bluuebunny/crossref_metadata_2025_split huggingface dataset:
Straightener Settings for Under-Straight Residual Curvature of Reel Laid Pipeline
Authors: Roy Alan , Rao Venu , Charnaux Carlos , Ragupathy P. , Sriskandarajah T. 
Published: September 2014

The pipeline inplace buckling design by residual curvature method for controlled thermal expansion during operation is a novel and cost effective method for initiating multiple expansion loops for a reel-laid pipeline. The controlled thermal expansion will be initiated and managed by planned buckle sites at regular intervals of say, 1km spacing with residual curvature corresponding to 0.20%–0.25% residual strain.
The pipelines installed by the reel Lay process are required to be straightened by a reverse curvature process which results in pipeline with nominally zero curvature and axial strain. In order to achieve a residual strain of 0.20%–0.25%, two options are available either to over-straight or under-straight the pipelines. This paper discusses the methodology used laying of pipeline with 0.20%–0.25% residual strain at pre-determined intervals by an under-straightening process with a combination of a central 40m under straight section with a residual strain of 0.2%–0.25% and a 15m transition section on either side of the central section, at 1km intervals.
The paper presents the methodology used to determine the settings for the top straightener module of reel lay vessel using finite element analyses, as the equipment settings for under or over straight pipes are not readily available from analytical methods. The optimum settings were obtained after substantial number of FEA simulations allowing for the statistical range in pipe material properties from “strong” to “weak” and these settings are used in reeling trials to make necessary adjustments. The residual strain, out-of-straightness and axial force distributions in pipe sections for straight, under-straight and transition sections are discussed.
The paper discusses how these settings were used on-board the vessel and the modifications and adjustments required to select the final settings for the under-straight curvature for the field development of Statoil Skuld project as a case study. This paper briefly discusses the vessel equipment specific features and limitations that may need to be taken into consideration in finite element analyses to optimise the straightener settings for residual strain.
Fasteners in Subsea Applications: End User Experiences and Requirements
Authors: Rørvik Gisle , Haaland Bjørnar Øvrum , Kirkemo Finn 
Published: September 2014

Fasteners used for critical applications subsea represent a challenge in terms of material selection, quality control, traceability and documentation for manufacture and delivery to ensure adequate performance, integrity and avoidance of costly failures. The definition of critical subsea fasteners are both pressure containing and primary load bearing members, but may in a wider sense also include fasteners which may affect functionality of valves, equipment and instruments for safe, reliable and cost effective operation.
The major failure mechanism experienced during the last decades is so-called hydrogen induced stress cracking (HISC) or hydrogen embrittlement (HE) primarily resulting from the hydrogen charging conditions of the cathodic protection (CP) system. The main bulk of fasteners used subsea is of low alloyed steel grade type (e.g. ASTM 320 Grade L7, L7M, L43 bolts with ASTM 194 Grade 4, 7M, 7 nuts) which relies on electrical continuity to the cathodic protection system to avoid sea water corrosion, but may be prone to HISC/HE if the fastener hardness and strength level exceed the specified and established limits. If higher strength materials are needed from design, either cold formed or precipitation hardened CRA’s are usually selected (e.g. Grade 59, 660, 625, 686, 718, 725), but these may also be susceptible to HISC/HE depending on strength level and manufacturing practice.
The present paper will give some field experience and typical examples of recent HISC failure case histories for low alloyed steel grades, but also for some CRA type of subsea fasteners. Furthermore, some in-house low alloyed steel grade (L7, L43) fastener HISC test results will be presented to indicate the robustness of today’s hardness and strength level restrictions, and at which loading and pre-tension level a given strength grade may be prone to HISC failure. Finally, some experience from manufacturing stage as well as focus areas in materials specification, quality assurance / quality control and design will be discussed.
Environmental Contours for Multicomponent Response
Authors: Leira Bernt J. , Lindstad Halvor Borgen 
Published: September 2014

Approaches for derivation of joint design parameters in relation to multi-component environmental processes are briefly summarized. Within the context of structural design, this is frequently referred to as a “load combination problem”. It is focused on application of design contours for analysis of such load combinations. Contours of this type can be utilized for cases where the different load processes are both correlated and uncorrelated. Existing procedures for construction of such contours are summarized, and extensions to situations where the characteristic time scales for the different process components are widely different are outlined. Development of such tools based on application of “translation processes” (i.e. transformed Gaussian processes) is highlighted.
Analysis of mechanical design formulations which involve several interacting response quantities is further addressed. Utilization of so-called contour response tubes within such a framework is discussed. An example of application is given for a cross-section at the upper end of a flexible riser configuration where the interaction between the tension and curvature processes needs to be taken into accounted.
The Arctic Ship Shape Platform for Well Maintenance, Survey and Workover
Authors: Verbitsky Sergey V. , Agafonov Alexey A. , Fomitchyov Eduard N. , Kovalev Maksim V. , Chesnokova Irina G. , Shinkarenko Olga V. 
Published: September 2014

The conceptual design of floating ship shape platform for well maintenance, survey and workover in prospective fields of Russian Arctic and Sakhalin Island shelf (further The platform) was developed by Krylov State Research Centre specialists with the assistance of CDB “Korall”. The platform under design intended for operation in the Arctic conditions and designed to resist the ice formations such as continuous thin first-year ice and broken ice being the first one in the world practice. The form and chosen hull ice strengthening class allow ensuring safe operation in the mentioned ice conditions.
The main purpose for development of the platform was to minimize the offshore wells downtime providing the cost effective way for maintenance of subsea production systems comparing with floating drilling rigs and drilling vessels that takes a significant investment. The economic assessments have shown that operation of such platform will cost two to three times less than renting of a rig or drillship. Having the working deck space of about 1,000 m2 and the ability to download a variety of equipment the platform can perform a variety of testing and wells repairing procedures both for underwater wellhead and for wells operated on fixed platforms.
Concept to Design: A Novel Seawater Intake Riser System
Authors: Chakkarapani Venkat , Chaudhury Gautam 
Published: September 2014

FLNG cooling process uses large volume of cold seawater drawn from 500–1000 feet below the mean sea level utilizing several vertical risers (20in–30in ID) hanging from the vessel. These risers have requirements very different from conventional risers supported at hang-off and seabed. The design challenges are hang-off loads (in both strength and fatigue), minimum bend radius (MBR) and interference. Hang-off loads can be lowered using low stiffness and light weight risers, but the associated deflections and riser motions will be excessive leading to low MBR and potential interference issues. On the other hand, interference and MBR issues can be addressed by using suffer and heavier weight risers, but this will increase hang-off loads and stresses at the platform base. Weight mass not only affects the dynamics but also provides valuable restoring moment thus helps to reduce static displacement due to current forces. Stiffness affects the bending deflections and helps achieve an acceptable MBR. Based on this, a novel alternative design for seawater intake is to use a single large diameter (60in-70in) steel caisson riser. This paper will briefly outline the preliminary concept verification and concentrate on the engineering of the concept in terms of design optimization, cost/schedule, construction, and installation. Other materials such as High Density Polyethylene Pipe (HDPE), Glass Fiber Reinforced Plastic (GFRP), will be examined for feasibility.
FLNG process technology is continuing to develop to be safe, compact, and cost-efficient which also increases the possibilities of developing a number of stranded deep water gas reservoirs around the world. FLNG processes will become more efficient and cost effective with the proposed novel seawater intake system. Cost effectiveness will be evaluated in a qualitative manner.
Resource Scalability at Wave Energy Test Sites
Authors: Cahill Brendan 
Published: September 2014

Harnessing the power of ocean waves offers enormous potential as a source of renewable energy. To date the technologies for capturing this resource, collectively known as wave energy converters (WECs), have yet to reach commercial viability and continued research and development efforts are required to move wave energy to the industrial scale. Integral to this process is ensuring that technologies progress along a staged development pathway; proving WEC concepts using small scale physical models in controlled settings such as laboratory wave tanks before eventually advancing to testing sub-prototype and full scale devices in real sea conditions.
The primary objective of this research is to improve the understanding of how best to address the scaling of wave resource measurements and wave energy device power production when analyzing the results of sea-trials. This paper draws on measured data from three test sites; Galway Bay in Ireland, the Pacific Marine Energy Test Centre off the coast of Oregon, and Lake Washington, and assesses how accurately they recreate, at reduced scale, the conditions that commercial WEC installations are likely to encounter at exposed deployment locations. Appropriate techniques for extrapolating these results to predict the performance of commercial WECs at energy-rich locations on the west coasts of Ireland and the US are also demonstrated and discussed.
The output from this research will be a set of protocols for addressing wave energy resource scalability to help guide device developers through this important stage of technology progression. Improved knowledge regarding resource scalability will allow for more streamlined progression of WEC concepts from wave tanks to sea-trials, and eventually to full-scale ocean deployment. It will also result in a reduced uncertainty about device power output and survivability, which are key drivers in determining the economic viability of projects.
Determination of Design Metocean Conditions by Response Based Analysis
Authors: Drobyshevski Y. , Whelan J. R. , Wadhwa H. , Anokhin V. 
Published: September 2014

Response Based Analysis (RBA) aims at prediction of the long term distributions of critical responses such as motions, accelerations, wave loads, which have significant impact on the design of a floating system. As compared with the conventional analysis, which predicts the responses of the facility to the N-year return period metocean conditions, RBA provides directly the N-year return period responses by analysing the statistics of their long term time histories. Another outcome of RBA is the Design Metocean Conditions (DMCs) which are combinations of sea state, wind and current causing the corresponding N-year response. The knowledge of the DMCs enables the more detail time domain analysis and model tests to be performed for a set of critical combinations of metocean parameters. It also enables all the associated responses to be determined.
The RBA framework is generally well addressed in the literature, but the DMC identification methods are not necessarily clearly established. The objective of this paper is to present the theoretical background, numerical method and an example for the determination of the N-year return period responses and the associated DMCs for a floating facility. The method includes prediction of the N-year response, identification of the metocean combinations within the available time history which produce this response, determination of the required percentile of the short term response to match the N-year response, and the search for the most probable DMC within the joint probability density of the metocean parameters. Features of the method are discussed and results are presented for several critical responses of a weather vaning vessel.
Implementing New Nonlinear Term in Third Generation Wave Models
Authors: Gramstad Odin , Babanin Alexander 
Published: September 2014

The non-linear interaction term is one of the three key source functions in every third-generation spectral wave model. An update of physics of this term is discussed.
The standard statistical/phase-averaged description of the nonlinear transfer of energy in the wave spectrum (wave-turbulence) is based on Hasselmann’s kinetic equation [1]. In the derivation of the kinetic equation (KE) it is assumed that the evolution takes place on the slow O(ε−4) time scale, where ε is the wave steepness. This excludes the effects of near-resonant quartet interactions that may lead to spectral evolution on the ‘fast’ O(ε−2) time scale.
Generalizations of the KE (GKE) that enable description of spectral evolution on the O(ε−2) time scale [2–4] are discussed. The GKE, first solved numerically in [4], is implemented as a source term in the third generation wave model WAVEWATCH-III. The new source term (GKE) is tested and compared to the other nonlinear-interaction source terms in WAVEWATCH-III; the full KE (WRT method) and the approximate DIA method. It is shown that the GKE gives similar results to the KE in the case of a relatively broad banded and directional spread spectrum, while it shows somewhat larger difference in the case of a more narrow banded spectrum with narrower directional distribution.
We suggest that the GKE may be a suitable replacement to the KE in situations where ‘fast’ spectral evolution takes place.
Predicting the Gain From Deliquification Measures for European Wells
Authors: Nennie E. D. , de Boer J. P. , Schiferli W. 
Published: September 2014

Various Dutch operators have identified a need for increased application of deliquification measures in their North Sea wells. To help meet this need a Joint Industry Project (JIP) was set up to identify knowledge and experience gained in the United States on gas well deliquification and transfer this to European wells. In the first phase of the project a broad overview of the techniques used to deliquify gas wells suffering from liquid loading was made together with a set of available guidelines predicting the range of application.
Having identified potential techniques, a selection tool was developed which suggests the most suitable deliquification technique for a given well. The selection tool can predict the gains in production and ultimate recovery resulting from applying a range of techniques.
The selection tool is based on Tubing Performance Curve (TPC) analysis combined with Inflow Performance Relationship (IPR) analysis; performance therefore depends on the pressure drop over the wellbore (as modelled in the TPC) and on reservoir characteristics. For each of these techniques, a model was available or developed to simplify their operating principles to a TPC.
Results from this tool can aid in deciding which deliquification technique to implement, as it gives a clear overview of the production gain that can be expected for the different techniques [8].
Hydrodynamic Forces Acting on Objects in a Moonpool
Authors: Aspelund Leiv , Pettersen Bjørnar , Visscher Jan , Idsøe Næss Tor-Bjørn 
Published: September 2014

Traditionally, it has often been assumed that the flow conditions in a moonpool are only moderately altered when an object is introduced therein. Moreover, the hydrodynamic forces acting on the object has typically been estimated by Morison’s equation for small volume structures, using the fluid kinematics of the empty moonpool as a basis and applying correction factors for the confined flow conditions, as for an object in a tube or a channel.
To investigate the validity of the traditional approach, an experimental study on the forces acting on objects in a moonpool was performed at NTNU/MARINTEK in Trondheim, Norway in 2013. The experiments were done using a simplified 2-dimensional moonpool model which was given a forced heave motion. Two objects, both with square cross sections but of different sizes, were put inside the moonpool one at the time. The resulting wave elevations inside the moonpool and the forces acting on the objects were recorded and analyzed. To get a deeper understanding of the flow characteristics in the moonpool, PIV measurements were used to obtain the fluid velocity fields.
The experiments revealed that even moderately sized objects (relative to the size of the moonpool) change the fluid motions in the moonpool to a large extent; the overall wave elevation amplitude is strongly reduced and the resonance period is altered. A consequence of this is that there is a large discrepancy between the hydrodynamic forces acting on the objects measured in the experiments and the forces calculated using the traditional approach. The PIV results showed the formation of vortices at the inlet of the moonpool and at the edges of the objects, which is the main source of non-linear damping of the wave elevation inside a moonpool.
Experimental Study of Strucural Responses of a Ship With Multi-Segments and Variable Cross-Section Beams
Authors: Ding Jun , Tian Chao , Wang Xueliang , Cheng Xiaoming , Yang Peng 
Published: September 2014

The motion and structural response to wave loading are studied experimentally for a large ship modeled with multiple segments and beams of variable cross-sections. As opposed to the traditional method with small number of segments and beams of uniform cross-section, the multi-segmented model with beams of variable cross-sections can more accurately simulate some of the hull properties that will otherwise be neglected.
In this paper, the design method for the multi-segmented model is presented, and the model test results for the multi-segmented model with variable cross-section beams are compared with the traditional uniform beams and less segmented model for calm water, regular and irregular wave conditions. The influences of the segment number, variable cross-section, vessel speed and wave height are investigated using the load forecasting methods based on the rigid body and hydroelastic theories. It has been found that using variable cross-section beams can simulate hull stiffness of each section more accurately, and with the increase of the segment number in the ship model, the high frequency characteristics of the bending response are better reflected. Furthermore, the calculation results agree well with the experimental data, and the hydroelastic theory is found to be able to predict the higher frequencies of the hull structural responses. At the same time, with the increase of the vessel speed and wave height, the bending moment and wave height show an obvious nonlinear relationship.
The methods and results presented in this paper have a certain guiding significance for the tank model tests and design of large ship structures.
A Male and Female Gametocyte Functional Viability Assay To Identify Biologically Relevant Malaria Transmission-Blocking Drugs
Authors: Ruecker A. , Mathias D. K. , Straschil U. , Churcher T. S. , Dinglasan R. R. , Leroy D. , Sinden R. E. , Delves M. J. 
Published: September 2014

ABSTRACT

Malaria elimination will require interventions that prevent parasite transmission from the human host to the mosquito. Experimentally, this is usually determined by the expensive and laborious
Plasmodium falciparum
standard membrane feeding assay (PfSMFA), which has limited utility for high-throughput drug screening. In response, we developed the
P. falciparum
dual gamete formation assay (PfDGFA), which faithfully simulates the initial stages of the PfSMFA
in vitro
. It utilizes a dual readout that individually and simultaneously reports on the functional viability of male and female mature stage V gametocytes. To validate, we screen the Medicines for Malaria Venture (MMV) Malaria Box library with the PfDGFA. Unique to this assay, we find compounds that target male gametocytes only and also compounds with reversible and irreversible activity. Most importantly, we show that compound activity in the PfDGFA accurately predicts activity in PfSMFAs, which validates and supports its adoption into the transmission-stage screening pipeline.
Detection of Variants of the pRAS3, pAB5S9, and pSN254 Plasmids in Aeromonas salmonicida subsp. salmonicida: Multidrug Resistance, Interspecies Exchanges, and Plasmid Reshaping
Authors: Vincent Antony T. , Trudel Mélanie V. , Paquet Valérie E. , Boyle Brian , Tanaka Katherine H. , Dallaire-Dufresne Stéphanie , Daher Rana K. , Frenette Michel , Derome Nicolas , Charette Steve J. 
Published: September 2014

ABSTRACT

The ubiquitous water-borne Gram-negative bacterium
Aeromonas salmonicida
subsp.
salmonicida
is the causative agent of furunculosis, a worldwide disease in fish farms. Plasmids carrying antibiotic resistance genes have already been described for this bacterium. The aim of the present study was to identify and characterize additional multidrug resistance plasmids in
A. salmonicida
subsp.
salmonicida
. We sequenced the plasmids present in two multiple antibiotic-resistant isolates using high-throughput technologies. We also investigated 19 other isolates with various multidrug resistance profiles by genotyping PCR and assessed their resistance to tetracycline. We identified variants of the pAB5S9 and pSN254 plasmids that carry several antibiotic resistance genes and that have been previously reported in bacteria other than
A. salmonicida
subsp.
salmonicida
, which suggests a high level of interspecies exchange. Genotyping analyses and the antibiotic resistance profiles of the 19 other isolates support the idea that multiple versions of pAB5S9 and pSN254 exist in
A. salmonicida
subsp.
salmonicida
. We also identified variants of the pRAS3 plasmid. The present study revealed that
A. salmonicida
subsp.
salmonicida
harbors a wide variety of plasmids, which suggests that this ubiquitous bacterium may contribute to the spread of antibiotic resistance genes in the environment.