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61.
Satellite communications at KU, KA, and V bands: Propagation impairments and mitigation techniques 总被引:1,自引:0,他引:1
Panagopoulos Athanasios D. Arapoglou Pantelis-Daniel M. Cottis Panayotis G. 《Communications Surveys & Tutorials, IEEE》2004,6(3):2-14
This article surveys the alternative fade mitigation techniques for satellite communication systems operating at Ku, Ka and V frequency bands. The specific phenomena influencing the propagation of radiowaves on Earth-space links are also overviewed. Emphasis is placed on modeling, experimental work carried out in the past, and practical implementations related to each mitigation technique. 相似文献
62.
63.
Jenkins C. David; Zyzanski Stephen J.; Ryan Thomas J.; Flessas Athanasios; Tannenbaum Saul I. 《Canadian Metallurgical Quarterly》1977,45(6):1060
Tests measuring the coronary-prone Type A behavior pattern, anxiety, and neuroticism (Jenkins Activity Survey and a series of true–false items dealing with the latter 2 characteristics) were administered to 95 26–68 yr old male patients undergoing coronary angiography. Item analyses suggest that Ss with more serious coronary atherosclerosis were hard-driving, hard-working Type A individuals who put pressure on themselves to solve problems, meet deadlines, and move up the social ladder. At the same time, these patients were often uncomfortable in their interpersonal relationships, and they felt awkward and insecure in groups. They obtained their rewards in life from seeking achievement rather than from socializing with people. They seemed to have a low threshold for becoming tense or depressed. Results suggest that the combination of these 2 sets of essentially independent psychological characteristics, Type A behavior and social insecurity, portends a greater severity of atherosclerosis than the possession of either single characteristic alone. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
64.
A physically based stochastic-deterministic procedure for the estimation of flood frequency 总被引:2,自引:1,他引:1
A procedure based on the method of derived distributions is proposed for the estimation of flood frequency from ungauged watersheds. The results of previous research on rainfall characteristics and watershed response are incorporated into the proposed procedure. These rainfall characteristics are storm depth, storm duration, space and time distribution. A simplified watershed model is used which has previously given good simulation of the watershed response. Some of the rainfall and watershed model parameters are stochastic in nature and are assumed to follow various probability distributions. Monte Carlo simulation is used for the generation of the various parameter values and simulation of the peak flow hydrographs. After 5000 realizations, the frequency of the hourly and daily peak flow and the flood volume is estimated. The proposed procedure is applied to eight coastal British Columbia watersheds and the results compare well with the observed data and with fitted probability distributions. The method is easy to apply, requires limited data and is shown to be reliable. Sensitivity analysis shows that the procedure is not very sensitive to uncertainty of the parameter values and is not dependent on the parameter probability distributions used. 相似文献
65.
Überblick über die Veröffentlichungen auf dem Gebiet des Ringwalzens. Versuchsergebnisse beim Ringwalzen über die Druckverteilung im Walzspalt. Modell für die Abschätzung von Walzkraft und Drehmoment. 相似文献
66.
Jeff H. Harwell Athanasios I. Liapis R. Litchfield Daniel T. Hanson 《Chemical engineering science》1980,35(11):2287-2296
A mathematical model for adiabatic adsorption of multiple components onto a fixed bed of adsorbent is developed. The model consists of a set of coupled, hyperbolic, parial-differential equations. Heat and mass transfer resistances evident in real systems are included in the model. Solutions of the equations are obtained by numerical application of the method of characteristics. Results show non-ideal mass and thermal wavefronts and complex wave-wave interactions in adiabatic adsorption of benzene and cyclohexane onto activated carbon. Phenomena of inversions in relative adsorptivity due to temperature changes are also shown. Column performance is indicated to be greatly affected by these phenomena. Cases considered demonstrate that time on stream before breakthrough may be doubled by increasing influent and initial bed temperatures. It is shown, in contrast to results obtained fron using the non-equilibrium model, that models based on assumptions of local equilibrium cannot quantitatively describe behavior of a typical industrial adsorption system. 相似文献
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68.
Wim Verbeke Federico J.A. Pérez-Cueto Marcia D. de Barcellos Athanasios Krystallis Klaus G. Grunert 《Meat science》2010
This paper presents the combined mid-term findings of the consumer research components of two EU Sixth Framework Programme integrated projects concerning meat, ProSafeBeef and Q-PorkChains. The consumer pillar of ProSafeBeef carried out eight focus group discussions in May 2008, in France, Germany, Spain and the UK. Q-PorkChains conducted a large-scale, web-based, consumer survey in January 2008 in Belgium, Denmark, Germany, Greece and Poland. The first project provides a set of qualitative data from a small cohort of focus groups and the second a set of quantitative data from a larger consumer sample. This paper draws together the main findings of both projects and provides a comprehensive overview of European citizens’ and consumers’ attitudes towards and preferences regarding beef and pork. In general, consumers consider meat to be a healthy and important component of the diet. Consumers support the development of technologies that can improve the health attributes of meat products and guarantee eating quality, but they have a negative view of what they see to be excessive manipulation and lack of naturalness in the production and processing of beef products. In the Q-PorkChains study consumer and citizen segments are identified and profiled. Consumer segments were built upon the frequency and variety of pork consumption. The citizen segments were built upon their attitudes towards pig production systems. Overall, the relationship between individuals’ views as citizens and their behaviour as consumers was found to be quite weak and did not appear to greatly or systematically influence meat-buying habits. Future studies in both projects will concentrate on consumers’ acceptance of innovative meat product concepts and products, with the aim of boosting consumer trust and invigorating the European beef and pork industries. 相似文献
69.
70.
Athanasios Stefanou 《Journal of Electronic Materials》2008,37(2):172-175
Four interface models for crystalline oxynitride on (001)Si substrates are proposed and investigated. All four models are
proposed to model thin oxynitride films on Si substrates, according to experimental findings and theoretical studies on amorphous
oxynitride films and nitrogenated SiO2. State-free insulating interfaces were obtained by expanding the bulk oxynitride cell by approximately 12% and 1% along the
[100] and [010] axes, respectively, and interfacing it with (001)Si. Results demonstrate state-free insulating interfaces
for all models with, however, valence-band offsets slightly above or below 1 eV. The significant decrease in the valence-band
offsets is mainly attributed to the significant expansion of the oxynitride’s lattice constant to lattice-matched (001)Si,
as well as to the high concentration of nitrogen atoms in the oxynitride bulk. 相似文献