SIMULATION: Transactions of The Society for Modeling and Simulation International

doi: 10.1177/003754977502400401pmid: N/A

McLeod, John; McLeod, Suzette

doi: 10.1177/003754977502400407pmid: N/A

Forsythe, William

doi: 10.1177/003754977502400402pmid: N/A

Eatock, Robert; Al-Dabass, David

doi: 10.1177/003754977502400403pmid: N/A

This paper discusses an external function program that has been developed to enable a PDP11-BASIC user to control the operations of a general-purpose analo gue computer and other external devices using the EXF statement. The result is in effect a digital/analogue hybrid computing facility that can play an important role in undergraduate education and postgraduate research in the department.

Sherwood, Arthur M.; Sengupta, Debasis

doi: 10.1177/003754977502400404pmid: N/A

The evaluation of the performance of individuals or devices at the man-machine interface can, in most instances, be accomplished through the simulation of typical dynamic tasks. This paper describes a simple, flexible technique for the generation of waveforms for use as forcing functions in such situations. The technique uses an analog computer under the control of external digital logic. A one-dimensional tracking problem illus trates the use of the technique. Diagrams and all relevant parameters for this problem are given. The simulation system creates a straight-line- segment graph to control the target. The system includes an automated scoring feature with digital printou t.

Gutierrez, Luis T.; Fey, Willard R.

doi: 10.1177/003754977502400406pmid: N/A

Ecological succession is the process that dominates the dynamic behavior of ecosystems as they proceed from immaturity to a stage in which the living com munity achieves equilibrium with its physical envi ronment. Secondary succession refers to the tran sients that arise in response to a perturbation of a mature ecosystem. The growth-then-saturation dynamic pattern associated with this process is well known, but not well understood. The research reported in this paper formulates a dynamic model embodying a hypothesis to explain successional modes of behavior as they arise from the internal feedback structure of the ecosystem, and tests it by means of simulation experiments. The general structure of the model is based on Odum's tabular model of ecological succession;16it traces the mutual causalities between energy, living and non- living matter, and the diversity of species as they interact in time and space to produce succession. The equations are derived from grassland observations and research, biological theory, and logical neces sity. Simulation results are shown for secondary succession in a shortgrass prairie ecosystem. The simulated patterns exhibit consistency with the over all successional patterns observed in nature. Pro spective generalizations of the model to account for successional dynamics in grasslands and other eco systems are pointed out.

Forrester, Jay W.

doi: 10.1177/003754977502400405pmid: N/A