纯斜压基流上斜压波的发展和锋生过程

利用地转动量近似和水平坐标变换建立的三维半地转方程,讨论了具有均匀位涡的基态流上非线性斜压扰动的发展和锋面的形成过程。计算结果表明,对于纯斜压流,斜压波的发展既取决于初始扰动,也与基流的垂直切变有关,垂直切变越大,斜压波增长越快。不同的基流.扰动有不同的增长率。对于某个确定的基流,斜压波在各个时刻的特性仅取决于初始扰动。斜压扰动发展到一定程度,形成大的风速和等温线密集区,即产生锋。     

浅谈规划竣工测量的三维测绘与成果表示

社会与科技的发展,现实生活中建筑风格、建筑结构和样式越来越复杂和新颖,原始的2＋1维测绘的成果已不能完全满足社会发展和经济建设的需要,三维测绘及成果表示的需求日益迫切,应及时跟上.本文阐述了基于三维激光扫描仪进行三维测绘的原理、流程以及后期数据处理的一些应用,提出了构建数字城市地理空间框架的构想.     

武汉市城市管线规划管理一张图建设研究

以武汉市为例,针对现阶段我国部分城市管线信息"为了普查而普查"、系统建设重复、共享程度低下、应用范围狭窄等现象,从平台整体设计、数据体系建设、功能设计等3个方面介绍了武汉市城市管线规划管理一张图建设的情况;详细阐述了系列比例尺地图编制、地图服务Cache创建、空间数据与全景数据坐标匹配等技术的实现。     

数字校园3维场景的构建方法

自"数字地球"提出以来,数字城市、数字流域和数字校园等概念相继涌现。3维可视化数字校园信息系统作为"数字校园"的建设的一部分离不开3维模型的构建。本文针对当今常用3维模型的构建方法,介绍郑州测绘学校在构建数字校园实践过程中3维模型的构建方法。     

新时期中越友好合作的新模式

中越友好是大势所趋,人心所向,中越合作是两国政治稳定和经济发展的基础与可靠保障。本文在分析新时期中越关系的背景和我国周边外交基本方针的基础上,基于《新时期深化中越全面战略合作的联合声明》,提出中越陆海联动合作的总体框架和主要内容。陆上合作主要有涉及河口三角洲和海岸带综合开发、陆上交通体系、产业结构和经济合作区建设等方面,海上合作主要包括南海渔业、油气资源共同开发及海洋贸易等。本文重点阐述如何推进中越海上、陆上共同开发和金融合作的具体建议,如南海相关海域及北部湾共同开发的设想、共同探讨湄公河和红河三角洲发展模式等,为中越友好合作的新一轮发展提供某些可以进一步具体操作的思路。     

Modelling three‐dimensional geoscientific fields with the Voronoi diagram and its dual

Fields as found in the geosciences have properties that are not usually found in other disciplines: the phenomena studied are often three‐dimensional (3D), they tend to change continuously over time, and the collection of samples to study the phenomena is problematic, which often results in highly anisotropic distributions of samples. In the geographical information system (GIS) community, raster structures (voxels or octrees) are the most popular solutions, but, as we show in this paper, they have shortcomings for modelling and analysing 3D geoscientific fields. As an alternative to using rasters, we propose a new spatial model based on the Voronoi diagram (VD) and its dual the Delaunay tetrahedralisation (DT), and argue that they have many advantages over other tessellations. We discuss the main properties of the 3D VD/DT, present some GIS operations that are greatly simplified when the VD/DT is used, and, to analyse two or more fields, we also present a variant of the map algebra framework where all the operations are performed directly on VDs. The usefulness of this Voronoi‐based spatial model is demonstrated with a series of potential applications.     

Geotechnical parameter estimation in tunnelling using relative convergence measurement

Accurate estimation of geotechnical parameters is an important and difficult task in tunnel design and construction. Optimum evaluation of the geotechnical parameters have been carried out by the back‐analysis method based on estimated absolute convergence data. In this study, a back‐analysis technique using measured relative convergence in tunnelling is proposed. The extended Bayesian method (EBM), which combines the prior information with the field measurement data, is adopted and combined with the 3‐dimensional finite element analysis to predict ground motion. By directly using the relative convergence as observation data in the EBM, we can exclude errors that arise in the estimation of absolute displacement from measured convergence, and can evaluate the geotechnical parameters with sufficient reliability. The proposed back‐analysis technique is applied and validated by using the measured data from two tunnel sites in Korea. Copyright © 2005 John Wiley & Sons, Ltd.     

Numerical simulation of overbank processes in topographically complex floodplain environments

This article presents results from an investigation of the hydraulic characteristics of overbank flows on topographically‐complex natural river floodplains. A two‐dimensional hydraulic model that solves the depth‐averaged shallow water form of the Navier–Stokes equations is used to simulate an overbank flow event within a multiple channel reach of the River Culm, Devon, UK. Parameterization of channel and floodplain roughness by the model is evaluated using monitored records of main channel water level and point measurements of floodplain flow depth and unit discharge. Modelled inundation extents and sequences are assessed using maps of actual inundation patterns obtained using a Global Positioning System, observational evidence and ground photographs. Simulation results suggest a two‐phase model of flooding at the site, which seems likely to be representative of natural floodplains in general. Comparison of these results with previous research demonstrates the complexity of overbank flows on natural river floodplains and highlights the limitations of laboratory flumes as an analogue for these environments. Despite this complexity, frequency distributions of simulated depth, velocity and unit discharge data closely follow a simple gamma distribution model, and are described by a shape parameter (α) that exhibits clear systematic trends with changing discharge and floodplain roughness. Such statistical approaches have the potential to provide the basis for computationally efficient flood routing and overbank sedimentation models. Copyright © 2002 John Wiley & Sons, Ltd.     

A simulation using a hybrid method for predicting fault zones ahead of a tunnel face

By monitoring and analysing three‐dimensional absolute displacement during tunnel excavation, it is possible to predict discontinuity zones ahead of tunnel face. This paper presents results of the three‐dimensional displacement obtained from three‐dimensional simulations using hybrid method for assessing the effect of discontinuity zones on monitoring data. The influence of fault zones and in situ initial stresses on the three‐dimensional tunnel movement is evaluated. Copyright © 2002 John Wiley & Sons, Ltd.