Journal of the Operational Research Society

Ormerod, R J

doi: 10.1057/palgrave.jors.2600465pmid: N/A

AbstractThis paper attempts to set out a personal view of the future of OR in the UK. Against a context of a changing political, economic, social and technical environment those areas where OR can contribute are identified. Three areas are selected and illustrated with examples from personal experience. Firstly, in a world awash with data, the smart bits, the algorithms are often primitive. OR is successfully established in this area and can maintain itself as the pre-eminent provider of smart bits. Secondly, OR has developed helpful ways, consulting approaches, to guide successful interventions. Here OR competes with other professional groups. OR has developed unique approaches but will need to contest the ground, vigorously and with imagination. Thirdly, OR can contribute to things that matter, important strategic, political and social issues of the day. OR will have no automatic right to be heard. The contribution will depend on the motivation and skill of key individuals. The recent trend away from in-house OR groups to external consultancies and small firms provides OR with the opportunity to become the discipline that underpins consultancy, offering exciting opportunities for young academics and practitioners.

Nass, R; Dekker, R; Van Sonderen-Huisman, W

doi: 10.1057/palgrave.jors.2600460pmid: N/A

AbstractWe present a case study on physical distribution management for a production company in Western Europe. The company delivers finished goods both from distribution centres and directly from plants to its customers. The lead time from distribution centres is shorter, but higher costs are involved. The choice for delivery of an individual order is based on the so-called stockmix and cutoff order size. The stockmix is the set of products stocked at the distribution centre, which for efficiency reasons is restricted. Orders smaller than the cutoff order size are delivered from the distribution centre closest to the customer, provided that the product ordered is present in its stockmix. Otherwise they are delivered from the production plant that makes the product. In this paper we develop methods to determine both the stockmix and the cutoff order size for each distribution centre. The objective considered is the minimisation of distribution and handling costs subject to service constraints.

Ülengin, F; Topçu, İ

doi: 10.1057/palgrave.jors.2600444pmid: N/A

AbstractThis paper discusses how to use an integrated cognitive map-knowledge based decision support model to help the transportation planners in their selection of the most suitable alternative for a water crossing infrastructure. It also illustrates the evolution of this research since 1994. In this latest version, the knowledge is acquired from 19 experts on the subject and then an expert system is used to evaluate the alternatives based on their centrality, namely relative importance, shown by the aggregated cognitive map. Finally, this version of the model is applied to solve the water crossing traffic congestion of the Bosphorus at Istanbul and the validity of the results is discussed.

Tcha, D-W; Choi, T-J; Myung, Y-S

doi: 10.1057/palgrave.jors.2600448pmid: N/A

AbstractWith an increasing population of mobile subscribers, the signalling traffic to control the subscriber mobility expands rapidly. Subscriber mobility is controlled through location registration based on the so-called location area, the basic area unit for paging which consists of a number of cells. There is a tradeoff between the two kinds of signalling traffic: paging and location updating. As location areas include a larger number of cells, the traffic volume for paging increases while that for location updating decreases. Given not only the pattern of call arrivals but also that for subscriber mobility, our problem is to minimise the total signalling traffic by optimally partitioning the whole area into location areas. We show that this problem can be transformed to the so-called clique partitioning problem (CPP). Also we demonstrate the process of implementing the algorithm for solving the CPP for real-world problems defined on the cellular network in Seoul.

Willcocks, L P; Lester, S

doi: 10.1057/palgrave.jors.2600463pmid: N/A

AbstractDespite the massive investments in Information Technology (IT) in the developed economies, the IT impact on productivity and business performance continues to be questioned. The paper critically reviews this ‘IT productivity paradox’ debate. It suggests that important elements in the uncertainty about the IT payoff relate to deficiencies in measurement at the macroeconomic level, but also to weaknesses in organisational evaluation practice. The paper reports evidence from a 1996 UK survey pointing to such weaknesses. Focusing at the more meaningful organisational level, an integrated systems lifecycle approach is put forward as a long term way of strengthening evaluation practice. This incorporates a cultural change in evaluation from ‘control through numbers’ to a focus on quality improvement. The approach is compared against 1995–96 research findings in a multinational insurance company, where senior managers in a newly created business division consciously sought related improvements in evaluation practice, and IT productivity.

Glen, J J

doi: 10.1057/palgrave.jors.2600477pmid: N/A

AbstractFishery policy evaluation should take account of the initial state of the fishery and the population dynamics of the fish stock. Although multicohort bioeconomic fishery policy evaluation models have been developed, the results from these models depend on the choice of planning period and the desired state of the stock at the end of this period. In this paper it is noted that these limitations can be overcome by evaluating fishery policy over an infinite time horizon, and a mixed integer programming (MIP) model is developed for carrying out this form of analysis in a multicohort single species fishery. This new MIP model allows policies to be evaluated over an infinite horizon by incorporating results from a steady state fishery model into a multiperiod framework. The use of this MIP model in determining policies for reaching and maintaining a steady state is illustrated.

Hurrion, R D

doi: 10.1057/palgrave.jors.2600468pmid: N/A

AbstractA method of finding the optimum solution for a stochastic discrete-event system is described. A simulation model of the system is first built and then used to train a neural network metamodel. The optimisation process consists of using the metamodel to find an approximate optimum solution. This solution is then used by the simulation as the starting point in a more precise search for an optimum. The approach is demonstrated with an example that finds the optimum number of kanbans needed to control a manufacturing system.

Karaesmen, F; Gupta, S M

doi: 10.1057/palgrave.jors.2600462pmid: N/A

AbstractWe consider finite buffered queues where the arrival process is controlled by shutting down and restarting the arrival stream. In the absence of holding costs for items in the queue, the optimal (s, S) policy can be characterised by relating the arrival control problem to a corresponding service control problem. With the inclusion of holding costs however, this characterisation is not valid and efficient numerical computation of the queue length probability distribution is necessary. We perform this computation by using a duality property which relates queue lengths in the controlled arrival system to a controlled service system. Numerical results which analyse the effect of setup and holding costs and the variability of the arrival process on the performance of the system are included.

Sepil, C; Ortac, N

doi: 10.1057/palgrave.jors.2600458pmid: N/A

AbstractAll large scale resource constrained projects involve cash flows occurring during their life cycle. Several recent studies consider the problem of scheduling projects to maximise the net present value (NPV) of these cash flows. Their basic common assumption is that cash flows are mainly associated with specific events and they occur at event realisation times. An alternative assumption, which can be more realistic, is that cash inflows occur periodically, for example every month, as progress payments. This article considers the problem of maximising NPV given the alternative assumption. Three different heuristic rules are developed. The performance of these heuristic rules is analysed through a full factorial experiment with 108 scheduling conditions. The results indicate that three rules provide near-optimal schedules with respect to NPV maximisation while producing time schedules that do not delay the project completion time extensively.

Hadjinicola, G C; Kumar, K R

doi: 10.1057/palgrave.jors.2600455pmid: N/A

AbstractIn this paper we examine the impact of changes of such factors as tariffs/import cost, exchange rate, and unit savings derived from economies of scale, on the product design of four international strategies which are characterised by two dimensions. The first dimension describes whether the company offers a standardised or a customised product. The second indicates whether the company centralises its production to a single facility in one country or decentralises its production to facilities located in each country. To address the above issue, we present a model that has elements from marketing and manufacturing.For the case where the product has one attribute, we show that when tariffs/import cost decrease, an international enterprise should respond by enhancing the features of its products. Similarly, the product features should be enhanced when the exchange rate increases or the unit savings derived from economies of scale increases. Numerical examples indicate that an international enterprise should change its production configuration from decentralised to centralised, in environments of high tariffs/import cost. Furthermore, an international enterprise should change its product policies from customised to standardised when the savings derived from economies of scale are high, and the exchange rate increases.