“…We are particularly interested in the bright soliton solution given in (25a) for μ < 0 and c 0 = −1. In this case, with k(t) = k, g(t) = g as constants, from previous analysis (19a) and (23), it is not hard to see that p(t)σ (t) = κ is constant, q(t) = t( is constant), the solution (25) in this situation is of bright soliton type(|ψ(x, t)| ∼ sech 1/γ ( √ −μ(κ x + t − ξ 0 ))) moving with constant speed /κ. When g(t)(or k(t))depends on t, p(t)σ (t), which indicates the compressing ratio of the travelling wave along the x-direction, generally is not constant and the format of q(t)/(p(t)σ (t)) is complicated, which mean that there is shape variation in the traveling wave and the wave peak move with acceleration.…”