In order to find out the contact pressure intensity distribution and its effects on the workepiece flatness error in plane polishing with retaining ring,the contact model and the boundary conditions are built up based...In order to find out the contact pressure intensity distribution and its effects on the workepiece flatness error in plane polishing with retaining ring,the contact model and the boundary conditions are built up based on the axial symmetric elastic contact theory.The pressure intensity distribution is calculated and analyzed with the help of the Hankel transform theory and the constructing solution method of Chebyshev orthogonal polynomials.And then,the effects of the dimensionless ring-workpiece gap,the load ratio of the retaining ring and the dimensionless ring width on the contact pressure intensity distribution are obtained.Finally,based on the distribution theory of material removal volume,the effects of the pressure intensity distributions on the flatness errors of polished workpiece are also investigated experimentally.The results show that the contact pressure intensity distribution becomes more uniform and the better profile of polished workpiece can also be obtained,if the dimensionless ring-workpiece gap is reduced,the load ratio is selected as 0.6 to 0.85,and the dimensionless ring width is taken as 0.13 to 0.40.展开更多
A left ideal I of a ring R is small in case for every proper left ideal K of R, K ＋ I ≠R. A ring R is called left PS-coherent if every principally small left ideal Ra is finitely presented. We develop, in this paper...A left ideal I of a ring R is small in case for every proper left ideal K of R, K ＋ I ≠R. A ring R is called left PS-coherent if every principally small left ideal Ra is finitely presented. We develop, in this paper, PS-coherent rings as a generalization of P-coherent rings and J-coherent rings. To characterize PS-coherent rings, we first introduce PS-injective and PS-flat modules, and discuss the relation between them over some spacial rings. Some properties of left PS-coherent rings are also studied.展开更多
The design of a bolted flat cover is extremely important for the structural integrity of pressure vessels.The present design codes provide the thickness calculation equations for a bolted flat cover with single metal ...The design of a bolted flat cover is extremely important for the structural integrity of pressure vessels.The present design codes provide the thickness calculation equations for a bolted flat cover with single metal gasket.However,the rules for a bolted flat cover with double metal sealing rings are not developed to date.In the study,a new thickness calculation equation for the bolted flat cover with double metal sealing rings is proposed.First,the theoretical stress solution for bolted flat cover with the double metal sealing rings is obtained,based on the theory of simply supported circular plate and then verified using the results from finite element analyses.The results indicate that the influence of double metal sealing ring on the stress of the flat cover is more serious compared to single metal gasket.Second,a more accurate and reasonable equation is proposed to calculate the thickness of bolted flat cover with double metal sealing rings based on the derived theoretical equations of maximum stress.Finally,the influence of linear load and the spacing between rings on the thickness are discussed.Subsequently,a few suggestions are provided to design low-pressure or atmosphere pressure vessels.The study provides a theoretical foundation to develop design codes of pressure vessels in nuclear reactors.展开更多
In [1], Saroj Jain Posed an open Problem: Is a right IF-ring left coherent? In this note, we discuss this problem and Prove that a two-sided IF-ring certainly is twosided coherent,
设T=A 0 U B是形式三角矩阵环,其中A,B是环,U是(B,A)-双模.利用Hom函子和伴随同构等理论,刻画形式三角矩阵环T上的F-Gorenstein平坦模结构,并证明若BU的平坦维数有限,U A的平坦维数有限且对任意的余挠左A-模C,有U■AC是余挠左B-模,则左T...设T=A 0 U B是形式三角矩阵环,其中A,B是环,U是(B,A)-双模.利用Hom函子和伴随同构等理论,刻画形式三角矩阵环T上的F-Gorenstein平坦模结构,并证明若BU的平坦维数有限,U A的平坦维数有限且对任意的余挠左A-模C,有U■AC是余挠左B-模,则左T-模M_(1)/M_(2)φ^(M)是F-Gorenstein平坦模当且仅当M_(1)是F-Gorenstein平坦左A-模,Cokerφ^(M)是F-Gorenstein平坦左B-模,且φ^(M):U■AM 1→M_(2)是单射.展开更多
基金Sponsored by the National Nature Science Foundation of China (50875179)
文摘In order to find out the contact pressure intensity distribution and its effects on the workepiece flatness error in plane polishing with retaining ring,the contact model and the boundary conditions are built up based on the axial symmetric elastic contact theory.The pressure intensity distribution is calculated and analyzed with the help of the Hankel transform theory and the constructing solution method of Chebyshev orthogonal polynomials.And then,the effects of the dimensionless ring-workpiece gap,the load ratio of the retaining ring and the dimensionless ring width on the contact pressure intensity distribution are obtained.Finally,based on the distribution theory of material removal volume,the effects of the pressure intensity distributions on the flatness errors of polished workpiece are also investigated experimentally.The results show that the contact pressure intensity distribution becomes more uniform and the better profile of polished workpiece can also be obtained,if the dimensionless ring-workpiece gap is reduced,the load ratio is selected as 0.6 to 0.85,and the dimensionless ring width is taken as 0.13 to 0.40.
文摘A left ideal I of a ring R is small in case for every proper left ideal K of R, K ＋ I ≠R. A ring R is called left PS-coherent if every principally small left ideal Ra is finitely presented. We develop, in this paper, PS-coherent rings as a generalization of P-coherent rings and J-coherent rings. To characterize PS-coherent rings, we first introduce PS-injective and PS-flat modules, and discuss the relation between them over some spacial rings. Some properties of left PS-coherent rings are also studied.
基金supported by the‘‘Strategic Priority Research Program’’of the Chinese Academy of Sciences(No.XDA02010000)
文摘The design of a bolted flat cover is extremely important for the structural integrity of pressure vessels.The present design codes provide the thickness calculation equations for a bolted flat cover with single metal gasket.However,the rules for a bolted flat cover with double metal sealing rings are not developed to date.In the study,a new thickness calculation equation for the bolted flat cover with double metal sealing rings is proposed.First,the theoretical stress solution for bolted flat cover with the double metal sealing rings is obtained,based on the theory of simply supported circular plate and then verified using the results from finite element analyses.The results indicate that the influence of double metal sealing ring on the stress of the flat cover is more serious compared to single metal gasket.Second,a more accurate and reasonable equation is proposed to calculate the thickness of bolted flat cover with double metal sealing rings based on the derived theoretical equations of maximum stress.Finally,the influence of linear load and the spacing between rings on the thickness are discussed.Subsequently,a few suggestions are provided to design low-pressure or atmosphere pressure vessels.The study provides a theoretical foundation to develop design codes of pressure vessels in nuclear reactors.
文摘In [1], Saroj Jain Posed an open Problem: Is a right IF-ring left coherent? In this note, we discuss this problem and Prove that a two-sided IF-ring certainly is twosided coherent,
