Li+的水合结构和近似饱和水合层:基于密度泛函理论的研究

结合密度泛函理论,运用B3LYP/aug-cc-pVDZ方法对[Li(H₂O)_n]⁺(n=1~10)水合团簇的结构进行了研究。研究结果表明,在气相和液相中,四配位结构的[Li(H₂O)_n]⁺水合团簇比其五配位的异构体稳定,即在水溶液中Li⁺易形成四配位的四面体结构。随着同时水分子数的增加,Li-O键长增大,Li⁺上的电荷密度减小。但是当水分子数大于4时,Li-O键长和Li⁺上的电荷密度变化很小。[Li(H₂O)_n]⁺水合团簇中每个水分子的结合能计算结果表明,7个水分子已足以形成Li⁺的近似饱和水合层。另外红外光谱显示[Li(H₂O)_n]⁺水合团簇中O-H伸缩振动随着水分子数的增加发生蓝移,而~3 600 cm-1和~3 500 cm-1处的吸收峰是第二水合层与第一水合层、第三水合层和第二水合层的水分子形成氢键引起的。     

栓皮栎叶芽休眠解除过程的模拟*

树木的休眠及其解除是一个在理论和实践中都十分重要又悬而未决的问题。本文利用全国范围内获得的观测资料,对栓皮栎这个重要用材树种的叶芽休眠之解除过程进行了模拟。其出发点是:林木存在绝对低温需要,在此需要得到满足后,进一步的低温和驱温的协同作用使林木的生长能力逐步恢复直到休眠解除。研究表明:接近林木基点的温度对低温积累是最有效的,休眠后期的不稳定高温会部分抵消前期低温的影响。栓皮栎对低温的绝对需要量为5个低温单位,休眠完全解除共需34个低温单位和194个驱温单位。在整个分布区内,栓皮栎的休眠解除被划分成四个基本类型,即北方型、中部型、华南型及西南型。并对树木的休眠解除现象进行了深入的讨论。     

三种土壤铅和镉的质量基准初步研究*

在制定地下水源保护区污染控制措施时,最常遇到的问题之一是缺少土壤包气带和含水层中化学物质的基准和标准。文中以铅、镉为例,结合北京、唐山地下水水源地实际情况,运用“平衡分配法”,根据土壤对铅和镉的吸附容量和分配系数研究包气带土壤中的铅和镉的质量基准。结果表明,土壤中铅和镉的质量基准与溶液pH值成对数线性关系,据此可计算不同pH条件下的土壤中重金属的质量基准。     

基于交通状态分析的南昌市区区际联系通达性研究

综合考虑交通状态日变化规律、区际联系出入口等级及高速公路、过江大桥和隧道等对通达性的影响,引入路网饱和度模型分析南昌市区区际联系通达性的时空分布特征,研究表明：① 南昌市区区际通达性主干路指向性强,整体呈由中心向外围不规则辐射状;② 全区通达性格局受交通状态影响,不同时段通达性格局差异明显,尤其是南昌市核心区变化更为显著;③ 过江大桥、隧道的交通状态对区域通达性影响较大,高峰期过江大桥及隧道的拥堵凸显出河流、铁路线等因素对交通的阻隔,河流及铁路线两侧通达性差距拉大。在此基础上,为提升区际联系通达性提出了南昌市区际公路及市内道路空间组织的优化建议。     

Finding shortest paths on real road networks: the case for A*

The problem of identifying the shortest path along a road network is a fundamental problem in network analysis, ranging from route guidance in a navigation system to solving spatial allocation problems. Since this type of problem is solved so frequently, it is important to craft an approach that is as efficient as possible. Based upon past research, it is generally accepted that several efficient implementations of the Dijkstra algorithm are the fastest at optimally solving the ‘one‐to‐one’ shortest path problem (Cherkassky et al. 1996 Cherkassky, B. V., Goldberg, A. V. and Radzik, T. 1996. Shortest paths algorithms: theory and experimental evaluation.. Mathematical Programming: Series A and B, 73: 129–174. [Crossref], [Web of Science ®] , [Google Scholar]). We show that the most efficient state‐of‐the‐art implementations of Dijkstra can be improved by taking advantage of network properties associated with GIS‐sourced data. The results of this paper, derived from tests of different algorithmic approaches on real road networks, will be extremely valuable for application developers and researchers in the GIS community.     

基于空间可达性分析的客家民系迁移路径模拟

以人地关系为视角,引入空间可达性的概念,探讨赣闽粤交界地区客家先民迁移路线的选择与所处的自然环境和社会历史背景之间的关系。利用GIS技术建立地形和古交通通道数据库,分别构建栅格与矢量数据结构最优路径模型,分析了客家民系迁移路径选择与空间可达性的关系。结果表明:可达性分析结果与客家民系的空间分布拟合的较好,受迁移时期的生产力水平限制,高大山脉、隘口等地形因素对迁移路线影响巨大,自然、社会、历史因素共同影响客家民系迁移及分布格局,赣州、长汀、梅州等"客家首府"城市位于所模拟的最优迁移路径上。     

Impacts of traffic accessibility on ecosystem services: An integrated spatial approach

The continuous degradation of ecosystem services is an important challenge faced by the world.Improvements in transportation infrastructure have had substantial impacts on economic development and ecosystem services.Exploring the influence of traffic accessibility on ecosystem services can delay or stop their deterioration;however,studies on its impact are lacking.This study addresses this gap by analysing the impact of traffic accessibility on ecosystem services using an integrated spatial regression approach based on an evaluation of the ecosystem services value (ESV) and traffic accessibility in the Middle Reaches of the Yangtze River Urban Agglomeration (MRYRUA) in China.The results indicated that the ESV in the MRYRUA continuously decreased during the study period,and the average ESV in plain areas,areas surrounding the core cities,and areas along the main traffic routes was significantly lower than that in areas along the Yangtze River and the surrounding moun-tainous areas.Traffic accessibility continued to increase during the study period,and the high-value areas centred on Wuhan,Changsha,Nanchang,and Yichang were radially dis-tributed.The global bivariate spatial autocorrelation coefficient between the average ESV and traffic accessibility was negative.The average ESV and traffic accessibility exhibited signifi-cant spatial dependence and spatial heterogeneity.Spatial regression also proved that there was a negative association between the average ESV and traffic accessibility,and scale ef-fects were evident.The findings of this study have important policy implications for future ecological protection and transportation planning.     

基于可达性的中国城市群空间范围识别研究

作为指示区域间相互作用的重要度量,空间可达性是刻画城市及其腹地间空间关联格局的表达方式,已经成为城市与区域系统发挥集聚与扩散功能的显著表征。考虑空间异质性,本文综合集成自然地表要素和陆地交通网络,构建更为逼近真实场景的可达性分析方法,精确刻画中国城市空间可达性宏观格局,在此基础上,提取中国城市群空间范围。从空间可达性视角,都市区、都市圈、城市区域和城市群等不同尺度城市与区域系统格局凸显,多尺度城市功能地域系统逐步浮现。从空间连续性、关联性和紧凑性出发,基于城市等时圈,以省会城市或区域中心城市为抓手,最终共提取出15个城市群结构。与国家“十三五”规划纲要提出的19个城市群相比,本文共识别出15个城市群,既存在共性,也存在明显的差别。总体上,本文识别出的城市群空间范围要普遍小于国家或各级政府批复的城市群。科学认识“自然生长的”和“规划引导的”城市群之间的差别,对于更好地发挥城市群功能地域作用、推进城市群可持续发展具有重要价值。     

广东省乡村聚落空间分布的影响机制及研究内容框架展望（英文）

Based on land use classification data of remote sensing images, using kernel density, the minimal cumulative resistance model of road traffic accessibility, and a logistic regression model, the characteristics of the spatial pattern and the main factors influencing it were quantitatively examined in Guangdong Province from 1990 to 2013. The framework of the research concerning rural settlement evolution and its effect mechanisms were also discussed and generalized for the future. The results are as follows:(1) The spatial distribution of rural settlements showed spatial directivity of low altitude, low slope, and adjacent to rivers, as well as to villages and towns; thus a special pattern was formed, which was dense on the plains, sparse in mountainous areas, and included two core high density regions of rural settlements in the Chaoshan plain in the east and the Zhanjiang plain tableland region in the west. The spatial distribution of rural settlements was located along the rivers, valleys, and roads with traffic in the mountainous regions surrounding the Pearl River Delta region.(2) In addition to the spatial orientation of the open road, it was important to show that the accessibility of road traffic to the township has had the greatest influence on the spatial distribution of the rural settlements. The connected transport network between towns and villages is significant for rural transformation as a comprehensive increase in township production and service capacity will be the key to optimizing the town-village system in rural areas.(3) Elevation and slope were two basic but influential factors that have affected the distribution, scale, and form of rural settlements. The attributes of the physical geography are the first elements in optimizing village layout and planning spatial reconstruction.(4) In the current Internet and social media era, the reconstruction of market network system orders connects with the global market network system in rural areas. The rural life service circle will be constructed with the township at its core to explore the theory and practice of spatial reconstruction, including its production, life and ecology, and socio-cultural heritage and protection. It will also allow for exploration of the rural settlements' evolution, rural spatial production, rural social networks, group behavior, social autonomy, and social and cultural fields, which will bethe core focus of China's rural spatial reconstruction research against a background of globalization.     

基于铁路客运网络的省际可达性及经济联系格局

基于铁路客运交通网络把各省会城市抽象为铁路网络中的节点,以2003和2008年省会城市间铁路客运网络的最短旅行时间为度量指标,对我国铁路客运网络的空间可达性及空间格局进行分析,测算各省区间的省际经济联系强度,进而探讨省际间经济联系的空间指向。研究表明:(1)经过第五、六次铁路客运提速,省际可达性获得了显著提升,尤其西部地区提升幅度更大,省际可达性表现出自东部沿海向西北内陆逐渐降低的圈层式空间格局,高于全国平均水平的地区范围在扩展,干线指向性越来越强;(2)各省区对外经济联系总量地域差异突出,东部地带省区的经济联系总量远高于中西部地带省区;(3)地区间经济联系依托京沪、京广以及京哈等主要铁路干线形成了省际联系的主导轴线,并且随着地区经济的发展和铁路网络的大幅度提速,地区经济联系的空间网络格局逐步形成。     

基于社会需求与交通可达性的新疆通勤机场布局研究

从经济、人口、资源、交通以及社会公益性综合层面评价县域民航需求与交通可达性水平空间差异,采用断裂点模型对现有干、支线机场布局进行评价,确定新疆通勤机场布局与功能。结论：（1）影响新疆县域民航发展需求的各类因素中,经济因子客观权重高于社会与环境因子。（2）民航发展需求水平与交通可达性综合水平县域间差距较大,整体偏低。（3）民航发展需求指数与交通可达性综合指数组合为6类区域,且大部分为"低需求低可达性"。（4）机场吸引力有效断裂点为70个,集中分布在民航发展需求与综合交通可达性中低水平区域。（5）新疆民航机场布局可发展干-支-通勤三层轴-辐与南北疆环线布局模式。     

Rural settlement spatial patterns and effects: Road traffic accessibility and geographic factors in Guangdong Province,China

Journal of Geographical Sciences - Based on land use classification data of remote sensing images, using kernel density, the minimal cumulative resistance model of road traffic accessibility, and a...     

基于经济社会活动视角的城市空间演化过程模型

中国的快速城市化带来了诸多问题,亟需制定合理有效的城市空间政策以确保城市发展的可持续性。因此,开展城市空间发展过程模拟、实施政策检验对于推进新型城镇化和城市的健康发展具有重要意义。本文基于“土地利用/交通相互作用模型”(Land Use/Transport Interaction Model, LUTI),以经济社会活动为切入点,构建了城市空间演化过程模型(Urban Activity Spatial Evolution Model, UASEM),并进一步给出了UASEM模型各子模型的具体实现和模块之间衔接的逻辑结构,从可操作层面给出了模型的实现方法。该模型可用于模拟城市空间演化过程、检验政策实施等,将成为城市空间可持续发展模拟分析研究的重要工具。