振动系统的逆与优化问题(Part-Ⅱ)部分边界值再构内部场(I)理论(英文)

研究由一振动体的部分边界测量数据再构振动体内部场的逆问题。提出基于偏微分方程控制方法的一种算法 ,并证明原用于处理散射问题的 Null- field method可用来求解优化问题的随伴问题。     

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…     

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.     

Nonlinear Effect of Wave Propagation in Shallow Water

—In this paper,a nonlinear model is presented to describe wave transformation in shallow wat-er with the zero-vorticity equation of wave-number vector and energy conservation equation.Thenonlinear effect due to an empirical dispersion relation(by Hedges)is compared with that of Dalrymple＇sdispersion relation.The model is tested against the laboratory measurements for the case of a submergedelliptical shoal on a slope beach,where both refraction and diffraction are significant.The computation re-sults,compared with those obtained through linear dispersion relation.show that the nonlinear effect ofwave transformation in shallow water is important.And the empirical dispersion relation is suitable for re-searching the nonlinearity of wave in shallow water.     

The Optimal Design of TMD for Offshore Structures

This paper presents the optimal design procedure of Tuned Mass Damper(TMD)for re-ducing vibration of an actual steel jacket offshore platform excited by random wave loading.In this study,a frequency domain is taken.The force on the structure is determined by use of the linearized Morisonequation for an input Power Spectral Density(PSD)of wave elevation.The sensitivity of optimum valuesof TMD to characteristic parameters of random wave spectrum is analyzed.An optimized TMD designfor the modeled platform is given based on design conditions and the findings of the study.     

华北克拉通北缘西段中元古代花岗岩类的特征及其形成构造环境

华北克拉通北缘西段中元古代花岗岩类仅见于查干础鲁－霍尔森构造带以南的雅布赖－巴音诺尔公构造带中，整体上受NEE向长寿命线性构造控制。据岩性可分为斜长花岗岩和石英闪长岩两类。斜长花岗岩为S型花岗岩，但具有向I型过渡的特征，富含Cr,Ni,SiO2,Al2O3，其均值分别为672μg/g，405μg/g,71.40%和14．93％。δEu值变化大，介于0．34和3．95之间，起源于幔源岩浆与壳源物质的混合。石英闪长岩为典型的I型花岗岩，其Cr,Ni含量的均值分别为220μg/g和162μg/g，类似于华南同熔型花岗岩。斜长花岗岩中的锆石U－Pb等时线上交年龄为1256Ma，代表了发生于华北克拉通北缘西段的一次构造－热事件。伴随这一构造－热事件，华北克拉通北缘西段发生拉伸裂解，进入拉张型过渡壳阶段。中元古代花岗岩类是这一构造热事件的重要产物。在这一构造－热事件中，推测查干础鲁－霍尔森一线地壳减薄最大，其北侧的宗乃山－沙拉扎山构造带因无同时代岩浆作用，为非火山型被动陆缘，南侧的雅布赖－巴音诺尔公构造带广泛发育了花岗岩类，镁铁质、超镁铁质侵入岩，以及火山－沉积组合，为火山型被动陆缘，二者构成被动陆缘“对”。     

Effect of Internal Flow on Vortex-Induced Vibration of Submarine Free Spanning Pipelines

At present, most researches on the vortex-induced vibration of submarine free spanning pipelines ignore the effect of internal flowing fluid; furthermore, there are no research reports considering the coupling effect of internal and external fluid with the free span. In this paper, combining Iwan‘s wake oscillator model with the differential equation derived for the dynamic response of submarine free spanning pipelines with inclusion of internal flow, the pipe-fluid coupling equations are developed to investigate the effect of internal flow on the vortex-induced vibration of the free spans. The finite dement approximation is implemented to derive the matrix equations of equilibrium. The Newmark method combined with simple iteration is used to solve the system of equations. The results indicate that the internal fluid flow may cause the shift of resonance band to the lower frequency and a slight decrease in the peak value; the effect will be mare pronounced with the increase of the span length and can be weakened in the presence of the axial tension.     

高度计资料监测日本以南黑潮主轴特性的变化

应用1993年至2001年TOPEX／Poseidon(以下简写为T／P)卫星高度计3条下行轨道的沿轨资料，计算分析了日本以南黑潮主轴的摆动特性，发现在1993年和2000—2001年010轨道上有2次空间尺度较大、持续时间较长的弯曲。黑潮处于平直路径时流速比较大；呈稳定弯曲状态时流速与多年平均值相差不大；而黑潮在两种稳态之间转换时，伴随着流速负距平的出现。     

Beta Distribution of Surface Elevation of Random Waves

A probability density function (PDF) is derived of beta distribution with both λ3 (skewness) and λ4 (kurtosis) as parameters for weakly nonlinear wave surface elevation by use of a method recently proposed by Srokosz. This PDF not only has a simpler form than the well-known Gram-Charlier Series PDF derived by Longuet-Higgins. but also overcomes an obvious shortcoming of the latter that when the series is unsuitably truncated, the resulting PDF is locally negative. To test the derived beta PDF, laboratorial experiments of wind waves are conducted. The experimental data indicate that the theoretical requirements of the parameters in the beta PDF are fulfilled. The experimental results show that the present PDF is in better agreement with the measured data than the beta PDF only including parameter λ3, and also than the Gram-Charlier Series PDF truncated up to the term of H6.