The acoustic scattering with impedance boundary condition is transferred into solving a problem in a minimum norm sense.

Aim To recover the impedance coefficient from the far field pattern of the scattered wave of the acoustic scattering problem with impedance boundary condition.

Potential theory is used to transfer the impedance boundary condition scattering problem into the boundary integral equations of the second kind.

The present paper summarizes the characteristics of the malfunction in the damper bar of the main drive motor in the Hot Strip Rolling Mill and describes the over all course of repair on the malfunction and its key technical points.

Analysis of the overdamping character of a linear oscillator;

Then two methods available for measuring the relative overdamping of a geophone were discussed.

After analysing the linear oscillator in the overdamping states,it is concluded that under the special initial conditions the linear oscillator can cross the position of equilibrium only once;but under the other special initial conditions,it can come back the position of equilibrium at the fastest speed.