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- 저자 : Zhiyuan Qi (검색결과 2 건)
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Engineering of a Bacillus subtilis Strain Deficient in Cellulase: Application in Degumming of Ramie
Qi Yang,Shengwen Duan,Lifeng Cheng,Xiangyuan Feng,Ke Zheng,Chunliang Xie,Zhiyuan Liu,Yuande Peng 한국섬유공학회 2019 Fibers and polymers Vol.20 No.1
Degumming is the most important step before ramie fibers are used in textile industry. Conventional chemical degumming technology with alkaline treatment at high temperature causes critical problems in environment. In addition to multiple degumming enzymes (e.g. pectinases and xylanases), Bacillus subtilis strain 168 can also produce cellulase which brings irreversible damage to ramie fibers. In this study, a strain deficient in cellulase was constructed by insertional inactivation of gene eglS to make it suitable for microbial degumming. Results showed that the cellulase activity was not detected in strain ΔeglS, after 25 h of incubation with strain ΔeglS, the weight loss of the ramie fibers was 20.20 %. Though the residual gum content of ramie fibers obtained in microbial degumming process was 19.67 %, microbial intervention followed by diluted alkaline solution treatment showed lower residual gum content (2.73 %) than chemical degumming (2.96 %). The single fiber breaking strength value of ramie fibers from bio-chemical degumming process reached 27.19 cN, which was the highest of three samples. Moreover, bio-chemical degumming process resulted in a 75 % decrease of alkali dosage as compared with chemical degumming process. This study provides a suggestion to genetically modify wild-type strain in order to protect ramie fibers from cellulase damage, and indicates a sustainable alternative for the traditional chemical degumming in the textile industry.
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Evaluation of Frequency-Dependent On-Resistance of GaN Devices at High Frequency
Kangping Wang,Bingyang Li,Zhiyuan Qi,Laili Wang,Xu Yang,Aici Qiu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
The switching frequency of GaN-based power converters has been pushed to several MHz and even higher. At such high frequencies, this paper finds that the onresistance of GaN devices may be much higher than their DC values, especially for the devices with low on-resistance. The frequency-dependent characteristics of on-resistance are studied through electrical and thermal experiments for the first time in this paper. A simplified finite-element-simulation model is proposed to illustrate the mechanism of the frequency-dependent characteristics. The results show that the frequency-dependent characteristics of the on-resistance are closely related to the current distribution inside the GaN device and affected by the layout. In addition, two same GaNbased 10MHz DC-DC converters were designed to operate under the same conditions, and the only difference comes from the layout of GaN devices. The experimental results show that the efficiency of the converter with optimized layout is improved by 2% compared to that with conventional layout.
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