基于复杂网络特征的P2P系统模型的研究

研究表明小世界和无尺度是很多大型复杂网络的重要特征,研究具有复杂网络特征的P2P网络模型对研究网络的拓扑结构和行为有着重要的意义.针对现有模型不能全面地反映实际网络提出了基于复杂网络特征的P2P网络模型.本文在基于组增长和选择具有较大吸引力的节点这些特征基础上建立一个新的模型,经过实验证明此模型更接近实际网络.     

具有时变时滞耦合的两个不同复杂网络的自适应同步

针对两个不同的时变时滞耦合复杂网络,提出一个新的网络同步模型.该模型中的两个网络在节点数目、拓扑结构、内部耦合、耦合时滞及节点动态均可不相同.基于LaSalle不变原理,设计自适应控制器使得两个网络获得同步.进一步研究了具有未知拓扑结构的两个复杂网络的自适应同步问题.数值结果表明了本文方法的有效性.     

复杂网络无尺度特征及其演化机理研究

根据复杂网络演化的两个基本机理抽象出一种复杂网络演化的一般模型(GP Model),该模型具备增长和择优两个普遍特征,并根据连续动力学原理分析了该模型的平凡特征量.在平凡特征量的基础上,利用极大似然原理得出了该模型网络在经历长期演化后节点分布具有幂律特征这一结论,从概率理论上解释了这一类网络度分布特征的成因.此外,利用GP模型研究了互联网度分布的指数截断特征以及长期演化的节点度分布特征,并分析了互联网的长期演化态势和节点行为特征.     

基于有向权值网络的航班运行风险传播与控制

为了分析航班运行风险传播过程,进而有效控制保障飞行安全,基于复杂网络理论,首先参照民航局咨询通告选取机组、航空器、运行环境共29个终端因素作为网络节点,统计民航安全监察记录,根据事件中节点关系,构建无向网络;统计前后节点间的作用关系和发生概率,提出一种有向带权的航班运行风险网络;然后,引入改进感染率和改进恢复率概念,构建一种适用于航班运行风险传播分析的改进SIR(Susceptible-infected-recovered)模型;定义感染起始范围,最后采取多参数控制方式,大规模计算该有向带权网络的传播和控制过程。结果表明:有向网的平均最短路径为1.788,属于小世界网络;参照使用民航常规管控措施,有向网节点感染下降幅度可达到37.4%;对入度值排序前3或前4的节点控制后,感染节点峰值下降率高达50.6%和58.1%,网络传播抑制明显。结果证实:在该航班运行风险有向带权网络中,按入度值控制节点对抑制风险传播最为有效。      

基于核心继承树的软件网络特征量的研究

基于继承树的思想对软件网络进行了重新定义,提出了基于核心继承树的软件网络模型,并对其特征量进行统计分析.结果发现:核心继承树内部节点在软件的功能性和结构性方面都起着重要的作用,核心继承树内部节点的核数和度之间存在着线性关系,核心继承树内部节点的聚类系数和度、核数间存在着幂率分布关系.利用继承树网络模型去发现大规模复杂软件系统中隐藏的普遍规律,并对软件系统进行度量和评价,有助于将传统的"经验型"软件工程转变为"计算型"软件工程.     

警报接收端优化部署

基于个体脆弱性模型将毒气扩散场景下人员疏散过程中的个人风险量化,并根据警报传播和人员跃迁规律求解不同警报接收端部署比例下的个人风险.运用运筹学中图论及多目标优化方法建立高含硫井场警报接收端部署双目标优化模型,并基于贪心算法思想提出求解该模型的实用算法,从而获得模型的较好非劣解.以某山区高含硫井场应急预警通知项目为例,通过程序运算得到该井场警报接收端部署子区域的边界及对应的部署比例.分析表明,在降低部署成本及缓解道路拥塞水平方面,该优化部署方法比传统的平均部署方法更具优越性.      

基于C++ Builder的凝汽器故障诊断系统

为了有效地对电厂凝汽器进行故障诊断并给予操作指导,开发了凝汽器故障诊断系统.该故障诊断系统分别采用标准BP算法和改进BP变步长附加动量法进行网络的学习训练.以凝汽器故障知识库为依据,构造了17个输入层节点、13个隐含层节点、12个输出层节点的三层反向传播网络.经过对比,说明采用经过改进BP变步长附加动量法进行网络的学习训练,能够快速收敛,误差小于0.01.实例数据测试表明,训练的网络能够得到较为准确的故障诊断效果.软件系统的设计选用C++Builder6.0快速开发工具,该软件系统具有友好的用户界面,操作简单.     

一类新旧节点同时演化的混合网络模型

在随机网络和无标度网络的基础上,提出了一个新旧节点同时演化的随机-无标度混合网络模型.在模型中,新旧节点都能够主动产生新的连边,并且新连边在选择目标节点的过程中具有随机和择优两种连接机制.理论计算和计算机模拟表明:可以通过4个参数将随机网络和无标度网络统一起来,通过调节参数,可以生成不同形态结构的网络.该模型能够在随机网络和无标度网络之间连续过渡,其普适性较以往的模型更大.     

基于C4.5算法的无线传感器网络农业环境部署节点故障诊断方法

通过采集农业环境下无线传感器网络节点所采集的数据,基于C4.5算法挖掘故障诊断关联规则,建立了农业环境部署节点故障诊断模型.结果表明,该模型能够比较好地对故障无线传感器网络节点进行识别.     

基于能源网络节点输入输出模型的能量流动态仿真

建立能量流网络节点输入输出动态模型是从系统和全局角度了解节能降耗环节及进行多介质协调优化的关键。从能量流网络结构出发,以冶金流程工程学为理论基础,研究了能量流网络中主工序生产单元节点的消耗回收模型、能源单元节点的生产消耗模型。以某钢铁企业实际数据为基础,进行了能量流网络节点输入输出动态仿真,仿真结果表明所建立的能量流网络节点模型误差较小,可有效模拟实际钢铁企业能源调配。所做研究对企业进行计划排产,不同工况下的调度分配具有指导意义。     

Algorithm for Automatic Detection of Topological Changes in Water Distribution Networks

Topological and pressure-driven analyses are an integral part of reliability/risk considerations for a water distribution system. For example, it is often necessary to identify which parts of the distribution network are isolated from water sources after the valves have been closed in response to a mechanical pipe failure. Pressure-driven analysis is then necessary to ascertain the consequences of pipe failures in terms of the performance of the functioning subsystem while pipe breaks are being fixed in the isolated area. Therefore, it is extremely useful to have an algorithm for the automatic identification of nodes/pipes disconnected from the water source(s). However, this is a complex problem because valves sometimes significantly modify the network topology. Furthermore, the use of isolation valves can cause a demand shortage to some customers (due to pressure reduction) during the abnormal operating conditions in the system. Thus, pressure-driven simulation of the network behavior is required. For these reasons, a novel algorithm capable of automatic detection of topological network changes is coupled with a robust pressure-driven simulation model. This algorithm is tested on two case studies involving a small artificial water distribution system and a larger, real-life network. The results obtained clearly demonstrate the robustness of the algorithm developed.     

River Stage Forecasting in Bangladesh: Neural Network Approach

A relatively new approach, artificial neural network, was demonstrated in this study to be a highly suitable flow prediction tool yielding a very high degree of water-level prediction accuracy at Dhaka, Bangladesh, even for up to 7 lead days. The goodness-of-fit R2 value, root-mean-square error, and mean absolute error, ranging from 0.9164 to 0.9958, 0.0788 to 0.2756 m, and 0.0570 to 0.2050 m, respectively, were obtained from the training and verification simulation. In addition, the high degree of accuracy is accompanied with very small computational time. Both results make the artificial neural network a desirable advanced warning forecasting tool. Sensitivity analysis was also performed to investigate the importance of each of the input neurons. The sensitivity study suggested a reduction of three from eight initially chosen input neurons. The reduction has insignificantly affected the prediction accuracy level. The finding enables the policymakers to reduce the unnecessary data collection at some gauging stations and, thus, results in lower costs.     

能量均衡的间断连接无线网络数据转发策略

针对间断连接无线网络中节点负载不均衡和能量资源受限的问题,提出了一种能量有效的数据转发策略.该策略根据网络运行的历史相遇信息,充分考虑网络特性,以分布式方式估计节点的活跃度、剩余能量和数据转发率,准确地估计节点效用值,感知网络节点的服务能力,以帕累托最优作为自适应选择最佳下一跳中继节点的理论依据,执行数据转发操作,有效地解决了由于节点自私性所导致的网络性能下降.数值结果表明,与其他能量管理机制相比,所提出的机制能够均衡网络节点负载,有效解决网络"热点"问题,延长网络生存时间,使投递率、时延等系统性能都得到大幅度提升.      

一种新型BP神经网络的生成算法

提出了一种新型的神经网络的训练方法，包括输入层节点的自动寻找技术和隐含层节点的自动生成技术．为了验证该算法的正确性，利用该算法对同向回转观机驱动振动系统进行了神经网络逼近分析，计算机模拟结果表明该算法可以准确地确定输入层和隐含层节点的数目．     

高碳钢盘条冷却线FeO层厚百分比模型及其应用

72A高碳钢（0.67%~0.73%C）盘条的氧化铁皮总量和氧化铁皮中FeO层厚百分比显著影响盘条的剥离性能。利用人工神经网络和数理方法,建立BP网络模型,实现了高碳钢线材氧化过程中的冷却制度与氧化后生成的FeO层厚百分比之间的复杂的非线性映射关系。将实测的参数与网络模拟结果进行比较得出,建立的BP网络训练精度非常高,泛化能力强,能很好的反应各个因素对FeO层厚百分比的影响。生产应用结果表明,根据BP网络模拟结果改进冷却工艺,适当降低吐丝温度,提高850~720℃区间冷却速度,使氧化铁皮中FeO层厚百分比减小,改善了机械剥离性能。     

基于按需和贪婪转发的移动自组网路由协议

移动自组网的动态拓扑特性给路由协议的设计带来了一定的挑战,尤其是在高动态的网络环境中.本文针对该问题,提出了一种新的基于按需和贪婪转发的路由协议,该协议是在RGR模式的基础上提出以下三点改进,即:（1）通过受限的洪泛机制降低网络在路由发现阶段的控制开销;（2）通过移动预测机制,在被动寻路阶段监视被动路径的状态和在GGF阶段帮助节点选取适当的邻居作为下一跳节点;（3）通过路径请求延迟机制以减少不必要的资源浪费.仿真结果表明:改进的RGR协议与现有的RGR、AODV、Modified-RGR和Optimized-RGR相比,不仅具有较高的数据包接收成功率,而且平均路由开销和端到端时延也相对较低.      

Prognostic value of exercise thallium-201 imaging in a community population

The purpose of this study was to determine how horizon-scanning organizations can encourage the implementation of recommendations contained in their early warning messages about emerging health technologies. We reviewed the conclusions of the EUR-ASSESS Project Subgroup report on dissemination and impact, an overview of systematic reviews of interventions to promote implementation of research findings by health care professionals, and various Cochrane Effective Practice and Organisation of Care Group protocols and reviews. The evidence on the effectiveness of different implementation strategies aimed at distinct target groups is of variable quality. There is some evidence from rigorous study designs on the effectiveness of strategies designed to influence the behavior of health care professionals; the quality of the evidence relating to policy makers and the general public is more limited. Horizon-scanning organizations can improve the likelihood of their recommendations being acted upon by developing active implementation strategies based on the best available evidence, establishing links with key groups, and directing early warning messages at specific target audiences. Given the relative lack of good quality evidence, it is important that implementation strategies be rigorously evaluated to determine their effectiveness.     

Considering Actual Pipe Connections in Water Distribution Network Analysis

The classical assumption of representing total demand along a pipe as two lumped withdrawals at its terminal nodes is hitherto common. It is a simplification of the network topology which is useful in order to drastically reduce the number of nodes during network simulation. Conversely, this simplification does not preserve energy balance equation of pipes and, for this reason, it is an approximation that could generate significant head loss errors. This paper presents a modification of the global gradient algorithm (GGA) which entails an enhancing of GGA (EGGA) permitting the effective introduction of the lumped nodal demands, without forfeiting correctness of energy balance, by means of a pipe hydraulic resistance correction. The robustness and convergence properties of the algorithm are compared with those of the classical GGA. Furthermore, the effectiveness of EGGA is demonstrated by computing the network pressure status under different configurations of the connections along the pipes of a test network.