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EN
This article presents the process of innovation diffusion in the context of Systems Thinking. The Bass diffusion model is built and converted into a computer simulation model with all variables defined in terms of the System Dynamics (stocks and flows). The computer simulation on the Bass' model confirms a typical for real-life innovations behavior. Various initial assumptions and their impact upon the innovation diffusion are tested.
EN
The aim of our paper is to present the new results of research work on optimization and simulation for some logistic problems in the company. The System Dynamics (SD) method and the Vensim simulation language are applied in order to solve specific managerial problems described by Forrester in the model of supply chain. The historical model of Customer-Producer-Employment System by Forrester (Forrester, 1961) has not been examined with the sensitivity analysis, from the “automatic” testing perspective. Optimization experiments have not been conducted, either. It is surprising, since the model is old and widely known. The opportunities offered by the Vensim language allow us to perform such analysis. The visualization called “confidence bounds“ is used, to show the behaviour of chosen variables over a period of time. The Monte-Carlo method is applied for sampling a set of numbers from within bounded domains (distribution for each searching parameters is specified). The authors of this paper conducted numerous experiments in this scope. This paper presents their results and offers some conclusions formulated at the end.
Organizacija
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2010
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vol. 43
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issue 3
102-112
EN
The design of strategies for social systems requires the use of qualitative information owing to the fact that quantitative information can be insufficient to solve the problems involved. The information that the specialists and the decision makers obtain is often incomplete and unreliable. Nevertheless, leaders have to make strategic decisions despite these deficiencies which should be based on the formal models (Kljajić et al. 2000; Škraba et al, 2003; Škraba et al 2007).This paper describes a methodology elaborated to design the strategy of the city of Santa Cruz (on the Canary Islands). It has two main sections: the elaboration of a qualitative model and the use of System Dynamics. We combine them in a way that allows mixing qualitative and quantitative information to achieve a better understanding of the structure of the region, to know the tendencies of the present scenario and to estimate of the effects of alternative strategic decisions. We have obtained these results working with scarce quantitative information. This methodology may be applied to any social systems with similar characteristics.
PL
W artykule zaprezentowano wyniki badań symulacyjnych i optymalizacyjnych wykonanych na modelu kolejkowym typu MX/G/1/N z polityką wielokrotnych okresów przestoju (okresów bezczynności stanowiska obsługi). Model został wykonany w oprogramowaniu Vensim przy użyciu metody Dynamiki Systemowej, co pozwala na wspomaganie podejmowania decyzji w zakresie ustalenia optymalnej długości czasu trwania pojedynczego przestoju (co bezpośrednio wpływa na uzyskanie optymalnych charakterystyk całkowitego okresu bezczynności i zajętości stanowiska obsługi względem zadanej intensywności ruchu, np. strumienia pakietów). W tym celu wykorzystane zostały wbudowane w aplikację Vensim narzędzia do symulacji i kalibracji, a rezultaty badań zostały zaprezentowane w postaci wykresów prezentujących otrzymane charakterystyki. Na koniec przedstawiono możliwe zastosowania wraz z kwestiami otwartymi dla dalszej pracy badawczej.
EN
The article presents the results of simulation and optimization tests performed on a type MX/G/1/N-type queueing model with multiple vacation policy (periods of inactivity of the service station). The model was made in the Vensim software using the System Dynamics method, which allows to support decision making in determining optimal lengths of individual holiday duration in order to obtain selected optimal queuing characteristics in relation to a given traffic intensity (e.g. packet stream). For this purpose, the simulation and calibration tools built into the Vensim application were used, and the test results were presented in the form of graphs presenting the obtained characteristics. Finally, possible applications are presented along with open issues for further research work.
PL
Analiza, modelowanie i symulacja złożonych nieliniowych, dynamicznych i wielopoziomowych systemów ma długą historię, szczególnie w obszarze słynnej metody Dynamiki Systemowej. Współczesne języki symulacyjne, takie jak Vensim, pozwalają na łączenie symulacji z optymalizacją, co umożliwia ocenę wrażliwości parametrów w modelowanych obiektach i wybór optymalnych decyzji. Zakres modelowanych obiektów jest bardzo szeroki: od modeli przemysłowych, po ekologiczne i ekonomiczne. Problem badawczy artykułu odnosi się do takich dyscyplin, jak: Teoria Decyzji, Teoria Organizacji, Badania Operacyjne.
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