普适型GPS用于黄河盐锅峡水位监测分析

黄河水文变化复杂,现有水位监测方法费时费力且不能很好满足时间分辨率和空间分辨率两个方面的需求.地基GPS-IR技术的出现为水位监测提供了新的手段,但目前大多数地基GPS-IR技术采用的接收机为高精度大地测量型接收机,成本高、时效性差,不适合大范围推广.首先介绍了普适型GPS接收机的组成,并对GPS数据观测质量进行了分析;其次给出了地基GPS-IR技术用于水位监测的基本原理;最后利用黄河盐锅峡GPS实测数据进行GPS-IR水位提取,以兰州水文站水位监测数据为参考分析了普适型GPS接收机反演水位的精度,得到了最佳RMSE为0.21 m的精度.实验结果表明,普适型GPS接收机可用于长时间水位监测.     

Poynting and polarization vectors based wavefield decomposition and their application on elastic reverse time migration in 2D transversely isotropic media

With the progress in computational power and seismic acquisition, elastic reverse time migration is becoming increasingly feasible and helpful in characterizing the physical properties of subsurface structures. To achieve high-resolution seismic imaging using elastic reverse time migration, it is necessary to separate the compressional (P-wave) and shear (S-wave) waves for both isotropic and anisotropic media. In elastic isotropic media, the conventional method for wave-mode separation is to use the divergence and curl operators. However, in anisotropic media, the polarization direction of P waves is not exactly parallel to the direction of wave propagation. Also, the polarization direction of S-waves is not totally perpendicular to the direction of wave propagation. For this reason, the conventional divergence and curl operators show poor performance in anisotropic media. Moreover, conventional methods only perform well in the space domain of regular grids, and they are not suitable for elastic numerical simulation algorithms based on non-regular grids. Besides, these methods distort the original wavefield by taking spatial derivatives. In this case, a new anisotropic wave-mode separation scheme is developed using Poynting vectors. This scheme can be performed in the angle domain by constructing the relationship between group and polarization angles of different wave modes. Also, it is performed pointwise, independent of adjacent space points, suitable for parallel computing. Moreover, there is no need to correct the changes in phase and amplitude caused by the derivative operators. By using this scheme, the anisotropic elastic reverse time migration is more efficiently performed on the unstructured mesh. The effectiveness of our scheme is verified by several numerical examples.     

Physical modelling and numerical analysis of slope instability subjected to reservoir impoundment of the Three Gorges

Increasing attention is being given to investigations of failure mechanisms of unstable slopes influenced by water fluctuation during impoundment, such as in the case of reservoir landslides surrounding the Three Gorges, China. In this paper, two typical soil slopes with thin and thick rear edges are considered in a systematic investigation of the large-scale landslides triggered by reservoir impoundment. Physical model test, centrifugal modelling and numerical analysis are presented; these show the deformation evolution process and are aimed at obtaining the physical and mechanical laws that govern deformation and failure of such typical slopes during increasing water levels in a reservoir. The results indicate that deformation of the soil slopes triggered by impoundment can be divided into three stages: the rapid deformation stage, the slow development stage and the convergence creep stage. Moreover, deformation increases rapidly in the initial water level increase, and deformation growth slows with continued increase in water levels. Although the failure modes of the two typical slopes were not identical, the deformation in both started when soil softening occurred, suggesting that the initial phase of water level rise is likely the most dangerous phase with respect to soil slope stability. The results are likely to provide a foundation for further disaster mechanism studies, as well as disaster prevention and reinforcement design of reservoir soil slopes.     

Estimation of Blast-Induced Air Overpressure in Quarry Mines Using Cubist-Based Genetic Algorithm

In the present work, blast-induced air overpressure is estimated by an innovative intelligence system based on the cubist algorithm (CA) and genetic algorithm (GA) with high accuracy, called GA–CA model. Herein, CA initialization model was developed first and the hyper-parameters of the CA model were selected randomly. Subsequently, the GA procedure was applied to perform a global search for the optimized values of the hyper-factors of the CA model. Root-mean-square error (RMSE) is utilized as a compatibility function to determine the optimal CA model with the lowest RMSE. Gaussian process (GP), conditional inference tree (CIT), principal component analysis (PCA), hybrid neural fuzzy inference system (HYFIS) and k-nearest neighbor (k-NN) models are also developed as the benchmark models in order to compare and analyze the quality of the proposed GA–CA algorithm; 164 blasting works were investigated at a quarry mine of Vietnam for this aim. The results revealed that GA significantly improved the performance of the CA model. Based on the statistical indices used for model assessment, the proposed GA–CA model was confirmed as the most superior model as compared to the other models (i.e., GP, CIT, HYFIS, PCA, k-NN). It can be applied as a robust soft computing tool for estimating blast-induced air overpressure.

     

GIS支持下计算格网自动生成技术

计算格网生成是流体力学数值模拟过程中的一项主要工作,以往普遍采用手工剖分方法,其结果对数值模拟产生很大影响。将地理信息系统(GIS)技术引入格网生成过程,利用计算机自动生成计算格网,并在此基础上讨论了以GIS为主控过程的集成数值模拟环境及其功能。     

Reverse‐time migration from rugged topography using irregular,unstructured mesh

We developed a reverse‐time migration scheme that can image regions with rugged topography without requiring any approximations by adopting an irregular, unstructured‐grid modelling scheme. This grid, which can accurately describe surface topography and interfaces between high‐velocity‐contrast regions, is generated by Delaunay triangulation combined with the centroidal Voronoi tessellation method. The grid sizes vary according to the migration velocities, resulting in significant reduction of the number of discretized nodes compared with the number of nodes in the conventional regular‐grid scheme, particularly in the case wherein high near‐surface velocities exist. Moreover, the time sampling rate can be reduced substantially. The grid method, together with the irregular perfectly matched layer absorbing boundary condition, enables the proposed scheme to image regions of interest using curved artificial boundaries with fewer discretized nodes. We tested the proposed scheme using the 2D SEG Foothill synthetic dataset.     

Prediction of Blast-Induced Ground Vibration in Open-Pit Mines Using a New Technique Based on Imperialist Competitive Algorithm and M5Rules

Natural Resources Research - In this paper, blast-induced ground vibration (BIGV) was considered as the primary objective, and a new artificial intelligence system was proposed to predict BIGV with...     

基于神经网络方法的不确定非线性微分-代数子系统的鲁棒反推镇定控制

对于指数1且关联可测的不确定非线性微分-代数子系统,将反推方法和神经网络相结合,研究了其鲁棒渐近镇定控制问题.基于反推方法来构造镇定控制器,利用3层的神经网络来逼近每一步控制器构造过程中的不确定项.提出一种新的自适应算法对神经网络权值进行在线调节,并适当选取每一步虚拟控制器的参数,最终得到的控制器使得闭环系统是渐近稳定的.