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71.
Analytical solutions for advective–dispersive solute transport in double‐layered finite porous media
Peter John Cleall 《国际地质力学数值与分析法杂志》2011,35(4):438-460
Analytical solutions for advection and dispersion of a conservative solute in a one‐dimensional double‐layered finite porous media are presented. The solutions are applicable to five scenarios that have various combinations of fixed concentration, fixed flux and zero concentration gradient conditions at the inlet and outlet boundaries that provide a wide number of options. Arbitrary initial solute concentration distributions throughout the media can be considered via explicit formulations or numerical integration. The analytical solutions presented have been verified against numerical solutions from a finite‐element‐based approach and an existing closed‐form solution for double‐layered media with an excellent correlation being found in both cases. A practical application pertaining to advective transport induced by consolidation of underlying sediment layers on contaminant movement within a capped contaminated sediment system is presented. Comparison of the calculated concentrations and fluxes with alternative approaches clearly illustrates the need to consider advection processes. Consideration of the different features of contaminant transport due to varying pore‐water velocity fields in primary consolidation and secondary consolidation stages is achieved via the use of non‐uniform initial concentration distributions within the proposed analytical solutions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
72.
Iftikhar U. Sikder 《International Journal of Digital Earth》2016,9(12):1206-1223
This paper presents a granular computing approach to spatial classification and prediction of land cover classes using rough set variable precision methods. In particular, it presents an approach to characterizing large spatially clustered data sets to discover knowledge in multi-source supervised classification. The evidential structure of spatial classification is founded on the notions of equivalence relations of rough set theory. It allows expressing spatial concepts in terms of approximation space wherein a decision class can be approximated through the partition of boundary regions. The paper also identifies how approximate reasoning can be introduced by using variable precision rough sets in the context of land cover characterization. The rough set theory is applied to demonstrate an empirical application and the predictive performance is compared with popular baseline machine learning algorithms. A comparison shows that the predictive performance of the rough set rule induction is slightly higher than the decision tree and significantly outperforms the baseline models such as neural network, naïve Bayesian and support vector machine methods. 相似文献
73.
Simulation of groundwater level recovery in abandoned mines,Fengfeng coalfield,China 总被引:1,自引:0,他引:1 下载免费PDF全文
MA Luan WANG Guang-cai SHI Zhe-ming GUO Yu-ying XU Qing-yu HUANG Xu-juan 《地下水科学与工程》2016,4(4):344-353
Abandoned mines are of high potential risk as they could be a large underground storage of pollutants(heavy metals and organic wastes, etc.). Various physical, chemical and biological reactions would take place when groundwater flows into underground spaces, which makes abandoned mine a huge potential hazard to groundwater environment. The recovery of groundwater level is one of the key elements controlling the reactions and causing such hazards. This paper simulated groundwater level recovery processes in the abandoned mines, Fengfeng coalfield by using the computer program FEFLOW. The paper integrated the pipe flow model, "three zones" model and groundwater inrush(discharge) model in the simulation of groundwater in the complex laneway-aquifer system. Groundwater flow in the laneway systems was considered pipe flow and described in Bernoulli equation. The water-bearing medium(coal seam roof) overlying the laneway systems was divided into "three zones" composed of the caving zone, fissure zone and bending zone based on the disruption degrees of previous mining. Groundwater in the Ordovician limestone aquifer(bottom of coal seam) flowing into laneway systems was considered a major inrush/recharge source, and its flow rate was calculated by an inrush(discharge) model which was newly developed in this study and incorporated into FEFLOW. The results showed that it would take approximately 95 days for groundwater in abandoned mines to recover to regional groundwater level elevation, and the total amount of water filling up would be about 1.41195×10~7 m~3, which is consistent with the actual data. The study could be of theoretical and practical significance to mitigate abandoned mines' hazards and improve mine groundwater utilization. 相似文献
74.
75.
Revisiting the death of geography in the era of Big Data: the friction of distance in cyberspace and real space 总被引:1,自引:0,他引:1
Many scholars have argued that the importance of geographic proximity in human interactions has been diminished by the use of the Internet, while others disagree with this argument. Studies have noted the distance decay effect in both cyberspace and real space, showing that interactions occur with an inverse relationship between the number of interactions and the distance between the locations of the interactors. However, these studies rarely provide strong evidence to show the influence of distance on interactions in cyberspace, nor do they quantify the differences in the amount of friction of distance between cyberspace and real space. To fill this gap, this study used massive amounts of social media data (Twitter) to compare the influence of distance decay on human interactions between cyberspace and real space in a quantitative manner. To estimate the distance decay effect in both cyberspace and real space, the distance decay function of interactions in each space was modeled. Estimating the distance decay in cyberspace in this study can help predict the degree of information flow across space through social media. Measuring how far ideas can be diffused through social media is useful for users of location-based services, policy advocates, public health officials, and political campaigners. 相似文献
76.
Scott Pezanowski Alan M MacEachren Alexander Savelyev Anthony C Robinson 《制图学和地理信息科学》2018,45(5):420-437
SensePlace3 (SP3) is a geovisual analytics framework and web application that supports overview + detail analysis of social media, focusing on extracting meaningful information from the Twitterverse. SP3 leverages social media related to crisis events. It differs from most existing systems by enabling an analyst to obtain place-relevant information from tweets that have implicit as well as explicit geography. Specifically, SP3 includes not just the ability to utilize the explicit geography of geolocated tweets but also analyze implicit geography by recognizing and geolocating references in both tweet text, which indicates locations tweeted about, and in Twitter profiles, which indicates locations affiliated with users. Key features of SP3 reported here include flexible search and filtering capabilities to support information foraging; an ingest, processing, and indexing pipeline that produces near real-time access for big streaming data; and a novel strategy for implementing a web-based multi-view visual interface with dynamic linking of entities across views. The SP3 system architecture was designed to support crisis management applications, but its design flexibility makes it easily adaptable to other domains. We also report on a user study that provided input to SP3 interface design and suggests next steps for effective spatiotemporal analytics using social media sources. 相似文献
77.
Rapid flood mapping is critical for local authorities and emergency responders to identify areas in need of immediate attention. However, traditional data collection practices such as remote sensing and field surveying often fail to offer timely information during or right after a flooding event. Social media such as Twitter have emerged as a new data source for disaster management and flood mapping. Using the 2015 South Carolina floods as the study case, this paper introduces a novel approach to mapping the flood in near real time by leveraging Twitter data in geospatial processes. Specifically, in this study, we first analyzed the spatiotemporal patterns of flood-related tweets using quantitative methods to better understand how Twitter activity is related to flood phenomena. Then, a kernel-based flood mapping model was developed to map the flooding possibility for the study area based on the water height points derived from tweets and stream gauges. The identified patterns of Twitter activity were used to assign the weights of flood model parameters. The feasibility and accuracy of the model was evaluated by comparing the model output with official inundation maps. Results show that the proposed approach could provide a consistent and comparable estimation of the flood situation in near real time, which is essential for improving the situational awareness during a flooding event to support decision-making. 相似文献
78.
79.
为研究震后九寨沟钙华景区的溶洞、裂隙、暗流等地质特性,丰富钙华景区岩溶洞穴无损探测技术,探讨了多物探技术在多孔疏松钙华地区作业的可靠性。首次运用地质雷达法及高密度电法相结合的无损探测技术,在九寨沟景区火花海特定区域进行了现场勘查和无损探测试验。结合对比两种无损探测成果与测区内出露地质剖面3组勘探数据,结果发现:高密度电法与地质雷达法相结合,两者能优劣互补,相互佐证,在解决钙华区域浅部溶洞、暗流、裂隙等工作中,对探测目标体具有极高的识别度。两种方法探测数据与震后出露剖面地质特征保持极高的一致性,验证了两种无损检测方法在多孔疏松介质条件下数据的真实可靠性,解决了多物探技术在多孔疏松介质地区施工的疑点和难点,丰富了工程物探领域技术。 相似文献
80.
原油粘度变化对水驱油开发动态影响的数学模拟方法 总被引:1,自引:0,他引:1
为了研究注水开发油田原油粘度升高对开发效果的影响, 通过对实际油藏原油粘度统计, 回归出了原油粘度增长模型.在三维三相黑油渗流模型的基础上, 建立了一个原油粘度随含水和压力变化的油藏渗流数学模型, 并采用有限差分方法建立了相应的数值模型, 采用超松弛法对该模型进行了求解, 用Fortran90语言开发了一个新的数值模拟器.应用该模拟器模拟了不同的原油粘度变化规律对水驱效果的影响, 并与常规模拟器的结果进行了对比.结果表明: 初始水油粘度比为1∶10、含水达到98%时, 粘度增长指数由0增加到0.02, 对应的原油采出程度由44.80%降低到34.29%.目前商业软件中忽略了原油粘度随含水升高而增加的因素, 使得预测的采收率明显偏高. 相似文献