Marine diatoms of the Xisha Islands, South China Sea Mastogloia Thw, Ex, Wm, Smith: species of Group Ellipticae     

Liu Shicheng 《海洋学报(英文版)》1995,14(1):59-71

ＭａｒｉｎｅｄｉａｔｏｍｓｏｆｔｈｅＸｉｓｈａＩｓｌａｎｄｓ，ＳｏｕｔｈＣｈｉｎａＳｅａＭａｓｔｏｇｌｏｉａＴｈｗ，Ｅｘ，Ｗｍ，Ｓｍｉｔｈ：ｓｐｅｃｉｅｓｏｆＧｒｏｕｐＥｌｌｉｐｔｉｃａｅ￥ＬｉｕＳｈｉｃｈｅｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＢｉｏｌｏｇ...  相似文献   

东海黑潮混沌特征的数值分析     

山峰  林霄沛  吴德星 《中国海洋大学学报(自然科学版)》2003,33(1):15-21

以英国 OCCAM(The Ocean Circulation and Climate Advanced Modeling Project)全球环流模式的 1 994年计算结果作为初始场和边界条件 ,用 POM模式 ,对东中国海黑潮季节变化进行了数值模拟 ,特别注意了海水运动的混沌特点和质点移动轨迹。研究结果表明 :东海黑潮区地形引起的黑潮流剪切是导致混沌的主要原因 ;东海黑潮区混沌运动有明显的季节变化 ;黑潮主轴区基本是输运的屏障区。  相似文献   

Hygroscopic growth of aerosol particles and its influence on nucleation scavenging in cloud: Experimental results from Kleiner Feldberg   总被引：8，自引：0，他引：8  

Birgitta Svenningsson  Hans-Christen Hansson  Alfred Wiedensohler  Kevin Noone  John Ogren  Anneli Hallberg  Roy Colvile 《Journal of Atmospheric Chemistry》1994,19(1-2):129-152

The hygroscopic growth of individual aerosol particles has been measured with a Tandem Differential Mobility Analyser. The hygroscopic growth spectra were analysed in terms of diameter change with increasing RH from 20% to 85%. The measurements were carried out during the GCE cloud experiment at Kleiner Feldberg, Taunus, Germany in October and November 1990.Two groups of particles with different hygroscopic growth were observed. The less-hygroscopic group had average growth factors of 1.11, 1.04 and 1.02 for particle diameters of 50, 150 and 300 nm, respectively. The more-hygroscopic group had average growth factors of 1.34, 1.34, and 1.37 for the same particle diameters. The average fraction of less-hygroscopic particles was about 50%. Estimates of the soluble fractions of the particles belonging to the two groups are reported.Hygroscopic growth spectra for total aerosol, interstitial aerosol and cloud drop residuals were measured. A comparison of these hygroscopic growths of individual aerosol particles provides clear evidence for the importance of hygroscopic growth in nucleation scavenging. The measured scavenged fraction of particles as a function of diameter can be explained by the hygroscopic growth spectra.  相似文献   

利用相控阵及双偏振雷达对2016年6月3日华南一次强对流过程的分析   总被引：3，自引：3，他引：0  

于明慧  刘黎平  吴翀  肖艳娇 《气象》2019,45(3):330-344

本文结合X波段相控阵雷达(XPAR)和S波段双偏振天气雷达(SPOL)及地面和探空观测资料,分析了2016年6月3日发生在华南的一次超级单体中小尺度特征,结果表明：(1)SPOL的多普勒参量和双偏振参量可以观测到超级单体的强度、速度和相态分布,超级单体的入流和出流影响钩状回波的形成。(2)XPAR可以获取时空分辨率远高于SPOL的观测资料,可以弥补SPOL仰角层严重不足的缺陷,观测到超级单体完整的垂直结构,可更精确地描述超级单体的短时演变。(3)超级单体钩状回波附近给地面带来了降温、大风和强降水,超级单体经过地区均有明显降温和风区。研究结果证明相控阵雷达和双偏振雷达对认识对流单体中小尺度系统的发展演变有较大帮助。  相似文献   

SIMULATED FINE STRUCTURES OF SPIRAL RAINBANDS IN TYPHOON CHANCHU (2006)     

王咏青  蔡敏敏  葛旭阳 《热带气象学报(英文版)》2019,25(2):141-152

In this study, fine structures of spiral rainbands in super Typhoon Chanchu (2006) are examined using an Advanced Research Weather Research and Forecast (WRF-ARW) model simulation with the finest grid size of 2 km. Results show that the simulation reproduces well Typhoon Chanchu’s track, intensity and basic structures. According to their locations and features, spiral rainbands are classified into principal, secondary, inner and distant rainbands, and their dynamic and thermodynamic features are investigated. The principal rainbands remain quasi-stationary with respect to Chanchu’s center and exhibit a wavenumber-1 feature with their outer edges separated by dry air. The secondary rainbands that occur on the radially inward side of the principal rainbands move around Chanchu''s center. The inner rainbands are closest to the center. They propagate both radially outward and azimuthally with time. The distant rainbands are located outside the inner-core region, and have stronger and continuous updrafts compared to the other rainbands. Distant rainbands are inward-sloping with height along the radial direction and have a cold pool in the low layers, whereas the principal and secondary rainbands lean radially outward with height. The inner rainbands do not show tilting with height along the radial direction. However, there are few vertical tilting cells along the azimuthal orientation among the four types of rainbands. The simulated radar reflectivity cores in all rainbands are collocated with the maxima of updrafts and equivalent potential temperatures in the low layer, indicating the important roles of energy supply in the boundary layer in determining the development of the rainband convection.  相似文献   

南方山地丘陵区典型地质灾害成因机制与风险评价     

铁永波  孙强  徐勇  张勇  魏云杰  杨秀元  张泰丽  谭建民 《中国地质调查》2022,9(4):1-9

南方山地丘陵区地域跨度大,地质灾害孕灾背景复杂、成灾模式多样,是我国地质灾害高易发区。针对南方山地丘陵区地质灾害潜在风险高的问题,在中国地质调查局“南方山地丘陵区地质灾害调查工程”实施进展基础上,对南方山地丘陵区地质灾害控灾的气候动力特征及地质构造背景进行了系统分析,对典型地质灾害成灾模式和多尺度风险调查评价示范性成果进行了总结,揭示了东南沿海地区典型台风地质灾害、南方岩溶塌陷、西南高寒山区冰碛土泥石流及川西高原区火后泥石流形成机理与物源侵蚀机制。在此基础上,开展了南方山地丘陵区基于县域、重点城镇及典型灾害点的多尺度地质灾害风险评价应用示范,相关成果在西南重大工程规划选线及县城搬迁选址中得到应用。  相似文献   

基于零膨胀贝叶斯时空建模的精细尺度伪基站垃圾短信分析方法     

史雨飞  陶海燕  卓莉 《地球信息科学学报》2022,24(11):2089-2101

伪基站垃圾短信活动存在显著的时空自相关和异质性现象,采用时空分析方法可以精准把握伪基站的移动规律和行为模式,为相关部门综合施策、探索长效管理机制提供科学的依据。然而,精细尺度下垃圾短信数据集中过多零数据导致的零膨胀问题,使当前的时空分析方法并不适用。为此,本文以2017年2月23日至2017年4月26日北京市色情服务类垃圾短信数据为例,构建零膨胀贝叶斯时空模型,不仅可以解决零膨胀问题,而且可以综合分析伪基站的空间、时间、时空效应以及外部影响因素,以识别伪基站活动的相对风险高值区、探究城市建成环境对其的影响。结果发现：在数据集中零值占比高达83.46%的情况下,基于零膨胀泊松分布的贝叶斯时空模型具有更好的拟合精度;色情服务类垃圾短信空间上的高风险区域主要聚集在北京市主城区的东部,风险值最高的区域属于朝阳区;周四、五、六风险趋势会相对增加,且18:00至次日02:00为高发时期;伪基站一般18:00从主城区的西南部开始向东北方向移动,凌晨01:00聚集在朝阳区西北部区域;商务住宅与住宿服务类城市环境与垃圾短信呈正相关,餐饮服务与派出所类城市环境呈负相关。研究表明,零膨胀贝叶斯时空模型为精细尺度的伪基站垃圾短信研究,提供了一个可以有效整合多个时间截面的分析数据、充分考虑伪基站的时空关系和外部影响因素并解决数据中存在零过多现象的方法,为发展和验证伪基站的环境犯罪学理论提供了一种重要的分析方法。  相似文献   

Optically stimulated luminescence dating of loess in South-Eastern China using quartz and polymineral fine grains     

《Quaternary Geochronology》2022

Loess deposits distributed in southeastern China play an important role for paleoclimate reconstruction of the subtropical regions. These loess-paleosol deposits are mainly spread within the middle and lower reaches of the Yangtze River as well as in the drainage area of the Huai River. The ages of loess paleosol sequences that are distributed along the Huai River are not well constrained. In this study, the standard single-aliquot regenerative dose (SAR) optically stimulated luminescence (OSL) protocol and two elevated temperature post infrared-infrared stimulated luminescence SAR protocols (pIRIR₂₂₅ and pIRIR₂₉₀) were applied on 4–11 μm quartz and polymineral fine grains, respectively, in order to obtain the first numerical luminescence chronology for a loess-paleosol sequence in northern Jiangsu Province. Our results show a good agreement between quartz SAR-OSL and polymineral pIRIR ages up to ~70 ka. These findings confirm that Xiashu loess accumulated during the Last Glaciation. For samples older than this, the ages increasingly deviate with depth. Fine quartz ages beyond 70 ka are interpreted as underestimates, as previous studies reported that quartz ages >70 ka from various sedimentary origins worldwide may underestimate even if they pass rejection criteria and dose recovery tests. On the other hand, the pIRIR ages are most likely overestimating the true depositional ages as indicated by the results of dose recovery tests, where a 30–60% overestimation of the recovered dose is reported for values larger than ~400 Gy. The overestimation of pIRIR protocols was also confirmed by the results obtained when large beta doses were added on top of the natural accrued dose. Moreover, our dating results suggest that L1/S1 transition (corresponding to MIS 5/4 boundary) occurred much higher in the stratigraphic sequence than may have been interpreted from the magnetic susceptibility enhancement. This inconsistency can be assigned to invalidity of magnetic susceptibility as a chronostratigraphical proxy due to ferrimagnetic minerals dissolution or transformation during paedogenesis processes in this humid subtropical region in the southeastern China.  相似文献   

精细油藏描述研究进展   总被引：7，自引：0，他引：7  

陈欢庆  石成方  曹晨 《地质论评》2015,61(5):1135-1146

从国内外研究现状人手,详细介绍了目前精细油藏描述研究的现状。国外研究的重点已由常规的野外露头分析、实验分析、数值模拟向地震反演储层预测、微地震方法储层表征、人工智能神经网络等新技术新方法转变,研究对象也由传统的砂岩和碳酸盐岩向致密油致密气储层转变。研究方法中综合性、地震技术以及计算机技术进一步加强。天然裂缝储层表征等专项研究进步很大。国内已经从最初的简单模仿学习国外油藏描述研究方法,发展形成了一整套较为成熟的精细油藏描述程序和方法,研究内容也比较全面完善,几乎涵盖了储层地质研究的各个方面。结合研究自身实践,将精细油藏描述研究总结为高分辨率层系地层学指导下的地层精细划分与对比、沉积成因分析基础上的储层构型分析、储层定量分类评价、储层流动单元研究和储层地质建模研究等5个关键问题。在此基础上分析了精细油藏描述研究存在的问题,认为目前精细油藏描述定量研究还需要加强,各种地震和测井等新技术手段有待加强,实验技术、多点地质统计学建模等方面还需发展完善。储层在开发过程中的变化研究等还未引起足够的重视。最后针对上述问题指出了该项研究8个方面的发展趋势。  相似文献   

Speciation Study of Cr in a Geochemical Reference Material Sediment Series Using Sequential Extraction and XANES Spectroscopy          下载免费PDF全文

Atsuyuki Ohta 《Geostandards and Geoanalytical Research》2015,39(1):87-103

Speciation of Cr in geochemical reference materials was characterised by sequential extraction and X‐ray absorption near‐edge structure (XANES) spectroscopy to identify Cr(III) resulting from the reduction of pollutant Cr(VI). Sequential extraction suggested that the amount of Cr associated with an acetic acid soluble fraction was low; Cr associated with a reducible phase and an oxidisable phase was extracted at 5–10% of the total Cr concentration, and the residual phase was found to be the dominant Cr‐containing fraction. Cr speciation in soil artificially doped with Cr(VI) and sediment samples collected from highly populated and industrialised areas was different from that in naturally occurring materials. Substantial Cr was extracted as a reducible phase (15–30%) and an oxidisable phase (30–60%) for these samples. Through subsequent XANES spectroscopy analysis, the reducible phase was explained by Cr bound to Fe hydroxide, while the oxidisable phase was a mixture of Cr bound to humic substances and Cr hydroxides. That is, Cr(VI) present as a contaminant in sediments and soils was reduced to Cr(III), which then bound to Fe hydroxide and humic substances, precipitating as a hydroxide. Thus, a combination of sequential extraction and XANES spectroscopy allows for effective identification and quantification of the chemical forms of Cr in sediments and soils.  相似文献