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本文提出了一种无需检测电感电流及其过零点的简单数字控制方案,实现了临界连续模式功率因数校正器的控制。取得了功率开关管的ZVZCS,消除了整流二极管和快恢复二极管的反向恢复带来的损耗,提高了变换器的效率和可靠性;另外,数字控制器克服了模拟IC控制器的开关频率限制问题,消除了输入电流的低频畸变,提高了功率因数;同时,也降低了输入电感的值,降低了成本的同时提高了功率密度。为实现中小功率数字控制功率因数校正器的产品化提供了一个良好的解决方案。 相似文献
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针对采用芯片nRF905的LED屏无线通信,分别给出了上位机和下位机的系统框图,分析了系统的功耗,比较了无线模块和串口通信的通信速率,验证了系统的可行性,设计了串口通信协议,为保证数据质量,设计了数据通信协议,针对串口数据的nRF905分包转发,设计了无线芯片通信协议,例举了状态机的5种状态,介绍了状态间的转换条件,巧妙地编程设计了通信数据的定时器检查,论述了基于状态机的嵌入式单片机软件编程。 相似文献
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在当今的社会中,人们已经离不开电子通信了,其作为了一个新兴产业,并得到了良好的应用,对各行各业起到了促进作用,同时,传统的产业收到了冲击。我国的电子通信发展较快,达到了先进的水平,不过,由于发展时间较短,存在很多不足之处,拉低了整体水平。特别是干扰问题,严重影响了电子通信的发展。本文对电子通信进行了概述,探讨了干扰要素,并且,提出了相关的应对策略。 相似文献
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铝电解电容器技术的新进展 总被引:3,自引:3,他引:0
详细讨论了电子技术的发展对铝电解电容器的性能要求,提出了其技术对策,分析了存在的技术瓶颈,找出了它的技术出路,探讨了它的技术难点,给出了当前我国铝电解电容器行业的技术现状,指出了未来发展方向。 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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Michael Reilly 《半导体技术》2004,29(12)
DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system. 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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The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high. 相似文献
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在LCD的LED背光腔体的底面设计了新型曲面形状及性能的反光膜,将扩散膜反射回灯腔底部的光重新反射回出光口以改善亮度均匀性能;在侧面设计了镜面反射膜,将位于LED矩阵边缘区域由LED射向灯腔侧壁的光反射重新射向出光口,增加了LED背光边缘区域的亮度,从而改善了背光边缘区域较暗的亮度不均匀状况.根据此类反射膜的设计完成了反射膜的制备,并应用于38 cm LED背光源样品.测试结果显示,设置反射膜的LED背光的亮度均匀性值为10.2%,明显优于未设置反射膜的值16.8%,亮度提高了29%左右,表明该种新型反射膜可以提高亮度并改善亮度均匀性. 相似文献
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Design and nonlinearity compensation of Fabry-Perot type tunable optical filters for dynamic strain sensing systems 总被引:1,自引:0,他引:1
The collected spectrum of the fiber Bragg grating (FBG) and the loss of the detected optical power are discussed with respect to the 3-dB bandwidth of a Fabry-Perot (F-P) type tunable optical filter (TOF), respectively. And the optimized parameters of the TOF are obtained consequently. It is demonstrated that the relationship between the transmission wave- length of the TOF and its drive voltage is nonlinear. A new method to compensate the nonlinearity of the TOF is proposed. The linear sweeping of the transmission wavelength of the TOF is achieved through modifying the drive voltage using interpolation algorithm. It is observed that the average error and the maximum error of the transmission wavelength are reduced sharply under linear fit. The dynamic strain sensing is realized by use of a reference FBG and moving averaging algorithm in this system. 相似文献
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研究了圆球微腔在水蒸汽传感中应用的可行性。通过测试在有/无水蒸汽的气室环境下,圆球微腔透射光谱的变化来对气室水蒸汽浓度情况进行传感测试。仿真实验结果显示:在有无水蒸汽干扰的条件下系统输出光强有明显的变化,即研制基于圆球微腔的传感器是可行的。 相似文献
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Ulkuhan Guler Ali Emre Pusane Günhan Dundar 《International Journal of Electronics》2013,100(9):1465-1482
Although studies have investigated the effects of flicker noise on randomness, such effects demand further examination. Despite the random nature of flicker noise, a coloured distribution is observed in the power spectral density of flicker noise, indicating to a correlation in between adjacent samples. Studies have employed ring oscillators (ROs) that produce random numbers by sampling the digitised analogue signals of their outputs. This sampling procedure may change the spectral properties of flicker noise resulting from the folding effect of noise. Another topic of interest regarding sampled flicker noise is its random behaviour. To investigate the contribution of flicker noise, white noise, and their combination to randomness, we produce synthetic bit streams of these noise sources. From observations, we find that flicker noise contributes to the entropy of bit streams. Using the generated synthetic bit streams, we also explore the entropy dependence of a bit stream on the sampling period and analyse and compare the entropy levels of the outputs of ROs operating in strong and weak inversion. Results of the comparison demonstrate that only one RO operating in weak inversion may be sufficient to attain the required entropy level for qualifying the generated bit stream as random. The results of the analysis are also confirmed by measurements. In addition, the paper proposes an efficient design of a RO-based random number generator. 相似文献