The application of GIS for flood defence in the Anglian Region: developing for the future     

Daniel J. Leggett  Anthony Jones 《International journal of geographical information science》2013,27(1):103-116

The spatio‐temporal relationship between unusual sightings of dead birds and human West Nile virus infections has been observed in many studies and has been proposed as an indicator of an intense amplification cycle between birds and mosquitoes. However, to date, no single study has provided quantitative evidence that the amplification cycle occurs at the local level and that it operates within certain temporal parameters. Here, we use a novel geostatistical and spatial analytic methodology and present the first evidence that the localized unusual space–time correspondence of dead birds models the amplification cycle and that this cycle peaks 15–16 days prior to human onset of West Nile virus infections. During the process of establishing this relationship, we extend the traditional Knox space–time interaction measure to overcome pair‐dependency limitations and use a novel implementation of the kappa non‐chance agreement measure to identify the temporal characteristics of the association of bird deaths to human West Nile infections.  相似文献   

Efficient regionalization techniques for socio‐economic geographical units using minimum spanning trees     

R. M. AssunÇão  M. C. Neves  C. Da Costa Freitas 《International journal of geographical information science》2013,27(7):797-811

Regionalization is a classification procedure applied to spatial objects with an areal representation, which groups them into homogeneous contiguous regions. This paper presents an efficient method for regionalization. The first step creates a connectivity graph that captures the neighbourhood relationship between the spatial objects. The cost of each edge in the graph is inversely proportional to the similarity between the regions it joins. We summarize the neighbourhood structure by a minimum spanning tree (MST), which is a connected tree with no circuits. We partition the MST by successive removal of edges that link dissimilar regions. The result is the division of the spatial objects into connected regions that have maximum internal homogeneity. Since the MST partitioning problem is NP‐hard, we propose a heuristic to speed up the tree partitioning significantly. Our results show that our proposed method combines performance and quality, and it is a good alternative to other regionalization methods found in the literature.  相似文献   

基于手机信令数据的深圳市二元居住空间迁居模式研究     

易行  仝德  吴雅莹  沈月  储君  吕婷苗 《地理研究》2023,42(1):137-155

迁居是城市空间重构的基础动力,了解其行为机制对改善住房结构、优化空间组织具有重要意义,然而目前针对大城市内部、正规与非正规二元居住空间并存的迁居研究仍较薄弱。本文基于生命历程理论与家庭迁居理论,利用2018年12月至2019年12月的手机信令等多源数据,识别深圳市二元居住空间分布和迁居流样本,从迁居流特征、邻里属性和二元空间类型三方面选取指标开展基于主成分分析的K-means聚类,探究迁居模式、结构特性与形成原因。结果表明：(1)非正规内部、正规与非正规交互、正规内部三层次迁居类型间存在年龄和居住质量递增的趋势,但均呈现通勤导向;(2)二元迁居的主体是短距离迁移,形成了4个大规模迁居网络集群,总体方向表现出郊区化趋势;(3)迁居模式可聚类为社区型、改善型、家庭型、事业型4类,结合二元空间分异影响呈现出8亚类,不同类型迁居群体属性和动因存在显著差别,总体反映出人们在不同生命历程下的迁居过程。最后,文章针对不同迁居模式提出差异化空间治理政策建议。  相似文献   

三元空间视角下长三角四省市旅游空间的耦合协调研究     

宋娜  毛娅琪  何亚丽  唐亦博 《世界地理研究》2023,32(1):104-116

以三元空间为研究视角,对旅游物理空间、旅游信息空间和旅游人本空间进行内涵解释并构建指标体系,以长三角四省市为研究区域,运用综合评价模型、耦合协调度模型和灰色关联分析模型等,测算2013—2018年旅游三元空间的发展水平、耦合协调度及各子指标对系统协调度的影响程度。结果表明（：1）从综合发展水平来看,四省市的三个旅游空间整体发展水平较低,但均呈上升态势,旅游物理空间综合发展水平最高,旅游人本空间次之,旅游信息空间的发展程度最低。从综合评价指数的年均增长率来看,上海市和安徽省均属于旅游信息空间发展优先型,江苏省和浙江省均属于旅游人本空间发展优先型（;2）从耦合度和耦合协调度来看,旅游空间呈现出不断协调发展的趋势,但整体耦合协调程度还处于中低水平,四省市的两两空间耦合度好于三元空间耦合结果（;3）从指标关联分析来看,评价指标体系中各二级指标均对三元空间耦合协调度有较大影响,灰色关联度全部处于“强关联”或“较强关联”状态,但不同空间的二级指标影响力不同,对不同省份的影响程度也略有差别。  相似文献   

基于超效率SBM模型的中国海洋渔业经济效率评价及影响因素分析     

田鹏  李加林  曹罗丹  张海涛  沈杏雯  王彩依 《海洋通报》2022,(3)

海洋渔业作为海洋经济的重要组成部分,对其进行经济效率评价有助于了解渔业资源转化利用效率,推动实现海洋渔业经济的高质量发展。基于2006—2018年我国海洋渔业经济投入产出数据,结合超效率SBM模型测算了我国海洋渔业经济效率,分析其时空变化特征并预测未来空间格局变化,再以相关性系数分析渔业经济效率的影响因素。结果表明：（1）海洋渔业经济效率均位于DEA模型最优前沿面的98.00%以上,空间分布差异性显著。（2）海洋渔业经济效率与投入产出关系趋于复杂化,渔业经济效率高值区趋于集聚,且高值区范围趋于扩张。（3）渔业经济效率重心由南向北移动,未来渔业经济效率重心趋于向东北迁移。（4）海洋渔业资源利用率、人均海洋渔业经济总产值、科研机构、海洋水产加工品总量、海洋水产出口贸易、渔业就业专业化指数对区域渔业经济效率以正向促进作用为主,海洋渔业经济发展需加快推动产业结构升级,发展绿色、低碳、智慧、生态渔业,政府政策积极支持,并加快对外合作,从而引领沿海渔业经济高质量发展。  相似文献   

一种逐级合并OD流向时空联合聚类算法     

项秋亮  邬群勇  张良盼 《地球信息科学学报》2020,22(6):1394-1405

现有OD流向聚类多将O点和D点相分离或者将OD流向看作4维空间的数据点进行聚类处理,忽视了流向长度、方向、时间对流向聚类的影响。本文以流向作为研究对象,提出一种基于流向间相似性度的逐级合并OD流向时空联合聚类算法。首先在充分研究OD流向的空间信息和时间信息的基础上,构建合理的OD流向间时空相似性度量方法,对OD流向间的时空相似性进行量化;然后提出逐级合并OD流向聚类策略,优化类簇合并的顺序,以减少层次聚类的时间开销,实现OD流向的时空联合聚类。以成都市的滴滴出行OD数据和纽约市出租车数据为例对本文方法进行了验证,结果表明：① 本算法聚类获得的流向类簇不仅带有空间特征还具备时间特征;② 在不同参数下本方法可以得到不同时空尺度的聚类结果;③ 与现有较高水平的流向聚类算法相对比,本文方法的聚类效果更好。这体现在流向类簇内部的流向之间有着充分的相似性,以及本文方法不仅可以提取出显著的流向类簇,还可以提取出非热点区域之间的流向类簇。本算法顾及空间因素和时间因素,可以通过调整时空相似性度量方法中的时间参数和空间参数以实现不同时空尺度的流向聚类,这使得从不同时空角度研究城市居民出行模式成为可能。本文提出的OD流向时空联合聚类算法从联合时间信息和空间信息的角度获得对运动数据的新见解,有助于合理全面地研究居民的移动模式、区域之间的空间联系、已知出行结构的确定以及出行目的的探索,是后续一系列分析工作的基础。  相似文献   

Effects of sand-mulch thickness on soil evaporation during the freeze–thaw period     

Junfeng Chen  Xue Xie  Xiuqing Zheng  Jing Xue  Chunyan Miao  Qi Du  Yongxin Xu 《水文研究》2020,34(13):2830-2842

Control of evaporation from seasonally frozen soil is an important method for alleviating water shortages in arid and semi-arid areas. To investigate the inhibition of soil evaporation by sand and the major factors that influence soil evaporation, a series of field experiments with five sand-mulch thicknesses (0 cm, bare soil [BS], 1 cm [T1], 2 cm [T2], 3 cm [T3] and 4 cm [T4], with an average diameter of 1 mm) were conducted during the freeze–thaw period in Northern China. Soil evaporation characteristics in the three freeze–thaw stages were revealed and the major factors influencing soil evaporation were analysed using grey correlation analysis. The results showed that the cumulative soil evaporation decreased with increasing sand-mulch thickness during the freeze–thaw period, and only small differences in soil evaporation were observed between the T3 and T4 treatments. The reduction in soil evaporation under different sand-mulch thicknesses was 19.2–62.6% in the unstable freezing stage (P1), 2.0–28.3% in the stable freezing stage (P2) and 4.8–20.4% in the thawing stage (P3). In P1, solar radiation was a major factor influencing soil evaporation in all treatments and vapour pressure was a major factor in the sand-mulch treatments, and the influence of relative humidity on soil evaporation decreased in the T4 treatment. During the coldest P2, solar radiation was lowest so that relative humidity and wind speed became the more dominant influence factors on soil evaporation in all treatments, and surface soil water content was a major factor in the sand-mulch treatments. In P3, average air temperature and solar radiation were major factor influencing soil evaporation in all treatments and vapour pressure was a major factor in the BS and T1 treatments, whereas water surface evaporation was the major factor in the T2, T3 and T4 treatments. The results suggest that the addition of sand mulch in agricultural fields may be a beneficial practice to reduce water stress in arid and semi-arid areas.  相似文献   

DBSCAN聚类和改进的双边滤波算法在点云去噪中的应用     

曲金博  王岩  赵琪 《测绘通报》2019,(11):89-92

采用基于密度的DBSCAN聚类算法对点云数据进行去噪处理，然后通过改进的双边滤波方法进行光顺处理实现点云平滑效果，最终的结果不仅有效去除了噪声点，还保留了点云模型的特征。以沈阳民国时期代表性的建筑——沈阳金融博物馆为试验模型进行试验，结果表明：通过DBSCAN聚类算法处理后得到的点云数据，再经改进的双边滤波处理所得到的数据远远比原点云数据直接运用改进的双边滤波处理得到的数据精度高，点云去噪效果更好。  相似文献   

一种北斗卫星钟差短期预报新方法     

柴伟杰  杭芬  刘国光 《测绘通报》2020,(3):78-82

为提高北斗卫星的定位与授时精度，必须准确计算出卫星钟差数值。本文考虑北斗卫星钟差中随机部分误差的影响，尝试建立北斗卫星钟差拟合推估模型，根据拟合推估两步极小解法解算该模型，在求解协方差函数系数中，依据模型残差拟合多项式系数；并与常用的灰理论模型、拟合推估的正常解法钟差预报模型结果进行比对，算例结果表明了两步极小解法及拟合推估模型在北斗卫星钟差短期预报方面的有效性。  相似文献   

大连地区地震的空间分布聚类分析     

刘洋  张凤君  马顺  张小平  张银龙  赵安生  刘超 《东北地震研究》2011,27(2):30-35

本文对聚类分析的原理进行了阐述,并且对大连地区1970年以来的3级以上地震进行了聚类分析,通过分析可以发现,大连地区的地震活动主要集中在2、4、6和13号这4个区域内。  相似文献