Suchergebnisse

The investigation of special topics in systems dynamics -uncertain dynamic processes, viability theory, nonlinear dynamics in models for biomathematics, inverse problems in control systems theory-has become a major issue at the System and Decision Sciences Research Program of the International Insti­ tute for Applied Systems Analysis. The above topics actually reflect two different perspectives in the investigation of dynamic processes. The first, motivated by control theory, is concerned with the properties of dynamic systems that are stable under vari­ ations in the systems' parameters. This allows us to specify classes of dynamic systems for which it is possible to construct and control a whole "tube" of trajectories assigned to a system with uncertain parameters and to resolve some inverse problems of control theory within numerically stable solution schemes. The second perspective is to investigate generic properties of dynamic systems that are due to nonlinearity (as bifurcations theory, chaotic behavior, stability properties, and related problems in the qualitative theory of differential systems). Special stress is given to the applications of non­ linear dynamic systems theory to biomathematics and ecoloey.

This paper examines factors influencing implemention and use of computer models that have been successfully institutionalized as part of federal policy-making. It is based upon detailed case studies of two kinds of models that have been widely assimilated and used in federal agencies - microanalytic simulation models and macroeconomic models. It concludes that the most important influences on successful modeling are the means to do modeling (supply factors) and the desire of bureaucrats and politicians to use model-generated information (demand factors). Of these, demand factors are most important. The availability and promotion of computer models alone is insufficient to generate use, whereas their political saliency is critical. Thus, where the means to do modeling are weak, but the desire to use models is strong, government agencies invest heavily in the creation of new modeling efforts.

The field of economics proves to be a matter of metaphor and storytelling - its mathematics is metaphoric and its policy-making is narrative. Economists have begun to realize this and to rethink how they speak. This volume is the result of a conference held at Wellesley College, involving both theoretical and applied economists, that explored the consequences of the rhetoric and the conversation of the field of economics

From earlier ecological studies it has become apparent that simple univariate or bivariate statistics are often inappropriate, and that multivariate statistical analyses must be applied. Despite several difficulties arising from the application of multivariate methods, community ecology has acquired a mathematical framework, with three consequences: it can develop as an exact science; it can be applied operationally as a computer-assisted science to the solution of environmental problems; and it can exchange information with other disciplines using the language of mathematics. This book comprises the invited lectures, as well as working group reports, on the NATO workshop held in Roscoff (France) to improve the applicability of this new method numerical ecology to specific ecological problems