5,602 research outputs found
Effects of low energy proton, electron, and simultaneously combined proton and electron environments in silicon and GaAs solar cells
Degradation of silicon and GaAs solar cells due to exposures to low energy proton and electron environments and annealing data for these cells are discussed. Degradation of silicon cells in simultaneously combined electron and low energy proton environments and previous experimental work is summarized and evaluated. The deficiencies in current solar array damage prediction techniques indicated by these data and the relevance of these deficiencies to specific missions such as intermediate altitude orbits and orbital transfer vehicles using solar electric propulsion systems are considered
On the logical structure of Bell theorems without inequalities
Bell theorems show how to experimentally falsify local realism. Conclusive
falsification is highly desirable as it would provide support for the most
profoundly counterintuitive feature of quantum theory - nonlocality. Despite
the preponderance of evidence for quantum mechanics, practical limits on
detector efficiency and the difficulty of coordinating space-like separated
measurements have provided loopholes for a classical worldview; these loopholes
have never been simultaneously closed. A number of new experiments have
recently been proposed to close both loopholes at once. We show some of these
novel designs fail in the most basic way, by not ruling out local hidden
variable models, and we provide an explicit classical model to demonstrate
this. They share a common flaw, which reveals a basic misunderstanding of how
nonlocality proofs work. Given the time and resources now being devoted to such
experiments, theoretical clarity is essential. Our explanation is presented in
terms of simple logic and should serve to correct misconceptions and avoid
future mistakes. We also show a nonlocality proof involving four participants
which has interesting theoretical properties.Comment: 8 pages, text clarified, explicit LHV model provided for flawed
nonlocality tes
Radioisotope thermal photovoltaic application of the GaSb solar cell
An examination of a RTVP (radioisotopic thermophotovoltaic) conceptual design has shown a high potential for power densities well above those achievable with radioisotopic thermoelectric generator (RTG) systems. An efficiency of 14.4 percent and system specific power of 9.25 watts/kg were predicted for a system with sixteen GPHS (general purpose heat source) sources operating at 1100 C. The models also showed a 500 watt system power by the strontium-90 isotope at 1200 C at an efficiency of 17.0 percent and a system specific power of 11.8 watts/kg. The key to this level of performance is a high-quality photovoltaic cell with narrow bandgap and a reflective rear contact. Recent work at Boeing on GaSb cells and transparent back GaAs cells indicate that such a cell is well within reach
Class of Einstein--Maxwell Dilatons
Three different classes of static solutions of the Einstein--Maxwell
equations non--minimally coupled to a dilaton field are presented. The
solutions are given in general in terms of two arbitrary harmonic functions and
involve among others an arbitrary parameter which determines their
applicability as charged black holes, dilaton black holes or strings. Most of
the known solutions are contained as special cases and can be non--trivially
generalized in different ways.Comment: Published in Physical Review D, R310 (1995
Interference and complementarity for two-photon hybrid entangled states
In this work we generate two-photon hybrid entangled states (HES), where the
polarization of one photon is entangled with the transverse spatial degree of
freedom of the second photon. The photon pair is created by parametric
down-conversion in a polarization-entangled state. A birefringent double-slit
couples the polarization and spatial degrees of freedom of these photons and
finally, suitable spatial and polarization projections generate the HES. We
investigate some interesting aspects of the two-photon hybrid interference, and
present this study in the context of the complementarity relation that exists
between the visibilities of the one- and two-photon interference patterns.Comment: 10 pages, 4 figures. Accepted in Physical Review
Sports mega-events â three sites of contemporary political contestation
This article discusses the contemporary politics of sports mega-events, involving the Olympic Games and FĂ©dĂ©ration Internationale de Football Association (FIFA) Menâs Football World Cup Finals as well as other lower âorderâ sports megas, taking two main forms: the promotional and the protest. There is a politics in, and a politics of, sports mega-events. The former focuses on the internal politics of the organizing bodies, such as the International Olympic Committee and FIFA. This form of politics has been written about elsewhere, and hence, there is no detailed discussion in this article about it. Instead this article offers a brief discussion of the range and number of sports mega-events since 2000, an assessment of the contemporary politics of sports mega-events, a focus on three main sites of political contestation â rights, legacy and labour, and finally, it offers conclusions about research into the politics of sports mega-events
A search for starlight reflected from HD 75289 b
We have used a doppler tomographic analysis to conduct a deep search for the
starlight reflected from the planetary companion to HD 75289. In 4 nights on
VLT2/UVES in January 2003, we obtained 684 high resolution echelle spectra with
a total integration time of 26 hours. We establish an upper limit on the
planet's geometric albedo p < 0.12 (to the 99.9% significance level) at the
most probable orbital inclination i ~ 60 degrees, assuming a grey albedo, a
Venus-like phase function and a planetary radius R_p = 1.6 R_Jup. We are able
to rule out some combinations of the predicted planetary radius and atmospheric
albedo models with high, reflective cloud decks.Comment: 5 pages, 5 figures, MNRAS accepted 12 Oct 200
The Contrast Model of Similarity and Comparative Advertising
Two studies are reported which examine the existence of attribute redundancy as well as consumers\u27 ability to perceive attribute redundancy in consumer information environments. The results of the first study suggest that attribute redundancy varies widely from product category to product category. The results of the second study suggest that consumers\u27 ability to perceive attribute relationships improves with product knowledge. Unexpected was an observed U-shaped relationship between consumers\u27 perceptions of attribute redundancy and attribute knowledge. Together the results suggest a number of policy implications regarding the value of consumer information programs
An Examination of the Validity of Direct Product Perceptions
The validity of a class of direct product perceptions is examined. Consumers recorded their perception of different products directly within existing spatial or treelike representations of the productsâ competitors. A conceptual model is developed that describes consumersâ ability to provide direct perceptions within both space and tree representations for both brands and product categories. An empirical study is reported which supports the model and the validity of the recorded perceptions
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