Influence of structural flexibility and wave interference on dynamic behavior of idealized offshore platform

An approximate method is presented to estimate the hydrodynamic loading and structural response of an idealized offshore platform subjected to a regular train of linear surface waves. The platform is taken to consist of four bottom-mounted, flexible, circular cylinders supporting a rigid deck and is assumed to be aligned parallel to the incident wave direction. The response of each column is assumed to be one-dimensional and to be governed by linear beam theory. The solution technique for the fluid velocity potential involves replacing scattered waves by equivalent plane waves together with non-planar, first-correction terms, and can be shown to be a large spacing approximation.Numerical results are presented which show the effect of hydrodynamic interference and structural flexibility on the platform response.     

Formation of chemogenic calcite in super-anoxic seawater — Framvaren, southern Norway

Framvaren, a super-anoxic fjord in southern Norway, contains 7–8 mmoll⁻¹ of sulphide and a total carbonate concentration of 18.5 mmol kg⁻¹ in the bottom water. The chemistry of calcium has been studied, considering sources, biogenic and chemical processes and sedimentary sinks. Calcium associated with the bacteria biomass at the redox interface (18m depth) appears to be the primary source of dissolved calcium in the deep, anoxic water. Excess calcium and high total carbonate cause supersaturation of calcite, which is precipitated chemogenically. Calcite (and presumably some aragonite) is identified both in sediment trap material and the bottom sediments below the depth of supersaturation.     

The uptake and accumulation of Ni by Cerastoderma edule and its effect on mortality,body condition and respiration rate

The concentration of Ni in C. edule ranges from 17·8 μg/g to 53·82 μg/g with the highest concentration in the gills and mantle and the lowest in the foot and adductor muscles. The concentration does not change with either size or season.There is no significant increase in mortality even in the highest Ni concentration (100 μg/litre), nor is body condition correlated with experimental Ni concentrations. The rate of uptake of Ni (y) is described by the equation:

$\text{y=?16·903+11·674x}{}_1\text{+0·437x}{}_2$

where x₁ = Ni concentration (μg/litre) and x₂ = time (h).The respiration rates did not significantly change up to the highest Ni concentration used (1000 μg/litre).It is postulated that the main pathway for Ni uptake is through the gills, possibly through mucus sheet or transmembrane absorption, with a secondary uptake route via the viscera.C. edule may therefore be a suitable indicator species for Ni.     

Ionic activity coefficients in aqueous mixtures of NaCl and MgCl2

Methods developed earlier, based on hydration numbers for individual ionic species, have been extended to the calculation of ionic activity coefficients in aqueous systems of two electrolytes MX and NX₂ with a common unhydrated anion (X⁻). The data required include the mean activity coefficients of MX and NX₂ in the mixtures, together with the osmotic coefficient. The procedure is illustrated by a calculation of γ_Na, γ_Mg, and γ_Cl in a mixture of NaCl and MgCl₂ closely approximating the composition of seawater with salinity of 35‰.     

The role of damped equatorial waves in the oceanic response to winds

In inviscid shallow water models currents generated by spatially uniform winds are transient and are eliminated by Rossby and equatorial Kelvin waves excited at the eastern and western coasts, respectively. The inclusion of mixing processes can lead to an entirely different steady state in which currents are present. It is shown that the mixing of heat affects the steady state more than does the mixing of momentum because the waves that are important in the oceanic adjustment are divergent.     

Estimation of the leeway drift of small craft

Small craft (<6·4 m) leeway is determined as a function of the wind speed in the range of 5–20 knots (3·6–10·3 m/sec). Leeway is calculated relative to the surface current by measurement of the separation distance of the small craft from a dyed patch of surface water at sea, using time-sequenced aerial photography. Leeway increases linearly with wind speed for small craft equipped with or without a sea anchor in the wind range studied. Leeway for small craft without sea anchor can be calculated from the equation U_L = 0.07 U_W + 0.04 where U_W is the wind speed at 2 m elevation. Leeway for small craft drifted off the be calculated from the equation U_LD = 0·05 U_W − 0·12. The small craft drifted off the downwind direction in about 80% of the experiments. The drift angle is variable and difficult to predict.     

烟台市污水处理深海排放工程设计方案研究与选择

沿海城市污水处理深海排放工程在我国起步较晚，烟台市污水处理深海排放工程我国目前规模最大的同类工程，且已进入施工阶段，本文详细阐述了该工程及水工设计方案，在我国城市污水２深海排放工程领域作了积极有益的探索。     

黄海溶解氧垂直分布最大值的成因

本文对黄海溶解氧垂直分布中最大值的成因进行了探讨．认为：浮游植物春花期光合作用产生的大量氧，是溶解氧垂直分布最大值得以在春季（5月）形成的基础；而良好的温、密跃层的存在是氧最大值得以形成的必要条件，夏季叶绿素最大值层中较强的光合作用，是氧最大值在夏季得以维持甚至增强的主要原因．提出：黄海春、夏季溶解氧垂直分布中的最大值并非主要由冬季保持而来．