掺混生物柴油对6135Aca型柴油机NO_x排放的影响机理     

刘杰  魏立江  魏海军 《上海海事大学学报》2019,40(3):111-115

为探究船舶柴油机排放的NO_x中各成分的主要生成机理,基于6135Aca型柴油机,利用AVL Fire建立仿真模型,探究掺混生物柴油在不同负荷下对NO_x成分之间转换的影响机理。结果显示:柴油机排放的NO_2主要通过HO_2氧化NO生成,且高温和氧质量分数会影响NO_2的生成,其中高温会抑制NO_2的生成,氧质量分数增加会促进NO_2的生成;掺混生物柴油和增加负荷会使喷雾贯穿距增大,高温区域增加,从而抑制NO_2生成;掺混生物柴油使得燃烧室内氧含量增加,进而HO_2量增加促进NO_2生成;掺混比例较小时,NO_2主要受高温区域影响,当掺混到达一定比例时贯穿距不再增大,这时NO_2主要受氧含量影响。本文得到的NO_2生成机理,对降低NO_x中NO_2的排放比例有一定指导意义。  相似文献   

Making Video News Visible: Identifying the Optimization Strategies of the Cybermedia on YouTube Using Web Metrics     

Carlos Lopezosa  Enrique Orduna-Malea  Mario Pérez-Montoro 《Journalism Practice》2020,14(4):465-482

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Dictionary-based text categorization of chemical web pages     

Chun-Yan Liang  Li GuoZhao-Jie Xia  Feng-Guang NieXiao-Xia Li  Liang SuZhang-Yuan Yang 《Information processing & management》2006

A new dictionary-based text categorization approach is proposed to classify the chemical web pages efficiently. Using a chemistry dictionary, the approach can extract chemistry-related information more exactly from web pages. After automatic segmentation on the documents to find dictionary terms for document expansion, the approach adopts latent semantic indexing (LSI) to produce the final document vectors, and the relevant categories are finally assigned to the test document by using the k-NN text categorization algorithm. The effects of the characteristics of chemistry dictionary and test collection on the categorization efficiency are discussed in this paper, and a new voting method is also introduced to improve the categorization performance further based on the collection characteristics. The experimental results show that the proposed approach has the superior performance to the traditional categorization method and is applicable to the classification of chemical web pages.  相似文献   

基于本体论的数字图书馆搜索引擎的研究     

赵亚莉  魏淑琴 《现代情报》2007,27(8):104-106

基于本体（ontology）理论,利用本体对概念、术语及其相互关系的规范化描述,勾画出数字图书馆领域的基本知识体系,构建了数字图书馆领域本体库;然后,对现有的图书馆搜索引擎系统进行了改进,将构建的本体库引入到系统中,实现了基于本体的信息检索,方便用户对资源的查询,为用户提供高质量的个性化服务。  相似文献   

A study of results overlap and uniqueness among major Web search engines     

Amanda Spink  Bernard J. Jansen  Chris Blakely  Sherry Koshman 《Information processing & management》2006

The performance and capabilities of Web search engines is an important and significant area of research. Millions of people world wide use Web search engines very day. This paper reports the results of a major study examining the overlap among results retrieved by multiple Web search engines for a large set of more than 10,000 queries. Previous smaller studies have discussed a lack of overlap in results returned by Web search engines for the same queries. The goal of the current study was to conduct a large-scale study to measure the overlap of search results on the first result page (both non-sponsored and sponsored) across the four most popular Web search engines, at specific points in time using a large number of queries. The Web search engines included in the study were MSN Search, Google, Yahoo! and Ask Jeeves. Our study then compares these results with the first page results retrieved for the same queries by the metasearch engine Dogpile.com. Two sets of randomly selected user-entered queries, one set was 10,316 queries and the other 12,570 queries, from Infospace’s Dogpile.com search engine (the first set was from Dogpile, the second was from across the Infospace Network of search properties were submitted to the four single Web search engines). Findings show that the percent of total results unique to only one of the four Web search engines was 84.9%, shared by two of the three Web search engines was 11.4%, shared by three of the Web search engines was 2.6%, and shared by all four Web search engines was 1.1%. This small degree of overlap shows the significant difference in the way major Web search engines retrieve and rank results in response to given queries. Results point to the value of metasearch engines in Web retrieval to overcome the biases of individual search engines.  相似文献   

智能搜索引擎与数字图书馆个性化服务   总被引：13，自引：0，他引：13  

邹凯  汪全莉 《情报科学》2004,22(7):874-877

智能搜索引擎基于知识(概念)层面实行信息检索，以较强的自然语言理解和知识处理能力，表现出良好的个性化信息服务特色。因此，智能搜索引擎应用于数字图书馆个性化服务体系，不仅有效发挥前者数据挖掘、知识发现的功能，同时能较大地加深后者的主动性、智能性优势。  相似文献   

基于WEB挖掘的用户个性化配置方案研究     

卢雪峰 《中国科技信息》2007,(24):121-122

为每一位Web用户提供个性化服务已经成为电子商务网站发展的趋势。本文首先分析了Web挖掘的基本概念和工作流程，在此基础上提出了基于Web访问信息挖掘的用户个性化配置方案模型，并对模型实现的关键技术及其在电子商务中的应用进行了研究。  相似文献   

因特网信息检索模式及其优化设想     

张辉  赵需要 《情报科学》2007,25(1):77-81

本文论述了因特网环境下基于超文本的浏览模式和基于搜索引擎的检索模式两种信息检索模式的产生、原理和缺陷。并根据其现存问题及网络资源自身的特点,着重就建立专业性的网络资源指引库、受控语言的引入和使用、“智能代理”的应用、跟踪记录检索路径和内容提示以及使用语义——文献双层数据结构五点优化设想进行了简要分析。  相似文献   

网络计量学   总被引：19，自引：0，他引：19  

徐久龄  许莲莲 《情报科学》2002,20(1):62-65

本文回顾了计量学的产生和发展的历程，指出在网络环境下网络计量学产生的必然性。并着重探讨了网络计量学的主要特征、研究方法、研究对象范围和在网络环境中的应用。  相似文献   

新兴企业债市场发展的需求和供给引擎     

孙克  冯宗宪 《未来与发展》2007,28(3):45-50

企业债市场的增长引擎在各国有所不同，新兴企业债市场的发展及强劲的增长态势受到需求和供给双引擎的拉动。国内机构投资者管理的资产规模的迅速增长以及金融危机后各地企业的融资需求是新兴国内企业债市场发展的关键原因。继续扩大和深化新兴企业债市场需要除去供给方面的限制。同时需要改善市场微观结构。  相似文献