地理大数据挖掘——目标、内涵与研究问题     

裴韬  宋辞  郭思慧  舒华  刘亚溪  杜云艳  马廷  周成虎 《地理学报(英文版)》2020,30(2):251-266

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Brittleness characteristics of tight oil siltstones     

Wen-Hui Tan  Jing Ba  Meng-Qiu Guo  Hui Li  Lin Zhang  Ting Yu  Hao Chen 《应用地球物理》2018,15(2):175-187

Rock brittleness directly affects reservoir fracturing and its evaluation is essential for establishing fracturing conditions prior to reservoir reforming. Dynamic and static brittleness data were collected from siltstones of the Qingshankou Formation in Songliao Basin. The brittle–plastic transition was investigated based on the stress–strain relation. The results suggest that the brittleness indices calculated by static elastic parameters are negatively correlated with the stress drop coefficient and the brittleness index B₂, defined as the average of the normalized Young’s modulus and Poisson’s ratio, is strongly correlated with the stress drop. The brittleness index B₂, Young’s modulus, and Poisson’s ratio correlate with the brittle minerals content; that is, quartz, carbonates, and pyrite. We also investigated the correlation between pore fluid and porosity and dynamic brittle characteristic based on index B₂. Pore fluid increases the plasticity of rock and reduces brittleness; moreover, with increasing porosity, rock brittleness decreases. The gas-saturated siltstone brittleness index is higher than that in oil- or water-saturated siltstone; the difference in the brittleness indices of oil- and water-saturated siltstone is very small. By comparing the rock mechanics and ultrasonic experiments, we find that the brittleness index obtained from the rock mechanics experiments is smaller than that obtained from the ultrasonic experiments; nevertheless, both decrease with increasing porosity as well as their differences. Ultrasonic waves propagate through the rock specimens without affecting them, whereas rock mechanics experiments are destructive and induce microcracking and porosity increases; consequently, the brittleness of low-porosity rocks is affected by the formation of internal microcrack systems.  相似文献   

Detecting arbitrarily shaped clusters in origin-destination flows using ant colony optimization     

Ci Song  Ting Ma  Yunyan Du  Hua Shu  Sihui Guo 《International journal of geographical information science》2019,33(1):134-154

An origin-destination (OD) flow can be defined as the movement of objects between two locations. These movements must be determined for a range of purposes, and strong interactions can be visually represented via clustering of OD flows. Identification of such clusters may be useful in urban planning, traffic planning and logistics management research. However, few methods can identify arbitrarily shaped flow clusters. Here, we present a spatial scan statistical approach based on ant colony optimization (ACO) for detecting arbitrarily shaped clusters of OD flows (AntScan_flow). In this study, an OD flow cluster is defined as a regional pair with significant log likelihood ratio (LLR), and the ACO is employed to detect the clusters with maximum LLRs in the search space. Simulation experiments based on AntScan_flow and SaTScan_flow show that AntScan_flow yields better performance based on accuracy but requires a large computational demand. Finally, a case study of the morning commuting flows of Beijing residents was conducted. The AntScan_flow results show that the regions associated with moderate- and long-distance commuting OD flow clusters are highly consistent with subway lines and highways in the city. Additionally, the regions of short-distance commuting OD flow clusters are more likely to exhibit ‘residential-area to work-area’ patterns.  相似文献   

Integration of nighttime light remote sensing images and taxi GPS tracking data for population surface enhancement     

Bailang Yu  Ting Lian  Yixiu Huang  Xinyue Ye  Zuoqi Chen 《International journal of geographical information science》2019,33(4):687-706

The population distribution grid at fine scales better reflects the distribution of residents and plays an important role in investigating urban systems. The recent years have witnessed a growing trend of applying the nighttime light data to the estimation of population at micro levels. However, using the nighttime light data alone to estimate population may cause the overestimation problem due to excessively high light radiance in specific types of areas such as commercial zones and transportation hubs. In dealing with this issue, this study used taxi trajectory data that delineate people’s movements, and explored the utility of integrating the nighttime light and taxi trajectory data in the estimation of population in Shanghai at the spatial resolution of 500 m. First, the initial population distribution grid was generated based on the NPP-VIIRS nighttime light data. Then, a calibration grid was created with taxi trajectory data, whereby the initial population grid was optimized. The accuracy of the resultant population grid was assessed by comparing it with the refined survey data. The result indicates that the final population distribution grid performed better than the initial population grid, which reflects the effectiveness of the proposed calibration process.  相似文献   

Numerical Study on Tidal Mixing in the Bohai Sea     

Yifei Zhao  Ting Yu  Hu Wang 《Marine Geodesy》2019,42(1):46-63

The spatial and temporal variability of tidal mixing in Bohai Sea is studied using a numerical approach. In calculating tidal mixing, accurate barotropic tidal current is obtained via a harmonic analysis package utilizing the simulated current output from a high-resolution regional ocean model. And a “small-scale” roughness map is adopted to describe the detailed topographic features of Bohai Sea. It is shown that the tidal mixing estimated in Bohai Sea is much higher than the level of global background, and fluctuates considerably at some regions within a single day. In Liaodong Bay, Bohai Bay and Bohai Strait, the mixing varies greatly, with the peak value of O (10^?2) m² s^?1. The order of magnitude of mixing in Laizhou Bay is about O (10^?5～10^?3) m² s^?1. Mixing with background level of O (10^?5) m² s^?1 only appears in central area. Result also shows that rough topography plays relatively a more important role than tidal current in enhancing diapycnal mixing in Bohai Sea. The distributions of tidal mixing in selected sections reveal that the vertical stratification in Bohai Sea is not obvious, generally renders a barotropic structure.  相似文献   

Groundwater contaminant source identification based on iterative local update ensemble smoother          下载免费PDF全文

YANG Ai-lin  JIANG Si-min  LIU Jin-bing  JIANG Qian-yun  ZHOU Ting  ZHANG Wen 《地下水科学与工程》2020,8(1):1-9

Identification of the location and intensity of groundwater pollution source contributes to the effect of pollution remediation, and is called groundwater contaminant source identifcation. This is a kind of typical groundwater inverse problem, and the solution is usually ill-posed. Especially considering the spatial variability of hydraulic conductivity field, the identification process is more challenging. In this paper, the solution framework of groundwater contaminant source identification is composed with groundwater pollutant transport model (MT3DMS) and a data assimilation method (Iterative local update ensemble smoother, ILUES). In addition, Karhunen-Loève expansion technique is adopted as a PCA method to realize dimension reduction. In practical problems, the geostatistical method is usually used to characterize the hydraulic conductivity feld, and only the contaminant source information is inversely calculated in the identifcation process. In this study, the identification of contaminant source information under Kriging K-field is compared with simultaneous identification of source information and K-field. The results indicate that it is necessary to carry out simultaneous identification under heterogeneous site, and ILUES has good performance in solving high-dimensional parameter inversion problems.  相似文献   

中国古代牧业社会骨制品的初步考察:以新疆巴里坤石人子沟遗址为例     

李悦  马健  张成睿  刘欢  宗天宇  陈婷  黄泽贤  任萌  习通源  王建新  温睿 《第四纪研究》2020,(2):331-342

考古遗址出土骨制品的研究对于揭示古代社会的动物资源获取和利用、手工业生产、社会组织结构等问题具有重要意义.国内骨制品研究目前多集中在农业区域,这些研究为探讨新石器时代至青铜时代的动物使用及其与社会发展、早期国家形成的关系等问题作出了重要贡献.然而,针对牧业社会骨制品的考察十分缺乏.新疆哈密地区巴里坤草原分布有大量古代牧业文化遗址,石人子沟遗址(43°31′12.8″~43°34′28.9″N,93°13′44.8″~93°16′49.1″E)是其中一处青铜时代晚期至铁器时代早期的大型聚落.本文从动物考古学视角研究该遗址2006年至2011年发掘出土的426件骨制品.结果显示,石人子沟遗址骨制品的原料主要为以羊(Ovis aries/Capra hircus)、马(Equus caballus)为主的家养动物和以鹿(Cervidae)为主的野生动物,其中羊的比例最高(69.7%),鹿(13.8%)、马(2.3%)次之,这与中原地区青铜时代农业文化遗址的骨制品多以牛为原料的情况明显不同.羊在骨制品原料中占绝对多数且大量使用羊距骨制品的现象是对石人子沟遗址以牧业为主的生业经济方式的直接反映.石人子沟遗址不同类型骨制品的制作各具特点,但整体表现出"省时省力"的特点,即对使用部位细致打磨,对非使用部位仅做简单处理.与中原地区商周时期大型制骨作坊规范化、规模化、产业化的骨器生产不同,石人子沟遗址未见专门的制骨场所,骨制品生产的操作链条也并不完整.遗址的骨制品生产可能是以家庭为单元进行的,产品的专业化、精细化程度也相对较低.该研究填补了我国古代牧业文化遗址出土骨制品动物考古学专门研究的空白,为进一步探究我国古代不同区域、不同生业经济基础下的制骨手工业面貌提供了重要资料.  相似文献   

基于Mapbox矢量切片在线配图平台的设计与实现     

任福  黄婷  朱雪坚  翁世杰 《地理信息世界》2018,(4):64-68

矢量切片是以四叉树模型切割矢量数据而生成的矢量要素描述性文件,Web GIS开发中,矢量切片的配图是通过编写Json样式文件,最后浏览器根据样式文件实现地图在线渲染显示,但这种方式配图效率低,样式单一。为了优化配图过程,本文从矢量切片数据和浏览器渲染两个方面提出了一套基于Mapbox的矢量切片在线配图平台,包括基于Geo Server的矢量切片服务发布、基于MapboxGL的浏览器地图渲染等,设计实现了矢量切片在线配图平台应用于浙江省电子地图配图与在线制图研究项目,简化了矢量切片地图的配图过程,具有很强的实用性。  相似文献   

光裸方格星虫增养殖对滩涂底质的影响     

李俊伟  颉晓勇  郭永坚  朱长波  陈素文  丁贤  李婷  陈振国 《热带海洋学报》2018,37(1):37-44

基于2016年春、秋两个季节的现场实验数据, 研究光裸方格星虫(Sipunculus nudus Linnaeus)滩涂增养殖对滩涂底质的影响。实验对方格星虫单养区(S组)、方格星虫-贝类混养区(P组)和无星虫对照区(C组)进行了有机质、粒径组成、氧化还原电位(ORP)等指标测定, 结果表明: 1) 秋季S组20~30cm层次有机质含量和细沙比例均显著高于春季, 而C组仅表层物质有所增加, 表明方格星虫具有较强的表层物质迁移能力, 且其迁移深度为20~30cm。2) 秋季C组各层氧化还原电位值(ORP)均无明显降低趋势, 而S组仅10~20cm层次有一定程度降低, 表明方格星虫增养殖并不会明显降低滩涂底质状况。3) P组各层有机质以及细沙含量增加, 表明皱肋文蛤的过滤沉积作用可以提高滩涂颗粒物质的积累, 且方格星虫混养会加速颗粒物质的向下迁移; P组皱肋文蛤的栖息层次(0~3cm、3~10cm) ORP明显低于S组(p<0.05), 表明高密度的皱肋文蛤代谢活动会加剧0~10cm的底质恶化。4) 方格星虫与皱肋文蛤具有生态互补作用, 在同一区域进行增养殖可以提高滩涂物质利用率及碳汇功能; 方格星虫扰动引入富氧水可以缓解皱肋文蛤栖息层次的底质。  相似文献   

GNSS转发式欺骗干扰方法的改进     

何婷 《测绘通报》2019,(4):71-74,83

针对GNSS多天线转发式欺骗干扰在实际应用中，当干扰机与目标机距离大于一定范围时，将引起目标机钟差突跳，从而易被目标机检测和识别的缺陷，提出了基于干扰机阵列的转发式欺骗干扰新方法。干扰机阵列按照正六边形网型布设，可实现目标区域的无缝覆盖，并且灵活易拓展。不论目标机位于区域的任何位置，均有一个最优干扰机能够对其实施有效干扰。为了确定相邻干扰机的最优间距，本文在干扰机阵列不同间距下对具有钟差突跳自适应检测能力的目标机的干扰有效性进行了仿真研究。结论表明，综合考虑各种约束因素，相邻干扰机最优间距为17 km，满足该条件的干扰机阵列在实施欺骗干扰过程中，不会造成目标机钟差突跳，有效解决了该干扰方式易被目标机识别的问题。  相似文献