Moreover, it establishes mechanical model of roof structure after first destruction, and points out that sur-hinge-point is dangerous point by analyzing mechanical condition of sliding instability and rotary instabilit.

A feasible Laser Doppler Velocimetry technique based on Amplitude Discrimmation has been used to determine the local gas and solids velocity simultaneously, which can lead to the local slip velocity between the gas and solids in a cocurrent downflow circulating fluidized bed (CDCFB).