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  • Chemical Engineering  (70)
  • ASTRONOMY  (60)
  • METEOROLOGY AND CLIMATOLOGY  (60)
  • ENERGY PRODUCTION AND CONVERSION
  • 1990-1994  (204)
  • 1980-1984
  • 1993  (204)
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Keywords
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  • 1990-1994  (204)
  • 1980-1984
Year
  • 1
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    Gamma radiation from blazar PKS 0537-441 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) observed high-energy gamma rays from PKS 0537-441 during observations in 1991 July-August. Upper limits from later EGRET observations suggest time variability.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 410; 1; p. 87-89.
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    NASA TECHNICAL REPORTS
  • 2
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    Results from the energetic gamma-ray experiment telescope (EGRET) on the Compton Observatory (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) covers the high energy gamma ray energy range, approximately 30 MeV to 30 GeV, with a sensitivity considerably greater than earlier high energy gamma-ray satellites. Thus far, 4 pulsars have been detected and their properties measured, including in 3 cases the energy spectrum as a function of phase. The details of the galactic plane are being mapped and a spectra of the center region has been obtained in good agreement with that expected from cosmic ray interactions. The Magellanic clouds have been examined with the Large Magellanic Cloud (LMC) having been detected at a level consistent with it having a cosmic ray density compatible with quasi-stable equilibrium. Sixteen Active Galactic Nuclei (AGN's) have been seen thus far with a high degree of certainty including 12 quasars and 4 BL Lac objects, but no Seyferts. Time variation has been detected in some of these AGN's
    Keywords: ASTRONOMY
    Type: Advances in Space Research (ISSN 0273-1177); 13; 12; p. (12)637-(12)646
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    NASA TECHNICAL REPORTS
  • 3
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    Comparison of HRDI wind measurements with radar and rocket observations (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Wind fields in the mesosphere and lower thermosphere are obtained with the High Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) by observing the Doppler shifts of emission lines in the O2 Atmospheric band. The validity of the measured winds depends on an accurate knowledge of the positions on the detector of the observed lines in the absence of a wind-induced Doppler shift. These positions have been determined to an accuracy of approximately 5 m/s from the comparison of winds measured by HRDI with those obtained by MF radars. Excellent agreement is found between HRDI measured winds and winds observed with radars and rockets. In addition, the sensitivity of HRDI to migrating tides and other large scale waves is demonstrated.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 12; p. 1259-1262.
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  • 4
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    Direct 75 milliarcsecond images from the Multiple Mirror Telescope with adaptive optics (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report results from an adaptive optics system designed to provide imaging at the diffraction limit of resolution in the near-infrared at the Multiple Mirror Telescope (MMT). For the present experiment, the aperture consisted of five of the six primary mirrors of the MMT, operating as a coherently phased array. The largest components of the atmospherically induced wave-front aberration are the fluctuations in mean phase between the segments. These errors were derived in real time from the Fourier transform of short-exposure stellar images at 2.2 microns and corrected at an image of the telescope pupil with piston motion from a segmented adaptive mirror. At a correction rate of 43 Hz, this level of adaptive control resulted in an integrated image with a clear diffraction-limited component of 0.075 arcsec FWHM. This stabilized component is present directly in the light arriving at the detector and is not the result of postprocessing. We discuss future improvements to our adaptive wave-front control and its application to astronomical observations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 402; 2; p. L81-L84.
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  • 5
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    EGRET observations of 3C 273 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The quasar 3C 273 was detected by COS-B in the 1970's. EGRET observations of this sky region in June and October 1991 revealed a flux from 3C 273 lower than that measured by COS-B. The flux observed by EGRET in the June period is approximately 3 x 10 exp -7/sq cm s for energies greater than 100 MeV. During the October observation it appears to be even lower. For the first observation a preliminary spectrum which has a photon index of 2.4 has been derived.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 97; 1; p. 101-103.
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  • 6
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    Twenty-two emission-line AGNs from the HEAO-1 X-ray survey (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report 22 emission-line AGN as bright, hard X-ray sources. All of them appear to be new classifications with the exception of one peculiar IRAS source which is a known quasar and has no published spectrum. This sample exhibits a rich diversity in optical spectral properties and luminosities, ranging from a powerful broad-absorption-line quasar to a weak nucleus embedded in a nearby NGC galaxy. Two cases confer X-ray luminosities in excess of 10 exp 47 erg/s. However, there is a degree of uncertainty in the X-ray identification for the AGN fainter than V about 16.5. Optically, several AGN exhibit very strong Fe II emission. One Seyfert galaxy with substantial radio flux is an exception to the common association of strong Fe II emission and radio-quiet AGN. The previously recognized IRAS quasar shows extreme velocities in the profiles of the forbidden lines; the 0 III pair is broadened to the point that the lines are blended. Several of these AGN show evidence of intrinsic obscuration, illustrating the effectiveness of hard X-ray surveys in locating AGN through high column density.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 105; 6; p. 2079-2089, 2363-2
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  • 7
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    Observations of the Crab pulsar and nebula by the EGRET telescope on the Compton Gamma-Ray Observatory (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Crab pulsar and nebula were observed three times in 1991 April to June by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO): April 23 to May 7, May 16 to 30, and June 8 to 15. The results of analysis of the gamma-ray emission in the energy range from 50 MeV to more than 10 GeV are reported. The observed gamma-ray light curve exhibits two peaks separated in phase by 0.40 +/- 0.02, consistent with previous observations. The total pulsed emission from the Crab pulsar is found to be well represented by a power-law spectrum, softer than the spectrum measured by COS B (Clear et al., 1987). The interpulse emission has a harder spectrum than either of the pulses. The evidence for pulsed emission above 5 GeV in the EGRET data is not conclusive. Unpulsed emission in the energy range 50 MeV to 5 GeV was detected, with an indication of a hardening of the unpulsed spectrum above about 1 GeV. There was a significant change in the light curve over the 2 months of these observations, although the shape of the spectrum remained constant.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 409; 2; p. 697-704.
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  • 8
    Electronic Resource
    Electronic Resource
    Continuous electrochemically modulated complexation separations process (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 867-875 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A continuous electrochemically modulated complexation (EMC) process was devised to extract and concentrate a class of heterocyclic nitrogen compounds. This design is composed of flow-through electrolysis cells for redox modulation and cycling of the complexing agent and hollow-fiber membrane modules for phase contacting. The extent of both extraction and concentration was found to depend mainly on the magnitude of the distribution coefficients for both steps. Experimental results and modeling of this continuous EMC process are reported, as well as potential applications for this process for other separations.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390515
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  • 9
    Electronic Resource
    Electronic Resource
    Steps in CH4 oxidation on Pt and Rh surfaces: High-temperature reactor simulations (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1164-1177 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The direct oxidation of CH4 to H2 and CO in O2 and in air at high temperatures over alumina foam monoliths coated with high loadings of Pt and Rh has been simulated using a 19-elementary-step model of adsorption, desorption and surface reaction steps with reaction parameters from the literature or from fits to previous experiments. The surface reaction model for Pt is in good agreement with previously reported low-pressure(0.1 to 1 torr) reactor measurements of CH4 oxidation rates at temperatures from 600 to 1,500 K and of OH radical desorption during CH4 oxidation at 1,300 to 1,600 K over polycrystalline Pt foils. The model predictions for both catalysts are also consistent with product selectivities observed over monolithic catalysts in an atmospheric-pressure laboratory-scale reactor, and the differences between Pt and Rh can be explained by comparing individual reaction steps on these surfaces. Because of the good agreement between the model and both low-and atmospheric-pressure reactor simulations, a complete energy diagram for methane oxidation at low coverages is proposed. The model results show that under CH4rich conditions at high temperatures, H2 and CO are primary products of the direct oxidation of methane via a pyrolysis mechanism.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390708
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  • 10
    Electronic Resource
    Electronic Resource
    Modeling fountain flow and filling front shape in reaction injection molding (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 716-720 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A numerical model of the reaction injection molding process was developed to test front shape and flow approximations employed in previous models. The model was two-dimensional and simulated the flow, reaction, and heat transfer in the typically long axial dimension and the typically small thickness dimension of a mold. The filling front shape and the velocity profiles in the filling fluid were determined by numerical solution of the momentum equation with the appropriate stress boundary conditions using the method of Patankar (1980). The predicted temperature and conversion results agreed with calculations assuming that the front was flat perpendicular to the flow and that a parabolic velocity profile existed behind the fountain flow region at the front. Thus, simple assumptions about front shape and velocity in the thin dimension of a reaction injection mold can be employed without significant loss of accuracy in modeling reaction injection molding.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760331108
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