28,226 research outputs found

    Electronic and total energy properties of ternary and quaternary semiconductor compounds, alloys, and superlattices: Theoretical study of Cu/graphite bonding

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    The goals of the research were to provide a fundamental science basis for why the bonding of Cu to graphite is weak, to critically evaluate the previous analysis of the wetting studies with particular regard to the values used for the surface energies of Cu and graphite, and to make recommendations for future experiments or other studies which could advance the understanding and solution of this technological problem. First principles electronic structure calculations were used to study the problem. These are based on density functional theory in the local density approximation and the use of the linear muffin-tin orbital band structure method. Calculations were performed for graphite monolayers, single crystal graphite with the hexagonal AB stacking, bulk Cu, Cu(111) surface, and Cu/graphite superlattices. The study is limited to the basal plane of graphite because this is the graphite plane exposed to Cu and graphite surface energies and combined with the measured contact angles to evaluate the experimental adhesion energy

    Solar Irradiance Observed from PVO and Inferred Solar Rotation

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    Solar irradiance in the extreme ultraviolet flux (EUV) has been monitored for 11 years by the Pioneer Venus Orbiter (PVO). Since the experiment moves around the Sun with the orbital rate of Venus rather than that of Earth, the measurement gives us a second viewing location from which to begin unravelling which irradiance variations are intrinsic to the Sun, and which are merely rotational modulations whose periods depend on the motion of the observer. Researchers confirm an earlier detection, made with only 8.6 years of data, that the EUV irradiance is modulated by rotation rates of two families of global oscillation modes. One family is assumed to be r-modes occupying the convective envelope and sharing its rotation, while the other family (g-modes) lies in the radiative interior which as a slower rotation. Measured power in r-modes of low angular harmonic number indicates that the Sun's envelope rotated about 0.7 percent faster near the last solar maximum (1979 thru 1982) than it did during the next rise to maximum (1986 to 1989). No change was seen in the g-mode family of lines, as would be expected from the much greater rotational inertia of the radiative interior

    Fifth district banks' return on assets: highest in decade

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    Reduced provisions for loan losses in 1988 boosted bank profits in the Fifth District and nationwide. Profit ratios also may have been influenced somewhat by subsidiary banks’ payment of management fees to their holding companies.Federal Reserve District, 5th ; Bank profits

    Results of TC-1 boost pump icing tests in the space power facility

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    A series of tests were conducted in the space power facility to investigate the failure of the Centaur oxidizer boost pump during the Titan/Centaur proof flight February 11, 1974. The three basic objectives of the tests were: (1) demonstrate if an evaporative freezing type failure mechanism could have prevented the pump from operating, (2) determine if steam from the exhaust of one of the attitude control engine could have entered a pump seal cavity and caused the failure, and (3) obtain data on the heating effects of the exhaust plume from a hydrogen peroxide attitude control engine

    A review of bank performance in the Fifth district, 1986

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    Gains from sales of securities and lower loan loss previsions helped bring higher profits to large Fifth District commercial banks in 1986. At the same time, small- and medium-sized bank profits fell slightly in the District from the previous year. As in the past few years, Fifth District banks outperformed banks in the rest of the United States. For the benefit of those readers curious about the problems connected with measuring bank performance, the authors discuss the most common bank profitability measures and the consequences of relying on accounting rather than market data.Banks and banking ; Bank profits ; Federal Reserve District, 5th
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