广东省交通优势度及空间差异     

吴旗韬  张虹鸥  叶玉瑶  陈伟莲  陈静 《热带地理》2012,32(6):633-638,646

以广东省为研究对象,构建多维指标体系,从路网密度、交通设施影响度、交通枢纽辐射水平三方面分别对各县区的差异进行分析,并综合分析其交通优势度.研究表明,广东省交通优势度呈明显的圈层分布,从中心向外围递减,从沿海向内部递减;珠三角交通优势度在全省具有明显优势,其路网密度、交通设施影响度、交通枢纽辐射水平均为全省第一层次;广东省交通优势度还与地区经济发展水平有密切关系,通过对交通优势度和人均国民生产总值进行回归分析,发现交通优势度与经济发展水平呈明显的正相关.  相似文献   

长汀水土流失区生长季马尾松树干液流密度特征     

郑怀舟  朱锦懋  李守中  袁红伟  魏霞 《福建地理》2007,(2)

应用热扩散探针测定福建长汀水土流失区生长季马尾松东南西北4个方位的树干液流密度,并比较不同人工治理措施下马尾松树干液流密度的特征,利用自动气象站同步记录环境因子变化,以探讨先锋树种的水分生理生态特征及其对环境变化的响应.研究表明,马尾松4个方位的树干液流密度日变化均呈现单峰型变化规律;南向树干液流密度峰值最高,日变化幅度也最大;东、西、南、北4个方位的液流密度差异显著(P<0.01),但各方位液流间呈现显著的线性关系;树干4个方位液流的启动时间与太阳辐射之间存在约3个小时的时滞;4个方位液流与环境因子相关性均极显著(P<0.01),其中与液流密度相关性最强的是空气温度,其次为土壤温度和太阳辐射,4个方位液流受环境因子的影响程度存在差异;不同治理措施下的马尾松液流密度日变化规律相似,但数值差异显著(P<0.01),经过人工施肥的样地马尾松树干液流密度峰值明显高于未施肥的样地.  相似文献   

Mountain permafrost dynamics within a recently exposed glacier forefield inferred by a combined geomorphological,geophysical and photogrammetrical approach     

C. Kneisel  A. Kääb 《地球表面变化过程与地形》2007,32(12):1797-1810

Geomorphological observations, geoelectrical soundings and photogrammetric measurements of surface movement on the Muragl glacier forefield were used to obtain an integrative analysis of a highly complex glacial and periglacial landform consisting of a push moraine, creeping permafrost and permafrost‐free glacial till in close proximity. Electrical resistivity tomography is considered as an important multifunctional geophysical method for research in periglacial permafrost related environments. Joint application with measurements of surface displacements offers a promising tool for investigating periglacial landforms related to ice‐rich permafrost for a more comprehensive characterization of permafrost characteristics and geomorphological interpretation of periglacial morphodynamics. The patchy permafrost distribution pattern described in this paper is determined by several factors, including the sediment characteristics, the snow cover distribution and duration, the aspect and the former glacier distribution and thermal regime. Recent and modern permafrost dynamics within the glacier forefield comprise aggradation, degradation and permafrost creep. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

“All transport problems are essentially mathematical”: The uneven resonance of academic transport and mobility knowledge in Brussels     

Wojciech Kębłowski  David Bassens 《Urban geography》2018,39(3):413-437

This paper presents an inquiry into the capacity of transport and mobility studies to critically engage with contemporary policies. Drawing on the conceptualization of circuits of knowledge, the paper scrutinizes the extent to which transport policy agendas are framed around various approaches within academia. An extensive literature review reveals that the academic field of transport and mobility is organized around a hegemonic core of “neoclassical” and “sustainable” approaches. Meanwhile, a critique of these dominant approaches is emerging in an attempt to (re)embed mobility issues in urban political economy. This threefold knowledge typology visibly resonates within transport policy agendas in Brussels, where we detect a growth-oriented and largely depoliticized dual hegemony of neoclassical and sustainable narratives, with critical academic voices rarely entering official agendas. The paper concludes with a reflection on the difficulties, yet also the need to mobilize critical academic knowledge in the field of transport and mobility.  相似文献   

Catastrophic Outcomes in the Economics of Climate Change     

Richard b. Howarth 《Climatic change》2003,56(3):257-263

Monte Carlo simulations by Tol (2003) suggest that there is a small but positive probability that climate change will impose catastrophic impacts on future society unless sufficient steps are taken to reduce greenhouse gas emissions. This paper critically evaluates this finding and its implications for policy analysis and decision-making.  相似文献   

Local Scour Around Piles Under Wave Action   总被引：1，自引：0，他引：1  

陈国平左其华  黄海龙 《中国海洋工程》2004,18(3):403-412

The model tests are performed with regular waves, and the effect of wave height, wave period, water depth, sediment size and pile diameter is evaluated. The shape and size of local scour around piles are studied. There are three typical scour patterns due to wave action. It is found that a relationship exists between the erosion depth and the wave number. An empirical formula of the maximum local scour is thus derived.  相似文献   

Numerical Modeling of Water Wave Interaction with A Soft Mud Bed     

齐鹏王石青  侯一筠 《中国海洋工程》2004,18(4):605-612

A vertical 2-D numerical model is presented for simulating the interaction between water waves and a soft mud bed. Taking into aceotmt nonlinear theology, a semi-empirical theological model is applied to this water-mud model, reflecting the combined visco-elasto-plastic properties of soft mud under such oscillatory external forces as water waves. In order to increase the resolution of the flow in the neighborhood of both sides of the inter-surface, a logarithmic grid in the vertical direction is employed for numerical treatment. Model verifications are given through comparisons between the calculated and the measured mud mass transport velocities as well as wave height changes.  相似文献   

Experimental Study on Local Scour Around A Large Circular Cylinder Under Irregular Waves     

周益人  陈国平 《中国海洋工程》2004,18(2):245-256

1 .IntroductionWiththedevelopmentofexploitationofmarineresources ,theconstructionofoffshorestructuresdevelopsrapidly ,suchasmarineoilplatforms ,deep waterbreakwaters ,marinebridges ,largehar bors,etc .Thesestructureswillchangesurroundingwaveandcurrentconditionsandleadtolocalscourofseabed ,resultinginstructuraldamage .Therefore ,localscouraroundmarinestructuresaswellastheirprotectionhasdrawnmuchattentionfromrelativeengineeringfields .Manyscholarshaveconduct edtheoreticalanalysisandexperimentals…  相似文献   

Vibration and Acoustic Radiation from Submerged Spherical Double-Shell     

陈军明  黄玉盈  陈应波 《中国海洋工程》2003,17(3)

1 .IntroductionSphericalshellsandcircularcylindricalshellshavebecomethemajorstructuralformsfornaviga tiondevicesunderwater,suchassubmarine ,torpedo ,andsoon .Theintegratedsphericalshellsareoftenusedascommunicationandtransportationtools,andserveasworkroomsforexternalexaminationandrepairoflargenavigationdevicesunderwatertoo .Especiallyforthesphericaldouble shell,itisveryusefulforthedeepmarineworks .Inthesphericaldouble shell,severalinternalringplatesareusuallydesignedtoconnecttheinnerandoutersph…  相似文献   

Toe Structure Stability of Sloping Breakwater     

吴中  嵇才苏 《中国海洋工程》2003,17(2)

1 .IntroductionTheslopingbreakwateriswidelyusedintheprotectionofcoastalstructures ,withrubblemoundtoebermbuiltatthefootofthewave attackingslope .Thefunctionofarubblemoundtoestructureis ,inadditiontodecreasingthequantityofmainarmorstoneused ,toprovidestaticsupporttothemainarmorlayer,avoidingtherollingdownofmainarmorstonesandprotectingtheapronstonesfromero sion .TheweightoftoebermstonesisdecidedaccordingtotheCodeofBreakwaterDesignandBuildingformulatedbytheMinistryofCommunicationsofChina .When…  相似文献