感应叠加过程行波分析和模拟

 采用变换矩阵为研究工具对感应叠加过程中行波的传播、透射、反射进行了分析，得到了和集中参数分析一致的稳定解，给出了电压随时间变化的细节。建立了3.5 MeV注入器脉冲功率源和感应叠加结构的电路模型，得到的感应腔压模拟波形和实验波形基本一致，结合行波分析法基本解释了腔压波形和Blumlein线输出波形之间较大差异的成因，阴极叠加电压的模拟也反映了实验中主脉冲后的反射波形。     

Some theoretical aspects of elastic wave modeling with a recently developed spectral element method

A spectral element method has been recently developed for solving elastodynamic problems. The numerical solutions are obtained by using the weak formulation of the elastodynamic equation for heterogeneous media, based on the Galerkin approach applied to a partition, in small subdomains, of the original physical domain. In this work, some mathematical aspects of the method and the associated algorithm implementation are systematically investigated. Two kinds of orthogonal basis functions, constructed with Legendre and Chebyshev polynomials, and their related Gauss-Lobatto collocation points are introduced. The related integration formulas are obtained. The standard error estimations and expansion convergence are discussed. An element-by-element pre-conditioned conjugate gradient linear solver in the space domain and a staggered predictor/multi-corrector algorithm in the time integration are used for strong heterogeneous elastic media. As a consequence, neither the global matrices nor the effective force vector is assembled. When analytical formulas are used for the element quadrature, there is even no need for forming element matrix in order to further save memory without losing much in computational efficiency. The element-by-element algorithm uses an optimal tensor product scheme which makes this method much more efficient than finite-element methods from the point of view of both memory storage and computational time requirements. This work is divided into two parts. The first part mainly focuses on theoretical studies with a simple numerical result for the Che-byshev spectral element, and the second part, mainly with the Legendre spectral element, will give the algorithm implementation, numerical accuracy and efficiency analyses, and then the detailed modeling example comparisons of the proposed spectral element method with a pseudo-spectral method, which will be seen in another work by Lin, Wang and Zhang.     

光纤微机电系统法布里-珀罗压力传感器的波分复用

提出了一种用阵列波导光栅复用光纤微机电系统法布里-珀罗压力传感器的方法,实现了法布里-珀罗压力传感器的准分布式测量。传感器基于法布里-珀罗腔干涉的原理,采用微机电系统技术加工制作,用双波长方法解调干涉信号,利用传感器对两个不同波长光的反射率的比值与压力的单值关系确定所施加压力的大小,用阵列波导光栅实现传感器复用。理论分析与实验验证了传感器解调和复用的基本原理。实验结果表明:在压力的线性测量范围(0~1.5 MPa)内,系统的灵敏度(相对反射率比值/压力)可达到0.02026 MPa-1,测量结果具有较好的线形性,相对反射率比值的标准偏差小于3×10-4。该系统可以补偿传感器光网中和波长无关的变动引起的误差,具有好的线性、灵敏度和精度,复用能力强且复用传感器间无串扰。     

纳米材料用于吸收电磁波的物理机制

本文从物理学的角度分析吸波材料与电磁波作用的影响因素和纳米材料在吸波应用上的微观机制，随着纳米材料和纳米科技的深入发展，纳米吸波材料将以更优异的性能广泛应用于军事装备和民用电磁波防护上．     

THz波的产生及探测技术

THz技术是20世纪90年代发展起来的一门新兴学科,本文较为详细地介绍了目前产生THz波的主要方法、原理以及探测THz波的主要手段和机理.     

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.