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Fei Yang,Shaohua Bi,Xinmin Shen,Xiaocui Yang,Xinqing Wang,Xiangpo Zhang,Jinhong Xue,Xiaonan Zhang,Qin Yin,Juying Dai,Wenqiang Peng,Jingwei Zhu,Junhong Ren 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.12
To prevent noise pollution, a hexagonal acoustic metamaterial cell combining multiple parallel Helmholtz resonators with optional apertures is proposed. There were 6 trapezoidal chambers and 6 triangular chambers, and each front panel had 6 different apertures, which meant that there were 6 12 = 2176782336 possible permutations. The distribution of sound pressures obtained by acoustic finite element simulation revealed the acoustic absorption mechanism, which provided effective guidance to alter the absorption capacity. For certain scenarios, the acoustic absorption performance was optimized by the joint combination of artificial neural network and acoustic finite element simulation. Through manufacturing and testing the sample, actual average acoustic absorption coefficients were achieved at 0.6733, 0.7296, 0.8785 and 0.7065 for the target frequency ranges 350-950 Hz, 400-1000 Hz, 500-800 Hz and 350-700 Hz, respectively, with total thickness 40 mm. The tunable acoustic absorption property proved that the hexagonal acoustic metamaterial cell was appropriate for noise reduction with variable frequency ranges.
Shi, Ji-Ying,Xue, Fei,Qin, Zi-Jian,Zhang, Wen,Ling, Le-Tao,Yang, Ting The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1
Conventional maximum power point tracking (MPPT) methods are ineffective under partially shaded conditions because multiple local maximum can be exhibited on power-voltage characteristic curve. This study proposes an improved cuckoo search (ICS) MPPT method after investigating the cuckoo search (CS) algorithm applied in solving multiple MPPT. The algorithm eliminates the random step in the original CS algorithm, and the conception of low-power, high-power, normal and marked zones are introduced. The adaptive step adjustment is also realized according to the different stages of the nest position. This algorithm adopts the large step in low-power and marked zones to reduce search time, and a small step in high-power zone is used to improve search accuracy. Finally, simulation and experiment results indicate that the promoted ICS algorithm can immediately and accurately track the global maximum under partially shaded conditions, and the array output efficiency can be improved.
Shi, Ji-Ying,Xue, Fei,Ling, Le-Tao,Li, Xiao-Fei,Qin, Zi-Jian,Li, Ya-Jing,Yang, Ting The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2
Under partial shading conditions (PSCs), multiple maximums may be exhibited on the P-U curve of string inverter photovoltaic (PV) systems. Under such conditions, heuristic methods are invalid for extracting a global maximum power point (GMPP); intelligent algorithms are time-consuming; and model-based methods are complex and costly. To overcome these shortcomings, a novel hybrid MPPT (MPF-IP&O) based on a model-based peak forecasting (MPF) method and an improved perturbation and observation (IP&O) method is proposed. The MPF considers the influence of temperature and does not require solar radiation measurements. In addition, it can forecast all of the peak values of the PV string without complex computation under PSCs, and it can determine the candidate GMPP after a comparison. Hence, the MPF narrows the searching range tremendously and accelerates the convergence to the GMPP. Additionally, the IP&O with a successive approximation strategy searches for the real GMPP in the neighborhood of the candidate one, which can significantly enhance the tracking efficiency. Finally, simulation and experiment results show that the proposed method has a higher tracking speed and accuracy than the perturbation and observation (P&O) and particle swarm optimization (PSO) methods under PSCs.
Ji-Ying Shi,Fei Xue,Le-Tao Ling,Xiao-Fei Li,Zi-Jian Qin,Ya-Jing Li,Ting Yang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2
Under partial shading conditions (PSCs), multiple maximums may be exhibited on the P-U curve of string inverter photovoltaic (PV) systems. Under such conditions, heuristic methods are invalid for extracting a global maximum power point (GMPP); intelligent algorithms are time-consuming; and model-based methods are complex and costly. To overcome these shortcomings, a novel hybrid MPPT (MPF-IP&O) based on a model-based peak forecasting (MPF) method and an improved perturbation and observation (IP&O) method is proposed. The MPF considers the influence of temperature and does not require solar radiation measurements. In addition, it can forecast all of the peak values of the PV string without complex computation under PSCs, and it can determine the candidate GMPP after a comparison. Hence, the MPF narrows the searching range tremendously and accelerates the convergence to the GMPP. Additionally, the IP&O with a successive approximation strategy searches for the real GMPP in the neighborhood of the candidate one, which can significantly enhance the tracking efficiency. Finally, simulation and experiment results show that the proposed method has a higher tracking speed and accuracy than the perturbation and observation (P&O) and particle swarm optimization (PSO) methods under PSCs.
Jian-Xin Shen,Xue-Fei Qin,Wei-Zhong Fei,Yun-Chong Wang 한국자기학회 2019 Journal of Magnetics Vol.24 No.2
Pulse width modulation (PWM) of voltage source inverter (VSI) is common for speed regulation of permanent magnet (PM) brushless direct-current (BLDC) motor drives. However, when the motor runs at high speed, the conventional PWM technique may become unfeasible due to the low carrier ratio of inverter, which makes the motor current distorted and the motor core loss increased significantly. In this paper, two control strategies, namely single pulse variable width (SPVW) and dual pulses variable width (DPVW), are introduced for the high-speed PM BLDC motor drives, and are comprehensively investigated. Finite element method (FEM) is employed to evaluate and compare the drive system performance when using the conventional PWM, and the proposed SPVW and DPVW, respectively. Influence of the control techniques, especially on the loss distribution, is revealed.
Ji-Ying Shi,Fei Xue,Zi-Jian Qin,Wen Zhang,Le-Tao Ling,Ting Yang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1
Conventional maximum power point tracking (MPPT) methods are ineffective under partially shaded conditions because multiple local maximum can be exhibited on power–voltage characteristic curve. This study proposes an improved cuckoo search (ICS) MPPT method after investigating the cuckoo search (CS) algorithm applied in solving multiple MPPT. The algorithm eliminates the random step in the original CS algorithm, and the conception of low-power, high-power, normal and marked zones are introduced. The adaptive step adjustment is also realized according to the different stages of the nest position. This algorithm adopts the large step in low-power and marked zones to reduce search time, and a small step in high-power zone is used to improve search accuracy. Finally, simulation and experiment results indicate that the promoted ICS algorithm can immediately and accurately track the global maximum under partially shaded conditions, and the array output efficiency can be improved.
Sharpened VO<sub>2</sub> Phase Transition via Controlled Release of Epitaxial Strain
Lee, Daesu,Lee, Jaeseong,Song, Kyung,Xue, Fei,Choi, Si-Young,Ma, Yanjun,Podkaminer, Jacob,Liu, Dong,Liu, Shih-Chia,Chung, Bongwook,Fan, Wenjuan,Cho, Sang June,Zhou, Weidong,Lee, Jaichan,Chen, Long-Qin American Chemical Society 2017 NANO LETTERS Vol.17 No.9
<P>Phase transitions in correlated materials can be manipulated at the nanoscale to yield emergent functional properties, promising new paradigms for nanoelectronics and nanophotonics. Vanadium dioxide (VO2), an archetypal correlated material, exhibits a metal insulator transition (MIT) above room temperature. At the thicknesses required for heterostructure applications, such as an optical modulator discussed here, the strain state of VO2 largely determines the MIT dynamics critical to the device performance. We develop an approach to control the MIT dynamics in epitaxial VO2 films by employing an intermediate template layer with large lattice mismatch to relieve the interfacial lattice constraints, contrary to conventional thin film epitaxy that favors lattice match between the substrate and the growing film. A combination of phase-field simulation, in situ real-time nanoscale imaging, and electrical measurements reveals robust undisturbed MIT dynamics even at preexisting structural domain boundaries and significantly sharpened MIT in the templated VO2 films. Utilizing the sharp MIT, we demonstrate a fast, electrically switchable optical waveguide. This study offers unconventional design principles for heteroepitaxial correlated materials, as well as novel insight into their nanoscale phase transitions.</P>
Shi, Ji-Ying,Zhang, Deng-Yu,Ling, Le-Tao,Xue, Fei,Li, Ya-Jing,Qin, Zi-Jian,Yang, Ting The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3
This paper presents a dual-algorithm search method (GWO-GSO) combining grey wolf optimization (GWO) and golden-section optimization (GSO) to realize maximum power point tracking (MPPT) for photovoltaic (PV) systems. First, a modified grey wolf optimization (MGWO) is activated for the global search. In conventional GWO, wolf leaders possess the same impact on decision-making. In this paper, the decision weights of wolf leaders are automatically adjusted with hunting progression, which is conducive to accelerating hunting. At the later stage, the algorithm is switched to GSO for the local search, which play a critical role in avoiding unnecessary search and reducing the tracking time. Additionally, a novel restart judgment based on the quasi-slope of the power-voltage curve is introduced to enhance the reliability of MPPT systems. Simulation and experiment results demonstrate that the proposed algorithm can track the global maximum power point (MPP) swiftly and reliably with higher accuracy under various conditions.
Ji-Ying Shi,Deng-Yu Zhang,Le-Tao Ling,Fei Xue,Ya-Jing Li,Zi-Jian Qin,Ting Yang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3
This paper presents a dual-algorithm search method (GWO-GSO) combining grey wolf optimization (GWO) and golden-section optimization (GSO) to realize maximum power point tracking (MPPT) for photovoltaic (PV) systems. First, a modified grey wolf optimization (MGWO) is activated for the global search. In conventional GWO, wolf leaders possess the same impact on decision-making. In this paper, the decision weights of wolf leaders are automatically adjusted with hunting progression, which is conducive to accelerating hunting. At the later stage, the algorithm is switched to GSO for the local search, which play a critical role in avoiding unnecessary search and reducing the tracking time. Additionally, a novel restart judgment based on the quasi-slope of the power-voltage curve is introduced to enhance the reliability of MPPT systems. Simulation and experiment results demonstrate that the proposed algorithm can track the global maximum power point (MPP) swiftly and reliably with higher accuracy under various conditions.