区域综合运输通道抗毁性分析

区域运输通道是区域运输线路的骨干.通道抗毁性分析对发现通道网络薄弱环节、优化通道网络规划、保障运输安全等具有重要意义.以成渝经济区为例,抽取其运输通道网络,构建L空间下的复杂网络模型,构建基于节点度、节点运输重要度和节点介数的攻击策略,以网络全局效率和最大连通子图节点比为测度,借助Matlab和Pajek软件进行抗毁性分析仿真.结果表明：成渝经济区运输通道平均路径长度较大,连通性有待提高,在进行通道中公路、铁路网络规划时应注意联络线的布设,重庆、成都等应作为关键节点重点建设和保护.     

Scheduling for Uncertain Data Broadcast in Mobile Networks

With the increasing popularity of wireless sensor network and GPS (global positioning system) , uncertain data as a new type of data brings a new challenge for the traditional data processing methods. Data broadcast is an effective means for data dissemination in mobile networks. In this paper, the definition of the mean uncertainty ratio of data is presented and a broadcasting scheme is proposed for uncertain data dissemination. Simulation results show that the scheme can reduce the uncertainty of the broadcasted uncertain data effectively at the cost of a minor increase in data access time, in the case of no transmission error and presence of transmission errors. As a result, lower uncertainty of data benefits the qualities of the query results based on the data.     

无线传感器网络多路径路由算法的研究

在多路径路由算法的研究中,仍然存在着一定的局限性,如没有充分考虑网络中链路的多重特性.因此,文中在定向扩散路由算法的基础上提出了一种多路径路由算法(EDB-MRA).该算法在源节点和目的节点之间建立多条路径,根据网络链路中的3个特征值--能量消耗、延时和带宽,给每条路径赋予一定的选择概率,使得数据总能在链路性能较优的多路径中传输,从而延长了网络的生存周期,提高了传输的可靠性.     

An range-free localization scheme for large scale underwater wireless sensor networks

In this paper, we study an area localization problem in large scale underwater wireless sensor networks (UWSNs). The limited bandwidth, the severely impaired channel and the cost of underwater equipment all make the underwater localization problem very challenging. Exact localization is very difficult for UWSNs in deep underwater environment. We propose a range free method based on mobile detachable elevator transceiver (DET) and 3D multi-power area localization scheme (3D-MALS) to address the challenging problem. In the proposed scheme, the ideas of 2D multi-power area localization scheme (2D-ALS) and utilizing DET are used to achieve the simplicity, location accuracy, scalability and low cost performances. The DET can rise and get down to broadcast its position. And it is assumed that all the underwater nodes underwater have pressure sensors and know their z coordinates. We evaluate the performances of 2D-ALS and our proposed 3D-MALS schemes under both ideal and non-ideal channel propagation conditions, in terms of localization error and localization ratio. The simulation results show that our proposed scheme is much more efficient than the 2D-ALS.     

In-home power line communication media access control protocol based on collision resolution

Most existing media access control (MAC) protocols in power line communication (PLC) networks just discard the colliding data packets when collision occurs. The collision deteriorates throughput and delay performance of system under high traffic conditions. This article presents a novel media access scheme with fast collision resolution for in-home power line networks. It works by first recognizing the colliding stations through detecting the inserted unique ID sequence ahead of data packets, then the source nodes retransmitting their packets immediately after the collision slot. The proposed protocol maintains the benefits of ALOHA systems. It needs no scheduling overhead and is suitable for bursty sources, such as multimedia data packets. Computer simulations have demonstrated that this approach can achieve high throughput due to its ability of resolving collisions.     

Effects of denial of service attack in mobile ad hoc networks

Mobile ad hoc networks are often deployed in environments where the nodes of the networks are unattended and have little or no physical protection against tampering. The nodes of mobile ad hoc networks are thus susceptible to compromise. The networks are particularly vulnerable to denial of service (DoS) attacks launched through compromised nodes or intruders. In this paper, we investigated the effects of flooding attacks in network simulation 2 (NS-2) and measured the packet delivery ratio and packet delay under different flooding frequencies and different numbers of attack nodes. Simulation results show that with the increase the flooding frequencies and the numbers of attack nodes, network performance drops. But when the frequency of flooding attacks is greater than a value, the performance decrease gets smooth. Meanwhile the packet delay firstly increases and then declines to a value of stability at the end.     

遗传—神经网络在交通流预测中的应用

提出一种基于BP神经网络的遗传算法,分别利用其局部和全局寻优能力强的特点,综合为一种新的优化算法,并将改进的算法应用于交通流预测中。结果表明,改进方法的预测效果优于单一使用BP神经网络进行预测的效果。     

在NT4.0上实现基于PPTP的VPN服务

简要介绍了虚拟专用网络的技术背景,详细描述了如何在NT4上搭建基于PPTP协议的VPN服务器,最后简要阐述了利用VPN技术对铁路信息安全建设方面的意义.     

基于BP神经网络的静态手势识别方法

手势识别正成为人机交互技术研究中的一种重要模式.本文针对运用摄象机和计算机视觉技术捕获来的静态手势,提出了一种手势特征提取和基于神经网络分类的手势识别方法.实验表明该方法的正确识别率可以达到98%左右,是一种非常有效的静态手势识别方法.     

集通铁路长大隧道GSM-R冗余方案研究

针对集通铁路的长大隧道,论述分布式基站和数字光纤直放站的两种冗余方案,通过分析比较两种方案的单网交织以及同站址双网冗余覆盖方式,推荐采用分布式基站单网交织冗余方案.