SIMULATION

in industry, science, and education, a research or teaching technique that reproduces actual events and processes under test conditions. Developing a simulation is often a highly complex mathematical process. Initially a set of rules, relationships, and operating procedures are specified, along with other variables. The interaction of these phenomena create new situations, even new rules, which further evolve as the simulation proceeds. Simulation implements range from paper-and-pencil and board-game reproductions of situations to complex computer-aided interactive systems. Simulation techniques for experimentation permit researchers to perform exotic dry lab experiments or demonstrations without using rare materials or expensive equipment. In the automotive industry, proposed automobile designs undergo simulated wind-tunnel tests in computer simulations, thus saving hundreds of hours formerly devoted to prototype building and testing. Time compression is another cost-saving feature of simulation technology. Events that can take anywhere from hours to eons in real time can be simulated in a few minutes. Medical researchers, for example, often must isolate organs and keep them alive by artificial means, grow cultures, inject chemicals, and wait for results. When the normal functions of a selected organ can be simulated accurately, however, researchers can observe in a few minutes the effects of a broad range of events on that functioning. Likewise, astronomers using computer simulations of galactic movements can demonstrate events that take millions of years to completesuch as the collision of two galaxiesto test the validity of theoretical descriptions. As a technique for instruction, simulation allows students to deal in a realistic way with matters of vital concern but without dire consequences should they make wrong choices. The technique has proven especially useful in medical training, as, for example, in the University of Alberta Medical School, where the computer simulates patients in critical condition who will die without proper care. Aspiring doctors are asked to make swift diagnoses and prescribe treatments in an effort to keep the patient alive. Aircraft-pilot trainees also are exposed to realistic emergency situations by means of such sophisticated simulation devices as the Link trainer (see flight simulator). Simulations enable students to understand complex interactions of physical or social environment factors. Dartmouth College students, for example, play a simulation game in which they strive to grow a good rice crop under the constant threat of pests, fire, and flooding. The Graduate School of Management at Northwestern University has programmed its computer to simulate a micro-model of the American economy. Using portable terminals and television monitors, students propose solutions to economic problems and compare the predictions they yield with data taken from the model.