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  • Cell & Developmental Biology  (3,484)
  • SPACE RADIATION  (2,694)
  • STRUCTURAL MECHANICS  (2,565)
  • 1975-1979  (3,242)
  • 1970-1974  (4,442)
  • 1955-1959  (694)
  • 1930-1934  (365)
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Keywords
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Years
Year
  • 1
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    Combined vibration/temperature/sideload environmental testing of UHF blade antennas (1979)
    In:  CASI
    Details
    Publication Date: 2006-07-02
    Description: Service problems encountered on the F-4 aircraft showed that the environmental qualification requirements for the UHF blade antenna were not adequate. Although the individual environmental levels were stringent enough, only combined environmental testing could duplicate the conditions in which service problems occurred. Techniques for applying static side load simultaneously with vibration and temperature were developed. The combined environment testing was instrumental in the rapid assessment of antenna modifications and resulted in a final configuration which proved satisfactory in service. A need to include combined environmental testing for qualification of blade antennas was established.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Bull., Pt. 3; p 79-84
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  • 2
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    A simplified method of evaluating the stress wave environment of internal equipment (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: A simplified method called the transfer function technique (TFT) was devised for evaluating the stress wave environment in a structure containing internal equipment. The TFT consists of following the initial in-plane stress wave that propagates through a structure subjected to a dynamic load and characterizing how the wave is altered as it is transmitted through intersections of structural members. As a basis for evaluating the TFT, impact experiments and detailed stress wave analyses were performed for structures with two or three, or more members. Transfer functions that relate the wave transmitted through an intersection to the incident wave were deduced from the predicted wave response. By sequentially applying these transfer functions to a structure with several intersections, it was found that the environment produced by the initial stress wave propagating through the structure can be approximated well. The TFT can be used as a design tool or as an analytical tool to determine whether a more detailed wave analysis is warranted.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Bull., Pt. 1; p 89-96
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  • 3
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    High G pyrotechnic shock simulation using metal-to-metal impact (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: A technique for simulating high g level pyrotechnic shocks is described and the results of applying the technique to obtain the MIL-STD-1540A shock spectrum with a maximum acceleration of 18,000g at 2,000 Hz are presented. Designing the resonant beam and plate on which the test unit is mounted, and generating a proper impulsive load on them, were the essentials of the technique. One dimensional stress wave and Euler equations were employed in the design. A metal pendulum hammer was used to generate the impulsive load.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Bull., Pt. 1; p 97-100
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  • 4
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    Probability of failure prediction for step-stress fatigue under sine or random stress (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: A previously proposed cumulative fatigue damage law is extended to predict the probability of failure or fatigue life for structural materials with S-N fatigue curves represented as a scatterband of failure points. The proposed law applies to structures subjected to sinusoidal or random stresses and includes the effect of initial crack (i.e., flaw) sizes. The corrected cycle ratio damage function is shown to have physical significance.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Bull., Pt. 1; p 31-41
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  • 5
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    Prediction of energetic particle disturbances (1979)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The prediction of fluxes of energetic particles of solar or magnetospheric origin is addressed. Topics include the prediction of the properties of the particle populations generated by magnetospheric storms and substorms, and the prediction of long term variations in the populations of magnetospheric particles.
    Keywords: SPACE RADIATION
    Type: NASA. Marshall Space Flight Center Solar-Terrest. Predictions Proc., Vol. 2; p 415-432
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  • 6
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    Mechanics of fracture - Fundamentals and some recent developments (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An overview is presented of the fundamental aspects of and recent developments in fracture mechanics. Reference is made to linear elastic fracture mechanics including the state of stresses and displacements in the vicinity of cracks, effects of crack geometry and orientation on stress intensity factors, energy balance of Griffith, Irwin's stress intensity concept, and linear elastic fracture mechanics testing for fracture toughness. Other aspects of this paper include the non-linear behavior of materials and their influence on fracture mechanics parameters, consideration of viscoelasticity and plasticity, non-linear fracture toughness parameters as C.O.D., R-curve and J-integral, and a non-linear energy method, proposed by Liebowitz. Finite element methods applied to fracture mechanics problems are indicated. Also, consideration has been given to slow crack growth, dynamic effects on K(IC), Sih's criterion for fracture, Lee and Liebowitz's criterion relating crack growth with plastic energy, and applications of fracture mechanics to aircraft design. Suggestions are offered for future research efforts to be undertaken in fracture mechanics.
    Keywords: STRUCTURAL MECHANICS
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  • 7
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    NASA-Langley Research Center's participation in a round-robin comparison between some current crack-propagation prediction methods (1979)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A round-robin study was conducted which evaluated and compared different methods currently in practice for predicting crack growth in surface-cracked specimens. This report describes the prediction methods used by the Fracture Mechanics Engineering Section, at NASA-Langley Research Center, and presents a comparison between predicted crack growth and crack growth observed in laboratory experiments. For tests at higher stress levels, the correlation between predicted and experimentally determined crack growth was generally quite good. For tests at lower stress levels, the predicted number of cycles to reach a given crack length was consistently higher than the experimentally determined number of cycles. This consistent overestimation of the number of cycles could have resulted from a lack of definition of crack-growth data at low values of the stress intensity range. Generally, the predicted critical flaw sizes were smaller than the experimentally determined critical flaw sizes. This underestimation probably resulted from using plane-strain fracture toughness values to predict failure rather than the more appropriate values based on maximum load.
    Keywords: STRUCTURAL MECHANICS
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  • 8
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    A review and assessment of the stress-intensity factors for surface cracks (1979)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The stress-intensity factor solutions proposed for a surface crack in a finite plate subjected to uniform tension are reviewed. Fourteen different solutions obtained over the past 16 years using approximate analytical methods, experimental methods, and engineering estimates are compared. The accuracy of the various solutions is assessed by correlating fracture data on surface-cracked tension specimens made of a brittle epoxy material. Fracture of the epoxy material was characterized by a constant value of stress-intensity factor as failure. Thus, the correctness of various solutions is judged by the variations in the stress-intensity factors at failure. The solutions were ranked in order of minimum standard deviation. The highest ranking solutions correlated 95% of data analyzed within + or - 10% whereas the lowest ranking solutions correlated 95% of data analyzed within + or - 20%. Some solutions could be applied to all data considered, whereas others were limited with respect to crack shapes and crack sizes that could be analyzed.
    Keywords: STRUCTURAL MECHANICS
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  • 9
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    Source position loci for the gamma-ray bursts recorded October 20 and November 10, 1977 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Further constraints are imposed on the sites of the gamma-ray bursts recorded Oct. 20 and Nov. 10, 1977 with the Prognoz 6 satellite and the Helios 2 spacecraft. The loci of the burst sources are 1.7-arcmin-wide bands in which no X-ray sources, pulsars, supernova remnants, or galaxies brighter than 13m occur.
    Keywords: SPACE RADIATION
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  • 10
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    Diffuse fluxes of cosmic high-energy neutrinos (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Production spectra of high-energy neutrinos from galactic cosmic-ray interactions with interstellar gas and extragalactic ultrahigh-energy cosmic-ray interactions with microwave blackbody photons are presented and discussed. These production processes involve the decay of charged pions and are thus related to the production of cosmic gamma rays from the decay of neutral pions. Estimates of the neutrino fluxes from various diffuse cosmic sources are then made, and the reasons for significant differences with previous estimates are discussed. Small predicted event rates for a DUMAND (deep underwater muon and neutrino detector) type detection system, combined with a possible significant flux of prompt neutrinos from the atmosphere above 50 TeV, may make the study of diffuse extraterrestrial neutrinos more difficult than previously thought.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 228
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  • 11
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    Modeling of electron time variations in the radiation belts (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A review of the temporal variation in the trapped electron population of the inner and outer radiation zones is presented. Techniques presently used for modeling these zones are discussed and their deficiencies identified. An intermediate region is indicated between the zones in which the present modeling techniques are inadequate due to the magnitude and frequency of magnetic storms. Future trends are examined, and it is suggested that modeling of individual magnetic storms may be required in certain L bands. An analysis of seven magnetic storms is presented, establishing the independence of the depletion time of the storm flux and the storm magnitude. Provisional correlation between the storm magnitude and the Dst index is demonstrated.
    Keywords: SPACE RADIATION
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  • 12
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    A possible closure relation for heat transport in the solar wind (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The objective of the present paper is to search for an empirical closure relation for solar wind heat transport that applies to a microscopic scale. This task is approached by using the quasi-linear wave-particle formalism proposed by Perkins (1973) as a guide to derive an equation relating the relative drift speed between core-electron and proton populations to local bulk flow conditions. The resulting relationship, containing one free parameter, is found to provide a good characterization of Los Alamos Imp electron data measuring during the period from March 1971 through August 1974. An empirical closure relation is implied by this result because of the observed proportionality between heat flux and relative drift speed.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 84; Nov. 1
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  • 13
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    A search for low energy gamma rays from CG 195+4 (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A 13-deg-wide region of sky containing the high-energy gamma-ray source CG 195+4 was searched for X-ray and gamma-ray emission in the energy interval from 0.035 to 8.737 MeV. The balloon-altitude measurements were undertaken on October 4, 1977, at Palestine, Texas, and used an actively collimated scintillation counter. As a result of the measurements, low upper limits have been found for the spectrum from the source. Combined with the positive detections made with satellites at high energies, the measurements show that the photon number spectrum must have a spectral index harder than 2.0. The data appear inconsistent with models of the source in which the presumed neutron star is surrounded by a cloud thick to X-rays. Negative results of the search for periodicity are discussed.
    Keywords: SPACE RADIATION
    Type: Astronomy and Astrophysics; 79; 1-2,; Oct. 197
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  • 14
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    Finite dynamic element formulation for a plane triangular element (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Higher order correction terms for the stiffness and inertia matrices associated with a triangular plane stress-strain finite dynamic element are developed in detail. Numerical results are presented which indicate that the adoption of these matrices along with a suitable quadratic matrix eigenproblem solver effects a significant economy in the free vibration solution of structure when compared with the analysis based on the usual finite element procedure. Finally, a FORTRAN IV computer program listing of the various relevant matrices is given.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal for Numerical Methods in Engineering; 14; 10, 1; 1979
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  • 15
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    X-ray emission from gamma-ray sources in the galactic anticentre region (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An X-ray survey of three high energy gamma-ray sources in the galactic anticenter region conducted using the large area sky survey instrument on HEAO 1 is presented. The sensitivity of this survey is highest reported, and two, and possibly three, X-ray sources were detected in the vicinity of gamma 195+5. Three new X-ray sources have been discovered within a few degrees of CG176-7, but none overlaps the gamma-ray error box. These results demonstrate that gamma-ray sources like CG195+4 and CG176-7 have emission characteristics different from the Crab pulsar, but may be similar to the Vela pulsar. Alternatively, the lack of detectable X-ray flux suggests that the gamma-ray emission arises from cosmic-ray interactions in dense interstellar clouds. An interesting feature of the new X-ray sources is that four of them may be associated with early-type stars which exhibit emission lines.
    Keywords: SPACE RADIATION
    Type: Nature; 282; Dec. 13
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  • 16
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    Analysis of beam-like lattice trusses (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A simple procedure is presented for predicting the thermoelastic and free vibration responses of large repetitive beam-like trusses. The procedure is based on replacing the original lattice structure by an equivalent continuum beam model and obtaining closed-form (exact) solutions for the beam model. The equivalent beam model accounts for warping and shear deformation in the plane of the cross-section and is characterized by its thermoelastic strain and kinetic energies, from which the equations of motion and constitutive relations can be derived. The high accuracy of the results obtained by the proposed approach is demonstrated by means of numerical examples.
    Keywords: STRUCTURAL MECHANICS
    Type: Computer Methods in Applied Mechanics and Engineering; 20; Oct. 197
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  • 17
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    Some observations regarding the statistical determination of stress rupture regression lines (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations concerning the statistical evaluation of creep data are presented. Methods currently employed in the determination of stress rupture regression lines can result in conflicting and necessarily invalid results. Anomalous behavior is principally associated with the selection of the dependent variable. However, it is the least squares method of curve fitting which introduces regression bias. Methods to improve the validity of least squares regressions are suggested.
    Keywords: STRUCTURAL MECHANICS
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  • 18
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    Buckling of rotating beams (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The stability of a beam subjected to compressive centrifugal forces arising from steady rotation about an axis which does not pass through the clamped end of the beam is analyzed to determine the critical rotational speeds for buckling in the inplane and out-of-plane directions. The differential equations of motion are solved numerically using an integrating matrix method in combination with an eigenanalysis to determine the eigenvalues from which stability is assessed. The results clarify several differences which have been identified in the literature relating to the proper behavior of the critical rotational speed for buckling as the radius of rotation of the clamped end of the beam is reduced.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Mechanical Sciences; 21; 12, 1; 1979
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  • 19
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    Simple spline-function equations for fracture mechanics calculations (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper presents simple spline-function equations for fracture mechanics calculations. A spline function is a sequence of piecewise polynomials of degree n greater than 1 whose coefficients are such that the function and its first n-1 derivatives are continuous. Second-degree spline equations are presented for the compact, three point bend, and crack-line wedge-loaded specimens. Some expressions can be used directly, so that for a cyclic crack propagation test using a compact specimen, the equation given allows the cracklength to be calculated from the slope of the load-displacement curve. For an R-curve test, equations allow the crack length and stress intensity factor to be calculated from the displacement and the displacement ratio.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 15; Oct. 197
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  • 20
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    The mean intensity of radiation at 2 microns in the solar neighborhood (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Consideration is given to the value of the mean intensity at 2 microns in the solar neighborhood, and it is found that it is likely to be a factor of four greater than previously estimated on theoretical grounds. It is noted however, that the estimate does agree with a reasonable extrapolation of the results of the survey of the Galactic plane by the Japanese group. It is concluded that the mean intensity in the solar neighborhood therefore probably peaks somewhat longward of 1 micron, and that this result is important for understanding the temperature of interstellar dust and the intensity of the far infrared background. This means specifically that dark clouds probably emit significantly more far infrared radiation than previously predicted.
    Keywords: SPACE RADIATION
    Type: Astrophysical Letters; 20; 3, 19; 1979
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  • 21
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    A quarter-century of progress in the development of correlation and extrapolation methods for creep rupture data (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Developments in the analysis of creep-rupture data are reviewed with particular reference to time temperature relations for the correlation and extrapolation of creep and stress rupture data, the minimum commitment method, and successive regression methods. Some contributions to the development of time-temperature parameters are noted.
    Keywords: STRUCTURAL MECHANICS
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  • 22
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    Galactic plane gamma-radiation (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Analysis of the SAS 2 data together with the COS B results shows that the distribution of galactic gamma-radiation has several similarities to that of other large-scale tracers of galactic structure. The radiation is primarily confined to a thin disc which exhibits offsets from b = 0 degrees similar to warping at radio frequencies. The principal distinction of the gamma-radiation is a stronger contrast in intensity between the region from 310 to 45 degrees in longitude and the regions away from the center that can be attributed to a variation in cosmic-ray density as a function of position in Galaxy. The diffuse galactic gamma-ray energy spectrum shows no significant variation in direction, and the spectrum seen along the plane is the same as that for the galactic component of the gamma-radiation at high altitudes. The uniformity of the galactic gamma-ray spectrum, the smooth decrease in intensity as a function of altitude, and the absence of any galactic gamma-ray sources at high altitudes indicate a diffuse origin for bulk of the galactic gamma-radiation rather than a collection of localized sources.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 230
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  • 23
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    The annihilation of galactic positrons (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The annihilation of galactic positrons is studied in order to evaluate the probabilities of various channels of annihilation and to calculate the spectrum of the resulting radiation. The narrow width (FWHM less than 3.2 keV) of the 0.511-MeV line observed from the galactic center by Leventhal, McCallum, and Stang (1978) implies that a large fraction of positrons should annihilate in a medium of temperature less than 100,000 K and ionization fraction greater than 0.05. H II regions at the galactic center could be possible sites of annihilation.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 228
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  • 24
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    Wave propagation in transversely impacted composite laminates (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An experimental study was conducted to determine the wave-propagation characteristics, transient strains and residual properties of unidirectional and angle-ply boron/epoxy and graphite/epoxy laminates impacted with silicon-rubber projectiles at velocities up to 250 m/sec. Results include the following: (1) the predominant wave is the flexural wave propagating at different velocities in different directions; (2) peak strains and strain rates in the transverse to the (outer) fiber direction are much higher than those in the direction of the fibers; (3) strain rates up to 640/sec were measured; and (4) unidirectional laminates under impact showed appreciable modulus and strength degradation in the direction transverse to fibers.
    Keywords: STRUCTURAL MECHANICS
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  • 25
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    Analysis of misalignment in the tension test (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Many experimenters fail to appreciate the significance of test system alignment during a tensile test. Poor alignment can increase data scatter and significantly influence some of the test results. In this paper a comprehensive analytical study of the misalignment problem in the plastic strain range is presented and errors caused by misalignment estimated. The results show that the stress-strain curve is not significantly affected by misalignment. However, the strains at the outermost fibers of the specimen cross-section are strongly affected by misalignment. Therefore, the effect of misalignment is most important when properties sensitive to local strain concentrations are being investigated.
    Keywords: STRUCTURAL MECHANICS
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  • 26
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    Charge equilibrium and radiation of low-energy cosmic rays passing through interstellar medium (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, are considered. Electron loss of the beam has been taken into account by means of the first Born approximation, allowing for the target atom to remain unexcited or to be excited to all possible states. Electron-capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms and capture into all excited states of the projectile. The capture and loss cross sections are found to be within 20%-30% of the existing experimental values for most of the cases considered. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation, and collisional inner-shell ionization, taking into account the fluorescence yield of the ions, has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated, and error estimates made for the results.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 229
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  • 27
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    Helios 2-Vela-Ariel 5 gamma-ray burst source position (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The gamma-ray burst of January 28, 1976, one of 18 events thus far detected in interplanetary space with Helios 2, was also observed with the Vela 5A and 6A and the Ariel 5 satellites. A small source field is obtained from the intersection of the region derived from the observed time delays between Helios 2 and Vela 5A and 6A, with the source region independently found with the Ariel 5 X-ray detector. This area contains neither any steady X-ray source as scanned by HEAO 1 nor any previously cataloged X-ray, radio, or infrared sources, X-ray transients, quasars, Seyferts, globular clusters, flare stars, pulsars, white dwarfs, or high enery gamma-ray sources. The region is, however, within the source field of a gamma-ray transient observed in 1974 by Jacobson et al. (1978) which exhibited nuclear gamma-ray line structure.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 229
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  • 28
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    The dynamical halo and the variation of cosmic-ray path length with energy (1979)
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    Publication Date: 2011-08-17
    Description: It is shown that the dynamical halo model offers a natural explanation for the form of the variation of the cosmic-ray path length with energy. The variation above about 1 GeV per nucleon can be understood as due to the variation of the diffusion coefficient, and hence the resident time, with energy. The flattening of the curve below 1 GeV per nucleon is seen to mark a transition to a convection-dominated regime where the diffusion coefficient is no longer the determining parameter. A fit to the observations yields a halo outflow velocity of 8 km/s. An attempt is made to determine the overall scale of the halo and the diffusion coefficient using recent Be-10 flux measurements, but the data do not agree well enough to pin down these variables to within less than four or five orders of magnitude.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 229
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  • 29
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    Non-linear dynamic response of a wind turbine blade (1979)
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    Publication Date: 2011-08-17
    Description: The paper outlines the nonlinear dynamic analysis of an isolated three-degree flap-lag-feather wind turbine blade under a gravity field and with shear flow. Lagrangian equations are used to derive the nonlinear equations of motion of blade for arbitrarily large angular deflections. The limit cycle analysis for forced oscillations and the determination of the principal parametric resonance of the blade due to periodic forces from the gravity field and wind shear are performed using the harmonic balance method. Results are obtained first for a two-degree flap-lag blade, then the effect of the third degree of freedom (feather) is studied. The self-excited flutter solutions are obtained for a uniform wind and with gravity forces neglected. The effects of several parameters on the blade stability are examined, including coning angle, structural damping, Lock number, and feather frequency. The limit cycle flutter solution of a typical configuration shows a substantial nonlinear softening spring behavior.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Sound and Vibration; 63; Mar. 22
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  • 30
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    Recent finite element studies in plasticity and fracture mechanics (1979)
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    Publication Date: 2011-08-17
    Description: The paper reviews recent work on fundamentals of elastic-plastic finite-element analysis and its applications to the mechanics of crack opening and growth in ductile solids. The presentation begins with a precise formulation of incremental equilibrium equations and their finite-element forms in a manner valid for deformations of arbitrary magnitude. Special features of computational procedures are outlined for accuracy in view of the near-incompressibility of elastic-plastic response. Applications to crack mechanics include the analysis of large plastic deformations at a progressively opening crack tip, the determination of J integral values and of limitations to J characterizations of the intensity of the crack tip field, and the determination of crack tip fields in stable crack growth.
    Keywords: STRUCTURAL MECHANICS
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    Stress-intensity factors for a wide range of semi-elliptical surface cracks in finite-thickness plates (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Surface cracks are among the more common flaws in aircraft and pressure vessel components. Several calculations of stress-intensity factors for semi-elliptical surface cracks subjected to tension have appeared in the literature. However, some of these solutions are in disagreement by 50-100%. In this paper, stress-intensity factors for shallow and deep semi-elliptical surface cracks in plates subjected to tension are presented. To verify the accuracy of the three-dimensional finite-element models employed, convergence was studied by varying the number of degrees of freedom in the models from 1500 to 6900. The 6900 degrees of freedom used here were more than twice the number used in previously reported solutions. Also, the stress-intensity variations in the boundary-layer region at the intersection of the crack with the free surface were investigated.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics; 11; 4, 19; 1979
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  • 32
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    Correlated ground based observations in support of the HEAO-1 X-ray observatory (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Using X-ray and optical photometry of UBVRI fluxes, energetic compact extragalactic sources were studied, such as BL Lacerta (Lac) and BL Lac objects-Markarian (Mrk) 421, Mrk 501, and B2 1308+32. BL Lac and BL Lac objects were found to have predominantly nonthermal spectrums. Photometric and spectroscopic properties of X Persei, an unusual Be star associated with an intrinsically weak X-ray source, were also studied. Both its X-ray and optical emission show complex variability on many different time scales.
    Keywords: SPACE RADIATION
    Type: NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 214-222
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  • 33
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    Space Shuttle Orbiter AFT heat shield seal (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The evolution of the orbiter aft heat shield seal (AHSS) design, which involved advancing mechanical seal technology in severe thermal environment is discussed. The baseline design, various improvements for engine access, and technical problem solution are presented. It is a structure and mechanism at the three main propulsion system (MPS) engine interfaces to the aft compartment structure. Access to each MPS engine requires disassembly and removal of the AHSS. Each AHSS accommodates the engine movement, is exposed to an extremely high temperature environment, and is part of the venting control of the aft compartment.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 251-259
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  • 34
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    Hydrazine monopropellant reciprocating engine development (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A hydrazine fueled piston engine for providing 11.2 kW was developed to satisfy the need for an efficient power supply in the range from 3.7 to 74.6 kW where existing nonair-breathing power supplies such as fuel cells or turbines are inappropriate. The engine was developed for an aircraft to fly to 21.3 km and above and cruise for extended periods. A remotely piloted aircraft and the associated flight control techniques for this application were designed. The engine is geared down internally (2:1) to accommodate a 1.8 m diameter propeller. An alternator is included to provide electrical power. The pusher-type engine is mounted onto the aft closure of the fuel tank, which also provides mounting for all other propulsion equipment. About 20 hrs of run time demonstrated good efficiency and adequate life. One flight test to 6.1 km was made using the engine with a small fixed-pitch four-bladed propeller. The test was successful in demonstrating operational characteristics and future potential.
    Keywords: STRUCTURAL MECHANICS
    Type: The 13th Aerospace Mech. Symp.; p 1-14
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  • 35
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    Summary of the Orbiter mechanical systems (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Major mechanical systems of the Orbiter space vehicle are summarized with respect to general design details, manner of operation, expected performance, and, where applicable, unique features. A synopsis of data obtained during the five atmospheric flight tests of spacecraft OV-101 and status of the systems for the first orbital spacecraft STS-1 are presented.
    Keywords: STRUCTURAL MECHANICS
    Type: The 13th Aerospace Mech. Symp.; p 219-234
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  • 36
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    Optical identification and spectroscopy of X-ray sources precisely positioned with A-3 (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Using a scanning modulation collimator, the optical identification of X-ray sources by means of precise positioning was carried out. Two galactic identifications (4U2129+47 and 2A0311-227) and two extragalactic identifications (NGC 526a and Parkes H2155-304) are described.
    Keywords: SPACE RADIATION
    Type: NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 251-260
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  • 37
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    Diffuse X-ray emission from Abell clusters (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Abell clusters of galaxies, specifically Abell 401 and Abell 399 regions, are discussed. Two sets of satellite observations were made. One was a lunar occultation pointed observation where there were two orbits in which to look at the regions while the moon scanned over it. The other was a scanning observation through the area. Two diffuse models of the X-ray emission were developed. Also, during the investigation three binary cluster systems were found where at least one member was an X-ray source. They were Abell 508, 509, 2177, 2178, 2204, and 2210.
    Keywords: SPACE RADIATION
    Type: NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 209-213
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  • 38
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    X-ray emission from the region of gamma 195+5 (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: X-ray observations of nineteen unidentified discrete celestial gamma ray sources are discussed. Results show some indication of X-rays from the gamma ray source region. On the assumption that the results are valid, it is concluded that the source error box is smaller than what it was.
    Keywords: SPACE RADIATION
    Type: NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 201-208
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  • 39
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    Helical grip for the cable cars of San Francisco (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A helical cable car grip to minimize high maintenance costs of San Francisco's cable car operation is presented. The grip establishes a rolling contact between the cable and grip to reduce sliding friction and associated cable wear. The design, development, and testing of the helical cable car grip are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 83-93
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  • 40
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    Space Shuttle Orbiter payload bay door mechanisms (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The opening, closing, and latching of the first large clamshell door to operate in space presented some unusual challenges for the mechanism designer of the Space Shuttle Program. The requirements, hardware configuration, design trade-offs, and qualification testing in process to meet the challenge and to make the system operational for the Shuttle orbiter's approaching first orbital flight are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 261-269
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  • 41
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    Tests of a protective shell passive release mechanism for hypersonic wind-tunnel models (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A protective shell mechanism for wind tunnel models was developed and tested. The mechanism is passive in operation, reliable, and imposes no new structural design changes for wind tunnel models. Methods of predicting the release time and the measured loads associated with the release of the shell are given. The mechanism was tested in a series of wind tunnel tests to validate the removal process and measure the pressure loads on the model. The protective shell can be used for wind tunnel models that require a step input of heating and loading such as a thin skin heat transfer model. The mechanism may have other potential applications.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 167-181
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  • 42
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    Reliability breakthrough: An antenna deployment/positioning mechanism with electrical and mechanical redundancy (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An Antenna Positioner Mechanism (APM) was developed for deployment of an antenna reflector and for fine granularity closed loop tracking of the antenna in response to RF beacon error signals. By utilizing permanent magnet stepper motors, spur gearheads, irreversible single threat worm/wheel assemblies and a miter gear differential, full electrical and mechanical redundancy was realized. Two versions of this design were generated: one is a weight-optimized design with a clutch for overload protection and one is a more rugged unit without a clutch.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 137-149
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  • 43
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    Load proportional safety brake (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: This brake is a self-energizing mechanical friction brake and is intended for use in a rotary drive system. It incorporates a torque sensor which cuts power to the power unit on any overload condition. The brake is capable of driving against an opposing load or driving, paying-out, an aiding load in either direction of rotation. The brake also acts as a no-back device when torque is applied to the output shaft. The advantages of using this type of device are: (1) low frictional drag when driving; (2) smooth paying-out of an aiding load with no runaway danger; (3) energy absorption proportional to load; (4) no-back activates within a few degrees of output shaft rotation and resets automatically; and (5) built-in overload protection.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 95-110
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  • 44
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    A two-axis pointing system for an orbiting astronomical instrument (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The system described was built for incorporation into a solar flare X-ray instrument due to be orbited as one of a number of instruments on the NASA Solar Maximum Mission (SMM) satellite in late 1979. It enables the instrument to be rotated about 2 mutually perpendicular axes in 5 arc-second steps within a range of 7 arc-minutes, thus giving the instrument the capability to map areas of the sun.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 27-38
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  • 45
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    Automatic in-orbit assembly of large space structures (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The automated assembly of a large number of components required for the on-orbit erection of large tetrahedral space platforms is described. The assembly machine is a huge jig in which a multitude of mechanisms must operated continuously in the thermo vacuum environment of space and under the control of computers programmed to command every step of each motion. The concepts are presented to determine the most reliable solution. Continuous operation of mechanisms in space presents many unresolved problems, with regard to lubrication of unprotected devices, such as chain drives, which must maintain reasonable positioning tolerances.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 283-291
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  • 46
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    IUSThrust Vector Control (TVC) servo system (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The IUS TVC SERVO SYSTEM which consists of four electrically redundant electromechanical actuators, four potentiometer assemblies, and two controllers to provide movable nozzle control on both IUS solid rocket motors is developed. An overview of the more severe IUS TVC servo system design requirements, the system and component designs, and test data acquired on a preliminary development unit is presented. Attention is focused on the unique methods of sensing movable nozzle position and providing for redundant position locks.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 271-281
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  • 47
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    Payload installation and deployment aid for Space Shuttle Orbiter spacecraft remote manipulator system (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An aid concept known as the PIDA (Payload Installation and Deployment Aid) is presented as a way to assist the RMS (Remote Manipulator System) by relaxing the accuracy required during payload handling in the payload bay. The aid concept was designed and developed to move payloads through a prescribed path between the confined quarters of the payload bay and a position outside the critical maneuvering area of the Orbiter. A description of the design requirements and the modes of operation of the various functions of the deployment and the docking mechanisms are covered.
    Keywords: STRUCTURAL MECHANICS
    Type: The 13th Aerospace Mech. Symp.; p 235-249
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  • 48
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    Magnetic spring in oscillating mirror linear scanner for satellite camera (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: One of the main difficulties encountered in the development of a multispectral scanner is the realization of an oscillating mechanical device. A magnetic device which is characterized by the absence of friction is presented. The main developments concern the analysis of magnetic forces. A preliminary project of a device which could be used in a satellite is presented.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 183-193
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  • 49
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    Einstein observations of extended galactic X-ray sources (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Features of the X-ray pictures taken aboard the space observatory are presented. Imaging proportional counter pictures in three broad X-ray energy ranges were obtained. The X-ray spectrum of supernova remnants is described.
    Keywords: SPACE RADIATION
    Type: NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 368-389
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  • 50
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    X-ray iron-line emission from the SN 185 remnant (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Radio and optical research was carried out in order to show that the supernova remnant RCW86 is a remnant of the earliest supernova event ever recorded in history (185 AD). The results are as follows: (1) an iron-line emission was found at 6.7 keV; (2) the temperature measured from HEAO-1 was approximately 6 keV; and (3) the equivalent width was consistent within the uncertainties with a cosmic iron abundance. These results support the identification of the supernova remnant RCW86 (it's X-ray source) with the historic supernova event.
    Keywords: SPACE RADIATION
    Type: NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 244-250
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  • 51
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    Unfolding the air vanes on a supersonic air-launched missile (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: ASALM (Advanced Strategic Air-Launched Missile) is a supersonic air vehicle designed to be air-launched from a carrier aircraft. The four aft aerodynamic control vanes are folded to maximize the number of missiles carried on-board. The unfolding (erection) system must be small, energetic, fast, and strong. The materials selected and problems that arose during development of the unfolding system are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 207-217
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  • 52
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    On the design of an adjustable high precision latching hinge (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The design and test details of a high precision hinge and locking mechanism created principally in support of the Lockheed space deployable Flexrib Parabolic Antenna concept are presented. These developed improvements in the detail design of ultra-precise rib hinge and contour adjustment mechanisms will allow radio frequency antenna reflectors to expand into the 15-50 meter diameter size class and to support the .013 mm. deployment repeatability tolerance required to support the 12+ GHz frequency range.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 127-136
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  • 53
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    A telescopic jib for continuous adjustment (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: For special space applications, e.g. for experiments distant from any orbital platforms or manipulators a new kind of jibs with extreme extension capacity has to be designed. Considering the requirements, the telescopic principle is found to be the most promising. For the choice of the stiff structure, design criteria are evaluated. Special effort deals with the drive system. An electromechanical system can satisfy the requirements. First results of the development of such a drive are presented. The most significant features are: A telescopic assembly of tubes which can be mutually moved by a short spindle in the center of the package. An elastically suspended screw is located at the bottom of each tube. For the jib extension, these screws will be linked with the spindle. The control of their sequence and the adjustment of tubes in mutual end positions are performed by latches. A functional model proved the basic idea.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 49-58
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    Development of the Trident 1 aerodynamic saike mechanism (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Aerospike drag reduction mechanism was designed and developed for use on the Trident I submarine launched ballistic missile. This mechanism encounters a unique combination of environments necessitating unique design solutions to ensure satisfactory operation over its design life. The development of the Aerospike is reviewed emphasizing the unique and interesting problems encountered and their solutions.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 39-48
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    Gimbal bearing design considerations and friction control (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The design considerations of bearing selection, bearing fits, bearing installation, and thermal control are discussed for a gimbal with a high stiffness, low friction torque requirement. Tradeoffs between a quad set of small diameter spread apart or a large diameter bearing pair resulted in a cleaner, lighter, stiffer unit with the latter selection. Bearing fits were designed to eliminate clearances with tolerances of .00127 mm 00005 in) on the bearing shafts and housings. The problems in metrology are discussed and a perferred technique for measurement of small cross-section bearings described. A technique for installation to assure proper seating of the bearing is offered. Where transient thermal conditions are involved, a method of controlling bearing friction by active control of bearing temperature gradients including the use of bearing unload test curves is described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 71-81
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  • 56
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    Development of a beam builder for automatic fabrication of large composite space structures (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The composite material beam builder which will produce triangular beams from pre-consolidated graphite/glass/thermoplastic composite material through automated mechanical processes is presented, side member storage, feed and positioning, ultrasonic welding, and beam cutoff are formed. Each process lends itself to modular subsystem development. Initial development is concentrated on the key processes for roll forming and ultrasonic welding composite thermoplastic materials. The construction and test of an experimental roll forming machine and ultrasonic welding process control techniques are described.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 293-304
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  • 57
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    The impact of rare earth cobalt permanent magnets on electromechanical device design (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Specific motor designs which employ rare earth cobalt magnets are discussed with special emphasis on their unique properties and magnetic field geometry. In addition to performance improvements and power savings, high reliability devices are attainable. Both the mechanism and systems engineering should be aware of the new performance levels which are currently becoming available as a result of the rare earth cobalt magnets.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 195-206
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  • 58
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    Development of drive mechanisms for communicaton satellites (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A distinguished pedigree is an important asset in the development of Aerospace mechanisms. Four drives recently developed for communication satellites are outgrowths of a previously-proven drive configuration. Pedigree by itself, however is not enough to generate success. Inevitably, design changes which are thought to be minor, are generally introduced to fine tune the pedigreed hardware to meet particular requirements of a specific new application. Such design changes are often viewed too casually and are not thoroughly tested in the early development stages of the program. Two areas of design change are described on the solar array drive applied to the Japanese Broadcast Satellite which led to subsequent problems during the development phase of the program. The methods applied to establish the cause and the solution of these problems are described as well as the testing approach adapted to prevent similar occurrences on the current Communication Satellite Program, The Defense System Communications Satellite III.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 151-166
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  • 59
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    Design of a piezoelectric shaker for centrifuge testing (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The design of a prototype piezoelectric shaker and its development to date is described. Although certain design problems remain to be solved, the piezoelectric system shows promise for adaptation to a larger payload system, such as the proposed geotechnical centrifuge at the Ames Research Center.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 59-70
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  • 60
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    Design and development of a motion compensator for the RSRA main rotor control (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The RSRA, an experimental helicopter, is equipped with an active isolation system that allows the transmission to move relative to the fuselage. The purpose of the motion compensator is to prevent these motions from introducing unwanted signals to the main rotor control. A motion compensator concept was developed that has six-degree-of-freedom capability. The mechanism was implemented on RSRA and its performance verified by ground and flight tests.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Johnson Space Center The 13th Aerospace Mech. Symp.; p 15-25
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  • 61
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    Computer-aided fracture mechanics life prediction analysis (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The fracture mechanics analysis and computer logic used to perform design life predictions is described. Initial part-through crack defects are analyzed under the conditions of constant-amplitude loading to predict the number of loading cycles applied before breakthrough or failure. A criterion is provided to predict the transition from part-through crack growth characteristics to through crack growth characteristics. A breakthrough criterion is also provided.
    Keywords: STRUCTURAL MECHANICS
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  • 62
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    Effects of particle drift on the transport of cosmic rays. III - Numerical models of galactic cosmic-ray modulation (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 234
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  • 63
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    Note on the effect of transverse shear deformation in laminated anisotropic plates (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper describes the development of some computer methods in applied mechanics. It begins with a distribution of primary stresses in laminated plates, followed by a determination of the associated statically consistent transverse shearing stress. The last section deals with the use of an energy principle for the utilization of these expressions for primary and transverse stresses. The purpose of this is to obtain two-dimensional constitutive equations involving transverse shear deformations and transverse shear stress resultants.
    Keywords: STRUCTURAL MECHANICS
    Type: AD-A098868 , Computer Methods in Applied Mechanics and Engineering; 20; Nov. 197
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  • 64
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    Optimum design of laminated plates under shear (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: This paper is concerned with the optimum design of plates with orthotropic layers under shear. The plates considered are the laminates of N orthotropic layers whose principal material axes coincide with the plate axes. Each layer is assumed to have the same thickness and an equal number of fibers in the direction of + alpha sub i and - alpha sub i with respect to the plate axis. The fiber directions which give the highest shear buckling stress are found by utilizing a mathematical optimization technique.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composite Materials; 13; Oct. 197
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  • 65
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    Southern Hemisphere measurements of the anisotropy in the cosmic microwave background radiation (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A recent airborne measurement of the large-angular-scale anisotropy in the cosmic background radiation from the Southern Hemisphere (Lima, Peru) is in essential agreement with previous measurements from the northern hemisphere. The net anisotropy from the combined data can be described by a first-order spherical harmonic (Doppler) anisotropy of amplitude 3.1 plus or minus 0.4 mK with a quadrupole component of less than 1 mK. Additional ground-based measurements of the linear polarization yield an upper limit of l mK, or one part in 3000, at 95% confidence level for the amplitudes of any spherical harmonic through third order.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 234
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  • 66
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    Detection of 6.13 MeV gamma-rays within and at the top of the atmosphere (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A measurement of the 6.13 MeV gamma-radiation from excited O-16 in the atmosphere has been made with a high-resolution Ge(Li) spectrometer flown from Palestine, Texas, 1974 June 10, on a high-altitude balloon. This measurement, made both within and near the top of the atmosphere, is found to have the same general profile as predicted by a semiempirical model, but gives a flux about a factor of 2 higher than predicted. Certain variations in the intensity at float altitude have led to the hypothesis of an extraterrestrial source of 6.13 MeV gamma-radiation from the galactic anticenter. The 3 sigma upper limits for a number of other astrophysically significant line fluxes are also given. The data presented here are consistent with either a source or a no-source hypothesis.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 234
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  • 67
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    Gradient and curvature drifts in magnetic fields with arbitrary spatial variation (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: It is shown that, for a magnetic field of arbitrary spatial variation, a nearly isotropic distribution of charged particles drifts with a velocity given by the usual first-order orbit theory drifts averaged over pitch angle. It is assumed that the near-isotropy brought about by scattering, but conclusions concerning drift are insensitive to the details of the scattering process. It is found that this drift velocity is correct even for arbitrarily large ratios of particle gyroradius to magnetic spatial scale, although this velocity must, like all drift effects, be viewed on a scale larger than a gyroradius. Hence for many astrophysical applications, such as cosmic rays, where anisotropies are small, the usual drift velocities provide a valid approximation to convective motions even if the magnetic field scales are very small.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 234
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  • 68
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    Far-ultraviolet studies. V - Rocket observation of the diffuse cosmic background (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A far-ultraviolet spectrometer and several far-ultraviolet photometers have been carried to an altitude of 347 km to measure the spectrum of three regions at high galactic latitudes. After correction for O I airglow and for stars in the field of view, a nearly uniform residual intensity of 285 plus or minus 32 photons per (sq cm s sr A) is found over the spectral range 1230-1680 A, along with some evidence for a sharp rise in intensity longward of 1680 A. It is argued that the signal is not likely to be due to light scattering from interstellar dust. The flat spectrum could represent the integrated light of distance galaxies. The sharp rise must be due to some other phenomenon.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 234
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  • 69
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    Joule heating in the high-latitude mesosphere (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The contribution made by Joule dissipation to heating of the daytime high-latitude upper mesosphere is discussed. During solar proton precipitation events in regions of large electric fields, Joule dissipation can be substantially larger than the local solar heating rate. Altitude profiles of Joule dissipation are presented for the polar cleft region for the August 4, 1972, solar proton event.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 84; Nov. 1
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  • 70
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    A theory of local and global processes which affect solar wind electrons. II - Experimental support (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Strong observational support from data obtained on three different satellites and reported by three independent experimental groups is presented for all of the theoretically predicted correlations of a previous paper concerning local and global processes that affect solar-wind electrons. Specifically, it is shown that: (1) subthermal electrons behave most nearly as a classical gas; (2) the solar-wind extrathermal fraction of the electron density is anticorrelated within steady-state stream patterns with the local bulk speed; (3) the extrathermal electrons form a spectrally distinguishable subpopulation whose differential 'temperature' is anticorrelated with the local bulk speed; (4) the heat flux carried by electrons is anticorrelated with the bulk speed; and (5) the extrathermal 'temperature' is nearly independent of radius in the inner heliosphere. It is concluded that the previously discussed global and local Coulomb collisional effects are essential aspects of the solar-wind plasma as it is observed.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 84; Nov. 1
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  • 71
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    An energetic particle perspective of the magnetopause (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The present analysis deals with energetic (above 24 keV) particle data from the Isee satellites during a series of magnetopause crossings. The primary energetic particle data employed in the analysis are the three-dimensional distributions from the Isee A satellite. Correlative magnetic field measurements are used to relate the particle behavior to magnetic field characteristics at and earthward of the magnetopause. It is shown that, to first order, the magnetopause may be regarded as a perfectly absorbing boundary for the trapped energetic particles, that it is nearly always in motion, and that boundary waves are often present. The observed dayside magnetopause motion is consistent with a large-scale radial motion having an approximately 10-min period plus superimposed boundary waves with a 90- to 150-sec period.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 84; Nov. 1
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  • 72
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    Effect of transverse shear and material orthotropy in a cracked spherical cap (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The elastostatic problem for a relatively thin-walled spherical cap containing a through crack is considered. The problem is formulated for a specially orthotropic material within the confines of a linearized, shallow shell theory. The theory used is equivalent to Reissner's theory of flat plates and hence permits the consideration of all five physical conditions on the shell boundaries separately. The solution of the problem is reduced to that of a pair of singular integral equations and the asymptotic stress state around the crack tips is investigated. The numerical solution of the problem is given for an isotropic shell and for two specially orthotropic shells. The results indicate that the material orthotropy as well as the shell curvature and thickness may have a considerable effect on the stress intensity factors at the crack tips.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Solids and Structures; 15; 12, 1; 1979
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  • 73
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    The effect of transverse shear in a cracked plate under skew-symmetric loading (1979)
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    Publication Date: 2019-06-27
    Description: The problem of an elastic plate containing a through crack and subjected to twisting moments or transverse shear loads is considered. By using a bending theory which allows the satisfaction of the boundary conditions on the crack surface regarding the normal and the twisting moments and the transverse shear load separately, it is found that the resulting asymptotic stress field around the crack tip becomes identical to that given by the elasticity solutions of the plane strain and antiplane shear problems. The problem is solved for uniformly distributed or concentrated twisting moment or transverse shear load and the normalized Mode II and Mode III stress-intensity factors are tabulated. The results also include the effect of the Poisson's ratio and material orthotropy for specially orthotropic materials on the stress-intensity factors.
    Keywords: STRUCTURAL MECHANICS
    Type: ASME PAPER 79-WA/APM-16
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  • 74
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    The role of crack blunting in sustained load crack growth (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Sustained load crack growth occurs in metals following critical crack extension above KIc and in aggressive environments while maintaining a constant load below KIc. In this paper, crack arrest measurements are performed on precracked, 0.0254-m thick, side-grooved WOL specimens exposed to 34.5 MN/sq m hydrogen at ambient temperature. The specimens are loaded inside a pressure vessel while in contact with the high pressure hydrogen environment. Crack growth is observed with each loading increment. The crack blunting observed in the fracture mechanics tests on 321 stainless steel is found to be similar to that produced in the 321 stainless steel tensile specimens. Rounding and branching of the crack decreases the effective stress intensity at the crack tip. It is possible, for materials in which cracks tend to blunt or branch in hydrogen, that although cracks will arrest at a relatively high stress intensity in decreasing stress intensity test, a crack may begin to grow at a lower stress intensity when loaded in hydrogen, and the crack may continue to grow when the stress intensity is continually increasing.
    Keywords: STRUCTURAL MECHANICS
    Type: Scripta Metallurgica; 13; Oct. 197
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  • 75
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    The spectrum of the diffuse cosmic ultraviolet background (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A far-ultraviolet spectrometer and several far-ultraviolet photometers were carried to an altitude of 347 km and used to measure the spectrum of three regions at high galactic latitudes. After correction for O I airglow and for stars in the field of view, a nearly uniform residual intensity of 285 + or - 32 photons (per sq cm s sr A) over the spectral range 1230-1680 A is found, along with some evidence for a sharp rise in intensity longward of 1680 A. It is believed that the signal is not likely to be due to light scattering from interstellar dust. The flat spectrum is perhaps the integrated light of distant galaxies. The sharp rise must be due to some other phenomenon.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 233
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  • 76
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    Data reduction and analysis for the TRW IMP-7 plasma wave experiment (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Highlights from the IMP 7 plasma wave experiment are briefly outlined. The measurements in the tail revealed great complexities involving substorms and fireballs and provided insight into the overall dynamics of the magnetosphere. The low levels of magnetic turbulence may be of significance with respect to the development of tearing mode dissipation for reconnection events. The IMP wave observations in the distant magnetosphere boundary region showed that the boundaries were quite diffuse and frequently purely defined. Finally, nearly simultaneous IMP 7 and 8 comparisons were used to achieve an understanding of shock structure and propagation.
    Keywords: SPACE RADIATION
    Type: NASA-CR-160011 , REPT-22751-6011-RU-00
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  • 77
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    Finite-strain large-deflection elastic-viscoplastic finite-element transient response analysis of structures (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A method of analysis for thin structures that incorporates finite strain, elastic-plastic, strain hardening, time dependent material behavior implemented with respect to a fixed configuration and is consistently valid for finite strains and finite rotations is developed. The theory is formulated systematically in a body fixed system of convected coordinates with materially embedded vectors that deform in common with continuum. Tensors are considered as linear vector functions and use is made of the dyadic representation. The kinematics of a deformable continuum is treated in detail, carefully defining precisely all quantities necessary for the analysis. The finite strain theory developed gives much better predictions and agreement with experiment than does the traditional small strain theory, and at practically no additional cost. This represents a very significant advance in the capability for the reliable prediction of nonlinear transient structural responses, including the reliable prediction of strains large enough to produce ductile metal rupture.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159874 , ASRL-TR-154-15
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  • 78
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    X-ray measurements of stresses and defects in EFG and large grained polycrystalline silicon ribbons (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The Bond method was employed to measure the lattice parameter in an area of 0.4 mm in diameter of EFG Si-ribbons to an accuracy of + or - 0.00008 A. A Bond goniometer was built which included a goniostat with a special specimen holder to mount ribbons 1 m in length and 75 mm in width which could be rotated about two orthogonal axes, and a Leitz microscope for precision alignment of a particular area into the center of the goniostat and the small primary X-ray beam. The (321) planes were found to be parallel to the surface of the ribbons with an angular spread of about 15 deg. The poles of the (111) planes clustered about an angle of 25 deg away from the surface normal, again with a spread of 10 deg. The lattice parameter of a small piece of ribbon material was found to be a sub o = 5.43075 A. A maximum stress of 115 MPa was observed in a fractured ribbon which corresponded to the fracture stress of single crystals of Si.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-162629 , JPL-9950-315 , DOE/JPL-954851-79/2
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  • 79
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    The Unique Cosmic Event of 1979 March 5 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A transient that appears to be neither a typical gamma ray burst nor an X-ray burster was found to possess a variety of unusual properties that would seem to be mutually inconsistent. The observed parameters include a 200 microsecond onset time, a subsequent temporal intensity oscillation with an 0 second period, a spectral feature consistent with a moderately red shifted positron annihilation line, a maximum photon flux greater than any known gamma ray or x ray transient, and a very accurate source location measurement consistent with that of the N49 supernova remnant associated with the large Magellanic Cloud at 55 kpc distance.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80630
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  • 80
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    Columbia/Einstein observations of extragalactic X-ray sources (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results are presented of the analysis of data from observations of extragalactic objects with the imaging proportional counter on board the Einstein Observatory. Surveys of normal galaxies, radio galaxies, active galaxies, quasars and BL Lacs, and clusters of galaxies were studied in order to improve the understanding of the origin of the Milky Way Galaxy.
    Keywords: SPACE RADIATION
    Type: CONTRIB-180 , NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 439-459
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  • 81
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    A measurement of the cosmic-ray source abundance of Ca-40 (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The measured charge composition of the galactic cosmic rays from Ar to Ni and the isotopic composition of the elements Ca and Sc are presented. It is found that the ratio Ca-40/Fe at the cosmic-ray source is (5.9 plus or minus 1.9)%. This result is in good agreement with the meteoritic value (6.8 plus or minus 1.0)%.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 232
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  • 82
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    Acceleration of energetic protons by interplanetary shocks (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The University of Iowa instrument aboard Pioneer 11 detected 69 energetic proton events (EPE) (in the 0.6-3.4 MeV energy range) during 1973-1974 in the heliocentric radial range 1-5 AU. Sixty percent of the EPE peak within plus or minus 5 hours of a corotating interaction region (CIR) boundary, while 19% peak inside and 21% peak outside the interaction regions. Of the CIR boundaries at which an EPE peaks with plus or minus 5 hours, 80% have associated shocks. The observed intensities and pitch angle distributions of protons near shock fronts are consistent with a theoretical simulation of the acceleration of protons by a drift in the electric field at the shock front.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 84; Dec. 1
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  • 83
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    Transverse shear effect in a circumferentially cracked cylindrical shell (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The objectives of the paper are to solve the problem of a circumferentially-cracked cylindrical shell by taking into account the effect of transverse shear, and to obtain the stress intensity factors for the bending moment as well as the membrane force as the external load. The formulation of the problem is given for a specially orthotropic material within the framework of a linearized shallow shell theory. The particular theory used permits the consideration of all five boundary conditions as to moment and stress resultants on the crack surface. The effect of Poisson's ratio on the stress intensity factors and the nature of the out-of-plane displacement along the edges of the crack, i.e., bulging, are also studied.
    Keywords: STRUCTURAL MECHANICS
    Type: Quarterly of Applied Mathematics; 37; Oct. 197
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  • 84
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    Instructions for the use of the CIVM-Jet 4C finite-strain computer code to calculate the transient structural responses of partial and/or complete arbitrarily-curved rings subjected to fragment impact (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The CIVM-JET 4C computer program for the 'finite strain' analysis of 2 d transient structural responses of complete or partial rings and beams subjected to fragment impact stored on tape as a series of individual files. Which subroutines are found in these files are described in detail. All references to the CIVM-JET 4C program are made assuming that the user has a copy of NASA CR-134907 (ASRL TR 154-9) which serves as a user's guide to (1) the CIVM-JET 4B computer code and (2) the CIVM-JET 4C computer code 'with the use of the modified input instructions' attached hereto.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-159873 , ASTL-MR-154-1
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  • 85
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    Spacecraft damping considerations in structural design (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The role of damping in the prediction of spacecraft structural responses and loads, and in the structural design of spacecrafts is discussed. The methods used to incorporate damping in the structural analysis are summarized and some experiences and procedures relating to damping in recent spacecraft design are discussed. Methods for modal testing and the experimental determination of damping, the use of discrete dampers, and the estimation of payload response are studied. A collection of damping data for recent spacecraft and related hardware is provided in the appendix.
    Keywords: STRUCTURAL MECHANICS
    Type: AGARD Damping Effects in Aerospace Struct.; 18 p
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  • 86
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    Aeroelastic equations of motion of a Darrieus vertical-axis wind-turbine blade (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The second-degree nonlinear aeroelastic equations of motion for a slender, flexible, nonuniform, Darrieus vertical-axis wind turbine blade which is undergoing combined flatwise bending, edgewise bending, torsion, and extension are developed using Hamilton's principle. The blade aerodynamic loading is obtained from strip theory based on a quasi-steady approximation of two-dimensional incompressible unsteady airfoil theory. The derivation of the equations has its basis in the geometric nonlinear theory of elasticity and the resulting equations are consistent with the small deformation approximation in which the elongations and shears are negligible compared to unity. These equations are suitable for studying vibrations, static and dynamic aeroelastic instabilities, and dynamic response. Several possible methods of solution of the equations, which have periodic coefficients, are discussed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-79295 , DOE/NASA/1028-79/25 , E-238
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  • 87
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    Satellite Observations of Rapidly Varying Cosmic X-ray Sources (1979)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The X-ray source data obtained with the high energy celestial X-ray detector on the Orbiting Solar Observatory -8 are presented. The results from the 1977 Crab observation show nonstatistical fluctuations in the pulsed emission and in the structure of the integrated pulse profile which cannot be attributed to any known systematic effect. The Hercules observations presented here provide information on three different aspects of the pulsed X-ray emission: the variation of pulsed flux as a function of the time from the beginning of the ON-state, the variation of pulsed flux as a function of binary phase, and the energy spectrum of the pulse emission.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80285
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  • 88
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    The High Energy X-ray Spectrum of 4U1700-37 Observed from OSO-8 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The most intense hard X-ray source in the confused region in Scorpius is identified as 4U1700-37. The 3.4-day modulation is seen above 20 keV with the intensity during eclipse being consistent with zero flux. The photon-number spectrum from 20 to 150 keV is well represented by a single power law with a photo-number spectral index of -2.77 + or - 0.35 or by a thermal bremsstrahlung spectrum with kT = 27 96.8-min X-ray modulation previously reported at lower energies. Despite the difficulties in reconciling both the lack of periodic modulation in the emitted X-radiation and the orbital dynamics of the system with theories of the evolution and physical properties of neutron stars, the observed properties of 4U1700-37 are all consistent with the source being a spherically accreting neutron star rather than a black hole.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80583
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  • 89
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    Energy Spectra of Cosmic Ray Nuclei to Above 100 Gev/nucleon (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The chemical composition cosmic rays as a function of energy in the range of a few GeV/nucleon to some hundreds of GeV/nucleon for boron through iron are presented. The experiment combined an ionization spectrometer and a gas Cherenkov counter, which was flown on a balloon, to perform two different and independent energy measurements. The experimental apparatus is described in detail. The energy dependence of the cosmic ray escape length for boron and iron is reported and predicted changes in the energy dependence of the ratios of primary nuclei 0/C and iron/C+0 are discussed.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80587
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  • 90
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    On the use of coherence functions to evaluate sources of dynamic excitation (1979)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The use of coherence functions for identifying the relative contributions of multiple dynamic inputs to the measured vibration response of spacecraft components on a practical, complex structure was investigated. Data were generated by applying simultaneous vibratory and acoustic excitation to a test model (a modified Titan instrumentation truss). Up to three inputs were used. In some cases mutually coherent inputs were generated. A digital computer program was written to analyze the test data, using an approach based on iterative computational algorithms. The results showed that the coherence function technique was effective in identifying and evaluating sources of excitation, for both independent and coherent inputs. The effect of varying the number of data samples used in the necessary averaging process was briefly investigated.
    Keywords: STRUCTURAL MECHANICS
    Type: Shock and Vibration Inform. Center The Shock and Vibration Bull., Pt. 1; p 43-58
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  • 91
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    Columbia/Einstein observations of galactic X-ray sources (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The imaging observations of galactic clusters are presented. These fall into three categories: pre-main-sequence stars in the Orion nebulae, isolated-main-and-post main-sequence stars, and supernova remnants SNR. In addition to SNR, approximately 30 sources were detected.
    Keywords: SPACE RADIATION
    Type: CONTRIB-179 , NASA. Marshall Space Flight Center HEAO Sci. Symp.; p 422-438
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  • 92
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    A cracked beam or plate transversely loaded by a stamp (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: In this paper the problem of an infinite elastic beam or a plate containing a crack is considered. The medium is loaded transversely through a stamp which may be rigid or elastic. The problem is a coupled crack-contact problem which cannot be solved by treating the crack and contact problems separately and by using a superposition technique. First the Green's functions for the general case are obtained. Then the integral equations for a cracked infinite strip loaded by a frictionless stamp are obtained. With the question of fracture in mind, the primary interest in the paper has been in calculating the stress intensity factors. The results are given for a rigid flat stamp with sharp edges and for an elastic curved stamp. The effect of friction at the supports on the stress intensity factors is also studied and a numerical example is given.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Solids and Structures; 15; 12, 1; 1979
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  • 93
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    Astrophysical gamma-ray production by inverse Compton interactions of relativistic electrons (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The inverse Compton scattering of background photon gases by relativistic electrons is a good candidate for the production of high-energy gamma rays in the diffuse interstellar medium as well as in discrete sources. By discussing the special case of the scattering of the diffuse starlight in the interstellar medium by cosmic ray electrons, we demonstrate that previous derivations of the gamma ray source function for this process on the basis of the Thomson limit of the Klein-Nishina cross section lead to incorrect values for gamma-ray energies above 100 MeV. It is shown that the Thomson limit is not applicable for the calculation of gamma-ray source functions in astrophysical circumstances in which target photons with energies greater than 1 eV are scattered by relativistic electrons.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 233
    Format: text
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  • 94
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    Strain measurements in composite bolted-joint specimens (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Strain data from a series of bolted joint tests is presented. Double lap, double hole, double lap, single hole, and open hole tensile specimens were tested and the strain gage locations, load strain responses, and load axial displacement responses are presented. The open hole specimens were gaged to determine strain concentration factors. The double lap, double hole specimens were gaged to determine the uniformity of the strain in the joint and the amount of load transferred past the first bolt. The measurements indicated roughly half the load passed the first bolt to be reacted by the second bolt.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-163296 , VPI-E-79-17
    Format: application/pdf
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  • 95
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    High resolution spectroscopy of two gamma-ray bursts in November 1978 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The first results from the ISSEE-3 radiatively colled germanium gamma ray burst spectrometer are presented. Spectra and time histories from two events on the 1978 November 4 and 1978 November 19 are given. A significant difference in the continuum spectra for the two events was observed. Evidence is presented for two spectral features in the features in the November 19 events, a broad one at approximately 420 key KeV and a narrower one at 740 KeV with a suggestion of an accompanying high energy tail.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80575
    Format: application/pdf
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  • 96
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    Stress-intensity factors and crack-opening displacements for round compact specimens (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A two dimensional, boundary collocation stress analysis was used to analyze various round compact specimens. The influence of the round external boundary and of pin-loaded holes on stress intensity factors and crack opening displacements was determined as a function of crack-length-to-specimen-width ratios. A wide-range equation for the stress intensity factors was developed. Equations for crack-surface displacements and load-point displacements were also developed. In addition, stress intensity factors were calculated from compliance methods to demonstrate that load-displacement records must be made at the loading points and not along the crack line for crack-length-to-specimen-width ratios less than about 0.4.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-80174
    Format: application/pdf
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  • 97
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    Comparison tests and experimental compliance calibration of the proposed standard round compact plane strain fracture toughness specimen (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Standard round specimen fracture test results compared satisfactorily with results from standard rectangular compact specimens machined from the same material. The location of the loading pin holes was found to provide adequate strength in the load bearing region for plane strain fracture toughness testing. Excellent agreement was found between the stress intensity coefficient values obtained from compliance measurements and the analytic solution proposed for inclusion in the standard test method. Load displacement measurements were made using long armed displacement gages and hollow loading cylinders. Gage points registered on the loading hole surfaces through small holes in the walls of the loading cylinders.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81379 , E-284
    Format: application/pdf
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  • 98
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    Analysis of surface cracks in finite plates under tension or bending loads (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Stress-intensity factors calculated with a three-dimensional, finite-element analysis for shallow and deep semielliptical surface cracks in finite elastic isotropic plates subjected to tension or bending loads are presented. A wide range of configuration parameters was investigated. The ratio of crack depth to plate thickness ranged from 0.2 to 0.8 and the ratio of crack depth to crack length ranged from 0.2 to 2.0. The effects of plate width on stress-intensity variations along the crack front was also investigated. A wide-range equation for stress-intensity factors along the crack front as a function of crack depth, crack length, plate thickness, and plate width was developed for tension and bending loads. The equation was used to predict patterns of surface-crack growth under tension or bending fatigue loads. A modified form of the equation was also used to correlate surface-crack fracture data for a brittle epoxy material within + or - 10 percent for a wide range of crack shapes and crack sizes.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-1578 , L-13053
    Format: application/pdf
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  • 99
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    Implications of cyclotron features in the X-ray spectrum of Her X-1 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The X-ray spectra from binary pulsars is investigated through the modification of physical processes due to an intense magnetic field. An effective scattering cross section for line photons and the Coulomb cross section for electron-ion collisions, treating the electrons relativistically, are calculated. The quantization of electron orbits in strong fields are discussed. The absorption cross sections and emission rates for cyclotron photons are calculated. An application of the results to the data from Hercules X-1 is examined.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80588
    Format: application/pdf
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  • 100
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    Detection of high energy X-rays from the galactic center region (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Observations of the galactic center region made with the high energy X-ray detector on OSO-8 are discussed. A strong hard X-ray which was detected during these observations from the vicinity of the galactic center are examined. The counting rate spectrum and the photon number spectrum of the flux are determined. Comparisons with the high energy X-ray fluxes observed from sources in the region by others are discussed.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80584
    Format: application/pdf
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