基于LHS方法的地下水随机模拟及开采量风险性 评价

地下水流数值模拟过程中,水文地质参数的不确定性对模拟结果影响很大。以内蒙古鄂尔多斯市某水源地为例,利用拉丁超立方抽样(LHS)方法获得了含水层渗透参数的随机组合,进行地下水流随机模拟。通过对观测资料与计算水位的绝对值平均(MAE)误差和误差均方根(RMSE)的统计分析,获得了模型较为稳定的随机模拟次数是243次。利用该随机模型对水源地设计开采量进行水位预测,并给出允许降深的风险性分布图。结果表明,预测水位和标准差分布符合实际情况,水位降深大于35 m的风险性最大达到75%。     

公路水准测量的误差来源与控制

水准测量是确定公路工程地面点高程的方法之一,是高程测量中精度较高常用方法。实施过程中,需要几个人合作才能完成。误差允许范围内的精度由于仪器和人为的影响而不容易控制,而且易出现隐蔽性错误。如果不能及早发现基础资料是错误的,水准点高程不正确,直接影响路线纵断面设计和施工。本文就水准测量的工作原理、误差来源,误差控制等几方面结合工程实例进行分析。     

一次人工触发闪电事件的定位误差分析

利用一次包含8次回击过程的人工触发闪电事件的近距离光电观测数据,分析了广东省气象闪电定位系统对其回击过程的定位结果。结果表明,回击过程探测效率约为75%(6/8),回击平均定位误差约为3768m。为了分析定位误差来源,通过对比分析的方法,逐次引入各探测子站原始记录重新进行定位计算,发现剔除误差较大的探测子站后,平均定位误差为2192m,比原来降低42%。     

Array processing-a new method to detect and correct errors on array resistivity logging tool measurements

In recent years more and more multi-array logging tools, such as the array induction and the array lateralog, are applied in place of conventional logging tools resulting in increased resolution, better radial and vertical sounding capability and other features. Multi-array logging tools acquire several times more individual measurements than conventional logging tools. In addition to new information contained in these data, there is a certain redundancy among the measurements. The sum of the measurements actu- ally composes a large matrix. Providing the measurements are error-free, the elements of this matrix show certain consistencies. Taking advantage of these consistencies, an innovative method is developed to de- tect and correct errors in the array resistivity logging tool raw measurements, and evaluate the quality of the data. The method can be described in several steps. First, data consistency patterns are identified based on the physics of the measurements. Second, the measurements are compared against the consis- tency patterns for error and bad data detection. Third, the erroneous data are eliminated and the measure- ments are re-constructed according to the consistency patterns. Finally, the data quality is evaluated by comparing the raw measurements with the re-constructed measurements. The method can be applied to all array type logging tools, such as array induction tool and array resistivity tool. This paper describes the method and illustrates its application with the High Definition Lateral Log (HDLL, Baker Atlas) instru- ment. To demonstrate the efficiency of the method, several field examples are shown and discussed.     

Earthquake source model using strong motion displacement as response of finite elastic media

The strong motion displacement records available during an earthquake can be treated as the response of the earth as the a structural system to unknown forces acting at unknown locations. Thus, if the part of the earth participating in ground motion is modelled as a known finite elastic medium, one can attempt to model the source location and forces generated during an earthquake as an inverse problem in structural dynamics. Based on this analogy, a simple model for the basic earthquake source is proposed. The unknown source is assumed to be a sequence of impulses acting at locations yet to be found. These unknown impulses and their locations are found using the normal mode expansion along with a minimization of mean square error. The medium is assumed to be finite, elastic, homogeneous, layered and horizontal with a specific set of boundary conditions. Detailed results are obtained for Uttarkashi earthquake. The impulse locations exhibit a linear structure closely associated with the causative fault. The results obtained are shown to be in good agreement with reported values. The proposed engineering model is then used to simulate the acceleration time histories at a few recording stations. The earthquake source in terms of a sequence of impulses acting at different locations is applied on a 2D finite elastic medium and acceleration time histories are found using finite element methods. The synthetic accelerations obtained are in close match with the recorded accelerations.     

Evaluation on the accuracy of digital elevation models

There is a growing interest in investigating the accuracy of digital elevation model (DEM). However people usually have an unbalanced view on DEM errors. They emphasize DEM sampling errors, but ignore the impact of DEM resolution and terrain roughness on the accuracy of terrain representation. This research puts forward the concept of DEM terrain representation error (Et) and then investigates the generation, factors, measurement and simulation of DEM terrain representation errors. A multi-resolution and multi-relief comparative approach is used as the major methodology in this research. The experiment reveals a quantitative relationship between the error and the variation of resolution and terrain roughness at a global level. Root mean square error (RMS Et) is regressed against surface profile curvature (V) and DEM resolution (R) at 10 resolution levels. It is found that the RMS Et may be expressed as RMS Et = (0.0061 × V+ 0.0052) × R - 0.022 × V + 0.2415. This result may be very useful in forecasting DEM accuracy, as well as in determining the DEM resolution related to the accuracy requirement of particular application.     

Anisotropy of the upper mantle in Chinese mainland and its vicinity

IntroductionAnisotropy is a universal phenomenon in the upper mantle. The mechanisms, which cause elastic anisotropy of in-situ rocks, include lattice preferred orientation of the minerals composing the rocks and preferred orientation of magma chambers. Lattice preferred orientation (LPO) of olivine is widely believed to be the dominant cause of the upper mantle anisotropy. The observational results of the upper mantle anisotropy can be explained by tectonic process relating to plate motion.…     

建筑物震害直接经济损失评定的误差分析

本文概述了引起震害损失评定误差的主要因素。通过实际震害评定资料，定量分析了震害损失评估中各因素形成误差数值的大小。采用以采样平均相对误差或采样均方误差及损失值相对误差来评估震害评定质量的方法，并通过分析给出综合衡量评定精度的量化指标，对震害经济损失评定准确度进行评估。     

空气动力学方法在湍流通量计算中的误差分析

采用迭代方法检验了在近地面层大气中使用空气动力学方法时，温度、湿度和风速梯度等观测误差对感热和潜热通量计算的相对误差，结果表明，在微风和低温环境中，空气动力学方法的使用受到限制。     

T63模式对暴雨短期预报能力的分析检验

利用Ｔ６３模式的５００ｈＰａ数值形势预报图和客观分析实况图，对１９９４年７－９月我国出现的１２次较大范围暴－大暴雨天气过程的影响天气系统进行了预报能力的分析检验，并分析了产生误差的原因，所得结果有利于数值预报产品的释用及实时预报业务。