Seakeeping assessment of fishing vessels in conceptual design stage

The main idea of this paper is to identify functional relations between seakeeping characteristics and hull form parameters of Mediterranean fishing vessels. Multiple regression analysis is used for quantitative assessment through a computer software that is based on the SQL Server Database. The seakeeping attributes under investigation are the transfer functions of heave and pitch motions and of absolute vertical acceleration at stern, while the ship parameters influencing motion dynamics have been classified into two groups: displacement (Δ) and main dimensions (L, B, T), coefficients that define the details of the hull form (C_WP, C_VP, LCB, LCF, etc.).Four multiple regression models having different parameter combinations are here investigated and discussed, giving way to the so-called ‘Simple Model’, ‘Intermediate Model’, ‘Enhanced 1 Model’ and ‘Enhanced 2 Model’. The obtained results are more than satisfactory for seakeeping predictions during the conceptual design stage.     

9012号热带气旋维持的卫星云图和垂直结构特征分析

本文根据卫星云图的演变和常规天气分析相结合，对9012号热带气旋登陆后维持水消的成因进行了分析。指出该热带气旋经久不消的重要原因为其西南侧对流云团和东北侧高空槽前对流云带与热带气旋云系相衔接在中低层东北气流引导下卷入，热带气旋内部的两条云带的维持，以及利有的环流条件。     

Action mechanism of geotextile-reinforced cushion under breakwater on soft ground

Various measures including material experiments, centrifuge modeling tests and FEM numerical analyses were performed to study systematically the action mechanism of the geotextile-reinforced cushion under breakwater on soft ground and the effects of the strata characterization and the reinforcement condition on the stability of the breakwater-ground system. In the aspect of controlling the deformation, the geotextile-reinforced cushion under breakwater constrains the lateral displacement of both the embankment and the ground. From the viewpoint of stress, the reinforcement suppressed the range of high stress level in the system. In general, the weaker the ground is and the greater the modulus of the geotextile is, the more effective the reinforcement is. The tensile force in the geotextile is greater in the range of the main part of the embankment.     

Time domain modelling of the transient asymmetric flooding of Ro-Ro ships

This work aims at contributing to improve knowledge on transient asymmetric flooding through theoretical and experimental research. First, a time domain theoretical model of ship motions and flooding is described. Results from experimental work are presented evidencing that transient asymmetric flooding may cause the capsizing of a Ro-Ro shaped barge. The theoretical model is used to predict the capsize of the Ro-Ro shaped barge. Reasonable agreement between experimental and theoretical results was found. Finally, a review of the European Gateway accident is given and the theoretical model is applied to the study of this type of accident. The conclusion is that this theoretical model, together with an accurate modelling of the flooding of machinery compartments, reproduces successfully the capsizing of the European Gateway due to transient asymmetric flooding. Therefore, the internal arrangement of Ro-Ro ships should be carefully studied at the design stage in order to avoid this phenomenon.     

波群作用于垂直桩柱的峰力统计性质

研究具有窄谱和Ｗｅｉｂｕｌｌ波高分布的波群对非线性桩柱系统作用力的统计性质。求得了桩桩的波浪峰力的各种特征值及其比值。指出这些数值不仅是阻力一惯性力参数ｂＨ的函数，也随着波群因子而变化。本文模式更具广泛性。文中给出了一系列计算图表，可从理论计算波群作用于桩柱的波浪峰力。     

泰利台风对台湾东北黑潮入侵东海陆架影响的研究

本文利用卫星高度计数据和分析数据,并结合同时期现场深水潜标的流速观测数据,研究了超强台风泰利过境前后台湾东北附近海域流场、位势密度场、位势涡度场以及黑潮入侵东海陆架强度的变化。分析结果表明,泰利台风通过改变台湾东北陆坡附近海域的流场、位势密度场,显著地削弱(增强)了西段(东段)陆坡附近的位势涡度梯度,从而使得西段(东段)陆坡黑潮入侵东海陆架的强度显著增强(减弱)。此外,本文还区分了台湾东北西部陆坡附近表层的跨陆坡“上凸型”位势涡度分布与次表层的跨陆坡“下凹型”位势涡度分布,并认为次表层的跨陆坡“下凹型”位势涡度分布也应作为台湾东北西部陆坡附近“位势涡度障碍”的重要组成部分。本文的研究结果揭示了大气中的台风过程对台湾东北黑潮入侵东海陆架产生显著影响的关键过程及机制,相关结论可为台湾东北黑潮入侵东海陆架变化规律的研究提供有价值的参考。     

软土海岸地区测量控制点标志的设立

分析了软土、湿地、滩涂地区特殊地理环境对测量控制点的影响;主要探讨了此类地区控制点标志的设计、施工。借助于建筑桩基技术和道桥施工方法,首次成功实现了某三角洲湿地滩涂地区统一布网。几年来,结合滩涂湿地测量、海岸防护和滩涂开发工程对部分控制点进行了初步检测,给出了部分检测数据。应用和检测均表明:桩基标石可较好地解决软土、湿地、滩涂地区控制点布设难题,显著提高软土海岸地区测量控制点标志的稳固性,从而延长控制网的可使用期。     

Surface Elevation Distribution of Sea Waves Based on the Maximum Entropy Principle

A probability density function of surface elevation is obtained through improvement of the method introduced by Cieslikiewicz who employed the maximum entropy principle to investigate the surface elevation distribution. The density function can be easily extended to higher order according to demand and is non-negative everywhere, satisfying the basic behavior of the probability. Moreover because the distribution is derived without any assumption about sea waves, it is found from comparison with several accepted distributions that the new form of distribution can be applied in a wider range of wave conditions. In addition, the density function can be used to fit some observed distributions of surface vertical acceleration although something remains unsolved.