bluuebunny/crossref_metadata_2025_split huggingface dataset:
Outer Cover Damages on Flexible Pipes: Corrosion and Integrity Challenges
Authors: Eriksen Morten , Engelbreth Knut Inge 
Published: September 2014

According to published statistics for flexible pipes, penetrating holes in outside covers of flexible pipes is one of the most frequent damage mechanisms. The corrosion and fatigue performances of tensile and pressure armour wires are directly influenced by the fluids in the pipe wall annulus. There are several incidents where cover damages have led to serious pipe failures. In this perspective the best strategy is to avoid cover damage, but for those cases where damage occurs it is essential to have systems in place for early detection, as well as capabilities for repair.
Holes in the outside cover can create a range of different conditions in an annulus depending on location of the hole, configuration of the pipe and service conditions. CO2 driven corrosion in a confined water filled annulus has been investigated extensively and reported by several authors to give very low corrosion rates. However, the environments that armour wires are exposed to in certain parts of an annulus may differ significantly from confined water with CO2. One obvious example is the region around a penetrating hole in the outer cover where there may be repeated ingress of oxygenated seawater or air that mix with CO2 in the annulus. Such environments could cause high corrosion rates that may explain some observed failures.
In many cases it is difficult to quantify the annulus environments precisely and suitable corrosion models have not been established. The consequences are large uncertainties in the prediction of corrosion type and rate, giving challenges for integrity assessment. This paper will identify and discuss unresolved corrosion issues related to outer cover damage linking it to field experience. Needs for developing further knowledge and models will be addressed.
Efficient and reliable methods for repair of outer cover damage that can be mobilized soon are essential for restoring the integrity of pipes with damages to outer covers.
Hydrodynamic Module Coupling in the Offshore Wind Energy Simulation (OWENS) Toolkit
Authors: Fowler Matthew J. , Owens Brian , Bull Diana , Goupee Andrew J. , Hurtado John , Griffith D. Todd , Alves Marco 
Published: September 2014

When considering the future of offshore wind energy, developing cost effective methods of harnessing the offshore wind resource represents a significant challenge which must be overcome to make offshore wind a viable option. As the majority of the capital investment in offshore wind is in the form of infrastructure and operation and maintenance costs, reducing these expenditures could greatly reduce the cost of energy (COE) for an offshore wind project. Sandia National Laboratory and its partners (TU Delft, University of Maine, Iowa State, and TPI Composites) believe that vertical axis wind turbines (VAWTs) offer multiple advantages over other rotor configurations considering this new COE breakdown. The unique arrangement of a VAWT allows the heavy generator and related components to be located at the base of the tower as opposed to the top, as is typical of a horizontal axis wind turbine (HAWT). This configuration lowers the topside CG which reduces the platform stability requirements, leading to smaller and cheaper platforms. Additionally this locates high maintenance systems close to the ocean surface thus increasing maintainability. To support this project and the general wind research community, the Offshore Wind ENergy Simulation (OWENS) toolkit is being developed in conjunction with Texas A&M as an open source, modular aero-elastic analysis code with the capability to analyze floating VAWTS. The OWENS toolkit aims to establish a robust and flexible finite element framework and VAWT mesh generation utility, coupled with a modular interface that allows users to integrate easily with existing codes, such as aerodynamic and hydrodynamic codes.
Current efforts to include a hydrodynamic module are focused on coupling WavEC2Wire with OWENS. WavEC2Wire is a wave-to-wire numerical model developed by Marco Alves at the Insituto Superior Tecnico for the analysis of wave energy converter devices. It has been adapted from its original form and restructured for use as a hydrodynamic module capable of providing OWENS with necessary floating platform dynamics. Hence, WavEC2Wire functions as a rigid-body solver designed to calculate the platform motion due to wave loads, moorings, and the influence of the attached VAWT and tower. This paper presents the WavEC2Wire module and details the OWENS coupling method. Additionally, planned improvements in the WavEC2Wire module as well as future development in OWENS are presented.
An Experimental Investigation of Wave Impact Loads on a Slender Horizontal Cylinder
Authors: Haley Joseph F. , Swan Chris , Gibson Richard 
Published: September 2014

This paper concerns the difficulties arising in the prediction of the impact loads associated with an extreme wave event. A new set of experimental observations are presented. These concern the impact loads arising on a slender horizontal cylinder located at varying elevations above the still water level. The experimental observations incorporate a wide range of wave forms. In each case, data is provided describing (i) the incident water surface profiles, (ii) the incident fluid velocities and (iii) the load components acting on the cylinder.
Comparisons between the measured data and the classical impact load solutions confirm a number of important departures. In particular, it is shown that as the wave becomes very steep (approaching the breaking limit) the vector sum of the horizontal and vertical velocity components at the water surface may deviate significantly from the normal to the local water surface. In such cases it becomes unclear exactly what direction the impact force acts. The present data suggests that this is, in part, dependent on the rate of inundation of the body. Furthermore, the present results also show that if the direction of the force is correct modelled, the variations in the predicted loading (or slamming) coefficient are much reduced.
Development and Validation of Panels to Measure Slamming Forces
Authors: Spencer Don , Ryan Ron , Stockwood Blaine , Harris Trevor 
Published: September 2014

Ocean conditions have changed over the years, with severe and extreme wave generation occurring more frequently, resulting is larger loads and motions for offshore fixed and floating structures to contend with. It is not known exactly why ocean conditions are growing more severe, but we know that any structure being considered for offshore operations has to be designed to handle larger loads then in the past. Wave slamming, either directly or through run up is an area of growing concern with the offshore industry. During these slamming events the local forces can exceed the strength of the structural plating or the internal frames resulting in structural damage. It is often difficult to predict where these slamming events will occur, therefore large areas are required to be instrumented in order to capture these slamming events during model experimentation. Commercial pressure transducers are typically 5 mm in diameter, which corresponds to full-scale areas of approximately 0.05 m2 or less depended on the scale factor. Thus to cover a large area effectively, a large number of transducers are required. Alternatively a smaller number of larger devices such as force panels with areas of 8 m2 can be used. This area corresponds to the typical area that internal framing would experience slamming loading.
This paper describes the design and development iterations of Oceanic’s model-scale force panels and their applications on modeled offshore structures such as FPSO’s, FLNG’s, and GBS’s. A major advancement in construction of these force panels has been achieved through the use of in-house 3D printing technology to produce complex components.
The paper also presents results from controlled slamming experiments to validate the force panels with respect to piezoelectric pressure sensors and a theoretical slamming model based upon potential flow. Finally, the paper describes the transition from above water installation of the panels to submersion installation and the implementation of the inverse Duhamel analysis to remove the interference due to submerged panel dynamics from the measured response.
Spar Platform Installation: Tank Flooding Simulation
Authors: Medellin Abel , Arango-Turner Michelle , Fuhr Curtis 
Published: September 2014

Spars are towed to installation site horizontally and upended by progressive flooding of tanks. It is common practice to perform a dynamic time domain simulation for a self upending classic spar to determine hydrostatic pressures on compartments. There are many different flooding scenarios that create challenges in modeling and simulation during the design phase.
In one particular scenario, the spar upending is initiated by opening valves that allow water to flood into the skirt tank. The skirt tank will progressively fill, based on the differential hydrostatic pressure at valves, and cause the spar to upend. Flooding into keel tanks will commence once respective openings become submerged. Several openings from the skirt tank into the keel tanks reduce the differential pressure experienced in the keel tanks during upending.
Simulation of the transfer of water between tanks cannot be modeled with ease using the standard tank flooding options available within the software suite. This particular compartment flooding problem is solved by utilizing a scheme in which the time domain simulation was performed iteratively for a specified time interval. For every iteration the amount of water transferred between the skirt and keel tanks are calculated. The amount of water transferred is calculated using a custom modeling technique.
The openings from the skirt tank into the keel tanks are not modeled as a typical hole or valve into a compartment, but the location of these holes are modeled. The amount of water flowing through these openings is determined by the water level in the skirt tank, friction through the opening, and pressure inside the keel tanks.
This paper will describe in detail the scheme developed, the tank modeling requirements, and the results obtained.
Dynamic Responses of a Steel Cylinder in the Process of Lifting by a Floating Crane in Waves
Authors: Chen Keqiang , Zhang Hong , Niu Zhao , Zhou Lilan , He Wei , Wang Jiamei 
Published: September 2014

Dynamic responses of a heavy cycloidal object hanged by a large floating crane in the process of immersing into waves were studied experimentally and numerically in this paper. A floating crane with displacement of 14000t was selected as the reference. A model with the scale of 1:20 was conducted in a towing tank. The movement responses and forces of the heavy cycloidal object in the process of immersing in waves were researched.
Ocean engineering construction is always affected significantly by waves, so the selection of a shield to attenuate incoming waves is an important aspect for ocean engineering construction. The sea condition in our project is 3-state sea condition; it’s not an acceptable condition for real construction considering safety of crews and the ability of equipments. So an effective floating breakwater validated experimentally in a towing tank in our project was proposed as effective shields. The steel cylinder lifted by a floating crane in the process of water-entering was experimented, the movements of the steel cylinder and the subjected forces of the hoist were recorded; the effects of different shields on the responses of steel cylinder with different depth in water were studied. Numerical simulations of the motion of steel cylinder subjected to waves in the process of immersing were conducted to illustrate the effects of headings. The basis of model design, model-making and measurement methods are also introduced in this paper. The results are translated into full scale results which will be the basis for safety construction of ocean engineering and measurement proposed for accurate positioning and installation of the steel cylinder.
Which Sea States Are Dimensioning for Container Vessels When Whipping Is Included?
Authors: Storhaug Gaute 
Published: September 2014

Four container vessels have broken in two during the last four decades. There may not be one single cause explaining these severe accidents. They all broke in moderate storms, but they did not break in extreme storms in terms of extreme wave heights. How could this happen? This paper addresses one possible contributing effect to all of these accidents, i.e. whipping, and how whipping contribute in different sea states.
Whipping, as a sudden hull girder vibration caused by bow flare impacts, can contribute significantly to increase the vertical hull girder bending moments of container vessels, which have high design speeds and pronounced bow flare. Model tests have been carried out based on modern container ship designs covering one Panamax vessel, one Post Panamax vessel and one Ultra Large Container Ship. The tests have been carried out primarily in head seas. The whipping contribution depends on the vessel speed, and the tests have been carried out using realistic speed in each sea state. Lower sea states are more frequent than higher sea states, and lower sea states are associated with higher speeds. Does this speed dependence give other dimensioning sea states when whipping is considered?
For all three vessel designs, it is not the highest sea states, which define the dimensioning wave moments when whipping is included. Actually, realistic encountered storms can produce the dimensioning wave bending with whipping. These sea states differ considerably from the sea states, which produce the maximum wave moment without whipping. It is also demonstrated how different trades affect the dimensioning wave bending with whipping.
The industry seems most concerned about the effect of whipping for the largest vessels. These model tests demonstrate that the dimensioning moment with whipping for the largest vessel is not the main concern. The tests suggest that the bow flare angle is most important, and these may be high for Post Panamax vessels. The speed is well known to be important, while size in terms of length is not particularly important from these tests.
Modeling of Hydraulic Fracture Network Propagation in Shale Gas Reservoirs
Authors: Ahn Chong Hyun , Dilmore Robert , Wang John Yilin 
Published: September 2014

The most effective method for stimulating shale gas reservoirs is horizontal drilling with successful multi-stage hydraulic fracture treatments. Recent fracture diagnostic technologies have shown that complex fracture networks are commonly created in the field. The interaction between preexisting natural fractures and the propagating hydraulic fracture is a critical factor affecting the complex fracture network. However, many existing numerical models simulate only planar hydraulic fractures without considering the pre-existing fractures in the formation. The shale formations already contain a large number of natural fractures, so an accurate fracture propagation model needs to be developed to optimize the fracturing process.
In this paper, we first understood the interaction between hydraulic and natural fractures. We then developed a new, coupled numerical model that integrates dynamic fracture propagation, reservoir flow simulation, and the interactions between hydraulic fractures and pre-existing natural fractures. By using the developed model, we conducted parametric studies to quantify the effects of rock toughness, stress anisotropy, and natural fracture spacing on the geometry and conductivities of the hydraulic fracture network. Lastly, we introduced new parmeters Fracture Network Index (FNI) and Width Anistropy (Wani) which may describe the characteristics of the fracture network in shale gas reservoirs. This new knowledge helps one understand and optimize the stimulation of shale gas reservoirs.
Quantitative Risk Assessment (QRA) of an Exploratory Drilling Oil Spill in Deepwater Gulf of Mexico
Authors: Zulqarnain Muhammad , Tyagi Mayank 
Published: September 2014

Major offshore accidents such as Macondo well incident highlight one of the possible failure modes and subsequent disasters when an offshore engineering project could go wrong. Such events can potentially happen during any phase of an offshore well’s life — starting from the exploratory drilling phase to the final phase of plug and abandonment. Major factors that significantly contribute in defining such accident scenarios are the geological and operational complexities, equipment reliability, human factors, geographical/economy location, and environmental conditions. The path taken by the reservoir fluids to reach the sea floor is also an important factor in determining the worst case discharge rates. It is expected that the environmental risks from an oil/gas spill would also be function of the type of hydrocarbons released and duration of the spill.
A representative Neogene well is studied for quantitative risk assessment (QRA) for spill in exploratory phase from the Mississippi Canyon in the Gulf of Mexico with a water depth of 3,000ft and total vertical depth of 16,726 ft and the representative reservoir properties for this area are selected from the literature. Due to the large variation of reservoir properties, lognormal distributions have been assumed for some of the reservoir properties and from the Monte Carlo simulations P10, P50 and P90 values are estimated. Based on P50 and P90 values, the worst case discharge rates are calculated using a commercially available multiphase flow simulator with black oil model. Based on historical trends, release of hydrocarbons during blowouts are simulated for the following circumstances: seabed and topside releases, restricted and unrestricted flow through BOP, flow with drill pipe inside the wellbore and open hole flow without drill pipe and flow from the reservoir when it is either fully or partially penetrated. To incorporate the technological improvements and study their effects on the reduction of the overall risk associated with deepwater drilling activity, two cases are considered and compared to each other. First case is based on the historical data and the second case is a modified version of the first case by incorporating some of the recent technological improvements and newly built oil spill response systems e.g. capping stacks. The historical kick statistics and the equipment reliability data available in the literature is used to analyze various scenarios and corresponding flow rates. Risk is analyzed using the failure probability and consequence analysis and is presented in the form of a risk matrix for the different case studied and for the overall drilling activity as well.
Immunization of Mice with Live-Attenuated Late Liver Stage-Arresting Plasmodium yoelii Parasites Generates Protective Antibody Responses to Preerythrocytic Stages of Malaria
Authors: Keitany Gladys J. , Sack Brandon , Smithers Hannah , Chen Lin , Jang Ihn K. , Sebastian Leslie , Gupta Megha , Sather D. Noah , Vignali Marissa , Vaughan Ashley M. , Kappe Stefan H. I. , Wang Ruobing 
Published: September 2014

ABSTRACTUnderstanding protective immunity to malaria is essential for the design of an effective vaccine to prevent the large number of infections and deaths caused by this parasitic disease. To date, whole-parasite immunization with attenuated parasites is the most effective method to confer sterile protection against malaria infection in clinical trials. Mouse model studies have highlighted the essential role that CD8+T cells play in protection against preerythrocytic stages of malaria; however, there is mounting evidence that antibodies are also important in these stages. Here, we show that experimental immunization of mice withPlasmodium yoeliifabb/f−(Pyfabb/f−), a genetically attenuated rodent malaria parasite that arrests late in the liver stage, induced functional antibodies that inhibited hepatocyte invasionin vitroand reduced liver-stage burdenin vivo. These antibodies were sufficient to induce sterile protection from challenge byP. yoeliisporozoites in the absence of T cells in 50% of mice when sporozoites were administered by mosquito bite but not when they were administered by intravenous injection. Moreover, among mice challenged by mosquito bite, a higher proportion of BALB/c mice than C57BL/6 mice developed sterile protection (62.5% and 37.5%, respectively). Analysis of the antibody isotypes induced by immunization withPyfabb/f−showed that, overall, BALB/c mice developed an IgG1-biased response, whereas C57BL/6 mice developed an IgG2b/c-biased response. Our data demonstrate for the first time that antibodies induced by experimental immunization of mice with a genetically attenuated rodent parasite play a protective role during the preerythrocytic stages of malaria. Furthermore, they highlight the importance of considering both the route of challenge and the genetic background of the mouse strains used when interpreting vaccine efficacy studies in animal models of malaria infection.
CD66+ Cells in Cervical Precancers Are Partially Differentiated Progenitors with Neoplastic Traits
Authors: Pattabiraman Chitra , Hong Shiyuan , Gunasekharan Vignesh K. , Pranatharthi Annapurna , Bajaj Jeevisha , Srivastava Sweta , Krishnamurthy H. , Ammothumkandy Aswathy , Giri Venkat G. , Laimins Laimonis A. , Krishna Sudhir 
Published: September 2014

Abstract
Cervical cancers, a malignancy associated with oncogenic papilloma viruses, remain a major disease burden in the absence of effective implementation of preventive strategies. CD66+ cells have previously been identified as a tumor-propagating subset in cervical cancers. We investigated the existence, differentiation state, and neoplastic potential of CD66+ cells in a precancer cell line harboring HPV31b episomes. The gene expression profile of CD66high cells overlaps with differentiated keratinocytes, neoplastic mesenchymal transition, cells of the squamocolumnar junction, and cervical cancer cell line–derived spheroids. There is elevated expression of DNMT1, Notch1, and the viral gene product E1⁁E4 in CD66high cells. Thus, CD66high cells, in the absence of differentiating signals, express higher levels of key regulators of keratinocytes stemness, differentiation, and the viral life cycle, respectively. We also find a striking association of neoplastic traits, including migration, invasion, and colony formation, in soft agar with CD66high cells. These properties and a distinct G2–M–enriched cell-cycle profile are conserved in cells from cervical cancers. Principally, using a precancerous cell line, we propose that CD66high cells have an intermediate differentiation state, with a cellular milieu connected with both viral replication and neoplastic potential, and validate some key features in precancer lesions. Such pathophysiologically relevant systems for defining cellular changes in the early phases of the disease process provide both mechanistic insight and potential therapeutic strategies. Collectively, our data provide a rationale for exploring novel therapeutic targets in CD66+ subsets during cancer progression. Cancer Res; 74(22); 6682–92. ©2014 AACR.