Fuzzy Weirstrass theorem and convex fuzzy mappings

The convexity and continuity of fuzzy mappings are defined through a linear ordering and a metric on the set of fuzzy numbers. The local-global minimum property of real-valued convex functions is extended to convex fuzzy mappings. It is proved that a strict local minimizer of a quasiconvex fuzzy mapping is also a strict global minimizer. Characterizations for convex fuzzy mappings and quasiconvex fuzzy mappings are given. In addition, the Weirstrass theorem is extended from real-valued functions to fuzzy mappings.     

Towards understanding the gamification upon users’ scores in a location-based social network

Online social platform, such as Wikipedia and Foursquare, has been increasingly exploded due to not only various useful services provided but also social gaming mechanisms that can keep users actively engaged. For example, users are awarded ”virtual goods” like badges and points when they contribute to the community in the network by voluntarily sharing ideas and other information. In this paper, we aim to examine the effectiveness of a social gamification mechanism, named user scores, designed in Foursquare which is one of most popular location-based social networks. A user’s score in Foursquare is an aggregate measure based on recent check-in activities of the user, which reflects a snapshot summary of the user’s temporal and spatial behaviors. Whenever a user checks in to a venue, a list of scores of the user’s friends are visible to the user via a ”leaderboard” which ranks these users’ scores in a descending order. Given a pair of friends who participate in a score competition in such a gimification mechanism, we identify if one user’s scores have significant influence on the other user’s scores by utilizing the Granger Causality Test. To understand what types of users and what types of friends tend to participate in the score competition (i.e., their check-ins are more likely driven by such a gamification mechanism), we extract users’ features (e.g. user’s degree) as well as the features of pairs of friends (e.g., number of common friends, score similarity and ranking difference) to examine whether these features have correlations with those pairs of users who are identified as being involved in the score game. The identified influence on user scores has the important implication on applications including friend and venue recommendations in location-based social networks.     

FacetAtlas: multifaceted visualization for rich text corpora

Documents in rich text corpora usually contain multiple facets of information. For example, an article about a specific disease often consists of different facets such as symptom, treatment, cause, diagnosis, prognosis, and prevention. Thus, documents may have different relations based on different facets. Powerful search tools have been developed to help users locate lists of individual documents that are most related to specific keywords. However, there is a lack of effective analysis tools that reveal the multifaceted relations of documents within or cross the document clusters. In this paper, we present FacetAtlas, a multifaceted visualization technique for visually analyzing rich text corpora. FacetAtlas combines search technology with advanced visual analytical tools to convey both global and local patterns simultaneously. We describe several unique aspects of FacetAtlas, including (1) node cliques and multifaceted edges, (2) an optimized density map, and (3) automated opacity pattern enhancement for highlighting visual patterns, (4) interactive context switch between facets. In addition, we demonstrate the power of FacetAtlas through a case study that targets patient education in the health care domain. Our evaluation shows the benefits of this work, especially in support of complex multifaceted data analysis.     

基于多区域联合粒子滤波的人体运动跟踪

针对视频人体运动跟踪中的遮挡问题, 提出了一种基于多区域联合粒子滤波器的跟踪方法. 算法把人体划分为多个关键区域, 通过基于多区域无向图的联合运动模型, 构造联合粒子滤波器, 并运用区域关联的观测评估策略对目标状态进行联合预测, 从而完成遮挡情况下目标的跟踪. 实验结果表明, 与基于单区域粒子滤波的跟踪方法相比, 本文提出的算法在具有较长时间部分和全部遮挡的跟踪问题上, 取得了较好的实验结果.     

Characterizing users’ check-in activities using their scores in a location-based social network

Analysis of users’ check-ins in location-based social networks (LBSNs, also called GeoSocial Networks), such as Foursquare and Yelp, is essential to understand users’ mobility patterns and behaviors. However, most empirical results of users’ mobility patterns reported in the current literature are based on users’ sampled and nonconsecutive public check-ins. Additionally, such analyses take no account of the noise or false information in the dataset, such as dishonest check-ins created by users. These empirical results may be biased and hence may bring side effects to LBSN services, such as friend and venue recommendations. Foursquare, one of the most popular LBSNs, provides a feature called a user’s score. A user’s score is an aggregate measure computed by the system based on more accurate and complete check-ins of the user. It reflects a snapshot of the user’s temporal and spatial patterns from his/her check-ins. For example, a high user score indicates that the user checked in at many venues regularly or s/he visited a number of new venues. In this paper, we show how a user’s score can be used as an alternative way to investigate the user’s mobility patterns. We first characterize a set of properties from the time series of a user’s consecutive weekly scores. Based on these properties, we identify different types of users by clustering users’ common check-in patterns using non-negative matrix factorization (NMF). We then analyze the correlations between the social features of user clusters and users’ check-in patterns. We present several interesting findings. For example, users with high scores (more mobile) tend to have more friends (more social). Our empirical results demonstrate how to uncover interesting spatio-temporal patterns by utilizing the aggregate measures released by a LBSN service.     

Visual topic discovering,tracking and summarization from social media streams

Multimedia Tools and Applications - Nowadays, microblogging has become popular, with hundreds of millions of short messages being posted and shared every minute on a variety of topics in social...     

基于书写摩擦力的签名识别方法

由于动态测量坐标系的存在, 使得数字笔在不同的握笔姿态下, 引起书写平面内摩擦力的分解不同. 由此本文提出采用书写摩擦力进行在线签名识别. 该方法将摩擦力的方向在直角坐标系内进行特征量表示, 并与三维书写力的大小相结合, 实现概率值和距离测度信度级的融合. 在进行真假签名的判别中, 加入快速剔除的方法, 进行两级判别, 以提高识别效率. 实验结果表明, 基于签名书写力大小和方向特征的融合识别方法互相补充, 相对于单个方法具有更高的识别率, 系统性能得到显著改善.     

石油射孔现状和发展方向的探讨

增效射孔是国内外油田勘探开发普遍使用的一种完井方式,本文主要介绍了石油射孔技术的发展现状,并分析了几种增效射孔技术的优缺点.各种复合射孔技术得到了广泛的应用,但在实际操作中仍然存在不少问题,通过分析我国增效射孔技术与先进水平的差距,提出了增效射孔技术今后发展方向的一些建议,实现油气井较大幅度和较长周期的增产目的.     

The accumulation-mode field-effect transistor: a new ultralowon-resistance MOSFET

An ultralow specific on-resistance, vertical channel, power MOSFET structure, based on current conduction via an accumulation layer formed on the surface of a trench (UMOS) gate structure, is described. Two-dimensional numerical simulations and experimental results have been obtained, demonstrating that a specific on-resistance approaching 100 μΩ-cm² can be obtained for a silicon device capable of blocking 25 V     

大气湍流影响星地相干激光通信的数值仿真

由于解析法在研究相干光通信的相位补偿等问题中存在困难,采用多层相位屏分步传输的数值仿真方法研究大气湍流对星地相干光通信下行传输的影响。首先建立了卫星地面之间的大气湍流中激光传输的仿真模型,可以实现不同天顶角和不同湍流条件下的光传输仿真计算。然后用其进行地球同步轨道(GEO)卫星下行光通信的数值仿真分析,并通过与理论值的对比来检验算法的可靠性。最后结合二进制相移键控(binary phase shift keying, BPSK)相干激光通信系统的误码率（bit error rate, BER）模型,计算分析了下行激光通信信号的衰落系数和BER。