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Chaoqun Cai,Hongqiang Zhang,Jun Xie,Ligang Ma 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.9
Textured zinc-oxide (ZnO) thin films and Cu-doped ZnO (ZnO:Cu) thin films are deposited on glass substrates by using radio-frequency reactive magnetron sputtering. The effect of Cudoping concentration on the crystallization behavior, surface morphology, transmission spectrum, and luminescence properties of the ZnO thin films are systematically investigated by using X-ray diffraction, scanning probe microscopy and photoluminescence spectra. The results indicate that the crystallization quality, morphology, transmission, and luminescence of the ZnO films is affected by Cu-element doping. A stronger preferred orientation toward the c-axis is obtained after Cu doping at an appropriate concentration (3%). The transmittance rate gradually decreases with increasing Cu doping concentration. In the photoluminescence spectra of the samples measured at room temperature, four main emission peaks are observed: a violet peak located at about 390 nm, two blue peaks, one located at about 445 nm and the other at about 485 nm, and a green peak located at about 527 nm. The origins of these emissions are discussed in detail.
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Dominant Pole Placement with Modified PID Controllers
Huanchao Du,Xiaoguang Hu,Chaoqun Ma 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.11
In this paper, the limitations of the standard PID controller for dominant pole placement has been analyzed. Study shows that the modified PID controller, such as PI-D, I-PD, PI-PD and PD-PID controller, is an alternative to solve this problem. For the PI-PD and PD-PID controller, the zeros can be placed on the poles that are close to the specified dominant poles. The conditions for the existence of the dominant poles could be relaxed by pole-zero cancellation. Results show that a good dominant effect with fast response can be realized by the modified PID controllers.
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Wanxing Wang,Yan Zhang,Chaomin Xiao,Yang Li,Chaoqun Ma,Jinjun Liu 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
Space vector modulation (SVM) is widely used for voltage source inverters, but it is too complicated when extended to the cascaded H-bridge multilevel converter (CHMC) under faulty conditions. In this article, a fast and universal SVM strategy is proposed to realize postfault operation for CHMC. Different fault types can be reflected by the reduction of phase voltage so the proposed scheme first calculates all the available redundant switching states based on available output voltage in three phases. Final-selected switching state is within the selectable range based on the reduced common-mode voltage principle. To generate the switching sequence, discontinuous pulse-width modulation (DPWM) is used, which improves efficiency of the system. The proposed SVM scheme is independent of the number of levels and can be applied in different fault conditions. The performance and effectiveness of the proposed strategy are verified by simulation results.
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