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  • COMPOSITE MATERIALS  (47)
  • SOLAR PHYSICS  (45)
  • 1980-1984
  • 1975-1979  (92)
  • 1979  (92)
  • 1
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    Thermophysical properties data on graphite/polyimide composite materials (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Experimental data for the thermal conductivity, thermal expansion, specific heat, and emittance of laminates of HTS/NR 150B2 and HTS/PMR 15 are presented. Measurements were made over the temperature range 116 K to 588 K. Results for the two materials were similar with some differences attributable to laminate quality. Higher expansion coefficients for the HTS/PMR 15 specimens in the resin-dominated directions indicate a higher coefficient for PMR 15 than NR 150B2.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-159164 , GDC-NAS-79-002
    Format: application/pdf
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  • 2
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    Radiation transfer through a model sunspot (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A cylindrically symmetric model for a sunspot atmosphere using the similarity principle of Schlueter and Temesvary for the magnetic field configuration is presented. The equations of magnetostatic equilibrium are used, augmented by a radial Evershed flow. The LTE radiative transfer equations for the Stokes vector were solved under a variety of conditions for a ray emerging from a typical penumbral point. The contribution from isolated lines to the broadband circular polarization in sunspot penumbrae is evaluated using a more realistic model sunspot atmosphere than has hitherto been considered. Results indicate that the inclusion of a velocity field along the magnetic field vector is unable to give a net circular polarization of sufficient magnitude, although the variation with the angle between the line-of-sight and the magnetic field vector is in qualitative agreement with observations. The corresponding results for the net linear polarization are satisfactory.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 63; Sept
    Format: text
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  • 3
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    Stochastic acceleration of solar flare protons (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The acceleration of solar flare protons by the cyclotron damping of intense Alfven wave turbulence in a magnetic trap is considered. The energy diffusion coefficient is computed for a near-isotropic distribution of super-Alfvenic protons, and a steady-state solution for the particle spectrum is found for both transit-time and diffusive losses out of the ends of the trap. The acceleration time to a characteristic energy of about 20 MeV per nucleon can be as short as 10 sec. On the basis of phenomenological arguments, it is inferred that the Alfven wave spectrum typically has an inverse square frequency dependence and that the correlation time of the turbulence lies in the range between 0.5 and 50 msec.
    Keywords: SOLAR PHYSICS
    Type: AD-A081336 , Astrophysical Journal; vol. 233
    Format: text
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  • 4
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    Dynamo action in a thin slab (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: We consider the dynamo action produced by convection of a partially ionized, electrically conducting gas in a magnetic field. The model consists of two thin, Cartesian unipolar inductors connected in series by the magnetic field. For the case of a uniform magnetic field we compute the total current system generated by an arbitrary gas flow; for the case of a nonuniform field, we compute only the field-aligned coupling current. Application is made to the solar atmosphere.
    Keywords: SOLAR PHYSICS
    Type: AD-A069773 , Astrophysical Journal; vol. 228
    Format: text
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  • 5
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    Mechanical property degradation and chemical interactions in Borsic/titanium composite (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A study was undertaken to identify the mechanisms of mechanical property degradation in a Borsic (silicon-carbide coated boron) fiber reinforced Ti-3Al-2.5V composite exposed to elevated temperature. Samples containing 0.45 volume fraction of fibers were exposed, in vacuum, to temperatures from 700 K to 1255 K for times up to 240 hours. Room temperature tensile properties of unidirectional material were determined in both the longitudinal and transverse directions, before and after high-temperature exposure. Electron micro-probe analysis, scanning electron microscopy, and X-ray diffraction were used to determine the compounds formed and the extent of interaction between the boron, SiC coating, and matrix materials.
    Keywords: COMPOSITE MATERIALS
    Type: The enigma of the eighties: Environment, economics, energy; Twenty-fourth National Symposium and Exhibition; May 08, 1979 - May 10, 1979; San Francisco, CA
    Format: text
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  • 6
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    Plasma radiation diagnostics of the primary energy release region in solar flares (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The possibility is investigated that the plasma turbulence used in many recent models of the primary energy release and acceleration in solar flares should be detectable by radiation near the fundamental and second harmonic of the plasma frequency. Formulae are derived for fundamental emission due to the combination of ion-acoustic and Langmuir plasma turbulence and for second harmonic emission due to the combination of two Langmuir waves. These results are applied to recent primary energy release and acceleration models which shows that either such radiation should be detectable and possibly distinguishable with suitable microwave interferometers or that its absence places fairly stringent constraints on the possible level of Langmuir or Langmuir and ion-acoustic waves in these models.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 62; June 197
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  • 7
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    CO emission lines in the solar atmosphere (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: New identifications of CO emission lines in the EUV spectrum of a sunspot are reported. The spectra were obtained with the Naval Research Laboratory's High Resolution Telescope and Spectrograph. The emission is from the CO fourth positive system and is excited by the strong lines of C IV, Si IV and O IV. Transitions in the 0-3 band which lie above 1700 A and other lines at shorter wavelengths have been identified from the spectrum of the June 15, 1973 flare, obtained with the Naval Research Laboratory's normal incidence spectrograph on Skylab. The observed intensities in the sunspot are used to derive the CO column density.
    Keywords: SOLAR PHYSICS
    Type: Royal Astronomical Society; vol. 187
    Format: text
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  • 8
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    H2 emission in the solar atmosphere (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: New identifications of emission lines of molecular hydrogen in the EUV spectrum of sunspots are reported. The spectra were obtained during the first and second flights of the Naval Research Laboratory's High Resolution Telescope and Spectrograph (HRTS). While most of the lines originate in the Lyman bands, fluorescence from the Werner bands has been found for the first time in the solar atmosphere. H2 fluorescent emission has also been identified in the spectra of a solar flare observed with NRL's normal incidence spectrograph on Skylab. Column densities for H2 are derived from intensities of lines in the sunspot spectra.
    Keywords: SOLAR PHYSICS
    Type: Royal Astronomical Society; vol. 187
    Format: text
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  • 9
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    Study of high resistance inorganic coatings on graphite fibers (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Coatings made of boron, silicon carbide, silica, and silica-like materials were studied to determine their ability to increase resistance of graphite fibers. The most promising results were attained by chemical vapor depositing silicon carbide on graphite fiber followed by oxidation, and drawing graphite fiber through ethyl silicate followed by appropriate heat treatments. In the silicon carbide coating studies, no degradation of the graphite fibers was observed and resistance values as high as three orders of magnitude higher than that of the uncoated fiber was attained. The strength of a composite fabricated from the coated fiber had a strength which compared favorably with those of composites prepared from uncoated fiber. For the silica-like coated fiber prepared by drawing the graphite fiber through an ethyl silicate solution followed by heating, coated fiber resistances about an order of magnitude greater than that of the uncoated fiber were attained. Composites prepared using these fibers had flexural strengths comparable with those prepared using uncoated fibers, but the shear strengths were lower.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-159078 , R79-914212-9
    Format: application/pdf
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  • 10
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    Interfacial reactions in borsic/Ti-3Al-2-1/2V composite (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: The paper provides a detailed X-ray characterization of a borsic/Ti-3Al-2-1/2V composite, and to correlate the relative intensities of the reaction products with the mechanical properties. Based on X-ray integrated intensity data two stages of interface reactions were identified: during the first stage there is a simultaneous interdiffusion of Si, C, and Ti atoms at the filament/matrix interface resulting in the formation of Ti5Si3, TiSi and small amounts of TiSi2 and TiC. The second stage is associated with considerable TiSi2 and boride formation. It appears that the alpha-phase of Ti is more reactive in forming silicides and borides than the beta-phase. The silicide intensities and the reaction zone thicknesses are shown to be directly related to the reduction of the ultimate tensile strength by thermal degradation, and the results indicate that silicide reaction products are as detrimental to strength as the borides.
    Keywords: COMPOSITE MATERIALS
    Type: New developments and applications in composites; 17, 1978; Louis, MO.
    Format: text
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