bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparative Study of Mechanical Properties of Biodegradable PBSAT and PA Gillnets in Norwegian Coastal Waters
Authors: Su Biao , Moe Føre Heidi , Grimaldo Eduardo 
Published: November 2019

Abstract
This paper presents a comparative study of mechanical properties of biodegradable PBSAT (polybutylene succinate co-adipate-co-terephthalate) and conventional polyamide (PA) gillnets used in Norwegian fisheries. Field tests were performed to simulate abandoned, lost, or otherwise discarded fishing gear. Changes in mechanical properties of PBSAT and PA nets in two Norwegian coastal environments were studied. Samples of biodegradable PBSAT gillnets and PA gillnets were placed inside modified lobster pots at four different locations: two outside the island Hitra in the middle of Norway and two outside Tromsø in the north of Norway. For each pot, seawater temperature was logged each hour, and net samples were retrieved for analyses at 3 to 9 months intervals.
Tensile strength testing was performed to determine and compare mechanical properties of biodegradable and PA monofilaments and gillnets. Comparative analyses were conducted, aimed at investigating the different behaviors of biodegradable material and conventional PA material, and the possible influence of seawater temperature on the degradation process of biodegradable PBSAT gillnets. Reduced tensile strength and elongation at break, and a slight increase in stiffness was observed for both PA and PBSAT monofilaments after the field trial at Hitra, indicating degradation of both polymer materials. After 25 months immersion in seawater, the PBSAT gillnets exhibited a significant reduction of tensile strength due to seawater exposure (35%), and the tensile strength of PBSAT gillnets was then 26% lower than the average strength of the PA net samples.
Scaling of Pop-Ins During Brittle Fracture Testing
Authors: Coppejans O. J. , Walters C. L. 
Published: November 2019

Abstract
Measurement of the fracture toughness of steel is important for the assurance of the safety of ships and offshore structures, especially when these structures are made of thick sections and/or applied in cold environments. One key factor that will affect the determination of the fracture toughness is a pop-in, which is a short event in which unstable fracture is initiated and then self-arrests. If the pop-in is large enough, it will be used to calculate the fracture toughness. Pop-ins are believed to be the products of local brittle zones, which occur randomly at crack tips and have finite sizes. Fracture toughness testing codes have ways of determining whether a pop-in is critical (thus, identifying the maximum force and displacement to be used in the determination of the toughness of the material) or not important (thus, allowing for the test to proceed).
In an ongoing project on the use of small-scale fracture specimens to predict standard fracture toughness test results, we would like to know how pop-in acceptance criteria should be scaled for specimen size. It is expected that the physical size of the brittle zones that cause pop-ins is invariant of specimen size, meaning that the contribution of the pop-in will be proportionally more important for smaller specimens. An analytical method for relating the pop-ins on one specimen size to another specimen size is developed. This method is partially verified by observations on the size of a local brittle zone observed on a fracture surface and the effect of that pop-in on the force-displacement curve during a CTOD test. The analytical method showed that an equivalent pop-in for a small-scale specimen is indeed larger, but that the effect was subtle.
On the Use of Consumer-Grade Remotely Piloted Aircraft Systems for Monitoring Shallow Coral Reefs in Colombia: Case Old Providence Island
Authors: Lopera-Gil Manuela , Vásquez Rafael E. , Zuluaga Carlos A. , Zapata-Ramírez Paula A. 
Published: November 2019

Abstract
This work addresses the initiative to use consumer-grade Remotely Piloted Aircraft Systems (RPAS), known as Unmanned Aerial Vehicles (UAVs) or drones, as potential instruments for the evaluation and monitoring of shallow coral reefs in Colombia. This initiative started with the construction of an interdisciplinary team that includes institutions from academia, the Ministry of Defense, the Ministry of Environment and Sustainable Development, a marine surveying private company, and a German research center. The test was conducted inside the Marine Protected Area (MPA) of Old Providence; an island that is located at the Archipelago of San Andrs, Providencia and Santa Catalina, which includes the Seaflower Biosphere Reserve (the third largest true barrier reef in the world). Field data were acquired by using two DJI RPAS: Phantom 4 Pro and Mavic Air, and geo-referenced diving. In this work, we show the potential for using such technologies with a geometrically corrected mosaic of images of Crab Cay, a small cay located inside the MPA. This project is the first of its kind within the Seaflower Reserve and may support technology-based data collection, increasing the quality of information that can be useful to make important decisions regarding ocean space utilization. Additionally, obtained images will be shared for the benefit of local communities, other stakeholders, and visitors, in a manner that opens up science to broader society, promoting outreach activities and educational tool via photos and videos.
Estimating Extreme Waves in the Gulf of Mexico Using a Simple Spatial Extremes Model
Authors: Wada Ryota , Jonathan Philip , Waseda Takuji , Fan Shejun 
Published: November 2019

Abstract
We seek to characterize the behavior of extreme waves in the Gulf of Mexico, using a 109 year-long wave hindcast (GOMOS). The largest waves in this region are driven by strong winds from hurricanes. Design of offshore production systems requires the estimation of extreme metocean conditions corresponding to return periods from 1 year to 10,000 years and beyond. For extrapolation to long return periods, estimation using data for around 100 years from a single location will incur large uncertainties. Approaches such as spatial pooling, cyclone track-shifting and explicit track modeling have been proposed to alleviate this problem. The underlying problem in spatial pooling is the aggregation of dependent data and hence underestimation of uncertainty using naïve analysis; techniques such as block-bootstrapping can be used to inflate uncertainties to more realistic levels. The usefulness of cyclone track-shifting or explicit track modeling is dependent on the appropriateness of the physical assumptions underpinning such a model.
In this paper, we utilize a simple spatial statistical model for extreme value estimation of significant wave height under tropical cyclones, known as STM-E, proposed in Wada et al. (2018). The STM-E model was developed to characterize extreme waves offshore Japan, also dominated by tropical cyclones. The method relies on the estimation of two distributions from a sample of data, namely the distribution of spatio-temporal maximum (STM) and the exposure (E). In the current work, we apply STM-E to extreme wave analysis in Gulf of Mexico. The STM-E estimate provides a parsimonious spatially-smooth distribution of extreme waves, with smaller uncertainties per location compared to estimates using data from a single location. We also discuss the estimated characteristics of extreme wave environments in this region.
Pipeline Rockberm Design Principles for UHB Mitigation
Authors: Liu M. , Cross C. 
Published: November 2019

Abstract
Rockdumping may be necessary for pipeline UHB mitigation, crossings for separation, protection and stability. It is imperative that the structural reliability analysis for UHB is assessed with all aspects and factors taken into account to predict accurately the amount of rock and download required to ensure the integrity of pipelines. For UHB mitigation design, there are a number of analytical models available for download calculations to determine rockdump schedule.
This paper examines and highlights some fundamental issues and pitfalls for rockberm design with respect to UHB download assessment. The lateral breakout has been previously addressed by some engineers and researchers. The potential risk for pipe to breakout from the rockberm is studied herein focusing on the vertical direction due to upheaval load.
Based on the theoretical analysis and numerical FEA modelling, it is demonstrated that the common practice for rockbern design is not consistent resulting in unconservative rockdumping for UHB stability. Further design optimization can be compromised by lack of understanding of the failure mechanisms. Uplift resistance for stratified and layered soil types applicable for rock enhancement is also discussed and formulated. The design principle and rationale for selecting an appropriate rockberm profile and its sizing is proposed. Its effect on the UHB is illustrated by a detailed theoretical analysis and a series of numerical simulations with respect to pipeline dimensions.
Hydrodynamic Analysis of a Suspended Cylinder Under Regular Wave Loading Based on Computational Fluid Dynamics
Authors: Mucha Philipp , Robertson Amy , Jonkman Jason , Wendt Fabian 
Published: November 2019

Abstract
An investigation into the computation of hydrodynamic loads on a suspended cylinder in regular waves is presented. The primary goal was to perform a three-way validation of the loads between experimental measurements and simulations from two computational methods. Experimental measurements of the longitudinal in-line force on a cylinder suspended at a fixed position were available from the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project, Phase Ia. These measurements were compared to computational fluid dynamics (CFD) simulations based on the solution of Reynolds-averaged Navier-Stokes (RANS) equations, as implemented in STAR-CCM+. The study encompassed a sensitivity analysis of the loads computed in STAR-CCM+ based on wave modeling, boundary conditions, turbulence modeling, and spatial and temporal discretization. The analysis was supplemented by results generated with the offshore wind turbine engineering software OpenFAST, based on a hybrid combination of second-order potential flow and viscous drag from Morison’s equation. The focus of the investigation was on the assessment of the accuracy of the computation of first- and higher-order hydrodynamic loads. Substantial differences were observed in the numerical prediction of the second and third harmonic force contribution. Local flow field analysis with CFD was applied to study the physics of wave run-up and diffraction dynamics to identify the causes.
Nonlinear Fourier Analysis Algorithm and Models for Water Waves in Terms of Surface Elevation, Amplitude Modulations
Authors: Osborne Alfred R. 
Published: November 2019

Abstract
This paper addresses two issues with regard to nonlinear ocean waves. (1) The first issue relates to the often-confused differences between the coordinates used for the measurement and characterization of ocean surface waves: The surface elevation and the complex modulation of a wave field. (2) The second issue relates to the very different kinds of physical wave behavior that occur in shallow and deep water. Both issues come from the known, very different behaviors of deep and shallow water waves. In shallow water one often uses the Korteweg-deVries that describes the wave surface elevation in terms of cnoidal waves and solitons. In deep water one uses the nonlinear Schrödinger equation whose solutions correspond to the complex envelope of a wave field that has Stokes wave and breather solutions. Here I make clear the relationships between the two ways of characterizing surface waves. Furthermore, and more importantly, I address the issues of matching the two types of wave behavior as the wave motion passes from deep to shallow water, or vice versa. For wave measurements we normally obtain the surface elevation with a wave staff, resistance gauge or pressure recorder for getting time series. Remote sensing applications relate to the use of lidar, radar or synthetic aperture radar for obtaining space series. The two types of wave behavior can therefore crucially depend on where the instrument is placed on the “ground track” or “field” over which the lidar or radar measurements are made. Thus the matching problem from deep to shallow water is not only important for wave measurements, but also for wave modeling. Modern wave models [Osborne, 2010, 2018, 2019a, 2019b] that maintain the coherent structures of wave dynamics (solitons, Stokes waves, breathers, superbreathers, vortices, etc.) must naturally pass from deep to shallow water where the nature of the nonlinear physics, and the form of the coherent structures, change. I address these issues and more herein. This paper is directed towards the development of methods for the real time measurement of waves by shipboard radar and for wave measurements by airplane and helicopter using lidar and synthetic aperture radar. Wave modeling efforts are also underway.
Evolution of the Stress-Induced Magnetic Field of Pipeline Steel due to Fatigue Loading
Authors: Bao Sheng , Zhao Zhengye , Luo Qiang , Gu Yibin 
Published: November 2019

Abstract
The objective of this research is to explore the correlation between piezomagnetic fields and cyclic loading in X80 pipeline steel. A series of stress-controlled fatigue tests were carried out, and the magnetic field variations were recorded simultaneously during the whole loading process. The results demonstrate that the fatigue life of the investigated steel can be divided into three stages. The reversal points that appear during the loading and unloading processes can be used as new parameters to reflect the fatigue state and estimate the fatigue life.
Impact of a Plate on an Asymmetric Water Wedge
Authors: Wen Xueliang , Liu Peiqing , Qu Qiulin , Liu Qingchuan 
Published: November 2019

Abstract
The impacts of a plate on an asymmetric water wedge with a constant speed and with varying speed are studied in this paper by considering the fluid to be incompressible, inviscid, weightless and with negligible surface tension effect and the flow to be irrotational. We derive the analytical solution for the impact with a constant speed with the help of Wagner’s function and Schwarz-Christophel mapping technique, and then proceed the numerical process given by following an iterative method. The verification is conducted by comparing the profile of free surface and the pressure distribution predicted by the present method and the published data. The impact with varying speed is first studied by VOF method and compared with the impact with a constant speed. An approximate solution is provided for the impact with speed that satisfies a power law of time based on the CFD results from VOF method. The approximate solution can provide an explicit expression for the pressure that is acting on the plate, which can describe the effects of the changing impact speed and the acceleration of plate.
Situation Awareness of Autonomous Ship Navigation in a Mixed Environment Under Advanced Ship Predictor
Authors: Perera Lokukaluge P. , Murray Brian 
Published: November 2019

Abstract
Autonomous ship navigation in a mixed environment, where remote-controlled, autonomous and manned vessels are interacting, is considered. Since these vessels can have various encounter situations, adequate knowledge on such situations should be acquired to take appropriate navigation actions. That has often been categorized as situation awareness in a mixed environment, where appropriate tools and techniques to extract the respective knowledge on ship encounter situations should be developed. The collision risk assessment procedure has an important role in the same knowledge and that can eventually be used towards the respective collision avoidance actions. Hence, possible ship collision and near-miss situations can be avoided by both humans as well as systems due to their actions. Ship collision avoidance actions are regulated by the International Regulations for Preventing Collisions at Sea 1972 (COLREGs) in open sea areas and additional local navigation rules and regulations can also enforce especially in confined waters and maritime traffic lanes. It is expected that the COLREGs and other navigation rules and regulations will be interpreted by both humans as well as systems in future vessels and those interpretations will be executed as collision avoidance actions by the respective vessels in a mixed environment. Adequate understanding on situation awareness should be achieved to overcome possible regulatory failure due to human and system decisions in these situations. Hence, this study focuses on identifying such challenges in future ship encounters with possible solutions to improve situation awareness in a mixed environment as the main contribution.
Application of the MCC Model on 2-D Finite Element Analyses for the Assessment of Pipe-Soil Lateral Response
Authors: Thomaz Tianna Bloise , Carneiro Daniel , Bruno Ellwanger Gilberto , Sant’Anna do Nascimento Leonardo 
Published: November 2019

Abstract
The assessment of the pipe-soil interaction is an area of continuous research, either by the application of small- and full-scale tests in the attempt to reproduce accurately the interaction of the pipelines and the soil, or by the development of sophisticated numerical simulation models accounting for different sources of nonlinearities.
Motivated to investigate the interaction between subsea pipelines and the soil, with focus in the response under lateral loading, 2-D finite element numerical simulations have been developed applying soil plasticity mechanisms through the extended maximum distortion strain energy criteria [1] and critical state concept [2]. The modified-cam-clay MCC model has been adopted to simulate the soil behavior in large deformations, aiming to numerically reproduce site conditions for selected pipelines ranging from 12 in to 18 in.
The results are presented in terms of the lateral force-displacement curves for numerically representative drained and undrained cases. For the simulations investigated in this work, the agreement of the numerical results with the analytical breakout lateral resistances obtained from the SAFEBUCK guideline [3] formulations have been confirmed for cases where the ratio of initial pipe embedment and pipe diameter is below 0.4.
Enhanced Cement Composition for Preventing Annular Gas Migration
Authors: Kwatia George , Al Ramadan Mustafa , Salehi Saeed , Teodoriu Catalin 
Published: November 2019

Abstract
Cementing operations in deepwater exhibit many challenges worldwide due to shallow flows. Cement sheath integrity and durability play key roles in the oil and gas industry, particularly during drilling and completion stages. Cement sealability serves in maintaining the well integrity by preventing fluid migration to surface and adjacent formations. Failure of cement to seal the annulus can lead to serious dilemmas that may result in loss of well integrity.
Gas migration through cemented annulus has been a major issue in the oil and gas industry for decades. Anti-gas migration additives are usually mixed with the cement slurry to combat and prevent gas migration. In fact, these additives enhance and improve the cement sealability, bonding, and serve in preventing microannuli evolution. Cement sealability can be assessed and evaluated by their ability to seal and prevent any leakage through and around the cemented annulus. Few laboratory studies have been conducted to evaluate the sealability of oil well cement.
In this study, a setup was built to simulate the gas migration through and around the cement. A series of experiments were conducted on these setups to examine the cement sealability of neat Class H cement and also to evaluate the effect of anti-gas migration additives on the cement sealability. Different additives were used in this setup such as microsilica, fly ash, nanomaterials and latex.
Experiments conducted in this work revealed that the cement (without anti-gas migration additive) lack the ability to seal the annulus. Cement slurries prepared with latex improved the cement sealability and mitigated gas migration for a longer time compared to the other slurries. The cement slurry formulated with a commercial additive completely prevented gas migration and proved to be a gas tight. Also, it was found that slurries with short gas transit times have a decent potential to mitigate gas migration, and this depends on the additives used to prepare the cement slurry.
Environmental Regeneration for a Small-Scale Beach “Heda-Mihama Project”
Authors: Tabeta Shigeru , Okamoto Ken , Kato Takayoshi , Hisamatsu Rikito , Muto Hiroaki , Hino Akinori , Murai Motohiko , Ito Sho , Kitazawa Daisuke , Kinoshita Takeshi 
Published: November 2019

Abstract
In 1950’s and 1960’s, Mihama beach in Heda Bay located on western coast of Izu peninsular had been famous for the richness in shell fauna, for example, about 400 species including rare ones were collected. In 2000’s, however, the impoverishment of ecosystem function has become considerable, which led us to project the investigation on the origin and restoration. The authors carried out field survey in 2007–2008 and found that the impoverishment of Mihama is derived not from surface water but from the benthic environment. The measured water current at the site was quite small, which indicated the water exchange was very weak. It must be one of the main causes of unfavorable benthic environment. Thus environmental regeneration plans for Mihama was proposed in which the pears blocking the water current be removed. In order to assess the effect of proposed plans, simulation-based habitat evaluation was conducted. A three-dimensional hydrodynamic and sediment transport models were developed to reproduce the characteristics of currents and predict the sediment size around Mihama. For the assessment of the ecological status, HEP (Habitat Evaluation Procedure) was employed, in which one of the typical species of bivalves is chosen as a target species. Water depth, sediment size, friction velocity at the bottom, etc. were considered as the environmental factors for the target species. The suitability indices (SI) for each environmental factors were calculated by using the results of hydrodynamic and sediment transport simulations. By using the developed scheme, total habitat unit was evaluated for the proposed regeneration plans and compared to that without countermeasures. It was predicted that the removal of the piers will improve the habitat condition in the target site. Based on the proposal by the authors, a water pathway under the pier was built in 2009. The authors conducted field survey again in 2014 and confirmed that the benthic environment has been improved.