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

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.     

Non-linear seismic behavior of structures with limited hysteretic energy dissipation capacity

This paper investigates the non-linear seismic behavior of structures such as slender unreinforced masonry shear walls or precast post-tensioned reinforced concrete elements, which have little hysteretic energy dissipation capacity. Even if this type of seismic response may be associated with significant deformation capacity, it is usually not considered as an efficient mechanism to withstand strong earthquakes. The objective of the investigations is to propose values of strength reduction factors for seismic analysis of such structures. The first part of the study is focused on non-linear single-degree-of-freedom (SDOF) systems. A parametric study is performed by computing the displacement ductility demand of non-linear SDOF systems for a set of 164 recorded ground motions selected from the European Strong Motion Database. The parameters investigated are the natural frequency, the strength reduction factor, the post-yield stiffness ratio, the hysteretic energy dissipation capacity and the hysteretic behavior model (four different hysteretic models: bilinear self-centring, with limited or without energy dissipation capacity, modified Takeda and Elastoplastic). Results confirm that the natural frequency has little influence on the displacement ductility demand if it is below a frequency limit and vice versa. The frequency limit is found to be around 2 Hz for all hysteretic models. Moreover, they show that the other parameters, especially the hysteretic behavior model, have little influence on the displacement ductility demand. New relationships between the displacement ductility demand and the strength reduction factor for structures having little hysteretic energy dissipation capacity are proposed. These relationships are an improvement of the equal displacement rule for the considered hysteretic models. In the second part of the investigation, the parametric study is extended to multi-degree-of-freedom (MDOF) systems. The investigation shows that the results obtained for SDOF systems are also valid for MDOF systems. However, the SDOF system overestimates the displacement ductility demand in comparison to the corresponding MDOF system by approximately 15%.     

南京城区夏季低层逆温对人体舒适状况影响初探

利用2000年夏季南京志区地面气象要素和低层探空资料，分析了该夏季南京城区早、晚低层逆温的频率、厚度和强度变化特征，着重从统计角度研究了逆温的厚度、强度与城区地面温度、相对湿度变化的关系及对人体舒适状况的影响。结果表明：低层逆温对城区地面温湿变化及其幅度影响较大，当07时有逆温层时，08时至14时的温度增加幅度变大，相对温度减小幅度也变大，人体不适指数增加幅度变大；当19时有逆温层时，20时至23时温度减小幅度变小，相对湿度增加幅度也变小，人体不适指数减小幅度变小，并通过相关分析建立了人体舒适度指数与逆温强度之间的回归方程。     

星载极化SAR数据模拟

介绍了自行开发的星载极化SAR数据计算机模拟系统，此系统采用的模拟方法遵循了星载极化SAR系统实际运行的情况，按发射脉冲时间序列，分别依次计算各发射脉冲相应的回波数据，与常用的以点目标为基础逐点模拟方法相比，计算效率高，现贴近实际系统，便于模拟各种误差的影响和保持其对所有目标回波影响的一致性和相关性。给出了星载极化SAR数据模拟的实例。     

Oracle Spatial 在GIS中的应用

本文介绍了Oracle数据库系统中对空间数据存储的解决方案，并针对对象关系模式下空间数据的存储和管理，结合自己的实际工作体会提出了一些具体的解决方法。     

中国陆地生态系统脆弱带遥感模型

本研究通过对我国陆地生态系统8个典型样地的植被指数取样实验和图像计算结果发现，这8个样地植被指数随着水、热因子的季节变化，在时间和空间上具有一定的“绿波推移”和“景观更替”规律。在中国东部湿润的季风区（样地1－3），随着纬度的增高，其月平均植被指数与月平均气温有较大的相关。发现降水相对丰沛的地带，热量和光照条件的变化成为植被生长和变化的自然限制因子；而在中国北方森林－森林草原－典型昌原－荒漠草原－荒漠地带上，随着从东部（湿润地区）到西部（干旱地区）干湿条件的更替，月平均植被指数与降水多寡有较大的正相关关系。在8个样地上都呈现出共同的规律，即定向风的分布与植被指数的分布在时间和空间上具有逆相分布的“套合关系”。尤其在时间上有相逆套合关系，这正是中国北方沙尘暴和沙漠化加剧的自然原因。本研究定量地给出了我国陆地不同经纬度带生态系统脆弱季节和累积时间的分布。     

SAR图像斑点噪声抑制的本质

合成孔径雷达（SAR）图像的斑点噪声阻碍SAR的应用。在过去20多年中，提出了许多SAR图像去除斑点噪声方法，虽然每种去除斑点噪声方法都能有效去除斑点噪声，但都不同程度地损失了图像的边缘信息，本文首先以数学物理的观点描述了SAR图像斑点噪声抑制问题。其次分析了斑点噪声的统计特性和几种典型的去除斑点噪声方法并进行了简单的比较，在最后研究了SAR图像斑点噪声抑制的本质，这对开发既能有效去除斑点噪声，又能有效保持边缘信息的去除噪声方法十分重要。     

极化SAR干涉测量模拟研究

极化SAR干涉测量将极化测量技术和干涉测量技术巧妙地结合，能够提高干涉测量精度，尤其是在植被覆盖的情况下，不仅能够测量地表地形，而且使得估计植被高度成为可能。因此，近几年来国际上对极化SAR干涉测量技术的研究越来越重视，极化SAR干涉测量已成为SAR应用技术发展的重要方向。通过模拟技术深入研究极化SAR干涉测量理论和方法，并提出了一种新的极化SAR干涉测量改进算法，模拟实验结果表明，该算法可以进一步提高测量精度。     

路面基层压实度现场测试中的非理想因素分析--以广东西部沿海高速公路新会段为例

通过对广东西部沿海高速公路路面基层现场压实度检测过程的详细观察，并在不同的条件下反复进行试验、分析比较，找出了影响压实度现场检测精度的主要非理想因素，即标准砂密度、试样含水量和路面基层平整度，并提出了解决方法。     

PHREEQC在研究地浸溶质迁移过程中的应用

应用地球化学模式PHREEQC，揭示地浸过程中溶质迁移的存在形式及各种形式之间的转化关系。通过计算饱和指数，确定溶质水解沉淀的水文地球化学条件临界值。