bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonmarital Unions, Family Definitions, and Custody Decision Making
Authors: Holtzman Mellisa
Published: November 2011

Relationships that have not been formalized by marriage but that function like marriage are increasingly common among couples. Many of these relationships involve children who are related to only one of the adults but who have established parent‐child relationships with both adults. This raises questions about how best to preserve children's attachment relationships in the event that the adult relationship dissolves. Recent scholarship advocates two distinct approaches: some argue for legal recognition of expansive definitions of the family whereas others advocate for legal recognition of children's rights. This research examines the efficacy of these competing arguments. Findings suggest that judicial recognition of family definitions is not, on its own, enough to protect nonbiological attachments. Instead, family definitions must also be combined with a focus on children's rights. The legal and policy implications of these findings are discussed.
Layperson-Oriented vs. Clinical-Based Models for Prediction of Incidence of Ischemic Stroke: National FINRISK Study
Authors: Qiao Qing , Gao Weiguo , Laatikainen Tiina , Vartiainen Erkki
Published: November 2011

Background

A simplified model not requiring a clinic visit is important for cardiovascular prevention. We compared such a model, with one requiring clinical measurements for prediction of ischemic stroke.

Methods

Five population-based Finnish cohorts comprising 14 296 men and 16 065 women aged 25–64 years were randomly recruited from 1982, and followed up using the national registers until the end of the 2007. The final Cox model included age, prior history of diabetes and hypertension, happy marriage, capability to walk 500 m (self-estimate), regular exercise, vegetable/fruit intake, smoking, body mass index, and systolic blood pressure; the layperson-oriented model was developed by taking blood pressure away from the final model.

Results

Four hundred sixty-nine men and 371 women developed ischemic stroke events. The area under the receiver operating characteristic curve (95% confidence interval) for 10 years incidence of ischemic stroke was 0·817 (0·791–0·843) and 0·813 (0·787–0·839) for the model with and without systolic blood pressure in men and 0·815 (0·782–0·848) and 0·812 (0·779–0·844), respectively, in women ( P>0·10). The predicted 10-year events rate matched well with the observed one across deciles of the predicted risk in men (χ2 = 11·57, 9df, P = 0·239) and in women (χ2 = 11·18, P = 0·263). The overall net reclassification improvement after adding blood pressure was 8·8% ( P = 0·016) in men and 3·2% ( P = 0·234) in women. The predicted 10-year risk of the ischemic stroke based on global vascular event models that includes coronary heart diseases did not match well with the observed stroke risk.

Conclusions

The layperson model performed as well as the clinical-based one.
Methodological and Theoretical Issues in the Study of Chain Shifting
Authors: Gordon Matthew J.
Published: November 2011

A chain shift is a series of two or more sound changes that are related through a kind of chain reaction. The nature of the relationship between elements in a chain shift is a matter of debate among linguists from various sub‐fields. Examining this relationship raises questions about the nature of linguistic change and indeed about how language works in general. This article explores how the process of chain shifting is investigated with a focus on studies of active language changes (i.e., changes in progress) including the Northern Cities Shift and the New Zealand Front Vowel Shift. Among the questions considered are (1) how the changes involved in a chain shift are related, and (2) how phonemic contrasts are preserved during the chain‐shift process.
Cancerous Cell Death from Sensitizer Free Photoactivation of Singlet Oxygen
Authors: Anquez François , El Yazidi‐Belkoura Ikram , Randoux Stéphane , Suret Pierre , Courtade Emmanuel
Published: November 2011

Singlet oxygen (1O2) is an electronic state of molecular oxygen which plays a major role in many chemical and biological photo‐oxidation processes. It has a high chemical reactivity which is commonly harnessed for therapeutic issues. Indeed, 1O2 is believed to be the major cytotoxic agent in photodynamic therapy. In this treatment of cancer, 1O2 is created, among other reactive species, by an indirect transfer of energy from light to molecular oxygen via excitation of a photosensitizer (PS). This PS is believed to be necessary to obtain an efficient 1O2 production. In this paper, we demonstrate that production of 1O2 is achieved in living cells from PS‐free 1270 nm laser excitation of molecular oxygen. The quantity of 1O2 produced in this way is sufficient to induce an oxidative stress leading to cell death. Other effects such as thermal stress are discriminated and we conclude that cell death is only due to 1O2 creation. This new simplified scheme of 1O2 activation can be seen as a breakthrough for phototherapies of malignant diseases and/or as a noninvasive possibility to generate reactive oxygen species in a tightly controlled manner.
Critical Perspectives on Crime and Social Harm: Toward a Criminology of Human Rights
Authors: Criger David W.
Published: November 2011

Using Sutherland’s conceptualization of white‐collar crime as a significant point of departure, this article explores recent attempts to theorize crime and social harm from a critical criminological perspective. Arguing that the development of this approach is inextricably linked to theoretical and methodological concerns that strike at the very foundation of criminology as a discipline of study, I show how advances in state and corporate crime literature have advanced the field of criminology. Ultimately I argue that contemporary mainstream criminology, which tends to focus solely on the analysis of traditional ‘street’ crime, has failed to bring within its criminological purview those actions which have the greatest potential for causing significant human suffering.
Evolving Genomic Approaches to Idiopathic Pulmonary Fibrosis: Moving Beyond Genes
Authors: Kass Daniel J. , Kaminski Naftali
Published: October 2011

A little more than 10 years ago, the completed sequencing of the human genome boldly promised to usher in an era of enhanced understanding and accelerated development of treatments for most human diseases. Ten years later, many of these therapeutic goals have not been reached, but genomic technologies have dramatically enhanced our understanding of how genes and gene networks contribute to the pathogenesis of disease. In this review, we describe how genomic technologies have shaped our study of idiopathic pulmonary fibrosis (IPF), a devastating, progressive scarring of the lung parenchyma, a disease without a known cause, or treatment. We frame the important genomic discoveries in IPF of the previous decade in the clinical context of establishing a diagnosis of IPF and predicting the prognosis. Gene expression profiling of peripheral blood will help identify potential biomarkers for assessing the clinical severity of IPF. We highlight the growth of epigenetic research in IPF, including the contribution of microRNAs to the pathogenesis of disease. We suggest that the full power of genomic discoveries in IPF will be realized when researchers apply these techniques prospectively in large collaborative studies across institutions, support the training of young investigators in genomics, and employ systems biology approaches to the interpretation of genomic data. Clin Trans Sci 2011; Volume 4: 372–379
Art History: Re‐Viewing Recent Studies
Authors: BONEHILL JOHN
Published: November 2011

This article reviews studies in the visual arts of the eighteenth century, with an emphasis on recent interest in display and reception. The exhibition ‘Art on the Line’, at the Courtauld Institute in 2001, is taken as the starting‐point for scholarship that has addressed the spaces and topographies of display, institutional, commercial and domestic, and the new publics constituted by and in these arenas. Of particular concern is how dominant narratives of eighteenth‐century art have been modified and reinforced by attendance to these issues as well as by studies focused on its relationship to commerce, trade, war and empire.
English Literature: Early Novelists, Historicisms and the World Wide Web
Authors: DOWNIE J. A.
Published: November 2011

In the last thirty years scholarly attention has moved from the study of poets, playwrights and essayists towards the study of novelists, particularly women novelists. Academics in English departments are also increasingly concerned with a range of ‘non‐literary’ texts, and there has been burgeoning interest in the book trade and the history of the book. The irruption of ‘theory’ into eighteenth‐century English studies resulted in a huge shift in methodological awareness, but this pales into insignificance beside the impact of computers in general and the World Wide Web in particular.
The Americas: Recent Scholarship and Trends
Authors: IMBARRATO SUSAN C.
Published: November 2011

This article surveys recent research and writings about the long eighteenth century on genres that include poetry, drama, fiction, autobiography, slave narrative, travel narrative and the novel on both traditional topics, such as religion and history, and on emerging fields of research, such as literature and medicine, and an interest in expanding boundaries to include Transatlantic, Caribbean and West Indies studies. Throughout, a combination of active curiosity, intense archival research and an interdisciplinary approach has given rise to exciting scholarship and engaging scholarly interaction.
Female and Minority Judicial Nominees: President's Delight and Senators' Dismay?
Authors: ASMUSSEN NICOLE
Published: October 2011

Female and minority judicial nominations take longer and are less likely to be confirmed, yet presidents eagerly seek such nominations. I account for this puzzle by building a model in which senators face costs for opposing female and minority nominees. I predict that such nominations are more likely when the gridlock interval is large. Using appellate nominations from 1977 to 2004, I find that Republican presidents are more likely to pursue these nominations during periods of high gridlock. Furthermore, accounting for the gridlock interval erases the differences in confirmation duration and success between female/minority nominees and white male nominees.
Noise and Vibration Prediction for Semi-Submersible Drilling Rig
Authors: Gang Chen , Tao Yuan Hong , Qi Wang
Published: November 2011

Noise and vibration prediction technology based on acoustic FEM, hybrid method and SEA methods is applied to the design of a semi-submersible drilling rig. The modeling and vibra-acoustic computation are combined into the same software environment. Noise transmission paths are identified and feasible noise reduction designs are proposed with adding absorption and insulation materials. In order to meet with the strict requirements on sound pressure levels, damping materials are also used in some special areas.
Space-Time Extremes in Sea Storms
Authors: Fedele Francesco , Arena Felice , Tayfun M. Aziz
Published: November 2011

We present a stochastic model of sea storms to predict the maximum height of the wave surface over a given area during storms. To do so, we exploit the theory of Euler Characteristics of random excursion sets combined with a generalization of Boccotti’s equivalent triangular storm model (Boccotti, 2000) that describes an actual storm history in the form of a generic power law (Fedele and Arena, 2010). An analytical solution for the return period of extreme wave events over a given area and the associated statistical properties are given. We then assess the relative validity of the new model and its predictions by analyzing wave measurements retrieved from NOAA-NODC buoys moored offshore of the Atlantic and Pacific coasts.
Remaining Collapse Capacity of Corroded Pipelines
Authors: Chen Qishi , Marley Mark , Zhou Joe
Published: November 2011

It is known that, for given pipe material and diameter, collapse capacity of a plain pipe subjected to external pressure is proportional to the second or third power of wall thickness. In lieu of sophisticated numerical models and experimental data, conservative approaches such as those in which thickness losses at corrosion defects are extended to the entire circumference have been adopted in practices to assess the collapse resistance of corroded pipes. This reduced wall thickness is then used in the design equation of plain pipe to predict remaining collapse capacity. Such conservative assumptions result in substantial reduction of collapse capacity for pipelines with localized corrosion defects. During the course of a multiple-year PRCI research project, results of full-scale collapse tests and three-dimensional finite element analysis demonstrated that the reduction of collapse capacity was less than 10% for defects with a depth of 50% wall thickness, an axial length of one diameter and a circumferential width of half a diameter. These findings illustrated that the actual collapse capacity of corroded pipes is significantly higher than that estimated according to the conservative assumptions. This paper presents the development of a reliability-based, practical assessment method that allows remaining collapse capacity of corroded pipelines be determined based on defect size data obtained from in-line inspections. Work involved included characterization of corrosion defects, full-scale collapse tests, validation of finite element models using experimental data, analysis of parametric cases using finite element models, development of empirical equation based on experimental and numerical results, and calibration of partial safety factors which addressed the uncertainties associated with model error, load variation, and sizing inaccuracy of corrosion defects. Practical implications of the proposed assessment method were evaluated based on selected examples.
A Variational Wave Acquisition Stereo System for the 3-D Reconstruction of Oceanic Sea States
Authors: Gallego Guillermo , Yezzi Anthony , Fedele Francesco , Benetazzo Alvise
Published: November 2011

We propose a novel remote sensing technique that infers the three-dimensional wave form and radiance of oceanic sea states via a variational stereo imagery formulation. In this setting, the shape and radiance of the wave surface are minimizers of a composite cost functional which combines a data fidelity term and smoothness priors on the unknowns. The solution of a system of coupled partial differential equations derived from the cost functional yields the desired ocean surface shape and radiance. The proposed method is naturally extended to study the spatiotemporal dynamics of ocean waves, and applied to three sets of video data. Statistical and spectral analysis are carried out. The results shows evidence of the fact that the omni-directional wavenumber spectrum S(k) of the reconstructed waves decays as k−2.5 in agreement with Zakharov’s theory (1999). Further, the three-dimensional spectrum of the reconstructed wave surface is exploited to estimate wave dispersion and currents.
Wave Height Measurements Behind Submerged Lens-Shaped Structures
Authors: Bloxom Andrew L. , von Ellenrieder Karl D. , Anderson Matthew R. , Mieras Ryan S. , Weidle William S.
Published: November 2011

The ability of submerged lens-shaped structures to focus linear surface waves in deep water is explored through a series of experimental tests in a wave making basin. Three lenses were designed using a combination of linear strip theory and a surface wave analogy to geometrical optics. Two of these lenses were designed to focus waves of a single wavelength of 0.482 m (18.97 in.), one with a focal length to lens width ratio (f-number) of 2.0 and the other with an f-number of 0.5. The third lens was designed to function as a compound lens that could focus a range of wavelengths of between 0.39 m (15.37 in.) and 0.694 m (27.32 in.) at an f-number of 2.0. Using resistance wave height gauges, the sensitivity of wave height at the focus to variations in wavelength from between 0.39 m (15.37 in.) to 0.61 m (24.01 in.) was experimentally measured for all three lenses; the sensitivity of wave height at the focus to variations of lens depths of submergence spanning the range of between 0.75 to 1.25 times the design submergence depth was also explored for the two simple lenses. It was found that the linear strip theory and geometrical optics approach predicted the wave amplification to within ten percent at the design wavelengths and depths, but that the longitudinal position of the experimentally observed focal lengths differed substantially from that expected, by as much as a factor of 2.2 for an f-number of 0.5. Additionally, while the theory predicted a single focal point for each lens, multiple focal points were found to exist behind the compound lens.
Flexible Pipes: Influence of the Pressure Armor in the Wet Collapse Resistance
Authors: Gay Neto Alfredo , Martins Clo´vis de Arruda
Published: November 2011

When subjected to large valued external pressures, flexible pipes may collapse. If the external sheath is damaged, all the external pressure is directly applied to the internal polymeric layer that transmits the loading to the carcass layer. When the carcass layer fails due to this effect, the wet collapse occurs. This failure mode must be taken into account in the flexible pipe design. The study for this problem can be done neglecting the influence of the pressure armor, but this assumption may underestimate the wet collapse pressure value. This work aims to study the pressure armor effect in the numerical prediction of wet collapse. The main contribution of the pressure armor to the flexible pipe resistance to collapse is to be a constraint to the radial displacement of the carcass and the internal polymeric layers. Two models were developed and compared with the purpose of calculating the critical value of the external pressure that causes carcass layer to collapse. The first and most complete study is done using a ring 3D FEM model that takes into account both the real pressure armor and carcass real profiles. In the second model, the pressure armor is considered adopting an equivalent ring simplification. The comparison of the results of both the models clarifies how the behavior of the pressure armor in the wet collapse situation is. Parametric studies of initial ovalization of the carcass and initial gaps in manufacturing of flexible pipes are made and discussed.
A New Semisubmersible Design for Improved Heave Motion, Vortex-Induced Motion and Quayside Stability
Authors: Xu Qi
Published: November 2011

Recently the semisubmersible has become a favorable choice as a wet-tree floating platform supporting steel catenary risers (SCRs), mainly due to its capability of quayside topside integration and cost-effectiveness. However, it is still a challenge for a conventional semisubmersible to support SCRs, particularly large ones, in harsh environment and relatively shallow water due to its large heave motion. To answer this challenge, a new semisubmersible design has been developed at Technip as a wet-tree floater which achieves significantly improved heave motion and vortex-induced-motion (VIM) performance through hull form optimization while maintaining the simplicity of a conventional semisubmersible design. The difference between the NexGen semi-submersible design and a conventional semi-submersible design is in the blisters attached to the columns, distribution of pontoon volume, and pontoon cross section shape. In the NexGen semi-submersible design, the pontoon volume is re-distributed to minimize heave loading while maintaining sufficient structural rigidity, a long heave natural period and adequate quayside buoyancy. The blisters attached to the columns effectively break the vortex shedding coherence along the column length and therefore suppresses VIM. The blisters also provide much needed stability at quayside and during the hull deployment process, making the hull design less sensitive to topside weight increase. In the present paper the hydrodynamic aspects of this new design are discussed in detail. A benchmark case is presented in which the new design is compared against a more conventional design with the same principal dimensions. It is shown that the heave response in extreme sea states (100-yr hurricane) at the platform center of gravity is reduced by about 30–40%, and at the SCR hang-off locations by about 25–30%. Due to the reduced heave motion, SCRs experience about one third less stress at the touchdown point. A qualitative VIM analytical model is used to predict the VIM suppression effect of the new design. A highlight of a VIM model test for the proposed design is also presented. The reduced heave and VIM significantly improve the riser stress and fatigue near the touchdown point. This new design makes the semisubmersible a more robust wet-tree floater concept, and even a potentially good candidate as a dry-tree host concept in relatively benign environment.
Current Feed Forward Control in Dynamic Positioning
Authors: Smit M. R. , Tjallema A. R. , Huijsmans R. H. M.
Published: November 2011

The presented research investigates to what extent current feed forward control improves the positioning performance of Dynamically Positioned (DP) Floating Production Storage and Offloading (FPSO) vessels in varying currents. Positioning performance refers to the accuracy of positioning (both heading and horizontal position) and the associated power usage. Tidal current reversals and so called ‘internal soliton’ currents are examples of varying currents, in which current feed forward control is expected to improve positioning performance. Time domain simulations are carried out using the DpSim software, as developed by the Maritime Research Institute Netherlands (MARIN). In this research project, the DpSim software is extended with a module containing current feed forward control. When current feed forward control is applied in DP in varying currents, the mean and standard deviation of the control point excursion are reduced. The heading performance and power usage do not change significantly while achieving this reduction.
Development of 7%Ni-TMCP Steel Plate for LNG Storage Tanks
Authors: Kamo Takahiro , Arimochi Kazushige , Kawabata Tomoya , Onishi Kazushi , Andou Ryuichi , Yamashita Maki , Iwahashi Hiroshi , Kubo Naoshige , Fuchimoto Yoichi , Takata Masanori , Sakato Naokazu , Mitsumoto Masahiko , Hirai Syuichi , Hirose Hitoshi , Hagihara Yukito
Published: November 2011

Demand of natural gas continues to increase in the recent years due to the rise of environmental issue and the drastic increase of crude oil price. These events led the increase of constructions of LNG storage tanks worldwide. The inner tank material for above ground LNG storage tanks have mostly been made of a 9% nickel steel plate over the last 50 years as it has excellent mechanical properties under the cryogenic temperature of −160deg-C. During this period, the LNG storage tanks made of 9%Ni steel plate have safely been operated at the many LNG export and import terminals in the world. Meanwhile, technologies of steel making, refinement, design, analysis, welding and inspection have been improved significantly and enable us to achieve enlarging volumetric capacity of the tank to 2–3 times. There was a tendency of increase in nickel price in the recent years and hence the preparation corresponding to the risk to a great rise on the price of 9%Ni steel plate becomes necessary. In such a circumstance lowering Ni content was focused attention on the 9%Ni steel as nickel is an expensive and valuable rare metal and the 7%Ni steel plate was eventually researched and developed. It was a steel making process so that a 7%Ni steel would be made by adjustment of chemical compositions and processed by suitable Thermo–Mechanical Controlled Process (TMCP). As a result, it was demonstrated that 7%Ni-TMCP steel plate had excellent physical and mechanical properties equivalent to those of 9%Ni steel plate. In order to evaluate fitness of the 7%Ni-TMCP steel plate and its weld for LNG storage tanks a series of testing was conducted. Several different kinds of plate thicknesses i.e. 6,10,25,40 and 50 mm were chosen to run large scale fracture toughness tests such as duplex ESSO tests, cruciform wide plate tests as well as small scale tests. In this study, a comprehensive assessment was performed to confirm applicability of the 7%Ni -TMCP steel plate and its weld to LNG storage tanks. It was concluded that the 7%Ni-TMCP steel plate warrants serious consideration for use in LNG storage tanks. This paper reports details of the research and development of the 7%Ni-TMCP steel plate.
Oil Pollution in the Arctic: Risks and Mitigating Measures With Reference to the Deepwater Horizon Accident
Authors: Willemse C. A. , van Gelder P. H. A. J. M.
Published: November 2011

The accident with the Deepwater Horizon in the Gulf of Mexico has caused great concern, both in the offshore industry and in society in general. The response to the accident indicated that no clear emergency plan was in place and that many attempts at mitigation of the oil spill were improvised whilst the oil was already leaking. As a result it took several months to kill the well and stop the oil spill, causing the Deepwater Horizon to be one of the most severe environmental disasters in the history of offshore drilling. This paper analyses the probability that a similar accident could happen in the arctic region, taking into account the various steps and elements of the offshore drilling process. The measures to kill the subsequent oil flow and to contain the oil spill are addressed in the context of the complex arctic drilling challenges. Finally the paper estimates how the mitigation measures could reduce the probability of a spill.
Computational Fracture Mechanics Assessment of 3-D Crack-Like Defects in Complex Geometries
Authors: Bahtui Ali , Tkach Yuri
Published: November 2011

The application of a fracture mechanics based methodology for integrity assessment of complex structural components containing flaws often requires computational simulation where the flaws have to be modeled explicitly due to the absence of the appropriate analytical solutions. Moreover, for large flaws, re-distribution of loads may occur and therefore for an accurate assessment the flaw needs to be embedded within the structural model. A critical issue that must be addressed in a three-dimensional finite element simulation of a structural component containing a crack-like defect is that of mesh generation. In this paper, an efficient methodology has been developed based on the use of general purpose finite element packages and other commercial software to automatically generate the meshes. The model reflects the full complexity of a 3-D structure ensuring at the same time the required mesh resolution around the crack front for the determination of parameters used in fracture mechanics assessment. The approach is demonstrated through computational simulations of a tubular K-joint containing a crack-like defect with elastic and elastic-plastic material properties. From these analyses, the parameters required for construction of a geometry-dependent and material-specific failure assessment diagram (FAD) are derived. Results of the fully computational fracture mechanics assessment are compared with those generated in accordance with Annexes B and P of BS 7910:2005. It is demonstrated that the level of conservatism in fracture integrity assessment of tubular joints can be reduced if the crack driving force is determined directly from the computational analysis of the cracked geometry. A discussion on the application of different limit load and reference stress solutions is presented and the importance of the appropriate selection of the limit load solution is highlighted.
Multiphysics SPH Simulations With Local Particle Coarsening
Authors: Ulrich Christian , Bednarek Sven , Rung Thomas
Published: November 2011

The paper reports on Smoothed-Particle-Hydrodynamics (SPH) for multi-physics water/soil interaction computations with dynamic particle coarsening. The procedure is supposed to be applied to harbour and ocean engineering hydrodynamic problems focussing on sediment scouring. This type of simulation usually implies large computational domains, fluid-soil interaction and complex geometries leading to large numbers of particles. To achieve a reasonable time-to-solution even for full-scale simulations, effective strategies to increase the computational performance are needed. We present a dynamic particle refinement/coarsening strategy based on variable particle masses and spacings. The particle properties are updated in accordance to their current location. Validation studies refer to different water/soil interaction test cases. Results obtained from the present refinement/coarsening approach show an encouraging predictive and computational performance.
Experimental Wave Generation and Cancellation With a Cycloidal Wave Energy Converter
Authors: Siegel Stefan G. , Ro¨mer Marcus , Imamura John , Fagley Casey , McLaughlin Thomas
Published: November 2011

We investigate a lift based wave energy converter (WEC), namely, a cycloidal turbine, as a wave termination device. A cycloidal turbine employs the same geometry as the well established Cycloidal or Voith-Schneider Propeller. The main shaft is aligned parallel to the wave crests and fully submerged at a fixed depth. We show that the geometry of the Cycloidal WEC is suitable for single sided wave generation as well as wave termination of straight crested waves using feedback control.The cycloidal WEC consists of a shaft and one or more hydrofoils that are attached eccentrically to the main shaft. An experimental investigation into the wave generation capabilities of the WEC are presented in this paper, along with initial wave cancellation results for deep water waves. The experiments are conducted in a small 2D wave flume equipped with a flap type wave maker as well as a 1:4 sloped beach. The operation of the Cycloidal WEC both as a wave generator as well as a wave energy converter interacting with a linear Airy wave is demonstrated. The influence that design parameters radius and submergence depth on the performance of the WEC have is shown. For wave cancellation, the incoming wave is reduced in amplitude by ≈ 80% in these experiments. In this case wave termination efficiencies of up to 95% of the incoming wave energy with neglegible harmonic waves generated are achieved by synchronizing the rotational rate and phase of the Cycloidal WEC to the incoming wave.
Qualification of Multi-Composite Hoses for STS LNG Transfer
Authors: van der Weijde Gerard , Mallon Niels
Published: November 2011

Reliable transfer systems are a key element in developing floating LNG technology. Multi-composite hoses may prove to be a reliable and cost effective solution. TNO, the Dutch contract research organisation, has executed an extensive test program on the multi-composite hose of Gutteling B.V. for Ship-to-Ship (STS) LNG transfers. It has resulted in qualification of the hose in accordance to EN1474-part 2 [2]. This hose is the first product that has been qualified in accordance with this new internationally accepted standard. The test program was performed in close cooperation with Gutteling B.V., EXMAR and DNV. It focused on the mechanical and flow behaviour at ambient and cryogenic operating conditions. In excess of the EN1474-requirements, a multi-level test programme is performed, more samples are tested and more extreme load combinations are applied. The purpose was to provide a data set that enables transfer system qualification in accordance with EN1474-part 3. The hose appears to have a complex mechanical behaviour: elastic non-linear, coupling of deformation modes, hysteric behaviour and large damping. Damage tolerance tests, such as impact and crushing, show that the composite hose performs exceptionally. This paper summarises the test program and describes some of the tests performed in excess of the requirements. In particular, testing for off-spec operation conditions, fatigue and creep is addressed. Absences of engineering models to predict fatigue and creep performance are future obstacles for realising the interesting proposition of multi-composite hoses.
Nonlinear Two Stage Control Strategy of a Wind Turbine for Mechanical Load and Extreme Moment Reduction
Authors: Chauvin Jonathan , Creff Yann
Published: November 2011

This paper presents a new approach for the control of wind turbines. The proposed strategy can be decomposed in two part. In a first stage control strategy, we provide a nonlinear dynamic feedforward strategy for rotor speed regulation along with a nonlinear dynamic feedback to be robust to model uncertainties. It guarantees convergence of the rotor speed to its desired value. This first part only looks at the rotor dynamics and the aerodynamics. The tower dynamics is not taken into account. In a second stage control strategy, we provide a control action that minimize the tower fatigue. The strategy is largely validated for the onshore case. The proposed control approach can be extended to the offshore case and a first validation is proposed.
Squall Response Based Design of Floating Units in West Africa
Authors: Alvarez Juan , Orsero Pierre , Quiniou-Ramus Valerie , Franc¸ois Michel , Moysan Anne-Gae¨lle , l’Hostis Didier , Ledoux Alain
Published: November 2011

Squalls are one of the main issues for the design of West Africa floating units mooring systems. At the present time and due to the lack of more relevant information and models, squalls are represented by on site time series of time varying wind speed and relative heading. The first FPSO units were designed on the basis of a reduced Squall database. Nowadays, the number of squall records has been significantly increased and a response based analysis can be carried out. The present paper is focused on the Gulf of Guinea environment. The area has been divided into two zones: North (Nigeria…) and South (Congo, Angola…). This approach enabled us to deal with 90 Squall events for North zone and 115 Squall events for South zone. Two different mooring systems, with quite different natural periods, have been investigated in order to cover the range of already installed spread moored FPSO’s. For every Squall of the database, time domain and modal simulations have been carried out in order to obtain the maximum values of the axial tension in mooring lines and of the offset of a standard spread moored unit. Then a statistical procedure is applied a) to estimate 100-year return period values for these parameters and b) to assess overall trends besides the differences between results from both zones and both mooring systems. A comparative study has also been carried out to relate the 100-year return period extrapolations with the values derived from classical design procedures in order to evaluate the potential design margins for extreme responses. Finally, areas needing further investigation are identified.
Permanent Means of Access Structural Design Using Multi-Objective Optimization
Authors: Ma Ming , Hughes Owen F.
Published: November 2011

Permanent means of access (PMA) of oil tankers and bulk carries consists of a wide platform for walk through inspection. Since PMA structures have a tall web plate, they are vulnerable to elastic tripping. A previous paper [1] proposed a Rayleigh-Ritz method to analyze elastic tripping behavior of PMA structures. The method is parametric formulated, mesh free, computational efficient, and is able to predict both the flange plate critical tripping stress as well as the web plate local buckling stress; therefore the solution process is suitable for design space exploration. In this paper, multi-objective optimization methods are used to determine the Pareto solutions of a PMA structure based on the proposed tripping algorithm. The objective is to solve a design problem aimed at simultaneously minimizing the weight of a PMA structure and maximizing its critical buckling stress. Three multi-objective methods, Pareto Simulated Annealing (PSA), Ulungu Multi-objective Simulated Annealing (UMOSA) and Multi-objective Genetic Algorithm (MOGA) are presented for a case study. The numerical results show that all three methods can efficiently and effectively solve such optimization problems within a short search time. The critical buckling stress of the final optimal designs is validated by the linear and non-linear buckling analysis of NX-NASTRAN [2].
Airgap on Semi Submersibles: A Practical Guide on the Implementation of a Stochastic Approach
Authors: DaSilva Otto , Knecht Harris
Published: November 2011

Several articles in the literature cover methods for the prediction of semi submersible airgap. In general, using these methods, the reader will have to take care of the implementation, because in most cases not all factors that influence the final airgap are covered. This paper will describe the practical implementation of a calculation methodology covering all environmental aspects that affect the airgap for semi-submersibles. The proposed method utilizes a frequency domain stochastic approach (spectral method) to combine all known factors that can be calculated and that affect the airgap. These effects include the first order vessel motions under an undisturbed wave field, diffracted wave elevation along the free surface under the platform, slow drift quadratic transfer function (QTF), vessel set down and heel effects due to mooring stiffness into a single airgap prediction. Wave run up is not accounted in this procedure due to its high non-linearity, its difficult prediction and measurement. This is a local effect that is considered in the design phase by assuming that wave run up will hit the structures near columns and these components should be designed accordingly. The method proposes the combination of these statistical processes to be utilized for both the initial and final stages of the design. Model test results are also presented which show good correlation to the proposed method. A discussion of the limitations of this stochastic method, time simulations and model tests is also presented.
Free Roll Decay Study of a Damaged Ship for CFD Validation
Authors: Lee Sungkyun , You Ji-Myoung , Lee Hyun-Ho , Rhee Shin Hyung , Rhee Key-Pyo
Published: November 2011

Among many factors to be considered for higher safety level requirements, the hull stability in intact and damaged conditions in seaway is of utmost importance. Since the assessment of the damaged stability is complicated due to the highly non-linear behavior, it is widely acknowledged that computational fluid dynamics (CFD) methods are the only viable approach. Although many research activities are being reported on the damaged stability recently, most of them are not designed for validation of CFD studies. In this study, well-designed model tests are performed to build a CFD validation database, which is essential in developing better CFD methods for the damaged stability assessment. The geometry of the damaged compartment and test conditions are determined based on preliminary CFD simulations. The damping coefficient of the model becomes large when the ship is damaged. The amplitude of roll motion is decreased more rapidly in damaged condition because the flooding water motion. Detailed description of the tests and corresponding conditions are described to constitute a CFD validation database.
Large Displacement Finite Element Analysis of Submarine Slide due to Gas Hydrate Dissociation
Authors: Liu Jun , Yu Long , Kong Xianjing , Hu Yuxia
Published: November 2011

Gas hydrate dissociation will reduce the stability of the submarine slope, which has been increasingly considered as a potential geohazard. In this study, a conventional geotechnical model is used to simulate gas hydrate dissociation while the thermal and geochemical effects are considered by reducing geotechnical strength parameters (c-φ) and stiffness (E). The stability analysis of submarine slope due to gas hydrate dissociation is carried out using the large displacement finite element model – RITSS (Remeshing and Interpolating Technique with Small Strain model). The strength and stiffness parameters of gas hydrates are reduced gradually after each remesh according to the strength-dissociation relationship. The large displacement analysis procedure considering dissociation is given and the effects of the thickness of the top normal soil layer on slope stability is discussed.
Explosion Simulations/Structural Analysis With FLACS and USFOS
Authors: Vik Camilla Berge , Amdahl Jo̸rgen , Danielsen Ulf
Published: November 2011

A structural analysis performed by Scandpower combining explosion simulations and structural analysis utilising the the computer tools USFOS and FLACS is described. As of today, the most common procedure for elastic and plastic explosion response analyses is to define the explosion load as a uniform pressure vs. time function for all surfaces and elements in the model. Capabilities of the computer tools FLACS and USFOS allow for a more refined approach, recognizing that for large geometries explosion pressure will vary in both time and spatial domain. USFOS (Ultimate Strength for Offshore Structures) (Ref. /1/) is a leading computer program for nonlinear static and dynamic analysis of space frame structures. The program accurately simulates the collapse process, from the initial yielding, through to the formation of a complete collapse mechanism and the final toppling of the structure. FLACS (FLame ACcellerator Simulator) (Ref. /2, 3/) is a computational fluid dynamics (CFD) tool for modeling of ventilation, gas dispersion and explosions in complex process areas. The FLACS code allows for monitoring pressures at user defined surface areas, which can be chosen to correspond with an USFOS model. Results from FLACS simulations may be defined as individual time/pressure load histories to different parts of a steel structure. This high resolution of the explosion loads was further utilized by combining the results with USFOS. The combination of FLACS and USFOS in a structural analysis has shown that there may be significant capacity reserves compared to a standard “equal area pressure” analysis when analyzing a structure for a spatially variable explosion load.
Hydrogen Effect on Fracture Toughness of API 5L X70, X65 and X52 Pipeline Steel Welds: An Overview
Authors: Chatzidouros Elias V. , Papazoglou Vassilios J. , Pantelis Dimitrios I.
Published: November 2011

Steel welds representing three generations of pipeline steel were studied against hydrogen effect, using the fracture toughness parameter J integral which is a measure of the plastic work. The influence of hydrogen on the growth of a partial wall defect is studied and comparisons with the growth of the same defect in air are presented. The tests conducted were three-point bending fracture toughness tests, in air and in a hydrogen environment simulated by electrolysis. Reduction in J0 was observed in all pipeline steel grades as the current density increases, which was more pronounced in the base metal rather than in the heat affected zone. The different microstructures of the welded steels are observed and correlated to the reduction in plasticity. It is concluded that microstructure seems to be the decisive parameter for the selection of a pipeline steel for service in a hydrogen environment.
Offshore Use of Floating Sheerlegs
Authors: Koster Vincent , Vermeulen Kees Jan , Kortekaas Peter
Published: November 2011

The floating sheerlegs of SMIT are used for a large variety of tasks in sheltered, near shore as well as offshore environments. Generally the tasks vary from recovering operations (salvage) to inshore installation work. Originally, the usage of floating sheerlegs was driven by their robustness, needed for recovering work and shallow draft, needed for working near shore. In the past years the sheerlegs of SMIT became increasingly utilized for installation work offshore. As a result, the need for more detailed analysis showing the feasibility, related safety and reliability of operations emerged. In the engineering phase of such offshore installation projects these aspects are analyzed for each operational phase from load-out, towage to offshore lifting and installation. This paper addresses the crucial elements that need to be addressed when a floating sheerlegs is utilized for offshore installation work. The engineering topics that will be discussed in this paper are stability, strength and multi body dynamics. To demonstrate the relevance and validity of the discussed topics, an offshore installation project is analyzed in terms of measured motions and wave conditions.
Comparative Study of Slamming Loads on Cylindrical Structures
Authors: Vepa Kameswara S. , Van Nuffel Diederik , Van Paepegem Wim , Degroote Joris , Vierendeels Jan
Published: November 2011

Wave impact or slamming is a phenomenon characterized by large local pressures (10 bar or more) for very short durations (order of milliseconds). Slamming loads can cause severe damage to the structure [1]. Different numerical approximation methods are available for simulating the fluid structure interaction problems. Traditional mesh techniques use nodes and elements for approximating the continuum equations whereas particle methods like smoothed particle hydrodynamics (SPH) approximates the continuum equations using the kernel approximation technique and hence can be used for a wide range of fluid dynamics problems [2]. Since composite materials are finding increased application in the ship building industry because of their low weight and high strength properties, it is important to understand the effect of slamming loads on composite structures [3]. Normally, composite structures are made quasi-rigid to resist slamming loads, but inducing some deformability helps in reducing the incident pressures and at the same time reduces the overall weight of the structure and in turn the material cost. On the other side, inducing deformability effects the durability of the structure. In this paper, the effect of slamming on two-dimensional cylindrical structures is studied using three solvers i.e., 1) SPH solver, 2) Explicit solver and 3) Implicit solver. In the case of SPH solver, water is modelled using SPH particles and cylinder is modelled using finite elements (FE), in this case shell elements. A coupling between the SPH and FE solvers is made to simulate the fluid-structure interactions. Contact is modelled using the contact algorithms. In the case of the explicit solver, water is modelled using hexahedron or brick elements with one element in the thickness direction since symmetry is applicable along the thickness of the cylinder. Shell elements are used for modelling the cylinder and contact is handled using node to surface contact algorithm. In the case of the implicit solver, water is represented by pure two-dimensional elements. Quadratic elements are used to represent the continuum around the cylinder and triangular elements are used to represent the far off field and also to control the mesh movement. Line elements are used to represent the cylinder in this case. Two models are tested in all the three solvers: 1) rigid cylinder and 2) deformable cylinder. A comparative study of these three solvers shows that the implicit solver needed more calculation time compared to other solvers. The SPH method required less particles than the number of nodes in the other two methods to converge on the peak pressure. All three solvers show reduction of peak pressure in case of the deformable cylinder.