Dept.;
of;
Applied;
Mathematics,;
Northwestern;
Polytechnical;
University,;
Xi'an;
710072,;
China;
College;
of;
Science,;
Donghua;
University,;
Shanghai;
200051,;
China;
College;
of;
Math.;
and;
Information;
Science,;
Shaanxi;
Normal;
University,;
Xi'an;
710062,;
China;
Aircraft;
Strength;
Research;
Institute;
of;
China,;
Xi'an;
710065,;
China;
Department;
of;
Engineering;
Mechanics,;
Northwestern;
Polytechnical;
University,;
Xi'an;
710072,;
China;