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991.
The prohibitive - exponential in the number of users - computational complexity of the maximum-likelihood multiuser detector for direct-sequence code-division multiple-access communications has fueled an extensive research effort for the development of low-complexity multiuser detection alternatives. We show that we can efficiently and effectively approach the error rate performance of the optimum multiuser detector as follows. We utilize a multiuser zero-forcing or minimum mean-square error (MMSE) linear filter as a preprocessor and we establish that the output magnitudes, when properly scaled, provide a reliability measure for each user bit decision. Then, we prepare an ordered, reliability-based error search sequence of length linear in the number of users; it returns the most likely user bit vector among all visited options. Numerical and simulation studies for moderately loaded systems that permit exact implementation of the optimum detector indicate that the error rate performance of the optimum and the proposed detector are nearly indistinguishable over the whole predetection. signal-to-noise ratio range of practical interest. Similar studies for higher user loads (that prohibit comparisons with the optimum detector) demonstrate error rate performance gains of orders of magnitude in comparison with straight decorrelating or MMSE multiuser detection. 相似文献
992.
993.
This work examines the correlation between the 1H‐NMR T2 relaxation constant and the mechanical properties of aged crosslinked polyolefin cable insulation. T2 experiments on unswollen samples could not differentiate between unaged and highly aged materials; all exhibited 1H T2 constants of approximately 0.5 ms. To accentuate the effects of aging, samples were swollen in various solvents. Unaged samples had T2 values of approximately 15 ms in good solvents. With thermal aging, T2 values decreased as the ultimate tensile elongation decreased. However, the correlation between T2 and elongation differed for samples irradiated with high‐energy radiation and for materials aged above versus below the crystalline melting temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2578–2582, 2003 相似文献
994.
用于单芯片系统的改进型WXGA LCoS成像器 总被引:1,自引:1,他引:0
WillemA.Sloof MmthewS.Brennesholtz 《现代显示》2004,(3):36-39
本文讨论用于单芯片时序混色的菲利浦DD-720硅基液晶(LCoS)片。这种芯片主要用于HDTV背投影机和多媒体系统。与菲利浦以前的单片LCoS设计相比,由于该芯片具有电接口接点较少、封装简单和温度传感器内置等许多特点,使其应用于投影系统时成本降低。 相似文献
995.
Hambleton P.J. Ng B.K. Plimmer S.A. David J.P.R. Rees G.J. 《Electron Devices, IEEE Transactions on》2003,50(2):347-351
The nonlocal enhancement in the velocities of charge carriers to ionization is shown to outweigh the opposing effects of dead space, increasing the avalanche speed of short avalanche photodiodes (APDs) over the predictions of a conventional local model which ignores both of these effects. The trends in the measured gain-bandwidth product of two short InAlAs APDs reported in the literature support this result. Relatively large speed benefits are predicted to result from further small reductions in the lengths of short multiplication regions. 相似文献
996.
The planimetric shifts in channel location of large alluvial rivers are a critical component in the creation of diverse structures and functions in riverine habitats. Engineered management schemes must also compensate for this type of channel change to protect resources and maintain navigation channels. The stability of the Lower Mississippi River channel was assessed through an analysis of historical records of channel position produced and archived by the United States Army Corps of Engineers. Channel location was recorded for the years 1765, 1820, 1881, 1915, 1930, 1937, 1960 and 1970. Channel stability was measured by two introduced metrics on a cell‐by‐cell basis: (1) the standard deviation of Euclidean distance to a channel cell for the entire period of record, and (2) the rate of Euclidean distance change between years in the period of record. At a coarse spatial scale, channel instability increased in the downstream direction. The variability of channel stability also increased in the downstream direction. Analysis of this variability identified alternating areas of high and low stability occurring with greater frequency as distance downstream increased. These findings are validated by past studies of channel stability along the Lower Mississippi River. As a result, the proposed metrics provide a consistent, quantitative, efficient and cost‐effective means of identifying areas of channel instability at several spatial scales. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
997.
Oliveira F.D.C. Passos C.A.C. Fardin J.F. Simonetti D.S.L. Passamai J.L. Jr. Belich H. de Medeiros E.F. Orlando M.T.D. Ferreira M.M. Jr. 《Applied Superconductivity, IEEE Transactions on》2006,16(1):15-20
Hg/sub 0.82/Re/sub 0.18/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub 8+/spl delta// polycrystalline samples were successfully obtained by using different oxygen partial pressure in the annealing treatment of the precursor ceramic. The doping state was confirmed by X-ray powder diffraction pattern analysis and by observing distinct thermopower values at room temperature. Also, the intergrain regions have shown an improvement in the critical current density when using the precursor preparation with 10% O/sub 2/ and 90% Ar (optimal doped). The optimal doped sample has presented the highest /spl alpha/ exponent of the J/sub c//spl prop/[1-(T/T/sub c/)/sup 2/]/sup /spl alpha// dependence. For the case of (Hg,Re)-1223 polycrystalline superconductor applications, the /spl alpha/ exponent can be used as a junction quality parameter. 相似文献
998.
R. Maciel Filho C. B. Batistella P. Sbaite A. Winter C. J. G. Vasconcelos M. R. Wolf Maciel A. Gomes L. Medina R. Kunert 《Petroleum Science and Technology》2006,24(3):275-283
The term atmospheric residue describes the material at the bottom of the atmospheric distillation tower having a lower boiling point limit of about 340°C; the term vacuum residue (heavy petroleum fractions) refers to the bottom of the vacuum distillation, which has an atmospheric equivalent boiling point (AEBP) above 540°C. In this work, the objective is to evaluate the behavior of different kinds of Brazilian atmospheric and vacuum residues using molecular distillation. The Falling Film Molecular Distillator was used. For the results obtained through this process, a significant range of temperature can be explored avoiding the thermal decomposition of the material. So these results are very important to the refinery decisions and improvements. The Experimental Factorial Design results showed that the temperature has more influence on the process than the feed flow rate, when a higher percentage of distillate is required. 相似文献
999.
以基于eTOM的IT支撑架构模型为建设标准,对中国移动IT支撑架构集成整合的目标、形式、技术等进行了探讨,对下一步网管支撑系统架构的发展作了展望。 相似文献
1000.
Mobile devices are vulnerable to theft and loss due to their small size and the characteristics of their common usage environment. Since they allow users to work while away from their desk, they are most useful in public locations and while traveling. Unfortunately, this is also where they are most at risk. Existing schemes for securing data either do not protect the device after it is stolen or require bothersome reauthentication. Transient Authentication lifts the burden of authentication from the user by use of a wearable token that constantly attests to the user's presence. When the user departs, the token and device lose contact and the device secures itself. We show how to leverage this authentication framework to secure all the memory and storage locations on a device into which secrets may creep. Our evaluation shows this is done without inconveniencing the user, while imposing a minimal performance overhead 相似文献