Measuring Search Engine Quality   总被引：12，自引：3，他引：9  

David Hawking  Nick Craswell  Peter Bailey  Kathleen Griffihs 《Information Retrieval》2001,4(1):33-59

The effectiveness of twenty public search engines is evaluated using TREC-inspired methods and a set of 54 queries taken from real Web search logs. The World Wide Web is taken as the test collection and a combination of crawler and text retrieval system is evaluated. The engines are compared on a range of measures derivable from binary relevance judgments of the first seven live results returned. Statistical testing reveals a significant difference between engines and high intercorrelations between measures. Surprisingly, given the dynamic nature of the Web and the time elapsed, there is also a high correlation between results of this study and a previous study by Gordon and Pathak. For nearly all engines, there is a gradual decline in precision at increasing cutoff after some initial fluctuation. Performance of the engines as a group is found to be inferior to the group of participants in the TREC-8 Large Web task, although the best engines approach the median of those systems. Shortcomings of current Web search evaluation methodology are identified and recommendations are made for future improvements. In particular, the present study and its predecessors deal with queries which are assumed to derive from a need to find a selection of documents relevant to a topic. By contrast, real Web search reflects a range of other information need types which require different judging and different measures.  相似文献   

柴油机燃油喷射系统的仿真计算及分析     

虞金霞  胡先富 《上海海事大学学报》2001,22(2):11-14

较全面地分析了柴油机燃油喷射系统仿真计算的影响因素，给出了仿真计算的基本数学模型。研究并分析了传统和电控喷油系统仿真计算的特点，分析了现有计算模型的现状及部分缺陷，并就其发展提出了一些建议。  相似文献   

中文搜索引擎检索语言研究   总被引：1，自引：0，他引：1  

吴凤玉  柳家英 《津图学刊》2002,(3):22-24

中文搜索引擎在很大程度上满了用户检索中文网络信息资源的要求，但也存在检索效果不够理想等问题，本文人检索语言的角度对现有中文搜索引擎进行分析，指出将检索语言的原理与方法应用于中文搜索引擎，必然极大地提高搜索引擎的检索效率。  相似文献   

共轨式喷油系统数学模型     

虞金霞  郭海涛  卓斌 《上海海事大学学报》2002,23(2):30-34

针对高压共轨喷油系统所特有的工作过程和部件结构 ,建立了系统各部件综合的数学模型 ,并采用有限容积法对方程进行了离散 ,对系统的压力特性、电磁特性和控制参数等进行了仿真 ,为系统的参数设计、标定提供了依据。  相似文献   

图书馆如何构筑自己的搜索引擎   总被引：1，自引：0，他引：1  

赵培云 《津图学刊》2001,(3):14-16

主要由计算机和网络工作者设计开发的搜索引擎，经过一段时间的运行和实践，其弊端已越来越明显。专家们呼吁用“图书馆员的思维”来管理网上信息资源，这明网络信息的组织和管理呼唤以知识组织的理论来指导，才能达到高有序化。因此，图书馆应在网络信息时代抓住机遇，构筑自己的搜索引擎。  相似文献   

专业搜索引擎在高校图书馆个性化信息服务中的应用   总被引：1，自引：0，他引：1  

唐崇忻 《高校图书馆工作》2008,28(2):44-47

阐述了专业搜索引擎及其技术特点,针对高校图书馆个性化信息服务中科研和专业学科的特殊需要,运用专业搜索引擎的技术优势和特点,为用户提供专业学科信息资源的搜集,进一步增强高校图书馆个性化信息系统的服务能力.参考文献4.  相似文献   

中外搜索引擎的比较研究   总被引：2，自引：0，他引：2  

罗敏 《河南图书馆学刊》2004,24(3):59-61

从信息产业发展角度对中外搜索引擎进行比较研究，剖析了中外搜索引擎的研制人员、商业运作机制等方面的差异，提出中文搜索引擎发展的建议。  相似文献   

柴油机的可维修性研究   总被引：1，自引：0，他引：1  

张丽萍 《南通职业大学学报》2002,16(2):33-35

建立了柴油机具有共性的可维修系统的失效率模型,论述了柴油机的可维修性理论,探讨了其最佳维修周期的界定问题,给出了计算实例。该方法对其他系统的可维修性问题也具有普遍意义。  相似文献   

Analyzing imbalance among homogeneous index servers in a web search system     

C.S. Badue  R. Baeza-Yates  B. Ribeiro-Neto  A. Ziviani  N. Ziviani 《Information processing & management》2007

The performance of parallel query processing in a cluster of index servers is crucial for modern web search systems. In such a scenario, the response time basically depends on the execution time of the slowest server to generate a partial ranked answer. Previous approaches investigate performance issues in this context using simulation, analytical modeling, experimentation, or a combination of them. Nevertheless, these approaches simply assume balanced execution times among homogeneous servers (by uniformly distributing the document collection among them, for instance)—a scenario that we did not observe in our experimentation. On the contrary, we found that even with a balanced distribution of the document collection among index servers, correlations between the frequency of a term in the query log and the size of its corresponding inverted list lead to imbalances in query execution times at these same servers, because these correlations affect disk caching behavior. Further, the relative sizes of the main memory at each server (with regard to disk space usage) and the number of servers participating in the parallel query processing also affect imbalance of local query execution times. These are relevant findings that have not been reported before and that, we understand, are of interest to the research community.  相似文献   

基于模式识别理论的内燃机状态识别研究     

尚国清  沈一飞  宓为建 《上海海事大学学报》1996,(1)

用模式识别的理论和方法，对内燃机气门间隙的识别问题进行了探讨。在分析气门振动力学模型的基础上，通过测取振动信号获得故障特征信息，用模式识别的理论和方法，在建立状态特征模式空间的基础上实现对故障的分类识别。考虑到内燃机振动信号的复杂性，采用了外触发采样和有效截取的方法进行信号的数据采集和分析。  相似文献