Paul van Beek

Interactions between operational research and environmental management

Economic growth is frequently considered to be in conflict with sustainable development and environmental quality. Therefore, a decision maker needs to know how to deal with the environmental issues that come around. This article aims to inform Operational Researchers of the possibilities of incorporating environmental issues when analyzing industrial supply chains and to inform environmental scientists more generally of the value of using OR models and techniques in environmental research.

Modelling and simulating multi-echelon food systems

This paper presents a method for modelling the dynamic behaviour of food supply chains and evaluating alternative designs of the supply chain by applying discrete-event simulation. The modelling method is based on the concepts of business processes, design variables at strategic and operational levels, performance indicators, and business entities, as these concepts allow relevant aspects of a food supply chain to be described and modelled. Our simulation model is based on timed coloured Petri-nets to support decision-making when redesigning a supply chain for chilled food products. Scenario analysis allowed us to evaluate the potential benefits of alternative designs for this supply chain in terms of logistical performance. In this case study, major benefits were identified. The results of the scenario analysis are compared with the outcomes of a pilot project where one scenario was implemented in real life.

OR contributions to flexibility improvement in production/inventory systems.

Recently the notion of flexibility (especially with respect to Flexible Manufacturing Systems) has attracted considerable attention of OR workers. The majority of the contributions is focussed on operational aspects of production systems. A further very important issue concerns the design of production systems and investment decisions with respect to these systems. The aim of this paper is to illustrate how OR models can contribute to quantify effects of, for instance, investment in set-up time reduction or investment in supply leadtime reduction on logistic performance of production systems. Of course there are many more opportunities to improve logistic performance. The approach in this paper offers the opportunity to quantify the integral effects of these improvements and shows the direction for logistic innovation. In this way both design of production systems and quality of related investment decisions can be improved significantly. Some simple examples are worked out in order to illustrate the ideas and to give impetus for further research in this field.

An OR contribution to the solution of the environmental problems in the Netherlands caused by manure

Abstract In the Netherlands there is a serious manure problem. New legislation restricts the application of manure. It is becoming more difficult to give all manure an acceptable destination (application or processing). To gain a better insight into the logistic problem on a regional level, a Decision Support System (DSS) is being developed. This DSS can be used on tactical and strategic levels. A model is used to estimate the application of the farm of origin and in the vicinity and to optimize the application elsewhere and the processing. The optimization is carried out by linear programming or mixed-integer programming depending on whether location aspects and economies of scale are included. Some results are given.

Design and optimization of multi-echelon assembly networks: savings and potentialities

Abstract In the last decade considerable attention has been paid to the analysis and optimization of multi-echelon assembly networks. Research contributions in this field are mainly focussed on the determination of optimal batch quantities. In this paper two other issues concerning multi-echelon assembly networks are also discussed. The first point concerns the notion of flexibility in assembly operations. Flexibility can be achieved by spending on assembly engineering to cut set-up costs. The second point has to do with design of multi-level assembly systems. Furthermore the notion of minimum network leadtime is introduced. This turns out to be (besides minimal average cost per period) a performance indicator of considerable importance. To conclude an existing Philips product (called medsys ) is presented in order to illustrate the ideas discussed in this paper.

Modelling and analysis of a multi-echelon inventory system A case study

Abstract In this study we discuss multi-echelon inventory models dealing with the goods within the finished goods section of a product division of Philips Industries. A model study has been carried out in order to compare several alternatives for the way in which goods are forwarded from factory, via stores to the customers. The results have been compared with the outcomes of the model describing the actual way of forwarding. Based on the positive results of the study some recommendations could be made.

The limits of sequences of iterated overshoot distribution functions

In this paper, we deal with sequences of iterated overshoot distribution functions. Under certain norming conditions and under the assumption that these sequences are convergent, the limits are completely characterized. The paper can be considered as a continuation of the work by Harkness and Shantaram [4]. As has been indicated by the referee, Shantaram and Harkness recently published a continuation of their work (see [5]). The present paper, however, is more general than [5]. The attention of the authors was directed to this problem while studying the behaviour of market demand transmitted through a chain of stock points.

An application of dynamic programming and the HMMS rule on two-level production control

SummaryIn this paper the Dynamic Programming technique and the HMMS rule are applied on a production control model of an assembly factory.On the one hand the HMMS rule is applied to the production control of the factory in total. On the other hand Dynamic Programming is applied to the production control of each single capacity group. Next both approaches are integrated.Here, the HMMS rule figures as a ‘smoothing’ framework in which the production plans per capacity group are embedded.Furthermore, a new technique concerning the calculation of the value tables is introduced: this technique makes the usual interpolations superfluous and therefore reduces computation time drastically.ZusammenfassungIn diesem Beitrag werden dynamische Programmierung und die HMMS-Regel auf das Planungs- und Steuerungsmodell einer Montagefabrik angewendet. Während die HMMS-Regel auf die Gesamtfabrik angewendet wird, erfolgt die Fertigungssteuerung der einzelnen Kapazitätsgruppen mit dynamischer Programmierung. Beide Verfahren werden dann integriert. Hier zeigt sich die HMMS-Regel als glättendes Netzwerk, in das die Produktionspläne der Kapazitätseinheiten eingebettet sind.Außerdem wird eine neue Rechentechnik eingeführt, die die üblichen Interpolationen überflüssig macht und damit die Rechenzeit drastisch verkürzt.

OR Contributions to Flexibility Improvement in Production systems

Recently the notion of flexibility (especially with respect to Flexible Manufacturing Systems) has attracted considerable attention of OR workers. The majority of the contributions is focussed on operational aspects of production systems. A further very important issue concerns the design of production systems and investment decisions with respect to these systems.