摘要:

AbstractThe 40th anniversary of the Operational Research Society has prompted an informal survey of the successes of Operational Research over that period and the challenges still to be met. This triggers comments on the areas where the subject still needs development, including more concentration on publicizing the operational science aspects of the subject. Finally, the way the Society is shaping up to some of these challenges is discussed.

ISSN:0160-5682    

DOI:10.1057/jors.1994.211

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractIn the design of a new urban retail network, the size of each office can be determined—once the number and the location of outlets have been fixed—by means of a location-allocation model. In order to carry out this task, two different solutions have been considered: the best solution in the opinion of the firm's managers and the solution obtained by maximizing the outlets' accessibility, based on a spatial interaction model. Our biobjective program bridges the gap between both solutions by enabling the generation of a finite set of non-inferior points, and constitutes, therefore, a valuable decision-support tool. The paper closes with a case study in the banking sector.

ISSN:0160-5682    

DOI:10.1057/jors.1994.212

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractFor the last ten years or so, developments in simulation software and methodology have been focused in two areas: (1) automating the model-building process; and (2) interfacing with other techniques and systems. That both academic and commercial research continues to be carried out in these areas is evidence of the continued popularity of the simulation technique. The most popular application areas where simulation modelling is used include manufacturing (engineering and process), warehousing and communications; not surprisingly, research and developments have therefore been concentrated in these areas. This paper describes the development of a simulation model generator for a different application area, that of clerical office processing of paper and documents for financial service companies. It outlines the reasons why there is a need for such a model generator and discusses the initial design requirements. The paper goes on to detail the developments and re-defined criteria required as the model generator brief changes as a result of practical applications.

ISSN:0160-5682    

DOI:10.1057/jors.1994.213

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractMaterial recycling is quickly becoming the most visible component of municipal solid waste management systems, and optimization models could play a prominent role in the long-term cost-effective planning of these systems. In this paper, we develop a mixed integer programming model for the recycling of various by-product materials within the overall waste system. This model is solvable on a microcomputer for reasonable problem dimensions, and the planning methodology is applied to a hypothetical municipality to illustrate the potential utility of the developed modelling approach.

ISSN:0160-5682    

DOI:10.1057/jors.1994.214

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThis paper develops a Petri net-based decomposition approach to model and perform steady-state analysis of open queueing networks with multi-class customers. For each customer class we assume deterministic routeing and different service time distribution. The current decomposition may also consider equipment failures, defective units that have to be re-worked and on-line preparations (to switch from one mix of customers to another) as additional customer classes. In contrast to most of the published works on timed Petri nets, their present use is marked by input flows, originating from external sources. A simple method, directly derived from the timed Petri nets theories, is used for calculating the expected utilization of each server and eventually the maximal productivity of the system for the given deterministic routeing. An important application of the model is in validating discrete-event non-terminating simulation models.

ISSN:0160-5682    

DOI:10.1057/jors.1994.215

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractIn solving discrete time queueing models by numerical techniques, the computational requirements (computer memory and time) are a practical limitation and are particularly dependent on the number of discrete time intervals required in the discrete distribution chosen to match the general service distribution. This paper shows that the minimum number of points required for matching to the first two moments depends on the size of the discrete interval relative to the mean and also on the coefficient of variation. Equations and graphs are provided that will enable the OR practitioner to select the discrete distribution to be used as an approximation. Additionally, it is concluded that discrete time modelling, using these approximations to model service time, now provides a practical means to model both steady-state measures and transient behaviour of M/G/c, M(t)/G/c and M(t)/G/c(t) queueing systems on a personal computer.

ISSN:0160-5682    

DOI:10.1057/jors.1994.216

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe classical economic production lot size (EPL) model assumes a constant production rate that is predetermined and inflexible, and perfect quality. Recent models have removed the assumption of perfect quality while maintaining the inflexible production rate assumption. Production rates in many cases, such as orders filled by a machine, can be changed. Moreover, unit production cost and process quality depend on the production rate. In this paper, we extend the EPL model to cases where the production rate is a decision variable. Unit production cost becomes a function of the production rate. Also, the quality of the production process deteriorates with increased production rate. We solve the proposed model for special cost and quality functions and illustrate the results with a numerical example. The results show that, for cases where increases in the production rate lead to a significant deterioration in quality, the optimal production rate may be smaller than the rate that minimizes unit production cost. For cases where quality is largely independent of the production rate, the optimal production rate may be larger than the rate that minimizes unit production cost.

ISSN:0160-5682    

DOI:10.1057/jors.1994.217

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThe levelling process of a vast area of land, for irrigation or any other development plan, is usually done in two stages. The first stage starts by determining the levels of the terrain, while the second stage solves the earthwork allocation for the predetermined levels. The most recent attempt, reported in the literature, to find global optimality for this problem was a trial-and-error approach which solves a linear transportation problem for every possible terrain's level and selects the level that results in the lowest transportation cost. This approach, however, being an iterative procedure, can only come closer to the optimum solution depending on how small the iteration steps are, but does not guarantee global optimality. The paper presented here offers a linear programming model that combines the levelling of terrains and the associated transportation in a single linear programming problem, thus guaranteeing global optimality.

ISSN:0160-5682    

DOI:10.1057/jors.1994.218

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractThis paper is a report of a simulation study that investigates a dynamic approach to scheduling jobs in a multi-machine job shop. The workload information of a job is used in different forms to evaluate the shop performance based on three measures: mean job lateness, percentage of tardy jobs and lateness variance. Different combinations of due-date assignment methods and sequencing rules are compared based on specific performance criteria. The results indicate that using the cumulative distribution function of workload information can yield a better performance than using a proportional function of workload information or ignoring shop congestion information. A few situations are identified in which workload information is not critical.

ISSN:0160-5682    

DOI:10.1057/jors.1994.219

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractA simple method is presented for developing optimality regions and penalty analysis of the parameter space for machine replacement problems. Optimality regions are regions of the parameter space in which a given economic life is optimal. The optimality regions (penalty analysis) provide a simple,‘at a glance’, visual means to assess and illustrate the sensitivity of the economic life (cost implications) to errors in the problem parameters. A numerical example is presented in order to illustrate the use of the method in supporting machine replacement decisions.

ISSN:0160-5682    

DOI:10.1057/jors.1994.220

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor