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61.
目前SET协议在电子商务交易中应用越来越广泛,因此,对SET协议的安全性的要求就越来越高。论文在SET协议的交易流程基础上,分析了其安全机制采用的技术和优点,指出了SET协议安全性存在的一些问题。 相似文献
62.
入侵检测系统技术现状及其发展趋势 总被引:21,自引:0,他引:21
阐述了入侵检测系统(IDS)的起源、发展和分类,介绍了它的结构和标准化工作,对入侵检测系统存在的问题及发展趋势作了概述。 相似文献
63.
Shift in thinking to address the 21st century hunger gap 总被引:1,自引:1,他引:0
Malin Falkenmark 《Water Resources Management》2007,21(1):3-18
The present water policy debate is dominated by the 30 yr old mission to secure water supply and sanitation to all people.
The water needed to produce a nutritionally acceptable diet for one person is however 70 times as large as the amount needed
for domestic water supply. The food security dilemma is largest in arid climate regions, a situation constituting a formidable
challenge. It is suggested that an additional 5 600 km3/yr of consumptive water use will be needed to produce an adequate amount of food by 2050 – i.e almost a doubling of today’s
consumptive use of 6800 km3/yr. Past misinterpretations and conceptual deficiencies show the importance of a shift in thinking. Combining the scale of
the challenge and the time scale of the efforts to feed humanity and eradicate hunger leads to an impression of great urgency.
This urgency strengthens the call for international research both for supporting agricultural upgrading, and for much better
handling of issues of environmental sustainability. What stands out is the need of a new generation of water professionals,
able to handle complexity and able to incorporate water implications of land use and of ecosystem health in integrated water
resources management. It will for those reasons be essential and urgent to upgrade the educational system to producing this
new generation. 相似文献
64.
用于安全稳定控制的高压直流极闭锁判据 总被引:1,自引:0,他引:1
交直流并联运行电网中直流极闭锁后引起的安全稳定问题十分突出,如何正确判别直流极闭锁是安全稳定控制系统研究中的重要课题。采用数值仿真方法分析了直流极闭锁对电力系统稳定的影响,指出稳定控制装置必须正确、快速地判出不同形式的直流极闭锁。通过研究直流极闭锁的电气量特征以及直流控制保护系统的动作行为,提出了可靠的直流极闭锁综合判据,并进行了详细的阐述。通过介绍中国南方交直流混联电网安全稳定控制系统核心部分———高肇直流输电安全稳定控制系统,进一步论述了研究直流极闭锁判据及直流极闭锁后稳定控制的重要性。 相似文献
65.
Costas Chaikalis 《Wireless Personal Communications》2007,41(1):77-97
Reconfiguration concept represents reconfigurable functionalities of the radio interface for mobile radio systems. Particularly
for the physical layer, some possible reconfigurable architectures can be identified. We focus on outer interleaving for turbo
codes, which can improve their performance in flat Rayleigh fading environment. The larger the number of columns in the outer
interleaver, the better is the performance, but with the penalty of more complexity and delay. Furthermore, an incorrect choice
of the number of columns can increase the bit and frame error rates. Therefore, it would be advantageous to reconfigure the
outer interleaver in different operating environments with the optimum number of columns. Using two different data frame lengths,
in this contribution simulation results are presented for the four possible outer block interleaver configurations specified
for the 3GPP mobile standard in the case of flat Rayleigh fading channel. It is shown that different operating environments
require an optimum number of columns in terms of bit error rate and frame error rate performance. Finally, frame fade duration
is considered and the effect of the product of the Doppler frequency with the frame duration on the performance for the four
different 3GPP outer block interleaver configurations is discussed.
Costas Chaikalis was born in Athens, Greece, on March 7, 1973. He received the B.Sc. degree in electrical engineering in 1995 from Technological
Educational Institute of Lamia, Greece. He also received the M.Sc. and Ph.D. degrees from Department of Electronics and Telecommunications,
University of Bradford, Bradford, UK in 1999 and 2003, respectively. During his doctoral studies he worked as a Research Assistant
for Mobile Virtual Center of Excellence (Mobile VCE), Terminals Group, UK. Since 2003, he is a lecturer in the Department
of Electrical Engineering, Technological Educational Institute of Lamia, Greece. His research interests are in all areas of
mobile communications but especially in forward error correction coding, reconfigurable (software radio) architectures, cross
layer architectures and DSP applications. 相似文献
66.
公开可得到的无密码水印系统的安全性分析 总被引:4,自引:0,他引:4
在许多水印商用场合,水印嵌入和检测软件作为一个黑盒子能够公开地被得到,基于这种水印系统模型,针对目前常用的三种水印嵌入方法进行安全性分析。理论分析表明,攻击者能够在保证电子产品质量的前提下很容易地删除水印,最后,提出相应的改进方向。 相似文献
67.
Tokar David M.; Withrow Jason R.; Hall Rosalie J.; Moradi Bonnie 《Canadian Metallurgical Quarterly》2003,50(1):3
Structural equation modeling was used to test theoretically based models in which psychological separation and attachment security variables were related to career indecision and those relations were mediated through vocational self-concept crystallization. In contrast to previous studies, which have found either weak or no support for a relation between separation or attachment security variables and career indecision, results based on a sample of 350 college students indicated that some components of separation and attachment security did relate to career indecision in a theoretically supportable direction. Results also revealed that regardless of whether global or component career indecision measures were used, separation and attachment security effects on indecision were at least partially mediated through vocational self-concept crystallization. The strongest mediated relations were observed for the effects of attachment anxiety and maternal separation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
68.
中国光纤通信技术的研究、应用和发展 总被引:1,自引:0,他引:1
主要从光纤光缆、光器件与组件、光传输设备与系统、光网络建设等方面论述光纤通信技术在我国的研究、应用发展历程,并对我国光纤通信技术的未来发展进行展望。 相似文献
69.
将无线数传模块和具有低噪声的策控制电路集成设计为一体,构成检测信号和开关量控制信号无线传输的功能模块,并将该模块嵌入到探头和控制器内部,建立无线通讯子网,应用于智能能楼宇安防系统。很好的解决了无线信息冲突问题。经过试运行,系统工作稳定,无线探头报警可靠性达到了使用需求。 相似文献
70.
分析了现有移动通信网络存在的问题,阐述了第2代移动通信核心网向第3代移动通信核心网演进的必然性:讨论了第2代移动通信核心网向第3代移动通信核心网演进所采用的演进策略,介绍了两种可供选择的全IP核心网络的参考结构。 相似文献