自适应顺序采样Kriging方法及其在增量动力分析中的应用

复杂结构的增量动力分析（IDA）对于结构的抗震设计和分析有着重要意义,但需对结构进行大量的非线性时程分析,计算量成本高。本文结合Kriging元模型和自适应顺序采样并用于结构增量动力分析以提高其计算效率和精度,其中:Kriging元模型用于预测结构的地震响应,顺序采样根据候选点的熵值补充非线性时程分析逐步增加Kriging模型的预测精度。借助本文方法,IDA曲线可通过少量的时程分析实现较高的精度。为了校验本文方法的可行性与有效性,对二层和九层钢框架结构模型应用直接IDA、hunt&fill方法和本文方法分析并比较了上述三种方法的计算误差、计算效率和IDA曲线差别。在此基础上本文将自适应顺序采样Kriging方法用于考虑结构不确定性参数的IDA分析,并和传统的蒙特卡洛方法进行比较。结果表明:该方法具有较高的计算效率,可以保证IDA曲线的精度。     

基于钢筋混凝土足尺柱拟静力试验的离线模型更新混合试验方法

离线模型更新混合试验对构件拟静力数据进行恢复力模型参数识别,并更新数值子结构中相应构件的模型参数来提高混合试验精度,但该方法尚缺少真实试验的验证。本文基于课题组开展的足尺RC柱拟静力试验,取恢复力模型为集中塑性铰Ibarra-Medina-Krawinkler（IMK）模型,进行框架结构离线模型更新混合试验研究。结果表明,当物理子结构取为RC足尺柱时,离线模型更新混合试验能获得接近于真实试验情况下结构的地震响应,从而对该方法的有效性进行了试验验证。利用IMK经验公式,将真实试验模型参数识别值按轴压比进行对照修正,应用于不同层数的框架结构地震响应模拟,实现了试验数据的重复利用。     

针对应急救援的强余震特征统计

大地震后强余震活跃,震后快速判断最大余震震级和强余震发生可能性对提高应急救援效率有重大意义。针对震后应急救援,本文根据救援存活率将震后救援期分为8个时段:震后12 h、震后24 h、震后48 h、震后72 h、震后96 h、震后120 h、震后144 h和震后168 h。对我国大陆地区1966年以来6级及以上地震强余震资料进行分时段统计,分别拟合出8个时段的最大余震震级和主震震级的经验公式;并提出震后强余震发生可能性的经验判断方法,通过本文提出的可能性指数a,依据主震震级,震后可以快速判定强余震发生的可能性。     

基于IDA的层间隔震结构失效模式研究

层间隔震结构是由基础隔震结构发展而来的一种新型隔震结构。为研究层间隔震结构的倒塌,需先研究不同层间隔震结构的不同失效模式和失效位置,文章建立了3个不同结构参数的层间隔震结构有限元模型,选取20条与抗震规范反应谱吻合的地震动,采用增量动力分析（IDA）方法,分别对其失效模式和失效位置进行研究。研究表明:基于不同的结构参数,层间隔震的基本失效模式有三种,即隔震层水平位移超限导致结构失效、下部结构层间位移角超限导致结构失效、隔震层拉压应力超限导致结构失效;隔震层下部结构和隔震层最外边缘支座为结构的薄弱位置,应引起更多关注。此方法不仅可以研究结构的不同失效模式,还可以确定失效位置,可为下一步层间隔震结构的抗倒塌分析提供理论基础。     

Different Features of Jets and Isotropic Fireballs in Gamma-ray Burst Phase

We investigated physical quantities including the spectrum,emission lines and pulse profiles expected from a uniform jet,a spherical fireball and the 1/Γ region (the portion of the spherical fireball with opening angle 1/Γ)in the prompt emission phase,after taking into consideration of the Doppler effect under the fireball frame- work.Our study shows that:a)for these physical quantities the spherical fireball and the uniform jets do not present obvious differences,so we cannot use these to distinguish a spherical fireball from a uniform jet;b)for the spherical fireball and a uniform jet,the observed quantities mainly come from the 1/Г region,so we can simply use the 1/Г region in approximate calculations;c)broadening of emission lines is a general phenomena,which mainly comes from the curvature effect;d)the 1/Γ region plays different roles in different frequency ranges,and the radiation from the 1/Γ region is greater in the higher than in the lower frequencies.     

CCD Photometry of Asteroid （147） Protogeneia

We measured the light-curve of the asteroid (147) Protogeneia in November 2004, with a CCD detector attached to the 1-meter telescope at the Yunnan Observatory, China. The synodic period and maximum amplitude of (147) at this apparition are 7.852 hours and 0.25 mag, respectively. The value of a/b for (147), from a preliminary estimation, is not less than 1.26:1.     

An Efficient High-Resolution Shock-Capturing Scheme for Multi-Dimensional Flows I. Hydrodynamics

Many problems at the forefront of theoretical astrophysics require a treatment of dynamical fluid behavior. We present an efficient high-resolution shock-capturing hydrody-namic scheme designed to study such phenomena. We have implemented a weighted, essentially non-oscillatory (WENO) scheme to fifth order accuracy in space. HLLE approximate Riemann solver is used for the flux computation at cell interface, which does not require spectral decomposition into characteristic waves and so is computationally friendly. For time integration we apply a third order total variation diminishing (TVD) Runge-Kutta scheme. Extensive testing and comparison with schemes that require characteristic decomposition are carried out demonstrating the ability of our scheme to address challenging open questions in astrophysics.     

Magneto-induced Line Broadening of Magneto-sensitive Lines in Solar Magnetized Atmospheres

We analyze the spectral line broadening of those magneto-sensitive lines in solar magnetized atmospheres. The broadening at the line wings is due to the increase of the effective width of energy levels involved in Zeeman splitting, and the broadening at the line core also originated in Zeeman splitting under the condition that the Zeeman components are mixed. Therefore, the magnetoinduced or Zeeman broadening take effects on the whole line. The observed Stokes parameter data in a sunspot and outside it acquired by Solar Stokes Spectrum Telescope (S3T) are analyzed for the demonstration of this mechanism, and the Zeeman broadening rates are calculated for FeI6302.5 under some assumptions. Our result shows that the broadening is increased as the magnetic field strength becomes stronger, but the rate of increase at the line core is decreased as the field strength increases, while the rate at the wing does not show such an obvious regularity. The broadening is more effective in the line core than in the wings.     

Analysis on the decadal scale variation of the dust storm in North China

Dust storm is a disastrous weather that can cause serious environmental consequences and hazards. It causes excessive soil mass and nutrient loss in source areas, and air pollution in deposition area, which result in bad influence on agriculture, industry, traffic, and peoples’ daily life[1-4]. Dust storm can also affect the thermal balance of planetary radiation and then lead to meso- to macroscale climatic modification[5-7]. North- west China and North China are two high-frequency centers …     

不同跨高比对多层钢框架内填混凝土深梁结构抗震性能影响

为了研究不同跨高比多层钢框架内填混凝土深梁结构的抗震性能,在钢框架内填混凝土深梁滞回性能试验的基础上,利用ABAQUS对六层纯钢框架（结构一）、钢框架内填跨高比为2混凝土深梁结构（结构二）和钢框架内填跨高比为0.75混凝土深梁结构（结构三）进行弹塑性时程分析。结果表明:内填混凝土深梁使结构整体刚度明显增大;在地震波的作用下,结构二的最大顶点位移降低可达58.3%,结构三的最大顶点位移降低可达89.3%,内填混凝土深梁,结构的抗侧移性能得到了极大改善,且随着深梁跨高比的减小而大幅度提升;结构二滞回曲线饱满,呈现纺锤形,混凝土深梁充分起到了第一道防线作用。经济合理的钢框架内填混凝土深梁结构具有一定的工程应用价值。