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  • 21
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    Energy sources for Triton's geyser-like plumes (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Four geyser-like plumes were discovered near Triton's south pole in areas now in permanent sunlight. Because Triton's southern hemisphere is nearing a maximum summer solstice, insolation as a driver or a trigger for Triton's geyser-like plumes is an attractive hypothesis. Trapping of solar radiation in a translucent, low-conductivity surface layer (in a solid-state greenhouse), which is subsequently released in the form of latent heat of sublimation, could provide the required energy. Both the classical solid-state greenhouse consisting of exponentially absorbed insolation in a gray, translucent layer of solid nitrogen, and the 'super' greenhouse consisting of a relatively transparent solid-nitrogen layer over an opaque, absorbing layer are plausible candidates. Geothermal heat may also play a part if assisted by the added energy input of seasonal cycles of insolation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 250; 431-435
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  • 22
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    Triton's geyser-like plumes - Discovery and basic characterization (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: One model for the mechanism driving the plumes of the four active geyser-like eruptions observed by Voyager 2 on Triton is a heating up of nitrogen ice in a subsurface greenhouse environment, where nitrogen gas pressurized by solar heating explosively vents to the surface carrying clouds of ice and dark particles into the atmosphere. A temperature increase of less than 4 K above the ambient surface value of 38 + or - 3 K suffices to drive the plumes to 8-km altitude. Each eruption may last a year or more, over the course of which 0.1 cu km of ice is sublimed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 250; 410-415
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  • 23
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    Creeping flow of a conducting fluid past axisymmetric bodies in the presence of an aligned magnetic field (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The use of strong magnetic fields for the control of particle settling in metallic systems is investigated by altering the fluid mechanics in the melt. The fluid mechanism of particle settling is analyzed for the motion around single, axisymmetric particles in the limit of creeping flow for a fluid with a large electrical conductivity. The drag is found to increase proportionately to the intensity of the magnetic field or the Hartmann number Ha. The flowfield forms boundary layers, which thin out with increasing Ha, along the surfaces parallel to the flow. For axisymmetric bodies, the boundary layer separates as the poles of the surface are approached and encloses regions of almost stagnant fluid. These regions spread upstream and downstream along the body with increasing Ha, thereby trapping the particle in a column of stagnant fluid.
    Keywords: MATERIALS PROCESSING
    Type: Physics of Fluids A (ISSN 0899-8213); 2; 2230-223
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  • 24
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    Quadratic resonance in the three-dimensional oscillations of inviscid drops with surface tension (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The moderate-amplitude, three-dimensional oscillations of an inviscid drop are described in terms of spherical harmonics. Specific oscillation modes are resonantly coupled by quadratic nonlinearities caused by inertia, capillarity, and drop deformation. The equations describing the interactions of these modes are derived from the variational principle for the appropriate Lagrangian by expressing the modal amplitudes to be functions of a slow time scale and by preaveraging the Lagrangian over the time scale of the primary oscillations. Stochastic motions are predicted for nonaxisymmetric deformations starting from most initial conditions, even those arbitrarily close to the axisymmetric shapes. The stochasticity is characterized by a redistribution of the energy contained in the initial deformation over all the degrees of freedom of the interacting modes.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 29; 2788-279
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  • 25
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    Confining hot spots in 3C 196 - Implications for QSO-companion galaxies (1986)
    In:  Other Sources
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    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
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  • 26
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    Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth (1986)
    In:  Other Sources
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    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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  • 27
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    Convection and mass-transport in laser-induced chemical vapor deposition (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Gas flow and energy and species transport in laser-induced chemical vapor deposition (LICVD) of amorphous silicon films by silane pyrolysis are analyzed by finite element analysis of a two-dimensional model for the process. Spatial nonuniformity of the deposited film is shown to result from diffusion controlled transport of products between the beam and substrate. Deposition profiles are affected by buoyancy-driven convection only at increased gas pressures. Horizontal orientation of the reactor with respect to gravity is optimal because the stagnation-like flow, that results adjacent to the substrate, enhances mixing, and smoothes the film profile.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Electrochemical Society, Journal (ISSN 0013-4651); 135; 697-706
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  • 28
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    The global forest ecosystem as viewed by ERS-1, SIR-C and EOS (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A program is presented to perform coordinated global experiments designed to use the unique features of synthetic aperture radar (SAR) sensors such as the ones on ERS-1, SIR-C and EOS to characterize the physical nature of forest stands as input to global ecosystem and climatology models. Details about the objectives, program and expected results are presented.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 29
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    Convection and bulk transport (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Progress in the theoretical understanding of transport phenomena for materials processing systems in a microgravity environment is assessed. Fluid experiments and processing in space may be performed without containers. Processes that are secondary on the earth may become significant in space, e.g., the natural oscillation of a fluid. Results are summarized from experiments on oscillatory behavior, the effects of electrical charge, and nonaxisymmetric disturbances in suspended drops in a microgravity environment.
    Keywords: MATERIALS PROCESSING
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  • 30
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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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