机载LiDAR点云数据中电力线的提取方法研究

提出了一种基于机载LiDAR点云数据的电力线提取方法。首先在进行LiDAR数据滤波的基础上,分离地面点与非地面点;然后针对非地面点采取一种基于角度的滤波方法,分离非地面点中的植被点与电力线点,对电力线点,采用二维Hough变换进一步分离各条电力线点;最后使用双曲余弦函数模型,对单条电力线进行曲线拟合。实验结果表明,该方法能够从LiDAR点云数据中较完整地提取出电力线点,电力线点提取正确率达96.2%,并能够对电力线走廊进行三维重建。     

RESTORATION OF THE ORIGINAL TOPOGRAPHY OF THE XIAONANHAI LANDSLIDE IN CHONGQING AND CALCULATION OF ITS VOLUME

As documented in history, an M6¼ earthquake occurred between Qianjiang, Chongqing and Xianfeng, Hubei(also named the Daluba event)in 1856. This earthquake caused serious geological hazards, including a lot of landslides at Xiaonanhai, Wangdahai, Zhangshangjie and other places. Among them, the Xiaonanhai landslide is a gigantic one, which buried a village and blocked the river, creating a quake lake that has been preserved to this day. As the Xiaonanhai landslide is a historical earthquake-induced landslide, it is impossible to obtain the remote sensing image and DEM data before the earthquake, which brings certain difficulties to the estimation of landslide volume and the establishment of numerical simulation model. In this paper, the original topography before the earthquake is inferred by the methods of geomorphic analogy in adjacent areas and numerical simulation, and the volume of the Xiaonanhai landslide body is calculated. Firstly, the principle and application of UAV aerial photography are introduced. We employed an unmanned airplane to take pictures of the Xiaonanhai landslide and adjacent areas, yielding high-precision DOM images(digital orthophoto graph)and DEM data which permit generating terrain contours with a 25m interval. We also used the method of intensive manual depth measurement in waters to obtain the DEM data of bottom topography of Xiaonanhai quake lake. Based on field investigations, and combining terrain contours and DOM images, we described the sizes and forms of each slump mass in detail. Secondly, considering that the internal and external dynamic geological processes of shaping landforms in the same place are basically the same, the landforms such as ridges and valleys are also basically similar. Therefore, combining with the surrounding topography and landform of the Xiaonanhai area, we used MATLAB software to reconstruct two possible original landform models before the landslide. The original topography presented by model A is a relatively gentle slope, with a slope of 40°~50°, and the original topography presented by model B is a very high and steep slope, with a slope of 70°~80°. Thirdly, Geostudio software is used to conduct numerical simulation analysis on the slope stability. The safety factor of slope stability and the scale of landslide are analyzed under the conditions of static stability, seismic dynamic response and seismic dynamic response considering topographic amplification effect. The results show that large landslide is more likely to occur in model B, which is more consistent with the reality. In order to verify the credibility of recovered DEM data of valley bottom topography, we visited the government of Qianjiang District, collected the drilling data of 11 boreholes in two survey lines of Xiaonanhai weir dam. It is verified that the recovered valley bottom elevation is basically consistent with that revealed by the borehole data. Finally, according to the two kinds of topographic data before and after the landslide, the volume of the landslide is calculated by using the filling and excavation analysis function of ArcGIS software. There is a gap between the calculation results of filling and excavation, the filling data is 3×10⁶m³ larger than the excavation data. The reasons are mainly as follows: 1)Due to the disorderly accumulation of collapse blocks, the porosity of the accumulation body became larger, causing the volume of the fill to expand; 2)It has been more than 150a since the Xiaonanhai earthquake, and the landslide accumulation has been seriously reconstructed, therefore, there are some errors in the filling data; 3)The accumulation body in Xiaonanhai quake lake might be subject to erosion and siltation, this may affect the accuracy of the filling data. In conclusion, it is considered that the calculated results of the excavation are relatively reliable, with a volume of 4.3×10⁷m³.     

Velocity and concentration profiles of particle movement in sheet flows

Sheet flows occur widely in natural free-surface flows including rivers in flood, tidal estuaries and coastal waters in storm conditions when bed shear stress becomes sufficiently high. Particle volumetric concentration in sheet flows normally follows a linear distribution with the Rouse [Rouse H. Modern conceptions of the mechanics of fluid turbulence. Trans ASCE, 1937;102:463–543] distribution applicable in the dilute water column above the sheet-flow layer. However, a well-verified formula for determining particle velocity distribution in sheet flows is still lacking. This paper presents formulas to describe the particle velocity profile in steady or oscillatory sheet flows. They compare well with measured data. In particular, the novel formula for determining the particle velocity at the top of bedload–sediment-dominated sublayer in sheet flows is also well verified with measured data.     

基于高精度地层倾角线性反演的地震全体积拉平方法

地震数据的拉平分析是三维地震资料解释中的常见方法,一般通过拾取某一标准层位并将其校正到一个基准面的方式拉平地震数据,这样会导致距离标准层越远的层位拉平效果越差.近几年发展起来的三维地震数据全体积拉平方法是避免这种拉平缺陷的有效途径.本文提出一种基于高精度地层倾角的全体积自动拉平方法,该方法将一种自适应加权的向量滤波法获得高精度的局部地层倾角作为观测数据,根据拉平变换对每个数据样点产生的垂向偏移量与地层倾角之间的近似线性关系,建立最小二乘反演机制.在优化反演模型时,引入由梯度结构张量法得到的误差控制模板,抑制断层等复杂地质构造对拉平效果的影响;此外,增加模型参数的平滑度量项,避免拉平后的数据出现较大的畸变,并采用模型重新参数化方法,加快反演算法的收敛速度.三维合成数据和实际地震资料的试算结果表明这种三维全体积拉平方法是有效和可行的.     

地震序列的有序样品聚类方法研究

在应用最优分割法对地震活动性分类研究的基础上引进线性模型，扩大最优分割法在地震活动性分类中的应用范围，并将聚类问题与建模问题有机地结合起来，以揭示地震活动的某种内在规律，这对于探索地震预报和地震的发生规律有一定实际意义。     

二维线性流变体波的有限元模拟

用加里津方法推导了二维线性流变体内波传播的有限元方程，方程内包含了边界项，使得处理人工边界影响有较好的结果．同时考虑了其它一些因素，例如，吸收介质、爆炸源、自激自收等．实例表明，作者在仿真性方面的努力是成功的，计算的垂直地震剖面理论地震图质量比较好，结果也显示了地表低速层对地表水平记录剖面的干扰．     

Scattering of internal waves in a two-layer fluid flowing through a channel with small undulations

Using two-dimensional linear water wave theory, we consider the problem of normal water wave (internal wave) propagation over small undulations in a channel flow consisting of a two-layer fluid in which the upper layer is bounded by a fixed wall, an approximation to the free surface, and the lower one is bounded by a bottom surface that has small undulations. The effects of surface tension at the surface of separation is neglected. Assuming irrotational motion, a perturbation analysis is employed to calculate the first-order corrections to the velocity potentials in the two-layer fluid by using Green’s integral theorem in a suitable manner and the reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom undulation. Two special forms of the shape function are considered for which explicit expressions for reflection and transmission coefficients are evaluated. For the specific case of a patch of sinusoidal ripples having the same wave number throughout, the reflection coefficient up to the first order is an oscillatory function in the quotient of twice the interface wave number and the ripple wave number. When this quotient approaches one, the theory predicts a resonant interaction between the bed and the interface, and the reflection coefficient becomes a multiple of the number of ripples. High reflection of the incident wave energy occurs if this number is large. Again, when a patch of sinusoidal ripples having two different wave numbers for two consecutive stretches is considered, the interaction between the bed and the interface near resonance attains in the neighborhood of two (singular) points along the x-axis (when the ripple wave number of the bottom undulation become approximately twice as large as the interface wave number). The theoretical observations are presented in graphical form.     

非纵观测系统地震测深资料分析处理的人机对话过程

本文在三维壳幔结构中两点射线追踪分步搜索算法的基础上,在物探中心地震方法研究室ＳＵＮ工作站上研究开发出可应用于非纵观测系统深地震测深资料人机对话三维分析处理的方法及软件。对研究区域的三角形剖分减少了人机对话过程中的工作量及人为干预,并用该方法以反演得到的华北块状模型作为初始模型,对该模型的剩余ＰｍＰ波残差进行了人机对话拟合。     

线阵探测器(LDA)的现状及发展趋势

本文概述了当前的线阵探测器(LDA)技术及未来发展，同时详细说明了LDA的重要性能特征，并对不同应用下不同的阵列设计进行了讨论。目前芬兰探测技术公司已将该项技术成功应用于大型集装箱检测系统，工业CT，医用CT，L型双能探测器等工业医学应用中．     

A statistical assessment of the uncertainty in a 3-D geological framework model

Three-dimensional framework models are the state of the art to present geologists’ understanding of a region in a form that can be used to support planning and decision making. However, there is little information on the uncertainty of such framework models. This paper reports an experiment in which five geologists each produced a framework model of a single region in the east of England. Each modeller was provided with a unique set of borehole observations from which to make their model. Each set was made by withholding five unique validation boreholes from the set of all available boreholes. The models could then be compared with the validation observations. There was no significant between-modeller source of variation in framework model error. There was no evidence of systematic bias in the modelled depth for any unit, and a statistically significant but small tendency for the mean error to increase with depth below the surface. The confidence interval for the predicted height of a surface at a point ranged from ±5.6 m to ±6.4 m. There was some evidence that the variance of the model error increased with depth, but no evidence that it differed between modellers or varied with the number of close-neighbouring boreholes or distance to the outcrop. These results are specific to the area that has been modelled, with relatively simple geology, and reflect the relatively dense set of boreholes available for modelling. The method should be applied under a range of conditions to derive more general conclusions.