bluuebunny/crossref_metadata_2025 huggingface dataset:
Endurance exercise modifies the circadian clock in zebrafish (Danio rerio) temperature independently
Authors: Egg M. , Tischler A. , Schwerte T. , Sandbichler A. , Folterbauer C. , Pelster B.
Published: November 2011

Aim:  Several rodent and human studies revealed that physical exercise acts as a non‐photic zeitgeber for the circadian clock. The intrinsic entraining mechanism is still unknown, although it was assumed that the exercise‐mediated increase in core temperature could be the underlying zeitgeber. As the homoeostatic control of mammalian core temperature interferes strongly with the investigation of this hypothesis, the present study used the poikilotherm zebrafish to answer this question.

Methods:  Gene transcription levels of the two circadian core clock genes period1 and clock1 were quantified using real‐time qPCR of whole animal zebrafish larvae.

Results:  Long‐term endurance exercise of zebrafish larvae aged 9–15 days post‐fertilization (dpf) or 21–32 dpf at a constant water temperature of 25 °C caused significantly altered transcription levels of the circadian genes period1 and clock1. Cosinor analysis of diurnal transcription profiles obtained after 3 days of swim training revealed significant differences regarding acrophase, mesor and amplitude of period1, resulting in a phase delay of the gene oscillation. After termination of the exercise bout, at 15 dpf, oscillation amplitudes of both circadian genes were significantly reduced.

Conclusion:  The results showed that physical exercise is able to affect the transcription of circadian genes in developing zebrafish larvae. Considering the poikilothermy of zebrafish, an exercise‐mediated change in body core temperature could be excluded as the underlying intrinsic zeitgeber. However, the day‐active zebrafish arises as a useful model to address the synchronizing effect of exercise on the circadian clock.
Pain, Gender, and Systems of Belief and Practice
Authors: Juschka Darlene
Published: November 2011

In the Eurowest pain is discursively framed as something that eludes discourse and therefore is outside language. In this framing, pain, as outside language, is given a social and a historical status understood to be beyond human construction. This article is the first step in a larger project toward destablizing such a conceptualization of pain and begins by engaging feminist theorizing of body and pain. In this paper my effort is to trouble the way we think about the body and pain in the Eurowest and to examine some of the outcomes of such thinking. Thereafter, I propose a conceptualization of the body and pain that might be helpful for examining their discursive formation.
Comprehension of Linguistic Dependencies: Speed‐Accuracy Tradeoff Evidence for Direct‐Access Retrieval From Memory
Authors: Foraker Stephani , McElree Brian
Published: November 2011

Comprehenders can rapidly and efficiently interpret expressions with various types of non‐adjacent dependencies. In the sentence The boy that the teacher warned fell, boy is readily interpreted as the subject of the verb fall despite the fact that a relative clause, that the teacher warned, intervenes between the two dependent elements. We review research investigating three memory operations proposed for resolving this and other types of non‐adjacent dependencies: serial search retrieval, in which the dependent constituent is recovered by a search process through representations in memory, direct‐access retrieval in which the dependent constituent is recovered directly by retrieval cue operations without search, and active maintenance of the dependent constituent in focal attention. Studies using speed‐accuracy tradeoff methodology to examine the full timecourse of interpreting a wide range of non‐adjacent dependencies indicate that comprehenders retrieve dependent constituents with a direct‐access operation, consistent with the claim that representations formed during comprehension are accessed with a cue‐driven, content‐addressable retrieval process. The observed timecourse profiles are inconsistent with a broad class of models based on several search operations for retrieval. The profiles are also inconsistent with active maintenance of a constituent while concurrently processing subsequent material, and suggest that, with few exceptions, direct‐access retrieval is required to process non‐adjacent dependencies.
Polycationic Chitosan‐Conjugated Photosensitizer for Antibacterial Photodynamic Therapy†
Authors: Shrestha Annie , Kishen Anil
Published: November 2011

The complex nature of bacterial cell membrane and structure of biofilm has challenged the efficacy of antimicrobial photodynamic therapy. This study was aimed to synthesize a polycationic chitosan‐conjugated rose bengal (CSRB) photosensitizer and test its antibiofilm efficacy on Enterococcus faecalis (gram positive) and Pseudomonas aeruginosa (gram negative) using photodynamic therapy. During experiments, CSRB was tested along with an anionic photosensitizer rose bengal (RB) and a cationic photosensitizer methylene blue (MB) for uptake and killing efficacy on 7‐day‐old E. faecalis and P. aeruginosa biofilms. Microbiological culture based analysis was used to analyze the cell viability, while laser scanning confocal microscopy (LSCM) was used to examine the structure of biofilm. The synthesized CSRB showed absorbance spectrum similar to the RB. The concentration of CSRB uptaken by both the bacterial biofilms was significantly higher than that of RB and MB (P < 0.05). Photoactivation resulted in significantly higher elimination of both bacterial biofilms sensitized with CSRB than RB and MB. The structure of biofilm under LSCM was found to be disrupted following CSRB treatment. The present study highlighted the importance of inherent cell membrane permeabilizing effect of chitosan and increased cell/biofilm uptake of conjugated photosensitizer to produce significant antibiofilm efficacy during photodynamic therapy.
Liver X receptors bridge hepatic lipid metabolism and inflammation
Authors: LIU Yuan , QIU De Kai , MA Xiong
Published: November 2011

Liver X receptors (LXRs) are members of the superfamily of metabolic nuclear receptors, which play central roles in the regulation of cholesterol absorption, efflux, transportation and excretion and many other processes correlating with lipid metabolism. LXRs can also regulate inflammation in vitro and in vivo. Accumulating evidence demonstrates that LXR are involved in the metabolism and inflammation in human diseases. Nonalcoholic fatty liver disease (NAFLD) is classically associated with lipid metabolic disorders and inflammatory responses, especially in the nonalcoholic steatohepatitis (NASH) phase. The effects of LXRs on cholesterol metabolism and inflammation make them attractive as a potential target for the treatment of NAFLD. Since the ability to synthesize triglycerides may be protective in obesity and fatty liver, the hepatic lipogenesis by LXRs should not rule out the possibility of the use of LXRs in NAFLD.
The Greatest Gift? Happiness, Governance and Psychology
Authors: Cromby John
Published: November 2011

Both in the UK and internationally, governments are setting out to measure well‐being, life satisfaction and happiness. Whilst this might seem to offer opportunities for psychology, their chosen method – self‐report questionnaires – is problematic. Happiness questionnaires are troubled by problems of definition, introspection, memory and insight; their population‐level summation is grossly inaccurate as a representation of everyday emotional experience; and both their reliability and their validity might be better accounted for as products of their ability to model, rather than to measure, psychological processes. Psychology therefore runs the risk of discrediting itself if it becomes too closely associated with these initiatives.
French Studies: Nouvelles de la république des lettres
Authors: SETH CATRIONA
Published: November 2011

This essay sketches the state of French studies from contemporary fiction rooted in eighteenth‐century texts to born digital editions, looking at the changing shape of the literary canon, trends in publishing, the importance of anniversaries in galvanising research on specific authors or books, the part played by curricula, and the language in which French texts are taught to non‐native‐speakers. It observes an insufficient circulation of secondary literature and notes a gradual shift towards enhancing the role of eighteenth‐century authors long considered secondary, drawing on interdisciplinary approaches and taking into account a less linear narrative of the period.
British History: The Exploding Galaxy1
Authors: CORFIELD PENELOPE J.
Published: November 2011

The exploding galaxy of publications on eighteenth‐century British history is dazzling but distinctly diffuse, with thousands of relevant studies appearing annually. Three main trends are highlighted here. One is the multiplication of specialist research fields, from political history to the recent boom field of cultural history. A second trend is the magnificent enrichment of resources via the digitisation of individual‐level documentation, in which eighteenth‐century history is a noted pioneer. The third trend is the continuing quest to establish or re‐establish the big picture, putting the British eighteenth century into long‐term global narratives, stretching well before 1700 and beyond 1800.
The Muslim World: Recent Scholarship on the Ottoman Middle East
Authors: AKSAN VIRGINIA H.
Published: November 2011

Study of the Ottoman empire has flourished in the past two decades. Reaching beyond the imperial centre, new work probes the problem of living in far‐flung peripheries and what it meant to negotiate religious and ethnic differences in times of upheaval and change. With a remarkable array of languages and grasp of the complexity of early modern societies, young scholars are exploring not just the representation and practice of Ottoman sovereignty and the response of elites but also the experience of the frontier, and survival strategies of slaves, prisoners of wars, converts and captives.
Modeling wildlife and other trade‐offs with biofuel crop production
Authors: Stoms David M. , Davis Frank W. , Jenner Mark W. , Nogeire Theresa M. , Kaffka Stephen R.
Published: November 2011

Biofuels from agricultural sources are an important part ofCalifornia's strategy to reduce greenhouse gas emissions and dependence on foreign oil. Land conversion for agricultural and urban uses has already imperiled many animal species in the state. This study investigated the potential impacts on wildlife of shifts in agricultural activity to increase biomass production for transportation fuels. We applied knowledge of the suitability ofCalifornia's agricultural landscapes for wildlife species to evaluate wildlife effects associated with plausible scenarios of expanded production of three potential biofuel crops (sugar beets, bermudagrass, and canola). We also generated alternative, spatially explicit scenarios that minimized loss of habitat for the same level of biofuel production. We explored trade‐offs to compare the marginal changes per unit of energy for transportation costs, wildlife, land and water‐use, and total energy produced, and found that all five factors were influenced by crop choice. Sugar beet scenarios require the least land area: 3.5 times less land per liter of gasoline equivalent than bermudagrass and five times less than canola. Canola scenarios had the largest impacts on wildlife but the greatest reduction in water use. Bermudagrass scenarios resulted in a slight overall improvement for wildlife over the current situation. Relatively minor redistribution of lands converted to biofuel crops could produce the same energy yield with much less impact on wildlife and very small increases in transportation costs. This framework provides a means to systematically evaluate potential wildlife impacts of alternative production scenarios and could be a useful complement to other frameworks that assess impacts on ecosystem services and greenhouse gas emissions.
Omeonga—A possible large impact structure on the Eastern Kasai Province (D.R. Congo)?
Authors: MONEGATO Giovanni , MASSIRONI Matteo , MARTELLATO Elena , TEZA Giordano
Published: November 2011

Abstract– The Omeonga ring structure (D.R. Congo) shows a remarkable drainage pattern encircling an area up to 45 km wide and encompassing a central smoothed relief 20 km wide. This inner circular ridge is elevated about 70 m above the ring depression corresponding to the bed of the Unia River, which flows between the inner ridge and an outer irregular ridge. Landsat 7 ETM and ASTER DEM show that the structural characteristics resemble those of several wide impact structures known on Earth. Other geological modes of origin that could produce ring structures, such as magmatic activity, salt diapirism, and karst dissolution have been considered. However, after evaluating the regional stratigraphy, the distribution of volcanism, and morphometry, these processes seem to be rather unlikely. If of impact origin, the age of the Omeonga structure can be constrained to the Late Cretaceous‐Cenozoic according to the youngest units in which the ring structure was formed.
Time Domain Analysis of a Multi-Component Mooring and Steel Catenary Risers System in Ultra Deepwater
Authors: Ba Umaru Muhammad , Chan Hoi-Sang
Published: November 2011

With the gradual depletion of oil and gas resources onshore as well as shallow offshore waters, oil exploration is gradually moving deeper and deeper into the seas. One of the major means of oil exploration at such locations is by way of a Floating Production Storage and Offloading (FPSO) system. Because of the ever increasing depths of exploration and the prevailing harsh environmental conditions, there is a need to constantly re-evaluate or develop new methods for mooring system analyses. This paper presents the analysis of a coupled multi-component mooring/riser/FPSO system in ultra deepwater due to the first and second order wave induced motions in time-domain. Analysis was carried out for two case studies and the results were found to be quite practical.
Assessment of Fatigue Damage Initiation in Oil and Gas Steel Pipes
Authors: Pinheiro Bianca , Lesage Jacky , Pasqualino Ilson , Benseddiq Noureddine
Published: November 2011

Steel pipe structures used in oil and gas industry, such as drill pipes, rigid risers and pipelines, undergo the action of cyclic loadings that can cause their failure by fatigue. These structures are made of high strength steels, such as API 5L grades X for instance. A consistent evaluation of the fatigue behavior should fundamentally be based on a local approach, in the dislocation scale, and take into account the micromechanisms of fatigue damage initiation, including microdeformations and microstructural changes, which precede the macrocrack propagation leading to final failure. In this work, the microstructural mechanisms of fatigue damage initiation in API 5L X60 grade steel pipes are investigated. Material properties of API 5L X60 steel are estimated according to chemical composition analyses, microscopic analyses, uniaxial tensile tests and Vickers micro-hardness tests. Samples are submitted to fatigue tests with reversed stress bending loadings. Microdeformations and residual stresses are measured with the aid of the X-ray diffraction method in real-time during fatigue tests. A numerical model is developed to reproduce the fatigue test loadings. The aim of the work is to provide ground for the development of a microstructural criterion for fatigue damage initiation in API 5L X60 grade steel pipes from the obtained experimental results. This criterion could allow a good prediction of the residual life of steel pipes previously submitted to fatigue loadings, before macroscopic cracking, and help to increase the reliability of oil and gas pipes.
A Study on the Effect of Plate Stiffeners of Double Bottom During Ship Grounding With Large Contact Surface
Authors: Hu Zhiqiang , Amdahl Jo̸rgen
Published: November 2011

The effect of plate stiffeners of double bottom during ship grounding with large contact surface was analyzed in this paper, by numerical simulation technique. It is always taken for granted that the effect of the stiffeners on the plate can be neglected, but they should not be dealt with in such a simple way. The objective ship is a double bottom tanker, and four different finite element models are made. Five numerical simulations are designed for each model, with different indentations from 10 percent to 50 percent of the double bottom height. With the simulation results, two sets of comparisons are made. The purpose of the comparison is to demonstrate how much role the stiffeners play in the structural performance during the grounding, and whether the smeared thickness method can predict the role of the stiffeners adequately. It is found that the vertical and horizontal resistances of the cases with stiffeners are all larger than those cases without stiffeners quite a while, which can prove that the stiffeners do have obvious influences on the resistance of the double bottom structure. The difference for horizontal resistance is more obvious than that for vertical resistance. Besides, the value of resistance in the model with stiffeners can be nearly double of that in the corresponding case in the model without stiffeners, especially for those cases with small indentation, which means the stiffeners play an important role in the structure deformation in mild grounding course. Furthermore, it is also indicated that the effect of smeared thickness can not predict the role of the stiffeners adequately, due to the perpendicular disposal of the stiffeners on the plate is of crucial importance in the structural deformation mode. A conclusion is drawn that the influence of the stiffeners on the plate should be taken into consideration and the deformation mechanism of the stiffeners should be included in the simplified analytical method in future.
Sensitivity Analysis of a Generic Wake-Body Model for the Vortex-Induced Vibration of a Rigid Circular Cylinder Using Monte Carlo Simulations
Authors: Gabbai Rene D. , Hiebert Jonathan
Published: November 2011

A Monte Carlo analysis using pseudo-random sampling is carried out with the objective of determining the relative importance of each of k = 5 independent input parameters appearing in a typical wake-body model for the vortex-induced vibration of an elastically-mounted rigid circular cylinder in uniform flow. For simplicity, the marginal probability distribution of each parameter is assumed to be a uniform distribution. Furthermore, the standard deviation of each distribution is assumed to be the same. The choice of the uniform distribution is also a reflection of the fact that exact forms for the distributions are not known. The sensitivity analysis indicates that the most important factor from the point of view of the predicted steady-state amplitude of oscillation of the cylinder yo is parameter M, which represents the scaling of the effect of the wake on the structure.
Experimental Investigation of the Undrained Response of a Shallow Skirted Foundation Subjected to Vertical Compression and Uplift
Authors: Mana D. S. K. , Gourvenec S. , Hossain M. S. , Randolph M. F.
Published: November 2011

There is current uncertainty regarding the transient uplift capacity of skirted foundations, relative to compressive capacity, and also the time over which uplift can be sustained. In this paper, the first of these issues is addressed through half and full model tests conducted at 200g in a drum centrifuge. Undrained vertical bearing capacities in compression and uplift were measured in the full model tests, while the failure mechanisms were examined using Particle Image Velocimetry (PIV) analysis of the images captured during half model tests, aiding interpretation of the measured bearing responses. The study showed that a reverse end bearing mechanism can be mobilized in uplift and that undrained vertical bearing capacity factors of similar magnitude can be expected in compression and uplift, even for a foundation with relatively shallow embedment. The results are promising for optimizing shallow skirted foundation design for a range of offshore structures that experience transient uplift loading.
Ageing and Life Extension Considerations in the Integrity Management of Fixed and Mobile Offshore Installations
Authors: Stacey A. , Sharp J. V.
Published: November 2011

Ageing and life extension require specific consideration in the integrity management of offshore installations. It is important to recognise that differing approaches may be required for fixed and mobile installations due to the different design methods, operational requirements and maintenance procedures for the two categories of installation. This paper presents integrity management models which address ageing and life extension of fixed and mobile installations.
Challenges Faced in the Design of SLWR Configuration for the Pre-Salt Area
Authors: Senra Stael Ferreira , Mourelle Marcio Martins , de Andrade Edmundo Queiroz , Torres Ana Lu´cia Fernandes Lima
Published: November 2011

With the recent discoveries of the pre-salt reservoir, new areas of the Brazilian coast rose to prominence, especially for the Santos Basin. This area is adjacent to the Campos Basin, which now accounts for around 80% of Brazilian production. In this new area, in addition to the difficulties of drilling in salt rock, the deployment of subsea production systems have also to overcome new challenges, since environmental conditions are more severe than those in the Campos Basin. Other important issues are: the water depth of about 2200 meters; the high pressure for gas injection riser; and the high CO2 content, requiring special attention to the materials that will be in contact with the production fluid. At this new production frontier, priority was given to the use of floating units with storage capacity like VLCC hulls, in order to export oil production through shuttle tankers, as no pipeline grid is available. Depending on the motions level of these VLCC vessels, the selection of a viable configuration of riser becomes crucial. Thus, some alternatives have been studied and the Steel Lazy Wave Riser (SLWR) configuration was one of the options considered to be used for production and gas injection riser functions, besides being possibly used for risers with large diameters. As this area of the Santos Basin presents more severe conditions, the free-hanging configuration (SCR) was not feasible, even with the use of VLCCs with optimized motions. In this case, the SLWR configuration was better suited to overcome the problems faced by free-hanging configuration. This paper aims to present a set of variables and its right combination involved in SLWR configuration to make it feasible, considering some key points in the design of SLWRs, for example: motions level of the floating unit, thermal insulation required for the flow assurance of production risers; difficulties faced during the installation process and the need of using clad pipes or lined pipes due to the high level of corrosion imposed by CO2 fluid content.
Fatigue Life Estimation of Welded Joints Including the Effects of Crack Closure Phenomena
Authors: Sarzosa Burgos Diego Felipe , Ruggieri Claudio , Godefroid Leonardo Barbosa , Donato Gustavo H. B.
Published: November 2011

The integrity of mechanical components, particularly when they experience considerable fatigue damage during its operating life, can be strongly influenced by the presence of residual stress fields and mechanical heterogeneity. Premature closure of crack flanks greatly influences fatigue crack growth rate. Extensive elastic-plastic finite element analyses have been carried out to investigate detailed crack closure behavior in center cracked welded compact tension (CT) specimens with one level of weld strength mismatch. The finite element results show that homogeneous, soft material has higher crack opening loads than heterogeneous material with 50% overmatch conditions. Fracture testing conducted on C(T) specimens to measure fatigue crack growth rates for an ASTM A516 Gr. 70 steel weldment provide the experimental data to support such behavior. The fatigue life can be reduced by more than 100% for a condition of 50% overmatch when compared with the evenmatch condition. It was verified that most of time spent in fatigue propagation life is consumed at the beginning of the propagation life.
Lateral Movement of Pipelines on a Soft Clay Seabed: Large Deformation Finite Element Analysis
Authors: Chatterjee S. , White D. J. , Randolph M. F.
Published: November 2011

Large deformation finite element analysis using the commercial software ABAQUS has been performed to study the lateral response of pipelines on a soft seabed. Initially, pipe soil interaction simulations are presented for the case of ideal soil, with non-softening strength. Lateral resistance profiles and trajectories of the pipe during lateral motion are investigated for different initial embedment of the pipe. A more realistic soil model incorporating the effects of strain rate and strain softening is then explored. Lateral resistance profiles and trajectories of the pipes from this realistic model are compared with the ideal soil case. Finally, the concept of effective pipe embedment — which accounts for the geometric changes caused by the soil berm ahead of the pipe — is applied to both the ideal and realistic soil model responses. The normalized horizontal resistance response is shown to be linked to the effective embedment in a simple manner, regardless of the other soil and pipeline parameters. This provides a useful contribution towards the development of a general model for describing large-amplitude lateral pipe-soil interaction, taking due account of the effects of changing geometry and soil strength.
Effects of Strain Rate and Microstructure on Fracture Toughness of Duplex Stainless Steels Under Hydrogen Charging Conditions
Authors: Bahrami Amir , Bourgeon Anais , Cheaitani Mohamad
Published: November 2011

Failures of ferritic-austenitic stainless steel due to hydrogen induced stress cracking (HISC) have been very costly and raised concerns regarding subsea system integrity, some of which remain unresolved. The susceptibility to HISC crack initiation shows a strong correlation with austenite spacing and tests performed on smooth samples have shown that coarse-grained microstructures, with large austenite spacing, such as in forgings, are more susceptible to HISC than fine grained structures, eg as in pipe [1]. In all reported failures, cracking has been independent of the presence of fabrication flaws, even though welds were typically present, and initiated at external stress concentrators, so the importance of flaws remains undetermined. There is no well established method for determining fracture toughness values applicable to flaws in duplex stainless steel in the presence of hydrogen and hence reliable data do not exist, leading to a lack of understanding of the criticality of flaws and whether fine austenite spacing provides any benefit in resistance to extension of flaws. This paper provides new data from fracture toughness tests conducted on duplex pipe and forging parent materials, to explore the effect of product type/ microstructure and strain rate on fracture toughness under active charging in seawater under cathodic polarisation. This is part of ongoing work aimed at the development of an engineering critical assessment (ECA) approach for assessing flaw tolerance under hydrogen charging conditions.
Soil Cutting Processes: The Cutting of Water Saturated Sand
Authors: Miedema Sape A.
Published: November 2011

The cutting process in water saturated sand has been the subject of research in the dredging industry for decades already. The Dutch dredging industry started this research in the sixties, resulting in a number of models in the seventies and eighties (van Leussen & van Os (1987) and Miedema (1987 and later). The application of the theory in the offshore industry is rare, although Palmer (1999) used it. In the last decades trenching has been a practice where these theories can be applied and with the tendencies of working in deeper water and in arctic conditions it is useful to try to combine the knowledge from the dredging and the offshore industry regarding cutting processes. The cutting process in water saturated sand is dominated by the phenomenon of dilatancy. Due to shear stresses, the porosity of the sand increases, resulting in an absolute decrease of the pore water pressures. Since the soil stresses are a constant, and equal to the sum of the grain stresses and the pore water stresses, this implies that the grain stresses increase with decreasing pore water stresses. This results in much higher cutting forces. The decrease of the pore water stresses is limited by the water vapor pressure and so are the cutting forces. At shallow waters, the pore water may start to cavitate if the strain rates are high enough, but at very deep water this will probably not occur. In this paper the basics of the cutting theory are explained. This cutting theory however requires a lot of finite element calculations in order to determine the pore water pressures. The paper gives simplification that allows the user to apply the theory with the help of pre-calculated coefficients.
Numerical Analysis Assessment of the Contact Pressure Between the Flexible Pipe Outer Sheath and the I Tube Interface Equipment for Wearing Research Program
Authors: Nogueira Victor , Pires Fabio , Aquino Fabio , Clevelario Judimar , Sheldrake Terry
Published: November 2011

Wellstream is carrying out a research program to provide the adequate knowledge of the interaction between the flexible pipes outer sheath and the I-tube interface equipment used in the field. Wellstream has already completed a full scale dynamic test which was used also to evaluate the wearing behavior of this specific region of the flexible pipe. As a continuation of the mentioned research program Wellstream developed a FEA model of the test rig in order to assess the contact pressure between the flexible pipe outer sheath and the I-tube interface equipment used in the test during the full scale dynamic test. The numerical model used in this assessment was prepared based on the test sample dimensions and test rig characteristics in order to reproduce the actual test condition. Model calibration approach is based on the rigs reaction forces and displacements measured during its execution with strain gauges specially positioned in the test rig’s interest area. This paper introduces the test rig numerical model and presents a comparison between the contact pressure originated by the test loads and the ones expected for the field. Results show that the full scale test contact pressures are significantly higher than the ones expected for the field operation, making the performed test conservative to evaluate the wearing behavior in the field.
Defining a Parameter of Effectiveness for the Suppression of Vortex-Induced Vibration
Authors: Freire Cesar M. , Korkischko Ivan , Meneghini Julio R.
Published: November 2011

The vortex-induced vibration (VIV) phenomenon is a very important issue in ocean and offshore engineering. When bluff bodies are immersed in a current, the boundary layers separate and form shear layers that can interact causing a periodic vortex shedding. In such condition, the forces acting on the body can make it vibrate. In the offshore industry, among other engineering applications, the vibration of structures can cause fatigue problems, reducing the life span of the element. To reduce the vortex-induced vibration effect suppressors can be employed in order to avoid the body to move, or at least, reduce the amplitude of vibration. There is a great number of suppressor types, like strakes, splitter plates, shrouds, etc; and each one has its own flow mechanisms to avoid VIV. Until now there is no simple way to compare the results and effectiveness of each suppressor. The purpose of this work is to define a parameter called suppressor effectiveness, based on the amplitude of vibration and the reduced velocity range, and use the suppressor effectiveness to compare different suppressors. The data used in the comparisons was obtained from experiments by the authors and collected from the literature.
Calculation of Floating Crane Natural Frequencies Based on Linearized Multibody Dynamics
Authors: C´atipovic´ Ivan , Cˇoric´ Vec´eslav , Veic´ Duje
Published: November 2011

Natural frequencies and modes of a floating crane with a suspended load are studied. Both the floating crane and the suspended load are modeled as rigid bodies with six degrees of freedom. The suspended load is considered to be partially immersed in the sea water. A wire rope for load suspension is assumed to be non-extensible and without bending stiffness. Linearized governing equations for a coupled dynamic response are derived based on the multibody system dynamics with small displacements assumption. An added mass for the floating crane as well as the partially immersed load is determined using traditional potential theory and tree-dimensional boundary element method (in a frequency domain). Mapping from the frequency to the time domain is necessary to determine the correct added mass value for calculating above described natural frequencies and modes. A damping of the overall system can be calculated as some small portion of a critical damping. A numerical example is based on the floating crane during positioning of precast concrete piles. These piles are main part of foundations for over sea bridges.
On Lateral Buckling Failure of Armour Wires in Flexible Pipes
Authors: O̸stergaard Niels H. , Lyckegaard Anders , Andreasen Jens H.
Published: November 2011

This paper introduces the concept of lateral buckling of tensile armour wires in flexible pipes as a failure mode. This phenomenon is governed by large deflections and is therefore highly non-linear. A model for prediction of the wire equilibrium state within the pipe wall based on force equilibrium in curved beams and curvature expressions derived from differential geometry is presented. On this basis, a model of the global equilibrium state of the armour layers in flexible pipes is proposed. Furthermore, it is demonstrated how this model can be used for lateral buckling prediction. Obtained results are compared with experiments.
Experimental Investigations Into the Influences of SCRs and Appurtenances on Deepdraft Semisubmersible Vortex Induced Motion Response
Authors: Rijken Oriol , Schuurmans Sipke , Leverette Steve
Published: November 2011

Vortex Induced Motion (VIM) response of a deep draft semisubmersible with square columns has been observed various model test conditions and in the field. A good understanding of the VIM phenomenon is desired because VIM can lead to significant SCR fatigue, especially for the larger diameters SCRs. A VIM design guidance was developed from several previous experimental investigations. Those experimental investigations are characterized by hulls with limited detail, and a simplified mooring / SCR system where typically only the stiffness is taken into consideration. A comparative experimental study is performed to identify the differences in VIM response under the absence and presence of hull appurtenances. Further, the VIM responses of a semisubmersible restrained by a mooring system without and with an SCR system are compared. An evaluation of the experimental results leads to an improved understanding of the VIM response at model test scale.
Hydrodynamic Design and Analysis of Horizontal Axis Marine Current Turbines With Lifting Line and Panel Methods
Authors: Baltazar J. , Machado J. , Falca˜o de Campos J. A. C.
Published: November 2011

This paper presents the computational models used by the authors at MARETEC/IST for hydrodynamic design and analysis of horizontal axis marine current turbines. The models combine a lifting line method for the optimization of the turbine blade geometry and an Integral Boundary Element Method (IBEM) for the hydrodynamic analysis. The classical lifting line optimization is used to determine the optimum blade circulation distribution for maximum power extraction. Blade geometry is determined with simplified cavitation requirements and limitations due to mechanical strength. The application of the design procedure is illustrated for a two-bladed 300 kW marine current turbine with a diameter of 11 meters. The effects of design tip-speed-ratio and the influence of blade section foils on power and cavitation inception are discussed. A more complete analysis may be carried out with an IBEM in steady and unsteady flow conditions. The IBEM has been extended to include wake alignment. The results are compared with experimental performance data available in the literature.
Design and Testing of Scour Protection for Adriatic LNG GBS
Authors: Chen Zhiwen , Hurdle David , Kram Nick , Lomo´naco Pedro , Cornett Andrew
Published: November 2011

The Adriatic LNG terminal is a liquefied natural gas offshore terminal located about 17 km off the coast of Rovigo, Italy in the northern Adriatic, where the water depth is approximately 29 m. Scour protection was needed around the GBS and the mooring dolphins to prevent the bed material under them from washing out. This paper presents a description of the scour protection design for the GBS and the mooring dolphins. The paper will first present the design criteria and the design approach. The dynamic stability approach, which has been developed in the recent years, was applied. This approach allows the profile of the armor rock to deform, but damage (loss of rocks from the scour protection system) must be very limited under the specified design environmental conditions. Particular aspects influencing the design of the scour protection in this case are the use of skirts and the composition of the upper layers of the seabed. The paper will further highlight the way in which existing data and physical modeling were used to arrive at the final design. In particular it will be demonstrated that this is an effective way to carry out the design and that the adaptations of the final design developed and tested during the physical model tests are important. Finally, the paper will present the final design obtained.
Improved Structural Integrity for Arctic Designs by Ignition Isolation Control
Authors: Dalheim Joar , Nodland Sverre , Pappas Jan
Published: November 2011

The harsh environment of the arctic requires specialized safety solutions. One main safety issue in the arctic is the need for more enclosed modules. Enclosed modules are used for two reasons; to prevent ice and snow to expose the process equipment; and to prevent the cold climate to impose an unduly harsh working environment for operators. The enclosed mechanically ventilated process modules are different from the open naturally ventilated process modules that are normally used in offshore facilities. The explosion safety performance of the non-standard mechanically ventilated process modules has therefore been studied in detail through an extensive program of CFD simulations. It is seen that mechanically ventilated modules has explosion risk drivers that are distinctly different from risk drivers in naturally ventilated modules. It is seen that the ignition source isolation efficiency is significantly more important for confined modules than for standard naturally ventilated modules. The explosion design loads are therefore strongly depending on the ignition source isolation efficiency. Isolation control, and its impact on the explosion design loads, is discussed in this paper. The presented conclusions are of high importance in future developments in arctic climate.
Analysis of Phenomenological Models of Vortex Induced Vibrations
Authors: Fortaleza Eugenio
Published: November 2011

The objective of this article is to identify a model able to represent the first harmonic behavior of a rigid cylinder undergoing VIV in the most different cases of a rigid cylinder supported by a spring/damper system. This analysis of the first harmonic behavior is made considering three different non-dimensional variables: the damping coefficient, the reduced velocity and the mass ratio. The challenge is to define a model that represents the changes on the lock-in zone considering the different combination of damping coefficient and mass ratio thus able to represent the different real systems. Two new phenomenological models using the Van der Pol oscillator are studied. They follow the framework of the phenomenological model proposed by Facchinetti et al.
A System for Wave Driven Desalination of Seawater
Authors: Johannessen Thomas B. , Brandsvoll Rolf A. , Palmstro̸m Andreas , Sole Sindre , Pedersen Eilif , Steen Sverre
Published: November 2011

Water scarcity is a growing challenge in a large part of the world. Desalination of seawater is an energy intensive process and in coastline areas where water scarcity coincides with a significant wave climate, desalination of seawater is an attractive application for utilisation of wave energy. The bulk of the energy requirement in desalination by reverse osmosis goes into pressurising seawater. Wave energy can be used directly to achieve this thereby bypassing the challenges associated with electricity generation. The present paper describes a floating unit which produces fresh water using wave power as the main energy source. A double-acting combined pressure magnifier and energy recovery device uses the irregular motion between two floating bodies to drive prefiltered seawater through a reverse osmosis membrane. The unit is compact with one floating disc positioned in the moonpool of the main floating body. The total system may be completed in the yard, towed to field and anchored using light mooring lines which have only a minimal impact on the floater motions. The unit has been sized for a typical West Africa wave climate using a linearised but fully coupled radiation-diffraction analysis of the vertical relative motion between the bodies in waves. The linearised results have been compared with results from time domain analyses verifying the vertical motions but indicating that significant energy can be extracted also from the relative roll and pitch motion of the bodies. It is concluded that the unit can deliver desalinated water at a cost of 0.8 Euro/m3 even in a relatively benign North West Africa wave climate.
Engineering Properties of Carbonate Marine Sediments
Authors: Brandes Horst G.
Published: November 2011

Geotechnical properties of deep-sea sediments are examined in terms of their plasticity, compressibility and frictional strength characteristics, especially in terms of the relative abundance of carbonate and clay fractions. The effect of carbonate content in excess of 40% is to reduce Atterberg limits and compressibility, and to increase peak friction angles, compared to sediments from the deep ocean that have lower carbonate amounts. The presence of carbonate also tends to reduce flocculation and in situ water content.
CFD Simulation of Flow-Induced Motions of a Multi-Column Floating Platform
Authors: Kim Jang-Whan , Magee Allan , Guan Kenneth Yeoh Hock
Published: November 2011

Recent improvements in capabilities of both hardware and software allow solving the coupled rigid body motions for the floating platform together with the fluid transport equations. This makes CFD a possible alternative or complement to model tests for predicting VIM performance. In addition, CFD allows simulating certain factors which cannot be addressed in scale model tests, and the two methods can ideally serve as cross-validation tools to bound the remaining uncertainties. Previous applications of CFD to Spar VIM predictions have shown promising results. Building on this, flow-induced motion simulations of multi-column floating platforms are being carried out using CFD as part of the R&D effort within Technip. The purpose of this paper is to present the results of two separate preliminary simulations applied to the prediction of vortex-induced motions of a TLP design and compare to the model test results.
Finite Element Modelling of Deepwater UOE Linepipe Manufacturing
Authors: Wen Shuwen , Slater Simon , Freeman Richard , Connelly Martin
Published: November 2011

Advanced finite element (FE) modelling techniques have been developed for simulation of the UOE linepipe manufacturing process. A through-process modelling approach is adopted using the general purpose FE package ABAQUS, mainly based on 2D plane strain or generalised plane strain assumptions. The FE models developed so far are capable of simulating the UOE pipe forming procedures from plate with machined weld preps, including edge crimping, U-ing, O-ing and pipe expansion (UOE). The FE models also have the ability to simulate the submerged arc welding (SAW) process prior to pipe expansion so that the effect of welding induced residual stresses and strains as well as the weld geometry could be considered adequately in the following FE analysis that is to be performed. Some of the most important aspects of the FE models, such as the prediction of strain distribution, spring back and loading, have been validated against experimental measurements obtained from various plant trials. Extensive parametric studies have been carried out using these FE models to investigate the influence of lubrication on the forming performance, as well as the deformation characteristics of the edge preps in the O-press. The FE modelling techniques are being routinely used to provide practical guidance on tooling design, selection and setting, particularly for the production of smaller diameter and thick-walled linepipes for deep and ultra-deepwater oil and gas applications, where the quality, integrity and consistency of the pipes delivered are critical. Other aspects of the FE modelling exercise relevant to the in-service performance of the pipeline will also be briefly discussed in this paper, including the prediction of residual stress, distortion and ovality, and their affects on pipe collapse resistance.