PolyU IR Collection: LMS Journal/Magazine Articles
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Some properties of multiple parameters linear programming
http://hdl.handle.net/10397/6529
Title: Some properties of multiple parameters linear programming<br/><br/>Authors: Li, Maoqin; Li, Shanlin; Yan, Hong<br/><br/>Abstract: We consider a linear programming problem in which the right-hand side vector depends on multiple parameters. We study the characters of the optimal value function and the critical regions based on the concept of the optimal partition. We show that the domain of the optimal value function f can be decomposed into finitely many subsets with disjoint relative interiors, which is different from the result based on the concept of the optimal basis. And any directional derivative of f at any point can be computed by solving a linear programming problem when only an optimal solution is available at the point.<br/><br/>Description: DOI: 10.1155/2010/204263Bicriterion single machine scheduling with resource dependent processing times
http://hdl.handle.net/10397/6037
Title: Bicriterion single machine scheduling with resource dependent processing times<br/><br/>Authors: Cheng, T. C. Edwin; Janiak, Adam; Kovalyov, Mikhail Y.<br/><br/>Abstract: A bicriterion problem of scheduling jobs on a single machine is studied. The processing time of each job is a linear decreasing function of the amount of a common discrete resource allocated to the job. A solution is specified by a sequence of the jobs and a resource allocation. The quality of a solution is measured by two criteria, F₁ and F₂. The first criterion is the maximal or total (weighted) resource consumption, and the second criterion is a regular scheduling criterion depending on the job completion times. Both criteria have to be minimized. General schemes for the construction of the Pareto set and the Pareto set ϵ-approximation are presented. Computational complexities of problems to minimize F₁ subject to F₂ ≤ K and to minimize F₂ subject to F₁≤ K, where K is any number, are studied for various functions F₁ and F₂. Algorithms for solving these problems and for the construction of the Pareto set and the Pareto set ϵ-approximation for the corresponding bicriterion problems are presented.<br/><br/>Description: DOI: 10.1137/S1052623495288192Single machine scheduling to minimize batch delivery and job earliness penalties
http://hdl.handle.net/10397/6036
Title: Single machine scheduling to minimize batch delivery and job earliness penalties<br/><br/>Authors: Cheng, T. C. Edwin; Kovalyov, Mikhail Y.; Lin, Bertrand M.-T.<br/><br/>Abstract: We study a problem in which a set of n jobs has to be batched as well as scheduled for processing on a single machine. A constant machine set-up time is required before the first job of each batch is processed. A schedule specifies the sequence of batches, where each batch comprises a sequence of jobs. The batch delivery time is defined as the completion time of the last job in a batch. The earliness of a job is defined as the difference between the delivery time of the batch to which it belongs and the job completion time. The objective is to find a number B of batches and a schedule so as to minimize the sum of the total weighted job earliness and mean batch delivery time. The problem is shown to be strongly NP-hard. It remains strongly NP-hard if the set-up time is zero and B ≤ U for any variable U ≥ 2 or if B ≥ U for any constant U ≥ 2. The problem is proved to be ordinary NP-hard even if the set-up time is zero and B ≤ 2. For the case B ≤ U, a dynamic programming algorithm is presented, which is pseudopolynomial for any constant U ≥ 2. Algorithms with O(n²) running times are derived for the cases when all weights are equal or all processing times are equal. For the general problem, a family of heuristics is suggested. Computational experiments on the proposed heuristic algorithm are conducted. The results suggest that the heuristics are effective in generating near-optimal solutions quickly.<br/><br/>Description: DOI: 10.1137/S1052623494269540Ship investment at a standstill? An analysis of shipbuilding activities and policies
http://hdl.handle.net/10397/6002
Title: Ship investment at a standstill? An analysis of shipbuilding activities and policies<br/><br/>Authors: Xu, Jane Jing; Yip, T. L.<br/><br/>Abstract: In the wake of the global financial crisis which started around mid-2008, the global shipbuilding industry is no longer in a state of euphoria as before. The volume of new ship orders dropped dramatically after August 2008. We are motivated to examine three issues in this article: First, in the context of shipping industry, which variable(s) play the most important role in a ship investment decision? Second, do government support and favourable investment conditions really help to save shipbuilding industry from the distressing situation? Third, if we separate Japan, South Korea and China as leading shipbuilding clusters, what will the cluster effect be? Our results indicate that the investment of ships can be decided by the freight level, the supply of the market (fleet size), the demand of the ships (trade volume) and the transport service share (location advantage). However, the state of the freight market is of major importance to the investment decision of ships. Shipbuilding price, second-hand ship price and foreign direct investment in transport are proved to have no linkage to ship investment. Besides, the rising role of Japan, South Korea and China in shipbuilding is also identified.<br/><br/>Description: DOI: 10.1080/13504851.2011.572842