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Zhang WenXin,Li Hao,Cong Haofei,Zhou Ruifu,Qin Yuanbin,Xu Peilong,Liu Xuhai,Wang Fengyun 한국물리학회 2023 Current Applied Physics Vol.48 No.-
One-dimensional wide band-gap metal oxide semiconductors demonstrate enormous potential in high-performance ultraviolet photodetectors. Here, via tuned zinc oxide (ZnO) concentration ratio and heterojunction structure as well as decent VTH value, we electrospun tin zinc oxide (SnZnOX) nanowires for photoelectronic conversion function. The constructed optimized photodetectors based on Sn8Zn2OX nanowires can exhibit a remarkable detectivity of 1.77 × 1016 Jones, excellent responsivity of 2.23 × 103 A/W and relative high sensitivity over 104. In addition to the excellent photodetection performance, Sn8Zn2OX nanowire devices exhibit nonvolatile memory effect, which can maintain the light-induced low resistance state at 5 V without light. Moreover, a voltage of 30 V was applied to Sn8Zn2OX nanowires devices to realize light-writing state switching to bias-erasing state, and the device could come back to their initial high resistance state. These results indicate SnZnOX nanowires devices possess a tremendous potential in the circuit design of the artificial visual system.
A High Precision Time-frequency Analysis Method
Wenxin Zhang,Xiaojun Liu,Xiuwei Chen,Qing Liu,Guangyou Fang 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.7
To analysis the signal whose frequency changes as time, this article presents a new time-frequency analysis method based on short-time fractional Fourier transform (FRFT) and integration of midpoints. This method uses window functions to divide the signal to many pieces, then the FRFT is used to calculate the frequency modulation (FM) rate of each piece. A chirp signal can be built based on the FM rate and the intermediate frequency (IF) signal is obtained by mixing the chirp signal and the primary signal. The frequency of the midpoints can be estimated by the chirp-z transform (CZT), therefore the frequency of every piece can be calculated. This method avoids the impact that the quick change of frequency leads to the error of short-time Fourier transform. It also can reduce the error brought by the estimation of chirp rate. Therefore, the method can improve the accuracy of time-frequency analysis. This article also puts forward a method to search the order of fractional Fourier transform, and the computer simulation and measurement verifies the effectiveness of the proposed algorithm.
Xinglong Zhang,Youqun Zhao,Wenxin Zhang,Fen Lin,Haiqing Li 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.1
By solving driver’s optimal handling input, this paper presents a novel Lane Changing Assistance System (LCAS) which can provide guidance for driver’s lane changing behavior. In addition, vehicle handling inverse dynamics method is proposed to solve driver’s optimal handling input. Firstly, to recognize driver’s lane changing intention and decrease the false alarm rate of LCAS, a lane changing intention recognition model is established. Secondly, the handling inverse dynamics model is established; and then the inverse dynamics problem is converted into the optimal control problem. Finally, the optimal control problem is converted into a nonlinear programming problem based on GPM; then sequential quadratic programming (SQP) is applied to get the solution. The direct collocation method (DCM) is used as the contrast verification of GPM. The simulation results show that the driver’s optimal handling input can be obtained according to driver’s lane changing intention in the proposed LCAS; and GPM has higher computational accuracy compared with DCM. This method may provide a reference for the research of LCAS and unmanned vehicles.
Single-Point Grinding of Alumina and Zirconia Ceramics Under Two-Dimensional Compressive Prestress
Gaofeng Zhang,Zhigang Wang,Wenxin Chen,Jingtao Li,Hao Sun,Kui Zhang 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.1
In this study, single-point grinding experiments were performed on alumina and zirconia ceramics to investigate the grinding processes under two-dimensional compressive prestress (TCP). Grinding forces and grooves were measured under different values of TCP to evaluate the grinding defects. The material removal rate and actual grinding depth were exploited to investigate the grinding-induced damage and material
Impact of Grafting Density on the Self-Assembly and Hydrophilicity of Succinylated Collagen
Wenxin Wang,Feiyi Shu,Lingyu Pan,Shanshan Huang,Xiao Tu,Ping Li,Siman Li,Yuanyuan Li,Chengzhi Xu,Yang Sun,Juntao Zhang,Haibo Wang 한국고분자학회 2020 Macromolecular Research Vol.28 No.6
Modification of protein could give their new functionality but would affect their intrinsic property and activity. In this paper, a series of succinylated collagen (SCol(n/1)) (n≥1) were prepared by modification of collagen with succinic anhydride at different molar ratio to amino groups amount of collagen. The impact of grafting density on the intrinsic self-assembly and additional hydrophilicity of succinylated collagen was explored. The results revealed that excessive grafting density of succinylated collagen would improve their hydrophilicity but weaken their self-assembly property, although the triple helix of collagen could be reserved after succinylation. SCol(1/1) (grafting density of 17%) with self-assembly property and good hydrophilicity was chosen to compare with native collagen. Compared to native collagen, thermostability of SCol(1/1) decreased slightly, however, SCol(1/1) could form softer hydrogel, which was more favorable for the proliferation of NIH/3 T3. The present work would help us to further understand the importance of grafting density for the design of modified collagen with intrinsic self-assembly property and additional new functionality.
Least Squares Fuzzy One-class Support Vector Machine for Imbalanced Data
Jingjing Zhang,Kuaini Wang,Wenxin Zhu,Ping Zhong 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.8
Based on fuzzy one-class support vector machine (SVM) and least squares (LS) one-class SVM, we propose an LS fuzzy one-class SVM to deal with the class imbalanced problem. The LS fuzzy one-class SVM applies a fuzzy membership to each sample and attempts to solve the modified primal problem. Hence, we just need to solve a system of linear equations as opposed solving the quadratic programming problem (QPP) in fuzzy one-class SVM, which leads to an extremely simple and fast algorithm. Numerical experiments on several benchmark data sets demonstrate the feasibility and effectiveness of the proposed algorithm.
Ti, Wenxin,Wu, Huanchun,Xue, Fei,Zhang, Guodong,Peng, Qunjia,Fang, Kewei,Wang, Xitao Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8
The effect of thermal aging at 475 ℃ and 750 ℃ of Z3CN20.09M cast duplex stainless steel (CDSS) on microstructure, mechanical and intergranular corrosion properties were investigated by transmission electron microscope (TEM), nano indenter, scanning electron microscope (SEM) and corrosion fatigue test system. The result indicated that the spinodal decomposition and G precipitated were occurred after aged at 475 ℃, as well as sigma precipitated at 750 ℃. The microstructure degeneration of ferrite was saturated after aged for 2000h and 200 h at 475 ℃ and 750 ℃ respectively. The mechanical properties, intergranular corrosion resistance and corrosion fatigue lives were continuing deteriorated with increasing the aging time at both temperatures. The difference of the degeneration mechanisms of Z3CN20.09M CDSS aged at 475 ℃ and 750 ℃ was analyzed.
Yi Lingzhi,Jiang Ganlin,Zhang Guoyong,Yu Wenxin,Guo You,Sun Tao 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.4
In order to improve the accuracy and reliability of fault diagnosis for oil-immersed transformers, a fault diagnosis method for oil-immersed transformers based on improved Harris Hawks optimized random forest is proposed in this paper. First, logistic chaotic mapping is used to adjust the key parameters of the algorithm; then a nonlinear energy factor adjustment strategy is used to control the algorithm to transition from global search to local search; fi nally, the method of Gaussian mutation is introduced to strengthen the local search ability, and when the algorithm is stagnant, fi refl y perturbation is performed on the optimal solution to make the algorithm jump out of local optimum. The number of n_trees and n_layers of the random forest are jointly optimized by the improved Harris Hawks optimization algorithm, and the fault diagnosis model of oil-immersed transformer is established. The noncoded ratios of dissolved characteristic gases in oil are used as the characteristic input of the diagnosis model to obtain the fi nal diagnosis results. Compared with other models and verifi ed by examples, the results show that the proposed method has the advantage of high diagnostic accuracy and has certain practical engineering application value.