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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
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NASA NTRS1972

Classical scattering calculations for diatomic molecules: A general procedure and application to the microwave spectrum O2

Many properties of gaseous systems such as electromagnetic absorption and emission, sound dispersion and absorption, may be elucidated if the nature of collisions between the particles in the system is understood. A procedure for the calculation of the classical trajectories of two interacting diatomic molecules is described. The dynamics of the collision will be assumed to be that of two rigid rotors moving in a specified potential. The actual outcome of a representative sample of many trajectories at 298K was computed, and the use of these values at any temperature for calculations of various molecular properties will be described. Calculations performed for the O2 microwave spectrum are given to demonstrate the use of the procedure described.

Mingelgrin, U.↗
NASA NTRS1972

Tensile properties of PRD-49 fiber in epoxy matrix.

Recently a high-modulus and high-strength organic fiber, identified as PRD-49-III by the manufacturer, became commercially available. To assess the fiber performance and its potential as a reinforcement for fiber composites, the tensile properties of the fiber in an epoxy matrix were determined. During this study over 6000 fiber/epoxy strands were made using the filament winding process; these strands were representative samples taken from over 60 lb of single-end fiber. The fiber uniformity, its strength distribution at room and LN2 temperature, stress-strain characteristics, and the strain rate effect on the fiber strength were evaluated.

Chiao, T. T.↗
NASA NTRS1972

Two-micron spectra of carbon stars.

Medium resolution spectra in the two-micron region have been obtained for a representative sample of carbon variables. Observed variations in band strengths as function of color, carbon abundance, and variability type are interpreted as being due to thermal emission from a circumstellar dust shell.

Frogel, J. A.↗
NASA NTRS1972

Thermal expansion compatibility of ceramic chip capacitors mounted on alumina substrates.

The thermal expansion coefficients of a representative sample of BaTiO3 and TiO2 ceramic chip capacitors and alumina substrates have been examined. These data have revealed large potential mechanical stresses under thermal cycling. A mathematical analysis of a composite model of the capacitor to predict the thermal expansion and modulus of elasticity and an analysis of the capacitor-substrate system to predict the magnitude of thermally induced stresses have been conducted. In all cases studied, thermally induced stresses great enough to cause capacitor body rupture or termination failure was predicted.

Allen, R. V.↗
NASA NTRS1973

The control of a manipulator by a computer model of the cerebellum.

Extension of previous work by Albus (1971, 1972) on the theory of cerebellar function to an application of a computer model of the cerebellum to manipulator control. Following a discussion of the cerebellar function and of a perceptron analogy of the cerebellum, particularly in regard to learning, an electromechanical model of the cerebellum is considered in the form of an IBM 1800 computer connected to a Rancho Los Amigos arm with seven degrees of freedom. It is shown that the computer memory makes it possible to train the arm on some representative sample of the universe of possible states and to achieve satisfactory performance.

Albus, J. S.↗
NASA NTRS1974

Reflectance of vegetation, soil, and water

The author has identified the following significant results. Iron deficient and normal grain sorghum plants were sufficiently different spectrally in ERTS-1 band 5 CCT data to detect chlorotic sorghum areas 2.8 acres (1.1 hectares) or larger in size in computer printouts of the MSS data. The ratio of band 5 to band 7 or band 7 minus band 5 relates to vegetation ground cover conditions and helps to select training samples representative of differing vegetation maturity or vigor classes and to estimate ground cover or green vegetation density in the absence of ground information. The four plant parameters; leaf area index, plant population, plant cover, and plant height explained 87 to 93% of the variability in band 6 digital counts and from 59 to 90% of the variation in bands 4 and 5. A ground area 2244 acres in size was classified on a pixel by pixel basis using simultaneously acquired aircraft support and ERTS-1 data. Overall recognition for vegetables, immature crops and mixed shrubs, and bare soil categories was 64.5% for aircraft and 59.6% for spacecraft data, respectively. Overall recognition results on a per field basis were 61.8% for aircraft and 62.8% for ERTS-1 data.

Wiegand, C. L.↗
NASA NTRS1974

Remote sensing of coal mine pollution in the upper Potomac River basin

A survey of remote sensing data pertinent to locating and monitoring sources of pollution resulting from surface and shaft mining operations was conducted in order to determine the various methods by which ERTS and aircraft remote sensing data can be used as a replacement for, or a supplement to traditional methods of monitoring coal mine pollution of the upper Potomac Basin. The gathering and analysis of representative samples of the raw and processed data obtained during the survey are described, along with plans to demonstrate and optimize the data collection processes.

Source record↗
NASA NTRS1973

A cosmochemical view of cosmic rays and solar particles

The composition of cosmic rays and solar particles is reviewed with emphasis on the question of whether they are representative samples of Galactic and solar matter. The composition of solar particles changes with energy and from flare to flare. A strong excess of heavy elements at energies below a few MeV/nuc decreases with energy, and at energies above 15 MeV/nuc the composition of solar particles resembles that of galactic cosmic rays somewhat better than that of the solar atmosphere. The elements Ne through Pb have remarkably similar abundances in cosmic ray sources and in the matter of the solar system. The lighter elements are depleted in cosmic rays, whereas U and Th may be enriched or not, depending on whether the meteoritic or solar abundance of Th is used.

Price, P. B.↗
NASA NTRS1973

Investigation of the sensitivity of ionization-type vacuum gauges

A quantitative analysis of a large and representative sample of available data has been made to determine the best criteria for predicting the relative sensitivities of ionization-type vacuum gauges to different gases. The molecular property of the gas that correlates best with relative sensitivity is the ionization cross section (eV). For high-pressure ionization gauges, a cross section evaluated at 2/3 of the accelerating potential of the gauge is the best choice. For Bayard-Alpert and triode gauges, any of three choices are of approximately equal value. These are 100 eV cross section values, maximum cross section value for each gas, and a cross section evaluated at 2/3 of the accelerating potential for each gauge. For the Alphatron gauge, cross section values in the range 5000-10,000 eV provide the best correlation.

Holanda, R.↗
NASA NTRS1974

The Magnetization of Carbonaceous Meteorites

Alternating field demagnetization experiments have been conducted on representative samples of the carbonaceous meteorites (carbonaceous chondrites and ureilites). The results indicate that many, if not all, of these meteorites possess an intense and stable magnetic moment of extraterrestrial origin. Thermomagnetic analyses have been conducted on samples of all known carbonaceous meteorites. In addition to yielding quantitative magnetite estimates, these studies indicate the presence of a thermally unstable component, troilite, which reacts with gaseous oxygen to form magnetite. It is proposed that the magnetite found in some carbonaceous chondrites resulted from the oxidation of troilite during the early history of the solar system. The formation of pyrrhotite is expected as a natural consequence of magnetite formation via this reaction. Consideration is given to the implications of magnetite formation on paleointensity studies.

Herndon, James Herndon↗
NASA NTRS1974

The charge and isotopic composition of solar cosmic rays

The charge and isotopic composition of solar cosmic rays potentially contain a wealth of information on the acceleration and confinement of energetic particles at the sun. As the experimental techniques have improved and with the increasing number of measurements, this potential is now being realized. It is convenient to divide the composition studies into three areas: (1) helium-iron, with energies above 10 MeV per nuc; (2) helium-iron, and the trans-iron elements, with energies below 2 MeV per nuc; (3) the isotopic composition. In the first area at energies above 10 MeV per nuc, the solar cosmic rays appear to provide a representative sample of the solar corona. At lower energies complex enhancement effects are noted. These increase with Z and decrease with energy.

Mcdonald, F. B.↗
NASA NTRS1975

Optical studies of 10 high galactic latitude X-ray sources

Optical studies are reported for a representative sample of 10 unidentified high galactic latitude X-ray sources that are north of declination minus 25 deg and that have 3U error boxes less than or of the order of 0.5 square degrees. The source 3U 1410-03 is identified with a peculiar emission-line spiral galaxy, NGC 5506, and a distance group 4 rich cluster of galaxies, Abell 2142, is suggested as a possible identification for 3U 1555+27. It is shown that very few of the unidentified high galactic latitude sources are quasi-stellar sources brighter than 17.5 mag, although one possible X-ray quasar, NAB 0137-01, is reported.

Bahcall, J. N.↗
NASA NTRS1974

Composition of the gases associated with the magmas that produced rocks 15016 and 15065

Gases may be trapped in crystallizing minerals in many different ways but gas analyses can provide geologically meaningful information only if the gases can be related to their specific locations in the host mineral. The gases trapped in glass inclusions can be representative samples of the gases associated with the magma adjacent to the mineral at the time it crystallized. Analyses of the gases in glass inclusions in gabbro 15065,44 and basalt 15016,48 show that in both cases the gases in the parent magma started with a composition close to 46% oxygen, 42% carbon and 12% hydrogen and became more water-rich as crystallization progressed. This enrichment is probably due to a selective removal of the less soluble carbon compounds into the vapor phase. Some of the volatile components may react with the rock as temperature falls to give siderite and possibly hydrous phases.

Barker, C.↗
NASA NTRS1975

Apollo 17 neutron stratigraphy - Sedimentation and mixing in the lunar regolith

A report is presented concerning the Gd isotopic ratios in ten samples, representing nearly the entire depth of the drill stem which was recovered during the Apollo 17 mission. The lunar neutron energy spectrum is discussed along with questions regarding neutron fluence and neutron flux. The significance of the Apollo 17 deep drill stem is considered and attention is given to the statistical nature of the fluence in the lunar regolith. Vertical mixing models are also described.

Curtis, D. B.↗
NASA NTRS1976

Radionuclides in Chesapeake Bay sediments

Natural and manmade gamma-ray emitting radionuclides were measured in Chesapeake Bay sediments taken near the Calvert Cliffs Nuclear Power Plant site. Samples represented several water depths, at six locations, for five dates encompassing a complete seasonal cycle. Radionuclide contents of dry sediments ranged as follows: Tl-208, 40 to 400 pCi/kg; Bi-214, 200 to 800 pCi/kg; K, 0.04 to 2.1 percent; Cs-137 5 to 1900 pCi/kg; Ru106, 40 to 1000 pCikg Co60, 1 to 27 pCi/kg. In general, radionuclide contents were positively correlated with each other and negatively correlated with sediment grain size.

Cressy, P. J., Jr.↗
NASA NTRS1976

Concorde noise-induced building vibrations for Sully Plantation, Chantilly, Virginia

A study to assess the noise-induced building vibrations associated with Concorde operations is presented. The approach is to record the levels of induced vibrations and associated indoor/outdoor noise levels in selected homes, historic and other buildings near Dulles and Kennedy International Airports. Presented is a small, representative sample of data recorded at Sully Plantation, Chantilly, Virginia during the period of May 20 through May 28, 1976. Recorded data provide relationships between the vibration levels of walls, floors, windows, and the noise associated with Concorde operations (2 landings and 3 takeoffs), other aircraft, nonaircraft sources, and normal household activities. Results suggest that building vibrations resulting from aircraft operations were proportional to the overall sound pressure levels and relatively insensitive to spectral differences associated with the different types of aircraft. Furthermore, the maximum levels of vibratory response resulting from Concorde operations were higher than those associated with conventional aircraft. The vibrations of nonaircraft events were observed in some cases to exceed the levels resulting from aircraft operations. These nonaircraft events are currently being analyzed in greater detail.

Mayes, W. H.↗
NASA NTRS1976

Effect of polymer properties and adherend surfaces on adhesion

High temperature polymer surface characteristics associated with joint strength were evaluated. Selected samples represented composite adherends, aluminum filler and fiber glass carrier cloth. Detailed analysis of fractured joint surfaces revealed unique characteristics typical of the specific adhesive formulations and test conditions. A fracture mechanism model was developed for correlating macroscopic shear strength and microstructure of fracture surfaces. Applications were made to unpublished data on polyimides and fluoropolymers.

Dwight, D. W.↗