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- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- This paper describes a pilot model, the harbinger of a comprehensive package of interactive national, regional and sectoral models of Taiwan, to be used for long range planning. The model, called DMT (Development Model of Taiwan ) is distilled from many mental and verbal models of Taiwan, each of which involved various segments of the system with considerations given to certain variables and to various policy interventions involving still other variables.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- Research and Development (r&d) are the source for planned invention and innovation and therefore play a crucial role for the success of a company. New products and processes become indispensable because of technical progress and competition. Early long-range r&d planning is required.Despite the strategic importance of r&d budgeting, the usual approach resembles more a rule of thumb than a scientific method. The process most widely used takes a fixed percentage of sales for r&d. This sales orientation approach seems perhaps too simple, as there is no causal link between today's sales and tomorrow's products. Another method considers the product-innovation-rate; this is the fraction of total sales which comes from products that are younger than e.g. five years. The actual product-innovation-rate then is compared with an intended value (e.g. forty per cent) and the r&d budget is accordingly adjusted.Contrary to previous studies, a System Dynamics simulation shows that the rather sophisticated product-innovation approach does not lead to better results in terms of cumulated profit. In its place, a modified approach, which avoids the disadvantages and combines the benefits of both the sales and the product-innovation-rate orientation methods, has been developed and implemented. This sales-oriented product-innovation rate approach shows superior results in some of the scenarios tested, including expansion and shrinkage portfolio situations.The handy but accurate System Dynamics model (less than hundred equations) is easily adaptable to individual circumstances of specific industrial enterprises and therefore offers practical support for strategic long-range planning.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- In this paper we present methods developed to aid the application of modal analysis to large system dynamics models. The approach is based on a method of direct linearization which can be achieved using DYNAMO equations derived from the model being studied. The linearization is followed by identification of the sub-systems of the model and a modal analysis of the sub-systems. The sensitivities of the modes to structural and parameter changes are used along with a causal loop diagrams to propose changes in the model that will have a desired dynamic effect.Application is made to Lyneis' model of a firm. As suggested by the analysis, modifications both in the polarity of some relationships and in their strength are introduced to stabilize each sub-system and the results are shown to be positive using the criterion of over-all profitability of the model firm. The paper concludes with a discussion of further developments of the process and to account more completely for the non-linearity of the system.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- This paper describes a model of the life cycle of the petroleum resource in United States. Expanding on prior system dynamic models of petroleum resources, the model endogenously generates the complete life cycle of the resource. The model treats endogenously the petroleum demand, the development of technology for and investment in exploration and recovery, the discovery and production of petroleum and the development of petroleum substitutes. With only two exogenous variables (GNP and the international petroleum price), the model is able to portray the evolution the petroleum resource, and the associated industry, starting in 1870. The correspondence between simulated and actual data is examined through a variety of statistical measures. The model is used to show how the interplay of technological progress, depletion, and the development of substitutes create the lifecycle by altering the dominance of the feedback processes in the system. A full documentation may be found in (Davidsen, 1987).The model constitutes the basis for more comprehensive studies in the following areas of concern, all related to the management of depletable resources: 1. Adaptation of the model to different kinds of depletable resources, and generalizations to obtain a model portraying the generic structure of the life cycle of a depletable resource. 2. Analysis and evaluation of current practices in the management of depletable resources. 3. Design and evaluation of alternative strategies for the management of such resources.The model seems furthermore to be a promising tool for teaching resource management.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- A study of the management structures for state parks and natural resource protection areas is presented in this paper. This analysis vehicle is a system dynamics model of a typical park encompassing flora and fauna natural resources, cultural heritage resources, and recreational areas. Such systems are complex feedback structures where management goals must be drawn to achieve desired ends within fiscal and personnel constraints. The model is used to suggest methods of measuring the tradeoffs between goal accomplishment and resource constraints. The model was developed through an extensive study of the Parks System of Florida.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- This paper is based on direct observation of privately and government owned enterprises in Argentina, Italy, Poland, U.S.A. and Yugoslavia.A causal model is presented which is found in all enterprises operating successfully and efficiently over time. The frequently observed inefficiencies in government owned companies are explored with its help. The same method suggests why certain privately owned enterprises exhibit inefficient behaviour while on occasions government owned enterprises are an example of dynamic, foresighted and efficient management.The external pressure groups and their methods for exercising influence through government bureaucracy and other channels on company management are found to be of great importance and so is the legal structure and competitive environment in which management operates. The availability of adequately trained managers is another key element.Several general recommendations are formulated for policies that will ensure efficiency in both government and privately owned corporations.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- System Dynamic models, being causal simulation models, are in this sense very much like scientific theories. Hence, there is a relationship between validation of such models and verification of scientific theories. In evaluating System Dynamics models, we naturally apply our implicit “norms of scientific inquiry”. Most criticisms of such models hold that System Dynamics does not employ formal “objective”, quantitative model validation procedures. We show through a historical review of Philosophy of Science, that this type of criticism presupposes the logical-empiricist philosophy of science. This philosophy assumes that knowledge is entirely “objective representation” of reality, and that theory justification can be entirely objective, formal, “atomistic” process. According to the more recent “relativist” philosophy of science, on the other hand, knowledge is not “entirely objective Truth”, but it is relative to a given culture, epoch, and worldview. Theories can not be verified (falsified) by entirely formal, reductionist, “confrontational” methods. Completely objective (theory-free) observation is impossible. The act of observing itself requires an assumed theory. Theory justification is therefore a semi-formal, holistic, social, “conversational” process.We discover that these two opposing philosophies of science correspond to two opposing philosophies of model validation. Most critics of System Dynamics seem to assume the traditional empiricist philosophy of science, whereas System Dynamicists mostly agree with the recent relativist philosophy on the question of model validity. We show that these philosophical results do have practical implications for both the System Dynamicists and their critics. Finally, having shown that the relativist philosophy is consistent with System Dynamics practice, we emphasize that such a philosophy of model validity should not lead to a total rejection of formal quantitative tools of model validation. On the contrary, we argue that such tools, appropriately chosen, are most useful when interpreted with the relativist philosophical perspective.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- Advances in computer technology, since DYNAMO first appeared, promise significant developments for System Dynamics modeling and simulation. This paper discusses the future System Dynamics simulation languages as part of a human-engineered, integrated simulation programming environment. Many features of such languages and environments, that may become available in the next five years, are identified and discussed. The relevant advances in Simulation and Computer Science are presented with appropriate modifications in the context of System Dynamics methodology. Some aspects of implementation of such languages and environments are also discussed.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- This paper presents a general quantitative performance measure to analyze the performance of System Dynamics models for the desired model behavior. The advantages of using a quantitative performance analysis facility are discussed. Some possible applications including optimization and sensitivity analysis are discussed. Also discussed are the implementation aspects.
-
- Type:
- Document
- Date Created:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Description:
- The use of computers to improve general and task-specific mastery is the core of most computerized learning games. But they are also employed to communicate complex structures. Substantive theories explaining concept formation and learning has been developed by Piaget (1936) and used by Papert (1980) in a computer-specific sense. A recurring assumption in theories of learning is that people who learn from computer games learn in an abstract way, i.e., they learn more than to repeat efficient manipulations of the symbols on the screen.This study develops a theory of the learning process involved when simulation games are used to reveal the structure of a complex system. Within the framework of a sample of student exposure to a compute simulation game, we find evidence for a theory that games do transmit knowledge of a complex system. In particular, the study indicates that participants Initial Experience, as well as its Relevance to the situation plays a major role in the mastery of the game. Another factor determining understanding of the structure is the use of gradually increased complexity. A System Dynamics simulation model of the learning process is developed, giving new insights into how simulation models should be built to overcome dilemmas of game transparency and real world complexity. A sample of 8 students show a close fit to the model predictions. A framework for further behavioral research and the state of the art implications for System Dynamics modelling practice is outlined.