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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 667 records · Page 37
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NASA NTRS1978

Hard X-rays from U Geminorum

The A-2 experiment on HEAO 1 has discovered that the dwarf nova U Geminorum can be a weak source of hard X-rays at optical maximum. During the outburst in October 1977, when a strong soft X-ray flux was discovered, a 2-10-keV flux was also observed. Evidence is presented that this flux appeared with the rise to optical maximum, about half a day before the soft X-rays appeared, and persisted about 2 days. During these first 2 days of the outburst the average flux was 2.4 x 10 to the -11th erg/sq cm per sec, corresponding to a luminosity of 2.8 x 10 to the 31st erg/s for a distance of 100 pc and an absorbed thin thermal spectrum with kT of about 5 keV. During optical minimum an OSO 8 upper limit implies a luminosity less than 10 to the 31st erg/s. Restrictions on models of U Geminorum are discussed.

Swank, J. H.↗
NASA NTRS1980

Net radiation in the atmosphere of Venus - Measurements and interpretation

Aerodynamic testing of the Pioneer Venus small probe net flux radiometer (SNFR) has led to a better understanding of transient errors in the net flux measurements immediately following deployment. Corrections to the net flux profiles in this region produce profiles that are reasonably consistent with constraints imposed by ground-based and orbiter results for fluxes above the atmosphere. The tests raised questions about possible steady state errors associated with the changing atmospheric temperature encountered as the probes descended. However, the lack of sensor-to-sensor variability of the transient error (caused by a newly discovered flow-through mechanism) suggests that any related errors discovered by future testing will be correctable and will not alter the conclusions that net fluxes in the lower atmosphere vary considerably with location and are relatively large at the north and night probe sites.

Suomi, V. E.↗
NASA NTRS1981

Solar wind helium and hydrogen structure near the heliospheric current sheet - A signal of coronal streamers at 1 AU

Solar wind flow properties associated with very low helium to hydrogen abundance ratios have been observed with Los Alamos instruments on IMP 6, 7, and 8 during 1971-1978. A characteristic pattern has been discovered consisting of correlated interplanetary field reversals, high plasma density, low and nearly identical H(+) and He(2+) bulk velocities, low H(+) and He(2+) kinetic temperatures, and minima in their ratios. Because coronal streamers straddle the current sheet close to the sun, the pattern discovered is the 'signal' of a coronal streamer at 1 AU. A superposed epoch analysis of 74 well-defined sector boundary crossings provides verification of the above correlation featuring a pronounced minimum in the helium to hydrogen abundance ratio at the sector boundary passage.

Borrini, G.↗
NASA NTRS1982

An inventory of undiscovered Canadian mineral resources

Unit regional value (URV) and unit regional weight are area standardized measures of the expected value and quantity, respectively, of the mineral resources of a region. Estimation and manipulation of the URV statistic is the basis of an approach to mineral resource evaluation. Estimates of the kind and value of exploitable mineral resources yet to be discovered in the provinces of Canada are used as an illustration of the procedure. The URV statistic is set within a previously developed model wherein geology, as measured by point counting geologic maps, is related to the historical record of mineral resource production of well-developed regions of the world, such as the 50 states of the U.S.A.; these may be considered the training set. The Canadian provinces are related to this training set using geological information obtained in the same way from geologic maps of the provinces. The desired predictions of yet to be discovered mineral resources in the Canadian provinces arise as a consequence. The implicit assumption is that regions of similar geology, if equally well developed, will produce similar weights and values of mineral resources.

Labovitz, M. L.↗
NASA NTRS1982

The moons of Saturn

Knowledge gained of the 17 Saturn moons with observations by the Voyager spacecraft are reviewed. Titan was found to have the only atmosphere, which is opaque and precludes geologic inferences. Synchronous rotation is experienced by the 14 inner moons, with a constant inner face turned toward the planet. Phoebe is too far away from the planet to lose its spin to planetary tidal forces, and has an orbit inclined 150 deg from the equatorial plane, while Iapetus is inclined 14.7 deg in its orbit. The abundance of ice on the moons is accepted as evidence of condensation formation of the moons at very low temperatures. Newly discovered moons of Saturn, including both the shepherd moons, which are suspected to maintain the rings in place, and the moons discovered by earth-based astronomy, are discussed. Finally, photographs of all the moons are examined for definitive details.

Soderblom, L. A.↗
NASA NTRS1982

Discovery of a new BL Lacertae object /1E 1402.3 + 0416/ with the Einstein Observatory

It is noted that only one BL Lac object, designated 1E 1402.3 + 0416, has so far been discovered as part of an optical identification program for a complete sample of faint X-ray sources detected with the Einstein Observatory. Consistent with previously X-ray-discovered BL Lacs, this object is blue and radio weak (17 mJy at 6 cm). It is pointed out that the percentage of BL Lacs in the faint extragalactic X-ray sample (2%) is smaller than the percentage at higher X-ray fluxes (6%). Over the same range in X-ray flux, the percentage of emission-line active galaxy nuclei (QSO + Seyferts) rises from 40% to 74%). This is seen as suggesting that BL Lacs do not evolve in a manner similar to quasars and are, therefore, not substantial contributors to the X-ray background.

Stocke, J.↗
NASA NTRS1981

Outer satellite atmospheres: Their nature and planetary interactions

Modeling capabilities and initial model calculations are reported for the peculiar directional features of the Io sodium cloud discovered by Pilcher and the extended atomic oxygen atmosphere of Io discovered by Brown. Model results explaining the directional feature by a localized emission from the satellite are encouraging, but as yet, inconclusive; whereas for the oxygen cloud, an escape rate of 1 to 2 x 10 to the 27th power atoms/sec or higher from Io is suggested. Preliminary modeling efforts were also initiated for the extended hydrogen ring-atmosphere of Saturn detected by the Voyager spacecraft and for possible extended atmospheres of some of the smaller satellites located in the E-ring. Continuing research efforts reported for the Io sodium cloud include further refinement in the modeling of the east-west asymmetry data, the asymmetric line profile shape, and the intersection of the cloud with the Io plasma torus. In addition, the completed pre-Voyager modeling of Titan's hydrogen torus is included and the near completed model development for the extended atmosphere of comets is discussed.

Smyth, W. H.↗
NASA NTRS1982

Studies of the ionization states of solar and galactic cosmic ray heavy nuclei

Enhancement of abundances of heavy nuclei (e.g., Mg, Si, and Fe) at low energies relative to solar photospheric abundances and anomalously high abundances of iron relative to oxygen nuclei at low energies were recently discovered in solar energetic particles studied at low energy. These phenomena are not understood at present. The proposed experiment is designed to study the recently discovered anomalous component of low energy galactic cosmic ray ions of C, N, O, Ne, and Ca to Fe of energy 5- to 10-million electron volts per atomic mass unit in regard to their ionization states, composition, and intensity, and to study the ionization states of heavy elements from oxygen to iron in energetic solar particles emitted during flare events. The same detector system will serve for both studies, with the second objective being given priority if there are any solar particle events during the mission.

Biswas, S.↗
NASA NTRS1982

New members of the infrared cluster in the Orion Molecular Cloud

Near-infrared high-resolution scans (3.5 arcsec) of the core of the Orion Molecular Cloud (no. 1) have revealed 26 sources. Eleven of these are identified with faint visible stars. The remainder are thought to be highly reddened stars embedded in the molecular cloud and include at least two of the previously known infrared cluster members. Comparison of the distribution of infrared and visible stars on the plane of the sky and in an infrared color-magnitude diagram shows that the obscured infrared sources form a separate cluster of stars. The newly discovered sources appear to fall into two categories: (1) optically identified stars probably on the front surface of the cloud and associated with the Trapezium cluster; and (2) unidentified infrared stars probably associated with the molecular cloud and the embedded infrared cluster. It is plausible that the newly discovered infrared sources in the OMC-1 region are stars less massive than the previously known members and younger than visible stars of similar mass in Orion Association.

Lonsdale, C. J.↗
NASA NTRS1983

Multifrequency observations of the flaring quasar 1156+295

A report is presented on the optically violent variable quasar 1156+295, known also as 4C 29.45 and Ton 599. A large outburst of this quasar was discovered in April 1981 in the course of a program to obtain simultaneous multifrequency spectra of variable quasars. Ultraviolet observations taken with the International Ultraviolet Explorer satellite were coordinated with ground-based observations at radio, infrared, and optical wavelengths. Measurements were made at four epochs starting immediately after the outburst was discovered, when the B-magnitude was 14.0, and at intervals of 4 days, 60 days and 1 year. The luminosity integrated only over observed wavelength bands was approximately 3 x 10 to the 48th ergs/sec on the first epoch of observation. Modeling of the source with a synchrotron self-Compton model suggests that the core of the source has a linear dimension of 0.01 pc, a magnetic field strength in the range 0.1-30 gauss, and a bulk relativistic motion in the quasar rest frame characterized by a Lorentz factor in the range 2-8.

Glassgold, A. E.↗
NASA NTRS1984

Mental Models of Invisible Logical Networks

Subjects were required to discover the structure of a logical network whose links were invisible. Network structure had to be inferred from the behavior of the components after a failure. It was hypothesized that since such failure diagnosis tasks often draw on spatial processes, a good deal of spatial complexity in the network should affect network discovery. Results show that the ability to discover the linkages in the network is directly related to the spatial complexity of the pathway described by the linkages. This effect was generally independent of the amount of evidence available to subjects about the existence of the link. These results raise the question of whether inferences about spatially complex pathways were simply not made, or whether they were made but not retained because of a high load on memory resources.

Sanderson, P.↗
NASA NTRS1985

Triangular Berstein-bezier Patches, a Survey and New Results

Triangular Bernstein-Bezier patches are an alternative to the standard rectangular ones. They are maps of triangular domains into R cubed, where the patches are described by control nets similar to the rectangular case. One difference in the definition of surface normals at the patch corners: rectangular patches have inherent problems with so-called degenerate corners, i.e., edges collapsing into one point. Triangular patches do not have these problems. Since triangular shapes arise rather frequently in the design of complicated surfaces (e.g., interior car body panels), it seems that for such surfaces triangular patches are a promising addition to the usually employed rectangular patches. Another major application is the formulation of interpolants to solve the scattered data problem: here Bernstein-Bezier patches provide a very powerful tool; they can be used to discover new schemes as well as to discover new properties of existing methods.

Farin, G.↗
NASA NTRS1985

Texture etching of (100) silicon for solar cells

A chemical means of creating the proper kind of light collection texture on (100) silicon slices is discussed. Texturing of (100) silicon surfaces in sodium or potassium hydroxides occurs by the growth of a reaction product in a random array of surface sites, which leads to pyramids remaining at the sites after other parts of the surface dissolve away. A new texture-promoting influence, a proximity effect, was discovered in this work. An attempt was made to quantify the various promotional effects. The purpose of the present paper is to: (1) explain in detail the attempt at understanding and quantifying texturing; (2) give an experimental description with observations on the proximity effect and the effect of additions of water glass that were discovered during this work; and (3) show that the precipitate or growth models account for almost all of the known promotional effects.

Dyer, L. D.↗
NASA NTRS1985

Substructure coupling in the frequency domain

Frequency domain analysis was found to be a suitable method for determining the transient response of systems subjected to a wide variety of loads. However, since a large number of calculations are performed within the discrete frequency loop, the method loses it computational efficiency if the loads must be represented by a large number of discrete frequencies. It was also discovered that substructure coupling in the frequency domain work particularly well for analyzing structural system with a small number of interface and loaded degrees of freedom. It was discovered that substructure coupling in the frequency domain can lead to an efficient method of obtaining natural frequencies of undamped structures. It was also found that the damped natural frequencies of a system may be determined using frequency domain techniques.

Source record↗
NASA NTRS1985

The conjecture concerning time variations in the solar neutrino flux

The results of the Fourier transformation of the unequally-spaced time series of the recorded Ar-37 production rate of the solar neutrino experiment (runs 18 to 80, 1970 to 1983) are reviewed. Significance criteria for every period discovered by the harmonic analysis are determined. A Fourier synthesis of certain discovered harmonics are performed. It seems that the solar neutrino flux increases shock-like with a period of approximately 8.3 years and after that breaks down. Possible connections between the periods found by the harmonic analysis and several observed phenomena on the solar surface are indicated.

Haubold, H. J.↗
NASA NTRS1985

Ultraviolet, optical, and infrared observations of the intermediate polar TV Columbae

Forty-three IUE spectra of the X-ray discovered, triply periodic cataclysmic variable, TV Col are examined. The results show that the UV flux varies with the four-day period discovered by Motch in 1981. By fitting continuum models to the UV and optical fluxes, it is inferred that this modulation corresponds to the periodic heating of a normally 9000 K source within the binary system due to reprocessing of beamed X-ray and (possibly) EUV radiation from the vicinity of the degenerate star. The observed flux from this heated source is consistent with its origin at either the disk hot spot or the secondary star. Phasing arguments, however, favor the identification of the latter as the primary reprocessing site in the system. The infrared observations are not consistent with the model proposed by Watts et al. in 1982 and imply that the four-day period does not correspond to the orbital period of the binary.

Mateo, M.↗
NASA NTRS1986

KPD 2146+4117 - The coolest DBA white dwarf

When Wickramasinghe and Whelan (1977) discovered the first DBA white dwarf LDS 785A, the possibility was considered that this object represented an exotic oddity. The fact that Shipman et al. (1985) have discovered five additional objects of this type suggests that the DBA stars are in fact a real class of degenerate object. This paper is concerned with the DBA white dwarf KPD 2146+4117, which was observed spectroscopically in October 1982 on a 1.5-m telescope with an image-tube scanner. The spectrum, obtained with 13 A resolution, covered the 3900-6800 A range. It reveals prominent absorption lines of both hydrogen and He I. Methods of analysis are discussed.

Downes, R. A.↗
NASA NTRS1985

Discovery of fast-moving oxygen filaments in Puppis A

A number of faint filaments in the Puppis A supernova remnant have been found to have spectra with strong oxygen lines, extremely weak Balmer lines, and radial velocities greater than 1500 km/s. These are very different from the bright filaments, which are nitrogen-rich and have velocities less than 300 km/s. The newly discovered filaments are spectroscopically similar to those found in young, oxygen-rich remnants, as typified by the fast-moving knots in Cas A. These Puppis A filaments are interpreted as knots of oxygen-rich supernova ejecta which remain relatively uncontaminated by interstellar material, despite the probable age of Puppis A of several thousand years. Spectra of the newly discovered filaments show, in addition to strong forbidden lines of O I, O II, and O III, permitted lines of O I: 7774, 8446 A. The permitted lines are attributed to recombination of O(+), and their strength relative to H is used to estimate that the O:H mass ratio is about 30.

Winkler, P. F.↗