Nous avons montré que l'irradiation aux ions d'argon d'énergie comprise entre 1 et 15 MeV cause des dommages en surface du titane et du zirconium, qui prennent la forme d'une oxydation accélérée et/ou d'une cratérisation dont les effets évoluent en fonction de l'énergie du projectile et de l'atmosphère de recuit (température et pression), simulant les conditions environnementales représentatives de l'interface gaine/combustible d'un réacteur REP. Par AFM, nous avons montré que la surface du titane et du zirconium était attaquée par bombardement aux ions d'argon, à haute température (jusqu'à 500°C) en milieu faiblement oxydant (sous pression d'air sec raréfié comprise entre 5,7 10-5 Pa et 5 10-3 Pa) et à une dose moyenne fixée à environ 5 1014 ions.cm-2. On observe ainsi la formation de cratères nanométriques sur toute la surface du titane irradié entre 2 et 9 MeV et celle du zirconium irradié à 4 MeV, dont les caractéristiques varient en fonction de la température et de la pression. Dans le cas du couple Ar/Ti, l'efficacité d'endommagement superficiel augmente lorsque l'énergie du projectile diminue de 9 à 2 MeV. Par ailleurs, alors que la surface du titane apparaît transparente au faisceau d'ions à 15 MeV, celle du zirconium révèle de nombreux cratères micrométriques entourés d'un large halo sombre. Les caractéristiques des cratères (taille et densité superficielle) diffèrent de façon significative de celles observées à la fois dans le domaine des basses énergies (keV) où le dépôt d'énergie est contrôlé par les collisions balistiques (Sn) et dans le domaine des hautes énergies (MeV - GeV) où le dépôt d'énergie est contrôlé par les excitations électroniques (Se), ce qui n'était pas complètement inattendu dans le domaine d'énergie intermédiaire étudié, dans lequel des effets de pouvoir d'arrêt combiné Sn - Se sont envisageables. Par XPS couplé au décapage ionique, nous avons montré qu'il existe un effet d'irradiation sur l'oxydation thermique du titane, exacerbée sous faisceau d'ions d'argon entre 2 et 9 MeV, et qu'il existe aussi un effet d'énergie sur l'épaisseur et la stœchiométrie de l'oxyde. L'étude menée par Ellipsométrie Spectroscopique sur les films d'oxyde formés entre 1 et 9 MeV a corroboré ces résultats et montré précisément qu'il existe un pic d'oxydation en fonction de l'énergie d'ions d'argon, qui présente un maximum à 3 MeV, dans les conditions de l'expérience. Les mesures de gain d'oxygène effectuées par NBS confirment l'existence de ce pic d'oxydation. Les résultats acquis à ce jour par NBS concernant l'oxydation thermique du zirconium sous irradiation à l'argon de 4 et 9 MeV confirment les travaux antérieurs du groupe Aval du Cycle Electronucléaire de l'Institut de Physique Nucléaire de Lyon, et suggèrent fortement l'existence d'un pic d'oxydation dans la même plage d'énergie de projectile que pour le titane.

The primary challenge in wireless sensor network (WSN) deployment is the limited network lifetime due to the finite-capacity batteries. In accordance with this challenge, the vast majority of research efforts thus far have focused on the development of energy-efficient communication and computing mechanisms for WSNs. In this thesis, a fundamentally different approach and hence completely new WSN paradigm, i.e., the Passive Wireless Sensor Network (PWSN), is introduced. The objective of PWSN is to eliminate the limitation on the system lifetime of the WSNs. In PWSN, power is externally supplied to the sensor network node via an external RF source. Hence, the lifetime of the system is no longer determined by the lifetime of the batteries. An alternative communication scheme, modulated backscattering, is also discussed to be utilized in PWSN. The feasibility of the proposed system is investigated along with the open research challenges for reliable communication and networking in PWSN. Additionally, a new medium access schemee for PWSN, Ultra-Wideband PWSN Medium Access Control (UWB PWSN MAC), is presented.

Backscatter radio - the broad class of systems that communicate using scattered electromagnetic waves - is the driving technology behind many compelling applications such as radio frequency identification (RFID) tags and passive sensors. These systems can be used in many ways including article tracking, position location, passive temperature sensors, passive data storage, and in many other systems which require information exchange between an interrogator and a small, low-cost transponder with little-to-no transponder power consumption. Although backscatter radio is maturing, such systems have limited communication range and reliability caused, in part, by multipath fading. The research presented in this dissertation investigates how multipath fading can be reduced using multiple antennas at the interrogator transmitter, interrogator receiver, and on the transponder, or RF tag. First, two link budgets for backscatter radio are presented and fading effects demonstrated through a realistic, 915 MHz, RFID-portal example. Each term in the link budget is explained and used to illuminate the propagation and high-frequency effects that influence RF tag operation. Second, analytic envelope distributions for the M x L x N, dyadic backscatter channel - the general channel in which a backscatter system with M transmitter, L RF tag, and N receiver antennas operates - are derived. The distributions show that multipath fading can be reduced using multiple-antenna RF tags and by using separate transmitter and receiver antenna arrays at the interrogator. These results are verified by fading measurements of the M x L x N, dyadic backscatter channel at 5.8 GHz - the center of the 5725-5850 MHz unlicensed industrial, scientific, and medical (ISM) frequency band that offers reduced antenna size, increased antenna gain, and, in some cases, reduced object attachment losses compared to the commonly used 902-928 MHz ISM band. Measurements were taken with a custom backscatter testbed and details of its design are provided. In the end, this dissertation presents both theory and measurements that demonstrate multipath fading reductions for backscatter-radio systems that use multiple antennas.

Magister Scientiae - MSc (Chemistry) / Although cadmium and lead chalcogenide quantum dot have excellent optical and photoluminescent properties that are highly favorable for biological applications, there still exists increasing concerns due to the toxicity of these metals. We, therefore, report the synthesis of new aqueous soluble IrSe quantum dot at room temperature utilizing a bottom-up wet chemistry approach. NaHSe and H2IrCl6 were utilized as the Se and Ir source, respectively. High-resolution transmission electron microscopy reveals that the synthesized 3MPA-IrSe Qd are 3 nm in diameter. The characteristics and properties of the IrSe Qd are investigated utilizing, Selected Area electron diffraction, ATR- Fourier Transform Infra-Red Spectroscopy, Energy Dispersive X-ray spectroscopy, Photoluminescence, Cyclic Voltammetry and chronocoulometry. A 3 fold increase in the optical band gap of IrSe quantum dot in comparison to reported bulk IrSe is observed consistent with the effective mass approximation theory for semiconductor materials of particles sizes < 10 nm. The PL emission of the IrSe quantum dot is at 519 nm. Their electro-activity is studied on gold electrodes and exhibit reduction and oxidation at - 107 mV and +641 mV, with lowered reductive potentials. The synthesized quantum dot are suitable for low energy requiring electrochemical applications such as biological sensors and candidates for further investigation as photoluminescent biological labels.

abstract: The ability to monitor electrophysiological signals from the sentient brain is requisite to decipher its enormously complex workings and initiate remedial solutions for the vast amount of neurologically-based disorders. Despite immense advancements in creating a variety of instruments to record signals from the brain, the translation of such neurorecording instrumentation to real clinical domains places heavy demands on their safety and reliability, both of which are not entirely portrayed by presently existing implantable recording solutions. In an attempt to lower these barriers, alternative wireless radar backscattering techniques are proposed to render the technical burdens of the implant chip to entirely passive neurorecording processes that transpire in the absence of formal integrated power sources or powering schemes along with any active circuitry. These radar-like wireless backscattering mechanisms are used to conceive of fully passive neurorecording operations of an implantable microsystem. The fully passive device potentially manifests inherent advantages over current wireless implantable and wired recording systems: negligible heat dissipation to reduce risks of brain tissue damage and minimal circuitry for long term reliability as a chronic implant. Fully passive neurorecording operations are realized via intrinsic nonlinear mixing properties of the varactor diode. These mixing and recording operations are directly activated by wirelessly interrogating the fully passive device with a microwave carrier signal. This fundamental carrier signal, acquired by the implant antenna, mixes through the varactor diode along with the internal targeted neuropotential brain signals to produce higher frequency harmonics containing the targeted neuropotential signals. These harmonics are backscattered wirelessly to the external interrogator that retrieves and recovers the original neuropotential brain signal. The passive approach removes the need for internal power sources and may alleviate heat trauma and reliability issues that limit practical implementation of existing implantable neurorecorders. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2014

Cette thèse, co-dirigée par Jean-Marc Boucher et Ronan Fablet (IMT Atlantique) et co-encadrée par Didier Charlot (iXBlue), Gilles Le Chenadec et Michel Legris (ENSTA Bretagne), a été réalisée dans le cadre d'une convention CIFRE au sein de la société iXBlue. iXblue développe et commercialise un sondeur multifaisceaux (MBES) SEAPIX principalement dédié au marché de la pêche. Ce système a été développé pour offrir le meilleur compromis entre performances de détection et son coût de revient. Outre les caractéristiques classiques d'un MBES, il propose la particularité unique de pouvoir insonifier des fauchées différentes sous le navire par dépointage électronique du faisceau d'émission de bâbord à tribord et d'avant en arrière. Le travail de thèse a pour objectif d'étudier l'apport de ces nouvelles capacités multi-fauchées dans l'analyse et la classification des fonds marins. La première partie du travail a consisté à réaliser une analyse détaillée de la chaîne de mesure. Cette étude a permis d'évaluer la consistance des niveaux de rétrodiffusion entre les différents modes d'insonification. La deuxième partie s'est intéressée à la recherche des caractéristiques discriminantes du signal rétrodiffusé en tenant compte de la géométrie d'acquisition de chaque mode d'insonification. La dernière étape du travail a porté sur des méthodes de fusion des données acquises. Cette étude s'est réalisée en deux approches; la première considère des données venant du même mode d'insonification (intra-mode) et la seconde venant de modes différents (inter-mode), pour la cartographie des fonds marins. Les résultats expérimentaux obtenus mettent en évidence l'intérêt de la chaîne de traitement proposée et d'une architecture multi-mode sur les jeux de données réelles traitées. / This thesis, co-directed by Jean-Marc Boucher and Ronan Fablet (IMT Atlantique) and co-supervised by Didier Charlot (iXBlue), Gilles Le Chenadec and Michel Legris (ENSTA Bretagne), was realized in the context of a convention CIFRE with the company iXBlue.iXblue develops and commercializes a multibeam echosounder (MBES) SEAPIX primarily dedicated to the fishery market. The system is optimized to offer the best compromise between performances capabilities and cost. In addition to the classical characteristics of an MBES, it offers the unique feature of scanning the seafloor (and the water column volume) by electronical beamform multiple the emission swaths from port to starboard, as well as from forward to backward. The objective of the thesis is to study the contribution of these new multi-swath capacities in the analysis and classification of the seafloor.The first part of the work consisted in carrying out a detailed analysis of the measurement chain. This study evaluated the consistency in acquiring the backscattering strength from different insonification modes. The second part investigated the discriminant characteristics of the backscattered signal while taking into account the acquisition geometry of each insonification mode. The last stage of the work involved to methods of fusing the acquired data. This study was carried out in two approaches; the first considers data from the same insonification mode (intra-mode) and the second from different modes (inter-mode), for the seafloor classification. The obtained experimental results highlight the interest of the proposed processing chain and a multi-mode architecture on the real datasets.

Made available in DSpace on 2014-10-09T12:51:34Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:18Z (GMT). No. of bitstreams: 0 / O Laboratório de Aplicações Ambientais a Laser, situado no Centro de Lasers e Aplicações no IPEN (Instituto de Pesquisas Energéticas e Nucleares), efetua medidas das concentrações de aerossóis atmosféricos, enviando um feixe de laser à atmosfera e coletando a luz retroespalhada. Tal sistema fornece um grande número de parâmetros físicos que devem ser administrados de forma ágil para a obtenção de análises resultantes. Em conseqüência disso, a implementação de um banco de dados tornou-se imprescindível como instrumento de comunicação e visualização gráfica das medidas coletadas. Um critério de classificação destas valiosas informações foi adotado, estabelecendo níveis de armazenamento definidos a partir de características específicas aos tipos de dados determinados. A compilação e automação destas medidas promoverá a integração entre dados, análise e retorno otimizado de resultados das propriedades da atmosfera, propiciando futuras pesquisas e análise de dados. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

O Laboratório de Aplicações Ambientais a Laser, situado no Centro de Lasers e Aplicações no IPEN (Instituto de Pesquisas Energéticas e Nucleares), efetua medidas das concentrações de aerossóis atmosféricos, enviando um feixe de laser à atmosfera e coletando a luz retroespalhada. Tal sistema fornece um grande número de parâmetros físicos que devem ser administrados de forma ágil para a obtenção de análises resultantes. Em conseqüência disso, a implementação de um banco de dados tornou-se imprescindível como instrumento de comunicação e visualização gráfica das medidas coletadas. Um critério de classificação destas valiosas informações foi adotado, estabelecendo níveis de armazenamento definidos a partir de características específicas aos tipos de dados determinados. A compilação e automação destas medidas promoverá a integração entre dados, análise e retorno otimizado de resultados das propriedades da atmosfera, propiciando futuras pesquisas e análise de dados. / The LIDAR system (Light Detection and Ranging) laser remote sensing at the Nuclear and Energy Research Institute Laboratory of Environmental Laser Applications allows on line measurements of variations in the concentrations of atmospheric aerosols by sending a laser beam to the atmosphere and collecting the backscattered light. Such a system supplies a great number of physical parameters that must be managed in an agile form to the attainment of a real time analysis. Database implementation therefore becomes an important toll of communication and graphical visualization of measurements. A criterion for classification of this valuable information was adopted, establishing defined levels of storage from specific characteristics of the determined data types. The compilation and automation of these measurements will promote optimized integration between data, analysis and retrieval of the resulting properties and of the atmosphere, improving future research and data analysis.

Mon travail de thèse s’est développé, pour le cas particulier des observations satellitales à partir de l’orbite géostationnaire. Le but général a été de caractériser la variabilité diurne des propriétés optiques inhérentes (i.e. les coefficients d‘atténuation et de rétrodiffusion particulaire, cp et bbp) et apparentes (i.e. la réflectance, R) des eaux océaniques (« forme » du cycle diurne, amplitude, variations saisonnières, causes). Ces propriétés optiques déterminent le signal qu’un instrument embarqué à bord d’un satellite peut observer. Cette étude est une étape préliminaire permettant de comprendre la physique du problème, avant de pouvoir évaluer la possibilité de quantifier cette variabilité diurne à partir des observations satellitaires. La variabilité diurne de cp et bbp est donc étudiée en fonction des saisons définies selon les conditions physico-trophiques: le mélange, le bloom, son déclin, et l’oligotrophie. cp et bbp sont caractérisés par un cycle diurne, augmentation le jour et diminution la nuit, confirmant les tendances générales connues. Ce phénomène se produit durant toutes les saisons avec une variabilité intra-saisonnière qui différencie les cycles de cp et bbp: cp montre une amplitude plus large durant le bloom, contrairement à bbp les minima de cp et bbp sont synchronisés tandis que les maxima de bbp sont atteints 3 à 6 h avant ceux de cp, sauf pendant le bloom. L’augmentation journalière de bbp se reflète dans les changements de R. Toutefois, les résultats ont montré que l’inversion ne permet pas de reproduire l’augmentation journalière de bbp de façon satisfaisante. Les techniques d’inversion existantes ne sont pas adaptées pour une utilisation à haute fréquence. / My thesis is developed for the particular case of satellites observations from geostationary orbit. The overall aim was to characterize the diel variability of water inherent (i.e. the particulate beam attenuation and backscattering coefficients, cp and bbp) and apparent (i.e. reflectance, R) optical properties (“shape”of diel cycle, amplitude, seasonal variations, origins). These properties determine the signal which is observed from sensor aboard satellite. This study is a preliminary step in understanding the physical problem, before assessing the possibility of quantifying the diel variability from satellite observations. Diel variability of cp and bbp is studied by season, as defined by physical and trophic conditions: mixing, bloom proliferation, its decline, and oligotrophy. Both cp and bbp are characterized by a diel cycle of daytime increase and nighttime decrease, confirming known general trends. This occurs across all seasons, but intra-seasonal variability differed between cp and bbp cycles: unlike bbp, cp show larger amplitude of diurnal variation during the bloom cp and bbp minima are synchronized while bbp minima are attained 3-6 h before those of cp, except during the bloom. Daily changes of R are consistent with the variations of bbp. Nevertheless, it is still difficult to reproduce the diurnal increase of bbp by inversion of R. The differences observed between in situ and modeled values of bbp suggest that the performance of inversion is degraded when it is used at high frequency.

>Magister Scientiae - MSc / The growth of the Internet has led to many interesting developments for both educational and commercial purposes. In this project an attempt was made to use the Internet for a research purpose to facilitate the determination of the thermal stability of diffusion barriers. Another purpose of this thesis is to investigate the teaching and training use of the Internet through the development of online interactive tools and activities as well as materials. The training aspects are mentioned as it is hoped that this thesis can serve as a form of documentation of the use of the Internet, while the central part was the determination of thermal stability of TiN, TaN and TiW diffusion barriers on Ag.