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1.
一种增强移动自组网Internet连接的改进型方案 总被引：1，自引：0，他引：1
针对移动自组网因单向链路以及盲目转播网关发现分组而造成的与Internet互联性能下降,提出了一种增强型互联方案.同时结合了先应和后应网关发现策略优点的混合网关发现策略被用来获取良好的Internet连接并保持低开销.而通过交换携带有额外增加的对称邻居节点列表和非对称邻居节点列表字段的AODV hello分组,单向链路得以从路由计算中予以清除而广播风暴也同时得到抑制.基于ns-2的仿真结果表明此改进型Internet连接方案在单向链路数量及节点移动速度均变化的应用环境下能取得较其他方案为优的互联性能. 相似文献
2.
In this paper, the security technology of ad hoc networks is studied.To improve the previous multi-receiver signcryption schemes, an ID-based multi-message and multi-receiver signcryption scheme for rekeying in ad hoc networks is proposed.In this scheme, a sender can simultaneously signcrypt n messeges for n receivers, and a receiver can unsigncrypt the ciphertext to get his message with his own private key.An analysis of this scheme indicates that it achieves authenticity and confidentiality in the random oracle model while being of lower computation and communication overhead.Finally, for the application of our scheme in ad hoc, a threshold key updating protocol for ad hoc networks is given. 相似文献
3.
Optimal congestion control algorithm for ad hoc networks： Penalty function-based approach 总被引：2，自引：0，他引：2
XU Wei-qiang WU Tie-jun 《浙江大学学报(A卷英文版)》2006,7(12):2110-2117
INTRODUCTION Congestion control is a critical issue for ensuring the efficient and fair allocation of network resource among communication flows. In wireline networks, TCP has resolved this issue of concern. However, it was reported that TCP performance in a multihop ad hoc environment degrades severely (Xu and Wu, 2006). Thus, some optimization-based congestion control schemes have been proposed to improve TCP performance in ad hoc networks (Chiang, 2005; Chen et al., 2005; Lee et a… 相似文献
4.
葛文英 《安阳师范学院学报》2006,(5):45-48
目前,移动Ad Hoc网络越来越受到人们的重视。在Ad Hoc网络中,路由协议的性能优劣是一个很重要的问题。目前的协议大体可分为两类:表驱动类和按需驱动类路由协议。研究表明:表驱动类的路由协议带来了大量的路由开销,对于网络带宽比较紧张的Ad hoc网络环境,按需路由协议是更好的选择。 相似文献
5.
Xin-yu Wang Xiao-hu Yang Jian-ling Sun Wei Li Wei Shi Shan-ping Li 《浙江大学学报(A卷英文版)》2008,9(10):1318-1325
This paper proposes a connected dominating set （CDS） based mobility management algorithm, CMMA, to solve the problems of node entering, exiting and movement in mobile ad hoc networks （MANETs）, which ensures the connectivity and efficiency of the CDS. Compared with Wu＇s algorithm, the proposed algorithm can make full use of present network conditions and involves fewer nodes. Also it has better performance with regard to the approximation factor, message complexity, and time complexity. 相似文献
6.
随着移动自组织网络(MANET)的应用领域日益扩大,要求它必须提供一定的服务质量(QoS)保证,而QoS路由协议是MANET支持QoS的一个关键理论和技术,也是目前的一个研究热点。本文对当前自组织网络的QoS主要路由协议进行了详细的分析与研究,并从路由机制、单向链路的支持、多播功能、QoS参数选择以及节能几个方面进行了比较和分析;最后指出了今后的研究方向。 相似文献
7.
随着计算机网络的快速发展,网络在带来巨大经济效益的同时,安全性问题也日益突出。为了维护网络安全,防火墙设备被广泛使用,用户可通过管理口配置防火墙的参数,阻止访问源的攻击。防火墙针对这些攻击会做相应的处理,所以对防火墙管理口的保护也至关重要。Netfilter防火墙框架既简洁又灵活,可实现安全策略应用中的许多功能,所以基于Netfilter防火墙框架可以实现管理口防护功能。 相似文献
8.
A load-balanced minimum energy routing algorithm for Wireless Ad Hoc Sensor Networks 总被引：3，自引：0，他引：3
CAI Wen-yu JIN Xin-yu ZHANG Yu CHEN Kang-sheng 《浙江大学学报(A卷英文版)》2006,7(4):502-506
INTRODUCTION Wireless Sensor Network is one special type of wireless ad hoc networks without fixed infrastructure consisting of a collection of sensor nodes, and oper- ating on limited amount of battery energy consumed mostly in transmission and reception. In the WSNs described in Fig.1, every sensor node can sense, process data and communicate to base station (BS). WSNs have attracted much attention during the recent two years and some commercial implementations such as environmental … 相似文献
9.
无线传感器网络常常会受到各种安全威胁,特别是拒绝服务攻击,传统的方案无法建立全面的防御。在此提出一种安全管理架构,该架构针对各种攻击设置不同的安全级别并配置相应的规则,通过动态地激活相关安全组件,确保网络的安全性和可用性。仿真结果显示出该方案具有良好的节能性,能有效地延长网络的生命周期。 相似文献
10.
Diana Laurillard 《Higher Education》2007,54(1):21-39
The introduction of technology enhanced learning (TEL) methods changes the deployment of the most important resource in the
education system: teachers’ and learners’ time. New technology promises greater personalization and greater productivity,
but without careful modeling of the effects on the use of staff time, TEL methods can easily increase cost without commensurate
benefit. The paper examines different approaches to comparing the teaching time costs of TEL with traditional methods, concluding
that within-institution cost-benefit modeling yields the most accurate way of understanding how teachers can use the technology
to achieve the level of productivity that makes personalisation affordable. The analysis is used to generate a set of requirements
for a prospective, rather than retrospective cost-benefit model. It begins with planning decisions focused on realizing the
benefits of TEL, and uses these to derive the likely critical costs, hence the reversal implied by a ‘benefits-oriented cost
model’. One of its principal advantages is that it enables innovators to plan and understand the relationship between the
expected learning benefits and the likely teaching costs.
相似文献
| Diana LaurillardEmail: |
11.
The present work describes an experience of educational innovation in a university context. Its aim was to determine the relationship
between students’ frequency of use of online self-assessment with feedback and their final performance on the course, taking
into account both learners’ motivation and perceived usefulness of these resources for their learning process. Furthermore,
we studied the relationship between metacognitive variables and academic performance and/or execution of activities aimed
at learning the course content. To this end we created self-assessment material with the Hot Potatoes educational program and assessed the degree to which students took advantage of the tool, their satisfaction with it and
their perceived knowledge, using ad hoc questionnaires. The results indicate better academic performance in those students
that use interactive self-assessment. It should be pointed out that even students with low motivation levels made use of this
teaching tool. Finally, a relationship was found between metacognitive variables and students’ effort and performance. We
discuss the need to include self-assessment in the curriculum, with a view to improving students’ metacognitive knowledge. 相似文献
12.
在Ad hoc网络中入侵检测问题已经成为研究热点,本文首先对存在的安全隐患进行了分析描述,然后从会话过滤的角度出发,结合Ad hoc网络自身特点的基础上,提出了一种基于状态检测的入侵防护策略,用于提高整个网络的安全性. 相似文献
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Lindsey J. Wolff Smith 《Journal of Experimental Education》2017,85(1):3-23
Conventional multilevel modeling works well with purely hierarchical data; however, pure hierarchies rarely exist in real datasets. Applied researchers employ ad hoc procedures to create purely hierarchical data. For example, applied educational researchers either delete mobile participants' data from the analysis or identify the student only with the last school attended while including an explanatory variable indicating whether a student is mobile. This simulation study compared the parameter and standard error estimates of these two ad hoc procedures for handling and assessing the influence of mobility on outcomes with results based on use of the multiple membership random effects model. Substantial bias was found for some parameters when multiple membership data structures were ignored. 相似文献
16.
在Ad hoc网络中密钥的安全问题已经成为研究热点,本文首先对存在的安全隐患进行了分析描述,然后从节点间信任角度出发,结合Ad hoc网络自身特点,提出了一种带DoS入侵阻断功能的分布式密钥管理策略,用于保证整个网络的安全性,提高了网络性能。 相似文献
17.
在真实的网络环境中分析和设计MANET(Mobile Ad hoc Network)网络安全协议耗资巨大,因此开发对MANET网络安全协议进行性能分析的仿真软件具有重大意义.在分析MANET网络安全协议仿真的具体需求基础上,基于NS2设计和实现了集成可视化网络拓扑生成、安全协议配置、网络数据流的设置、攻击事件的设置、仿真脚本自动生成到攻击过程的仿真运行和协议性能的对比分析等功能于一体的仿真系统,通过对不同网络安全协议在不同攻击下仿真结果数据的延迟、控制开销、吞吐量,丢包率、包交付率和抖动等参数的对比分析,系统可实现不同ad hoc网络安全协议的性能分析,系统还可动画演示协议受攻击时的节点运动信息、数据包信息、数据流信息和攻击信息等细节的动态变化过程. 相似文献
18.
An adaptive load balancing scheme is proposed to balance the load in ad hoc networks. The new scheme can be applied in most on-demand routing protocols resulting in significant performance improvement. The proposed scheme is applied to the ad hoc on-demand distance vector (AODV) routing protocol. Simulation results show that the network load is balanced on the whole, and performance in packet loss rate, routing overhead and average end-to-end delay is also improved. 相似文献
19.
随着科技的发展,作为终端设备的GPS智能手机越来越多地应用于诸如公安、物流、测绘、车队管理等行业.定位精度高,使用方便稳定等优点,使得GPS智能手机成为这些行业进行信息化改造时的首选.GPS手机出警导航系统基于Windows Mobile操作系统,采用了全球卫星定位技术,监控中心通过解读GPS信息定位出巡逻警员当前和出警目标点位置,巡逻警员使用解码函数来解析监控中心发送的出警短信内容,通过GPS手机导航及特设时时通讯和高精度放大/缩小地图功能到达出警目标点. 相似文献
20.
This paper shows how the patterns of variation created in the teaching were critical in helping a class of Primary 3 students
in Hong Kong to learn about the colour of light, so that the students attained conceptual rather than procedural knowledge.
A ‘Learning Study’ approach was adopted, which is a Lesson Study grounded in a particular learning theory to improve teaching
and learning. This study, based on the learning theory of Variation advanced by Marton and Booth, was premised on three types
of variation: variation in students’ ways of experiencing what is to be taught/learnt (V1), variation in teachers’ ways of
dealing with the ‘object of learning’ (V2), and the use of ‘pattern of variation’ as a guiding principle of pedagogical design
to enhance students’ learning (V3). In planning the lesson, a conscious effort was made to create relevant patterns of variation,
i.e. varying certain critical aspect(s) while keeping other aspects of the object of learning invariant in order to help students
to discern those aspects. Comparison between the results of the pre- and post-test shows that there was significant gain in
the students’ learning outcomes with respect to the intended object of learning. The findings contribute knowledge to how
the Theory of Variation can be used in practice. It also illustrates how teachers can make use of this theoretical framework
to analyze their own teaching and thereby, develop an analytical awareness of teaching and learning. 相似文献