By using transducers with different central frequency and diameter , the approximate demands for the length of those samples and the transducers " frequency and diameter were presented in order to attain the phase or group velocities in the experiment 通过多种频率和不同直径的换能器，给出了实验室测试各向异性介质相速度和群速度时换能器频率和直径与样品长度之间的相对关系。
Since the flexural waves in the plate would produce scattered waves when they propagated through the flaw of a plate , the measured signals of a strain gauge contented the direct waves propagated from the impact source and the scattered waves propagated from the flaw 藉由小波转换进行讯号的时频分析，进而求得弯曲波由冲击点至各应变规的波程时间，并计算出弯曲波在各频率中的波群速度。
The origin of supercontinuum ( sc ) generation in optical fibers has been conjectured to be the interplay between fiber nonlinearities ( self phase modulation , cross phase modulation and raman self scattering ) and group - velocity dispersion ( gvd ) 光纤中超连续supercontinuum ( sc )谱的产生源于光纤中各种非线性效应(自相位调制效应、交叉相位调制效应，四波混频效应及受激raman散射等)和群速度色散的共同作用。
Generally speaking , the high group velocity and low attenuation factor and high qr in the same area , but relatively low group velocity and high attenuation factor and low qr in the same area in china is the general distribution 在不同周期，面波衰减系数或品质因子在整个中国大陆区域分布是不均匀的；总体表现为高群速度分布的区域呈现高丛和低衰减系数、低群速度分布的区域呈现低丛和高衰减系数分布的特点。
We derive an analytic expression of the group velocity dispersion ( gvd ) induced chirp and the self - phase modulation ( spm ) induced chirp in the normal dispersionregion of non - kerr - like optical fibers with saturable nonlinarity . the evolution of chirp is simulated by numerical methods . the studied results show that the more powerful saturable effects , the smaller is chirp and the gently is chirp . the net chirp is zero in the central region of the pulse 从理论上推导出具有饱和非线性的非克尔光纤正常色散区内，群速度色散效应导致的啁啾和自相位调制效应导致的啁啾解析表达式.利用数值解法模拟了非克尔光纤正常色散区啁啾演变过程.研究结果表明：当非克尔光纤的饱和非线性增强时，净啁啾不断减小，而且，越来越平缓，脉冲中心附近区域净啁啾接近零
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。
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。
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 。
