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GAO Yi-yang 《测绘学院学报》2008,(5)
决策树是用于分类的常用建模方法。首先对分类的概念和决策树方法分别进行了总体介绍,在此基础上对我国30个省市自治区的乡村劳动力、耕地面积以及农业总产值信息数据进行了挖掘分析,在运用决策树对数据进行分类过程中对连续数据采用聚类分析的方法进行离散化处理,从而避免了原始经验分类方法的主观性。最后,通过上述决策树分类方法,生成我国农业情况的决策树,获得相关空间分类规则,并对其进行分析说明。结果表明,决策树分类方法适合我国农业情况。 相似文献
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滑坡位移序列的正确分解对滑坡的预测、预警有重要影响。经验模态分解是一种常用的时间序列分解方法,但该方法在分解过程中存在端点效应,建立的预测模型端点发散,导致预测误差出现较大偏差。为此,本文基于函数延拓的原理对经典经验模态分解方法进行改进,提出一种抑制端点效应的经验模态分解方法,利用金沙江白格滑坡数据对改进方法进行分析验证。试验结果表明,改进方法的端点效应抑制效果良好,预测精度较经典方法有一定的提高。 相似文献
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几种建立DEM模型插值方法精度的交叉验证 总被引:5,自引:0,他引:5
建立DEM模型时需要对离散的高程点进行空间插值,实现这一目的的插值方法有很多种。文章主要选择了6种常用的插值方法,分别在平原、丘陵和高山几种不同复杂程度的环境下对其插值的精度使用交叉验证方法进行评估。结果表明,同样的插值方法对不同复杂程度的地形效果是不一致的,多种插值方法中以克里金插值方法的插值适用性最强,精度最高。 相似文献
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《International Journal of Digital Earth》2013,6(1):80-87
Abstract Cultures throughout the world are associating with the rivers. People depend upon the rivers and their tributaries for food, water, transport, and many other aspects of their daily lives. Unfortunately, human beings have not calculated the accurate lengths for the great rivers even today. The lengths of the rivers are very different in popular textbooks, magazines, atlases and encyclopedias, etc. To accurately determine the lengths of the principal rivers of the world, the combination of satellite image analysis and field investigations to the source regions is proposed in this paper. The lengths of the Nile, Amazon, Yangtze, Mississippi, Yellow, Ob, Yenisey, Amur, Congo and Mekong, with lengths over or close to 5000 km, were calculated using the proposed method. The results may represent the most reliable and accurate lengths of the principal rivers of the world that are currently achievable. 相似文献
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软科学这一术语是70年代在国外提出的.然而30多年以来,它在国外不仅未得到普遍的承认,而且对软科学的定义也还未能达成大体上一致的共识.而在改革开放后的中国,出于决策科学化和民主化的需要,经过一些领导人的提倡和支持,特别是通过1986年召开的软科学座谈会及1994年召开的全国软科学工作会议,软科学事业得到了蓬勃的发展.据初步统计,截止1998年底全国共有软科学研究机构1224个,研究人员32655人,初步形成了一支较为强大的研究队伍,并取得了数百项覆盖多个领域的研究成果,为支持各级各类的决策发挥了一定的作用. 相似文献
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Tobias Nilsson Benedikt Soja Kyriakos Balidakis Maria Karbon Robert Heinkelmann Zhiguo Deng Harald Schuh 《Journal of Geodesy》2017,91(7):857-866
The very long baseline interferometry (VLBI) Intensive sessions are typically 1-h and single-baseline VLBI sessions, specifically designed to yield low-latency estimates of UT1-UTC. In this work, we investigate what accuracy is obtained from these sessions and how it can be improved. In particular, we study the modeling of the troposphere in the data analysis. The impact of including external information on the zenith wet delays (ZWD) and tropospheric gradients from GPS or numerical weather prediction models is studied. Additionally, we test estimating tropospheric gradients in the data analysis, which is normally not done. To evaluate the results, we compared the UT1-UTC values from the Intensives to those from simultaneous 24-h VLBI session. Furthermore, we calculated length of day (LOD) estimates using the UT1-UTC values from consecutive Intensives and compared these to the LOD estimated by GPS. We find that there is not much benefit in using external ZWD; however, including external information on the gradients improves the agreement with the reference data. If gradients are estimated in the data analysis, and appropriate constraints are applied, the WRMS difference w.r.t. UT1-UTC from 24-h sessions is reduced by 5% and the WRMS difference w.r.t. the LOD from GPS by up to 12%. The best agreement between Intensives and the reference time series is obtained when using both external gradients from GPS and additionally estimating gradients in the data analysis. 相似文献
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In this letter, we are trying to resolve the electromagnetic problem for the movements of the superconducting particles of the protoplanetary cloud in the magnetic field of Saturn. The force of levitation (Meissner-Ochsenfeld phenomenon) is introduced to the field of planetary science for the first time. It is shown from our theoretical analysis that rings of Saturn might have a superconducting origin, and rings might levitate within magnetic equator plane of the planet. 相似文献
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跟踪世界发展动态 致力地球重力场研究 总被引:12,自引:6,他引:12
宁津生 《武汉大学学报(信息科学版)》2001,26(6):471-475
比较系统、扼要地叙述了笔者所在单位40余年来坚持跟踪世界发展动态,致力于地球重力场理论和方法的研究,并从教学和生产需要出发,在地球重力场研究方面所获得的一些有理论意义和实用价值的成果。 相似文献