In a recent paper a quadratic mixed-integerprogrammingmodel was presented for an industrial purchasing problem involving complicated discount structures. The solution method presented in the paper for this model inv...
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In a recent paper a quadratic mixed-integerprogrammingmodel was presented for an industrial purchasing problem involving complicated discount structures. The solution method presented in the paper for this model involved the solution of a series of quadratic zero-one programming problems. The disadvantages of such an approach are immediately obvious to anyone familiar with the state-of-the-art of solution methods for nonlinearintegerprogramming problems. In this paper a linearmodel is constructed for the same problem and its computational advantages over the nonlinearmodel are discussed.
The dwelling capacity of the station (mainly determined by its multi-track layout) is a practically significant factor to influence the quality of the train schedules, especially in a busy railway corridor with hetero...
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The dwelling capacity of the station (mainly determined by its multi-track layout) is a practically significant factor to influence the quality of the train schedules, especially in a busy railway corridor with heterogeneous trains and complex operations. To improve the passing capacity and transportation efficiency, this paper focuses on a network design problem over a railway corridor, in which some critical stations are considered to enlarge the number of siding tracks or platforms within the budget constraints. To evaluate the quality of design strategies, the construction cost and total travel time in the corresponding optimal train schedule are adopted as evaluation indexes. Based on two specific modeling methodologies, two types of optimization models are particularly formulated with different considerations. One is a single-level linearmixed-integerprogramming (S-LMIP) model based on the space-time network representation method;the other is a bi-level programmingmodel associated with the platform choice-based method, where the upper level of the proposed model aims to design new siding tracks/platforms in the candidate stations, and the lower level is a train scheduling model with assigning the tracks for each train at each station. The commercial software GAMS with CPLEX solver and local searching based heuristic with integrated CPLEX solver are respectively employed to solve the near-optimal solutions for these two types of models. Finally, two sets of examples, in which a sample railway corridor and the Wuhan-Guangzhou high-speed railway corridor are adopted as the experimental environments, are implemented to illustrate the performance and effectiveness of the proposed approaches. (C) 2016 Elsevier Ltd. All rights reserved.
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