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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.
791

PMU based PSS and SVC fuzzy controller design for angular stability analysis

Ahmed, Sheikh January 1900 (has links)
Master of Science / Department of Electrical and Computer Engineering / Shelli Starrett / Variability in power systems is increasing due to pushing the system to limits for economic purposes, the inclusion of new energy sources like wind turbines and photovoltaic, and the introduction of new types of loads such as electric vehicle chargers. In this new environment, system monitoring and control must keep pace to insure system stability and reliability on a wide area scale. Phasor measurement unit technology implementation is growing and can be used to provide input signals to new types of control. Fuzzy logic based power system stabilizer (PSS) controllers have also been shown effective in various studies. This thesis considers several choices of input signals, composed assuming phasor measurement availability, for fuzzy logic-based controllers. The purpose of the controller is to damp power systems’ low frequency oscillations. Nonlinear transient simulation results for a 4-machine two-area system and 50 machine system are used to compare the effects of input choice and controller type on damping of system oscillations. Reactive power in the system affects voltage, which in turn affects system damping and dynamic stability. System stability and damping can be enhanced by deploying SVC controllers properly. Different types of power system variables play critical role to damp power swings using SVC controller. A fuzzy logic based static var compensator (SVC) was used near a generator to damp these electromechanical oscillations using different PMU-acquired inputs. The goal was again improve dynamic stability and damping performance of the system at local and global level. Nonlinear simulations were run to compare the damping performance of different inputs on the 50 machine system.
792

Impacts of Base-Case and Post-Contingency Constraint Relaxations on Static and Dynamic Operational Security

January 2016 (has links)
abstract: Constraint relaxation by definition means that certain security, operational, or financial constraints are allowed to be violated in the energy market model for a predetermined penalty price. System operators utilize this mechanism in an effort to impose a price-cap on shadow prices throughout the market. In addition, constraint relaxations can serve as corrective approximations that help in reducing the occurrence of infeasible or extreme solutions in the day-ahead markets. This work aims to capture the impact constraint relaxations have on system operational security. Moreover, this analysis also provides a better understanding of the correlation between DC market models and AC real-time systems and analyzes how relaxations in market models propagate to real-time systems. This information can be used not only to assess the criticality of constraint relaxations, but also as a basis for determining penalty prices more accurately. Constraint relaxations practice was replicated in this work using a test case and a real-life large-scale system, while capturing both energy market aspects and AC real-time system performance. System performance investigation included static and dynamic security analysis for base-case and post-contingency operating conditions. PJM peak hour loads were dynamically modeled in order to capture delayed voltage recovery and sustained depressed voltage profiles as a result of reactive power deficiency caused by constraint relaxations. Moreover, impacts of constraint relaxations on operational system security were investigated when risk based penalty prices are used. Transmission lines in the PJM system were categorized according to their risk index and each category was as-signed a different penalty price accordingly in order to avoid real-time overloads on high risk lines. This work also extends the investigation of constraint relaxations to post-contingency relaxations, where emergency limits are allowed to be relaxed in energy market models. Various scenarios were investigated to capture and compare between the impacts of base-case and post-contingency relaxations on real-time system performance, including the presence of both relaxations simultaneously. The effect of penalty prices on the number and magnitude of relaxations was investigated as well. / Dissertation/Thesis / Doctoral Dissertation Engineering 2016
793

A Tool to Reduce Defects due to Dependencies between HTML5, JavaScript and CSS3

January 2016 (has links)
abstract: One of the most common errors developers make is to provide incorrect string identifiers across the HTML5-JavaScript-CSS3 stack. The existing literature shows that a significant percentage of defects observed in real-world codebases belong to this category. Existing work focuses on semantic static analysis, while this thesis attempts to tackle the challenges that can be solved using syntactic static analysis. This thesis proposes a tool for quickly identifying defects at the time of injection due to dependencies between HTML5, JavaScript, and CSS3, specifically in syntactic errors in string identifiers. The proposed solution reduces the delta (time) between defect injection and defect discovery with the use of a dedicated just-in-time syntactic string identifier resolution tool. The solution focuses on modeling the nature of syntactic dependencies across the stack, and providing a tool that helps developers discover such dependencies. This thesis reports on an empirical study of the tool usage by developers in a realistic scenario, with the focus on defect injection and defect discovery times of defects of this nature (syntactic errors in string identifiers) with and without the use of the proposed tool. Further, the tool was validated against a set of real-world codebases to analyze the significance of these defects. / Dissertation/Thesis / Masters Thesis Computer Science 2016
794

Load Sensitivity Studies and Contingency Analysis in Power Systems

January 2016 (has links)
abstract: The past decades have seen a significant shift in the expectations and requirements re-lated to power system analysis tools. Investigations into major power grid disturbances have suggested the need for more comprehensive assessment methods. Accordingly, sig-nificant research in recent years has focused on the development of better power system models and efficient techniques for analyzing power system operability. The work done in this report focusses on two such topics 1. Analysis of load model parameter uncertainty and sensitivity based pa-rameter estimation for power system studies 2. A systematic approach to n-1-1 analysis for power system security as-sessment To assess the effect of load model parameter uncertainty, a trajectory sensitivity based approach is proposed in this work. Trajectory sensitivity analysis provides a sys-tematic approach to study the impact of parameter uncertainty on power system re-sponse to disturbances. Furthermore, the non-smooth nature of the composite load model presents some additional challenges to sensitivity analysis in a realistic power system. Accordingly, the impact of the non-smooth nature of load models on the sensitivity analysis is addressed in this work. The study was performed using the Western Electrici-ty Coordinating Council (WECC) system model. To address the issue of load model pa-rameter estimation, a sensitivity based load model parameter estimation technique is presented in this work. A detailed discussion on utilizing sensitivities to improve the ac-curacy and efficiency of the parameter estimation process is also presented in this work. Cascading outages can have a catastrophic impact on power systems. As such, the NERC transmission planning (TPL) standards requires utilities to plan for n¬-1-1 out-ages. However, such analyses can be computationally burdensome for any realistic pow-er system owing to the staggering number of possible n-1-1 contingencies. To address this problem, the report proposes a systematic approach to analyze n-1-1 contingencies in a computationally tractable manner for power system security assessment. The pro-posed approach addresses both static and dynamic security assessment. The proposed methods have been tested on the WECC system. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016
795

Analyse statique de l'effet des erreurs de configuration dans des FGPA configurés par SRAM et amélioration de robustesse / Modeling faults in SRAM based FPGA and appropriate protections

Ferron, Jean-Baptiste 26 March 2012 (has links)
Cette thèse s'intéresse en premier lieu à l'analyse des effetsfonctionnels des erreurs dans laconfiguration de FPGAs à base de SRAM. Ces erreurs peuvent provenir deperturbations naturelles(rayonnements, particules) ou d'attaques volontaires, par exemple avecun laser. La famille Virtex IIde Xilinx est utilisée comme premier cas pratique d'expérimentation,puis une comparaison est réaliséeavec la famille AT40K de chez ATMEL. Ceci a permis de mieux comprendrel'impact réel dedifférentes sources de perturbations, et les motifs d'erreur devantréellement être pris en compte pouraméliorer la robustesse d'un circuit implanté sur ce type detechnologie. Cette étude a nécessité ledéveloppement d'outils de conception spécifiques, permettantd'automatiser les analyses. Uneméthodologie innovante est proposée pour l'évaluation de lasensibilité de la mémoire de configurationaux SEUs : une classification des bits de configuration est établie enfonction des effets produits parleur inversion sur le fonctionnement normal de l'application. Cecipermet de déterminer les zones lesplus critiques, autorisant le développement de stratégies deprotection sélectives et à faible coût. / This thesis deals primarily with the analysis of the functionaleffects of errors in the configuration ofSRAM-based FPGAs. These errors can be due either to naturalperturbations (radiations, particles) orto malicious attacks, for example with a laser. The Xilinx Virtex IIfamily is used as first case study,then a comparison is made with the ATMEL AT40K family. This workallowed us a betterunderstanding of the real impact of perturbations, and of the errorpatterns that need to be taken intoaccount when improving the robustness of a circuit implemented on thistype of technology. Thisstudy required the development of specific design tools to automatethe analyses. An innovativemethodology is proposed for the evaluation of the configuration memorysensitivity to SEUs: aclassification of configuration bits is made with respect to theeffects produced on the application by asingle bit-flip. This enables us to identify the most critical areas,and to propose selective hardeningsolutions, improving the global reliability of the application at low cost.
796

Une méthodologie de conception de modèles analytiques de surface et de puissance de réseaux sur puce hautement paramétriques basée sur une méthode d’apprentissage automatique / A machine-learning based methodology to design analytical area and power models of highly parametric networks-on-chip

Dubois, Florentine 04 July 2013 (has links)
Les réseaux sur puces (SoCs - Networks-on-chip) sont apparus durant la dernière décennie en tant que solution flexible et efficace pour interconnecter le nombre toujours croissant d'éléments inclus dans les systèmes sur puces (SoCs - Systems-on-chip). Les réseaux sur puces sont en mesure de répondre aux besoins grandissants en bande-passante et en scalabilité tout en respectant des contraintes fortes de performances. Cependant, ils sont habituellement caractérisés par un grand nombre de paramètres architecturaux et d'implémentation qui forment un vaste espace de conception. Dans ces conditions, trouver une architecture de NoC adaptée aux besoins d'une plateforme précise est un problème difficile. De plus, la plupart des grands choix architecturaux (topologie, routage, qualité de service) sont généralement faits au niveau architectural durant les premières étapes du flot de conception, mais mesurer les effets de ces décisions majeures sur les performances finales du système est complexe à un tel niveau d'abstraction. Les analyses statiques (méthodes non basées sur des simulations) sont apparues pour répondre à ce besoin en méthodes d'estimations des performances des SoCs fiables et disponibles rapidement dans le flot de conception. Au vu du haut niveau d'abstraction utilisé, il est irréaliste de s'attendre à une estimation précise des performances et coûts de la puce finale. L'objectif principal est alors la fidélité (caractérisation des grandes tendances d'une métrique permettant une comparaison équitable des alternatives) plutôt que la précision. Cette thèse propose une méthodologie de modélisation pour concevoir des analyses statiques des coûts des composants des NoCs. La méthode proposée est principalement orientée vers la généralité. En particulier, aucune hypothèse n'est faite ni sur le nombre de paramètres des composants ni sur la nature des dépendances de la métrique considérée sur ces mêmes paramètres. Nous sommes alors en mesure de modéliser des composants proposant des millions de possibilités de configurations (ordre de 1e+30 possibilités de configurations) et d'estimer le coût de réseaux sur puce composés d'un grand nombre de ces composants au niveau architectural. Il est complexe de modéliser ce type de composants avec des modèles analytiques expérimentaux à cause du trop grand nombre de possibilités de configurations. Nous proposons donc un flot entièrement automatisé qui peut être appliqué tel quel à n'importe quelles architectures et technologies. Le flot produit des prédicteurs de coûts des composants des réseaux sur puce capables d'estimer les différentes métriques pour n'importe quelles configurations de l'espace de conception en quelques secondes. Le flot conçoit des modèles analytiques à grains fins sur la base de résultats obtenus au niveau porte et d'une méthode d'apprentissage automatique. Il est alors capable de concevoir des modèles présentant une meilleure fidélité que les méthodes basées uniquement sur des théories mathématiques tout en conservant leurs qualités principales (basse complexité, disponibilité précoce). Nous proposons d'utiliser une méthode d'interpolation basée sur la théorie de Kriging. La théorie de Kriging permet de minimiser le nombre d'exécutions du flot d'implémentation nécessaires à la modélisation tout en caractérisant le comportement des métriques à la fois localement et globalement dans l'espace. La méthode est appliquée pour modéliser la surface logique des composants clés des réseaux sur puces. L'inclusion du trafic dans la méthode est ensuite traitée et un modèle de puissance statique et dynamique moyenne des routeurs est conçu sur cette base. / In the last decade, Networks-on-chip (NoCs) have emerged as an efficient and flexible interconnect solution to handle the increasing number of processing elements included in Systems-on-chip (SoCs). NoCs are able to handle high-bandwidth and scalability needs under tight performance constraints. However, they are usually characterized by a large number of architectural and implementation parameters, resulting in a vast design space. In these conditions, finding a suitable NoC architecture for specific platform needs is a challenging issue. Moreover, most of main design decisions (e.g. topology, routing scheme, quality of service) are usually made at architectural-level during the first steps of the design flow, but measuring the effects of these decisions on the final implementation at such high level of abstraction is complex. Static analysis (i.e. non-simulation-based methods) has emerged to fulfill this need of reliable performance and cost estimation methods available early in the design flow. As the level of abstraction of static analysis is high, it is unrealistic to expect an accurate estimation of the performance or cost of the chip. Fidelity (i.e. characterization of the main tendencies of a metric) is thus the main objective rather than accuracy. This thesis proposes a modeling methodology to design static cost analysis of NoC components. The proposed method is mainly oriented towards generality. In particular, no assumption is made neither on the number of parameters of the components nor on the dependences of the modeled metric on these parameters. We are then able to address components with millions of configurations possibilities (order of 1e+30 configuration possibilities) and to estimate cost of complex NoCs composed of a large number of these components at architectural-level. It is difficult to model that kind of components with experimental analytical models due to the huge number of configuration possibilities. We thus propose a fully-automated modeling flow which can be applied directly to any architecture and technology. The output of the flow is a NoC component cost predictor able to estimate a metric of interest for any configuration of the design space in few seconds. The flow builds fine-grained analytical models on the basis of gate-level results and a machine-learning method. It is then able to design models with a better fidelity than purely-mathematical methods while preserving their main qualities (i.e. low complexity, early availability). Moreover, it is also able to take into account the effects of the technology on the performance. We propose to use an interpolation method based on Kriging theory. By using Kriging methodology, the number of implementation flow runs required in the modeling process is minimized and the main characteristics of the metrics in space are modeled both globally and locally. The method is applied to model logic area of key NoC components. The inclusion of traffic is then addressed and a NoC router leakage and average dynamic power model is designed on this basis.
797

Gerador de indução com excitação estática, filtro ativo e armazenamento de energia para sistemas eólicos isolados / Induction generator with static excitation, active filter and energy storage for stand-alone wind systems

Trapp, Jordan Gustavo 01 March 2013 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The growing global demand for electricity, increasing scarcity of the conventional energy sources and the need to reduce environmental impacts contributed to the pronounced development of new technologies based on clean and renewable energy sources. In this context, the wind power is the technology that has had a greater development in recent decades. This source has played an important role in the advancement of alternative sources in the world energy matrix, because the technology is already consolidated and is economically viable. Accompanying the technological development of the alternative sources, the induction generator has stood out among the generators with the technology best suited to generating electricity for isolated energy systems. With this motivation, this thesis proposes a new configuration for an isolated wind energy conversion system using variable speed turbines, in which the induction generator is electronically excited by means of a static compensator. Also, the generator is associated to a shunt active filter for compensation of non-linear and unbalanced loads, and with a battery bank for energy storage and DC bus stabilization. It is also discussed the main problems with the induction generator related to the magnetization characteristic and its dynamic model, and the proposed solutions to mitigate these problems. The results confirm the effectiveness of the proposed wind energy conversion system, showing its operational capability with variable load and variable turbine speed. Finally it is presented the main conclusions of this work and suggestions for future works in the same line of research. / O crescente aumento da demanda mundial de energia elétrica, a escassez cada vez maior das fontes convencionais de energia e a necessidade de redução dos impactos ambientais contribuíram para o acentuado desenvolvimento de novas tecnologias baseadas em fontes limpas e renováveis. Neste contexto, a energia eólica foi uma das tecnologias que mais se desenvolveu nas últimas décadas. Esta fonte tem desempenhado importante papel no avanço das fontes alternativas na matriz energética mundial, pois é uma tecnologia já consolidada e viável economicamente. Acompanhando o desenvolvimento tecnológico das fontes alternativas, o gerador de indução tem se destacado dentre as tecnologias de geradores mais adequadas para sistemas isolados de geração de energia elétrica. Com esta motivação, esta tese propõe uma nova configuração de conversão de energia eólica isolada, utilizando turbinas de velocidade variável, na qual o gerador de indução é excitado eletronicamente por meio de um compensador estático. Ainda mais, o gerador é associado a um filtro ativo shunt para a compensação de cargas não-lineares e desbalanceadas e a um banco de baterias para armazenamento de energia e estabilização do barramento cc, comum aos conversores. São discutidos os principais problemas relacionados ao gerador de indução para esta aplicação através da característica de magnetização e do seu modelo dinâmico, com as soluções propostas para mitigar estes problemas. Os resultados práticos e de simulação obtidos comprovam a efetividade da configuração de conversão de energia eólica proposta, mostrando a capacidade de operação do gerador com carga variável e velocidade variável da turbina. Por fim são apresentadas as principais conclusões e sugestões para trabalhos futuros na mesma linha de pesquisa.
798

Compensadores estáticos de reativos empregados em redes de baixa tensão com geradores distribuídos de energia / Static var compensators applied in low voltage grids with distributed generators

Almeida, Felipe Augusto Ferreira de [UNESP] 03 November 2016 (has links)
Submitted by Felipe Augusto Ferreira de Almeida null (felipeafalmeida@gmail.com) on 2016-12-20T16:56:04Z No. of bitstreams: 1 DISSERTACAO_FELIPE_FINAL.pdf: 3666708 bytes, checksum: 18899b06cbe9a7091fd3f037b0656174 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-12-22T10:53:09Z (GMT) No. of bitstreams: 1 almeira_faf_me_bauru.pdf: 3666708 bytes, checksum: 18899b06cbe9a7091fd3f037b0656174 (MD5) / Made available in DSpace on 2016-12-22T10:53:09Z (GMT). No. of bitstreams: 1 almeira_faf_me_bauru.pdf: 3666708 bytes, checksum: 18899b06cbe9a7091fd3f037b0656174 (MD5) Previous issue date: 2016-11-03 / Instituto Federal de Educação, Ciência e Tecnologia de São Paulo (IFSP) / Este trabalho aborda o emprego do Compensador Estático de Reativos (SVC) em redes de baixa tensão com geração distribuída de energia, tendo como objetivo a compensação de tensão e de fator de potência. Os principais distúrbios de qualidade de energia elétrica em baixa tensão, bem como as normas e os limites operacionais para os principais indicadores foram revisados, visando confrontação com as situações resultantes da integração do SVC no sistema elétrico. O SVC possui operação estabelecida como carga reativa controlável em sistemas de transmissão de energia, fazendo parte dos condicionadores da tecnologia FACTS (Flexible AC Transmission Systems). A exploração desta tecnologia em outro nível de tensão é o objetivo deste trabalho. As análises foram realizadas através de simulações computacionais, desenvolvidas no ambiente MATLAB, contemplando o desenvolvimento de modelos relacionados com aplicações de RCT (Reator Controlado a Tiristor), FC (Capacitor Fixo), do CCT (Capacitor Chaveado a Tiristor) e de um sistema de geração distribuída de energia elétrica trifásico em uma rede de baixa tensão a quatro fios. A metodologia para o dimensionamento dos elementos passivos dos condicionadores é apresentada, bem como a análise dos valores de potência reativa, fator de potência, distorções harmônicas e a avaliação da necessidade de utilização ou não de filtros passivos. A teoria da potência conservativa (TPC) é a metodologia utilizada para definição das grandezas elétricas e fatores de conformidade. Por fim, as características operacionais de um SVC aplicado a uma rede de baixa tensão a quatro fios são exploradas através dos resultados de simulação, com o objetivo de demonstrar a manutenção de suas características operacionais estabelecidas, no nível de baixa tensão, e apontar aspectos diferenciados quanto à regulação de fator de potência e da forma de tensão providos pelo SVC, para servir como informação de confronto frente a outras tecnologias comumente utilizadas neste nível de tensão. / This paper discusses the use of Static Var Compensator (SVC) on low voltage grids with distributed generation with the aim of voltage and power factor compensation. The main electrical power quality disturbances at low voltage as well as the rules and operational limits for the main indicators were reviewed aiming to confront the situations resulting from SVC integration in the electrical system. SVC has established operation as controllable reactive load in power transmission systems, being part of FACTS (Flexible AC Transmission Systems) technology conditioners. The application of this technology in another level of tension is the objective of this work. The analyzes were carried out through computer simulations developed in the MATLAB environment, including the development of models related to RCT (Thyristor Controlled Reactor), FC (Fixed Capacitor), CCT (Thyristor Switching Capacitor) and a threephase electric power distributed generation system in a four-wire low voltage grid. The methodology for the dimensioning of the passive elements of the conditioners is presented, as well as the analysis of the values of reactive power, power factor, harmonic distortions and the evaluation of the need to use passive filters. The conservative power theory (CPT) is the methodology used to define the electrical magnitudes and compliance factors. Finally, the operational characteristics of a SVC applied to a low-voltage four-wire network are exploited through the simulation results, in order to demonstrate the maintenance of its established operational characteristics at the low voltage level and to point out different aspects as well as the power factor regulation and voltage form provided by the SVC, to serve as confronting information.
799

Características e interrelação da sensibilidade plantar e do equilíbrio de atletas e não-atletas / Characteristics and intercorrelation of the plantar sensitivity static balance of athletes and non-athletes

Faquin, Aline 28 February 2005 (has links)
Made available in DSpace on 2016-12-06T17:07:07Z (GMT). No. of bitstreams: 1 DISSERTACAOAlineFaquin.pdf: 2111665 bytes, checksum: f62f3993e44fe216cc518ccad77c9993 (MD5) Previous issue date: 2005-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The main goal of this exploratory descriptive study was evaluate the characteristics and the relationship among the sensibility of the plantar surface and the static balance in athletes and non-athletes. Participated 71 athletes of both genders, age varying between 15 and 35 years, from the judo, olympic gymnastics, volleyball, soccer and 27 nonathletes. The evaluation of sensibility was performed with Semmes-Weinstein® monofilaments and the AMTI, model OR6-5 force plate was used to verify COP sway. Data collection was composed by: a) to sensibility evaluation each filament was applied in calcaneal region, middle foot, first and fifth metatarsal heads and halux. The sensibility threshold was determined by the filament with the smaller diameter felt by the individual; b) the individual was oriented to stand on the force plate, with the feet lightly distant and the arms along side the body, in the bipodal and unipodal positon, with footwear and without footwear, with and without visual information. The sampling frequency was of 50Hz and time of acquisition of 30s (bipodal) and 20s (unipodal). Descriptive statistics (mean, standarddeviation, mediana and variation coefficient), inferencial (Anova 3x2x2) and non-parametric (Kruskall-Wallis test, U of Mann-Whitney s test and Correlation of Spearman) were used as statistical procedures. Results: The sensibility thresholds were between 4.31 and 3.61. The region with the worst and the best sensibility threshold were respectively the calcaneal region and the middle foot, for all the groups. The athletes of the practice with footwear had the largest values for the variables of the Center of Pressure, in the bipodal and unipodal position. There was no statistic difference between the groups for the variables of the Center of Pressure in the bipodal position. In the unipodal position the variables, except RMS, suffered effect of the visual information, with the largest increment observed for the area of displacement of COP (326,8%). To bipodal and unipodal position were possible to verify low correlation among the plantar sensitibility and static balance. Conclusion: except for the calcaneal region, the other areas there were no significant difference between the groups. The athletes that compete with footwear (volleyball and soccer) were more dependents of the visual information that the athletes of olympic gymnastics and judo and non-athletes. / Este estudo descritivo exploratório objetivou analisar as características e a relação entre a sensibilidade plantar e o equilíbrio na postura em pé de atletas cuja prática da modalidade é descalço, atletas cuja prática é com calçado e indivíduos não-atletas, nas condições com e sem informação visual e com e sem calçado. Participaram do estudo 71 atletas de ambos os sexos, com idade entre 15 e 35 anos, das modalidades de judô, ginástica olímpica, voleibol, futebol e 27 indivíduos não-atletas na mesma faixa etária. Os instrumentos foram: monofilamentos Semmes-Weinstein® e plataforma de força extensométrica AMTI® modelo OR6-5. Adotou-se os seguintes procedimentos de coleta: a) na avaliação da sensibilidade cada filamento foi aplicado nas regiões de calcâneo, médio pé medial, I e V metatarso e hálux. O nível de sensibilidade foi determinado pelo filamento com o menor diâmetro sentido pelo sujeito, ao responder 6 tentativas positivas, de um total de 10; b) os sujeitos foram orientados verbalmente a permanecer sobre a plataforma de força, com os pés ligeiramente afastados e os braços ao longo do corpo o mais imóvel possível, nas posições bipodal e unipodal, com calçado e sem calçado, olhos abertos e olhos fechados. A freqüência de amostragem foi de 50Hz com tempo de aquisição de 30s (bipodal) e 20s (unipodal). Utilizou-se estatística descritiva (média, desvio-padrão,mediana e coeficiente de variação), inferencial (Anova 3x2x2) e não-paramétrica (Teste da mediana de Kruskall-Wallis, teste U de Mann-Whitney e Correlação de Spearman) a p 0,05.Obteve-se os seguintes Resultados: Os níveis de sensibilidade estiveram entre 4.31 e 3.61, sendo o pior na região do calcâneo e o melhor na região do médio (3.61), para todos os grupos. Os atletas da prática com calçado tiveram os maiores valores para todas as variáveis do Centro de Pressão, tanto na posição bipodal quanto unipodal. Na posição bipodal todas as variáveis do Centro de Pressão foram semelhantes para os três grupos. Na posição unipodal as variáveis, com exceção do RMS, sofreram efeito da retirada da informação visual, com o maior acréscimo observado para a área de deslocamento do COP (326,8%). Para as posturas bipodal e unipodal considerado a mediana de toda a planta do pé foi possível constatar baixa correlação entre a sensibilidade plantar e variáveis de equilíbrio. Concluiu-se que exceto para a região do calcâneo, pior nos atletas da prática com calçado, nas demais áreas parece que a prática de modalidades com ou sem calçado não influencia na sensibilidade plantar. Para posição bipodal o fato de praticar modalidades com uso ou não de calçado, e ser ou não atletas parece não influenciar as variáveis. Os atletas que treinam e competem utilizando calçado (modalidade de voleibol e futebol) foram mais dependentes da informação visual que os atletas de ginástica olímpica e judô e indivíduos não atletas.
800

Avaliação da Aderência em Estruturas Tubulares Metálicas Revestidas com Material Cimentício sob Esforços estáticos e dinâmicos. / Evaluation of bond in structures tubular metal coated with cementitious material under static and dynamic stress

Silva, Elisângela Pereira da 26 March 2010 (has links)
Made available in DSpace on 2015-05-08T15:00:10Z (GMT). No. of bitstreams: 1 parte1.pdf: 2464209 bytes, checksum: 983291ff02a154d08eaacd514bfd9d61 (MD5) Previous issue date: 2010-03-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The bond on tubular steel coated with cementitious material, such as oil wells is quite complex. These are subject to change in temperature, pumping, steam injection, vibration caused by explosive charges, which can harm the interface of the tube cement paste through the loss of bond. Pullout tests in the laboratory are used for verification of the bond. However, this technique does not contemplate the life of the structural integrity of the well. This work aimed to contribute to the improvement of the technical verification of the bond through static and dynamic loading. For this, first using pullout tests has been proposed a study to test an improved speed of application loading. For this we used tubes coated partially of cement paste. Simulating the two contact conditions: no treatment on the surface of the tubes, and treatment with NaCl. It was observed that the presence of NaCl and a slower rate of load application positively influenced the bond stress. For the quasi-static dynamic test, by counting the number of cycles, it was felt that this substance in the interface showed a greater number of cycles. Thus it was concluded that this technique is feasible to evaluate the useful life of the well oil. / A aderência em estruturas tubulares metálicas revestidas com material cimentício, tais como, poço de petróleo é bastante complexa. Estes estão sujeitos a variação de temperatura, bombeamento, injeção de vapor, vibrações provocadas por cargas explosivas, que podem vir a prejudicar a interface do conjunto tubo-pasta de cimento, através da perda da aderência. Ensaios de arrancamento em laboratório são utilizados para verificação desta aderência. No entanto, esta técnica não contempla a vida útil da integridade estrutural do poço. O presente trabalho tem como objetivo contribuir para o aperfeiçoamento da técnica de verificação da aderência através de carregamento estático e dinâmico. Para isto, utilizou-se primeiro testes de arrancamento para verificação de uma melhor velocidade de aplicação de carga. Para isto utilizou-se tubos metálicos revestidos parcialmente por pasta de cimento. Simulou-se duas condições de contato: sem tratamento na superfície dos tubos, e com tratamento NaCl. Observou-se que a presença do NaCl e uma menor velocidade de aplicação de carga influenciaram de forma positiva a tensão de aderência. Para o ensaio dinâmico quase estático, através da contagem do número de ciclos, percebeu-se que a presença desta substância na interface apresentou um maior número de ciclos. Desta forma concluiu-se que esta técnica é viável para avaliação da vida útil do poço de petróleo.

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