Browsing by Author "Cheng, Chih-Wei"

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An Experimental Study on Micro Proton Exchange Membrane Fuel Cell
(2012-06-01)
Chen, Chiun-Hsun
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Chen, Tang-Yuan
;
Cheng, Chih-Wei
;
Peng, Rong-Guie
;
機械工程學系
This study fabricates a micro proton exchange membrane fuel cell (PEMFC) using micro electro mechanical systems (MEMS) technology. The active area of the membrane is 2 cm x 2 cm (4 cm(2)). The study is divided into two categories: [(1) the parametric experimental investigation, and (2) the durability test. This work is an attempt to find out how several parameters, including reheat temperature, the material of the current collector plates, the open ratio, and different cathode gases affect micro PEFMC performance. According to the experimental results obtained, both the conducting area and the material of the current collector plates exert great influences on the performance of the micro PEMFC, especially in the conducting area. The cell's performance is finite when the gas reheat temperature is increased. The results show that the cell performance is better for an open ratio of 75% as compared to ratios of 50% and 67%. The concentration polarization is improved by increasing the air flow rate at high current densities, and if the GDL diffusive capability in the latter cell could be promoted, the differences between these two cells' performances would be reduced. Furthermore, the performance at an operating voltage of 0.6 V was the most stable one among the four cases tested, and the performance deviation at a fixed operating voltage of 0.4 V was less than +/- 2.2%. [DOI:10.1115/1.4005612]
Effects of synthetic antiferromagnetic coupling on back-hopping of spin-transfer torque devices
(2020-08-17)
Chen, Kuan-Ming
;
Cheng, Chih-Wei
;
Wei, Jeng-Hua
;
Hsin, Yu-Chen
;
Tseng, Yuan-Chieh
A synthetic antiferromagnetic (SAF) layer is a key component in spin-transfer torque magneto-resistive random-access memory devices. This study reveals that slight fluctuations in SAF coupling at the margin of the reference layer and hard layer (i.e., concurrent reversal) can lead to write errors in the form of back-hopping (BH). It appears that variable BH behavior can be attributed to competition between antiparallel (AP) -> parallel (P) and P -> AP transitions associated with SAF coupling. Our conclusions are supported by careful analysis of switching phase diagrams and measurements of self-heating and voltage-controlled magnetic anisotropy. We also observed that one form of coupling provided higher perpendicular magnetic anisotropic energy and thermal stability, which is likely due to the Dzyaloshinskii-Moriya interaction (DMI) effect. Thus, minimizing variations in DMI by optimizing SAF coupling is crucial for minimizing write error rates.