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1.
基于粒子群算法的浮筒配置优化问题的研究 总被引：1，自引：0，他引：1
针对传统的验证法在解决浮筒配置问题中存在的计算量大、计算时间长、工作重复性强等缺点,提出了一种将浮筒纵向位置配置和浮筒充气量综合考虑、一体优化的方法。文章将各种合理性校验准则作为约束条件,通过逼近沉艇起浮瞬间和浮起后的平衡状态,来求取各对浮筒的纵向位置和充气量,将浮筒配置问题转换为一个多目标、多约束的最优化问题。在此基础上,根据粒子群优化算法的特点,提出了一种双向搜索策略,来求解浮筒配置优化问题。这种方法简单实用,计算时间短,无需人工干预,算法运行一次可获得多组配置方案供决策人员选择。算例表明用这种方法来解决浮筒配置问题是可行的、有效的。 相似文献
2.
Real-time video mosaicking of the ocean floor 总被引：2，自引：0，他引：2
An approach was developed for real-time creation of video mosaics of the ocean floor. The approach uses visual correspondence during both image acquisition and consolidation to insure that there are no gaps in the mosaic. The use of visual information for mosaic creation offers an accuracy previously unachievable in real time. A complete mosaicking approach was developed, including a technique for image registration and several strategies for image acquisition control. The approach was implemented and tested experimentally. Ocean-floor mosaics were created in real time using a remotely-operated vehicle. In addition, extensive mosaicking experiments were conducted in a test-tank environment using a semiautonomous underwater robot 相似文献
3.
《Marine Policy》2014
Integrated Coastal Zone Management (ICZM) development is described here in the broader context of European coastal management initiatives. The European approach to coastal governance revolves around the principles of ICZM, as enshrined in EC Recommendation 2002/413/EC. This study investigates the extent to which the FP6 funded project SPICOSA (Science Policy Integration for Coastal Systems Assessment) was able to implement these principles. The SPICOSA project aimed to test whether it was possible to develop and implement a systems approach framework via delivery of a structured engagement process between scientists and policymakers. A survey of representatives from 14 European study sites involved in the project revealed that the approach had been effective at implementing some ICZM principles, particularly the “holistic approach”. However, not all principles were fully implemented at all sites and the most challenging to implement was that of “a long term approach”. The paper concludes with a critical consideration of the role of a systems approach framework in progressing the current state of intellectual assent towards practical implementation of ICZM principles. The findings provide evidence of contributions and limitations of systems approaches to sustainability science and good governance. 相似文献
4.
Profiles of wave-induced current on plane beaches are generally smooth. Previously, the smooth nature was often explained by involving lateral mixing concept. This paper describes a new spreading approach instead of the previous lateral mixing approach. The spreading of the driving forces leads to similar results on the velocity profiles of the previous approach. The results of the new method show good agreement with some laboratory measurements for a plane beach. The present method was then extended for two-dimensional plan problems. The present approach was tested against a laboratory experiment, and the computed flow field agrees reasonably well with the measured flow field. A merit of the present method is that the computational time increment is not restricted by the lateral mixing. 相似文献
5.
A new process-based approach is introduced for a more efficient computation of the overflow-induced growth of an erosional channel in a non-cohesive homogeneous narrow landmass such as the breach growth in a sand-dike. The approach is easy to incorporate in a 1D/2DV morphodynamic model to compute the channel growth both vertically and laterally. 相似文献
6.
基于局部时间步长方法的潮流数值模型研究及应用 总被引：1，自引：1，他引：0
为了准确快速地模拟潮流过程,将局部时间步长(LTS)方法应用于基于黎曼近似解通量——有限体积法的浅水模型。LTS方法和传统整体最小时间步长方法的计算性能对比表明,两种方法的计算结果定量差异远小于模拟值与实测值之间相对误差;但由于LTS方法对每个网格采用了与稳定性条件相适应的尽可能大的时间步长,计算效率大幅度提高。本模型计算所得渤海、黄海、东海的潮流传播过程、潮汐调和常数的空间分布、无潮点位置,以及长江口和杭州湾区域的潮流过程与已有认识和实测资料吻合良好。 相似文献
7.
Mehmet Levent Koç 《Ocean Engineering》2009,36(14):1060-1721
This paper proposes a preliminary investigation of possibility and evidence theories in a risk analysis of a vertical breakwater. The results obtained from both theories are presented and compared to the Monte Carlo simulations. This study indicates that the evidence theory approach is more flexible than the possibility theory approach and may provide a useful tool for a joint handling of variability and imprecision in the computation of risk. On the other hand, the possibility theory approach may have a good potential to be used for risk assessment of coastal structures, when sufficient data are not available. 相似文献
8.
An array of elliptic ring radiators is proposed which generates a fan-type beam with controllable sidelobe levels. Such an array has applications in specialized acoustic systems such as sidescan sonars, sonars for fish finding and stock assessment, obstacle avoidance systems, and others. Two possible approaches to the design are presented. One approach utilizes a mapping which transforms a radiation pattern generated by a circular ring array to that of an elliptic ring array. This approach takes advantage of methodologies developed for the design of circular ring arrays. The other approach uses the concept of an equivalent linear array. This approach benefits from existing design techniques developed for linear arrays. It requires only simple matrix operations and does not involve any optimization. The design examples presented demonstrate that a fan-type beam with sidelobes suppressed to more than 40 dB in all possible directions is achievable 相似文献
9.
10.
Tarek Elsayed 《Applied Ocean Research》2009,31(3):179-185
A multiple attribute risk assessment approach using a fuzzy inference system is developed in this work. The approach is based on the use of fuzzy sets, a rule base and a fuzzy inference engine. Traditional input probabilities and consequences used in risk assessment are represented by fuzzy sets to take into account uncertainties associated with the assignment of their values. The output risk values can be presented as crisp values or fuzzy sets with associated degree of membership. The fuzzy inference system FIS is used as an alternative approach to qualitative risk matrix techniques currently used in many industries and by ship classification societies. Two approaches for fuzzy inference are adopted. These include the Mamdani approach in which output risk values are fuzzy sets and the Sugeno method of fuzzy inference, in which output risk values are constant or linear.The use of a fuzzy set approach is particularly suited for handling multiple attribute risk problems with imprecise data. It improves upon existing qualitative methods and allows the ranking of risk alternatives based on a unified fuzzy risk index measure. Results show that while the Mamdani method is intuitive and well suited to human input, the Sugeno method is computationally more efficient and guarantees continuity of the final risk output surface. Results also show that computed risk values using a fuzzy risk index measure are consistent with those obtained using a qualitative risk matrix approach. The proposed methodology is also applicable to other ship operating modes such as transit in open sea and/or entering/leaving port. A case study for a liquefied natural gas LNG ship loading/offloading at the terminal is presented to demonstrate the developed approach capability. 相似文献
11.
In this paper, a new approach to the design of broad-band time-domain element space antenna array processors is presented. The basic approach is based on the idea of minimizing the mean-square deviation between the desired look-direction response and the response of the processor over a frequency band of interest. With this approach, three types of presteering can be handled: no presteering, coarse presteering, and exact presteering. The elimination of presteering lime delays is important in a digital implementation of antenna array processors. The relationship that the new processor has to other broad-band processors is explored and the significance of the parameters associated with the new processor is established. Furthermore, the approach presented enables various types of errors and mismatches between signal model and actual scenario to be incorporated in the problem formulation. 相似文献
12.
Gornostaeva A. A. Demezhko D. Yu. Antipin A. N. 《Izvestiya Atmospheric and Oceanic Physics》2019,55(11):1766-1773
Izvestiya, Atmospheric and Oceanic Physics - This paper describes a new approach to orbital tuning for the adjustment of proxy-based paleoclimate chronologies; the approach involves the... 相似文献
13.
《Marine Policy》2005,29(6):481-493
Controlling the expansion of capture capacity has been a major challenge for the fisheries management systems around the North Atlantic. Despite focused attempts to reduce this capacity in recent years in different jurisdictions, it has continued to expand. This chapter uses a case study of changes in Norwegian fisheries to help explain why this has happened. The article supports the replacement of the rational actor approach that is currently hegemonic within fisheries management by a relational approach to the analysis of capture capacity expansion. A relational approach offers new insights into the ways political, economic, and technological forces continue to fuel capacity expansion within fishing. By use of this approach the article describes how the harvest machinery comes into existence. 相似文献
14.
The present study is employing the equivalent irregular wave approach to predict the wave loads for a ship encountering the worst sea state with respect to the critical dynamic loading parameter. Two different hydrodynamic numerical models, i.e. 3D pulsating source technique and 3D translating pulsating source technique, are applied to calculate the corresponding RAO of the ship moving in waves. Incorporating the RAO of the related physical properties, we can calculate the extreme value for the corresponding ship loading factor, which can be regarded as the worst sea state in the service lifetime of the ship. With the time and period of the occurrence of the corresponding extreme value, we can simulate the time history of the wave load in this period, which is so-called equivalent irregular wave approach. Comparing with the results calculated by the traditional equivalent regular wave approach, we find that the equivalent irregular wave approach can simulate the corresponding wave load more realistic, especially for dynamic pressure. Using the equivalent irregular wave approach can offer the effective and practical base for the ship structural analysis. 相似文献
15.
Dynamic analysis of three-dimensional marine cables 总被引：1，自引：0，他引：1
Shan Huang 《Ocean Engineering》1994,21(6)
Marine cables are widely used in a variety of offshore activities. In this paper, a numerical approach is presented which is capable of predicting the dynamic behaviour of three-dimensional marine cables. The solution of this problem is of practical importance in the estimation of dybamic loading and motion, and thus has direct application to the enhancement of safety and the effectiveness of the offshore activities. The approach is based upon the lump-mass-and-spring model and the finite difference method. Mathematical analysis is provided on the basic characteristics of the model and the numerical stability. A numerical example is given to demonstrate the validity of the approach. 相似文献
16.
This paper presents a hybrid behavior-based scheme using reinforcement learning for high-level control of autonomous underwater vehicles (AUVs). Two main features of the presented approach are hybrid behavior coordination and semi on-line neural-Q/spl I.bar/learning (SONQL). Hybrid behavior coordination takes advantages of robustness and modularity in the competitive approach as well as efficient trajectories in the cooperative approach. SONQL, a new continuous approach of the Q/spl I.bar/learning algorithm with a multilayer neural network is used to learn behavior state/action mapping online. Experimental results show the feasibility of the presented approach for AUVs. 相似文献
17.
针对网络控制系统中存在的不确定时滞,将网络控制系统模型转化为不确定系数的离散时间模型。利用Lya-punov稳定性理论和线性矩阵不等式技术,提出动态输出鲁棒控制器的设计方法,同时给出闭环系统鲁棒渐近稳定的充分条件。仿真例子验证了所提方法的有效性。 相似文献
18.
The ecosystem approach for fisheries management is a widely accepted concept and various international instruments require its application. However, there are various interpretations of the ecosystem approach and its application almost always brings about confrontations and resistance among managers, proponents, and stakeholders. This paper categorizes the ecosystem approach into four distinguishable types: bycatch mitigation, multi-species management, protection of vulnerable ecosystems, and integrated approach. Furthermore, the lack of identification and understanding of specific management goals is hampering the application of the ecosystem approach. Unless the stakeholders understand and accept the goals, the ecosystem approach will not succeed. 相似文献
19.
两种基于贝叶斯点估计理论的多声源定位方法研究 总被引：1，自引：1，他引：0
海洋环境参数失配是制约匹配场定位性能的主要因素之一。为了克服环境失配，本文基于贝叶斯理论，将环境参数与声源的距离和深度一起作为未知量进行反演。然而在进行多声源定位时，反演参数的维数几何增长，极大地增加了反演问题的复杂性和计算量。为此本文将声源强度和噪声方差表示成其极大似然估计值，从而将这些参数进行隐式采样，大大降低了反演的维数和难度。文章比较了两种贝叶斯点估计方法，最大后验概率密度方法和最大边缘后验概率密度方法。最大后验概率密度方法的解是令后验概率密度取得最大值的参数组合，可以利用优化算法快速获得。最大边缘后验概率密度法将其他参数积分，得到目标参数的一维边缘概率分布，分布的最大值为反演结果。该方法得到最优估计值的同时可以获取参数估计的不确定信息。在环境参数和声源参数都未知的情况下，利用蒙特卡洛法在不同信噪比情况下对两种声源定位方法进行分析，实验结果表明：(1)对于敏感参数，如声源距离、水深和海水声速，最大边缘后验概率密度法比最大边缘后验概率密度方法的性能好。(2)对于较不敏感的参数，如海底声速、海底密度和海底声衰减，当信噪比较低时，最大边缘后验概率密度方法能较好地平滑噪声，从而比最大边缘后验概率密度法具有更好的性能。由于声源距离和深度是敏感参数，研究表明最大边缘后验概率密度法提供了一种在不确知环境下更可靠的多声源定位方法。 相似文献
20.
K. L. Priya 《Ocean Science Journal》2018,53(3):449-459
Settling velocity is one of the important parameters in sediment transport modeling of estuaries. The methods adopted for its determination vary from theoretical equations to experimental methods. The theoretical equation generally adopted in the 1DV model include assumptions in order to simplify the solution. It is generally assumed that either the condition is steady or the vertical diffusion is negligible. This study evaluated the relative importance of the two assumptions made for the estimation of settling velocity. Two approaches were adopted: unsteady and negligible vertical diffusion (NS-NVD) and steady with vertical diffusion (S-VD) to estimate the settling velocity. The Muthupet Estuary in the Coromandal coast of India was selected for the study. The S-VD approach estimated settling velocity fairly well at the two locations with appreciable vertical diffusion. The NS-NVD approach was observed to be superior for estimating settling velocity at shallow reaches of the estuary having low flow velocity. The calculated settling velocity was further applied in 1DV model to predict the suspended sediment concentration. The S-VD approach predicted suspended sediment concentration at those locations with appreciable vertical diffusion with an R2 value of 0.82 against 0.67 for the NS-NVD approach. At the other shallow reach of the estuary with low flow velocity, the NS-NVD approach gave an R2 value of 0.822 against 0.71 for the S-VD approach. The vertical diffusion was observed to play a secondary role at those locations which are shallow with a water depth of 0.6 m and with a low flow velocity of the order of 0.01 m/s. The study demonstrated that localized hydrodynamic conditions influence the method adopted for the estimation of settling velocity. 相似文献