Step-frequency radar applied on thin road layers     

X. Drobert  C. Fauchard  Cte  E. Le Brusq  E. Guillanton  J. Y. Dauvignac  Pichot 《Journal of Applied Geophysics》2001,47(3-4)

In the field of road construction and maintenance, the need for information on the thickness of very thin road layers is not satisfied by means of commercial pulse GPR, due to the inability of such devices to operate over ranges of several gigahertz. As a result, research has focused on the design of a step-frequency radar technique, able to work with very high-frequency synthetic pulses.An ultrawide band antenna, belonging to the family of Vivaldi antennas, has been developed for road applications. It has been created using stripline technology and yields a band width greater than one decade. During an initial step, this antenna was tested on various bituminous concrete samples with a network analyzer. Different parameters were studied, including band width, offset between antennas, and height and shape of the frequency-dependent pulse.A second step involved GPR dynamic measurements. A customized software program enabled recording data from the network analyzer. Several radar profiles were developed from selected road construction and maintenance test sites (e.g. the Circular Pavement Fatigue Test Track, composed of a number of known structures). Results show improved resolution when compared to a commercial impulse GPR system.  相似文献   

从新构造应力场论公路水毁问题——兼论地貌发育的对抗性原理   总被引：2，自引：0，他引：2  

艾南山  陈洪凯 《地理科学》1996,16(4):298-304

根据沙依德格尔的对抗性原理，研究了新构造应力场对公路水毁的影响问题，发现在高应力区，如果公路走向平行于新构造应力场的剪切面或垂直于这个应力场的主压应力方向，公路的稳定性即将变坏。  相似文献   

亚洲中部干旱气候研究综述与机理分析     

戴新刚  汪萍 《沙漠与绿洲气象(新疆气象)》2020,14(1):1-12

综述了亚洲中部干旱气候若干研究进展,并对亚洲中纬度干旱区形成机理进行了深入分析。依据大尺度气候分类法将全球陆地划分为季风、地中海及西风带气候区,分别对应于年内季节循环中多雨—高温的同位相、反位相及不相关等类型水—热配置特征。亚洲中部干旱区南北部分属地中海和西风带气候区,其不同水—热位相配置又对应于不同的水汽通量及其散度等特征。研究揭示了欧亚大陆中部干旱区形成于降水不足且季节性水—热配置不当,起因于大气环流平均槽脊季节变化引起的大气动力—热力配置,其根源是海陆热力差异及大地形对大气环流强迫的结果。本文还讨论了季风区与非季风区之间平均气流水汽散度的季节性互动,以及行星尺度上不同气候区之间平均气流与瞬变涡动水汽散度之间的配置等问题。  相似文献   

The plain man's guide to plate tectonics     

E.R. Oxburgh 《Proceedings of the Geologists' Association. Geologists' Association》1974,85(3):299-357

  相似文献   

Population,urbanization and economic scenarios over the Belt and Road region under the Shared Socioeconomic Pathways   总被引：1，自引：0，他引：1  

Jing  Cheng  Tao  Hui  Jiang  Tong  Wang  Yanjun  Zhai  Jianqing  Cao  Lige  Su  Buda 《地理学报(英文版)》2020,30(1):68-84

The countries throughout the Belt and Road region account for more than 60% of the world's population and half of the global economy. Future changes in this area will have significant influences on the global economic growth, industrial structure and resource allocation. In this study, the proportion of the urban population to the total population and the gross domestic product were used to represent the levels of urbanization and economic development, respectively. The population, urbanization and economic levels of the Belt and Road countries for 2020–2050 were projected under the framework of the IPCC's shared socioeconomic pathways(SSPs), and the following conclusions are drawn.(1) The population, urbanization and economic levels in the Belt and Road region will likely increase under all five pathways. The population will increase by 2%–8%/10 a during 2020–2050 and reach 5.0–6.0 billion in 2050. Meanwhile, the urbanization rate will increase by 1.4%–7.5%/10 a and reach 49%–75%. The GDP will increase by 17%–34%/10 a and reach 134–243 trillion USD.(2) Large differences will appear under different scenarios. The SSP1 and SSP5 pathways demonstrate relatively high urbanization and economic levels, but the population size is comparatively smaller; SSP3 shows the opposite trend. Meanwhile, the economy develops slowly under SSP4, but it has a relatively high urbanization level, while SSP2 exhibits an intermediate trend.(3) In 2050, the population will increase relative to 2016 in most countries, and population size in the fastest growing country in Central Asia and the Middle East countries will be more than double. Urbanization will develop rapidly in South Asia, West Asia and Central Asia, and will increase by more than 150% in the fastest growing countries. The economy will grow fastest in South Asia, Southeast Asia and West Asia, and increase by more than 10 times in some counties with rapid economic development.  相似文献   

Development of a river delta: a case study of Cimanuk river mouth,Indonesia     

Nita Yuanita  Tawatchai Tingsanchali 《水文研究》2008,22(18):3785-3801

This paper describes delta development processes with particular reference to Cimanuk Delta in Indonesia. Cimanuk river delta, the most rapidly growing river delta in Indonesia, is located on the northern coast of Java Island. The delta is subject to ocean waves of less than 1 m height due to its position in the semi‐enclosed Java Sea in the Indonesian archipelago. The study has been carried out using a hydrodynamic model that accounts for sediment movement through the rivers and estuaries. As an advanced approach to management of river deltas, a numerical model, namely MIKE‐21, is used as a tool in the management of Cimanuk river delta. From calibration and verification of hydrodynamic model, it was found that the best value of bed roughness was 0·1 m. For the sediment‐transport model, the calibration parameters were adjusted to obtain the most satisfactory results of suspended sediment concentration and volume of deposition. By comparing the computed and observed data in the calibration, the best values of critical bed shear stress for deposition, critical bed shear stress for erosion and erosion coefficient were 0·05 N m^?2, 0·15 N m^?2, and 0·00001 kg m^?2 s^?1, respectively. The calibrated model was then used to analyse sensitivity of model parameters and to simulate delta development during the periods 1945–1963 and 1981–1997. It was found that the sensitive model parameters were bed shear stresses for deposition and erosion, while the important model inputs were river suspended sediment concentration, sediment characteristics and hydrodynamic. The model result showed reasonable agreement with the observed data. As evidenced by field data, the mathematical model proves that the Cimanuk river delta is a river‐dominated delta because of its protrusion pattern and very high sediment loads from the Cimanuk river. It was concluded that 86% of sediment load from the Cimanuk river was deposited in the Cimanuk delta. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

21世纪初期河南地质找矿战略理论与技术方法     

司马献章 《河南国土资源》1999,(3)

本文概述了新、老矿区的战略找矿方向和基础理论找矿模式,提出测试、钻探及最佳找矿技术方法组合,强化组织管理是地质勘查的正确思路  相似文献   

Combating piracy and armed robbery in Asia: The ReCAAP Information Sharing Centre (ISC)     

Joshua Ho 《Marine Policy》2009

The Regional Cooperation Agreement on Combating Piracy and Armed Robbery Against Ships in Asia (ReCAAP) Information Sharing Centre (ISC) is an international organisation that comprises 14 member countries in the region. Despite its many advantages, the ISC has some weaknesses, which when addressed could bring regional cooperation to a new level and which could make the ISC a model for other regions.  相似文献   

今天的中国为什么比任何时候都需要世界地理学   总被引：3，自引：2，他引：3  

秦大河  张国友  宋长青  金凤君  薛德升  杜德斌  陆玉麒  苗长虹  葛岳静  吴志峰  刘建忠  张振克  刘云刚  宁越敏  效存德  王荣成  陈俊华  李娟  胡志丁 《世界地理研究》2020,29(1):1-7

世界地理作为中国地理学的重要分支学科，特指研究中国以外区域或国家的地理学科，是中国特有的学科分类现象。中国地理学的这种内外有别的思想对世界地理发展危害甚大，至今都难以消弭。忽视世界地理研究，就会有只见树木、不见森林之虞。为了贯彻落实党的“十九大”精神，繁荣探索新型科研组织机制，打造一流世界地理学科，服务国家重大国际战略需求，来自国内高校、科研院所的百余人齐聚一堂，探讨中国世界地理学科发展之路。与会专家一致认为：地理学是国家发展的法宝，是立国之本。当前世界政治经济格局加速重构，为中国地理学发展带来了前所未有的历史机遇，也赋予地理学特别是世界地理学学科新的重大历史使命。为此，须充分发挥地理学科的优势和特长，紧跟国家和世界发展大势，树立全球眼光，面向国家重大战略需求，把自然与人文结合起来，面向可持续发展，团结国内各相关单位，进行跨学科研究，提升世界地理学科为二级学科，构建具有中国特色的世界地理学理论体系、逻辑框架和学科范式，提升中国地理学科，特别是世界地理学科服务国家和地方发展的能力。  相似文献   

The Belt and Road: Geographical pattern and regional risks     

Wu  Shaohong  Liu  Lulu  Liu  Yanhua  Gao  Jiangbo  Dai  Erfu  Feng  Aiqing  Wang  Wentao 《地理学报(英文版)》2019,29(4):483-495

Journal of Geographical Sciences - Building the Belt and Road is initiatives of China to promote win-win international cooperation in the new era, aiming at green, health, intellect and peace and...  相似文献