期刊文献+
共找到12篇文章
< 1 >
每页显示 20 50 100
几何画板在求内接图形体积极值中的应用
1
作者 王美能 《宜春学院学报》 2013年第3期15-18,共4页
几何画板能动态表现相关对象的几何关系,用动态效果展示三维内接图形的体积极值问题,在图形变化过程中每个小课件都有与之相应的精确的数字化描述,很好的实现了数与形的结合,并通过函数曲线、追踪轨迹和直方图三种不同的表现方法揭示图... 几何画板能动态表现相关对象的几何关系,用动态效果展示三维内接图形的体积极值问题,在图形变化过程中每个小课件都有与之相应的精确的数字化描述,很好的实现了数与形的结合,并通过函数曲线、追踪轨迹和直方图三种不同的表现方法揭示图形变化的规律。 展开更多
关键词 几何画板 内接图形 积极值 动态原理
下载PDF
基于K近邻和优化分配策略的密度峰值聚类算法 被引量:21
2
作者 孙林 秦小营 +1 位作者 徐久成 薛占熬 《软件学报》 EI CSCD 北大核心 2022年第4期1390-1411,共22页
密度峰值聚类(density peak clustering,DPC)是一种简单有效的聚类分析方法.但在实际应用中,对于簇间密度差别大或者簇中存在多密度峰的数据集,DPC很难选择正确的簇中心;同时,DPC中点的分配方法存在多米诺骨牌效应.针对这些问题,提出一... 密度峰值聚类(density peak clustering,DPC)是一种简单有效的聚类分析方法.但在实际应用中,对于簇间密度差别大或者簇中存在多密度峰的数据集,DPC很难选择正确的簇中心;同时,DPC中点的分配方法存在多米诺骨牌效应.针对这些问题,提出一种基于K近邻(K-nearest neighbors,KNN)和优化分配策略的密度峰值聚类算法.首先,基于KNN、点的局部密度和边界点确定候选簇中心;定义路径距离以反映候选簇中心之间的相似度,基于路径距离提出密度因子和距离因子来量化候选簇中心作为簇中心的可能性,确定簇中心.然后,为了提升点的分配的准确性,依据共享近邻、高密度最近邻、密度差值和KNN之间距离构建相似度,并给出邻域、相似集和相似域等概念,以协助点的分配;根据相似域和边界点确定初始聚类结果,并基于簇中心获得中间聚类结果.最后,依据中间聚类结果和相似集,从簇中心到簇边界将簇划分为多层,分别设计点的分配策略;对于具体层次中的点,基于相似域和积极域提出积极值以确定点的分配顺序,将点分配给其积极域中占主导地位的簇,获得最终聚类结果.在11个合成数据集和27个真实数据集上进行仿真实验,与最新的基于密度峰值的聚类算法作对比,结果表明:所提算法在纯度、F度量、准确度、兰德系数、调整兰德系数和标准互信息上均表现出良好的聚类性能. 展开更多
关键词 密度峰聚类 K近邻 簇中心 积极值 分配策略
下载PDF
抛物线中的动点三角形面积最大值问题
3
作者 安文鹏 《试题与研究(教学论坛)》 2018年第11期40-40,共1页
在中考数学压轴题中,以动点在拋物线上运动而引起三角形面积变化的问题频频出现。此类求三角形面积最大化的问题,因三角形的底与高的可变性,而不能直接利用三角形的面积公式求解,给许多考生带来解题思路的障碍而失分较多。如果我们灵活... 在中考数学压轴题中,以动点在拋物线上运动而引起三角形面积变化的问题频频出现。此类求三角形面积最大化的问题,因三角形的底与高的可变性,而不能直接利用三角形的面积公式求解,给许多考生带来解题思路的障碍而失分较多。如果我们灵活运用铅垂高法利用函数建模的数学思想方法便可得到一类“拋物线中动点三角形面积最大值问题”的通用解法。 展开更多
关键词 抛物线 动点 积极值
下载PDF
檐口形状及附属构造对低矮建筑双坡屋面风压特性的影响 被引量:5
4
作者 黄鹏 彭新来 顾明 《振动与冲击》 EI CSCD 北大核心 2012年第5期144-147,152,共5页
低矮房屋在风灾中首先是围护结构的破坏,因此对于低矮房屋抗风性能的改进,最为有效的方法是减小屋面的极值风压。根据我国东南沿海农村住宅的调研报告,并结合浙江省民用建筑图集,8种适用于我国东南沿海农村居民低矮房屋建筑的檐口形状(... 低矮房屋在风灾中首先是围护结构的破坏,因此对于低矮房屋抗风性能的改进,最为有效的方法是减小屋面的极值风压。根据我国东南沿海农村住宅的调研报告,并结合浙江省民用建筑图集,8种适用于我国东南沿海农村居民低矮房屋建筑的檐口形状(包括各种檐沟或挑檐)在TJ-2风洞试验室进行了缩尺模型测压试验。研究发现,对于3种具有不同坡度的双坡屋面低矮房屋,这些形状各异且具有附属构造的檐口的出现,抑制了迎风向来流的分离和再附,从而减小了迎风向屋面前沿区域的负风压值;对于减小的幅度而言,拥有26.6°和33.7°坡角的坡屋面要比拥有14.0°坡角的双坡屋面小得多;对于8种檐口而言,具有檐沟、悬挑盖板和竖直挡板的檐口表现出了优异的抗风性能,对最不利面积极值风压的影响,折减幅度可以达到47%以上。 展开更多
关键词 低矮房屋 双坡屋面 檐口形状 附属构造 风洞试验 积极值风压
下载PDF
计算机类期刊的引文环境分析 被引量:2
5
作者 周萍 Loet Leydesdorff 《情报学报》 CSSCI 北大核心 2007年第6期923-933,共11页
本文以中国科学技术信息研究所建立的《中国科技期刊论文与引文数据库》(CSTPCD)为基础,利用荷兰阿姆斯特丹大学Loet Leydesdorff教授开发的系列程序,将发生引用或被引关系的期刊聚集起来,然后利用可视化工具(Pajek)将期刊之间... 本文以中国科学技术信息研究所建立的《中国科技期刊论文与引文数据库》(CSTPCD)为基础,利用荷兰阿姆斯特丹大学Loet Leydesdorff教授开发的系列程序,将发生引用或被引关系的期刊聚集起来,然后利用可视化工具(Pajek)将期刊之间的引用,被引信息进行可视化表达。通过分析计算机学科领域的重要期刊《软件学报》和《计算机学报》的核心引用和被引环境,发现该领域的论文作者更愿意引用国际期刊,而对国内期刊论文的引用比例很小;尽管《软件学报》的影响因子略小于《计算机学报》,但前者在国内计算机科学类期刊中影响最大。有趣的是,当阈值为1%时,两种期刊在2003年的引用或被引环境中所包含的期刊数目完全一样;同样情形发生在2004年两刊的被引环境中。 展开更多
关键词 引文 C/N引用积极 引用影响 他引影响 可视化
下载PDF
Preparation of calcium phosphate coating on pure titanium substrate by electrodeposition method 被引量:11
6
作者 赵中伟 张刚 李洪桂 《Journal of Central South University of Technology》 2004年第2期147-151,共5页
The influences of pH value, electrolyte temperature and loading time on depositing calcium phosphate coating on pure titanium substrate by electrodeposition process were investigated. The process was carried out with ... The influences of pH value, electrolyte temperature and loading time on depositing calcium phosphate coating on pure titanium substrate by electrodeposition process were investigated. The process was carried out with an electrochemical work-station supplying a direct current power at potential of -0.8V (vs SCE). The electrolyte consists of 7 mmol·L-1 CaCl2·2H2O, 3 mmol·L-1 Ca(H2PO4)2·H2O and 2.5% H2O2. NaOH and HCl solutions were used to adjust pH value. The deposited samples were characterized by X-ray diffraction and scanning electron microscope. The comparison of the deposits obtained at lower and higher pH values demonstrates that the crystallization process at the interface is favoured by high pH value. With temperature increasing, the deposited hydroxyapatite is occasionally of plate-like shape, and the width and the length of the deposited calcium phosphates at 65 ℃ are larger than those at 55 ℃. Therefore, it is confirmed that the morphology and microstructure of electrochemically deposited calcium phosphates can be regulated. Additionally, the coating formed in electrolyte with H2O2 additive is homogeneous and the evolution of H2 bubble can be eliminated. 展开更多
关键词 calcium phosphate COATING ELECTRODEPOSITION XRD SEM
下载PDF
Foreign Language Enjoyment and Anxiety:Associations With General and Domain-Specific English Achievement 被引量:2
7
作者 Jean-Marc DEWAELE Chengchen LI 《Chinese Journal of Applied Linguistics》 2022年第1期32-48,150,共18页
Recent research has confirmed the predictive effect of general foreign language(FL) achievement on Foreign Language Enjoyment(FLE) and Foreign Language Classroom Anxiety(FLCA).However,few studies have examined the eff... Recent research has confirmed the predictive effect of general foreign language(FL) achievement on Foreign Language Enjoyment(FLE) and Foreign Language Classroom Anxiety(FLCA).However,few studies have examined the effect of domain-specific language achievement in shaping FL learning emotions.The present study thus aims to examine how FLE and FLCA are linked to overall FL achievement and self-perceived achievement in six different domains across listening,speaking,reading,writing,vocabulary,and grammar.A total of 1,415 Chinese senior secondary students participated in the questionnaire survey.Regression analyses showed that 1) both FLE and FLCA were predicted more by self-perceived general English proficiency,while less by actual English achievement;2) perceptions of speaking and grammar competence were significant predictors of both emotions;3) perceived reading competence predicted FLE significantly but not FLCA;and that 4) perceptions of listening,writing,and vocabulary competence predicted neither FLE nor FLCA.The implication is that domain-specificity should be taken into consideration in future explorations of FL emotions. 展开更多
关键词 foreign language enjoyment foreign language(classroom)anxiety positive psychology control-value theory
下载PDF
Positive Solutions of Boundary Value Problems for Systems of Nonlinear Second-order Differential Equations 被引量:3
8
作者 ZHENG Dong-mei LU Shi-ping 《Chinese Quarterly Journal of Mathematics》 CSCD 2011年第2期179-184,共6页
By using fixed-point index theory,we study boundary value problems for systems of nonlinear second-order differential equation,and a result on existence and multiplicity of positive solutions is obtained.
关键词 boundary value problems fixed-point index positive solution CONE
下载PDF
Existence of Positive Solution for Superlinear Semipositone Singular Second-order m-point Boundary Value Problem 被引量:4
9
作者 ZHANG Xing-qiu 《Chinese Quarterly Journal of Mathematics》 CSCD 2010年第1期151-158,共8页
By applying fixed point theorem, the existence of positive solution is considered for superlinear semipositone singular m-point boundary value problem -(Lφ)(x)=(p(x)φ′(x))′+q(x)φ(x) and ξi ∈ (0,... By applying fixed point theorem, the existence of positive solution is considered for superlinear semipositone singular m-point boundary value problem -(Lφ)(x)=(p(x)φ′(x))′+q(x)φ(x) and ξi ∈ (0,1)with 0〈ξ1〈ξ2……〈ξm-2〈1,αi ∈ R^+,f ∈C[(0,1)×R^+,R^+],f(x,φ) may be singular at x=0 and x=1,g(x):(0,1)→R is Lebesgue measurable, g may tend to negative infinity and have finitely many singularities. 展开更多
关键词 SEMIPOSITONE SUPERLINEAR singular m-point boundary value fixed point theo-rem positive solution
下载PDF
A new kind of wavelet-based method for spectrum deconvolution
10
作者 肖跃 崔一平 《Journal of Southeast University(English Edition)》 EI CAS 2003年第1期22-25,共4页
To subtract the slit function from the measured spectrum, a wavelet-based deconvolution method is proposed to obtain a regularized solution of the problem. The method includes reconstructing the signal from the wavele... To subtract the slit function from the measured spectrum, a wavelet-based deconvolution method is proposed to obtain a regularized solution of the problem. The method includes reconstructing the signal from the wavelet modulus maxima. For the purpose of maxima selection, the spatially selective noise filtration technique was used to distinguish modulus maxima produced by signal from the one created by noise. To test the method, sodium spectrum measured at a wide slit was deconvolved. He-Ne spectrum measured at the corresponding slit width was used as slit function. Sodium measured at a narrow slit was used as the reference spectrum. The deconvolutton result shows that this method can enhance the resolution of the degraded spectrum greatly. 展开更多
关键词 DECONVOLUTION slit function wavelet local maxima
下载PDF
Existence of Solutions for Generalized Sturm-Liouville m-point Boundary Value Problems in Banach Spaces
11
作者 YANG Jing-bao WEI Zhong-li 《Chinese Quarterly Journal of Mathematics》 CSCD 2011年第2期265-269,共5页
By applying the fixed-point theorem of strict-set-contraction,this paper establishes the existence of one solution or one positive solution to the generalized Sturm-Liouville m-point boundary value problem in Banach s... By applying the fixed-point theorem of strict-set-contraction,this paper establishes the existence of one solution or one positive solution to the generalized Sturm-Liouville m-point boundary value problem in Banach spaces. 展开更多
关键词 Banach spaces fixed-point theorem of strict-set-contraction STURM-LIOUVILLE m-pointt boundary value problem positive solution
下载PDF
Rigid Properties of Quasi-almost-Einstein Metrics
12
作者 Linfeng WANG 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2012年第5期715-736,共22页
In this paper,quasi-almost-Einstein metrics on complete manifolds are studied.Two examples are given and several formulas are established.With the help of these formulas,the author proves rigid results on compact or n... In this paper,quasi-almost-Einstein metrics on complete manifolds are studied.Two examples are given and several formulas are established.With the help of these formulas,the author proves rigid results on compact or noncompact manifolds,in which some basic tools,such as the weighted volume comparison theorem and the weak maximum principle at infinity,are used.A lower bound estimate for the scalar curvature is also obtained. 展开更多
关键词 Quasi-almost-Einstein metric Potential function Gradient estimate Rigid property
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部