Analysis of inequalities between the fishing capacities of the fleets of the European union

In the period 1983-2007, The European Union controlled the evolution of the capacity of its fishing fleet through the so-called Multi-Annual Guidance Programmes (MAGPs). As a result, The European Union reduced the number of fishermen, fishing vessels, gross tonnage and power. However, the end of this period saw an increase in the average size of the fishing vessel and a reduction in crew size. The new “average fishing-vessel” was a more technologically advanced vessel with a greater fishing capacity and a higher degree of autonomy. The aim of the study presented here is to determine the degree of inequality to be found between the fishing capacities of the fleets of the European Union, and to verify whether the evolution of the “average fishing-vessel” responds to a homogenous trend shared by all of the fishing fleets of the European Union or whether it is in fact more unequal. The study formalises a methodology, using Theil indices, which enables the inequalities found between the capacities of the fishing fleets during the period of application of the MAGP adjustment polices to be analysed. The study uses data on fishermen, boats and tonnages from 13 countries of the European Union and results are obtained for the inequality indices of the average size of the fishing vessels, their degree of technological advance and their average crews.     

Perceptions of occupational risk by US commercial fishermen

The dangers associated with commercial fishing are well documented, and fishermen consistently face one of the highest job-related mortality risks of all US occupations. This study explored fishermen's perceptions of these risks in a representative sample of Maine commercial fishing vessel captains. Data were collected on sociodemographic characteristics and risk preferences during sea boardings of working commercial fishing vessels (n=233) along the full extent of the Maine coastline. Trends in perceived risk were explored across the various sociodemographic categories. Fishermen in this study consistently undervalued their true occupational risk, and rated it as average despite consistent evidence to the contrary. Those more likely to downgrade the risk of fishing included state registered vessels and those found to be non-compliant with existing safety regulations. Less educated fishermen and those who come from a fishing family were also more likely to underrate the risks, as were those fishermen who displayed risk-loving tendencies in other facets of their lives such as smokers and those who did not use seat belts. Middle-aged fishermen were also more likely to underrate the risk than the youngest and oldest groups, suggesting that overconfidence grows and then wanes over time. The results of this study strongly suggest that the current safety training and awareness programs targeting fishermen are inadequate. Furthermore, widespread voluntary participation in organized safety training is unlikely since the majority of fishermen believed that the risks were not relevant to their own activities.     

基于AHP的舟山灯光围网渔船捕捞能力影响因子权重评价

根据3艘舟山灯光围网渔船的生产统计数据,通过层次 分析法(AHP),分析了影响渔船捕捞能力的因子(总吨位、主机功率、作业天数和水下灯功率),并根据各影响因子的重要性确定其权重,建立影响灯光围网渔船捕捞能力的多因子评价模式。结果表明:总吨位对灯光围网捕捞能力的影响最甚,其次是主机功率、作业天数和水下灯功率,其所占权重分别为0. 461 2,0.342 4,0.137 1和0.059 4。     

斜坡面波浪冲击力试验研究及现场资料分析

通过莆田试验站实测资料分析和物理模型试验,对单一斜坡护面板的打击力进行了研究,阐述了斜坡上最大相对波压力和波坦、堤坡坡度以及水深的关系,提出了波压力、波压力打击点位置以及波压力沿斜坡分布的计算公式,并给出了不同累积频率下的波压力换算关系。     

国内外泥石流活动关键指标估算方法之比较

泥石流流体容重、流速、冲击力是表征泥石流活动特征众多指标中的三个关键指标.本文在分析国内外对这些指标评估现状的基础上,总结了应用较普遍的估算公式,对比了不同公式的特点及其适用性.比较结果认为:由于泥石流组成和运动状态的复杂性以及影响因素的多样性,对于这三个指标,目前的估算公式都不具有普适性.在当前的认知水平下,建立基于各个地区泥石流特点的指标估算经验公式是最为实用的途径.在各个指标经验公式的建立方法上,考虑各个粒组的多变量容重统计分析方法相对较为合理;泥石流流速估算公式的建立途径在我国、前苏联和欧美国家之间有显著差异,前二者基于曼宁公式,后者基于强迫涡流公式、以弯道超高为主要参数;泥石流冲击力的估算方法国内外都以动量理论为基础,区别主要体现在经验系数取值上,巨石冲击力的计算则都考虑了拦挡建筑物的特点.     

泥石流冲击荷载的时频分析方法及应用

泥石流的能量转化主要集中于运动过程中,泥石流冲击压力随时间变化的过程是其能量不断变化的综合表现。本文分析了泥石流能量转化过程及冲击荷载的紊流形态,并根据其脉动特性,将泥石流冲击荷载作为信号进行研究。以大型泥石流模型试验为基础,利用小波时频分析方法将试验测取的泥石流冲击荷载映射为时间与频率的联合信号,得到同一时间9个频段内的能量强度。从冲击荷载的能量分布可以看出,稀性泥石流95%以上的波动能集中在低频段内（0～6.25Hz）,从而为深入研究泥石流冲击机制及防治结构动态荷载设计提供了一些理论依据。     

撞击地层学及其研究进展

地质历史中的地外物体撞击地球事件可在撞击点、近源区和远源区分别形成撞击坑熔融岩体、近源溅射岩席及海啸沉积和远源溅射层等一系列撞击地层层序。撞击地层有其独特的物理学和化学特征,与正常沉积作用、火山喷发和板块碰撞等成因的地层显然有别。通过对撞击地层层序的时空变化、所包含的撞击成因矿物、撞击微球粒和微玻璃陨石以及古生物和地球化学异常等的研究,可以了解撞击事件的发生频率、幅度和撞击天体的性质等,也为探索生物和地球环境的灾难性变化及其起因提供了新的思路。     

Proximate composition of albacore tuna,Thunnus alalunga,from the temperate South Pacific and Tasman Sea

The proximate composition was determined of the white muscle of albacore tuna, Thunnus alalunga, caught by surface trolling along the Subtropical Convergence Zone east of the South Island of New Zealand ("Area 1"), and to the north and west of the North Island ("Area 2"). Fish from Area 1 were 70 ± 10 cm (mean ± s.d.) in fork length, and higher in oil content (4.6 ± 2.9%), than Area 2 fish which measured 55 ± 10 cm and contained 2.8 ±1.7% oil. The ash content of the white muscle of all fish sampled was 1.2 ± 0.1%, and the soluble carbohydrate content 0.36 ± 0.04%. Crude protein contents were calculated at c. 25%. Statistical relationships between moisture and oil contents of both white and red muscle were determined; they can be used to predict oil content from a known moisture content. Oil content was positively correlated with fork length, and negatively correlated with the sea surface temperature at time of capture. Oil levels in the fillet were highest in the muscle layer immediately below the skin and decreased logarithmically with depth. In fish with low white‐muscle oil content (below 5%), the corresponding red‐muscle oil content was higher; above 6% white muscle oil content the corresponding red‐muscle oil content was lower. The proximate composition of whole fish, the head, frame, skin, and viscera is presented.     

基于随机森林的印度洋长鳍金枪鱼渔场预报

为了提高远洋渔场预报水平和满足渔业生产的需要,提出了一种基于随机森林建立印度洋长鳍金枪鱼(Thunnus alalunga)渔场预报模型的方法。选取2002-2009年各个月份印度洋5°×5°格点渔业环境和时空数据(包括海表温度、叶绿素a浓度、表温距平、叶绿素a浓度距平、海表温度梯度强度和海面高度异常等数据)作为预测变量,利用长鳍金枪鱼的CPUE(Catch per unit effort,单位:尾/千钩数)的三分位点将渔区划分为高CPUE、中等CPUE和低CPUE三种类型,作为响应变量,对数据进行训练。结果表明,当随机森林中决策树达到100以上时,袋外数据OOB(out-of-bag)的分类误差率趋于平稳。将训练得到的随机森林用于2010年印度洋长鳍金枪鱼分月渔场的预测,其概率等值面图与实际生产的渔场分布进行叠加比较,显示高CPUE渔场概率分布与实际渔场的位置及范围变化情况符合。通过ROC(Relative Operating Characteristic)分析,高CPUE、中等CPUE和低CPUE的AUC(Area Under ROC Curve)分别达到0.847、0.743和0.803,表明预测精度较高。最后对中等CPUE渔区预测精度相对较低的原因进行了分析。     

Geotechnical Investigation of the Titanic Wreck Site

Abstract

Recent marine forensic investigations have largely unravelled the sequence of events concerning the sinking of the R.M.S. Titanic and its descent through nearly 3800 m of water to the seafloor on the morning of 15 April 1912. In particular, the velocity and attitude of the Titanic's bow section (at present lying upright, reasonably intact, and embedded by ～12 m at the prow) as it hit the bottom are of general interest to marine accident investigators. During the 1998 Titanic Science Expedition, a single sediment sample was retrieved from the seafloor (depth 20–30 cm) near the wreck by the deep water submersible, Nautile. Published geological studies suggest the seafloor in this area has remained largely undisturbed since 1912. Geotechnical analysis of the sediment sample reveals that the impact was probably a substantially undrained event and that the characteristic undrained shear strength of the sediment is ～25kPa within 10–16 m below the seafloor. A simple analytical model was used to calculate the embedment of a cuboid with dimensions and mass of the water-filled bow as a function of impact velocity, impact angle, and the undrained shear strength of the sediment. The results indicate the impossibility of a steep angle of impact and fast velocity. The most likely scenario is an impact velocity of 5–10 m/s at a fairly shallow angle (<40°), which corroborates the results of hydrodynamic investigations.