黑龙江省中部森林沼泽区 超低密度深穿透地球化学调查采样介质的确定   总被引：2，自引：0，他引：2  

胡忠贤  杨兆武  程志中  王学求 《物探与化探》2005,29(2):105-107,115

通过对王水溶矿法与四酸溶矿法的对比,元素在泛滥平原A层、B层沉积物及水系沉积物中的分配,以及这3种介质圈定的异常对比等综合因素的研究,确定了泛滥平原A层沉积物是黑龙江省中部森林沼泽区开展超低密度深穿透地球化学调查的有效采样介质。  相似文献   

地球化学异常再现性与可对比性   总被引：1，自引：4，他引：1       下载免费PDF全文

王学求孙宏伟  迟清华程志中 赵善定 《中国地质》2005,32(1):135-140

不同密度采样是否可以获得稳定的和可追索的地球化学模式是检验采样是否具有代表性，分析技术是否成熟的重要依据。笔者选择新疆哈密大南湖地区约6400km^2面积，进行了从超低密度(1个样／100km^2)，甚低密度(1个样／25km^2)直到低密度(1个样／4km^2)地球化学采样，对比了3种密度地球化学采样所获得的地球化学数据和异常分布模式。得出如下结论：超低密度、甚低密度、低密度地球化学调查获得的元素含量平均值和背景值非常接近；超低密度、甚低密度、低密度调查所圈定的地球化学省在形态上和变化趋势上非常相似，浓集中心的位置重合，表明不同调查阶段可获得稳定的和可追索的地球化学模式；采样密度越大数据离散程度越高，即最小值更小，最大值更大，表明元素分布的局部不均匀性，正是这种局部的不均匀性才能通过加密采样刻画出地球化学模式的细节变化，为逐步追踪矿化体奠定了基础；超低密度和甚低密度采样可以有效圈定矿集区所形成的大规模地球化学异常，低密度地球化学调查不仅可以圈定矿集区异常，同时可以圈定分散矿化的小规模局部异常。  相似文献   

福建省滨海火电厂地质灾害问题及风险控制探讨   总被引：1，自引：0，他引：1  

郑承忠 《中国地质灾害与防治学报》2005,16(2):47-52

滨海火力发电厂工程主要包括厂区建筑、码头、管道、取排水、填海和贮灰场等工程。其主要面临着福建省海岸带构造运动、断裂及地震活动、港湾淤积、海底滑坡、软土地基、海底活动地貌、基岩不均匀风化以及人类工程活动等主要的灾害性地质因素。通过对这些因素潜在的致灾特点分析，提出了滨海火电厂地质灾害风险控制应包括选址阶段地质灾害风险回避、设计施工阶段地质灾害风险处理及运行阶段地质灾害风险监控等3方面。地质灾害风险评估是滨海火电厂地质灾害风险控制的首要任务。针对滨海电厂工程的特点，评估内容应着重于地质灾害危险性评估及易损性评估。选址阶段地质灾害风险回避主要是对构造不稳定的回避。地质灾害风险处理主要是电厂工程的基础处理及管道抗冲刷处理。电厂运行阶段地质灾害风险监控主要是对建筑物基础稳定性及海域冲淤变化的监控。  相似文献   

内蒙古中部重、磁场特征与地壳密度结构   总被引：2，自引：2，他引：2  

张季生  洪大卫王涛 《地质通报》2005,24(2):118-123

中亚造山带中的古生代——中生代花岗岩普遍具有正εNd值，在世界上是十分独特的。美国西部加利福尼亚中生代-新生代花岗岩同样具有正εNd值，并且其地壳的速度分布特征与内蒙古中部十分相似。本文通过与美国加利福尼亚的地球物理研究成果进行对比，来研究内蒙古中部的地壳密度结构，特别是下地壳的组成，试图探讨产生正￡。值花岗岩的深部地质原因。研究结果表明，在大兴安岭-内蒙古造山带下地壳中可能存在与美国加里福尼亚类似的洋壳物质。此外，还对重、磁异常进行了处理，以确定蛇绿岩带的延展情况。由于在西拉木伦河附近存在切割至莫霍面的深断裂，结合地表出现的蛇绿岩带，故提出温都尔庙-西拉木伦河一线可能是内蒙古中部最重要的地质构造界线。  相似文献   

基于DMN的高光谱图像分割方法研究     

曹建农  关泽群  李德仁 《遥感学报》2005,9(5):596-603

简述高光谱遥感光谱特征体系(包括光谱曲线特征、光谱变换特征和光谱度量特征3个层面)。研究马尔科夫网的概念和方法,生成基于光谱角(SA)特征度量的DMN,并以DMN为证据对高光谱图像进行分割;研究和实验表明基于SA信息的马尔科夫网可以很好地综合高光谱数据空间特征与光谱特征间的关系,为进一步数据处理提供优化控制(其实质是概率神经网络)。最后提出未来应用和研究方向。  相似文献   

北京及其周边地区夏季地闪活动时空特征分析   总被引：13，自引：9，他引：13       下载免费PDF全文

郑栋 孟青吕伟涛  张义军柴秀梅 马明 《应用气象学报》2005,16(5):638-644

利用M-LDARS闪电定位系统对北京及其周边地区1995～1997年6～9月的闪电观测数据, 分析闪电活动的时空分布特征。结果表明:闪电活动在时间分布上存在两个峰值时段, 13 :00～21:00和23:00～次日05 :00。通过对总地闪、分时段及峰值时段的地闪密度分析, 发现北京及周边地区闪电活动有几个明显的集中区域, 地闪高密度区主要出现在下垫面为山脉和水体的地方, 闪电活动与下垫面的水汽条件关系密切, 且正、负地闪的空间分布也呈现较大差异, 表明雷暴云的电荷结构存在一定差异。  相似文献   

计算非均匀地表通量的一种简化PDF及其应用   总被引：2，自引：4，他引：2  

刘晶淼  王纪军  丁裕国 《高原气象》2002,21(6):583-590

提出描述地表非均匀特性的简化概率密度函数（PDF），它可代替各种具体的PDF用于求解次网格尺度平均通量而不影响其精度，这种简化PDF可直接加入陆面过程模式方程组中进行陆－气通量交换的数值试验。它对非均匀地表陆面过程参数化具有一定的普适性。本文仅讨论了对称分布的简化计算（非对称分布另文讨论），列举了非均匀分布的观测事实，并以地表净红外辐射通量计算为例，详细验证了应用这种简化PDF的可行性和可靠性。  相似文献   

H2O-CH4-H2-CO2-CO-O2在高温、高压和高密度条件下的状态方程     

胡家文 《地球化学》2002,31(4):389-394

为了计算高温，高压和高密度流体的热力学性质，提出了一个具有19个参数的维里型状态方程，其中参数与温度间的函数关系采用由Sutherland位能函数导出的维里系数近似式。除临界点附近以外，在已报道的pVT数据所覆盖的大部分超临界区域内，该方程均可适用。用该方程对H2O，CH4，H2，CO2，CO和O2等流体pVT关系的计算结果令人满意，其中pVT上限分别为：91-610GPa,1.6-11.0cm^3/mol,4000-5000K。计算体积的平均偏 小于0．8％，最大偏差小于5．4％。  相似文献   

Analogue study of particle segregation in pyroclastic density currents, with implications for the emplacement mechanisms of large ignimbrites   总被引：3，自引：0，他引：3  

C. M. Choux  T. H. Druitt 《Sedimentology》2002,49(5):907-928

Abstract Analogue flume experiments were conducted to investigate the transport and sedimentation behaviour of turbulent pyroclastic density currents. The experimental currents were scaled approximately to the natural environment in three ways: (1) they were fully turbulent; (2) they had a very wide range of particle sizes and associated Rouse numbers (the ratio of particle settling velocity to effective turbulent eddy velocity in the current); and (3) they contained particles of two different densities. Two sets of surge‐type experiments were conducted in a 5 m long, water‐filled lock‐exchange flume at five different volumetric particle concentrations from 0·6% to 23%. In one set (one‐component experiments), the currents contained just dense particles; in the other set (two‐component experiments), they contained both light and dense particles in equal volume proportions. In both sets of experiments, the population of each component had a log‐normal size distribution. In the two‐component experiments, the size range of the light particle population was selected in order to be in hydrodynamic equivalence with that of the dense particles. Dense particles were normally graded, both vertically and downstream, in the deposits from both sets of experiments. The mass loading (normalized to the initial mass of the suspension) and grain size of the dense component in the deposits decreased with distance from the reservoir and were insensitive to initial total particle concentration in the currents. On the other hand, in the two‐component experiments, the light particles were extremely sensitive to concentration. They were deposited in hydrodynamic equivalence with the dense particles from dilute currents, but were segregated efficiently at concentrations higher than a few per cent. With increasing particle concentration, the large, light particles were carried progressively further down the flume because of buoyancy effects. Deposits from the high‐concentration currents exhibited reverse vertical grading of the large, light particles. Efficient segregation of the light component was observed even if the bulk density of the current was less than that of the light particles. In both sets of experiments, marked inflexions in the rate of downstream decline in mass loading and maximum grain size of the dense component can be attributed to the presence of two different particle settling regimes in the flow: (1) particles with Rouse numbers >2·5, which did not respond to the turbulence and settled rapidly; and (2) particles with Rouse numbers <2·5, which followed the turbulent eddies and settled slowly. The results are applied to the transport and sedimentation dynamics of pyroclastic density currents that generate large, widespread ignimbrites. Field data fail to reveal significant departures from aerodynamic equivalence between pumice and lithic clasts in three such ignimbrites: the particulate loads of some large ignimbrites are transported principally in turbulent suspensions of low concentration. In some ignimbrites, the well‐developed inflexions in curves of maximum lithic (ML) size vs. distance can be attributed to the existence of distinct high and low Rouse number particle settling regimes that mark the transition from an overcharged state to one in which the residual particulate load is transported more effectively by turbulence.  相似文献   

Probability Density Functions as Botanical-Climatological Transfer Functions for Climate Reconstruction     

Norbert Kühl  Christoph Gebhardt  Thomas Litt  Andreas Hense 《Quaternary Research》2002,58(3):381

We present a new procedure, the pdf method (pdf=probability density function), for reconstructing Quaternary climate utilizing botanical data. The procedure includes the advantages of the indicator species method by considering the fossil and modern presence and absence of taxa rather than their frequencies, thus avoiding the need for modern analog plant communities. Overcoming the problematic use of absolute limits to describe climate response ranges is the main progress of the pdf method in comparison to the indicator species method. This advantage results from estimating probability density functions (pdfs) for monthly mean January and July temperature conditional on the present day occurrence of single taxa. Gaussian distributions sufficiently approximate pdfs of many, although not all, studied taxa. On the assumption of statistical independence, the procedure calculates a joint pdf as the product of the pdfs of the individual taxa. This algorithm weights each taxon according to the extent of its climate response range expressed by its covariance structure. We interpret the maximum of the resulting pdf as the most likely climate and its confidence interval as the uncertainty range. To avoid an artificial reduction of uncertainty arising from the use of numerous similar pdfs, a preselection method is proposed based on the Mahalanobis distance between pdfs. The pdf method was applied to the Carpinus phase of a profile from Gröbern, Germany, that spans the last interglaciation (Eemian). The reconstructed most probable January and July temperatures of about 0.0°C and 18.4°C barely differ from the modern values of −0.5°C and 18.3°C.  相似文献