无穷小的

Using this method,we discussed for generalized Burger equation with variable coefficients and linear danping,obtained its symmetry group,simliar reduced equations,infinitesimal generator and Lie algebras;In chapter 6,using the Exp-function method,the generalized solutions of combined KdV-mKdV equation with variable coefficients are discussed.

首先介绍了Lie群分析法的基本思想，其次用Lie群分析法得到了带线性阻尼项的变系数广义Burgers方程的无穷小变换、无穷小算子的李代数结构，并具体求出了带线性阻尼项的变系数广义Burger方程的群不变解和约化方程。

In chapter 1, as a preparative knowledge, the main results about symmetry theoryand Wus method are introduced, in addition some fundamental definitions, such as trans-formation group, infinitesimal operator, prolongation, first integral, infinitesimal criterionfbr invariance of an ODE, characteristic set are recalled.

第一章中作为预备知识简单介绍了对称理论和吴方法，并给出了一些基本概念和理论，如变换群、无穷小算子、算子延拓、首次积分、微分方程在对称下不变的判别准则和微分特征列集算法。

Additionally, for these non-homogeneous materials, there is a relation between the material energy-momentum tensor and material coefficients under the infinitesimal translation, rotation and dilate of coordinates.

对于此种非均匀材料，物质能量-动量张量在坐标无穷小平移，转动和膨胀条件下与电磁焓中包含材料系数导数的形式有关。

If ,then is called a lower order infinitesimal of .

如果， 就说是比低阶的无穷小

If ,then is called an infinitesimal of the same order as .

如果， 就说与是同阶的无穷小

Never forget that the probability of a miracle, though infinitesimally small, is not exactly zero.

别忘记奇迹是有可能发生的，即使概率无穷小，但，它不是0

Meanwhile we present a kind of convex surfaces which are of infinitesimally nonrigidity and global nonrigidity.

在此基础上，给出一个非无穷小刚且非整体刚的例子。

A very small change in the function f, sufficiently small that the linear approximation to

df 函数 f 的无穷小变化，小至对於所有函数皆可利用线性近似表示。

The mathematical form of material energy-momentum tensor is the same as a sum of the energymomentum tensor in elastic material and the Maxwell stress tensor in electromagnetic field Moreover, under infinitesimal symmetrical transformations, the infinitesimal invariance condition gives a balance of the field variables and material energy-momentum tensor.

另外，在无穷小对称变换条件下，它指出—种场变量与物质能量-动量张量的平衡关系。

In the 19th century, infinitesimals were replaced by limits .

在19世纪，无穷小，取而代之的限制。

I can not make it blossom and suits me

我不能让树为我开花

When temperatures are above approximately 80 °C discolouration of the raceways or rolling elements is a frequent feature.

当温度高于 80 °C 左右时，滚道或滚动元件褪色是很常见的特征。