995 resultados para intermodal transportation problem
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O aumento da concentração de gases de efeito estufa na atmosfera levou a uma preocupação de como se reduzir as emissões destes gases. Desta preocupação surgiram instrumentos de regulação a fim de reduzir ou controlar os níveis de poluição. Dentro deste contexto, esta pesquisa analisou o setor de transportes de cargas, com ênfase no transporte de soja. No Brasil, o setor de transportes é um dos principais responsáveis pelas emissões de gases de efeito estufa provenientes da queima de combustíveis fósseis. No setor de transportes, as emissões diferem entre os modais, sendo que as ferrovias e hidrovias poluem menos que as rodovias. Desta forma, simulou-se por meio de um modelo de programação linear se a adoção de medidas regulatórias sobre as emissões de CO2 traria uma alteração no uso das ferrovias e hidrovias. Uma das constatações, ao se utilizar o modelo de Minimização de Fluxo de Custo Mínimo para o transporte de soja em 2013, foi que a capacidade de embarque nos terminais ferroviários e hidroviários desempenha um papel fundamental na redução das emissões de CO2. Se não houver capacidade suficiente, a adoção de uma taxa pode não provocar a redução das emissões. No caso do sistema de compra e crédito de carbono, seria necessária a compra de créditos de carbono, numa situação em que a capacidade de embarque nos terminais intermodais seja limitada. Verificou-se, ainda, que melhorias na infraestrutura podem desempenhar um papel mitigador das emissões. Um aumento da capacidade dos terminais ferroviários e hidroviários existentes, bem como o aumento da capacidade dos portos, pode provocar a redução das emissões de CO2. Se os projetos de expansão das ferrovias e hidrovias desenvolvidos por órgãos governamentais saírem do papel, pode-se chegar a uma redução de pouco mais de 50% das emissões de CO2. Consideraram-se ainda quais seriam os efeitos do aumento do uso de biodiesel como combustível e percebeu-se que seria possível obter reduções tanto das emissões quanto do custo de transporte. Efeitos semelhantes foram encontrados quando se simulou um aumento da eficiência energética. Por fim, percebeu-se nesta pesquisa que a adoção de uma taxa não traria tantos benefícios, econômicos e ambientais, quanto a melhoria da infraestrutura logística do país.
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Mode of access: Internet.
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Mode of access: Internet.
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With the advent of peer to peer networks, and more importantly sensor networks, the desire to extract useful information from continuous and unbounded streams of data has become more prominent. For example, in tele-health applications, sensor based data streaming systems are used to continuously and accurately monitor Alzheimer's patients and their surrounding environment. Typically, the requirements of such applications necessitate the cleaning and filtering of continuous, corrupted and incomplete data streams gathered wirelessly in dynamically varying conditions. Yet, existing data stream cleaning and filtering schemes are incapable of capturing the dynamics of the environment while simultaneously suppressing the losses and corruption introduced by uncertain environmental, hardware, and network conditions. Consequently, existing data cleaning and filtering paradigms are being challenged. This dissertation develops novel schemes for cleaning data streams received from a wireless sensor network operating under non-linear and dynamically varying conditions. The study establishes a paradigm for validating spatio-temporal associations among data sources to enhance data cleaning. To simplify the complexity of the validation process, the developed solution maps the requirements of the application on a geometrical space and identifies the potential sensor nodes of interest. Additionally, this dissertation models a wireless sensor network data reduction system by ascertaining that segregating data adaptation and prediction processes will augment the data reduction rates. The schemes presented in this study are evaluated using simulation and information theory concepts. The results demonstrate that dynamic conditions of the environment are better managed when validation is used for data cleaning. They also show that when a fast convergent adaptation process is deployed, data reduction rates are significantly improved. Targeted applications of the developed methodology include machine health monitoring, tele-health, environment and habitat monitoring, intermodal transportation and homeland security.
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With the advent of peer to peer networks, and more importantly sensor networks, the desire to extract useful information from continuous and unbounded streams of data has become more prominent. For example, in tele-health applications, sensor based data streaming systems are used to continuously and accurately monitor Alzheimer's patients and their surrounding environment. Typically, the requirements of such applications necessitate the cleaning and filtering of continuous, corrupted and incomplete data streams gathered wirelessly in dynamically varying conditions. Yet, existing data stream cleaning and filtering schemes are incapable of capturing the dynamics of the environment while simultaneously suppressing the losses and corruption introduced by uncertain environmental, hardware, and network conditions. Consequently, existing data cleaning and filtering paradigms are being challenged. This dissertation develops novel schemes for cleaning data streams received from a wireless sensor network operating under non-linear and dynamically varying conditions. The study establishes a paradigm for validating spatio-temporal associations among data sources to enhance data cleaning. To simplify the complexity of the validation process, the developed solution maps the requirements of the application on a geometrical space and identifies the potential sensor nodes of interest. Additionally, this dissertation models a wireless sensor network data reduction system by ascertaining that segregating data adaptation and prediction processes will augment the data reduction rates. The schemes presented in this study are evaluated using simulation and information theory concepts. The results demonstrate that dynamic conditions of the environment are better managed when validation is used for data cleaning. They also show that when a fast convergent adaptation process is deployed, data reduction rates are significantly improved. Targeted applications of the developed methodology include machine health monitoring, tele-health, environment and habitat monitoring, intermodal transportation and homeland security.
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Cette thèse est une contribution à la modélisation, la planification et l’optimisation du transport pour l’approvisionnement en bois de forêt des industries de première transformation. Dans ce domaine, les aléas climatiques (mise au sol des bois par les tempêtes), sanitaires (attaques bactériologiques et fongiques des bois) et commerciaux (variabilité et exigence croissante des marchés) poussent les divers acteurs du secteur (entrepreneurs et exploitants forestiers, transporteurs) à revoir l’organisation de la filière logistique d’approvisionnement, afin d’améliorer la qualité de service (adéquation offre-demande) et de diminuer les coûts. L’objectif principal de cette thèse était de proposer un modèle de pilotage améliorant la performance du transport forestier, en respectant les contraintes et les pratiques du secteur. Les résultats établissent une démarche de planification hiérarchique des activités de transport à deux niveaux de décision, tactique et opérationnel. Au niveau tactique, une optimisation multi-périodes permet de répondre aux commandes en minimisant l’activité globale de transport, sous contrainte de capacité agrégée des moyens de transport accessibles. Ce niveau permet de mettre en œuvre des politiques de lissage de charge et d’organisation de sous-traitance ou de partenariats entre acteurs de transport. Au niveau opérationnel, les plans tactiques alloués à chaque transporteur sont désagrégés, pour permettre une optimisation des tournées des flottes, sous contrainte des capacités physiques de ces flottes. Les modèles d’optimisation de chaque niveau sont formalisés en programmation linéaire mixte avec variables binaires. L’applicabilité des modèles a été testée en utilisant un jeu de données industrielles en région Aquitaine et a montré des améliorations significatives d’exploitation des capacités de transport par rapport aux pratiques actuelles. Les modèles de décision ont été conçus pour s’adapter à tout contexte organisationnel, partenarial ou non : la production du plan tactique possède un caractère générique sans présomption de l’organisation, celle-ci étant prise en compte, dans un deuxième temps, au niveau de l’optimisation opérationnelle du plan de transport de chaque acteur.
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The major objective of this thesis is to describe and analyse how a railcarrier is engaged in an intermodal freight transportation network through its role and position. Because of the fact that the role as a conceptualisation has a lot of parallels with the position, both these phenomena are evaluated theoretically and empirically. VR Cargo (a strategical business unitof the Finnish railway company VR Ltd.) was chosen to be the focal firm surrounded by the actors of the focal net. Because of the fact that networks are sets of relationships rather than sets of actors, it is essential to describe the dimensions of the relationships created through the time thus having a past, presentand future. The roles are created during long common history shared by the actors especially when IM networks are considered. The presence of roles is embeddedin the tasks, and the future is anchored to the expectations. Furthermore, in this study role refers to network dynamics, and to incremental and radical changes in the network, in a similar way as position refers to stability and to the influences of bonded structures. The main purpose of the first part of the study was to examine how the two distinctive views that have a dominant position in modern logistics ¿ the network view (particularly IMP-based network approach) and the managerial view (represented by Supply Chain Management) differ, especially when intermodalism is under consideration. In this study intermodalism was defined as a form of interorganisational behaviour characterized by the physical movement of unitized goods with Intermodal Transport Units, using more than one mode as performed by the net of operators. In this particular stage the study relies mainly on theoretical evaluation broadened by some discussions with the practitioners. This is essential, because the continuous dialogue between theory and practice is highly emphasized. Some managerial implications are discussed on the basis of the theoretical examination. A tentative model for empirical analysis in subsequent research is suggested. The empirical investigation, which relies on the interviews among the members in the focal net, shows that the major role of the focal company in the network is the common carrier. This role has some behavioural and functional characteristics, such as an executive's disclosure expressing strategic will attached with stable and predictable managerial and organisational behaviour. Most important is the notion that the focal company is neutral for all the other operators, and willing to enhance and strengthen the collaboration with all the members in the IM network. This also means that all the accounts are aimed at being equal in terms of customer satisfaction. Besides, the adjustments intensify the adopted role. However, the focal company is also obliged tosustain its role as it still has a government-erected right to maintain solely the railway operations on domestic tracks. In addition, the roles of a dominator, principal, partner, subcontractor, and integrator were present appearing either in a dyadic relationship or in net(work) context. In order to reveal differentroles, a dualistic interpretation of the concept of role/position was employed.
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"Sponsoring/monitoring agency report number: DOT-FHWA-JPO-97-008"--Report documentation page.
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Folded plan laid in.
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Mode of access: Internet.
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"January 4, 1993"--P. [1].
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"March 22, 1997--Coeur d'Alene, Idaho ... May 7 and June 6, 1997--Washington, DC"--Pt. 2.
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The best places to locate the Gas Supply Units (GSUs) on a natural gas systems and their optimal allocation to loads are the key factors to organize an efficient upstream gas infrastructure. The number of GSUs and their optimal location in a gas network is a decision problem that can be formulated as a linear programming problem. Our emphasis is on the formulation and use of a suitable location model, reflecting real-world operations and constraints of a natural gas system. This paper presents a heuristic model, based on lagrangean approach, developed for finding the optimal GSUs location on a natural gas network, minimizing expenses and maximizing throughput and security of supply.The location model is applied to the Iberian high pressure natural gas network, a system modelised with 65 demand nodes. These nodes are linked by physical and virtual pipelines – road trucks with gas in liquefied form. The location model result shows the best places to locate, with the optimal demand allocation and the most economical gas transport mode: by pipeline or by road truck.