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Zhang, Yimeng,Song, Qingwen,Tang, Xiaoyan,Zhang, Yuming The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.1
In this paper, a SiC MOSFETs gate driver for parallel connections is proposed and implemented. The proposed design enhances the reliability of parallel-connected SiC MOSFETs in high-frequency applications. High-speed over-current protections are applied for both over-voltage and under-voltage situations. In addition, a dynamic balancing current sharing scheme for SiC MOSFETs is proposed for high-speed parallel applications by current feedback and switching delay time compensation. With the proposed design, parallel-connected SiC MOSFETs can work at an operation frequency of 1 MHz with over-current protections. In addition, with the dynamic current balancing scheme, the operation temperature decreases from 115 to 86.9 ℃, while the temperature difference for paralleled devices drops from 25.8 to 1.8 ℃.
Yuming Zhou,Xiaoqin Fu,Xiaoli Sheng,Zhiwei Fu,Shuo Zhao,Zewu Zhang,Yiwei Zhang 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.6
Well-dispersed hierarchical zeolite Y, structure-directed by ionic liquid 1-methyl-3-[3'-(trimethoxysilyl) propyl] imidazolium chloride, was synthesized for the first time using a novel ultrasonic/microwave synergistic synthesis (UMSS). The time required for the synthesis of zeolite Y by UMSS method was remarkably reduced to 6 h instead of 24 h under conventional hydrothermal conditions. The structures of all samples were characterized by XRD, BET, FT-IR, SEM and TEM. The results clearly demonstrated that the UMSS is a promising strategy to achieve zeolite Y with improved crystallinity, large BET surface area, bulky mesopore volume, well-dispersed morphology, small zeolite nanoparticle. The catalytic activity of hierarchically micro-mesoporous zeolite Y was evaluated by using the alkylation of o-xylene with styrene. Mesoporous zeolite Y synthesized by UMSS method showed significantly higher catalytic activity, stability and reusability, compared with conventional hydrothermal synthesis. It might be ascribed to its large mesoporous volume, small crystal nanoparticle and high surface area, minimizing the diffusion length as the reactant molecules diffuse into the pores, and correspondingly the products diffuse out of zeolites. This study suggests that UMSS method is a good alternative for the synthesis of micro-mesoporous zeolite Y, which may be of remarkable benefit for industrial applications.
Catalytic Ozonation of Phenol in Aqueous Solution by Co3O4 Nanoparticles
Yuming Dong,Guangli Wang,Pingping Jiang,Aimin Zhang,Lin Yue,Xiaoming Zhang 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.10
The degradation efficiencies of phenol in aqueous solution were studied by semi-continuous experiments in the processes of ozone alone, ozone/bulky Co3O4 and ozone/Co3O4 nanoparticles. Catalyst samples (bulky Co3O4 and Co3O4 nanoparticles)were characterized by X-ray diffraction and transmission electron microscopy. The Brunauer-Emmett-Teller surface area, pHpzc and the density of surface hydroxyl groups of the two catalyst samples were also measured. The catalytic activity of Co3O4 nanoparticles was investigated for the removal of phenol in aqueous solutions under different reaction temperatures. Tert-butyl alcohol had little effect on the catalytic ozonation processes. Based on these results,the possible catalytic ozonation mechanism of phenol by Co3O4 nanoparticles was proposed as a reaction process between ozone molecules and pollutants.
Catalytic Ozonation of Phenol in Aqueous Solution by Co<sub>3</sub>O<sub>4</sub> Nanoparticles
Dong, Yuming,Wang, Guangli,Jiang, Pingping,Zhang, Aimin,Yue, Lin,Zhang, Xiaoming Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.10
The degradation efficiencies of phenol in aqueous solution were studied by semi-continuous experiments in the processes of ozone alone, ozone/bulky $Co_3O_4$ and ozone/$Co_3O_4$ nanoparticles. Catalyst samples (bulky $Co_3O_4$ and $Co_3O_4$ nanoparticles) were characterized by X-ray diffraction and transmission electron microscopy. The Brunauer-Emmett-Teller surface area, $pH_{pzc}$ and the density of surface hydroxyl groups of the two catalyst samples were also measured. The catalytic activity of $Co_3O_4$ nanoparticles was investigated for the removal of phenol in aqueous solutions under different reaction temperatures. Tert-butyl alcohol had little effect on the catalytic ozonation processes. Based on these results, the possible catalytic ozonation mechanism of phenol by $Co_3O_4$ nanoparticles was proposed as a reaction process between ozone molecules and pollutants.
THE GEOMETRIC CONVEXITY OF A FUNCTION INVOLVING GAMMA FUNCTION WITH APPLICATIONS
Chu, Yuming,Zhang, Xiaoming,Zhang, Zhihua Korean Mathematical Society 2010 대한수학회논문집 Vol.25 No.3
In this paper, we prove that $(\Gamma(x))^{\frac{1}{x-1}}$ is geometrically convex on (0, $\infty$). As its applications, we obtain some new estimates for $\frac{[\Gamma(x+1)]^{\frac{1}{x}}} {[\Gamma(y+1)]^{\frac{1}{y}}}$.
Shengjian Yu,Pingping Jiang,Yuming Dong,Pingbo Zhang,Yue Zhang,Weijie Zhang 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.2
A kind of nanosized sulfated zirconia was prepared by a hydrothermal method, and full characterized by XRD,TEM, BET, TGA, and FTIR. Its catalytic activity was evaluated in the esterification reactions, including the testing of the catalytic reusability and the optimization of reaction conditions. The obtained catalyst was revealed to be highly efficient solid catalyst for the esterification of acetic acid with n-butanol, presenting the advantages of high conversion and selectivity, easy recovery, and steady reusability.
Yu, Shengjian,Jiang, Pingping,Dong, Yuming,Zhang, Pingbo,Zhang, Yue,Zhang, Weijie Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.2
A kind of nanosized sulfated zirconia was prepared by a hydrothermal method, and full characterized by XRD, TEM, BET, TGA, and FTIR. Its catalytic activity was evaluated in the esterification reactions, including the testing of the catalytic reusability and the optimization of reaction conditions. The obtained catalyst was revealed to be highly efficient solid catalyst for the esterification of acetic acid with n-butanol, presenting the advantages of high conversion and selectivity, easy recovery, and steady reusability.
Zhang, Bingkun,Guo, Yuming Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.10
An experiment was conducted to investigate the mechanism for the effect of tetrabasic zinc chloride (TBZC) in enhancing growth performance of weanling piglets. Gut-brain peptides play an important role in the regulation of growth and appetite in animals. This study evaluated the effects of TBZC on blood concentrations of growth hormone (GH), ghrelin, insulin-like growth factor-I (IGF-I), cholecystokinin (CCK) and neuropeptide Y (NPY). Seventy-two weanling piglets (Landrace$\times$Large White) with an initial body weight (BW) of $6.7{\pm}0.16kg$ and aged $24{\pm}1days$ were assigned to three dietary treatments: i) control diet without TBZC supplement, ii) the control diet supplemented with 2,000 mg Zn from TBZC/kg and iii) TBZC-supplemented diet pair-fed with respect to the control diet. Each treatment had six replications (pens) of four piglets. At the end of a 14-d experimental period, piglets were weighed and feed consumption was measured, and blood samples were collected for assays of GH, ghrelin, IGF-I, CCK and NPY concentrations. The inclusion of TBZC in the diet increased average daily gain (p<0.01), average daily feed intake (p<0.05), and feed conversion ratio (p<0.05). Pair-fed piglets had higher ADG, and lower FCR than (p<0.05) Control piglets. Supplementation of the diet with TBZC increased (p<0.05) serum GH and plasma ghrelin levels in weanling piglets, but did not affect (p>0.05) serum IGF-I and plasma NPY and CCK concentrations. Pair-fed piglets had lower (p<0.05) serum GH levels than TBZC-supplemented piglets, but did not (p>0.05) differ from Control piglets. These data indicated that TBZC elevated the concentration of ghrelin and GH. This observation may partly explain the beneficial effects of TBZC on growth performance of weanling piglets.
Influence of Carbon Fiber on Corrosion Behavior of Carbon Steel in Simulated Concrete Pore Solutions
( Yuming Tang ),( Yuchao Dun ),( Guodong Zhang ),( Xuhui Zhao ),( Yu Zuo ) 한국부식방식학회(구 한국부식학회) 2017 Corrosion Science and Technology Vol.16 No.4
Galvanic current measurement, polarization curves, electrochemical impedance spectroscopy and weight loss test were used to study the corrosion behavior of carbon steel before and after carbon fibers coupling to the carbon steel in simulated concrete pore solutions, and the film composition on the steel surface was analyzed using XPS method. The results indicate that passive film on steel surface had excellent protective property in pore solutions with different pH values (13.3, 12.5 and 11.6). After coupling with carbon fibers the area ratio of carbon steel to carbon fiber was 12.31), charge transfer resistance Rct of the steel surface decreased and the Fe3+/Fe2+ value in passive film decreased. As a result, stability of the film decreased and the corrosion rate of steel increased. Decreasing of the area ratio of steel to carbon fiber from 12.3 to 6.15 resulted in the decrease in Rct and the increase in corrosion rate. Especially in the pore solution with pH 11.6, the coupling leads the carbon steel to corrode easily.