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Behaviors of RPC-filled double skin steel tubular stub columns under axial compression loading
Wenming Hao,Qifang Xie,Yun Zhang,Dunfeng Xu,Zhitian Zhang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.6
This paper presents the compressive behaviors of RPC-filled double skin steel tubular (RFDST) stub columns. Six RFDST stub column specimens, with different hollow ratios and constraint coefficients, were tested under axial compression loading. The compressive behaviors, such as failure mode, strength and ductility, were analyzed. It is found that the failure mode of RPC filled steel tube (RFST) stub column is shear failure, while RFDST stub columns are waist drum failure. The load deformation curves of RFDST specimens with different hollow ratio and constraint coefficient show different characteristics. RFDST specimens exhibit high bearing capacity and good ductility. Based on the test results of existing RFDST stub columns, a design formula for predicting the ultimate bearing capacity is given. A finite element model is also presented to analyze the compressive behaviors, and good agreement is obtained. The influences of hollow ratio and constraint coefficient on the ultimate bearing capacity are discussed.
Xiaozhan Li,Wenming Zhang,Mingke Wu,Fengxue Xin,Weiliang Dong,Hao Wu,Min Zhang,Jiangfeng Ma,Min Jiang 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.5
Succinic acid is a platform chemical with potential for bio-based synthesis. However, the production of bio-based succinate is limited because of insufficient succinate efflux capacity in the late stage of fermentation. In the present study, three different transporters, which have been reported to be responsible for C4-dicarboxylates transport, were employed for investigation of the transport capacity of succinate in Escherichia coli. After engineered strains were constructed, the fermentative production of succinic acid was studied in serum bottles and 3 L of fermentor. The results demonstrated that engineered strain showed better efflux capacity than control strain under high concentration of succinate. The highest production of succinate was 68.66 g/L, while the NCgl2130 transporter may be the best candidate for succinate export in E. coli. Further research showed that the expression levels and relative enzyme activities involved in the metabolic pathway all increased markedly, and the maximum activities of PPC, PCK, PYK, and MDH increased by 1.50, 1.38, 1.28, and 1.27-fold in recombinant E. coli AFP111/pTrc99a- NCgl2130, respectively. Moreover, the maximum level of intracellular ATP increased by 23.79% in E. coli AFP111/ pTrc99a-NCgl2130. Taken together, these findings indicated that engineered transporters can improve succinate production by increasing key enzyme activities and intracellular ATP levels. To the best of thew authors’ knowledge, this is the first report on a mechanism to improve succinate production by engineered transporters. This strategy set up a foundation for improving the biosynthesis of other C4-dicarboxylates, such as fumaric acid and malic acid.