共查询到19条相似文献,搜索用时 171 毫秒
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《中国海洋大学学报(自然科学版)》2017,(12)
本文提出无监督的基于隐含狄利克雷分布(LDA)的潜在语义模型来处理多语种混合文本的语种鉴别问题。区别于一般的依据困惑度对模型进行筛选的方法,本文介绍一种基于最小描述长度(MDL)的新方法,用collapsed Gibbs Sampling(CGS)学习算法来训练得到相应的LDA模型。本文采用mitlm工具包生成N-gram计数文件并构建了用于多语种识别的字符级语言模型。之后本文使用了3种不同的语种鉴别系统与LDA模型做对比实验。实验选取ECI/MCI标准数据库中9种欧洲系语言进行鉴别实验,在没有任何标注的情况下,实现了较好的准确率和召回率结果。 相似文献
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汉语和英语的宾语表示法有许多相同的地方。例如 :这两种语言的宾语主要由名词和代词来担任 ,介词短语一段不用作宾语等。然而这两种语言毕竟不是亲属语言 ,汉语属于汉藏语系 ,英语属于印欧语系 ;因此在宾语表示法方面还有着各种差异。本文就这方面作一粗浅的分析比较 ,并对汉语句子不同类型的宾语和译法作初步的探讨 相似文献
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相似性系数的选择可能会影响生物集群间的β多样性分析。Bray-Curtis相似性系数是目前使用最广的系数之一,还有一些研究使用了欧氏距离等系数。通过非度量多维标度的结果直观对比了两个相似性系数在处理生物数据时的结果,以便了解两个系数的差异。分析结果表明,Bray-Curtis相似性系数比欧氏距离更适合处理包含很多零值的生物数据。生物数据中的零值与环境数据中的不同,不应该影响集群间相似性的计算。如果遇到完全没有生物的集群,可以选用零调整的Bray-Curtis系数,或者剔除此类集群后再计算Bray-Curtis相似性系数。一些研究忽略了相似性系数的差异,在比较和分析多元分析结果时应该慎重,以免在生态环境评价时被误导。 相似文献
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为了提高船舶与海洋工程工业部门科技人员的英语水平,由上海交通大学船舶与海洋工程系编写的《船舶与海洋工程英语读本》和《英汉船舶与海洋工程词汇》将于今年四季度分别由海洋出版社和上海翻译出版公司印刷出版。《船舶与海洋工程英语读本》全书共25课,包括造船与海洋工程各个方面的基础知识,内容比较全面,各课选自于近年出版的大百科全书或比较权威的专著,内容比较严密而新颖,每课除列出该课内名词术语及其译文外,还补充若干与该课内容相关的名词术语及其中英对照,以扩大读者阅读本专业英文书刊的能力,对每课中比较疑难之句一一提出分析,这样不仅有助于自学,而且加强读者对原文的理解 相似文献
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异育银鲫准回交世代经济性状优势的遗传基础研究 总被引:2,自引:0,他引:2
用RAPD技术分析了方正银鲫、异育银鲫、异育银鲫准回交世代和兴国红鲤4个群体的遗传相似性。方正银鲫、异育银鲫和异育银鲫准回交世代多态位点数接近。且显著低于兴国红鲤;异育银鲫准回交世代存在特异带或特有带;方正银鲫与异育银鲫间的遗传相似性高于它与异育银鲫准回交世代间的遗传相似性,而兴国红鲤与异育银鲫间的相似性低于其与异育银鲫准回交世代间的遗传相似性。结果表明:三倍体群体遗传多样性低于正常二倍体;异育银鲫准回交世代存在遗传重组;随着兴国红鲤精子刺激次数增加。后代遗传背景与方正银鲫差异越来越大,而与兴国红鲤越来越相似。精子刺激三倍体卵发育,也能将一些遗传物质整合进卵细胞核,使后代经济性状呈现一定的优势。 相似文献
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Ichiro Ishikawa Shigeaki Aoki Ryo Furue Nobuo Suginohara 《Journal of Oceanography》1996,52(5):617-632
In recognition that similarity in the density balance leads to resemblance in circulation between the two-dimensional non-rotating and three-dimensional rotating systems which have similar density stratification, we investigate convection induced by cooling at one side wall and heating at the sea surface by using a two-dimensional non-rotating model as idealized representation for the deep Pacific circulation. In the model, various vertical profiles are taken for the side wall cooling, which are assumed to correspond to the density structure of the Anatarctic Circumpolar Current. In a small diffusivity range, two important features are found to be robust against change in the vertical profile of the side wall cooling. One is that the density stratification is horizontally almost uniform. The other is that the balance in the density equation between the vertical advection and the vertical diffusion holds in the interior. Consequently, the vertical density balance, together with the equation of continuity, determines the circulation pattern for the prescribed vertical profile of the side wall cooling. The multi-layered meridional flow, which is expected to exist in the deep Pacific, is shown to form for certain vertical profiles of the side wall cooling. 相似文献
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Chu Liangcheng Qu Naisi Guo Yonggang Lu Min Ph.D. Dalian University of Technology Dalian
Associate Professor Dalian University of Technology Dalian
Assistant M.S. Dalian University of Technology Dalian
Engineer Bohai Oil Company Tianjin 《中国海洋工程》1993,(4)
- Theoretically speaking, it is impossible to make the differential equation of motion uncoupled for the natural modes of a system in consideration of the attached water. The hydro-elastic structure is equal to the, non-proportional damping system. In this paper a perturbation analysis method is put forward. The structure motion equation is strictly solved mathematically, and the non-proportional damping problem is transformed into a series of proportional damping ones in the superposition form. The paper also presents the calculation formula of the dyanamic response of the structure being subjected to harmonic and arbitrary load. The convergence of the proposed method is also studied in this paper, and the corresponding convergence conditions are given. Finally, the proposed method is used to analyze the displacement response of a real offshore platform. The calculation results show that this method has the characteristics of high accuracy and fast convergence. 相似文献
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海洋缆体系统的统一凝集参数时域分析法 总被引:19,自引:5,他引:19
提出了海洋缆一体系统的三维动态性能时域分析法,并给出了计算机程序。采用凝集参数法模拟了缆一体结构系统,缆为圆形截面,可伸长,不考虑弯曲刚度,采用了四阶龙格一库塔法积分系统运动方程,计算了二个实例以验证程序的可靠性,程序可用于系泊,拖曳,潜器脐带缆等具有组合成分的海洋缆体系统的初步设计。 相似文献
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考虑阻尼海底悬跨段管道的动力特性及允许悬空长度 总被引:8,自引:0,他引:8
以海底悬跨段输液管道为研究对象,考虑管道结构阻尼、流体附加阻尼、管内流体流动及管道轴向力和压强的作用,对其进行受力分析,导出管道振动微分方程,进而得到管道动力特性方程。用Hermit插值函数对管道的动力特性方程进行离散得到有限元表达式,采用复模态分析法,求得管道的自振频率。为防止管道发生横向涡激振动,用约化速度作为控制条件,确定管道允许悬空长度。结果表明,管道允许悬空长度随着内流流速、轴向压力和管内压强的增加而减小,随着轴向拉力的增加而加大。 相似文献
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N. Booij 《Coastal Engineering》1983,7(3):191-203
The mild-slope equation is a vertically integrated refraction-diffraction equation, used to predict wave propagation in a region with uneven bottom. As its name indicates, it is based on the assumption of a mild bottom slope. The purpose of this paper is to examine the accuracy of this equation as a function of the bottom slope. To this end a number of numerical experiments is carried out comparing solutions of the three-dimensional wave equation with solutions of the mild-slope equation.For waves propagating parallel to the depth contours it turns out that the mild-slope equation produces accurate results even if the bottom slope is of order 1. For waves propagating normal to the depth contours the mild-slope equation is less accurate. The equation can be used for a bottom inclination up to 1:3. 相似文献
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Subrata Chakrabarti Jeffrey Barnett Harish Kanchi Anshu Mehta Jinsuk Yim 《Ocean Engineering》2007,34(3-4):621-629
Truss pontoon semi-submersible (TPS) is a new offshore structure concept in industry, where a truss spar is used to create the added mass by the heave plates. In the present paper, the effect of the heave plates on the vertical motion of the floating structure is demonstrated. A TPS is analyzed by utilizing the linear diffraction theory as well as the linear part of the Morison equation. The close agreement of the analysis results with the experimental results suggests that the simplified Morison equation can be used for the present analysis without sacrificing the quality of the results. However, good engineering judgment is required for estimating the values of the hydrodynamic coefficients as well as the amount of damping introduced in the structure. It is also found that the heave plates indeed introduce large added mass and considerable damping in the system motion in the vertical direction such that the resonant oscillation becomes less of a problem. This suggests that the TSP concept may have merits as a heave-controlled floating production structure in the deepwater development. 相似文献
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本文用二维水流方程和平面热扩散方程模拟电厂温排水在浦阳江中的扩散情况。在数值计算中,对二维水流方程采用显式迎流有限元方法,对平面热扩散方程采用显式直接差分法,并对这两种方法进行了耦合计算。比较全面地分析了电厂向浦阳江排水和取水后,浦阳江水温的分布特性,为选择电厂取排水的工程方式提供了判断依据。 相似文献
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应用内外解匹配的方法和驻相法推导了柱坐标系下地震引起的水面波动方程的解,即推导了地震海啸波生成与传播的理论方程,并对越洋地震海啸理论方程进行了求解。基于Boussinesq方程出发,建立了二维越洋海啸波传播数学模型,并对越洋海啸进行了数值计算,计算方法采用有限差分方法,差分格式采用交替方向隐格式(Alternating Direction Implicit即ADI方法)。利用越洋海啸计算模式对发生在大洋中的地震海啸进行了模拟,将数值模拟结果与地震海啸波理论方程的计算结果进行了比较,两种计算结果吻合较好。 相似文献