摘要:

AbstractThe dimensions of a bloom, which is a rectangular piece of steel, are critical for efficiently and effectively rolling the bloom into a finished structural shape (I-beam) for sale to the customer. To achieve maximum productivity and yield, the bloom size (thickness, width and length) to be rolled on a finishing mill into a structural shape must be determined by steel deformation experts. Suppose, for a particular finishing mill, these‘rolled' blooms are all produced from a‘cast' bloom of the same cross-section but with many different lengths. It is necessary to consolidate the many‘cast' bloom length-metallurgical grade combinations to a number that can be managed by the casting operation and bloom stockyard without significantly impacting productivity and yield. An uncapacitated facility location problem formulation and algorithm were used to solve this problem. The way in which this approach was used to solve a real-world application is discussed.

ISSN:0160-5682    

DOI:10.1057/jors.1996.33

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThis paper concerns a computer system which produces the bulk of the timetable for a large comprehensive school in England. The complexities of the school's lesson structure are discussed and the various constraints and objectives described. The timetable thus produced was successfully implemented for the academic year starting in September 1994 and was considered by the school to represent a marked improvement on previous timetables as well as being achieved much more swiftly. The solution method involves four phases of heuristic search with little or no manual intervention necessary. In contrast with other timetabling systems, the system completes all the difficult parts of the process to a high-quality standard, with only the final straightforward stages being left to the timetabler. Details of the solution method are outlined and dyiscussed in further detail in an appendix, especially the more innovative parts which involve a form of tabu search with influential diversification guided by the values of the subcosts as well as the overall cost. The system could be generalised so as to be applied to other schools.

ISSN:0160-5682    

DOI:10.1057/jors.1996.34

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThis paper presents a case study of short term manpower planning in an agency which processed contract clerical work. The problem originated when the agency was presented with an unexpectedly large batch of work and a backlog quickly developed. Management took the obvious action of increasing staff numbers but this had little effect on the throughput of work. The situation deteriorated and a rapid response was required from management. This meant that only models that were readily accessible for use by management could be considered. A decision support approach was adopted and a spreadsheet based model developed. This was effectively a time based simulation of the situation, but it gave management the flexibility to evaluate alternative solutions, unaided. The model proved to be a highly successful tool. It demonstrated that simply increasing temporary staff or working overtime were insufficient to remove the backlog of work within a year. This encouraged management to search for alternative solutions.

ISSN:0160-5682    

DOI:10.1057/jors.1996.35

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractWhen public transport is put out to tender, the task of allocating contracts to operators can be far from trivial. In addition to vehicle constraints, there can be group bids wherein a discount is offered for certain contracts in combination. An efficient integer programming formulation is presented which is then used to solve a large-scale real-life example.

ISSN:0160-5682    

DOI:10.1057/jors.1996.36

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractExamination timetabling is an important operational problem in many schools, colleges and universities. The authors have developed a computerized examination timetabling system called EXAMINE. In this article several algorithmic strategies for this problem are investigated and compared. Computational results are reported on randomly generated problems and on some real problems.

ISSN:0160-5682    

DOI:10.1057/jors.1996.37

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThis paper examines economic order quantity and optimal order quantity under both all-units and incremental-quantity discounts when purchase cost, order cost, and carrying cost are all incurred on date-terms supplier credit. Payment dates for the three cost components need not be the same. The traditionally-used periodic-cost minimization methodology which is insensitive to differences in the timing of various within-period cash flows is replaced with a discounted cash flow methodology. Differences in the characteristics of day-terms and date-terms solutions to the quantity discount case are high-lighted.

ISSN:0160-5682    

DOI:10.1057/jors.1996.38

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractIn this paper the use of the generalisedλ-type distribution (GLD) is proposed for the analysis of standard inventory problems. Using this distribution to approximate the lead time demand distribution we analyse the generalised newsboy problem and a (Q, r) policy. The standard inventory measures like optimal order size, reorder level, average demand lost, etc. are obtained under the GLD and are compared with those given by Shore's approximation and also under exact distributional assumptions. Through a numerical study the various inventory measures are compared using the GLD and Shore's approximation with the exact distributions. The comparison reveals that the GLD approximation is better suited than Shore's approximation to model the lead time demand.

ISSN:0160-5682    

DOI:10.1057/jors.1996.39

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractA review of the methods and purposes of optimization in system dynamics models is undertaken. It is suggested that, given the typical client set involved, an optimization strategy embracing search-based techniques is preferable to one based on optimal control methods. When conducting an optimization, various tactical problems may need to be resolved and ways of doing this are described. The resolution of the problems is independent of the particular software tool being used for search-based optimization. A range of studies is discussed and these studies both calibrate and exemplify the adoption of a search routine to optimize a system dynamics model.

ISSN:0160-5682    

DOI:10.1057/jors.1996.40

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractIn this paper we consider the single machine scheduling problem of minimizing the mean absolute deviation (MAD) of job completion times from a restricted common delivery window. This problem is NP-hard. A Lagrangian relaxation procedure is proposed to solve the problem. Two efficient heuristics are also proposed. An experimental study on randomly generated problems is carried out to test the performance of the proposed methods. The computational results show that the obtained lower bounds are very good and the proposed heuristics generate near-optimal solutions.

ISSN:0160-5682    

DOI:10.1057/jors.1996.41

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThe problem where a number of facilities need to be sited along a line is often encountered in practice. In this paper, we consider the case where the objective is to achieve equity of service, which we accomplish by minimizing the maximum distance between two adjacent facilities. We also consider a stronger variation where the objective is not only to minimize the maximum distance, but also to hierarchically minimize the second maximum distance and so on. We then assume that there is a cost for siting a facility at a given point, and consider bicriteria extensions where the objective is to simultaneously achieve cost efficiency and service equity. Only the first among these various cases has thus far been addressed in the literature. We provide simple and effective solutions for all of them (indicating where and how solutions can be obtained using available methods).

ISSN:0160-5682    

DOI:10.1057/jors.1996.42

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor