进一步研究了由Ara首次引入并研究的没有单位元的exchange环.给出了它的一些新的等价刻画和性质.例如:一个一般环,是exchange的当且仅当对它的任意理想L以及a^-=a^-2∈I/L,存在w∈r.ureg(I)使得w^-=a^-;E(R,I)(环R通过它的理想I生成的理想扩张)是一个exchange环当且仅当R和I都是exchange环.还证明了如果环尺的双边理想I是一个exchange一般环,则I的每一个中心元素都是I中一个clean元素.
The exchange rings without unity, first introduced by Ara, are further investigated. Some new characterizations and properties of exchange general rings are given. For example, a general ring I is exchange if and only if for any left ideal L of I and a^-= a^-2 ∈I/L, there exists w ∈ r. ureg(I) such that w^- = a^-; E(R, I) ( the ideal extension of a ring R by its ideal I) is an exchange ring if and only if R and I are both exchange. Furthermore, it is presented that if I is a two-sided ideal of a unital ring R and I is an exchange general ring, then every central element of I is a clean element in 1.