Factors controlling the spatial and temporal variability of dust emissions     

John A. Gillies William G. Nickling Vicken Etyemezian James King Mark Sweeney 《中国地球化学学报》2006,25(B08):219-220

New field measurement techniques are allowing researchers to better understand how surficial properties affect the temporal and spatial variability of dust emissions. In this paper we review the current understanding of the dust emission process and present new field measurements that examine how three surface properties： roughness, crust strength, and temporal changes of surface properties affect dust emissions. These data were collected using three unique measurement systems developed by our team. Roughness exerts considerable control on the entrainment threshold and emissions of dust from a surface. We have carried out a series of experiments designed to quantify roughness effects on aeolian sediment entrainment and transport in a shear stress partitioning framework. Our results show that the model of Raupach et al. （1993） provides very good agreement with available data to predict the amount of shearing stress on the intervening surface among roughness elements, relatively independent of their size and distribution. However, element size affects the aeolian sediment transport process beyond that attributable only to the reduction of surface shear stress caused by the roughness. Additional interactions of the elements with the saltation cloud appear to reduce the transport efficiency and potentially dust emissions as well. The effect of crust strength on dust emissions was assessed using a newly-developed pin penetrometer, which can measure crust strength in-situ. Previous researchers suggested that variation in crust strength even within a small area could lead to considerable spatial variability in dust emissions. Our measurements showed that crust strength is highly variable over a scale of centimeters. This variability may help to explain some of the observed scatter in field measurements of dust emissions for what appear to be homogeneous surfaces. Variability of dust emissions in time and space was also evaluated using a new instrument, the Portable In-Situ Wind Erosion Lab （PI-SWERL） developed to measure dust emissions from soil surfaces.  相似文献   

A Connectivity Index for Discrete Fracture Networks     

C. Xu  P. A. Dowd  K. V. Mardia  R. J. Fowell 《Mathematical Geology》2006,38(5):611-634

Connectivity is an important measure for assessing flow transport in rock, especially through fractures. In this paper, rock fracture systems are modelled by a discrete fracture model simulated by a marked point process. A connectivity index is then introduced to quantify the connectivity between any two points in space. Monte Carlo simulation is used to evaluate the connectivity index for stationary cases and relationships between the connectivity index and the parameters of the discrete fracture model are analysed. The average number of intersections per fracture, X_f, and the fracture intensity, P12 (P32), are calculated and the relationships between these parameters and the connectivity index are investigated, concluding that X_f is the more suitable parameter for the classification of rock mass flow properties. The relationships between the connectivity index and the percolation state of the fractured medium are also discussed. An edge correction is briefly discussed and a practical example is used to demonstrate the method of computing the connectivity index.  相似文献   

Influence of sedimentary environments on mechanical properties of clastic rocks     

Zhaoping Meng  Jincai Zhang  Suping Peng 《Environmental Geology》2006,51(1):113-120

The sedimentary environments are the intrinsic factor controlling the mechanical properties of clastic rocks. Examining the relationship between rock sedimentary environments and rock mechanical properties gives a better understanding of rock deformation and failure mechanisms. In this study, more than 55 samples in coal measures were taken from seven different lithologic formations in eastern China. Using the optical microscope the sedimentary characteristics, such as components of clastic rocks and sizes of clastic grains were quantitatively tested and analyzed. The corresponding mechanical parameters were tested using the servo-controlled testing system. Different lithologic attributes in the sedimentary rocks sampled different stress–strain behaviors and failure characteristics under different confining pressures, mainly due to different compositions and textures. Results demonstrate that clastic rocks have the linear best-fit for Mohr-Coulomb failure criterion. The elastic moduli in clastic rocks are highly dependent upon confining pressures, unlike hard rocks. The envelope lines of the mechanical properties versus the contents of quartz, detritus of the grain diameter of more than 0.03 mm, and grain size in clastic rocks are given. The compressive strength or elastic modulus and the grain diameter have a non-monotonic relation and demonstrate the “grain-diameter softening” effect.  相似文献   

Relationship of Uncertainty and Line Segment for Between Polygon Segment Spatial Data in GIS     

LIU Chun TONG Xiaohua 《地球空间信息科学学报》2005,8(3):183-188

The mathematic theory for uncertainty model of line segment are summed up to achieve a general conception, and the line error hand model of εσ is a basic uncertainty model that can depict the line accuracy and quality efficiently while the model of εm and error entropy can be regarded as the supplement of it. The error band model will reflect and describe the influence of line uncertainty on polygon uncertainty. Therefore, the statistical characteristic of the line error is studied deeply by analyzing the probability that the line error falls into a certain range. Moreover, the theory accordance is achieved in the selecting the error buffer for line feature and the error indicator. The relationship of the accuracy of area for a polygon with the error loop for a polygon boundary is deduced and computed.  相似文献   

房产测绘平面图系统的实现研究   总被引：1，自引：0，他引：1  

陈洋  张宏  蒋文明  乔延春  温永宁 《现代测绘》2005,28(3):15-16,19

随着城市规划管理的不断发展．使得城市房产测绘单位采用大型空间数据库管理测绘平面图资料成为必然。通过建立房产测绘平面图系统，可以有效地解决数据标准不一致．图数不能互访，测绘各部门无法协调一致等问题，充分发挥网络功能，提升整个城市的房产管理水平．达到房产管理和房产服务一体化的目标。本文详细论述了房产测绘平面图系统的概念、设计原则和系统功能．在南京数字房产共享平台的建设中得到了实现．并取得了良好的效果。  相似文献   

相对湿度对气溶胶辐射特性和辐射强迫的影响   总被引：14，自引：4，他引：14  

张立盛  石广玉 《气象学报》2002,60(2):230-337

采用已有的气溶胶折射指数等资料 ,计算了在不同的相对湿度条件下硫酸盐气溶胶的辐射特性。结合两种不同化学输送模式 (CTM )的模拟结果及LASGGOALS/AGCM模式 ,模拟估算了考虑相对湿度影响后全球硫酸盐气溶胶的辐射强迫。结果表明 :(1)随着相对湿度的增加 ,硫酸盐气溶胶的质量消光效率因子在短波波段有所减小 ,单次散射反照率仅在长波波段有所增加 ,不对称因子在整个波段均有所增加 ;(2 )用两个CTM资料模拟辐射强迫的结果相差较大 ,其全球平均辐射强迫分别为 - 0 .2 6 8和 - 0 .816W/m2 ;(3)在考虑相对湿度的影响后 ,硫酸盐气溶胶辐射强迫的分布类型与相应干粒子的强迫分布类型基本相同 ,但全球平均的强迫值减少了 6 %左右。  相似文献   

静压预制桩工程性状研究──以河南某电厂技改工程为例   总被引：1，自引：1，他引：1  

蒋孝成  黄志全  张长存 《工程地质学报》2002,10(3):288-292

以河南某电厂技改工程为例 ,根据现场检测结果 ,探讨了影响静压预制桩沉桩深度成因 ,分析了静压桩承载力的分布规律。研究结果证明静压桩的沉桩深度和承载力与地基土的性状密切相关。对于河南某电厂技改工程场地 ,尽管桩端进入砂较小深度 ,却可以在桩端平面附近良好土层的作用下提供较大的端阻力。  相似文献   

南水北调中线工程上第三系膨胀性硬粘土的工程地质特性研究   总被引：7，自引：5，他引：7  

张永双  曲永新  周瑞光 《工程地质学报》2002,10(4):367-377

上第三系硬粘土在中国东部新生代沉积盆地具有广泛的分布 ,因其性质复杂而成为中国区域性特殊岩土研究的重要对象。纵贯于南阳盆地和华北盆地西缘的南水北调中线工程长距离地开挖在不同的上第三系硬粘土中。本文在对南阳盆地、方城宝丰、邯郸永年三渠段上百个原状样的物质组成、物理性质、物化性质、膨胀性和收缩性、强度特性系统测试分析的基础上 ,总结了各类硬粘土的工程地质特性及其形成机理和变化规律 ,并根据不同湿度、围压状态下的试验结果分析了硬粘土的工程环境效应 ,这对于认识上第三系硬粘土在开挖运营条件下的变形破坏机理有着重要的理论和实际意义。  相似文献   

准噶尔盆地西北缘侏罗系储层   总被引：13，自引：5，他引：13       下载免费PDF全文

庄锡进  胡宗全  朱筱敏 《古地理学报》2002,4(1):90-96

准噶尔盆地西北缘侏罗系陆相碎屑岩储层的岩性差异较大，岩性对物性的控制作用明显。储层的孔隙类型多样，不同类型的孔隙在发育规模、丰度及有效性方面都存在显差异，次生溶蚀孔隙、原生粒间孔隙和残余粒间孔隙是最重要的有效孔隙类型。储层渗透率与孔隙度之间存在较好的半对数相关关系。通过设置一定的孔隙度和渗透率参数界线，对储层储集性能进行评价，将侏罗系储层的孔渗性能划分为5个级别，可与当前流行的砂岩储层孔渗性能分级相对应。通过对大量压汞参数样本的聚类分析，将储层的孔隙结构划分为4个类型。通过各类参数统计及曲线形态对比，对孔隙结构类型进行了定量结合定性的优劣评价。最后，结合孔渗性能级别、储集空间类型、孔隙结构类型、岩性等特征，对准噶尔盆地西北缘侏罗系储层进行了综合分类评价。  相似文献   

质量传输和同位素交换:流动几何学和交换机制     

刘伟 《地学前缘》2002,9(4):423-428

耦合的质量传输和动力学限制的同位素交换模型综合考虑了平流、扩散、热液弥散 ,以及岩石与水之间的不平衡同位素交换等项因素。把耦合模型应用于 2个构造环境下的古热液系统 ,进而解释稳定同位素数据。对于造成环绕浅成侵入岩体分布的18O亏损环带的流体的流动几何学 ,以及浅部正断层流体流动的几何学 ,耦合模型提供了不同于单一同位素交换模型的解释。耦合模型也提供了关于同位素相对交换速率和同位素交换机制的信息。结果表明 ,断层带的动态重结晶促进了表面反应 ,进而便利了同位素交换 ;在化学不反应性和未变形的矿物中 ,同位素交换可能受制于固态条件下的扩散。  相似文献