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GLOBAL DIMENSION OF FACTOR RINGS
HIRANO, YASUYUKI,PARK, JAE KEOL,ROGGENKAMP, KLAUS W. 경북대학교 위상수학 기하학연구센터 1995 硏究論文集 Vol.4 No.-
Let R be a right Noetherian ring with right global dimension bounded by 2, which is integral over its centre, and let a be a regular non-unit element in R. Then R/aㆍR is right hereditary if and only if a is not in the square of any maximal ideal of R. More generally, we compare for a right Noetherian ring R which is integral over its center, the global dimension of R with the global dimension of R/(a_(1)R+a_(2)R+…+a_(r)R) for a regular R-sequence {a_(i)}, which will allow us to give a considerable extension of a result of Hillman.
COUNTABLE RINGS WITH ACC ON ANNIHILATORS
HIRANO YASUYUKI,KIM HONG KEE Korean Mathematical Society 2005 대한수학회보 Vol.42 No.3
We consider countable rings with ascending chain condition on right annihilators. We determine the structure of a countable right p-injective Baer ring, a countable semi prime quasi-Baer ring and a countable quasi-Baer biregular ring.
ON RINGS IN WHICH EVERY IDEAL IS WEAKLY PRIME
Yasuyuki Hirano,Edward Poon,Hisaya Tsutsui 대한수학회 2010 대한수학회보 Vol.47 No.5
Anderson-Smith [1] studied weakly prime ideals for a commutative ring with identity. Blair-Tsutsui [2] studied the structure of a ring in which every ideal is prime. In this paper we investigate the structure of rings, not necessarily commutative, in which all ideals are weakly prime.
ON RINGS IN WHICH EVERY IDEAL IS WEAKLY PRIME
Hirano, Yasuyuki,Poon, Edward,Tsutsui, Hisaya Korean Mathematical Society 2010 대한수학회보 Vol.47 No.5
Anderson-Smith [1] studied weakly prime ideals for a commutative ring with identity. Blair-Tsutsui [2] studied the structure of a ring in which every ideal is prime. In this paper we investigate the structure of rings, not necessarily commutative, in which all ideals are weakly prime.
RINGS CHARACTERISED BY SEMIPRIMITIVE MODULES
HIRANO, YASUYUKI,IIUYNII, DINII VAN,PARK, JAE KEOL 경북대학교 위상수학 기하학연구센터 1995 硏究論文集 Vol.4 No.-
A module M is called a CS-module if every submodule of M is essential in a direct summand of M. It is shown that a ring R is semilocal if and only if every semiprimitive right R-module is CS. Furthermore, it is also shown that the following statements are equivalent for a ring R: (ⅰ) R is semiprimary and every right (or left) R-module is injective; (ⅱ) every countably generated semiprimitive right R-module is a direct sum of a projective module and an injective module.
Countable rings with ACC on annihilators
Yasuyuki Hirano,김홍기 대한수학회 2005 대한수학회보 Vol.42 No.3
We consider countable rings with ascending chain con-dition on right annihilators. We determine the structure of a count-able right p-injective Baer ring, a countable semiprime quasi-Baerring and a countable quasi-Baer biregular ring.
Study on an Impeller with Radial and Circumferential-Flow Channels
Takeshi Konishi,Yasuyuki Hirano,Yasuyuki Nishi 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.2
Various types of centrifugal impellers have been proposed to achieve low flow rates and high heads. To improve the performance and suppress an upward-sloping unstable characteristic in the head curve, this paper suggested a new impeller in which radial and circumferential flow passages are regularly and geometrically arranged, and a onedimensional performance prediction method is also proposed. As a result, the impeller suppressed an upward-sloping unstable characteristic in the head curve, and the best efficiency was found to be about 40% for a flow rate of 0.061 m³/min. Furthermore, the results clearly indicate that a one-dimensional performance-prediction method can easily calculate the total loss of the impeller from the best-efficiency-point flow rate to the excess-flow rate.
Takeshi Konishi,Yasuyuki Hirano,Yasuyuki Nishi 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.1
To provide stable operation over a wide flow range, centrifugal pumps should have high pump efficiency at a low flow rates and high total head. A new impeller with radial and annular flow channels that has higher pumping performance than conventional design impellers with the same specific speed and flow rate at a low specific speed was proposed. however, a high unsteady flow was observed inside the pump. In this study, to predict performance and clarify internal flow accurately, unsteady CFD was used to investigate pump performance and internal flow, including different hydraulic losses when the impeller rotates once rotation. The results show that pump performance can be estimated more accurately using unsteady CFD than using steady CFD. Moreover, the constant drop in total head with flow rate is owing to the hydraulic losses in the impeller, which exclude friction, growing in proportion to flow rate