Automorphisms of the Nilpotent Subalgebras Generated by the Positive Root Vectors of Chevalley Algebras of Some Types Over Communicative Rings ( for Case that There is Only the Trivial Graph Automorphism) 交换环上某些Chevalley代数的由正根基向量生成的幂零子代数的自同构(只有平凡的图自同构的情况)