The implementation of visually-oriented software for graphics support on the high-performance computer graphics hardware at NASA's Johnson Space Center is the latest step in the evolution of an interactive computer applications technology being developed by the Computer Graphics Group at The Applied Research Laboratory of Penn State University. This technology is designed to aid the typical scientist or engineer in learning and using computer graphics productively, including writing his own programs and interfacing to software specialists who will write and maintain his programs. Key aspects of the current development include the creation and incorporation of a visually-oriented learning package for graphics geometric perception and graphics programming, as well as a sophisticated control environment which aids the user in obtaining a quick understanding of and access to the system. Preliminary results indicate that this software support can substantially reduce the startup time for a novice graphics user with some background in Fortran.
An experimental study designed to detect and measure the contribution of creeping waves to the acoustic field backscattered by simple geometric bodies was performed. The tests utilized acoustically hard models of cylinders, spheres, and prolate spheroids irradiated in air, where a very good approximation to the ideally rigid case can be obtained. The various scattering components were separated both by the use of pulse/gating techniques and by comparisons of data taken with a range of incident pulse lengths. Although some evidence of creeping wave effects was noted near the model surfaces, the expected backscattered components could not be found in the returned field of any of the models. These results seem to reduce the practical significance of the concept of creeping waves as diffraction rays which interfere with specular and edge-formed rays to create the total backscattered field. [Work supported by NAVSEA.]
Much theoretical material has been published on acoustic scattering by simple geometries, but in most cases numerical results are limited to asymptotic cases. This paper describes an experimental set-up at Penn State designed to make diffraction measurements in air at frequencies up to 40 kHz, providing for convenient use of models 1–100 wavelengths in dimension. It also presents the results of a study done on the prolate spheroid to determine the sources of reflection and diffraction at various angles of incidence. These results show that a body having two radii of curvature and no surface discontinuities scatters very little energy, and that what is scattered can be attributed soley to “specular” reflection. Examples are shown which demonstrate that, for the range of frequencies used, the results can be accurately predicted by simple geometric calculations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.