Periodically varied initial offset boosting behaviors in a memristive system with cosine memductance

A four-dimensional memristive system is constructed using a novel ideal memristor with cosine memductance. Due to the special memductance nonlinearity, this memristive system has a line equilibrium set(0, 0, 0, δ) located along the coordinate of the inner state variable of the memristor, whose stability is periodically varied with a change of δ. Nonlinear and one-dimensional initial offset boosting behaviors, which are triggered by not only the initial condition of the memristor but also other two initial conditions, are numerically uncovered. Specifically, a wide variety of coexisting attractors with different positions and topological structures are revealed along the boosting route. Finally, circuit simulations are performed by Power SIMulation(PSIM) to confirm the unique dynamical features.

Dynamic analysis,FPGA implementation,and cryptographic application of an autonomous 5D chaotic system with offset boosting

An autonomous five-dimensional(5D)system with offset boosting is constructed by modifying the well-known three-dimensional autonomous Liu and Chen system.Equilibrium points of the proposed autonomous 5D system are found and its stability is analyzed.The proposed system includes Hopf bifurcation,periodic attractors,quasi-periodic attractors,a one-scroll chaotic attractor,a double-scroll chaotic attractor,coexisting attractors,the bistability phenomenon,offset boosting with partial amplitude control,reverse period-doubling,and an intermittency route to chaos.Using a field programmable gate array(FPGA),the proposed autonomous 5D system is implemented and the phase portraits are presented to check the numerical simulation results.The chaotic attractors and coexistence of the attractors generated by the FPGA implementation of the proposed system have good qualitative agreement with those found during the numerical simulation.Finally,a sound data encryption and communication system based on the proposed autonomous 5D chaotic system is designed and illustrated through a numerical example.

忆阻超混沌映射的可调控性设计及光纤保密通信系统构建

通过引入平方忆阻函数非线性反馈,构建离散超混沌映射,并实现超混沌序列的全局调幅、局部调幅以及直接偏置调控。混沌映射的可调控性通过离散忆阻的阻值函数和内部变量积分速度来实现。简易的忆阻约束关系同时赋予了直接偏置调控的可能性,通过额外引入常数项参数可实现一维状态变量的直接偏置调控。基于RISC-V单片机CH32V307实现了所提出的可调控超混沌映射,并通过美国国家标准与技术研究院测试证明了超混沌序列的伪随机属性。基于以上超混沌映射构建了正交啁啾复用-非正交多址接入物理层加密方案,实验完成了2 km弱耦合七芯光纤通信的误码率测试,进一步证明了基于离散忆阻构建的超混沌加密正交啁啾复用-非正交多址接入系统可实现数据的可靠传输和解密,有效保护数据安全。

含大范围参数四维混沌系统的吸引子共存

为确保图像加密和保密通信中信息安全传输,在YANG和CHENG构造的三维混沌系统基础上增加1维,提出改进的四维混沌系统.使用分岔图和Lyapunov指数谱对该系统进行动力学分析,证明该系统存在大范围参数混沌特性.通过改变系统初值,得到周期与周期、周期与拟周期、混沌与混沌多种吸引子共存.多角度观察相图和Poincare截面图,发现系统参数k能够控制吸引子在相空间中的伸缩,且当k到一定值后吸引子相图会停止缩小.通过对新系统设计偏移升压控制器,表明系统在工程应用中能改变信号极性.对新系统采用NIST测试方法,结果表明新系统具有良好伪随机性.研究结果说明新系统在实际应用中具有较大的潜在价值.

无线电能传输系统基于Buck-Boost拓扑的最大功率传输研究

近年来,无线电能传输(WPT)技术迅速发展,并广泛应用于消费领域。影响无线电能系统传输效率有诸多因素,如负载变化、线圈偏移、频率分裂等。为解决接收端负载变化引起系统传输效率降低的问题,在接收端串入Buck-Boost电路拓扑,并建立WPT系统电路数学模型以及线圈偏移模型,推导线圈偏移互感关系式,最后通过仿真得到线圈同轴模型系统和线圈偏移模型系统传输功率与占空比对应的关系图。仿真结果表明调节Buck-Boost电路占空比可保证负载变化时线圈同轴模型系统和线圈偏移模型系统均可实现系统的最大传输功率,证明串入Buck-Boost电路拓扑结构可降低负载变化对传输效率的影响。

一个新的具有超级多稳态的五维忆阻超混沌系统

为了描述更加复杂的非线性动力学特性并且得到更适合工程应用的混沌信号,使用一个磁控忆阻器去替换改进的四维Lü混沌系统中的耦合参数,得到了一个新的五维忆阻超混沌系统。采用相图、分岔图、Lyapunov指数谱等常规的非线性分析手段研究新系统丰富的动力学特性。在新系统的基础上,通过引入一个绝对值函数使系统达到新的极性平衡,构建了一个新的条件对称的忆阻超混沌系统。结果表明:新的忆阻系统可以表现出依赖于忆阻器初始状态的超级多稳态特性、持续的混沌或超混沌动力学以及偏移增量控制行为;特别地,当改变系统参数并取适当的初始状态时,可以观察到独特的共存超级多稳态现象;新的条件对称忆阻系统可产生无限多对具有相反极性且吸引子结构相似的共存吸引子。利用Multisim进行电路仿真,验证了系统的存在性和可实现性,从而使超混沌系统能更好地应用在保密通信等实际工程领域。

Linear synchronization and circuit implementation of chaotic system with complete amplitude control

Although chaotic signals are considered to have great potential applications in radar and communication engineering, their broadband spectrum makes it difficult to design an applicable amplifier or an attenuator for amplitude conditioning. Moreover, the transformation between a unipolar signal and a bipolar signal is often required. In this paper, a more intelligent hardware implementation based on field programmable analog array （FPAA） is constructed for chaotic systems with complete amplitude control. Firstly, two chaotic systems with complete amplitude control are introduced, one of which has the property of offset boosting with total amplitude control, while the other has offset boosting and a parameter for partial control. Both cases can achieve complete amplitude control including amplitude rescaling and offset boosting. Secondly, linear synchronization is established based on the special structure of chaotic system. Finally, experimental circuits are constructed on an FPAA where the predicted amplitude control is realized through only two independent configurable analog module （CAM） gain values.

Embedding any desired number of coexisting attractors in memristive system

A simple variable-boostable system is selected as the structure for hosting an arbitrarily defined memristor for chaos producing.The derived three-dimensional(3-D)memristive chaotic system shows its distinct property of offset,amplitude and frequency control.Owing its merits any desired number of coexisting attractors are embedded by means of attractor doubling and self-reproducing based on function-oriented offset boosting.In this circumstance two classes of control gates are found:one determines the number of coexisting attractors resorting to the independent offset controller while the other is the initial condition selecting any one of them.Circuit simulation gives a consistent output with theoretically predicted embedded attractors.

一种具有共存吸引子的超混沌系统的动力学分析

提出了一个具有共存吸引子的新五维超混沌系统,系统无平衡点,因此具有隐藏吸引子.通过Lyapunov指数谱、分岔图、相轨迹图、Poincaré截面、参数盘等动力学分析,系统呈现出从周期、倍周期到混沌、超混沌的动力学行为,同时系统具有对称不变性.在参数不变仅改变初值的情况下,系统出现周期与超混沌吸引子共存、周期与混沌吸引子共存.该系统可以引入两个偏置,使吸引子能同时在两个方向上平移.通过参数盘的分析可见,在平移过程中吸引子类型发生了改变,而且具有超混沌与周期吸引子共存特性.改变初值和偏置两种情况均产生共存吸引子,进一步体现出该系统具有复杂的动力学特性.

基于BRT的森林旅游地游客碳补偿意愿及其影响因素分析——以明月山国家森林公园为例

在全球气候变化日益加剧,极端气候频繁,倡导低碳经济的背景下,碳补偿的展开将带来生态、经济、社会等多重效益,作为利益相关者之一的游客,其行为意愿对于碳补偿市场的发展起着重要作用。基于对255位江西省明月山国家森林公园游客的有效问卷调查及访谈,运用描述性统计及增强回归树模型,分析游客碳补偿意愿及其影响因素。结果表明,职业、文化程度、气候变化感知度、是否知道森林具有固碳作用、对森林碳汇及其交易渠道的了解程度、是否认为旅游碳排放减少有利于生态环境等因素与森林旅游地游客碳补偿参与意愿具有显著的相关性。

一种10位200ksps双模式循环型模数转换器的设计

为解决大多数循环型(cyclic)模数转换器(analog-to-digital convertor, ADC)不能实现双输入模式的问题,提出了一种10位的可实现单端和差分两种输入模式的cyclic ADC结构.采用RSD算法,实现对比较器阈值偏差的修正,提出一种两级自补偿结合增益自举的改进型运放结构,在实现高增益的同时,能够保证输出结果不受环路失调影响.仿真结果表明在5.2 MHz工作时钟和2.5 V电源电压下,提出的cyclic ADC实现了200 ksps的转换速度,信噪比60.98 dB,有效位数9.8 bit,功耗4.97 mW,版图面积0.059 mm2.研究结论表明该电路有较高的转换速度和精度,且由于能够实现单端和差分两种输入模式,使得该电路的适用范围得到了扩展.

基于梯度提升回归树的发酵过程软测量研究

生物发酵过程的优化控制需要很多变量的参与,其中有许多无法实现实时在线测量。对此,论文结合群体智能算法和机器学习技术,提出了一种基于梯度提升回归树的发酵过程软测量方法,同时利用果蝇算法对回归树的关键参数进行寻优,以及偏移补偿技术对模型输出值进行校正。以Pensim仿真平台所得的青霉素发酵数据检验论文方法的效果,结果表明,该方法的预测精度在5.42%以内,明显优于BPNN、SVR、AdaBoost和RF方法,对发酵过程的关键变量预测有指导意义。

忆阻Hopfield神经网络的初值位移调控动力学及其图像加密应用

利用改进的多稳态忆阻器模拟神经元耦合突触,提出一种忆阻Hopfield神经网络(HNN)模型。用分岔图、Lyapunov指数谱、相图、庞加莱截面等对其动力学行为进行理论分析与数值仿真。结果表明:该忆阻HNN不仅能够产生不同拓扑结构的混沌吸引子,而且能够产生高度依赖忆阻初值的位移调控动力学行为。最后,基于该忆阻HNN设计一种混沌图像加密系统,重点分析系统的直方图、相关性、信息裔以及密钥敏感性。结果表明:所设计的图像加密算法能够有效抵抗各种内外统计分析攻击,具有较高的安全性。

具有隐藏超级多稳态的新5维忆阻超混沌系统的动力学分析

为进一步研究忆阻器及其应用,提出了一个具有隐藏吸引子的光滑5维忆阻超混沌系统,通过绘制相图和李雅普诺夫指数谱,验证了系统的混沌特征。分析了系统的分岔参数,实现了对两个状态变量的偏移增量控制,进行了吸引子的调幅分析。在此系统中发现了基于初值的超级多稳态现象。揭示了当初值分别沿着x轴、u轴及x-u平面内的不同直线移动时,关于吸引子偏移增量控制的新现象。最后,建立了系统的非线性电路模拟方程,验证了所提出的磁通控制忆阻系统物理实现的可行性。