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991.
体全息相关器能够进行快速的光学并行相关识别.但是在相关识别的过程中,页间串扰导致相关结果中旁瓣太多,影响了相关峰的判断,大大降低了相关器的识别准确率。为了抑制旁瓣.对传统的体全息相关公式中所产生串扰的因子进行了分析,引入了随机函数的自相关函数作为调制因子对公式进行修正.可以实现在水平方向和竖直方向同时抑制旁瓣.抑制效果与全息图的厚度无关。并提出在相关器的物光光路中物的前方放置随机相位器,实现对物函数的散斑调制。理论分析、数值计算及实验结果表明.该方法可以抑制旁瓣.突出相关峰.提高体全息相关器的识别准确率和通道密度。 相似文献
992.
993.
将码分多址(CDMA)思想引入水印系统以实现多水印方案。在水印嵌入过程中,每一用户以自己的密钥作为种子生成一个伪随机分布的地址码,并用该地址码将自己的欲嵌入信息调制为载波信号,然后以相加的方式把载波信号叠加入载体。在提取时,该用户使用相同的地址码,通过计算地址码和载体之间的相关系数,从载体中提取自己的嵌入信息。实验证明该算法可以实现多个用户独立嵌入和检测自己的水印信息,完全能满足多水印的要求。 相似文献
994.
This paper concentrates on issues of implementation of the method proposed for checking the consistency of formulae of the
language L and described in the first part of this work. Upper-bound estimates of time complexity of the corresponding algorithms
are obtained.
Part I of this article is published in No. 4 (2005).
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 11–19, November–December 2005. 相似文献
995.
婴幼儿配方食品和乳粉中维生素B2的测定 总被引:1,自引:0,他引:1
采用高效液相-二极管阵列检测器检测婴幼儿配方食品和乳粉中核黄素(维生素B2),样品在稀盐酸环境中高温水解、酶解,经C18反相色谱柱分离,流动相为乙酸钠(pH=4.5)-甲醇(体积比为65∶35),检测波长为450nm。本方法中维生素B2线性范围为0~26.5μg/mL,检出限为0.02μg/mL。维生素B2平均加标回收率为94.0%,维生素B2相对标准偏差为0.44%,合成标准不确定度为4.917×10-3。该方法简单、快速、测定干扰小,结果与国家标准测定方法比较无显著性差异。 相似文献
996.
997.
Nikolaos D. Skentos Athanasios G. Kanatas Panagiotis I. Dallas Philip Constantinou 《Wireless Personal Communications》2006,36(4):339-361
This paper reports results from wideband MIMO measurements performed in short range fixed wireless environments at 5.2 GHz. The objective is to provide MIMO channel characterization results for the measured environments and contribute to the limited available similar studies. Two kinds of propagation scenarios are investigated, rooftop to rooftop and street to rooftop, at three different sites always under LOS propagation conditions. The analysis of measurement data is performed in the context of non physical modeling, providing insight into the statistics of the measured channels. In particular, the slow time varying nature of the channel is studied and the narrow Doppler spectrum shape is approximated. Furthermore, frequency correlation results are obtained and the typical delay dispersion measures are extracted. Then, the antenna correlation is studied and the error of the Kronecker product approximation is evaluated. Finally, capacity results are provided and the channel measurements are characterized in terms of spatial multiplexing quality and multipath richness through condition number analysis.
Nikolaos D. Skentos received his Diploma in Electrical and Computer Engineering from the National Technical University of Athens (NTUA), Greece in October 2000. Since January 2001 he has been a research associate at the Mobile Radio Communications Laboratory at the NTUA, and he is currently working towards the Ph.D. degree. His research interests include channel measurements, MIMO channel characterization, MIMO algorithms and space time processing. He has been active in the IST STINGRAY project, the COST 273 Action and the ACE Network of Excellence. He is also a member of the National Technical Chamber of Greece since 2001.
Athanasios G. Kanatas received the Diploma in Electrical Engineering from the National Technical University of Athens, Greece, in 1991, the M.Sc. degree in Satellite Communication Engineering from the University of Surrey, Surrey, UK in 1992, and the Ph.D. degree in Mobile Satellite Communications from the National Technical University of Athens, Greece in February 1997. From 1993 to 1994 he was with National Documentation Center of National Research Institute. In 1995 he joined SPACETEC Ltd. where he was Technical Project Manager for VISA/EMEA VSAT Project in Greece. In 1996 he joined the Mobile Radio Communications Laboratory as a research associate. From 1999 to 2002 he was with the Institute of Communication & Computer Systems. In 2000 he became a member of the Board of Directors of OTESAT S.A. He is an Assistant Professor in the Department of Technology Education and Digital Systems at University of Piraeus. His current research interests include channel characterization and estimation, simulation and modeling for mobile, mobile satellite, and future wireless communication systems. He has been a Senior Member of IEEE since 2002, and is also a member of the Technical Chamber of Greece. In 1999 he was elected Chairman of the Communications Society of the Greek IEEE Section.
Panagiotis I. Dallas was born 1967 in Thessaloniki, Greece. He obtained his diploma and Ph.D. degree from the Electrical and Computer Engineering Department of Aristotle University of Thessaloniki, Greece, in 1990 and 1997, respectively. Since 1998 he joined with INTRACOM where he currently is Section Manager of Advanced Communications Technologies branch of Emerging Technologies & Markets department, leading the next generation of broadband wireless access systems for internal and EU projects. He runs the relevant standardization activities (IEEE 802.16 and ETSI/BRAN HIPERMAN) in INTRACOM and he represents the company in WiMAX forum. Finally, he has over 30 publications in international journals and conferences.
Philip Constantinou received the Diploma in Physics from the National University of Athens in 1972, the Master of Applied Science in Electrical Engineering from the University of Ottawa, Ontario, Canada in 1976, and the Ph.D. degree in Electrical Engineering in 1983 from Carleton University, Ottawa, Ontario, Canada. From 1976 to 1979 he was with Telesat Canada as a Communications System Engineer. In 1980 he joined the Ministry of Communications in Ottawa, Canada where he was engaged in the area of Mobile Communication. From 1984 to 1989 he was with the National Research Center Demokritos in Athens, Greece where he was involved in several research projects in the area of Mobile Communications. In 1989 he joined the National Technical University of Athens where he is currently a Professor and Director of the Mobile Radio Communications Laboratory. His current research interests include Personal Communications, Mobile Satellite Communications, and Interference Problems on Digital Communications Systems. 相似文献
998.
999.
基于队列理论、Logistic映射和Tent映射,从增大跳频序列的线性复杂度和抗预测性出发,提出了利用队列排序方式产生混合混沌映射跳频序列的方法。理论研究和仿真结果证明这种方法极大地增加了系统的抗预测能力,同时该跳频序列的平衡性、相关性、频率间隔等性能良好,且码的数量巨大,容易实现,应用前景广泛。 相似文献
1000.