不变形的

Only with such characteristics, the movement equations can be expressed as matrices, and the idea of transforming the movement equations to the simplest form through a nonlinear transformation can be realized;(2) The form of Zi =Yi + YTH2i Y + Y7H3i Y(2)+ Y(2)T H4i Y(2)+ YTH5i Y(3) is adhibited in the nonlinear transformation, so that the multivalued problem caused by the nonlinear transformation is avoided, and the higher order transformation can be taken next;(3) The fourth order nonlinear transformation matrices H21,H31,H41 and H51 are derived, by which the original movement equations of electric power system is transformed to Jodan form in Z space;(4) By use of the fourth order nonlinear transformation, the approximate expression of the stability boundary is obtained, in Z space it is Z1= 0,in Y space it is Y1 + YTH21 Y + YTH31 Y(2)-i- Y(2) TH41 Y(2)+YTH51 Y(3)= 0;(5) The criterion used in this paper to judge whether the system critical unstable is simple and quick;(6) The method used in this paper is a direct method, and no need to construct an energy function.

正是由 于电力系统的运动方程具有这样的特性，才能写成矩阵的形式，通过非线性变换将电力系统的运动方程变换为最简单的线性形式的思想才能得以实现；（2）将通常运用于电力系统暂态稳定性分析的Normal Form变换的形式由 Yi＝ Zi＋ ZTh2riZ变形为 Zi＝ Yi＋YTH2iY＋YTH3iY（2）＋Y（2）TH4iY（2）＋YTH5iY（3），从而使得在对持续故障轨线实施同样的非线性变换以确定临界切除时间时，避免了非线性变换带来的多值性的问题，而只有在没有多值性问题的困扰下，才能采用较高阶的变换：（3）推导出了将原始电力系统系统的运动方程变换到Z空间的约当形式的非线性变换矩阵H21、H31、H41、HS1：（4）在运用四阶了「线性变换的情况下，给出了受扰动后系统的稳定边界的近似的解析表达，在Z空间为Z1=0，在y空间为： Y1+YTH21Y+YTH31Y(2)+Y(2)TH41Y(2)+YTH51Y(3)=0 （5）确定临界失稳的判据简单、快捷：对于一个复杂的电力系统，其稳定边界是相当复杂的一个高维曲面，即便是已知系统稳定边界的解析表达，要求出系统持续故障轨线何时与这一高维曲面相交，在数学上几乎是不可能实现的。

The results show that with the increase of strain rate, the grain sizes of thermal simulation AZ31B alloys with different deformation all decrease; however, when other conditions are the same, the higher deformation will lead to the formation of the smaller grain size, and as the cooling intensity decreases, typical cast structure of AZ31B will appear. With the decrease of roll casting temperature, the dendritic size of roll casting AZ31B alloy sheet prepared by the same strain rate is also reduced, but with the increase of strain rate, the dendritic size of the alloy sheet prepared by the same initial roll casting temperature is decreased, and the tendency of dendritic streamline is strengthened. During the roll casting process of AZ31B alloy, rolling force should not be large, otherwise it will cause heat cracking.

研究结果表明：在不同应变量下，热模拟样品的晶粒粒度均随应变速率的增加而减小，而当其他条件相同时，变形量越大晶粒粒度越小，冷却强度降低，合金呈典型铸态组织；利用铸轧技术生产的AZ31B合金，当应变速率一定时，随着初始铸轧温度的降低，铸轧态板材的树枝晶粒度逐渐减小；而在初始铸轧温度一定时，随着应变速率的增大，铸轧态合金板材的树枝晶粒度也逐渐减小；而随着应变速率的提高，树枝晶沿轧向呈流线状排列的趋势增强；在AZ31B合金铸轧过程中，轧制力不能太大，否则容易引起热裂。

They weren't aggressive, but I yelled and threw a rock in their direction to get them off the trail and away from me, just in case.

他们没有侵略性，但我大喊，并在他们的方向扔石头让他们过的线索，远离我，以防万一。

In slot 2 in your bag put wrapping paper, quantity does not matter in this case.

在你的书包里槽2把包装纸、数量无关紧要。