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  • Other Sources  (1,938)
  • AERODYNAMICS  (845)
  • ASTRONOMY  (642)
  • COMMUNICATIONS AND RADAR  (451)
  • 1980-1984  (1,938)
  • 1983  (989)
  • 1981  (949)
  • 1
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    Curved-flow, rolling-flow, and oscillatory pure-yawing wind-tunnel test methods for determination of dynamic stability derivatives (1981)
    In:  CASI
    Details
    Publication Date: 2011-10-14
    Description: The test capabilities of the Stability Wind Tunnel of the Virginia Polytechnic Institute and State University are described, and calibrations for curved and rolling flow techniques are given. Oscillatory snaking tests to determine pure yawing derivatives are considered. Representative aerodynamic data obtained for a current fighter configuration using the curved and rolling flow techniques are presented. The application of dynamic derivatives obtained in such tests to the analysis of airplane motions in general, and to high angle of attack flight conditions in particular, is discussed.
    Keywords: AERODYNAMICS
    Type: AGARD Dyn. Stability Parameters; 13 p
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  • 2
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    Spectroscopy in X-ray astronomy (1981)
    In:  CASI
    Details
    Publication Date: 2006-06-04
    Description: Detailed features in cosmic X-ray sources and their associated temporal variation over a wide energy range were studied. Excess emission and absorption at approximately 6 to 7 kiloelectron volts in the spectra of supernova remnants, binary X-ray sources, and clusters of galaxies were observed. A gas scintillation proportional counter (GSPC) will be used as the detector system. In the gas scintillator the principal limitation is due to the statistics of the initial ionization process only.
    Keywords: ASTRONOMY
    Type: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
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  • 3
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    Far ultraviolet astronomy using the FAUST telescope (1981)
    In:  CASI
    Details
    Publication Date: 2006-06-04
    Description: The Far Ultraviolet Space Telescope (FAUST) a compact, wide field-of-view, far ultraviolet instrument designed for astronomical observations of extended and point sources is discussed. The design and application of the instrument are described. The prime objective is to observe faint astronomical sources with sensitivities higher than previously available. Scientific programs will include: (1) a search for ultraviolet stars which are predicted to exist at the stage of evolution prior to the final death of a star; (2) observations of galaxies and quasars; and (3) joint programs with other Spacelab 1 experiments. The secondary objective is to verify the suitability of the Spacelab as a platform for far ultraviolet astronomy: data will be provided on the ultraviolet background levels due to astronomical, terrestrial, and spacecraft generated sources; the levels of contaminants which affect ultraviolet instruments; and the capability of the Orbiter for stable pointing at celestial sources for useful periods of time.
    Keywords: ASTRONOMY
    Type: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
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  • 4
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    Prediction techniques (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Prediction methods and related propagation results for the evaluation of Earth-space communication paths operating above 10 GHz are presented. Gaseous attenuation, rain, cloud, fog, sand, and dust attenuation, path diversity, signal fluctuations and low angle fading, depolarization effects, bandwidth coherence, and sky noise are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 195-348
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  • 5
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    Characteristics of rain and rain systems (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The description and measurement of the macroscopic and microscopic characteristics of rain and rain systems are discussed. The statistical relationships of these characteristics and their effect on polarization and attenuation are considered. Macroscopic characteristics include the size, distribution, and movements of rain cells, the height of melting layers, and the presence of ice crystals. Microscopic characteristics include the size distribution, density, and oblateness of rain drops and ice crystals. The estimation of a major propagation effect, specific attenuation, is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 5-39
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  • 6
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    Propagation data bases (1981)
    In:  CASI
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    Publication Date: 2006-02-14
    Description: Existing data bases accumulated as the result of experiments to gather propagation data on millimeter wave Earth-space links are described. The satellites used are described and results of the significant experiments conducted in the United States are summarized. The data bases consist primarily of cumulative attenuation statistics, though some depolarization measurements are included. Additional summaries of propagation data are cited.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Its Propagation Effects Handbook for Satellite Systems Design; p 155-194
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  • 7
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    An overview of several rain and attenuation models (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The key features of the Rice-Holmberg, Dutton-Dougherty, Global, Lin, and Piecewise Uniform Rain Rate models for estimation of cumulative attenuation statistics on Earth-space millimeter paths are summarized. The models provide either rain rate statistics or attenuation statistics, which can be related by use of the specific attenuation and the effective path length relation. The effective path length is defined. The advantages and disadvantages of each model for specific applications are discussed. The Global model is recommended as the design tool for predicting propagation effects in Earth-space communication systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 41-101
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  • 8
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    Application of propagation predictions to Earth/space telecommunications system design (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The corresponding between a given propagation phenomenon and system performance is considered. Propagation data are related to system performance parameters, allowing the systems engineer to perform the analyses determining how well requirements are met by a given system design, and enabling the systems engineer to modify that design if necessary. The various ways of specifying performance criteria for different kinds of systems are discussed, and a general procedure for system design is presented and demonstrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 349-404
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  • 9
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    Depolarization on Earth-space paths (1981)
    In:  CASI
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    Publication Date: 2006-02-14
    Description: Sources of depolarization effects on the propagation paths of orthogonally-polarized information channels are considered. The main sources of depolarization at millimeter wave frequencies are hydrometeor absorption and scattering in the troposphere. Terms are defined. Mathematical formulations for the effects of the propagation medium characteristics and antenna performance on signals in dual polarization Earth-space links are presented. Techniques for modeling rain and ice depolarization are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 103-154
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  • 10
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    An analytic solution to the classical two-body problem with drag (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The two body problem was analyzed with a specific drag model. The model treats drag as a force proportional to the vector velocity and inversely proportional to the distance to the center of attraction. The solution is expressed in terms of known functions and is of a simple and compact form. The time of flight is expressed as a quadrature in the true anomaly. The results are: (1) development of a vector differential equation which allows analysis of an infinite number of gravitational and drag models; and (2) obtaining the solution of a linear differential equation using the inverse method of laplace transforms.
    Keywords: AERODYNAMICS
    Type: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 22 p
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  • 11
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    Langley high-lift research on a high-aspect-ratio supercritical wing configuration (1981)
    In:  CASI
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    Publication Date: 2006-02-14
    Description: To determine the low speed performance characteristics of a representative high aspect ratio supercritical wing, two low speed jet transport models were fabricated. A 12-ft. span model was used for low Reynolds number tests in the Langley 4- by 7-Meter Tunnel and the second, a 7.5-ft. span model, was used for high Reynolds number tests in the Ames 12-foot Pressure Tunnel. A brief summary of the results of the tests of these two models is presented and comparisons are made between the data obtained on these two models and other similar models. Follow-on two and three dimensional research efforts related to the EET high-lift configurations are also presented and discussed.
    Keywords: AERODYNAMICS
    Type: Advan. Aerodyn.: Selected NASA Res.; p 55-77
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  • 12
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    Measured transonic unsteady pressures on an energy efficient transport wing with oscillating control surfaces (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Highlight results are presented from subsonic and transonic pressure measurement studies conducted in the Langley Transonic Dynamics Tunnel on a supercritical wing model representative of an energy efficient transport design. Steady- and unsteady-pressure data were acquired on the upper and lower wing surface at an off-design Mach number of 0.60 and at the design Mach number of 0.78, for a Reynolds number of 2.2 x 10(6) (based on the wing average chord). The model configuration consisted of a sidewall-Mounted half-body fuselage and a semi-span wing with an aspect ratio of 10.76, a leading-edge sweepback angle of 28.8 degrees, and supercritical airfoil sections. The wing is instrumented with 252 static pressure orifices and 164 dynamic pressure gages. Model test variables included wing angle of attack, control-surface mean deflection angle, control-surface oscillating deflection angle and frequency, and phasing between oscillating leading-edge and trailing-edge controls when used together.
    Keywords: AERODYNAMICS
    Type: Advan. Aerodyn.: Selected NASA Res.; p 21-36
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  • 13
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    Viscous wing code development: A 3-D viscid-inviscid interactive analysis (1983)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 607-63
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  • 14
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    Computation of separated flow on airfoils with the Grumfoil code (1983)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 557-58
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  • 15
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    Analysis of airfoil transitional separation bubbles (1983)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 539-55
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  • 16
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    Entropy effects and shock fitting in conical supersonic full potential flows (1983)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center, Theoretical Aerodynamics Contractors' Workshop, Volume 2; p 461-49
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  • 17
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    Atmospheric attenuation for correlated satellite communication ground sites (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Link margin estimates are calculated for 30/20 GHz satellite communication systems employing closely-spaced (4 to 100 km) 'dual diversity' switched ground sites. The link margin estimates are based on a new analysis in which the bivariate rain attenuation density function for two correlated ground sites is modelled by an exponential density function. The results of the exponential density function analysis enable derivation of a direct relation between rain margin estimates and probability of exceedance (link availability). Margins typically in the range 2 to 12 dB are calculated for various ground site separations and summarized for seven city locations and five satellite orbit positions over the U.S. The results can be easily extended to other EHF satellite frequencies and other locations.
    Keywords: COMMUNICATIONS AND RADAR
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  • 18
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    Effects of ISI and satellite channel nonlinearity on Viterbi demodulation/decoding (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is shown that, for convolutionally coded transmission over bandwidth-constrained channels, a mere reversal of the switching direction at the encoder output produces a change in the system bit error probability performance. This change is significant when the Viterbi demodulator/decoder is matched to the total channel memory and is more significant for linear channels than for nonlinear ones. The reversal of switching direction is a simple demonstration of the fact that the well-known optimum codes for the linear AGWN channel are no longer necessarily optimum for a bandwidth-constrained channel with or without the addition of channel nonlinearity. It is concluded that potentially significant performance improvement can be obtained by matching the encoder (through the appropriate choice of tap weights and modulo-2 summers) to the channel in addition to matching the demodulator/decoder to the channel for a given encoder.
    Keywords: COMMUNICATIONS AND RADAR
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  • 19
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    Detection of silicate emission features in the 8- to 13-micron spectra of main belt asteroids (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A presentation is given of 8.0-13.0 micron spectra (Delta lambda/lambda = 0.02-0.03) for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 56; 393-397
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  • 20
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    An exploratory study of area-efficient vortex flap concepts (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The potential of planform modification and hinge-line relocation to improve the thrust efficiency of vortex flaps was experimentally investigated on a 60-deg cropped delta wing model. Spanwise segmentation of the flap, together with chord-tailoring of the segments, allowed the vortex to be maintained on the outboard flap surfaces to higher angles of attack. In addition, location of the flap hinge aft of and underneath the wing leading edge generated substantial thrust from the vortex suction acting on the leading-edge lower surface. A combination of these beneficial effects allowed the flap/wing area to be reduced from 11.4 percent of the continuous flap to 6.3 percent of segmented flap, essentially without detriment to the incremental lift-to-drag ratio due to flap addition in the lift coefficient range 0.5-0.7 based on the basic wing area.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 20; 1062-106
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  • 21
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    Observations and implications of natural laminar flow on practical airplane surfaces (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 20, p. 3138, Accession no. A82-40893
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft (ISSN 0021-8669); 20; 993-1006
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  • 22
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    The evolution of the infrared emission from the Type II supernova 1980k in NGC 6946 - The dust formation model (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The paper presents 1-4 micron photometry of supernova 1980 k in NGC 6946 obtained over a period of 1 year following the outburst. During the period between 1980 November 1 and December 19, the infrared emission probably originated from the extended atmosphere of the expanding star. The JHKL colors and a 1.3-2.6-micron spectrum observed during this period correspond to those of a blackbody with an average temperature of about 5000 K. Observations around 1981 May 31 showed that the supernova developed an infrared excess after 1980 December. This infrared excess persisted through 1981 October and is consistent with the appearance of thermal emission from about 700 to 900 K dust in addition to a hotter photosphere. The similarity of this behavior to that of the infrared evolution of some novae suggests that dust formation may be occurring in the supernova ejecta. The hypothesis, that the emission arises from preexisting grains in a circumstellar shell which are heated by the supernova outburst, is also consistent with the data.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 168-174
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  • 23
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    Stability of shock waves attached to wedges and cones (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 06, p. 799, Accession no. A82-17876
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 21; 1611-161
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  • 24
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    Ultraviolet and optical studies of binaries with luminous cool primaries and hot companions. III - Reticon radial velocities (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Radial velocities for 72 stars, most of them known or suspected binaries with F - K giant-supergiant primaries, are derived from Reticon spectra in the region 6005-6235 A at a scale of 7 km/s per diode. Cross-correlation of the spectra normally produces results accurate to better than 1.0 km/s. Eight new radial velocity variables are found (HR 2786, R Pup, HR 3291, HR 4451, HD 114520, HR 5667, HR 7014, and Nu1 Sgr). Improved orbits are determined for 15 known spectroscopic binaries, and provisional orbits are obtained for seven new spectroscopic binaries.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 53; 553-571
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  • 25
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    Infrared observations of RS CVn stars (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The paper presents infrared photometry of the RS CVn binary stars AR Lac (1.2-10 microns) and MM Her (1.2-3.5 microns) as they egressed from their primary and secondary eclipses; of the eclipsing systems RS CVn and Z Her at maximum light (1.2-10 microns) and of the non-eclipsing systems UX Ari and HR 1099 (1.2-10 microns). An analysis of these and published V data based on flux ratio diagrams (linear analogues of color-color diagrams) shows that G and K stars supply the infrared light of these systems. In AR Lac, the combined light of a G5-K0 subgiant and either a late F dwarf or an early F subgiant can account for the observed visual and infrared light curves. None of these systems shows infrared emission from circumstellar matter. This result is simply understood: dust grains would not be expected to form in the physical conditions surrounding the subgiant, and the corona and chromosphere (whose properties have been deduced from spectroscopic X-ray observations) should not produce appreciable infrared emission.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 205; 859-873
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  • 26
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    Ultraviolet high-resolution spectroscopy from the Space Telescope (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The High Resolution Spectrograph is one of five scientific instruments which will be part of the Space Telescope observatory. The spectrograph was designed to take advantage of the imaging and pointing capabilities of the telescope to obtain ultraviolet spectra with spectral resolution comparable to large, ground-based coudeinstruments. Some of the results of the ground-based testing program will be described, along with applications of these properties to future science programs.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 543-549
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  • 27
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    Theoretical studies of the effects of grain noise on photographic stellar astrometry and photometry (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A method of incorporating the effects of photographic emulsion grain noise into digital image centering algorithms is presented which improves the accuracy of the derived stellar positions and magnitudes. Theoretical formulae are then derived for the limiting error of the center, and the photometric parameters. For IIIa-J, this error is 0.2-0.3 mu for bright unsaturated images, which agrees quite well with measurements made with the Yale PDS microdensitometer. It is expected that, with further improvements in the positional accuracy of the PDS, it should be possible to reach the emulsion grain noise limit, providing that emulsion shifts or other large scale errors do not dominate. It is also shown that, with appropriate trimming, marginal distribution image centering algorithms can yield an accuracy only slightly poorer than that obtained with two-dimensional distributions.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 88; 1683-168
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  • 28
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    A chimera grid scheme (1983)
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    Publication Date: 2011-08-18
    Description: A mesh system composed of multiple overset body-conforming grids is described for adapting finite-difference procedures to complex aircraft configurations. In this so-called 'chimera mesh,' a major grid is generated about a main component of the configuration and overset minor grids are used to resolve all other features. Methods for connecting overset multiple grids and modifications of flow-simulation algorithms are discussed. Computational tests in two dimensions indicate that the use of multiple overset grids can simplify the task of grid generation without an adverse effect on flow-field algorithms and computer code complexity.
    Keywords: AERODYNAMICS
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  • 29
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    Differential versus limiter-discriminator detection of narrow-band FM (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The error probability performance of differential detection of narrow-band FM is determined and compared with the analogous results for limiter-discriminator detection of the same modulation. It is shown that over a large class of benign and hostile environments, e.g., Gaussian IF filter, AWGN, partial-band noise jamming, the differential detector offers no theoretical performance advantage over the limiter-discriminator receiver with integrate-and-dump postdetection filtering.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications (ISSN 0090-6778); COM-31; 1227-123
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  • 30
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    Conservative full-potential calculations for axisymmetric, transonic flow (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Previously cited in issue 17, p. 2873, Accession no. A81-38082
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 21; 1492-149
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  • 31
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    An improved celestial radio reference frame: JPL 1982-4 (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: In the development of a celestial radio reference frame, there are now over 100 sources whose relative positions are known with an average uncertainty less than 5 milliarcseconds. These sources are fairly uniformly distributed over the celestial sphere north of -40 deg declination. Their positions are expressed in the new IAU system. This presentation describes the analysis involved in obtaining these results, as well as future plans for linking this system to the JPL planetary ephemerides.
    Keywords: ASTRONOMY
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  • 32
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    Comets (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The nature and origin of comets is discussed. Observations of the principal parts of comets, the dust and plasma tails, the hydrogen cloud, the coma and the cometary nucleus, are presented, and the icy conglomerate model of Whipple as extended by Delsemme accounting for the observed properties and their variation with heliocentric distance is examined. The origin of comets is considered in relation to the orbital statistics of the long-period comets and the existence of the Oort cloud on the edge of the solar system, and possible roles for comets in the solar nebula and the evolution of the solar system are indicated. Particular attention is then given to the discovery and properties of Halley's Comet, which is expected to reach perihelion in 1986, and to possible flyby and rendezvous missions to Halley's Comet and others.
    Keywords: ASTRONOMY
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  • 33
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    Electron densities for 10 planetary nebulae derived from the semiforbidden C III lambda 1907/1909 ratio. II (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Electron densities for IC 351, IC 2165, J900, IC 3568, NGC 6644, NGC 6891, IC 4997, NGC 7009, Hu 1-2, and IC 5217 are derived from high-dispersion semiforbidden C III spectrograms. For seven of these nebulae, the derived electron density is larger than the values derived from either surface brightness measurements or forbidden line ratios. Only one object, Hu 1-2, shows pronounced splitting of the semiforbidden C III emission lines due to a large expansion velocity.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 34
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    Medium energy gamma ray astronomy with transpacific balloon flights (1981)
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    Publication Date: 2011-08-18
    Description: Transpacific balloon flights with the University of California, Riverside (UCR) double scatter telescope are discussed. With flight durations from 5 days up to perhaps 15 days the long observation times necessary for medium energy (1-30 MeV) gamma ray astronomy can be obtained. These flights would be made under the auspices of the Joint U.S.-Japan Balloon Flight Program at NASA. It is proposed that flights can provide at least 30 hours of observation time per flight for many discrete source candidates and 120 hours for detecting low intensity cosmic gamma ray bursts.
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    Studies in astronomical time series analysis. I - Modeling random processes in the time domain (1981)
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    Publication Date: 2011-08-18
    Description: Several random process models in the time domain are defined and discussed. Attention is given to the moving average model, the autoregressive model, and relationships between and combinations of these models. Consideration is then given to methods for investigating pulse structure, procedures of model construction, computational methods, and numerical experiments. A FORTRAN algorithm of time series analysis has been developed which is relatively stable numerically. Results of test cases are given to study the effect of adding noise and of different distributions for the pulse amplitudes. A preliminary analysis of the light curve of the quasar 3C 272 is considered as an example.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series; 45; Jan. 198
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    Three new 'nonterrestrial' molecules (1981)
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    Publication Date: 2011-08-18
    Description: Eight new interstellar lines have been detected from three molecules not previously observed spectroscopically in space or in the laboratory. One is a linear or nearly linear molecule with microwave constants B0 equals 21,337.15 plus or minus 0.06 MHz, D0 equals 21.4 plus or minus 1.5 kHz. This is the thioformyl ion HCS(plus), first identified because B0 and D0 are close to those calculated, and now confirmed by laboratory detection of one of the present lines (Gudeman et al.). The second molecule, also linear or nearly so, has microwave constants B0 equals 10,691,406 plus or minus 0.043 MHz, D0 equals 1.84 plus or minus 0.91 kHz close to those expected for the isoelectronic systems HOCO(plus) and HOCN; a choice between the two cannot be made on the basis of the available astronomical data. The existence of a third molecule is deduced from an unidentified line at 85,338 MHz that has been found in many sources, is fairly intense in several, and may be self-absorbed in Sgr B2.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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    Discovery of phase-locked variable polarization in an RS Canum Venaticorum-like star, HR 5110 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Using measurements on 79 nights in 1980 January-August, it is established that the polarization in the ultraviolet (U band) varies synchronously on the known binary period of 2.6132 days, with a peak-to-peak amplitude of 0.03%. The pattern is mainly second harmonic in character, as typical of binary star examples such as Algol and Upsilon Her. Reflection by the cooler star, by a plasma concentration, or both, is suggested. The scale of the polarization seems to be consistent with Rayleigh scattering by neutral hydrogen on the cooler star, and a roughly lambda to the -4th wavelength dependence should be searched for. The QU curve suggests a sizeable inclination for the system, of about 45 deg, but this is preliminary. Separately, a possible weak periodicity might be present on a subsidiary period, conceivably related to a rotating star spot.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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    Vortex-flow aerodynamics - An emerging design capability (1981)
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    Publication Date: 2011-08-18
    Description: Promising current theoretical and simulational developments in the field of leading edge vortex-generating delta, arrow ogival wings are reported, along with the history of theory and experiment leading to them. The effects of wing slenderness, leading edge nose radius, Mach number and incidence variations, and planform on the onset of vortex generation and redistribution of aerodynamic loads are considered. The range of design possibilities in this field are consequential for the future development of strategic aircraft, supersonic transports and commercial cargo aircraft which will possess low-speed, high-lift capability by virtue of leading edge vortex generation and control without recourse to heavy and expensive leading edge high-lift devices and compound airfoils. Attention is given to interactive graphics simulation devices recently developed.
    Keywords: AERODYNAMICS
    Type: Astronautics and Aeronautics; 19; May 1981
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  • 39
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    The 45 micron H2O ice band in the Kleinmann-Low Nebula (1981)
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    Publication Date: 2011-08-18
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 245
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    Longitudinal grooves for bluff body drag reduction (1981)
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    Publication Date: 2011-08-18
    Description: Wind tunnel test results are presented for four axisymmetric bluff body configurations in order to determine their effect on form and pressure drag. It was found that drag reductions on the order of 40% are obtainable with an afterbody incorporating four longitudinal 'V' grooves. Although this effect may be due to the functioning of the grooves as longitudinal, continuous vortex generators, it is concluded that further research is needed to elucidate the physical basis of the test results. Optimization of the effect will be useful in base drag reduction for such vehicles as automobiles and cargo aircraft with sharply upswept afterbodies.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Apr. 198
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  • 41
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    Concerning the Wolf-Rayet and other luminous early-type stars (1981)
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    Publication Date: 2011-08-18
    Description: Effective temperatures, radii, and luminosities were determined from S2/68, ANS, UBV, and uvby photometry for four B0/B1 supergiants, four O4 stars, and four WN7/WN8 stars as well as for four test stars having spectral types between B1.5 V and 09 V and five stars with known angular diameters and effective temperatures. The effective temperatures of B1 Ia+ stars are found to be near 17,000 K, those of O4 stars near 45,000, and those of WN7/WN8 stars near 26,000 K. The question of modeling the atmospheres of hot luminous stars is examined, and it is noted that the photosphere can be modeled adequately using a classical plane-parallel layer model atmosphere. In addition, it is found that the Wolf-Rayet stars of types WN7/WN8 fall in the H-R diagram near the B0 Ia stars, while the others fall near B0.5 III stars. The evolutionary relationship between the Wolf-Rayet and O stars is considered; it is suggested that a Wolf-Rayet spectrum is a short-lived phase in the life of a massive star.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 244
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    Observation of the core of the Perseus cluster with the Einstein solid state spectrometer - Cooling gas and elemental abundances (1981)
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    Publication Date: 2011-08-18
    Description: Solid State Spectrometer observations of the core of the Perseus cluster have resulted in the detection of X-ray emission lines due to Si, S, and Fe. Analysis of the spectrum indicates that the X-ray emission has at least two characteristic temperatures. This is interpreted in the framework of radiative accretion in the core of the cluster. The derived parameters are a cooling time less than or approximately equal to 2 x 10 to the ninth years for the low-temperature gas, a mass accretion rate of approximately 300 solar masses per year, and a characteristic size of 10-20 kpc for the cool gas. The Fe abundance in the core (approximately 0.4) is similar to the Fe abundance averaged over the whole cluster, indicating that Fe emission is not strongly concentrated about NGC 1275. The Si and S abundances are consistent with solar values.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 244
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  • 43
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    Non-linear stability around the triangular libration points (1981)
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    Publication Date: 2011-08-18
    Description: The configuration space around the triangular libration points in the Earth-Moon system is partitioned according to the stability of the motion. The regions around L4 and L5 are established where particles placed with zero initial velocity will librate. The complexity of the partitioning is revealed.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 23; Mar. 198
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    High-resolution observations of the QSO 3C 345 at 1.3 centimeters (1981)
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    Publication Date: 2011-08-18
    Description: High-resolution VLBI observations made at a frequency of 22.235 GHz of the quasar 3C 345 are discussed. Antennas located at the Crimean Astrophysical Observatory, USSR; Onsala, Sweden; Effelsberg, West Germany; and the Haystack Observatory, Massachusetts were employed at 4-min integration times to provide baselines ranging up to 5.5 x 10 to the 8th wavelengths. About 40% of the total flux density of 7.85 Jy, observed in November 1977, and 8.05 Jy, observed in October 1978, is found to originate in an unresolved component of the quasar core in a region less than 0.1 milliarcsec in diameter. The elongated jet-like component of the quasar is observed to contain several peaks of emission extending up to 6 milliarsec from the core which decreased in extent between the two observations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 243
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  • 45
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    Vectored injection into compressible laminar and turbulent boundary layers (1981)
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    Publication Date: 2011-08-18
    Description: A fundamental analysis of two-dimensional supersonic boundary layer flow, both laminar and turbulent, is presented for a wide range of normal and nonnormal mass-transfer velocities. The analysis is based on the numerical solution of the Navier-Stokes equations, and results are compared with available theoretical and experimental data. Certain cases of practical importance, for which results are not presently available, are referred to.
    Keywords: AERODYNAMICS
    Type: Computer Methods in Applied Mechanics and Engineering; 25; Jan. 198
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  • 46
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    Report of the panel on theoretical aerodynamics (1981)
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    Description: Interactions between theoretical aerodynamics and the NTF are discussed. The development and validation of computational fluid dynamics computer codes, the determination of Reynolds number scaling laws, and extension of the data bases of entrainment type turbulence models to include high Reynolds number data are recommended areas of study. The major benefit theoretical aerodynamics could have on the NTF is in the quantitative description of wind tunnel wall interference effects.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 277-286
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    High Reynolds number research requirements for space vehicle design (1981)
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    Publication Date: 2011-08-18
    Description: Requirements of entry vehicle design requiring high Reynolds number wind tunnel testing are discussed. The space shuttle orbiter, development of future space transportation systems, and planetary entry data analysis are considered.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 265-274
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    Report of the panel on aeroelasticity and unsteady aerodynamics (1981)
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    Publication Date: 2011-08-18
    Description: The status of recommended areas of study for the NTF are reviewed. Transonic and control surface unsteady aerodynamics, and buffet onset and loads are considered. Testing of dynamically scaled flutter models is discussed.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 237-246
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    Model experience in the Langley 0.3-m transonic cryogenic tunnel (1981)
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    Publication Date: 2011-08-18
    Description: The model building, development, and testing experience gained during 8 years of operation of the 0.3-m Transonic Cryogenic Tunnel (TCT) is summarized. The summary is divided into four portions: (1) models tested in the 0.3-m TCT's original octagonal test section; (2) models tested in the present two dimensional test section; (3) models tested as a part of tunnel calibration and the development of advanced technology airfoils; and (4) development of a new way to construct two dimensional airfoil models. Design requirements imposed on the models by high Reynolds number testing at cryogenic temperatures are reviewed.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 53-73
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    Burst statistics of Viterbi decoding (1981)
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    Publication Date: 2011-08-18
    Description: A mathematical model of Viterbi decoder burst error performance is presented. This model allows for computer generation of Viterbi-like error sequences quickly and inexpensively for applications where large amounts of data are required. The model is corroborated through comparisons with actual software decoder simulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 187-193
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    An efficient technique for the performance evaluation of antenna arrays with noisy carrier reference (1981)
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    Publication Date: 2011-08-18
    Description: An efficient computational technique is developed to evaluate the performance of coherent receivers with noisy carrier reference and multiple antennas. The received signal is assumed to be uncoded residual carrier BPSK (binary phase shift keying), with a PLL (phase locked loop) used for extracting the carrier. Explicit relationships between the error probabilities and the various system parameters are given. Specific results are given for the performance gain of combined carrier referencing over baseband only combining when the channel alignment process is ideal. A simple asymptotic expression for the performance gain is determined when the number of antennas used is increased without bound. An example using a Block 3 Deep Space Network PLL illustrates the performance of each arraying structure. The technique used is applicable to the performance evaluation for other receivers having similar decision statistics.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 194-206
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    The DSN VLBI system Mark 4-85 (1981)
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    Publication Date: 2011-08-18
    Description: The DSN VLBI System was established as a network system in 1978. The evolution of the VLBI System from Mark 1-79 to Mark 4-85 is described, and the system functional requirements for Mark 4-85 are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 61-76
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    DSN command system (1981)
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    Publication Date: 2011-08-18
    Description: Modification of the currently operational DSN Command System MK 3-80 consisted of improvement of the uplink carrier frequency tuning capability to satisfy Voyager 2 requirements. Upgrading of Command System monitoring functions in the Network Operations Control Center is discussed. The DSN Command System requirements and functional design are described for the Mark 4 Network.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 53-60
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    Project ORION microwave subsystem design (1981)
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    Publication Date: 2011-08-18
    Description: The proposed design for the microwave subsystem of Project ORION is presented. Performance characteristics and subsystem capabilities are discussed. Functional requirements and key performance parameters are stated for the subsystem as well as a proposed schedule of events.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 10-17
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    Radio astronomy (1981)
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    Publication Date: 2011-08-18
    Description: The activities of the Deep Space Network in support of radio astronomy operations during the first quarter of 1981 are reported. Results of the use of a low noise maser are presented, as well as updates in DSN support of experiments sanctioned by the Radio Astronomy Experiment Selection Panel.
    Keywords: ASTRONOMY
    Type: The Telecommun. and Data Acquisition Rept.; p 1-2
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    A multiple access communication network based on adaptive arrays (1981)
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    Publication Date: 2011-08-18
    Description: A single frequency communication system is considered consisting of K possibly moving users distributed in space simultaneously communicating with a central station equipped with a computationally adapted array of n = or K antennas. Such a configuration could result if K spacecraft were to be simultaneously tracked by a single DSN complex consisting of an n antennas array. The array employs K sets of n weights to segregate the signals received from the K users. The weights are determined by direct computation based on known position information of the K users. Currently known techniques require (for n = K) about (4/3)K to the 4th power computer operations (multiply and add) to perform such computations. A technique that accomplishes this same goal in 8 K to the 3rd power operations, yielding a reduction by a factor K/6, was developed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 118-127
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    Atmospheric noise temperature measurements (1981)
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    Publication Date: 2011-08-18
    Description: Radiometric microwave noise temperature measurements were used to estimate atmospheric transmission loss. The following lumped element model expression is used for the noise temperature contribution, T double prime = T sub p (1 - 1/L). This relationship is used to estimate the transmission loss L in terms of T double prime and the atmosphere effective physical temperature T sub p. This report evaluates T sub p in terms of assumed distributed loss and temperature models. Simplified expressions are presented for low loss applications. For these applications L was determined directly and accurately without integration or iteration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 87-96
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    Effects of the gaseous and liquid water content of the atmosphere on range delay and Doppler frequency (1981)
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    Publication Date: 2011-08-18
    Description: When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 71-86
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    The 34-meter antenna-subreflector translations to maximize RF gain (1981)
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    Publication Date: 2011-08-18
    Description: The extension of the 26 meter antenna to 34 meter diameter decreased the F/D ratio. This F/D change resulted in unacceptable gain losses due to the hyperboloid's lateral deflections. A three direction translating mounting device was added to the hyperboloid. This device was controlled by a microprocessor to minimize the offsets of the phase centers in the cassegrain RF system and also compensated for boresight directions. The use of the radiation program to predict the gain losses from displacements computed by a structural computing program using an analytical model of the 34 meter reflector structure is discussed. Field test results showed accurate predictions for the Y and Z hyperboloid translations. In the X direction, the prediction value was low. However, the computed gain losses vs primary foci offsets by the radiation program were verified by field tests.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 112-120
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    Frequency standard test facility data acquisition and processing system (1981)
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    Publication Date: 2011-08-18
    Description: The interim frequency standards test facility tests all frequency standards used in the DSN. It is also the central testing facility for testing all ultrastable hydrogen maser frequency standards. This proposed data acquisition/processing system was designed to support the IFSTF by acquiring and processing the large amounts of data generated there.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 22-30
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    Station stability measurement (1981)
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    Publication Date: 2011-08-18
    Description: Methods and instrumentation are being developed to determine the frequency stability of Deep Space Stations. The efforts are presently focused on the verification of the stability of the X-band uplink and other RF and microwave subsystems which contribute to the overall stability of the system. The measurement methodology is presented as well as frequency stability data generated with the development measurement system. The system characteristics are highlighted and the potential areas where improvements could be made are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 35-42
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    Control of large space antennas based on electromagnetic-structural models (1983)
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    Publication Date: 2011-08-18
    Description: A general approach to the optimal control of large space antennas based on their RF/structural characteristics is described. The approach consists of defining a cost functional based on the degradation of the RF performance of the antenna and using the structural model as the dynamic system. The method is applied to the design of an optimal controller for a 55-m, wrap-rib offset-fed antenna. The controller's goal is to minimize the variations of the peak electric field of the antenna due to feed displacements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Proc. of the Workshop on Appl. of Distributed System Theory to the Control of Large Space Struct.; p 181-194
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    High-resolution IUE observations of the 1981 eclipse of 32 CYG (1981)
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    Publication Date: 2011-08-18
    Description: 32 Cyg shows a spectacular pure emission line spectrum during eclipse. Six weeks later, most lines, which were observed in emission during eclipse, are seen as P Cygni type profiles with strong absorption components. The lines are formed through line scattering of B star light in the extended atmosphere (wind) of the K supergiant. During eclipse, the emission parts of the P Cyg lines remain visible since the size of the line scattering sphere around the B star is larger than the red giant. Other emission lines are formed in a shock front near the B star (CIV, SiIV, FeIII) and possibly in an accretion disk. The strong FeII UV Mult. 191 lambda lambda 1785-88 A is shown to be formed through optical pumping via FeII UV Mult. 9 photons. The phase dependence of the P Cyg type profiles is modelled by means of line transfer calculations in nonspherical, 3-dimensional geometry with velocity fields.
    Keywords: ASTRONOMY
    Type: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 245-259
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    DSN ground communications facility (1983)
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    Description: A functional description of the GCF and its relationships with other elements of the DSN and NASCOM is presented together with development objectives and goals and comments on implementation activites in support of flight projects.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 200-209
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    MV-3 communication subsystem (1983)
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    Publication Date: 2011-08-18
    Description: The operational mobile VLBI data acquisition system (MV-3) requires that a voice link be established between the mobile data system and a fixed site. A communications subsystem was incorporated in the MV-3 design which consists of HF radio, VHF mobile radio telephone and conventional land line telephone. The HF antenna design was optimized for short and long range transmission using both inverted V and yagi antennas mounted on a self-supporting telescoping mast.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 210-219
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    S-band aperture efficiency of the DSS 13 26-meter antenna with the S-X common aperture feed (1983)
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    Publication Date: 2011-08-18
    Description: Measurements of the S-band performance of the DSS 13 26-meter antenna, equipped with the second generation S-X common aperture feed, are reported. Aperture efficiency and overall antenna gain results are compared with predicted values. The elevation dependence of the aperture efficiency is reported.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 89-94
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    Antenna arraying performance for deep space telecommunications systems (1983)
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    Publication Date: 2011-08-18
    Description: Antenna arraying is a crucial Deep Space Network technique in maximizing the science return of planetary and comet encounters. The equations which describe the total figure of merit for a multiple system of arrayed antennas are developed. An example is given for three Canberra DSN antennas and the Parkes 64-m antenna to be arrayed for the Voyager 2 Uranus flyby.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 83-88
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    VLBI collimation tower technique for time-delay studies of a large ground station communications antenna (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A need for an accurate but inexpensive method for measuring and evaluating time delays of large ground antennas for VLBI applications motivated the development of the collimation tower technique. Supporting analytical work which was performed primarily to verify time delay measurement results obtained for a large antenna when the transmitter was at a collimation distance of 1/25 of the usual far field criterion is discussed. Comparisons of theoretical and experimental results are also given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 20-29
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  • 69
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    A near-optimum receiver structure for the detection of M-ary optical PPM signals (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A class of receivers called conditionally nulling receivers is defined for quantum noise limited optical communications. These receivers have the ability to decide at each moment in time whether or not to coherently combine a predetermined local oscillator field with the received optical field, prior to performing an energy measurement (photodetection) on the combined field. Conditionally nulling receivers are applicable to pulse position modulation and related modulation schemes, which have the property that, at each moment in time, the transmitted signal is in one of only two states, on or off. The local oscillator field which may or may not be added by the receiver is an exact replica of the negative of the received on field; hence, the receiver can exactly null the on signal if the on signal is present and the receiver chooses to use the local field. An ideal conditionally nulling receiver achieves very nearly the same error probability (within a multiplicative factor varying froom 1 to 2.15) as the optimum quantum measurement for quantum noise limited detection of M-ary PPM signals. In contrast, other known receiving methods, such as direct, heterodyne, and homodyne detection, are exponentially suboptimum.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 30-42
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  • 70
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    Optical photometry of SS 433 - 200 nights of data 1979-1980 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Results from over 200 nights of optical photoelectric photometry of SS 433 during the period July 1979-October 1980 are presented. The data, taken in unfiltered light, the V band, an interference filter band centered on stationary H-alpha and a far-red band, provide evidence for an underlying 164-day light variation of peak-to-peak amplitudes 0.50 magnitude in V and 0.7 magnitude at 6567 A, and a binary-like variation with period 13.074 days and peak-to-peak amplitudes 0.50 and 0.60 magnitudes, respectively. The 13-day light curves are found to change slightly as a function of phase in the 164-day cycle, while seemingly erratic light fluctuations of up to 1 magnitude in 1 day and about 2 magnitudes in 3-4 days are imposed on both cyclic variations. It is noted that a conventional close-binary model is incapable of accounting for all the observed features, and alternatives involving some sort of luminous, rapidly changing extended low-mass envelope or screen in the binary system must be sought.
    Keywords: ASTRONOMY
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  • 71
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    Infrared photometry of comets Bowell and P/Stephan-Oterma (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Broadband IR photometry in the 1-20 micron range of the comets P/Stephan-Oterma and Bowell shows JHK colors similar to P/Meier and P/Tuttle, which are compatible with the scattering of sunlight by micron-sized grains. In addition, the P/Stephan-Oterma thermal emission was found to have an effective temperature higher than that expected from a blackbody in equilibrium. It is demonstrated that the thermal emission can be fit by models of the dust coma consisting of micron-sized grains, and that most of the flux at all observed wavelengths comes from the dust grains rather than the nucleus.
    Keywords: ASTRONOMY
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  • 72
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    X-ray and VLBI radio observations of the quasars NRAO 140 and NRAO 530 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Einstein X-ray Observatory has confirmed the HEAO 1 detection of the NRAO 140 and NRAO 530 quasars, and found that the low-energy X-ray flux of NRAO 140 is consistent with the high-energy results from the earlier satellite. It is also determined that the X-ray emission from NRAO 530 has either decreased by an order of magnitude, from 1978.0 to 1979.7, or the HEAO 1 field contained a second bright source. The two sources have been observed at 2.8 cm, using a four-station intercontinental VLB array, to find whether the X-ray emission is caused by Compton scattering within the radio components. Dissection of the NRAO 140 into its separate components shows radio parameters that imply a 'Compton problem', in that X-ray emission three orders of magnitude greater than that observed is predicted in one of the components if the source is static. Because the effect is independent of distance, relativistic motion with a Lorentz factor greater than about 40 is required to bring the predicted X-ray flux down to the observed value.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 249
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  • 73
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    Observations of SMC X-1 with the monitor proportional counter on the Einstein /HEAO 2/ X-ray Observatory - The pulse period and its history (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The results of the sixth determination of the pulse period of the X-ray source SMC X-1 are presented. The observations were made in April 1979. The pulse period at this epoch was found to be (0.713683 + or - 0.000032) s referred to phase zero of the binary motion. This result together with all available historical data is utilized to quantify the observed trend toward spin-up. It is found that simple secular trends are not applicable. This finding is interpreted as evidence for additional variations in the pulse period. The obtained results are discussed in the context of present theoretical models for period variations in the binary pulsating X-ray sources. The apparent absence of spin-down episodes in the period history of SMC X-1 is also considered.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 74
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    Two-component X-ray emission from RS Canum Venaticorum binaries (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A summary is presented of results from the Solid State Spectrometer on the Einstein Observatory for seven RS CVn binaries. The spectra of all require two emission components, evidenced by line emission characteristics of plasma at 4-million to 8-million K and bremsstrahlung characteristic of 20-million to 100-million K. The data are interpreted in terms of magnetic coronal loops similar to those seen on the sun, although with different characteristic parameters. The emission regions could be defined by separate magnetic structures. For pressures less than 10 dynes/sq cm the low temperature plasma would be confined within the stellar radii, while the high temperature plasma would, for the synchronous, close binaries, fill the binary orbits. However, for loop pressures exceeding 100 dynes sq cm, the high temperature components would also be confined to within the stellar radii, in loops covering only small fractions of the stellar surfaces. While the radio properties and the occurrence of X-ray flares suggest the larger emission regions, the observations of time variations leave the ambiguity unresolved.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 246
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  • 75
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    Pulsar gamma-rays - Spectra, luminosities, and efficiencies (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The general characteristics of pulsar gamma-ray spectra are presented for a model in which the gamma rays are produced by curvature radiation from energetic particles above the polar cap and attenuated by pair production. It is found that the shape of the spectrum depends on pulsar period, magnetic field strength, and primary particle energy. Comparing numerically calculated spectra with the observed spectra of the Crab and Vela pulsars, it is determined that primary particles must be accelerated to energies of approximately 3 x 10 to the 7th m c-squared. A general formula is determined for pulsar gamma-ray luminosity; it is found to depend on period and field strength.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 245
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  • 76
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    The Uranus occultation of 10 June 1979. I - The rings (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 86; Apr. 198
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  • 77
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    Infrared observations of AE Aquarii (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Broadband infrared observations of the cataclysmic variable AE Aquarii are reported. The observations were obtained in the J, H, K and L filters with the InSb photometer attached to the 1-m telescope of the European Southern Observatory. The infrared energy distribution observed from 0.35 to 3.5 microns for phase 0.5 suggests a spectral type of K5 V for the secondary and a distance to the system of approximately 70 pc if an absolute magnitude of 7.3 is assumed. Monitoring of the flux at 2.2 microns reveals a variability with an amplitude of approximately 0.3 magnitude over one third of the orbital period, the nature of which is under investigation.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific; vol. 93
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  • 78
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    Effectiveness of leading-edge vortex flaps on 60 and 75 degree delta wings (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A series of wind tunnel tests were run on 60 and 75 deg sweep delta wings to examine the effectiveness of leading-edge vortex flaps. Tests results showed that leading-edge vortex flaps are effective in giving large increases in lift-to-drag ratio and decreases in drag over a wide range of angle of attack. Tests on inverted flaps on the 60 deg delta wing showed substantial increases in lift and drag and may indicate a possibility of using inverted flaps on delta wings in the landing portion of flight. The 60 deg data were compared with that for a 75 deg sweep delta wing confirming that leading-edge vortex flap effectiveness is stronger as sweep is increased. Pitching moment effects due to vortex flaps use were also examined.
    Keywords: AERODYNAMICS
    Type: Journal of Aircraft; 18; Apr. 198
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  • 79
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    An X-ray survey of nine historical novae (1981)
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    Publication Date: 2011-08-18
    Description: The Einstein Observatory Imaging Proportional Counter has been used to search for X-ray emission from nine nearby historical novae. Six of the novae have been detected with estimated X-ray intensities between 0.1 and 4 keV of 10 to the -13th to 10 to the -11th erg/sq cm-sec, comparable to the intensities of previously detected cataclysmic variables. The X-ray intensity of one of the novae, V603 Aql, varies over times of several hundred seconds. The data suggest a correlation between the decay rate of the historical outburst and the current X-ray luminosity. Alternatively, the X-ray luminosity may be related to the inclination of the binary system.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 244
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  • 80
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    Pulsar and diffuse contributions to observed galactic gamma radiation (1981)
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    Publication Date: 2011-08-18
    Description: The first calculation of a gamma-ray production spectrum from pulsars in the Galaxy, along with a statistical analysis of data on 328 known radio pulsars, are presented. The implications of this point source contribution to the general interpretation of the observed galactic gamma-ray spectrum are indicated. The contributions from diffuse interstellar cosmic-ray induced production mechanisms are then re-examined, concluding that pulsars may be contributing significantly to the galactic gamma-ray emission.
    Keywords: ASTRONOMY
    Type: Nature; 290; Mar. 26
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  • 81
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    Variable X-ray spectra of BL Lacertae objects - HEAO 1 observations of PKS 0548 - 322 and 2A 1219 + 305 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 243
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  • 82
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    Phase-correlated P Cygni profile variations of the C III multiplet in UW Canis Majoris (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The interacting close binary system UW CMa has been observed, in the wavelength range from 1161 to 1188 A, continuously during a complete orbital cycle in 1979 with the Copernicus (OAO-3) U2 spectrometer. The C III multiplet at 1175 A, observed as a P Cygni feature, exhbits a clear dependence on the orbital phase of the binary; the radial velocity variation of this feature lags behind that of the O7 primary component by 0.1 orbital phase, which agrees with the anticipations in an earlier study by the same authors. The radiation-driven matter, flowing out of the binary, originates in the primary component.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 94; 2, Fe; Feb. 198
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  • 83
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    Partially confined multiple jet mixing (1981)
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    Publication Date: 2011-08-18
    Description: Results of hot-wire measurements in an incompressible partially confined jet issuing from an array of rectangular nozzles, equally spaced with their small dimensions aligned are presented. The quantities measured include mean velocity and the Reynolds stress in the two central planes of the jet at stations covering up to 115 widths (small dimension of a nozzle) downstream of the nozzle exit. For downstream distances greater than 60 widths, the flowfield is observed to be nearly homogenous and the turbulence appears to be quite similar to that of a grid generated turbulence.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 84
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    Unsteady Newton-Busemann flow theory. I - Airfoils (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Newtonian flow theory for unsteady flow at very high Mach numbers is completed by the addition of a centrifugal force correction to the impact pressures. The correction term is the unsteady counterpart of Busemann's centrifugal force correction to impact pressures in steady flow. For airfoils of arbitary shape, exact formulas for the unsteady pressure and stiffness and damping-in-pitch derivatives are obtained in closed form, which require only numerical quadratures of terms involving the airfoil shape. They are applicable to airfoils of arbitrary thickness having sharp or blunt leading edges. For wedges and thin airfoils these formulas are greatly simplified, and it is proved that the pitching motions of thin airfoils of convex shape and of wedges of arbitrary thickness are always dynamically stable according to Newton-Busemann theory. Leading-edge bluntness is shown to have a favorable effect on the dynamic stability; on the other hand, airfoils of concave shape tend toward dynamic instability over a range of axis positions if the surface curvature exceeds a certain limit. As a byproduct, it is also shown that a pressure formula recently given by Barron and Mandl for unsteady Newtonian flow over a pitching power-law shaped airfoil is erroneous and that their conclusion regarding the effect of pivot position on the dynamic stability is misleading.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 85
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    Evidence of imbedded vortices in a three-dimensional shear flow (1981)
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    Publication Date: 2011-08-18
    Description: Vortex phenomena encountered in an investigation of the streamwise development of the three-dimensional wake region behind the tip of a three-dimensional wedge model are reported. Pressure profiles were measured by pitot probes downstream of a tip with a nearly constant surface pressure level and a nearly continuous surface curvature in a blowdown air tunnel operating at Mach 6. Rather than the simple three-dimensional quasi-parallel shear flow expected, the measurements indicated the presence of a flow with large deficits in longitudinal pitot pressure, which are usually associated with the core region of quasi-steady longitudinal vortices. Vapor screen flow visualizations also support the presence of longitudinal vortices located primarily in the tip region and evidently forming in the vicinity of the wake neck. An increase in overall wake thickness by 100% is also observed. The origin of the vortices as quasi-steady Taylor-Gortler vortices generated in the concavely curved shear layer near the wake neck is considered. It is pointed out that the existence of longitudinal vortexes suggests that three-dimensional turbulence modeling may be much more difficult than previously supposed.
    Keywords: AERODYNAMICS
    Type: AIAA Journal; 19; Mar. 198
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  • 86
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    VRI photometry of selected SAO stars (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Johnson V, R, and I photoelectric photometry has been obtained for 199 SAO stars in support of the Near Infrared Photographic Sky Survey. These data are utilized in the calibration of survey photographs and are presented here to assist other programs reliant upon access to photometry in the photographic infrared.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific; vol. 92
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  • 87
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    Deformation of a line-element in the phase space at the triangular libration point (1981)
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    Publication Date: 2011-08-18
    Description: The flow in the projection of the phase space into the configuration space is presented in the neighborhood of a neutrally (or critically) stable equilibrium point in the restricted problem of three bodies. The projection is a line-element every point of which has zero initial velocity. After the elapse of various times the mapping (the rotations and elongations) of the line-element is described showing chaotic behavior.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 23; Feb. 198
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  • 88
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    Fundamental limitations caused by RF propagation (1981)
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    Publication Date: 2011-08-18
    Description: Propagation phenomena affect the design of radio frequency (RF) transmission systems. Propagation phenomena limit the suitability of portions of the frequency band for some applications, limit the reliability of RF transmission systems, and provide a means of coupling unwanted signals from one system to another with the potential of producing interference. The possibility of interference is the fundamental limitation to the unrestricted use of the frequency band. Phenomena affecting suitability, reliability, and the potential for interference are considered for frequencies in the 1- to 300-GHz range.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE; vol. 69
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  • 89
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    Stability of outer planetary systems (1981)
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    Publication Date: 2011-08-18
    Description: The conditions for stability in the Liapunov-Hill sense of outer planetary systems are given in terms of radii of planetary orbits. The outer planets of the solar system are found stable and the possible existence of other than the presently known planets between Jupiter and Pluto are indicated. The existence of other planetary systems with arbitrary mass ratios of the primaries is suggested, and the stability conditions for such systems are derived.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 23; Jan. 198
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  • 90
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    In quest of telescopes (1981)
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    Publication Date: 2011-08-18
    Description: This article deals with the author's decision to study star formation and reviews the early days of infrared astronomy at O'Brien Observatory. The infrared equipment used to observe the T Tauri variable class is described.
    Keywords: ASTRONOMY
    Type: Sky and Telescope; 61; Feb. 198
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  • 91
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    Proposed aeroelastic and flutter tests for the National Transonic Facility (1981)
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    Publication Date: 2011-08-18
    Description: Tests that can exploit the capability of the NTF and the transonic cryogenic tunnel, or lead to improvements that could enhance testing in the NTF are discussed. Shock induced oscillation, supersonic single degree control surface flutter, and transonic flutter speed as a function of the Reynolds number are considered. Honeycombs versus screens to smooth the tunnel flow and a rapid tunnel dynamic pressure reducer are recommended to improve tunnel performance.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 153-161
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  • 92
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    Report of the wind tunnel/flight correlation panel (1981)
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    Publication Date: 2011-08-18
    Description: Basic calibration of the tunnel prior to conducting any tests, the areas requiring wind tunnel/flight test correlation for validating the NTF, and recommendations for achieving validation of the NTF are discussed.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 249-262
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  • 93
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    High lift technology (1981)
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    Publication Date: 2011-08-18
    Description: The NASA Langley high lift technology program is reviewed and elements of the program which are considered Reynolds number sensitive are discussed. The Energy Efficient Transport (EET) and Supersonic Cruise Research (SCR) models proposed for high lift studies in the National Transonic Facility (NTF) are described. Recommendations regarding the NTF facility and test techniques are presented.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 197-213
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  • 94
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    Wall interference effects: Status review (1981)
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    Publication Date: 2011-08-18
    Description: The interference technology incorporated into the NTF design (hardware) and the emerging transonic wall interference assessment correction procedures (software) to be employed when the NTF becomes operational was reviewed. It is anticipated that the early experiments will provide data relevant to wall interference effects.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 123-241
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  • 95
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    Configuration aerodynamics (1981)
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    Publication Date: 2011-08-18
    Description: Static aerodynamic research related to aircraft configurations in their cruise or combat modes is discussed. Subsonic transport aircraft, transonic tactical aircraft, and slender wing aircraft are considered. The status and plans of Langley's NTF configuration research program are reviewed. Recommendations for near term configuration research are made.
    Keywords: AERODYNAMICS
    Type: High Reynolds Number Res. - 1980; p 217-234
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  • 96
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    Comments on Reynolds number effects and the role of NTF in the development of air vehicles (1981)
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    Publication Date: 2011-08-18
    Description: The National Transonic Facility (NTF) capability to match the full scale Reynolds numbers of all but the largest airplanes is discussed. Conversion factors to enable calculation of Sl-unit equivalents for all U.S. units are listed. Using data from several facilities, analytic methods, and flight test data, a competetive aircraft in the relatively low Reynolds number was developed. The NTF offers the capability to obtain data at full scale Reynolds numbers in the cruise condition for most of the products, and will be much closer than previous tunnels to full scale Reynolds number for the operating envelopes. It is primarily on the operating envelope that Reynolds number effects are most important and least predictable.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Research Center High Reynolds Number Res. - 1980; p 143-148
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  • 97
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    Narrow channel bandwidth receiver for VLBI (1981)
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    Publication Date: 2011-08-18
    Description: An introduction to the phase four receiver subsystem to be implemented into the DSN for VLBI applications is presented. The key design areas are discussed along with the design approach. Preliminary evaluation data indicate a feasible, straightforward design may be obtained.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 18-29
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  • 98
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    Radio astronomy (1981)
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    Publication Date: 2011-08-18
    Description: The activities of the Deep Space Network in support of Radio Astronomy Operations during April and May 1981 are reported. Work in progres in support of an experiment selected for use of the DSN by the Radio Astronomy Experiment Selection Panel, Twin Quasi-Stellar Object VLBI, is reported.
    Keywords: ASTRONOMY
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 1-9
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  • 99
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    Planetary radar (1981)
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    Publication Date: 2011-08-18
    Description: The radar astronomy activities supported by the Deep Space Network during the first quarter of 1981 are reported. The bodies observed include the asteroids Apollo and Toro, comet Bradfield, and the rings of Saturn.
    Keywords: ASTRONOMY
    Type: The Telecommun. and Data Acquisition Rept.; p 226
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  • 100
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    Capacity of a multimode direct detection optical communication channel (1981)
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    Publication Date: 2011-08-18
    Description: The capacity is derived under both peak and average signal power constraints and without a signal bandwidth constraint. A random telegraph wave type signalling scheme of Kabanov is known to achieve capacity provided enough signalling bandwidth is available. In the absence of received background noise, an optimally coded PPM system is shown to achieve capacity with greatly reduced bandwidth as compared to Kabanov signals.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 51-70
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