波的传播

With the algebraic result in form of piecewise function expressions, the excitation and propagation processes of stress waves, including the longitudinal wave, the transverse wave, and Rayleigh-wave, are discussed in detail.

基于该分段函数形式的代数结果，纵波、横波、Rayleigh波等应力波成分在弹性表面的激发和传播过程得到详尽分析，其中很多结论是已有的解析积分结果或者数值计算结果不曾得到的。

Secondly, a lot of electrical equipment in substations (esp. transformers) is very sensitive to the steepness of lightning surge. At present, more and more research data indicate that impact corona is a crucial factor to attenuation and distortion of lightning surge.

其次，变电站的电气设备，特别是变压器，对于沿线路袭来的雷电入侵波陡度十分敏感，而最近越来越多的研究资料表明：入侵波沿导线传播过程中发生衰减和畸变的关键因素是冲击电晕。

The first one is caused by electromagnetic wave refraction phenomena at air-soilinterface and the second one is caused by spherical wave propagation loss andtransmission loss.

前者主要是由于电磁波在媒质表面产生的折射效应造成的，后者主要是电磁波在传播过程中的衰减造成的，包括球面波传播损耗、媒质表面的反射损耗和有耗媒质媒质对电磁波的衰减效应。

It is found in field detection that ultra high frequency signals can diffract from the joint of transformer. The feasibility of using external UHF sensor for detecting partial discharge activities is discussed, and the external propagation characteristic of UHF electromagnetic wave is investigated via the lab experiment.

针对变压器箱体的接缝处可以衍射出局部放电特高频电磁波信号的现象，在分析变压器箱体接缝对局部放电特高频电磁波传播影响的基础上，探讨了接收天线外部检测特高频信号的可行性，并通过实验研究了局部放电特高频电磁波的外传播特性，通过对信号进行小波包分析，比较了外部接收和内部接收信号的差异。

Testing results of piles under low strain integrity are normally interpreted using one-dimensional stress wave theory. While one-dimensional stress wave theory is acceptable for pile-driving analysis the responses of piles integrity tests can not be adequately simulated when the hammer and the incident wave length are small in relation to the diameter of the pile.

基桩动测问题的理论基础一维应力波理论只有在锤径桩径比、波长桩径比、桩长桩径比足够大时才能近似成立，否则该问题实际上为应力波在柱体中传播的三维问题。

Using the two-stream fluid model, the linear dispersion relation is derived assuming a two-dimensional spatial geometry. Two cases are considered, one is that the 2D spatial geometry is defined by the plane containing the two counterstreaming electron populations and the perturbation wave vector , and the other is that the geometry is defined by the plane being vertical to the two counterstreaming electron populations .

对高能束流和电子回流构成的双流系统，建立冷等离子体流体模型，采用简正模分析方法，分别考虑扰动波矢在平行于电流传播方向的平面上和在垂直于电流传播方向的平面上这两种情况，推导了不稳定性的色散关系。

Seismic anisotropy can be studied by four basic seismic wave behaviors, e.g, direction-dependent travel time anomalies, shear-wave birefringence, surface-wave scattering, and direction-dependent conversion of compressional waves to shear waves.

目前人们利用4种基本的地震波现象研究地震各向异性，如横波双折射、面波散射、与传播方向有关的走时异常和PS转换波震相。

Based on the wavelet transformation and the theory of modal acoustic emission,the dispersion of guided wave propagated in thin plate was investigated by acoustic emission experiment.

基于小波变换和模态声发射理论，通过模态声发射试验的方法确定了管道中导波传播的频散特性。

According to the guided wave technique, the displacement of guided wave propagation at an arbitrary time and point on the surface of a pipe is described.

在导波传播理论和频散波形预测理论的基础上，研究了超声导波在检测管道时，如何利用时域波形重构缺陷图像的问题。

First, the paper describes the forming and parameter characteristics of tropospheric ducts and the impacts on electromagnetic waves under duct condition.

本文首先描述了大气波导形成的环境特征、参数特征及波导对电磁波传播的影响。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。