Department;
of;
Mathematics,;
Nanjing;
University,;
Nanjing;
210093,;
China;
Department;
of;
Mathematics,;
Changshu;
College,;
Changshu;
215500,;
China;
Department;
of;
Mathematics,;
Nankai;
University,;
Tianjin;
300071,;
China;
quadratic; Lie; superalgebra,; decomposition,; graded; ideal,; isotropic.;