Successful innovation management depends upon both, the intrinsic attributes of the new product to be marketed and the firm's internal performance like cost management, timely delivery and quality assurance. The impact of these latter aspects is frequently neglected in the design of models for supporting decision making in innovative firms.A model is outlined to study the market response of different manufacturing policies for innovative goods. It allows e.g. the evaluation of an aggressive strategy with large production capacities from the outset, or a more tentative behavior to avoid the pressures stemming from high fixed cost and the risks of eventually idle capacity.
Innovations in automated intelligent knowledge based systems (IKBS) including expert systems (ES) could have a major impact on the development of system dynamics methodology. This paper reports on the characteristics of an integrated system for modelling and managing complex, dynamic systems currently being developed. Essentially, the system consists of five sectors namely a simulation model; a set of quantitative measures as macros; means; a real world data set; an adaptive knowledge based system including an expert system; a policy decision making system. It is suggested that such an integrated approach to system dynamics could further enhance the usefulness of the methodology to modelling and managing complex systems.
This paper presents a system dynamics model of the transportation energy demand in Singapore. The transportation sector in Singapore is heavily dependent on oil and is one of the major consumers of energy. Thus, it is essential to model the transportation energy demand to be able to see the implications of changes in economic situation and oil prices.The transportation sector is divided into passenger transport and freight transport. Five modes of passenger transport are considered. The Mass Rapid Transit is included in this model as it will be the major mode of public transport in 1990's. The ratio of per capita energy consumption to per capita income is used to indicate the change in energy consumption as income changes. With this as a basis policy changes such as price of fuel and regulation of ownership of private motor vehicles are made.The model can be used to test various scenarios, e.g., changes in economic conditions and in fuel prices. The simulation results can then be used to examine the various policies that could be implemented to alter the transportation energy demand situation. The model has been calibrated using available information and some policy analyses have been performed with the model.
The study on urban ecology has its world-wide significance due to the phenomenon of growing “urbanization” nowadays. With System Dynamics, the author has studied the simulation model of ecosystem in Beijing. While determining the variable set and doing the sensitivity analysis , the author has posed a new method. A retrospective verification is done with historical data and then several strategies are analyzed by using this model. The research shows that the simulation model is an important method in urban ecosystem study and of great value to practical use.
In previous work, the analysis of the effects of aggregating simple dynamic systems has been studied by applying methods developed for thermodynamic systems in order to take account of stochastic effects. This approach is based on the Master Equation for the probability density of the contents of a vector of system levels. The goal of these studies is to determine the dynamic characteristics of systems composed of a population of sub-systems with the same dynamic structure while accounting for novel behavior that is introduced by the process of aggregating the sub-systems into the larger system.In this paper, the Master Equation analysis is applied to four versions of a Commodity Cycle model to determine the nature of modes of behavior that arise from the process of aggregating a population of entities whose dynamic structure is derived from the oscillatory structure of the commodity cycle model. The approach used here is novel in two respects. It contracts with the more recently developed analysis of chaotic systems in which non-linear, aggregate or lumped-parameter models generate behavior that is unpredictable while not being stochastic. In those models, no attempt is made to explain the large-scale or aggregate chaotic behavior in terms of the sub-systems. Compared to previous work in the same vein, this paper addresses itself to a slightly larger model as part of a natural progression in the analysis of ever-more complex systems by Master Equation methods.
The growing amount of the foreign debt of the developing countries shapes a gloomy future for most of them. The chances for maintained growth fueled by internal saving is nil if the service of the debt is satisfied, as it has to be to avoid international isolation. This is particularly true in the case of Argentina, with a debt equivalent to two thirds of its GDP, and its debt service representing more than 5 per cent of the GDP. After showing the historical facts about the Argentine economy, this paper presents a very simple version of a growth model type Harrod-Domar, adapted to the parameters of the local economy. Then the model is used for answering to “what-if” type of questions, wich arise from different plausible scenarios. Finally, it is analyzed the probabilistic generation of scenarios and related technical problems using DYNAMO.
During the last year, the Technical Education Research Centers (TERC) has been combining microcomputer-based data gathering instruments with model-building software using the system dynamics approach to develop curriculum materials and software for high school students. The microcomputer laboratory aids students in collecting real-time data in such areas as heat, light, sound, motion, and water movement. Model-building helps students develop and test theories to study the data. An integrated software environment is being developed that will allow the data collected to be input directly into the models. In addition, the software will include an icon driven modeling language, algebraic function grapher, and spreadsheet to provide students with several different approaches to expressing model-building and simulation.
This paper outlines the characteristics of a search process for a planning paradigm to supplant the rational approach. After a brief discussion of the ongoing debate about the shortcomings of the prevailing paradigm, the central issues and assumptions in planning method are identified. These are then used to develop a set of criteria for procedural development and evaluation to guide the search for new approaches to planning. In the first part of the paper such criteria are operationalized to develop a series of procedures and models for community development planning and measures for evaluating these are given. The second part of the paper reports on the actual implementation and evaluation of the approach as an appropriate search strategy. The context, the models, and the evaluation results obtained in two applications, Door County Wisconsin and Janesville Wisconsin, are presented. Based on these applications the potential of the overall approach as a search strategy is discussed.
Earlier work demonstrated the presence of two long waves of colonial administration of different lengths (1490-1825 and 1826-1969). Whether these were separate episodes or examples of deeper underlying cyclical dynamics has implications for the existence of a common system dynamic over the long wave. To further inquire into the existence of a common cyclical rhythm these larger waves were decomposed through the use of a non-parametric stochastic measurement model.To do this a 490 year time series of colonial administrations is divided into ten episodes. A conditional Normal-Poisson model is proposed based on the assumptions of a stochastic process. The mean number of colonial administrations established and terminated over each episode are estimated, controlling for a quadratic time trend which would be induced if the system was not constant throughout an episode as assumed. Two sub-cycles are observed withing each of the two long waves of colonial administrations previously reported (Bergesen and Schoenberg, 1980).The presence of these matching sub-cycles provides a strong evidence supporting a common system dynamic in not only economic but political aspects in international life.
This paper describes the work of an M.I.T. research project (the Systems Thinking and the New Management Style Project) to bring systems thinking to top management groups in several large, successful corporations. The principal research tool, the “strategic forum” is described and critiqued. The paper then presents a case study to illustrate the strategic forum. Concluding remarks and supporting figures are presented at the end.
Dental diseases dealt with in this study are cavities (fillings, extractions and crowns), pyorrhea and baby teeth.The total number of teeth with dental diseases in Japan changes year by year depending on oral conditions ans are affected by the number of dentists, economic conditions and technical progress.This model contains 4 sectors: demography, cavities, pyorrhea, and baby teeth. The demographic sector covers populations of 5 three-year age groups under 14 years of age and 13 five-year age groups above 15 years of age. The cavities sector and pyorrhea sector are composed of populations of five-year age groups, on the other hand, the baby teeth sector uses populations of three-year age groups.From the total number of defective teeth, dental busyness and total dental care costs in Japan are calculated yearly from 1963 to 2010. The simulation results are used to modify the dental policies of Japanese administrators.This study is a research project of the Japan Dental Association.
This is a paper about possibilities. It is the beginning of an investigation into the influence of perceptions of money on the dynamics of major economic policies. No concrete results are reported.We begin with anecdotal evidence that many economic policies are based on a local and static perception of money. Local in that it only considers the part of the economic environment which directly impacts on, or is impacted by, the policies being made. Static in that it considers this environment to be essentially unaffected by those policies.This usual perception of money is illustrated by exploring a number of common thoughts about money. This exploration reveals the confusion surrounding this perception. In order to penetrate this confusion, a step-by-step examination is conducted of the role that money plays in an economy. This examination leads to another perception of money: Money has no value itself; it is merely a proxy for economic product that already exists. This perception is more global and dynamic than the usual point of view. Global because the focus on economic product forces one to consider the full economic context of a transaction. Dynamic because that emphasis leads one to consider the impact of decisions on the whole economy.A number of everyday economic transactions are illuminated by the new perception of money in such a way that consideration of those transactions naturally relates them to a wider economic system. Armed with this appreciation of economic transactions, the anecdotes presented early in the paper are revisited. In this visit, the new perception of money automatically suggests different approaches that the decision maker could take.
R-SD is a dynamic system model used to study the comprehensive development and utilization of water resources of rivers. This problem covers a wide range of aspects, such as hydraulic power generation, water transportation, flood cotrol, water consumption of industry and households, irrigation in agriculture, reservoir fishery, around-reservoir tourism and recreation facilities. R-SD also relates to the thermal power generation and land transportation. It is a system with multivariables, nonlinear and complex feedback structure. Usually, it is called as economic system of river-valley.This paper emphasises on the structure of R-SD model. First, it gives the interrelationship figures between the subsystems, then the main cause-and-effect chains and flowchart of the system. Finally, a part of the results of a case study is given. It turns out that during the comprehensive development and utilization of water resources of rivers, the emphasises should be placed on the development of hydraulic power generaion in association with water transportation and other aspects. Meanwhile, thermal power generation and land transportation should be jointly developed to promote the economic prosperity in the river-valley. In R-SD, we have also posed three degrees of satisfaction, which are guided to decide the development velocities and investment proportions of power generation, transportation, and water supply.
The regional demand-supply and training mechanism of talent is regarded as a feedback-cnotrol structure under the synergetic actions of education, society and economy. By building ESE simulation system, we have studied its stability in operation and its sensibility to main parameters. We have attempted the combination of SD with LP (Linear Programming), and some initial conclusions are reached which can further be discussed.Using the principles of the Education-Economics and SD methods to forecast and program the demand-supply of talent is becoming very popular in the educational theory circle of our country recently. There are many scholars whose studies have really shown the originality of SD method, but there are two problems that little attentions have been paid in their studies. One is that forecasting is not the strong point of SD, and it is also not competent for programming by SD methods only, the other is that we often pay more attention to the supply but neglect the demand between Education and Economy, which easily results in the lack of enough impetus to the system operation. Our paper tries to do some studies on overcoming the above two inadequate aspects.
System Dynamics, founded by professor Forrester at Massachusetts Iustitute of Technology in 1956, is a discipline which analyzes and studies the system of information feedback. Basic views of theories of system dynamics distinctively show its dialectical characteristics. More attention should be paid to the features of complicated nonlinear systems. The model simulation of system dynamics is a kind of structure-function simulation. One of the remarkable advantages of system dynamics is that it can handle problems of high order, nonlinear, and multiple-feedback system.
Being two different branches of the system science, System Dynamics and Synergetics share many common concepts and mathematical manipulation techniques. The comparative study of the two subjects will help accelerate the developments of both subjects as well as the whole system science. In this paper, the authors first introduce the basic ideas and mathematical handling techniques of synergetics, then that of system dynamics. Finally, the two subjects are compared from the angles of both the concept and the mathematical manipulation technique. The following are the major points of this paper: 1) Synergetics deals with systems that are self-organized. It studies how such systems evolve in a self-organized fashion, how new patterns are brought about, or in a philosophical sense, how the animate and the inanimate world evolve. In contrast, the systems, with which system dynamics deals, are partially self-organized, partially man-made. It studies the relationship between system structure and system function. 2) The general equations of both synergetics and system dynamics are nonlinear, stochastical partial differential equations of high order. 3) Synergetics focuses its attentions on nonequilibrium phase transition, i.e. pattern formulation, while system dynamics endeavors, with most its efforts, to study the dynamic behavior of a system with some kinds of structure.4) There are many concepts as well as mathematical handling techniques that are counterpart and can be used as a reference to each other, such as order parameter vs. sensitive parameter or minor structure; order parameter equations vs. dominant loop equations; slaving principle vs. the principle that dominant loops mainly determine the dynamic behavior of a system; adiabetic elimination vs. the insensitivity of system behavior to most parameters; linear stability analysis vs. Lyapunov method I & II, gain and phase shift analysis, etc.
The rapid development and wide application of microelectronics has been making the production activity and life style changing, with great reformation in world economies. Weather or not can a country make achievement in developing hi-teches such as microelectronics is a serious challenge to both developed countries and developing countries including China. What can be done by China under the chelange and how about the future of microelectronics in China are of most concerns amonog decision makers in China.A brief study is presented in the paper on the interrelation between microelectronics and socio-economic environment and all the effects from the relevant environmental factors. The paper also shows the research work on the development of scienice and technology in Chinia which is considered the most concerning problem to the development of microelectronics. Some viewpoints on the future of microelectronics in China derived from the research are given at the end of the paper.
With the sustained development in science and technology method of system optimization has more and more widely been applied to the area of science, technique, engineering, economy, etc. The optimization theory is strongly supported by the birth and the development of computers. System dynamics models are good at understanding complex systems with the characteristics of high-order, multi-loops and nonlinear (say socio-economic systems). The purpose of this paper is to combine the modeling process of a system dynamics model with the optimization method so as to make the system synthesis more perfect. Because of the specific properties of large scale systems, there are some serious difficulties in completely optimizing systems. In many cases, it is impossible to find an overall optimization for complex systems. However, the quasi-optimization for dynamic systems is still available. This paper develops some ideas of the parameter quasi-optimization for system dynamic models and presents a practical method. Its advantages include that the goal of the parameter quasi-optimization is clear, the precision is controllable, the quasi-optimal indices are conveniently regulated, the whole process can be automatically completed by a computer, repeating computations and simulations are not needed. Besides system synthesis, this method can also be applied to system analysis such as the parameter quasi-optimization after decoupling a system, selecting the dominant loops, separating the interest substructures, etc. The final goal of this paper is to make a solid fundation for a common used modeling software package.
System dynamics created by professor Jay W. Forrester at MIT, is a field which bases on system theory, absorbs the quintessence of control theory, and draws support from computer simulation technique. Established by professor Deng Julong at Central China Institute of Science and Technology in 1982, grey system theory derives its idea and methodology mainly from control theory and operations research. Although system dynamics and grey system theory both have their own features in methodology and processing technique, there are still a lot of common points between them. From the comparative study on these two fields, the paper arrives at that it is not only necessary but also possible to infiltrate and draw on the experiences of each other to develop themselves.
Based on the system dynamics approach, this paper tries to examine the structural causes of the long term performance of the economy after the reform, make the comparative researches on the financial and monetary system before and after the reform, and evaluate whether the system dynamics approach is a powerful tool to analyze the economy in a developing country such as China. After the description of the structure of the national financial and monetary model of China, the modeling approach is summarized in the paper. The formulation of the principal subsystems and the interactions among them are briefly introduced. The behavior of the model, and the four economic leverages -- price, tax rate, interest rate, and loan leverage, are mainly concerned and discussed. The policies designed for economic reform are examined with the DYNAMO simulation, the different results related to the different policies are compared. At last the programs and the possible futures related to them for the economic reform are given in suggestion.
In contrast with those fast growing of small- or mid-size cities' economy, big cities in China are suffering a lot of difficulties: the deterioration of the external condition of production, the decay of the industry structure, the shortage of municipal infrastructure, the fund scarcity, etc.. People have been discussing the limit factors of big cities for times, but we still need more quantitative and dynamic analysis of the whole system. In this paper we use the system dynamics model to simulate the behavior of a big city, conclude that within this century the main limits to the economic growth of a big city is the production condition, including energy, material, and transportation supply, while after the early years of the next century, the market demand, which is determined by the cost and the quality of product as well as the economic development of other areas, will be the real limit to a big city. Policy testing shows that the effective adjustments to big cities are the improvement of material supply as well as the speeding up of the capital discarding.
In the past thirty years of initial industilization of its economy, China has established a primary industry system. But the unbalanced development in economy resulting from the industry policy of laying under stress on the industry aggregates to form a obstacle which hinders the further development. A great change in economy has occurred since 1984. The paper presents a historical review about the causes of the unbalanced structure, analyzing the present situation and discussing the possible impacts of the structure changes by means of a system dynamics model. The analyses and the simulation results of the model show that pertaining to past industry policy would put limits on the further development, new policy must be carried out. But on the other hand, a long period of time would be required for the completion of the changes. The expectation of rapidly change would prove to be unrealistic.
The paper researches into a typical example of a developed region with a boomtown of China, studies the coordinate development of economy, and population migration of that region, analyzes the mechanism and theory of industrialization of the rural area. A systems dynamics model created to study of urbanization is exhibited and explained. The paper makes comments on current policy. And by the simulation, various policies are examined, the paper finds out the more reasonable coordinative growth rate and scale among industry, agriculture and town construction. The interaction between a special region and outside in the process of industrialization and urbanization is also a subject of discussion. The general conclusions and suggestions on industrialization and urbanization of rural area of China are put forward.
This paper presents a system dynamics model of China's industrial and investment structures. The dynamic behavior of the two structures has been analyzed in the change of demand and supply structure. The model has given special concern to China's limited resources and their allocation to different industries. A resource allocation mechanism is developed and the external robustness of the model is examined to test the control of the resources allocation system.
By means of the system dynamics theory and approach, A system dynamics model of the forest industry system for certain area is set up, and the future developing tendency of the forest industry system, under the conditions of various developing strategies and policies, is discussed quantitatively using the computer simulation based on the model. This model can provide scientific basis for making a long-term programme for the developing of the forest industry system.
In this paper we use system dynamics approach to build a policy lab focusing on the exploitation and protection of the rural resources in a southern province of China at first. Then we proceed, after validating the model thoroughly, model-based policy analyses.
System dynamics modeling has been applied in a wide variety of areas. However, as a means of simulating models in computers, there is no any general DYNAMO compiler system that can be used in various types of computer. The purpose of this paper is to deal with a general compiler software system ZU-DYNAMO, which is used to simulate models in various types of computer with outputs in English or Chinese. Being different from traditional method, a new idea suggested in this paper is the selection of C language instead of assemble language as objective code. The aim of such selection is to make ZU-DYNAMO independent on a particular computer. The overall structure and design principle of the system are presented. The algorithms and techniques used in the system, and the structure of objective code are designed and analysed. The description of extensions of Arrays, FOR card, etc. and the ways to implement them are also given.
The systems of oil and engine production of our complete planned economy before 1979 and market economy guided by planned economy after1980 are simulated and some conclusions are given in these models.The complete planned economy can't meet the national requiment for oil and engines and the market economy guided by planned economy can develop equilibrumly under the instruction of mixed policies applied to the production of oil and engines.The main items of microeconomics are simulated and some useful plots and conclusions are given. Further study of many fields of macroeconomics and microeconomics is expected.
The confliction between the need of R&D expenditure and the limitation of R&D resources in certain time period is a serious issue facing both developing and developed countries. This paper deals with not only the mechanism of interaction between R&D, economy and education systems, also the mechanism and relation among basic research, applied research and development. Two system dynamics models were developed focusing on the above two problems respectively. And, through modeling and policy analysis, some new findings, such as the proper scale and growth-rate of national R&D expenditure, the relation between technology acquisition and self-developing R&D, the proper ratio of R&D expenditure, etc., were accomplished.
This paper discusses the application of System Dynamics approach to the study of local education development planning which fosters a tentative SD model applicabl to local education development strategy and policy analysis in the urban area of Shanghai. It can help decision making of the local government education authorities in this area. Based on education economic theory and the socio-economic development situation in Shanghai, this model, using DYNAMOIII language, contains four socio-economic sectors – education, economic, social structure and social life, from which 730 variables were attained with 90 level equations 179 rate equations.The present study shows that the simulation model is not only feasible and practical for the study on local education system in Shanghai, but also applicable and useful to other urban areas as well.
Since the Third Plenary Session of the Eleventh Central Committee of the CCP, there have been great achievements in the development of economy in our country and the living standard of the people has been raised year by year. However, at this moment of the great boom, there appeared two protound contradictions in the macroeconomy: One is the investment hanger and the other is the consuming expansion. This is a universal persistent ailment in developing cotries.
This paper is based on the historical and current situation of rural socio-economic development of a provincial lake area. At present, economic development of the lake area is considerably lag behind. Meanwhile, there exist rich natural resources and hidden unemployment of rural population. By describing the several facets of difficulty facing the lake area, the author addresses the issue of adjusting industry structure of the entire lake area, upon which the System Dynamics approach is employed in modeling and policy analysis.The System Dynamics Model of the lake area rural socio-economic development consists of 8 sub-models, which are farming, fishery, animal husbandry, rural industry, forestry and side- occupation, energy, water conservancy and population. By simulating and analysing, policy recommendations are set force.
The modern researches on physiology verify that there are close relationships between central nervous system (CNS) and autonomic nervous system (ANS) and some autonomic functions can be regulated by CNS to some extent. In this paper, the mechanisms of cardiovascular system, especially of BP regulation, under CNS control are researched. A blood circulatory system dynamic model is established and applied practically to treatment of hypertensives trained with biofeedback technique, in which pulse transit time (PTT) is employed as an indirect index of BP change. The result shows that the curative effect of this method is efficient for BP control.
This poster is concerned with the application of system dynamics as a decision support tool to assist the five-year development planning process in Kuwait.The Kuwaiti Government, and in particular the Ministries of the Interior and Planning, have been progressively introducing more elaborate procedures for development planning. A five year plan currently exists and is being implemented. Work is now in progress on the extension of the plan into the 1990's and a system dynamics group is to be formed to consolidate and extend existing support of the planning process. The group will use micro computer software (DYSMAP2) and plans to train Kuwaiti technicians are underway.This poster presents an example of how system dynamics is being used in Kuwait to analyse objectives and plans for feasibility and compatibility prior to implementation. The example concerns police labour force planning and preliminary results and conclusions are presented.
The following is meant to be an example of the combination of an Expert System (XPS) and a System Dynamics (SD) model in which the farreaching effects of cash management decisions in a complex of feedback relationships in a company are illustrated.The great advantage in proceeding this way is to use the results of an Expert System as constants and initials in a System Dynamics model. That means, that the user is enabled to study the results of a static Expert System in a dynamic model.The mentioned System Dynamics model is created on the background of an ancillary supplier for the car industry. Rather to simulate the real system in a very detailed way the model reduces this real system to the main areas of the company. As in this paper the point of main emphasis is to demonstrate a possible way of linkage of the two systems a short problem definition is followed by the description of the most important feedback-loops in causal-loop diagrams of the System Dynamic model. Subsequently the outcome of a model simulation with it's graphic and tabular results is to be analysed under the aspect of influence of constants and initials originating from the Expert System concerning cash management decisions.
This paper discusses the general structure and implementation of a System Dynamics model of the New Zealand economy. The model, called SDMACRO, has been developed at the New Zealand Planning Council to provide likely trend movements, some 10-15 years into the future, in the key macro-economic aggregates including gross domestic product, capital formation, population, employment, exports, imports, and the current account balance. The base case run of the model is presented together with scenarios which show optimistic and pessimistic future outlooks for the New Zealand economy. In addition, the paper briefly describes how SDMACRO is used with a 22 sector general equilibrium model, Julianne, as part of another Planning Council study which examines national and sectoral development paths of the New Zealand economy up to 1995. Finally, some recent extensions to SDMACRO are outlined.
Figure 1 illustrates the structure of the model.People flow from a Susceptible Population after invasion by HIV and become members of the HIV population capable of infecting other susceptibles.Then, infected people either move into a state of(i) clinical AIDS ( governed by the Symptom Emergence Ratio, SER) or into one of several other states(ii) die from other unrelated causes(iii) retire altogether from sexual activity on account of their age(iv) retire altogether from sexual intercourse as a reaction to knowledge of their condition(v) acquire a medically non-infectious stateAll these states render the host non-infectious since we assume that patients with clinical AIDS will no longer be sexually active.
A participatory simulation based on the market growth model is developed. The performance of eight subjects is evaluated and compared against the results of simulation analysis of the model. Compared to the benchmark derived from the simulation analysis, the subjects' performance is surprisingly low. It is argued that participatory simulations can be valuable teaching instruments but that they need to be combined with additional learning support tools.
Bank institutions occupy a special position in the economy as they have to guarantee a frictionless money movement. Compared with industrial companies, banks do not produce concrete products but provide abstract services with money as their output object. These services- when they are included in balance sheet- are reflected in the accounts as sales relations. Therefore a balance sheet model is applied in order to reflect general decisions in banking and to show how these decisions affect banking business in terms of volume and profit.The analysed bank is the London branch of a Continental bank. The branch acts on the markets as a commercial bank. These kind of representations are the most common ones in the financial center of London.The branch offers four different kind of products: Traditional, specialized, contingent and treasury products. These products determine the statement of asset and liabilities and in addition are also the income earners of the branch.The behaviour of the branch is determined by decision rules, market developments, the juristical position and internal restrictions. This behaviour is tested by adopting different scenarios.The System Dynamics bank model is adaptable to individual circumstances of other banks and therefore it offers practical support for the management of financial institutions.
Well structured system dynamic models are often quite useful in the analysis of the policy impacts in the face of multiple sources of uncertainty. Simulation searches for a “robust” policy that performs well under widely varying conditions are often the most rewarding portion of a system dynamics study. This paper reports the results of two studies where the analysis of uncertainty is carried a step further. Here, we are interested not only in policy impacts under widely varying conditions but whether a policy can reduce the uncertainty of the system.
The purpose of this research is to describe the impact that linguistic structure has had on the method of modeling in system dynamics. In the structuralist framework, language is viewed as a system of signs which structure our patterns of thought and influence our behavior. Learned languages are incorporated into the structure of the unconscious which then contains and constrains the capacity for communication and discourse. Linguistic systems are not isomorphic. Thus, when the language used in communicating social, political, and economic ideas changes, (i.e., from verbal to static linear mathematics; or from verbal to dynamic nonlinear mathematics), this affects the theoretical structure of the discipline. The symbolic linguistic structure employed in system dynamic models offers a powerful alternative methodology for scientists to investigate social reality.
The purpose of this research is to evaluate the relation between the development of financial markets and their institutions and the process of economic growth and development. Throughout the world less developed countries are facing various stages of an international financial crisis. Major banks in the industrialized world, as well as the IMF and World Bank have extended credit to these countries expecting the resulting economic growth to yield the necessary dividends for repayment. However the most expeditious road to growth and development has never been a certain one. One controversy deals with the timing and maturity of the financial institutions and financial markets. This overall process is called “financial deepening.” Previous published research polarizes the role of financial institutions in the process of economic development between supply-leading position and the demand-following hypothesis.
Synthetic data methods are used to test the robustness of estimators of the parameters within a simple linear oscillator. Econometric methods are used to estimate the known parameters in the model.The major result is that the deviations from the estimates to the true values of the parameters increase with the sample interval. The influence from stochastic inputs is marginal.This is due to, that for great sample interval, the lag in the causal dependency is relatively small compared to the interval between the observations involved.
For many years, system dynamicists have speculated that most corporate troubles could be explained by a small number (perhaps ten to twenty) of generic models, behavior modes, and syndromes (sets of symptoms) they create. Recent advances have renewed interest in creating management education materials, using such generic models to provide a consistent and known environment for active learning, using actual case studies for realism and detail, and using the computer-supported hypertext format of user-directed inquiry. A project at MIT integrated these advances in computer-based studies. This paper precedes systematic development of computer-based cases; it identifies 17 problematic syndromes and behavior modes. They are generic in the sense that they occur commonly in a variety of companies, as a result of common structures and policies. The 17 were identified from published modeling studies, interviews with executives, and unpublished consulting studies. The list of common corporate syndromes will be used in selecting the cases upon which to base the computer-based case studies. The list should also facilitate the problem-identification phase of consulting for individual corporations.
The apparent slow growth of System Dynamics as a field may be due in part to the relative isolation of many practitioners of SD around the world. Not only is the field geographically dispersed and in the minority in most instances, it is also changing rapidly along with the rest of the computer world. In this context, it seems critical that practitioners have easy and timely access to information and people that could both assist and amplify their research and teaching endeavors and give them psychological support to continue working in the field.SDNET is an integrated electronic network and database that is intended to provide such access to practitioners of SD around the world. SDNET has been developed and tested at USC’s System Dynamics Laboratory as an initiative of the Institute of Safety and Systems Management. It is currently available to be used by anyone who has access to an account on the academic BITNET network or any other electronic network (such as ARPANET) that links with BITNET. The database (SDBASE, housed on an Apple Macintosh) is structured to contain and fully relate information on people and institutions, publications, models, conferences interest groups, and electronic messages in the world of System Dynamics. This information may be easily added to, modified, or extracted upon request.This poster demonstrates some of SDNET’s capabilities and discusses its current status and plans for the future.
The System Dynamics Lab at the University of Southern California’s (USC) has worked with Hughes Aircraft Company’s Electro-Optical and Data Systems Group to develop a system dynamics model for analyzing alternative policies available to a defense contractor for managing the production program life cycle. Program lifecycle management is of prime importance to firms, like Hughes, that design, manufacture and maintain complex military equipment. These firms have come under increasing government scrutiny and control, particularly with regard to cost and schedule risks.The USC-Hughes model addresses the notion that cost and schedule risks can be substantially reduced through improved program management, even in the face of possible hurdles thrown up by customers and suppliers. The model suggests, for example, that overruns, particularly cost overruns, may be significantly reduced--without adversely affecting product quality--by carefully limiting the number and type of discretionary mid-production design improvements.This presentation outlines the background and basic structural elements of the USC-Hughes model, demonstrates the model’s ability to track historical data from two different cases, and highlights some of the policy findings that have emerged from the model.
This paper discusses the author’s version of some of the pros et cons in modern project modelling. His main view is that projects have many features that make them well fitted for using the Systems Approach in the analysis and improvement of their performance, but many of the traditional “rules” for “correct” project execution and monitoring should be questioned. He particularly advocates revision of (1) the traditional firm definition of project boundaries as time, cost and quality which because of the uniqueness and unpredictability of project work, almost always have to be changed or adjusted, but where advice on which one to “adjust” when under pressure seldom exists (2) the necessity of basing the project performance on a strict “sequencing” of the project work when real life project work often experiences substantial “overlapping” between project phases , and (3) using common rigid organizational structures in a project environment where the real requirement is structures that favour the mastering of fast changes and organizational flexibility.The author then elaborates on how the three arguments above could be part of a more “complete” project model, including a much stronger emphasis on the human factor as a major component in dealing with the suggested more complex nature of project work.This leads to the authors own version of a more comprehensive Project Dynamic Model. The model is described in the paper by its main features and some of its initial findings, but a fully computer-implemented model using the STELLA compiler will be demonstrated at the conference based on the research undertaken by the author.
This paper begins by summarising some milestones in the expansion of the system dynamics methodology to give a background to multi- criteria optimization in system dynamics. The case of ‘Inventory Control Policies’ from Jarmain’s (Editor) “Problems in Industrial Dynamics” is then used as an example to show how Wierzbicki’s method in multi-criteria optimization can be adapted to system dynamics. The solution procedure transforms the model into a discrete trajectory in time.
In this research we study the dynamic behavior of an industrial firm. Special emphasis is placed on the financing of manufacturing fixed capacity and working capital. Firstly, we construct a corporate model of a sample firm. Then the experimental firm is operated using following strategy groups: cash flow management strategies, depreciation strategies and retained earning strategies.Next, the emphasis is moved to the evaluation of outcomes. At this stage, an analytical hierarchy process is used. We insist that the decision analyst should decompose the problem into a hierarchy of interrelated decision elements. At the top of the hierarchy lies the most general objective of the decision problem, i.e., the well-being of the firm. The lower levels of the hierarchy consist of various decision criteria. The lowest levels of the hierarchy consist of decision alternatives, i.e., strategy groups. Finally, the best strategy is reached.
Technological investment planning is of crucial importance for industrial enterprises. Successful investment decisions and the right process technology increase the companies competitive strength. If the wrong technology is applied this leads to high fixed costs diminishing the return on investment. Methodical long-range planning is required. The necessity to introduce new technologies is emphasized in numerous publications. For evaluation of such strategic investments the classical methods of project calculations are not sufficient due to non-consideration of specific economic parameters changed by modern process technologies. A holistic view will be developed, considering all effects of new technologies on the enterprise. The proposed System Dynamics approach simulates the changes of cost relations due to the introduction of a Flexible Manufacturing System (FMS) in an industrial enterprise.The handy SD model can be easily adapted to individual circumstances. Therefore, it offers practical support to demonstrate the economic efficiency of capital investment already in the planning stage of preinvestment analysis.
The strategic planning process involves anticipatory decision making for the business as a whole. The integrated functioning of a business and its interaction with the environment are complex enough to comprehend by intuition alone. Choice of modelling strategy as well as method of its application therefore attain significance. Modular approach during corporate model design is recommended for dealing with complexity. System Dynamics method is found most suitable to do so. Corporate model can be constructed from the modules of marketing, production, and finance. Production system has been analysed to illustrate the modular approach using system dynamics method for the purpose of corporate modelling. A generic set of eight basic feedback modules has been designed to model any capacity centre. A few such sets integrated result in model of a production system. This approach has been applied for modelling a steel plant. The production model has been historically validated. It has been extended to incorporate financial consequences. The steel pant model so designed has been used for simulation experiments.
This paper constructs a system dynamics model which simulates the behavior of the structure of a large radio appliance factory administered by government department in China. Because the factory present focus is orders unfilled and profits reduced, we carry out several policy experiments on the model. The experimental results show that if the factory manager will add sales expense properly and adjust product price in time, orders and profit will been increased to higher level. In addition, the model exposes that there are lack of management systems and policies in state enterprises of China, these problems limit their development.Input data of the model come from the database of the management information system of the factory. Data are transmitted quickly and accurately. The model is provided with good dynamic state and applied conveniently.
A model of the dynamics of a family problem was developed as a prototype of future work in family therapy. In this situation, a family was in crisis over the problem of managing the son's illness. The father refused to recognize the severity of the disease, while the mother begrudgedly took responsibility for the care of the child.The model describes the dynamics underlying the mutual anger between the parents, the guilt of the father, and the effects of therapeutic interventions on this family system. The output of the model was oscillatory in nature. The timing of these oscillations of the parents anger and the father's guilt matched the sequence of emotions actually observed by the clinical team when dealing with this family.The modeler, who was not in possession of all the facts, predicted a relapse of the father's behavior and a recycling of bouts of anger between parents after about six months following the termination of therapy. The therapists substantiated this prediction, giving confidence in the model.
Intelligent behavior involves subjective variables, it is guided by fuzzy goals and constraints, and it applies multi-valued rules of inference to reach its conclusion. Decision or strategy support systems- in order to serve as reliable tools for testing the consequences of alternative courses of action- must reflect these essential aspects of the problem under investigation.The paper presents a corporate model designed for the investigation of a firm's resource allocation strategy. It discusses the applicability of fuzzy set theory to computer simulation in general and to System Dynamics in particular. After qualitative variables and fuzzy goals have been explicitly included, the model exhibits improved performance with respect to behavior and acceptance by management.
In the past ten years, system dynamics has become more accessible to managers and more applicable to strategic issues. The paper reviews developments in software, theory, gaming and methods of simulation analysis that have brought about this change. Together these developments allow modellers to create computer-based learning environments (or microworlds) for managers to “play-with” their knowledge of business and social systems and to debate strategic change.
The “escalation phenomenon” (Staw 1976; Staw and Ross 1978) refers to the tendency for decision makers to “throw good money after bad,” that is, to invest beyond the point where benefits equal costs. The commonly accepted view is that such 'escalation” occurs as a result of decision makers becoming overcommitted to a previously chosen course of action through a series of decision errors. This paper presents a generic system dynamics model of resource recommitment behavior that is able to produce “escalation” without the presence of decision error. Implications of this model to the theory and practice of project management are discussed.
While the informal modelling procedure of system dynamics qualifies as scientific according to the definitions of the epistemological literature, the application of this procedure may create models of phenomena that provide few clues to the design of change. Policy design exercises based on such models may often end with a moral statement about what should be done by the organization as a whole instead of providing motivational instruments through which its various members realize evolutionary change. Unfortunately, a change prescribed by a moral statement can only be realized by a powerful intervention by an outside agent which is, if at all possible to implement, often dysfunctional. This paper attempts to define heuristics for the construction of models that may lead to viable designs of evolutionary change. A model is viewed as instrument for understanding a problem not as a source of design. Guidelines for partitioning complex problems into multiple models are discussed. Models containing conservative systems capable of generating a large number of time variant patterns, which are in reality separated by time and location, appear to be sound instruments for facilitating the design of change.
This paper is attempting at modeling and simulation of an educational problem at junior and senior high schools. Our model consists of seven level-variables, ten rate- variables and twenty auxiliary -variables. Also we discuss marks of students in the model that are figured from 0 to 100. Results of the computer simulation are given to illustrate the our model.
Studies in the psychology of individual choice have identified numerous cognitive, informational,temporal, and other limitations which bound human rationality, often producing systematic errors and biases in judgments and choice. Yet for the most part models of aggregate phenomena in management science and economics have not adopted postulates of human behavior consistent with such micro-empirical knowledge of individual decisionmaking. One reason has been the difficulty of extending the experimental methods used to study individual decisions to aggregate, dynamic settings. This paper reports an experiment on the generation of macro-dynamics from microstructure in a common and important managerial context. Subjects play the role of managers in a simulated inventory management system, the “Beer Distribution Game”. The simulated environment contains multiple actors, feedbacks, nonlinearities, and time delays. The interaction of individual decisions with the structure of the simulated firm produces aggregate dynamics which systematically diverge from optimal behavior. Subjects generate large amplitude oscillations with stable phase and gain relationships among the variables. An anchoring and adjustment heuristic for stock management is proposed as a model of the subject's decision process. The parameters of the rule are estimated and the rule is shown to explain the subjects’ behavior well. Analysis shows the subjects fall victim to several 'misperceptions of feedback' identified in prior experimental studies of dynamic decisionmaking. Specifically, they fail to account for control actions which have been initiated but have not yet had their effect. More subtle, subjects are insensitive to the presence of feedback from their decisions to the environment and attribute the dynamics to exogenous variables, leading their normative efforts away from the source of difficulty. The experimental results are related to prior tests of the proposed heuristic and the generality of the results is considered. Finally the implications for behavioral theories of aggregate social and economic dynamics are explored.
A bifurcation sequence in the Waycross model is studied by means of Poincaré section techniques. The bifurcation parameter B is gradually reduced from 2.00 to 1.50. This parameter measures the inclination of one type of minority families (Lomanians) to move into the districts with many families of another type of minority population (Itrachians). Because of symmetry the attractors in this 4-dimensional migratory model occur in pairs with opposite directions of cyclic population movements. A pair of simple limit cycle attractors are found to remain stable under formation of a pair of period-2 attractors. In a certain parameter range, the model thus contains four entangled attractors. We follow how the period-2 attractor become chaotic through formation and subsequent destabilization of 2-dimensional tori. On the way, regular period-14, period-18 and period-4 attractors are produced through frequency-locking. We thereafter observe a case of type-III intermittency when the two period-1 orbits become unstable, and finally the two chaotic attractors merge with each other.
The continuous model for a deterministic continuous growth, one-predator-one-prey system is that of Lotka and Volterra. It is well known that this model predicts neutral stability in which the constant amplitudes of the oscillations are determined by the initial conditions. Without changing the underlying model assumptions and by altering only the predator functional response to prey density, it is shown that damped oscillations towards stable equilibrium or explosive oscillations or a stable limit cycle can be generated as model input.
In this poster we analyse the chaotic motion of a model which describes the behavior of a prey-predator-food system.This system can be modeled by mixing two well known models: the predator-prey model (Henize, 1971) and the Kaibab plateau model, which copes with the prey-food part of the model (Godman, 1974).This model has previously been introduced in (Toro and Aracil, 1988).
The purpose of this paper is to present a possible way in which a marriage between Artificial Intelligence and Modeling can take place. More specifically it is the purpose of the paper to explore some basic concepts related to Artificial Intelligence and by using an expert system shell called GURU to aid in the development of system dynamics models. The concept is one of going from data base to knowledge base to models and to examine the line of reasoning that is used in formulating the problem. Simple examples will explore the potential of this approach.
Model development for policy purposes often involves consulting one or more experts to acquire knowledge about the system that cannot be found in the literature. This poses a knowledge acquisition problem: how to derive the necessary knowledge from the expert(s). This is particularly acute if the number of potential experts to be consulted is large, as might be the case in public policy making. In this paper we will discuss a structured approach to consult a great number of potential experts. The approach was developed for the construction of a simulation model of a regional health care system. The adopted approach, however, is sufficiently general to be employed in other model development processes as well.
This study describes policy making and its implementation in water resources to facilitate proactive policy making. A system Dynamics model is constructed, evaluated, and revised with extensive inputs of the actual actors/interested parties in the policy arena.
The most fundamental health studies issue is the discrepancy between expected and actual performances of the Health Care System: the deployment of curative biomedicine is expected to decrease morbidity and costs, but we see everywhere a rise in both. Technological lag, environmental damage, administrative slippage, professional pressures, and new wealth consumption are conventional but, at best, partial explanations. It appears that the rationale is flawed by the use of an inappropriate image of the system out of which morbidity phenomena emerge. The Socio-Ecological Model proposed here links HCS operations with a more appropriate morbidity construct. The individual's subsystems interact with the social-physical environment to create two distinguishable types of morbidity: anatomico-physiological conditions constituting the 'lesions' of the disease process, and interacting experiential, behavioural, and role changes of the illness state. The HCS becomes a significant part of the sick person's environment, and affects the four resulting sub-populations differentially. Care and prevention goals are to move sick individuals/populations toward illness-free and disease-free quadrants and to prevent/slow movement away from them. The counter-intuitive HSC production of morbidity (through, e.g., coronary care, increased life expectancy, pursuit of fitness, early diagnosis, and psychosocial counselling) is no longer surprising. The model suggests a revision of health planning goals, with major shifts in resource allocation.
There are a large number of references in the literature to the problem of evaluating Information Systems in terms of both efficiency (the technical aspects) and effectiveness (the user's view, and the effect the system has on the organisation). Whereas the efficiency can be defined clearly in mathematical terms, measurement of effectiveness tends to be subjective and is usually measured retrospectively (i.e. some time after installation) using a questionnaire approach, or by expensive simulators, prior to installation.This presentation deals with the initial thinking behind the development of a quick and less costly system dynamics approach to measuring effectiveness, by using a simple model to examine the effect the proposed system will have on the organisation into which it is to be installed.
Some principle conceptions in microeconomics are simulated by System Dynamic (in brief S.D) in this article. The simulating of two fundamental theories in microeconomics concerned with balanced prices and margin analysis leads to some significant conclusions. Most of these conclusions are now in heated argument in microeconomic field. Our achievement is provided as a test of the proceeding ideas.
This paper establishes a system dynamics model to analyse a dynamic productive procedure of an enterprise in Shanghai. The model consists of five sectors, order and supply sector, production sector, material sector, advertising sector and financial sector.There are many products which the enterprise expects to produce, and in the model these products are transformed into two standard products according to the kind of products. The paper analyses the impacts of some soft factors, such as worker's quality, bonus, advertising, etc., on the profit, and also the policy of purchasing materials. The model presents the strategy of how to work out plans between two standard products when the input surpasses the productive capacity of the enterprise.The model is run by using real initial input values in 1985 and 1986. The results are very close to real situations of the enterprise. The sensitivity tests shows that the model is insensitive. So it is adquate to consider that the model is reliable and can be used as basis for dicision making by managers.
This paper provided a two-stage invertory system. It Descrips its problem behavior and structure implement. Analyse the policy design: use inventory and backlog to absorb differences between production and demand, change production to match change in demand, change demand to match production abilities, finally, forecasting reslove permanat and temorory change and lag in production's responce to change.
The economy in Taiwan grew rapidly in the last decade. This steep increase strongly affects its transportation system: the number of cars in the urban areas increased dramatically. Some studies forecasted that the number of car in Taiwan urban areas in 2000 will be three times of that in 1984. However, those studies did not consider the feedbacks from the traffic and parking conditions to the car ownership. In addition, some of the possible changes in the system environment are also not being considered, such as the increasing life expectancy of the car, the shortening car renewal period and more and more attractive car purchasing loans policies. This study is an attempt to apply system dynamics methodology to analyze the trend with inclusion of feedback and the above mentioned system environment changes. The results show that due to feedbacks from the limited capacity of roadway and parking and the influence from the system environment, the number of cars in urban areas will only be doubled in the year of 2000. Although the data for this research were very limited, by using the system dynamics methodology we are able to have a better picture of the future trend of car ownership in Taiwan.
Since the dynamic input-output method was put forward by W. Leontief, some results have been obtained to a greater or less degree in various fields of quantitative economy, which have played an important role in the application of the method. Yet, insolving the delay-having dynamic input-output models, whether the matrix converse exists or not has not had sufficient mathematical proofs. Having taken these problems into consideration, our paper attempted to solve the problem of multiyear delay-having dynamic input-output model with the application of the properties of system dynamics in structure and time sequence, the properties of BOXLIN and SUM functions, and has combined these two models, the combination of which is possible in the sense of the economy. The DIOSD (Dynamic Input-Output and System Dynamic Model) not only has the advantage of man-and-machine conversation as well as screen display, but also we can put the DIOSD completely into the SD model with the consideration of the overall system structure. Therefore, we can make full use of the advantages of the dynamic input-output model in economy planning and forcasting, and also provide an efficient tool for its future application.
This paper demonstrates the use of System Dynamics as a device to simulate a system of infantry and artillery cooperating in joint combat operation.The system under study does not represent a real or actual battle-field. The model represents a scenario describes hypothetical system of accepted theoretical structure of how infantry and artillery may co-operate in order to achieve a desired advance on a real battle-field.The paper will give attention to the planning and controlling of any need to such co-operation, and will give better insights to decision makers before and during such joint operations.We make no claim for revealing analysis of any army strategy, and seek only to show how a System Dynamics model could do if it were constructed by people who fully understood the problems and had access to information at which we can only make guesses.
In this paper we will assume that the qualitative information about a given concrete system comprises no numerical information beyond the signs of the influences, the relative value of these influences and the classification of the variables in a system as levels, rates and auxiliaries. With this information we try to get as much knowledge as possible on the behavior modes of the system, in the concrete meaning given to behavior mode in the qualitative theory of nonlinear dynamical systems.Our aim is to explore how the formal qualitative analysis techniques, based on the second of the above senses of qualitative, can be used to solve the kind of questions suggested by the first of the uses. In this way a synthesis of both senses can be reached.The results here reported are still in a work progress stage. For instance, a computer implementation of them is being developed. However we think that they are interesting enough to deserve publication.
In a dynamic simulation game portraying a multiplier-accelerator problem, there are major differences between high and low performers; high performers voice specific concerns for future states of the system, while low performers are less likely to think about the future. Planning, especially incorporating the deceptive nature of feedback, is necessary in systems that exhibit diverging long and short term behaviors. A comparison of game results with written reports show that there is a positive relationship between performance and understanding of the game. These results are contrary to previous research where performance and understanding have been unrelated (Broadbent et al. 1978, 1986), but can be explained by the added complexity of non-linear feedback tasks with shifts in loop dominance. Such tasks are, in contrast to simple regression models, non-routine and therefore verbal and behavior aspects of decision makers' mental models correspond.
In this paper, using simulation experiments, we demonstrate that the “structurally-oriented” behavior tests and other standard behavior tests are different in a fundamental sense. We also show how the structurally-oriented behavior tests can help diagnose/remove structural flaws. Thus, we suggest that such tests be identified and analyzed by System Dynamics in more detail. It is hoped that the tests will be improved, standardized and implemented as part of all major SD simulation software.
This paper intends to explore the potential of the System Dynamics approach as a new auxiliary science for the historical analysis. To this end a portable DYNAMO-like package, called STEC, has been developed.The paper, first, describes the peculiarities of the System Dynamics method as a tool for historical research, and gives an outline of the project; second, it argues that the scanty diffusion of System Dynamics might be due, among other factors, to the lack of public domain software; third, it asserts that the “old style” data processing (command line interface and batch mode) can prove itself still usable and fruitful; and last, it shows the STEC main features.
We have developed a dynamic model of DNA replication control in bacterial cells and of the subsequent cell division. The main hypothesis is that a certain protein, which has a negative feedback regulation on its own production, is an essential factor in initiation of the replication. The model is stochastic in the sense that the kinetic association and dissociation processes are assumed to take place in accordance with a Poisson probability distribution with mean values that match experimentally determined constants. An important feature of our model is that it shows correlation between the magnitude of the kinetic rate constants and the size, stability and the dynamics of the cell. The model thus allows us to analyze the distribution of cell volumes at the time of initiation for different growth rate, different association and dissociation constants, and different promoter strengths.
The results from studies on more complex tasks, such as concept learning and problem solving, are confusing: some results indicate negative effects of feedback delays, other results no effects of delays and even some positive effects (see Brehmer & Allard, 1988a). Thus, the problem of the effects of feedback delays is in need of study. This paper will review some of the results from a research program designed to investigate the problem of delays in a relatively complex computer simulated micro world which subjects must learn to control.
Criteria for evaluating success of management schools in terms of contribution to society are presented. The network of interactions that make a management school successful is described. It contains links with the dominant power groups: business community, government, unions and public institutions in general. It includes students, alumni, and staff. Business needs, research results, schools' prestige and attractiveness to faculty are also part of it. The nature of the interrelations and their relative importance are examined during the four phases of a management training institution: feasibility analysis, planning, launching and sustained operations. Some causes peculiar to mature management schools' frequent stagnation and decay are examined and preventative actions suggested.
Operational Research (OR) had its origins in the need to make decisions about the use of resources in support of national defence. The specific case was the invention of radar in the late 1930's and the military problem was to decide how this new technology could best be employed, in conjunction with the existing assets, such as fighter aircraft, for the air defence of the United Kingdom. It was, in short, necessary to conduct research into how military operations could be carried out, and hence the discipline was born. In fact, for the last 50 years, the military have been the major users of mathematical modelling. System Dynamics is, however, a relatively new tool in military analysis. This paper surveys a few published applications and suggests reasons why SD is particularly appropriate for certain classes of military problems. The paper then goes on to discuss the potential role of SD in the analysis of strategic problems. Finally, some problems of military theory are discussed.
Results of an ongoing study investigating the effect of different task feedback characteristics on human performance are reported. In a computer-assisted experiment, subjects were asked to perform a dynamic stock-adjustment control. A subject's control action enters the system in two ways: it effects the stock to be adjusted and it feeds back on the disturbance that impinges on the system. The latter effect is varied with respect to its strength and its delay. The major finding that emerges from the experiment is that increasing strength in the feedback link (in either a positive or negative direction) worsens performance. An effect of delay length on performance could not be shown.
The purpose of this paper is to show some of the schemes used by systems researchers and consultants to collect data about their clients' perceptions of problem situations. These various schemes--which use both words and graphics, consisting more or less of curved lines and arrows-- are useful for 1. helping clients express their perception of a problem situation 2. organizing clients' thinking 3. helping to overcome traditional rivalry between individuals and between groups 4. helping “to create a consensus and commitment to action in a team” (Eden, 1988,2).My paper will discuss three such schemes, proceeding from the 'soft' systems methodology (Checkland, 1981); then 'cognitive mapping' (Eden, 1988); and finally, two system dynamics studies dealing with health care systems.
The use of gaming to study contemporary warfare has evolved rapidly in recent years. Particularly important strides were taken during the 1960's and 1970's with advances in computer technology and the development of broader ranges of subject matter. The past two decades have seen a tremendous expansion in the role and influence of computer models as “policy assisting” devices – first in the analysis of national security issues, and now for the analysis of problems arising throughout the entire affairs of Government.
Rapidly growing cities cause inadequate transformation in the use of land. Government policies tend to be obsolete shortly after implementation, supply of basic services becomes insufficient and expensive, and food prices tend to increase. All these factors are certainly the case in many developing countries where large amounts of population often migrate to settle down, sometimes in dangerous or unhealthy locations, but other times in areas suitable for agricultural purposes in the periphery of the city.The land surrounding the metropolis enters a transitional stage. The territory becomes uneconomical for rural exploitation, but it requires to be supplied with basic services for urban housing. The System Dynamics approach is then appropriate to study and plan these unstable systems.This paper presents a model to assess the growth of peripheral districts of the city. It is a useful aid for policy making in land use issues and a good tool for planning basic services such as health, schooling, transport and recreation.A simulation is carried out for the Periurban District of El Corazon in Medellin, Columbia. A good approximation between historical data and model results can be appreciated. Some scenarios of future growth are explored and the consequence of land-use policies are confronted.
We have modeled the highly non-linear dynamic phenomena which arise in Gunn diodes by interaction between the internally generated domain mode and an external microwave signal. As the frequency of the microwave signal is changed, a devil's staircase of frequency-locked oscillations develops, interspersed with quasiperiodic solutions. Period- doubling and other forms of mode-converting bifurcations can be seen in the interval of some of the steps. At higher microwave amplitudes, deterministic chaos arises. The transitions to delayed, quenched, and limited space charge accumulation modes are followed.
The System Dynamic National Model was undertaken to show how local policies governing decentralized decisions in an economy create observed overall economic behavior. I feel we have succeeded well beyond our original expectations. The model, endogenously, without any external driving time series, generates the major observed modes of economic behavior: business cycles, inflation, the economic long wave and growth.
In recent years the way in which problems are approached in the assembly area within the manufacturing firm has gained increasing importance for economic planning. In connection with this, the demand for long term economic flexibility of assembly systems comes to the forefront. A firm should not limit itself purely to investment decisions in the planning of assembly systems, if it is to successfully meet growing demand (on both the market and technology fronts). However, it has become essential even in this field that strategic thinking and planning are considered more important than they have been in the past.There are considerable difficulties, however, associated with the strategic decision-making processes involved in the planning of flexible assembly systems. System Dynamics assembly models are currently being developed at the Business Management Institute at Stuttgart University ( within the framework of the “Sondereforchungsbereich 158” sponsored by the DFG).The aim of this is to understand and cope with these problems more easily, with specific reference to long-term decisions, the lacking objective assessment criteria and the high complexity of the problem.
The Cyclades, a group of over thirty dispersed islands in the middle of the Aegean Sea can become a case study for energy-driven regional development. High cost, low reliability and scarcity of energy have significantly contributed to the underdevelopment of the region. There is a lack of local conventional energy sources, but the potential of renewable energy sources, namely geothermal, wind and solar is many times greater than the region's energy needs.The Energy Policy Unit has constructed an Energy Plan for Cyclades up to the year 2000 concerning the development of local economic resources in connection with programmes promoting the exploitation of local energy potential. New energy investments, mainly in the renewables and energy saving options were examined in detail. For this reason, consistent alternative scenarios of energy supply, energy demand and economic growth were developed and assessed through an integrated modelling system. In this paper, the emphasis will be placed on the energy supply model.
There is growing interest in combining system dynamic models with conventional case studies in order to create learning environments for management education. Such computer-based case studies promise improvement in strategic thinking skills and better integration of modeling in the policy and strategy area. Moreover, these models-with-cases are tangible products with which to conduct research in computer-based learning. This paper surveys the opportunities for using computer-based case studies in management education and for conducting novel research on management learning.The paper first examines how models-with-cases fit in the established areas of strategic management and business policy. Which issues, in the broad range covered by strategic management, do models-with-cases address? Next, two current examples of computer-based case studies are presented (People Express Airlines and Intecom PBXs) to show explicitly how cases and models are combined and used. Finally, the paper explores research questions that arise in conjunction with such work; 1) how to teach effective inquiry skills, 2) how to teach conceptualization skills, 3) how to enhance the ability to apply learned theories to new situations, and 4) adapting measurement methods to evaluating the educational effectiveness of computer-based cases in teaching these mental skills.
A system dynamics model is presented in this paper along with the results of some policies and their consequences automation. The automation seems to be the answer for faster growth and development throughout the world whether or not there is excessive labor or its shortage in a nation. Higher productivity, lower costs, better quality of products and services, remaining competitive and new innovations are benefits of automation and they are very important factors in industrialization and as well in sustaining the jobs in the long run. Very often, particularly in the developing countries, the politicians either exploit or in most cases misunderstand the total effects of automation and computerization. In India, for example, computerization of even very important services like airlines and trail reservations, insurance and banking have suffered due to political decisions for two decades. Only recently they have realized their mistakes and are trying to catch up. This simple system dynamics model can be easily used for systems analysis to study the effects of automation and thus can help in making strategic decisions in automation and policy guidelines formulations.
A Rössler band is presumably the simplest of all chaotic attractors. It can develop in systems with only three state variables if two of these produce an outward spiralling trajectory, and the third folds this trajectory back towards its center when the amplitude of the expanding oscillation becomes sufficiently large. In the present paper we show how Rössler bands can develop through slight modifications of well-established economic and biological models.
The overall design is sketched of a training game and behavioral decision making research tool based on a System Dynamics corporate simulation model of a magazine publishing company. The organization of the program to run the game and the type of output generated is described. Some of the possible uses of the game to investigate behavioral decision making and group learning in a complex decision environment is mentioned.
SADT™ (A trademark of SofTech, Inc.,Waltham, MA), a hierarchical system description notation, was used to create System Dynamics models. This paper discusses the two SADT model types, data and activity, and their correspondence with System Dynamics patterns. Rules for transforming an SADT data model to a System Dynamics model, semi-automatically, are proposed. This information is then used in a step by step translation from a SADT data model to a System Dynamics simulation model. An example is given showing how the SADT hierarchy enhances the understanding of the simulation model.
Organizations have to adapt to their environments in order to survive (Lawrence and Lorsch, 1967; Weick, 1969; Galbraith, 1967). Hence, recurrent structural changes are strategic responses of organizations to the growing turbulence of modern society (e.g., Tichy, 1983). While most organizations can alter their strategies, structures and procedures to some extent, many changes do not achieve their stated goals because of inertial forces blocking the way (Hannan and Freeman, 1984). Many of the factors affecting organizational change processes have already been identified (cf. Zaltman and Duncan, 1977), but we still lack a comprehensive view that integrates the various interplaying forces (Nadler, 1981; Carnell 1986).
Accounting Dynamics is a methodology for modeling and simulation of accounting using System Dynamics. Our reasons for presenting Accounting Dynamics are as follows.
The use of interactive gaming environments to teach system principles has recently been gaining in popularity. One of the most promising applications of system dynamics model-based games is “learning laboratories,” workshops that blend system dynamics principles and repeated simulation game trials with ongoing conceptualization and feedback sessions to help managers gain a deeper understanding of the system within which they operate. This paper will first describe the design of such a learning laboratory, its implementation, and its use as a vehicle for learning to think more systemically. This will be followed by a discussion on how the learning lab helps unearth deep-rooted assumptions and encourages people to challenge them in a “double-loop learning” mode. Finally, the paper concludes with a brief discussion on possible future steps toward developing systems thinking skills in an organization.
Over the past decade, as a result of world-wide stagnation – combined with the entrance of low wage competitors to the market – the situation of the manufacturing industries in the industrialized economies became more competitive. Although it is not accompanied by an increasing output, the application of flexible manufacturing as a new process technology seems to enable the enterprise to gain productivity and to push up it's competitive strength.Therefore, the necessity to introduce these technologies is emphasized in numerous discussions. On the other hand these technologies require capital-intensive investments. So the capacity of reducing costs seems to be a decisive measure of economic advantage.