1,721,215 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
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A greedy adaptive search procedure for multi-dimensional multi-container packing problems
Full text linkTech. Rep. CIRRELT-2012-10, CIRRELT, Montrea
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
A Progressive Hedging algorithm for the Stochastic Variable Cost and Size Bin Packing Problems: An application to capacity planning in logistics
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Optimizing Dry Port Based Freight Distribution Planning
No full textIn this paper we review the dry port concept and its outfalls in terms of optimal design and management of freight distribution. Some optimization challenges arising from the presence of dry ports in freight distribution systems are presented and discussed.
Then we consider the tactical planning problem of defining the optimal routes and schedulesfor the fleet of vehicles providing transportation services between the terminals of a dry port based intermodal system. An original service network design model based on a mixed integer programming mathematical formulation is proposed to solve the considered problem.
An experimental framework built upon realistic instances nspired by regional cases is described and the computational results of the model are presented and discussed
Logistics capacity planning: A stochastic bin packing formulation and a progressive hedging meta-heuristic
Full text linkWe consider the logistics capacity planning problem arising in the context of supply-chain management. We address the tactical-planning problem of determining the quantity of capacity units, hereafter called bins, of different types to secure for the next period of activity, given the uncertainty on future needs in terms of demand for loads (items) to be moved or stored, and the availability and costs of capacity for these movements or storage activities. We propose a modeling framework introducing a new class of bin packing problems, the Stochastic Variable Cost and Size Bin Packing Problem. The resulting two-stage stochastic formulation with recourse assigns to the first stage the tactical capacity-planning decisions of selecting bins, while the second stage models the subsequent adjustments to the plan, securing extra bins and packing the items into the selected bins, performed each time the plan is applied and new information becomes known. We propose a new meta-heuristic based on progressive hedging ideas that includes advanced strategies to accelerate the search and efficiently address the symmetry strongly present in the problem considered due to the presence of several equivalent bins of each type. Extensive computational results for a large set of instances support the claim of validity for the model, efficiency for the solution method proposed, and quality and robustness for the solutions obtained. The method is also used to explore the impact on the capacity plan and the recourse to spot-market capacity of a quite wide range of variations in the uncertain parameters and the economic environment of the firm
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