bluuebunny/crossref_metadata_2025 huggingface dataset:
A Pyrazolo Imine‐based Colorimetric and Turn‐on Fluorescent Sensor Probe for Determination of Hg2+ Ion and its Application in Test Paper Strips
Authors: Krishnan Uma , Iyer Sathiyanarayanan Kulathu
Published: October 2021

In this work, we synthesized diethylamino substituted pyrazolo imine (3) fluorescent probe for recognition of Hg2+ion.The sensor probe 3 can detect Hg2+ by colorimetric method, and there is a 10‐fold enhancement in fluorescence response. When the fluorescent probe bound with Hg2+ ion, turn‐on fluorescence was observed via the coordination. Probe 3 has an excellent selectivity toward Hg2+ in the CH3CN/H2O (8:2, v/v) solution with low limit of detection and high binding association constant of 551 parts per billion (ppb) and 6.6067 × 106 m−1 for 3+Hg2+, respectively. Furthermore, the formation of 3+Hg2+ complex with 1:1 binding mode was evidenced by Job's plot, 1H NMR spectroscopy and Mass analysis. In addition, probe 3 is a feasible option to detect Hg2+ in various sources of water samples. Bio‐imaging experiments have demonstrated that probe 3 can be used to monitor Hg2+ in Escherichia coli bacterial cell. The sensor 3 was also used for paper strip application to detect Hg2+ ion.
Characterization of the novel HLA‐C*06:312 allele by two next‐generation sequencing methods
Authors: De Olmos Orane Calvo , Bonneville Francoise , Blanchet Gaelle , Walencik Alexandre
Published: October 2021

The novel HLA‐C*06:312 allele was characterized using two next generation sequencing technologies.
Genome‐wide identification of seed storage protein gene regulators in wheat through coexpression analysis
Authors: Luo Guangbin , Shen Lisha , Zhao Shancen , Li Ruidong , Song Yanhong , Song Shuyi , Yu Kang , Yang Wenlong , Li Xin , Sun Jiazhu , Wang Yanpeng , Gao Caixia , Liu Dongcheng , Zhang Aimin
Published: October 2021

Only a few transcriptional regulators of seed storage protein (SSP) genes have been identified in common wheat (Triticum aestivum L.). Coexpression analysis could be an efficient approach to characterize novel transcriptional regulators at the genome‐scale considering the correlated expression between transcriptional regulators and target genes. As the A genome donor of common wheat, Triticum urartu is more suitable for coexpression analysis than common wheat considering the diploid genome and single gene copy. In this work, the transcriptome dynamics in endosperm of T. urartu throughout grain filling were revealed by RNA‐Seq analysis. In the coexpression analysis, a total of 71 transcription factors (TFs) from 23 families were found to be coexpressed with SSP genes. Among these TFs, TuNAC77 enhanced the transcription of SSP genes by binding to cis‐elements distributed in promoters. The homolog of TuNAC77 in common wheat, TaNAC77, shared an identical function, and the total SSPs were reduced by about 24% in common wheat when TaNAC77 was knocked down. This is the first genome‐wide identification of transcriptional regulators of SSP genes in wheat, and the newly characterized transcriptional regulators will undoubtedly expand our knowledge of the transcriptional regulation of SSP synthesis.
Risk factors for intracranial hemorrhage in adults with acute leukemia
Authors: Maze Dawn , Al‐Abri Mahmood , Farooq Khadija , Atenafu Eshetu G. , Nixon Shannon , Lieberman Lani
Published: October 2021

Background

Intracranial hemorrhage (ICH) is a rare, but serious complication in patients with acute leukemia. Little is known about why some patients experience serious bleeding, including ICH, while others do not.

Materials and Methods

Adults between 18 and 80 years old with acute leukemia and ICH between January 1, 2009 and December 31, 2016 were included. Matched controls were identified using the propensity score matching method. Clinical and laboratory characteristics and outcome data were collected to identify variables associated with ICH.

Results

Of 2578 patients diagnosed with acute leukemia during the study period, 55 cases and 161 matched controls were included. Patients who experienced ICH were older (62 vs. 55 years, p = .004) and more likely to have diabetes mellitus (p = .04). Patients with ICH had a higher baseline white blood cell count (mean 84.5 ± 115.8 vs. 28.7 ± 58.5 × 109/L, p = .001), peripheral blast count (61.3 ± 96.5 vs. 21.2 ± 50.8 × 109/L, p = .004), and a longer PT (16.5 ± 2.06 vs. 15.3 ± 3.2 s, p = .002). Neither the platelet count at diagnosis, the platelet nadir, the number of days with a platelet count of less than 10 × 109/L, or a diagnosis of platelet refractoriness were associated with ICH.

Conclusions

Older age and more proliferative disease appear to be associated with ICH, whereas thrombocytopenia alone does not. In patients with newly diagnosed acute leukemia, aggressive cytoreduction in those with leukocytosis may help mitigate the risk of ICH.
Relación entre patrimonio, política y territorio en el caso de Calcha (Potosí, Bolivia)
Authors: Müller Seborga Juliane Angie
Published: October 2021

Calcha es un término polisémico que puede referirse tanto al pueblo de Nuestra Señora de Calcha, como al Distrito Municipal Indígena del mismo nombre o al grupo étnico. El Distrito Municipal Indígena de Calcha, en el cual se encuentran tanto el pueblo como el grupo étnico, está ubicado en el Municipio de Vitichi, provincia Nor Chichas del departamento de Potosí. El gobierno municipal, en conjunto con las autoridades originarias, promulgó en 2017 la Ley Municipal N° 020 de declaratoria patrimonial, material e inmaterial, de la cultura calcheña, donde la vestimenta, los instrumentos, la música y las fiestas se reconocen como patrimonio cultural material e inmaterial.

El análisis de este proceso de activación patrimonial, entre los años 2017 y 2018, nos permitió visibilizar tres dimensiones correlacionadas que existen con respecto al patrimonio en general: economía, identidad y política. Inherente a toda activación patrimonial se encuentra la dimensión política, que comienza cuando las expresiones culturales son extraídas de su contexto; una acción realizada por parte de distintos grupos involucrados de tal forma que la expresión cultural cobra significados y usos diferentes.

Dentro de la dimensión política del patrimonio se encuentra la reconfiguración territorial de Calcha en el imaginario colectivo de sus habitantes y autoridades. A partir del año 2002 aparece el Jatun Ayllu o gran ayllu de Calcha que engloba a cinco distritos del Municipio de Vitichi. Teóricamente este gran ayllu pertenece a la Nación Chichas, una nación precolombina que se presume ocupaba parte del territorio de las actuales provincias de Sud Chichas y Nor Chichas. La Nación Chichas reaparece en el escenario nacional como un discurso de continuidad y reivindicación de los pueblos precolombinos. Forma parte importante de las leyes de declaratoria patrimonial de la cultura calcheña, que descansa sobre el pasado idealizado de una nación y un gran ayllu (re)construidos recientemente a partir de una herencia cultural que ellos consideran “ancestral”.

Dentro de esta dimensión política creemos que la declaratoria patrimonial tiene la función de: 1) brindar visibilidad y representatividad al grupo étnico a nivel regional y nacional. 2) legitimar a nivel regional y nacional la existencia de los territorios del Jatun Ayllu de Calcha y la Nación Chichas. Todo esto nos permite reflexionar acerca de las motivaciones que existen detrás de una activación patrimonial y sus posibles consecuencias, así como el de analizar la relación que existe entre las expresiones culturales declaradas y el pasado histórico, y la influencia mutua del patrimonio con la construcción territorial.

Palabras clave: Patrimonio cultural, territorio, política, Bolivia, Antropología
La figuración poética de la ruina en la última poesía de José Emilio Pacheco
Authors: Pascual Battista Rosario Pascual Battista
Published: October 2021

El presente artículo estudia en Como la lluvia [2001-2008] y La edad de las tinieblas [2009] la imagen poética de la ruina como un modo de responder al paso inevitable del tiempo. La enunciación en ambos libros se sostiene en un yo poético que, mientras identifica un mundo cada vez más inmerso en la destrucción, percibe la proximidad de la propia muerte. La ruina, entonces, está atravesada por el tópico del tiempo como marca de destrucción y señal de muerte; pero, como lo analizamos en este artículo, el tiempo también posibilita, mediante el valor del instante, contrarrestar ese mundo en ruinas y rescatar el valor de la poesía.
Tres autores caribeños: la esclavitud y la esfera pública decimonónica en las obras de Mary Prince, Mary Seacole y Martín Morúa Delgado
Authors: Maxwell Elsa
Published: October 2021

Este trabajo examina los escritos de tres autores caribeños decimonónicos que abordaron la esclavitud y la raza en sus obras: la narrativa de Mary Prince, una mujer esclavizada; el relato de viaje de la jamaiquina Mary Seacole, y la obra inicial del cubano Martín Morúa Delgado. Se analiza su relación con la esfera pública en un período en el cual las personas de color en el Caribe fueron mayoritariamente excluidas de los debates letrados que giraban en torno a la esclavitud. La investigación se enmarca en las teorías de la esfera pública y de los contrapúblicos, y dialoga con la periodización de la esfera pública caribeña propuesta por Raphael Dalleo.
Experimental Analysis and Modeling of a Novel Thermosyphon System for Electronics Cooling
Authors: Cataldo Filippo , Crea Yuri Carmelo
Published: October 2021

In an era of ever-growing digitalization, the absorbed power of processing units is becoming an actual challenge for cooling systems. The effectiveness is imperative, but compactness and passiveness are driving factors in the design as well. The goal of this paper is twofold: (1) to present a detailed experimental campaign on a thermosyphon system for high-heat-load electronics and (2) to propose a model of the thermosyphon system using a Machine Learning approach. The thermosyphon system is composed of a microchannel evaporator plate directly attached to the heat-generating device and an air-cooled multiport condenser. The height between the evaporator and condenser inlets is 12 cm. The condenser is also proposed in two solutions: the first one has a footprint heat exchange area of 180 × 120 mm2, which allows a single fan's placement; the second one has a footprint area of 240 × 120 mm2, allowing the placement of two fans. The working fluid used in the system is R1234ze(E) with different charges. The experimental results show that the single-fan condenser reached a maximum heat rejection of 330 W, corresponding to a heat flux of 21.9 W/cm2. The double-fan condenser bore a maximum heat rejection of 570 W (37.7 W/cm2). The model, constructed purely via a machine learning tool, shows a satisfactory agreement between experimental and predicted data.
The Wake Dynamics Behind a Near-Wall Square Cylinder
Authors: Addai Samuel , Fang Xingjun , Mante Afua A. , Tachie Mark F.
Published: October 2021

Particle image velocimetry is used to experimentally study the wake dynamics behind a near-wall square cylinder subjected to a thick oncoming turbulent boundary layer. The turbulent boundary layer thickness was 3.6 times the cylinder height (h) while the Reynolds number based on the freestream velocity and the cylinder height was 12,750. The gap distance (G) between the bottom face of the cylinder and the wall was varied, resulting in gap ratios (G/h) of 0, 0.3, 0.5, 1.0, 2.0, 4.0, and 8.0. The effects of varying the gap ratio on the mean flow, Reynolds stresses, triple velocity correlation, two-point autocorrelation, and the unsteady wake characteristics were examined. The results indicate that as gap ratio decreases, asymmetry in the wake flow becomes more pronounced, and the size of the mean separation bubbles increases. The magnitudes of the Reynolds stresses and triple velocity correlations generally decrease with the decreasing gap ratio. Moreover, the size of the large-scale structures increases with decreasing gap ratio, and the critical gap ratio, below which Kármán vortex shedding is suppressed, is found to be 0.3. The dominant Strouhal number in the wake flow expressed in terms of the streamwise mean velocity at the cylinder vertical midpoint increases as gap ratio decreases while that based on the freestream velocity is less sensitive to gap ratio for the offset cases (G/h > 0).
Process Monitoring in Ultrasonic Metal Welding of Lithium Batteries by Power Signals
Authors: Shi Xinhua , Li Lin , Yu Suiran , Yun Lingxiang
Published: October 2021

Ultrasonic metal welding is one of the key technologies in manufacturing lithium batteries, and the welding quality directly determines the battery performance. Therefore, an online welding process monitoring system is critical in identifying abnormal welding processes, detecting defects, and improving battery quality. Traditionally, the peak welding power is used to indicate abnormal process signals in welding process monitoring systems. However, since various factors have complex impacts on the electric power signals of ultrasonic welding processes, the peak power is inadequate to detect different types of welding defects. Therefore, a signal pattern matching method is proposed in this study, which is based on the electric power signal during the entire welding process and thus is capable of identifying abnormal welding processes in various conditions. The proposed method adopts isometric transformation and homogenization as signal pretreatment methods, and Euclidean distance is used to calculate the similarity metric for signal matching. The effectiveness and robustness of the proposed method are experimentally validated under different abnormal welding conditions.
B-Spline-Based Corner Smoothing Method to Decrease the Maximum Curvature of the Transition Curve
Authors: Huang Nuodi , Hua Li , Huang Xi , Zhang Yang , Zhu Limin , Biermann Dirk
Published: October 2021

Toolpath represented by linear segments leads to tangency discontinuity between blocks, which results in fluctuation of feedrate and reduction of machining efficiency and quality. To eliminate these unwanted external factors, optimal corner smoothing operation is essential for computerized numerical control systems to achieve a smooth toolpath. This work proposes a corner smoothing approach by generating a B-spline transition curve with seven control points. By adjusting the position of the control points, the resulting transition curve is not limited to smooth the corner in the convex side of the corner, but shuttles back and forth between the convex and concave sides to decrease the maximum curvature, while respecting the given error tolerance. The approximation errors in convex and concave sides can be analytically calculated. Experimental results demonstrate the effectiveness of the proposed method on machining efficiency improvement.
Towards Safety Barrier Analysis of Hydrogen Powered Maritime Vessels
Authors: Balestra Lorenzo , Yang Ruochen , Schjølberg Ingrid , Utne Ingrid B. , Ulleberg Øystein
Published: October 2021

This paper focuses on the use of safety barrier analysis, during the design phase of a vessel powered by cryogenic hydrogen, to identify possible weaknesses in the architecture. Barrier analysis can be used to evaluate a series of scenarios that have been identified in the industry as critical. The performance evaluation of such barriers in a specific scenario can lead to either the approval of the design, if a safety threshold is met, or the inclusion of additional barriers to mitigate risk even further. By conducting a structured analysis, it is possible to identify key barriers that need to be included in the system, intended both as physical barriers (sensors, cold box) and as administrative barriers (checklist, operator training). The method chosen for this study is the Barrier and Operational Risk Analysis (BORA) method. This method, developed for the analysis of hydrocarbon releases, is described in the paper and adapted for the analysis of cryogenic hydrogen releases. A case study is presented using the BORA method, developing the qualitative barrier analysis. The qualitative section of the method can be easily adapted to vessels of different class and size adopting the same storage solution. The barrier analysis provides a general framework to analyze the system and check that the safety requirements defined by the ship operator and maritime certification societies are met.
Mooring Designs for Floating Offshore Wind Turbines Leveraging Experience From the Oil & Gas Industry
Authors: Ma Kai-tung , Wu Yongyan , Stolen Simen Fodstad , Bello Leopoldo , ver der Horst Menno , Luo Yong
Published: October 2021

As renewable energy developers start venturing into deeper waters, the floating offshore wind turbines (FOWTs) are becoming the preferred solutions over fixed supporting structures. Many similarities can be identified between a FOWT and a floating oil & gas facility, such as floater concepts (spar, semi-submersible, tension leg platform, etc) and their mooring system designs. This paper focuses on the mooring designs for FOWTs by leveraging the extensive experience gained from the offshore oil & gas industry. Similarities and differences are highlighted in design criteria, mooring analysis, long-term integrity management, installation method and project execution. The established practices regarding mooring design and analysis are reviewed. Anchor radius is recommended based on water depth by referencing sample mooring designs from the oil & gas industry. Long-term mooring integrity and failure rates are summarized. Meanwhile, a few well-known issues are discussed, such as line break due to fatigue, corrosion on chain, and known issues with components such as clump weights. Regarding mooring installation, the established method for prelay and hook-up is reviewed. Finally, opportunities for cost reduction of mooring systems of FOWTs are presented related to project execution of large scale wind farms as well as potential areas of innovation, such as installation methods, use of synthetic fiber rope, and digitalization. In summary, the state-of-the-art practices from the oil & gas industry are reviewed and documented to benefit the developments of upcoming FOWT projects.
Experimental and Numerical Study of the Influence of Drag Coefficient on Snap Loads in Mooring Lines of a Floating Offshore Wind Turbine
Authors: Guillouzouic Brendan , Pétrié François , Lafon Vincent , Fremont Fabien
Published: October 2021

Mooring is one of the key components of a floating offshore wind turbine since the mooring rupture may lead to the total loss of one or even several turbines in a farm.

Even if a large experience in moorings of floating bodies was gained in the oil & gas industry, the renewable energies face new challenges such as reducing the cost as much as possible, reducing the footprint to limit environmental impact or avoid any interference between mooring lines and electrical cables in a farm composed of several tens of turbines.

Those constraints may lead to designs suffering snap loads which shall be avoided as far as practicable or addressed with a particular attention, as this quasi-instantaneous stretching of the mooring lines may lead to very high tensions governing the design.

This paper presents the results of physical model tests and numerical simulations performed on a typical floating wind turbine concept of semi-submersible type. Both qualitative and quantitative comparisons are performed. The objective is to provide guidelines for FOWT mooring designers regarding the selection of the drag coefficient to consider.

A very significant influence of the line’s drag coefficient, on both the probability of occurrence and the magnitude of snap loads, was found. This subject is hereby fully documented on a given case study and general discussions on scale effects, marine growth effects and other parameters are also made.

The numerical simulations were performed using the dynamic analysis software ‘OrcaFlex’.

The experiments have been carried out by Océanide, in south of France.
Numerical Estimation of Relative Wave Elevation on a Semi-Submersible Vessel
Authors: Lena Christian , van Basten Batenburg Rinnert
Published: October 2021

Ambition of this research was to numerically reproduce the relative wave elevations measured on and around a semi-submersible vessel during model tests performed at MARIN (Maritime Research Institute of the Netherlands).

Model tests were performed on a semi-submersible model representing, in different setup configurations, a heavy lift vessel and a LPD (Landing Platform Dock). Relative wave elevations were measured at 47 locations on and around the vessel. Tests were made with different regular wave conditions and headings, at anchor, with the model fixed in a soft mooring setup. Data from model tests were used to calibrate and run a time domain potential flow boundary element tool with particular focus on the relative wave elevation at the 47 locations. A comparison between numerical and experimental results is proposed in this paper.
Implementation of a Method for Free-Spanning Pipeline Analysis
Authors: Gullaksen Joannes
Published: October 2021

The scope of this paper is to provide a method implemented in an application for assessment of dynamic response of free spanning pipelines subjected to combined wave and current loading. The premises for the paper are based on application development within pipeline free span evaluation in a software development project. A brief introduction is provided to the basic hydrodynamic phenomena, principles and parameters for dynamic response of pipeline free spans. The choice of method for static and dynamic span modelling has an influence on calculated modal frequencies and associated stresses. Due to the importance of frequencies and stresses for fatigue and environmental loading calculations, the choice of analysis approach influences the partial safety factor format. The aim of the structural analysis is to provide the necessary input to the calculations of VIV and force model response, and to provide realistic estimations of static loading from functional loads. Environmental flow conditions are implemented in the application, such as steady flow due to current, oscillatory flow due to waves and combined flow due to current and waves. Combined wave and current loading include the long-term current velocity distribution, short-term and long-term description of wave-induced flow velocity amplitude and period of oscillating flow at the pipe level and return period values. Inline and cross-flow vibrations are considered in separate response models. For pipelines and risers, modes are categorized in in-line or cross-flow direction. A force model is also considered for the short-term fatigue damage due to combined current and direct wave actions. Design criteria can be specified for ultimate limit state (ULS) and fatigue limit state (FLS) due to in-line and cross-flow vortex induced vibrations (VIV) and direct wave loading.
Pressure Losses Generated by a Thixotropic Fluid When Subject to an Oscillating Flowrate
Authors: Cayeux Eric , Leulseged Amare
Published: October 2021

Rapid variations in the fluid velocity field influence pressure loss calculations. In this paper, we propose numerical methods for estimating pressure losses in a circular pipe when the flow rate oscillates. The method is described for Newtonian and two non-Newtonian rheological behaviors: the power law and the Quemada models. Also, as drilling fluids are usually thixotropic, i.e., their rheological behavior depends on the shear history, an expansion of the Quemada model is proposed to account for shear history effects.

A laboratory flow-loop has been assembled and measurements conducted with a non-thixotropic aqueous solution of Carbopol and a thixotropic potassium chloride solution of xanthan gum. The measurements were analyzed and compared with estimates made with the proposed models.

It is found that when applying a square wave oscillating flowrate to a non-thixotropic fluid, large surge and swab pressure spikes are generated. The same square wave signal does not produce pressure spikes when circulating a thixotropic fluid; on the contrary the acceleration and deceleration fronts are largely attenuated.

When applying a triangular or sinusoidal wave form to the flowrate while circulating a non-thixotropic fluid, the peak-to-peak pressure gradient gets progressively larger when the oscillation amplitude increases or the signal period reduces, compared to the expected value when estimating the pressure losses with the steady state approximation. However, under the same conditions, when circulating a thixotropic fluid, the peak-to-peak pressure gradients are lower than those estimated with the steady state approximation.
Uplift Capacity of Suction Caissons in Sand for General Conditions Of Drainage
Authors: Gogoi Ragini , Aubeny Charles P. , Watson Phillip , Bransby Fraser
Published: October 2021

Suction caissons have emerged as a viable solution for the foundations of offshore wind turbines, which are gaining momentum worldwide as an alternate energy source. When used in a multi-bucket jacket system, the system capacity is often governed by the uplift capacity of the windward bucket foundation. Seabed conditions at offshore windfarm sites often comprise dense sand where the soil response may be drained, partially drained or undrained depending on the loading regime, the foundation dimensions and the soil conditions. Given the large difference in uplift capacity of caissons for these different drainage conditions, predicting the behavior of a suction caisson under a range of drainage conditions becomes a paramount concern. Consequently, this paper presents the findings of a coupled finite element investigation of the monotonic uplift response of the windward caisson of a multi-bucket jacket system in a typical dense silica sand for a range of drainage conditions. The study adopts a Hypoplastic soil constitutive model capable of simulating the stress-strain-strength behavior of dense sand. This choice is justified by conducting a comparative study with other soil models — namely the Mohr Coulomb and bounding surface sand models — to determine the most efficient soil failure model to capture the complex undrained behavior of dense sand. The numerical predictions made in this study are verified by recreating the test conditions adopted in centrifuge tests previously conducted at the University of Western Australia, and demonstrating that the capacity from numerical analysis is consistent with the test results. The Hypoplastic soil constitutive model also provides an efficient method to produce accurate load capacity transition curves from an undrained to a drained soil state.
Experimental Study on Plugging Inside a Pipe Using Carbonated Ice as a Substitute for Methane Hydrate
Authors: Yamamoto Joji , Yamamoto Marcio , Nakajima Yasuharu , Takano Satoru , Kanada Shigeo , Ono Masao , Otsubo Kazuhisa
Published: October 2021

Methane hydrate has been found below the seafloor in the Exclusive Economic Zone (EEZ) of Japan in a large amount. During the methane hydrate transportation, it is concerned that the riser pipe or the flowline can be plugged by the hydrate reformation and the freezing of seawater. The degradation and reformation kinetics of methane hydrate are mainly controlled by temperature, pressure, and methane concentration in the system; however, it is difficult to predict these factors in the multiphase flow because they are affected by fluid dynamics and heat transfer. To obtain the experimental data of the degradation kinetics, we developed a closed-loop experimental apparatus consisting of jacketed tubings used as heat exchangers, three acrylic units to observe the flow, and a slurry pump. The flow rate, salinity, temperature, and pressure in the apparatus were continuously measured in the circulation experiments. The experiment results showed that the freezing condition of the fluid in the pipe is affected by the temperature of the outside of the pipe or the particle in the fluid. This paper reports some experimental data obtained in several cases, including those conducted under freezing conditions.
Experimental Investigation of Fluid-Structure Interaction in Linked Flexible Net Cages
Authors: Dong Shuchuang , Zhou Jinxin , Li Qiao , Yoshida Takero , Kitazawa Daisuke
Published: October 2021

In the present study, three flexible net cage groups (a single net cage, two net cages arrayed in one column, and three net cages arrayed in one column) were investigated in a flume tank, in order to analyze the hydrodynamic characteristics of the flow and linked flexible net cage, such as the drag force, cage deformation, and flow field inside and around. Based on these results, the fluid-structure interactions of the flexible net cage were discussed. The drag forces and cage deformation of a single flexible net cage were first studied, and their relationships to the current speed were found consistent with existing literature. The averaged current speed inside the single net cage was 0.72 for all incoming current speeds. Furthermore, significant current speed reductions occurred behind the single net cage, at the downstream, for all incoming current speeds. Within the measurement range, the current speed reduction area downstream from the single net cage was almost as wide as the cage diameter, and the length was up to 1.4 times cage diameters along the incoming current direction. The location of this area gradually approached the water surface as the current speed increased. In the case of two flexible net cages arrayed in one column, the differences in drag force occurred when the distance between the two cages was changed. In addition, the current speed incident on the downstream cage tended to decrease, as the distance between the cages increased. The averaged current speeds incident on the downstream cage were 0.54, 0.44, 0.77, and 0.40 when the distances between two cages were 30.0 cm, 60.0 cm, and 90.0 cm, respectively. In the case of three flexible net cages arrayed in one column, the total drag force of three flexible net cages was 2.2 times that of a single net cage. On the other hand, at the maximum current speed of 50 cm/s, the cross-sectional areas of the first net cage, the second net cage, and the third net cage were 177.10 cm2, 274.19 cm2, and 277.37 cm2, respectively. Overall, the findings of this study could not only help to understand and optimize flexible net cage structures but also provide useful information for the configuration of the net cages at the farm sites.
Numerical Towing Model for LNG Carrier Approach in Exposed Environment Calibrated With Full-Scale Measurements and Operability Criterion
Authors: Auburtin Erwan , Delivré Quentin , McConochie Jason , Brown Jim , Drobyshevski Yuriy
Published: October 2021

The Prelude Floating Liquefied Natural Gas (FLNG) platform is designed to offload liquefied natural and petroleum gas products to carrier vessels moored in a Side-by-Side (SBS) configuration. Prior to the mooring operation, the carrier vessel is escorted and held alongside the FLNG with the assistance of tugs connected to her bow and stern to ensure sufficient control over the vessel in this critical phase.

In order to better understand the impact of environmental conditions, to determine the optimum length, strength, material and configuration of the towline stretcher, and to estimate the maximum operable environments, coupled multi-body simulations have been performed in time domain. The numerical model, which considered both the LNG carrier and the forward tug, was calibrated using full-scale measurements of tug motions and tow line tension recorded during a real approach and berthing manoeuvre at Prelude FLNG.

The measured environment effects were generated numerically and the model parameters were adjusted to reproduce the recorded behavior as accurately as possible. Since actions of the tug master are difficult to model numerically and only the statistical environment parameters are known, a simplified approach has been adopted for modelling the tug propulsion and steering using a combination of static forces, stiffness and linear and quadratic damping for relevant horizontal degrees of freedom.

The calibrated numerical model was first subjected to several sensitivity assessments of the modelling level (single- or multi-body, inclusion of second-order wave loads, inclusion of forward speed). Then sensitivity studies were performed to help address operational requirements related to the wave height and direction, and the stretcher length and strength. The conclusions have been taken into consideration for the selection of the tow line configurations for future operations.

Finally, the calibrated coupled LNG carrier and tug model was used to derive Prelude-specific tug operability criteria that may be used for decision-making based on weather forecasts, prior to the SBS offloading operations. A large matrix of swell and wind driven waves was simulated over a range of wave heights, periods, directions and static towing forces to allow a criterion to be developed based on a stochastic extreme tow line tension. Such criterion considers relevant wave parameters while remaining simplified enough for easy use in operations.

This paper describes the assumptions and process to numerically model the towing configuration and calibrate the different coefficients, discusses the results obtained for the various sensitivities, and explains the operability criteria. Important conclusions and lessons learnt are also shared.
First Iteration Design of the Flotant Concept
Authors: Serret Jordi , Kahn Bernardo , Cavanagh Bruce , Lorente Patricia , Pascal Remy , Girandier Clementine , Cortes Carlos , Duran Ruben , McEvoy Paul , Castro Ayoze
Published: October 2021

This paper presents the first iteration design of the Flotant concept developed within the framework of a Cooperation Research Project funded by the European Union’s Horizon 2020 research and innovation programme. The Flotant concept is a hybrid concrete-plastic barge-type floating offshore substructure holding a 12MW wind turbine with the singularity of getting floatability by using plastic foam material fitted within the floater substructure.

The INS12MW generic wind turbine, an upscaling exercise based on the DTU10MW reference wind turbine, is presented and simulated using open-source certified aeroelastic code.

The floating platform and the mooring system are designed for two different sites, West of Barra and South East of Gran Canaria island. The principal dimensions are presented along with the hydrostatic and hydrodynamic properties of the floating system.

A relevant subset of design load cases derived from International Electrotechnical Commission and Det Norske Veritas standards was simulated using an open-source aeroelastic code (NREL FAST) to check the coupled aero-hydro-elastic behaviour of the floating system and to generate the required load-matrix for the structural assessment of the different components.

The evaluation of the design includes the seakeeping performance, the stability of the floating platform and the global performance analysis for the abovementioned sites. It demonstrates the technology developed within the Flotant project is feasible even in rough conditions like the ones in the West of Barra site.
On Uncertainty Assessment of Fatigue Damage of Propulsion Shaft Under Ice Impact
Authors: Purcell Etienne , Nejad Amir R. , Valavi Mostafa , Bekker Anriëtte
Published: October 2021

In this paper, the importance of maintenance of marine propulsion is discussed with specific focus on the use of condition monitoring to inform maintenance schedules. The design requirements of DNV GL for shafts expected to operate in ice infested waters is adapted and a method is proposed to calculate the short-term fatigue damage during ice impacts. This method uses the Palmgren-Miner rule to calculate fatigue damage based on a transient, lumped-mass model simulation of the shaft with ice loads calculated from shaft measurements using inverse methods. Relevant sources of uncertainty in this assessment method are identified and quantified in order to express the short-term fatigue damage in a stochastic form. Sources of uncertainty include uncertainty in the calculation of ice loads, uncertainty of the transient analysis and uncertainty regarding the actual failure of the shaft as predicted by the S-N material curve and the Palmgren-Miner method. Uncertainties that influence the stress history are found to be the greatest contributor to fatigue damage uncertainty. A method is discussed that calculates the remaining useful life of the shaft as a function of short-term fatigue damage and the identified sources of uncertainty. The S.A. Agulhas is used as a case study to quantify the fatigue damage.
The Influence of Leading-Edge Tubercles on the Sheet Cavitation Development of a Benchmark Marine Propeller
Authors: Stark Callum , Shi Weichao
Published: October 2021

Cavitation is an undesirable phenomenon in the maritime industry as it causes damage to the propeller, degrading hydrodynamic performance and increasing the subsequent underwater radiated noise (URN). Therefore, mitigating cavitation on marine propellers is an important area of research in order to reduce carbon emissions emitted from the shipping industry and reduce the rate at which ocean ambient noise levels are increasing. The Humpback whale has provided inspiration to research in the fluid-structure interaction field due to the presence of leading-edge (LE) tubercles on the pectoral fins that allow it to perform acrobatic maneuvers to catch prey. This paper assesses the cavitation containment capability of the LE tubercles on a benchmark marine propeller in both heavy and light cavitating conditions using commercial code STAR-CCM+, unsteady incompressible Reynolds-averaged Navier Stokes (RANS) solver and the Schnerr-Sauer cavitation model to quantify the sheet cavitation present over a range of operating conditions. In summary, in heavy-cavitating conditions, a reduction in sheet cavitation with the inclusion of LE tubercles was observed to a maximum value of 2.75% in all operating conditions considered. A maximum improvement of 3.51% and 1.07% was predicted in propulsive thrust and hydrodynamic efficiency, respectively. In light cavitating conditions, although in some conditions a reduction in cavity volume was observed, this did not result in an improvement in hydrodynamic performance.
A Reactive Flex Joint System for Reducing Wellhead Fatigue: Analysis and Measurement
Authors: Gustad Halvor S. , Moe Per Thomas , Fjeldstad Dag André , Sønåsen Knut Olav , Bjørset Arve
Published: October 2021

The Reactive Flex-Joint (RFJ) is a nitrogen gas torsion springfully integrated in the LMRP-BOP stack. Its purpose is to reduce the dynamic loads and the fatigue damage applied to wellheads during drilling operations. The system achieves the reduction by applying a bending moment opposing and inverting the bending moment at the Lower Flex-Joint (LFJ). The RFJ is continuously monitored by the WAMS measurement system.

The second generation RFJ has been extensively tested in a full scale workshop test rig before being shipped offshore for a year of operations on two semi-submersible rigs operating in the North Sea/Barents Sea. This paper demonstrates by calculation and measurement that the RFJ is capable of reducing wellhead loads by more than 50% and the wellhead fatigue by more than 95%. The accuracy of the measurement system is discussed.
Structural Analysis and Load Monitoring of a Loss of Tension Incident
Authors: Fjeldstad Dag André , Liu Junyan , Moe Per Thomas , Gustad Halvor S. , Hansen Mathias , Bjørset Arve
Published: October 2021

Monitoring of riser motion and loads is increasingly being used to assess metal fatigue and to assist rigs in operating safely. Monitoring systems provide valuable information on unexpected incidents. This paper shows how sensor data have been used in combination with structural analysis to assess consequences of a loss of tension for a top-tensioned CWO riser. In order to avoid that a single failure in a tensioning system causes total loss of tension and riser buckling risers should be operated using both rucker tensioners and top drive. However, prior to the retrieval of the riser only top tension was applied. Due to a power out the top drive tension was lost, and the resulting set down caused the riser to buckle. The consequence could in the worst case have been permanent damage to key riser components such as the Lower Tapered Stress Joint and Weak Link. However, as the riser was equipped with a monitoring system that provided accurate data on deformation at key locations, it was possible to show that the system had not been exposed to permanent deformations and could be safely used further. It is advisable to perform continuous monitoring of tension and put in place mitigation to avoid that such incidents lead to permanent damage in the future.
Benchmark Study of Supervised Machine Learning Methods for a Ship Speed-Power Prediction at Sea
Authors: Lang Xiao , Wu Da , Mao Wengang
Published: October 2021

The development and evaluation of energy efficiency measures to reduce air emissions from shipping strongly depends on reliable description of a ship’s performance when sailing at sea. Normally, model tests and semi-empirical formulas are used to model a ship’s performance but they are either expensive or lack accuracy. Nowadays, a lot of ship performance-related parameters have been recorded during a ship’s sailing, and different data driven machine learning methods have been applied for the ship speed-power modelling. This paper compares different supervised machine learning algorithms, i.e., eXtreme Gradient Boosting (XGBoost), neural network, support vector machine, and some statistical regression methods, for the ship speed-power modelling. A worldwide sailing chemical tanker with full-scale measurements is employed as the case study vessel. A general data pre-processing method for the machine learning is presented. The machine learning models are trained using measurement data including ship operation profiles and encountered metocean conditions. Through the benchmark study, the pros and cons of different machine learning methods for the ship’s speed-power performance modelling are identified. The accuracy of various algorithms based models for ship performance during individual voyages is also investigated.
Performance Modeling of a Variable-Geometry Oscillating Surge Wave Energy Converter on a Raised Foundation
Authors: Burge Cole , Tom Nathan , Thiagarajan Krish , Davis Jacob , Nguyen Nhu
Published: October 2021

This paper analyzes the power capture potential, structural loadings, and costs associated with an oscillating surge wave energy converter (OSWEC) operating on a raised foundation. The raised OSWEC offers opportunities for reduced installation costs, improved energy production, and greater flexibility of deployment when compared with fixed-bottom models. In this investigation, we simulated several different foundation geometries using WEC-Sim to estimate power capture and structural loads. In an effort to maximize power capture, several cases in which flat plates of varying size were attached to the top of the foundation, under and parallel with the OSWEC, were also simulated. These plates were found to enhance power capture by preventing the wave-induced pressure from passing underneath the OSWEC, diverting this pressure toward the OSWEC instead. The OSWEC was simulated in the six Wave Energy Prize sea states, which were chosen as a representative sample of U.S. deployment sites. A first-order estimate of structural costs was calculated using the Wave Energy Prize ACE metric, with the foundation comprised predominantly of steel-reinforced concrete and the OSWEC comprised of A36 steel. Influence of foundation geometry on power capture, structural loadings, and ACE are topics of particular interest. This work has been inspired by advances in large-scale additive manufacturing techniques that have the potential to dramatically reduce the cost of subsea foundations. These advancements may enable cost-effective WEC systems to be deployed on raised foundations.
On Lifetime Extension of Wind Turbine Drivetrains
Authors: Tartt Kelly , Nejad Amir R. , Kazemi-Amiri Abbas , McDonald Alasdair
Published: October 2021

The focused shift to reduce carbon emissions by substituting fossil fuels with renewable energy sources, including wind, is increasing. This means that more and more wind turbines are being installed, both onshore and offshore and as this number increases, more and more turbines are reaching their end of designed service life. Extending this designed service life, which is commonly referred to as lifetime extension (LTE), is particularly favoured by owner/operators, due to economic reasons. Whilst there are relatively well-established practices for lifetime extension of structural members or those preserving structural integrity, the electro-mechanical and drivetrain systems are often overlooked. Therefore, this paper reviews lifetime extension assessment practices executed within a variety of industries, such as oil and gas, marine vessels, electrical machines, mechanical rotating equipment and bearings, to determine if any of these practices can be implemented or adapted within the wind industry, particularly on wind turbine drivetrains.
Numerical Analysis of Cuttings Accumulation Tendency in Horizontal Annulus at Different Drilling Conditions
Authors: Rasul Golam , Rahman Mohammad Azizur , Butt Stephen
Published: October 2021

The influence of rotational speed and eccentricity of the drill pipe as well as the effect of fluid flow rate on the accumulation of cuttings in the horizontal annulus are the focus of this study. Computational Fluid Dynamics (CFD) is utilized to model a horizontal annulus section which conveys solid-liquid two-phase flow at different drilling conditions. In this numerical study, the Eulerian multiphase flow model has been adopted for solidliquid characteristics analysis. Here the basic continuity and momentum equations have been considered, which have further been reduced to solve the conservation of mass and momentum equations with appropriate boundary and initial conditions. The study has considered the transient, turbulent model (k-epsilon) with no-slip conditions at pipe walls as well as velocity inlet and pressure outlet at the boundaries. The result indicates the clear impact of rotational speed on the cuttings removal process in the horizontal annulus section. As the rotational speed of the drill pipe increases, the cuttings concentration drops down significantly in the annulus section. Around 20% less accumulation is noticed if the drill pipe rotation is increased from 0 RPM to 120 RPM, which happens due to momentum created by the rotation that does not allow the particles to be accumulated. The eccentricity has a significant impact on solid accumulation as well. However, with increased flow rate and eccentricity, the pressure across the annulus section drops substantially. The difference in pressure drop is noticed as much as around 61 Pa/m with the flow rate change. Consequently, a higher pressure drop per length for the higher velocity of fluid implies higher pumping power consumption. The findings from this study may help to understand the optimum operating conditions for horizontal drilling. The effects of drilling conditions are identified and the complex multiphase flow in the annulus is modeled that could be extended to further related studies.