5,751 research outputs found
Dynamic empty car management in railyards
No full textThis paper is concerned with accelerating the flow of empty cars in a major classification railyard in North America. Due to fluctations in inbound traffic, empty cars experience long delays at the yard. Such delays can be prevented by dynamic car reassignments. We describe a procedure using a sliding time window in order to reduce the time that empty cars spend in the yard and present the associated computational results
Decomposition algorithms for multicommodity network design problems with penalized constraints
No full textSimulation of intermodal freight transportation systems: a taxonomy
No full textIntermodal transportation refers to multimodal chains or networks involving at least two transportation modes, freight being packed into a "container" and not being handled at intermodal-transfer terminals on its trip from its origin to its destination. This characterization makes intermodal transportation a multi-actor complex system involving a broad range of interacting stakeholders, decision makers, operations, and planning activities. Due to this complexity, simulation is much studied and used within the field of operations research, yielding models, methods, and tools to manage transportation activities and support the decision-making processes. The literature includes a large number of contributions on particular issues, but a broad view of the field is still missing. This paper aims to fill this gap, using a new taxonomy to structure the recent relevant literature. The proposed taxonomy thus appears a useful instrument to classify the literature and support further analyzes, identifying main findings, trends, and future paths of intermodal freight transportation systems across several dimensions (e.g., modes, geographical extensions, time horizons, and simulation objectives)
Models for evaluating and planning city logistics systems
No full textCity logistics aims to reduce the nuisances associated to freight transportation in urban areas while supporting their economic and social development. The fundamental idea is to view individual stakeholders and decisions as components of an integrated logistics system. This implies the coordination of shippers, carriers, and movements as well as the consolidation of loads of several customers and carriers into the same environment-friendly vehicles. City logistics explicitly aims to optimize such advanced urban transportation systems. We focus on a challenging city logistics planning issue, the integrated short-term scheduling of operations and management of resources, for the general case involving a two-tiered distribution structure. We investigate the main issues related to the problem, introduce a new problem class, propose both a general model and formulations for the main system components, and identify promising solution avenues. © 2009 INFORMS
Lagrangean decomposition for the multicommodity capacitated network design problem
No full textTraditional Lagrangean relaxations for the multicommodity capacitated network design problem (MCNDP) involve dualizing either arc capacity or flow conservation constraints. The former (shortest-path relaxation) results in loosing the capacity structure whereas the latter (knapsack relaxation) does not maintain any information related to the network structure. In this talk, we discuss a new relaxation for the MCNDP, based on Lagrangean decomposition, which allows one to decompose the problem by nodes, and the subproblems partially preserve both the network and the capacity structure
Optimization challenges and literature overview in the intermodal rail-sea terminal
No full textThis work focuses on a particular node of the intermodal chain of transportation, i.e. the maritime port area that represents the link between rail and sea transportation modes. Since this exchange node of the chain has not been addressed much yet, the aim of the present study is to provide a description of the process of rail operations in port area, to give an overview of the optimization challenges and to review the existing literature on it. The purpose of the paper is to attract the researchers attention on this particular intermodal node, where there is room for improvements
Multimodal Capacity Planning with Uncertainty on Contract Fulfilment
No full textContracting with carriers or third-party logistics firms is a way to secure transportation or warehousing capacity for the next planning period. However, contracts are concluded under uncertainty regarding the demand of loads to be transported, the availability of contracted capacity and of the extra one if needed. The question is how much to contract of each type of capacity to minimize the costs of the contract and of ad-hoc future actions to redress an unfavorable situation. We model this planning problem by extending the Stochastic Variable Cost and Size Bin Packing Problem. Extensive numerical experiments are conducted considering the case of an express courier in a City Logistics environment
Advanced freight transportation systems for congested urban areas
No full textUrban freight transportation constitutes both an extremely important and a rather disturbing activity. Increasingly, one observes efforts to measure and control freight movements within city centers. We introduce a possible organizational and technological framework for the integrated management of urban freight transportation and identify important associated planning and operation issues and models. We then describe a formulation for one of these problems, the design of the proposed logistical structure, and discuss algorithmic and implementation issues. Our model city and challenge is Rome. (C) 2004 Elsevier Ltd. All rights reserved
El Teodor Llorente de Josep Piera
No full textLlorente va ser coronat com a poeta de València l’any 1909 en el marc de
la magnificent Exposició Regional Valenciana davant l’entusiasme de més de
100.000 persones.
L’any 1936 Miquel Duran de València, el més agosarat dels poetes modernistes valencians, escrivia en un número especialment dedicat a Teodor
Llorente de la revista La República de les Lletres: «Contribuí Llorente a ressucitar la nostra llengua, a desvetllar la nostra consciència col·lectiva, a descobrir i refer el nostre patrimoni espiritualGarcia Frasquet, G. (2012). El Teodor Llorente de Josep Piera. Revista de la Safor. (4):79-88. https://riunet.upv.es/handle/10251/1299837988
Integrating c2e and c2c traffic into city logistics planning
No full textCity Logistics generally addresses inbound movements, from regions outside the city to the zone under City Logistics control. Integrating outbound and intra-city traffic may contribute to make freight transportation more efficient and less intrusive on mobility, the environment, and general quality-of-life conditions in the city. It may also raise significant managerial and methodological challenges, which increase with the degree of integration of fleets and operations. We describe and analyze a number of representative service-integration scenarios, discuss operational and managerial issues, examine corresponding methodological challenges, and identify associated research avenues
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