Improving zero-shot retrieval using dense external expansion

Pseudo-relevance feedback (PRF) is a classical technique to improve search engine retrieval effectiveness, by closing the vocabulary gap between users’ query formulations and the relevant documents. While PRF is typically applied on the same target corpus as the final retrieval, in the past, external expansion techniques have sometimes been applied to obtain a high-quality pseudo-relevant feedback set using the external corpus. However, such external expansion approaches have only been studied for sparse (BoW) retrieval methods, and its effectiveness for recent dense retrieval methods remains under-investigated. Indeed, dense retrieval approaches such as ANCE and ColBERT, which conduct similarity search based on encoded contextualised query and document embeddings, are of increasing importance. Moreover, pseudo-relevance feedback mechanisms have been proposed to further enhance dense retrieval effectiveness. In particular, in this work, we examine the application of dense external expansion to improve zero-shot retrieval effectiveness, i.e. evaluation on corpora without further training. Zero-shot retrieval experiments with six datasets, including two TREC datasets and four BEIR datasets, when applying the MSMARCO passage collection as external corpus, indicate that obtaining external feedback documents using ColBERT can significantly improve NDCG@10 for the sparse retrieval (by upto 28%) and the dense retrieval (by upto 12%). In addition, using ANCE on the external corpus brings upto 30% NDCG@10 improvements for the sparse retrieval and upto 29% for the dense retrieval.     

五年制大专建筑工程班英语学困与教困的分析

当前,职业教育迎来了一个空前大好的时机。扩招与发展的结果难免降低生源质量的标准,直接导致各校开设的英语必修课遇到更加严峻的挑战。学生基础更差,没有自学能力、迫于学校纪律出勤要求勉强到课;出现教师怕教,怕管大专班等厌学厌教现象。各种教与学的现实问题令人困惑,亟待解决。为了提高教学的有效性,本文简要总结自己班级英语课上学困、教困的主要问题。在实践中尝试解决好这些问题的办法,以期能够促进五年制高职英语教学的顺利进行。     

体育拓展课程如何提高高校大学生的终身体育意识

在全面贯彻教育方针,落实素质教育,以提高学生身心素质为根本宗旨的今天,如何体现学生的主体地位,充分发挥学生的学习积极性和学习潜能,提高学生终身体育意识,是21世纪我国学校体育发展的趋势。体育拓展课程作为一门体育分类项目纳入大学体育课程体系是当代体育课程改革的必然趋势,而体育拓展课程如何提高高校大学生的终身体育意识则成为关键问题。     

山东省高校扩招后体育师资、场馆设施现状的调查研究

采用访谈和问卷调查等方法，对扩招后山东省24所高校的体育场地设施状况、体育教师数量及体育教师与学生的比例进行调查。结果显示：山东省普通高校的体育场地缺口较大，特别是田径场、排球场、游泳池以及一些新兴项目的场地尤为严重；体育教师严重缺编，大部分学校的体育教师与学生的比例在1：400以上，远远低于国家教育部规定的1：120～150的比例。认为应采取加强体育师资队伍建设，采取措施缓解体育场地不足和深化体育课程教学改革等方法缓解这一矛盾。     

全面建设小康社会进程中高校体育功能的拓展

从我国小康社会标准中对身体健康标准的欠缺入手,分析我国群众体育的现状及存在的问题,从五个方面提出拓展高校体育功能的建议。认为应尽快论证出台“健康素质”的标准;高等院校体育教学的目标应确定在“终身体育”和“健康第一”;拓展高校体育的功能,应充分发挥高校体育设施、场地等资源优势;高校应充分加强对先进的体育理论和体育思想的研究工作,充当好全民健身活动宣传员的角色。     

Query expansion with terms selected using lexical cohesion analysis of documents

We present new methods of query expansion using terms that form lexical cohesive links between the contexts of distinct query terms in documents (i.e., words surrounding the query terms in text). The link-forming terms (link-terms) and short snippets of text surrounding them are evaluated in both interactive and automatic query expansion (QE). We explore the effectiveness of snippets in providing context in interactive query expansion, compare query expansion from snippets vs. whole documents, and query expansion following snippet selection vs. full document relevance judgements. The evaluation, conducted on the HARD track data of TREC 2005, suggests that there are considerable advantages in using link-terms and their surrounding short text snippets in QE compared to terms selected from full-texts of documents.     

Efficient implementation of associative classifiers for document classification

In practical text classification tasks, the ability to interpret the classification result is as important as the ability to classify exactly. Associative classifiers have many favorable characteristics such as rapid training, good classification accuracy, and excellent interpretation. However, associative classifiers also have some obstacles to overcome when they are applied in the area of text classification. The target text collection generally has a very high dimension, thus the training process might take a very long time. We propose a feature selection based on the mutual information between the word and class variables to reduce the space dimension of the associative classifiers. In addition, the training process of the associative classifier produces a huge amount of classification rules, which makes the prediction with a new document ineffective. We resolve this by introducing a new efficient method for storing and pruning classification rules. This method can also be used when predicting a test document. Experimental results using the 20-newsgroups dataset show many benefits of the associative classification in both training and predicting when applied to a real world problem.     

收益管理的战略扩展与系统升级——基于中国民航的分析

论述了收益管理对我国航空公司的重要性和必要性。追随收益管理的演进历程,探讨了收益管理的产生、发展及其战略内涵和系统架构。运用定性和定量方法对我国航空公司收益管理进行系统评价与分析,对升级收益管理系统提出了自己的建议:我国航空公司只有让员工满意和员工忠诚,才能最终获得顾客满意和顾客忠诚,真正实现收益的长远化与最大化。     

SDQE: towards automatic semantic query optimization in P2P systems

Conventional information retrieval technology (i.e. VSM) faces many difficulties when being implemented in complex P2P systems for the lack of global statistic information (e.g. IDF) and central services. In this paper, we suggest a novel query optimization scheme (Semantic Dual Query Expansion, SDQE) that makes full use of the context information supplied by the local document collection. Latent Semantic Indexing (LSI) is used to explore the local context information. By comparing the different local context information hidden in different document collections, it is possible to solve the synonymy–polysemy problem in VSM. The experiments prove that our scheme is effective to improve the retrieval performance in P2P systems without knowing the global statistic information.     

Two direct Tustin discretization methods for fractional-order differentiator/integrator

This paper deals with fractional calculus and its approximate discretization. Two direct discretization methods useful in control and digital filtering are presented for discretizing the fractional-order differentiator or integrator. Detailed mathematical formulae and tables are given. An illustrative example is presented to show the practically usefulness of the two proposed discretization schemes. Comparative remarks between the two methods are also given.