Minimal explanations of missing values by chasing acquisitional data

Acquisitional issues widely exist in GPS and sensor networks. They pertain to where, when, and how often data is physically acquired (sampled) and delivered to some query processing systems. Due to the dynamic environment that the data is acquired with the change of monitoring time, acquisitional data are typically a time-stamped stream where a time-stamped value could either contain noises or be missing. Aiming to improve the quality of data acquisition, we focus on the explanations of missing values in this paper. Several techniques have been developed to provide the explanation on relational data, however, they cannot be directly applied in acquisitional stream data due to its dynamic feature, such as the “change” of acquisitional stream data between two adjacent monitoring time is often constrained by some rules. We show that an explanation could be incorrect or unreasonable if those constraints are not taken into account. We propose one novel chasing technique by considering both spatial and temporal correlations to explain missing values and guarantee a minimal explanation. Experimental results show that our approach can efficiently return high-quality and minimal explanations of missing values.     

Time-variant global reliability sensitivity analysis of structures with both input random variables and stochastic processes

Structural and Multidisciplinary Optimization - The ubiquitous uncertainties presented in the input factors (e.g., material properties and loads) commonly lead to occasional failure of mechanical...     

采用碳足迹分析的产品低碳优化设计

为了给低碳产品开发提供辅助支持,采用模块化思想和生命周期分析方法建立了基于产品结构的碳足迹分析模型;基于敏感性分析方法研究关键低碳设计参数变化与碳排放变化之间的映射关系,在对分析结果进行处理的基础上,以各低碳设计参数改进引起的碳足迹最小为优化目标,构建关键模块单元低碳设计改进的多约束目标优化模型,并采用回溯算法和遗传算法对优化模型进行求解.最后以洗碗机为例,验证了文中方法的可行性和有效性.     

网络机器人在数据库比对系统中的应用

网络机器人(Web Robo)t是一种自动化获取网页数据的程序。实践中使用对特定主题感兴趣的网络机器人获取数据,与数据库中数据进行比对,得出有用的结果。     

校园无线网络安全防范浅析

无线网络已成为校园网的重要组成部分.剖析了校园无线网络存在的问题,给出了无线网络安全防护对策、安全认证方式和基础技巧.     

基于.Net的Excel和数据库数据转换——以军事理论练习系统为例

根据军事理论练习系统的需求,分析了将Excel电子表格中的试题数据导入到Access数据库中,以及将学生成绩等信息导出到Excel电子表格的原理和方法,并应用于实际解决方案,有效提高了工作效率。     

基于NS2的802.11效果异常现象仿真研究

在802.11 WLAN(Wireless Local Network)中,当一些无线节点的传输速率明显低于其他节点与AP(Access Point)间的传输速率时,将会使区域内所有节点的传输性能降低,这种现象称为效果异常(Performance Anomaly),Hyogon K等人在文献[6-7]中提出用改变封包容量和竞争窗口大小的方式来解决这个问题.文章通过在NS2网络仿真环境下,设计实验拓扑,编写性能分析脚本,对效果异常现象进行仿真并验证了上述两种方案能够有效缓解该现象并保持系统传输性能稳定.     

基于积件思想的高职计算机课程项目式教学探索——以C语言程序设计为例

基于积件思想,对五年制高职计算机课程项目式教学进行探索,以C语言程序设计为例研究分析,并组建C语言程序设计课程知识点积件库,编写高职C语言程序设计课程项目式校本教材,分析C语言程序设计课程教学项目“阶梯电价计费”.并借助开源平台Moodle实现了教学项目的应用.     

On event design in event-triggered feedback systems

This paper studies event design in event-triggered feedback systems. A novel event-triggering scheme is presented to ensure exponential stability of the resulting sampled-data system. The scheme postpones the triggering of events over previously proposed methods and therefore enlarges the intersampling period. The resulting intersampling periods and deadlines are bounded strictly away from zero when the continuous time system is input-to-state stable with respect to measurement errors.     

Group path covering and distance two labeling of graphs

For a positive integer d, an L(d,1)-labeling f of a graph G is an assignment of integers to the vertices of G such that |f(u)−f(v)|?d if uv∈E(G), and |f(u)−f(v)|?1 if u and u are at distance two. The span of an L(d,1)-labeling f of a graph is the absolute difference between the maximum and minimum integers used by f. The L(d,1)-labeling number of G, denoted by λd,1(G), is the minimum span over all L(d,1)-labelings of G. An L^′(d,1)-labeling of a graph G is an L(d,1)-labeling of G which assigns different labels to different vertices. Denote by the L^′(d,1)-labeling number of G. Georges et al. [Discrete Math. 135 (1994) 103-111] established relationship between the L(2,1)-labeling number of a graph G and the path covering number of Gc, the complement of G. In this paper we first generalize the concept of the path covering of a graph to the t-group path covering. Then we establish the relationship between the L^′(d,1)-labeling number of a graph G and the (d−1)-group path covering number of Gc. Using this result, we prove that and for bipartite graphs G can be computed in polynomial time.