Extremal dynamics of the generalized Hutchinson equation

A scalar nonlinear differential-difference equation with two delays that generalizes Hutchinson’s equation is considered. The bifurcation of self-oscillations of this equation from the zero equilibrium is studied in the extremal situation when one delay is asymptotically large while the other parameters are on the order of unity. Analytical methods combined with numerical techniques are used to show that the well-known buffer phenomenon occurs in the equation in this case. This means that an arbitrary finite number of different attractors coexist in the phase space of the equation with suitably chosen parameters.     

光伏碲镉汞探测器在波段内连续激光辐照下的非线性响应机理研究

利用波段内连续激光, 辐照禁带宽度为0.33 eV的中波光伏碲镉汞探测器. 实验结果表明, 随着辐照激光光强的逐渐增大, 探测器从线性响应过渡为非线性响应. 当探测器进入非线性状态, 探测器的开路电压随激光光强的增大而减小, 且在激光开启辐照时开路电压信号迅速下跳, 在激光停止辐照时开路电压信号迅速上跳. 通过考虑激光辐照下探测器的温度场分布以及温度对p-n结内建电场的影响, 结合考虑机械快门在开启和关闭时对激光光强变化的影响, 建立了光伏探测器在波段内连续激光辐照下的解析模型, 模型计算结果与实验结果吻合得较好. 研究表明, 激光辐照过程中的非线性响应, 主要由温度对p-n结内建电场的影响决定, 激光开启和关闭时的开路电压的幅值是由光强和温度共同决定.     

加长棒脉冲钕玻璃激光器异常实验现象理论研究

以激光原理为基础, 以大量精确的实验数据为依据;考虑被忽略的自发辐射的影响, 对加长到抽运腔外的钕玻璃棒, 未受到抽运, 反而产生光放大异常实验现象的机理进行了理论研究.理论研究结果与实验结果基本相符.     

Critical behavior in Co-doped manganites La0.67Pb0.33Mn1−xCoxO3 (0≤x≤0.08)

The critical properties of perovskite manganite La_0.67Pb_0.33Mn_1−xCo_xO₃ (0≤x≤0.08) around the paramagnetic-ferromagnetic phase transition are investigated through various techniques such as the modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis. Though the nature of this transition was found to be in second order, the estimated critical exponents β (0.233≤β≤0.368), γ (1.03≤γ≤1.40) and δ (4.32≤δ≤5.54) are in between the theoretically predicted values for three-dimensional Heisenberg and tricritical mean-field model. This model suggests the coexistence of the short-range and long-range ferromagnetic orders around the critical temperature. The values of the critical exponents obtained from different methods and the well-obeyed scaling behavior confirm that the calculated exponents are unambiguous and purely intrinsic to the system.     

LOW-LYING SPECTRA AND E2 TRANSITION RATES IN EVEN--EVEN Pd ISOTOPES IN THE INTERACTING BOSON MODEL

The positive parity collective states in the even-even ¹⁰⁰Pd-¹¹⁶Pd isotopes are studied in the framework of the interacting boson model. A schematic Hamiltonian capable of describing their spectra and transition is used. It is found that the spectra can be well described by a U(5) plus SU(3) perturbation interaction. As the valence neutron number changes, the structure of the isotopes shows regular patterns of change. In the meantime, the behaviour of 0⁺₂ can also be partially described by the model.     

Transition between regular and Mach reflection of shock waves: new numerical and experimental results

New numerical and experimental results on the transition between regular and Mach reflections of steady shock waves are presented. The influence of flow three-dimensionality on transition between steady regular and Mach reflection has been studied in detail both numerically and experimentally. Characteristic features of 3D shock wave configuration, such as peripheral Mach reflection, non-monotonous Mach stem variation in transverse direction, the existence of combined Mach-regular-peripheral Mach shock wave configuration, have been found in the numerical simulations. The application of laser sheet imaging technique in streamwise direction allowed us to confirm all the details of shock wave configuration in the experiments. Close agreement of the numerical and experimental data on Mach stem heights is shown. Received 23 November 2000 / Accepted 25 April 2001     

Slowing Down in Chemical Tristability Systems

In this paper two kinds of slowing down in the chemical tristability systems are studied. One is the critical slowing down at the edges of tristable region, and the other is the slowing down far from the critical point, which has much to do with the unstable steady‐points. The results possess some universal properties.     

不可逆化学凝胶化过程的计算机模拟

该文提出一个改进的渗流模型,能把自由基交联共聚反应的主要特征包括进去,更真实地模拟化学凝胶化过程,特别是凝胶化点附近表现出来的临界行为。从模拟St-DVB体系凝胶化过程所得的临界指数与急冷法测得的实验值基本一致。     

Structural Evolution Process in Solvent-Induced Crystallization Phenomenon of Syndiotactic Polystyrene

Structural change has been traced in the solvent-induced crystallization phenomenon of syndiotactic polystyrene through the time-resolved measurements of infrared and Raman spectra and X-ray diffraction. Immediately after the solvent is supplied to the glassy sample, the random coils start a micro-Brownian motion and locally change to short regular helical segments after some induction time. These segments grow longer and gather together to form the crystal lattice. This crystallization occurs even at room temperature far below the original glass transition temperature (Tg = ca. 100°C), because Tg is shifted to ca. −90°C (in the case of chloroform) due to the plasticizing effect, as revealed by the temperature-dependent infrared spectral measurement and the molecular dynamics calculation. The thus-created sPS-solvent complex was found to show a fast and reversible solvent exchange phenomenon between the originally-existing solvent (toluene, for example) and the newly-supplied different type of solvent (chloroform, for example). The time-dependent measurement of wide-angle and small-angle X-ray scatterings using a synchrotron radiation source revealed that the solvent exchange occurs with keeping both the columnar structure of the crystal and the stacked lamellar structure, and that the solvent exchange rate is in the order of chloroform > benzene > toluene, reflecting the difference in diffusion rate of solvent molecules and polymer-solvent interaction.