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  • 04. Solid Earth::04.08. Volcanology::04.08.01. Gases  (25)
  • Astronomy
  • J24
  • 2015-2019  (8)
  • 2010-2014  (26)
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Keywords
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Year
  • 1
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    Enhancement of the Accretion of Jupiters Core by a Voluminous Low-Mass Envelope (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: We present calculations of the early stages of the formation of Jupiter via core nucleated accretion and gas capture. The core begins as a seed body of about 350 kilometers in radius and orbits in a swarm of planetesimals whose initial radii range from 15 meters to 100 kilometers. We follow the evolution of the swarm by accounting for growth and fragmentation, viscous and gravitational stirring, and for drag-induced migration and velocity damping. Gas capture by the core substantially enhances the cross-section of the planet for accretion of small planetesimals. The dust opacity within the atmosphere surrounding the planetary core is computed self-consistently, accounting for coagulation and sedimentation of dust particles released in the envelope as passing planetesimals are ablated. The calculation is carried out at an orbital semi-major axis of 5.2 AU and an initial solids' surface density of 10/g/cm^2 at that distance. The results give a core mass of 7 Earth masses and an envelope mass of approximately 0.1 Earth mass after 500,000 years, at which point the envelope growth rate surpasses that of the core. The same calculation without the envelope gives a core mass of only 4 Earth masses.
    Keywords: Astronomy
    Type: ARC-E-DAA-TN10762 , NCTS# 16972-14; Annual Meeting, Division for Planetary Science; Oct 06, 2013 - Oct 11, 2013; Denver, CO; United States
    Format: application/pdf
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  • 2
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    DP Capabilities: LWA Current and Future Users Meeting (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astronomy
    Type: LWA Current and Future Users Meeting; May 12, 2011 - May 13, 2011; Albuquerque, NM; United States
    Format: text
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  • 3
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    A FPGA-based Fast Transient Search Platform for the Australian Square Kilometre Array Pathfinder (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astronomy
    Type: National Radio Science Meeting (USNC-URSI); Jan 05, 2011 - Jan 09, 2011; Boulder, CO; United States
    Format: text
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  • 4
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    Photoevaporation and the Dispersal of Disks (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Disk disperse in a few million years, before which they must form planets. Photoevaporation and viscosity are mainly responsible for disk dispersal. EUV, FUV and X-rays have all been suggested as photoevaporation agents, disk evolutionary scenarios and predicted mass loss rates in each case differ. Stellar mass and radiation field, disk properties, magnitude of viscosity, and dust evolution all play significant roles in determining the evolution of the disk and its lifetime. Observational diagnostics of photoevaperative flows include [Nell] and perhaps [OI]. These are at present inconclusive and better diagnostics are needed.
    Keywords: Astronomy
    Type: ARC-E-DAA-TN17213 , The Disk in Relation to The Formation of Planets And Their Protoatmospheres; Aug 25, 2014 - Aug 29, 2014; Beijing; China
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  • 5
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    Signal Processing for a Lunar Array: Minimizing Power Consumption (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Motivation for the study is: (1) Lunar Radio Array for low frequency, high redshift Dark Ages/Epoch of Reionization observations (z =6-50, f=30-200 MHz) (2) High precision cosmological measurements of 21 cm H I line fluctuations (3) Probe universe before first star formation and provide information about the Intergalactic Medium and evolution of large scale structures (5) Does the current cosmological model accurately describe the Universe before reionization? Lunar Radio Array is for (1) Radio interferometer based on the far side of the moon (1a) Necessary for precision measurements, (1b) Shielding from earth-based and solar RFI (12) No permanent ionosphere, (2) Minimum collecting area of approximately 1 square km and brightness sensitivity 10 mK (3)Several technologies must be developed before deployment The power needed to process signals from a large array of nonsteerable elements is not prohibitive, even for the Moon, and even in current technology. Two different concepts have been proposed: (1) Dark Ages Radio Interferometer (DALI) (2)( Lunar Array for Radio Cosmology (LARC)
    Keywords: Astronomy
    Type: National Radio Science Meeting; Jan 05, 2011; Boulder, CO; United States
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  • 6
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    The Most Powerful Flaring Activity from the NLSy1 PMN J0948+0022 (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma rays, PMN J0948+0022 (z equal to 0.5846). A gamma-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 plus or minus 31)10(exp 8) ph cm (exp 2) s (exp 1) on 2013 January 1, corresponding to an apparent isotropic luminosity of approximately 1.510)exp 48) erg s(exp 1). The gamma-ray flaring period triggered Swift and VERITAS observations in addition to radio and optical monitoring by OVRO, MOJAVE, and CRTS. A strong flare was observed in optical, UV, and X- rays on 2012 December 30, quasi-simultaneously to the gamma-ray flare, reaching a record flux for this source from optical to gamma rays. VERITAS observations at very high energy (E greater than 100 GeV) during 2013 January 6-17 resulted in an upper limit of F(sub greater than 0.2 TeV) less than 4.0 10(exp 12) ph cm(exp 2) s(exp 1). We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.
    Keywords: Astronomy
    Type: GSFC-E-DAA-TN24339 , Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711) (e-ISSN 1365-2966); 446; 3; 2456-2467
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  • 7
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    A Low-Power Correlator ASIC for Arrays with Many Antennas (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report the design of a new application-specific integrated circuit (ASIC) for use in radio telescope correlators. It supports the construction of correlators for an arbitrarily large number of signals. The ASIC uses an intrinsically low-power architecture along with design techniques and a process that together result in unprecedentedly low power consumption. The design is flexible in that it can support telescopes with almost any number of antennas N. It is intended for use in an "FX" correlator, where a uniform filter bank breaks each signal into separate frequency channels prior to correlation.
    Keywords: Astronomy
    Type: United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM); Jan 06, 2016 - Jan 09, 2016; Boulder, CO; United States
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  • 8
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    An Integrated Circuit for Radio Astronomy Correlators Supporting Large Arrays of Antennas (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-08-26
    Description: Radio telescopes that employ arrays of many antennas are in operation, and ever larger ones are being designed and proposed. Signals from the antennas are combined by cross-correlation. While the cost of most components of the telescope is proportional to the number of antennas N, the cost and power consumption of cross-correlationare proportional to N2 and dominate at sufficiently large N. Here we report the design of an integrated circuit (IC) that performs digital cross-correlations for arbitrarily many antennas in a power-efficient way. It uses an intrinsically low-power architecture in which the movement of data between devices is minimized. In a large system, each IC performs correlations for all pairs of antennas but for a portion of the telescope's bandwidth (the so-called "FX" structure). In our design, the correlations are performed in an array of 4096 complex multiply-accumulate (CMAC) units. This is sufficient to perform all correlations in parallel for 64 signals (N=32 antennas with 2 opposite-polarization signals per antenna). When N is larger, the input data are buffered in an on-chipmemory and the CMACs are re-used as many times as needed to compute all correlations. The design has been synthesized and simulated so as to obtain accurate estimates of the IC's size and power consumption. It isintended for fabrication in a 32 nm silicon-on-insulator process, where it will require less than 12mm2 of silicon area and achieve an energy efficiency of 1.76 to 3.3 pJ per CMAC operation, depending on the number of antennas. Operation has been analyzed in detail up to N = 4096. The system-level energy efficiency, including board-levelI/O, power supplies, and controls, is expected to be 5 to 7 pJ per CMAC operation. Existing correlators for the JVLA (N = 32) and ALMA (N = 64) telescopes achieve about 5000 pJ and 1000 pJ respectively usingapplication-specific ICs in older technologies. To our knowledge, the largest-N existing correlator is LEDA atN = 256; it uses GPUs built in 28 nm technology and achieves about 1000 pJ. Correlators being designed for the SKA telescopes (N = 128 and N = 512) using FPGAs in 16nm technology are predicted to achieve about 100 pJ.
    Keywords: Astronomy
    Type: Journal of Astronomical Instrumentation; 5; 2; 1650002
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  • 9
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    Low-Power Architectures for Large Radio Astronomy Correlators (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The architecture of a cross-correlator for a synthesis radio telescope with N greater than 1000 antennas is studied with the objective of minimizing power consumption. It is found that the optimum architecture minimizes memory operations, and this implies preference for a matrix structure over a pipeline structure and avoiding the use of memory banks as accumulation registers when sharing multiply-accumulators among baselines. A straw-man design for N = 2000 and bandwidth of 1 GHz, based on ASICs fabricated in a 90 nm CMOS process, is presented. The cross-correlator proper (excluding per-antenna processing) is estimated to consume less than 35 kW.
    Keywords: Astronomy
    Type: 2011 URSI General Assembly and Scientific Symposium; Aug 13, 2011 - Aug 20, 2011; Istanbul; Turkey
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  • 10
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    The Ancient Gates to Hell and Their Relevance to Geogenic CO2 (2014)
    Academic Press
    Details
    Publication Date: 2017-04-04
    Description: No abstract
    Description: Published
    Description: 92-117
    Description: 4V. Vulcani e ambiente
    Description: restricted
    Keywords: geogenic gases ; gas hazard ; geomithology ; underworld ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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