Problems with biogenic silica measurement in marginal seas

Surface sediment samples from the Bohai, Yellow Sea, and the Pacific were used to assess biogenic silica (BSi) content and to study uncertainties in BSi measurements. The contents of BSi in the Bohai and Yellow Sea are all less than 1%. The dissolution of BSi in sediments from the Bohai and Yellow Sea is very important to maintain high levels of silicate in the water column. The non-biogenic silica from clay minerals has an obvious effect on BSi of sediment samples in the Bohai and Yellow Sea with low BSi and high clay minerals. The solid to solution ratio was found to have a great influence on BSi measurement, which can induce uncertainties up to 75%. The effect of loss by sorption and centrifugation is negligible. Interlaboratory comparison of techniques for BSi measurement by the wet alkaline extraction technique of Mortlock and Froelich [Deep-Sea Res. 36 (1989) 1415-1426] with clay correction was suggested to give no significant differences. However, differences in sediment compositions and reagent to sample ratio may limit the application of the wet alkaline extraction method.     

Rain-Flow and Reverse Rain-Flow Counting Method for the Compilation of Fatigue Load Spectrum

The rain-flow counting method is widely used to compile the fatigue load spectrum. The second stage counting of the rain-flow method is a troublesome process. In order to overcome this drawback, the rain-flow and reverse rain-flow counting method is proposed in this paper. In this counting method, the rule for counting of the rain-flow method is modified, so that the sequence of load-time need not be adjusted. This is a valid and useful method to count cycles and compile the load spectrum and it can be widely used in ocean engineering.     

Parameter identification of a compliant nonlinear SDOF system in random ocean waves by reverse MISO method

The determination of the drag and inertia coefficients, which enter into the wave force model given by Morison's equation, is particularly uncertain and difficult when a linear spectral model is used for ocean waves, and the structure is compliant and has nonlinear dynamic response. In this paper, a nonlinear System Identification method, called Reverse Multiple Inputs–Single Output (R–MISO) is applied to identify the hydrodynamic coefficients as well as the nonlinear stiffness parameter for a compliant single-degree-of-freedom system. Four different types of problems have been identified for use in various situations and the R–MISO has been applied to all of them. One of the problems requires iterative solution strategy to identify the parameters. The method has been found to be efficient in predicting the parameters with reasonable accuracy and has the potential for use in the laboratory experiments on compliant nonlinear offshore systems.     

A method of determining dominant wave direction from multiparameter hydrological gauge measurements and its application

Multi-parameter hydrological gauge is an instrument developed by the South China Sea Institute of Oceanology,the Chinese Academy of Sciences to make simultaneous observation of current, wave, tide, water temperature and conductivity.By using the well-known "PUV method", the directional wave spectrum can be calculated and the dominant wave direction is then obtained.The comparison of the dominant wave directions derived from the measurements using both the multi-parameter hydrological gauge and the MARK Ⅱ "Wave-Rider" directional buoy shows that the dominant wave directions derived from the two kinds of measurements are in good agreement.     

Fluctuations of peak energy and peak frequency of local wavelet energy spectrum for wind waves

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双峰谱型海浪的波高和周期分布

本文利用收集到的实测双峰谱型海浪过程资料，把这些资料以波高和周期的相关系数为参数分成５组，讨论每组双峰谱型下被高、周期的统计分布．并探讨了相关系数对波高分布和周期分布的影响。     

A proposed directional function and wind-wave directional spectrum

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GPS数据采集技术及其在海洋调查中的应用

本文应用VB6．0开发了智能化的GPS数据采集软件．对该软件的功能进行了简单的介绍，同时对一些关键技术作了较详细的描述。利用该软件、GPS接收机及PC机的组合，可对走航式测量仪器(或移动设备)进行实时定位并保存定位记录，且大大减少一些不必要的数据，使得软件更为实用。     

吹扫-捕集气相色谱法测定海水中挥发性卤代烃

挥发性卤代烃(VHC)是大气中的痕量气体,对臭氧层损耗和温室效应有重要作用。海洋是大气中VHC的主要自然排放源,开展海洋VHC的研究有助于了解海洋对大气VHC和全球变暖的贡献。本文建立了吹扫-捕集与气相色谱-微池电子捕获检测器联用技术(P-T-GC-(ECD)分析海水中6种VHC的方法,确定了吹扫-捕集条件和气相色谱分离条件。该方法的检测限在0.003~0.369 ng.L-1之间;相对标准偏差是1.83~3.97;加标回收率为98.1%~110.2%;相关系数在0.997 3~0.999 8之间。可准确地测定海水中6种VHC。     

Outer wave number spectrum and statistical distribution of apparent wave number vector

Based on the ray theory and Longuet-Higgins’s linear model of sea waves, the joint distribution of wave envelope and apparent wave number vector is established. From the joint distribution, we define a new concept, namely the outer wave number spectrum, to describe the outer characteristics of ocean waves. The analytical form of the outer wave number spectrum, the probability distributions of the apparent wave number vector and its components are then derived. The outer wave number spectrum is compared with the inner wave number spectrum for the average status of wind-wave development corresponding to a peakness factor P = 3. Discussions on the similarity and difference between the outer wave number spectrum and inner one are also presented in the paper.