Comparison of Positron Emission Tomography and X-ray radiography for studies of physical processes in sandstone     

Patrick Goethals  Anneke Volkaert  Patric Jacobs  Staf Roels  Jan Carmeliet 《Engineering Geology》2009,103(3-4):134-138

The migration of moisture in cores of porous homogeneous sandstone of Ledian age (Belgian Eocene, Tertiary) is monitored with PET (Positron Emission Tomography) and micro-focus X-ray radiography. In the case of PET, a nuclear medical imaging technique, ⁵⁵Co-EDTA (Ethylenediamine Tetraacetic acid) and R-¹⁸F were used as water-soluble tracers. The X-ray projection method has evolved from the better-known medical technique and allows a fast and accurate determination of the two-dimensional transient moisture content profiles. Results indicate that both techniques can deliver important information concerning physical processes in situ.  相似文献   

On the swelling potential of compacted high plasticity clays     

Valry Ferber  Jean-Claude Auriol  Yu-Jun Cui  Jean-Pierre Magnan 《Engineering Geology》2009,104(3-4):200-210

We conducted a study of the spatial distributions of seismicity and earthquake hazard parameters for Turkey and the adjacent areas, applying the maximum likelihood method. The procedure allows for the use of either historical or instrumental data, or even a combination of the two. By using this method, we can estimate the earthquake hazard parameters, which include the maximum regional magnitude Mˆ_max, the activity rate of seismic events and the well-known bˆ value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship. These three parameters are determined simultaneously using an iterative scheme. The uncertainty in the determination of the magnitudes was also taken into consideration. The return periods (RP) of earthquakes with a magnitude M ≥ m are also evaluated. The whole examined area is divided into 24 seismic regions based on their seismotectonic regime. The homogeneity of the magnitudes is an essential factor in such studies. In order to achieve homogeneity of the magnitudes, formulas that convert any magnitude to an M_S-surface scale are developed. New completeness cutoffs and their corresponding time intervals are also assessed for each of the 24 seismic regions. Each of the obtained parameters is distributed into its respective seismic region, allowing for an analysis of the localized seismicity parameters and a representation of their regional variation on a map. The earthquake hazard level is also calculated as a function of the form Θ = (Mˆ_max,RP_6.0), and a relative hazard scale (defined as the index K) is defined for each seismic region. The investigated regions are then classified into five groups using these parameters. This classification is useful for theoretical and practical reasons and provides a picture of quantitative seismicity. An attempt is then made to relate these values to the local tectonics.  相似文献   

Confocal laser scanning microscopy and Raman imagery of ancient microscopic fossils     

J. William Schopf  Anatoliy B. Kudryavtsev   《Precambrian Research》2009,173(1-4):39

Among all problems confronting the study of ancient permineralized (petrified) microscopic fossils, two stand out, the need for (1) accurate documentation of their three-dimensional morphology, and (2) direct analysis of their chemical composition and that of their surrounding mineral matrices. To address these problems we demonstrate the use of two techniques that we have recently introduced to Precambrian paleobiology: confocal laser scanning microscopy and Raman imagery. These techniques, both of which are non-intrusive and non-destructive, can provide data by which to characterize, in situ and at micron-scale resolution, the cellular and organismal morphology of thin section-embedded organic-walled fossils. In addition, Raman imagery provides direct analyses of the molecular–structural composition of the kerogenous components of such fossils and of their surrounding matrices, and a means to assess quantitatively the geochemical maturity of the preserved organics. Use of these techniques for studies of ancient microscopic fossils can provide information in three dimensions at high spatial resolution about their morphology and cellular anatomy, taphonomy and fidelity of preservation, composition and mode of preservation, and their biogenicity and syngenetic origin with the rocks in which they occur.  相似文献   

Study on the Area Variation of Qinghai Lake Based on Long-Term Landsat 5/8 Multi-Band Remote Sensing Imagery   总被引：1，自引：0，他引：1  

Weixiao Han  Chunlin Huang  Yunchen Wang  Juan Gu 《地球科学进展》2019,34(4):346-355

  相似文献   

Measuring fishery profitability: An index number approach     

《Marine Policy》2014

Tracking the financial well-being of vessels that depend on a marine fishery resource is an important function of regulators. This research demonstrates how simple indices can be constructed and utilized to track the economic well-being of vessels operating in the Northeast (USA) Multispecies (Groundfish) Fishery. The indices, which use both public and private data, can separately track trends in inputs, outputs, and prices. For the Northeast Multispecies Fishery, the indices reveal that the economic well-being of the groundfish fleet has improved under catch share management through gains in productivity.  相似文献   

Mapping crime harm and priority locations in New Zealand: A comparison of spatial analysis methods     

《Applied geography (Sevenoaks, England)》2017

Despite progress being advanced with spatial approaches to crime and crime control, the geography of crime harm has to date received little attention. The recent development of “Crime Harm Indices”, which weight crimes by an estimate of the relative harm they cause, offers an opportunity to improve on volume based spatial analysis approaches to identify where crime harm concentrates.This study aims to address this issue via the use of a Crime Harm Index (CHI) developed for New Zealand. By contrast to localized ‘harm-spotting’ analysis, we apply a census unit based approach to identify, at a macro level, the neighborhoods and wider communities suffering the highest crime harm in New Zealand. This approach enables harm to be viewed not only as a total Index but as a rate controlled for population and allows for the identification of census based sociodemographic factors which predict harm. Specifically, this paper compares the CHI with the New Zealand Priority Locations Index (PLI), an existing census unit based crime analysis tool which combines crime and demographic variables to identify communities vulnerable to crime and disorder issues.In this study CHI and PLI scores were calculated for Census Area Units (normally containing 3000–5000 population) across New Zealand. Bivariate correlations and a general linear model were used to determine the relationships between the CHI and PLI and additional population related variables. The CHI and PLI were weakly correlated, with population size and urban/rural categorization also accounting for CHI variance. Mapping techniques are used to illustrate outlier locations where the CHI and PLI differ widely and to identify location features which may assist in explaining CHI/PLI differences.This work exemplifies a novel geographic approach to the problem of crime harm with implications for resource allocation at national through to local levels. Wider implications for the theory and practice of crime and crime harm control are discussed, along with limitations of the study and areas for further research.  相似文献   

中国公路运输全要素生产率时空演化及区域竞争——基于Hicks-Moorsteen指数框架     

刘宏伟  吴杰  梁雯  方叶林 《地理科学》2017,37(11):1640-1648

运用Hicks-Moorsteen TFP指数法对中国公路运输业全要素生产率进行测度和演化分析。结果发现：2009~2012年中国公路全要素生产率实现了增长,2013~2015年出现下降。2009年来技术进步推动了东部地区公路运输全要素生产率的增长,而运营效率提升则在推动中西部地区公路运输全要素生产率增长时起到了关键作用。中西部地区公路运输效率增长优于东部地区。东部地区在引领技术进步的同时,应注重公路运输效率的提升;中西部地区应注意加大先进技术的引进。政府和主管部门对中西部公路运输应推出持续性支持政策。  相似文献   

基于冠层温度的作物缺水研究进展   总被引：35，自引：2，他引：35  

袁国富  唐登银  罗毅  于强 《地球科学进展》2001,16(1):49-54

冠导温度信息可以很好地反映作物的水分状况。自20世纪70年代以来，基于冠层温度的作物缺水指标的研究经历了三个阶段，即单纯研究冠层温度本身变化特征的第一阶段、以冠层能量平衡原理为基础的作物水分胁迫指数的第二阶段和考虑冠层和土壤的复合温度的水分亏缺指数的第三阶段。指标的局长也由使用手持式红外辐射仪信息扩大到使用航空和卫星遥感信息。这一类指标在点和区域尺度上均可应用。加强这一类指标的研究对于我国北方地区农作物的有效灌溉和区域水资源的管理都有重要意义。  相似文献   

非户籍与户籍人口居住空间分异的多维度解析——以深圳为例   总被引：4，自引：3，他引：1  

张瑜  仝德  IanMacLACHLAN 《地理研究》2018,37(12):2567-2575

在居住空间相异指数基础上,构建了集聚—分散度、中心—边缘度和极化—均质度指数,进一步挖掘由于人口聚居形态、居住区位和居住质量等方面差异导致的居住空间分异的多维内涵,及其所揭示出的社会经济空间现象、成因及空间治理重点。利用全国第六次人口普查数据开展深圳实证研究,在计算全市及各区分维指数的基础上,分析深圳人口居住空间相异指数特征及空间尺度差异,多维居住空间分异格局特征及成因,并通过聚类分析将深圳非户籍与户籍人口居住空间分异类型划分为三类,分类提出空间治理政策建议。从而为深入理解中国大城市日益出现的居住分异现象及机制提供新鲜视角和多样化测度方法,为解决其带来的社会及空间治理问题提供更有针对性的政策建议。  相似文献   

降水集中度的变化特征及影响因素分析——以山西为例     

袁瑞强  王亚楠  王鹏  王仕琴  陈宇宏 《气候变化研究进展》2018,14(1):11-20

基于山西14个站点1957—2014年逐日降水资料,计算年尺度与多年尺度下的降水集中指数（CI）和极端降水指数（R_95p和R_99p),利用统计方法,研究了山西降水集中度的时空变化和影响因素。结果表明,CI值与R_99p显著正相关,CI值增大则发生极端强降水几率增大。多年尺度CI值体现出明显的纬度地带性和较大的局地空间差异。受温带大陆性季风气候控制,山西省降水CI值介于0.59~0.64,相对亚热带地区较小,且变化范围较小。总体上年尺度CI值呈下降趋势,五台山、右玉、五寨、运城等站点下降趋势显著。盆地区域较高山高原区的CI值更大且下降趋势不显著,更易于发生极端降水事件。较高的高程和较大的变幅可增强高程对CI值的影响。太平洋年代际振荡（PDO）与年尺度CI值显著负相关。PDO冷位相时期,西太平洋副高西进、偏强,CI值偏高,发生极端强降水的可能性增大。本研究揭示了自然地理条件和海-气相互作用对区域尺度降水集中度存在复杂的影响。  相似文献