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1.
极值分布和P-III型分布线性矩法在区域洪水频率分析中的检验 总被引：1，自引：2，他引：1
以江西省和福建省的86个水文站的年最大洪水资料为样本,在成因水文分区———模糊聚类法的基础上,采用线性矩区域综合方法进行区域洪水频率分析,并选用两种区域洪水分布线型:通用极值分布(GEV)、P-III型分布来检验这两省的洪水特性。结果表明,P-III型分布优于GEV分布。 相似文献
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线性矩法估计参数的保证修正值系数B的推求 总被引：3，自引：0，他引：3
在设计洪水的抽样误差估计中,采用保证修正值系数B方法估计均方差简单易用。应用线性矩法估计频率分布曲线的参数,有较好的无偏性和有效性,具有一定的应用前景。目前线性矩法的B值诺模图尚未确定,给用线性矩法确定参数时估计抽样误差带来了难度与不便。采用统计试验,分析了离差系数、偏态系数和样本长度对B值的影响,结果表明线性矩法估计参数时仍可采用保证修正值系数B值诺模图方法来估计抽样误差,并推求了不同偏态系数、设计频率情形下的B值,制成了线性矩法的B值诺模图备用。 相似文献
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为了提高矿产储量估算的精确性,减小普通克里格法的平滑效应对储量计算的影响,建立了基于相空间重构的克里格法。结合限制性克里格法的计算过程,修订了限制参数及条件并结合实例给出了对原始数据预处理的矿藏储量估计方法和结果。比较普通克里格法的相应结果后,在数值上得到该方法在抑制平滑效应方面较为理想的结论。 相似文献
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极值分布和P-Ⅲ型分布线性矩法在区域洪水频率分析中的检验 总被引：6，自引：0，他引：6
以江西省和福建省的86个水文站的年最大洪水资料为样本，在成因水文分区--模糊聚类法的基础上，采用线性矩区域综合方法进行区域洪水频率分析，并选用两种区域洪水分布线型：通用极值分布（GEV）、P-Ⅲ型分布来检验这两省的洪水特性。结果表明，P-Ⅲ型分布优于GEV分布。 相似文献
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水文频率分析计算过程中,水文极值样本系列容量一般都较小、代表性不高,使得水文设计值估计具有不确定性。利用Bootstrap方法,研究样本抽样不确定性对水文设计值的影响。与传统水文频率分析方法相比,基于Bootstrap方法不仅可提供设计值的点估计和区间估计,同时能够对设计值的不确定性进行定量评价。此外,基于Bootstrap技术,结合矩法、权函数法及线性矩法,设置3套方案,分析了该方法在不同参数估计方法间的有效性。以南通市1970-2011年共42年的年降雨量数据资料为例,对所提方法进行实例应用分析,结果表明,从期望设计值、90%置信区间及最终设计值角度而言,基于所提方法的设计成果受参数估计方法的选取影响不大,且可回避规范中B值诺莫图通用性较差及误差显著问题。 相似文献
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线性矩法的特点评析和应用问题 总被引：1，自引：1，他引：1
介绍了线性矩法的无偏估计与直接计算的关系，讨论了在概率权重矩计算过程中各系列之间的高度相关性及其对结果的影响，建立了直接计算线性矩法的Cv和Cs近似公式，叙述了适线问题和相应的经验频率公式。文中认为，水文频率计算时，由于资料的随机性和处理方法上的概化性，故用任何计算方法得到的结果，具有不同程度的不确定性，只能作为估计的初值，需通过时空上综合平衡，再经合理性分析和调整后，才能取用。 相似文献
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自由网离散数据的地球化学编图以任意方式进行网格化成图存在明显不确定性,会导致地球化学特征的改变或歪曲。克里格法提供了一种更科学合理的空间估计插值方法。笔者运用该方法对津巴布韦超低密度地球化学调查数据进行了空间分析并编制了地球化学图件,研究和讨论了自由网离散数据的地球化学编图方法,评价了采用克里格法编制地球化学图的效果。 相似文献
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Sample schemes used in geostatistical surveys must be suitable for both variogram estimation and kriging. Previously schemes
have been optimized for one of these steps in isolation. Ordinary kriging generally requires the sampling locations to be
evenly dispersed over the region. Variogram estimation requires a more irregular pattern of sampling locations since comparisons
must be made between measurements separated by all lags up to and beyond the range of spatial correlation. Previous studies
have not considered how to combine these optimized schemes into a single survey and how to decide what proportion of sampling
effort should be devoted to variogram estimation and what proportion devoted to kriging
An expression for the total error in a geostatistical survey accounting for uncertainty due to both ordinary kriging and variogram
uncertainty is derived. In the same manner as the kriging variance, this expression is a function of the variogram but not
of the sampled response data. If a particular variogram is assumed the total error in a geostatistical survey may be estimated
prior to sampling. We can therefore design an optimal sample scheme for the combined processes of variogram estimation and
ordinary kriging by minimizing this expression. The minimization is achieved by spatial simulated annealing. The resulting
sample schemes ensure that the region is fairly evenly covered but include some close pairs to analyse the spatial correlation
over short distances. The form of these optimal sample schemes is sensitive to the assumed variogram. Therefore a Bayesian
approach is adopted where, rather than assuming a single variogram, we minimize the expected total error over a distribution
of plausible variograms. This is computationally expensive so a strategy is suggested to reduce the number of computations
required 相似文献
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针对目前参数估计方法存在稀遇洪水频率设计值偏大的问题,提出采用基于数值次序统计量期望值的适线法计算洪水频率设计初始值;针对目前参数估计方法存在常遇洪水频率设计值偏小的问题,提出采用周文德公式修正目前频率设计偏小的情形,计算洪水频率设计修正值;针对目前传统方法计算洪水频率设计值抽样误差大的问题,提出采用基于数值次序统计量标准差的方法计算洪水频率设计保证值。定量分析表明,提出的基于数值次序统计量期望值的优化适线法具有良好的无偏性和有效性;寸滩站洪水频率设计修正值大于频率设计初始值,且两者偏差随着频率减小而减小;寸滩站洪水频率设计保证值明显大于修正值。 相似文献
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采用频率分析法计算入库设计洪水时,需要通过相关分析将坝址洪水系列插补得到对应的入库洪水系列。常用的线性回归法假设两者满足线性关系且入库洪水系列服从正态分布,可能与实际情况并不相符。引入Copula函数构建坝址洪水与入库洪水的联合概率分布和条件概率分布,计算给定坝址洪水时入库洪水的条件最可能值和置信区间,提出了一种基于Copula函数的入库洪水插补新方法。三峡水库的应用实例表明:线性回归法得到的入库洪水值在坝址洪水量级较大时明显偏小,甚至稀遇洪水时不在90%置信区间内。所提方法能较好地反映坝址洪水与入库洪水的内在关系,不仅可以计算入库洪水的各种点估计值,而且能够定量评价估计的不确定性。 相似文献
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气候变化及人类活动影响的加剧,改变了水文极值系列产生的平稳性条件,给现行水文频率分析计算方法带来挑战,亟需发展非平稳性条件下的水文频率分析理论与方法。讨论了等可靠度法的基本思想,拓宽了该方法在变化环境下工程水文设计方面的应用,以解决变化环境下工程水文设计值中的两类问题:①对于待建工程,依据非平稳性的水文极值系列,如何推求给定标准的设计值;②对于已建工程,如何协调/调整已建工程的洪水设计值,以适应变化环境对其产生的影响。以黄龙滩1956—2014年共59年的15日洪量系列为对象,对等可靠度法进行应用示例研究,并分析了参数估计不确定性对水文设计值的影响。结果表明,在非一致性条件下,给定设计标准下的水文设计值随着工程设计使用年限的变化而变化,且设计值估计的不确定性随着工程设计使用年限的增加而增大。 相似文献
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因为克里金插值方法考虑了样本的空间统计特征而被广泛应用于地层建模。但对于地层尖灭、缺失等不连续地层情况,常用的克里金方法（如普通克里金方法）通常给出较为平滑的地层厚度估计结果,在地层分布边缘的局部范围内与实际情况相差较大。针对不连续地层,提出一种采用指示克里金和普通克里金相结合的地层厚度估计方法。该方法首先采用指示克里金方法估计地层分布范围,然后采用普通克里金方法估计分布范围内的地层厚度,并根据估计标准差来评价地层厚度的不确定性。将提出的方法应用于上海长江隧道的地层建模,通过交叉验证,证明了该方法在地层分布边缘的局部范围内能明显改善地厚度估计结果,标准差降低了15%～18%,得到了比普通克里金和线性插值方法更接近真实情况的地层厚度估计值。 相似文献
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Compensating for estimation smoothing in kriging 总被引：2，自引：0，他引：2
Smoothing is a characteristic inherent to all minimum mean-square-error spatial estimators such as kriging. Cross-validation can be used to detect and model such smoothing. Inversion of the model produces a new estimator—compensated kriging. A numerical comparison based on an exhaustive permeability sampling of a 4-ft2 slab of Berea Sandstone shows that the estimation surface generated by compensated kriging has properties intermediate between those generated by ordinary kriging and stochastic realizations resulting from simulated annealing and sequential Gaussian simulation. The frequency distribution is well reproduced by the compensated kriging surface, which also approximates the experimental semivariogram well—better than ordinary kriging, but not as well as stochastic realizations. Compensated kriging produces surfaces that are more accurate than stochastic realizations, but not as accurate as ordinary kriging. 相似文献
18.
Application of universal kriging for estimation of earthquake ground motion: Statistical significance of results 总被引：1，自引：0，他引：1
Universal kriging is compared with ordinary kriging for estimation of earthquake ground motion. Ordinary kriging is based on a stationary random function model; universal kriging is based on a nonstationary random function model representing first-order drift. Accuracy of universal kriging is compared with that for ordinary kriging; cross-validation is used as the basis for comparison. Hypothesis testing on these results shows that accuracy obtained using universal kriging is not significantly different from accuracy obtained using ordinary kriging. Tests based on normal distribution assumptions are applied to errors measured in the cross-validation procedure;t andF tests reveal no evidence to suggest universal and ordinary kriging are different for estimation of earthquake ground motion. Nonparametric hypothesis tests applied to these errors and jackknife statistics yield the same conclusion: universal and ordinary kriging are not significantly different for this application as determined by a cross-validation procedure. These results are based on application to four independent data sets (four different seismic events). 相似文献
19.
Ore reserves forecasts are required to aid in investment decisions, mine design and valuation, short and long term production plans and proper and efficient mill design. In random multivariable fields with limited data and high levels of uncertainty, the kriged block estimates produce a smoothing effect resulting in underestimating high values and overestimating low values. The modified conditional simulation (MCS) methodology solves these problems by simulating the random field to preserve its mean and the variance structure. The simulation model is conditioned to reproduce the data at known sample points to minimize the variability between the simulated data and the true field data. In this study, the authors develop the MCS methodology to simulate ore reserve grades using the best linear unbiased estimation (BLUE) and the local average subdivision (LAS) techniques. The MCS methodology is applied to simulate block grades in a section of the Sabi Gold Project in Zimbabwe. The results are compared with the kriged estimates for this section. Analysis of the results shows that the MCS methodology reproduces the known sample grades with minimum estimation error of 0.001 while the estimation error associated with the kriged estimates is 1.104, a 100% efficiency of the MCS method over the kriging technique. 相似文献
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Shahab Shahbeik Peyman Afzal Parviz Moarefvand Mania Qumarsy 《Arabian Journal of Geosciences》2014,7(9):3693-3704
Estimation of mineral resources and reserves with low values of error is essential in mineral exploration. The aim of this study is to compare inverse distance weighted (IDW) and ordinary kriging (OK) methods based on error estimation in the Dardevey iron ore deposit, NE Iran. Anisotropic ellipsoid and variograms were calculated and generated for estimation of Fe distribution by both methods. Density, continuity of ore and waste, the number of points involved, and the discretization factor in the estimation of ore and waste boundaries were determined and the resource estimated by IDW and OK methods. Estimation errors were classified based on JORC standard, and both methods were compared due to distribution of error estimation. Results obtained by the study indicate that error estimation of OK method is less than IDW method and that the results of OK method are reliable. 相似文献