微极广义磁热弹性固体界面上波的传播(英文)

给出了微极广义热弹性固体的一般控制方程;研究了在定常磁场作用下具有均匀初始温度的两理想接触微极弹性介质平面分界面上磁热弹性波的传播特性;给出了分别在缺少磁场、热场作用或不同广义热传导理论下反射或折射热波、纵向位移波、耦合横向和微旋转波与入射纵向位移波的振幅比随入射角变化的关系曲线,讨论了热松弛及磁场对振幅比的影响。结果表明:热松弛时间及磁场对振幅比均有显著影响,改变热松弛时间或磁场强度可以明显改变波的传播形式。     

微极广义磁热弹性固体界面上波的传播

给出了微极广义热弹性固体的一般控制方程；研究了在定常磁场作用下具有均匀初始温度的两理想接触微极弹性介质平面分界面上磁热弹性波的传播特性；给出了分别在缺少磁场、热场作用或不同广义热传导理论下反射或折射热波、纵向位移波、耦合横向和微旋转波与入射纵向位移波的振幅比随入射角变化的关系曲线，讨论了热松弛及磁场对振幅比的影响。结果表明：热松弛时间及磁场对振幅比均有显著影响，改变热松弛时间或磁场强度可以明显改变波的传播形式。     

Propagation of Plane Waves Through Two Parallel Dielectric Sheets

A study is presented of the standing waves created in the region between two parallel dielectric sheets when a plane electromagnetic wave propagates through the system in a direction normal to the dielectric boundaries. This model closely resembles the exposure of experimental animals, housed within restrainers of dielectric materials, to free-field microwave radiation. Data are presented giving the ratio of the standing waves set up for various sheet thicknesses and different dielectric materials, and it is demonstrated that significant changes in estimated power density levels are created by the restrainers.     

Reflection And Transmission of Electromagnetic Waves at a Rough Interface between Two Different Media

An iterative technique is developed to rigorously compute the electromagnetic wave reflection and transmission at a rough interface between two media. The method is based upon a wave-function expansion technique in which the electromagnetic field equations and the radiation condition are satisfied analytically, while the boundary conditions at the interface are satisfied numerically. The latter is accomplished by an iterative minimization of the integrated square error in the boundary conditions. In each step of the iteration, only Fourier transforms of the spectral and spatial variables occur. As starting value, the Sommerfeld-Weyl plane interface results can be employed.     

The Generation and Propagation of Acoustic Surface Waves at Microwave Frequencies

The generation and propagation of acoustic surface waves is reviewed with particular emphasis on the microwave-frequency range. Theoretical work on optimizing the generation efficiency and the bandwidth of interdigital transducers is compared with recent experimental results. The minimum Iinewidth of 0.9 /spl mu/m which can be produced by optical photolithographic techniques places an upper limit of about 1 GHz on the maximum frequency that can be generated at the fundamental mode. Overtone operation has been used to generate 3 GHz surface waves on LiNbO/sub 3/ but this method has the disadvantage of reduced efficiency plus the complication of volume-wave generation. A better solution for generation above 1 GHz is the fabrication of interdigital transducers by means of electron beam exposure of the photoresist. The surface-wave propagation loss gives a significant contribution to the total insertion loss of delay lines operating at microwave frequencies. Losses of 1.1 dB//spl mu/s and 3.8 dB//spl mu/s at 0.9 GHz and 2 GHz, respectively, have been measured for propagation along the Z-direction of Y-cut LiNbO/sub 3/ by means of a laser deflection method. Larger losses have been observed for quartz. The additional complexities for surface-wave propagation due to the anisotropic single-crystal substrates which are necessary at microwave frequencies are also described.     

Waves Guided Between Open Parallel Concave Reflectors (Short Papers)

Wave propagation between two open parallel concave reflectors is usually considered by a wave-beam or a multiple-reflection approach. It is shown that the field distribution in elliptic waveguides, for specific wave modes, approaches that in open reflector waveguides.     

超声波在换能器接触界面传播的特性研究

在研究超声换能系统的过程中发现,系统存在非线性特性.引起超声波非线性的主要因素是换能器子结构接触界面上传递的不连续造成的.该文对超声波在超声键合换能器中的传播为研究对象,建立了超声波在单一均质材料和两种材料接触界面传递的一维数学模型,并采用机械动力学软件进行了仿真,推导出界面预紧力和超声波传播的关系,并试验测试了超声换能器在不同预紧力条件下,换能器换能杆末端振动速度和键合强度的变化规律.为超声键合换能器系统的设计、安装和维护提供了可靠依据.     

超声波脉冲在固-固界面传播的数值模拟分析

为了直观地显示超声波脉冲在固-固界面的传播规律,建立了两种玻璃组成的固-固界面有限元模型,模拟了超声波脉冲在固-固界面的传播情况。通过不同时刻的波场快照图,清晰地显示出超声波脉冲在不同声学参数的两种固-固界面的传播情况,模拟得到的结果与理论和实验结果相符。模拟结果表明,通过有限元模拟方法正确的模拟了超声波脉冲在固-固界面中的传播过程,清晰地观察到了在界面上形成的复杂声场情况,模拟结果可为超声无损检测技术在检测参数选择、缺陷特征提取等方面提供一定的参考。     

固态微波毫米波、太赫兹器件与电路的新进展(续)

正4 GaN HEMT20世纪90年代中期GaN HEMT诞生。GaN是宽禁带材料,具有电子饱和速度高、击穿场强高、SiC衬底导热性好、抗辐照等特点,且在AlGaN/GaN界面上存在自极化和压电等新的物理效应,其二维电子气密度高达2×1013 cm-2,因此GaNHEMT在微波毫米波具有高功率密度的能力。进入21世纪后,优化了SiC衬底上GaN异质结外延材     

Addendum and Corrections to "Propagation of Plane Waves Through Two Parallel Dielectric Sheets"

Additional data, needed to complete the problem solution and omitted in the above communication,1 are presented showing actual maximum and minimum/E/2 values for the standing waves which exist between the two sheets. Two corrections to the original work are also given.     

Coupling and Propagation of Sommerfeld Waves at 100?and 300?GHz

The coupling between a linearly-polarized gaussian beam and a Sommerfeld wave propagating on a circular metallic wire is obtained owing to a differential phase element inserted in front of the metal wire. At millimeter-wavelengths we calculate a theoretical maximum coupling efficiency of 32% for this system in spite of the metal nature and radius in the range of a few hundreds of microns. A detailed experimental study of 100 and 300 GHz Sommerfeld waves propagating on stainless steel and tungsten wires is reported. The measured field at any distance from the wire compares well with theoretical predictions.