Hysteretic models for sliding bearings with varying frictional force

The friction pendulum system is a sliding seismic isolator with self‐centering capabilities. Under severe earthquakes, the movement may be excessive enough to cause the pendulum to hit the side rim of the isolator, which is provided to restrain the sliding. The biaxial behavior of a single friction pendulum, in which the slider contacts the restrainer, is developed using a smooth hysteretic model with nonlinear kinematic hardening. This model is extended to simulate the biaxial response of double and triple friction pendulums with multiple sliding surfaces. The model of a triple friction pendulum is based on the interaction between four sliding interfaces, which in turn is dependent upon the force and displacement conditions prevailing at these interfaces. Each of these surfaces are modeled as nonlinear biaxial springs suitable for a single friction pendulum, using the yield surface, based on the principles of the classical theory of plasticity, and amended for varying frictional yield force, due to variation in vertical load and/or velocity‐dependent friction coefficient. The participation of the nonlinear springs is governed by stick‐slip conditions, dictated by equilibrium and kinematics. The model can simulate the overall force‐deformation behavior, track the displacements in individual sliding surfaces, and account for the ultimate condition when the sliders are in contact with their restrainers. The results of this model are verified by comparison to theoretical calculations and to experiments. The model has been implemented in programs IDARC2D and 3D‐BASIS, and the analytical results are compared with shake table experimental results. Copyright © 2013 John Wiley & Sons, Ltd.     

顾及信号相关关系的GPS坐标监测序列噪声分析

时间序列分析、谱分析和小波分析理论是对信号进行时、频域分析的主要方法,对GPS坐标监测序列研究并分析其噪声序列发现,GPS坐标监测序列中的噪声主要包含白噪声和闪烁噪声,但是大多数噪声分析方法未考虑信号之间的相关关系。针对GPS站坐标监测序列,在分析2维坐标信号之间相关性的基础上,采用多变量小波去噪工具实现坐标监测序列的2维去噪,对得到的2维噪声序列进行谱分析,并与传统1维去噪方法比较。以苏通大桥GPS坐标监测序列为实例进行分析,结果表明:顾及信号间相关关系的GPS坐标监测序列的噪声分析更加符合实际情况。     

IMU/GPS辅助ADS80数字航空摄影测量系统的技术研究

详细介绍了IMU/GPS辅助ADS80数字航空摄影测量系统的基本参数和影像数据结构,对ADS80数据的空三加密精度、坐标系转换等生产中需要注意的问题进行了研究探讨,总结出ADS80数字航空摄影测量系统的多项技术特点。     

Search for Star Groups in the Solar Neighborhood

Two methods are proposed for finding star groups in coordinate and velocity spaces, which were used to investigate stars of the Hipparcos Catalog with known radial velocities in the solar neighborhood with a radius of 125 pc. Thirteen probable nonrandom star groups in coordinate space and five moving groups in velocity space were found. These results are compared with the results of other authors.     

A re‐investigation of the low Reynolds number uniform flow past a porous spherical shell

This work reinvestigates the flow field of a uniform flow past a porous spherical shell based on Song and Huang's (2000) theory of laminar poroelastic media flow with proper boundary conditions. The analytical solution of this study not only indicates viscous effects inside the porous spherical shell, but it also preserves the continuities of tangential velocity and shear stress at the interfaces. The result reveals that as the porosity approaches unity, the flow is entirely comprised of the incident stream; as the porosity approaches zero, the well‐known Stokes' solution of a uniform flow past a sphere with low Reynolds number is obtained. Copyright © 2004 John Wiley & Sons, Ltd.     

Report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites: 2000

Every three years the IAU/IAG Working Group on cartographic coordinates and rotational elements of the planets and satellites revises tables giving the directions of the north poles of rotation and the prime meridians of the planets, satellites, and asteroids. Also presented are revised tables giving their sizes and shapes. Changes since the previous report are summarized in the Appendix.Merton Davies, The original chairman of this Working Group, died on April 17, 2001.     

后牛顿近似下旋转椭球体的内外度规

在后牛顿近似下,得到由均匀不可压缩理想流体在刚体自转下形成的扁球体的内外度规．对由后牛顿效应产生的度规分量利用椭球坐标系及级数展开求得解析解．对这一具体问题,在级数展开中仅存若干项,因此结果有可能用于这一度规下粒子运动的研究．     

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Multivariate techniques as alternative statistical tools applied to magnetic proxies for pollution: a case study from Argentina and Antarctica

Several statistical analyses—as alternative tools—were applied to magnetic monitoring studies. Magnetic and chemical data from two environments have been gathered from previous papers and studied separately. Univariate and multivariate analyses were first examined, revealing a link between magnetic and chemical variables. The latter analyses, in particular, canonical correlation analysis, showed very good canonical correlations: R = 0.950 (Antarctica) and R = 0.891 (Argentina). On the other hand, in order to classify the data according to the degree of contamination, principal coordinates and discriminant analyses, as well as the comparison of several multivariate means were performed. Three groups were distinguished in both case studies, which were well classified at a low margin of error and quite different from each other at a significant level: 0.01 (Antarctica) and 0.05 (Argentina). The joint use of these statistical analyses also showed, in agreement with previous studies, that the relevant variables in order to identify atmospheric pollution are: magnetic susceptibility, saturation of isothermal remanent magnetisation, anhysteric susceptibility/magnetic susceptibility, remanent coercivity, and copper, lead, zinc and chromium contents.