Research and Advances

Interference detection among solids and surfaces

In many industrial environments it is necessary to determine whether there is interference among components. There are many potential interference problems in products made up of assemblies of components and in product manufacturing and testing. Typically, drawings are used in an attempt to detect such unwanted interferences, but the two-dimensional, static drafting medium does not always show interferences among three-dimensional, moving parts. This paper presents a computer representation for solids and surfaces and algorithms which carry out interference checking among objects so represented. Objects are represented as polyhedra or as piecewise planar surfaces. Two types of interference checking are discussed: detection of intersections among objects in fixed positions and detection of collisions among objects moving along specified trajectories.

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Research and Advances

Execution characteristics of programs in a page-on-demand system

h show the execution characteristics of two types of commonly used programs in a large-scale, time-shared computer system. A software monitoring facility built into the supervisor was used for data collection during normal system operation. These data were analyzed, and results of this analysis are presented for a Fortran compiler and an interactive line file editor. Probability distribution functions and other data are given for such things as CPU intervals, I/O intervals, and the number of such intervals during execution. Empirical distributions are compared with simple theoretical distributions (exponential, hyperexponential, and geometric). Other data show paging characteristics of tasks as a function of the number of pages those tasks have in core.

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