共查询到20条相似文献，搜索用时 562 毫秒
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[目的/意义] 为了提高传统协同过滤算法的计算速度,解决目标用户随着时间推移发生兴趣偏移而导致推荐系统质量下降的问题,以期进一步提升推荐系统运行效率和推荐质量。[方法/过程] 提出预先计算用户相似度算法和引入时间评分权重计算相似度矩阵的两种算法的改进,并利用Hadoop平台实证分析改进后的算法。[结果/结论] 实验结果证明：预先计算用户相似度算法缩短了对读者推送相关信息的时间,从而有效地提升了计算速度;引入时间评分权重计算相似度矩阵大大降低了MAE值,从而提高了推荐质量,两种算法同时应用后推荐系统在计算速度、准确率和新颖性方面都有显著提升。 相似文献
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Adding Compression to Block Addressing Inverted Indexes 总被引：8，自引：1，他引：7
Gonzalo Navarro Edleno Silva de Moura Marden Neubert Nivio Ziviani Ricardo Baeza-Yates 《Information Retrieval》2000,3(1):49-77
Inverted index compression, block addressing and sequential search on compressed text are three techniques that have been separately developed for efficient, low-overhead text retrieval. Modern text compression techniques can reduce the text to less than 30% of its size and allow searching it directly and faster than the uncompressed text. Inverted index compression obtains significant reduction of its original size at the same processing speed. Block addressing makes the inverted lists point to text blocks instead of exact positions and pay the reduction in space with some sequential text scanning.In this work we combine the three ideas in a single scheme. We present a compressed inverted file that indexes compressed text and uses block addressing. We consider different techniques to compress the index and study their performance with respect to the block size. We compare the index against three separate techniques for varying block sizes, showing that our index is superior to each isolated approach. For instance, with just 4% of extra space overhead the index has to scan less than 12% of the text for exact searches and about 20% allowing one error in the matches. 相似文献
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基于属性值偏好矩阵的协同过滤推荐算法 总被引：7，自引：2，他引：5
传统的协同过滤推荐算法面临用户评分数据稀疏性和冷启动问题的挑战.针对上述问题,提出了基于属性值偏好矩阵的协同过滤推荐算法,首先采用奇异值分解(SVD)对用户-项目评分矩阵降维得到目标用户的初始邻居用户集,生成新的用户-项目评分矩阵;然后将用户评分映射到相应的项目属性值上,生成每个用户的属性值偏好矩阵,并基于属性值偏好矩阵进行用户相似性度量,从而缓解了评分数据稀疏性;将新项目的属性值与用户的属性值偏好矩阵进行匹配,从而找出匹配度最高的前N个用户作为新项目的推荐受众.实验结果表明了该算法的有效性. 相似文献
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[目的/意义] 为解决高校图书推荐过程中面临的“数据稀疏”和“冷启动”问题,研究表明：优化读者评价矩阵和相似度模型是提高图书推荐质量的关键。[方法/过程] 提出一种协同过滤改进方法,以图书分类为项目生成用户评价矩阵,并考虑借阅方式、借阅时间和图书相似度对用户兴趣度的影响,优化矩阵中的样本数据;同时,在计算读者相似度时融入读者特征和图书特征。[结果/结论] 实验结果表明,该方法可有效解决“数据稀疏”和“冷启动”问题,显著降低计算量。与基本协同过滤和聚类改进的协同过滤方法相比,无论是在推荐准确率还是在用户满意率上都有较大的提高,综合推荐效果更好。 相似文献
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适应用户兴趣变化的协同过滤增量更新机制 总被引：1，自引：0，他引：1
高维、稀疏的用户-项目评分矩阵对基于项目的协同过滤推荐算法造成严峻的可扩展性问题.传统的解决方法是离线计算项目相似性并保存在系统中以供算法调用,但是不能充分利用最新评分数据以体现用户兴趣的变化.针对上述问题,提出了适合在线应用的协同过滤项目相似性增量更新机制,使得推荐系统在当前用户提交项目评分之后,能够实时完成相应项目与其他项目之间的相似性数据更新,从而推荐系统可以基于最新的项目相似性数据进行推荐处理,以适应用户兴趣的变化.实验结果表明,本文提出的项目相似性增量更新机制能够有效提高基于项目的协同过滤算法可扩展性. 相似文献
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学术文献引文推荐研究进展 总被引：1，自引：0，他引：1
[目的/意义]学术文献引文推荐是指对于给定的学术文献,自动化地为其推荐合适的引文和参考文献。借助于引文推荐,用户可以在一定程度上提高撰写学术文献的效率,降低对重要相关文献的漏引。[方法/过程]分析国内外引文推荐研究的最新进展,阐述引文推荐问题的演化过程,从局部引文推荐和全局引文推荐等方面对引文推荐进行梳理,重点归纳文档相似性、主题模型、翻译模型、协同过滤和混合推荐等5种引文推荐常用方法,并总结引文推荐常用数据集和测评方法。[结果/结论]已有引文推荐研究的主要问题在于未考虑用户偏好的动态变化性及研究领域的综合性,在用户研究和实际应用方面仍有所欠缺;未来引文推荐的研究可运用语义化表达方法和自然语言生成技术,从基于上下文的引文推荐和跨语言引文推荐等方面进行展开。 相似文献
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为促进学生思考并提高响应速度,提出一种从历史研讨记录中挖掘相关信息的在线问答推荐方法。该方法包括建立技术词汇层次树、提取任务词汇、文本段落划分、特征抽取、主题识别过滤和计算文档得分6个步骤。通过设计两个实验来评估所提出的方法:第一个实验比较TF-IDF、TF-IDF+主题过滤以及TF-IDF+LSA+主题过滤三种推荐方法,结果表明使用TF-IDF+主题过滤的算法可以获得最好的推荐效果;第二个实验将系统用于一个学期的在线课程研讨中,现场评估结果表明,文档推荐系统可以促进学生研讨,并且有较高的感知有用性和易用性。本研究表明,中等相关程度的历史研讨记录可以被自动挖掘出来,并且向学生提供这些信息可以促进学生思考和研讨。 相似文献
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Information filtering is an area getting more important as we have long been flooded with too much information, where product brokering in e-commerce is a typical example. Systems which can provide personalized product recommendations to their users (often called recommender systems) have gained a lot of interest in recent years. Collaborative filtering is one of the commonly used approaches which normally requires a definition of user similarity measure. In the literature, researchers have proposed different choices for the similarity measure using different approaches, and yet there is no guarantee for optimality. In this paper, we propose the use of machine learning techniques to learn the optimal user similarity measure as well as user rating styles for enhancing recommendation acurracy. Based on a criterion function measuring the overall prediction error, several ratings transformation functions for modeling rating styles together with their learning algorithms are derived. With the help of the formulation and the optimization framework, subjective components in user ratings are removed so that the transformed ratings can then be compared. We have evaluated our proposed methods using the EachMovie dataset and succeeded in obtaining significant improvement in recommendation accuracy when compared with the standard correlation-based algorithm. 相似文献
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基于群体兴趣偏向度的数字图书馆协同过滤技术研究* 总被引：1，自引：1，他引：1
马丽 《现代图书情报技术》2007,2(10):19-22
针对数字图书馆协同过滤推荐系统所面临的用户评分数据稀疏性问题，提出群体兴趣偏向度的计算方法，对用户－项目评分矩阵空缺值进行预测。实验结果表明，该算法能有效提高推荐质量。 相似文献
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基于协作过滤的Web智能信息推荐方法 总被引：1，自引：0，他引：1
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Collaborative filtering (CF) is a popular method for personalizing product recommendations for e-commerce applications. In order to recommend a product to a user and predict that user’s preference, CF utilizes product evaluation ratings of like-minded users. The process of finding like-minded users forms a social network among all users and each link between two users represents an implicit connection between them. Users having more connections with others are the most influential users. Attacking recommender systems is a new issue for these systems. Here, an attacker tries to manipulate a recommender system in order to change the recommendation output according to her wish. If an attacker succeeds, her profile is used over and over again by the recommender system, making her an influential user. In this study, we applied the established attack detection methods to the influential users, instead of the whole user set, to improve their attack detection performance. Experiments were conducted using the same settings previously used to test the established methods. The results showed that the proposed influence-based method had better detection performance and improved the stability of a recommender system for most attack scenarios. It performed considerably better than established detection methods for attacks that inserted low numbers of attack profiles (20–25 %). 相似文献
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Compressing Inverted Files 总被引：2，自引：0，他引：2
Andrew Trotman 《Information Retrieval》2003,6(1):5-19
Research into inverted file compression has focused on compression ratio—how small the indexes can be. Compression ratio is important for fast interactive searching. It is taken as read, the smaller the index, the faster the search.The premise smaller is better may not be true. To truly build faster indexes it is often necessary to forfeit compression. For inverted lists consisting of only 128 occurrences compression may only add overhead. Perhaps the inverted list could be stored in 128 bytes in place of 128 words, but it must still be stored on disk. If the minimum disk sector read size is 512 bytes and the word size is 4 bytes, then both the compressed and raw postings would require one disk seek and one disk sector read. A less efficient compression technique may increase the file size, but decrease load/decompress time, thereby increasing throughput.Examined here are five compression techniques, Golomb, Elias gamma, Elias delta, Variable Byte Encoding and Binary Interpolative Coding. The effect on file size, file seek time, and file read time are all measured as is decompression time. A quantitative measure of throughput is developed and the performance of each method is determined. 相似文献
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基于地区间差异的我国互联网发展数字鸿沟分析 总被引：1，自引：0，他引：1
指出我国地区间存在着巨大的互联网数字鸿沟。通过计算互联网鸿沟系数，结合发展速度分析与互联网综合指数分析进行实证研究，结果表明：我国地区间网民、域名差距正逐渐缩小，网站差距则相对不变，互联网应用深度差距有增大的趋势，互联网数字鸿沟总体上缩小。最后，提出缩小地区数字鸿沟的建议。 相似文献
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基于社会化标签系统的个性化信息推荐探讨 总被引：4，自引：0，他引：4
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针对高校图书馆场景存在的无显式反馈、借阅数据稀疏和传统推荐算法效果不好问题,提出基于时间上下文优化协同过滤的推荐算法,包含读者阅读行为评分、时间上下文和内容兴趣变迁3个要素。在数据准备阶段,通过制定评分转化规则、设计标准化函数来构建一种基于用户行为操作的兴趣评分模型,以解决用户评分缺失问题;在推荐召回阶段,提出一种非线性的时间衰减模型来对评价矩阵进行优化,以提高推荐效果;在推荐排序阶段,提出一种兴趣捕捉模型对召回结果按照图书类别进行精排序,以缓解数据稀疏问题并进一步提高推荐效果。实验结果表明,文章提出的优化算法在Top5的F值较未经优化的协同过滤提升增幅达141%。 相似文献
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基于项目分类预测的协同过滤推荐算法 总被引：3，自引：0，他引：3
在电子商务系统中,为了帮助用户有效地发现、过滤和利用信息,信息过滤技术应运而生.协同过滤技术作为其中的一种技术被成功地应用于推荐系统中.随着电子商务用户数目和商品数目的日益增加,整个项目空间上用户评分数据极端稀疏,传统的相似性度量方法均存在各自的弊端,导致推荐系统的推荐质量急剧下降.针对这一不足,提出基于项目分类预测的协同过滤算法,通过对用户评分矩阵中的项目进行相应的分类,缩小邻近搜索的范围,预测项目评分,减少稀疏性,并采用新的相似度计算方法.实验结果表明,该算法能提高个性化推荐算法的准确性. 相似文献