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81.
东川铜矿床同位素地球化学研究:I.地层年代与铅同位素化探应用 总被引:7,自引:0,他引:7
采用Pb-Pb等时线法测定了昆阳群中亚群落雪组白云岩、黑山组碳质板岩和上亚群大营盘组碳质板岩样品,获得了(1716±56)Ma、(1607±128)Ma和(1258±70)Ma的年龄,确定了昆阳群中亚群时代约为1600—1800Ma,属晚古元古代,上亚群大营盘组约为1200—1300Ma,属中元古代。还应用铅同位素化探技术系统研究了汤丹铜矿1号硐中段西14穿脉岩石-矿石的铅同位素组成,结果表明铅同位素V1值与铜含量呈反相关系。这是运用系统剖面方法开展铅同位素化探的首次尝试。 相似文献
82.
M. W. Kemblowski C-M. Chang I. Kamil 《Stochastic Environmental Research and Risk Assessment (SERRA)》1997,11(3):255-266
It has been observed that the field biodegradation rates for soluble hydrocarbon plumes are significantly smaller than the
aerobic rates observed in the laboratory. It is believed that this difference is related to the fact that in the field oxygen
and hydrocarbon must be mixed before the biodegradation reaction can occur, and that the effective degradation rate is controlled
by the actual, not mean, concentrations of oxygen and hydrocarbon. In this work, we present a conceptual model of oxygen-mixing
limited biodegradation, which indicates that the effective degradation rate should depend on the cross correlation between
the oxygen and hydrocarbon concentration fluctuations. This is followed by a development of a rigorous, field-scale model. 相似文献
83.
昌仁民 《CT理论与应用研究》1997,6(2):27-29
本文报道了我院连续六只X-CT球管的使用情况。寿命最长的曝光达358300秒,而最短的只有135000秒,其主要原因是缺乏正确地使用和维护知识,要想延长球管使用寿命,首先需加强对使用人员的专业素质训练,其次,在保证图像质量的前提下,降低mAs;第三,保持扫描室恒业的温湿度;第四,定期检查球管的冷却散热系统。 相似文献
84.
辽宁北票盆地中侏罗世海房沟组含丰富的生物化石,其中的水生昆虫、水生植物、叶肢介、水生软体动物和鱼类共同构成一个复杂的水生生物群落。根据其营养水平划分为生产者、消费者和分解者。这些生物通过捕食关系构成一个复杂的食物链 相似文献
85.
Summary Analysis of ozonesonde data shows that in the lower troposphere above Hong Kong, there is a relative maximum with respect to height in all seasons except winter. In the upper troposphere, there is with respect to height a relative minimum in the seasonally averaged ozone mixing ratio in winter. Ozone mixing ratios in the upper troposphere in winter and spring can be significantly enhanced by stratospheric intrusions associated with the passage of cold fronts and upper cut-off lows.For Hong Kong, the seasonally averaged total ozone has the highest value in spring, and the lowest in winter. The seasonally averaged total tropospheric ozone also has the highest value in spring, but the lowest in summer. In a relative sense, total tropospheric ozone contributes most to the total ozone in spring and the least in summer.The phase of the total ozone anomaly above Hong Kong is influenced by the Quasi-Biennial Oscillation (QBO), with the positive anomaly associated with the easterly phase of QBO, and the negative anomaly the westerly phase. 相似文献
86.
In this study a procedure for determining the optimum size and location of viscoelastic dampers is proposed using the eigenvalue assignment technique. Natural frequencies and modal damping ratios, required to realize a given target response, are determined first by the convex model. Then the desired dynamic structural properties are realized by optimally distributing the damping and stiffness coefficients of viscoelastic dampers using non‐linear programming based on the gradient of eigenvalues. This optimization method provides information on the optimal location as well as the magnitude of the damper parameters. The proposed procedure is applied to the retrofit of a 10‐story shear frame, and to a three‐dimensional structure with an asymmetric plan. The analysis results confirm that the responses of model structures retrofitted by the proposed method correspond well with the given target response. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
87.
A fast intensity-hue-saturation fusion technique with spectral adjustment for IKONOS imagery 总被引:11,自引:0,他引:11
Te-Ming Tu Huang P.S. Chung-Ling Hung Chien-Ping Chang 《Geoscience and Remote Sensing Letters, IEEE》2004,1(4):309-312
Among various image fusion methods, intensity-hue-saturation (IHS) technique is capable of quickly merging the massive volumes of data. For IKONOS imagery, IHS can yield satisfactory "spatial" enhancement but may introduce "spectral" distortion, appearing as a change in colors between compositions of resampled and fused multispectral bands. To solve this problem, a fast IHS fusion technique with spectral adjustment is presented. The experimental results demonstrate that the proposed approach can provide better performance than the original IHS method, both in processing speed and image quality. 相似文献
88.
89.
90.
南秦岭十里坪锑矿床成矿时代及成因的初步研究 总被引:1,自引:1,他引:1
十里坪锑矿床受赵川陆缘隆_滑构造的主滑脱拆离带的控制。矿体呈脉状赋存于韧_脆性主滑脱带上部的脆性次级断层_节理中,矿石类型主要为萤石石英辉锑矿型。围岩为太古宙_元古宙变质岩系,围岩蚀变弱。成矿流体属H2O_CO2_NaCl体系,流体包裹体盐度w(NaCleq)为3.6%~11.3%,均一温度为109~232℃,形成压力大致为800×105Pa。硫、铅同位素研究表明,矿质主要来源于变火山岩围岩;氢、氧同位素显示,成矿流体以大气降水为主,初步将该矿床定为变质岩源就地式大气降水热液矿床。矿石中萤石Sm_Nd等时线年龄为(392±24)Ma,与南秦岭北部晚古生代拗陷区热水喷流_沉积成矿时代相一致,它们都形成于秦岭微板块泥盆纪非造山裂解阶段。 相似文献