A computer method to calculate the convolution of statistical distributions     

Thomas A. Jones 《Mathematical Geology》1977,9(6):635-647

It is becoming increasingly important to determine probability distributions of combinations of random variables. Convolution is a technique by which the distribution of a sum of random variables can be determined. This paper presents some simplifications in order to reduce the numerical integrations and computer time. In addition, the method may be used with empirical nonanalytic distributions. While Monte Carlo methods are also appropriate for calculating the distribution, convolution can give at least as much accuracy as Monte Carlo methods with a reduction in computation. Two applications are presented: one approximates the distribution of percent sand in an area, and the other indicates a method of determining sample size when using the distribution of means to approximate normality.  相似文献   

Stratigraphic analysis and the asymptotic distribution of the coefficient of cross-association     

Miloslav Nosal  Jan Vrbik 《Mathematical Geology》1982,14(1):11-36

The asymptotic distribution of the coefficient of cross-association between two sequences of nominal data is investigated under the assumption of independent random sampling from a multinomial distribution slightly modified to suit geological applications. This modification is due to merging consecutive strata of the same rock type into one lithological unit, and can be described by a simple Markov chain. A distinction is made between the case in which the theoretical frequencies are known, and the situation where these have to be estimated from the observed data.  相似文献   

Distribution of <Superscript>226</Superscript>Ra in the Arctic Ocean and the Bering Sea and its hydrologic implications     

Na?XingEmail author  Min?Chen  Yipu?Huang  Pinghe?Cai  Yusheng?Qiu 《中国科学D辑(英文版)》2003,46(5):516-528

Radium-226 (²²⁶Ra) activities were measured in the surface water samples collected from the Arctic Ocean and the Bering Sea during the First Chinese National Arctic Research Expedition. The results showed that ²²⁶Ra concentrations in the surface water ranged from 0.28 to 1.56 Bq/m³ with an average of 0.76 Bq/m³ in the Arctic Ocean, and from 0.25 to 1.26 Bq/m³ with an average of 0.71 Bq/m³ in the Bering Sea. The values were obviously lower than those from open oceans in middle and low latitudes, indicating that the study area may be partly influenced by sea ice meltwater. In the Bering Sea, ²²⁶Ra in the surface water decreased northward, probably as a result of the exchange between the ²²⁶Ra-deficient sea ice meltwater and the ²²⁶Ra-rich Pacific water. In the Arctic Ocean, ²²⁶Ra in the surface water increased northward and eastward. This spatial distribution of ²²⁶Ra reflected the variation of the ²²⁶Ra-enriched river component in the water mass of the Arctic Ocean. The vertical profiles of ²²⁶Ra in the Canadian Basin showed a concentration maximum at 200 m, which could be attributed to the inputs of the Pacific water or/and the bottom shelf water with high ²²⁶Ra concentration. This conclusion was consistent with the results from ²H, ¹⁸O tracers.  相似文献   

Thermal bidirectional gap probability model for row crop canopies and validation   总被引：2，自引：0，他引：2  

阎广建  蒋玲梅  王锦地  陈良富  李小文 《中国科学D辑(英文版)》2003,46(12):1241-1249

Land surface temperature is a key parameter in monitoring the status of crop water stress by remote sensing, and studying the water and energy balance in cropland ecosystem. The component temperatures of crop and soil are especially significant in remote …  相似文献   

Distribution of ionospheric O<Superscript>+</Superscript> ion in synchronous altitude region     

Jiankui?Shi?Email author  Zhenxing?Liu  Zhang?T.?L.  Jianshan?Guo  Manlian?Zhang  Sheping?Shang  Xigui?Luo 《中国科学D辑(英文版)》2003,46(10):986-993

Based on satellite observation data, using dynamics equation, the ionospheric O⁺ ion’s distribution in the synchronous altitude region for different geomagnetic activity indexK _p is studied by theoretical modeling and numerical analyzing, and semi-empirical models for the O⁺ ion’s density and flux versus longitude in the synchronous altitude region for differentK _p are given. The main results show that in the synchronous altitude region: (i) The O⁺ ion’s density and flux in day-side are larger than those in nightside. (ii) With longitude changing, the higher the geomagnetic activity indexK _p is, the higher the O⁺ ion’s density and flux, and their variation amplitude will be. The O⁺ ion’s density and flux whenK _{p ≥} 6 will be about ten times as great as that whenK _p = 0. (iii) WhenK _p = 0 orK _{p ≥} 6, the O⁺ ion’s density reaches maximum at longitudes 120° and 240° respectively, and minimum in the magnetotail. WhenK _p = 3−5, the O⁺ ion’s density gets to maximum at longitude 0°, and minimum in the magnetotail. However, the O⁺ ion’s flux reaches maximum at longitude 120° and 240° respectively, and minimum in the magnetotail for anyK _p value.  相似文献   

额尔齐斯河流域及某稀有多金属矿废水铀、钍含量分布及其环境影响   总被引：5，自引：0，他引：5  

李社红  郑宝山  朱建明  王滨滨 《矿物学报》2003,23(4):308-312

运用简易、快捷、灵敏的ICP-MS法直接测定稀有多金属矿以及河水样品中的铀钍含量,并推算其与比放射性活度之间的定量关系,客观评价了某稀有多金属矿废水中的放射性水平以及额尔齐斯河流域的放射性污染现状。研究表明,某稀有多金属选矿废水铀含量可达78．311μg/L,钍含量达0．627μg/L。额尔齐斯河流域各支流河水铀、钍平均含量分别为0．584μg/L、0．025μg/L,其干流河水钍平均含量为0．019μg/L,而铀平均含量达2．234μg/L,远高于世界河水铀平均含量0．309μg/L。  相似文献   

云南境内澜沧江流域土地利用时空变化特征及动因分析   总被引：16，自引：0，他引：16  

张佩芳  许建初 《地球科学进展》2003,18(6):947-953

    澜沧江-湄公河是一条集内河、界河、国际河流为一体的河流。云南境内澜沧江流域涉及云南西部 7个地州39个县市。复杂的地形地貌结构和多种气候带,形成植被垂直分布和地域分布的特点,呈现出多样性变化特征;域内94％为山区;占流域人口83％的民族（18个少数民族）大分散小聚居立体分布在山区,土地资源一直是他们赖以生存的最主要的生产生活资料,不同民族土地利用习俗,使流域内土地利用格局呈现出多元化特征。在这样一个边疆山区民族地区,寻求一条多元民族文化下土地资源合理利用和可持续发展战略,是加强民族团结,寻求均等发展机会脱贫致富,实现各民族共同繁荣和富裕的关键。
    采用遥感（RS）、地理信息系统（GIS）、全球卫星定位系统（GPS）高新技术,典型地区启用了快速农村评估（PRA,RapidRuralAppraise）方法,对流域1990年、1998年土地利用现状及空间结构演变进行了时空动态叠合研究、森林土地时空动态的整体演变研究以及变化动因分析,在此基础上,就多元民族文化下土地利用人地系统演变和流域发展的关联问题,提出一些看法,仅供商榷。  相似文献   

鄂尔多斯盆地白垩系含水层沉积学初探   总被引：21，自引：5，他引：16  

谢渊 王剑殷跃平  武选民文冬光江新胜  罗建宁魏伦武李明辉  郑万模 《地质通报》2003,22(10):818-828

“含水层沉积学”是沉积学、水文地质学、油气储层地质学、地球化学等相互交叉综合的产物,是以沉积学、水文地质学理论为基础,以沉积含水层为主要研究对象,以查明地下水赋存和循环条件、地下水系统结构特征、地下水水质成因与分布以及地下水富集规律为主要研究内容,最终服务于地下水资源勘查评价的一门边缘分支学科。含水层沉积学及水文地质综合研究表明,受到沉积相类型及其空间展布的明显控制,鄂尔多斯盆地白垩系地下水赋存、循环、富集条件以及地下水水质分布总体具有北好南差、盆地南部具有下好上差的宏观规律。  相似文献   

从三个平面看概数词“好多”与“好几”     

蔡晓 《广东海洋大学学报》2003,23(5):72-77

概数词“好多”与“好几”在分布、语义辖域、和语用倾向等方面既具有其相同的一面 ,也有相对的一面 ,还有相交叉的一面。它们所能出现的语法位置有异有同 ,“好几”表数范围具有定性和“好多”表数范围则无定性 ,同时还“好几”具有显示个体作用的性质  相似文献   

Subcellular distribution of trace elements in the liver of sea turtles     

Anan Y  Kunito T  Sakai H  Tanabe S 《Marine pollution bulletin》2002,45(1-12):224-229

Subcellular distribution of Cu, Zn, Se, Rb, Mo, Ag, Cd and Pb was determined in the liver of green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) from Yaeyama Islands, Japan. Also, hepatic cytosol from sea turtles was applied on a Sephadex G-75 column and elution profiles of trace elements were examined. Copper, Zn, Se, Rb, Ag and Cd were largely present in cytosol in the liver of both species, indicating that cytosol was the significant site for the accumulation of these elements in sea turtles. In contrast, Mo and Pb were accumulated specifically in nuclear and mitochondrial fraction and microsomal fraction, respectively. Gel filtration analysis showed that Cu, Zn, Ag and Cd were bound to metallothionein (MT) in the cytosol of sea turtles. To our knowledge, this is the first report on the association of trace elements with MT in sea turtles.  相似文献