Chaotic Motion Analysis for a Coupled Magnetic-Flow-Mechanical Model of the Rectangular Conductive Thin Plate

The chaotic motion behavior of the rectangular conductive thin plate that is simply supported on four sides by airflow andmechanical external excitation in a magnetic field is studied.According to Kirchhoff’s thin plate theory,considering geometric nonlinearity and using the principle of virtualwork,the nonlinearmotion partial differential equation of the rectangular conductive thin plate is deduced.Using the separate variable method and Galerkin’s method,the system motion partial differential equation is converted into the general equation of the Duffing equation;the Hamilton system is introduced,and the Melnikov function is used to analyze the Hamilton system,and obtain the critical surface for the existence of chaos.The bifurcation diagram,phase portrait,time history response and Poincarémap of the vibration system are obtained by numerical simulation,and the correctness is demonstrated.The results showthatwhen the ratio of external excitation amplitude to damping coefficient is higher than the critical surface,the system will enter chaotic state.The chaotic motion of the rectangular conductive thin plate is affected by different magnetic field distributions and airflow.

融合历史记忆的单纯形引导鲸鱼优化算法

针对鲸鱼优化算法存在易陷入局部最优、收敛速度慢等缺点,提出一种融合历史记忆的单纯形引导鲸鱼优化算法。首先,为了避免初始化种群过于集中而陷入局部最优,提出了使用混沌映射对初始化种群进行改进,增加了种群多样性;其次,为了解决算法收敛精度低和收敛速度慢的问题,提出了融合历史记忆的单纯形引导策略,利用单纯形法和构建的历史记忆表求解出一个虚拟最优解作为下次随机搜索阶段的引导者,帮助种群在前期的勘探过程中进行细致地搜索;最后提出一种新的非线性参数策略,平衡算法的开发和勘探能力。将算法应用于12个典型的复杂函数优化问题,并与其他5种智能算法比较,实验结果表明,改进后的算法在收敛精度与速度方面均为第一,具有良好的全局搜索能力和局部开发能力。

基于双通道生成对抗网络的城市用电负荷缺失数据补全方法

用电负荷数据的完整性与有效性在负荷预测等应用中具有重要意义。传统的缺失数据补全方法缺乏对用电负荷和多种外部时空关联信息的挖掘,难以获得高精度的补全结果。文中提出了一种双通道生成对抗网络,对缺失的负荷数据进行补全。首先,根据负荷的周期性变化特征和时空关联性构建三阶负荷张量,并将影响负荷变化的多种外部因素构建为三阶辅助信息张量。然后,为满足两种张量的双输入需求,在生成对抗网络的输入层引入双通道机制,通过卷积与反卷积运算提取张量的特征;为提升网络对张量数据的训练效果和补全精度,将张量分解损失引入原始损失函数,并采用改进的混沌映射粒子群优化算法联合优化超参数和网络。最后,在真实负荷数据集上开展数据补全实验。结果表明,所提方法能够对随机缺失率不超过50%、连续缺失不超过3天的负荷数据进行准确补全。

考虑运营成本和用户体验的电动汽车充电站布局优化模型

针对电动汽车充电站布局优化问题,综合考虑充电站建设运营成本和交通流量变化情况下的用户体验,据此建立充电站布局优化模型。先分析充电站城市土地转让成本、基建及充电设备成本、运营成本各项构成要素,并建立相应的数学模型,再结合交通拥堵指数建立用户体验数学模型,最终以满足充电站建设运营成本最低和用户体验最优为预期目标,建立充电站布局优化模型。引入Tent混沌映射对初始解空间进行均布化,采用AVOA优化算法对该模型进行问题求解。仿真结果表明:与对比文献模型相比,新的充电站选址方案与随机产生的需求点距离更近、更平均;在典型测试场景下,新选址方案可有效降低配电网络的网损率、提升充电站效能,并能为用户提供更优的用户体验,充分说明该模型能够较好解决充电站优化布局问题。

数字图像混沌序列抽样加权强置乱算法仿真

数字图像置乱关系到个人隐私和信息安全问题,为了保护图像中的敏感信息,提出一种基于位交换和混沌优化的数字图像置乱算法。使用散列函数获得数字图像明文的密钥流,采用与明文相关的子密钥推导像素初始值,通过非线性交叉生成位交换算子,增强明文信息敏感性;运用Logistic方程得到混沌序列,引入抽样加权方法提高图像置乱强度,采用混合蛙跳方法按照族群划分实施信息传输,将混沌序列内的实数从小到大排列,初始混沌抽样后构成的混沌序列用于图像中,显著提升图像置乱强度,完成数字图像置乱。仿真结果表明,上述方法拥有极高的安全性和优秀的加密性能,可以为数字图像在各领域的安全使用提供可靠借鉴。

Control and Stabilization of Chaotic System Based on Linear Feedback Control Method

In this paper, two kinds of chaotic systems are controlled respectively with and without time-delay to eliminate their chaotic behaviors. First of all, according to the first-order approximation method and the stabilization condition of the linear system, one linear feedback controller is structured to control the chaotic system without time-delay, its chaotic behavior is eliminated and stabilized to its equilibrium. After that, based on the first-order approximation method, the Lyapunov stability theorem, and the matrix inequality theory, the other linear feedback controller is structured to control the chaotic system with time-delay and make it stabilized at its equilibrium. Finally, two numerical examples are given to illustrate the correctness and effectiveness of the two linear feedback controllers.

基于混沌优化算法的列车动力学模型参数辨识

针对列车动力学参数未知问题,设计基于混沌优化算法的非线性列车模型参数辨识方法。将高速列车参数估计问题转化为优化问题,给出混沌优化参数估计框架,采用变尺度优化方法,在搜索进程中不断缩小优化变量的搜索空间及二次搜索调节系数,提高搜索精度。计算机仿真验证算法的有效性和可行性,基本混沌优化算法的参数辨识相对误差较遗传算法提高26.8%,基于变尺度混沌优化算法的参数辨识相对误差较基本算法提高了48.7%。

CHAOTIC BEHAVIOR ON REDUCTION OF PERTURBED KdV EQUATION IN FORM OF PARAMETRIC EXCITATION

The chaotic dynamic behaviors of a reduction of perturbed Korteweg-de Vries （KdV） equation in form of a parametric excitation are studied. Chaotic behaviors from homoclinic crossings are analyzed with an improved Melnikov method and are compared for the systems with a periodically external excitation, with a linear periodically parametric excitation, or with a nonlinear periodically excitation. The critical curves separating chaotic regions and non-chaotic regions of the above systems are different from each other. Especially, a dead frequency is presented for the system with a nonlinear periodically parametric excitation. The chaos excited at the frequency does not occur no matter how large the excitation amplitude is. A time integration scheme is used to find the numerical solutions of these systems. Numerical results agree with the analytical ones.

人字齿行星齿轮系统激励参数二维域界特性

为探究人字齿行星齿轮系统激励参数二维域界特性,课题组构建了系统的平移-扭转动力学模型,运用Runge-Kutta法对消除刚体位移和量纲一化的系统微分方程组进行数值求解,基于离散空间域胞映射法绘制了啮合阻尼比与太阳轮输入转速和太阳轮输入功率构成的二维域界图,并结合位移分岔图、FFT频谱图、相图和Poincaré映射对系统激励参数二维域界特性进行分析。结果表明:在满足系统工况条件下,适当增大啮合阻尼比可使系统由混沌运动转变为周期运动;啮合阻尼比较小时,系统对太阳轮输入转速变化敏感,提高太阳轮输入转速可使系统进入稳定1周期运动,减轻系统振动响应;太阳轮输入功率较小时,系统处于大范围混沌运动区域,通过增加太阳轮输入功率,系统更趋向于稳定周期运动,提高系统运行稳定性。研究结果可为人字齿行星齿轮系统选择稳定运行的激励参数范围提供参考。

基于混沌时域反射技术的电力电缆绝缘缺陷检测方法

为提高电力电缆绝缘缺陷检测的精度,提出一种基于混沌时域反射技术的电力电缆绝缘缺陷检测方法。采用变分模态分解方法将噪声信号在不同的模态分量中分解,通过自适应小波包分解将电力电缆信号分解在高低频分量中,使用阈值法将不含有局部信号的分量过滤处理,完成信号去噪处理。信号经过去噪处理后,通过混沌时域反射技术将电力电缆信号划分为参考信号和探测信号,根据信号和电力电缆绝缘位置故障点的反射信号完成采样处理,在相关峰的时间延迟以及幅值信息中获取缺陷发生的位置,判断故障类型,进而实现电力电缆绝缘缺陷检测。经实验测试结果表明,所提方法可以全面提升检测结果的准确性。

基于CPSO方法的伺服系统故障树诊断分析

采用单一诊断方法无法达到合理的故障诊断率,综合故障树分析(FTA)与混沌粒子群(CPSO)方法相结合的方式可较好实现故障诊断。从实际测试信号角度出发,并与人工神经网络(ANN)与粒子群(PSO)方法结果进行对比。结果表明:CPSO方法故障诊断准确率获得比ANN高出7.55%,比PSO高出5.18%,实现了准确率的显著提升。CPSO方法 200次迭代后达到稳定适应值,可以在最短时间内完成迭代,有效避免产生局部极值问题,大幅提升了诊断精度。该研究可以拓展到其他机械信号测试领域,具有很好的应用价值。

A Study of Weak Laser-DNA Molecule Interaction and Its Chaotic Behaviour

The motion equations with the effect of laser-deoxyribonucleic acid(DNA)molecule interaction are advanced.The chaotic behaviour about these equations were studied by Afelnikov’s method.It is found that DNA molecule system can turn into chaotic state under the weak laser action.This result is helpful for the explanation of laser-induced biological genetic variation effect.

Artificial Bee Colony Algorithm-based Parameter Estimation of Fractional-order Chaotic System with Time Delay

It is an important issue to estimate parameters of fractional-order chaotic systems in nonlinear science, which has received increasing interest in recent years. In this paper, time delay and fractional order as well as system's parameters are concerned by treating the time delay and fractional order as additional parameters. The parameter estimation is converted into a multi-dimensional optimization problem. A new scheme based on artificial bee colony ABC algorithm is proposed to solve the optimization problem. Numerical experiments are performed on two typical time-delay fractional-order chaotic systems to verify the effectiveness of the proposed method. © 2014 Chinese Association of Automation.

Optical Image Encryption Based on Mixed Chaotic Maps and Single-Shot Digital Holography

Random phase masks play a key role in optical image encryption schemes based on double random phase technique. In this paper, a mixed chaotic method is proposed, which can efficiently solve some weaknesses that one-dimensional (1-D) single chaotic maps encounter to generate random phase masks. Based on the chaotic random phase masks, optical image encryption and decryption are realized with a single-shot digital holographic technique. In the proposed encryption scheme, the initial value and parameters of mixed chaotic maps serve as secret keys, which is convenient for the key management and transmission. Moreover, it also possesses high resistance against statistical attack, brute-force attack, noise attack and shear attack. Simulation results and security analysis verify the validity and security of the proposed encryption scheme. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

A new look at the response surface method for reliability analysis using chaos theory

To overcome excessive computation errors and convergence failures encountered in an iterative calculation of the reliability index using the response surface method （RSM） for some nonlinear limit state functions, this study investigates an essential factor based on chaotic dynamics theory. The bifurcation diagrams of the reliability index are presented for some typical nonlinear limit state functions, and the computation results from the mapping functions due to the RSM iterations show the complicated dynamic phenomena such as the periodic oscillation, as well as bifurcation and chaos. From the numerical examples, it is concluded that the parameter of selection range fplays an important role in the convergence of the RSM iteration, and an improved RSM iterative algorithm is proposed with regard to the incorporation of the iterative sequential function of selection rangef The proposed method is shown to be efficient and to yield accurate results.

H∞ synchronization of chaotic neural networks with time-varying delays

In this paper, we investigate the problem of H∞ synchronization for chaotic neural networks with time-varying delays. A new model of the networks with disturbances in both master and slave systems is presented. By constructing a suitable Lyapunov–Krasovskii functional and using a reciprocally convex approach, a novel H∞ synchronization criterion for the networks concerned is established in terms of linear matrix inequalities （LMIs） which can be easily solved by various effective optimization algorithms. Two numerical examples are given to illustrate the effectiveness of the proposed method.

Breaking chaotic shift key communication via adaptive key identification

This paper proposes an adaptive parameter identification method for breaking chaotic shift key communication from the transmitted signal in public channel. The sensitive dependence property of chaos on parameter mismatch is used for chaos adaptive synchronization and parameter identification. An index function about the synchronization error is defined and conjugate gradient method is used to minimize the index function and to search the transmitter＇s parameter （key）. By using proposed method, secure key is recovered from transmitted signal generated by low dimensional chaos and hyper chaos switching communication. Multi-parameters can also be identified from the transmitted signal with noise.

Hopf bifurcation control of a Pan-like chaotic system

This paper is concerned with the Hopf bifurcation control of a modified Pan-like chaotic system. Based on the Routh-Hurwtiz theory and high-dimensional Hopf bifurcation theory, the existence and stability of the Hopf bifurcation depending on selected values of the system parameters are studied. The region of the stability for the Hopf bifurcation is investigated.By the hybrid control method, a nonlinear controller is designed for changing the Hopf bifurcation point and expanding the range of the stability. Discussions show that with the change of parameters of the controller, the Hopf bifurcation emerges at an expected location with predicted properties and the range of the Hopf bifurcation stability is expanded. Finally,numerical simulation is provided to confirm the analytic results.

Ergodic sensitivity analysis of one-dimensional chaotic maps

Sensitivity analysis in chaotic dynamical systems is a challenging task from a computational point of view.In this work,we present a numerical investigation of a novel approach,known as the space-split sensitivity or S3 algorithm.The S3 algorithm is an ergodic-averaging method to differentiate statistics in ergodic,chaotic systems,rigorously based on the theory of hyperbolic dynamics.We illustrate S3 on one-dimensional chaotic maps,revealing its computational advantage over na?ve finite difference computations of the same statistical response.In addition,we provide an intuitive explanation of the key components of the S3 algorithm,including the density gradient function.

NOISE-INDUCED CHAOTIC MOTIONS IN HAMILTONIAN SYSTEMS WITH SLOW-VARYING PARAMETERS

This paper studies chaotic motions in quasi-integrable Hamiltonian systems with slow-varying parameters under both harmonic and noise excitations. Based on the dynamic theory and some assumptions of excited noises, an extended form of the stochastic Melnikov method is presented. Using this extended method, the homoclinic bifurcations and chaotic behavior of a nonlinear Hamiltonian system with weak feed-back control under both harmonic and Gaussian white noise excitations are analyzed in detail. It is shown that the addition of stochastic excitations can make the parameter threshold value for the occurrence of chaotic motions vary in a wider region. Therefore, chaotic motions may arise easily in the system. By the Monte-Carlo method, the numerical results for the time-history and the maximum Lyapunov exponents of an example system are finally given to illustrate that the presented method is effective.