Zagrebin问题的两个新解

本文建立了求解Zagrebin问题的两种更为一般的方法,即格林法和单层位法,并以此为基础,导出了求解这个问题的两个新公式。     

Consumption preferences and environmental externalities: A hedonic analysis of the housing market in Guangzhou

The urban housing market of China has been transformed since the 1980s from a centrally-planned to a free-market system. This study aimed to (1) investigate the position of outdoor environmental quality in house-buyers’ preferences; (2) assess monetary values attributed to environmental externalities by the hedonic pricing method (HPM); and (3) test the applicability of HPM in China. The study area was Guangzhou, the major city of south China with a booming real-estate market. A questionnaire survey was conducted with households in new residences sold in 2004. The main buying motives were improving living quarters and floor area. Security concerns and a preference for high-rise buildings were somewhat unexpected. Good outdoor environment, including green space provision, proximity to parks, and views of green space and water, carried significant hedonic values. Differences between the submarkets of old and new towns were found; new town households expected apartments in high-rise blocks, exclusive residential land use, and views of green space, while old town households preferred proximity to shopping areas and workplaces, green space within the development and proximity to nearby parks. The findings could help to fine tune the developing housing market to match supply with demand in quality terms. Values accorded to environmental attributes could justify funding for urban green spaces and nature conservation. The study verified the applicability of HPM to the housing context in China.     

冷却屋顶对北京城市热环境影响的模拟研究

两种类型冷却屋顶(高反照率屋顶、绿色屋顶)的研究对于北京夏季城市高温的缓解作用具有重要的意义。耦合单层城市冠层模式(SLUCM)与天气研究与预报(WRF3.8)模式, 采用北京市及其外围地区158个站点气象资料评估模式对照案例(case1)的模拟性能, 并选取7组不同反照率屋顶案例(case2—4)和不同覆盖比例的绿色屋顶案例(case5—8)进行敏感性试验。研究结果表明:(1)在北京城市区域, 高反照率为0.85的屋顶(case4)比绿色占比100%的屋顶(case8)具有更好的降温效果, case4的3 d平均降温可达到0.90℃, 而case8降温为0.46℃。(2)屋顶反照率每增加0.1, 会导致北京城市区域最高气温降低0.27℃; 绿色屋顶比例的增大也会导致温度的降低, 每增加10%, 最高气温降低0.16℃。(3)两种冷却屋顶对城市热岛也存在显著的影响, 在13—14时(北京时), case4与case1对比的城市热岛(UHI)降温最大差值为1.47℃, 比case8的城市热岛降温更加明显。(4)在城市区域垂直高度上, 冷却屋顶的降温作用可达到1.2 km, 同时湍流运动存在明显的减弱; 在3 d的12—18时, case4、case8与case1对比, 边界层高度平均降低了669与430 m。      

层状土场中冲刷作用下部分埋置单桩动力响应分析

桩周土场受冲刷作用的变化是部分埋置单桩结构失效的主要原因之一。工程中土场多呈层状,此类场地中桩基的力学特性研究日益受到关注。为精确揭示冲刷作用对层状土场中部分埋置单桩动力响应的影响,基于改进Vlasov地基模型,利用Hamilton原理建立层状土场中横向受荷单桩的动力学模型。利用有限差分法求解受冲刷作用单桩的固有频率,实现对冲刷作用下土−结构相互作用系统的准确建模,进而用Green函数法求得单桩受迫振动的解析解。通过数值计算和参数分析,研究了层状土场的物理特性对受冲刷作用部分埋置单桩动力响应的影响。结果表明：基于改进Vlaosv地基模型建立的层状土场中部分埋置单桩动力学模型可精确预测冲刷作用对桩基动力学特性的影响。随冲刷程度加剧,层状土场中单桩的第一阶固有频率显著降低,改进Vlasov地基模型中各层土体的地基反力系数均减小,剪切系数则增大。当冲刷至非埋置段桩长 （ 为桩长）时,部分埋置单桩在动荷载作用下出现横向失稳现象。随底层土体厚度增加,各冲刷等级下单桩的第一阶固有频率均增大。如果第1层土的弹性模量增大了约0.43倍、1.14倍、1.86倍,则冲刷等级为0时单桩第一阶固有频率分别增大了约8.9%、19.5%、27.1%。     

Urban green resilience: Experience from post-industrial cities in Poland

De-industrialisation triggered economic, spatial and environmental changes in cities. Therefore, this study identifies whether there has been a reorientation of spatial development in post-industrial cities towards the creation of green spaces. The aim of the study is to analyse and evaluate the transformation of green spaces in 32 major cities in Poland, including 12 post-industrial cities. Data sources were vector land cover data models from the Urban Atlas for 2006 and 2018, administrative boundaries from the National Boundary Register and building layers from the Topographic Objects Database. The research procedure was carried out using the GIS environment, through spatial analysis, geoprocessing algorithms, and spatial statistics. The results have shown that post-industrial cities do not develop their urban resilience based on the expansion of green spaces and, consequently, do not build green urban resilience. In addition, the research has proven that the greatest loss of green spaces is noticeable in parts of post-industrial cities with medium and high development intensity, where there is an intensification of construction activity. The dominant direction of the transformation of green spaces has been the conversion of agricultural areas into green spaces (87.79%). In contrast, the main direction of loss in green space has been the creation of new industrial units (24.80%) and the expansion of the urban fabric (23.53%). The article is original due to the fact that there is a gap in the literature regarding the study of green spaces in post-industrial cities with regard to the concept of green urban resilience.     

做好传统地质、建好绿水青山——在中国地质学会第十二次全国会员代表大会上的讲话

正各位代表,同志们:下午好!在刚刚结束的全体理事大会上,大家选举我担任中国地质学会第40届理事会理事长,我感到非常荣幸,也深感责任重大。在此,我代表新当选的第40届理事会对大家的信任表示衷心的感谢!我将认真履行理事长的职责,和全体常务理事一道,在中国科协和国土资源部的领导下,在历届理事会工作的基础上,团结带领全体理事,认真学习宣传贯彻党的十九大精神,以习近平新时代中国特色社会主义思想为指     

应用格林积分直接以地面边值确定外部扰动重力场

以地面为边界的Molodensky问题通常得到的是级数形式的解,高阶项体现了地面边值到某一光滑面上的改正,在应用中不仅遇到计算的复杂性、稳定性问题,也存在对数据密集要求的困难。本文从推求外部扰动重力场的应用出发,将格林公式用于数字地形面,在忽略水平分量的积分影响的情况下,得到以地面重力异常和高程异常差为边值确定外部扰动位的表达式,其核函数分别为距离倒数和Poisson核。该方法不需要对地面数据进行延拓处理,且核函数形式简洁,适于外部扰动重力场的随机计算。     

Integrating multi-source remotely sensed datasets to examine the impact of tree height and pattern information on crimes in Milwaukee,Wisconsin

There have been a great number of debates about the impacts of trees on crimes: some researchers believed that trees are a crime facilitator because of the concealment provision for potential criminals, while others argued that they are a crime deterrent because of the increased surveillance possibility and the therapeutic effect on psychological fatigue. To better answer this question, this study incorporated detailed tree features by using multi-source remotely sensed data at a very high resolution into environmental criminology analysis across the entire City of Milwaukee. Trees were extracted from aerial photographs, and broken down into two categories based on their heights to consider the effects of tree height on view obstruction. By controlling for confounding socioeconomic variables, the relationship between crimes and a series of composition and configuration indicators of trees with different height were investigated by using global and local spatial regressions. Results from classic and spatial statistical techniques finds complicated relationship between crimes and trees, which can be summarized in two aspects. First, the mixed effects of trees can be observed among different crime types. Second, the trends of spatial nonstationarity of the composition and configuration of trees with different heights were observed across the entire study area. The study outcomes could provide reasonable implications for making appropriate policies for crime prevention through environmental design to strengthen neighborhoods and communities in a city.     

宜居黄河科学构想

黄河问题表象于河,形成于域,根植于地。针对于黄河流域高质量发展面临的地球科学问题特点及挑战,本文提出了“宜居黄河”科学构想,旨在构建一个包括“安全黄河”、“绿色黄河”、“生态黄河”、“和谐黄河”和“智慧黄河”5大核心内容的体系完善的宜居黄河研究科学架构,并对这5个方面的科学内涵和关键研究内容进行了阐述。其中,(1)安全黄河立足于工程地质学,研究黄河流域地质地表过程及其灾害效应,以保障地质安全需求,构建安全黄河体系;(2)绿色黄河立足于水文地质学,研究黄河流域水循环过程及其水土环境变化效应,构建绿色黄河体系;(3)生态黄河立足于环境地质学,研究黄河流域生态系统演化规律及其生态屏障效应,构建生态黄河体系;(4)和谐黄河立足于资源地质学,研究黄河流域资源开发与人地协调的发展模式,构建和谐黄河体系;(5)智慧黄河立足于大数据及信息科学,研究黄河流域地学信息集成与智慧决策平台,构建智慧黄河体系。这5个部分相互支撑融合,共同解决宜居黄河的核心关键问题,从而为保障黄河长治久安、促进全流域高质量发展,最终形成造福中华民族的“幸福黄河”起到科技支撑作用。     

电法勘探中有覆盖层的点源二维、点源三维边界元法正演

本文提出用二层介质格林函数作为余量加权函数,归化边界积分方程的边界单元法。通过对有水平覆盖层的点源二维、点源三维正演计算表明,本算法明显地优化了以往的边界元法,计算精度高,方程组规模小,节省内存空间,仅在一般微机上即可实现,扩大了边界单元法在电法勘探中的应用范围。