20,263 research outputs found

    Rapid billet loader aids extrusion of refractory metals

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    A combination gravity and manually powered rapid billet loader reduces the time required for transferring hot metal billets from a heating furnace to an extrusion press. Positioned between the furnace and extrusion press, this loader is a simple slide-delivery device

    An analysis of the Venera 8 measurements

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    Analysis of the Venera 8 measurements yielded equatorial morning terminator horizontal and vertical winds which are similar to the winds obtained from the Venera 7 measurements. The lower boundary of the horizontal retrograde 4-day wind is defined by a 50-60% decrease in wind speed in the vicinity of 44 km and there exists a retrograde wind plateau of 15 to 40 m/s winds extending from 40 km down to the vicinity of 18 km where the winds decrease rapidly to the order of 0.1 m/s near the surface. Up drafts of 2 to 5 m/s exist in the vicinity of 20 to 30 km and are apparently associated with a slightly super adiabatic lapse rate. The temperature lapse-rate, surface radius, surface topography, and atmospheric structure are discussed

    On the reality of the Venus winds

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    The Venera measurements of wind speed along with the Mariner measurements of lower-region of strong turbulence are evidence for a wide band of variable high speed retrograde horizontal winds which girdle Venus at the equator. In one interpretation of the Mariner 10 UV photographs, the 20km region above the top of the visible cloud is characterized by variable high-speed retrograde horizontal winds which orbit Venus with an average period of 4 earth days, and by many features indicating vertical convection. This suggests that the Venera-Mariner band of winds at 45km extends to the top of the UV cloud and beyond, and that the upper-region of strong turbulence detected by the Mariners may result from vertical convection currents carried along by high speed horizontal winds. In another interpretation, the predominate motions are attributed to wavelike disturbances with a 4-day period. For this case the upper-region of strong turbulence may be due in large part to vertical wind-shear resulting from a rapid decrease in wind speed within a relatively short distance about the Venera-Mariner band of high speed winds

    An analysis of the Venus measurements

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    Plots of the Mariner 5 and Venera 4, 5, and 6 pressure vs temperature show that the Venera profiles are essentially congruent with the Mariner 5 day and night profiles, but are displaced 28 percent higher in pressure. Data suggest a variability in the atmospheric water vapor content in the region from 30 to 50 km. The Venera 7 measurements are interpreted as evidence for updrafts, down-drafts, horizontal wind layers, and nonaqueous precipitation. The previously observed band of retrograde winds which circle the equator with an average speed of 110 m/s is found to extend downward to the one atmosphere level at the equatorial morning terminator. The possibility of a low altitude equator-to-pole circulation with warm gas rising at the poles is inferred. Venera 7 temperature data used with radar topography and microwaves interferometer measurements suggest that the variation of surface temperature with altitude in a band about the equator is less than 5 K/km. The available data are used to calculate a model of the structure of the Venus atmosphere for the first 75 km above the equatorial region

    Optical Dielectric Functions of III-V Semiconductors in Wurtzite Phase

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    Optical properties of semiconductors can exhibit strong polarization dependence due to crystalline anisotropy. A number of recent experiments have shown that the photoluminescence intensity in free standing nanowires is polarization dependent. One contribution to this effect is the anisotropy of the dielectric function due to the fact that most nanowires crystalize in the wurtzite form. While little is known experimentally about the band structures wurtzite phase III-V semiconductors, we have previously predicted the bulk band structure of nine III-V semiconductors in wurtzite phase.Here, we predict the frequency dependent dielectric functions for nine non-Nitride wurtzite phase III-V semiconductors (AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs and InSb). Their complex dielectric functions are calculated in the dipole approximation by evaluating the momentum matrix elements on a dense grid of special k-points using empirical pseudopotential wave functions. Corrections to the momentum matrix elements accounting for the missing core states are made using a scaling factor which is determined by using the optical sum rules on the calculated dielectric functions for the zincblende polytypes. The dielectric function is calculated for polarizations perpendicular and parallel to the c-axis of the crystal

    Sulfur-house operation /

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    C38

    Unpaid Britain: wage default in the British labour market

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