统一方差分量估计公式     

李广云 《测绘学院学报》1993,(3)

本文提出了一种适用于协方差阵奇异或非奇异、设计阵列满秩或降秩时的方差分量估计方法;其公式推导简单,形式统一,不需解线性方程组,同时可保证迭代计算方差分量的非负要求。作为特例还和Helmert法及MINQUE法作了比较。最后讨论了用真误差进行方差分量估计的计算公式,并给出了一个测距误差分析的实例。  相似文献   

乾安县浅层高氟地下水的分布规律及成因的初步探讨     

诚俊华 《吉林地质》1991,10(1):71-74

本文主要阐述了乾安县浅层高氟地下水的分布规律;探讨了浅层高氟地下水的成因与构造、地貌、古气候、地层岩性和水文地质条件的关系,从而闸明了广泛分布的湖沼相松散沉积物的组成和水文地质条件是本区浅层高氟地下水的主要原因。  相似文献   

BAYES方差分量估计在虚拟权平差中的应用     

覃辉 《四川测绘》1994,17(3):110-114

本文把近似Bayes方基分量估计公式应用于矿区扩建网的虚拟权平差中，解决了具体计算中的一些实际问题，最后，通过一矿区扩建网平差实例验证了该方法的可行性．  相似文献   

水准测量往返测较差方差之估计     

冯延明 《武汉大学学报(信息科学版)》1987,(4)

现有文献中以水准测量往返测较差为统计量估计较差方差已提出许多观点和公式,但对于较差误差模型既没有回答其正确性,也缺乏严密可行的参数估计方法。本文将方差分量的最小范数二次无偏估计(MINQUE)法用于较差方差估计,并提出了以近代回归分析原理为基础的较差误差模型统计检验与比较选择的基本方法。这些估计、分析方法既简单易行又严密合理。最后通过对部分一等水准实测数据试算分析,也初步证实了它们的实际效益。  相似文献   

多维地震动各方向相关性对拱坝动应力的影响     

吴健  金峰  徐艳杰 《地震工程与工程振动》2005,25(2):50-54

本文将随机振动的虚拟激励法与拱坝-地基动力相互作用FE-BE-IBE时域模型结合，发展了一个可以考虑多维随机地震动作用下的拱坝动力响应计算模型，并用Monte Garlo方法对模型进行了验证，计算结果表明，地震动分量的相关性对结构的动力响应存在一定影响，合理考虑地震动各方向分量的相关性可以更好地计算实际地震作用下的拱坝动力响应。  相似文献   

Seismic fragility methodology for highway bridges using a component level approach     

Bryant G. Nielson  Reginald DesRoches 《地震工程与结构动力学》2007,36(6):823-839

Bridge fragility curves, which express the probability of a bridge reaching a certain damage state for a given ground motion parameter, play an important role in the overall seismic risk assessment of a transportation network. Current analytical methodologies for generating bridge fragility curves do not adequately account for all major contributing bridge components. Studies have shown that for some bridge types, neglecting to account for all of these components can lead to a misrepresentation of the bridges' overall fragilities. In this study, an expanded methodology for the generation of analytical fragility curves for highway bridges is presented. This methodology considers the contribution of the major components of the bridge, such as the columns, bearings and abutments, to its overall bridge system fragility. In particular, this methodology utilizes probability tools to directly estimate the bridge system fragility from the individual component fragilities. This is illustrated using a bridge whose construction and configuration are typical to the Central and Southeastern United States and the results are presented and discussed herein. This study shows that the bridge as a system is more fragile than any one of the individual components. Assuming that the columns represent the entire bridge system can result in errors as large as 50% at higher damage states. This provides support to the assertion that multiple bridge components should be considered in the development of bridge fragility curves. The findings also show that estimation of the bridge fragilities by their first‐order bounds could result in errors of up to 40%. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Acceleration response modification factors for nonstructural components attached to inelastic moment‐resisting frame structures     

Ragunath Sankaranarayanan  Ricardo A. Medina 《地震工程与结构动力学》2007,36(14):2189-2210

A statistical analysis of the peak acceleration demands for nonstructural components (NSCs) supported on a variety of stiff and flexible inelastic regular moment‐resisting frame structures with periods from 0.3 to 3.0 s exposed to 40 far‐field ground motions is presented. Peak component acceleration (PCA) demands were quantified based on the floor response spectrum (FRS) method without considering dynamic interaction effects. This study evaluated the main factors that influence the amplification or decrease of FRS values caused by inelasticity in the primary structure in three distinct spectral regions namely long‐period, fundamental‐period, and short‐period region. The amplification or decrease of peak elastic acceleration demands depends on the location of the NSC in the supporting structure, periods of the component and building, damping ratio of the component, and level of inelasticity of the supporting structure. While FRS values at the initial modal periods of the supporting structure are reduced due to inelastic action in the primary structure, the region between the modal periods experiences an increase in PCA demands. A parameter denoted as acceleration response modification factor (R_acc) was proposed to quantify this reduction/increase in PCA demands. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Spatial organization of decadal and bidecadal rainfall fluctuations in southern North America and southern South America     

Omar Abel Lucero  Norma C. Rodriguez 《Atmospheric Research》2001,57(4)

The spatial organization of decadal and bidecadal components (fluctuations) of annual rainfall is identified in this research for two regions: (1) southern South America, and (2) southern North America (conterminous USA, southeastern Canada and northern and central Mexico). Findings indicate that these decadal and bidecadal components have highly coherent wave-like spatial organization. Two types of organization of decadal and bidecadal components of annual rainfall were identified: a train of propagating fluctuations and quasi-standing fluctuations. For decadal components, such patterns alternate in time. A widespread change in the spatial organization of decadal component of annual rainfall took place simultaneously in both continents in 1932. The bidecadal component is organized as standing fluctuations in southern North America and as travelling fluctuations in southern South America, The spatial pattern of decadal fluctuations of annual rainfall has 12- and 13-year cycles, and the spatial pattern of bidecadal fluctuations has predominantly 21- and 22-year cycles.  相似文献   

地震面波产生的地震动转动分量研究   总被引：7，自引：0，他引：7  

李宏男  孙立晔 《地震工程与工程振动》2001,21(1):15-23

本文利用弹性波动理论对地面转动分量，即瑞利（Rayleigh)波和乐夫（Love)波产生的转动分量进行了研究，给出了相应的计算公式和计算方法，特别注意到面波的散射效应对转动分量的影响，并将这一特性引入到转动分量的求取中，使问题的解决更切合于实际，最后选取实际地震记录，利用得到的公式计算出地震面波产生的转动分量。  相似文献   

A note on the useable dynamic range of accelerographs recording translation   总被引：2，自引：0，他引：2  

M. D. Trifunac  M. I. Todorovska 《Soil Dynamics and Earthquake Engineering》2001,21(4)

Since the late 1970s, the dynamic range and resolution of strong motion digital recorders have leaped from 65 to 135 dB, opening new possibilities for advanced data processing and interpretation. One of these new possibilities is the calculation of permanent displacement of the ground or of structures, associated with faulting or with non-linear response. Proposals on how permanent displacements could be recovered from recorded strong motion have been published since 1976. The analysis in this paper concludes that permanent displacements of the ground and of structures in the near-field can be calculated provided all six components of strong motion (three translations and three rotations) have been recorded, and the records are corrected for transducer rotation, misalignment and cross-axis sensitivity.  相似文献