Engineering Costs and Production Economics最新文献

This paper deals with a chemical process interpreted as a paper mill. In order to improve certain properties of the process, an additive is injected at various points in the process flows. At certain stages there are diverging feedback flows leading back to earlier stages, occasionally via storage tanks. Also there may be feedback flows coming from other externally connected processes. The problem treated is to determine the concentration of the additive in different process flows. For this purpose, the process is interpreted as a general linear input-output system. It is shown that the solution can be obtained by computing two inverse matrices, both related to the Leontief inverse.

In this paper a multi-location inventory model with redistribution is considered for the discounted cost criterion. Periodically each location gets a fixed amount of a given product.

At the beginning of a period it is possible to sell some product out of the system. At the end of a period the rest stock can be redistributed for decreasing system's cost. Unused product is lost as well as the unsatisfied demand.

We investigate the existence and the properties of optimal selling and redistribution decisions. For the 2-location model we have solved two numerical examples.

Economists modeling firm-decisions generally have to assume that the firms form their expectations according to some hypothesis. Recently it has been fashionable to assume rational expectations, whereas earlier researchers used a variety of simpler models. This paper provides evidence on which of these various theoretical assumptions is ‘best’ by examining which model best explains observed data on manufacturers' sales expectations. The results suggest that these manufacturers used simple extrapolative or autoregressive models to forecast their sales.

A lot-size model with non-linear demand patterns is considered. Under certain conditions the correctness of Harris's formula for the optimal lot size is shown even in the stochastic case.

The purpose of this paper is to contribute to the transfer to service organisations of managements concepts developed in manufacturing. We assume that the reader is aware of the classical materials management concepts and techniques. What we want to do is to provide a conceptual framework describing various situations of different service organisations which helps to see where and how these concepts and techniques are applicable.

The classical dynamic lot size problem without backlogging is usually solved with the aid of various heuristics. Most heuristics are sequential, i.e. the demand is considered period for period, and a decision whether to include the demand in a certain period in the preceding batch is taken without regarding the future demand. Recently, it has been shown how to design a sequential lot sizing rule that will optimize the average performance, provided that a typical demand looks like a sequence of independent and identically distributed random numbers. The purpose of this paper is to evaluate if and how this methodology can be implemented in practice. The new lot sizing techniques are evaluated in a simulation study for different types of demand.

This paper deals with the use of cost parameters in optimization models. The components of order and holding costs are analyzed - these greatly affect the cost level and the validity of the model. On the basis of empirically tested results, the background for the suggestions on the determination of unit costs and on the ways of costs calculations is given.

Despite the emphasis on and success of Just-in-Time (JIT), and the drive towards zero inventories implying lot sizes of one, companies for the time being still have to deal with lot sizes. The determination of optimum order quantities revolves around the inventory holding costs, and set up costs. In the literature on economic order quantities, holding costs are considered as variable costs only. However, decisions regarding storage capacity (for holding raw materials, semi-finished or finished items) have also to be made and these capacity decisions introduce a fixed cost component to the holding costs. The present paper develops a model which incorporates a fixed cost component in the holding costs, presents the determination of the optimum EOQ and the consequent storage size requirement.

The paper links the problem of inventory hoarding in centrally planned economies to the more general question of economic reforms. Any reform not only attempts to change the performance of a national economy but also formulates the principles of social change; economic reforms have their ethical dimension. Special interest is devoted to the conditions which influence the behaviour of socialist enterprises, particularly in Czechoslovakia.

Reserves of spare parts are inventories of spare parts earmarked for specific purposes and for specific equipment with the aim of making these spare parts available without delay to the maintenance department in case of need. There are some characteristics of these reserves and some principles of its disposition. Based on this knowledge a computer aided disposition was designed including the following functions: modification service and determination of standard stock, stocking, stock availability checking, supervision of stocks, and ordering and contract treatment.