“…Many works on nonlinear evolution equations have been studied, such as the Hamiltonian structure [1,2], the infinite conservation laws [3,4], the Bäcklund transformation [5,6] and so on [7][8][9]. Besides, the exact solution of these equations, which can be expressed in various forms by different methods, is also a significant subject of soliton research [10][11][12][13][14][15][16][17][18][19][20][21][22]. In recent years, with the development of soliton theory, more and more researchers pay attention to the Riemann-Hilbert approach.…”