期刊文献+
共找到183篇文章
< 1 2 10 >
每页显示 20 50 100
高阶数值导数的分数阶Landweber方法
1
作者 李刚刚 《理论数学》 2024年第7期61-68,共8页
本文研究高阶数值微分问题,这是一个经典的不适定问题。首先对问题的不适定性进行分析并给出条件稳定性结果,之后通过分数阶Landweber迭代方法给出正则解,最后在正则化参数的先验选取规则下,得到正则解和精确解之间的误差估计。
关键词 数值微分 分数阶Landweber迭 不适定问题 误差估计
下载PDF
电动加载系统分数阶迭代学习复合控制 被引量:5
2
作者 吕帅帅 林辉 《北京航空航天大学学报》 EI CAS CSCD 北大核心 2016年第9期1944-1951,共8页
针对电动加载系统存在多余力矩扰动的问题,提出一种以位置闭环和力矩闭环为反馈控制、迭代学习控制为补偿控制的复合控制策略。为提高加载系统动态性能及降低建立模型的复杂性,驱动永磁同步电机采用直接转矩控制方式,建立加载系统频域... 针对电动加载系统存在多余力矩扰动的问题,提出一种以位置闭环和力矩闭环为反馈控制、迭代学习控制为补偿控制的复合控制策略。为提高加载系统动态性能及降低建立模型的复杂性,驱动永磁同步电机采用直接转矩控制方式,建立加载系统频域模型。在位置闭环和力矩闭环采用分数阶PIλD~μ控制器代替常规PID控制器,迭代学习补偿控制采用分数阶迭代学习控制器,利用分数阶微积分的信息记忆特性提高控制系统的动态性能和鲁棒性,通过理论分析给出分数阶PD型迭代学习控制器的收敛条件。对正弦和梯形波载荷进行力矩加载实验及多余力矩抑制实验,验证了该控制方法的有效性。 展开更多
关键词 电动加载系统 分数阶PIλDμ 分数阶迭学习控制 多余力矩 高精度力矩伺服
下载PDF
识别Rayleigh-Stokes方程源项的分数阶Landweber迭代正则化方法 被引量:1
3
作者 杨帆 王乾朝 李晓晓 《数学物理学报(A辑)》 CSCD 北大核心 2021年第2期427-450,共24页
该文研究具有Riemann-Liouville时间分数阶导数的Rayleigh-Stokes方程未知源识别问题.首先证明这个问题是不适定的,并应用分数阶Landweber正则化方法求解此反问题.基于条件稳定性结果,在先验和后验正则化参数选取规则下,分别给出精确解... 该文研究具有Riemann-Liouville时间分数阶导数的Rayleigh-Stokes方程未知源识别问题.首先证明这个问题是不适定的,并应用分数阶Landweber正则化方法求解此反问题.基于条件稳定性结果,在先验和后验正则化参数选取规则下,分别给出精确解与正则解之间的误差估计.最后通过数值例子说明此方法求解此类反问题的有效性和可行性. 展开更多
关键词 Rayleigh-Stokes方程 反问题 识别源项 分数阶Landweber迭正则化方法
下载PDF
含多重时滞非线性系统的分数阶迭代学习控制的收敛性分析(英文) 被引量:1
4
作者 李娜娜 蒋威 《纯粹数学与应用数学》 2017年第1期69-81,共13页
本文研究了含多重时滞非线性系统的分数阶迭代学习控制(FOILC).它包含了外部干扰和输出控制噪音,通过引入λ-范数,获得在开环和闭环迭代学习控制作用下,系统控制输入以及跟踪误差收敛的充分条件.最后,通过数值仿真验证所提方法的有效性.
关键词 分数阶迭学习控制 收敛 多重时滞
下载PDF
一类双分数布朗运动迭代过程局部时的存在性和联合连续性 被引量:2
5
作者 徐锐 申广君 祝东进 《应用数学》 CSCD 北大核心 2014年第3期637-646,共10页
本文研究取值在Rd上的一类双分数布朗运动迭代过程X(t)=(X1(t),…,Xd(t))局部时的存在性和联合连续性.这类过程是由阶为α的严格稳定的Lévy过程{Y(t),t>0}替代双分数布朗运动{BH,K(t),t>0}中的时间参数t所构成的双分数布朗... 本文研究取值在Rd上的一类双分数布朗运动迭代过程X(t)=(X1(t),…,Xd(t))局部时的存在性和联合连续性.这类过程是由阶为α的严格稳定的Lévy过程{Y(t),t>0}替代双分数布朗运动{BH,K(t),t>0}中的时间参数t所构成的双分数布朗运动迭代过程{Z(t)=BH,K(Y(t)),t>0},其中0<α≤2,0<H<1,0<K≤1,且BH,K与Y是相互独立的,并且X1,…,Xd是相互独立的,且与Z同分布. 展开更多
关键词 分数布朗运动 分数布朗运动迭过程 阶为α严格稳定的Lévy过程 局部时
下载PDF
基于迭代学习的电动直线加载复合控制 被引量:2
6
作者 徐志伟 陶键 +2 位作者 范元勋 王厚浩 张纪林 《机床与液压》 北大核心 2018年第20期139-143,共5页
为测试某型航天用电动伺服机构的实际工作性能,设计一种以大导程精密滚珠丝杠副为力矩/力转换元件的电动直线加载系统。为克服电动直线加载系统多余力扰动问题,提出一种引入角速度前馈补偿、串入电流内环和位置内环的多闭环复合控制策略... 为测试某型航天用电动伺服机构的实际工作性能,设计一种以大导程精密滚珠丝杠副为力矩/力转换元件的电动直线加载系统。为克服电动直线加载系统多余力扰动问题,提出一种引入角速度前馈补偿、串入电流内环和位置内环的多闭环复合控制策略;采用一种以分数阶PIλDμ控制器作为力外环的反馈控制、分数阶迭代学习控制(FO-ILC)作为补偿控制的方法。直线加载仿真实验和多余力抑制仿真实验表明,所提控制策略较好地抑制了直线加载多余力。 展开更多
关键词 电动直线加载系统 分数阶PI^λD^μ控制 分数阶迭学习 多余力矩抑制 多闭环复合控制
下载PDF
原子力显微镜的分数阶PID控制设计 被引量:1
7
作者 赵田锋 许红梅 +1 位作者 李岩 陈诚 《电子测量与仪器学报》 CSCD 北大核心 2021年第5期91-99,共9页
原子力显微镜(AFM)是测量材料物体表面形貌的重要工具。为了实现AFM的高速扫描成像,设计一种基于分数阶前馈-反馈PID控制算法的AFM扫描成像控制器。将分数阶迭代学习控制(FOILC)用于前馈回路,在跟踪过程中对当前周期的误差信息进行学习... 原子力显微镜(AFM)是测量材料物体表面形貌的重要工具。为了实现AFM的高速扫描成像,设计一种基于分数阶前馈-反馈PID控制算法的AFM扫描成像控制器。将分数阶迭代学习控制(FOILC)用于前馈回路,在跟踪过程中对当前周期的误差信息进行学习,实现输出沿迭代轴的快速收敛;在反馈回路中采用分数阶比例积分(FOPI)控制增加高速成像时的精度。轨迹跟踪仿真和实验成像结果表明,该算法能有效提高AFM成像速度和改善系统非线性的影响,在扫描频率为25 Hz时,控制精度达到10-5量级,AFM成像质量得到显著提高。 展开更多
关键词 原子力显微镜 分数阶控制 分数阶迭学习 高速扫描成像
下载PDF
基于FRFT的天波雷达多机动目标检测 被引量:8
8
作者 李会勇 许丁文 +2 位作者 胡进峰 戴文娟 何子述 《系统工程与电子技术》 EI CSCD 北大核心 2014年第9期1725-1730,共6页
天波超视距雷达(over-the-horizon radar,OTHR)中,机动目标信号存在频谱扩展,导致目标检测性能下降。强的海杂波进一步增加了机动目标的检测难度。针对该问题,考虑到海杂波信号能量主要集中在零频附近,而且可以建模为一个自回归(auto-re... 天波超视距雷达(over-the-horizon radar,OTHR)中,机动目标信号存在频谱扩展,导致目标检测性能下降。强的海杂波进一步增加了机动目标的检测难度。针对该问题,考虑到海杂波信号能量主要集中在零频附近,而且可以建模为一个自回归(auto-regressive,AR)过程,用AR滤波器抑制海杂波;考虑到机动目标信号近似为线性调频信号,而分数阶傅里叶变换(fractional Fourier transform,FRFT)能有效积累线性调频信号的能量,因此采用FRFT算法估计目标运动参数,实现机动目标检测;在此基础上用分级迭代的FRFT进一步降低运算量;针对多目标检测问题,用"CLEAN"方法逐个检测机动目标。仿真结果表明,与已有的离散多项式变换(discrete polynomial transform,DPT)算法相比,本文算法可以更好地适用于多目标检测;与Radon-Wigner变换算法相比,本文算法可以达到更高的参数估计精度。 展开更多
关键词 天波超视距雷达 机动目标检测 海杂波抑制 分级迭代分数阶傅里叶变换
下载PDF
On the growth of transcendental entire solutions of algebraic differential equations 被引量:2
9
作者 朱玲妹 杨德贵 王小灵 《Journal of Southeast University(English Edition)》 EI CAS 2003年第1期98-102,共5页
In this paper, we investigate the growth of transcendental entire solutionsof the following algebraic differential equation a(z)f'~2 +(b_2(z)f^2 +b_1(z)f +b_0(z))f'=d_3(z)f^3+d_2(z)f^2 +d_1(z)f +d_0(z), where ... In this paper, we investigate the growth of transcendental entire solutionsof the following algebraic differential equation a(z)f'~2 +(b_2(z)f^2 +b_1(z)f +b_0(z))f'=d_3(z)f^3+d_2(z)f^2 +d_1(z)f +d_0(z), where a(z), b_i(z) (0<- i <=2) and d_j (z) (0<=j<= 3) are allpolynomials, and this equation relates closely to the following well-known algebraic differentialequation C(z,w)w'~2 + B(z,w)w' + A(z,w) =0, where G(z,w)not ident to 0, B(z,w) and A(z,w) are threepolynomials in z and w. We give relationships between the growth of entire solutions and the degreesof the above three polynomials in detail. 展开更多
关键词 algebraic differential equation DEGREE entire solutions
下载PDF
Poisson's Theory of the Chaplygin's Equations 被引量:1
10
作者 梅凤翔 史荣昌 张永发 《Journal of Beijing Institute of Technology》 EI CAS 1995年第2期129+123-129,共8页
Puts forward an algebraic structure of the Chaplygin's equations of nonholonomic systems, establish the Poisson's theory of the integration equations and gives an example for illustrating the application of th... Puts forward an algebraic structure of the Chaplygin's equations of nonholonomic systems, establish the Poisson's theory of the integration equations and gives an example for illustrating the application of the result. 展开更多
关键词 analytical mechanics algebra/nonholonomic system
下载PDF
π-quasitriangular group-cograded multiplier Hopf algebras
11
作者 杨涛 王栓宏 《Journal of Southeast University(English Edition)》 EI CAS 2009年第4期552-556,共5页
Let G be a group and (A, B) be a pair of multiplier Hopf algebras, where B is regular G-cograded. Let π be a crossing action of G on B, D^π=A^cop∝B=+p∈GDπ^p with Dπ^p=A^cop∝Bp, is the Drinfeld double of the ... Let G be a group and (A, B) be a pair of multiplier Hopf algebras, where B is regular G-cograded. Let π be a crossing action of G on B, D^π=A^cop∝B=+p∈GDπ^p with Dπ^p=A^cop∝Bp, is the Drinfeld double of the pair (A, B), and then the deformation D^π becomes a multiplier Hopf algebra. B×A can be considered as a subalgebra of M(D^π×D^π), the image of element b×a in B×A is (1∝b)×(a∝1) in M(D^π×D^π). Let W =∑αWα∈ M(B×A) be a π-canonical multiplier for the pair (A, B) with Wα∈M(Bα×A) for all α∈G. The image of W in M(D^π×D^π)is a π-quasitriangular structure over D^π. 展开更多
关键词 multiplier Hopf algebra group-cograded Drinfeld double quasitriangular
下载PDF
An Introduction to the Theory of C~*-modules
12
作者 邓宏钧 刘德权 《Chinese Quarterly Journal of Mathematics》 CSCD 1992年第2期72-77,共6页
This paper,combined algebraical structure with analytical system,has studied the part of theory of C~*-modules over A by using the homolgical methods, where A is a commutative C~*-algebra over complex number field C. ... This paper,combined algebraical structure with analytical system,has studied the part of theory of C~*-modules over A by using the homolgical methods, where A is a commutative C~*-algebra over complex number field C. That is to say we have not only defined some relevant new concept,but also obtained some results about them. 展开更多
关键词 commutative C~*-algebra C~*-module C~*-homomorphism
下载PDF
On Algebroid Solutions of Generalized Complex Differential Equations
13
作者 高凌云 《Chinese Quarterly Journal of Mathematics》 CSCD 2001年第1期20-25,共6页
Using the Nevanlinna theory of the value distribution of meromorphic functions, we investigate the existence problem of admissible algebroid solutions of generalized complex algebraic differential equations and obtain... Using the Nevanlinna theory of the value distribution of meromorphic functions, we investigate the existence problem of admissible algebroid solutions of generalized complex algebraic differential equations and obtain some results. 展开更多
关键词 algebroid functions admissible solution generalized differential equations
下载PDF
Signed Additive Fuzzy Measure
14
作者 纪爱兵 《Chinese Quarterly Journal of Mathematics》 CSCD 2000年第4期43-48,共6页
In this paper, we introduce the concept of signed additive fuzzy measure on a class of fuzzy sets, then, on certain condition, a series of decomposition theorems of signed additive fuzzy measure are proved.
关键词 generated fuzzy σ-algebra signed additive fuzzy measure Hahn decomposition theorem Jordan decomposition theo
下载PDF
A New Rational Algebraic Approach to Find Exact Analytical Solutions to a (2+1)-Dimensional System 被引量:7
15
作者 BAI Cheng-Jie ZHAO Hong 《Communications in Theoretical Physics》 SCIE CAS CSCD 2007年第5X期801-810,共10页
In this paper, we present a new rational algebraic approach to uniformly construct a series of exact analytical solutions for nonlinear partial differential equations. Compared with most existing tanh methods and othe... In this paper, we present a new rational algebraic approach to uniformly construct a series of exact analytical solutions for nonlinear partial differential equations. Compared with most existing tanh methods and other sophisticated methods, the proposed method not only recovers some known solutions, but also finds some new and general solutions. The solutions obtained in this paper include rational form triangular periodic wave solutions, solitary wave solutions, and elliptic doubly periodic wave solutions. The efficiency of the method can be demonstrated on (2+1)-dimensional dispersive long-wave equation. 展开更多
关键词 rational algebraic approach (2+1)-dimensional dispersive long-wave equation exact solutions
下载PDF
Generalized Multi-component TC Hierarchy and Its Multi-component Integrable Coupling System 被引量:1
16
作者 XIA Tie-Cheng YOU Fu-Cai 《Communications in Theoretical Physics》 SCIE CAS CSCD 2005年第5X期793-798,共6页
A new 3M-dimensional Lie algebra X is constructed firstly. Then, the corresponding loop algebra X is produced, whose commutation operation defined by us is as simple and straightforward as that in the loop algebra A1.... A new 3M-dimensional Lie algebra X is constructed firstly. Then, the corresponding loop algebra X is produced, whose commutation operation defined by us is as simple and straightforward as that in the loop algebra A1.It follows that a generalscheme for generating multi-component integrable hierarchy is proposed. By taking advantage of X, a new isospectral problem is established, and then well-known multi-component TC hierarchy is obtained. Finally,an expanding loop algebra FM of the loop algebra X is presented. Based on the FM, the multi-component integrable coupling system of the generalized multi-component TC hierarchy has been worked out. The method in this paper can be applied to other nonlinear evolution equations hierarchies. It is easy to find that we can construct any finite-dimensional Lie algebra by this approach. 展开更多
关键词 loop algebra multi-component TC hierarchy multi-component integrable coupling system
下载PDF
Lie algebraic analysis for the beam transport in the spherical electrostatic analyser 被引量:1
17
作者 吕建钦 张卓 《Chinese Physics B》 SCIE EI CAS CSCD 2007年第5期1280-1284,共5页
This paper uses the Lie algebraic method to analyse the charged particle trajectories in the spherical electrostatic analyser, and obtains the nonlinear solutions. The results show that the focusing abilities both in ... This paper uses the Lie algebraic method to analyse the charged particle trajectories in the spherical electrostatic analyser, and obtains the nonlinear solutions. The results show that the focusing abilities both in the x and y directions of the analyser are almost the same. Moreover, there exist dispersion effects in the x direction, and no dispersion effects in the y direction. 展开更多
关键词 Lie algebraic method spherical electrostatic analyser optical properties NONLINEARITY
下载PDF
PARALLEL REGION PRESERVING MULTISECTION METHOD FOR SOLVING GENERALIZED EIGENPROBLEM 被引量:1
18
作者 曾岚 周树荃 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 1996年第2期51+46-50,共6页
The parallel multisection method for solving algebraic eigenproblem has been presented in recent years with the development of the parallel computers, but all the research work is limited in standard eigenproblems of ... The parallel multisection method for solving algebraic eigenproblem has been presented in recent years with the development of the parallel computers, but all the research work is limited in standard eigenproblems of symmetric tridiagonal matrix. The multisection method for solving the generalized eigenproblem applied significantly in many science and engineering domains has not been studied. The parallel region preserving multisection method (PRM for short) for solving generalized eigenproblems of large sparse and real symmetric matrix is presented in this paper. This method not only retains the advantages of the conventional determinant search method (DS for short), but also overcomes its disadvantages such as leaking roots and disconvergence. We have tested the method on the YH 1 vector computer, and compared it with the parallel region preserving determinant search method the parallel region preserving bisection method (PRB for short). The numerical results show that PRM has a higher speed up, for instance, it attains the speed up of 7.7 when the scale of the problem is 2 114 and the eigenpair found is 3, and PRM is superior to PRB when the scale of the problem is large. 展开更多
关键词 parallel processing structural analysis numerical algebra generalized eigenproblem parallel multisection method
下载PDF
基于CMCPSO-SVM的轴承微弱故障诊断方法 被引量:2
19
作者 纪俊卿 孔晓佳 +3 位作者 邹方豪 张静 许同乐 袁伟 《机床与液压》 北大核心 2022年第5期185-190,共6页
针对旋转机械轴承微弱故障振动信号易被强噪声掩盖难以识别的问题,提出一种改进混沌粒子群优化支持向量机的故障诊断方法。将信号通过局部均值分解算法分解处理得到乘积函数(PF)分量,并进行能量归一化处理获得时频域特征集;通过迭代拉... 针对旋转机械轴承微弱故障振动信号易被强噪声掩盖难以识别的问题,提出一种改进混沌粒子群优化支持向量机的故障诊断方法。将信号通过局部均值分解算法分解处理得到乘积函数(PF)分量,并进行能量归一化处理获得时频域特征集;通过迭代拉普拉斯得分降低时频域特征集的空间维度;以PF分量的排列熵作为混沌粒子群的适应度,并加入交叉和变异新策略,建立一种新的交叉变异混沌粒子群优化方法;利用改进的粒子群算法优化支持向量机的核函数和惩罚因子,并将优化后的分类模型应用于轴承故障诊断。结果表明:该故障分类模型的识别准确率高于其他分类模型。 展开更多
关键词 轴承微弱故障 交叉变异混沌粒子群 拉普拉斯分数 支持向量机 故障诊断
下载PDF
Diagonal Invariant Ideals of Topologically Graded C~*-algebras 被引量:2
20
作者 XU Qing-xiang ZHANG Xiao-bo 《Chinese Quarterly Journal of Mathematics》 CSCD 北大核心 2005年第4期338-341,共4页
We study diagonal invariant ideals of topologically graded C*-algebras over discrete groups. Since all Toeplitz algebras defined on discrete groups are topologically graded, the results in this paper have improved the... We study diagonal invariant ideals of topologically graded C*-algebras over discrete groups. Since all Toeplitz algebras defined on discrete groups are topologically graded, the results in this paper have improved the first author's previous works on this topic. 展开更多
关键词 Fell bundle topologically graded C*-algebra diagonal invariant ideal
下载PDF
上一页 1 2 10 下一页 到第
使用帮助 返回顶部