9,035 research outputs found
Theologies in dialogue: the place of religion in the 21st century university
Paper presented at the conf Faith, freedom and the academy: the idea of the university in the 21st century, Univ of Prince Edward Island, O 1-3 2004
Experiment measurement of Alford's force in axial-flow turbomachinery
Results of experimental measurements made on a small high speed, axial flow test apparatus are presented to verify the existence of Alford's force (that circumferential variation of blade-tip clearances in axial-flow turbomachinery will produce cross-coupled (normal to the eccentricity) aerodynamic forces on the rotor) and to investigate the validity of his mathematical prediction model
Experimental results concerning centrifugal impeller excitations
The effect of working fluid on the dynamics of an impeller with radial vanes was investigated. The impeller was supported vertically from a very flexible quill shaft in order to produce a low critical speed, and to allow the fluid dynamic effects on the impeller to predominate. The shaft was supported from ball bearings, so that there was no possibility of oil whip from fluid film bearings as a destabilizing influence. The impeller was run both in the atmosphere, and submerged in working fluids contained in a cylindrical housing, open at the top. Variable speed was obtained with a dc gearmotor drive unit. The speed was measured with a proximity probe pulse tachometer and electronic digital counter
Identifying Identical Distributed Lag Structures by the Use of Prior SumConstraints
This paper derives an estimation procedure which, when the same distributed lag appears twice in an equation to be estimated by least-squares regression, identifies all of the relevant coefficients and lag weights and also constrains the two sets of individual lag weights to be identical. The procedure for solving this identification-constraint problem involves prior imposition of a restriction on the lag weight sum -- i.e., it is necessary to impose the sum restriction before estimating the equation. A further useful feature of the derived procedure is that it facilitates conveniently imposing the sum restriction on all of the weights in a distributed lag even if the leading weight is independent of a polynomial restriction imposed on the others.
Aspects of Investor Behavior Under Risk
The three sections of this paper support three related conclusions. First, asset demands with the familiar properties of wealth homogeneity and linearity in expected returns follow as close approximations from expected utility maximizing behavior under the assumptions of constant relative risk aversion and joint normally distributed asset returns. Second, although such asset demands exhibit a symmetric coefficient matrix with respect to the relevant vector of expected asset returns, symmetry is not a general property, and the available empirical evidence warrants rejecting it for both institutional and individual investors in the United States. Finally, in a manner analogous to the finite maximum exhibited by quadratic utility, a broad class of mean-variance utility functions also exhibits a form of wealth satiation which necessarily restricts it range of applicability.
Temporal Variation in the Interest-Rate Response to Money Announcements
A number of studies find significant temporal variation in the interest-rate response to money announcement surprises. An unresolved question, however, is whether the response changes immediately as different policy regimes are adopted, or whether the change is gradual reflecting the establishment of Federal Reserve credibility. This paper conducts tests that allow for both discrete shifts in the interest-rate response to money announcements and a gradual evolution in this response. The evidence is consistent with the hypothesis that temporal variation in the interest-rate response is limited to discrete shifts in October 1979, October 1982, arid February 1984.
Experimental measurement of the dynamic pressure distribution in a squeeze film bearing damper executing circular centered orbits
A review of previous experimental measurements of squeeze film damper (SFD) forces is given. Measurements by the authors of SFD pressure fields and force coefficients, for circular centered orbits with epsilon = 0.5, are described and compared with computer predictions. For Reynolds numbers over the range 2-6, the effect of fluid inertia on the pressure fields and forces is found to be significant
Effects of fluid inertia and turbulence on force coefficients for squeeze film dampers
The effects of fluid inertia and turbulence on the force coefficients of squeeze film dampers are investigated analytically. Both the convective and the temporal terms are included in the analysis of inertia effects. The analysis of turbulence is based on friction coefficients currently found in the literature for Poiseuille flow. The effect of fluid inertia on the magnitude of the radial direct inertia coefficient (i.e., to produce an apparent added mass at small eccentricity ratios, due to the temporal terms) is found to be completely reversed at large eccentricity ratios. The reversal is due entirely to the inclusion of the convective inertia terms in the analysis. Turbulence is found to produce a large effect on the direct damping coefficient at high eccentricity ratios. For the long or sealed squeeze film damper at high eccentricity ratios, the damping prediction with turbulence included is an order of magnitude higher than the laminar solution
A Note on the Derivation of Linear Homogeneous Asset Demand Functions
Among the numerous familiar sets of specific assumptions sufficient to derive mean-variance portfolio behavior from more general expected utility maximization in continuous time, the assumptions of constant relative risk aversion and joint normally distributed asset return assessments are also jointly sufficient to derive asset demand functions with the two desirable (and frequently simply assumed) properties of wealth homogeneity and linearity in expected returns. In addition, in discrete time constant relative risk aversion and joint normally distributed asset return assessments are sufficient to yield linear homogeneous asset demands as approximations if the time unit is small.
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