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- 저자 : Yankun Xia (검색결과 6 건)
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Xia Yankun,Li Xinyang,Luo Yujie 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.3
Due to prolonged high load operation, the insulation performance of the stator winding coil in a permanent magnet synchronous motor (PMSM) tends to deteriorate, resulting in an inter-turn short circuit. At this time, there will be signifcant changes in the stator winding current and motor vibration intensity. In view of this phenomenon, a more accurate and complete detection method is proposed. In this study, wavelet packet transform (WPT) is combined with energy spectrum to process the current signal of PMSM, and the main fault features of the current signal are obtained. Then, complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) is combined with Hilbert transform (HT) to form a CEEMDAN-HT nonlinear signal analysis method. Firstly, the vibration signal is decomposed using the CEEMDAN algorithm to obtain a series of intrinsic mode functions (IMFs), and the variance contribution rate in principal component analysis (PCA) is applied to discriminate the IMFs containing fault feature information. Then, HT is used to process the IMF with high contribution rate, and the time, instantaneous frequency and amplitude are presented using a three-dimensional joint time–frequency diagram to obtain the main fault features of the vibration signal. Finally, a short-circuit fault simulation is built using ANSYS fnite element software, and a short-circuit fault experiment is built. By comparing and analyzing the results of fnite element simulation and experiment, the accuracy of the method proposed in this study is verifed.
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The Brachypodium distachyon methionine sulfoxide reductase gene family
Yankun Gao,Jiantang Zhu,Pengcheng Ding,Guangmin Xia,Fanguo Chen 한국유전학회 2017 Genes & Genomics Vol.39 No.9
The methionine sulfoxide reductases (MSRs) are a group of thiol-dependent enzymes able to catalyze the conversion of methionine sulfoxide to methionine. Although some plant MSRs are known to act as protectants against various abiotic stresses, their activity in the model grass species Brachypodium distachyon has not been characterized as yet. Here, six B. distachyon MSR (BdMSR) genes have been isolated; they generate eight distinct cDNAs, since two of them (BdMSRB1 and -B5) produce a pair of alternatively spliced messages. The genes were transcribed in the root, culm, leaf and during various stages of caryopsis development. Those induced by abiotic stress (salinity, drought, low temperature, CdCl2, H2O2 and abscisic acid) harbored known stress-responsive cis elements in their promoter sequences. The heterologous expression of five of the BdMSRs (-A2, -A4, -B1.1, -B3 and -B5.1) in yeast revealed that their products gave a measure of protection against salinity, mannitol and oxidative stress. Substrate specificity analysis revealed that BdMSRB1.1 could reduce free Met-R-SO to Met. The enzymatic activities of BdMSRA4, -B1.1 and -B5.1 in transformed yeast under salt treatment have checked and increased obviously resulting in reducing more Met-SO to Met including the peptide and the free types under salt stress than those in control.
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An Improved SPWM Strategy to Reduce Switching in Cascaded Multilevel Inverters
Xiucheng Dong,Xiaomei Yu,Zhiwen Yuan,Yankun Xia,Yu Li 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2
The analysis of the switch status of each unit module of a cascaded multi-level inverter reveals that the working condition of the switch of a chopper arm causes unnecessary switching under the conventional unipolar sinusoidal pulse width modulation (SPWM). With an increase in the number of cascaded multilevel inverters, the superposition of unnecessary switching gradually occurs. In this work, we propose an improved SPWM strategy to reduce switching in cascaded multilevel inverters. Specifically, we analyze the switch state of the switch tube of a chopper arm of an H-bridge unit. The redundant switch is then removed, thereby reducing the switching frequency. Unlike the conventional unipolar SPWM technique, the improved SPWM method greatly reduces switching without altering the output quality of inverters. The conventional unipolar SPWM technique and the proposed method are applied to a five-level inverter. Simulation results show the superiority of the proposed strategy. Finally, a prototype is built in the laboratory. Experimental results verify the correctness of the proposed modulation strategy.
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An Improved SPWM Strategy to Reduce Switching in Cascaded Multilevel Inverters
Dong, Xiucheng,Yu, Xiaomei,Yuan, Zhiwen,Xia, Yankun,Li, Yu The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2
The analysis of the switch status of each unit module of a cascaded multi-level inverter reveals that the working condition of the switch of a chopper arm causes unnecessary switching under the conventional unipolar sinusoidal pulse width modulation (SPWM). With an increase in the number of cascaded multilevel inverters, the superposition of unnecessary switching gradually occurs. In this work, we propose an improved SPWM strategy to reduce switching in cascaded multilevel inverters. Specifically, we analyze the switch state of the switch tube of a chopper arm of an H-bridge unit. The redundant switch is then removed, thereby reducing the switching frequency. Unlike the conventional unipolar SPWM technique, the improved SPWM method greatly reduces switching without altering the output quality of inverters. The conventional unipolar SPWM technique and the proposed method are applied to a five-level inverter. Simulation results show the superiority of the proposed strategy. Finally, a prototype is built in the laboratory. Experimental results verify the correctness of the proposed modulation strategy.
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Chao Su,Liu Liu,Haipei Liu,Brett J. Ferguson,Yanmin Zou,Yankun Zhao,Tao Wang,Youning Wang,Xia Li 한국식물학회 2016 Journal of Plant Biology Vol.59 No.3
The accumulation and redistribution of the plant hormone auxin plays a crucial role in root development and patterning. Plants can alter their root system architecture (RSA) to adapt to different biotic and abiotic stresses. In addition, reactive oxygen species (ROS), such as H2O2, are known to increase in plants undergoing stress. Here, we present evidence that H2O2 can regulate auxin accumulation and redistribution through modulating polar auxin transport, leading to changes in RSA. Plants exposed to different concentrations of H2O2 formed a highly branched root system with abundant lateral roots and a shorter primary root. Monitoring of the auxin responsive DR5::GUS indicated that auxin accumulation decreased in lateral root primordia (LRP) and emerging lateral root tips. In addition, polar auxin transport, including both basipetal and acropetal transport modulated by AUX1 and PIN protein carriers, was involved in the process. Taken together, our results suggest that H2O2 could regulate plastic RSA by perturbing polar auxin transport as a means of modulating the accumulation and distribution of auxin.
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