Detecting clusters over intercity transportation networks using K-shortest paths and hierarchical clustering: a case study of mainland China

Intercity transportation infrastructures and services determine the depth and breadth of the spatial interactions among cities within an urban agglomeration, and have profound impacts on the spatial structure of the urban agglomeration. To evaluate whether the public intercity ground transportation infrastructures and services (i.e. passenger trains and long-distance buses) can support the integration and development of urban agglomerations, we propose a method for ‘transportation cluster’ detection (TCD), which has three unique features: (1) the K-shortest paths are used to quantify the proximity between cities, which is more in line with people’s travel behaviors; (2) a dendrogram is obtained through hierarchical clustering to reveal the structural hierarchies of transportation clusters; and (3) the integration of geo-modularity and hierarchical clustering assures high strength of division of transportation networks. The proposed TCD method was applied to the network of passenger trains, the network of long-distance buses, and the combined network of both in mainland China, respectively. By comparing the resultant transportation clusters with the urban agglomerations delineated by the Chinese government, cities that have weak transportation connections with other cities within an urban agglomeration were identified, and such findings could help devise transportation planning to better support the integrated development of urban agglomerations.     

Identification of tourist hot spots based on social networks: A comparative analysis of European metropolises using photo-sharing services and GIS

New sources of geolocated information, associated with big data and social networks, show great promise for geographical research, especially in the field of tourism geography. Photo-sharing services comprise one of these sources. The aim of this article is to demonstrate the potential of photo-sharing services for identifying and analyzing the main tourist attractions in eight major European cities: Athens, Barcelona, Berlin, London, Madrid, Paris, Rome and Rotterdam. Geotagged photographs on Panoramio were differentiated according to whether they had been taken by tourists or local residents, and their spatial distribution patterns were analyzed using spatial statistical techniques in a GIS. The results indicated the concentration and dispersion of photographs in each city and their main hot spots, and revealed marked differences between tourists' and residents' photographs, since the former showed higher spatial concentrations. In addition, differences were observed between cities; Barcelona and Rome presented a strong spatial concentration compared with London or Paris, which showed much greater dispersion.     

Watershed simulation in a sandy terrain of the Thar desert using GIS

The sandy landscape in a desert contains very few stream channels. This poses a problem for delineating watersheds for analysis. Since large-scale topographical sheets of sandy terrain also contain very little information on height, delineation of watersheds from topographical sheets often becomes difficult. In order to find a simple solution to the problem in the Thar desert of Rajasthan, India, the authors used the well-known ARC/INFO software for simulation of height and drainage network using the scarce topographical information for a sandy terrain near Jodhpur. Superimposition of data layers generated from remote sensing and secondary sources validated the simulation results, and suggested suitability of the method for application in similarly handicapped areas.     

小尺度环境地形相对高度认知及影响因素——以南京大学浦口校区为例

地形认知虽然是探讨人地互动的重要命题, 但目前研究甚少。本文选取南大浦口校园 为案例地, 在实验设计基础上, 采用非概率和分层比例抽样, 使用问卷调查和深度访谈的数 据收集方法, 历时两年, 共访谈调查了644名被试, 并运用定性与定量数据分析方法, 得出 小尺度环境地形认知一致性、参照体系特征、个体日常环境对认知的影响性等特点, 具体结 论如下:(1)认知一致性:被试在地形相对高度的认知方式与状况、地形特征点的辨识方面 具有较高一致性;且认知偏误率在空间上呈现一定的分布规律。(2)参照体系特征:被试使 用的环境参照物附近的地形多呈凹陷状且地势较低、空间临近特征显着, 并且它们多是被试 熟悉, 视觉通达性较好, 到访率较高的场所。(3)个体日常环境对认知的影响性:地形特征 的辨识及其相对高度认知受地理环境、认知、行为、情绪和态度等多方面因素影响, 其中决 定性因素是个体的日常生活环境。     

交通网络与城市结构研究——理论框架与中美两国实证案例

本文从城市体系和城市内部两个尺度上总结交通网络与城市结构之间的关联.通过中美两国城市的实证案例,从交通网络和交通流的视角,提出了一个城市体系结构和城市内部结构研究的理论框架.其中城市的有序性是其共同理论的出发点,包括城市规模体系和城市内部人口密度空间分布的有序性,其在很大程度上决定了人类居行的空间分布模式.可采用交通网络位置决定区位优劣,从而影响城市兴衰(城际尺度)、地价高低、人口疏密(市域尺度)和出行模式等加以理论解释.城市体系分布的有序性、城市内部结构的规律性、城市间以及城市内交通网络的拓扑特征,共同影响了微观层面个体的时空间移动以及群体层面的交通流分布,从而为链接微观与宏观两个尺度的地理环境影响奠定了基础.     

中国“四纵四横”高铁网络可达性综合评估与对比

传统测算可达性的方法较为单一,缺乏多层面、多角度的综合研究和对比分析。基于时间、经济与重心视角利用可达性模型并结合ArcGIS 空间分析手段探究高铁通车前后沿线城市可达性的动态变化;利用综合变异系数、层级分析法和改进的哈夫模型分析高铁可达性空间演变特征及规律,构建高铁可达性评价体系并结合熵权法定量评估各高铁可达综合实力。研究表明：京广、京沪可达综合实力最强,沪昆、杭福深次之,沪汉蓉、哈大、青太再次之,郑西、兰新可达实力最弱;全国高铁可达性强弱变化呈明显地带性规律,东、中部高铁可达性强于东北,东北强于西部,纵向高铁强于横向;经济潜力的增加率明显高于加权平均旅行时间的减少率,可达性重心偏移驱使不同等时圈蔓延交叠;高铁以“核心—核心”逐步向“核心—网络”空间链接模式过渡,产生上海、北京、广州、深圳4 个高铁“国家服务中心”,天津、武汉、重庆等6 个“大区域服务中心”,形成“多中心”高铁服务格局以及日益庞大而复杂的高铁特质空间集群;高铁网络影响下的中国区域空间格局的渐变与重塑日趋复杂,“T”型轴带呈现出由空间极化向空间均衡转变,跨城流动性特征突显,加速空间对接与同城化进程。     

Performance analysis of radial basis function networks and multi-layer perceptron networks in modeling urban change: a case study

The majority of cities are rapidly growing. This makes the monitoring and modeling of urban change’s spatial patterns critical to urban planners, decision makers, and environment protection activists. Although a wide range of methods exists for modeling and simulating urban growth, machine learning (ML) techniques have received less attention despite their potential for producing highly accurate predictions of future urban extents. The aim of this study is to investigate two ML techniques, namely radial basis function network (RBFN) and multi-layer perceptron (MLP) networks, for modeling urban change. By predicting urban change for 2010, the models’ performance is evaluated by comparing results with a reference map and by using a set of pertinent statistical measures, such as average spatial distance deviation and figure of merit. The application of these techniques employs the case study area of Mumbai, India. The results show that both models, which were tested using the same explanatory variables, produced promising results in terms of predicting the size and extent of future urban areas. Although a close match between RBFN and MLP is observed, RBFN demonstrates higher spatial accuracy of prediction. Accordingly, RBFN was utilized to simulate urban change for 2020 and 2030. Overall, the study provides evidence that RBFN is a robust and efficient ML technique and can therefore be recommended for land use change modeling.     

Simulation of currents, ice melting, and vertical mixing in the Barents Sea using a 3-D baroclinic model

A baroclinic. 3-D model is described. It is adapted to the Barents Sea and includes thermodynamics and atmospheric input. The freezing and melting of ice is allowed for in the model. The main task of the study is to look at the development of the ice cover, the vertical mixing, and the vertical and horizontal density gradients.
Despite simple approximations in the air temperature input, realistic ice-cover is produced in the model area during simulation of a "freezing period" (winter). This intermediate result is briefly discussed and also forms the start of a "melting period" simulation (spring/summer). Atmospheric input data (wind, air pressure, and heat flux) from the spring and summer 1983 is used, and details about vertical mixing, temperature, and salinity are discussed. The simulation results demonstrate the temporal variation of the thermocline depth, the variation of the ice cover, and the horizontal changes of density. The conclusion is that despite often simplified input, the model seems to produce a physical picture characteristic of the Barents Sea.     

Network-scape metric analysis: a new approach for the pattern analysis of urban road networks

The spatial patterns of road networks reflect the morphological and structural characteristics of cities. Previous studies have focused mainly on seeking universal laws in road networks rather than explaining their differences. A new approach for road network pattern analysis is proposed that has been inspired by landscape metric analysis. The utility of this approach is illustrated through (but is not limited to) the extraction of the main factors in network landscapes, or network-scapes for short. Twenty-four metrics were calculated for network-scapes of 100 cities worldwide, before an exploratory analysis is performed to detect the main factors. Four main factors were revealed and may be regarded as the characteristic indicators of road networks, which were identified to be evenness, richness-density, shape irregularity, and size and shape variation. The meanings of these factors are explained, and their spatial distributions are illustrated. Compared to existing road network analytics, these factors depict better the characteristic differences of road networks. The proposed approach provides a new framework for road network pattern analysis from a cellular perspective.     

Quantifying the sequence stratigraphy and drowning mechanisms of atolls using a new 3-D forward stratigraphic modelling program (CARBONATE 3D)

This paper describes a new 3‐D forward numerical model (CARBONATE 3D) that simulates the stratigraphic and sedimentological development of carbonate platforms and mixed carbonate–siliciclastic shelves by simulating the following sedimentary processes: (1) Carbonate shallow, open‐marine production, dependent on water depth, restriction and sediment input; (2) Carbonate shallow, restricted‐marine production, dependent on water restriction; (3) Pelagic sediment production and deposition; (4) Coarse and fine siliciclastic input; (5) Erosion, transport and redeposition of sediment, dependent on currents, slope, depth and restriction as well as sediment grain‐size and composition; (6) Dissolution of subaerially exposed carbonate. In this paper the model is used to investigate the controlling mechanisms on the sequence stratigraphy of isolated carbonate platforms and atolls and to predict distinctive architectural signatures from different drowning mechanisms. Investigation of the mechanisms controlling atoll strata shows that although relative sea‐level is the major control, antecedent topography, environmental setting and early diagenesis have profound influence on what stratigraphic geometries and facies develop. Hence care must be taken if sea‐level curves are interpreted from real stratigraphies. Atoll drowning by fast sea‐level rise, by lowered production and by repeated exposure and fast subsequent sea‐level rises are investigated and different stratigraphic signatures for the respective mechanisms predicted. A fast relative sea‐level rise results in a bucket‐shaped morphology developed prior to drowning and a sharp transition from the platform margin facies to a pelagic cover. Drowning caused by lowered platform margin production is predicted to result in the development of a dome‐shaped, shallow‐water shoal over the whole platform top prior to drowning. Fourth order amplitudes of several tens of metres, typical of ‘icehouse’ settings, cause atoll drowning at subsidence rates where atolls subject to fourth order amplitude of only a few metres, typical of ‘greenhouse’ settings, can keep up with the rising sea‐level. In the resultant strata, vertical facies belts are less well developed but horizontally extensive facies bands are more prominent. High fourth order amplitudes (up to 80 m) without sufficient third order scale subsidence will not lead to drowning, however, as the platform can recover in each fourth order lowstand. These results suggest that atolls might be easier to drown in ‘icehouse’ rather than in ‘greenhouse’ conditions but only in situations with suitably high rates of longer‐term relative sea‐level rise or sufficient lag times.     

Planning hierarchical hospital service areas for maternal care using a network optimization approach: A case study in Hubei,China

Improving maternal health is one of the Sustainable Development Goals. Hospital service areas (HSAs), which contain most hospitalization behaviors at the local scale, are crucial for health care planning. However, little attention has been given to HSAs for maternal care and the hierarchy structure. Considering Hubei, central China, as a case study, this study aims to fill these gaps by developing a method for delineating hierarchical HSAs for maternal care using a network optimization approach. The approach is driven by actual patient flow data and has an explicit objective to maximize the modularity. It also establishes the hierarchical structure of maternal care HSAs, which is fundamental for the planning of hierarchical maternal care and referral systems. In our case study, 45 secondary HSAs and 22 tertiary HSAs are delineated to achieve maximal modularity. The HSAs perform well in terms of indices such as the Localization Index and Market Share Index. Furthermore, there is a complementary relationship between secondary and tertiary hospitals, which suggests the need for referral system planning. This study can provide evidence for the validity of the HSA and the planning of maternal care HSAs in China. It also provides transferable methods for planning hierarchical HSAs in other developing countries.