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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Applications of liquid state physics to the earth's core

New results derived for application to the earth's outer core using the modern theory of liquids and the hard-sphere model of liquid structure are presented. An expression derived in terms of the incompressibility and pressure is valid for a high-pressure liquid near its melting point, provided that the pressure is derived from a strongly repulsive pair potential; a relation derived between the melting point and density leads to a melting curve law of essentially the same form as Lindemann's law. Finally, it is shown that the 'core paradox' of Higgins and Kennedy (1971) can occur only if the Gruneisen parameter is smaller than 2/3, and this constant is larger than this value in any liquid for which the pair potential is strongly repulsive.

Stevenson, D. J.↗
NASA NTRS1980

Elastic stability of superplastically formed/diffusion-bonded orthogonally corrugated core sandwich plates

The paper concerns the elastic buckling behavior of a newly developed superplastically formed/diffusion-bonded (SPF/DB) orthogonally corrugated core sandwich plate. Uniaxial buckling loads were calculated for this type of sandwich plate with simply supported edges by using orthotropic sandwich plate theory. The buckling behavior of this sandwich plate was then compared with that of an SPF/DB unidirectionally corrugated core sandwich plate under conditions of equal structural density. It was found that the buckling load for the former was considerably higher than that of the latter.

Ko, W. L.↗
NASA NTRS1980

Hydromagnetic dynamo in the cores of Uranus and Neptune

It is noted that the explanation of the origin of a magnetic field of Uranus is difficult because the structure of the planet's interior is not well known and the strong thermal flux, which is associated with the operation of hydromagnetic dynamos in Jupiter and Saturn, seems to be absent or very low. It is shown that the composition, physical state and electrical conductivity of the planet's core permits the generation of a magnetic field within the very low observational limits of its heat emission. Further, it is suggested that the higher density and higher pressures in the core of Neptune could explain the suspected absence of a measurable field on that planet even though it is a relatively strong source of heat.

Torbett, M.↗
NASA NTRS1982

Metal Sandwith Panel With Biaxially Corrugated Core

Biaxially-corrugated sandwich core, formed by concurrent diffusion bonding and superplastic deformation, makes a proposed sandwich panel unusually strong and stiff. New panel should be useful where light-weight panel that resists bending is needed. Panel would have internal core consisting of multitude of hollow, truncated pyramids. Four layers of panel would be diffusion-binded at all contacting areas.

Ko, W. L.↗
NASA NTRS1981

Conditioned pressure spectra and coherence measurements in the core of a turbofan engine

Multiple and partial coherence functions and the corresponding conditioned coherent output spectra are computed between fluctuating pressures measured at two locations within the tailpipe of a turbofan engine and far-field acoustic pressure. The results are compared with the ordinary coherent output spectrum as obtained between a single tailpipe pressure measurement and the far-field acoustic pressure. The comparison indicates apparent additional "coherent output" (i.e., core-noise) beyond that detectable with an ordinary coherent measurement, thus suggesting the tailpipe as a core-noise source region. Further evidence suggests, however, that these differences may be attributed to the presence of transverse acoustic modes in the tailpipe and that the tailpipe is not, in fact, a significant source region.

Karchmer, A.↗
NASA NTRS1981

Ultraviolet slit spectroscopy in the core of 30 Doradus with the International Ultraviolet Explorer

Low resolution (about 7 A) IUE observations of the core of the 30 Doradus Nebula in the Large Magellanic Cloud are presented. Data were obtained through the large entrance aperture at 11 different positions in both the long wavelength (1900-3200 A) and short wavelength (1150-2000 A) cameras. The aperture was stepped in 10-arcsec intervals, in the direction of the long axis of the aperture, effectively yielding a 2-arcmin long slit with the central object, R136, close to the center. The brightness distribution is strongly peaked at the position of R136, but it is found that the far-ultraviolet fluxes are dominated by luminous early-type stars at any position along the slit. The behavior of the ultraviolet colors along the slit implies that the core of 30 Dor lies behind a cloud of dust extending over at least 2 arcmin = 30 pc and suggests that the reddening law changes with distance from R136.

Koornneef, J.↗
NASA NTRS1982

Out-of-Core Solutions of Complex Sparse Linear Equations

ETCLIB is library of subroutines for obtaining out-of-core solutions of complex sparse linear equations. Routines apply to dense and sparse matrices too large to be stored in core. Useful for solving any set of linear equations, but particularly useful in cases where coefficient matrix has no special properties that guarantee convergence with any of interative processes. The only assumption made is that coefficient matrix is not singular.

Yip, E. L.↗
NASA NTRS1981

Investigation of geomagnetic field forecasting and fluid dynamics of the core

Progress in the use of MAGSAT data to confirm that the radius of the Earth's core-mantle boundary can be accurately determined magnetically is reported. The MAGSAT data was used in conjunction with a high quality manfield model for epoch 1965. The unsigned flux linking the core and mantle of the Earth is considered to be a legitimate invariant for a span of time. The value from MAGSAT of this constant is 16.056 GWb (gigawebers).

Benton, E. R.↗
NASA NTRS1982

Investigation of geomagnetic field forecasting and fluid dynamics of the core

Progress in the development, testing, and evaluation of kinematic geomagnetic forecast models and their utility in magnetic prediction of the core-mantle boundary of the Earth and in determination of the core radius is reported. The GFSC 9/80 model, which uses MAGSAT data, was determined to be of high quality.

Benton, E. R.↗
NASA NTRS1981

Conditioned pressure spectra and coherence measurements in the core of a turbofan engine

Multiple and partial coherence functions and the corresponding conditioned coherent output spectra are computed between fluctuating pressures measured at two locations within the tailpipe of a turbofan engine and far-field acoustic pressure. The results are compared with the ordinary coherent output spectrum as obtained between a single tailpipe pressure measurement and the far-field acoustic pressure. The comparison indicates apparent additional 'coherent output' (i.e., core-noise) beyond that detectable with an ordinary coherence measurement, thus suggesting the tailpipe as a core-noise source region. Further evidence suggests, however, that these differences may be attributed to the presence of transverse acoustic modes in the tailpipe and that the tailpipe is not, in fact, a significant source region.

Karchmer, A.↗
NASA NTRS1980

The Apollo 17 drill core - Chemistry of size fractions and the nature of the fused soil component

It is shown that the Apollo 17 drill core 70009-70001 is heterogeneous with depth, containing five stratigraphic units, and has a bulk soil chemistry governed by the coarse fractions because of their greater weight proportions. The four components (1) KREEP, (2) anorthositic gabbro, (3) mare basalt, and (4) orange glass are used to model the compositions of the coarse and fine fractions of the entire drill core. It is found that the chemistry of the fused soil component in the five stratigraphic units is more similar to the chemistry of the fine, less than 20-micron fractions than the coarse fraction, suggesting that agglutinates may prefferentially meld and replicate the chemistry of the finer size fractions. The sources of Zn are the orange/black glasses, and the Zn profile is anticorrelated with the maturity index of Morris et al (1979), indicating the liberation of Zn during soil maturation.

Laul, J. C.↗
NASA NTRS1980

Solar and cosmogenic nitrogen in the Apollo 17 deep drill core

It is established that the greatest distinction in origin of the soils in the Apollo 17 drill core is between the surface layer, down to 25 cm, and the remainder. The surface layer was not derived by the reworking of underlying material, but was deposited from elsewhere. The soils in the core below 25 cm have had similar surface histories, with first exposure to the solar wind 1.0-1.5 million years ago and accumulation of solar wind continuously over hundreds of millions of years thereafter. The soil with the least, and most ancient, surface exposure is 25-60 cm deep, while that with the greatest and most recent exposure, other than the present surface layer, lies at a depth of 110-170 cm. A major stratigraphic sequence disturbance has therefore deposited the soils in their present positions.

Thiemens, M. H.↗
NASA NTRS1980

Recent depositional history of Apollo 16 and 17 cores

Measurements of Al-26 and Mn-53 in the Apollo 17 drive tube 76001 show a clear integral excess of activity above expected production down to a depth of at least 9 gm/sq cm. This excess is interpreted as a continuous accretion of highly irradiated surface material slowly transported downslope by impact or other processes at a buildup rate of 1.5 cm/m.y. This drive tube, 76001, was collected near a change in slope on the North Massif. Integral excesses have also been observed in other Apollo 16 and 17 cores. Evidence in the Al-26 and Mn-53 record for continuous accretion is shown for Apollo 16 cores 60007 and 60010 and the Apollo 16 deep drill string 70009-70001. This evaluation shows that accretion at specific sites, either through continuous downslope movement or regolith material on the moon, or simply through small impact redistribution, is common on both small and large scales.

Evans, J. C.↗
NASA NTRS1980

Depositional and irradiational history of the Hadley Rille core 15010/11

Soils from the 15010/11 double drive tube collected at the edge of Hadley Rille have been analyzed for FeO concentrations, I(s)/FeO maturity index values, and noble gas isotopic abundances. Cosmogenic noble gases indicate a total cosmic ray exposure age of less than about 300 million years for the core soils, and it is found that while the production profile of these gases as a function of depth is not consistent with single-stage, in situ irradiation, it is in keeping with pre-irradiated soils deposited or exposed within the past 100 million years. Although significant isotopic differences due to mass fractionation exist on the lunar surface, the solar noble gases in most core soils show little or no evidence of long-term isotopic changes.

Bogard, D. D.↗
NASA NTRS1982

Chemical bonding and charge redistribution - Valence band and core level correlations for the Ni/Si, Pd/Si, and Pt/Si systems

Via a systematic study of the correlation between the core and valence level X-ray photoemission spectra, the nature of the chemical bonding and charge redistribution for bulk transition metal silicides has been examined. Particular emphasis is placed on Pt2Si and PtSi. It is observed that the strength of the metal (d)-silicon (p) interaction increases in the order Ni2Si, Pd2Si, Pt2Si. It is also observed that both the metal and silicon core lines shift to higher binding energy as the silicides are formed. The notion of charge redistribution for metallic bonds is invoked to explain these data.

Grunthaner, P. J.↗
NASA NTRS1982

Depositional history of core 15008/7 - Some implications regarding slope processes

Structures and associated vertical changes in lithology of core 15008/7 are discussed with a view to providing data for interpretation of regolith-forming and accumulation processes that can take place on a continuous slope upon an impact-dominated surface. The light-colored soil between 49.1 and 55.6 cm in core 15007 is rich in clasts which contain abundant green glass and appears to be ejecta from downslope. The dark massive soils between 17.5 and 49.1 cm contain many crater bottom structures and crater fill, but apparently no rim-crest or proximal ejecta. The higher parts of the crater deposits appear to be removed by erosion, whereas the crater fill is preferentially preserved. Such material may be typical of slope deposits. The light-colored soil with contorted, friable clasts, between 0 and 17.5, appears to be ejecta from the crater seen in the sampling photographs.

Nagle, J. S.↗
NASA NTRS1981

An excitation mechanism for the free 'core nutation'

The earth is believed to possess a free nutational mode due to its rotating, elliptical, fluid core, with an eigenfrequency of approximately (1 + 1/460) cycle per sidereal day as seen from the sidereally rotating earth. This free 'core nutation' has not yet been undisputably observed. Furthermore, there has been considerable doubt that any known mechanism could excite this mode to an observable level. It is shown here that diurnal atmospheric and oceanic loading of the earth's surface provides an efficient excitation mechanism which depends critically on the physical damping of the mode. Possible effects of the mode on geodetic measurements are discussed. The effects of 'wobble' and 'nutation' on astrometric observations are also considered.

Sasao, T.↗