SIMULATION: Transactions of The Society for Modeling and Simulation International

doi: 10.1177/003754977803100501pmid: N/A

McLeod, John; McLeod, Suzette

doi: 10.1177/003754977803100506pmid: N/A

Wittie, Larry D.

doi: 10.1177/003754977803100502pmid: N/A

MICRONET is a reconfigurable network of closely cou pled microcomputers intended for general-purpose com puting. The initial system will consist of 16 Digital Equipment Corporation LSI-11 microcomputer nodes, each with its own set of peripherals. The nodes are linked via front-end computers which send packet-switched messages over shared buses which form a passive com munications network.The specially designed front ends are on interface cards which fit in LSI-11 backplanes in each node. Each front end controls three high-speed ports: two for communications on shared buses at 0.7 megabytes per second and one for direct memory access at 0.3 megabytes per second to the LSI-11. Each front end contains 4096 bytes of memory for use in queuing message packets. Each uses two microprocessors: a Signetics 8X3006 for logic control and a Zilog Z-808 for communications routines.MICRONET has been designed to be a flexible research and simulation tool for studying distributed computer hardware and software. The topology of its communi cations network can be altered simply by reconnecting cables to a bus-definition board. Software for MICRONET will include a distributed operating system, parallel programming languages, and a network version of a simulation system for modeling the brain.

Levi, Adriana; De Luca Cardillo, Dorotea

doi: 10.1177/003754977803100503pmid: N/A

This paper describes the use of simulation in plan ning a production line. Simulation allows the mani pulation of critical factors that determine the effi ciency of the line. The model requires some special techniques such as inverting the roles of the elements and advancing the track in irregular steps to decrease simulation time while retaining proper synchroniza tion. For part of the analysis the model simplifies the behavior of the machines by disregarding accidents, which facilitates finding the optimal values of the controllable parameters. More accurate measures of line efficiency would require the inclusion of the neglected factors. Model validation required the calibration of fixed mechanical parameters so that simulation results could be checked against the theo retical productivity of the line as it was simulated. Proper starting and ending conditions are defined.

Ray, Asok

doi: 10.1177/003754977803100504pmid: N/A

A nonlinear dynamic model of a relief valve is for mulated in state-space form from fundamental princi ples of rigid-body motion and fluid dynamics. Model parameters are calculated from steady-state character istics and the physical dimensions of the valve. The transient response of the nonlinear model (as well as system eigenvalues and the frequency response of a linearized model) is obtained by digital simulation. Results indicate that the opening time of the valve is linearly related to the dimensionless parameter given by the ratio of orifice length to its radius.The analysis provides design information and perform ance evaluation for fluid systems incorporating relief valves. It is particularly suitable for relief valves for liquids and it can be adapted for other applications.

Schroeder, Charles; DeMichele, Don W.; Pooch, Udo W.; Teague, William Ray

doi: 10.1177/003754977803100505pmid: N/A

This paper describes a new model of the simultaneous flow of heat and moisture in soils. The model is a user-oriented experimental tool specifically designed for use in research. Computer optimization techni ques, numerical methods, and soil physics were used in developing the model. The model has been used in simulating the two-dimensional transfer of heat and moisture. It includes the effects of the environment and of subsurface sources and sinks.