Polymer matrix types of fiber hybrid composites are key factors to improve ballistic impact damage tolerances.Here we report ballistic penetration damages of Kevlar/ultra-high molecular weight polyethylene(UHMWPE)hybr...Polymer matrix types of fiber hybrid composites are key factors to improve ballistic impact damage tolerances.Here we report ballistic penetration damages of Kevlar/ultra-high molecular weight polyethylene(UHMWPE)hybrid composites with thermoplastic polyurethane(PU)matrix.The hybrid composites were penetrated by fragment-simulating projectiles(FSPs)using an air gun impact system.The effects of stacking sequences on the ballistic performance of hybrid composites were analyzed.Two types of specific energy absorption(the energy absorption per unit area density and the energy absorption per unit thickness)were investigated.It was found that the main damage modes of PU hybrid composites were fiber breakage,matrix damage,fiber pullout and interlayer delamination.The instantaneous deformation could not be used as a reference index for evaluating the ballistic performance of the target plate.The energy absorption process of the PU hybrid composites showed a nonlinear pattern.The hybrid structure affected the specific energy absorption of the materials.展开更多
[Objective] This study aimed to establish the technical system for forcing ornamental pineapple in Guzmania to flower and further provide technical parameters for large-scale cultivation.[Method] The effect of differe...[Objective] This study aimed to establish the technical system for forcing ornamental pineapple in Guzmania to flower and further provide technical parameters for large-scale cultivation.[Method] The effect of different concentrations of ethephon solution on flowering in Guzmania ornamental pineapple was studied by using randomized block design.[Results] All the different concentrations of ethephon solution were capable to force the four mainly-cultivated ornamental pineapple varieties to flower to varying degrees.After the flower forcing,it took about 180 d for the pineapple to stay in the ornamentation period,and there were no significant differences in inflorescence shape,inflorescence height,inflorescence diameter and bract number among different treatment pineapples.[Conclusion] All the four varieties have shown high sensitivity to ethephon.The optimal ethephon concentration is 400 mg/L for treating G.lingulata,G.remembrance and G.denise and 500 mg/L for treating G.conifera.After treatment,their major ornamentation traits are were able to satisfy the requirements for commercial production of pineapple.展开更多
The potential energy profile of the reaction between the atomic oxygen radical anion and acetonitrile has been mapped at the G3MP2B3 level of theory. Geometries of the reactants, products, intermediate complexes, and ...The potential energy profile of the reaction between the atomic oxygen radical anion and acetonitrile has been mapped at the G3MP2B3 level of theory. Geometries of the reactants, products, intermediate complexes, and transition states involved in this reaction have been optimized at the （U）B3LYP/6-31＋G（d,p） level, and then their accurate relative energies have been improved using the G3MP2B3 method. The potential energy profile is confirmed via intrinsic reaction coordinate calculations of transition states. Four possible production channels are examined respectively, as H＋ transfer, H-atom transfer, H2＋ transfer, and bi- molecular nucleophilic substitution （SN2） reaction pathways. Based on present calculations, the H2＋ transfer reaction is major among these four channels, which agrees with previous experimental conclusions.展开更多
Aim To study the saponin constituents of the seeds of Aesculus chinensis Bunge var. chekiangensis (Hu et Fang) Fang. Methods Compounds were separated and purified by macroreticular resin column chromatography and high...Aim To study the saponin constituents of the seeds of Aesculus chinensis Bunge var. chekiangensis (Hu et Fang) Fang. Methods Compounds were separated and purified by macroreticular resin column chromatography and high-performance liquid chromatography. Their structures were elucidated by spectroscopic and hydrolysis analysis. Results Six compounds were isolated from the 70% ethanolic extracts. They were identified as escins IVc, IVd, Ia, Ib, isoescins Ia and Ib, respectively. Conclusion The above compounds were obtained from the seeds of Aesculus chinensis Bunge var.chekiangensis (Hu et Fang) Fang for the first time.展开更多
Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PE...Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PEG） 400, where three types of additives with different molecular chain lengths of PEG4000, PEG6000, and PEG10000 were used. For PEG10000, different concentrations, including 0, 1%, 3%, and 5%, were selected to study the influences of additive concentrations. Rheological properties of the samples were measured with a rheometer. The results show that the shear thickening effect was significantly enhanced with the increase of the concentration and the molecular chain length of additives. The mechanism of enhancement was quantitatively explained with the formation of large particles clusters.展开更多
基金National Natural Science Foundation of China(No.51875099)。
文摘Polymer matrix types of fiber hybrid composites are key factors to improve ballistic impact damage tolerances.Here we report ballistic penetration damages of Kevlar/ultra-high molecular weight polyethylene(UHMWPE)hybrid composites with thermoplastic polyurethane(PU)matrix.The hybrid composites were penetrated by fragment-simulating projectiles(FSPs)using an air gun impact system.The effects of stacking sequences on the ballistic performance of hybrid composites were analyzed.Two types of specific energy absorption(the energy absorption per unit area density and the energy absorption per unit thickness)were investigated.It was found that the main damage modes of PU hybrid composites were fiber breakage,matrix damage,fiber pullout and interlayer delamination.The instantaneous deformation could not be used as a reference index for evaluating the ballistic performance of the target plate.The energy absorption process of the PU hybrid composites showed a nonlinear pattern.The hybrid structure affected the specific energy absorption of the materials.
文摘[Objective] This study aimed to establish the technical system for forcing ornamental pineapple in Guzmania to flower and further provide technical parameters for large-scale cultivation.[Method] The effect of different concentrations of ethephon solution on flowering in Guzmania ornamental pineapple was studied by using randomized block design.[Results] All the different concentrations of ethephon solution were capable to force the four mainly-cultivated ornamental pineapple varieties to flower to varying degrees.After the flower forcing,it took about 180 d for the pineapple to stay in the ornamentation period,and there were no significant differences in inflorescence shape,inflorescence height,inflorescence diameter and bract number among different treatment pineapples.[Conclusion] All the four varieties have shown high sensitivity to ethephon.The optimal ethephon concentration is 400 mg/L for treating G.lingulata,G.remembrance and G.denise and 500 mg/L for treating G.conifera.After treatment,their major ornamentation traits are were able to satisfy the requirements for commercial production of pineapple.
文摘The potential energy profile of the reaction between the atomic oxygen radical anion and acetonitrile has been mapped at the G3MP2B3 level of theory. Geometries of the reactants, products, intermediate complexes, and transition states involved in this reaction have been optimized at the （U）B3LYP/6-31＋G（d,p） level, and then their accurate relative energies have been improved using the G3MP2B3 method. The potential energy profile is confirmed via intrinsic reaction coordinate calculations of transition states. Four possible production channels are examined respectively, as H＋ transfer, H-atom transfer, H2＋ transfer, and bi- molecular nucleophilic substitution （SN2） reaction pathways. Based on present calculations, the H2＋ transfer reaction is major among these four channels, which agrees with previous experimental conclusions.
文摘Aim To study the saponin constituents of the seeds of Aesculus chinensis Bunge var. chekiangensis (Hu et Fang) Fang. Methods Compounds were separated and purified by macroreticular resin column chromatography and high-performance liquid chromatography. Their structures were elucidated by spectroscopic and hydrolysis analysis. Results Six compounds were isolated from the 70% ethanolic extracts. They were identified as escins IVc, IVd, Ia, Ib, isoescins Ia and Ib, respectively. Conclusion The above compounds were obtained from the seeds of Aesculus chinensis Bunge var.chekiangensis (Hu et Fang) Fang for the first time.
文摘Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PEG） 400, where three types of additives with different molecular chain lengths of PEG4000, PEG6000, and PEG10000 were used. For PEG10000, different concentrations, including 0, 1%, 3%, and 5%, were selected to study the influences of additive concentrations. Rheological properties of the samples were measured with a rheometer. The results show that the shear thickening effect was significantly enhanced with the increase of the concentration and the molecular chain length of additives. The mechanism of enhancement was quantitatively explained with the formation of large particles clusters.
