Population abundance and seasonal migration patterns indicated by commercial catch-per-unit-effort of hakes (Merluccius capensis and M. paradoxus) in the northern Benguela Current Large Marine Ecosystem

We developed generalised additive models (GAMs) to estimate standardised time-series of population abundance indices for assessment purposes and to infer ecological and behavioural information on northern Benguela hakes, Merluccius capensis and M. paradoxus, using haul-by-haul commercial trawl catch-rate data as proxies for hake densities. The modelling indicated that individual ship identifiers should be used rather than general vessel characteristics, such as vessel size. The final models explained 79% and 68% of the variability in the commercial catch rates of M. capensis and M. paradoxus, respectively. The spatial density patterns were consistent and confirmed existing knowledge about these species in the northern Benguela system. Furthermore, seasonal migration patterns were described for the first time and were found to correspond to the known spawning areas and seasons for M. capensis and M. paradoxus. Spatial density patterns were validated using the geostatistical modelling results of fisheries-independent trawl survey data. Improved understanding of the relationships between fleet dynamics and fish movement can be achieved by taking into consideration the present catch-rate model and spatial and seasonal distribution maps. We conclude that the yearly standardised CPUE time-series are problematic as proxies for total stock abundance because of spatial coverage issues. Consequently, such CPUE data should not be used for stock-size assessments and fisheries advice concerning northern Benguela hakes until this is solved. We generally recommend the exclusion of standardised CPUE time-series from stock assessments when important and changing parts of the stock distribution cannot be targeted by the fishery, such as due to closed areas or seasons.     

基于分区间泛化Kriging近似模型的船舶局部结构形状优化

为提高Kriging近似模型在船舶结构性能多维度响应预测方面的适用性,对常规Kriging近似模型进行分区间泛化改进:一是对设计样本点的各个维度(分量)进行划区,并在每一个分区间内采用最优拉丁超立方(OLhd)取样;二是引入比例系数w1组合高斯与指数型相关函数提高模型对数据的泛化能力,从而在每个划分的区间内建立泛化的Kriging近似模型。通过SCH测试函数,验证了构造的分区间泛化Kriging模型有效性。结合参数化建模和改进Kriging近似模型对某过渡肘板和舱口角隅边界进行形状优化,优化第一阶段由改进的近似模型通过多岛遗传算法得到全局初步的最优解,第二阶段在初步解的基础上缩小优化变量范围,由少量的FEM计算即可在小范围内搜寻到精确的最优设计变量。结果表明:分区间泛化Kriging近似模型在预测多维度响应时较常规Kriging模型预测精度更高;分阶段的形状优化流程在保证极小误差和缩小计算成本的情况下能够得到理想的应力分布和重量优化结果,有助于船舶结构的轻量化研究。     

基于结构特征的SAR船只类型识别能力分析

1 引言 SAR是船只探测的有效手段,利用SAR影像不仅可以检测船只目标,而且还可以提取船只的长度、宽度以及航速、航向等信息.随着星载SAR空间分辨率的提高,使基于星载SAR影像的船只类型识别成为可能.利用星载SAR可以检测出大面积范围内的船只和初步识别其类型.     

大连港外海域船舶尾迹光学特征研究

通过大连港外海上实验测量船舶含气泡尾迹表观光学特征(如离水辐亮度、遥感反射率),分析了尾迹气泡对极度混浊的Ⅱ类水体海水表观光学特征的影响.实验结果证明:无论在可见光还是近红外波段,尾迹气泡都增强了海水表观光学量,如"耘海"船尾迹遥感反射率在可见光波段相对背景海水提高了50%,在近红外波段相对提高了159%.数据分析结果表明在此种水体中,气泡使得尾迹海水水色变黄,而不是在Ⅰ类水体中使水色变绿.随着观测点在尾迹中的位置靠近目标船,气泡数密度不断增加,遥感反射率也随之增强.     

Econometric analysis of the ship demolition market

The topic of ship recycling has obtained considerable attention during the last two decades for a variety of reasons with the likelihood of the adoption of a new international convention under the auspices of the International Maritime Organization (IMO). This study applies econometric modeling to a unique data set to provide insight into the dynamics of the ship recycling market. The data set contains information on 51,112 ships over 100 gt and includes 748,621 events over a period of 29 years. The analysis confirms a negative relationship of earnings and a positive relationship of scrap prices for all locations while Bangladesh seems to be more sensitive to changes in earnings than the other locations and more likely demolishes larger and older vessels. The results for flag and ownership vary across scrapping locations with Malta and Cyprus indicating potential importance from a registry perspective. The overall safety profile of a vessel seems to be less important towards the probability of a ship being scrapped. Possible implementation of the convention at EU level will mostly likely affect Turkey while non-ratification of one of the major flags will most likely affect China or Bangladesh.     

中国海洋志愿观测船现运行状态及发展

志愿船观测是中国必须履行的国际义务。目前,中国海洋志愿观测船只呈逐年减少趋势,从过去的百余艘船只降至三、四十艘,并且从观测能力上也存在较多问题,比如观测手段比较落后、观测要素单一、观测资料缺乏。从根本上讲,志愿船运行机制缺乏有效的制度化保障,因此难以形成业务化能力,并且不能有效的履行国际义务。本文将对志愿船现运行状态及发展进行论述。     

中国南海中小渔船动力装置的几点论证

就２２０～４４１ｋｗ的中小型渔船动力装置选型的历史沿革，从船、机、桨匹配理论分析，结合中国南部海区渔民实践造就已使用的情况，论述大家所关心的几个问题。认为：不能只用“单机单桨”一种推进型式；双机双桨能发挥主机功率，合理安排动力装置，安全性及其经济性均有优越之处，适合我国南海大多数渔区渔港实际情况。     

压电材料智能力矩控制器对具有不确定参数升船结构顶部厂房地震反应的鲁棒控制

文中建立了压电材料智能力矩控制器对具有不确定参数升船结构顶部厂房地震反应鲁棒控制的设计计算方法，并对中国某升船结构的等效结构体系进行了仿真分析。计算结果表明，智能力矩控制器能有效地减小顶部厂房的鞭梢效应。在考虑顶部厂房因端部山墙引起的侧移刚度不确定性的条件下，智能力矩鲁棒控制器的控制效果和稳定性要优于常规的主动控制器。     

基于弧段检测的高频地波雷达特定目标航迹跟踪方法研究

本文对现有的高频地波雷达目标跟踪方法进行了概述,提出了一种地波雷达目标长时连续跟踪的方法,基本思想是:充分挖掘航迹弧段特征,基于特征对船只运动建模,并结合杂波背景进行融合决策。进一步,为了达到长时间连续跟踪的需求,借鉴深度学习的思想,利用新获取的弧段数据对算法估计结果不断递归校正,使得随着获取数据的增加跟踪越准确。该方法适用于杂波环境且在航道附近存在众多干扰船只的情况下对机动目标航迹的实时稳定跟踪,为高频地波雷达在复杂干扰环境下特定目标持续跟踪提供理论基础和方法指导,为充分发挥地波雷达在海上监视监测中的作用提供技术支撑。