As the subsurface medium is widely viscous, it is necessary to compensate absorption and to correct dispersion of seismic waves in true-amplitude pre-stack imaging. The instability problem encountered in conventional inverse-Q migration hinders the application of the method. In this work, imaging was treated as a linear inverse problem named least-squares reverse time migration (LSRTM). Firstly, we linearized the wave equation and defined the cost function. Then based on the derived equations of the adjoint wave propagation operator, iterative solution was derived using the adjoint-state method. At last dynamical phase encoding technology was used to reduce computation cost. This method breaks a new way for imaging in visco-acoustic media while avoiding the instability problem. The true-amplitude imaging results can be obtained while compensating absorption and correcting dispersion automatically. It is also a good way to suppress the imaging noise and correct amplitude unbalance caused by geometrical spreading or weak illumination. Compared with conventional reverse time migration (RTM), this method can yield results with higher resolution and lower imaging noise. The validity of the method was demonstrated by the numerical test on synthetic seismic data.

In order to effectively suppress the transverse random vibration of a class of irregular shape and structure valve for launch vehicle in the ground test, adopting the method of combining finite element simulation and experiment, the influence of different structure tools on the transverse vibration of the valve is investigated. Moreover, the impact of arrangement position of valve and semi-circular tool assembly on transverse vibration of valve is studied. Based on the analysis of the influence of tooling of different structures on the transverse random vibration of the valve, it is proposed that semi-circular fixture can effectively reduce the transverse vibration for this kind of valve. Furthermore, when placed in the center of vibration table or near the vibration source, can decrease transverse vibration of the valve remarkably.