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In this paper, we discuss the 2-harmonic spacelike submanifolds in a locally symmetric and conformally flat pseudo-riemannian manifold and get two sufficient conditions under which Mn turns into a maximal submanifold,and the results in [2] are improved.

讨论局部对称共形平坦伪黎曼流形的2-调和类空子流形，得到这类子流形成为极大的二个充分条件，推广了文[2]中的结论。

Alternative Title, A Novel Design of the low-pass Filter in the Harmonic Detecting Method ...

Subject/Title，一种瞬时功率理论谐波检测的低通滤波器设计新方法。

Firstly, the function sinx that appears in the simple pendulum equation is replaced with a polynomial of degree 3 using Maclaurin series expansion and Chebyshev polynomial approximation. Subsequently, the resulting equation which is a Duffing type equation is approximately solved with combing Newton's method and the harmonic balance method.

首先，利用Maclaurin展开和Chebyshev多项式加速技术将单摆振动方程中的正弦型恢复力用三次多项式近似代替，得到一个Duffing型方程；然后，将牛顿法与谐波平衡法结合起来建立Duffing方程的解析逼近周期及周期解，从而给出单摆振动的解析逼近解。

Switching power amplifier of magnetic bearing worked in hard switching. To overcome drawbacks of large loss of switching and current harmonic distortion, a parallel resonant DC link soft-switching power amplifier was adopted in this paper.

为克服磁悬浮轴承开关功率放大器工作在硬开关状态时存在的开关损耗和电流纹波干扰严重的缺点，提出一种磁悬浮轴承并联谐振直流环节的软开关功率放大器电路。

A typical Mathieu equation subject to harmonic excitation is acquired by means of the theory of linear vibration. By using integral transformation, the series solutions to the Mathieu equation are obtained.

根据线性振动理论对系统运动微分方程组进行分析，得到了一个受简谐激励的Mathieu方程，通过积分变换，得到了Mathieu方程的级数形式解。

Based on the Timoshenko-Mindlin hypothesis and the Hamilton Principle, a set of governing equations of motion for the laminated non-circular cylindrical thick shells were founded.Using the Galerkin procedure,the Mathieu equation only with time variable was obtained,and this equation was solved by the method of increase harmonic balance.

基于Timoshenko-Midlin假设及Hamilton变分原理，建立了层合中厚非圆柱壳的非线性运动控制方程，采用伽辽金技术，得到仅含时间参数的Mathieu型方程，然后应用增量谐波平衡法进行求解。

By employing the harmonic expansion and matrix inversion, we calculate the polarization of the medium and analyze the interference effect of the coherent field is investigated.

本文采用密度矩阵元的谐振展开方法，理论上研究了处于环型腔内的二能级原子系统的光学双稳和多稳现象的相干控制。

Matrix element of coordinate operator ~l of harmonic oscillator is discussed by using coherent state and normal product.

利用相干态和正规乘积对谐振子任意次幂坐标算符^Xl矩阵元进行了讨论，导出了计算^Xl矩阵元的一般公式，为处理谐振子的微扰问题提供了一种新的方法。

Supposition of two vibrations with same frequency and direction, condition generated mechanical wave, dynamic equation of plane harmonic wave.

同方相同频率的两个简谐振动的合成；机械波产生的条件；平面简谐行波的运动学方程。

Week 4 Supposition of two vibrations with same frequency and direction, condition generated mechanical wave, dynamic equation of plane harmonic wave.

第4周 同方相同频率的两个简谐振动的合成；机械波产生的条件；平面简谐行波的运动学方程。

I didn't watch TV last night, because it .

昨晚我没有看电视，因为电视机坏了。

Since this year, in a lot of villages of Beijing, TV of elevator liquid crystal was removed.

今年以来，在北京的很多小区里，电梯液晶电视被撤了下来。