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1.
仇朴章  刘忠 《天文学进展》1996,14(3):175-180
在文献」1「4 基础上,根据近年文选址实践中提出的问题,先进一步讨论了大气相干直径和时间的的物理和意义,然后强调了自由大气湍流的天文成像效应及选址中进行研究和测量的重要性。最后对差分像运动方法测量视宁度的定标和系统误差等问题作了分析。  相似文献   
2.
New chronological, geochemical, and isotopic data are reported for Triassic (219–236 Ma) adakite-magnesian andesite-Nb-enriched basaltic rock associations from the Tuotuohe area, central Qiangtang terrane. The adakites and magnesian andesites are characterized by high Sr/Y (25–45), La/Yb (14–42) and Na2O/K2O (12–49) ratios, high Al2O3 (15.34–18.28 wt%) and moderate to high Sr concentrations (220–498 ppm) and εND (t) (+0.86 to +1.21) values. Low enrichments of Th, Rb relative to Nb, and subequal normalized Nb and La contents, and enrichments of light rare earth elements combine to distinguish a group of Nb-enriched basaltic rocks (NEBs). They have positive εND (t) (+2.57 to +5.16) values. Positive correlations between Th, La and Nb and an absence of negative Nb anomalies on mantle normalized plots indicate the NEBs are products of a mantle source metasomatized by a slab melt rather than by hydrous fluids. A continuous compositional variation between adakites and magnesian andesites confirms slab melt interaction with mantle peridotite. The spatial association of the NEBs with adakites and magnesian andesites define an “adakitic metasomatic volcanic series” recognized in many demonstrably subduction-related environments (e.g., Mindanao arc, Philippines; Kamchatka arc, Russia; and southern Baja California arc, Mexico). The age of the Touhuohe suite, and its correlation with Triassic NEB to the north indicates that volcanism derived from subduction-modified mantle was abundant prior to 220 Ma in the central Qiangtang terrane.  相似文献   
3.
本文从辐射方程出发,简述洋面温度与亮度温度之间的非线性关系,进行非线性洋面温度反演的方案设计,用正演算法 计算出非线性洋面温度反演公式的回归系数,对样进行检验。  相似文献   
4.
Based on the 1st order cnoidal wave theory, the nonlinear wave diffraction around a circular cylinder in shallow water is studied in this paper. The equation of the wave surface around the cylinder is formulated and by using this formula the wave surface elevation on the cylinder surface can be obtained. In this paper, the formula for calculating the cnoidal wave force on a circular cylinder is also derived. For the wave conditions which are often encountered in practical engineering designs, the ratios of the nonlinear wave forces to the linear wave forces are calculated, and the results are plotted in this paper for design purposes. In order to verify the theoretical results, model tests are conducted. After comparing the test results with the theoretical ones, it is concluded that, in shallow water, for the case of T g / d~(1/2) > 8-10 and H / d > 0.3, the cnoidal wave theory should be used to calculate the wave action on a cylindrical pier.  相似文献   
5.
Frequency-selective attenuation of sound propagaion and reverberation in shallow waterTXFrequency-selectiveattenuationofsoundp...  相似文献   
6.
In this paper, the irregular wave force on a cylindrical pier group is calculated by the method of spectrum analysis, and the coefficients of the group effect of piers in the pier group are given here. The calculated results, using P-M and Bretshneider's. (B's) spectra, are obtained for the cases of 2 piers, 3 piers and 4 piers. To compare these results with those obtained for regular waves, we can come to some significant conclusions. Under the action of the irregular wave, when the distance between the piers in the pier group increases, the coefficient of the group effect decreases and tends rapidly to the case of a single pier. In general, when the ratio of the distance between the piers to the diameter of the pier is greater than 4, the group effect can be neglected.  相似文献   
7.
南海北部—观测点内潮特征的初步分析   总被引:2,自引:0,他引:2  
采用功率谱分析、调和分析等方法,对南海北部-观测点连续9d(1988年5月8—16日)的温度。盐度和海流及跨越该期间较长的(1988年4月24日-7月22日)潮位资料进行了分析研究。结果表明,观测点存在着一种内潮现象,其波动的周期在24h左右,它传播的方向大体是偏北。  相似文献   
8.
南海西沙西南海域表层沉积物特征   总被引:3,自引:1,他引:3  
西沙西南海域表层沉积物样品矿物成分,地球化学,微体古生物分析测试结果表明:沉积物可分为7种类型,沉积环境主要是陆坡,部分为深海平原,海洋生物,海洋化学以及火山物质的沉积起到了积极的作用,陆源物质的影响较小,它们主要来源于北部大陆和南部岛礁等物源区。  相似文献   
9.
10.
In this study, representative samples from thermal wells and springs were chemically analyzed and geothermometers were used to calculate the deep temperatures of geothermal reservoirs on the basis of water–mineral equilibrium. In some cases, however, the chemical components are not in equilibrium with the minerals in the reservoir. Therefore, log(Q/K) diagrams are used to study the chemical equilibrium for the minerals that are likely to participate. The Na–K–Mg triangular diagram is also applied to evaluate the equilibrium of water with reservoir rocks. Standard curves at the reference temperatures are prepared to reveal which type of silica geothermometer is appropriate for the specified condition. This study shows that water samples from geothermal wells W9 and W12 are in equilibrium with the selective minerals, and chalcedony may control the fluid–silica equilibrium. It is estimated that there is an exploitable low-temperature reservoir with possible temperatures of 80–90°C in the Guanzhong basin.  相似文献   
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