Research is carried out on the discrete noise theory and calculation method, the calculation model of discrete noise and the approximate formula under small Mach number are verified by experiments.
对低马赫数叶轮离散噪声的机理及计算方法进行了研究，并推导了离散噪声的声压计算式、低马赫数下近似计算式和轴心线上的计算式，还实验验证了计算模型。
As an approximate method, with the trigonometric function, the simple pendulum dynamical equation is simplified, and the approximate formula for the period of simple pendulum movement is presented.
利用三角函数作为一种近似方法，对单摆的动力学方程进行了简化，给出了大角度条件下单摆运动的周期的近似公式。
A new approximate formula for the large deflection problem of compression bar with two ends are simply supported is obtained, by the use of Ritz-Galerkin method.
通过非线性振动中常用的里兹-伽辽金法，推出了两端铰支压杆大挠度问题的一个新近似公式，计算结果表明具有较高的精度。
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