Wavelet triangulated irregular networks     

Jingsong Wu  Kevin Amaratunga 《International journal of geographical information science》2013,27(3):273-289

GIS applications have recently begun to emerge on the Internet. The management of three-dimensional geographic datasets in this distributed environment poses a particularly challenging problem, which highlights the need for a good data representation. This paper presents a new multiresolution data representation: the Wavelet Triangulated Irregular Network (WTIN). Compared to the traditional cell-based Digital Elevation Model (DEM) format and the Triangulated Irregular Network (TIN) format, it is more compact and suitable for scalable distributed GIS services. This format is based on the second-generation wavelet theory and is specially designed for geographical height field data. The modified Butterfly scheme is used for constructing the wavelet transform. For every point in the geographic surface, only a single wavelet coefficient is used, which makes the final data representation very efficient and easy to compress. Because the transform used in the data representation is a linear filter operation, the computational efficiency is better than other multiresolution data formats for terrain surfaces. Results from numerical experiments on real data are given to demonstrate that the proposed data representation can be efficiently implemented. The results show that the proposed WTIN data format can provide multiresolution data sets, which achieve significant compression while preserving geographical features. The quality is found to be quite acceptable for geographical terrain representation.  相似文献   

Generating hierarchical strokes from urban street networks based on spatial pattern recognition     

Bisheng Yang  Xuechen Luan  Qingquan Li 《International journal of geographical information science》2013,27(12):2025-2050

Strokes are products of a higher-level aggregation of street segments that can reflect functional importance and perceptual significance that is associated with them in human spatial mental conceptualizations, which is of vital importance for network analysis, street selection, and map generalization. Street properties (e.g., street names) and angles between street segments are the two main elements used for generating street strokes according to the continuity principle of perceptual grouping into networks. However, it is difficult to automatically generate strokes with good continuity from street networks with multiple lanes such as dual carriageways or complex street junctions. This article proposes a method for generating street strokes that maintain good continuity across multiple lanes and complex street junctions. The proposed method first detects dual carriageways and complex junctions in street networks and then generates strokes according to the continuity principle of perceptual grouping. Finally, it groups the generated street strokes across the dual carriageways and complex street junctions to maintain good continuity. Moreover, the generated strokes are hierarchically ranked based on stroke length and centrality measurements. Experimental studies demonstrate the validity and effectiveness of the proposed method. The result shows that the generated street strokes maintain good continuity and reflect well the hierarchical structure of the street networks.  相似文献   

作为复杂适应系统的农业文化遗产：复杂性的挑战   总被引：1，自引：0，他引：1  

Tony FULLER  闵庆文 《资源与生态学报(英文版)》2013,4(3):195-201

本文首先阐述了农业系统的复杂性,并对农业系统所面对不确定性,以及外部系统的冲击和压力而形成的动态性进行了分析,提出“复杂适应性系统理论”为研究活态的农业系统,尤其为研究中国的全球重要农业文化遗产（GIAHS）提供了可能,而这些农业文化遗产系统（或其中某些部分）对于研究抵抗力和自我良性管理具有重要的意义.本文认为当前研究中的相关方法将会对整个系统的认识产生新的见解,同时避免把系统分解为各组分进行微观研究再重新还原成整体的研究思路.本文通过综述与GIAHS相关的方法并将旅游引入农村系统（作为一种扰动）,认为可以创造新的方法来认识农村发展干预措施对古老景观的影响,特别是分布在中国农村的许多景观.  相似文献   

Revealing Mars’ deep interior: Future geodesy missions using radio links between landers, orbiters, and the Earth     

V. Dehant  S. Le Maistre 《Planetary and Space Science》2011,59(10):1069-1081

In the frame of a comparison between Earth, Venus, and Mars, a vision on future geodesy missions to Mars is discussed with particular focus on furthering our understanding of the interior, rotation, and orientation of this terrestrial planet. We explain how radioscience instruments can be used to observe the rotation and orientation and therewith to study the deep interior of Mars and its global atmosphere dynamics. Transponders in X-band and Ka-band are proposed with radio links between a lander or a rover and an orbiter around Mars and/or directly to the Earth. The radio budget links are studied in the frame of possible mission constraints and simulations are performed, which show that important information on the interior of Mars can be obtained from the radioscience data. From the observation of Mars’ orientation in space and of tidal effects on a spacecraft orbiting around Mars we show that it is possible for instance to constrain the dimension and composition of the core, the percentage of light element within the core, and to determine the presence of a pressure-induced mineral-phase transition at the bottom of the mantle.  相似文献   

文昌鱼精子发生的核孔复合体冷冻蚀刻电镜观察     

林加涵  林海宁  方永强 《海洋与湖沼》1999,30(3):245-249

1994-1996年每年3月、7月在厦门同安琼头海域采集雄性文昌鱼,采用冷冻蚀刻的常规技术,研究文昌鱼精子发生核孔复合体的变化规律。结果表明,在核孔复合体结构中很可能存在着作为运输物质的中央颗粒。各种生殖细胞中的核孔复合体的大小和密度不同,平均值约为:精原细胞（60±1.20）nm,（2.9±0.04）孔／μm2;初级精母细胞（76±1.80）nm,（4.8±0.05）孔／μm2;次级精母细胞（72±1.30）nm,（4.6±0.03）孔／μm2;精细胞（97±1.40）nm,（5.4±0.06）孔／μm2。这与细胞的生理功能有关。核孔复合体的分布具有明显的极性特点,主要集中在靠初级精母细胞的高尔基区一侧和靠精细胞的前项体一侧的核膜上,表明了细胞核局部的功能差异。  相似文献   

医巫闾山变质核杂岩中金矿的稳定同位素特征     

孟宪刚  邵兆刚  曲玮  王津  朱大岗 《地球学报》2004,25(3):299-302

医巫闾山变质核杂岩中金矿及相关岩石的氢、氧、铅、硅、碳、硫稳定同位素测试结果为：成矿流体泐为-97‰～-72‰,δ^18O为0．3‰～3．8‰,在δ^18O-δD分布图上,位于变质水、岩浆水与当地雨水之间;其他稳定同位素数据及综合资料均说明,以排山楼金矿为代表的该区金矿成矿具有长期性、复杂性和多源性;医巫闾山变质核杂岩构造系统对区内金矿有一定控制作用。  相似文献   

岩浆成矿体系的热演化和剥露史的数字模拟     

傅清平  BrentI.A.Mclnnes  PeterJ.Davies 《地球科学》2004,29(5):555-562

通过对岩浆冷却过程的数字模拟研究,揭示出岩浆在冷却成矿过程中的温度分布和变化规律及影响因素．在此基础上,进一步应用高精度的温龄计组合来限定岩浆成矿体系的热演化和剥露历史,精确地计算出岩浆的初始侵位时间和深度、矿物结晶时间、冷却速率、冷却和暴露地表时间,以及剥露和剥蚀速率等重要参数,并将模拟结果应用于斑岩铜矿床的成矿研究中．研究表明,将精确的年龄测试手段与计算机模拟技术相结合,可为定量研究岩浆矿床的热演化和剥露史、深入了解矿床的成因机制提供一种有效方法．  相似文献   

热液金刚石压腔（HDAC）高温高压实验平台简介          下载免费PDF全文

李胜虎  熊玉新  单伟  舒磊  迟乃杰 《山东国土资源》2021,37(1)

热液金刚石压腔(HDAC)高温高压实验平台是在金刚石压腔的基础上发展起来的一种高温高压原位实验模拟设备。近年来,HDAC技术已经在地质科研领域取得了大量成果,多篇重要研究成果被《Science》《Nature》等知名期刊刊发。本文介绍了HDAC高温高压实验平台结构与组成、实验优势和应用前景。  相似文献   

大数据时代的人类移动性研究   总被引：2，自引：0，他引：2  

陆锋  刘康  陈洁 《地球信息科学学报》2014,(5):665-672

人类个体/群体移动特征是多学科共同关注的研究主题。移动定位、无线通讯和移动互联网技术的快速发展使得获取大规模、长时间序列、精细时空粒度的个体移动轨迹和相互作用定量化成为可能。同时,地理信息科学、统计物理学、复杂网络科学和计算机科学等多学科交叉也为人类移动性研究的定量化提供了有力支撑。本文首先系统总结了大数据时代开展人类移动性研究的多源异构数据基础和多学科研究方法,然后将人类移动性研究归纳为面向人和面向地理空间两大方向。面向人的研究侧重探索人类移动特性的统计规律,并建立模型解释相应的动力学机制,或分析人类活动模式,并预测出行或活动;面向地理空间的研究侧重从地理视角分析人类群体在地理空间中的移动,探索宏观活动和地理空间的交互特征。围绕这两大方向,本文评述了人类移动性的研究进展和存在问题,认为人类移动性研究在数据稀疏性、数据偏斜影响与处理、多源异构数据挖掘、机器学习方法等方面依然面临挑战,对多学科研究方法的交叉与融合提出了更高要求。  相似文献   

复杂网络中多话题信息传播仿真研究     

苟智坚  范明钰  王光卫 《成都信息工程学院学报》2014,29(5):458-463

传统复杂网络话题传播研究,重点关注的是单个话题在网络中的传播,较少考虑多话题之间的相互影响因素。论文分析舆论传播过程中多个话题之间的竞争关系对话题传播的影响机制,建立基于复杂网络的多话题信息传播模型。通过对模型仿真实验及其结果分析表明,当引入个体信息环境影响因素后,一个话题的影响力大于舆论话题环境中其他话题的平均影响力,才会有较大概率影响到更多个体,否则只能在小范围内传播;个体对于话题记忆能力的变化在不同网络中会产生不同影响,在随机网络和BA网络中,人们对于话题的记忆越深,其传播的影响范围越大,而在规则网络和小世界网络中,较小的记忆长度能够让话题传播影响力更大;同时,在具有社群结构的网络中,度大的节点并非会一定会更多的参与某一话题的传播,因为度大的节点有更大概率获得更多的话题。  相似文献