冲绳海槽有孔虫壳体的微量元素Sr,Nd同位素地球化学

钙质生物壳的微量元素组合和Sr,Nd同位素组成是识别海底混合源沉积物中生物源物质相对贡献的重要参数.冲绳海槽有孔虫壳体强烈富集Sr,P,Mn和Ba,富集Li,U,Th,Sc,Co,Pb,Zn,Cr,Rb,Y,Sb和轻稀土元素,弱富集V,Ga,Zr,Nb,Cd和中稀土元素,相对贫Ge,Mo,In,Sn,Cs,Hf,Ta,W,Tl,Bi和重稀土元素,海水中微量元素的背景含量和生物活动对微量元素的选择性吸收是有孔虫壳体中微量元素发生富集和贫化的主要机制,冲绳海槽有孔虫壳体的稀土元素配分模式与海水和太平洋有孔虫的有明显差异,表现出中稀土元素相对富集,并具有微弱的负Ce异常.有孔虫壳体的Sr,Nd同位素比值也与大洋海水不同,分别为0.709769和0.512162,前者略高于大洋海水,后者略低于大洋海水,表明冲绳海槽海水明显受大陆河水影响.     

Internal generation of waves: Delta source function method and source term addition method

In this study, we investigate two internal wave generation methods in numerical modeling of time-dependent equations for water wave propagation, i.e., delta source function method and source term addition method, the latter of which has been called the line source method in literatures. We derive delta source functions for the Boussinesq-type equations and extended mild-slope equations. By applying the fractional step splitting method, we show that the delta source function method is equivalent to the source term addition method employing the energy velocity. This suggests that the energy velocity should be used rather than the phase velocity for the transport of incident wave energy in the source term addition method. Finally, the performance of the delta source function method is verified by accurately generating nonlinear cnoidal waves as well as linear waves for horizontally one-dimensional cases.     

Numerical and experimental study on hydrodynamic interaction of side-by-side moored multiple vessels

This paper aims to investigate the basic interaction characteristics of side-by-side moored vessels both numerically and experimentally. A higher-order boundary element method (HOBEM) combined with generalized mode approach is applied to analysis of motion and drift force of side-by-side moored multiple vessels (LNG FPSO, LNGC and shuttle tankers). Model tests were carried out for the same floating bodies investigated in the numerical study in regular and irregular waves. Global and local motion responses and drift forces of three vessels are compared with those of calculations. Discussions is highlighted on applicability of numerical method to prediction of sophisticated multi-body interaction problem of which motion behavior is very important to analysis of mooring dynamics of deep sea floating bodies.     

Freely floating-body simulation by a 2D fully nonlinear numerical wave tank

Nonlinear interactions between large waves and freely floating bodies are investigated by a 2D fully nonlinear numerical wave tank (NWT). The fully nonlinear 2D NWT is developed based on the potential theory, MEL/material-node time-marching approach, and boundary element method (BEM). A robust and stable 4th-order Runge–Kutta fully updated time-integration scheme is used with regriding (every time step) and smoothing (every five steps). A special φ_n-η type numerical beach on the free surface is developed to minimize wave reflection from end-wall and wave maker. The acceleration-potential formulation and direct mode-decomposition method are used for calculating the time derivative of velocity potential. The indirect mode-decomposition method is also independently developed for cross-checking. The present fully nonlinear simulations for a 2D freely floating barge are compared with the corresponding linear results, Nojiri and Murayama’s (Trans. West-Jpn. Soc. Nav. Archit. 51 (1975)) experimental results, and Tanizawa and Minami’s (Abstract for the 6th Symposium on Nonlinear and Free-surface Flow, 1998) fully nonlinear simulation results. It is shown that the fully nonlinear results converge to the corresponding linear results as incident wave heights decrease. A noticeable discrepancy between linear and fully nonlinear simulations is observed near the resonance area, where the second and third harmonic sway forces are even bigger than the first harmonic component causing highly nonlinear features in sway time series. The surprisingly large second harmonic heave forces in short waves are also successfully reproduced. The fully updated time-marching scheme is found to be much more robust than the frozen-coefficient method in fully nonlinear simulations with floating bodies. To compare the role of free-surface and body-surface nonlinearities, the body-nonlinear-only case with linearized free-surface condition was separately developed and simulated.     

A new form of generalized Boussinesq equations for varying water depth

A new set of equations of motion for wave propagation in water with varying depth is derived in this study. The equations expressed by the velocity potentials and the wave surface elevations include first-order non-linearity of waves and have the same dispersion characteristic to the extended Boussinesq equations. Compared to the extended Boussinesq equations, the equations have only two unknown scalars and do not contain spatial derivatives with an order higher than 2. The wave equations are solved by a finite element method. Fourth-order predictor–corrector method is applied in the time integration and a damping layer is applied at the open boundary for absorbing the outgoing waves. The model is applied to several examples of wave propagation in variable water depth. The computational results are compared with experimental data and other numerical results available in literature. The comparison demonstrates that the new form of the equations is capable of calculating wave transformation from relative deep water to shallow water.     

Full-range nonlinear analysis of fatigue behaviors of reinforced concrete structures by finite element method

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标志沉积层磁组构特征及其古环境意义研究

通过对长江三角洲及其邻近区域埋藏古土壤、潮坪、长江下游河道浸滩、舟山滨岸风成沙丘、南京黄土古土壤序列沉积体的磁组构测量统计分析，取得了各自的标志特征。该２特征揭示出，舟山滨岸风成沙丘与南京黄土吉土壤序列沉积的搬运介质能量位相基本一致，其物源来向却显示出巨大差异；上述两类沉积体与上述现今潮坪、河道漫滩沉积体地搬运介质能量位相及物源来向均显示出绝然不同的标志特征。然而浸滩物源来民南京黄土的物尖兵为向却     

台湾海峡海洋捕捞业管理策略和投资方向

本文收集了１９８５￣１９９４年福建省在台湾海峡生产的具有代表性的５０对拖网渔船、１２０艘单拖渔船、４８组灯光围网渔船、３８对大围缯渔船、３１艘定置网渔船的技术参数及生产资料，计算并分析了其适正捕捞力量、经济指标，得出了一些有益的结论：（１）根据台湾海峡渔业资源，把握正确的投资方向，已成为进一步发展海洋捕捞业的关键。（２）由于台湾海峡的渔业资源正遭受越来越大的压力，为了保护渔业资源，应当限制捕捞力量     

Numerical Analysis of Wave Forces on Arbitrarily Shaped Multi-Pillars Over Varying Topography

The modified hybrid element method (MHEM) is utilized to predict and analyze wave forces on arbitrarily shaped multiple bodies. This method can be applied to waves of all water depths, i. e. shallow, intermediate, and deep waters, on slowly varying seabed. The MHEM employs the ICCG method to save CPU and storage, thus the computation of wave forces for large multi-body systems can be carried out on microcomputers. Numerical results of the present method are compared with experimental data and other solutions. It is shown that the MHEM provides more accurate solutions of the wave forces than other numerical methods do. Therefore, the methodology presented herein can be used in the design of coastal and ocean structures.