地学自由曲面径向基函数网络重建的详细算法

径向基函数(RadialBasisFunction,简称RBF)神经网络是一种理想的地学离散数据网格化工具,能够适应各种不同分布形式和边界条件的数据,收敛速度较快,可以逼近任何复杂曲面。这里详细介绍了RBF神经网络的算法。适当径向基函数的形式和偏差系数是使用RBF神经网络作地学曲面重建的关键。大量的实际数据验证结果表明,当选用Gauss型径向基函数时,一般可获得比较理想的网格化效果,同时具备"曲面平滑"和"拟合度高"的特点。     

火山射气岩浆喷发作用研究进展

射气岩浆喷发是一种特殊类型的火山活动，水在这类火山活动中起到至关重要的作用，且其喷发产物——低平火山口和基浪堆积物在我国乃至全世界都有广泛的分布。国际上对射气岩浆喷发的研究始于1921年，迄今为止已有80余年的历史。国内外许多学者运用火山地质学、岩石学、沉积学、物理火山学及数值模拟等多学科研究手段，对射气岩浆喷发作用及其产物进行详细的野外观测描述，并探讨其成因机制。本文在前人研究基础上，以我国南方北部湾周边第四纪火山区大量存在的射气岩浆喷发成因的低平火山口和基浪堆积物为研究对象，深入讨论了基浪堆积物的地质特征、射气岩浆喷发形成的基本条件、喷发过程的动力学机制以及基浪流的搬运过程等几方面重要问题，并对已有的研究成果进行了概括和总结，提出有待解决的难点，揭示了这类火山活动特有的属性。     

房产测绘平面图系统的实现研究

随着城市规划管理的不断发展．使得城市房产测绘单位采用大型空间数据库管理测绘平面图资料成为必然。通过建立房产测绘平面图系统，可以有效地解决数据标准不一致．图数不能互访，测绘各部门无法协调一致等问题，充分发挥网络功能，提升整个城市的房产管理水平．达到房产管理和房产服务一体化的目标。本文详细论述了房产测绘平面图系统的概念、设计原则和系统功能．在南京数字房产共享平台的建设中得到了实现．并取得了良好的效果。     

Selective controlled base isolation system with magnetorheological dampers

A base isolation system composed of low‐damping isolation bearings and magnetorheological (MR) fluid dampers is described. The MR fluid changes its properties under the influence of a magnetic field resulting in a damper with characteristics that may be modified in real time. This feature enables optimal control under changing excitations in a stable and cost‐effective manner. The voltage is applied according to a selective control strategy. According to the proposed approach the dampers are activated only within a given range of the base displacements. The selective control improves the efficiency of the system and significantly reduces the control forces required for an optimal structural behaviour. Models of five‐ and eight‐storey buildings are used to study the efficiency of the proposed system. Copyright © 2002 John Wiley & Sons, Ltd.     

Pseudodynamic tests on rubber base isolators with numerical substructuring of the superstructure and strain‐rate effect compensation

A pseudodynamic testing procedure has been applied by which the seismic response of a base‐isolated building is obtained by using as specimen the isolators, while the superstructure is numerically simulated. The procedure also takes advantage of the continuous pseudodynamic testing capabilities of the ELSA laboratory, which increase the accuracy of the results and reduce the strain‐rate effect of the rubber bearings. A simple proportional correction of the measured forces compensates the remaining strain‐rate effect due to the unrealistic speed of the test. The correction factor is obtained by means of a characterizing test on the specific rubber isolators. The developed method has been successfully applied to the prediction of the seismic response of a base‐isolated four‐storey building submitted to several specified accelerograms. The results for those earthquakes as well as the effects of some changes of the parameters of the system are discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Study on effects of damping in laminated rubber bearings on seismic responses for a ⅛ scale isolated test structure

The effects of damping in various laminated rubber bearings (LRB) on the seismic response of a ?‐scale isolated test structure are investigated by shaking table tests and seismic response analyses. A series of shaking table tests of the structure were performed for a fixed base design and for a base isolation design. Two different types of LRB were used: natural rubber bearings (NRB) and lead rubber bearings (LLRB). Three different designs for the LLRB were tested; each design had a different diameter of lead plug, and thus, different damping values. Artificial time histories of peak ground acceleration 0.4g were used in both the tests and the analyses. In both shaking table tests and analyses, as expected, the acceleration responses of the seismically isolated test structure were considerably reduced. However, the shear displacement at the isolators was increased. To reduce the shear displacement in the isolators, the diameter of the lead plug in the LLRB had to be enlarged to increase isolator damping by more than 24%. This caused the isolator stiffness to increase, and resulted in amplifying the floor acceleration response spectra of the isolated test structure in the higher frequency ranges with a monotonic reduction of isolator shear displacement. Copyright © 2002 John Wiley & Sons, Ltd.     

Approximate analysis methods for asymmetric plan base‐isolated buildings

An approximate method for linear analysis of asymmetric‐plan, multistorey buildings is specialized for a single‐storey, base‐isolated structure. To find the mode shapes of the torsionally coupled system, the Rayleigh–Ritz procedure is applied using the torsionally uncoupled modes as Ritz vectors. This approach reduces to analysis of two single‐storey systems, each with vibration properties and eccentricities (labelled ‘effective eccentricities’) similar to corresponding properties of the isolation system or the fixed‐base structure. With certain assumptions, the vibration properties of the coupled system can be expressed explicitly in terms of these single‐storey system properties. Three different methods are developed: the first is a direct application of the Rayleigh–Ritz procedure; the second and third use simplifications for the effective eccentricities, assuming a relatively stiff superstructure. The accuracy of these proposed methods and the rigid structure method in determining responses are assessed for a range of system parameters including eccentricity and structure flexibility. For a subset of systems with equal isolation and structural eccentricities, two of the methods are exact and the third is sufficiently accurate; all three are preferred to the rigid structure method. For systems with zero isolation eccentricity, however, all approximate methods considered are inconsistent and should be applied with caution, only to systems with small structural eccentricities or stiff structures. Copyright © 2001 John Wiley & Sons, Ltd.     

工业革命以来青藏高原与南极冰芯高分辨率甲烷记录对比研究

自工业革命以来全球大气CH4含量呈快速的增长趋势, 但达索普冰芯记录所显示的北半球中低纬度地区大气CH4增长的启动时间要晚于极地冰芯记录近100 a. 由于受北半球人类活动CH4排放、CH4在大气中的寿命及大气中CH4的传输等过程的影响, 最近150 a以来, 中低纬度大气CH4与南极大气CH4含量在不同的时段表现出不同的净积累量和增长速率, 且20世纪两次世界大战期间达索普冰芯记录明确显示出人类活动排放的减缓使大气CH4呈负增长. 对比研究认为, 到20世纪中叶人类活动的甲烷排放已达到极高值, 中低纬度大气中CH4增长率及年积累逐步趋于平稳且略有降低. 可以认定, 工业革命以来中低纬度地区大气CH4与南极大气CH4含量的变化在不同的时段在受控于人类活动影响的同时, CH4在大气中的行为和传输过程以及东亚中低纬度季风气候的影响决定了两地之间大气CH4含量变化存在显著的差异.     

鄂尔多斯盆地上古生界高分辨率层序地层分析

按基准面旋回原理，将鄂尔多斯盆地上古生界本溪组（C2b)、太原组（P1t）、山西组(P1s)和下石盒子组（P1xs)划分为3个超长期、8个长期、19个中期和62个短期旋回层序：较为详细地介绍了各级别层序的结构类型、叠加样式和沉积演化序列；建立以长期旋回层序为年代地层框架，中期旋回层序为等时地层对比单元的层序的地层格架；并讨论高分辨率层序地层与天然气藏的关系。     

Principal axes of m-DOF structures PartⅠ:Static loading

This paper is the first in a two-part series that discusses the principal axes of M-DOF structures subjected to static and dynamic loads. The primary purpose of this series is to understand the magnitude of the dynamic response of structures to enable better design of structures and control modification devices/systems. Under idealized design conditions, the structural responses are obtained by using single direction input ground motions in the direction of the intended control devices/systems,and by assuming that the responses of the structure is decoupleable in three mutually perpendicular directions. This standard practice has been applied to both new and retrofitted structures using various seismic protective systems. Very limited information is available on the effects of neglecting the impact of directional couplings (cross effects - of which torsion is a component) of the dynamic response of structures. In order to quantify such effects, it is necessary to examine the principal axes of structures under both static and dynamic loading.This first paper deals with quantitative definitions of principal axes and "cross effects" of three-dimensional structures under static load by using linear algebra. It shows theoretically that, for three-dimensional structures, such principal axes rarely exist. Under static loading conditions, the cross effect is typically small and negligible from the viewpoint of engineering applications. However, it provides the theoretical base for subsequent quantification of the response couplings under dynamic loads, which is reported in part Ⅱ of this series.