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Qi Shi,Yongpeng Lei,Yingde Wang,Huaping Wang,Lehua Jiang,Hongliang Yuan,Dong Fang,Bing Wang,Nan Wu,Yanzi Gou 한국물리학회 2015 Current Applied Physics Vol.15 No.12
B, N-codoped carbon nanofibers were massively prepared by heat treatment of electrospun carbon nanofibers with the mixture of boric acid/urea in N2 (BNCf-N) and subsequently activated in NH3 (BNCf- NA). The directly electrospun self-standing 3D non woven structure with void spaces between each fiber facilitates the mass transport of reactant and resulted molecules. Further NH3 activation gives BNCf-NA a high surface area of 306.3 m2 g-1 with micro/mesoporous structure, providing abundant passageway for proton transfer. Simultaneously, NH3 activation also realizes the optimization of surface functionalities, such as more BeNeC and pyridinic-N. These intriguing features render BNCf-NA excellent catalytic behavior with nearly four-electron oxygen reduction reaction (ORR) process in alkaline media, especially much better stability and methanol tolerance than the commercial Pt/C catalyst. Our work provides a large-scale preparation method for efficient metal-free catalysts toward ORR, thus further intensifying the commercial application of fuel cells.
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Lehua Cheng,Dongrui Yu,Enzhu Hu,Yuchao Tang,Kunhong Hu,Karl David Dearn,Xianguo Hu,Min Wang 한국탄소학회 2018 Carbon Letters Vol.26 No.-
An electroless deposition method was used to modify the surface properties of rice husk ceramic particles (RHC) by depositing nano-nickel on the surface of the RHC (Ni-RHC). The dry tribological performances of aluminum matrix composite adobes containing different contents of RHC and Ni-RHC particles have been investigated using a micro-tribometer. Results showed that the Ni–RHC particles substantially improved both the friction and wear properties of the Ni-RHC/aluminum matrix adobes. The optimal concentration was determined to be 15 wt% for both the RHC and Ni–RHC particles. The improvements in the tribological properties of aluminum adobes including the Ni-RHC were ascribed to frictioninduced peeling off of Ni coating and formation of protection layer on the wear zone, both of which led to low friction and wear volume.
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Arching Effect between the Pipes of a Pipe Umbrella Support Systemin a Shallow-Buried Tunnel
Chao Yang,Yanhua Chen,Da Huang,Lehua Wang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12
The pipe umbrella is one of the most commonly used prereinforcement techniques in tunnel construction. Current theoretical analyses of the pipe umbrella support mechanism are primarily based on the elastic foundation beam principle, whereby only a single pipe is concerned, and the interactions among pipes are ignored. In this study, a double-parameter elastic foundation beam theory-based model was established with consideration of the arching effect between two pipes. The model can simulate the support mechanism of the pipe umbrella system in shallow-buried tunnels. The support mechanisms of a pipe umbrella system installed in a rectangular tunnel and an arched tunnel were investigated. In the two cases, the arching effect and a single pipe were considered. The results indicate that the arching effect leads to larger pipe deflection and internal forces than considering a single pipe. The influences of the diameter of a single pipe, the distance between two pipes and the shear parameters of the surrounding rock on the pipe deflection and the arching effect are discussed. In addition, the proposed model was validated by the in situ monitoring results.
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Ultimate Lateral Bearing Capacity and Group Effect of Belled Wedge Pile Groups
Gangqiang Kong,Huaifeng Peng,Hongyu Qin,Lehua Wang,Yongdong Meng 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12
Pile foundation of ports, high-voltage transmission line tower are subjected to amount of lateral loading, prediction on lateral bearing capacity is one of the most important projects in structure design. This paper pertains to the model tests on pile-soil interaction of single pile, 2 × 1 and 2 × 2 belled wedge pile groups embedded in sand under lateral load. The load versus displacement, and the soil pressures along depth surrounding piles are measured, the ultimate lateral bearing capacities and group effects of belled wedge piles are analyzed and discussed. An simplified theoretical calculation method on predicting the lateral bearing capacities of shaped pile groups with considering group pile p-y curves, and longitudinal cross-section variation are proposed. The accuracy and reliability of this developed calculation method are verified through the comparative analysis with model test results obtained in this study and previous literature. The predicted values of lateral bearing capacities have suitable agreement with the measured data. It also shows that the ultimate lateral bearing capacities of belled wedge pile group are nearly 1.8 − 2.0 times of those of traditional belled pile with the same concrete usage in this study’s condition.
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