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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
491

Symmetries of Maldacena - Wilson Loops from Integrable String Theory

Münkler, Hagen 09 October 2017 (has links)
In der vorliegenden Arbeit werden versteckte Symmetrien innnerhalb der N=4 supersymmetrischen Yang--Mills Theorie oder der nach der AdS/CFT Korrespondenz dualen Beschreibung durch eine String-Theorie in AdS5 x S5 besprochen. Dabei betrachten wir die Maldacena--Wilson Schleife, die sich für diese Untersuchungen besonders eignet, da ihr Vakuum-Erwartungswert für glatte Kurven nicht divergiert und die vermutete Dualität zu Streuamplituden wenigstens konzeptionell eine Möglichkeit bietet, etwaige Symmetrien zu anderen Observablen zu übertragen. Ihre Beschreibung durch Minimalflächen in AdS5 erlaubt es, Symmetrien mithilfe der Integrabilität der zugrunde liegenden klassischen String-Theorie zu konstruieren. Dieser Zugang wurde bereits in der Herleitung der Yang'schen Symmetrie der Maldacena--Wilson Schleife bei starker Kopplung sowie in der Beschreibung von Deformationen gleiches Flächeninhalts von Minimalflächen in AdS3 verwendet. Diese beiden Ergebnisse werden in der vorliegenden Arbeit miteinander verbunden und erweitert. Im Sinne einer systematischen Herangehensweise besprechen wir zunächst die Symmetriestruktur der zugrunde liegenden String-Theorie. Diese Diskussion lässt sich auf die Diskussion von String-Theorien in symmetrischen Räumen verallgemeinern. Dabei zeigt sich, dass die Symmetrie, welche die Deformationen gleiches Flächeninhalts in AdS3 erzeugt, in der Symmetriestruktur dieser Modelle eine zentrale Rolle einnimmt: Sie wirkt als Aufsteige-Operator auf den unendlich vielen erhalten Ladungen und generiert somit den Spektralparameter. Weiterhin lässt sie sich anwenden, um ausgehend von der globalen Symmetrie sämtliche Symmetrien des zugrunde liegenden Modells zu konstruieren. Sie wird daher als die Master-Symmetrie dieser Modelle bezeichnet. Zusätzlich wird die Algebra der Symmetrie-Variationen sowie der erhaltenen Ladungen ausgearbeitet. Für den konkreten Fall von Minimalflächen in AdS5 diskutieren wir die Deformation der Minimalflächenlösung für den Fall eines lichtartigen Vierecks. Diese liefert die duale Beschreibung der Streuamplitude für vier Gluonen. Damit unternehmen wir einen ersten Schritt zur Übertragung der Master-Symmetrie auf Streuamplituden. Weiterhin berechnen wir die Variation der Randkurven der Minimalflächen unter der Master- und Yang'schen Symmetrie für allgemeine, glatte Randkurven. Das Ergebnis dieser Rechnung führt auf eine Verallgemeinerung der Master-Symmetrie zu einer Variation, die von der Kopplungskonstanten abhängt und für beliebige Werte der Kopplungskonstanten eine Symmetrie der Maldacena--Wilson Schleife darstellt. Unsere Diskussion erklärt das Scheitern vorheriger Versuche, die entsprechende Symmetrie im Spezialfall von Minimalflächen in AdS3 zu schwacher Kopplung zu übertragen. Wir besprechen verschiedene Ansätze, die Yang'sche Symmetrie zu schwacher oder beliebiger Kopplung zu übertragen, schlussfolgern aber letztendlich, dass eine Yang'sche Symmetrie der Maldacena--Wilson Schleife nicht vorzuliegen scheint. Die Situation ändert sich, wenn wir Wilson Schleifen in Superräumen betrachten. Diese sind die natürlichen supersymmetrischen Erweiterungen der Maldacena--Wilson Schleife. Für die Yang'sche Invarianz ihres Vakuum-Erwartungswerts wurden wichtige Anhaltspunkte gefunden und sowohl die Beschreibung dieser Operatoren als auch der Beweis der Yang'schen Invarianz bei schwacher Kopplung wurden parallel zur Arbeit an der vorliegenden Dissertation vervollständigt. Wir diskutieren das Gegenstück zu diesem Ergebnis bei starker Kopplung. Dort wird die Wilson Schleife durch eine Minimalfläche beschrieben, welche im Superraum der Superstring-Theorie vom Typ IIB in AdS5 x S5 liegt. Der Vergleich der bei starken Kopplung etablierten Invarianz mit den entsprechenden Generatoren bei schwacher Kopplung zeigt, dass die Symmetrie-Generatoren einen lokalen Anteil enthalten, der auf nicht-triviale Weise vom Wert der Kopplungskonstanten abhängt. Zusätzlich finden wir sogenannte Bonus-Symmetrien. Diese sind die analogen Generatoren in den höheren Ordnungen zum Hyperladungs-Generator, der selbst keine Symmetrie darstellt. Wir zeigen, dass diese Symmetrien in allen höheren Ordnungen der Yang'schen Algebra vorliegen. / This thesis discusses hidden symmetries within N=4 supersymmetric Yang--Mills theory or its AdS/CFT dual, string theory in AdS5 x S5. Here, we focus on the Maldacena--Wilson loop, which is a suitable object for this study since its vacuum expectation value is finite for smooth contours and the conjectured duality to scattering amplitudes provides a conceptual path to transfer its symmetries to other observables. Its strong-coupling description via minimal surfaces in AdS5 allows to construct the symmetries from the integrability of the underlying classical string theory. This approach has been utilized before to derive a strong-coupling Yangian symmetry of the Maldacena--Wilson loop and describe equiareal deformations of minimal surfaces in AdS3. These two findings are connected and extended in the present thesis. In order to discuss the symmetries systematically, we first discuss the symmetry structure of the underlying string model. The discussion can be generalized to the discussion of generic symmetric space models. For these, we find that the symmetry which generates the equiareal deformations of minimal surfaces in AdS3 has a central role in the symmetry structure of the model: It acts as a raising operator on the infinite tower of conserved charges, thus generating the spectral parameter, and can be employed to construct all symmetry variations from the global symmetry of the model. It is thus referred to as the master symmetry of symmetric space models. Additionally, the algebra of the symmetry variations and the conserved charges is worked out. For the concrete case of minimal surfaces in AdS5, we discuss the deformation of the four-cusp solution, which provides the dual description of the four-gluon scattering amplitude. This marks the first step toward transferring the master symmetry to scattering amplitudes. Moreover, we compute the master and Yangian symmetry variations of generic, smooth boundary curves. The results leads to a coupling-dependent generalization of the master symmetry, which constitutes a symmetry of the Maldacena--Wilson loop at any value of the coupling constant. Our discussion clarifies why previous attempts to transfer the deformations of minimal surfaces in AdS3 to weak coupling were unsuccessful. We discuss several attempts to transfer the Yangian symmetry to weak or arbitrary coupling, but ultimately conclude that a Yangian symmetry of the Maldacena--Wilson loop seems not to be present. The situation changes when we consider Wilson loops in superspace, which are the natural supersymmetric generalizations of the Maldacena--Wilson loop. Substantial evidence for the Yangian invariance of their vacuum expectation value has been provided at weak coupling and the description of the operator as well as its weak-coupling Yangian invariance were subsequently established in parallel to the work on this thesis. We discuss the strong-coupling counterpart of this finding, where the Wilson loop in superspace is described by minimal surfaces in the superspace of type IIB superstring theory in AdS5 x S5. The comparison of the strong-coupling invariance derived here with the respective generators at weak coupling shows that the generators contain a local term, which depends on the coupling in a non-trivial way. Additionally, we find so-called bonus symmetry generators. These are the higher-level recurrences of the superconformal hypercharge generator, which does not provide a symmetry itself. We show that these symmetries are present in all higher levels of the Yangian.
492

On integrable deformations of semi-symmetric space sigma-models / Deformações integráveis do modelo sigma da supercorda em espaços semi-simétricos

Huamán, René Negrón 05 October 2018 (has links)
In this thesis we review some aspects of Yang-Baxter deformations of semi-symmetric space sigma models. We start by giving a short review of the sigma model description of superstrings and then we offer a self contained introduction to the Yang-Baxter deformation technique. We then show how to obtain an integrable deformation of the hybrid sigma model. Also, we show that the gravity dual of beta-deformed ABJM theory can be obtained as a Yang-Baxter deformation. This is done by selecting a convenient combination of Cartan generators in order to construct an Abelian r-matrix satisfying the classical Yang-Baxter equation. / Nesta tese revisamos alguns aspectos das deformações de Yang-Baxter de modelos sigma em espaços semi-simétricos. Damos uma breve revisão do modelo sigma de supercordas e, em seguida, oferecemos uma introdução ao método de deformação de Yang-Baxter. Em seguida, mostramos como obter uma deformação integrável do modelo sigma híbrido. Além disso, mostramos que o dual gravitacional da teoria ABJM beta-deformada pode ser obtida como uma deformação de Yang-Baxter. Isso é feito selecionando-se uma combinação conveniente de geradores de Cartan para construir uma matriz r Abeliana satisfazendo a equação clássica de Yang-Baxter.
493

Gerenciamento de risco em tecnovigilância: aplicação dos conceitos seis sigma e técnica delphi para o desenvolvimento e validação de instrumento de avaliação de material médico-hospitalar / Risk management in technovigilance: application of Six Sigma concepts and the Delphi Technique for the development and validation of a medical-hospital material assessment instrument.

Kuwabara, Cleuza Catsue Takeda 01 September 2009 (has links)
O Gerenciamento de Risco Hospitalar é um processo complexo de ações gerenciais multidisciplinares que tem como propósito implantar um sistema de monitoramento e identificação da provável origem de eventos adversos e seus danos, tomar decisões apropriadas e executar ações concernentes às áreas de Farmacovigilância, Hemovigilância e a Tecnovigilância. Esta última tem como parte das atividades, procedimentos para aquisição, utilização e controle da qualidade de produtos e equipamentos em uso na área da saúde. Nesse sentido, este estudo teve como objetivo geral construir e validar um instrumento de avaliação de produto médicohospitalar. Trata-se de um estudo quantitativo, exploratório, longitudinal e de desenvolvimento metodológico. A investigação foi estruturada utilizando-se de técnicas de gestão de qualidade com o uso da metodologia Seis Sigma para subsidiar o gerenciamento de risco na área de Tecnovigilância e a Técnica Delphi para a obtenção dos dados. A metodologia Seis Sigma possui como base principal, as etapas componentes do Ciclo DMAIC, onde a melhoria da performance com uso de abordagens estatísticas e estratégicas possibilitou o estudo das variabilidades dos processos. A Técnica Delphi foi utilizada para a obtenção de dados dos profissionais especialistas e juízes da Rede Brasileira de Hospitais Sentinela. Considerando que o equipo de infusão venosa é de amplo uso na área de saúde, foi elaborado um questionário, composto de três perguntas e 55 itens, para indicação daqueles itens a compor o instrumento de avaliação desse produto. A concretização da validação inicial contou com a participação de 134 profissionais especialistas que atenderam aos critérios de inclusão no estudo, e foi estabelecido o consenso de 80% de concordância, o que foi obtido com duas rodadas da Técnica Delphi-1. A seguir, desenvolveu-se um instrumento que possui duas partes: a Geral que se compõe de dados administrativos e do produto; a parte Específica que contém 9 tópicos e 43 itens de avaliações. O quadro de avaliação, contem cinco diferentes atributos de qualificação (péssimo, regular, bom, ótimo e excelente) e que possuem pontuações de 1 a 5 respectivamente. Na etapa Delphi-2, cinco juízes participaram de duas rodadas para a validação de conteúdo do modelo desenvolvido obtendo-se 100% de consenso. Na etapa Delphi-3, os juízes aplicaram o instrumento em três marcas de equipos simples e três de equipos com reservatório. Os resultados deste estudo contribuem não apenas para a avaliação dos produtos, mas também propõe uma metodologia para o desenvolvimento de um instrumento, extensível a outros produtos médico-hospitalares. Concluiu-se que o instrumento desenvolvido possibilitou avaliar os produtos diferenciando os resultados das marcas testadas, retratando o propósito inicial do estudo em se qualificar as avaliações de equipo de infusão. / Hospital risk management is a complex process, which involves multidisciplinary management actions. Its goal is to set up a system to monitor and identify the probable origin of adverse events and their damage; make appropriate decisions; and perform actions related to Pharmacovigilance, Hemovigilance and Technovigilance. The latter, among other functions, performs activities and procedures for the acquisition, use and quality control of products and equipment used in the health area. This study aims to construct and validate an instrument to assess medicalhospital products. A quantitative, exploratory, longitudinal and methodological development study was carried out. The research structure was based on quality management techniques, using the Six Sigma method to support risk management in Technovigilance and the Delphi technique for data collection. The premise of the Six Sigma method comprises the component steps of the DMAIC Cycle, in which performance improvement through the use of statistical and strategic approaches made it possible to study the processes variabilities. The Delphi technique was used to obtain data from specialized professionals and judges from the Brazilian Sentinel Hospital Network. As venous infusion equipment is widely used in the hospital area, a questionnaire was elaborated, consisting of three questions and 55 items, to indicate the items to be included in that products assessment instrument. In the initial validation, 134 specialized professionals took place, who complied with the criteria for inclusion in the study. The agreement level was set at 80%, obtained after two rounds of the Delphi technique. Next, a two-part instrument was developed: General, addressing administrative and product data; and Specific, with 9 topics and 43 assessment items. The assessment chart contains five different qualifications (Very bad, Regular, Good, Very Good and Excellent) and scores from 1 to 5, respectively. In the Delphi 2 phase, five judges participated in two round to validate the content of the developed model, achieving a 100% consensus. In the Delphi 3 phase, the judges applied the instrument to three brands of Simple equipment and three brands of equipment with Reserve. The study results not only contribute to product assessment, but also propose an instrument development method that can be extended to other medical-hospital products. It is concluded that the developed instrument permitted product assessment, providing distinct results for the tested brands, in line with the studys initial goal of qualifying infusion equipment assessments.
494

Caracterização do papel de dois fatores sigma de função extracitoplasmática da família FecI em Caulobacter crescentus. / Characterization of the role of two FecI-like extracytoplasmic function sigma factors in Caulobacter crescentus.

Heloise Balhesteros 12 December 2014 (has links)
Fatores sigma de carência de ferro, representados por FecI de E. coli, direcionam a transcrição de genes de transporte de sideróforos (quelantes de ferro), e são geralmente regulados por fatores antissigma (FecR), que liberam o fator sigma após ligação do sideróforo no receptor de membrana externa (FecA). Caulobacter crescentus possui quatro genes para fatores sigma desta família. Ensaios de expressão gênica e crescimento indicaram que estes genes não respondem à disponibilidade de ferro. Em microarranjos de cDNA, apenas o gene fecA2 foi induzido em DfecR2 comparado à linhagem parental, sugerindo que este é o único gene alvo do fator sigma FecI2. Já DfecR4 mostrou indução em mais de 50 genes, alguns envolvidos na utilização de fontes alternativas de carbono. Ensaios fenotípicos com DfecI4 sugeriram que este gene é importante para o crescimento em g-ciclodextrina ou ácido caproico. Os resultados sugerem que o fator sigma FecI2 é bem específico, enquanto FecI4 parece regular uma resposta geral relacionada a compostos carbônicos, e não à homeostase de ferro. / Iron starvation sigma factors, whose prototype is E. coli FecI, direct transcription of genes involved in siderophore (iron chelators) transport, being usually regulated by anti-sigma factors (FecR), which release the sigma factor after siderophore binding to the outer membrane receptor (FecA). Caulobacter crescentus possesses four genes encoding FecI-like sigma factors. Gene expression and growth assays indicated that these genes do not respond to iron availability. In cDNA microarrays, only the fecA2 gene was induced in DfecR2 relative to the wild-type strain, suggesting that this is the only target gene of the FecI2 sigma factor. However, in DfecR4 there was induction of over 50 genes, some of them involved in utilization of alternative carbon sources. Phenotypic microarrays with the DfecI4 strain showed that this gene is important for growth in g-cyclodextrin or caproic acid. The results suggest that the FecI2 sigma factor is very specific, whereas FecI4 seems to regulate a more general response, related to carbon compounds rather than iron homeostasis.
495

Design Methodology for High-performance Circuits Based on Automatic Optimization Methods. / Mise en place d'une démarche de conception pour circuits hautes performances basée sur des méthodes d'optimisation automatique

Tugui, Catalin Adrian 14 January 2013 (has links)
Ce travail de thèse porte sur le développement d’une méthodologie efficace pour la conception analogique, des algorithmes et des outils correspondants qui peuvent être utilisés dans la conception dynamique de fonctions linéaires à temps continu. L’objectif principal est d’assurer que les performances pour un système complet peuvent être rapidement investiguées, mais avec une précision comparable aux évaluations au niveau transistor.Une première direction de recherche a impliqué le développement de la méthodologie de conception basée sur le processus d'optimisation automatique de cellules au niveau transistor et la synthèse de macro-modèles analogiques de haut niveau dans certains environnements comme Mathworks - Simulink, VHDL-AMS ou Verilog-A. Le processus d'extraction des macro-modèles se base sur un ensemble complet d'analyses (DC, AC, transitoire, paramétrique, Balance Harmonique) qui sont effectuées sur les schémas analogiques conçues à partir d’une technologie spécifique. Ensuite, l'extraction et le calcul d'une multitude de facteurs de mérite assure que les modèles comprennent les caractéristiques de bas niveau et peuvent être directement régénéré au cours de l'optimisation.L'algorithme d'optimisation utilise une méthode bayésienne, où l'espace d’évaluation est créé à partir d'un modèle de substitution (krigeage dans ce cas), et la sélection est effectuée en utilisant le critère d’amélioration (Expected Improvement - EI) sujet à des contraintes. Un outil de conception a été développé (SIMECT), qui a été intégré comme une boîte à outils Matlab, employant les algorithmes d’extraction des macro-modèles et d'optimisation automatique. / The aim of this thesis is to establish an efficient analog design methodology, the algorithms and the corresponding design tools which can be employed in the dynamic conception of linear continuous-time (CT) functions. The purpose is to assure that the performance figures for a complete system can be rapidly investigated, but with comparable accuracy to the transistor-level evaluations. A first research direction implied the development of the novel design methodology based on the automatic optimization process of transistor-level cells using a modified Bayesian Kriging approach and the synthesis of robust high-level analog behavioral models in environments like Mathworks – Simulink, VHDL-AMS or Verilog-A.The macro-model extraction process involves a complete set of analyses (DC, AC, transient, parametric, Harmonic Balance) which are performed on the analog schematics implemented on a specific technology process. Then, the extraction and calculus of a multitude of figures of merit assures that the models include the low-level characteristics and can be directly regenerated during the optimization process.The optimization algorithm uses a Bayesian method, where the evaluation space is created by the means of a Kriging surrogate model, and the selection is effectuated by using the expected improvement (EI) criterion subject to constraints.A conception tool was developed (SIMECT), which was integrated as a Matlab toolbox, including all the macro-models extraction and automatic optimization techniques.
496

Caracterização de fatores sigma da subfamília ECF em Caulobacter crescentus / Characterization of sigma factors ECF subfamily in Caulobacter crescentus

Martinez, Cristina Elisa Alvarez 13 December 2004 (has links)
Em bactérias, os fatores sigma alternativos permitem a rápida adaptação da célula a alterações no ambiente. Dentre estes, os fatores sigma ECF (função extra-itoplasmática) caracterizam-se pelo envolvimento na resposta a sinais da região extra-citoplasmática da célula. O sequenciamento do genoma de Caulobacter crescentus indicou a presença de 13 ORFs codificando fatores ECF. Este trabalho descreve a caracterização de cepas mutantes em cinco genes que codificam fatores sigma ECF de C. crescentus, sendo eles sigL, sigM, sigN, sigU e sigF. A regulação da expressão destes genes em respostas a diferentes estresses foi também analisada, pelo uso de fusões de transcrição de suas regiões promotoras ao gene reporter lacZ. Todos os mutantes mostraram-se viáveis, sendo também tão resistentes quanto a cepa parental a uma série de estresses ambientais testados, indicando que estes genes não são essenciais. Verificou-se, porém, que os mutantes nos genes sigL e sigM são mais sensíveis ao choque térmico extremo (48°C). A caracterização da cepa mutante em sigF mostrou que este gene é essencial para a resistência da célula a estresse oxidativo durante a fase estacionária. A análise da expressão de sigF indicou um controle pós-transcricional, com o acúmulo da proteína SigF durante esta fase do crescimento, sem um aumento na transcrição do gene. Oito genes regulados por &#963;F durante a fase estacionária foram identificados em experimentos de \"microarray\", incluindo os genes de resposta a estresse oxidativo, sodA e msrA. A análise da atividade do promotor de sigU mostrou sua indução na entrada na fase estacionária e após estresse salino e osmótico. No entanto, o mutante nulo em sigU não se apresentou mais sensível que a cepa parental a esses estresses. Os resultados aqui descritos permitiram identificar a importância de alguns dos fatores ECF de C. crescentus na resposta a estresses nesta bactéria. / Alternative sigma factors permit the rapid adaptation to environmental changes in bacteria. Among them, members of the ECF subfamily (extrac</i<ytoplasmic function) are characterized by their involvement in responses to changes in the extracytoplasmic compartment of the cell. Analysis of the complete genome sequence of Caulobacter crescentus has led to the identification of 13 ORFs encoding putative sigma factors of the ECF subclass. The present work describes the characterization of mutant strains in five genes encoding ECF sigma factors from C. crescentus, named sigL, sigM, sigN, sigU and sigF. The expression of these genes in response to distinct stress conditions was also investigated, using transcriptional fusions of their promoter regions to the lacZ reporter gene. The five mutants strains obtained were viable and did not show increased sensitivity, when compared to the parental strain, to a series of environmental stress conditions, indicating that these genes are not essential. However, the sigL and sigM mutant strains were shown to be more sensitive to extreme heat shock (48°C). Furthermore, the characterization of the sigF mutant strain demonstrated that this gene is essential for oxidative stress survival during stationary phase. Analysis of sigF expression indicated a post-transcriptional control, with an increase in the levels of SigF protein during this growth phase, without changes in the transcription rate of the gene. Eight genes regulated by &#963;F during stationary phase were identified in microarray experiments, including the oxidative stress response genes sodA and msrA. Analysis of sigU promoter activity in response to distinct stress conditions showed induction upon entry into stationary phase and during saline and osmotic stress. Nevertheless, the sigU null mutant did not show increased sensitivity to these stresses. The results described here identified the importance of some of the C. crescentus ECF sigma factors in the response to stresses in this bacterium.
497

Projeto de um modulador sigma-delta de baixo consumo para sinais de áudio / Low power audio sigma delta modulator design

Alarcón Cubas, Heiner Grover 23 May 2013 (has links)
Este trabalho descreve o projeto de um modulador Analógico-Digital (A/D) Sigma-Delta de 16 bits (98 dB de SNR) de baixo consumo em tecnologia CMOS para a aquisição de sinais de áudio. Para projetar o modulador foi utilizada a metodologia top down, a qual consiste em projetar desde o nível de sistema até os blocos básicos em nível de transistores. O sistema foi analizado e projetado utilizando equacões e modelos comportamentais para obter as especificações de cada bloco do modulador. Considerando um baixo consumo de potência foi escolhida a topologia CIFF (do inglês Chain of Integrator with FeedForward) de terceira ordem e quatro bits implementado com capacitores chaveados. O modulador projetado é composto por três integradores chaveados, um somador analógico, um weigthed DAC e um quantizador de quatro bits. A técnica de Chopper é incluida no modulador para diminuir o ruído Flicker na entrada do modulador. Os blocos de maior consumo dentro do modulador são as OTAs. Por esta razão eles são projetados utilizando a metodologia gm/ID reduzindo assim o consumo de potência. O projeto foi realizado na tecnologia IBM 0,18 \'mü\'m sendo utilizado o simulador spectre do Cadence. O modulador Sigma-Delta atinge um SNR de 98 dB para uma banda de 20 kHz e um consumo de potência de 2,4 mW para uma fonte de alimentação de 1,8 V. / This work describes the design of a 16 bits low power Sigma-Delta modulator (98 dB SNR) in a CMOS technology for the acquisition of audio signals. To design the modulator it was used the top-down methodology, which consists on the design from system level to the transistor-level basic blocks. The system was analyzed and designed using behavioral models and equations to obtain the specifications of each block of the modulator. Considering a low power consumption it was chosen a third-order four bits CIFF topology (Chain Integrator with feedforward) implemented with switched capacitors. The modulator is composed by three integrators, one analog adder, one weigthed DAC and one four bit quantizer. The Chopper technique is included in the modulator to reduce the Flicker noise at the input of the modulator. The blocks of higher consumption within the modulator are the OTAs. Hence, they was designed using the methodology gm/ID to reduce power consumption. It was designed on the 0.18 \'mü\'m IBM technology and using the Cadence Spectre simulator. The Sigma-Delta modulator achieves a SNR of 98 dB for a bandwidth of 20 kHz and a power consumption of 2.4 mW with a 1.8 V power supply.
498

Solutions à courbure constante de modèles sigma supersymétriques

Lafrance, Marie 12 1900 (has links)
No description available.
499

Relation between Globalisation and the Real Convergence: Does convergence of globalisation influence convergence of real GDP per capita? / Vztah mezi globalizací a reálnou konvergencí: ovplyvňuje konvergence v globalizaci konvergenci reálného HDP na hlavu?

Rybanová, Soňa January 2011 (has links)
This dissertation poses the question of whether there is a relationship between the speed of convergence of globalisation and the speed of convergence of GDP per capita. Firstly, the concepts of globalisation and real convergence and their relationship are thoroughly explained from both the theoretical and empirical point of view. And secondly, the answer to the question comes in the form of beta and sigma convergence analysis of this relationship. Thirdly, the analysis splits the countries into two groups (developed and developing countries) and finds interesting but ambiguous results in their comparison. Finally, in order to correctly interpret the results of absolute and conditional beta and sigma convergence, their theoretical and empirical overview is discussed in depth. The dissertation concludes by providing some answers to the initial question for every particular analysis. Namely, it shows that this relationship is indeed very ambiguous.
500

Passive Loop Filter Zoom Analog to Digital Converters

January 2018 (has links)
abstract: This dissertation proposes and presents two different passive sigma-delta modulator zoom Analog to Digital Converter (ADC) architectures. The first ADC is fullydifferential, synthesizable zoom-ADC architecture with a passive loop filter for lowfrequency Built in Self-Test (BIST) applications. The detailed ADC architecture and a step by step process designing the zoom-ADC along with a synthesis tool that can target various design specifications are presented. The design flow does not rely on extensive knowledge of an experienced ADC designer. Two example set of BIST ADCs have been synthesized with different performance requirements in 65nm CMOS process. The first ADC achieves 90.4dB Signal to Noise Ratio (SNR) in 512µs measurement time and consumes 17µW power. Another example achieves 78.2dB SNR in 31.25µs measurement time and consumes 63µW power. The second ADC architecture is a multi-mode, dynamically zooming passive sigma-delta modulator. The architecture is based on a 5b interpolating flash ADC as the zooming unit, and a passive discrete time sigma delta modulator as the fine conversion unit. The proposed ADC provides an Oversampling Ratio (OSR)- independent, dynamic zooming technique, employing an interpolating zooming front-end. The modulator covers between 0.1 MHz and 10 MHz signal bandwidth which makes it suitable for cellular applications including 4G radio systems. By reconfiguring the OSR, bias current, and component parameters, optimal power consumption can be achieved for every mode. The ADC is implemented in 0.13 µm CMOS technology and it achieves an SNDR of 82.2/77.1/74.2/68 dB for 0.1/1.92/5/10MHz bandwidth with 1.3/5.7/9.6/11.9mW power consumption from a 1.2 V supply. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

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