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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

ISEE 1 charged particle observations indicative of open magnetospheric field lines near the subsolar region

On November 20, 1977, at 0230-0300 UT, ISEE 1 encountered unusual charged particle distributions within the magnetosphere. The three-dimensional distribution observations for energetic (greater than 24 keV) ions and plasma show the development of field-aligned asymmetries in the energetic ion distributions simultaneously with a marked change in plasma flow. It is concluded that the most likely explanation for these observations is that ISEE 1 encountered open magnetospheric field lines at its position within the magnetosphere (1030 LT and 1200 plus or minus 300 km from the magnetopause). Field lines were open near the geomagnetic equator, and the geometry was spatially or temporally variable. Other features of the field line topology are presented.

Williams, D. J.↗
NASA NTRS1982

Acoustic Emissions Could Indicate Weld Quality

Preliminary tests show quality of welds can be assessed by acoustic-emission monitor mounted on welder. Nondestructive measurement technique allows operator to determine uniformity and integrity of weld as being made, evaluate equipment performance and condition, and initiate corrective action if quality is not satisfactory.

Gustafson, P. E.↗
NASA NTRS1981

Two-photon excitation of nitric oxide fluorescence as a temperature indicator in unsteady gasdynamic processes

A laser-induced fluorescence technique based on the pulsed two-photon excitation of NO is presented which is especially suited for the measurement of fluctuating temperatures in cold turbulent flows. The technique uses the fluorescence from the UV gamma bands of NO produced by two-photon excitation of NO (A 2 Sigma +, nu-prime = 0 - X 2 Pi, nu-double prime = 0) to obtain a rotational temperature. An analysis is presented of relevant aspects of the two-photon absorption process including microphysical processes, spectral intensities as a function of transition and laser spectral widths, line-shape integrals, the nonequilibrium response of the medium to a laser pulse, fluorescence energies, signal to noise ratio, and focusing effects. An analysis of absolute two-photon absorptivity measured in a nonflowing cell is then presented and used to predict signal to noise ratios greater than 50 for supersonic flows at temperatures below 300 K.

Mckenzie, R. L.↗
NASA NTRS1982

Analysis of volatile metabolites in biological fluids as indicators of prodromal disease condition

The volatile profile cannot be defined as a single class of substances, rather it is a broad spectrum of materials of different polarities characterized by having a boiling-point in the low to medium range (up to approximately 300 C) and the fact that the compounds are suitable for gas chromatography without derivatization. The organic volatile profiles are very complex mixtures of metabolic byproducts, intermediates, and terminal products of enzymatic degradations composed mainly of alcohols, ketones, aldehydes, pyrazines, sulfides, isothiocyanates, pyrroles, and furans. The concentration of organic volatiles in biological fluids covers a wide range with many important components present at trace levels. The complexity of the organic volatile fraction requires the use of capillary columns for their separation.

Zlatkis, A.↗
NASA NTRS1981

Optimal use of electrophysiological indicators of muscular effort and fatigue

Electromyograms (EMG) from working muscles convey information on effort and fatigue. Their application, e.g., to assess the demands of vehicle control tasks, is complicated by the cooperative action of sets of muscles, by both intrinsic and imposed filtering, and by numerous other sources of variation. Fourier analyses of these noise like signals offer one approach to interpretation; downward spectral shifts accompany fatigue. Techniques are being sought (in both time and frequency domains) for further condensing the wideband EMG signals, while retaining essential information, into a concise 'state vector' usable in comparing control system designs.

Updike, O. L.↗
NASA NTRS1981

A meteorologically driven maize stress indicator model

A maize soil moisture and temperature stress model is described which was developed to serve as a meteorological data filter to alert commodity analysts to potential stress conditions in the major maize-producing areas of the world. The model also identifies optimum climatic conditions and planting/harvest problems associated with poor tractability.

Taylor, T. W.↗
NASA NTRS1981

A meteorologically driven grain sorghum stress indicator model

A grain sorghum soil moisture and temperature stress model is described. It was developed to serve as a meteorological data filter to alert commodity analysts to potential stress conditions and crop phenology in selected grain sorghum production areas. The model also identifies optimum conditions on a daily basis and planting/harvest problems associated with poor tractability.

Taylor, T. W.↗
NASA NTRS1981

Solute partitioning under continuous cooling conditions as a cooling rate indicator

A model of solute partitioning in a finite body under conditions of continuous cooling is developed for the determination of cooling rates from concentration profile data, and applied to the partitioning of zirconium between ilmenite and ulvospinel in the Apollo 15 Elbow Crater rocks. Partitioning in a layered composite solid is described numerically in terms of concentration profiles and diffusion coefficients which are functions of time and temperature, respectively; a program based on the model can be used to calculate concentration profiles for various assumed cooling rates given the diffusion coefficients in the two phases and the equilibrium partitioning ratio over a range of temperatures. In the case of the Elbow Rock gabbros, the cooling rates are calculated from measured concentration ratios 10 microns from the interphase boundaries under the assumptions of uniform and equilibrium initial conditions at various starting temperatures. It is shown that the specimens could not have had uniform concentrations profiles at the previously suggested initial temperature of 1350 K. It is concluded that even under conditions where the initial temperature, grain sizes and solute diffusion coefficients are not well characterized, the model can be used to estimate the cooling rate of a grain assemblage to within an order of magnitude.

Onorato, P. I. K.↗
NASA NTRS1980

Armalcolite - An oxygen fugacity indicator

Lunar armaloclites, (Fe, Mg)Ti2O5, contain appreciable amounts of Ti(3+) (less than 1 to 17% of Ti mole fraction). This is a function of the oxygen fugacity occurring at the time of its formation, with lower fugacities being reflected in higher Ti(3+) contents. Controlled cooling-rate and isothermal experimentation on synthetic analog and natural specimens of 70017 and 74275 have been used to calibrate an oxygen geobarometer. Most lunar rocks have followed crystallization paths in oxygen fugacity/T space such that the prevailing oxygen fugacity can be represented by a curve near parallel to the I/W buffer curve. The oxygen fugacity estimates derived from Ti(3+) considerations of armalcolites range from the iron/wustite curve to about 1.5 log units below.

Stanin, F. T.↗
NASA NTRS1980

Instrument scan - Is it an indicator of the pilot's workload

Results of an investigation of the relationship between an aircraft pilot's visual scanning of instruments and the level of mental activity during a simulated approach and landing are presented. Noting that periods of activity which demand either close to 100% of human capacity or low levels of capacity are the times when most errors are committed, trials were conducted with three NASA test pilots in a terminal configured vehicle simulator. The pilots flew a normal approach while verbally responding to three digit stimuli to be judged plus or minus according to an order of magnitude scheme, and also while using a control stick to extinguish a light that came on and off to the right and left of the instrument panel. Eyescans of the instrumentation were monitored, and determinations were made of the most common instruments used during approach and flare. Fixation on instruments was found to increase with the arithmetic tasks.

Ephrath, A. R.↗
NASA NTRS1980

Hamiltonian indices and rational spectral densities

Several (global) topological properties of various spaces of linear systems, particularly symmetric, lossless, and Hamiltonian systems, and multivariable spectral densities of fixed McMillan degree are announced. The study is motivated by a result asserting that on a connected but not simply connected manifold, it is not possible to find a vector field having a sink as its only critical point. In the scalar case, this is illustrated by showing that only on the space of McMillan degree = /Cauchy index/ = n, scalar transfer functions can one define a globally convergent vector field. This result holds both in discrete-time and for the nonautonomous case. With these motivations in mind, theorems of Bochner and Fogarty are used in showing that spaces of transfer functions defined by symmetry conditions are, in fact, smooth algebraic manifolds.

Byrnes, C. I.↗
NASA NTRS1982

Martian surface properties indicated by the opposition effect

Radiative transfer expressions are used to derive average surface particle single-scattering albedos, phase functions and porosities from a photometric comparison of Viking Orbiter opposition measurements of the Martian Arabia, Syrtis Major and Elysium Planitia regions with several generic features. The best functional fit to the data includes consideration of atmospheric scattering, two-particle populations and surface roughness. It is found that (1) the presence of high albedo, high porosity surface particles is ubiquitous, (2) opposition surge is absent in the Syrtis Major region, and (3) the Chryse areas possess the largest surface roughness.

Thorpe, T. E.↗
NASA NTRS1982

July 29, 1977, magnetospheric studies - Impulsive waves, global dynamics and geomagnetic indices

Problems of magnetospheric physics addressed by the Coordinated Data Analysis Workshop are grouped into general areas. Immediate magnetospheric response to changes in the solar wind is considered in studies of impulsive waves traced through the magnetosphere to the ground, and interpreted in terms of fast-mode wave propagation. Magnetopause geometry and microstructure after the arrival of the interplanetary shock were analyzed with data from near-geostationary satellites. A model of particle convection during the first quarter of the day gave important evidence that the convection electric field penetrated to small radial distances for extended intervals, and another model is presented which relates the local time of substorm onset to the sector of the tail that was stressed immediately after the onset of daytime reconnection. The evidence for different reconnection patterns is assessed, and a pattern not previously considered is introduced.

Kivelson, M. G.↗
NASA NTRS1982

Measurement of the dispersive and refractive indices of germanium using diode lasers

Germanium Fabry-Perot etalons are commonly used in diode laser spectroscopy to establish relative frequency calibration scales for molecular absorption spectra. Typically the channel spectrum of the etalon is recorded simultaneously with the molecular spectrum as the laser injection current is tuned linearly, and the etalon free spectral range (fringe spacing) is used to measure the frequency separations among lines in the molecular spectrum. For this purpose, the etalon free spectral range must be known for the measurement wavelength, and this in turn relies on knowledge of the etalon length and the dispersive index at this wavelength. It is pointed out that the most satisfactory approach is to measure directly the free spectral range or dispersive index of the etalon at the wavelength of interest. A description is presented of measurements of this type, performed near 7.9 and 10.1 micrometers for a 7.7-cm long germanium etalon.

Jennings, D. E.↗