耦合双稳映象格子模型的时空混沌控制

变量反馈技术实现了耦合双稳映象格子模型的时空混沌控制.数值实验结果表明,利用不同的反馈技术和不同的反馈强度,可以将双稳映象系统的混沌及耦合双稳映象格子模型的时空混沌控制到不动点或周期轨道.变量反馈控制法除了局域双稳映象系统的定态点外,不需要先获取耦合双稳映象格子时空系统的动力学信息,它对抑制耦合双稳映象系统中的湍流具有一定的指导作用.     

耦合映象格子中时空混沌的控制

采用相同的相空间压缩方法,有效地控制了均匀及非均匀耦合映象格子中的时空混沌.数值模拟结果表明,在一定的相空间压缩参数区域内,控制时空混沌到均匀稳定状态时,控制结果与控制参数之间存在确定的函数关系.利用这个控制方程,选择不同的相空间压缩参数控制耦合映象格子中的时空混沌,获得了各种所需要的稳定斑图 关键词： 时空混沌 耦合映象格子     

二维均匀耦合映象格子中的时空周期图案

目的——构造二维均匀耦合映象格子中的时空周期图案;方法——通过一维耦合映象格子模型的相空间中已知低空间周期轨道,直接构造二维均匀耦合映象格子模型中一系列空间周期轨道,而不必求解其模型方程,并对构造轨道的稳定性进行分析;结果——L²×L²雅可比矩阵可化简为几个2×2矩阵组成的对角矩阵;结论——所构造轨道的稳定性不可能比原来轨道的稳定性高. 关键词： 耦合映象格子 时空周期图案 雅可比矩阵     

一个强、弱耗散功能可分隔系统中的特征激变

报道一个由保守映象和耗散映象不连续、不可逆地分段描述的系统，以及在其中发生的一例特征激变.激变的独特之处在于逃逸孔洞.由映象的不连续、不可逆性而导致相平面中出现一个胖分形迭代禁区网，它使得一个混沌吸引子突然失稳而发生激变后出现的两个周期吸引子的吸引域边界成为点滴状.仅仅在每个周期点邻近存在这样的一个作为逃逸孔洞的、受到强耗散性支配和禁区边界限制的规则边界吸引域. 关键词： 激变 保守映象 耗散映象 逃逸孔洞     

“守恒—映象”电荷沉积算法

从半径映象函数出发，给出了“守恒－映象”电荷沉积公式中积分限的确定方法和电荷沉积精度的确定方法，从而使“守恒－映象”电荷沉积方法成为计算电流密度和电荷密度的一种切实可行的精确的电荷沉积方法。     

一维映象中混沌区的度量性质

本文用数值和分析的办法讨论了:(1)一维映象中的Hausdorff维数与Ляпунов指数的关系d(λ),指出在N(ε)关系中存在反映点集在不同尺度上的结构的多标度区现象,认真分析这个现象对d的计算有重要意义;(2)根据动力系统Poincar映象与一维映象的关系,及一维映象d(λ)在λ=0处的不连续性和多值性,猜测动力系统λ=(0,0,—)处的d(λ)关系也具有不连续性和多值性;(3)在d(λ)关系的基础上,以λ>0为判据,用统计抽样法估计了logistic模型混沌区内混沌轨道在参数轴上的测度,结果为m_c=0.893±0.022(归一于混沌区的总测度为1)。 关键词：     

标准映象的周期分岔及其向混沌的过渡

本文研究了标准映象的周期轨道在其余数R=1和R=0附近的行为,对于前者出现倍周期分岔序列,其分岔率δ及标度因子α和β与其它二维保面积映象的结果一致;对于后者发生同周期分岔,这与标准映象的奇对称性有关。文中还计算了混沌轨道的李雅普诺夫指数,发现在倍周期分岔序列的聚点k_∞附近,存在标度关系: λ=λ_∞+A(k—k_∞)+B(k—k_∞)^τ, 其中因子τ=0.32。这与理论推断的结果τ=(ln(2))/(l 关键词：     

用数字有限脉冲响应滤波器控制混沌

利用数字有限脉冲响应滤波器稳定微分动力系统和二维离散映象混沌吸引子中不稳定周期轨道的方法，实现了高周期轨道的稳定控制.分别研究了Lorenz系统和Henon映象，给出了初步的分析和数值模拟结果.这种方法的主要特点是不需要获取混沌系统中不稳定周期轨道的任何信息，控制参数的选择与被控混沌系统无关. 关键词：     

数据矩阵的特性映象及其线谱估计应用

许多信号处理问题归结为求解一线性方程组。对此线性方程组的系数矩阵进行可能的特性映象,比如低秩化和Toeplitz结构化的处理,可以明显地降低噪声的影响,提高信号参量估计的准确度。本文讨论了数据矩阵的特性映象,并给出了叠代映象系列收敛的简单而形象的证明。在线谱估计的应用中,从正弦波自相关函数的模型出发,推导了该情况下数据矩阵的特性映象算法。通过一实例的计算和比较,可以看出此方法显著地改善了谱估计的性能。     

非线性耦合时空混沌系统的反同步研究

利用非线性耦合方法研究了离散型时空混沌系统的反同步问题.对时空混沌系统的线性项和非线性项进行适当的分离,利用系统本身的非线性项作为耦合函数,实现了两个二维耦合映象格子的反同步.进一步将这种非线性耦合方法推广应用到由二维耦合映象格子构成复杂网络的反同步研究中,仿真模拟发现仍具有理想的反同步效果. 关键词： 反同步 非线性耦合 耦合映象格子 复杂网络     

单幅对称变形相位图分离二维变形分量的相移电子散斑干涉技术

提出了利用相移电子散斑干涉测量物体二维变形分量的方法.单光束照明的传统电子散斑干涉技术,测量得到的是一幅物体变形的混合相位场.当物体具有对称变形时,可由这一幅相位图求得二维变形分量.方法是将该相位图镜像翻转得到第二幅相位图,通过二幅相位图的叠加、复位和分离运算,获得物体的二维变形场的分量值.利用三点加载的简支梁进行了实验,给出了实验结果,并与对称光照明实验结果进行了对比,验证了该方法的正确性.     

Stability diagram of a few-electron triple dot

Individual and coupled quantum dots containing one or two electrons have been realized and are regarded as components for future quantum information circuits. In this Letter we map out experimentally the stability diagram of the few-electron triple dot system, the electron configuration map as a function of the external tuning parameters, and reveal experimentally for the first time the existence of quadruple points, a signature of the three dots being in resonance. In the vicinity of these quadruple points we observe a duplication of charge transfer transitions related to charge and spin reconfigurations triggered by changes in the total electron occupation number. The experimental results are largely reproduced by equivalent circuit analysis and Hubbard models. Our results are relevant for future quantum mechanical engineering applications within both quantum information and quantum cellular automata architectures.     

Interfacial wave propagation due to an interfacial line source

Interfacial wave propagation parallel to a dielectric interface has been studied by considering an electric current line source present at the interface. The first order asymptotic evaluation of field components shows a null of the electric field at the interface. An amplitude null represents an unstable structure in the phase map and a phase front discontinuity across the interface. Higher order asymptotic evaluation has been employed to gain further insight into this propagation problem. The results show that the wavefronts need not be discontinuous. The continuity of the phase fronts is preserved with the help of interesting and stable structures such as saddle points and center points in the phase map of the electric field in both half spaces.      

具有均匀天空背景的高精度静态星模拟器设计

为解决现有星模拟器只关注星图模拟精度而忽略天空背景模拟的问题,设计了具有均匀天空背景的高精度静态星模拟器.重点阐述星模拟器的组成和工作原理,详细论述光学系统优化设计方法.根据模拟器光学系统透镜大、精度高的特点,采用筒套筒的镜筒设计形式;为了保证星图模拟精度,采用激光直写技术制作星点板,刻划精度优于±1μm.测试结果表明:设计的具有均匀天空背景的高精度静态星模拟器的星图模拟精度优于3″,天空背景均匀性优于95％,满足导航敏感器的高精度地面标定与功能测试需求.     

Enveloping algebra-valued gauge transformations for non-abelian gauge groups on non-commutative spaces

An enveloping algebra-valued gauge field is constructed, its components are functions of the Lie algebra-valued gauge field and can be constructed with the Seiberg-Witten map. This allows the formulation of a dynamics for a finite number of gauge field components on non-commutative spaces. Received: 17 July 2000 / Published online: 31 August 2000     

Color image encryption using skew tent map and hyper chaotic system of 6th-order CNN

The paper designs a color image encryption scheme based on skew tent map and hyper chaotic system of 6th-order CNN. The essence of the image encryption is to confuse and diffuse the pixels, the skew tent map is applied to generate the confusion sequence, and the hyper chaotic system of 6th-order CNN is applied to generate the diffusion sequence, for 6 state variables in the system, there are total 120 combinations. For each pixel of the plain image, one combination is chosen to encryption the red, green and blue components, and the combination is determined by one of the state variables. Each pixel is encrypted by the cipher value of the previous pixel and the combination value of the CNN system. Experimental results and security analysis demonstrate that the scheme can achieve good encryption result and larger key space, and can resist common attacks, so the scheme can be applied in secure communication to enhance the security of transmitting image.     

概念图--物理教学的有效工具

文章首先介绍了一般概念图的六个组成成分：概念、分支、水平层次、同一分支下概念间的连接线和连接语、不同分支下概念间的连接线和连接语、例子；在此基础上，总结了制作物理知识概念图的具体策略；而后从四个方面论述了概念图的教学功能：概念图作为先行组织者；概念图作为学生复习时整理知识的工具；概念图作为识别学生对知识的错误理解、知识欠缺和错误概念的工具；概念图作为评价学生知识理解的工具．     

On the behaviour of dispersion-managed soliton from the perspective of its energy components

We investigate the behaviour of dispersion-managed (DM) soliton from its energy. Using the variational analysis, it is possible to represent the energy of the DM soliton as a combination of three components, respectively, one component for the average dispersion of the optical fiber, second component for the local dispersion of the dispersion map and the third component for the Hamiltonian of the anomalous fiber section. From the results of the numerical simulations, we show that the Hamiltonian component of the DM soliton energy plays a vital role in the determination of its stability.     

Generalized Darboux maps and massless spin-s fields

We consider conformally invariant massless spin-s field equations on a spherically symmetrical space-time. Precisely when these equations are consistent appropriately defined field components are shown to satisfy wave equations related by a generalization of the classical Darboux map.     

Expectations of Fermionic Fields with N Components

In this Letter, we show with a concrete example that the behaviour in N independent components (flavours) of the expectation of fermionic fields can be different from that suggested by its expansion in terms of Feynman graphs. To prove this result, we study the asymptotic behaviour of a nonautonomous discrete time map.