为实现高灵敏度、低温漂的高性能电流传感器,提出将声表面波技术与磁致伸缩效应相结合的电流检测方法,分析了其敏感机理并改善其温度特性。这种声表面波电流传感器采用128°YX-Li Nb O3作为压电基片,表面覆盖SiO_2薄膜来改善器件温...为实现高灵敏度、低温漂的高性能电流传感器,提出将声表面波技术与磁致伸缩效应相结合的电流检测方法,分析了其敏感机理并改善其温度特性。这种声表面波电流传感器采用128°YX-Li Nb O3作为压电基片,表面覆盖SiO_2薄膜来改善器件温度稳定性,并溅射超磁致伸缩Tb Dy Fe薄膜以响应电流。在电流作用下,Tb Dy Fe薄膜会发生磁致伸缩效应和ΔE效应,引起声表面波相速度的改变。结合层状介质中声传播理论,分析了给定电流下层状结构中声表面波的传播特性,特别分析了Tb Dy Fe和SiO_2膜厚对传感器响应的影响。计算结果表明,Tb Dy Fe和SiO_2薄膜厚度分别为0.5μm、2μm时,该声表面波电流传感器具有最大检测灵敏度58.2 k Hz/A,有良好温度稳定性和较高的灵敏度,从而为高性能声表面波电流传感器的研制奠定理论基础。展开更多
洛阳盆地位于黄河中游,属中原腹地,史前资料丰富,是揭示河流水文系统对于季风气候变化响应规律以及研究史前大洪水事件对中国古代文化发展演变影响的理想区域。鉴于此,我们在洛阳盆地洛河流域开展广泛的野外考察,在其下游发现了全新世...洛阳盆地位于黄河中游,属中原腹地,史前资料丰富,是揭示河流水文系统对于季风气候变化响应规律以及研究史前大洪水事件对中国古代文化发展演变影响的理想区域。鉴于此,我们在洛阳盆地洛河流域开展广泛的野外考察,在其下游发现了全新世古洪水沉积剖面——太学村(TXC)剖面。对其进行细致的观察与地层划分,并重点结合地球化学元素指标,对剖面中三组古洪水泛滥沉积层(overbank flood deposits,OFD)与黄土层、古土壤层不同的地球化学特征进行了对比研究,结果表明:(1)在近代黄土层(L_(0))和古土壤层(S_(0))内,常量元素地球化学参数(残积系数、淋溶系数、退碱系数)、微量元素(Zr、Zn、Mn、Rb、Sr)含量及Rb/Sr比值的变化,受到全新世气候变化及风化成壤环境的影响;在古洪水泛滥沉积层中,常量元素地球化学参数、微量元素含量和Rb/Sr比值的变化,深受沉积物物质来源原始特征的影响;(2)古洪水泛滥沉积层的地球化学特征显著区别于近代黄土层、古土壤层,其中Zn、Mn、Rb含量及残积系数、Rb/Sr比值表现为OFD3/OFD1>S_(0)>L_(0)>OFD2;而淋溶系数、退碱系数及Zr、Sr含量则表现为OFD3/OFD1<S_(0)<L_(0)<OFD2。其中,古洪水OFD2记录的古洪水事件发生时间为4000-3800 a B.P.。这期大洪水事件对河谷平原区龙山文化晚期人们的生产生活造成了严重威胁,并使得新石器时代龙山文化晚期向青铜器时代二里头文化转折变化期间出现长达几百年的文化断层。展开更多
Heavy metal pollution is hazardous for the environment and human health.However,there are few studies of heavy metal pollution caused by historic metallurgical activity.The Laoniupo site in the Bahe River valley,Guanz...Heavy metal pollution is hazardous for the environment and human health.However,there are few studies of heavy metal pollution caused by historic metallurgical activity.The Laoniupo site in the Bahe River valley,Guanzhong Basin,China,was an important settlement of the Shang Culture(1600-1046 BCE).We studied two stratigraphic profiles at the Laoniupo site,which were used for measurements of magnetic susceptibility,heavy metal concentrations,and AMS 14C ages to provide evidence of copper smelting activity at the site during the Shang Dynasty.The Nemerow Pollution Index and Geoaccumulation Index were calculated to assess the heavy metals record(Cu,Zn,Ni,Pb,Cr,and As)in the topsoil on the loess tableland.According to the Single Pollution Index,the topsoil was slightly polluted by As and unpolluted by Cu,Zn,Ni,Pb and Cr;according to the Nemerow Composite Pollution Index the topsoil was mildly polluted;and according to the Geoaccumulation Index,the topsoil was moderately polluted by As,slightly polluted by Cu,and unpolluted by Zn,Ni,Pb and Cr_The main cause of the heavy metal pollution in the topsoil is the presence of copper slag in the cultural layers that was disturbed by modern farming activity.展开更多
通过对青藏高原东北部黄河源开展广泛细致的野外考察,选择位于玛曲段黄河左岸第二级河流阶地(T2)之上,赋存典型风成黄土-古土壤序列的达尔琼东(DEQ-E)剖面进行系统采样。在室内对采集样品进行了磁化率、烧失量、吸湿水、粒度、土壤微形...通过对青藏高原东北部黄河源开展广泛细致的野外考察,选择位于玛曲段黄河左岸第二级河流阶地(T2)之上,赋存典型风成黄土-古土壤序列的达尔琼东(DEQ-E)剖面进行系统采样。在室内对采集样品进行了磁化率、烧失量、吸湿水、粒度、土壤微形态、地球化学元素和光释光(OSL)测年等综合分析,结论表明:(1)黄河源玛曲段DEQ-E剖面地层序列由上至下依次为现代草甸土层(MS)-全新世中期古土壤层(S_(0))-全新世早期过渡性黄土层(Lt)-阶地漫滩相沉积层(T2-al);(2)黄河源玛曲段DEQ-E剖面风成黄土-古土壤序列风化成壤强度呈现出全新世中期古土壤层(S_(0))>全新世早期过渡性黄土层(Lt)>现代草甸土层(MS)的变化特征;(3)黄河源全新世的古气候演变可分为3个阶段:全新世早期(11000 a BP—9000 a BP),西风势力减弱,东亚夏季风逐步增强,气温趋于变暖,降水有所增加;全新世中期(9000 a BP—3100 a BP),东亚夏季风作用强盛,气候整体温暖湿润;全新世晚期(3100 a BP以来),东亚夏季风衰退,西风势力有所增强,导致气候转向干冷。该研究成果有助于理解青藏高原东北缘的古气候演化机制,同时对于预测未来区域气候变化具有重要的科学意义。展开更多
文摘为实现高灵敏度、低温漂的高性能电流传感器,提出将声表面波技术与磁致伸缩效应相结合的电流检测方法,分析了其敏感机理并改善其温度特性。这种声表面波电流传感器采用128°YX-Li Nb O3作为压电基片,表面覆盖SiO_2薄膜来改善器件温度稳定性,并溅射超磁致伸缩Tb Dy Fe薄膜以响应电流。在电流作用下,Tb Dy Fe薄膜会发生磁致伸缩效应和ΔE效应,引起声表面波相速度的改变。结合层状介质中声传播理论,分析了给定电流下层状结构中声表面波的传播特性,特别分析了Tb Dy Fe和SiO_2膜厚对传感器响应的影响。计算结果表明,Tb Dy Fe和SiO_2薄膜厚度分别为0.5μm、2μm时,该声表面波电流传感器具有最大检测灵敏度58.2 k Hz/A,有良好温度稳定性和较高的灵敏度,从而为高性能声表面波电流传感器的研制奠定理论基础。
文摘洛阳盆地位于黄河中游,属中原腹地,史前资料丰富,是揭示河流水文系统对于季风气候变化响应规律以及研究史前大洪水事件对中国古代文化发展演变影响的理想区域。鉴于此,我们在洛阳盆地洛河流域开展广泛的野外考察,在其下游发现了全新世古洪水沉积剖面——太学村(TXC)剖面。对其进行细致的观察与地层划分,并重点结合地球化学元素指标,对剖面中三组古洪水泛滥沉积层(overbank flood deposits,OFD)与黄土层、古土壤层不同的地球化学特征进行了对比研究,结果表明:(1)在近代黄土层(L_(0))和古土壤层(S_(0))内,常量元素地球化学参数(残积系数、淋溶系数、退碱系数)、微量元素(Zr、Zn、Mn、Rb、Sr)含量及Rb/Sr比值的变化,受到全新世气候变化及风化成壤环境的影响;在古洪水泛滥沉积层中,常量元素地球化学参数、微量元素含量和Rb/Sr比值的变化,深受沉积物物质来源原始特征的影响;(2)古洪水泛滥沉积层的地球化学特征显著区别于近代黄土层、古土壤层,其中Zn、Mn、Rb含量及残积系数、Rb/Sr比值表现为OFD3/OFD1>S_(0)>L_(0)>OFD2;而淋溶系数、退碱系数及Zr、Sr含量则表现为OFD3/OFD1<S_(0)<L_(0)<OFD2。其中,古洪水OFD2记录的古洪水事件发生时间为4000-3800 a B.P.。这期大洪水事件对河谷平原区龙山文化晚期人们的生产生活造成了严重威胁,并使得新石器时代龙山文化晚期向青铜器时代二里头文化转折变化期间出现长达几百年的文化断层。
基金National Natural Science Foundation of China,No.41801060The Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA20060201The Open Foundation of the Key Laboratory of Cultural Heritage Research and Conservation of the Education Ministry in Northwest University of China,No.GXYDFA2018XBD003,No.WYSYS2019。
文摘Heavy metal pollution is hazardous for the environment and human health.However,there are few studies of heavy metal pollution caused by historic metallurgical activity.The Laoniupo site in the Bahe River valley,Guanzhong Basin,China,was an important settlement of the Shang Culture(1600-1046 BCE).We studied two stratigraphic profiles at the Laoniupo site,which were used for measurements of magnetic susceptibility,heavy metal concentrations,and AMS 14C ages to provide evidence of copper smelting activity at the site during the Shang Dynasty.The Nemerow Pollution Index and Geoaccumulation Index were calculated to assess the heavy metals record(Cu,Zn,Ni,Pb,Cr,and As)in the topsoil on the loess tableland.According to the Single Pollution Index,the topsoil was slightly polluted by As and unpolluted by Cu,Zn,Ni,Pb and Cr;according to the Nemerow Composite Pollution Index the topsoil was mildly polluted;and according to the Geoaccumulation Index,the topsoil was moderately polluted by As,slightly polluted by Cu,and unpolluted by Zn,Ni,Pb and Cr_The main cause of the heavy metal pollution in the topsoil is the presence of copper slag in the cultural layers that was disturbed by modern farming activity.
文摘通过对青藏高原东北部黄河源开展广泛细致的野外考察,选择位于玛曲段黄河左岸第二级河流阶地(T2)之上,赋存典型风成黄土-古土壤序列的达尔琼东(DEQ-E)剖面进行系统采样。在室内对采集样品进行了磁化率、烧失量、吸湿水、粒度、土壤微形态、地球化学元素和光释光(OSL)测年等综合分析,结论表明:(1)黄河源玛曲段DEQ-E剖面地层序列由上至下依次为现代草甸土层(MS)-全新世中期古土壤层(S_(0))-全新世早期过渡性黄土层(Lt)-阶地漫滩相沉积层(T2-al);(2)黄河源玛曲段DEQ-E剖面风成黄土-古土壤序列风化成壤强度呈现出全新世中期古土壤层(S_(0))>全新世早期过渡性黄土层(Lt)>现代草甸土层(MS)的变化特征;(3)黄河源全新世的古气候演变可分为3个阶段:全新世早期(11000 a BP—9000 a BP),西风势力减弱,东亚夏季风逐步增强,气温趋于变暖,降水有所增加;全新世中期(9000 a BP—3100 a BP),东亚夏季风作用强盛,气候整体温暖湿润;全新世晚期(3100 a BP以来),东亚夏季风衰退,西风势力有所增强,导致气候转向干冷。该研究成果有助于理解青藏高原东北缘的古气候演化机制,同时对于预测未来区域气候变化具有重要的科学意义。
