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doi: 10.1057/palgrave.jors.2601477pmid: N/A
AbstractIn order to understand the requirements of people engaged in business process simulation (BPS), a survey was conducted among potential business process simulation users. The survey had a 37% response rate and revealed a low usage of simulation in the design, modification and improvement of business processes. It confirms that BPS projects are typically short, relatively non-technical, and rely on good project management for their success. Most BPS users employ general-purpose simulation software rather than purpose-designed business process simulators. There is no evidence of a skills gap, rather a feeling that there is no net gain from employing simulation methods when simpler methods will suffice. These findings are discussed and conclusions drawn.
Vasko, F J; Newhart, D D; Stott, K L; Wolf, F E
doi: 10.1057/palgrave.jors.2601469pmid: N/A
AbstractThe traditional, uncapacitated facility location problem (UFLP) seeks to determine a set of warehouses to open such that all retail stores are serviced by a warehouse and the sum of the fixed costs of opening and operating the warehouses and the variable costs of supplying the retail stores from the opened warehouses is minimized. In this paper, we discuss the partial coverage uncapacitated facility location problem (PCUFLP) as a generalization of the uncapacitated facility location problem in which not all the retail stores must be satisfied by a warehouse. Erlenkotter's dual-ascent algorithm, DUALOC, will be used to solve optimally large (1600 stores and 13 000 candidate warehouses) real-world implemented PCUFLP applications in less than two minutes on a 500 MHz PC. Furthermore, a simple analysis of the problem input data will indicate why and when efficient solutions to large PCUFLPs can be expected.
Boffey, B; Yates, D; Galvão, R D
doi: 10.1057/palgrave.jors.2601485pmid: N/A
AbstractIn order to reduce infant mortality in the municipality of Rio de Janeiro it is desired to encourage all mothers-to-be to attend the appropriate health care facilities. A 3-level hierarchical prenatal–neonatal health care system is described together with a basic model for optimising accessibility to facilities. A genetic algorithm to solve the basic model is developed and some numerical experience reported. Extensions to the basic model and planned future research are briefly indicated.
doi: 10.1057/palgrave.jors.2601476pmid: N/A
AbstractCoordinated replenishment is a supply chain policy that affects many operational performance measures, including cost, lead time, and quality. In this paper, we develop a mathematical model of a simplified supply chain in which conformance quality is one of the supplier's decision variables and both the supplier and its customer are trying to minimize expected annual cost. Our expected cost model includes the important quality costs (appraisal, prevention, internal failure, and external failure) as well as holding, set-up, and ordering costs. Our results indicate that coordination leads to a decline in total cost but that coordination does not necessarily lead to an improvement in quality. In other words, buyers who are using coordinated replenishment may be trading higher quality for lower cost.
Shirmohammadi, A H; Love, C E; Zhang, Z G
doi: 10.1057/palgrave.jors.2601450pmid: N/A
AbstractIn this study we investigate systems that experience random failures and establish decision rules for performing renewal maintenance; that is, a preventive replacement (PR) policy. We seek a policy that is both simple to execute from the point of view of the maintenance planner but also a policy that is an improvement on existing schemes. We show that our policy is a hybrid of traditional time-based and age-based schemes and one that yields considerable cost savings. Our hybrid policy involves two decision variables. One decision variable is the time between PRs. Hence, for the maintenance planner, the times at which PRs are performed are chronologically fixed. Random failures can occur, however, and the machine receives an emergency renewal (ER) at these times. Hence, within these chronological times, a second decision time is identified. Should an ER occur between the start of a cycle and this second decision time, then the planned PR would still be performed at the end of the cycle. However, if the first ER occurs after this second decision time, then the PR at the end of the cycle is skipped over and the next planned PR would take place at the end of the subsequent cycle. With this simple mechanism, PRs that follow on too closely after an ER are avoided, thus saving the unnecessary expense. Numerical examples are given to examine the validity of the model, using four different failure density functions, namely Weibull, normal, uniform, and negative exponential.
doi: 10.1057/palgrave.jors.2601475pmid: N/A
AbstractRatio analysis is a commonly used analytical tool for verifying the performance of a firm. While ratios are easy to compute, which in part explains their wide appeal, their interpretation is problematic, especially when two or more ratios provide conflicting signals. Indeed, ratio analysis is often criticized on the grounds of subjectivity, that is the analyst must pick and choose ratios in order to assess the overall performance of a firm.In this paper we demonstrate that Data Envelopment Analysis (DEA) can augment the traditional ratio analysis. DEA can provide a consistent and reliable measure of managerial or operational efficiency of a firm. We test the null hypothesis that there is no relationship between DEA and traditional accounting ratios as measures of performance of a firm. Our results reject the null hypothesis indicating that DEA can provide information to analysts that is additional to that provided by traditional ratio analysis. We also apply DEA to the oil and gas industry to demonstrate how financial analysts can employ DEA as a complement to ratio analysis.
doi: 10.1057/palgrave.jors.2601473pmid: N/A
AbstractWe study the hub covering problem which, so far, has remained one of the unstudied hub location problems in the literature. We give a combinatorial and a new integer programming formulation of the hub covering problem that is different from earlier integer programming formulations. Both new and old formulations are nonlinear binary integer programs. We give three linearizations for the old model and one linearization for the new one and test their computational performances based on 80 instances of the CAB data set. Computational results indicate that the linear version of the new model performs significantly better than the most successful linearization of the old model both in terms of average and maximum CPU times as well as in core storage requirements.
Tarantilis, C D; Kiranoudis, C T; Vassiliadis, V S
doi: 10.1057/palgrave.jors.2601443pmid: N/A
AbstractIn real life situations most companies that deliver or collect goods own a heterogeneous fleet of vehicles. Their goal is to find a set of vehicle routes, each starting and ending at a depot, making the best possible use of the given vehicle fleet such that total cost is minimized. The specific problem can be formulated as the Heterogeneous Fixed Fleet Vehicle Routing Problem (HFFVRP), which is a variant of the classical Vehicle Routing Problem. This paper describes a variant of the threshold accepting heuristic for the HFFVRP. The proposed metaheuristic has a remarkably simple structure, it is lean and parsimonious and it produces high quality solutions over a set of published benchmark instances. Improvement over several of previous best solutions also demonstrates the capabilities of the method and is encouraging for further research.
doi: 10.1057/palgrave.jors.2601479pmid: N/A
AbstractThis paper considers a combined problem of establishing virtual paths (VPs) and routing traffic (packet) demands through the virtual paths in a layered communication network where each physical link is subject to its capacity constraints. The problem is modeled as a path-based formulation for which a branch-and-price solution algorithm is derived. The solution algorithm is composed of an efficient pricing algorithm, and also a branching rule based on a variable dichotomy, which does not destroy the structure of the associated pricing problems. Computational experiments are performed to test the efficiency of the algorithm, which show that the algorithm works quite well in finding optimal solutions (for the test instances) within reasonable time. Its immediate application may be made to a centralized network management on mid-term global reconfiguration and long-term VP planning.
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