复杂应力条件下饱和松砂单调与循环剪切特性的比较研究

本文利用大连理工大学新引进与开发的“土工静力-动力液压-三轴扭转多功能剪切仪”,针对福建标准砂,在不排水条件下同时进行了单调剪切试验与循环剪切试验,进而对其进行了对比分析。通过比较表明,应力-应变关系的应变软化和硬化特性与流滑变形和循环流动特性密切相关,当循环剪切应力水平高于单调剪切过程中应变软化阶段最小强度时将会发生流滑变形。无论在单调剪切中,还是在循环剪切中,稳定状态时的有效偏应力比随着大主应力方向与竖向之间夹角的增大而减小,在中主应力系数相同的条件下,循环剪切中呈现显著剪胀时的有效偏应力比和最终稳定状态时的有效偏应力比峰值分别与单调剪切中达到相变状态时的有效偏应力比和最终稳定有效偏应力比基本上一致。然而不排水条件下单调与循环剪切过程中孔隙水压力的增长特性却并不相同,循环剪切中的最大孔隙水压力随着初始主应力方向角的增大而减小,单调剪切中的最大孔隙水压力却随着主应力方向角的增大而增大。     

Dunefield Activity and Interactions with Climatic Variability in the Southwest Kalahari Desert

An analysis is undertaken of the temporal variability of climatic parameters that influence dunefield aeolian activity. Data from seven meteorological stations in the southwestern Kalahari Desert are used, spanning the period 1960–1992. Erosivity is considered through analysis of wind data, and erodibility through analysis of precipitation and potential evapotranspiration, which together influence dune surface plant growth. The data are integrated using Lancaster's ‘mobility’ index which provides a measure of potential dune surface sand transport. This is renamed ‘potential dune surface activity index’, to reflect the actual characteristic that is measured. The subsequent analysis indicates that dunefield activity is episodic and temporally variable, that both erosivity and erodibility vary through time, and that present levels of activity cannot be characterized by a single simple state. © 1997 by John Wiley & Sons, Ltd.     

城市的垂直流动：广州再领域化中的人地关系重构

流动性重塑了人地关系,地的再领域化过程可以视为一种跨阶层的垂直流动。20世纪80年代起,中国开始了撤县设区的行政区划调整,重塑了原有的城市行政结构体系。撤县设区是典型的城市的垂直流动过程。在这过程中,县城本地居民的身份政治,以及他们与县城、新城之间的关系亦随之改变。以广州为例,通过研究撤县设区中本地居民与领域空间的关系重构,进而探讨流动性背景下的人地关系变化。研究发现：对于本地居民而言,其身份政治在再领域化的过程中,从旧领域的多数群体转变为新领域的少数群体。这种转变导致本地居民排他策略的形成,并由此形成了新领域中的一个抵抗空间,重构了本地居民、旧领域和新领域之间的人地关系。研究城市的再领域化过程是对地理学探讨流动性的有效补充,有利于从地的视角更深入理解流动性的影响及意义。     

基于大数据的流空间研究进展

流空间是认识城市网络结构和演化的重要手段。近年来大数据的快速发展为流空间研究提供了新的机遇和挑战。论文系统综述了基于大数据的流空间研究进展。首先,论文梳理了基于大数据流空间研究的背景和历史,然后总结了基于大数据的流空间研究的主题、数据类型、方法和主要发现,最后展望了未来的研究挑战。2011年以后,基于大数据的流空间研究呈指数增长趋势,中英文论文年均发表量从2010年的11篇增长到2018年的106篇。大数据主要从提供新的数据源、激发新的分析方法和提供新的研究视角三方面推进了流空间研究。常用于流空间研究的大数据主要包括手机信令数据、社交媒体签到数据、公共交通刷卡数据和出租车轨迹数据,它们比传统统计数据更能直接提供人流、物流和信息流的时空动态信息。研究方法也从传统的基于距离的重力模型发展为网络分析方法。未来在交叉学科研究、大数据和传统数据的耦合、大数据与深度学习和云计算等新方法的结合方面仍需进一步探索,从理论、数据和方法上全面深化流空间研究。     

合作伙伴关系视角下的海外园区政策移动性研究——以泰中罗勇工业园为例

政策移动性是国际政治地理学研究的经典理论。作为包容性全球化和“一带一路”倡议重要空间载体的海外园区,是检验政策移动性理论框架的新兴空间载体。本文以泰中罗勇工业园为例,以合作伙伴为切入点,检验政策移动性理论在海外园区的适用性,并强调海外园区的政策移动性是渐进发展的过程,关键角色的合作伙伴关系对于政策移动性起着重要作用。本文系统分析了泰中罗勇工业园的制度背景、主体合作伙伴,甄别出国家、地方政府、主导企业等关键角色的合作伙伴关系及其在税收、土地、人才等要素政策移动性过程中的机制。在此基础上,提出未来“一带一路”建设中海外园区可持续发展的政策建议。     

The effect of temporal sampling intervals on typical human mobility indicators obtained from mobile phone location data

Mobile phone location data have been extensively used to understand human mobility patterns through the employment of mobility indicators. The temporal sampling interval (TSI), which is measured by the temporal interval between consecutive records, determines how well such data can describe human activities and influence the values of human mobility indicators. However, systematic investigations of how the TSI affects human mobility indicators remain scarce, and characterizing those relationships is a fundamental research question for many related studies. This study uses a mobile phone location dataset containing 19,370 intensively sampled individual trajectories (TSI < 5 minutes) to systematically assess the impacts of the TSI on four typical mobility indicators that describe human mobility patterns from different aspects, which are movement entropy, radius of gyration, eccentricity, and daily travel frequency. We find that different TSIs have complex impacts on the values of different mobility indicators. Specifically, (1) coarser TSIs tend to underestimate the values of the four selected indicators with different degrees; (2) the degrees of underestimation vary significantly among users for eccentricity and daily travel frequency but exhibit high inter-user consistency for radius of gyration and movement entropy. The above findings can help better understand the variations among human mobility studies.     

流动性视角下流动家庭的空间实践和情感重构

流动性的增强使迁移活动达到前所未有的广度和强度,“家”的流动日渐成为重要的流动形式,“家”的流动亦成为流动性研究的重要关注点。在新型城镇化进程中,伴随着家庭式迁移的发展浪潮,流动家庭的空间实践和情感重构成为一个重要话题。在流动过程中,移民的流动性实践往往赋予了“家”不断转换和流动的意义和内涵。基于流动性理论视角,延循“家”的地理学脉络,选取两个典型的流动家庭案例,通过质性研究方法分析对比其在流动过程中的空间实践及其对“家”的情感建构与重构的影响。研究发现：时间性、空间性和地方性是研究“家的流动性”的重要变量和维度。作为刻画流动性的基础尺标,流动轨迹的多位移空间性和流动过程的多阶段时间性使得“家”的地方性处于一个动态关联的状态。“家”的情感归属、“家”的观念和意义通过“家”的流动和营造实践在解构中被延续与重建。     

Resistance to relocation in flood-vulnerable coastal areas: a proposed composite index

The increasing number of coastal floods in recent years in France has resulted in the design of new adaptation principles for the most endangered coastal areas. The aim of the government is to reduce the vulnerability of these areas by relocating property and infrastructure. These measures have, however, come up against considerable opposition from the population concerned. Using a survey of 421 inhabitants of Hyères, a coastal town in the South of France, this article proposes the study of resistance to relocation through the creation of an index for resistance that incorporates attachment to place, residential mobility and risk perception. The results show a correlation for the index and distance from the sea that highlights the existence of conflicting interests with adaptation measures depending upon population categories.

Key policy insights

• In France, although coastal flooding risk is a key issue in numerous populated coastal areas, coastal dwellers show little willingness to relocate.

• Resistance to relocation can be assessed through a composite index integrating place attachment, residential mobility and risk perception.

• Application of such an index shows a correlation between willingness to relocate and distance from the sea.

• Conflicts of interest with adaptation measures also depend on the age of the dwellers, their standard of living and on home ownership.

     

Labour mobility in the public sector: the impact of job opportunities

This paper investigates the mobility of highly skilled labour, using doctors in public hospitals in Denmark as an example. From the perspective of regional development, the concentration of human capital is one of the contributors to regional growth and consequently to inequality between places, being associated most often with differences in economic growth between regions. The decentralisation of highly skilled public jobs to even out the concentration of human capital could be one way to stimulate growth outside city regions. However, such initiatives are somewhat dependent upon the cooperation of the highly skilled public employees, whose preferences have been little studied thus far. Based on data from a survey of 1600 publicly employed doctors, PLUM regression modelling was applied to test the relative significance of four professional preferences influencing choice of workplace. It was found that professional preferences have different influences on doctors’ choices, depending on their place of residence measured in terms of a location’s population density. The paper concludes that opportunities in employment depend on one’s stage in life and can serve to explain choices and mobility among highly skilled public employees.