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5 Systems : journal of transdisciplinary systems science

5 2007

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Diagnostics of "UUUU…" type situations in Logistic Systems

100%

Przystupa F. W.

tom Vol. 12, nr 2

21-28

In the case of a sometimes appearing disturbing process of the UUUU type: Unforeseeable (probability), Unexpected/Sudden (time), Unknown (knowledge) or Ungovernable (increments) in the functioning of Logistic Systems (LS's), diagnostic is not being introduced. As usual, because of lack of consciousness and awareness of the character of action in such a specific situation, one behaves and acts ineffectively or even wrong. The methodological ordering of diagnosing in UUUU... situations in logistic systems will permit to improve diagnosing by utilizing already existing possibilities or by building new tools for conscious, new conditions

Problems of designing a logistic support system with time dependency

80%

Werbińska S.

tom Vol. 12, nr 2

37-50

The paper considers the time dependent system of systems where the system total task must be executed during constrained time resource. For the developed model, general analytical equations for the evaluation of system of systems downtime, availability function, and total expected cost function are derived. Furthermore, the theoretical results with sensitivity analysis are discussed when all probability density functions are to be exponential

Analiza porównawcza klasycznych modeli sterowania zapasami

80%

Jodejko A.

tom Vol. 12, nr 2

79-89

Celem artykułu jest analiza wyników, jakie uzyskać można przy jednakowej charakterystyce popytu i czasu realizacji dostaw przy zastosowaniu odmiennych modeli sterowania zapasami: (Q/ s), (S, t), (S, s). Rezultaty badania przedstawiają m.in. różne możliwości adaptacyjne poszczególnych modeli do losowych warunków działania przedsiębiorstwa oraz wyniki poszczególnych modeli z punktu widzenia wybranej funkcji celu.

Various kinds of inventories are one of the basic ways to control the random character of economic processes. The inventory literature gives a great number of models which may be used in order to gain specified goals of an enterprise: financial or other results. When a company works in random conditions, the literature and the market practice propose effective inventory control models, which have an ability to adapt to existing situation. The most popular are models called: re-order point (Q,s) and re-order cycle (S,t) and their combinations. The question is -- which model one should choose and what results it will show? The aim of this paper is to analyze the effect of different inventory control models in such exemplary system, when the demand and lead time are the same. The models (Q,s), (S,t) and their combination (S,s) are examined. The investigation was made on the base of simulation experiments, separately for every inventory control model. The assumed demand had normal and exponential probability distribution and the lead time was constant, normally or exponentially distributed. Two types of outcomes were tested: the total inventory cost per unit time and the service level. The research allows stating that the same input data cause different results, depending on the inventory control model. The (S,s) model has the best ability to adapt to random conditions of the enterprise functioning. It produces higher service level than (Q,s) for almost all tested values of order quantity Q. The financial results of both models were comparable. The (Q,s) model is the policy whose parameters should be precisely selected. When the enterprise has to especially avoid inventory lack, it is better to apply (S,s) model. When speaking about lead time, the examination allows saying that constant lead time causes the lowest inventory lack probability. When lead time is exponentially distributed, it is much harder to reduce the inventory shortage risk than in other cases. That is why, when the enterprise has to take into account some safety restrictions, it should analyze lead time character while determining inventory policy. The total inventory cost of various models related to service level shows that the cost mainly depends on demand and lead time character and the kind of inventory control model has lesser meaning.

Relations between probabilities of high states describing the bottleneck of a certain inventory system and the dynamic parameters of an aggregated input

80%

Mercik J. , Galanc T.

tom Vol. 12, nr 3

3-7

The authors investigate a bottleneck in an inventory system composed of the following subsystems: production, transport, storage, and receiver. In order to obtain a mathematical description of the bottleneck in the system, the authors derive a system of differential equations which is satisfied by the probabilities of the high states of a process controlled by an aggregated product supply process.

Diagnostics of "UUUU…" type situations in systems

80%

Przystupa F. W.

tom Vol. 12, nr 3

36-48

During the functioning of systems sometimes unknown events occur - being by nature dangerous, redoubtable and destructive events. The possibility of a preventive observation by diagnosing methods assures minimizing the consequences of such events. In the case of a sometimes appearing disturbing process of the UUUU type: Unforeseeable (probability), Unexpected/Sudden (time), Unknown (knowledge) or Ungovernable (increments), diagnostic generally is not introduced in the functioning of technical systems. As usual, because of lack of consciousness and awareness of the character of action in such a specific situation, one behaves and acts ineffectively or even wrong. The methodological ordering of diagnosing in UUUU... situations in technical systems will permit to improve diagnosing by utilizing already existing possibilities or by building new tools for conscious, new conditions