期刊文献+
共找到587篇文章
< 1 2 30 >
每页显示 20 50 100
基于连续分布方向图和改进的Poincaré Index的指纹分类 被引量:20
1
作者 聂桂军 吴陈 +1 位作者 叶锡君 徐荣青 《电子学报》 EI CAS CSCD 北大核心 2006年第5期947-952,共6页
本文提出了指纹连续分布方向图(场)的概念及其算法,连续分布方向图具有很好的连续性、渐变性、抗噪性和较高的精确度;对经典的PoincaréIndex计算公式和指纹奇异点检测算法进行了改进,改进后的PoincaréIndex不仅能精确表示向... 本文提出了指纹连续分布方向图(场)的概念及其算法,连续分布方向图具有很好的连续性、渐变性、抗噪性和较高的精确度;对经典的PoincaréIndex计算公式和指纹奇异点检测算法进行了改进,改进后的PoincaréIndex不仅能精确表示向量场的旋转角度,而且还能精确表示向量场的旋转方向,能够在像素级水平精确定位指纹奇异点(core点和delta点).在此基础上,提出了一种新的基于连续分布方向图和改进的PoincaréIn-dex的5类自动指纹分类算法,在江苏科技大学指纹库(含4000幅指纹)上的分类结果表明,本算法能抗任意角度的指纹图像旋转,成功地解决了指纹分类中的图像平移、旋转和形变不变性问题,分类正确率达到97.05%,具有较好的健壮性,满足实用要求. 展开更多
关键词 自动指纹识别系统 指纹分类 连续分布方向图 奇异点检测 poincaré INDEX
下载PDF
Vectorial optical fields: recent advances and future prospects 被引量:17
2
作者 Jian Chen Chenhao Wan Qiwen Zhan 《Science Bulletin》 SCIE EI CSCD 2018年第1期54-74,共21页
Driven by their potential applications, vectorial optical fields with spatially inhomogeneous states of polarization within the cross section have drawn significant attention recently. This work intends to review some... Driven by their potential applications, vectorial optical fields with spatially inhomogeneous states of polarization within the cross section have drawn significant attention recently. This work intends to review some of the latest development of this rapidly growing field of optics and offer a general overview of the current status of this field in a few areas. Mathematical descriptions of generalized vectorial optical fields are provided along with several special examples. A time-reversal methodology for the creation of a wide variety of exotic optical focal fields with prescribed characteristics within the focal volume is presented. Recently developed methods for the generation of vectorial optical fields that utilize fiber lasers,digital lasers, vectorial optical field generator, metasurfaces or photoalignment liquid crystals are summarized. The interactions of these vectorial optical fields with various micro-and nano-structures are presented and the prospects of their potential applications are discussed. The connection of vectorial optical fields with higher dimensionality in quantum information is summarized. 展开更多
关键词 Vectorial optical field Cylindrical vector beam Full poincaré beam Spatial light modulator Metasurface Spin-orbit interaction Quantum information Quantum communication
原文传递
Nonlinear dynamics analysis of a new autonomous chaotic system 被引量:14
3
作者 CHU Yan-dong LI Xian-feng +1 位作者 ZHANG Jian-gang CHANG Ying-xiang 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2007年第9期1408-1413,共6页
In this paper,a new nonlinear autonomous system introduced by Chlouverakis and Sprott is studied further,to present very rich and complex nonlinear dynamical behaviors. Some basic dynamical properties are studied eith... In this paper,a new nonlinear autonomous system introduced by Chlouverakis and Sprott is studied further,to present very rich and complex nonlinear dynamical behaviors. Some basic dynamical properties are studied either analytically or nu-merically,such as Poincaré map,Lyapunov exponents and Lyapunov dimension. Based on this flow,a new almost-Hamilton chaotic system with very high Lyapunov dimensions is constructed and investigated. Two new nonlinear autonomous systems can be changed into one another by adding or omitting some constant coefficients. 展开更多
关键词 Lyapunov exponents BIFURCATION CHAOS Phase space poincaré sections
下载PDF
Spin-controlled wavefront shaping with plasmonic chiral geometric metasurfaces 被引量:13
4
作者 Yang Chen Xiaodong Yang Jie Gao 《Light(Science & Applications)》 SCIE EI CAS CSCD 2018年第1期262-271,共10页
Metasurfaces,as a two-dimensional(2D)version of metamaterials,have drawn considerable attention for their revolutionary capability in manipulating the amplitude,phase,and polarization of light.As one of the most impor... Metasurfaces,as a two-dimensional(2D)version of metamaterials,have drawn considerable attention for their revolutionary capability in manipulating the amplitude,phase,and polarization of light.As one of the most important types of metasurfaces,geometric metasurfaces provide a versatile platform for controlling optical phase distributions due to the geometric nature of the generated phase profile.However,it remains a great challenge to design geometric metasurfaces for realizing spin-switchable functionalities because the generated phase profile with the converted spin is reversed once the handedness of the incident beam is switched.Here,we propose and experimentally demonstrate chiral geometric metasurfaces based on intrinsically chiral plasmonic stepped nanoapertures with a simultaneously high circular dichroism in transmission(CDT)and large cross-polarization ratio(CPR)in transmitted light to exhibit spin-controlled wavefront shaping capabilities.The chiral geometric metasurfaces are constructed by merging two independently designed subarrays of the two enantiomers for the stepped nanoaperture.Under a certain incident handedness,the transmission from one subarray is allowed,while the transmission from the other subarray is strongly prohibited.The merged metasurface then only exhibits the transmitted signal with the phase profile of one subarray,which can be switched by changing the incident handedness.Based on the chiral geometric metasurface,both chiral metasurface holograms and the spin-dependent generation of hybrid-order Poincarésphere beams are experimentally realized.Our approach promises further applications in spin-controlled metasurface devices for complex beam conversion,image processing,optical trapping,and optical communications. 展开更多
关键词 poincaré CHIRAL GEOMETRIC
原文传递
Lie symmetries, perturbation to symmetries and adiabatic invariants of Poincaré equations 被引量:10
5
作者 陈向炜 刘翠梅 李彦敏 《Chinese Physics B》 SCIE EI CAS CSCD 2006年第3期470-474,共5页
Based on the invariance of differential equations under infinitesimal transformations, Lie symmetry, laws of conservations, perturbation to the symmetries and adiabatic invariants of Poincaré equations are presen... Based on the invariance of differential equations under infinitesimal transformations, Lie symmetry, laws of conservations, perturbation to the symmetries and adiabatic invariants of Poincaré equations are presented. The concepts of Lie symmetry and higher order adiabatic invariants of Poincaré equations are proposed. The conditions for existence of the exact invariants and adiabatic invariants are proved, and their forms are also given. In addition, an example is presented to illustrate these results. 展开更多
关键词 poincaré equations perturbation to symmetry exact invariant adiabatic invariant
下载PDF
Talagrand's T_2-Transportation Inequality and Log-Sobolev Inequality for Dissipative SPDEs and Applications to Reaction-Diffusion Equations 被引量:9
6
作者 Liming WU Zhengliang ZHANG 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 2006年第3期243-262,共20页
We establish Talagrand's T2-transportation inequalities for infinite dimensional dissipative diffusions with sharp constants, through Galerkin type's approximations and the known results in the finite dimensional ca... We establish Talagrand's T2-transportation inequalities for infinite dimensional dissipative diffusions with sharp constants, through Galerkin type's approximations and the known results in the finite dimensional case. Furthermore in the additive noise case we prove also logarithmic Sobolev inequalities with sharp constants. Applications to Reaction- Diffusion equations are provided. 展开更多
关键词 Stochastic partial differential equations (SPDEs) Logarithmic Sobolev inequality Talagrand's transportation inequality poincaré inequality
原文传递
Polynomials,Higher Order Sobolev Extension Theorems and Interpolation Inequalities on Weighted Folland-Stein Spaces on Stratified Groups 被引量:9
7
作者 Guozhen Lu Department of Mathematics,Wayne State University,Detroit,MI 48202,USA 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2000年第3期405-444,共40页
This paper consists of three main parts.One of them is to develop local and global Sobolev interpolation inequalities of any higher order for the nonisotropic Sobolev spaces on stratified nilpotent Lie groups.Despite ... This paper consists of three main parts.One of them is to develop local and global Sobolev interpolation inequalities of any higher order for the nonisotropic Sobolev spaces on stratified nilpotent Lie groups.Despite the extensive research after Jerison’s work[3]on Poincaré-type inequalities for Hrmander’s vector fields over the years,our results given here even in the nonweighted case appear to be new.Such interpolation inequalities have crucial applications to subelliptic or parabolic PDE’s involving vector fields.The main tools to prove such inequalities are approximating the Sobolev func- tions by polynomials associated with the left invariant vector fields on G.Some very useful properties for polynomials associated with the functions are given here and they appear to have independent interests in their own rights.Finding the existence of such polynomials is the second main part of this paper.Main results of these two parts have been announced in the author’s paper in Mathematical Research Letters[38]. The third main part of this paper contains extension theorems on anisotropic Sobolev spaces on stratified groups and their applications to proving Sobolev interpolation inequalities on(εδ)domains. Some results of weighted Sobolev spaces are also given here.We construct a linear extension operator which is bounded on different Sobolev spaces simultaneously.In particular,we are able to construct a bounded linear extension operator such that the derivatives of the extended function can be controlled by the same order of derivatives of the given Sobolev functions.Theorems are stated and proved for weighted anisotropic Sobolev spaces on stratified groups. 展开更多
关键词 poincaré inequalities Extension theorems Interpolation inequalities Anisotropic Sobolev spaces A_p weights δ)domains Vector fields Polynomials on stratified groups
原文传递
Bifurcations of rough heteroclinic loop with two saddle points 被引量:8
8
作者 金银来 朱德明 《Science China Mathematics》 SCIE 2003年第4期459-468,共10页
The bifurcation problems of rough 2-point-loop are studied for the caseρ 1 1 >λ 1 1 ,ρ 2 1 <λ 2 1 ,ρ 1 1 ρ 2 1 <λ 1 1 λ 2 1 , where ?ρ i 1 <0 and λ i 1 >0 are the pair of principal eigenvalues... The bifurcation problems of rough 2-point-loop are studied for the caseρ 1 1 >λ 1 1 ,ρ 2 1 <λ 2 1 ,ρ 1 1 ρ 2 1 <λ 1 1 λ 2 1 , where ?ρ i 1 <0 and λ i 1 >0 are the pair of principal eigenvalues of unperturbed system at saddle point pi, i = 1,2. Under the transversal and nontwisted conditions, the authors obtain some results of the existence of one 1-periodic orbit, one 1-periodic and one 1-homoclinic loop, two 1-periodic orbits and one 2-fold 1-periodic orbit. Moreover, the bifurcation surfaces and the existence regions are given, and the corresponding bifurcation graph is drawn. 展开更多
关键词 local coordinates poincaré map 1-homoclinic loop 1-periodic orbit 2-fold 1-periodic orbit bifurcation surface
原文传递
常微分方程定性理论与稳定性理论的哲学思考 被引量:6
9
作者 陈明晖 邓明立 《自然科学史研究》 CSCD 北大核心 2005年第1期45-52,共8页
常微分方程在经历了长期的求精确解的努力后逐渐停滞,庞加莱在分析的基础上引入几何方法,开创了常微分方程定性理论,李雅普诺夫则在庞加莱定性分析的基础上,转而进入了新的稳定性研究。通过对两者的比较研究,我们能够对科学历程中新思... 常微分方程在经历了长期的求精确解的努力后逐渐停滞,庞加莱在分析的基础上引入几何方法,开创了常微分方程定性理论,李雅普诺夫则在庞加莱定性分析的基础上,转而进入了新的稳定性研究。通过对两者的比较研究,我们能够对科学历程中新思想、新理论的产生和发展规律有所感悟。 展开更多
关键词 庞加莱 定性理论 李雅普诺夫 稳定性理论
下载PDF
Passive walker that can walk down steps:simulations and experiments 被引量:5
10
作者 Ning Liu Junfeng Li Tianshu Wang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2008年第5期569-573,共5页
A planar passive walking model with straight legs and round feet was discussed. This model can walk down steps, both on stairs with even steps and with random steps. Simulations showed that models with small moments o... A planar passive walking model with straight legs and round feet was discussed. This model can walk down steps, both on stairs with even steps and with random steps. Simulations showed that models with small moments of inertia can navigate large height steps. Period-doubling has been observed when the space between steps grows. This period-doubling has been validated by experiments, and the results of experiments were coincident with the simulation. 展开更多
关键词 Passive walking Period-doubling Simulation - Experiments poincaré map Nonlinear dynamics
下载PDF
Dead-zone-free atomic magnetometer based on hybrid Poincarébeams
11
作者 KE TIAN WEIFENG DING ZHAOYING WANG 《Photonics Research》 SCIE EI CAS CSCD 2024年第5期1093-1097,共5页
In this paper,we present the experiment and the theory scheme of light-atom interaction in atomic magnetometers by using a hybrid Poincarébeam(HPB)to solve an annoying problem,named“dead zone.”This kind of magn... In this paper,we present the experiment and the theory scheme of light-atom interaction in atomic magnetometers by using a hybrid Poincarébeam(HPB)to solve an annoying problem,named“dead zone.”This kind of magnetometer can be sensitive to arbitrary directions of external magnetic fields.The HPB has a complex polarization distribution,consisting of a vector radially polarized beam and a scalar circularly polarized beam in our experiment.These two kinds of beams have different directions of dead zones of external magnetic fields;thereby,the atomic magnetometer with an HPB can avoid the non-signal area when the direction of the external magnetic field is in the plane perpendicular to the light polarization plane.Furthermore,the optical magnetic resonance(OMR)signal using an HPB still has no dead zones even when the direction of the external magnetic field is in the plane parallel to the polarization plane in our scheme.Our work has the potential to simplify and optimize dead-zone-free atomic magnetometers. 展开更多
关键词 poincaré MAGNETOMETER ATOMIC
原文传递
本刊英文版2024年67卷第9期(1957-2194)摘要
12
《中国科学:数学》 CSCD 北大核心 2024年第9期I0003-I0006,共4页
Center of the Yangian double in type A Fan Yang&Naihuan Jing Abstract We prove that the R-matrix and Drinfeld presentations of the Yangian double in type A are isomorphic.The central elements of the completed Yang... Center of the Yangian double in type A Fan Yang&Naihuan Jing Abstract We prove that the R-matrix and Drinfeld presentations of the Yangian double in type A are isomorphic.The central elements of the completed Yangian double in type A at the critical level are constructed.The images of these elements under a Harish-Chandra-type homomorphism are calculated by applying a version of the Poincaré-Birkhoff-Witt theorem for the R-matrix presentation.These images coincide with the eigenvalues of the central elements in the Wakimoto modules. 展开更多
关键词 poincaré ELEMENTS YANGIAN
原文传递
布劳威尔关于向量分布的研究
13
作者 刘丹丹 王昌 《内蒙古师范大学学报(自然科学版)》 CAS 2024年第4期350-355,361,共7页
布劳威尔通过将球面不动点定理和向量场联系起来,推动了布劳威尔不动点定理的产生,也促进了代数拓扑学的发展。基于相关原始文献,围绕布劳威尔关于向量分布的研究,分析布劳威尔对庞加莱指数工作的推广,及其对二维布劳威尔不动点定理新... 布劳威尔通过将球面不动点定理和向量场联系起来,推动了布劳威尔不动点定理的产生,也促进了代数拓扑学的发展。基于相关原始文献,围绕布劳威尔关于向量分布的研究,分析布劳威尔对庞加莱指数工作的推广,及其对二维布劳威尔不动点定理新证明方法的思想演变过程,以期厘清布劳威尔将庞加莱的指数工作应用于一般连续向量分布的过程,及二维不动点定理新证明的具体思想。 展开更多
关键词 布劳威尔 庞加莱 向量分布 球面不动点定理 向量场奇点
下载PDF
路面激励下车辆悬架滞回模型的混沌研究 被引量:4
14
作者 吴参 王维锐 +2 位作者 徐博侯 李兴林 江伟光 《浙江大学学报(工学版)》 EI CAS CSCD 北大核心 2011年第7期1259-1264,1287,共7页
为了分析车辆悬架在实际路面激励下的振动状态,根据试验所得的磁流变减振器示功曲线,采用Matlab软件拟合修正的Bouc-Wen模型,建立带滞回特性的非线性模型以及基于减振器试验数据的两自由度四分之一悬架模型.研究该半主动悬架的频率响应... 为了分析车辆悬架在实际路面激励下的振动状态,根据试验所得的磁流变减振器示功曲线,采用Matlab软件拟合修正的Bouc-Wen模型,建立带滞回特性的非线性模型以及基于减振器试验数据的两自由度四分之一悬架模型.研究该半主动悬架的频率响应特性,通过相平面图、Poincaré截面图和分叉图分析半主动悬架在不同路面激励下的振动形式,研究随着路面变化或者悬架自身参数变化引起的振动形式的改变,揭示悬架系统在各种工况下发生的混沌行为,为地面车辆的动力学设计提供依据. 展开更多
关键词 悬架非线性 Bouc-Wen 稳定性 poincaré 分叉
下载PDF
On the Construction and Classification of the Common Invariant Solutions for Some P(1,4) -Invariant Partial Differential Equations
15
作者 Vasyl M. Fedorchuk Volodymyr I. Fedorchuk 《Applied Mathematics》 2023年第11期728-747,共20页
We consider the following (1 + 3)-dimensional P(1,4)-invariant partial differential equations (PDEs): the Eikonal equation, the Euler-Lagrange-Born-Infeld equation, the homogeneous Monge-Ampère equation, the inho... We consider the following (1 + 3)-dimensional P(1,4)-invariant partial differential equations (PDEs): the Eikonal equation, the Euler-Lagrange-Born-Infeld equation, the homogeneous Monge-Ampère equation, the inhomogeneous Monge-Ampère equation. The purpose of this paper is to construct and classify the common invariant solutions for those equations. For this aim, we have used the results concerning construction and classification of invariant solutions for the (1 + 3)-dimensional P(1,4)-invariant Eikonal equation, since this equation is the simplest among the equations under investigation. The direct checked allowed us to conclude that the majority of invariant solutions of the (1 + 3)-dimensional Eikonal equation, obtained on the base of low-dimensional (dimL ≤ 3) nonconjugate subalgebras of the Lie algebra of the Poincaré group P(1,4), satisfy all the equations under investigation. In this paper, we present obtained common invariant solutions of the equations under study as well as the classification of those invariant solutions. 展开更多
关键词 Symmetry Reduction Classification of Invariant Solutions Common Invariant Solutions The Eikonal Equations The Euler-Lagrange-Born-Infeld Equations The Monge-Ampère Equations Classification of Lie Algebras Nonconjugate Subalgebras poincaré Group P(1 4)
下载PDF
The Poincaré Bifurcation of a Class of Planar Hamiltonian Systems 被引量:4
16
作者 宋燕 《Northeastern Mathematical Journal》 CSCD 2006年第2期167-172,共6页
In this paper, we discuss the Poincaré bifurcation of a class of Hamiltonian systems having a region consisting of periodic cycles bounded by a parabola and a straight line. We prove that the system can generate ... In this paper, we discuss the Poincaré bifurcation of a class of Hamiltonian systems having a region consisting of periodic cycles bounded by a parabola and a straight line. We prove that the system can generate at most two limit cycles and may generate two limit cycles after a small cubic polynomial perturbation. 展开更多
关键词 periodic region Hamiltonian system poincaré bifurcation limit cycle
下载PDF
Physical conversion and superposition of optical skyrmion topologies 被引量:1
17
作者 HOUAN TENG JINZHAN ZHONG +2 位作者 JIAN CHEN XINRUI LEI QIWEN ZHAN 《Photonics Research》 SCIE EI CAS CSCD 2023年第12期2042-2053,共12页
Optical skyrmions are quasiparticles with nontrivial topological textures that have significant potential in optical information processing,transmission,and storage.Here,we theoretically and experimentally achieve the... Optical skyrmions are quasiparticles with nontrivial topological textures that have significant potential in optical information processing,transmission,and storage.Here,we theoretically and experimentally achieve the conversion of optical skyrmions among Néel,Bloch,intermediate skyrmions,and bimerons by polarization devices,where the fusion and annihilation of optical skyrmions are demonstrated accordingly.By analyzing the polarization pattern in Poincarébeams,we reveal the skyrmion topology dependence on the device,which provides a pathway for the study of skyrmion interactions.A vectorial optical field generator is implemented to realize the conversion and superposition experimentally,and the results are in good agreement with the theoretical predictions.These results enhance our comprehension of optical topological quasiparticles,which could have a significant impact on the transfer,storage,and communication of optical information. 展开更多
关键词 poincaré SUPERPOSITION TOPOLOGICAL
原文传递
Arbitrarily polarized bound states in the continuum with twisted photonic crystal slabs 被引量:1
18
作者 Haoye Qin Zengping Su +7 位作者 Mengqi Liu Yixuan Zeng Man-Chung Tang Mengyao Li Yuzhi Shi Wei Huang Cheng-Wei Qiu Qinghua Song 《Light(Science & Applications)》 SCIE EI CSCD 2023年第4期542-550,共9页
Arbitrary polarized vortex beam induced by polarization singularity offers a new platform for both classical optics and quantum entanglement applications.Bound states in the continuum(BICs)have been demonstrated to be... Arbitrary polarized vortex beam induced by polarization singularity offers a new platform for both classical optics and quantum entanglement applications.Bound states in the continuum(BICs)have been demonstrated to be associated with topological charge and vortex polarization singularities in momentum space.For conventional symmetric photonic crystal slabs(PhCSs),BIC is enclosed by linearly polarized far fields with winding angle of 2π,which is unfavorable for high-capacity and multi-functionality integration-optics applications.Here,we show that by breakingσz-symmetry of the PhCS,asymmetry in upward and downward directions and arbitrarily polarized BIC can be realized with a bilayer-twisted PhCS.It exhibits elliptical polarization states with constant ellipticity angle at every point in momentum space within the vicinity of BIC.The topological nature of BIC reflects on the orientation angle of polarization state,with a topological charge of 1 for any value of ellipticity angle.Full coverage of Poincarésphere(i.e.,-π/4≤X≤4 and-π/2≤ψ≤π/2)and higher-order Poincarésphere can be realized by tailoring the twist angles.Our findings may open up new avenues for applications in structured light,quantum optics,and twistronics for photons. 展开更多
关键词 poincaré POLARIZED TWISTED
原文传递
庞加莱定性思想的决定论意涵 被引量:1
19
作者 李娟 高洋 《自然辩证法研究》 北大核心 2023年第1期116-122,共7页
常微分方程理论与决定论之间存在历史关联,二者相互影响。在经典数学物理中,决定论与微分方程的存在唯一性定理一致,随着微分方程理论和决定论不断取得发展,庞加莱的定性理论及其相关哲学思考开启了二者之间新的关系模式。在庞加莱之前... 常微分方程理论与决定论之间存在历史关联,二者相互影响。在经典数学物理中,决定论与微分方程的存在唯一性定理一致,随着微分方程理论和决定论不断取得发展,庞加莱的定性理论及其相关哲学思考开启了二者之间新的关系模式。在庞加莱之前,决定论或者采取线性的、形而上学的观点,或者并未受到同时代数学科学研究的实质性影响;而在庞加莱之后,微分方程理论成为讨论决定论问题不可或缺的思想资源,并为决定论的哲学讨论打开了新的视野。庞加莱的定性思想可被视为现代非完全决定论的起源。 展开更多
关键词 庞加莱 定性思想 决定论
原文传递
A secure identification system using coherent states 被引量:3
20
作者 何广强 曾贵华 《Chinese Physics B》 SCIE EI CAS CSCD 2006年第2期371-374,共4页
A quantum identification system based on the transformation of polarization of a mesoscopic coherent state is proposed. Physically, an initial polarization state which carries the identity information is transformed i... A quantum identification system based on the transformation of polarization of a mesoscopic coherent state is proposed. Physically, an initial polarization state which carries the identity information is transformed into an arbitrary elliptical polarization state, To verify the identity of a communicator, a reverse procedure is performed by the receiver, For simply describing the transformation procedure, the analytical methods of Poincaré sphere and quaternion are adopted. Since quantum noise provides such a measurement uncertainty for the eavesdropping that the identity information cannot be retrieved from the elliptical polarization state, the proposed scheme is secure. 展开更多
关键词 quantum identification polarization encryption and decryption quantum noise poincaré sphere
下载PDF
上一页 1 2 30 下一页 到第
使用帮助 返回顶部