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RISS 인기검색어
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- 저자 : Zhenghua Qian (검색결과 3 건)
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Zhenghua Qian,Jianan Song,Zijin Liu,Zonglin Peng 한국고분자학회 2019 Macromolecular Research Vol.27 No.11
To fully utilize the fascinating comprehensive properties of graphene oxide (GO) and carbon nanotubes (CNTs), GO was used to promote the dispersion of carboxylated multi-walled carbon nanotubes (CC) in rubber matrix. Additionally, carboxylated acrylonitrile butadiene rubber (xNBR) was used to enhance the interfacial interaction between the styrene-butadiene rubber (SBR) and the GO/CC hybrid fillers for the formation of hydrogen bonds between the oxygenated functional groups of GO/CC hybrid fillers and the carboxyl groups of xNBR. Moreover, the interfacial interaction was investigated by Fourier transform infrared spectroscopy and further proved by differential scanning calorimetry. As a result, the mechanical property and thermal conductivity of SBR composites were improved significantly compared with the neat SBR vulcanizate, which were much higher than those of the SBR composites without xNBR. In contrast to adding GO/CNTs directly to the rubber matrix, enhancing the interfacial interaction between GO/CC hybrid fillers and rubber matrix as demonstrated herein is a valuable strategy to prepare rubber composites with remarkable comprehensive properties.
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Energy trapping of thickness-extensional modes in thin film bulk acoustic wave resonators
Zinan Zhao,Zhenghua Qian,Bin Wang,Jiashi Yang 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.7
We perform a theoretical analysis on a rectangular trapped-energy piezoelectric resonator operating with thickness-extensional modesof a thin zinc oxide film on a silicon layer. The driving electrode covers the central part of the resonator only. The two-dimensional scalardifferential equation for such a structure derived by Tiersten and Stevens is employed which can describe in-plane mode variations. Avariational formulation is developed which provides the theoretical foundation for the Ritz method used in our analysis. Free vibrationfrequencies and modes are obtained and examined. Modes with vibrations trapped under the driving electrode are found. An approximationused to obtain the classical result of the resonator by Tiersten and Stevens, i.e., the neglect of the four corner regions of the resonator,is removed in our variational analysis. It is shown that their approximation causes a frequency difference on the order of dozens of partsper million for the fundamental thickness-extensional operating mode, quite significant in resonator design and operation.
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Liang Zhang,Zhongyang Ding,Peng Xu,Yuhong Wang,Zhenghua Gu,Zhu Qian,Guiyang Shi,Kechang Zhang 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.3
Tyrosinase is a key enzyme in the biosynthesis of melanin, and the use of inhibitors against tyrosinase can prevent hyperpigmentation by inhibiting enzymatic oxidation. However, the current use of tyrosine inhibitors is limited by their low activities and high toxicities. The aim of the present research was to develop novel whitening agents, or tyrosinase-targeted medicine, from a submerged culture of the fungus Ganoderma lucidum. Methyl lucidenate F was isolated from the ethanol-soluble-acidic components (ESACs) of G. lucidum, with the structure of ESACs elucidated via UV, LC-MS, and ^(13)C-NMR spectral analysis. The tyrosinase inhibitory activity was measured using catechol as a substrate. Methyl lucidenate F displayed uncompetitive inhibition of the potato tyrosinase activity,for which Lineweaver-Burk plots revealed a maximum reaction rate (V_(max)) of 0.4367/min, Michaelis constant (K_m)of 6.765 mM and uncompetitive inhibition constant (K_i) of 19.22 μM. Meanwhile, methyl lucidenate F (tetra cyclic triterpenoid) exhibited high tyrosinase inhibitory activity,with an IC_(50) of 32.23 μM. These results suggest that methyl lucidenate F may serve as a potential candidate for skin-whitening agents.
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