基于空变阻抗约束的贝叶斯稀疏脉冲反演     

肖开攀  张达  张繁昌 《CT理论与应用研究》2015,24(6):809-817

常规的基于贝叶斯理论的稀疏脉冲反演中,各约束项的拉格朗日算子均采用的是恒定的常系数。反演实际资料发现,波阻抗反演剖面与钻井资料的油气显示并不能很好地对应。考虑到反演不同地震道数据时,低频趋势模型所起的约束作用应当不同。本文在常规反演的基础上做出了改进,假定阻抗约束系数是一个空间变量,由各地震道的实际地震数据与合成记录之间的振幅残差来确定该道的阻抗约束系数。实际资料应用表明,改进后的反演结果更稳定,能更准确地反映地下阻抗信息。   相似文献   

地基沉降修正系数的Bayes概率推断   总被引：2，自引：0，他引：2  

王永和  李珍玉  胡萍  杨果林 《岩土力学》2009,30(2):323-327

通过分析常规方法在沉降修正系数的选取中具有的定值性和随意性,引入建立在过去信息和现在样本信息之上的Bayes理论,结合某客运专线红黏土路基工程,提出用后验分布得到修正系数的取值范围。实例研究表明,用以往经验综合样本信息,估计修正系数的先验概率在某一区间上服从均匀分布。由现场载荷试验实测沉降量与理论计算沉降量分析所得的修正系数,将现场量测的沉降变形信息与先验信息结合起来,利用Bayes统计理论,由小样本试验数据推算得到修正系数的后验概率服从正态分布。对后验分布所得参数进行区间估计,得到该区域红黏土地基沉降修正系数的取值优化区间为 [1.0, 1.7],分析了不同荷载作用条件下沉降修正系数的概率分布模型。  相似文献   

土地利用变化预测的案例推理方法   总被引：3，自引：0，他引：3  

杜云艳  王丽敬  季民  曹峰 《地理学报》2009,64(12):1421-1429

当前,基于案例的推理(Case-Based Reasoning,CBR)在解决复杂的地学问题时.对地学案例的表达和历史案例的相似性计算与推理存在明显缺陷,需要在CBR的表达模型和空间相似性计算与推理算法进行拓展.本文针对土地利用变化问题,首先在分析土地利用变化各种定量方法基础上,提出利用CBR进行土地利用变化分析的研究思路:其次,针对土地利用变化的空间特性及隐含的空间关系特性.给出土地利用变化案例的表达模型,案例间内蕴空间关系抽取算法,以及考虑案例间空间关系的CBR相似性推理模型:最后,进行珠江口区域土地利用变化的CBR方法试验.预测精度达到80%.为了进一步评价CBR方法对土地利用变化预测的有效性.在实例部分采用同样的实验数据进行贝叶斯网络的预测方法实验.由两种方法对比可知.CBR是从复杂到简单进行地学问题求解的一种有效方法.  相似文献   

BET_EF: a probabilistic tool for long- and short-term eruption forecasting   总被引：6，自引：3，他引：3  

Warner Marzocchi  Laura Sandri  Jacopo Selva 《Bulletin of Volcanology》2008,70(5):623-632

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Prediction of response spectra via real-time earthquake measurements     

Vincenzo Convertito  Iunio Iervolino  Aldo Zollo  Gaetano Manfredi 《Soil Dynamics and Earthquake Engineering》2008,28(6):492-505

The development and implementation of an earthquake early warning system (EEWS), both in regional or on-site configurations can help to mitigate the losses due to the occurrence of moderate-to-large earthquakes in densely populated and/or industrialized areas. The capability of an EEWS to provide real-time estimates of source parameters (location and magnitude) can be used to take some countermeasures during the earthquake occurrence and before the arriving of the most destructive waves at the site of interest. However, some critical issues are peculiar of EEWS and need further investigation: (1) the uncertainties on earthquake magnitude and location estimates based on the measurements of some observed quantities in the very early portion of the recorded signals; (2) the selection of the most appropriate parameter to be used to predict the ground motion amplitude both in near- and far-source ranges; (3) the use of the estimates provided by the EEWS for structural engineering and risk mitigation applications.In the present study, the issues above are discussed using the Campania–Lucania region (Southern Apennines) in Italy, as test-site area. In this region a prototype system for earthquake early warning, and more generally for seismic alert management, is under development. The system is based on a dense, wide dynamic accelerometric network deployed in the area where the moderate-to-large earthquake causative fault systems are located.The uncertainty analysis is performed through a real-time probabilistic seismic hazard analysis by using two different approaches. The first is the Bayesian approach that implicitly integrate both the time evolving estimate of earthquake parameters, the probability density functions and the variability of ground motion propagation providing the most complete information. The second is a classical point estimate approach which does not account for the probability density function of the magnitude and only uses the average of the estimates performed at each seismic station.Both the approaches are applied to two main towns located in the area of interest, Napoli and Avellino, for which a missed and false alarm analysis is presented by means of a scenario earthquake: an M 7.0 seismic event located at the centre of the seismic network.Concerning the ground motion prediction, attention is focused on the response spectra as the most appropriate function to characterize the ground motion for earthquake engineering applications of EEWS.  相似文献   

非线性二次规划贝叶斯叠前反演   总被引：23，自引：11，他引：12       下载免费PDF全文

杨培杰  印兴耀 《地球物理学报》2008,51(6):1876-1882

叠前反演的目的是基于弹性波理论从地震数据中获得地层参数的可靠估计,进而用于描述地层的流体和岩性特征.然而叠前反演问题都是高维的和非适定的,并且容易受各种噪声和采集过程中不确定因素的影响,因此,为了获得稳定可靠的解必需对反演过程加以合理的约束.本文提出了一种基于非线性二次规划的叠前三参数反演方法.首先基于贝叶斯参数估计理论,假设似然函数服从高斯分布,并使待反演的参数服从于改进的Cauchy分布,从而提高了反演结果的分辨率;其次用协方差矩阵来描述参数间的相关程度,进一步提高了反演结果的稳定性;最后将问题转化为一个非线性二次规划的求解问题,并在多种约束下得到问题的解.仿真实验和实际应用皆已表明,本文提出的反演方法运算速度快捷,既使在信噪比很低的情况下也可获得较好的反演结果,为储层的进一步识别提供更多的物性参数.  相似文献   

利用参考图像的遥感图像模糊估计与恢复   总被引：1，自引：0，他引：1  

王天慧  李盛阳  李绪志 《遥感学报》2010,14(3):464-474

提出一种新的利用参考图像的模糊估计与恢复方法。同一场景不同时相的图像,由于拍摄条件的不同,清晰化程度也往往不同,将高质量的图像作为参考,为模糊估计和恢复提供先验知识,在Bayes统一的框架内进行快速PSF估计,然后使用总变分最小化方法进行恢复。通过真实遥感图像实验,结果表明所提出的方法可以有效地估计退化模糊、恢复未失真图像。  相似文献   

基于Membrane MRF模型的SAR图像贝叶斯去斑          下载免费PDF全文

宋珩  王世唏  计科峰  郁文贤 《遥感学报》2009,13(2):203-207

SAR图像可以看作是真实反映地物后向散射特性的无噪图像与相干斑噪声的乘积,通过贝叶斯估计从图像观测值估计出图像真值即可去除相干斑.而贝叶斯去斑的关键在于建立能与SAR图像特性相匹配的先验信息模型.用MembraneMRF模型对先验信息建模,克服了以往所用GMRF模型对参数估计十分敏感的问题,并通过对该模型邻域结构的自适应调整来分类处理处于匀质区域和含结构特征区域的像元,在有效抑制相干斑的同时较好地保持图像的结构特征.仿真和实际SAR图像数据的实验结果,验证了所提方法的有效性.  相似文献   

地理信息系统研究新范式          下载免费PDF全文

华一新  赵鑫科  张江水 《地球信息科学学报》2023,25(1):15-24

随着大数据时代的到来，地理信息系统（GIS）的时空范畴、信息内容和应用场景都得到了前所未有的扩展，地理信息系统需要由例外处理的被动适应方式，转变为内核支持的主动扩展方式，将地理信息系统扩展为新一代时空信息系统。本文在分析地理信息系统本质是以地图数据模型为核心的信息系统的基础上，从研究对象、基本原理和技术方法3个方面总结梳理了地理信息系统研究范式，并分析阐述了时空信息扩展对地理信息系统研究范式的新要求。其次，在分析全空间信息系统（PSIS）认知模型与多粒度时空对象数据模型的基础上，归纳出全空间信息系统基于时空实体的理论与技术路线，并总结其在多个领域的实践与应用。然后，系统分析了全空间信息系统对地理信息系统研究对象、基本原理和技术方法的具体扩展方式，提出全空间信息系统研究范式。最后，总结梳理了全空间信息系统研究范式的基本内容，并与地理信息系统研究范式进行了核心内容的分析对比，展望了地理信息系统研究范式进阶将带来的影响和变化。  相似文献   

Using microcomputed tomography (μCT) to count varves in lake sediment sequences: Application to Lake Sagtjernet,Eastern Norway     

《Quaternary Geochronology》2023

Varved lake sediments are one of the most important natural archives that allow annual resolution paleoclimate reconstructions. Conventional varve counting techniques use thin sections to manually identify lamina. However, this technique is destructive, labour intensive and limited to a 2D representation of complex 3D features which may lead to misidentification of varve boundaries. This study presents the use of microcomputed tomography (μCT) scans in constructing varve chronologies, utilizing scanning resolutions of ∼50 μm (binned to ∼200 μm) for core sections up to 150 cm long. To evaluate this method, we cored and analysed Lake Sagtjernet in Eastern Norway — revealing a 593 cm-long sediment record of the past 10274 (⁺²²⁰/_-329) years, with continuous laminations from 84 to 533 cm depth (75% of the sediments). Through limnological monitoring and microfacies analyses we demonstrate that the laminations are rare ferrogenic varves, with an annual deposition pattern comprised of seasonal changes in biogenic production superimposed on seasonal precipitates of iron and manganese hydroxides. The floating μCT-counted varve chronology presented here is the first non-glacial varve chronology in Norway and covers 4023 ⁺¹¹³/_-185 years. We find that μCT scans allow for a very fast and non-destructive way of counting varves with sufficient detail of varve boundaries. In the few sections where varve boundaries are too vague to resolve, we recommend using complimentary techniques such as thin sections in parallel. The varve chronology is in good agreement with the 95% confidence interval of the independent radiocarbon chronology based on 16 ¹⁴C dates, and ²¹⁰Pb and ¹³⁷Cs activity peaks, indicating that the varve chronology can be equated to calendar age.  相似文献