扬子地台北缘早前寒武纪结晶基底构造样式及变形特征   总被引：1，自引：0，他引：1  

刘援朝  魏显贵  吴德超  杜思清  何政伟 《矿物岩石》1997,(Z1)

四川省南江地区出露的早前寒武纪结晶基底中存在有晚太古—元古代时期形成的多期面理及面理置换叠加；断裂构造以韧性剪切带占主导地位；褶皱构造则随时代的演化依次发育等轴卵形穹盆构造、短轴卵状背、向形构造、线状同斜倾竖褶皱。  相似文献   

江西彭泽大港周地区萍乡式滑脱构造的基本特征     

吴新华  胡肇荣 《江西地质》1997,(1)

本文以１∶５万区调资料为基础，对大港周地区滑脱构造的层块特征、岩石力学性质及物性特征，主滑面及次滑面的基本特征作了较详细的描述，把本区滑脱构造归属为萍乡式（叠瓦式）。从而对其成因构式进行了探讨  相似文献   

经Ⅲ型光学经纬仪竖轴,水平盘的结构和拆卸     

谢长湘 《四川测绘》1997,20(2):88-89

本文以解剖麻雀的方法，阐述了经Ⅲ型光学经纬仪坚轴系和水平盘的结构及其特点、拆卸方法和注意事项，对仪器维修具有实践性的指导价值。  相似文献   

WRITING FOR NONGEOGRAPHERS: LESSONS FROM THE J. B. JACKSON PRIZE     

KENNETH D. MADSEN 《Geographical review》2002,92(1):63-72

ABSTRACT. Recent presidents of the Association of American Geographers have made it clear that as a discipline we need to do more to reach outside the confines of academia. Since 1985, the J. B. Jackson Award has recognized individuals whose books provide examples of how to share professional geographical knowledge with the educated lay public. Through correspondence with these individuals, recommendations for improving geographers' outreach are presented.  相似文献   

Elastodynamical mechanism of rate‐dependent friction     

Dmitri Pisarenko 《Geophysical Journal International》2002,148(3):499-505

  相似文献   

由古代天象记载研究揭示的地球自转变化的两个重要现象     

韩延本 《地球物理学进展》1996,(4)

本文简要介绍了利用古代天象观测记载研究地球自转长期变化所揭示的两个重要现象，即存在着使自转速率加速的非潮汐因素；地球自转在约千余年之前出现过较大的起伏。  相似文献   

Dynamic characteristics of spring sandstorms in 2000   总被引：11，自引：0，他引：11  

周秀骥  徐祥德  颜鹏  翁永辉  王建林 《中国科学D辑(英文版)》2002,45(10):921-930

Systematical analyses of spring sandstorms in 2000 affecting Beijing area are carried out. Results revealed the key dynamic mechanisms of dust storm during its mobilization, lifting, horizontal advection and deposition processes. It turns out that in the processes of sandstorms influencing Beijing area in March–April 2000, the dynamic conditions for dust mobilization are significantly correlated with phenomena, such as cold air-related climatic activities, clay soils area of North China and surface friction velocity anomaly. The characteristics of sandstorm can be described by composite mode of dust particles mobilization-lifting-long-range transport. This paper will provide scientific evidences for further studies, prediction and harness of sandstorms in China.  相似文献   

不同时间尺度下农田土壤风蚀可蚀性的变化   总被引：1，自引：1，他引：0  

王仁德  安晨宇  苑依笑  张春来  李庆  查慧敏  常春平  郭中领 《中国沙漠》2021,41(5):202-209

土壤风蚀可蚀性（简称土壤可蚀性）作为风蚀模型的必要输入参数之一,会随风蚀事件过程、耕作措施以及气象气候等因素发生显著变化,但目前对其变化趋势尚认识不足。本文采用野外观测、采样分析与空间换时间的方法,就次风蚀事件、风蚀月、风蚀季、多年4个时间尺度下坝上地区农田土壤可蚀性变化问题进行研究。结果表明：严重风蚀事件过程中,地表土壤中粒径<0.85 mm干团聚体颗粒的含量明显降低,临界起沙摩阻风速明显升高,输沙率明显减弱,三者均显示土壤可蚀性出现明显降低的趋势。风蚀月、风蚀季和多年3个时间尺度下,农田特别是翻耕农田土壤可蚀性均呈下降的趋势,并且时间尺度越长,土壤可蚀性的下降幅度越大。强烈的风蚀搬运作用可能是造成各时间尺度下坝上地区农田土壤可蚀性普遍下降的主因。为了降低坝上地区农田风蚀的危害,应减少新农田的开垦并尽量避免在风蚀事件高发期进行农田翻耕。  相似文献   

Chain-based polyline tessellation algorithm for cartographic rendering     

Mingguang Wu  Peibei Zheng  Guonian Lu  A-Xing Zhu 《制图学和地理信息科学》2017,44(6):491-506

ABSTRACT

Although the extrusion of 1D polylines into a 2D polygon and the tessellation of the polygon into primitives has been performed in the field of computer graphics, the efficient, robust, and high-quality tessellation of thick polylines that supports various cartographic styles for polyline rendering remains a practical challenge. We examined and compared existing vertex-, segment-, and polygon-based algorithms, and present a chain-based tessellation algorithm for cartographic rendering: points in the polyline are classified into abrupt and smooth points according to their point spacing, angle and thickness. The polylines are then divided into abrupt and smooth chains by clustering points that are adjacent and of the same type. An optimal algorithm is also presented to continuously tessellate the smooth chains into minimum geometric primitives and efficiently tessellate the abrupt chains into geometric primitives. We implemented the proposed algorithm and present the results of robustness, efficiency, quality, and cartographic styling tests conducted on real-world polylines. The results indicate that this approach has substantial advantages when considering all four requirements (robustness, efficiency, quality, and the support for various cartographic styles).  相似文献   

龙门山冲断带构造特征研究主要进展及存在问题探讨   总被引：25，自引：0，他引：25  

金文正  汤良杰  杨克明  万桂梅  吕志洲 《地质论评》2008,54(1):37-46

在前人研究成果基础上,对龙门山冲断带差异构造变形特征,构造几何样式,构造演化等几个方面进行了综述。研究表明,龙门山冲断带具有明显差异构造变形特征,即东西分带、南北分段、上下分层,同时发育大量构造变形样式,如断层相关褶皱、三角带、飞来峰、双重构造等等,在经历了多期复杂构造演化之后,构造变形样式具有多期叠加特征,最后提出详细地表构造地质建模、地震剖面精细解释及合理模型的建立,同时结合多种量化测试分析手段能够有效推进龙门山冲断带复杂构造样式与多期构造演化阶段分析研究工作,以及推动该地区的油气勘探。  相似文献