Browsing by Author "Wen, H. C."

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Enhancement of mechanical properties of electron beam-welded D6ac steel tube
(2015-04-01)
Wu, S. C.
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Tseng, K. H.
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Wen, H. C.
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機械工程學系
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Department of Mechanical Engineering
A forward flow-formed D6ac steel tube was joined through the electron beam welding process and was then subjected to post-weld heat treatment. The mechanical properties and hardness profiles of the as-welded (without heat treatment after welding) steel and different post-weld heat treatment weldments were investigated. The results show that the as-welded D6ac steel exhibited very poor mechanical strength and elongation. After post-weld heat treatment, a large improvement in the mechanical properties of the weldment was achieved. Forward flow-formed D6ac electron beam weldment subjected to post-weld heat treatment at 350 degrees C reached the largest yield strength and ultimate tensile strength values (approximately 1359.2 and 1494.3 MPa, respectively). Forward flowformed D6ac electron beam weldment subjected to post-weld heat treatment at a temperature of 650 degrees C exhibited an overtempered state, which led to mechanical strength and hardness deteriorations of the weldment. This study found that the forward flow-formed D6ac electron beam weldment heat-treated at 350-450 degrees C and held at this temperature range for 2 h exhibits high mechanical strength, sufficient elongation and a yield strength/ultimate tensile strength ratio of 0.91.
Optimal design of integrally gated CNT field-emission devices using a genetic algorithm
(2007-10-03)
Chen, P. Y.
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Chen, C. H.
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Wu, J. S.
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Wen, H. C.
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Wang, W. P.
A method to optimize the focusing quality of integrally gated CNT field- emission ( FE) devices by combining field- emission modeling and a computational intelligence technique, genetic algorithm ( GA), is proposed and demonstrated. In this work, the e- beam shape, as a characteristic parameter of electron- optical properties, is calculated by field- emission simulation modeling. Using a design tool that combines GA and physical modeling, a set of structural and electrical parameters for four FE device groups, including double- gate, triple- gate, quadruple- gate and quintuple- gate type, were optimized. The resultant FE devices exhibit satisfactory e- beam focusabilities and the extracted parameters with the best performance for each type of FE device were represented to be fabricated by a VLSI technique. The GA- based automatic design parameter extraction will significantly benefit the design of integrated electron- optical systems for versatile vacuum micro- and nano-electronic applications.