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Preliminary study on radiocarbon AMS dating of pollen

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Science China Earth Sciences 1999年第5期42卷 524-530页

作者：周卫建周杰萧家仪 d.donahue A.J.T.Jull NSF-AMS Facility University of Arizona

17 samples were collected from aeolian and lacustrine profiles within the environment sensitive zone of the Loess Plateau, and an experimental method was established which is suitable for pollen extraction from aeolian sediment. A comparative study of pollen dating was carried out using the accelerator mass spectrometry （AMS） 14C dating of known age samples, and then an experiment with the pollen concentrates was performed. The results indicate that pollen that has been deposited simultaneously with sediment in a stable environment can provide reliable ages. This technique will provide a way of improving the chronological framework for the Loess Plateau since the late Pleistocene. The 14C dating was combined with field investigations, and from the geological record within this zone, evidence was extracted of four major monsoon precipitation changes during the transition from the late Pleistocene to Holoeene.

关键词： pollen concentrates AMS14C dating paleomonsoon precipitation environment sensitive zone.

Correlation of climatic events between East Asia and Norwegian Sea during last deglaciation

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Science China Earth Sciences 1997年第5期40卷 496-501页

作者：周卫建安芷生 S.C.Porter d.donahue A.J.T.Jull department of Geology Northwest University Xi'an 710069 China State Key Laboratory of Loess and Quaternary Geology Chinese Academy of Sciences Xi'an 710054 China Quaternary Research Center University of Washington Seattle 98195 USA NSF-AMS-Facility University of Arizona Tucson 85721 USA

Using a high resolution 14C chronology, Sl C values and organic carbon content, from loess/paleosol and peat profiles in China, we can demonstrate century scale warm-cold East Asian monsoon paleoclimatic fluctuation events and significant precipitation variability within the last deglaciation. The major climatic events recognized are the Boiling (1 300-12 500 a B. P.), Older dryas (12 500-11 750 a B. P. ), Allerod (11 750-11 200 a B. P.) and Younger dryas (11 200-10 000 a B.P. ). The stratigraphic structure of the last deglaciation sediments is characterized by frequent changes in sedimentation phases reflecting climatic instability. These high frequency, rapid climatic events can correlate with fluctuations recorded by sea surface temperatures in the Norwegian Sea. This indicates a pale-oclimate teleconnection between polar, high latitude areas and East Asian monsoon areas through westerlies and the related atmospheric pressure system.

关键词： last rieglaciation East Asian monsoon paleoclimatic fluctuation loess-paleosol

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末次冰消期东亚和挪威海气候事件的对比

中国科学（d辑） 1997年第3期27卷 260-264页

作者：周卫建安芷生 S.C.Porter d.donahue A.J.T.Jull 中国科学院黄土与第四纪地质国家重点实验室西安710054 Quaternary Research Center University of Washington USA98195 NSF-AMS Facility University of Arizona USA85721

通过对黄土-古土壤和泥炭剖面的高分辨率~14C年代学以及有机质的δ^(13)C值和有机碳百分含量的研究,揭示了末次冰消期百年尺度温暖-寒冷的东亚季风气候颤动事件及其反映的有意义的降水变率.它们由波令(Bolling13～12.5ka BP),老仙女木(O... 详细信息

通过对黄土-古土壤和泥炭剖面的高分辨率~14C年代学以及有机质的δ^(13)C值和有机碳百分含量的研究,揭示了末次冰消期百年尺度温暖-寒冷的东亚季风气候颤动事件及其反映的有意义的降水变率.它们由波令(Bolling13～12.5ka BP),老仙女木(Older dryas 12.5～11.75ka BP),阿勒鲁德(Allerod 11.75～11.2 ka BP)和新仙女木(Younger dryas 11.2～10 ka BP)事件构成.其地层结构表现出多种沉积相的变化,反映了气候的不稳定性.这些高频、快速的气候事件可与挪威海海面温度记录的气候事件—一对比.反映了东亚季风气候通过西风带及与其相关的气压系统与极地.高纬地区古气候的遥相关.

关键词：末次冰消期东亚季风气候黄土古土壤古气候

若尔盖高原全新世气候变化的泥炭记录与加速器放射性碳测年

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科学通报 2001年第12期46卷 1040-1044页

作者：周卫建卢雪峰武振坤邓林 A.J.T.Jull d.donahue W.Beck 中国科学院地球环境研究所黄土与第四纪地质国家重点实验室西安710054 NSF-AMS Facility University of ArizonaArizona NSF-AMS Facility University of ArizonaArizona NSF-AMS Facility University of ArizonaArizona

对若尔盖高原泥炭沉积的可靠加速器（ＡＭＳ）～１４Ｃ测年和分辨率达１５～３０年夏季风气候代用指标序列的建立，揭示了青藏高原全新世的多次干冷事件．其中较为显著的事件分别为１２８００，１１３００，１０２００，９５８０，８... 详细信息

对若尔盖高原泥炭沉积的可靠加速器（ＡＭＳ）～１４Ｃ测年和分辨率达１５～３０年夏季风气候代用指标序列的建立，揭示了青藏高原全新世的多次干冷事件．其中较为显著的事件分别为１２８００，１１３００，１０２００，９５８０，８９００，６４００，４４００，３７００，２８００，１５００ａＢＰ（校正年龄），它们既可与高纬北大西洋浮冰碎屑事件一一对比，又可与低纬海面的一些降温事件相对应．频谱分析表明全新世的高频变化具有百年至千年尺度的准周期，反映了全新世气候的不稳定性以及百年至千年尺度的韵律在中纬度地区同样存在．

关键词：若尔盖高原全新世高分辨率记录泥炭 AMS测年气候不稳定性气候变化加速器放射性碳测年

新仙女木期沙漠/黄土过渡带高分辨率泥炭记录——东亚季风气候颤动的实例

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中国科学（d辑） 1996年第2期26卷 118-124页

作者：周卫建李小强董光荣 S.C.Porter M.Stuiver d.donahue A.J.T.Jull 中国科学院西安黄土与第四纪地质研究室中国科学院兰州沙漠研究所 Quaternary Research Center University of Washington USA 98195 NSF-AMS Facility University Arizona USA 85721

通过对气候敏感的沙漠/黄土过渡带中湖沼沉积进行高分辨率的^(14)C年代学和气候代用指标的研究,揭示了东亚季风气候存在着干冷(11.2～10.6kaBP)、湿凉(10.6～10.2kaBP)和干冷(10.2～10.0kaBP)的颤动特征。沙漠/黄土过渡带地处欧洲下风区... 详细信息

通过对气候敏感的沙漠/黄土过渡带中湖沼沉积进行高分辨率的^(14)C年代学和气候代用指标的研究,揭示了东亚季风气候存在着干冷(11.2～10.6kaBP)、湿凉(10.6～10.2kaBP)和干冷(10.2～10.0kaBP)的颤动特征。沙漠/黄土过渡带地处欧洲下风区,通过西风带与极地北大西洋气候相联系。晚冰期上述地区大气和海面温度变化引起西伯利亚～蒙古高压强度的变化,进一步影响东西区域性海-陆气压梯度的增强与减弱。因此,这一时期东亚季风气候这种百年尺度的快速颤动可视为高纬极地大陆气团与太平洋暖湿气团相互作用的写照。

关键词：沙漠黄土过渡带泥炭记录东亚季风气候变化

花粉浓缩物的加速器^(14)C年代测定初探

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中国科学（d辑） 1998年第5期28卷 453-458页

作者：周卫建周杰萧家仪 d.donahue A.J.T.Jull 黄土与第四纪地质国家重点实验室西安710054 南京师范大学南京210097 MSF_AMSFacility

在环境敏感带的风积物、湖积物剖面中采集了 1 7个样品 ,建立了适用于风积物中花粉浓缩物提取的实验方法 .将花粉浓缩物的测年结果与某些已知年代样品作了对比研究 ,进行了花粉浓缩物的加速器14 C测年的初步探索 .结果表明 ,在稳定环境... 详细信息

在环境敏感带的风积物、湖积物剖面中采集了 1 7个样品 ,建立了适用于风积物中花粉浓缩物提取的实验方法 .将花粉浓缩物的测年结果与某些已知年代样品作了对比研究 ,进行了花粉浓缩物的加速器14 C测年的初步探索 .结果表明 ,在稳定环境下与沉积物同时沉积的花粉测年具有一定的可信度 .它将为改善黄土高原晚更新世以来年代测定提供一条新的可能途径 .同时 ,将14 C测年与野外地质观察相结合 ,提取了该敏感带晚更新世向早全新世转换过程中

关键词：花粉浓缩物加速器碳同位素年代测定

Snapshot imaging of ultrashort electron bunches

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Light(Science & Applications) 2024年第7期13卷 1226-1228页

作者： Andreas döpp Ludwig-Maximilian-Universität München Am Coulombwall 185748GarchingGermany Max Planck Institut für Quantenoptik Hans-Kopfermann-Strasse 1Garching85748Germany

New measurements combine spatial and temporal information from optical transition radiation to estimate the three-dimensional structure of electron bunches from a laser wakefield accelerator.

关键词： ultrashort Snapshot electron

Influence of variable viscosity and double diffusion on the convective stability of a nanofluid flow in an inclined porous channel

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Applied Mathematics and Mechanics(English Edition) 2024年第3期45卷 563-580页

作者： N.HUMNEKAR d.SRINIVASACHARYA department of Mathematics National Institute of TechnologyWarangal 506004TelanganaIndia

The influence of variable viscosity and double diffusion on the convective stability of a nanofluid flow in an inclined porous channel is *** darcyBrinkman model is used to characterize the fluid flow dynamics in porous *** analytical solutions are obtained for the unidirectional and completely developed *** on a normal mode analysis,the generalized eigenvalue problem under a perturbed state is *** eigenvalue problem is then solved by the spectral ***,the critical Rayleigh number with the corresponding wavenumber is evaluated at the assigned values of the other flow-governing *** results show that increasing the darcy number,the Lewis number,the dufour parameter,or the Soret parameter increases the stability of the system,whereas increasing the inclination angle of the channel destabilizes the ***,the flow is the most unstable when the channel is vertically oriented.

关键词： nanofluid inclined channel variable viscosity linear stability double dif-fusion porous medium

decomposition mechanisms of nuclear-grade cationic exchange resin by advanced oxidation processes:Statistical molecular fragmentation model and dFT calculations

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Journal of Environmental Sciences 2024年第1期135卷 433-448页

作者： Xiang Meng Pierre désesquelles Lejin Xu department of Nuclear Engineering and Technology School of Energy and Power EngineeringHuazhong University of Science&TechnologyWuhan 430074China CNRS Laboratoire de Physique des Gaz et des PlasmasUniversitéParis-SaclayOrsay 91405France State Key Laboratory of Coal Combustion School of Energy and Power EngineeringHuazhong University of Science and TechnologyWuhan 430074China

The treatment and disposal of radioactive waste are presently facing great *** ion exchange resins have become a focus of attention due to their high production and serious environmental *** this paper,a simplified model of cationic exchange resin is proposed,and the degradation processes of cationic resin monomer initiated by hydroxyl radicals(·OH)are clarified by combining statistical molecular fragmentation(SMF)model and density functional theory(dFT)*** prediction of active sites indicates that the S-O bonds and the C-S bond of the sulfonic group are more likely to react during the *** meta-position of the sulfonic group on the benzene ring is the most active site,and the benzene ring without the sulfonic group has a certain *** C11-C14 and C17-C20 bonds,on the carbon skeleton,are the most easily *** is also found that dihydroxy addition and elimination reactions play a major role in the process of desulfonation,carbon skeleton cleavage and benzene ring *** decomposition mechanisms found through the combination of physical models and chemical calculations,provide theoretical guidance for the treatment of complex polycyclic aromatic hydrocarbons.

关键词： Cationic exchange resin Statistical molecular fragmentation model density functional theory Hydroxyl radical decomposition mechanism