bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear Wave Loads Affected by the Low-Frequency Oscillations in the Horizontal Plane
Authors: Kinoshita Takeshi , Bao Weiguang
Published: January 2009

To investigate the effects of the low-frequency oscillations on the nonlinear wave loads, the interaction of the low-frequency oscillations with the ambient wave fields is considered. The frequency of the slow oscillations is assumed to be much smaller than the wave frequency. Perturbation expansion based on two small parameters, i.e. the incident wave amplitude and the low frequency, is performed to simplify the problem. Nonlinear wave loads including the wave drift damping and wave drift added mass are evaluated by the integration of the hydrodynamic pressure over the instantaneous wetted body surface. The problem is solved for a uniform circular cylinder by means of the Green’s theorem and semi-analytical solutions are presented. The far field conditions for each order of potentials are proposed to ensure the existence of a unique solution. The restriction on the validation of the solutions is discussed.
Kristin Titanium Catenary Risers (TCR)
Authors: Dretvik Svein-Egil , Svardal Stian , Kristoffersen Steinar
Published: January 2009

The gas export from A˚sgard B has experienced vortex induced vibrations (VIV) internally in the flow caused by the irregularities in the carcass of the flexible risers. The VIV is amplified through resonance in the topside piping causing vibrations and fatigue resulting in gas leakage. So far extensive work have been carried out without succeeding in establishing predictable model for description of the VIV phenomena. For the Kristin project Titanium Catenary Risers (TCR) have been developed as an alternative to gas export through flexible risers. This paper will present the work performed to establish the TCR concept including design, production, installation and qualification.
Estimation of Corrosion Rates of Structural Members in Oil Tankers
Authors: Wang Ge , Spencer John , Elsayed Tarek
Published: January 2009

An accurate estimation of corrosion rates plays an important role in determining corrosion allowances for structural designs, planning for inspections, and scheduling for maintenance. This paper presents an estimation of corrosion rates of structural members in oil tankers based on a corrosion wastage database of over 110,000 thickness measurements from 140 single hull oil tankers. Corrosion rates may be described by a Weibull distribution function. Mean, standard deviation and maximum values of corrosion rates for structural members are obtained based on the entire population of the database. They are compared with the ranges of corrosion rate published by Tanker Structure Co-operative Forum (TSCF). The study aims to update knowledge on corrosion rates in steel ships, and to contribute to the efforts of mitigating the risks of corrosion.
Approximation of Surge and Pitch Loads on Truncated Vertical Cylinders
Authors: Sadeghi Keyvan , Incecik Atilla , Downie Martin , Chan Hoi-Sang
Published: January 2009

Truncated vertical circular cylinders are used to make deep water floating offshore platforms like Truss Spars. When the draft of the cylindrical hull is not deep enough, prediction of the surge and pitch diffraction loads by integration of McCamy and Fuchs expression of the force per unit length over the cylinder draft causes an error which is not negligible. Using hydrodynamic arguments the approximated surge and pitch loads by McCamy and Fuchs diffraction theory are modified. The modified results are compared with the results of a parametric study using the computer program WaMIT 4.01 based on the linear diffraction theory, reported by Weggel [1].
SENT Specimens an Alternative to SENB Specimens for Fracture Mechanics Testing of Pipelines
Authors: Nyhus Ba˚rd , Polanco Mario Loria , O̸rjasæther Oddvin
Published: January 2009

During installation operations offshore pipes are often strained beyond yielding. Due to the high loading condition and the high costs of these operations it is important with accurate defect assessment analysis to avoid delays caused by unnecessary repairs or failure because of flaws that should have been detected and repaired. There is therefore a need for an accurate assessment procedure that can be a tool for defect assessment analysis for this application. It is commonly accepted that the fracture toughness is dependent on the geometry constraint at the crack tip. The traditional single edge notch bend (SENB) specimens have a high geometry constraint, and give lower bound fracture toughness for all geometries. For reeling operations these fracture toughness values are often too low to be used in defect assessment of reeling operations. The same is the assumption of plastic collapse when the net section stress is equal to the average between the yield strength and tensile strength. In this paper, the single edge notch tension specimen (SENT) is presented as an alternative fracture mechanics specimen. This specimen has a geometry constraint that is much closer to flaws in pipes than SENB specimens, which will give more realistic fracture properties of the pipe. In the procedure for defect assessments we present, both the fracture toughness and plastic collapse properties are taken from testing of SENT specimens. FE simulations and full scale testing verify the procedure.
Assessment of the Emerging Technologies for the Detection and Measurement of Corrosion Wastage of Coated Marine Structures
Authors: Saidarasamoot Sittha , Olson David L. , Mishra Brajendra , Spencer John S. , Wang Ge
Published: January 2009

The application of a resistant coating on ships, offshore structures and pipelines is the primary prevention method of corrosion wastage in the marine industries. To guarantee coating integrity and to be able to thoroughly survey for corrosion wastage on marine structures, new advanced nondestructive methods are being sought. The requirements of convenient and rapid determination of corrosion wastage on coated structures, even in the difficult spatial positions of the structure, will require advanced technologies which are being developed for other industries that also require very high structural integrity. A review of the developments in electromagnetic wave (advanced microwave and eddy current practices) sensors, in elastic wave (advanced ultrasonic practices) sensors, in time-resolved thermography (thermal imaging), in electrochemical sensors and in other emerging analytical techniques is presented. Each of the identified emerging technologies was assessed based on a set of requirements necessary to be an acceptable marine corrosion wastage testing tool. This technology review and assessment include the use of both active and passive sensors and monitors, and the use of sensor arrays. The state of development and availability of the most promising technologies will be described.
Three Dimensional Finite Displacements and Rotations of Flexible Beams Including Non-Equal Bending Stiffnesses
Authors: O’Brien Patrick J. , McNamara John F. , Lane Michael
Published: January 2009

This paper addresses the issue of the accuracy of finite element computations for flexible beams undergoing extreme states of three-dimensional finite displacements and rotations of cross-sections including the case of unequal principal bending stiffnesses. An important consideration is the ability to compute post lateral classical buckling configurations and to determine the rate of convergence for such solutions. These extreme states are most likely to occur when structures such as flexible pipelines are being installed or subjected to severe operational loading conditions and during emergency deployment situations. A number of classical benchmark solutions and a practical example using a flexible riser are presented to illustrate the need for accuracy.
Numerical Offshore Tank: Development of Numerical Offshore Tank for Ultra Deep Water Oil Production Systems
Authors: Nishimoto K. , Ferreira M. D. , Martins M. R. , Masseti I. Q. , Martins C. A. , Jacob B. P. , Russo A. , Caldo J. R. , Silveira E. S. S.
Published: January 2009

There are several developments concerned to simulate the behavior of floating bodies under waves in the restricted boundary conditions so called numerical wave tank. The main feature of these tanks is to calculate full Navier-Stokes equations taking account the viscosity and free surface conditions. However, the dynamic behavior of oil floating exploitation units in actual ocean environmental condition, in waves, wind and current, is more complex and very difficult to simulate using full non-linear Navier Stokes equations. In addition, in the ultra-deep water, it is the primer importance to consider the more precise mooring line and riser’s dynamics in the analysis. The present numerical simulator laboratory called Numerical Offshore Tank is a development that takes account almost all physical phenomena acting on the floating bodies and mooring and risers lines. Since full non-linear solution is not available, the several numerical, empirical and analytical models are being considered and integrated to numerical simulator. The time domain potential problem is solved to wave forces acting on the bodies and empirical models are used to simulate current and wind forces. To represent mooring & riser lines, the finite element model with more realistic hydrodynamic force models is used. Even the simulator is using the full hydrodynamic equation, the calculation time of the simulation for floating bodies with several risers & mooring lines is very high. Therefore, special cluster with 60 PC based computer was built running the code in the parallel processing. Since the preparation of all data set for numerical experiment is very tedious work, the special pre-processor PREA3D was developed for this purpose. This pre-processor allows the fast change of the environmental and system conditions to run several test conditions. Another important feature is the visualization of the results of the simulation tests. The entire 3D view of the system is presented in the Virtual Reality room with stereoscopic projection of the Numerical Tank Laboratory.
High Strength UOE Pipe With Excellent CTOD Properties and Deformability
Authors: Terada Yoshio , Kojima Akihiko , Kiyose Akihito , Sawai Takashi , Uemori Ryuji , Tanaka Kazuaki , Nakashima Takao , Kadoya Tetsuji , Murata Masahiko , Kawaguchi Takashi
Published: January 2009

New steel manufacturing technology has been developed to attain excellent HAZ toughness of high-strength steels. In this steel, the HAZ microstructure near a weld fusion line is refined markedly by utilizing the strong retardation of austenite grain growth as well as the formation of intragranular ferrite. A dual phase microstructure is very effective for obtaining both high uniform elongation and low Yield / Tensile ratio in the high strength UOE pipe body. High strength, low Y/T ratio and high uniform elongation of the steel pipe can be attained by optimizing the area fraction of ferrite and the grain size by applying accelerated cooling technology. New high strength UOE pipes called “Tough-Ace” possessing both excellent HAZ toughness and deformability have been developed, and the X60 UOE pipe has been mass-produced for the Sakhalin Project.
X100 Linepipe With Excellent HAZ Toughness and Deformability
Authors: Terada Yoshio , Tamehiro Hiroshi , Morimoto Hiroshi , Hara Takuya , Tsuru Eiji , Asahi Hitoshi , Sugiyama Masaaki , Doi Naoki , Murata Masahiko , Ayukawa Naoshi
Published: January 2009

Good low-temperature toughness of the base material (BM) and weld heat-affected zone (HAZ), and good deformability of the pipe body together with good field weldability are required for X100 linepipe to ensure the safety of pipelines and to facilitate field welding. It is, however, very difficult to attain these properties simultaneously because of the large addition of alloys. The technology of improving HAZ toughness by reducing carbon content through the reduction of M-A constituents harmful to low-temperature toughness was developed, and accelerated cooling after controlled rolling was applied to attain good low-temperature toughness of BM and high uniform elongation together with sufficient strength corresponding to X100. Two newly developed types of X100 linepipe, a “high HAZ toughness type” and a “high uniform elongation type”, exhibited excellent low-temperature toughness of the HAZ and high uniform elongation together with sufficient strength, respectively.
Oceanographic and Motion Response Statistics for the Operation of a Weathervaning LNG FPSO
Authors: Ewans Kevin , van der Valk Clemens , Shaw Christopher , den Haan Joost , Tromans Peter , Vanderschuren Luc
Published: January 2009

An oceanographic database is used to estimate the operability of a weathervaning LNG FPSO (FLNG) in multidirectional seas with swells. The oceanographic data consist of directional wave data, current profile measurements, and a wind dataset. Response functions are used to convert the oceanographic data into an equivalent dataset of vessel motion response parameters and turret mooring line tensions. The resulting response data have enabled operational type statistics to be computed, as well as the environmental conditions that induce responses with a one-year return period. In addition to the analysis of the responses of the FLNG alone, the method has been applied to a system where a LNG shuttle carrier is moored alongside the FLNG for offloading of the products. In this case, important responses are the combined roll and pitch of the two vessels and tension in the mooring lines between the shuttle carrier and the FLNG. The same method can be applied for a stern-to-bow offloading system, where the shuttle carrier is moored with a hawser or soft yoke. The diversity of the directionality of the oceanographic variables makes this a particularly interesting exercise. The analysis included significant inertial currents, a high level of background swell and frequent local-wind seas that act at an angle to the prevailing swell direction. A method for separating a sea state into a sea and swell component has been derived and is reported, along with a programme for visualising the oceanographic conditions together with the induced responses corresponding to the existing conditions.
Poisson-Logistic Compound Bivariate Extreme Distribution and Its Application for Designing of Platform Deck Clearance
Authors: Liu Defu , Song Yan , Shi Hongda , Yu Yifa , Ma Li
Published: January 2009

This paper proposes a new bivariate extreme probability model-Poisson-Logistic compound extreme distribution. Because the routes and frequencies of Typhoons vary each year, the frequencies of Typhoons occurring in certain sea areas also differ from year to year. This may cause a discrete distribution. Typhoon induced sea environments may be a kind of multivariate joint extreme distribution. By compounding the discrete distribution with a bivariate distribution of two extreme maritime factors, a new distribution-Poisson-Logistic compound bivariate extreme distribution is proposed in this paper. As one of the application example, a platform deck clearance can be estimated by compounding Typhoon induced maximum wave crest height and surge with 100 yrs joint occurring return period instead of traditional method, which proposed to use separate 100 yrs return period wave create height and surge.
Flexible and Rigid Pipe Solutions in the Development of Ultra-Deepwater Fields
Authors: Novitsky Adriano , Gray Fin
Published: January 2009

The development of the offshore segment during the last three years was remarkably important for the oil industry due to some major achievements observed in the technical area, more specifically on the development of pipe solutions for ultra deepwater (UDW) applications. Brazil and Gulf of Mexico (GoM) have lately been the two main regions for application of proven pipe solutions in UDW. In Brazil, flexible pipes have been widely used in the development of UDW fields by Petrobras, while in the GoM, rigid pipelines and SCRs have been used for the majority of deepwater field developments. The main advances in flexible pipe technology are linked to the development of two major Petrobras fields located in the Campos Basin named Roncador and Marlim South. Technip-Coflexip has, through Technical Cooperation Agreements with Petrobras, designed, tested and installed flexible pipes, proving the fitness of this kind of product to UDW applications. The qualification of flexible risers for 1500m WD and flexible flowlines for 2000m WD are highlighted as being the main achievements. Extensive testing programs including, collapse, fatigue and offshore full scale tests have been put in place in order to simulate the design conditions to be seen by the pipes during installation and operation phases. The main design aspects in UDW like collapse, radial and lateral buckling of tensile armours, fatigue and thermal insulation will be covered in this paper and the current available technologies to tackle these issues will be presented. Similar design and qualification issues exist for rigid pipelines and risers (SCRs). The following three areas are specifically covered in this paper: collapse resistance of steel pipe; fatigue strength of plastically strained girth welds: and qualification of pipe-in-pipe thermal performance. These are some of the key areas of reeled pipe in deepwater applications that require successful project qualification. Technip-Coflexip has performed internal R&D programs on these areas as well as project specific qualifications. Both will be addressed by the paper.
Determination of Wave Field Properties in the Spatial Domain From Space Borne SAR Images
Authors: Nieto Borge Jose C. , Niedermeier Andreas , Lehner Susanne , Rosenthal Wolfgang
Published: January 2009

New techniques have been developed to study single wave events and wave groupiness from space borne SAR images of the sea surface. These techniques are based on the determination of wave groupiness features from the local wave envelope, estimated by using a two dimensional Hilbert transform, and the analysis of the local variability of the wave height within SAR images. This analysis is carried out on a global scale by using 34,310 SAR images, taken by the European satellite ERS-2. The obtained results are used to generate global maps of maximum wave heights, and other parameters of describing wave events, which are able to inform about potentially dangerous situations for navigation and offshore structures.
Wind Measurements for Optimal Siting, Construction and Operation of Offshore Wind Farms With Synthetic Aperture Radar
Authors: Lehner Susanne , Horstmann Jochen , Schneiderhan Tobias , Schulz-Stellenfleth Johannes
Published: January 2009

In all European countries with shallow coastal waters and strong mean wind speed at the coast the planning and construction of offshore wind farms is on the way and large parts of the North Sea and the Baltic are under investigation as to whether they are suitable for offshore parks. In this paper it is demonstrated how satellite images taken by spaceborne radar sensors can be used to determine mesoscale wind fields and thus help in the task of planning offshore wind farms. High resolution SAR images acquired by the European remote sensing satellite ERS 2 are presented which show single wind turbines (Fig. 1). The derivation of high resolution wind fields from SAR images is explained and comparisons with numerical models are presented.
Design of Ice Protection Barrier in Caspian Sea
Authors: Lengkeek H. J. , Croasdale K. R. , Metge M.
Published: January 2009

Several offshore platforms and artificial islands will be constructed in the Caspian Sea for the exploration and production of oil. In some cases, vulnerable structures can be protected against severe ice loading using rock mound barriers. These barriers will be constructed in shallow water on a soft sediment layer. This paper discusses the assessment of ice interaction scenarios and the FEM stability analyses for the design of the ice barriers. In normal winters, rock slopes will cause the thin ice to fail in bending at low forces creating ice rubble. In this scenario, barrier stability has to be checked against local edge failure due to initial interaction of thin ice. Later in the winter, global failure has to be evaluated in the situation when ice rubble has extended only to the toe of the rock slope and thick ice acts against the ice-rubble, rock-mound combination. Various other extreme scenarios require analysis including direct action by thick ice and a frozen-in condition, which prevents edge failure and encourages decapitation if the barrier freeboard is low. The stability of the barriers under ice loading has been analyzed with a FEM program. From the analyses several failure types can be recognized which can also be found in literature.
Sub-Surface Buoy Hybrid Riser System for Deepwater Application
Authors: Fernandes Antonio C. , Jacob Breno P. , Vardaro Eduardo , Franciss Ricardo , Almeida Jose´ Carlos L.
Published: January 2009

A Sub-Surface buoy hybrid riser system is considered as a solution for deepwater export systems. Besides the in place static and dynamic loads, the installation operation was analyzed. The development includes the reduced model tests in a (so far) unique Deep Water Ocean Basin. A reduced model in an adequate scale was designed and constructed. It was submitted to an almost full equivalent depth and a comprehensive equivalent environment. The later corresponds to representative Campos Basin currents together with critical high crossing waves, which were made to excite resonance of the FPSO (Floating Production Storage and Offloading) hull. Typical moored FPSOs’ motions are much more than other platforms like Semi-Submersibles or TLPs and therefore the SSB is very adequate, since it resists easily to the cited critical environment conditions. Besides describing the system main characteristics, the paper describes the model testing in detail and present main results. Some problematic aspects has been are clearly appreciated for the first time, anticipating that what could happen in full scale. This therefore, requires a design improvement as also discussed.
Thermal Analysis of Sandwich Pipes With Active Electrical Heating
Authors: Su Jian , Cerqueira Djane R. , Estefen Segen F.
Published: January 2009

Sandwich pipes consisting of two concentric metal pipes with insulation material in annulus have been developed to meet challenging mechanical and thermal requirements of deep and ultra deepwater oil and gas production. Passive thermal insulation is designed to meet flow assurance requirements under steady-state production conditions, but is unlikely to meet more severe conditions during transient events such as warm-up and cool-down. In this work, we propose a new sandwhich pipe system with active electrical heating, provided by a number of electrical resistance strips stuck longitudinally over the outer surface of the inner metal pipe. A steady-state heat transfer analysis is carried out to determine the temperature distribution in a cross section of the sandwich pipe, the power requirement of electrical heating, and the overall heat transfer coefficient. It is shown that the sandwich pipe with active heating is a viable solution to meet server flow assurance requirements of ultra deepwater oil production.
A New Approach to Repair of FPSO’s Without Hot Work
Authors: Echtermeyer Andreas T. , Larsen Martin J. , Fischer Karl P.
Published: January 2009

FPSO’s stay in production at sea for a period of 20 years or more. Repairs of an FPSO in service can be difficult to perform. Welding, which is the most common repair method creates a fire hazard. Consequently there is a need to consider alternative repair methods. An adhesive bonded patch is an alternative repair method. The paper present the challenges for qualifying the composites patches repair of FPSO hulls.
Production of High-Strength and High-Toughness Steel for Offshore Structures
Authors: Nagai Yoshihide , Fukami Hidenori , Inoue Hajime , Nakashima Takao , Kojima Akihiko , Kajitani Toshiyuki , Adachi Toshihiko , Yoshida Yuzuru
Published: January 2009

By the utilization of new fine particles, steels refining the heat affected zone (HAZ) structure have been developed. This has made possible the mass-production of offshore structural steels which have high-strength of 460–500N/mm2 in yield strength (YS) and excellent crack-tip opening displacement (CTOD) properties. These newly developed steels for offshore structures have been mass-production to over 45,000 tons. The new particles are dispersed finely in the developed steels and show a strong pinning effect. The newly developed steels also use the intragranular ferrite (IGF) like titanium oxide bearing steel (TiO steel). In mass-production heats, γ grain size is restricted below 200 μm under conditions of 1400°C for 60 seconds. The improvement of HAZ toughness and the utilization of the thermo-mechanical control process (TMCP) has restrained the increase in carbon equivalent (Ceq,PCM) far as possible. By application of these technologies, it has been possible to mass-produce steels with high-strength, excellent CTOD properties and good weldability. As for steel plates of YS500N/mm2, the production of steel plates up to 70mm in thickness was carried out. The properties of welded joints for the 70mm-thick plates of YS500N/mm2 steel have been evaluated under heat input in 0.7kJ/mm of flux-cored are welding (FCAW) and 3.5kJ/mm of sub-merged arc welding (SAW). They have shown excellent CTOD and Charpy impact properties at welded joints; and have moreover indicated good weldability when PCM has been restricted to 0.22% or lower.
Interaction of a Flexible Floating Carpet With Ocean Waves
Authors: Chakrabarti Subrata K. , Koola Paul K.
Published: January 2009

A concept of wave energy extraction using a large thin floating structure called ‘wave carpet’ is analyzed. This paper examines the hydroelastic properties of the wave carpet. In determining the motion of the carpet, a simplified linear two-dimensional problem is formulated. The carpet is assumed to be a slender elastic beam with free ends. The hydrodynamic pressures along the carpet in waves are computed taking into account the dry eigenmodes of the carpet and the wave diffraction/radiation effect on the carpet. The amplitudes of carpet deflection and available energy stored in the carpet are estimated. The amount of energy that can be extracted for a typical carpet size is determined. The analysis is extended to random waves. The simplified method shows that it represents physical displacements of such a configuration by comparing the deflection of the carpet with available model test data on such plates.
Investment Analysis for Deepwater Oil and Gas Field Developments
Authors: Critsinelis Antonio
Published: January 2009

The effective stewardship of capital is cardinal to ensure economic return to compensate shareholders for capital invested at risk. This paper outlines how investment analysis can be used to improve the decision-making process of deepwater oil and gas field developments. The paper focuses on the key drivers and boundary conditions that impact the economics of the entire field life cycle. It also highlights the relationships between these key drivers and the selection of the layout and main subsystems of the field architecture. A typical deepwater field scenario is used to illustrate the methodology of investment analysis and associated simulations that reflect the uncertainties along the stages of the decision process. Sensitivity analysis is utilized to identify how much each uncertain driver contributes to the uncertainty in the project economic outcome.
Uncertainty and Bayesian Updating Considering Inspection for Ship Structures Subjected to Corrosion Deterioration
Authors: Li Dianqing , Zhang Shengkun , Tang Wenyong
Published: January 2009

The classical probability theory cannot effectively quantify the parameter uncertainty in probability of detection. Furthermore, the conventional data analytic method and expert judgment method fail to handle the problem of model uncertainty updating with the information from nondestructive inspection. To overcome these disadvantages, a Bayesian approach was proposed to quantify the parameter uncertainty in probability of detection. Furthermore, the formulae of the multiplication factors to measure the statistical uncertainties in the probability of detection following the Weibull distribution were derived. A Bayesian updating method was applied to compute the posterior probabilities of model weights and the posterior probability density functions of distribution parameters of probability of detection. A total probability model method was proposed to analyze the problem of multi-layered model uncertainty updating. This method was then applied to the problem of multi-layered corrosion model uncertainty updating for ship structures. The results indicate that the proposed method is very effectively in analyzing the problem of multi-layered model uncertainty updating.
Amplitude Bounds for Nonlinear Internal Waves
Authors: Makarenko Nikolai I. , Maltseva Janna L.
Published: January 2009

Amplitude bounds imposed by the conservation of mass, momentum and energy for internal gravity waves are considered. We discuss the theoretical schemes intended for a description of permanent waves just up to the broadening limit. Analytical methods which allow to determine the critical amplitude values for the current with a given density profile are considered. Attention is focused on the continuously stratified flows having multiple broadening limits. The role of the mean density profile and the influence of fine-scale stratification are analysed.
Modelling of Seabed Interaction in Frequency Domain Analysis of Mooring Cables
Authors: Ong Paul P. A. , Pellegrino Sergio
Published: January 2009

Mooring cables under wave loading interact dynamically with the seabed; this interaction is nonlinear and can be modelled in full only by performing lengthy time integration of the equations of motion. However, time domain integration is far too computationally expensive to be carried out for all load cases. A new method of modelling the interaction between a cable and the seabed in the frequency domain, but without considering frictional effects and impact, is therefore proposed. The section of cable interacting with the seabed is truncated and replaced with a system of coupled linear springs, with stiffnesses linearised from static catenary equations. These springs would model the behaviour of the truncated cable and hence the time-varying boundary condition at the touchdown. The entire cable-spring system is then analysed in the frequency domain with a centred finite difference scheme. The proposed method has shown to increase the accuracy of frequency domain analysis in certain cases with affordable computational overhead.
Corrosion Testing of Armour Wire in Simulated Annulus Environments of Flexible Pipelines: An Update
Authors: Clements Richard , Ethridge Andrew D.
Published: January 2009

This paper describes further investigations, utilising small scale test cells, into the general corrosion which can occur on wires within the inherent annulus space in a flexible pipe, particularly, and for the first time, in a sour service (H2S containing) environment. The work enhances data presented previously in 2002. Tests have been performed in cells specifically designed to simulate, as closely as possible, the environment and confines of a flexible pipe annulus, using solutions of both deionized water and seawater (to represent seawater flooding and condensed water). The systems were saturated with CO2 and H2S to simulate permeation of gases through the polymer pressure sheath (as predicted by validated permeation models). Weight loss measurements were undertaken in order to quantify the corrosion rate in these simulated annulus environments and metallography was undertaken to characterise the corrosion and check for HIC/SOHIC.
Dynamic Analysis of an Offshore Platform With Excessive Vibration Under Wave Loading
Authors: Ji Chunyan , Li Huajun , Wang Shuqing
Published: January 2009

An offshore platform of jacket type in Bohai Bay vibrates excessively under design environmental conditions, which has affected the normal operation of the platform. In order to mitigate the vibration of the platform, it is essential important to explore the cause of the vibration. So the objective of this study is to investigate the cause of the excessive vibration. In this paper, dynamic characteristics of the offshore platform are analyzed by numerical simulation using finite element (FE) modeling. To further verify the numerical results, a model experiment is conducted. Numerical and experimental results demonstrate that there are relative movement and impact between the piles and the jacket, i.e. the piles and the jacket didn’t connect well to an entity. It is this cause that the stiffness of the platform deceases and impact between piles and the jacket legs induce excessive vibration. And also the grouting measure is advised to reduce the vibration of the offshore platform according to the analysis results.
Riser Technology and Industry-University Cooperation: Part I — Riser Mechanics
Authors: Pesce Celso P. , Martins Clo´vis A. , Aranha Jose´ A. P. , Pinto Marcos O. , Ramos Roberto , da Silva Renato M.
Published: January 2009

This is the first of two companion papers intending to summarize and pointing out some of the main engineering achievements obtained through a continuous cooperative research effort, jointly conducted by Industry and University. Part I covers Riser Mechanics and design issues. Part II is dedicated to Riser Loading and Dynamic Positioning. The work starts with the first SCR (Steel Catenary Riser) concept and engineering analysis that paved the road toward a mature and reliable design which has been applied with success in floating production in Campos Basin, offshore Brazil. Several computer codes, numerical methods and analytical tools were developed and verified based on experimental results. In Part I, SCR dynamics, touch down point dynamic interaction loading, catenary riser dynamic compression under twist, as well as risers and umbilical cables structural mechanics, are treated and modeled through analytical and numerical methods. SCR design issues and fatigue assessment of flexible pipes are also addressed. In Part II [1], VIV (Vortex-Induced Vibration), extreme dynamic loading, nonlinear dynamics of FPSOs and turret positioning are presented. Nonlinear control techniques are also addressed aiming to optimize FPSO heading, constrained to a cost function that takes into account risers loading, mooring tension, roll motion and fuel consumption.
Towards Satellite Production System Selection for Moderate Water Depths
Authors: Ronalds Beverley F. , Simpson Scott M. , Foo K. F. Thomas
Published: January 2009

A large database of North Sea subsea satellites and minimum facilities platforms is used to derive and justify key drivers influencing the selection process for satellite production systems in shallow and moderate water depths. The key drivers include reservoir fluid, tieback length, water depth (d), and well count (w) and pattern. In particular, it is found that an approximate dividing line between subsea and surface satellite facilities occurs at d = kw, where k ≈ 8.5m and 15m for oil- and gas-dominated fields, respectively.
Seismic Response of Submarine Slopes
Authors: Biscontin Giovanna , Pestana Juan M.
Published: January 2009

The geological profile of submerged slopes on the continental shelf typically includes soft cohesive soils with thicknesses ranging from a few meters to tens or hundreds of meters. The response of these soils in simple shear tests is largely influenced by the presence of an initial consolidation shear stress, inducing anisotropic stress-strain-strength properties which depend also on the direction of shear. In this paper, a new simplified effective-stress-based model describing the behavior of normally to lightly overconsolidated cohesive soils is used in conjunction with a one-dimensional seismic site response analysis computer code to illustrate the importance of accounting for anisotropy and small strain nonlinearity. In particular, a simple example is carried out to compare results for different slope inclinations. Depth profiling of the maximum shear strains and permanent deformations provide insight into the mechanisms of deformation during a seismic event, and the effects of sloping ground conditions.
Refined Model for Inclined Load Capacity of Suction Caissons
Authors: Aubeny Charles P. , Han Seungwoon , Murff J. Don
Published: January 2009

Suction caissons used as mooring anchors for offshore structures can, depending on design concept, be subjected to pullout forces ranging from nearly vertical for tension leg platforms, to intermediate inclination angles for taut mooring systems, to nearly horizontal for catenary moored systems. Hence, the ability to understand and predict suction anchor pullout resistance for a full range of load orientations is becoming of increasing importance. A previous paper by the authors presents a plastic limit analysis for estimating the load capacity of suction anchors over a full range of load inclination ranging from horizontal to vertical. The model was capable of predicting load capacity for various load attachment (padeye) depths, caisson aspect ratios, and soil undrained strength profiles that vary linearly with depth. Loading conditions are assumed to be undrained; therefore, a purely cohesive soil is assumed. The original analysis assumed full adhesion on the boundaries of the caisson; i.e., a skin resistance coefficient α equal to unity. However, actual values of this coefficient are less than unity, with specific values varying according to soil conditions and the method of caisson installation. To overcome the limitation of the original model, this paper presents a modified formulation that allows a skin resistance less than unity. The modified formulation develops an interaction relationship between vertical and horizontal soil resistance on the sides of the caisson that is applicable for any skin resistance conditions ranging from no to full adhesion.
Comparison of Analytical and Centrifuge Model Tests for Suction Caissons Subjected to Combined Loads
Authors: Clukey Edward C. , Aubeny Charles P. , Murff J. Don
Published: January 2009

The holding capacity of suction caissons increases significantly when the mooring line is attached below the mudline. In addition to the position of the attachment point, the soil profile, caisson geometry and the loading angle at the attachment point (padeye) will also influence the holding capacity. Various combinations of these parameters will control the failure mechanism that determines the holding capacity. The failure capacity can be dominated by the vertical or horizontal failure mechanisms — or a combination of the two. When the combination controls, the caisson response is referred to as being in the ‘interaction’ region’. If the suction caisson response is in the interaction region, methods of analyses required to predict the ultimate holding capacity are more complex than for pure vertical or horizontal failure mechanisms. This paper considers the response of suction caissons for all three failure mechanisms. The various failure mechanisms were primarily investigated through comparisons of an upper bound plasticity model and centrifuge model tests. Finite element results were also obtained and compared to the plasticity model solutions. The general foundation conditions investigated are considered fairly typical of suction caissons currently being used to anchor deepwater facilities in normally consolidated soils. The caisson scaled diameters investigated were slightly less than 5.36 m. with embedment (L) to diameter (D) ratios (L/D) slightly less than 5 for comparisons between the plasticity and centrifuge models. Comparisons were made between the finite element and plasticity models for an L/D ratio of 6. The padeye attachment point was about 2L/3 below the mudline for the plasticity and centrifuge comparisons and 0 (mudline) and L/2 for the finite element and plasticity model comparisons. The finite element estimates were slightly less than the plasticity model estimates (3 to 9%) with the largest differences in the interaction region. Both the plasticity and centrifuge models indicated that the transition from a vertical mechanism to an interaction failure mechanism occurs at a load angle of 40 to 45° from the horizontal. In the interaction region the centrifuge results were generally less than the plasticity model predictions. Centrifuge tests with a bevel at the caisson tip were inconclusive in terms of establishing the effectiveness of the bevel for displacing more soil to the outside of the caisson and thereby increasing the external skin friction.
Spectral Characteristics of Earthquakes Recorded on the Gulf of Me´xico Seafloor and Modeling of Soft Marine Sediments
Authors: Huerta Lo´pez Carlos I. , Pulliam Jay , Stokoe Kenneth H. , Roe¨sset Jose´ M. , Valle-Molina Celestino
Published: January 2009

The overall goal of this work was to develop a cost-effective method of characterizing offshore geotechnical sites in deep water. The generic approach was to place an ocean bottom seismograph on the seafloor and record ambient noise and distant earthquakes over periods of a month or more. Horizontal-to-vertical (H/V) spectral ratios were then calculated and used to characterize the local sediment response in terms of the distribution of motions with their respective resonant frequencies. One-dimensional wave propagation modeling using the stiffness matrix method was used to estimate sediment properties (mainly layering, shear stiffness, density and material damping) by matching the resonant frequency and amplification factors of the shallow sediment layers. The resulting sediment properties fall well within the expected range, indicating the potential of the proposed exploration approach for characterizing deep water sites.
Function of Mitochondrial Stat3 in Cellular Respiration
Authors: Wegrzyn Joanna , Potla Ramesh , Chwae Yong-Joon , Sepuri Naresh B. V. , Zhang Qifang , Koeck Thomas , Derecka Marta , Szczepanek Karol , Szelag Magdalena , Gornicka Agnieszka , Moh Akira , Moghaddas Shadi , Chen Qun , Bobbili Santha , Cichy Joanna , Dulak Jozef , Baker Darren P. , Wolfman Alan , Stuehr Dennis , Hassan Medhat O. , Fu Xin-Yuan , Avadhani Narayan , Drake Jennifer I. , Fawcett Paul , Lesnefsky Edward J. , Larner Andrew C.
Published: January 2009

Cytokines such as interleukin-6 induce tyrosine and serine phosphorylation of Stat3 that results in activation of Stat3-responsive genes. We provide evidence that Stat3 is present in the mitochondria of cultured cells and primary tissues, including the liver and heart. In Stat3
â/â
cells, the activities of complexes I and II of the electron transport chain (ETC) were significantly decreased. We identified Stat3 mutants that selectively restored the protein's function as a transcription factor or its functions within the ETC. In mice that do not express Stat3 in the heart, there were also selective defects in the activities of complexes I and II of the ETC. These data indicate that Stat3 is required for optimal function of the ETC, which may allow it to orchestrate responses to cellular homeostasis.
Harmonic Convergence in the Love Songs of the Dengue Vector Mosquito
Authors: Cator Lauren J. , Arthur Ben J. , Harrington Laura C. , Hoy Ronald R.
Published: January 2009

The familiar buzz of flying mosquitoes is an important mating signal, with the fundamental frequency of the female's flight tone signaling her presence. In the yellow fever and dengue vector
Aedes aegypti
, both sexes interact acoustically by shifting their flight tones to match, resulting in a courtship duet. Matching is made not at the fundamental frequency of 400 hertz (female) or 600 hertz (male) but at a shared harmonic of 1200 hertz, which exceeds the previously known upper limit of hearing in mosquitoes. Physiological recordings from Johnston's organ (the mosquito's “ear”) reveal sensitivity up to 2000 hertz, consistent with our observed courtship behavior. These findings revise widely accepted limits of acoustic behavior in mosquitoes.
Self-Sustained Replication of an RNA Enzyme
Authors: Lincoln Tracey A. , Joyce Gerald F.
Published: January 2009

An RNA enzyme that catalyzes the RNA-templated joining of RNA was converted to a format whereby two enzymes catalyze each other's synthesis from a total of four oligonucleotide substrates. These cross-replicating RNA enzymes undergo self-sustained exponential amplification in the absence of proteins or other biological materials. Amplification occurs with a doubling time of about 1 hour and can be continued indefinitely. Populations of various cross-replicating enzymes were constructed and allowed to compete for a common pool of substrates, during which recombinant replicators arose and grew to dominate the population. These replicating RNA enzymes can serve as an experimental model of a genetic system. Many such model systems could be constructed, allowing different selective outcomes to be related to the underlying properties of the genetic system.
Neuropathogenesis of Congenital Cytomegalovirus Infection: Disease Mechanisms and Prospects for Intervention
Authors: Cheeran Maxim C.-J. , Lokensgard James R. , Schleiss Mark R.
Published: January 2009

Congenital cytomegalovirus (CMV) infection is the leading infectious cause of mental retardation and hearing loss in the developed world. In recent years, there has been an improved understanding of the epidemiology, pathogenesis, and long-term disabilities associated with CMV infection. In this review, current concepts regarding the pathogenesis of neurological injury caused by CMV infections acquired by the developing fetus are summarized. The pathogenesis of CMV-induced disabilities is considered in the context of the epidemiology of CMV infection in pregnant women and newborn infants, and the clinical manifestations of brain injury are reviewed. The prospects for intervention, including antiviral therapies and vaccines, are summarized. Priorities for future research are suggested to improve the understanding of this common and disabling illness of infancy.
Epidemiology, Diagnosis, Treatment, and Control of Trichinellosis
Authors: Gottstein Bruno , Pozio Edoardo , Nöckler Karsten
Published: January 2009

Throughout much of the world,Trichinellaspp. are found to be the causative agents of human trichinellosis, a disease that not only is a public health hazard by affecting human patients but also represents an economic problem in porcine animal production and food safety. Due to the predominantly zoonotic importance of infection, the main efforts in many countries have focused on the control of Trichinella or the elimination ofTrichinellafrom the food chain. The most important source of human infection worldwide is the domestic pig, but, e.g., in Europe, meats of horses and wild boars have played a significant role during outbreaks within the past 3 decades. Infection of humans occurs with the ingestion ofTrichinellalarvae that are encysted in muscle tissue of domestic or wild animal meat. Early clinical diagnosis of trichinellosis is rather difficult because pathognomonic signs or symptoms are lacking. Subsequent chronic forms of the disease are not easy to diagnose, irrespective of parameters including clinical findings, laboratory findings (nonspecific laboratory parameters such as eosinophilia, muscle enzymes, and serology), and epidemiological investigations. New regulations laying down rules for official controls forTrichinellain meat in order to improve food safety for consumers have recently been released in Europe. The evidence that the disease can be monitored and to some extent controlled with a rigorous reporting and testing system in place should be motivation to expand appropriate programs worldwide.