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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Remote measurement of salinity: Repeated measurements over a single flight line near the Mississippi Sound

Experiments to remotely determine sea water salinity from measurements of the sea surface radiometric temperature over the Mississippi Sound were conducted. The line was flown six times at an altitude of 244 meters. The radiometric temperature of the sea surface was measured in two spectral intervals. The specifications of the equipment and the conditions under which the tests were conducted are described. Results of the tests are presented in the form of graphs.

Thomann, G. C.↗
NASA NTRS1974

Repeated action of a constant magnetic field on the blood coagulation system in artificially produced anemia

Changes are discussed in the coagulatory system of the blood in rabbits under the influence of a constant magnetic field of an intensity of 2500 oersteds against the background of artificially induced anemia. Reversibility of the changes produced and the presence of the adaptational effect are noted. Taking all this into consideration, the changes involving the coagulatory system of the blood which arise under the influence of a constant magnetic field may be considered to have a nerve-reflex nature.

Zabrodina, L. V.↗
NASA NTRS1980

Repeatable, multiple-peaked structure in Type I X-ray bursts

A distinct, identifiable, multiple-peaked structure has been observed in Type I X-ray bursts from three sources. At energies below 6 keV, the light curves look like typical Type I bursts. At higher energies, the burst is double-peaked, with both the depth of the dip and the separation between the peaks increasing with energy. A light curve of the energy-integrated intensity shows no distinct double peak, suggesting that only a single energy release occurs. Blackbody fits to the evolving burst spectra yield changing radii and temperatures, inversely correlated, during the early part of the burst. The physical interpretation of these changes is uncertain. Burst decay spectra yield relatively constant radii with decreasing temperatures. It is proposed that Compton scattering may be responsible for the dips in the higher-energy light curves by shifting photons to lower energies.

Hoffman, J. A.↗
NASA NTRS1981

Cumulative hardware distortion effects on coded and uncoded performance via a satellite repeater

An analytical investigation is presented of the cumulative impact of numerous hardware-induced distortions on BPSK bit-error-rate performance. Attention is given to 16 user and eight transponder constraints, as well as to the effect of filter bandlimiting. Uncoded and coded performance is evaluated with respect to both NRZ and Manchester signaling formats, and tight upper bounds to coded and uncoded SNR degradation are determined. Computed results based on TDRSS (Tracking and Data Relay Satellite System) specifications are presented as an example.

Benjamin, T.↗
NASA NTRS1983

Repeated-Measures Analysis of Image Data

It is suggested that using a modified analysis of variance procedure on data sampled systematically from a rectangular array of image data can provide a measure of homogeneity of means over that array in single directions and how variation in perpendicular directions interact. The modification of analysis of variance required to account for spatial correlation is described theoretically and numerically on simulated data.

Newton, H. J.↗
NASA NTRS1984

Repeated shock and thermal metamorphism of the Abernathy meteorite

Based on the example of Abernathy (L6 chondrite), it is shown how petrographic investigation can be used to unravel the nature, chronology and conditions of superposed metamorphic events in chondrites. Features considered include the texture of the rock, optical characteristics of olivine, pyroxene and plagioclase, refractive index of plagioclase, metallographical characteristics and microhardness of Fe-Ni alloys. It is deduced that Abernathy has been involved in at least six metamorphic events since the formation of the chondrite. Four distinct shock events and two separate reheating events have been identified. The chronology of these events is established. The conditions for the last four events are reasonably well constrained. These include severe reheating (T greater than 1200 C); severe shock causing complete melting of plagioclase and local melting of the rock (P between 90 and 110 GPa, T between 1250 and 1350 C); mild shock (P between 10 and 25 GPa, T less than 500 C); and reheating below 800 C.

Lambert, P.↗
NASA NTRS1985

Precise Electrochemical Drilling of Repeated Deep Holes

Tooling enables maintenance of close tolerances. Tooling includes guide that holds electrochemical drilling electrodes in proper relative alinement and guide-positioning fixture clamps directly on reference surfaces of strut. High precision achieved by positioning tooling anew on each strut before drilling: Tolerances of (0.008 mm) maintained in some details.

Kincheloe, J. P.↗
NASA NTRS1985

Empirical model of the composition of the Venus ionosphere Repeatable characteristics and key features not modeled

In-situ measurements of positive ion composition of the ionosphere of Venus are combined in an empirical model which is a key element for the Venus International Reference Atmosphere (VIRA) model. The ion data are obtained from the Pioneer Venus Orbiter Ion Mass Spectrometer (OIMS) which obtained daily measurements beginning in December 1978 and extending to July 1980 when the uncontrolled rise of satellite periapsis height precluded further measurements in the main body of the ionosphere. For this period, measurements of 12 ion species are sorted into altitude and local time bins with altitude extending from 150 to 1000 km. The model results exhibit the appreciable nightside ionosphere found at Venus, the dominance of atomic oxygen ions in the dayside upper ionosphere and the increase in prominence of atomic oxygen and deuterium ions on the nightside. Short term variations, such as the abrupt changes observed in the ionopause, cannot be represented in the model.

Taylor, H. A., Jr.↗
NASA NTRS1987

The discovery of a source of repeated soft short gamma bursts in Sagittarius

Twelve short cosmic gamma-ray bursts were observed during July-December, 1983. The results of the localization of this source on the basis of Prognoz-9 and ICE data are presented. The source is situated 10 deg away from the Galactic Center. These localizations indicate that the January 7, 1979 burst originated from the same source.

Atteia, J. L.↗
NASA NTRS1988

The hemodynamic effects of repeated bed rest exposure

The effects of three 2-week periods of bed rest (with and without isometric/aerobic exercise, and separated by 3-week ambulatory recovery periods) on hemodynamic responses to stepwise application of LBNP (-20 to -40 mm Hg) are investigated experimentally in seven physically active male subjects aged 19-21 years. The data are presented in extensive tables and graphs and characterized in detail. It is found that bed rest produces significant changes in the responses of heart rate and end-diastolic volume index which (1) are greater than can be accounted for by lowered plasma volume, (2) persist during the recovery periods, and (3) do not respond to the exercises employed to prevent deconditioning.

Sandler, Harold↗
NASA NTRS1990

A resistance strain gage with repeatable and cancellable apparent strain for use to 800 C

A temperature compensated static strain gage, which is fabricated from palladium-13w/o chromium (Pd13Cr) alloy and a platinum (Pt) compensator, is being developed and was tested over a temperature range to 800 C at NASA-Lewis. The PdCr compensated strain gage has significantly lower apparent strain to 800 C than other high temperature strain gages. The PdCr compensated gage is protected from oxidation by a flame-sprayed alumina-4w/o zirconia overcoating. Test results to 800 C indicate apparent strain variations of less than 300 micro-epsilon and reproducibility between thermal cycles within 50 micro-epsilon. Apparent strain of the coated PdCr compensated gage can be predicted and cancelled due to its reproducibility and low value.

Lei, Jih-Fen↗
NASA NTRS1991

Analysis of the individual risk of altitude decompression sickness under repeated exposures

In a case-control study, researchers examined the risk of decompression sickness (DCS) in individual subjects with higher number of exposures. Of the 126 subjects, 42 showed one or more episodes of DCS. Examination of the exposure-DCS relationship by odds ratio showed a linear relationship. Stratification analysis showed that sex, tissue ratio, and the presence of Doppler microbubbles were cofounders of this risk. A higher number of exposures increased the risk of DCS in this analysis.

Kumar, K. Vasantha↗
NASA NTRS1989

Ignition of nonmetallic materials by impact of high-pressure oxygen. II - Evaluation of repeatability of pneumatic impact test

The gaseous oxygen pneumatic impact test is used to evaluate the suitability of nonmetallic materials for use in high-pressure oxygen systems. The test was evaluated by testing the reactivity of four materials over a range of impact pressures. The evaluation also investigated the effect of valve opening time and other test variables on the frequency of reaction. The variability of the data obtained for each test material was too large for the test method to be capable of distinguishing other than gross differences in the reactivity of materials. No relation was found between this variability and changes in valve opening time and other test variables. The materials studied were found to be unacceptable for use as reference standards. Because of the high variability of the test data, it is recommended that new methods be developed for evaluating the suitability of materials for use in high-pressure oxygen systems.

Schmidt, Naomi↗