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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.
91

Shared Mobility Optimization in Large Scale Transportation Networks: Methodology and Applications

January 2018 (has links)
abstract: Optimization of on-demand transportation systems and ride-sharing services involves solving a class of complex vehicle routing problems with pickup and delivery with time windows (VRPPDTW). Previous research has made a number of important contributions to the challenging pickup and delivery problem along different formulation or solution approaches. However, there are a number of modeling and algorithmic challenges for a large-scale deployment of a vehicle routing and scheduling algorithm, especially for regional networks with various road capacity and traffic delay constraints on freeway bottlenecks and signal timing on urban streets. The main thrust of this research is constructing hyper-networks to implicitly impose complicated constraints of a vehicle routing problem (VRP) into the model within the network construction. This research introduces a new methodology based on hyper-networks to solve the very important vehicle routing problem for the case of generic ride-sharing problem. Then, the idea of hyper-networks is applied for (1) solving the pickup and delivery problem with synchronized transfers, (2) computing resource hyper-prisms for sustainable transportation planning in the field of time-geography, and (3) providing an integrated framework that fully captures the interactions between supply and demand dimensions of travel to model the implications of advanced technologies and mobility services on traveler behavior. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2018
92

Metodologia para detecção e localização de áreas de defeitos de alta impedância com a presença da geração distribuída

Ledesma, Jorge Javier Giménez 12 February 2017 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-18T13:24:16Z No. of bitstreams: 1 jorgejaviergimenezledesma.pdf: 4002237 bytes, checksum: 74e94889e9e4afbc4463915274bf7e33 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-18T14:07:36Z (GMT) No. of bitstreams: 1 jorgejaviergimenezledesma.pdf: 4002237 bytes, checksum: 74e94889e9e4afbc4463915274bf7e33 (MD5) / Made available in DSpace on 2017-05-18T14:07:36Z (GMT). No. of bitstreams: 1 jorgejaviergimenezledesma.pdf: 4002237 bytes, checksum: 74e94889e9e4afbc4463915274bf7e33 (MD5) Previous issue date: 2017-02-12 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho propõe o desenvolvimento de modelos e métodos numéricos, baseados em redes neurais artificiais, para a detecção e localização de áreas com defeitos de alta impedância em sistemas de distribuição. De forma paralela, também é avaliada a eficiência da utilização de diferentes tipos de formas de medição de dados no desempenho do método, que é implementada através de duas etapas. A primeira etapa consiste na adaptação de um programa existente para cálculo de faltas, tendo como objetivo gerar de forma aleatória vários tipos de defeitos, assim como a localização dos mesmos. A metodologia de cálculo de defeitos foi desenvolvida utilizando as equações de injeção de correntes em coordenadas retangulares. Neste programa, também serão considerados os modelos de carga variantes com a tensão durante os defeitos e modelos de diversas gerações distribuídas, convencionais e não convencionais. Em seguida, foi desenvolvido e implementado um método baseado em redes neurais artificiais, para detecção e identificação de faltas, assim como para estimar a localização de faltas em um sistema de distribuição. Esta rede neural possui como entrada módulos e ângulos das tensões e correntes do sistema elétrico, obtidas através das medições fasoriais dos PMUs e/ou IEDs. As saídas da rede neural correspondem à detecção e localização de áreas de defeitos. O método proposto foi desenvolvido no ambiente MatLab® e com o intuito de avaliar sua eficiência, foi testado em alguns sistemas IEEE e em um sistema real. Os resultados obtidos dos estudos são apresentados sob a forma de tabelas e gráficos com suas respectivas acurácias, números de neurônios e as diferentes configurações adotadas. / This work proposes the development of numerical models and methods, based on artificial neural networks, for the detection and localization of high impedance faults in distribution systems. In parallel, the efficiency is also evaluated using different types of measurement data techniques in the performance of the method, which is implemented through two steps. The first step consists in the adaptation of an existing program for calculation of faults, aiming to generate randomly several types of faults, as well as their location. The faults calculation methodology was developed using current injection equations in rectangular coordinates. In this program the models of load variation with the voltage during the faults and a variety of conventional and unconventional models for distributed generation, are considered. Next, a method based on artificial neural networks is developed and implemented for the detection and identification of faults, as well as to estimate the fault location within a distribution system. The neural network inputs are modules and angles of the voltages and currents of the electrical system, obtained from the PMUs and / or IEDs. The outputs of the neural network correspond to the detection and location of faults. The proposed method was developed in MatLab® environment and tested in some IEEE systems and in a real system in order to evaluate its efficiency. The results obtained from the studies was presented in the form of tables and graphs with their respective accuracy, numbers of neurons and the different configurations adopted.
93

Problemas de roteamento de veículos com dependência temporal e espacial entre rotas de equipes de campo / Vehicle routing problems with temporal and spatial dependencies among routes

Dhein, Guilherme 26 August 2016 (has links)
This thesis presents two new routing problems, both with objective functions focused on relative positioning of teams during the routing horizon. The relative positioning results in temporal and spatial dependencies among routes and is quantified with a nonlinear dispersion metric, designed to evaluate the instantaneous distances among teams over a time interval. This metric allows the design of objective functions to approximate teams during routes execution, when minimized, or disperse them, when maximized. Both approximation and dispersion are important routing characteristics in some practical applications, and two new optimization problems are proposed with these opposite objectives. The first one is a variation of the Multiple Traveling Salesman Problem, and its goal is to find a set of tours where the salesmen travel close to each other, minimizing dispersion. A Local Search Genetic Algorithm is proposed to solve the problem. It includes specialized genetic operators and neighborhoods. A new set of benchmark instances is proposed, adapted for the new problem from literature instances. Computational results show that the proposed approach provides solutions with the desired characteristics of minimal dispersion. The second problem is a bi-objective arc routing problem in which routes must be constructed in order to maximize collected profit and dispersion of teams. The maximization of the dispersion metric fosters the scattering of the teams during routing procedure. Usually, profit and dispersion objectives are conflicting, and by using a bi-objective approach the decision maker is able to choose a trade-off between collecting profits and scattering teams. Two solution methods are proposed, a Multi-objective Genetic Algorithm and a Multi-objective Genetic Local Search Algorithm, both specialized in order to exploit the characteristics of the problem. It is demonstrated, by means of computational experiments on a new set of benchmark instances, that the proposed approach provides approximation sets with the desired characteristics. / Esta tese apresenta dois novos problemas de roteamento, ambos com funções objetivo voltadas para o posicionamento relativo das equipes durante o horizonte de roteamento. O posicionamento relativo resulta em uma dependência temporal e espacial entre rotas e é quantificado com uma métrica de dispersão não-linear, projetada para avaliar as distâncias instantâneas entre as equipes ao longo de um intervalo de tempo. Esta métrica permite a concepção de funções objetivo para aproximar as equipes durante a execução das rotas, quando minimizada, ou para dispersá-las, quando maximizada. Tanto a aproximação quanto a dispersão são características importantes de roteamento em algumas aplicações práticas, e dois novos problemas de otimização são propostos com esses objetivos opostos. O primeiro é uma variação do Problema de Múltiplos Caixeiros Viajantes, e seu objetivo é encontrar um conjunto de rotas em que os caixeiros viajam próximos uns dos outros, minimizando a dispersão. Um Algoritmo Genético com Busca Local é proposto para resolver o problema. Ele inclui operadores genéticos e vizinhanças especializados. Um novo conjunto de instâncias é proposto, adaptado para o novo problema de instâncias da literatura. Resultados computacionais mostram que a abordagem proposta proporciona soluções com as características desejadas de dispersão mínima. O segundo problema é um problema de roteamento de arcos biobjetivo em que as rotas devem ser construídas de modo a maximizar o lucro recolhido e o distanciamento entre as equipes. A maximização da métrica promove a dispersão das equipes durante a execução das rotas. Normalmente, os objetivos de lucro e dispersão são conflitantes, e com uma abordagem biobjetivo o tomador de decisão é capaz de avaliar a troca entre a coleta de lucros e a dispersão de equipes. Dois métodos de solução são propostos, um Algoritmo Genético Multiobjetivo e um Algoritmo Genético Multiobjetivo com Busca Local, ambos especializados para explorar as características do problema. É demonstrado, por meio de experimentos computacionais sobre um novo conjunto de instâncias, que a abordagem proposta fornece conjuntos de aproximação com as características desejadas.
94

Petriho sítě pro expertní systémy / Petri nets for expert systems

Million, Pavel January 2010 (has links)
Purpose of this master thesis is description of base parts of expert system with using Petri nets. Attention is mainly concentrate to knowledge base, way of storing knowledge. Next parts are describing main different between production base knowledge for planning or diagnostic expert system from Petri nets view. In this thesis conditions of using Petri nets and way of interpretation knowledge for inference mechanism in planning and diagnostic expert system are described. Using of high level Petri nets and language describing Petri nets structure and behaviour are demonstrated in next part of this thesis.
95

A Combination of Automata and Grammars / A Combination of Automata and Grammars

Kučera, Jiří January 2013 (has links)
V této práci byly zavedeny a studovány nové systémy formálních modelů, zvané stavově synchronizované automatové systémy stupně n . Výpočet je v těchto prezentovaných systémech řízen pomocí slov patřících do konečného řídícího jazyka, kde každé slovo z tohoto jazyka je složeno ze stavů komponent systému. Dále byla v této práci studována výpočetní síla zavedených systémů. Praktické použití zavedených systémů bylo demonstrováno na příkladu z oblasti překladu přirozených jazyků a dále na příkladu z oblasti paralelního překladu.
96

[en] METHODS BASED ON SYNCHRONIZED PHASOR MEASUREMENTS FOR VOLTAGE STABILITY MONITORING / [pt] MÉTODOS BASEADOS EM MEDIÇÕES FASORIAIS SINCRONIZADAS PARA O MONITORAMENTO DA ESTABILIDADE DE TENSÃO

DIOGO CARDOSO LIMA 03 December 2020 (has links)
[pt] O fenômeno associado à estabilidade de tensão se caracteriza pela existência de valores máximos de potência ativa e reativa que podem ser transferidas a uma barra de carga, ou injetada na rede através dos geradores e compensadores síncronos. Sua relevância para o setor elétrico é constantemente reforçada pelo registro de ocorrências de colapsos de tensão em diversos países do mundo e, embora a instabilidade de tensão manifeste-se localmente, suas consequências se refletem na ampla deterioração do sistema. Impulsionado pelo crescente interesse a respeito dos métodos baseados em medições fasoriais sincronizadas para a detecção do máximo carregamento, este trabalho apresenta os principais modelos encontrados na literatura baseados em medições locais e no vasto monitoramento do sistema, com maior ênfase aos métodos de Corsi-Taranto e Circuito Acoplado de Porta-Simples Aprimorado (CAPS Aprimorado). Algumas contribuições são sugeridas ao modelo CAPS Aprimorado tendo em vista sua aplicação ao conjunto de barras de transferência e de geração. Explora-se a utilização dos equivalentes multi-portas como índice de avaliação das condições de estabilidade de tensão, comparando a identificação da barra crítica aos métodos da matriz D e dos autovalores e autovetores. São evidenciadas as principais limitações dos modelos mediante a um conjunto de análises estáticas e dinâmicas, considerando diferentes cenários de carregamento, a sensibilidade dos modelos ao ruído e a resposta dos métodos em face da atuação dos limitadores de sobre-excitação. / [en] The voltage stability phenomenon is characterized by the existence of a maximum active and reactive power that can be transferred to a load bus or injected into the network through the generators and synchronous compensators. Its relevance to the electric power sector is constantly reinforced by the record of occurrences of voltage collapses in several countries around the world. Although the voltage instability manifests itself locally, its consequences is reflected in the wide deterioration of the system. Driven by growing interest in methods based on synchronized phasor measurements for maximum loadability detection, this work presents the main models found in the literature based on local measurements and wide area monitoring, emphasizing the Corsi-Taranto method and Improved Coupled Single-Port Circuit (Improved CAPS). Some contributions are suggested to the Improved CAPS model considering its application to the set of transit and controlled buses. The use of the multi-port equivalents is explored as the evaluation index of voltage stability conditions, comparing the identification of the critical bus to the D matrix method and eigenvalues and eigenvalues method. The main limitations of the models are demonstrated through a static and dynamic studies, as well different loading scenarios, the sensitivity of the models to the noise and the response of the methods when the over-excitation limiters are considered.
97

Hodnocení posturální stability u akvabel / Rating postural stability in synchronized swimming

Koubková, Natálie January 2016 (has links)
Title: Rating postural stability in synchronized swimming Objectives: The aim of the diploma thesis is to detect, with a use of the system Gaitview ® AFA - 50 systém (Foot Scanner), if synchronized swimming has effect on postural stability of synchronized swimmers. Methods: Therotical part of diploma thesis is about synchronized swimming, influence of the aquatic environment, postural stability, stabilization and balance. A sample of 113 female athletes aged 6-35, who were long term synchronized swimmers at competition level, was chosen for this survey. Postural stability of athletes was tested while standing still with open and closed eyes by Gaitview ® AFA-50 system (Foot Scanner). Measured data were processed through Gaitview software, Microsoft Excel 2010 and anaylzed by statistical methods (average percentage, ratio, linear trend). Results: Results confirmed the effect of synchronized swimming on athletes postural stability. The longer are athletes dedicated to synchronized swimming the better is postural stability. From the age of 15 years and after 9 years of experience in synchronized swimming postural stability was shown to be better without access to visual information than with it. In the youngest category there is the biggest difference in postural stability while standing still with...
98

Contribution à l'étude de la qualité de l'audit légal : évaluation de la pertinence des spécificités réglementaires françaises / Contribution to the study of audit quality : evaluation of the suitability of french regulatory features

Chihi, Hamida 03 March 2014 (has links)
La promulgation de la loi de la sécurité financière (LSF) en 2003 a modifié l’architecture institutionnelle et la pratique d’audit en France. Au travers l’adjonction de nouvelles règles imposées par cette loi aux spécificités persistantes depuis 1966 comme le co-commissariat aux comptes et la durée du mandat de six ans, le marché d’audit se montre unique. Cette recherche examine l’impact de cette fusion réglementaire sur la qualité et le coût de l’audit en France. En se basant sur un échantillon composé par 888 observations du SBF 250 sur la période 2005-2010, nous avons révélé l’apport de la rotation des équipes signataires dans la restriction de la discrétion managériale. Outre son avantage dans la promotion de la qualité de l’audit, ce dispositif favorise la négociation à la baisse des honoraires d’audit. Nous avons aussi souligné l’évolution sous forme parabolique de la composante discrétionnaire sur la durée de mandat. En effet, la qualité de l’audit est inférieure pendant la première et la dernière phase de l’engagement. Ce postulat renvoie au renforcement de la compétence dans le temps et l’érosion de l’esprit critique à la fin du mandat. Le décalage, issu de la fusion réglementaire, favorise le maintien du niveau de la qualité élevé sur le marché français. L’association des deux équipes avec des durées auditeur-audité différentes est une contrainte à la discrétion managériale. Toutefois, ce décalage ne doit pas être excessif pour limiter la domination du plus ancien. Cet inconvénient du régime du co-commissariat aux comptes s’est trouvé limité sur le marché français. Nos résultats confirment son efficacité, essentiellement dans le cas d’un collège composé par deux Big 4. / In 2003, the promulgation of the financial security act (LSF) has changed the institutional architecture and audit practice in France. Through the addition of new rules imposed by this act to the persistent specificities since 1966 as the joint audit and tenure of six years, the audit market shows unique. This research examines the impact of this regulatory merger on the quality and the cost of the audit in France. Based on a sample composed by 888 observations of the SBF 250 over the 2005-2010, we found the contribution of rotation audit partners in restricting managerial discretion. Besides its advantage in promoting audit quality, this device supports the negotiation of lower audit fees. We also emphasized the evolution in the parabolic form of the discretionary accruals over tenure. Indeed, the audit quality is lower during the first and last phase of the engagement. This assumption refers to strengthening the skills over time and erosion of critical appraisal at the end of audit tenure. The shift from regulatory fusion helps to maintain the level of high quality on the French market. The combination of the two teams with different listener-audited tenures is a constraint to managerial discretion. However, this shift should not be excessive to limit the oldest’ domination. This drawback of the system of joint audits is limited in the French market. Our results confirm its effectiveness, mainly in the case of two Big 4.
99

Contribution au renvoi de tension et à la reconstitution du réseau. Identification des paramètres d'un réseau. Estimation des flux rémanents dans un transformateur / Contribution to the power plant re-energization and the network restoration. Parameters identification of a network. Estimation of the residual flux in a transformer.

Cavallera, Didier 03 November 2011 (has links)
Lors de la réalimentation des auxiliaires d’une tranche nucléaire, l’étape la plus à risque est la remise sous tension brusque du transformateur à cause des surtensions. Dans un soucis perpétuel d’amélioration de la modélisation de ces transitoires, les modèles et techniques doivent évoluer. Le but de ces travaux de thèse est de proposer de nouvelles méthodologies permettant d’évaluer les paramètres mal connus de la modélisation. Lors des mises sous tension des lignes électriques, une méthodologie s’appuyant sur l’identification (optimisation ou techniques issues du traitement du signal) permet de déterminer les paramètres variables de la modélisation. Cependant, un des paramètres influents pour les surtensions est le flux rémanent. Face aux problèmes actuels rencontrés pour l’estimer (méthode non directe, dérive, …), une nouvelle méthode basée sur la mesure des flux de fuites du circuit magnétique est proposée. Des mesures réelles utilisant des capteurs de technologie « fluxgate » sont réalisées et permettent d’estimer le flux rémanent. / During the re-energization of the auxiliaries of a nuclear power plant, the more dangerous step is the re-energization of the power transformer, because of the temporary overvoltages. In order to improve the transient modeling, models and techniques may be improved. The purpose of this thesis is to suggest new methodologies to identify the uncertain parameters of the model. When the line re-energization occurs, an identification methodology (optimization or methods using signal processing) allows determining the model variable parameters. However, one of the most important parameters in the overvoltages is the residual flux. Given the actual problems found on estimation strategies (no direct method, derivation,…), a new method established for the leakage flux measurement of the magnetic circuit is proposed. Real measurements using « fluxgate » technology sensors were realized, permitting to estimate the residual flux.
100

On model-checking pushdown systems models / Vérification de modèles de systèmes à pile

Pommellet, Adrien 05 July 2018 (has links)
Cette thèse introduit différentes méthodes de vérification (ou model-checking) sur des modèles de systèmes à pile. En effet, les systèmes à pile (pushdown systems) modélisent naturellement les programmes séquentiels grâce à une pile infinie qui peut simuler la pile d'appel du logiciel. La première partie de cette thèse se concentre sur la vérification sur des systèmes à pile de la logique HyperLTL, qui enrichit la logique temporelle LTL de quantificateurs universels et existentiels sur des variables de chemin. Il a été prouvé que le problème de la vérification de la logique HyperLTL sur des systèmes d'états finis est décidable ; nous montrons que ce problème est en revanche indécidable pour les systèmes à pile ainsi que pour la sous-classe des systèmes à pile visibles (visibly pushdown systems). Nous introduisons donc des algorithmes d'approximation de ce problème, que nous appliquons ensuite à la vérification de politiques de sécurité. Dans la seconde partie de cette thèse, dans la mesure où la représentation de la pile d'appel par les systèmes à pile est approximative, nous introduisons les systèmes à surpile (pushdown systems with an upper stack) ; dans ce modèle, les symboles retirés de la pile d'appel persistent dans la zone mémoire au dessus du pointeur de pile, et peuvent être plus tard écrasés par des appels sur la pile. Nous montrons que les ensembles de successeurs post* et de prédécesseurs pre* d'un ensemble régulier de configurations ne sont pas réguliers pour ce modèle, mais que post* est toutefois contextuel (context-sensitive), et que l'on peut ainsi décider de l'accessibilité d'une configuration. Nous introduisons donc des algorithmes de sur-approximation de post* et de sous-approximation de pre*, que nous appliquons à la détection de débordements de pile et de manipulations nuisibles du pointeur de pile. Enfin, dans le but d'analyser des programmes avec plusieurs fils d'exécution, nous introduisons le modèle des réseaux à piles dynamiques synchronisés (synchronized dynamic pushdown networks), que l'on peut voir comme un réseau de systèmes à pile capables d'effectuer des changements d'états synchronisés, de créer de nouveaux systèmes à piles, et d'effectuer des actions internes sur leur pile. Le problème de l'accessibilité étant naturellement indécidable pour un tel modèle, nous calculons une abstraction des chemins d'exécutions entre deux ensembles réguliers de configurations. Nous appliquons ensuite cette méthode à un processus itératif de raffinement des abstractions. / In this thesis, we propose different model-checking techniques for pushdown system models. Pushdown systems (PDSs) are indeed known to be a natural model for sequential programs, as they feature an unbounded stack that can simulate the assembly stack of an actual program. Our first contribution consists in model-checking the logic HyperLTL that adds existential and universal quantifiers on path variables to LTL against pushdown systems (PDSs). The model-checking problem of HyperLTL has been shown to be decidable for finite state systems. We prove that this result does not hold for pushdown systems nor for the subclass of visibly pushdown systems. Therefore, we introduce approximation algorithms for the model-checking problem, and show how these can be used to check security policies. In the second part of this thesis, as pushdown systems can fail to accurately represent the way an assembly stack actually operates, we introduce pushdown systems with an upper stack (UPDSs), a model where symbols popped from the stack are not destroyed but instead remain just above its top, and may be overwritten by later push rules. We prove that the sets of successors post* and predecessors pre* of a regular set of configurations of such a system are not always regular, but that post* is context-sensitive, hence, we can decide whether a single configuration is forward reachable or not. We then present methods to overapproximate post* and under-approximate pre*. Finally, we show how these approximations can be used to detect stack overflows and stack pointer manipulations with malicious intent. Finally, in order to analyse multi-threaded programs, we introduce in this thesis a model called synchronized dynamic pushdown networks (SDPNs) that can be seen as a network of pushdown processes executing synchronized transitions, spawning new pushdown processes, and performing internal pushdown actions. The reachability problem for this model is obviously undecidable. Therefore, we compute an abstraction of the execution paths between two regular sets of configurations. We then apply this abstraction framework to a iterative abstraction refinement scheme.

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