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Zan Wang,Chaofei Gao,Liwei Zheng,Jikun Ren,Wei Wang,Yushuai Zhang,Shijie Han 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.1
Ultrasonic signals will be generated when partial discharge occurs in internal insulation faults in large oil immersed power transformers: because the ultrasonic signal has strong anti-interference ability and has no direct electromagnetic contact with the equipment, it is widely used in transformer fault detection and positioning. In this paper, the fi nite element method (FEM) is used to simulate the ultrasonic signal in a 35 kV power transformer. The infl uence of transformer case on ultrasonic signal propagation is considered, and the propagation law of the ultrasonic signal inside the transformer is obtained. Fabry–Pérot (F–P) fi bre acoustic sensors with a centre frequency of 28 kHz were fabricated. A partial discharge detection test was carried out in a 35 kV transformer winding model using the F–P sensors. The test results show that the ultrasonic waveform detected by the F–P sensors are in good agreement with the simulation results, and the propagation of the ultrasonic wave inside the transformer is verifi ed. It lays a foundation for detecting and locating PDs in power transformer by F–P acoustic sensors.
Hui Li,Haiqi Zheng,Liwei Tang 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.11
In the present work, cutting-force models of single-tooth and multi-teeth face-milling cutters were set up. Based on a spectrum analysis of cutting force, the vibration mechanism of a face-milling cutter of irregular pitch was investigated theoretically. The single-objective function and constraint conditions were derived. A general-purpose irregular-pitch face-milling cutter subsequently was designed and tested, and its performance was compared with that of a regular-pitch cutter. The experimental results showed that the irregular-pitch face-milling cutter not only reduces vibration and noise but also enhances surface-finish quality.
Liangliang Xue,Lifei Wang,Pengbin Lu,Qiang Zhang,Hua Zhang,Guangsheng Huang,Liwei Lu,Liuwei Zheng,Hanuma Reddy Tiyyagura,Hongxia Wang,Shuyong Jiang,Kwang Seon Shin 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10
Pre-twin is widely accepted as an efficient method for weakening the basal texture to improve the plasticity of magnesium alloys, particularly for formability. However, the enhancement is limited since the largest Schmid factor (SF) of basal slip cannot be achieved. In-plane simple shear strain is used to control the twin orientation in accordance with Schmid law to further decrease the basal texture and improve the formability of the Mg alloys sheet. Consequently, secondary regulation of initial twin orientation (SRITO) technology, a novel combination procedure, was developed. In this method, the AZ31 Mg alloys sheet is compressed to pre-twins with various volumes (1%, 3%, and 5%), then the twin orientation is regulated by in-plane simple shear strain for the second time. Compared with the as-received sample, the average fracture elongation of the annealed sample with the best properties improves from 15.3 to 28.8%, and the Erichsen value increases from 2.8 to 6.1 mm due to the regulation of twin orientation.
Li, Wei,Zheng, Chang-Ji,Sun, Liang-Peng,Song, Ming-Xia,Wu, Yan,Li, Yin-Jing,Liu, Yi,Piao, Hu-Ri 대한약학회 2014 Archives of Pharmacal Research Vol.37 No.7
A series of arylhydrazone derivatives bearing a rhodanine moiety have been synthesized, characterized, and evaluated as antibacterial agents. Some of these compounds showed potent antibacterial activities against several different strains of Gram-positive bacteria, including multidrug-resistant clinical isolates. Of the compounds tested, IIk and IIIk were identified as the most effective, with minimum inhibitory concentration values of $2-4{\mu}g/mL$ against multidrug-resistant Gram-positive organisms, including methicillin-resistant and quinolone-resistant Staphylococcus aureus. None of the compounds exhibited any activity against the Gram-negative bacteria Escherichia coli 1356 at $64{\mu}g/mL$.