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  • 1
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    Capacity and interference in a PCS system (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: In order to increase the capacity of a Personal Communication Service (PCS) system, the PCS system environment needs to be understood. The PCS system environment is briefly described in this paper. Because the frequency reuse concept is used to increase the capacity of PCS, the cochannel cells created cause cochannel interference. There are two approaches to reduce cochannel interference. One is the microcell approach (within the existing system) and the other is the reduction of cochannel cell separation approach (developing a new system). In-building communications using PCS systems has been addressed. Also, the Intelligent Network (IN) is described to show its importance. The cellular system has great potential to be the future PCS system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL, Proceedings of the Workshop on Advanced Network and Technology Concepts for Mobile, Micro, and Personal Communications; p 197-206
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  • 2
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    Crystallization and characterization of Y2O3-SiO2 glasses (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Glasses in the yttria-silica system with 20 to 40 mol pct Y2O3 were subjected to recrystallization studies after melting at 1900 to 2100 C in W crucibles in 1 and 50 atm N2. The TEM and XRD results obtained indicate the presence of the delta, gamma, gamma prime, and beta-Y2Si2O7 crystalline phases, depending on melting and quenching conditions. Heat treatment in air at 1100 to 1600 C increased the amount of crystallization, and led to the formation of Y2SiO5, cristabalite, and polymorphs of Y2Si2O7. Also investigated were the effects of 5 and 10 wt pct zirconia additions.
    Keywords: SOLID-STATE PHYSICS
    Type: Ohio State Univ., Crystallization of the GlassyGrain Boundary Phase in Silicon Nitride Ceramics; 18 p
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  • 3
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    Microstructural changes in Beta-silicon nitride grains upon crystallizing the grain-boundary glass (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Crystallizing the grain boundary glass of a liquid phase sintered Si3N4 ceramic for 2 h or less at 1500 C led to formation of gamma Y2Si2O7. After 5 h at 1500 C, the gamma Y2Si2O7 had transformed to beta Y2Si2O7 with a concurrent dramatic increase in dislocation density within beta Si3N4 grains. Reasons for the increased dislocation density is discussed. Annealing for 20 h at 1500 C reduced dislocation densities to the levels found in as-sintered materials.
    Keywords: SOLID-STATE PHYSICS
    Type: Crystallization of the Glassy Grain Boundary Phase in Silicon Nitride Ceramics; 12 p
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  • 4
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    Performance and Calibration of H2RG Detectors and SIDECAR ASICs for the RATIR Camera (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Reionization And Transient Infra,.Red (RATIR) camera has been built for rapid Gamma,.Ray Burst (GRE) followup and will provide simultaneous optical and infrared photometric capabilities. The infrared portion of this camera incorporates two Teledyne HgCdTe HAWAII-2RG detectors, controlled by Teledyne's SIDECAR ASICs. While other ground-based systems have used the SIDECAR before, this system also utilizes Teledyne's JADE2 interface card and IDE development environment. Together, this setup comprises Teledyne's Development Kit, which is a bundled solution that can be efficiently integrated into future ground-based systems. In this presentation, we characterize the system's read noise, dark current, and conversion gain.
    Keywords: Instrumentation and Photography
    Type: GSFC.CPR.00394.2012 , 15632-12 SPIE Astronomical Telescopes and Instrumentation Conference; Jul 01, 2012 - Jul 06, 2012; Amsterdam; Netherlands
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  • 5
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    Merger of a Neutron Star with a Newtonian Black Hole (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Newtonian smooth particle hydro simulations are presented of the merger of a 1.4 solar mass neutron star with a black hole of equal mass. The initial state of the system is modeled with a stiff polytrope orbiting a point mass. Dynamical instability sets in when the orbital separation is equal to about three stellar radii. The ensuing mass transfer occurs on the dynamical timescale. No accretion torus is formed. At the end of the computation a corona of large extent shrouds an apparently stable binary system of a 0.25 solar mass star orbiting a 2.3 solar mass black hole.
    Keywords: Astrophysics
    Type: NASA/CR-95-207166 , NAS 1.26:207166 , ACTA Astronomica; 45; 705-723
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  • 6
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    The Type IIb Supernova 2013df and its Cool Supergiant Progenitor (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We have obtained early-time photometry and spectroscopy of supernova (SN) 2013df in NGC 4414. The SN is clearly of Type II b, with notable similarities to SN 1993J. From its luminosity at secondary maximum light, it appears that less Ni-56 (is approximately less than 0.06M) was synthesized in the SN 2013df explosion than was the case for the SNe II b 1993J, 2008ax, and 2011dh. Based on a comparison of the light curves, the SN 2013df progenitor must have been more extended in radius prior to explosion than the progenitor of SN 1993J. The total extinction for SN 2013dfis estimated to be A(sub V) = 0.30 mag. The metallicity at the SN location is likely to be solar. We have conducted Hubble Space Telescope(HST) Target of Opportunity observations of the SN with the Wide Field Camera 3, and from a precise comparison of these new observations to archival HST observations of the host galaxy obtained 14 yr prior to explosion, we have identified the progenitor of SN 2013df to be a yellow supergiant, somewhat hotter than a red supergiant progenitor for a normal Type II-Plateau SN. From its observed spectral energy distribution, assuming that the light is dominated by one star, the progenitor had effective temperature T(sub eff) = 4250+/-100 K and a bolometric luminosity L(sub bol) =10(exp 4.94+/-0.06) Solar Luminosity. This leads to an effective radius Reff = 545+/-65 Solar Radius. The star likely had an initial mass in the range of 13-17Solar Mass; however, if it was a member of an interacting binary system, detailed modeling of the system is required to estimate this mass more accurately. The progenitor star of SN 2013df appears to have been relatively similar to the progenitor of SN 1993J.
    Keywords: Solar Physics
    Type: GSFC-E-DAA-TN22121 , The Astronomical Journal; 147; 2; 37
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  • 7
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    Microstructural changes in beta-silicon nitride grains upon crystallizing the grain-boundary glass (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Crystallizing the grain-boundary glass of a liquid-phase-sintered Si3N4 ceramic for 2 h or less at 1500 C led to formation of delta-Y2Si2O7. After 5 h at 1500 C, the delta-Y2Si2O7 had transformed to beta-Y2Si2O7 with a concurrent dramatic increase in dislocation density within beta-Si3N4 grains. Reasons for the increased dislocation density are discussed. Annealing for 20 h at 1500 C reduced dislocation densities to the levels found in as-sintered material.
    Keywords: NONMETALLIC MATERIALS
    Type: American Ceramic Society, Journal (ISSN 0002-7820); 72; 1931-193
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  • 8
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    Bulk Current Injection Testing of Close Proximity Cable Current Return, 1kHz to 1 MHz (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents the results of an experiment examining the percentage of current that returns on adjacent wires or through a surrounding cable shield rather than through a shared conducting chassis. Simulation and measurement data are compared from 1 kHz 1 MHz for seven common cable configurations. The phenomenon is important to understand, because minimizing the return current path is vital in developing systems with low radiated emissions.
    Keywords: Electronics and Electrical Engineering
    Type: NF1676L-10049 , 2010 Asia-Pacific Symposium on Electromagnetic Compatibility; Apr 12, 2010 - Apr 16, 2010; Beijing; China
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  • 9
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    DDOTI: the Deca-Degree Optical Transient Imager (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: DDOTI (Deca-Degree Optical Transient Imager) will be a wide-field robotic imager consisting of six 28-centimeter telescopes with prime focus CCDs (Charge-Coupled Devices) mounted on a common equatorial mount. Each telescope will have a field of view of 12 degrees squared, will have 2 arcsec pixels, and will reach a 10 sigma limiting magnitude in 60 seconds of r (redshift) equal to 18.7 in dark time and r (redshift) equal to 18.0 in bright time. The set of six will provide aninstantaneous field of view of about 72 degrees squared. DDOTI uses commercial components almost entirely. The first DDOTI willbe installed at the Observatorio Astronmico Nacional in Sierra San Pedro Martir, Baja California, Mexico in early 2017. The main science goals of DDOTI are the localization of the optical transients associated with GRBs (Gamma Ray Bursts) detected by the GBM (Gamma Ray Burst Monitor) instrument on the Fermi satellite and with gravitational-wave transients. DDOTI will also be used for studies of AGN (Active Galactic Nuclei) and YSO (Young Stellar Object) variability and to determine the occurrence of hot Jupiters. The principal advantage of DDOTI compared to other similar projects is cost: a single DDOTI installation costs only about US $500,000. This makes it possible to contemplate a global network of DDOTI installations. Such geographic diversity would give earlier access and a higher localization rate.We are actively exploring this option.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN41808 , Proceedings of SPIE 9910, Observatory Operations: Strategies, Processes, and Systems; Jun 26, 2016; Edinburgh; United Kingdom|Proceedings of SPIE 9910, Observatory Operations: Strategies, Processes, and Systems VI, ; 9910; 99100G
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