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96 results on '"Fang, Gaoliang"'

29. Equivalent Linear Model Based Torque Control and Performance Improvement For Switched Reluctance Motor (SRM) Drives

Author

Fang, Gaoliang, Emadi, Ali, and Electrical and Computer Engineering

Subjects
Current Control, Switched Reluctance Motor, Torque Control, Radial Force
Abstract

Switched reluctance machines (SRMs) are gaining increasing interest in industrial applications due to their low manufacturing cost, simple and robust structure, excellent fault-tolerant capability, and reliable operation in high-temperature operating environments. However, the inherent pulsative torque and radial force lead to the well-known torque ripples and acoustic noise issues. Although there are numerous advanced methods to address the above two issues, the high nonlinearity inevitably brings difficulties in controlling the SRMs. Since the linear SRM voltage and toque equations are simple, it would be beneficial to explore the control algorithm by using such simple linear model. The application of the linear torque model is firstly explored. To utilize such simple model, the connections between the linear toque model and the nonlinear torque model are built through the mapping. The features of these mapping curves are studied in detail. Applying the linear torque equation to generate the reference currents in the optimization-based torque sharing function method shows a significant reduction of the time consumption in solving the bi-optimization problem. Later, the complete equivalent linear SRM model is constructed by introducing the linear voltage equation and corresponding mapping. Since the linear model is easy to predict the behaviour of SRMs, it is beneficial to apply such model in the model predictive torque control (MPTC) methods. The application of the equivalent linear model in the finite control set (FCS) MPTC method shows a low computational burden and occupies less storage space. Besides, the improved switching table in the proposed FCS MPTC method also enhances the torque control performance in high-speed operation conditions. To further reduce the torque ripples, the continuous control set (CCS) MPTC method is developed based on the constructed equivalent linear SRM model. The impossibility in analytically solving the optimization problem in the CCS MPTC method if using the original nonlinear SRM model is innovatively addressed by using the equivalent linear SRM model and properly modifying the cost function. Extensive simulation and experimental results prove the low-ripple feature of the proposed CCS MPTC method in a wide speed range. The high nonlinearity also makes the current control of SRM drives difficult. An intersection-method-based current controller is presented to ensure good current tracking performance for SRMs. The employed adaptive flux-linkage observer makes this current controller show robust performance when there is a deviation on the employed flux-linkage characteristics. Finally, the key but unmeasurable radial force information for the advanced acoustic reduction method is reconstructed based on the measured flux-linkage curves and some core relationship. This core relationship, which is between the square root of the radial force and the flux-linkage, is explored in detail. Simulation results reveal that the proposed method shows good radial force estimation accuracy when there is even 50% airgap length variation. Thesis Doctor of Philosophy (PhD)

Published
2021

39. Promoting Charge Separation in g-C3N4/Graphene/MoS2 Photocatalysts by Two-Dimensional Nanojunction for Enhanced Photocatalytic H2 Production

Author

Yuan, Yong-Jun, primary, Yang, Yan, additional, Li, Zijian, additional, Chen, Daqin, additional, Wu, Shiting, additional, Fang, Gaoliang, additional, Bai, Wangfeng, additional, Ding, Mingye, additional, Yang, Ling-Xia, additional, Cao, Da-Peng, additional, Yu, Zhen-Tao, additional, and Zou, Zhi-Gang, additional

Published
2018
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47. Mn-Doped CsPbCl3 perovskite nanocrystals: solvothermal synthesis, dual-color luminescence and improved stability.

Author

Chen, Daqin, Fang, Gaoliang, Chen, Xiao, Zhong, Jiasong, Mao, Qinan, Zhou, Su, Li, Junni, and Lei, Lei

Abstract

All inorganic CsPbX3 (X = Cl, Br, I) perovskite quantum dots have attracted extreme attention due to their excellent optical performance. Unfortunately, heavy usage of the toxic Pb element is still a serious problem that needs to be solved. In the present work, Mn-doped CsPbCl3 nanocrystals are successfully prepared via a facile solvothermal reaction for the first time. A high Cs-to-Pb feeding ratio is necessary to achieve pure cubic perovskite phase and the incorporation of Mn dopants into the CsPbCl3 host is highly related to the Mn-to-Pb feeding ratio. Importantly, it is demonstrated that Mn-doped CsPbCl3 NCs synthesized by the solvothermal method have better stability than those prepared by traditional hot injection. To finely adjust the bandgap of CsPbCl3 NCs, Cl-to-Br anion exchange is used to fabricate Mn-doped CsPb(Cl/Br)3 NCs with tunable multi-color luminescence. Finally, the as-prepared Mn-doped CsPb(Cl/Br)3 products are demonstrated to be applicable as color converters for constructing white light-emitting diodes and optical thermometric medium for accurate temperature sensing. [ABSTRACT FROM AUTHOR]

Published
2018
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48. Reverse synthesis of CsPbxMn1−x(Cl/Br)3 perovskite quantum dots from CsMnCl3 precursors through cation exchange.

Author

Ji, Zhenguo, Chen, Daqin, Lei, Lei, Fang, Gaoliang, Zhou, Su, Chen, Xiao, and Zhong, Jiasong

Abstract

Successful development of all-inorganic CsPbX3 (X = Cl, Br, or I) perovskite quantum dots (PQDs) has been witnessed due to their unique optical and electrical properties. However, the heavy usage of Pb element in PQDs has limited the commercial application of these PQDs, and the preparation of low-Pb or Pb-free PQDs is imperative. In this study, we report room-temperature reverse synthesis of CsPbxMn1−xCl3 PDQs from CsMnCl3 precursor nanocrystals through cation exchange. Interestingly, two-step phase transformation processes from hexagonal CsMnCl3 to rhombohedral Cs4PbxMn1−xCl6 and finally to cubic CsPbxMn1−xCl3 are evidenced. With an increase in the reaction time, Mn2+ ions in the PQD lattice are gradually replaced by Pb2+ ions. Notably, Mn2+ d → d broadband luminescence is not detected for the Cs4PbxMn1−xCl6 product, but it is intense for the CsPbxMn1−xCl3 sample owing to efficient energy transfer from CsPbCl3 to Mn2+. Moreover, it is found that the introduction of Br− into the reaction system will prohibit the complete phase transformation from rhombohedral Cs4PbxMn1−x(Cl/Br)6 to cubic CsPbxMn1−x(Cl/Br)3. By controlling the ratio between the CsMnCl3 precursor and PbBr2, tunable luminescence is easily achieved due to the combined emissions from both CsPb(Cl/Br)3 PQDs and Mn2+-emitting centers. [ABSTRACT FROM AUTHOR]

Published
2018
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49. High light harvesting efficiency CuInS2 quantum dots/TiO2/MoS2 photocatalysts for enhanced visible light photocatalytic H2 production.

Author

Yuan, Yong-Jun, Fang, Gaoliang, Chen, Daqin, Huang, Yanwei, Yang, Ling-Xia, Cao, Da-Peng, Wang, Jingjing, Yu, Zhen-Tao, and Zou, Zhi-Gang

Subjects
*COPPER compounds, *QUANTUM dots, *TITANIUM dioxide
Abstract

Expanding the photoresponse range of TiO2-based photocatalysts is of great interest for photocatalytic H2 production. Herein, noble-metal-free CuInS2 quantum dots were employed as a novel inorganic dye to expand the visible light absorption of TiO2/MoS2 for solar H2 generation. The as-prepared CuInS2/TiO2/MoS2 photocatalysts exhibit broad absorption from the ultraviolet to near-infrared region. Under visible light irradiation (λ ＞ 420 nm), the CuInS2/TiO2/MoS2 photocatalyst with 0.6 mmol g−1 CuInS2 and 0.5 wt% MoS2 showed the highest H2 evolution rate with a value of 1034 μmol h−1 g−1. Moreover, a considerable H2 evolution rate of 141 μmol h−1 g−1 was obtained under the irradiation of the optimized CuInS2/TiO2/MoS2 photocatalyst with ＞500 nm light. The reaction mechanism of the CuInS2/TiO2/MoS2 photocatalyst for photocatalytic H2 evolution was investigated in detail by photoluminescence decay study, and the results showed that the photoexcited electrons of CuInS2 can be transferred efficiently through TiO2 to MoS2 and then react with the absorbed protons to generate H2. The reported sensitization strategy tremendously improves the visible light absorption capacity and the photocatalytic performance of TiO2-based photocatalysts. [ABSTRACT FROM AUTHOR]

Published
2018
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50. Tunable CsPbBr3/Cs4PbBr6 phase transformation and their optical spectroscopic properties.

Author

Chen, Xiao, Chen, Daqin, Li, Junni, Fang, Gaoliang, Sheng, Hongchao, and Zhong, Jiasong

Subjects
CESIUM compounds, PHASE transitions, OPTICAL spectroscopy
Abstract

As a novel type of promising materials, metal halide perovskites are a rising star in the field of optoelectronics. On this basis, a new frontier of zero-dimensional perovskite-related Cs4PbBr6 with bright green emission and high stability has attracted an enormous amount of attention, even though its photoluminescence still requires to clarification. Herein, the controllable phase transformation between three-dimensional CsPbBr3 and zero-dimensional Cs4PbBr6 is easily achieved in a facile ligand-assisted supersaturated recrystallization synthesis procedure via tuning the amount of surfactants, and their unique optical properties are investigated and compared in detail. Both Cs4PbBr6 and CsPbBr3 produce remarkably intense green luminescence with quantum yields up to 45% and 80%, respectively; however, significantly different emitting behaviors are observed. The fluorescence lifetime of Cs4PbBr6 is much longer than that of CsPbBr3, and photo-blinking is easily detected in the Cs4PbBr6 product, proving that the zero-dimensional Cs4PbBr6 is indeed a highly luminescent perovskite-related material. Additionally, for the first time, tunable emissions over the visible-light spectral region are demonstrated to be achievable via halogen composition modulations in the Cs4PbX6 (X = Cl, Br, I) samples. Our study brings a simple method for the phase control of CsPbBr3/Cs4PbBr6 and demonstrates the intrinsic luminescence nature of the zero-dimensional perovskite-related Cs4PbX6 products. [ABSTRACT FROM AUTHOR]

Published
2018
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