in this paper, we introduce a class of rings which is a generalization of reversible rings. let r be a ring with identity. a ring r is called central reversible if for any a,b ∈ r, ab=0 implies ba belongs to the center of r. since every reversible ring is central reversible, we study sufficient conditions for central reversible rings to be reversible. we prove that some results of reversible ri...

in this paper we focus on a special class of commutative local‎ ‎rings called spap-rings and study the relationship between this‎ ‎class and other classes of rings‎. ‎we characterize the structure of‎ ‎modules and especially‎, ‎the prime submodules of free modules over‎ ‎an spap-ring and derive some basic properties‎. ‎then we answer the‎ ‎question of lam and reyes about strongly oka ideals fam...

This paper studies wavelength assignment algorithms on WDM all-optical trees of rings under different models: static, incremental and dynamic. It is shown that 5L/2 is the tight bound of the number of required wavelengths for static trees of rings with load L. This paper also proposes an O[log2(t+1)]-approximation and a  ∑ = ∈ h i R r r V i 1 | ) ( | log max   +h-approximation algorithm for ...