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  • Other Sources  (444)
  • ENERGY PRODUCTION AND CONVERSION  (241)
  • ASTRONOMY  (203)
  • 2020-2020
  • 1980-1984  (444)
  • 1982  (219)
  • 1980  (225)
  • 11
    Publication Date: 2011-08-18
    Description: A quantitative method for astrometrically detecting perturbations induced in a star's motion by the presence of a planetary object is described. A periodogram is defined, wherein signals observed from a star show exactly periodic variations, which can be extracted from observational data using purely statistical methods. A detection threshold is defined for the frequency of occurrence of some detectable signal, e.g., the Nyquist frequency. Possible effects of a stellar orbital eccentricity and multiple companions are discussed, noting that assumption of a circular orbit assures the spectral purity of the signal described. The periodogram technique was applied to 12 yr of astrometric data from the U.S. Naval Observatory for three stars with low mass stellar companions. Periodic perturbations were confirmed. A comparison of the accuracy of different astrometric systems shows that the detection accuracy of a system is determined by the measurement accuracy and the number of observations, although the detection efficiency can be maximized by minimizing the number of data points for the case when observational errors are proportional to the square root of the number of data points. It is suggested that a space-based astrometric telescope is best suited to take advantage of the method.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 263
    Format: text
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  • 12
    Publication Date: 2016-05-11
    Description: The solubility of sulfur dioxide in 50% (wt./wt.) sulfuric acid was evaluated by regular solution theory, and the results verified by experimental measurements in the temperature range of 25 C to 70 C at pressures of 60 to 200 PSIA. The percent (wt./wt.) of sulfur dioxide in 50% (wt./wt.) sulfuric acid is given by the equation %SO2 = 2.2350 + 0.0903P - 0.00026P 10 to the 2nd power with P in PSIA.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: MCC Associates, Inc. Proc. of the 6th Ann. Thermal and Chem. Storage Contractors' Rev. Meeting; p 52-56
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  • 13
    Publication Date: 2016-06-07
    Description: Bulk samples of Te-doped n-type GaAs were irradiated using 10 MeV to 24 MeV protons to fluences between 2 x 10 to the 11th power protons/sq cm and 2 x 10 to the 14th power protons/sq cm. Majority carrier electrical effects were measured using the vanderPauw techniques and it was observed that radiation damage was minimal at the 10 to the 11th power proton/sq cm fluence. For the higher fluences, carrier removal was proportional to Delta E/Delta x for the protons indicating ionization interactions between the protons and atoms. Thermal annealing was observed at 155 C.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Space Photovoltaic Res. and Technol.; p 265-275
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  • 14
    Publication Date: 2016-06-07
    Description: The solar powered system located near Willard, New Mexico, generates mechanical or electrical power at a capacity of 19 kW (25 HP). The solar collection system incorporates east/west tracking parabolic trough collectors with a total aperture area of 1275 sq m (13,720 sq ft). The hot oil type thermal energy storage is sufficient for approximately 20 hours of power system operation. The system utilizes a reaction type turbine in conjunction with an organic Rankine cycle engine. Total collector field efficiency reaches a maximum of 20 percent near the winter solstice and about 50 percent during the summer. During the month of July, 1979, the system pumped 60 percent of the 35,300 cu m (28.6 acre-feet) of water delivered. Operating efficiencies for the turbine component, organic Rankine cycle engine and the complete power system are respectively 65 to 75 percent, 12 to 15 percent and 5 to 6 percent. Significant maintenance time was expended on both the collector and power systems throughout the operational period.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: JPL Proc. of the First Semiann. Distributed Receiver Program Rev.; p 241-246
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  • 15
    Publication Date: 2016-06-07
    Description: Experimental data, together with supporting analysis, are presented on the power conversion performance and blade loading of large, horizontal-axis wind turbines tested at electric utility sites in the U.S. Four turbine rotor configurations, from 28 to 61 meters in diameter, and data from five test sites are included. Performance data are presented in the form of graphs of power and system efficiency versus free-stream wind speed. Deviations from theoretical performance are analyzed statistically. Power conversion efficiency averaged 0.34 for all tests combined, compared with 0.31 predicted. Round blade tips appeared to improve performance significantly. Cyclic blade loads were normalized to develop load factors which can be used in the design of rotors with rigid hubs.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Large Horizontal-Axis Wind Turbines; p 447-468
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  • 16
    Publication Date: 2016-06-07
    Description: Annealing of radiation damage was observed for the first time in VPE-grown, 2- by 2-cm, n+/p/p+ GaAs shallow homojunction solar cells. Electrical performance of several cells was determined as a function of 1-MeV electron fluence in the range of 10 to the 13th power to 10 to the 15th power e-/sq cm and as a function of thermal annealing time at various temperatures. Degradation of normalized power output after a fluence of 10 to the 15th power 1-MeV electrons/sq cm ranged from a low of 24 to 31 percent of initial maximum power. Normalized short circuit current degradation was limited to the range from 10 to 19 percent of preirradiated values. Thermal annealing was carried out in a flowing nitrogen gas ambient, with annealing temperatures spanning the range from 125 to 200 C. Substantial recovery of short circuit current was observed at temperatures as low as 175 C. In one case improvement by as much as 10 percent of the postirradiated value was observed. The key features of these cells are their extremely thin emitter layers (approxmately 0.05 micrometers), the absence of any Al sub xGd sub 1-x As passivating window layer, and their fabrication by vapor phase epitaxy.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: Space Photovoltaic Res. and Technol. 1982: High Efficiency, Radiation Damage, and Blanket Technol.; p 179-184
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  • 17
    Publication Date: 2019-06-28
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 240
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  • 18
    Publication Date: 2019-06-28
    Description: The low cost production of silicon by deposition of silicon from a hydrogen/chlorosilane mixture is described. Reactor design, reaction vessel support systems (physical support, power control and heaters, and temperature monitoring systems) and operation of the system are reviewed. Testing of four silicon deposition reactors is described, and test data and consequently derived data are given. An 18% conversion of trichlorosilane to silicon was achieved, but average conversion rates were lower than predicted due to incomplete removal of byproduct gases for recycling and silicon oxide/silicon polymer plugging of the gas outlet. Increasing the number of baffles inside the reaction vessel improved the conversion rate. Plans for further design and process improvements to correct the problems encountered are outlined.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: NASA-CR-164162 , DOE/JPL-955269-80/5 , JPL-9950-515 , QPR-5
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  • 19
    Publication Date: 2019-06-27
    Description: Observations of Cygnus X-2 using the Copernicus satellite have revealed a novel relationship between the spectral hardness and the intensity of this source in the 3-8 keV band. This behavior is very similar to that predicted for a spherically accreting nonmagnetic degenerate dwarf. The data, interpreted in terms of this model, determine solar mass, luminosity, and the distance for Cyg X-2; these parameters are at variance with the values derived from optical observations of the system. The implications of this discrepancy for the understanding of the source are examined.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 235
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  • 20
    Publication Date: 2019-06-27
    Description: Quasi-simultaneous observations of the BL Lacertae (Lac) objects MK 501 were performed for the first time at X-ray, ultraviolet, visible, infrared, and radio frequencies. The observed spectral slope from the X-ray to UV regions is positive and continuous, but that from the mid UV to visible light region becomes gradually flat and possibly turns down toward lower frequencies; the optical radio emission can not be accounted for by a single power law. Several theoretical models were considered for the emission mechanism. A quantitative comparison was performed with the synchrotron-self-Compton model; the total spectrum is found consistent with this model. The spectrum from visible light to X-ray is consistent with synchrotron radiation or with inverse-Compton scattering by a hot thermal cloud of electrons. The continuity of the spectral slope from X-ray to UV implied by the current data suggests that the previous estimates of the total luminosity of this BL Lac object is underestimated by a factor of about three or four.
    Keywords: ASTRONOMY
    Type: NASA-TM-81985
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