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Yongwei Yu,Qing Yang,Jiangquan Ma,Wenliang Sun,Chong Yin,Xiazhang Li,Jun Guo,Qingyan Jiang,Zhiyuan Lu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.11
A novel strontium titanate/binary metal sulfide (SrTiO3/SnCoS4) heterostructure was synthesized by a simple two-step hydrothermal method. The visible-light-driven photocatalytic performance of SrTiO3/SnCoS4 composites was evaluated in the degradation of methyl orange (MO) under visible light irradiation. The photocatalytic performance of SrTiO3/SnCoS4-5% is much higher than that of pure SrTiO3, SnCoS4, SrTiO3/SnS2 and SrTiO3/CoS2. The SrTiO3/SnCoS4 composite material with 5 wt.% of SnCoS4 showed the highest photocatalytic efficiency for MO degradation, and the degradation rate could reach 95% after 140 min irradiation time. The enhanced photocatalytic activity was ascribed to not only the improvement of visible light absorption efficiency, but also the construction of a heterostructure which make it possible to effectively separate photoexcited electrons and holes in the two-phase interface.
A Phase-Shift Modulation Strategy for a Bidirectional CLLC Resonant Converter
Wenmin Hua,Hongfei Wu,Zhiyuan Yu,Yan Xing,Kai Sun 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
A novel phase-shift modulation strategy is applied to a bidirectional CLLC resonant converter (RC). Different from the well-known pulse-frequency modulation strategy, the switching frequency of the CLLC RC is constant, which is beneficial for optimal design and control of the converter. Theoretical analysis proves that voltage gain is independent on load and resonant tank. As a result, topology is optimized with ensuring symmetry of converter. Simulation model is built in Simulink and a 1kW prototype is made. Simulation and experimental results verify the voltage transfer ratio. Dynamic response with load stepping up and down is stable and rapid. In addition, soft-switching of all the power switches can be achieved to reduce switching losses and improve efficiency. Detailed operation principles and characteristics of the modulation strategy are analyzed and verified with experimental results.
Ma, Yanyun,Li, Weiyang,Cho, Eun Chul,Li, Zhiyuan,Yu, Taekyung,Zeng, Jie,Xie, Zhaoxiong,Xia, Younan American Chemical Society 2010 ACS NANO Vol.4 No.11
<P>This paper describes a facile method for generating Au@Ag core−shell nanocubes with edge lengths controllable in the range of 13.4−50 nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride (CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1.2 to 20 nm by varying the ratio of AgNO<SUB>3</SUB> precursor to Au seeds. We also investigated the growth mechanism by examining the effects of seeds (capped by CTAC or cetyltrimethylammonium bromide(CTAB)) and capping agent (CTAC <I>vs</I> CTAB) on both size and shape of the resultant core−shell nanocrystals. Our results clearly indicate that CTAC worked much better than CTAB as a capping agent in both the syntheses of Au seeds and Au@Ag core−shell nanocubes. We further studied the localized surface plasmon resonance properties of the Au@Ag nanocubes as a function of the Ag shell thickness. By comparing with the extinction spectra obtained from theoretical calculations, we derived a critical value of <I>ca.</I> 3 nm for the shell thickness at which the plasmon excitation of the Au cores would be completely screened by the Ag shells. Moreover, these Au@Ag core−shell nanocubes could be converted into Au-based hollow nanostructures containing the original Au seeds in the interiors through a galvanic replacement reaction.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-11/nn102237c/production/images/medium/nn-2010-02237c_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn102237c'>ACS Electronic Supporting Info</A></P>
ALMA Reveals Sequential High-mass Star Formation in the G9.62+0.19 Complex
Liu, Tie,Lacy, John,Li, Pak Shing,Wang, Ke,Qin, Sheng-Li,Zhang, Qizhou,Kim, Kee-Tae,Garay, Guido,Wu, Yuefang,Mardones, Diego,Zhu, Qingfeng,Tatematsu, Ken’ichi,Hirota, Tomoya,Ren, Zhiyuan,Liu, Sheng-Yu American Astronomical Society 2017 The Astrophysical journal Vol.849 No.1
<P>Stellar feedback from high-mass stars (e.g., H II regions) can strongly influence the surrounding interstellar medium and regulate star formation. Our new ALMA observations reveal sequential high-mass star formation taking place within one subvirial filamentary clump (the G9.62 clump) in the G9.62+0.19 complex. The 12 dense cores (MM1-MM12) detected by ALMA are at very different evolutionary stages, from the starless core phase to the UC H II region phase. Three dense cores (MM6, MM7/G, MM8/F) are associated with outflows. The mass-velocity diagrams of the outflows associated with MM7/G and MM8/F can be well-fit by broken power laws. The mass-velocity diagram of the SiO outflow associated with MM8/F breaks much earlier than other outflow tracers (e.g., CO, SO, CS, HCN), suggesting that SiO traces newly shocked gas, while the other molecular lines (e.g., CO, SO, CS, HCN) mainly trace the ambient gas continuously entrained by outflow jets. Five cores (MM1, MM3, MM5, MM9, MM10) are massive starless core candidates whose masses are estimated to be larger than 25 M-circle dot, assuming a dust temperature of <= 20 K. The shocks from the expanding H II regions ('B' and 'C') to the west may have a great impact on the G9.62 clump by compressing it into a filament and inducing core collapse successively, leading to sequential star formation. Our findings suggest that stellar feedback from H II regions may enhance the star formation efficiency and suppress low-mass star formation in adjacent pre-existing massive clumps.</P>