bluuebunny/crossref_metadata_2025 huggingface dataset:
Rejection sensitivity and mental well‐being: The positive role of friendship quality
Authors: Efeoglu Begum , Sen Celia K. Naivar
Published: October 2021

Previous research shows a link between rejection sensitivity (RS) and various psychological disorders; however, its relation to the positive psychological construct of mental well‐being remains unstudied. This study investigates the relationship between RS and mental well‐being while taking the role of friendship quality into consideration for 323 emerging adults using decision tree analysis. In training (R2 = .29) and test trees (R2 = .18), RS had the strongest relationship with mental well‐being where those higher in RS had lower mental well‐being scores. For those lower in RS, higher combined (same‐sex and opposite‐sex) friendship quality was associated with higher mental well‐being. Whereas for those higher in RS, higher same‐sex friendship quality was associated with higher mental well‐being. As our findings indicate, friendship quality may play a buffering role for emerging adults, keeping their mental well‐being at more preferable levels especially for those with higher RS. Implications for future studies and interventions to boost friendship quality are discussed.
The unrevisability of logic
Authors: Hofweber Thomas
Published: October 2021

Can it ever be rational to revise one's own logic by one's own lights? In this paper I argue that logic is never rationally revisable, even if one's own logic gives rise to paradoxes and allows one to derive any conclusion whatsoever. Instead of revising logic, we need to revise a certain widely held position in the philosophy of logic, one tied to the standard conception of validity and to the alleged monotonicity of deductive reasoning. I develop the alternative conception of validity and of deductive reasoning, which explains why we are generally entitled to the conclusions of deductive reasoning, even though we rationally do not accept them in certain circumstances tied to paradoxes.
Intergovernmental Representation at Different Levels of Government: The Effect of Gender Representation
Authors: Park Sanghee , Charles Mwihambi Yesse
Published: October 2021

This study examines whether and where bureaucratic representation occurs within the bureaucratic hierarchy and how intergovernmental representation contributes to government efforts to reduce social disparities and improve gender‐related outcomes. The context is the national/central, ministerial, and regional governments of the United Republic of Tanzania for 14 years (2006–2019). The findings reveal that gender representation at the upper level of government plays a primary role in reducing poverty, but its impact on women's socioeconomic status, i.e., women's education and unemployment rate, is limited within the study context. The findings also highlight that the existence and the impact of intergovernmental representation depend on the primary missions of the government at different levels, policy outcomes of interest, and social contexts where identities are constructed and interpreted. This study claims that the potential interdependence of bureaucratic representation across multiple government agencies and institutions deserves more attention in the representative bureaucracy scholarship.
Environmental enrichment in fish aquaculture: A review of fundamental and practical aspects
Authors: Arechavala‐Lopez Pablo , Cabrera‐Álvarez Maria J. , Maia Caroline M. , Saraiva Joao L.
Published: October 2021

Environmental enrichment (EE) can improve the welfare of captive fish. Its objective is to provide new sensorial and motor stimulation in order to help meet their behavioural, physiological, morphological and psychological needs, whilst reducing stress and frequency of abnormal behaviours. In fish farms, rearing environments are usually designed from a human perspective and based on economic requirements, mainly for practical reasons for the farmer, with little consideration for animal welfare. Throughout aquaculture production cycles, many farming operations can be stressful for fish, and EE may not only help them cope with these stressful events but also improve their overall welfare. In recent years, increasing interest on the effects of EE in captive fish has focussed mainly on structural enrichment. However, there are many other enrichment strategies that merit attention (e.g. sensorial, occupational, social and dietary enrichment) and which may be of interest for fish farming. Here, we review in depth the existing literature on EE and its effects on the welfare of a wide range of farmed fish species, discussing the feasibility and potential applications of different EE strategies to promote fish welfare at a commercial scale. We also present a practical framework to address the design, validation and implementation of EE by the aquaculture industry, taking in consideration the technical challenges of providing enrichment for farmed fish.
Are importing and exporting complements or substitutes in an emerging economy? The case of Colombia
Authors: Gómez‐Sánchez Andrés Mauricio , Mañez Juan A. , Sanchis‐Llopis Juan A.
Published: October 2021

The aim of this paper is to investigate the impact of two trading strategies (exporting and importing) on total factor productivity (TFP) and the potential complementarity/substitutability effects of these strategies. In order to assess these effects, robust estimates of TFP are obtained using a general method of moments approach that explicitly determines the ability of a firm's trading experience to affect productivity. Data from the Annual Manufacturing Survey spanning from 2007 to 2016 is used for Colombian manufacturing firms. Our estimation results suggest that, regardless of the technological intensity of the industry in which the firm operates, active trading strategies (exporting only, importing only, both importing and exporting) pay positive rewards in terms of productivity. Nevertheless, whilst positive (complementary) synergies are found between exporting and importing for firms in med/high‐tech sectors, for firms operating in low‐tech and med/low‐tech sectors, importing and exporting appear to be substitutes.
Call to arms: Research directions to substantiate a unified model of attachment and personality pathology
Authors: Smith Madison Shea , South Susan C.
Published: October 2021

Personality pathology and adult attachment are “made of the same stuff” (Meyer & Pilkonis, 2005). They share crucial phenomenological features, etiologies, and genetic bases; however, these shared features have not been appropriately represented in empirical literature as reflective of a common dysfunction. Continuing to conceptualize attachment and personality pathology as separable constructs shackles clinical efforts, particularly with regard to identifying persons and relationships that may be most prone to interpersonal problems. In the current review, we argue that adult attachment and personality pathology may indeed be iterations of the same underlying dysfunction, and that empirical work conducted to date has been insufficient in this characterization. We also argue that to accurately represent the nature of attachment and personality pathology, the empirical integration of interpersonal dysfunction must be conducted across nosologies, demographic groups, and time. We support our arguments using empirical, theoretical, and clinical material that demonstrates the unity of attachment and personality disorders.
The novel HLA‐DQB1*03:445 allele was identified in two unrelated bone marrow donors from Russia
Authors: Ananeva Anastasiia , Nizamov Shamil , Shagimardanova Elena
Published: October 2021

HLA‐DQB1*03:445 has one nucleotide change from HLA‐DQB1*03:03:02:01 at nucleotide 692.
Cerámica Panzaleo y Puruhá como recurso para el diseño artesanal en la Parroquia Sucre del cantón Patate.
Authors: Bedón Vaca Concepción Del Carmen
Published: October 2021

El presente trabajo centra su investigación en el análisis del conjunto cerámico de las culturas Panzaleo y Puruhá registradas en la Parroquia Sucre (Provincia de Tungurahua, Ecuador), mediante la identificación iconográfica de sus elementos simbólicos. El desarrollo de la propuesta parte de una investigación de campo; de la observación directa de la composición estética de las piezas cerámicas, con la finalidad de caracterizar los vestigios en relación a su funcionalidad en contextos domésticos, ceremoniales y/o rituales, de los cuales se desprenden las categorías formales de las actividades realizadas en el sitio de hallazgo. El resultado final del análisis, lo constituye el registro catalográfico, compuesto por procesos morfológicos, criterios geométricos y atributos del diseño como la simetría, estructura, contorno, forma, dimensiones y espesor, lo cual permite, mediante la interpretación formal: la identificación analógica y la estructuración de nuevas alternativas artesanales dirigidas al desarrollo social, cultural y productivo de la zona. Palabras clave: Puruhá - Panzaleo; Parroquia Sucre; morfología; iconografía
Magdalenas americanas: “endemoniadas” novohispanas ante la Inquisición
Authors: Schlau Stacey
Published: October 2021

La causa de Bárbara de Echegaray ejemplifica la aplicación del vínculo del cuerpo femenino, la sexualidad y la acusación de tener relaciones íntimas con el diablo. El proceso se llevó a cabo a finales del siglo XVIII, cuando ya entraban las nuevas corrientes filosóficas de la Ilustración en la Colonia, pero el texto refleja poco más que la versión de la cosmovisión católica ya normalizada en el siglo y medio anterior. En este ensayo, se analiza el choque entre la autoexpresión femenina y los preceptos que se predicaban en los sermones y que se enseñaban en el confesionario, en torno a la realidad percibida y al simbolismo del demonio como un elemento antagónico al progreso espiritual. Enfocándose en la figura de Bárbara de Echegaray, con referencia a otras castas coloniales en la Nueva España, se investiga el nexo genérico-sexual y las normas socioreligiosas, para revelar cómo se articula el libre albedrío cuando se confronta con la ideología eclesiástica hegemónica.
Numerical Analysis of Thermal, Fluid, and Electrical Performance of a Photovoltaic Thermal Collector at New Micro-Channels Geometry
Authors: Hoseinzadeh Siamak , Garcia Davide Astiaso
Published: October 2021

In this article, different paths (direct, spiral, and curved) for water flow in a photovoltaic/thermal (PV/T) system are studied, and they are compared together. The intensity of radiation to the cell surface is taken 800 W/m2, and the fluid flow is considered to be laminar in the micro-channels. The PV cell absorbing radiation is of an aluminum type. The numerical solution of the three geometries is carried out using the finite volume method using ansys-fluent software. The pressure decomposition, momentum and energy discretization, and the solution of the pressure–velocity coupling are performed based on the standard method, the second-order upwind method, and the semi-implicit method for pressure-linked equations (SIMPLE) method, respectively. The convergence factor is considered to be respected and for continuity and energy equations. The results indicate that the cell surface temperature and the outlet fluid temperature decrease by increasing the Reynolds (Re) number. Moreover, electricity efficiency increases with the increased Reynolds number. The curved path has the highest electrical efficiency in comparison to other two paths. The decrease in fluid pressure of the curved path in Re = 600 is 4% and 1.3% higher than the direct and spiral paths, respectively.
Influence of Lubricant Supply on Thermal and Efficient Performances of a Gear Reducer for Electric Vehicles
Authors: Zhu Bo , Wang Xiang , Luo Liang , Zhang Nong , Liu Xijian
Published: October 2021

The amount of lubricating oil in a gear reducer greatly influences components’ temperature and efficiency of the reducer. A thermal network simulation model of a gear reducer for electric vehicles based on amesim software was built for thermal and efficiency analysis of the reducer, where heat production and transfer processes of each component in the reducer are considered. Moreover, secondary development submodels were developed to calculate the convection coefficients in real time based on different lubricating oil temperatures and working conditions. Next, the experiments were conducted to verify the developed model regarding transmission efficiency and lubricating oil equilibrium temperature in the reducer. The deviation between the numerical and experimental results is less than 5%, which indicates high accuracy of the developed thermal network model. Thereafter, efficiency and heat balance simulation tests under different working conditions were performed to determine an optimal lubricating oil supply, which is 14 mm gear-oil-immersion oil supply in this study. Finally, a comparison between the reducer with the optimal oil supply and that with normally used 22 mm gear-oil-immersion supply in the NEDC cycles in low temperature was done. The reducer with the optimal oil supply shows 1.032% energy saving. The method presented in this article provides a good guide to design and optimization of the gear reducer for electrical vehicles.
Component-based machine learning paradigm for discovering rate-dependent and pressure-sensitive level-set plasticity models
Authors: Vlassis Nikolaos Napoleon , Sun Waiching
Published: October 2021

Conventionally, neural network constitutive laws for path-dependent elasto-plastic solids are trained via supervised learning performed on recurrent neural network, with the time history of strain as input and the stress as input. However, training neural network to replicate path-dependent constitutive responses require significant more amount of data due to the path dependence. This demand on diverse and abundance of accurate data, as well as the lack of interpretability to guide the data generation process, could become major roadblocks for engineering applications. In this work, we attempt to simplify these training processes and improve the interpretability of the trained models by breaking down the training of material models into multiple supervised machine learning programs for elasticity, initial yielding and hardening laws that can be conducted sequentially. To predict pressure-sensitivity and rate dependence of the plastic responses, we reformulate the Hamliton-Jacobi equation such that the yield function is parametrized in the product space spanned by the principle stress, the accumulated plastic strain and time. To test the versatility of the neural network meta-modeling framework, we conduct multiple numerical experiments where neural networks are trained and validated against (1) data generated from known benchmark models, (2) data obtained from physical experiments and (3) data inferred from homogenizing sub-scale direct numerical simulations of microstructures. The neural network model is also incorporated into an offline FFT-FEM model to improve the efficiency of the multiscale calculations.
Design and Compliant Control of a Piggyback Transfer Robot
Authors: Liu Yuxin , Guo Shijie , Yin Yuting , Jiang Zhiwen , Liu Teng
Published: October 2021

Patient transfer, such as lifting and moving a bedridden patient from a bed to a wheelchair or a pedestal pan, is one of the most physically challenging tasks in nursing care. Although many transfer devices have been developed, they are rarely used because of the large time consumption in performing transfer tasks and the lack of safety and comfortableness. We developed a piggyback transfer robot that can conduct patient transfer by imitating the motion when a person holds another person on his/her back. The robot consisted of a chest holder that moves like a human back. In this paper, we present an active stiffness control approach for the motion control of the chest holder, combined with a passive cushion, for lifting a care-receiver comfortably. A human-robot dynamic model was built and a subjective evaluation was conducted to optimize the parameters of both the active stiffness control and the passive cushion of the chest holder. The test results of 10 subjects demonstrated that the robot could transfer a subject safely, and the combination of active stiffness and passive stiffness were essential to a comfortable transfer. The objective evaluation demonstrated that an active stiffness of k = 4 kPa/mm along with a passive stiffness lower than the stiffness of human chest was helpful for a comfort feeling.
So You Think Your System Is Complex?: Why and How Existing Complexity Measures Rarely Agree
Authors: Hennig Anthony , Topcu Taylan G. , Szajnfarber Zoe
Published: October 2021

In an increasingly interconnected & cyber-physical world, complexity is often cited as the root cause of adverse project outcomes, including cost-overruns and schedule delays. This realization has prompted calls for better complexity management, which hinges on the ability to recognize and measure complexity early in the design process. However, while numerous complexity measures (CMs) have been promulgated, there is limited agreement about “how” complexity should be measured and what a good measure should entail. In this paper, we propose a framework for benchmarking CMs in terms of how well they are able to detect systematic variation along key aspects of complexity growth. Specifically, the literature is consistent in expecting that complexity growth is correlated with increases in size, number of interconnections, and randomness of the system architecture. Therefore, to neutrally compare six representative CMs, we synthetically create a set of system architectures that systematically vary across each dimension. We find that none of the measures are able to detect changes in all three dimensions simultaneously, though several are consistent in their response to one or two. We also find that there is a dichotomy in the literature regarding the archetype of systems that are considered as complex: CMs developed by researchers focused on physics-based (e.g., aircraft) tend to emphasize interconnectedness and structure whereas flow-based (e.g., the power grid) focus on size. Our findings emphasize the need for more careful validation across proposed measures. Our framework provides a path to enable shared progress towards the goal of better complexity management.
On Vessel Motion Induced Vortex-Induced Vibrations of a Steel Lazy Wave Riser
Authors: Yin Decao
Published: October 2021

Deepwater steel lazy wave risers (SLWR) subject to vessel motion will be exposed to time-varying oscillatory flow, vortices could be generated and the cyclic vortex shedding force causes the structure vibrate, such fluid-structure interaction is called vortex-induced vibrations (VIV). To investigate VIV on a riser with non-linear structures under vessel motion and oscillatory flows, time domain approaches are needed. In this study, a time-domain approach is used to simulate a full-scale SLWR. Two cases with simplified riser top motions are simulated numerically. By using default input parameters to the time domain approach, the key oscillatory flow induced VIV response characteristics such as response frequency, curvature and displacements are examined and discussed. More accurate VIV prediction could be achieved by using realistic hydrodynamic inputs into the time domain model.
Experimental Study on Void Fractions and Pressure Drops in Three-Phase Flow for Deep Sea Mining
Authors: Takano Satoru , Masanobu Sotaro , Kanada Shigeo , Ono Masao
Published: October 2021

Subsea minerals exist in the deep water within Japan’s exclusive economic zone. There are many technical issues which should be addressed for subsea mining.

The air-lift pumping systems are one of promising methods for subsea minerals transport. Flow assurance for three-phase flow is important to design the air-lift pumping system for subsea mining. It is important to establish methods for estimating void fractions and frictional pressure drops.

To establish the methods for three-phase flow, we reviewed previous studies for two- or three-phase flow. There are some models to estimate the void fractions such as slip flow model and drift flux model. There are also some models to estimate the frictional pressure drops such as homogeneous model and separated flow model. We calculated void fractions and frictional pressure drops by existing correlation and compared calculated results with experimental data in two- or three-phase flow.

In addition, we proposed the methods for estimating the void fractions and frictional pressure drops in three-phase flow. These had fewer number of experimental constants than existing correlations, these could calculate void fractions and frictional pressure drops in more various conditions than existing correlations.
A Combined Vortex Lattice Lifting Line Method for Unsteady Propeller Calculations
Authors: Büsken Andreas , Krüger Stefan
Published: October 2021

This paper presents a Combined Method for the calculation of propeller forces in inhomogeneous inflow. It consists of an extended Goldstein approach based on Lifting Line Theory and a Vortex Lattice Method. After a brief overview of both methods is given, the coupling strategy is described and the additional modifications are explained. A correction factor accounting for the vortex which develops under a separated and later reattached flow on the suction side of the propeller blade is implemented as the first modification. Further, the Lamb-Oseen vortex model is used for the vortices in the free vortex system of the propeller. Finally, some results achieved with the described method are presented and compared to measured values.
A CFD Approach for Modelling the Fluid-Structure Interaction of Offshore Aquaculture Cages and Waves
Authors: Martin Tobias , Bihs Hans
Published: October 2021

Open ocean aquaculture cages became recently a promising alternative to traditional fish cage designs. The offshore environment implies larger loads on the structures and higher risk of fish loss. Floating rigid aquaculture cages with stiff nets are considered as a possible solution to cope with these new challenges. Their design process requires more advanced tools to account for the non-linear fluid-structure interaction. This paper presents a suitable numerical approach for analysing the interaction of offshore aquaculture cages and waves using Computational Fluid Dynamics. Here, a numerical wave tank accounts for the accurate propagation of the waves, and structural dynamics solutions are utilised for the cage system. Two-way coupling is enabled by accounting for the influence of the net on the fluid. The numerical model is validated against measurements for the loads on and the responses of a mobile floating fish farm in waves and current.
A Framework for Condition Monitoring and Risk-Based Decision Support Involving a Vessel State Observer
Authors: Han Xu , Leira Bernt J. , Sævik Svein , Radhakrishnan Gowtham , Skjong Stian , Kyllingstad Lars T.
Published: October 2021

Digital twins have attracted significant attention across different domains for decades. In the maritime and the energy industries, digital twins have been mainly used for system condition monitoring, project visualization, crew training, real-time decision making/support, and predictive maintenance based on onsite measurement data from onboard sensors. Such a digital twin normally presumes the vessel’s operational condition by assistance from sensors and engineering judgement. However, a vessel’s operational condition and loading state may shift quite often due to the frequently changing operational scenarios, tasks, and environmental conditions. In addition, the true vessel state (e.g., inertia distribution) may deviate from the intended one according to planning due to possible engineering errors. Even though there are sensors helping to monitor vessel condition such as draft monitoring systems and ballast systems, several important vessel parameters are difficult to measure directly, e.g., moment of inertia, center of gravity, and nonlinear hydrodynamic damping. This paper proposes a framework for monitoring vessel condition and providing decision support based on quantitative risk assessment, through a vessel state observer which is able to self-tune the important but uncertain vessel parameters by utilizing the available prior knowledge, vessel measurements, and information about the associated sea states. The tuned vessel parameters improve the information about the real-time vessel condition and consequently assist to improve the prediction accuracy of vessel seakeeping performance in the near future for the emerging wave conditions. Furthermore, the tuned results and the response prediction can then be applied to a decision support system, quantitatively evaluating potential risk and providing suggestions. The framework consists of 5 modules, i.e., wave data acquisition and processing, vessel data acquisition and processing, vessel seakeeping model tuning, real-time vessel motion and critical structural response prediction, and risk awareness and avoidance. Details of each module are described in the paper. The proposed framework can also assist in the development of autonomous ships.
Study on the Mechanism of Sand-Carrying and Comprehensive Performance of Viscous Slickwater
Authors: Bai Hao , Zhou Fujian , Wang Jie , Zhang Mengchuan
Published: October 2021

From the using history, we can see that conventional slickwater and guar fracturing fluid will be widely replaced by viscous slickwater in unconventional oil/gas fracturing. The viscous slickwater combines the advantages of slickwater and guar fracturing fluid but avoids the disadvantages of both, that includes drag reduction and good sand carrying capacity. This paper will analyze the viscous reducer’s molecular structure and viscoelasticity to find out the sand carrying mechanism. Using Haake RS6000 rheometer to test the elastic modulus and viscous modulus of conventional slickwater and viscous slickwater, reveal the sand-carrying performance from the perspective of viscoelasticity; using JEM 2100 LaB6 transmission electron microscope to test the molecular structure of two polymers, from the molecular space structure to analysis of its drag reduction performance. Finally, systematically evaluated the viscosity, drag reduction rate, sand-carrying, and gel-breaking properties of the viscous slickwater. The polymer enhances the viscous slickwater’s sand carrying performance by increasing the elastic modulus of fluid and reduces the drag in the flow through the intermolecular framework structure. The comprehensive performance evaluation results show that: 1) The apparent viscosity of the 0.6 wt% viscous slickwater is 80 mPa.s, which is close to conventional guar gum fracturing fluid; 2) When the linear flow rate reaches 5 m/s, the viscous slickwater drag reduction rate is greater than 75 %; 3) The viscous slickwater fluid static and dynamic sand carrying performance is better than conventional slickwater, which is close to guar gum fracturing fluid; 4) When the breaker concentration is equal to 50 ppm, the gel breaking time of viscous slickwater is about 35 mins and the residue content is less than 45 ppm. The conventional fracturing fluid will be more and more replaced by viscous slickwater during the fracturing of unconventional oil and gas reservoirs. This article provides a reference for researchers to understand its drag reduction and sand carrying performance.
Dynamic Failure Probability Evaluation of Subsea High Integrity Pressure Protection System by Bayesian Networks
Authors: Wang Chuan , Gou Jun , Yu Chao , Liu Yupeng , Luo Jianjun , Chen Qiufan
Published: October 2021

Safety instrument system is composed of sensor, logic solver and final actuator. It is widely used in process industry, such as oil and gas industry, chemical industry, metallurgy and electric power industry. It is an important measure to ensure the safety of production, which can effectively avoid the potential danger to people, equipment and the environment. However, when it breaks down, the consequences can be expected to be extremely serious. Therefore, HIPPS requires low risk, so it is necessary to quantitatively evaluate the dynamic performance of HIPPS to ensure the high safety of HIPPS during the design life cycle.

In this paper, a Bayesian network based method is proposed to evaluate the dynamic performance of HIPPS. The effects of different detection methods and maintenance methods on the dynamic performance of HIPPS were analyzed quantitatively. The results show that the performance of the system has been improved obviously after maintenance. Compared with the traditional method, the performance of HIPPS is improved by introducing partial stroke test. The sensitivity analysis shows that the failure rate has a great influence on the risk of HIPPS valve. Increased coverage of PST may improve the performance of HIPPS.
Dynamic Model Development of Wind Turbine Drivetrains by Using Sensor Measurements
Authors: van Binsbergen Diederik , Nejad Amir R. , Helsen Jan
Published: October 2021

This paper aims to analyze the feasibility of establishing a dynamic drivetrain model from condition monitoring measurements. In this study SCADA data and further sensor data is analyzed from a 1.5MW wind turbine, provided by the National Renewable Energy Laboratory. A multibody model of the drivetrain is made and simulation based sensors are placed on bearings to look at the possibility to obtain geometrical and modal properties from simulation based vibration sensors. Results show that the axial proxy sensor did not provide any usable system information due to its application purpose. SCADA data did not meet the Nyquist frequency and cannot be used to determine geometrical or modal properties. Strain gauges on the shaft can provide the shaft rotational frequency, while torque and angular displacement sensors can provide the torsional eigenfrequency of the system. Simulation based vibration sensors are able to capture gear mesh frequencies, harmonics, sideband frequencies and shaft rotational frequencies.
Performance of a Near Shore Oscillating Wave Surge Converter With Variable Flap Configurations in Various Sea Conditions
Authors: Sugar Landon , Filho Faete , Abdel-Salam Tarek , Muglia Michael , Duba Kurabachew
Published: October 2021

Oscillating Wave Surge Converters (OWSCs) are designed to enter survival mode during extreme wave conditions where they forego the opportunity to extract energy to preserve structural integrity. While this is a good tradeoff, it is important that OWSC technology progresses to a point where energy is constantly extracted as long as waves are present. This work addresses the need for an OWSC that can extract wave energy in a wide range of sea conditions while minimizing structural overloading by regulating the fluid-structure interaction. The OWSC being studied here was conceptually designed and patented by researchers at NREL. It consists of a flap face that resembles household blinds, where the flaps can be opened or closed to accommodate the sea conditions. The performance of this variable geometry OWSC in various, shallow wave states was studied in two numerical modeling programs. Of particular interest were the flap’s hydrodynamic coefficients and potential power generation at a specific reference site. This configuration was predicted to mitigate wave forces by allowing some of the wave energy to pass through the device, thus preserving its structural integrity.
Estimation of Wind Turbine Gearbox Loads for Online Fatigue Monitoring Using Inverse Methods
Authors: Mehlan Felix C. , Nejad Amir R. , Gao Zhen
Published: October 2021

In this article a novel approach for the estimation of wind turbine gearbox loads with the purpose of online fatigue damage monitoring is presented. The proposed method employs a Digital Twin framework and aims at continuous estimation of the dynamic states based on CMS vibration data and generator torque measurements from SCADA data. With knowledge of the dynamic states local loads at gearbox bearings are easily determined and fatigue models are be applied to track the accumulation of fatigue damage. A case study using simulation measurements from a high-fidelity gearbox model is conducted to evaluate the proposed method. Estimated loads at the considered IMS and HSS bearings show moderate to high correlation (R = 0.50–0.96) to measurements, as lower frequency internal dynamics are not fully captured. The estimated fatigue damage differs by 5–15 % from measurements.
Residual Strength of Tubular Columns With Localized Thickness Loss
Authors: Atteya Mostafa , Mikkelsen Ove , Oma Narve , Ersdal Gerhard
Published: October 2021

This paper provides a comprehensive finite element analysis to investigate the ultimate capacity of corroded members under concentric axial loads. The paper investigates previous experimental work on stocky and slender tubular columns with simulated patch corrosion and provides a numerical model that can estimate the columns capacities. Further, a parametric study is performed to investigate the effect of geometric parameters such as location, height, and width of corrosion patch on the ultimate capacity of corroded columns. Finally, the paper presents a comparison between laboratory tests to the formulae of superseded standards and numerical analysis using nonlinear finite element methods. The numerical model proposed in this paper show good agreement with the results from the experimental work.
The Impact of Cyclic Loading on the Flexural Strength of Ice
Authors: Kaplan Ihsan , von Bock und Polach R. U. Franz
Published: October 2021

Flexural strength measurements of sea ice in far inlying regions can experience continuous cyclic loading due to wave interactions. Furthermore, global warming leads to a continuous decrease of the Polar ice masses, resulting in an increased vulnerability of the integrity of the ice and its exposure to wave interactions and in consequence a growth of the marginal ice zone. In order to investigate the impact of cyclic loading on the flexural strength of ice, experiments with periodically loaded and previously unloaded ice samples is performed and analyzed. Previous research indicated both a weakening and a strengthening of the ice and the scope of this paper is also to enhance the understanding of the impact of cyclic loading of ice. This is relevant as ice might be subjected to several loading cycles before wave induced break-up and the question is whether the impact of cyclic loading needs to be accounted for in models. of its impact is addressed. The results show that the flexural strength of periodically loaded samples increases instead of fatigueing. Furthermore the ice has a very dynamic behaviour even at very low loading frequencies and small displacement-amplitudes in the micrometre range.
Modeling Relation Between Forward Speed and Propeller Speed of the Cruising AUV Using Multiple Regression Analysis
Authors: Umeda Jun , Fujiwara Toshifumi
Published: October 2021

This study addresses predicting the relationship between forward speed and propeller speed of an autonomous underwater vehicle (AUV) with a towed flexible cable using multiple regression analysis. Accurate prediction of the propeller speed corresponding to forward speed is important. The prediction requires considering various factors such as the dynamic behavior of a flexible cable, tidal currents, and AUV motions. The regression analysis based on in-service data of the AUV, therefore, established the relation between the forward speed and propeller speed considering the other factors. On the other hand, minimal independent variables in the regression model are desirable to avoid multicollinearity and overfitting. Variable selection based on the t-Test and sparse modeling was carried out to remove insignificant variables. We confirmed that the regression model presented in this study was in agreement with the observed data sufficiently, and the residuals of the regression model followed a normal distribution. The propeller speed predicted by the regression model considering only the forward speed of the AUV was comparable to the result predicted by the CFD calculation, not including the other factors. The result indicates the regression analysis can validate the results based on experiments and a numerical simulation.
State Estimation and Slug Control of the Subsea Multiphase Pipeline
Authors: Yu Chao , Wang Chuan , Deng Xin , Zhang XueLiang , Sun HaiFang , Peng WeiMing , Liu YuPeng
Published: October 2021

The simulation and control of the severe slugging flow in the subsea multiphase pipeline is the focus of research in the production and exploitation of oil companies. Severe slug flow results in severe fluctuations of pressure and flow rate at both the wells end and the receiving host processing facilities, causing safety and shutdown risks. To prevent the severe slugging flow regime in multiphase transport pipelines, an Ordinary Differential Equation (ODE) model is established by using the mass conservation law for individual phases in the pipeline and the riser sections. Then, the proposed model is compared to the results from the OLGA simulation. A comparative study of different slugging flow control solutions is conducted. Unscented Kalman Filter (UKF), Wavelet Neural Network (WNN) and UKF&WNN are used for state estimation and combined with PI controller. The UKF and WNN are good nonlinear filters. However, when the nominal choke opening is increased, they work unsatisfying. The UKF&WNN observer shows slightly better results than UKF and WNN when the system has high input disturbance.
Minimum Miscibility Pressure of CO2/Hydrocarbon Systems Within Nanopores
Authors: Yang Gang , Li Xiaoli
Published: October 2021

Minimum miscibility pressure (MMP), as a key parameter for the miscible gas injection enhanced oil recovery (EOR) in unconventional reservoirs, is affected by the dominance of nanoscale pores. The objective of this work is to investigate the impact of nanoscale confinement on MMP of CO2/hydrocarbon systems and to compare the accuracy of different theoretical approaches in calculating MMP of confined fluid systems. A modified PR EOS applicable for confined fluid characterization is applied to perform the EOS simulation of the vanishing interfacial tension (VIT) experiments. The MMP of multiple CO2/hydrocarbon systems at different pore sizes are obtained via the VIT simulations. Meanwhile, the multiple mixing cell (MMC) algorithm coupled with the same modified PR EOS is applied to compute the MMP for the same fluid systems. Comparison of these results to the experimental values recognize that the MMC approach has higher accuracy in determining the MMP of confined fluid systems. Moreover, nanoscale confinement results in the drastic suppression of MMP and the suppression rate increases with decreasing pore size. The drastic suppression of MMP is highly favorable for the miscible gas injection EOR in unconventional reservoirs.
Buoyant Miscible Jets in the Plug and Abandonment of Oil and Gas Wells
Authors: Hassanzadeh Hossein , Eslami Ali , Taghavi Seyed Mohammad
Published: October 2021

The plug and abandonment (P&A) operation is the final stage in the life cycle of oil and gas wells. The aims of the P&A operation are to seal the well and permanently maintain the well-integrity similar to that of the original natural caprock. Using this approach, it is possible to isolate fluids movement between different strata, to prevent environmental disasters. Generally, the main steps in the P&A operation are (i) accessing the annulus section of the well, (ii) cleaning the defected area, and (iii) placing the cement plug barriers into the target area. To prepare the target area and avoid cement plug contamination, a cleaning process is required inside and outside the casing. The jet cleaning process is one of the effective methods for the cleaning step, in which a liquid of a higher density is usually injected into the target area to displace a lighter ambient fluid. During the jet cleaning process, several forces affect the cleaning efficiency, including inertial, viscous and buoyancy forces.

In this work, we analyze a fundamental component of the jet cleaning process in the P&A operation, via experimentally studying the characteristics of a miscible positively buoyant jet. In our work, a heavy fluid is injected downwards into a large rectangular tank filled with a light ambient fluid. Due to the large dimensions of the experimental tank, the wall effects on the flow are neglected, i.e. we consider a free jet. We investigate some of the parameters affecting the behaviour of our positively buoyant jets, such as the injection velocity, the nozzle diameter, and the ratio between the viscosity of the jet fluid to that of the ambient fluid. In the parameter ranges of our interest, the jet flow exhibits certain critical flow features, such as the laminar length (i.e. the initial stable part of the jet where the injection fluid remains laminar and does not mix with the ambient fluid) and the spread angle (i.e. the area occupied by the jet). Our results show that both the laminar length and the spread angle decrease by increasing the injection velocity. In addition, increasing the viscosity ratio results in increasing the maximum laminar length and decreasing the spread angle. These results can help to better design an efficient cleaning in the P&A operation of oil and gas wells.
Benchmark Study and Uncertainty Assessment of Planar Motion Mechanism Tests on KVLCC2 in a Circulating Water Channel
Authors: Ma Chengqian , Ma Ning , Gu Xiechong
Published: October 2021

The benchmark experiment research for the maneuverability of a small-scaled ship model is critical for investigating the scaled effect on the maneuvering hydrodynamic derivatives, and validating the CFD technology. Till now, there is little research on the benchmark study and uncertainty analysis for the small-scaled ship which is frequently used in the Circulating Water Channel (CWC). Therefore, an experimental study of the planar motion mechanism (PMM) tests is performed in the CWC of the SJTU. The PMM tests performed in the CWC can avoid some disadvantages of those in the towing tank, such as the limitations on the acquisition time and frequency due to the size of the towing tank, interference of the carriage on the signal acquisition. In addition, the flow field visualization for the tests in the CWC is easier to achieve compared with the experiments in the towing tank, which helps the scholars to understand the characteristic of the wake field during maneuvers. The benchmark ship is the KVLCC2 with a scaled ratio of 1/128.77. The hull forces are recorded and processed to obtain the maneuvering hydrodynamic derivatives. To assess the quality of the acquired data, randomness analysis, stationarity analysis, normality analysis, and statistical convergence are performed for the PMM tests in the CWC for the first time. Finally, the uncertainty analysis (UA) method for the PMM tests performed in the CWC is also developed.
Evaluation of Residual Life of Existing Offshore Platforms in Western Offshore, India
Authors: Renugadevi A. , Nallayarasu S. , Karunanithi S.
Published: October 2021

Western offshore oil field in India has nearly 300 offshore platforms for oil and gas exploration, of which almost 50% of platforms have outlived their life. Life extension of these platforms has become essential for further production activities. In many cases, design level analyses combined with ultimate strength assessment, life extension has been granted. However, risk-based assessment based on the probability of failure based on available reserve strength linked to additional life extension could be a logical method. The Reserve Strength Ratio (RSR) is defined as a ratio of reserve capacity of the jacket structure and the design level environmental loads (1 year or 5year or 10 year or 100-year return period). The encounter probability of these design storms for the life extension period has been established probability for the extension period has been used as a threshold to determining the required RSR using the probability of collapse. For the present study, four typical aged wellhead platforms with different water depths are selected, and RSR is evaluated by carrying out push over analysis. The Monte Carlo Simulation method is used to generate the statistical values of RSR. The probability of failure is then calculated by First Order Reliability Method (FORM) using MATLAB for different RSR values. Reassessment criteria for the existing offshore platforms have been described from the reliability analysis results based on probability failure and encounter probability.
RMS Control of Response of Jacket Structure Using Tuned Liquid Column Ball Gas Damper Under Random Ocean Waves
Authors: Jothinathan Satheesh , Kumar Deepak
Published: October 2021

Jacket structures are one of the most important offshore structures for extracting oil and gas. The fatigue life is affected due to the continuous dynamic wave force experienced by the structure. Generally, the structure is designed so that the dynamic response is small, which increases the cost. So, controlling its response is a good alternative to increase its life span. In this work, a simplified jacket structure under a random sea state is controlled for its response using a tuned liquid column ball gas damper (TLCBGD). The jacket structure in a water depth of 60m is modeled in a surge degree of freedom. The parameters of TLCBGD are optimized using a genetic algorithm for achieving better control in response quantities. For the analysis purpose, the wave is considered stochastic and presented by Pierson–Moskowitz (PM) spectrum of significant wave height 10m. In such a case, the jacket structure response can be presented using the root mean square (RMS) values obtained from the Lyapunov technique. Based on the random vibration analysis theory, the Lyapunov method can be employed to obtain the RMS of the system driven directly without solving the governing differential equation. This method requires the system to be driven by white noise. So, in this study, filters are developed to get the required narrow banded ocean spectrum. It is noticed that the response quantity is highly sensitive to the filter parameters. This is because a slight change in excitation parameters and a change in filter parameters near the system’s natural frequency affect the response significantly. Further, it is seen that the use of the genetic algorithm for tuning the TLCBGD gives very good control on the response quantity of the jacket structure.
Optimization of Segmented Wave-Maker Control to Generate Spatially Uniform Regular Waves in a Rounded-Rectangular Wave Basin
Authors: Ota Daichi , Houtani Hidetaka , Sawada Hiroshi , Taguchi Harukuni
Published: October 2021

A wave field in a wave basin inevitably has spatial variation due to the wave’s cylindrical propagation property. Therefore, we aimed to develop an optimization method for the control of wave-makers to produce a spatially uniform wave field in a specified test zone inside a wave basin with an arbitrary arrangement of wave-makers. The optimization is based on the simulated annealing algorithm, a method for finding a globally optimal solution, which was combined with a numerical wave basin based on linear wave-maker theory. A wave generation experiment was performed in the actual sea model basin (80 m long, 40 m wide, and 4.5 m deep) at the National Maritime Research Institute to validate the proposed optimization method. A case study was conducted with a long-crested regular-wave with a wave height of 10 cm, wavelength of 4.0 m, and wave direction of 180 degrees, which corresponds to the longitudinal direction of the wave basin. A 40-m × 14-m test zone was set in the middle of the wave basin. The experimental results with and without the proposed optimization were compared, which confirmed that the spatial uniformity of the wave field was improved, and the coefficient of variation for the wave height in the test zone decreased from 0.127 to 0.029.