Mapping spatiotemporal patterns of events using social media: a case study of influenza trends     

Yizhao Gao  Anand Padmanabhan  Junjun Yin  Guofeng Cao 《International journal of geographical information science》2018,32(3):425-449

Tracking spatial and temporal trends of events (e.g. disease outbreaks and natural disasters) is important for situation awareness and timely response. Social media, with increasing popularity, provide an effective way to collect event-related data from massive populations and thus a significant opportunity to dynamically monitor events as they emerge and evolve. While existing research has demonstrated the value of social media as sensors in event detection, estimating potential time spans and influenced areas of an event from social media remains challenging. Challenges include the unstable volumes of available data, the spatial heterogeneity of event activities and social media data, and the data sparsity. This paper describes a systematic approach to detecting potential spatiotemporal patterns of events by resolving these challenges through several interrelated strategies: using kernel density estimation for smoothed social media intensity surfaces; utilizing event-unrelated social media posts to help map relative event prevalence; and normalizing event indicators based on historical fluctuation. This approach generates event indicator maps and significance maps explaining spatiotemporal variations of event prevalence to identify space-time regions with potentially abnormal event activities. The approach has been applied to detect influenza activity patterns in the conterminous US using Twitter data. A set of experiments demonstrated that our approach produces high-resolution influenza activity maps that could be explained by available ground truth data.  相似文献   

Modeling of landslide generated impulsive waves considering complex topography in reservoir area   总被引：2，自引：0，他引：2  

Wei Wang  Guangqi Chen  Kunlong Yin  Yang Wang  Suhua Zhou  Yiliang Liu 《Environmental Earth Sciences》2016,75(5):372

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The identification of precipitation amount effect with a water isotope-enabled threshold model in vadose zone: a case study in Ordos Plateau     

H. Ma  Q. Yang  L. Yin  J. Zhang  X. Wang  J. Zhang  C. Li  J. Dong 《Environmental Earth Sciences》2016,75(10):922

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In situ dynamic monitoring of stress revolution with time and space under coal seam floor during longwall mining   总被引：1，自引：1，他引：0  

Huiyong Yin  Liliana Lefticariu  Jiuchuan Wei  Jianbin Guo  Zhongjian Li  Yunzhang Guan 《Environmental Earth Sciences》2016,75(18):1249

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Extraction and Analysis of Land Cover Heterogeneity over China     

Yu Wentao  Li Jing  Liu Qinhuo  Zeng Yelu  Yin Gaofei  Zhao Jing  Xu Baodong 《地球科学进展》2016,31(10):1067-1077

Spatial heterogeneity exists in land surface at every scale, and it is one of key factors to bring uncertainty to land parameter retrieval from remote-sensed data. This paper proposed a methodology to use the boundary length among different land cover types to characterize and quantify land surface heterogeneity based on high-resolution land cover images. Then the heterogeneity feature at 1 kilometer scale in China was extracted from “GlobalLand30” land cover datasets with the spatial resolution of 30 m. The mixed structure, degree of fragmentation and intra-heterogeneity of eight main vegetation biomes from MODIS land cover product over heterogeneous surface in china were analyzed. Mountain area and ecotone are more heterogeneous than other regions. Savanna biome (average boundary length is 7 426 meters) is the most heterogeneous zone followed by forest, grass/crop and shrub biome with average boundary length of 4 323, 3 160, 1 779 meters, respectively.  相似文献   

Modeling sediment concentration and transport induced by storm surge in Hengmen Eastern Access Channel     

Kai Yin  Sudong Xu  Wenrui Huang 《Natural Hazards》2016,81(1):617-639

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东昆仑白石崖地区铁多金属矿田找矿新发现及其意义          下载免费PDF全文

尹利君 《地质与勘探》2016,52(1):40-46

白石崖铁多金属矿田位于东昆仑东段,距青海省都兰县城西20多公里,矿田内的矿床大多赋存于下石炭统大干沟组碳酸盐岩与中酸性火山岩或酸性侵入体接触带矽卡岩带中。白石崖地区成矿特征显示,本区具有寻找铁铜铅锌钨锡的地质条件。以M20矿床为突破口,采用磁法、EH4连续电导率剖面测量及钻探查证等技术,开展了以铁多金属为主的找矿工作,发现并探明了一批有一定储量的多金属矿体,并于深部岩体附近发现钨矿体,实现了近年来白石崖地区找矿的重大突破。  相似文献   

A Multi-method Approach for Estimating the Failure Depth of Coal Seam Floor in a Longwall Coal Mine in China     

Huiyong?Yin  Liliana?Lefticariu  Jiuchuan?WeiEmail author  Lu?Zhu  Jianbin?Guo  Zhongjian?Li  Yunzhang?Guan 《Geotechnical and Geological Engineering》2016,34(5):1267-1281

Determining the failure depth of coal seam floor is necessary for safe mining operations, especially when the coal seam is located above confined aquifers with high water pressure. Geomechanical, geophysical, and hydrogeological data collected during the longwall mining of the first working face of coal seam no. 16 in the Nantun coal mine, Shandong Province, China, were used to calculate the failure depth of the coal seam floor above the Ordovician limestone confined aquifer. The multiple method approach employed by this study made use of the plastic sliding theory, empirical formulas, water injection test, and numerical simulation. Multiple methods can compensate for and validate each other and also overcome the intrinsic limitations of any single method. The results showed that the most appropriate value of the failure depth of the coal seam floor in the mine was 14.6 m and this value proved useful for knowing the effective thickness of water pressure-resistant layer below the coal seam. The failure depth also proved to be an important parameter when preventing groundwater flow into the mine from the coal seam floor.  相似文献   

基于极限分析上限方法的海底斜坡稳定性评价   总被引：2，自引：1，他引：1       下载免费PDF全文

刘博  年廷凯  刘敏  郑德凤  宋雷  印萍 《海洋学报》2016,38(7):135-143

极限平衡法仍是当前海底斜坡稳定性的主要工程评价方法,但该法只能给出稳定性分析的近似解答。基于极限分析运动学定理,假定海底斜坡发生对数螺线型滑移破坏模式,将滑体有效自重和简化波浪力等以外荷载形式叠加引入到虚功率方程中,与潜在滑动面上由黏聚力产生的内能耗散率相平衡,建立考虑一阶简化波浪效应的海底斜坡上限解法;利用多变量无导数求极值的逐级迭代方法与最优化技术,结合抗剪强度折减思想,求解波浪加载下不同时刻的海底斜坡稳定性与相应的临界破坏机构,并针对典型算例开展有限元数值解的验证。进而联合采用数值法与上限解,探讨波高、波长、水深等波浪参数对海底斜坡稳定性与滑动机制的影响。结果表明,本文提出的上限解与数值解吻合较好,获得的安全系数与破坏模式等符合一般规律,为波浪作用下海底斜坡的稳定性评价提供了新的途径。  相似文献   

Experimental study of dissolved oxygen transport by regular waves through a perforated breakwater     

Zegao Yin  Ning Yu  Bingchen Liang  Jixiong Zeng  Shaohua Xie 《中国海洋大学学报(英文版)》2016,15(1):78-82

The perforated breakwater is an environmentally friendly coastal structure,and dissolved oxygen concentration levels are an important index to denote water quality.In this paper,oxygen transport experiments with regular waves through a vertical perforated breakwater were conducted.The oxygen scavenger method was used to reduce the dissolved oxygen concentration of inner water body with the chemicals Na_2SO_3 and Co Cl_2.The dissolved oxygen concentration and wave parameters of 36 experimental scenarios were measured with different perforated arrangements and wave conditions.It was found that the oxygen transfer coefficient through wave surface,K_1a_1,is much lower than the oxygen transport coefficient through the perforated breakwater,K_2a_2.If the effect of K_1a_1 is not considered,the dissolved oxygen concentration computation for inner water body will not be greatly affected.Considering the effect of a permeable area ratio α,relative location parameter of perforations δ and wave period T,the aforementioned data of 30 experimental scenarios,the dimensional analysis and the least squares method were used to derive an equation of K_2a_2(K_2a_2=0.0042α~(0.5)δ~(0.2)T~(-1)).It was validated with 6 other experimental scenarios data,which indicates an approximate agreement.Therefore,this equation can be used to compute the DO concentration caused by the water transport through perforated breakwater.  相似文献