群速度

Group velocity of the optical pulse propagation would be reduced based on coherent population oscillation effect in an absorbing medium.

由于相干布居振荡效应，光脉冲通过处于吸收状态的掺铒光纤介质时，将导致群速度传输减慢。

The conclusions show that with γP0 increasing the nonlinear dispersion curves shift to the negative region of δ,the upper branch of the curve will form a ring when γP0 exceeds a critical value,while the anomalous dispersion region of group velocity dispersion induced by fiber Bragg grating vanishes,group velocity dispersion becomes only one normal dispersion region.

结果表明：随着βg2的增加，非线性色散曲线的上、下两支向δ的负值区移动，当超过某一临界值时，曲线上支开始形成环，这时光纤光栅引起的群速度色散中的反常色散区消失，全部变成正常色散。

When the chirped pulse with area smaller than propagates in the medium, splitting doesn't occur and the chirped pulse evolves gradually to an approximate normal Gaussian pulse (C=0), and this characteristic doesn't vary when the chirp coefficient; however, variation of the chirp coefficient will change amplitude and group velocity of the pulse.

面积小于的啁啾脉冲，在介质中传播时不发生分裂，且啁啾脉冲逐渐演化为一个近似的无啁啾(C=0)脉冲，这一特点不随啁啾系数的改变而改变；但啁啾系数的变化将改变脉冲的振幅和群速度。

Phase and group velocity are the important parameters for researching seismic wave propagation and describing the media property, and they are key contents in theory of elastic wave propagation and play a role in theory and application.

相速度和群速度是研究地震波传播规律和描述介质特性的重要参数，是弹性波传播理论中的核心内容，在理论研究和实际应用中有重要作用。

It consists of:(1) numerical filtering of both constant and variable parameters;(2) techniques of measuring group velocities by using "moving window" and "multiple filtering";(3) cross-correlation method of measuring phase velocities.

包括：(1)参数固定的和可变的数值滤波；(2)测定群速度的"移动窗"和"多重滤波"技术；(3)测定相速度的互相关法。

Because of the collective modulation of the periodic dielectric distribution to the incident electromagnetic waves, the directions of the group velocity and the phase velocity can be opposite, a photonic crystal slab can work as a negative refractive-index material.

由于介电函数的周期性分布对入射光的调制作用，使得特定频率区域的入射光在光子晶体中传播时的群速度方向和相速度方向相反，因而使得光子晶体平板表现出负折射特性。

Various forms of wave equations, definitions of wave number and frequency, derivations of phase speed and group velocity, and a quick discussion on dispersion relationships.

各种形式的波动方程，波数和频率的定义，相速度和群速度的引入，以及一个关於色散关系的小讨论。

Then the azimuthally phase and group velocity formulas of plane wave propagation in horizontal plane are deduced according to Christoffel equation, and the azimuthally dependent velocities in dry and water saturated cracked medium are calculated.

而后，根据Christoffel方程推导了由各向同性背景介质中含两组非正交的垂直裂隙而形成的等效单斜各向异性介质中，在水平面内随方位变化的相速度和群速度的计算公式，并对干裂隙和饱和流体填充裂隙介质两种具体情况进行了计算。

We extend the second order elastic tensor of Husdon's and turn it to a matrix which makes the calculation of second order perturbation much more concise. Then the azimuthally phase and group velocity formulas of plane wave propagation in horizontal plane are deduced according to Christoffel equation, and the azimuthally dependent velocities in dry and water saturated cracked medium are calculated.

而后，根据Christoffel方程推导了由各向同性背景介质中含两组非正交的垂直裂隙而形成的等效单斜各向异性介质中，在水平面内随方位变化的相速度和群速度的计算公式，并对干裂隙和饱和流体填充裂隙介质两种具体情况进行了计算。

The numerical results of stationary and transient Green'sfunction for high-velocity surface-head wave on some selected crystals are comparedThrough the above analyse,it is indicate that the first arrival wave mode is thelongitudinal-wave head-wave,and its propagate velocity is equal to the groupvelocity of the longitudinal bulk wave alone the surface.Furthermore,this modedoes not have the Δv/v effect,i.e.,its velocity is the same no matter the surface isfree or metalized.

通过对表面激发的瞬态和稳态Green理论分析和数值计算，表明在压电晶体表面上实际上看到的最高速的最先到达的波动模式是纵波头波，它具有沿表面纵波的群速度，而且对压电晶体，它不具有Δv/v效应，即在自由表面和金属化表面其传播速度是一样的，而压电晶体表面波及伪表面波均存在Δv/v效应。

Plunder melds and run with this jewel!

掠夺melds和运行与此宝石！

My dream is to be a crazy growing tree and extend at the edge between the city and the forest.

此刻，也许正是在通往天国的路上，我体验着这白色的晕旋。