The features of phase and group velocity were advanced by means of preparing samples with different shaping . the phenomenon of " cusp " in group surface of quasi - shear wave ( qsv ) was observed . the inversed velocity surface according to calculated elastic constants in real orthotropic media is consistent with practical measured velocity surface 用加工不同样品形态的方法给出了正交各向异性介质的相速度和群速度特征，观测到各向异性介质群速度面上的尖点现象，并用测试得到的正交介质的弹性常数进行了数学模拟，其波场特征与测试的速度面特征相符。
X4 ? gridding attenuation and 2 ? x2 ? gridding group velocity are calculated respectively , based on the attenuation and velocity , the distribuation of rayleigh wave quality factor qr are yielded finally . ( 3 ) building the s - wave quality factor og3d structure of the continental crust and upper mantle of china area 为此把中国大陆区域划分成4 4网格和2 2网格，利用lsqr方法分别进行衰减系数和群速度网格化反演，得到4 4单元格的衰减系数分布和2 2单元网格的群速度分布。
We have calculated and plotted the curves of the refractive index , group velocity index , lowest - order and second - order dispersion indexes as a function of wavelength . the lowest - order and higher - order dispersion - induced broadening and deforming of light pulses is analyzed for various pulse shapes , such as gaussian , super - gaussian and hyperbolic secant pulses 给出了折射率、群速指数、低阶和二阶色散系数随波长变化的关系曲线，研究了高斯脉冲、超高斯脉冲和双曲正割脉冲等超短脉冲在clbo晶体中传播时，由于低阶色散和高阶色散引起的脉冲展宽和形变。
In this paper , first , the study of the distribution of electromagnetic field , energy , power , reflection coefficient and transmission coefficient in waveguide with piecewise different dielectric constants are studied . then , the behavior of propagation of am signal and gauss pulse signal through the waveguide are simulated by magic code ， and the plots of electromagnetic field , energy , ponyting vector and their spectrums at different time and different position are obtained . and , the group velocity and energy velocity of wave packet through barrier are calculated 从90年代开始， emig和martin 、 landauer等人研究了分段填充不同介质的波导中的电磁脉冲的传播。在本论文中，作者首先推导出分段填充不同介质的波导中的电磁场分布、能量、传输功率以及反射系数和传输系数的表达式,然后，采用magic程序模拟了这种波导结构中电磁波的传播情况，得到了在不同时刻和不同位置处的电磁场分布图、能量图、坡印廷矢量图以及它们的频谱图,并由模拟结果计算了波包穿越势垒的群速和能量速度。
Based on these foundations , we give a perfect scheme of the bbo opos : single pass amplification coefficient of the opg under different pump intensity is calculated ; collinear type - i and type - ii phase matching tuning curve pumped by the q switch nd : yag various harmonics as well as noncollinear type - i tuning curve are calculated in details ; the effect of the walkoff for the nonlinear effect coefficient and the group velocity matching are analyzed ; the acceptance angle in parametric process is calculated ; the numerical threshold of the bbo opo is calculated ; the process of the saturation and depletion of the pump beam are analyzed ; the relationship of the conversion efficiency and reflectance of output mirror are discussed ; various linewidth controlling methods are discussed ; the improvement of the beam quality applying the unstable cavity is discussed ; and the crystal bbo design is considered 在此基础上，给出了一整套bbo - opo激光参数设计方案：计算了不同泵浦强度下的参量放大倍数；详细计算了在nd : yag调q激光器各次谐波泵浦条件下的共线类和类相位匹配的调谐曲线，以及非共线类相位匹配调谐曲线；分析了走离角对非线性系数和群速匹配的影响；计算了参量过程的允许角；计算了bbo - opo的理论阈值条件；分析了饱和与泵浦光束的消耗过程；给出了转换效率与超过泵浦阈值的倍数的关系；讨论了转换效率与输出镜反射率的关系；讨论了线宽控制的各种方法；研究了利用非稳腔改善光束质量的方法；考虑了bbo晶体的设计。
There has been a revolutionary advance in ultrashort pulse technology since the discovery of self - mode locking of ti : sapphire lasers . few - femtosecond pulses have already been generated from ti : sapphire lasers , by means of combining self - phase modulation with negative group velocity dispersion , which is similar to the way of soliton generation 钛宝石激光自锁模的发现使得超短脉冲技术发生了革命性的变化，利用自相位调制和负群速度色散结合的类孤子产生方式，人们已经在钛宝石锁模激光器上得到了脉宽只有几个飞秒的光脉冲。
The accurately controlled signal source generates sinusoidal elastic wave accurately controlled in frequency and stable in phase to " illustrate " underground media . time signal stacker receive signal by stacking and doing fft to measure the transfer function of media . " sompi " cepstrum method retrieve group velocity travel times and decayed factors of wave element from observational data of transfer function in a limited frequency window 精密可控震源用于产生频率精确相位稳定的正弦弹性波以照射地层内部，信号叠加器通过对接收信号进行叠加和进行傅立叶变换的方式实现对介质传递函数的精密测量， “存否”倒谱方法能够根据一段窄带频域传递函数数据获得时域上各个波成分的群速度传播时间和介质衰减因子。
In the picosecond and femtosecond time field , the durations of the pump and signal pulses are so short that special propagating characteristics of ultrashort pulse laser should be taken into account , especially the pulse broadening induced by the group velocity mismatch and the group velocity dispersion 在皮秒和飞秒时域，由于泵浦光与产生的信号光的持续时间特别短，故在讨论超短脉冲与物质相互作用时必须计及超短脉冲在介质中传输的特殊性质，尤其是群速失配与群速色散引起的脉冲展宽。
When the pulse width of input gaussian wave packet was reduced and the length of forbidden region retained , the result displayed the output signal distorted seriously and its spectrum changed very hard . a frequency above the cut - off frequency became the main frequency and the group velocity was below than c 在保持截止区长度不变，而减小输入高斯波包的脉冲宽度时，模拟显示输出波形严重失真，而且，频谱也发生很大的变化，主频已变为一高于截止频率的频率，群速度小于光速c 。
The thesis mainly deals with the third part of across : " sompi " cepstrum methods . the principle and system structure of across a re first introduced . the propagation of wave in media is simply studied and its transfer function in frequency domain is modeled as superimposed damped exponential sinusoids , each damped exponential sinusoid is called as a wave element and its exponential index part consists of two factors : group velocity travel time and decayed factor 为此，首先介绍了across的原理与组成和通过简单地讨论地震波在介质中的传播情况建立起介质的传递函数模型，指出：在一个狭窄的频率窗口里，介质的传递函数可以用有限个阻尼正弦项的叠加的形式表示，每个阻尼正弦项代表一个波成分，其指数部分包括两个因子：波成分在介质中的传播时间和衰减因子。
