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RISS 인기검색어
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- 저자 : Lingfeng Gao (검색결과 5 건)
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Gao, Lingfeng,Oh, Joongsuk,Tu, Yingfeng,Chang, Taihyun Elsevier 2018 Polymer Vol.135 No.-
<P><B>Abstract</B></P> <P>Cyclic polymers synthesized by ring-closure method from linear precursors contain some of linear contaminates. In this work, the origin of linear contaminates in cyclic polystyrenes (<I>c</I>-PS) is demonstrated by the coupling of liquid chromatography at the critical condition (LCCC) with matrix-assisted laser desorption/ionization time-of-flight mass spectra. The linear contaminates are revealed to be the “dead” chains during ATRP by chain termination, the unreacted linear polystyrene (<I>l</I>-PS) precursors, and the dimers by the imperfect ring-closure reaction. The <I>c</I>-PS are purified by LCCC fractionation, and the results show the LCCC fractionation at the critical adsorption point (CAP) of <I>c</I>-PS is more efficient than that at the CAP of linears for low molecular weight (<10,000) PS. A two-step LCCC method is presented for the preparation of <I>c</I>-PS with high purity (>99.6%) via the tandem-coupled LCCC fractionation at the CAP of <I>l</I>-PS and at the CAP of <I>c</I>-PS.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The linear contaminates in cyclic polystyrenes (<I>c</I>-PS) were identified. </LI> <LI> The LCCC fractionation at the CAP of <I>c</I>-PS is very efficient. </LI> <LI> Highly purified <I>c</I>-PS were obtained by a tandem-coupled LCCC fractionation method. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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An investigation on the dynamics of domain switching of Bi0.5Na0.5TiO3-based ferroelectric ceramics
Zhipeng Gao,Hang Zhang,Yi Liu,Lingfeng Wu,Jia Yang,Tao Zhang,Haiyan Wang,Xuefeng Chen,Genshui Wang,Hongliang He 한국물리학회 2017 Current Applied Physics Vol.17 No.4
The dynamics of domain switching of Bi0.5Na0.5TiO3-based ferroelectric ceramic was investigated. With the electric field increasing, the domain switch experienced three sections of no domain switch region, creep region and flow region. In the creep region, the domain switch is dominated by the thermally activated domain wall movement. In flow region, the domain wall experience the viscous flow motion. For the BNT-BA-Zn ceramic, the activation energy of creep domain switch is much higher than it in flow region. With temperature increasing, the sensitivity of domain wall motion to the frequency is decreasing. This result demonstrated the domain switch of different ferroelectric materials could be quantitatively analyzed and compared based on the simple polarization - current - electric field data.
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Analysis on the safe distance between shield tunnel through sand stratum and underlying karst cave
Wei Wan,Shiming Gao,Lingfeng Liu,Wushuang Wen,Ping Li,Jianping Chen 한국자원공학회 2019 Geosystem engineering Vol.22 No.2
When a subway tunnel passes through a karst geological area, in order to ensure the stability of the tunnel, the safe distance between the tunnel and karst cave needs to be researched. This article is based on the construction project of Wuhan metro line 6 from Qianjincun station to Mayinglu station. In view of the geological condition of overlying sand and underlying limestone, by using numerical simulation and theoretical calculation and selecting a characteristic section, the influence law and degree of karst cave span, height-span ratio, and filling degree on the safe thickness of karst cave roof are studied and a forecasting model of the safe thickness of karst cave roof is established. Combined with dichotomy and numerical simulation, the critical horizontal safe distance beyond which cave collapse does not cause tunnel instability is calculated. The results show that: (1) the safe thickness of karst cave roof increases linearly with the increase of karst cave span, and decreases with the increase of height-span ratio and filling degree; (2) among the three factors, the effect of karst cave span is the most significant, the filling degree of karst cave is the second, and the influence of height-span ratio of karst cave is the weakest; (3) the proposed forecasting model passes the significance test, indicating that the model is very reasonable; and (4) the critical horizontal safe distance from the tunnel border to the karst cave boundary is 22.4 m. The research results can provide guidance for the design and construction of shield tunnels and karst cave treatment in karst areas.
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Influence of Different Inlet Conditions on Micromixer
Wei Xu,Xiuhua He,Lingfeng Gao,Tian Xia,Zhengying Yu 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.2
This paper presents the influence of different inlet conditions on the performance of micromixer. On the purpose of obtaining the internal flow fields and mixing characteristics, there are 28 micromixers with different structural parameters have been studied by numerical simulations. The influence of different inlet conditions on the mixing performance of micromixers with periodic triangle baffles and rectangle baffles was examined by experiments. The results of experiment and numerical simulation were completely discussed and analyzed. The consistency between results of experiment and numerical simulation proves the reliability of research method and the accuracy of numerical simulation. It also indicates that different numbers of inlets have significant effects on the mixing performance of micromixers. The optimum inclination angles of inlets for each kind of micromixer were obtained under different conditions. For optimizing or designing passive micromixers, it is an effective way to improve the performance of micromixers by increasing the number of inlets or changing the angle of the inlets.
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( Yuepeng Song ),( Miaomiao Chen ),( Baoyan Xu ),( Dongsheng Gao ),( Jing Guo ),( Lingfeng Xu ),( Zheng Wang ),( Hyoung Seop Kim ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.11
Herein, we report the results of our investigation on the effect of friction and anvil design on the heterogeneous plastic-deformation characteristics of copper during the compressive stage of high-pressure torsion (HPT), using the finite element method. The results indicate that the friction and anvil geometry play important roles in the homogeneity of the deformation. These variables affect the heterogeneous level of strain in the HPT compressed disks, as well as the flash in the disk edge region. The heterogeneous plastic deformation of the disks becomes more severe with the increasing depth of the cavity, as anvil angle and friction coefficient increase. However, the homogeneity increases with increases in the wall angle. The length of flash and the area of the dead metal zone increase with the depth of the cavity, while they decrease at a wall angle of 180°. (Received March 17, 2016; Accepted May 25, 2016)
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