岩石圈流变结构的一种新的应变率约束

对目前存在的3种应变率约束条件（常应变率,常构造力,与应变率有关的构造力约束）进行了讨论,它们都不能真实地反映岩石圈内的应变率分布及实际观测.基于近几年GPS测量的研究结果,提出利用GPS实测应变率对岩石圈流变结构进行约束的新方法.对华北地区实际流变剖面的计算结果表明,本文方法克服了上述三种约束条件的不足,利用它所确定的岩石圈流变结构更为合理,在流变性质上较好地反映了与大地构造的对应关系,而且一定程度上反映岩石圈内各种状态参量及物质参量对流变结构的影响.同时还讨论了这种约束存在的问题.     

Multiple-Step Predictive Control for Offshore Structures

—Ocean wave propagation is slow,visible and measurable,so a wave theory can be used to approxi-mately predict the imminnent wave force on an offshore structure based on measured,real-time wave elevation nearthe structure.This predictability suggests the development of a more efficient algorithm,than those that have beendeveloped for structures under wind and seismic loads,for the active vibration control of offshore structures.Thepresent study delveops a mutiple-step predictive optimal control(MPOC)algorithm that accounts for multiple-step external loading in the determibation of optimal control forces.The control efficiency of the newly developedMPOC algorithm has been investigated under both regular(single-frequency)and irregular(multiple-frequency)wave loads,and compared with that of two other well-known optimal control algorithms:classical linear optimalcontrol(CLOC)and instantaneou optimal control(IOC).     

A Modified Form of Mild-Slope Equation with Weakly Nonlinear Effect

Nonlinear effect is of importance to waves propagating from deep water to shallow water.Thenon-linearity of waves is widely discussed due to its high precision in application.But there are still someproblems in dealing with the nonlinear waves in practice.In this paper,a modified form of mild-slope equa-tion with weakly nonlinear effect is derived by use of the nonlinear dispersion relation and the steady mild-slope equation containing energy dissipation.The modified form of mild-slope equation is convenient to solvenonlinear effect of waves.The model is tested against the laboratory measurement for the case of a submergedelliptical shoal on a slope beach given by Berkhoff et al,The present numerical results are also comparedwith those obtained through linear wave theory.Better agreement is obtained as the modified mild-slope e-quation is employed.And the modified mild-slope equation can reasonably simulate the weakly nonlinear ef-fect of wave propagation from deep water to coast.     

层序成因动力学中的构造因素研究

本文以层序－盆地－构造为主线，对层序成因动力学中的构造控制进行了研究。结果表明，层序发育的构造控制主要表现为：1）构造控制盆地边界，进而控制层序充填轮廓；2）构造级次控制层序和层序级别；3)构造属性控制盆地性质，进而控制层序成因格架和界面成因类型；4)随着层序规模和界面级别的增大，构造控制的意义和痕迹越明显；5)同沉积断裂活动控制层序的内部构型；6)构造基底活动形式控制着层序容纳空间和结构型式；7)构造演化控制着盆地演化及性质，进而控制着层序充填样式和组合类型。     

Mathematical Models for Combined Refraction-Diffraction of Waves on Non-Uniform Current and Depth

Two mathematical models for combined refraction-diffraction of regular and irregular waves on non-uniform current in water of slowly varying topography are presented in this paper. Model I is derived by wave theory and variational principle separately. It has two kinds of expressions including the dissipation term. Model n is based on the energy conservation equation with energy flux through the wave crest lines in orthogonal curvilinear coordinates and the wave kinematic conservation equation. The analysis and comparison and special cases of these two models are also given.     

Study on topographic compensation model of the Okinawa Trough I. Calculation of theoretical isostatic response function

INTRODUCTIONTo study the compensation model of sea topography and isostatic states by using toPOgraphicand gravity data, is an imPOrtant mean for further researching deep structures as elastic structure,stress state of lithosphere, and so on. Since Airy and Pratt proPOsed local isostatic model in the1850' s, greater development on the theoretical study has been attained. Veining Meinesz (1941 )introduced regional compensation mechanism by considering it as floating crust in elastic fie…     

本刊加入万方数据(ChinaInfo)系统科技期刊群的声明

为了实现科技期刊编辑、出版发行工作的电子化,推进科技信息交流的网络化进程,我刊现已入网"万方数据(ChinaInfo)系统科技期刊群",所以,向本刊投稿并录用的稿件文章,将一律由编辑部统一纳入万方数据(ChinaInfo)系统,进入因特网提供信息服务.凡有不同意者,请另投它刊.本刊所付稿酬包含刊物内容上网服务报酬,不再另付.     

A Global Reliability Assessment Method on Aging Offshore Platforms with Corrosion and Cracks

Corrosion and fatigue cracks are major threats to the structural integrity of aging offshore platforms. For the rational estimation of the safety levels of aging platforms, a global reliability assessment approach for aging offshore platforms with corrosion and fatigue cracks is presented in this paper. The base shear capacity is taken as the global ultimate strength of the offshore platforms. It is modeled as a random process that decreases with time in the presence of corrosion and fatigue crack propagati...     

Model Test Study on Ice-Induced Vibrations of Compliant Multi-Cone Structures

For the study on the ice-induced vibration of a compliant mono-cone structure,a series of model tests were performed from 2004 to 2006.In these tests,the ice sheet before the compliant conical structure was found to be failed in two-time breaking.Based on this important finding,model tests study of the ice force on a compliant multi-cone structure were performed from 2006 to 2007.in these tests,the ice sheet broke before each single cone non-simultaneously.The exciting energy of the total ice force was found to be in a wide range of frequencies,and the structure can be easily excited with nonlinear resonance.     

Effect of Fly Ash on Frost-Resistance and Chloride Ions Diffusion Properties of Marine Concrete

It is necessary to pay more attention to the durability of concrete undergoing freeze-thaw cycles and seawater attack simultaneously.Investigated are the effects of water-binder ratio,fly ash (FA) contents and air-entraining agent on resistance to frost and chloride diffusion of marine concrete blended with FA in natural seawater.The results show that fly ash does not improve the frost resistance of concrete but can improve its resistance to chloride diffusion by addition of less than 30%.The resistance to frost and chloride diffusion of FA concrete can be improved with the decrease of water-binder ratio,and FA may improve both of them simultaneously only being mixed with air-entraining agent.A ratio (named as R) of the frost-resisting durability factor to chloride diffusion coefficient can be used to evaluate the durability of marine concrete.Scanning electron microscope (SEM) analyses are consistent with the evaluations by the value of R.