bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Analysis of Data Repeatability Measures
Authors: Wang Zeyi , Bridgeford Eric , Wang Shangsi , Vogelstein Joshua T. , Caffo Brian
Published: August 2024

The advent of modern data collection and processing techniques has seen the size, scale and complexity of data grow exponentially. A seminal step in leveraging these rich datasets for downstream inference is understanding the characteristics of the data which are repeatable—the aspects of the data that are able to be identified under duplicated analyses. Conflictingly, the utility of traditional repeatability measures, such as the intra‐class correlation coefficient, under these settings is limited. In recent work, novel data repeatability measures have been introduced in the context where a set of subjects are measured twice or more, including: fingerprinting, rank sums and generalisations of the intra‐class correlation coefficient. However, the relationships between, and the best practices among, these measures remains largely unknown. In this manuscript, we formalise a novel repeatability measure, discriminability. We show that it is deterministically linked with the intra‐class correlation coefficients under univariate random effect models and has the desired property of optimal accuracy for inferential tasks using multivariate measurements. Additionally, we overview and systematically compare existing repeatability statistics with discriminability, using both theoretical results and simulations. We show that the rank sum statistic is deterministically linked to a consistent estimator of discriminability. The statistical power of permutation tests derived from these measures are compared numerically under Gaussian and non‐Gaussian settings, with and without simulated batch effects. Motivated by both theoretical and empirical results, we provide methodological recommendations for each benchmark setting to serve as a resource for future analyses. We believe these recommendations will play an important role towards improving repeatability in fields such as functional magnetic resonance imaging, genomics, pharmacology and more.
Optimal drone deployment for cost‐effective and sustainable last‐mile delivery operations
Authors: Kumar Gaurav , Tanvir Oqais , Kumar Akhilesh , Goswami Mohit
Published: August 2024

Delivery by drones holds significant potential to solve issues (such as high costs, access to remote areas, etc.) faced in last‐mile delivery operations, particularly in the e‐commerce industry. Still, it involves complex issues such as multi‐trip operations, energy estimation, and battery recharge planning. A sound drone delivery problem entails an optimal drone deployment plan with routing details at the lowest possible cost. To this end, this study focuses on formulating a delivery problem that involves multi‐trip drone routing, energy optimization, and travel time optimization problems where energy consumption by drones is modeled as a non‐linear function. We develop a mixed integer non‐linear programming model as an integrated optimization model. This model aims to: (a) maximize revenue by meeting demand completely without leaving idle drones, (b) optimize energy use by drones, and (c) minimize the required drone fleet size for an optimal plan. The proposed model is solved using the Gurobi Solver, which employs data supplied by a well‐known e‐commerce firm. We introduce a two‐phase heuristic solution methodology to tackle larger networks’ complexities. This method consists of the clustering phase (K‐means clustering method) and the optimization phase. The robustness of the developed mathematical modeling is demonstrated by testing with varied large problem instances. The evaluation shows that expanding destination options boosts drone demand until saturation, necessitating more drones. Efficient route planning and fleet adjustments are crucial for meeting rising demand and satisfying customers amidst dense clustering. This model helps e‐commerce manage daily last‐mile drone deliveries and anticipate future growth.
Impact of intrapartum quality improvement interventions on stillbirths and other adverse pregnancy outcomes: A protocol for systematic review and meta‐analysis
Authors: Gopinathan Preetha , Tripathi Vinay , Swain Sumant , Lakshman Neha , Tolani Himanshu , Prasad Jagdish , Prajapat Manish , Bindal Eshika
Published: August 2024

Background

Stillbirths are a major global health concern. Half of stillbirths occur during intrapartum period, mostly in low‐ and middle‐income countries of sub‐Saharan Africa and South Asia. Achieving a stillbirth rate of less than 12 per 1000 births by 2030 is the global target of Every Newborn Action Plan and Sustainable Development Goals. Evidence suggests that improving intrapartum quality of care can help reduce stillbirths and other adverse pregnancy outcomes. This study will explore whether quality improvement (QI) packages at intrapartum care points can reduce stillbirths and other outcomes such as maternal and neonatal mortality.

Methods

We will conduct a systematic literature review and meta‐analysis. Comprehensive search strategy will be developed for databases PubMed, Web of Science, ScienceDirect, ProQuest, Cochrane and China National Knowledge Infrastructure. We will include randomized controlled trials, controlled non‐randomized trials, controlled clinical trials, interrupted time series, cohort studies, case–control and nested case–control studies which assess the impact of QI interventions at intrapartum points of care on stillbirths and other adverse pregnancy outcomes. We will search grey literature such as unpublished research studies, dissertations and unfinished trials. English and non‐English language articles will be included to avoid language bias. We will also evaluate reporting quality and risk of bias. Sensitivity tests will be carried out for heterogeneity. Pooled estimates of effect sizes will be computed with random‐effects models. Supplementation of the quantitative synthesis with a qualitative narrative synthesis would be added, if deemed necessary. We will explore publication bias using funnel plot and Egger's regression test will be used for evaluation, if needed.

Discussion

We will report pooled effectiveness of different intrapartum QI interventions across multiple settings in averting stillbirths and other adverse outcomes such as maternal mortality and neonatal mortality.
Four cancer cases with pathological germline variant RAD51D c.270_271dup
Authors: Ishihara Eiko , Matsubayashi Hiroyuki , Nishimura Seiichiro , Isaka Mitsuhiro , Konno Hayato , Goto Seiya , Yamaguchi Ken , Urakami Kenichi
Published: August 2024

Pathological germline variants (PGVs) of RAD51D increase the risk of breast and ovarian cancer. In East Asia, c.270_271dup is the most frequently detected PGV of RAD51D; however, only a few cases have been reported in Japan. We report four cancer cases with a germline RAD51D c.270_271dup PGV. Three of them (lung cancer: 2, oral cancer: 1) were incidentally identified by whole genome sequencing in patients negative for the associated cancer histories, homologous recombination (HR) deficiency, or a second hit of RAD51D in the cancer DNA. For genetic counseling, we provided information on surveillance and cascade testing based on Western guidelines. The PGVs of moderate‐risk HR‐related genes are difficult to detect based on phenotype, especially in male‐predominant pedigrees. The current spread of cancer genomic analysis will increase opportunities for incidental variant identification. The establishment of Japanese guidelines is expected to aid in the management of PGV carriers of moderate‐risk genes.
Intersectional bonds: Delinquency, arrest, and changing family social capital during adolescence
Authors: DeMarco Laura M. , Leppard Tom R. , Lindsay Sadé L.
Published: August 2024

Objective

This study uses an intersectional approach to examine whether bonding and bridging family social capital change after adolescent delinquency and arrest.

Background

Family social capital (the resources and energy investments parents make in their children) has important implications for numerous youth outcomes. To date, little research has examined how stressful behaviors (like delinquency) and life events (such as arrest) strain or strengthen parent–child relationships, particularly across Black, White, and Hispanic families.

Methods

Drawing on data from the National Longitudinal Survey of Youth, 1997 cohort, the authors use fixed effects, dynamic panel, and correlated random effects models to analyze how delinquent behavior and arrest impact bonding and bridging forms of family social capital in adolescence. Stratified models by race/ethnicity and gender test whether the effects vary across groups.

Results

Results show that delinquency is negatively associated with bonding and bridging family social capital. Black girls experienced the sharpest reduction in family social capital resulting from delinquent behavior. Arrest was significantly associated with decreased bridging capital for Hispanic boys and increased bridging capital for Black girls.

Conclusion

Delinquency creates stress for parents and reduces investments in children, especially for Black girls. The effects of arrest vary by race and gender.

Implications

This study demonstrates the dynamism of family social capital and the impact of adolescent delinquency and arrest on parent–child ties, providing insights into the racialized and gendered development of family social capital amid heightened concern about youth deviance and incarceration.
Seating accuracy of removable partial denture frameworks fabricated by different digital workflows in comparison to conventional workflow
Authors: Korkes Andrea , Jomaa Janine , Kavouris Anastasios , Lalani Tahyr , King Phillip , Lee Samantha , Li Hongyi , Li Aixi , Khuu Wilson , Law Ka Ho Jesper , Abduo Jaafar
Published: August 2024

Purpose

To evaluate the seating accuracy of removable partial denture (RPD) frameworks fabricated by two digital workflows involving selective laser melting (SLM) in comparison to the conventional workflow.

Materials and Methods

A Kennedy class III modification 1 partially edentulous mandibular arch was used as a master model. Three RPD framework groups were included: (1) a conventional workflow group with conventional impression and casting (CC), (2) a partial digital workflow group with conventional impression and digital fabrication (CD), and (3) a complete digital workflow group with digital impression and digital fabrication (DD). A total of 10 frameworks were produced for each group. The marginal gaps at the occlusal rests, retention arms, and reciprocating arms were measured by a traveling microscope. The data were analyzed with the one‐way analysis of variance test.

Results

At the framework level, the most superior fit was observed for the CD group (79.5 µm) followed by DD (85.3 µm) and CC (114.2 µm) groups. The CD and DD groups were significantly superior to CC (p < 0.001). This fit pattern was consistent for the retention and reciprocating arms, while the occlusal rest fit was similar among all the groups.

Conclusions

The SLM frameworks had a promising seating accuracy in comparison to conventional frameworks. The type of impression, conventional or digital, did not affect the accuracy of SLM frameworks. The differences observed in the present study are likely to be of minimal clinical significance.
Understanding Community Perceptions on the Role of Schools in Youth Mental Health
Authors: Neher Taylor , Smith Megan , Rossetto Kelly , Mujak Irma , Romero Alyssa , Griffin Kaydin
Published: August 2024

BACKGROUND

Youth mental health rates of depression and anxiety continue to climb. Schools have a role to play to support youth mental health but often struggle to navigate community expectations.

METHODS

Focus groups (n = 17) were conducted with over 100 participants to understand community perceptions on the role of schools.

RESULTS

Three themes emerged around what schools should be doing: (1) provide accurate education about mental health, (2) create mental health promoting environments that positively supports young people, and (3) act as a common space to bring community members and organizations together for their young people.

IMPLICATIONS FOR SCHOOL HEALTH POLICY, PRACTICE, AND EQUITY

School professionals and systems should be equipped to adequately address youth mental health. The current US institutional response to this crisis is underdeveloped and exacerbates equity issues and health outcome disparities. Schools need institutional support for addressing mental health in ways that incorporate building a shared understanding with families and providing efforts to prevent and detect rather than just treat mental health.

CONCLUSIONS

Schools should work with their communities to promote shared understanding and accountability for all to engage in building rich protective environments that promote mental well‐being for kids in their care.
Spontaneous enteric nervous system activity generates contractile patterns prior to maturation of gastrointestinal motility
Authors: Dershowitz Lori B. , Bueno Garcia Hassler , Perley Andrew S. , Coleman Todd P. , Kaltschmidt Julia A.
Published: August 2024

Background

Spontaneous neuronal network activity is essential to the functional maturation of central and peripheral circuits, yet whether this is a feature of enteric nervous system development has yet to be established. Although enteric neurons are known exhibit electrophysiological properties early in embryonic development, no connection has been drawn between this neuronal activity and the development of gastrointestinal (GI) motility patterns.

Methods

We use ex vivo GI motility assays with newly developed unbiased computational analyses to identify GI motility patterns across mouse embryonic development.

Key Results

We find a previously unknown pattern of neurogenic contractions termed “clustered ripples” that arises spontaneously at embryonic day 16.5, an age earlier than any identified mature GI motility patterns. We further show that these contractions are driven by nicotinic cholinergic signaling.

Conclusions & Inferences

Clustered ripples are neurogenic contractile activity that arise from spontaneous ENS activity and precede all known forms of neurogenic GI motility. This earliest motility pattern requires nicotinic cholinergic signaling, which may inform pharmacology for enhancing GI motility in preterm infants.
Cystic fibrosis dermatitis arthritis syndrome: A series of four cases
Authors: Schwartzman Gabrielle , Zlotoff Barrett J. , Gru Alejandro A. , Guffey Darren J.
Published: August 2024

Dermatologic manifestations of cystic fibrosis (CF) include nutrient deficiency dermatoses, vasculitis, transient reactive papulotranslucent acrokeratodema, digital clubbing, and increased rates of atopy and drug reactions. Few cases of a characteristic eruption in patients with episodic arthritis of CF have been described with prior reports primarily occurring outside of the dermatology literature. We report four cases consistent with this presentation to add to the literature and propose a new and unifying name to recognize this entity as cystic fibrosis dermatitis arthritis syndrome (CF‐DAS). Clinical suspicion should remain high in young female patients with cystic fibrosis presenting with episodic joint pain and rash, independent of pulmonary exacerbations.
Responses of soil seed banks and soil microbial activity to grazing exclusion in cold semiarid grasslands
Authors: Hazhir Shadi , Erfanzadeh Reza , Pirkhezri Seyed Zanko , Razavi Bahar S. , Török Péter
Published: August 2024

The soil seed bank (SSB) and soil microbial communities are among the most crucial drivers of belowground biodiversity in grasslands. Changes in components of soil biodiversity following protection from grazing were observed in cold, semiarid grasslands. To study these changes, soil samples were taken in an intensively grazed area and in an exclosure established 20 years prior to this study. In particular, changes in biodiversity components such as SSB and microbial activities in two soil depths (0–5 and 5–10 cm) were measured. Nonmetric dimensional scaling showed that after grazing removal, the SSB had changed. SSB density, richness, and diversity were higher in the ungrazed plots. The increase in SSB density and diversity in the exclosure may have been caused by the absence of direct adverse effects of grazing on the SSB, like trampling and plant consumption, or by reduced indirect effects, such as seed germination facilitation in canopy gaps created by grazing animals. The effect of grazing removal on basal respiration, substrate‐induced respiration, and urease activity was highly significant (p < 0.01) and may be due to an increase in soil moisture after grazing exclusion. The effect of grazing removal on soil biological parameters was greater in the upper layer than in the deeper soil layer. This study shows that grazing exclusion can be a useful approach in restoring components of soil biodiversity.
Exploring neuronal mechanisms of osteosarcopenia in older adults
Authors: Karacan Ilhan , Türker Kemal Sıtkı
Published: August 2024

Until recently, research on the pathogenesis and treatment of osteoporosis and sarcopenia has primarily focused on local and systemic humoral mechanisms, often overlooking neuronal mechanisms. However, there is a growing body of literature on the neuronal regulation of bone and skeletal muscle structure and function, which may provide insights into the pathogenesis of osteosarcopenia. This review aims to integrate these neuronal regulatory mechanisms to form a comprehensive understanding and inspire future research that could uncover novel strategies for preventing and treating osteosarcopenia. Specifically, the review explores the functional adaptation of weight‐bearing bone to mechanical loading throughout evolutionary development, from Wolff's law and Frost's mechanostat theory to the mosaic hypothesis, which emphasizes neuronal regulation. The recently introduced bone osteoregulation reflex points to the importance of the osteocytic mechanoreceptive network as a receptor in this neuronal regulation mechanism. Finally, the review focuses on the bone myoregulation reflex, which is known as a mechanism by which bone loading regulates muscle functions neuronally. Considering the ageing‐related regressive changes in the nerve fibres that provide both structural and functional regulation in bone and skeletal muscle tissue and the bone and muscle tissues they innervate, it is suggested that neuronal mechanisms might play a central role in explaining osteosarcopenia in older adults.

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A Monte Carlo Method to Decision-Making in Maintenance Strategies
Authors: Cheikh Khamiss , Boudi EL Mostapha , Rabi Rabi , Mokhliss Hamza
Published: August 2024

Health prognosis is an advanced approach for anticipating the future status of systems, structures, and components. While it is accepted as an important step in boosting maintenance performance and resilience of a system, the subject of post-prognosis maintenance decision-making remains unsettled. To address this problem, we present one of the most effective economic criteria for concurrently assessing the performance and resilience of the time-based and condition-based maintenance methods. This criteria is a linear combination of the asymptotic average cost per unit of time and the standard deviation of the mean cost per renewal cycle of maintenance charges per renewal cycle. Ultimately, we will evaluate these two maintenance procedures to select the one that gives the optimum mix of lifetime and robustness for our system. We will also study how to fine-tune our new criteria to obtain the ideal balance of performance and robustness for two systems, the first is a system with changeable behavior, while the second one presents a system with more or less stable behavior. The inclusion of the Monte Carlo method improves the comparative study of maintenance methods, delivering insights into the performance and resilience of each adaptation in decision-making.
An Evaluation of Design Wave Selection Methods for Floating Offshore Structure Design
Authors: Kim Youngkook , Yu Lei
Published: August 2024

For floating offshore structures, the structure design should consider site-specific environmental loads in a target return period, typically 100-year (annual probability of occurrence of 10−2). The equivalent design wave (EDW) approach has been a popular method to represent long-term extreme responses in a site-specific environment. Although the method is convenient and efficient, the EDW approach is a great simplification that represents extreme responses with a number of wave scenarios. Therefore, the EDWs have to be chosen with great care. The conventional method to choose EDWs is based on the heading angles and the wave frequencies at the peak of the response amplitude operators (RAOs). This approach works well for trading vessels but may not be the case for offshore applications where equal probability of occurrences cannot be assumed for every wave heading angle.

The EDW selection determines the load combinations which are applied not only to structural analysis but also to prescriptive local scantling calculations, therefore, an appropriate method should be adopted so that realistic wave scenarios can be applied to the structural design of offshore structures. In this study, several EDW selection methods are reviewed and evaluated for the rational design of floating offshore units.
The Effect of Extra Mass Moment of Inertia on S-Shaped Vertical Axis Autorotation Current Turbine (VAACT)
Authors: Soares Rodrigo B. , Fernandes Antonio C. , S. Sales Junior Joel
Published: August 2024

This study examines how the extra mass moment of inertia affects the performance of the S-shaped Vertical Axis Autorotation Current Turbine (VAACT). Tests were performed at the Laboratory of Waves and Currents (LOC-COPPE/UFRJ) to obtain the efficiency curves of this geometry. The test facility has dimensions of 22 meters in length, 1.4 meters in width, and 0.5 meters in water depth, resulting in a blockage ratio of 21%. The experiments were performed by varying the moment of inertia from 0.0135 kg · m2 to 3.0 kg · m2 at Reynolds numbers ranging from 30,000 to 135,000. The power output was estimated using a weight-lifting approach, where the power is calculated by the time derivative of the weight’s potential energy. The results show that additional mass moment of inertia can improve the turbine’s power harvesting by about 60%. Moreover, the tests indicate that increasing the mass moment of inertia stabilizes VAACT’s dynamics and enables it to operate at the design tip speed ratio. Additionally, the analysis reveals that the turbine’s efficiency can reach 25% when operating at a tip speed ratio of 1.5, a Reynolds number of 90,000, and a dimensionless moment of inertia of 1.160. However, the turbine’s performance at higher Reynolds numbers is poor due to the high vortex-shedding observed in the wake.
Active Flow Control of Flow Over a Stationary Cylinder Using a Flapping Rod at Low Reynolds Number
Authors: Chua Ming Han , Liu Bin
Published: August 2024

A numerical investigation of the active flow control mechanism of flow over a stationary circular cylinder using a flapping rod was conducted at low Reynolds number. The Galerkin-least-square (GLS) stabilized Finite Element formulation in Arbitrary Lagrangian-Eulerian (ALE) description is employed to investigate the fluid dynamics and structural motions in the simulations. A rotating dynamic mesh model is utilized to precisely trace the flapping dynamics of the control rod in the wake downstream. A control rod of very small diameter (d = 0.1) is used as an active flow control mechanism and flaps behind a cylinder (D = 1.0) in an orbital manner at a range of frequencies, amplitudes, and distance. The primary objective of this study is to investigate the effectiveness of this flapping rod to enhance the structural stability of the cylinder subject to hydrodynamic forces. The results show that this active flow control mechanism, flapping control rod, can effectively change the wake modes downstream and enhance the structural stability by minimizing the fluctuation of lift force.
J-Lay Installation of Steel Catenary Risers for Lingshui 17-2 Project
Authors: Hou Jing , Cheng Yongming , Yu Chenteh Alan , Zhang Cheng
Published: August 2024

CNOOC Lingshui 17-2 (termed LS17-2) was the first regional ultradeep water project in South China sea. The field development encompasses a deep draft semi-submersible for processing gas that is produced and exported through pipelines and Steel Catenary Risers (SCRs). This paper presents J-lay installation of SCRs for LS 17-2 project.

LS17-2 commenced gas production successfully in June of 2021. The J-lay installation was the method of choice for the installation of 10″, 12″, and 18″ risers. This paper first introduces the layout and description of SCRs for LS17-2 project. With the site-specific metocean design basis, this paper presents a J-lay installation design, installation procedures, installation analysis of key steps, and inspection after installation of the SCRs for the CNOOC Lingshui 17-2 field.

Using the field’s 12″ SCRs as an example, this paper discusses the key parameters of the field, installation procedures, and the installation analysis to ensure that the structural integrity of riser during laydown, handover, and pull-in is maintained. The maximum top tension and lifting load are also computed to check against load capacity of installation equipment.

This paper finally summarized the findings for J-lay installation of risers for LS 17-2 project. The lessons learned from the installation are also discussed.
Modeling and Control Design for Ship Hybrid Propulsion Systems
Authors: Gao Fan , Brodtkorb Astrid H. , Zadeh Mehdi , Mo Sigrid Marie
Published: August 2024

This paper presents the modeling and controller design of hybrid propulsion systems with shaft generator. The proposed modeling framework is simulated and validated with a case study of a line-fishing ship, M/S Geir. The studied hybrid propulsion system consists of a main diesel engine, a shaft system with gearbox, and a controllable-pitch propeller (CPP), while the electric system incorporates two auxiliary gensets, a shaft generator, a bidirectional drive, and a battery set. Efficiency models have been developed and analyzed for each individual component in the proposed framework. The proposed methodology of integrating simplified dynamic models with efficiency models enables a comprehensive evaluation of efficiency and dynamic analysis for large hybrid ship power and propulsion systems. The presented analysis provides insights into the coordinated functioning of the various components, offering a holistic perspective on the hybrid system’s efficiency and performance within the specific operational context of the use case vessel M/S Geir.
Lateral Buckling Control With Residual Curvature Method for Ultra Deep Water Flowlines
Authors: Jebali Adel , Solano Rafael F. , Caine Julien , Romero Antonio P. G. , Dos Santos Thiago L. A. , Hansen Alexandre S. , Amarante Jonylson
Published: August 2024

The lateral buckling design process for deep and ultra deep water fields has matured in recent years, particularly with steel sleepers and/or distributed buoyancies as the main triggering concepts (buckling initiators). However, depending on field conditions and geographical location, complex engineering, manufacturing, or installation may be encountered. Furthermore, the solution may not be cost-effective, especially for projects requiring a large number of triggers.

The residual curvature method (RCM), which offers an economical and practical solution with low environmental impact, has been used frequently for shallow water projects and rarely proposed for deep and ultra deep water. This is essentially due to the challenges in terms of landing orientation of the RCM on very soft soils associated with deep water and the resulting in-place reliability question.

This paper will present how the Residual Curvature Method can be used as a reliable buckling control measure for ultra deep water flowlines operating under high internal pressure and high temperature (HPHT) conditions. The case study is the Mero 2 project offshore Brazil.

The Mero 2 ultra deep water project includes rigid mechanically lined pipeline (MLP) systems which operate under HPHT for oil production and water alternating gas injection. The pipelines are exposed (unburied) with fully restrained anchoring systems at both ends using pin-piles. They will withstand high operating conditions, including permanent and transient flow regimes with several shutdown/restart cycles predicted during the design life. This induces large compressive axial forces in the pipeline without expansion absorption at either end (no sliding, i.e. fixed-fixed) and requires, therefore, buckle initiators such as RCM to control the lateral buckling behavior.

The solutions and measures proposed to ensure acceptable RCM lateral offset, under as-laid conditions, will be presented. The interaction between the residual curvature (RC) and soil, as well as the competition with on-bottom rogue buckles, will be shown. The reliability and robustness of the proposed lateral buckling solution for Mero 2 pipelines will be discussed. In addition, the advantages of the RCM and its limitations will be reviewed.
The Front Runner of Roll Waves in Mudflow
Authors: Yu Boyuan , Chu Vincent H.
Published: August 2024

Mudflow is destructive because of its intrinsic tendency to become unstable, leading to roll waves that can impact structures with great force. We examined the rheological properties of landslide muds, conducted direct numerical simulations of the roll waves in the mudflow, and compared the results obtained from a shallow mudflow model. Simulations are performed to study (i) the temporal growth of periodic disturbances of different wavelengths and Froude numbers and (ii) the spatial development of the wave packet produced by a local disturbance. Most existing studies of roll waves are concerned with periodic roll waves derived from shallow mudflow models, assuming hydrostatic pressure variation and a constant velocity profile over the depth. However, this paper focuses on the spatial development of front-runners. The solution to the hyperbolic equations, derived from the shallow-mudflow approximation, is shock waves of depth and velocity discontinuities at the wavefronts. On the other hand, the direct numerical simulations of the laminar mudflow can show a more realistic mudflow instability that includes wave breaking and entrapment of air during the beaking. Nevertheless, despite the discontinuity, the shallow-mudflow model is still a reasonable approximation in the region away from waves breaking when the wavelength of the front runner becomes sufficiently large.
Optimization of Offshore FPV Modules in Early Design Phase
Authors: Jin Jingzhe , Zhang Liqing , Lin Zhiliang , Kong Jiehong , Gao Zhen
Published: August 2024

Offshore Floating Photovoltaic (FPV) systems are gaining attention due to the high Technology Readiness Levels (TRL) of PV panels and offshore structures. Numerous offshore FPV design proposals exist, but none have yet met industrial standards. The designs fall into two main categories: membrane type supported by a floating collar/air cushion and modular structure type comprising interconnected FPV modules. This paper uses semi-analytical methods to optimize the modular structure type design, considering fabrication cost, module stability, and hydrodynamic response in waves.
Navigating the Future: Strategic Management of a Mobile Aquaculture System With Receding-Horizon Control
Authors: Pillai Ajit C. , Ashton Ian G. C. , Johanning Lars , Cook Denham G. , Vennell Ross , Black Suzanne E.
Published: August 2024

The New Zealand-based Whakapōhewa ki ahumoana Reimagining Aquaculture project (funded by the Ministry for Business, Innovation and Employment Endeavour Fund) lead by Plant & Food Research, is designing a mobile aquaculture system for finfish, towed by an autonomous vessel, powered by renewable energy sources.

This work presents the vessel management strategy for this mobile aquaculture solution, inspired by receding-horizon control, which uses available weather forecasts to minimize the energy consumption by the autonomous vessel while maintaining an optimal flow speed through the fish enclosure such that the optimal biological conditions (e.g. swim speed) for the fish can be maintained. The simulations performed for a generalized salmonid fish species cultured in Tasman Bay, New Zealand show that the food storage capacity of the autonomous vessel is consistently a limiting factor at low swim speeds (≤ 0.4 m s−1), while energy capacity limits at higher swim speeds. The simulations highlight how such a strategy allows the system to successfully shelter from storms and by virtue of going further from its “safe haven” can maintain optimal conditions for the fish through the enclosure. We anticipate this work to be a starting point for more sophisticated management strategies considering engineering criteria, species specific requirements, and environmental parameters such as temperature and water quality that impact fish welfare explicitly.
Simplified Three-Dimensional Finite Element Models of a Flexible Pipe Interlocked Carcass Under Bending
Authors: Geremias Toni Fernando , Provasi Rodrigo , de Arruda Martins Clóvis
Published: August 2024

A flexible pipe interlocked carcass is characterized by having both high flexibility and radial stiffness, being, therefore, a layer of relevant structural function. When designing a carcass, these two properties must be met at the same time, which is only possible thanks to its helical and interlocked geometry. On the other hand, the geometric complexity makes its modeling process equally complex, whether numerical or analytical. In this context, over the last years, the authors published some papers with the objective of better understanding the mechanical behavior of the carcass under tension and bending loads, as it is important for the development of more efficient modeling techniques. Regarding bending, two fully three-dimensional finite element models of the interlocked carcass were recently presented, which considered the exact helical shape of the carcass and all contacts involved in the interlocking. Despite being very complete, these models were quite computationally expensive models. To simplify the carcass modeling process, the ring hypothesis is commonly adopted, which consists of disregarding its lay angle. This approach has already been widely used and studied for collapse problems, but, to the authors’ knowledge, its impact has not yet been evaluated for the bending case. Therefore, the present work proposes a series of simplified finite element models of the interlocked carcass under bending loads and that are computationally efficient, in addition to a detailed evaluation of the impacts of all adopted simplifications, always having as paradigm for comparison the costly, most complete, fully helical interlocked versions.
Evaluation of the Inner Liner in Unbounded Flexible Pipelines in the Sealing System of End-Fitting
Authors: Saneian Mohsen , Bai Yong
Published: August 2024

Unbonded flexible pipelines are widely used in the offshore oil and gas industry due to their numerous structural configurations and their adaptability to different environmental requirements. However, designing the end-fitting for connecting these pipes to the floating structure is one of the most challenging tasks. This connector has two main functions, ensuring sealing of the pipe fluid and transferring the loads from the pipe to the connecting system unit. The flexible pipes consist of many layers including carcass, inner liner, pressure armour, tensile armour, and outer sheath. The carcass prevents the collapse of the pipe against high hydrostatic pressure, and the inner liner plays the most significant part in the sealing system of the end-fitting. The current study assesses this role. The sealing method is based on dividing the termination of risers into two devices; barrier seal which is the mechanical restraint on the polymer barrier, and the seal system that is applied to seal the fluid of the riser. Therefore, two leak paths are observed; between the barrier seal and the polymer barrier, as well as, between the barrier seal and the body. Consequently, to improve the metal seal ring under high pressure, the compression on the polymer barrier must be enough. Besides, the contact pressure at the metal-to-the-metal interface has to be adequate.
A Flexible Support System for Large Wind Turbines
Authors: Zhao Wangwen
Published: August 2024

As offshore wind turbines scale up for LCOE reduction, foundation costs could spiral out of control. We propose a revolutionary flexible support system that slashes loads on the tower by up to 90%.

This design prioritizes load reduction over resistance with the following key features:

• Aerodynamic Shaped Tower Section: Minimizes wind forces while maximizing structural efficiency.

• Self-Alignment with Wind: Eliminates complex active yaw systems, boosting energy capture and simplifying design.

• Passive Yaw Control: Harnesses wind to guide the rotor, lowering maintenance and enhancing reliability.

These features lead to large LCOE reduction by reducing CAPEX from lighter and simpler tower and foundation, reducing OPEX via simplified maintenance, and increased energy production. This disruptive approach unlocks wider wind adoption including floating or fixed, onshore and repurposement, accelerating the transition to a sustainable future.
On the Applicability of DNN-Based Models Trained Under the Fixed Spar Condition to Control Force Estimation of a TLP Moored PA-WEC
Authors: Kawagishi Tatsuki , Murai Motohiko , Han Jialin
Published: August 2024

One of the ocean renewable energy sources is wave energy. This study focuses on a floating point-absorber wave energy converter (PA-WEC). A PA-WEC is composed of a float and a spar, with the float moving in heave relative to the spar. The relative motion generates electricity. However, the generated electric energy may decrease sharply when the heave motions of the float and the spar are in phase. To address this issue, one of the approaches is to minimize the heave motion of the spar by mooring it with a tension leg platform (TLP) that consists of a footing and tendons (mooring lines).

In real sea, the appropriate control force cannot be identified instantaneously. This is because the periodic components of the irregular waves are “unknown”. The authors have investigated that the appropriate control force could be estimated instantaneously using deep neural network (DNN)-based trained models by considering only the heave motion of the float assuming the spar remains fixed in space. However, in fact, the spar is moored. Even if a TLP moored PA-WEC, the surge/sway motions may have an influence on the heave motion of the float relative to the spar, and consequently affect the power generation performance of the PA-WEC.

The purpose of this study is to reveal whether the DNN-based models trained under the condition where the spar remains fixed can be applied to a TLP moored PA-WEC. These trained models can be built without a prior knowledge of the mooring of a PA-WEC. Time domain simulation with 7 degrees of freedom (7DOFs) of a TLP moored PA-WEC is conducted with the control force estimated using the trained models in regular waves and irregular waves.
A Study on Validation of Linear Seakeeping Codes With Benchmark Tank Tests for Container Ship and VLCC
Authors: Takeda Katsutoshi , Matsui Sadaoki , Sugimoto Kei
Published: August 2024

Direct load-structure analysis can apply ship responses through seakeeping analysis to structural strength assessment and has been put into practical use. To employ this method, it is imperative to validate the accuracy of the seakeeping code with experimental data. In this study, model ships for a very large container ship and a VLCC (Very Large Crude oil Carrier) were designed to acquire measured data of ship responses in tank tests. In the validation process of the seakeeping code, it is necessary to investigate the cause of differences in ship responses. Our initial focus is how to input the weight and KG (Vertical center of gravity from keel) distribution. We found that the difference of these distributions affects the variations in ship responses. Subsequently, a comparative study was carried out with two seakeeping codes based on the 3-dimensinal Green’s function method. The measured ship responses and numerical results by the codes were generally in good agreement. However, there were significant discrepancies in some responses. This was due to minor differences in a part of method in which the codes calculated hull girder sectional force, despite the same basic theory.
Development of Two-Phase Flow-Induced Vibration Predicting Method for a Piping System With Elbows
Authors: Komuro Yoshiteru , Nakanishi Hiroaki , Kondo Yoshiyuki , Takemoto Masashi , Hirota Kazuo , Matsumoto Shunsaku , Sugimura Tadashi , Honjo Shintaro
Published: August 2024

Gas-liquid intermittent two-phase flow in the piping system may cause piping vibration due to the repeating collision of liquid chunk onto the inner wall of elbow fittings. To design and monitor of piping system with elbows in Oil & Gas production plants or chemical plants, it is necessary to develop a prediction method for unsteady two-phase flow in the piping, vibration of the piping and the piping fatigue strength.

Several cases of unsteady two-phase flow Computational Fluid Dynamics (CFD) analysis were conducted to calculate excitation forces at each elbow of a jumper piping. In a slugging condition, the intermitted two-phase flow was simulated in CFD analysis and the frequency characteristics of fluid excitation force were obtained.

Conducting the vibration analysis, the stress at each section was evaluated and the maximum stress in a slugging velocity condition was larger than that in other velocity conditions such as bubbly flow condition and stratified flow condition. Fatigue analysis in frequency domain was carried out to estimate the lifetime of elbow fittings, using the stress response spectrum in each elbow estimated by the vibration analysis.

Through these analyses, it is confirmed that the developed analysis method can predict the two-phase flow and vibration characteristics which are qualitatively expected in advance.
Hydroelastic Analysis of Interconnected Modular Systems for Floating Offshore Solar Photovoltaic Use
Authors: Chen Yongqiang , Zhang Yifan , Ren Xiudi , Li Jun , Zhang Xiantao
Published: August 2024

An interconnected-modular system can be used as the floating foundation for offshore solar photovoltaic. The modular alone is a middle-hollow rectangular plate, where the hollow part sits the photovoltaic panel. A large number of modulars are interconnected to form a very large floating structure of huge hectares and a large length-to-thickness ratio, which makes its dynamic response a typical FSI problem. The Discrete Module Finite Element (DMFE) method is applied to the structure to calculate hydroelasticity under regular waves. The DMFE method first divides the structure into a certain number of macro-submodules with each of them treated as rigid bodies to perform a multi-rigid-body hydrodynamic analysis to obtain the hydrodynamic coefficients using the 3D potential flow theory. Each macro-submodule is treated as a lumped mass and the shell element is used to discretize the structure with the nodes being categorized into lumped masses, boundary nodes and inner nodes. The lumped-mass stiffness matrix is derived based on the sub-structure approach and matrix manipulations. Recovery of displacement response is given. Good agreement with the mode-superposition method verifies the current model.
Laserline SD® Seam Welded Super Duplex Umbilical Tubing for Up to 15 KSI DWP
Authors: Kim Yong-Joo , Melvin Tucker , Signorelli Rodrigo
Published: August 2024

The main objective of this paper is to present the product and process performance capabilities of seam-welded S32750 umbilical tubing for 10 KSI and 15 KSI DWP applications and discuss the specialized processes, project management, and documentation systems used for umbilical tube production. This paper also provides an overview of super duplex steel and sheet coil making, along with the manufacturing process for key seam welded tube, tube inspection, and testing. Actual technical data is presented and compared with typical industry requirements.

This paper addresses the relevant aspects of S32750 cold-rolled strip used for seam welded umbilical tubing. The requirements imposed by the criticality of the subsea umbilicals raise the bar on the steel manufacturer. From a chemical composition to meet the desired minimum pitting resistance equivalent, to the production of clean steel and mechanical properties in the final tube, all processes are essential to withstand the high-pressure environment, without compromising the fabricability and fatigue life which can be up to thirty years.

With the evolution of modern laser beam welding technology & highly specialized process monitoring and control systems, seam welded super duplex umbilical tube produced in compliance with API 17E, ASTM A789 and end user’s specific requirements has now gained a respectable record of proven performance. This paper also provides product attributes including dimensional data, mechanical properties, ferrite balance, corrosion, and fatigue performance for dynamic applications.
Design Considerations for Fuel Cell Systems Employed in Long-Endurance Autonomous Small-Sized Subsea Robots
Authors: Penga Željko , Xing Yihan , Bodner Merit , Berntzen Tor-Olav
Published: August 2024

Autonomous robots have the potential to significantly decrease operational costs associated with human operations and increase safety through the reduction of human errors. With the advancement in robotics today, many more are considering using autonomous subsea robots in various industries, such as fish farming, subsea oil and gas, ocean renewables and even subsea mineral mining. The ability to have long endurance, i.e., to operate for long periods without refuelling, is crucial to reap the benefits of robot autonomy better. Fuel cells, with their significantly higher energy storage capacity than lithium batteries, offer an attractive option to provide the long endurance required. Fuel cells have been successfully used in various land-based applications, such as cars and trains. However, to date, fuel cells have not been very much employed in underwater vehicles. Several subsea-related challenges arise when fuel cells are employed in subsea robots, which must be addressed. These include (i) underwater storage of hydrogen and oxygen, (ii) subsea-ambient environmental issues such as large hydrostatic pressures and cold ambient underwater conditions, (iii) dynamic manoeuvring actions by the robot that can cause large trim motions and (iv) fuel cell operations in a sealed container and with pure oxygen. This paper will discuss the most important design conditions that can arise when employing fuel cell systems for autonomous small-sized subsea robots with long endurance requirements.