In this study,a coniferous tree species(Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains(QLM) to detect the trends in carbon i...In this study,a coniferous tree species(Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains(QLM) to detect the trends in carbon isotope ratio( δ^(13)C),leaf nitrogen content(LNC) and stomatal density(SD) with altitude variation in northsubtropical humid mountain climate zone of China.The results showed that LNC and SD both significantly increased linearly along the altitudinal gradient ranging from 1000 to 2200 m,whereas leafδ^(13)C exhibited a significantly negative correlation with the altitude.Such a correlation pattern differs obviously from that obtained in offshore low-altitude humid environment or inland high-altitude semi-arid environment,suggesting that the pattern of increasing δ^(13)C with the altitude cannot be generalized.The negative correlation between δ ^(13)C and altitude might be attributed mainly to the strengthening of carbon isotope fractionation in plants caused by increasing precipitation with altitude.Furthermore,there was a remarkable negative correlation between leaf δ ^(13)C and LNC.One possible reason was that increasing precipitation that operates to increase isotopic discrimination with altitude overtook the LNC in determining the sign of leaf δ ^(13)C.The significant negative correlation between leaf δ ^(13)C and SD over altitudes was also found in the present study,indicating that increases in SD with altitude would reduce,rather than enhance plant δ^(13)C values.展开更多
Utilization of novel materials,particularly high-T_(c)(critical temperature)superconductors,is essential to pursue the United Nations’Sustainable Goals,as well as to meet the increasing worldwide demand for clean and...Utilization of novel materials,particularly high-T_(c)(critical temperature)superconductors,is essential to pursue the United Nations’Sustainable Goals,as well as to meet the increasing worldwide demand for clean and carbon-free electric power technologies.Superconducting magnets are beneficial in several real-life applications including transportation,energy production,magnetic resonance imaging(MRI),and drug delivery systems.To achieve high performance,one must develop uniform,large-grain,infiltration-growth(IG)processed bulk YBa_(2)Cu_(3)O_(y)(Y-123)super-magnets.In this study,we report the magnetic and microstructural properties of a large-grain,top-seeded,IG-processed Y-123 pellet,which is 20 mm in diameter and 6 mm in height;the pellet is produced utilizing liquid Yb-123+Ba_(3)Cu_(5)O_(8) as the liquid source.All the samples cut from the top of the bulk exhibit a sharp superconducting transition(approximately 1 K wide)with the onset T_(c) of approximately 90 K.However,in the samples cut from the bottom surface,the onset T_(c) values slightly decreased to between 88 and 90 K,although still exhibiting a sharp superconducting transition.The top and bottom samples exhibited the highest remnant value of J_(c)(critical current density)at 77 K H//c-axis of 50 and 55 kA/cm^(2),respectively.The remnant J_(c) and irreversibility field values significantly fluctuated,being fairly low in some bottom samples.Scanning electron microscopy identified nanometer size Y-211(Y2BaCuO5)secondary-phase particles dispersed in the Y-123 matrix.Energy-dispersive spectroscopy clarified that the decreased both T_(c) and J_(c) for the bottom samples were attributed to liquid phase dispersion within the Y-123 phase.展开更多
利用张衡一号卫星搭载的电场探测仪(Electric Field Detector,EFD)获得的VLF频段2019年电场功率谱数据,研究赤道附近区域近东西向电场的背景分布、季节变化以及与电离层背景的关系。结果表明:白天电场背景在赤道及其附近随季节呈不同波...利用张衡一号卫星搭载的电场探测仪(Electric Field Detector,EFD)获得的VLF频段2019年电场功率谱数据,研究赤道附近区域近东西向电场的背景分布、季节变化以及与电离层背景的关系。结果表明:白天电场背景在赤道及其附近随季节呈不同波形结构,以3波、4波为主;夜间电场背景规律性稍差,仍呈随季节变化的经向波形结构分布特征;白天电场背景与电离层背景的季节变化呈高度正相关性,春秋季为峰值;夜间电场背景的季节变化特征是夏冬季峰值,与夜间电离层背景整体上呈负相关性。VLF电场功率谱观测数据与电离层观测数据在较大和较小空间尺度上的统计特征上都具有一致性。EFD载荷为电离层相关科学问题的研究及应用提供了一个可以使用的电场观测数据集。展开更多
The radial wave functions of inner electron shell and outer electron shell of a Ne atom were obtained by the approximate analytical method and tested by calculating the ground state energy of the Ne atom. The equivale...The radial wave functions of inner electron shell and outer electron shell of a Ne atom were obtained by the approximate analytical method and tested by calculating the ground state energy of the Ne atom. The equivalent volume of electron cloud and the refractive index of Ne were calculated. The calculated refractive index agrees well with the experimental result. Relationship between the refractive index and the wave function of Ne was discovered.展开更多
基金supported by Hunan Province Natural Science Foundation (No.2015JJ2062)the State Key Laboratory of Soil and Sustainable Agriculture (Grant No.Y412201416)the Scientific Research Fund of Hunan Provincial Education Department (Grant No.14A054)
文摘In this study,a coniferous tree species(Pinus tabuliformis Carr.) was investigated at a moderate-altitude mountainous terrain on the southern slope of the middle Qinling Mountains(QLM) to detect the trends in carbon isotope ratio( δ^(13)C),leaf nitrogen content(LNC) and stomatal density(SD) with altitude variation in northsubtropical humid mountain climate zone of China.The results showed that LNC and SD both significantly increased linearly along the altitudinal gradient ranging from 1000 to 2200 m,whereas leafδ^(13)C exhibited a significantly negative correlation with the altitude.Such a correlation pattern differs obviously from that obtained in offshore low-altitude humid environment or inland high-altitude semi-arid environment,suggesting that the pattern of increasing δ^(13)C with the altitude cannot be generalized.The negative correlation between δ ^(13)C and altitude might be attributed mainly to the strengthening of carbon isotope fractionation in plants caused by increasing precipitation with altitude.Furthermore,there was a remarkable negative correlation between leaf δ ^(13)C and LNC.One possible reason was that increasing precipitation that operates to increase isotopic discrimination with altitude overtook the LNC in determining the sign of leaf δ ^(13)C.The significant negative correlation between leaf δ ^(13)C and SD over altitudes was also found in the present study,indicating that increases in SD with altitude would reduce,rather than enhance plant δ^(13)C values.
基金This work was presented at the International Conference on Carbon Materials and Nanotechnology,Osaka,Japan(JICCMAN 2020)which was held during June 30–July 1 of 2020 as an online summit.This work was delivered as an oral presentation and was acknowledged with the Outstanding Young Researcher Award.
文摘Utilization of novel materials,particularly high-T_(c)(critical temperature)superconductors,is essential to pursue the United Nations’Sustainable Goals,as well as to meet the increasing worldwide demand for clean and carbon-free electric power technologies.Superconducting magnets are beneficial in several real-life applications including transportation,energy production,magnetic resonance imaging(MRI),and drug delivery systems.To achieve high performance,one must develop uniform,large-grain,infiltration-growth(IG)processed bulk YBa_(2)Cu_(3)O_(y)(Y-123)super-magnets.In this study,we report the magnetic and microstructural properties of a large-grain,top-seeded,IG-processed Y-123 pellet,which is 20 mm in diameter and 6 mm in height;the pellet is produced utilizing liquid Yb-123+Ba_(3)Cu_(5)O_(8) as the liquid source.All the samples cut from the top of the bulk exhibit a sharp superconducting transition(approximately 1 K wide)with the onset T_(c) of approximately 90 K.However,in the samples cut from the bottom surface,the onset T_(c) values slightly decreased to between 88 and 90 K,although still exhibiting a sharp superconducting transition.The top and bottom samples exhibited the highest remnant value of J_(c)(critical current density)at 77 K H//c-axis of 50 and 55 kA/cm^(2),respectively.The remnant J_(c) and irreversibility field values significantly fluctuated,being fairly low in some bottom samples.Scanning electron microscopy identified nanometer size Y-211(Y2BaCuO5)secondary-phase particles dispersed in the Y-123 matrix.Energy-dispersive spectroscopy clarified that the decreased both T_(c) and J_(c) for the bottom samples were attributed to liquid phase dispersion within the Y-123 phase.
文摘利用张衡一号卫星搭载的电场探测仪(Electric Field Detector,EFD)获得的VLF频段2019年电场功率谱数据,研究赤道附近区域近东西向电场的背景分布、季节变化以及与电离层背景的关系。结果表明:白天电场背景在赤道及其附近随季节呈不同波形结构,以3波、4波为主;夜间电场背景规律性稍差,仍呈随季节变化的经向波形结构分布特征;白天电场背景与电离层背景的季节变化呈高度正相关性,春秋季为峰值;夜间电场背景的季节变化特征是夏冬季峰值,与夜间电离层背景整体上呈负相关性。VLF电场功率谱观测数据与电离层观测数据在较大和较小空间尺度上的统计特征上都具有一致性。EFD载荷为电离层相关科学问题的研究及应用提供了一个可以使用的电场观测数据集。
基金Supported by the New Star Program of Beijing Science and Technology, China (Grant No. 952870400)the Beijing Municipal Commission of Education,and the Excellent Young Teachers Program of Ministry of Education, China
文摘The radial wave functions of inner electron shell and outer electron shell of a Ne atom were obtained by the approximate analytical method and tested by calculating the ground state energy of the Ne atom. The equivalent volume of electron cloud and the refractive index of Ne were calculated. The calculated refractive index agrees well with the experimental result. Relationship between the refractive index and the wave function of Ne was discovered.
