Force-directed layout of origin-destination flow maps   总被引：1，自引：0，他引：1  

Bernhard Jenny  Daniel M. Stephen  Ian Muehlenhaus  Brooke E. Marston  Ritesh Sharma  Eugene Zhang 《International journal of geographical information science》2017,31(8):1521-1540

This paper introduces a force-directed layout method for creating origin-destination flow maps. Design principles derived from manual cartography and automated graph drawing to increase readability of flow maps and graph layouts are taken into account. The origin-destination flow maps produced with our algorithm show flows with quadratic Bézier curves that reduce flow-on-flow and flow-on-node overlaps, and avoid sharp or irregular bends in flow lines. A survey of expert cartographers found that flow maps created with our automated method are similar in quality to manually produced flow maps.  相似文献   

滤波原理和一般线性时间不变系统──地震学上用的数字信号处理的基本原理与实例(讲座1)     

陈祥熊  江燕 《地震地磁观测与研究》1997,(6)

从滤波和系统理论的一些基本概念出发，介绍了简单的阻容滤波器原理，它的微分方程表达，频率响应函数，传递函数以及在离散数据处理中滤波器的差分方程表达。最后推广到对一般线性时间不变系统的处理。这些概念和原理是数字信号处理的基础。  相似文献   

岩矿分析中湿法分解试样的原理与规律     

张燮 《华东地质学院学报》1991,14(2):180-188

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Hydrogen Incorporation in Crystalline Jadeite: Insight from First Principles Calculations     

ZHANG Xiaoling  FAN Xiaoyu  MENG Dawei  WU Xiuling  LIU Weiping 《《地质学报》英文版》2016,90(3):939-945

Hydrogen incorporation is critical for explaining defect energies, structure parameters and other physical characteristics of minerals and understanding mantle dynamics. This work analyzed the hydrogen complex defects in jadeite by the plane-wave pseudo-potential method based on density functional theory, and optimized the atomic positions and lattice constants in all configurations(different defective systems). Incorporation mechanisms considered for hydrogen(H) in jadeite include:(1) hydrogen incorporating with the O2 site oxygen and coexisting with M2 vacancy;(2) one H atom combined with an Al atom replacing Si in tetrahedron;(3) 4H atoms directly replacing Si in tetrahedron and(4) 3H atoms replacing Al on the M1 site. The four incorporation mechanisms mentioned above form the corresponding V_(Na)-H_i, Al_(Si)-H_i, V_(Si)-4H_i and V_(Al)-3H_i point defects. The molecular dynamics simulation to the ideal, V_(Na)-H_i, Al_(Si)-H_i, V_(Si)-4H_i and V_(Al)-3H_i point defects under the P-T conditions of 900 K, 2 GPa, the V_(Na)-H_i and Al_(Si)-H_i point defects under different pressures at T = 900 K, and Al_(Si)-H_i point defects under different temperatures at P = 3 GPa was performed to examine the preferential mode of hydrogen incorporation in jadeite by means of first-principles calculations. The calculations show that the averaged O–H bond-length in the hydrogen point defects system decreased in the order of Al_(Si)-H_i, V_(Na)-H_i, V_(Si)-4H_i and V_(Al)-3H_i. V_(Na)-H_i complex defects result in a contraction of the jadeite volume and the presence of Al_(Si)-H_i, V_(Si)-4H_i and V_(Al)-3H_i defects could increase the supercell volume, which is the most obvious in the V_(Al)-3H_i defects. The energy of formation of Al_(Si)-H_i and V_(Al)-3H_i complex defects was much lower than that of other defect systems. The V_(Al)-3H_i defects system has the lowest energy and the shortest O–H bond-length, suggesting that this system is the most favorable. The analytical results of vacancy formation energy, O–H bondlength, and the stability of the hydrogen defects in jadeite have suggested that the preferred hydration incorporation mode in jadeite is V_(Al)-3H_i complex defect.  相似文献   

定向运动地图的空间认知和设计表达研究     

温锐  马京振  朱燕  胡健健 《测绘与空间地理信息》2016,(5):23-26

定向运动地图,作为定向运动中必不可少的工具,是用图者进行空间认知的手段。本文以空间认知理论为指导,从地图符号、表达内容和使用环境3个方面分析了定向地图的内容设计与表达特性。定向运动中的识图用图是一种亲历与阅读相结合的过程,用图者使用定向地图是一种基于最佳路径选择的空间认知方式,本文分析了运动状态下用户使用定向地图的空间认知过程,最后给出了定向地图的设计原则。  相似文献   

改革开放以来中国县改市地名中的专名更名问题及其建议     

陈冰 《地理研究》2019,38(5):1222-1235

改革开放以来,我国75例县改市更改专名的历史经验是,应尽量维持地名稳定,能不改的尽量不要改,必须更改专名时,要严格执行相关法律法规的规定,新市名的命名要参考更名经验中得出的禁止性、建议性原则,原有政区专名存在问题的,应借区划调整之机加以改正。禁止性原则包括,全国范围内县市及以上政区不能同名、同音;不能以跨政区的地物、驻地以外的乡镇、捏造的历史政区和不稳定时期或破坏领土主权完整、民族团结的地名命名新市名。建议性原则包括,不以驻地为名;不要改掉重要的历史地名;不应出现单名市;不要叠加政区通名;以历史政区命名,应尽量与当时所代表的地域范围相吻合。新时期有序推动县改市应谨慎更名、科学命名。  相似文献   

Astrophysical smooth particle hydrodynamics     

Stephan Rosswog   《New Astronomy Reviews》2009,53(4-6):78-104

The paper presents a detailed review of the smooth particle hydrodynamics (SPH) method with particular focus on its astrophysical applications. We start by introducing the basic ideas and concepts and thereby outline all ingredients that are necessary for a practical implementation of the method in a working SPH code. Much of SPH’s success relies on its excellent conservation properties and therefore the numerical conservation of physical invariants receives much attention throughout this review. The self-consistent derivation of the SPH equations from the Lagrangian of an ideal fluid is the common theme of the remainder of the text. We derive a modern, Newtonian SPH formulation from the Lagrangian of an ideal fluid. It accounts for changes of the local resolution lengths which result in corrective, so-called “grad-h-terms”. We extend this strategy to special relativity for which we derive the corresponding grad-h equation set. The variational approach is further applied to a general-relativistic fluid evolving in a fixed, curved background space-time. Particular care is taken to explicitly derive all relevant equations in a coherent way.  相似文献   

Nature and theoretical foundation of ecoregionalization:a case study in China   总被引：1，自引：0，他引：1  

LI Shuang-cheng  YANG Qin-ye 《地理学报(英文版)》1999,(1)

lintroductionPhysicalgeographers,ecologistSandotherresearchershavebeeninvolvedinanal}aingspahalchrenhationofvariousfactorsontheearthsurface,suchasbiome,close,andsoil,toexplainandunderstandthephysicogeographicalprocessesandtheirSPatialpatternssincetheestablislunentoftheacademicfieldsofgeogT'aphyandecology.Theynotedablythattheregional~onoffactorsonthe~~cewashelpfulnotonlytoimpellingthedevelopmentofgeographyandecology,butalsotobroadeningtheirapplicahons,andtheybeganclasssingfactorswithvallousmet…  相似文献   

秋冬季节珠三角典型区域气溶胶浓度垂直分布的激光雷达反演     

吴仪  邓孺孺  秦雁  王春梅  梁业恒  熊龙海 《遥感学报》2020,24(3):302-318

气溶胶与全球热辐射平衡、水循环、人类健康密不可分,其观测精度直接影响天气预测、气候建模以及对人类健康影响评估的精度,激光雷达能监测气溶胶的垂直分布,对污染气溶胶的扩散趋势、污染源反演、气候预测等均有重要意义。本文基于激光在大气中的辐射传输过程,根据米散射激光雷达的工作原理,使用雷达的多个系统参数计算雷达常数,建立激光雷达气溶胶质量浓度反演模型,从地面向上在晴空条件下进行了珠三角地区典型区域的秋冬季节气溶胶垂直观测的实验,计算气溶胶质量浓度的垂直廓线,反演气溶胶的垂直分布情况。验证与分析结果表明:(1)激光雷达反演结果显示,白天的反演结果中噪声大大减少,表明反演算法能够有效减弱太阳光的影响。(2)相比于传统方法,使用雷达常数而非边界值的反演结果波动较小,更符合实际,能够有效避免高空噪声的影响。(3)高层大气在晴朗静稳天气状况下较为干净,气溶胶基本分布在低空区域,质量浓度随高度基本呈负指数分布。  相似文献   

对军事地理学学科体系构成的认识     

刘建忠 《测绘学院学报》1993,(1)

本文针对现代军事地理学科的发展和学科体系的构成,以及目前在划分学科体系中存在的一些问题,提出了该学科的分类原则和基本体系构成方案,供同行研究和探讨。  相似文献