bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical study of 16 patients with thalamic infarction
Authors: Ogawa Katsuhiko , Akimoto Takayoshi , Hara Makoto , Fujishiro Midori , Nakajima Hideto
Published: September 2023

Background

The pathophysiology of sensory impairment in thalamic infarction is unclear.

Aim

The association between extents of lesions in the ventroposterior nucleus (VP) and distributions of sensory impairments after thalamic infarction was studied.

Methods

Neurological symptoms and locations of lesions in 16 patients with thalamic infarction were analyzed. Locations of lesions were grouped into the four regions (region 1–4) in the front to back direction.

Results

The lateral part of the region3 within the intermediate to caudal levels where the VP exists was frequently involved. Subjective superficial sensory impairments were noted in eight patients. The other six patients showed objective sensory impairment alone. The most frequent type was the face/arm in 6 patients. In these six patients, sensory impairments were distributed to the distal part of the arm and the mouth surrounding in five patients each. Sensory impairments were distributed to the half of the body in four patients, the face/trunk/arm in one patient, the face/arm/leg in two patients, and the arm in one patient.

Conclusions

The principal inferolateral branch supplies the VP and has no anastomosis. In ischemic conditions, blood flow can be decreased in the inside part of the VP, which corresponds to the field of the hand and the mouth surrounding. The detection threshold of superficial sensations for hand and mouth is low. These phenomena were associated with frequent involvement limited to the face/arm. Distributions of sensory impairments were considered to depend on the detection threshold and the lower blood flow in the inside part.
Allelopathy‐selected microbiomes mitigate chemical inhibition of plant performance
Authors: Revillini Daniel , David Aaron S. , Reyes Alma L. , Knecht Leslie D. , Vigo Carolina , Allen Preston , Searcy Christopher A. , Afkhami Michelle E.
Published: September 2023

Allelopathy is a common and important stressor that shapes plant communities and can alter soil microbiomes, yet little is known about the direct effects of allelochemical addition on bacterial and fungal communities or the potential for allelochemical‐selected microbiomes to mediate plant performance responses, especially in habitats naturally structured by allelopathy.

Here, we present the first community‐wide investigation of microbial mediation of allelochemical effects on plant performance by testing how allelopathy affects soil microbiome structure and how these microbial changes impact germination and productivity across 13 plant species.

The soil microbiome exhibited significant changes to ‘core’ bacterial and fungal taxa, bacterial composition, abundance of functionally important bacterial and fungal taxa, and predicted bacterial functional genes after the addition of the dominant allelochemical native to this habitat. Furthermore, plant performance was mediated by the allelochemical‐selected microbiome, with allelopathic inhibition of plant productivity moderately mitigated by the microbiome.

Through our findings, we present a potential framework to understand the strength of plant–microbial interactions in the presence of environmental stressors, in which frequency of the ecological stress may be a key predictor of microbiome‐mediation strength.
Establishment of a high‐efficiency transformation and genome editing method for an essential vegetable and medicine Solanum nigrum
Authors: Ding Mengdou , Piao Chun‐Lan , Zhang Xinyu , Zhu Ying , Cui Min‐Long
Published: September 2023

Solanum nigrum, which belongs to the Solanaceae family, is an essential plant for food and medicine. It has many important secondary compounds, including glycoproteins, glycoalkaloids, polyphenolics, and anthocyanin‐rich purple berries, as well as many ideal characteristics such as self‐fertilization, a short life cycle and a small genome size that make it a potential model plant for the study of secondary metabolism and fruit development. In this study, we report a highly efficient and convenient tissue culture, transformation and genome editing method for S. nigrum using leaf segments after 8 weeks of tissue culture, with a required period from transformation initiation to harvest of about 3.5 months. Our results also show multi‐shoot regeneration per leaf segment and a 100% shoot regeneration efficiency in a shoot regeneration medium. Moreover, over 82% of kanamycin‐resistant plants exhibited strong green fluorescence marker protein expression, with genetic integration confirmed by PCR results and green fluorescence protein expression in their T1 progeny. Furthermore, we successfully applied this transformation method to achieve an average of 83% genome editing efficiency of SnMYB1, a gene involved in regulating the anthocyanin biosynthetic pathway of S. nigrum in response to missing nutrients. Taken together, the combination of highly efficient tissue culture, transformation and genome editing systems can provide a powerful platform for supporting fundamental research on the molecular mechanisms of secondary metabolism, fruit development, and production of important compounds by biotechnology.
Microstructural characterisation of 3D printed and injection‐moulded glass fibre‐reinforced polypropylene by image analysis, simulation and experimental methods
Authors: Lienhard Jörg , Barisin Tin , Grimm‐Strele Hannes , Kabel Matthias , Schladitz Katja , Schweiger Timo
Published: September 2023

The mechanical properties of fibre‐reinforced thermoplastics and their dependencies on the manufacturing process, fibre properties, fibre concentration and strain rate have been researched intensively for years in order to predict their macroscopic behaviour by numerical simulations as precisely as possible. Including the microstructure in both real and virtual experiments has improved prediction precision for injection‐moulded glass fibre‐reinforced thermoplastics significantly. In this work, we apply three established methods for characterisation and modelling to an injection‐moulded and to a 3D printed material. The geometric properties of the fibre component as fibre orientation, fibre length and fibre diameter distributions are identified by analysing reconstructed tomographic images. For comparing the fibre lengths, a recently suggested new method is applied. Based on segmentations of the tomographic images, we calculate the elastic stiffness of both composites numerically on the microscale. Finally, the mechanical behaviour of both materials is experimentally characterised by micro tensile tests. The simulation results agree well with the measured stiffness in case of the injection‐moulded material. However, for the 3D printed material, measurement and simulation differ strongly. The prediction from the simulation agrees with the values expected from the image analytic findings on the microstructure. Therefore, the differences in the measured behaviour have to be contributed to the matrix material. This proves demand for further research for 3D printed materials for predictable prototypes, preproduction series and possible serial application.
Glycocalyx dynamics and the inflammatory response of genetically modified porcine endothelial cells
Authors: Milusev Anastasia , Ren Jianfang , Despont Alain , Shaw Jane , Längin Matthias , Bender Martin , Abicht Jan‐Michael , Mokelke Maren , Radan Julia , Neumann Elisabeth , Kemter Elisabeth , Klymiuk Nikolai , Ayares David , Wolf Eckhard , Reichart Bruno , Sorvillo Nicoletta , Rieben Robert
Published: September 2023

Xenotransplantation is a promising approach to reduce organ shortage, while genetic modification of donor pigs has significantly decreased the immunogenic burden of xenotransplants, organ rejection is still a hurdle. Genetically modified pig organs are used in xenotransplantation research, and the first clinical pig‐to‐human heart transplantation was performed in 2022. However, the impact of genetic modification has not been investigated on a cellular level yet. Endothelial cells (EC) and their sugar‐rich surface known as the glycocalyx are the first barrier encountering the recipient's immune system, making them a target for rejection. We have previously shown that wild type venous but not arterial EC were protected against heparan sulfate (HS) shedding after activation with human serum or human tumor necrosis factor alpha (TNF𝛼). Using a 2D microfluidic system we investigated the glycocalyx dynamics of genetically modified porcine arterial and venous EC (Gal𝛼1,3 Gal knock‐out, transgenic for human CD46 and thrombomodulin, GTKO/hCD46/hTM) after activation with human serum or human TNF𝛼. Interestingly, we observed that GTKO/hCD46/hTM arterial cells, additionally to venous cells, do not shed HS. Unscathed HS on GTKO/hCD46/hTM EC correlated with reduced complement deposition, suggesting that protection against complement activation contributes to maintaining an intact glycocalyx layer on arterial EC. This protection was lost on GTKO/hCD46/hTM cells after simultaneous perfusion with human serum and human TNF𝛼. HS shedding on arterial cells and increased complement deposition on both arterial and venous cells was observed. These findings suggest that GTKO/hCD46/hTM EC revert to a proinflammatory phenotype in an inflammatory xenotransplantation setting, potentially favoring transplant rejection.
Weighted Sobolev estimates of the truncated Beurling operator
Authors: Pan Yifei , Zhang Yuan
Published: September 2023

Given a bounded planar domain with boundary, , and a weight , we show that the corresponding truncated Beurling operator is a bounded operator sending into itself. Weighted Sobolev estimates for other Cauchy‐type integrals are also obtained.
Plasticity of gastrointestinal vagal afferents in terms of feeding‐related physiology and pathophysiology
Authors: Page Amanda J.
Published: September 2023

Gastrointestinal vagal afferents play an important role in communicating food related information from the gut to the brain. This information initiates vago‐vagal reflexes essential for gut functions, including gut motility and secretions. These afferents also play a role in energy homeostasis, signalling the arrival, amount and nutrient composition of a meal to the central nervous system where it is processed ultimately leading to termination of a meal. Vagal afferent responses to food related stimuli demonstrate a high degree of plasticity, responding to short term changes in nutritional demand, such as the fluctuations that occur across a 24‐hr or in response to a fast, as well as long term changes in energy demand, such as occurs during pregnancy. This plasticity is disrupted in disease states, such as obesity or chronic stress where there is hypo‐ and hypersensitivity of these afferents, respectively. Improved understanding of the plasticity of these afferents will enable identification of new treatment options for diseases associated with vagal afferent function.

image
Adaptive Artificial Neural Network-Based Control Through Attracting-Manifold Design and Lipschitz Constant Projection
Authors: Zhou Xingyu , Maweu John , Wang Junmin
Published: September 2023

This article presents an adaptive artificial neural network-based control scheme that strategically integrates the attracting-manifold design and a smooth Lipschitz-constant projection operator. The essence of the scheme is elaborated through the design of the reference-command-tracking control law of an nth-order single-input uncertain nonlinear system that can be transformed into the Brunovsky form. The method offers two major advantages: First, by employing the attracting-manifold design, it is possible to achieve asymptotic recovery of the ideal (deterministic) closed-loop dynamics. In other words, the perturbation caused by parametric uncertainties will be driven to zero asymptotically as a result of such a design, fostering a superior control performance. Second, the established smooth projection operator ensures the Lipschitz constant of the adaptive artificial neural network is bounded from above, thereby providing a certain degree of robustness against adversarial perturbations. The proposed method is validated through a numerical simulation example and compared with a standard certainty-equivalent neural-adaptive control method to demonstrate its superior performance.
Performance Analysis of Textured Spherical Hybrid Journal Bearings Operated With Magnetorheological Fluid
Authors: Tomar Adesh Kumar , Sharma Satish C. , Sahu Krishnkant
Published: September 2023

Recently, textured surfaces have been used to enhance the performance of tribological systems. This paper examines the effect of textured surfaces on hole-entry spherical hybrid journal bearings operated using magnetorheological (MR) fluid. The different geometric shapes of textured surfaces, including spherical, rectangular, and conical, have been selected for numerical analysis. Next-generation design for tribological systems based on MR fluid lubrication emphasizes dynamic performance. MR fluid responds quickly, and its rheological characteristics can be simply adjusted. The present paper also deals with the non-Newtonian behavior of MR fluid on the bearing performance characteristics parameters. The finite element method is used to solve the modified Reynolds equation. The findings of numerical simulation show that the application of textured surfaces and MR fluid improves the values of minimum fluid film thickness and stability of the bearing.
Bragg Resonance of Surface Gravity Waves by Surface-Piercing Vertical Multi-Plate Breakwaters
Authors: Chang-Zhe Chen , Wu Jing-Ping , Pan Jun , Zou Zao-Jian
Published: September 2023

The interaction between surface gravity waves and surface-piercing vertical multi-plate breakwaters in finite water depth is investigated under the assumption of potential flow. The time-domain desingularized boundary integral equation method (DBIEM) is adopted to solve the boundary value problem. A decomposition method based on the superposition principle is used to obtain reflected waves. The effect of the vertical plates as a floating breakwater by making full use of Bragg resonance is analyzed. Firstly, the waveforms calculated without breakwaters are compared with the second-order Stokes regular waves to obtain the appropriate desingularization distance. Then, the interaction of surface gravity waves with the breakwaters of single plate, double and triple plates are analyzed. The transmission and reflection coefficients of the breakwater of single plate are verified with the analytical solutions in the literature. The transmission and reflection coefficients of the breakwaters of double and triple plates are verified with the experimental results. Finally, the transmission and reflection coefficients of surface-piercing vertical multi-plate breakwaters with different plate numbers and drafts are calculated. The occurring condition of Bragg resonance and its values affected by the plate number and the draft are analyzed. The present results have reference values for the optimal design of vertical plates as a floating breakwater for offshore and coastal engineering applications by fully using Bragg resonance.
Estimation for Efficiency of Offshore Installation Process of Floating Offshore Wind Turbines in Japan
Authors: Hasumi Tomohiro , Yokoi Takeshi , Haneda Ken , Chujo Toshiki , Fujiwara Toshifumi
Published: September 2023

In order to estimate the construction cost of floating offshore wind turbines (FOWTs) more precisely than before, it is necessary to calculate the installation time of FOWTs more precisely. Therefore, we proposed a model to estimate the installation time of FOWTs by dividing the offshore construction into major processes and quantitatively evaluating the efficiency of each installation process. On the basis of the Cost Breakdown Structure (CBS), the total offshore installation time can be formulated as the sum of the installation time of the following five processes: (1) pre-anchoring, (2) verification of anchor ultimate holding capacity, (3) towing, (4) mooring, and (5) other operational processes. This study introduces “installation time per mooring line” as a benchmark for measuring efficiency. First, the model proposed in this paper is applied to an FOWT demonstration project in Japan and the efficiency of the installation processes is analyzed. It is found that the installation time per mooring line for (2) verification of anchor ultimate holding capacity and (4) mooring were reduced by 69% and 95%, respectively, from the initial time. The proposed model is also applied to a large wind farm and the authors conduct a sensitivity analysis. It is concluded that the installation time for (1) pre-anchoring is the most strongly affected by the number of mooring lines per FOWTs. The installation time for (1) pre-anchoring was 1.6 times longer than that of (2) verification of anchor ultimate holding capacity and eight times longer than that of (4) mooring. This study revealed that (1)pre-anchoring and (2) verification of anchor ultimate holding capacity are expected to have a large impact on cost reduction and improve efficiency.
Linearized Model for Subsea Installation Based on Natural KC Number
Authors: Fernandes Antonio C. , Batista Soares Rodrigo , Martins de Andrade Emerson , Sena Sales Junior Joel
Published: September 2023

The behaviour of subsea equipment has been widely studied by companies to minimise risks during subsea installation, which bring huge costs on the operation. The prediction of equipment motions typically is accomplished utilizing either commercial software or recommended practices from Classification Societies to comply with the minimum requirements on launching operations. This paper analyzes subsea installation in time and frequency domains using experimental, numerical and analytical approaches. Experiments have been carried out at Instituto de Pesquisas Tecnológicas (IPT) to investigate the dependency of drag andadded mass coefficients on Keulegan-Carpenter number and at Laboratory of Waves and Currents (LOC-COPPE/UFRJ) to study equipment and cable responses on the installation. A numerical model is made in OrcaFlex® for determining the transmissibility of displacement and force in function of frequency ratio, and the time series of manifold responses. Linearized models from DNV [1] and the so-called natural KC (proposed in the present paper) are taken in the investigation and compared to previous methodologies. The natural KC approach arises as an innovative way of investigating subsea equipment as the literature only provides parametric analysis considering an arbitrary KC value (i.e., Pestana et al. [3]). The analyses notice a good agreement among experiments, OrcaFlex® model and natural KC model whereas the curves found by DNV method usually overpredict the response of subsea equipment specially around resonance region.
Uncertainty Analysis of the Safety Operating Envelope of a Subsea Shuttle Tanker
Authors: Yousef Hassan Hasan , Ma Yucong , Xing Yihan , Xu Xiaosen
Published: September 2023

The subsea shuttle tanker (SST) was proposed as a cost-effective alternative to pipelines and shuttle ships for transporting liquid CO2 from offshore/land facilities to marginal subsea wells for injection. When evaluating the safety of such a submarine, it is critical to study its survivability in the presence of serious failures. The safety operating envelope (SOE) is a depth-velocity graph that encloses the safe-to-operate region based on different malfunctions scenarios, including jam-to-rise, jam-to-dive, and partial flooding. The SOE typically considers only deterministic worst-case currents in its calculations. This may be over-conservative for a vessel like the SST that needs to maximise its payload by minimising structural and machinery weight. Motivated by this, this paper will extend the previous work on the SOE by determining the uncertainty band in the presence of a stochastic current for the jam-to-rise case. A 2D manoeuvring model that includes hydroplanes, propeller and environmental loads effect is used. Free-running simulations are carried out considering two current load cases of 0.5 and 1 m/s with 5 % and 10 % standard variations. Gumbel distribution is used to determine the extreme recovery depth values and, subsequently, the corresponding uncertainty band for each case. The simulations considered two current directions and load cases of 0.5 and 1 m/s with 5 % and 10 % standard variation that yielded results showing varying increase in the recovery depth from 1.6% to 20% compared to the deterministic case. Preliminary results show that the uncertainties in the SOE can be large under stochastic current loads.
CFD Simulations of the DeepCwind Semi-Submersible in Bichromatic Waves and Validation With the Experiments From OC6 Phase 1B
Authors: Zhang Yali , Santo Harrif
Published: September 2023

Second-order potential flow models were found to under-predict the low-frequency surge and pitch responses of the floating DeepCwind semi-submersible platform as concluded from the OC6 Phase 1A study. Subsequently, a component level approach was undertaken to examine the hydrodynamic loads on the individual parts of the semi-submersible in isolation using bichromatic wave in the OC6 Phase 1B study. Therefore, a direct assessment of the difference frequency wave loading could be obtained which further enabled numerical validation using the experimental dataset arising from the OC6 Phase 1B study. In this paper, a numerical approach based on Computational Fluid Dynamics (CFD) using StarCCM+ was used to simulate some of the OC6 Phase 1B experimental test cases. Fixed platform scenarios were simulated and compared with the experimental results in terms of surge force and pitch moment. Relatively good agreement could be achieved using the numerical model. Sensitivity studies such as the choice of laminar or turbulence flow model and domain length were carried out to establish robustness in the simulated results. The CFD results established the importance of considering up to 3rd order wave force/moment and viscous effects. The same semi-submersible platform was then made to be freely-floating with soft mooring, and additional bichromatic cases were simulated to analyse and compare the resultant low-frequency and wave-induced motion responses. Significant responses at the difference frequency could be excited due to non-linear interactions of the two wave frequency components.
Parameter Estimation for 1-eq./2-eq Turbulence Models by EnKF Data Assimilation: Twin Experiment With 2D Flat Plate
Authors: Sakamoto Nobuaki
Published: September 2023

Representative turbulence models typically used for viscous flow computation in the field of ship hydrodynamics include Spalart-Allmaras (SA), k-omega, explicit algebraic stress and detached eddy simulation. In these models, several model constants are introduced, yet they have rarely been changed from nominal values. Tuning of these constants to adapt ship flow simulations will be feasible using data assimilation technique together with available measurement data. As a very 1st step for such development, a data assimilation code using an Ensemble Kalman Filter (EnKF) is implemented and integrated to an in-house viscous flow solver for ship hydrodynamics developed at the National Maritime Research Institute. Twin experiments of parameter estimation for SA and k-omega shear stress transport (SST) turbulence models are carried out aiming to confirm fundamental functionality of the developed framework for data assimilation. A simple flow field around a two dimensional flat plate is of the interest. The assimilation results show different trends. When the SA model is adopted and 5 constants are assimilated, all the constants statistically converge to the nominal values within 80 filtering steps using 40 ensemble members. When the k-omega SST model is adopted and 1 to 4 constants are assimilated, two constants (one parameter associated with viscous diffusion term of turbulent kinetic energy, and the other parameter associated with the cross-diffusion term of specific frequency) show difficulty in statistical convergence even after 500 times of filtering with 40 ensemble members.
Numerical Analysis of Flexible Tube Wave Energy Convertor Using CFD-FEA Method
Authors: Huang Yang , Xiao Qing , Idarraga Guillermo , Yang Liu , Dai Saishuai , Abad Farhad , Brennan Feargal , Lotfian Saeid
Published: September 2023

To better understand the performance of flexible tube wave energy converters (WECs) in ocean waves, a coupled numerical analysis tool based on computational fluid dynamics and a finite element method is employed to perform numerical simulations for the well-known Anaconda WEC under given different regular wave conditions. The nonlinear behaviour of Natural Rubber is considered by using YEOH hyper-elastic model. Fluid-structure interaction responses of the Anaconda WEC are compared considering the impact of incident wave speed on the performance of the device. The free surface around the WEC, internal pressure and velocity in the flexible tube, structure deformation and stress distribution are fully explored. The results show that the proposed numerical analysis tool in this work is able to predict the complex fluid-structure interactions of flexible tube WEC in waves, including wave nonlinearity and inhomogeneous distribution of stress at cross-section. The typical resonant responses are also captured when the incident wave speed matches the bulge wave speed. The internal pressure amplitude, capture width, structural deformation and hoop stress all increase at resonance. Moreover, the deformed shape of the flexible tube is found to depend on the ratio of wavelength to tube length.
Determination of Mooring Load Levels on a Cage Designed for Exposed Aquaculture in Chile
Authors: Cifuentes Cristian , Tampier Gonzalo , Echevarría Alonso , Hurtado Carlos Felipe
Published: September 2023

The determination of mooring tension on a prototype cage for salmon production on exposed areas in southern Chile is obtained using experiments at laboratory scale, numerical simulations as well as on site measurements using a submersible load cell. The 40m diameter prototype cage used in this study is constructed out of HDPE pipe and has a ballast tank attached to the bottom to control the operational depth in case of high waves. The cage uses a copper nickel alloy net cancelling the need for a predatory net as in traditional systems. First, drag coefficients for the net were obtained at the Wave/Towing tank at Universidad Austral de Chile (UACh), plus the characterization of dynamic response and deformation of two cage models. These results were used as input for numerical simulations of the cage using the commercial software AquaSim. The last stage of the campaign was the measurement of tension on the prototype cage, using a load cell on a mooring line along with measurements of tides, wind, waves, and currents. The results are the base for a more complex analysis, since the net, due to its geometry, stiffness and wet weight, has a particular behavior when compared to traditional fiber-based nets.
Scaling Characteristics of the Unified Similarity Criterion for Geometrically Distorted Scale Models
Authors: Wang Yao , Wang Qinghu , Wang Deyu
Published: September 2023

Model test is the most common and important method to evaluate the performance of structures. For large and complex structures like hull structures, test objects need to be down-scaled and even simplified. The simplified and small-scale model is called the geometrically distorted scale model. A unified similarity criterion and a design method is proposed for the distorted scale model for ultimate strength model tests recently, which states that if the plate and stiffener slenderness of the scale model and the original model keep a certain relation, the similarity of the ultimate strength and collapse behavior of the two models are guaranteed. When designing the scale model, the designers need to decrease the count of stiffeners on every plate and increase their size to meet the criterion. Nevertheless, only a few examples are provided to prove the correctness of the criterion. The characteristics are still not clear, which means that the similarity of the scale model is unclear unless a numerical analysis is performed. In this paper, two typical hull structures, the stiffened plate, and the box girder are taken as examples to investigate the scaling characteristics. 23 scale models with different combinations of 8 length scale ratios (1, 1/2, 1/3, 1/4, 1/5, 1/6, 1/8, 1/10) and 4 thickness scale ratios (1, 2/3, 1/2, 1/3, 1/4) are designed and analyzed for both structures respectively. From the results, the influence of scale ratios is revealed. Several suggestions are proposed to guide the design of scale models to reduce the cost of trial and error.
Wakes of Surface-Piercing Cylinders
Authors: Potts Douglas , Leong Zhi , Binns Jonathan , Marcollo Hayden , Skvortsov Alex
Published: September 2023

The hydrodynamics of surface-piercing cylinders differ from fully submerged cylinders due to the generation of surface wakes and under increasing flow velocities the formation of a ventilated pocket in the lee of the cylinder, both of which grow with increasing velocity, with concomitant effects on the hydrodynamic loading. Laboratory testing of surface-piercing cylinders to date has predominantly been confined to characterising the wakes of a rigid cylinder cantilevered down into the water from a towing tank carriage, which under certain test conditions will exhibit significant Vortex-Induced-Vibration (VIV).

The wake characteristics of cylindrical structures such as those protruding through the free surface from a submerged platform do alter substantially depending on the structure, geometrical properties, and operating parameters. The relative length of submergence, or immersed aspect ratio (AR) and end conditions of the cylinder do also impact the wake formation. The wake characteristics can be described by two major regions: above and below the waterline. Where the above waterline wakes are derivatives of the bow wave run-up on the leading face of the cylinder, and the below waterline wakes are derivatives of the ventilation, which is the entrapment of air of the rear face of the cylinder.

This paper presents an experimental programme in a towing tank to characterise the wake of cylindrical structures of different diameters, submergence, and forward speeds. Conventional experiments have the model attached from above the surface, however, this method is not representative of some real-world applications such as structures that are bottom mounted. [To the best of our knowledge] The authors developed the novel design of a bottom mount test platform, where the model is cantilevered from a single connection pointed up through the water column. The experiments collected a range of results including the forces, motions and wakes of the models where this paper will focus on presenting and defining the different wakes and insights into these phenomena.
Creating a Realistic Piloted Simulation of Helicopter Recovery to an Offshore Platform
Authors: Watson Neale A. , Prior Mark , Owen Ieuan , White Mark D.
Published: September 2023

This paper describes the development of a realistic piloted simulation of helicopter recovery to an offshore platform, which has been used to assess the effect of turbulent air flow on a helicopter landing on a full-scale offshore platform. Time-accurate CFD was used to create the unsteady turbulent airwake generated by an offshore platform. The computed unsteady airwake velocities were integrated with a flight dynamics model representative of a Sikorsky SH-60B Seahawk helicopter in a six-degree-of-freedom motion flight simulator. A simulated flight trial was conducted in which a test pilot was instructed to perform a series of helideck landings to the platform for wind speeds of 20 to 50 kt and to give workload ratings for the difficulty of the task. The workload ratings, along with the corresponding pilot control activity and helicopter positional accuracy, are discussed in relation to the effect of the airwake on the helicopter and pilot workload. The results show that as the freestream wind speed increased, the vertical velocity fluctuations and pilot workload also increased. The paper demonstrates the potential for realistic piloted flight simulation to be used to support helicopter operations to offshore platforms.
Dynamic Response Analysis of an End-Anchored Floating Bridge With a Damaged Pontoon Under Repair Operation
Authors: Cui Minghao , Cheng Zhengshun , Chen Peng , Moan Torgeir
Published: September 2023

During the lifetime of floating bridges, the structural components are exposed to ship collision hazards. In the situation where a pontoon is damaged from a collision accident, an in-site repair operation is needed. If a significant damage has occurred, a floating drydock may be used to ensure that the pontoon can be repaired in a dry atmosphere and to compensate for the lost buoyancy. As the repair might take months, a main issue is then whether the bridge can be open for road traffic in the damaged condition and especially during the repair. The aim of this study is to investigate the feasibility of using a drydock for the repair. In this study, a comparative dynamic analysis of an intact end-anchored floating bridge and the bridge with a damaged pontoon under repair operation, is carried out under various combinations of environmental loads. Hydrodynamic analysis of the drydock indicates that the added mass and the wave excitation force can be multiple times of the original pontoon. Eigenvalue analysis is conducted and pendulum modes of oscillation are found with an eigen-period of around 15s. The dynamic responses are analyzed by conducting a series of fully-coupled time-domain simulations under various combinations of environmental conditions. It is found that the standard deviation of the moment about the girder weak axis increases significantly at the damaged pontoon axis due to the excitation of low-frequency resonant response. Swell wave loads can cause significant dynamic amplification with relatively small wave height. Actions to reduce the risk of a possible road traffic disruption in this connection are briefly discussed.
The Safety Assessment of Ship-Bridge Collision Based on a Simplified Dynamic Model
Authors: Zhang Wenzhe , Pan Jin , Li Na , Xu Mingcai
Published: September 2023

With the continued development of transportation, the risk of ship-bridge collision has been rising persistently. Meanwhile, a great mass of old bridges which were built decades ago can’t meet the anti-collision requirement nowadays. Many countries and regions noticed that problem and have been taking various measures to protect those bridges and provide a better navigable environment. For tabling reasonable protective proposals for each bridge, the first step is assessing the safety based on the design, current representative vessels, and so on. Hence, it is necessary to propose a simple, fast, and accurate method that can be widely used in practical engineering. Kinds of simplified formulae, e.g. AASHTO and IABSE, are used to calculate the ship collision force, however, the results are static forces that have errors. Consequently, the PRC Ministry of Transport (MOT) published the Specifications for Collision Design of Highway Bridges in 2020 which calculates the collision force as a simplified dynamic history. This paper compares the simplified dynamic histories with the numerical results obtained from LS-DYNA by using several ship models in different cases. Subsequently, a method of safety assessment for bridges against ship collisions based on Midas Civil is designed. The applicability and accuracy of this new specification in force calculations and safety assessments are discussed based on acceptable errors. The comparison indicates that for 500∼10000DWT ships, the simplified formula can calculate the momentum precisely with a certain error on the peak force and total time though. To expand the scope of the application, the specification still has relatively large errors and limitations in some cases.
Early Stuck Pipe Detection Using Graph Attention Machine Learning
Authors: Inoue Tomoya , Nakagawa Yujin , Kaneko Tatsuya , Wada Ryota , Miyoshi Keisuke , Abe Shungo
Published: September 2023

Early detection of stuck pipes during drilling operations is crucial and challenging. Some of the studies on stuck detection have adopted supervised machine learning approaches that employ datasets for “stuck” and “normal”. However, that is, for early detection before stuck occurs, the application of ordinal binary classification in supervised machine learning has presented several elemental concerns, such as limited stuck data, and lack of an exact “stuck sign” before occurrence. Our previous studies proposed an unsupervised machine learning approach using data on the normal activities with LSTM-AE (Long Short-Term Memories and Autoencoder) and the mixture probability mode, and presented the possibility of predicting a stuck pipe.

These approaches independently handle the drilling data, which are multivariate time series data. However, there are relationships among some data. To improve the prediction performance to utilize the dependencies among the drilling data must be utilized. Hence, this paper applies graph neural network that can handle the dependencies between data. In addition, self-attention, a state-of-the-art machine learning approach that can determine the dependencies between multiple input data is applied.

This study performs the stuck prediction with the graph attention unsupervised machine learning using the scientific drilling data containing few stuck events to discuss the possibility of early stuck detection before stuck occurrence and the advantage of graph attention network.
Nonlinear Fourier Analysis Using Quasiperiodic Fourier Series
Authors: Osborne Alfred R.
Published: September 2023

“Linear Fourier analysis” is based on the application of “periodic Fourier series” to a wide range of wave simulation and data analysis problems. A key feature of the method is the direct computation of the “correlation function” and its Fourier transform which is the “power spectrum.” A key idea in these applications is the assumption that the “phases” of the periodic Fourier transform are “random numbers on zero to two pi.” The method leads to simple ways to compute the “coherence functions” and “transfer functions” between two signals. Many books have been written about the “linear model” and its myriad applications. In the present talk I address the infinite number of “nonlinear wave equations” that are solvable by the “periodic/quasiperiodic inverse scattering transform” and, amazingly, I show how such equations are solvable with “quasiperiodic Fourier series.” This means that all operations of the nonlinear problems of water waves are isomorphic to those of the linear problem! All operations that one can conduct for the linear problem with periodic Fourier series can also be conducted for nonlinear problems with quasiperiodic Fourier series: This means the correlation function, power spectrum, coherence functions, and transfer functions for the nonlinear problem can be computed in analogy with the linear problem. This further means further the nonlinear problem is just as easy to work with as the linear problem! I give a fast Fourier transform for quasiperiodic Fourier series and show how to conduct numerical simulations of nonlinear waves using the procedure. The methods discussed here provide for a new future in which nonlinear problems are just as easy to treat as linear ones. This work emphasizes one dimension in space, but two-dimensions are easily found by extension.
Combining Model-Based and Data-Driven Methods to Estimate the Roll Motion of a Spread-Moored FPSO
Authors: Cotrim Lucas P. , Huang Alex S. , Bisinotto Gustavo A. , Cunha Rodrigo Da S. , Barreira Rodrigo A. , Costa Anna H. R. , Gomi Edson S. , Tannuri Eduardo A.
Published: September 2023

The roll motion of a Floating Production Storage and Offloading (FPSO) unit has complex interactions that are difficult to be modeled precisely: non-linear damping depending on the motion amplitude and velocity and influence of the mooring lines forces, for example. In order to improve the estimation of the roll motion of an FPSO, a new model is proposed combining the already established physics model with a regression neural network developed to calculate the residue between the physics model and the vessel’s actual measured motions. More specifically, the regression neural network corrects the maximum roll amplitude and its standard deviation obtained from a time domain simulation of the physics model.

This study considers a typical spread-moored FPSO located offshore on the Brazilian coast. The physics model considers the 6 degrees of freedom dynamics of a floating body subject to different drafts, mooring lines and environmental forces (wind, current, waves). A conventional Multi-Layer Perceptron (MLP) neural network is trained with data from more than 44,000 samples taken from actual environmental conditions and corresponding measurements of the platform roll motion between the years 2007 and 2014. The resulting hybrid physics-MLP model receives as input the environmental conditions and the FPSO draft, executes a 1-hour simulation of the physics model, derives the maximum roll amplitude and its standard deviation, and then the MLP compensates for the expected residue of the physics model. By adding information from real measurements to the mathematical model, the previously non-modeled effects are now considered.

The present paper concludes that the hybrid architecture combining a physics-based model and an MLP has improved the estimation of the roll motion, correcting the overdamping previously observed.
Numerical Study on Green Water on Deck and Impact Loads of a Ship Model Advancing in Head Wave
Authors: Dong Guohua , Yao Chaobang , Liu Wuyang , Feng Dakui
Published: September 2023

Under rough sea conditions, the green water on the ship deck may induce great impact loads on the hull structure, which will cause serious structure damage and pose a threat to the safe ship navigation. Therefore, the study of green water and the impact load is particularly important. In this study, the numerical verification and validation of green water on deck and impact load is carried out. Commercial viscous flow CFD software STAR-CCM+ is used for calculation. The unsteady Reynolds Average Navier-Stokes (URANS) equation is used to numerically solve the process of green water in time domain. The volume of fluid (VOF) method is used to capture the water surface and interface. The model investigated in this study is a modified Wigley ship. Numerical simulation conditions are set according to the experiments conducted in the towing tank at RIAM, Kyushu University. Ship loads and pressure measured at five monitoring points on the deck are compared with experimental data, while the ship motion is fixed in head waves. The numerical uncertainty of time steps and grid sizes is discussed in details. A set of simulation results with appropriate grid and time step are compared with the experimental data. Brief conclusions are given by analyzing the parameter time history, global hydrodynamic force, peak pressure values at gauges and green water process.
Real-Time Deterministic Prediction of Ship Motion Based on Multi-Layer LSTM
Authors: He Guolian , Dong Guohua , Yao Chaobang , Sun Xiaoshuai
Published: September 2023

Ship motion prediction is applied to the ship maneuvering to keep the motion attitude stable all the time, which is of great practical significance to the safety and efficiency of the sailing and shipboard equipment operation. However, ship motion is a complex time-varying nonlinear process, which varies with sailing conditions and environmental factors. Long short-term memory (LSTM) deep learning model provides a potential way for nonlinear ship motion prediction due to its powerful capability in nonlinearity processing. Determination of a reasonable dimension of the input vector and output vector is critical in training the LSTM model. The input vector represents the hidden time autocorrelation in random ship motion, and the output vector is used to evaluate the prediction performance. Therefore, a ship motion prediction synthesis method based on multi-layer LSTM model is proposed. In the Bohai Sea, China, the original motion data are obtained and used as the basis for analysis and demonstration. Inevitably, there is high-frequency noise interference and low-frequency certain trend in the measured data. Low pass filtering and empirical mode decomposition (EMD) methods are used to remove noise. Based on the multi-layer LSTM model, the ship motion data under different speed conditions are analyzed, and the optimal relationship between input vector and output vector is investigated. Numerical results show that this method can improve the prediction result, and realize the prediction function for 20 timestep. This research is of great practicability for ensuring the safety of navigation and improving the efficiency of maritime operations and the intellectualization level of ships.
CFRP-Based Strengthening of Perforated Tubular Members
Authors: Hernández Irving D. , Vaz Murilo A. , Cyrino Julio C. R. , Martinez Jorge L. , Torres Victor D. , Perrut Valber A. , De Paula Gustavo G.
Published: September 2023

Steel offshore tubular members corrode over their lifespan. If there is inadequate protection, corrosion might lead to a perforation. The bulk of the time, techniques for repairing perforations in tubular steel structures include welding operations, which raise the risk of accidents when large areas are involved. Alternative repair procedures based on composite materials are gaining popularity since they do not require heat sources. However, there have been few investigations on its mechanical performance, and there are no guidelines for dimensioning strengthening repairs. In this study, a carbon fiber patch is used to strengthen perforated steel tubular members. The mechanical properties of the repair composite material were determined experimentally. A series of experimental tests on 1:3 scale samples of flare-boom structures, with varying perforation levels, are carried out to investigate the strengthening performance. This study also evaluates the effectiveness of a numerical model proposed to predict the performance of perforated steel tubular members reinforced with CFRP laminate and to estimate the suitable patch size. The numerical and experimental results indicated that strengthened tubes retrieved substantially higher compressive force than unrepaired tubes, suggesting the feasibility of this strengthening procedure with lower risk and shorter implementation times.