Evaluation of methods to remove inertial force from measured model wave impact force signals

The subject of wave impact on offshore structures and their components is important to vessel designers and operators for many reasons. They are often required to quantify these impact loads. Standard methods for wave load prediction will underestimate the forces on these structures due to intermittent loading. This necessitates the use of physical model tests to establish wave impact loads. The model measurement systems are designed to have high stiffness. This ensures that the natural frequency of the structure is above the wave frequency. However, it is widely believed that impacting waves contain high-frequency energy components that cause the structure to vibrate at its modal frequencies. This impact-induced vibration is recorded by the measuring system as a force (inertial force), and corrupts the actual applied force measurement. Before scaling can occur, the inertial force must be removed from the measured signal.A number of techniques for removing inertial force from measured signals are described in the published literature. Three methods are discussed, implemented and compared in this paper. The algorithms and procedures are presented. Each technique contains inherent and unique problems, while some are common to all methods.Neither of the techniques produced results that are fully satisfactory. The main problem is unwanted high-frequency content after the application of the methods. While neither method offers the perfect solution, the use of digital filtering techniques is recommended based on their relative performance and ease of implementation.     

大亚湾试验挂板上的附着硅藻

本文分析了大亚湾核电站进水口和澳头港试验挂板上的周年样品(1986年12月—1987年11月),共鉴定出附着硅藻123种和变种,隶属38属。核电站进水口和澳头港试板上的主要优势种不同,附着量年高峰出现的时间亦不同。文中并对硅藻的集群结构进行了分析。     

Construction of a pile-based offshore airport

The feasibility of construction of a pile-based offshore airport in open sea is considered. The concept of a pile-based airport relies on technology used to construct long concrete bridges, over sea arms and straits, during the last four decades. The features of four major bridges, in conjunction with prefabrication of prestressed structural elements, are described. The airport platform, which is set 16 m above sea level, obviates the need for protective embankments. The platform consists of modular units, supported by piers, which are based on foundations of steel piles. The modular units comprise tube girders, 35–60 m long, set on piers 15 m apart. Longer girder spans are expected to diminish the impact of the airport on the coast. Cost estimates are provided for a pile-based offshore airport serving medium haul aircraft, using 45×15 m² and 60×15 m² grids, and long haul aircraft, using 60×15 m² grids. Cost comparison with a fill island airport is provided using two different geometries. It is shown that the pile-based airport is a viable option, both technologically and economically. This new concept provides advantages over the fill island option regarding the requirement of materials, technology of construction, the modular approach and the diminished environmental impact.     

世界著名水下开沟机械设计施工公司与机型介绍

本文重点介绍了１５家世界著名的水下开沟机械研究、开发及施工应用公司的基本情况，主要机型的结构特征、技术参数和最新进展。笔者认为：引进先进、成熟的水下开沟机械，或与著名的专业公司联合设计开发，对于中小型海洋工程公司而言，不失为一条投资少、起点高、见效快的好的途径。     

广东海水鱼类寄生海盘虫属两新种的记述

记述了寄生于黑鲷(Sparusmacrocephalus(Basilewsdy))鳃上的海盘虫属两新种。华南海盘虫,新种Haliotremaaustrosinensesp.nov与螺旋海盘虫(HaliotremaspiraleYamaguti,1968)相比,交接器形状相似但量度有明显的差异,且已知种的交接管具有3条几丁质丝;中央大钩与联结片的形态与已知种相异,表现在:新种的2对中央大钩形态各异,背中央大钩基部不加厚,内外突发达,腹中央大钩基部加厚,内外突粗壮发达,背联结片长片状,中间有两个似驼峰状的突起,两端略尖,腹联结片弧形,中间细,两端膨大,而已知种的2对中央大钩形态相似,钩基部两边加厚,内突非常粗壮发达,背联结片较平直,腹联结片呈“V”形。大弯管海盘虫,新种Haliotremagrossecurvitubussp.nov与HaliotremakurodaiOgawa&Egusa,1978相比,交接管形状相似,但交接管的据弯度较已知种长近1倍,且新种交接器具有一台状的基座;2对中央大钩形态各异。     

深圳湾福田红树林潮滩大型底栖动物的垂直分布

2002年1月对深圳湾福田红树林潮滩0～10、10～20、20～30cm层的大型底栖动物的垂直分布进行了研究．结果表明，羽须鳃沙蚕主要分布在10～20cm层，奇异稚齿虫、德氏狭口螺、尖刺樱虫、寡鳃齿吻沙蚕、莫顿长尾虾、沼蚓和小头虫主要分布在0～10cm层．大型底栖动物在0～10cm层呈高密度分布是各种类型潮间带生物分布的共性，其原因是沉积物越深含氧量越低、食物越少．大型底栖动物个体的分布深度与其种类有关．     

近海对台风的响应注记──Ⅰ.大亚湾海况对8708和8710号台风的综合响应

根据大亚湾海洋生态零点调查获得的水温、海流、潮位和气象观测资料，分析了1987年8月间大亚湾对8708和8710号台风的综合响应。结果显示，台风期间除增水外，整个大亚湾的水文结构因台风的影响发生了显著变化。其主要特征表现为：湾内垂直环流改变，海水层化消失，以及总体水温升高。分析表明，台风作用下垂直环流的调整可能是造成台风过程中大亚湾层化消失、总体水温升高的重要因素，而陆地边界的存在显然改变了海洋对热带风暴的响应特征。     

Investigation of the effects of offshore breakwater parameters on sediment accumulation

Littoral sediment transport is the main reason for coastal erosion and accretion. Therefore, various types of structures are used in shore protection and littoral sediment trapping studies. Offshore breakwaters are one of these structures. Construction of offshore breakwaters is one of the main countermeasures against beach erosion. In this paper, offshore protection process is studied on the effect of offshore breakwater parameters (length, distance and gap), wave parameters (height, period and angle) and on sediment accumulation ratio, one researched in a physical model. In addition to the experimental studies, numerical model in which the formulae of the sediment discharge (i.e. the formulae of CERC and Kamphuis), was used was developed and employed. The results of the experimental and numerical studies were compared with each other.     

粤东汕尾岬间海滩剖面月内日变化过程特征分析

运用经验特征函数方法，结合逐日实测波浪、潮汐及剖面冲淤变化资料，对粤东汕尾寮咀口岬间海滩重复测量的剖面数据加以分析。结果表明，海滩的月内日变化过程可客观地通过对应于2个最大特征值的2个经验特征函数来描述：1）第1经验特征函数表征主要的海滩剖面过程，称为要模式，它是响应叠加在月潮汐周期性循环上的波浪动力作用；2）第2经验特征函数反映了海滩剖面快速变化过程，称为次要模式，它又可分为前滨上部过程、冲淤过渡段及后演上部过程。     

Statistical response predictions for a nonlinearly moored large volume structure in random seas

The challenge to calculate the response statistics of nonlinear, compliant offshore structures subjected to a random seaway is still substantial. In this paper the results are presented of a renewed effort to use the method of numerical path integration for this purpose. In particular, the goal is to calculate the response statistics of a nonlinearly moored large volume floater designed for use in oil production in deep waters. Specific emphasis has been placed on the modelling of nonlinear wave loads in addition to the nonlinear mooring characteristics. The results calculated for the response statistics are compared with the results obtained by Monte Carlo simulation, and the agreement is found to be very good.