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- 저자 : Ruyan Li (검색결과 2 건)
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Ruyan Liu,Yin Chi,Shengyun Chen,Qinghui Jiang,Xiaoyu Meng,Kun Wu,Shengjia Li 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.4
Pervious concrete has been widely used in parking lots and other lightweight streets. Performances of pervious concrete are strongly dependent on its pore structure characteristics. This paper investigates the relationship among porosity, permeability, compressive strength, durability and the pore structure characteristics of pervious concrete. The influences of basalt fiber and fine aggregate on the pervious concrete are also discussed. Pervious concrete specimens with different pore structures were prepared by combining basalt aggregate with size of 5-10 mm and 10-15 mm at different proportion. The pore structure characteristics such as area porosity, pore sizes, and pore distribution of pervious concrete were obtained and analyzed using image analysis method. Experimental results showed that the pore structure characteristics of pervious concrete have effects on its mechanical and durability behaviors. Homogeneous pore distribution and large distances between pores increase the compressive strength and improve freeze-thaw durability of pervious concrete. Due to the difference in the internal pore structure of pervious concretes, specimens with similar volumetric porosities had different permeability coefficients. A series of numerical models were regenerated through a MATLAB code using pore structural parameters derived from the image analysis method, then the numerical models were fed to ANSYS for meshing and further simulation. The comparison of the simulation and experimental results showed close accuracy, which verified the applied simulation analysis method based on image analysis technology.
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Xin Sun,Ruyan Li,Guochen Wan,Wanli Peng,Shuangjun Lin,Zixin Deng,Rubing Liang 한국미생물학회 2021 The journal of microbiology Vol.59 No.2
Putrescine, a typical polyamine compound important for cell growth and stress resistance, can be utilized as an energy source. However, the regulation of its catabolism is unclear. Here the small RNA (sRNA) Spot 42, an essential regulator of carbon catabolite repression (CCR), was confirmed to participate in the post-transcriptional regulation of putrescine catabolism in Escherichia coli. Its encoding gene spf exclusively exists in the γ-proteobacteria and contains specific binding sites to the 5 -untranslated regions of the puuE gene, which encodes transaminase in the glutamylated putrescine pathway of putrescine catabolism converting γ-aminobutyrate (GABA) into succinate semialdehyde (SSA). The transcription of the spf gene was induced by glucose, inhibited by putrescine, and unaffected by PuuR, the repressor of puu genes. Excess Spot 42 repressed the expression of PuuE significantly in an antisense mechanism through the direct and specific base-pairing between the 51–57 nt of Spot 42 and the 5 - UTR of puuE. Interestingly, Spot 42 mainly influenced the stability of the puuCBE transcript. This work revealed the regulatory role of Spot 42 in putrescine catabolism, in the switch between favorable and non-favorable carbon source utilization, and in the balance of metabolism of carbon and nitrogen sources.
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