Integration and Sharing of Geo-spatial Data Based on Data Engine

Through analyzing the principle of data sharing in the database system, this paper discusses the principle and method for integrating and sharing GIS data by data engine, introduces a way to achieve the high integration and sharing of GIS data on the basis of VCT in VC , and provides the method for uniting VCT into RDBMS in order to implement a spatial database with object-oriented data model.     

Tide-induced variability in beach surface moisture: Observations and modelling

The moisture content w_s of a beach surface strongly controls the availability of sand for aeolian transport. Our predictive capability of the spatiotemporal variability in w_s, which depends to a large extent on water table depth, is, however, limited. Here we show that water table fluctuations and surface moisture content observed during a 10-day period on a medium-grained (365μm) planar (1:30) beach can be predicted well with the nonlinear Boussinesq equation extended to include run-up infiltration and a soil–water retention curve under the assumption of hydrostatic equilibrium. On the intertidal part of the beach the water table is observed and predicted to continuously fall from the moment the beach surface emerges from the falling tide to just before it is submerged by the incoming tide. We find that on the lower 30% of the intertidal beach the water table remains within 0.1–0.2 m from the surface and that the sand is always saturated (w_s≈20%, by mass). Higher up on the intertidal beach, the surface can dry to about 5% when the water table has fallen to 0.4–0.5 m beneath the surface. Above the high-tide level the water table is always too deep (>0.5 m) to affect surface moisture and, without precipitation, the sand is dry (w_s < 5 − 8%). Because the water table depth on the emerged part of the intertidal beach increases with time irrespective of whether the (ocean) tide falls or rises, we find no need to include hysteresis (wetting and drying) effects in the surface-moisture modelling. Model simulations suggest that at the present planar beach only the part well above mean sea level can dry sufficiently (w_s < 10%) for sand to become available for aeolian transport. ©2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Material exchange as heat engine for the corona-chromosphere transition region

We think that a steady material exchange in the upper solar atmosphere can act as a heat engine that cools the corona and heats the corona-chromosphere transition region. We have considered heat conduction from the corona and radiation loss in the transition region and have calculated the temperature, density and velocity distributions in the transition region. Also discussed is the relation between the material flux, the velocity boundary value and the thickness of the transition region.     

体视化关键技术

体视化技术有着广泛的应用前景。对体视化的几种关键技术进行了分类综述，介绍了体数据的表示和分类，面绘制、体绘制和混合绘制各类典型算法的原理和特点。体数据的表示方式涉及到表示精度、存储量和处理时间之间的矛盾，要根据实际问题的具体特点和要求加以选择。体数据的分类是整个可视化算法中的一个关键步骤。只有对体数据进行准确的分类，才能经过处理得出合理的图像。近年来为加快绘制速度和提高图像质量提出了许多改进的体视化算法，并对部分改进算法进行了介绍。     

面向地理信息服务链的工作流技术应用研究

通过分析借鉴当今服务链技术与工作流技术研究成果,充分考虑地理信息数据量大、数据源异构性的特点,对适于地理信息服务链的过程建模方法、过程定义语言、建模工具以及工作流引擎的体系结构、调度算法、应用框架进行重新设计,实现了地理信息服务的可视化组合建模和服务链的自动执行。     

复杂机场环境的多维动态可视化方法

针对飞行器可视导航中复杂机场空地环境多维要素动态交互可视化的难题,基于空地环境要素威胁语义统一的信息场模型,采用体绘制、面绘制与切片绘制混合的方法对机场近区域复杂多样的地形地貌、电磁和气象等威胁态势信息进行交互式动态可视化表达。以某机场的典型模拟数据为例,实现了威胁态势的动态交互可视化,验证了该方法的实用性和有效性。     

正二十面体全球剖分模型的Geometry Clipmap球面绘制

地形绘制一直是图形学研究的热点问题,尤其是球面地形绘制,其在形状和数据组织方面比平面地形绘制更加复杂。在已有球面地形绘制算法的基础上,提出一种基于Geometry Clipmap的球面地形剖分与绘制方法。该方法以构建正二十面体球面网格为基础,将正二十面体划分为十个菱形区域,采用球面菱形网格的剖分,针对每个菱形区域的周边网格进行重新剖分和组合,形成一个虚拟的3×3的大菱形区域,扩大了Clipmap的活动范围,并在一定程度上解决了Clipmap的跨边界问题。实验结果表明了本文方法的可行性和有效性。     

三维地形可视化中不同图元渲染效率比较分析

大规模地形场景一般由几百万甚至更多的顶点构成,地形瓦片的图元组织与绘制效率直接决定了地形渲染的速度和质量。为明确Triangles,Triangle Strip,Triangle Fan和优化的Triangle Strip图元渲染效率,选取常用的11种大小瓦片样本进行对比试验。从初始化时间、索引缓存大小和实时绘制时间3个方面评估图元效率。结果表明：在地形瓦片小于256时,Triangles和优化的Triangle Strip具备较高的渲染效率,Triangles会占用较大的索引缓存;在地形瓦片超过256时,优化后的Triangle Strip图元具有最高绘制效率,并且占用最小的索引缓存。     

中文名片识别系统

在实际的商务活动中,名片已经作为一个重要的身份信息载体,使用频繁。然而随着名片数量的增多,管理越来越麻烦。在实际应用中,研究名片识别的方法,介绍一个独立自主开发的中文商务名片识别系统。该系统首先结合实际中的一些具体问题对名片图像进行预处理;然后在传统版面分析技术的基础上针对版面的特点进行版面分析;最后在对分割区域的字符进行识别之后,根据识别结果中的语义和版面分析得到的位置信息对识别结果进行基于知识规则的理解,从而实现了名片的识别。整个系统在实际应用中表现出良好的性能。     

一种嵌入式空间数据引擎的设计与实现

空间数据引擎是实现高效空间数据访问和管理的关键技术之一。本文提出一种基于内存映射文件和改进堆组织表方式的嵌入式空间数据引擎设计与实现方法,分析了该数据引擎的组成部分和关键算法,并在其基础上讨论了日志及事务的实现方法。通过对实际数据的实验对比,其结果表明:基于本文方法开发的系统和目前主流嵌入式数据库相比,具有数据访问速度快,占用内存少的特点,适合于空间数据的编辑环境。