期刊文献+
共找到180篇文章
< 1 2 9 >
每页显示 20 50 100
Application of Sturm Theorem in the Global Controllability of a Class of High Dimensional Polynomial Systems
1
作者 XU Xueli LI Qianqian SUN Yimin 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2015年第5期1049-1057,共9页
In this paper, the global controllability for a class of high dimensional polynomial systems has been investigated and a constructive algebraic criterion algorithm for their global controllability has been obtained. B... In this paper, the global controllability for a class of high dimensional polynomial systems has been investigated and a constructive algebraic criterion algorithm for their global controllability has been obtained. By the criterion algorithm, the global controllability can be determined in finite steps of arithmetic operations. The algorithm is imposed on the coefficients of the polynomials only and the analysis technique is based on Sturm Theorem in real algebraic geometry and its modern progress. Finally, the authors will give some examples to show the application of our results. 展开更多
关键词 Global controllability high dimensional systems number of sign variations polynomial Sturm theorem.
下载PDF
The Counterintuitive Increase of Information Due to Extra Spacetime Dimensions of a Black Hole and Dvoretzky’s Theorem 被引量:2
2
作者 Mohamed S. El Naschie 《Natural Science》 2015年第10期483-487,共5页
As per Hawking and Bekenstein’s work on black holes, information resides on the surface and there is a limit on it amounting to a bit for every Planck area. It would seem therefore that extra dimensions would logical... As per Hawking and Bekenstein’s work on black holes, information resides on the surface and there is a limit on it amounting to a bit for every Planck area. It would seem therefore that extra dimensions would logically lead to a hyper-surface for a black hole and consequently a reduction of the corresponding information density due to the dilution effect of these additional dimensions. The present paper argues that the counterintuitive opposite of the above is what should be expected. This surprising result is a consequence of a well known theorem on measure concentration due to I. Dvoretzky. 展开更多
关键词 Higher dimensional BLACK HOLES Dvoretzky’s theorem INFORMATION PARADOX E-INFINITY Theory Counterintuitive Geometry Bekenstein Limit Hawking Radiation 'tHooft-Susskind BLACK HOLES
下载PDF
三维加筋边坡抗震稳定性的拟动力上限分析
3
作者 王振 孙志彬 +2 位作者 杨胜宇 聂秀鹏 谭晓慧 《合肥工业大学学报(自然科学版)》 CAS 北大核心 2024年第9期1288-1296,共9页
拟动力法可以更好地考虑地震传播的时空变化特性,文章采用拟动力分析方法研究均匀加筋与三角加筋2种不同加筋模式下,加筋土坡的三维地震稳定性问题;基于极限分析上限定理,构建三维加筋土边坡的破坏机构,推导地震边坡三维安全系数的表达... 拟动力法可以更好地考虑地震传播的时空变化特性,文章采用拟动力分析方法研究均匀加筋与三角加筋2种不同加筋模式下,加筋土坡的三维地震稳定性问题;基于极限分析上限定理,构建三维加筋土边坡的破坏机构,推导地震边坡三维安全系数的表达式,并考察拟静力与拟动力分析结果之间的差异性;通过参数分析揭示三维加筋边坡的拟动力安全系数变化规律。结果表明:相对于拟动力分析,拟静力分析获得的安全系数解更为保守,特别是对于水平地震力系数k_(h)和坡角β较大的情况,两者差异更加显著;随着水平地震力系数k_(h)、宽高比B/H、放大系数f的增加,加筋土边坡的稳定性明显降低;而随着平均加筋强度k_(0)增加,边坡稳定性显著提高;地震波周期T对边坡稳定性的影响较小;2种加筋模式对边坡稳定性的影响规律一致,且三角加筋模式效果更优。 展开更多
关键词 边坡工程 三维稳定性分析 拟动力法 加筋模式 上限定理 安全系数
下载PDF
三维桥式放大机构的柔性微定位平台的研究与改进
4
作者 赵智全 祝锡晶 +1 位作者 李婧 崔佳俊 《机械传动》 北大核心 2024年第9期152-159,共8页
在微定位平台的设计中,引入能够产生高位移放大倍数的三维桥式放大机构,并在此基础上引入了能够有效减少输出端寄生位移的四杆对称式导向机构,从而使所设计的微定位平台能够充分结合二者优势。根据应变能理论、卡氏第二定理、拉格朗日定... 在微定位平台的设计中,引入能够产生高位移放大倍数的三维桥式放大机构,并在此基础上引入了能够有效减少输出端寄生位移的四杆对称式导向机构,从而使所设计的微定位平台能够充分结合二者优势。根据应变能理论、卡氏第二定理、拉格朗日定理,建立该微定位平台的静动态数学模型,理论分析了平台关键尺寸对平台位移放大倍数的影响;并通过计算获得了最优参数下的放大倍数和固有频率,其值分别为19.90和193.26 Hz。通过有限元方法验证了放大倍数和固有频率,其相对误差分别为4.3%和5.9%,从而证明了所改进的微定位平台的优越性能以及理论分析方法的准确性,为放大机构的柔性微定位平台的数学模型构建提供了一定的理论指导。 展开更多
关键词 三维桥式放大机构 四杆对称式柔性机构 柔性微定位平台 卡氏第二定理 有限元 仿真
下载PDF
二维三次映射的混沌动力学
5
作者 陈凤娟 丁文豪 钟溢 《浙江师范大学学报(自然科学版)》 2024年第1期1-8,共8页
为了研究二维三次映射的混沌动力学,运用Moser定理和多项式零点斜率的性质,证明映射存在Smale马蹄,并且映射在不变集上拓扑共轭于三符号动力系统.计算不动点和2周期点的Lyapunov指数谱表明,它们的最大Lyapunov指数均大于零.
关键词 二维三次映射 SMALE马蹄 Moser定理 混沌
下载PDF
Effective and Efficient Feature Selection for Large-scale Data Using Bayes' Theorem 被引量:7
6
作者 Subramanian Appavu Alias Balamurugan Ramasamy Rajaram 《International Journal of Automation and computing》 EI 2009年第1期62-71,共10页
This paper proposes one method of feature selection by using Bayes' theorem. The purpose of the proposed method is to reduce the computational complexity and increase the classification accuracy of the selected featu... This paper proposes one method of feature selection by using Bayes' theorem. The purpose of the proposed method is to reduce the computational complexity and increase the classification accuracy of the selected feature subsets. The dependence between two attributes (binary) is determined based on the probabilities of their joint values that contribute to positive and negative classification decisions. If opposing sets of attribute values do not lead to opposing classification decisions (zero probability), then the two attributes are considered independent of each other, otherwise dependent, and one of them can be removed and thus the number of attributes is reduced. The process must be repeated on all combinations of attributes. The paper also evaluates the approach by comparing it with existing feature selection algorithms over 8 datasets from University of California, Irvine (UCI) machine learning databases. The proposed method shows better results in terms of number of selected features, classification accuracy, and running time than most existing algorithms. 展开更多
关键词 Data mining CLASSIFICATION feature selection dimensionality reduction Bayes' theorem.
下载PDF
The symplectic eigenfunction expansion theorem and its application to the plate bending equation 被引量:5
7
作者 黄俊杰 阿拉坦仓 王华 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第9期3616-3623,共8页
This paper deals with the bending problem of rectangular plates with two opposite edges simply supported. It is proved that there exists no normed symplectic orthogonal eigenfunction system for the associated infinite... This paper deals with the bending problem of rectangular plates with two opposite edges simply supported. It is proved that there exists no normed symplectic orthogonal eigenfunction system for the associated infinite-dimensional Hamiltonian operator H and that the two block operators belonging to Hamiltonian operator H possess two normed symplectic orthogonal eigenfunction systems in some space. It is demonstrated by using the properties of the block operators that the above bending problem can be solved by the symplectic eigenfunction expansion theorem, thereby obtaining analytical solutions of rectangular plates with two opposite edges simply supported and the other two edges supported in any manner. 展开更多
关键词 plate bending equation symplectic eigenfunction expansion theorem infinite dimensional Hamiltonian operator analytical solution
下载PDF
GALIN’S THEOREM HOLDS FOR MOVING PUNCH 被引量:2
8
《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1991年第1期82-87,共6页
This paper presents a formulation for solving three-dimensional moving punch problem. It proves that Galin's theorem holds for the punch. As an example, the study offers some results (including numerical data) of ... This paper presents a formulation for solving three-dimensional moving punch problem. It proves that Galin's theorem holds for the punch. As an example, the study offers some results (including numerical data) of dynamic displacement over an ellipse contact region. 展开更多
关键词 three-dimensional moving contact Lame potentials double Fourier transform influence functions Galin's theorem
下载PDF
The Generalized Sine Theorem for Mixed Vertex Angle of Two Simplices and Applications
9
作者 WANG Wen YANG Shi-guo QI Ji-bing 《Chinese Quarterly Journal of Mathematics》 2015年第2期190-198,共9页
Some related problems of two n-dimensional simplices which are on an(n- 1)-dimensional hypersphere are investigated and a sine theorem of the k-dimensional mixed vertex angles which are defined in this paper is given.... Some related problems of two n-dimensional simplices which are on an(n- 1)-dimensional hypersphere are investigated and a sine theorem of the k-dimensional mixed vertex angles which are defined in this paper is given. This result is a generalization of the sine theorem established. By using the generalized sine theorem, we present some new interesting geometric inequalities involving the k-dimensional vertex angles of each n-simplex and the k-dimensional mixed vertex angle of two n-simplices. These results can improve some recent results. 展开更多
关键词 simplex k-dimensional vertex angle k-dimensional mixed vertex angle the sine theorem geometric inequalities
下载PDF
On the Far Field Pattern for Acoustic Scattering by a Piecewise Homogeneous Obstacle in Two Dimensions
10
作者 Evagelia S. Athanasiadou Paraskevi Roupa 《Journal of Applied Mathematics and Physics》 2022年第10期2951-2964,共14页
A time-harmonic plane acoustic wave is scattered by a piecewise homogeneous obstacle with a penetrable or impenetrable core. We construct in the close form an integral representation for the far field pattern in which... A time-harmonic plane acoustic wave is scattered by a piecewise homogeneous obstacle with a penetrable or impenetrable core. We construct in the close form an integral representation for the far field pattern in which we have incorporated the physical and geometrical characteristics of the scatterer. Through this representation, we obtain the far field pattern for this scatterer. We prove scattering relations between the far field patterns of two scattering problems due to two distinct incident waves on the same scatterer. In particular, we prove reciprocity and general scattering theorems. The optical theorem, connecting the total power that the scatterer extracts from the incident plane wave either by radiation or by absorption with the corresponding far field pattern of an incident plane wave, is recovered as a corollary of the general scattering theorem. Moreover, if we consider incident waves to be both a plane and a spherical, we derive a mixed reciprocity theorem. We define the corresponding far field operators and using these relations, we prove some properties that can be used for solving inverse scattering problems. 展开更多
关键词 Two-dimensional Electromagnetic Scattering Piecewise Obstacle Reciprocity Principle Optical theorem
下载PDF
高速列车轮轴缩比关系及微动参量仿真分析
11
作者 舒易亮 刘志明 +1 位作者 高敬宇 杨广雪 《摩擦学学报》 EI CAS CSCD 北大核心 2023年第1期39-48,共10页
车轴与车轮通过过盈配合组成轮对,承受着车辆的全部重量,是保证高速动车组运行安全的最重要部件.高速列车轮轴的疲劳周次长达109,实物轮轴试验的过程复杂、周期长且试验费用高.因此,通过缩比模型反映和预示实物轮轴试验结果具有极大的... 车轴与车轮通过过盈配合组成轮对,承受着车辆的全部重量,是保证高速动车组运行安全的最重要部件.高速列车轮轴的疲劳周次长达109,实物轮轴试验的过程复杂、周期长且试验费用高.因此,通过缩比模型反映和预示实物轮轴试验结果具有极大的理论价值和工程意义.本文中结合相似定理和量纲分析原理,分析并推导了轮轴过盈配合微动参量随在不同缩比系数下的相似关系,采用ABAQUS有限元软件对微动参量分布进行仿真分析,结果表明,微动参量在不同缩比系数模型中的分布规律和理论推导的相似关系一致;轮轴接触压应力以及轴向摩擦剪切应力的最大值,位于车轴轮座区域靠近齿轮箱座的内侧,高速列车车轴轮座内侧接触边缘最容易发生微动疲劳失效. 展开更多
关键词 高速列车轮轴 微动疲劳 微动参量 相似定理 量纲分析
下载PDF
Functional Limit Theorems for C-R Increments of k-Dimensional Brownian Motion in Holder Norm 被引量:11
12
作者 Qicai Wei School fo Economics, Zhejiang University. Hangzhou 310028. P. R. China 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2000年第4期637-654,共18页
In this paper. based on large deviation formulas established in stronger topology generated by Hlder norm, we obtain the functional limit theorems for C-R increments of k-dimensional Brownian motion in Hlder norm
关键词 Large deviation formulas k-dimensional Brownian motion Functional limit theorems C-R increments Holder norm
原文传递
Functional Limit Theorems for d-dimensional FBM in H lder Norm 被引量:2
13
作者 Zheng Yan LIN Wen Sheng WANG Kyo Shin HWANG 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2006年第6期1767-1780,共14页
In this paper, we obtain functional limit theorems for d-dimensional FBM in HSlder norm via estimating large deviation probabilities for d-dimensional FBM in HSlder norm.
关键词 large deviation probability Holder norm functional limit theorem d-dimensional fractional Brownian motion Gaussian random vector
原文传递
图像采样定理和几何变换教学内容探析
14
作者 巢海远 肖青云 《电气电子教学学报》 2023年第5期161-164,共4页
图像采样定理和图像几何变换是“数字图像处理”课程教学的重要知识点。但是由于知识断层和课时限制,学生对于采样定理和几何变换有关的数学原理和知识逻辑理解不透。为避免学生学习上的困惑,一是详细分析证明了图像信号的采样定理,二... 图像采样定理和图像几何变换是“数字图像处理”课程教学的重要知识点。但是由于知识断层和课时限制,学生对于采样定理和几何变换有关的数学原理和知识逻辑理解不透。为避免学生学习上的困惑,一是详细分析证明了图像信号的采样定理,二是由浅入深逐步分析证明了几何变换的分解性。 展开更多
关键词 数字图像处理 采样定理 几何变换
下载PDF
AN INFINITE DIMENSIONAL ANALOGUE OF THE ALBEVERIO-RCKNER'S THEOREM ON FUKUSHIMA'S CONJECTURE
15
作者 宋士奇 《Acta Mathematicae Applicatae Sinica》 SCIE CSCD 1993年第2期115-124,共10页
Let X be the solution of the SDE:dX_t=σ(X_t)dB_t+b(X_t)dt,with σ and b ∈C_B~∞(R) such that σ≥λ>0 for some constant λ,and B a real Brownian motion.Let μ be the law of X on E=C([0,1],R)and k ∈E~*-{0},where ... Let X be the solution of the SDE:dX_t=σ(X_t)dB_t+b(X_t)dt,with σ and b ∈C_B~∞(R) such that σ≥λ>0 for some constant λ,and B a real Brownian motion.Let μ be the law of X on E=C([0,1],R)and k ∈E~*-{0},where E~* is the topological dual space of E.Consider the classical form:where u and v are smooth functions on E.We prove that,if is closable for any k in a dense subset of E~* and if the smooth functions are contained in the domain of the generator of the closure of ε_k,σ must be a constant function. 展开更多
关键词 CKNER’S theorem ON FUKUSHIMA’S CONJECTURE AN INFINITE dimensional ANALOGUE OF THE ALBEVERIO-R SDE
原文传递
On the k-dimensional Piatetski-Shapiro prime number theorem
16
作者 翟文广 《Science China Mathematics》 SCIE 1999年第11期1173-1183,共11页
Thek-dimensional Piatetski-Shapiro prime number problem fork?3 is studied. Let π(x 1 c 1,?,c k ) denote the number of primesp withp?x, $p = [n_1^{c_1 } ] = \cdots [n_k^{c_k } ]$ , where 1<c 1<?<c k are fixed... Thek-dimensional Piatetski-Shapiro prime number problem fork?3 is studied. Let π(x 1 c 1,?,c k ) denote the number of primesp withp?x, $p = [n_1^{c_1 } ] = \cdots [n_k^{c_k } ]$ , where 1<c 1<?<c k are fixed constants. It is proved that π(x;c 1,?,c k ) has an asymptotic formula ifc 1 ?1 +?+c k ?1 >k?k/(4k 2+2). 展开更多
关键词 k-dimensional Piatetski-Shapiro prime number theorem onential sum mptotic formula
原文传递
铁矿粉烧结液相流动性能的特征数方程的建立 被引量:8
17
作者 吴铿 申威 +3 位作者 杜瑞岭 闫广 门正朝 员晓 《重庆大学学报(自然科学版)》 EI CAS CSCD 北大核心 2015年第5期26-31,45,共7页
为解决在研究铁矿粉烧结液相流动性能时通常只考虑面积增长率这一终点信息,而没有考虑过程信息的缺陷以及采用多个指标来表征流动性能在使用上的不便,对影响流动性的因素进行了分析,结合量纲分析和白金汉定理推导出了能定量表征流动性... 为解决在研究铁矿粉烧结液相流动性能时通常只考虑面积增长率这一终点信息,而没有考虑过程信息的缺陷以及采用多个指标来表征流动性能在使用上的不便,对影响流动性的因素进行了分析,结合量纲分析和白金汉定理推导出了能定量表征流动性强弱的流动性特征数(LD),简化特征数方程后得到等效流动性特征数(LdΘ)。试验采用了可视卧式高温炉,记录了铁矿粉烧结液相流动的整个过程信息,通过基础实验和对照实验确定液相流动的起点和终点之后,可以得到每一种矿粉相应的等效流动性特征数数值。测量5种铁矿粉在两种方法下的流动性指标,当只考虑面积增长率时的流动性强弱顺序为A>C≈D>B>E,新方法下为LdΘA>LdΘD>LdΘC≈LdΘE>LdΘB,两种方法下的指标相近,但是综合了各种重要信息的新指标能进一步区分出各个因素对流动性能的影响程度。 展开更多
关键词 铁矿粉 烧结 流动性 量纲分析 白金汉定理
下载PDF
量纲分析法在土工模型试验中的应用 被引量:5
18
作者 杨宇友 张钦喜 +2 位作者 张在明 刘艳 李聪 《北京工业大学学报》 EI CAS CSCD 北大核心 2009年第6期785-789,共5页
量纲分析对试验设计和试验结果的简明表达十分有用,有效的量纲分析可以产生一组无量纲成果.以地基承载力为例说明了Buckingham的π定理及Butterfield对其计算方法的改进.通过数值计算的方法对岸坡虹吸排水模型试验进行了分析,初步验证... 量纲分析对试验设计和试验结果的简明表达十分有用,有效的量纲分析可以产生一组无量纲成果.以地基承载力为例说明了Buckingham的π定理及Butterfield对其计算方法的改进.通过数值计算的方法对岸坡虹吸排水模型试验进行了分析,初步验证了量纲分析的成果,对模型试验的关键参数选取提出了一些建议. 展开更多
关键词 量纲分析 模型试验 π定理 数值模拟 相似常数
下载PDF
一种改进的纳米压入测试方法 被引量:7
19
作者 宋仲康 马德军 +1 位作者 郭俊宏 陈伟 《中国有色金属学报》 EI CAS CSCD 北大核心 2012年第2期520-525,共6页
利用过量纲理论和有限元模拟分析了Oliver-Pharr方法识别材料折合弹性模量的精度。结果表明:理论测试误差明显依赖于卸载后的残余深度与最大压入深度的比值(hf/hm)和材料的应变硬化指数n。当hf/hm>0.7、n=0时,Oliver-Pharr方法计算... 利用过量纲理论和有限元模拟分析了Oliver-Pharr方法识别材料折合弹性模量的精度。结果表明:理论测试误差明显依赖于卸载后的残余深度与最大压入深度的比值(hf/hm)和材料的应变硬化指数n。当hf/hm>0.7、n=0时,Oliver-Pharr方法计算的折合弹性模量最大测试误差将近32%,其原因是由于估算得到的接触深度明显低于真实的接触深度。在此基础上,提出一种改进的计算方法,对接触深度的估算进行修正,应用改进方法确定材料折合弹性模量时,最大误差可控制在±15%以内。两种铝合金材料的压入试验也证明了此结论。 展开更多
关键词 纳米压入 弹性模量 量纲分析 有限元方法 硬化指数
下载PDF
量纲分析的基本理论及其应用 被引量:24
20
作者 徐婕 詹士昌 田晓岑 《大学物理》 北大核心 2004年第5期54-58,共5页
量纲分析是研究物理问题的重要方法之一.本文在研究量纲分析的基本理论Π定理的基础上,提出了量纲分析矢量空间的待定系数法,并举了一些实例,使量纲分析的应用和推广深入了一步.
关键词 量纲分析 Ⅱ定理 量纲分析矢量空间
下载PDF
上一页 1 2 9 下一页 到第
使用帮助 返回顶部