基于NS2的Ad Hoc网络DRMR协议计算机仿真

针对现存多种Ad Hoc组播路由协议的有效性差、控制开销大等问题,设计并实现了一种基于动态广播环的组播路由(DRMR:Dynamic Ring based Multicast Routing)协议,确定了DRMR协议的实现框架,定义了各功能模块.在该协议中,组播路由建立和维护每个组成员广播环所构成的连通环图,当组成员广播环离开连通环图时,采用逐步扩大广播环的半径恢复其连通性.仿真结果表明,DRMR协议具有较高的数据分组递交率和较低的路由维护开销,其总体控制开销比基于需求的多播路由协议节省,能满足Ad Hoc网络对组播应用的要求,对研究Ad Hoc网络人员具有实际参考价值.     

主被动相结合的Ad Hoc网络拓扑重构算法

根据性能与拓扑的相关性,提出一种分级Ad Hoc网络拓扑重构算法.主动重构分为簇内、簇间两部分:在簇内,通过收集邻居信息进行局部拓扑发现,维护邻域拓扑的k-连通实现簇内拓扑k-连通;在邻簇间,通过计算由各簇边界节点及其链路所组成赋权二分图的最优匹配,以维护k条不邻接的链路,k值根据局部拓扑特性和应用要求动态调整;网络故障时,采用k跳邻域扩散连通性恢复方案进行被动重构,并在故障恢复后,对故障区域进行局部拓扑优化.仿真结果表明,主被动相结合拓扑重构方案能够提高网络的抗毁性、可靠性和有效性.     

基于Agent的安全协议对抗Ad Hoc网络下的拒绝服务攻击

拒绝服务攻击是AdHoc网络安全领域中的难题,本文提出一种新型的基于Agent的安全路由协议,Agent可根据其邻节点的可信度定期更新以适应AdHoc分布式路由计算环境,有效提高网络的可信性,降低网络安全计算的复杂度;根据拒绝服务攻击的特征抽取出Agent安全规则与检测算法.采用NS2网络模拟器的仿真结果表明,该方法能有效的检测出拒绝服务攻击并进行及时响应,使网络性能迅速恢复正常.     

基于模型分析的城市环境下车载移动Ad hoc网络路由协议改进策略

在Manhattan移动模型的基础上,深入分析了车载移动Ad hoc网络路由协议的性能问题.结合AODV路由协议,提出了一种可以量化分析车载Ad hoc网络路由断链率和路由负载的模型.模型分析指出,传统的移动Ad hoc网络路由协议应用于车载Ad hoc网络时性能会严重下降.针对这一问题,提出了一种基于车辆运动方向信息的类AODV路由协议DBAP,将车辆的运动方向信息作为其路由发现过程中的辅助参数,从而显著地增强了路由稳定性.仿真结果验证了模型的正确性,同时证明了本文所提出的DBAP路由协议在城市车载环境中具有较低的路由负载和路由断链率,在协议性能等方面相对于AODV协议具有显著提高.     

一种改进的移动IP注册认证协议

通过分析一种移动IP注册认证协议的安全性,提出了一种新的移动IP注册认证模型.该协议在保持原有协议特点的同时,能够提供更高的安全性,从而有效地抵御重放攻击和中间人攻击等安全威胁.     

如何解决局域网内盗用IP的问题

主要列举了当前局域网的使用当中在网内出现IP地址冲突 ,造成局域网管理混乱的几种主要现象 ,针对这几种现象 ,讨论、分析在局域网的使用中如何有效避免网内IP地址盗用 ,提高局域网使用效率的几种方法     

一种新的基于ECC的Ad hoc组密钥协商协议

在Ad hoc网络中进行安全的组通信,安全的组密钥协商协议是关键.采用椭圆曲线密码方案(elliptic curve cryptosystems,ECC),提出了一种安全有效的Ad hoc网络组密钥协议,并对其可行性和安全性进行了证明.针对Ad hoc 网络节点有随时加入或离开组的特点,提出有效的具有前向保密与后向保密的组密钥更新方案.与其他组密钥管理协议相比较,本协议更加注重每个组成员公平产生组密钥,且只用两轮来计算组密钥,还具有计算量少、存储开销小等特点,适合应用于 Ad hoc 网络.     

介入移动汇聚节点的无线传感器网络高效数据收集方法

引入移动汇聚节点解决无线传感器网络高效数据收集问题.网络中固定汇聚节点与移动汇聚节点共存,全部传感器节点都拥有维护到固定汇聚节点的路由,移动汇聚节点进入网络后定期向其附近小范围内的传感器节点扩散自己的声明信息,传感器节点向距自己跳数最小的汇聚节点发送或转发数据包.移动汇聚节点和距离其一跳的传感器节点之间通过有效的应答机制来保证数据的可靠传榆.通过仿真结果显示引入移动汇聚节点的数据收集在节省能耗方面明显优于传统网络.在延长网络生存时间的同时,可以获得较高的数据传输成功率和较短的数据传输延迟.     

车载通信网中基于DSR分层机制的移动代理路由策略研究

分析了现有动态源路由(dynamic source routing,DSR)协议机制以及在车载通信网路由发现中存在的问题,提出一种基于DSR分层机制的移动代理路由策略(cluster mobile agent-dynamic source routing,CM-DSR),并对设计的算法进行仿真实验.结果表明,所提出的CM-DSR协议与DSR路由协议相比较,较大幅度地降低了端到端的传输延迟,减少了路由请求次数,包的提交率也有一定程度的提高.     

无线传感器网络中节点移动场景下的密钥管理方法

为了探讨无线传感器网络中节点移动场景下的密钥管理方法,克服现有方案在移动节点重新加入网络方面的安全缺陷,提出了基于椭圆曲线数字签名算法的复合安全机制来验证移动场景下的节点身份,解决了其他密钥管理方案中存在的节点易受拒绝服务攻击和密钥易被敌人推算出等安全性问题.采用阶为160 bit的椭圆曲线,在带有XMTS300CB传感器板的IRIS传感器节点上实施了该密钥管理方案,通过与新邻居安全地建立对密钥和本地广播密钥,达到帮助移动场景下的节点安全地加入网络的目的.安全与性能分析表明,该方案能够有效抵御针对无线传感器网络的主要攻击手段,并且具有较低的计算、通信和存储负载.     

分布式自组织网络动态功率控制机制的研究与实现

针对自组织网络的功率控制机制,提出了一种适用于自组织网络的分布式动态功率控制机制.源节点首先向目的节点申请保护时隙作为专用数据通信时隙,申请成功后源节点根据接收到的响应报文的发送功率和接收信号强度指示器,计算出源节点到目的节点的最优发送功率,减少发送功率从而节省节点能耗.基于CC2430无线模块开发了实验验证平台对该机制进行验证,调整节点的发射功率可以延长节点的生命周期,减少通信冲突碰撞,而基于信标帧调度的网络提升了网络的容量.实验结果表明,该动态功率控制机制能有效降低网络能耗,同时网络整体容量也得到了一定的改善.     

Formal logic and dialectical thinking are not incongruent.

Comments on the article by K. Peng and R. E. Nisbett (see record 1999-11125-001) that made a number of assertions that reveal problems in logic and argumentation. In their studies, Peng and Nisbett found that Chinese tended to like dialectical proverbs and social resolution better than did Americans, and Chinese tended to prefer dialectical arguments over classic Western logical arguments. In this article, the author rejects 2 key assertions made by Peng and Nisbett: the first asserting that Chinese dialectical thinking and the laws of formal logic are incongruent, and the second asserting that there are 2 distinct argument forms (logical vs 'dialectical'). Because these 2 assertions are central to their entire argument, the theoretical rationale and consequently the empirical work of their study are suspect the author asserts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recommendations for medical management of hereditary breast and ovarian cancer: the French National Ad Hoc Committee

BACKGROUND AND PURPOSE: Almost 10% of breast and ovarian cancers are familial, and the majority are linked to BRCA1 and BRCA2 germline mutations. Despite uncertainty about the management of female gene carriers, consensus guidelines have been established to assist practitioners and consultees in making health care decisions. METHODOLOGY: The Ad Hoc Committee was composed of 14 experts appointed by the French National Institute for Health and Medical Research, all of whom attended eleven workshops at which more than 3500 articles were systematically analyzed. Five additional experts critically analysed the first version of the report. CRITERIA AND DECISION PROCESS: On a probability scale of the risk of developing breast or ovarian cancers, two thresholds were defined for use in determining whether an intervention would be worthwhile. The first is the threshold above which an intervention can be envisaged or recommended, and the second is the one below which an intervention can be ruled out; between the two, the decision has to be made on a case-by-case basis. SCREENING AND PREVENTIVE STRATEGIES ANALYZED: With respect to breast cancer: 1) hormonal interventions; 2) primary prevention (diet, family planning and chemoprevention); 3) screening (breast self-examination, clinician breast examination, tumor markers, imaging); 4) prophylactic mastectomy. With respect to ovarian cancer: 1) hormonal stimulation; 2) screening (clinical screening, ultrasound and tumor markers); 3) prophylactic oophorectomy. MAIN CONCLUSIONS: For each strategy the following points were addressed: the information to be given to the consultee, the procedure and the indications. In addition, the committee's opinion about BRCA1 and BRCA2 mutation screening is that population-based, or even large-scale, implementation are not justified. Although no scientific evidence is available, the committee feels that specific management is indispensable and advocates the use of defined and evaluated procedures, and participation in clinical trials.     

Robust Mobile Ad Hoc Space for Collaboration to Support Disaster Relief Efforts Involving Critical Physical Infrastructure

When an extreme event hits an urban area, the efficiency and effectiveness of the first response have a profound effect on disaster relief efforts. The redefinition of the civil engineers’ role and responsibilities as first response team members, along with an enhanced collaboration between disaster relief organizations, will greatly improve first response efforts and the securing of affected infrastructures. To improve collaboration efforts, the currently used radio systems-based interaction medium needs to be modified due to the impossibility of storing, retrieving, and transferring digital information, and limited support to implement information dissemination policies. This paper presents a reliable, transparent, and portable mobile ad hoc space for collaboration (MASC) based on a short range wireless communication platform to address these limitations in order to provide more consistent and efficient collaboration among first responders. The system was designed around a robust data redundancy core, and tested through software simulations and by conducting a search and rescue exercise involving civil engineers and firefighters. The simulation results highlight that the number of machines, the replication level, the size of the replication unit, and the wireless communication range are key design elements of the system in providing high availability. The search and rescue exercise allowed this research to confirm the high availability simulation results and to demonstrate that MASC is able to adequately manage and disseminate information in disaster scenarios. These encouraging results allow this research effort to conclude that MASC is able to address these new challenges.     

Global estimates for prevalence of diabetes mellitus and impaired glucose tolerance in adults. WHO Ad Hoc Diabetes Reporting Group

OBJECTIVE: To assemble standardized estimates of abnormal glucose tolerance in adults in diverse communities worldwide and provide guidelines for the derivation of comparable estimates in future epidemiological studies. RESEARCH DESIGN AND METHODS: The project was limited to population-based investigations that had used current WHO criteria for diagnosis and classification of abnormal glucose tolerance. Raw data were obtained by WHO from surveys conducted during 1976-1991 of over 150,000 persons from 75 communities in 32 countries. Data within the truncated age range of 30-64 yr were adjusted to the standard world population of Segi. Age-specific prevalences also are reported for selected populations. RESULTS: Within the chosen age range, diabetes was absent or rare (< 3%) in some traditional communities in developing countries. In European populations, age-standardized prevalence varied from 3 to 10%. Some Arab, migrant Asian Indian, Chinese, and Hispanic American populations were at higher risk with prevalences of 14-20%. The highest prevalences were found in the Nauruans (41%) and the Pima/Papago Indians (50%). Age-standardized prevalence of IGT was low (< 3%) in some Chinese, traditional American Indian, and Pacific island populations. Moderate (3-10%) or high (11-20%) prevalences of IGT were observed in many populations worldwide. The highest estimates for prevalence of IGT were seen in female Muslim Asian Indians in Tanzania (32%) and in urban male Micronesians in Kiribati (28%). Prevalence of diabetes rose with age in all populations in which age-specific data were examined. This trend was most pronounced in those at moderate to high risk. The ratio of prevalence of diabetes in men versus women varied markedly between populations with little discernable trend, although IGT was generally more common in women. In most communities, at least 20% of diabetes cases were unknown before the survey, and in many communities, > 50% were previously undiagnosed. In both Chinese and Indian migrant populations, relative prevalence was high when compared with indigenous communities. CONCLUSIONS: Diabetes in adults is now a global health problem, and populations of developing countries, minority groups, and disadvantaged communities in industrialized countries now face the greatest risk.     

CTCS-3级列控系统车地交互流程形式化建模与验证

正在建设的时速300km/h以上的高速铁路已采用CTCS-3级列车运行控制系统.车地信息交互流程是影响CTCS-3级列控系统的效率、可靠性和安全性的主要因素之一.基于时间自动机理论对车地交互流程进行建模与验证具有重要意义.首先将车地交互流程分为4个典型的子流程:任务启动流程、正常行车流程、RBC切换流程和任务结束流程,然后针对这些子流程建立无线闭塞中心(RBC)、车载设备(ATP)和铁路专用移动通信网(GSM-R)的时间自动机网络模型,最后利用时间自动机模型验证工具UPPAAL进行仿真分析,验证了CTCS-3级列控系统的车地交互流程的安全性和受限活性.