多播同步协作的动态安全机制

分析了多播同步协作应用的安全问题,提出了一种比较实用的安全机制方案。并据此实现了一个多播视频会议的安全管理模块。     

CDMA基站上行干扰的定位和清除

重点介绍如何有效地进行CDMA基站上行干扰的定位和清除,详细介绍干扰定位和清除的方法和流程,并给出复杂干扰定位和清除案例。     

Near optimality of stochastic control in systems with unknown parameter processes

Stochastic control for systems with an unknown parameter is considered in this paper. The underlying problem is to minimize a functional subject to a system described by a singularly perturbed differential equation with an unknown parameter process driven by fast fluctuating random disturbances. This problem arises in the context of stochastic adaptive control, adaptive signal processing, and failure-prone manufacturing systems. Due to the nature of the wide-bandwidth noise processes, identifying the parameter process for eacht is very hard since the driving noise changes very rapidly. An alternative approach is used, and an auxiliary control problem is introduced to overcome the difficulties. By means of weak convergence methods and comparison control techniques, nearly optimal controls are obtained.This research was supported in part by the National Science Foundation under Grant DMS-9022139 and DMS-9224372.     

Using stochastic optimization to determine threshold values for the control of unreliable manufacturing systems

A manufacturing system with two tandem machines producing one part type is considered in this work. The machines are unreliable, each having two states, up and down. Both surplus controls and Kanban systems are considered. Algorithms for approximating the optimal threshold values are developed. First, perturbation analysis techniques are employed to obtain consistent gradient estimates based on a single simulation run. Then, iterative algorithms of the stochastic optimization type are constructed. It is shown that the algorithms converge to the optimal threshold values in an appropriate sense. Numerical examples are provided to demonstrate the performance of the algorithms.The research of these authors was supported in part by grants from URIF, MRCO, National Science Foundation, and Wayne State University. The authors would like to thank Dr. X. R. Cao, Digital Equipment Corporation, for the valuable initial discussion and Dr. X. Y. Zhou, University of Toronto, for his helpful comments.     

垃圾邮件过滤技术分析

主要介绍基于邮件的过滤技术,对目前邮件过滤采用的模式———单机模式和将来可能采用的模式———网络模式做了个评估,并重点介绍了在单机模式中的一种基于邮件内容的过滤算法———贝叶斯算法,以及这种算法的不足和改进。     

浅析C620型普通车床电气控制线路原理及故障维修

随着加工制造行业的发展,数控机床的使用需求得到进一步提升,同时也带动了企业生产效率和产品质量水平的提高.但在实际加工过程中难免会出现各类故障,当故障发生后怎样做好故障的排查与维修,保障生产线的正常运行,提高效率.因此,本文以机床当中的一种C620型普通车床为例,就其电气原理及故障展开分析讨论.同时希望可以为相关工作的人...     

低气压激光介质氦氖共振转移速率系数的测量

为了对Ｈｅ－Ｎｅ激光器的放电机理进行动力学研究，本文报导采用脉冲余辉法测量Ｈｅ－Ｎｅ共振转移速率系数，我们的测量方法比流动余辉法简单，我们测量的情况完全类似于Ｈｅ－Ｎｅ激光器的工作条件。     

Survivable routing,spectrum and waveband assignment strategy in cloud Optical and Data Center Network

These years, data centers are developing quickly and cloud Optical and Data Center Network (ODCN) has been shown to be the most viable solution for inter-data-center network implementation with less energy consumption and higher transmit rate. At the same time, elastic optical networks and waveband switching can address the problems caused by dramatic increase in network scale. In cloud hierarchical ODCN with flexible spectrum and waveband switching, survivability is an important and complex issue which is needed to be researched. So, we study the survivable routing, spectrum and waveband assignment strategy in cloud hierarchical ODCN, and in this paper, a novel hierarchical shared-protection (HSP) strategy is proposed. We consider spectrum fragmentation, waveband and shared-protection simultaneously. By quantifying the influence of spectrum assignment and the emergence of fragmentation, slots are assigned to the optimal paths. In order to share protection resource or wavebands, a heuristics algorithm named HSPGA is proposed for optimally picking out the two protection paths. Simulation results show that the proposed HSP strategy decreased the amount of employed ports significantly. In addition, the spectrum efficiency is improved.     

Dual-mode gain control for a 1?V CMOS hearing aid device with enhanced accuracy and energy-efficiency

A dual-mode gain control (DMGC) technique is presented for accurate and energy-efficient pre-amplification in the front-end system of a hearing aid chip. Compared with the conventional automatic gain control (AGC) approach, the DMGC approach is characterized by an amplification switching mechanism between the pro-linearity discrete gain setting mode and the energy-efficient AGC mode. Thus, the total harmonic distortion (THD) should be significantly improved without incurring any degradation concerning other performances parameters (e.g. gain, noise and power consumption). In order to further enhance the system power efficiency, a self current-adapting (SCA) circuit design technique is proposed. Such SCA circuits are capable of automatically adjusting the bias current in accordance with the sound level. A prototype chip was designed with a 0.13???m standard CMOS process and tested with 1?V supply voltage. The measurement results show that, for a typical output level of 500?mV_p-p, the THD is somewhere below ?64?dB, achieving approximately ten times reduction compared to the previously reported works. The power consumption of less than 45???W has also been obtained. In addition, the typical input referred noise is only 2???V_rms and the maximum gain attainable is up to 39?dB.     

法国宽带接入市场现状与分析

介绍法国近几年宽带接入在技术、用户和业务等各方面的发展。法国宽带接入住宅市场目前应用最广泛的技术是ADSL,其次是有线电视网,其他如BLR,WiFi和电力网等技术应用有限。专业市场除了以上技术外,还有光纤专网,但小企业更愿意选择大众化服务,且许多用户将从专网向DSL转移。总体来讲,住宅市场的竞争程度高于专业市场,因而发展更快。由于相关法律的出台,有线电视市场处于重组之中。