Microstructure character of AZ80 magnesium alloy ingots cast under electromagnetic vibration

Microstructure evolutions of an AZ80 magnesium alloy ingot with 300 mm in diameter cast with and without the electromagnetic vibration was investigated. The microstructures of the ingot cast with the conventional DC exhibited relatively fine dendritic grains at the surface area, but coarse dendritic grains at the 1/2 radius and large equiaxed dendritic grains at the center. However, under the electromagnetic vibration casting condition, the microstructures of the ingot is significantly refined, especially those at the surface and at the center.     

一种基于假名的分簇式无线传感器网络节点匿名性增强方案(英文)

Security problem is an important issue for Wireless Sensor Network.The paper focuses on the privacy protection of WSN applications.An anonymity enhancement tactic based on pseudonym mechanism is presented for clustered Wireless Sensor Network,which provides anonymity for both the sensors within a cluster and the cluster head nodes.Simulation experiments are launched through NS2 platform to validate the anonymity performance.The theoretical analysis and empirical study imply that the proposed scheme based on pseudonym can protect the privacies of both the sensor nodes and the cluster head nodes.The work is valuable and the experimental results are convincible.     

A novel SVM ensemble approach using clustering analysis

A novel Support Vector Machine （SVM） ensemble approach using clustering analysis is proposed. Firstly, the positive and negative training examples are clustered through subtractive clustering algorithm respectively. Then some representative examples are chosen from each of them to construct SVM components. At last, the outputs of the individual classifiers are fused through majority voting method to obtain the final decision. Comparisons of performance between the proposed method and other popular ensemble approaches, such as Bagging, Adaboost and k-fold cross validation, are carried out on synthetic and UCI datasets. The experimental results show that our method has higher classification accuracy since the example distribution information is considered during ensemble through clustering analysis. It further indicates that our method needs a much smaller size of training subsets than Bagging and Adaboost to obtain satisfactory classification accuracy.     

客户／服务器方式下VFP3.0与SQL Server的连接访问

使用ＶＦＰ３．０作为前端开发工具，通过ＯＤＢＣ（开放式数据库互连）来完成对远程ＳＱＬ Ｓｅｒｖｅｒ数据库的数据访问，可以有效地利用ＶＦＰ的数据库和客户／服务器技术。本文主要对ＶＦＰ与ＳＱＬ Ｓｅｒｖｅｒ的ＯＤＢＣ连接、使用及经常遇到的问题加以叙述。     

基于CFL的去中心工控系统签名认证方案

近来, 工业控制系统的身份认证和数字签名等安全问题受到越来越多的关注. 本文将去中心化的CFL认证体制引入到工控系统身份认证中, 提出了基于CFL的工控系统签名认证方案, 建立了基于CFL认证体制的工控系统认证模型CFL-SYS, 引入UKey作为证书载体, 实现了签名验证过程去中心化; 通过计算用户ID的哈希值生成随机私钥和标志私钥实现一人一密, 满足了用户对私钥的私有权并且保护了用户的隐私. 理论分析和实验结果表明, 本文方案在吞吐量、系统验证响应时间等性能上能够满足毫秒级应用需求, 能为大规模工业控制系统提供一种自主、可靠、高效的签名认证方案.     

基于CFL的工控系统认证通信方案

针对工控系统（ICS）中广泛采用的中心认证方案所存在的密钥泄露、单点失效、通信开销大的问题，将具有国内自主知识产权的密码基础逻辑（CFL）认证技术引入ICS的认证与通信过程中，并提出一种基于CFL的ICS认证通信方案。首先，通信双方通过交换并验证基于彼此身份标识和权限信息所生成的动态含权证书，实现双方身份的去中心认证和会话密钥的协商；然后，通过会话密钥、CFL动态签名和访问控制规则保证双方的安全通信；最后，将控制过程详细日志进行加密存储，以实现可溯源过程。理论分析和实验结果表明，所提方案在身份验证阶段不再需要远程认证中心的参与，并实现了工控设备间的本地高效认证。在面对大量认证请求时，与公钥基础设施（PKI）方案、基于身份加密（IBE）方案相比，所提方案的系统吞吐量分别至少提升了92.53%和141.37%，意味着所提方案能够更好地满足ICS的大规模认证和毫秒级安全通信的需求。