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- 저자 : Huimin Mao (검색결과 4 건)
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Experimental Research on Impact Resistance of Partially Precast Concrete Beams
Huimin Mao,Xueyuan Yan,Chenchen Zong,Cihang Lin,Xuhong Liu 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.9
A building may be subjected to multiple accidental loads during its service-life. Partially precast concrete (PC) beam is a primary force-bearing member. When subjected to an impact load, its impact resistance will significantly affect the overall safety of the structure. In this study, five PC beams were designed and manufactured, and drop-hammer impact tests were performed. The influences of impact mass and impact height on the failure mode and the dynamic response of the component under different loading conditions were examined. The typical failure mode of the test beam under a dynamic load was derived from the failure mode and crack distribution. The dynamic responses such as impact force, supporting reaction force, and displacement–time-history curve were obtained by the test. With increasing impact energy, the peak impact force increased from 3,353 to 3,708 kN, the peak mid-span displacement increased from 33.6 to 47.3 mm, and the residual mid-span displacement increased from 11.9 to 15.1 mm. Subsequently, the law of energy dissipation in the impact process was analyzed using the combined curves of the impact force-mid-span displacement and support reaction force-mid-span displacement. Furthermore, the result obtained by the integration of the reaction force-displacement curve in the middle of the span is more suitable for evaluating the overall energy consumption of the beam. The vibration energy and internal energy of the beam itself account for the primary part of the remaining energy.
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Huimin Mao,Xueyuan Yan,Chenchen Zong,Cihang Lin 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.5
A building can be subject to multiple accidental loads during its service life. Partially precast concrete (PC) beams are primary force-bearing members. When subjected to an impact load, their impact resistance considerably affects the overall safety of the structure. In this study, we performed numerical analyses of the dynamic response of PC beams subjected to impact loading. The related parameters, including the element type, material model, contact type, and hourglass control, were discussed in detail. The simulation and test results were compared. The model's validity is verified from four aspects: energy conversion, failure form, impact-force time history curve, and midspan-displacement time history curve. Based on these findings, the effects of the concrete strength, longitudinal reinforcement ratio, and stirrup ratio on the impact resistance of the components were evaluated. Furthermore, the differences in the equivalent plastic strain cloud diagram, impact-force time history curve, and midspan-displacement time history curve under different parameters were compared. The results show that an increase in the strength of the post-pouring concrete can reduce local damage to PC beams, and improving the overall strength of concrete can reduce overall damage of PC beams. In addition, an increase in the longitudinal reinforcement ratio can ease the failure of the normal cross-section of PC beams, and an increase in the stirrup ratio can effectively inhibit the generation and development of oblique cracks. Then, by fitting the parameters, we established simplified formulas for calculating the peak and residual values of the midspan displacement. According to the formulas, when the external impact mass and height are known, the component's damage degree can then be predicted, which provides a basis for the design of fabricated structures.
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Huimin Xiao,Jun Mao 서울대학교 교육연구소 2021 Asia Pacific Education Review Vol.22 No.1
Based on the spatial Durbin model, this paper explored postgraduate education’s influence and spatial effects on technological innovation. Using China’s provincial panel data from 2004 to 2018, study results revealed that distribution of postgraduates in China showed spatial autocorrelation and non-equilibrium. Overall, postgraduate education positively impacted technological innovation. The study measured spatial spillover using three spatial weight matrices, finding that postgraduate education significantly promoted innovation in similar provinces. The spatial spillover effect in the economic matrix was stronger than that in the adjacent matrix. In economic and economic-geographical matrices, postgraduate education’s spatial spillover effect was stronger than its direct effect. This paper can deepen understanding of characteristics and functions of postgraduate education in a rapidly developing economy.
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Zhi Chen,Shuangfeng Chu,Xin Xu,Jingyi Jiang,Wenqiang Wang,Hongliang Shen,Mingxun Li,Huimin Zhang,Yongjiang Mao,Zhangping Yang 한국유전학회 2019 Genes & Genomics Vol.41 No.10
Background As cattle represent one of the most important livestock species for meat production, control of muscle development in regards to quality is an important research focus. Objectives In this study, the phenotypic quality traits and its associations with DNA methylation levels of the longissimus muscle in two cattle breeds were studied. Methods The pH value, water loss rate, fat and protein and fatty acid content were measured in three beef cattle breeds of longissimus mucle; The longissimus mucle was analyzed by MethylRAD-seq and RNA-seq. The differentially methylated and differentially expressed related genes were subjected to BSP. Results Methylation status of longissimus mucle was analyzed by MethylRAD-seq. Compared with Simmental, there were 39 differentially methylated and expressed genes in muscle of Yunling cattle, and 123 differentially methylated and expressed genes in Wenshan muscle. A combined analysis of MethylRAD-seq and RNA-seq results revealed differential methylation and expression level of 18 genes between Simmental and Wenshan cattle, and 14 genes between Simmental and Yunling cattle. In addition, 28 genes were differentially methylated between Wenshan and Yunling cattle. Results of promoter methylation analysis of ACAD11, FADS6 and FASN showed that the overall degree of DNA methylation of FADS6 and FASN was negatively correlated with their expression levels. Methylation level of FASN in Simmental was greater than Yunling and Wenshan. The degree of methylation at the FADS6 CpG4 site was significantly higher in Simmental than that in Yunling. The levels of methylation at the CpG7 locus of the Simmental and Yunling breeds were greater than Wenshan cattle. A negative correlation was detected between the methylation levels and the expression of FASN CpG1, CpG2, CpG3, CpG5, CpG7, and CpG10. Conclusion The functional and molecular regulatory mechanism of the genes related to meat quality can be revealed systematically from aspects of the genetic and epigenetic regulation. These studies will help to further explore the molecular mechanisms and phenotypic differences that regulate growth and quality of different breeds of cattle.
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