基于Haar-NMF特征和级联AdaBoost的脱岗检测算法

针对值班室人员的岗位执勤情况进行实时检测的需求,设计了一种脱岗检测系统,它使用低维的Haar-NMF特征代替Haar特征的方法以减少计算量,同时采用级联分类器代替单一的分类器结构以提高检测的准确性。该系统分为训练和测试两个部分,训练部分包括利用非负矩阵分解对Haar特征进行降维生成Haar-NMF特征和级联AdaBoost分类器的训练,经过数次训练后得到的各弱分类器根据训练过程中的权值加权组成一个强分类器,该分类器具有较高的学习效率,检测速度有明显提升。测试部分根据实际检测效果中存在的误检情况对检测算法进行修正和优化。实验验证了该系统具有相当高的检测率和较低的误检率,有助于避免在岗位无人值守时发生意外及损失财产。     

A 2-Stage Strategy for Non-Stationary Signal Prediction and Recovery Using Iterative Filtering and Neural Network

Journal of Computer Science and Technology - Predicting the future information and recovering the missing data for time series are two vital tasks faced in various application fields. They are...     

融合显式反馈与隐式反馈的协同过滤推荐算法

显式反馈与隐式反馈相结合,可以有效提升推荐性能.但是现有的融合显式反馈与隐式反馈的推荐系统存在未能发挥隐式反馈数据缺失值反映用户隐藏偏好的能力,或者未能保留显式反馈数据反映用户偏好程度的能力的局限性.为了解决这个问题,提出了一种融合显式反馈与隐式反馈的协同过滤推荐算法.该算法分为两个阶段:第1阶段利用加权低秩近似处理隐式反馈数据,训练出隐式用户/物品向量;第2阶段引入了基线评估,同时将隐式用户/物品向量作为补充,通过显隐式用户/物品向量结合,训练得出用户对物品的预测偏好程度.该算法与多个典型算法在标准数据集上进行了实验比较,其可行性和有效性得到验证.     

融合隐含信任度和项目关联度的矩阵分解推荐算法

随着社交网络的发展,融合社交信息的推荐系统在一定程度上解决了协同过滤推荐系统的冷启动和数据稀疏等问题,但是在信任数据稀疏情况下,仍会造成推荐精度降低等问题。为此,提出了一种融合隐含信任度和项目关联度的矩阵分解推荐算法。首先,利用矩阵分解模型将信任数据进行分解,得到用户的潜在被信任矩阵,在此基础上引入用户的影响力,从而提出了基于隐含信任度的推荐模型;然后,为了更好的利用项目间的关联信息,反映项目间的有向性,提出了基于项目关联度的推荐模型;最后,综合两种推荐模型并构建了一种推荐算法TCRMF。实验结果表明,所提算法在评分数据和信任数据稀疏的情况下仍然可以有效地提高推荐算法的精度,具有良好的应用前景。     

融合标签相似度的差分隐私矩阵分解推荐算法

推荐系统需要利用到大量的用户行为数据,这些数据极有可能暴露用户的喜好,给人们关心的隐私问题带来巨大的挑战。为保证推荐精度与用户隐私,提出一种结合差分隐私与标签信息的矩阵分解推荐模型。该模型首先将标签信息加入到项目相似度的计算过程;随后融入到矩阵分解推荐模型中提高推荐精度;最后运用随机梯度下降法求解模型最优值。为解决用户隐私问题,将拉普拉斯噪声划分成两部分,分别加入项目相似度与梯度求解过程中,使得整个推荐过程满足ε-差分隐私,并在一个真实的数据集上分析验证算法的有效性。实验表明,提出的方法能在保证用户隐私的情况下,仍具有较高的推荐精度。     

From separability/identifiability properties of bilinear and linear-quadratic mixture matrix factorization to factorization algorithms

Blind source separation (BSS) and Blind Mixture Identification (BMI) methods typically concern unknown source signals, transferred through a given class of functions with unknown parameter values, which yields mixed observations. Using only these observations, BSS/BMI aims at estimating the source signals and/or mixing parameters. Most investigations concern linear instantaneous mixing functions. They contain two aspects. The first one consists in proposing general BSS/BMI principles, e.g. Independent Component Analysis, Sparse Component Analysis or Nonnegative Matrix Factorization (NMF), and/or deriving associated practical algorithms. The second aspect consists in analyzing the properties resulting from these principles. This is of utmost importance, to determine if the proposed BSS/BMI principles are guaranteed to separate the source signals and to identify the considered mixing model up to acceptable indeterminacies. These separability/identifiability analyses are even more important for nonlinear mixtures, that were shown to potentially yield higher indeterminacies. Among them, bilinear and linear-quadratic mixtures are receiving increasing attention, e.g. due to their application to remote sensing. Especially, extensions of NMF were recently proposed for them, but the resulting separability/identifiability properties were not analyzed. We here address this topic, moreover proceeding further by investigating Bilinear and Linear-Quadratic Mixture Matrix Factorization (BMMF and LQMMF) approaches without nonnegativity constraints. We especially show that, whereas nonlinearity is often considered to be a burden, it yields an essentially unique decomposition under mild conditions for BMMF. On the contrary, full LQMMF is shown to yield spurious solutions, which increases the usefulness of combining it with nonnegativity constraints in applications where data meet these constraints. Algorithms based on this framework are also defined in this paper and their performance is reported.     

A Maximum Margin Matrix Factorization based Transfer Learning Approach for Cross-Domain Recommendation

Recommender systems usually employ techniques like collaborative filtering for providing recommendations on items/services. Maximum Margin Matrix Factorization (MMMF) is an effective collaborative filtering approach. MMMF suffers from the data sparsity problem, i.e., the number of items rated by the users are very small as compared to the very large item space. Recently, techniques like cross-domain collaborative filtering (transfer learning) is suggested for addressing the data sparsity problem. In this paper, we propose a model for transfer learning in collaborative filtering through MMMF to address the data sparsity issue. The latent feature matrices involved in MMMF are clustered and combined to generate a cluster-level rating pattern called codebook and a codebook transfer is used for transfer of information. Transferring of codebook and finding the predicted rating matrix is done in a novel way by introducing a softness constraint into the optimization function. We have experimented our methods with different levels of sparsity using benchmark datasets. Results from experiments show that our model approximates the target matrix well.     

融合社交关系与地理信息的兴趣点推荐模型

基于LBSN的兴趣点推荐存在用户签到矩阵稀疏、推荐精度不高、上下文信息利用不充分等问题,提出一种融合社交信任的矩阵分解算法TGMF（Trust-Geo?Matrix?Factorization）来缓解以上问题。利用BPR模型优化矩阵分解的过程,改进偏序关系的生成策略。把信任影响和相似度计算相结合,提高推荐精度。融合两种模型得到用户的最终偏好列表。把偏好列表中的top-[k]个兴趣点推荐给用户。实验结果表明,在真实数据集Gowalla和Foursquare上,TGMF算法在准确率和召回率两个指标上均优于传统的兴趣点推荐算法。     

社会化推荐系统综述

推荐系统可以帮助网民从大量纷繁的信息中找到目标信息,能有效提高网民信息检索能力,然而推荐系统存在数据稀疏性、冷启动以及系统性能方面的问题。为解决这方面的问题,提出将社交关系应用于推荐系统,该方法是提高推荐准确性的一个重要途径,在多年的科研实践中取得了重要进展,因此该研究方向也日益成为众多学者关注的领域,有关这方面的研究也越来越活跃。通过对社会化推荐系统概念进行梳理,对社会化推荐系统与传统推荐系统进行比较,回顾总结了社会化推荐系统的研究现状,希望能从研究现状中找出新规律,寻求新的突破点,并对社会化推荐系统的发展趋势进行展望,以期对后来研究者有所帮助。     

基于异构信息网络的推荐系统

随着互联网、计算机等技术的深入发展,互联网为用户带来了各类网络服务用于增进用户交流。其中,问答社区为用户提供了提问和回答的交流平台,其目的是通过互联网实现用户间的知识经验分享和信息传播。但仍存在一些问题限制问答社区的发展,例如随着用户数量的不断增长,大量问题得不到及时回答且提问者对已有问题的回答并不满意。因此,对于问答社区来说,如何从大量的用户中找到专家用户是非常重要的。针对以上问题,本文提出一种基于异构信息网络的推荐方法,首先对问答社区中的问题属性和用户属性建立异构信息网络,利用元路径来捕捉异构信息网络中丰富的语义信息,然后使用基于元路径的相似度计算方法分别计算问题与用户的相似度矩阵,采用3种方式将得到的相似度矩阵与问题-用户评分矩阵相融合,然后使用矩阵分解获得问题和用户的潜在特征,最后使用因子分解机进行训练和推荐。在海川化工问答数据集上将本文提出的方法同多种先进的推荐算法进行对比,并利用评价指标对模型进行评估。实验结果表明,本文提出的算法在相关评估指标方面相较于之前的算法具有一定优势。