58,118 research outputs found

    Wind tunnel wall interference (January 1980 - May 1988): A selected, annotated bibliography

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    This selected bibliography lists 423 entries on the subject of wall interference during testing in wind tunnels. It is the third in a series of bibliographies on the subject. The first, NASA TM-87639, August 1986, is concerned with the reduction of wall interference by the use of adaptive walls. The second, NASA TP-89066, December 1986, is on wall interference in V/STOL and high lift testing. This, the third in the series, covers the wall interference literature published during the period January 1980 through May 1988, generally excluding those topics covered in the first two parts

    Simulating study of the interaction between the propulsion and flight control systems of a subsonic lift fan VTOL

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    The possibility of interactions between the propulsion and flight control systems of a three-fan subsonic VTOL aircraft was studied using nonreal time simulation. Time histories of critical internal engine parameters were obtained and possible deleterious effects of engine dynamics on flight control were identified and analyzed. No deleterious effects, with the exception of the effects of the fan actuator deadband, were found. A method of alleviating these effects through feedback of the actuator output to the flight controller was developed

    Aggregate returns to scale: why measurement is imprecise

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    The extent to which there are aggregate returns to scale at the level of aggregate production has important implications both for the types of shocks generating business cycles and for optimal policy. However, prior attempts to measure the extent of these returns using instrumental variable techniques have yielded quite imprecise estimates. In this article, we show that the production shocks implied by a range of returns to scale that encompasses both large increasing returns and large decreasing returns are almost identical. This makes clear that there is a fundamental reason for the imprecision of prior estimates and casts doubt on our ability to generate more precise estimatesBusiness cycles

    FINANCIAL CHARACTERISTICS OF NORTH DAKOTA FARMS 1992-1994

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    End-of-year financial data from 700 farms enrolled in North Dakota Farm Business Management Education Program for the years 1992 to 1994 are analyzed according to 16 financial standards. All median profitability measures, median term debt coverage, term debt and capital margin, and median net farm income as a percent of gross revenue are lower in 1994 than in 1993. The median for all 16 financial measures deteriorated for 1994 in the south central and west regions due to lower livestock profitability. Financial performance of the north central region improved each of the three years.Agricultural Finance,

    Shrinking money and monetary business cycles

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    In the postwar period velocity has risen so sharply in the U.S. that the ratio of money to nominal output has fallen by a factor of three. We analyze the implications of shrinking money for the real effects of a monetary shock in two classes of equilibrium monetary business cycle models: limited participation (liquidity) models and predetermined (sticky) price models. We show that the liquidity model predicts that a rise in velocity leads to a substantial reduction in the real effects of a monetary shock. In sharp contrast, we show that the real effects of a monetary shock in the sticky price model are largely invariant to changes in velocity. We provide evidence that suggests that the real effects of monetary shocks have fallen over the postwar period.Business cycles

    The Great Depression in the United States from a neoclassical perspective

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    Can neoclassical theory account for the Great Depression in the United States—both the downturn in output between 1929 and 1933 and the recovery between 1934 and 1939? Yes and no. Given the large real and monetary shocks to the U.S. economy during 1929–33, neoclassical theory does predict a long, deep downturn. However, theory predicts a much different recovery from this downturn than actually occurred. Given the period’s sharp increases in total factor productivity and the money supply and the elimination of deflation and bank failures, theory predicts an extremely rapid recovery that returns output to trend around 1936. In sharp contrast, real output remained between 25 and 30 percent below trend through the late 1930s. We conclude that a new shock is needed to account for the Depression’s weak recovery. A likely culprit is New Deal policies toward monopoly and the distribution of income.Depressions

    Operations research investigations of satellite power stations

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    A systems model reflecting the design concepts of Satellite Power Stations (SPS) was developed. The model is of sufficient scope to include the interrelationships of the following major design parameters: the transportation to and between orbits; assembly of the SPS; and maintenance of the SPS. The systems model is composed of a set of equations that are nonlinear with respect to the system parameters and decision variables. The model determines a figure of merit from which alternative concepts concerning transportation, assembly, and maintenance of satellite power stations are studied. A hybrid optimization model was developed to optimize the system's decision variables. The optimization model consists of a random search procedure and the optimal-steepest descent method. A FORTRAN computer program was developed to enable the user to optimize nonlinear functions using the model. Specifically, the computer program was used to optimize Satellite Power Station system components

    Valuation equilibria with clubs

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    This paper considers model worlds in which there is a continuum of individuals who form finite-sized associations to undertake joint activities. We show how, through a suitable choice of commodity space, restrictions on the composition of feasible groups can be incorporated into the specification of the consumption and production sets of the economy. We also show that if there are a finite number of types, then the classical results from the competitive analysis of convex finite-agent economies can be reinterpreted to apply.Consumption (Economics)
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