基于MapReduce的网络爬虫设计与实现

针对单机爬虫效率低、可扩展性差等问题,本文设计并实现了一种基于MapReduce的网络爬虫系统。该系统首先采用HDFS和HBase对网页信息进行存储管理,基于行块分布函数的方法进行网页信息抽取;然后通过URL和网页信息相似度分析相结合的去重策略,采用Simhash算法对抓取的网页信息进行相似度度量。实验结果表明,该系统具有良好的性能和可扩展性,较单机爬虫相比平均抓取速度提高了4.8倍。     

基于coroutine模型的网络爬虫设计与实现

网络爬虫在中文信息处理中被大量使用,根据待处理的问题定向爬取相关领域的数据,为后续中文信息处理提供基础.传统多线程模型在处理高并发和大量I/O阻塞操作时,存在较为明显的限制和不足.针对以上问题,提出了一种基于coroutine模型的解决方案.从coroutine的基本原理和实现方法上作了较为详细的阐述,并给出基于coroutine网络爬虫的完整实现.实验表明,该方案能够有效地降低系统负荷,提高爬虫的爬取效率.     

基于语义相似聚合的主题爬虫算法研究

互联网的迅速发展,数据不断增加,使得个性化数据的获取难度越来越大.主题爬虫作为一种垂直检索方式,已经成为一个热门研究领域.传统的主题爬虫往往是通过网页链接之间的关系下载网页,然后再计算下载的网页与给定主题之间的相关关系.传统的主题爬虫一方面割裂了网页链接结构和网页内容主题之间的关系,使得两个部分分开计算; 另一方面下载过程的网页主题相关性不强,会下载大量的主题无关网页.本文提出一种新的基于PageRank 算法主题爬虫算法将网页主题相似度计算与传统的PageRank 算法相结合,将网页链接结构与网页主题相关性结合在一起.另外本文将语义相似性引入到主题爬虫里,实验结果表明本文提出的基于语义相似聚合的主题爬虫算法大大提高了主题爬虫的查全率.     

基于Python的网页信息爬取技术分析

基于大规模数据下载的需求,针对以往人工下载数据过程中存在的影响效率的问题,结合Python语言提出一种能够用于网页信息数据爬取的技术,用于减少数据下载前期的繁琐工作,提高网络信息系统和技术的开发效率。该文以网页信息爬取技术为主要研究对象,基于现代化信息数据的应用和发展需求,着重对融合了Python语言的网页信息爬取技术进行研究和分析。     

搜索服务中基于云计算的垃圾网页识别研究

为了快速、有效地对垃圾网页进行识别,提出了一种基于云计算平台的垃圾网页识别方案.在Hadoop分布式平台下构建一个基于页面内容和连接结构的支持向量机分类器,对垃圾网页进行识别,通过对数据进行分析.结果表明:垃圾网页的识别准确率较高,处理时间随着集群节点数的增加而明显减少.     

聚焦爬虫爬行性能研究

爬虫作为网页搜索下载程序,其网络爬行性能决定了搜索引擎的性能和数据质量。本文通过分析聚焦爬虫的特点和网络环境,总结出三类制约爬行性能的主要问题,分别是DNS查询及缓存设置、内外部分布式爬行特点和网页URL静态与动态分配策略。结论为聚焦爬虫使用URL静态分配策略结合异步DNS查询及缓存设置,在内部分布式爬行时可有效提高网络爬行性能。     

基于Hadoop集群的分布式日志分析系统研究

当数据存储和计算遇到瓶颈时,分布式技术相对于传统的向上扩展技术在伸缩性和成本上都具有巨大的优势。本文介绍了开源的分布式编程框架Hadoop,并通过具体的代码说明了基于Hadoop集群的分布式日志分析系统的工作方式。     

基于Hadoop的改进遗传算法

利用Hadoop的并行式处理技术改进了遗传算法.通过将种群划分为多个子种群,并将每个子种群由一个单一的MapReduce任务来处理,实现了遗传算法的并行化.通过解决OneMax问题的一系列实验,验证了基于Hadoop的遗传算法提高了运行效率与正确性.     

基于Hadoop平台的图像分类

随着图像数据的增加,海量的图像分类过程成为了一个耗时的过程。Hadoop是一个开源的分布式处理系统基础架构,有着优秀的海量数据处理性能。首先对Hadoop系统和编程框架进行了介绍,然后将图像分类中的海量数据处理过程在Hadoop平台上实现。与运行环境DELL powerEdge R170比较显示:基于Hadoop平台的图像分类在小图特征提取处理上Hadoop平台优势不明显,但对于大图特征提取、向量运算和kNN运算,耗时大大缩短,数据处理能力的优势明显。     

基于Scrapy的分布式爬虫系统的设计与实现

随着互联网的快速发展,其信息量和相关服务也随之快速增长.如何从海量的信息中快速、准确地抓取所需要的信息变得越来越重要,因此负责互联网信息收集工作的网络爬虫将面临着巨大的机遇和挑战.目前国内外一些大型搜索引擎只给用户提供不可制定的搜索服务,而单机的网络爬虫又难当重任,因此可定制性强、信息采集速度快和规模大的分布式网络爬虫便应运而生.通过对原有Scrapy框架的学习和研究,将Scrapy和Redis结合改进原有的爬虫框架,设计并实现了一个基于Scrapy框架下的分布式网络爬虫系统,然后将从安居客、58同城、搜房等网站抓取的二手房信息存入MongoDB中,便于对数据进行进一步的处理和分析.结果表明基于Scrapy框架下的分布式网络爬虫系统同单机网络爬虫系统相比效率更高且更稳定.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.