发展中的我国卫星电视接收技术

本文综述了我国卫星电视接收的发展情况，论述了当前卫星电视接收中的关键技术－超低噪声高频头和一体化高频头，低噪声天线和天线的小型化，多制式微处理器控制的低门限接收机，多星广播的接收和多波束天线，卫星电视信道的综合利用。     

中波调幅广播的发展方向

调幅立体声作为80年代发展起来的一项新技术日前在中波调幅广播中已处于逐步成熟与完善的阶段。本文详细介绍这项技术的发展历史以及与日前调频立体声的比较,并解释了调幅立体声中应用最广泛的美国MOTOROLA公司兼容正交调制(C—QuAM)的原理与发射系统。     

一种在无线自组织网络中延长网络生存时间的累积广播算法

文章考虑一个无线自组织网络中的广播问题,分析研究了传统累积广播算法及其性能表现,提出了一种新颖的算法,延长生存时间累积广播算法(ELAB算法)。然后通过一个4节点网络模型详细阐述了这一算法,并将它扩展到N节点无线自组织网络中。理论分析和仿真结果证明,相比于传统累积广播算法,对于不同的网络结构和节点数量,ELAB算法可延长网络的生存时间至少50%。     

基于ZigBee节点的按需时间同步算法

简要阐述近年来无线传感网络时间同步（TPSN）算法的发展概况和影响无线传感器网络时间同步的因素,结合无线传感网络中路由节点与终端节点的特点,提出一种融合了参考广播同步（RBS）与TPSN算法设计,在保持同步精确度前提下,整个网络的功耗大大降低。通过实验采集到的数据分析了协议的可行性,证明该算法较适合于对节点密度高,终端节点较多的无线网络中,如工业有害气体的检测。     

中小电视台播控机房的安全策略

从保证安全播出的角度,阐述了中小电视台播控机房系统设计与维护可以采取的策略及应注意的事项,重点阐述了硬件方面的安全策略。     

山西中波台播控自动化的开发和应用

山西中波台的广播发射机经历了从板调机、脉宽机、PSM数字调幅、全固态机PDM、的发展历程。从电子管到全固态的转变就为数字化改造奠定了基础。发射机控制系统也经历了从继电器控制、数字逻辑电路到今天信息时代的微机控制,所有这些改进和更新都是在技术进步的推动下完成的,不仅能对输入信号源和输出功率的定性监测而且能对发射机实时定量监测,这就使山西中波台播出更安全、更经济、指标更优良、操作更简单,值机人员劳动强度大大降低,基本上可以实现机房播出自动化,大大节约人力资源,最终达到"有人留守、无人值班"。     

Broadcasting from multiple originators

We begin an investigation of broadcasting from multiple originators, a variant of broadcasting in which any k vertices may be the originators of a message in a network of n vertices. The requirement is that the message be distributed to all n vertices in minimum time. A minimumk-originator broadcast graph is a graph on n vertices with the fewest edges such that any subset of k vertices can broadcast in minimum time. B_k(n) is the number of edges in such a graph. In this paper, we present asymptotic upper and lower bounds on B_k(n). We also present an exact result for the case when . We also give an upper bound on the number of edges in a relaxed version of this problem in which one additional time unit is allowed for the broadcast.     

An Efficient Framework for Scalable Defect Isolation in Large Scale Networks of DNA Self-Assembly

This paper proposes and evaluates an approach for defect isolation of DNA self-assembled networks made of a large number of processing nodes. The complexity of DNA self-assembled networks makes impractical to add a large amount of redundancy and employ inefficient and unscalable defect tolerant schemes. A previous framework based on a broadcast algorithm isolates defective nodes without incorporating redundancy for nodes. However, its disadvantage is the limited scalability, thus making it unsuitable for extremely large scale networks built by DNA self-assembly. The proposed framework improves upon the previous framework by involving three algorithmic tiers; namely, 1-hop wave expansion, efficient via placement, and unsafe node detection. The performance of the proposed framework is evaluated and compared with the original framework by considering large scale networks (up to 2,000 × 2,000 nodes), and a novel gross defect model (as well as a conventional random defect model as assumed in previous works). Simulation results indicate that the proposed framework outperforms the original framework in broadcast latency and efficiency and shows excellent scalability for DNA self-assembled nano-scale networks.

Improved algorithm for broadcast scheduling of minimal latency in wireless ad hoc networks

A wide range of applications for wireless ad hoc networks are time-critical and impose stringent requirement on the communication latency. One of the key communication operations is to broadcast a message from a source node. This paper studies the minimum latency broadcast scheduling problem in wireless ad hoc networks under collision-free transmission model. The previously best known algorithm for this NP-hard problem produces a broadcast schedule whose latency is at least 648（rmax/rmin）^2 times that of the optimal schedule, where rmax and rmin are the maximum and minimum transmission ranges of nodes in a network, respectively. We significantly improve this result by proposing a new scheduling algorithm whose approximation performance ratio is at most （1 ＋ 2rmax/rmin）^2＋32, Moreover, under the proposed scheduling each node just needs to forward a message at most once.