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Locally Exponential Stability of Discrete-time Complex Networks with Impulsive Input Saturation
Keyu Chen,Chuandong Li,Liangliang Li 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.4
In this paper, the problem of exponential stabilization for a class of discrete-time complex network withsaturated impulse input is investigated. Based on the inductive method, convex analysis, and auxiliary matrix,several Lyapunov-type stability criteria are derived for exponential stability of discrete-time complex network withimpulsive input saturation. Two examples are also presented to illustrate the effectiveness and the feasibility of theobtained results.
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Sifting process of EMD and its application in rolling element bearing fault diagnosis
Hongbo Dong,Keyu Qi,Xuefeng Chen,Yanyang Zi,Zhengjia He,Bing Li 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.8
Among the vibration-based fault diagnosis methods for rolling element bearing, the shock pulse method (SPM) combined with the demodulation method is a useful quantitative technique for estimating bearing running state. However, direct demodulation often misestimates the shock value of characteristic defect frequency. To overcome this disadvantage, the vibration signal should be decomposed before demodulation. Empirical mode decomposition (EMD) can be an alternative for preprocess bearing fault signals. However, the trouble with this method’s application is that it is time-consuming. Therefore, a novel method that can improve the sifting process’s efficiency is proposed, in which only one time of cubic spline fitting is required in each sifting process. As a consequence, the time for EMD analysis can be evidently shortened and the decomposition results simultaneously maintained at a high precision. Simulations and experiments verify that the improved EMD method, combined with SPM and demodulation analysis, is efficient and accurate and can be effectively applied in engineering practice.
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Yin Li,Keyu Zhang,Zhengjie Chen,Yunke Wang,Li Wang,Feng Liang,Yaochun Yao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2020 NANO Vol.15 No.02
The olivine LiFePO4 with various morphologies and different growth lattice planes was prepared by a controllable hydrothermal method with changing precursor concentration and using phytic acid as phosphorus source. The microstructure, crystal orientation and electrochemical performance of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and charge–discharge tests. The results show that the morphologies of all samples change from spindle-like to hierarchical plate-like and then to long plate-like shape, and the main exposed facets transform from (100) to (001). This indicates that the precursor concentration and phytic acid play important roles in exposing facets and controlling the morphology of LiFePO4. In order to illustrate these phenomena, a reasonable assembly process is provided and the formation is explained. Li ion diffusion coefficient along [100] and [001] directions was calculated by using electrochemical impedance spectroscopy (EIS). The results show that the diffusion coefficient of (100) facet is higher than that of (001) facet, indicating a good electrochemical performance for (100) facet. In addition, the capacity test is carried out, which also confirms the above results. With the precursor concentration of 0.5 M, the obtained LiFePO4 with self-assembled hierarchical structure, smaller size and (100) facet shows the best electrochemical performance: 162.1 mAh/g at 0.1C and 112.4 mAh/g at 10 C. Using phytic acid as phosphorus source and controlling precursor concentration to prepare high performance LiFePO4 open up a new prospect for the production of cathode materials for lithium ion batteries.
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Enhanced UV emission and photocatalytic activity due to morphology evolution of ZnO thin films
Zang Aoxin,Chen Keyu,Xu Linhua,Xian Fenglin,Ma Wenyang,Tian Zhen 한국물리학회 2023 Current Applied Physics Vol.54 No.-
Tuning the optical properties of nanomaterials through morphology evolution has attracted extensive attention. In this study, ZnO films were deposited on substrates using sol-gel approach, and ZnO nanocolumn arrays were formed on the film surface induced by doped ions. XRD results show that the nanocolumns all have a growth orientation along the c-axis and good crystallization quality. Compared with pure ZnO film, the ones with nanocolumn arrays on the film surface exhibit higher UV emission efficiency and photocatalytic activity. The enhanced UV emission efficiency is attributed to the higher crystalline quality and fewer surface defects of the nanocolumn arrays. The improved photocatalytic activity is mostly ascribed to two factors: (1) nanocolumns are more conducive to the migration of photogenerated electrons and holes to the photocatalyst surface to participate in redox reactions, (2) the formation of nanocolumn arrays improves light absorption of the ZnO films.
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Pan Xuchi,Xie Kun,Chen Keyu,He Ziyu,Kozue Sakao,Hou De-Xing 대한암예방학회 2022 Journal of cancer prevention Vol.27 No.1
6-(Methylsulfinyl) hexyl isothiocyanate (6-MSITC) is an active ingredient present in Wasabi, which is a popular pungent spice used in Japanese cuisine. Our previous studies suggested that the primary antioxidant activity of 6-MSITC may link to other biological activity. This study aimed to clarify how the antioxidant activity of 6-MSITC contributes to preventing overloaded lipid stress in hepatic cell model. HepG2 cells were treated with 6-MSITC at defined concentrations and times in normal medium or in combined fatty acids (CFA) medium, and the targeted proteins were detected by Western blotting. The kinetic data revealed that 6-MSITC activated AMP-activated protein kinase α (AMPKα) and nuclear factor (erythroid-derived 2) like 2 (Nrf2), and then enhanced the protein expression of Forkhead box protein O1 (FOXO1) and Sirtuin1 as well as that of the Nrf2 target proteins, NAD(P)H:quinone oxidoreductase 1 (NQO1) and heme oxygenase (HO-1). Furthermore, lipid metabolic stress was mimicked in HepG2 cells by overloading CFA. 6-MSITC significantly alleviated CFA-induced formation of thiobarbituric acid reactive substances and fat accumulation. Signaling analysis data revealed that 6-MSITC enhanced phosphorylation of AMPKα, upregulated the expression of Nrf2, NQO1, heme oxygenase 1, FOXO1, and Siruin1, and downregulated the expression of PPARα. Taken together, our results suggested that the AMPKα/Nrf2-mediated signaling pathways might be involved in the cytoprotective effects of Wasabi 6-MSITC against metabolic lipid stress.
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