Progress of research on transportation geography in China

As an important branch of human geography, transportation geography has experienced three periods of evolution: foundation, systematization, and rapid development of the discipline. It has gradually become a relatively mature discipline. During the period 1930–1980, the development of transportation geography consisted mainly of the publication of theoretical texts. During 1980–2000, it gradually became a systematic discipline. Since the start of the 21st century, transportation geography has focused mainly on exploring the impacts of transportation on socio-economic development. Currently, studies on transportation geography have led to significant developments in a number of areas, including transportation theory, facility distribution and planning, transportation flows and network analysis, evaluation of transport modes, transportation planning, and simulation and assessment of urban transportation. Such studies have also enriched human geography research, provided a wider geographical overview and elucidated the development mechanism of transportation, as well as helped to understand the impacts of transport development on socio-economic systems. Some findings obtained by geographers have been widely used in transportation geography and related fields, including the four basic laws of transportation generation, the hub–spoke mode of transport organization, the subordinating and guiding functions of transportation on socio-economic development, regional transport dominance measures, accessibility measures, and spatial organization of port systems.     

Spatiotemporal evolution of urban air quality and socioeconomic driving forces in China

Air pollution is a serious problem brought by the rapid urbanization and economic development in China, imposing great challenges and threats to population health and the sustainability of the society. Based on the real-time air quality monitoring data obtained for each Chinese city from 2013 to 2014, the spatiotemporal characteristics of air pollution are analyzed using various exploratory spatial data analysis tools. With spatial econometric models, this paper further quantifies the influences of socioeconomic factors on air quality at both the national and regional scales. The results are as follows: (1) From 2013 to 2014, the percentage of days compliance of urban air quality increased but air pollution deteriorated and the worsening situation in regions with poor air quality became more obvious. (2) Changes of air quality show a clear temporal coupling with regional socioeconomic activities, basically “relatively poor at daytime and relatively good at night”. (3) Urban air pollution shows a spatial pattern of “heavy in the east and light in the west, and heavy in the north and light in the south”. (4) The overall extent and distribution of regional urban air pollution have clearly different characteristics. The formation and evolution of regional air pollution can be basically induced as “the pollution of key cities is aggravated—pollution of those cities spreads—regional overall pollution is aggravated—the key cities lead in pollution governance—regional pollution joint prevention and control is implemented—regional overall pollution is reduced”. (5) At the national level, energy consumption, industrialization and technological progress are the major factors in the worsening of urban air quality, economic development is a significant driver for the improvement of that quality. (6) Influenced by resources, environment and the development stage, the socioeconomic factors had strongly variable impacts on air quality, in both direction and intensity in different regions. Based on the conclusion, the regional differentiation and development idea of the relationship between economic development and environmental changes in China are discussed.     

基于TM影像的城市建筑用地信息提取方法研究

本文选用金华市Landsat TM影像为研究的数据源,在归一化裸露指数基础上,利用归一化植被指数提取出非植被信息,通过图像二值化、叠加分析以及掩膜处理去除了低密度植被覆盖区域的噪音信息,自动提取了金华城市建筑用地信息。研究结果表明,归一化裸露指数和归一化植被指数相结合的方法弥补了单一利用归一化裸露指数来提取城市建筑用地信息的不足,提高了提取精度,而且结果客观可信,是一种不经人为干预的、快速有效的提取城市建筑用地方法。     

黄土地区活动断层的显微构造和显微沉积学探测

以发育在黄土地层的陕西省西安市临潼—长安断裂为对象,采用显微构造和显微沉积学分析的方法,从微观的角度探讨黄土地层中的活动断层。观测了该断裂上的7个露头剖面和一条探槽剖面,采集样品42件。在室内对所采集的样品进行了显微构造、超微构造和能谱测定(扫描电镜)以及显微沉积学分析。研究结果表明,野外宏观观测难以辨认的断层迹象,在断层带样品的切片(大薄片)上肉眼即可清楚辨别。显微构造观测发现,断层在微观上可以表现为错动面、较宽的断层带、断层破碎带、变形条带、泥质条带和愈合的张裂隙等。扫描电镜观测和能谱测定显示,断层破碎带或泥质条带与其外围地层具有不同的超微结构,而且成分有所变化,表明断层活动过程中有流体的参与,并导致某些元素的带出和带入。粒度分析结果发现,断层样品相对于外围样品,粒度>0.03mm的颗粒减少,<0.03mm的颗粒和粘土质增加,表明黄土地层的断层活动仍有碎裂作用发生。分形分析结果表明,黄土地层的碎屑颗粒分形特征呈弧形分布,但断层样品更趋于线性分布。此外,在其中一个剖面的样品中,发现了震击物(seismite)的一些微观标志,如球状体构造、负荷构造和流体通道构造等。所有研究结果表明,显微构造和显微沉积学分析是黄土地层中活动断层研究的有效手段。     

Modeling Groundwater in Multimodal Porous Media with Localized Decompositions

In the present paper, a new stochastic framework is introduced to decompose random variables. This decomposition method is shown to better capture and reflect the medium heterogeneity for multimodal porous media than the classical Reynolds decomposition does. In particular, with this decomposition method, the variance of log conductivity is decomposed into two parts. The first one measures the mean differences of log conductivity across different units having high contrasting conductivity. The second part measures the variation of log conductivity arisen within individual units. Based on this localized decomposition, a new stochastic model is proposed for flow in a highly heterogeneous porous media. This stochastic model shall produce much sharper approximations under the assumption that only the second part of the variance of log conductivity is small. Therefore, the proposed model can partially overcome the assumption of small composite variance for log conductivity in current theory for both flow and transport.     

Observed spatiotemporal variation of three-dimensional structure and heat/salt transport of anticyclonic mesoscale eddy in Northwest Pacific

Journal of Oceanology and Limnology - As in-situ observations are sparse, targeted observations of a specific mesoscale eddy are rare. Therefore, it is difficult to study the three-dimensional...     

Can Langmuir Circulations Solve the Problem of Insufficient Upper-Ocean Mixing?

Insufficient vertical mixing in the upper ocean during summer is a common problem of oceanic circulation and climate models. The turbulence associated with non-breaking waves is widely believed to effectively solve this problem. In many studies, non-breaking surface wave processes are attributed to the effects of Langmuir circulations(LCs). In the present work, the influences of LCs on the upper-ocean thermal structure are examined by using one-and three-dimensional ocean circulation, as well as climate, models. The results indicated that the effect of vertical mixing enhanced by LCs is limited to the upper ocean. The models evaluated, including those considering LC effects alone and the combined effects of LCs and wave breaking, failed to produce a reasonable summertime thermocline, resulting in a large cold bias in the subsurface layer. Therefore, while they can slightly reduce the biases of mixed layer depths and sea surface temperatures in models, LCs are insufficient to solve the problem of insufficient vertical mixing. Moreover, restriction of non-breaking surface wave-induced processes in LCs may be questionable.