bluuebunny/crossref_metadata_2025 huggingface dataset:
The effector PHYL1JWB from Candidatus Phytoplasma ziziphi induces abnormal floral development by destabilising flower development proteins
Authors: Xue Chaoling , Zhang Liman , Li Hongtai , Liu Zhiguo , Zhang Yao , Liu Mengjun , Zhao Jin
Published: August 2024

Phytoplasmas can induce complex and substantial phenotypic changes in their hosts in ways that favour their colonisation, but the mechanisms underlying these changes remain largely unknown. Jujube witches' broom (JWB) disease is a typical phytoplasma disease causing great economic loss in Chinese jujube (Ziziphus jujuba Mill.). Here, we reported an effector, PHYL1JWB from Candidatus Phytoplasma ziziphi, which implicated in inducing abnormal floral organogenesis. Utilising a combination of in vivo and in vitro methods, we investigated the influence of PHYL1JWB on the proteins associated with floral development. Our findings reveal that PHYL1JWB facilitates the proteasome‐mediated degradation of essential flower morphogenetic regulators, including AP1, SEP1, SEP2, SEP3, SEP4, CAL, and AGL6, through a distinctive pathway that is dependent on the activity of the 26S proteasome, thus obviating the requirement for lysine ubiquitination of the substrates. Further, the Y2H analysis showed that the leucine at position 75th in second α helix of PHYL1JWB is fundamental for the interactions of PHYL1JWB with AP1 and SEP1‐4 in jujube and Arabidopsis. Our research carry profound implications for elucidating the contribution of PHYL1JWB to the aberrant floral development in diseased jujube, and help to establish a robust theoretical underpinning for the prophylaxis and therapy of JWB disease.
Causal relationships between dietary antioxidant vitamin intake and atopic dermatitis: A two‐sample Mendelian randomization study
Authors: Wang Siqing , Dan Wenchao , Wang Zixuan , Sun Yujie , Zhang Guangzhong
Published: August 2024

Objective

Oxidative stress is strongly associated with atopic dermatitis (AD), and increased antioxidant intake could potentially reduce the risk of or alleviate its symptoms. However, the argument is disputed. Therefore, we conducted a Mendelian randomization (MR) analysis to explore the causal relationship between dietary antioxidant vitamin intake and AD.

Methods

We applied MR analysis to examine the causative association between dietary antioxidant vitamin intake (vitamin C, vitamin E, carotene, and retinol) and AD. The genome‐wide association study (GWAS) summary data for antioxidant vitamins intake and AD were obtained from the IEU OpenGWAS database and the UK biobank. Our study consisted of two major parts, MR analysis to detect the causal relationship between exposure and outcome, and sensitivity analysis as supplemental evidence to verify the robustness of the results.

Result

The results revealed a suggestive causal relationship between vitamin E intake and AD (p = 0.038, OR 95% CI = 0.745–0.992). However, there was no causal relationship between the other three vitamins (vitamin C, carotene, and retinol) and AD (p = 0.507, OR 95% CI = 0.826–1.099) (p = 0.890, OR 95% CI = 0.864–1.184) (p = 0.492, OR 95% CI = 0.893–1.264). None of the single nucleotide polymorphisms (SNPs) were detected as heterogeneous and pleiotropy in the sensitivity analysis (p > 0.05).

Conclusion

The analysis suggested that dietary intake of vitamin E may potentially lower the risk of AD. Conversely, intake of vitamin C, retinol, and carotene is not causally related to AD. Although vitamin E intake could be protective against AD, intake of dietary antioxidant vitamins to prevent or treat AD is not necessary.
Enhance Road Detection Data Processing of LiDAR Point Clouds to Specifically Identify Unmarked Gravel Rural Roads
Authors: Huston Rhett G. , Wilhelm Jay P.
Published: August 2024

Gravel roads lack standardized features such as curbs or painted lines, presenting detection challenges to autonomous vehicles. Global positioning service (GPS) and high resolution maps may not be reliable for navigation of gravel roads, as some roads may only be width of the vehicle and GPS may not be accurate enough. Normal distribution transform (NDT) LiDAR scan matching may be insufficient for navigating on gravel roads as there may not be enough geometrically distinct features for reliable scan matching. This paper examined a method of classifying scanning LiDAR spatial and remission data features for explicit detection of unmarked gravel road surfaces. Exploration of terrain classification using high resolution scanning LiDAR data of specific road surfaces may allow for predicting gravel road boundary locations potentially enabling confident autonomous operations on gravel roads. The principal outcome of this work was a method for gravel road terrain detection using LiDAR data for the purpose of predicting potential road boundary locations. Random decision forests were trained using scanning LiDAR data terrain classification to detect unmarked gravel and asphalt surfaces. It was found that a true-positive accuracy for gravel and asphalt surfaces was 75% and 87%, respectively, at an estimated rate of 13 ms per 360 deg scan. Overlapping results between manually projected and actual road surface areas resulted in 93% intersecting gravel road detection accuracy. Automated post-process examination of classification results yielded an true-positive gravel road detection rate of 72%.
Experimental Study on the Effects of Aquaculture Net Cages on the Motion Responses of a Spar-Type Floating Structure
Authors: Bai Shenyi , Dong Shuchuang , Li Qiao , Zhou Jinxin , Kitazawa Daisuke
Published: August 2024

An innovative concept for a spar-type floating wind turbine that incorporates aquaculture cages not only meets the Sustainable Development Goals (SDGs) but also optimizes the use of offshore ocean space. The integration of floating offshore wind turbines with aquaculture has the potential to bring economic benefits to both industries. In this feasibility study, a 1/56 scale model of a 2MW Spar floating wind turbine is used and the target cage is silver salmon farming cage with dimensions of around 25 m in diameter and 9 m in depth. An experimental investigation was carried out in an experimental tank to examine the surge, heave and pitch dynamic responses of a spar-type floating offshore wind turbine with aquaculture cages. Under regular wave conditions, aquaculture cages of varying quantities and distances were positioned in front of the spar-type floating structure facing the wave direction, with accelerometers recording the spar-type floating structure’s surge, heave, and pitch motion.

The study revealed that cages have a predominantly shadowing influence on the spar’s motion responses, compared to scenarios without cages. This effect is more pronounced when cages are situated nearer to the spar. When wave period was less than 1.0 second, the presence of the cages exerted a more pronounced influence on the movement of the spar. However, when the ratio of incident wavelength to cage diameter is close to 4, the motion responses of the Spar were significantly amplified under the influence of the aquaculture cages. Also, the impact of cages on the spar’s motion is relatively minor, varying from less than 10% for wave periods in excess of 1.2 seconds. Furthermore, the insignificant impact of the number of cages on spar motion attenuation was found but different setting methods will affect the wave field near the cages.

The findings of this study possess significant practical and theoretical implications, as they furnish experimental evidence of the feasibility of integrating renewable energy enterprises with marine aquaculture ventures. In summary, the study determined that the deployment of net cages has an almost negligible impact on the oscillatory movements of spar-type floating platforms in most scenarios but reduces the motion amplitudes under specific wave periods. These discoveries provide crucial guidance for future offshore industry operations, indicating the necessity for further investigations to explore the interplays between floating structures and net cages under diverse conditions.
Numerical Study on the Dynamic Response of Mooring Systems for an Offshore Floating Photovoltaic Platform
Authors: Lian Yushun , Chen Quan , Shen Shutian , Zheng Jinhai , Chen WenXing , Yim Solomon C.
Published: August 2024

Offshore floating photovoltaic (OFPV) platforms have emerged as a new development trend. However, conventional floating photovoltaic platforms designed for inland water areas are not suitable for use directly in ocean environments. Hence, an OFPV platform incorporating three types of mooring systems is proposed. These mooring systems employ various combinations of mooring lines, including all chains, chain-polyester ropes-chain, and chain-nylon ropes-chain, respectively. Dynamic response analysis of the three mooring systems for the offshore floating photovoltaic platform is conducted. The results indicate that the mooring system with nylon ropes shows the lowest tension and the largest displacements of the OFPV platform. However, the mooring systems with all chains show the largest tension under the same environmental load. In addition, the dynamic response of mooring systems with one-line failure is investigated. Results show that the floating platform undergoes significant displacement motion once a mooring line fails. Furthermore, the tension distribution of the remaining mooring lines becomes uneven, potentially leading to overall mooring system failure. This numerical study provides valuable insights into the design of mooring systems incorporating fiber ropes for OFPV platforms.
Identification of Hydrodynamic Coefficients in Nonlinear Maneuvering Model for an ESSO 190000 dwt Tanker by Least-Squares Support Vector Regression With Linear System
Authors: Chua Ming Han , Tam Ivan , Dev Arun , Liu Bin
Published: August 2024

In this article, the least-squares support vector machine (LS-SVM) with linear system of equations is used to identify the hydrodynamic derivatives of a three degree-of-freedom (3-Dofs) maneuvering model for an ESSO 190000 dwt tanker. Instead of identifying the hydrodynamic derivative independently, the highly-correlated hydrodynamic derivatives are identified together by LS-SVM and subsequently distinguished in sets of linear system of equations. The issue of parameter drift is briefly discussed and diminished with the proposed approach. The training data are sampled from the simulated zigzag maneuver. The computational procedures and set up of the support vector machine are discussed in detail. A number of predicted maneuvers are compared with the reference maneuvers. Excellent accuracy and generality of the estimated maneuvering model are achieved based on the proposed system identification technique.
Equivalent Drag Approach for Wave Loads on Slender Structures
Authors: Xia Jinzhu
Published: August 2024

The Morison equation has been widely used to describe flow-induced loads on slender structures in waves and currents. However, as far as the load magnitudes and their probabilistic distributions in irregular seas are concerned, it is more effective to formulate a hydrodynamic load prediction model using an equivalent drag expression because this avoids the necessity to define the added mass and calculate the flow acceleration. Since the inertia effect contributes to the total load, the equivalent drag coefficient is constructed to account for this influence. One obvious advantage of this alternative approach is that the equivalent drag coefficient can be calibrated against the results of total hydrodynamic load measurement or CFD calculations without having to measure or quantify the added mass coefficient and the inertia contribution.

In this paper, the equivalent drag approach is introduced in the regular wave condition as a general method for calculating the amplitude of the total wave loading on any slender structure cross-section. In an irregular sea state, the most probable maximum (MPM) value of the wave load amplitude is expressed in terms of the MPM value of the relative flow velocity and the equivalent drag coefficient which is dependent on a newly defined period number χ. The short-term probability distribution of the wave load magnitudes is represented by a Weibull distribution as a function of the equivalent drag coefficient. The long-term magnitude distribution can be developed by summing the short-term distribution of each sea state weighted by the probability of occurrence. As a special application, the equivalent drag coefficient is determined by fitting a modified hyperbolic relation to the model test results of the measured total wave load on the bilge keel of a floating production vessel (FPSO) in irregular sea states. An example of bilge keel fatigue assessment is presented based on the long-term wave load prediction, while load sensitivity is demonstrated.
Layout Optimization of Wave Energy Park Based on Multi-Objective Optimization Algorithm
Authors: Guo Xinhai , Liu Yao , Zhang Xinshu
Published: August 2024

In this paper, we apply a semi-analytical method and numerical simulation to study the hydrodynamic behavior of large arrays of point-absorber wave energy converters (WECs) and the multi-objective optimization of the arrays layout using particle swam optimization (PSO) algorithm based on surrogate models. To investigate wave interactions among multiple WECs among an array, a semi-analytical model is developed based on the linear potential flow theory and the matched eigen-function expansions method. The fluid domain is divided into two kinds of regions, interior regions underneath the cylinders and an exterior region surrounding all the cylinders. The matched eigen-function expansions method is used to solve the radiation potential problem in each domain, and the hydrodynamic coefficients and motion response of the cylinders in the array are evaluated. To validate the accuracy of our semi-analytical method, the hydrodynamic software WAMIT is adopted to simulate the wave energy park numerically. Results obtained by the semi-analytical method are compared with the numerical simulation results. The hydrodynamic characteristics and power absorption performance of the WECs within the wave energy park are discussed. The power performance of a wave energy park is studied as functions of global geometry, incident wave direction and separating distance between WECs, respectively. Finally, a multi-objective optimization algorithm based on a surrogate model is used to optimize the layout of wave energy array. A surrogate model is established based on radial basis function (RBF) to improve the computing efficiency. With the power output and power smoothing of wave energy array as two optimization objectives, the safety of cylinders and the occupied sea area of wave energy park as constraint conditions, the multi-objective particle swarm optimization (MOPSO) was used to search for the Pareto-optimal solution, and the feasible optimization scheme of wave energy array was given.
Design Challenges of Riser and Lifting System for Ultradeep Sea
Authors: Hou Jing , Yu Chenteh Alan , Cheng Yongming , Zhang Cheng
Published: August 2024

Recent exploration has generated a resurgence of interest in ultradeep sea mining. Deepsea mining industry has revealed many potential fields in the water depth of 4,000 to 6,000 meters. Different from risers used in the oil and gas industry, deepsea mining risers will be towed to cover fields with areas many times of a football field. The bottom end of the riser needs to be freely moved both vertically and horizontally. This paper investigates design challenges of a riser and lift system used for ultradeep sea mining. As application moves to ultra deepsea, design challenges of a Riser and Lifting System (RALS) increase in terms of riser design, analysis, installation, and global performance.

This paper first introduces the state of the art of a typical Riser and Lifting System (RALS) used for ultradeep sea mining. The RALS design issues cover riser wall thickness, tension limits, and high payload. The installation concerns come from hook capacity limit, riser Vortex-Induced Vibration (VIV) when the riser is disconnected, and riser bottom drift caused by vessel motion during installation. This paper further investigates the coupling between the risers and floating platform, riser VIV, and riser dynamic performance. Examples are given to illustrate design challenges of the RALS in ultradeep sea mining. This paper finally summarizes the design challenges of RALS for ultradeep sea mining. In addition, this paper also explores likely solutions to the design challenges.
Forecasting Mooring Tension of Semi-Submersible Oil Production and Storage Platform Using a Novel Transformer Neural Network Model
Authors: Chen Yang , Yuan Lihao
Published: August 2024

This study presents the Transformer framework, which is a top performer in the field of natural language time-series prediction, and suggests an enhanced Transformer neural network model to address the application needs of semi-submersible production platforms for very short-term prediction of mooring tension during operation. Compared with the traditional recurrent neural network, the Transformer neural network has faster computation speed, better generalization ability and scalability, and stronger ability to capture long-range dependencies. In this paper, the proposed Transformer model is used for mooring tension prediction of semi-submersible production platforms, and the proposed neural network model is trained and validated using the actual monitoring data of the first ultra-deepwater semi-submersible production, storage, and offloading platform in the South China Sea during operation. The results show that the proposed method can achieve almost the same prediction results as the current mainstream LSTM model, which has the value of engineering application and promotion.
Maximum Cumulative Fatigue Damage Assessment of Bottom-Fixed Wind Turbine Structures in the Design Phase by AK-MDAmax Approach
Authors: Ren Chao , Xing Yihan
Published: August 2024

Wind energy has become crucial in the worldwide transition towards more sustainable alternatives. Ensuring the reliability of wind turbines is contingent upon the design process. The process of designing structures for wind turbines is iterative and necessitates the examination of design load situations in consideration of fatigue and ultimate limit states. Over the last decade, considerable work has been devoted to determining the ultimate limit states. Yet, efficient methods for estimating fatigue damage in wind turbine structural design are still lacking. Thousands of simulations are often required to estimate the cumulative fatigue damage, and each simulation can be time-consuming. In recent publications, the AK-MDAmax machine-learning methodology has been introduced to estimate the maximum cumulative fatigue damage to wind towers in floating wind turbines. For estimating fatigue damage, the initial works published revealed the excellent efficiency and precision of the AK-MDAmax method. Nevertheless, these initial studies only examined the local locations of the wind turbine tower base of a specific floating wind turbine at a specific location. The applicability of the AK-MDAmax method to bottom-fixed wind turbine systems and the influence of various offshore locations remains uncertain. To estimate the maximum cumulative fatigue damage to a bottom-fixed wind turbine, we implemented the AK-MDAmax method in this study. This article utilises an IEA 15MW wind turbine supported by monopiles at four distinct points inside the turbine structure. To consider the influence of offshore locations, this analysis also considers two distinct offshore metocean conditions. The findings indicate that the AK-MDAmax method can accurately predict the maximum cumulative fatigue damage to wind turbine structures by considering various components. With an error of less than 4 percent, the efficiency may be raised by about 55 times compared to the simulation references, highlighting the benefits of using the AK-MDAmax method for offshore wind turbine design.
Evaluation of Frequency Effects on Corrosion-Fatigue Behaviour of Offshore Steel Pipelines
Authors: Mehmanparast Ali
Published: August 2024

During the operational lifespan, offshore steel pipelines are subject to cyclic loading condition introducing fatigue damage into the material in conjunction with corrosion damage as a result of operation in the marine environment. An important issue that needs to be understood in asset integrity management of offshore pipelines is the cyclic loading frequency effects on corrosion-fatigue cracking behaviour of the material. In this study, a newly proposed approach for corrosion-fatigue analysis of offshore steel structures has been employed to examine its suitability for evaluation of the cracking behaviour in offshore steel pipelines. For this purpose, the experimental corrosion-fatigue data on API 5L X56 steel at different frequencies were collated from the literature and re-analysed using a newly proposed time-dependent fracture mechanics parameter. Moreover, a predictive model was developed to estimate the corrosion-fatigue cracking trends at various frequencies using the high frequency test data in air. The results from this study show that while the frequency effects on corrosion-fatigue cracking behaviour of steels cannot be described using the traditional data analysis method, the new time-dependent approach facilitates accurate characterisation of corrosion-fatigue data at a wide range of frequencies. Also, knowing that corrosion-fatigue testing at low frequencies is time-consuming and costly, it has been shown in this study that the long-term cracking behaviour of the material can be predicted using much faster tests at higher frequencies in air. This study showcases the potential of the newly proposed corrosion-fatigue life prediction approach using a time-dependent fracture mechanics parameter for structural integrity assessment of steel pipelines. Last but not least, the results from this study highlight the need for employment of innovative approaches for long-term structural integrity assessment of offshore steel structures and pipelines.
A Progressive Screening Approach for Mooring Configuration Selection: A Case Study of the Arven Offshore Wind Farm
Authors: Glasspool Jonathan , Tao Longbin , Venugopal Vengatesan , Pillai Ajit C.
Published: August 2024

The mooring system of a floating offshore wind turbine (FOWT) impacts both the capital and operational expenses. The future success of floating offshore wind is, therefore, dependent on finding optimum mooring system designs from the wide field of possibilities.

This paper introduces a methodology to identify appropriate mooring systems with the lowest cost using Arven Offshore Wind Farm as a case study. The methodology employs a systematic screening pipeline, utilizing short-duration time domain simulations in OrcaFlex to assess mooring line systems’ suitability based on DNV-ST-0437 and DNV-ST-0119 compliant load cases. Through progressively more detailed simulations, the pipeline efficiently narrows down the field of mooring configurations, assessing design parameters in one tenth of the time of a full enumeration.

This approach allows for the identification of a lowest-cost mooring system, highlighting the design trade-offs between cost and key design parameters. For the Arven case study, the methodology has identified a semi-taut three-line nylon system with 225 m anchor radius, 1200 kN pretension and a 192 mm line diameter as being the most efficient system. The outlined methodology provides a broadly applicable and efficient means to identify optimum mooring systems for diverse development sites worldwide.
A Toolbox for Towing Dynamics Predictions for Floating Offshore Wind Turbines: Validation and Parametric Study
Authors: Davis Samuel , Verma Amrit , Viselli Anthony , Allen Christopher
Published: August 2024

The floating offshore wind industry is growing rapidly, with increased capacity goals and expanding commercial project opportunities in the coming years. An important marine operation related to floating offshore wind is towing. The safety and cost of a tow operation are highly dependent on the choice of a suitable tug and tow speed, as well as the forces expected to act on the towing system. In the presence of waves, significant dynamic towline tensions can be experienced that may cause the towline to break. Therefore, predicting the tensions in the towline is important for efficient design and planning of the towing system.

The present paper describes a methodology for towing dynamics predictions and is implemented into MATLAB as a toolbox for planning future tow operations. The proposed methodology is able to (a) estimate the bollard pull requirements and static towing forces crucial for planning the tow operation; as well as (b) predict the mean and dynamic towline tensions in the presence of a given sea state. Two separate analyses are performed. In the first analysis, the towline tension predictions from the toolbox are validated against measured towline tension data from the University of Maine’s VolturnUS 1:8 deployment together with the results from a time domain model developed in OrcaFlex. In the second analysis, a parametric study is performed using the toolbox. The results of the study show the toolbox was able to closely predict the measured static and dynamic towline tensions. In addition, the effect of propeller race interactions with the towed floating offshore wind turbine was shown to significantly impact the predicted towline tension.
Application of a Geometric Common Model Modeling Method Based on Skeleton Model in Lashing Bridge Design
Authors: Xu Sihao , Li Hairui , Tang Xiaoyang , Wang Deyu
Published: August 2024

The lashing bridge is considered one of the core technologies in container ships. It is used to secure containers above the main deck and transfer the loads generated by container stacking to the ship’s structure. Its design is influenced by various factors. Therefore, it faces challenges in terms of design changes and collaborative design. In addition, lashing bridge design not only requires generating drawings and bill of material (BOM), but also involves activities such as finite element analysis and virtual prototyping validation, all of which have different geometric requirements. This paper proposes a product structure built upon the concept of geometric common modeling, leveraging skeleton models within the CATIA V6. The study underscores the pivotal role of skeleton models in organizing and linking all design information, facilitating efficient interaction between different models. Practical lashing bridge applications illustrate the effectiveness of this methodology. Moreover. the product structure based on skeleton models also embodies the philosophies of top-down and concurrent engineering. This method not only achieves geometric common modeling but also holds promise for broader applications, offering valuable insights for integrated design and serving as a beneficial reference for complex product design methodologies.
Influence of Bag Shapes on the Hydrodynamics of Subsea Filter Unit in Power Cable Protection
Authors: Tong Feifei , Griffiths Terry , Draper Scott , An Hongwei , Cheng Liang
Published: August 2024

Filter units (FUs), which resemble cylindrical mesh bags filled with rock aggregates, are commonly used for scour protection and secondary stabilization of subsea infrastructure, such as subsea power cables in offshore wind farms. A key consideration in the stability design of the FUs is the assessment of hydrodynamic drag, inertia, and lift forces acting on the FUs. These forces’ magnitude is expected to be influenced by the as-laid geometric configuration of the FUs. This study explores a range of bag configurations to gain insights into the hydrodynamics of FU bags, which include (i) a configuration derived from field observations, (ii) a configuration generated from a 3D scan of a model-scale FU used in laboratory testing, an idealized hemisphere configuration and (iv) an idealized configuration of an ice hockey puck. The study also examines various flow conditions, including steady flow and oscillatory flow induced by surface waves. To enable a meaningful comparison, the same volume of the FUs with different configurations was used in the analysis. The findings indicate that the hemispherical FU experiences the least drag forces and is much less likely to roll under steady flow conditions. These results contribute novel insights into the understanding of hydrodynamic forces acting on FUs. It is expected that this understanding will enhance the stability design of FUs for various metocean conditions, consequently reducing the risks of subsea power cable damage resulting from cable-FU interactions.
Mechanistic Study on the Stabilization of CO2 Oil-Based Foam by a Novel Compound Surfactant
Authors: Wang Zhoujie , Li Songyan , Li Shaopeng , Li Minghe
Published: August 2024

The effectiveness of CO2 oil-based foam in conventional and unconventional oil and gas development, as well as CO2 storage, relies on its stability. This study delves into the gas-liquid surface properties and liquid film behavior of a compound surfactant FS oil-based foam system, with a focus on understanding the mechanisms influencing its stability. The investigation reveals that the viscoelastic modulus of the FS surfactant system initially rises and then stabilizes with increased concentration, reaching a peak of 15.43 mN/m at 1.5 wt%. In the FS oil-based foaming system, the inhibition of sliding between liquid molecules enhances resistance to external deformation, promoting stability. Observing the liquid film of FS oil-based foam, color transitions signify evolving film thickness. The film initially displays various colors, gradually shifting from cyan and purple to deep blue and brown. As the film stratifies, forming dark domains that expand and eventually lead to rupture, FS significantly prolongs thinning time and reduces film thickness. At 2 wt% FS concentration, the foam rupture time is maximized at 4550 s. The presence of surfactant molecules forming a molecular layer in the liquid film strengthens and toughens the film, enhancing durability against external forces. This research suggests that the FS oil-based foam system with a 2 wt% concentration exhibits superior stability. Insights gained from this study contribute to the strategic use of oil-based foam, offering potential benefits for enhancing oilfield development efficiency and supporting carbon reduction goals.
Sensitivity Analysis of Different Welding Parameters on the Vibration Characteristics of Butt-Welded Plates
Authors: Chen Ziheng , Lin Yongshui , Feng Xiliang , Gan Jin , Wu Weiguo
Published: August 2024

To investigate the sensitivity of different welding parameters on the vibration characteristics, this study employs a typical butt-welded plate structure for experimental testing and numerical analysis. A sensitivity analysis method for various welding parameters on vibration characteristics is also introduced to investigate the impact of welding parameters on plate structures. Initially, the accuracy of the numerical calculation method is validated by comparing the X-ray diffraction (XRD) measurements and modal tests of flat-plate butt structures with the numerical simulation results. Subsequently, the thermal elastic-plastic finite element (TEP-FE) method is utilized to calculate the welding residual stress of plate structures under different welding parameters. Finally, the vibration calculation of plate structures with different welding parameters is carried out based on the finite element method (FEM), and sensitivity analysis is applied to identify the primary influence parameter on vibration characteristics among the various welding parameters. The results demonstrate a stable range for transverse and longitudinal residual stress changes when welding parameters vary. It is possible to optimize welding parameters within this range. The varied welding parameters significantly affect the natural frequency and vibration characteristics of the plate structure, leading to the discovery of remarkable phenomena. As the order of the natural frequency increases, so does the amount of variation, with a maximum change rate of up to 10%. Through sensitivity analysis, the natural frequency is more sensitive to changes in welding voltage, while the sensitivity to changes in welding current should be noticed. The amount of variation and sensitivity coefficients of the total vibration acceleration level and amplitude of vibration acceleration increase with increasing welding parameters and are more sensitive to changes in welding voltage. Through sensitivity analysis, it is feasible to refine the vibrational qualities of the butt-welded plate structure by adapting relevant welding and numerical simulation input parameters. Consequently, considering the influence of welding, this study is a valuable resource for optimizing structural vibrations.
Fluid-Structure Coupling Study of Ship-Ice Interaction Based on a Mixed-Parameter Cohesive Method
Authors: Gu Zhuhao , Lu Yu , Zhu Xianghang , Zhang Lizhi , Zhang Shuoyan
Published: August 2024

Ship-ice interaction is an important engineering issue in the polar region. Choosing the appropriate sea ice simulation method in the simulation of ship-ice collision will have a greater impact on the collision force of the ship hull. Sea ice is a complex solid. If you want to truly Simulating actual sea ice properties presents significant challenges. In order to more accurately simulate the interaction of ship ice in actual navigation, this study uses the nonlinear explicit finite element method for calculation, and establishes a sea ice calculation model based on the piecewise linear plastic constitutive model. The cohesion is used as a calculation method for sea ice fracture, the hull uses an elastic-plastic constitutive model, and the ALE method is finally used to solve the complex fluid-solid coupling problem of the ship, water, and ice phases. By comparing the simulations of cohesive models with the same parameters and hybrid parameters, the calculation results show that during the ship ice fluid-solid coupling calculation process, the hybrid cohesive simulates the circumferential and longitudinal crack forms of sea ice better, and the ice load is consistent with The hull stress is closer to the empirical formula. This study provides a useful reference for improving ice operations and offshore structure design in Arctic shipping, and has great research significance for improving ship performance and safety.
Static Obstacle Avoidance With Path Following of ASVs by Using Twin Delayed Deep Deterministic Policy Gradients
Authors: Thirumurugan Vishnu , Rajendran Suresh , Somayajula Abhilash Sharma
Published: August 2024

In the field of autonomous surface vehicle (ASV) navigation, ensuring safety is paramount, necessitating an advanced collision avoidance system. This study focuses on the Twin Delayed Deep Deterministic Policy Gradients (TD3) algorithm, which operates in a continuous action space. We introduce an innovative epsilon-greedy exploration strategy for TD3, improving its performance by mitigating per-update errors and effectively balancing exploration and exploitation phases. The reward function is meticulously designed to reduce both cross-track and heading errors, exemplified using the L3 model of the KVLCC2 tanker, with an emphasis on minimizing rudder deflections. Error assessments are based on the Line of Sight (LOS) algorithm. The primary goal of this research is to enhance ASV navigation’s safety and efficiency by integrating collision avoidance of static obstacle with path-following capabilities through deep reinforcement learning. The developed model adeptly avoids collisions, continuously refining its policy to adapt to diverse conditions of static obstacles while prioritizing safety and optimal navigation. The study’s success lies in effectively developing, training, and testing a neural network architecture tailored for evading static obstacles, showcasing significant advancements in ASV navigational technologies.
Development Review of Open Water Economical Floating Photovoltaic Platform
Authors: Fu Qiang , Wang Wenping , Li Dejiang , Li Shumin , Chen Kuiying , Zheng Long , Wang Chuanwen , Chen Peng
Published: August 2024

Building up safe, reliable, green photovoltaic (PV) power generation plant has become one key national development direction among China new energy industry. Nowadays, the available land for deploying PV is getting shorter, plus, national restrictions on deploying PV in lakes, reservoirs and other freshwater areas are also announced to ensure further environmental protection. Therefore, deploying floating PV platform on the seashore open water is emerging as national level urgent needs.

A four body interconnected platforms (400kW) has been installed at 4km away from coastline of Yantai, China for concept proof and data collection purpose. One bamboo-based composite material floating platform is also installed nearby for material testing. Together with a bottom seating steel platform carrying various kind of testing equipment, the first Offshore PV Demonstration Base dedicated for PV testing under sea environment has been established by CIMC Raffles in China.

This paper is a project development review for our semi-submersible type floating platforms. It states our novel weight optimization concepts in various aspects. Special highlight is a fully coupled time-domain hydro-structure-mooring multi-body analysis workflow, including composite material modelling, has been used to give an accurate global strength analysis. In addition, bamboo-based composite material platform, a totally lightweight and low-carbon platform is briefly introduced.

Our illustrated experience covers design, fabrication, installation, and operation with field monitoring. This project review gives readers a project reference for assessment to any seashore floating PV platform. Our continuous research for developing a lightweight and low-carbon floating platform shall be one recommended option for future.
Dynamic Responses of the Tower and Blades on a Spar-Type Floating Wind Turbine Under Freak Waves
Authors: Li Yan , Li Haoran , Cui Yiwen , Su Ouming , Li Guoyan , Tang Yougang
Published: August 2024

A floating offshore wind turbine would be subjected to various abnormal waves. Among them, the freak waves which have high energy may suddenly enlarge the stress and deformation of the upper flexible structures such as the tower and blades. The numerical model of a Spar-type floating wind turbine is established, the freak waves are numerically generated and modulated. Fluctuated freak waves and elevated freak waves are obtained based on the phase angle modulation method. The dynamic performances of the wind turbine under the freak waves are simulated in the time domain, and the internal loads of the tower and blades are analyzed. The results of the tower load responses under the different freak waves show that fluctuated freak waves have a significant effect on the shear force and torque. When fluctuation rises by 15.0 %, shear force increases by 15.0 %, and torque by 9.3 %. Elevated freak waves have slight effects on the torque. The fluctuated freak waves have an obvious effect on the blades. When fluctuation increases by 15%, shear force increases by 8.72 %, and torque by 4.09 %. The torque moment of the blade root is not significantly affected by the change of different freak waves (less than 5%).
Development of Low Energy Consumption Motion Stabilized Platform for Offshore Wind Observations Floating Platform
Authors: Yamamoto Yusuke , Taniguchi Tomoki , Katayama Toru
Published: August 2024

It is necessary to obtain accurately actual wind state at the sea where offshore wind farm will be constructed, in order to guarantee its safety and profitability. In this study, it is proposed that motion of the non-restoring counter-weight type motion stabilized platform on a buoy is made smaller than that of the buoy by using a linear damper to get regenerative energy and skyhook spring and damper controlled by using the regenerative energy. Then, the energy consumption and motion reduction performance of the system is evaluated, and it is tried by system optimization that the energy balance becomes positive.
Application of Hierarchical Analyst Domino Evaluation System (HADES) in Floating Offshore Wind Farm (FOWF) Operation Stage
Authors: Li Yihong , Hu Zhen-Zhong , Li Binbin
Published: August 2024

In light of the escalating greenhouse effect and the increasing frequency of extreme weather events, the global spotlight has shifted towards the development of green energy solutions. Notably, Floating Offshore Wind Turbines (FOWTs) have gained prominence as a high-tech innovation in harnessing wind resources in deep-sea field. However, an expanded perspective that encompasses entire wind farms necessitates a more comprehensive approach to risk assessment and safety management.

This paper introduces the application of the Hierarchical Analyst Domino Evaluation System (HADES), originally designed for offshore oil and gas facilities decommissioning, to assess the domino risk of the Floating Offshore Wind Farm (FOWF) situated near the Wanning Sea area, Hainan, China. The assessment includes scenarios involving navigating vessels collisions, typhoons, storm surges, and large waves, which can lead to accidents such as capsizing, deviation, and structural damage. HADES offers a Quantitative Risk Assessment (QRA) framework that hierarchically models the development of domino accidents, providing a clear visualization of the accident progression. Unlike other domino risk assessment methods, HADES incorporates Frequentist Approach to reconstruct the trigger mechanisms and propagation logic of these accidents. HADES simplifies calculations and reduces the reliance on extensive historical data. Through the analysis of accident scenarios, probabilities, and consequences, this study aims to address the concerns of FOWF operators regarding the layout, operation, and monitoring of FOWTs. The results of the analysis indicate that due to the lower integration and density of equipment in FOWFs, domino incidents are unlikely to occur and propagate. The majority of domino events are caused by external structural failures of the FOWTs themselves and collisions with vessels within the wind farm area. The focus of research on domino accident assessment for FOWFs should be placed on the reliability of FOWT components such as blades, towers, floating foundations, and anchor chains, as well as on strategies to avoid collisions with vessels. This study enhancing our understanding and preparedness for potential accidents in this dynamic and critical sector.
Evaluation of a Multi-Turbine Floating Platform Concept Considering Wake Effect
Authors: Li Shen , Brennan Feargal
Published: August 2024

Floating offshore wind currently implements a one-turbine-one-platform strategy. A nominal offshore wind farm with 1GW capacity will require more than 60 floating platforms, 200 mooring lines and complex distributed power take-off infrastructure, leading to costly inspection and maintenance. Hence, upscaling the one-turbine-one-platform strategy to GW-scale floating offshore wind array represents a major challenge. A multi-turbine shared platform approach has the potential to reduce this complexity and cost. However, to space the turbines effectively and prevent turbine interference on power production due to wake effect, these structures need to be of unconventional size, i.e., Very Large Floating Structures (VLFS). The unprecedented size of VLFS imposes techno-economic challenges such as demanding structural integrity requirement and significant increase of material cost. In view of this, this paper evaluates the trade-off between the mitigation of wake effect and the cost-effectiveness of platform’s structural design. Constrained by structural integrity considerations, a multi-objective optimisation is completed in which the Pareto front of maximum power output and minimum total cost is evaluated. A Jensen’s single wake model is employed to assess the impact of turbine interference. Comparison with a previously developed reference design with 600 metres’ total length indicates the potential to extend the length by 200 metres, enhancing the power output without compromising cost-effectiveness.
Identification Modeling of Ship Maneuvering Motion Based on Echo State Gaussian Process
Authors: Liu Si-Yu , Zou Zao-Jian , Zou Lu
Published: August 2024

The mathematical model of ship maneuvering motion is a crucial foundation for both prediction of ship navigation state and automatic control of ship motion. This paper proposes a practical and robust nonparametric identification method based on echo state Gaussian process (ESGP) to establish the nonparametric model of ship maneuvering motion. The traditional echo state networks (ESNs) and basic Gaussian processes (GPs) have found successfully applications in nonparametric modeling and time-series forecasting. The proposed method combines the strengths of both ESN and GP approaches. On the one hand, it offers a more robust alternative to conventional reservoir computing networks; on the other hand, it can directly generate confidence intervals for prediction results. The KVLCC2 ship model is taken as the object of this research. The datasets collected from several standard and nonstandard zigzag maneuvers of free-running model, which are provided by SIMMAN 2008, are used as training and testing data. To assess the robustness and generalization ability of the established nonparametric model, the prediction results of the ESGP method are compared with the experimental data. It is shown that the ESGP method proposed in this paper can achieve high prediction accuracy and provide a measure of credibility for the output results, which makes it more practical and applicable for modeling and prediction of ship maneuvering motion.
An Experimental Investigation on Vortex-Induced Vibration of Double Risers in Tandem Under Bidirectionally Sheared Flow
Authors: Bai Yingli , Zhang Mengmeng , Fu Shixiao , Chu Yaopeng , Fu Xuepeng , Ren Haojie , Xu Yuwang
Published: August 2024

The interfering characteristics of vortex-induced vibration (VIV) responses for tandem double risers under the recently discovered bidirectionally sheared flow are unclear. To reveal the interfering VIV characteristics in bidirectionally sheared flow, a rotating test rig was built to simulate bidirectionally sheared flow in the ocean basin. A series of VIV experiments for two scaled riser models were carried out, which included a single riser and tandem double risers with two different center-to-center spacing (3D and 5D). Then the modal superposition method was used to reconstruct the VIV displacements in cross-flow (CF) direction and the drag displacement. Furthermore, the drag coefficient was identified and analyzed. Results indicate that the VIV frequency of tandem double risers remains consistent at same spacing. When the reduced velocity (Vr) is in range of 5.0 to 18.0, the VIV amplitude of tandem double risers is basically same, but slightly smaller than that of the single riser. However, the VIV amplitude of riser 2 is significantly higher than that of riser 1 at Vr > 18.0. Moreover, it is found that the overall average drag coefficient in tandem double risers is lower than 1.38 of single riser, with values of 1.25 (S = 3D) and 1.33 (S = 5D) respectively.