The formability of magnesium alloys at ambient temperature can be enhanced by alloying additions such as Ca and RE elements,which is ascribed to the weakened basal texture.To produce magnesium alloy sheets with excell...The formability of magnesium alloys at ambient temperature can be enhanced by alloying additions such as Ca and RE elements,which is ascribed to the weakened basal texture.To produce magnesium alloy sheets with excellent comprehensive performance,the evolution of texture characterization during fabrication process and subsequent effect of texture on mechanical properties are vital controlling factors.In this investigation,three experimental Mg-3Al series alloys were hot rolled and annealed to sheets with 1 mm thickness.The microstructure evolution during rolling and annealing process was investigated.Furthermore,the influence of texture on tensile properties along different tensile directions was also studied.The results show that weakened basal texture and refined grains were achieved with the co-addition of Ca and RE element.However,strengthening of mechanical properties wasn't obtained.During hot rolling process,microstructure was refined,second phase particles broken,and basal texture was increased.While basal texture was weakened during annealing process.Recrystallization behavior influenced by formation of second phase was dominated to attenuate basal texture.Tensile deformation behavior was controlled by basal slip and followed Schmid factor criterion.Moreover,the weakened basal texture and activation of non-basal slips during hot rolling process can contribute to diminish the anisotropy of tensile properties.展开更多
Human activities such as the implementation of ecological protection projects and expansion of construction land can cause complex land use changes that affect ecosystem service values (ESV). In this study, we inves...Human activities such as the implementation of ecological protection projects and expansion of construction land can cause complex land use changes that affect ecosystem service values (ESV). In this study, we investigated changes in ESV in response to land use changes in Ningwu County, in eastern Loess Plateau of China. Our aim is to provide guidance for sustainable land use planning in this region. We used remote sensing to evaluate land use changes, and applied a fast, proxy-based method for evaluating ESVat three points in time: 1990, 2000, and 2010. More than 89% of the total ESV in Ningwu County was attributable to woodland and grassland. The ESV in western mountain areas show the greatest increase from 1990 to 2010, but ESV decreased the most in the low-elevation northeastern area of flat terrain These tradeoffs led to a slight net decrease (1.0%) in Ningwu County's total ESV. Although the decline in ESV was relatively low compared to the rate of economic growth, total ESV was much lower than global and national average levels at the end of the study period.展开更多
Present studies on the coupling relationship and hydrology mechanism between basin ecosystem and hydrological process has become an international research frontier in hydrology. This paper investigates this coupling r...Present studies on the coupling relationship and hydrology mechanism between basin ecosystem and hydrological process has become an international research frontier in hydrology. This paper investigates this coupling relationship, and also summarizes research and presents a method of combining isotopic technology with hydro-chemical methods, for the study of eco-hydrological process and function in different landscape zones. We then examine research trends for future direction and development of this field.展开更多
The dielectric confinement effect plays an essential role in optoelectronic devices.Existing studies on the relationship between the dielectric confinement and the photoelectric properties are inadequate.Herein,three ...The dielectric confinement effect plays an essential role in optoelectronic devices.Existing studies on the relationship between the dielectric confinement and the photoelectric properties are inadequate.Herein,three organic spacers with different dielectric constants are employed to tune the exciton dynamics of quasi-two-dimensional(quasi-2D)Ruddlesden–Popper perovskite films.Femtosecond transient absorption spectroscopy reveals that the small dielectric constant ligand enables a weak dynamic disorder and a large modulation depth of the coherent phonons,resulting in a more complete energy transfer and the inhibition of a trap-mediated nonradiative recombination.Additionally,the increase in the bulk-ligand dielectric constant reduces the corresponding exciton binding energy and then suppresses the Auger recombination,which is beneficial for high-luminance lightemitting diodes.This work emphasizes the importance of dielectric confinement for regulating the exciton dynamics of layered perovskites.展开更多
The integration of luminescence and chirality in carbon dots(CDs) encourages candidates to explore novel functions and applications of CDs, however, the preparation of chiral CDs is very limited. Herein, we report a h...The integration of luminescence and chirality in carbon dots(CDs) encourages candidates to explore novel functions and applications of CDs, however, the preparation of chiral CDs is very limited. Herein, we report a hydrothermal method to fabricate chiral CDs by utilizing amino acid enantiomers as the precursors. LGln-CDs or DGln-CDs with uniform size of 3–4 nm show excitation-dependent blue fluorescence in solutions. Circular dichroism measurement confirms the opposite optical rotation of chiral CDs in the region from 200 nm to 300 nm, and the signals can be regulated by concentrations of CDs solution. Timedependent density functional calculation reveals that polypeptides may exist on the surface of CDs due to the polycondensation of L/DGln at high temperature, and the optical activity of CDs originates from the stacking of neighboring carbonyl groups. The facile synthetic methodology proposed will provide potential opportunities for the preparation and application of chiral and chiroptical CDs-based materials.展开更多
基金The authors would like to thank the financial support of Fundamental Research Funds for the Central Universities(No.2302019FRF-IC-19-018)Aviation Science Foundation Project(No.20181174001).
文摘The formability of magnesium alloys at ambient temperature can be enhanced by alloying additions such as Ca and RE elements,which is ascribed to the weakened basal texture.To produce magnesium alloy sheets with excellent comprehensive performance,the evolution of texture characterization during fabrication process and subsequent effect of texture on mechanical properties are vital controlling factors.In this investigation,three experimental Mg-3Al series alloys were hot rolled and annealed to sheets with 1 mm thickness.The microstructure evolution during rolling and annealing process was investigated.Furthermore,the influence of texture on tensile properties along different tensile directions was also studied.The results show that weakened basal texture and refined grains were achieved with the co-addition of Ca and RE element.However,strengthening of mechanical properties wasn't obtained.During hot rolling process,microstructure was refined,second phase particles broken,and basal texture was increased.While basal texture was weakened during annealing process.Recrystallization behavior influenced by formation of second phase was dominated to attenuate basal texture.Tensile deformation behavior was controlled by basal slip and followed Schmid factor criterion.Moreover,the weakened basal texture and activation of non-basal slips during hot rolling process can contribute to diminish the anisotropy of tensile properties.
基金supported by the Open Fund Project of the Key Laboratory of Desert and Desertification,Chinese Academy of Sciences(No.KLDD-2014-001)the Important Specialized Science and Technology Item of Shanxi Province,China(No.20121101011)the Natural Science Foundation of China(Nos.41271513,41271030)
文摘Human activities such as the implementation of ecological protection projects and expansion of construction land can cause complex land use changes that affect ecosystem service values (ESV). In this study, we investigated changes in ESV in response to land use changes in Ningwu County, in eastern Loess Plateau of China. Our aim is to provide guidance for sustainable land use planning in this region. We used remote sensing to evaluate land use changes, and applied a fast, proxy-based method for evaluating ESVat three points in time: 1990, 2000, and 2010. More than 89% of the total ESV in Ningwu County was attributable to woodland and grassland. The ESV in western mountain areas show the greatest increase from 1990 to 2010, but ESV decreased the most in the low-elevation northeastern area of flat terrain These tradeoffs led to a slight net decrease (1.0%) in Ningwu County's total ESV. Although the decline in ESV was relatively low compared to the rate of economic growth, total ESV was much lower than global and national average levels at the end of the study period.
基金supported by the Projects Internation-al Science&Technology Cooperation Program of China(2012DFA20770)National Natural Science Foundation of China(41201043)+1 种基金Natural Science Foundation of Shanxi Province(2012021026-3)Science and Technology Major Projects of Shanxi Province(20121101011)
文摘Present studies on the coupling relationship and hydrology mechanism between basin ecosystem and hydrological process has become an international research frontier in hydrology. This paper investigates this coupling relationship, and also summarizes research and presents a method of combining isotopic technology with hydro-chemical methods, for the study of eco-hydrological process and function in different landscape zones. We then examine research trends for future direction and development of this field.
基金supported by the West Action Program of Chinese Academy of Sciences (KZCX2-XB2-04-03)the Chinese National Natural Science Fund (40801021)+1 种基金the West Light Foundation of West Doctor of CASthe China Postdoctoral Science Foundation (200801244, 20070420135)
基金National Natural Science Foundation of China(12347158,11804084,12074104,61627818,U1804261)Natural Science Foundation of Henan Province(222300420057)Young Backbone Teacher Training Program in Higher Education of Henan Province(2019GGJS065)。
文摘The dielectric confinement effect plays an essential role in optoelectronic devices.Existing studies on the relationship between the dielectric confinement and the photoelectric properties are inadequate.Herein,three organic spacers with different dielectric constants are employed to tune the exciton dynamics of quasi-two-dimensional(quasi-2D)Ruddlesden–Popper perovskite films.Femtosecond transient absorption spectroscopy reveals that the small dielectric constant ligand enables a weak dynamic disorder and a large modulation depth of the coherent phonons,resulting in a more complete energy transfer and the inhibition of a trap-mediated nonradiative recombination.Additionally,the increase in the bulk-ligand dielectric constant reduces the corresponding exciton binding energy and then suppresses the Auger recombination,which is beneficial for high-luminance lightemitting diodes.This work emphasizes the importance of dielectric confinement for regulating the exciton dynamics of layered perovskites.
基金financially supported by the National Natural Science Foundation of China (No. 21621001)the 111 Project (No. B17020)。
文摘The integration of luminescence and chirality in carbon dots(CDs) encourages candidates to explore novel functions and applications of CDs, however, the preparation of chiral CDs is very limited. Herein, we report a hydrothermal method to fabricate chiral CDs by utilizing amino acid enantiomers as the precursors. LGln-CDs or DGln-CDs with uniform size of 3–4 nm show excitation-dependent blue fluorescence in solutions. Circular dichroism measurement confirms the opposite optical rotation of chiral CDs in the region from 200 nm to 300 nm, and the signals can be regulated by concentrations of CDs solution. Timedependent density functional calculation reveals that polypeptides may exist on the surface of CDs due to the polycondensation of L/DGln at high temperature, and the optical activity of CDs originates from the stacking of neighboring carbonyl groups. The facile synthetic methodology proposed will provide potential opportunities for the preparation and application of chiral and chiroptical CDs-based materials.