semiclassical interpretation of the Wigner function \[10\]. Assuming the background density and velocity vary slowly on the soliton scale, Busch derived the equation of motion for dark soliton propagating through an effectively one-dimensional cloud of BEC, by using a multiple scale boundary layer theory. Recently, Filho et al. investigated the dynamics of the growing and collapsing of BEC in a system of trapped ultracold atoms with negative scattering lengths and found that the number of atoms can go far beyond the static stability limit \[12\].

Current efforts are being focused on coupled two-component and multi-component BEC. Interference and dynamics of component separation in two-component BEC was observed \[4,13\]. The quantum statistics of the ground state of a two-mode model for coupled BECs was analyzed \[14\], and strong squeezing of the number difference for positive nonlinearities and a regime of squeezing in the relative phase for negative nonlinearities were revealed. The dynamics of Josephson-like oscillations between two coupled BECs was studied using the time-dependent variational method \[15\], from the calculation result, the tunneling dynamics is $``$coherent$"$ when the trap is not displaced, that is, the orbitals of each condensate do not change; on the other hand, the change in the condensate 