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951.
In this study, the null-field boundary integral equation method (BIEM) and the image method are used to solve the SH wave scattering problem containing semi-circular canyons and circular tunnels. To fully utilize the analytical property of circular geometry, the polar coordinates are used to expand the closed-form fundamental solution to the degenerate kernel, and the Fourier series is also introduced to represent the boundary density. By collocating boundary points to match boundary condition on the boundary, a linear algebraic system is constructed. The unknown coefficients in the algebraic system can be easily determined. In this way, a semi-analytical approach is developed. Following the experience of near-trapped modes in water wave problems of the full plane, the focusing phenomenon and near-trapped modes for the SH wave problem of the half-plane are solved, since the two problems obey the same mathematical model. In this study, it is found that the SH wave problem containing two semi-circular canyons and a circular tunnel has the near-trapped mode and the focusing phenomenon for a special incident angle and wavenumber. In this situation, the amplification factor for the amplitude of displacement is over 300. 相似文献
952.
恰达地区的二叠系哈尔加乌组火山岩分布于唐巴勒蛇绿岩带东侧、准噶尔盆地西南缘,主要岩性为灰绿色-紫红色(气孔)(杏仁)玄武岩-玄武安山岩-安山岩。LA-ICP-MS锆石U-Pb年龄为(296.6±8.1) Ma,MSWD=7.7(93%置信度),时代属早二叠世。地球化学研究表明:该火山岩属亚碱性系列,全碱含量较高(w(Na2O+K2O)=3.95%~6.39%)且相对富钠。轻稀土(LREE)相对富集((La/Yb)N=3.49~14.66)且分馏较好((La/Sm)N值均大于1.00(1.68~3.51)),重稀土分馏较差((Gd/Yb)N=1.38~2.56)。仅部分样品有微弱的负铕异常(δEu=0.88~1.15)。微量元素具有大离子亲石元素(LILE)相对富集,高场强元素(HFSE)Nb、Ta相对亏损,Zr、Hf轻微富集的特征。综合火山岩的地球化学特征,结合相关构造判别图解及火山岩所处的区域地质背景,认为哈尔加乌组火山岩的形成背景以板内大陆环境为主,兼有部分弧火山岩的特征,形成于俯冲碰撞造山期后的区域伸展背景下,火山岩的岛弧特征是对碰撞前混染弧组分的继承。 相似文献
953.
撰山子角闪二长花岗岩位于华北克拉通与兴蒙造山带结合部位的中生代构造岩浆活动带,对其开展了主量元素、稀土和微量元素分析以及LA-ICP-MS锆石U-Pb定年等工作,目的在于精确厘定岩体的形成时代和研究其形成的动力学背景。结果表明:花岗岩的LA-ICP-MS锆石U-Pb谐和年龄为(245.8±3.1)Ma(MSWD=3.7,n=17),属早三叠世。岩石地球化学成分特征显示为,其具有高硅(w(SiO2)=71.68%~72.85%)、富碱(w(Na2O+K2O)=8.98%~9.20%)、高铝(w(Al2O3)=13.45%~13.77%)、低钙(w(CaO)=0.81%~0.99%)及低TFeO/MgO值(平均值为6.55)的特征,属高钾钙碱性、高分异I型弱铝质花岗岩;稀土配分曲线呈现向右倾斜的配分模式,Eu具有明显的亏损(δEu=0.66~0.68),表明斜长石发生了明显的分离结晶作用;在微量元素原始地幔标准化图谱上呈现清晰的Th、U、La、P富集,Ba、Nb、Ti、Sr、Ta等相对亏损的特征。综合分析认为,撰山子角闪二长花岗岩主要形成于下地壳部分熔融作用,可能有少量的地幔组分加入,其形成于华北板块和西伯利亚板块最终拼合后的后碰撞/后造山伸展作用构造环境。 相似文献
954.
Rural heritage that involves agricultural heritage could be critical to enhancing community identity through a conservational approach. The purpose of this research is to develop conservational methods for rural heritage that include agricultural heritage areas through the use of ecomuseums. To conduct the research, we first reviewed the concepts of ecomuseum and rural heritage. Secondly, we defined the concept of the Korean rural ecomuseum by taking into consideration the concept defined by Riviere, Globally Important Agricultural Heritage Systems (GIAHS), the rural heritage policy of Europe, and the agricultural heritage systems of Korea. Thirdly, we also describe methods that are applicable to Korean rural ecomuseums, which include type classification and components. Finally, we applied the ecomuseum concept to two pilot models in the Cheongsando and Gurae areas, both Korea Important Agricultural Heritage System (KIAHS) sites. We conclude that it is desirable to expand the range of targets for conservation from agricultural heritage to rural heritage areas. From this point of view, the rural ecomuseum can be a highly valuable tool that can help preserve agricultural heritage sites and neighboring areas. Furthermore, the ecomuseum can enhance community identities, and strengthen local economies. 相似文献
955.
956.
Te-Hsien Lin Ching-Hua Lo Sun-Lin Chung Fang-Jui Hsu Meng-Wan Yeh Tung-Yi Lee Jian-Qing Ji Yi-Zhau Wang Dunyi Liu 《Journal of Asian Earth Sciences》2009,34(5):674-685
We conducted a comprehensive 40Ar/39Ar geochronological study of the Jiali and Gaoligong shear zones to obtain a better understanding of crustal deformation and tectonic evolution around the Eastern Himalayan Syntaxis (EHS). The new age data reveal that the main phase of deformation in the Jiali and Gaoligong shear zones occurred from 22 to 11 Ma and from 18 to 13 Ma, respectively. Structural data collected during this study indicate that the Jiali shear zone underwent a change in shear sense from sinistral to dextral during its movement history. Based on a comparison with the deformation histories of other major shear zones in the region, we argue that the initial sinistral motion recorded by the Jiali shear zone was coincident with that of the Ailao Shan–Red River shear zone, which marked the northern boundary of the southeastward extrusion of the Indochina block during the Early Miocene. From the Middle Miocene (~18 Ma), the Jiali shear zone changed to dextral displacement, becoming linked with the dextral Gaoligong shear zone that developed as a consequence of continued northward indentation of the Indian continent into Asia. Since this time, the Jiali and Gaoligong shear zones have been united, defining the southwestern boundary of the EHS during clockwise rotation of the eastward-extruding Tibetan block, as revealed by recent GPS data. The temporal change in regional deformation pattern from southeastward block extrusion to clockwise rotation of crustal fragments may have played an important role in the development of the eastern Himalayan drainage system around the EHS. 相似文献
957.
958.
Jay Lee William A. Kretzschmar Jr 《International journal of geographical information science》2013,27(6):541-560
Abstract During the 1980s techniques for analysis of geographical patterns have been refined to the point that they may be applied to data from many fields. Quantitative spatial analysis and existing functions available in geographical information systems (GIS) enable computerized implementations of these spatial analysis methods. This paper describes the application of quantitative spatial analysis and GIS functions to analysis of language data, using the extensive files of the Linguistic Atlas of the Middle and South Atlantic States (LAMSAS). A brief review of recent development of using quantitative and statistical methods for analysing linguistic data is also included. 相似文献
959.
Xiaohua Tong Wenzhong Shi Dajie Liu 《International journal of geographical information science》2013,27(11):1413-1432
In this paper, a least‐squares based cadastral parcel area adjustment in geographic information systems (GIS) is developed based on (1) both the areas and coordinates being treated as observations with errors; and (2) scale parameters being introduced to take the systematic effect into account in the process of cadastral map digitization. The area condition equation for cadastral parcel considerations of scale parameters and geometric constraints is first constructed. The effects of the scale error on area adjustment results are then derived, and statistical hypothesis testing is presented to determine the significance of the scale error. Afterwards, Helmert's variance component estimation based on least‐squares adjustment using the condition equation with additional parameters is proposed to determine the weight between the coordinate and area measurements of the parcel. Practical tests are conducted to illustrate the implementation of the proposed methods. Four schemes for solving the inconsistencies between the registered areas and the digitized areas of the parcels are studied. The analysis of the results demonstrates that in the case of significant systematic errors in cadastral map digitization, the accuracies of the adjusted coordinates and areas are improved by introducing scale parameters to reduce the systematic error influence in the parcel area adjustment. Meanwhile, Helmert's variance component estimation method determines more accurate weights of the digitized coordinates and parcel areas, and the least‐squares adjustment solves the inconsistencies between the registered areas and the digitized areas of the parcels. 相似文献
960.
This research is motivated by the need for 3D GIS data models that allow for 3D spatial query, analysis and visualization of the subunits and internal network structure of ‘micro‐spatial environments’ (the 3D spatial structure within buildings). It explores a new way of representing the topological relationships among 3D geographical features such as buildings and their internal partitions or subunits. The 3D topological data model is called the combinatorial data model (CDM). It is a logical data model that simplifies and abstracts the complex topological relationships among 3D features through a hierarchical network structure called the node‐relation structure (NRS). This logical network structure is abstracted by using the property of Poincaré duality. It is modelled and presented in the paper using graph‐theoretic formalisms. The model was implemented with real data for evaluating its effectiveness for performing 3D spatial queries and visualization. 相似文献