Study of Urban Expansion and Driving Factors in Xi’an City based on Nighttime Light Data

The dynamic monitoring of urban expansion information is of great significance to understand the social and economic activities of cities and the implementation and feedback of urban planning.Using DMSP / OLS night-time light image as data source,the urban expansion data were corrected and extracted by using rational function model and threshold dichotomy.By using the light index,urban spatial expansion rate and intensity index and the index of center of gravity migration,The results show that the urban built-up area in Xi’an has expanded 2.2 times from 148 km² in 1993 to 473 km² in 2013.The direction of urban expansion expands from southwest to south and north,and the spatial expansion mode also increases from the early stage The single-core concentric expansion mode gradually transformed into a multi-level nuclear growth expansion mode;thus using gray relational analysis to analyze the socio-economic indicators of the suburbs in Xi’an in 2008~2013 (Weiyang district,Yanta district,Baqiao district and Chang’an district) It is confirmed that secondary industry,population density,tertiary industry and fixed assets of the whole society are the main driving factors of urban expansion in four districts respectively.     

Evaluation of Urban Expansion in Chongqing City based on the Nighttime Light Data

Urbanization is an important embodiment of regional economic development.Its progress reflects the level of economic development in the region.Since Chongqing being directly under the Central Government in 1997,it has enjoyed rapid economic growth and rapid urbanization.Looking for an intuitive and efficient method of urbanization is of great practical significance to correctly grasp the achievements of urbanization in Chongqing from the overall situation.Through the comparison of statistical data on night lighting data,we can extract the built-up area of Chongqing year after year.The city gravity model is based on the results.A night light index is established and used to calculate the speed of urban expansion.The result indicates that the urban distributions in Chongqing is spatially distributed and expanded in all directions.There are great differences between urban areas and rural areas and urban area urbanization level is higher.The city gravity gradually shifted from Yuzhong district to Yubei district.The speed of city expansion maintains high.Our study can afford refers for the planning and construction of the Chongqing city.     

Spatio-temporal Characteristics of Urban Land Cover Structures in Prefecture-level Cities of Inner Mongolia Autonomous Region based on Remote Sensing Imagery

The urban land cover structures play an important role in providing urban ecological service and altering the quality of human settlements environment.In this study,2000~2015 Landsat TM series satellite data along with fine resolution remote sensing images were used to capture information of each 5-year land cover structures in 12 prefecture-level cities of Inner Mongolia Autonomous Region.Subsequently,there land cover information was used to monitor and analyze the spatiotemporal dynamics of urban expansion,and differences of land cover structures and expansion types.The results showed that：in 2000~2015,the overall changes of land cover structures in 12 prefecture level cities of Inner Mongolia Autonomous Region were rapid.Specifically,the urban area expanded by 278.93 km².By comparison,the proportion of urban area expansion in 2010~2015 was 1.61 times and 1.91 times than that of the first two periods (in 2000~2005 and in 2005~2010).Since 2010,the most dramatic changes has been observed.Particularly,obvious urban impervious surface expansion was found.Also urban vegetation showed obviously increased with varying degrees.At the past decade,urban expansion has undergone three stages.Specifically,the main process experienced from urban interior filling to urban interior filling and then to urban extension,of which Baotou and Hulunbeier belonging to the internal filling city.Population growth and socio-economic development are responsible for these differences.     

The spatial and temporal distribution of metals in an urban stream: A case study of the Don River in Toronto,Canada

Widespread growth of cities, the association of trace metals with urban runoff, and the potentially deleterious effect of metals on aquatic ecology have made it important to understand the distribution and transport of metals through surface water channel networks. The Don River in Toronto, Canada has been identified as an Area of Concern for pollution to Lake Ontario, with historically high levels of metal contamination. Sampling programs are sparse, therefore a model is needed to understand the spatial and temporal variability of metals in the river network. The objectives of the current study are to: i) describe the sampled spatial and temporal variability of metals in the Don River and ii) develop a modelling strategy to describe within flood metal transport dynamics. A model setup tool is developed that links Storm Water Management Model (SWMM) with the Environmental Fluid Dynamics Code (EFDC) to allow a seamless transition from catchment hydrology to in-stream hydraulic and chemical processes. Results show that lead pollution in the Don River is decreasing, likely as a result of policy changes and sediment dredging in the mouth of the river. However, zinc and copper pollution are increasingly problematic, with copper exceeding recommended lower guidelines, particularly during floods. Model results confirm that most of the sediment and metals are transported in relatively short bursts within longer flood durations and are stored in depositional hotspots within the Lower Don River. A better monitoring strategy is needed to understand and more accurately parametrize these processes in an urban river system.     

城市建(构)筑物拆除爆破重大危险源的辨识与控制

拆除爆破是种高风险、高危害性的行业,城市建(构)筑物爆破拆除的安全控制与管理非常重要。本文阐述了城市建(构)筑物拆除爆破重大危险源辨识的依据、方法和主要类型,并提出相应的控制原则、控制措施及程序。可为控制爆破拆除行业安全管理的系统化、规范化和程序化提供参考。     

我国城市配电网技术改造浅析--中压配电10kV应升压至20kV

文章论述了四个问题：（１）根据存在的诸多问题,强烈呼吁改造城网和进行体制改革;（２）我国城网改造应吸收国外的一些有益经验,应将１０ｋＶ升压至２０ｋＶ,且避免大拆大换,节约投资;（３）城网升压改造,必然随之要改变原配电网中性点的接地方式,对此文章作了论述;（４）呼吁我国电工制造企业积极研制开发２０ｋＶ产品,并迅速投放市场,以满足国内城网改造的需要。     

城市配电网格化规划探讨

随着城市经济建设和市政功能日臻完善的发展趋势,提出了以网格化概念,规范城市（公用）配电网络的建设和发展,并由此化解目前配电生产组织、营业收费管理以及市政改造发展中的诸多矛盾,为逐步实现城市配电供电高可靠性目标打好基础。     

对遥感在城市更新监测应用中的认知和思考

对城市更新改造的监测是目前较新的遥感应用领域。鉴于当前城市更新领域有关的遥感监测研究现状,对城市更新中遥感监测的概念、涉及方法以及与业务应用关系等方面进行了介绍,通过简要综述城市遥感监测的研究进展,分析适用于城市更新中的遥感数据类型,给出遥感在城市更新中的应用实例,尝试论证遥感在城市更新改造中的价值和作用,填补该领域遥感应用认知上的空缺,提出遥感在该领域工作可能的发展方向和研究思路。     

基于VIIRS夜间灯光数据的山东半岛城市群发展特征研究

NPP-VIIRS夜间灯光数据是在中大尺度上开展城市发展变化研究的稳定数据源。基于2012~2018年NPP-VIIRS夜间灯光数据,以山东半岛城市群为研究对象,采用参考比较法提取城市建成区图斑,选取9个景观格局指数对山东半岛城市群的城市化发展特征进行定量分析。结果表明：①整体上,域内斑块总面积以4.5%的速度增长,边缘总长度和边缘密度年均增长3.15%,斑块数量和密度增长较快（分别为1.95%和1.98%）,表明山东半岛城市群整体城市面积增长迅速,城市范围持续扩张;②从不同指标变化趋势来看,各城市斑块总面积增长最快的是青岛市和东营市（分别为9.66%和6.01%）;青岛市的斑块数量和密度增速最快（分别为9.54%和8.55%）,日照市的斑块数量和密度均以3.65%的速率显著降低;景观形状指数整体增速缓慢;平均回旋半径在日照市具有较高的年均增长速度（5.99%）;③从各城市发展特征的差异性来看,青岛市的平均斑块面积和回旋半径分别以0.56%和1.53%的速度降低,其他各指标均显著增加,表明青岛市出现了较多的新兴城镇,城区面积不断扩大;济南、日照和东营市的城区面积增长较快,斑块数量、景观形状指数等指标增长缓慢,城市发展以旧城区的扩张为主;潍坊、淄博和烟台市在2015年和2016年前后经历了新兴城镇出现,城镇融合的阶段,城市发展较快。总体而言,山东半岛城市群城市化发展较快,但空间差异性明显。     

基于点云数据的单木三维绿量估算方法

针对不同树种的树叶疏密及空间结构不同,提出基于激光点云数据,顾及冠层叶面积密度的树木三维绿量（Living Vegetation Volume, LVV）计算方法。该方法首先根据树木局部点云的主方向相似度和局部点云轴向分布密度分离枝干与树叶,剔除非光合作用成分,提取树叶点云;然后建立体元模型,引入Graham算法确定分层树冠边界,获取激光接触频率,从而基于体元冠层分析（Voxel-based Canopy Profiling, VCP）方法求出冠层叶面积密度（Leaf Area Density, LAD）;最后分层棱柱体积乘以叶面积密度,累加得到树木的三维绿量。利用Riegl VZ-400地面激光扫描仪获取13棵不同形状和树种的树木点云数据,利用该方法估算各树木三维绿量,并与传统的凸包法和台积法的结果对比。实验结果表明,台积法计算的三维绿量值最大,凸包法计算的三维绿量次之,顾及冠层叶面积密度的树木三维绿量方法计算的三维绿量值最小,为台积法的36.69%,为凸包法的47.80%。相比传统方法,顾及冠层叶面积密度的树木三维绿量计算方法侧重光合作用组分叶片点云的统计,并考虑了树冠内部树叶分布情况,更符合树木的实际情况,能充分利用三维点云数据特性,反映树冠内部三维绿量分布。