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Shiquan Hong,Yong Yu,Zhijie Yi,Haijun Zhu,Wencheng Wu,Peiyan Ma 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.11
A highly efficient visible-light-driven g-C3N4/CuO hybrid nanocomposite catalyst with different molar contents of CuO are successfully fabricated via a simple liquid phase synthesis process and applied to the degradation of Rhodamine B (RhB) solution. The results reveal that monodisperse CuO nanoparticles with a size of less than 10 nm are uniformly distributed on the surface of gC3N4 nanosheets. Compared with the pure g-C3N4 and CuO, the as-prepared nanocomposite displays significantly enhanced photocatalytic performance under visible-light irradiation. Attractively, the photocatalytic activities of the nanocomposite catalysts can be tuned by adjusting the molar ratio of g-C3N4 and CuO. When the molar ratio reaches 2:1, the nanocomposite exhibits the highest photocatalytic activity, which can decompose RhB completely in 5 min. The improved performance could be ascribed to the formation of heterostructure between g-C3N4 and CuO as well as the decreased particle size of CuO, the presence of H2O2, large surfaceexposure area and the suitable band position of g-C3N4/CuO nanocomposite. Interestingly, the nanocomposite shows excellent stability and recyclable property toward the photodegradation of RhB. Finally, a possible photocatalytic mechanism is proposed.
Effects of Welding Parameters and Surface Pretreatments on Resistance Spot Welding of AZ31B Mg Alloy
Shiquan Zhou,Lei Liu,정재필,이목영,Y. Norman Zhou 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.6
The resistance spot weldability of AZ31B magnesium alloy using AC (alternating current) was investigated in this paper. The surfaces of sheet coupons were prepared by acetone cleaning (as-received) and some coupons were also cleaned with chromic acid (H2Cr2O7) after acetone cleaning (acid-cleaned). The surfaces of the as-received AZ31B sheets consisted of MgO, Mg(OH)2, and MgCO3. The extent and thickness of the surface oxide/reaction layer of the sheets varied according to the fabrication process of the sheets, and resulted in different contact resistance. Effects of welding current and weld time were investigated while the electrode force was kept constant. The results indicated that the as-received sheets produced expulsion both at the faying surface and at the work piece/electrode interface due to high contact resistance. Diluted chromic acid cleaning reduced contact resistance and produced good weld quality. Increasing the welding current and weld time enhanced not only the nugget size and joint strength, but also increased indentation on the weld surfaces. A weld lobe was established considering the minimum joint strength, weld expulsion, and surface indentation based on a relevant American Welding Society Standard.
Shiquan Zhu,Zhihua Chen,Hui Zhang,Zhen-gui Huang,Huanhao Zhang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.5
To ensure the safe separation process of a missile from internal weapons bay, the control device is mounted in front of the internal weapons bay to control the separation process. Based on the coupling of Navier-Stokes (N-S) equations and six-degrees-of-freedom (6DOF) rigid-body motion equations, the separation process of missile under four different conditions (free separation, and rectangle, prism and wedge control) was numerically simulated. The separation process and flow fields were obtained, the aerodynamic parameters and trajectory parameters of four cases compared. Our results show that, the control device can improve the aerodynamic characteristics of the flow field, enhancing the safety of the missile separation. The wedge control device has the best control effect and makes the missile stable, the rectangular and prism control devices have strong bow shock wave and make the pitch angle of the missile large.
Total Resource Requirements-Based Priority Queuing Scheme for DS/CDMA Cellular Networks
Shiquan Piao,박재원,박용완 한국전자통신연구원 2006 ETRI Journal Vol.28 No.3
We propose and analyze a priority queuing scheme that gives priority in the same class of calls according to their total resource requirements (TRRs). The proposed scheme gives a higher priority to the calls that have a lower TRR over the calls that have a higher TRR. The numerical results show that the proposed priority queuing scheme provides better performance than the traditional queuing schemes in call blocking probability.