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71.
线性最小二乘估计在对非线性函数进行线性近似的过程中会产生模型误差,而一些非线性参数估计方法可能因为函数复杂而难以求导,法方程系数矩阵秩亏或呈病态矩阵时难以求解,非线性迭代解法有时对初始值的选择存在依赖性,不恰当的初始值会导致迭代无法收敛。针对这些问题,引入了模拟退火算法,介绍了该算法的基本原理、计算步骤和收敛性,并以3个控制网平差应用为例,说明该算法具有无需求导求逆,简洁实用,易于编程等优势,并能实现全局优化,获得高精度的平差结果。 相似文献
72.
Wenbin Shen Jin Li Jiancheng Li Zhengtao Wang Jinsheng Ning Dingbo Chao 《地球空间信息科学学报》2008,11(4):273-278
Given the second radial derivative Vrr(P) |δs of the Earth's gravitational potential V(P) on the surface δS corresponding to the satellite altitude, by using the fictitious compress recovery method, a fictitious regular harmonic field rrVrr(P)^* and a fictitious second radial gradient field V:(P) in the domain outside an inner sphere Ki can be determined, which coincides with the real field V(P) in the domain outside the Earth. Vrr^*(P)could be further expressed as a uniformly convergent expansion series in the domain outside the inner sphere, because rrV(P)^* could be expressed as a uniformly convergent spherical harmonic expansion series due to its regularity and harmony in that domain. In another aspect, the fictitious field V^*(P) defined in the domain outside the inner sphere, which coincides with the real field V(P) in the domain outside the Earth, could be also expressed as a spherical harmonic expansion series. Then, the harmonic coefficients contained in the series expressing V^*(P) can be determined, and consequently the real field V(P) is recovered. Preliminary simulation calculations show that the second radial gradient field Vrr(P) could be recovered based only on the second radial derivative V(P)|δs given on the satellite boundary. Concerning the final recovery of the potential field V(P) based only on the boundary value Vrr (P)|δs, the simulation tests are still in process. 相似文献
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通过分析虚拟参考站技术和主辅站技术的不足,提出了一种新的网络RTK技术——增强参考站技术(ARS).分析了这种技术的原理并阐述了该技术中改正数的生成方法,同时,提出了一种基于RTCM编码的适合于该技术的改正数编码格式.在此基础上,分析了该技术的RTK定位精度、数据传输效率和系统可靠性,从理论上说明了增强参考站的技术优势.最后,以四川综合GPS服务网(SIGN)的子网数据对该技术进行了验证,结果表明,该技术具有高定位精度、高数据传输效率的特点,是一种理想的网络RTK技术. 相似文献
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Artificial neural network and liquefaction susceptibility assessment: a case study using the 2001 Bhuj earthquake data,Gujarat, India 总被引:2,自引:0,他引:2
D. Ramakrishnan T. N. Singh N. Purwar K. S. Barde Akshay. Gulati S. Gupta 《Computational Geosciences》2008,12(4):491-501
This study pertains to prediction of liquefaction susceptibility of unconsolidated sediments using artificial neural network
(ANN) as a prediction model. The backpropagation neural network was trained, tested, and validated with 23 datasets comprising
parameters such as cyclic resistance ratio (CRR), cyclic stress ratio (CSR), liquefaction severity index (LSI), and liquefaction
sensitivity index (LSeI). The network was also trained to predict the CRR values from LSI, LSeI, and CSR values. The predicted
results were comparable with the field data on CRR and liquefaction severity. Thus, this study indicates the potentiality
of the ANN technique in mapping the liquefaction susceptibility of the area. 相似文献
79.
Heinz Schneider Marco Schwab Fritz Schlunegger 《International Journal of Earth Sciences》2008,97(1):179-192
This paper uses the results of landscape evolution models and morphometric data from the Andes of northern Peru and the eastern
Swiss Alps to illustrate how the ratio between sediment transport on hillslopes and in channels influences landscape and channel
network morphologies and dynamics. The headwaters of fluvial- and debris-flow-dominated systems (channelized processes) are
characterized by rough, high-relief, highly incised surfaces which contain a dense and hence a closely spaced channel network.
Also, these systems tend to respond rapidly to modifications in external forcing (e.g., rock uplift and/or precipitation).
This is the case because the high channel density results in a high bulk diffusivity. In contrast, headwaters where landsliding
is an important sediment source are characterized by a low channel density and by rather straight and unstable channels. In
addition, the topographies are generally smooth. The low channel density then results in a relatively low bulk diffusivity.
As a consequence, response times are greater in headwaters of landslide-dominated systems than in highly dissected drainages.
The Peruvian and Swiss case studies show how regional differences in climate and the litho-tectonic architecture potentially
exert contrasting controls on the relative importance of channelized versus hillslope processes and thus on the overall geomorphometry.
Specifically, the Peruvian example illustrates to what extent the storminess of climate has influenced production and transport
of sediment on hillslopes and in channels, and how these differences are seen in the morphometry of the landscape. The Swiss
example shows how the bedding orientation of the bedrock drives channelized and hillslope processes to contrasting extents,
and how these differences are mirrored in the landscape.
An erratum to this article can be found at 相似文献
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