Statistical regression applied to borehole strain measurements data analysis

Summary In mining and geotechnical engineering, it is usually necessary to carry out field measurements in order to obtain information. Parameters are often measured indirectly and calculated based on certain relationships to the measured quantities. More often, the number of measurements taken is greater than the minimum required, in order to increase the reliability of results. However, some data points are less reliable than others for reasons such as measurement errors; a solution which best fits the measurement data is obtained accordingly. As a result, there is a residual or a difference between the individual quantities measured and those predicted from the best-fit solution. This brings about a question of how big a residual is acceptable for a solution to be reliable. It is also important to know whether the data point with the largest residual is the most erroneous, whether those data points with large residuals should be deleted and how many of them should be deleted. Standard deviation may provide a measure of the data divergence but it is questionable if this parameter can be used as a measure of the reliability of solution. In order to solve these problems, the author has done extensive study in this area, especially as part of geotechnical data analysis. In this paper, the statistical multiple regression method is introduced to analyse the measurement data. The method is applied to the analysis ofin situ stress measurement and can be easily adopted to analyse data from other field measurements and laboratory tests. An example is included which illustrates the analysis procedure and shows the advantages of the method.     

北斗系统精密卫星钟差精度评价

针对目前北斗卫星导航系统尚未形成统一的事后轨道和钟差产品的现状,该文提出了一种较为全面的北斗卫星导航系统精密卫星钟差精度评价方法,从钟差拟合残差标准差和天跳变等方面对北斗系统事后精密卫星钟差的精度进行了评价。使用相同方法对2013年全年、2014年上半年的北斗系统精密卫星钟差产品进行了评价,以此来分析定轨策略调整对卫星钟差的影响。结果表明,武汉大学分析中心解算的北斗系统精密卫星钟差产品的精度为分米级,大部分卫星的钟差精度优于0.2m,且定轨策略调整后倾斜地球同步轨道/中地球轨道卫星钟差产品的精度有小幅度提升;定轨策略调整前卫星钟差天跳变在0.2~0.5m间,但是调整后钟差天跳变显著增大,变化范围为2~3m,建议在实际应用中对其加以慎重处理。     

Robust methods for assessing the accuracy of linear interpolated DEM

Methods for assessing the accuracy of a digital elevation model (DEM) with emphasis on robust methods have been studied in this paper. Based on the squared DEM residual population generated by the bi-linear interpolation method, three average-error statistics including (a) mean, (b) median, and (c) M-estimator are thoroughly investigated for measuring the interpolated DEM accuracy. Correspondingly, their confidence intervals are also constructed for each average error statistic to further evaluate the DEM quality. The first method mainly utilizes the student distribution while the second and third are derived from the robust theories. These innovative robust methods possess the capability of counteracting the outlier effects or even the skew distributed residuals in DEM accuracy assessment. Experimental studies using Monte Carlo simulation have commendably investigated the asymptotic convergence behavior of confidence intervals constructed by these three methods with the increase of sample size. It is demonstrated that the robust methods can produce more reliable DEM accuracy assessment results compared with those by the classical t-distribution-based method. Consequently, these proposed robust methods are strongly recommended for assessing DEM accuracy, particularly for those cases where the DEM residual population is evidently non-normal or heavily contaminated with outliers.     

多点支撑托管架支撑下的海洋管道铺设中的静力分析

本文以实际工程中点支撑托管架支撑下的海洋管道为分析对象,采用Ｂ样条函数分段拟合了从张紧器到海床间整段管道在铺设时的空间曲线,利用样条函数配点法求解管道的平衡微分方程,得到了管道在铺设过程中所必须的数据。本方法适用性好,理论简明,求解快,精度高。     

Application of teleseismic tomography to the study of shallow structure beneath Shizigou in the western Qaidam basin

Teleseismic body wave traveltime tomography is used to inverse the three-dimensional seismic velocity structure beneath Shizigou in the western Qaidam basin.The travel time are picked from the continuous observation data on a small seismic array of stations deployed during 2004-2007.The tomographic results obtained indicate that a NW-trending low velocity anomaly just beneath the target region insert northeastwards with a high dip angle.In the north, northeast and east of the low velocity anomaly, some high...     

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建立华北及西北地区垂线变化试验监测网的意义和可行性

本文介绍了天文时间和纬度观测资料的残差值在天体测量仪器周围一定范围内的地震发生前夕出现短期异常波动的现象,及不同地区天体测量仪器的观测残差与地震关系的特征,认为地方铅垂线的震前异常变化是造成天文时纬观测资料的残差值出现异常波动的主要原因.相关的研究结果曾两次获得中国科学院科技进步奖.本文还论述了该现象发展成为有效的短期地震前兆的可能性和目前该研究面临的情况,及利用天体测量仪器监测垂线变化及对其开展深入研究的意义.讨论了利用一定数量的天体测量仪器组建试验观测网对认识什么构造区带上的什么类型的地震更容易使处于何种构造区带上的时纬仪器提前出现残差异常,异常特征和时间提前量出现差别的主要原因是什么,异常与地震三要素的定量或半定量的关系,以及优化观测和提取有效信息的方法的必要性.讨论了组建观测网所需观测仪器的性能,简要介绍了中国科学院国家天文台与山东科技大学测绘学院合作试制的新仪器的特征.再次提出了在多震的华北、西北地区组建试验观测网的建议,讨论了组网的意义、可行性和有关问题.     

精密单点定位的可靠性研究

从传统最小二乘的可靠性理论出发,推导了卡尔曼滤波观测方程和预计状态向量的可靠性理论,并与传统多余观测分量的可靠性进行比较。结果表明,两种方案的观测方程的内部可靠性不仅与观测值的精度有关,还与卫星几何结构和卫星高度角有关。卡尔曼滤波的预计状态向量的内部可靠性比观测方程的内部可靠性更易受卫星几何结构的影响。虽然两种方案的外部可靠性在收敛之后都在mm级,但伪距的收敛速度要快于载波相位。     

相位单差残差评估北斗区域导航系统载波相位观测量质量

由于北斗区域导航系统采用混合星座设计,其不同类型卫星载波相位观测量的质量得到广泛关注。当基线较短且模糊度正确固定后,卫星残差信息可有效反映观测数据质量。本文采用优化的站际单差算法获取不同卫星单差残差序列,并对其进行统计分析与假设检验。结果表明,北斗GEO与IGSO卫星数据质量无系统性差异,其质量随卫星高度角的降低而明显变差。良好环境下,GEO与IGSO卫星相位单差残差基本服从正态分布,可依据卫星高度角等信号质量指标建立合适的随机模型。