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《卫星电视与宽带多媒体》2008,(11)
近两个月来,本刊网站的论坛里又不太安静。有个叫"高清迷"的香港网友遭到了广东一些网友的质疑。彼此论战的焦点大部分在说香港电视好看或不好看。"高清迷"网友说大陆电视越来越好,水平已经超过香港的电视节目。广东网友们则是缅怀香港电视的辉煌历史。这原本是简单的我说你好你说我好,互相捧场的事情,但是网络的奇妙性在于事情并没有朝积极的方向发展,其结果是吵架不可避免的发生了。外来的和尚是不是会念经,我们先不去管他。重要的是我们要弄清楚自己是怎么回事。本文,是专业电视人对我国各省卫视台做的调查评估。让我们了解一下我国的电视台的现状吧。 相似文献
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热闹了多年,也翻炒了多年,但中国的3G进程到现在仍处于一片迷茫当中。是谁卡住了中国3G进程的脖子?毫无疑问,部分跨国公司设置的高昂专利费是阻碍中国3G步伐前进的一块巨石。2005年4月23日,信息产业部副部长奚国华在参加2005年博鳌亚洲论坛年会时公开表示,跨国公司收取过高3G专利费这一行为导致3G进程缓慢,并呼吁这些跨国公司降低专利费用。奚国华副部长的一席话成为“3G专利谈判受阻”事件的最好注解。据悉,在这场关于WCDMA的专利费谈判过程中,高通公司在其他专利拥有者摩托罗拉、诺基亚、爱立信等同意降低专利费的情况下,谈判最终因高通公司的拒绝接受而搁浅。作为世界最大的通讯市场,中国通讯业的每一步进展都充满着坎坷;作为世界知名的通讯公司,高通公司已演变成CDMA生态圈里的巨鳄,其拥有的1400多项专利足以让人望而却步。这家出售知识产权的公司真的是阻拦中国3G进程的巨石吗?也许,从另一侧面观察,更能了解高通的真实面目。雷鸣先生是高通公司大中华区前总裁,他见证了高通的成长,更熟悉高通的一切事务。到底谁是卡住中国3G脖子的幕后主角?现在,经过雷鸣先生的观察和反思,一件件鲜为人知的事终于曝光在读者的面前。相信看完此文披露的诸多内幕,答案就在你的心中! 相似文献
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高频电磁辐射作用于人体后,一部分被反射,一部分会被人体吸收,被吸收的电磁能量使人体组织内的分子和电介质的偶极子产生振动,媒质的磨擦把动能变为热能,从而导致使人体产生温升的热效应.电磁辐射的功率、频率、波形、环境温度以及人体被照射的部位等因素影响热效应伤害的深度和程度. 相似文献
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作为下一代无线通信系统的关键技术,协作多点传输能够有效降低相邻小区之间的干扰,提高小区边缘用户的频谱效率。在频分双工系统中,其性能依赖于各基站获取的基于有线反馈的信道状态信息的准确性。然而,所有协作基站都获得相同精确程度的信道状态信息会导致用户终端的反馈开销随着协作基站数线性增长。本文关注于如何在性能增益和反馈开销之间取得折中,提出一种适用于协作多点联合传输的自适应预编码矩阵索引反馈方法。用户终端根据不同协作基站下行链路的信道质量指示的相对大小,自适应的用不同的比特数表示不同强度链路的预编码矩阵索引,即用较多比特数表示具有较高信道质量指示的预编码矩阵索引,反之亦然。仿真结果表明,与传统反馈方案相比,该方法在几乎不牺牲频谱效率的前提下,大幅降低了反馈开销。 相似文献
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汶川5·12大地震,这场突如其来的灾难让大半个中国遭受重创.我们每天被迫面对无数死伤的同胞和几乎被夷为平地的城市和村镇,悲痛欲绝的同时却又让我们达到空前的团结,5·12是悲惨的,也是悲壮的.我们感受到了全方位的力量,灾民、政府、同胞……尤其媒体的表现让所有人震撼,电视、广播、网络成为灾难的发言人,成为灾区与整个中国乃至全世界连接的信息生命线. 相似文献
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通信技术的进步推动了电信市场的发展,当前ADSL用户的需求旺盛,给北京通信的发展创造了有利的商机,同时也给我们带来一些急需解决的新课题,如何利用北京通信的传统优势克服发展瓶颈、充分满足ADSL市场的需要.本文首先分析了目前阻碍ADSL发展的原因,结合北京通信的实际情况提出了利用语音分配点安装OSLAM设备以解决瓶颈问题的新思路,然后介绍了新研制的多功能有源交接箱的设计特点和应用前景及用户纤光缆交换点的建立储备.最后对采用本文的思路和应用新设备的投资、回报等进行了经济性分析,从而系统完整地提出了一套可行的解决方案和相关实施建议. 相似文献
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介绍了一种利用厂商发布的漏洞补丁信息分析漏洞细节的方法.该方法的关键是利用PE文件在安装补丁前后的不同,综合运用模式比较的方法建立模式匹配图,从而分析处漏洞的细节以及问题代码.该方法函数比较算法的清晰,以及模式图的差异的直观性,很容易分析出问题代码的位置,从而有效地提高了漏洞分析的成功率. 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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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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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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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