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- 저자 : Guangsheng Yang (검색결과 3 건)
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Jun Peng,Qian Wang,Jin Wang,Jun Yang,Taijun Jiang,Guangsheng Zeng 한국고분자학회 2022 Macromolecular Research Vol.30 No.11
Cardo containing phenoxy and -CF3 derivate diamine was synthesized, and further it was polymerized with 3,3',4,4'-biphenyl tetracarboxylic dianhydride to prepare polyetherimide containing Cardo group. The transmittance of the prepared polymer increased from 82% to 88% and the dielectric constant decreased from 2.91 to 2.83 with a slight decline in thermal and mechanical performance when -CF3 was introduced. The molecular simulation in terms of charge distribution, electric potential energy, chain stiffness and aggregation state revealed that -CF3 could restrain charge transfer and decrease the unit dipole moment and polarization for its larger volume. The optical and dielectric performance was significantly enhanced, but the thermal and mechanical performance decreased slightly when the -CF3 group was introduced. The glass transition temperature of the polymer declined from 329℃ to 311℃. The investigation conducted in this paper can offer valuable reference to the optimization and development of synthesis and comprehensive performance of polyimide.
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Lili Wan,Xiuyun Xia,Dengfeng Hong,Ji Li,Guangsheng Yang 한국식물학회 2010 Journal of Plant Biology Vol.53 No.2
In the recessive genic male sterile line 9012A of Brassica napus, pollen development is affected during the tetrad stage. According to the light and electron microscopy analysis of tapetal cells and tetrads, the sterile tapetal cells swelled with expanded vacuoles at the early tetrad stage and finally filled the center of the locules where a majority of tetrads encased with the thick callose wall collapsed and degraded. We suggested that an absence of callase, which is a wall-degrading enzyme stored in the vacuoles of tapetal cells before secretion, resulted in the failure of tetrad separation. Moreover, transmission electron microscopy analysis showed that the secretory tapetal cells were not observed in sterile anthers, which indicated that the transition of the tapetum from the parietal type to the secretory type was probably aberrant. In plants, degeneration of the tapetum is thought to be the result of programmed cell death (PCD). PCD of tapetal cells was investigated by terminal deoxynucleotidyl transferasemediated dUTP nick-end labeling assay and signals indicative of deoxyribonucleic acid fragmentation were detected much earlier in sterile anther than in fertile anther. This suggests that tapetal breakdown does not occur by the normal procession of PCD and might be following an alternative mechanism of unscheduled apoptosis in line 9012A. This research supports the hypothesis that premature PCD is associated with male sterility in B. napus.
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Influence of Li Addition on the Microstructures and Mechanical Properties of Mg–Li Alloys
Jun Zhao,Jie Fu,Bin Jiang,Aitao Tang,Haoran Sheng,Tianhao Yang,Guangsheng Huang,Dingfei Zhang,Fusheng Pan 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6
In this study, Mg-xLi (x = 0, 1, 2, 3 and 5 wt%) alloys have been extruded to examine the role of Li content on microstructuresand tensile properties. The results revealed that Li addition increased the grain size and led to the formation of the transversedirection (TD)-split texture. These were mainly attributed to the promoted DRX process and the increased activity of prismatic⟨a⟩ slip during extrusion. Tensile tests revealed that the elongation of Mg-5Li sheet reached ~ 22.4% along the ED. Moreover, it exhibited a higher elongation of ~ 27.3%, three times than pure Mg, along the TD. During tension along the ED,with increasing Li content, more prismatic ⟨a⟩ slip and preferable intergranular strain coordination ability to accommodatethe plastic strain, leading to the enhanced room-temperature ductility. In contrast, more basal ⟨a⟩ slips and extension twinswere also activated along the TD, which further contributed to the enhanced ductility. Therefore, the ductility of Mg sheetsat room temperature gradually improved with Li addition due to the combining effects of basal ⟨a⟩ slip, prismatic ⟨a⟩ slip,extension twin and preferable intergranular strain coordination ability.
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