ELECTROMAGNETIC FIELD OF SOURCES AT THE SURFACE OF A HOMOGENEOUS CONDUCTING HALFSPACE WITH HORIZONTAL ANISOTROPY: APPLICATION TO FISSURED MEDIA*     

D. LE MASNE  G. VASSEUR 《Geophysical Prospecting》1981,29(5):803-821

The electric and magnetic fields generated by horizontal electric and vertical magnetic dipoles lying on the surface of a conducting medium with horizontal anisotropy are investigated. Full expressions of their Fourier transforms are given, and the fields for a vertical magnetic dipole are calculated numerically. The radial and vertical magnetic components are found to be independent of the receiver-transmitter direction, whereas the other magnetic and electric components strongly vary with this direction. These results give useful criteria for defining the direction and amplitude of anisotropy from ground data; a ground experiment on fissured limestone was found to confirm the expected variations of the various field components. It is believed that this electromagnetic method can be used in order to provide information about the direction and amplitude of electric anisotropy.  相似文献   

Contrasting Sodic and Potassie Glassy Inclusions in Apatite Crystals from an Ijolite     

LE BAS  M. J.; ASPDE  J.; WOOLLEY  A. R. 《Journal of Petrology》1977,18(2):247-262

Electron probe analysis of isotropic to weakly birefringentglassy inclusions in apatite crystals within the Usaki ijoliteof western Kenya, indicates that two contrasting compositionsexist. These inclusions are thought to represent samples oforiginal silicate melts. One is rich in K₂O(6 weight per cent),poor in Na₂O(0.3 weight per cent), and oversaturated with respectto silica; and the other is rich in Na₂O(6–14 weight percent), poor in K₂O(0.2 weight per cent), has an antipatheticrelation between Na₂O and CaO (together they usually total 15weight per cent) and is undersaturated with respect to silica.One inclusion shows these two compositions co-existing, apparentlyin an immiscible relationship. Other inclusions show compositionsintermediate between the Na-rich and K-rich types, and theyare interpreted as the result of reduced immiscibility. Thepresence of halides and calcium phosphate is considered to enhancethe immiscibility process. The parental composition, estimatedon a volatile-free basis is: SiO₂ 54.9, Al₂O₃, 27.4, CaO 7.3,Na₂O 3.4, K₂O 6.9, which corresponds to a lime-rich aluminoussyenite.  相似文献   

基于空间语义角色的自然语言空间概念提取   总被引：4，自引：1，他引：4  

乐小虬  杨崇俊  于文洋 《武汉大学学报(信息科学版)》2005,30(12):1100-1103

根据空间信息的特点,从定义的空间语义角色入手,通过语义角色标注、短语识别以及概念模式匹配等手段,具体分析了自然语言中的空间实体、实体间空间关系以及空间过程的表达与提取方法。  相似文献   

Recognition of ancient carbonate wind deposits: lessons from a modern analogue, Chrissi Island, Crete   总被引：1，自引：0，他引：1  

PIERRE LE GUERN  ERIC DAVAUD 《Sedimentology》2005,52(5):915-926

Carbonate aeolian deposits are common along arid to semiarid, wind-exposed, present-day coastlines bordered by productive carbonate ramps. Lithified carbonate dunes (aeolianites) have been described around the world in marine terraces of Quaternary age, but these deposits have seldom been identified in the Pre-Quaternary record. Several authors have suggested that this scarcity reflects that these deposits form and are preserved only during icehouse periods characterized by high-amplitude sea-level changes. Others [e.g. McKee and Ward Carbonate Depositional Environments (1983) , AAPG Memoirs, Vol. 33, pp. 131–170] suggest that the scarcity of aeolianites in the Pre-Quaternary record could reflect the ‘great difficulty in recognising wind blown carbonate deposits and in differentiating between them [aeolianites] and other carbonate sands of nearshore environments’. It has been considered that carbonate shoreface/foreshore deposits are very difficult to discriminate petrographically from backshore deposits. This petrographic study of recent sediments from the shoreface to backshore along the northern coast of Chrissi Island, Crete, confirms that carbonate aeolian sands can be very easily misinterpreted as shoreface deposits. Textural examination of thin sections by image analysis techniques indicates, however, that grain orientation patterns differ between facies. Shoreface deposits exhibit a unimodal distribution of grain orientation (flat rose diagram), whereas backshore deposits show a tendency towards a bimodal distribution with a significant proportion of vertical grains. This observation has been confirmed in Pleistocene aeolianites from Tunisia and Western Australia. Grain verticality thus seems to be a reliable criterion for discriminating wind-lain carbonate bodies from shoreface deposits. Vertical grains in aeolian carbonate deposits could reflect gravity effects (e.g. reorientation of grains because of meteoric water percolation and air pull-up). Laboratory experiments conducted on carbonate sands under the action of percolating waters confirm this hypothesis. This reorganization process is preferentially developed in recently deposited and loosely packed sands resulting from grainfall and/or grainflow. In addition, this suggests that the presence of vertical grain orientation might be an indicator of the frequency and intensity of rainfalls during deposition.  相似文献   

阿司匹林的合成条件研究   总被引：7，自引：0，他引：7  

丁健桦郝丽  乐长高王宁 《华东地质学院学报》2005,28(1):76-78

以水杨酸和醋酐为原料经O-酰化反应合成阿司匹林，比较了三氯化铝、三氯化铋和无水碳酸钠三种不同催化剂以及反应条件对合成的影响，找到了最佳催化剂和最佳反应务件，即以三氯化铝为催化剂，其用量为水杨酸的2％，水杨酸与醋酐的摩尔比为1：2，反应时间为30min，回流温度为85℃左右，阿司匹林产率可迭72．6％。实验表明该催化剂催化效果好．不污染环境，是一种环境友好的催化剂。同时，本法简单、快速、经济、无污染，产品质量好，适于工业化生产。  相似文献   

A High-K, Mantle Derived Plutonic Suite from 'Linga', near Arequipa (Peru)   总被引：2，自引：0，他引：2  

LE BEL  L.; COCHERIE  A.; BAUBRON  J. -C.; FOUILLAC  A. M.; HAWKESWORTH  C. J. 《Journal of Petrology》1985,26(1):124-148

The Linga Group consists of a suite of Cretaceous high-K calc-alkalinerocks intruded into 2?0 Ga old basement in S.E. Peru. The rocksrange in composition from gabbros, through diorites and grandioritesto granites. Microprobe, major and trace element and isotopedata suggest the suite evolved by fractional crystallization,with plagioclase as the dominant phase and with surprisinglylittle interaction with the pre-existing crust. The rocks yieldan Rb/Sr whole rock isochron of 68 ? 3 Ma with an initial Sr-isotoperatio 0.70516 ? 8, and from three Nd-isotope analyses initialNd = – 1?4 to – 2?0. ¹⁸ O increases from 5?0 permil in a gabbro to 7?0 per mil in a granite, and models arepresented which suggest that the suite evolved from parentalmagmas which had ¹⁸O = 5?8 to 6?0 per mil, 1.5 per cent K₂O,63 p.p.m. Rb, 582 p.p.m. Sr, 35 p.p.m. Ce, 0.38 p.p.m. Ta, ⁸⁷Sr/⁸⁶Sr= 0.7052, and ¹⁴³Nd/¹⁴⁴Nd = 0.51247. Trace element considerationsimply that these magmas contain contributions from incompatibleelement enriched upper mantle material and from a componentassociated with subduction. The latter is thought to reflectthe preferential mobilization of alkali and alkaline earth elementsby H₂O-rich fluids from the subducted slab, and preliminarycalculations indicate that it was responsible for {small tilde}45 per cent of the Sr and {small tilde} 80 per cent of the Kin the more primitive Linga rocks. However, the isotope datasuggest that while the fluids may be from the subducted slab,the elements in this component may also have been mobilizedfrom the overlying mantle wedge.  相似文献   

Two decades of ocean CO₂ sink and variability     

C. LE QUÉRÉ  O. AUMONT  L. BOPP  P. BOUSQUET  P. CIAIS  R. FRANCEY  M. HEIMANN  C. D. KEELING  R. F. KEELING  H. KHESHGI  P. PEYLIN  S. C. PIPER  I. C. PRENTICE  P. J. RAYNER 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):649-656

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A Chemical and Multi-Isotope Study of the Western Cape Olivine Melilitite Province, South Africa: Implications for the Sources of Kimberlites and the Origin of the HIMU Signature in Africa   总被引：5，自引：3，他引：5  

JANNEY  P. E.; LE ROEX  A. P.; CARLSON  R. W.; VILJOEN  K. S. 《Journal of Petrology》2002,43(12):2339-2370

We present major and trace element and Sr–Nd–Pb–Hf–Osisotopic data for the 76–58 Ma Western Cape melilititeprovince, an age-progressive magmatic lineation in which primitiveolivine melilitite intrusives and alkali basalt lavas have beenemplaced on the southwestern margin of South Africa. The magmasrange from alkali basalts with strong HIMU isotopic and traceelement affinities on the continental shelf to melilitites withkimberlite-like incompatible element compositions and EM 1 isotopicaffinities on thick Proterozoic lithosphere (i.e. ⁸⁷Sr/⁸⁶Sr_i= 0·7029–0·7043,  相似文献   

自动测氡数据干扰因素浅析     

汲大山  王亚男  张维东  郭红霞 《东北地震研究》2002,18(3):46-49

本文对引起氡值变化的干扰因素进行了讨论，分析了盘一井自动测氡资料变化特征及其规律。重点研究了固体潮，气压，室温变化对观测数据的影响。针对氡值出现的夏低冬高的变化，采取了加装等温装置的措施。  相似文献   

旅游目的地传统风俗影响因素与模型构建——以喀什地区为例     

由亚男  卢小静  张志敏 《干旱区地理》2012,35(5):822-828

 随着旅游业发展的日渐成熟,旅游研究定性分析的局限性也日渐显示出来,成为制约当今此类研究的瓶颈。基于上述考虑,通过结构方程模型的定量分析,以喀什地区为示例,研究了旅游目的地家庭文化、道德规范、价值观念等影响因素对传统风俗的影响。结果表明：价值观念对传统风俗的影响显著,家庭文化、道德规范对传统风俗的影响并不显著,而是通过对价值观念产生正向和反向影响,外化为人们的行为方式间接对传统风俗产生影响。从而,为相关研究的定量分析进行了有益的探索与尝试。  相似文献