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RISS 인기검색어
- 검색키워드
- 저자 : Yongfeng Ju (검색결과 4 건)
- 무료
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An Improved Algorithm for AC Impedance Extraction
Muhammad Saad,Yongfeng Ju,Shahbaz Khan,Husan Ali,Abdul Wadood,Sang Bong Rhee 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.6
The overall system stability of interconnected electrical and electronic systems is associated with the input and output impedances of each individual system, therefore, accurate AC impedance measurement for a linear and nonlinear systems are imperative. These impedances are normally measured using small-signal frequency injection techniques. However, the harmonic transfers from the output side to the input side and vice versa deteriorates the measured results, making them ambiguous. These harmonic transfers cause the problems of frequency aliasing as well as spectral leakages leading to inaccurate measurements of results. In order to achieve the precise and accurate results, there is a need to adopt such an impedance measuring technique which is the best among the available techniques. A new algorithm is proposed to modify the range of frequencies of interest and inject such small-signal frequencies which do not interfere with the system harmonics. The measurement of the AC impedance of the three-phase RL circuit utilizing three diff erent small-signal injection techniques is performed. From the results displayed, it is clear that all the techniques perform well, therefore, the most simple, single phase line-current injection was selected for the AC impedance measurement of the nonlinear switching circuit such as sixpulse rectifi er. The issues discussed above are more serious in nonlinear switching circuit because of the presence of higher order switching harmonics in the circuit. The proposed algorithm is applied to measure the output-impedance of the threephase AC power supply as well as the AC input-impedance of the six-pulse rectifi er. These results of the switch vs average model and that of average model vs. experimental prototype are displayed for comparison, and it is clear that the proposed algorithm off ers much-improved results.
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Jiacheng Song,Yongfeng Ju,Maode Yan,Panpan Yang 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.4
This paper studies the adaptive control problem for unknown time-varying high-order nonlinear multiagent systems (MASs) with directed topology. A novel low-complexity distributed adaptive backstepping controller is developed to achieve the asymptotic synchronization. The designed controller regards the unknown system nonlinearities as “disturbance-like” terms, which are guaranteed to be bounded by using the barrier functions, such that detail models of system nonlinearities are released. Then, the “disturbance-like” terms are compensated adaptively by designing the novel compensator at each step, such that the synchronization error is eliminated to zero eventually for each agent. In addition, unlike the existing backstepping-like synchronization approaches for high-order nonlinear MASs, the “explosion of complexity” issue is avoided without extra low-pass filters. Some simulations are shown to demonstrate the effectiveness and advantages of the developed method.
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Guojun Yuan,Jianbin Zhang,Yongfeng Zhang,Yinan Yan,Xinxin Ju,Junmin Sun 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.3
A highly stable silicate material from high-alumina coal fly ash was prepared and characterized using X-raydiffraction, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermal analysis, Xrayphotoelectron spectroscopy, and elemental analysis. The spectral results show that the silicate material was mainlycomposed of six elements, C, Ca, O, Si, Mg, and Al, in the form of Ca2+, Mg2+, Al3+, SiO32−, and CO32− ions. Some adsorbedwater and/or water of crystallization was also observed. The silicate material showed exceptionally high capabilityto adsorb volatile organic compounds (VOCs). The results of dynamic adsorption behavior show that the silicatematerial presents similar properties with commercial activated carbon and stronger absorption properties than commercialdiatomite for the adsorption of VOCs. The FTIR spectral results show weak hydrogen bonding interactions ofthe silicate material with three VOCs.
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Xinchun Wu,Ping Li,Aizhong Ju,Jie Kang,Yongfeng Zhang,De Yao 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.1
A new phosphor of the K2[Al(B5O10)]:Eu3+ was prepared by annealing of the as-prepared of the precursor of K2[Al(B5O10)]∙4H2O:Eu3+ at 300?400 °C, and which has been synthesized under facile hydrothermal conditions. All the samples were characterized by the EDS, XRD, FT-IR, and SEM. A systematic study on their luminescent properties has been performed by the PL and PLE. A series of influencing factors on the luminescent properties were also investigated. The PL and PLE studies reveal that the phosphor of K2[Al(B5O10)]:Eu3+ with optimal luminescent intensity and higher red-orange ratio were obtained by sintering the precursor at 400 °C for 5.5 h, with 9% doping concentration, which suggests that it might as a potential application of the light display systems.
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