2003年江淮流域强降水过程与30—70d天低频振荡的联系   总被引：9，自引：1，他引：8  

夏芸  管兆勇  王黎娟 《南京气象学院学报》2008,31(1):33-41

利用NCEP／NCAR再分析和地面观测站的逐日降水资料,研究了2003年夏季江淮流域强降水过程与低频振荡的联系。结果显示,主周期为30～70d的低频振荡对2003年江淮流域暴雨的形成具有重要贡献：低频涡旋在江淮地区降水期的对流层高、低层呈负、正配置,具有斜压结构,利于降水发生;850hPa上正涡度系统的传播具有明显的北传和西传特征;存在于西太平洋、西北太平洋及其以东地区的低频波列（P—J）的活动过程影响了我国2003年江淮低频强降水的形成;整层低频水汽通量显示来自副热带高压外围的西南季风对水汽输送的贡献较显著,且2003年江淮地区30-70d时间尺度上降水的水汽来源为南海而非孟加拉湾或西太平洋。  相似文献   

年轻星天体的质量     

尹佳  江治波 《天文学进展》2009,27(4)

质量是恒星最基本、最重要的物理量之一,它在恒星形成和演化过程中起着至关重要的作用.年轻星天体的形成机制以及早期演化过程是彻底解决恒星形成问题的关键所在,而年轻星天体形成过程中的物质下落、质量吸积以及外流等物理过程都与年轻星天体的质量密切相关.该文介绍了确定年轻星天体质量的一些常用方法,包括利用开普勒定律的动力学方法、赫罗图方法、年轻星天体脉动方法和磁层吸积方法等.并对这些方法的适用范围及测量精度进行了评述,还综述了各种方法的研究进展及未来可能的发展.  相似文献   

The old metal-poor open cluster ESO 92-SC05: accreted from a dwarf galaxy?     

S. Ortolani †  E. Bica  B. Barbuy 《Monthly notices of the Royal Astronomical Society》2008,388(2):723-728

The study of old open clusters outside the solar circle can bring constraints on formation scenarios of the outer disc. In particular, accretion of dwarf galaxies has been proposed as a likely mechanism in the area. We use BVI photometry for determining fundamental parameters of the faint open cluster ESO 92-SC05. Colour–magnitude diagrams are compared with Padova isochrones, in order to derive age, reddening and distance. We derive a reddening   E ( B − V ) = 0.17  , and an old age of ∼6.0 Gyr. It is one of the rare open clusters known to be older than 5 Gyr. A metallicity of   Z ∼ 0.004  or  [M/H]∼−0.7  is found. The rather low metallicity suggests that this cluster might be the result of an accretion episode of a dwarf galaxy.  相似文献   

Acoustic-Gravity Waves from Bolide Sources     

Douglas O. ReVelle 《Earth, Moon, and Planets》2008,102(1-4):345-356

We have developed a new approach to modeling the acoustic-gravity wave (AGW) radiation from bolide sources. This first effort involves entry modeling of bolide sources that have available satellite data through procedures developed in ReVelle (Earth Moon Planets 95, 441–476, 2004a; in: A. Milani, G. Valsecchi, D. Vokrouhlicky (eds) NEO Fireball Diversity: Energetics-based Entry Modeling and Analysis Techniques, Near-earth Objects: Our Celestial Neighbors (IAU S236), 2007b). Results from the entry modeling are directly coupled to AGW production through line source blast wave theory for the initial wave amplitude and period at (at 10 blast wave radii and perpendicular to the trajectory). The second effort involves the prediction of the formation and or dominance of the propagation of the atmospheric Lamb, edge-wave composite mode in a viscous fluid (Pierce, J. Acoust. Soc. Amer. 35, 1798–1807, 1963) as a function of the source energy, horizontal range and source altitude using the Lamb wave frequency that was deduced directly during the entry modeling and that is used as a surrogate for the source energy. We have also determined that Lamb wave production by bolides at close range decreases dramatically as either the source energy decreases or the source altitude increases. Finally using procedures in Gill (Atmospheric-Ocean Dynamics, 1982) and in Tolstoy (Wave Propagation, 1973), we have analyzed two simple dispersion relationships and have calculated the expected dispersion for the Lamb edge-wave mode and for the excited, propagating internal acoustic waves. Finally, we have used the above formalism to fully evaluate these techniques for four large bolides, namely: the Tunguska bolide of June 30, 1908; the Revelstoke bolide of March 31, 1965; the Crete bolide of June 6, 2002 and the Antarctic bolide of September 3, 2004. Due to page limitations, we will only present results in detail for the Revelstoke bolide.  相似文献   

湖南临湘虎形山矿区蚀变地球化学过程研究          下载免费PDF全文

刘烨  赖健清  徐军伟  肖文舟 《地质找矿论丛》2019,34(2):187-195

湖南省临湘市虎形山钨矿是近年来新发现的大型钨铍矿床。矿区内围岩蚀变类型较多,主要有云英岩化、硅化、绢云母化、碳酸盐化、绿泥石化等。为了探究矿区围岩蚀变与成矿的关系,对蚀变硅质板岩分别作了主微量元素分析,通过元素相关性分析探究了各元素的迁移特征,并探讨了主要蚀变过程中出现的矿化类型以及矿化过程中一些金属矿物的生成顺序;利用标准化Isocon图解法,对围岩蚀变过程中组分的带入带出进行质量平衡计算。研究结果表明,板岩中组分迁移受绢云母化影响强烈,其中云英岩化与成矿关系最为密切,碳酸盐化与钨矿化也有一定联系。通过对湘东北地区、虎形山矿区冷家溪群和上地壳W、Cu、Pb、Zn、As、Sb丰度值的对比,反映了矿区地层富含成矿物质,但并未给成矿提供物质来源。  相似文献   

A comparison of neighbourhood relations based on ordinary Delaunay diagrams and area Delaunay diagrams: an application to define the neighbourhood relations of buildings     

Hiroyuki Usui  Akihiro Teraki  Kei-ichi Okunuki  Toshiaki Satoh 《International journal of geographical information science》2020,34(11):2177-2203

ABSTRACT

The aim of this article is to describe a convenient but robust method for defining neighbourhood relations among buildings based on ordinary Delaunay diagrams (ODDs) and area Delaunay diagrams (ADDs). ODDs and ADDs are defined as a set of edges connecting the generators of adjacent ordinary Voronoi cells (points representing centroids of building polygons) and a set of edges connecting two centroids of building polygons, which are the generators of adjacent area Voronoi cells, respectively. Although ADDs are more robust than ODDs, computation time of ODDs is shorter than that of ADDs (the order of their computation time complexity is O(nlogn)). If ODDs can approximate ADDs with a certain degree of accuracy, the former can be used as an alternative. Therefore, we computed the ratio of the number of ADD edges to that of ODD edges overlapping ADDs at building and regional scales. The results indicate that: (1) for approximately 60% of all buildings, ODDs can exactly overlap ADDs with extra ODD edges; (2) at a regional scale, ODDs can overlap approximately 90% of ADDs with 10% extra ODD edges; and (3) focusing on judging errors, although ADDs are more accurate than ODDs, the difference is only approximately 1%.  相似文献   

基于SuperMap的空间大数据可视化技术研究与应用     

崔雪  云惟英  周强  冯振华  陈颖  张振琦 《测绘与空间地理信息》2017,40(Z1)

人类正从IT时代走向DT时代,诸多的技术手段使大数据处理技术能够从大规模数据中分析出相关模式或趋势,让我们对海量数据的价值挖掘充满了期待.当可视化呈现让大数据的潜力达到最大时,以往未被观察到的现象或趋势很容易被发现,用户能够快速地获得更多信息,发现他们所需要的价值.因此,如何最大化地呈现大数据中隐含的价值变得尤为关键.本文将重点研究空间大数据的可视化方法,充分发挥数据可视化的作用,帮助用户挖掘隐藏在空间大数据中的价值.  相似文献   

Point grid map: a new type of thematic map for statistical data associated with geographic points     

Mengjie Zhou  Fuquan Xiong  Rui Wang 《制图学和地理信息科学》2017,44(5):374-389

ABSTRACT

Social, economic, and environmental statistical data associated with geographic points are currently globally available in large amounts. When conventional thematic maps, such as proportional symbol maps or point diagram maps, are used to represent these data, the maps appear cluttered if the point data volumes are relatively large or cover a relatively dense region. To overcome these limitations, we propose a new type of thematic map for statistical data associated with geographic points: the point grid map. In a point grid map, an input point data set is transformed into a grid in which each point is represented by a square grid cell of equal size while preserving the relative position of each point, which leads to a clear and uncluttered appearance, and the grid cells can be shaded or patterned with symbols or diagrams according to the attributes of the points. We present an algorithm to construct a point grid map and test it with several simulated and real data sets. Furthermore, we present some variants of the point grid map.  相似文献   

Cultivated land change in the Belt and Road Initiative region   总被引：3，自引：1，他引：2  

Di Chen  Qiangyi Yu  Qiong Hu  Mingtao Xiang  Qingbo Zhou  Wenbin Wu 《地理学报(英文版)》2018,28(11):1580-1594

The Belt and Road Initiative (BRI)–a development strategy proposed by China – provides unprecedented opportunities for multi-dimensional communication and cooperation across Asia, Africa and Europe. In this study, we analyse the spatio-temporal changes in cultivated land in the BRI countries (64 in total) to better understand the land use status of China along with its periphery for targeting specific collaboration. We apply FAO statistics and GlobeLand30 (the world’s finest land cover data at a 30-m resolution), and develop three indicator groups (namely quantity, conversion, and utilization degree) for the analysis. The results show that cultivated land area in the BRI region increased 3.73×10⁴ km² between 2000 and 2010. The increased cultivated land was mainly found in Central and Eastern Europe and Southeast Asia, while the decreased cultivated land was mostly concentrated in China. Russia ranks first with an increase of 1.59×10⁴ km² cultivated land area, followed by Hungary (0.66×10⁴ km²) and India (0.57×104 km2). China decreased 1.95×10⁴ km² cultivated land area, followed by Bangladesh (–0.22×10⁴ km²) and Thailand (–0.22×10⁴ km²). Cultivated land was mainly transferred to/from forest, grassland, artificial surfaces and bare land, and transfer types in different regions have different characteristics: while large amount of cultivated land in China was converted to artificial surfaces, considerable forest was converted to cultivated land in Southeast Asia. The increase of multi-cropping index dominated the region except the Central and Eastern Europe, while the increase of fragmentation index was prevailing in the region except for a few South Asian countries. Our results indicate that the negative consequence of cultivated land loss in China might be underestimated by the domestic- focused studies, as none of its close neighbours experienced such obvious cultivated land losses. Nevertheless, the increased cultivated land area in Southeast Asia and the extensive cultivated land use in Ukraine and Russia imply that the regional food production would be greatly improved if China’ “Go Out policy” would help those countries to intensify their cultivated land use.  相似文献   

CINRAD/SA(B)发射机触发器芯片级故障诊断流程     

潘新民  尹春光  崔炳俭  弓宇恒 《气象科技》2018,46(3):443-449

发射机触发放大器主要为调制器中SCR开关管提供放电触发脉冲,同时兼具调制组件的保护功能。发射机触发器芯片级故障诊断流程将触发器故障定位到芯片级,大大降低了触发器故障维修成本,同时为雷达测试平台中触发器故障自动诊断建模提供了技术支持。在发射机触发器信号流程基础上,依据发射机触发器关键点波形或关键点电平,通过触发器故障树图了解故障因果关系,研究出规范化的触发器芯片级故障诊断流程。列举了依据触发器芯片级故障诊断流程,修复了由于单稳态触发器无触发信号输出,导致无-200V放电触发信号的单稳态触发器故障个例。结果表明:芯片级触发器故障诊断流程可以快速定位发射机触发器故障点到最小可更换芯片。具有操作方法简洁、诊断思路清晰、操作规范,基层雷达站技术人员容易掌握的特点,可有效提高新一代天气雷达技术保障水平,保证雷达观测数据的可靠性。  相似文献