System Dynamics modeling is used as an instructional aid for the teaching of production and inventory management techniques. The roles of Material Requirements Planning (MRP) and just-in-time (JIT) systems in production and inventory management are presented and discussed. By modeling these manufacturing systems, the student can acquire an appreciation of the dynamic relationships between the elements of each system. Some elements of the Dynamo models of these systems are presented. The future opportunities and research needs are discussed.
This paper tries first to put some key factors together in an integrated system (The System Dynamics· Socio-Economic Model of China), and then reveals the dynamics of stimulations and obstructions. The stimulation results of the model show that the stimulation function of different factor changes with time, and at different times, different stimuli will be the leading factors. Overpopulation, shortage in energy supply, transportation backlog, and severe pollution are all serious problems troubling China currently and in the future. The paper also studies some possible ways to remove those barriers.
In this article, we analyze the tendency of technological development and the possibility to catch up with the advanced level in China. The technology progress has been playing an important part in the future, in turn, the economic growth has significant influence on technology level. According to the policy test results, we give the proposal and get the conclusions about developing technology in China.
The purpose of this paper is to identify the main important variables and quantities which interact with the accumulation and accumulation rate, and then to analyze the intrinsic relations among them which are important in accumulation rate decisionmaking. Especially we concentrate on the relations among the accumulation rate and energy, total consumption and effectiveness of accumulation.
STELLA is a new software program that has been designed to bring system dynamics to broad-based audiences. A series of books is being developed to disseminate STELLA and system dynamics into one of these broad-based groups -- the college educational market. The books center on a "learning laboratory" approach to learning. This approach uses STELLA as the basis for an experiential, learner-controlled learning process. One of these books, "Learning Laboratories In: Physics," is described in this paper. The book contains three sections: mechanics, thermodynamics and electromagnetism. Within each section are five to six lab sessions. The lab sessions progress from simple structural models of fundamental concepts to more complex models that integrate the work from the previous labs. A sample session on Newton's laws is presented to illustrate the approach.
The question as to how sensitive a System Dynamics Model is to combination parameter changes in general is a complex one. A recent technique due to J.W. Hearne enables one to find the combination of parameter changes to which the system is most sensitive. The technique is applied here to an ecological model and a perturbation of the system along the most sensitive direction in parameter space is compared with single parameter perturbations of the same magnitude. The method may be useful in population control.
The relationship between system dynamics (SD) .and other research areas is a subject of universal interest. Attention of the paper is to the possible links between SD and GERT (short for Graphical Evaluation and Review Technique). A new simulating design for a class of GERT network is proposed and the equivalence of GERT networks to SD models established, thus a new solution to the network obtained. According to the approach, a GERT network is converted into a SD model in which levels are used to model the random variables associated with the network, such as the expected time to realize a node and the probability that it is realized. The resulting basic model can be used for calculations of any parameter of interest in the analysis of GERT networks. Its advantages and implications are discussed.
Estimates of petroleum and natura1 gas resources vary substantially, both over time and across estimation methods. This paper develops a simulation model of global oil resources to evaluate different resource estimation techniques. Protocols for the Hubbert life cycle and USGS geologic analogy methods are developed and applied to synthetic data generated by the model. It is shown that the Hubbert method can generate an accurate estimate as early as twenty years before the peak of global production, but the geologic analogy approach overestimates the true resource base over the life cycle of the resource. The results show the applicability of simulation and the synthetic data approach to the problem of evaluating forecasting methods.
The economic crisis of the 1980s has revived interest in the economic long wave or Kondratiev cycle. This paper describes a simulation game which demonstrates how long waves can arise. The game vividly shows how the investment and production policies pursued by individual firms, though rational from the point of view of the individual actors, interact in the context of the whole system to produce "irrational" behavior--periodic over and under-expansion of the economy. The game illustrates te theory of capital self-ordering developed in the System Dynamics National Model Project. The paper describes the structure and rules of the game, including protocols for operating the game. The game can be played manually or on personal computers. The paper includes virtually all the materials needed to play the game, in either the board version or the personal computer version. The game board, record sheet, and a listing of the computer program (in BASIC and suitable for IBM PCs) are included.
Increasingly, citizens and policymakers are faced with the results of computer models and must make judgments about the model's relevance and validity. How can such decisions be made in an intelligent and informed manner? Can modeling be made accessible to the ordinary person or will it remain the special magic of a technical priesthood? This paper offers tentative answers to these questions. It first highlights the characteristics and capabilities of computer models such as are used in foresight and policy analysis. The advantages and disadvantages, uses and misuses of formal models are presented. What are the fundamental assumptions of the major modeling techniques? How appropriate are these techniques for foresight activities? What are the crucial questions a model user or model consumer should ask when evaluating the appropriateness and validity of a model? The paper is designed to help model consumers peek inside these computerized black boxes.