基于流量和时延的网络性能测量系统的研究

提出了一种间接测量网络吞吐率的新方法，建立了基于流量和时延的网络性能分析模型，基于这个模型对网络性能测量方法进行分析，设计并实现了一个基于流量和时延的网络性能测量系统，对网络性能进行了测量和分析。     

通过路由策略实现网络控制

本文探讨了通过路由策略实现网络控制。首先介绍了子网访问控制存在的问题,然后提出了路由工作原理,接着,详细阐述了静态路由实现网络访问的控制,并探讨了如何利用软件路由器来实现局域网内部的流量控制。     

基于重力模型的枢纽辐射航空网络构建方法及应用

枢纽辐射航空网络中,航线中转造成的航程延长会减少旅客流量.为了在枢纽辐射航空网络规划时,充分考虑航空运输成本节约和旅客量减少造成的社会净收益变化,融合了交通分布重力模型和p-hub枢纽中位问题,给出一种枢纽航空网络设计的新方法,并以社会净收益最大化为目标建立了相应混合整数规划模型.以中国15个城市机场为例,应用以上方法求解,分别在不同参数情况下设计出枢纽辐射航空网络.算例结果表明本文方法有效且实用,可为枢纽网络规划设计应用提供指导.     

车载自组织网络信息流量特性分析

为了揭示车载自组织网络动态拓扑特性,预测车载自组织网络行为和缓解网络拥堵,本文从微观角度分析了信息流量分布的一般特性,研究了在不同交通需求下车载自组织网络信息流量分布特性及信息流量与节点度值之间的关系.首先提出度、度分布指数与信息流量的关系,用复杂网络理论以静态、动态两种方式建立无容量限制的无标度网络模型,采用数值模拟实验和仿真实验方法讨论了参数变化时车载自组织网络信息流量变化规律;其次,借助非线性动力学理论研究了考虑容量限制的信息流量分布特性.研究结果表明,信息流量分布指数是无标度网络的通用特征参数,度值大的节点对网络影响较大,传播信息更快,信息流量与度值之间满足幂律分布规律;当信息流量需求增大时,Hub节点可能负担过重,许多信息流量可能会选择其他节点避免与Hub节点连通,这时较小度值的节点承担这部分信息流量.     

软交换呼叫控制模型研究

软交换是下一代网络中的核心控制设备,呼叫控制模型设计是软交换控制器软件设计的核心,现有的呼叫控制模型都和具体的网络相关,不利于同时支持多媒体业务和移动业务。在分析常见的几种呼叫控制模型的基础上,本文提出了一种可以支持多媒体和移动业务的呼叫控制模型,阐述了其结构和特点,并和现有的呼叫控制模型做了比较。     

基于分层令牌桶的通讯流量控制模型的设计

当前,大流量的网络应用已越来越成为主流,而这些应用对网络带宽的占用也越来越大,如何对网络进行有效的通讯流量控制,已经成为一个急需解决的难题。提出一种基于分层令牌桶的通讯流量控制模型,利用分层令牌桶排队策略较好地实现对通讯流量的监控与限制,在很大程度上减轻网络负担。     

带误差补偿的GPC对网络控制系统时延的解决

针对网络控制系统(NCS)具有不确定时延的特性，提出了将广义预测控制(GPC)应用于网络控制系统的思想。为了克服模型失配和系统不确定性的影响，基于BP神经网络建立一个误差的预测模型，用误差预测值对输出预测值进行补偿，构成新型的广义预测控制算法，并采用了平滑滤波的加权输入控制律。在网络控制系统中，测试了网络数据传输的随机延迟时间特性，比较了GPC和具有BP网络预测误差补偿的GPC两种控制方法，验证了具有BP网络预测误差补偿的GPC在模型失配时的更好的控制性能。     

使用SNIFFER对ICMP报文进行分析

Sniffer是一种嗍络监听软件，是利用计算机网络接口截捩数据报的一种工具．它工作在底层，能够把网络传输的数据记录下来。它主要是一种网络管理工具，可以用来分析网络协议、定位网络故障、检测网络性能、分析网络的流量等等。     

基于测量的网络生成树拓扑优化

提出一种基于测量的网络生成树拓扑优化算法，可以根据网络上的流量分布动态地调整网络拓扑。仿真结果表明，在网络输入相同时，这种算法可以显著降低网络资源的占用，并可以有效地消除网络上短期流量波动对拓扑稳定性的影响，防止网络拓扑频繁变化。     

基于径向基函数网络的煤粉质量流量测量

为了提高工业生产中煤粉质量流量检测的测量精度,在双弯管法测量固相质量流量原理的基础上,利用人工神经网络优良的非线性映射能力,将固相质量流量难以确定的影响因素反映到网络的连接权值中,建立基于径向基函数网络的软测量模型;在气力输送煤粉实验平台上进行实验,获取实验数据,以实验数据为样本对模型进行训练与仿真。结果表明,模型测量误差不超过3%,是煤粉固相质量流量测量的一种简单、有效的方法。     

基于演化博弈论的可变导向车道设置策略研究

可变导向车道的设置，在提高道路通行效率的同时会造成驾驶人情绪紧张或者因不了解路况导致违规甚至发生事故，对交通系统的安全和稳定运行产生负面影响。以交管部门设置可变导向车道的策略选择为研究目标，结合驾驶人走可变导向车道时产生的紧张情绪损失等因素，构建交管部门−驾驶人群体两方博弈模型。采用演化博弈论的方法分析博弈双方选择行为演化和稳定策略，对系统中存在的5个演化均衡点进行分析，得到系统的3种理想稳定状态和相对应的参数条件，为交管部门设置可变导向车道进行策略选择提供理论支撑。     

信号控制对交通噪声的影响分析

用实验方法测定三种不同车型单辆车在参考距离处的噪声排放量及加减速噪声修正值。然后结合微观交通仿真、车辆噪声排放量和传播衰减模型分别对信号控制下的间断流交通噪声和无控制的连续流交通噪声进行动态模拟。最后对两种不同交通流状况下的等效声级、噪声标准差、交通噪声指数和噪声的频数分布进行对比分析,得到两种不同交通流状况下交通噪声的若干重要差别。     

道路交叉口不同控制方式交通噪声预测

以不同行驶状态的机动车噪声排放模型为基础，对三种典型控制方式下的交叉口噪声进行预测研究。采用实验的方法分别对大、中、小型单辆车在怠速、匀速、加速、减速等各种行驶状态下的噪声值进行测定，通过回归分析得到不同行驶状态下的机动车噪声排放模型，并以某信号控制交叉口的实测数据为例，用计算机仿真的方法证明该模型对于交叉口噪声模拟的较高适用性。进而将该排放模型应用于信号控制、无信号控制以及环形等控制方式的交叉口进行噪声预测，通过不同交通流量时交叉口的平均噪声级以及噪声的分布情况等对比，得到各种控制方式下交叉口噪声的若干特点和区别。     

Micro-simulation of vehicle conflicts involving right-turn vehicles at signalized intersections based on cellular automata

At intersection, vehicles coming from different directions conflict with each other. Improper geometric design and signal settings at signalized intersection will increase occurrence of conflicts between road users and results in a reduction of the safety level. This study established a cellular automata (CA) model to simulate vehicular interactions involving right-turn vehicles (as similar to left-turn vehicles in US). Through various simulation scenarios for four case cross-intersections, the relationships between conflict occurrences involving right-turn vehicles with traffic volume and right-turn movement control strategies are analyzed. Impacts of traffic volume, permissive right-turn compared to red-amber-green (RAG) arrow, shared straight-through and right-turn lane as well as signal setting are estimated from simulation results. The simulation model is found to be able to provide reasonable assessment of conflicts through comparison of existed simulation approach and observed accidents. Through the proposed approach, prediction models for occurrences and severity of vehicle conflicts can be developed for various geometric layouts and traffic control strategies.     

QoS Model of a Router with Feedback Control

The Internet has evolved into a shared, integrated platform of a broad range of applications with different Quality‐of‐Service (QoS) requirements. Routers are an important part of the Internet and play a critical role in assuring QoS. A router is usually placed between two networks to receive data packets from one network and then transmit those data packets to another network if necessary. Data packets are the actual units of data traveling on computer networks. A data packet has two parts: header and data. The data carries messages, such as e‐mail text, from computer applications. The header carries information that is required to control and manage the transmission of the data packet on computer networks. Existing approaches for providing QoS involve prediction or estimation for traffic characterization to determine parameters required of static traffic admission control. However, prediction or estimation inaccuracy in traffic characterization can result in inappropriate parameter settings for static admission control and, in turn, compromise QoS or resource utilization. This study presents a QoS model of a router with feedback control that monitors the state of resource usage and adaptively adjusts parameters of traffic admission control to overcome prediction or estimation inaccuracy and achieve a balance between QoS and resource utilization. The QoS model of a router with feedback control is simulated to test its performance on QoS and resource utilization in both heavy and light traffic conditions. The performance of the QoS model of a router with feedback control is also compared with that of two basic QoS models of a router with static admission control using admission control parameters resulting from over‐ and under‐characterization of traffic, respectively. The simulation results show that the QoS model of a router with feedback control achieves a better balance between QoS and resource utilization than the basic QoS models with over‐ and under‐characterizations of traffic in the heavy traffic condition. This study also shows that the three models of routers demonstrate similar QoS performances and resource utilization in the light traffic condition. Copyright © 2005 John Wiley & Sons, Ltd.     

城市道路交通系统供需协同演化模型与实证研究

文章以耗散结构理论为基础，选取道路网容量与交通量作为序参量构建了城市道路交通系统演化模型，并对模型进行了仿真模拟，针对不同引导控制强度模拟得到小汽车、公共交通和混合交通三种交通发展模式，针对不同增长速度模拟得到供需追随型、引导型和超前型三种交通供给模式。最后对现实世界中存在的上述几种交通发展与供给模式进行了实证分析。     

自重构机器人的自变形研究

首先根据自重构机器人系统结构的基本特征提出一种有效的描述模型,可以对自重构机器人的拓扑结构进行统一的描述。然后与这种描述模型相结合,提出了一种建立在全离散的局部智能基础上的自重构机器人的自组织变形策略,通过建立统一的模块运动规则和规则进化使机器人由局部自主运动产生全局系统自组织的结果。     

A generic approach for examining the effectiveness of traffic control devices in school zones

The effectiveness and performance of traffic control devices in school zones have been impacted significantly by many factors, such as driver behavioral attributes, roadway geometric features, environmental characteristics, weather and visibility conditions, region-wide traffic regulations and policies, control modes, etc. When deploying traffic control devices in school zones, efforts are needed to clarify: (1) whether traffic control device installation is warranted; and (2) whether other device effectively complements this traffic control device and strengthens its effectiveness. In this study, a generic approach is developed to examine and evaluate the effectiveness of various traffic control devices deployed in school zones through driving simulator-based experiments. A Traffic Control Device Selection Model (TCDSM) is developed and two representative school zones are selected as the testbed in Beijing for driving simulation implementation to enhance its applicability. Statistical analyses are conducted to extract the knowledge from test data recorded by a driving simulator. Multiple measures of effectiveness (MOEs) are developed and adopted including average speed, relative speed difference, and standard deviation of acceleration for traffic control device performance quantification. The experimental tests and analysis results reveal that the appropriateness of the installation of certain traffic control devices can be statistically verified by TCDSM. The proposed approach provides a generic framework to assess traffic control device performance in school zones including experiment design, statistical formulation, data analysis, simulation model implementation, data interpretation, and recommendation development.     

基于逻辑回归模型的流量异常检测方法研究

网络流量作为异常检测的基本数据源,其行为特征的准确描述,是网络异常行为实时检测的重要依据.本文针对流量异常检测问题,提出了一种基于逻辑回归模型的网络流量异常检测方法.通过分析源IP、目的 IP等多个网络流量基本特征,构造了网络异常行为和正常行为的训练机,并且在此基础上采用逻辑回归建立起网络异常流量挖掘模型.利用实验室所采集的真实网络流量对所构建的模型进行检测,以验证该模型的有效性.实验结果表明本文所建立的网络模型在异常流量挖掘方面准确度高、实时性好.     

Performance evaluation of tandem and conventional AGV systems using generalized stochastic Petri nets

This paper investigates the different policies and concepts followed in the traffic management of automated guided vehicle (AGV) systems, and develops the controls for automatically eliminating potential vehicle conflicts in an AGV system. The planning of the AGV system is performed in such a way that there are no conflicts or deadlocks for the vehicles using stochastic Petri nets (SPNs). The major effort is devoted to determining the benefits of the tandem AGV control in comparison with the conventional AGV control method. SPNs have been used to model the different designs of flexible manufacturing systems (FMSs) and with different policies for the movement of material, vehicle path control, inventory planning and tool control. The SPN model is solved and the performance of the system can be evaluated. In this study, the effort is directed to model an FMS with two different types of AGV traffic management methods, namely the conventional and tandem AGV control. A SPN program is used which takes the FMS Petri net model as the input and evaluates the different properties of the Petri net. Finally the performance measures are obtained, which helps in evaluating and comparing the two different AGV traffic management methods.