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Lee, K.

Publications and source records attributed to Lee, K..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Land Mobile Satellite Antenna Development at JPL

JPL has developed several mobile-vehicular antenna systems for satellite service throughout the last decade. The frequency bands cover UHF through Ka-band, and the antennas vary from high-gain with automatic satellite-tracking to omni-directional.

Mobile Satellite Antenna↗
NASA NTRS1993

The use of antioptimization to compare alternative structural models

Structural models are usually tested by comparing their response with that of a reference structure (an actual structure or a more refined model) to a limited number of arbitrary loads. This test is not always reliable because the loads are arbitrary. An antioptimization-based method is proposed to test structural models. This method compares a structural model with a reference model or an actual structure under the worst loading case that maximizes the error in the model. Specifically, the method identifies the loading case that maximizes the difference between the responses of two models of the same structure using optimization. This method can be used to design experiments in order to validate a structural model. It can also be applied to identify damage in a structure by determining the load that maximizes the difference in the behavior of the damaged and the intact structure. The proposed method is illustrated by applying it to a plate and an automotive structure.

Gangadharan, S. N.↗
NASA NTRS1984

Collisionless dissipation in quasi-perpendicular shocks

Microscopic dissipation processes in quasi-perpendicular shocks are studied by two-dimensional plasma simulations in which electrons and ions are treated as particles moving in self-consistent electric and magnetic fields. Cross-field currents induce substantial turbulence at the shock front reducing the reflected ion fraction, increasing the bulk ion temperature behind the shock, doubling the average magnetic ramp thickness, and enhancing the upstream field aligned electron heat flow. The short scale length magnetic fluctuations observed in the bow shock are probably associated with this turbulence.

Forslund, D. W.↗
NASA NTRS1984

The Prochloron symbiosis

Colonies of L. patella were collected from inshore water adjacent to small islets near Babelthaup Island, Republic of Palau, for the purpose of studying Prochloron symbionts. Examination of the algal symbionts after fixing, dehydrating, and embedment in Epon, showed Prochloron's central body to consist of a granular ground substance with a few electron-dense inclusions and to be enclosed by prominent photosynthetic membranes. Also found around the central body were thylakoids in a concentric pattern. After comparing the results with those of former studies, it was suggested that Prochloron morphology is host specific. Finally the network of host tissue extensions that entraps the symbionts was noted as possibly being a site for metabolic exchange.

Pardy, R. L.↗
NASA NTRS1983

Collisionless dissipation processes in quasi-parallel shocks

The evolution of collisionless, quasi-parallel shocks (the angle between the shock normal and the upstream magnetic field being less than 45 deg) is examined using two dimensional particle simulations. Reflected ions upstream from the shock are observed with average guiding center velocity and gyrational energy which agree well with the prediction of simple specular reflection. Strong ion heating through the shock ramp is apparently caused by large amplitude whistler turbulence. A flux of suprathermal electrons is also the magnetic field direction. Much stronger ion heating occurs in the shock than electron heating. The relevance of this work to the earth's bow shock is discussed.

Quest, K. B.↗
NASA NTRS1983

Design of hydraulic output Stirling engine

A hydraulic output system for the RE-1000 free piston stirling engine (FPSE) was designed. The hydraulic output system can be readily integrated with the existing hot section of RE-1000 FPSE. The system has two simply supported diaphragms which separate the engine gas from the hydraulic fluid, a dynamic balance mechanism, and a novel, null center band hydraulic pump. The diaphragms are designed to endure more than 10 billion cycles, and to withstand the differential pressure load as high as 14 MPa. The projected thermodynamic performance of the hydraulic output version of RE-1000 FPSE is 1.87 kW at 29/7 percent brake efficiency.

Toscano, W. M.↗
NASA NTRS1976

Application of remote sensor data to geologic analysis of the Bonanza test site, Colorado

The author has identified the following significant results. The Hayden Pass (Orient mine area) includes 60 sq miles of the northern Sangre de Cristo Mountains and San Luis Valley in south-central Colorado. Based on interpretation of the remote sensor data, a geologic map was prepared and compared with a second geologic map, prepared from interpretation of both remote sensor data and field data. Comparison of the two maps gives an indication of the usefulness and reliability of the remote sensor data. The relative utility of color and color infrared photography was tested. The photography was used successfully to locate 75% of all faults in a portion of the geologically complex Bonanza volcanic center and to map and correctly identify 93% of all quaternary deposits and 62% of all areas of tertiary volcanic outcrop. Using a filter wheel photometer, more than 8,600 measurements of band reflectance of several sedimentary rocks were performed. The following conclusions were drawn: (1) the typical spectral reflectance curve shows a gradual increase with increasing wavelength; (2) the average band reflectance is about 0.20; and (3) within a formation, the minimum natural variation is about 0.04, or about 20% of the mean band reflectance.

Lee, K.↗
NASA NTRS1976

Ground water recharge to the aquifers of northern San Luis Valley, Colorado: A remote sensing investigation

The author has identified the following significant results. Ground water recharge to the aquifers of San Luis Valley west of San Luis Creek was primarily from ground water flow in the volcanic aquifers of the San Juan Mountains. The high permeability and anisotropic nature of the volcanic rocks resulted in very little contrast in flow conditions between the San Juan Mountains and San Luis Valley. Ground water recharge to aquifers of eastern San Luis Valley was primarily from stream seepage into the upper reaches of the alluvial fans at the base of the Sangre de Cristo Mountains. The use of photography and thermal infrared imagery resulted in a savings of time and increase in accuracy in regional hydrogeologic studies. Volcanic rocks exhibited the same spectral reflectance curve as sedimentary rocks, with only the absolute magnitude of reflectance varying. Both saline soils and vegetation were used to estimate general ground water depths.

Lee, K.↗
NASA NTRS1975

Evaluation of Skylab photography for water resources, San Luis Valley, Colorado

The author has identified the following significant results. Skylab S190A photography used in a stereo mode is sufficient for defining the drainage divides and drainage patterns at the regional level. This data, combined with geologic information, define the boundaries and distribution of ground water recharge and discharge areas within the basin.

Lee, K.↗
NASA NTRS1975

Geologic and mineral and water resources investigations in western Colorado, using Skylab EREP data

The author has identified the following significant results. Skylab photographs are superior to ERTS images for photogeologic interpretation, primarily because of improved resolution. Lithologic contacts can be detected consistently better on Skylab S190A photos than on ERTS images. Color photos are best; red and green band photos are somewhat better than color-infrared photos; infrared band photos are worst. All major geologic structures can be recognized on Skylab imagery. Large folds, even those with very gentle flexures, can be mapped accurately and with confidence. Bedding attitudes of only a few degrees are recognized; vertical exaggeration factor is about 2.5X. Mineral deposits in central Colorado may be indicated on Skylab photos by lineaments and color anomalies, but positive identification of these features is not possible. S190A stereo color photography is adequate for defining drainage divides that in turn define the boundaries and distribution of ground water recharge and discharge areas within a basin.

Lee, K.↗
NASA NTRS1975

Geological significance of features observed in Colorado from orbital altitudes

Three major investigations using LANDSAT and Skylab imagery concerned with analyses of color anomalies and linear features of central Colorado are discussed. The studies conducted are concerned with the geological significance of spectral and spatial features on the images. Color anomalies in Skylab photographs were analyzed and evaluated for locating indicators of mineralization. The relationships were determined of all linear features in a LANDSAT image to the rock joint systems and the detectable larger geologic structures; techniques for extracting that geologic information are indicated. Some anomalous megalinear features in LANDSAT and Skylab images are analyzed which transect major structures and, their associated geologic features are described.

Sawatzky, D. L.↗
NASA NTRS1975

Application of remote sensor data to geologic analysis of the Bonanza test site Colorado

Selected samples of anomalous surface features commonly associated with the various types of uranium deposits are presented and recommendations for sensor applications are given. The features studied include: epigenetic uranium ore roll type; precambrian basal conglomerate type; vein-type uranium deposits; pipe-structure or diatreme deposits; evaporitic uranium deposits. The hydrogeology of the Mosquito Range and the San Luis Valley is also examined.

Lee, K.↗