P2P网络中负载均衡策略的研究

负载均衡是使P2P网络能更高效地工作的一个关键问题.从最大化处理器利用率和提高系统吞吐量等方面,综述现有P2P系统负载均衡策略及其研究成果.结合当前新兴的计算机和网络技术,分析负载均衡策略下一步研究的问题和方向.     

基于复杂网络特征的P2P系统模型的研究

研究表明小世界和无尺度是很多大型复杂网络的重要特征,研究具有复杂网络特征的P2P网络模型对研究网络的拓扑结构和行为有着重要的意义.针对现有模型不能全面地反映实际网络提出了基于复杂网络特征的P2P网络模型.本文在基于组增长和选择具有较大吸引力的节点这些特征基础上建立一个新的模型,经过实验证明此模型更接近实际网络.     

P2P技术在语言实验室中的应用

本文介绍了当前比较流行的P2P(Peer-to-Peer)技术,并分析了P2P技术与传统的客户机/服务器技术的区别与优势.同时将P2P技术引入到外语语言实验室,提出使用P2P技术构架外语语言实验室的构想.最后分析了P2P技术使用在外语语言实验室的可行性,总结了P2P系统下的外语语言实验室的特点.     

P2卡安全防护策略简述

P2卡是一种小型固态数码存储卡,P2卡的安全防护与传统的磁带有很大的区别.本文结合我台实际应用,从主动防护和被动防护两方面阐释了P2卡安全防护策略.最后总结全文,指出课题中有待进一步深入研究的问题.     

时空相关性的P2P网络信任模型

结合时间和空间特性,提出一个新的动态信任模型,该模型包含近期信任、长期信任、滥用信任和反馈信任等4个基本组件;针对P2P网络中节点动态性的问题,提出用社区信任度来表示物理位置相关的群体信任程度.模拟实验结果显示,该模型具有较好的动态适应能力和反馈信息聚合能力,能够有效地防止合谋、诋毁等恶意攻击行为.     

P2P应用层数据流量优化

为减少对主干网络带宽的消耗,提出了一套数据流量优化方法.首先通过把Peer间的邻居关系明确划分为物理邻居关系和逻辑邻居关系,并用探路者算法来发现Peer的物理邻居,实现拓扑匹配;然后在数据调度算法中,引入通报/退避机制,把大部分数据传输控制在城域网络内部.通过建立模拟仿真环境进行实验分析,证实了该方法可以减少90%以上的网络数据流量.     

P含量对CaO-SiO2-P2O5-FetO-MgO渣系P固溶行为的影响及nC2S-C3P超重力分离

研究不同P含量对CaO-SiO2-P2O5-FetO-MgO渣系中P固溶行为的影响,并利用超重力分离出含P固溶体.采用XRD衍射仪和扫描电子显微镜(SEM-EDS)对不同P含量渣系在1350℃下的物相和微观结构进行表征分析.结果表明:不同P含量的渣系中都形成了nCa2SiO4-Ca3(PO4)2(nC2S-C3P)固溶体,且随着P含量由3％增加至12％,nC2S-C3P固溶体中P2O5含量不断增加,P含量为12％时,nC2S-C3P固溶体中P2O5含量最高达23.27％.在此基础上,P含量为12％时,利用超重力从熔渣中分离出nC2S-C3P固溶体,P2O5的质量分数和回收率分别为22.16％和93.32％.     

面向P2P网络的DDoS攻击抑制方法

提出了一种分布式的基于对P2P网络中各节点进行分级的DDoS攻击抑制方法,采集了多个能分别反映当前节点本身或周围节点网络状况的评级因子,并通过不确定性推理确定当前节点分级值.分级值决定转发率.使用线性分类作为丢包策略对需发送数据包进行分组、丢弃,以降低误报率.仿真实验表明该方法能够有效抑制P2P网络上的DDoS攻击,提高整个网络抗攻击弹性.     

组播VPN以及P2MP技术在广电网络中的应用

本文介绍了关于MPLS VPN组播以及P2MP技术与组播技术结合方面的一些信息.     

超(超)临界电站锅炉用P92钢的开发

介绍了超(超)临界电站锅炉用P92钢研发的背景,对其化学成分、组织结构及性能进行了讨论.常规理化性能测结果表明:所试制的P92(lOCr9MoW2VNbBN)钢管(ΦD610mm×102mm)的化学成分、组织、室温及短时高温性能均符合ASME SA335 P92及GB5310～2008的要求.     

P2P环境下基于兴趣的分布式信任模型

为解决P2P网络中节点的不合作行为和恶意攻击等问题,提出了一种分布式兴趣信任模型DITM.模型通过划分兴趣域聚集兴趣相似的节点来解决节点间因兴趣不对称难以建立直接信任关系的问题.利用兴趣相似度刻画节点在其偏好领域上的服务行为相似性,并通过兴趣相似度加权域推荐信任度计算域服务信誉.节点在不同域内的服务信誉组成一个服务信誉向量,该向量维护了节点在各个兴趣域的服务行为细节,从而能有效抵御恶意节点针对特定兴趣域的攻击,并能激励好节点在多个域内贡献资源.仿真实验表明,DITM较已有的信任模型在迭代的收敛速度、下载成功率和模型的安全性等问题上有较大提高.     

Interactions of substrate and product with cytochrome P450: P4502B4 versus P450cam

OBJECTIVE: To determine the relative abilities of somatostatin receptor scintigraphy (SRS) and conventional imaging studies (computed tomography, magnetic resonance imaging, ultrasound, angiography) to localize gastrinomas before surgery in patients with Zollinger-Ellison syndrome (ZES) subsequently found at surgery, and to determine the effect of SRS on the disease-free rate. SUMMARY BACKGROUND DATA: Recent studies demonstrate that SRS is the most sensitive imaging modality for localizing neuroendocrine tumors such as gastrinomas. Because of conflicting results in small series, it is unclear in ZES whether SRS will alter the disease-free rate, which gastrinomas are not detected, what factors contribute to failure to detect a gastrinoma, or whether the SRS result should be used to determine operability in patients without hepatic metastases, as recently recommended by some investigators. METHODS: Thirty-five consecutive patients with ZES undergoing 37 exploratory laparotomies for possible cure were prospectively studied. All had SRS and conventional imaging studies before surgery. Imaging results were determined by an independent investigator depending on surgical findings. All patients underwent an identical surgical protocol (palpation after an extensive Kocher maneuver, ultrasound during surgery, duodenal transillumination, and 3 cm duodenotomy) and postoperative assessment of disease status (fasting gastrin, secretin test imaging within 2 weeks, at 3 to 6 months, and yearly), as used in pre-SRS studies previously. RESULTS: Gastrinomas were detected in all patients at each surgery. Seventy-four gastrinomas were found: 22 duodenal, 8 pancreatic, 3 primaries in other sites, and 41 lymph node metastases. The relative detection order on a per-patient or per-lesion basis was SRS > angiography, magnetic resonance imaging, computed tomography > ultrasound. On a per-lesion basis, SRS had greater sensitivity than all conventional studies combined. SRS missed one third of all lesions found at surgery. SRS detected 30% of gastrinomas < or =1.1 cm, 64% of those 1.1 to 2 cm, and 96% of those >2 cm and missed primarily small duodenal tumors. Tumor size correlated closely with SRS rate of detection. SRS did not increase the disease-free rate immediately after surgery or at 2 years mean follow-up. CONCLUSIONS: SRS is the most sensitive preoperative imaging study for extrahepatic gastrinomas in patients with ZES and should replace conventional imaging studies as the preoperative study of choice. Negative results of SRS for localizing extrahepatic gastrinomas should not be used to decide operability, because a surgical procedure will detect 33% more gastrinomas than SRS. SRS does not increase the disease-free rate. In the future, more sensitive methods to detect small gastrinomas, especially in the duodenum and in periduodenal lymph nodes, or more extensive surgery will be needed to improve the postoperative disease-free rate in ZES.     

P507和P204在稀土分离中的应用

文章详细报道了P507和P204两种萃取剂在轻稀土镧铈-镨钕分离工业生产中的实际应用,并且对其共性、特性及生产能力等进行了比较和分析,为稀土分离领域提供了一些技术参数和投资依据。