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111.
A detailed field and laboratory study has been made of a well-exposedglaucophane schist sequence within the Jurassic and CretaceousFranciscan Formation of northern California. Three types ofglaucophane-bearing metamorphic rocks have been distinguishedin and around the area of the detailed study. Each is characterizedby distinctive textures and mineral assemblages that are interpretedto represent different grades of metamorphism within the glaucophaneschist facies. From the combination of small- and large-scale mapping in thearea described it is clear that coarsely schistose blocks, tensof feet in diameter, commonly rest directly upon and withinless intensely metamorphosed terrain. In the Cazadero area theseisolated blocks of coarsely crystalline rocks are concentratedin a band that is roughly concordant with some of the majorfaulting, and their metamorphic fabric shows no consistent relationto local or regional structures. It is tentatively suggestedthat these blocks have been transported upward tectonicallyand that they are not stratigraphically equivalent to the othertypes of glaucophane-bearing metamorphic rocks in the area. Chemical and petrographic evidence indicates that basalt andsediments have been converted to glaucophane-bearing rocks underconditions of metamorphism that were essentially isochemical,except for fugitive components and some minor elements. 相似文献
112.
云和雨的相干散射与雷达气象方程 总被引:1,自引:0,他引:1
研究了云雨质点对雷达波的相干散射,从而推得比较普遍的雷达气象方程。旧的雷达气象方程是新方程在云雨质点互相独立时的特殊表现形式。对新方程作了一些讨论,发现旧方程之所以在某些方面与实验不符,可能是因为忽略了相干散射作用的缘故。 相似文献
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T. LEE 《Geophysical Prospecting》1983,31(5):766-781
The presence of a conducting environment about a spherical ore body must be considered when calculating the transient electromagnetic response of the ore body due to a step current flowing in a large circular loop at the earth's surface. Failure to do this can easily lead to errors in excess of 10% in numerical calculations. Moreover, there is only a limited time interval in which the response of the spherical conductor is easily seen. In a poorly conducting ground the resonance response of the sphere is the first to be excited. Later, however, the non-resonance or wave-type response is excited. These waves destructively interfere and finally the response of the sphere decays with time as t?7/2. For a range of times and depths the best loop for detecting the sphere has about the same radius as the sphere. 相似文献
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本文用统计方法研究1930—1939年期间逐月北半球气压偏距中心的活动规律.发现同一月份的气压偏距中心在北半球某些地区有集中出现的情况,这些集中地区如在阿拉斯加的南方、大西洋的东北部以及亚欧大陆的北冰洋沿岸.这些地区可以认为是北半球环流异常的关鍵性地区.绝大多数的偏距中心在逐月之间可以发现它们的联系.在过渡季节,大多数偏距中心自西向东移动.在偏距中心相互作用的基础上,本文还讨论了北半球某些地区的气候特点. 相似文献
118.
LEE LANGAN 《Geophysical Prospecting》1966,14(Z2):488-503
The development of optically pumped and monitored “atomic” magnetometers has allowed the application of greater resolution in geomagnetic measurements for exploration purposes. This paper presents a survey of instrumentation in use, the variety of exploration techniques that are being used in practice, and an estimate of their state of development. Alkali metals (rubidium and cesium) and helium have been used as active elements to obtain the magnetic-field dependent Larmor frequency. Each of these instruments is capable of obtaining high resolution data (data with sensitivity numerically smaller than one-tenth gamma). They have been adapted for airborne, land, and marine usage. Such sensitivity has enabled the rapid development of geomagnetic gradiometers, high sensitivity aeromagnetics, diurnally reduced ground surveys, broad-band magneto-telluric surveys, susceptibility measurements, and convenient magnetic search and location techniques. Outlines of each procedure and an example of its application are given. 相似文献
119.
Chin-yu LEE Professor Department of Soil Water Conservation National Pingtung University of Science Technology Pingtung Taiwan R.O.C. 《国际泥沙研究》2004,(2)
To recognize the geographical characteristics of the landslide areas will be helpful for the watershedmanagement in the reservoir watershed. According to the quantitative analysis, we'll take differentscores and weighting for the potential parameters of the landslide areas in the Tsengwen reservoirwatershed, and in the meanwhile, we'll extract the different factors, including the slope, aspect,altitude, soil and geological textures etc., and the results shown as maximum one--day rainfall, ratio offorests and average relief is the most affecting parameters on the potential risk map of landslide areas. 相似文献
120.
CHEN Zhaonan 《中国科学D辑(英文版)》2004,47(3)
Are human able to foresee the future? For thou-sands of years close attention has been paid to this issue. At the present day, in order to survive from competition and to predominate over the nature, hu-man抯 desire of forecasting things has become more and more intense. Compared to conquering space, more people yearn for being able to control the time. From ancient to the present, mankind always dream of contacting the past, governing the present and tran-scending the future. Recent years in… 相似文献