THE SIGNIFICANCE OF POTENTIAL-DENSITY REGRESSIONS

Strong correlations have been observed between potential indices and the densities of spatial variables. The conventional null hypothesis of bivariate regression is inappropriate for testing their significance. A randomization test is proposed and is applied to 1975 US population data by state. The resulting relationship has a significant correlation, but its slope could occur frequently under the null hypothesis. The correlation is shown to be related to the spatial autocorrelation of densities by constructing arrangements with prescribed values of the modified Moran index.     

A density-based approach for detecting network-constrained clusters in spatial point events

Existing spatial clustering methods primarily focus on points distributed in planar space. However, occurrence locations and background processes of most human mobility events within cities are constrained by the road network space. Here we describe a density-based clustering approach for objectively detecting clusters in network-constrained point events. First, the network-constrained Delaunay triangulation is constructed to facilitate the measurement of network distances between points. Then, a combination of network kernel density estimation and potential entropy is executed to determine the optimal neighbourhood size. Furthermore, all network-constrained events are tested under a null hypothesis to statistically identify core points with significantly high densities. Finally, spatial clusters can be formed by expanding from the identified core points. Experimental comparisons performed on the origin and destination points of taxis in Beijing demonstrate that the proposed method can ascertain network-constrained clusters precisely and significantly. The resulting time-dependent patterns of clusters will be informative for taxi route selections in the future.     

Earthquake prediction: the null hypothesis

The null hypothesis in assessing earthquake predictions is often, loosely speaking, that the successful predictions are chance coincidences. To make this more precise requires specifying a chance model for the predictions and/or the seismicity. The null hypothesis tends to be rejected not only when the predictions have merit, but also when the chance model is inappropriate. In one standard approach, the seismicity is taken to be random and the predictions are held fixed. 'Conditioning' on the predictions this way tends to reject the null hypothesis even when it is true, if the predictions depend on the seismicity history. An approach that seems less likely to yield erroneous conclusions is to compare the predictions with the predictions of a 'sensible' random prediction algorithm that uses seismicity up to time t to predict what will happen after time t. The null hypothesis is then that the predictions are no better than those of the random algorithm. Significance levels can be assigned to this test in a more satisfactory way, because the distribution of the success rate of the random predictions is under our control. Failure to reject the null hypothesis indicates that there is no evidence that any extra-seismic information the predictor uses (electrical signals for example) helps to predict earthquakes.     

广西城镇体系空间结构分形研究

基于分形理论对广西城镇体系空间结构进行研究,发现广西城镇空间分布具有统计分形特征。关联维数和牛鸦维数测算结果显示:广西城镇高度集中于河流和交通线两侧,城市之间的交通网络发育较为成熟。聚集维数测算结果表明:广西城镇空间分布不均衡,密度差异大,"双核心"结构明显。认为这些特征的出现是地理位置、自然条件、历史、交通、政策等因素共同作用的结果。     

Proximity to Job Opportunities and African American Male Unemployment: A Test of the Spatial Mismatch Hypothesis in Indianapolis

Despite the lack of substantive research, the spatial mismatch hypothesis remains a pervasive explanation for the high rate of African American male unemployment. This research tests the hypothesis that census tract African American male unemployment rates are negatively related to the number of local job opportunities. This hypothesis is tested for Marion County, Indiana, the central county of the Indianapolis MSA. Weighted partial correlation coefficients of the logit of African American male census tract unemployment rates and indices of the availability of local job opportunities in manufacturing, services, and retail trade are statistically insignificant. The findings reject the spatial mismatch hypothesis in the specific context of Indianapolis in 1990.     

基于基尼系数空间分解的江苏省经济发展差异分析

不平等性是区域研究的重点,空间集中作为衡量不平等性的重要手段,是非空间与空间属性的二维统一体。传统的研究仅仅关注了全局非空间上的不均衡性,而忽略了地理空间上的集聚特点,往往不利于识别地理属性的集中特点。引进基尼系数的空间分解这一概念,通过对其空间随机分布性的零假设采用蒙特卡罗方法进行检验,从而判定其分解形式是否内生衡量区域不平等与空间自相关的特性。以1978—2015年江苏省区域经济发展差异的演变进行案例分析,通过蒙特卡罗99次随机模拟检验后,将分解的非邻居项与Moran’s I值进行显著性检验,结果进一步证实了这一分解的有效性与简洁性,表明空间基尼系数可内生测度空间的集聚性与非空间的差异性。     

高速公路流的距离衰减模式与空间分异特征——基于福建省高速公路收费站数据的实证研究

交通流是社会经济空间联系的直观反映,其距离衰减规律对空间秩序的形成与演化意义重大。利用2016年10月份的福建省高速公路收费站数据,以县区为基本单位,识别高速公路流O-D矩阵;在此基础上,利用空模型法模拟省和县区2个尺度上高速公路流的距离衰减规律,并结合空间分析和相关分析法,探讨高速公路流距离衰减规律的空间分异特征与规律。结果显示,①高速公路流主要集中在0~200 km与0~200 min区段,较好地契合了公路运输的经济半径与交通流的时空断裂特征;②省域层面上,高速公路流随距离的增加有显著的衰减趋势,当采用路网距离、幂律型衰减函数时,距离衰减系数为2.674,显著高于常规所选数值2;③不同县区高速公路流的距离衰减速度在空间上呈显著的圈层模式,与高速公路流的空间分布形成较好的耦合关系;④距离衰减规律内生于社会经济空间联系格局,不仅影响空间秩序的形成与演化,也会受空间秩序演化的影响,一定条件下,节点的对外社会经济空间联系强度会随节点规模、人口与经济密度的提高以及区位条件的优化形成自我加速的反馈过程,形成循环累积效应。     

中印城镇化区域差异及城镇体系空间演化比较

中国和印度作为两个正在崛起的大国,发展历程较为相似,但发展路径和模式差异较大。两个国家政治制度、经济体系、发展环境等的显著差异已经吸引了学者的广泛关注,本文将从地理学视角出发,重点关注两国城镇化及城镇体系的区域差异和空间演化过程。以人口普查和联合国城市人口数据为基础,采用空间分析、参数估计、非参数估计等多种方法,对中印两国城镇化和城镇体系的空间特征进行系统的比较分析,结果表明：① 20世纪90年代以来,中国城镇化的区域差异由南北差异转变为沿海—内部差异,而印度南北差异的格局则基本稳定;② 从省（邦）级空间尺度来看,中国和印度的人口密度和城镇化率都呈现正相关关系,当城镇化率超过50%后,两者的相关性更为显著,但是近年来中国人口密度与城镇化率的相关性不断增强,而印度则呈现降低的趋势;③ 现阶段中印两国以大中城市为主的城镇体系符合位序—规模分布的特征,但是经济改革对于两个国家城镇体系空间演化的影响差异明显,改革使得中国城镇发展的主要驱动力由地理历史因素向经济系统空间结构转变,而印度城镇发展的驱动力始终是地理历史因素,经济改革甚至降低了经济系统空间结构对城镇发展的影响。     

节能减排约束下中国省域旅游生态效率评估及空间格局研究

旅游生态效率评估及空间格局研究是揭示中国省域旅游业发展质量与态势的重要基础.论文以"自下而上"法核算中国省域旅游能源消耗与碳排放为基础,综合运用考虑非期望产出的Super-SBM模型、Malmquist指数及探索性空间数据分析等方法,探究节能减排约束下2000-2017年中国省域旅游生态效率及其空间分异、收敛和关联格局...     

山东省农村居民点转型的空间特征及其经济梯度分异

为探究农村居民点转型的空间结构及其与经济发展的关联性,以山东省为例,基于农村宅基地转型的理论假设与测度方法,运用空间关联分析方法研究农村居民点转型的空间布局和集聚特征,并以人均GDP作为特征指标划分各县级行政区的经济发展梯度,从省级全域层面和“点、线、面”特征单元综合的角度,揭示农村居民点转型与经济发展的相关性及其耦合关系。结果显示,在空间分布上,2005-2014年山东省农村居民点转型指数呈现西高东低和南高北低的态势;在全局趋势上,Moran's I指数达到0.6317,说明农村居民点转型存在显著的空间集聚现象;在局部趋势上,农村居民点转型的热点区和次热点区集中分布在鲁西黄泛平原、鲁西南淮河平原以及鲁中沂蒙山区,次冷点区分布在次热点区外围,冷点区分布在胶东丘陵地区和鲁北黄河三角洲地带;在相关性分析上,农村居民点转型与经济发展水平具有明显的数理统计相关性和空间耦合性,无论是全域层面还是特征单元,农村居民点转型均表现出从低级到高级经济梯度的递减规律、且乘幂变化趋势显著。本文探索了农村居民点转型的空间特征,弥补了土地利用转型空间性分析的不足;同时研究结果也较好地验证了前人提出的理论假设。     

A statistical method for detecting spatiotemporal co-occurrence patterns

Spatiotemporal co-occurrence patterns (STCOPs) are subsets of Boolean features whose instances frequently co-occur in both space and time. The detection of STCOPs is crucial to the investigation of the spatiotemporal interactions among different features. However, prevalent STCOPs reported by available methods do not necessarily indicate the statistically significant dependence among different features, which is likely to result in highly erroneous assessments in practice. To improve the reliability of results, this paper develops a statistical method to detect STCOPs and discern their statistical significance. The proposed method detects STCOPs against the null hypothesis that the spatiotemporal distributions of different features are independent of each other. To construct the null hypothesis, suitable spatiotemporal point-process models considering spatiotemporal autocorrelation are employed to model the distributions of different features. The performance of the proposed statistical method is assessed by synthetic experiments and a case study aimed at identifying crime patterns among multiple crime types in Portland City. The experimental results demonstrate that the proposed method is more effective for detecting meaningful STCOPs than the available alternative methods.     

地理探测器：原理与展望

空间分异是自然和社会经济过程的空间表现,也是自亚里士多德以来人类认识自然的重要途径。地理探测器是探测空间分异性,以及揭示其背后驱动因子的一种新的统计学方法,此方法无线性假设,具有优雅的形式和明确的物理含义。基本思想是：假设研究区分为若干子区域,如果子区域的方差之和小于区域总方差,则存在空间分异性;如果两变量的空间分布趋于一致,则两者存在统计关联性。地理探测器q统计量,可用以度量空间分异性、探测解释因子、分析变量之间交互关系,已经在自然和社会科学多领域应用。本文阐述地理探测器的原理,并对其特点及应用进行了归纳总结,以利于读者方便灵活地使用地理探测器来认识、挖掘和利用空间分异性。     

城市地表温度与NDVI空间相关性的尺度效应

城市地表温度与NDVI的空间相关性已被广泛研究,但是其尺度效应常常被忽略,给研究结果带来不确定性。本文以郑州市为例,基于四幅Landsat8影像,经辐射传导法反演地表温度(LST),运用半变异函数识别地表温度的空间相关性分析尺度,并结合空间相关指数Moran's I,从多尺度、多季节、多邻接范围3个方面对地表温度与植被覆盖的空间相关性的尺度效应进行了探讨,结果表明：①LST和NDVI的单变量空间自相关和双变量空间相关尺度均在300 m左右;②300 m相关尺度内,单变量空间自相关性存在显著尺度效应,相比之下双变量空间相关性尺度效应较为微弱;③LST和NDVI的单变量空间自相关性和双变量空间相关性尺度效应均表现出明显的季节差异;④随着邻接范围增大,LST和NDVI的空间自相关性减弱,尺度效应更明显。因此度量LST和NDVI的空间相关性要考虑时空尺度效应,本文研究结果有助于进一步认识LST和NDVI间空间相关性的尺度效应。     

产业地理集中、产业集聚与产业集群:测量与辨识

本文综述了产业地理集中、产业地理集聚以及产业集群的测量与辨识方法。传统的测量 产业地理集中方法包括集中系数、变差系数、赫芬代尔系数、赫希曼- 赫芬代尔系数、信息熵、锡尔 系数以及基尼系数等, 这些系数测量产业总体地理集中程度, 没有考虑企业规模分布对产业地理 集中的影响。基于企业区位选择模型, 经济学家发展了测量产业地理集聚的指数, 控制产业内企 业规模分布对产业地理集中的影响。无论地理集中指数还是地理集聚系数都以行政单元为基础, 仅描述单一空间尺度上的产业区位模式。Ripley 的K 函数通过计算某个企业一定距离内的邻居 企业个数来测量产业的地理集聚程度, 可同时反映产业在不同空间尺度的集聚程度。相互联系的 一群企业在地理空间上的集聚构成了产业集群, 产业集群的辨识不仅要测量产业间联系, 也要考 虑产业地理临近性。区位商和标准化区位商法、空间相关与产业联系法、因子分析和聚类分析等 多元统计方法以及基于投入产出关系的图谱分析方法等可以用来作为辨识区域产业集群手段。     

技术扩散还是效率优先——基于“美团网”的中国O2O电子商务空间渗透探讨

关于电子商务的空间发展问题,学界提出了技术扩散假说和效率假说。技术扩散假说认为发达城市地区的电子商务发展更好,效率假说则认为欠发达城市地区的电子商务发展更好,两者内涵存在明显争议。以中国286个地级市的O2O电子商务为例,采用空间计量模型、多元线性回归等方法,尝试探讨了其空间发展更倾向于技术扩散还是效率优先。结果表明：① 中国O2O电子商务的规模指数在空间上呈现出由东部沿海向西北内陆逐渐递减的等级式特征,但其发展水平指数的空间格局表现出均质化特征,其渗透指数呈现出由东部沿海向西北内陆逐渐递增的“逆等级”式空间格局。② 实体商业对O2O电子商务的发展具有显著约束力,但交通条件对其具有明显的促进作用,因此,中国O2O电子商务的空间发展更倾向遵循效率假说内涵,但也并非完全契合于该假说。③ 中国O2O电子商务“逆等级”式的空间格局对欠发达城市地区实体商业有更强的促进作用,这会引导中国宏观商业格局趋于均质化。     

On the age calibration of the geomagnetic polarity timescale

Knowledge of the age of undated events is not null if a time-order relationship can be found among these events. The knowledge of such a time-ordered sequence can be formalized by using non-informative (uniform) prior probability densities for the ages of undated events and Bayes' theorem to introduce the time-order relationship condition. We show that the conditional probability densities of the ages of events of unknown age are given by various forms of Euler's beta distribution. These distributions yield an estimate of the probability for an undated event to occur in a given age interval.
  We use this method to propose appropriate probabilistic representations of our actual knowledge of the dating of the magnetic polarity reversals during the Cenozoic. These representations take into account the uncertainties arising from irregularities in accretion process and from the quality of a few calibration points. Both types of uncertainties generate large ambiguities in the age of magnetic reversals, which should be taken into consideration when the geomagnetic polarity timescale is used for dating purposes. We propose to use the entropy function to quantify these ambiguities.     

基于人口流的中国省域城镇化空间关联特征及形成机制

空间关联是区域相互作用和影响的纽带,以人口流动为载体的城镇化空间关联影响并不断调整着中国区域经济社会发展格局。根据省际人口流动数据,构建城镇化空间关联模型,通过分析1990-2015年中国省域城镇化空间关联强度与关联网络结构变化,揭示城镇化空间关联特征及形成机制。结果发现：① 中国省域城镇化空间关联强度演变过程可以解析出7种类型,其中主导类型与全国的吻合程度最高,并决定着全国城镇化空间关联强度演变过程;非主导类型的城镇化空间关联强度演变特征以2005年为界,之前增长缓慢甚至为负,之后与主导类型共同推动全国城镇化空间关联强度持续增长。② 对城镇化空间关联进行不同尺度的结构分析,全国城镇化空间关联网络结构日趋复杂,关联路径由集中转向分散,不同属性的地域子群间关联密度差异开始缩小,高等级节点由东部向中西部扩散。③ 采用面板向量自回归和面板分位数回归检验城镇化空间关联强度与关联网络中心度的互动机制,并解释了居民收入水平和区域产业结构对城镇化空间关联特征的影响方式。城镇化空间关联不仅深化了城镇化的研究,也为中国人口城镇化发展和产业空间转移调控提供理论依据。     

An exploration of direct and indirect drivers of herbivore reproductive performance in arid and semi arid rangelands by means of structural equation models

Climate variability affects both animal and plant populations. Understanding how this variability is modulated by topography, vegetation and population densities and how this impact on ungulate demography is an important step in order to forecast consequences of alternative management scenarios or the effects of climate change.Structural equation modeling (SEMs) is a tool particularly suited to this kind of situations, and allowed us to study the direct and indirect effects of climate, topography, structural and functional aspects of vegetation and population density upon reproductive performance of Patagonian sheep flocks, measured at paddock scale. The application of SEMs in conjunction with information criteria and related techniques for model selection, model averaging and multi-model inference revealed that despite considerable model uncertainty, those paddocks towards the East, with a greater spatial variability in July temperatures and greater primary production during fall-winter (estimated by remote sensing) showed greater lambing rates. Paddocks with higher proportion of meadows and with more intense forage consumption, were also associated with a better reproductive performance. Our results not only provide quantitative hypothesis about the controls at the landscape level of herbivore performance but also provide the basis to devise better management alternatives.     

1990年以来东北地区铁路运输的空间极化

以运输区段为研究单元, 以区段客流密度、货流密度、区段长度为原始数据, 将1990 年、1994 年、1999 年、2000 年和2005 年的东北地区铁路运输区段划分加以统一。首先运用 GIS 技术分析铁路运输密度变化的空间特征; 然后通过计算基尼系数、泰尔指数、集中指数 和崔王指数, 分析各年度铁路客货流分布的空间差异和极化程度;最后比较哈大线、沈山线 和滨洲－滨绥线等铁路干线的客货运周转量及比重变化。研究表明： ① 20 世纪90 年代铁路客流的空间极化比较明显, 2000 年以后极化趋势变缓或有所逆转; ② 货流在上行方向(向中部哈大线方向、向南部关内方向) 有趋于极化的特征; ③ 不管客流分布的总体特征向极化或分散方向如何变化, 哈大线在东北铁路网中的地位都在持续加强, 哈大线以外地区客流分布 趋向均衡。1990 年以来东北铁路运输分布的变化支持这样的区域空间极化过程： 向哈大沿线 集聚; 东北地区地域系统的层级减少, 哈大轴带作为顶层结构对整个东北地区的控制范围和程度增加。东北地区铁路网的整体性和区域一体化程度加深。     

游荡河型造床实验过程中河型的时空演替和复杂响应现象

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