一种移动无线自组网即时语音通信系统的实现

近年来,移动无线自组织网络迅速发展,在该平台上实时语音通信的需求也日益显现。在linux平台下,利用VOIP和RTP等技术实现了无线移动自组织网络的多跳即时语音通信系统。并通过上网本组成的硬件实验平台进行了移动实验,在低速移动条件下的实时语音通信效果MOS评分在3.5以上,能够满足即时语音通信的需求。     

Ad hoc网络中一种基于学习Petri网的入侵检测模型

移动自组织网络是由无线移动节点组成的复杂分布式通信系统.研究了移动自组织网络的入侵检测问题,对当前Ad hoc网络上的入侵行为和入侵检测技术进行了分析,论述了学习Petri网络应用于入侵检测系统中的优势,给出了一个基于学习Petri网络的入侵检测实施模型,并在网络仿真软件ns2中对其进行了评估.     

车辆网络通信平台的Internet接入研究

本文介绍了一种车辆通信系统嵌入式终端通过CPRS无线网络接入方式.车辆移动自组织网络与Internet互联的网络结构,车辆移动自组织网络与Internet网络相互通信的基本原理,以及以PPP协议为基础接入Internet互联网的方法,并针对车辆通信嵌入式系统平台的特点给出了车辆通信系统通过GPRS模块无线接入Internet的一些系统关键技术和方法.     

军用无线移动自组织通信系统媒质接入技术概述

无线移动自组织网络的发展为新一代军事通信系统的发展注入了新的生命力。媒质接入技术是无线移动自组织网络的关键技术之一。本文介绍了美军近年来研发的基于移动自组织网技术的军用无线通信系统并对媒质接入问题进行了分析与总结。     

军用无线移动自组织通信系统媒质接入技术概述

无线移动自组织网络的发展为新一代军事通信系统的发展注入了新的生命力.媒质接入技术是无线移动自组织网络的关键技术之一.本文介绍了美军近年来研发的基于移动自组织网技术的军用无线通信系统并对媒质接入问题进行了分析与总结.     

话说移动因特网

移动因特网是一种新的网络技术,它支持自组织移动组网结构。从本质上说,移动因特网是一种移动路由网络,这种网络用在未来的商用和军用通信上具有诸多优点。目前,国特网工程特别工作组(IETF)正在对移动因特网制定标准。本文就移动因特网的有关技术和应用问题作一简要讨论。     

基于机器学习的移动自组织网络入侵检测方法

移动自组织网络是由无线移动节点组成的复杂分布式通信系统。研究了移动自组织网络的入侵检测问题,采用了一种新型的基于机器学习算法的异常入侵检测方法。该方法获取正常事件的内部特征的相互关系模式,并将该模式作为轮廓检测异常事件。在Ad hoc 按需距离向量协议上实现了该方法,并在网络仿真软件QualNet中对其进行了评估。     

车载自组织网络中并发广播冲突研究

车载自组织网络(VANET)是移动自组织网络(MANET)在车辆通信领域的特殊应用.其通过专用短程通信(DSRC)技术为车-车(V2V)、车-路(V2I)基单元提供安全可靠的通信服务.然而,VANET网络内广泛存在的并发广播冲突问题使得车辆频繁丢失数据包,遭受潜在的交通安全隐患.针对并发广播冲突问题,目前已有较多的解决...     

MANET中分布式拒绝服务攻击研究综述

随着移动自组织网络在各个领域内得到广泛的使用,其安全性研究显得越来越重要。DDoS攻击给有线网络造成了很大的威胁,同样也威胁到了移动自组织网络的安全性。由于移动自组织网络和有线网络存在着结构型差异,因此移动自组织网络中的DDoS攻击研究与有线网络中的DDoS攻击研究有较大的不同。论文首先描述了移动自组织网络的安全状况;然后从移动自组织网络的网络架构出发,分别分析移动自组织网络中针对物理层、MAC层、网络层以及传输层的DDoS攻击,同时总结针对不同网络层次的攻击所需要采取的防御措施;最后为移动自组织网络建设过程中就如何防范DDoS攻击提出参考意见。     

基于P2P的大规模MANET多路径路由模型研究*

由于P2P网络与移动自组织网络存在许多相似特性,提出基于P2P的大规模移动自组织网络多路径路由模型,以提高移动自组织网络可扩展性和路由效率。新模型通过掩码轮换匹配机制发现多路径路由,并按照最优传输权重机制进行流量分配,达到动态感知移动自组织网络物理拓扑变化和平衡网络负载的目的。仿真实验证明,新模型能够适用于大规模移动自组织网络环境,并且有效提高了大规模移动自组织网络路由性能。     

图像定尺在钢铁板坯二次切割中的应用

简单介绍利用摄像头进行图像采集后，通过对图像信号进行处理．实现非接触式板坯长度测量，并依据测量结果，驱动切割设备自动定住，实现连铸钢坯的高精度自动定尺切割。     

应用S7-300 PLC实现混凝土养护过程中温度量的模糊控制

养护是混凝土制品生产的一个重要环节,根据养护过程中温度变化过程的专家经验和模糊控制理论为设计依据,应用西门子S7—300PLC控制设备,实现养护过程温度变化过程的合理控制。对目前高效的蒸汽养护混凝土方式的温度量控制进行了探索与应用,在实践中证实了这种养护方式的良好性能。     

What artificial experts can and cannot do

One's model of skill determines what one expects from neural network modelling and how one proposes to go about enhancing expertise. We view skill acquisition as a progression from acting on the basis of a rough theory of a domain in terms of facts and rules to being able to respond appropriately to the current situation on the basis of neuron connections changed by the results of responses to the relevant aspects of many past situations. Viewing skill acquisition in this ways suggests how one can avoid the problem currently facing AI of how to train a network to make human-like generalizations. In training a network one must progress, as the human learner does, from rules and facts to wholistic responses. As to future work, from our perspective one should not try to enhance expertise as in traditional AI by attempting to construct improved theories of a domain, but rather by improving the learner's access to the relevant aspects of a domain so as to facilitate learning from experience.     

防火墙在组建局域网中的应用

防火墙作为网络安全设备越来越多地应用于局域网络与公用网络的互联中,具有服务代理、包过滤、入侵检测等功能。防火墙作为一个网络互连设备,在组建网络中还有着局域网与Internet互联、隐藏防火墙外网IP地址、隐藏内部网络、IP地址重定向、安全访问控制以及构建VPN等应用。文中结合某单位的局域网规划设计就防火墙的应用作了重要的阐述。     

微机监测与铁道信号设备安全

目前我们铁路运输事业快速发展,全国各地都新建了高铁铁路。速度是提升了,安全问题也不能忽视。列车在运行过程中要想保证安全,就需要铁道各处的信号信息正确。控制台通过相关的信号设备将运行的指令传递给列车,以保证铁路的整体运行情况。在新的时期,需要能够全天候检测铁路安全的方法,以便维修人员能够及时了解问题并处理。本文通过对TJWX-2006型信号设备监测系统进行研究,来分析在铁路上使用微机来检测铁路的运行情况。这对研究信号设备安全有着积极的意义。     

How practice produces suboptimal heuristics that render backup instruments ineffective

The operation of machines typically requires attention to instruments that signal the state of the machine. One safeguard against primary instrument malfunction is to provide backup instruments, but this works only if the operators react to malfunction by switching attention to the backups. Little is known about the effect of negative outcomes or feedback on allocation of attention to backup instruments. Four experiments demonstrated that prior practice causes operators of a simulated machine to adapt to instrument malfunction by changing to a suboptimal decision rule rather than by reallocating attention to a different set of instruments. This fallacy appears linked to the operators' failures to notice feedback that they should switch during the simulations and operators' failures to correctly interpret outcome feedback following the simulations. The results raise theoretical questions and warn interface designers not to overrate backup instruments.     

Holarchy formation and optimization in holonic manufacturing systems with contract net

Holonic manufacturing systems (HMS) is based on the notion of holon, an autonomous, cooperative and intelligent entity to provide a econfigurable, flexible and decentralized manufacturing environment to respond to changing needs and opportunities. A set of holons that cooperate to achieve a goal forms a holarchy. How to design a mechanism to form a holarchy to achieve a goal while minimizing the overall cost is a challenge. The objectives of this paper are to propose models and develop collaborative algorithms to guide the holons to form a holarchy to coherently move toward the desired goal state ultimately. We adopt contract net protocol (CNP) to model mutual selection of holons in forming a holarchy. We formulate a holarchy optimization problem to minimize the cost subject to the feasibility constraints. To analyze the feasibility of a holarchy, a Petri net (PN) model is proposed. As classical PN models do not take into account the cost involved in firing transitions, we augment the PN model with cost functions in the problem formulation. Due to the distributed architecture of HMS, the internal structure of each potential holarchy that acts as bidder in CNP is not available to the manager. A key issue is to determine the feasibility of a holarchy without constructing the whole PN model of the given hierarchy. We study the feasible conditions for a holarchy and propose a collaborative algorithm to analyze the feasibility and award contracts to holons without constructing the whole model of a holarchy.     

Virtual surfaces and the influence of cues to surface shape on grasp

This research compared grasps to real surfaces with grasps to virtual surfaces, and used virtual surfaces to examine the role of cues to surface shape in grasp. The first experiment investigated the kinematics of overhand grasps to real and virtual objects. The results showed that, compared with grasps to real surfaces, grasps to virtual objects were different in the deceleration phase of the grasp movement and were more variable in their endpoint position. The second experiment used several measures to examine the relationship between the visual perception of a surface and the decision to grasp the surface with either an over-or underhand grasp. It was found that visual perception of the surface was consistent with the grasping decision. The third experiment used virtual surfaces to examine how the removal of visual cues to shape affected the decision to switch from over- to underhand grasp. Results showed that the orientation at which the decision switched was dependent on the visual information content. Overall, the results showed that subtle differences existed between the reach to grasp movements towards real and virtual surfaces and that the decision to choose between grasp types was dependent on the visual information used to depict the virtual surface. These results are discussed in relation to the design and use of input devices to enable manipulation of three-dimensional objects in virtual worlds.     

Habituation effects in computer security warning

Security warning is a form of computer dialog communication used to inform the users on the risks of allowing random applications to run on a computer system. Accordingly, it is specifically designed to impersonate a legitimate security alerting function (e.g., notify, warn, and advice) to a user about the consequence effect of an action. However, most of the computer users tend to ignore those security warnings conveying the same message over and over again. This eventually leads to habituation. Considering the fact that there is a significant lack of focus paid to address this issue, the main objective of this article is to describe and summarize the related studies on users’ habituation to the security warnings. This article presents a systematic literature review to explore the current key issues, challenges, and the possible solutions related to habituation effects in security warnings. It is expected that this article could contribute to a more complete understanding of the habituation effects in security warnings and eventually bring benefits to the research communities or general publics.     

一种动态统计系统的设计与实现

随着信息技术的飞速发展,企业的信息化程度越来越高。企业对其内部的各种数据进行统计进而进行数据的分析活动也日趋频繁,因此使得用户对数据统计的要求具有不定性和多变性的特点。同时,由于企业自身的行业特点,又要求动态统计软件对于经常需要统计的内容具有学习能力,从而才能满足用户既灵活多变,又具有一些相对固定的统计要求。文中主要针对此类企业用户对动态统计灵活多变的要求,通过对进行统计的内容按其功能进行SQL语句的分类、定义,设计并实现了一种动态统计软件。通过对此软件的测试及用户使用,能够满足企业相对灵活多变的动态统计需求。