曲线简化中节点重要性度量方法比较及垂比弦法的改进

在曲线简化过程中,一个最基础的问题是如何度量曲线上节点的重要性程度.该文简要回顾了现有的一些节点重要性度量方法,即角度度量法、面积度量法、弧比弦度量法和垂比弦度量法,指出其局限性.结合弧比弦度量法与垂比弦度量法的优点,提出了一种改进的垂比弦度量方法,并给出具体的评价方法.最后,根据曲线简化实验结果,发现相比于弧比弦度量法.改进后的垂比弦度量法选取的节点能较好地保持曲线的形状.     

关联矩阵法与城市宜居指标的结构关系度量——以中国老年人宜居城市评价指标体系为例

城市宜居环境综合评价本质上是城市内部包括物质空间、社会文化空间等众多要素之间的结构关系研究。城市系统结构可以分为不同的亚系统,亚系统之间的关系可以用数量方法确定。以中国老年人宜居城市评价指标体系为例,介绍和比较了各种宜居环境评价指标体系指标赋权的方法,应用关联矩阵法确定老年人城市宜居环境各亚系统之间,以及亚系统内部各个指标的重要性。旨在说明关联矩阵法在确定城市结构中各亚系统关联度上具有合理、简便的特点,尤其是具有将客观性与主观性评价相结合的优势。     

市场间邻近性与广东省出口企业的地理集聚

对外贸易是塑造广东省产业空间分布格局的重要力量,深入地探讨出口贸易与广东省企业集聚的内在联系机制,具有重要意义。本文从出口市场与本地市场之间的多维邻近性角度,为广东省的企业集聚发生机制提供了新的解释,具有一定的理论与政策参考价值。本文认为,企业的出口市场与本地邻近性越低,企业自身越难以远距离地直接获取关于目的市场的出口知识。在这种情况下,企业为了实现出口的成功扩张,其在空间上倾向于集聚分布,以在本地获取相关知识的溢出。基于2000—2016年中国海关进出口贸易数据,本文对广东省出口企业的外部出口市场格局以及内部空间集聚格局进行了描述,并实证测度了企业的出口市场与广东省在地理、经济、文化、政治和制度五个维度上的邻近性与企业地理集聚水平之间的关系。特别地,本文运用DO方法对企业集聚水平进行定量测度,还原了企业集聚的原始微观形态,一定程度上弥补了现有对于集聚水平测度方法的不足。描述性分析表明,一方面,广东省企业的出口市场具有多样化的特点,其扩张一定程度上遵循“邻近性”原则;另一方面,广东省的企业空间分布呈现明显的“核心-边缘”格局。实证结果表明,当出口至与本地在经济、政治和制度三个维度上邻近性较低的市场时,企业在本地更加集聚。市场间地理和文化邻近性对企业集聚水平的影响不显著。同时,该影响效应在出口市场为发达地区和发展中地区的企业样本中具有差异。     

近30年来新疆经济重心转移路径

运用空间均值地图演示的方法,研究了新疆近30年以来经济重心的转移问题.得出以下结论:(1)新疆经济重心与中心并不重合,位于其地理重心的东北部,经济重心与地理重心之间的距离总体呈逐年增大趋势;(2)1978-2007年间经济重心移动轨迹由西南向东北呈"S"型态势发展,总方向为东偏北10.49°,总移动距离为103.87 km,其中东西方向移动102.13 km,而南北方向仅移动18.91 km,绝大多数年份的经度向变化大于纬度向变化;(3)新疆经济重心的移动与区域经济发展政策密切相关,不同历史时期的区域发展政策使得新疆经济重心呈现一定的阶段性和规律性.新疆区域经济差异总体是在不断扩大的,建议区域经济发展政策应继续向新疆西部、西南部地区倾斜.     

区域沙漠化程度评价研究进展、问题及分析

通过回顾景观尺度及区域尺度的沙漠化程度评价发展过程,概括了国内外典型的区域沙漠化程度评价方法,通过假设各种情景分析、总结了目前各类区域沙漠化程度评价方法中存在的典型共性问题：(1)当被比较评价的几个区域中各类沙化土地面积相等时,目前所有的评价模型失去比较能力;(2)忽略了不同类型沙化土地空间分布的生态学意义及其对区域沙化整体程度的影响;(3)目前考虑了不同类型沙化土地空间分布的模型由于指标因子选择不恰当其评价结果在有些情况下与实际情况有距离。提出了在现有评价方法的基础上根据景观生态学原理引进景观生态学方法,特别是景观格局分析的方法,可以弥补现有区域沙漠化程度评价方法中存在的缺陷和不足,并且可以使区域沙漠化程度评价具有生态学意义。     

Fabric analyses of some Saudi Arabian pediment gravels

Two- and three-dimensional gravel fabric analyses have been performed on a number of pediments located in central, western Saudi Arabia. Standard methods of vector analysis were used to measure orientation. It is concluded that long axes of pediment gravels tend to point downslope and that fabrics are remarkably uniform over pediment surfaces. The results indicate that agents such as sheetfloods, rather than channel flow, may be most effective in bringing about such fabrics.     

大气降尘收集方法及相关问题研究

降尘监测是探索大气降尘对环境的影响和生态效应评估不可缺少的手段之一。根据集尘容器内同定降尘介质的不同，目前常用的收集方法分为干法、湿法和玻璃球法3种。在实际监测中，每种方法都有不同的研究者采用，3种方法的收集效率也有一定的差别。研究表明，干法的集尘效率为湿法的73％和玻璃球法的95％；玻璃球法的集尘效率为湿法的77％。3种方法的集尘量之间具有良好的线性关系，可以依此进行数据的转换。不同的收集容器会对集尘效率产生影响，其测量精度也不相同。另外，这3种收集方法不能很好地区别干沉降和湿沉降过程，应该加以改进。因此，采用统一的标准开展大气降尘的合作研究很有必要。     

全国分县土地经济系数计算方法及比较

阐述土地经济系数的设置意义和目标,针对全国分县土地经济系数计算,提出并分析比较了统计指标法和分区样点法等思路及其数学处理方法。其中统计指标法中的农业产值消耗法基础数据来源可靠、便利,便于操作,计算结果较好,符合土地经济系数含义要求。     

Estimating the effect of turn penalties and traffic congestion on measuring spatial accessibility to primary health care

Geographic variations in spatial accessibility to public resources, such as health care services, raise important questions about the efficiencies and inequities of the processes that determine where these services are located. Spatial accessibility can be measured many different ways, but many of methods in use today involve some measure of travel cost (in time or distance). In this study we explore a simple methodological question: how much are models of spatial accessibility influenced by the precise metric of travel cost? We address this question by comparing spatial accessibility to primary care physicians for two different methods of calculating travel cost (in time) on a street network: free-flow travel time and congested with turn penalties travel time—which augments free-flow travel times with the burden of traffic congestion and traffic intersection controls. We consider the effect of these two metrics of travel cost on a gravity-based measure of spatial accessibility to primary health care services in Edmonton, Alberta, Canada. Our results suggest that while travel times between locations of demand and locations of primary care providers greatly differ based on how travel cost is calculated, the gravity-based measure of spatial accessibility provides similar information for both travel cost metrics. Using congested with turn penalties travel time can be an onerous addition to the analysis of spatial accessibility, and is more useful for measuring absolute travel time rather than modeling relative spatial accessibility.     

Biological improvement of saline alkali soil reference system: A review

This work presents a reference system overview to improve the efficiency of biological improvement of saline-alkali soil developed during the last thirty years, ranging from connotation, general methods and species, soil desalination, soil structure, soil organic content, microbial flora, enzyme activity, yield and economic benefits. The reference system presented is divided into three main groups: suitable varieties, suitable cultivation measures, and a comprehensive evaluation system.There has been a lot of research on biological improvement of saline alkali soil, but these studies are very fragmented and lack a comprehensive standard system. Also, there is a lack of practical significance, particularly with regard to optimal species, densities and times of sowing for particular regions. On the other hand, the corresponding cultivation measure is very important. Therefore, a reference system plays an important role to the effect of biological improvement of saline alkali soil.     

中国中部地区城市影响范围划分方法的比较

随着城市化、区域一体化的不断推进,各种类型的城市与区域规划陆续推出。其中,识别城市的腹地范围、促进城市与腹地的协同发展是其关键内容。因此,城市影响范围的划分具有重要的现实意义。已有的研究成果多以单一年份的静态研究及单一方法的应用研究为主,缺乏时间序列上的动态演变分析,更无多种方法综合集成分析。正是基于以上考虑,在详细梳理与比较不同理论的差异性基础上,采用引力模型和改进场模型两种方法对中国中部地区的城市影响范围进行测度和比较研究,细致比较这两种基于不同视角的模型方法在识别城市影响范围的优势与劣势,进而提出综合集成研究的基本框架,分析中国中部地区城市影响范围及其动态变化特征。希望能为合理选择和运用城市影响范围的分析方法,有效制定区域等级体系规划、城市空间组织方案提供科学参考。     

Experimental Investigations of Single Bubble Rising in Static Newtonian Fluids as a Function of Temperature Using a Modified Drag Coefficient

Natural Resources Research - In the oil production industry, it is of significance to measure and predict the form of multi-phase flow and gas flow that are present within petroleum production and...     

Is the analysis of plant community structure better than common species-diversity indices for assessing the effects of livestock grazing on a Mediterranean arid ecosystem?

Grazing in arid Mediterranean ecosystems brings about changes in species diversity, but the best way to measure such changes is unclear. In this study we compared various methods in order to identify indicators that might be useful for the management and conservation of grazed arid Mediterranean ecosystems.Changes in community structure and composition were compared along a previously studied grazing gradient in Cabo de Gata-Nijar Natural Park. Plant diversity was measured by calculating diversity (Shannon information index), evenness (Pielou index) and richness (species number). Rarefaction curves were used to measure plant species richness and the results were compared with traditional richness values. Community structure was measured as the percentage of bare ground and the coverage of overall perennial grasses, Stipa tenacissima L., perennial shrubs and annual plants. Our results showed that the proportion of bare ground, the cover of perennial shrubs and the relative abundance of S. tenacissima are good indicators of grazing effects on vegetation. Overall plant community structure was more sensitive to the grazing gradient than were the diversity indices. Finally, the adequacy of standardized methods for comparing species richness (i.e. rarefaction curves) along a grazing gradient are discussed.     

国际工序贸易的空间经济分布效应研究——克鲁格曼开放度假说的再考察

基于开放经济新中心是否与封闭经济原有中心空间重合的视角,以中国为背景对国际工序贸易影响空间经济分布的三大渠道进行理论阐释,在全球价值链背景下重新考察克鲁格曼的开放度假说。在理论分析基础上,借助加工贸易集聚熵指数和空间赫希曼-赫芬达尔指数（及校正地理集中指数）分别度量各省国际工序贸易嵌入程度和空间经济集聚水平,以中国23个省2001~2016年的面板数据构建动态面板模型,利用差分和系统广义矩估计对提出的理论假说进行实证分析和稳健性检验。结果表明：与开放度假说相反,国际工序贸易促进省域空间经济集聚;且工序贸易对经济集聚的促进作用在沿海要大于内陆。     

基于“湖泊效应”模型的辽宁省海岸带陆地范围测度及其时空分异分析

目前国内外对海岸带的界定尚不存在统一说法,虽然海岸带向海范围的界定相对一致,但海岸带向陆范围差异较大。而海岸带向陆范围的界定是海岸带空间合理规划、海岸带区域综合承载力准确评估的重要保证,对海岸带的相关研究起着重要的作用。此外,传统的海岸带界定方法均没有考虑海岸带的动态性及空间差异性,因此,基于Bass扩散模型原理,构建了“湖泊效应”模型,提出了等辐射力曲线的概念,设计了可行的海岸带陆地范围量化方法。以辽宁省为例,结合2001~2012年人口与经济的面板数据,通过GIS与1stOpt软件平台,测度了辽宁省6个沿海城市的海岸带陆地范围,并对其进行了时空差异分析。运用Gompertz模型,预测了辽宁省2013~2020年的海岸带范围,分析了其空间差异趋势。结果表明：① 海洋的辐射带动力持续增长,辽宁省海岸带范围随着时间在稳步向内陆扩张;② 区域经济较发达的地区,海岸带范围也较广;③ 大连市和营口市是辽宁省海岸带的增长极;④ 辽宁省未来8 a海岸带范围将继续向内陆扩张而空间差异将逐步缩小。     

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。     

Uncertainty Estimate in Resources Assessment: A Geostatistical Contribution

For many decades the mining industry regarded resources/reserves estimation and classification as a mere calculation requiring basic mathematical and geological knowledge. Most methods were based on geometrical procedures and spatial data distribution. Therefore, uncertainty associated with tonnages and grades either were ignored or mishandled, although various mining codes require a measure of confidence in the values reported. Traditional methods fail in reporting the level of confidence in the quantities and grades. Conversely, kriging is known to provide the best estimate and its associated variance. Among kriging methods, Ordinary Kriging (OK) probably is the most widely used one for mineral resource/reserve estimation, mainly because of its robustness and its facility in uncertainty assessment by using the kriging variance. It also is known that OK variance is unable to recognize local data variability, an important issue when heterogeneous mineral deposits with higher and poorer grade zones are being evaluated. Altenatively, stochastic simulation are used to build local or global uncertainty about a geological attribute respecting its statistical moments. This study investigates methods capable of incorporating uncertainty to the estimates of resources and reserves via OK and sequential gaussian and sequential indicator simulation The results showed that for the type of mineralization studied all methods classified the tonnages similarly. The methods are illustrated using an exploration drill hole data sets from a large Brazilian coal deposit.     

古尔班通古特沙漠春季土壤含水量空间格局

春季积雪融水是古尔班通古特沙漠土壤水分的重要补给源之一,为早春植物的萌发和生长创造了有利的条件。为掌握该地区春季沙丘的土壤水分分布状况,采用探地雷达测量技术,于2010年4月进行了多次野外测量,并通过对地面直达波信号的提取和分析,初步获得了一致的测量结果。结果表明：（1）探地雷达地面直达波测量的土壤平均含水量与20 cm深同步TDR的测量结果非常接近,两者总体相差在0.02 cm3/cm3以内,充分反映了GPR地面直达波测量结果的有效性和精确性;（2）春季积雪完全融化后,沙丘/沙垄顶部土壤水分明显低于垄间低地,这与前人的研究一致,反映了积雪和冻土层在消融过程中,沙丘表面融水在坡面重力作用下,沿难以透水的冻土层上界自坡上向坡下迁移,形成了垄间最高、坡部次之和垄顶最少的分布格局;（3）垄间低地的土壤水分明显受到低矮灌草丛的影响进行再分布,这是由于积雪最初沿植丛基部开始消融,并以植丛为中心形成漏斗状融洞,从而形成以植丛为中心汇集较多融雪水的格局,而垄间低地中较为高大的梭梭乔木对融雪水的再分布影响明显不如低矮的灌草丛,这与其地表茎基过少有关。此外,探地雷达测量实验提供了详实可靠的表层土壤含水量分布信息,可为荒漠生态系统的空间尺度研究提供真实可靠的数据基础。     

Effect of climate and seasonality on depressed mood among twitter users

Location-based social media provide an enormous stream of data about humans' life and behavior. With geospatial methods, those data can offer rich insights into public health. In this research, we study the effect of climate and seasonality on the prevalence of depression in Twitter users in the U.S. Text mining and geospatial methods are used to detect tweets related to depression and their spatiotemporal patterns at the scale of Metropolitan Statistical Area. We find the relationship between depression rates, climate risk factors and seasonality are varied and geographically localized. The same climate measure may have opposite association with depression rates at different places. Relative humidity, temperature, sea level pressure, precipitation, snowfall, weed speed, globe solar radiation, and length of day all contribute to the geographic variations of depression rates. A conceptual compact map is designed to visualize scattered geographic phenomena in a large area. We also propose a three-stage framework that semi-automatically detects and analyzes geographically distributed health issues using location-based social media data.     

城市绿地空间环境公平研究进展

始于1980年代的环境公平研究近年来重点转向环境资源,尤其是公园绿地在不同族群和不同收入人群中的空间分布。经过对国内外文献的梳理,从绿地空间环境公平研究主题、绿地公平性影响因素及其测度指标和方法进行了系统综述。分析发现：1）国内外关于绿地空间环境公平的研究主要集中在近十年,呈现稳步增长的态势。总体上从环境公平视角来关注城市绿地空间的研究仍不多,案例绝大多数来自发达国家的城市,更多集中在美国;2）研究主题集中在可进入性与环境公平、绿地空间改造与环境绅士化、绿地使用中的文化公平与环境公平问题以及绿地环境公平感知与地方依恋四个方面;3）城市绿地公平性的测度最常用的是可达性、服务面积等绿地供给性指标,近年越来越多研究开始使用绿地供给与使用者需求的综合测度指标。最后,基于中国快速城市化和快速工业化带来日益紧张的土地利用冲突与经济发展压力,再加上中国特殊的人口、环境特征与文化背景,中国城市普遍面临着对绿地空间需求的日益增长,未来应特别重视城市绿地空间的环境公平问题。