Road impacts on spatial patterns of land use and landscape fragmentation in three parallel rivers region, Yunnan Province, China   总被引：1，自引：0，他引：1  

Jun Liang  Ye Liu  Lingxiao Ying  Peng Li  Yue Xu  Zehao Shen 《中国地理科学(英文版)》2014,24(1):15-27

The structure and function of network is a central issue in landscape ecology.Road networks with hierarchical structure are crucial for understanding landscape dynamics.In this study,we compared the distribution of national road,provincial road,county road and rural road in the Three Parallel Rivers Region(TPRR)in Yunnan Province of China,and estimated the effect of roads(and other factors)on the spatial patterns of land use and land cover with logistic regression.In addition,we analyzed the land use and land cover change(LUCC)and landscape fragmentation in 1989–2005 along a buffer zone of the primary traffic corridor,national road G214.The results showed that,county and rural roads had much higher percentage of length extending into more natural habitats at higher elevation and steeper slope,compared with the higher level roads in this region.While the distributions of natural land cover types were dominated by environmental factors,human land use types i.e.,building land and farmland types were significantly related with roads,linking more closely with lower level roads.The LUCC dynamics(1989–2005)of the G214 buffer zone showed a general trend of land transformation from conifer forests and valley arid shrubs to building land and farmland,and from ice and snow to alpine shrubs and forests.With the length of G214 unchanged during the time,the overall landscape pattern changed little in the buffer zone,but habitat fragmentation and area decrease had occurred for the natural vegetation types,in contrast to patch mergence and expansion of human land use types,and landscape fragmentation was intensified above 2500 m a.s.l.but declined below the elevation.The results indicated the dynamics of landscape composition and patch type level distribution in spite of the stability of the overall landscape pattern,and implied the potential role of roads,especially the low level roads on landscape changes.  相似文献   

Theoretical basis and numerical simulation of parallel seismic test for existing piles using flexural wave     

《Soil Dynamics and Earthquake Engineering》2016

This paper presents theoretical analysis of the parallel seismic (PS) method for evaluating existing piles using the flexural mode wave exited by a horizontal impact on the lateral surface of a pile. A simplified theoretical model of the flexural wave for PS method was established to elaborate the theoretical basis. A correction factor was then obtained and proposed to correct the pile depth obtained from the PS method, thus providing a more accurate estimation. A three dimension (3-D) finite element (FE) model was developed and the existence of the flexural waves on branch F(1, 1) in the pile shaft has been verified. Two time domain methods were used to calculate the flexural wave velocity in the pile. One was based on the pile tip reflection signal using a model where pile head reflection was minimized, and another method used the slope of the upper fitted line in the PS test. The flexural wave velocities from both methods match well with the predicted flexural wave group velocity determined from the dispersion curve of a 1-D rod embedded in the soil. The accuracy in estimation of pile tip depth is improved by applying the correction factor. A series of parametric studies were carried out to demonstrate the effectiveness of using flexural wave for PS test and the correction factor proposed in this study.  相似文献   

全球气候变化模拟结果数据的远程抽取及其可视化     

谭清海  邓春林  刘俊  单桂华  张怀 《地震》2013,33(4):153-161

本文针对气候模式在超大规模数值模拟中产生的Tb至Pb量级的四维体数据的可视化和分析诊断方法, 提出了基于Server-Client方式的远程数据抽取和并行可视化解决方案。 针对气候模拟数据中的海洋模式和大气模式数值模拟结果数据的抽取和可视化数值试验分析, 验证了解决方案的可行性和抽取算法的高效性、 可靠性和灵活性。 本文提出的远程数据抽取方法对于帮助气候模式领域中的专家快速抽取、 快速可视化和实现实时交互式模拟结果的诊断分析具有重要的应用价值。  相似文献   

大地电磁三维数据空间反演并行算法研究   总被引：6，自引：4，他引：2  

胡祥云  李焱  杨文采  魏文博  高锐  韩波  彭荣华 《地球物理学报》2012,55(12):3969-3978

目前大地电磁三维反演实际应用的主要问题是计算效率低.在对大地电磁三维数据空间反演算法进行深入分析的基础上,本文提出了基于频点和矩阵划分的大粒度并行反演方案和具体实现步骤,并在曙光TC5000A高性能计算平台上实现了基于MPI的大地电磁三维数据空间反演并行算法.该算法实现了包括三维正演、灵敏度矩阵、叉积矩阵以及模型改正量的并行执行,不仅计算效率高,而且每个节点机上灵敏度矩阵的存储空间只需原来微机上的2/N(N是参加并行计算的节点机个数),大大地减少了内存开销.通过两个理论模型合成的数据对实现的三维数据空间反演并行算法进行试算,对比分析了多个节点机下程序的执行效率.测试结果表明,所实现的三维数据空间反演并行算法是可行的、高效的,与单机相比,不仅可以提高运行速度,缩短计算时间,而且还可以扩大计算规模,极大地推动了大地电磁三维反演的实用化.  相似文献   

巷道超前探测的并行Monte Carlo方法及电阻率各向异性影响   总被引：1，自引：1，他引：0       下载免费PDF全文

刘洋  吴小平 《地球物理学报》2016,59(11):4297-4309

直流电阻率法通过观测单极-双极装置视电阻率曲线最小值位置估计掌子面前方低阻异常体距离,在巷道超前探测及矿井水害预测与防治工作中有广泛应用,并形成多种经验预测模型.本文基于直流电法巷道超前探测的各向异性电阻率三维有限元数值模拟,给出超前探线性预测模型.然而,实际井下地质结构复杂,异常大小不定且任意分布,而且可能存在有电阻率各向异性,使得目前由简单模型实验或数值模拟获得的预测公式不确定性较大,而且可靠性难于评价.Monte Carlo方法用随机化思想解决非确定性问题,我们将该方法与并行算法结合,对大量不确定的随机模型进行三维数值模拟,以验证各预测模型的准确度及可靠性.结果表明,本文的超前探线性预测模型较其他预测模型更为准确及可靠.但介质各向异性的影响很大,尤其当围岩电阻率具有各向异性时,所有预测模型的准确度及可靠性较差,给安全生产带来很大隐患.  相似文献   

Improved numerical solvers for implicit coupling of subsurface and overland flow     

《Advances in water resources》2014

Due to complex dynamics inherent in the physical models, numerical formulation of subsurface and overland flow coupling can be challenging to solve. ParFlow is a subsurface flow code that utilizes a structured grid discretization in order to benefit from fast and efficient structured solvers. Implicit coupling between subsurface and overland flow modes in ParFlow is obtained by prescribing an overland boundary condition at the top surface of the computational domain. This form of implicit coupling leads to the activation and deactivation of the overland boundary condition during simulations where ponding or drying events occur. This results in a discontinuity in the discrete system that can be challenging to resolve. Furthermore, the coupling relies on unstructured connectivities between the subsurface and surface components of the discrete system, which makes it challenging to use structured solvers to effectively capture the dynamics of the coupled flow. We present a formulation of the discretized algebraic system that enables the use of an analytic form of the Jacobian for the Newton–Krylov solver, while preserving the structured properties of the discretization. An effective multigrid preconditioner is extracted from the analytic Jacobian and used to precondition the Jacobian linear system solver. We compare the performance of the new solver against one that uses a finite difference approximation to the Jacobian within the Newton–Krylov approach, previously used in the literature. Numerical results explores the effectiveness of using the analytic Jacobian for the Newton–Krylov solver, and highlights the performance of the new preconditioner and its cost. The results indicate that the new solver is robust and generally outperforms the solver that is based on the finite difference approximation to the Jacobian, for problems where the overland boundary condition is activated and deactivated during the simulation. A parallel weak scaling study highlights the efficiency of the new solver.  相似文献   

Global SH-wavefield calculation for a two-dimensional whole-Earth model with the parallel hybrid PSM/FDM algorithm          下载免费PDF全文

Yanbin Wang  Yang Luo  Yanfang Qin  Xianbing Zhang 《地震科学（英文版）》2014,27(3):277-284

We present a parallel hybrid algorithm based on pseudospectral method (PSM) and finite difference method (FDM) for two-dimensional (2-D) global SH-wavefield simulation. The whole-Earth model is taken as a cross section of spherical Earth, and corresponding wave equations are defined in 2-D cylindrical coordinates. Spatial derivatives in the wave equations are approximated with efficient and high accuracy PSM in the lateral and high-order FDM in the radial direction on staggered grids. This algorithm allows us to divide the whole-Earth into sub-domains in radial direction and implement efficient parallel computing on PC cluster, while retains high accuracy and efficiency of PSM in lateral direction. A transformation of moment tensor between 3-D spherical Earth and our 2-D model was proposed to give corresponding moment tensor components used in 2-D modeling. Comparison of modeling results with those obtained by direct solution method shows very good accuracy of our algorithm. We also demonstrate its feasibility with a lateral heterogeneous whole-Earth model with localized velocity perturbation.  相似文献   

pGTIOL:GeoTIFF数据并行I/O库     

胡树坚  关庆锋  龚君芳  刘洋  范天恒  云硕 《地球信息科学学报》2015,17(5):575-582

在地理栅格并行计算处理中,数据I/O 已成为制约计算性能的主要瓶颈之一。本文针对该问题,首先分析广泛应用于GIS 栅格数据存储的GeoTIFF 格式,重点研究数据的2 种存储模式(即条带存储与块状存储),并根据这2 种存储方式,分别构建了栅格数据从逻辑结构向物理存储结构的映射模型。然后,针对地理空间并行计算的需要,提出了栅格数据的并行读写框架,并利用MPI 并行I/O 技术的文件视图方法,实现了GeoTIFF 数据并行I/O库(pGTIOL)。结果表明,对比开源栅格空间数据转换库(GDAL)的主从I/O 模式,本文提出的pGTIOL 准确读写数据,具有更高的性能。该库隐藏了底层并行I/O 的细节,提供简单易用的并行读写GeoTIFF 栅格数据的接口,支持多数据类型和多种空间分割,实现了对条带存储与块状存储数据的异步并行读写,从而满足动态负载均衡的需求。  相似文献   

The origin of the Parallel Roads of Glen Roy: a review of 19th Century research     

《Proceedings of the Geologists' Association. Geologists' Association》2017,128(1):26-31

This paper summarises the 19th Century research conducted in the Lochaber area and which sought to answer the enigma of the Parallel Roads of Glen Roy. This should be seen as an introduction to the main theories that were developed by a number of scientists, including Darwin, Agassiz and Jamieson. They considered the landforms to be a product of either lacustrine, marine or glaciolacustrine processes, the latter of which proposed by Jamieson, became the accepted explanation by the end of the century.  相似文献   

Parallel and scalable block system generation     

《Computers and Geotechnics》2017

Generating a realistic representation of a fractured rock mass is a first step in many different analyses. Field observations need to be translated into a 3-D model that will serve as the input for these analyses. The block systems can contain hundreds of thousands to millions of blocks of varying sizes and shapes; generating these large models is very computationally expensive and requires significant computing resources.By taking advantage of the advances made in big data analytics and Cloud Computing, we have a developed an open-source program—SparkRocks—that generates block systems in parallel. The application runs on Apache Spark which enables it to run locally, on a compute cluster or the Cloud. The block generation is based on a subdivision and linear programming optimization as introduced by Boon et al. (2015). SparkRocks automatically maintains load balance among parallel processes and can be scaled up on the Cloud without having to make any changes to the underlying implementation, enabling it to generate real-world scale block systems containing millions of blocks in minutes.  相似文献