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  • 1
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    Confining hot spots in 3C 196 - Implications for QSO-companion galaxies (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: VLBI observations of the extremely compact hot spot in the northern radio lobe of the QSO 3C 196 reveal the angular size of its smallest substructure to be 0.065 arcsec x 0.045 arcsec or about 300 pc at the redshift distance. The morphology of the hot spot and its orientation relative to the more diffuse radio emission suggest that it is formed by an oblique interaction between the nuclear QSO jet and circum-QSO cloud. The inferred density in this cloud, together with its apparent size, imply that the cloud contains a galactic mass, greater than a billion solar masses of gas. The effect of the jet will be to hasten gravitational collapse of the cloud. If many QSOs such as 3C 196 are formed or found in gas-rich environments, the QSO radio phase may commonly stimulate the metamorphosis of circum-QSO gas to QSO-companion galaxies or it may play a significant part in catalyzing star formation in existing companions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 306; 107-109
    Format: text
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  • 2
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    Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Results are presented from finite element analysis of the Czochralski (CZ) and Liquid Encapsulated Czochralski (LEC) crystal growth processes based on a thermal-capillary model which governs the heat transfer in the system simultaneously with setting the shapes of the melt/solid interface, the melt and encapsulant menisci, and the radius of a steadily growing crystal. Calculations are performed for the small-scale growth of silicon (CZ) and gallium arsenide (LEC). The effects of melt volume and crucible position relative to the heater on the radius of the crystal and the shape of the melt/solid interface are predicted for the CZ system, and the importance of including an accurate representation of the melt meniscus for modeling the process is demonstrated. The additional effect of an encapsulant layer on heat transfer is treated for the LEC method for the cases of totally transparent and opaque encapsulant. The responses of these LEC prototype systems are examined for changes in pull rate and encapsulant volume.
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Crystal Growth (ISSN 0022-0248); 74; 605-624
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  • 3
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    Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth. II - Processing strategies (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The pseudosteady-state heat transfer model developed in a previous paper is augmented with constraints for constant crystal radius and melt/solid interface deflection. Combinations of growth rate, and crucible and bottom-heater temperatures are tested as processing parameters for satisfying the constrained thermal-capillary problem over a range of melt volumes corresponding to the sequence occuring during the batchwise Czochralski growth of a small-diameter silicon crystal. The applicability of each processing strategy is judged by the range of existence of the solution, in terms of melt volume and the values of the axial and radial temperature gradients in the crystal.
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Crystal Growth (ISSN 0022-0248); 75; 227-240
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  • 4
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    Thermal-capillary analysis of small-scale floating zones Steady-state calculations (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Galerkin finite element analysis of a thermal-capillary model of the floating zone crystal growth process is used to predict the dependence of molten zone shape on operating conditions for the growth of small silicon boules. The model accounts for conduction-dominated heat transport in the melt, feed rod and growing crystal and for radiation between these phases, the ambient and a heater. Surface tension acting on the shape of the melt/gas meniscus counteracts gravity to set the shape of the molten zone. The maximum diameter of the growing crystal is set by the dewetting of the melt from the feed rod when the crystal radius is large. Calculations with small Bond number show the increased zone lengths possible for growth in a microgravity environment. The sensitivity of the method to the shape and intensity of the applied heating distribution is demonstrated. The calculations are compared with experimental observations.
    Keywords: SOLID-STATE PHYSICS
    Type: Journal of Crystal Growth (ISSN 0022-0248); 75; 367-389
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  • 5
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    Fluid mechanics and mass transfer in melt crystal growth: Analysis of the floating zone and vertical Bridgman processes (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This research program focuses on analysis of the transport mechanisms in solidification processes, especially one of interest to the Microgravity Sciences and Applications Program of NASA. Research during the last year has focused on analysis of the dynamics of the floating zone process for growth of small-scale crystals, on studies of the effect of applied magnetic fields on convection and solute segregation in directional solidification, and on the dynamics of microscopic cell formation in two-dimensional solidification of binary alloys. Significant findings are given.
    Keywords: SOLID-STATE PHYSICS
    Type: The materials processing research base of the Materials Processing Center; p 27-48
    Format: application/pdf
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  • 6
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    Thermal-capillary model for Czochralski growth of semiconductor materials (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The success of efficiently calculating the temperature field, crystal radius, melt mensicus, and melt/solid interface in the Czochralski crystal growth system by full finite-element solution of the government thermal-capillary model is demonstrated. The model predicts realistic response to changes in pull rate, melt volume, and the thermal field. The experimentally observed phenomena of interface flipping, bumping, and the difficulty maintaining steady-state growth as the melt depth decreases are explained by model results. These calculations will form the basis for the first quantitative picture of Cz crystal growth. The accurate depiction of the melt meniscus is important in calculating the crystal radius and solidification interface. The sensitivity of the results to the equilibrium growth angle place doubt on less sophisticated attempts to model the process without inclusion of the meniscus. Quantitative comparison with experiments should be possible once more representation of the radiation and view factors in the thermal system and the crucible are included. Extensions of the model in these directions are underway.
    Keywords: SOLID-STATE PHYSICS
    Type: JPL Proceedings of the Flat-Plate Solar Array Project Workshop; p 195-214
    Format: application/pdf
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  • 7
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    Mathematical Modelling of High-speed Ribbbon Systems: a Case Study of Edge-defined Film-fed Growth (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: Finite element numerical analysis was used to solve the coupled problem of heat transfer and capillarity to describe low and high speed silicon sheet growth in meniscus defined systems. Heat transfer models which neglect the details of convective heat flow in the melt are used to establish operating limits for an EFG system in terms of the growth rate, die temperature and the static head acting on the meniscus. It is shown that convective heat transfer in the melt becomes important only at high growth rates or for materials with low thermal conductivities.
    Keywords: SOLID-STATE PHYSICS
    Type: JPL Proc. of the Flat-Plate Solar Array Proj. Res. Forum on the High-Speed Growth and Characterization of Crystals for Solar Cells; p 311-329
    Format: text
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  • 8
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    Energetic secondary electrons and the nonthermal galactic radio background - A probe of the magnetic field in interstellar clouds (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A previous analysis of the manifestations of charged-pion-decay secondary electrons in interstellar cloud material is extended to include those contributions to the Galactic radio and soft gamma-ray backgrounds that are directly attributable to energetic secondaries. The equilibrium distribution of secondary electrons in dense interstellar clouds is calculated, synchrotron emissivity from isolated interstellar clouds is examined, and it is shown how the value of the magnetic field in these clouds may be determined by observing the radio emission in their directions. The contribution that such clouds make to the integrated radio background is evaluated, and the Galactic distribution of bremsstrahlung gamma rays that arise from interactions of secondary electrons with thermal material in dense clouds is computed. The results indicate that a magnetic field of no more than 80 microgauss is characteristic of dense clouds and that the integrated synchrotron radiation from secondary electrons in interstellar clouds will contribute a significant fraction of the nonthermal brightness along the Galactic equator even if the mean cloud field is as low as 35 microgauss.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 221
    Format: text
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  • 9
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    Origin and evolution of the radio emission from immediate postoutburst supernovae (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Several models for the radio emission from immediate postoutburst supernovae are examined under the assumption that the expanding remnant consists of a homogeneously mixed distribution of relativistic particles, magnetic field, and thermal plasma. The evolutionary models are: (1) an adiabatic expansion model; (2) a model incorporating the existence of a central pulsar; and (3) variations on the first two models in which relativistic electrons are accelerated either instantaneously or over an extended period of time and in which ionization, bremsstrahlung, synchrotron, Compton, and expansion losses are explicitly included. The character of the radio emission expected from these models is quite dissimilar. Whereas in adiabatic expansion models the emission is expected to increase slowly and become most intense at high frequencies, in models involving a central pulsar the emission should increase rapidly with a maximum flux density that is the same at all frequencies. The theoretical evolution of the radio emission for each model is compared with observations of SN 1970g.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 220
    Format: text
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  • 10
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    Cosmological baryon-number domain structure from symmetry breaking in grand unified field theories (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: It is suggested that grand unified field theories with spontaneous symmetry breaking in the very early big bang can lead more naturally to a baryon-symmetric cosmology with a domain structure than to a totally baryon-asymmetric cosmology. The symmetry is broken in a randomized manner in causally independent domains, favoring neither a baryon nor an antibaryon excess on a universal scale. Arguments in favor of this cosmology and observational tests are discussed.
    Keywords: ASTROPHYSICS
    Type: Physical Review Letters; 43; July 23
    Format: text
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