Validation of the SCEC Broadband Platform simulations for tall building risk assessments considering spectral shape and duration of the ground motion

Earthquake simulation technologies are advancing to the stage of enabling realistic simulations of past earthquakes as well as characterizations of more extreme events, thus holding promise of yielding novel insights and data for earthquake engineering. With the goal of developing confidence in the engineering applications of simulated ground motions, this paper focuses on validation of simulations for response history analysis through comparative assessments of building performance obtained using sets of recorded and simulated motions. Simulated ground motions of past earthquakes, obtained through a larger validation study of the Southern California Earthquake Center Broadband Platform, are used for the case study. Two tall buildings, a 20‐story concrete frame and a 42‐story concrete core wall building, are analyzed under comparable sets of simulated and recorded motions at increasing levels of ground motion intensity, up to structural collapse, to check for statistically significant differences between the responses to simulated and recorded motions. Spectral shape and significant duration are explicitly considered when selecting ground motions. Considered demands include story drift ratios, floor accelerations, and collapse response. These comparisons not only yield similar results in most cases but also reveal instances where certain simulated ground motions can result in biased responses. The source of bias is traced to differences in correlations of spectral values in some of the stochastic ground motion simulations. When the differences in correlations are removed, simulated and recorded motions yield comparable results. This study highlights the utility of physics‐based simulations, and particularly the Southern California Earthquake Center Broadband Platform as a useful tool for engineering applications.     

遥感数据产品真实性检验不确定性分析研究进展

不确定性分析是遥感产品真实性检验最重要的部分,本文以叶面积指数LAI为例,从测量、模型以及蕴含在测量和模型中的尺度效应3个方面分析产品真实性检验过程的不确定性来源,并针对问题提出减小其不确定性的办法。对于相对均一的地表,地面测量的空间代表性比较好,可不考虑地表空间代表性引起的尺度效应和蕴含在模型中的尺度效应引起的不确定性。针对异质性地表,分为两种情况:若模型是线性的,蕴含在模型中的尺度效应可以忽略,只需要考虑测量的不确定性、模型本身的不确定性、以及地面测量的空间代表性引起的尺度效应;若模型是非线性的,则测量、模型和蕴含在测量和模型中的尺度效应引起的不确定性都需要考虑。     

An examination of the validation of a model of the hydro/thermo/mechanical behaviour of engineered clay barriers

This paper focuses attention on the development of a numerical model of the hydro/thermo/mechanical behaviour of unsaturated clay and its consequent verification and validation. The work presented describes on-going collaboration between the Cardiff School of Engineering and Atomic Energy of Canada. The model development, which was carried out at Cardiff, can be described as being based on a mechanistic approach to coupled heat, moisture and air flow. This is then linked to a deformation analysis of the material within a ‘consolidation’ type of model. The whole is solved via the finite element method to yield a computer software code named COMPASS (COde for Modelling PArtly Saturated Soil). Some aspects of verification and validation of the model have been addressed in-house. However, the purpose of current AECL work is to provide an independent, rigorous, structured programme of validation and the paper will also explore the further validation of COMPASS within this context. © 1998 by John Wiley & Sons, Ltd.     

Calibration and validation of a general infiltration model

A general infiltration model proposed by Singh and Yu (1990) was calibrated and validated using a split sampling approach for 191 sets of infiltration data observed in the states of Minnesota and Georgia in the USA. Of the five model parameters, f_c (the final infiltration rate), S_o (the available storage space) and exponent ‘n’ were found to be more predictable than the other two parameters: m (exponent) and a (proportionality factor). A critical examination of the general model revealed that it is related to the Soil Conservation Service (1956) curve number (SCS‐CN) method and its parameter S_o is equivalent to the potential maximum retention of the SCS‐CN method and is, in turn, found to be a function of soil sorptivity and hydraulic conductivity. The general model was found to describe infiltration rate with time varying curve number. Copyright © 1999 John Wiley & Sons, Ltd.     

基于NDVI先验知识的LAI地面采样方法

针对非均质中低分辨率像元的叶面积指数LAI验证中如何布设基本采样单元ESU的问题,提出基于NDVI先验知识的ESU布设方法,并采用不同植被类型、不同均匀程度的地表作为模拟场,分析对比了方法的精度及稳定性。结果显示,本文方法用NDVI先验知识描述植被的生长空间分布信息,能相对准确地划分植被的不同生长水平,有效降低层内方差。在草地和森林地区的试验中,精度与稳定性均优于传统的随机采样、均匀采样和基于分类图的3种采样方法。因此,本文提出的采样方法为大尺度非均质区域LAI地面验证的采样方案提供了新的设计思路。     

风云三号C星微波湿温探测仪的定标和验证

风云三号C星(FY-3C)已经于2013年9月23日发射升空,其上装载的微波湿温探测仪(MWHTS)已于9月30日开机正常工作.MWHTS具有对大气温度和湿度垂直分布进行同步探测的能力.MWHTS为跨轨扫描式微波辐射计,在89~191GHz毫米波段内设置了十五个探测通道,其中包括118.75GHz氧气吸收线附近的8个大气温度探测通道,183.31GHz水汽吸收线附近的5个大气湿度探测通道,以及89GHz和150GHz两个窗区通道.设置在118.75GHz的一组毫米波探测通道是国际上业务卫星首次使用的大气探测通道,这组通道和183.31GHz通道对大气进行联合探测,将获得更加精细的大气温湿度垂直分布数据,为数值预报和气候研究提供丰富信息.为保证MWHTS观测资料的定量应用,对仪器性能和定标精度进行了在轨测试.利用MWHTS在轨正常工作后的三个月数据,对仪器在轨定标的基础数据:冷空和黑体计数值,黑体和仪器温度进行监测分析和质量检验,经过质量检验的在轨定标基础数据,结合发射前真空试验得到的非线性订正项在轨定标生成MWHTS观测亮温数据.评估MWHTS在轨辐射定标结果的精度和偏差特性使用了三种方法:1通过场地定标试验获取大气温湿廓线和地面温度等大气参数信息,结合微波逐线正演辐射传输模式MonoRTM(Monochromatic Radiative Transfer Model)模拟MWHTS的上行微波辐射亮温,与MWHTS实际观测结果进行对比分析;2两个通道特性一致的同类星载被动微波载荷同时观测同一目标,观测亮温的差异主要取决于两个载荷的定标系统偏差.选取美国SNPP上搭载的微波探测仪器ATMS作为MWHTS的参考载荷,基于SNO(simultaneous nadir overpass)技术,对两个仪器的观测亮温进行交叉比对,观测亮温时空匹配及均匀性检验的条件为:观测时间差异小于20min,观测像元中心距离小于3km,观测角度在星下点附近差异小于5°,观测像元周围3×3像元内的亮温标准差小于1K;3基于美国国家环境预测中心的全球数据同化系统GDAS(Global Data Assimilation System)数据,利用快速辐射传输模式CRTM(Community Radiative Transfer Model)对MWHTS各通道亮温进行正演模拟,模拟结果(O)和仪器实际观测的亮温(B)之间的差异记为"O-B",对偏差值"O-B"进行统计特征分析.仪器中心频率的变化、正演模式模拟精度和模式输入廓线自身的误差都会对"O-B"产生影响.但是对于首次使用的探测频点而言(如118.75GHz通道),由于国际上没有同类载荷可以进行交叉比对,借助于正演辐射传输模式计算得到"O-B"偏差的分析结果可以在一定程度上反映仪器整体定标情况.外场地定标试验结果显示除通道14外,其他14个通道的亮温差都在1.3K以内;与同类载荷ATMS的在轨观测进行直接交叉比对表明通道14与ATMS的亮温偏差最大,但中心频点一致的5个水汽探测通道的标准差都小于1K;将MWHTS观测结果和正演辐射传输模式模拟结果即"O-B"进行偏差分析显示,靠近118.75GHz吸收线中心的通道2—6"O-B"标准差小于0.5K,其他通道"O-B"标准差和ATMS相应通道的结果相当;MWHTS观测和模拟偏差随角度变化的研究表明通道1,7~13和15观测结果对角度有一定依赖性.     

Dynamic FE simulation of four‐story steel frame modeled by solid elements and its validation using results of full‐scale shake‐table test

Dynamic finite element analyses of a four‐story steel building frame modeled as a fine mesh of solid elements are performed using E‐Simulator, which is a parallel finite element analysis software package for precisely simulating collapse behaviors of civil and building structures. E‐Simulator is under development at the National Research Institute for Earth Science and Disaster Prevention (NIED), Japan. A full‐scale shake‐table test for a four‐story frame was conducted using E‐Defense at NIED, which is the largest shaking table in the world. A mesh of the entire structure of a four‐story frame with approximately 19 million degrees of freedom is constructed using solid elements. The density of the mesh is determined by referring to the results of elastic–plastic buckling analyses of a column of the frame using meshes of different densities. Therefore, the analysis model of the frame is well verified. Seismic response analyses under 60, 100, and 115% excitations of the JR Takatori record of the 1995 Hyogoken‐Nanbu earthquake are performed. Note that the simulation does not reproduce the collapse under the 100% excitation of the Takatori record in the E‐Defense test. Therefore, simulations for the 115% case are also performed. The results obtained by E‐Simulator are compared with those obtained by the E‐Defense full‐scale test in order to validate the results obtained by E‐Simulator. The shear forces and interstory drift angles of the first story obtained by the simulation and the test are in good agreement. Both the response of the entire frame and the local deformation as a result of elastic–plastic buckling are simulated simultaneously using E‐Simulator. Copyright © 2014 John Wiley & Sons, Ltd.     

卫星高光谱大气CO2遥感反演精度地基验证研究

利用TCCON网站提供的北半球7个地面观测站CO₂干空气混合比（XCO₂）数据,对3种卫星反演的XCO₂产品进行了验证,包括SCIAMACHY产品、NIES-GOSAT产品和ACOS-GOSAT产品。结果表明：卫星CO₂遥感反演产品与地基遥感资料具有较一致的季节性周期变化,一年中月平均浓度最高值均出现在4月和5月,最低值均出现在8月和9月;相对于地面观测,3种卫星产品均低估了XCO₂;ACOS-GOSAT产品与NIES-GOSAT产品的精度大体相当,误差标准差分别为2.26×10^-6和2.27×10^-6;SCIAMACHY产品的精度略差,误差标准差为2.91×10^-6。     

利用地基微波辐射计验证积雪微波辐射传输模型

积雪雪水当量参数是水文、气候、水资源利用与管理模型中非常重要的输入参数,积雪辐射理论模型可以模拟积雪物理参数与微波辐射的关系.因此,准确模拟积雪辐射信息,验证积雪辐射模型显得尤为重要.采用改进的基于能量守恒的干雪微波辐射传输理论模型(DMRT-AIEM-MD),利用2008年3月24 日黑河地区联合实验获取的地面测量数据以及车载辐射计18.7 GHz和36.5 GHz两个频率的辐射亮温值,考虑地形的影响,分析积雪辐射散射特性以及验证该模型.结果表明:该模型模拟值与地面实测值吻合的比较好,该模型能较好的模拟中国地区自然地表积雪辐射信号.分析了部分模型模拟值和地面实测值偏差的可能原因,该积雪区是多次堆积形成,积雪垂直剖面的密度、温度不规则变化可能会引起偏差.     

Limnology of Bird Pond,Ross Island,Antarctica

The physical, chemical and biological properties of Bird Pond, Cape Bird, Ross Island, Antarctica (77° 13’ 10” S, 166° 28’ 30” E), were investigated at weekly intervals for 2 months in the summer of 1970–71. The above properties were also investigated over a 24‐h period. Salinity and temperature tolerance of the rotifer Philodina gregaria were investigated in the laboratory at Cape Bird.

Bird Pond is characterised by a high conductivity and chloride ion concentration, and an alkaline pH. It has a water temperature as high as 15°c in mid summer, with the bottom water temperature often 3°c higher than the surface temperature. Diurnal measurements suggest a vertical movement of phytoplankton during a 24‐h period. P. gregaria survives ionic concentrations up to 250 000 g.m^‐3 Na⁺ + Cl^‐, and water temperatures up to 32°c.