique l'accélération observée à température croissante.
La substitution de l'argon par du néon, du krypton ou du xénon, a permis de montrer, en accord complet avec le modèle, que le mécanisme d'origine intermoléculaire est plus efficace dans la matrice qui a le paramètre de maille le plus faible.
Seron, David. "Caractérisation des propriétés hyperfréquences de films minces supraconducteurs et de leur comportement non-linéaire en fonction de la puissance micro-onde incidente : étude de l'influence d'un champ magnétique statique et application à l'accordabilité en fréquence." Paris 6, 2002. http://www.theses.fr/2002PA066334.
Thomas, Catherine. "Mesures du gradient accélérateur maximum dans des cavités supraconductrices en régime impulsionnel à 3 GHz." Phd thesis, Université Paris Sud - Paris XI, 2000. http://tel.archives-ouvertes.fr/tel-00006564.
Saniour, Isabelle. "Exploitation des effets électro-optiques pour la sécurité en IRM : applications des liaisons optiques pour des capteurs RF endoluminaux et des sondes de mesure du TAS." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1330/document.
The recent advancement in MRI systems and the increase of the static magnetic field strength were accompanied by a strong concern about the effect of RF electromagnetic fields on patients. The effect can be increased by the use of conductive elements inside the volume coil as in the case of endoluminal coils used to analyze digestive walls. These coils lead to an increase of the local SAR which is induced by RF electric field in the presence of the coaxial cable connecting the coil to the MR system, resulting in strong local heating. Giving that these coils have the potential to present a real benefit to the patient, it worth to overcome these limitations. Accordingly, the first objective of the thesis is the development of a fully optical endoluminal receiver coil. An optical active detuning system has been developed and characterized. The NMR images show a signal-to-noise ratio distribution similar to that obtained with conventional detuning techniques, thus validating the efficiency of the optical detuning. Concerning the electro-optical conversion and the optical transmission of the NMR signal, experiments were performed to overcome constraints related to the use of waveguide for electro-optical conversion by Pockels effect. Moreover, the importance of monitoring global and local SAR during MRI exams remains a need which is not limited only to the endoluminal coils. The second objective of the thesis is then the experimental validation of an electro-optical probe for real-time measurements of RF electric field. This probe can measure the RF electric field in air and in biological media at 3 T and 4.7 T MRI systems and allows the estimation of the local SAR
BON, NGUYEN ROMUALD. "Etude de la diffusion Ve-e auprès de la tranche 5 du centre de production nucléaire du Bugey : simulation de l'expérience MUNU de mesure du moment magnétique du neutrino." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10173.
Amor, Zaineb. "Non-Cartesian Sparkling encoding for High spatio-temporal resolution functional Magnetic Resonance Imaging (fMRI) at 7 Tesla and beyond." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST032.
Functional MRI (fMRI) is currently one of the most commonly used functional neuroimaging techniques to probe brain activity non-invasively through the blood oxygen level-dependent (BOLD) contrast that reflects neurovascular coupling. It offers an interesting trade-off between spatial and temporal resolution in order to study the whole brain as an aggregation of intrinsic functional systems. The quest for higher spatial and/or temporal resolution in fMRI while preserving a sufficient temporal signal-to-noise ratio~(tSNR) has generated a tremendous amount of methodological contributions in the last decade ranging from Cartesian vs. non-Cartesian readouts, 2D vs. 3D acquisition strategies, parallel imaging and/or compressed sensing~(CS) accelerations and simultaneous multi-slice acquisitions to cite a few. In this work, we focus on the use of CS in fMRI; more specifically, we consider Spreading Projection Algorithm for Rapid K-space sampLING (SPARKLING) encoding scheme.The main focus and goal of this thesis involves the evaluation of 3D-SPARKLING as a viable acquisition scheme for high-resolution whole-brain fMRI. In this regard, we initially compared its capabilities with state-of-the-art 3D-EPI. After observing higher sensitivity to static and dynamic magnetic field imperfections in 3D-SPARKLING data, we established an experimental protocol to correct them. Finally, we studied the capabilities and limitations of employing a sliding-window reconstruction in combination with the SPARKLING encoding scheme to enhance temporal resolution during image reconstruction in fMRI retrospectively. A simulation study where the ground truth is controlled was conducted and demonstrated the possibility of detecting high-frequency oscillations in the BOLD signal and separating physiological noise from neural activity
Fabbro, Hervé. "Capteurs magnétiques résonnants." Grenoble 1, 1998. http://www.theses.fr/1998GRE10149.
Cherief, Wahid. "Etude des ferrofluides et de leurs applications à l'intensification des transferts de chaleur par convection forcée." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT102/document.
This thesis aims to study the thermal and rheological performances of ferrofluids under magnetic field for an application in cooling systems. The approach consists on macroscopic analysis based on experimental studies. Our approach is focused on three aspects: i) rheology ii) internal forced convection iii) thermal conductivity. We developed different characterization benches. For rheological studies, a magnetic circuit is developed and integrated into rheometer to create magnetic fields reaching 0,8 T. This approach demonstrates the influence of magnetic flux density on the shear forces. Concerning heat transfers, we carried out experimental tests based on the use of a closed loop flow system to study forced convection of ferrofluids with imposed wall flux under magnetic field. This test bench allows us to understand the impact of several parameters related to the configuration of the applied magnetic field on the enhancement of convective heat transfers. To analyze why convective heat transfers are better under magnetic field, we carried out a system for measuring the thermal conductivity. This bench tests allows us to show the effect of temperature and magnetic flux density on this physical property. All these tests are paving the way for new research activities and to the ferrofluids applications in cooling systems