The Velocity of Viscous Vortex Rings

The motion of vortex rings of small cross section is considered. A formula is derived for the velocity of a ring in an ideal fluid with an arbitrary distribution of vorticity in the core. The effects of viscosity are then examined. A definition of the velocity of an unsteady diffusing ring is given and it is shown that the method used to calculate the ring speed in an ideal fluid can be extended to give the velocity of a vortex ring subject to viscous diffusion.     

ON ORDER RINGS OF SEMI-PRIMARY RINGS

The main results of this paper are stated as follows.Let R be an orderring in thesemi-primary ring Q.Suppose that R satisfies the maximal condition for nil right ideals ofR,Then we have(i)if an ideal I of R has a finite length as right R-module,then I alsohas a finite length as left R-module;(ii)denote by A(R)the Artinian radical of R,andN the nil radical of R,then A(R)+N/N=A(R/N),if R satisfies the commutative condi-tion on the zero product of prime ideals of B.     

一般环之分式环

本文给出一般环R之分式环△^-1R的构造和△^-R的理想的一些性质,推广了现有中外教科书的结论．证明了（1）△^-1R中理想有且仅有形式△^-1I,其中△3R．（2）如果P是R的素理想,且△∩P=Ф,则△^-1P是△^-1R的素理想,且θ^-1（△^-1P）=P。     

正则环和GP-内射环

A ring R is called left Gp-injective if for any a∈R, there exists a positive integer n such that any left R-homomorphism of Raⁿ into R extends to one of R into R. In this paper, we prove that the centre of semiprime (left nonsingular) left GP- injective ring is regular ring, and improve some propositions in [3].     

On Quotient Rings in Alternative Rings

We introduce a notion of left nonsingularity for alternative rings and prove that an alternative ring is left nonsingular if and only if every essential left ideal is dense, if and only if its maximal left quotient ring is von Neumann regular (a Johnson-like Theorem). Finally, we obtain a Gabriel-like Theorem for alternative rings.     

On CS Rings and QF Rings

In this paper, we shall discuss the conditions for a right SC right CS ring to be a QF ring. In particular, we prove that if R is a right SI right CS ring satisfying the reflexive orthogonal condition (*) and if every CS right R-module is -CS, then R is a QF ring.AMS Subject Classification (1991): 16L30 16L60     

环与剩余类环的同调维数

Ｓａｎｄｏｍｉｅｒｓｋｉ Ｆ．Ｌ,Ｓｍａｌｌ Ｌ．Ｗ,和 Ｆｉｅｌｄｓ Ｋ．Ｌ．［１－２］在“幂零”条件下研究了环与约化环的同调维数．然而对一些环（如交换 Ｖｏｎ Ｎｅｕｍａｎｎ正则环）,“幂零’的条件是不成立的．因此,在本文中我们考虑非“幂零”条件下（如Ｒ（Ｒ／Ｉ）（（Ｒ／Ｉ）Ｒ）是Ｒ－投身的或Ｒ（Ｒ／Ｉ）Ｒ是Ｒ－平坦的）,环与约化环的同调维数．     

关于半交换环与强正则环

本文得到了环Ｒ是强正则环的若干充分必要条件，证明了下面条件是等价的：（１）Ｒ是强正则的；（２）Ｒ是半交换正则的；（３）Ｒ是半交换的左ＳＦ－环；（４）Ｒ是半交换的ＥＬＴ环，且使得每个单左Ｒ－模是Ｐ－内射的或者平坦的；（５）Ｒ是半交换右非奇异的左ＳＦ－环；（６）Ｒ是半素的半交换左（或右）Ｐ－内射环．     

On Köthe Rings

Mathematische Annalen -     

On the Representation of Finite Rings by Matrices over Commutative Rings

In this paper, it is shown that all finite associative rings satisfying the identities nx?=?0 and x ³ f(x)?+?x ²?=?0, where n is an odd natural number and f(x) ∈ ?[x], are embeddable in the ring of matrices over some suitable commutative ring.     

子半理想环

本文提出了环论中的一个新概念：子半理想，得到了群环为子半理想环的一个充要条件。     

关于SIS环

通过自内射环和半本原环给出了SIS环的定义,即如果RRR是内射的并且J(R)=0,我们称此环为SIS环;并且得到了它的一些刻画和性质.     

On d-Free Rings

Abstract

The recent development of the theory of functional identities is based on the concept of d-freeness introduced by Beidar and Chebotar. This concept involves two conditions, the first one concerns the situation when the expression ∑ _i E _i x _i  + ∑ _j x _j F _j is always zero, and the second one the situation when this expression is always central. We discuss the relationship between these two conditions and in particular we establish that in general they are independent of each other.     

On Clean Rings

A ring R is called clean if every element of R is the sum of an idempotent and a unit. Let M be a R-module. It is obtained in this article that the endomorphism ring End(M) is clean if and only if, whenever A = M′ ⊕ B = A₁ ⊕ A₂ with M′ ? M, there is a decomposition M′ =M₁ ⊕ M₂ such that A = M′ ⊕ [A₁ ∩ (M₁ ⊕ B)] ⊕ [A₂ ∩ (M₂ ⊕ B)]. Then unit-regular endomorphism rings are also described by direct decompositions.     

关于半准素环

交换环Ｒ称为（受限制的）半准素环，如果对Ｒ的每个（非零）主理想Ａ，都有A^1/2是Ｒ的素理想，本文刻画了受限制的半准素环，给出了有单位元的Ｎｏｅｔｈｅｒ受限制的半准素环的分类以及半准素整环是伪赋值整环的一个条件     

On Hopfian Rings

The main results proved in this paper are:(i) If R is a boolean hopfian ring then the polynomial ring R[T] is hopfian.(ii) Let R and S be hopfian rings. Suppose the only central idempotents in S are 0 and 1 and that S is not a homomorphic image of R. Then R × S is a hopfian ring.     

On Valuation Rings

In this article, we provide necessary and sufficient conditions for R = A ∝ E to be a valuation ring where E is a non-torsion or finitely generated A-module. Also, we investigate the (n, d) property of the valuation ring.     

关于NF-环的构造

研究了无限的ＮＦ－环及有限的ＮＦ－环，并且给出了有限ＮＦ－环的构造．     

环的弱正则性

本文给出了环的弱正则性的一个充要条件，还讨论了Ｍｕｎｎ环的弱正则性．最后对环的半格和及补半格和，给出了弱正则性的刻画．