在周期性热源强迫下,非线性大气强迫波振幅的非周期和准周期振荡——无耗散系统

本文从一个斜压稳定的非线性系统出发,在一个随时间周期变化的外源作用下,通过近共振强迫不稳定,讨论波幅振荡的动力学。第一部分,首先分析热强迫系统中的线性共振条件和弱非线性共振问题,然后解出无耗散动力系统中的大、小振幅两类周期解。当外源在两类不同的周期解的存在域内变化时,系统出现不规则的非周期振荡,即所谓“混沌”现象。     

颗粒流体系统的非线性行为

该文讨论颖粒流体系统的研究现状和可能的发展方向。认为非线性行为是实现颖粒流体系统定量化的难点所在,它可分为来源于颖粒流体相互作用的内在非线性和来源于外界影响和非理想物性的次生非线性。内在非线性引起系统内的自组织现象、分支现象和混沌运动,次生非线性则使得内在非线性的分析更加复杂。提出了认识非线性行为的两种可能途径:(1)把系统进行多方面的分解,即运动分解为极值和动态,能耗分解为可逆和耗散,过程分解为有序和无序,结构分解为不同尺度;(2)将该系统处理为尺度差别很大的两种介质的相互作用并进行计算机图形仿真。     

混沌系统的变量变化率反馈控制方法研究

设计了一种控制连续非线性系统中混沌的新方法--变量变化率脉冲反馈(VRPF)方法.介绍了VRPF方法的控制原理以及反馈系数和脉冲间隔的选择技巧.将此方法应用到BZ反应3D模型系统混沌的控制中,计算机仿真模拟显示,通过恰当地选择反馈系数和脉冲间隔,可以将系统稳定在1p、2p、3p、4p、…、2n×3mp (n、m为整数)这样不同的周期轨道,从而使系统的功率谱也由混沌态时的连续谱转变为具有分立单峰的分立谱.此外,仿真模拟还发现VRPF方法具有极宽的控制域.     

基于模糊最小二乘支持向量机的蒸发过程预测控制研究

针对氧化铝蒸发过程的多变量、非线性和大滞后特点及不同时间和空间样本数据不同的特征,提出了基于末位淘汰机制的混沌粒子群算法的综合加权模糊最小二乘支持向量机蒸发过程预测控制方法.用变异混沌粒子群算法对模型预测控制进行滚动优化,计算出最优控制序列.以某氧化铝厂蒸发过程生产数据进行实验验证分析,结果表明: 模型预测结果中相对误差小于8%的样本达到93.9%,出口浓度稳定在240 g/L附近,其控制性能得到显著改善,同时也起到了降低能耗的目的.     

具有双稳态的化学反应中的涨落现象

化学反应中的非线性动力学行为一直受到人们的普遍的关注[1-3]Schlogl等人[4,5]曾用两个自催化反应模式说明连续的二级相变和不连续的一级相变特征．而在文献[6，7]中，我们提出在具有双稳态的化学反应中，存在类一级与类二级相变之间的转变点，而此转变点也具有类似Landau二级     

一种控制化学混沌的新方法--在全混沌区的非线性人工神经网络偶然微扰反馈控制

提出了一种控制化学混沌的新方法以稳定控制不稳定周期轨道 (UPO) .这是一种偶然比例反馈控制 (OPF)战略的扩展 ,它克服了OPF局限性 ,即OPF控制律的线性限制 ,并扩展到全混沌区 .本方法利用反传人工神经网络 (BP ANN)来表达非线性控制律 ,以增加控制的鲁棒性 .其有效性通过一个混沌自催化反应模型的数值模拟进行了检验 .     

一种控制化学混沌的新方法

提出了一种控制化学混沌的新方法以稳定控制不稳定周期轨道(UPO).　这是一种偶然比例反馈控制(OPF)战略的扩展,它克服了OPF局限性,即OPF控制律的线性限制,并扩展到全混沌区.　本方法利用反传人工神经网络(BP-ANN)来表达非线性控制律,以增加控制的鲁棒性.　其有效性通过一个混沌自催化反应模型的数值模拟进行了检验.     

金属有机电荷转移盐(CpFeBz)n[M(L)2](L=mnt或dmit)的合成及其三阶非线性光学性质

合成了两种类型共九个新的金属有机电荷转移盐(CpFeBz)n[M(mnt)2]和(CpFeBz)n[M.(dmit)2](M=Ni, Pd, Pt,Cu, Co; Cp代表环戊二烯基; Bz代表苯; 通过元素分析、IR和1H NMR对化合物进行了鉴定。用简并四波混频的方法首次研究了金属有机电荷转移盐的三阶非线性光学性质。结果表明, 这类金属有机电荷转移有较大的近共振三阶非线性光学响应。     

金属有机电荷转移盐(CpFeBz)n[M(L)2](L=mnt或dmit)的合成及其三阶非线性光学性质

合成了两种类型共九个新的金属有机电荷转移盐(CpFeBz)_n[M(mnt)_2]和(CpFeBz)_n[M·(dmit)_2](M=Ni,Pd,Pt,Cu,Co;Cp代表环戊二烯基;Bz代表苯;mnt代表(?);dmit代表(?);n=1或2).通过元素分析IR和~1H NMR对化合物进行了鉴定.用简并四波混频的方法首次研究了金属有机电荷转移盐的三阶非线性光学性质.结果表明,这类金属有机电荷转移盐有较大的近共振三阶非线性光学响应.     

实验控制Belousov-Zhabotinsky-CSTR化学混沌反应

用两种方法来控制在连续流动釜式反应器(CSTR)中的Belousov-Zhabotinsky(BZ)化学混沌反应:(1)自适应延迟时间反馈控制方案;(2)线性自相互作用控制方案。第一种控制方案是一种微扰控制,并能将BZ-CSTR化学混沌稳定控制到其内嵌的不稳定周期轨道(UPO)上去。这种方法的优越之外可以由系统延迟时间的自适应调节得以显示。第二种控制方案可以驱动BZ-CSTR混沌动力学到达一系列规则的动力学状态,这些动力学状态可能并不是混沌轨道中内嵌的本征轨道。在控制BZ-CSTR化学混沌反应的实验中,这两种方案显示出了很大的灵活性和有效性。     

Reentrant onset of chaos in tubular image states

We investigate the reentrant onset of chaos in "tubular image states," which are loosely bound states of electrons formed in the vicinity (20-40 nm) of conducting nanotubes. Chaos is shown to arise when an electron is placed in the vicinity of two metallic nanotubess with a magnetic field applied along the tubes. At stronger magnetic fields B approximately 10 T, we observe the formation of Landau-like states encircling the two-tube system, which wipe out the chaos. We can reinstall the chaos by charging oppositely the nanotubes, thus breaking the symmetry of the system and correspondingly the shape of the Landau-like states. Detailed analysis of the onset of chaos is done by studying the statistical properties of the eigenvalues spectrum and by investigating the spatial autocorrelation functions of individual eigenstates.     

Chaos Synchronization in the Belousov-Zhabotinsky Chemical Reaction by Self-Adaptive Parameter Adjustment Scheme

Employing the self-adaptive parameter adjustment scheme, the chaotic dynamical behaviors in the coupled Belousove-Zhabotinsky-CSTR chemical system were investigated numerically. The confirmation of synchronization is using the criteria of maximum transverse Lyapunov exponent. The results show that when all the variables are involved in the parameter adjustment rule, the chaos synchronization between the response and the target systems were obtain. However, as only some of the variables can be detected easily in the real experiment, there are difficulties in employing this scheme experimentally. Therefore, that scheme to investigate the role of single variable separately were modified. The results show that no chaos synchronization can be obtained when Br- and HBrO2 are used separately, except when Ce4+ and BrMA are used. However, there is no easy way to detect BrMA in the experiment, Ce4+ becomes the unique feasible variable involved in the adjustment role. Besides, the synchronization efficiency of different combinations of stiff constant and damping constants has been studied by means of synchronization-arriving time.     

PO反应中混沌控制的变量交叉反馈方法研究

The variable cross feedback（VCF）method is proposed to control the nonlinear chaos system. The control principle is introduced,and the Peroxidase-Oxidase（PO）system is taken as a typical example to demonstrate the effectiveness of this method. The dynamical behaviors of the PO system controlled using the VCF method are given by computer numerical simulation. The results show that the return map of the system can be changed into the finite isolated points from the assemblage of discrete points having regular distribution and structure by appropriately     

Study on Electrochemical Fingerprints and Identification of Different Varieties of Rice and Mouldy Rice by B‐Z Oscillation Reaction System

The electrochemical fingerprints of different varieties of rice and mouldy rice were studied by Belousov‐Zhabotinskii (B‐Z) oscillation reaction system with malonic acid as dissipative material under the condition of constant temperature. The results indicated that the chemical composition of rice may influence the kinetic parameters of the B‐Z oscillation reaction, which lead to the electrochemical fingerprint characteristic parameters and the intuitive information changes obviously. The varieties of rice and mouldy rice can be identified and evaluated by the difference of the electrochemical characteristic information.     

化学自催化混沌反应模型中的耦合作用与混沌同步

选用混沌自催化反应作为子系统,构造了耦合自催化反应系统,研究了耦合变量、耦合系数对混沌动力学行为的影响,给出了不同耦合系数下系统的动力学特征,探讨了耦合作用机制.结果表明,耦合作用能明显地改变子系统的动力学行为,强化系统间的相关性.耦合后的混沌运动受到调整与抑制,耦合强度加大时,呈现出混沌运动轨线的周期化,耦合系数大于临界值,两子系统实现了完全的同步.不同变量的耦合时,影响最大的是第二种变量.对于三种物质均有耦合时,更容易出现混沌的抑制、运动状态的锁相与周期化和混沌的完全同步.     

Total synthesis of (-)-saliniketals A and B

A stereocontrolled total synthesis of the orthinine decarboxylase inhibitors saliniketals A and B is described. Key features of the 17-step route include the use of two boron aldol/reduction sequences to control six of the nine stereocenters, an intramolecular Wacker-type cyclization to install the bicyclic acetal core, and a late-stage Stille coupling to append the requisite (2 Z,4 E)-dienamide.     

Flow-induced control of chemical turbulence

We report spatiotemporal chaos in the Oregonator model of the Belousov-Zhabotinsky reaction. Spatiotemporal chaos spontaneously develops in a regime, where the underlying local dynamics show stable limit cycle oscillations (diffusion-induced turbulence). We show that spatiotemporal chaos can be suppressed by a unidirectional flow in the system. With increasing flow velocity, we observe a transition scenario from spatiotemporal chaos via a regime of travelling waves to a stationary steady state. At large flow velocities, we recover the known regime of flow distributed oscillations.     

A novel chaos control strategy for discrete-time Brusselator models

This article deals with the dynamical analysis of discrete-time Brusselator models. Euler’s forward and nonstandard difference schemes are implemented for discretization of Brusselator system. We investigate the local dynamics related to equilibria of both discrete-time models. Furthermore, with the help of bifurcation theory and center manifold theorem, explicit parametric conditions for directions and existence of flip and Hopf bifurcations are investigated. A novel chaos control method is implemented in order to control chaos in discrete-time Brusselator models under the influence of flip and Hopf bifurcations. Numerical simulations are provided to illustrate theoretical discussion and effectiveness of newly introduced chaos control strategy.     

Study of Lotka-volterra food chain chemostat with periodically varying dilution rate

In this paper, we introduce and study a model of Lotka-volterra chemostat food chain chemostat with periodically varying dilution rate, which contains with predator, prey, and substrate. We investigate the subsystem with substrate and prey and study the stability of the periodic solutions, which are the boundary periodic solutions of the system. The stability analysis of the boundary periodic solution yields an invasion threshold. By use of standard techniques of bifurcation theory, we prove that above this threshold there are periodic oscillations in substrate, prey, and predator. Simple cycles may give way to chaos in a cascade of period-doubling bifurcations. Furthermore, we numerically simulate a model with sinusoidal dilution rate, by comparing bifurcation diagrams with different bifurcation parameters, we can see that the system experiences following process: periodic solution → periodic doubling cascade → chaos.