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RISS 인기검색어
- 검색키워드
- 저자 : Qinglei Liu (검색결과 5 건)
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A comparative study of hydraulic fracturing with various boreholes in coal seam
Honglei Liu,Tianhong Yang,Tao Xu,Qinglei Yu 한국지질과학협의회 2015 Geosciences Journal Vol.19 No.3
Comparative numerical study on hydraulic fracturing with various boreholes in coal seam combined with in situ experiments was carried out to investigate the fracturing mechanism and loosening effect of hydraulic fracturing in coal seam. Hydraulic fracturing models with single-borehole, three-borehole and fiveborehole were built based on in situ tests in Chengshan coalmine, Jixi city, Heilongjiang province, China and the changes of water pressure and shear stress around boreholes during hydraulic fracturing were analyzed. The influence of hydraulic fracturing with controlling borehole on crack initiation and propagation was discussed. According to the in situ testing results, it is found that controlling boreholes in hydraulic fracturing not only can control the direction of crack propagation, but also can judge the effect of crack initiation and breakdown. The work in this paper is of great importance for the design of hydraulic fracturing technology and the alternative of the parameters in theory and practice.
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Miao Cui,Qinglei Bu,Yutao Cai,Ruize Sun,Wen Liu,Huiqing Wen,Sang Lam,Yung. C. Liang,Ivona Z. Mitrovic,Stephen Taylor,Paul R. Chalker,Cezhou Zhao 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This study proposed a 100 kHz, 5V/11V boost converter with an integrated gate driver for a power switching device using recessed E-mode MIS-HFETs. The integrated gate driver consisting of multi-stages DCFL (Direct-Coupled FET Logic) inverters and a buffer stage, has large input swing (up to 10 V) and wide noise margin with gate dielectric, which benefits applications requiring large gate swing without any additional drivers or level shifters. The impact of transistor size on rise times and fall times have been studied. Either buffer stage or larger width of DCFL inverter can reduce rise times from 2.4 μs to less than 0.5 μs at 100 kHz, so the output voltage of boost converter is increased by 10 % at a duty cycle of 0.7. However, large buffer width can result in high gate overshoot and oscillation, indicating careful design to balance switching speed and oscillation.
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Li, Yao,Zhu, Shenmin,Liu, Qinglei,Gu, Jiajun,Guo, Zaiping,Chen, Zhixin,Feng, Chuanliang,Zhang, Di,Moon, Won-Jin The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.6
<P>A high-performance anode material was prepared from a hierarchically structured activated carbon which contains <I>in situ</I> graphene and nano-graphite. The activated carbon was immersed in a solution of SnCl<SUB>2</SUB>·2H<SUB>2</SUB>O and subjected to ultrasound. As a result, nanoparticles of SnO<SUB>2</SUB> were uniformly deposited on the surface of the activated carbon. The composite material was then coated with a thin layer of carbon by soaking it in a sucrose solution, followed by carbonization of the adsorbed sucrose at 500 °C. The resulting composite showed an outstanding high-rate cycling performance that can deliver an initial discharge capacity of 1417 mAh g<SUP>−1</SUP> and maintain a discharge capacity of more than 400 mAh g<SUP>−1</SUP> after 100 cycles at a high current density of 1000 mA g<SUP>−1</SUP>. This outstanding electrochemical performance is likely to be related to a unique combination of the excellent electrical conductivity of the activated carbon with graphite layers formed inside, its hierarchical pore structure which enhances lithium-ion transportation, and the carbon coating which alleviates the effects of volume changes, shortens the distance for Li<SUP>+</SUP> diffusion, facilitates the transmission of electrons, and keeps the structure stable.</P> <P>Graphic Abstract</P><P>Carbon-coated SnO<SUB>2</SUB>@C nanocomposite with hierarchically porous structures and graphite layers inside was prepared by ultrasound and hydrothermal treatment, which showed an outstanding high-rate cycling performance for lithium-ion battery. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm14290a'> </P>
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Tan, Yongwen,Zang, Xining,Gu, Jiajun,Liu, Dingxin,Zhu, Shenmin,Su, Huilan,Feng, Chuanliang,Liu, Qinglei,Lau, Woon Ming,Moon, Won-Jin,Zhang, Di American Chemical Society 2011 Langmuir Vol.27 No.19
<P>Through a simple room-temperature photoreduction process, this letter conformally replicates 3D submicrometer structures of wing scales from two butterfly species into Ag to generate practical surface-enhanced Raman scattering (SERS) substrates. The Ag replicas of butterfly scales with higher structural periodicity are able to detect rhodamine 6G at a low concentration down to 10(-9) M, which is three orders of magnitude lower than the detectable concentration limit of using quasi-periodic Ag butterfly structures. This result presents a way to select suitable scale morphologies from 174,500 species of Lepidopterans to replicate, as consumable SERS substrates with low cost and high reproducibility.</P>
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Qiang Li,Bin Li,Xiuwei Li,Quntao Xie,Qinglei Liu,Weiwei Xu Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.6
To study the lubrication performance of tilting-pad thrust bearing (TPTBs) during start-up in nuclear pump, a hydrodynamic lubrication model of TPTBs was established based on the computational fluid dynamics (CFD) method and the fluid-structure interaction (FSI) technique. Further, a mesh motion algorithm for the transient calculation of thrust bearings was developed based on the user defined function (UDF). The result demonstrated that minimum film thickness increases first and then decreases with the rotational speed under start-up condition. The influence of pad tilt on minimum film thickness is greater than that of collar movement at low speed, and the establishment of dynamic pressure mainly depends on pad tilt and minimum film thickness increases. As the increase of rotational speed, the influence of pad tilt was abated, where the influence of the moving of the collar dominated gradually, and minimum film thickness decreases. For TPTBs, the circumferential angle of the pad is always greater than the radial angle. When the rotational speed is constant, the change rate of radial angle is greater than that of circumferential angle with the increase of loading forces. This study can provide reference for improving bearing wear resistance.
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