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The spring-spawning Baltic Sea herring spawn in coastal areas that also serve as nursery areas for the young fish during their first summer. In a bay known as a herring spawning and nursery area, the pelagic fish abundance was quantified using hydroacoustics every second week from late spring to autumn in 2000 and 2001. A dense system of survey transects allowed determination of the acoustic index (the nautical area scattering coefficient) for fish abundance with high precision. The variation, expressed as the geostatistical coefficient of variation, was on average 5% both years and ranged from 3–11% (2000) and 3–8% (2001). Through the hydroacoustic data intra-annual dynamics in acoustic fish abundance, densities and size composition could be followed, which showed similar trends in both years. In spring and early summer acoustic fish densities were low, followed by a drastic, 20-fold increase in late summer. Hydroacoustic data and biological samples suggest that the increase was caused mainly by the recruitment of young-of-the-year herring to the acoustically assessable pelagic fish community. This age class is commonly not well represented in catches when using traditional sampling gears such as gill nets and trawls, and hydroacoustics may help to improve quantitative estimates of small juvenile fish in order to increase the understanding of biological processes in coastal nursery areas. 相似文献
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Ayla Sayli Ahmet Dursun Alkan Radoslav Nabergoj Ayse Oncu Uysal 《Ocean Engineering》2007,34(5-6):724-738
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 (CWP, CVP, 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. 相似文献
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Alberto Omar Vazquez-Hernandez Gilberto Bruno Ellwanger Luís Volnei Sudati Sagrilo 《Applied Ocean Research》2006,28(6):398-406
The characteristic environmental load effect for the design of mooring systems of floating units can be defined by means of three procedures: (a) the one associated to an extreme sea state with a given return period, (b) the worst one from a set of sea states on a contour line associated to a return period or (c) the extreme one based on response statistics for a long-term period. This work presents the result of a reliability-based partial safety factor calibration study for a LRFD mooring line design criteria considering the three approaches mentioned above. The calibration exercise is applied to three FPSOs considering North Sea environmental conditions and different water depths: 200, 800 and 3000 m. The mooring systems investigated take into account mooring lines made up of chains and polyester ropes. It is shown that, among all cases investigated, the design procedure based on the long-term response is the one that presents less scattered reliability indices around the target level. 相似文献
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The floating oil storage system has been proposed as a new facility for Strategic Petroleum Reserve (SPR) in China. Mooring is one of the key technologies to ensure the safety, reliability, and performance of the oil storage system. This paper describes the concept, analysis, design and reliability of the mooring system. For mooring system design of these oil vessels, analysis is essential of the behavior of the vessel in connection with mooring facilities of nonlinear resilience. A nonlinear mathematical model for analyzing a moored vessel is established and solved. Some results of numerical simulations are presented. Assessment of the safety regarding the mooring system in terms of failure probability is carried out. Another simulation model for calculating the failure probability of the mooring system is proposed. The design parameters that have an influence on the characteristics of the failure probability have been identified. The simulation results show that the mooring system has an annual reliab 相似文献
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GIS和RS技术在城市规划设计中的应用探讨 总被引:3,自引:0,他引:3
数字技术时代的到来,城市规划行业面临机遇和挑战。本文针对国内目前3S技术在城市规划管理层次应用较广而在规划设计方面应用薄弱这一现状,结合规划设计相关案例介绍GIS和RS技术在规划设计方面的辅助应用。案例选用ArcGIS软件介入规划设计的全过程,进行现状地形分析、三维模拟等辅助分析,并与Sketchup建模充分结合制作大范围三维漫游动画,辅助推敲规划建筑与周边环境相互关系,同时还充分利用GoogleEarth与Sketchup和ArcGIS之间的接口,将规划方案和建筑模型导入全球卫星影像,从而更好地辅助规划决策和公众参与等。 相似文献
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