摘要:

AbstractIn 1980 a seminar of operational researchers and practitioners from a variety of different countries concluded that there was a remarkable consensus about the way that the process of operational research and systems analysis should be understood and practised. Since then the development of new methods has continued apace, stimulated by interaction with the social sciences and paradigms other than natural science. This paper enters the debate, started in this journal, about the nature of OR's status as science or technology. It recognizes the historic claims of science on OR, but it suggests that for‘private’consumption, technology will prove more fruitful, and for‘public’consumption practitioners will increasingly adopt the label‘consultant’. Ackoff's original six-step method of OR is updated to reflect current OR practice. The process suggested acknowledges the importance of context, socio-political factors and the growing role of facilitation.

ISSN:0160-5682    

DOI:10.1057/jors.1996.1

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThis paper presents an innovative method of measuring and assessing financial performance for hospitals using data envelopment analysis (DEA). A 6% national sample of acute care hospitals was used to compare conventional ratio analysis with the financial performance index (FPI), an aggregate measure of financial performance, developed in this study. The results showed that FPI has captured what various financial ratios indicate independently. The development of a FPI across many financial ratios eases the comparison of an individual hospital with its peers. Development and uses of a FPI can also be applied to other industries.

ISSN:0160-5682    

DOI:10.1057/jors.1996.2

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractTransportation decisions and production decisions can usually be made separately. Under certain conditions, however, there are important interactions between transportation and production. An example of a combined production and routeing environment exists in the United States Postal Service (USPS). The daily movement and sorting of first class letter mail requires balancing transportation and mail sorting production costs, while considering the time dependent accumulation of mail during the day. The focus of this paper is on the practical application of a combined production/routeing model to a specific USPS division and the use of insights from this model to re-design the operation. A mixed integer linear program using candidate route integer variables is solved to near optimality. Specific routes and production schedules detailed by the model indicate that the division could save up to 5% of their combined production and routeing costs, amounting to $298 000 per year. More importantly, the model provides insight on potential heuristics to choose routes under these circumstances.

ISSN:0160-5682    

DOI:10.1057/jors.1996.3

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThis case study was carried out for Thomas Bolton Ltd, a copper component manufacturer. The focus was on the first major production operation that is carried out in the foundry. This operation consists of three processes—melting scrap metal, casting it as‘logs’and cutting logs into‘billets’. The timely production of the billets is essential as these feed a bottleneck process. The objective of the study was to investigate alternative methods of generating a production plan for the foundry that minimized costs whilst meeting the demand for billets at the bottleneck. The production plan was required to include a daily production schedule and a list of the cutting patterns to use when cutting the logs into billets. Thus, both the scheduling and cutting stock problems were addressed. A two-stage solution procedure was proposed. Alternative heuristic methods were investigated at the first stage and an optimal solution using Integer Programming (IP) was proposed for the second stage. It is shown that current performance could be improved using all of the heuristics considered at the first stage, but that using an IP-based heuristic method gives the best results.

ISSN:0160-5682    

DOI:10.1057/jors.1996.4

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractManufacturers in many countries are facing increasing market pressures to use returnable containers. Few studies address the day-to-day operational problems of controlling production and distribution that are inherent in closed systems that reuse containers. In this paper we present a formulation of an optimal configuration of this type of system. In particular, we model the reusable bottle production and distribution activities of a large soft drink manufacturer located in Mexico City, Mexico. Two types of operational research models are combined to form the overall optimization system. A pair of linear programs (one aggregated, the other disaggregated) determines a master plan that is subsequently fined-tuned on a shift-by-shift basis using a difference equation simulation model. The simulation model mimics the heuristic‘rules of thumb’used by production planners for product distribution and container reuse planning. The results of our study indicate that this formulation provides a timely response in the field to key operational problems addressed by no previous approach. Included are better organizational control (through providing one-week production and distribution plans), feedback allowing modification of heuristic rules previously used in controlling the distribution of product and container reuse, and improvement in inventory behaviour such as avoiding shortages. These improvements have resulted in considerable market share gains since the models were implemented.

ISSN:0160-5682    

DOI:10.1057/jors.1996.5

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractAs linear programs have grown larger and more complex, infeasible models are appearing more frequently. Because of the scale and complexity of the models, automated assistance is very often needed in determining the cause of the infeasibility so that model repairs can be made. Fortunately, researchers have developed algorithms for analysing infeasible LPs in recent years, and these have lately found their way into commercial LP computer codes. This paper briefly reviews the underlying algorithms, surveys the computer codes, and compares their performance on a set of test problems.

ISSN:0160-5682    

DOI:10.1057/jors.1996.6

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractData envelopment analysis has become an important technique for modelling the relationship between inputs and outputs in the production process, particularly in the public sector. However, whenever measures of the output of public sector activity receive public attention, there is a strong possibility that there will be a feedback from the achieved output to the resources devoted to the activity. In other words, the level of resources is endogenous. The implications of such endogeneity for standard econometric estimation techniques are well known, and methods exist to deal with the problem. Most commentators have assumed that endogeneity poses no analogous problems for DEA because the technique merely places an envelope around feasible production possibilities. Using Monte Carlo simulation techniques, however, this paper shows that the efficiency estimates generated by DEA in the presence of endogeneity can be subject to bias, in the sense that inefficient units using low levels of the endogenous resource may be set tougher efficiency targets than equally inefficient units using more of the resource, particularly when sample sizes are small. The paper concludes that, in such circumstances, great caution should be exercised when comparing efficiency measures for units using different levels of the endogenous input.

ISSN:0160-5682    

DOI:10.1057/jors.1996.7

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractResearch suggests that many schools have a differential effectiveness with pupils of different ability. For example a school may be more effective in raising the performance of pupils of low rather than higher ability or vice versa. The identification of the existence of any differential effectiveness at a school is important as it can prompt a review of teaching practices, which will benefit ability ranges hitherto disadvantaged and thereby improve the overall effectiveness of the school. The most appropriate data for assessing differential effectiveness would be at pupil or, at least, at ability range level. Such data is not generally available. This paper develops a data envelopment analysis (DEA) based method that can identify the existence, and indicate the direction of, differential effectiveness at a school using data covering the full range of pupil abilities. The method can also identify role model schools for a school seeking to alter the bias in its differential effectiveness.

ISSN:0160-5682    

DOI:10.1057/jors.1996.8

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThe problem of ordering a single or a series of production runs to meet a single make-to-order demand, where the various stages in the production process have binomial yields, is addressed. Use of additional procurement of part-finished products or reworking defective material previously made to supplement yields at any stage is considered. The costs of this and manufacture, disposal of surplus or shortages are assumed to be proportional to the numbers involved. It is shown that when a single production run is considered, the optimal policy is defined by two critical numbers (control limits) at each stage. The treatment of ordering a series of production runs follows from and builds on the single run analytical result by developing an approximation in which the problem is decomposed into a series of single runs. Set-up costs may or may not be incurred.

ISSN:0160-5682    

DOI:10.1057/jors.1996.9

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractIn a service environment, a stockist usually has many slow moving items whose infrequency of demand can give rise to forecasting problems. Moreover, when a demand occurs, the request is sometimes for more than a single unit, which results in so-called lumpy demand. In this paper, the standard method for dealing with such intermittent demand is reassessed. Some general results are presented that enable variance estimates to be made, and these are particularly straightforward when the demand occasions can be represented as a Poisson process. Some experimental evidence is advanced to support this model in the specific situation under study. Since EWMA forecasts are central to many commercial systems, a simulation analysis was conducted to determine under what conditions intermittent demand requires its own model, rather than an unadjusted EWMA. Superior performance is demonstrated for items that have an average inter-order interval greater than 1.25 forecast review periods, and the magnitude of the improvement increases as the average interval lengthens.

ISSN:0160-5682    

DOI:10.1057/jors.1996.10

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor