Driving forces and their interactions of built-up land expansion based on the geographical detector – a case study of Beijing,China

Scientific interpretation of the driving forces of built-up land expansion is essential to urban planning and policy-making. In general, built-up land expansion results from the interactions of different factors, and thus, understanding the combined impacts of built-up land expansion is beneficial. However, previous studies have primarily been concerned with the separate effect of each driver, rather than the interactions between the drivers. Using the built-up land expansion in Beijing from 2000 to 2010 as a study case, this research aims to fill this gap. A spatial statistical method, named the geographical detector, was used to investigate the effects of physical and socioeconomic factors. The effects of policy factors were also explored using physical and socioeconomic factors as proxies. The results showed that the modifiable areal unit problem existed in the geographical detector, and 4000 m might be the optimal scale for the classification performed in this study. At this scale, the interactions between most factors enhanced each other, which indicated that the interactions had greater effects on the built-up land expansion than any single factor. In addition, two pairs of nonlinear enhancement, the greatest enhancement type, were found between the distance to rivers and two socioeconomic factors: the total investment in fixed assets and GDP. Moreover, it was found that the urban plans, environmental protection policies and major events had a great impact on built-up land expansion. The findings of this study verify that the geographical detector is applicable in analysing the driving forces of built-up land expansion. This study also offers a new perspective in researching the interactions between different drivers.     

Influence of urban expansion on the urban heat island effect in Shanghai

The urban heat island (UHI) effect resulting from rapid urbanization is attracting increasing attention among the global scientific community. This research analyzed the relationship between urban expansion and the UHI effect utilizing an integrated approach, including urban land interpretation and retrieving land surface temperature based on remote sensing, and spatial overlay analysis for revealing the relationship for different time periods between 1984 and 2014 in Shanghai, China. The results show that (1) the spatiotemporal changes in UHI are consistent with the expansion of urban land, and rapid urban expansion leads to an expansion of the UHI, in particular along roadways. (2) The mode of urban expansion is an important factor influencing the UHI effect. Urban sprawl (urban expansion in the edge-expansion way) is a form of typical expansion that leads to the rapid increase in the UHI. When the urban compactness ratio is less than 0.15, a compact design can effectively control the expansion rate of the UHI and mitigate its range of influence and intensity. However, when the urban compactness ratio is greater than 0.15, the urban design has a marked influence on the UHI ratio index: a more compact form produces a stronger UHI effect. So, finding an equilibrium between urban compactness ratio and urban expansion rate is good for effective urban management and planning.     

Decoding the Development Strategy of a Major Retailer: Wal-Mart's Expansion in the United States

This research aims to provide insight regarding Wal-Mart's retail development strategy in its expansion across the continental United States. The study examines store location patterns and relationships between Wal-Mart's store and distribution center locations and markets. The study shows that, although radial expansion is broadly characteristic of the dense store patterns that have been well established for Wal-Mart at the national level, expansion patterns at the regional level are consistent with a selective process based on factors other than store density. These results provide a new perspective on Wal-Mart's expansion, providing insights of value to retail practitioners and local government.     

应用两次展开法求解系泊柱体慢漂运动方程

在深海中系泊的海洋平台,如Spar平台,水下部分为带有系泊的圆柱结构,其水平方向运动响应往往具有较低的自振频率,容易在低频波浪力(源于非线性的差频效应)作用下发生共振响应,使结构发生大幅水平慢漂。当浮体的瞬时位置大幅偏离初始位置时,基于初始平衡位置的摄动展开法会存在较大误差。针对这一问题,采用两次展开方法,对大幅慢漂运动开展时域模拟研究。对双色波作用下自由漂浮圆柱的大幅运动响应问题进行数值分析,并与采用基于初始平衡位置的摄动展开法的计算结果进行了对比。结果表明,采用新的两次展开法可以计算出波浪遭遇频率的变化和波浪漂移阻尼,而这无法从基于初始平衡位置的常规摄动展开法中得到,体现了两次展开法在分析大幅慢漂问题上的优势。     

基于多源数据约束的成矿动力学模拟——以宁芜盆地钟姑矿田典型矿床为例

数据驱动是大数据分析的特点之一。成矿过程的数值模拟即采用数据驱动方式,在基本的物理化学方程及地质模型基础上,通过定量的手段,模拟不同阶段、不同条件下成矿系统的演化过程,从而能够更深入、直观的讨论各种地质要素对成矿系统的影响,验证已有的成矿理论,获得新的认识。姑山铁矿床和杨庄铁矿床是宁芜火山岩盆地钟姑矿田内的典型矿床。前人研究显示,杨庄铁矿床为典型的充填-接触交代型热液矿床,而姑山铁矿床目前在成因上仍存在争议,存在岩浆成因和热液成因等多种观点。为了更好的对比和了解姑山铁矿床和杨庄铁矿床的成因及成矿过程,本文基于多源数据的综合解译剖面,采用力-热耦合数值模拟方法对与热液矿床密切相关的扩容空间的形成机制和特点开展研究。模拟结果显示,姑山铁矿床和杨庄铁矿床可能分属不同的成因类型;随着岩体的逐渐冷却,杨庄铁矿床内岩体和地层接触带会出现明显的扩容空间,可为成矿流体的汇聚及矿质的沉淀提供良好的条件,有利于热液矿床的形成;而姑山铁矿床内岩体和地层接触带只有局部区域出现扩容空间,同时体应变数值较小且形态变化大,并不利于大规模的流体汇聚及矿质的沉淀,姑山铁矿床可能主要为岩浆成因,并受少量热液的叠加改造。     

Spatiotemporal change patterns of urban lakes in China’s major cities between 1990 and 2015

China has experienced unprecedented urbanization in the past decades, resulting in dramatic changes in the physical, limnological, and hydrological characteristics of lakes in urban landscapes. However, the spatiotemporal dynamics in distribution and abundance of urban lakes in China remain poorly understood. Here, we characterized the spatiotemporal change patterns of urban lakes in China’s major cities between 1990 and 2015 using remote-sensing data and landscape metrics. The results showed that the urban lake landscape patterns have experienced drastic changes over the past 25 years. The total surface area of the urban lakes has decreased by 17,620.02?ha, a decrease of 24.22%, with a significant increase in the landscape fragmentation and a reduction in shape complexity. We defined three lake-shrinkage types and found that vanishment was the most common lake-shrinkage pattern, followed by edge-shrinkage and tunneling in terms of lake area. Moreover, we also found that urban sprawl was the dominant driver of the lake shrinkage, accounting for 67.89% of the total area loss, and the transition from lakes to cropland was also an important factor (19.86%). This study has potential for providing critical baseline information for government decision-making in lake resources management and urban landscape design.     

内蒙古北山地区阿民乌素蛇绿岩的年代学、地球化学特征及大地构造意义

内蒙古北山地区阿民乌素蛇绿岩是芨芨台子-小黄山蛇绿岩带的重要组成部分,主要由变质辉长岩和极少强蛇纹石化橄榄岩组成。变质辉长岩LA-ICP-MS锆石U-Pb年龄453±12 Ma,形成于晚奥陶世。强蛇纹石化橄榄岩MgO(36.90%~37.44%)、Ni(1980×10^-6~2232×10^-6)、Cr(2312×10^-6~2506×10^-6)含量高,而Al2O3(0.59%~1.41%)、TiO 2(0.01%~0.02%)和∑REE(0.85×10^-6~3.25×10^-6)含量低,具亏损地幔岩特征;变质辉长岩MgO(7.22.20%~11.66%)相对含量高;Al2O3(15.61%~18.79%)、TiO 2(0.20%~0.29%)、P2O5(0.01%)、K2O+Na2O(1.36%~2.43%)含量低,且K2O相似文献   

土工试验规范变更对膨胀计算和判定的影响

对土工试验方法标准的新旧规范中无荷膨胀率和有荷膨胀率的变化内容进行对比分析,发现两者的计算公式发生显著变化,新规范的计算结果与旧规范相比,膨胀率明显变大,膨胀量随之增大,这将对工程勘察、设计、施工等产生明显影响。以某工程为例,新规范计算后地层总膨胀量由旧规范的16.7 mm变为51.8 mm,增加了2倍左右,地基土的胀缩等级由Ⅰ级变为Ⅱ级,地基基础设计等级由丙级变为乙级,地基处理措施和施工方案随之也发生改变。因此,工程技术人员对此应综合考虑,严谨对待。     

Progress in Semi-arid Climate Change Studies in China

This article reviews recent progress in semi-arid climate change research in China.Results indicate that the areas of semiarid regions have increased rapidly during recent years in China,with an increase of 33%during 1994-2008 compared to 1948-62.Studies have found that the expansion rate of semi-arid areas over China is nearly 10 times higher than that of arid and sub-humid areas,and is mainly transformed from sub-humid/humid regions.Meanwhile,the greatest warming during the past 100 years has been observed over semi-arid regions in China,and mainly induced by radiatively forced processes.The intensity of the regional temperature response over semi-arid regions has been amplified by land-atmosphere interactions and human activities.The decadal climate variation in semi-arid regions is modulated by oceanic oscillations,which induce land-sea and north-south thermal contrasts and affect the intensities of westerlies,planetary waves and blocking frequencies.In addition,the drier climates in semi-arid regions across China are also associated with the weakened East Asian summer monsoon in recent years.Moreover,dust aerosols in semi-arid regions may have altered precipitation by affecting the local energy and hydrological cycles.Finally,semi-arid regions in China are projected to continuously expand in the 21st century,which will increase the risk of desertification in the near future.     

Cavity expansion analyses of crushable granular materials with state‐dependent dilatancy

Crushability is one of the important behaviors of granular materials particularly under high stress states, and affects both the deformability and strength of the materials that are in essence associated with state‐dependent dilatancy. In this presentation, first, a new critical state model is proposed to take into account the three different modes of compressive deformation of crushable granular materials, i.e. particle rearrangement, particle crushing and pseudo‐elastic deformation. Second, the governing equations for cavity expansion in crushable granulates are introduced, in which the state‐dependent dilatancy as well as the bounding surface plasticity model are used. Then, the procedure to obtain semi‐analytical solutions to cavity expansion in the material is described in detail, in which a commercial differential equation solver is employed. Finally, cavity expansion analyses are carried out on Toyoura sand, a well‐documented granular material, to demonstrate the effects of crushability and state‐dependent dilatancy. The study shows that particle crushing does occur at both high stress and critical states and affects the stress fields and the deformation behavior of the material surrounding the cavity in association with state‐dependent dilatancy. This leads to conclusion that particle crushing and state‐dependent dilatancy have to be taken into account when cavity expansion theory is used to interpret cone penetration tests and pressuremeter tests. Copyright © 2011 John Wiley & Sons, Ltd.