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Lee, S. W.

Publications and source records attributed to Lee, S. W..

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

NASA Adaptive Multibeam Phased Array (AMPA): An application study

The proposed orbital geometry for the adaptive multibeam phased array (AMPA) communication system is reviewed and some of the system's capabilities and preliminary specifications are highlighted. Typical AMPA user link models and calculations are presented, the principal AMPA features are described, and the implementation of the system is demonstrated. System tradeoffs and requirements are discussed. Recommendations are included.

Mittra, R.↗
NASA NTRS1981

Realizable feed-element patterns for multibeam reflector antenna analysis

The radiation pattern of a feed element is approximately described by a simple function (cos theta) to the q power. For a given element spacing of the feed array, simple formulas for estimating the practical value of q when the element is an open-ended rectangular waveguide, an open-ended circular waveguide, a pyramidal horn, or a cigar antenna are given.

Rahmat-Samii, Y.↗
NASA NTRS1981

Determination of specular points on a surface of revolution

For a given source and observation point, specular points on a conducting surface must be found in order to apply the geometrical optics theory to calculate the reflected field. An efficient method is presented for finding all the specular points for the special case in which the conducting surface is a part of a surface of revolution. Our method, which reduces the conventional two-dimensional search to a one-dimensional search also makes it economically feasible to obtain a global solution for certain classes of surface, source, and observation point geometries that do not render solutions in the more conventional two-dimensional searches.

Lee, S. W.↗
NASA NTRS1980

Near-surface flow of volcanic gases on Io

Significant near-surface flow of gas several hundred kilometers from Pele (Plume 1) on Io is indicated by a series of bright, elongate albedo markings. Particles produced at small, local vents are apparently carried as much as 70 km farther 'downwind' from Pele. The gas densities and velocities necessary to suspend 0.1 to 10 micron particles at such a distance imply mass flow rates of 10 to the 7th - 10 to the 9th g/sec. Such flow rates are consistent with other estimates of mass transport by the plume. The large flow rates so far from the source allow an estimate of the rate of resurfacing of Io by lava flows and pyroclastics that is independent of estimates based on meteorite flux or on the amount of solids carried within the plumes themselves.

Lee, S. W.↗
NASA NTRS1971

Singular perturbation methods and the warm plasma model

The application of techniques of the singular perturbation theory to the analysis of warm plasma is discussed. Typically, the cold plasma model can be applied over wide ranges of parameters and only over narrow ranges forming so-called boundary layers is the warm plasma model used. Simplified equations can be used and the solutions matched on both sides of the layer's boundary. Simple examples to illustrate the solution are presented. The analysis confirms that some results are highly sensitive to the values of: (1) wire radius or gap size for an antenna, (2) temperature of the medium, and (3) incident angle of a plane wave.

Lee, S. W.↗