通过CNR实现Cable Modem MAC认证

基于Cable Modem的认证系统的开发一直相对滞后,这也相对制约了Cable Modem高级业务的发展.介绍了笔者对Cable Modem认证的一些新的思路及尝试,通过建立Cable Modem MAC认证弥补现有认证系统的不足.     

基于X射线检测的电力电缆常见缺陷分析

X射线数字成像技术由于高灵敏度、无损检测等优势,可以检测出常规手段较难直观判断的设备缺陷部位及老化状况,近年来在电力电缆的缺陷检测中的应用越来越多。本文在阐述了X射线检测原理和检测参数的基础上,例举了2个X射线检测现场受损电缆的实际案例。在电缆外护套受损的情况下,通过X射线成像,可以快速判断主绝缘层是否有缺陷。非破坏性的X射线检测方法是一种高效的、节约成本的现场检测技术。     

CATV fibre-optic supertrunking: A comparison of parameters and topologies using analog and/or digital techniques

Fibre-optic supertrunking has a well-established place in larger CATV networks. Supertrunks have to be transparent to the quality of the transmitted TV signals and they have to have a negligible impact on the system reliability of the total network. At least 60 dB (weighted) video SNR has to be achieved and down times of less than one hour per year per fibre are desirable. AM on fibre can achieve these goals only in shorter supertrunks. FM and digital modulation techniques with a higher loss budget than AM are well suited for high transmission quality as well as for redundant supertrunk topologies, achieving excellent system availability numbers at the expense of increased equipment complexity.     

光纤接续和配线产品与测试仪器的使用

介绍光缆施工过程中使用的各种接续产品和相关的设备,包括光纤配线柜、光纤熔接机和OT-DR等,就使用经验和技巧提出个人的看法.     

Adaptive robust control of fully-constrained cable driven parallel robots

In this paper, adaptive robust control (ARC) of fully-constrained cable driven parallel robots is studied in detail. Since kinematic and dynamic models of the robot are partly structurally unknown in practice, in this paper an adaptive robust sliding mode controller is proposed based on the adaptation of the upper bound of the uncertainties. This approach does not require pre-knowledge of the uncertainties upper bounds and linear regression form of kinematic and dynamic models. Moreover, to ensure that all cables remain in tension, proposed control algorithm benefit the internal force concept in its structure. The proposed controller not only keeps all cables under tension for the whole workspace of the robot, it is chattering-free, computationally simple and it does not require measurement of the end-effector acceleration. The stability of the closed-loop system with proposed control algorithm is analyzed through Lyapunov second method and it is shown that the tracking error will remain uniformly ultimately bounded (UUB). Finally, the effectiveness of the proposed control algorithm is examined through some experiments on a planar cable driven parallel robot and it is shown that the proposed controller is able to provide suitable tracking performance in practice.     

月表温度变化下电缆装联材料性能影响分析

在探月任务中,由于月球表面温度变化非常大,探测器上的电缆需要经历高温达125℃,低温达-180℃的严酷极限温度条件,因此电缆装联所用的电连接器、热缩套管、灌封胶等材料是否能经受住如此严酷的温度是一个疑问。为此开展了高低温下电缆用材料的特性变化试验,并对出现的问题进行了分析,得出了可适用于深空探测的合适的材料。试验结果如下:(1)airborn微小型电连接器在125℃高温下绝缘性能显著下降,国产J30JH微小型连接器高温绝缘性能较稳定;(2)125℃高温下国产RSG热缩套管发生熔化并粘连;(3)高低温循环作用下,采用ATUM套管加热缩带或纯热缩带的方式可保证尾罩处理满足使用要求。     

光缆拉伸应变分布测量的新方法：布里渊光纤时域分析技术

通信光缆拉伸应变分布测量对于保证光纤通信线路的长期可靠性具有十分重要的意义。文章论述了布里渊光纤时域分析技术的背景、现状、描述了该技术的基本原理，存在的问题以及目前研究的最新进展。     

地下隧道中电力电缆的线路阻抗矩阵相序阻抗矩阵和参数的分析

在研究电力电缆发生短路对周围通讯系统的危险影响时,短路电流的分布和入地电流系数的计算是至关重要的,这必然涉及线路阻抗,相序相抗和自互阻抗等参数,文章给出了电缆线芯不换位,金属护套交叉互联两端接地系统的线路阻抗矩阵,相序阻抗矩阵的直观表达式,分析了它们的一些性质,介绍了隧道中电缆参数的一种分析方法,即虚拟媒质法,应用该法可以方便地处理道空气区对其自互阻抗的影响,由于该法是数值方法,隧道横截面形状可以     

活动发射平台大摆杆机械结构与液压系统联合仿真研究

大摆杆是活动发射平台重要的组成部分,当摆杆快速摆开时,如果发生急停情况,将会对大摆杆液压缸及其管路、大摆杆结构及安装的连接器产生较大的冲击载荷.基于ADAMS和AMESim联合仿真的方法对活动发射平台大摆杆的运动过程进行仿真,主要分析急停工况下大摆杆上不同位置的角速度和角加速度,为大摆杆的设计和试验提供指导.     

从国办发[2008]1号文件看广电有线网络改造的紧迫性

从国办发[2008]1号文件的出台,论述广电有线电视网络双向化改造的紧迫性,以及有线电视网络双向化改造采用技术方案的选择建议。