采空区上方修建大型建筑物地基稳定性评价   总被引：6，自引：0，他引：6  

郭惟嘉  王勇义 《岩土力学》2004,25(Z1):57-59

地表移动变形随时间的稳定性及剩余变形问题一直是采动覆岩沉陷研究的重要方面。笔者分析了采动地表移动变形的时间过程,探讨了地表沉陷的延续时间及地表剩余沉陷的预计方法,给出了采空区上方修建大型建筑物地基稳定性评价的指标,对采空区上建设建筑物提出了相应的技术措施。  相似文献   

On Some Simplifications of Cokriging Neighborhood   总被引：2，自引：0，他引：2  

Jacques Rivoirard 《Mathematical Geology》2004,36(8):899-915

Choosing the cokriging neighborhood is often difficult. A poor choice, ignoring influent data, can result in a loss of information as well as in artifacts in simulations based on cokriging. Then it is convenient to use if possible, or to refer to models that lead to simplified cokriging neighborhood. We essentially consider the case of two stationary variables, a target variable and an auxiliary one. By examining possible simplifications, we set up a list of models (essentially models with residuals) that, in general or under specific configurations, lead to simplifications of cokriging neighborhood. Collocated, dislocated, and other types of neighborhood are identified, that are optimal in some models and configurations. Possible extensions to cokriging with unknown means, and to more variables, are included.  相似文献   

Analysis of Sediments and Soils by X-Ray Fluorescence Spectrometry Using Matrix Corrections Based on Fundamental Parameters   总被引：2，自引：0，他引：2  

Jacinta Enzweiler  Maria Aparecida Vendemiatto 《Geostandards and Geoanalytical Research》2004,28(1):103-112

Wavelength dispersive X-ray fluorescence spectrometry (WD-XRF) is widely used for the analysis of soils and sediments using well characterised procedures. However, difficulties can occur with samples such as unknowns containing small amounts of ore materials and samples collected from contaminated sites where trace elemental concentrations can exceed the concentration range for routine analysis. We studied the performance of a commercially available method, based on fundamental parameters (FP) to correct matrix effects. The spectrometer was originally calibrated with elemental or simple compound calibrants. Samples were analysed as pressed powder pellets. Eighteen sediment and soil reference materials, three of them with certified values for some of their constituents, were used to evaluate accuracy, by comparing results with recommended values and their standard deviations (RV ± 2s) or certified values and their confidence intervals (CV ± Cl). When results fell systematically outside these intervals, calibrations were refined with geochemical reference materials. The best agreement of results with recommended and certified values was obtained when the contents of H₂O and C in each sample were included as matrix constituents during calculations. The detection limits of trace elements tended to be relatively high, because the measuring conditions employed were not maximised for sensitivity. The main advantage of the method tested was that it enabled the analysis of samples with high concentrations of trace elements and the determination of elements such as F, Bi, Sb and W, which are not commonly included in quantitative XRF analysis of geological samples.  相似文献   

基于EM算法和单幅雷达图像阴影的控制点坡度校正   总被引：1，自引：0，他引：1  

钱俊  舒宁 《武汉大学学报(信息科学版)》2004,29(12):1089-1092

对在我国现有的条件下进行控制点坡度校正的必要性进行了阐述，并分析了EM算法。根据EM算法以及基于区域增长的余弦散射模型建立了控制点坡度校正模型，并用河北省张北地区的雷达影像进行了实验，取得了较高的精度初值。  相似文献   

MODIS 1B影像几何纠正方法研究及软件实现   总被引：24，自引：0，他引：24  

蒋耿明  刘容高  牛铮  庄大方 《遥感学报》2004,8(2):158-164

MODIS影像是一种新型和重要的数据。对MODIS 1B影像几何畸变原因进行了深入分析，选择了一种合适的纠正方法。对于1km分辨率MODIS 1B影像，直接采用1km分辨率的空间坐标进行几何纠正；对于250m和500m分辨率的MODIS 1B影像，先用三次样条曲线对坐标进行插值生成同分辨率的坐标，然后利用坐标插值结果对其进行几何纠正。由于MODIS影像在空问分布上的特殊性，采用前向和后向映射相结合的方式确定纠正后某一像素点在原始影像中的位置。根据该位置的条带重叠度，可以确定参与计算像素个数、搜索窗口的大小以及窗口的精确位置；采用归一化反距离加权插值法计算纠正后像素点的属性值。上述优化算法不仅保证了纠正后影像的质量，而且提高了数据处理速度。作者在Visual C 6．0环境下开发实现了上述算法。从坐标插值和几何纠正结果分析，无论是数据处理速度还是纠正后的影像质量和精度均达到要求。  相似文献   

Correcting method of eddy covariance fluxes over non-flat surfaces and its application in ChinaFLUX     

ZHU Zhilin  SUN Xiaomin  ZHOU Yanlian  Xu Jinping  YUAN Guofu  ZHANG Renhua 《中国科学D辑(英文版)》2005,48(Z1)

Although Eddy Covariance (EC) technique is one of the best methods for estimating the energy and mass exchanges between underlying surface and atmosphere in micrometeorology, errors and uncertainties still exist without necessary corrections. In this paper, we will focus on the effect of coordinate system on the eddy fluxes. Based on the data observed over four sites (one farmland site, one grassland site and two forest sites), the effects of three coordinate system transforming methods (Double Rotation-DR, Triple Rotation-TR and Planar Fit-PF)on the turbulent fluxes are analyzed. It shows that (i) the corrected fluxes are more or less than the uncorrected fluxes, which is related mainly to the sloping degree of surface, wind speed and wind direction; and (ii) pitch angle has a sinusoidal dependence on wind direction, especially in the regular sloping terrain; and (iii) PF method is something like the simplification of TR or DR,and there are not obvious distinctions in correction in sloping grassland and flat farmland, but PF method is not suitable for uneven and irregular forest sites.  相似文献   

Temporal and spatial cyclicity of accretion at slow-spreading ridges—evidence from the Reykjanes Ridge     

Christine Peirce  Alex Gardiner  Martin Sinha 《Geophysical Journal International》2005,163(1):56-78

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Using raw regional climate model outputs for quantifying climate change impacts on hydrology          下载免费PDF全文

Jie Chen  François P. Brissette  Pan Liu  Jun Xia 《水文研究》2017,31(24):4398-4413

General circulation model outputs are rarely used directly for quantifying climate change impacts on hydrology, due to their coarse resolution and inherent bias. Bias correction methods are usually applied to correct the statistical deviations of climate model outputs from the observed data. However, the use of bias correction methods for impact studies is often disputable, due to the lack of physical basis and the bias nonstationarity of climate model outputs. With the improvement in model resolution and reliability, it is now possible to investigate the direct use of regional climate model (RCM) outputs for impact studies. This study proposes an approach to use RCM simulations directly for quantifying the hydrological impacts of climate change over North America. With this method, a hydrological model (HSAMI) is specifically calibrated using the RCM simulations at the recent past period. The change in hydrological regimes for a future period (2041–2065) over the reference (1971–1995), simulated using bias‐corrected and nonbias‐corrected simulations, is compared using mean flow, spring high flow, and summer–autumn low flow as indicators. Three RCMs driven by three different general circulation models are used to investigate the uncertainty of hydrological simulations associated with the choice of a bias‐corrected or nonbias‐corrected RCM simulation. The results indicate that the uncertainty envelope is generally watershed and indicator dependent. It is difficult to draw a firm conclusion about whether one method is better than the other. In other words, the bias correction method could bring further uncertainty to future hydrological simulations, in addition to uncertainty related to the choice of a bias correction method. This implies that the nonbias‐corrected results should be provided to end users along with the bias‐corrected ones, along with a detailed explanation of the bias correction procedure. This information would be especially helpful to assist end users in making the most informed decisions.  相似文献   

基于OSM的浮动车轨迹数据校正方法     

胡向勇  郭圆 《测绘通报》2020,(10):139

浮动车轨迹数据具有覆盖范围广、更新周期短、获取成本低等特点，对于地图的生产和更新具有重要意义，但是由于受到卫星信号被遮挡及多路径效应的影响，其精度普遍较低。本文采用一种基于OSM作为参考数据的方式对浮动车轨迹数据进行校正。首先通过一种分层时空地图匹配的方式将轨迹数据与OSM进行匹配；然后采用引力模型对数据进行校正；最后在武汉市出租车轨迹数据上进行了试验。结果表明，本文提出的数据校正方法可以有效地提高浮动车轨迹数据的精度。  相似文献   

长江口外潮汐精细化模型研究与精度分析     

季凯敏  路川藤 《海洋技术学报》2019,38(5)

长江口外海上测量除受风浪影响较大外,最重要的问题是潮位控制非常困难。文中简要阐述了开展长江口外潮汐精细化模型研究的方法,介绍了利用潮汐精细化模型对长江口外航路任意点进行潮汐预报的方法,并通过实测数据进行了精度分析,提出了建议。  相似文献