Engineering and Process Economics最新文献

The problem which is analysed in this paper is from a wall-paper factory. The products here has a finite life cycle, which is known. The demand is uncertain but has to be supplied. Furthermore the set up costs are high compared with the variable production and inventory costs.

The main contribution of this paper is the approach which makes it possible to analyze the production-inventory problem of a wall-paper factory. This approach leads to a suggestion of a concrete production-strategy for a wall-paper factory.

This paper discussed economic aspects of metal cutting conditions on the basis: 1. maximum productivity, 2. minimum costs and 3. minimum machining costs per unit time. The optimal cutting condition with the set of criteria are given with the simulation. For the purpose of computation and efficiency it is requested to develope the computer program.

When applying an aggregate approach to production planning the system has a natural hierarchical structure. The solution of the aggregate problem is disaggregated on the lower level by changing the objective functions and the constraints in the more detailed short range problems. Often the aggregate model is formulated as a linear program since non-linear costs like set-up costs instead can be recognized on the lower level.

The traditional formulation of the aggregate model has several disadvantages, especially in case production and inventory on the lower level are controlled by separate subsystems. Therefore an alternative model with the following properties is formulated:

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  The production in different machine groups as well as the flow of orders for different product groups are obtained from the model. These results constitute relevant inputs into the lower level production planning on the one hand and inventory control on the other.

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  The work-in-progress is represented explicitly.

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  The material requirements planning is part of the model.

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  If only a small number of seasonal patterns need to be considered the size of our model will be very small compared to the traditional model.

A number of Swedish business firms and public authorities in the building sector were interviewed as to their practice and use of methods for the economic evaluation of energy conservation investments. Both the frequency and the motives for using different methods were investigated as well as some general problems concerning the basis for the calculations.

Cyclic, stepvise, on customer orders based production is a normal practice in steel plants. This, however, causes many problems to all planning horizons. In this paper a hierarchic short term planning and control system of a special steel plant is introduced. Corporate planning hierarchy is also described in short.

This paper deals with two familiar ordering policies with are usually refered to as (Q,s) policy and (s,S) policy. It is demonstrated that the (Q,s) policy which is implemented in IMPACT, does not work satisfactorily in a periodic review system since the obtained service will be very different from the desired service. In contrast to the (Q,s) policy the (s,S) policy nearly yields the desired service-level.

A production line is a series arrangement of k work stations. Each production item passes through all of the stations in sequence. The service time for a single item at station j is assumed to be a random variable. In this mode of operation any station will at any time be either busy, or idle, or blocked. A measure of the productivity of such a line is its mean production rate r. It has been conjectured that the production rate remains invariant under reversal of the production line. Line reversal means that every item passes through the stations in the reverse order, that is, beginning with station k and ending with station 1. A summary of a general proof of the reversibility property is given.

While U.K. and European based process plant construction contractors still tend to make their initial assessment of the site manpower requirements for a project in terms of the performance of their own nationals, increasingly the actual construction team will be recruited on a multi-national basis.

The general spread of categories of skills required for a project are suggested and the availability of local labour in areas of high construction activity is examined to show that it rarely can match the requirements without supplementation from outside the work area with essentially “expatriate” labour.

Areas of recruitment are examined together with mention of some of the problems associated with the host country's entry, exit and work permit requirements. The overall management of the multi-national team on site is suggested as normally no more difficult than one recruited from one country.

Although the economic justification may be marginal the authors conclude that the stability engendered on a large site by minimising the incidence of major labour disruption and possibly making the whole operation more acceptable to the host country, is increasingly sufficient reason for recruiting large construction teams on a multi-national basis.