基于改进鱼群算法的几何约束求解

几何约束求解是CAD建模中的关键技术。针对求解质量不高和求解速度慢的问题,进行了研究。提出了一种鱼群算法和混沌算法相结合的几何约束求解方法。首先,将CAD模型中的几何约束关系表示为一组代数方程组;然后,利用代数方程组来构造目标函数。将几何约束求解问题转换为目标函数的优化问题。最后,使用混沌算法来改进鱼群算法以寻找目标函数的最优解。实验结果表明：该方法可以有效地解决几何约束问题。     

小型振动搅拌机的混沌特性

目的建立混凝土搅拌机系统力学模型与运动微分方程,分析系统运动状态．方法利用数值模拟的方法,在一定的参数下,以转速为分叉参数,结合波形图、轴心轨迹图和poincar6截面图,来分析搅拌机系统的混沌特性．结果当搅拌轴转速在工作转速范围内时,系统的宏观运动状态是周期1运动,而微观运动状态是无序的混沌运动,即系统的运动状态是周期运动中包含有比较强烈的混沌运动;当搅拌轴转速在工作转速范围之外时,系统的运动状态只是周期运动．结论在一定的参数数值下,混凝土搅拌机具有混沌运动特性,这种运动状态能较好地破坏水泥凝聚团,增加有效的碰撞次数,能有效地改善混凝土的微观匀质性．提高微观搅拌效果．     

一种混沌神经元系统的参数识别与控制

基于Lyapunov稳定性理论,解析地设计了一类状态观测器,对一类混沌神经元系统的参数进行了快速准确的识别,数值模拟证实了参数观测器的可靠性。进一步研究了参数跃变和慢周期变化下的识别问题,数值计算表明该方法仍然是有效的。     

一种基于三像素点分块的信息隐藏算法*

提出了一种新的空域隐藏算法。该算法利用三像素值之间的大小关系来隐藏信息,将载体图像分成包含三像素的小块,修改第一、第三像素值来调整大小关系;另外对秘密图像进行了Arnold置乱预处理,利用混沌序列进行间隔隐藏。实验表明,该算法实现容易、隐藏量大、安全性和不可见性好,当嵌入率达到98.8%,峰值信噪比PSNR＞38 dB。     

Bifurcation and chaos of the bladed overhang rotor system with squeeze film dampers

To study the nonlinear dynamic behavior of the bladed overhang rotor system with squeeze film damper (SFD), a blade-overhang rotor-SFD model is formulated using the lumped mass method and the Lagrange approach. The cavitated short bearing model is employed to describe the nonlinear oil force of the SFD. To reduce the scale of the nonlinear coupling system, a set of orthogonal transformations is employed to decouple the one nodal diameter equations of blades, which are coupled with the dy- namical equations ...     

一类离散动力系统的混沌研究

主要研究Kopel系统的混沌行为．首先,应用中心流形定理和分岔理论,证明了系统会发生倍周期分岔;然后,通过计算最大李雅普诺夫指数,确定了系统中混沌行为的存在;最后,数值模拟的结果显示了与理论分析的一致性．     

基于混沌粒子群支持向量回归的高炉铁水硅含量预测

参数的优化选择对支持向量回归算法(SVR)的预测精度和泛化能力影响显著,提出混沌粒子群优化算法(CPSO)寻优一种改进支持向量回归算法(v-SVR)参数的新方法,在此基础上建立高炉铁水硅含量预测模型(CPSO -vSVR)用于对某钢铁厂3号高炉铁水硅含量的实际数据进行预测,研究结果表明：基于CPSO确定的最优参数建立的铁水硅含量粒子群支持向量回归预测模型的预测效果最佳,平均相对误差为5.32%。与使用粒子群优化算法训练的神经网络(PSO-NN)、v-SVR、最小二乘支持向量回归(LS-SVR)进行比较,CPSO -vSVR模型对铁水硅含量进行预测时预测绝对误差小于0.03的样本数占总测试样本数的百分比达到90%以上,预测效果明显优于PSO-NN,且比v-SVR稳定性更强,可用于高炉铁水硅含量的实际预测。     

基于FPGA技术的数字混沌信号产生

为了产生数字混沌PN序列,提出了一种连续混沌的数字化技术。首先对连续的混沌系统离散化,然后在SIMULINC平台上借助于DSPBUILDER里的模块构建了该离散化混沌系统的模型,并通过MATLAB相图仿真以及QUARTUSⅡ里的时序仿真证实了设计的可行性。最后将工程中的HDL文件下载到FPGA芯片,在实验中获得了数字混沌PN序列。同时,利用D/A转换验证了这种数字化技术的精确性。     

Stochastic Chaos with Its Control and Synchronization

The discovery of chaos in the sixties of last century was a breakthrough in concept,revealing the truth that some disorder behavior,called chaos,could happen even in a deterministic nonlinear system under barely deterministic disturbance.After a series of serious studies,people begin to acknowledge that chaos is a specific type of steady state motion other than the conventional periodic and quasi-periodic ones,featuring a sensitive dependence on initial conditions,resulting from the intrinsic randomness of a nonlinear system itself.In fact,chaos is a collective phenomenon consisting of massive individual chaotic responses,corresponding to different initial conditions in phase space.Any two adjacent individual chaotic responses repel each other,thus causing not only the sensitive dependence on initial conditions but also the existence of at least one positive top Lyapunov exponent(TLE) for chaos.Meanwhile,all the sample responses share one common invariant set on the Poincaré map,called chaotic attractor,which every sample response visits from time to time ergodically.So far,the existence of at least one positive TLE is a commonly acknowledged remarkable feature of chaos.We know that there are various forms of uncertainties in the real world.In theoretical studies,people often use stochastic models to describe these uncertainties,such as random variables or random processes.Systems with random variables as their parameters or with random processes as their excitations are often called stochastic systems.No doubt,chaotic phenomena also exist in stochastic systems,which we call stochastic chaos to distinguish it from deterministic chaos in the deterministic system.Stochastic chaos reflects not only the intrinsic randomness of the nonlinear system but also the external random effects of the random parameter or the random excitation.Hence,stochastic chaos is also a collective massive phenomenon,corresponding not only to different initial conditions but also to different samples of the random parameter or the random excitation.Thus,the unique common feature of deterministic chaos and stochastic chaos is that they all have at least one positive top Lyapunov exponent for their chaotic motion.For analysis of random phenomena,one used to look for the PDFs(Probability Density Functions) of the ensemble random responses.However,it is a pity that PDF information is not favorable to studying repellency of the neighboring chaotic responses nor to calculating the related TLE,so we would rather study stochastic chaos through its sample responses.Moreover,since any sample of stochastic chaos is a deterministic one,we need not supplement any additional definition on stochastic chaos,just mentioning that every sample of stochastic chaos should be deterministic chaos.We are mainly concerned with the following two basic kinds of nonlinear stochastic systems,i.e.one with random variables as its parameters and one with ergodical random processes as its excitations.To solve the stochastic chaos problems of these two kinds of systems,we first transform the original stochastic system into their equivalent deterministic ones.Namely,we can transform the former stochastic system into an equivalent deterministic system in the sense of mean square approximation with respect to the random parameter space by the orthogonal polynomial approximation,and transform the latter one simply through replacing its ergodical random excitations by their representative deterministic samples.Having transformed the original stochastic chaos problem into the deterministic chaos problem of equivalent systems,we can use all the available effective methods for further chaos analysis.In this paper,we aim to review the state of art of studying stochastic chaos with its control and synchronization by the above-mentioned strategy.     

基于混沌的远程安全访问一次性口令认证模型

一次性口令认证(OTP)是为防止黑客通过一次成功的口令窃取而永久地获得系统访问权,而设计的一种认证技术.它规定用户每次登录时使用不同的口令,限制了同一口令的生存周期.本文在论述基于混沌的一次性口令认证的基本原理基础上,提出了一种基于混沌的远程安全访问一次性口令认证模型,并给出了模型的算法实现,解决了对远程安全访问中的用户鉴别问题.性能分析结果表明,本算法在混沌映射的基础上产生摘要信息,在较小代价上实现了系统安全强度的较大提升,较好地实现了安全性与易用性的平衡.