An instrument for measuring ultrasonic attenuation by means of comparing the ultrasonic pulse echo with a calibrated exponential decay wave-form is described.
本装置用超声脉冲回波与定标指数波形比较的方法测量超声衰减。
By using the perturbed-energy method, the exponential decay of the solution is obtained for the nonlinear wave equations with time-dependent coefficients and dissipative boundary condition.
利用能量法证明了具耗散边界条件和时间依赖系数的非线性波方程的能量指数衰减性。
By using one-dimension FDTD method we simulates the decay of double exponential pulse through the soil media, and its refractive time-domain wave shape is discussed in detail.
用一维FDTD方法模拟了双指数脉冲在单层岩土介质中的衰减，并对电磁波在岩土层中的穿透进行了详细的讨论。
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