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User-perceived quality of service in wireless data networks 总被引:1,自引:0,他引:1
Anthony J. Saliba Michael A. Beresford Milosh Ivanovich Paul Fitzpatrick 《Personal and Ubiquitous Computing》2005,9(6):413-422
For so long, the term quality of service (QoS) has been a pursuit area for network engineers trying to dimension wireless
networks to run in the most efficient way possible. Of late, there has been a trend reversal, looking at the user perceptions
of the network performance to decide where dimensioning can have the greatest impact. This paper demonstrates the importance
of defining the concept of user-perceived QoS and linking this to specific wireless data network parameters for some anticipated
valuable applications. It has been shown that a quantitative rating can be obtained for a variety of important factors in
the assessment of service quality, and mapped to specific values of multiple network parameters. We found QoS to be application-specific,
where various applications require different levels of network performance to satisfy users. The role of physical location
was also examined, investigating the influence of being indoors versus outdoors on the user perception of QoS. 相似文献
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Vladimir Ivanovich Lysenko Sergey Bardakhanov Alexey Korchagin Nikolay Kuksanov Alexander Lavrukhin Rustam Salimov Sergey Fadeev Vladislav Cherepkov Mikhail Veis Andrey Nomoev 《Bulletin of Materials Science》2011,34(4):677-681
Electron-beam evaporation of various natural and industrial materials in the atmosphere of different gases at atmospheric
pressure can be used for the synthesis of nanosize powders. These powders are characterized by high purity and may exhibit
unusual properties. In particular, nanopowders of silicon dioxide and oxide (SiO2, SiO), magnesia (MgO), alumina (Al2O3), titania (TiO2), gadolinium oxide (Gd2O3), various metals (tantalum, molybdenum, nickel, aluminium, copper, silver), semiconductor (Si), nitrides (AlN, TiN), and
some other substances had been produced. The process of nanopowder synthesis is highly effective; in particular, the yield
of oxides can exceed ten kilograms per hour. 相似文献
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M Bonomini S Forster V Manfrini F De Risio M Steiner MI Vidovich H Klinkmann P Ivanovich A Albertazzi 《Canadian Metallurgical Quarterly》1996,72(2):197-204
The effects of the adsorption of the fluorescent potential-sensitive dyes RH-421, RH-237 and RH-160 on the bilayer lipid membrane were studied. It was shown that a dipole potential drop, positive in the hydrophobic part of the membrane, arose due to the dye adsorption. The dye adsorption led to a considerable increase of the rate constant of hydrophobic anion translocation through the membrane, but did not affect their partition coefficient between membrane and water. It implies that the region of the membrane where the potential drops is located deeper than the adsorption plane of hydrophobic ions. The values of boundary potential differences were estimated by two independent methods with unilateral and bilateral application of the dyes to lipid bilayer membranes. The results suggest that RH dye molecules penetrate through the lipid bilayers. The values of zeta-potential in liposomes did not change on dye adsorption. Hence, dye molecules are adsorbed in a form that does not change the surface charge. We estimated the effects of electric field of dye dipole layer on an individual dipole located in the same layer and on ion transport through a membrane protein Na+/K+-ATPase. It turned out that the local electric field of each dye dipole decayed so rapidly that a neighbouring dye molecule did not feel it. It also appeared that RH dyes could have but a minor effect on the electrogenic transport performed by the sodium pump in the examined range of dye concentrations. 相似文献
7.
Son JY Bobrinev VI Kim KT 《Journal of the Optical Society of America. A, Optics, image science, and vision》2005,22(9):1739-1745
The depth resolution and the recordable object depth range, obtainable with parallel, toed-in and sliding aperture camera configurations for multiview image acquisition in the three-dimensional imaging systems, are found by assuming that the camera lens resolution is diffraction limited and the resolution of the recorded image is limited by a pixel pitch of the imaging sensor. The depth resolution for the holographic image is calculated and compared with that of the multiview images for the same parameter values. The influence of the viewer's eye resolution limit on the depth resolution of the multiview images and hologram is also found. 相似文献
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Kook-Young Ahn Han-Seok Kim Vjacheslav Ivanovich Antonovsky 《Journal of Mechanical Science and Technology》2001,15(9):1319-1327
The results of stand and field testing of a combustion chamber for a heavy-duty 150 MW gas turbine are discussed. The model represented one of 14 identical segments of a tubular multican combustor constructed 1∶1 scale. The model experiments were executed at a lower pressure than that in a real gas turbine. Combustion efficiency, pressure loss factor, pattern factor, liner wall temperature, flame radiation, fluctuating pressure and NOx emission were measured at partial and full loads for both model and on-site testing. The comparison of these items in the stand and field test results led to has the development of a method of calculation and the improvement of gas turbine combustors. 相似文献
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A. I. Zboromirs'kii G. S. Ivanits'ka M. V. Ivanovich O. P. Ostash V. V. Panasyuk 《Materials Science》1990,26(1):35-43
Summary The C model and singular integral equations have been used to solve for the elastoplastic state of stress and strain in a disk containing an edge crack, and the solution has been used to determine crack edge separations, including those at the vertex and at the edge of the disk. The critical loads calculated from the C model and Irvin's criterion have been compared with measurements.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 26, No. 1, pp. 38–46, January–February, 1990. 相似文献
10.
We present a comprehensive survey of proposed Quality of Service (QoS) mechanisms in the Media Access Control (MAC) sublayer of WiMAX based wireless networks. QoS support in WiMAX is a fundamental design requirement, and is considerably more difficult than in wired networks, mainly because of the variable and unpredictable characteristics of wireless links.We discuss various QoS architectures, signaling mechanisms and admission control techniques proposed in the WiMAX research literature, summarizing the operation of each, and providing comparative evaluations that include advantages and limitations. 相似文献