(color online) The maximum amplitude in the colliding processes as a function of the amplitude of the solitary wave L. Panels (a) and (c) corresponding to A L = A R , but the amplitude of the solitary wave R is fixed in panels (b) and (d). The red dots are from the numerical results, the black ones are the analytical results by further considering the higher order terms of O ( ε ) , A L + A R + O ( ε ) , the blue ones are the linear results of A L + A R , where A L and A ^R are the amplitudes of solitary waves L and R, respectively.