With the current demand for mixed-signal SoCs, an increasing number of designers are looking for ADC architectures that can be easily implemented over digital substrates. Since ADC performance is strongly dependent upon physical and electrical features, it gets more difficult for them to benefit from more recent technologies, where these features are more variable. This way, analog signal acquisition is not allowed to follow an evolutionary trend compatible with Moore’s Law. In fact, such trend shall get worst, since newer technologies are expected to have more variable characteristics. Also, for a matter of economy of scale, many times a mixed-signal SoC presents a good amount of idle processing power. In such systems it is advantageous to employ more costly digital signal processing provided that it allows a reduction in the analog area demanded or the use of less expensive analog blocks, able to cope with process variations and uncertainty. Besides the technological concerns, other factors that impact the cost of the design also advise to transfer problems from the analog to the digital domain whenever possible: design automation and self-test requirements, for instance. Recent surveys indicate that the total cost in designer hours for the analog blocks of a mixed-signal system can be up to three times the cost of the digital ones. This manuscript explores the concept of bottom-up analog acquisition design, using statistical sampling as a way to reduce the analog area demanded in the design of ADCs within mixed-signal systems. More particularly, it investigates the possibility of using digital modeling and digital compensation of non-idealities to ease the design of ADCs. The work is developed around three axes: the definition of target applications, the development of digital compensation algorithms and the exploration of architectural possibilities. New methods and architectures are defined and validated. The main notions behind the proposal are analyzed and it is shown that the approach is feasible, opening new paths of future research. Keywords:

Orientador: Daniel Mario Ugarte / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T07:13:58Z (GMT). No. of bitstreams: 1 LagosParedes_MaureenJoel_M.pdf: 3881181 bytes, checksum: 517e8507ccdf35f0fa7a7f9fcb4b3b84 (MD5) Previous issue date: 2007 / Resumo: O estudo de fios metálicos de tamanho atômico (NF's) tem atraído grande interesse devido aos novos efeitos químicos e físicos neles observados. Entre esses novos fenômenos podemos destacar a quantização da condutância, efeito que deve ser fundamental no desenho dos novos nanodispositivos eletrônicos. NF's são usualmente gerados através de um procedimento simples de deformação mecânica: duas superfícies metálicas são colocadas em contato e depois afastadas. Nos últimos estágios do estiramento antes da ruptura, um fio de alguns átomos de diâmetro é gerado enquanto a condutância é medida. Os NF's têm sido estudados por diferentes grupos e, em diversas condições de temperatura (4 - 300 K) e pressão (de ambiente a UHV). Os resultados apresentam importantes variações e, têm gerado interpretações muito controversas. Devemos enfatizar que muitas interpretações têm sido feitas sem considerar que a deformação estrutural dos NF's deve depender fortemente da temperatura. Nesta tese estudamos as propriedades estruturais e eletrônicas NF's e, em particular analisamos a influência de efeitos térmicos no arranjo atômico, e sua manifestação na condutância. A estrutura dos NF's foi estudada por microscopia eletrônica de transmissão de alta resolução resolvidas no tempo. A condutância foi medida utilizando um sistema de quebra controlada de junções operado em ultra-alto-vácuo. Os experimentos foram realizados a ~150 e 300 K. Nossos resultados mostraram que, à temperatura ambiente os NF's são sempre cristalinos e livre de defeitos nas regiões mais finas; e deformam unicamente ao longo dos eixos cristalográficos [111], [100] e [110]. A baixa temperatura duas importantes diferenças foram observadas: (i) NF's de ouro apresentam defeitos, principalmente falhas de empilhamento e maclas. (ii) NF's alongados na direção [110] evoluem em cadeias atômicas, de comportamento mecânico muito diferente da temperatura ambiente, onde quebram abruptamente. Segundo as imagens de microscopia eletrônica, discordâncias parciais (Shockley) geram falhas de empilhamento; e cadeias de átomos suspensos são observados a ~150 e 300 K. Histogramas globais de condutância adquiridos a baixa temperatura revelaram: (i) aumento da intensidade do pico ~1 Go; (ii) leve diminuição da condutância devido ao aumento de defeitos; e (iii) a existência de uma sub-estrutura no pico ~2 Go, indicando a formação de dois arranjos atômicos estáveis. Resumidamente, nossos resultados mostram que a formação de defeitos é um evento freqüente a ~150 K. Provavelmente, mais defeitos na estrutura devem acontecer para temperaturas menores (4 - 10 K). Portanto, uma importante mudança na evolução da condutância durante a elongação de NF's deve ser esperado a baixa temperatura. Assim, a comparação direta de medidas de transporte de NF's realizadas a diferentes temperaturas pode levar a sérias discrepâncias. Esperamos ter contribuído a melhorar a compreensão e interpretação de experimentos de transporte realizados em diferentes condições, de modo tal, a gerar um modelo único e coerente que explique as propriedades físicas de NF's metálicos / Abstract: The study of atomic-size metal nanowires (NW's) is attracting a great interest due to occurrence a novel physical and chemical phenomena. Among these new phenomena, we can mention conductance quantization that will certainly influence the design of nanodevices. NW's are usually generated by means of a simple procedure: two metallic surfaces are put into contact and, then retracted. Just before rupture atomic-size NW's are formed, and the conductance is measured during the wire elongation. The interpretation of the results is troublesome, because conductance is measured during the modification of the atomic structure. This kind of experimental study has been performed by many research groups and, a quite wide range of temperatures (4 - 300 K) and vacuum condition have been used (from ambient to UHV). In fact, the results display significant variation, what has generated several controversial interpretations. It must be emphasized that many models have been derived without taking into account that the NW structural deformation should be significantly dependent on temperature. In this Thesis research work, we have studied the structural and electronic properties of gold NW's, in particular addressing how thermal effects influence the atomistic aspects of the NW deformation and how this influences the quantum conductance behavior. The structure of NW's has been studied by means of time-resolved high resolution transmission electron microscopy; the NWs transport measurements were based on a mechanically controlled break junction operated in ultra-high-vacuum. The experiments were performed at ~150 and 300 K. Our results have shown that at room temperature the atomic-size NW's. are always crystalline and free of defects, and the atomic structure is spontaneously deformed such that one of the [111]/[100]/[110] crystallographic axis becomes approximately parallel to the stretching direction. Low temperature observations revealed two important differences: i) Au NWs show extended defects, mainly stacking faults and, twinning; ii) NWs elongated along the [110] axis evolve to suspended atomic chains, while at room temperature they break abruptly. Partial Schockley dislocations generate the staking faults; suspended atoms chains are both observed at ~150 and 300 K. The global histograms of conductance at ~150 K showed that: i) a increase of the 1 Go peak intensity; ii) slight reduction of the NWs conductance due to scattering at defects and; iii) the peak at ~2 Go shows a sub structure, what is due to the occurrence of two different atomic arrangements with similar conductance. Briefly, our results revealed that the formation of defects is very frequent in NWs generated at ~150 K; the occurrence of more defects should be expected when NWs are studied at cryogenic temperatures. Then, a significant modification of the NW conductance behavior should be expected at low temperature. In these terms, the direct comparison of conductance measurements realized at different temperature regimes can lead to serious discrepancies. We hope that this work contribute to improve the interpretation and understanding of NW transport studies in order to develop a coherent and complete model that explain the physical properties of atomic-size metal NWs / Mestrado / Física da Matéria Condensada / Mestre em Física

Orientador: Daniel Mario Ugarte / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T07:13:40Z (GMT). No. of bitstreams: 1 LagosParedes_MaureenJoel_M.pdf: 10524108 bytes, checksum: 4c8c3fb76ef4ed87845ad6eb88cf42e9 (MD5) Previous issue date: 2007 / Resumo: O estudo de fios metálicos de tamanho atômico (NF's) tem atraído grande interesse devido aos novos efeitos químicos e físicos neles observados. Entre esses novos fenômenos podemos destacar a quantização da condutância, efeito que deve ser fundamental no desenho dos novos nanodispositivos eletrônicos. NF's são usualmente gerados através de um procedimento simples de deformação mecânica: duas superfícies metálicas são colocadas em contato e depois afastadas. Nos últimos estágios do estiramento antes da ruptura, um fio de alguns átomos de diâmetro é gerado enquanto a condutância é medida. Os NF's têm sido estudados por diferentes grupos e, em diversas condições de temperatura (4 - 300 K) e pressão (de ambiente a UHV). Os resultados apresentam importantes variações e, têm gerado interpretações muito controversas. Devemos enfatizar que muitas interpretações têm sido feitas sem considerar que a deformação estrutural dos NF's deve depender fortemente da temperatura. Nesta tese estudamos as propriedades estruturais e eletrônicas NF's e, em particular analisamos a influência de efeitos térmicos no arranjo atômico, e sua manifestação na condutância. A estrutura dos NF's foi estudada por microscopia eletrônica de transmissão de alta resolução resolvidas no tempo. A condutância foi medida utilizando um sistema de quebra controlada de junções operado em ultra-alto-vácuo. Os experimentos foram realizados a ~150 e 300 K. Nossos resultados mostraram que, à temperatura ambiente os NF's são sempre cristalinos e livre de defeitos nas regiões mais finas; e deformam unicamente ao longo dos eixos cristalográficos [111], [100] e [110]. A baixa temperatura duas importantes diferenças foram observadas: (i) NF's de ouro apresentam defeitos, principalmente falhas de empilhamento e maclas. (ii) NF's alongados na direção [110] evoluem em cadeias atômicas, de comportamento mecânico muito diferente da temperatura ambiente, onde quebram abruptamente. Segundo as imagens de microscopia eletrônica, discordâncias parciais (Shockley) geram falhas de empilhamento; e cadeias de átomos suspensos são observados a ~150 e 300 K. Histogramas globais de condutância adquiridos a baixa temperatura revelaram: (i) aumento da intensidade do pico ~1 Go; (ii) leve diminuição da condutância devido ao aumento de defeitos; e (iii) a existência de uma sub-estrutura no pico ~2 Go, indicando a formação de dois arranjos atômicos estáveis. Resumidamente, nossos resultados mostram que a formação de defeitos é um evento freqüente a ~150 K. Provavelmente, mais defeitos na estrutura devem acontecer para temperaturas menores (4 - 10 K). Portanto, uma importante mudança na evolução da condutância durante a elongação de NF's deve ser esperado a baixa temperatura. Assim, a comparação direta de medidas de transporte de NF's realizadas a diferentes temperaturas pode levar a sérias discrepâncias. Esperamos ter contribuído a melhorar a compreensão e interpretação de experimentos de transporte realizados em diferentes condições, de modo tal, a gerar um modelo único e coerente que explique as propriedades físicas de NF's metálicos / Abstract: The study of atomic-size metal nanowires (NW's) is attracting a great interest due to occurrence a novel physical and chemical phenomena. Among these new phenomena, we can mention conductance quantization that will certainly influence the design of nanodevices. NW's are usually generated by means of a simple procedure: two metallic surfaces are put into contact and, then retracted. Just before rupture atomic-size NW's are formed, and the conductance is measured during the wire elongation. The interpretation of the results is troublesome, because conductance is measured during the modification of the atomic structure. This kind of experimental study has been performed by many research groups and, a quite wide range of temperatures (4 - 300 K) and vacuum condition have been used (from ambient to UHV). In fact, the results display significant variation, what has generated several controversial interpretations. It must be emphasized that many models have been derived without taking into account that the NW structural deformation should be significantly dependent on temperature. In this Thesis research work, we have studied the structural and electronic properties of gold NW's, in particular addressing how thermal effects influence the atomistic aspects of the NW deformation and how this influences the quantum conductance behavior. The structure of NW's has been studied by means of time-resolved high resolution transmission electron microscopy; the NWs transport measurements were based on a mechanically controlled break junction operated in ultra-high-vacuum. The experiments were performed at ~150 and 300 K. Our results have shown that at room temperature the atomic-size NW's. are always crystalline and free of defects, and the atomic structure is spontaneously deformed such that one of the [111]/[100]/[110] crystallographic axis becomes approximately parallel to the stretching direction. Low temperature observations revealed two important differences: i) Au NWs show extended defects, mainly stacking faults and, twinning; ii) NWs elongated along the [110] axis evolve to suspended atomic chains, while at room temperature they break abruptly. Partial Schockley dislocations generate the staking faults; suspended atoms chains are both observed at ~150 and 300 K. The global histograms of conductance at ~150 K showed that: i) a increase of the 1 Go peak intensity; ii) slight reduction of the NWs conductance due to scattering at defects and; iii) the peak at ~2 Go shows a sub structure, what is due to the occurrence of two different atomic arrangements with similar conductance. Briefly, our results revealed that the formation of defects is very frequent in NWs generated at ~150 K; the occurrence of more defects should be expected when NWs are studied at cryogenic temperatures. Then, a significant modification of the NW conductance behavior should be expected at low temperature. In these terms, the direct comparison of conductance measurements realized at different temperature regimes can lead to serious discrepancies. We hope that this work contribute to improve the interpretation and understanding of NW transport studies in order to develop a coherent and complete model that explain the physical properties of atomic-size metal NWs / Mestrado / Física da Matéria Condensada / Mestre em Física

nÃo hà / Nesta tese aborda-se o problema de identificaÃÃo de sistemas dinÃmicos sobre a Ãtica dos modelos locais, em que o espaÃo de entrada à particionado em regiÃes de operaÃÃo menores sobre as quais sÃo construÃdos modelos de menor complexidade (em geral, lineares). Este tipo de modelo à uma alternativa aos chamados modelos globais em que a dinÃmica do sistema à identificada usando-se uma Ãnica estrutura (em geral, nÃo-linear) que cobre todo o espaÃo de entrada. Assim, o tema alvo desta tese à o projeto de modelos lineares locais cujo espaÃo de entrada à particionado por meio do uso de algoritmos de quantizaÃÃo vetorial, principalmente aqueles baseados em redes neurais competitivas. Para este fim, sÃo propostos trÃs novos modelos lineares locais baseados na rede SOM (self-organizing map), que sÃo avaliados na tarefa de identificaÃÃo do modelo inverso de quatro sistemas dinÃmicos comumente usados na literatura em benchmarks de desempenhos. Os modelos propostos sÃo tambÃm comparados com modelos globais baseados nas redes MLP (multilayer perceptron) e ELM (extreme learning machines), bem como com outros modelos lineares locais, tais como o modelo fuzzy Takagi-Sugeno e o modelo neural LLM (local linear mapping). Um amplo estudo à realizado visando comparar os desempenhos de todos os modelos supracitados segundo trÃs critÃrios de avaliaÃÃo, a saber: (i) erro mÃdio quadrÃtico normalizado, (ii) anÃlise dos resÃduos, e (iii) teste estatÃstico de Kolmogorov-Smirnov. De particular interesse para esta tese, à a avaliaÃÃo da robustez dos modelos locais propostos com relaÃÃo ao algoritmo de quantizaÃÃo vetorial usado no treinamento do modelo. Os resultados obtidos indicam que os desempenhos dos modelos locais propostos sÃo superiores aos dos modelos globais baseados na rede MLP e equivalentes aos modelos globais baseados na rede ELM. / In this thesis the problem of nonlinear system identification is approached from the viewpoint of local models. The input space is partitioned into smaller operational regions with lower complexity models (usually linear) built for each one. This type of model is an alternative to global models, for which the system dynamics is identified using a single structure (usually nonlinear ones) that covers the whole input space. The aim of this thesis is to design of local linear models whose input space is partitioned by means of vector quantization algorithms, special those based on competitive learning neural networks. For this purpose, three novel local linear modeling methods based on the SOM (self-organizing map) are introduced and evaluated on the identification of the inverse model of four dynamical systems commonly used in the literature for performance benchmarking. The proposed models are also compared with global models based on the MLP (multilayer perceptron) and ELM (extreme learning machines), as well as with alternative local linear models, such as the Takagi-Sugeno fuzzy model and the LLM(local linear mapping) neural model. A comprehensive study is carried out to compare the performances of all the aforementioned models according to three evaluation criteria, namely: (i) normalized mean squared error, (ii) residual analysis, and (iii) Kolmogorov-Smirnov test. Of particular interest to this thesis is the evaluation of the robustness of the proposed local models with respect to the vector quantization algorithm used to train the model. The obtained results indicates that the performance of the proposed local models are superior to those achieved by the MLP-based global models and equivalent to those achieved by ELM-based global models.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-26T17:48:21Z No. of bitstreams: 1 brunoferreirarizzuti.pdf: 507162 bytes, checksum: 6ccfc7f9025a41c3c8bc647f63d413ea (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-13T12:04:02Z (GMT) No. of bitstreams: 1 brunoferreirarizzuti.pdf: 507162 bytes, checksum: 6ccfc7f9025a41c3c8bc647f63d413ea (MD5) / Made available in DSpace on 2017-05-13T12:04:02Z (GMT). No. of bitstreams: 1 brunoferreirarizzuti.pdf: 507162 bytes, checksum: 6ccfc7f9025a41c3c8bc647f63d413ea (MD5) Previous issue date: 2012-02-29 / Passados mais de 60 anos da sua formulação inicial, o método de Dirac-Bergmann para hamiltonização de sistemas lagrangianos singulares continua sendo uma ferramenta poderosa para análise e investigação de modelos atuais de física teórica. Como motivação, apresentaremos vários exemplos onde o método é utilizado e o descreveremos em detalhes em uma sequência de passos. O objetivo central deste trabalho será então apresentar uma série de aplicações distintas do método de Dirac, incluindo a busca de simetrias locais para teorias singulares, a construção da proposta de relatividade especial dupla de Magueijo-Smolin, a formulação da mecânica clássica com invariância de reparametrizações e sua quantização e por fim, discutiremos um modelo semiclássico mecânico que, quando quantizado, reproduz a equação de Dirac. / After more than 60 years of its initial development, the Dirac-Bergmann method for hamiltonization of constrained systems is still a powerful tool for analysis and investigation of modern theoretical models. As a motivation, we shall present several models where the method is applied, then we will describe it in details, with a sequence of steps. The main objective of this work is to provide distinct applications of the Dirac method, including the search for local symmetries of singular theories, the construction of the Magueijo-Smolin doubly special relativity proposal, the formulation of classical mechanics with reparametrization invariance and its quantization and finally, we discuss a semiclassical mechanical model that produces the Dirac equation through quantization.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-10-10T14:48:12Z No. of bitstreams: 1 guilhermeenriquealemanlopez.pdf: 6728480 bytes, checksum: d96cb4f60e6df31a85d6b383dec056f1 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-10-16T13:35:18Z (GMT) No. of bitstreams: 1 guilhermeenriquealemanlopez.pdf: 6728480 bytes, checksum: d96cb4f60e6df31a85d6b383dec056f1 (MD5) / Made available in DSpace on 2018-10-16T13:35:18Z (GMT). No. of bitstreams: 1 guilhermeenriquealemanlopez.pdf: 6728480 bytes, checksum: d96cb4f60e6df31a85d6b383dec056f1 (MD5) Previous issue date: 2018-08-24 / O objetivo deste trabalho é o estudo de procedimento de quantização canônica de uma partícula em um espaço curvo e sobre uma superfície de espaço Euclidiano. Estudaremos quantização canônica em coordenadas curvilineares, e em seguida vamos adaptar no caso de espaço curvo. Fizemos comparação crítica deste formalismo com três procedimentos principais apresentados na literatura desta área. / The aim of this work is to study the canonical quantization procedure of a particle in a Riemann space, as well as on a surface embedded in Euclidean space. To this aim, we rewrite quantum mechanics of a particle in Euclidean space in curvilinear coordinates. This allows us to formulate certain quantization procedure in a Riemann space. The resulting picture is compared with three quantization proposals known in the literature.

The rapid increasing interest in wireless communication has led to the continuous development of wireless devices and technologies. The modern convergence and interoperability of wireless technologies has further increased the amount of services that can be provided, leading to the substantial demand for access to the radio frequency spectrum in an efficient manner. Cognitive radio (CR) an innovative concept of reusing licensed spectrum in an opportunistic manner promises to overcome the evident spectrum underutilization caused by the inflexible spectrum allocation. Spectrum sensing in an unswerving and proficient manner is essential to CR. Cooperation amongst spectrum sensing devices are vital when CR systems are experiencing deep shadowing and in a fading environment. In this thesis, cooperative spectrum sensing (CSS) schemes have been designed to optimize detection performance in an efficient and implementable manner taking into consideration: diversity performance, detection accuracy, low complexity, and reporting channel bandwidth reduction. The thesis first investigates state of the art spectrums sensing algorithms in CR. Comparative analysis and simulation results highlights the different pros, cons and performance criteria of a practical CSS scheme leading to the problem formulation of the thesis. Motivated by the problem of diversity performance in a CR network, the thesis then focuses on designing a novel relay based CSS architecture for CR. A major cooperative transmission protocol with low complexity and overhead - Amplify and Forward (AF) cooperative protocol and an improved double energy detection scheme in a single relay and multiple cognitive relay networks are designed. Simulation results demonstrated that the developed algorithm is capable of reducing the error of missed detection and improving detection probability of a primary user (PU). To improve spectrum sensing reliability while increasing agility, a CSS scheme based on evidence theory is next considered in this thesis. This focuses on a data fusion combination rule. The combination of conflicting evidences from secondary users (SUs) with the classical Dempster Shafter (DS) theory rule may produce counter-intuitive results when combining SUs sensing data leading to poor CSS performance. In order to overcome and minimise the effect of the counter-intuitive results, and to enhance performance of the CSS system, a novel state of the art evidence based decision fusion scheme is developed. The proposed approach is based on the credibility of evidence and a dissociability degree measure of the SUs sensing data evidence. Simulation results illustrate the proposed scheme improves detection performance and reduces error probability when compared to other related evidence based schemes under robust practcial scenarios. Finally, motivated by the need for a low complexity and minmum bandwidth reporting channels which can be significant in high data rate applications, novel CSS quantization schemes are proposed. Quantization methods are considered for a maximum likelihood estimation (MLE) and an evidence based CSS scheme. For the MLE based CSS, a novel uniform and optimal output entropy quantization scheme is proposed to provide fewer overhead complexities and improved throughput. While for the Evidence based CSS scheme, a scheme that quantizes the basic probability Assignment (BPA) data at each SU before being sent to the FC is designed. The proposed scheme takes into consideration the characteristics of the hypothesis distribution under diverse signal-to-noise ratio (SNR) of the PU signal based on the optimal output entropy. Simulation results demonstrate that the proposed quantization CSS scheme improves sensing performance with minimum number of quantized bits when compared to other related approaches.

Les entreprises doivent traiter quotidiennement de gros volumes de documents papiers de toutes sortes. Automatisation, traçabilité, alimentation de systèmes d’informations, réduction des coûts et des délais de traitement, la dématérialisation a un impact économique évident. Pour respecter les contraintes industrielles, les processus historiques d’analyse simplifient les images grâce à une séparation fond/premier-plan. Cependant, cette binarisation peut être source d’erreurs lors des étapes de segmentation et de reconnaissance. Avec l’amélioration des techniques, la communauté d’analyse de documents a montré un intérêt croissant pour l’intégration d’informations colorimétriques dans les traitements, ceci afin d’améliorer leurs performances. Pour respecter le cadre imposé par notre partenaire privé, l’objectif était de mettre en place des processus non supervisés. Notre but est d’être capable d’analyser des documents même rencontrés pour la première fois quels que soient leurs contenus, leurs structures, et leurs caractéristiques en termes de couleurs. Les problématiques de ces travaux ont été d’une part l’identification d’un nombre raisonnable de couleurs principales sur une image ; et d’autre part, le regroupement en couches couleur cohérentes des pixels ayant à la fois une apparence colorimétrique très proche, et présentant une unité logique ou sémantique. Fournies sous forme d’un ensemble d’images binaires, ces couches peuvent être réinjectées dans la chaîne de dématérialisation en fournissant une alternative à l’étape de binarisation classique. Elles apportent en plus des informations complémentaires qui peuvent être exploitées dans un but de segmentation, de localisation, ou de description. Pour cela, nous avons proposé une segmentation spatio-colorimétrique qui permet d’obtenir un ensemble de régions locales perceptuellement cohérentes appelées superpixels, et dont la taille s’adapte au contenu spécifique des images de documents. Ces régions sont ensuite regroupées en couches couleur globales grâce à une analyse multi-résolution. / Industrial companies receive huge volumes of documents everyday. Automation, traceability, feeding information systems, reducing costs and processing times, dematerialization has a clear economic impact. In order to respect the industrial constraints, the traditional digitization process simplifies the images by performing a background/foreground separation. However, this binarization can lead to some segmentation and recognition errors. With the improvements of technology, the community of document analysis has shown a growing interest in the integration of color information in the process to enhance its performance. In order to work within the scope provided by our industrial partner in the digitization flow, an unsupervised segmentation approach was chosen. Our goal is to be able to cope with document images, even when they are encountered for the first time, regardless their content, their structure, and their color properties. To this end, the first issue of this project was to identify a reasonable number of main colors which are observable on an image. Then, we aim to group pixels having both close color properties and a logical or semantic unit into consistent color layers. Thus, provided as a set of binary images, these layers may be reinjected into the digitization chain as an alternative to the conventional binarization. Moreover, they also provide extra-information about colors which could be exploited for segmentation purpose, elements spotting, or as a descriptor. Therefore, we have proposed a spatio-colorimetric approach which gives a set of local regions, known as superpixels, which are perceptually meaningful. Their size is adapted to the content of the document images. These regions are then merged into global color layers by means of a multiresolution analysis.

La technique de la microscopie à grille de balayage (SGM) consiste à mesurer la conductance d'un gaz bidimensionnel d'électrons (2DEG) sous l'influence d'une pointe balayant la surface de l'échantillon. Dans ce travail, une approche analytique complétée par des simulations numériques est développée pour étudier la relation entre les mesures SGM et les propriétés électroniques locales dans des systèmes mésoscopiques. La correspondance entre la réponse SGM et la densité locale partielle (PLDOS) est étudiée pour un contact quantique entouré d’un 2DEG en présence ou en absence de désordre, pour une pointe perturbative ou non perturbative. Une correspondance SGM-PLDOS parfaite est trouvée pour des transmissions entières et des pointes locales. La dégradation de la correspondance en dehors de cette situation est étudiée. D’autre part, la liaison entre la réponse SGM et la transformée de Hilbert de la densité locale est discutée. Pour étudier le rôle de la force de la pointe sur la conductance SGM, une formule analytique donnant la conductance totale est obtenue. Dans le cas d'une pointe à taille finie nous proposons une méthode basée sur les fonctions de Green permettant de calculer la conductance en connaissant les propriétés non-perturbées. En plus, nous avons étudié la dépendance des branches de la PLDOS en fonction de l’énergie de Fermi. / The scanning gate microscopy (SGM) technique consists in measuring the conductance of a two dimensional electron gas (2DEG) under the influence of a scanning tip. In this work, an analytical approach complemented by numerical simulations is developed to study the connection between SGM measurements and local electronic properties in mesoscopic devices. The connection between the SGM response and the partial local density of states (PLDOS) is studied for the case of a quantum point contact surrounded by clean or disordered 2DEG for perturbative or non-perturbative, local or extended tips. An SGM-PLDOS correspondence is found for integer transmissions and local tips. The degradation of this correspondence out of these conditions is studied. Moreover, a presumed link between the SGM response and the Hilbert transform of the LDOS is discussed. To study the role of the tip strength, an analytical formula giving the full conductance in the case of local tips is obtained. Furthermore, a Green function method enabling to calculate the quantum conductance in the presence of a finite size tip in terms of the unperturbed properties is proposed. Finally the dependence of the PLDOS branches on the Fermi energy is studied.

Digital filters play a key role in many DSP applications and FIR filters are usually selected because of their simplicity and stability against IIR filters.In this thesis eight architectures for multi-stream FIR filtering are studied. Primarily, three kinds of architectures are implemented and evaluated: one-toone mapping, time-multiplexed and pipeline interleaving. During implementation, practical considerations are taken into account such as implementation approach and number representation. Of interest is to see the performance comparison of different architectures, including area and power. The trade-off between area and power is an attractive topic for this work. Furthermore, the impact of the filter order and pipeline interleaving are studied.The result shows that the performance of different architectures differ a lot even with the same sample rate for each stream. It also shows that the performance of different architectures are affected by the filter order differently. Pipeline interleaving improves area utilization at the cost of rapid increment of power. Moreover, it has negative impact on the maximum working frequency.All the FIR filter architectures are synthesized in a 65nm technology.