INDIRECT UTILITY FUNCTIONS AND TESTABLE CONDITIONS

We develop testable hypotheses for utility maximization given risk averse producers based on a general specification of the utility function. This is a direct expansion of the model posed by Pope (1978). Empirical tests using production data with a translog specification indicate that utility maximization does not always hold.Research Methods/ Statistical Methods,

Structural tailoring of counter rotation propfans

The STAT program was designed for the optimization of single rotation, tractor propfan designs. New propfan designs, however, generally consist of two counter rotating propfan rotors. STAT is constructed to contain two levels of analysis. An interior loop, consisting of accurate, efficient approximate analyses, is used to perform the primary propfan optimization. Once an optimum design has been obtained, a series of refined analyses are conducted. These analyses, while too computer time expensive for the optimization loop, are of sufficient accuracy to validate the optimized design. Should the design prove to be unacceptable, provisions are made for recalibration of the approximate analyses, for subsequent reoptimization

Decomposing the Persistence of International Equity Flows

The portfolio flows of institutional investors are widely known to be persistent. What is less well known, however, is the source of this persistence. One possibility is the ?informed trading hypothesis?: that persistence arises from autocorrelated trades of investors who believe they have information about value and who face an imperfectly liquid market. Another possibility is that there are asynchroneities with respect to investment decisions across funds, across investments, or both. These asynchroneities could be due to wealth effects (across investments for a single fund), investor herding (across funds for a single investment), or generalized contagion (across funds and across investments). We use daily data on institutional flows into 21 developed countries by 471 funds to measure and decompose aggregate flow persistence. We find that the informed trading hypothesis explains about 75% of total persistence, and that the remaining amount is attributable entirely to cross-fund own-country persistence. In other words, we find statistically and economically significant flow asynchroneities across funds investing in the same country. There are no meaningful asynchroneities across countries, either within a given fund, or across funds. The cross-fund flow lags we identify might result from different fund investment processes, or from some funds mimicking others? decisions. We reject the hypothesis that wealth effects explain persistence.

Trajectory optimization and guidance for an aerospace plane

The first step in the approach to developing guidance laws for a horizontal take-off, air breathing single-stage-to-orbit vehicle is to characterize the minimum-fuel ascent trajectories. The capability to generate constrained, minimum fuel ascent trajectories for a single-stage-to-orbit vehicle was developed. A key component of this capability is the general purpose trajectory optimization program OTIS. The pre-production version, OTIS 0.96 was installed and run on a Convex C-1. A propulsion model was developed covering the entire flight envelope of a single-stage-to-orbit vehicle. Three separate propulsion modes, corresponding to an after burning turbojet, a ramjet and a scramjet, are used in the air breathing propulsion phase. The Generic Hypersonic Aerodynamic Model Example aerodynamic model of a hypersonic air breathing single-stage-to-orbit vehicle was obtained and implemented. Preliminary results pertaining to the effects of variations in acceleration constraints, available thrust level and fuel specific impulse on the shape of the minimum-fuel ascent trajectories were obtained. The results show that, if the air breathing engines are sized for acceleration to orbital velocity, it is the acceleration constraint rather than the dynamic pressure constraint that is active during ascent

An Integrated Approach for Evaluating Students' Achievement of Clinical Objectives

During the clinical phase of undergraduate medical education (UME) students are often geographically dispersed and assigned to preceptors throughout the community. Monitoring, documenting, and evaluating their clinical experiences and achievement of clinical objectives in this venue becomes a challenge, especially for large UME programs. The purpose of this manuscript is to discuss a method for developing and implementing a school-wide evaluation system for the clinical phase of UME. This type of evaluation system links students' clinical experiential data with the objectives of a clerkship, using technological advances, such as the Personal Digital Assistant (PDA), Internet, and intranet. Clerkship directors are provided real-time reports on student's progress toward achieving clerkship objectives and are able to monitor the clinical activities of the clerkship. Students on the other hand, will be empowered to take more control of their educational experiences by monitoring their own progress

Grain boundary partitioning of Ar and He

An experimental procedure has been developed that permits measurement of the partitioning of Ar and He between crystal interiors and the intergranular medium (ITM) that surrounds them in synthetic melt-free polycrystalline diopside aggregates. ^(37)Ar and ^(4)He are introduced into the samples via neutron irradiation. As samples are crystallized under sub-solidus conditions from a pure diopside glass in a piston cylinder apparatus, noble gases diffusively equilibrate between the evolving crystal and intergranular reservoirs. After equilibration, ITM Ar and He is distinguished from that incorporated within the crystals by means of step heating analysis. An apparent equilibrium state (i.e., constant partitioning) is reached after about 20 h in the 1450 °C experiments. Data for longer durations show a systematic trend of decreasing ITM Ar (and He) with decreasing grain boundary (GB) interfacial area as would be predicted for partitioning controlled by the network of planar grain boundaries (as opposed to ITM gases distributed in discrete micro-bubbles or melt). These data yield values of GB-area-normalized partitioning, K¯^(Ar)_(ITM), with units of (Ar/m^3 of solid)/(Ar/m^2 of GB) of 6.8 x 10^3 – 2.4 x 104 m^(-1). Combined petrographic microscope, SEM, and limited TEM observation showed no evidence that a residual glass phase or grain boundary micro-bubbles dominated the ITM, though they may represent minor components. If a nominal GB thickness (δ) is assumed, and if the density of crystals and the grain boundaries are assumed equal, then a true grain boundary partition coefficient (K^(Ar)_(GB) = X^(Ar)_(crystals)/X^(Ar)_(GB) may be determined. For reasonable values of δ, K^(Ar)_(GB) is at least an order of magnitude lower than the Ar partition coefficient between diopside and melt. Helium partitioning data provide a less robust constraint with K¯^(He)_(ITM) between 4 x 10^3 and 4 x 10^4 cm^(-1), similar to the Ar partitioning data. These data suggest that an ITM consisting of nominally melt free, bubble free, tight grain boundaries can constitute a significant but not infinite reservoir, and therefore bulk transport pathway, for noble gases in fine grained portions of the crust and mantle where aqueous or melt fluids are non-wetting and of very low abundance (i.e., <0.1% fluid). Heterogeneities in grain size within dry equilibrated systems will correspond to significant differences in bulk rock noble gas content

Verification of TG-61 dose for synchrotron-produced monochromatic x-ray beams using fluence-normalized MCNP5 calculations

Ion chamber dosimetry is being used to calibrate dose for cell irradiations designed to investigate photoactivated Auger electron therapy at the Louisiana State University CAMD synchrotron facility. This study performed a dosimetry intercomparison for synchrotron-produced monochromatic x-ray beams at 25 and 35 keV. Ion chamber depth-dose measurements in a PMMA phantom were compared with the product of MCNP5 Monte Carlo calculations of dose per fluence and measured incident fluence. Monochromatic beams of 25 and 35 keV were generated on the tomography beamline at CAMD. A cylindrical, air-equivalent ion chamber was used to measure the ionization created in a 10x10x10-cm3 PMMA phantom for depths from 0.6 to 7.7 cm. The American Association of Physicists in Medicine TG-61 protocol was applied to convert measured ionization into dose. Photon fluence was determined using a NaI detector to make scattering measurements of the beam from a thin polyethylene target at angles 30 degrees to 60 degrees. Differential Compton and Rayleigh scattering cross sections obtained from xraylib, an ANSI C library for x-ray-matter interactions, were applied to derive the incident fluence. MCNP5 simulations of the irradiation geometry provided the dose deposition per photon fluence as a function of depth in the phantom. At 25 keV the fluence-normalized MCNP5 dose overestimated the ion-chamber measured dose by an average of 7.2+/-3.0% to 2.1+/-3.0% for PMMA depths from 0.6 to 7.7 cm, respectively. At 35 keV the fluence-normalized MCNP5 dose underestimated the ion-chamber measured dose by an average of 1.0+/-3.4% to 2.5+/-3.4%, respectively. These results showed that TG-61 ion chamber dosimetry, used to calibrate dose output for cell irradiations, agreed with fluence-normalized MCNP5 calculations to within approximately 7% and 3% at 25 and 35 keV, respectively.Comment: 22 pages, 5 figure

Comptonization and the Spectra of Accretion-Powered X-Ray Pulsars

Accretion-powered X-ray pulsars are among the most luminous X-ray sources in the Galaxy. However, despite decades of theoretical and observational work since their discovery, no satisfactory model for the formation of the observed X-ray spectra has emerged. In this paper, we report on a self-consistent calculation of the spectrum emerging from a pulsar accretion column that includes an explicit treatment of the bulk and thermal Comptonization occurring in the radiation-dominated shocks that form in the accretion flows. Using a rigorous eigenfunction expansion method, we obtain a closed-form expression for the Green's function describing the upscattering of monochromatic radiation injected into the column. The Green's function is convolved with bremsstrahlung, cyclotron, and blackbody source terms to calculate the emergent photon spectrum. We show that energization of photons in the shock naturally produces an X-ray spectrum with a relatively flat continuum and a high-energy exponential cutoff. Finally, we demonstrate that our model yields good agreement with the spectra of the bright pulsar Her X-1 and the low luminosity pulsar X Per.Comment: 6 Pages, 2 Figures, To appear in "The Multicoloured Landscape of Compact Objects and their Explosive Progenitors" (Cefalu, Sicily, June 2006). Eds. L. Burderi et al. (New York: AIP

Particle Dynamics in Damped Nonlinear Quadrupole Ion Traps

We examine the motions of particles in quadrupole ion traps as a function of damping and trapping forces, including cases where nonlinear damping or nonlinearities in the electric field geometry play significant roles. In the absence of nonlinearities, particles are either damped to the trap center or ejected, while their addition brings about a rich spectrum of stable closed particle trajectories. In three-dimensional (3D) quadrupole traps, the extended orbits are typically confined to the trap axis, and for this case we present a 1D analysis of the relevant equation of motion. We follow this with an analysis of 2D quadrupole traps that frequently show diamond-shaped closed orbits. For both the 1D and 2D cases we present experimental observations of the calculated trajectories in microparticle ion traps. We also report the discovery of a new collective behavior in damped 2D microparticle ion traps, where particles spontaneously assemble into a remarkable knot of overlapping, corotating diamond orbits, self-stabilized by air currents arising from the particle motion

Artificial reef plan for sport fish enhancement

Hard bottom substrate provides habitat for a multitude of marine fishes, invertebrates, and plants - particularly giant kelp - which are of direct and indirect importance to sport and commercial fisheries. These reefs also enhance esthetic uses of the marine environment. This document sets forth the plan of the California Department of Fish and Game (CDFG) for the construction of artificial reefs. The plan includes an outline for defining the purpose of reef construction, gathering information pertinent to reef placement and design, selecting a reef site, preparing a project narrative, obtaining permits and approvals for reef construction, developing a general permit for reef construction, and establishing a system of fisheries habitat enhancement areas. Procedures for constructing and mapping reefs are discussed and an outline for conducting short- and long-term biological studies of reef communities is presented. Since 1958, CDFG has constructed 31 reefs off southern California. Thirteen of the largest and most frequently used reefs were mapped using hydroacoustic and radio-locating techniques. Maps of these reefs were published in a 1989 CDFG booklet entitled "A Guide to the Artificial Reefs of Southern California". Since 1978, seven developmental reefs have been constructed: 1) Pendleton Artificial Reef (1980) - San Diego County; 2) Pitas Point Artificial Reef (1984) Ventura County; 3) Marina Del Rey Artificial Reef (1985) - Los Angeles County; 4)Oceanside Artificial Reef (1987) - San Diego County; 5) Pacific Beach Artificial Reef (1987) - San Diego County; 6) Santa Monica Artificial Reef (1987) - Los Angeles County; and 7) Topanga Artificial Reef (1987) - Los Angeles County. These reefs were built to improve habitat for sport fishes and associated fauna and to evaluate the enhancement characteristics of reefs related to geographic location, depth, height, rock size, and reef spacing. Short-term studies revealed that all reefs have provided shelter, food, nesting, and nursery areas for important fish species and have increased sport fishing opportunities. Furthermore, giant kelp has been observed on all reefs built at suitable depths. More extensive long-term studies are planned in 1998 when reef communities will be at successional equilibrium. These studies will provide additional information concerning the long-term potential of artificial reefs as habitat for sport fish, invertebrates, and plants. The plan discusses different types of man-made reefs, including developmental, production, and fishing access reefs, and provides examples of each. It documents CDFG policy regarding the use of reefs as mitigation for impacts on rocky habitat and kelp. It also documents the laws authorizing CDFG to administer reef construction and studies in California. The activities involved in designing, permitting, constructing, and evaluating Pendleton Artificial Reef are provided as an example of the reef building and study process. A list of reefs is provided to document the location, depth, area, materials, and funding sources for all reefs constructed and/or augmented in California. (85pp.