Simulation Modeling

SIMULATION by modeling may be classified into three related methods. 1. We may use analog models which obey the same laws as the phenomena we wish to study. Instruments such as network analyzers, slide rules, and electrolytic tanks are examples of devices that are used to make analog models. 2. We may use mathematical models to describe phenomena we wish to study. Quite often we resort to high-speed computing machines or differential analyzers to solve specific problems from the equations derived in our ma thema tical models. 3. We may subject scaled models of equipment to actual or simulated environments. Wind-tunnel testing of airfoils is a notable example. Actual equipment may also be subjected to simulated expected or known environments, for example, experimentation with personnel and equipment in high-altitude chambers. Many of our complex phenomena may be studied effectively by simulation. The design of multidimension filters, sometimes called space filters, may be studied in this manner.l We are all familiar with the problem of detecting a message from an electrical signal which contains the message and noise. Suppose we wanted to detect a particular geometric shape in a field which contained a large number of configurations as well as the desired form. Let us choose the letter Z as our geometric shape, surrounded by a number of other configura tions; we could detect our letter Z by surveying the entire field with a filter which had the letter Z detailed to give full transmission while the response of the remainder of the filter gave small transmission. Obviously, when the configuration of the filter matches the desired information, a high degree of transmission is obtained, compared with that obtained from a nonmatching condition. If we were to reverse the Z to OS we would not be able to find our message. 2 A special case of this type of filtering is that in which a small aperture is used to scan the field. This technique may in general be treated as a unidimensional process, and it has been rather thoroughly explored for many scanning devices, such as equipment for the facsimile process and for television. In general, space filtering may be extended to n dimensions, where color, intensity, and location as well as geometric shape may be introduced. The analogy