基于半解析有限元法的管道中导波传播特性分析

为了分析管道中导波传播特性,首先使用半解析有限元法,推导出了圆柱坐标系下管道中弹性导波传播的特征值方程,对特征值方程求解特征值,计算出了圆形管道中导波频散曲线,并通过实验对计算结果进行了验证;然后,计算得到了L(0,2)、T(0,1)、F(1,1)三种导波模态下管道截面的位移分布及截面变形特征图,计算结果可以有效直观地反映各导波模态的振动特征;最后,对L(0,2)、T(0,1)两种模态下管道截面上的能流密度分布进行了计算,结合ANSYS数值模拟分析发现,T(0,1)、L(0,2)导波对管道内、外壁处缺陷的检测能力与能流密度分布密切相关,缺陷检测信号的幅值比与能流密度比具有较高的一致性。

基于导波传播模型的MUSIC损伤识别算法

针对结构健康监测领域的损伤近场定位问题,提出了适用于复合材料结构损伤识别的近场二维多重信号分类(MUSIC)损伤识别算法。该损伤识别算法将导波传播模型引入近场二维MUSIC损伤识别模型,构造损伤散射信号与实验差信号的互相关矩阵,通过信号子空间与噪声子空间正交特性构造近场二维MUSIC空间谱。通过数值仿真和实验验证了所提出的损伤识别算法能够有效地识别复合材料结构损伤位置信息,具有很高的定位精度和分辨率。针对飞机垂直尾翼的加强筋结构对导波传播特性影响较大的问题,提出了分区域监测的损伤检测策略,并利用基于导波传播模型的二维MUSIC空间谱损伤识别算法成功地识别飞机垂直尾翼结构损伤,实现了复杂复合材料结构损伤识别的工程验证。

基于稀疏重构的蜂窝夹层复合材料板中Lamb波传播特性估计方法

针对航天器装备中蜂窝夹层复合材料板中的超声Lamb波传播特性难以准确估计的问题,提出基于导波信号稀疏表达与重构方法的传播特性曲线估计方法。首先,根据Lamb波传播的散射模型建立Lamb波在频率-波数域下的稀疏表达方程;然后,以Lamb波频率-波数域表达的稀疏性为约束条件,建立基于l_(1)范数的基追踪消噪求解方法;最后,通过提取重构的导波频率-波数域表达结果脊线,可准确获取Lamb波传播的频散速度曲线。在蜂窝夹层复合材料机翼结构上进行测试实验验证的结果表明,该方法能在有限次数的测试下保证传播特性曲线的估计精度,具有较好的工程应用前景。

长天线导波与隧道通信分析

本文从理论上分析了以长天线为导波系统，在隧道内进行移动通信的可行性。并对该系统中电磁波沿隧道纵向传播过程的衰减情况、衰减与频率的关系作了具体的分析计算。

A High-Efficiency Fiber-to-Waveguide Coupler with Low Polarization Dependence Using a Diluted Waveguide in InP Substrate with a 1.55μm Wavelength

We propose a fiber-to-waveguide coupler for side-illuminated p-i-n photodiodes to obtain high responsivity and low polarization dependence that is grown on InP substrate and is suitable for surface hybrid integration in low cost modules. The fiber-to-waveguide coupler is based on a diluted waveguide,which is composed of ten periods of undoped 120nm InP/80nm InGaAsP （1.05μm bandgap） multiple layers. Using the semi-vectorial three dimensional beam propagation method （BPM） with the central difference scheme,the coupling efficiency of fiber-to-waveguide under different conditions is simulated and studied,and the optimized conditions for fiber-to-waveguide coupling are obtained. For TE-like and TM-like modes,the calculated maximum coupling efficiency is higher than 94% and 92% ,respectively. The calculated polarization dependence is less than 0. ldB,showing good polarization independence.

The study of acoustic emission (AE) forecasting coal and rock disaster technique

Introduced the coal and rock AE propagation rule,wave guide fixing technics onAE sensors,and AE forecasting coal and rock disaster on the scene and so on,The coaland rock AE propagation rule that follows the exponent attenuation function on different AEfrequencies,different quality factors and different propagation distances were analyzedand deduced by theory,numerical simulation,and by actual experiment.Consequently,itwas deduced that the coal and rock AE propagation rule follows the exponent attenuationfunction.Based on the correlative theory of wave dynamics and AE sensor,the AE waveguide propagation mechanical model on the sensor fixing manner is found,and the relationsof displacement and speed and acceleration between the AE signal source and theAE signal receiving terminal are presented.The effect of the AE sensor fixing manners oncoal and rock surfaces,coal and rock bottoms and wave guides were studied by actualexperiment.For the results,the effect of the AE sensor fixing manner on wave guides isbetter than on coal and rock surfaces,and was equivalent to the fixing manner on coal androck bottoms.Based on the above study results,actual coal and rock dynamistic disasterswere successfully forecasted.

Pathways of intraseasonal Kelvin waves in the Indonesian Throughflow regions derived from satellite altimeter observation

The gridded sea level anomaly（SLA） data-set provided by AVISO is used to track the propagation of intraseasonal Kelvin waves in the Indonesian Throughflow（ITF） region. The large root mean square of intraseasonal SLA along the Sumatra and Java coast is closely related to the propagation of intraseasonal Kelvin waves that derive from the equatorial Indian Ocean. These Kelvin waves are further found to propagate following different pathways at the Lombok Strait. Pathway A propagates eastward throughout the Sumba Strait and Savu Sea to reach the Ombai Strait. Pathway B penetrates into Lombok and propagates northward to reach the Makassar Strait. Pathway C propagates southeastward along the southwest coast of the Sumba Island. The equatorial Kelvin waves take around 15 days to travel from the equatorial Indian Ocean to Lombok Strait, and around 5 days to penetrate into the Makassar and Ombai straits. The Kelvin wave-induced SLA persists in the ITF region for an additional 5 days and then diminishes subsequently. The phase speeds of these intraseasonal Kelvin waves along Pathways A, B, and C are 1.91–2.86, 1.69, and 1.96 m s^-1,respectively—in agreement with the first two baroclinic modes of Kelvin waves.

Analysis of wave propagation on human body based on stratified media model

Human body communication(HBC) is a promising near-field communication(NFC) method emerging in recent years. But existing theoretical models of HBC are too simple to simulate the wave propagation on human body. In this work, in order to clarify the propagation mechanism of electromagnetic wave on human body, a surface waveguide HBC theoretical model based on stratified media cylinder is presented. A numerical model analyzed by finite element method(FEM) is used for comparing and validating the theoretical model. Finally, results of theoretical and numerical models from 80 MHz to 200 MHz agree fairly well, which means that theoretical model can characterize accurate propagation mechanism of HBC signal. Meanwhile, attenuation constants derived from two kinds of models are within the range from 1.64 to 3.37, so that HBC signal can propagate effectively on human body. The propagation mechanism derived from the theoretical model is useful to provide design information for the transmitter and the modeling of the propagation channel in HBC.

Interface waves between two piezoelectric half-spaces with a semiconductor film

In this work propagation of anti-plane (SH) waves in two piezoelectric ceramic half-spaces with a thin layer of a semiconducting material between the half-spaces is studied, and wave attenuation and dispersion caused by semiconduction as well as wave amplification by a biasing electric field are examined. Key words Piezoelectricity - Semiconductor - Wave - Attenuation - Dispersion Document code A CLC number TH11

Propagation properties for five-layer symmetric slab waveguides including left-handed materials

In this paper,we discussed a slab wave-guide of five layers,The core is a left-handed material,but the claddings are right-handed materials. A dispersion equation of TE modes is obtained by using Maxwell's equations,and some new dispersion characteristics are obtained based on the equation.

Opti mal design of alow-loss2-bit electrooptic analog-to-digital converter

The structure of the optical waveguide of 2-bit electrooptic A/D converter with proton-exchange micro prisms is optimized by the finite-difference beam propagation method (FD-BPM). The electrode parameters of the converter are optimized by conformal mapping. The optimal parameters are a half-wave voltage of (Vπ= 4.5 V) and a bandwidth of (Δf=1.4 GHz).A normalized transmitted power of 69.75% is obtained by FD-BMP and the output waveguide gap is 300 μm.

Resonance and Antiresonance in Electronic Transport Process Through a T-Shaped Quantum Waveguide

By means of the transfer matrix approach, the linear conductance spectrum for electronic transport through a T-shaped quantum waveguide is calculated. The resonant peaks and the antiresonant dips in the conductance spectrum are mainly focused. The previous prediction about their positions by other theoretical approaches is checked. In addition, a function of spin filtering is suggested based on the interplay of the resonance and antiresonance in this T-shaped quantum waveguide.

Numerical Spectral Model Based on BPMfor Er-doped Waveguide Amplifiers

A spectral numerical analysis method to analyze the Er-doped waveguide amplifiers(EDWA) in wavelength division multiplexing is presented. This model is based on finite difference beam propagation method modified by Douglas scheme, which can efficiently reduce the truncation error and time consumption. By superposing the Lorentzian function for the experimental curves, the spectral properties of EDWA can be investigated. Results show that the pump efficiency of EDWA pumped at 980nm is higher than that at 1480nm. Meanwhile, by rationally increasing the pump length and the erbium concentration, larger signal gains can be acquired. Taking account of the up-conversion and cross-relaxation effects of cooperation, the spectrum analysis of highly doped EDWA is carried out over a wider frequency band.

Modified Wide-angle Beam Propagation Method Using Douglas Operators

A modified wide-angle beam propagation based on the Douglas operators is presented.The truncation error in the modified wide-angle beam propagation is reduced to o (Δ x ) 4 in the transverse direction nearly without any increase of the computation time,whereas the error in the ordinary wide-angle beam propagation method is typically o (Δ x ) 2.With trivial programming changes,the accuracy is higher,especially in wide-angle propagation.

从薄膜波导传播衰减的角度研究光学薄膜的损耗:(Ⅰ)理论分析

本文从理论上分析了光学薄膜中的三种基本缺陷:折射率消光系数、表面粗糙度以及折射率不均匀性对薄膜内导波传播衰减的影响.基于这些缺陷对光学薄膜内不同导模传播衰减作用的不同,提出了一种区分薄膜中的吸收与散射损耗的方法.

Interaction of Counter Propagating Electromagnetic Waves with the Absorbing Plate in the Waveguide

The interaction of two coherent counter propagating TE （transverse-electric） and TM （transverse-magnetic） electromagnetic waves with different initial phases in the absorbing plate placed in the regular ideal waveguide is considered. The losses of energy of TE and TM waves in the absorbing plate are calculated. Some features of tunnel interference in the absorbing plate in the waveguide are revealed. It is shown that the losses of energy strongly depend on the various parameters describing the interaction of the counter propagating waves. Definitely choosing the parameters we can control the electromagnetic processes in this case.

A numerically stable coupled-mode formulation for acoustic propagation in range-dependent waveguides

In this paper,a stepwise coupled-mode model with the use of the direct global matrix approach is proposed.This method is capable of handling two-dimensional problems with either a point source in cylindrical geometry or a line source in plane geometry.With the use of the direct global matrix approach,this method is numerically stable.In addition,by introducing appropriately normalized range solutions,this model is free from the numerical overflow problem.Furthermore,we put forward source conditions appropriate for the line-source problem in plane geometry.As a result,this method is capable of addressing the scenario with a line source on top of a sloping bottom.Closed-form expressions for coupling matrices are derived and applied in this paper for handling problems with pressure-release boundaries and a homogeneous water column.The numerical simulations indicate that the proposed model is accurate,efficient,and numerically stable.Consequently,this model can serve as a benchmark model in range-dependent propagation modeling.Although this method is verified by an ideal wedge problem in this paper,the formulation applies to realistic problems as well.

Description of squeezed surface plasmons

Surface plasmon polaritons (SPPs) are the combined electron oscillations and electromagnetic waves propagating along the interface between a conductor and a dielectric. Recently Huck et al. [Huck A, et al. Phys Rev Lett, 2009, 102: 246802] proved that SPPs can be in a squeezed state, and the squeezed surface plasmons can propagate in a gold waveguide. In this paper, we introduce a quantum mechanical description of the squeezed surface plasmons at first, and discuss the influence of the waveguide losses on the squeezed surface plasmons.

Homogenization and Upscaling for Diffusion,Heat Conduction,and Wave Propagation in Heterogeneous Materials

We present a general homogenization method a periodic heterogeneous material with piecewise constants for diffusion, heat conduction, and wave propagation in The method is relevant to the frequently encountered upscaling issues for heterogeneous materials. The dispersion relation for each problem is first expressed in the general form where the frequency co （or wavenumber k） is expanded in terms of the wavenumber k （or frequency ω）. A general homogenization model can be directly obtained with any given dispersion relation. Next step we study the unit cell of the heterogeneous material and derive the exact dispersion relation. The final homogenized equations include both leading order terms （effective properties） and high order contributions that represent the effect of the microscopic heterogeneity on the macroscopic behavior. That effect can be lumped into a single dimensionless heterogeneity parameter β, which is bounded between -1/12≤β≤ 0 and has a universal expression for all three problems. Numerical examples validate the proposed method and demonstrate a significant computational saving.

New computational treatment of optical wave propagation in lossy waveguides

In this paper, the optical wave propagation in lossy waveguides is described by the Helmholtz equation with the complex refractive-index, and the Chebyshev pseudospectral method is used to discretize the transverse operator of the equation. Meanwhile, an operator marching method, a one-way re-formulation based on the Dirichlet- to-Neumann （DtN） map, is improved to solve the equation. NumericM examples show that our treatment is more efficient.