Affiliation: | 1. Department of Applied Mathematics, Northwestern Polytechnical University, Xi’an 710072, Shaanxi, PR China;2. Department of Applied Mathematics, University of Waterloo, Waterloo, N2L 3G1 Ontario, Canada;1. Department of Applied Mathematics, Northwestern Polytechnical University, Xi''an, Shaanxi 710072, PR China;2. School of Astronautics, Northwestern Polytechnical University, Xi''an, Shaanxi 710072, PR China |