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  • Other Sources  (218)
  • ASTROPHYSICS  (103)
  • AIRCRAFT PROPULSION AND POWER  (43)
  • ASTRONOMY  (38)
  • STRUCTURAL MECHANICS  (34)
  • CHEMISTRY
  • 1980-1984  (218)
  • 1970-1974
  • 1960-1964
  • 1980  (218)
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  • Other Sources  (218)
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  • 1980-1984  (218)
  • 1970-1974
  • 1960-1964
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  • 1
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    Hercules X-1 hard X-ray pulsations observed from HEAO 1 (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The 1.24-sec pulsations of Her X-1 in the energy range 13-75 keV have been analyzed in data obtained from the UCSD/MIT experiment on HEAO 1 during observations of the source on three dates in February 1978 and three in August 1978. Observational results are (1) the main pulse broadens somewhat with increasing energy; (2) the pulsation light curve undergoes pronounced changes at the leading edge of the main pulse from day to day; (3) spectral hardening within the main pulse is confirmed; (4) a 40-60 keV spectral feature in the spectrum is confirmed; (5) this feature is resolved, the pulse width broadening is greater than 20%, and its centroid varies with pulsation phase; and (6) the 13-75 keV spectrum does not noticeably vary from day to day, except for an overall intensity factor. Some implications of these results for the prevailing models of Her X-1 and the HZ Her-Her X-1 system are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
    Format: text
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  • 2
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    Comparison of several inflow control devices for flight simulation of fan tone noise using a JT15D-1 engine (1980)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: To enable accurate simulation of in-flight fan tone noise during ground static tests, four devices intended to reduce inflow disturbances and turbulence were tested with a JT15D-1 turbofan engine. These inflow control devices (ICD's) consisted of honeycomb/screen structures mounted over the engine inlet. The ICD's ranged from 1.6 to 4 fan diameters in size, and differed in shape and fabrication method. All the ICD's significantly reduced the BPF tone in the far-field directivity patterns, but the smallest ICD's apparently introduced propagating modes which could be recognized by additional lobes in the speeds; at supersonic fan tip speed the smallest ICD's had some measurable loss, but the largest had no loss. Data from a typical transducer show that the unsteady inflow distortion modes (turbulence) were eliminated or significantly reduced when either of the ICD's was installed. However, some steady inflow distortion modes remained.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-81505 , E-443 , Aeroacoustics Conf.; Jun 04, 1980 - Jun 06, 1980; Hartford
    Format: application/pdf
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  • 3
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    Comparison of several inflow control devices for flight simulation of fan tone noise using a JT15D-1 engine (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The paper describes the tests of four devices intended to reduce inflow disturbances and turbulences using a JT15D-1 turbofan engine. The tests were made to simulate the in-flight fan tone noise; the inflow control devices (ICD's) consisted of honeycomb/screen structures mounted over the engine inlet. The ICD's ranged from 1.6 to 4 fan diameters in size, and were made with several fabrication methods. All the ICD's significantly reduced the BPF tone in the far-field directivity patterns, but the smallest ICD's introduced propagating modes which could be recognized by additional lobes in the patterns. The JT15D-1 engine had a tone source which generated a strong propagating mode at fan speeds corresponding to 'approach' power and higher. Data from a typical transducer showed that the unsteady inflow distortion modes were eliminated or reduced when either of the ICD's was installed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 80-1025 , Aeroacoustics Conference; Jun 04, 1980 - Jun 06, 1980; Hartford, CT
    Format: text
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  • 4
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    Binary model of Circinus X-1. I - Eccentricity from combined X-ray and radio observations (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A binary star model is used to account for the 16.59-d flaring behavior of the X-ray emission from Circinus X-1. The orbital eccentricity of 0.8 + or - 0.1 is derived from the X-ray light curve by assuming that the sharp X-ray cut-off every 16.59-d is a result of bound-free absorption in the primary star's stellar wind. The shape of the light curve has changed over the last eight years, and this is interpreted as due to orbital precession of the binary system. Simultaneous radio and X-ray observations of the flare from Circinus X-1 on February 1-5, 1978 are reported. These are accounted for within the framework of the model. The radio observations at 5 GHz are used independently to derive a high value of the orbital eccentricity (e = 0.7).
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 86; 3, Ju; July 198
    Format: text
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  • 5
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    Response of a panel to a supersonic turbulent boundary layer - Studies on a theoretical model (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A study of the response of a clamped panel to a supersonic turbulent boundary layer, based on a recently developed theoretical model, is presented. It is demonstrated that the model incorporates the effect of coupling between the panel motion and the flow of the surrounding fluid. Further, a Ritz-Galerkin method is used to obtain approximate solutions for the statistics of the panel response to the turbulence. The numerical results are compared with previous experimental data and the theoretical model is assessed.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 71; July 22
    Format: text
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  • 6
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    Ultraviolet, X-ray, and infrared observations of HDE 226868 equals Cygnus X-1 (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: During April, May, and July of 1978, HDE 226868, the optical counterpart of Cygnus X-1, was repeatedly observed in the ultraviolet with the IUE satellite. Some X-ray and infrared observations have been made during the same period. The general shape of the spectrum is that expected from a late O supergiant. Strong absorption features are apparent in the ultraviolet, some of which have been identified. The equivalent widths of the most prominent lines appear to be modulated with the orbital phase. This modulation is discussed in terms of the ionization contours calculated by Hatchett and McCray, for a binary X-ray source in the stellar wind of the companion.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 242
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  • 7
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    Preparing aircraft propulsion for a new era in energy and the environment (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Improving fuel efficiency, new sources of jet fuel, and noise and emission control are subjects of NASA's aeronautics program. Projects aimed at attaining a 5% fuel savings for existing engines and a 13-22% savings for the next generation of turbofan engines using advanced components, and establishing a basis for turboprop-powered commercial air transports with 30-40% savings over conventional turbofan aircraft at comparable speeds and altitudes, are discussed. Fuel sources are considered in terms of reduced hydrogen and higher aromatic contents and resultant higher liner temperatures, and attention is given to lean burning, improved fuel atomization, higher freezing-point fuel, and deriving jet fuel from shale oil or coal. Noise sources including the fan, turbine, combustion process, and flow over internal struts, and attenuation using acoustic treatment, are discussed, while near-term reduction of polluting gaseous emissions at both low and high power, and far-term defining of the minimum gaseous-pollutant levels possible from turbine engines are also under study.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Astronautics and Aeronautics; 18; Jan. 198
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  • 8
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    Interplanetary sector boundaries 1971-1973 (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The large-scale morphology and internal structure of sector boundaries (SB) are investigated, using observations at 1 AU of interplanetary SB crossings. It was found that the durations of the SBs were either relatively short (less than about 10 min) or relatively long (longer than about 3 hours). Using the minimum variance technique, it was found that the SB surfaces were inclined appreciably with respect to the ecliptic at this epoch of the solar cycle (1971-1973). Magnetic holes were found in thick SBs at a rate about three times that elsewhere. In addition, an analysis of tangential discontinuities showed that their orientations were generally not related to the orientations of the SB surface, but their characteristics were very similar to those for discontinuities outside the SBs.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research; 85; May 1
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  • 9
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    Extreme-UV and far-UV observations of the white dwarf HZ 43 from Voyager 2 (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 242
    Format: text
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  • 10
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    The contribution of young galaxies to the X-ray background (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The contribution of young galaxies to the diffuse X-ray background is estimated and two mechanisms by which young galaxies may emit hard X-rays are considered. The first mechanism is direct thermal bremsstrahlung emission from a hot galactic wind powered by supernovae. Estimating mass-loss rates from galaxies by arguments based on metallicity and on the X-ray spectroscopic observations of rich clusters, it is shown that galactic winds may contribute substantially to the background. The second mechanism relies on the decreased metallicity of young galaxies to increase the number of supergiant stars and hence the numbers of hard X-ray binaries. This effect quantitatively explains the relatively large X-ray luminosity of the Magellanic clouds and also indicates that binaries in young galaxies may contribute a significant fraction of the diffuse X-ray background. Both mechanisms require that the epoch of galaxy formation be recent (redshift less than 2-3) in order to account for the observed spectral temperature (45 keV) of the hard X-ray background.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 237
    Format: text
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