Gravity die casting(GC) and squeeze casting(SC) T4-treated Al-7.0Zn-2.5Mg-2.1Cu alloys were employed to investigate the microstructures,mechanical properties and low cycle fatigue(LCF) behavior.The results show that m...Gravity die casting(GC) and squeeze casting(SC) T4-treated Al-7.0Zn-2.5Mg-2.1Cu alloys were employed to investigate the microstructures,mechanical properties and low cycle fatigue(LCF) behavior.The results show that mechanical properties of SC specimens are significantly better than those of GC specimens due to less cast defects and smaller secondary dendrite arm spacing(SDAS).Excellent fatigue properties are obtained for the SC alloy compared with the GC alloy.GC and SC alloys both exhibit cyclic stabilization at low total strain amplitudes(less than 0.4%) and cyclic hardening at higher total strain amplitudes.The degree of cyclic hardening of SC samples is greater than that of GC samples.Fatigue cracks of GC samples dominantly initiate from shrinkage porosities and are easy to propagate along them,while the crack initiation sites for SC samples are slip bands,eutectic phases and inclusions at or near the free surface.展开更多
Nowadays, oil spills have led to a serious environmental crisis of the world. To deal with this problem, inspired from super-hydrophobic lotus leaf, this study fabricated super-hydrophobic and super-lipophilic functio...Nowadays, oil spills have led to a serious environmental crisis of the world. To deal with this problem, inspired from super-hydrophobic lotus leaf, this study fabricated super-hydrophobic and super-lipophilic functionalized graphene oxide/polyurethane （FGP） sponge by a simple and inexpensive dip coating method. The resulting FGP sponge was characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and water contact angle. The results expressed that FGP sponge exhibited a similar surface structure to that of a lotus leaf, and possessed the super-hydrophobic characteristic with the water contact angle （WAC） of 152°± 1 °. The absorption capacity and reusability were also investigated. It can be seen that, the FGP sponge can remove a wide range of oils and organic solvents from water with good absorption capacities （up to 35 times of its own mass）. Significantly, after 10 cycles the absorption capacity of the oils and organic solvents was higher than 90°; for the reused FGP sponge, demonstrating the good reusability of the FGP sponge. Therefore, this study probably provided a simole way to remove the pollutions ofoil spills and toxic organism from water.展开更多
Knowledge on stocking density enables the farmer decide on the density limits that will enhance fish yield when intuition and experience are used as guide. Twelve weeks experiment conducted in concrete tanks assessed ...Knowledge on stocking density enables the farmer decide on the density limits that will enhance fish yield when intuition and experience are used as guide. Twelve weeks experiment conducted in concrete tanks assessed the growth performance and survival rate at different stocking densities of test specimens. Data analysis revealed that the highest stocking density produced the highest （157.85 ±36.54a） mean weight gain for C. gariepinus. Mean weight gain for O. niloticus in the same tank as just mentioned, took the reverse order. Specific growth data recorded for C. gariepinus revealed an intermediate value at the highest （4.25 ±1.3ab） and lowest （4.23 ±1.2ab） stocking densities, while the highest value was recorded at the intermediate stocking density （4.41 ± 1.34a）. Data on performance index revealed significant differences between the lowest （339.24 ± 86.95b） and intermediate （397.07±103.81a） and also between the lowest （339.24 ± 86.95b） and the highest （397.81±113.14a） stocking densities. The lowest stocking density recorded the highest food conversion efficiency, while the least was recorded at the highest stocking density. Clarias gariepinus recorded 98.3% survival at the highest stocking density, whereas O. niloticus in the same tank recorded 70.83%. The authors therefore conclude that since the highest stocking density gave the best yield in most of the output parameters, it should be recommended to farmers.展开更多
This paper aims to investigate the effects of recasts and working memory on the acquisition of Korean morphological causatives by advanced Chinese learners of Korean. Participants were randomly assigned to two groups...This paper aims to investigate the effects of recasts and working memory on the acquisition of Korean morphological causatives by advanced Chinese learners of Korean. Participants were randomly assigned to two groups： A experimental group and a control group. The experimental group received intensive recasts during task-based interaction, whereas the control group did not. The effects of recasts were measured by two types of tests： An elicited imitation test, as a measure of implicit knowledge, and an untimed grammaticality judgment test, as a measure of explicit knowledge. The findings are as follows. First, from the pretest to the delayed posttest, recasts facilitated the learners＇ acquisition of causative construction by developing both their implicit and explicit knowledge. Second, the results of delayed posttests showed that recasts were more effective in aiding the development of implicit knowledge than explicit knowledge. Third, working memory was found to be a significant covariate in the facilitative effects of recasts on explicit knowledge; that is, it mediated the development of explicit knowledge via recasts as a significant individual difference factor. The effects of recasts were maintained even when the impact of working memory was controlled. （189 words）展开更多
基金Project(2015A030312003)supported by the Guangdong Natural Science Foundation for Research Team,ChinaProject(51374110)supported by the National Natural Science Foundation of China
文摘Gravity die casting(GC) and squeeze casting(SC) T4-treated Al-7.0Zn-2.5Mg-2.1Cu alloys were employed to investigate the microstructures,mechanical properties and low cycle fatigue(LCF) behavior.The results show that mechanical properties of SC specimens are significantly better than those of GC specimens due to less cast defects and smaller secondary dendrite arm spacing(SDAS).Excellent fatigue properties are obtained for the SC alloy compared with the GC alloy.GC and SC alloys both exhibit cyclic stabilization at low total strain amplitudes(less than 0.4%) and cyclic hardening at higher total strain amplitudes.The degree of cyclic hardening of SC samples is greater than that of GC samples.Fatigue cracks of GC samples dominantly initiate from shrinkage porosities and are easy to propagate along them,while the crack initiation sites for SC samples are slip bands,eutectic phases and inclusions at or near the free surface.
基金Supported by the National Natural Science Foundation of China(21776319)
文摘Nowadays, oil spills have led to a serious environmental crisis of the world. To deal with this problem, inspired from super-hydrophobic lotus leaf, this study fabricated super-hydrophobic and super-lipophilic functionalized graphene oxide/polyurethane （FGP） sponge by a simple and inexpensive dip coating method. The resulting FGP sponge was characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and water contact angle. The results expressed that FGP sponge exhibited a similar surface structure to that of a lotus leaf, and possessed the super-hydrophobic characteristic with the water contact angle （WAC） of 152°± 1 °. The absorption capacity and reusability were also investigated. It can be seen that, the FGP sponge can remove a wide range of oils and organic solvents from water with good absorption capacities （up to 35 times of its own mass）. Significantly, after 10 cycles the absorption capacity of the oils and organic solvents was higher than 90°; for the reused FGP sponge, demonstrating the good reusability of the FGP sponge. Therefore, this study probably provided a simole way to remove the pollutions ofoil spills and toxic organism from water.
文摘Knowledge on stocking density enables the farmer decide on the density limits that will enhance fish yield when intuition and experience are used as guide. Twelve weeks experiment conducted in concrete tanks assessed the growth performance and survival rate at different stocking densities of test specimens. Data analysis revealed that the highest stocking density produced the highest （157.85 ±36.54a） mean weight gain for C. gariepinus. Mean weight gain for O. niloticus in the same tank as just mentioned, took the reverse order. Specific growth data recorded for C. gariepinus revealed an intermediate value at the highest （4.25 ±1.3ab） and lowest （4.23 ±1.2ab） stocking densities, while the highest value was recorded at the intermediate stocking density （4.41 ± 1.34a）. Data on performance index revealed significant differences between the lowest （339.24 ± 86.95b） and intermediate （397.07±103.81a） and also between the lowest （339.24 ± 86.95b） and the highest （397.81±113.14a） stocking densities. The lowest stocking density recorded the highest food conversion efficiency, while the least was recorded at the highest stocking density. Clarias gariepinus recorded 98.3% survival at the highest stocking density, whereas O. niloticus in the same tank recorded 70.83%. The authors therefore conclude that since the highest stocking density gave the best yield in most of the output parameters, it should be recommended to farmers.
文摘This paper aims to investigate the effects of recasts and working memory on the acquisition of Korean morphological causatives by advanced Chinese learners of Korean. Participants were randomly assigned to two groups： A experimental group and a control group. The experimental group received intensive recasts during task-based interaction, whereas the control group did not. The effects of recasts were measured by two types of tests： An elicited imitation test, as a measure of implicit knowledge, and an untimed grammaticality judgment test, as a measure of explicit knowledge. The findings are as follows. First, from the pretest to the delayed posttest, recasts facilitated the learners＇ acquisition of causative construction by developing both their implicit and explicit knowledge. Second, the results of delayed posttests showed that recasts were more effective in aiding the development of implicit knowledge than explicit knowledge. Third, working memory was found to be a significant covariate in the facilitative effects of recasts on explicit knowledge; that is, it mediated the development of explicit knowledge via recasts as a significant individual difference factor. The effects of recasts were maintained even when the impact of working memory was controlled. （189 words）
