11,926 research outputs found
Luminary 1B DAP preflight performance evaluation
Preflight analysis of LUMINARY 1B DAP simulation and performance testing for Apollo Mission H
PARTICIPATION DECISIONS, ANGLER WELFARE, AND THE REGIONAL ECONOMIC IMPACT OF SPORTFISHING
We link a stochastic binary choice model of individual decisions to participate in the marine sport fisheries in Cook Inlet, Alaska, with a simulation- based sample enumeration procedure for aggregating estimates of individual angler welfare and a regionally adjusted zip code-level input-output model of regional economic activity. The result is a behaviorally based model for predicting changes in angler welfare and regional economic activity occasioned by changes in the demand for sportfishing that arise from changes in trip costs or the expected number, size, or mix of species caught. The advantages of this approach are that: changes in angler participation are determined by variables that are observable, predictable, or subject to management control; participation reflects declining marginal utility, and substitution and complementary effects across trip attributes; estimates of changes in aggregate angler welfare and changes in regional economic impacts are derived from changes in individual participation probabilities.Resource /Energy Economics and Policy,
Uranus evolution models with simple thermal boundary layers
The strikingly low luminosity of Uranus (Teff ~ Teq) constitutes a
long-standing challenge to our understanding of Ice Giant planets. Here we
present the first Uranus structure and evolution models that are constructed to
agree with both the observed low luminosity and the gravity field data. Our
models make use of modern ab initio equations of state at high pressures for
the icy components water, methane, and ammonia. Proceeding step by step, we
confirm that adiabatic models yield cooling times that are too long, even when
uncertainties in the ice:rock ratio (I:R) are taken into account. We then argue
that the transition between the ice/rock-rich interior and the H/He-rich outer
envelope should be stably stratified. Therefore, we introduce a simple thermal
boundary and adjust it to reproduce the low luminosity. Due to this thermal
boundary, the deep interior of the Uranus models are up to 2--3 warmer than
adiabatic models, necessitating the presence of rocks in the deep interior with
a possible I:R of solar. Finally, we allow for an equilibrium
evolution (Teff ~ Teq) that begun prior to the present day, which would
therefore no longer require the current era to be a "special time" in Uranus'
evolution. In this scenario, the thermal boundary leads to more rapid cooling
of the outer envelope. When Teff ~ Teq is reached, a shallow, subadiabatic zone
in the atmosphere begins to develop. Its depth is adjusted to meet the
luminosity constraint. This work provides a simple foundation for future Ice
Giant structure and evolution models, that can be improved by properly treating
the heat and particle fluxes in the diffusive zones.Comment: 13 pages, Accepted to Icaru
Level and Witt groups of real enriques surfaces
The Witt group of a real Enriques surface having real points is computed purely in terms of the topology of the real part. For a real Enriques surface without real points the level of the function field is shown to be 2, and the Witt group is computed in this case as well
Scalar Representation and Conjugation of Set-Valued Functions
To a function with values in the power set of a pre-ordered, separated
locally convex space a family of scalarizations is given which completely
characterizes the original function. A concept of a Legendre-Fenchel conjugate
for set-valued functions is introduced and identified with the conjugates of
the scalarizations. Using this conjugate, weak and strong duality results are
proven.Comment: arXiv admin note: substantial text overlap with arXiv:1012.435
Optimization of Single-Sided Charge-Sharing Strip Detectors
Simulation of the charge sharing properties of single-sided CZT strip detectors with small anode pads are presented. The effect of initial event size, carrier repulsion, diffusion, drift, trapping and detrapping are considered. These simulations indicate that such a detector with a 150 µm pitch will provide good charge sharing between neighboring pads. This is supported by a comparison of simulations and measurements for a similar detector with a coarser pitch of 225 µm that could not provide sufficient sharing. The performance of such a detector used as a gamma-ray imager is discussed
Single-sided CZT strip detectors
We report progress in the study of thick CZT strip detectors for 3-D imaging and spectroscopy and discuss two approaches to device design. Unlike double-sided strip detectors, these devices feature both row and column contacts implemented on the anode surface. This electron-only approach circumvents problems associated with poor hole transport in CZT that normally limit the thickness and energy range of double-sided strip detectors. The work includes laboratory and simulation studies aimed at developing compact, efficient, detector modules for 0.05 to 1 MeV gamma radiation measurements while minimizing the number and complexity of the electronic readout channels. These devices can achieve similar performance to pixel detectors for both 3-D imaging and spectroscopy. The low channel count approach can significantly reduce the complexity and power requirements of the readout electronics. This is particularly important in applications requiring large area detector arrays. We show two single-sided strip detector concepts. One, previously reported, features rows established with collecting contacts and columns with noncollecting contacts. Another, introduced here, operates on a charge sharing principle and establishes both rows and columns with collecting contacts on the anode surface. In previous work using the earlier strip detector concept we reported simulations and measurements of energy and spatial resolution for prototype 5- and 10-mm-thick CZT detectors. We now present the results of detection efficiency and uniformity measurements conducted on 5-mm-thick detectors using a specific configuration of the front-end electronics and event trigger. We discuss the importance of the detector fabrication processes when implementing this approach
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