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RISS 인기검색어
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- 저자 : Dongwen Zhang (검색결과 3 건)
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Dongwen Zhang,JOHN MICHAEL RASSIAS,Yongjin Li 강원경기수학회 2022 한국수학논문집 Vol.30 No.4
By established a Banach space with the Hausdorff distance, we introduce the alternative fixed-point theorem to explore the existence and uniqueness of a fixed subset of Y and investigate the stability of set-valued Euler-Lagrange functional equations in this space. Some properties of the Hausdorff distance are furthermore explored by a short and simple way.
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Automated Refactoring from Synchronized Locks to Reentrant Locks
Yang Zhang,Dongwen Zhang,Huiyong Wang 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.6
Multi-threaded Java applications using synchronized or reentrant locks respectively exist performance trade-off. Parallel programmers usually use manual refactoring to test the performance of locks in a particular environment. However, manual refactoring is labor-intensive and error-prone. There is a strong need for automated support to find which one is more suitable to exert the performance of applications. This paper presents a refactoring framework to enable the transformation from synchronized locks to reentrant locks automatically. The framework analyzes global monitors based on Quad intermediate representation and visitor pattern in the Joeq compiler, validates the consistency of analysis results, and performs the transformation. The framework is evaluated on three benchmarks including red-black tree, producer-consumer problem, and SPECjbb2005. The total time is less than 4s for all three benchmarks on common desktop computer, and the successful refactoring results are observed.
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Dongwen Wang,Wei Yang,Jiafeng Yang,Kongming Jiang,Junjie Zhang,Yang Fu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9
Research on the vibration characteristics of the permanent magnet synchronous motor (PMSM) is hindered by the harmonic characteristics of the unbalanced magnetic pull force when air-gap eccentricity is neglected. Thus, the effects of both air-gap eccentricity and mass eccentricity on the rotor vibration have not yet been fully elucidated. To address this, a unified expression for the unbalanced magnetic pull force of the motor was derived under various pole pairs and air-gap eccentricities. The distribution of the radial electromagnetic force under different eccentricities is revealed. An electromagnetic simulation model of the fan motor was established for three eccentric cases and the effect of the unbalanced magnetic pull distribution and harmonic frequency characteristics on the rotor were analyzed. Furthermore, the influence of the gyroscopic effects on the modal frequency of the rotor structure was studied. The harmonic response of the rotor shaft system was first established using multi-physical field coupling, then the vibration amplitude-frequency laws of the rotor-shaft system under the influence of air-gap eccentricity and mass eccentricity were investigated. To reduce the vibration of the unbalanced PMSM rotor-shaft system, a multi-objective optimization was performed using the genetic algorithm in ANSYS Workbench. Research on the vibration characteristics of the permanent magnet synchronous motor (PMSM) is hindered by the harmonic characteristics of the unbalanced magnetic pull force when air-gap eccentricity is neglected. Thus, the effects of both air-gap eccentricity and mass eccentricity on the rotor vibration have not yet been fully elucidated. To address this, a unified expression for the unbalanced magnetic pull force of the motor was derived under various pole pairs and air-gap eccentricities. The distribution of the radial electromagnetic force under different eccentricities is revealed. An electromagnetic simulation model of the fan motor was established for three eccentric cases and the effect of the unbalanced magnetic pull distribution and harmonic frequency characteristics on the rotor were analyzed. Furthermore, the influence of the gyroscopic effects on the modal frequency of the rotor structure was studied. The harmonic response of the rotor shaft system was first established using multi-physical field coupling, then the vibration amplitude-frequency laws of the rotor-shaft system under the influence of air-gap eccentricity and mass eccentricity were investigated. To reduce the vibration of the unbalanced PMSM rotor-shaft system, a multi-objective optimization was performed using the genetic algorithm in ANSYS Workbench. The optimization results show that when the motor rotor core is shifted 2 mm in the positive X direction and the distance between the double-row bearing and rotor core is 7 mm, the vibration acceleration amplitude is reduced by 54.9 % compared with the original model.
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