Focused web crawling in the acquisition of comparable corpora

Cross-Language Information Retrieval (CLIR) resources, such as dictionaries and parallel corpora, are scarce for special domains. Obtaining comparable corpora automatically for such domains could be an answer to this problem. The Web, with its vast volumes of data, offers a natural source for this. We experimented with focused crawling as a means to acquire comparable corpora in the genomics domain. The acquired corpora were used to statistically translate domain-specific words. The same words were also translated using a high-quality, but non-genomics-related parallel corpus, which fared considerably worse. We also evaluated our system with standard information retrieval (IR) experiments, combining statistical translation using the Web corpora with dictionary-based translation. The results showed improvement over pure dictionary-based translation. Therefore, mining the Web for comparable corpora seems promising.     

Hybrid index maintenance for contiguous inverted lists

Index maintenance strategies employed by dynamic text retrieval systems based on inverted files can be divided into two categories: merge-based and in-place update strategies. Within each category, individual update policies can be distinguished based on whether they store their on-disk posting lists in a contiguous or in a discontiguous fashion. Contiguous inverted lists, in general, lead to higher query performance, by minimizing the disk seek overhead at query time, while discontiguous inverted lists lead to higher update performance, requiring less effort during index maintenance operations. In this paper, we focus on retrieval systems with high query load, where the on-disk posting lists have to be stored in a contiguous fashion at all times. We discuss a combination of re-merge and in-place index update, called Hybrid Immediate Merge. The method performs strictly better than the re-merge baseline policy used in our experiments, as it leads to the same query performance, but substantially better update performance. The actual time savings achievable depend on the size of the text collection being indexed; a larger collection results in greater savings. In our experiments, variations of Hybrid Immediate Merge were able to reduce the total index update overhead by up to 73% compared to the re-merge baseline.

采用文献复制方式解决图书馆文献缺藏问题——以武夷学院图书馆特色书库建设为例

文献缺藏是所有图书馆都存在的必须解决的疑难问题。笔者认为,可依据实际需要,制订目标,投入经费,通过对经典源文献的复制方式来解决这一问题,以扩容图书馆的藏书量,满足读者的实际需求,消除文献的供需矛盾。     

提高公文撰写水平刍议

要掌握公文写作的特点并不断提高公文写作能力，就必须加强政治理论和思想修养，提高业务素质；必须掌握大量的、丰富的材料；必须学习语法、逻辑、修辞知识，掌握公文写作规律；必须刻苦实践，多写多练勤改。     

基于中国专利数据库的专题技术检索策略--以循环肿瘤细胞技术为例?

专利文献侧重于技术创新成果。在技术创新研究中,研发人员有必要对所研究的专题技术实施较为全面的专利信息检索。作者以循环肿瘤细胞（Circulating Tumor Cells,CTC）技术为例,系统阐述专题技术的专利检索策略,主要包括：专利检索工具的选择、关键词的确定、分类号的确定、检索式的设定、查全率与查准率的验证、补充检索。作者通过扩展技术分支检索,提高了检索结果的查全率;通过合理地选取专利分类号,降低了检索结果的噪声。     

新形势下对文检课教学改革的探讨

结合献检索课教学实践，从教学内容、教学方法、教学实习环境以及师资队伍建设四个方面，提出献检索课教学改革的设想，以加强学生创新能力的培养。     

基于GIS和高分辨SAR数据的机场净空建筑物高度提取

随着SAR图像分辨率的进一步提高,建筑物在SAR图像中的特征更加明显,使得基于单幅高分辨率SAR图像进行建筑物提取和三维重构成为可能。分析高分辨率SAR图像中建筑物的成像散射特征,多次反射及阴影效应;阐述基于GIS空间数据进行SAR图像中建筑物定位和估算建筑物的高度的算法。利用高分辨率TerraSAR-X数据,估算天津机场净空区某小区建筑物高度,与实际高度数据相比较,发现计算结果精度较高。结果表明:该方法是一种可行的建筑物高度提取方法,可为需要大面积建筑物高度的相关应用提供很好的借鉴方法。     

基于自动词频的网页索引算法

引入一种新的基于词频的数据自动检索网页的模型,它结合Web页面使用了全新的特征词汇提取公式,在保持精确率的情况下同时获得较高回现率,为精确描述Web页面提供了依据.同时该模型还能减少检索中存在的一致性的问题,简化Web页面索引维护工作量.     

国家科技图书文献中心科技词表的构建与应用

本文主要针对国家科技图书文献中心（NSTL）科技词表的构建特点及智能化文献服务应用方法开展研究。采 用实例剖析的方法,分析词表通用构建方法与常规应用模式,在此基础上重点研究NSTL科技词表的构建特点和应用方 式。NSTL文献服务平台从生产到服务的各个业务流中引入NSTL科技词表,提升了国家科技文献信息战略资源的有效 组织、深度揭示和知识关联,提供智能检索服务。在新的互联网应用环境下,词表规范不再是一种约束,而是一种引 导,一种知识关系汇聚方式,融入科技文献服务的方方面面,产生新的应用方式。