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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.
571

Estabilidade de sistemas detetáveis com custo médio a longo prazo limitado / Stability of detectable systems with bounded long run average cost

Barbosa, Brenno Gustavo 28 March 2012 (has links)
Neste trabalho estudamos a estabilidade assintótica de Lagrange para duas classes de sistemas, sob as hipóteses de detetabilidade fraca e de limitação do custo medio a longo prazo. Para sistemas lineares com saltos markovianos com rudo aditivo, a equivalência entre estabilidade e as condições mencionadas sera provada. Para sistemas dinâmicos generalizados, provaremos a estabilidade sob uma condição adicional / In this work we study Lagrange asymptotic stability for two classes of systems, under conditions of weak detectability and boundedness of the long run average cost. For Markov jump linear systems with additive noise, the equivalence between stability and the aforementioned conditions is proved. For generalized dynamical systems, we prove stability under an additional condition
572

Avaliação ergonômica do membro superior esquerdo de operadores de trem metropolitano: uma investigação de sobrecargas no sistema osteomuscular / Ergonomic evaluation of the left upper limb of metropolitan train drivers: an investigation of overloads in the musculoskeletal system

Melo, Wilson Viana de Castro 14 February 2008 (has links)
A Biomecânica Ocupacional procura aprimorar as condições de trabalho objetivando prevenir e reduzir as lesões, aumentar o desempenho dos operários reduzindo sobrecargas. Pesquisas nesta área indicam que não apenas a manipulação de materiais pesados, mas também posturas pouco naturais e movimentos súbitos e inesperados provocam lesões no sistema osteomuscular que afetam principalmente o pescoço, membros superiores e região lombar. Alguns profissionais apresentam alto risco ao aparecimento desses distúrbios envolvendo principalmente os membros superiores e região lombar, particularmente os digitadores, operadores de caixa de supermercados, dentistas, motoristas profissionais e operadores de trens metropolitanos. Este estudo teve como objetivo estimar a carga mecânica e a atividade muscular no membro superior esquerdo de maquinistas condutores de trens metropolitanos durante o trabalho. Especificamente, o estudo procurou estimar a carga mecânica sobre a articulação do ombro, avaliar a atividade muscular dos músculos tríceps e flexores do punho e verificar a ocorrência de fadiga muscular durante a realização da tarefa, para isto foram investigados o fator de risco relacionado a enfermidades dos membros superiores, o torque sobre a articulação do ombro e a freqüência mediana do sinal eletromiográfico. O método RULA indicou para atividade estudada um escore final quatro, que sugere mais investigações e mudanças podem ser requeridas, pois a postura adotada gera desconforto. O torque calculado sobre a articulação do ombro é aplicado por cerca da metade da jornada de trabalho e apresentou valor médio de -4,1 Nm com o manete na posição 0. A instauração de fadiga sobre os músculos Tríceps Braquial e flexores do punho não foi observada. Estudos futuros são recomendados para desenvolvimento de cabinas de trens metropolitanos com layout ergonômico e posicionamento de instrumentos que possibilite uma postura mais adequada dos operadores / Occupational biomechanics seeks to improve the conditions of work aiming to prevent and to reduce the injuries, to increase the performance of workers reducing overloads. Previous researches in this area indicate that not only handling the of heavy material, inadequate postures and unexpected and sudden movements provoke injuries in the musculoskeletal system that affect mainly the neck, upper limbs and the lumbar region. Some workers present high risk to the develop those disturbances involving mainly the upper limbs and the lumbar region, particularly the keyboarders, supermarket cashiers, dentists, professional drivers and operators metropolitan train. This study aimed to estimate the mechanical load and the muscular activity in the left upper limb of metropolitan train drivers during the work. Specifically, the study sought to estimate the mechanical load on the joint of the shoulder, evaluate the muscular activity of the muscles triceps and flexors of the wrist and verify the occurrence of muscular fatigue during the achievement of the task. For this purpose, it were investigated the risk factor related to the diseases of the upper limbs, the torque on the joint of the shoulder and the median frequency of the electromyographic signal. The method RULA indicated for activity a score final four, which suggests more investigations and changes may be required because the usual posture adopted generates discomfort. The calculated torque on the joint of the shoulder is applied by about half of the day at work and showed the average value of -4.1 Nm with the handle in position 0. The instauration of fatigue on the muscles Tríceps brachial the wrist flexor was not observed. Thus, future studies are recommended to the development of the metropolitan trains\' berths with ergonomic layout and positioning of instruments that enables an adequate posture of its users
573

Propriedades de filtros lineares para sistemas lineares com saltos markovianos a tempo discreto / Properties of linear filters for discrete-time Markov jump linear systems.

Gomes, Maria Josiane Ferreira 12 March 2015 (has links)
Este trabalho é dedicado ao estudo do erro de estimação em filtragem linear para sistemas lineares com parâmentros sujeitos a saltos markovianos a tempo discreto. Indroduzimos o conceito de alcançabilidade média para uma classe de sistemas. Construímos um conjunto de matrizes de alcançabilidade e mostramos que o conceito usual de alcan- çabilidade definido através da positividade do gramiano é caracterizado pela definição por posto completo destas matrizes. A alcançabilidade média funciona como condição necessária e suficiente para positividade do segundo momento do estado do sistema, resultado esse que auxilia na caracterização da positividade uniforme da matriz de covariância do erro de estimação. Abordamos a estabilidade de estimadores com a interpretação de que a covariância do erro permanece limitada na presença de erro de qualquer magnitude no modelo do ruído, que é uma característica relevante para aplicações. Apresentamos uma prova de que filtros markovianos são estáveis sempre que o segundo momento condicionado é positivo. Exemplos numéricos encontram-se inclusos. / This work studies linear filtering for discrete-time systems with Markov jump parameters. We introduce a notion of average reachability for these systems and present a set of matrices playing the role of reachability matrices, in the sense that their rank is full if and only if the system is average reachable. Reachability is also a sufficient condition for the second moment of the system to be positive. Uniform positiveness of the error covariance matrix is studied for general (possibly non-markovian) linear estimators, relying on the state second moment positiveness. Satbility of linear markovian estimators is also addressed, allowing to show that markovian estimators are stable whenever the system is reachable, with the interpretation that the error covariance remains bounded in the presence of error of any magnitude in the model of the noise, which is a relevant feature for applications. Numerical examples are included.
574

Sugarcane yield gap in Brazil: a crop modelling approach / Quebra de produtividade (Yield Gap) da cana de açúcar no Brasil: uma abordagem baseada em modelo de simulação de culturas

Monteiro, Leonardo Amaral 09 November 2015 (has links)
Currently, the cropping area is around 10 million hectares, in which the sugarcane fields are expanding for marginal regions, mainly where grains and pasture were previously cultivated. From that, the objectives of this study were: to calibrate and evaluate a sugarcane yield model using data from 12 fields conducted under high technology field conditions; to evaluate the performance of a gridded system (NASA/POWER) to increase the spatial density of the weather stations in Brazil, to be employed as input data of crop simulation models; to map, in micro-region scale, the potential (Yp), the best farmer\'s (Ybf) and average actual (Yavg) sugarcane yields in Brazil, in order to determine the sugarcane yield gaps by water deficit (YGWD) and by crop management (YGCM), and to define strategies for a most sustainable sugarcane crop production. The yield model showed a good performance in the yield simulation, during the calibration and validation phases. The estimated yield in the calibration phase was 81.9 Mg ha-1 while the observed one was 82.3 Mg ha-1. In the validation phase, the estimated yield was 82.9 Mg ha-1 and the observed was 86.9 Mg ha-1. These results suggested that this kind of model can be used for yield estimation, mainly for agricultural planning purposes, at regional and national scales. The NASA/POWER weather data showed a reasonable performance when compared to observed data that control Yp (solar radiation and air temperature). On the other hand, although the annual average rainfall were very similar in all locations evaluated, this variable presented unsatisfactory statistical coefficients (R2 = 0.60 and MAPE = 233.4%), being suggested, therefore, to replacement of rainfall data from the gridded system by the ones from local rainfall stations (ANA). In the majority of the locations, the percentage errors of Yp were ±15%, while the attainable yield was overestimated by 14% when estimated without replace the rainfall data by the ANA\'s data. Otherwise, when the rainfall data were modified by the ones from ANA, a better adjustment was obtained, revealing an overestimation of only 5%. Finally, 259 virtual weather stations were generated with NASA/POWER data and rainfall from ANA database to estimate yields. The yield types were spatialized through software ArcGis 9.3® at micro-region level. The yield gaps by water deficit and crop management were determined. It was observed that the sugarcane yield losses in Brazil are mainly caused by water deficit (74% of total yield gap), while 26% was due crop management. These results contribute for a better understanding about the factors that control sugarcane production and, therefore, they can be used to define strategies, such use of drought tolerant cultivars, irrigation, and soil decompaction, to make sugarcane production in Brazil more efficient and sustainable. / Atualmente, a cana de açúcar ocupa uma área de aproximadamente 10 milhões de hectares, revelando um pronunciado avanço dos canaviais para regiões marginais, onde anteriormente predominavam os cultivos de grãos e pastagens. Assim, os objetivos deste estudo foram calibrar e avaliar um modelo de estimativa da produtividade de colmos da cana de açúcar em 12 locais, sob elevado padrão tecnológico e operacional de cultivo; avaliar o desempenho de um sistema de dados meteorológicos em grid (NASA/POWER, 1°x1°) para incrementar a densidade espacial de estações meteorológicas no Brasil para serem empregados em modelos de simulação de culturas; e mapear, a produtividade potencial (Yp), a produtividade obtida pelos produtores com elevado nível tecnológico (Ybf) e a produtividade real média (Yavg) de colmos no Brasil, para, posteriormente, determinar a quebra de produtividade da cana de açúcar decorrente do déficit hídrico (YGWD) e do manejo da cultura (YGCM), a fim de indicar estratégias para um cultivo mais sustentável. O modelo agrometeorológico de estimativa apresentou desempenho satisfatório na simulação das produtividades, tanto na fase de calibração como na validação. A produtividade estimada na calibração foi de 81.9 Mg ha-1 enquanto que a observada foi 82.3 Mg ha-1. Na validação, a produtividade estimada foi 82,9 Mg ha-1 e a observada foi 86,9 Mg ha-1. Esses resultados sugerem a possibilidade do emprego desse modelo para a estimativa da produtividade da cultura da cana-de-açúcar, principalmente em termos de planejamento agrícola em média e grande escalas. O sistema NASA/POWER apresentou desempenho satisfatório em relação às variáveis meteorológicas que controlam a Yp (radiação solar e temperatura do ar). Por outro lado, embora os totais anuais de precipitação tenham sido bastante semelhantes, a precipitação apresentou coeficientes estatísticos apenas razoáveis, principalmente para aplicações em modelos de simulação da produtividade (R2 = 0,60 e MAPE = 233,4%), sendo sugerido, portanto, o uso de dados dessa variável provenientes de estações pluviométricas locais. Na grande maioria dos locais avaliados o erro percentual da produtividade potencial variou entre ±15%, enquanto que a produtividade atingível foi superestimada em 14% quando esta foi estimada com os dados de precipitação do sistema NASA/POWER. Por outro lado, quando os dados de precipitação foram modificados pelos dados de estações pluviométricas da ANA, houve apenas 5% de superestimativa da produtividade. Por fim, foram geradas 259 estações meteorológicas virtuais com os dados do sistema NASA/POWER e a precipitação das estações pluviométricas da ANA. Posteriormente, os yield gaps por efeito do déficit hídrico e do manejo da cultura foram determinados. Os resultados indicaram que o principal fator restritivo da produtividade da cana de açúcar no Brasil é o déficit hídrico (74% do YG total), enquanto que as práticas de manejo da cultura sub-ótimas contribuem com 26% da quebra total. Isso contribuiu para um melhor entendimento dos aspectos que afetam a produção de cana de açúcar em diferentes regiões brasileiras, sendo, portanto, possível se delimitar estratégias, como o uso de cultivares tolerantes à seca, a irrigação e a descompactação dos solos, que tornem a cultura mais resiliente e produção canavieira mais eficiente e sustentável.
575

Uma proposta para o ensino da noção de taxa de variação instantânea no ensino médio

Silva, Edson Rodrigues da 09 October 2012 (has links)
Made available in DSpace on 2016-04-27T16:57:20Z (GMT). No. of bitstreams: 1 Edson Rodrigues da Silva.pdf: 2574600 bytes, checksum: fe11256e07c5f09808b243d5f8f0ce49 (MD5) Previous issue date: 2012-10-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work aims to lead students in the 3rd year of high school to construct meaning to the idea of instantaneous rate of change. With this intention, and based on the premises of Didactic Engineering, we elaborated, applied and analyzed a didactic sequence for eight students of a public school in the state of São Paulo. As theoric support, we used the Theory of Didactical Situation (TDS) and the Representation Theory of Semiotics Register. The TDS assisted us in development, tests and analysis of results of didactic sequence, while the Representation Theory of Semiotics Registers emphasized the diversity and articulation of different registers of representation in mathematical activities. The analysis of didactic sequence indicated that teaching students in the 3rd year of high school, through the simultaneous mobilization of records graphing, algebraic and tabular can construct meaning to the idea of rate of change / O presente trabalho tem por objetivo conduzir estudantes do 3º ano do Ensino Médio a construir significado para a ideia de taxa de variação instantânea. Com esse intuito, e fundamentados nos pressupostos da Engenharia Didática, elaboramos, aplicamos e analisamos uma sequência didática para oito alunos de uma escola pública do Estado de São Paulo. Como aporte teórico utilizamos a Teoria das Situações Didáticas (TSD) e a Teoria de Registros de Representação Semiótica. A TSD nos auxiliou na elaboração, experimentação e análise dos resultados da sequência didática, enquanto a Teoria de Registros de Representação Semiótica, enfatizou a diversidade e a articulação de diferentes registros de representação nas atividades matemáticas. A análise da sequência didática apontou que estudantes do 3º ano do Ensino Médio, por meio da mobilização simultânea dos registros de representação gráfica, algébrica e tabular, podem construir significado para a ideia de taxa de variação
576

Modélisation d’un réacteur de gazéification a lit fixe / Modeling of a fixed bed gasifier

Deydier, Alexandre 15 February 2012 (has links)
Dans le cadre d’une thématique générale du Laboratoire Thermique Energétique et Procédés de Pau consacré à l’étude et à la valorisation des déchets tels que la pyrolyse, la combustion et la gazéification, la thèse se focalise sur la modélisation des phénomènes de transports de masse, de quantité de mouvement et d’énergie en milieu multiphasique multiconstituant réactif dans le cas d’un réacteur de gazéification à lit fixe. La première étape de la modélisation consiste à décrire classiquement le mouvement de chacune des phases continues par les équations de conservation de la masse, de la quantité de mouvement et de la chaleur. Bien qu’à cette échelle les mécanismes soient parfaitement décrits, le passage à la simulation impose une étape d’homogénéisation par prise de moyenne. Ce changement d’échelle, décrit dans ce travail, conduit à un système d’équations homogène à l’échelle locale. Ce modèle est appliqué au cas du procédé de gazéification de déchets de la société Europlasma nommé CHO-Power. Les simulations bidimensionnelles instationnaires du problème ont permis de mettre en lumière les différents mécanismes en présence au cours du procédé ainsi qu’un certain nombre de verrous dans l’obtention du chemin de convergence conduisant au régime permanent. / One of the thematics of the “Laboratoire Thermique Energétique et Procédés de Pau” is the study and the valorization of waste as pyrolysis, combustion and gasification for example. In this context, this work deals with modeling of heat, mass and momentum transport in a multiphase multi components reactive medium for a fixed bed gasifier. Conservation equations are first written for each phase. The macroscopic partial differential equations are expressed by integrating these microscopic conservation laws over a representative volume. This change of scale, described in this work, leads to a homogeneous system of equations. This model is applied to the case of the gasification of waste process of the Europlasma company named CHO-Power. The unsteady two-dimensional simulations of the problem allowed to highlight the different mechanisms present during the process and a number of locks in obtaining convergence path leading to the steady state.
577

Analyse mathématique des modèles cinétiques en présence d'un champ magnétique intense / Mathematical analysis of kinetic models with strong magnetic field

Finot, Aurélie 26 January 2017 (has links)
Cette thèse propose une analyse mathématique des modèles cinétiques en présence d'un champ magnétique intense.L'objectif de ce projet est le développement d'outils mathématiques nécessaires à la modélisation des plasmas de fusion. Les phénomènes physiques rencontrés dans les plasmas de fusion mettent en jeu des échelles caractéristiques disparates. L'interaction entre ces ordres de grandeurs est un enjeu important et requiert une analyse multi-échelle. Il s'agit d'un problème d'homogénéisation par rapport au mouvement rapide de rotation des particules autour des lignes de champ magnétique. Nous étudions le régime du rayon de Larmor fini pour le système de Vlasov-Poisson, dans le cadre de champs magnétiques uniformes, en appliquant les méthodes de gyro-moyenne. Nous donnons l'expression explicite du champ d'advection effectif de l'équation de Vlasov, dans laquelle nous avons substitué le champ électrique auto-cohérent, via la résolution de l'équation de Poisson moyennée à l'échelle cyclotronique. Nous mettons en évidence la structure hamiltonienne du modèle limite et présentons ses propriétés : conservations de la masse, de l'énergie cinétique, de l'énergie électrique, etc.Nous généralisons ensuite cette étude dans le cadre de champs magnétiques non uniformes. Comme précédemment, les principales propriétés des modèles limites sont mises en évidence : conservations de la masse, de l'énergie, structure hamiltonienne.Nous prenons en compte également les effets collisionnels, en présence d'un champ magnétique intense. Après identification des équilibres et invariants du noyau de collision moyenné, on s'intéresse à la dérivation de modèles fluides. / This thesis proposes a mathematical analysis of kinetic models in the presence of strong magnetic fields.The objective of this project is the development of mathematical tools required for modelisation of fusion plasmas. The physical phenomena encountered in fusion plasmas involve disparate characteristic scales. The interaction between these orders of magnitude is an important issue and requires a multi-scale analysis. We appeal to homogenization techniques with respect to the fast rotation motion around the magnetic field lines.We study the finite Larmor radius regime for the Vlasov-Poisson system, in the framework of uniform magnetic fields, by appealing to gyro-average methods. We indicate the explicit expression of the effective advection field entering the Vlasov equation, after substituting the self-consistent electric field, obtained by the resolution of the averaged (with respect to the cyclotronic time scale) Poisson equation. We emphasize the hamiltonian structure of the limit model and present its properties : conservation of mass, of kinetic energy, of electric energy, etc.Then we generalize this study to general magnetic shapes. As before, the main properties of the limit model are emphasized : mass and energy balances, hamiltonian structure.We also take into account the collisional effects, under strong magnetic fields. After identifying the equilibria and the invariants of the average collision operator, we inquire about fluid models.
578

Hispanic students' connection to school: The relation between extracurricular participation and grade point average

Towe, Chad R., 1973- 06 1900 (has links)
x, 84 p. : ill. / This study examines the relation between Hispanic students' extracurricular participation and GPA. Research suggests that participation in extracurricular activities is positively related to academic achievement in high school. This study addresses the Social Capital connection to school as a contributing factor in academic achievement. This study's findings provide evidence to support the hypothesis that extracurricular activities have a positive relation to freshman year GPA scores, specifically for Hispanic students. The study's findings also suggest there is a difference in terms of GPA for Hispanic students across trimesters. This study adds to the growing body of literature on the positive relation between extracurricular activities and cumulative GPA for Hispanic students. / Committee in charge: Dr. David Conley, Chair Dr. Paul Yovanoff, Member Dr. Keith Zvoch, Member Dr. Geraldine Moreno, Outside Member
579

A Rela??o entre a sa?de organizacional e a S?ndrome de Burnout

Dantas, Etienne Andrade de Medeiros 26 November 2003 (has links)
Made available in DSpace on 2014-12-17T15:38:46Z (GMT). No. of bitstreams: 1 EtienneAMD.pdf: 633997 bytes, checksum: a1c6aef8df161229449aa5c834ae4cee (MD5) Previous issue date: 2003-11-26 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / We studied about the organizational health and the syndrome of burnout in professionals of the education and health field, with the objective of establishing a connection between those two constructs. This research was realized in three public schools and in three hospitals, two publics and one from the military. We obtained 168 valid questionnaires for investigation about the syndrome of burnout, being 83 in the hospitals and 85 in the schools, among the questionnaires given in those two organizations. Worked with accidental sample, although it was decided the professional proportions, with the objective of reproducing the population characteristics. In the schools the sample was planned with the teachers. In the hospitals the sample was planned with doctors, nurses and nurse assistants, nutritionists, psychologists, dentists and social assistants. To assure the syndrome of burnout, it was used the Maslach Burnout Inventory (MBI), followed with social demographic information. We used semi-structured interviews, based in the indicators, with the organizations key persons, directors, coordinators, and people involved in the human resources department, for research about the organizational health. Only among the hospitals were found significant statistics differences between the scores of factors and the incidence of burnout. Besides that, it was observed as well that it is possible to establish a connection between the organizational health and the syndrome of burnout, this research main objective / Estudamos sobre a sa?de organizacional e a s?ndrome de burnout em profissionais de educa??o e sa?de, objetivando estabelecer uma rela??o entre esses dois construtos te?ricos. A pesquisa foi realizada em tr?s escolas p?blicas de ensino m?dio e em tr?s hospitais, dois p?blicos e um hospital militar. Dos question?rios aplicados nos dois tipos de organiza??es, obtivemos 168 question?rios v?lidos para investiga??o da incid?ncia da s?ndrome de burnout, sendo que 83 nos hospitais e 85 nas escolas. Trabalhamos com amostras acidentais, embora tenha sido planejada a propor??o de profissionais, visando reproduzir as caracter?sticas da popula??o. Nas escolas as amostras foram planejadas com professores. Nos hospitais, com m?dicos, enfermeiros, auxiliares de enfermagem, nutricionistas, psic?logos, odont?logos e assistentes sociais. Para aferi??o da s?ndrome de burnout, utilizamos o Invent?rio de Burnout de Maslach (MBI), acrescido de uma ficha sociodemogr?fica. Para an?lise de sa?de organizacional, utilizamos entrevistas semi-estruturadas com pessoas-chave das organiza??es, diretores, coordenadores pedag?gicos e pessoas envolvidas com o setor de recursos humanos, utilizando um roteiro baseado nos indicadores. Somente entre os hospitais encontramos diferen?as estatisticamente significavas em rela??o aos escores dos fatores e a incid?ncia de burnout. Al?m disso, observamos tamb?m que ? vi?vel estabelecer a rela??o entre a sa?de organizacional e a s?ndrome de burnout, principal objetivo da pesquisa
580

Daň z příjmů fyzických osob a její redistribuční dopady / Individual income tax and its redistributive impacts

Kavková, Petra January 2011 (has links)
This thesis analyzes the redistributive impact of the individual income tax over the time. The aim is to analyze and compare the tax burden on taxpayers and the degree of progressivity from 2000 to 2010. During those ten years, several significant changes, regarding the components of individual income tax, had occurred. In particular, there was transition from the standard deduction from the tax base to the tax credits in 2005 and 2005, and then in 2008 a change in the tax base as so-called super-gross wage, the introduction of linear 15% tax rate and in the case of the social insurance to the introduction of the maximum assessment base for employees. In this thesis the requirements for personal income tax are described at first, with focus on equity and related redistribution and measurements of the tax progressivity. The second part of this thesis describes the various structural elements of the personal income tax and their changes in individual years. The final section contains both analysis of the impact of these changes on the average tax rate for individual taxpayers and the degree of progressivity and then comparison of the average tax rate and the degree of progressivity in these ten years.

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