液固及气液固三相并流系统的动力学行为和混沌产生的研究

运用时域、频域、吸引子及混沌特征参数相关维和Kolmogrov熵研究了液固并流系统动力学行为,揭示了液固并流系统是由拟周期过渡到混沌的。在拟周期行为的液固并流系统中引入气体,结果表明:低气速下,床层中只有冠状气泡,它表现为拟周期行为。随着气速的增大,床层中小气泡的出现及浆料湍动的作用使拟周期冠状气泡过渡为混沌,进而整个系统通向了混沌。     

分布参数系统中混沌的控制

提出了分布参数系统中混沌行为控制的方法．这一方法只要求过程的动态测量值而不要求关于过程的数学模型．首先,利用Karhunen-Loeve法即特征主元分析法把分布参数系统中混沌的时空模式分解为不随时间变化的空间模式和随时间变化的时序系数．随后,在Poincare截面上应用首回映射确定具有主要能量的特征空间模式的控制设定值．最后,运用负反馈策略和“系统松弛”技术控制混沌系统．以两个模拟反应器为例,考察了化工过程中由扩散引起的分别由两类不同途径产生的混沌行为的控制．仿真结果表明,该方法能镇定混沌系统而变为一周期系统．对于周期倍增系统,控制得到的被稳定周期即为混沌吸引子中所期望的不稳定一周期;而对于准周期倍增系统,则存在一定的偏差．     

垂直上升管中油水两相流流型表征

在含水率 5 1%～ 91%、油水两相流总流量 10～ 6 0m³·d^-1范围内 ,对垂直上升油水两相流流动工况的电导波动信号进行了分形及混沌时间序列分析 .当含水率为 6 0 .5 %～ 91%时 ,所提取的分形维数及吸引子相关维分别在 1.0 0 6～ 1.6 31及 4.30～ 6 .77之间 ;当含水率为 5 1%或 5 1.5 %时 ,所提取的分形维数及吸引子相关维分别在 1.17～ 1.75 8及 5 .46～ 7.0 5之间 ,且分形维数及混沌吸引子相关维数随总流量呈不规则突变 ,并与复杂功率谱特征及流型图上的过渡流型相对应 ,表明了分形维数及混沌吸引子相关维数对油水两相流流型变化具有敏感的“指示器”特性     

分数阶和整数阶混沌系统的投影同步

介绍了一种新的三维分数阶混沌系统,通过理论解析、Lyapunov指数与维数求解以及变换分数阶混沌系统阶数时,系统相图和吸引子的变化情况验证了该系统是混沌的。通过研究追踪信号的理念和模拟整数阶混沌同步控制器的原理,发现了一个新的非线性控制器。理论推导和Matlab实例仿真结果表明:该非线性控制器可使分数阶混沌系统与同维整数阶混沌系统之间具有良好的投影同步效果。     

气液固三相并流系统流型的混沌识别

运用确定性混沌分析技术，研究了气液固三相并流系统散式鼓泡流、聚式鼓泡流、柱塞流、泡沫流及环状流压力波动信号的混沌动力学行为。结果表明，吸引子可以用来表征气液固三相并流系统的动力学行为，混沌特征参数相关维D2和K熵可以用来定量识别以上五种流型。以混沌定量识别为基础，给出了三相并流系统的流型图。     

氯碱电解槽内压力波动的混沌分析及流型识别

为研究氯碱电解槽内气液两相流动的压力波动特性和流型特点，对冷模电解槽阳极室内循环板上开口处的压力信号进行了混沌特性分析；利用高速摄像仪照相法及Kolmogorov熵下降法对流动形态进行了识别，绘制了流型图；利用流型图对不同电流密度下的两相流型进行了判定。结果表明，电解槽压力信号的吸引子具有分数维数，当电流密度大于6 kA·m^-2时，Lyapunov指数大于0，说明电解槽内两相流动具有混沌特性；对于测压点位置及电解槽下部，当电流密度小于5 kA·m^-2时，分别为射流充分发展段和孤立气泡流；电流密度为5 ~ 8 kA·m^-2时为射流过渡段和合并气泡流；电流密度大于8 kA·m^-2时为射流的初始段和合并气泡流。     

油水两相流流型混沌吸引子形态特性

基于在垂直上升管中采集到的61组油水两相流电导波动信号,通过在混沌吸引子域中放置参考截面方法,考察了混沌吸引子形态特征量与油水两相流流型转变之间的关系,发现水包油流型在3阶及4阶吸引子矩特征量平面上分布相对稳定,而过渡流型在3阶吸引子矩特征量平面上呈不规则剧烈变化,在4阶吸引子矩特征量平面上呈线性变化。研究结果表明,油水两相流混沌吸引子形态特征量对流型转化敏感,有助于理解油水两相流流型转化的非线性动力学机制。     

印制PVC墙纸用(甲基)丙烯酸酯乳液光油

考察了聚合工艺、N-羟甲基丙烯酰胺(NMA)，甲基丙烯酸二甲氨基乙酯(DMAEMA)、甲琏丙烯酸甲酯(MMA)及乳化剂等原材料的用量对印制PVC墙纸用乳液光油及涂膜性能的影响。研究结果表明采用改进型半连续种子乳液聚合工艺能制得粒径为35．6nm，粒径分散性为0．133的乳液，DMAEMA能明显抑制合成含羧酸基和N-羟甲基的聚合物过程中N-羟甲基的自缩聚反应．提高涂膜性能；当ω(NMA)=2％～4％．ω(DMAEMA)=0．5％～1％．ω(MMA)=60％～70％，ω(乳化利)=2%～4％时制得的罩光油在PVC底材表面具有优异的光泽度、润湿性、附着性以及耐高温热粘性。     

颗粒流体系统的流域特性及其混沌行为

应用混沌动力学方法研究了颗粒流体系统的流域特性以及流域之间的过渡，从奇异吸引子图及波动频率、平均绝对偏差（ＡＡＤ）、Ｋｏｌｍｏｇｏｒｏｖ熵（Ｋ）和相关维数（Ｄ）等动力学参数的角度出发，论证了系统随气速增大依次出现颗粒控制的固定床（Ｐａｒｔｉｃｌｅ－Ｄｏｍｉｎａｔｉｎｇ，ＰＤ）、颗粒流体协调的流化床（Ｐａｒｔｉｃｌｅ－Ｆｌｕｉｄ－Ｃｏｍｐｒｏｍｉｓｉｎｇ，ＰＦＣ）和流体控制的稀相输送（Ｆｌｕｉｄ－Ｄｏｍｉｎａｔｉｎｇ，ＦＤ）等不同流域，讨论了流域之间的过渡。     

挤出过程物料停留时间分布的在线测量和模型

采用荧光检测方法在线测量了同向双螺杆挤出机中物料的停留时间分布(τ)，研究了示踪剂浓度和电压信号强度的关系以及螺杆转速(ω)和喂料速率(Q)对双螺杆挤出机τ的影响，比较了多级理想混合(TIS)模型、回流多级理想混合(BFC)模型和双回流多级理想混合(DBFC)模型描述该挤出机的符合程度。结果表明，当9为10．0～16．0kg/h，ω为60～120r／min时，示踪剂浓度和电压信号具有线性关系；ω和Q对平均停留时间有显著的影响，对轴向混合强度的影响不明显。BFC模型和DBFC模型适合描述双螺杆挤出机的流动状况，而TIS模型偏差较大。     

Chloride ion influencing potential oscillation generated by formaldehyde oxidation

The effect of chloride ions (10⁻⁷ to 10⁻¹ M) on the potential oscillation generated by the oxidation of formaldehyde is investigated with polycrystalline platinum at 315 K in a sulfuric acid solution containing 0.1 M formaldehyde. When the chloride ion concentration is 10⁻⁵ M or lower, between the two current regions for the appearance of relaxational oscillations, a large-amplitude trapezoidal oscillation appears, which is alternately accompanied by a relaxational one at a lower current. At a still lower current, the relaxational oscillation changes to a sinusoidal one, which then produces a well-known chaos. When the chloride ion concentration is between 10⁻⁴ and 3 × 10⁻⁴ M, the relaxational oscillations disappear and the alternating oscillation shows chaos, the properties of which are different from those of the chaos already stated. When the chloride ion concentration is 10⁻³ M or greater, a simple large-amplitude trapezoidal oscillation prevails without alternation with the relaxational one, along with much less chaos. The surface adsorption state during the various observed oscillations is discussed on the basis of voltammograms measured at various chloride ion concentrations.     

Potential oscillation generated by formaldehyde oxidation in the presence of dissolved oxygen

The influence of dissolved oxygen on the potential oscillation patterns is investigated during the oxidation of 0.1 M formaldehyde on polycrystalline platinum in an acidic solution at 315 K under galvanostatic conditions. We have found that, with increasing dissolved oxygen concentration from 0 to 1 mM, chaotic oscillations persist to appear as well as periodic ones, both oscillations show fluctuations in their amplitude and the period length doubles. Voltammograms show that a current peak appears at ca. 0.6 V and becomes large, which is found to be due to the oxidation of the adsorbed CO with oxygen but not due to the slowing down of the formation velocity of the adsorbed CO. The results are discussed regarding the conditions for the appearance of chaos.     

氧浓度强制振荡下的丙烯氨氧化反应过程

<正>自从70年代初有学者对催化反应过程的强制振荡操作进行实验研究以来,人们已越来越注意到,对于某些催化反应过程,采用合适的强制周期振荡操作条件比相应的稳态操作产生更优的反应效果,尤其是一些催化氧化反应过程,国内外已有许多研究者开展了大量的实验研究,发现在一定强制振荡周期及振幅操作下能显著提高反应速率（转化率）、主产物的选择性及收率。同时,有许多周期性反应体系的数学模拟理论研究也表明强制振荡操作能     

A FOUR-VARIABLE CHAOTIC CHEMICAL REACTION

A four-variable reaction system, consisting of a three variable chaos producing subsystem and a weakly coupled fourth variable, is presented. Considering the slow fourth variable as a parameter, the amplitude of the three-variable chaotic subsystem abruptly changes from a small to a large value without hysteresis. The fourth variable is made dependent on the mean value of this amplitude, so that a superimposed slow oscillation results. A Poincaré cross section and a set of Lyapunov characteristic exponents are presented. The question of the dimensionality of the attractor is discussed.     

Dynamical modeling of chaos single‐screw extruder and its three‐dimensional numerical analysis

The Chaos Screw (CS) nonlinear dynamical model is proposed to describe the development of chaos in a single‐screw extrusion process and the model is verified by three‐dimensional numerical simulations. The only‐barrier channel is the unperturbed Hamiltonian system, which consists of two homoclinic orbits and nested elliptic tori of nonlinear oscillation in periodic (extended) state space. A periodically inserted no‐barrier zone represents a perturbation. For small perturbations, homoclinic tangle leads to the Cantor set near the homoclinic fixed point and elliptic rotations are changed into the resonance bands or KAM tori, depending on the commensurability of frequency ratio of the corresponding orbits. A finite element method of multivariant Q?1+PO elements is applied to solve the velocity fields and a 4th order Runge‐Kutta method is used for the particle tracing. The resulting Poincaré section verifies the proposed dynamical model, showing the resonance band corresponding to rotation number 1/3 under small perturbations. As the strength of perturbation increases, the Poincaré sections indicate wider stochastic regions in which random particle motions take place.     

Residence time distribution measurements in a pulsed baffled tube bundle

Experimental flow pattern and associated residence time distribution measurements are reported for a tube bundle where periodic baffles and fluid oscillation may be present. When there is no fluid oscillation, high Reynolds number flow conditions are required to give sharp residence time distributions. When baffles are present, fluid oscillation can give sharp residence time distributions for modest low net flow Reynolds numbers. These observations extend our previous results and also show the viability of the system, for example in use as a reactor or heat exchanger where a multi-tube configuration might be required.     

Altering oscillatory dynamics of an electrochemical system using external forcing

We report results (numerical and experimental) indicating control of observed oscillatory dynamics in an electrochemical system under the influence of superimposed sinusoidal forcing. By varying the frequency and amplitude of the external forcing (control parameters) not only were the chaotic dynamics converted to periodic states (controlling chaos via entrainment), but the period-1 (P1) behavior could also be transformed to oscillatory dynamics of higher periodicity (for example: P2). Therefore for appropriate values of control constants and nature of the unperturbed (periodic and/or chaotic) dynamics, a final state of either lower (chaos→P1) or higher complexity (P1→P2) can be attained. Since no prior information regarding the system dynamics is required for implementation of the forcing control it is thus relevant for application to real systems.     

强制浓度周期振荡对丙烯部分氧化反应的影响

研究了强制浓度周期振荡对丙烯在 Mo-Co-Bi 氧化物催化剂上部分氧化制丙烯醛的影响。实验考察了在不同强制振荡周期与振幅下的丙烯转化率和丙烯醛选择性及收率的变化,并与稳态反应条件下的结果作了比较。发现丙烯浓度的各种脉冲方式及氧浓度的微量脉冲方式均可改善反应性能,但氧浓度的全脉冲方式效果不佳。对强制周期操作效应的机理作了探讨。     

支承松动的转子-滚动轴承系统的分岔与混沌

根据转子动力学、非线性动力学及Hertz理论,建立了带有一端支座松动故障的滚动轴承—转子系统的非线性动力学模型。通过数值积分和Poincare映射方法对其非线性动力学行为进行了数值仿真研究,给出了系统响应随转子转动频率变化的分岔图和一些典型的轴心轨迹图及Poincarc截面图,并分析了转动频率对转子系统动力学行为的影响。结论表明,转子在滚动轴承和支承松动这两种非线性因素作用下,具有周期运动、拟周期运动、混沌运动和倍周期分岔等复杂的动力学行为。