Let $R$ be a commutative ring. The purpose of this article is to introduce a new class of ideals of R called weakly irreducible ideals. This class could be a generalization of the families quasi-primary ideals and strongly irreducible ideals. The relationships between the notions primary, quasi-primary, weakly irreducible, strongly irreducible and irreducible ideals, in different rings, has bee...

notions of strongly regular, regular and left(right) regular $gamma$−semigroupsare introduced. equivalent conditions are obtained through fuzzy notion for a$gamma$−semigroup to be either strongly regular or regular or left regular.

In this paper, we introduce the notions of interval-valued fuzzy prime (resp. strongly prime and semiprime) bi-ideals of a semigroup. By using these ideas we characterize those semigroups for which each interval-valued fuzzy bi-ideal is semiprime and strongly prime.

generalizing the concepts of -fuzzy (left, right, lateral) ideals, -fuzzy quasi-ideals and   -fuzzy bi (generalized bi-) ideals in ternary semigroups, the notions of -fuzzy (left, right, lateral) ideals, -fuzzy quasi-ideals and -fuzzy bi (generalized bi-) in ternary semigroups are introduced and several related properties are investigated. some new results are obtained.

A surface automorphism is strongly irreducible if every essential simple closed curve in the surface intersects its image non-trivially. We show that a three-manifold admits only finitely many surface bundle structures with strongly irreducible monodromy.

in this paper we define ( , ) k  q -fuzzy h -sub hemirings, ( , ) k  q -fuzzy h -ideals, ( , ) k  q - fuzzy     h -bi-ideals and ( , ) k  q -fuzzy h -quasi-ideals. we characterize h -hemiregular and h -intrahemiregular hemirings by the properties of their     ( , ) k  q -fuzzy h -ideals, ( , ) k  q -fuzzy h -bi-ideals and     ( , ) k  q -fuzzy h -quasi-...

it is known that the directed cycle of order $n$ uniquely achieves the minimum spectral radius among all strongly connected digraphs of order $nge 3$. in this paper, among others, we determine the digraphs which achieve the second, the third and the fourth minimum spectral radii respectively among strongly connected digraphs of order $nge 4$.