一种可考虑历史洪水的马氏权函数法研究   总被引：1，自引：0，他引：1       下载免费PDF全文

陈元芳 《水科学进展》1994,5(3):174-178

导出了非连序样本下,马氏权函数法(适用于P-Ⅲ型分布)参数估计公式.在不偏性、有效性的标准下,统计试验结果表明,推导的非连序样本下的计算公式是较为有效的,且拓宽了马氏权函数法的使用范围.  相似文献   

Location　of　Tibetan　earthquakes──a　nonlinear　approach　by　a　simplex　optimized　technique   总被引：1，自引：0，他引：1  

赵珠  丁志峰  易桂喜  王建格 《地震学报(英文版)》1994,(2)

Ｌｏｃａｔｉｏｎ　ｏｆ　Ｔｉｂｅｔａｎ　ｅａｒｔｈｑｕａｋｅｓ──ａ　ｎｏｎｌｉｎｅａｒ　ａｐｐｒｏａｃｈ　ｂｙ　ａ　ｓｉｍｐｌｅｘ　ｏｐｔｉｍｉｚｅｄ　ｔｅｃｈｎｉｑｕｅ（赵珠）（丁志峰）（易桂喜／）（王建格）ＬｏｃａｔｉｏｎｏｆＴｉｂｅｔａｎｅａ...  相似文献   

Cyclotella-taxa (Bacillariophyceae) in lakes of the Alpine region and their relationship to environmental variables     

Sybille Wunsam  Roland Schmidt  Rolf Klee 《Aquatic Sciences - Research Across Boundaries》1995,57(4):360-386

Surface sediment diatom assemblages for 86 Alpine lakes were analysed focusing on the dominant genusCyclotella and corresponding environmental data. The range of morphological variability of theCyclotella bodanica/radiosa, C. distinguenda, C. ocellata, C. comensis andC. stelligera complexes was documented. Significance tests included in the canonical correspondence analysis (CCA) indicated that total phosphorus, conductivity and surface water temperature were significantly correlated withCyclotella taxa assemblage distribution. Numerical species optima and tolerances were calculated in respect to these significant variables using weighted averaging (WA) regression and calibration. CCA and WA were able to provide information about the environmental preferences of the various morphotypes observed.  相似文献   

Appraisal of regional and index flood quantile estimators     

J. R. Stedinger  L. -H. Lu 《Stochastic Hydrology and Hydraulics》1995,9(1):49-75

Our results illustrate the performance of at-site and regional GEV/PWM flood quantile estimators in regions with different coefficients of variation, degrees of regional heterogeneity, record lengths, and number of sites. Analytic approximations of bias and variance are employed. For realistic GEV distributions and short records, the index-flood quantile estimator performs better than a 2-parameter GEV/PWM quantile estimator with a regional shape parameter, or a 3-parameter at-site GEV/PWM quantile estimator, in both humid and especially in arid regions, as long as the degree of regional heterogeneity is moderate. As regional heterogeneity or record lengths increases, 2-parameter estimators quickly dominate. Flood frequency models that assign probabilities larger than 2% to negative flows are unrealistic; experiments employing such distributions provide questionable results. This appraisal generally demonstrates the value of regionalizing estimators of the shape of a flood distribution, and sometimes the coefficient of variation.  相似文献   

Hybrid Estimation of Semivariogram Parameters   总被引：1，自引：0，他引：1  

Hao Zhang  Dale L. Zimmerman 《Mathematical Geology》2007,39(2):247-260

Two widely used methods of semivariogram estimation are weighted least squares estimation and maximum likelihood estimation. The former have certain computational advantages, whereas the latter are more statistically efficient. We introduce and study a “hybrid” semivariogram estimation procedure that combines weighted least squares estimation of the range parameter with maximum likelihood estimation of the sill (and nugget) assuming known range, in such a way that the sill-to-range ratio in an exponential semivariogram is estimated consistently under an infill asymptotic regime. We show empirically that such a procedure is nearly as efficient computationally, and more efficient statistically for some parameters, than weighted least squares estimation of all of the semivariogram’s parameters. Furthermore, we demonstrate that standard plug-in (or empirical) spatial predictors and prediction error variances, obtained by replacing the unknown semivariogram parameters with estimates in expressions for the ordinary kriging predictor and kriging variance, respectively, perform better when hybrid estimates are plugged in than when weighted least squares estimates are plugged in. In view of these results and the simplicity of computing the hybrid estimates from weighted least squares estimates, we suggest that software that currently estimates the semivariogram by weighted least squares methods be amended to include hybrid estimation as an option.  相似文献   

带权约束参数平差在工程控制网优化中的应用     

鲍峰  程效军 《测绘学报》2002,31(Z1):73-76

介绍用带权约束平差原理编制的工程控制网试验修正法设计和平差程序,并用于设计工程导线和平差变形观测控制网等实际工程的例子,据此提供一些结论和建议.  相似文献   

近海多种卫星测高联合数据处理技术     

高永泉  章传银 《测绘科学》2002,27(2):20-25

海域海况复杂多变 ,潮汐不但受外海能量输入的控制 ,而且在复杂的海岸线、浅海海底和内陆河流运输的作用下变得异常复杂。卫星测高由于受复杂的海洋动力环境和陆地反射的影响 ,数据质量普遍较深海差。将多种卫星测高数据联合处理 ,可以大大提高近海海域平均海面高的精度与分辨率 ,增强测高卫星监测近海复杂动力现象与反演近海复杂动力机制的能力。本文讨论近海多种卫星联合数据处理的技术与方法 ,分别从提取海平面稳态和时变信息的角度较系统地研究了多种卫星测高联合数据处理方法 ,通过提取不同测高卫星海平面观测数据中与时间无关的系统偏差 ,建立多种卫星测高数据的海平面时变基准 ,从而将多种测高卫星海面监测数据融合到一个动力系统中。大大提高测高卫星海平面监测的时空分辨率 ,为联合多种卫星测高数据在大地测量与近海海洋动力学研究中的应用创造基本条件。  相似文献   

一种基于GIS的矿产资源潜力评价的自动制图模型     

陈永良  刘大有 《地质论评》2002,48(3):324-329

在基于GIS技术的矿产资源评价工作中,矿产资源潜力评价的自动制图模型通常用来统计综合多源地学信息以便自动圈定成矿远景靶区。在本文中,笔者以人工智能研究领域中的一种不确定推理模型——确定性理论为基础,提出了一种新的矿产资源潜力评价的自动制图模型——合成有矿可信度模型。该模型可以根据研究区各种成矿有利和不利证据的空间分布图,统计生成对应于每一种证据的有矿可信度栅格图,然后,按照特定的有矿可信度合成规则,将所有的有矿可信度栅格图统计综合生成合成有矿可信度栅格图。以该图为依据,可以把研究区内合成有矿可信度相对较高的成矿远景区圈定出来。也可以生成研究区合成有矿可信度等值线图。应用该模型预测了新疆北部多拉纳萨依—阿舍勒地区的多金属成矿远景,并将预测结果与证据加权模型预测结果进行了比较,两种模型的预测结果基本相似,证明了该模型的有效性和实用性。  相似文献   

模糊数学在水化学寻找可地浸铀矿中的应用     

王军 《新疆地质》2002,20(2):167-169

利用水化学找铀，有成本低、效率高、速度快等特点，在寻找可地浸砂岩型铀矿也有明显的效果，但是在找铀过程中仅用水化学成份、氡含量、酸碱度和氧化还原电位等数值进行描述，说明它们与铀矿化的关系，这种单一因素不能综合反映与铀矿化的联系程度，以定量评价铀矿化与上述因素的关系，从而影响了水化学找矿的效果，通过模糊数学方法建立数学模型处理水化学数据，巳知可地浸砂岩型铀矿的特征值为参数进行定量评价未知区铀成矿的前景，使该方法成为今后铀矿预测中一种可靠有效的水文地质方法。  相似文献   

近百年全球平均气温年际变率中的QBO长期变化特征   总被引：18，自引：0，他引：18       下载免费PDF全文

丁裕国  余锦华  施能 《大气科学》2001,25(1):89-102

应用奇异谱分析(SSA)方法和奇异交叉谱分析(SCSA)方法，对全球及南北半球近100多年(1856～1997年)逐月地面气温距平序列中的准两年周期振荡(QBO)的长期演变特征进行诊断分析。结果表明:全球平均气温序列蕴含显著的QBO分量，它们与全球气候系统中其他各个子系统所隐含的QBO信号具有各种耦合对应关系，尤其突出地表现在Nino区海温和以SLP序列为代表的全球大气环流系统中QBO信号的耦合对应关系上。而平均气温的QBO的年代际特征及其变率的阶段性，不但表现在振幅上，而且其位相亦很明显。上述特征在全球、两半球具有明显的差异。  相似文献