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  • Other Sources  (771)
  • STRUCTURAL MECHANICS  (254)
  • AIRCRAFT PROPULSION AND POWER  (240)
  • ELECTRONICS AND ELECTRICAL ENGINEERING  (139)
  • 42.75
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  • BSSA
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  • SPACE RADIATION
  • 1975-1979  (771)
  • 1960-1964
  • 1930-1934
  • 1976  (771)
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  • 1975-1979  (771)
  • 1960-1964
  • 1930-1934
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  • 1
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    Dynamics of an expanding circular fault (1976)
    In:  Bull. Seism. Soc. Am., San Francisco, Pergamon, vol. 66, no. 5496, pp. 639-666, pp. B05315, (ISSN: 1340-4202)
    Details
    Publication Date: 1976
    Keywords: SModelling ; Source mechanics ; Source ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    An analysis of tidal strain observations from the United States of America II. The inhomogeneous tide (1976)
    In:  Bull. Seism. Soc. Am., San Francisco, Pergamon, vol. 66, no. 6, pp. 1821-1846, pp. 1246
    Details
    Publication Date: 1976
    Keywords: Earth tides ; TIDES ; Inhomogeneity ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    The mechanics of locating earthquakes (1976)
    In:  Bull. Seism. Soc. Am., Tulsa, 3-4, vol. 66, no. 3-4, pp. 173-187, pp. B09405, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1976
    Keywords: Seismology ; Location ; AUD ; Hypocenter determination ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Time-domain determination of earthquake fault parameters from short-period P-waves (1976)
    In:  Bull. Seism. Soc. Am., Roma, Polish Geothermal Association, vol. 66, no. 2, pp. 1459-1484, pp. B05406, (ISSN: 1340-4202)
    Details
    Publication Date: 1976
    Keywords: High frequency ... ; Data analysis / ~ processing ; Fault plane solution, focal mechanism ; Seismology ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 5
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    Responsibilities in earthquake prediction (1976)
    In:  Bulletin of the Seismological Society of America, Tokyo, Am. Geophys. Union, vol. 66, no. 6, pp. 2069-2074, pp. 8043
    Details
    Publication Date: 1976
    Keywords: Earthquake precursor: prediction research ; ethics ; Seismology ; society ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 6
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    The effect of tectonic stress release on explosion P-wave signatures (1976)
    In:  Bull. Seism. Soc. Am., Hannover, Bundesanstalt für Geowissenschaften und Rohstoffe, vol. 66, no. 40, pp. 1441-1457, pp. L08305
    Details
    Publication Date: 1976
    Keywords: Nuclear explosion ; Stress ; P-waves ; Seismology ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 7
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    Seismicity of northern Anatolia (1976)
    In:  Bull. Seism. Soc. Am., London, Geological Society, vol. 66, no. 3, pp. 843-868, pp. L24307, (ISBN 1-86239-117-3)
    Details
    Publication Date: 1976
    Keywords: Seismicity ; Turkey ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 8
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    Simplified procedures for estimating the fundamental period of a soil profile (1976)
    In:  Bull. Seism. Soc. Am., Amsterdam, Academic Press (Elsevier), vol. 66, no. 4, pp. 1293-1321, pp. 2486, (ISBN 1-86239-117-3)
    Details
    Publication Date: 1976
    Keywords: Site amplification ; Spectrum ; method ; noksp ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 9
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    A two-dimensional analysis of surface deformation due to dip-slip faulting (1976)
    In:  Bull. Seism. Soc. Am., Heidelberg, 1, vol. 66, no. 4-5, pp. 667-675, pp. B01401, (ISBN: 0534351875, 2nd edition)
    Details
    Publication Date: 1976
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Elasticity ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 10
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    Scaling relations for earthquake source parameters and magnitudes (1976)
    In:  Bull. Seism. Soc. Am., Regensburg, Inst. Electrical & Electronics Engineers, vol. 66, no. 3, pp. 1501-1523, pp. TC5001, (ISBN: 0534351875, 2nd edition)
    Details
    Publication Date: 1976
    Keywords: Source parameters ; Magnitude ; Source ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 11
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    Body force equivalents for stress-drop seismic sources (1976)
    In:  Bull. Seism. Soc. Am., Regensburg, Inst. Electrical & Electronics Engineers, vol. 66, no. 3, pp. 1801-1804, pp. TC5001, (ISBN: 0534351875, 2nd edition)
    Details
    Publication Date: 1976
    Keywords: Body waves ; Stress drop ; Elasticity ; Seismology ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 12
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    Abnormal seismology (1976)
    In:  Bull. Seism. Soc. Am., Warszawa, Elsevier, vol. 66, no. 1, pp. 617-623, pp. 2091, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1976
    Keywords: Seismology ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 13
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    Inversion of the body waves from the Borrego Mountain earthquake to the source mechanism (1976)
    In:  Bull. Seism. Soc. Am., Hannover, FU Berlin, vol. 66, no. 3, pp. 1485-1499, pp. 5091692, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1976
    Keywords: Inversion ; Body waves ; Earthquake ; Source ; Source parameters ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 14
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    Seismic characteristics of southeast Missouri as indicated by a regional telemetered microearthquake array (1976)
    In:  Bull. Seism. Soc. Am., Houston, Akademie-Verlag, vol. 66, no. 6, pp. 1953-1964, pp. L08310, (ISSN: 1340-4202)
    Details
    Publication Date: 1976
    Keywords: Seismology ; Teleseismic events ; Seismic arrays ; Schafer ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 15
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    A portable digital seismic recorder with event recording capability (1976)
    In:  Bull. Seism. Soc. Am., New York, Scientific American, vol. 66, no. Nov., pp. 979-985, pp. B10302, (ISSN: 1340-4202)
    Details
    Publication Date: 1976
    Keywords: Seismology ; Instruments ; Detectors ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 16
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    Preliminary empirical model for scaling Fourier amplitude spectra of strong ground acceleration in terms of earthquake magnitude, source-to-station distance and recording site conditions (1976)
    In:  Bull. Seism. Soc. Am., Warszawa, EGS, vol. 66, no. 4, pp. 1343-1373, pp. 1089, (ISSN: 1340-4202)
    Details
    Publication Date: 1976
    Keywords: Site amplification ; Earthquake engineering, engineering seismology ; Spectrum ; Strong motions ; Magnitude ; Attenuation ; Modelling ; noksp ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 17
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    Automatic seismic array and network detection (1976)
    In:  Bull. Seism. Soc. Am., Hannover, Elsevier, vol. 66, no. 4, pp. 1375-1380, pp. L15S14, (ISSN: 1340-4202)
    Details
    Publication Date: 1976
    Keywords: Detectors ; Data analysis / ~ processing ; ARRAY ; Seismic networks ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 18
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    A computer program for the application Zoeppritz's amplitude equations and Knott's energy equations (1976)
    In:  Bull. Seism. Soc. Am., Corvallis, x + 406 pp., Oregon State University Press, vol. 66, no. 1, pp. 1881-1885, pp. L13610, (ISSN: 1340-4202)
    Details
    Publication Date: 1976
    Keywords: EDV ; Energy (of earthquakes) ; Amplitude ; Data analysis / ~ processing ; Reflectivity ; BSSA
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    BIBLIOGRAPHY SEISMOLOGY
  • 19
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    Rapid interface flaw extension with friction (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: An idealized two-dimensional example of rapid interface flow extension is described. Initially undisturbed dissimilar isotropic, homogeneous, linearly elastic half-spaces are perfectly bonded along the interface y=0. Quantities associated with the half-space or = to 0 are denoted by the prime superscript or the subscripts 3 or 4 while those in y or = to 0 carry the subscripts 1 or 2. At time t=0 adjacent material points at x=0, y= + or - 0 are forced apart horizontally with a constant relative velocity delta v. This results in a zone of bond failure which extends symmetrically along the interface at a constant rate c. The newly created flaw surfaces are in sliding contact resisted by Coulomb friction. The friction coefficient is gamma.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 1; p 239-246
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  • 20
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    Influence of a circular hole under uniform normal pressure on the stresses around a line crack in an infinite plate (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: Based on the two dimensional theory of elasticity and by the use of Muskhelishvili's technique, the influence of a circular hole, under uniform normal pressure, on the stresses around a line crack in an infinite plate subjected to tension is discussed. Numerical calculations were carried out, and the variation of the crack tip stress intensity factor due to the geometry was clarified.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 1; p 275-282
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  • 21
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    Errors in short circuit current measurements due to spectral mismatch between sunlight and solar simulators (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: For abstract, see N77-26620.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Terrest. Photovoltaic Meas., 2; p 161-182
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  • 22
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    Gamma rays, cosmic rays and galactic structure (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Working primarily from the recent SAS-2 observations of galactic gamma rays, the relation of these observations to the large scale distribution of cosmic rays and interstellar gas in the galaxy is reviewed and reexamined. Starting with a discussion of production rates, the case for pion decay being the predominant production mechanism in the galactic disk above 100 MeV is reestablished and it is also pointed out that Compton gamma rays can be a significant source. To facilitate discussion, the concepts of four distinct galactic regions are defined, viz. the nebulodisk, ectodisk, radiodisk and exodisk. Bremsstrahlung and pion decay gamma rays are associated with the first two (primarily the first) regions, and Compton gamma rays and synchrotron radiation are associated with the latter two regions. On a large scale, the cosmic rays, interstellar gas (primarily H2 clouds in the inner galaxy) and gamma ray emissivity all peak in a region between 5 and 6 kpc from the galactic center. This correlation is related to correlation with other population I phenomena and is discussed in terms of the density wave concept of galactic structure. The singular nature of the HI distribution appears to follow the supernova remnant and pulsar distributions in the galaxy.
    Keywords: SPACE RADIATION
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 357-391
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  • 23
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    The non-thermal radiation in the galaxy (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The distribution of nonthermal emissivity with height z above the galactic plane is examined. The main result is that recent observations of the distribution of brightness at intermediate latitudes in the galaxy and of the edge-on spiral galaxy NGC 891 indicate that the emissivity extends to heights of several kpc perpendicular to the plane. The relationship between the nonthermal emissivity and the neutral gas is also studied. In several galaxies the angular distributions of neutral hydrogen and nonthermal emission are roughly coextensive and show similar features such as spiral structure. If radio galaxies and normal galaxies with strong nuclear radio sources are excluded, there appears to be a proportionality between their total HI content and their nonthermal radio luminosity.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 206-221
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  • 24
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    Gamma rays and supernova explosions (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The detection of gamma rays from supernovae will provide interesting tests of current theory. Some current ideas on the expected gamma ray flux, as modified by recent theoretical results are reviewed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 289-298
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  • 25
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    COS-B observations of localised sources of gamma-ray emission (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: In October 1975 the high energy gamma ray flux from the Vela pulsar was measured by COS-B to be 1.6 to 2.1 times higher than the flux measured by SAS-2 in 1973. The existence is confirmed of a second region of enhanced radiation in the galactic anticenter in addition to that from the Crab pulsar.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 45A-51
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  • 26
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    SAS-2 galactic gamma ray results, 1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Continuing analysis of the data from the SAS-2 high energy gamma-ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitude 310 and 45 deg, corresponding to a region within 7kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315 deg, 330 deg, 345 deg, 0 deg, and 35 deg. These peaks appear to be correlated with such galactic features and components as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic ray concentrations, and photon fields.
    Keywords: SPACE RADIATION
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 1-11C
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  • 27
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    Extreme ultraviolet survey experiment MA-083 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: A grazing incidence telescope sensitive to radiation in the 5- to 100-nanometer band was flown in the Apollo service module. On 10 nighttime revolutions, the command and service module was maneuvered to point the instrument at 30 different stellar targets for periods of 1 to 20 minutes, thus constituting the first sensitive search for extreme ultraviolet radiation from nonsolar sources. Several hours of supplementary data were also obtained during nighttime orbits when other experiments in the scientific instrument module bay were operating. Preliminary analysis of a small fraction of the total data indicates the definite detection of a strong source of extreme ultraviolet radiation during observations made during revolution 109. The source is located in Coma Berencies. The suggested optical identification is the white dwarf HZ 43. If this association is correct, the star has the highest temperature of any known white dwarf. Regardless of the optical identification, however, this object is the first nonsolar source to be detected in the extreme ultraviolet band.
    Keywords: SPACE RADIATION
    Type: NASA. Lyndon B. Johnson Space Center Apollo-Soyuz Test Project; 16 p
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  • 28
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    Cosmic X-ray observations with OSO-8 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The GSFC Cosmic X-ray Spectroscopy experiment aboard OSO-8 has operated successfully since launch providing spectral and temporal data on X-ray sources in tha energy range 2-60 keV. Analysis of quick look data shows a variety of spectral features, some stable, others variable, which will increase understanding of the nature of individual sources. In particular, observed emission and absorption features that can be attributed to iron will result in abundance measures of this important element in sources such as some X-ray binaries, the supernova remnant Cas A, and the nucleus of the galaxy Cen A.
    Keywords: SPACE RADIATION
    Type: X-ray Binaries; p 67-79
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  • 29
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    Cosmic ray propagation and containment (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The cosmic rays, an active gaseous component of the disk of the galaxy, are considered along with their propagation and containment as a part of the general dynamics of the disk. The sources of cosmic rays are a matter of speculation. The disk is inflated by the cosmic ray gas pressure comparable to the magnetic pressure, but the rate of inflation is unknown. The time spent by the individual cosmic ray particles in the disk is inversely proportional to the cosmic ray production rate. It is evident from the decay of Be(1c) that the cosmic rays circulate through a volume of space perhaps ten times the thickness of the gaseous disk, suggesting a magnetic halo extending out approximately 1 kpc from either face of the disk. The cosmic rays may be responsible for the halo by inflating the magnetic fields of the disk. Extension of the fields to 1 kpc would imply a high production rate and short life of cosmic rays in the dense gaseous disk of the galaxy.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 320-340
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  • 30
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    Low and medium energy galactic gamma-ray observations (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Observation of 0.2-100 MeV diffuse gamma radiation emitted from the Galaxy can provide information on the intensities of 5-50 MeV/nucleon cosmic-rays and 50 MeV electrons in interstellar space. Recent measurements of gamma-rays emitted from the galactic center region provide evidence for a diffuse continuum between 10 and 100 MeV. The intensities of the recently reported nuclear line gamma rays, also observed in the direction of the galactic center, require the presence of intense fluxes of low-energy cosmic-rays in the inner Galaxy if the gamma-rays are produced on a galactic scale. Current detection techniques for 0.1-100 MeV gamma-ray measurements are summarized and their capabilities for measuring the diffuse galactic emission are evaluated.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center. The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 65-83
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  • 31
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    Crystal activation experiment MA-151 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The crystal activation experiment consisted of two sample packages that were flown in the command module and returned to earth for analysis of the radioactivity induced in them during the flight. The objective of the experiment was to define the background caused by detector activation that interferes when gamma radiation is measured in the 0.02- to 10-megaelectronvolt range from earth orbit. Preliminary results show that the activation of the NaI(Tl) crystal was a factor of 3 below that from a similar measurement on Apollo 17. The identification of certain species and the level of activation observed show an important contribution from the interactions of thermal and energetic neutrons produced as secondaries in the spacecraft. That the activation was reduced by only a factor of 3 compared with the Apollo 17 experiment, despite the geomagnetically shielded orbit, possibly indicates more efficient secondary neutron production by the more energetic cosmic rays.
    Keywords: SPACE RADIATION
    Type: Apollo-Soyuz Test Project; 10 p
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  • 32
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    Gamma rays and large scale galactic structure (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Many theoretical models were developed in an attempt to explain the spatial structure in the observed emission which results from interactions of energetic cosmic rays with the interstellar gas. The peaks in the observed distribution are remarkably well correlated with longitudes corresponding to tangential directions to known spiral arm features. Based on theoretical and experimental arguments, it is assumed that on the scale of galactic arms the cosmic rays are more intense where the mass of the gas to which they are coupled is greatest. Refining this model with the results of recent surveys of the interstellar gas, a good fit to the observations is obtained whether the cosmic rays are confined to the spiral arms in the disk or are more evenly confined as in a flat halo model.
    Keywords: SPACE RADIATION
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 341-354
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  • 33
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    The time structure of the gamma-ray emission from the Crab and Vela pulsars (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: High resolution data on the pulsed gamma ray emission from the Crab and Vela pulsars are presented. The light curves of these two pulsars at gamma ray energies show striking similarities.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 52-64
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  • 34
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    Preliminary Results from the European Space Agency's COS-B satellite for gamma-ray astronomy (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The COS-B satellite carries a single experiment, capable of detecting gamma rays with energies greater than 30 MeV. Its objectives are to study the spatial, energy, and time characteristics of high energy radiation of galactic and extragalactic origin. The capability to search for gamma ray pulsations is enhanced by the inclusion in the payload of a proportional counter sensitive to X-rays of 2-12 Kev. The experiment was calibrated using particle accelerators. The results of these measurements are presented and the performance of the system in orbit is discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 23-38
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  • 35
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    Soft X-ray observation experiment MA-048 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The Apollo Soyuz Test Project Soft X-ray Experiment was designed to observe celestial X-ray sources in the energy range from 0.1 to 10 kiloelectronvolts. The instrument that was used in the experiment obtained energy and fast timing data to characterize both the spectrum and the variability of known X-ray sources. Data were obtained on approximately 12 sources. During the mission, the instrument developed an intermittent high voltage discharge problem that resulted in the loss of approximately 75 percent of the anticipated data, including the scans intended for mapping of the low energy diffuse X-ray background.
    Keywords: SPACE RADIATION
    Type: NASA. Lyndon B. Johnson Space Center Apollo-Soyuz Test Project; 11 p
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  • 36
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    SAS-2 galactic gamma ray results. 2. Localized sources (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Gamma-ray emission was detected from the radio pulsars PSR1818-04 and PSR1747-46, in addition to the previously reported gamma-ray emission from the Crab and Vela pulsars. Since the Crab pulsar is the only one observed in the optical and X-ray bands, these gamma-ray observations suggest a uniquely gamma-ray phenomenon occurring in a fraction of the radio pulsars. Using distance estimates it is found that PSR1818-04 has a gamma-ray luminosity comparable to that of the Crab pulsar, while the luminosities of PSR1747-46 and the Vela pulsar are approximately an order of magnitude lower. This survey of SAS-2 data for pulsar correlations has also yielded upper limits to gamma-ray luminosity for 71 other radio pulsars.
    Keywords: SPACE RADIATION
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 12-22
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  • 37
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    COS-B observations of the high energy gamma radiation from the galactic disc (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: During the first months of operation, COS-B has observed galactic high energy gamma rays from the galactic disc. In the galactic center and Vela regions the disc emission distribution was measured. From these data the existence of a local ( 1 kpc) and a distant ( 3 kpc) emitting region is apparent in the general direction of the inner galaxy.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center The Galaxy and Galactic Gamma Rays; p 39-44
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  • 38
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    Interstellar helium flow experiment MA-088 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The Apollo Soyuz Test Project Interstellar Helium Glow Experiment (MA-088) studied the motion of helium in the local interstellar medium as that medium passed through the solar system to determine several poorly known properties of the local interstellar gas. The instrument used was a photometer sensitive to two solar extreme ultraviolet spectral lines that are resonantly scattered by helium gas. The instrument surveyed the entire celestial sphere during a series of slow, rolling maneuvers by the Apollo spacecraft. The equipment operated properly, and usable data were obtained.
    Keywords: SPACE RADIATION
    Type: NASA. Lyndon B. Johnson Space Center Apollo-Soyuz Test Project; 15 p
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  • 39
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    A study of the effect of subcritical crack growth on the geometry dependence on nonlinear fracture toughness parameters (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: The effect of subcritical crack growth on the geometry dependence of nonlinear fracture toughness parameters was studied by comparing the toughness values for different specimen geometries at the onset of subcritical crack growth and at the initiation of unstable crack propagation. Center-cracked thin sheet specimens of 2024-T3 and 7075-T6 aluminum alloys were tested by varying the specimen length L, width w, and crack length-to-width ratio c/w. When the onset of unstable crack propagation was selected as the critical point, the nonlinear energy toughness and the R curve toughness increased with increasing w and decreasing L and c/w. However, when the onset of subcritical crack growth was taken as the critical point, energy toughness and the linear toughness values were independent of these geometrical variables.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 1; p 257-266
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  • 40
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    Influence of specimen boundary on the dynamic stress intensity factor (1976)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: The problem to be considered is the sudden appearance of a flaw or crack in a strip of material of finite height subjected to tensile loading. Stress waves are generated within the strip and are reflected from boundary to boundary. Of interest is the maximum value of the dynamic stress intensity factor at a given instance of time as the strip height to crack length ratio is varied.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Advan. in Eng. Sci., Vol. 1; p 205-214
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  • 41
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    Long term performance of the advanced thermal control flight experiment (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The Advanced Thermal Control Flight Experiment (ATFE) is providing the first zero-g flight data for the performance of a thermal diode heat pipe and an electrical Feedback Controlled Heat Pipe (FCHP). The temperature stability derived from the melting and freezing of octadecane is also being evaluated in this experiment. Flight data for the different operational modes are compared to ground test data, and the performance of the individual components is analyzed. Also, the ATFE's long term behavior from launch through September 30, 1975, is evaluated. The temperature control capability of a thermal diode, phase change material, and FCHP was demonstrated over more than 500 days of flight operation and each of these components should be considered in future applications. Both the diode and FCHP transport more than 20 W in the normal and passive modes during maximum conditions. Up to 30 W has been carried by the FCHP when the auxiliary heater is applied. The "OFF-conductance" of the diode has improved substantially in flight. A 1.4 W decrease in backflow has been realized by more complete blockage. The variable conductance behavior of the FCHP is essentially unchanged with time and relative to ground tests. Degradation of the radiator and reservoir surfaces have resulted in a partial loss of control by the FCHP during normal mode operation; however, manual control at an elevated set point has demonstrated the FCHP's ability to provide regulated temperature control to within + or - 2 C. The same pipe when operated as a passive VCHP controlled at 35 + or - 10 C with the same test conditions.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: ESA Heat Pipes; p 629-643
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  • 42
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    Wave propagation in laminated orthotropic circular cylindrical shells (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An exact three-dimensional analysis of wave propagation in laminated orthotropic circular cylindrical-shells is developed. Numerical results are presented for three-ply shells, and for various axial wave lengths, circumferential wave numbers, and thicknesses. Results from a thin shell theory and a refined approximate theory are compared with the exact results.
    Keywords: STRUCTURAL MECHANICS
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  • 43
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    Whence cometh /and goeth/ Jupiter's high energy electrons (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Jupiter's decimetric emission is universally identified as synchrotron radiation from about 10 MeV electrons. These electrons radiate away their energy in a few months and hence must be continuously replaced. A theory in which electrons are injected at Jupiter's magnetopause and radially diffuse toward the planetary surface, gaining energy in the process is summarized. The radial diffusion coefficient in the inner magnetosphere is determined. This diffusion coefficient, which also holds for protons, is sufficiently small that the inner Galilean satellites can wipe out large fractions of the incoming proton and electron fluxes. The reduction of the proton flux is extremely important to the survival of the Pioneer experimental payloads.
    Keywords: SPACE RADIATION
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  • 44
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    Plane-stress fracture of compact and notch-bend specimens (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Thin-gaged or high toughness materials containing cracks usually fail in a ductile manner with nominal failure stresses approaching the ultimate strength of the material. For such materials, a two-parameter fracture criterion was developed. An equation which related the linear elastic stress-intensity factor, elastic nominal stress, and two material parameters has previously been derived and has been used as a fracture criterion for surface- and through-cracked specimens under tensile loading. In the present paper the two-parameter fracture criterion was rederived in a more general form and was extended to compact and notch-bend fracture specimens. A close correlation was found between experimental and calculated failure stresses.
    Keywords: STRUCTURAL MECHANICS
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  • 45
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    Bakeable UHV gate valve for microwave tube experimentation (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The performance characteristics and design of an ultrahigh-vacuum (UHV) gate valve intended for experiments on high-power microwave tubes are described. Tests run on the valve indicate open/close cycles can run into the hundreds or thousands without trouble. The valve was baked at 450 C or higher for at least 4 h. Applications of the valve include evaluation of NASA-design multistage depressed collectors for high-power PPM focused helix-type traveling-wave tubes.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Journal of Vacuum Science and Technology; 13; Nov
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  • 46
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    The shear-stress intensity factor for a centrally cracked stiff-flanged shear web (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: By use of the principle of superposition the stiff-flanged shear web is modeled mathematically by an infinite elastic strip with fixed longitudinal edges. The shear-stress intensity factor for a central longitudinal crack is calculated for various values of the ratio of strip width to crack length, h/a, in the range 0.1-10. The interaction of the crack with the boundaries is illustrated by boundary shear-stress distributions for three values of h/a. Some implications of the results for the design of damage-tolerant shear webs are discussed briefly.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 12; Apr. 197
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  • 47
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    Scintillating plastic fibers as light pipes for a cosmic ray hodoscope: Feasibility calculations and measured attenuation characteristics (1976)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A candidate hodoscope uses arrays of scintillator fibers, followed by an image intensifier and imaging system such as that proposed for the X-ray shadowgraph. A literature search was performed to ascertain the experience of other workers with hodoscopes using this or similar principles. Calculations were performed to determine the feasibility of candidate systems and some laboratory experiments were performed to attempt to check these numbers.
    Keywords: SPACE RADIATION
    Type: The Specific Light Output of Cesium Iodide Crystals; p 45-58
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  • 48
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    Application of axial grooves to cryogenic variable conductance heat pipe technology (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Tests results obtained with an ATS axial groove aluminum extrusion adapted for use as a cryogenic thermal diode and/or a variable conductance heat pipe are presented. Ethane at a nominal operating temperature of 185 C was used as working fluid. In addition to both active and passive gas control, diode designs utilizing gas blockage or liquid trap were investigated. Specific requirements and performance parameters such as transient behavior, reservoir sizes, shutdown energy, etc., were evaluated. Results are also presented for tests where the liquid trap was used as a secondary heat pipe to demonstrate thermal switching with simultaneous heat pipe operation and diode shutdown.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: ESA Heat Pipes; p 183-195
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  • 49
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    Heat pipes for spacecraft temperature control: An assessment of the state-of-the-art (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Spacecraft applications that require the efficient cooling of high-powered components, the precise temperature control of sensitive electronic and optical components, and the protection of cooled components from temporary, adverse environmental conditions are increasing. Heat pipes using gas, vapor, liquid, or voltage control to provide variable conductance or diode thermal behavior have been and are continuing to be developed to meet increasingly difficult requirements. The various control techniques are critically evaluated using characteristic features and properties, including heat transport capability, volume and mass requirements, complexity and ease of fabrication, reliability, and control characteristics. As a result, advantages and disadvantages of specific approaches are derived and discussed. Using four development levels, the state-of-the-art of the various heat pipe temperature control techniques is assessed.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: ESA Heat Pipes; p 167-181
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  • 50
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    Reliability and structural integrity (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An analytic model is developed to calculate the reliability of a structure after it is inspected for cracks. The model accounts for the growth of undiscovered cracks between inspections and their effect upon the reliability after subsequent inspections. The model is based upon a differential form of Bayes' Theorem for reliability, and upon fracture mechanics for crack growth.
    Keywords: STRUCTURAL MECHANICS
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  • 51
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    Irradiate-anneal screening of total dose effects in semiconductor devices (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Judicious choice of radiation dose and parameter change acceptance criteria, absence of anomalous anneal phenomena, and absence of anomalous reirradiation effects are recognized as essential for a successful irradiation-anneal (IRAN) screening procedure to ensure that no device will fall, upon reirradiation, above parametric limits assigned for the worst case application. Reirradiation and irradiation-anneal behavior of various semiconductor devices are compared and those that do not lend themselves to IRAN screening are singled out. Information needed to judge the suitability of an IRAN type screening program is detailed. Reasons for success of the limited IRAN screening of flight parts for the Mariner Jupiter/Saturn (MJS '77) spacecraft are indicated.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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  • 52
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    Resizing procedure for structures under combined mechanical and thermal loading (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The fully-stressed design (FSD) appears to be the most widely used approach for sizing of flight structures under strength and minimum-gage constraints. Almost all of the experience with FSD has been with structures primarily under mechanical loading as opposed to thermal loading. In this method the structural sizes are iterated with the step size, depending on the ratio of the total stress to the allowable stress. In this paper, the thermal fully-stressed design (TFSD) procedure developed for problems involving substantial thermal stress is extended to biaxial stress members using a Von Mises failure criterion. The TFSD resizing procedure for uniaxial stress is restated and the new procedure for biaxial stress members is developed. Results are presented for an application of the two procedures to size a simplified wing structure.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 14; Oct. 197
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  • 53
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    Theory and applications of sampled analog recursive CTD comb filters (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Sampled analog comb filter using a recursive filter implementation was studied. Charge transfer device delay lines were used as the delay elements. The similarities and differences between sampled analog recursive filter and digital recursive filter were pointed out. Both canceller type and integrator type comb filter using the first order or the second order canonical circuits were studied. Experimental results of frequency response are presented to show their difference from that of digital filters. A theoretical analysis was presented based essentially on the digital filter theory but modified to take into account the differences described above. The usefulness of this theory in analyzing the comb filter characteristics was discussed. Several applications of both the canceller type comb filter and the integrator type comb filter were demonstrated.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; 10 p
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  • 54
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    The effect of direct current bias in the computation of power spectra (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The effect of dc bias in the approximate computation of spectra of Gaussian processes is determined by hard limiting.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: The Deep Space Network; p 53-57
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  • 55
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    Local and large scale galactic gamma-ray emission (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A study of the gas-to-dust ratio suggests that interstellar reddening may provide an accurate way of assessing column densities in various directions in the Galaxy. A gamma ray intensity of 7.25 x 10 to the -5th E sub B-V photon/sq cm/s/sterad is predicted for regions of the Galaxy where the medium cosmic ray density is equal to that observed close to the sun. It is found that in the longitude range of about 0-180 degrees, the large scale cosmic ray distribution producing the gamma rays follows that of extreme population I stars put in evidence by giant H II regions, and that of molecular hydrogen traced by carbon monoxide emission. The gamma-ray production exhibits a maximum at R roughly equal to 5 kpc, and practically vanishes at R not less than 11 kpc, beyond the location of the outermost H II regions.
    Keywords: SPACE RADIATION
    Type: Astronomy and Astrophysics; 50; 2, Ju; July 197
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  • 56
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    Effect of longitudinal or inplane deformation and inertia on the large amplitude flexural vibrations of slender beams and thin plates (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 49; Dec. 8
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  • 57
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    Electrons in a closed galaxy model of cosmic rays (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper considers the consistency of positrons and electrons with a propagation model in which the cosmic rays are stopped by nuclear collisions or energy losses before they can escape from the Galaxy (the closed-galaxy model). The fact that no inconsistency is found between the predictions and the data implies that the protons which produce the positrons by nuclear reactions could have their origin in a large number of distant sources, as opposed to the heavier nuclei which in this model come from a more limited set of sources. The closed-galaxy model predicts steep electron and positron spectra at high energies. None of these are inconsistent with present measurements; but future measurements of the spectrum of high-energy positrons could provide a definite test for the model. The closed-galaxy model also predicts that the interstellar electron intensity below a few GeV is larger than that implied by other models. The consequence of this result is that electron bremsstrahlung is responsible for about 50% of the galactic gamma-ray emission at photon energies greater than 100 MeV
    Keywords: SPACE RADIATION
    Type: Astrophysics and Space Science; 45; Nov. 197
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  • 58
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    Germanium-overcoated niobium Dayem bridges (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Overcoating constriction microbridges with semiconducting germanium provides additional thermal conductivity at liquid-helium temperatures to reduce the effects of self-heating in these Josephson junctions. Microwave-induced steps were observed in the I-V characteristics of an overcoated Dayem bridge fabricated in a 15-nm-thick niobium film; at least 20 steps could be counted at 4.2 K. No steps were observed in the I-V characteristics of the bridge prior to overcoating. In addition, the germanium overcoat can protect against electrical disturbances at room temperature.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Applied Physics Letters; 28; May 15
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  • 59
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    Large area ion chambers for a high energy cosmic ray experiment (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: High resolution measurement of the iron group nuclei was performed with the intention of determining individual abundances in the cosmic ray flux at the earth of particles with z = 22 to 30. Of the three types of dE/dx detectors used in the experiment, pulse ion chambers, Cerenkov radiators and scintillators, the first has the best z resolution over a wide range of particle z and energy. The plastic scintillators define the particle acceptance cone of the telescope while the Cerenkov detector aids in rejection of low energy particle background and measurement of particle velocity.
    Keywords: SPACE RADIATION
    Type: The Specific Light Output of Cesium Iodide Crystals; p 1-44
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  • 60
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    A sub-nanosecond CCD (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A 32-cell silicon n-channel PCCD was fabricated and tested for charge transfer efficiency versus transfer time. A charge transfer time of 550 picoseconds with a 0.9998 transfer efficiency was obtained when operated in the uni-phase mode. These conditions correspond to an operating rate of 900 MHz when operated as an analog data or digital device.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 89-94
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  • 61
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    Metal-insulator-semi-conductor studies of lead telluride (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The capacitance and conductance-voltage characteristics were measured on metal-insulator-semiconductor capacitors fabricated with zirconium dioxide films on single-crystal lead telluride. At 77 K, on both n- and p-type substrates, evidence of surface potential control was obtained. Comparison of the measured capacitance-voltage characteristics with those calculated from the equilibrium solution of the one-dimensional Poisson equation indicated qualitative agreement, although the slope of the measured capacitance in the region near the capacitance minimum was less steep than calculated.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 45-48
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  • 62
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    Measurement of the primary cosmic electron spectrum from 10 to about 250 GeV (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The intensity and energy spectrum of primary cosmic electrons from 10 to about 250 GeV have been studied by using balloon-borne detectors. The detectors were large-area ionization calorimeters which sampled showering particles frequently and demonstrated an energy resolution of about 7% in calibration tests. On one of the flights a time-of-flight system and detectors to sample the lateral properties of showers were used to examine and to test background rejection. The results of the balloon flights from Alamogordo, N. Mex., in 1970 and Cape Girardeau, Mo., in 1972 indicated that the primary cosmic ray electron differential energy spectrum exhibits no change of slope in the energy range measured and is well represented by a power law. The results indicate that the cosmic electron spectrum is steeper than the cosmic ray proton spectrum. It is shown that these data are consistent with the leakage lifetime model for the propagation of cosmic electrons in the galaxy, although other more complex models cannot be excluded on the basis of these data.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 81; Aug. 1
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  • 63
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    Solar modulation and a galactic origin for the anomalous component observed in low-energy cosmic rays (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The current theory of solar modulation can be used to argue that the cosmic-ray component at low energies, which is observed to have an anomalous composition, is not of galactic origin, i.e., it is not a component of the galactic cosmic-ray flux. The current theory predicts, from quite general considerations, that an unreasonably large intensity of cosmic rays, by many orders of magnitude, would be required in the interstellar medium to account for the observed fluxes. Conceivably, the current modulation theory could be modified so that only reasonable interstellar fluxes are predicted. One such modification involves an unusual scheme for particle diffusion in the interplanetary medium. Particles are assumed to diffuse not as a result of their own motion among small-scale irregularities in the magnetic field, but rather in a process in which they are trapped between time-varying constrictions in the large-scale field.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 206; May 15
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  • 64
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    Photonuclear interactions of ultrahigh energy cosmic rays and their astrophysical consequences (1976)
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    Publication Date: 2011-08-16
    Description: Results are presented for detailed Monte Carlo calculations of the interaction histories of ultrahigh-energy cosmic-ray nuclei with intergalactic radiation fields, using improved estimates of these fields and empirical determinations of photonuclear cross sections, including multinuclear disintegrations for nuclei up to Fe-56. Intergalactic and galactic energy-loss rates and nucleon-loss rates for nuclei up to Fe-56 are also given. Astrophysical implications are discussed in terms of expected features in the cosmic-ray spectrum between 10 to the 18th and 10 to the 21st power eV for the universal and supercluster origin hypotheses. The results of these calculations indicate that ultrahigh-energy cosmic rays cannot be universal in origin regardless of whether they are protons or nuclei. Both the supercluster and galactic origin hypotheses, however, are possible regardless of nuclear composition.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 205; Apr. 15
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  • 65
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    Three-dimensional interplanetary stream magnetism and energetic particle motion (1976)
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    Publication Date: 2011-08-16
    Description: Cosmic rays interact with mesoscale configurations of the interplanetary magnetic field. A technique is presented for calculating such configurations in the inner solar system, which are due to streams and source conditions near the sun, and maps of magnetic field are constructed for some plausible stream and source conditions. One effect of these mesoscale configurations on galactic cosmic rays is shown to be an out-of-the-ecliptic gradient drift sufficient to explain Forbush decreases. The effects on solar energetic particles include small polar drifts due to the field gradients and a possibly large modification of the time-intensity profiles and anisotropy characteristics due to the formation of mirror configurations in space. If a diffusion model is applicable to solar particles, the true diffusion coefficient will be masked by the effects of streams. A conceptual model which incorporates these ideas and those of several other models is presented.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 81; May 1
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  • 66
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    Static load-carrying capacity of circular rigid-plastic plates under Gaussian distribution of pressure (1976)
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    Publication Date: 2011-08-16
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Solids and Structures; 12; 8, 19; 1976
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  • 67
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    Large amplitude free vibrations of tapered beams (1976)
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    Publication Date: 2011-08-16
    Description: The Galerkin method is used to investigate the large-amplitude free vibrations of simply supported and clamped tapered beams of rectangular cross-section which are frequently encountered in practical structures. Two types of linear tapers are considered: breadth and depth tapers. Two solutions are obtained for each type of taper, using trigonometric and polynomial displacement distributions. Frequency-amplitude relationships are obtained for all these cases for the fundamental flexural mode. The results indicate good agreement between trigonometric and polynomial solutions for all cases. The nonlinearity is noted to be always of the hardening type and, as expected, it is severe for beams with depth taper as compared with beams with breadth taper.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 14; Feb. 197
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  • 68
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    Determination of the interaction impedance of coupled cavity slow wave structures (1976)
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    Publication Date: 2011-08-16
    Description: The interaction impedance of coupled cavity slow wave structures can be measured by perturbing the resonances of a shorted length of the structure using a dielectric rod. An analysis of this procedure is presented. The analysis retains radial as well as axial electric fields and all significant space harmonics. The results obtained are easily programmed formulas for calculating total interaction impedance or Pierce impedance using the experimental data.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Electron Devices; ED-23; May 1976
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  • 69
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    The interplanetary acceleration of energetic nucleons (1976)
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    Publication Date: 2011-08-16
    Description: Corotating proton and electron streams are the dominant type of low-energy (i.e., 0.1-10 MeV per nucleon) particle event observed at 1 AU. The radial dependence of these events has been studied between 1 and 4 AU using essentially identical low-energy detector systems on IMP-7, Pioneer-10, and Pioneer-11. It had been expected that at a given energy, the intensity of these streams would decrease rapidly with heliocentric distance due to the effects of interplanetary adiabatic deceleration. Instead, it is observed that from event to event, the intensity either remains roughly constant or increases significantly (more than an order of magnitude) between 1 and 4 AU. It appears that interplanetary acceleration processes are the most plausible explanation. Several possible acceleration models are discussed.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 203; Feb. 1
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    Structural optimization via a design space hierarchy (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Mathematical programming techniques provide a general approach to automated structural design. An iterative method is proposed in which design is treated as a hierarchy of subproblems, one being locally constrained and the other being locally unconstrained. It is assumed that the design space is locally convex in the case of good initial designs and that the objective and constraint functions are continuous, with continuous first derivatives. A general design algorithm is outlined for finding a move direction which will decrease the value of the objective function while maintaining a feasible design. The case of one-dimensional search in a two-variable design space is discussed. Possible applications are discussed. A major feature of the proposed algorithm is its application to problems which are inherently ill-conditioned, such as design of structures for optimum geometry.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal for Numerical Methods in Engineering; 10; 3, 19; 1976
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  • 71
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    Stall flutter and nonlinear divergence of a two-dimensional flat plate wing (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Tests were conducted in a small wind tunnel to study the torsional stall flutter behavior of a two-dimensional flat-plate wing pivoted about the midchord. The nonlinear static divergence equilibrium properties of the wing were well predicted from the measured static moment characteristics. Large amplitude limit cycles ranging from plus or minus 11 degrees to plus or minus 100 degrees were observed. Stall flutter occurred above a critical value of a reduced frequency of about 2. Self-excitation occurred for initial angles of attack between 0 and 8 degrees. Nondimensional harmonic coefficients were extracted from the free transient vibration tests for amplitudes up to 80 degrees.
    Keywords: STRUCTURAL MECHANICS
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  • 72
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    Evaluation of clad scintillating light pipes (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Arrays of fibers made of scintillating material were used as position-sensitive detectors or hodoscopes for beam-finding at ion accelerators. Experiments were made with alpha's from an Am241 source incident upon one end of the fiber, the other end being viewed with a photomultiplier tube. The scintillation light was not detected in any of the fibers tested beyond about 5 cm. The effective useful lengths for detection of relativistic heavy ions were given.
    Keywords: SPACE RADIATION
    Type: The Specific Light Output of Cesium Iodide Crystals; p 59-63
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  • 73
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    Significance of medium-energy gamma-ray astronomy in the study of cosmic rays (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The paper examines the medium-energy (about 10-30 MeV) galactic gamma-ray radiation from primary and secondary electrons and calculates the expected gamma-ray distribution for the specific model of Bignami et al. (1975) on the assumption that the cosmic rays are correlated with the matter on the scale of galactic arms. The energy spectrum typical of regions near the galactic center indicates a dramatic shift from a predominantly cosmic-ray nucleonic mechanism at higher energies to a cosmic-ray electron mechanism at the lower energies. This provides a most important and direct means of probing the cosmic-ray electrons as a function of galactic position by making gamma-ray observations in the few to 40 MeV energy range. Medium-energy gamma-ray astronomy is shown to be a valuable tool in galactic research.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 208; Aug. 15
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  • 74
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    Aeroacoustics: Jet noise, combustion and core engine noise (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The papers in this volume deal essentially with the question whether the amplification of noise is due to the jet noise phenomenon or perhaps an interaction of airframe and core engine noise. In the area of jet noise suppression, various promising suppressor concepts are examined. The swirling flow jet noise suppressor is shown to provide significant noise reduction with minimal thrust losses. Progress in the aircraft engine core noise problem is reflected by seven research-type papers. Two possible mechanisms are seen to be responsible for core noise. One is the direct noise radiated from the turbulent combustion in the primary combuster and transmitted through the turbine, passing out the nozzle into the far field. The other mechanism is the noise that is emitted from hot spots being convected through the turbine. Which of these mechanisms (or perhaps both mechanisms) is responsible for core noise, and what are the coupling mechanisms of core engine noise and jet noise are the questions confronting researchers.
    Keywords: AIRCRAFT PROPULSION AND POWER
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  • 75
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    Conceptual studies for new low-cost 64-m antennas (1976)
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    Publication Date: 2011-08-16
    Description: Recent software developments expedite design investigations of proposed new 64-m antenna structures. The software consists of programs to generate structure model data and a design program that chooses preferential cross sectional sizes of the structural members. Numerous new designs are summarized that can represent weight savings of from 25% to 50% with respect to the tipping weight of the existing Mars antenna. These designs provide a more favorable symmetrical support for the reflector backup and tend to provide superior surface accuracy for gravity, although not necessarily wind, loading on the antenna.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: The Deep Space Network; p 55-67
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  • 76
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    Lattice theory of three-dimensional cracks (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The problem of the stability of a three-dimensional crack is analyzed within a lattice-statics approximation. The consequence of introducing a jog into the crack face as well as the effects of various nonlinear-force laws are studied. The phenomenon of lattice trapping (upper and lower bounds on the applied stress for an equilibrium crack of given length) is again obtained. It is possible to obtain some physical insight into which aspects of the force law are critical for crack stability. In particular, the inadequacy of a thermodynamic approach - which relates the critical stress to a surface energy corresponding to the area under the cohesive-force-vs-displacement curve - is demonstrated. Surface energy is a global property of the cohesive-force law. Crack stability is sensitive to much more refined aspects of the cohesive-force law. Crack healing is sensitive to the long-range portion of the cohesive force. Crack expansion is sensitive to the position of the maximum in the cohesive-force relation.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Applied Physics; 47; Feb. 197
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  • 77
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    Dielectric loss in microstrip lines (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A technique is presented for calculating dielectric loss in microstrip lines. Numerical results for several different substrates are included. These are compared with other available results and experimental data.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Microwave Theory and Techniques vol. MTT-24; Feb. 197
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  • 78
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    Advances in gamma-ray burst astronomy (1976)
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    Publication Date: 2011-08-16
    Description: The paper reviews the current status of observational research into the highly puzzling problem of cosmic gamma-ray bursts. Up to now there is no convincing temporal or spatial correlation with any known celestial processes or objects. The typical burst source strength is somewhere between 10 to the 26th power ergs and 10 to the 52nd power ergs. A list of 39 confirmed and 9 unconfirmed cosmic gamma-ray bursts observed by satellite is given, showing times of occurrence and in some cases, the size in erg per square centimeter. Several approaches to the problem of source object identification are discussed: (1) accumulation of observation statistics with their present poor resolution and research for correlative phenomena, (2) mapping out celestial source distributions with moderate resolution in order to search for galactic or other anisotropies in direction or to look for repeating source regions, and (3) very high-accuracy localization of the source directions of one or several bursts in order to pinpoint a tiny fraction of the celestial sphere for correlative radio, optical and X-ray studies. Planned future instrumentation for deep space probes and multiple-balloon studies is described.
    Keywords: SPACE RADIATION
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  • 79
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    Magnetoresistance and noise properties of chevron stretcher detectors for field access bubble domain devices (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Experiments were devised to study the angular variation of the resistance and noise properties of one- and two-level chevron stretcher magnetoresistive detectors for use in field access bubble memory devices. All measurements, made with an electronic system, were performed on glass or garnet samples upon which 1 micron of SiO2 was sputter-deposited, followed by 4000 A of Permalloy for the 28-micron-period devices and 0.8 microns of SiO2, followed by 3000 A of Permalloy for the 20-micron-period devices. The geometrical and drive-state dependence of the zero-state noise were studied, as was its frequency dependence. It is found that both types of detectors operate primarily in the amplitude-shift mode for drive fields of interest and that the presence of a bubble in a detector causes a magnetoresistance change equal to that produced by increasing the in-plane drive field about 8 Oe in the absence of a bubble.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Journal of Applied Physics; 47; July 197
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  • 80
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    Homogeneous magnetic fields produced by circular current loops (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: (For abstract see issue 24, p. 3529, Accession no. A75-47672)
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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  • 81
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    Rapid and precise measurement of flatband voltage (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The paper outlines the design, principles of operation, and calibration of a five-IC network intended to give a rapid, precise, and automatic determination of the flatband voltage of MOS capacitors. The basic principle of measurement is to compare the analog output voltage of a capacitance meter - which is directly proportional to the capacitance being measured - with a preset or dialed-in voltage proportional to the calculated flatband capacitance by means of a comparator circuit. The bias to the MOS capacitor supplied through the capacitance meter is provided by a ramp voltage going from a negative toward a positive voltage level and vice versa. The network employs two monostable multivibrators for reading and recording the flatband voltage and for resetting the initial conditions and restarting the ramp. The flatband voltage can be held and read on a digital voltmeter.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Review of Scientific Instruments; 47; May 1976
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  • 82
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    Symmetric stiffness matrix for incompressible hyperelastic materials (1976)
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    Publication Date: 2011-08-16
    Description: Symmetric structure matrices are derived for solving plane strain and axisymmetric problems involving incompressible hyperelastic materials. An infinite hollow cylinder subjected to internal pressure is considered as an example. Displacement and hydrostatic pressure profiles are calculated using the Newton-Raphson iteration technique. The results are in good agreement with the exact curves.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 14; Mar. 197
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  • 83
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    Dynamic response of membranes with finite elements (1976)
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    Publication Date: 2011-08-16
    Description: A general set of finite-element equations is developed for treating the nonlinear dynamic response of membranes consisting of complex nonlinear materials. The approach proposed by Key (1974) for a most complete treatment of the finite-element method to the nonlinear dynamic analysis of solids is used in developing the nonlinear equations of motion for membranes with cubic quadrilateral finite elements. The computations are kept general with respect to material modeling by computing the deformation gradient and requiring a constitutive subroutine to supply the Cauchy stress. An example calculation of the vibration of a square membrane demonstrates the accuracy of the formulation for small deformation theory and shows the nonlinear effect of large deformations.
    Keywords: STRUCTURAL MECHANICS
    Type: American Society of Civil Engineers; Journal
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  • 84
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    Disjoint design spaces in the optimization of harmonically excited structures (1976)
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    Publication Date: 2011-08-16
    Description: The paper deals with a method of optimizing harmonically or dynamically excited structures which removes the frequency constraint (that specifies that the structure's first natural frequency of vibration must be greater than the excitation frequency), replaces the displacement constraint by an inequality constraint on the allowable stress and applies finite element approximations to the continuous one-dimensional structures. When the problem is posed in this manner, the feasible design space is disconnected or 'disjoint'. An attempt is made to explain this disjointness by studying the optimal design of a thin-walled cantilevered rod subjected to steady, simple harmonic torsional excitation. The finite element method is applied to the optimization of a harmonically excited structure with an arbitrary number of design variables, with the disjointness of the design space, a complicating factor.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal; 14; Feb. 197
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  • 85
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    A nonlinear theory of cosmic-ray pitch-angle diffusion in homogeneous magnetostatic turbulence (1976)
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    Publication Date: 2011-08-16
    Description: A plasma strong turbulence, weak coupling, theory is applied to the problem of cosmic-ray pitch-angle scattering in magnetostatic turbulence. The theory used is a rigorous generalization of Weinstock's 'resonance broadening' theory and contains no ad hoc approximations. A detailed calculation is presented for a model of 'slab' turbulence with an exponential correlation function. The results agree well with numerical simulations. The rigidity dependence of the pitch-angle scattering coefficient differs from that found by previous researchers. The differences result from an inadequate treatment of particle trajectories near 90 deg pitch angle in earlier work.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 204; Mar. 15
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  • 86
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    Cosmic-ray positron and negatron spectra between 20 and 800 MeV measured in 1974 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The flux density of cosmic-ray positrons and electrons was measured by a balloon-borne spark chamber magnetic spectrometer in two flights in an attempt to study the solar modulation of galactic cosmic rays. The total electron flux was found to be about 0.03/cu m/s/sr/MeV between 70 and 800 MeV and to increase toward lower energies, while the positron flux decreased sharply toward lower energies from about 0.008/cu m/s/sr/MeV at 650 MeV and only upper limits were obtained for positrons below 200 MeV. At energies above 180 MeV, the spherically symmetrical Fokker-Planck equation with a diffusion coefficient proportional to the particle rigidity provided a reasonable fit to both positron and total electron data, while at energies below 180 MeV, the data were consistent with a continuation of the same diffusion coefficient and local source of electrons, or a change in the diffusion coefficient to a constant value.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; 204; Mar. 15
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  • 87
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    Ionising flux of cosmic background radiation (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The indirect method of estimating the diffuse metagalactic flux of ionizing radiation proposed by Sunyaev (1969) is reconsidered in the light of further studies of the interaction of this radiation with galactic gas. An upper limit is derived for the intensity of the metagalactic background radiation to which the neutral interstellar medium is exposed. This limit on the ionizing radiation flux severely restricts the emission from a galactic corona containing gas in the temperature range 100,000 to 1,000,000 K. An upper limit of 10 to the 29.2 erg/sec/Hz is obtained for the mean luminosity radiated by a quasar in the energy band 40-170 eV. The 21-cm observations examined indicate that further than about 30 kpc from the center of the galaxy self-shielding by H II is possible only when the critical metagalactic ionizing flux is not exceeded.
    Keywords: SPACE RADIATION
    Type: Nature; 260; Apr. 8
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  • 88
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    Solar-cosmic-ray variability (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Keywords: SPACE RADIATION
    Type: Lunar Science Inst., Abstracts of Papers Presented at a Special Session of the Seventh Annual Lunar Science Conference on Utilization of Lunar Materials and Expertise for Large Scale Operations in Space; p 81-86
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  • 89
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    Turbofan compressor dynamics during afterburner transients (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: The effects of afterburner light-off and shut-down transients on the compressor stability are investigated. The reported experimental results are based on detailed high response pressure and temperature measurements on the TF30-P-3 turbofan engine. The tests were performed in an altitude test chamber simulating high altitude engine operation. It is shown that during both types of transients, flow breaks down in the forward part of the fan bypass duct. At a sufficiently low engine inlet pressure this resulted in a compressor stall. Complete flow breakdown within the compressor was preceded by a rotating stall. At some locations in the compressor, rotating stall cells initially extended only through part of the blade span. For the shutdown transient the time between first and last detected occurrence of rotating stall is related to the flow Reynolds number. An attempt was made to deduce the number and speed of propagation of rotating stall cells.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AGARD Unsteady Phenomena in Turbomachinery; 12 p
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  • 90
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    Assessment of Variable-Cycle Engines for Supersonic Transports (1976)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: Propulsion systems are evaluated in terms of relative aircraft range for a fixed payload and takeoff gross weight with a design cruise Mach number of 2.7. In order to put the performance of these engines in perspective, a comparison of these engines and the former U.S. SST engine is made with an idealized variable cycle engine whose performance at all operating points matches that of an optimized point design cycle within specified limits. Range comparisons are made with and without noise level constraints to determine the influence of noise upon cycle selection. The critical areas requiring new or improved technology for each cycle are delineated.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AGARD Variable Geometry and Multicycle Eng.; 19 p
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  • 91
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    NASTRAN used in a production environment (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A finite element analysis procedure built around the NASTRAN system is assessed. A number of support programs that were either written or modified to interface with NASTRAN and some improvements that were made to NASTRAN itself are noted. Some typical models are analyzed and an actual schedule is followed for constructing and analyzing the models to support a large design program.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 531-554
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  • 92
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    Modal seismic analysis of a nuclear power plant control panel and comparison with SAP 4 (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The application of NASTRAN to seismic analysis by considering the example of a nuclear power plant control panel was considered. A modal analysis of a three-dimensional model of the panel, consisting of beam and quadri-lateral membrane elements, is performed. Using the results of this analysis and a typical response spectrum of an earthquake, the seismic response of the structure is obtained. ALTERs required to the program in order to compute the maximum modal responses as well as the resultant response are given. The results are compared with those obtained by using the SAP IV computer program.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center MATRAN: User's Experiences; p 515-530
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  • 93
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    Some applications of the NASTRAN level 16 subsonic flutter analysis capability (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The Level 16 flutter analysis capability was applied to an aspect-ratio-6.8 subsonic transport type wing, an aspect-ratio-1.7 arrow wing, and an aspect-ratio-1.3 all movable horizontal tail with a geared elevator. The transport wing and arrow wing results are compared with experimental results obtained in the Langley transonic dynamic tunnel and with other calculated results obtained using subsonic lifting surface (kernel function) unsteady aerodynamic theory.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: User's Experiences; p 495-512
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    A postprocessor system for the data reduction and post analysis of NASTRAN results (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: NASTRAN analysis results are scanned to determine maximum and minimum displacements, forces and stresses. Allowables and margins of safety are computed, and in the case of multiple loading conditions, envelopes for displacements, forces, stresses and margins of safety are also produced for specified element sets. Graphical plots of the reduced or the regular NASTRAN results may be obtained superimposed either of a developed fuselage strip or on a projection of any specified part of the finite element model. The use of the data reduction, post analysis and graphical plotting capabilities provide the analyst with a fast and convenient tool for the study of NASTRAN analysis results and their presentation for project documentation.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 555-580
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  • 95
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    Addition of higher order plate elements to NASTRAN (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Two plate elements, the linear strain triangular membrane element CTRIM6 and the higher order plate bending element CTRPLT1, were added to NASTRAN Level 16.0. The theoretical formulation, programming details, and bulk data information pertaining to the addition of these elements are discussed. Sample problems illustrating the use of these elements are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 439-478
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  • 96
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    Implementation on a nonlinear concrete cracking algorithm in NASTRAN (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A computer code for the analysis of reinforced concrete structures was developed using NASTRAN as a basis. Nonlinear iteration procedures were developed for obtaining solutions with a wide variety of loading sequences. A direct access file system was used to save results at each load step to restart within the solution module for further analysis. A multi-nested looping capability was implemented to control the iterations and change the loads. The basis for the analysis is a set of mutli-layer plate elements which allow local definition of materials and cracking properties.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 479-494
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    The quarter-point quadratic isoparametric element as a singular element for crack problems (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The quadratic isoparametric elements which embody the inverse square root singularity are used for calculating the stress intensity factors at tips of cracks. The strain singularity at a point or an edge is obtained in a simple manner by placing the mid-side nodes at quarter points in the vicinity of the crack tip or an edge. These elements are implemented in NASTRAN as dummy elements. The method eliminates the use of special crack tip elements and in addition, these elements satisfy the constant strain and rigid body modes required for convergence.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 419-438
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  • 98
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    Analysis of the Learjet 35/36 Wing and Correlation with Experimental Results (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two NASTRAN models of the Gates Learjet Corporation Model 35/36 Wing were developed. The models and the problems encountered in their development are discussed. A skin buckling analysis used for the ultimate loading conditions is presented. A discussion of the static tests and the correlation of the static test with the NASTRAN results and the results of a supplementary semimonocoque beam analysis are also included.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 331-352
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    Application of NASTRAN to large space structures (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The application of NASTRAN to design studies of two very large-area lightweight structures is described. The first is the Satellite Solar Power Station, while the second is a deployable three hundred meter diameter antenna. A brief discussion of the operation of the SSPS is given, followed by a description of the structure. The use of the NASTRAN program for static, vibration and thermal analysis is illustrated and some results are given. Next, the deployable antenna is discussed and the use of NASTRAN for static analysis, buckling analysis and vibration analysis is detailed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Ames Res. Center NASTRAN: User's Experiences; p 295-330
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    NASTRAN as an analytical research tool for composite mechanics and composite structures (1976)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Selected examples are described in which NASTRAN is used as an analysis research tool for composite mechanics and for composite structural components. The examples were selected to illustrate the importance of using NASTRAN as an analysis tool in this rapidly advancing field.
    Keywords: STRUCTURAL MECHANICS
    Type: NASTRAN: User's Experiences; p 381-418
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