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522.
在分析了地籍测量课程的产生、作用及存在的问题后,针对土地资源调查其它方面工作的逐步开展,提出了将其内容扩充,改革为土地资源调查课程的必要性,重点探讨了土地资源调查的内容与技术及其课程的主要内容与体系。 相似文献
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西天山智博铁矿床磁铁矿地球化学及氧同位素特征 总被引:2,自引:1,他引:1
智博铁矿是阿吾拉勒铁铜成矿带成矿作用演化的典型代表。本文在详细的野外地质调查和室内研究的基础上,将该矿床的成矿阶段划为岩浆成矿期和热液成矿期两个期次,并将其矿石产状类型划分为块状矿石、浸染状矿石、角砾状矿石、网脉状矿石等。本文选取智博铁矿两期磁铁矿单矿物作为研究对象,通过其稀土微量元素及氧同位素等特征的研究来查明该矿床成矿物质特征及其来源。研究表明,智博铁矿的两期磁铁矿微量元素特征具有一定差异性,岩浆型磁铁矿相对富V、Ni、Ga等元素,而热液型矿石中相对富Co,贫V、Ni。两期磁铁矿单矿物稀土配分模式与矿区火山岩接近,暗示成矿物质与火山岩同源;Y/Ho比值接近球粒陨石,在Y/Ho-La/Ho图中和(La/Sm)_N-(La/Yb)_N图中,两期磁铁矿表现出同源性,暗示矿区内多数矿石的形成与火山岩浆作用有关。岩浆期的磁铁矿δ~(18)O值平均为3.4‰,与基鲁纳型铁矿和拉科铁矿的磁铁矿δ~(18)O非常接近;而热液期的磁铁矿δ~(18)O值平均为4.1‰,比岩浆期磁铁矿的δ~(18)O值范围更大些,可能与热液流体参入及矿物重结晶等因素有关。磁铁矿的地球化学特征及氧同位素均暗示智博铁矿矿石的形成主要与火山-岩浆活动密切相关,但也受到后期热液活动的影响。 相似文献
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The impact of irrigation water supply rate on agricultural drought disaster risk: a case about maize based on EPIC in Baicheng City,China 总被引:2,自引:0,他引:2
This study presents a methodology for risk analysis, assessment, and combination of drought disasters under the different irrigational levels in Baicheng City, which is supported by run theory, copula functions, crop growth model, and technique of natural disaster risk assessment from the viewpoints of climatology, geography, hydrology, agricultural science, disaster science, environmental science, and so on. Along with the global warming, the occurrences of water-related disasters become more frequent and more serious. It is necessary to determine the laws of the relationship between irrigational ability and the loss caused by drought. Drought events were identified by using run theory; the drought frequency was calculated by using copula function; the loss of every drought event was simulated by using EPIC model; and the relationship curves under the different irrigational supply conditions between the drought frequency and the yield reduction rate of the drought event were fitted to assess the impact of irrigational supply rate on the loss caused by drought. The results show that in the range of crop water demand, the loss caused by drought decreases as the result of the increase in irrigational supply rate; however, their variations are not proportional. The loss caused by the certain frequency drought event under the certain irrigational supply condition could be calculated by the curve of drought disaster risk assessment constructed by this study. The results obtained from this study are specifically intended to support local and national governmental agencies on agricultural disaster management. 相似文献
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栾兰 《测绘与空间地理信息》2013,(3):187-188
结合工作实践,介绍了全数字摄影测量系统VirtuoZo在数字化测图中一些新的应用方法。 相似文献
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There is little information on the performance of vegetative filter strips (VFS) in filtering high‐concentration sediment from subcritical overland flow. Flume experiments on simulated grass strips were conducted using combinations of three slope gradients (3°, 9° and 15°), five 1‐m‐wide slope positions (from upslope to downslope), two flow rates (60 and 20 L min‐1 m‐1) and sediment concentrations of 100–300 kg m‐3 under simulated rainfall and non‐rainfall conditions. The results showed that sediment deposition efficiency increased with VFS width as a power function. Rainfall significantly reduced sediment deposited within VFS. Higher sediment concentration corresponded to a larger sediment deposition load but reduced deposition efficiency. Flow rate had a negative effect on deposition efficiency but no effect on deposition load. Sediments were more easily deposited at the upper slope position than downslope, and the upper slope position had a higher percentage of coarse sediments. The deposited sediment had significantly greater median diameters (D50) than the inflow sediment. A greater proportion of coarse sediments larger than 25 µm in diameter were deposited, and particles smaller than 1 µm and of 10–25 µm had a better deposition performance than particles of 1–10 µm. Rainfall reduced the deposited sediment D50 at a slope gradient of 3° and had no significant influence on it at 9° or 15°. A higher sediment concentration led to a smaller D50 of the deposited sediment. Rainfall had no significant effect on overland flow velocity. Both the deposited sediment load and D50 decreased with increasing flow velocity, and flow velocity was the most sensitive factor impacting sediment deposition. The results from this study should be useful to control sediment flowing into rivers in areas with serious soil erosion. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献