An ant colony optimisation algorithm for aggregated multicast based on minimum grouping model

The tree‐based delivery structure of the traditional Internet protocol multicast requires each on‐tree router to maintain a forwarding state for a group. This leads to a state scalability problem when large numbers of concurrent groups exist in a network. To address this state scalability problem, a novel scheme called aggregated multicast has recently been proposed, in which multiple groups are forced to share one delivery tree. In this paper, we define the aggregated multicast problem based on the minimum grouping model, and propose an ant colony optimisation algorithm. The relative fullness of the tree is defined according to the characteristics of the minimum grouping problem and is introduced as an important component in identifying the aggregation fitness function between two multicast groups. New pheromone update rules are designed based on the aggregation fitness function. To improve the convergence time of the algorithm, we use the changes (brought by each group) in the relative fullness of the current tree as the selection heuristic information. The impact of the relative fullness of the tree is analysed using the hypothesis test, and simulation results indicate that introducing relative fullness to the fitness function can significantly improve the optimisation performance of the algorithm. Compared with other heuristic algorithms, our algorithm has better optimisation performance and is more suitable for scenarios with larger bandwidth waste rates. Copyright © 2011 John Wiley & Sons, Ltd.     

基于最小像素误差控制的曲线矢量数据自适应数学描述

 矢量数据的B样条曲线拟合算法被广泛地应用于数据的可逆压缩和矢量曲线数据的数学表达.但现有算法的误差评估大都是针对各坐标轴具有相同尺度单位的,而对各坐标轴尺度单位不同的工程曲线图则无能为力.据此提出了一种不大于1个像素最小栅格误差的矢量数据自适应序号参变量样条曲线拟合算法.该算法首先从矢量数据中以近乎相等的曲线弧长选出若干型值节点,并通过盈亏修正获得节点误差限为0.001的序号参变量样条曲线拟合.然后遍历拟合曲线对应的全部栅格点,检测它所在3×3邻域内是否有矢量数据栅格点或栅格图像曲线点位于其中,若有则该点满足于1个像素的误差限,反之将该曲线型值节点段进行标记,并转到曲线的下一型值节点段继续进行检测.对不满足要求的曲线型值节点段,通过添加一个型值节点或曲线序号数的移位等使之满足误差要求.实验结果表明该算法具有更高的准确性和使用的方便性.     

架空线路异物激光清除技术研究

为了解决传统工具和方法难以经济、高效、安全地清除架空输电线路异物的问题,提出了陆基定向能红外激光远程切割清除架空线路异物的方法,并进行了理论分析、有限元仿真和实验验证。基于上述研究,研制了架空线路异物激光清除设备,并进行了模拟实验和现场工程应用。结果表明,清除异物所需最小功率密度为20W/cm2,该功率密度的激光对导线不会造成损伤。该设备可远程、快速、带电、安全地清除架空线路异物。     

逆合成孔径雷达成像仿真

逆合成孔径雷达的运动补偿问题已有很多讨论,并在实际中得到成功的应用。运动补偿是ISAR成像技术的关键,分两步进行：包络对齐和相位校正。本文从全局效果出发,研究了平均包络最小熵包络对齐法和最小熵相位校准法的原理及算法实现,并对仿真数据进行成像处理。实验结果表明,平均包络最小熵法和最小熵相位校正法在ISAR雷达的运动补偿算...     

光电设备机箱模块锁体的优化仿真

根据光电设备机箱模块锁体的载荷和约束条件要求,按照锁体最小质量原则和实际使用工况,对锁体的相关参数进行优化仿真,通过UG NX7.0有限元软件对锁体给出相关参数设置,软件多次对质量和草图驱动尺寸进行迭代计算,计算结果趋于收敛,得出锁体在满足强度和刚度的条件下质量最小,经分析计算和试验验证,满足了设备减重要求,为整机其他零件进行优化设计提供了参考。     

Soft-Decision Decoding of Punctured Convolutional Codes in Asynchronous-CDMA Communications Under Perfect Phase-Tracking Conditions

In this paper, the performance of punctured convolutional codes of short constraint lengths is discussed. The punctured codes are used to provide error protection to a particular user in an asynchronous CDMA system. A perfect phase reference is assumed to be available throughout this paper. A slow fading Rician channel is assumed. Maximum likelihood decoding through a Viterbi algorithm is used to decode the information symbols. Soft-decision decoding of punctured convolutional codes is considered in this paper. The upper bounds with Viterbi decoding are derived and plotted for the various punctured codes considered. The simulated results are found to agree very well with their upper and lower bounds.     

内容寻址网络中内容的有效定位

P2P(Peer—to—Peer)的最基本的问题是如何高效地查找到存放文件的节点。本文提出在保持内容寻址网络(Content Addressable Network：CAN)现有特性的基础上建立一种更快捷有效的内容定位结构：基于快捷链接和最小距离的内容定位。本文首先介绍了内容寻址网络的基本工作原理，然后详细描述了基于快捷链接和最小距离进行内容定位的方法，并通过仿真证实了该方法很大程度上改善了CAN的性能。     

使用EASE声学设计软件应注意的几个问题

EASE是当今世界最流行的计算机声学辅助设计软件,可预测声频系统的各种指标,但很多使用者在使用上对EASE的某些功能或概念不甚了解,并且对使用EASE的目的性不明确,认为使用EASE只是为了应付投标或客户的需要而已,忽略了EASE对实际的工程项目所具有的前瞻和指导意义。对使用EASE应注意的几个声学问题进行了阐述,例如常被人忽略的扬声器的各向相频数据对干涉的影响、如何获得更符合实际的混响时间数值等。并明确了EASE实用化的前提条件和指导意义。     

基于最小费用最大流的无线多媒体传感网多路径路由算法

为了解决多媒体数据的实时传输和网络生存时间优化问题,提出基于最小费用最大流的无线多媒体传感网多路径路由算法(MRAMCMF).MRAMCMF分析了数据传输能耗、节点剩余能量和最小数据传输时延,提出了新的权值函数,并利用最小费用最大流算法构建多路径的数据路由方案.所有多媒体传感节点沿着多个传输路径将数据传输到sink节点.仿真结果表明,该算法能延长网络生存时间,降低和平衡节点能耗,降低数据传输时延,在一定的条件下,比Ratio_w算法和TPGF算法更优.