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- Type:
- Document
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- The Institute of Safety and Systems Management of the University of Southern California (USC) operates a Masters of Science Program in Systems Management (MSSM) at the main campus in Los Angeles and at 70 study centers located throughout the United States, Europe and the Pacific Far East. An introductory course in system dynamics is offered as an elective in the program. The students are interested in how managers use system dynamics and in the lessons from previous applications of system dynamics in large organizations.One such application is the on-going project for the Bonneville Power Administration (Bonneville). System dynamics models are used at Bonneville to assist in the formulation of conservation policies. This paper provides a brief summary of the Bonneville project before turning to the main question of interest: What lessons from the Bonneville project are generally applicable to large organizations and worthy of attention in the MSSM program?
-
- Type:
- Document
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- This paper gives a brief account of the technical details of Chinese Character DYNAMO compiler, which follows the current DYNAMO grammar. The compiler is in the form of modules, which lays good foundation for further expansion. Taking DYNAMO as a kernel, reinforcing its internal function and statistical analysis of results, joining other programming languages, methods and modules, adding verification of model and using advanced ideas of other branches of system science, we can build a Modelling System with Chinese Character DYNAMO as the kernel. This paper gives the logic design of the Modelling System.
-
- Type:
- Document
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- Models are continually changed and altered, and it is clear that more effective techniques for accomplishing this can make modeling easier and faster. One common way that models are changed is to remove selected pieces of structure from the model. This type of model alteration can be done for debugging a model, for tuning a model, and for performing policy analysis. In this paper we present techniques that automate the processes involved in removing components of model structure. By taking out some of the drudgery of changing a model, and guaranteeing consistency in the resulting altered model, the techniques greatly enhance modeling fluency and speed. These techniques are implemented in a software package that is part of Professional DYNAMO.
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- Type:
- Document
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- 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
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- 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
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- 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
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- 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
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- 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
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- 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
- Fecha de Creacion:
- 1987
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, 83d7d84d4a906b77a877f50ccddf0ccd, and ef456d2a6c943c510d5169405dfd9416
- Descripción:
- 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.