实现标量混沌信号同步控制的神经网络方法

本文给出了一种利用线性输出神经网络实现标量混沌信号同步控制的方法。该方法利用线性输出神经网络构造被控混沌系统的模型，并基于Lyapunov理论与非线性系统控制方法，设计出神经网络权值变化规律与非线性反馈控制器，使神经网络模型的标量输出能大范围同步于给定的标量混沌信号。理论分析与计算机模拟结果都证实了这种方法的有效性。     

基于混沌理论的汉语语音信号的分析与预测

目前语音信号的分析与预测都是采用线性理论和线性预测技术,而语音信号的产生系统是一个复杂的非线性时变系统,而且具有混沌性,所以采用线性方法是不够的.深入研究了汉语语音信号的非线性特性,包括相空间重构理论及延迟时间、嵌入维数等相空间重构参数的确定方法,并求解出汉语语音音素的李雅普诺夫指数、延迟时间、嵌入维数和关联维数,所得结果表明汉语语音信号既非确定性的信号,又非随机信号,而是具有混沌特性的信号;根据汉语语音音素的延迟时间及嵌入维数的均值确定RBF神经网络(Radical Basis Function Network)模型中三层网络的神经元个数,结合 RBF 神经网络分析方法构造了一个非线性预测模型.仿真结果表明:基于 RBF 神经网络构造的非线性预测模型与线性预测模型相比,预测误差明显减小,预测性能上有所提高.     

一种基于改进教学优化的微弱信号检测方法

为了快速准确地检测混沌背景中的微弱信号,提高网络泛化能力,文中利用改进教学优化算法优化贝叶斯回声状态网络的模型参数,提出了一种改进教学优化的混沌背景中微弱信号检测方法。通过建立混沌序列单步预测模型,分析预测误差的幅值,检测混沌背景中微弱瞬态信号和周期信号。对Lorenz系统和实测的海杂波数据进行实验研究,验证预测模型的有效性,结果表明,贝叶斯回声状态网络模型的预测结果比支持向量机和径向基神经网络模型的均方根误差降低了2个数量级,缩短了预测时间,提高了预测精度和预测效率,能快速有效地检测混沌背景中微弱信号,且具有更低的门限。     

基于混沌预测的雷达微弱目标检测研究综述

传统的雷达目标检测是将海杂波建模为随机过程,而最新的研究成果表明海杂波具有混沌特性,从而可将海杂波建模为非线性混沌模型。基于混沌预测检测微弱雷达目标信号是根据杂波信号和目标信号的动力学差异。通过海杂波训练预测器,假如待测信号当中含有雷达目标信号,则预测误差会突然增大,从而检测出目标信号。文章主要介绍了基于混沌预测检测雷达微弱目标在检测原理、国内外的研究现状以及未来的发展趋势。     

混沌背景中微弱信号检测的回声状态网络方法

对复杂非线性系统的相空间重构理论进行了研究分析,提出了混沌背景中微弱信号检测的回声状态网络方法。针对回声状态网络模型参数选取困难这一问题,采用遗传算法对其模型参数进行优化。将回声状态网络模型参数作为遗传算法的个体,混沌时间序列预测均方根误差的倒数作为适应度函数,通过选择、交叉、变异等操作获得适合数据特点的最优模型参数。根据回声状态网络强大的学习和非线性处理能力,利用得到的回声状态网络模型最优参数建立混沌背景噪声的单步预测模型,将淹没在混沌背景噪声中的微弱瞬态信号和周期信号从预测误差中检测出来。以Lorenz系统和实测的海杂波数据作为混沌背景噪声进行仿真实验,仿真结果表明,本文所提方法在预测精度和训练速度方面均优于支持向量机和神经网络模型,能够有效地检测出混沌背景噪声中的微弱目标信号,且具有较小的预测误差。      

应用混沌优化方法的月用电量预测

利用混沌运动的初值敏感性、遍历性、随机性等特点。通过对混沌优化搜索过程的分析，提出了基于混沌优化方法的月用电量预测模型。在此基础上，应用混沌优化方法确定月用电量预测模型参数，给出了具体实现步骤。实际月用电量预测的结果表明：此模型能够更为快速、准确地预测月用电量。     

基于混沌调频信号的超宽带穿墙SAR成像

混沌调频信号具有良好的自相关特性,又类似随机信号,具有较强的抗干扰性能。该文将基于Bernoulli映射的混沌调频信号用于超宽带穿墙雷达成像,建立了信号模型,分析了混沌调频穿墙雷达系统的目标检测性能,分辨能力和抗墙壁多径干扰能力,并与线性调频雷达系统进行了比较。仿真结果表明,与线性调频信号相比,混沌调频信号用于穿墙雷达系统可获得较好的目标检测性能,更好的分辨能力,而且具有抗墙壁多径干扰能力。     

基于粒子滤波的混沌时间序列局域多步预测

对混沌时间序列进行预测研究具有重要的价值和实用性,例如,进行股票预测,降雨量预测,温度预测。混沌时间序列预测的难点在于其不确定性和多步预测的困难性。一般利用最小二乘法求解模型参数,从而对混沌时间序列进行局域预测,但是预测精度不是很高。为了提高局域线性预测的精度,提出基于粒子滤波(PF)的混沌时间序列局域多步预测法,利用粒子滤波进行参数优化得到更准确的优化模型进行多步预测。仿真实验结果表明,该方法的单步和多步预测效果明显得到了提升。     

噪声对信号混沌特性的影响研究与分析

基于Lorenz混沌系统模型,用小数据量方法计算研究了噪声对信号混沌特性的影响.通过对不同信噪比下的混沌吸引子及相关参数仿真结果进行深入对比分析与研究,得出结论:噪声强度增加,时间延迟减小,嵌入维数增加,Lyapunov指数波动变大,信号混沌特性变弱,混沌系统的可预测时间减小,使混沌信号重构更困难.对抑制混沌信号噪声方...     

宽带混沌信号在汽车防撞雷达中的应用

随着汽车用量的增长，汽车防撞雷达对提高交通安全性有着极其晕要的现实意义，而传统的线性调频连续波雷达体制中存在着严重的多用户同频电磁干扰问题。由于宽带混沌信号具有良好的相关特性，文中提出了数字处理方式的宽带混沌调频连续波雷达，采用混沌调频信号来代替传统的线性调频信号的方案，结果显示它很好地解决丁加性高斯白噪声干扰和多用户间的交叉干扰问题；系统利用了离散混沌序列驱动连续混沌系统产生宽带混沌信号的方法，其电路结构简单，所得频谱平坦宽阔，在汽车防撞雷达和其他雷达、通信系统中具有很好的应用前景。     

Optimal nonlinear filtering for independent increment processes--Part I

A new formulation of the multidimensional optimal nonlinear filtering problem is presented in this two-part paper. This formulation permits generalization and unification of some well-known recent results on optimal nonlinear filtering theory. [1]-[7] Specifically, the problem investigated is that of determining the conditional probability density function ofx(t)given{y(tau); t_{0} leq tau leq t}, wherex(t)is then-dimensional state vector of a non-linear system perturbed by an independent increment noise process, andy(t)is anm-dimensional measurement vector which is a nonlinear function ofxand contains an additive independent increment noise process. The results are obtained through use of characteristic functions and the theory of independent increment processes. The foundation for the treatment of general independent increment noise processes is given in Part I, but the final results in Part I are restricted to Gaussian independent increment noise processes. The extension to general independent increment noise processes is considered in Part II. It is shown in Part I that the results for the linear-Gaussian case can be obtained in two different ways, one of which cannot be used for the general case. Some important properties of general independent increment processes and a special property of Gaussian independent increment processes are discussed.     

Kinetics simulation of high-power gas lasers

Numerical simulation of high-power gas lasers requires the integration of a variety of numerical techniques; simultaneous solutions must be obtained to a large set of ordinary differential equations, and several nonlinear partial differential equations. A family of codes employing similar methods has been devised and has demonstrated remarkable success in predicting laser performance over a broad range of parameters. We describe here the appropriate techniques for dealing with gas kinetic equations, the steady-state Boltzmann equation, and physical optics. Modeling of bothe-beam pumped ande-beam sustained discharge-pumped lasers is described; complex electron kinetic processes are included. Results are shown for both krypton-fluoride and xenon-fluoride lasers.     

若干弱光非线性光学效应及其应用

简要介绍了弱光非线性光学领域中一些研究方向的进展,如弱光非线性光子学材料中的缺陷结构、介观量子相干系统中光传播动力学和慢光非线性光学等,着重描述了近期在新型激子与紫外弱光非线性光学效应、位相耦合与光速调控以及非相干空间孤子阵列诱导光学晶格与光非线性传输行为等研究中得到的研究结果。弱光非线性光学将成为非线性光学应用领域中的一个重要分支。     

A note invalidating some recent stability conjectures

Some recent stability conjectures for second- and third-order nonlinear systems [1], [2] are shown to be incorrectly analyzed, and thus the assertions obtained are misleading and false in general.     

Tunable alexandrite lasers: Development and performance

Some major recent developments in alexandrite laser research are reviewed. Emphasis is placed on key material characteristics, and their relationship to laser performance. Alexandrite's favorable thermomechanical properties and high capacity for energy storage have led to laser performance levels that, in certain areas, exceed those of established solid-state laser sources. Here we review performance achievements for a variety of pulsed and CW laser configurations including single-mode, multimode, and mode-locked resonators, high-power amplifiers, and zig-zag slabs. In these configurations, operating performance levels have been demonstrated that are comparable to those of older, more familiar solid-state laser technologies. Alexandrite's broad tunability offers additional advantages. Together with nonlinear frequency conversion processes, alexandrite lasers provide high-brightness output over most of the UV, visible, and near IR.     

Analysis of free processes in time varying circuit by means of generalized characteristic equations method

Developing methods of analysis of free processes in time varying circuit is important both for time varying and nonlinear radio circuits. The principle of linear connection brings together processes in time varying and nonlinear circuits. It is of special interest to extend the existing methods developed for radio circuits with stable parameters to time varying circuits. This article is devoted to one of such methods-the method of characteristic equations for differential equations with fixed factors.     

The effects of small contaminating signals in nonlinear elements used in frequency synthesis and conversion

Many electronic systems use nonlinear elements to add or subtract two frequencies or to multiply or divide a frequency by an integer. Some level of contamination by small undesired signals is always present and the ability to predict the effects produced by their passage through the nonlinear elements is important in analyzing system performance. These effects can often be predicted, for frequency mixing (addition and subtraction), multiplication and division, by decomposition of the contaminating signal into equivalent AM and FM sidebands whose effects are more easily estimated. One important effect that occurs in frequency division is a sampling process which translates the frequencies of the interfering signals. A method for predicting these effects is explained and experimental results, demonstrating the application and applicability of the method, are reported.     

On nonlinear fractional Klein-Gordon equation

Numerical methods are used to find exact solution for the nonlinear differential equations. In the last decades Iterative methods have been used for solving fractional differential equations. In this paper, the Homotopy perturbation method has been successively applied for finding approximate analytical solutions of the fractional nonlinear Klein-Gordon equation can be used as numerical algorithm. The behavior of solutions and the effects of different values of fractional order α are shown graphically. Some examples are given to show ability of the method for solving the fractional nonlinear equation.     

适应频繁波动特点的移动话务量预测系统

移动通信话务量的时间序列具有较强的非线性和随机性，易受各种突发情况的影响。特别是在有频繁剧烈变动的情况下，很难用传统的预测方法进行预测。本文根据移动通信话务量的这一特点，采用分解及建模的方法，对话务量进行综合预测，经实践可以达到更好的效果。     

State-dependent vector hybrid linear and nonlinear ARMA modeling: Applications

In a recent companion paper, a new method has been presented for modeling general vector nonstationary and nonlinear processes based on a state-dependent vector hybrid linear and nonlinear autoregressive moving average (SVH-ARMA) model. This paper discusses some potential applications of the SVH-ARMA model, including signal filtering, time series prediction, and system control. First, a state-space model governed by a hidden Markov Chain is shown to be equivalent to the SVH-ARMA model. Based on this state-space model, the extended Kalman filtering and Bayesian estimation techniques are applied for noisy signal enhancement. The result of a noisy image enhancement verifies that the model can track the time-varying statistical characteristics of nonstationary and nonlinear processes adaptively. Second, the SVH-ARMA model is used for a vector time series prediction, which can attain more accurate multiple step ahead prediction, than conventional forecasting methods. Third, a new technique is developed for predicting scalar long correlation time series in the wavelet scale space domain based on the SVH-ARMA model. Dyadic wavelet transform is employed to convert a scalar time series to a vector time series, to which the SVH-ARMA model is applied for vector time series prediction. More accurate and robust forecasting results in both one step and multiple step ahead prediction can be gained. See also the companion paper on theory, by Zheng et al., pp. 551–574, this issue.