基于Web的CCGIS浏览器插件的设计与实现   总被引：15，自引：1，他引：15  

朱庆  李霞飞  张叶挺 《测绘学报》2002,31(1):22-27

首先介绍了网络3维虚拟现实的发展现状和一般实现方法，结合数码城市GIS软件的研发，提出了基于Web的3D城市模型浏览器插件的3层浏览器／服务器体系结构，然后重点介绍了采用Java和Java 3D实现客户端3维数据在线操作与动态显示和服务器端一体化数据库管理功能的实现方法。该插件能用于Internet上发布3维城市信息，实现3维空间信息的数据共享，并提供给用户一个逼真的、实时的、可交互的虚拟3维城市。最后给出了一个实验例子和几点结论。  相似文献   

矿床数学—经济模型及其在元江金矿的应用   总被引：11，自引：3，他引：11  

燕永锋  秦德先 《矿物学报》2001,21(4):619-624

利用地质统计学的原理和方法，编制出矿床数学－经济模型软件包，它作为一种储量计算和矿床经济评价方法。介绍了该软件包各模块的功能，并以元江金矿应用为例，展示了该软件包的功能及效果。  相似文献   

油水双相饱和孔隙模型核磁特性理论研究   总被引：6，自引：2，他引：6       下载免费PDF全文

翁爱华  李舟波  王雪秋  陆敬安  莫修文 《地球物理学报》2003,46(4):553-560

利用特征函数展开方法，给出了基于扩散效应的核磁共振Bloch控制方程的弛豫模式解表达式, 在此基础上分别给出了水饱和与油水双相饱和孔隙模型的核磁共振特性模拟结果. 结果表明，孔隙流体的核磁弛豫与孔隙大小、孔隙表面弛豫率、孔隙流体的扩散能力以及含油饱和度等有密切的关系. 对于水饱和孔隙，弛豫时间主要由孔隙大小控制. 当孔隙较大时，即使均匀大小孔隙，孔隙流体的弛豫也会表现为多指数弛豫. 而且最小模式弛豫时间与孔隙大小为非线性关系. 对于油水双相饱和孔隙，在孔隙较小时，含油饱和度对弛豫的影响主要表现在弛豫时间随含油饱和度的增加而线性减小；但在孔隙较大时，含油饱和度的增加对弛豫影响表现在两个方面，其一，孔隙水弛豫由多个弛豫模式控制逐渐转变为由最小弛豫模式控制；其二，孔隙水弛豫时间与含油饱和度表现为非线性关系. 对由实际岩芯抽象出的孔隙模型，采用本文获得的理论公式，在油水双相饱和时进行了正反演模拟. 计算结果与已有的实验结果较为一致.  相似文献   

On the gravitational terms of the <Emphasis Type="Italic">k</Emphasis>-ɛ and other turbulence models     

Samuel Hassid 《Ocean Dynamics》2002,52(4):169-178

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土地资源单要素计算机解译模式化研究     

朱博勤  张渊智 《遥感学报》1996,(2)

本文在研究遥感数据特性、典型地物光谱特性和象元几何组构类型的基础上，分析了一物多谱、多物一谱的原因，提出土地资源属性按大类、类、亚类、组、属分类型分等级单要素解译模式；试验区土地资源单要素计算机解译在ＤＴＭ数据的支持下，取得了较好的分类结果。  相似文献   

Using multi-date satellite imagery to monitor invasive grass species distribution in post-wildfire landscapes: An iterative,adaptable approach that employs open-source data and software     

《International Journal of Applied Earth Observation and Geoinformation》2017

Among the most pressing concerns of land managers in post-wildfire landscapes are the establishment and spread of invasive species. Land managers need accurate maps of invasive species cover for targeted management post-disturbance that are easily transferable across space and time. In this study, we sought to develop an iterative, replicable methodology based on limited invasive species occurrence data, freely available remotely sensed data, and open source software to predict the distribution of Bromus tectorum (cheatgrass) in a post-wildfire landscape. We developed four species distribution models using eight spectral indices derived from five months of Landsat 8 Operational Land Imager (OLI) data in 2014. These months corresponded to both cheatgrass growing period and time of field data collection in the study area. The four models were improved using an iterative approach in which a threshold for cover was established, and all models had high sensitivity values when tested on an independent dataset. We also quantified the area at highest risk for invasion in future seasons given 2014 distribution, topographic covariates, and seed dispersal limitations. These models demonstrate the effectiveness of using derived multi-date spectral indices as proxies for species occurrence on the landscape, the importance of selecting thresholds for invasive species cover to evaluate ecological risk in species distribution models, and the applicability of Landsat 8 OLI and the Software for Assisted Habitat Modeling for targeted invasive species management.  相似文献   

Urbanization on the Mongolian Plateau after economic reform: Changes and causes     

《Applied geography (Sevenoaks, England)》2017

In response to changes in human and natural environments over the past three decades, transitional countries have experienced dramatic urbanization. In the context of socioeconomic and biophysical changes, our knowledge on these urbanization processes remains limited. Here, we used the Mongolian Plateau (i.e., Inner Mongolia (IM) and Mongolia (MG)) as a testbed and applied the coupled natural and human (CNH) concept to understand the processes and causes of urbanization. We selected six cities on the Mongolian Plateau, classified their urban built-up areas using Geographic Object-Based Image Analysis (GEOBIA) from 1990 through 2015, and examined the driving forces of urbanization (i.e., economy, social goods, and environmental variables) through Partial Least Squares Structural Equation Modeling (PLS-SEM). We found that the spatial characteristics of urbanization in IM and MG have both similarities and differences. The cities in IM and MG have experienced rapid urban expansion, with urban areas increasing by 4.36 times and 3.12 times, respectively, since 1990. Cities in IM, however, were less dense and more sprawling whereas cities in MG were linearly aggregated. We also found through PLS-SEM that multiple driving forces affected urbanization in IM and MG during the transitional period. Results (path coef.) demonstrated that economic development (0.559) is a major driver for urbanization in IM, whereas social goods (0.646) and economic development (0.433) strongly influence urbanization in MG. These differences are likely due to the divergent governmental roles in urban development and in infrastructure/social support, as well as the differing economic structures in IM and MG.  相似文献   

海水入侵问题理论与实践   总被引：4，自引：1，他引：4  

邱汉学  张维冈 《海洋湖沼通报》1993,(4):20-27

本文综述了海水入侵的机理，入侵引起的生态变化及模型化、计算方法的研究现状、已发生入侵区的治理措施，指出了目前研究中存在的问题并探讨了今后的研究方向。  相似文献   

Modeling hydrological responses of karst spring to storm events: example of the Shuifang spring (Jinfo Mt., Chongqing,China)   总被引：4，自引：0，他引：4  

Yuexia Wu  Yongjun Jiang  Daoxian Yuan  Linli Li 《Environmental Geology》2008,55(7):1545-1553

Reproduction of hydrographs at karst springs has been an approach of understanding the karst aquifer, which normally acts as drains for the groundwater flow. However, its numerical modeling is difficult since factors for the internal geometry and connectedness are unknown and hard to quantify. Hydrographs of the karst aquifer with well-developed conduits in Shuifang spring catchment were obtained from the automatic gauging station at the spring orifice. Data as to the conduit system were also obtained based on results and analyses of tracer tests. With these data, the hydrological responses of Shuifang spring to storm events were simulated by storm water management model (SWMM) developed by USA EPA (Environmental Protection Agency). Nash–Sutcliffe efficiencies are used to compare the computed flow to the observed, which are 0.95 and 0.92 for calibration and validation. SWMM was verified and applicable in karst conduit drainage system. The model illustrated correctly quick recharge through conduits and slow and low inflow from the fissured aquifer matrix. The SCS-CN (soil conservation service-curve number) infiltration method was used for computation of losses and runoff. Field tests indicated that permeability was extremely high but different in karst area, which was less sensitive to the computed runoff when exceeded the common value provided by SWMM. Therefore, an improved quantitative infiltration model for karst area will make SWMM possible to be a useful tool for assessing and reproducing spring hydrographs.  相似文献   

考虑面极化效应时谐变电磁场的计算和模拟相似准则          下载免费PDF全文

孟永良  罗延钟 《地球物理学报》1989,32(1):89-98

根据频率域激发极化法（以下简称激电）的现有实验资料,导出了包括面极化激电效应和电磁效应的定解条件,提出了从Maxwell方程组出发同时考虑电法两大效应时谐变电磁场的计算方法。在此基础上讨论了电法的模拟相似准则。  相似文献