Engineering and Process Economics最新文献

The knowledge of the factors that can influence directly or indirectly the productivity of a credit institution has a considerable importance for the decisions' makers especially in order to decide the optimal solution of management problems.

This paper describes a methodology for a systematic approach to the problem of the business control.

Particularly it is shown an operational model representing the business behaviour of a credit institution.

This model allows an immediate evaluation of the productivity of a credit institution by some indexes drawn from the normal system of banking book-keeping.

Although the Universities have contributed through R + D very much in the production area, there is still a large gap between theory and practice. This paper points out some of the major areas for development and suggests how Universities can support the Industry.

In this paper the problem of synthesizing control policies that ensure a good steady-state behaviour for single-input time-invariant continuous time production-inventory systems is treated. The synthesis procedure is based on modal control theory, [1], which involves generation of the input vector of a system by linear feedback of the state vector so that the eigenvalues of the closed-loop system are assigned prescribed values. The state equation of the system describes the development of inventory, work-load queue and production rate over time. The amount of initiated orders or production-order rate is used as control variable. Various aspects of the realization of the appropriate control law are discussed.

This paper treats the relationships between multiproduct LP-models and accounting principles. It shows how an LP-formulation should be adapted to the needs of financial analysts, and how ancillary cause-and-effect relationships can be formulated for costing or recompensing purposes.

A more fully expressed mathematical definition of equilibrium between supplies and demands of an intermediate product is introduced. It relates the unit value of an intermediate product to one determinate inflowing or onflowing product stream, with a specific volume. This makes decomposition techniques practicable for large decentralized organizations.

Product values and/or their corresponding inflowing or onflowing product streams, which are called linking streams, are different for different purposes of accounting or optimization. So are the components of costs and revenues to be reallocated.

This paper discusses models for a combined inventory policy where customer orders can be met either from stock or by special production runs. The daily demands are assumed to be independent random variables. No shortages may occur. Costs consist of production set-up costs, inventory holding costs, and a differential product handling cost on demand met from stock. Two models are formulated based on the following policy: If the daily demand exceeds a cutoff point P, demand is met by a special production run, otherwise it is met from stock. Stocks are replenished to a level S (a) upon depletion, or (b) jointly with a special production run provided the stock level is below a critical review point R, whichever occurs first. Computationally efficient approximations to the optimal solution are developed.

An optimal linear time-invariant control policy and an optimal linear time-variant control policy are developed to control a general linear stochastic production-inventory system with non-quadratic costs per period. The two policies are compared and the time-variant policy turns out to be better. Solution techniques are discussed and first-order necessary conditions are given.

During the last few years economists and operations researchers have paid much attention to multi-criteria analysis as a tool in modern decision-making. The basic feature of multi-criteria analysis is the fact that a wide variety of relevant decision aspects can be taken into account without a necessity to translate all these aspects in monetary terms. This article will give a brief survey of these new methods in both a quantitative and in a qualitative sense. After this survey the relevance of multi-criteria analysis for entrepreneurial decisions in the field of production and investments will be exposed. The analysis will be illustrated by means of two examples of entrepreneurial decision-problems, which have been solved by means of multi-criteria analysis.

We can make a difference between linear programming with partial and simulataneous capacity expansions. For the partial expansions it can be shown under some special conditions that the optimal shadow prices of an incomplete problem are dominating the optimal shadow prices of the complete form. The result indicates that under some special conditions we have to obserrve too hhigh optimal shadow prices caused by incomplete restrictive systems. In the case of simultanious expansions analogous reflections on optimal shadow prices are not possible, because the problem has to be solved by mixed-integer programming. However, by special indicators evaluations of expansions are possible.

A valuable commodity will tie up capital during transportation. A faster means of transport would lower capital costs whereas the transportation costs would increase. The transportation time is also influencing the lead-time and consequently the requirements of safety stock. In this paper we formulate different inventory models in which we are considering transportation costs and holding costs for inventory in transit as well as the usual inventory holding costs, order costs and shortage costs. The decision variables in the general case are velocity, order quantity and safety stock level.

The objective of the paper is to show how costs may be valued in Production Planning when Linear Programming is used and the objective is to maximize profits. In order to do this the concept of “decision relevant” cost is introduced. A basic principle for the valuation of decision relevant cost is presented, based on opportunity costs. It is shown, that, by using the valuation principle described it is possible to rewrite the objective function in a way that valuation of cost becomes much easier than in the objective function usually used without affecting the production program that maximizes profit.