人群异常识别技术研究进展

人群行为分析是计算机视觉领域最活跃的研究方向之一. 有许多针对人群异常行为及检测的算法如人群密度估计、人群中运动检测、人群跟踪和群体行为识别. 在对目前人群异常行为进行总结分析,并概括出人群异常的三大关键特征. 并在次基础上,分别针对人群特征提取、异常识别技术、异常分类技术以及人群异常识别数据库方面,对人群异常识别技术现状进行总结概括,并并对存在的问题,以及未来发展方向提出了研究的建议和意见. 文章对相关领域的研究具有一定的参考价值.     

小麦产量实时测报系统

针对当前河南地区小麦产量估测信息滞后问题,集成传感技术、GPS和无线通信技术,对接农机收获装备,构建基于多传感器技术的小麦产量测报信息服务系统,实现小麦收割与产量测报同步进行.系统的应用实验于2015年6月在许昌市长葛县800亩试验田进行,实验结果表明,系统的产量测报误差小于5%,可以满足小麦产量测报的实际需求.系统的推广应用为河南及全国的小麦产量测报提供数据参考,为获知农田信息的时空差异性提供数据支撑,为实施“精细农作”提供决策依据.     

Compact microstrip‐via‐fed wideband circularly polarized antenna with monofilar spiral stub for C‐band applications

A wideband circularly polarized printed antenna is proposed and fabricated, which employs monofilar spiral stubs and a slit in the asymmetrical ground plane which is fed by an asymmetrical microstrip feedline using a via. The CP operation is realized by embedding an inverted‐L shaped strip and a modified ground plane and can be markedly improved by loading monofilar spiral stubs connected to the asymmetric feedline by means of a via. A parametric study of the key parameters is made and the mechanism for circular polarization is described. After optimization, the impedance bandwidth is approximately 3.6 GHz (4.4‐8 GHz) and the 3 dB axial ratio bandwidth is approximately 3.3 GHz (4.7‐8 GHz), which represent fractional bandwidths of approximately 58.1% and 52%, respectively. Therefore, the proposed antenna is suitable for circular polarization applications in C (4‐8 GHz) band. Compared with other recent works, the simpler structure, wider axial ratio, impedance bandwidths, and more compact size are the key features of the proposed antenna.     

Wideband asymmetric microstrip‐fed circularly polarized antenna with monofilar spiral stub for WLAN application

A wideband circularly polarized printed antenna is proposed and fabricated, which employs monofilar spiral stubs and a slit in the asymmetrical ground plane which are fed by an inverted L‐shaped microstrip feedline. The CP operation is realized by embedding an inverted‐L shaped strip and modified ground plane and can be markedly improved by loading monofilar spiral stubs asymmetrically connected at the edge of the ground plane. After optimization, the measured results of the finally structure demonstrate that a 10‐dB bandwidth of 67.6% from 4.6 to 9.3 GHz and a 3‐dB axial‐ratio bandwidth (ARBW) for circular polarization (CP) of 60.1% from 5 to 9.3 GHz could be achieved which could completely cover the WLAN (5.725‐5.85 GHz) band. Therefore, the proposed antenna is suitable for circular polarization applications in C band. To explain the mechanism of broadband circular polarization operation, the analysis of magnetic fields distributions and a parametric study of the design are given. Compared to other recent works, a simpler structure, wider axial ratio and impedance bandwidths and a more compact size are the key features of the proposed antenna.     

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.     

Finding users preferences from large-scale online reviews for personalized recommendation

Along with the growth of Internet and electronic commerce, online consumer reviews have become a prevalent and rich source of information for both consumers and merchants. Numerous reviews record massive consumers’ opinions on products or services, which offer valuable information about users’ preferences for various aspects of different entities. This paper proposes a novel approach to finding the user preferences from free-text online reviews, where a user-preference-based collaborative filtering approach, namely UPCF, is developed to discover important aspects to users, as well as to reflect users’ individual needs for different aspects for recommendation. Extensive experiments are conducted on the data from a real-world online review platform, with the results showing that the proposed approach outperforms other approaches in effectively predicting the overall ratings of entities to target users for personalized recommendations. It also demonstrates that the approach has an advantage in dealing with sparse data, and can provide the recommendation results with desirable understandability.     

Topology optimization based on level set for a flexible multibody system modeled via ANCF

A topology optimization methodology is proposed for the flexible multibody system undergoing both large overall motion and large deformation. The system of concern is modeled via the absolute nodal coordinate formulation. The equivalent static load method is employed to transform the topology optimization of the nonlinear dynamic response of the system into a static one, and evaluated to adapt to the absolute nodal coordinate formulation by splitting the elastic deformations of the flexible components from the overall motions of those components. During the static topology optimization, the material interface is implicitly described as the zero level set of a higher-dimensional scalar function. Then, the semi-implicit level set method with the additive operator splitting algorithm is employed to solve the corresponding Hamilton-Jacobi partial differential equation. In addition, the expert evaluation method of weights based on the grey theory is utilized to define the objective function, and a modified augmented Lagrange multiplier method is proposed to treat the inequality volume constraint so as to avoid the oscillation and drift of the volume. Finally, two numerical examples are provided to validate the proposed methodology.     

大型网站的架构研究及解决方案

随着互联网业务的发展,网站规模越来越大,各种技术被提出以用于提升网站的性能、可用性、伸缩性、扩展性、安全性。在分析影响性能、可用性、伸缩性、扩展性和安全性等架构因素的基础上,提出了一套网站架构解决方案,并为图书馆集成发现系统的管理运维探索总结成功经验。     

基于半边结构和√3细分的渐进网格生成方法

渐进网格可以满足生成多分辨率模型的需求.在现有渐进网格生成方法中,一个顶点的简化往往关联四个以上的相邻顶点.并且,现有方法多采用网格的点面列表结构表示.本文采用√3细分预测方法生成渐进网格,每个顶点的存储仅关联三个相邻顶点.同时也使用半边数据结构替代网格的点面列表表示形式,加快了邻接信息查询.实验结果表明,本方法提升渐进网格的空间效率,缩短渐进网格的生成时间.     

云存储系统管理节点故障自恢复算法

为了解决大规模云存储系统中管理节点发生故障导致存储服务不可用的问题,建立了管理节点故障影响分析模型,提出了一种基于消息的管理节点动态自我恢复算法FRA-M.该算法通过基于负载均衡的元数据备份更新控制方法完成多个管理节点之间相互协作、透明接管和故障自我恢复.测试结果表明,FRA-M算法能够使得管理节点发生故障时自动进行切换,并且能够合理地分配资源达到良好的负载均衡状态.通过控制TCP超时时限、故障检测周期以及故障检测超时,能够使得FRA-M算法的性能保持在相对稳定的区间,随失效时刻的适应性也比较强.当管理节点发生故障时,FRA-M能够较好地保证存储服务可用性、数据可用性和数据可靠性.