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1.
云计算及其关键技术   总被引:87,自引:2,他引:85  
云计算是一种新兴的计算模型,它是在网格计算的基础上发展而来的.介绍了云计算的发展历史和应用场景,比较了现有的云计算的定义并给出了新的定义,以谷歌的云计算技术为例,总结了云计算的关键技术:数据存储技术(Google File System)、数据管理技术(BigTable)、编程模型和任务调度模型(Map-Reduce)等,分析了云计算和网格计算以及传统超级计算的区别,并指出了云计算的广阔发展前景.  相似文献
2.
主动轮廓线模型(蛇模型)综述   总被引:77,自引:1,他引:76       下载免费PDF全文
李培华  张田文 《软件学报》2000,11(6):751-757
在传统的计算机视觉领域,严格的各自独立的分层理论有广泛的影响.这种理论认为,底层的视觉任务的完成只能依赖于从图像本身获得的信息.Kass等人对这种模型提出了挑战,于1987年提出了称为Snake的主动轮廓线模型(active contour model).近10多年来,Snake模型在计算机视觉领域得到了广泛应用,取得了许多重要的进展.该文回顾了近10多年来Snake模型的研究、发展及应用情况,并对未来的发展方向进行了展望.  相似文献
3.
一种基于非均匀分簇的无线传感器网络路由协议   总被引:66,自引:0,他引:66  
在路由协议中利用分簇技术可以提高无线传感器网络的可扩展性.当簇首以多跳通信的方式将数据传输至数据汇聚点时,靠近汇聚点的簇首由于转发大量数据而负载过重,可能过早耗尽能量而失效,这将导致网络分割.该文提出一种新颖的基于非均匀分簇的无线传感器网络多跳路由协议.它的核心是一个用于组织网络拓扑的能量高效的非均匀分簇算法,其中候选簇首通过使用非均匀的竞争范围来构造大小不等的簇.靠近汇聚点的簇的规模小于远离汇聚点的簇,因此靠近汇聚点的簇首可以为簇间的数据转发预留能量.模拟实验结果表明,该路由协议有效地平衡了簇首的能量消耗,并显著地延长了网络的存活时间.  相似文献
4.
一种数据仓库的多维数据模型   总被引:53,自引:0,他引:53       下载免费PDF全文
李建中  高宏 《软件学报》2000,11(7):908-917
数据模型是数据仓库研究的核心问题之一.很多研究表明,传统数据模型(如实体联系模型和关系模型)不能有效地表示数据仓库的数据结构和语义,也难以有效地支持联机分析处理(on-line analysis processing,简称OLAP).最近,人们提出了几种多维数据模型.但是,这些多维数据模型在表示数据仓库的复杂数据结构和语义以及OLAP操作方面仍显不足.该文以偏序和映射为基础,提出了一种新的多维数据模型.该数据模型能够充分表达数据仓库的复杂数据结构和语义,并提供一个以OLAP操作为核心的操作代数,支持层次结构间的复杂聚集操作序列,能够有效地支持OLAP应用.该数据模型支持聚集函数约束的概念,提供了表示层次结构间聚集函数约束的机制.  相似文献
5.
Learning Information Extraction Rules for Semi-Structured and Free Text   总被引:43,自引:0,他引:43  
A wealth of on-line text information can be made available to automatic processing by information extraction (IE) systems. Each IE application needs a separate set of rules tuned to the domain and writing style. WHISK helps to overcome this knowledge-engineering bottleneck by learning text extraction rules automatically.WHISK is designed to handle text styles ranging from highly structured to free text, including text that is neither rigidly formatted nor composed of grammatical sentences. Such semi-structured text has largely been beyond the scope of previous systems. When used in conjunction with a syntactic analyzer and semantic tagging, WHISK can also handle extraction from free text such as news stories.  相似文献
6.
The MEME algorithm extends the expectation maximization (EM) algorithm for identifying motifs in unaligned biopolymer sequences. The aim of MEME is to discover new motifs in a set of biopolymer sequences where little or nothing is known in advance about any motifs that may be present. MEME innovations expand the range of problems which can be solved using EM and increase the chance of finding good solutions. First, subsequences which actually occur in the biopolymer sequences are used as starting points for the EM algorithm to increase the probability of finding globally optimal motifs. Second, the assumption that each sequence contains exactly one occurrence of the shared motif is removed. This allows multiple appearances of a motif to occur in any sequence and permits the algorithm to ignore sequences with no appearance of the shared motif, increasing its resistance to noisy data. Third, a method for probabilistically erasing shared motifs after they are found is incorporated so that several distinct motifs can be found in the same set of sequences, both when different motifs appear in different sequences and when a single sequence may contain multiple motifs. Experiments show that MEME can discover both the CRP and LexA binding sites from a set of sequences which contain one or both sites, and that MEME can discover both the –10 and –35 promoter regions in a set of E. coli sequences.  相似文献
7.
E-Commerce Recommendation Applications   总被引:32,自引:0,他引:32  
Recommender systems are being used by an ever-increasing number of E-commerce sites to help consumers find products to purchase. What started as a novelty has turned into a serious business tool. Recommender systems use product knowledge—either hand-coded knowledge provided by experts or mined knowledge learned from the behavior of consumers—to guide consumers through the often-overwhelming task of locating products they will like. In this article we present an explanation of how recommender systems are related to some traditional database analysis techniques. We examine how recommender systems help E-commerce sites increase sales and analyze the recommender systems at six market-leading sites. Based on these examples, we create a taxonomy of recommender systems, including the inputs required from the consumers, the additional knowledge required from the database, the ways the recommendations are presented to consumers, the technologies used to create the recommendations, and the level of personalization of the recommendations. We identify five commonly used E-commerce recommender application models, describe several open research problems in the field of recommender systems, and examine privacy implications of recommender systems technology.  相似文献
8.
Constructing support vector machine ensemble   总被引:30,自引:0,他引:30  
Hyun-Chul  Shaoning  Hong-Mo  Daijin  Sung 《Pattern Recognition》2003,36(12):2757-2767
Even the support vector machine (SVM) has been proposed to provide a good generalization performance, the classification result of the practically implemented SVM is often far from the theoretically expected level because their implementations are based on the approximated algorithms due to the high complexity of time and space. To improve the limited classification performance of the real SVM, we propose to use the SVM ensemble with bagging (bootstrap aggregating) or boosting. In bagging, each individual SVM is trained independently using the randomly chosen training samples via a bootstrap technique. In boosting, each individual SVM is trained using the training samples chosen according to the sample's probability distribution that is updated in proportional to the errorness of the sample. In both bagging and boosting, the trained individual SVMs are aggregated to make a collective decision in several ways such as the majority voting, least-squares estimation-based weighting, and the double-layer hierarchical combining. Various simulation results for the IRIS data classification and the hand-written digit recognition, and the fraud detection show that the proposed SVM ensemble with bagging or boosting outperforms a single SVM in terms of classification accuracy greatly.  相似文献
9.
从Petri网到形式描述技术和协议工程   总被引:30,自引:0,他引:30       下载免费PDF全文
罗军舟  沈俊  顾冠群 《软件学报》2000,11(5):606-615
10.
一种自适应的蚂蚁聚类算法   总被引:29,自引:0,他引:29       下载免费PDF全文
徐晓华  陈崚 《软件学报》2006,17(9):1884-1889
受蚂蚁分巢居住行为的启发,提出一种人工蚂蚁运动(ant movement,简称AM)模型和在此模型上的一个自适应的蚂蚁聚类算法(adaptive ant clustering,简称AAC).将人工蚂蚁看成一个行为简单的Agent,代表一个数据对象.在AM中,人工蚂蚁有睡眠和活跃两种状态.在AAC算法中,定义了一个适应度函数用来衡量蚂蚁与其邻居的相似程度.人工蚂蚁通过其适应度和激活概率函数来决定处于活跃态或者睡眠态.整个蚂蚁群体在移动中动态地、自适应地、自组织地形成多个独立的子群体,使不同类别的蚂蚁之间相互  相似文献
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