Thick-plate flexure re-examined

Summary. The flexure of an incompressible, thick elastic plate floating on an inviscid substratum and subject to an external gravity field is re-analysed. The solution is derived from momentum equations which account for the advection of hydrostatic pre-stress. This is contrasted with a recently published thick-plate solution derived from momentum equations without a pre-stress term. It is demonstrated that neglecting pre-stress advection renders the solution singular when the model degenerates into an inviscid half-space. If pre-stress advection is included, the solution remains correct in this limit. A numerical comparison of both types of thick-plate solution with results based on conventional thin-plate theory further shows that, for geophysically relevant models, the difference in the momentum balance entails discrepancies between the thick-plate solutions which are comparable to the errors introduced by the thin-plate approximation.     

Electromagnetic response of an ocean-coast model to E-polarization induction

summary . An ocean-coast model which consists of a uniformly conducting half-space screened by a perfectly conducting half-plane (the model ocean) is studied. On the land the electric field decreases continuously to zero as the coast is approached. The horizontal magnetic field component is found to vary rapidly, but remains finite; the vertical component on the other hand, increases to infinity at the coast. On the surface of the model ocean as well as on the sea floor, electric field and vertical magnetic field are both nil, but the horizontal magnetic field becomes singular as the seashore is approached. This horizontal magnetic field however, is different on the sea floor and at the ocean surface, because the integrated ocean current is finite, even growing to infinity as the shore is approached. The very large ocean currents near the shore act as an extremely long line antenna, which radiates far afield. This antenna feature explains the very long range of the ocean-coast effects observed under E -polarization induction, compared to the corresponding H -polarization effects where no such antenna-like feature occurs. A similarly large difference of ranges can be expected for all shallow structures with large lateral conductivity contrasts. The present study may therefore be of some interest in relation to geomagnetic depth soundings by the inductive and magnetotelluric methods, as well as in understanding the ocean-coast effect known for some time from records of coastal observatories.     

The effect of noise on seismograms

Summary. We describe a method which provides an estimate of the accuracy to which time-domain features of seismic signals can be measured in the presence of noise. Observed seismograms are simulated by adding random noise with the same frequency spectrum and signal-to-noise ratio to matching synthetic seismograms. The effect of noise on synthetic and observed P -wave first motions is used as an illustration. It is shown that the apparent reliability of such observations, as determined by visual estimation, is often illusory.     

城市建筑空间设计的犯罪防控效应

建筑空间设计包括外部空间设计与内部空间设计,前者设计建筑物之间的空间组合形态,后者设计建筑内部的空间组合形态。合理的建筑物空间设计是创造可防控空间的有效手段,是消除建筑空间盲区的有力措施,也是实施城市犯罪空间防控的重要途径。建筑外部空间组合设计发挥防控效应有两个工作层面,一是将建筑单体组合成群体,二是将建筑群体组合成组团。建筑内部空间组合设计发挥防控效应包括住宅建筑内部空间设计、公共设施建筑内部空间设计、高层建筑与智能化建筑内部空间设计。     

城市景观格局对城市内涝的影响研究——以深圳市为例

近年来,城市内涝问题频发,引发了强烈关注。现有有关城市内涝问题的研究多关注土地利用与城市内涝的关系,而对于城市景观格局对城市内涝影响的研究则不多。本文以内涝问题严重的深圳市为研究区,利用深圳市2014年5月11日暴雨期间内涝点数据（共278个）,选取类型水平上的最大斑块面积比例（Largest Patch Index, LPI）、斑块聚集度（Patch Cohesion Index, PCI）、景观破碎度（Landscape Division Index, DIVISION）、景观水平的蔓延度（Contagion Index, CONTAG）、香农多样性指数（Shannon's Diversity Index, SHDI）共5个景观指数,并结合土地利用类型、不透水率、植被覆盖度、降雨量、地形地势及雨水管网密度等内涝影响因子,运用相关分析和多元逐步回归分析,探究深圳市景观格局对内涝的影响。结果表明：① 土地利用类型中,住宅用地等建设用地对内涝灾害影响最大,其面积比例的增加会加剧区域内涝程度;② 城市各类型景观格局特征中,建设用地斑块的优势度、聚集度越高,景观破碎化程度越低,区域的内涝程度越高,绿地的景观格局对城市内涝的影响与建设用地相反;③ 城市整体景观特征中,景观整体越复杂越不易引发内涝灾害;④ 不透水率等人为因素比降雨量等自然因素对城市内涝的影响程度大。本研究的结果可以使人关注到地表景观格局对内涝的重要作用,为内涝治理和景观格局的规划管理提供参考和借鉴。     

The price ripple effect in the Vancouver housing market

Attempts to model the dynamic characteristics of a housing market include examining the spatial diffusion of price changes from an epicenter through a regional or national network of geographic units. Less common has been the study of a ripple effect of price changes within a single metropolitan area, with implications for the erosion of residential affordability. Such trends have particular salience within the Vancouver metropolitan area, the least affordable housing market in North America. Using quarterly price data from local real estate boards, we examine price changes through municipal regions from 2005–2017, a period including several externally-induced price shocks. Several techniques test for a ripple effect in price movements. A time lag of three months consistently exists in the communication of price shocks from an originating epicenter to other parts of the metropolitan region, with longer lags with several more distant municipalities, confirming the presence of an intra-metropolitan ripple effect.     

俄罗斯东进的背景与成效

俄罗斯在反思发期向西方一边倒政策的过程中,开始重视东方外交,改善与东方国家的关系,本文在分析俄罗斯东进背景的基础上,重点阐述了俄罗斯政治、外交东进快、经贸合作东进慢的特点与趋向,并探讨了俄罗斯东进的动机。     

The driving effect of informal economies on urbanization in China

Journal of Geographical Sciences - This paper examines the rise of informal economies in China, a hidden driving force overlooked in studies on China’s urbanization. Estimating the size of...     

中国海港空间效应的识别与测度

在全球化和世界产业转移浪潮推动下,沿海港口已成为全球生产链条与地方网络链接的地理枢纽。与此同时,港口发展演化在推动港口自身运输体系及港口空间演化的同时,对腹地经济发展产生重大影响。首先,从经济地理学视角,提出海港空间效应的概念及其内涵,从港口势能、港—腹引力、作用通道三个方面阐述海港空间效应的动力结构和形成要素。其次,以海港空间效应的动力结构为理论依据,建立海港空间效应的测度模型。最后,以我国东部沿海港口为研究样本,运用海港空间效应测度模型,得到海港空间效应指数。以港口吞吐量、集装箱吞吐量、外贸吞吐量为指标表征沿海港口对腹地的运输效应分布格局,以港口城市工业、对外贸易和金融指标表征沿海港口对腹地的非运输效应格局,对不同区域特点和差异进行比较分析,验证模型的准确性和可操作性。结果表明,模型可较好地从宏观尺度识别不同港口及其腹地的港口经济空间效应,对于揭示港口的区位本质,比较不同区域的临港化倾向,刻画港口—腹地型城市地域系统的空间联系具有指导意义。     

The effect of low temperature on Antarctic endolithic green algae

Laboratory experiments show that undercooling to about -5 degrees C occurs in colonized Beacon sandstones of the Ross Desert, Antarctica. High-frequency temperature oscillations between 5 degrees C and -5 degrees C or -10 degrees C (which occur in nature on the rock surface) did not damage Hemichloris antarctica. In a cryomicroscope, H. antarctica appeared to be undamaged after slow or rapid cooling to -50 degrees C. 14CO2 incorporation after freezing to -20 degrees C was unaffected in H. antarctica or in Trebouxia sp. but slightly depressed in Stichococcus sp. (isolated from a less extreme Antarctic habitat). These results suggest that the freezing regime in the Antarctic desert is not injurious to endolithic algae. It is likely that the freezing-point depression inside the rock makes available liquid water for metabolic activity at subzero temperatures. Freezing may occur more frequently on the rock surface and contribute to the abiotic nature of the surface.     

人力资本空间效应与区域经济增长

基于资本外溢性和省域技术水平间存在空间依赖性的假设,在Mankiw、Romer和Weil模型(简称MRW模型)中引入了变量的空间滞后项,构建了空间MRW模型,运用中国全域及东部、西部面板数据进行固定效应的空间面板估计,证实了模型假设的正确性,得到以下主要结论:第一,在中国全域及东、西部区域中,人力资本及其空间外溢效应对经济增长的贡献均不显著;第二,东部地区人力资本及其空间外溢效应对区域经济增长的贡献值均约为西部地区的两倍。     

城市化对北京市极端气候的影响研究

利用北京地区20个气象站点35年（1980—2014年）的逐日降水、气温资料和社会经济、人口、土地覆被以及夜间灯光遥感的栅格数据,通过聚类分析和层次分析相结合的方法将站点分类,对北京市城市化进程中的极端气候变化趋势和城市化影响的响应进行了分析。结果表明：北京市整体的极端冷事件呈减少趋势,极端暖事件呈增加趋势,极端降水事件没有明显变化趋势;城市化对极端温度事件有着显著的影响,相对于乡村站点来说,城市化使得极端冷事件减少的更快,极端暖事件增加的更快,造成城市的气温日较差明显变小;城市化对极端降水的影响虽不显著,但在乡村站点年降水量总量和降水日数减小的趋势下,城市化造成城市降水总量和降水日数均多于乡村,减缓了连续无降水日数的增长趋势,同时城市的极端降水有向更加极端的情景发展。