随机参数Duffing系统中的随机混沌及其延迟反馈控制

研究了谐和激励下含有界随机参数Duffing系统(简称随机Duffing系统)中的随机混沌及其延迟反馈控制问题.借助Gegenbauer多项式逼近理论，将随机Duffing系统转化为与其等效的确定性非线性系统.这样，随机Duffing系统在谐和激励下的混沌响应及其控制问题就可借等效的确定性非线性系统来研究.分析阐明了随机混沌的主要特点，并采用Wolf算法计算等效确定性非线性系统的最大Lyapunov指数，以判别随机Duffing系统的动力学行为.数值计算表明，恰当选取不同的反馈强度和延迟时间，可分别达到抑制或诱发系统混沌的目的，说明延迟反馈技术对随机混沌控制也是十分有效的. 关键词： 随机Duffing系统 延迟反馈控制 随机混沌 Gegenbauer多项式     

D→Klv～l衰变过程的研究

用光锥QCD求和规则研究D→Klv～_l衰变过程，首先计算D→K跃迁形状因子，通过构造新的关联函数，消除了twist-3波函数的不确定性给计算结果所带来的影响，从而使计算结果更加精确. 计算得到的分支比与最近的实验数据相一致. 关键词： QCD光锥求和规则 D介子半轻衰变 分支比 形状因子     

CoNiZ系列合金的结构和马氏体相变性质

利用X射线衍射研究了CoNiZ(Z=Si,Sb,Sn,Ga等)合金在不同热处理条件下的相组成.当Z元素为Sn,Sb时,材料是完全的B2结构;但Z为Si时,材料变成面心立方的γ相.形成B2还是γ相由电子浓度和原子尺寸效应两种因素共同决定.而CoNiGa的研究结果表明,在合金中除了形成B2结构的同时还容易形成γ相,常表现出两相共存的特性.对材料进行不同方式的热处理可以使合金中两相的含量有所消长,γ相含量的多少对CoNiGa合金的马氏体相变有很大的影响.分析指出,两相共存及其所带来的物性变化是CoNiGa铁磁性形状记忆合金非常有利用价值的物理性质.     

耦合发电机系统的自适应控制与同步

讨论了耦合发电机系统的自适应控制和参数未知时的自适应同步问题.设计了自适应控制器，将耦合发电机系统的混沌轨道镇定到平衡点，并使得两个参数未知的耦合发电机系统达到了混沌同步.数值模拟验证了所设计的控制器的有效性. 关键词： 耦合发电机系统 自适应控制 平衡点 同步     

Plant tissue-based chemiluminescence biosensor for ethanol.

A plant tissue-based chemiluminescence biosensor for ethanol based on using mushroom (Agaricus bisporus) tissue as the recognition element is proposed in this paper. The principle for ethanol sensing relies on the luminol-potassium hexacyanoferrate(III)-hydrogen peroxide transducer reaction, in which hydrogen peroxide is produced from the ethanol enzymatic catalytic oxidation by oxygen under the catalysis of alcohol oxidase in the tissue column. Under optimum conditions, the method allowed the measurement of ethanol in the range of 0.001 - 2 mmol/l with a detection limit (3 sigma) of 0.2 micromol/l. The relative standard deviation (RSD) was 4.14% (n = 11) for 0.05 mmol/l ethanol. The proposed method has been applied to the determination of ethanol in biological fluids and beverages with satisfactory results.     

复合结构丝中的电流密度分布和巨磁阻抗效应

提出了由中间为高电导率的非铁磁性金属丝外面包裹一层铁磁材料组成的复合结构丝的电流 密度分布和巨磁阻抗(GMI)效应模型，并对Cu/FeCoNi复合丝进行了数值模拟. 结果表明：在 相同的磁性材料几何尺寸和磁特性时，Cu/FeCoNi复合丝铁磁层内的电流随频率的升高比匀 质FeCoNi铁磁丝内的电流更趋于表面分布，而且开始出现趋肤效应时对应的频率明显降低. 当在比较低的频率下就可以观察到明显的MI变化时，复合结构丝中的电阻和电抗变化主要是 由趋肤效应引起，趋肤效应仍然是引起复合结构材料(包括多层薄膜结构) 关键词： 电流密度 巨磁阻抗效应 趋肤效应     

Flicker noise in degenerately doped Si single crystals near the metal-insulator transition

In this paper we report some of the important results of experimental investigations of the flicker noise near the metal-insulator (MI) transition in doped silicon single crystals. This is the first comprehensive work to study low-frequency noise in heavily doped Si over an extensive temperature range (2 K<T<500 K). The measurements of conductance fluctuations (flicker noise) were carried out in the frequency range 10⁻²<f<4 × 10¹ Hz in single crystalline Si across the MI transition by doping with phosphorous and boron. The magnitude of noise in heavily doped Si is much larger than that seen in lightly doped Si over the whole temperature range. The extensive temperature range covered allowed us to detect two distinct noise mechanisms. At low temperatures (T<100 K) universal conductance fluctuations (UCF) dominate and the spectral dependence of the noise is determined by dephasing the electron from defects with two-levels (TLS). At higher temperatures (T>200 K) the noise arises from activated defect dynamics. As the MI transition is approached, the 1/f spectral power, typical of the metallic regime, gets modified by the presence of discrete Lorentzians which arise from generation-recombination process which is the characteristic of a semiconductor.     

Equitable Total Coloring of Graphs with Maximum Degree 3

 The equitable total chromatic number χr d q u o; _e (G) of a graph G is the smallest integer k for which G has a total k-coloring such that the number of vertices and edges in any two color classes differ by at most one. We prove in this paper that χr d q u o; _e (G)≤5 if G is a multigraph with maximum degree at most 3. Received: February 24, 2000 Final version received: February 2, 2001 Acknowledgments. The author would like to thank the referee for valuable suggestions to improve this work.