我国砷中毒病区的环境特征研究   总被引：18，自引：0，他引：18  

林年丰  汤洁 《地理科学》1999,19(2):135-139

我国饮水型砷中毒的流行屡见报道,台湾嘉南,新疆奎屯,内蒙古河套及山西大同等地是我国几个有代表性的病区。病区多为河湖相和滨海相沉积,粘土,粘土质淤泥和有机淤泥层发育,为富含有要质的还原环境,地下水中的含量一般为０．２－０．６ｍｇ／Ｌ。有时还有氟,腐殖酸,甲基胂酸和某些烷烃类等的有害有机化合物。  相似文献   

1980～～2014年中国中东部持续性霾天气的多尺度变化特征     

王素  黄刚  胡开明  王林 《气候与环境研究》2020,25(1):103-112

对1980～2014年中国中东部地区324个台站的持续性霾天气的时空变化和相关气象影响因子进行分析，结果表明:中东部地区年平均持续性霾事件和其在所有霾事件的贡献比例逐年增加，增长率分别为0.79 (10 a)-1和2.7% (10 a)-1。主要表现为3个大值区:华北平原地区（包括山西省、京津冀地区）、长江三角洲和四川盆地东部，增加最显著的区域位于黄淮地区，增长率分别为6.3 (10 a)-1、13.95 d (10 a)-1。1月是持续性霾事件的高发月，月均2.56 d。夏季和秋季持续性霾事件增加最为明显，增长率分别为0.38 (10 a)-1和0.46 (10 a)-1。不利的气象条件，如静风日数的增加，风速和大风日数的减少，以及不利的环流形势，如东亚冬季风的减弱，都可能造成持续性霾天气的增加和异常维持。  相似文献   

CT-1地震计传递函数测试仪的设计   总被引：6，自引：4，他引：2  

周云耀  蔡亚先  吕永清  程骏玲 《大地测量与地球动力学》2002,22(3):117-121

将计算机控制技术应用到甚宽频带地震计的传递函数测试中。讨论了基本的测试方法和原理，阐述了传递函数测试系统的软、硬件设计，给出了测试系统的应用实例。该测试系统具有正弦波自动扫频、阶跃信号法和脉冲信号法等标定方法，满足了甚宽频带地震计的传递函数测试在观测频带、动态范围和测试精度等方面的要求。  相似文献   

ANALYSIS OF LOCATION CONDITIONS OF FINANCIAL CENTRES IN CHINA     

叶立梅  程志刚 《中国地理科学(英文版)》1993,3(4):297-307

First of all, the necessity of establishing financial centres is expounded. The establishment of financial centres has a lot of benefits to the world economic development, China's economy and the occupied cities. The location conditions of financial centres may be summarized as follows: the location of trade centre, the factors of geographical position, the circumstances of finance, etc.. We consider that the first batch of financial centres in China should be established in the eastern cities of China. So 9 eastern cities in China are chosen as the spare financial centres. According to the location conditions of financial centres, 12 indices are chosen and the method of synthetic weighted average is used to find the best locations of financial centres. The conclusions are that the grade A financial centres should be in Shanghai and the grade B should be in Tianjin and Guangzhou.  相似文献   

一降水工程的施工和从中引出的思考     

程礼来  王先保  彭建洋  武开文 《河南国土资源》1997,(4)

基坑降水是岩土工程中经常遇到的施工问题。本文展示了一个降水工程实例，从中引伸出本工程尚未遇到而在其他项目中可能会出现并应及时解决的一些技术问题，引起同行的关注与重视。  相似文献   

A rigorous method of calculating the deflection of light in the gravitational field of the sun     

Pan Rong-shi  Wang Jia-ji  Yan Hao-jian  Tang Guo-qiang  Huang Cheng 《Chinese Astronomy and Astrophysics》1984,8(4):319-324

Starting from the equation for the path of a photon in a gravitational field, we give a method of calculating the deflection of starlight in the solar field. The transformation from the non-inertial system at the Sun to the locally inertial system of the observer is considered. Calculation was made under the Schwarzschild metric. Our calculated results for the deflection before making coordinate transformation agree well with the results according to the IAU formulae, but when an accuracy of 0'.'001 is required, then the coordinate transformation must be included.  相似文献   

Heating of the solar flare plasma by high energy electrons     

Chung-Chieh Cheng 《Solar physics》1972,22(1):178-188

Heating of the ambient plasma by high energy electrons in solar flares is discussed. It is shown that for large flares the heating is enough to produce a thermal plasma of a temperature up to a few times of 10⁷K rapidly in the initial phase of the flares. Thus thermal bremsstrahlung in addition to non-thermal bremsstrahlung should be considered for the X-ray emission of solar flares in the initial phase.NAS-NRC Resident Research Associate.  相似文献   

Solar flare injection and propagation of low-energy protons and electrons in the event of 7–9 July, 1966     

R. P. Lin  S. W. Kahler  E. C. Roelof 《Solar physics》1968,4(3):338-360

Simultaneous observations of the 7–9 July 1966 solar particle event by energetic particle detectors on three satellites, IMP-III, OGO-III and Explorer 33 are utilized to show that large spatial gradients are present in the fluxes of 0.5–20 meV protons and 45 keV electrons. The event is divided into three parts: the ordinary diffusive component, the halo, and the core. The core corotates with the interplanetary field, and therefore it and the surrounding halo are interpreted as spatial features which are connected by the interplanetary magnetic field lines to the vicinity of the flare region. Upper limits to the interplanetary transverse diffusion coefficient for 4–20 meV protons at 1 AU are derived from the width of the halo. These are at least two orders of magnitude less than the parallel diffusion coefficient for the same energy particles.It is argued that the observed flux variations cannot be explained by an impulsive point source injection for any physically reasonable diffusion model. Instead, since the interplanetary transverse-diffusion coefficient is small for these low-energy particles, the observed spatial features are interpreted as the projection to 1 AU by the interplanetary field lines of an extensive injection profile at the sun. The geometry of the injection mechanism is discussed and it is suggested that some temporary storage of the flare particles occurs near the sun.Now at NASA, Goddard Space Flight Center, Greenbelt, Md., U.S.A.  相似文献   

Cosmic-ray exposure histories of two Antarctic meteorites from Chinese collections and the Guangmingshan and Zhuanghe chondrites   总被引：5，自引：0，他引：5  

王道德  林杨挺  刘小汉  琚宜太 《中国科学D辑(英文版)》2003,46(12):1236-1240

In this paper, we report cosmic-ray exposure ages (3He, 21Ne, 38Ar) and gas retention ages (4He, 40Ar) of two Antarctic meteorites, and the Guangmingshan and Zhuanghe ordinary chondrites. The Antarctic meteorites (GRV98002 and GRV98004) were collected on …  相似文献   

<Emphasis Type="Italic">In-situ</Emphasis> trace element analyses and Pb-Pb dating of zircons in granulite from Huangtuling,Dabieshan by LAM-ICP-MS     

Yuanbao?WuEmail author  Daogong?Chen  Qunke?Xia  Xianglin?Tu  Hao?Cheng  Xiaozhi?Yang 《中国科学D辑(英文版)》2003,46(11):1161-1170

It is revealed by CL images that there are multi-stage growth internal structures of zircons in the Huangtuling granulite, including the inherited zircons, protolith zircons, sector and planar zone zircons and retrograde zircons. In-situ trace element compositions and Pb-Pb ages have been analyzed by LAM-ICP-MS. The sector and the planar zone domains show typical trace element characteristics of granulite zircon (low Th, U, Th/U, total REEs, clear negative Eu anomalies, relatively depleted HREE and small differential degree between MREE and HREE, etc.), indicating that they formed during granulite-facies metamorphism. The protolith zircons have trace element characteristics of crustal zircon (high Th, U, Th/U, total REEs and enriched HREEs, etc.). 12 analyzed spots on granulite-facies domains give a weighted mean ²⁰⁷Pb/²⁰⁶Pb age of (2154±26) Ma (MSWD = 3.8), which is the best estimated age of granulite-facies metamorphism of this sample. The weighted mean ²⁰⁷Pb/²⁰⁶Pb age of 5 analyzed spots on protolith zircon domains is (2714 ± 22) Ma (MSWD = 1.4), which represents the protolith forming time. The discovery of ca. 3.4 Ga inherited zircon indicates that there are Palaeoarchean continental materials in this area. The interpretation of formation conditions and the ages of zircons can be constrained by simultaneous in-situ analysis of trace elements and ages.  相似文献