研究了w-平坦模与w-投射模的直和性质,分别给出了PVMD与w-平坦模、Krull整环与w-投射模之间的关联.此外,讨论了正合列中的w-平坦模.证明了若R是整环,0→N→F→M→0是无挠R-模正合列,其中N,F是平坦模,则M是w-平坦模当且仅当对R的任何w-理想I,N∩IF=IN,当且仅当对R的任何有限型w-理想I,N∩IF=IN.
The direct sum properties of w-flat modules and w-projective modules are studied.And some connections between the PVMDs and the w-flat modules,between the Krull domains and the w-projective modules are shown.Meanwhile,the w-flat modules are discussed in an exact sequence.It is proved that if R is a domain,0 → N → F → M→ 0 is an exact sequence of torsionfree R-modules,where N,F are flat,then M is w-flat if and only if N ∩ IF=IN for any w-ideal I of R,if and only if N ∩ IF=IN for any finite type w-ideal I of R.