基于VirtuoZo全数字摄影测量系统的无人机遥感数据后处理

针对无人机遥感数据特点,介绍了利用VirtuoZo全数字摄影测量系统和PATB平差软件进行空三加密及制作数字高程模型DEM以及数字正射影像DOM的无人机影像数据后处理方法。     

采用数据可听化的地形剖面线分析方法

提出一种使用音高和时值对沿分水线布设的地形剖面线进行分析的方法.以5 m分辨率的数字高程模型(DEM)数据为基础,选取神木县、绥德县、延川县、富县县、宜君县、淳化县等6个典型研究样区,并选择安塞样区对实验结果进行验证.研究结果表明:6个样区分水线剖面线的声音指标存在差异,其声音模式与实际地貌类型存在明显的对应关系;7个声音指标可以直接进行地貌类型的区分,安塞与绥德样区地貌类型最接近,欧式距离为最小值48.456.说明声音指标可以用来分析分水线剖面线特征,比单一的高程信息蕴涵更多的地形起伏、转折信息,可以从乐理角度整体刻画地貌类型.     

Development and validation of SuperDEM for non-spherical particulate systems using a superquadric particle method

This article presents the development and validation of the Superquadric Discrete Element Method (SuperDEM) for non-spherical particle simulation using a superquadric particle method in open-source CFD suite MFiX. A superquadric particle–particle contact algorithm with accelerating and stabilizing strategy was developed. A superquadric particle–arbitrary wall contact algorithm was developed, which enables the simulation in complex geometry. The solver was validated by comparing with experimental data generated in this study or available in the literature. Tests include cylinder contacting with a wall, static packing of M&M chocolate candies in a cylindrical container, static packing of cylinders in a cylindrical container, dynamic angle of repose of cylinders in a rotating drum, and discharging of chocolate candies from a hopper. Besides, MPI parallelization of the solver was implemented and the parallel performance of the solver using MPI was assessed through large-scale simulations of 1 million, 10 million, and 100 million particles on up to 6800 cores, which demonstrates that the SuperDEM solver has great potential for industrial-scale systems simulation.     

DEM investigation of mixing indices in a ribbon mixer

Mixing index is an important parameter to understand and assess the mixing state in various mixers including ribbon mixers, the typical food processing devices. Many mixing indices based on either sample variance methods or non-sample variance methods have been proposed and used in the past, however, they were not well compared in the literature to evaluate their accuracy of assessing the final mixing state. In this study, discrete element method (DEM) modelling is used to investigate and compare the accuracy of these mixing indices for mixing of uniform particles in a horizontal cylindrical ribbon mixer. The sample variance methods for mixing indices are first compared both at particle- and macro-scale levels. In addition, non-sample variance methods, namely entropy and non-sampling indices are compared against the results from the sample variance methods. The simulation results indicate that, among the indices considered in this study, Lacey index shows the most accurate results. The Lacey index is regarded to be the most suitable mixing index to evaluate the steady-state mixing state of the ribbon mixer in the real-time (or without stopping the impeller) at both the particle- and macro-scale levels. The study is useful for the selection of a proper mixing index for a specific mixture in a given mixer.     

基于ARCINFO及ERDAS的地形景观图的制作--以西安市浐灞生态区为例

以西安市浐灞生态区为例，利用1：1万地形图在ARCINFO中构建DEM，采用QUCKBIRD影像制作的正射影像作为三维表面的纹理信息．详细叙述了该项目中DEM构建及遥感影像处理的流程方法，包括：矢量化、拓扑关系、构建DEM、波段组合、影像增强、几何校正、图像拼接、投影变换、去箍处理以及三维地形景观图的生成．三维地形景观图是一种由基础测绘数字产品相互结合的专题地图产品，并对三维地形景观图的应用前景作了展望．     

三峡地区地貌演化模拟

为揭示三峡地区地貌演化过程,利用GIS技术,基于DEM,建立起了地貌演化模型,提出了一种可形象直观地进行地貌演化模拟的方法,形象再现了50×104a前三峡地区的地貌形态,并对50×104a以来三峡地区地貌演化进行了过程模拟,结果表明50×104a以来,中部抬升幅度最大.     

An entropy-based filtering approach for airborne laser scanning data

Parameter-tuning is a challenging task when generating digital terrain models from airborne laser scanning (light detection and ranging, LiDAR) data. To address this issue, this paper presents a filtering method for near-infrared laser scanning data that exploits the principle of entropy maximization as the optimization objective. The proposed approach generates ground elevation of point cloud by constructing a triangulated irregular network, calculates the entropy of the elevation from different parts, and automatically separates ground and non-ground points by the principle of entropy maximization. Experimental results from different ground surfaces show that the proposed entropy-based filtering method can effectively extract bare-earth points from the point cloud without adjusting thresholds.     

大区域地形三维可视化应用研究

“数字地球”概念的提出促进了地形三维可视化的快速发展,本文以大区域地形三维可视化为研究对象,详细阐述了三维可视化的研究意义,研究进展及应用领域,而后讨论了基于二叉树的大地形实时可视化算法,最后,笔者详细阐述了大区域三维可视化的发展方向。     

DEM地形复杂度对坡度提取的影响分析

引入分形理论中的信息维数值作为衡量地形复杂度的指标,讨论了DEM地形复杂度对坡度提取的影响。结果表明,信息维数值能够较好地反映不同区域的地形复杂度;信息维数值越大,地形就越复杂,坡度提取的精度也就越低。     

CFD–DEM simulation of the pneumatic conveying of fine particles through a horizontal slit

Fine particles play a significant role in many industrial processes. To study the dynamic behavior of fine particle and their deposition in rock fractures, the pneumatic conveying of fine particles (approximately 100 μm in diameter) through a small-scale horizontal slit (0.41 m × 0.025 m) was studied, which is useful for the sealing technology of underground gas drainage in coal mining production. The CFD–DEM method was adopted to model the gas-particle two-phase flow; the gas phase was treated as a continuum and modeled using computational fluid dynamics (CFD), particle motion and collisions were simulated using the DEM code. Then, the bulk movement of fine particles through a small-scale horizontal slit was explored numerically, and the flow patterns were further investigated by visual inspection. The simulation results indicated that stratified flow or dune flow can be observed at low gas velocities. For intermediate gas velocities, the flow patterns showed pulsation phenomena, and dune flow reappeared in the tail section. Moreover, periodic flow regimes with alternating thick and sparse stream structures were observed at a high gas velocity. The simulation results of the bulk movement of fine particles were in good agreement with the experimental findings, which were obtained by video-imaging experiments. Furthermore, the calculated pressure drop versus gas velocity profile was investigated and compared with relative experimental findings, and the results showed good agreement. Furthermore, the particle velocity vectors and voidage distribution were numerically simulated. Selected stimulation results are presented and provide a reference for the further study of fine particles.