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140 results on '"Yao Jinmei"'

1. FRICTION PROPERTIES AND DISTRIBUTION RULE OF LUBRICANT FILM OF FULL CERAMIC BALL BEARING UNDER DIFFERENT SERVICE CONDITION

Author

Jian Sun, Yuhou Wu, Yang Jiaxing, Yao Jinmei, and Xia Zhongxian

Subjects
full ceramic ball bearing, friction properties, lubricant film, distribution rule, mathematical model, Clay industries. Ceramics. Glass, TP785-869
Abstract

Full ceramic ball bearings are widely used in extreme and complex conditions, such as ultra-high/low temperature, ultra-high speed, corrosion and insulation, because of their material specificity. In order to reveal the friction and lubrication properties, improve the service performance life of all ceramic ball bearings, a mathematical model of the oil lubrication for full ceramic ball bearings has been established in this paper. The distribution rule of the lubricant film in the contact area under different speeds and loads were analysed. The main factors influencing the peak mutation of the lubricant film pressure are clearly defined. The results are compared and analysed by using a ball-disc rolling lubricant film test machine. The study found that the thickness of the lubricant film of a full ceramic ball bearing is positively correlated with the bearing speed and negatively correlated with the bearing loads. The bearing speed has a relatively large effect on the change in the lubricant film thickness. The pressure of the lubricant film in the contact area is positively correlated with the bearing speed, but it is not affected by the bearing load. Unlike metal ball bearings, the thickness and pressure of the lubricant film have a greater relative rate of change in different positions in the contact area of full ceramic ball bearings. With an increase in the bearing speed, the necking-down effect has a greater influence on the peak mutation of the oil pressure. Only one pressure peak occurs in the oil film in the contact area. The results of this paper play an important role in revealing the friction and lubrication properties of full ceramic ball bearings and improving their service performance and life under oil lubrication conditions.

Published
2022
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5. The Trade-Off Between Microwave Frequency and Output Power in SiC Photoconductive Switches Based on Carrier Lifetime

Author

He, Ting, Yi, Muyu, Niu, Xinyue, Yao, Jinmei, Xun, Tao, Wang, Langning, and Shu, Ting

Abstract

The trade-off between microwave frequency and output power in VCSI 4H-silicon carbide (SiC) photoconductive semiconductor switch (PCSSs), based on carrier lifetime is investigated. PCSSs with two different vanadium doping concentrations are fabricated and tested across a frequency range of 0.5–2 GHz. The output power and modulation depth ratio trends with microwave frequency indicate a trade-off between microwave frequency and output power. The two devices exhibit output powers of approximately 40 W (@0.5 GHz) and 160 W (@0.5 GHz), respectively. Employing transient absorption (TA) techniques, the carrier lifetime of the two devices is determined to be 30 and 460 ps, revealing a relationship between longer carrier lifetime and increased output power. Nevertheless, the longer carrier lifetime also leads to a lower modulation depth ratio. Furthermore, when carrier lifetime ceases to be the primary constraining factor for the device’s frequency response, the upper cut-off frequency is constrained by the interstage capacitance.

Published
2025
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6. A Compact V-Band Transit Time Oscillator with Reflective Modulation Cavity.

Author

Chen, Zulong, Wang, Lei, Ling, Junpu, Song, Lili, He, Juntao, Yao, Jinmei, and Xu, Weili

Subjects
REFLECTANCE, MAGNETIC fields, MICROWAVES, VOLTAGE, DIODES, ELECTRON beams
Abstract

Improving compactness is essential for high-power microwave (HPM) sources. In this paper, a novel reflective modulation cavity is proposed and investigated in a V-band relativistic coaxial transit-time oscillator (RCTTO). The cold cavity analyses and particle-in-cell simulations show that the reflective modulation cavity has larger reflection coefficients of TEM mode and stronger electron beam modulation capability when compared with a uniform modulation cavity. When the input diode voltage is 391 kV, the beam current is 4.91 kA, and when the guiding magnetic field is 0.6 T, the compact V-band RCTTO produces an output microwave power of 518 MW (conversion efficiency of 27.0%). Compared with the original RCTTO, the compact V-band RCTTO featuring a reflective modulation cavity exhibits a 24.8% increase in output power and a 5.4% improvement in efficiency, and the axial length of the magnetic field uniform region is reduced by 24.2%. The compact V-band RCTTO also demonstrates a broad operation voltage range, indicating potential for stable operation with voltage fluctuations in experiments. Furthermore, the reflective modulation cavity can be integrated into other high-frequency O-type HPM devices to enhance compactness, thereby diminishing the demands on the magnetic field region, which is advantageous for the future permanent packaging of HPM sources. [ABSTRACT FROM AUTHOR]

Published
2024
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29. Research on the Roundness Approximation Search Algorithm of Si 3 N 4 Ceramic Balls Based on Least Square and EMD Methods.

Author

Sun, Jian, Chen, Wei, Yao, Jinmei, Tian, Zhonghao, and Gao, Longfei

Subjects
APPROXIMATION algorithms, LEAST squares, SEARCH algorithms, SILICON nitride, HILBERT-Huang transform, STANDARD deviations, CERAMICS, CIRCLE
Abstract

This paper aims to obtain the best shape accuracy evaluation algorithm for silicon nitride ceramic balls after lapping, and to extract the initial signal of the ball surface to improve the accuracy and reliability of the algorithm. The research methods of this paper are as follows: Firstly, an analysis of the uniform envelope of the lapping trajectory of ceramic balls is carried out to verify whether the lapping trajectory after processing can achieve a consistent envelope on the balls' surface. On this basis, it is found through experiments that the standard deviation SD between the roundness deviations of different contour sections is small. The value is maintained at approximately 0.03 μm, and the roundness deviation can approximately replace the spherical deviation. Then the different contour sections of the sphere are sampled by the Taylor roundness instrument. Considering the uncertainty, the sampling points of different contour sections are averaged and used as the original signal of the sphere surface. Then the EMD method is used to process the signal to be detected on the sphere surface. The initial signal of the sphere surface is extracted by judging whether the number of ripples Kc obtained by decomposition is greater than the critical value. Then the initial signal is used as the input value of the approximation algorithm. Through the roundness deviation approximation algorithm based on the least square method, the given minimum approximation domain range is finely processed. The divided fine points are used as the center of the circle to intersect with the initial signal. The maximum, minimum, and range of each circle are calculated to obtain the roundness error based on the minimum circumscribed circle, the maximum inscribed circle, and the minimum region method. Finally, the calculated values are compared with those obtained by the traditional algorithm. The experimental results of this paper show that the algorithm is consistent with the roundness error measured by the instrument, compared with the mainstream evaluation criteria. In summary, the conclusions can be drawn as follows: Through a large number of experimental cases and comparative experiments, the algorithm has high accuracy and reliability. The research results of this paper have essential reference significance for accurately evaluating the shape accuracy of ceramic balls in actual production. [ABSTRACT FROM AUTHOR]

Published
2023
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35. Virus strain of a mild COVID-19 patient in Hangzhou represents a new trend in SARS-CoV-2 evolution related to Furin cleavage site

Author

Jin, Xi, primary, Xu, Kangli, additional, Jiang, Penglei, additional, Lian, Jiangshan, additional, Hao, Shaorui, additional, Yao, Hangping, additional, Jia, Hongyu, additional, Zhang, Yimin, additional, Zheng, Lin, additional, zheng, Nuoheng, additional, Chen, Dong, additional, Yao, Jinmei, additional, Hu, Jianhua, additional, Gao, Jianguo, additional, Wen, Liang, additional, Shen, Jian, additional, Ren, Yue, additional, Yu, Guodong, additional, Wang, Xiaoyan, additional, Lu, Yingfeng, additional, Yu, Xiaopeng, additional, Yu, Liang, additional, Xiang, Dairong, additional, Wu, Nanping, additional, Lu, Xiangyun, additional, Cheng, Linfang, additional, Liu, Fumin, additional, Wu, Haibo, additional, Jin, Changzhong, additional, Yang, Xiaofeng, additional, Qian, Pengxu, additional, Qiu, Yunqing, additional, Sheng, Jifang, additional, Liang, Tingbo, additional, Li, Lanjuan, additional, and Yang, Yida, additional

Published
2020
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37. Virus strain from a mild COVID-19 patient in Hangzhou represents a new trend in SARS-CoV-2 evolution potentially related to Furin cleavage site

Author

Jin, Xi, primary, Xu, Kangli, additional, Jiang, Penglei, additional, Lian, Jiangshan, additional, Hao, Shaorui, additional, Yao, Hangping, additional, Jia, Hongyu, additional, Zhang, Yimin, additional, Zheng, Lin, additional, Zheng, Nuoheng, additional, Chen, Dong, additional, Yao, Jinmei, additional, Hu, Jianhua, additional, Gao, Jianguo, additional, Wen, Liang, additional, Shen, Jian, additional, Ren, Yue, additional, Yu, Guodong, additional, Wang, Xiaoyan, additional, Lu, Yingfeng, additional, Yu, Xiaopeng, additional, Yu, Liang, additional, Xiang, Dairong, additional, Wu, Nanping, additional, Lu, Xiangyun, additional, Cheng, Linfang, additional, Liu, Fumin, additional, Wu, Haibo, additional, Jin, Changzhong, additional, Yang, Xiaofeng, additional, Qian, Pengxu, additional, Qiu, Yunqing, additional, Sheng, Jifang, additional, Liang, Tingbo, additional, Li, Lanjuan, additional, and Yang, Yida, additional

Published
2020
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42. Use of autologous platelet rich fibrin-based bioactive membrane in pressure ulcer healing in rats

Author

Yu, Yajuan, primary, Shen, Jian, additional, Fang, Guizhen, additional, Wang, Lingcong, additional, Lei, Shu, additional, Cai, Danli, additional, Shi, Ying, additional, Jin, Shuifang, additional, Lu, Qiaoli, additional, Wang, Sisi, additional, Sun, Yunlei, additional, Yao, Jinmei, additional, Hu, Peiya, additional, Wu, Xiaofei, additional, and He, Xujun, additional

Published
2019
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43. Stress and Wear Analysis of the Disc Cutter of Rock Tunnel Boring Machine

Author

Zou Defang, Wu Yuhou, Zhou Peng, Liu Min, Yao Jinmei, and Sun Jian

Subjects
Stress (mechanics), Engineering, business.industry, Mechanical Engineering, Head (vessel), Disc cutter, Theoretical research, Geotechnical engineering, Edge (geometry), Rock tunnel, business, Rock breaking
Abstract

Full face rock tunnel boring machine is one of the main machineries and equipments for underground engineering, and the failure of its disc cutter is the main failure form of this machinery. In order to find out the factors of wear of disc cutters and improve the rock breaking efficiency, a lot of research has been done. In this paper, the methods of theoretical research, simulation analysis and engineering application are used. The laws of wear of disc cutters on the cutter head are researched at the process of cutting migmatitic gneiss, and its influence factors are analyzed. The results show that the wear on the edge of disc cutter is serious. The main factor for the wear of disc cutters is its stress from the rocks, and its variance is continual. And wear rate of the disc cutters is proportional to the integrality index of the rocks. With the increase of the amount of wear, the area of contact between a disc cutter and the rock gets bigger, and their extrusion strength gets lower on the contrary. These results are very helpful to the structure optimization of the disc cutter and the improvement of working efficiency.

Published
2015
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45. Mid-infrared flattened supercontinuum generation in all-normal dispersion tellurium chalcogenide fiber

Author

Jiao, Kai, primary, Yao, Jinmei, additional, Zhao, Zheming, additional, Wang, Xiange, additional, Si, Nian, additional, Wang, Xunsi, additional, Chen, Peng, additional, Xue, Zugang, additional, Tian, Youmei, additional, Zhang, Bin, additional, Zhang, Peiqing, additional, Dai, Shixun, additional, Nie, Qiuhua, additional, and Wang, Rongping, additional

Published
2019
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