高精度锥体棱镜的“自差法”检测技术   总被引：2，自引：0，他引：2  

殷达安  林银森 《测绘学报》1994,23(3):216-221

本文提出一种采用“自差法”检测高精度锥体棱镜的新方法，阐述检测原理与装置，建立检测角度和面形误差的定量判据，并给出一个实例说明其应用。实践表明，“自差法”检测技术对于产品质量的控制，具有快速准确和简便实用等特点。  相似文献   

以反应谱和功率谱密度函数表征的强震运动的统计特性   总被引：1，自引：0，他引：1  

江近仁  孙景江 《中国地震》1994,10(4):327-340

文中利用我国海城和唐山地震１９０条强震记录和美国西部１３８条强震记录研究了以反应谱和功率谱密度函数表征的强震运动的统计特性。反应谱用最大地面加速度归一化，即表为谱放大系数，功率谱密度函数用金井清谱描述。文中研究了参数的统计值和依赖性，以及谱放大系数和金井清谱参数与场地条件、震源和震中距等之间的相关性，分析比较了中美两国强震运动谱的统计特性，并对我国地震工程应用的强震运动谱的统计参数值的选取提出了建议。  相似文献   

均质土坡的安全系数     

徐金明  陈文才 《上海国土资源》1995,(3):43-48

本文用变分法的基本理论的方法，推导出了均质土坡稳定性在平面应变情况下的基本方程，将简单边坡无粘性土（Ｃ＝０）与纯粘性土ψ＝０）的情况作为特例导出了相应的计算方法与计算公式，并对传统的条分法与土坡临界高度计算方法进行了讨论。  相似文献   

宁夏及青海地震活动性统计指标及未来地震趋势的综合概率预报     

许文俊 《高原地震》1995,(2)

本文叙述了地震活动的综合概率预报方法，并对宁夏及青海地区（３５°００’－４１°００’Ｎ，１００°００’－１０７°４０’Ｅ）１９７０年以来的地震活动资料进行了统计计算，对１９９２年－１９９３年该区地震活动进行了综合预报效能检验。并据此对该区１９９４年－１９９５年的地震趋势做了估计。  相似文献   

全球最优插值客观分析   总被引：7，自引：0，他引：7  

屠伟铭  张跃堂 《气象学报》1995,53(2):148-156

主要叙述国家气象中心实时运行的全球资料同化系统中的客观分析方案，该方案采用最优插值统计方法，使用所有可以使用的各种类型有不同误差的观测资料和模式的６ｈ预报值，给出数值形式的全球分析值。在两年的业务运行中，为Ｔ４２中期数值预报谱模式提供了较好的初始场。  相似文献   

欧亚500 hPa月平均大气环流的年际振荡特征   总被引：5，自引：0，他引：5       下载免费PDF全文

何敏  罗艳 《应用气象学报》1995,6(4):461-467

文章用主分量、功率谱、带通滤波及复主分量分析方法，对欧亚地区1951～1992年的500hPa月平均高度场进行分析，研究了欧亚大气环流年际振荡的时空分布特征。结果表明:欧亚500hPa月平均大气环流主要存在准2.5年、准3.5年振荡周期。副热带地区大气环流以准3.5年振荡为主要周期；中高纬地区以准2.5年振荡为主要周期。复主分量分析还表明了这两种振荡的传播方向和随时间变化各不相同。欧亚500hPa月平均大气环流的准3.5年振荡特征与赤道东太平洋海温的变化及厄尔尼诺现象有密切的关系。  相似文献   

气候变化对江河流量变化趋势影响研究进展   总被引：9，自引：0，他引：9  

刘春蓁 《地球科学进展》2007,22(8):777-783

气候变化对基于自然稳定气候假定的流量变化趋势的检测和水资源评价方法提出了挑战。在流量变化趋势的检测中分离出气候变化的影响,不仅对水资源管理和水利工程设计有重要的应用价值,而且有助于了解气候变化以何种方式、在何时、何地、已经或尚未对水文循环产生影响,对改进气候模型的模拟与预测有重要的科学价值。 统计方法是检验流量变化趋势显著性的有效工具。直接用气候模型模拟和预测未来径流变化的可靠性取决于模型对当代降水模拟的可信度。多个气候模型集合分析有可能在一定程度上减少模型对降水、径流模拟的不确定性。近年发展起来的多个气候模型集合分析与统计显著性检验技术结合的方法,有可能模拟并预测出气候强迫导致大尺度径流空间分布的变化。随着气候模型尤其是陆—气耦合的区域气候模型对降水模拟的改进,可以预见径流变化的检测、归因和预测的趋同化模拟已为期不远。将温室气体外强迫导致的水文气候变化作为一个因子引入到水资源评价中,对于水资源管理经济与生态评估,以及未来的发展规划将是一件十分重要的变革。   相似文献   

Large to intermediate-scale aquifer heterogeneity in fine-grain dominated alluvial fans (Cenozoic As Pontes Basin,northwestern Spain): insight based on three-dimensional geostatistical reconstruction     

O. Falivene  L. Cabrera  A. Sáez 《Hydrogeology Journal》2007,15(5):861-876

Facies reconstructions are used in hydrogeology to improve the interpretation of aquifer permeability distribution. In the absence of sufficient data to define the heterogeneity due to geological processes, uncertainties in the distribution of aquifer hydrofacies and characteristics may appear. Geometric and geostatistical methods are used to understand and model aquifer hydrofacies distribution, providing models to improve comprehension and development of aquifers. However, these models require some input statistical parameters that can be difficult to infer from the study site. A three-dimensional reconstruction of a kilometer scale fine-grain dominated Cenozoic alluvial fan derived from more than 200 continuously cored, closely spaced, and regularly distributed wells is presented. The facies distributions were reconstructed using a genetic stratigraphic subdivision and a deterministic geostatistical algorithm. The reconstruction is only slightly affected by variations in the geostatistical input parameters because of the high-density data set. Analysis of the reconstruction allowed identification in the proximal to medial alluvial fan zones of several laterally extensive sand bodies with relatively higher permeability; these sand bodies were quantified in terms of volume, mean thickness, maximum area, and maximum equivalent diameter. These quantifications provide trends and geological scenarios for input statistical parameters to model aquifer systems in similar alluvial fan depositional settings.  相似文献   

Whole mantle SH velocity model constrained by waveform inversion based on three-dimensional Born kernels   总被引：1，自引：0，他引：1  

Nozomu Takeuchi 《Geophysical Journal International》2007,169(3):1153-1163

A whole mantle SH velocity model is obtained by using a unique data set and techniques. Body and surface waveforms including major and multi-orbit phases are used as a data set and are inverted by using 3-D Born kernels. The resultant model, SH18CE, reveals the different natures of the two major upwelling systems: the strong low velocity anomalies beneath Africa extend for more than 1000 km from the core–mantle boundary (CMB), whereas those beneath the Pacific are restricted to 300–400 km from the CMB. The results also show the variable natures of stagnant slabs on the 670 discontinuity around Japan: the depths of the strongest high velocity anomalies within the stagnant slabs are different region by region, which is consistent with the detailed delay time tomography model in this area.  相似文献   

Approaches for modeling longitudinal dispersion in pore-networks     

R.C. Acharya  S.E.A.T.M. Van der Zee  A. Leijnse 《Advances in water resources》2007

The purpose of this study is to quantify the dispersivity in the longitudinal direction by upscaling pore scale mixing over a network domain and to verify the dispersivity with that obtained through the more rigorous upscaling technique, the Brownian particle tracking model (BPTM). We model a porous medium with a network of pore-units that are comprised of pore bodies and bonds of finite volume. Such a pore-unit is assumed to be a mixing cell with the steady state flow condition for a single fluid. Dispersivity can be obtained by solving the mixing cell model (MCM) for the concentration in each pore-unit and by averaging the concentrations for a large number of pore units (as a function of time and space). A minimal size of network that ascertains an asymptotic value of dispersivity was determined and verified with large size pore networks. This numerically computed dispersivity is compared with the results from the BPTM for the same porous medium and flow conditions. We show that the dispersivity obtained from the MCM is equally reliable for the heterogeneous pore-networks and can be estimated as a function of pore size heterogeneity. For homogeneous networks with the MCM, the iteration time step plays an important role. On the other hand, for networks with the BPTM, the assumption of intra-bond velocity profile affects the results.  相似文献