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991.
Coastal Wetlands of China: Changes from the 1970s to 2007 Based on a New Wetland Classification System 总被引:1,自引:0,他引:1
A new classification of coastal wetlands along the coast of China has been generated that is compatible with the Ramsar Convention of 1971. The coastal wetlands have been divided into two broad categories with overall nine subcategories. On this basis, a series of coastal wetland maps, together covering the coast of mainland China, have been produced based on topographic maps acquired in the 1970s and satellite images acquired in 2007. These document substantial wetland losses over this period. In the 1970s, the total coastal wetland area in China was 5.76?×?104?km2, whereas in 2007, it was 5.36?×?104?km2, indicating a loss of 7 %. Over this approximately 40-year period, the area of natural coastal wetlands decreased from 5.74?×?104 to 5.09?×?104?km2, while that of artificial coastal wetlands increased from 240 to 2,740 km2. Due to shoreline and sea-level changes, newly formed coastal wetlands amounted to 2,460 km2, while coastal wetland loss amounted to 6,310 km2 in the period from the 1970s to 2007. When excluding shallow coastal waters (depths between 0 and ?5 m), nearly 16 % of Chinese coastal wetlands have been lost between the 1970s and 2007. 相似文献
992.
东嘎花岗岩体位于冈底斯一念青唐古拉板片北缘、班公错一怒江结合带中段班戈一崩错板片。岩体时代为燕山晚期,属印度一欧亚板块碰撞造山构造环境。岩石属富钠、硅铝过饱和类型,该岩体位于斑戈一嘉黎一波密一察隅锡成矿远景带内,岩浆分异程度高,具有S型花岗岩体的典型特征,与滇西、川西含锡花岗岩体特征相似,成矿条件有利。区域化探资料显示锡异常明显,异常为Sn、Rb、Y、u、Nb、Ag、w、Th、Pb等多元素组合。sn元素的强度高、规模大。据区域地质、岩石化学及地球化学特征及区域成矿资料,东嘎花岗岩体具有良好的锡成矿前景。 相似文献
993.
Many methods have been used to study wind erosion, a common phenomenon in arid and semi-arid regions. This paper documents a 2006 field study in which sediment samplers and steel pins were used to measure soil erosion, and sand drift potential was used to estimate wind erosion and transport in the eastern part of Ningxia Province, China. Wind energy in the study area was found to be moderate and sediments were transported from northwest to southeast. Sediment transport differed depending on the surface type: sediment transport was greatest in areas of shifting dunes, with cultivated land, semi-fixed dunes, and fixed dunes showing progressively less transport. Sediment transport was lowest in shrubland areas. The depth of erosion was 66 in cultivated areas, 33 in shifting dunes, 28 in semi-fixed dunes, 20 in fixed dunes, and 3 mm in shrublands. The extensive erosion of sediment in cultivated lands and the resultant decrease in surface height results in serious degradation and loss of soil fertility. 相似文献
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提要:达连河油页岩含矿区位于黑龙江省依兰地区,该区是一个半地堑式断陷盆地。古近系达连河组为一个完整的三级层序,油页岩形成于水进体系域和高水位体系域发育时期。本文认为达连河组油页岩存在两种成矿模式,即湖泊-沼泽相油页岩成矿模式、浅湖相-半深湖相油页岩成矿模式;不同成矿类型油页岩分布于层序的不同体系域,古地貌型、沉积密集段型油页岩成矿常分布于水进体系域,沉积密集段型、气候型油页岩成矿位于高水位体系域。 相似文献
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Natural Resources Research - The application of deep learning algorithms in mineral prospectivity mapping (MPM) is a hot topic in mineral exploration. However, few studies have focused on recurrent... 相似文献
999.
Journal of Geographical Sciences - Rocky desertification poverty (RDP) refers to rural poverty triggered or exacerbated by rocky desertification, which deprives farmers of opportunities for... 相似文献
1000.
Ji Yang Ying-Xi Zuo Zheng LOU Jing-Quan Cheng Qi-Zhou Zhang Sheng-Cai Shi Jia-Sheng Huang Qi-Jun Yao Zhong Wang 《天体物理学报》2013,(12):1493-1508
As the highest, coldest and driest place in Antarctica, Dome A provides exceptionally good observing conditions for ground-based observations over terahertz wavebands. The 5 m Dome A Terahertz Explorer (DATES) has been proposed to explore new terahertz windows, primarily over wavelengths between 350 and 200 pm. DATE5 will be an open-air, fully-steerable telescope that can function by unmanned operation with remote control. The telescope will be able to endure the harsh polar environment, including high altitude, very low temperature and very low air pressure. The unique specifications, including high accuracies for surface shape and pointing and fully automatic year-around remote operation, along with a stringent limit on the periods of on-site assembly, testing and maintenance, bring a number of challenges to the design, construction, assembly and operation of this telescope. This paper intro- duces general concepts related to the design of the DATE5 antenna. Beginning from an overview of the environmental and operational limitations, the design specifications and requirements of the DATE5 antenna are listed. From these, major aspects on the conceptual design studies, including the antenna optics, the backup structure, the pan- els, the subreflector, the mounting and the antenna base structure, are explained. Some critical issues of performance are justified through analyses that use computational fluid dynamics, thermal analysis and de-icing studies, and the proposed approaches for test operation and on-site assembly. Based on these studies, we conclude that the specifications of the DATE5 antenna can generally be met by using enhanced technological approaches. 相似文献