System Theories and Practice, 2013, vol. 9, issue 2


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  • Pozycja
    The Modeling Process of the Materials Management System in a Manufacturing Company Based on the System Dynamics Method
    (Nowy Sacz School of Business – National-Louis University, 2013) Baran, Małgorzata
    The article presents the steps of modeling of the material management system in a manufacturing company. First, the modeling procedures indicating by Forrester, Łukaszewicz, Souček, Tarajkowski and Sterman were described and the essence of materials management in a manufacturing company was presented. Next, modeling of the materials management system was shown - step by step. Initially, the variables of the mental model connected with materials were defined, then variables in casual loop diagrams were linked. Diagrams were transformed into a simulation model that has been verified. The validation of the simulation model was conducted by using the following methods: assessing the correctness of the boundary of modeling, adequacy of the model structure and adopted values (constants) compared with available knowledge about the modelled system; test of the accuracy and consistency of the units of variables adopted in the model and test of the model behavior in extreme conditions. The study endpoints included the simulation of the model on empirical data, which were collected in the company Alpha and test of the “what ... if ...”. The test showed that the small changes in control norms (constants), which control the system, could have influenced to more rational management of that system.
  • Pozycja
    Context and Animacy Play a Role in Dynamic Decision-Making
    (Nowy Sacz School of Business – National-Louis University, 2013) Osman, Magda; Ananiadis-Basias, Alexandros
    Perception, judgment, and reasoning are all processes that are sensitive to cues to animacy (i.e. the presence of signals that indicate an object behaves as if it has intentions and internal goals). The present study investigated the following question: Does animacy facilitate decision-making in a dynamic control system? To address this, the present study used a dynamic decision-making task and compared behavior in four different contexts (Abstract, Animate-Social, Inanimate-Social, Inanimate-Non-social). Participants were randomly allocated to one of these contexts, and in each version they were required to learn to manipulate variables in order to bring the dynamic system to a desirable state and maintain it at that level. The findings suggest that it is not animacy per se that facilitates decision-making behavior, but rather the presence of a context. However, animacy made an impact on the type of strategic behavior implemented when interacting with the dynamic system. We argue that context induces general beliefs about causal relationships in dynamic environments that generalize across animate as well as inanimate contexts.
  • Pozycja
    Validation of System Dynamics Models – a Case Study
    (Nowy Sacz School of Business – National-Louis University, 2013) Lemke, Justyna; Łatuszyńska, Małgorzata
    The purpose of this article is the analysis of the system dynamics model validation illustrated by the example of a model of the manufacturing resource allocation. In the first part of the article the authors present an overview of the definitions of validation and verification that can be found in the reference literature. Also, they emphasize the role which validation and verification play in the modeling process. Furthermore, they discuss the techniques of system dynamics model validation with particular focus on tests of the model structure, behavior and policy implications. The second part of the article contains an example of the validation process of a system dynamics model simulating manufacturing resource allocation in an electronic company. The purpose of the model is to assess the long-term effect of assigning workers to individual tasks on such production process parameters as efficiency or effective work time. The authors focus their particular attention on that part of the model which deals with a storehouse, one of the company production units. They conduct tests of its structure and behavior. When validating the structure the authors make use of the information obtained in a series of interviews with the company staff. They also refer to the generally accepted knowledge found in the reference literature. The results generated by the model in the course of the behavior tests are compared with the real data. The authors evaluate both the logic of the system behavior and the level of accuracy of the output data in reference to the real system.
  • Pozycja
    Sensitivity Analysis and Optimization for Selected Supply Chain Management Issues in the Company – Using System Dynamics and Vensim
    (Nowy Sacz School of Business – National-Louis University, 2013) Kasperska, Elżbieta; Mateja-Losa, Elwira; Marjasz, Rafał
    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.
  • Pozycja
    Exploring Alternatives for Sustainable Development in the Tamiahua Wetlands
    (Nowy Sacz School of Business – National-Louis University, 2013) Luna-Reyes, Luis Felipe; Durán-Encalada, Jorge A.; Bandala, Erick R.
    This article presents a preliminary System Dynamics model developed to analyze the sustainability of a natural reserve in Mexico: the Tamiahua Wetlands. Wetlands are often referred to as nature’s kidneys because they filter contaminants from water. In spite of their importance, wetlands are endangered areas around the world. In order to build the model we take into account the Fishbanks model developed by Meadows (2004) as a starting point. Then, the model considers variables related to changes in total and economically active populations, and contaminants in water. The preliminary model presented in this study implies that fishing activity in the Tamiahua Wetlands, together with contaminants from human activity, have the potential to damage the diversity of species in the ecosystem, endangering its sustainability. Continued work on the model is intended to explore appropriate ways of preserving Tamiahua, providing inhabitants with economic activities that promote the sustainability of the region.