bluuebunny/crossref_metadata_2025 huggingface dataset:
False‐belief understanding in 2.5‐year‐olds: evidence from two novel verbal spontaneous‐response tasks
Authors: Scott Rose M. , He Zijing , Baillargeon Renée , Cummins Denise
Published: November 2011

Recent research indicates that toddlers and infants succeed at various non‐verbal spontaneous‐response false‐belief tasks; here we asked whether toddlers would also succeed at verbal spontaneous‐response false‐belief tasks that imposed significant linguistic demands. We tested 2.5‐year‐olds using two novel tasks: a preferential‐looking task in which children listened to a false‐belief story while looking at a picture book (with matching and non‐matching pictures), and a violation‐of‐expectation task in which children watched an adult ‘Subject’ answer (correctly or incorrectly) a standard false‐belief question. Positive results were obtained with both tasks, despite their linguistic demands. These results (1) support the distinction between spontaneous‐ and elicited‐response tasks by showing that toddlers succeed at verbal false‐belief tasks that do not require them to answer direct questions about agents’ false beliefs, (2) reinforce claims of robust continuity in early false‐belief understanding as assessed by spontaneous‐response tasks, and (3) provide researchers with new experimental tasks for exploring early false‐belief understanding in neurotypical and autistic populations.
Performing Development in Street Markets: Hegemony, Governmentality, and the Qat Industry of Sana’a, Yemen
Authors: Lauermann John
Published: November 2011

Abstract:  A legal drug commonly consumed in Yemen, qat is often a flashpoint over development and business practice. Qat markets are sites for exploring the interaction between cultural economic practices surrounding qat production, urban politics, and broader questions of development in Yemen. Given the weakness of the Yemeni state relative to other institutions, this context is particularly helpful in theorizing localized forms of governance. Using interviews with various members of the qat industry in Sana’a, Yemen's largest city, this paper discusses the spatial and discursive strategies of qat vendors as they seek to produce and regulate their economic spaces. Central to this discussion is an exploration of Laclau's framework of hegemony and Foucault's ideas of governmentality, in the context of struggles for control over economic space playing out on the streets of Sana’a.
Demographic differences in estimated blood donor eligibility prevalence in the United States
Authors: James Adelbert B. , Hillyer Christopher D. , Shaz Beth H.
Published: November 2011

BACKGROUND: The prevalence of blood donor eligibility factors has a major impact on the availability of blood donors and thus the blood supply in the United States. The prevalence of these factors may differ between demographic groups and thus help explain the differences in blood donation rates.

STUDY DESIGN AND METHODS: The study population (18‐69 years old who were African American [AA], white, or Hispanic) was 185,073,489. Forty eligibility factors determined by US Food and Drug Administration's Code of Federal Regulations and AABB Standards for Blood Banks and Transfusion Services were used to calculate whole blood donation eligibility rates. Eligibility data were obtained from the 2007 to 2008 National Health and Nutrition Examination Survey, National Ambulatory Medical Care Survey, US Census Bureau, and Centers for Disease Control and Prevention. Eligibility rates were determined by race/ethnicity, sex, and age groups (18‐39 and 40‐69 years).

RESULTS: In 2007 to 2008, 122 million Americans (65.9% of the study population and 41.0% of the total US population) were estimated to be eligible to donate blood in the United States. Significant differences in eligibility rates by demographic characterizers were determined (p < 0.001): AAs (36.5%), whites (46.4%), and Hispanics (40.7%); males (45.4%) and females (42.7%); individuals 18 to 39 years old (35.8%); and individuals 40 to 69 years old (32.9%).

CONCLUSIONS: AAs were significantly less eligible to donate blood than whites and Hispanics. Disparities in donor eligibility exist by race/ethnicity, sex, and age groups.
An Accessory Mitral Valve Leaflet Causing Left Ventricular Outflow Tract Obstruction and Associated with Severe Aortic Incompetence
Authors: Tamin Syahidah Syed , Dillon Jeswant , Aizan Kamarul , Kadiman Suhaini , Latiff Haifa Abdul
Published: November 2011

This case report describes a 20‐year‐old woman with Turner's syndrome who presented with reduced effort tolerance limited by dyspnea. She had previously been on pediatric cardiology follow‐up for congenital subvalvular aortic stenosis first diagnosed at age 7. Unfortunately she defaulted after two visits before any intervention could be done. Transthoracic echocardiography demonstrated severe aortic incompetence (AI) with a membrane‐like structure in the left ventricular outflow tract (LVOT). The mean pressure gradient across the LVOT on continuous wave Doppler was 41 mmHg. The membranous interventricular septum appeared aneurysmal and it was observed that the “subaortic membrane” had a connection to the anterolateral papillary muscle via a strand of chordal tissue. Further images were captured using two‐dimensional and three‐dimensional transthoracic and transesophageal echocardiography (iE33, Philips Medical Systems, Andover, MA, USA). After a review of the literature it was concluded that this appeared to be an accessory mitral valve (AMV) leaflet causing LVOT obstruction associated with AI. AMV tissue is a rare congenital malformation causing LVOT obstruction. Because it is so unusual, it may not be immediately recognizable even in a high volume echocardiography laboratory. The clue which helped with the diagnosis was the strand of chordal tissue which connected the mass to the papillary muscle. This anomaly is often associated with LVOT obstruction. (Echocardiography 2012;29:E34‐E38)
Epigenetic control of CCR5 transcript levels in immune cells and modulation by small molecules inhibitors
Authors: Wierda Rutger J. , Kuipers Hedwich F. , van Eggermond Marja C. J. A. , Benard Anne , van Leeuwen Jan C. , Carluccio Silvia , Geutskens Sacha B. , Jukema J. Wouter , Marquez Victor E. , Quax Paul H. A. , van den Elsen Peter J.
Published: November 2011

Previously, we have shown that CCR5 transcription is regulated by CREB‐1. However, the ubiquitous pattern of CREB‐1 expression suggests the involvement of an additional level of transcriptional control in the cell type–specific expression of CCR5. In this study, we show that epigenetic changes (i.e. DNA methylation and histone modifications) within the context of the CCR5 P1 promoter region correlate with transcript levels of CCR5 in healthy and in malignant CD4+ T lymphocytes as well as in CD14+ monocytes. In normal naïve T cells and CD14+ monocytes the CCR5 P1 promoter resembles a bivalent chromatin state, with both repressive and permissive histone methylation and acetylation marks. The CCR5‐expressing CD14+ monocytes however show much higher levels of acetylated histone H3 (AcH3) compared to the non–CCR5‐expressing naïve T cells. Combined with a highly methylated promoter in CD14+ monocytes, this indicates a dominant role for AcH3 in CCR5 transcription. We also show that pharmacological interference in the epigenetic repressive mechanisms that account for the lack of CCR5 transcription in T leukaemic cell lines results in an increase in CREB‐1 association with CCR5 P1 chromatin. Furthermore, RNA polymerase II was also recruited into CCR5 P1 chromatin resulting in CCR5 re‐expression. Together, these data indicate that epigenetic modifications of DNA, and of histones, contribute to the control of CCR5 transcription in immune effector cells.
CD68 and CD163 as prognostic factors for Korean patients with Hodgkin lymphoma
Authors: Yoon Dok Hyun , Koh Young Wha , Kang Hyo Jeong , Kim Shin , Park Chan‐Sik , Lee Sang‐wook , Suh Cheolwon , Huh Jooryung
Published: November 2011

Background:  Limited progress had been made in prognostic stratification of patients with Hodgkin lymphoma (HL) until recent studies suggested that the number of CD68‐expressing macrophages is prognostic in classical HL. However, its significance in Asian patients with HL has not been explored yet perhaps because of its low incidence in Asia.

Methods:  In this work, we performed immunohistochemical analysis of CD163, as well as CD68, in 144 Korean patients with HL treated between November 1990 and December 2009 in a single center. The relative percentages of CD68+ and CD163+ cells with respect to the overall cellularity (CD68 index and CD163 index, respectively) were correlated with clinical outcomes.

Results:  Both high CD68 and CD163 indices (>20%) were associated with a rise in treatment‐related deaths and poorer event‐free survival (P = 0.009 and P = 0.0023, respectively), disease‐specific survival (P = 0.011 and P = 0.001), and overall survival (P = 0.023 and P = 0.001). In particular, a high CD163 index was related to lower complete response (CR) rate (P = 0.022) and shorter duration of CR (P = 0.030).

Conclusions:  High index of either CD68 or CD163 (>20%) is significantly correlated with poor prognosis in Korean patients with HL. CD163, a specific marker of macrophages, seems to be another prognostic factor for classical HL.
Parenting Stress, Perceived Child Regard, and Depressive Symptoms Among Stepmothers and Biological Mothers
Authors: Shapiro Danielle N. , Stewart Abigail J.
Published: November 2011

Although stepmothering is a common undertaking in American families, little research has investigated the mental health consequences, and their correlates, associated with adopting a stepmother role. To help fill this gap, the current study examines parenting stress and participants' perceptions of their (step)children's regard toward them and the family as mediators in the relation between parenting role (stepmother or biological mother) and depressive symptoms. Participants included 60 biological mothers and 75 stepmothers living in the United States. Stepmothers reported more depressive symptoms and parenting stress and lower perceptions of child regard than did biological mothers. Further, the relation between parenting role and depressive symptoms was mediated by parenting stress and perceptions of child regard. Results suggest that stepmothers are at risk for depressive symptoms and illuminate possible contributors to this risk, providing important directions for research and intervention.
Family Characteristics, Custody Arrangements, and Adolescent Psychological Well‐being After Lesbian Mothers Break Up
Authors: Gartrell Nanette , Bos Henny , Peyser Heidi , Deck Amalia , Rodas Carla
Published: November 2011

As part of the largest, longest running prospective American study of same‐sex parent families, the present investigation examined relationship dissolution in planned lesbian families. Data were collected from 40 separated couples and their 17‐year‐old adolescent offspring—19 girls and 21 boys. Nearly all breakups occurred before the former couples could have obtained the legal equivalent of same‐sex marriage in their state of residence. A majority of the mothers rated the communication with their ex‐partners as cordial. Seventy‐one percent of separated mothers were sharing custody, and they were more likely to do so if the comother had legally adopted the index offspring. There were no differences in adolescent psychological well‐being associated with coparent adoption or shared custody. The percentage of adolescents who reported closeness to both mothers was significantly higher in families with coparent adoption.
The Specter of Divorce: Views From Working‐ and Middle‐Class Cohabitors
Authors: Miller Amanda J. , Sassler Sharon , Kusi‐Appouh Dela
Published: November 2011

Young Americans increasingly express apprehension about their ability to successfully manage intimate relationships. Partially in response, cohabitation has become normative over the past few decades. Little research, however, examines social class distinctions in how emerging adults perceive challenges to sustaining intimate unions. We examine cohabitors' views of divorce and how these color their sentiments regarding marriage. Data are from in‐depth interviews with 122 working‐ and middle‐class cohabitors. More than two thirds of respondents mentioned concerns with divorce. Working‐class women, in particular, view marriage less favorably than do their male and middle‐class counterparts, in part because they see marriage as hard to exit and are reluctant to assume restrictive gender roles. Middle‐class cohabitors are more likely to have concrete wedding plans and believe that marriage signifies a greater commitment than does cohabitation. These differences in views of marriage and divorce may help explain the bifurcation of cohabitation outcomes among working‐ and middle‐class cohabitors.
Relationship‐Specific Investments, Family Chaos, and Cohabitation Dissolution Following a Nonmarital Birth
Authors: Kamp Dush Claire M.
Published: November 2011

Predictors of two types of cohabitation dissolution, dissolution with a continued romantic relationship and without (i.e., breakup), were examined using data from mothers cohabiting at the time of a nonmarital birth in the Fragile Families and Child Wellbeing Study (N = 1,624). Life tables indicated 64% of unions dissolved within 5 years; of these, 76% broke up. Black mothers had the highest rates of dissolution. Maximum likelihood discrete‐time event history results revealed that younger mothers were more likely to experience cohabitation dissolution into a breakup. Fewer relationship‐specific investments and more family chaos were also associated with greater risk of cohabitation dissolution into a breakup. Mothers' multipartnered fertility and fewer relationship‐specific investments were associated with greater risk of cohabitation dissolution with a continued romantic relationship. Postdissolution, mothers who maintained a romantic relationship were more likely to reenter a union with their former partner whereas mothers whose union broke up most often remained so.
Geography: Space, Place and Intellectual History in the Eighteenth Century1
Authors: WITHERS CHARLES W. J. , MAYHEW ROBERT J.
Published: November 2011

The paper reviews work on geography as a subject and, more fully, studies that emphasise the value of ‘thinking geographically’– about the significance of place, space and scale – in understanding the nature of eighteenth‐century life and intellectual culture.
Modifying Preconceptions about the Safe and Effective Use of Aspirin: Product Label Comprehension as Knowledge Updating
Authors: Ryan Michael P.
Published: November 2011

Background: Errors in reading label information for nonprescription drugs are often ascribed to poorly written labels or to low health‐literacy levels. However, the contribution of drug product preconceptions to these errors has received little attention. This study improves on existing label‐comprehension research by assessing label effectiveness in terms of the updating of preconceptions about nonprescription drugs. Method: Ninety undergraduates rated the truth of 35 aspirin claims before and after reading a simulated aspirin label. Some claims were congruent with the Drug Facts; other claims were discrepant from those Drug Facts. Still other claims contained information absent from the Drug Facts. Results: Increases in truth ratings for congruent claims and decreases for discrepant claims were significant, but this knowledge‐updating effect is significantly greater for congruent claims. Ratings for absent claims were unchanged. Neither reading care nor verbal ability significantly influenced updating effects. In addition, label inspection was significantly more likely to produce comprehension‐beneficial and less likely to produce comprehension‐detrimental reversals of initial judgments for congruent claims than was the case for discrepant claims. Conclusions: Literate young adults who carefully read aspirin Drug Facts information are less able to correct aspirin preconceptions refuted by those Facts than to confirm aspirin preconceptions affirmed by those Facts.
OCTG: Downhole Tubulars Based on Mechanically Lined BuBi®-Pipes
Authors: Rommerskirchen Iris , Meyer Jana , Holler Gernold , Schlundt Mathias , Ahrberg Heinz
Published: November 2011

Consistently rising global energy consumption results in a shortage of finite fossil fuel.
Ship Motions From Unsteady Maneuvering in Two-Dimensional Waves: Part II—Analysis of Data
Authors: Klamo Joseph T. , Lin Ray-Qing
Published: November 2011

An experimental test has been conducted to measure the six degrees-of-freedom motions of a remote-controlled model attempting to hold heading while at forward speed in a two-dimensional wave field. During testing, the two underlying components of the wave field were always orthogonal to each other but various relative headings of the model to the dominant wave were explored. Of particular interest is understanding the nonlinear effects of the two distinct underlying wave encounter frequencies on the model response and the severity to which it causes the response in the two-dimensional wave field to differ from the linear summation of responses from equivalent one-dimensional waves. Since the experimental data contains the full wave-wave and wave-ship interactions of the two-dimensional wave field, we will use numerical results from the Digital, Self-consistent Ship Experimental Laboratory (DiSSEL) to generate the necessary one-dimensional wave results. This allows us to compare the predicted ship response motions from linear superposition of two one-dimensional wave field responses to the measured motions in a two-dimensional wave field for various relative wave heading combinations. It will be shown that for waves forward of beam, the predicted pitch results from superposition are fairly accurate while the roll prediction is not. However, for waves aft of beam, the motion predictions from linear superposition of pitch and roll are both poor. In such aft of beam cases, the disagreement can be quite large due to deviations in the ship heading caused by drift forces.
Differential Burst Pressure of Marine Pipelines as an Independent Layer of Protection
Authors: Yasseri Sirous F. , Mahani R. B.
Published: November 2011

Offshore pipelines and risers are designed to different codes leading to different reliability targets, and different wall thicknesses. Pipeline design codes also differentiate between areas where people are present and those with no population or less environmentally sensitive. As a result, the offshore section of the pipeline (with “thinner walls”) could be considered to work as a structural fuse during an unforeseen pressure surge; if the pipeline bursts first, then the occupants of platform would be exposed to less risk than if the riser or pipeline in the vicinity of the platform were to fail. This implies that differential burst pressure could act as an Independent Protection Layer (IPL). This paper explores conditions that sections of a pipeline must satisfy in order to be considered as an IPL. A first order reliability method is outlined for determining the required target reliability. The application of this approach is described in a case study.
Experimental Investigation on Vortex-Induced Vibration of Risers With Staggered Buoyancy
Authors: Li Lin , Fu Shixiao , Yang Jianmin , Ren Tie , Wang Xuefeng
Published: November 2011

In this paper, model tests of a riser with an aspect ratio of 263 were performed in a towing tank by towing the model with constant speeds. The riser was tested with various configurations of buoyancy, including 0% coverage, 25% coverage, 50% coverage and 100% coverage of the buoyancy modules. Furthermore, for the 25% and 50% coverage conditions, the portion without buoyancy modules of the model was covered with helical strakes of 17.5D/0.25D (pitch/height). In the experiments, the strain information in cross-flow (CF) direction was measured using Fiber Bragg Grating (FBG) sensors. The VIV characters of flexible risers with different buoyancy configurations were studied and compared with each other in detail.
Criticality Rating of Ageing Fixed Offshore Structures
Authors: Gupta S. , Sanderson D. , Stacey A.
Published: November 2011

The effective structural integrity management of the ever-increasing population of ageing offshore installations on the UKCS requires the identification of key parameters which provide a measure of the criticality of installations to structural failure, thus enabling priorities to be set. This paper describes a model for the evaluation of the criticality rating of fixed offshore installations.
An Innovative Oil Pollution Containment Method for Ship Wrecks Proposed for Offshore Well Blow-Outs
Authors: Andritsos Fivos , Cozijn Hans
Published: November 2011

In the aftermath of the PRESTIGE disaster, an innovative system for the prompt intervention on oil pollution sources (primarily ship wrecks) at great depths was conceived at the Joint Research Center of the European Commission. This system, with some re-engineering, could also serve for collecting oil and gas leaking after an offshore well blow-out and could constitute a reference method for prompt intervention on deep water oil pollution sources like ship wrecks and blown-out offshore wells. A large fabric dome, solidly anchored at the sea bed, covers entirely the pollution source and channels the leaking oil to a large open bell-shaped reservoir just under the sea surface so as not to be affected by the waves. Oil occupies the upper part of the bell and is periodically recuperated by a shuttle tanker while water escapes from the open bottom. The buoyancy of the reservoir keeps the whole system in tension. The concept was validated and optimized through detailed engineering, laboratory experiments and numerical simulations performed by a consortium of European institutes and industries in a dedicated collaborative research project called DIFIS (Double Inverted Funnel for the Intervention on Shipwrecks). The project resulted in a light, modular and easy to deploy system design. Such a system, suitably dimensioned and re-engineered to take account the gas flow, could also be used to cover the wellhead area so as to collect all leaking oil and gas until the implementation of the relief drilling. The present paper outlines the DIFIS system and elaborates on its advantages and risks in containing oil well blow-outs.
A Study on Dynamic Behavior of Offshore Structures Under the Blast Load
Authors: Lee Kun-Hee , Yoon Ki Young
Published: November 2011

Safety verification against blast load is important in offshore structure for oil and gas development which have the high possibility of explosion accident. The structural response against blast is a nonlinear dynamic phenomenon, it is necessary the nonlinear dynamic analysis for accurate structural behavior. But it requires much more computing resource and manpower than conventional linear analysis. Therefore, simple approaches such as modified code check and Biggs’ simplified SDOF have been widely used for the structural verification. These approaches are very useful in design for simplicity and conservativeness. However, they don’t represent proper dynamic characteristics, thus sometimes they may cause excessively conservative. In this paper, the dynamic characteristic of structures beyond the yield point is studied by using nonlinear dynamic FE analysis and more safe and economic approach is suggested.
Effects of Microstructure and Hydrogen Charging on Fatigue Performance of Duplex and Superduplex Stainless Steels
Authors: Bahrami Amir , Zhang Yanhui , Tubby Peter
Published: November 2011

Steel Catenary Risers (SCRs) are a viable solution for production and export of offshore hydrocarbons in many deepwater developments. In addition to exposure to seawater from the outside, the pipes and their girth welds in an SCR are often exposed to aggressive environments on the inside surfaces due to the produced fluids. The fatigue life of pipe girth welds in aggressive environments is dependent on the material-environment interactions. Duplex and superduplex stainless steels are particularly good candidate materials for construction of corrosion resistant steel centenary risers. However, these steels have shown susceptibility to hydrogen induced stress cracking (HISC) when in seawater and under cathodic protection (CP). In addition there is very little published knowledge related to their sour service performance under fatigue loading. This paper provides new fatigue endurance data for superduplex riser girth welds tested in air, seawater with CP and sour environment. It further compares the fatigue crack growth rate (FCGR) in the same welded material in air and sour environment. Finally preliminary results of investigations made on the effect of frequency, microstructure and grain coarseness on FCGR in parent superduplex and duplex materials in seawater and under cathodic protection are presented.
Calculation of Wave Forces and Internal Loads on a Semi-Submersible at Shallow Draft Using an iVOF Method
Authors: de Bruijn Rogier , Huijs Fons , Bunnik Tim , Huijsmans Rene´ , Gerritsma Marc
Published: November 2011

When semi-submersibles are floating at shallow draft, only a relatively thin layer of water may be present above the floaters. Model tests and full scale observations have shown that in such cases, even in low waves, non-linear effects significantly influence the wave pattern around the floaters. These non-linear effects make conventional methods based on linear diffraction theory less reliable for the calculation of wave forces and internal loads on a semi-submersible at shallow draft. This paper describes and analyzes the non-linear hydrodynamics affecting the wave loads and internal loads at shallow draft. The feasibility of both ComFLOW and linear diffraction method for the calculation of these loads are assessed. CFD simulations were performed using ComFLOW, a program based on the incompressible Navier-Stokes equations and the improved Volume Of Fluid (iVOF) method. First, the wave loads acting on a fixed semi-submersible in regular waves were calculated with ComFLOW and compared with linear diffraction theory and model tests. Secondly, internal loads were calculated for a moving semi-submersible in regular waves using both ComFLOW and linear diffraction theory. In the ComFLOW simulations, the motions of the semi-submersible were prescribed instead of solved by the method itself. Calculations and comparisons were performed for deep draft and shallow draft conditions. The wave loads on the semi-submersible for shallow draft conditions derived with ComFLOW were reasonably close to the results from model testing, while the results from the linear diffraction method showed significant deviations from the model tests results. The internal loads calculated with ComFLOW were quite close to the results from the linear method, even for shallow draft conditions. Additional model testing is required for validation of the internal loads.
The Influence of the UOE-SAWL Forming Process on the Collapse Resistance of Deepwater Linepipe
Authors: Mantovano Luciano O. , Chebaro Mohamed R. , Ernst Hugo A. , de Souza Marcos , Timms Chris M. , Chad Luis C.
Published: November 2011

The UOE-SAWL pipe manufacturing process introduces considerable plastic deformations and residual stresses to feedstock plate material. Previous experimental and analytical studies have demonstrated that the effects of this process, predominantly in its final expansion stage, significantly reduce the collapse resistance of deepwater linepipe. Finite element analyses, sensitivity analyses and full-scale tests were conducted by Tenaris and C-FER Technologies (C-FER) over the last several years to better comprehend the impact of cold forming on collapse resistance. This paper presents the findings of the latest segment of this ongoing study, the objective of which was to optimize the collapse resistance of UOE-SAWL linepipe by varying three key thermal ageing parameters: time, temperature and number of thermal cycles. Six X70M and four X80M UOE pipe samples were manufactured and thermally treated with varied parameters. Full-scale collapse and buckle propagation tests were then carried out in an experimental chamber that simulates deepwater conditions. These experimental results were evaluated with respect to collapse predictions from API RP 1111 and DNV OS-F101. Material and ring splitting tests were also performed on samples obtained from these pipes to better assess the extent of the UOE pipe collapse resistance recovery. The outcomes of this study will be employed to further optimize the collapse resistance of subsea linepipe in order to reduce material and offshore installation costs.
A Design Procedure for Evaluating the Air Gap on a Large-Volume Semi-Submersible Platform
Authors: Matsumoto Fabio Tadao , Sparano Joa˜o Vicente , Watai Rafael de Andrade , Simos Alexandre Nicolaos , Ferreira Marcos Donato A. S.
Published: November 2011

This paper presents a design procedure for the evaluation of the air-gap response on semi-submersible platforms subjected to irregular sea conditions. The suggested procedure takes into account both first and second order (low frequency) effects on hull motions when evaluating the air gap. As a first step of the procedure, a large range of sea conditions with different returning periods and directions of incidence are simulated using a frequency domain model. This first step is intended to determine the critical sea conditions regarding the air gap response of that particular floating unit. For those conditions, it is suggested to be performed a more complete analysis of the problem, including time-domain CFD simulations, in order to improve the results, especially for areas that may be susceptible to intense wave run-up effects. Experimental results for some typical sea states of Campos Basin have been employed to validate the procedure using as an example a large displacement four column semi-submersible platform operating at Campos Basin, Brazil. Results have confirmed that the sea state with the highest significant wave height, or peak period, may not lead to the worst air-gap situation. It’s also shown that, although for the critical sea conditions the first order effects were dominant in the air gap response, at many non-critical sea states the second order effects presented magnitudes comparable to those of first order, indicating that the resonant response of the unit should not be disregarded a priori when dimensioning the air-gap of similar deep-draft semi-submersibles.
Application of Reduced Order Modeling for Design of Interacting Maritime Structures
Authors: Holterman Jan , Peters Jan , de Ridder Erik-Jan
Published: November 2011

A model based design approach for maritime structures is presented. This approach, involving reduced order modeling, is especially intended for floating maritime structures with one or more separate dynamical systems. It can be used for qualitative ranking of engineering solutions, but also for quantitative optimization of engineering activities. The approach is illustrated for a practical application, i.e., dredging at deep sea by means of a draghead suspended by wires.
Issues for Consideration in Life Extension and Managing Ageing Facilities
Authors: Ha˚brekke Solfrid , Bodsberg Lars , Hokstad Per , Ersdal Gerhard
Published: November 2011

A large number of facilities and parts of the infrastructure on the Norwegian Continental Shelf are approaching or have exceeded their original design life. Many fields, however, have remaining recoverable oil and gas reserves which may be profitable if the field’s life is extended. From a safety point of view, the condition of systems, structures and components may not be acceptable for extended operation. Ageing and life extension have been a top priority for the Petroleum Safety Authority Norway (PSA) and PSA has asked SINTEF to conduct a study of various aspects of ageing and life extension. The paper presents main results from the study, including how to document the safety of an ageing facility and how to uphold the safety level by means of a maintenance programme balancing three aspects of ageing: 1) Material degradation, 2) Obsolescence, i.e. operations and technology being “out of date” and 3) Organisational issues. The paper presents six main steps of the life extension process and discusses important issues to consider for operators in a life extension process.
A Rational Approach to Automated Pre- and Post-Processing of Offshore Structure Global Strength Finite Element Analysis
Authors: Yang Zhiyong , DaSilva Otto
Published: November 2011

Offshore structure global strength analysis based on finite element plate model is a requirement for today’s classification societies and designers. Wave, wind, current loads have to be applied to the global strength model as a pre processing step to allow the analysis to take place. After the analysis, code checking must be performed to verify if the structure meets class or other requirements. Due to its complex nature, a large amount of engineering hours have to be spent for the pre and post processing. This is not only lengthy if performed manually or semi-automatically, but also mistake prone. General guidelines from classification societies exist, but general purpose commercial software is scarce and often still requires significant amount of engineering time to perform these tasks. This paper shows a rational approach to automate the pre and post processing of offshore structure global strength finite element analysis. Utilizing the FEMAP Application Program Interface (API), a complete automatic pre and post processing is implemented in one integrated program, Exmar Design Suite (EDS). The program will load the model from WAMIT generated wave pressure, apply internal pressure induced from motions to internal tanks, and also apply other environmental loads. After the finite element analysis, the program can execute strength code checking including yielding and buckling for the model. Both beam and stiffened plate panels can be identified using an automatic search algorithm, which is not a function available for general finite element software. The panels and beams are then checked against various common codes such as API/AISC/ABS/DNV. In addition, fatigue analysis can also be performed in either spectral or simplified approach. The benefits of automation are timesaving, accuracy and reliability. It also makes the check of whole model possible. Instead of relying more on “screening” or experience based structure check, engineers will have more confidence in the results by going through the whole model.
On the Dynamic Collapse of Cylindrical Shells Under Hydrostatic and Impulsive Pressure Loadings: Experimental and Numerical Analysis
Authors: Loureiro Silva L. , Netto T. A.
Published: November 2011

The dynamic collapse of submerged cylindrical shells subjected to lateral impulsive pressure loads caused by underwater explosions is studied via coupled experimental and numerical work. Two sets of experiments were performed. Initially, 50.6mm outside diameter aluminum tubes with diameter-to-thickness ratio of 32.3 were tested inside a pressure vessel. Hydrostatic pressure was applied quasi-statically up to the onset of collapse in order to obtain the collapse pressure of the tubes tested. Subsequently, similar tubes were tested in a 5m × 5m × 1.6m deep water tank under various explosive charges placed at different distances. Explosive charges and standoff distances were combined so as to eventually cause collapse of the specimens. Dynamic pressures were recorded using a fit-for-purpose data acquisition system with sampling rates of up to 1 mega samples/sec/channel. In parallel, finite element models were developed using commercially available software to simulate underwater explosion, pressure wave propagation, its interaction with a cylindrical shell and the subsequent onset of dynamic collapse. The surrounding fluid was modeled as an acoustic medium, the shells as J2 flow theory based materials with isotropic hardening, and proper fluid-structure interaction elements accounting for relatively small displacements of the boundary between fluid and structure were used. Finally, the physical explosion experiments were numerically reproduced with good correlation between results.
Ice Model Testing of Structures With a Downward Breaking Cone at the Waterline JIP: Presentation, Set-Up and Objectives
Authors: Bruun Per Kristian , Lo̸set Sveinung , Gu¨rtner Arne , Kuiper Guido , Kokkinis Ted , Sigurdsen Arild , Hannus Henrik
Published: November 2011

Two large ice model test campaigns were performed in the period 2007–2010 as a part of a Joint Industry Project. The objectives of the project were to investigate different floater geometries and ice model test set-ups (model fixed to a carriage and pushed through the ice vs. ice pushed towards a floating model moored to the basin bottom) and their influence on the ice failure mode and structure responses in the various tested ice conditions. This paper presents the objectives and motivations for the project, the models tested, the target test set-up for the various tested configurations and the test matrix. Initial results from a fixed model tested in three first-year ice ridges with similar target ice properties are also presented and compared. Fixed models of both deep and shallow water platforms were tested in various ice conditions. All models except one had a downward breaking cone at the waterline. The influences of the waterline diameter, the angle of the downward breaking cone and the vertical cone height on the ice failure mode and the resulting ice load were investigated. Tests were conducted in level ice with a thickness ranging from 2 to 3 m and variable ice drift speeds ranging from 0.1 to 1.0 m/s in full scale values. The models were subjected to tests in managed level ice with varying speeds, ice concentrations and ice floe sizes. Fixed structures were also subjected to testing in typical first-year design ice ridge conditions with ridges of different depths and widths, as well as one multi-year ice ridge. One fixed model was also utilised for testing of the repeatability of scaled ice model testing. Moored models with the same waterline geometry as the fixed models were also tested. The moored models were tested in ice conditions similar to those of the fixed models with the objective of comparing their influences on the ice load due to structural responses.
Effects of Coupled Hydrodynamic in the Performance of a DP Barge Operating Close to a FPSO
Authors: Vieira Daniel P. , Malta Edgard B. , Rampazzo Fabiano P. , Silva Joa˜o Luis B. , Tannuri Eduardo A.
Published: November 2011

In ocean systems composed by two or more closing floating bodies, coupled hydrodynamics effects must be considered. Dynamic positioned systems (DP), for example, need an accurate determination of environmental forces to guarantee a safe operation. This work presents a numerical methodology, using the WAMIT code, to evaluate both first order motions and mean drift forces of a system composed by a DP Crane Barge operating close to a turret-moored FPSO. The first order wave forces were evaluated using the code standard method. The second order forces (or mean drift forces) were obtained using the alternative control surface method. The work discussions are centered on the effects of FPSO presence on DP Barge hydrodynamics. Two relative positions between vessels were evaluated as well as three FPSO drafts (full, intermediate and ballasted). The effects of wave incidence angle were also discussed.
Benchmark Study on Thruster-Hull Interaction on a Semi-Submersible Crane Vessel
Authors: Ottens Harald , van Dijk Radboud , Meskers Geert
Published: November 2011

During offshore heavy lift or pipelay operations the station keeping capabilities of a DP-vessel have an important influence on operability limits of these operations. Heerema Marine Contractors has two DP3-class semi-submersible crane vessels for these operations; the Thialf and Balder. An assessment of the thrust efficiency of the DP thrusters of these vessels has been made by comparing CFD computations with dedicated model tests. A numerical study using CFD is performed to assess thruster-hull interaction on a semi-submersible vessel. The CFD results are validated with a series of model tests, including an open water thruster, single thruster-hull interaction without current and full thruster-hull interaction with all thrusters active without current. The CFD calculation results show good agreement with the model test data. The forces on the semi-submersible as well as on the individual floaters with active thrusters using CFD are within 10% of the model test data. The largest discrepancies are in the bow quartering conditions when the thruster-hull interaction show the most complex flow pattern due to the location and shape of the stern keel. The comparison between the CFD and model test data demonstrates that CFD is able to predict the relevant force components well within a sufficient accuracy for engineering purposes. The paper also addresses lessons learnt to improve the CFD computations as well as practical aspects and limitations of thrust efficiency modeling using CFD from an engineering perspective.
Effect of Foundation Modelling Methodology on the Dynamic Response of Offshore Wind Turbine Support Structures
Authors: Van Buren Eric
Published: November 2011

When preliminarily investigating offshore wind turbine tower concepts it is common to develop optimization software for determining the best possible structural layout. This type of optimization procedure requires a large number of iterations to determine the best possible design and can be quite time consuming, particularly if the dynamic performance of each structure is to be investigated using an aero-hydro-servo-elastic type solver. When performing this type of “dynamic optimization” it is convenient to simply assume fixed boundary conditions at the soil-structure interface and ignore the dynamic properties of the foundation. Using fixed conditions allows for each of the layouts to be compared quickly and makes the computer models simple to create and more efficient in computation than if the foundation is included. Alternatively, the foundations of offshore wind turbine support structures can be represented with several different methods of varying complexity and detail. The most widely used method is the use of a distributed spring model commonly known as the p-y method. This approach is the primary method in most offshore wind turbine design standards for determining the static and cyclic reaction of offshore piles. In this work, two offshore wind support structure layouts are modeled and analyzed in the wind turbine analysis program HAWC2. Dynamic time series analyses under operating conditions are carried out for each tower with fixed conditions and with foundation models based on the p-y method in order to determine the appropriateness of utilizing fixed foundation conditions for optimization procedures.
Development of Structural Steel With High Resistance to Fatigue Crack Initiation and Growth: Part 4
Authors: Konda Noboru , Arimochi Kazushige , Inami Akinori , Takaoka Yukichi , Yoshida Takumi , Lotsberg Inge
Published: November 2011

For many years, fatigue design has been based on the fundamental that the fatigue strength of welded structures is independent of the steel material and/or strength. Nothing has been studied from the viewpoint of material because fatigue strength of welded joints converges much to the same capacity regardless of material strength. For improvement of fatigue lives, the designers have been advised to improve the geometry of the details, to reduce the nominal stress level or to use some post weld improvement method like toe grinding. In 2001, a new steel material was developed that showed extended fatigue initiation life as well as extended crack growth life, and a new alternative method for fatigue life extension appeared. This steel was denoted FCA (Fatigue Crack Arrester) due to the improved fatigue properties. The improved fatigue strength in welded joints is explained by flat hardness distribution and very fine microstructure at heat affected zone (HAZ). It was clarified that fatigue strength of HAZ in FCA where fatigue crack initiates generally was higher than that in conventional steel. And the improved fatigue crack propagation properties in base steel is explained by a decreased crack growth rate when a fatigue crack passes a grain boundary from a soft phase (feritte) to a hard phase (bainite) that is present in these new dual phase steels. FCA steel has now been used for details of a number of newly built ships, where good fatigue properties are required. In order to establish a general design S-N curve that can be used for the FCA steel, it was agreed in 2007 to start a joint industry project among Kawasaki Shipbuilding Corporation, Det Norske Veritas and Sumitomo Metal Industries. This JIP is now being finished and a design S-N curve has been proposed based on 66 data from small scale testing of specimens made from FCA steel, and 18 data from conventional steel. These test results have been supplemented by some large scale tests of relevant ship details. The discussed results from this JIP including a recommended design S-N curve for FCA steel will be shown in this paper.
Buckling Analysis of Offshore Jackets in Removal Operations
Authors: Xia Wenjing , Hoogenboom P. C. J.
Published: November 2011

In analysis of the removal of offshore jackets an important failure mode is buckling. In current practice, a buckling check involves manual determination of the buckling lengths of each frame member. It is estimated that 5 to 10% of the man-hours in structural analysis of removal projects is spend on checking and correcting buckling lengths. Fortunately, an alternative method is available that does not require determining buckling lengths. In this paper it is shown how this method can be derived from the NORSOK standard for tubular steel frame structures. The method is demonstrated in a removal analysis of an offshore jacket. It is concluded that this method can be successfully applied.
Detailed Contact Analysis of the J-Tube Riser Pull-In Method
Authors: Farid-Afshin Farzad , Reva Christian , Vistnes Erlend R.
Published: November 2011

J-tube method of riser installation is a conventional method of connecting the subsea pipelines to fixed offshore platforms which are abundant in the Norwegian and international waters. The integrity of the J-tube, its supports, riser itself and the platform has to be maintained during pull-in of a riser into a J-tube. To ensure this, it is required that the pull-in and reaction forces, in addition to the riser plastic strain and J-tube stresses should be established either by detailed finite element contact analysis or by simplified methods available in literature. With the advances made in the finite element procedures and tools in the past decades and due to the higher degree of accuracy that they can capture, the contact analysis is often the preferred approach. Various parameters contribute to the riser pull-in operation which should be represented accurately in a finite element analysis to provide reliable results. Among others, they include the riser back tension (lay tension, seabed friction, etc.), riser J-tube friction, riser material’s yield stress and constitutive model, riser and J-tube fabrication tolerances, boundary conditions, clearances, etc. In addition, there are numerical modeling parameters such as the friction model (contact friction-clearance/overclosure relationship) and the details of the material’s constitutive model which can affect the accuracy and convergence of the analyses. In this paper, the general trends of response are presented with respect to physical variations of these parameters. Pull-in force, J-tube equivalent von-Mises stress and riser plastic strain are the response indicators which are studied. Analyses are performed using ABAQUS general-purpose finite element package [1]. The conclusions based on the observed trends can help to decide these input parameters as every individual project (i.e. study, detailed phase, etc.) and client requires.