Jahn–Teller coupled charge density wave in a double exchange system

In a two orbital model, we formulate Jahn–Teller coupled charge density wave in one electron per lattice site limit. Softening of Jahn–Teller phonons corresponding to distortion modes Q₂ or Q₃ associated with perfect nesting of Fermi surface leads to this instability at low temperature. The gap equation for charge density wave state and its dependences on electron–lattice coupling are calculated explicitly when any one of the Jahn–Teller modes is excited cooperatively. We find that the Q₂ distortion mode yields lowest free energy. Effect of electron–lattice interaction on collective mode, such as amplitude mode, is more pronounced when the excited mode is Q₂.     

Application of inertia-induced excitation theory for nonlinear acoustic modes in colloidal plasma equilibrium flow

Application of inertia-induced acoustic excitation theory offers a new resonant excitation source channel of acoustic turbulence in the transonic domain of plasma flow. In bi-ion plasmas like colloidal plasma, two well-defined transonic points exist corresponding to the parent ion and the dust grain-associated acoustic modes. As usual, the modified ion acoustic mode (also known as dust ion-acoustic (DIA) wave) dynamics associated with parent ion inertia is excitable for both nanoscale-and micronscale-sized dust grains. It is found that the so-called (ion) acoustic mode (also known as dust-acoustic (DA) wave) associated with nanoscale dust grain inertia is indeed resonantly excitable through the active role of weak but finite parent ion inertia. It is interestingly conjectured that the same excitation physics, as in the case of normal plasma sound mode, operates through the active inertial role of plasma thermal species. Details of the nonlinear acoustic mode analyses of current interest in transonic domains of such impure plasmas in hydrodynamic flow are presented.      

Calculation of the Effect on the Reflection of the Plane Electromagnetic Wave for Non-Magnetized Plasma with Different Electron Density Distributions

In this paper, shift operator finite-difference time-domain (SO-FDTD) method is applied for the calculation of the dispersive medium. The high efficiency and accuracy of this method is verified by calculating the reflection of the plane electromagnetic wave impinging on a non-magnetized plasma slab with different electron density distributions. The results show that the average electron density only determines overall trends of the reflection, and different distributions affect the oscillating process of the reflection. If the average electron density maintains the same, the distribution of electron density with homogenous or inhomogeneous alternation will sharply take effects on the reflection. And magnitude of alternation of electron density affects the incident frequency directly when the reflection tends to uniform.     

Propagation of laser beams and caustics in crystals

We investigated the propagation and transformation of laser beams and the formation of caustics in particular directions, including optical axes of crystals. We found a direct connection between the particular directions and the curvature of wave surfaces that is determined by the symmetry and optical properties of the crystals. We demonstrated that caustics in particular directions are characterized by a degree of the curvature degeneracy and are described by particular solutions of the corresponding nonlinear equations. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 491–498, July–August, 2007.     

An investigation into EMI-induced noise in nanometer multi-quantum well InGaN LEDs

This study investigates the low-frequency noise induced by electromagnetic radiation interference (EMI) in a nanometer multi-quantum well InGaN LED (NMQLED). Theoretical models of the noise spectra and the EMI are constructed. In general, a good agreement is identified between the experimental and theoretical results. Both sets of results reveal that the magnitude of the EMI-induced noise is related to the pulse height, the output load, the parasitic capacitance, the interference frequency and the interference amplitude. It is shown that the harmonic noise increases with an increasing interference amplitude and frequency. The techniques presented in this study provide a systematic approach for obtaining the interference noise and signal-to-noise ratio (SNR) in LEDs and similar wavelength-based semiconductor devices.     

Effect of Te doping on superconductivity and charge-density wave in dichalcogenides 2H-NbSe2-xTex （x = 0, 0.1, 0.2）

Single crystals of Te-doped dichalcogenides 2H-NbSe2-xTex （x ---- 0, 0.10, 0.20） were grown by vapour transport method. The effect of Te doping on the superconducting and charge-density wave （CDW） transitions has been investigated. The sharp decrease of residual resistance ratio, RRR = R（3OOK）/R（SK）, with increasing Te content was observed, indicating that the disorder in the conducting plane is induced by Te doping. Meanwhile the superconducting transition temperature, Tc, decreases monotonically with Te content. However, the CDW transition temperature, TCDW, shown by a small jump in the temperature dependence of the resistivity near 30 K, increases slightly. The results show that the suppression of superconductivity might be caused by the enhancement of CDW ordering. The disorder has little influence on the CDW ordering.     

立方非线性Schr?dinger方程的Weierstrass椭圆函数周期解

利用Weierstrass椭圆函数展开法对非线性光学、等离子体物理等许多系统中出现的立方非线性 Schr(o)dinger方程进行了研究.首先通过行波变换将方程化为一个常微分方程,再利用Weierstrass椭圆函数展开法思想将其化为一组超定代数方程组,通过解超定方程组,求得了含Weierstrass椭圆函数的周期解,以及对应的Jacobi椭圆函数解和极限情况下退化的孤波解.该方法有以下两个特点:一是可以借助数学软件Mathematica自动地完成;二是可以用于求解其它的非线性演化方程(方程组).     

利用PVDF传感器检测激光超声的实验研究

简要介绍了激光超声技术以及声表面波的基本特点、激光超声产生和接收的基本原理及激光超声技术的应用。概述了聚偏二氟乙烯（PVDF）压电薄膜材料的结构、性质和应用，以及薄膜压电性产生的机理。对PVDF换能器的设计思路和实验方法进行了简单讨论。具体实验采用脉冲激光器激发声表面波，利用PVDF传感器接收实验信号，调试实验信号，得出波形，并对实验现象作出初步分析。证实了该实验装置应用于激光超声无损检测的可行性与可靠性。     

太赫兹波光子晶体光纤传输特性分析

利用矢量有限元法分析了太赫兹波光子晶体光纤单模截止频率和波导色散随光纤结构的变化特性．结果表明，太赫兹波光子晶体光纤的单模截止频率随着光纤空气孔占空比的变大而降低，零波导色散点频率随着空气孔占空比变大而增加，约束损耗随着空气孔的圈数增加而降低．     

气体火焰驻波演示实验的理论分析

对通过声场使可燃气体产生火焰驻波的波形进行研究,得出火焰驻波在波节处(固定反射端)出现火焰,在波腹处几乎不出现火焰的结论,理论分析与实验观测相符.