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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.
421

Análise das forças de contato e comportamento dinâmico de rodeiro ferroviário. / Analysis of creep forces and the dynamic behavior of wheelset.

Almeida, Fabio Cardoso 26 May 2006 (has links)
Sistemas dinâmicos ferroviários são modelados levando-se em consideração as forças de contato roda trilho. As equações de movimento são fortemente influenciadas pela determinação dessas forças, o que requer o conhecimento da mecânica de contato, ferramenta imprescindível na previsão do comportamento de uma composição ferroviária. O rodeiro é responsável por receber as excitações na forma de irregularidades e imperfeições da via e transferi-la para a suspensão primária. A proposta dessa dissertação consiste em realizar simulações no domínio do tempo, da resposta do comportamento dinâmico do rodeiro ferroviário de 2 graus de liberdade. O modelo matemático equivalente é desenvolvido. A rigidez de contato e a conicidade são linearizados em torno de um ponto de operação, próximo ao centro da via. É apresentada a influência da velocidade na estabilidade para o modelo linearizado e para a conicidade variando de 0.1 a 1.0. Os respectivos modos de vibrar também são apresentados. Em seguida, o modelo matemático não linear do rodeiro ferroviário é gerado por software especializado na criação de sistemas de multicorpos, VAMPIRE, que permite a criação das equações de movimento através da topologia do sistema. O modelo é criado seguindo a proposta do benchmarck apresentada pela International Association of Vehicle System Dynamics (IAVSD). O rodeiro recebe uma força lateral crescente que se estabiliza em 20kN. O rodeiro é excitado com a aplicação de outra força lateral a uma taxa de 50kN/s até o descarrilamento. As forças longitudinais, laterais que aparecem no contato, o ângulo do plano de contato, ângulo de yaw e afastamento lateral são comparados com o benchmarck e outros autores. / Railway dynamics systems are modeled regarding the creep forces between wheel-rail. The equations of movement are strongly influenced by these forces, what requests the knowledge of the theory in mechanical of contact, necessary tool to foresee the behavior of a railway vehicle. The wheelset is responsible by receiving the perturbations of irregularities and transfer them to the primary suspension. A railway vehicle is composed by primary and secondary suspensions. The proposal is based on performing simulations in the time domain, dynamic mresponse of a railway wheelset of two degrees of freedom. The mathematical model is developed. The stiffness of contact and conicity are linearized around an operation point, near to track center. The influence of speed is determined to linearized model and to a range of 0.1 to 1.0 in the conicity. The eigenvectors are presented. In the following, the non linear model of the wheelset is generated using a specialized package of multi body system, VAMPIRE. The package creates equations of movement after the generation of the topology. The non linear mathematical model are defined by the benchmark proposed by International Association of Vehicle System Dynamics (IAVSD). The wheelset is submitted to 20kN at the rail level. In a second case, the wheelset is submitted to a rate of 50kN/s of lateral force until derailing. The determined longitudinal and lateral forces on contact, yaw angle and displacement of the center of gravity of the wheelset, contact angle are compared with the benchmark results and other authors.
422

A rigid body and a master-master contact formulation for multibody railway applications. / Uma formulação de corpo rígido e contato master-master para aplicações ferroviárias multicorpos.

Refachinho de Campos, Paulo Roberto 13 September 2018 (has links)
In computer simulation the term \"multibody system\" is usually employed to describe a system of interconnected bodies. Several examples of multibody systems can be found in railway engineering. A wheelset interacting with a track through a contact interface is just one example of practical interest. Modelling mechanical systems in a virtual environment contributes to the understanding of subjects such as dynamic behaviour, stability, durability, wear, fatigue, etc. In the context of a rigid-flexible multibody system mathematically described by a weak-form, the purpose of the present work is to evaluate the contributions due to rigid bodies considering their contact interactions. Inertial contributions due to distribution of mass of a rigid body are fully developed, considering a general pole position associated with a single node, representing a rigid body element. Rodrigues rotation parameters are used to describe finite rotations, by an updated Lagrangian description. Then, the so-called master-surface to master-surface contact formulation is adapted to be used in conjunction with the rigid body element and flexible bodies, aiming to consider their interaction in a rigid-flexible multibody environment. New surface parameterizations are proposed to establish contact pairs, permitting pointwise interaction in a frictional scenario. The proposed formulation is used to represent mechanical systems from different contexts, including a numerical example of the wheel-rail contact interface. The obtained results show the robustness and applicability of the methods. / Em simulação computacional o termo \"sistema multicorpos\" é usualmente empregado para descrever um sistema de corpos interconectados. Diversos exemplos de sistemas multicorpos podem ser encontrados no campo da engenharia ferroviária. Um rodeiro interagindo com a via através de uma interface de contato é apenas um dos exemplos de interesse prático. A modelagem de sistemas mecânicos em um ambiente virtual contribui para o entendimento de assuntos como comportamento dinâmico, estabilidade, durabilidade, desgaste, fadiga, etc. No contexto de um sistema multicorpos rígido-flexível descrito matematicamente por uma forma fraca, o propósito do presente trabalho é avaliar as contribuições devido à presença de corpos rígidos considerando interações de contato. Contribuições inerciais devido à distribuição de massa do corpo rígido são desenvolvidas e apresentadas em totalidade, considerando um polo genérico associado a um único nó, representando o corpo rígido. Parâmetros de rotação de Rodrigues são usados para descrever rotações finitas em uma descrição Lagrangiana atualizada. A formulação de contato master-surface to master-surface é adaptada para ser usada em conjunto com o elemento de corpo rígido e corpos flexíveis, estabelecendo a interação entre esses corpos em um ambiente de simulação multicorpos. Novas parametrizações de superfícies de contato são desenvolvidas para estabelecer os pares de contato, assumindo-se interações pontuais, em um cenário de contato com atrito. A formulação proposta é usada para representar sistemas mecânicos em diferentes contextos, incluindo um exemplo numérico do caso de contato roda-trilho. Os resultados obtidos mostram a robustez e a aplicabilidade dos métodos.
423

Komunikační strategie společnosti RegioJet. / Communication strategy of RegioJet

Frysová, Pavla January 2011 (has links)
The aim of the Master's Thesis is to analyze communication strategy of the Czech passenger train operator, RegioJet. The theoretical part of the thesis focuses on marketing mix of the company operating in the sector of transport services and on marketing communication as one of the tools of marketing mix. Further theoretical chapters deal with six forms of communication mix and new trends of marketing communication with a focus on digital marketing. The first chapter of the practical part characterizes the passenger rail transport market in the Czech Republic and introduces the company, RegioJet. Based on the evaluation of information from primary and secondary sources, the communication mix of the company is analyzed and the comparison with communication activities of competitors is made. The last chapter provides an evaluation of communication strategy with emphasis on its strengths and weaknesses and the recommendations to the communication strategy are suggested.
424

Design urbain et tramway : recherche méthodologique autour de cinq villes moyennes françaises et tchèques / Urban Design and Light Rail : Methodological Research around Five French and Czech Medium-sized Cities

Zelezny, Richard 15 December 2016 (has links)
Cette thèse s’inscrit dans le champ de l’aménagement urbain orienté vers le transport collectif (TC). Elle focalise sur deux contextes culturels différents, celui de la République tchèque et celui de la France, au sein desquels, néanmoins, les enjeux de promouvoir les TC sont partagés aujourd’hui, dans le cadre de la recherche d’un développement urbain durable. A l’échelle de quartier urbain, le travail s’intéresse, à part la densité et la mixité urbaine, plus particulièrement à des caractéristiques de l’accessibilité piétonne aux stations. A cette fin, des démarches originales d’appréciation qualitative et quantitative sont proposées. Les points forts et les points faibles marqués dans chacun des contextes ainsi que les potentiels de transférabilité réciproque de bonnes pratiques sont enfin considérés / My work explores transit-oriented development within two different cultures, France and the Czech Republic, which nevertheless have significant factors in common with regard to the goal of promoting the modal share of mass transit from a sustainable urban development perspective. Besides the basic urban variables, such as density and functional mix, our work attempts to explore characteristics of pedestrian accessibility, all these at the neighbourhood scale around the stations. For the appreciation, original qualitative and quantitative approach to the appreciation are proposed. The strengths and weaknesses on each side and the potential for reciprocal transfer of best-practices are finally considered
425

L'agencement des grandes gares historiques pour le marché ferroviaire européen : analyse comparée de l'intégration des principes concurrentiels dans l'aménagement et la gestion des gares de London St Pancras, Paris Nord et Milano Centrale / Agencing historic major railway stations for the EU rail market : a comparative analysis of the embeddedness of competition principles into the planning and the management of London St Pancras, Paris Nord and Milano Centrale stations

Riot, Etienne 06 November 2015 (has links)
Cette thèse en urbanisme et aménagement analyse les interactions entre les grandes gares historiques et les logiques du marché ferroviaire européen. L'interférence entre les principes du marché et ceux de l'aménagement des lieux de transport invite à mobiliser de nouveaux concepts pour présenter l'évolution des grandes gares historiques dans une perspective contemporaine. Pour ce faire, il est proposé d'utiliser les méthodes de la sociologie économique des marchés et de comparer trois terrains: la gare de St Pancras à Londres, la gare du Nord à Paris et la gare centrale de Milan. Dans un premier temps, la thèse présente les différentes formes d'encastrement des principes concurrentiels (historiques, culturels, institutionnels et sociaux) dans l'aménagement des gares, en prenant le parti d'une analyse diachronique au long cours de chacun des cas. Dans un second temps, la thèse détaille les agencements marchands à l'œuvre - selon le modèle analytique synthétisé par Michel Callon. Trois agencements marchands ont été identifiés qui correspondent à trois formes d'économisation de l'objet-gare: l'agencement de l'infrastructure de transport, l'agencement du bien immobilier, l'agencement de la place marchande. Cette thèse démontre combien la rationalisation économique des gares formate autant qu'elle est formatée par ces infrastructures. In fine, elle invite à considérer les processus d'économisation de l'espace pour en comprendre l'aménagement qui en résulte / This research in urban planning and studies analyses the interaction between major historic railway stations and the logics of the European rail market. Interferences between the market principles and those of the planning and the management of transport places are an issue that requires new concepts to understand how do major historic railway stations evolve in our time. This research applies mehods developed in the field of economic sociology, especially on markets, and compares three cases: London St Pancras, Paris Nord and Milano Centrale stations. The first part of this dissertation presents the different forms of embeddedness (historical, cultural, institutional and social) that implement competition principles into the planning and the management of railway stations. A long-term diachronical approach of each case is presented. The second part of the dissertation uses the theoretical approach of market agencing developed by Michel Callon in the fields of economic sociology and of science and technology studies. Three ways of agencing railway stations are analysed: agencing the essential facility, agencing the real estate asset and agencing the “market square facility” – a new kind of market square especially developed in transit places. This dissertation shows how economic rationalisation frames railway stations as far as those infrastructures frame this economic rationalisation in return. It invites us to consider the process of economisation of space as a key part of planning practices
426

Estudo de pontos promissores para instalação de terminais intermodais rodo-ferroviários de contêineres no Estado de São Paulo / Study of promising points to install road-rail intermodal container terminals in the state of São Paulo

Renato Pereira Tiago 12 August 2002 (has links)
Este trabalho visa identificar, a partir de um levantamento de dados dos fluxos de cargas conteinerizadas e custos operacionais de transporte, os locais mais promissores para a instalação de futuros terminais intermodais de carga rodo-ferroviários, com auxílio de um Sistema de Informações Geográficas (TransCAD), objetivando a redução dos custos e otimização das operações logísticas envolvidas na rede de transportes do estado de São Paulo. Simulações são feitas para a instalação de até dez terminais intermodais rodo-ferroviários em pontos estratégicos do interior do Estado, considerando-se duas condições: a primeira com um terminal existente só em Santos e todos os pontos candidatos escolhidos pelo modelo de localização das p-medianas do TransCAD e, a segunda, considerando-se, além de Santos, os oito terminais intermodais já existentes no Estado. Apresenta-se uma análise dos custos de rede e os mapas temáticos de áreas de influência de cada uma das soluções obtidas pelo modelo. Os resultados são comparados com o trabalho de TONDO (1992). Conclui-se que as soluções encontradas através de um novo enfoque de modelagem do problema, são significativamente diferentes daqueles propostos por TONDO (1992). / Based on a data collection of containerized cargo flows and operational transport costs, this study has the objective of identifying promising points to install future road-rail intermodal container terminals, using a Geographic Information System (TransCAD) and the objective function of reducing costs and optimising logistic operations on the transport network of the state of São Paulo. Simulations are presented for the instalation of up to ten road-rail intermodal terminals at strategic locations in the interior of the State, considering two conditions: the first one, with only one terminal placed at the port of Santos and all the candidate points beeing chosen by the p-median location model of TransCAD, and the second one, considering Santos and the other eight existing intermodal terminals in the State. An analysis of the network costs and thematic maps of the influence areas of each solution are presented. The results are compared with the study by TONDO (1992). It is concluded that the solutions obtained by this new modeling focus of the problem, are considerably different from the ones obtained by TONDO (1992).
427

Simulating Heavy Vehicles on Australian Rural Highways

Fry, John January 2005 (has links)
The major purpose of this thesis is to offer a detailed look at the development of two models used to assist in the detailed study of Australian two lane two way highways with particular reference to heavy vehicles. The first model governs the acceleration behaviour of vehicles on upgrades and downgrades. The second model controls overtaking manoeuvres on two lane two way highways where movement into the lane of oncoming traffic is required. Both models are implemented through a suite of transport simulation modelling software called Paramics.
428

Diagnostic des systèmes à l'aide d'observateurs à mémoire finie. Application au Common Rail.

Graton, Guillaume 14 December 2005 (has links) (PDF)
L'objectif de ce travail a été de proposer une méthode de détection de défaut sur le système d'injection directe à haute pression (le système Common Rail) mis en place sur les véhicules Diesel. L'importance de l'implémentation d'une procédure de détection de défauts a été mise en évidence grâce à la description des enjeux (baisse de la consommation, diminution des émissions polluantes et sonores, augmentation des performances) et des contraintes liées au Common Rail (haute pression, haute fréquence, lubrification par le gasoil, usinage de haute précision, respect des normes EURO, ...) mais aussi à travers un listing des pannes pouvant survenir sur le Common Rail. Un état de l'art sur les différentes méthodes de diagnostic des systèmes a permis de dégager une méthode de détection de défaut répondant aux performances attendues (détection du défaut naissant, rapidité de détection, isolation et caractérisation des défauts détectés ainsi que minimiser les fausses alarmes et les mauvaises détections). Après une étude approfondie (propriétés,<br />formulations séquentielles et étude de sensibilité) de la méthode de détection choisie (observateurs<br />à mémoire finie) et une modélisation du comportement des différents organes du Common Rail, l'algorithme de détection a été testé sur trois modélisations différentes du système Common Rail.<br />De plus, la comparaison entre l'observateur à mémoire finie et un observateur de Luenberger et un<br />filtre de Kalman ont permis d'apprécier le degré de robustesse des résidus. Dans l'ensemble, les résultats obtenus permettent de conclure sur la bonne détection des défauts actionneurs et capteurs.
429

Paramétrisation et classification de signaux en contrôle non destructif. Application à la reconnaissance des défauts de rails par courants de Foucault

Oukhellou, Latifa 04 July 1997 (has links) (PDF)
Le travail présenté dans ce mémoire traite d'un dispositif embarqué de détection et de reconnaissance des défauts de rail débouchants. Une structure multicapteur à courants de Foucault permettant le contrôle non destructif de l'intégrité des rails en voie, sans contact et en condition d'exploitation commerciale est détaillée dans le premier chapitre. Les principales options de conception (mesures différentielles, bi-fréquences, blindages...) y sont décrites, et validées a posteriori par des essais sur site dans des conditions de mesure réelles. Une liste des classes de défauts détectables par le capteur a été établie (fissures, écaillages...) ainsi qu'une base de données représentative du site pour la mise au point des traitements haut niveau. La première phase des traitements concerne le mode de représentation des signaux complexes issus du capteur. Cette paramétrisation doit posséder un fort potentiel descriptif tout en restant insensible à certaines opérations sur les signaux définies comme des invariants du problème (retournement, homothéties, lift-off). Une procédure originale de paramétrisation des signatures dénommée "Descripteurs de Fourier Modifiés", a été mise au point et comparée à des paramétrisations de type autorégressive. Sur l'ensemble des paramètres d'une signature, une sélection doit ensuite être effectuée en termes de pertinence à la discrimination entre classes. Une méthode d'ordonnancement par orthogonalisation et des méthodes séquentielles constructive et destructive pour le classement des paramètres sont comparées. Différents critères d'arrêt permettent de choisir le nombre réduit de paramètres retenus; des résultats de mise en oeuvre sur la base de données de ces différentes méthodes sont présentés. Le dernier chapitre de ce mémoire traite de la classification neuronale supervisée à l'aide de réseaux de type perceptron multicouche ou de réseaux à fonctions radiales de base. Pour ces deux types de réseaux, des approches globales de classification (discrimination des K classes simultanément) et des approches par partition (problème de classification initial décomposé en sous-problèmes de classification) sont exposées. Des performances de classification sont données pour les deux approches et nous montrons la supériorité de l'approche par partition dans notre application en relation avec la faible dimension de la base de données.
430

Reconfiguration des réseaux de transport et Renouveau urbain. L'enjeu d'un urbanisme orienté vers le rail

Leysens, Thomas 28 September 2011 (has links) (PDF)
La consommation d'espace engendrée par l'étalement urbain doit être limitée dans le cadre d'un développement urbain durable. Cet étalement urbain est entretenu, pour partie, par la dépendance automobile. Il convient donc de s'interroger sur les possibilités de reconfigurer les réseaux et l'espace pour développer un renouveau urbain. La densification et l'urbanisme orienté vers le rail, et plus largement les transports collectifs, apparaissent comme des solutions pertinentes pour répondre à ces enjeux, notamment en mobilisant le potentiel représenté par les friches ferroviaires. Cet objectif demande une coordination des transports et de l'usage du sol, qui doit s'appuyer sur une observation croisée foncier/transports. C'est dans cette optique qu'ont été développés des outils d'aide à la décision pour les acteurs de l'aménagement, en vue de favoriser le développement d'un urbanisme orienté vers le rail, notamment dans le cadre du projet franco allemand BahnVille 2.

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