河南省县域交通优势度综合评价及空间格局演变

从路网密度、可达性和区位优势度3个方面构建区域交通优势度综合评价指标,并采用熵权TOPSIS法对河南省2003年和2008年县域单元的交通优势度进行综合评价;进而运用ESDA法对交通优势度及增长空间格局进行探讨。研究表明,河南各县市交通优势度均获得了不同程度的改善,交通优势度呈现出显著的空间相关性和空间集聚特征,中心与外围间、平原与山区间的交通优势度空间差异显著;高速公路网络的构建使中原城市群地区大多数县市的交通优势度获得了大幅度提升,但豫南和豫西南山区、盆地的相对增长率较高;最后指出,充分利用地区交通优势和规避交通劣势是地区经济发展战略制定、产业选择和空间结构优化需要考虑的基础要素。     

Exploring the relationship between street centrality and land use in Stockholm

This paper examines the relationship between different street centralities and land-use types in Stockholm. Major centrality measures of closeness, betweenness, and straightness are calculated at both global and local levels in both the primary and dual representations of the urban street network. Adaptive kernel density estimation is adopted to transform all unevenly distributed datasets to one continuous raster framework for further analysis. After computing statistical and spatial distribution of each centrality and land-use density map, we find that the density of each street centrality is highly correlated with one type of land use. Results imply that various centralities representing street properties from different aspects can capture the land development patterns of different land-use types by reflecting human activities, and are consequently important indicators to describe urban structure.     

湖底深基坑围护结构变形与受力特性研究

基坑围护结构是基坑安全的重要保证。通过三维有限单元模拟,考虑地下水渗流的影响及结构与土体之间的相互作用,对某湖底明挖隧道基坑支护结构在施工过程中的变形和受力变化规律进行研究,并与现场监测结果进行对比验证。结果表明:围护结构的不同部位对基坑开挖的响应规律并不一致;水平向支护结构受开挖影响,向坑内倾倒,竖直向桩体随开挖应力重分布影响中段发生弯曲变形,总体稳定。模拟变形结果与监测结果较为一致,验证了基坑围护结构的有效性和模拟计算的准确性。研究结果为基坑后续施工提供了参考依据。     

Assessing the implications of the recent community opening policy on the street centrality in China: A GIS-based method and case study

Recently, the Chinese government raised an urban planning policy which suggests communities open their private roads for public transport and establish street networks with high spatial density in cities. In this context, the purpose of this study is to analyze the potential changes to street network accessibility using GIS techniques and to provide spatial information that may influence the decision making of urban managers. In addition to the existing street network data in the case study city, Shenzhen, intra-community roads are extracted from building footprints in GIS topographic database and used to construct a potential street network with respect to the community opening policy. An automatic GIS-based method is proposed here to analyze the location advantage information in the simulated urban environment, by combining Delaunay triangulation model and graph theory concepts. Specifically, we establish a two-step framework based on the spatial relationships between roads and buildings. Firstly, intra-community roads between neighboring building footprints are generated using a Delaunay triangulation skeleton model, and with the existing inter-community roads they form the simulated network. Secondly, street centrality indices of the current and simulated networks are compared in terms of closeness, betweenness and straightness. Results indicate that after applying the policy the global accessibility in the city would be increased at some places and decreased at others, and places' directness among others would be generally improved. In addition, the skeleton of central routes for through traffic would not change much. The presented method can also be applied to other cities.     

基于空间统计理论的新疆各地州经济林营养物质积累空间关系特征分析及应用

积累营养物质是森林生态服务功能中的重要组成部分,它反映了林木生长情况和生产投入情况。基于2014年新疆七种主要经济林木积累营养物质调查数据,核算了2014年全疆经济林木氮、磷和钾的物质积累总量,折合当年化肥价值3.14×10⁸元。并利用全局空间自相关模型和地理加权模型（GWR）对该结果进行了分析。结果表明：（1）全疆不同经济林品种积累营养物质价值量的空间分布符合空间集聚理论,呈现某种经济林木在某个地区具有高度集中的种植现象;（2）GWR模型分析结果表明经济林在南疆林业中占有重要地位;（3）南疆各地州经济林发展存在明显差异,其中克孜勒苏柯尔克孜自治州、和田地区和喀什地区处在经济林发展期;阿克苏地区和巴音郭楞蒙古自治州则处在经济林衰产期。上述结果表明通过深入挖掘新疆生态服务功能价值信息,能够提取对新疆经济林产业发展规划具有重要参考价值的信息。研究所使用的思路和方法对其他类似研究具有重要的借鉴意义。     

基于SVD与机器学习的华南降水预报订正方法

降水是在多种天气系统和复杂物理过程共同影响下形成的,因此降水预报难度较大。由于数值预报模式的局限性,使得模式预报产品存在一定误差。为探讨更加有效的模式预报产品误差订正方法,基于奇异值分解（SVD）与机器学习（多元线性回归、套索回归、岭回归）构建订正模型,对2007—2019年4月1日—6月30日华南前汛期欧洲中期天气预报中心（EC）模式降水预报产品进行误差订正试验。结果表明：基于SVD与机器学习相结合的订正模型能有效降低EC模式降水预报产品在华南的预报误差,均方根误差最大优化率达4.2%,累计超过69%的站点得到不同程度的优化;SVD与机器学习相结合的订正模型能很好地处理因子间共线性问题,具有更好的鲁棒性;而对多个订正模型加权集成,均方根误差优化率达5.7%,累计超过77%的站点得到优化,显然加权集成方法订正效果不仅优于EC模式预报产品,也优于参与集成的任一订正模型。     

基于空间加权距离的自适应Fuzzy C-Means算法研究

空间聚类不仅应考虑GIS对象属性特征的相似性,还应考虑对象的空间邻近性。不同属性、位置特征在聚类中起到的作用不同。采用信息熵方法计算空间距离中各属性距离、位置距离的权重,权值大小用于度量相应特征在fuzzy c-means隶属度计算时的作用大小,并引入相似性指标,当两个聚类之间的相似度高于某个合并阈值时,则对应的一对聚类进行合并,从而克服需预先设置聚类类数的问题。通过应用实例的聚类有效性分析,与普通空间距离相比,基于空间加权距离的FCM算法具有稳定性和有效性。     

加权整体最小二乘的验后估计在三维坐标转换中的应用

在求解三维小角度坐标转换EIV模型的过程中,顾及到两套坐标系下点坐标初始单位权方差可能不同导致定权不准确的问题,应用Helmert方差分量估计方法,对加权整体最小二乘的随机模型进行验后估计,从而重新分配观测向量和系数矩阵的权,使得解算模型更加合理。算例证明,利用该方法求解坐标转换参数的精确度有所提高,参数估值更接近真值。     

基于二次曲面的拟合推估法在GPS高程测量中的应用

针对GPS水准拟合常用的多项式拟合模型、多面函数拟合模型和加权平均拟合模型存在的缺陷,采用最小二乘拟合推估的方法提高拟合精度,并通过某工程实例比较和分析,认为该拟合方法比单一模型精度更高、稳定性更强且具有较高的可靠性和实用价值。     

Local population and housing changes associated with destination redevelopments in Detroit (1990-2010): a geographically weighted shift-share analysis

The aim of this research is to utilize a novel approach called geographically weighted shift-share (GWSSA) analysis to estimate the degree and manner to which recent destination redevelopments have played a role in changing the characteristics of the nearby population and housing in Detroit between 1990 and 2010. The main benefit of geographically weighted shift-share analysis is that this technique isolates the local changes due to such projects while simultaneously controlling for the amount of the change expected for unrelated factors (e.g., the exodus of people leaving Detroit due to its overall negative reputation). Results suggest that such destination redevelopments in Detroit seem to be connected to a number of surprising positive local impacts during this period related to total population, 18-to-29-year-olds, non-Hispanic whites, employed civilians, unemployed civilians, households earning between $50,000 and $100,000 in annual income, total housing units, occupied housing units and vacant housing units.