杠杆点评估及设计空间抗差     

黄幼才 《测绘学报》1993,22(4):289-293

本分析了杠杆点的几何含义和统计特征,从杠杆点的保差性,矩阵的摄动和参数估值可靠性的观点出发讨论了杠杆点的不利和有利的两个方面,提出了一个全面的设计空间抗差方案。  相似文献   

Infinitesimal orbits around lagrange points in the elliptic,restricted three-body problem     

Dan Şelaru  Cătălin Cucu-Dumitrescu 《Celestial Mechanics and Dynamical Astronomy》1995,61(4):333-346

This study presents a method of obtaining asymptotic approximations for motions near a Lagrange point in the planar, elliptic, restricted three-body problem by using a von Zeipel-type method. The calculations are carried out for a second-order escape solution in the proximity of the equilateral Lagrange point, L ₄, where the primaries' orbital eccentricity is taken as the small parameter .  相似文献   

DDT residue in soil and water in and around the abounded area of DDT manufacturing factory     

Mohammad Rasul Jan Mahmood A Khawaja Jasmin Sha Kashif Gul 《中国地球化学学报》2006,25(B08):182-182

Due to the persistent nature of DDT, a persistent organic pollutant and its adverse environmental and health impacts, the present study was undertaken to examine the residual DDT in and around DDT manufacturing factory in Amman Gharh, Nowshera, NWFP. The factory was established in 1963 and remained in operation till 1994. Composite samples of soil, sediments and water were collected in and around the factory area, nearby DDT stores, main factory drain leading to river and nearby villages. Standard procedures were used for the collection, transportation and storage of samples for analysis. Physical parameters for the collected water samples measured were temperature, pH and conductance. Extraction of each sample for DDT analyses was carried out in triplicates using soxhlet extraction apparatus. The extract was transferred to well washed, clean; dry glass vial, sealed and put in the refrigerator. Gas Chromatograph with electron capture detector and capillary column was used for analysis. DDT in the samples was identified on the basis of their retention time and quantified on the basis of peak areas. It is evident from the analytical data obtained in the present study that both water and soil in and around the factory area are still contaminated with DDT, despite the closure of the factory since the past few years.  相似文献   

Microwave-assisted extraction of organochlorine pesticides from sediments and determination by gas chromatograph with electron capture detection     

Rama Mohan Kurakalva Narasimha Murthy Nyasavajhala Phani Homeshwari Mamidi Venkata Anjaiah Kanukuntla 《中国地球化学学报》2006,25(B08):202-203

A simple and rapid procedure to extract organochlorine pesticides （OCPs） from sediments by means of microwave energy is proposed. Sediment samples were irradiated with microwaves in a closed vessel system while immersed in hexane-acetone （1 ： 1, v/v）. The sample extracts were cleaned up using solid phase extraction with Florisil as adsorbent. Pesticides were eluted with hexane-ethyl acetate （80 ： 20, v/v） and determined by gas chromatographic separation with electron capture detection. Three oven programs were assayed with two different solvent mixtures in order to achieve adequate experimental conditions for the complete extraction of organochlorine pesticides from the matrix. Different variables such as the composition of extraction solvent,  相似文献   

Speciation analysis and significance of ecological geochemistry     

Yaping WANG Chunxue XU Ziyi AN Suming WANG 《中国地球化学学报》2006,25(B08):205-205

Different species of one element have different activities, so it has different effects on environment and human health. To analyze qualitatively and quantitatively the speciation of a special element in sample, which is the important basis for appraising the toxicity and studying the rule of transfer and translation of elements. Since the 1970＇s, the scheme of sequential extraction has already been used at many laboratories both at home and abroard, to get the information about heavy metals＇ activity in polluted soils. Because this method has the experimental nature, many schemes of problem has taken place, the absence of consistency of these sequential extraction have been formed. Thus the complexity of the schemes, the lack of selectivity of reagent, the lack of quality control, the result mainly related to the extraction scheme used, and so on. In the face of these problems, the study of experimental methods of sequential extraction on three different soils, sediment in Dongting Lake, soil in Jiangsu Province and loess in Shanxi Province was made. Reference materials of heavy metal speciation following sequential extraction in soil and sediment had been developed. Nowadays two kinds of sequential extraction methods which are widely used are BCR （three steps） and improved Tessier methods （seven steps）. Based on three steps of BCR, water-soluble speciation and the residual speciation were increased in our research. BCR701 was determined eight times at different laboratories using BCR three steps. The results showed that determined data obtained eight times were identical to the standard value, and it is indicated that this method has good reproducibility. The stability and homogeneity experiments indicated that the preparation of three types of candidates accorded with our requirements. Eight laboratories had afforded the determined values of 12 heavy metal elements （Cu, Pb, Zn, Mn, Co, Ni, Cd, Cr, Mo, As, Sb, Hg, Se et al.） using BCR three steps. Also, these three candidates afforded the determined values by seven steps, and 12 laboratories had participated.  相似文献   

Assessment of mercury mobility and bioavailability by fractionation method in sediments from coastal zone inundated by the 26 December 2004 tsunami in Thailand     

Leonard Boszke  Artur Kowalski  Witold Szczuciński  Grzegorz Rachlewicz  Stanisław Lorenc  Jerzy Siepak 《Environmental Geology》2006,51(4):527-536

The 26 December 2004 tsunami covered significant portion of a coastal zone with a blanket of potentially contaminated sediments. In this report are presented results on mercury concentrations in sediments deposited by the tsunami in a coastal zone of Thailand. Since the total mercury concentrations are insufficient to assess mercury mobility and bioavailability in sediment, its fractionation was applied. Sediments were sampled within 50 days after the event and analyzed by sequential extraction method. The procedure of sequential extraction involved five subsequent stages performed with solutions of chloroform, deionized water, 0.5 M HCl, 0.2 M NaOH, and aqua regia. The mean concentration of total mercury in sediments was 119 ± 50 ng g⁻¹ dry mass (range 66–230). The fractionation revealed that mercury is mainly bound to the least bioavailable sulphides 75 ± 6% (range 62–86), organomercury compounds 14 ± 7% (range 4–26), and humic matter 9 ± 7% (range 1–27). The lowest contributions bring fractions of water-soluble mercury 0.8 ± 1.0% (range 0.1–3.6) and acid soluble mercury 0.9 ± 0.5% (range 0.2–2.1). Although, the total mercury content is similar in a reference sample and in the tsunami sediments, the highly toxic organomercury fraction contribution is higher in the latter. The results were compared with chemical and sedimentological properties of the sediments but no significant correlations were obtained between them.  相似文献   

Distribution of cadmium, chromium, copper, lead and zinc in marine sediments in Hong Kong waters     

S. C. Choi  Onyx W. H. Wai  Thomas W. H. Choi  X. D. Li  C. W. Tsang 《Environmental Geology》2006,51(3):455-461

Partitioning of heavy metals (Cd, Cr, Cu, Pb, Zn) in marine sediments collected from various sites in Hong Kong waters were determined using sequential extraction method. Sediments from Kellette Bank, located in Victoria Harbour, had higher metal concentrations especially Cu and Zn than most other sites. Slightly over 20% of total Cu and Cr existed as readily available forms in Peng Chau and Kellette Bank. At most sampling sites, over 15% of the Cu existed as the exchangeable form indicating that Cu could be readily released into the aqueous phase from sediments. A significantly higher percentage of Pb and Zn was associated with the three non-residual fractions. Hence, there is a greater environmental concern for remobilization of Pb and Zn compared with Cr. The high amount of residual Cd (>50%) and the relatively lower Cd content indicate that little environmental concern is warranted for the remobilization of Cd. Distribution of metals in sediments collected from different depth at Kellette Bank shows that metal concentrations decreased with profile depth. The levels of Pb and Zn associated with the two readily available fractions increased sharply in the surface sediment. These metals represented the pollutants, which were introduced into the area in the mid-eighties through early nineties as a result of rapid economic and industrial development in the territory. As significant portions of these metals were bound to the readily available phases in the surface sediments, metal remobilization could be a concern. An erratum to this article can be found at  相似文献   

Vertical variation of phosphorus forms in surface sediments from Wuli Bay, Taihu Lake, China   总被引：1，自引：0，他引：1  

李军  刘丛强  王仕禄  朱兆洲  周志华  肖化云 《中国地球化学学报》2006,25(3):279-284

1IntroductionPhosphorus,an essential nutrient for the primaryproductivity in freshwater systems,is an important fac-tor controlling lacustrine eutrophication.Although ex-ternal input of phosphorus has been assumed as the vi-tal responsibility for the eutrophication of lakes(ZhuJun et al.,2005),the remobilization of phosphorus insediments has a distinct influence on it as well(Bostr m et al.,1982).The concentrations of totalphosphorus(Ptotal)in the sediments are often related tothe trophic st…  相似文献   

基于广义Hough变换的不规则形状目标提取方法   总被引：1，自引：0，他引：1  

刘德刚余旭初  张鹏强 《测绘学院学报》2005,22(2):125-127

提出了一种基于广义Hough变换的不规则形状目标的提取方法。该方法主要包括目标参数描述和目标提取两部分。实验表明，该方法精度好、效率高。  相似文献   

环境样品中痕量元素的化学形态分析Ⅰ．分析技术在化学形态分析中的应用   总被引：21，自引：7，他引：21  

何红蓼 李冰杨红霞  倪哲明 《岩矿测试》2005,24(1):51-58

文章介绍了形态分析的基本概念,常用的联用分析技术,如气相色谱原子吸收光谱、气相色谱原子荧光光谱、气相色谱微波诱导等离子体原子发射光谱、气相色谱电感耦合等离子体质谱、高效液相色谱电感耦合等离子体质谱等在环境样品(水、土壤、沉积物)中痕量元素化学形态(价态、金属有机化合物等)分析中的应用,土壤和沉积物中污染元素的顺序提取步骤,以形态分析发展动态。引用文献72篇。  相似文献