InfoSigs:一种面向Web对象的细粒度聚类算法

面向Web对象的细粒度聚类已经成为学术界研究的热点.然而现有大多数聚类模型只关注如何对文本内容或文章主题进行聚类,聚类结果粒度较粗,无法满足大规模网络信息检索的质量要求.针对上述挑战,充分挖掘Web文档中词汇间的树状概率层次关系,提出一种以词汇信息分布作为特征标志的聚类算法InfoSigs,实现对Web对象的细粒度聚类.算法构建一个信息传递有向无环图,根据词汇在图中信息分布的集中度赋予其合理的权重,产生更具代表性的特征向量;同时算法提出了一个自适应的记录合并模型,有效提高记录簇中记录间的相似度,减少噪音对合并过程的影响.实验结果表明,InfoSigs算法比传统聚类算法—I-Match和Shingling—在F-Measure值上平均约有21.3%的提高,可以有效地运用到多领域Web对象的聚类问题.     

不完全标记的多个并行事务踪迹的“剥离”

新型分布式软件的多个并行处理事务导致每个事务产生的事件按随机排序,如果这些事件的标记不完全或不可用,将无法区分这些事件到底属于哪个事务.将不完全标记事件的“剥离”问题转化成偶图最大权重完全匹配问题.对于事件间的转换时间是独立等同分布的情况,将所有可能状态(事件)划分为若干个割集,每个割集构成一个偶图.在这些偶图系统中,采用所提出的偶图最大权重完全匹配的改进算法进行分散匹配,通过拼接匹配结果得到各事务产生的最可能踪迹序列.仿真实验证实:该方法可以有效实现不完全标记的事务踪迹的“剥离”;与传统的偶图匹配方法相比,改进算法具有更高的匹配效率.     

A Framework for Providing User Level Quality of Service Guarantees in Multi-Class Rate Adaptive Systems

The problem of channel sharing by rate adaptive streams belonging to various classes is considered. Rate adaptation provides the opportunity for accepting more connections by adapting the bandwidth of connections that are already in the system. However, bandwidth adaptation must be employed in a careful manner in order to ensure that (a) bandwidth is allocated to various classes in a fair manner (system perspective) and (b) bandwidth adaptation does not affect adversely the perceived user quality of the connection (user quality). The system perspective aspect has been studied earlier. This paper focuses on the equally important user perspective. It is proposed to quantify user Quality of Service (QoS) through measures capturing short and long-term bandwidth fluctuations that can be implemented with the mechanisms of traffic regulators, widely used in networking for the purpose of controlling the traffic entering or exiting a network node. Furthermore, it is indicated how to integrate the user perspective metrics with the optimal algorithms for system performance metrics developed earlier by the authors. Simulation results illustrate the effectiveness of the proposed framework.

基于可变Cookie的跨域单点登录

针对单点登录中的跨域身份认证问题,提出了一种基于可变Cookie的方案解决跨域单点登录,使用随机数字生成票据,并作为传统加密算法的会话密钥对客户端的Cookie进行加密,采用现代加密算法在异域系统之间安全传递票据,每次认证产生新的票据并更新异域应用系统的Cookie。通过对票据产生和传输以及Cookie加密和常见攻击的安全性分析,可以实现跨域单点登录的功能并保证身份认证安全可信。     

加密设备接口标准研究及实现分析

加密设备的接口规范是网络安全能统一实施的关键。Cryptoki是基于PKCS#11加密设备接口标准的编程接口，可用于各种可移植的密码设备。本文在阐述Cryptoki通用模型特点的基础上，具体分析了作为Unix类平台工业标准的OpenCryptoki的实现过程，为基于相关标准的编程接口的开发提供了参考。     

Boosting Search with Variable Elimination in Constraint Optimization and Constraint Satisfaction Problems

There are two main solving schemas for constraint satisfaction and optimization problems: i) search, whose basic step is branching over the values of a variables, and ii) dynamic programming, whose basic step is variable elimination. Variable elimination is time and space exponential in a graph parameter called induced width, which renders the approach infeasible for many problem classes. However, by restricting variable elimination so that only low arity constraints are processed and recorded, it can be effectively combined with search, because the elimination of variables may reduce drastically the search tree size.In this paper we introduce BE-BB(k), a hybrid general algorithm that combines search and variable elimination. The parameter k controls the tradeoff between the two strategies. The algorithm is space exponential in k. Regarding time, we show that its complexity is bounded by k and a structural parameter from the constraint graph. We provide experimental evidence that the hybrid algorithm can outperform state-of-the-art algorithms in constraint satisfaction, Max-CSP and Weighted CSP. Especially in optimization tasks, the advantage of our approach over plain search can be overwhelming.     

干熄焦旋转焦罐车设计中的几个问题

对干熄焦旋转焦罐车的开门机构、传动机构、定位机构、材料等设计问题进行了分析 ,探讨了解决的方法 ,提出了设计思路     

基于PDES乐观时间管理的周期时间桶算法研究

时间管理是影响并行离散事件仿真PDES系统高效运行的重要因素之一。文章首先分析了离散事件仿真的原理,以及PDES所面临的时间管理方面的挑战;然后阐述了乐观时间管理机制,重点提出了周期时间桶算法的设计与实现,并对其性能作了大体上的评估。     

深水海上风机吸力桶导管架基础承载特性

针对海洋深水环境,设计适应70 m水深的四桶导管架结构形式,并在此基础上设计相同高度和主腿斜度的三桶导管架基础。采用Abaqus有限元软件建立导管架结构-吸力桶-土体整体有限元模型,通过对比分析探究海上风电深水吸力桶导管架基础的承载力特性。研究发现：吸力桶与土体的位移一致性程度可反映基础水平极限承载力大小,四桶导管架基础的综合承载特性优于三桶导管架基础;加载高度对四桶导管架基础的水平承载力特性有重要影响,基础水平承载力随着加载高度增加逐渐减小;加载方向对四桶导管架基础水平承载力影响较小。     

受水流冲刷影响后的吸力桶基础水平极限承载力

以某海域海上风机吸力桶基础为研究对象,采用Abaqus有限元数值模拟软件,考虑基础在不同土层中由水流冲刷导致其周围土体缺失时吸力桶基础的水平承载力。结果表明,桶内土体的缺失对吸力桶水平承载力的影响不大,随着吸力桶基础外周围土体缺失的扩大,其水平承载力逐渐降低,并影响海上风机的正常使用。