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The Effect of Hygrothermal Aging on the Properties of Epoxy Resin
Youyuan Wang,Yu Liu,Kun Xiao,Can Wang,Zhanxi Zhang 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.2
Because of excellent electrical properties, epoxy resin is widely used in packaging and casting power equipment. Moisture and temperature in the environment are inclined to seriously affect the insulation tolerance of epoxy resin. This work focuses on the aging characteristics of epoxy resin in hygrothermal environment. Scanning electron microscopy images show that there are micro-crack, micro-slit and holes inside aged samples. The moisture absorption process undergoes three equilibrium stages and it does not follow the Fick’s second law. Observing the change of hydrogen bonds in the infrared spectra of the dried samples, it is found that chemically moisture absorption immerges when the physical moisture absorption entered the third equilibrium stage. By Debye equation to fit the imaginary part of the dielectric constant, it is concluded that the uniformity of water molecule has a great influence on the electrical conductivity loss. Furthermore, the polarization loss can be more easily affected by water molecules than small free molecules. After the aged samples being dried, their real and imaginary part of the dielectric constant descend, but their original electrical properties cannot completely restored. After chemical moisture absorption appears inside the material, the residual space charges increase significantly and the charge dissipation rate slow down obviously.
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Youyuan Lu,Zongjin Li 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.8 No.3
Acoustic emission (AE) monitoring was conducted for mortar specimens under three types of static loading patterns (cubic-splitting, direct-shear and pull-out). Each of the applied loading patterns was expected to produce a particular fracture process. Subsequently, the AEs generated by various fracture or damage processes carried specific information on temporal micro-crack behaviors of concrete for post analysis, which was represented in the form of detected AE signal characteristics. Among various available characteristics of acquired AE signals, frequency content was of great interest. In this study, cement-based piezoelectric sensor (as AE transducer) and home-programmed DEcLIN monitoring system were utilized for AE monitoring on mortar. The cement-based piezoelectric sensor demonstrated enhanced sensitivity and broad frequency domain response range after being embedded into mortar specimens. This broad band characteristic of cement-based piezoelectric sensor in frequency domain response benefited the analysis of frequency content of AE. Various evaluation methods were introduced and employed to clarify the variation characteristics of AE frequency content in each test. It was found that the variation behaviors of AE frequency content exhibited a close relationship with the applied loading processes during the tests.
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Signal-based AE characterization of concrete with cement-based piezoelectric composite sensors
Youyuan Lu,Zongjin Li,Lei Qin 사단법인 한국계산역학회 2011 Computers and Concrete, An International Journal Vol.8 No.5
The signal-based acoustic emission (AE) characterization of concrete fracture process utilizing home-programmed AE monitoring system was performed for three kinds of static loading tests (Cubic-splitting, Direct-shear and Pull-out). Each test was carried out to induce a distinct fracture mode of concrete. Apart from monitoring and recording the corresponding fracture process of concrete, various methods were utilized to distinguish the characteristics of detected AE waveform to interpret the information of fracture behavior of AE sources (i.e. micro-cracks of concrete). Further, more signal-based characters of AE in different stages were analyzed and compared in this study. This research focused on the relationship between AE signal characteristics and fracture processes of concrete. Thereafter, the mode of concrete fracture could be represented in terms of AE signal characteristics. By using cement-based piezoelectric composite sensors, the AE signals could be detected and collected with better sensitivity and minimized waveform distortion, which made the characterization of AE during concrete fracture process feasible. The continuous wavelet analysis technique was employed to analyze the wave-front of AE and figure out the frequency region of the P-wave & S-wave. Defined RA (rising amplitude), AF (average frequency) and P-wave & S-wave importance index were also introduced to study the characters of AE from concrete fracture. It was found that the characters of AE signals detected during monitoring could be used as an indication of the cracking behavior of concrete.
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Chen Youyuan,Yu Haisheng,Meng Xiangxiang,Ding Hao,Gao Xunkai 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.3
In this paper, a novel cooperative controller combining Linear Quadratic optimal control based on feedback linearization (LQ-FL) and state error port-Hamiltonian (EPH) with integral term is proposed for permanent magnet synchronous motor. Firstly, the LQ-FL is presented to ensure rapid dynamic performance, and the EPH method makes up for the shortcomings of the system in steady-state performance. The integral term is utilized to eliminate the position tracking steady-state error. Secondly, the Gaussian function is utilized to coordinate the two controllers and make them play their respective superiorities. Then, a nonlinear disturbance observer is used to resolve the total disturbance caused by parameter changes, modeling errors and external disturbance. Finally, the efectiveness and robustness of the proposed controller are verifed by simulation and experiments.
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Lu, Youyuan,Li, Zongjin Techno-Press 2011 Smart Structures and Systems, An International Jou Vol.8 No.3
Acoustic emission (AE) monitoring was conducted for mortar specimens under three types of static loading patterns (cubic-splitting, direct-shear and pull-out). Each of the applied loading patterns was expected to produce a particular fracture process. Subsequently, the AEs generated by various fracture or damage processes carried specific information on temporal micro-crack behaviors of concrete for post analysis, which was represented in the form of detected AE signal characteristics. Among various available characteristics of acquired AE signals, frequency content was of great interest. In this study, cement-based piezoelectric sensor (as AE transducer) and home-programmed DEcLIN monitoring system were utilized for AE monitoring on mortar. The cement-based piezoelectric sensor demonstrated enhanced sensitivity and broad frequency domain response range after being embedded into mortar specimens. This broad band characteristic of cement-based piezoelectric sensor in frequency domain response benefited the analysis of frequency content of AE. Various evaluation methods were introduced and employed to clarify the variation characteristics of AE frequency content in each test. It was found that the variation behaviors of AE frequency content exhibited a close relationship with the applied loading processes during the tests.
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Ni Youyuan,Zhang Xin,Chen Qiuming,Huang Ya,Wang Qunjing 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.3
The electromagnetic performances of surface-inset machines with two layer equal/unequal magnet-arc Halbach magnets are compared. The magnetic feld distribution is analytically obtained by analyzing the outer/inner layer Halbach magnets separately. Through presented analytical technique, the magnetization angles of each layer Halbach magnets are analytically optimized. Considering the practical application of relatively large usage of magnets, the larger the outer layer magnet-arc ratio, the better the performances. The analytical predictions show that the optimal two layer unequal magnet-arc Halbach machine has a much higher sine degree of both the airgap fux density and the back-electromotive force and a much lower torque ripple than the optimal two layer equal magnet-arc Halbach machine. The fnite element analysis and analytical prediction results are compared.
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The Effect of Hygrothermal Aging on the Properties of Epoxy Resin
Wang, Youyuan,Liu, Yu,Xiao, Kun,Wang, Can,Zhang, Zhanxi The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.2
Because of excellent electrical properties, epoxy resin is widely used in packaging and casting power equipment. Moisture and temperature in the environment are inclined to seriously affect the insulation tolerance of epoxy resin. This work focuses on the aging characteristics of epoxy resin in hygrothermal environment. Scanning electron microscopy images show that there are micro-crack, micro-slit and holes inside aged samples. The moisture absorption process undergoes three equilibrium stages and it does not follow the Fick's second law. Observing the change of hydrogen bonds in the infrared spectra of the dried samples, it is found that chemically moisture absorption immerges when the physical moisture absorption entered the third equilibrium stage. By Debye equation to fit the imaginary part of the dielectric constant, it is concluded that the uniformity of water molecule has a great influence on the electrical conductivity loss. Furthermore, the polarization loss can be more easily affected by water molecules than small free molecules. After the aged samples being dried, their real and imaginary part of the dielectric constant descend, but their original electrical properties cannot completely restored. After chemical moisture absorption appears inside the material, the residual space charges increase significantly and the charge dissipation rate slow down obviously.
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Peng Youyuan,Zeng Xiuya,Lian Mingjian,Wang Yanfeng 대한독성 유전단백체 학회 2022 Molecular & cellular toxicology Vol.18 No.3
Background FXYD3, as a regulator of ion transporting membrane protein, plays a key role in the progression of various cancers. It is reported that FXYD3 is overexpressed in pancreatic cancer, but the molecular mechanism of FXYD3 regulating pancreatic cancer is not well illustrated. Objective The aim of this work was to study the role of FXYD3 in pancreatic cancer and the underlying mechanism. Results The expression of FXYD3 was aberrantly high in pancreatic cancer tissues and cells compared to the controls. High expression of FXYD3 was associated with the patient’s poor prognosis and promoted the proliferation, migration, and invasion of pancreatic cancer cells. Furthermore, FXYD3 expression was positively correlated with the activation of cGMP-PKG signaling pathway, and FXYD3 could enhance cGMP content. Conclusion Our study speculated that FXYD3 was likely to activate the cGMP-PKG signaling pathway to promote tumor proliferative activity. These findings contribute to understanding the role of FXYD3 in the development of pancreatic cancer and provide new therapeutic targets for its treatment.
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