Plagioclase porphyroblast growth and its relation to deformation in the Alhamilla unit (Sierra Alhamilla, Betic Cordilleras, SE Spain)     

B. VAN DEN EECKHOUT  G. KONERT † 《Journal of Metamorphic Geology》1983,1(3):227-240

Abstract. Plagioclase porphyroblasts from silvergrey schists belonging to the Nevado Filabride Complex in the Sierra Alhamilla (Betic Zone, SE Spain) are interpreted as having been formed preand synkinematically with respect to the second phase of deformation. Different types of inclusion patterns represent 'snap-shots'(high growth-rate/strain-rate ratio features) of the formation of a diffentiated crenulation cleavage during this second phase of deformation, by the processes of kinking, crenulation and associated differentiation.
Regional considerations indicate an Alpine age for this tectono-metamorphic event, which can be explained by the'hot emplacement'of the higher Nevado Filabride units. The observed structural evolution is not consistent with a pre-Alpine polyphase deformation history.  相似文献   

中国人口迁移的区域差异与流场特征   总被引：40，自引：4，他引：36  

丁金宏  刘振宇  程丹明  刘瑾  邹建平 《地理学报》2005,15(1):106-114

通过2000年人口普查省际迁移数据的分析,揭示了当代中国人口迁移的区域分异性,以及不同原因的流场新模式。研究发现,中国人口迁移进入高活性、高能力的新阶段;东中西部人口迁移的不平衡性不断加剧,“中部塌陷”不仅是经济意义上的,而且也是社会意义上的;人口省际迁移的辐合流场与辐散流场在进一步发展,珠江三角洲是最大的迁移辐合中心;东北与山东的对流渐趋消失,西北取代东北成为非沿海区域新的人口引力中心;以秦岭-淮河线东段和黑河-腾冲线南段为界,人口迁移分裂为东南和西北两大“流域”。就业迁移的优势程度在进一步加大,市场取代计划成为人口和人才流动的第一动力;婚姻迁移的主流方向是西南贫困山区指向华东农村,形成了西南“喀斯特新娘输出区”。  相似文献   

The Trade and Industries of Western South America     

《The Journal of geography》2012,111(3):109-122

Abstract

This research was based on an instructional module developed and used to investigate whether GIS can be used to enhance fourth grade students' geographic knowledge and map skills. Another goal was to identify challenges the teachers and the students face using GIS.

Findings from the study suggest that using GIS in the classroom helps students improve their geographic knowledge and maps skills. In addition, this study found that the students' geographic content knowledge tended to improve gradually and the knowledge transferred to the subsequent lessons, while certain map skills tended to develop in a more specific manner.  相似文献   

River Views of Beginning Pre-service Teachers: Content Knowledge Use     

《The Journal of geography》2012,111(2):61-68

Abstract

How beginning teachers organize themselves to teach new or unfamiliar topics is an important issue for research. This paper discusses information about rivers in pre-service teachers' lessons taught to fourth grade students. Lessons were videotaped and transcribed for analysis. The data consisted of all information about rivers found in the lessons. Lesson content was analyzed for accuracy, coherence, centrality, over-simplification, and undue emphasis.

Seven kinds of problems with lesson content occurred because the beginning teachers lacked sufficient knowledge about rivers. Inaccurate information was either presented or allowed to stand unchallenged in the lessons. The lessons lacked coherence, because the beginning teachers tended to make passing references to concepts. About twice as many of the lesson concepts were peripheral to the study of rivers, the problem of centrality. The relationships between some river-related ideas were misunderstood or ignored. Both physical and human geography concepts were consistently over-simplified. The recreational use of rivers was consistently over-emphasized.  相似文献   

旅游网站信息流距离衰减形态分异特征及其与网站功能的关系     

张秋娈  朱苏加  路紫  聂学东 《地理与地理信息科学》2012,28(4):94-97

应用10个样本旅游网站日均访问量的空间分布数据及网站功能资料,对样本旅游网站日均访问量与实际距离进行空间关系逆曲线拟合,进行距离衰减形态分异及其与网站功能相关性的研究。结果发现:1)旅游网站信息流距离衰减形态具有显著的波动性分异特征和地方性分异特征,随着旅游网站信息流距离衰减波动性分异特征从显著性到不显著性的变化,其距离衰减程度依次增强,其逆曲线衰减的符合程度依次上升;而随着旅游网站信息流距离衰减地方性分异特征由显著性到不显著性的变化,其距离衰减程度依次减弱,其逆曲线衰减的符合程度依次下降。表明不同网站间信息流距离衰减存在多样性变化。2)旅游网站信息流距离衰减形态的分异特征与旅游网站的主要功能之间关系密切:信息发布为主兼有预订功能的旅游网站距离衰减形态较为复杂;预订为主兼有信息发布的旅游网站和论坛为主的旅游网站距离衰减形态基本一致,波动性较小、地方性显著;政务为主的旅游网站距离衰减形态表现为波动性较大、地方性不显著的特征。依据旅游网站信息流距离衰减形态的规律,可指导旅游网站服务功能的建设和组织不同距离上的旅游流。  相似文献   

辽宁省沈大双核与其他城市的分化     

赵映慧  齐艳红  姜博  张慧 《云南地理环境研究》2012,24(3):21-24,36

分析辽宁省沈阳大连的核心作用,将辽宁省城市分为核心城市组(沈阳、大连)和外围城市组(其他城市);再以人口、GDP和人均GDP为基本指标,利用Theil指数计算组内差异、组间差异和总体差异,利用KZ指数模型计算核心城市与外围城市的分化。结果表明沈阳大连与其他城市的分化总体上加大;分化具有波动性特征,分化在地域空间上也体现为辽中南城市群被以沈阳为核心的辽中城市群和以大连为核心的辽南城市群取而代之,其他地区城市聚集不明显;沈阳大连与辽宁省其他城市的分化是自然和社会经济因素综合作用的结果,分化机制主要有地理位置的先导机制、区域发展战略的催化机制和政府规划的引导机制。  相似文献   

Dark matter annihilation at cosmological redshifts: possible relic signal from annihilation of weakly interacting massive particles     

A. N. Baushev 《Monthly notices of the Royal Astronomical Society》2009,398(2):783-789

We discuss the possibility of observing the products of the dark matter annihilation that was going on in the early Universe. Of all the particles that could be generated by this process, we consider only photons, as they are both uncharged and easily detectable. The younger the Universe was, the higher the dark matter concentration n and the annihilation rate (proportional to n ²) were. However, the emission from the very early Universe cannot reach us because of the opacity. The main part of the signal was generated at the moment the Universe had just become transparent for the photons produced by the annihilation. Thus, the dark matter annihilation in the early Universe should have created a sort of relic emission. We obtain its flux and the spectrum.
If weakly interacting massive particles (WIMPs) constitute dark matter, it is shown that we may expect an extragalactic gamma-ray signal in the energy range 0.5–20 MeV with a maximum near 8 MeV. We show that an experimentally observed excess in the gamma-ray background at 0.5–20 MeV could be created by the relic signal from the annihilation of WIMPs only if the dark matter structures in the Universe had appeared before the Universe became transparent for the annihilation products  ( z ≃ 300)  . We discuss in more detail physical conditions whereby this interpretation could be possible.  相似文献   

Solar-stellar astrophysics and dark matter     

Sylvaine Turck-Chieze  Ilidio Lopes 《天体物理学报》2012,(8):1107-1138

  相似文献   

Solution of Lane-Emden type equations using Bernstein operational matrix of differentiation     

Rajesh K. Pandey  Narayan Kumar 《New Astronomy》2012,17(3):303-308

The purpose of this paper is to propose an efficient numerical method for solving Lane-Emden type equations arising in astrophysics using Bernstein polynomials. First Bernstein operational matrix of differentiation is derived using Bernstein polynomials and then applied to solve the linear and nonlinear differential equations of Lane-Emden type. Some illustrative examples are given to demonstrate the efficiency and validity of the proposed algorithm.  相似文献   

内蒙古双尖子山银铅锌(锡)矿床石英正长斑岩U-Pb年龄、地球化学及其地质意义   总被引：1，自引：0，他引：1  

赵家齐  周振华  欧阳荷根  陈宝全  刘文杰  杨帆 《矿床地质》2022,41(2):324-344

内蒙古双尖子山超大型银铅锌多金属矿是亚洲最大的银矿床,除了目前已经探明的银、铅锌以外,近年来地质工作者研究发现勘查发现该矿床深部还存在寻找锡矿的潜力.文章对钻孔新揭露的隐伏石英正长斑岩开展了岩石地球化学、锆石U-Pb定年和Hf同位素研究.结果表明:双尖子山石英正长斑岩LA-MS-ICP锆石U-Pb加权平均年龄为(131...  相似文献