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81.
82.
本文讨论利用三维反射地震数据进行波场反演的一种方法,旨在取得高分辨率的地球模型.这种方法用Backus-Gilbert的理论构造波动方程非线性反问题的逐次线性化迭代格式,用逆散射原理导出泛函的Frechet导数,并用最佳折衷准则求解线性化后的方程组.根据迭代过程中不断提高分辨率的思想和减少计算成本的原则,设计了可供实用的反演算法流程. 相似文献
83.
进一步讨论了大中尺度Rossby波与惯性重力波的非线性相互作用问题.从共振相互作用曲线来看,Rossby波和惯性重力波可以在相当广泛的角谱范围内发生共振非线性相互作用.在一定条件下,一个大振幅波包可以激发两个小振幅波包不稳定增长而出现参量不稳定现象,这三个波包可以是同种类型或不同类型的波包.当两个大振幅波包发生相互作用时,非线性过程会产生另一个波包并使它增长,并且增长速度大于仅有一个大振幅波包时的增长速度.大尺度Rossby波包税发两个较小尺度惯性重力波的过程是一种重要的能量串级(cascade)过程. 相似文献
84.
在地球物理非线性反演方法中,模拟退火法是一种较先进的启发式蒙特卡洛(MonteCarlo)方法.但是,在处理实际资料时,该方法存在着计算效率不够高的缺点,有时还会失效.为此,从模拟退少法的关键问题──最低温度的选择入手,根据模拟退火法与统计力学的吉布斯-马尔柯夫(Gibbs-Markov)模型之间的关系导出临界温度的近似表达式;用此式分析目标函数超曲面形状对模拟退火法计算的影响;提出利用模糊先验信息确定最低温度、改造目标函数等改进措施. 相似文献
85.
The paper describes a stationary model of the boundary layer of a large-scale vortex. The model takes into account two types of nonlinearities: (1) advection of the momentum and centrifugal accelerations, that is related to large values of the Rossby number; (2) a nonlinear turbulent friction on the lower boundary (generally speaking, not only quadratic, but also more complicated). Nevertheless, the model may be studied analytically. This approach allows discovery and analysis of several universal regularities, which are not revealed by numerical modeling. The model provides the actual values for the speed of the surface wind and the angle of cross-isobar surface flow in the tropical cyclones. 相似文献
86.
This paper presents two numerical case studies of medium and strong motion events, namely Loma-Prieta 1989 and Hyogoken-Nambu
(Kobe) 1995. These simulations were performed using CyberQuake model. The cyclic elastoplastic constitutive model is fully detailed in the companion paper. Through these case studies,
we demonstrate the importance of using appropriate constitutive modelling when the part played by nonlinear phenomena is preponderant.
The need to account for 3D kinematics (i.e. the three components of the input motion), is also demonstrated, even though a
1D geometry is considered, as the plastic coupling existing between components of motion during the earthquake, strongly affects
the seismic soil response. 相似文献
87.
A time-domain method for the analysis of arch dam-foundation rock dynamic interaction during earthquake was proposed, and
the dynamic relaxation technique was adopted to obtain the initial static response for dynamic analysis by [Du et al. (2005).
The paper has been contributed to Bulletin of earthquake engineering]. In this paper, a nonlinear explicit method in time
domain considering the opening and closing effect of contact joints on arch dam during earthquake is further proposed by introducing
the dynamic contact force model into the method. The simulation accuracy of dynamic contact force model is verified by comparing
its calculation result and test result of scale model on shaking table. Finally, the influence of joints on the seismic response
of Xiaowan arch dam is studied by the proposed method and some conclusions are given. 相似文献
88.
In recent years, more and more studies are focused on the performance in seismic design instead of the strength of structures. People have realized that the structure deformation (displacement) can describe the damage more properly and directly than the strength (force). The displacement design spectra need to be constructed within more wide range of the period and the damping for the displacement-based seismic design. 相似文献
89.
This paper points to the need for seismic risk and vulnerability assessment of infrastructure systems, most notably tall structures and coastal facilities, in Kuwait and other Arabian Gulf countries. Building codes in the region currently lack seismic provisions, despite evidence of a potential threat from large-magnitude earthquakes originating from the southern part of the Zagros fold belt. The historical record of Iranian earthquakes that may have caused significant ground motion in the Gulf region is examined, as are reports of coastal damage from tsunamis. Various specific tasks, expected to constitute research priorities of a Joint Center for Risk Research, a cooperative research program involving Princeton and Kuwait Universities, are outlined. 相似文献
90.
An electrical substation consists of a complex set of equipment items that are interconnected through conductor buses or cables. If the connections are not sufficiently flexible, significant dynamic interaction may occur between the connected equipment items during a seismic excitation. This interaction is believed to be responsible for some of the observed substation equipment damage in recent earthquakes. This paper investigates the interaction between two equipment items connected by a linear spring‐dashpot or spring‐dashpot‐mass element representing a conductor bus. It is found that the interaction between the two equipment items may significantly amplify the response of the higher‐frequency equipment item. The influences of various key parameters on the interaction effect are quantified. Means for reducing the adverse interaction effect are described. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献