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633 results on '"Wu, Guangning"'

109. Highly conductive graphite matrix/copper composites by a pressureless infiltration method.

Author

Wei, Wenfu, Li, Xiaobo, Yang, Zefeng, Huang, Zhanglin, Zuo, Haozi, Liao, Qianhua, Xie, Wenhan, Yin, Guofeng, and Wu, Guangning

Subjects
INTERFACIAL bonding, TUNGSTEN carbide, ELECTRIC conductivity, CONTACT angle, ECONOMIC efficiency, GRAPHITE
Abstract

Graphite matrix/copper composites have found significant potential uses in numerous areas. Until now, a high ambient gas pressure has to be applied to overcome the non-wettability between the copper melt and graphite matrix, which has restricted the technological and economic efficiencies, as well as the composite performance. In this paper, we have proposed a pressureless infiltration strategy to realize the preparation of highly conductive graphite matrix/copper composites. A tungsten carbide network is first in situ constructed in the graphite matrix, transforming the capillary force from the resistance mode to the impetus mode. Results show that the contact angle of graphite/copper decreased from 138.5° to 23° due to the constructed tungsten carbide network. The composites exhibit good interfacial bonding, and the electrical conductivity reaches 15.1 × 105 S/m, far higher than the requirement of the industry standard. [ABSTRACT FROM AUTHOR]

Published
2021
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110. Equivalent Bandwidth Matrix of Relative Locations: Image Modeling Method for Defect Degree Identification of In-Vehicle Cable Termination

Author

Liu, Kai, Jiao, Shibo, Nie, Guangbo, Ma, Hui, Gao, Bo, Sun, Chuanming, Xin, Dongli, Kumar Saha, Tapan, and Wu, Guangning

Abstract

The detection of defect severity in cable terminations plays a critical role in ensuring the safe and stable operation of high-speed trains (HSTs). However, the partial discharge (PD) characteristics of the same type of defect can appear similar across different severities, posing challenges for accurate insulation defect degree identification. Consequently, this article proposes an image transformation method, named the equivalent bandwidth matrix of relative locations (EBMRLs), coupled with the self-guided transformer (SG-Former) algorithm, which is more effective for fine-grained image recognition, to accurately identify different degrees of defects with similar PD characteristics. In the proposed approach, the original PD signals are first converted into images using EBMRL. This transformation embeds the characteristic and bandwidth information from the original PD data into the images, thereby reducing the similarity of information between classes in the transformed images and enhancing their distinguishability. Subsequently, the local and global features of the transformed EBMRL images are extracted to train the SG-Former model. The model is finally utilized to identify the severity of defects in cable terminations. The results demonstrate that the method proposed in this article achieves better performance compared with some of the state-of-the-art methods.

Published
2024
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111. Defect Identification Method of Cable Termination based on Improved Gramian Angular Field and ResNet

Author

Sun, Chuanming, Wu, Guangning, Xin, Dongli, Liu, Kai, Gao, Bo, and Gao, Guoqiang

Abstract

Background: This paper proposes a defect identification method for vehicle-mounted cable terminals in electric multiple units (EMUs) based on the improved Graham angle field and residual network to address the issue of low recognition accuracy caused by the lack of partial discharge (PD) and identification data for Ethylene Propylene Rubber (EPR) cable terminal defects. Methods: The improved Gramian angular field (IGAF) characteristic transformation method was used to transform the PD one-dimensional time-series signal into a two-dimensional one after cable terminals with four common insulation defects were constructed, and a PD detection platform was built. Finally, an anti-aliasing downsampling module and attention mechanism were added to the residual network ResNet101 model. The Center loss and Softmax loss functions were integrated to increase accuracy for training and recognition classification. Topological feature images improved the distinguishability of defect categories. Results: The test results showed that the diagnostic method has an accuracy rate of 97.3% for identifying PD at the cable terminal. Conclusion: The proposed diagnosis model has higher recognition accuracy and better balance than other conventional fault diagnosis methods, making it suitable for diagnosing high-voltage cable faults in EMU trains.

Published
2024
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112. Influence Mechanism of the Mobile Grounding Reflux on the “Wheel-Rail” Rolling Arc at Insulated Joints of High-Speed Railway

Author

Xiao, Song, Yu, Jie, Wu, Guangning, Guo, Yujun, Gao, Guoqiang, Zhang, Xueqin, Liu, Jie, Cao, Ye, Wang, Zijing, Zhang, Yuhui, Chen, Zheng, Liu, Puyang, Li, Pupu, and Zhu, Tao

Abstract

As a unique reflux path for trains, the ‘train-rail’ mobile grounding system has the double functions – the traction power feedback and the transmission of train's communication signal. With the constant increment of operational velocity and traction power for high-speed railway, the coupling relationship existing in the ‘train-rail’ mobile coupling grounding system becomes complicated, when the train's wheels roll over the insulated joint. It may result in the frequent occurrence of rolling arc and the ablation of rail ends and insulated joints, which might lead to the series connection of the rail circuit or even trigger the misjudgment of operational control system. As the impedances existing in the grounding system vary transiently when the relative distance between the train and the fixed terrestrial grounding installations changes, the dynamic coupling mechanism between the transiently-varying topology of reflux path and the distribution of reflux at each grounding wheel tends to be analyzed. Depending on the built ‘catenary-train-rail’ dynamic coupling grounding reflux model, the correlation between the ‘train-rail’ mobile grounding reflux and the evolutionary process of rolling arc is explored. In order to reduce the risk of ‘wheel-rail’ arcing phenomenon, a novel method of automatically controlling insulated joint is proposed herein, as its feasibility is verified via the comparison with the original type of the insulated joint.

Published
2024
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114. Aging Mechanisms and Evaluation Methods of Silicone Rubber Insulator Sheds: A Review

Author

Wu, Guangning, Fan, Yihan, Guo, Yujun, Xiao, Song, Liu, Yang, Gao, Guoqiang, and Zhang, Xueqin

Abstract

So far, silicone rubber (SiR) insulators are widely used in the power industry all over the world, due to their outstanding insulation properties and high reliability. In practice, some of the insulators are applied in remote places with harsh environmental conditions such as high altitude, high temperature, high humidity, etc. Herein, the currently existing aging mechanisms are investigated, and some novel insights into these testing and evaluation methods are proposed. Via the investigation, it was found that thermal oxygen aging tends to occur when insulators are exposed to an environment surrounded by hot air. To analyze the different aging mechanisms of SiR insulator sheds, four types of aging testing and evaluation methods are systematically summarized based on the surface’s structural, chemical, optical, and electrical properties. The conclusion is that nondestructive and noncontact methods, such as hyperspectral imaging (HSI), along with the multisource information fusion methods, are becoming increasingly popular in the assessment of SiR insulator sheds aging. These research efforts provide assurance for reducing the incidence of pollution flashover accidents in power transmission lines and ensuring the safe and stable operation of power transmission and transformation equipment.

Published
2024
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116. Measurement of transient temperature using laser-induced breakdown spectroscopy (LIBS) with the surface temperature effect.

Author

Yang, Zefeng, Tang, Bo, Qiu, Yan, Wu, Jian, Wei, Wenfu, Huang, Xuefei, Luo, Xingmao, and Wu, Guangning

Subjects
SURFACE temperature, TEMPERATURE effect, LASER-induced breakdown spectroscopy, STANDARD deviations, TEMPERATURE measurements, RADIANT intensity
Abstract

A method based on LIBS technology for measuring transient surface temperatures with a time resolution of several μs was proposed in this study, which holds great significance for fast sliding friction processes in linear electromagnetic propulsion, gun barrels, and high-speed trains. The effects of surface temperature on laser-induced plasma emission spectra were studied, and it was found that both the spectral intensity and signal-to-noise ratio increased with increasing temperature. The mechanism of the surface temperature effect was revealed by interferometry and spectral analysis techniques, which were mainly related to the processes of plasma ablation and surface air heating. Finally, three algorithms including SPF, PLS, and BP-ANN were used to predict the surface temperature, and the results showed that BP-ANN performed best in the 1 μs, 2 μs, and 3 μs exposure time. Under an exposure time of 3 μs, the regression coefficient (R2) and root mean square error (RMSE) could reach 0.9992 and 2.466, respectively. This research would provide a new measurement technology for transient temperature in high-speed physical processes. [ABSTRACT FROM AUTHOR]

Published
2023
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121. Influence mechanism of the mobile grounding reflux on the ‘wheel-rail’ rolling arc at insulated joints of high-speed railway

Author

Xiao, Song, primary, Yu, Jie, additional, Wu, Guangning, additional, Guo, Yujun, additional, Gao, Guoqiang, additional, Zhang, Xueqin, additional, Liu, Jie, additional, Cao, Ye, additional, Wang, Zijing, additional, Zhang, Yuhui, additional, Chen, Zheng, additional, Liu, Puyang, additional, Li, Pupu, additional, and Zhu, Tao, additional

Published
2023
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136. Characteristic analysis of the VCB operational overvoltage for high-speed trains considering arc reignition phenomenon

Author

Xiao, Song, Hou, Hao, Jin, Yaoyao, Gao, Guoqiang, Guo, Yujun, Zhou, Jie, Ju, Changlei, Shen, Yixiang, Liu, Jie, Chen, Siyan, and Wu, Guangning

Abstract

ABSTRACTDue to the constant pursuit for higher operating velocity, the traction power capacity for high-speed trains needs to be enlarged. When the train passes approach the insulating sections set between the two neighbouring contact lines carrying the traction current with different phases, the vehicle-mounted vacuumed circuit breaker (VCB) needs to be switched off. Generally, the arc may generate when connecting or separating the contacts, when switching on or off the VCB. In order to investigate the characteristics of the reignition overvoltage the ‘train-rail-catenary’ traction power supply model considering the reignition process between the VCB’s contacts is launched in this paper. The impact of the dielectric strength recovery rate between the contacts of the VCB on the number of reignition and the amplitude of the reignition overvoltage is analysed based on the experimental and simulation results. Ultimately, the corresponding restraining measures are proposed for suppressing the reignition overvoltage.

Published
2023
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139. Tailoring carbon-matrix composites interfaces using reduced graphene oxide for high strength

Author

Chen, Qichen, primary, Wei, Wenfu, additional, Xiao, Song, additional, Yang, Zefeng, additional, Huang, Guizao, additional, Li, Hao, additional, Yin, Haojie, additional, Lin, Jiahui, additional, Kang, Qi, additional, Li, Pengli, additional, Wang, Hong, additional, Tu, Chuanjun, additional, Gao, Guoqiang, additional, Huang, Xingyi, additional, and Wu, Guangning, additional

Published
2022
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142. Scalable, low-cost, and environment-friendly preparation of high strength carbon-matrix composites with tree-root-like structured reinforcements

Author

Chen, Qichen, primary, Yang, Zefeng, additional, Lin, Jiahui, additional, Wei, Wenfu, additional, Li, Hao, additional, Yin, Guofeng, additional, Liu, Yijie, additional, Li, Pengli, additional, Tu, Chuanjun, additional, Gao, Guoqiang, additional, Huang, Xingyi, additional, and Wu, Guangning, additional

Published
2022
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144. The evolution law of the pantograph–catenary arc with the multi-stress coupled force analysis under the sub-atmospheric pressure strong-airflow condition.

Author

Gao, Guoqiang, Qian, Pengyu, Xu, Zhilei, Dong, Keliang, Wang, Qingsong, Peng, Wei, Liu, Yuxin, Ma, Yaguang, Xiao, Song, Huang, Guizao, and Wu, Guangning

Subjects
AIR resistance, AIR flow, HIGH speed trains, WIND pressure, AIR pressure, ATMOSPHERIC pressure, BUOYANCY
Abstract

As the unique power entrance, the pantograph–catenary plays a vital role in providing traction power for high-speed railways. Along with the operational velocity of trains constantly increasing, the poor contact between the contact wire and the pantograph strip happens frequently due to the "rigid point" existing on the contact wire, forming the "off-line" phenomenon. The off-line phenomenon is normally accompanied by the pantograph–catenary arc occurring, which seriously threatens the safety of the power supply for the high-speed train. Nowadays, as some railways have been built in remote places at high altitude, the motion characteristics of the pantograph–catenary arc under the sub-atmospheric pressure with strong airflow are extremely different from the case under normal pressure. Herein, a pantograph–catenary arc experimental platform is built for observing the evolutionary process of the arc under the sub-atmospheric pressure strong-airflow condition. The impact brought from different air pressures and airflows on the arc is analyzed, as the experimental results show that the pantograph–catenary arc has different motion characteristics when the arcing process is at different stages. To further explore the reason resulting in the varying motion characteristics of the arc, a multi-stress coupled force analysis model is established, with the consideration of the influence of air pressure, wind load, thermal buoyancy, air resistance, arc self-magnetism, etc. From the perspective of force acting on the arc, the arc formation mechanism at the development evolutionary stages is investigated under sub-atmospheric pressure strong-airflow conditions, which lays a theoretical foundation for effectively restraining the pantograph–catenary arc. [ABSTRACT FROM AUTHOR]

Published
2023
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