Dissertations / Theses on the topic 'Schéma passif'

Les méthodes stochastiques d'optimisation globale ont fait preuve d'une plus grande performance sur certains problèmes que sur d'autres. La méthode que nous avons choisie comme outil d'optimisation est la méthode du recuit simule : c'est une méthode issue de la thermodynamique statistique, qui a montré son efficacité sur des fonctions analytiques complexes, comme les fonctions de Rosenbrock à 100 variables, Shekel à 4 variables et Zakharov à 100 variables. Grâce à un couplage entre un simulateur de circuits linéaires et le recuit simulé, nous avons pu résoudre non seulement les problèmes d'optimisation combinatoire mais aussi ceux d'optimisation à variables continues, notamment la caractérisation des modèles de composants électroniques. Il s'agit de déterminer, à partir de données expérimentales caractérisant le composant, les valeurs des paramètres d'un modèle de composant électronique et aussi sa topologie. Nous avons d'abord effectué la caractérisation de modèle de composant passifs, notamment un modèle d'inductance MMIC de THOMSON-CSF. Puis, nous nous sommes intéressés aux modèles de composants actifs, en particulier un modèle de transistor bipolaire. Nous avons ensuite procédé à la recherche de la topologie des modèles de composant par simplification d'une structure complexe jusqu'a l'aboutissement d'une structure simple. Cette simplification est basée sur deux méthodes, soit la comparaison des impédances, soit la technique des moyennes glissantes. Elle a nécessité la mise au point d'une variante du recuit simulé, permettant la recherche des paramètres dans un domaine de grande amplitude (plus de 10 décades) : le recuit simulé logarithmique. La recherche de la topologie a permis l'ouverture sur un autre domaine d'application : celui de l'adaptation à large bande. Dans ce cas, la connaissance de la topologie du correcteur à insérer entre le générateur et la charge est nécessaire afin de maximiser le gain de transfert en puissance.

Suite à la tendance de miniaturisation des convertisseurs d'électronique de puissance, un type de composant passif hybride mariant trois composants conventionnels y compris une inductance, un condensateur et un transformateur est étudié au G2Elab depuis 2001. Ce composant baptisé LCT donne plusieurs avantages tant en terme d'intégration qu'en performance. Pourtant, le dimensionnement classique des composants passifs ne garantisse pas de résultats optimaux pour les composant LCT. En contexte d'optimiser du dimensionnement des ces composants, cette thèse propose une nouvelle approche. L'optimisation se base tout d'abord sur une modélisation électrodynamique qui est quand à-t-elle basé sur la méthode du schéma équivalent des plaques déjà développé au G2Elab, ensuite sur une modélisation thermique analytique des composant magnétique planar. L'outil d'optimisation du dimensionnement permet de minimiser le volume des composants LCT sous une contrainte principale de la thermique. Les travaux expérimentaux constituent un moyen important pour la validation des modèles développés.

Dans cette thèse, nous étudions d'abord le problème de l'optimisation d'ordre zéro dans le cadre actif pour des fonctions lisses et trois classes différentes de fonctions : i) les fonctions qui satisfont la condition de Polyak-Łojasiewicz, ii) les fonctions fortement convexes, et iii) la classe plus large des fonctions non convexes fortement lisses.De plus, nous proposons un nouvel algorithme basé sur la randomisation de type l1, et nous étudions ses propriétés pour les fonctions convexes Lipschitz dans un cadre d'optimisation en ligne. Notre analyse est due à la dérivation d'une nouvelle inégalité de type Poincar'e pour la mesure uniforme sur la sphère l1 avec des constantes explicites.Ensuite, nous étudions le problème d'optimisation d'ordre zéro dans les schémas passifs. Nous proposons une nouvelle méthode pour estimer le minimiseur et la valeur minimale d'une fonction de régression lisse et fortement convexe f. Nous dérivons des limites supérieures pour cet algorithme et prouvons des limites inférieures minimax pour un tel cadre.Enfin, nous étudions le problème du bandit contextuel linéaire sous contraintes d'équité où un agent doit sélectionner un candidat dans un pool, et où chaque candidat appartient à un groupe sensible. Nous proposons une nouvelle notion d'équité qui est pratique dans l'exemple susmentionné. Nous concevons une politique avide qui calcule une estimation du rang relatif de chaque candidat en utilisant la fonction de distribution cumulative empirique, et nous prouvons sa propriété optimale
In this thesis, we first study the problem of zero-order optimization in the active setting for smooth and three different classes of functions: i) the functions that satisfy the Polyak-Łojasiewicz condition, ii) strongly convex functions, and iii) the larger class of highly smooth non-convex functions.Furthermore, we propose a novel algorithm that is based on l1-type randomization, and we study its properties for Lipschitz convex functions in an online optimization setting. Our analysis is due to deriving a new Poincar'e type inequality for the uniform measure on the l1-sphere with explicit constants.Then, we study the zero-order optimization problem in the passive schemes. We propose a new method for estimating the minimizer and the minimum value of a smooth and strongly convex regression function f. We derive upper bounds for this algorithm and prove minimax lower bounds for such a setting.In the end, we study the linear contextual bandit problem under fairness constraints where an agent has to select one candidate from a pool, and each candidate belongs to a sensitive group. We propose a novel notion of fairness which is practical in the aforementioned example. We design a greedy policy that computes an estimate of the relative rank of each candidate using the empirical cumulative distribution function, and we proved its optimal property

Suite à la tendance de miniaturisation des convertisseurs d'électronique de puissance, un type de composant passif hybride mariant trois composants conventionnels y compris une inductance, un condensateur et un transformateur est étudié au G2Elab depuis 2001. Ce composant baptisé LCT donne plusieurs avantages tant en termes d'intégration qu'en performance. Pourtant, le dimensionnement classique des composants passifs ne garantit pas de résultats optimaux pour les composants LCT. En contexte d'optimiser le dimensionnement de ces composants, cette thèse propose une nouvelle approche. L'optimisation se base tout d'abord sur une modélisation électrodynamique qui est, quant à elle, basée sur la méthode du schéma équivalent des plaques déjà développé au G2Elab, ensuite sur une modélisation thermique analytique des composants magnétiques planar. L'outil d'optimisation du dimensionnement permet de minimiser le volume des composants LCT sous une contrainte principale de la thermique. Les travaux expérimentaux constituent un moyen important pour la validation des modèles développés
Due to the trend of integration in power electronics, a hybrid device combining three conventional passive components including an inductor, a capacitor and a transformer has been studied at G2Elab since 2001. This component called LCT provides both advantages in size reduction and performance. However, classical design methods do not guarantee optimal results. Therefore this thesis proposes a new optimization approach. The optimization firstly base on an electromagnetic modeling developped from the Lumped Element Equivalent Circuit (LEEC) method that had already studied at G2Elab, then on an analytical thermal modeling. The design optimization tool can minimize the volume of LCT components in subjecting to principal thermal constraint. Experimental works is essential manner to validate these developed models

Les phénomènes de transport en milieux poreux sont étudiés depuis près de deux siècles, cependant les travaux concernant les milieux fortement poreux sont encore relativement peu nombreux. Les modèles couramment utilisés pour les poreux classiques (lits de grains par exemple) sont peu applicables pour les milieux fortement poreux (les mousses par exemple), un certain nombre d’études ont été entreprises pour combler ce manque. Néanmoins, les résultats expérimentaux et numériques caractérisant les pertes de charge dans les mousses sont fortement dispersés. Du fait des progrès de l’imagerie 3D, une tendance émergente est la détermination des paramètres des lois d’écoulement à partir de simulations directes sur des géométries reconstruites. Nous présentons ici l’utilisation d’une nouvelle approche cinétique pour résoudre localement les équations de Navier-Stokes et déterminer les propriétés d’écoulement (perméabilité, dispersion, ...)
A novel kinetic scheme satisfying an entropy condition is developed, tested and implemented for the simulation of practical problems. The construction of this new entropic scheme is presented. A classical hyperbolic system is approximated by a discrete velocity vector kinetic scheme (with the simplified BGK collisional operator), but applied to an inviscid compressible gas dynamics system with a small Mach number parameter, according to the approach of Carfora and Natalini (2008). The numerical viscosity is controlled, and tends to the physical viscosity of the Navier-Stokes system. The proposed numerical scheme is analyzed and formulated as an explicit finite volume flux vector splitting (FVS) scheme that is very easy to implement. It is close in spirit to Lattice Boltzmann schemes, but it has the advantage to satisfy a discrete entropy inequality under a CFL condition and a subcharacteristic stability condition involving a cell Reynolds number. The new scheme is proved to be second-order accurate in space. We show the efficiency of the method in terms of accuracy and robustness on a variety of classical benchmark tests. Some physical problems have been studied in order to show the usefulness of both schemes. The LB code was successfully used to determine the longitudinal dispersion of metallic foams, with the use of a novel indicator. The entropic code was used to determine the permeability tensor of various porous media, from the Fontainebleau sandstone (low porosity) to a redwood tree sample (high porosity). These results are pretty accurate. Finally, the entropic framework is applied to the advection-diffusion equation as a passive scalar

Esta tese apresenta elucidações técnicas e interpretações póscomposicionais de quatro peças compostas durante o doutorado: “Io” e “Calisto”, para piano solo, “Ganimedes” e “Europa”, para dois pianos. A composição musical é abordada em três etapas: a) descrição dos aspectos musicais e extramusicais dos primeiros estágios da composição; b) investigação das características sonoras das peças; c) construção de interpretações ficcionais pós-composicionais, imaginando as luas de Júpiter como ímpeto composicional e interpretativo. O terceiro estágio é realizado na perspectiva da teoria contemporânea das metáforas, tal qual proposta por George Lakoff e Mark Johnson e, posteriormente, por Mark Turner e Gilles Falconnier. Através da apresentação das categorias de metáforas, cruzamentos de mapeamento de domínios, esquemas de imagens, princípio de invariância, espaços conceptuais e mesclagem conceptual, se estabelecem, neste trabalho, conexões entre os conceitos metafóricos e a conceptualização metafórica da música. Isso contribui para a aproximação entre as características marcantes das peças e as cenas/ações propostas como primeira etapa das interpretações pós-composicionais, construídas pelo compositor. O trabalho propõe-se a pensar sobre a atribuição de significados da composição musical em uma perspectiva global, em que elementos extramusicais podem expandir a assimilação do fenômeno musical, bem como contribuir para a pedagogia da composição musical e para a produção de trabalhos colaborativos.
This thesis presents technical elucidations and post-compositional interpretations of four pieces composed during my doctorate degree: "Io" and "Calisto", for solo piano, "Ganimedes" and "Europa" for two pianos. The music composition is approached in three steps: a) description of the musical and extra musical aspects of the first stages of the composition; b) investigation of the sonorous characteristics of the pieces; c) construction of fictional postcompositional interpretations, imagining Jupiter's moons as compositional and interpretative impetus. The third stage is achieved under the perspective of the contemporary theory of metaphor proposed by George Lakoff and Mark Johnson, and posteriorly developed by Mark Turner and Gilles Falconnier. Through the introduction of metaphor categories, the cross-domain mapping, the image schema, the invariance principle, the mental spaces and the conceptual blending, some connections are established between the metaphoric concepts and the metaphoric conceptualization of music. This contributes to the approximation between the main characteristics of the pieces and the scenes/actions proposed in the first step of the post-compositional interpretations. This work proposes a reflection about the attribution of meanings on the musical composition in a global perspective, where extra musical elements can expand the assimilation of the musical phenomenon, as well as to contribute to the pedagogy of musical composition and the production of collaborative works.

The gas transfer process across the air-water interface in a buoyant-convective environment has been investigated by Direct Numerical Simulation (DNS) to gain improved understanding of the mechanisms that control the process. The process is controlled by a combination of molecular diffusion and turbulent transport by natural convection. The convection when a water surface is cooled is combination of the Rayleigh-B´enard convection and the Rayleigh-Taylor instability. It is therefore necessary to accurately resolve the flow field as well as the molecular diffusion and the turbulent transport which contribute to the total flux. One of the challenges from a numerical point of view is to handle the very different levels of diffusion when solving the convection-diffusion equation. The temperature diffusion in water is relatively high whereas the molecular diffusion for most environmentally important gases is very low. This low molecular diffusion leads to steep gradients in the gas concentration, especially near the interface. Resolving the steep gradients is the limiting factor for an accurate resolution of the gas concentration field. Therefore a detailed study has been carried out to find the limits of an accurate resolution of the transport for a low diffusivity scalar. This problem of diffusive scalar transport was studied in numerous 1D, 2D and 3D numerical simulations. A fifth-order weighted non-oscillatory scheme (WENO) was deployed to solve the convection of the scalars, in this case gas concentration and temperature. The WENO-scheme was modified and tested in 1D scalar transport to work on non-uniform meshes. To solve the 2D and 3D velocity field the incompressible Navier-Stokes equations were solved on a staggered mesh. The convective terms were solved using a fourth-order accurate kinetic energy conserving discretization while the diffusive terms were solved using a fourth-order central method. The diffusive terms were discretized using a fourth-order central finite difference method for the second derivative. For the time-integration of the velocity field a second-order Adams-Bashworth method was employed. The Boussinesq approximation was employed to model the buoyancy due to temperature differences in the water. A linear relationship between temperature and density was assumed. A mesh sensitivity study found that the velocity field is fully resolved on a relatively coarse mesh as the level of turbulence is relatively low. However a finer mesh for the gas concentration field is required to fully capture the steep gradients that occur because of its low diffusivity. A combined dual meshing approach was used where the velocity field was solved on a coarser mesh and the scalar field (gas concentration and temperature) was solved on an overlaying finer submesh. The velocities were interpolated by a second-order method onto the finer sub-mesh. A mesh sensitivity study identified a minimum mesh size required for an accurate solution of the scalar field for a range of Schmidt numbers from Sc = 20 to Sc = 500. Initially the Rayleigh-B´enard convection leads to very fine plumes of cold liquid of high gas concentration that penetrate the deeper regions. High concentration areas remain in fine tubes that are fed from the surface. The temperature however diffuses much stronger and faster over time and the results show that temperature alone is not a good identifier for detailed high concentration areas when the gas transfer is investigated experimentally. For large timescales the temperature field becomes much more homogeneous whereas the concentration field stays more heterogeneous. However, the temperature can be used to estimate the overall transfer velocity KL. If the temperature behaves like a passive scalar a relation between Schmidt or Prandtl number and KL is evident. A qualitative comparison of the numerical results from this work to existing experiments was also carried out. Laser Induced Fluorescence (LIF) images of the oxygen concentration field and Schlieren photography has been compared to the results from the 3D simulations, which were found to be in good agreement. A detailed quantitative analysis of the process was carried out. A study of the horizontally averaged convective and diffusive mass flux enabled the calculation of transfer velocity KL at the interface. With KL known the renewal rate r for the so called surface renewal model could be determined. It was found that the renewal rates are higher than in experiments in a grid stirred tank. The horizontally averaged mean and fluctuating concentration profiles were analysed and from that the boundary layer thickness could be accurately monitored over time. A lot of this new DNS data obtained in this research might be inaccessible in experiments and reveal previously unknown details of the gas transfer at the air water interface.

L’objectif de cette thèse est de généraliser les protocoles de sécurité GQ2 et Rabin- Williams, tous deux reliés au problème difficile de la factorisation des grands nombres. Nous évaluons la sécurité du schéma GQ2, en particulier à travers l’estimation de la capacité d’usurper une identité relativement à la capacité de factoriser la clé publique. Puis, nous montrons la forte probabilité de générer des clés GQ2 compatibles avec l’utilisation de modules RSA généraux, de modules multi-facteurs, ou de plus grands exposants publics. Dans le domaine de la signature, aucun schéma de type Rabin-Williams n’a jamais réussi à concilier l’utilisation d’un exposant unique de signature quel que soit le module considéré. Nous proposons ici une solution qui généralise naturellement les précédents schémas. Le dernier chapitre reprend une technique de preuve de validation du module. Sans améliorer les résultats antérieurs, un protocole couvrant une classe de modules de forme particulière est présenté
This thesis is about the generalization of the GQ2 and Rabin-Williams schemes. Their security relies on the problem of factorization of large numbers. First we have a look at the security of the GQ2 protocol by giving an estimation of the power of cheating related to the power of factorizing the public key number. Then we prove the overwhelming probability to generate GQ2 keys from general RSA moduli, from moduli composed by more than two factors, or from larger public exponents. Up until now, none of Rabin-Williams type digital signatures have a unique signature exponent when considering any two-factor modulus. We present here a solution that also generalizes the previous schemes. The last chapter is based on an article by Gennaro, Micciancio and Rabin (CCS99). Their results are not improved here but a new proof is given, using technical tools, to prove the validity of some two-factor moduli

La présente thèse s’intéresse aux modèles d’allocation stratégiques d’actifs et à leurs applications pour la gestion des réserves financières des régimes de retraite par répartition, en particulier ceux partiellement provisionnés. L’étude de l’utilité des réserves pour un système par répartition et a fortiori de leur gestion reste un sujet peu exploré. Les hypothèses classiques sont parfois jugées trop restrictives pour décrire l'évolution complexe des réserves. De nouveaux modèles et de nouveaux résultats sont développés à trois niveaux : la génération de scénarios économiques (GSE), les techniques d’optimisation numérique et le choix de l’allocation stratégique optimale dans un contexte de gestion actif-passif (ALM). Dans le cadre de la génération de scénarios économiques et financiers, certains indicateurs de mesure de performance du GSE ont été étudiés. Par ailleurs, des améliorations par rapport à ce qui se pratique usuellement lors de la construction du GSE ont été apportées, notamment au niveau du choix de la matrice de corrélation entre les variables modélisées. Concernant le calibrage du GSE, un ensemble d’outils permettant l’estimation de ses différents paramètres a été présenté. Cette thèse a également accordé une attention particulière aux techniques numériques de recherche de l'optimum, qui demeurent des questions essentielles pour la mise en place d'un modèle d'allocation. Une réflexion sur un algorithme d’optimisation globale d’une fonction non convexe et bruitée a été développée. L’algorithme permet de moduler facilement, au moyen de deux paramètres, la réitération de tirages dans un voisinage des points solutions découverts, ou à l’inverse l’exploration de la fonction dans des zones encore peu explorées. Nous présentons ensuite des techniques novatrices d'ALM basées sur la programmation stochastique. Leur application a été développée pour le choix de l’allocation stratégique d’actifs des régimes de retraite par répartition partiellement provisionnés. Une nouvelle méthodologie pour la génération de l’arbre des scénarios a été adoptée à ce niveau. Enfin, une étude comparative du modèle d’ALM développé avec celui basé sur la stratégie Fixed-Mix a été effectuée. Différents tests de sensibilité ont été par ailleurs mis en place pour mesurer l’impact du changement de certaines variables clés d’entrée sur les résultats produits par notre modèle d’ALM
This thesis focuses on the strategic asset allocation models and on their application for the financial reserve management of a pay-as-you-go (PAYG) retirement schemes, especially those with partial provision. The study of the reserve utility for a PAYG system and of their management still leaves a lot to be explored. Classical hypothesis are usually considered too restrictive for the description of the complex reserve evolution. New models and new results have been developed over three levels : economic scenario generation (ESG), numerical optimization techniques and the choice of optimal strategic asset allocation in the case of an Asset-Liability Management (ALM). For the generation of financial and economic scenarios, some ESG performance indicators have been studied. Also, we detailed and proposed to improve ESG construction, notably the choice of the correlation matrix between modelled variables. Then, a set of tools were presented so that we could estimate ESG parameters variety. This thesis has also paid particular attention to numerical techniques of optimum research, which is an important step for the asset allocation implementation. We developed a reflexion about a global optimisation algorithm of a non convex and a noisy function. The algorithm allows for simple modulating, through two parameters, the reiteration of evaluations at an observed point or the exploration of the noisy function at a new unobserved point. Then, we presented new ALM techniques based on stochastic programming. An application to the strategic asset allocation of a retirement scheme with partial provision is developed. A specific methodology for the scenario tree generation was proposed at this level. Finally, a comparative study between proposed ALM model and Fixed-Mix strategy based model was achieved. We also made a variety of a sensitivity tests to detect the impact of the input values changes on the output results, provided by our ALM model

Myocardial infarctions induce a maladaptive ventricular remodeling process that independently contributes to heart failure. In order to develop effective treatments, it is necessary to understand the way and extent to which the heart undergoes remodeling over the course of healing. There have been few studies to produce any data on the in-vivo material properties of infarcts, and much less on the properties over the time course of healing. In this paper, the in-vivo passive material properties of an infarcted porcine model were estimated through a combined use of magnetic resonance imaging, catheterization, finite element modeling, and a genetic algorithm optimization scheme. The collagen fiber orientation at the epicardial and endocardial surfaces of the infarct were included in the optimization. Data from porcine hearts (N=6) were taken at various time points after infarction, specifically 1 week, 4 weeks, and 8 weeks post-MI. The optimized results shared similarities with previous studies. In particular, the infarcted region was shown to dramatically increase in stiffness at 1 week post-MI. There was also evidence of a subsequent softening of the infarcted region at later time points post infarction. Fiber orientation results varied greatly but showed a shift toward a more circumferential orientation.

Thesis (M.S. in Meterology and Physical Oceanography)--Naval Postgraduate School, September 2008.
Thesis Advisor(s): Chiu, Ching-Sang ; Miller, Christopher W. "September 2008." Description based on title screen as viewed on .November 4, 2008. Includes bibliographical references (p. 35-36). Also available in print.

Les régions de haute latitude sont actuellement les plus sensibles aux effets du réchauffement climatique, et avec des élévations de température pouvant atteindre les 3 à 8 ◦C au niveau du pôle sur les 100 prochaines années. Les pergélisols (sols présentant des températures négatives deux années consécutives) sont présents sur 25 % des terres émergées de l’hémisphère nord et contiennent de grandes quantités de carbone « gelé », estimées à 1400 Gt (40 % de la quantité de carbone terrestre global). Des études récentes ont montré qu’une partie non négligeable (50 %) des premiers mètres des pergélisols pourraient fondre d’ici 2050, et 90 % d’ici 2100. Le but de l’étude est donc d’améliorer les moyens de suivi de l’évolution des températures du sol dans les zones arctiques, et plus particulièrement dans les régions couvertes de neige. L’objectif est de décrire la température du sol tout au long de l’année y compris sous un manteau neigeux, et d’analyser l’évolution de l’épaisseur de la couche active des pergélisols en relation avec la variabilité du climat. Nous utilisons des données satellites (fusion de données de température dans l’infra-rouge thermique “LST” et de température de brillance micro-onde AMSR-E « Tb ») assimilées dans le schéma de surface du modèle climatique canadien (CLASS, V 3.6) couplé à un modèle simple de transfert radiatif (HUT). Cette approche bénéficie des avantages de chaque type de donnée de manière à réaliser deux objectifs spécifiques : 1-construire une méthodologie solide permettant de retrouver les températures du sol, avec et sans neige, en zone de toundra, et 2-à partir de ces températures du sol, dériver la durée de fonte estivale et l’épaisseur de la couche active du pergélisol. Nous décrivons le couplage des modèles ainsi que la méthodologie permettant l’ajustement des paramètres météorologiques d’entrée du modèle CLASS (essentiellement les températures de l’air et les précipitations issues de la base de données des réanalyses météorologiques NARR) de manière à minimiser les LST et Tb simulées en comparaison aux mesures satellites. Par rapport aux données de mesures de sol de stations météorologiques prises comme référence pour validation dans les zones de toundra d’Amérique du Nord, les résultats montrent que la méthode proposée améliore significativement la simulation des températures du sol lorsqu’on utilise les données LST MODIS et Tb à 10 et 19 GHz pour contraindre le modèle, en comparaison avec les sorties du modèle sans les données satellites. Dans ce processus d’inversion, la correction de l’évolution des conditions de neige au cours de l’hiver contrainte avec le rapport de polarisation à 11 GHz constitue une approche originale. Une analyse de l’erreur pour 4 sites de toundra et sur plusieurs années (18 cas) est effectuée pour la période estivale (1,7 -3,6 K) ainsi que pour la période hivernale couverte de neige (1,8 -3,5 K). L’indice des degrés-jours de fontes annuel, dérivé des températures du sol simulés par notre approche, permet de cartographier les zones de pergélisols continu en accord avec les cartes actuelles. Un meilleur suivi des processus d’évolution des pergélisols, et tout particulièrement de l’impact de la couverture de neige, devrait permettre une meilleure compréhension des effets du réchauffement climatique sur la fonte des pergélisols et l’avenir de leurs stocks de carbone.
Abstract : High latitude areas currently are the most sensitive to global warming effects. In the next 100 years, temperature could rise up to 3 to 8 ◦C at the North Pole. Permafrost (ground with negative temperatures two years in a row) represents 25% of northern hemisphere lands, and contains huge quantities of "frozen" carbon estimated at 1400 Gt (40 % of the global terrestrial carbon). Recent studies showed that a part (50 %) of the permafrost first few meters could melt by 2050, and 90 % by 2100. The goal of our study is to improve our understanding of ground temperature evolution in arctic areas, especially in snow covered regions. The objective is to discribe the ground temperature all year long with and without a snow cover, and to analyze the evolution of the permafrost’s active layer in relation with the climate variability. We use remote sensing data (fuzzed of MODIS "LST" surface temperatures and AMSR-E "Tb" brightness temperatures) assimilated in the canadian landscape surface scheme (CLASS) coupled to a simple radiative transfer model (HUT). This approach takes into account the advantages of each kind of data in order to achieve two objectives : 1 - build a solid methodology allowing to retrieve ground temperatures, with and without a snow cover, in tundra areas ; 2 - from those retrieved ground temperatures, derive the summer melting duration which can be linked to the permafrost active layer thickness. We describe the models coupling as well as the methodology allowing the adjustement of CLASS input meteorological parameters (essentially the air temperatures and precipitations from the NARR meteorological data base) in order to minimize the simulated LST and Tb in comparison to remote sensing data. By using meteorological station’s ground temperature measurments as a reference for validation in North America tundra areas, results show that the proposed method improves the simulation of ground temperatures when using LST MODIS and Tb at 10 and 19 GHz data to constrain the model, in comparison with model outputs without satellite data. Using the Tb polarization ratio H/V at 10 GHz allows an improvement of the constrain on winter period simulations. An analyze of the error is conducted for summer (1,7 - 3,6 K) and winter (1,8 - 3,5 K). We present climatic applications for future work that meets the second objective of the Ph.D. A better understanding of evolution processes of permafrost, and particularly of the impact of the snow cover, should allow us a better understanding of global warming effects on the permafrost’s melting and the future of their carbon stocks.

Les récifs coralliens sont l’écosystème marin le plus complexe, mais aussi le plus menacé par les perturbations croissantes liées aux activités anthropiques. Leur conservation représente un véritable défi. Alors que le maintien des récifs au plus proche de leurs configurations et dynamiques actuelles doit être privilégié, nous devons également nous préparer à une évolution rapide de leur fonctionnement et adapter réseaux et outils de suivis à cette nouvelle situation. Des avancées technologiques récentes ont permis l’émergence d’outils innovants qui pourraient permettre à court terme d’augmenter considérablement la résolution spatio-temporelle des suivis. Parmi eux, l’acoustique passive est en plein essor. L’objet de cette thèse a été d’affiner son cadre d’utilisation pour évaluer et suivre l’état écologique et le fonctionnement des écosystèmes coralliens. Des enregistrements des paysages sonores et des relevés écologiques (assemblages de poissons et habitat) ont été réalisés sur 31 récifs de pente externe autour de trois îles de l’Indo-pacifique avec des caractéristiques environnementales variables, incluant des pressions anthropiques contrastées. L’analyse des résultats obtenus avec différentes combinaisons de paramètres d’échantillonnage (bande de fréquences, moment du cycle journalier choisi pour réaliser l’enregistrement, durée des échantillons de son) a permis de sélectionner un protocole d’échantillonnage basé sur les deux types d’indices écoacoustiques les plus utilisés pour l’étude des récifs coralliens. Ce protocole permet la caractérisation rapide et fiable de l’état écologique des récifs. En se basant sur ces lignes directrices, la capacité de six indices écoacoustiques à évaluer des fonctions clé de l’écosystème corallien a ensuite été démontrée. En comparant les apports de l’acoustique passive et de données environnementales pouvant être collectées par télédétection, la plus-value de l’utilisation d’indices écoacoustiques pour prédire la structure des assemblages de poissons récifaux a été identifiée et quantifiée. Une application de l’approche écoacoustique au suivi continu d’un site isolé a mis en évidence le potentiel particulièrement important de l’acoustique passive comme outil d’appui à la gestion dans ce type de contexte. Face à l’ampleur et à la vitesse des changements climatiques annoncés, les méthodes de suivi employées aujourd’hui, basées sur la présence d’observateur in situ, seront vraisemblablement insuffisantes. Combinée à d’autres outils de suivi, l’acoustique passive pourrait contribuer à détecter rapidement les perturbations des écosystèmes, condition indispensable pour en comprendre les causes et mettre en œuvre des réponses rapides et adaptées
Coral reefs are the most complex of marine ecosystems, but also the most threatened by ecological disruption resulting directly or indirectly from human activities. Their conservation represents a huge challenge. While maintaining coral reefs as close as possible to their current configurations and dynamics is among the highest priorities, we must also prepare for rapid changes in their functioning and adapt monitoring tools and networks to this new situation. Recent technological advances enabled the emergence of innovative tools with the potential to drastically increase the spatio-temporal resolution of coral reef monitoring. Among these, Passive Acoustic Monitoring (PAM) is on the rise. The aim of this thesis was to improve and facilitate the use of PAM as a tool for the assessment and monitoring of coral reefs’ ecological states and functioning. Soundscape recordings and ecological surveys (reef fish assemblages and habitat) were performed at 31 outer reef slope sites around three Indo-Pacific islands with variable environmental characteristics, including contrasted anthropogenic pressures. Analysing the results obtained with multiple combinations of sampling settings (frequency bandwidth, time of sampling (day/night), and sample duration) allowed the selection of a sampling scheme based on the two types of indices mostly used in coral reef studies. This scheme enables a rapid and reliable categorisation of reef’s ecological states. Based on these sampling guidelines, the capacity of six ecoacoustic indices to evaluate coral reef key functions was demonstrated. By comparing the contributions of PAM and coarse environmental data that could be sampled remotely, the added value of using ecoacoustic indices to predict reef fish assemblage structure was identified and quantified. An application of ecoacoustics to the continuous monitoring of a remote site highlighted the strong potential of PAM as a supporting tool for managers in such context. In view of the amplitude and velocity of expected climatic changes, current observer-based monitoring methods are likely to be exceeded. Combined to other monitoring tools, PAM could contribute to promptly detect ecosystem disturbances, which is essential to understand their causes and put in place rapid and adapted responses

Ce travail vise au développement de nouvelles méthodes numériques adaptatives pour la simulation numérique de phénomènes physiques multi-échelles en temps et en espace. Nous nous concentrons sur les écoulements réactifs à faible nombre de Mach, caractéristiques d'un grand nombre de configurations industrielles telles que la convection naturelle, la dynamique de fronts de flamme ou encore les décharges plasmas. La raideur associée à ce type de problèmes, que ce soit via le terme source chimique qui présente un large spectre d'échelles de temps caractéristiques ou encore via la présence de forts gradients très localisés associés aux fronts de réaction, génère des difficultés numériques considérables. Il est donc nécessaire de concevoir des méthodes sur mesure pour traiter la raideur de telles applications, afin d'obtenir des résultats d'une grande précision avec un coût calcul raisonnable. Dans ce cadre général, nous introduisons de nouvelles méthodes numériques pour la résolution des équations de Navier-Stokes incompressibles, une étape importante dans la réalisation d'un solveur hydrodynamique pour les écoulements à faible nombre de Mach. Nous construisons un solveur volumes finis avec adaptation de maillage par l'analyse de multirésolution, qui permet un contrôle a priori des erreurs générées par l'adaptation de maillage. Pour ce faire, nous développons un nouveau schéma de volumes finis collocalisé, avec un traitement original des modes de pression et de vitesse parasites qui n'affecte pas la précision de la discrétisation spatiale. Cette dernière est couplée à un nouveau schéma de Runge-Kutta additif d'ordre 3 pour les écoulements incompressibles, qui présente des propriétés de stabilité adaptées à la raideur des équations différentielles algébriques semi-explicites d'index 2. L'ensemble de cette stratégie est implémentée dans le code de calcul scientifique mrpy. Ce dernier est écrit en Python, et repose sur la librairie PETSc, écrite en C, pour le traitement des opérations d'algèbre linéaire. Nous évaluons l'efficacité algorithmique de cette stratégie par la simulation numérique d'un transport de scalaire passif dans un écoulement incompressible sur maillage adaptatif. Ce travail présente donc un nouveau solveur hydrodynamique d'ordre élevé pour les écoulements incompressibles, avec adaptation de maillage par multirésolution et contrôle d'erreur, qui peut être étendu aux écoulements à faible nombre de Mach
We address the development of new numerical methods for the efficient resolution of stiff Partial Differential Equations modelling multi-scale time/space physical phenomena. We are more specifically interested in low Mach reacting flow processes, that cover various real-world applications such as flame dynamics at low gas velocity, buoyant jet flows or plasma/flow interactions. It is well-known that the numerical simulation of these problems is a highly difficult task, due to the large spectrum of spatial and time scales caused by the presence of nonlinear The adaptive spatial discretization is coupled to a new 3rd-order additive Runge-Kutta method for the incompressible Navier-Stokes equations, combining a 3rd-order, A-stable, stiffly accurate, 4-stage ESDIRK method for the algebraic linear part of these equations, and a 4th-order explicit Runge-Kutta scheme for the nonlinear convective part. This numerical strategy is implemented from scratch in the in-house numerical code mrpy. This software is written in Python, and relies on the PETSc library, written in C, for linear algebra operations. We assess the capabilities of this mechanisms taking place into dynamic fronts. In this general context, this work introduces dedicated numerical tools for the resolution of the incompressible Navier-Stokes equations, an important first step when designing an hydrodynamic solver for low Mach flows. We build a space adaptive numerical scheme to solve incompressible flows in a finite-volume context, that relies on multiresolution analysis with error control. To this end, we introduce a new collocated finite-volume method on adaptive rectangular grids, with an original treatment of the spurious pressure and velocity modes that does not alter the precision of the discretization technique. new hydrodynamic solver in terms of speed and efficiency, in the context of scalar transport on adaptive grids. Hence, this study presents a new high-order hydrodynamics solver for incompressible flows, with grid adaptation by multiresolution, that can be extended to the more general low-Mach flow configuration

O problema estudado relaciona-se ao planejamento de redes ópticas de acesso TWDM (Time and Wavelength Division Multiplexing), tendo como meta prover meios para atender ao consumo crescente de banda e, ao mesmo tempo, associar o mesmo ao menor consumo de energia possível e disponibilizar serviços de qualidade aos usuários da rede. Neste contexto, após a apresentação de uma revisão bibliográfica, alguns trabalhos foram selecionados como referências base para o estudo. Neste, foram analisadas técnicas de gerenciamento do comprimento de onda numa possível migração tecnológica dos equipamentos de acesso à rede pelo lado do usuário, as unidades de rede óptica (ONUs), considerando ser possível aproveitar de forma eficiente a distribuição de ONUs em cada par de comprimentos de onda, e como resultado, desligar interfaces de gerenciamento para economia de energia. Em paralelo a este objetivo, foram agregados métodos de \"registro adaptativo\" para melhorar o desempenho das ONUs que estão migrando e/ou entrando na rede, evitando colisões entre seus sinais e aumentando as chances de registro no terminal de linha óptico (OLT). Além do mais, o trabalho aborda o cumprimento do contrato de serviços (SLA) por parte das operadoras de telecomunicações, bem como oferece meios de estruturar uma rede óptica passiva (PON) para oferecer serviços com garantia de métricas de qualidade (QoS). Diferentes cenários foram tratados ao variar a porcentagem de usuários ativos na rede, e percebeu-se que, quando a PON opera com baixo índice de atividade (média 10% de ONUs ativas), foi possível economizar mais de 80% de energia em interfaces de gerenciamento. Por outro lado, ao envolver cenários mais realistas em redes ópticas (média de 50% de ONUs ativas), o TWDM-PON economizou quase 50% de energia nestas interfaces ao ser configurado com baixo período de migração (5 minutos). Além disso, alcançou um SLA de aproximadamente 100%, um valor considerado acima do usual quando se trata de cumprimento de serviços. Como uma tecnologia emergente, o TWDM-PON destaca-se num cenário que deve ser planejado para ser compatível com tecnologias implantadas, e além de disso, superar o legado de redes PON na economia de energia e qualidade de serviços oferecidos.
The problem studied is related to the planning of optical access networks TWDM (Time and Wavelength Division Multiplexing), aiming to provide means to meet the increasing bandwidth consumption and, at the same time, associating it to the lowest possible power consumption and providing quality services to the network users. In this context, following the presentation of a literature review, some studies were selected as a reference basis for the study. In this, some wavelength management techniques were analyzed aiming a possible technological migration of the network access equipment at the user side, the optical network units (ONU), whereas it is possible to use efficiently the ONUs distribution in each pair of wavelength. As a result, it becomes possible to switch off some management interfaces thus assuring a degree of power consumption save. In parallel, methods for providing an \"adaptive record\" of ONUs have been aggregated to improve the performance of those ONUs that are migrating and/or entering the network, avoiding collisions between their signals and increasing the chance of their registration in the optical line terminal (OLT). Furthermore, this work deals with the fulfillment of the service agreement (SLA) signed by telecommunications operators and proposes ways to design a passive optical network (PON) in order to offer services with quality metrics assurance (QoS). Different scenarios were treated to vary the percentage of active users on the network, and it was noticed that when the PON operates with low rate of activity (average 10% of active ONUs), it was possible to save over 80% energy in the management interfaces. Moreover, by involving more realistic scenarios in optical networks (50%, in average, of active ONUs), the TWDM-PON saved almost 50% of energy at the interfaces to be configured with low migration period (5 minutes). Additionally, it reached an SLA of approximately 100%, a value considered above the usual when it comes to compliance services. As an emerging technology, TWDM-PON stands out in a scenario that should be designed to be compatible with deployed technologies, and beyond that, to overcome the legacy of PON networks in energy saving and quality of services offered.

碩士
國立臺灣大學
電子工程學研究所
91
Abstract Small size passive matrix organic light emitting display (PM-OLED) has the advantages of simple manufacture process and low total cost. Base on the PMOLED characteristics, a low power consumption column driver and row driver was developed for color PMOLED. We provide two methods for reducing the power consumption of driving system: low total current 16-gray scale pulse width modulation (PWM) output driving current control circuit, and a energy recovery design for precharge circuit.

碩士
國立成功大學
會計學系碩博士班
95
If we apply checkpoint-based protocols to achieve fault-tolerance, besides taking checkpoints, it is a significant issue to ensure that consistent global states can be recovered when failures occur. Additional failure-free coordination overheads are ineluctable so that reduce the performance. Recently, many intensive researches have been studied to eliminate such overheads including by analyzing distributed programs and statically inserting checkpoint statements at the proper places in the source code. In this thesis, we propose a hybrid checkpoint scheme to leverage the advantages of both static analysis and online checkpointing. An algorithm to find orphan-free coupling nodes in extended control flow graph is shown and we apply it to several commonly used inter-process interacting paradigms. Tightly coupling strategy is to avoid any trouble path that checkpoint X happened before checkpoint Y from different processes in the CFG. However,if the application being analyzed may have trouble paths while executing operations in loops, it is unnecessary for tightly coupling strategy to move the checkpoint statement outside the loop to avoid trouble paths. Under our hybrid checkpoint scheme, the extent of recovery from failures can be bounded to at most one checkpoint interval such that domino effect will never appear.

Zhang, Yin.
Thesis submitted in: December 2008.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (leaves 56-60).
Abstracts in English and Chinese.
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Telecommunications network hierarchy --- p.2
Chapter 1.2 --- PON architectures for access networks --- p.4
Chapter 1.2.1 --- TDM-PON --- p.5
Chapter 1.2.2 --- WDM-PON --- p.7
Chapter 1.3 --- Data delivery mode in WDM-PON --- p.8
Chapter 1.3.1 --- Point-to-point --- p.8
Chapter 1.3.2 --- Broadcast --- p.9
Chapter 1.3.3 --- Multicast --- p.10
Chapter 1.4 --- Motivation of this thesis --- p.10
Chapter 1.5 --- Outline of this thesis --- p.13
Chapter Chapter 2 --- Previous Multicast Architectures in WDM-PON --- p.14
Chapter 2.1 --- Introduction --- p.15
Chapter 2.2 --- Previous WDM-PON architectures with multicast capability --- p.15
Chapter 2.2.1 --- Subcarrier multiplexing --- p.16
Chapter 2.2.2 --- All-optical based multicast enabled architecture --- p.18
Chapter 2.3 --- Summary --- p.21
Chapter Chapter 3 --- A Multicast enabled WDM-PON Architecture Using ASK-DPSK Orthogonal Modulation --- p.23
Chapter 3.1 --- Introduction --- p.24
Chapter 3.2 --- System architecture --- p.25
Chapter 3.3 --- Experimental Demonstration --- p.27
Chapter 3.4 --- Discussion --- p.31
Chapter 3.5 --- Summary --- p.36
Chapter Chapter 4 --- A WG filtering and its suppression in quaternary ASK-DPSK based multicast enabled WDM-PON --- p.37
Chapter 4.1 --- Introduction --- p.38
Chapter 4.2 --- Principle of narrowband filtering --- p.38
Chapter 4.3 --- Simulation model --- p.40
Chapter 4.4 --- Simulation results and discussion --- p.42
Chapter 4.4.1 --- Different extinction ratios --- p.43
Chapter 4.4.2 --- Different AWG filter shape and bandwidth --- p.47
Chapter 4.5 --- Summary --- p.50
Chapter Chapter 5 --- Summary and Future Works --- p.51
Chapter 5.1 --- Summary of the thesis --- p.52
Chapter 5.2 --- Future works --- p.53
List of Publications --- p.55
BIBLIOGRAPHY --- p.56

碩士
國立中央大學
光電科學研究所碩士在職專班
96
This work proposes the dynamic wavelength allocation mechanism to solve the problem of sudden traffic loading for the Ethernet passive optical networks(PON). Ethernet PON has recently been considered as the most prospective application technology in access network. It is adopted the point-to-multi-point(P2MP) topology construction,Which can greatly reduce the amount of optical fiber and the disbursement. Moreover the DWA mechanism provides the bandwidth sharing across multiple physical PONs. A flexible new optical access solution is reached by combing the tunable lasers, the arrayed waveguide gratings, and the coarse/fine filters. The excellent stability of the network can bridge the gap between conventional TDM PONs and WDM PONs, and the powerful architecture is a promising candidate of the optical access networks for the next generation. This structure is composed of the single mode laser, the tunable laser, the array waveguide, and the buffer storage device. The probability model distribution is calculated by the MATLAB, and the mechanism of optimal separation is determined by the computer simulation. This system is tested through the measured reaction time or the flow capacity of network on campus network when the traffic load increases up to a loading level. It is shown that the DWA system, can effectively solve the problems when the load increases, Which is the most economical and simplest local network infrastructure for the PONs.

碩士
中興大學
資訊科學系所
94
Ethernet Passive Optical Network (EPON) has been considered as a promising solution for next-generation broadband access networks due to its low cost, simplicity, and scalability. A critical issue of EPONs is bandwidth allocation of the shared upstream channel between end users. Some bandwidth allocation schemes based on interleaved polling have been proposed. However, none of them outperforms the others under all traffic loads. The credit-based scheme has an edge over the others in the case of light load, while the limited scheme prevails in the case of heavy load. We propose a new credit-based bandwidth allocation scheme that performs well under all traffic loads. In the proposed scheme, the size of the credit is dynamically determined by the OLT (Optical Line Terminal) according to each ONU''s (Optical Network Unit''s) traffic situation and the entire system load. Besides, the OLT has a maximum transmission window size limit for each ONU. Every ONU can transmit data up to the maximum window size per cycle. Simulation results verify that our proposed scheme has impressive performance under all traffic loads.

碩士
國立交通大學
資訊科學與工程研究所
94
Radio Frequency Identification (RFID) is said to be the next generation bar code, which features contactless identification without visibility. We benefit greatly by adopting RFID in a variety of daily applications such as warehouse management, toll collection, library management, etc. However, RFID transmits data through radio frequency signals; therefore, attackers could analyze the radio frequency signals to acquire private data from users. If user privacy is not protected, users will be susceptible to personal identification and tracking by an adversary. User privacy may include data privacy and location privacy. To protect both of them, the output of tags must be encrypted and unpredictable. Furthermore, the acceptable cost of a passive RFID tag, which is no more than five cents, severely restricts the resources available for security. Schemes that protect user privacy in RFID applications are classified into three main categories: authentication, encryption, and dynamic identity. However, authentication-based schemes are easily broken. Because low-cost RFID tags do not contain tamper-resistant mechanisms, an adversary can steal the key for the authentication protocol. Encryption-based schemes can protect data privacy, but location privacy is still vulnerable since the ciphertext remains the same. Dynamic identity schemes are limited by exhaustive search problem, and the tag is still traceable in the period between identity updates. In this thesis, we proposed a feasible scheme based on one-way hash function for low-cost passive RFID tags. Each tag has a dynamic identity. Therefore the output of tag changes each time. We also proved that the scheme can protect both data privacy and location privacy against threats of replay attacks, eavesdropping, spoofing, man-in-the-middle attack, and message loss.

碩士
國立高雄應用科技大學
資訊管理系
99
In VANETs, each vehicle should obtain an IP address for its identification before connecting to the Internet or getting some information from the Internet. Due to the rapid movement of vehicles, each vehicle must perform a handoff procedure between different access points. To ensure that the transmission of packets is not interrupted, the handoff scheme for VANETs is a key design issue. In view of this, we design a V2V-based fast handoff scheme using IP address passing for VANETs in this thesis. The proposed scheme allows a leaving vehicle in the exit area to pass an IP address which has been identified by the duplicate address detection (DAD) procedure to the vehicles in the entry area directly. In addition, the leaving vehicle in the exit area can also pass an IP address to the vehicles in the middle area if there is no vehicles in the entry area. Therefore, our scheme can reduce the use of Dynamic Host Configuration Protocol (DHCP) to obtain an IP address. Because DAD results in the largest delay of the whole DHCP procedure, our scheme can thus improve the utilization of IP address, reduce the time of acquiring an IP address, and reduce the whole handoff time.

This research is aimed to develop a migration-based earthquake location algorithm and a passive seismic imaging approach to investigate microseismicity and image steep crustal structures in the mining area Schlema-Alberoda. The dataset includes single-component records of several microseismic events which occurred between 1998 and 2012 in the area. Through some tests and comparisons, the accuracy of the localization algorithm is proved. An expected extension of pre-existing faults within the granitic body and the connection between some of the structures is comfirmed by the location results. The passive imaging procedure is conducted using only P-wave secondary arrivals from the relocated events and by applying 3-D coherency migration. The reliability of the passive imaging results is verified by comparing the final image with the results of a 3-D active reflection seismic survey in the same area. In addition, the passive image complements the 3-D active image and reveals new structures that have not been imaged previously.

Li, Pulan.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.
Includes bibliographical references (p. 60-66).
Abstracts in English and Chinese.
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Overview of wavelength division multiplexed passive optical network (WDM-PON) and colorless optical network unit (ONU) --- p.1
Chapter 1.2 --- Implementation of colorless ONU --- p.4
Chapter 1.3 --- Rayleigh backscattering in WDM-PON --- p.6
Chapter 1.4 --- Motivation of this thesis --- p.9
Chapter 1.5 --- Outline of this thesis --- p.11
Chapter Chapter 2 --- Previous works of remodulation for WDM-PON --- p.12
Chapter 2.1 --- Introduction --- p.12
Chapter 2.2 --- Devices utilized by colorless ONU in remodulation schemes --- p.13
Chapter 2.2.1 --- Injection-locked Fabry-Perot laser diode at ONU --- p.13
Chapter 2.2.2 --- Reflective semiconductor optical amplifier --- p.15
Chapter 2.2.3 --- Reflective electro-absorption modulator and semiconductor optical amplifier (REAM-SOA) --- p.17
Chapter 2.3 --- Modulation methods in remodulation schemes --- p.18
Chapter 2.4 --- Summary --- p.23
Chapter Chapter 3 --- A remodulation scheme based on time-interleaved DPSK modulation format --- p.25
Chapter 3.1 --- Introduction --- p.25
Chapter 3.2 --- Operation principle: time-interleaving technology for phase-modulated signal --- p.27
Chapter 3.3 --- System architecture --- p.28
Chapter 3.4 --- Experimental results and discussion --- p.31
Chapter 3.5 --- Effect of timing misalignment on proposed remodulation scheme --- p.33
Chapter 3.6 --- Summary --- p.35
Chapter Chapter 4 --- Enhanced Tolerance to Rayleigh Backscattering in Remodulation Scheme Using Time-Interleaved DPSK Format --- p.37
Chapter 4.1 --- Introduction --- p.37
Chapter 4.2 --- Studies on Rayleigh backscattering suppression in optical domain --- p.39
Chapter 4.2.1 --- RB suppression in carrier-distributed schemes --- p.39
Chapter 4.2.2 --- RB suppression in remodulation schemes --- p.40
Chapter 4.2 --- Experimental setup and results --- p.42
Chapter 4.3 --- Discussion on RB suppression effect of the proposed scheme --- p.46
Chapter 4.3.1 --- Theoretical study and simulation results --- p.46
Chapter 4.3.2 --- Experimental demonstration of spectral relationship between signals and RB crosstalk --- p.49
Chapter 4.4 --- Summary --- p.53
Chapter Chapter 5 --- Conclusion and Future Works --- p.55
Chapter 5.1 --- Conclusion of this thesis --- p.55
Chapter 5.2 --- Future works --- p.57
List of Publications --- p.59
Bibliography --- p.60

La technologie planar est très intéressante pour les transformateurs utilisés dans les équipements aéronautiques car elle mène à des composants minces et utilisables dans des espaces confinés. Malheureusement, le dimensionnement des transformateurs de ce type, lorsqu'ils fonctionnent au-delà de 100 kHz, est un travail aléatoire car les règles et les outils de conception ne sont pas les mêmes que pour un transformateur bobiné classique.
Au long de ce mémoire, on apprend à représenter ces composants par un circuit équivalent et à identifier ce circuit équivalent par des mesures d'impédances. Compte tenu du grand nombre de paramètres ajustables, l'optimisation d'un tel transformateur serait compromise s'il fallait compter sur des simulations à éléments finis pour déduire les éléments du circuit équivalent. C'est pourquoi nous essayons de déduire, par des moyens analytiques, les éléments de ce circuit en partant des caractéristiques physiques et géométriques du composant. Le but est atteint pour tous les éléments du transformateur de fuites obtenus à l'aide d'un calcul original exploitant les formules de la méthode PEEC.
Nous étudions ensuite les problèmes posés par la mise en parallèle de spires, inévitable lorsqu'on veut faire circuler des centaines d'Ampères. Une approche analytique simple s'avère alors très efficace et, grâce à elle, la meilleure disposition des spires peut être recherchée à l'aide d'un logiciel de simulation de circuits de type PSpice.
Enfin, diverses solutions sont envisagées et testées par simulation fem pour réduire les pertes par courants induits dans les transformateurs et dans les conducteurs méplats. Le développement multipolaire du champ magnétique est largement mis à contribution pour mener ces études.

The convergence of optical and wireless technologies has given rise to the fiber-wireless (Fi-Wi) network. This network combines the huge capacity of optical fiber with the ubiquity and mobility of wireless networks. Fiber to the premises (FTTP) combined with wireless local area network (WLAN) in home distribution is now becoming a reality. However, network congestion in the wireless access link still limits end user performance, especially in dense residential areas. Therefore, this thesis focuses on the enhancement of the wireless media in Fi-Wi networks. The thesis considers the realisation of Fi-Wi networks using the gigabit passive optical network (GPON) and the infrastructure based WLAN. The study shows the binary exponential backoff (BEB) adopted in the medium access control (MAC) pro- tocol for the IEEE 802.11 WLAN standard is the key factor inhibiting WLAN perfor- mance. The standard distributed coordination function (DCF) access method used by WLAN today provides equal chance of transmissions to all stations. This equal- ity can lead to unfairness between uplink (UL) and downlink (DL) transmissions because the number of active wireless users normally exceeds the number of access points. Generally the Fi-Wis access point (AP) requires greater media access than any of its associate wireless users (WUs) because of the predominance of downlink traffic. Thus, techniques to maximize the network throughput and provide fairness between UL and DL transmissions are proposed. Traffic information obtained from monitoring both GPON and WLAN networks is utilized in the proposed schemes.