基于深度卷积嵌入式聚类（DCEC）的海洋环境特征提取对渔情预报模型的改进研究     

张天蛟  廖章泽  宋博  袁红春  宋利明  张闪闪 《海洋学报》2021,43(8):105-117

In order to improve the forecasting ability of the fishery forecast model for the longline bigeye tuna (Thunnus obesus), we proposed a marine environment feature extraction method based on deep convolutional embedded clustering (DCEC), combined with generalized additive model (GAM) for forecasting the longline bigeye tuna fishing grounds in the Southwest Indian Ocean. We used the MODIS-Aqua and MODIS-Terra sea surface temperature (SST) three-level inversion image data (in days) from January to December in 2018 at 0.041 6°×0.041 6° to construct a DCEC model, determined the optimal number of clusters based on the Davies-Bouldi index (DBI), and extracted the category feature value (F_M) of each month’s sea surface temperature (SST); we used monthly 1°×1° bigeye tuna longline fishery data from January to December in 2018 generated from the Indian Ocean Tuna Commission (IOTC), and calculated the catch per unit effort (CPUE); we matched the monthly category feature value F_M and the monthly average value of Chl a concentration with the CPUE data to construct an improved GAM; we matched the monthly average SST, the monthly average Chl a concentration and CPUE data to build a basic GAM; we used the joint hypothesis test (F test) to verify the influence of model explanatory variables; we used akaike information criterion (AIC), mean square error (MSE), and draw the frequency distribution diagrams and box diagrams of measured and predicted values, etc., to analysis the improvement effect of the improved GAM compared to the basic GAM. The results showed that: (1) the category feature value (F_M) extracted based on the DCEC model could better reflect the temporal and spatial dynamic characteristics of SST in the Southwest Indian Ocean, and was related with the climatic conditions, monsoon conditions, and hydrological characteristics in the Southwest Indian Ocean; (2) the factor interpretation of F_M was higher than that of the monthly average SST in GAM, which means F_M had more significant impact on the CPUE of bigeye tuna. The high catch rate was concentrated in the areas where the F_M category was 2, 10, 24 with intersections between the warm and cold currents; (3) the AIC of the improved GAM was reduced by 9.17% than that of the basic GAM and MSE of the improved GAM was reduced by 26.7% than that of the basic GAM; the frequency distribution of the CPUE logarithmic value predicted by the improved GAM was closer to the normal distribution, and the high frequency distribution interval was closer to that of the measured value; the scatter plot showed that the CPUE predicted by the improved GAM had a significant correlation with the measured CPUE, with r equaled to 0.60. This study proves the effectiveness of the DCEC model in extracting marine environmental features, and can provide a reference for the further study on the bigeye tuna fishery forecast.  相似文献   

Scale and scope of maritime cargoes through the Arctic Passages     

ZHANG Xia  SHOU Jianmin  ZHOU Haojie 《极地研究(英文版)》2013,(3):158-166

This paper investigates the sources of goods being shipped through the Arctic passages, and trade generated in the Arc- tic, including oil and gas exploitation. Furthermore, it assesses the present situation for maritime cargo shipped from the Far East to Northwestern Europe and North America. Two main types of cargo are predicted to pass through the Arctic passages in the future. First, about 10 million t of liquefied natural gas will be delivered from Russia and the Nordic Arctic to the Far East by 2030. Second, there will be two-way trade flow of containerized cargo from the Far East to Europe and the United States through the North- east, Central and Northwest Passages. This will relieve pressure on present routes from the Far East to Northwestern Europe and North America. If Arctic navigation is technically possible in all seasons and shipping costs fall to those of ordinary ships, then assuming an equal share of shipping volume with the traditional canal routes, the maximum container freight passing through the Arctic passages by 2030 will be approximately 17.43 million TEUs （Twenty-foot Equivalent Units） per year, which is 85% of the volume transported on traditional canal routes in 2011. We conclude that there will be large-scale gas transportation through the Northeast Passage in the near future, and transit shipping across the Arctic will focus more on container transportation. The differences in shipping costs between Arctic routes and traditional canal routes are also compared.  相似文献   

国外陆上碳捕获和封存的立法及其启示     

王慧  魏圣香 《气候变化研究进展》2012,8(1):68-73

碳捕获和封存技术正越来越受到国际社会重视,很多国家通过立法推动碳捕获和封存技术的发展。其中,陆上碳捕获和封存的发展较为引人注目。陆上碳捕获和封存涉及CO2的捕获、运输、注入和封存4个流程,其中捕获和运输可以由各国现行的法律加以规范,而注入和封存则需要新的法律予以制约。根据国外陆上碳捕获和封存技术的立法经验,以及我国现行的相关法律法规来看,为了推动陆上碳捕获和封存在我国的健康发展,应当构建注重监管的公法体系和注重救济的私法体系。  相似文献   

Second-order theory for coupling 2D numerical and physical wave tanks: Derivation,evaluation and experimental validation     

《Coastal Engineering》2013

A full second-order theory for coupling numerical and physical wave tanks is presented. The ad hoc unified wave generation approach developed by Zhang et al. [Zhang, H., Schäffer, H.A., Jakobsen, K.P., 2007. Deterministic combination of numerical and physical coastal wave models. Coast. Eng. 54, 171–186] is extended to include the second-order dispersive correction. The new formulation is presented in a unified form that includes both progressive and evanescent modes and covers wavemaker configurations of the piston- and flap-type. The second order paddle stroke correction allows for improved nonlinear wave generation in the physical wave tank based on target numerical solutions. The performance and efficiency of the new model is first evaluated theoretically based on second order Stokes waves. Due to the complexity of the problem, the proposed method has been truncated at 2D and the treatment of regular waves, and the re-reflection control on the wave paddle is also not included. In order to validate the solution methodology further, a series of nonlinear, periodic waves based on stream function theory are generated in a physical wave tank using a piston-type wavemaker. These experiments show that the new second-order coupling theory provides an improvement in the quality of nonlinear wave generation when compared to existing techniques.  相似文献   

Research on propeller dynamic load simulation system of electric propulsion ship     

黄辉  沈爱弟  褚建新 《中国海洋工程》2013,27(2):255-263

A dynamic marine propeller simulation system was developed, which is utilized for meeting the experimental requirement of theory research and engineering design of marine electric propulsion system. By applying an actual ship parameter and its accurate propeller J’~ KT’ and J’~KP’ curve data, functional experiments based on the simulation system were carried out. The experiment results showed that the system can correctly emulate the propeller characteristics, produce the dynamic and steady performances of the propeller under different navigation modes, and present actual load torque for electric propulsion motor.  相似文献   

基于ANP-PRS-SENCE框架的崇明岛生态安全评价   总被引：6，自引：0，他引：6  

李华  蔡永立 《地理与地理信息科学》2009,25(3)

将复杂系统的网络分析法(ANP)作为生态安全评价指标体系构建的基本方法,综合复合生态系统理论(SENCE)和"压力-状态-响应"(PSR)模型,提出ANP-PRS-SENCE框架体系,并以崇明岛为例进行实证研究.结果表明,近十余年崇明岛综合得分呈现逐渐提高的趋势,2007年综合得分为0.513,处于中等偏上水平,反映了崇明岛长期交通阻隔、相对落后的经济发展状况导致生态压力和环境污染较小;随着越江隧桥工程的建成通车,未来跨越式发展将使生态安全面临巨大压力.二级综合指数中,生态风险和生态保障指数较低,因此加强生态建设,完善管理和保障措施,降低生态风险对崇明岛生态系统的影响,应是提高生态安全综合指数等级的主要途径.  相似文献   

砂土中等截面桩的上拔机制分析     

刘文白  刘兹胜  周健 《岩土力学》2009,30(Z1):201-205

桩的上拔承载性能的宏观力学现象与桩周土细观结构变化相关,应用细观力学的颗粒流（PFC2D）数值模拟方法对承受上拔荷载作用的桩基进行了分析,数值模拟了上拔荷载作用的桩及桩周土的细观力学特征,研究了桩侧摩阻力的分布、桩周土剪切带的形成过程,较好的再现了桩的荷载－位移关系的实验结果,并与宏观物理实物试验的位移实测结果作了对比分析。分析了土体中剪切带形成过程中的颗粒间的细观变化及其形成过程,当上拔荷载达到极限时,上拔桩的剪切带形成原因是密砂的应变软化效应;颗粒流数值模拟的颗粒接触力与实物物理试验桩侧摩阻力是同一的,数值模拟的荷载-位移曲线与实物物理试验的荷载-位移曲线一致;桩侧摩阻力、桩上拔过程中剪切带的形成过程、桩上拔荷载-位移关系与颗粒流数值模拟的颗粒分布、速度、接触力的细观参数的变化密切相关。桩承受荷载过程中土颗粒细观结构变化的颗粒流仿真,是关于细观力学特征与宏观力学响应的初步研究。  相似文献   

Practical evaluation of sinkage and trim effects on the drag of a common generic freely floating monohull ship     

《Applied Ocean Research》2017

A practical method to account for the influence of sinkage and trim on the drag of a freely floating (free to sink and trim) common monohull ship at a Froude number F ≤ 0.45 is considered. The sinkage and the trim are estimated via two alternative simple methods, considered previously. The drag is also estimated in a simple way, based on the classical Froude decomposition into viscous and wave components. Specifically, well-known semiempirical expressions for the friction drag, the viscous pressure drag and the drag due to hull roughness are used, and the wave drag is evaluated via a practical linear potential flow method. This simple approach can be used for ship models as well as full-scale ships with smooth or rough hull surfaces, and is well suited for early ship design and optimization. The method considered here to determine the sinkage and the trim, and their influence on the drag, yields theoretical predictions of the drag of the Wigley, S60 and DTMB5415 hulls that are much closer to experimental measurements than the corresponding predictions for the hull surfaces of the ships in equilibrium position at rest. These numerical results suggest that sinkage and trim effects, significant at Froude numbers 0.25 < F, on the drag of a typical freely floating monohull ship can be realistically accounted for in a practical manner that only requires simple potential flow computations without iterative computations for a sequence of hull positions.  相似文献   

Flow patterns of a low mass-damping cylinder undergoing vortex-induced vibration: Transition from initial branch and upper branch     

《Applied Ocean Research》2017

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CFD analysis of the sensitivity of propeller bearing loads to stern appendages and propulsive configurations     

《Applied Ocean Research》2017

The present investigation focuses on the effects of the stern appendages and the propulsion system on the hydro-loads generated by the propeller during off-design conditions, with particular emphasis on the in-plane components. Recent experimental investigations carried out by free running model tests [7], [8] and CFD analysis [5] for a modern twin screw model, highlighted that maneuvers at small drift angles and yaw rates might be as critical as the tighter ones due to complex propeller-wake interactions. Therefore, design criteria should take into account also these operative conditions, in order to reduce the effects of propeller-wake interaction phenomena that degrade the overall propulsive efficiency, induce shaft/hull structural vibration and increase noise emission. In the present study we analyze the effects of geometric and propulsive modifications with respect to the twin screw configuration studied in [5]. In particular, the effect of the centreline skeg, propeller direction of rotation and control strategies of the propulsion plant on the propeller bearing loads have been investigated from the analysis of the nominal wake in maneuvring conditions, computed by unsteady RANSE simulations coupled with a propeller model based on Blade Element Theory. The considered test cases were turning circle maneuvers with different rudder angles at F_N = 0.265.  相似文献