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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Determination of the Fe-rich portion of the Fe-Ni-C phase diagram

The iron-enriched section of the phase diagram for the ternary alloy Fe-Ni-C of various compositions is determined at 773, 873, 923, and 1003 C. The two-phase tie lines and three-phase tie triangles are measured by electron microprobe analyses. Tie lines in samples without bulk equilibrium are obtained by extrapolated interface compositions under the assumption of local equilibrium at the interface. It is shown that Ni addition somewhat reduces carbon solubility in austenite while decreasing the stability of the carbide phase. In particular, the carbide is always poor in Ni relative to the coexisting metal phase(s).

Romig, A. D., Jr.↗
NASA NTRS1980

An observational H-R diagram for early-type stars

An observational H-R diagram for the O and B stars is discussed and compared with the predicted positions of massive model stars for the case of no mass loss and the case of mass loss. It is shown that the flux effective temperatures of O and B supergiants and of early O stars are less than the effective temperatures which might be inferred from the relative intensities of lines from two stages of ionization of an element.

Underhill, A. B.↗
NASA NTRS1980

Theoretical regime diagrams for thermally driven flows in a beta-plane channel in the presence of variable gravity

The effect of a power law gravity field on baroclinic instability is examined, with a focus on the case of inverse fifth power gravity, since this is the power law produced when terrestrial gravity is simulated in spherical geometry by a dielectric force. Growth rates are obtained of unstable normal modes as a function of parameters of the problem by solving a second order differential equation numerically. It is concluded that over the range of parameter space explored, there is no significant change in the character of theoretical regime diagrams if the vertically averaged gravity is used as parameter.

Geisler, J. E.↗
NASA NTRS1981

The self-consistent calculation of pseudo-molecule energy levels, construction of energy level correlation diagrams and an automated computation system for SCF-X(Alpha)-SW calculations

The self consistent calculation of the electronic energy levels of noble gas pseudomolecules formed when a metal surface is bombarded by noble gas ions is discussed along with the construction of energy level correlation diagrams as a function of interatomic spacing. The self consistent field x alpha scattered wave (SCF-Xalpha-SW) method is utilized. Preliminary results on the Ne-Mg system are given. An interactive x alpha programming system, implemented on the LeRC IBM 370 computer, is described in detail. This automated system makes use of special PROCDEFS (procedure definitions) to minimize the data to be entered manually at a remote terminal. Listings of the special PROCDEFS and of typical input data are given.

Schlosser, H.↗
NASA NTRS1981

The cool half of the H-R diagram in soft X-rays

The results of an Einstein Observatory program to map the occurrence of hot coronae (T greater than 1 million K) in the cool half of the Hertzsprung-Russell diagram are reported. F-M dwarfs, and late F through early K star giants characterized by 10,000 K chromospheric and 20,000-200,000 K FUV emission lines were studied in one region, while a second region study included red giants later than K2 III and supergiants later than G5 Ib with weaker chromospheric emission and no high temperature species. Program goals comprised determination of the C IV division as seen in soft X-rays, and identification of stellar parameters which distinguish strong from weak coronal X-ray sources. A summary of target stars, X-ray fluxes, and UV emission profiles is provided, and coronal emissions, comparisons of C IV and wind boundaries, hybrid-spectrum supergiants, the energy balance of stellar outer atmospheres, stellar rotation and coronae, and evolutionary considerations are discussed, along with lines of future research.

Ayres, T. R.↗
NASA NTRS1982

On the reality of a boundary in the H-R diagram between late-type stars with and without high temperature outer atmospheres

The Linsky-Haisch hypothesis (1979) that a boundary exists in the H-R diagram separating yellow giants from red giants and supergiants is tested. IUE 1150-2000 A low-resolution spectra of 10 stars chosen to constitute a reverse bias sample are presented and discussed. Despite the bias, weak C IV emission indicative of high-temperature plasma was observed in four of the six stars chosen to be probable red stars, while no C IV emission was detected in the four stars chosen to be yellows. In a second test using the entire sample of 39 stars, nearly all of the yellow giants and supergiants were found to have an emission feature at 1549 A, which is attributed to C IV. The large magnitude dispersion could be attributed to temporal or spatial variability, differing magnetic field strengths and geometries, or age-related effects during post-main-sequence evolution. It is concluded that the Linsky-Haisch transition region boundary is a real phenomenon.

Simon, T.↗
NASA NTRS1982

Mollier-I, S-Diagrams for Combustion Gases in Data Processing

In order to have all the thermal and caloric states of combustion gases accessible in a computer, closed mathematical approximation equations were established for the real factors, the enthalpy and the entropy of a real combustion gas. The equations approximate the various effects of molecular forces real gas influence and dissociation - at temperatures of 200 K to 6,000 K, pressures of 0.001 to 1,000 bar, and in the range from stoichiometric composition to air. A system of subprograms is listed in FORTRAN, by means of which thermodynamic calculations can be carried out in the same manner as with Mollier I,S diagrams.

Zacharias, F.↗
NASA NTRS1984

Determination of the succinonitrile-benzene and succinonitrile-cyclohexanol phase diagrams by thermal and UV spectroscopic analysis

Equilibrium temperature-composition diagrams were determined for the two organic systems, succinonitrile-benzene and succinonitrile-cyclohexanol. Measurements were made using the common thermal analysis methods and UV spectrophotometry. Succinonitrile-benzene monotectic was chosen for its low affinity for water and because UV analysis would be simplified. Succinonitrile-cyclohexanol was chosen because both components are transparent models for metallic solidification, as opposed to the other known succinonitrile-based monotectics.

Kaukler, W. F.↗
NASA NTRS1984

Determination of the phase diagram for carbon tetrabromide and hexachloroethane

Differential scanning calorimetry is used to determine the binary eutectic phase diagram of the CBr4/C2Cl6 system and measure the enthalpies of fusion of various compositions. The eutectic composition and temperature are found to be 8.4 + or - 0.1 weight percent C2Cl67 and 83 + or - 0.1 C, respectively. A micrograph showing the coarse lamellar structure at the interface is provided.

Kaukler, W. F.↗
NASA NTRS1986

The ammonia-water phase diagram and its implications for icy satellites

A Holzapfel-type diamond anvil cell is used to determine the NH3 - H2O phase diagram in the region from 0 to 33 mole percent NH3, 240 to 370 K, and 0 to 5 GPa. The following phases were identified: liquid; water ices Ih, III, V, VI, VII, and VIII; ammonia monohydrate, NH3.H2O; and ammonia dihydrate NH3.2H2O. Ammonia dihydrate becomes prominent at moderate pressures (less than 1 GPa), with planetologically significant implications, including the possibility of layering in Titan's magma ocean.

Johnson, M. L.↗
NASA NTRS1987

Thermodynamic budget diagrams for the hurricane subcloud layer

The idealized hurricane boundary layer budget from Malkus and Riehl (1960) are reexamined using vector diagrams for the thermodynamic budgets in the light of recent observational studies. A large air-sea temperature difference can only be maintained with both large fluxes through cloud-base level and a large evaporative cooling of the subcloud layer. The high equivalent potential temperature values observed in hurricane eyewalls can be reached if these cloud-base and evaporative fluxes are reduced and the subcloud layer moves toward the sea surface virtual potential temperature.

Betts, Alan K.↗
NASA NTRS1987

The ammonia-water phase diagram and its implications for icy satellites

A Holzapfel-type diamond anvil cell is used to determine the NH3 - H2O phase diagram in the region from 0 to 33 mole percent NH3, 240 to 370 K, and 0 to 5 GPa. The following phases were identified: liquid; water ices Ih, III, V, VI, VII, and VIII; ammonia monohydrate, NH3.H2O; and ammonia dihydrate NH3.2H2O. Ammonia dihydrate becomes prominent at moderate pressures (less than 1 GPa), with planetologically significant implications, including the possibility of layering in Titan's magma ocean.

Johnson, Mary L.↗
NASA NTRS1987

On the prospect of using butterfly diagrams to predict cycle minimum

Features enabling the prediction of the beginning and the length of a solar cycle, in addition to the turning points in the period-growth dichotomy, have been identified based on butterfly diagrams for the period from 1874 to the present. The present results indicate that cycle 21 will be a long-period cycle ending after July 1987. On the assumption that April 1985 was the first occurrence of high latitude new cycle (cycle 22) spots during the decline of cycle 21 (the old cycle), it is suggested that the last occurrence of high latitude old cycle spots was September 1983 and that the minimum for cycle 22 will be about 1986.7 + or - 1.1 yr.

Wilson, Robert M.↗
NASA NTRS1988

High-pressure phase diagram and equation of state of solid helium from single-crystal X-ray diffraction to 23.3 GPa

Single-crystal X-ray diffraction measurements have been performed on solid He-4 from 15.6 to 23.3 GPa at 300 K with synchrotron radiation. The diffraction patterns demonstrate that the structure of the solid is hexagonal close packed over this pressure-temperature range, contrary to both the interpretation of high-pressure optical studies and to theoretical predictions. The solid is more compressible than is indicated by equations of state calculated with recently determined helium pair potentials. The results suggest that a significant revision of current views of the phase diagram and energetics of dense solid helium is in order.

Mao, H. K.↗
NASA NTRS1988

Color-magnitude diagrams for six metal-rich, low-latitude globular clusters

Colors and magnitudes for stars on CCD frames for six metal-rich, low-latitude, previously unstudied globular clusters and one well-studied, metal-rich cluster (47 Tuc) have been derived and color-magnitude diagrams have been constructed. The photometry for stars in 47 Tuc are in good agreement with previous studies, while the V magnitudes of the horizontal-branch stars in the six program clusters do not agree with estimates based on secondary methods. The distances to these clusters are different from prior estimates. Redding values are derived for each program cluster. The horizontal branches of the program clusters all appear to lie entirely redwards of the red edge of the instability strip, as is normal for their metallicities.

Armandroff, Taft E.↗