对云中微物理过程的研究是研究云降水形成过程和人工影响降水的重要基础,目前对积层混合云的对流区/对流泡中的微物理结构了解甚少。本文利用河北省"十三五"气象重点工程--云水资源开发利用工程的示范项目(2017~2019年)"...对云中微物理过程的研究是研究云降水形成过程和人工影响降水的重要基础,目前对积层混合云的对流区/对流泡中的微物理结构了解甚少。本文利用河北省"十三五"气象重点工程--云水资源开发利用工程的示范项目(2017~2019年)"太行山东麓人工增雨防雹作业技术试验"飞机和地面雷达观测数据,重点分析研究了2017年5月22日一次典型稳定性积层混合云对流泡和融化层的结构特征。研究结果表明,此次积层混合云高层存在高浓度大冰粒子,冰粒子下落过程中的增长在不同区域存在明显差异,在含有高过冷水含量的对流泡中,冰粒子增长主要是聚并和凇附增长,而在过冷水含量较低的云区以聚并增长为主。由于聚并增长形成的大冰粒子密度低,下落速度小,穿过0℃层时间更长,出现大量半融化的冰粒子,使融化现象更为明显。镶嵌在层状云中的对流泡一般处于0℃^-10℃(高度4~6 km)层之间,垂直和水平尺度约2 km,最大上升气流速度可达5 m s^-1。对流泡内平均液态水含量是周围云区的2倍左右,小云粒子平均浓度比周围云区高一个量级,大粒子(直径800μm以上)的浓度也更高。在具有较高过冷水含量的对流泡中降水形成符合"播撒-供给"机制,但在过冷水含量较低的区域并不符合这一机制。展开更多
In this study, the Pb/U fractionation between zircon and uraninite during femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry （fs-LA-ICP-MS） analysis was studied in detail. The results show signi...In this study, the Pb/U fractionation between zircon and uraninite during femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry （fs-LA-ICP-MS） analysis was studied in detail. The results show significant Pb/U fractionation between zircon and uraninite during fs-LA-ICP-MS analysis that when calibrated against the zircon standard M257, the obtained U-Pb age of the Chinese national uraninite standard GBW04420 is 17% older than the recommended value. Thus, the accurate in-situ U-Pb dating of uraninite by LA-ICP-MS requires matrix-matched external standards for calibration. Uraninite in thin sections of two U-mineralized leucogranite from the Gaudeanmus in Namibia was analyzed by a fs-LA-ICP-MS equipped with a Signal Smooth Device （SSD）, using laser spot and frequency of 10 μm and 1 Hz, respectively. When calibrated using GBW04420 as the external standard, two samples give weighted mean 2066pb/238U ages of 504±3 Ma （2σ, n=21） and 503±3 Ma （2σ, n=22）, and only one of two samples yields a concordia U-Pb age of 507±1 Ma （2or, n=21）. These results are consistent with ID-TIMS U-Pb ages of 509±1 and 508±12 Ma and are also indistinguishable from zircon U-Pb upper intercept ages of 506±33 Ma （2σ, n=29） and 501±51 Ma （2σ, n=29）. The present study shows that in-situ U-Pb dating of uraninite can deliver more reliable formation ages of the deposit than dating coeval high-U zircon because the latter commonly suffer significant Pb loss after formation. Our results confirm that GBW04420 is an ideal matrix matching standard for in-situ U-Pb dating of uraninite.展开更多
The 1.4–1.8μm eye-safe lasers have been widely used in the fields of laser medicine and laser detection and ranging.The diamond Raman lasers are capable of delivering excellent characteristics,such as good beam qual...The 1.4–1.8μm eye-safe lasers have been widely used in the fields of laser medicine and laser detection and ranging.The diamond Raman lasers are capable of delivering excellent characteristics,such as good beam quality concomitantly with high output power.The intra-cavity diamond Raman lasers have the advantages of compactness and low Raman thresholds compared to the external-cavity Raman lasers.However,to date,the intra-cavity diamond cascaded Raman lasers in the spectral region of the eye-safe laser have an output power of only a few hundred milliwatts.A 1485 nm Nd:YVO_4/diamond intra-cavity cascaded Raman laser is reported in this paper.The mode matching and stability of the cavity were optimally designed by a V-shaped folded cavity,which yielded an average output power of up to 2.2 W at a pulse repetition frequency of 50 kHz with a diode to second-Stokes conversion efficiency of 8.1%.Meanwhile,the pulse width of the second-Stokes laser was drastically reduced from 60 ns of the fundamental laser to 1.1 ns,which resulted in a high peak power of 40 kW.The device also exhibited single longitudinal mode with a narrow spectral width of<0.02 nm.展开更多
文摘对云中微物理过程的研究是研究云降水形成过程和人工影响降水的重要基础,目前对积层混合云的对流区/对流泡中的微物理结构了解甚少。本文利用河北省"十三五"气象重点工程--云水资源开发利用工程的示范项目(2017~2019年)"太行山东麓人工增雨防雹作业技术试验"飞机和地面雷达观测数据,重点分析研究了2017年5月22日一次典型稳定性积层混合云对流泡和融化层的结构特征。研究结果表明,此次积层混合云高层存在高浓度大冰粒子,冰粒子下落过程中的增长在不同区域存在明显差异,在含有高过冷水含量的对流泡中,冰粒子增长主要是聚并和凇附增长,而在过冷水含量较低的云区以聚并增长为主。由于聚并增长形成的大冰粒子密度低,下落速度小,穿过0℃层时间更长,出现大量半融化的冰粒子,使融化现象更为明显。镶嵌在层状云中的对流泡一般处于0℃^-10℃(高度4~6 km)层之间,垂直和水平尺度约2 km,最大上升气流速度可达5 m s^-1。对流泡内平均液态水含量是周围云区的2倍左右,小云粒子平均浓度比周围云区高一个量级,大粒子(直径800μm以上)的浓度也更高。在具有较高过冷水含量的对流泡中降水形成符合"播撒-供给"机制,但在过冷水含量较低的区域并不符合这一机制。
基金supported by the National Natural Science Foundation of China(Grant Nos.41203027 and 41473031)the State Administration of Foreign Expert Affairs of China(Grant No.B07039)the Special Fund for Basic Scientific Research of Central Colleges,China University of Geosciences(Wuhan)(Grant No.CUGL140403)
文摘In this study, the Pb/U fractionation between zircon and uraninite during femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry （fs-LA-ICP-MS） analysis was studied in detail. The results show significant Pb/U fractionation between zircon and uraninite during fs-LA-ICP-MS analysis that when calibrated against the zircon standard M257, the obtained U-Pb age of the Chinese national uraninite standard GBW04420 is 17% older than the recommended value. Thus, the accurate in-situ U-Pb dating of uraninite by LA-ICP-MS requires matrix-matched external standards for calibration. Uraninite in thin sections of two U-mineralized leucogranite from the Gaudeanmus in Namibia was analyzed by a fs-LA-ICP-MS equipped with a Signal Smooth Device （SSD）, using laser spot and frequency of 10 μm and 1 Hz, respectively. When calibrated using GBW04420 as the external standard, two samples give weighted mean 2066pb/238U ages of 504±3 Ma （2σ, n=21） and 503±3 Ma （2σ, n=22）, and only one of two samples yields a concordia U-Pb age of 507±1 Ma （2or, n=21）. These results are consistent with ID-TIMS U-Pb ages of 509±1 and 508±12 Ma and are also indistinguishable from zircon U-Pb upper intercept ages of 506±33 Ma （2σ, n=29） and 501±51 Ma （2σ, n=29）. The present study shows that in-situ U-Pb dating of uraninite can deliver more reliable formation ages of the deposit than dating coeval high-U zircon because the latter commonly suffer significant Pb loss after formation. Our results confirm that GBW04420 is an ideal matrix matching standard for in-situ U-Pb dating of uraninite.
基金financially supported by the Science and Technology Major Project of Henan Province(No.221100230300)the National Natural Science Foundation of China(No.11774301)。
文摘The 1.4–1.8μm eye-safe lasers have been widely used in the fields of laser medicine and laser detection and ranging.The diamond Raman lasers are capable of delivering excellent characteristics,such as good beam quality concomitantly with high output power.The intra-cavity diamond Raman lasers have the advantages of compactness and low Raman thresholds compared to the external-cavity Raman lasers.However,to date,the intra-cavity diamond cascaded Raman lasers in the spectral region of the eye-safe laser have an output power of only a few hundred milliwatts.A 1485 nm Nd:YVO_4/diamond intra-cavity cascaded Raman laser is reported in this paper.The mode matching and stability of the cavity were optimally designed by a V-shaped folded cavity,which yielded an average output power of up to 2.2 W at a pulse repetition frequency of 50 kHz with a diode to second-Stokes conversion efficiency of 8.1%.Meanwhile,the pulse width of the second-Stokes laser was drastically reduced from 60 ns of the fundamental laser to 1.1 ns,which resulted in a high peak power of 40 kW.The device also exhibited single longitudinal mode with a narrow spectral width of<0.02 nm.
