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doi: 10.1177/003754977201900605pmid: N/A
This paper addresses some problems and progress in the develop ment of mathematical simulation models in which the mathe matical relations are not fully understood — in particular, models of biological systems. Three types of utility of models are defined, as are sharp and fuzzy laws. With these concepts in mind, models of various sizes are discussed. Modeling is analyzed from the point of view of making concepts specific, of sharpening fuzzy laws, and of producing useful results. The practical difficulties encountered when a team of experts in different fields attempt to develop a model are considered. Finally, the question of cost is addressed vis-à-vis the benefits that can accrue as a result of modeling activity.
doi: 10.1177/003754977201900602pmid: N/A
Ecosystem modeling for simulation and systems analy sis is complicated by (i) size and complexity of ecosystems, (ii) lack of data and methods for obtain ing needed measurements, and (iii) inadequacies of modeling theory for macrosystem applications. This paper presents an S/360 CSMP simulation of a gener alized shortgrass prairie scaled large enough to preserve meaningful biological detail, but still small enough for computer implementation. Both nomi nal and small perturbation behaviors are described, together with a modeling rationale tied to the closed-loop recycling structure of ecosystems. The model, which is piecewise linear and piecewise stationary, demonstrates in the context of system complexity and insufficient data the potential of linear methods for successfully characterizing ecosystem dynamics.
Savage, Gordon J.; Andrews, Gordon C.
doi: 10.1177/003754977201900603pmid: N/A
This paper describes briefly a digital simulation program developed at the University of Waterloo, Canada. The program accepts the description of a dynamic three-dimensional mechanical system as input (presently limited to particle masses) and then formulates and integrates the equations of motion of the system. The resulting dynamic response is displayed on a CRT screen for observa tion. The theoretical basis for the program is the vector-network model, a recently-developed formula tion process based on graph theory. The computer graphics subroutines include a novel package for previewing and photographing the dynamic sequences on 16-mm motion-picture film. With some further development, the program could become a useful engineering tool for the design of dynamic mechanical systems.
Burley, R.; Flower, J.R.; Rattee, I.D.
doi: 10.1177/003754977201900606pmid: N/A
Commencing with a simple but realistic mathemati cal model of dispersion, absorption, and desorp tion of dye within a cylindrical packed bed of fibers, a finite difference scheme of equations was developed capable of analog solution.By varying the main kinetic and mass-transfer pa rameters, the dynamic response of the system was determined and preferred changes of operating values were indicated.We suggest that these methods could be widely ap plied in the study of systems involving mass trans fer and reaction; to determine the individual effect of descriptive physical parameters on a pro cess without recourse to complex mathematical procedures.
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