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基于模式识别聚类思想的无源光网络规划 总被引:2,自引:0,他引:2
使用聚类思想对无源光网络(PON)规划进行优化设计,并进行了仿真实验,对结果进行了分析,并与传统算法及遗传算法进行了比较,取得了令人满意的结果,并指出了进一步研究的方向。 相似文献
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《通信业与经济市场》2004,(2):21-21
2003年,我们在原有基础上进行了无线电频率规划,编写完成了无线电频率规划英文版工作,调整1800兆无线接入频率的容量,从原来5兆扩展到现在的20兆。对全国的台站进行了一次普查,而且对数据库进行了重新跟踪,对集群频率进行了 相似文献
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红外光谱信号的预处理 总被引:1,自引:1,他引:1
介绍了一种对光谱信号进行预处理的高低通综合滤波法,它对高频噪声和低频扰动分别采用不同的措施进行处理,高频噪声采取平滑滤波法进行去除,低频扰动采取低通数字滤波器进行去除,试验结果表明,这样做既去除了高频噪声和低频扰动,同时又保留了光谱的细节部分,最后,文中将高低通滤波法和带通滤波法的处理结果进行了比较。 相似文献
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一种提高相位激光测距精确度的方法 总被引:3,自引:0,他引:3
描述了一种采用相位式激光测距提高测距精度的方法,给出了采用相位式进行激光测距的原理,指出了采用单一频率进行测距时存在的矛盾,从而提出了在单一频率的基础上添加多个辅助频率进行测距,分析了采用多个辅助频率进行相位激光测距的原理,并对采用该方法进行了精度分析。从分析的结论看,采用的辅助频率个数越多,则越能提高测距精度,同时该方法还能提高测量范围,解决了单一频率测量时的矛盾,达到了测距时高精度、大范围的工程应用要求。 相似文献
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本文首先介绍了几种无线电干扰机的技术方案,并对几种方案进行了比较,提出了一种性价比比较高的技术方案,然后在对几款GSM和CDMA手机进行实际测试的基础之上,对干扰机整机电路进行了分析和计算,并进行了实际的验证。 相似文献
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相位干涉仪中均匀阵列测向精度研究 总被引:1,自引:0,他引:1
对相位干涉仪体制中所使用的两种均匀阵列进行了研究,对阵列的测向算法进行了改进,并用matlab软件进行了计算机仿真,仿真结果表明在同等条件下,虽然平面阵的算法较复杂,但是测量误差更小,测向精度更高,具有更好的性能。 相似文献
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本文介绍了测定材料漫反射特性的原理和检测系统的结构,利用该检测系统,对氧化镁,硫酸钡,聚四氟乙烯等制成的白板材料进行了紫外波段的实测,并且把它们同朗伯漫反射体进行了比较,对其偏差进行了讨论,此项研究结果,为太阳紫外光谱监视器的辐射定位奠定了基础。 相似文献
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介绍了中央电视台英语新闻演播室技术质量调改背景,对演播室布局和承担的任务进行了详细说明,对存在的问题进行了分析,提出了调改建议,具体介绍了演播室总体视觉效果调改的方案,并对后续的制度保障进行了简要说明。 相似文献
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The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation. 相似文献
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Three alternative schemes for secure Virtual Private Network (VPN) deployment over the Universal Mobile Telecommunication
System (UMTS) are proposed and analyzed. The proposed schemes enable a mobile node to voluntarily establish an IPsec-based
secure channel to a private network. The alternative schemes differ in the location where the IPsec functionality is placed
within the UMTS network architecture (mobile node, access network, and UMTS network border), depending on the employed security
model, and whether data in transit are ever in clear-text, or available to be tapped by outsiders. The provided levels of
privacy in the deployed VPN schemes, as well as the employed authentication models are examined. An analysis in terms of cost,
complexity, and performance overhead that each method imposes to the underlying network architecture, as well as to the mobile
devices is presented. The level of system reliability and scalability in granting security services is presented. The VPN
management, usability, and trusted relations, as well as their behavior when a mobile user moves are analyzed. The use of
special applications that require access to encapsulated data traffic is explored. Finally, an overall comparison of the proposed
schemes from the security and operation point of view summarizes their relative performance.
Christos Xenakis received his B.Sc. degree in computer science in 1993 and his M.Sc. degree in telecommunication and computer networks in
1996, both from the Department of Informatics and Telecommunications, University of Athens, Greece. In 2004 he received his
Ph.D. from the University of Athens (Department of Informatics and Telecommunications). From 1998–2000 was with the Greek
telecoms system development firm Teletel S.A., where was involved in the design and development of advanced telecommunications
subsystems for ISDN, ATM, GSM, and GPRS. Since 1996 he has been a member of the Communication Networks Laboratory of the University
of Athens. He has participated in numerous projects realized in the context of EU Programs (ACTS, ESPRIT, IST). His research
interests are in the field of mobile/wireless networks, security and distributed network management. He is the author of over
15 papers in the above areas.
Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Greece, in
1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and
1984, respectively. From 1983 to 1986, he was on the faculty of Electrical Engineering and Computer Science at the University
of Connecticut, Storrs. From 1986 to 1994 he was on the faculty of the Electrical and Computer Engineering Department at Northeastern
University, Boston, MA. During the period 1993–1994 he served as Director of the Communications and Digital Processing Research
Center at Northeastern University. During the summers of 1990 and 1991, he was a Visiting Scientist at the IBM T. J. Watson
Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens, Greece, where he
is presently a Professor in the Department of Informatics and Telecommunications, and Director of the Communication Networks
Laboratory (UoA-CNL) and the Networks Operations and Management Center. His research interests are in the design and performance
analysis of broadband networks, and wireless/mobile communication systems and services. He has authored more than 150 papers
in the above areas. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in
the framework of the Advanced Communication Technologies & Services (ACTS) and Information Society Technologies (IST) programmes
funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE). He is chairman of the board of
the Greek Universities Network, the Greek Schools Network, and member of the board of the Greek Research Network. In 1994,
he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications. 相似文献
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文中针对单相无刷直流电机结构设计及驱动方式展开研究,推导出电机理想工况下的基本方程,根据工程实际需求并结合无刷直流电机的设计原则确定该电机的设计方案。利用设计方案设计一台额定功率38 W,额定转速750 rpm的单相无刷直流电机,并分析了渐变气隙对电机起动性能和齿槽转矩的影响,确定了最优气隙长度。通过对比单极性绕组和双极性绕组形式的优缺点确定绕组形式,结合传统电机设计公式确定绕组匝数。文中利用有限元法初步验证了设计方案的合理性。根据电机动态数学模型在Simulink环境中搭建了电机系统的模型,仿真得到电机的转速、转矩变化曲线,结果与理论分析吻合良好,验证了电机设计方案的合理性和电机模型的有效性。 相似文献
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针对RFID树型防碰撞算法中时隙数多、数据通行量大等问题,提出了一种改进的多叉树防碰撞算法,阅读器准确检测碰撞位并向标签反馈碰撞位信息,标签对阅读器已知的ID位进行屏蔽,把ID号转换成连续碰撞的序列号.阅读器利用屏蔽位信息和标签返回的碰撞位编码信息,对标签进行分层分类搜索.通过对标签ID进行屏蔽,阅读器和标签间仅发送对方不知道的碰撞位信息.该算法减少了碰撞时隙和识别时隙,避免了空闲时隙,减少了阅读器和标签间的数据通信量.理论分析和仿真结果表明,该算法减少了系统的时隙总数和数据通信量,提高了阅读器的识别效率. 相似文献
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This paper presents a unified treatment of various important signal processing techniques for the extraction of the instantaneous envelope and phase of a real signal. These techniques include Complex Demodulation, Hilbert Transformation, In-Phase and In-Quadrature Filtering, Phase-Locked Loop Demodulation, and Peak Amplitude and Zero-Crossing Detection. The salient points in the mathematical theory and implementation of these techniques are outlined, as well as their interrelationships via the theory of analytic signals. The advantages and limitations of each of these techniques are elaborated upon, and Complex Demodulation is shown to be the most effective and flexible method from an implementation point of view. The relation of the above techniques to Fourier spectrum analysis is elucidated, and an example is presented of applying Complex Demodulation for the quantification of time nonstationarities in the electrographic morphology of an EEG waveform. 相似文献
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The anisotropic growth of one-dimensional or filamental crystals in the form of microwires and nanowires constitutes a rich domain of epitaxy and newly enabled applications at different length and size scales. Significant progress has been accomplished in controlling the growth, morphology, and properties of semiconductor nanowires and consequently their device level performance. The objective of this review is two-fold: to highlight progress up to date in nanowire doping and to discuss the remaining fundamental challenges. We focus on the most common semiconductor nanowire growth mechanism, the vapor-liquid-solid growth, and the perturbation of its kinetic and thermodynamic aspects with the introduction of dopants. We survey the origins of dopant gradients in nanowire growth and summarize quantification techniques for dopants and free-carrier concentrations. We analyze the morphological changes due to dopants and the influence of growth droplet seeds on composition and morphology and review growth aspects and alternatives that can mitigate these effects. We then summarize some of the remaining issues pertaining to dopant control in nanowires. 相似文献
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