Browsing by Author "Yu, Ming-Ta"

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A study on the optimization methods for optomechanical alignment
(2006-01-01)
Yu, Ming-Ta
;
Lin, Tsung-Yin
;
Lia, Yi-You
;
Shu, Pei-Feng
;
機械工程學系
The alignment for optomechanical components is important in designing and manufacturing optical systems. This study uses optical fibers for example to find suitable optimization strategies for optomechanical alignment. The core diameter of the single-mode fiber is about 6 mu m to 9 mu m. Any slight misalignment or deformation of the optical mechanism will cause signification optical losses during connections. The alignment methods can be divided into passive and active ones. In the passive alignment, optical connectors, ferrules, and sleeves are used to align two optical fibers. In the active alignment, the best connection position with minimum connection losses must be found, and users usually take a lot of effort to do this. This study uses different optimum methodologies: non-gradient-based, gradient-based, and Hessian-based methods, to find the optimum position. The non-gradient-based method has low accuracy and the efficiency cannot be increased. The gradient-based methods seem to have better efficiency to find the optimum position because it uses gradient information to calculate the search direction in every iteration. Finally for the Hessian-based methods, it is found that the advantage of using Hessian matrix is not obvious because the light intensity distribution is similar to the Gaussian distribution.
A study on the optimization methods for optomechanical alignment - art. no. 62890Y
(2006)
Yu, Ming-Ta
;
Lin, Tsung-Yin
;
Lia, Yi-You
;
Shu, Pei-Feng
;
機械工程學系
The alignment for optomechanical components is important in designing and manufacturing optical systems. This study uses optical fibers for example to find suitable optimization strategies for optomechanical alignment. The core diameter of the single-mode fiber is about 6 mu m to 9 mu m. Any slight misalignment or deformation of the optical mechanism will cause signification optical losses during connections. The alignment methods can be divided into passive and active ones. In the passive alignment, optical connectors, ferrules, and sleeves are used to align two optical fibers. In the active alignment, the best connection position with minimum connection losses must be found, and users usually take a lot of effort to do this. This study uses different optimum methodologies: non-gradient-based, gradient-based, and Hessian-based methods, to find the optimum position. The non-gradient-based method has low accuracy and the efficiency cannot be increased. The gradient-based methods seem to have better efficiency to find the optimum position because it uses gradient information to calculate the search direction in every iteration. Finally for the Hessian-based methods, it is found that the advantage of using Hessian matrix is not obvious because the light intensity distribution is similar to the Gaussian distribution.
Effects of powders on the precision of a powder metallurgy helical gear
(2008)
Yu, Ming-Ta
;
Tsay, Chung-Biau
;
機械工程學系
;
Department of Mechanical Engineering
This study refers to the conditions of practical powder metallurgy manufacture process, and proceeds to experiments and gear precision measurements as well as investigation on the effects of two parameters, powders and pitch circle radius, on gear precision. The relationship between gear parameters and gear surface deviations was derived from the mathematical model of the involute helical gear and the analysis of gear surface deviations. In accordance with the measurement results of experiments, an ideal correction on the parameters of a forming die is obtained from the computer simulations of gear surface deviations.
Performance simulation and thermal stress analysis of ceramic recuperators formed by SIC and MAS
(2008)
Yang, Chun-Hsiang
;
Yu, Ming-Ta
;
Chen, Chiun-Heng
;
Chen, Chiun-Hsun
;
機械工程學系
This study conducted performance simulations for ceramic recuperators and performed thermal stress analysis to provide reliable guidance for heat recuperator designers. A numerical simulation was conducted utilizing STAR-CD to predict thermal and pressure flow fields inside two 50W ceramic compact heat exchangers, one made of SiC and the other made of MAS. The predicted temperature and pressure profiles from performance simulations were then used to compute thermal stress analysis of the ceramic plate recuperators. Thus, three issues were discussed-the impact of fluid pressure and the thermal expansion on the ceramic recuperators, the effects of the constraint condition of the model boundary on the ceramic plates, and the different effects of the two different ceramic recuperator cores could made to the outer metal shells.