bluuebunny/crossref_metadata_2025 huggingface dataset:
Interdependency of Human Factors and Turbine State in Offshore Wind Farm Operations
Authors: Golestani Nima , Arzaghi Ehsan , Garaniya Vikram , Abbassi Rouzbeh
Published: September 2023

The effectiveness of operation and maintenance (O&M) activities significantly impacts the availability of offshore wind farms (OWFs) and the total cost of energy production. When a turbine is stopped to rectify a failure of any critical equipment or to perform preventive maintenance, there is a substantial cost for repair or replacement. Simultaneously, there is a production loss associated. Humans play a critical role in every stage of the O&M in the offshore wind industry. Human errors may jeopardize maintenance effectiveness, increase a system’s failure rate, or cause faster degradation, which may have substantial costs to the entire operation and cause pressure on the production to compensate for the downtime. This production pressure and repair cost pressure directly impact human performance, for instance, by shortening the time available to complete required maintenance activities. The cost pressure may also affect the industry’s operational budget, leading to hiring less trained and inexperienced maintenance crews or postponing training. These effects may lead to failure in different maintenance phases, including fault diagnosis and mistakes during repair tasks, further increasing human error probability (HEP). This paper proposes a causal loop diagram for the maintenance system of the offshore wind turbine, accounting for the interdependencies amongst human error likelihood, equipment health state, and associated uncertainties. By implementing various maintenance planning approaches, the dynamics of the system are modelled with more accuracy to identify the factor affecting the maintenance strategy and minimize human errors in the O&M of OWFs.
Algorithm to Develop Wave Scatter Table From Hindcast Data
Authors: Mangalathu Raj Samuel , Enshaei Hossein , Abdussamie Nagi
Published: September 2023

Any offshore structure requires engineering feasibility and fatigue study during the design and/or maintenance process. The studies mentioned above require an understanding of wave loading on the structure. Most wave loading studies consider wave scatter diagrams. However, the probability of wave occurrence depicted on wave scatter diagram change over region, season and period. Hence, the study based on any static wave diagram doesn’t reflect the probability of wave occurrence for a required region. Further, these waves scatter diagrams are not readily available for the specific local region of interest. Hence, in this study, an algorithm is developed to make a wave scatter diagram using hindcast Australian Meteorological data for a local region for a particular season or period of time. The data has 0.4 × 0.4 degrees spatial and one-hour temporal resolution and contain mean, wind and swell sea state; hence enables to make wave scatter diagram for mean, wind and swell sea for any offshore application. The advantage of the proposed hindcast wave scatter diagram includes flexibility and ease of customising wave scatter for any region, season or period of time compared to available sea area-specific wave scatter diagram. Also, the hindcast model is very well tested and updated regularly and hence wave scatter diagram is developed based on recently validated data. Since these data are free, making a more reliable and accurate wave scatter diagram is free. Additionally, in this study, the graphical comparison of the hindcast wave diagram with two additional sources for the North Atlantic wave and Australian water is provided for validation. The graphical comparison shows the differences and similarities of the wave scatter diagrams over different regions, seasons and periods.
Data Driven Identification of Ship Maneuvering Coefficients
Authors: Deogaonkar Vallabh Vinod , Jadhav Aditya Kailas , Ramachandran Krishnavelu , Somayajula Abhilash Sharma
Published: September 2023

Maneuvering models of a ship are quite complex and require accurate knowledge of the various hydrodynamic derivatives and coefficients to model the maneuvering trajectories undertaken by a ship accurately. Discerning these coefficients through practical tests in specialized facilities is expensive and time-consuming. Data-driven identification of the ship maneuvering coefficients using free-running model data is a possible alternative. In this study, the maneuvering motions of the KCS hull are simulated using the MMG model, which are then used as a starting point to identify an Abkowitz model for the vessel. The coefficients of the Abkowitz model are predicted without presuming any knowledge of the MMG model used to generate the data. Three different approaches — Least squares, LASSO optimization, and Support Vector Machines — are used to identify the hydrodynamic coefficients of the Abkowitz model. The identified coefficients are used to generate test trajectories not seen in training data and are compared with the MMG model to verify that the dynamics are accurately captured. The common issue of parameter drift occurring due to the problem being ill-posed is discussed, and sparsity-based solutions are suggested to overcome them.
Numerical Simulation of Marine and Coastal Zone Multidimensional System Sustainable Development
Authors: Deng Yue , Li Yaning , Li Jiarui , Sun Yanli , Cao Yingzhi , Zhao Jingli
Published: September 2023

The long-term strategy of Blue Economy aims to release the potential of marine resources through the sustainable development of the production system of marine products and renewable marine resources. As one of the most dynamic areas for the development of blue economy, the coastal zone is also a zone with strong interaction between land and sea. It is a complex nonlinear system with the most intensive space development and utilization, the most prominent pressure on resources and environment, and the most concentrated contradictions. This study uses the system dynamics method to establish the marine model and the coastal model, calculates and analyzes the sustainable development of the ocean and coastal zone system through the coupling of the land and the ocean model, focuses on the development of marine renewable energy, aquaculture, fisheries, marine pollution, marine engineering and other industries, as well as the development and utilization of marine resources, and studies the interaction between various factors. Better promote the development of marine blue economy through system coupling and coordinated development.
Fatigue Strength of 3” Subsea Pressure Containing Bolts in Air and Seawater Environment
Authors: Horn Agnes Marie , Fjeldstad Arne , Wernø Tore Geir , Muff Anthony D.
Published: September 2023

Three inch bolts have been fatigue tested to quantify the fatigue strength in air environment and seawater with cathodic protection. The motivation behind the laboratory test project was to justify the use of cathodic protection against corrosion for bolts used in subsea systems. In fatigue design standards such as DNV-RP-C203, the use of cathodic protection is not recommended for bolts because high strength steel is prone to hydrogen embrittlement when subjected to high loads. However, based on published fatigue test data of bolts the last 2–3 years the revised DNV-RP-C203 that is currently undergoing industry hearing has proposed the following update: “The recommended practice is valid for bolts in air environment for grades up to 10.9, ASTM A490 or equivalent. In seawater with cathodic protection the recommended practice is valid for grades up to 8.8 or equivalent.

Present industry subsea practice is to use preloaded bolts exposed to cathodic protection. The objective of this paper it to assess the fatigue strength of bolts with cut threads in seawater with cathodic protection. It will further be considered whether standard design principles can be assumed, more specifically if the difference in fatigue life between air and seawater environment can be assumed equal to a factor of 2.5. The long-term aim is to gather sufficient relevant laboratory test data such that a revision of the design recommendations for bolt operating in marine environment can be justified. This is considered important as the industry seem to prefer cathodic protection as primary means of protecting bolts against corrosion.
Experimental and Numerical Analysis on the Hydrodynamic Force of an Ice Piece in Synthetic Brash Ices With Defined Distance
Authors: Hayashi Ryota , Konno Akihisa , Zhou Jinxin , Li Qiao , Dong Shuchuang , Kitazawa Daisuke
Published: September 2023

The necessity of the Arctic route has promoted the development of polar ships, whose power requirements must be evaluated due to brash ices covering that region. The ice resistance is required in one approach of ship power estimations. However, the hydrodynamic force calculation in brash ices has not been fully generalized. In this study, the horizontal hydrodynamic force of an ice piece in synthetic brash ices was examined experimentally and numerically. The towing experiment was conducted at the water tank of the Marine Ecosystem Engineering Laboratory, Institute of Industrial Science, the University of Tokyo. Using identical specifications to the experiments, numerical calculations were conducted using the volume of fluid method, which is embedded in the Simcenter STAR-CCM+ platform. The force of one ice piece moving downstream of another increased linearly, while only the trend had been numerically reproduced. The present brash ices were arranged in a staggered manner, and the relationship between the force of the measured ice and the rows of ice pieces in its front was examined. In the experiments but not in the calculations, the force on the measured ice increased almost linearly. Further investigation is necessary to improve the numerical simulation and estimate the power of polar ships.
Nonlinear and Extreme Wave Group Interactions With a Circular Cylinder
Authors: He Yuchen , Kanehira Taiga , Mori Nobuhito , Gamaleldin Muhannad , Babanin Alexander , Chauhan Kapil , Chabchoub Amin
Published: September 2023

The evaluation of extreme wave kinematics is decisive to determine design standards for marine structures. Offshore rogue waves in high wind areas can emerge as a consequence of unstable wave group focusing. Large-amplitude waves in such wave groups have different kinematic properties compared to those resulting from the superposition principle. This experimental study has been carried out to evaluate the wave load forces of highest amplitudes within unstable wave groups acting on a submerged, vertical, and circular cylinder. Different wave steepness parameters have been systematically adopted. It is shown that for moderate steepness values the wave loads show the presence of three harmonic components. Higher wave steepness parameters are responsible for the change of the cylinder’s response in the form of a transient ringing. In fact, even though higher harmonics of the underlying regular wave trains do not resonate with the lowest resonant frequency of the cylinder, the severe broadening of the wave spectra in all bound wave components, resulting from the wave focusing within the unstable wave packet, triggers a ringing frequency excitation.
Numerical Study of Underwater Implosion of Spherical Pressure Hull on Deep-Sea Submersibles
Authors: Zheng Jiancai , He Yupei , Zhao Min
Published: September 2023

The failure of the pressure hull is the key subsystem of underwater vehicles, and seriously threatens the vitality of the whole underwater vehicle. Moreover, the shock waves from underwater implosions of failure pressure hull will cause deformation and even collapse to the adjacent structures, which is detrimental to the vehicles such as underwater robots and manned deep submersible vehicles working in the deep sea environment. In this work, the open-source solver OpenRadioss is adopted to conduct the numerical analysis of the spherical pressure hull within the shock waves of the underwater implosion and structure deformation and failure. The compressible multiphase flow is simulated by the arbitrary Lagrange-Euler method with multi-physical materials and the structures are described by constitutive models of brittleness and metal ductility, respectively. Firstly, the underwater implosion of a thin-glass sphere is simulated. The pressure of shock waves is compared with the experiment to verify the accuracy of the numerical method. Secondly, the dynamic response of the spherical hollow ceramic pressure hulls with internal perfect gas is investigated accordingly to reveal the fluid-structure coupling effects of underwater implosion induced by the failure of brittle materials, where the structure no longer bears any pressure after failure. Finally, the underwater implosion under the same environment pressure is simulated based on the Johnson-Cook plasticity and failure model. The implosion characteristics in the failure process of metal pressure hulls are summarized by analyzing the coupling pressure, structural deformation and damage, and energy evolution, respectively. Moreover, the differences between the hollow brittle ceramic sphere and ductile titanium alloy sphere in the process of underwater implosion are discussed. The influence of fluid-structure interaction and the mechanism without different materials are analyzed for the spherical pressure hull, which provides a basis for the design and material selection of the pressure support structure of the underwater vehicle.
A Model for Friction Stresses in Cable Core
Authors: Skeie Geir , Sødahl Nils , Pettersen Sune , Verde Lars Helge
Published: September 2023

Accurate evaluation of friction stress is important for reliable fatigue life calculations of High Voltage Alternating Current cables used in off-shore wind installation. The cable cross section lay-up place the power-phase in the center of the cross section resulting in circumferential contact between the components. The stick-slip evolution for components in circumferential contact is different than for components in radial layer contact. A model for both onset and progression of slip for a three-core power phase design is explored. The slip progression involves equilibrium considerations of all three components. The slip zones of the individual components evolve in the longitudinal direction until they coalesce. The knowledge of global behaviour of slip onset and progression allows evaluation of bending and friction stresses on one individual component. This is similar to the bending and slip of a helix component resting on a cylinder layer. The assumptions used to verify the stick-slip progression are verified by numerical simulations.
The Effect of Steady Currents in Weather Downtime Assessment
Authors: Schira Bepo , Shoukat Gohar , Thusyanthan Indrasenan
Published: September 2023

Weather downtime is a major factor in any offshore operation as it affects both the project program and budget. Therefore, knowledge of potential weather downtime for a given site is valuable to de-risk the project by improved planning and estimates of the financial performance.

Severe sea states limit the allowable operational time offshore, thus extending the time required to complete the project. The metocean parameters used to estimate the weather impact on offshore operations are usually wind speed, significant wave height and wave period. However, steady currents may significantly impact the project, even during workable sea state conditions. This can especially be the case in offshore windfarms construction as they are often located in shallow water areas with high currents making it crucial to understand their effects on the weather downtime.

In this paper we discuss how the effect of the currents may be more realistically accounted for in weather downtime estimations by considering the “waiting on current periods”, or the time the construction vessel will have to cease the operations due to periods of peak currents within an otherwise workable weather window. To understand this effect, we have developed a tool known as “GDG-WDAT” which is capable of interacting with the ERA5 database, enabling effective operational planning and cost savings in offshore operations.
On the Development of Aft Body Hull Form for Ship-Type Offshore Structures
Authors: Kim Joo-Sung , Song Gi Su , Son Hye-Jong , Kim Bo Hee , Park Jung Ki , Kim Hyun Joe
Published: September 2023

This paper describes in detail the hydrodynamic issues examined in the development of aft body hull form equipped with three azimuth thrusters. Hydrodynamic performance considered include roll damping, transit performance, thruster interference with hull and with other thrusters, and stern slamming. Constructability issues which may be encountered during a fabrication stage are discussed. Two issues are examined; bilge keel and headbox.

The transit performance is assessed using model testing and CFD simulation. The conventional barge-type hull without headbox leads to much lower resistance. However, when large headboxes are added, the transit performance for the two hulls is almost similar to each other. The thruster-hull and thruster-thruster interactions are examined using CFD simulation. The results clearly show that the flat bottom hull leads to lower thruster-hull interaction and provides greater flexibility of thruster arrangement.
Squeeze Cementing, a Mathematical Model and Parametric Investigation
Authors: Izadi Mahdi , Frigaard Ian A. , Taghavi Seyed Mohammad
Published: September 2023

This paper discusses the capabilities of a developed numerical framework for modeling squeeze cementing, in terms of a constant pressure displacement of a Newtonian preflush by a viscoplastic suspension, representing cement slurry. The approach is a continuum model, based on the Suspension Balance Model, which takes particle migration into account and considers the effects of particles on the jamming and the shear-dependent rheology of the suspending fluid, which allows exploration of different stoppage mechanisms. The model considers the transition from suspension flow into a packed bed formation and the possibility of interstitial flow, leading to interesting dispersion effects. This paper investigates slurry penetration in a long conduit with different conditions, quantifies the solid concentration, the penetration length and time, and the stoppage mechanisms in various scenarios over relevant parameter ranges. We show that the transversal distribution of particles in yield stress fluids can be non-monotone adjacent to unyielded regions and predict depleted layers close to the wall.
Cognitive Models for Human Reliability Analysis Applications to the Oil & Gas Industry
Authors: Alvarenga Marco Antonio Bayout , Frutuoso e Melo Paulo Fernando , Maturana Marcos C. , Martins Marcelo Ramos
Published: September 2023

In the quantitative risk analysis (QRA) of O & G equipment, it is necessary to consider the application of cognitive models (in use in the nuclear industry), which can very effectively predict human performance. First generation Human Reliability Analysis (HRA) methods are used in O&G primarily in an emergency scenario QRA and second-generation methods for design and normal operation. These methods can be inefficient. First generation HRA models do not have a cognitive architecture capable of processing human information. Second-generation models consider mechanisms of cognitive errors. Most of third generation HRA models are dynamic simulations of cognitive tasks, coupled with an event/accident simulation code, often designed more for human-machine interface assessment than for human error analysis. There are also cognitive psychology models designed to assess human performance without the intention of serving as HRA tools. These models have a detailed understanding of the cognitive mechanisms of human error, which is the key to a complete HRA model. One of these models, ACT-R, contains adequate quantification to serve as an HRA model. This article discusses cognitive psychology models and their internal structures in human information processing to provide human error probabilities that arise from the architecture itself and are not dependent on Performance Shaping Factors (PSFs), which are quantified by HRA current methodologies.
Wave Attenuation by Submerged Oscillating Plates
Authors: Chen Yongbo , Hayatdavoodi Masoud , Zhao Binbin , Ertekin R. Cengiz
Published: September 2023

Submerged oscillating plates are used as heaving plates to reduce the motion of floating objects, in wave energy devices to extract the wave energy, and as breakwaters to attenuate the wave field in shallow water. In this study, we consider a horizontal, submerged plate in shallow water that is allowed to oscillate in the vertical direction due to the wave loads. The plate is attached to a linear spring and damper to control the oscillations. The focus of this study is on the transformation of the wave field by the submerged oscillating plate. To estimate the energy attenuation, wave reflection and transmission coefficients are determined from four wave gauges; two placed upwave and two placed downwave of the oscillating plate. The fluid is governed by the nonlinear Level I Green-Naghdi (GN) equations, coupled with the equations of vertical motion of the plate to determine its oscillations. Time series of water surface elevation recorded at gauges upwave and downwave of the plate, and the wave-induced plate oscillations, obtained by the GN model are compared with available laboratory experiments and other data, and very good agreement is observed. Wave reflection and transmission coefficients are then determined for a range of involved parameters, including wave condition (wave height and wave period), initial submergence depth of the plate, plate length, and the spring-damper system. It is found that a single submerged oscillating plate can have remarkable effect on the wave field, and that nonlinearity plays an important role in this wave-structure interaction problem. Discussion is provided on how the wave reflection and transmission vary with the wave condition, plate characteristic, initial submergence depth and spring-damper system.
DEA Model Applied to Risk Based Inspection for Offshore Flexible Pipelines With Virtual Relative Risk Frontier From Event Trees
Authors: Jaques Honorato Henrique , Antoun Netto Theodoro , Lourenço De Souza Marcelo Igor , Ferraz Netto Carolina
Published: September 2023

The identification of the main nonconformities (NCIs) that occur in offshore flexible pipelines, as well as the recognition of failure mechanisms through event trees, are fundamental points for the generation of the risk-based inspection methodology (RBI-Flex) of these Structures. To ensure the operational safety of subsea flexible pipelines, it is essential to identify the main failure modes that can lead to the total loss of structural integrity due to leakage. In the methodology proposed here, the Submarine Risers System will be subdivided into inspection regions, to better calculate the relative risk of failure to the DEA (Data Envelopment Analysis). The organization of failure mechanisms through event trees allows the visualization of the chronological occurrence of nonconformities in the stages until the final failure mode is reached, which will be the top event. This article aims to propose a two-dimensional and multidimensional DEA model for assessing the relative risk of loss of structural integrity in a scenario whose risk boundary is calibrated by virtual pipelines. In this sense, it is possible to model the temporal evolution of nonconformities at each inspection instant. The DEA RBI Flex model generates a decision-making tool for inspection teams through risk rankings.
A Preliminary Study of Learning a Wave Energy Converter System Using Physics-Informed Neural Network Method
Authors: Chen Bo-Chen , Yu Yi-Hsiang
Published: September 2023

Physics-informed neural network (PINN) is a new type of neural network method that can be used to solve the physical problem by providing a given data set in the machine learning process with embedded physics information directly described by differential equations. A PINN model was applied in this study to solve the governing equation of motion for the analysis of a floating sphere wave energy converter (WEC), and a time-series segmentation approach was implemented to effectively handle the time-dependent problem. A series of PINN simulations are presented in this paper, including a decay test and a set of wave conditions, where the PINN solutions are verified against those obtained from other time-domain numerical models. This work aims to investigate the feasibility of using PINN for WEC applications with a focus on numerical benchmarking, and the studies of collection point resolution, the overall model accuracy, and the corresponding computational efficiency are also investigated.
Flow-Induced Vibration Analysis Using a Low-Cost Inertial Measurement Unit
Authors: Peres Leal Aline , Luís Condino Fujarra André , Matos Carnier Rodrigo , Trentin Gonçalves Rodolfo , Suzuki Hideyuki
Published: September 2023

Flow-induced movements have been investigated for more than 20 years, especially in offshore platforms, where Vortex-Induced Movements (VIM) impact platform productivity, mooring lines, and risers fatigue life. However, monitoring these systems with standard methods (i.e. robots) is very expensive. In this work, a low-cost alternative is developed: we carried out experiments in the towing tank at The University of Tokyo (UTokyo), measuring the movements of a spar-type platform model with a low-cost Inertial Measurement Unit (IMU). The IMU application is beyond the computation of orientation: by measuring movements, displacement amplitudes and frequencies, we analyzed Flow-Induced Vibrations (FIV) in the spar model. The model was free to move in six degrees of freedom (6DOF), while its acceleration, rotation rate and magnetic field were recorded using the commercial IMU GY-87. A robust signal treatment methodology is developed based on the Kalman filter, Fast Fourier Transform (FFT) filter, Intrinsic Mode Function (IMF) decomposition, and coordinate manipulation using quaternion rotations, to remove drift and noise problems, and extract the model displacement in the three axes. The IMU application is evaluated by comparing its results with a high-accuracy optical tracking system, showing the potential of low-cost sensors for FIV analysis. Maximum amplitudes were found for cross-flow displacement at the reduced velocity VR = 10.13, with a significant amplitude of 0.7D for the IMU and 1D for the optical system.
Study of Crack Initiation and Fracture in OC4 Jacket Structure Under Cyclic Loading by Peridynamic Approach
Authors: Bachimanchi Pranitha , Saha Nilanjan
Published: September 2023

The offshore structures are frequently subjected to the cyclic loads generated by environmental conditions leading to structural damage. The analysis of such damage that manifest as cracks become non-trivial due to mathematical abstraction of their classical governing equations in the presence of structural discontinuities. In this study, we employ peridynamic theory [1] that modifies the classical mathematical model by replacing spatial derivatives with integrals through non-local bond interactions between material points. This approach helps us model the breakage of bonds pertaining to structural cracks. In the peridynamic fatigue model [2], the breakage of bonds is evaluated through the remaining life parameter that accounts for the cumulative damage at every load cycle caused by in-plane cyclic deformation in a 2D plate. In this work, we model OC4 jackets with peridynamic beam formulation [3], where the fatigue model considers the bond’s cyclic in-plane, shear, bending, and torsional deformation. We successfully identify the critical locations for crack initiation in the jacket under constant amplitude cyclic point loading. We further evaluate the number of load cycles required for crack initiation and fracture under different maximum load magnitudes of cyclic loading.
Seakeeping Behavior of a Helicopter Landing in Waves
Authors: Tadashi Katsuno Eduardo , Peters Andreas , El Moctar Ould
Published: September 2023

This work analyzed the behavior of a helicopter that needed to land in water and compared the results from two methods, Boundary Element Method (BEM) and Computational Fluid Dynamics (CFD), in terms of their predictions of the helicopter’s response to waves. The study concluded that while BEM can provide quick results for estimating loads on the floaters in not-so-rough wave conditions, it cannot predict capsizing and should be used with caution. On the other hand, CFD can provide accurate results, but it has a higher computational cost. The results of the study showed that BEM and CFD produce similar results in terms of the natural period of roll and pitch, and that the time-domain simulation of 600 seconds using BEM can be used to estimate cabin acceleration. However, CFD simulations are necessary to check for capsize or water inside the cabin in future works.
Experimental Hydrodynamic Investigation of a Co-Located Wind Turbine and Wave Energy Converter
Authors: Gubesch Eric , Nader Jean-Roch , Ding Boyin , Cazzolato Ben , Li Ye , Sergiienko Nataliia , Penesis Irene
Published: September 2023

As part of the Australia-China Joint Research Centre of Offshore Wind and Wave Energy Harnessing project, a new extensive experimental investigation was performed to study the hydrodynamic interactions between a fixed offshore wind turbine and a heaving wave energy converter (WEC). This paper presents the experimental setup and preliminary results for the investigation. The experimental objectives were to evaluate the use of a WEC to reduce the surge forces and overturning moments on the wind turbine foundation under operational and extreme conditions. The experimental investigation was conducted in the Model Test Basin at the Australian Maritime College. The WEC’s motions were restricted to heave and were controlled with a LinMot linear motor. The experimental wavefield consisted of regular, irregular, and focused wave groups, which covered a wide range of conditions from small amplitude linear waves to highly nonlinear and breaking waves. Preliminary analysis included: 1) radiation tests for the WEC; 2) independent diffraction tests for the WEC and wind turbine; 3) combined diffraction tests for the co-located WEC and wind turbine; and 4) the effects of the WEC’s heaving motions on the wind turbines surge forces and pitch moments. The resulting dataset provides a solid scientific foundation for investigating the hydrodynamic interactions for co-located arrays of wind turbines and WECs. The obtained data is highly suitable for validating a range of numerical models, which may then be used to optimise the interactions between an array of WECs and wind turbines.
Positive Interaction of Hydrodynamic Motions of an Offshore Wind Turbine With Co-Located WEC
Authors: Hewins Shelby , Nader Jean-Roch , Gubesch Eric , Sergiienko Nataliia
Published: September 2023

Renewable marine energy is plentiful and available, with most systems moving further offshore to capture this resource as a higher energy power density can be extracted. Both offshore wind turbines and Wave Energy Converters (WECs) are generally existing within similar geotechnical locations and therefore could benefit from co-location of devices, as shared infrastructure would be a major factor for reducing Levelized Cost of Energy (LCOE). This paper is focused on the benefits of having a co-located hybrid renewable marine system, which consists of offshore wind turbine and WEC in conjunction, for the Joint Research Centre (JRC) of Offshore Wind and Wave Energy grant. The principal focus of the grant is to minimise capital costs and/or maximise productivity. However, by maximising power performance, the maximum fluid-structure interactions between the device, the waves, and wind are required. A numerical approach was simulated using ANSYS AQWA to solve for interaction between a co-located Wind Turbine (WT) and WEC device. The simulation was validated against analytical sources and alternative software NEMOH. Effects of the co-location for the power efficiency and reduction of the force related to the WT, showed that the positioning of the WEC provides a greater influence on results than the radiation damping effect.
Evaluation of VIV Prediction Practice of Deep-Water Steel Lazy Wave Risers (SLWRs)
Authors: Wu Jie , Jiang Fengjian , Lie Halvor , Passano Elizabeth , Yin Decao , Sævik Svein , Grytøyr Guttorm , Hogg Brendan Francis , Resvanis Themistocles , Vandiver Kim
Published: September 2023

Vortex Induced Vibrations (VIV) are one of the major design concerns for deep-water riser systems. Large uncertainties and limitations in the existing prediction tools and design practice lead to not only costly riser designs, but also have a negative impact on the floaters. These are creating technology barriers for the development towards ultra-deep water. The present study aims to improve VIV prediction practice of deep-water Steel Lazy Wave Risers (SLWRs) system. A case study using a SLWR has been carried out with traditional frequency domain (FD) VIV prediction tools, e.g., VIVANA-FD/Shear7. It is shown that similar prediction results can be obtained with equivalent empirical hydrodynamic parameters. The recently developed non-linear time domain (TD) tool, VIVANA-TD, has also been evaluated for the same case, which can consider non-linear structural properties, e.g., soil-pipe interaction at the touch down area. In addition, uncertainty in VIV prediction lies also on the use of empirical hydrodynamic parameters, which are generalized based on various test data. Differences in prediction using these tools can also be related to the philosophy of prediction tools to treat uncertainty and conservatism. The gaps and uncertainties in the present prediction practice are discussed and assessed. Further work is suggested.
Structural Integrity Risk Assessment of Offshore Terminals Based on Key Measurable Indicators
Authors: Mazaheri Sam
Published: September 2023

Structural Integrity Risk Analysis (SIRA) is a crucial tool for any maritime structures and asset owners to ensure the current condition of their assets, are in safe condition and there are no risks to personnel, business, and environment. Nevertheless, there is no single standard method to conduct this kind of structural risk analysis and so, asset owners and authorities are utilising different methods based on their best practice to come up with suitable structural risk figures for their assets. Despite best efforts, there is a chance to miscalculate the actual risk and, in most cases, underestimate the current structural risk. This has become particularly more important for the assets that are complex and aged. This paper tries to fill this gap by introducing some key indicators which can enhance the accuracy of SIRA and provide a better understanding for key decision makers to keep their assets in fair conditions and prevent any unwanted business interruption. To address this issue and minimise the risk of underestimating the actual structural risk, reliable indicators such as Condition Rating (CR), Section Utilisation (SU), Defect Heatmap (DH) and, Structural Criticality (SC) are introduced. These indicators can be fed later into any risk matrix / system to estimate the inherent and future risk of structural sections in offshore terminals. To evaluate this method in practice, more than 5 years of structural condition data of one of the offshore terminals in Australia has been considered. Next, the key structural indicators and their variation over a 24-month time window were developed, analysed, and monitored. Furthermore, the outcome has been used to update the structural asset management and maintenance strategy. Finally, to monitor the structural risk over time, two additional indicators; Defect Completion Rate (DCR) and Defect Overdue Index (DOI) have been introduced.
Application of Extended Game in Multi-UUV Pursuit-Escape Task
Authors: Yu Dan , Wang Hongjian , Huang Weiquan , Huang Shihao
Published: September 2023

With the extensive deployment of unmanned systems in various fields, the requirements for unmanned underwater vehicles (UUV) are becoming higher and higher. A single UUV can no longer meet the task requirements, and the cooperative control of multiple UUVs is required. In this paper, facing the hunting-escape task, establishing the kinematics and observation communication model of UUV, the multi-UUV pursuit task is completed based on this model. The multi-UUV maneuvering strategy set, payoff function and Nash equilibrium solution are given by using dynamic extended form game. In the game task, the pursuit UUVs decompose many-to-one game toone-to-one, and the escape UUV calculates the highest income among the multiple UUVs, that is, in the process of the task, the pursuit party simplifies the task to one-to-one interception, and the other is the best strategy for many-to-one selection. Finally, the pursuit and escape simulation experiments are carried out to verify the effectiveness and superiority of the algorithm. From the perspective of effectiveness, after 29 games, the pursuit UUV successfully encircles the escape UUV. The effectiveness of the algorithm is verified from the encircling path, the change of the distance between the pursuit UUV and the breaching party’s UUV, and the final situation. The effectiveness of UUV controller is analyzed from lateral, longitudinal velocity and heading control. In terms of the superiority of the algorithm, when the pursuit party chooses the maneuver strategy given by the interception and breakthrough theory, the pursuit party fails after the same time and strategy selection steps, and the escape succeeds. The superiority of the algorithm can be obtained from the comparison of the simulation results.
Genome-wide variation in the Angolan Namib Desert reveals unique pre-Bantu ancestry
Authors: Oliveira Sandra , Fehn Anne-Maria , Amorim Beatriz , Stoneking Mark , Rocha Jorge
Published: September 2023

Ancient DNA studies reveal the genetic structure of Africa before the expansion of Bantu-speaking agriculturalists; however, the impact of now extinct hunter-gatherer and herder societies on the genetic makeup of present-day African groups remains elusive. Here, we uncover the genetic legacy of pre-Bantu populations from the Angolan Namib Desert, where we located small-scale groups associated with enigmatic forager traditions, as well as the last speakers of the Khoe-Kwadi family’s Kwadi branch. By applying an ancestry decomposition approach to genome-wide data from these and other African populations, we reconstructed the fine-scale histories of contact emerging from the migration of Khoe-Kwadi–speaking pastoralists and identified a deeply divergent ancestry, which is exclusively shared between groups from the Angolan Namib and adjacent areas of Namibia. The unique genetic heritage of the Namib peoples shows how modern DNA research targeting understudied regions of high ethnolinguistic diversity can complement ancient DNA studies in probing the deep genetic structure of the African continent.
Draft genome sequence of
Staphylococcus gallinarum
BAU_KME002 strain isolated from egg surface in Bangladesh
Authors: Ballah Fatimah Muhammad , Islam Md. Saiful , Rana Md. Liton , Khatun Mst. Minara , Rahman Marzia , Hassan Jayedul , Rahman Md. Tanvir
Published: September 2023

This report describes the genome sequence of the
Staphylococcus gallinarum
BAU_KME002 strain isolated in Bangladesh in 2021 from a chicken egg surface. Our assembled genome had 50 contigs, an estimated genome length of 2,866,882 bp (with coverage of 90.0×), 36 predicted antibiotic resistance genes, and 28 predicted virulence factor genes.
S. aureus
virulence factors decrease epithelial barrier function and increase susceptibility to viral infection
Authors: Moran Mary C. , Brewer Matthew G. , Schlievert Patrick M. , Beck Lisa A.
Published: September 2023

Individuals with atopic dermatitis (AD) are highly colonized by
Staphylococcus aureus
and are more susceptible to severe viral complications. We hypothesized that
S. aureus
secreted virulence factors may alter keratinocyte biology to enhance viral susceptibility through disruption of the skin barrier, impaired keratinocyte differentiation, and/or inflammation. To address this hypothesis, human keratinocytes were exposed to conditioned media from multiple
S. aureus
strains that vary in virulence factor production (USA300, HG003, and RN4220) or select purified virulence factors. We have identified the
S. aureus
enterotoxin-
like
superantigen SE
l
Q, as a virulence factor of interest, since it is highly produced by USA300 and was detected on the skin of 53% of AD subjects (
n
= 72) in a study conducted by our group. Treatment with USA300 conditioned media or purified SE
l
Q resulted in a significant increase in keratinocyte susceptibility to infection with vaccinia virus, and also significantly decreased barrier function. Importantly, we have previously demonstrated that keratinocyte differentiation influences susceptibility to viral infection, and our qPCR observations indicated that USA300
S. aureus
and SE
l
Q alter differentiation in keratinocytes. CRISPR/Cas9 was used to knock out CD40, a potential enterotoxin receptor on epithelial cells. We found that CD40 expression on keratinocytes was not completely necessary for SE
l
Q-mediated responses, as measured by proinflammatory cytokine expression and barrier function. Together, these findings support that select
S. aureus
virulence factors, particularly SE
l
Q, enhance the susceptibility of epidermal cells to viral infection, which may contribute to the increased cutaneous infections observed in individuals with AD.

Importance

Staphylococcus aureus
skin colonization and infection are frequently observed in individuals with atopic dermatitis. Many
S. aureus
strains belong to the clonal group USA300, and these strains produce superantigens including the staphylococcal enterotoxin-
like
Q (SE
l
Q). Our studies highlight that SE
l
Q may play a key role by altering keratinocyte differentiation and reducing barrier function; collectively, this may explain the AD-specific enhanced infection risk to cutaneous viruses. It is unclear what receptor mediates SE
l
Q’s effects on keratinocytes. We have shown that one putative surface receptor, CD40, was not critical for its effects on proinflammatory cytokine production or barrier function.
Neuroimaging in infants with congenital cytomegalovirus infection and its correlation with outcome: emphasis on white matter abnormalities
Authors: Alarcón Ana , de Vries Linda S , Parodi Alessandro , Arnáez Juan , Cabañas Fernando , Steggerda Sylke J , Rebollo Mónica , Ramenghi Luca , Dorronsoro Izaskun , López-Azorín Manuela , Schneider Juliane , Noguera-Julian Antoni , Ríos-Barnés María , Recio Manuel , Bickle-Graz Myriam , Martínez-Biarge Miriam , Fortuny Clàudia , García-Alix Alfredo , Truttmann Anita C
Published: September 2023

Objective

To evaluate the association between neuroimaging and outcome in infants with congenital cytomegalovirus (cCMV), focusing on qualitative MRI and quantitative diffusion-weighted imaging of white matter abnormalities (WMAs).

Methods

Multicentre retrospective cohort study of 160 infants with cCMV (103 symptomatic). A four-grade neuroimaging scoring system was applied to cranial ultrasonography and MRI acquired at ≤3 months. WMAs were categorised as multifocal or diffuse. Temporal-pole WMAs (TPWMAs) consisted of swollen or cystic appearance. Apparent diffusion coefficient (ADC) values were obtained from frontal, parieto-occipital and temporal white matter regions. Available follow-up MRI at ≥6 months (N=14) was additionally reviewed. Neurodevelopmental assessment included motor function, cognition, behaviour, hearing, vision and epilepsy. Adverse outcome was defined as death or moderate/severe disability.

Results

Neuroimaging scoring was associated with outcome (p<0.001, area under the curve 0.89±0.03). Isolated WMAs (IWMAs) were present in 61 infants, and WMAs associated with other lesions in 30. Although TPWMAs and diffuse pattern often coexisted in infants with IWMAs (p<0.001), only TPWMAs were associated with adverse outcomes (OR 7.8; 95% CI 1.4 to 42.8), including severe hearing loss in 20% and hearing loss combined with other moderate/severe disabilities in 15%. Increased ADC values were associated with higher neuroimaging scores, WMAs based on visual assessment and IWMAs with TPWMAs. ADC values were not associated with outcome in infants with IWMAs. Findings suggestive of progression of WMAs on follow-up MRI included gliosis and malacia.

Conclusions

Categorisation of neuroimaging severity correlates with outcome in cCMV. In infants with IWMAs, TPWMAs provide a guide to prognosis.
Real-life data of hypoglycemic events in children and adolescents with type 1 diabetes
Authors: Hill Henrik , Klaar Per , Espes Daniel
Published: September 2023

Introduction

Hypoglycemia composes an always present risk in the treatment of type 1 diabetes (T1D) and can be a fatal complication. Many studies on hypoglycemic events are based on self-reported data or focused on the aggregated time below range. We have processed continuous glucose monitoring (CGM) data in children and adolescents with T1D in order to examine all occurring hypoglycemic events.

Research design and methods

CGM data (mean 168±3 days) from 214 children and adolescents with T1D were analyzed using computer-based algorithms. Patients were divided into three groups based on estimated HbA1c (eHbA1c): (1) ≤48 mmol/mol (n=58); (2) 49–64 mmol/mol (n=113); (3) ≥65 mmol/mol (n=43). The groups were compared concerning descriptive data and CGM metrics with emphasis on the frequency of hypoglycemic events.

Results

Only one self-reported event of severe hypoglycemia was registered, while 54 390 hypoglycemic events (<3.9 mmol/L (<70 mg/dL)) were identified from CGM data out of which 11 740 were serious (<3.0 mmol/L (<54 mg/dL)). On average there were 1.5±0.1 hypoglycemic events per 24 hours out of which 1.2±0.1 were mild (3.0–3.9 mmol/L) and 0.3±0.02 serious. Group 1 had a higher frequency of both total and mild hypoglycemic events compared with both groups 2 and 3. However, the frequency of serious hypoglycemic events was similar in all groups. A negative correlation was observed for eHbA1c and total daily and mild hypoglycemic events (r=−0.57 and r=−0.66, respectively, p<0.0001), whereas for serious hypoglycemic events there was only a borderline significance (r=−0.13, p=0.05).

Conclusions

This study shows that hypoglycemic events are a frequent phenomenon in children and adolescents with T1D, occurring regardless of overall metabolic control. Although patients with an HbA1c ≤48 mmol/mol had a higher frequency of mild hypoglycemic events there was no increase in serious hypoglycemic events.