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981.
The No. 6 Coal-bed from the Heidaigou Mine, Jungar Coalfield, Inner Mongolia is a super-large Ga deposit. The dominant carrier of Ga is boehmite in coal. The study of coal facies may provide genetic enrichment information of Ga and its carrier (boehmite) in the Ga deposit. On the basis of study on coal petrology and mineralogy, it was found that the No. 6 Coal-bed from the Heidaigou Mine of Jungar was enriched in inertinites and the microlitho-types were dominated by clarodurite. The maceral morphological features and association indicate that the coal-bed was formed in a dry sedimentary environment or in a periodic dry sedimentary environment caused by the alternating variations of groundwater level. The optimum conditions for the enrichment of Ga and its particular carrier (boehmite) were dominated by four transitional conditions: (1) the upper delta plain which was the transitional zone between alluvial and lower delta plains, (2) the transitional zone between the dry and wet forest swamps, being slightly apt to the dry one, (3) the transitional tree density between the thick and loose ones, and (4) the low moor that was the transitional zone between two high moors during peat accumulation. 相似文献
982.
This paper presents a robust H∞ output feedback control approach for structural systems with uncertainties in model parameters by using available acceleration measurements and proposes conditions for the existence of such a robust output feedback controller. The uncertainties of structural stiffness, damping and mass parameters are assumed to be norm-bounded. The proposed control approach is formulated within the framework of linear matrix inequalities, for which existing convex optimization techniques, such as the LMI toolbox in MATLAB, can be used effectively and conveniently. To illustrate the effectiveness of the proposed robust H∞ strategy, a six-story building was subjected both to the 1940 El Centro earthquake record and to a suddenly applied Kanai-Tajimi filtered white noise random excitation. The results show that the proposed robust H∞ controller provides satisfactory results with or without variation of the structural stiffness, damping and mass parameters. 相似文献
983.
Geochemistry of the high-Mg andesites at Zhangwu, western Liaoning: Implication for delamination of newly formed lower crust 总被引:6,自引:0,他引:6
Ten volcanic samples at Zhangwu,western Liaoning Province,North China were selected for a sys-tematic geochemical,mineralogical and geochronological study,which provides an opportunity to ex-plore the interaction between the continental crust and mantle beneath the north margin of the North China craton.Except one basalt sample(SiO2= 50.23%),the other nine samples are andesitic with SiO2 contents ranging from 53% to 59%.They have relatively high MgO(3.4%―6.1%,Mg#=50―64) and Ni and Cr contents(Ni 27×10?6―197×10?6,Cr 51×10?6―478×10?6).Other geochemical characteristics of Zhangwu high-Mg andesites(HMAs) include strong fractionation of light rare earth elements(LREE) from heavy rare earth elements(HREE),and Sr from Y,with La/Yb greater than 15,and high Sr/Y(34― 115).Zircons of andesite YX270 yield three age groups with no Precambrian age,which precludes ori-gin of the Zhangwu HMAs from the partial melting of the Precambrian crust.The oldest age group peaking at 253 Ma is interpreted to represent the collision of the Siberia block and the North China block,resulting in formation of the Central Asian orogenic belt by closure of the Mongol-Okhotsk Ocean.The intermediate age group corresponds to the basalt underplating which caused the wide-spread coeval granitoids in the North China craton with a peak 206Pb/238U age of 172 Ma.The youngest age group gives a 206Pb/238U age of 126±2 Ma,which is interpreted as the eruption age of the Zhangwu HMAs.The high 87Sr/86Sri(126 Ma)>0.706 and low εNd(t)= ?6.36―?13.99 of the Zhangwu HMAs are distinct from slab melts.The common presence of reversely zoned clinopyroxene phenocrysts in the Zhangwu HMAs argues against the origin of the Zhangwu HMAs either from melting of the water saturated mantle or melting of the lower crust.In light of the evidence mentioned above,the envisaged scenario for the formation of the Zhangwu HMAs is related to the basaltic underplating at the base of the crust,which led to the thickening of the lower crust and formation of lower crustal eclogite,followed by foundering of the eclogitic lower crust into the asthenosphere.The foundered eclogite then melted and the resul-tant melts interacted with surrounding peridotite during their upward transport,which finally produced the high-Mg andesites.This well explains the high-Mg adakitic characters and absence of ancient in-herited zircon in the Zhangwu lavas. 相似文献
984.
985.
986.
利用TOGA—TAO赤道次表层海流与海温观测资料,比较清楚地揭示了1997/1998年El Nino期间在赤道西太平洋暖池上空西风异常的驱动下,次表层异常海流的产生机制和向东传播过程中的变化特征。对比分析了海表、次表层异常海流的两种热力平流过程,即水平温度平流和因海流水平辐合辐散造成的垂直上翻(或下沉)运动对混合层及海表温度异常的贡献,结果证实了后一效应对ENSO发生发展的重要意义。最后还对文中的海流异常是否就是理论分析得到的Kelvin波在海流场上的反映进行了讨论。 相似文献
987.
海温变化对台风路径的影响 总被引:8,自引:2,他引:8
在台风模式中采用周平均海温和多年的月平均海温,对一些台风个例进行了比较,分析了数值模式中影响台风路径的海温因子变化对台风移动路径的影响。 相似文献
988.
989.
将物探电法的测点数据及测点的大地直角坐标按每条测线上测点由西向东的顺序 ,以统一编号、线号、点号、横坐标、纵坐标、测点数据为字段建成MicrosoftAccess数据库。根据制图比例尺和测点的大地直角坐标逐个计算数据库中所有测点在图纸上的坐标值 ,绘制测点位置子图 ,并在测点位置沿垂直测线方向向东移动 1/ 2测点数据注释的字符宽度 ,并以测点位置为圆心顺时针旋转 6 0°的位置绘制测点数据注释。按照上述方法 ,以MicrosoftVC + + 6 0为工具 ,利用MAPGIS 6 1地理信息系统二次开发技术 ,编制数据处理程序 ,实现电法原始数据图的微机制图 相似文献
990.