Normal graphs are defined in terms of cross-intersecting set families: a graph is normal if it admits a clique cover Q and a stable set cover S s.t. every clique in Q intersects every stable set in S. Normal graphs can be considered as closure of perfect graphs by means of co-normal products (K ̈orner [6]) and graph entropy (Czisz ́ar et al. [5]). Perfect graphs have been recently characterized a...

To a given type of algebraic systems # there corresponds at least one first order language L. One can then ask whether a property P, defined for members of #, is expressible in the language L. In other words, is there a set of sentences II such that a member M of # has property P if and only if all sentences in n are true in M. If the set II exists we say that P is definable in L. Further, Q) i...

Abstract. Let R be a quotient ring of a commutative coherent regular ring by a finitely generated ideal. Hovey gave a bijection between the set of coherent subcategories of the category of finitely presented R-modules and the set of thick subcategories of the derived category of perfect R-complexes. Using this isomorphism, he proved that every coherent subcategory of finitely presented R-module...

An electron beam in a storage ring seems to be a perfect driver for a free electron laser. The understanding of storage rings is very well advanced to.project designs with high peak current, small beam sizesand short damping times. Since the beam is recycled after passage through the optical cavity we can expect a relatively high overall efficiency. On the other hand, however the fact that we d...

Abstract Vortex beams carrying orbital angular momentum (OAM) open a new perspective in various terahertz research. Multichannel and divergence controllable vortex beam generation holds the key to promoting development of OAM related Here, we introduced experimentally demonstrated quasi-perfect (Q-PVB) with angle independent topological charge multichannel Q-PVBs all-dielectric multifunctional ...

in this paper, we introduce the new notion of n-f-clean rings as a generalization of f-clean rings. next, we investigate some properties of such rings. we prove that mn(r) is n-f-clean for any n-f-clean ring r. we also, get a condition under which the de nitions of n-cleanness and n-f-cleanness are equivalent.

a topoframe, denoted by $l_{ tau}$,  is a pair $(l, tau)$ consisting of a frame $l$ and a subframe $ tau $ all of whose elements are complementary elements in$l$. in this paper, we define and study the notions of a$tau $-real-continuous function on a frame $l$ and the set of realcontinuous functions $mathcal{r}l_tau $ as an $f$-ring.we show that $mathcal{r}l_{ tau}$is actually a generalization ...

for a fixed positive integer , we say a ring with identity is n-generalized right principally quasi-baer, if for any principal right ideal of , the right annihilator of is generated by an idempotent. this class of rings includes the right principally quasi-baer rings and hence all prime rings. a certain n-generalized principally quasi-baer subring of the matrix ring are studied, and connections...

We define the mesh signature primitive as an anonymous signature similar in spirit to ring signatures, but with a much richer language for expressing signer ambiguity. The language can represent complex access structures, and in particular allows individual signature components to be replaced with complete certificate chains. Because withholding one’s public key from view is no longer a shield ...