Geochemistry and environment evolution of Core E in the Laizhou Bay since last stage of Middle Pleistocene

IwrincrIONOn the evolution of palcoenvironment, salt-water encroachmnt and the distributionof subsurface brine in the LaizhOu Bay area, many researches had been carried out, and muchknowledge abeut the gcolOgical features in this area since Late QUaternary was aCquired' ) (H8nand Wu, l992; Han and Meng, l994; Wen et al. l989). However there was IittIe studyon the sediment geOChemical characteristics since Quaternary. In this Paper, the element strati-graphic characteristics and evolut…     

非常规管节点疲劳寿命分析与计算

对非常规管节点的疲劳寿命进行了分析研究，用SESAM计算疲劳载荷，应用精细有限元分析计算热点应力，用规范的S—N曲线计算管节点的疲劳寿命。通过实例计算表明，这些处理对非常规管节点疲劳寿命分析与计算是很有效的。     

夏、冬两季长江口及邻近海域悬浮物的分布特征及其沉积量

利用2001年7～8月 ,2002年1月两个航次的悬浮物浓度资料 ,并参考其它水文参数 ,简要分析长江口及邻近海域悬浮物的分布特征 :无论夏季还是冬季 ,长江入海悬浮物总是向东南方输运 ;冬季由于再悬浮作用显著 ,悬浮物浓度明显高于夏季 ,且南北分布范围也明显增大 ,垂向分布均匀。同时采用数值模拟的海流流速值和观测的悬浮物浓度值计算悬浮物的断面通量 ,并最终得计算区悬浮物夏、冬两季的沉积量 ,夏、冬季长江口及邻近海域悬浮物的沉积量分别为0.79×108t,1.44×108t。     

Geochemistry of trace elements and Sr-Nd isotopes of foraminifera shell from the Okinawa Trough

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Quantum yield for the photochemical production of dissolved inorganic carbon in seawater

The direct photooxidation of coloured dissolved organic matter (CDOM) to dissolved inorganic carbon (DIC) may provide a significant sink for organic carbon in the ocean. To calculate the rate of this reaction on a global scale, it is essential to know its quantum yield, or photochemical efficiency. We have determined quantum yield spectra, φ(λ), (moles DIC/mole photons absorbed) for 14 samples of seawater from environments ranging from a turbid, eutrophic bay to the Gulf Stream. The spectra vary among locations, but can be represented quite well by three pooled spectra for zones defined by location and salinity: inshore φ(λ)=e^{−(6.66+0.0285(λ−290))}; coastal φ(λ)=e^{−(6.36+0.0140(λ−290))}; and open ocean φ(λ)=e^{−(5.53+0.00914(λ−290))}. Production efficiency increases offshore, which suggests that the most highly absorbing and quickly faded terrestrial chromophores are not those directly responsible for DIC photoproduction.     

Structural modeling and testing of a concrete canoe

A finite element model is set up and experimental tests are performed to help understand the behavior of a concrete canoe and subsequently optimize its design. First, the performance criteria that must be satisfied to participate at the annual ASCE/Master Builders competition are described. Then, the finite element model and the different loading cases that were studied are presented. Results from these loading cases are discussed and used to optimize the material properties as well as the thickness of the hull and the dimensions of the gunwale and reinforcing ribs. Static and dynamic experimental tests were also conducted to validate the results of the finite element analyses. The results indicate that the main stresses and strains are caused by the static load cases. The additional stresses caused during races are small.     

Distributions of dissolved and particulate biogenic thiols in the subartic Pacific Ocean

Dissolved and particulate concentrations of the biogenic thiols cysteine (Cys), arginine–cysteine (Arg–Cys), glutamine–cysteine (Gln–Cys), γ-glutamate–cysteine (γ-Glu–Cys) and glutathione (GSH) were measured in the subartic Pacific Ocean in the summer of 2003 using high performance liquid chromatography (HPLC) with precolumn derivatization as reported in previous work. In this study, a preconcentration protocol for the derivatized thiols was utilized to extend detection limits of dissolved thiols to picomolar levels. The measured concentrations of particulate and dissolved thiols were uncoupled, with distinctive depth profiles and large differences in the particulate to dissolved ratios between individual compounds. Glutathione was the most abundant particulate thiol whereas the most abundant dissolved thiol was γ-Glu–Cys, with concentrations as high as 15 nM. Given the relatively small pool of intracellular γ-Glu–Cys and the very low dissolved concentrations of GSH, we hypothesize that glutathione released from cells is rapidly converted to the potentially degradation resistant γ-Glu–Cys outside the cell. The relatively high concentrations of other dissolved thiols compared to particulate concentrations implies both biological exudation and slow degradation rates. Some thiols appear to vary with changes in nutrient availability but this effect is difficult to decouple from changes in community structure inferred from pigment analyses. Dissolved thiol concentrations also exceed typical metal concentrations in the subartic Pacific, supporting previous arguments that they may be important in metal speciation.     

Complexation of mercury by dissolved organic matter in surface waters of Galveston Bay, Texas

The chemical speciation of dissolved mercury in surface waters of Galveston Bay was determined using the concentrations of mercury-complexing ligands and conditional stability constants of mercury-ligand complexes. Two classes of natural ligands associated with dissolved organic matter were determined by a competitive ligand exchange-solvent solvent extraction (CLE-SSE) method: a strong class (L_s), ranging from 19 to 93 pM with an average conditional stability constant (K_HgLs) of 10²⁸, and a weak class (L_w) ranging from 1.4 to 9.8 nM with an average K_HgLs of 10²³. The range of conditional stability constants between mercury and natural ligands suggested that sulfides and thiolates are important binding sites for dissolved mercury in estuarine waters. A positive correlation between the estuarine distribution of dissolved glutathione and that of mercury-complexing ligands supported this suggestion. Thermodynamic equilibrium modeling using stability constants for HgL, HgCl_x, Hg(OH)_x, and HgCl(OH) and concentrations of each ligand demonstrated that almost all of the dissolved mercury (> 99%) in Galveston Bay was complexed by natural ligands associated with dissolved organic matter. The importance of low concentrations of high-affinity ligands that may originate in the biological system (i.e., glutathione and phytochelatin) suggests that the greater portion of bulk dissolved organic matter may not be important for mercury complexation in estuarine surface waters.     

A finite element model of interaction between viscous free surface waves and submerged cylinders

This paper describes the simulation of the flow of a viscous incompressible Newtonian liquid with a free surface. The Navier–Stokes equations are formulated using a streamline upwind Petrov–Galerkin scheme, and solved on a Q-tree-based finite element mesh that adapts to the moving free surface of the liquid. Special attention is given to fitting the mesh correctly to the free surface and solid wall boundaries. Fully non-linear free surface boundary conditions are implemented. Test cases include sloshing free surface motions in a rectangular tank and progressive waves over submerged cylinders.     

Modified mild slope equation and open boundary conditions

A numerical model to compute wave field is developed. It is based on the Berkhoff diffraction-refraction equation, in which an energy dissipation term is added, to take into account the breaking and the bottom friction phenomena. The energy dissipation function, by breaking and by bottom friction, is introduced in the Berkhoff equation to obtain a new equation of propagation.The resolution is done with the hybrid finite element method, where lagrangians elements are used.