Application of the weighted residual method to diffraction by 2-D canyons of arbitrary shape: I. Incident SH waves   总被引：1，自引：0，他引：1  

Vincent W. Lee  Xiaoyun Wu 《Soil Dynamics and Earthquake Engineering》1994,13(5)

A solution for the two-dimensional scattering and diffraction of plane SH waves by canyons of arbitrary shape in an elastic half space is presented. The wave field for arbitrary geometry in this paper is computed numerically by the method of weighted residues (moment method). The wave displacement field computed by the present residual method for the case of a semi-circular canyon was shown to agree analytically and numerically with that computed by the exact closed form series solution. The same observations about ground amplifications, their dependence on frequencies and orientations of the incident waves, can be stated here for canyons of arbitrary shape as previously made for circular canyons.  相似文献   

A probability-weighted moment test to assess simple scaling     

Praveen Kumar  Peter Guttarp  Efi Foufoula-Georgiou 《Stochastic Environmental Research and Risk Assessment (SERRA)》1994,8(3):173-183

We present a statistically robust approach based on probability weighted moments to assess the presence of simple scaling in geophysical processes. The proposed approach is different from current approaches which rely on estimation of high order moments. High order moments of simple scaling processes (distributions) may not have theoretically defined values and consequently, their empirical estimates are highly variable and do not converge with increasing sample size. They are, therefore, not an appropriate tool for inference. On the other hand we show that the probability weighted moments of such processes (distributions) do exist and, hence, their empirical estimates are more robust. These moments, therefore, provide an appropriate tool for inferring the presence of scaling. We illustrate this using simulated Levystable processes and then draw inference on the nature of scaling in fluctuations of a spatial rainfall process.  相似文献   

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   

青藏高原地区最高,最低气温Mos预报的检验     

王希娟 《高原气象》1991,10(1):99-104

  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   

在地面三角网中布设卫星观测站的最低精度要求     

周忠谟 《武汉大学学报(信息科学版)》1986,(3)

本文从地面三角网和卫星同联合平差的原理出发,讨论了对卫星网的最低精度要求。指出,为改善地面三角网而布设卫星网时,卫星观测站的最低精度主要决定于以下因素: ——地面三角网的精度; ——对地面三角网精度改善程度的要求; 一卫星观测站之间的距离。这里通过模拟计算对卫星网的最低精度要求与上列因素之间的关系作了数字分析,并建立了估算卫星网最低精度的数学模型。预期,在一般情况下,该模型的估算误差将不会超过10％。  相似文献   

A heuristic search method for optimal zonation of well logs   总被引：1，自引：0，他引：1  

Hui-Chuan Chen  J. H. Fang 《Mathematical Geology》1986,18(5):489-500

Optimal zonation of well-log data, that is, determining an optimal number of major segments such as waveforms in a log, may be achieved by employing a criterion of minimum variance (within a segment) and a heuristic search of potential boundary (link) points of digitized log data. This new method is based on an algorithm originally devised by D. M. Hawkins and D. F. Merriam in 1973. Their method can be improved by introducing a heuristic search procedure, thereby decreasing computer time by 7- to 50-fold, depending on the number of data points and configuration of the logs. Time saving is proportional to the size of the data set. Three examples—one hypothetical and two real—are used to illustrate the modification of the Hawkins and Merriam algorithm.Presented at the Geological Society of America Annual Meeting, Orlando, Florida, 1985.  相似文献   

地学数据的分形插值与成图   总被引：4，自引：0，他引：4       下载免费PDF全文

李才伟 《地球科学》1995,20(2):191-198

本文将分形几何学的思想和方法引进对地学数据的插值处理与计算机成图的研究中，建立了适合于具有随机形特征的地学数据的“局部分数布朗场”数学模型，在讨论和分析了Ｖｏｓｓ提出的“逐次随机添加”与Ｂａｒｎｓｌｅｙ提出的“分形插值函数”这两种可用于分形插值法，并将它们应用到对地貌，化探，物探等地学数据进行插值，网格化和计算机成图上。  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   

计算最小走时和射线路径的界面网全局方法   总被引：27，自引：16，他引：27       下载免费PDF全文

刘洪  孟凡林 《地球物理学报》1995,38(6):823-832

用慢度分块均匀正方形模型将介质参数化，仅在正方形单元的边界上设置计算结点，这些结点构成界面网．根据Ｈｕｖｓｅｎｓ和Ｆｅｒｍａｔ原理，由不断扩张、收缩的波前点扫描代替波前面搜索，在波前点附近点的局部最小走时计算中对波前点之间的走时使用双曲线近似，通过比较确定最小走时和相应的次级源位置，记录在以界面网点位置为指针的３个一维数组中．借助这些数组通过向源搜索可计算任意点（包括界面网以外的点）上的全局最小走时和射线路径．这一方法不受介质慢度差异大小限制，占内存少，计算速度较快，适于走时反演和以Ｍａｓｌｏｖ射线理论为基础的波场计算．  相似文献