ISSN:0883-7066    

DOI:10.1002/sdr.4260010102

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractA combination of administrative theory and traditional system dynamics modeling promises a flexible model‐based tool to assist businesses in designing policies and programs to support new strategic moves. Administrative theory helps clarify the firm's organization and decision‐making structure. System dynamics highlights feedback loops in the decision‐making structure and shows how structure is related to business behavior. With this dual conceptual framework, a business policy modeling project divides into two distinct phases, each of which has a value in policy analysis. Phase 1 is a descriptive survey of the firm's decision‐making structure, rather like traditional conceptualization but made richer by use of administrative theory. Phase 2 is conventional simulation modeling that builds on the phase 1 survey. Several business cases illustrate the kinds of policy insights that a phase 1 survey can provide. The article also comments on the value that a full‐fledged simulation model adds to the phase 1

ISSN:0883-7066    

DOI:10.1002/sdr.4260010103

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractA preliminary mathematical model of fluid dynamics in acute large area burns at present incorporates plasma water, urine output, burn water loss, insensible losses via the nonburned skin, lungs, and GI tract, as well as inputs of maintenance water and therapeutic (Brooke formula) fluids. The model is an initial step in a longer‐term project to identify the pathogenetic mechanisms that control fluid shifts and to evaluate the effects of crystalloid (sodium ion), colloid (albumin), and other guidelines for fluid resuscitation. The model is initialized in homeodynamic equilibrium for a standard 70‐kg person and gives reasonable, realistic responses to a wide range of parameter variations (body sizes, burn wound loss factors), step functions (burn size, discontinuation of maintenance water), and rates of therapeutic fluid administration, given its present structure. The addition of burn and nonburn interstitial and intracellular spaces and their constituents (water, sodium, albumin, and potassium) will (1) permit validation against a wide range of clinical and experimental data, (2) suggest refinements of current resuscitation guidelines, (3) suggest more incisive research on pathogenetic mechanisms and treatment modalities, and (4) permit comparison of system dynamics with alternative modeling and simulation approac

ISSN:0883-7066    

DOI:10.1002/sdr.4260010104

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper explores the dynamics of worker burnout, a process in which a hard‐working individual becomes increasingly exhausted, frustrated, and unproductive. The author's own two‐year experience with repeated cycles of burnout is qualitatively reproduced by a small system dynamics model that portrays the underlying psychology of workaholism. Model tests demonstrate that the limit cycle seen in the base run can be stabilized through techniques that diminish work‐related stress or enhance relaxation. These stabilizing techniques also serve to raise overall productivity, since they support a higher level of energy and more working hours on the average. One important policy lever is the maximum workweek or work limit; an optimal work limit at which overall productivity is at its peak is shown to exist within a region of stability where burnout is avoided. The paper concludes with a strategy for preventing burnout, which emphasizes the individual's responsibility for understanding the self‐inflicted nature of this problem and pursuing an effective course of st

ISSN:0883-7066    

DOI:10.1002/sdr.4260010105

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractResearchers and practitioners in system dynamics usually follow a trial‐and‐error process to design new policy decisions. They mainly use influence diagrams for this purpose. However, these diagrams portray the direction of influence but not its strength. Therefore, the process of policy design becomes time‐consuming, especially for beginners and those working with insufficient computer facilities. This paper presents an alternative approach for policy design using modal control theory. Policy variables are treated as control variables by delinking them from other variables. This generally leads to greatly simplified models that are free from many nonlin‐earities. Provided that this reduced system is linear and controllable, it is possible to synthetically generate control policies by modal control theory to ensure any prescribed degree of stability. These theoretical control policies then can be used to design realistic policy decisions. This approach has been used in a test

ISSN:0883-7066    

DOI:10.1002/sdr.4260010106

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractOptimization methods have the potential to improve the processes of policy analysis and design in system dynamics models. To demonstrate the use of optimization approaches, this article applies routines developed by Keloharju to a simple model of unstable inventory dynamics. Policies derived from the optimization approach are compared with policies obtained in earlier, more intuitive analyses. The results suggest that optimization methods could significantly improve both the speed and power of policy analysis in formal models.

ISSN:0883-7066    

DOI:10.1002/sdr.4260010107

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper presents a formal stability analysis of a simplified Kondratieff wave model. For normal parameter values the model has a single unstable equilibrium point which, combined with nonlinear constraints in the model's table functions, creates a characteristic limit cycle behavior. For other parameter values, the model generates damped oscillations instead of the limit cycle or overwhelms the nonlinear constraints and exhibits sustained exponential growth or total collapse.By linear stability analysis we first determine the conditions for a Hopf bifurcation, the transition from a stable to an unstable equilibrium. Using global analysis, we outline the phase portrait of a fully developed limit cycle. By the same method we examine the conditions under which the nonlinear functions fail to contain the system so that exponential runaway or collapse occurs. We then develop a DYNAMO program to calculate the Lyapunov exponents of the system during a simulation and discuss how these can be measures of the divergence or convergence of nearby trajectories. Finally, we illustrate how subsequent period doublings and chotic behavior can occur if the model is driven exogennously by a weak sine wave, representing, for instance, the shorterm business cycle.

ISSN:0883-7066    

DOI:10.1002/sdr.4260010108

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractStochastic aspects of systems have generally been ignored in most system dynamics studies except for purposes of sensitivity testing. Yet any model that claims to be more than simply a phenomenological description of a system must treat the underlying stochasticity explicitly in terms of its contribution to the dynamics. Recent work in chemical, biological, and hydrodynamic systems has shown that the aggregation of stochastic effects can lead to novel behavior (self‐organization in dissipative systems).In this paper, an analogy between models of these physical systems and system dynamics models is developed, in which dynamic models are seen to be an approximation (to lowest order in an expansion in system size) to a stochastic model for the system. The theoretical results derived for the physical system models are evaluated for their application to system dynamics models. A research strategy to elaborate this approach to analyzing a more general class of systems is propose

ISSN:0883-7066    

DOI:10.1002/sdr.4260010109

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractNotes andInsightsis a forum for discussion and debate about current issues in the philosophy and application of the system dynamics approach, and a marketplace for the exchange of information about current research, policy issues, and teaching experiences. Manuscripts treating material particularly suited to presentation in short form (less than 2,000 words) should be sent to Erich Zahn. Betriebswirtschaftliches Institut. Universität Stuttgart, Herdweg 23, D‐7000 Stuttgart 1, West Germa

ISSN:0883-7066    

DOI:10.1002/sdr.4260010110

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractIn this section theSystem Dynamics Reviewpresents problems having the potential to stimulate system dynamics research. Articles may address real‐world dynamic problems that could be approached fruitfully from the system dynamics perspective, or methodological problems affecting the field. A paper submitted to theResearch Problemssection should concisely motivate and define a problem and start a process of conceptualization or formulation that can open the way for further studies. Manuscripts not exceeding 2,000 words should be sent to George P. Richardson, Department of Mathematics and Computer Science, Wheaton College, Norton, MA 02766, U.S.

ISSN:0883-7066    

DOI:10.1002/sdr.4260010111

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY