Efficient distance-based representative skyline computation in 2D space

Representative skyline computation is a fundamental issue in database area, which has attracted much attention in recent years. A notable definition of representative skyline is the distance-based representative skyline (DBRS). Given an integer k, a DBRS includes k representative skyline points that aims at minimizing the maximal distance between a non-representative skyline point and its nearest representative. In the 2D space, the state-of-the-art algorithm to compute the DBRS is based on dynamic programming (DP) which takes O(k m ²) time complexity, where m is the number of skyline points. Clearly, such a DP-based algorithm cannot be used for handling large scale datasets due to the quadratic time cost. To overcome this problem, in this paper, we propose a new approximate algorithm called ARS, and a new exact algorithm named PSRS, based on a carefully-designed parametric search technique. We show that the ARS algorithm can guarantee a solution that is at most ?? larger than the optimal solution. The proposed ARS and PSRS algorithms run in O(klog2mlog(T/??)) and O(k ² log3m) time respectively, where T is no more than the maximal distance between any two skyline points. We also propose an improved exact algorithm, called PSRS+, based on an effective lower and upper bounding technique. We conduct extensive experimental studies over both synthetic and real-world datasets, and the results demonstrate the efficiency and effectiveness of the proposed algorithms.     

基于uC/OS-II的数字电能表计量软件系统

首先介绍了将模拟小信号电能表与纯数字电能表的计量综合成一个系统以后的体系结构, 然后分析了在嵌入式实时操作系统uCOS-II环境下计量系统的实现: 包括任务的划分、任务间的通信以及数据的共享问题, 其中重点研究了任务间通信时数据的共享问题, 最后总结了任务间的总体通信情况, 为设计出高精度的数字电能表计量软件奠定了坚实的基础.     

改进k-means 算法在电信CRM 客户分类中的应用

电信市场的竞争在于客户的竞争,为了在激烈的竞争中保持优势,必须将客户进行细分,针对不同的客户,研究出相应的营销策略．K-means算法能对大型数据集进行高效分类,但对“噪声”敏感,聚类结果不准确,本文对该算法进行改进,使其能够实现更加准确和全面的客户细分．     

多核环境下面向仿真组件的HLA 成员并行框架

提出了一种面向仿真组件的并行联邦成员框架,以解决基于HLA(high level architecture)复杂仿真系统联邦成员开发的问题,并提升多核处理器环境下联邦成员的运行性能.并行联邦成员框架通过仿真组件的组合、装配来构建联邦成员.通过仿真引擎管理、数据分发管理、对象管理、组件管理服务和负载平衡功能,并行联邦成员框架为仿真模型构建了一个多核的并行执行环境,并确保并行成员能与RTI正确交互.通过实验来研究并行成员框架引入的额外开销,并比较并行成员和普通成员的性能.实验结果表明,并行框架能够充分利用多核处理器的计算能力来减少仿真系统运行时间,提高系统性能.     

基于VIIRS数据洪泽湖悬浮物浓度估算算法研究

基于2012~2015年洪泽湖4次星地同步试验数据,建立了较高精度的水体悬浮物浓度单波段(671 nm)模型(R~2=0.74,RMSE=8.58 mg/L),并进行了验证(R~2=0.72,RMSE=11.98 mg/L);然后,将该算法成功应用到了2012~2015年464景VIIRS无云影像上.结果表明,洪泽湖悬浮物浓度呈现春夏低、秋冬高的季节特征和东、中部高,西、北部低的空间分布特征;在年际变化尺度上,悬浮物浓度年均值呈现较小的减少趋势.总体来说,VIIRS在浑浊水体悬浮物浓度上表现了较好的探测能力,在湖泊水色遥感领域具有较大潜力.     

P2P分布式存储系统

设计了一个基于P2P的分布式存储系统.该存储系统采用高可扩展的P2P体系结构,将大量分散的节点组织成一个逻辑网络,充分利用原先被忽视的端系统资源,构建大规模分布式存储系统.该存储系统采用高效的结构化P2P路由机制、动态自适应的副本管理、信任机制和激励机制为用户提供高效、可靠的分布式存储服务.     

两性高分子絮凝剂P(AM-DM-MA)的合成及性能评价

在引发剂存在下使丙烯酰胺 (AM)、二甲基二烯丙基氯化铵 (DM)、马来酸 (MA)在水溶液中共聚合 ,将共聚物提纯后得到了两性共聚物P(AM /DM/MA) ,收率约 92 %。红外光谱图、1H核磁共振谱图确证了共聚物的结构 ,用元素分析法测定了共聚物的组成 ,AM、DM、MA(以 COOH 计 )的摩尔分数分别为 87.5 %、8.9%和 3.6 %。以3%硅藻土水悬浮液充当模拟污水 ,考察了不同加剂量和 pH值下共聚物的絮凝性能 (通过沉降体积和透光率测定 )。共聚物加量为 8mg/L时透光率即高达 97.5 %,加量在 8～ 30 0mg/L时絮凝效果保持优良 ;pH <6 .7时透光率维持高值 ,pH值在 6 .7～ 9.3时 (等电点附近 )透光率很差 ,絮凝效果不良。P(AM/DM /MA)是一种极具发展潜力的水处理剂。     

Study on Simulation of Airflow within the Enclosure in the Semiconductor Factory Cleanroom

The application of mini-environment and SMIF (standard mechanical interface) enclosure in the cleanroom can efficiently reduce airborne particles and isolate the personnel from the product. The purpose of this article is to analyze the airflow field and pressure distribution of SMIF enclosure and to investigate the air cleanliness inside the mini-environment. Based on the continuity, momentum and energy equations of airflow motion, the simulation code CFX will be used to study the flow field of air movement corresponding to the associated boundary conditions. The results show that proper drilling holes or slots can improve the circulation zones of SMIF enclosure. The positive pressure of SMIF enclosure is mainly affected by inlet air flux, area of outlets, and leakage area. The calculated results will provide the design rules for SMIF Robot inside the SMIF enclosure and reduce the particle accumulation during robot moving.     

Solvothermal-induced construction of ultra-tiny Fe2O3 nanoparticles/graphene hydrogels as binder-free high-capacitance anode for supercapacitors

Three-dimensional (3D) ultra-tiny Fe2O3 nanoparticles/graphene hydrogels were prepared using a facile and efficient solvothermal reaction,by which the phase of ...     

基于非参数密度估计的不确定轨迹预测方法

随着大量移动设备的出现,准确和高效的轨迹预测有助于提高面向位置的应用和服务的质量和水平.针对现有方法对轨迹不确定性缺乏有效建模的问题,提出了基于非参数密度估计的不确定轨迹终点预测方法.在轨迹建模及模型训练阶段,利用非参数估计对起点与终点相同的轨迹构建基于密度分布的不确定轨迹模型;在轨迹预测阶段,将待预测轨迹视为轨迹数据流,并通过KS（Kolmogorov-Smirnov）检验方法与具有相同起点的不确定轨迹模型进行匹配,其中匹配程度最高的不确定轨迹即为预测轨迹.通过真实轨迹数据集上的实验表明,与现有各类主要轨迹预测方法相比,本方法在不同条件下的预测效率与准确性都有较明显优势.