N. Ashrafi
Semnan UniversityFaculty of Mathematics, Statistics and Computer Science, Semnan University, Semnan, Iran.
[ 1 ] - The unit sum number of Baer rings
In this paper we prove that each element of any regular Baer ring is a sum of two units if no factor ring of R is isomorphic to Z_2 and we characterize regular Baer rings with unit sum numbers $omega$ and $infty$. Then as an application, we discuss the unit sum number of some classes of group rings.
[ 2 ] - The unit sum number of discrete modules
In this paper, we show that every element of a discrete module is a sum of two units if and only if its endomorphism ring has no factor ring isomorphic to $Z_{2}$. We also characterize unit sum number equal to two for the endomorphism ring of quasi-discrete modules with finite exchange property.
[ 3 ] - THE LATTICE OF CONGRUENCES ON A TERNARY SEMIGROUP
In this paper we investigate some properties of congruences on ternary semigroups. We also define the notion of congruence on a ternary semigroup generated by a relation and we determine the method of obtaining a congruence on a ternary semigroup T from a relation R on T. Furthermore we study the lattice of congruences on a ternary semigroup and we show that this lattice is not generally modular...
[ 4 ] - On Twin--Good Rings
In this paper, we investigate various kinds of extensions of twin-good rings. Moreover, we prove that every element of an abelian neat ring R is twin-good if and only if R has no factor ring isomorphic to Z2 or Z3. The main result of [24] states some conditions that any right self-injective ring R is twin-good. We extend this result to any regular Baer ring R by proving that every elemen...
[ 5 ] - مقایسه ای بین روش های ماکسیمم درستنمایی و بیزی برای برآورد پارامترهای سه مدل اقتصادسنجی فضایی
گاهی در اقتصادسنجی مشاهدات مورد مطالعه مستقل نیستند و وابستگی آن‌ها ناشی از موقعیت قرار گرفتن مشاهدات در فضای مورد مطالعه است. برای تحلیل این نوع از دادهها از مدلهای رگرسیونی فضایی استفاده میشود. به دلیل وجود تعداد زیاد پارامتر در این مدلها، برای به دست آوردن برآوردهای ماکسیمم درستنمایی از الگوریتم‌های تکرار شونده استفاده میشود که با مشکل پیچیدگی محاسبات مواجه است. علاوه بر این در مطالعات ...
[ 6 ] - Classification of Monogenic Ternary Semigroups
The aim of this paper is to classify all monogenic ternary semigroups, up to isomorphism. We divide them to two groups: finite and infinite. We show that every infinite monogenic ternary semigroup is isomorphic to the ternary semigroup O, the odd positive integers with ordinary addition. Then we prove that all finite monogenic ternary semigroups with the same index...
[ 7 ] - Diagonal Matrix Reduction over Refinement Rings
Abstract: A ring R is called a refinement ring if the monoid of finitely generated projective R- modules is refinement. Let R be a commutative refinement ring and M, N, be two finitely generated projective R-nodules, then M~N if and only if Mm ~Nm for all maximal ideal m of R. A rectangular matrix A over R admits diagonal reduction if there exit invertible matrices p and Q such that PAQ is...
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