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本文论述双频透射电磁波电导率层析成象方法。设｜Ｅ１｜，｜Ｅ２｜为在远场区观测的同一电偶极天线的两个辐射电场强度。如地质介质的电导率连续变化，观测场强的辐射频率ω１，ω２之差较小，则有如下的电导率层析成象方程｜Ｅ１｜－｜Ｅ２｜＝２０ｌｏｇ（ω１／ω２）＋２０ｌｏｇ（ｅ）μ／２（ω２－ω１）∫σ～（ｒ）ｄｒ式中σ＾＝σ，σ为介质的电导率。双频透射电磁波电导率层析成象方法克服了长期困扰电磁波吸收层析成象的初始辐射场强计算问题，应用实例表明它可获得更精确的层析图。 相似文献
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为了解西沙群岛珊瑚礁海域浮游动物的群落特征, 于2015年5月末至7月初在西沙群岛8个岛礁(七连屿、永兴岛和东岛3个岛屿以及浪花礁、盘石屿、玉琢礁、华光礁和北礁5个环礁)进行了浮游动物采样, 分析了浮游动物的多样性、丰度和群落结构特征, 并比较了5个环礁潟湖内和向海礁坡区浮游动物群落组成的差异。调查海域共鉴定浮游动物180种(包括浮游幼虫13个类群), 其中桡足类最多, 达83种, 其次是水母类(38种)、浮游软体类(14种)、毛颚类(11种)和浮游被囊类(7种); 浮游动物平均丰度为256.4±117.8个·m-3, 桡足类占总丰度的51.08%, 其次是浮游幼虫(16.30%)、浮游被囊类(13.22%)和毛颚类(7.70%)。浮游动物种数、多样性和均匀度指数、丰度在岛屿和环礁之间以及环礁的潟湖区和向海礁坡区均存在差异; 浮游动物多样性和丰度在东岛、玉琢礁和华光礁较高, 而在七连屿和北礁较低; 5个环礁向海礁坡区的浮游动物多样性和丰度皆高于潟湖区的。多元统计分析结果表明调查岛礁的浮游动物可划分两个聚群(相似水平85%); 岛屿近岸及环礁的潟湖群落(Ⅰ)和岛屿远岸及环礁的向海礁坡群落(Ⅱ); 两个聚群浮游动物组成差异较显著(r=0.832, p<0.001); 前者的种数、多样性指数、总丰度和主要浮游动物类群如桡足类、毛颚类和浮游幼虫的丰度显著低于后者。环礁潟湖区和向海礁坡区的空间异质性和生态环境差异可能是导致浮游动物群落结构呈现不同特征的主要因素。 相似文献
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文章于2018年1月（冬季）、4月（春季）、7月（夏季）、10月（秋季）对我国考洲洋海域海水中的溶解氧（DO）、化学需氧量（COD）、无机氮（DIN）、活性磷酸盐（DIP）4个主要海水水质因子进行了综合调查。结果表明,4个水质因子DIP、DIN、COD、DO的平均浓度由高到低的季节变化分别为：冬季（0.058 mg/L）、春季（0.046 mg/L）、夏季（0.009 mg/L）、秋季（0.006 mg/L）;冬季（0.465 mg/L）、春季（0.171 mg/L）、夏季（0.064 mg/L）、秋季（0.040 mg/L）;夏季（1.57 mg/L）、冬季（1.26 mg/L）、秋季（1.22 mg/L）、春季（0.89 mg/L）;冬季（11.70 mg/L）、夏季（7.41 mg/L）、秋季（7.36 mg/L）、春季（7.18 mg/L）。评价结果显示,春季和冬季主要超标因子为DIP和DIN,夏季超标因子为DIP,秋季水质因子均满足要求。同时,本研究利用单因子标准指数法、富营养化指数法和有机污染评价指数法对考洲洋地区水质状况进行评价并对其进行初步比较和分析,结果表明,3种方法在季节性变化上的评价结果基本一致（由高到低均为:冬季、春季、夏季、秋季）,然而,同一季节不同评价方法的超标站位比例不同（单因子指数法:冬季占100%,春季占80%,夏季占10%,秋季则无;富营养化指数法:冬季占90%,春季占70%,夏季和秋季均为无;有机污染指数评价法:冬季和春季均占80%,夏季和秋季均为无）,比较分析表明,3种评价方法具有不同的评价作用和适用性。 相似文献
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Junxing Zheng Roman D. Hryciw Andrea Ventola 《Geotechnical and Geological Engineering》2017,35(5):2037-2051
This study quantifies the influence of various intrinsic soil properties including particle roundness, R, sphericity, S, 50% size by weight, D 50, coefficient of uniformity, C u, and the state property of relative density, D r, on the compression and recompression indices, C c and C r, of sands of various geologic origins at pre-crushing stress levels. Twenty-four sands exhibiting a wide range of particle shapes, gradations, and geologic origins were collected for the study. The particle shapes were determined using a computational geometry algorithm which allows characterization of a statistically large number of particles in specimens. One dimensional oedometer tests were performed on the soils. The new data was augmented with many previously published results. Through statistical analyses, simple functional relationships are developed for C c and C r. In both cases, the models utilized only R and D r since other intrinsic properties proved to have lesser direct influence on the compression indices. However, previous studies showed that the contributions of S and C u are felt through their effects on index packing void ratios and thus on D r. The accuracy of the models was confirmed by comparison of predicted and observed C c and C r values. 相似文献
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Jinxiang LI Guangming LI Kezhang QIN Bo XIAO Lei CHEN Junxing ZHAO 《Resource Geology》2012,62(1):19-41
The Early Cretaceous Duolong gold‐rich porphyry copper deposit is a newly discovered deposit with proven 5.38 Mt Cu resources of 0.72% Cu and 41 t gold of 0.23 g t?1 in northern Tibet. Granodiorite porphyry and quartz diorite porphyrite are the main ore‐bearing porphyries. A wide range of hydrothermal alteration associated with these porphyries is divided into potassic, argillic and propylitic zones from the ore‐bearing porphyry center outward and upward. In the hydrothermal alteration zones, secondary albite (91.5–99.7% Ab) occurs along the rim of plagioclase phenocryst and fissures. Secondary K‐feldspar (75.1–96.9% Or) replaces plagioclase phenocryst and matrix or occurs in veinlets. Biotite occurs mainly as matrix and veinlet in addition to phenocryst in the potassic zone. The biotite are Mg‐rich and formed under a highly oxidized condition at temperatures ranging from 400°C to 430°C. All the biotites are absent in F, and have high Cl content (0.19–0.26%), with log (XCl/XOH) values of ?2.74 to ?2.88 and IV (Cl) values of ?3.48 to ?3.35, suggesting a significant role of chloride complexes (CuCl2‐ and AuCl2‐) in transporting and precipitating copper and gold. Chlorites are present in all alteration zones and correspond mainly to pycnochlorite. They have similar Fe/(Fe+Mg), Mn/(Mn+Mg) ratios, and a formation temperature range of 280–360°C. However, the formation temperature of chlorite in the quartz‐gypsum‐carbonate‐chlorite vein is between 190°C and 220°C, indicating that it may have resulted from a later stage of hydrothermal activity. Fe3+/Fe2+ ratios of chlorites have negative correlation with AlIV, suggesting oxygen fugacity of fluids increases with decreasing temperature. Apatite mineral inclusions in the biotite phenocrysts show high SO3 content (0.44–0.82%) and high Cl content (1–1.37%), indicating the host magma had a high oxidation state and was enriched in S and Cl. The highest Cl content of apatite in the propylitic zone may have resulted from pressure decrease, and the lowest Cl content of apatite in the argillic zone may have been caused by a low Cl content in the fluids. The low concentration of SO3 content in the hydrothermal apatite compared to the magmatic one may have resulted from the decrease of oxygen fugacity and S content in the hydrothermal fluid, which are caused by the abundant precipitation of magnetite. 相似文献