冬小麦蒸腾速率在不同土壤水分条件下的修正   总被引：1，自引：1，他引：0  

张红卫  申双和  陈怀亮 《气象科技》2008,36(4):436-439

为找到不同土壤含水量对蒸腾速率的影响程度,通过对L1-6200便携式作物生理测定仪在不同土壤水分处理下的蒸腾速率观测值与气象条件计算得出的理论值进行比较,确定不同土壤水分条件下的蒸腾速率修正系数.分析发现:①在不同的土壤含水量下,未考虑修正系数的情况时,土壤含水量越小,理论计算误差越大;土壤含水量越大,理论计算误差越小.②土壤含水量小时蒸腾速率计算值的修正系数大,而土壤含水量偏大时修正系数小.③考虑修正系数后,计算误差显著减小,除了土壤含水量为14.89％稍有偏差外,其它土壤含水量状态下的理论计算值非常接近实际观测值.同时验证了不同土壤水分下的修正系数足显著的.  相似文献   

Understanding governance and networks: EU-US interactions and the regulation of genetically modified organisms     

Joseph Murphy  Helen Yanacopulos 《Geoforum》2005,36(5):593-606

EU-US (European Union-United States) interactions in relation to the regulation of genetically modified organisms (GMOs) have been examined in detail in recent years. To do this scholars have tended to focus on a small number of high profile processes, such as the formal complaint of the US to the World Trade Organisation regarding the regulation of GMOs in the Europe. It is important to analyse developments of this kind but overemphasis on them has also lead to a distorted view of the case and a failure to appreciate the significance of other, less visible, types of interaction. In this paper we focus instead on trying to understand the roles played by various EU-US transnational networks—The Transatlantic Business Dialogue, The Transatlantic Economic Partnership, The Transatlantic Consumer Dialogue, The Transatlantic Environmental Dialogue and the EU-US Consultative Forum on Biotechnology. These networks have been trying to shape the regulation of GMOs in both jurisdictions since the mid 1990s. By analysing them through a ‘governance lens’ we find that we can better understand EU-US interactions and the dynamics and influences around the regulation of GMOs. This gives us valuable insights into processes of contemporary governance.  相似文献   

变性绕极深层水入侵时南极普里兹湾湍流混合特征研究     

胡俊洋  梁楚进  蔺飞龙 《海洋学报》2021,(3):1-12

基于中国第28、29和31次南极科学考察中的CTD数据,利用Thorpe尺度方法计算了普里兹湾及其附近海域湍动能耗散率,分析了其分布特征,并对当地的水团结构进行研究。结果表明,普里兹湾及其附近海域中,前两个航次观测中次表层湍动能耗散率强度在陆架坡折区域达到最大。在水团分布方面,在第28和29航次中均观测到了变性绕极深层水陆架入侵现象,水团分别向上涌升至海表以下100 m和200 m深度,向南均可达到67.5°S处。普里兹湾陆架坡折区域次表层湍动能耗散率强度分布与当地水团结构存在良好对应关系。研究认为变性绕极深层水入侵陆架,会使该深度水体变得不稳定,发生水体交换现象,最终造成该区域湍流混合强度加强。  相似文献   

基于MSAVI-WI特征空间的新疆渭干河-库车河流域绿洲土壤盐渍化研究   总被引：5，自引：0，他引：5  

丁建丽  瞿娟  孙永猛  张永福 《地理研究》2013,32(2):223-232

土壤盐渍化是造成干旱区土地荒漠化及生态恶化的重要原因,及时获取大尺度高精度土壤盐渍信息是防治工作的基础。选取新疆塔里木盆地北缘渭干河—库车河流域三角洲绿洲为研究区,利用Lansat-TM数据与野外实测数据分析盐渍化土壤与修改型土壤调整植被指数(MSAVI)、湿度指数(WI)之间的关系,在此基础上提出了MSAVI-WI特征空间概念,构建了土壤盐渍化遥感监测指数模型(MWI)。结果表明:MWI与土壤表层含盐量相关性较高,其相关性为0.844,精度高于土壤盐渍监测常用的盐分指数与实测数据的相关性。MWI能较好的反映盐渍化土壤地表植被及土壤水分的组合变化,具有明确的生物物理意义,并且特征参量简单,理论上易于理解,实践上易于实现,MWI模型的构建有利于干旱区大尺度土壤盐渍化定量监测与评价工作的开展。  相似文献   

特征约束六面体网格生成的改进栅格法     

庞宇  郭飞  李想  何梅芳 《地球信息科学学报》2014,(5):691-698

目前,针对地学对象的非结构化六面体网格生成问题仍未得到很好的解决。为满足相关地学研究对六面体网格的需求,促进地学模拟及传统GIS空间分析的进一步发展,本文对传统栅格法进行扩展,提出了一种面向地学研究的六面体网格生成的改进栅格法。通过提取实体模型表面的几何特征,考虑内部孔、洞约束生成骨干网格,在此基础上构建一套特征约束模板来处理复杂的特征约束,使之既能保持地学研究对象的几何形态特征,又能实现加密区域与非加密区域的平滑过渡,从而满足地学分析与模拟的需求。  相似文献   

Amodified discrete element model for sea ice dynamics     

LI Baohui  LI Hai  LIU Yu  WANG Anliang  JI Shunying 《海洋学报(英文版)》2014,33(1):56-63

Considering the discontinuous characteristics of sea ice on various scales,a modified discrete element model（DEM） for sea ice dynamics is developed based on the granular material rheology.In this modified DEM,a soft sea ice particle element is introduced as a self-adjustive particle size function.Each ice particle can be treated as an assembly of ice floes,with its concentration and thickness changing to variable sizes under the conservation of mass.In this model,the contact forces among ice particles are calculated using a viscous-elastic-plastic model,while the maximum shear forces are described with the Mohr-Coulomb friction law.With this modified DEM,the ice flow dynamics is simulated under the drags of wind and current in a channel of various widths.The thicknesses,concentrations and velocities of ice particles are obtained,and then reasonable dynamic process is analyzed.The sea ice dynamic process is also simulated in a vortex wind field.Taking the influence of thermodynamics into account,this modified DEM will be improved in the future work.  相似文献   

中国科技资源配置效率测度及其时空格局演变特征(英文)     

范斐  杜德斌  王馨竹 《地理学报(英文版)》2014,24(3):492-508

According to the connotation and structure of science and technology resources and some relevant data of more than 286 cities at prefecture level and above during 2001–2010, using modified method—Data Envelopment Analysis(DEA), science and technology(ST) resource allocation efficiency of different cities in different periods has been figured out, which, uncovers the distributional difference and change law of ST resource allocation efficiency from the time-space dimension. Based on that, this paper has analyzed and discussed the spatial distribution pattern and evolution trend of ST resource allocation efficiency in different cities by virtue of the Exploratory Spatial Data Analysis(ESDA). It turned out that:(1) the average of ST resource allocation efficiency in cities at prefecture level and above has always stayed at low levels, moreover, with repeated fluctuations between high and low, which shows a decreasing trend year by year. Besides, the gap between the East and the West is widening.(2) The asymmetrical distribution of ST resource allocation efficiency presents a spatial pattern of successively decreasing from Eastern China, Central China to Western China. The cities whose ST resource allocation efficiency are at higher level and high level take on a cluster distribution, which fits well with the 23 forming urban agglomerations in China.(3) The coupling degree between ST resource allocation efficiency and economic environment assumes a certain positive correlation, but not completely the same. The differentiation of ST resource allocation efficiency is common in regional development, whose existence and evolution are directly or indirectly influenced by and regarded as the reflection of many elements, such as geographical location, the natural endowment and environment of ST resources and so on.(4) In the perspective of the evolution of spatial structure, ST resource allocation efficiency of the cities at prefecture level and above shows a notable spatial autocorrelation, which in every period presents a positive correlation. The spatial distribution of ST resource allocation efficiency in neighboring cities seems to be similar in group, which tends to escalate stepwise. Meanwhile, the whole differentiation of geographical space has a diminishing tendency.(5) Viewed from LISA agglomeration map ofST resource allocation efficiency in different periods, four agglomeration types have changed differently in spatial location and the range of spatial agglomeration. And the continuity of ST resource allocation efficiency in geographical space is gradually increasing.  相似文献   

基于GIS的合肥市BRT和Metro交通可达性研究   总被引：1，自引：0，他引：1  

朱传华  张守文 《地理与地理信息科学》2014,30(6)

评价了合肥市中心城区的BRT和在建Metro线路对可达性的影响。基于GIS网络分析模拟复杂的多模式交通网络,应用修正潜能模型指标度量了居民区与CBD、与商业金融中心、与行政中心以及与工业区的可达性,对比有无BRT和Metro两种情景下的可达性变化。研究结果表明:在有BRT和Metro时,居民区至CBD的可达性均值变化幅度为45.8%,出行时间从65.5min减至35.5min;居民区至商业金融中心的可达性均值变化幅度为45.7%,时间从74.8min减至40.6min;居民区至行政中心的可达性均值变化幅度为18.9%,时间从104.7min减至84.9min;居民区至工业区的可达性均值变化幅度为37.4%,时间从92.1min减至57.7min。BRT和Metro线路显著地节省了居民出行时间,改善了城市边缘区域的交通可达性,其中经开区的可达性变化幅度最高,其次是滨湖新区、高新区和东区、老城区、南区、西区和北区。  相似文献   

改性红辉沸石的制备及去除水中CODcr的性能研究     

张静  肖筱瑜  徐文炘 《矿产与地质》2010,24(6):570-573

天然红辉沸石经过氯化铝及氯化镁共同改性后,制备出改性红辉沸石。研究了改性红辉沸石和天然红辉沸石对生活污水中CODcr的吸附效果,表明改性红辉沸石的吸附效果明显优于红辉沸石,并通过X射线粉末衍射、热重分析、红外光谱对改性红辉沸石表面结构进行了表征。  相似文献   

深部围岩流变特性试验研究及其模型辨识   总被引：2，自引：2，他引：0       下载免费PDF全文

刘正  高文华  刘栋  邓修甫 《水文地质工程地质》2012,39(4):43-48

采用分级增量循环加卸载方式,对湖南湘煤集团牛马司矿业公司水井头煤矿-300m东大巷二煤层底板粉砂岩进行了单轴蠕变特性试验,详细探讨了轴向蠕变变形特征,蠕变速率与时间和应力水平的关系,瞬时弹性模量和变形模量变化特征.试验结果表明,当应力水平低于岩石的长期强度时,粉砂岩只发生衰减蠕变,应力水平对蠕变速率变化的影响不明显;当应力水平高于岩石的长期强度时,岩石等速蠕变阶段明显.对流变试验数据进行深入分析的基础上,进行了流变模型辨识和基于最小二乘法的参数确定.根据不同应力水平下加卸载过程中岩石的蠕变特点,提出了采用改进的两原模型模拟岩石的蠕变特性.模型计算结果表明,改进后的西元模型既能够较好地描述低应力下的衰减蠕变,又能较精确地描述高应力下岩石的衰减蠕变和等速蠕变特性.  相似文献