Lyapunov指数混沌特性判定研究

探讨了Lyapunov指数混沌特性判据原理，分析了时间序列Lyapunov指数的计算过程，通过计算我国上证综合指数收益率时间序列的Lyapunov指数谱系，分析了我国资本市场的混沌特性。     

双频调制的单环铒光纤激光器的混沌产生和同步

首先通过对单环掺铒光纤激光器的损耗进行双频调制研究其混沌的产生,数值结果表明:通过适当地调节双频正弦信号的幅值和频率,该系统可以进入混沌状态,给出了进入混沌状态的途径和混沌态的参数区间.然后利用混沌信号驱动法研究了双频调制的单环铒光纤激光器的混沌同步,结果表明,无论两个双频调制的单环铒光纤激光器被驱动前处于混沌状态还是周期状态,只要在适当的驱动强度下使最大条件李指数为负,就能实现这两个单环铒光纤激光器的混沌同步.     

小世界模型的个体决策微粒群算法

微粒群算法是一种模拟动物行为的群智能优化算法.由于微粒(个体)在不同环境中生存与觅食,积累了不同的经验,因此不同个体在觅食或者其他行为中会做出不同的决策,但是这种决策机制在标准微粒群算法中并没有体现出来.微粒在决策时会考虑周围其它粒子的信息,因此本文通过引入个体决策机制与小世界模型的邻域结构来改进微粒群算法,同时利用李雅普诺夫稳定性理论对改进的算法进行稳定性分析,并给出相应的参数选择方式.在改进的微粒群算法中,微粒被周围理想微粒的位置和群体最优位置所吸引,改变了传统微粒群算法只被群体最优位置吸引的弊端.对常用的几个测试函数进行仿真,与其它两种改进的微粒群算法相比,结果表明该算法有更好的性能.     

基于RBF网络的动力系统Lyapunov指数的计算方法

提出一种基于径向基函数(RBF)神经网络的动力系统Lyapunov指数计算方法，设计了一个RBF网络结构，推导了基于RBF网络的Lyapunov指数计算公式．仿真实验表明，与其它现有方法相比，此方法计算精度较高，收敛速度较快，而且只需要较少的样本数据量．本方法能更准确、更快速地计算动力系统的Lyapunov指数．     

基于纳米压痕的氧化镓不同晶面的蠕变特性

使用Berkovich压头,采用恒载荷法对氧化镓的(100)及(010)晶面进行纳米压痕试验,通过数据拟合获得氧化镓晶体的蠕变应力指数.单晶氧化镓(100)晶面的蠕变应力指数范围在15.5～27.8,(010)晶面的蠕变应力指数范围在46.1～63.4.纳米压痕法能够有效测量氧化镓的蠕变变形量;氧化镓的2个晶面均呈现了...     

一个新自治混沌系统的动力学分析

为产生复杂的混沌信号用于混沌保密通讯,构造了一个不同于经典的Lorenz系统、Chen系统和L系统的三维连续自治混沌系统,该系统含有二个参数,二个非线性项.利用理论分析和数值仿真、Lyapunov指数谱、分岔图、相图、时间响应和功率谱等非线性动力学分析方法,研究了新混沌系统的一些基本动力学特性.分析结果表明,该混沌系统具有丰富的动力学行为,并能通过一个常数控制器控制到稳定的周期轨道.     

一种用于感应电机控制的新型滑模速度观测器研究

提出一种新颖的用于感应电机控制的滑模速度观测器。与传统的滑模速度观测器相比,此观测器具有结构简单、新颖、易于实现的特点,且有效消除了在无速度传感器的电机控制系统中,运用滑模观测器所固有的高频速度抖动现象。该观测器利用电压和电流信号构成观测器估计电机转速、转子磁通值及转子磁通位置,其理论的正确性由李雅普诺夫理论证明。将其运用于采用磁场定向矢量控制方法的无速度传感器感应电机控制系统,实验证明在整个调速范围内都取得了良好的效果,系统具有良好的稳态精度及动态响应性能。     

Constructing hyperchaotic systems at will

Over the last two decades, chaotification has received increasing attention from various communities of science and engineering. This paper aims at developing a unified chaotification framework for generating desired higher‐dimensional dissipative hyperchaotic systems by using a single‐parameter controller. The main idea is to use a block diagonal matrix in the design of the nominal system, so as to construct a desired hyperchaotic system. Specifically, the proposed scheme is to assign desired closed‐loop poles to the controlled system, allocating the corresponding numbers of eigenvalues with positive real parts at two types of saddle‐focus equilibria. For the non‐degenerate case, the number of positive Lyapunov exponents of the controlled system is given by the largest number of positive Lyapunov exponents of the desired hyperchaotic system. Two representative examples are given to illustrate and verify the proposed design method. Finally, the digital signal processor is employed to implement the above 10‐dimensional hyperchaotic systems, and the experimental observation is also given. Copyright © 2015 John Wiley & Sons, Ltd.     

空间相关的二维海杂波仿真与混沌评估

在舰载雷达设计和性能评估的过程中,海杂波的仿真模拟是必需的。根据实际雷达回波的信号形式,使用ZMNL法产生距离和方位均统计相关的二维海杂波数据。混沌特性可以用来描述实测海杂波数据,因此使用分形维数和最大Lyapunov指数来评估仿真数据与实测数据的相似程度,从非线性角度描述了二维仿真海杂波的实用性。     

Chaotic mixing behavior of non-Newtonian fluid intensified by multilayer rigid-flexible impeller induced flow field interface instability

The traditional multilayer rigid impeller has large dead zone for the mixing of pseudoplastic non-Newtonian fluid, stable flow field interface and low mixing efficiency. A method for enhancing the chaotic mixing of non-Newtonian fluid by multilayer rigid-flexible impeller induced flow field interface instability was proposed. In the experiment, sodium carboxymethylcellulose was used as the non-Newtonian fluid system. The power characteristics were measured by the torque sensor. The mixing time was determined by the acid-base neutralization and decolorization method. The largest Lyapunov exponents were calculated by using Matlab software programming. The chaotic characteristics and mixing performance in the mixing process are analyzed. The results show that when the combination mode was RF-(PBTD+PBTD+DT), the impeller arrangement mode θ=60°, and the flexible sheet length installation ratio r=0.8, 1.2, the degree of chaos was higher and the mixing performance was better. Multilayer rigid-flexible impeller can generate multiple spiral flows, and realize the flow field interface instability under the disturbance frequency difference of the flexible sheet between the layers, the stirring dead zone was reduced, and the system enters a chaotic state at a lower speed (when the multilayer rigid-flexible impeller system N>88 r/min, LLE>0; when the multilayer rigid impeller system N>125 r/min, LLE>0). At the same speed, the mixing rate and power per unit volume of the multilayer rigid-flexible combined impeller are higher than that of the multilayer rigid impeller, but the mixing energy per unit volume is approximately the same.