RepDNet:A re-parameterization despeckling network for autonomous underwater side-scan sonar imaging with prior-knowledge customized convolution

Side-scan sonar(SSS)is now a prevalent instrument for large-scale seafloor topography measurements,deployable on an autonomous underwater vehicle(AUV)to execute fully automated underwater acoustic scanning imaging along a predetermined trajectory.However,SSS images often suffer from speckle noise caused by mutual interference between echoes,and limited AUV computational resources further hinder noise suppression.Existing approaches for SSS image processing and speckle noise reduction rely heavily on complex network structures and fail to combine the benefits of deep learning and domain knowledge.To address the problem,Rep DNet,a novel and effective despeckling convolutional neural network is proposed.Rep DNet introduces two re-parameterized blocks:the Pixel Smoothing Block(PSB)and Edge Enhancement Block(EEB),preserving edge information while attenuating speckle noise.During training,PSB and EEB manifest as double-layered multi-branch structures,integrating first-order and secondorder derivatives and smoothing functions.During inference,the branches are re-parameterized into a 3×3 convolution,enabling efficient inference without sacrificing accuracy.Rep DNet comprises three computational operations:3×3 convolution,element-wise summation and Rectified Linear Unit activation.Evaluations on benchmark datasets,a real SSS dataset and Data collected at Lake Mulan aestablish Rep DNet as a well-balanced network,meeting the AUV computational constraints in terms of performance and latency.

预测规则波浪中船舶运动和载荷的频域三维计算机程序

The development of an in-house computer program for determining the motions and loads of advancing ships through sea waves in the frequency domain,is described in this paper.The code is based on the potential flow formulation and originates from a double-body code enhanced with the regular part of the velocity potential computed using the pulsing source Green function.The code is fully developed in C++language with extensive use of the object-oriented paradigm.The code is capable of estimating the excitation and inertial radiation loads or arbitrary incoming wave frequencies and incidence angles.The hydrodynamic responses such as hydrodynamic coefficients,ship motions,the vertical shear force and the vertical bending moment are estimated.A benchmark container ship and an LNG carrier are selected for testing and validating the computer code.The obtained results are compared with the available experimental data which demonstrate the acceptable compliance for the zero speed whereas there are some discrepancies over the range of frequencies for the advancing ship in different heading angles.

Computation of Ship Hydrodynamic Interaction Forces in Restricted Waters using Potential Theory

计算机代码基于双身体潜力流动模型和经典来源，面板方法被开发了包括海床学习和稳固的边界的在轮船和另外的对象之间的水动力学相互作用的各种各样的问题。建议实现的一个怪癖是为模仿大延期的稳定的边界的所谓的动人补丁的方法的应用程序。方法基于在任何时刻，就谎言关门到交往的轮船的边界(动人的补丁) 的部分为近地的相互作用是重要的一个假设。为扁平的底部的一个特定的盒子，比较计算被执行基于在可接受的精确性和合理效率之间的交易决定补丁并且组成的面板的最佳的尺寸。方法被使用在越过一条挖出的隧道倾斜地移动的轮船壳上估计摇摆力量。当坦克数据是可得到的时，方法为 ship-to-ship 相互作用的一个盒子被验证。这研究也包含对为与精炼的各种各样的度创造轮船壳的一致 discretizations 必要的一个最新发达的花键近似算法的描述。

System Reliability Analysis of an Offshore Jacket Platform

This study investigates strategies for solving the system reliability of large three-dimensional jacket structures.These structural systems normally fail as a result of a series of different components failures.The failure characteristics are investigated under various environmental conditions and direction combinations.Theβ-unzipping technique is adopted to determine critical failure components,and the entire system is simplified as a series-parallel system to approximately evaluate the structural system reliability.However,this approach needs excessive computational effort for searching failure components and failure paths.Based on a trained artificial neural network(ANN),which can be used to approximate the implicit limit-state function of a complicated structure,a new alternative procedure is proposed to improve the efficiency of the system reliability analysis method.The failure probability is calculated through Monte Carlo simulation(MCS)with Latin hypercube sampling(LHS).The features and applicability of the above procedure are discussed and compared using an example jacket platform located in Chengdao Oilfield,Bohai Sea,China.This study provides a reference for the evaluation of the system reliability of jacket structures.

A Simplified Model for the Effect of Weld-Induced Residual Stresses on the Axial Ultimate Strength of Stiffened Plates

The present work investigates the compressive axial ultimate strength of fillet-welded steel-plated ship structures subjected to uniaxial compression,in which the residual stresses in the welded plates are calculated by a thermo-elasto-plastic finite element analysis that is used to fit an idealized model of residual stress distribution.The numerical results of ultimate strength based on the simplified model of residual stress show good agreement with those of various methods including the International Association of Classification Societies(IACS)Common Structural Rules(CSR),leading to the conclusion that the simplified model can be effectively used to represent the distribution of residual stresses in steel-plated structures in a wide range of engineering applications.It is concluded that the widths of the tension zones in the welded plates have a quasi-linear behavior with respect to the plate slenderness.The effect of residual stress on the axial strength of the stiffened plate is analyzed and discussed.

Correction to:Buckling Properties of a Subsea Function Chamber for Oil/Gas Processing in Deep Waters

The article“Buckling Properties of a Subsea Function Chamber for Oil/Gas Processing in Deep Waters”,written by Amer Ali Al-Hamati,Menglan Duan,Chen An,C.Guedes Soares and Segen Estefen,was originally published Online First without Open Access.After publication in volume 19,issue 4,page 642–657 the author decided to opt for Open Choice and to make the article an Open Access publication.

海上液化天然气行业风险分析研究综述

This research presents a review and classification of the published work related to applied risk analysis and risk management in the maritime liquefied natural gas(LNG)sector from 2000 to 2023.The papers are categorised under two primary contexts.The first is the risk analysis theory context which represents the classification with respect to(w.r.t.)the used risk analysis method,the used risk analysis tool,and the objective of risk analysis,whereas the second is the presented case in the risk analysis context which represents the classification w.r.t.the analysed LNG ship type,the analysed operation,and the inclusion level of human error in risk analysis.The above process has revealed that the interest in this domain of research has increased significantly during the past decade.In addition,the use of dynamic risk analysis(DRA)tools,and the inclusion of human error in the risk analysis model have been observed significantly in the past five years,in particular,for modelling the risk of external LNG transfer operations.It is concluded that the inclusion of the effect of human and organisational factors(HOFs)in risk analysis,and the use of DRA methods for modelling the risk of the daily routine operations of the complex maritime LNG systems can improve the management of the operational risk of these systems.

海上自主水面船舶(MASS)路径跟踪控制系统综述

A review presents the state-of-the-art path-following control systems for maritime autonomous surface ships,where the special focus is placed on the guidance subsystem and control subsystem.The path following control system is one of the basic requirements for autonomous ships since it guarantees that the ship can track the predefined path with small crosstrack errors.The path following problem is firstly defined,and the cross-track error dynamics are derived from the kinematic equations of marine surface ships.The classical guidance laws are introduced,and the governing equations are also presented in this paper.A review of the guidance laws and controllers for the maritime autonomous surface ships has been carried out based on relevant journal and conference papers.Several important properties and characteristics,such as control structure,guidance law,control method,stability,environmental disturbance and vessel dynamics,are defined for the comparative analysis.Finally,the summary and a discussion on the most used technologies for the path following control of marine autonomous surface ships are presented and highlighted.

某散货船单桨、双桨推进系统燃油消耗分析

This paper presents a comparative analysis between single and twin-screw propulsion systems of a bulk carrier to evaluate the ship and propeller performance in terms of fuel consumption as well as to discuss the cavitation and noise criteria.An optimization model is developed to select the optimum propeller geometry and operational point along the engine load diagram for the selected engines of each case.The engines are selected from the same series due to the same behaviour along the engine load diagram.The propellers are selected from the B-series as fixed-pitch propellers.It has been concluded that while the components of the single-screw propulsion system are larger than the twin-screw,the single-screw propulsion system shows a reduction in fuel consumption than the twin screw by around 19%,thus affecting the amount of exhaust emissions from the ship.This model helps the ship designers to select a suitable propeller to improve the energy efficiency of the ships.

国际海事组织船舶能效提案及其影响综述

This paper presents a review of the different International Maritime Organization(IMO)initiatives to improve the ship energy efficiency of new and existing ships,which is considered one of the essential tasks to reduce Greenhouse Gas(GHG)in the maritime industry.First,the IMO effort and initiatives and the different indices suggested by the IMO are presented till the last version of the Marine Environment Protection Committee(MEPC),showing the effect of different technologies on reducing the level of indices and the suggested improvement of the terms of indices in the next years.Second,the short-and long-term strategies suggested by the IMO are presented,showing that the effect of indices will be noticed in the short term,while the new fuels will show a significant improvement in the long term.Finally,several examples of cooperation between the different organizations are presented,showing that transferring knowledge and experience will significantly impact the maritime industry and thus lead to the concept of green ships in the near future.This paper shows that the combination of different solutions,the cooperation between stakeholders and the sharing of the data and information are important to achieve the required goal.

编者按

The need to reduce the trends associated with climate change imposes measures to reduce the emissions of greenhouse gases to the atmosphere and increase the efficiency of the use of energy.The International Maritime Organization(IMO)has been active since 1997 in promoting the implementation of measures that lead to more efficient ship operation with less fuel consumption and less emissions(Tadros et al.,2023a).The measures include improved ship design and improved operational practices.Several indexes have been created to quantify different aspects of these improvements.The shipping industry has been very actively implementing several actions aiming at the decarbonization of ship operation and more need to continue being implemented.

物理生成的长峰不规则波的非高斯统计特性

An experimental study is presented on the non-Gaussian statistics of random unidirectional laboratory wave fields described by JONSWAP spectra.Relationships between statistical parameters indicative of the occurrence of largeamplitude waves are discussed in the context of the initial steepness of the waves combined with the effect of spectral peakedness.The spatial evolution of the relevant statistical and spectral parameters and features is also considered.It is demonstrated that over the distance the spectra exhibit features typical for developing nonlinear instabilities,such as spectral broadening and downshift of the peak,along with lowering of the high-frequency tail and decrease of the peak magnitude.The wave fields clearly show an increase of third-order nonlinearity with the distance,which can be significant,depending on the input wave environment.The steeper initial conditions,however,while favouring the occurrence of extremely large waves,also increase the chances of wave breaking and loss of energy due to dissipation,which results in lower extreme crests and wave heights.The applied Miche-Stokes-type criteria do confirm that some of the wave extremes exceed the limiting individual steepness.Eventually,this result agrees with the observation that the largest number of abnormal waves is recorded in sea states with moderate steepness.

极端海浪对LNG运输船影响的试验研究

This paper presents a comprehensive experimental study on the effect of extreme waves on a LNG carrier.The LNG carrier model was equipped with a variety of sensors to measure motions,green water height on deck as well as local and global loads.Experiments in transient wave packets provided the general performance in waves in terms of response amplitude operators and were accompanied by tests in regular waves with two different wave steepness.These tests allowed detailed insights into the nonlinear behavior of the vertical wave bending moment in steep waves showing that green water on deck can contribute to a decrease of vertical wave bending moment.Afterwards,systematic model tests in irregular waves were performed to provide the basis for statistical analysis.It is shown that the generalized extreme value distribution model is suitable for the estimation of the extreme peak values of motions and loads.Finally,model tests in tailored extreme wave sequences were conducted comparing the results with the statistical analysis.For this purpose,analytical breather solutions of the nonlinear Schrödinger equation were applied to generate tailored extreme waves of certain critical wave lengths in terms of ship response.Besides these design extreme waves,the LGN carrier was also investigated in the model scale reproduction of the real-world Draupner wave.By comparing the motions,vertical wave bending moment,green water column and slamming pressures it is concluded that the breather solutions are a powerful and efficient tool for the generation of design extreme waves of certain critical wave lengths for wave/structure investigations on different subjects.

Rolling Bearing Fault Diagnosis Based On Convolutional Capsule Network

Fault diagnosis technology has been widely applied and is an important part of ensuring the safe operation of mechanical equipment.In response to the problem of frequent faults in rolling bearings,this paper designs a rolling bearing fault diagnosis method based on convolutional capsule network(CCN).More specifically,the original vibration signal is converted into a two-dimensional time–frequency image using continuous wavelet transform(CWT),and the feature extraction is performed on the two-dimensional time–frequency image using the convolution layer at the front end of the network,and the extracted features are input into the capsule network.The capsule network converts the extracted features into vector neurons,and the dynamic routing algorithm is used to achieve feature transfer and output the results of fault diagnosis.Two different datasets are used to compare with other traditional deep learning models to verify the fault diagnosis capability of the method.The results show that the CCN has good diagnostic capability under different working conditions,even in the presence of noise and insufficient samples,compared to other models.This method contributes to the safe and reliable operation of mechanical equipment and is suitable for other rotating scenarios.

散货船与桥墩碰撞力的经验公式与数值模拟对比研究

介绍了目前几种常见的船桥碰撞力估算公式,并采用这些公式分别计算了四艘三峡标准散货船在各种航速下撞击桥墩的碰撞力。根据三峡标准散货船的设计图纸建立船体有限元模型,通过数值模拟计算了不同吨级、船速下的船桥碰撞力曲线。在桥梁设计时,该曲线可以为该类船舶一桥墩碰撞力计算及评估提供参考。结合经验公式的推导过程,通过船桥碰撞力经验公式与有限元数值仿真分析计算结果表明,铁路桥涵设计规范的船桥碰撞力公式更适合于斜艏500至3 000 t级散货船,而美国公路桥梁设计规范的船桥撞击力计算公式对该类型吨级船舶的碰撞力结果偏大。

桥梁防船撞钢套箱的碰撞力快速估算

研究船舶与单墩桥梁防撞钢套箱艏尖舱的碰撞过程,探讨碰撞力快速估算及防撞装置模块化设计的可行性。首先采用非线性有限元方法模拟1 000吨级三峡标准散货船与钢套箱式桥梁防船撞装置的碰撞过程,分析了防撞钢套箱艏尖舱在不同的斜边角和船舶碰撞速度下的能量吸收特性以及传递至桥墩的碰撞力特性,得到的结果可为防撞钢套箱外形的选择提供参考。对所选择的防撞钢套箱形式,采用Boltzmann函数拟合了撞击船速与桥梁所受横桥向及顺桥向碰撞力之间的关系,该拟合公式可以用于此类防撞钢套箱方案设计阶段的撞击力快速估算。

双曲壳的非线性动力分析

本文用实时动力松弛法分析了具有材料和几何非线性的双曲壳的动力响应。采用Mises屈服准则和结合应变强化规律的Prandtl-Reuss流动理论,导得适宜的弹塑性本构关系。在介绍求解运动方程方法时,特别论述了估算时间步长的问题。对不同网格尺寸和沿厚度弹塑性层数对结果精度的影响也作了讨论。并以受突加均匀外压的浅球盖壳为例进行了分析,其结果与文献中的解相当吻合。

基于条件的近岸风能维修策略综述（英文）

The existing maintenance strategies of offshore wind energy are reviewed including the specific aspects of condition-based maintenance, focusing on three primary phases, namely, condition monitoring, fault diagnosis and prognosis, and maintenance optimization. Relevant academic research and industrial applications are identified and summarized. The state of art, capabilities,and constraints of condition-based maintenance are analyzed. The presented research demonstrates that the intelligent-based approach has become a promising solution for condition recognition, and an integrated data platform for offshore wind farms is significant to optimize the maintenance activities.

优化船用柴油机的性能以减少氧化硫SO_x排放物的形成

Optimization procedures are required to minimize the amount of fuel consumption and exhaust emissions from marine engines.This study discusses the procedures to optimize the performance of any marine engine implemented in a 0D/1D numerical model in order to achieve lower values of exhaust emissions.From that point,an extension of previous simulation researches is presented to calculate the amount of SOx emissions from two marine diesel engines along their load diagrams based on the percentage of sulfur in the marine fuel used.The variations of SOx emissions are computed in g/k W·h and in parts per million(ppm)as functions of the optimized parameters:brake specific fuel consumption and the amount of air-fuel ratio respectively.Then,a surrogate model-based response surface methodology is used to generate polynomial equations to estimate the amount of SOx emissions as functions of engine speed and load.These developed non-dimensional equations can be further used directly to assess the value of SOx emissions for different percentages of sulfur of the selected or similar engines to be used in different marine applications.

Fatigue Reliability Assessment of Correlated Welded Web-frame Joints

The objective of this work is to analyze the fatigue reliability of complex welded structures composed of multiple web-frame joints, accounting for correlation effects. A three-dimensional finite element model using the 20-node solid elements is generated. A linear elastic finite element analysis was performed, hotspot stresses in a web-frame joint were analyzed and fatigue damage was quantified employing the S-N approach. The statistical descriptors of the fatigue life of a non-correlated web-frame joint containing several critical hotspots were estimated. The fatigue reliability of a web-frame joint wasmodeled as a series system of correlated components using the Ditlevsen bounds. The fatigue reliability of the entire welded structure with multiple web-frame joints, modeled as a parallel system of non-correlated web-frame joints was also calculated.