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1.
多光谱水深遥感方法及研究进展   总被引:1,自引:0,他引:1  
文中简单回顾了多光谱水深遥感的国内外研究进展。将当前水深反演模型归为3类:即波浪法、统计法和水体散射遥感测深法,对各模型作了简单介绍,以时间为顺序列出了各模型在实践中的应用状况,分析对比了各种模型的优势和劣势。最后对当前水深遥感的发展趋势谈了自己的两点认识:即高分辨率数据的应用,改进的或新的水深反演方法不断涌现。  相似文献   

2.
在过去的一段时间里,许多技术在各自的领域范围内得到了迅猛的发展。本文中我们致力于讨论这些技术的一体化。我们的目的在于展示一种行之有效的一体化方法,用此法处理环境问题时,综合利用所有工具和技术将比彼此分离的使用它们更有效。本文主要基于近期在遥感国际期刊(International Journal of Remote Sensing)(Xue et a1.2002)发表的一篇论文,以及一些在该论文发表后的由中国科学院遥感应用研究所的薛勇博士领导的研究小组在研究这一课题产生的其他想法。  相似文献   

3.
A theoretical analysis of the potential accuracy of early modern planetary models employing compound circles suggests that fairly simple extensions of those models can be sufficiently accurate to meet the demands of Tycho Brahe's observations in both ecliptic longitude and latitude. Some of these extensions, such as the substitution of the true sun for the mean sun, had already been taken by Kepler before he abandoned circular models. Other extensions, involving one or two extra epicycles, were well within the mathematical capabilities of sixteenth-century and seventeenth-century astronomers. Hence neither the failure of astronomers before Kepler to correct errors in planetary positions nor Kepler's decision to abandon circular models was a consequence of inherent limitations in those models.  相似文献   

4.
提出一种基于DCT和DWT的遥感影像数字水印方案。首先对水印图像进行Arnold置乱预处理,以破坏像素之间的空间相关性,增强算法鲁棒性;鉴于小波变换良好的局部性和时频分析特性以及多分辨率分析特性,而离散余弦变换具有较好的聚能效应,算法将载体遥感影像进行DWT变换,并选取其子带图像HLl进行DCT变换;最后自适应的将数字水印嵌入所选子块的DC系数上。实验证明本文算法有效提高了水印的不可见性,对JEPG压缩、滤波和叠加噪声等攻击具有较好的鲁棒性。  相似文献   

5.
The anonymous set of astronomical tables preserved in Paris, Bibliothèque nationale de France, MS lat. 10262, is the first set of displaced tables to be found in a medieval Latin text. These tables are a reworking of the standard Alfonsine tables and yield the same results. However, the mean motions are defined differently, the presentation of the tables is unprecedented, and some new functions are introduced for computing true planetary longitudes. The absence of any instructions as well as unusual technical terms in the headings make it difficult to appreciate the cleverness that went into the construction of these tables that are extant in a unique copy. In this article we provide a detailed analysis of these tables and their underlying parameters. The displaced tables are typical of a pervasive tendency in Islamic science to provide extensive and elegant numerical tables for the convenience of practitioners. The underlying astronomical theory is neither questioned nor affected. Edward S. Kennedy   相似文献   

6.
The technological sciences have at least six defining characteristics that distinguish them from the other sciences. They (1) have human-made rather than natural objects as their (ultimate) study objects, (2) include the practice of engineering design, (3) define their study objects in functional terms, (4) evaluate these study objects with category-specified value statements, (5) employ less far-reaching idealizations than the natural sciences, and (6) do not need an exact mathematical solution when a sufficiently close approximation is available. In combination, the six characteristics are sufficient to show that the technological sciences are neither branches nor applications of the natural sciences, but form a different group of sciences with specific characteristics of their own.  相似文献   

7.
利用TM遥感影像和地表热量平衡模型估算平凉市崆峒区水土保持世行贷款项目区的蒸散发量,并结合地面实测资料进行检验,分析了该区域蒸散发的分布规律,研究了蒸散发量与土地利用、地表参数、地形参数的关系。结果表明:研究区当日蒸散发量介于0.46~7.85mm之间,平均3.81mm,空间分布差异明显;不同下垫面的蒸散发能力有一定差别,其中水体和林地的日蒸散发量最大;蒸散发量与NDVI和斋程等呈线性正相关,而与地表温度呈线性负相关。本研究可为区域地表水循环和生态修复提供数据支持。  相似文献   

8.
Despite deserving a place amongst the historic milestones of the philosophy of disciplines, the system of the sciences put forward by Whewell has so far received little interest. Yet his ideas had a significant impact on the researches subsequently carried out on the topic, exerting in particular a decisive influence on Peirce and Spencer. The present paper aims to display the innovatory nature of the philosophical foundations of the Whewellian classification of the sciences. In this respect, we will argue that the most striking feature of his disciplinary system lies in a heuristic categorization of the sciences according to their “methods of discovery”. This represents a double departure from both the Aristotelian and the Baconian disciplinary paradigms, which are instead underpinned by ontological and epistemological criteria, respectively. Next, we will explore the pivotal role of Whewell's classification of the sciences for his overall project of a philosophy of scientific discovery.  相似文献   

9.
我国农作物遥感估产研究进展   总被引:1,自引:0,他引:1  
概述了遥感在我国农作物长势监测、种植面积测算和产量估算等方面的应用和研究进展,同时分析了近来MODIS在农作物遥感估产方面的应用和存在的问题。展望了我国遥感估产的研究及发展方向,认为3S技术一体化、高光谱遥感、定量遥感是今后遥感估产应用的发展方向。  相似文献   

10.
针对现有遥感图像水印算法抵抗旋转、剪切、水平镜像及联合几何攻击能力差的问题,提出一种局部化遥感图像数字水印新方法.算法首先对水印图像进行 Arnold置乱预处理,并将其行扫描形成一维向量作为待嵌入的水印信息;在宿主遥感图像中提取 Harris Laplace特征点,依据特征点确定水印嵌入特征区域;规范所选特征区域,对其进行归一化后实施 Contourlet变换,利用奇偶量化方法将数字水印嵌入选定的变换系数内.实验证明算法对滤波、噪声、JEPG压缩等常规信号处理具备较好鲁棒性,并且能够更好地抵抗旋转、缩放、平移及其联合等几何攻击  相似文献   

11.
I bring out the limitations of four important views of what the target of useful climate model assessment is. Three of these views are drawn from philosophy. They include the views of Elisabeth Lloyd and Wendy Parker, and an application of Bayesian confirmation theory. The fourth view I criticise is based on the actual practice of climate model assessment. In bringing out the limitations of these four views, I argue that an approach to climate model assessment that neither demands too much of such assessment nor threatens to be unreliable will, in typical cases, have to aim at something other than the confirmation of claims about how the climate system actually is. This means, I suggest, that the Intergovernmental Panel on Climate Change’s (IPCC׳s) focus on establishing confidence in climate model explanations and predictions is misguided. So too, it means that standard epistemologies of science with pretensions to generality, e.g., Bayesian epistemologies, fail to illuminate the assessment of climate models. I go on to outline a view that neither demands too much nor threatens to be unreliable, a view according to which useful climate model assessment typically aims to show that certain climatic scenarios are real possibilities and, when the scenarios are determined to be real possibilities, partially to determine how remote they are.  相似文献   

12.
A familiar story of seismology is that of a small field originally focused on local studies of earthquakes through diverse disciplinary perspectives being transformed, in the second half of the twentieth century, into a highly specialized field focused on global studies of the earth's deep interior via sophisticated instruments and transnational networks of seismological stations. Against this backdrop, this essay offers a complementing account, highlighting the significance of local circumstances and disciplinary agendas that were contingent not only on transformations in the geophysical sciences but also on the concurrently changing biological sciences during the Cold War. Using examples of the studies of unusual animal behavior prior to earthquakes conducted under the auspices of the US Geological Survey on the West Coast of the United States in the 1970s, this essay examines a variety of motivations behind the attempts to bridge geophysics and biology. These examples illustrate the ways in which earthquake prediction became entangled with concerns over the use of seismological data, pioneering research on biological rhythms, and the troubled field of Cold War-driven military brain studies.  相似文献   

13.
水质遥感监测研究进展   总被引:12,自引:0,他引:12  
本文对近年来应用遥感技术对地表水水质进行监测的研究进展做了总结.在描述地表水体的光谱特征基础上,简述了水质遥感监测的基本原理,其次总结了水质反演的方法和可用的卫星遥感数据源;最后,对此领域存在的问题和今后的重点研究方向作了探讨。  相似文献   

14.
本文综述了遥感在监测城市扩展及其引起的生态环境变化方面的应用和发展情况,并对当前研究中采用的城市动态变化检测方法和城市生态遥感监测指标进行了分析和总结,最后,针对当前存在的问题进行了探讨。  相似文献   

15.
随着无人机遥感技术逐步从研究开发阶段发展到实际应用阶段,采用无人机图像进行大比例尺的真正射影像生成方法的研究具有重要的现实意义.本文旨在探索将计算机视觉中获得巨大成功的多视三维重建技术应用到对无人机影像处理中,给出了一种基于运动恢复结构重建算法和多视图立体视觉算法全自动生成大比例真正射影像的方法.本文首先分析了无人机图像PMVS重建点云的特点,给出一种由基于面片多视图立体视觉稠密点生成数字表面模型的方法,然后详细介绍了包括正射影像图像坐标映射模型、可见性计算、基于Markov随机场能量优化的面片选择和匀光处理等真正射影像生成的关键步骤.实验结果以及与商业软件的比较表明:本文给出的方法在野外地形和城市区域均能获取有效的真正射影像结果.  相似文献   

16.
This article addresses knowledge transfer dynamics in agent-based computational social science. The goal of the text is twofold. First, it describes the tensions arising from the convergence of different disciplinary traditions in the emergence of this new area of study and, second, it shows how these tensions are dealt with through the articulation of distinctive practices of knowledge production and transmission. To achieve this goal, three major instances of knowledge transfer dynamics in agent-based computational social science are analysed. The first instance is the emergence of the research field. Relations of knowledge transfer and cross-fertilisation between agent-based computational social science and wider and more established disciplinary areas: complexity science, computational science and social science, are discussed. The second instance is the approach to scientific modelling in the field. It is shown how the practice of agent-based modelling is affected by the conflicting coexistence of shared methodological commitments transferred from both empirical and formal disciplines. Lastly, the third instance pertains internal practices of knowledge production and transmission. Through the discussion of these practices, the tensions arising from converging dissimilar disciplinary traditions in agent-based computational social science are highlighted.  相似文献   

17.
This paper considers the consequences of the stochastic error process in large non-linear forecasting models. As such models are non-linear, the deterministic forecast is neither the mean nor the mode of the density function of the endogenous variables. Under a specific assumption as to the class of the non-linearity it is shown that the deterministic forecast is actually the vector of marginal medians of the density function. Stochastic simulation techniques are then used to test whether one large forecasting model actually lies within this class.  相似文献   

18.
Summary 7-Chloro-3-(4-methyl-1-piperazinyl)-4H-1,2,4-benzothiadiazine-1,1-dioxide (DU-717) is a new compound having sustained antihypertensive activity in a similar manner to that of hydrochlorothiazide. However, this compound shows neither diuretic nor hyperglycemic effect, being different from those of hydrochlorothiazide or diazoxide.  相似文献   

19.
为使通信设备能安全稳定运行、无人职守机房故障能被及时地发现,通过对集中监控系统的构成、监控内容进行详细研究,开发了基于网络的通信电源监测软件。基本实现了被监控设备和被监测信号遥测、遥感、遥控。  相似文献   

20.
首先介绍了农田渍害的表现特征;其次根据监测原理,将国内外农田溃害遥感监测的主要方法分为地表指示标志法、地下水位反演法和与非遥感方法相结合的综合分析法,并分别对各类方法的原理、技术、适用范围及优缺点进行分析,发现各种方法均能解决特定的农田渍害监测问题,同时也存在着缺陷和局限性;最后,进行了总结并指出了两种潜在的遥感监测方...  相似文献   

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