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Numerical simulation and experimental studies of mandrel effect on flow-compaction behavior of CFRP hat-shaped structure during curing process

100%

Li S. , Zhan L. , Chang T.

Archives of Civil and Mechanical Engineering

2018

tom Vol. 18, no. 4

1386--1400

CFRP hat-shaped structure is a typical stiffened structure used in aerospace field. In this work, aimed to provide a theoretical basis for manufacturing CFRP hat-shaped structure, the multi physical field coupling model considering influence of mandrel was established. Effect of mandrel on resin flow and fiber compaction during curing process was studied by simulation and experiment. Results showed that temperature and curing degree affected by mandrel can be negligible in hat-shaped structure, and the distribution of temperature and curing degree was relatively homogeneous. However, the behavior of resin flow and fiber compaction during curing process was not uniform. There was a larger gradient among resin flow, pressure, fiber volume fraction and laminate thickness. Presetting a suitable hole in mandrel can effectively improve the uniformity of resin flow and fiber compaction. By simulation analysis and optimization, the acceptable aperture of 11.5–12.5 mm was obtained. Finally, the model and simulation developed in this study was validated by experiment. The reliability coefficient of 93.4–99.6% was obtained, which indicated a good agreement between simulation and experiment.

Mild Method to Synthesize TATB by Amination of 1,3,5-Trialkoxy-2,4,6-Trinitrobenzene under Phase Transfer Catalysis Conditions

88%

Chang T. , Li B. , Chen L. , Ge L. , Lu M.

Central European Journal of Energetic Materials

2017

tom Vol. 14, no. 1

47--59

Nucleophilic amination, as a vital step in the synthesis of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using 1,3,5-trialkoxy-2,4,6-trinitrobenzene (TORTNB) and aqueous ammonia as the starting materials and catalyzed by phase transfer catalysis (PTCs) under mild conditions is described. Various phase transfer catalysts, such as crown ethers, tertiary amines, quaternary ammonium salts, poly ethers and cyclodextrin, and various experimental parameters, such as no. of equivalents of PTC, mole ratio of ammonium hydroxide to the starting material, reaction time, reaction temperature and cycle times of the organic phase were investigated. The crown ethers, especially 18-crown-6, show good catalytic activity and re-usability for the amination of 1,3,5-triethoxy-2,4,6-trinitrobenzene giving a yield of 96.52%. This makes for a safe process and suitable for scale-up, because the reactions are carried out under atmospheric conditions. The material synthesised by the new system was characterized by DSC, SEM and LPS.

Transformation of wheat Triticum aestivum with the HvBADH1 transgene from hulless barley improves salinity-stress tolerance

75%

Li P. , Cai J. , Luo X. , Chang T. , Li J. , Zhao Y. , Xu Y.

Acta Physiologiae Plantarum

2019

tom 41

nr 09

Studies have shown that the stress tolerance of cereal plants to osmotic or salinity stresses can be improved to varying degrees by the overexpression of an introduced betaine aldehyde dehydrogenase (BADH) gene. In the present study, the HvBADH1 gene from Hordeum vulgare L. var. nudum Hook. f., encoding a cytosolic BADH, was transferred into Triticum aestivum via traditional Agrobacterium tumefaciens-mediated transformation. Molecular methods, such as PCR, Southern blot analysis, and real-time quantitative RT-PCR were used to identify the successful integration and expression of the HvBADH1 transgene in genetically transformed wheat lines. To detect the efficacy of the HvBADH1 transgene in the transformants, some pivotal physiological indicators that reflected abiotic stress tolerance were measured in individual transgenic plant lines. These indicators included intracellular K⁺ and Na⁺ contents or K⁺/Na⁺ ratio, relative conductivity, and malondialdehyde and glycine betaine (GB) concentrations in cells. The results revealed that all the tested transgenic lines could significantly increase the recruitments of K⁺ in their cytosol than the wild-type seedlings. Similarly, 11.59- to 21.82-fold greater accumulation of GB, 2.11–2.56 times higher calli relative growth rates, and 26.2–29.1% seedling survival rates were found in transgenic lines under 150 mM NaCl stressed conditions. Our results demonstrated that by overexpressing the HvBADH1 transgene in genetically transformed wheat, the overall salt tolerance of the target plants was significantly increased, and the damaging effects of high salinity were significantly reduced.