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991.
992.
配电网GIS的一种开发模式探讨 总被引:3,自引:0,他引:3
开发配电GIS主要有3种组织: GIS厂商及GIS二次开发商、配电自动化厂商、电力系统单位.分析了他们在开发中的优势与劣势, 提出一种把配电GIS系统分层, 由GIS厂商开发配电GIS平台, 自动化厂商及电力系统单位在该平台上进行2次开发的模式.论述了配电GIS平台的功能范围及海量数据管理、拓扑关系管理、设备库、按设备分层的拓扑关系模型、组件技术等关键技术, 并介绍了这种模式的一个实例. 相似文献
993.
探讨了全国重点防洪城市长沙市防洪建设中的若干重要问题:防洪标准、设计洪水位、防洪大堤高度等的确定;建设方针与程序、整体防洪能力建设、防洪建设与基础设施建设和景观建设协调发展等。长沙设计洪水位的确定应综合考虑以下几个方面:湘江长沙段洪水与其支流和东洞庭湖洪水不存在高标准洪水同期遭遇问题,更不存在同频率洪水遭遇问题;湘江洪水流量与水位关系不是长沙洪水设计的主要依据;而南洞庭湖洪水位顶托和河道槽蓄量减少是影响长沙洪水位高低的动、静态因素。目前,长沙城市堤防设防高度偏高,减少了大堤的稳定性,造成了无效投资,影响了城市景观。防洪工程建设应分期实施、先除险后加固、注重整体防洪能力的提高,并处理好与城市基础设施建设和景观建设的关系。 相似文献
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995.
Measuring and modeling vertical gradients in suspended sediments in the Solimões/Amazon River 下载免费PDF全文
E. Armijos A. Crave R. Espinoza P. Fraizy A.L.M.R. Dos Santos F. Sampaio E. De Oliveira W. Santini J.M. Martinez P. Autin N. Pantoja M. Oliveira N. Filizola 《水文研究》2017,31(3):654-667
Accurately measuring sediment flux in large rivers remains a challenge due to the spatial and temporal cross‐sectional variability of suspended sediment concentrations in conjunction with sampling procedures that fail to accurately quantify these differences. This study presents a field campaign methodology that can be used to improve the measurement of suspended sediment concentrations in the Amazon River or similarly large rivers. The turbidity signal and Rouse model are together used in this study to define the spatial distribution of suspended sediment concentrations in a river cross‐section, taking into account the different size fractions of the sediment. With this methodology, suspended sediment fluxes corresponding to each sediment class are defined with less uncertainty than with manual samples. This paper presents an application of this methodology during a field campaign at different gauging stations along a 3,000‐km stretch of the Solimões/Amazon River during low water and flood periods. Vertical concentration profiles and Rouse model applications for distinctive sediment sizes are explored to determine concentration gradients throughout a cross‐section of the river. The results show that coupling both turbidity technology and the Rouse model may improve our understanding of the spatial distribution of different sediments fractions sizes in the Solimões/Amazon River. These data are very useful in defining a pertinent monitoring strategy for suspended sediment concentrations in the challenging context of large rivers. 相似文献
996.
Polar Bear Pass is a large High Arctic low‐gradient wetland (100 km2) bordered by low‐lying hills which are notched by a series of v‐shaped valleys. The spring and summer hydrology of two High Arctic hillslope‐wetland catchments, a first‐order stream, 0·2 km2 Landing Strip Creek (LSC) and a larger second‐order basin, 4·2 km2 Windy Creek (WC), is described here. A water balance framework was employed in 2008 to examine the movement of water from upland reaches into the low‐lying wetland. Snowcover was low in both basins (<50 mm in water equivalent units), but they both exhibited nival‐type regimes. After the main snowmelt season ended, runoff ceased in the smaller catchment (LSC), but not at the larger basin (WC) which continued to flow throughout the summer. Both basins responded to summer rains in different ways. At LSC, late‐summer continuous streamflow occurred only when rainfall satisfied the large soil moisture deficit in the upper bowl‐shaped zone of the basin. At WC, the presence of thinly thawed, ice‐rich polygonal terrain within the stream channel and in the upper reaches of the catchment likely limited infiltration in these near‐stream zones and enhanced runoff in response to both moderate and high rainfall. Subsequently, seasonal runoff ratios differed between the two sites (0·19 vs 0·68) as did the seasonal storage + residual (+16 vs ?50 mm). This suggests that the post‐snowmelt season runoff response to summer precipitation is very much modified by the unique basin characteristics (soil‐type, vegetation, ground ice) and their location within each stream order type. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
997.
Matthew S. M. Bolton Britta J. L. Jensen Kristi Wallace Nore Praet David Fortin Darrell Kaufman Marc De Batist 《第四纪科学杂志》2020,35(1-2):81-92
Glass composition-based correlations of volcanic ash (tephra) traditionally rely on extensive manual plotting. Many previous statistical methods for testing correlations are limited by using geochemical means, masking diagnostic variability. We suggest that machine learning classifiers can expedite correlation, quickly narrowing the list of likely candidates using well-trained models. Eruptives from Alaska's Aleutian Arc-Alaska Peninsula and Wrangell volcanic field were used as a test environment for 11 supervised classification algorithms, trained on nearly 2000 electron probe microanalysis measurements of glass major oxides, representing 10 volcanic sources. Artificial neural networks and random forests were consistently among the top-performing learners (accuracy and kappa > 0.96). Their combination as an average ensemble effectively improves their performance. Using this combined model on tephras from Eklutna Lake, south-central Alaska, showed that predictions match traditional methods and can speed correlation. Although classifiers are useful tools, they should aid expert analysis, not replace it. The Eklutna Lake tephras are mostly from Redoubt Volcano. Besides tephras from known Holocene-active sources, Holocene tephra geochemically consistent with Pleistocene Emmons Lake Volcanic Center (Dawson tephra), but from a yet unknown source, is evident. These tephras are mostly anchored by a highly resolved varved chronology and represent new important regional stratigraphic markers. 相似文献
998.
利用NCEP格点再分析资料和WRF模式输出的高分辨率资料、自动站降水资料、雷达资料对2010年8月14 16日发生在重庆的一次大暴雨过程进行了数值模拟和诊断分析。结果表明:此次暴雨过程分为两个阶段,降水系统主要有两个:第一阶段的主要降水系统是低空切变线;第二阶段的主要降水系统是低空切变线和850 h Pa西南低涡,并且第二个阶段内的降水量较大、持续时间也较长。风垂直廓线的时间演变表明,暴雨发生、发展过程中,中低层强西南风风速的下传和低层切变辐合的存在对中尺度对流系统的增强有着重要的作用;数值模拟分析显示,第一阶段,弱的冷平流影响暴雨区,在低空切变线的作用下,引起气团在水平方向辐合,触发中尺度对流系统的发生、发展;第二阶段,中高层强的冷空气倾入降水区,850 h Pa低涡生成后东移至重庆东北地区,其低涡附近的垂直上升运动与700 h Pa切变线附近的上升运动相耦合,强迫抬升中低层暖湿空气并再次触发降水区域的中尺度对流系统。 相似文献
999.
1000.
Weronika Gorczyk Hugh Smithies Fawna Korhonen Heather Howard Raphael Quentin De Gromard 《地学前缘(英文版)》2015,6(1):23-37
The Musgrave Province developed at the nexus of the North,West and South Australian cratons and its Mesoproterozoic evolution incorporates a 100 Ma period of ultra-high temperature(UHT) metamorphism from ca.1220 to ca.1120 Ma.This was accompanied by high-temperature A-type granitic magmatism over an 80 Ma period,sourced in part from mantle-derived components and emplaced as a series of pulsed events that also coincide with peaks in UHT metamorphism.The tectonic setting for this thermal event(the Musgrave Orogeny) is thought to have been intracontinental and the lithospheric architecture of the region is suggested to have had a major influence on the thermal evolution.We use a series of two dimensional,fully coupled thermo-mechanical-petrological numerical models to investigate the plausibility of initiating and prolonging UHT conditions under model setup conditions appropriate to the inferred tectonic setting and lithospheric architecture of the Musgrave Province.The results support the inferred tectonic framework for the Musgrave Orogeny,predicting periods of UHT metamorphism of up to 70 Ma,accompanied by thin crust and extensive magmatism derived from both crustal and mantle sources.The results also appear to be critically dependent upon the specific location of the Musgrave Province,constrained between thicker cratonic masses. 相似文献