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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Constant energy partitioning in the photoionization of NO and O2

Published data on the photoelectron spectra of NO and O2 are analyzed, and the energy distributions are found to have averages proportional to the available energy. Hence, vibration takes a constant fraction of the energy. Average distributions are found as a function of the fraction of available energy.

Lawrence, G. M.↗
NASA NTRS1977

Partitioned counting digital filter

High-speed variation of counting digital filter implements count in a way which allows shortest permissible spacing between samples of input signal to be small fraction of time it takes to compute output sample.

Zohar, S.↗
NASA NTRS1976

Recursive partitioned inversion of large (1500 x 1500) symmetric matrices

A recursive algorithm was designed to invert large, dense, symmetric, positive definite matrices using small amounts of computer core, i.e., a small fraction of the core needed to store the complete matrix. The described algorithm is a generalized Gaussian elimination technique. Other algorithms are also discussed for the Cholesky decomposition and step inversion techniques. The purpose of the inversion algorithm is to solve large linear systems of normal equations generated by working geodetic problems. The algorithm was incorporated into a computer program called SOLVE. In the past the SOLVE program has been used in obtaining solutions published as the Goddard earth models.

Putney, B. H.↗
NASA NTRS1976

Partitioning of chromium between silicate crystals and melts

Experiments were performed determining the distribution of chromium between olivine, pyroxenes, and melt at oxygen fugacity values near those of lunar rocks for a wide range of bulk compositions. The range of values of D-Cr (wt% of Cr2O3 in crystals/Cr2O3 in melt) is 0.6-1.3 for olivine and 1.6-3.5 for pyroxene; this ratio shows no obvious dependence on any experimental parameter.

Huebner, J. S.↗
NASA NTRS1976

Chromium basalts - Experimental determination of redox states and partitioning among synthetic silicate phases

Experiments were performed on silicate compositions in the forsterite-anorthite-silica and forsterite-anorthite-diopside systems to determine the relative amounts of Cr(II), Cr(III), and Cr(VI) over a wide range of oxygen partial pressures from 10 to the -10th to 1 atm at 1500 and 1550 C. Redox states were measured by visible absorption spectroscopy and electron paramagnetic resonance spectroscopy and titration. It was found that Cr is present almost exclusively as Cr(III) in terrestrial basaltic liquids and as a mixture of Cr(III) and Cr(II) in lunar basaltic liquids.

Schreiber, H. D.↗
NASA NTRS1977

Test of a model for trace element partition during closed-system solidification of a silicate liquid

Trace-element concentrations in separated minerals and rock fragments from a coarsely crushed and sieved sample of medium-grained lunar basalt are determined by high-precision instrumental neutron activation analysis for three main purposes. These are: (1) to test a previously proposed model for describing trace-element behavior during solidification of a silicate liquid under conditions of a closed system; (2) to compare trace-element concentrations among different size fractions of a comminuted basalt; and (3) to investigate small-scale heterogeneity within a single medium-grained basalt. It is found that an excellent mass balance for the whole rock is attained in terms of the trace-element concentrations of the component minerals and mesostasis, that the mixing model describing this mass balance yields a superior modal analysis for the whole rock, and that different size fractions of the coarsely crushed basalt vary in mineral composition. The closed-system model is shown to account properly for the average behavior of the trace elements during solidification of the basalt, and values of distribution coefficients are obtained for incompatible elements in that rock.

Haskin, L. A.↗
NASA NTRS1978

Partitioning of Ni/2+/ between basaltic and synthetic melts and olivines An experimental study

Olivine/liquid distribution coefficients for Ni in basaltic and simple synthetic melts are found in the 1400-1070 C temperature range. The results suggest that: (1) the Ni distribution coefficients and NiO activity coefficients are strongly temperature dependent, (2) the Ni distribution coefficients are functions of melt composition and structure at a constant temperature although the dependence is small for most basaltic magmas, (3) differences in melt composition do not significantly influence generally 'basaltic' melts, (4) the Ni distribution coefficients may be used as geothermometers to predict the olivine crystallization temperatures of basaltic magmas to within plus or minus 50 C, (5) the Ni distribution coefficients are greater than one at all natural magmatic temperatures, and (6) the Ni distribution coefficients do not significantly vary as functions of the Ni content of the melt to at least one mole percent.

Leeman, W. P.↗
NASA NTRS1978

Zr and Nb partition coefficients - Implications for the genesis of mare basalts, KREEP, and sea floor basalts

The distribution coefficients of Zr and Nb have been found between armalcolite, ilmenite, clinopyroxene, rutile, plagioclase, and a coexisting high-Ti mare basalt melt in the 1105-1128 C temperature range. Henry's Law is not broken over the compositional range evaluated. The distribution coefficients of clinopyroxene are strongly dependent on melt and crystal compositions. The Al2O3 activity in the melt is a strong controlling parameter. It is concluded that: (1) Apollo 11 (low K) and Apollo 17 high-Ti mare basalts may have been generated by the partial melting of an ilmenite-rich cumulate, (2) Apollo 11 (high K) basalts may have been generated by a small amount of partial melting of a more fractionated ilmenite-rich cumulate, (3) KREEP magmas may have been formed as residual melts produced by fractional crystallization of the lunar magma ocean, and (4) anomalous (type II) MOR basalts may have been generated by small degrees of partial melting of a relatively undepleted mantle with clinopyroxene remaining in the residium.

Mccallum, I. S.↗
NASA NTRS1978

The development and application of strainrange partitioning as a tool in the treatment of high temperature metal fatigue

The effects of frequency, stress and strain hold periods, stress and strain ramping, creep-fatigue interspersion, and thermomechanical cycling were studied. Of special interest was the establishment of a set of universalized life relations which were normalized by the ductility of the material. These relations together with a set of rules that were devised for treating multiaxiality by the method, were, for example, useful in predicting torsion behavior, and in particular in establishing a new relationship between torsion and tension that had previously not been considered. They also were useful in the development of a framework for treatment of environmental effects.

Manson, S. S.↗