16,855 research outputs found

    A polarimeter for infrared astronomy

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    RESOURCE QUALITY, AGRICULTURAL PRODUCTIVITY, AND FOOD SECURITY

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    USDA's Economic Research Service estimates that about 33 percent of the developing world's people suffer from insufficient food intake. Growth in agricultural productivity is critical to improvements in food security. We will examine the impact of changes in acreage and fertilizer response on production in 67 study countries and review the implications for food security.Food Consumption/Nutrition/Food Safety, Productivity Analysis,

    Nonet Symmetry and Two-Body Decays of Charmed Mesons

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    The decay of charmed mesons into pseudoscalar (P) and vector (V) mesons is studied in the context of nonet symmetry. We have found that it is badly broken in the PP channels and in the P sector of the PV channels as expected from the non-ideal mixing of the \eta and the \eta'. In the VV channels, it is also found that nonet symmetry does not describe the data well. We have found that this discrepancy cannot be attributed entirely to SU(3) breaking at the usual level of 20--30%. At least one, or both, of nonet and SU(3) symmetry must be very badly broken. The possibility of resolving the problem in the future is also discussed.Comment: 9 pages, UTAPHY-HEP-

    A two-layer calculation for the initial interaction region of an unseparated supersonic turbulent boundary layer with a ramp

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    The interaction of an unseparated supersonic turbulent boundary layer with a compression corner produces an extremely rapid rise in pressure at the corner, followed by a more gradual increase to the final pressure. In this paper, the flow in the corner region is analyzed by an integral method with the objective of predicting the initial pressure rise. Comparisons with experimental pressure rise data are presented for cases covering supersonic and hypersonic flows of practical interest. Also presented are some calculations and comparisons of downstream pressure distributions obtained by using the predicted corner rise as the first point in an existing inviscid method

    The NBS: Processing/Microstructure/Property Relationships in 2024 Aluminum Alloy Plates

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    As received plates of 2024 aluminum alloy were examined. Topics covered include: solidification segregation studies; microsegregation and macrosegregation in laboratory and commercially cast ingots; C-curves and nondestructive evaluation; time-temperature precipitation diagrams and the relationships between mechanical properties and NDE measurements; transmission electron microscopy studies; the relationship between microstructure and properties; ultrasonic characterization; eddy-current conductivity characterization; the study of aging process by means of dynamic eddy current measurements; and Heat flow-property predictions, property degradations due to improve quench from the solution heat treatment temperature

    Interstitial gas and density-segregation in vertically-vibrated granular media

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    We report experimental studies of the effect of interstitial gas on mass-density-segregation in a vertically-vibrated mixture of equal-sized bronze and glass spheres. Sufficiently strong vibration in the presence of interstitial gas induces vertical segregation into sharply separated bronze and glass layers. We find that the segregated steady state (i.e., bronze or glass layer on top) is a sensitive function of gas pressure and viscosity, as well as vibration frequency and amplitude. In particular, we identify distinct regimes of behavior that characterize the change from bronze-on-top to glass-on-top steady-state.Comment: 4 pages, 5 figures, submitted to PRL; accepted in PRE as rapid communication, with revised text and reference
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