Towards an efficient failure detection in MANETs

Mobile ad hoc networks (MANETs) are characterized by a dynamic topology and generally deployed in a hostile environment with limited resources. As a result, the nodes are more vulnerable and are often subject to failures. Therefore, the design of an efficient failure detector in MANETs is a very challenging issue as the detection is proved to be unreliable. Such an achievement amounts to balance between the performances of the accuracy, the completeness and the resource consumption. We present and discuss in this paper a solution for an efficient failure detection in MANETs. This new protocol, called efficient failure detection for MANETs, exploits different mechanisms to improve the completeness and the accuracy of the detection while reducing the traffic overhead. The number of used timers are limited to two for each node thus reducing the complexity of the algorithm. The simulations performed on NS2 platform show the efficiency of efficient failure detection for MANETs comparing with other protocols. Copyright © 2016 John Wiley & Sons, Ltd.     

一种基于有限信息反馈的最佳中继选择协议研究

针对多用户的TDMA无线自组织协同通信网络,深入研究了基于有限信息反馈的最佳编码协作中继选择策略,在瑞利和莱斯信道条件下对该协议的中断概率和误码率性能进行了计算机仿真,并对协议做了进一步细化和优化。仿真和分析结果表明,该中继选择策略的中断概率和误比特率性能较传统策略有较大提升,且改进后的方案能明显减少协同交互信息开销。     

城市环境VANETS下的基于beacon控制的路由方案

车载网络(Vehicular ad hoc networks,VANETs)是一种特殊形式的网络,具有节点高速移动、拓扑频繁的变化的特性。这些特性为消息的传播带来挑战。路由机制是实现消息传递的关键因素。地理位置路由被广泛地应用于VANETS,要求节点周期广播beacon消息。然而,节点周期地广播beacon消息,降低了路由性能,特别是在城市区域,由于节点密集,每个节点均广播beacon消息,恶化了路由性能。为此,针对城市环境,提出基于beacon控制的路由协议RPBC(Routing protocol with beacon control)。在RPBC中,并非每个节点广播beacon消息,而设置有效的机制选择部分节点广播,从而降低了beacon冗余,同时,采用最短路径算法,减少数据传输跳数。仿真结果表明,提出的RBPC在分组投递率、端到端传输时延以及路由开销方面均有较好的性能。     

架空绝缘导线在配网改造工程中的使用

架空绝缘导线与裸导线不同,两者在配网改造工程中的使用存在较大差别,若不按技术标准操作,工艺细节稍不注意都会对电网产生不利影响.文中阐述了架空绝缘导线在配网改造工程中的适用范围及选型,并介绍了一些需要注意的问题.     

Parallelism of multi-scale quantum harmonic oscillator algorithm

MQHOA was a novel intelligent algorithm constructed by quantum harmonic oscillator's wave function.Sampling was the basic operation and main computational burden of MQHOA.The independence of sampling operation constructs MAHOA’s parallelism.Parallel granularity was obtained by experiments of group parameter and sampling parameter,and MQHOA-P was proposed.Experiments were done in a cluster of ten nodes on six standard test functions.By changing node number,function dimension and sampling parameter,experiments of MQHOA-P’s speed-up ratio were done.The experimental results show the good performance of MQHOA-P’s speed-up ratio and expansibility.MQHOA-P can be deployed and run on multiple nodes in a large-scale cluster.     

基于新型随机度分布的压缩喷泉码

该文提出二进制指数随机度分布(Binary Exponential Random Degree Distribution, BERDD)函数,用BERDD函数生成度时提高了度1生成的概率,同时降低度1断层出现的概率,提高了迭代效率。进一步,为解决喷泉码需要传输带宽大的问题,提出基于码本压缩的传输方式。仿真表明BERDD分布较二进制指数度分布及稳健孤子度分布更能有效提高译码效率,在瑞利衰落信道条件下,基于码本压缩喷泉码传输方法能有效降低编码占用信道带宽。     

基于JASMIN平台的复合材料方舱SE快速评估

在时域有限差分（FDTD）法中采用亚网格边界条件（SGBC）法对复合材料薄层结构进行建模,可以突破复合材料薄层对空间步长的限制从而大大降低计算成本。基于大规模并行化平台JASMIN实现了SGBC-FDTD算法,通过对复合材料薄层结构的自动建模和适配,实现对复合材料薄层的快速并行化处理。利用所开发的并行SGBC-FDTD算法计算分析了含不同电磁特性复合材料薄层方舱在0.1～1.0 GHz内的电磁屏蔽效能,结果表明采用并行SGBC-FDTD算法的计算结果与全波分析软件计算结果吻合完好,且计算效率显著提升。     

密度矩阵重正化群的异构并行优化

密度矩阵重正化群方法（DMRG）在求解一维强关联格点模型的基态时可以获得较高的精度，在应用于二维或准二维问题时，要达到类似的精度通常需要较大的计算量与存储空间.本文提出一种新的DMRG异构并行策略，可以同时发挥计算机中央处理器（CPU）和图形处理器（GPU）的计算性能.针对最耗时的哈密顿量对角化部分，实现了数据的分布式存储，并且给出了CPU和GPU之间的负载平衡策略.以费米Hubbard模型为例，测试了异构并行程序在不同DMRG保留状态数下的运行表现，并给出了相应的性能基准.应用于4腿梯子时，观测到了高温超导中常见的电荷密度条纹，此时保留状态数达到10⁴，使用的GPU显存小于12 GB.     

Hardware reduction in continuous checksum-based analog checkers: Algorithm and its analysis

Fault-tolerant design of analog circuits is more difficult than that of digital circuits. Chatterjee has proposed a continuous checksum-based technique to design fault-tolerant linear analog circuits. However, hardware overhead of the embedded checker is an important issue in this technique, which has never been addressed before. This paper proposes an algorithm for reduction of hardware overhead in the checker. Without changing the original circuit, the proposed algorithm can not only reduce the number of passive elements, but also the number of analog operators so that the error detection circuitry in the checker has optimal hardware overhead. As the basis of the algorithm, a serial of theoretic results, including the concept and existence conditions of all-non-zero solutions, have also been presented to verify the algorithm.     

密度矩阵重正化群的异构并行优化

密度矩阵重正化群方法（DMRG）在求解一维强关联格点模型的基态时可以获得较高的精度，在应用于二维或准二维问题时，要达到类似的精度通常需要较大的计算量与存储空间.本文提出一种新的DMRG异构并行策略，可以同时发挥计算机中央处理器（CPU）和图形处理器（GPU）的计算性能.针对最耗时的哈密顿量对角化部分，实现了数据的分布式存储，并且给出了CPU和GPU之间的负载平衡策略.以费米Hubbard模型为例，测试了异构并行程序在不同DMRG保留状态数下的运行表现，并给出了相应的性能基准.应用于4腿梯子时，观测到了高温超导中常见的电荷密度条纹，此时保留状态数达到10⁴，使用的GPU显存小于12 GB.