1995-2010年中国省际人口迁移态势与空间格局演变——基于社会网络分析的视角

采用第五次人口普查、2005年人口抽样调查和第六次人口普查数据,基于社会网络分析的视角,研究了省级尺度下中国人口迁移态势与空间格局演变特征。结果显示:(1)1995-2010年间,中国人口迁移规模迅速增大,省际间人口迁移规模差异明显;上海、浙江人口迁入率显著上升,河南、安徽人口迁出率显著上升。(2)北京、上海、安徽、四川等13省是我国人口迁移网络的核心节点,人口迁移网络表现出中心性、收敛性和地区非均衡性特点。(3)京津地区、长三角地区、广东是我国主要人口辐合流场,安徽、四川、河南、湖南等中部省份是我国主要人口辐散流场。研究表明,不同地区的人口迁移有显著的空间异质性,各地应根据自身人口迁移趋势及在全国人口迁移网络中角色,科学制定区域人口政策与经济社会发展规划。     

我国旅游流研究进展与展望

旅游流研究是旅游地理学研究的核心问题之一,为了总结我国旅游流研究成果,找出我国旅前流研究的不足并指出未来的研究方向,本文对1987-2010年我国旅游流文献进行了梳理。我国旅游流研究历程可以划分为起步、成长和发展三个阶段,可划分为时间分布特征、空间结构特征、时空演化特征、影响因素、驱动机制和规模预测等六类研究主题,但我国旅游流研究也存在六方面的不足,特别是要深入挖掘研究内容,创新研究方法,以推动我国旅游流研究更进一步发展。     

中国城市间交通流强度的空间格局

以全国321个地级以上行政区为研究对象,基于城市间汽车、火车和航空班次联系测算各城市对外联系强度,通过核密度估计、位序-规模及探索性空间数据分析,对多元交通流视角下城市间交通流强度的空间格局进行提取和解析。研究表明:在整个城市体系中,高位次城市规模凸显,中小规模城市有待于进一步发育。基于公路和铁路联系的城际交通流分别表现为由沿海向内陆逐级减弱、以国家铁路大动脉沿线为中心的核心-边缘结构;基于航空联系的城际交通流表现出高度极化和点状镶嵌特征。     

地铁站点可达性、客流与站点商圈零售商业结构关系研究——以广州市为例

地铁与城市商业地域的结构存在极大关系。实地调查获取广州15个地铁站点商圈零售商业营业面积、地铁网络等数据,利用栅格分析方法计算不同地铁站点的可达性程度的差异性。运用回归模型分析不同地铁站点可达性、客流与站点商圈零售商业空间结构的相关关系。以广州天河市级商业中心为例,微观上分析地铁站点客流对商业中心空间结构的影响。结果表明:地铁站点交通可达性、客流量与站点零售商业营业面积存在较强关联性,但换乘站点的可达优势与客流优势在商业上未能完全体现;地铁客流与较高等级的商业存在较大的相关性,而与低等级的商业相关性小,甚至负相关;客流的增加促进了地铁附近的商业形态从传统零售业向更高级业种演化。     

基于新地理信息技术的南京市游客流动性空间特征研究

利用新地理信息技术,采集500个游客GPS地理标记照片,运用GIS空间分析方法,分析游客在南京城市内部及其与长三角其它城市空间流动特性,并提炼游客空间行为一般模式。发现:①南京城市内部旅游流在主城区集聚,整体上呈现中心城区向四周扩散的趋势;且在空间形态上形成小型化、斑块化的布局特征。②南京与长三角周边城市的线形路线以点-点模式为主导,地域模式以便利的同城市中心流动为多数,其旅游流流动模式与已有典型模式基本吻合,同时长三角地区旅游流呈现等级扩散特征。     

翠华山水湫池及其附近崩塌堆积形成年代探疑

通过对相关史料的分析,论证了翠华山主景区崩塌堆积不可能是唐天宝年间地震诱发山崩形成的。通过实地考察,认为这些崩塌堆积不是同时发生,而是多期崩塌活动的结果,并且崩塌活动又都发生在水湫池被堰塞成湖之后。因此,水湫池不可能是唐代的地震山崩形成的。     

旅游流空间模式基本理论:问题分析及其展望

旅游流是旅游地理学的基本问题,而旅游流空间模式的研究,自20世纪50年代以来则是旅游流研究的热点问题。通过文献分析法,本文将旅游流空间模式基本理论梳理为圈层结构理论、核心边缘理论、空间扩散理论。在此基础上,揭示其存在的若干问题,包括研究中存在的"区域视角"和"旅游者个体视角"混淆的认知问题、旅游客源地和旅游目的地在区域视角下如何界定的问题、空间模式研究中广泛存在的"二元陷阱"问题、区域间旅游职能分化及其分化程度尚无科学分析的问题等。文末对未来研究进行了展望,以期从理论意义上深化旅游流基本问题的建构。需指出的是,旅游流作为"非工作流"的一种,其"流现象"、"流空间"和"流效应"同样可适用于其它形式的"流研究"。     

Transient fluid flow in and around a fault

We present the results of simple numerical experiments in which we study the evolution with time of fluid flow around and within a permeable fault embedded in a less permeable porous medium. Fluid movement is driven by an imposed vertical pressure gradient. The results show that fluid flow is controlled by two timescales: τ_f = Sl²/κ_F and τ_F = Sl²/κ_M, where S is the specific storage of the porous material, l the length of the fault, and κ_M and κ_F are the hydraulic conductivities of the porous material and the fault, respectively. Fluid flow and the associated fluid pressure field evolve through three temporal stages: an early phase [t < τ_f] during which the initial fluid pressure gradient within the fault is relaxed; a second transient stage [τ_f < t < τ_F] when fluid is rapidly expelled at one end of the fault and extracted from the surrounding rocks at the other end leading to a reduction in the pressure gradient in the intact rock; a third phase [t < τ_F] characterized by a steady‐state flow. From the numerical experiments we derive an expression for the steady‐state maximum fluid velocity in the fault and the values of the two timescales, τ_f and τ_F. A comparison indicates excellent agreement of our results with existing asymptotic solutions. For km‐scale faults, the model results suggest that steady‐state is unlikely to be reached over geological timescales. Thus, the current use of parameters such as the focusing ratio defined under the assumption of steady‐state conditions should be reconsidered.     

How should permeability be measured in fine‐grained lithologies? Evidence from the chalk

Two chalk data sets from the Central North Sea (UK/Norway and Denmark) with a similar lithological classification and porosity values (5–20%) have a difference in permeability of up to three orders of magnitude. The method of measuring permeability was different for the two data sets: samples from UK/Norway were measured by transient pulse decay (TPD), while the Danish samples were measured by routine core analysis. Petrological and petrophysical characterization of samples from the two data sets have revealed that all samples display a similar range of rock properties; the differences are not due to regional facies variations. It is likely that the low permeability values reported by TPD have more validity than routine core analyses in measuring lower porosity and permeability chalk (5–20% porosity, <0.01 mD). The fact that large sections of North Sea chalk potentially have much lower permeability than previously reported has widespread implications for petroleum migration and entrapment, and overpressure generation.     

Cyclic loading of an idealized clay‐filled fault: comparing hydraulic flow in two clay gouges

The flow of water along discontinuities, such as fractures or faults, is of paramount importance in understanding the hydrogeology of many geological settings. An experimental study was undertaken comprising two experiments on a 30° slip‐plane filled with kaolinite or Ball Clay gouge using a bespoke Angled Shear Rig (ASR). The gouge was initially loaded in equal step changes in vertical stress, followed by unloading of the sample in similar equal steps. This was followed by reloading to a new maximum stress, followed by unloading; the test history was therefore load‐unload‐reload‐unload (LURU). The transmissivity of the kaolinite and Ball Clay gouge showed a power‐law relationship with vertical stress. The LURU history showed considerable hysteresis, with flow effectively unchanged during unloading, even when vertical stress was close to zero. Reloading resulted in flow similar to that seen during unloading suggesting that the unloading‐reloading path is similar to the rebound‐reconsolidation line in classic soil mechanics. These observations show the importance of stress history on fracture flow; consideration of just the current stress acting upon a fracture may result in inaccuracies of predicted hydraulic flow. Once a new stress maximum was achieved the transmissivity of the fracture continued to reduce. No significant variation was seen in the flow response of kaolinite and Ball Clay gouge suggesting that the inclusion of illite and quartz did not have a significant influence on the form of the relationship between stress and flow, i.e. both described by a power‐law.