Optimization of some factors affecting the performance of query expansion

This paper examines the factors affecting the performance of global query expansion based on term co-occurrence data and suggests a way to maximize the retrieval effectiveness. Major parameters to be optimized through experiments are term similarity measure and the weighting scheme of additional terms. The evaluation of four similarity measures tested in query expansion reveal that mutual information and Yule's Y, which emphasize low frequency terms, achieve better performance than cosine and Jaccard coefficients that have the reverse tendency. In the evaluation of three weighting schemes, similarity weight performs well only with short queries, whereas fixed weights of approximately 0.5 and similarity rank weights were effective with queries of any length. Furthermore, the optimal similarity rank weight achieving the best overall performance seems to be the least affected by test collections and the number of additional terms. For the efficiency of retrieval, the number of additional terms needs not exceed 70 in our test collections, but the optimal number may vary according to the characteristics of the similarity measure employed.     

Parsimonious translation models for information retrieval

In the KL divergence framework, the extended language modeling approach has a critical problem of estimating a query model, which is the probabilistic model that encodes the user’s information need. For query expansion in initial retrieval, the translation model had been proposed to involve term co-occurrence statistics. However, the translation model was difficult to apply, because the term co-occurrence statistics must be constructed in the offline time. Especially in a large collection, constructing such a large matrix of term co-occurrences statistics prohibitively increases time and space complexity. In addition, reliable retrieval performance cannot be guaranteed because the translation model may comprise noisy non-topical terms in documents. To resolve these problems, this paper investigates an effective method to construct co-occurrence statistics and eliminate noisy terms by employing a parsimonious translation model. The parsimonious translation model is a compact version of a translation model that can reduce the number of terms containing non-zero probabilities by eliminating non-topical terms in documents. Through experimentation on seven different test collections, we show that the query model estimated from the parsimonious translation model significantly outperforms not only the baseline language modeling, but also the non-parsimonious models.     

An empirical study of query expansion and cluster-based retrieval in language modeling approach

The term mismatch problem in information retrieval is a critical problem, and several techniques have been developed, such as query expansion, cluster-based retrieval and dimensionality reduction to resolve this issue. Of these techniques, this paper performs an empirical study on query expansion and cluster-based retrieval. We examine the effect of using parsimony in query expansion and the effect of clustering algorithms in cluster-based retrieval. In addition, query expansion and cluster-based retrieval are compared, and their combinations are evaluated in terms of retrieval performance by performing experimentations on seven test collections of NTCIR and TREC.     

长征期间《红星》报整理及其现实意义

《红星》报是第二次国内革命战争时期中央革命军事委员会的机关报,也是唯一公开文字记录红军长征的原始资料,其内容是研究长征历史的重要史料。文章简要介绍了《红星》报的情况,探讨了《红星》报利用中所存在的问题以及对《红星》报整理的重要意义。     

大学生成长评价分层模式构建

当下的大学生评价往往过多强调共性和一般性趋势,忽视了大学生的个体差异和个性化发展的价值,不利于人才培养和大学生的成长与发展。大学生成长评价分层模式是根据大学生素质状况区分不同层次,分别确定不同的成长评价内容和标准的大学生评价体系。大学生成长评价分层模式强调具体问题具体分析。     

建构主义视野中教师学习解析

作为改造教师主观世界的活动,教师学习的实质是教师内在的思想、能力和情感的变化。建构主义教师学习是教师以主动发现和探究的态度与过程,在拓展和提升原有知识和经验基础上获致丰富教育理想和知识、增进专业理解和技能,不断更新自我,培育创造性生命力的成长过程。改善我国教师教育中的教师学习要有自我超越的意识和勇气,营造促进教师理解与思考的环境,涵养诤友式的合作文化。     

自适应信号分解实验装置

用开关电容滤波器和锁相环构成的二阶自适应带通滤波器,运用锁相环原理为开关电容滤波器提供时钟信号,使其带通滤波中心频率将跟随输入信号频率变化,克服了传统滤波器带通中心频率不易改变的缺点。实验结果表明,该滤波器较好地实现了自适应带通滤波的功能,可用于教学和科研中周期信号的分解。     

显微网络互动多媒体系统在遗传学实验教学中的应用效果

在遗传学实验教学中运用显微网络互动多媒体系统,弥补了单纯使用显微镜的不足;教师的演示、学生的反馈更及时,教师的指导更具有针对性,并加强了信息沟通和互动;强大的图片采集、保存与处理功能,有利于激发学生的实验兴趣,有利于加深对理论知识的理解;多画面的监控转播功能,可控制教学进度,提高实验课程效率和教学效果。     

论中外合作办学的可持续发展

当前,中外合作办学面临新的机遇与挑战。要实现中外合作办学可持续发展,必须遵循中外合作办学的基本规律,坚持引进优质教育资源的原则,坚持公益性原则,完善评估机制,加强质量监控与管理,坚持规范办学,严格依法管理。     

Religious Development in African American Adolescents: Growth Patterns That Offer Protection

Although religiosity promotes resilient outcomes in African American (AA) adolescents, there is a lack of research that examines the protective role of religious development in the context of stressful life events (SLEs). In 1,595 AA adolescents, a cohort-sequential design was used from ages 12 to 18 to examine subtypes of religiosity, as well as distinct developmental patterns within subtypes. The protective role of religious development was also examined in the context of SLEs. The study findings indicated two subtypes of religiosity—extrinsic and intrinsic religiosity—as well as low and high developmental patterns in the identified subtypes. Furthermore, the protective influence of extrinsic and intrinsic religiosity gradually diminished from age 12 to 18 in the context of SLEs.