HCONoC: a novel high-performance hierarchical optical network on chip

针对传统的片上电互连在带宽、时延等方面遇到的问题,提出一种基于光分组交换技术的分层簇的光片上网络(HCONoC).设计了该网络的拓扑结构连接方式、布局方法、节点编址命名方法以及扩展方式等.为HCONoC的不同层次结构分别构建了新的无阻塞片上光路由器结构,并分析了损耗特性.根据网络拓扑的具体特点和编址方式,设计了有效的路由算法,可提高网络吞吐同时减少时延.最后,使用OPNET搭建仿真平台,对所提网络结构的时延和吞吐性能进行了仿真,结果表明该网络结构在本地流量模式下显示出更强的性能优势.     

应用于Ad Hoc网络的时延敏感自适应路由协议

针对Ad Hoc网络中实时业务对网络平均时延的要求，提出了一种应用于Ad Hoc网络的新型路由协议——时延敏感的自适应路由协议。该协议在保持“最少跳数”的最佳路由条件下，增加了“平均最短时延”的约束条件，从而不仅可以为实时业务(即时延敏感的业务)提供可靠的路由，同时还能根据网络节点当前的业务流量，动态地选择最佳路径，降低网络的平均时延。这是一种新型的有QoS保证的路由协议。仿真结果表明，该协议的确可以有效地改善网络的性能。     

面向测试任务的交换机结构设计

针对现有交换机不能满足网络化测试应用实时性要求的问题，以及目前网络闭环时间传递方法存在的缺点与不足，设计了一种具有时间传递、时间检测、时钟再生功能的同步介质访问控制器（SMAC，Synchronized Medium Access Controller）．同时设计了用于测量网络链路时延的SMAC时间帧结构．在此基础上对现有交换机结构进行了改进，给出了基于SMAC的以太网交换机结构设计方案，同时分析了基于SMAC的时间链路组成结构，提出了基于SMAC的开环时间传递方法，并进一步阐述了链路时延的测量过程．最后构建了实验平台，验证了基于SMAC的开环时间传递方法的有效性．实验结果表明，在经过一级SMAC交换设备的以太网环境中实现了25ns的时间传递精度．     

双基阵被动定位位置估计算法研究

根据双基阵被动定位的特点，分别论述了仅利用方位测量信息的交叉测向法定位原理和利用方位及时延差测量信息的测向测时差法定位原理，并在相同的仿真条件下，对两种方法的定位性能进行了比较。介绍了可提高被动定位精度的数据预处理和最小二乘拟合方法。通过蒙特卡洛仿真分析比较了基阵位置、基阵间距及各种测量参数改变对定位性能的影响。仿真结果表明，基于纯方位测量信息和方位—时延差测量信息的双基阵被动定位方法，避免了观测平台的机动，具有较好的可观测性，经过必要的改进，可用于对海上机动目标的无源定位。     

排队论与通信网络性能影响的研究

本文通过排队论的知识来分析网络带宽,充分体现数学模型在网络研究中的应用。然后介绍通信网络的几个性能指标,并对三种最常用的以太网进行性能分析。本文对网络带宽时延的测量具有重要的理论指导意义。     

OBS接入TCP和UDP的性能分析

仿真分析了光突发交换(OBS)网络在接入TCP和UDP协议以及不同输入流量特性业务时的性能,以及端到端延迟和组装时延对TCP和UDP协议的数据发送速率的影响。结果表明：在正常负载下,OBS边缘节点对UDP协议的支持能力高于对TCP协议的支持能力;而无论在TCP还是UDP协议下,边缘节点对恒定比特率(CBR)流量的支持都要好于对指数分布(EXP)流量的支持;在TCP协议下,数据发送速率随端到端延迟和组装时延的增大而降低;而UDP协议下,数据发送速率不受延迟和组装时延的影响。     

混响室内时延特性测量关键不确定度分量分析

混响室内,信道特性测量的不确定度决定了基于混响室进行的无线通信设备性能测试的准确性。本文以测量实验为基础,针对均方根时延扩展这一核心信道参数,对两个关键不确定度来源,给出了不确定度分析的方法和流程。首先,利用蒙特卡洛法分析了由核心测量设备网络分析仪引入的不确定度。其次,分析了固有场不确定度。对不确定度的深入分析为测量中一些关键设置的设定提供了量化的参考依据,有助于测量系统的设计与优化。     

基于模式识别的自适应时钟重置检测算法

为解决网络测量中因测量主机的时钟重置导致单向时延测量误差的问题,根据时钟重置发生的不定时性和发生次数未知的特征,提出了一种基于模式识别的自适应时钟重置检测算法（PRBA）。该算法基于模式识别中的最大最小距离聚类算法对单向时延测量值进行聚类,同时利用时间序列技术中的一种低通滤波器过滤出噪声区间,从而有效识别网络行为特征,自适应地检测时钟值瞬时调整方式的时钟重置。实验结果表明,与现有同类算法相比,该算法具有较高准确性和自适应性。     

Ad hoc网络中一种跨层流量分配算法——CLATA

针对ad hoc网络各协议层的功能都相互关联的特点,提出了一种在ad hoc网络中基于网络平均时延最小的跨层自适应流量分配算法（CLATA）。该算法将网络层自适应流量分配信息传递给媒体接入控制（MAC）层,以改进MAC层中的冲突退避算法,实现网络平均时延最小化,提高网络的利用率。仿真实验结果表明,该算法可以动态调整链路之间的流量,并具有快速的自适应性,优化网络资源的利用。     

分簇无线传感器网络的双时槽混合MAC协议

基于事件驱动的无线传感器网络应用,提出了一个基于分簇优化的低时延混合MAC协议--CHMAC.CHMAC采用双时槽传输调度和载波检测多路接入/时分多址接入(CSMA/TDMA)混合模式,采用适合分簇网络的时槽分配,优先保证紧急事件的最小延迟发送,并充分利用分簇网络的数据流特点,精细控制节点的侦听、睡眠以及传输功率,以提高能量有效性和网络吞吐量.理论分析和模拟试验表明,该协议能够以良好的适应性和健壮性在各种流量条件下均表现良好的性能.     

Neural networks to model dynamic systems with time delays

An algorithm is proposed to identify a neural network model that represents a nonlinear dynamic system with a multivariate time delay response. The algorithm consists of two major parts. The first one identifies the time delay vector for a given neural network structure. This task is accomplished by using an exhaustive integer enumeration algorithm that minimizes a statistical parameter to assess the performance of the neural network model. The second part uses a cross-validation strategy to identify the best neural network model. Since the structure that models a nonlinear system is usually unknown, the identification strategy consists of selecting several neural network structures and identifying the best time delay vector for each network. The modeling process starts with the simplest structure and progressively the complexity of the network is increased to end up with a complex structure. Finally, the network that offers the simplest structure with the best network performance is the one that exhibits the appropriate neural network structure with the corresponding optimal time delay vector. The Monte Carlo simulation technique was used to test the performance of the algorithm under the presence of linear and nonlinear relationships among several variables of dynamic systems and with a different time delay applied to each input variable. The introduced algorithm is used to detect a chemical reaction delay among enriched amyl acetate, acetic acid, water, and the pH of erythromycin sail. An appropriate neural network model was designed to model the pH of the erythromycin during a continuous extraction process. To the best of the authors knowledge the proposed algorithm is the only one currently available to identify time delay interactions in the multivariate input output variables of a system. The major drawback of the introduced algorithm is that it becomes very slow as the number of system inputs increases. This algorithm works efficiently in a system that involves five inputs or less.     

Estimating the impact of abnormal loads on network performance

The English Highways Agency is required to improve network performance including journey time reliability measured by average delay on the 10% slowest journeys along a specified set of primary routes in the strategic road network. Abnormal indivisible loads, which behave as moving bottlenecks, can cause significant delay, but the factors involved are complex, so methods have been developed to model their effect. These methods have been extended to estimate their impact through the Average Vehicle Delay (formerly PSA1 delay) measure, allowing mitigations through intelligent transportation system or policy options to be evaluated. Environmental impacts are also considered.     

喷雾参数对喷雾冷却换热特性影响的实验研究

搭建了一套封闭式喷雾冷却实验系统(水为工质),利用高速摄像仪对实验进行了可视化研究,分析对比了喷雾高度和喷雾压力在光滑表面及微结构表面对喷雾冷却换热特性的影响。结果发现:相比于光滑表面,在微结构表面上,喷雾高度和喷雾压力对喷雾冷却换热的影响更加明显。当喷雾高度较高时,降低喷雾高度可明显提高热流密度,直至喷雾高度较低且喷雾底圆与换热面内接时,继续降低喷雾高度,热流密度也略有上升;反之,提高喷雾高度则会降低热流密度,减小工质的有效流量,使换热表面过早出现干涸,表面温度均匀性变差。但大幅降低喷雾高度会延迟喷雾冷却进入两相区换热,降低喷雾冷却效率,并不利于换热。所以,喷雾高度对喷雾冷却换热特性的影响具有两面性,而喷雾压力的影响则趋于单一性,增大喷雾压力能提高喷雾冷却热流密度,增强表面温度均匀性,尤其在单相区,随着喷雾压力的增大,热流密度明显增大,最后趋近于一个固定值。     

一种新的基于移动预测的MANET路由协议

移动自组网是一种由一系列可以自由移动的节点主机聚集而成的一个临时性动态网络。它没有固定基站，也没有作为控制管理中心的节点主机，由于其拓扑的动态性，其路由协议与其他传统网络有很大的区别。为了能更有效地移动自组网中实现数据的传送，本文提出了一种基于移动预测下的MANET路由协议，该协议综合考虑了传输路径的延时和稳定性，选择在延时限制下平均拥有最稳特性的传输路径，模拟结果表明，这种方法比基于移动预测量稳路径路由协议的传输时延要短，传送成功概率要高，而控制开销却相关不大。     

Integrated availability model based on performance of computer networks

An efficient computer network can realize bulk data transfer and real time control with high reliability and precision. Its availability is dependent on its topological structure and network services performed simultaneously. To explore the dynamic interactions between software and hardware failures, generalized stochastic petri net (GSPN) is adopted to model the availability of nodes in the network, and then the study is developed through path selection and service performance evaluation. Network performance indices such as throughput and time delay can be obtained by modeling the network service with queueing theory. With Power formula, this paper presents an integrated availability model. This model considers both topological connectivity and operational performance, developing the availability analysis from the viewpoint of a user.     

Hierarchical wireless mobile MPLS mechanism using foreign tracking agent based on M/G/1 with capacity c queueing model

Within the Multiprotocol Label Switching (MPLS) network, packets with the same forwarding equivalent class can easily be identified by their attached label value. The cross-layer topology associates with access protocol and IP mobility agents. The necessity of agent discovery is reduced and an approach to enhance handoff efficiency proposed. This efficient handoff scheme is performed by a foreign tracking agent (FTA) that plays a role as an administrator of a hierarchy that consists of some foreign agents (FAs) to localise the routing operation of forwarded packets. To analyse the performance of a hierarchical mobile MPLS network, the system is modelled as an M/G/1 system with capacity c, where c represents the number of FAs that can be administered for an FTA. The mean delay time of the FTA to process the forwarding of packets is analysed using M/M/l with capacity c queueing model. The minimum number of FAs that can be administered for an FTA is derived to improve network performance by minimising mean delay time.     

基于跨层设计的机械振动WSNs同步采集多跳累积误差控制方法

针对机械振动无线传感器网络跨层同步采集精度随网络深度增加而急剧降低的问题,建立同步采集关键同步信息传输模型,分析多跳同步误差累积机理,得出嵌入式软件调度实时性不高、晶振随机抖动及无线链路随机迟滞是多跳误差累积主要原因。由此提出基于跨层设计的机械振动无线传感器网络同步采集多跳累积误差控制方法:提出多路硬件跨层设计消除嵌入式软件调度迟滞影响,提高同步任务实时性;采用高精度有源晶振抑制晶振随机抖动;建立无线链路跨层传输随机迟滞数学模型,采用回归分析方法校准由此导致的同步信息随机抖动及传输时延计算误差,提升同步采集精度。最后组建4跳网络进行同步采集对比试验,实验结果表明多跳累积误差得到有效抑制。     

Design and simulation on the publication delay control system

Based on the simulation study of the publication delay control process [Yu & al., 2005], transfer function models of delay control processes by adjusting the accepted contribution flux and the published contribution flux are identified using system identification. According to Cybernetics, the feedback control system of the publication delay is designed and control processes are simulated and analyzed when the average publication delay are regarded as the controlled object. On the basis of the relation between the average publication delay and the deposited contribution quantity, another control method is proposed that the deposited contribution quantity is regarded as the controlled object and the simulation result proves that the method is an excellent means and can help editors expediently manage their journals and control publication delays.     

万吨巨轮水下切割爆破

为了疏通航道需将万吨沉船进行爆破切割后打捞。根据施工环境和船体结构,采用矩形截面TNT药块作用于结构面实施爆破切割。文中介绍了确定切割方案、选择布药点、合理设计药量、TNT药块的组合加工及起爆网路的敷设,最后爆破拆除沉船取得圆满成功。此经验可供类似工程参考借鉴。     

数码电子雷管逐孔起爆网路延时时间应用探讨

为了获取数码电子雷管逐孔起爆网路的最佳延时时间,改善爆破效果,结合甘肃白银市白银区武川乡榆树沟大理岩矿山的石灰岩开采工程,通过调整孔间、排间的延时时间,进行了5次爆破试验。采用控制变量法,即在保持爆破孔网参数和单耗等参数均不变的情况下,孔间延时时间由原来25 ms调整为20 ms,每米孔距延时3～4 ms;排间延时时间由原来的75～110 ms调整为45 ms,每米排距延时9 ms,取得了较好的爆破效果,提高了矿山挖装效率和采场平整度,为类似工程施工提供可借鉴的数据和经验支撑。但相关爆破理论研究表明,排间延时时间受排数影响,孔和排间延时时间不可能无限制缩小,延时时间缩小和增大都存在一个临界值,超过这个临界值将会造成爆破事故,临界值的变化规律与岩石性质、结构和炸药性能等各种条件有关,有待于爆破同行们根据矿山实际情况进一步研究。