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.     

基于执行依赖启发式动态规划的船舶减摇鳍在线最优控制

针对船舶线性横摇系统,设计了一种基于执行依赖启发式动态规划（ADHDP）方法的在线学习最优减摇鳍控制器.在设计过程中直接使用输入输出数据获取系统状态值.利用评价网络来逼近针对船舶减摇鳍控制系统设计的性能指标函数,并通过执行网络获得最优控制律,这两个网络都是多层前馈神经网络,即反向传播（BP）神经网络.在训练过程中,这两个神经网络不仅可以使用实时测量数据,也可以减少船舶横摇模型的内部误差和不确定性干扰的影响,从而提高系统的鲁棒性.最后,仿真结果表明所提出的ADHDP控制器对于降低船舶横摇有很好的控制效果.     

舟山海域淡水资源调查岩心钻探技术

舟山海域淡水资源调查项目DZS1孔,水深15 m、钻孔深度达202.1 m,在以粘土层和砂层为主的第四系覆盖层全孔取心、在风化基岩层取心2 m。在第四系覆盖层不下套管直接利用φ127 mm钻具进行绳索锤击取心钻探,基岩采用φ127 mm钻具作为套管、φ50 mm钻具单动双管回转取心钻探。介绍了该孔的主要施工工艺与质量控制方法,包括勘探船抛锚定位、潮汛对钻杆的影响、钻探取心过程控制、用取心钻头不取心扫孔技术、更换钻头技术、泥浆工艺等。     

Stability and capsizing analysis of nonlinear ship rolling in wind and stochastic beam seas

Considering the actual seaway condition, stability and capsizing of nonlinear ship rolling system in stochastic beam seas is of significant importance for voyage safety. Safe zone are defined in the phase space plan of the unperturbed Hamilton system to qualitatively distinguish ship motions as capsize and noncapsize. Capsize events are defined by solutions passing out of the safe zone. The probability of such an occurrence is studied by virtue of the random Melnikov function and the concept of phase space flux. In this paper, besides conventional wave excitation, the effect of wind load is also taken into account. The introduction of wind load will lead to asymmetry, in other words, it transforms the symmetric heteroclinic orbits into asymmetric homoclinic orbits. For asymmetric dynamical system, the orbital analytic solutions and its power spectrum are not readily available, and the technique of discrete time Fourier transformation (DTFT) is used. In the end, as verification of theoretical critical significant wave height, capsizing probability contour diagram is generated by means of numerical simulation. The contour diagram shows that these analytical methods provide reliable and predictive results about the likelihood of a vessel capsizing in a given seaway condition.     

全水深多波束测深系统Seabeam3012在西太平洋马里亚纳海山区地形测量中的应用

中国科学院海洋研究所在开展西太平洋马里亚纳海山区多学科综合科学考察的过程中,利用"科学"轮船载的全水深多波束测深系统Seabeam3012对多个海山进行了地形测量工作。针对作业过程中遇到的恶劣海况导致采集数据质量差、多波束系统易检测错误海底信息、测线布设难度大等问题,提出了基于船体姿态对数据质量影响分析的多波束测线方向优化、基于地形变化并参考浅地层剖面资料的作业参数优化和基于实时采集情况的多波束采集测线布设优化等一系列措施,有效地提高了海山区多波束数据采集质量,并提高了作业效率。获得的高品质地形数据,为多学科协同研究奠定了基础,为ROV等设备的现场作业提供了安全保障。     

基于无人船的水质监测及控制系统设计

针对执行水质监测任务过程中固定浮标监测站单点监测存在局限性、船载观测人员取样耗时耗力等问题,本文设计了一种搭载多点、分层自动采水取样装置的智能无人船水质监测系统,可实现目标水域的多点、分层连续水质数据测量及取样。该智能无人船具备基于快速随机树(Rapid Random Tree)算法的自主避障和快速路径规划功能,解决了现有无人船技术存在的多障碍自主路径规划难等问题。同时,本设计结合了ARM9控制芯片、M5310无线传输模块,通过可视化的显示界面和远程WEB访问的功能,大大提升了科研人员及时处理特殊情况便捷性。通过实验测试及比对分析,证明本设计具有智能高效、稳定可靠等优点,能够满足职能部门对于水质监测工作的需要。     

一种带自由面的三维船体贴体网络的数值生成

本文提出了一个生成自由面的三维船体贴体网格的数值方法。文中以静水面以上的船体型线作为描述非定常自由面的计算网格域，进一步完善了我们以往开发的无法考虑兴波与静水面以上的船体型线相互作用对船舶粘性流动影响的网格生成方法。静水面以上的初始自由面网格分别沿船面法线η及切线ζ方向的曲线长的指数进行分布，即可极方便地调节自由面在船面及静水面附近的网格间距，也保证了在数值离散三维Ｐｏｉｓｓｏｎ方程时具有相当好的收敛性。这种方法的特点是计算量相当小，尤其能极方便地控制网格在船面簿粘性层中及静水面附近的分布。以Ｓｅｒｉｅｓ６０船模作为计算算例，带自由面的网格分布是相当满意的     

物探船拖缆姿态及拉力预报

针对海洋地震物探船布设探测网络实际工况的要求,提出一种拟合数值计算与模型实验结果预报拖缆姿态及拉力的方法,应用此方法进行多方案比较研究,获得优化的拖缆－扩展器－检测电缆组合探测系统。经海上拖航实验验证,此种预报方法查可行,预报精度完全能满足工程实用要求。     

Modeling of Multi-Freedom Ship Motions in Irregular Waves with Fuzzy Neural Networks

1 .IntroductionAshiptravelingatseaundergoesundesirablewave inducedmotions ,namely ,surge ,sway ,heav ing ,rolling ,pitchingandyaw .Thesemotionsoftencauseproblemstothecrew ,theonboardequip mentand ,intheworstcase ,thesafetyofthevessel.Tominimizethewave inducedshipmotions ,controlsystemsmaybeapplied .Theaccuratemodelingofshipmotionsisthereforeveryimportantforshipdesignanddesignofmotioncontrolsystems .Manyresearchershavedevelopedshipmotionpredictionmethodsbasedonthepotentialflowtheo ries (Dong ,…     

Test Study on Current Force on Mooring Ships

In respect of an offshore berthing pillar, the test study result of current force acting on mooring ships is described in this paper. Empirical and semi-empirical relationships of current force coefficient are given according to the angle between the flow direction and the ship's longitudinal axis, which are coincident with the result of theoretical analysis.