La traduction des Entités Nommées (EN) est un axe de recherche d'actualité vu la multitude des documents électroniques échangés à travers Internet. Ainsi, le besoin de traiter ces documents par des outils de TALN est devenu nécessaire et intéressant. La modélisation formelle ou semi formelle de ces EN peut intervenir dans les processus de reconnaissance et de traduction. En effet, elle permet de rendre plus fiable la constitution des ressources linquistiques, de limiter l'impact des spécificités linguistiques ct de faciliter les transformations d'une représentation à une autre. Dans ce contexte, nous proposons un outil de reconnaissance ct de traduction vers le français des EN arabes basé essentiellement sur une représentation formelle et sur un ensemble de transducteurs. L'outil prend en compte l'intégration d'un module de translittération. L'implémentation de cet outil a été effectuée en utilisant la plateforme NooJ. Les résultats obtenus sont satisfaisants / The translation of named entities (NEs) is a current research topic with regard to the proliferation of electronic documents exchanged through the Internet. So, the need to process these documents with NLP tools becomes necessary and interesting. Formal or semi-formal modeling of these NEs may intervene in both processes of recognition and translation. Indeed, it makes the accumulation of linguistic resources more reliable, limits the impact of linguistic specificities and facilitates the transformation from one representation to another. In this context, we propose a tool for the recognition and translation of Arabic NEs into French, based primarily on formal .representation and a set of transducers. This tool takes into account the integration of a module of transliteration. Its implementation was performed using the NooJ platform and the results obtained proved to be satisfactory

Un nouvel axe de recherche sur les réseaux de capteurs a été initié au LAAS par la réalisation de nouveaux capteurs sans fil passifs utilisant une transduction électromagnétique dans la détection de pression et de gaz. Ces capteurs fortement intégrés ne nécessitent aucune alimentation embarquée et leur fréquence de fonctionnement se situe dans la bande de fréquence Ka (26 à 40 GHz). Cette thèse s'inscrit donc dans la conception et la réalisation d'un lecteur adapté à l'interrogation à distance de capteurs à transduction électromagnétique. Son principe de fonctionnement est basé sur une technologie radar de type FMCW. L'avantage principal de la lecture radar des données issues de ce type de capteurs passifs réside dans la possibilité d'avoir des portées de plusieurs dizaines de mètres, bien supérieures à celles classiquement obtenues dans les technologies SAW ou RFID. Dans une première étape est présenté le principe de fonctionnement du lecteur radar et la réalisation de deux prototypes centrés sur les fréquences de 3GHz et 30GHz. Une étude du spectre de la sortie radar, appelé signal de battement radar, est abordée afin de montrer comment les positions et les mesures des capteurs sont lues à distance par ce type de lecteur. Par la suite, un travail d'analyse de la communication sans fil permet de déterminer les paramètres de rétrodiffusion électromagnétique à prendre en compte, tels que les impédances et les fréquences de fonctionnement des capteurs. Ces paramètres sont la base d'une optimisation du système global en termes de sensibilité, de portée radar et des niveaux minimaux de Surface Equivalente Radar (SER) des cibles interrogées. La validation de cette analyse se borne à la mesure de la portée maximale associée à ce type de lecteur et aux différentes mesures de SER de plusieurs types de capteurs dans les bandes de fréquence de 3GHz et 30GHz. Deux principes d'identification de cellules passives sont ensuite présentés. Le premier est basé sur l'utilisation des deux modes de rétrodiffusion de la SER d'un capteur (mode de structure et mode d'antenne) favorisant dans le même temps l'identification sur un mode et la mesure de la grandeur physique sur l'autre, a distance du lecteur. Le deuxième principe utilise le spectre d'un diffuseur multi-bande dont sa SER reconfigurable permet d'associer l'identification de chaque capteur dans un réseau, à la manière d'un code barre. En conclusion, les résultats obtenus dans cette étude valident le principe d'interrogation à longue distance de réseau de capteurs passifs et ouvrent de nouvelles perspectives sur la conception de nouvelles cellules de mesures pour de nouvelles applications dans les secteurs de l'aéronautique, du nucléaire, et de l'environnement. / A new development on sensor networks has been started by LAAS to implement new wireless sensors using passive electromagnetic transduction in the detection of pressure and gas. These highly integrated sensors require no power and the embedded operating frequency is in the Ka band (26 to 40GHz). This thesis is on the design and the realization of a reader suitable for remote sensing of sensor electromagnetic transduction. Its working principle is based on an FMCW radar technology. The main advantage of this radar when reading passive sensors is the ability to have ranges of several tens of meters, much higher than those obtained with conventional SAW or RFID technology. In the first step, the principle of operation of the reader and also the realization of two prototypes focused on the frequencies of 3GHz and 30GHz are presented. A study of the output radar spectrum, called beat signal radar, is discussed to show how the positions and measurements from the sensors are read remotely by the reader. Afterwards, an analysis of the wireless communication is performed to take into account parameters of electromagnetic backscatter such as the impedance and operating frequency of these sensors. These parameters are the basis of an optimization of the global system in terms of sensitivity radar range and the minimal levels of Radar Cross Section (RCS) of the interrogated targets.The validation of this analysis is limited by the reader's maximum range and by various RCS measurements of several types of sensors in the frequency bands of 3GHz and 30GHz. Two principles of sensor passive identification are then presented. The first is based on the simultaneous use of both modes of the sensor's RCS (structural mode and antenna mode), facilitating the identification by one mode and measuring the physical quantity using the other mode. The second principle uses the spectrum of a multiband scatterer where its reconfigurable RCS can associate the identification of each sensor in a network, such as a barcode. In conclusion, the result obtained in this thesis validate the principle of an interrogating network of passive sensors over a long reading range and consequently open a new way of sensor design for future aerospace, nuclear and environment applications.

[pt] Nesta dissertação é realizada uma análise experimental da influência da pressão estática na medição de pressão diferencial com transmissores eletrônicos, dotados de sensores capacitivos ou sensores de silício ressonante, cuja tecnologia é amplamente difundida nos dias atuais por serem de elevada repetitividade, reprodutibilidade, exatidão e baixa histerese. A medição de pressão diferencial é amplamente utilizada na indústria de Petróleo, com o objetivo de medição de vazão, nível, entupimento de filtros e medição de interface óleo água. A calibração dos transmissores de pressão diferencial é feita no país a pressão atmosférica, não se preocupando com a influência da pressão estática do processo sobre seu desempenho. Como sua principal contribuição, o trabalho apresenta uma metodologia inovadora ainda não disponível no país de calibração de transmissores de pressão diferencial na pressão de operação, melhorando a confiabilidade e a incerteza das medições de vazão de líquidos e gases nas indústrias em geral. As faixas estudadas de pressão estática (0 a 20000 KPa) e diferencial (40 a 250 KPa), atendem a utilização interna da área de produção e exploração da Petrobras. A simples substituição da máquina de ensaio e seus instrumentos é suficiente para a calibração em uma faixa mais ampla, utilizando-se da mesma metodologia. Para alcançar os resultados, um dispositivo de amplificação de pressão foi desenvolvido neste estudo e utilizado em cada extremidade do transmissor de pressão, para aumentar a pressão desde valores próximos da atmosférica, que podem ser medidos com boa exatidão e repetitividade, até sua pressão de operação. Durante sua utilização, a pressão diferencial em suas extremidades é deduzida a partir dos valores medidos próximos da pressão atmosférica e do fator de amplificação. A incerteza dos resultados foi estimada e a metodologia foi utilizada para mostrar que a curva de calibração de um transmissor de pressão varia com sua pressão de operação. / [en] This paper deals with an experimental analysis of the static pressure influence upon the measurement of the differential pressure. Using capacitive or silicon resonator transducers, the electronic transmitters used in the experiment are thoroughly diffused nowadays due to their repetitiveness, reproducibility, accuracy and low hysteresis. The measurement of the differential pressure is widely employed in the petrol industry for determining the flow rate, level, blockage of filters and the oil-water interface. The calibration of the differential pressure transmitters is made in Brazil at atmospheric pressure, since there is little concern about the static pressure influence on the transducer performance. As a main contribution, this study presents a calibration methodology of differential pressure transmitters, still unavailable in the country, increasing its reliability and reducing the uncertainty of measuring the flow of liquid or gaseous substances. The ranges of the studied static pressure (from 0 to 20000 KPa) and differential pressure (from 40 to 250 KPa) cover Petrobras production and exploration operating conditions. The same methodology can be applied to wider ranges, by properly sizing the calibrating device and the related instruments. To achieve the results, a pressure amplification device was developed and used at each port of the pressure transmitter. A methodology was also developed in this study to determine the amplification factor from near atmospheric values, which can be measured very accurately, up to the operating pressure of the transmitter. Thus, during the calibration of a pressure transmitter, the pressure differential at the transmitter ports is deduced from the measured value at nearly atmospheric pressure and the amplification factor. The uncertainty of the results were estimated and the methodology was used for the calibration of a pressure transmitter, showing that its calibrating curve varies with the operating pressure.

Para que um transdutor ultrassônico gere e transmita um pulso curto e receba ecos com elevada sensibilidade, além de uma camada de retaguarda que absorva as ondas emitidas para trás, é necessário que haja um bom casamento de impedância acústica entre a cerâmica piezelétrica e o meio externo (camada de acoplamento). Quando comparado ao acoplamento em líquido, o acoplamento em ar é ainda mais complexo, pois este tipo resulta em perdas elevadas durante a transmissão e a recepção dos sinais acústicos, devido à grande diferença de impedância acústica entre a cerâmica e o ar. Certas aplicações requerem um acoplamento em ar e, para isso, os transdutores ultrassônicos usados devem ter banda larga, além de uma baixa impedância acústica. O aumento da largura de banda de um transdutor piezelétrico pode ser alcançado com o emprego de piezocompósitos, de uma camada de retaguarda, de camadas de acoplamento frontal e melhorias na parte eletrônica. A contribuição deste trabalho visa a estudar e desenvolver piezocompósitos com maior largura de banda para aplicação em transdutores de ultrassom para acoplamento em ar. De modo geral, os piezocompósitos possibilitam um maior fator de acoplamento eletromecânico e uma menor impedância acústica quando comparado às cerâmicas piezelétricas convencionais. Neste trabalho foram realizadas a modelagem, a construção e a caracterização de três tipos de piezocompósitos: piezocompósitos com gradação da densidade, piezocompósitos 2-2, e piezocompósitos 1-3. Naqueles com gradação da densidade,variaram-se os parâmetros profundidade, largura e distribuição dos cortes. O método de elementos finitos foi utilizado para analisar a influência dos parâmetros dos cortes. Os piezocompósitos foram construídos a partir de piezocerâmicas circulares e retangulares. Alguns dos piezocompósitos construídos foram submetidos a experimentos de interferometria a laser, mostrando a variação da distribuição dos deslocamentos máximos na superfície em função da frequência. A partir do espectro de frequência da condutância e dos valores inferiores e superiores da largura de banda foram analisados os deslocamentos máximos nas diversas regiões da superfície dos piezocompósitos. Nos piezocompósitos gradados observou-se que os deslocamentos máximos em determinadas regiões da superfície do piezocompósito dependiam da frequência de excitação. Desse modo, os piezocompósitos gradados apresentaram fator de acoplamento eletromecânico e largura de banda maiores do que os dos piezocompósitos 1-3. Transdutores com emissão em ar construídos a partir de piezocompósito gradado e do tipo 1-3 foram caracterizados e medidos os parâmetros largura de banda e fator de acoplamento eletromecânico. O transdutor construído a partir do piezocompósito gradado apresentou maior largura de banda quando comparado com o transdutor do tipo 1-3. / In order to generate and emit a short pulse and receive the echoes with high sensitivity, an ultrasound transducer requires a backing layer to attenuate the signal going backwards and a matching layer to match the acoustical impedances of the piezoceramic and the medium. When compared to liquid coupling, air coupling is further complicated because the large mismatch in acoustic impedance between the ceramic and air results in high losses during transmission and reception of acoustic signals. Certain applications require air-coupling and, therefore, the ultrasonic transducers used must be broadband and have low acoustic impedance. The increase of the bandwidth of a piezoelectric transducer can be achieved with the use of piezocomposites, a back layer, frontal coupling layers and improvements in the electronic part. The contribution of this work aims to study and develop piezocomposites with higher bandwidth for application in ultrasonic transducers with air coupling. In general, the piezocomposites allow a higher electromechanical coupling factor and a lower acoustic impedance when compared to conventional piezoelectric ceramics. In this work, three types of piezocomposites were made: piezocomposites with density gradation, piezocomposites 2-2, and piezocomposites 1-3. In those with density gradation, depth, width and distribution of the cuts were varied. The finite element method was used to analyze the influence of the cut parameters. The piezocomposites were constructed from circular and rectangular piezoceramics. Some of the constructed piezocomposites were submitted to laser interferometry experiments, which showed the variation of the distribution of the maximum displacements in the surface as a function of the frequency. From the frequency spectrum of the conductance curve and of the lower and upper values of bandwidth, the maximum displacements in the various surface regions of the piezocomposites were analyzed. In the graded piezocomposites it was observed that the maximum displacements in certain regions of the surface of the piezocomposite depend on the frequency of excitation. Thus, the graded piezocomposites presented higher electromechanical coupling factor and bandwidth than the piezocomposites 1- 3. Air-coupled transducers constructed from graded piezocomposite and type 1-3 were characterized and measured the parameters bandwidth and electromechanical coupling factor. The transducer constructed from the graded piezocomposite presented higher bandwidth when compared to the type 1-3 transducer.

Este trabalho apresenta um estudo de transdutores piezelétricos de potência usados em máquinas de estampagem e soldagem de tecidos sintéticos por ultra-som, através de modelos de elementos finitos implementados no software ANSYS e verificações experimentais. O transdutor é do tipo sanduíche e está acoplado a um amplificador mecânico e a um sonotrodo. Os comportamentos elétrico e vibracional do transdutor tipo sanduíche foram analisados em relação à quantidade de discos de piezocerâmicas em modelos axi-simétricos com quatro e oito discos. Comparam-se os resultados numéricos da resposta em frequência da impedância elétrica e do coeficiente de acoplamento eletromecânico com resultados experimentais de protótipos. Apresentam-se também análises numéricas do comportamento vibracional do amplificador mecânico e de dois tipos de sonotrodos, um cilíndrico e outro com o formato de uma lâmina larga, usados no processo de corte e soldagem de tecidos por ultra-som. É feita uma análise da distribuição de amplitude de vibração ao longo da face de trabalho dos dois sonotrodos. Os resultados simulados são comparados com os resultados experimentais de uma varredura feita na superfície de trabalho de cada protótipo usando-se um vibrômetro laser Doppler. Mostra-se que a vibração na face do sonotrodo cilíndrico ocorre com maior amplitude em uma região na sua borda. Considerando que para o processamento adequado do tecido é necessário que todos os pontos ao longo da face de trabalho do sonotrodo vibrem com a mesma amplitude, verifica-se a necessidade de modificar a forma do sonotrodo visando obter uma distribuição uniforme de deslocamentos em sua face. Para isso utiliza-se a modelagem do sonotrodo com a técnica de otimização paramétrica disponível no ANSYS, com o objetivo de se obter uma distribuição de vibração uniforme ao longo de sua face de trabalho. Os resultados experimentais do protótipo do sonotrodo cilíndrico otimizado são comparados com os resultados numéricos da distribuição de vibração ao longo de sua face de trabalho mostrando uma boa concordância e, portanto, validando o modelo numérico. / This work presents a study of high power piezoelectric sandwich transducers used in ultrasonic cutting and welding of thermoplastic textiles using finite element models with ANSYS and experimental verifications. The electrical/vibrational behaviour of transducers with four and eight piezoceramics is analysed using axisymetric models. The numerical results of electrical impedance frequency response and electromechanical coupling factor are compared with experimental results of prototypes. There are presented the numerical analysis of the vibrational behaviour of an acoustical amplifier and two types of sonotrodes, a cylindrical and an wide blade shape, used in the ultrasonic cutting and welding of thermoplastic textiles. It is performed an analysis of the distribution of vibration amplitude along the work surface of both sonotrodes and the simulated results are compared with esperimental measurements of the prototypes using a laser Doppler vibrometer. The results show that the amplitude of vibration of the cylindrical sonotrode is not uniform on its working surface. A maximum of amplitude occurs in its border. In order to guarantee the process quality it is necessary that all points along the working surface vibrate with the same amplitude. It is used the parametric optimization technic of ANSYS in order to obtain an uniform amplitude of displacement on the working surface of the cylindric sonotrode. The simulated and experimental results optimized prototype of the cylindric sonotrode are compared showing good agreement and therfore validating the numerical model.

Este trabalho apresenta um estudo de transdutores piezelétricos de potência usados em máquinas de estampagem e soldagem de tecidos sintéticos por ultra-som, através de modelos de elementos finitos implementados no software ANSYS e verificações experimentais. O transdutor é do tipo sanduíche e está acoplado a um amplificador mecânico e a um sonotrodo. Os comportamentos elétrico e vibracional do transdutor tipo sanduíche foram analisados em relação à quantidade de discos de piezocerâmicas em modelos axi-simétricos com quatro e oito discos. Comparam-se os resultados numéricos da resposta em frequência da impedância elétrica e do coeficiente de acoplamento eletromecânico com resultados experimentais de protótipos. Apresentam-se também análises numéricas do comportamento vibracional do amplificador mecânico e de dois tipos de sonotrodos, um cilíndrico e outro com o formato de uma lâmina larga, usados no processo de corte e soldagem de tecidos por ultra-som. É feita uma análise da distribuição de amplitude de vibração ao longo da face de trabalho dos dois sonotrodos. Os resultados simulados são comparados com os resultados experimentais de uma varredura feita na superfície de trabalho de cada protótipo usando-se um vibrômetro laser Doppler. Mostra-se que a vibração na face do sonotrodo cilíndrico ocorre com maior amplitude em uma região na sua borda. Considerando que para o processamento adequado do tecido é necessário que todos os pontos ao longo da face de trabalho do sonotrodo vibrem com a mesma amplitude, verifica-se a necessidade de modificar a forma do sonotrodo visando obter uma distribuição uniforme de deslocamentos em sua face. Para isso utiliza-se a modelagem do sonotrodo com a técnica de otimização paramétrica disponível no ANSYS, com o objetivo de se obter uma distribuição de vibração uniforme ao longo de sua face de trabalho. Os resultados experimentais do protótipo do sonotrodo cilíndrico otimizado são comparados com os resultados numéricos da distribuição de vibração ao longo de sua face de trabalho mostrando uma boa concordância e, portanto, validando o modelo numérico. / This work presents a study of high power piezoelectric sandwich transducers used in ultrasonic cutting and welding of thermoplastic textiles using finite element models with ANSYS and experimental verifications. The electrical/vibrational behaviour of transducers with four and eight piezoceramics is analysed using axisymetric models. The numerical results of electrical impedance frequency response and electromechanical coupling factor are compared with experimental results of prototypes. There are presented the numerical analysis of the vibrational behaviour of an acoustical amplifier and two types of sonotrodes, a cylindrical and an wide blade shape, used in the ultrasonic cutting and welding of thermoplastic textiles. It is performed an analysis of the distribution of vibration amplitude along the work surface of both sonotrodes and the simulated results are compared with esperimental measurements of the prototypes using a laser Doppler vibrometer. The results show that the amplitude of vibration of the cylindrical sonotrode is not uniform on its working surface. A maximum of amplitude occurs in its border. In order to guarantee the process quality it is necessary that all points along the working surface vibrate with the same amplitude. It is used the parametric optimization technic of ANSYS in order to obtain an uniform amplitude of displacement on the working surface of the cylindric sonotrode. The simulated and experimental results optimized prototype of the cylindric sonotrode are compared showing good agreement and therfore validating the numerical model.

En France, en Europe et dans le monde entier, le vieillissement de la population est une réalité. Une partie de cette population âgée est dite dépendante car elle n’est plus en mesure d’assumer seule les tâches de la vie quotidienne. L’enjeu sociétal est alors de garantir un niveau de bien-être et de sécurité à ces personnes, compatible avec l’évolution du niveau de vie et des usages et habitudes ‘modernes’. Très logiquement, les domaines de recherche liés à la problématique des personnes âgées à domicile font preuve d’un grand dynamisme, alors que la maison de retraite, qui reste la solution pour la grande dépendance, a été un peu délaissée. Néanmoins, la pénurie de personnel conjuguée à l’augmentation des coûts et des exigences des résidents offre une opportunité à des solutions innovantes basées sur les TIC. Les travaux de cette thèse de doctorat sous convention CIFRE se sont déroulés dans ce contexte au sein de l’équipe de recherche de Legrand et du département d’Electronique et Physique de Télécom SudParis à Evry. Le sujet concerne la conception d’un nouveau capteur (non-porté) intégrant l’installation électrique du lieu de vie du patient ainsi que la fusion avec d’autres capteurs de l’infrastructure afin de suivre l’activité du résident et, le cas échéant, soit signaler en temps réel des situations nécessitant le recours d’un aidant, soit identifier des dérives lentes dont l’interprétation sera du ressort du personnel médical. Les travaux de la thèse ont été en partie intégrés au projet FUI14 « E-monitor’âge » dont l’objectif est précisément la « supervision » des résidents. Ce mémoire est structuré de manière à présenter l’historique de ces travaux et la démarche opérée pour leur réalisation. Nous introduisons le contexte et les besoins identifiés pour le suivi des personnes âgées dans les maisons de retraites. Nous faisons un point sur les systèmes de supervision/monitoring existants et nous présentons les méthodes et les techniques de détection de situations d’urgence. Nous terminons cette partie du mémoire (chapitre 1) par la spécification du problème majeur rencontré par ces systèmes de supervision qui est celui de la détection de présence d’une personne. En s’appuyant sur la technologie des capteurs pyro-électriques, la partie suivante propose une solution originale de traitement de signal pour la détection d’une présence humaine dans une chambre voire la détection de présence de plusieurs personnes à la fois (chapitre 2). Le chapitre 3 introduit ensuite un capteur thermique à base de thermopiles afin de détecter la présence d’une personne dans son lit, ce que ne permet pas la technologie pyro-électrique qui ne détecte pas un corps chaud immobile. Dans cette partie nous limitons l’utilisation de ce capteur à la détection de la présence de la personne dans son lit (chapitre 4) voire à l’estimation de la qualité de son sommeil qui constitue d’une part l’originalité de nos travaux s’appuyant sur des approches de classification non-supervisée, et qui ouvre des perspectives encourageantes quant à l’utilisation de ce capteur pour caractériser relativement finement le type de sommeil d’autre part (chapitre 5) / In France, in Europe and worldwide, the aging population is a reality. Some of these elderly people lose their autonomy as they are no longer able to manage alone the tasks of daily life. The societal issue is therefore to ensure a level of well-being and safety of these persons, consistent with changes in living standards, customs and modern habits. The research areas related to the problems of elderly people at home are showing great dynamism, while the nursing home, which remains the solution for cases of high dependence, is somewhat neglected. Nevertheless, staff shortages combined with rising costs and residents’ demands offer an opportunity for innovative ICT-based solutions. The work presented here was performed, in the context of a CIFRE doctoral thesis, within the Legrand research team and at the physics and electronics department of Mines-Telecom SudParis at Evry. The subject and project aim was twofold: firstly, designing a new sensor which will be incorporated in the electrical installation of the patient’s living space, and secondly, a multi-sensor merger to monitor the activity of the resident in order to enable real-time reporting of situations requiring the caregiver’s intervention or to detect slow drifts whose interpretation will be the responsibility of the medical staff. The work carried out for the purpose of this thesis has been included partially in the FUI 14 project whose propose is precisely the “supervision of residents in the nursing home”. The present paper is structured in such a way as to introduce the background of the work and the approach taken to perform it. The context and needs identified for monitoring of nursing home residents are also introduced. We begin by describing existing monitoring systems and the technical methods used to detect emergency situations. We end the first part (chapter 1) of this paper by specifying the major problem encountered when testing existing monitoring systems based on ambient sensors: namely how to detect the presence of an immobile and silent person in the room. Using an existing pyro-electric infrared sensors network installation in a nursing home, the next section proposes an original solution for detecting human presence in a room and also for differentiating between the presence of one and the presence of more than one person (chapter 2). Chapter 3 presents a new sensor integrated into the electrical installation of the patient’s living space. Here, we introduce a thermopile based thermal sensor in order to detect the presence of a person in his/her living space. In this work we restrict the use of this sensor to detecting the presence of the person in bed (chapter 4). The estimation of sleep quality which represents the original dimension of our work is presented in chapter 5. Differentiation between different phases of sleep is based on unsupervised classification approaches. Our project opens up encouraging prospects for the use of this type of sensor for relatively fine characterization of different kinds of sleep

Ce travail rentre dans le cadre de la caractérisation des couches minces, de revêtements et de surfaces fonctionnelles (épaisseur, constantes élastiques,…). Parmi les méthodes de caractérisation potentielles, les méthodes ultrasonores employant des ondes de surface sont particulièrement intéressantes. Pour ce faire, nous avons choisi d’exploiter la dispersion des ondes de surface de type Rayleigh. En effet, les ondes acoustiques de surface (SAW) de type Rayleigh se propagent à la surface d’un matériau et l’énergie véhiculée par ces ondes est confinée sous la surface dans une couche d’épaisseur de l’ordre d’une longueur d’onde. Afin de caractériser ces revêtements, il est nécessaire de travailler sur une large gamme de fréquences. D’autre part, ces couches peuvent être fragiles et transparentes, c’est pourquoi, des transducteurs interdigités (IDT) sont envisagés. Pour optimiser ce type de capteurs, et en particulier leur bande passante, il est nécessaire d’étudier différentes configurations sachant qu’il est notamment possible de faire varier le nombre d’électrodes, les dimensions des électrodes, leurs formes et leurs espacements. Enfin, pour exciter ces ondes de surface dans une large gamme de fréquence avec des niveaux de déplacement suffisants pour la caractérisation des couches minces et revêtements, la technique à double Chirp spatio-temporel basée sur des transducteurs SAW-IDT a été privilégiée. Nous avons montré les potentialités de cette approche en caractérisant premièrement des structures à couche mince métalliques d’épaisseurs de 100 nm et plus, et deuxièmement des revêtements transparents de type sol-gel. / This work is within the scope of characterization of thin layers, coatings and functional surfaces (thickness, elastic constants,…). Among the characterization methods, the ultrasonic methods using surface acoustic waves are particularly interesting. In order to do this, we chose to make use the dispersion phenomenon of Rayleigh-like surface acoustic waves. Indeed, the propagation of these waves is close to the surface of material and the energy is concentrated within a layer under the surface of about one wavelength thick. In order to characterize these coatings and structures, it is necessary to perform measurements in high frequencies. On the other hand, these coatings can be fragile and transparent, this is why in this study, SAW-IDT sensors are achieved for surface acoustic wave generation. For optimization of these SAW-IDT sensors, particularly their band-width, it is necessary to study various IDT configurations by varying the number of electrodes, dimensions of the electrodes, their shapes and spacings. Finally, to generate the surface acoustic waves over a wide frequency range with sufficient displacement amplitude for the characterization of thin films and coatings, a time-space chirp technique with SAW-IDT sensors was selected. We have shown the potential of this approach by characterizing firstly thin metallic layers, and secondly transparent coatings obtained by the sol-gel process.

Que ce soit dans le domaine médical ou en contrôle non destructif, les systèmes d’imagerie ultrasonore sont devenus de plus en plus utilisés de nos jours. Leurs applications ne cessent de s’élargir et des performances toujours plus accrues sont vivement recherchées, afin d’améliorer la qualité des diagnostics réalisés. Nous sommes donc passés de l’utilisation de systèmes à base de transducteurs ultrasonores mono-élément à des systèmes utilisant des réseaux de transducteurs à une dimension (1D) et à deux dimensions (2D) composés d’éléments de plus en plus nombreux et petits. Néanmoins, un phénomène indésirable est fortement présent dans ces réseaux de transducteurs ultrasonores : il s’agit du couplage inter-éléments tendant à limiter leurs performances acoustiques et à modifier leur diagramme de rayonnement. Tout au long de ce travail de recherche, nous avons donc cherché à comprendre ce phénomène parasite et à apporter des solutions pour le réduire voire le supprimer. En se basant sur des modélisations éléments finis 2D et 3D et grâce à la fabrication de prototypes, nous avons d’une part, mis en évidence les différents types de couplages présents dans un réseau de transducteurs (acoustique, mécanique) et d’autre part, deux méthodes de correction basées l’une comme l’autre sur l’application de tensions convenables aux différents éléments du réseau ont été testées. La première méthode utilise les déplacements normaux moyens à la surface de chaque élément du réseau pour évaluer ces tensions, tandis que la deuxième fait appel aux courants motionnels parcourant chaque élément pour les déterminer. Les résultats numériques et expérimentaux concernant les déplacements et les diagrammes de rayonnement sont en bon accord. En outre, les deux méthodes s’avèrent particulièrement efficaces pour réduire le couplage inter-éléments. / Whether in medicine or in non-destructive testing, ultrasonic imaging systems have become increasingly used nowadays. Their applications continue to expand and good performances are needed to improve the quality of the diagnosis. Moreover, significant progress has been made since these systems were originally based on single element ultrasonic transducers and are now made of mono-dimensional (1D) and bi-dimensional (2D) elements arrays ever more numerous and smaller. However, an undesirable phenomenon is strongly present in the ultrasonic transducer arrays: it is the cross-talk, which limits their acoustic performances and modifies their radiation pattern. Throughout this research, we have attempted on one hand to understand this parasitic phenomenon and on the other hand to provide solutions in order to reduce it or even remove it. To highlight the cross-talk types (acoustic and mechanical) and to test the proposed correction methods, we developed two-dimensional (2D) and three-dimensional (3D) finite element modeling and fabricated some prototypes. Both correction methods rely on the application of suitable voltages to the array elements. The first method uses the average of the normal displacements at the surface of each element to evaluate the voltages, while the second one utilizes the motional currents through each element to determine them. The numerical and experimental results concerning the displacements and the radiation patterns are in good agreement. In addition to this, both methods have been efficiently performed to reduce the cross-talk.

Ce travail de thèse a pour but de développer et de caractériser de nouveaux systèmes d'assurance qualité en curiethérapie, à base de sondes dosimétriques en Nitrure de Gallium (GaN). L'étude comprend d'une part la caractérisation et la simulation du transducteur GaN et de la sonde dosimétrique, et d'autre part la mise en œuvre et les tests de 2 systèmes d'assurance qualité.Les propriétés de radioluminescence du transducteur GaN ont été étudiées afin d'optimiser le signal dosimétrique des sondes. La sonde dosimétrique encapsulant un petit volume de cristal GaN a ensuite été caractérisée en vue de son intégration dans des systèmes d'assurance qualité. Des simulations Monte Carlo sur la sonde GaN ont également été effectuées et comparées aux mesures.Pour l'assurance qualité en curiethérapie, nous avons proposé une méthode utilisant plusieurs sondes GaN, pour permettre de déterminer en temps réel les principaux paramètres physiques d'un projecteur de source : la position, le temps de pause et l'activité de la source. Nous avons conçu et réalisé deux prototypes de systèmes d'assurance qualité mettant en œuvre cette méthode : un fantôme instrumenté pour le contrôle prétraitement et un applicateur gynécologique instrumenté pour le contrôle pendant le traitement. Ces deux prototypes ont été testés en conditions cliniques, et leurs principales caractéristiques sont satisfaisantes. Ils répondent aux besoins applicatifs et offrent une perspective intéressante pour de nouveaux outils de contrôle qualité en curiethérapie / This work aims to develop and characterize novel quality assurance systems based on Gallium Nitride (GaN) dosimeter probe for brachytherapy. It includes characterization and simulation studies of the GaN transducer and of the dosimeter probe as well as the implementation and testing of two quality assurance system prototypes.The radioluminescence properties of the GaN transducer have been studied for optimization of the dosimeter response. Characterization studies of dosimeter probes incorporating miniaturized GaN transducers have been carried out in the frame of the quality assurance systems development. Monte Carlo simulations of the GaN probe under irradiation has also been performed and compared with measurements.A method which processes simultaneously the output signals from several GaN probes has been proposed for real time determination of the projector’s physical parameters (dwell position, dwell time and activity of the source). Two quality assurance system prototypes implementing this method have been designed and fabricated: an instrumented phantom for pre-treatment quality assurance and an instrumented gynecological applicator for in vivo quality control. These two prototypes have been tested and evaluated in clinical conditions and their main characteristics are satisfactory. Both systems are in line with the application requirements and offers new perspectives for quality assurance in brachytherapy