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Chen Shiming,Zhang Huifeng 국제구조공학회 2012 Steel and Composite Structures, An International J Vol.13 No.3
The interaction between steel tube and concrete core is the key design considerations for concrete-filled steel tube columns. In a concrete-filled steel tube (CFST) column, the steel tube provides confinement to the concrete core which permits the composite action among the steel tube and the concrete. Due to construction faults and plastic shrinkage of concrete, the debonding separation at the steel-concrete interface weakens the confinement effect, and hence affects the behaviour and bearing capacity of the composite member. This study investigates the axial loading behavior of the concrete filled circular steel tube columns with debonding separation. A three-dimensional nonlinear finite element model of CFST composite columns with introduced debonding gap was developed. The results from the finite element analysis captured successfully the experimental behaviours. The calibrated finite element models were then utilized to assess the influence of concrete strength, steel yield stress and the steel-concrete ratio on the debonding behaviour. The findings indicate a likely significant drop in the load carrying capacity with the increase of the size of the debonding gap. A design formula is proposed to reduce the load carrying capacity with the presence of debonding separation.
Yunsong Lian,Huifeng Chen,Chenliang Mu 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.6 No.2
Microtextures were successfully fabricated on the rake face of the cemented carbide (WC/TiC/Co) tools through inductively coupled plasma etching technology. Two types of microtextured tools were designed and fabricated. Their performance in cutting the AISI 1045 medium carbon steel was tested and compared to that of conventional non-textured tools. The comparison involved cutting forces, cutting temperature, friction coefficient, tool wear, chip adhesion, and machined workpiece surface roughness. The results show that microtextures on the rake face of the cutting tool can make the cutting process more stable than a conventional non-textured tool, and different textures may be suitable for different ranges of the cutting speed. In the latter range 100–200 m/min, microtextures significantly reduce the cutting force, cutting temperature, friction coefficient at the tool–chip interface, while the anti-adhesion property of textured tools and the surface quality of machined workpieces attain their maximal values. The effectiveness of textures is shown to be affected by chip adhesion and blockage resulting from derivative cutting, which appears at high cutting speeds. Moreover, the violation of the structural integrity of textures and their damage can strongly deteriorate the cutting process at low cutting speeds.
Yunsong Lian,Huifeng Chen,Chenliang Mu,Jianxin Deng,Shuting Lei 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.5 No.2
A new dry cutting tool named WS2 soft coated Micro-Nano textured self-lubricating dry cutting tool (WTT tool) is developed and tested. Dry turning tests have been carried out on 45# quenched and tempered steel with a WTT tool and three other types of alternative tools. The machining performance was assessed in terms of the cutting forces, cutting temperature, friction coefficient at the tool-chip interface, chip deformation, tool wear, and the surface roughness of the machined workpiece. The results show that the WTT tool has the best cutting performance among all the tools tested under the same cutting conditions. Through theoretical analysis and experimental results, the mechanisms of the WTT tool in improving cutting performance were put forward. Meanwhile, the effect of Micro-Nano texture and WS2 soft coating on the cutting forces and the cutting temperature is analyzed. It can be concluded that the WTT tool can effectively improve the anti-adhesion and wear-resistance properties and increase the tool life.
AN IMPROVED METHOD FOR TRANSFERRING GRAPHENE GROWN BY CHEMICAL VAPOR DEPOSITION
YUJIE REN,CHAOFU ZHU,WEIWEI CAI,HUIFENG LI,YUFENG HAO,YAPING WU,SHANSHAN CHEN,QINGZHI WU,RICHARD D. PINER,RODNEY S. RUOFF 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.1
In this paper, we report an improved transfer of graphene by directly picking up the graphene with target substrates and the comparison of such transferred graphene samples with other graphene samples transferred by the commonly used "PMMA-based transfer" method. Raman spectroscopy studies show that this "direct transfer method" does not degrade the graphene structure and field effect transistor measurements show that it does not introduce any extra doping in graphene; in contrast, PMMA-based transfer samples have strong n-type doping. We also find that graphene samples achieved by this direct transfer method show higher mobility than graphene obtained from the PMMA-based transfer method.
Selective surface functionalization at regions of high local curvature in graphene
Wu, Qingzhi,Wu, Yaping,Hao, Yufeng,Geng, Jianxin,Charlton, Matthew,Chen, Shanshan,Ren, Yujie,Ji, Hengxing,Li, Huifeng,Boukhvalov, Danil W.,Piner, Richard D.,Bielawski, Christopher W.,Ruoff, Rodney S. The Royal Society of Chemistry 2013 Chemical communications Vol.49 No.7
<P>Monolayer graphene was deposited on a Si wafer substrate decorated with SiO<SUB>2</SUB> nanoparticles (NPs) and then exposed to aryl radicals that were generated <I>in situ</I> from their diazonium precursors. Using micro-Raman mapping, the aryl radicals were found to selectively react with the regions of graphene that covered the NPs. The enhanced chemical reactivity was attributed to the increased strain energy induced by the local mechanical deformation of the graphene.</P> <P>Graphic Abstract</P><P>Due to the increased strain energy caused by local mechanical deformation, aryl radicals were found to selectively react with regions of graphene that were curved by underlying SiO<SUB>2</SUB> nanoparticles. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cc36747e'> </P>
Huang Peng,Qin Xiaofei,Fan Chuiqin,Wang Manna,Chen Fuyi,Liao Maochuan,Zhong Huifeng,Wang Hongwu,Ma Lian 한국조직공학과 재생의학회 2023 조직공학과 재생의학 Vol.20 No.5
BACKGROUND: Despite the progress in perinatal-neonatal medicine, complications of extremely preterm infants continue to constitute the major adverse outcomes in neonatal intensive care unit. Human umbilical cord Wharton’s Jellyderived mesenchymal stem cells (HUMSCs) may offer new hope for the treatment of intractable neonatal disorders. This study will explore the functional differences of HUMSCs between extremely preterm and term infants. METHODS: UMSCs from 5 extremely preterm infants(weeks of gestation: 22?5 w,24?4 w,25?3 w,26 w,28 w) and 2 term infants(39 w,39?2 w) were isolated, and mesenchymal markers, pluripotent genes, proliferation rate were analyzed. HUVECs were injured by treated with LPS and repaired by co-cultured with HUMSCs of different gestational ages. RESULTS: All HUMSCs showed fibroblast-like adherence to plastic and positively expressed surface marker of CD105,CD73 and CD90, but did not expressed CD45,CD34,CD14,CD79a and HLA-DR; HUMSCs in extremely preterm exhibited significant increase in proliferation as evidenced by CCK8, pluripotency markers OCT-4 tested by RT-PCR also showed increase. Above all, in LPS induced co-cultured inflame systerm, HUMSCs in extremely preterm were more capable to promote wound healing and tube formation in HUVEC cultures, they promoted TGFb1 expression and inhibited IL6 expression. CONCLUSIONS: Our results suggest that HUMSCs from extremely preterm infants may be more suitable as candidates in cell therapy for the preterm infants.