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Dongwen Wang,Wei Yang,Jiafeng Yang,Kongming Jiang,Junjie Zhang,Yang Fu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9
Research on the vibration characteristics of the permanent magnet synchronous motor (PMSM) is hindered by the harmonic characteristics of the unbalanced magnetic pull force when air-gap eccentricity is neglected. Thus, the effects of both air-gap eccentricity and mass eccentricity on the rotor vibration have not yet been fully elucidated. To address this, a unified expression for the unbalanced magnetic pull force of the motor was derived under various pole pairs and air-gap eccentricities. The distribution of the radial electromagnetic force under different eccentricities is revealed. An electromagnetic simulation model of the fan motor was established for three eccentric cases and the effect of the unbalanced magnetic pull distribution and harmonic frequency characteristics on the rotor were analyzed. Furthermore, the influence of the gyroscopic effects on the modal frequency of the rotor structure was studied. The harmonic response of the rotor shaft system was first established using multi-physical field coupling, then the vibration amplitude-frequency laws of the rotor-shaft system under the influence of air-gap eccentricity and mass eccentricity were investigated. To reduce the vibration of the unbalanced PMSM rotor-shaft system, a multi-objective optimization was performed using the genetic algorithm in ANSYS Workbench. Research on the vibration characteristics of the permanent magnet synchronous motor (PMSM) is hindered by the harmonic characteristics of the unbalanced magnetic pull force when air-gap eccentricity is neglected. Thus, the effects of both air-gap eccentricity and mass eccentricity on the rotor vibration have not yet been fully elucidated. To address this, a unified expression for the unbalanced magnetic pull force of the motor was derived under various pole pairs and air-gap eccentricities. The distribution of the radial electromagnetic force under different eccentricities is revealed. An electromagnetic simulation model of the fan motor was established for three eccentric cases and the effect of the unbalanced magnetic pull distribution and harmonic frequency characteristics on the rotor were analyzed. Furthermore, the influence of the gyroscopic effects on the modal frequency of the rotor structure was studied. The harmonic response of the rotor shaft system was first established using multi-physical field coupling, then the vibration amplitude-frequency laws of the rotor-shaft system under the influence of air-gap eccentricity and mass eccentricity were investigated. To reduce the vibration of the unbalanced PMSM rotor-shaft system, a multi-objective optimization was performed using the genetic algorithm in ANSYS Workbench. The optimization results show that when the motor rotor core is shifted 2 mm in the positive X direction and the distance between the double-row bearing and rotor core is 7 mm, the vibration acceleration amplitude is reduced by 54.9 % compared with the original model.
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Identification of Software NFR based on the Fuzzy-QFD Model
Shucheng Xiao,Jiafeng Wu,Erhua He,Zhendong Yang 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.11
NFR determination of the software products is an important link in the requirement development. Considering the correlation and inter-dependence between FR and NFR of software, this paper puts forward a NFR system identification method of the software products based on the fuzzy-QFD model through constructing the FR-NFR correlation matrix of software. The model express correlation evaluation with the 7-level natural language, build the software FR-NFR correlation matrix, fuzzy the matrix vector by the trapezoidal fuzzy number, then calculate the relative importance and absolute importance of NFR, at last get the importance NFR by the NFR screening algorithm.
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Tianjiao Bi,Jiafeng Wan,Shilin Yang,Xiujuan Yu,Fangwei Ma 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.5
Nitrogen-doped mesoporous carbon spheres (NMCSs) supporting anatase TiO2 (NMCSs – TiO2) were prepared by a simple two-step solvothermal approach. The characterizations for the physicochemical properties of prepared samples under different solvothermal temperatures were carried out by X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption – desorption (Brunauer – Emmett – Teller (BET) measurements), Fourier transform infrared (FT-IR) spectroscopy, Raman scattering and UV-Vis diffuse reflectance spectra, were combined in order to determine the crystal phase and grain size, shape, degree of mesoporous carbon incorporation, and nature of the resultant oxy-carbide chemical bonding on the surface and in the bulk. The high relative photocatalytic activity of NMCSs – TiO2 nanoparticle was evaluated through a study of the decomposition of phenol under visible-light excitation.
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A New Method for Separating Temperature Effect of Bridge Strain Monitoring
Lei Huang,Jingzhou Xin,Jiafeng Yang,Shuangjiang Li,Jianting Zhou 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.8
Temperature has a significant influence on bridge strain monitoring data. To improve the accuracy of temperature effect separation in strain monitoring data, this paper proposes a temperature effect separation method comprising variational nonlinear chirp mode decomposition (VNCMD), principal component analysis (PCA) and blind source separation. Firstly, VNCMD was used to decompose the monitoring data of strain and temperature, and the intrinsic mode functions (IMF) of strain and temperature signals were obtained. Secondly, PCA was used to reduce the dimension of IMF, and the false components were eliminated to select the optimal components. After reducing the dimension, the components were used as the input of fast independent component analysis model for blind source separation. Finally, the feasibility and accuracy of the method was verified via the signal-to-noise ratio (SNR) in the simulated signal, and the separation results were evaluated using the Pearson correlation coefficient between the strain component and the corresponding temperature component in real bridge monitoring data. The proposed method performed better than the empirical mode decomposition (EMD) method. The signal-to-noise ratio (SNR) of VNCMD improved 51.80% for daily temperature difference effect and 32.41% for annual temperature difference effect in the numerical study, respectively; the correlation coefficients of VNCMD improved 52.90% for daily temperature difference effect and 4.26% for annual temperature difference effect in practical verification, respectively.
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