基于用户特征和评分的精准推荐策略研究

个性化推荐系统是帮助用户发现内容,克服信息过载的重要工具.为了提高推荐算法的准确率和效率,综合协同过滤推荐算法和K-means聚类算法,设计了一种基于用户特征和评分的精准推荐策略.该策略一方面针对新用户冷启动问题,引入K-means聚类算法对全体用户特征进行聚类,将新用户所属类中其他用户喜好的物品中的Top N个推荐给...     

基于K-means的语义协同过滤推荐算法

传统的基于图书和读者的协同过滤方法缺乏语义知识,易混杂不符合读者喜好的噪音数据,从而影响聚类效果和推荐的准确度.针对该问题,提出一种基于K-means的语义协同过滤推荐算法.为了反映读者对图书的偏爱程度,首先定义读者-图书关联矩阵,然后通过K-means聚类算法寻找相邻集合,在聚类过程中兼顾关联矩阵和语义知识,分别计算读者和图书的相似度,最后通过相似程度排序向用户推荐图书.结果表明,该算法在保证计算效率的情况下能显著提高推荐的准确度.     

基于K-medoids项目聚类的协同过滤推荐算法

针对传统协同过滤推荐算法通常针对整个评分矩阵进行计算,存在效率不高的问题,提出一种基于K-medoids项目聚类的协同过滤推荐算法.该算法根据项目的类别属性对项目进行聚类,构建用户的偏好领域,使用用户偏好领域内的评分矩阵进行用户间相似度的计算,得到目标用户的最近邻居集,并生成推荐结果.与常用的K-means聚类方法相比,采用K-medoids方法对项目类别属性进行聚类,不仅克服了评分聚类可靠性不高的问题,而且算法还具有更好的鲁棒性.实验结果表明,该算法能有效提高推荐质量.     

基于模糊聚类的并行推荐算法

为提高传统协同过滤算法在个性化推荐系统中的大数据处理能力,研究了一种基于模糊聚类的并行推荐算法。在Hadoop平台下首先通过PCA降维和FCM聚类对用户物品评分矩阵进行预处理,采用皮尔逊相关系数计算用户间的相似度,通过得到的聚类簇集合构建最近邻集合,生成基本预测评分。最后实现算法的并行化处理并得到推荐结果。实验结果表明,与基于PCA降维的协同过滤和单机式传统协同过滤算法相比,该算法提高了推荐的准确性和实时性。     

基于改进的协同过滤算法的练习测试推荐系统

在传统的协同过滤推荐算法的基础上,设计了一个基于改进的协同过滤算法的练习测试推荐系统。首先,根据学科、试题和学生的特点,有效的解决了矩阵稀疏和"冷启动"的问题;其次,使用机器学习中的K-means聚类算法对用户进行聚类,且初始聚类中心由Prim最小生成树算法确定,增加了聚类的稳定性;然后在每个聚类中搜索用户的最近邻居,缩小了计算用户之间相似度问题的规模;最后,通过实验将改进的算法与传统的算法进行了比较。实验结果表明,改进的算法提高了推荐系统的质量和准确度。     

基于用户聚类的图书协同推荐算法研究

针对协同过滤推荐算法中因图书评分数据稀疏,导致推荐质量和推荐效率低的问题,提出结合用户聚类的图书协同过滤推荐算法。首先将用户身份特征数据和行为数据进行向量化表示,并利用K-means聚类算法进行用户聚类成为不同的类别;其次计算目标用户与各类别的距离,并选择最近距离的类别作为目标用户的检索空间;最后,从检索空间中通过相似度计算确定目标用户的最近邻居,在此基础上产生推荐列表。实验结果表明,所提算法能够有效提高推荐精度,降低推荐所耗时长。     

基于局部优化奇异值分解和K-means聚类的协同过滤算法

为了克服传统协同过滤(CF)推荐方法数据稀疏和可扩展性差的不足,该文提出1种基于局部优化降维和聚类的协同过滤算法。采用局部优化的奇异值分解(SVD)降维技术和K-均值(K-means)聚类技术对用户-项目评分矩阵中的相似用户进行聚类并降低维度。利用近似差分矩阵表示评分矩阵的局部结构,实现局部优化。局部优化的SVD降维技术可以利用更少的迭代次数缓解CF中数据稀疏和算法可扩展性差的问题。K-means聚类技术可以缩小邻居集查找范围,提高推荐速度。将该文算法与基于Pearson相关系数的协同过滤算法、基于SVD的协同过滤算法、基于K-means聚类的协同过滤算法相比较。在MovieLens数据集上的实验结果表明,该算法的平均绝对误差(MAE)较其他算法降低了大约12%,准确性(Precision)提高了7%。     

融合隐性社交网络社团划分和协同过滤的推荐算法

协同过滤算法是个性化推荐系统中广泛使用的经典算法。针对传统协同过滤算法存在的相似度计算不准确、可扩展性差等问题,设计了一种融合隐性社交网络社团划分和协同过滤的推荐算法ICDCF。该方法将用户对项目的共同兴趣视为社交关系。首先用考虑了用户隐性关系的改进的Jaccard相似系数衡量用户间的社交关系强弱,以用户为顶点、以用户相似度为连边的权值,构建无向加权的隐性社交网络;然后基于隐性社交网络,用谱聚类思想对用户进行社团划分;最后在社团内实施基于用户的协同过滤推荐。该方法可以避免协同过滤推荐阶段因共同评分项目少而导致的相似度计算不准确问题,同时可以减少搜索近邻的计算量,提高时间效率。在数据集MovieLens-100K和FilmTrust上的实验结果体现了ICDCF算法在推荐准确性和可扩展性方面的优势。     

基于混合蛙跳模糊聚类的电子商务协同过滤推荐

针对传统协同过滤推荐算法生成推荐速度慢、推荐质量不高等缺陷,提出了一种基于混合蛙跳模糊聚类的改进协同过滤推荐算法。算法首先利用模糊C-均值(FCM)聚类方法对用户数据进行预处理,得到用户数据聚类中心,有效地降低了推荐工作量。然后选取相似度最优的若干聚类组成候选用户邻居集合,并利用混合蛙跳算法快速地全局寻优能力得到用户最近邻居集合,提高了推荐精度。最后,通过计算预测评分生成推荐结果。仿真结果表明,相比于传统协同过滤推荐算法,该算法在推荐速度和推荐精度上有明显改善。     

基于用户和项目双向聚类的协同过滤推荐算法

针对传统协同过滤算法数据稀疏性问题,提出一种基于用户和项目双向聚类的协同过滤推荐算法CFBC(Collaborative Filtering based on Bidirectional Clustering),将评分矩阵从用户和项目两个方向进行聚类,降低数据稀疏性的影响,提出一种改进的相似度计算方法P-J(Pearson-Jaccard)相关系数,提高相似度计算精度。实验证明,相较于传统协同过滤算法,该算法能有效提高推荐准确度。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with