bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Automatic Target Detection System for 11,000M-Class Underwater Vehicles
Authors: Kakami Hitoshi , Nakatani Takeshi , Maeda Yosaku , Aso Tatsuya , Shinohara Yusuke 
Published: August 2024

Abstract
An underwater vehicle with a tether cable is called a remotely operated vehicle (ROV), and an operator on the mother ship can observe video images and collect samples in real time. However, when operating in very deep sea, the tether cable becomes extremely long, and its handling is technically difficult.
Against this background, the authors are currently developing a vehicle that can operate at great depths without relying on tether cables. In this case, the vehicle requires a higher degree of autonomy since the operator cannot remotely control the vehicle. As a technology necessary for autonomous sample collection, we have developed a system that automatically detects and tracks targets from camera images.
Machine learning methods are widely used as a means of detecting target objects from camera images. We adopted Detection Transformer (DETR) from among multiple methods as a target detection model. We then created an underwater model by training it with videos of deep-sea creatures and dummy targets recorded by our organization. Since camera images in the underwater environment are different from those on land, we applied data augmentation to add lens distortion and blur during training.
We also compared multiple methods for tracking models for detected objects and implemented the Byte-Track algorithm.
The developed system consists of an underwater camera and an image processing device, each housed in a pressure-resistant container designed to be used at great depths. The underwater camera uses a stereo camera system so that it can detect and track the target and measure its position at the same time. The image processing device was sized to fit in a pressure-resistant container, and hardware capable of image processing using a graphics processing unit (GPU) was selected, and the processing performance was confirmed.
After basic confirmation of the developed system through tank tests, it was installed on an 11,000m-class lander owned by our organization and a demonstration test was conducted at a triple junction (depth of 9,200m). Since the possibility of encountering living things at this depth is low, a dummy target was also attached to the lander to confirm detection. As a result, the system successfully detected and tracked targets in real time. On the other hand, detection performance sometimes deteriorated in certain situations such as hiding behind objects.
In order to improve the issues identified this time, the authors plan to conduct additional learning using newly acquired video data. Through continued testing and evaluation, we plan to install it on 11,000m class vehicles in the future.
A Fast Manoeuvring Calculation to Assess the Optimal Vessel Speed in Shallow Water
Authors: Emmersberger Christian , Krüger Stefan 
Published: August 2024

Abstract
The need of improving the energy demand in ship’s operation is driven by growing regulations regarding shipping emission. Therefore, this paper describes an approach to determine the optimal speed of a ship traveling a route with changing water depths. The power demand of vessels in shallow water is higher than in deep water at the same speed. Regarding the energy consumption, it is profitable to slow down in shallow water and compensate the lost time in deeper water. The presented tool enables to find the optimal speed for every water depth segment of a specific ship route by solving an optimization problem. The aim is to obtain the least energy consumption by retaining the same travel time. The approach is built on a fast and adaptable manoeuvring calculation, which is used to determine the fuel consumption of a ship traveling a specific ship route given by waypoints. The additional power demand due to shallow water calculation is obtained by the Schlichting method. The manoeuvring calculation is based on a body force model, that determines the ship’s motion from all forces acting on the ship. The approach is demonstrated by a specific use case and can results in fuel savings of up to 8% dependent on the reference case.
Two-Dimensional Simulation of the Flow Around a Three-Straight Bladed Vertical-Axis Wind Turbine for Different Pitch Angles
Authors: Satyam S. , Fabregat-Sanjuan A. , Huera-Huarte F. J. 
Published: August 2024

Abstract
This two-dimensional Computational Fluid Dynamics (CFD) study, investigates the effect of blade pitch angle on the performance of a vertical-axis wind turbine (VAWT). The research is focused on the analysis of the variations in blade aerodynamic loads and blade-wake interactions for different blade pitch angles. The CFD model deals with a three-straight-bladed VAWT based on NACA-0015 profiles. The rotor has a diameter of 0.75 m with a chord-to-diameter ratio of 0.16. Blade pitch angles, ranging from 8 degrees toe-in to 6 degrees toe-out, have been investigated using Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations at a fixed diameter-based Reynolds number of 5·105. The results show that modifying the blade pitch angle, impacts the flow around the blades and the blade aerodynamic loads, altering overall turbine performance. Adjusting the blade pitch angle from 0 degrees to 2 degrees toe-out, led to a significant increase (over 6%) in the turbine power coefficient (Cp). However, a further increase in the pitch angle leads to a gradual power coefficient decrease. We show that the results, obtained using a two-dimensional CFD model, allow to describe the main features observed in this type of problems.
Lazy Wave Cables and Risers VIV Response: On the Impact of Buoyancy Modules Aspect Ratios and Arrangement
Authors: Jara-Bravo Cristian , Minguez Matthieu , Cinello Alexandre , Marty Antoine , Rippol Thierry 
Published: August 2024

Abstract
In this paper, the impact of buoyancy modules aspect ratios and arrangement on the VIV response of a power cable or riser is addressed through a dual approach coupling experimental and numerical simulations.
Two sets of experiments are performed in the ‘South France – Ocean Basin’ located in La Seyne-Sur-Mer and operated by Océanide. On the first one, rigid sections of pipe equipped with a single buoyancy module are submitted to a pure harmonic crossflow oscillation with over imposed steady flow conditions. From load measurements on the buoyancy modules themselves, a database of hydrodynamic coefficients for several aspect ratios is obtained. Then, the VIV response of a line installed across the basin and fitted with different buoyancy module arrangements was tracked to investigate the impact of buoyancy module aspect ratio, as well as their arrangement.
The data extracted from the second set of tests is used as a benchmark case to validate the numerical approach via Shear 7. Both the default hydrodynamic data from the software and the hydrodynamic database obtained from the first set of tests are compared.
A weaker power input from the buoyancy modules was found compared to the expected results for an infinite cylinder, as well as a possible modification of vortex shedding frequency (Strouhal number). When focusing on the buoyancy module arrangement, the experimental results emphasize the impact of gap between buoyancy modules on the global cable response. Moreover, this experimental/numerical benchmark provides some insight on the validity of the simplified approach of software as Shear7 for this type of riser or power cable configuration.
Service Life Prediction Method for a Free Spanning Pipeline Undergoing Vortex Induced Vibrations
Authors: Song Qing-Yuan , Liu Jun , Gao Fu-Ping 
Published: August 2024

Abstract
Free spans of a subsea pipeline may undergo vortex-induced vibrations (VIVs) and could be damaged by fatigue failure. The free span length is a key parameter for determining the structural natural frequency, which would correspondingly influence the reduced velocity (Vr) for the VIV responses. The existing flume tests indicated that the VIVs of a near-bed cylinder may be triggered effectively in moderate shear flows. This may imply that the vibration cycles of a free spanning pipeline could be up to ten-millions, and the very-high-cycle fatigue (VHCF) could be encountered during the engineering service. On the basis of the dimensionless vibration amplitude A/D-Vr curve and the recommended S-N curve for the high-strength steel pipelines with cathodic protection under seawater environments, a prediction method is proposed for the service life of a free spanning pipeline undergoing VIVs. A case study is then performed to evaluate the service life (in terms of vibration cycles) of the free-spans with the focus on VHCF. It is indicated that, if the characteristic flow velocity is given, the variation of the service life with the span length is generally nonlinear, which is attributed to being involved in various VIV branches of the A/D-Vr curve.
Probabilistic Analyses of Floating Offshore Marine Drilling Operations Using Active Learning Methods
Authors: Garlid Stian , Ren Chao , Xing Yihan 
Published: August 2024

Abstract
Garlid et al. [1] previously showed that it is feasible to determine marine riser disconnect criteria for a mobile offshore drilling unit (MODU) using the structural reliability analysis (SRA) method. The method was presented through a case study of a notional MODU moored, with static thruster assist, in shallow water and subjected to harsh environments. The case study was performed with a series of simplifications that might introduce unwanted conservatism for the end user, such as co-linear environmental forces and static thruster settings. Further, only ten environmental load cases were used to populate the response surfaces, leading to a relatively coarse response surface grid. Still, many time domain (TD) analyses were needed to populate the response surfaces that describe the relevant short-term response statistics. Although more computationally expensive, the SRA method offers several advantages over the conventional frequency-domain method currently employed in the industry. These advantages include the possibility of considering non-linear effects more accurately when considering extreme responses and the possibility of considering the coupling effects between the different components, such as the MODU and marine riser. Therefore, the SRA method is more accurate, allowing operators to run more efficient marine operations and possibly extending operational windows. In this paper, the authors will develop the SRA method further by utilizing active learning when performing the response surface generation to significantly reduce computational efforts. This paper will use the Kriging model to model the response surface. Stochastic noise in the sampling points is included in the model to avoid potential over-fitting. A significant reduction in analysis effort could make the SRA method closer in performance in terms of computational efforts against the conventional frequency domain, but with the added advantages of a high-fidelity method that can consider full-coupling and non-linear effects.
Determining Submarine Dynamic Cable Stiffness and Fatigue Characteristics Through Physical Testing
Authors: Thies Philipp R. , Georgallis Georgios 
Published: August 2024

Abstract
Offshore wind farms are moving into deeper waters, where fixed foundations are not economically viable, forcing the development of floating wind turbines. Recent global estimates by 4C Offshore expect a total of 14 GW of floating wind turbines to be installed by 2030, with another 40GW installation forecasted up to 2050. This will necessitate the manufacture, installation, and commissioning of thousands of floating wind platforms. Electricity will need to be exported from these installations, and therefore dynamic submarine power cables will be one of the most critical and exposed components, connecting the floating platform to static subsea export cables or floating export / production platforms. Dynamic submarine power cables must now have the ability to support increased loads caused by this move into deeper waters and the movement of the floating vessel or platform. They must also be able to tolerate fatigue associated with load changes that occur during their movement in the water column. The structural characteristics of dynamic power cables are often approximated through numerical modelling, and full-scale cable mechanical testing is essential for accurate measurement of key properties, including axial stiffness and bending stiffness. This paper presents a case study and characteristic results of a mechanical cable test campaign, quantifying cable stiffness and fatigue. The example illustrates the value of mechanical testing to better inform both global hydrodynamic models with cable properties and to better calibrate local finite element analysis tools. The paper is useful for researchers and practitioners concerned with the modelling, design and testing of submarine dynamic power cables. It is also useful for project investors and underwriters to better understand the assurance testing of cables as a critical component.
Dual Shear Gun for Efficient Fluid Mixing and Dispersion: Effect of Design Parameters
Authors: Taghipour Ali , Lund Bjørnar , Yterhus Jan David , Saasen Arild , Ånesbug Geir Olav , Pallin Jan Egil 
Published: August 2024

Abstract
Invert emulsion fluids where water droplets are dispersed in an oil phase are often the preferred choice when drilling through problematic formations such as reactive shales. Bulk volume of OBM is typically leased and mixed offsite and transported to the site with truck or ship to the offshore drilling rigs. The solid particle phase of the OBM emulsion often settles during transportation and the emulsion therefore needs reconditioning on site. However, preparing on the order of 100 m3 of stable emulsion requires both high shear and high elongation as well as time and space due to the large volumes of fluid involved. Current shear guns used offshore are not efficient enough and do not provide sufficient emulsification to generate a stable fluid. Therefore, a common practice is also to use the bit nozzles as emulsification device when adding fresh drilling fluid to the circulating fluid. This must be done at a slow rate to ensure the stability of the fluid and is therefore a time-consuming process. A compact solution for efficient on-site recondition emulsification of the drilling fluid would therefore reduce time and costs of drilling operations.
On-site pump pressure capacity may be limited, and on-site energy use should ideally be kept as low as possible. With these restrictions in mind, it is desirable to be able to provide a stable emulsion with as little pressure drop as possible, while high pump rate is also preferable in order to minimize mixing time. Both criteria favour larger nozzle sizes.
We here present results from full-scale laboratory tests with a dual shear gun unit, investigating the effect of different design parameters on the oil-water mixing process and on the stability of the resulting dispersion. Surfactants (emulsifiers) have not been added, to allow fluids to separate and to be re-used after each test, and separation time is used as an indicator of droplet size and thus of the expected fluid stability in a system with emulsifiers.
In this paper we present and discuss experimental results of effects of nozzle sizes, nozzle-nozzle distance, pressure drop over nozzles, flow rates (which depend on pressures and nozzle sizes), as well as fluid aging.
Analysis of the Dynamic Response of ROV System Experiencing Vessel Motion During Deployment and Recovery Processes
Authors: Yu Xiaoqi , Guo Yucheng , Guo Shuangxi , Liu Xiangxu , Kong Yue , Chen Weimin 
Published: August 2024

Abstract
Remotely operated vehicle (ROV) system is significantly affected by the excitations coming from the top-end vessel motion and the hydrodynamic disturbances. Especially, during initial deployment and final recovery stages, the cable length might be so short that the relative motion between the ROV and the vessel may cause a severe collision. At the same time, the cable tension can also be changed by the ROV motion, and consequently cable slack may occur, which seriously affects structural safety. This study focuses on the dynamic responses of ROV system induced by the vessel heave during initial deployment and final recovery processes. Through numerical simulation, the ROV response and cable tension time histories of the ROV system with moving boundary, also considering hydrodynamic force on ROV, are presented. It is found that the vessel heave induces the parametric excitation response to the ROV system. The influences of vessel motion amplitude, vessel motion frequency, and initial angular displacement of ROV on the responses of ROV system are discussed. Meanwhile, the governing equation of ROV motion with a vertical moving boundary is established, and a dimensionless control parameter called amplitude-frequency factor which characterizes the strength of vessel heave is proposed. Under the nonlinear damping generated by hydrodynamic force, the parametric resonance can be excited when the amplitude-frequency factor reaches the threshold. The hydrodynamic damping ratio is fitted based on the numerical simulation results. Finally, under consideration of the nonlinear damping effect, the unstable regions of vessel motion amplitude and frequency at different displacement amplitudes are obtained.
Soil Deformation and Erosion Near Mooring Chains in Clay Based on Cyclic T-Bar Tests
Authors: Rui Shengjie , Zhou Zefeng , Jostad Hans Petter , Yang Hongkuan , Dou Yuzhe , Wang Baoxuan 
Published: August 2024

Abstract
Soil deformation and erosion induced by anchor chain motion has a significant influence on the formation of trenches into the seabed near the touchdown area. However, the soil deformation and erosion are not well understood in the present trench formation, which limits the wide application in the prediction method. This paper presents a series of monotonic and cycle T-bar penetration tests to investigate the soil deformation and erosion phenomena at the seabed. Different soil undrained shear strengths were adopted, and a camera was used to record the soil deformation in real time. During the monotonic and the first penetration in the cyclic tests, the soil was displaced by the T-bar. In the cyclic tests, the degradation of soil resistance mainly appears in the first 20 cycles, and the final resistance is originated from the water replacement in the trench. The soil erosion near the T-bar mainly appears in the cracks formed during the initial penetration. When the water in the trench is replaced by the T-bar, water flows and erodes fine particles through the cracks. The trenches are initially caused by the T-bar penetration, and then the soil along the trench wall and bottom are eroded away during cyclic loading to form stable trench profiles.
The Optimization of Nozzle-Diffuser Duct for an Innovative Wave Energy Conversion System
Authors: Wu Shing-nan , Yeh Po-hung , Chen Bang-fuh 
Published: August 2024

Abstract
An innovative wave energy converter is proposed. In present study, a nozzle-diffuser duct (NDD) is used to transfer wave energy into current energy. If the energy is to be transferred more efficiently, the NDD needs to be optimally designed. First of all, the model in present paper is introduced. Then, the research methods, including the numerical method as well as the optimization algorithm, are explained. Before further investigation, validation needs to be carried out. After the simulation result is validated by comparison with previous studies, the overall discrepency is less than 4 %. Therefore, more advanced analysis is then performed. The NDD geometry is optimized by the Taguchi method, initiated by a Japanese scholar and then widely adopted and recognized worldwide due to the method’s reliability. The result shows that when NDD geometry is optimally designed, the energy flux generated by NDD reaches the maximal value, and so does the velocity inside NDD. The best design outperforms the best case in the nine selected cases by 27%. This also implies that when the wave condition of Hualien Harbor in the east coast of Taiwan is applied, the feasibility of the NDD installation to garner energy from the wave is possible.
Efficiency and Innovation in Offshore Renewable Energy: A Surrogate Modeling Approach to Mooring System Optimization
Authors: Moradinia Zohreh , Vandierendonck Hans , Murphy Adrian 
Published: August 2024

Abstract
This paper introduces an advanced framework for the multi-objective optimization of mooring systems in offshore renewable energy applications. Employing a machine learning-based surrogate model integrated with the Non-dominated Sorting Genetic Algorithm II (NSGA-II), the approach efficiently navigates the complex design space. The framework, demonstrated through the optimization of a mooring system for a wave energy converter, emphasizes minimizing manufacturing costs and maximizing x-direction offset motion while adhering to specified constraints. Utilizing validated numerical models, the surrogate model is trained on a comprehensive dataset, enabling accurate predictions of tension and platform motion. The integration of a genetic algorithm systematically explores design possibilities, with the surrogate model validating each generation, eliminating the need for time-intensive simulations. The study produces a spectrum of optimal solutions, offering insights into the intricate interplay between design modifications, cost considerations, and platform motion. This nuanced understanding facilitates informed decision-making in the realm of offshore renewable energy projects, providing a valuable contribution to mooring system design optimization.
Inequality in Physical Activity in Organized Group Settings for Children: A Cross-Sectional Study
Authors: Rogers Ann E. , Wichman Christopher S. , Schenkelberg Michaela A. , Dzewaltowski David A. 
Published: August 2024

Background: Adult-led organized settings for children (eg, classrooms) provide opportunities for physical activity (PA). The structure of setting time may influence inequalities (ie, unequalness) in the distribution of PA. This study examined differences in PA inequality by setting and time-segment purpose in time-segmented organized group settings for children. Methods: PA and setting meetings were assessed using accelerometer and video observation data from school, before-/after-school, and youth club groups (n = 30) for third- through sixth-grade children (n = 699) in 2 rural US communities. Meetings (n = 130) were time-segmented into smaller units (sessions; n = 835). Each session was assigned a purpose code (eg, PA). Accelerometer data were paired with the meetings and sessions, and the Gini coefficient quantified inequality in activity counts and moderate to vigorous PA minutes for each segment. Beta generalized estimating equations examined differences in PA inequality by setting and session purpose. Results: Activity count inequality was lowest (P < .05) during youth club meetings (Gini = 0.17, 95% CI, 0.14–0.20), and inequality in moderate to vigorous PA minutes was greatest (P < .01) during school (Gini = 0.34, 95% CI, 0.30–0.38). Organized PA sessions (Gini = 0.20, 95% CI, 0.17–0.23) had lower activity count inequality (P < .0001) than academic (Gini = 0.30, 95% CI, 0.27–0.34), enrichment (Gini = 0.31, 95% CI, 0.27–0.36), and nonactive recreation (Gini = 0.30, 95% CI, 0.25–0.34) sessions. Inequality in moderate to vigorous PA minutes was lower (P < .05) in organized PA (Gini = 0.26, 95% CI, 0.20–0.32) and free play (Gini = 0.28, 95% CI, 0.19–0.39) than other sessions. Conclusions: PA inequality differed by setting time structure, with lower inequality during organized PA sessions. The Gini coefficient can illuminate PA inequalities in organized settings and may inform population PA improvement efforts in rural communities.