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Jianyong Zheng,Yi Pan,Fei Mei,Huiyu Miao,Kedong Zhu,Haoyuan Sha 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.1
Traditional fault diagnosis for a high-voltage circuit breaker (HVCB) encounters the following problems: the fault features extracted by traditional shallow models is of weak expression ability, and the accuracy of fault identification can be affected by the lack of labeled training samples. To overcome these problems, we present a new approach for HVCB mechanical fault diagnosis based on a deep belief network (DBN) and a transfer learning strategy. This approach uses a DBN to achieve the deep mining and adaptive extraction of the inherent features of sample data, and combines the transfer learning method to improve the accuracy of the fault diagnosis model, which uses a large amount of selective auxiliary data to augment the tiny amount of target data learning by adjusting the weight of training samples. The target sample data are obtained by collecting the coil current signal of the HVCB from fault simulation experiments, and the auxiliary sample data are obtained through simulation based on the electromagnetic system mathematical model of the HVCB spring mechanism. The experimental results show that compared with the traditional feature extraction and fault diagnosis method, the DBN approach combined with transfer learning can achieve stronger feature learning and generalization ability
An Improved MMC Control Strategy with Single-Phase to Ground Fault-Tolerance Capability
Huiyu Miao,Jun Mei,Jianyong Zheng,Chenyu Zhang,Chao Zhu,Tian Ma,Fei Mei 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.5
In this paper, an improved modular multilevel converter (MMC) control strategy based on one-cycle control (OCC) is proposed. With the introduction of OCC, the stability, rapidity and disturbance rejection of MMC is greatly improved. Based on the volt-second equilibrium, the control is distributed to every single submodule (SM). For further stability, an unbalanced OCC strategy is designed based on feed-forward control for negative sequence voltage with no need for measuring the positive and negative current sequence, considering single phase to ground fault and the second harmonic ripples of the DC voltage. As the switch frequency of every SM is different, the virtual loop mapping is used in this paper to balance the capacitor voltage with less hardware dependence. And a new simplified structure is also proposed with RS flip-flop abandoned. At last, simulation and experiment results prove the validity of the control theory.
Jianming Wang,Siqi Luan,Jianyong Zhu,Xiaodong Mao,Junqiang Wu 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.2
The flow field structure of a single injection port fluidic thrust vectoring nozzle was studied by introducing secondary flow injection in the expansion section of the two-dimensional convergent-divergent nozzle. To determine the motion characteristics of unsteady flow in a shock-induced fluidic vectoring nozzle, detached eddy simulation was conducted to simulate the three-dimensional flow field, and the flow mechanism in the nozzle was analyzed. Fourier mode decomposition was used to analyze the pressure coefficient on the symmetrical surface of the nozzle. Results show three natural frequencies in the flow field of the shock-induced fluidic vectoring nozzle. The first-order mode corresponding to frequency f1 = 512.8 Hz mainly illustrates the oscillation of shock waves. The second-order mode corresponding to frequency f2 = 2825 Hz illustrates the shedding of vortices. The third-order mode corresponding to frequency f3 = 4650 Hz is similar to the second-order mode; however, the spatial scales of vortices decrease.
Xiao Kai,Liu Xiaohui,Zhang Aidong,Zha Dingshi,Zhu WeiMin,Tan Feng,Huang Qianru,Zhou Yaru,Zhang Min,Li Jianyong,Wu Xuexia 한국원예학회 2022 Horticulture, Environment, and Biotechnology Vol.63 No.5
Browning of fresh-cut eggplant (Solanum melongena L.) reduces its sensory and nutritional qualities and further influences consumption. Polyphenolic oxidases (PPOs) are key enzymes involved in browning, but the mechanisms that regulate the expression of PPO genes are still unclear. Here, 12 SmPPO genes were identified and phylogenetic analysis clustered these genes into four branches. Protein and cis-regulatory element analyses showed that the SmPPO gene family has a conserved gene structure and diverse functions. Gene expression analysis in different tissues showed that the expression of SmPPO2, SmPPO3, SmPPO6, SmPPO7, and SmPPO10 was higher in the flesh of the browning-sensitive inbred line ‘36’ than in the flesh of the browning-resistant line ‘Fu’. Furthermore, almost all SmPPO genes in ‘36’ were upregulated at 4 °C and 36 °C compared with those in ‘Fu’, and the expression increased earlier after harvest. In addition, SmPPO1, SmPPO6, SmPPO7, and SmPPO10 expression was significantly elevated in ‘36’ after 2 days at 36 °C. These results suggest that SmPPOs are key modulators of eggplant browning and provide candidate genes for further research on the mechanisms regulating fruit browning.