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在国家大力建设数字化图书馆的背景下,笔者在《重庆历史地图集》编制过程中,总结了一套关于地方舆图整理与编目的思路,提高了实际工作的效率,并为其他城市在类似项目中提供借鉴,同时为以后建设城市变迁资料数据库打下基础。 相似文献
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中国南方红壤区铅的分布特征、运移规律及生物效应尚不明确。本文以福建龙海市土壤和稻米为研究对象,系统分析了土壤铅的分布特征、形态组成、生物富集能力及影响机理,总结了铅在母岩-土壤-稻米迁移过程的富集分配规律。结果表明,龙海市中部区域表层土壤的铅含量高,其余区域较低,92.5%样点值在10~90 mg/kg,对应p H为4.0~7.5,强酸性和碱性土壤铅含量略低;稻米铅(0.018~0.398 mg/kg)超标率仅4.1%,对土壤铅的富集能力较弱(富集系数0.23%±0.16%),所以研究区土壤铅超标时稻米不一定超标。影响土壤铅的主要因素是成土母岩和土壤类型,不同成土母岩区的土壤铅含量规律为:第四纪海积物第四纪残坡积物花岗岩和酸性火山岩佛昙组基性玄武岩,不同土壤类型的铅含量规律为:潮土滨海盐土水稻土红壤赤红壤滨海风沙土。土壤铅有效态(离子交换态、水溶态)仅占铅全量的4.95%,强有机态和残渣态等其余形态合计占94.99%,说明土壤铅主要以稳定态存在,难于被植物吸收,进一步为合理解释"土壤铅超标而稻米不超标"这一现象提供了调查依据。研究还表明,稻米铅与表层土壤铅之间无明显相关性,保持土壤p H值在弱酸性至弱碱性范围可降低土壤铅活性。 相似文献
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为揭示GFRP锚杆在土遗址加固中的性能,进而克服现有竹、木、复合锚杆锚固的局限性,拓展该新型材料在古遗址加固中的应用,选择直径22mm和25mm的GFRP锚杆开展了现场锚固测试试验。通过单级和循环两种加载模式,获取了两种杆体的破坏模式与极限锚固力; 在杆体砂浆界面布设应变片,获取了受荷过程中界面监测点剪应变的变化特征与分布规律。结果表明:两种锚固系统均失效于砂浆土体界面,22mm GFRP杆体极限锚固力50kN,而25mm GFRP杆体超过120kN; 从加载端到末端监测界面剪应变呈衰减分布,在较大荷载下由于加载方向与杆体轴向微弱偏离导致局部出现受压现象,试验过程中监测界面未出现脱黏现象。研究表明GFRP锚杆可以部分替代复合锚杆,在土遗址载体加固中具有良好的应用前景。 相似文献
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The National Bureau of Surveying and Mapping of China has planned to speed up the development of spatial data infrastructure (SDI) in the coming few years. This SDI consists of four types of digital products, i. e., digital orthophotos, digital elevation models, digital line graphs and digital raster graphs. For the DEM, a scheme for the database building and updating of 1∶10 000 digital elevation models has been proposed and some experimental tests have also been accomplished. This paper describes the theoretical (and/or technical) background and reports some of the experimental results to support the scheme. Various aspects of the scheme such as accuracy, data sources, data sampling spatial resolution, terrain modeling, data organization, etc are discussed. 相似文献
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We describe a remote sensing method for measuring the internal interface height field in a rotating, two-layer annulus laboratory experiment. The method is non-invasive, avoiding the possibility of an interaction between the flow and the measurement device. The height fields retrieved are accurate and highly resolved in both space and time. The technique is based on a flow visualization method developed by previous workers, and relies upon the optical rotation properties of the working liquids. The previous methods returned only qualitative interface maps, however. In the present study, a technique is developed for deriving quantitative maps by calibrating height against the colour fields registered by a camera which views the flow from above. We use a layer-wise torque balance analysis to determine the equilibrium interface height field analytically, in order to derive the calibration curves. With the current system, viewing an annulus of outer radius 125?mm and depth 250?mm from a distance of 2?m, the inferred height fields have horizontal, vertical and temporal resolutions of up to 0.2?mm, 1?mm and 0.04?s, respectively. 相似文献
79.
The experimental study of the hydrodynamics of the sediments and the physical analysis of the process of exchange at the water-sediment interface in a zone of swash are essential for the understanding of the sedimentary transport processes in coastal environments, in particular to control and forecast the evolution of the coastline. The objective of this study was to exploit the technique of Ultrasonic Doppler Velocimetry (UDV) to examine the evolution of the velocity field at the water-sediment interface in a zone of swash in various conditions of incidental regular waves in a wave flume. The velocities were measured in different conditions of the swash within the sediment bed, and in the fluid vein at the swash edge. These measurements show: an exponential distribution of velocities inside the sediment bed; a difference in the velocity gradient at the water-sediment interface, between the velocity in the water vein at the swash edge and the interstitial flow in the swash. The measurements obtained in the wave flume made it possible to observe an evolution of the velocity profiles according to the phases of the swash, which are characterized by a phase shift between the free flow at the swash edge and the interstitial flow during the two phases of the swash: uprush and backwash. 相似文献
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