随机误差传递与合成的蒙特卡罗模拟

对分析测试过程中随机误差的传递与合成进行了蒙卡罗模拟，并偏制了ＢＡＳＩＣ程序。该方法解决了当被合成误差不相互独立时泰勒级数公式所遇到的困难，当被合成误差相互独立时，与泰勒公式计算结果一致。     

Robust algorithms for polyhedral modelling of fractured rock mass structure

This paper presents robust algorithms for application in polyhedral modelling of rock mass structure based on discrete fracture networks. The algorithms improve the robustness of current polyhedral modellers to challenging or degenerate geometries and geometrical errors. These issues are inevitably encountered when the fracture network realisations incorporate large numbers of fractures, or regions of densely packed fractures are modelled, or when the number of fracture network realisations interrogated is large. Several stages in the polyhedral modelling process which are sensitive to geometrical errors are reviewed and algorithms which are robust and capable of handling topological errors in the input fracture network geometry are presented.     

Application of universal kriging for estimation of earthquake ground motion: Statistical significance of results

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).     

On the calculation of mean-weighted value in astronomy

Although the calculation of the weighted mean of several individual values (one of the most frequently used operations in scientific analysis) is straightforward, the calculation of the corresponding uncertainty does not always receive the attention it requires. The application of methods of classical statistics to real observational data is often not justified, since the assumptions lying at the basis of these methods are not satisfied. The presence of systematic uncertainties in the averaged measurements and underestimation of the corresponding random errors used to define the weights are typical examples. A new approach to calculating the uncertainty of weighted mean based on a combination of known methods is considered. The proposed method makes it possible to automatically take into account both the random errors and scatter of the input data, making the method suitable for determining realistic errors for mean values in the case of observational data displaying both good and poor consistency.     

Quantitative Control of Migration: A Geostatistical Attempt

This paper is devoted to a geostatistical attempt at modeling migration errors when localizing a reflector in the ground. Starting with a probabilistic velocity model and choosing the simple geometrical optics background for the wave propagation in such media, we give the expression of the errors. This may be quantified provided the covariance of the velocity field is known. Variance of arrival times at constant offset is related to the covariance of the velocity field at hand. A practical application is given in the same paragraph. After that we give a typical schema for migration and uncertainty modeling: starting with seismic data, we make the weak seismic inversion. We then obtain the covariance of the velocity field that we use for simulating migration errors. The main issues of this methodology are discussed in the last paragraph.     

Application of dynamic parameters for recording during acoustic profiling

The possibilities for the application of dynamic parameters of acoustic records (amplitude, reflection polarity, and frequency composition) for identifying the lithology of deposits and their physical properties, as well as their gas saturation, are discussed. Using examples of different field measurements it is shown that application of the dynamic parameters of acoustic records during interpretation allowed us in some cases to understand in detail the physical nature of visually recognized acoustic anomalies, while in other cases it provided grounds for a different interpretation of the data, and in some cases even permitted correction of errors of visual interpretation of time sections.     

Bayesian methods applied to the interpretation of multiple OSL dates: high precision sediment ages from Old Scatness Broch excavations,Shetland Isles

In this paper, we illustrate the ways in which Bayesian statistical techniques may be used to enhance chronological resolution when applied to a series of OSL sediment dates. Such application can achieve an optimal chronological model by incorporating stratigraphic and age information. The application to luminescence data is not straightforward owing to the sources of uncertainty in each date, and here we present one solution to overcoming these difficulties, and introduce the concept of “unshared systematic” errors. Using OSL sediment dates from the site of Old Scatness Broch, Shetland Isles, UK, many measured with a high degree of precision, we illustrate some of the ways in which Bayesian techniques may be applied, as a tool for assessing systematic errors when combined with independent chronological information, and to determine the optimum chronological information for specific events and contexts. We provide a detailed procedure for the application of Bayesian methods to OSL dates using the widely available radiocarbon calibration programme OxCal.     

The influence of systematically incomplete shallow landslide inventories on statistical susceptibility models and suggestions for improvements

Complete landslide inventories are rarely available. The objectives of this study were to (i) elaborate the influence of incomplete landslide inventories on statistical landslide susceptibility models and to (ii) propose suitable modelling strategies that can reduce the effects of inventory-based incompleteness. In this context, we examined whether the application of a novel statistical approach, namely mixed-effects models, enables predictions that are less influenced by such inventory-based errors.The study was conducted for (i) an area located in eastern Austria and (ii) a synthetically generated data set. The applied methodology consisted of a simulation of two different inventory-based biases and an in-depth evaluation of subsequent modelling results. Inventory-based errors were simulated by gradually removing landslide data within forests and selected municipalities. The resulting differently biased inventories were introduced into logistic regression models while we considered the effects of including or excluding predictors that are directly related to the respective inventory-based bias. Mixed-effects logistic regression was used to account for variation that was due to an inventory-based incompleteness.The results show that most erroneous predictions, but highest predictive performances, were obtained from models generated with highly incomplete inventories and predictors that were able to directly describe the respective incompleteness. An exclusion of such bias-describing predictors led to systematically confounded relationships. The application of mixed-effects models proved valuable to produce predictions that were least affected by inventory-based errors.This paper highlights that the degree of inventory-based incompleteness is only one of several aspects that determine how an inventory-based bias may propagate into the final results. We propose a four-step procedure to deal with incomplete inventories in the context of statistical landslide susceptibility modelling.     

固结不排水剪总应力强度指标的几点讨论

建立了偏离室内常规三轴压缩试验应力条件下的总应力强度指标和有效固结压力强度指标的理论公式;讨论了这两种强度指标的变化规律及其与室内常规CU试验指标的差异;简要地分析了直接将室内常规CU试验指标用于压缩与伸长土单元的强度计算、用于有效固结压力法确定抗剪强度和用于土压力与地基极限承载力计算时的偏差情况。     

Solution of the transfer equation in a moving medium

The integral transfer equation for resonance radiation in a semi-infinite medium expanding with a constant velocity gradient is considered. A method for the numerical-analytical solution of this problem is presented, together with an estimation of the associated errors. This method is based on a discretization in optical depth and the application of non-linear equation factorization equations.     

GIS空间数据的质量探讨

空间数据直接影响着GIS应用分析结果的可靠程度和应用目标的真正实现,因此,有效地控制空间数据的质量是非常必要的。该文结合山东省1：1万基础地理信息数据采集与建库实践,分析了空间数据质量问题的来源及影响,根据空间数据质量标准,采用软件检查和人机交互检查2种方法,制定各工序相应的检查方案,以减少误差,防止粗差。     

一种测量断裂构造信息维的方法及其应用

基于分形理论,提出了一种快速测量单区和多区断裂构造信息维的方法。按直线、正方形、Koch曲线及Sierpinski垫片4种图形的测量结果,信息维测量值与其理论值之间最大的相对误差绝对值仅为0.5%,表明采用该方法测量出的信息维具有较高的可靠性和准确度。在某火山岩型铀矿田开展了该方法的应用试验。该铀矿田内有超过92%的铀矿床均位于断裂信息维大于1.24的区域内,说明断裂构造信息维越大,越有利于火山岩型铀矿成矿,从而为建立新的铀矿预测标志提供了新的思路和方法。     

工程地质类比分析的扩展及实现方法

本文借助于计算机技术,将传统的工程地质类比方法作了扩展,称之为工程地质类比系统。根据地质体复杂多样的特点,提出了不追求概括出一般知识和它的应用,而是从每个个体的特征类比入手,把成功的经验、失利的教训应用到研究对象中去的模型及实现方法,它的应用能避免其它评价方法对条件的过于简化而产生的偏差,还能有助于发掘出隐含在地质体内还不被认识的有用信息,并加以利用。初步应用表明,该方法具有良好的适用性和发展前景。     

Entropy-Based Weighting in One-Dimensional Multiple Errors Analysis of Geological Contacts to Model Geological Structure

In each step of geological modeling, errors have an impact on measurements and workflow processes and, so, have consequences that challenge accurate three-dimensional geological modeling. In the context of classical error theory, for now, only spatial positional error is considered, acknowledging that temporal, attribute, and ontological errors—and many others—are part of the complete error budget. Existing methods usually assumed that a single error distribution (Gaussian) exists across all kinds of spatial data. Yet, across, and even within, different kinds of raw data (such as borehole logs, user-defined geological sections, and geological maps), different types of positional error distributions may exist. Most statistical methods make a priori assumptions about error distributions that impact their explanatory power. Consequently, analyzing errors in multi-source and conflated data for geological modeling remains a grand challenge in geological modeling. In this study, a novel approach is presented regarding the analysis of one-dimensional multiple errors in the raw data used for model geological structures. The analysis is based on the relationship between spatial error distributions and different geological attributes. By assuming that the contact points of a geological subsurface are decided by the geological attributes related to both sides of the subsurface, this assumption means that the spatial error of geological contacts can be transferred into specific probabilities of all the related geological attributes at each three-dimensional point, which is termed the “geological attribute probability”. Both a normal distribution and a continuous uniform distribution were transferred into geological attribute probabilities, allowing different kinds of spatial error distributions to be summed directly after the transformation. On cross-points with multiple raw data with errors that follow different kinds of distributions, an entropy-based weight was given to each type of data to calculate the final probabilities. The weighting value at each point in space is decided by the related geological attribute probabilities. In a test application that accounted for the best estimates of geological contacts, the experimental results showed the following: (1) for line segments, the band shape of geological attribute probabilities matched that of existing error models; and (2) the geological attribute probabilities directly show the error distribution and are an effective way of describing multiple error distributions among the input data.

     

数字化地质中的误差校正

分析数字化过程中图形数据输入时引起误差的原因,说明了误差校正的原理,通过几何变换、最小二乘法线性校正、分块校正等方法对图形数据进行校正,经过仿射变换、双线性变换、平方变换、双平方变换、立方变换、四阶多项式变换等对图像进行校准。实践表明MAPGIS提供的误差较正功能模块进行图形校正,在地质图件的应用中效果很好。     

The use of post-earthquake residual displacements as a performance indicator in seismic assessment

A new post-earthquake seismic performance assessment method for structures which takes into account residual displacements is proposed. The post-earthquake residual displacements and the observable damage to the structure are considered to obtain improved estimates of the maximum deformations that took place during the earthquake. The improved estimates of the maximum deformations are expected to yield a better picture of the extent of damage to the structure. As a result, better informed decisions regarding the post-earthquake usability and repairability of the structure can be taken. Both the uncertainties associated with the structural properties and the probable errors owing to the imperfectness of the analytical models are considered in the proposed method. A trial application of the method to a real structure tested on a shaking table is presented.     

Control-Volume Discretization Method for Quadrilateral Grids with Faults and Local Refinements

This paper extends the multipoint flux-approximation (MPFA) control-volume method to quadrilateral grids for which the adjacent cells do not necessarily share corners. Examples are grids with faults and locally refined grids. This paper gives a derivation of the method for such grids. The difference between two-point flux-approximation (TPFA) results and MPFA results for faults and local grid refinements is demonstrated for synthetic problems. Further, the results are compared with results from uniform fine-grid simulations. The effect of repeated fault patterns as well as anisotropy is investigated. Large errors may be found for the TPFA method for flow through a series of faults in an anisotropic medium. Finally, a comparison is done for a reservoir field application.     

GPS卫星星历对测站及基线精度的影响

通过采用高精度的数据处理软件gamit/globk对观测数据的认真分析处理,对比广播星历与精密星历对测站LC相位残差的影响,认为在相同条件下同一测站相同时间的广播星历轨道误差比采用精密星历时要大1.5～27.2mm,这一差值与测站含有短基线数目及短基线的长度有一定的关系;同时通过采用双频差分技术处理数据后,对于长度在300km以内的基线,采用广播星历时的基线误差在5～8mm之间,采用精密星历时基线误差在3.2～6.8mm之间,基线误差互差在1.2～1.8mm之间。通过实例分析后认为基线长度在300km范围内广播星历与精密星历具有相当的解算效果。较前人[1～6]提出的100km适用基线长度大幅度提高,究其原因主要是选用了高精度的数据处理分析软件,同时采用了较高精度的初始坐标、合适的约束条件、观测数据有效组合和各项误差改正模型。     

边坡稳定离心模型试验中离心力分布不均匀的影响

边坡稳定离心模型试验中离心力分布不均匀会给试验结果带来误差。本文用圆弧滑动计算法探讨了这种误差的大小、影响因素及变化规律，提出了减少误差的措施。     

测井解释最优化方法中的误差和约束条件

最优化技术是目前国内外进行岩生分析和煤层分析中技术较先进，应用效果较发了的一种方法，,煤田测井的CASSAY程序所采用了最优化方法，其目标函数中引入了误差和约束项，但由于煤田测井方法的特点以及其数字，物理和地质意义不明确，给实际应用该程度带来许多困难，当解释模型确定后，测量误差，响应方程误差和约束误差的取值是最优化结果的关键。本文将就煤田测井解释的最优化方法中有关的误差，误差取值，约束条件和约束误差进行讨论，并给出适合于煤田测井的民化解释流程。