bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of Fluid Flow in Sediments and the Effect of Tidal Pumping
Authors: Whitehead John , Waltrich Paulo , Hughes Richard , Thompson Karsten
Published: October 2016

Offshore drilling and production operations can result in spills or leaks of hydrocarbons into seabed sediments, which can potentially contaminate these sediments with oil. If this oil trapped later migrates to the water surface it has the potential for negative environmental impacts. For proper contingency planning and to avoid larger consequences in the environment, it is essential to understand mechanisms and rates for hydrocarbon migration from oil containing sediments to the water surface as well as how much will remain trapped in the sediments. It is believed that the amount of oil transported out of the sediment can be affected by tidal pumping, a common form of Subterranean Ground Water Discharge (SGD). However, we could find no study investigating the phenomenon of fluid flow in subsea sediments saturated with oil and the effects of tidal pumping.

This study presents an experimental investigation of tidal pumping to determine if it is a possible mechanism to describe the appearance of an oil on the ocean surface above a sediment bed containing oil. An experimental apparatus was constructed of clear PVC pipe allowing for oil migration to be monitored as it flowed out of a sand pack containing oil, while tidal pressure oscillations were applied in three different manners.

The effect of tidal pumping was simulated via compression of air above the water (which simulated the increasing static head from tidal exchange). Experimental results show that sustained oil release occurred from all tests, and tests with oscillating pressure produced for longer periods of time. Furthermore, the experimental results showed that the oil migration rate was affected by grain size, oil saturation, and oscillation wave type. In the static experiments, a linear relationship between grain size and permeability was observed, as is well-known in fluid flow in porous medium. However, the oil recovery does not show a linear relationship with viscosity, as the oil recovery only changed by 50% for a nearly 400% variation in viscosity. In all oscillating experiments the rate and ultimate recovery was less than the comparable static experiments. This leads to the preliminary conclusion that with an oscillating pressure on top of a sand pack, movement of a non-replenishing source of oil is suppressed by pressure oscillation.
Characteristic Levels of Strongly Nonlinear Extreme Wave Load Effects
Authors: Johannessen Thomas B. , Hagen Øistein
Published: October 2016

Offshore structures are typically required to withstand extreme and abnormal load effects with annual probabilities of occurrence of 10−2 and 10−4 respectively. For linear or weakly nonlinear problems, the load effects with the prescribed annual probabilities of occurrence are typically estimated as a relatively rare occurrence in the short term distribution of 100 year and 10 000 year seastates. For strongly nonlinear load effects, it is not given that an extreme seastate can be used reliably to estimate the characteristic load effect. The governing load may occur as an extremely rare event in a much lower seastate.

In attempting to model the load effect in an extreme seastate, the short term probability level is not known nor is it known whether the physics of the wave loading is captured correctly in an extreme seastate. Examples of such strongly nonlinear load effects are slamming loads on large volume offshore structures or wave in deck loads on jacket structures subject to seabed subsidence. Similarly, for structures which are unmanned in extreme weather, the governing load effects for the manned structure will occur as extremely rare events in a relatively frequent seastate.

The present paper is concerned with the long term distribution of strongly nonlinear load effects. Using a simple point estimate of the wave elevation correct to second order and a crest kinematics model which takes into account the possibility of wave breaking, the long term distribution of drag load on a column above the still water level is studied and compared with a similar loading model based on second order kinematics which does not include the effect of wave breaking.

The findings illustrate the challenges listed above. Model tests are useful in quantifying strongly nonlinear load effects which cannot be calculated accurately. But only a relatively small number of seastates can be run in a model test campaign and it is not feasible to estimate short term responses far beyond the three hour 90% fractile level. Similarly, Computational Fluid Dynamics (CFD) is increasingly useful in investigating complex wave induced load effects. But only a relatively small number of wave events can be run using CFD, a long term analysis of load effects cannot in general be carried out.

It appears that there is a class of nonlinear problems which require a long term analysis of the load effect in order for the annual probability of occurrence to be estimated accurately. For problems which cannot be estimated by simple analytical means, the governing wave events can be identified by long term analysis of a simple model which capture the essential physics of the problem and then analysed in detail by use of CFD or model tests.
Impact of Bathymetry on the Mooring Design of an Offshore Floating Unit
Authors: Jaiswal Vivek , Vishnubhotla Srinivas , Cole Sean , Gordon Robert B. , Sharma Partha
Published: October 2016

Moored offshore floating units may operate in regions where the bathymetry changes significantly over the mooring spread. Traditional mooring analysis methods make the assumption that the seabed slope is constant along the azimuth direction of each mooring line. This assumption, while reasonable for a seabed with nearly constant slope, can lead to significant errors with respect to the line tensions and vessel offsets in the mooring design assessment when the seabed slope is variable.

This paper demonstrates the impact of bathymetry changes on the mooring design with the help of numerical analysis examples. The floating vessel considered is a semi-submersible moored by an eight point all chain catenary mooring system.

Two methods of analysis are compared. In the first method, a true representation of the seabed surface that accounts for all variations in the bathymetry is used. In the second method, the anchor depths and the seabed slopes at the anchor locations estimated in the previous method are used, however, with the assumption of constant seabed slopes along the line azimuth directions. The dynamic analysis program Orcaflex is used for performing the numerical analyses in the time domain for both the methods. Differences in the performance of the mooring system are demonstrated by comparing the static and the dynamic line tensions as well as the vessel offsets in different environmental conditions. The paper also discusses how maximum offsets and line tensions are estimated.
Crack Propagation and Local Failure Simulation of Reinforced Concrete Subjected to Projectile Impact Using RBSM
Authors: Yamamoto Yoshihito , Okazaki Soichiro , Nakamura Hikaru , Beppu Masuhiro , Shibata Taiki
Published: October 2016

In this paper, numerical simulations of reinforced mortar beams subjected to projectile impact are conducted by using the proposed 3-D Rigid-Body-Spring Model (RBSM) in order to investigate mechanisms of crack propagation and scabbing mode of concrete members under high-velocity impact.

The RBSM is one of the discrete-type numerical methods, which represents a continuum material as an assemblage of rigid particle interconnected by springs. The RBSM have advantages in modeling localized and oriented phenomena, such as cracking, its propagation, frictional slip and so on, in concrete structures. The authors have already developed constitutive models for the 3D RBSM with random geometry generated Voronoi diagram in order to quantitatively evaluate the mechanical responses of concrete including softening and localization fractures, and have shown that the model can simulate cracking and various failure modes of reinforced concrete structures.

In the target tests, projectile velocity is set 200m/s. The reinforced mortar beams with or without the shear reinforcing steel plates were used to investigate the effects of shear reinforcement on the crack propagation and the local failure modes. By comparing the numerical results with the test results, it is confirmed that the proposed model can reproduce well the crack propagation and the local failure behaviors. In addition, effects of the reinforcing plates on the stress wave and the crack propagation behaviors are discussed from the observation of the numerical simulation results. As a result, it was found that scabbing of reinforced mortar beams subjected to high velocity impact which is in the range of the tests is caused by mainly shear deformation of a beam.
Optimization of Floating Offshore Wind Energy Systems Using an Extended Pattern Search Method
Authors: Forinash Caitlin , DuPont Bryony
Published: October 2016

An Extended Pattern Search (EPS) approach is developed for offshore floating wind farm layout optimization while considering challenges such as high cost and harsh ocean environments. This multi-level optimization method minimizes the costs of installation and operations and maintenance, and maximizes power development in a unidirectional wind case by selecting the size and position of turbines. The EPS combines a deterministic pattern search algorithm with three stochastic extensions to avoid local optima. The EPS has been successfully applied to onshore wind farm optimization and enables the inclusion of advanced modeling as new technologies for floating offshore wind farms emerge. Three advanced models are incorporated into this work: (1) a cost model developed specifically for this work, (2) a power development model that selects hub height and rotor radius to optimize power production, and (3) a wake propagation and interaction model that determines aerodynamic effects. Preliminary results indicate the differences between proposed optimal offshore wind farm layouts and those developed by similar methods for onshore wind farms. The objective of this work is to maximize profit; given similar parameters, offshore wind farms are suggested to have approximately 24% more turbines than onshore farms of the same area. EPS layouts are also compared to those of an Adapted GA; 100% efficiency is found for layouts containing twice as many turbines as the layout presented by the Adapted GA. Best practices are derived that can be employed by offshore wind farm developers to improve the layout of platforms, and may contribute to reducing barriers to implementation, enabling developers and policy makers to have a clearer understanding of the resulting cost and power production of computationally optimized farms; however, the unidirectional wind case used in this work limits the representation of optimized layouts at real wind sites. Since there are currently no multi-turbine floating offshore wind farm projects operational in the United States, it is anticipated that this work will be used by developers when planning array layouts for future offshore floating wind farms.
WEC-Sim Phase 1 Validation Testing: Experimental Setup and Initial Results
Authors: Bosma Bret , Simmons Asher , Lomonaco Pedro , Ruehl Kelley , Gunawan Budi
Published: October 2016

In the wave energy industry, there is a need for open source numerical codes and publicly available experimental data, both of which are being addressed through the development of WEC-Sim by Sandia National Laboratories and the National Renewable Energy Laboratory (NREL). WEC-Sim is an open source code used to model wave energy converters (WECs) when subject to incident waves. In order for the WEC-Sim code to be useful, code verification and physical model validation is necessary. This paper describes the wave tank testing for the 1:33 scale experiments of a Floating Oscillating Surge Wave Energy Converter (FOSWEC). The WEC-Sim experimental data set will help to advance the wave energy converter industry by providing a free, high-quality data set for researchers and developers. This paper describes the WEC-Sim open source wave energy converter simulation tool, experimental validation plan, and presents preliminary experimental results from the FOSWEC Phase 1 testing.
CFD Calculations of the Vortex-Induced Motions of a Circular-Column Semi-Submersible
Authors: Rosetti Guilherme Feitosa , Gonçalves Rodolfo , Fujarra André Luís Condino , Koop Arjen
Published: October 2016

The vortex-induced motions (VIM) of offshore platforms stand as an intriguing and challenging engineering problem, drawing attention from industry, universities and research institutes. Field observations, model tests and calculations have extensively showed that the complex fluid-structure interaction can result in appreciable motions and increased fatigue of mooring and risers. It is thus a very relevant issue from the engineering standpoint. A large volume of experimental research has been carried out, mainly to verify designs and characterize the occurrence of VIM. Conversely, the numerical investigations applying CFD tools have shown to be a more flexible approach enabling better understanding of the physics at play due to the possibility of investigating the effects of different parameters upon the vortex induced motions of floating platforms. Moreover, the CFD calculations enable investigation of the full-scale behavior of the platforms under VIM, a very controversial issue presently. Bearing upon these issues, the VIM Joint Industry Project aims at increasing physical insight of this phenomenon by means of investigating the influence of geometric design variations, flow conditions and scale effects with the objective of improving practical knowledge that can be applied in the design stage of floating platforms. In this paper, we present some of the CFD studies, results and observations carried out within the JIP, regarding the VIM of a semi-submersible with circular columns in 0 and 45 degrees and over a wide range of reduced velocities. It is confirmed that the 0 degree incidence results in larger motions than the 45 degrees-incidence case, in contrast to the VIM behavior of a semi-submersible with square columns. The tests campaign carried out at the University of São Paulo for the same platform agree with these results. Within the lock-in range, the frequency synchronization of the lift forces on columns and pontoons cause large net transverse forces. Appreciable sway motions thus result. For larger reduced velocities, synchronization of the flow around the columns cease, but the forces on the pontoons then largely contribute to the total force. In this high-reduced velocity range, the phasing between total force and motion is such that energy transfer from the fluid to the body occurs, causing the amplification of the motions.
Fundamental Study on the Development of a Tsunami Hazard Map for Moored Vessels in a Port
Authors: Masuda Koichi , Ikoma Tomoki , Hoshino Satoshi
Published: October 2016

The Great East Japan Earthquake in 2011 revealed the vulnerability of modern ports to damage caused by drifting vessels as a result of a tsunami. The goal of the present study is to develop a tsunami hazard map for moored vessels in order to evaluate the potential for damage caused by drifting vessels that were previously moored at a port. The proposed map consists of four components: a maximum tsunami-height map, a maximum inundation depth map, a maximum flow velocity map, and an evaluation map of maximum mooring tension. The proposed tsunami hazard map for mooring vessels can be used to reduce the number of possible mooring locations and to obtain information for selecting a promising candidate mooring location. Furthermore, information on the tsunami force on moored vessels and on the grounding of vessels by a tsunami can be obtained, and information required for the development of preemptive measures for tsunami relief can be obtained using the proposed hazard map. In the present study, the suitability of mooring locations at Kisarazu port was analyzed, and the results are presented in the form of a map.
Extreme Typhoon Loads Effect on the Structural Response of Offshore Meteorological Mast and Wind Turbine
Authors: Lin Tsung-Yueh , Quéméner Yann
Published: October 2016

Recently, Taiwan started to evaluate the potential of wind energy production on its West coast. The concern was raised about employing existing solutions validated by experience for mild environment regions to Taiwan which is frequently subject to Typhoon. This study investigated the strength under typhoon condition of two offshore wind farm units: a meteorological mast supported by a monopile and a 3.6 MW wind turbine supported by a 4-leg jacket. Especially, two critical load cases were analyzed. First, the study provided a simplified approach to evaluate the wave run-up load on a monopile. The dynamic structure response of the meteorological mast evaluated through finite element analyses showed that large vibrations excited the tower after the slamming. In a second time, the study evaluated the extreme wind loads exerted on the blades of the parked wind turbine considering a blade pitch control fault. As a result, for a constant gust wind speed of 70 m/s, the loads at the nacelle increased tremendously by approximately 220% compared to the parked wind turbine without fault condition.
Study on Weld Fatigue Evaluation Incorporating Welding Induced Residual Stress Effect
Authors: Hong Jeong K.
Published: October 2016

For fatigue assessment of a welded structure, an important characteristic is the failure location. The fatigue crack begins from the pre-existing crack-like flaw which is an inherent feature of a weld toe or root. Residual stress in the welded joints is another important characteristic. It is also well known that tensile residual stress in welded structures can be as high as the material yield strength level and so the fatigue strength of the welded joint is governed by the applied stress range regardless of the applied load ratio. However, when the presumed conditions with high tensile residual stress in the weld regime are not satisfied, the fatigue behavior in welded structure deviates from the general weld fatigue behavior.

In this paper, firstly the applied load ratio effect on fatigue behavior is investigated for two different residual stress levels of welds, i.e., as-welded and stress relieved. It has been observed that stress-relieving effect of welds is apparent when the applied loading introduces stress fluctuations in compressive loading. When the load ratio effect is considered in Battelle structural stress based fatigue parameter, the stress relieved weld fatigue data was consolidated within the master S-N curve.

Based on this investigation, the Battelle structural stress based effective load ratio considering both applied loading and detailed residual stress is introduced for the weld fatigue behavior. The two-stage crack growth model is reformulated with the structural stress based effective load ratio, which is a function of crack length.

Lastly, a fatigue life prediction procedure incorporating residual stress effect is proposed and validated using the existing fatigue test results. The proposed procedure clearly shows that the compressive residual stress distributions at the weld prone to crack provide great benefits for fatigue life improvement.
A Study on Motion Characteristics of Wind Turbine on a Floating Platform in Blade Pitch Control Malfunction
Authors: Mizukami Yuki , Nihei Yasunori , Iijima Kazuhiro , Hara Naoyuki
Published: October 2016

Wind power generation has been paid much attention all over the world with the increasing crisis awareness of climate change mainly caused by excessive fuel consumption. For real wind turbine, each blade pitch angle is controlled not only to keep output power constant depending on fluctuation of wind speed but also to avoid the failure of generating system due to over speed of the rotor rotation.

Nowadays, a few demonstration projects for Floating Offshore Wind Turbine (FOWT) are under way. It is essential to improve the safety of FOWT. For that, it will be more required to conduct tank test with scale model including control system so as to provide the behavior similar to the actual FOWT. However, almost every institute has never incorporated control system in scale model. This is because every institute faces to the difficulty of incorporating control system in scale model in terms of weight. The larger FOWT would be from now on, the more necessary it is to lighten scale model in consideration of the capacity of existing facilities.

Therefore, we conducted 1/100th-scale model tests with control system using a geometrically scaled model of the National Renewable Energy Laboratory (NREL) 5MW reference wind turbine. As for this model, a new control system consisting of bevel gears was developed. Owing to this system, the mass of the scaled turbine is 41% lighter than the conventional one. In addition, this control system realized the shortening of control period in reference to scaling down of the actual control period. This tank test showed this control system is enough effective to keep rotor rotation frequency.

Moreover, this paper clarifies the motion of FOWT in control malfunction. If blade pitch angle abruptly changes due to the failure of control system, the number of the rotor rotation increases and floating platform inclines greatly. This great inclination causes the sudden rise of mooring tension and bending moment on the base of tower. This phenomenon jeopardizes the base of tower or the mooring line. We call this phenomenon “Pitch Error”. This is because of the rapid increase of thrust. In addition to this, the influence of nacelle’s inertia induces the inclination of FOWT. In case of offshore, we have to pay attention to nacelle’s inertia caused by inclination because the base of tower is not fixed. FOWT would be more severe than onshore in control malfunction. Finally, how dangerous Pitch Error would be for real FOWT is discussed.
Comparison Between Stress Obtained by Numerical Analysis and In-Situ Measurements on a Flexible Pipe Subjected to In-Plane Bending Test
Authors: Lukassen Troels Vestergaard , Glejbøl Kristian , Lyckegaard Anders , Berggreen Christian
Published: October 2016

To predict the lifetime and long-term properties of tensile armour wires in a dynamically loaded pipe, it is essential to have a tool which allows detailed prediction of the stress variations in the tensile armour wires during global pipe loading. Furthermore, detailed understanding of the stress variations will allow for performance optimization of the armour layers. To study the detailed stress variations in flexible pipes during dynamic loading, a comprehensive three-dimensional implicit nonlinear finite element model has been developed. The predicted numerical stress variations will be compared to stress patterns obtained during in-situ OMS measurements carried out during an actual experimental inplane bending test. The study showed a good correlation between the stress variation predicted with the finite element model and the measured stress variation.
Structural Engineering of Aluminum Helideck Structure Based on the NORSOK Requirement
Authors: Park Joo Shin , Kishore R. Krishna , Ha Yeong Su , Jang Ki Bok
Published: October 2016

Recently, the numbers of large offshore structures and fixed jacket type platforms are rapidly increasing for oil and gas companies. Generally, a shuttle vessel or helicopter is used to access offshore structures such as a fixed platform, floating platform, jack-up rig and so on. The helideck structure should be installed in these offshore structures for landing and taking-off of the helicopter. The helideck structure comprises of pancakes, girders using aluminum materials and supporting steel structures. The helideck structure should be designed to accommodate a safe landing area suitable for the largest and heaviest helicopter that is anticipated to land on the helideck. The helideck and its supporting structure are safety critical elements as a result of their role in emergency evacuation, as well as during normal operations.

The codes and standards applicable for the structural design of the helideck will be determined by where the helideck is to be operated and the national jurisdiction governing the installation or vessel of which the helideck will become part. International standards such as ISO(International Organization for Standardization) codes, Eurocodes, or national standards, e.g. BS(British Standards)5950, NORSOK N-004 or AISC(American Institute of Steel Construction) may be specified for detailed design.

The objective of this study is to present the results of structural analysis and design that has been performed for a 28.54 meter diameter octagonal standard aluminum helideck with support truss & lower steel support structure of jackup drilling rig based on the NORSOK requirements. The supporting structure is designed to provide the adequate resistance to the external force produced by the design helicopter and environmental conditions.
Numerical Investigation on Gas Hydrate Production by Depressurization in Hydrate-Bearing Reservoir
Authors: Long Xiaoyan , Tjok Komin , Adhikari Sudarshan
Published: October 2016

Gas hydrates are anticipated to be a promising energy source with global distribution underneath the oceans and in permafrost regions. Hydrate dissociation referring to the phase transition of the solid gas hydrate into gas and liquid water, can occur due to altered environmental conditions like increase in temperature, decrease in pressure, or the injection of hydrate inhibitors. Numerical modeling work suggested that energy efficiency of the thermal simulation and inhibitor injection to dissociate gas hydrate in geological formations are quite low, and possibly negative. Depressurization is expected to be effective in many situations; however, the hydrate bearing sediments should be well enough confined by low permeability strata for the depressurization to be effective.

In current study, numerical analyses were performed using the open-source reservoir simulator HYDRATERESSIM (HRS) to investigate methane gas hydrate dissociation behavior and production by depressurization, where the system pressure is lowered below the hydrate three-phase (gas-MH-water) stability pressure. Two-dimensional (2D) axisymmetric radial coordinates are used for the numerical simulations with local grid refinement.

This paper presents the approach and results of numerical investigation conducted for a hypothetical hydrate-bearing reservoir in an offshore deep water site. A comprehensive parametric sensitivity study was undertaken to assess the effects of (1) various reservoir properties including sediment permeability (absolute permeability and relative permeability function), hydrate distribution, pore compressibility, porosity formation heterogeneity and thermal conductivity; and (2) operational condition on hydrate dissociation and production. Gas productivity and advance of hydrate dissociation front with time after the commencement of depressurization are discussed. This numerical study highlights the need and importance to obtain an accurate evaluation of reservoir properties from different data source, including seismic data, logging while drilling (LWD) data, core samples, field and laboratory testing data and drilling information, on gas hydrate production prediction. It can provide useful insights on the planning and design of a field production well test.
The Use of Coupled and Uncoupled Analysis Techniques in the Assessment of Blast Wall Response to Explosions
Authors: Burgan Bassam , Chen Anqi , Choi Jae-Woong , Ryu Yonghee
Published: October 2016

Floating oil and gas production facilities are highly weight sensitive. Yet, certain safety critical structural elements of these facilities have to be designed to withstand high explosion loads. This is particularly the case for blast walls. The situation is made more acute as some such walls are free standing with no lateral support at the top edge of the wall making them prone to high deflection at the top and large strain at their supports. It is therefore important to use analysis techniques that enable a realistic assessment of such structures without being over-conservative so that their weight may be controlled. In the present study, three analysis techniques were used with a view to comparing the effect this has on the response of the blast wall: (a) Lagrangian, (b) uncoupled Eulerian-Lagrangian (UEL) and (c) coupled Eulerian-Lagrangian (CEL). In the first Lagrangian approach, the blast loading is approximated as a reflected pressure-time curve (normally obtained from a CFD simulation of the blast); this is applied to the surface of the wall. The UEL approach requires an Eulerian simulation to be performed using as input the overpressure parameters obtained from a CFD analysis. The Eulerian analysis can be used to give a better estimate of the overpressure distribution on the wall) and is followed by a Lagrangian analysis. In the Eulerian analysis, the blast wall is treated as a rigid object and the analysis is used to determine the blast load distribution over the wall surface. This is followed by a Lagrangian analysis to determine the structural response under the pre-determined blast load distribution. Finally, CEL involves coupling of the Eulerian (blast wave) and the Lagrangian (structure) to describe the interaction between the blast wave and the structural response throughout the response time. Both loading and response can be described more accurately by this approach even when deformations are large. The paper demonstrates how coupled analysis allows the effect of the interaction between the load and the response of the wall to be accounted for. The results are compared with those from Lagrangian and uncoupled analysis and the differences are reconciled through intermediate analysis steps. It is shown how deflection and strain performance criteria can be satisfied using the coupled analysis whilst avoiding unnecessary increases in the weight of the structure. As the complexity of the analysis increases from Lagrangian to UEL and CEL, the computational demand increases significantly. A comparison of the times needed for the analysis in this study is also given.
Feasibility Study of a Subsea to Shore Production System
Authors: Carrano Porto Scudino Alves Anna Carolinna , Paranhos Pasqualino Ilson
Published: October 2016

This work develops a technical and economic comparative study between a scenario with exploitation using stationary production units and a scenario with subsea to shore. Moreover, evaluates the subsea to shore scenario varying parameters of oil type (heavy, medium and light), water depth (80 m, 500 m 1000 m) and distance to the coast (50 km and 100 km), aiming the optimization of the subsea equipment for the different scenarios created from the combination of the three parameters mentioned above and the flow simulation success. A pilot field was designed for this study and used in the flow simulations performed. The results corroborate with the difficulties of flowing expected with the increase of the water depth and the distance to the coast and decrease of the oil density.
Three-Dimensional Finite Element Analysis of Antisymmetric Four-Point Shear Specimen
Authors: Cohen Mark , Wang Xin
Published: October 2016

In this paper, the four-point shear (FPS) specimen is studied for different combinations of crack depth (a/W) and specimen thickness (t/W) to width ratios. Extensive 3D finite element analysis (FEA) has been carried out, and comprehensive solutions of fracture parameters produced. From the results of the finite element analysis, the size of the plastic zone is studied at various points through-thickness. Through these analyses, the effects of considering finite-thickness specimens are illustrated.
Numerical Analysis for Impact Force in High-Energy Ship-Bridge Pier Collisions
Authors: Pan Jin , Huang Shi Wen , Xu Ming Cai
Published: October 2016

In the present paper, the collision force and the response of bulbous bows in the ship-bridge collisions are investigated by the numerical analysis, in which a bulbous bow of vessel with 5000-ton displacement is generated in the finite element (FE) code. The considered scenarios include ship bow impacts against rigid walls, rigid cylindrical piers and rigid rectangular piers with different velocities. The force - displacement curves and the energy absorption of the collision are studied in the nonlinear finite elements. The collision forces from the bulbous bow are compared with the suggested force-displacement curves in the requirement formulas, and then the difference between the FE analysis and these formulas are discussed.
Calibration of the Ultrasonic Technique Using the Deep Hole Drilling, Neutron Diffraction and Contour Residual Stress Measurement on a Ring Stiffened Cylindrical Structures
Authors: Ficquet Xavier , Romac Remi , Cave Douglas , Kingston Ed J.
Published: October 2016

This paper presents the residual stress measurements carried out on a t-section representative of a ring stiffened cylindrical structures. This paper presents the work carried out to ascertain the residual stresses present within a T-plate section representative of a ring stiffened cylindrical structures. The contour, the deep hole drilling (DHD) and the neutron diffraction (ND) methods were applied to determine the longitudinal component of residual stress in the weld toe of the fillet weld in the as-welded condition. The results of these measurements are presented and compared to highlight agreements and discrepancies in the measured residual stress distributions using these different techniques. Finally, non-destructive residual stress measurement using the ultrasonic (US) technique was carried out on the component. The ultrasonic measurement provides a relative measurement and usually requires a tensile test in order to determine the acoustoelastic constant and the time of flight in a stress-free state. The tensile test requires some material to be extracted from the component. The tensile test can be avoided if other residual stress measurement techniques are used for the calibration. After the calibration the US technique can be deployed on a full-scale ring stiffened cylindrical structures to detect abnormal variation in the residual stress field.
Numerical Simulation on Response of Foam Core Sandwich Panels Subjected to Underwater Explosion
Authors: Ai Dongjie , Cheng Yuansheng , Liu Jun , Liu Jianhu , Wang Haikun , Zhang Pan
Published: October 2016

Sandwich panel structures, which consist of two thin faces and low relative density cores, can significantly mitigate the possibilities of panel fractures. In the present paper, numerical simulations are conducted to study the deformation and fracture modes of sandwich structures under near-field underwater blasts and contact underwater blasts. Two different core materials are employed, namely aluminum foam and PVC foam. Main focus of this paper was placed to (i) study the failure mechanisms and energy absorption characteristics of sandwich structures in typical conditions, (ii) to demonstrate the benefits of such structures compared with solid plates of equal weight, and (iii) to obtain the properties of withstanding underwater explosion for single core material sandwich panels. In addition, the effects of panel thickness configuration and core height on deformation and energy absorption of the plates were explored. Results indicated that sandwich structures showed an effective reduction in the maximum panel deflection compared with a monolithic plate of same mass. The design parameters have great impacts on the results.
Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds
Authors: Arnela Marc , Dabbaghchian Saeed , Blandin Rémi , Guasch Oriol , Engwall Olov , Van Hirtum Annemie , Pelorson Xavier
Published: October 2016

For many years, the vocal tract shape has been approximated by one-dimensional (1D) area functions to study the production of voice. More recently, 3D approaches allow one to deal with the complex 3D vocal tract, although area-based 3D geometries of circular cross-section are still in use. However, little is known about the influence of performing such a simplification, and some alternatives may exist between these two extreme options. To this aim, several vocal tract geometry simplifications for vowels [ɑ], [i], and [u] are investigated in this work. Six cases are considered, consisting of realistic, elliptical, and circular cross-sections interpolated through a bent or straight midline. For frequencies below 4–5 kHz, the influence of bending and cross-sectional shape has been found weak, while above these values simplified bent vocal tracts with realistic cross-sections are necessary to correctly emulate higher-order mode propagation. To perform this study, the finite element method (FEM) has been used. FEM results have also been compared to a 3D multimodal method and to a classical 1D frequency domain model.
The Influence of Familiarization on Physical Fitness Test Results in Primary School-Aged Children
Authors: Vrbik Ivan , Sporiš Goran , Štefan Lovro , Madić Dejan , Trajković Nebojša , Valantine Irena , Milanović Zoran
Published: October 2016

Purpose:

The number of familiarization sessions in fitness assessments seems to be critical and inconsistent. Therefore, the primary aim of this research was to determine the number of familiarization attempts that stabilize the results in particular physical fitness tests. The secondary aim was to establish the test reliability through familiarization sessions.

Methods:

Thirty-nine primary school children participated in this research (age: 10.8 years, body mass: 40.6 ± 8.9 kg, and body height: 145.3 ± 7.2 cm). During six sessions, with one session every third day, participants performed the following tests to assess explosive strength (vertical jump and standing long jump), coordination (polygon backward and polygon with turn) and flexibility (toe touch).

Results:

The results of repeated analysis of variance (ANOVA) showed that there were significant increases (p < .05) in the polygon backward and polygon with turn performances from the first to third familiarization session. The standard error of measurement decreased as sessions progressed, indicating little within subject variation between the coordination test results following a familiarization period. Statistically significant differences were identified in the vertical jump test from the fourth test session compared with the first session. On the other hand, statistically significant differences for the standing long jump test were only found in the final session compared with the initial session. In the toe touch test, there were no significant increases from the first to the final familiarization session. All tests showed high a reliability coefficients, ranging from 0.979 to 0.991.

Conclusion:

Polygon backward and polygon with turn performance may be a practical, reliable method to assess coordination in primary school-aged children. However, completion of at least 3 practice sessions is suggested for participants to obtain a stable score. In addition, both jump tests are feasible for assessing skill-related fitness in young children, although the scientific reliability of the two tests should be questioned and the tests should be tailored to fit the age group of the children.
Coupling an EML4-ALK–centric interactome with RNA interference identifies sensitizers to ALK inhibitors
Authors: Zhang Guolin , Scarborough Hannah , Kim Jihye , Rozhok Andrii I. , Chen Yian Ann , Zhang Xiaohui , Song Lanxi , Bai Yun , Fang Bin , Liu Richard Z. , Koomen John , Tan Aik Choon , Degregori James , Haura Eric B.
Published: October 2016

A network built around the kinase ALK reveals potential targets to enhance ALK inhibitor efficacy in some lung cancer patients.
Escherichia coli Probiotic Strain ED1a in Pigs Has a Limited Impact on the Gut Carriage of Extended-Spectrum-β-Lactamase-Producing E. coli
Authors: Mourand G. , Paboeuf F. , Fleury M. A. , Jouy E. , Bougeard S. , Denamur E. , Kempf I.
Published: October 2016

Four trials were conducted to evaluate the impact of
Escherichia coli
probiotic strain ED1a administration to pigs on the gut carriage or survival in manure of extended-spectrum-β-lactamase-producing
E. coli
. Groups of pigs were orally inoculated with strain
E. coli
M63 carrying the
bla
CTX-M-1
gene (
n
= 84) or used as a control (
n
= 26). In the first two trials, 24 of 40
E. coli
M63-inoculated pigs were given
E. coli
ED1a orally for 6 days starting 8 days after oral inoculation. In the third trial, 10
E. coli
M63-inoculated pigs were given either
E. coli
ED1a or probiotic
E. coli
Nissle 1917 for 5 days. In the fourth trial,
E. coli
ED1a was given to a sow and its 12 piglets, and these 12 piglets plus 12 piglets that had not received
E. coli
ED1a were then inoculated with
E. coli
M63. Fecal shedding of cefotaxime-resistant
Enterobacteriaceae
(CTX-RE) was studied by culture, and
bla
CTX-M-1
genes were quantified by PCR. The persistence of CTX-RE in manure samples from inoculated pigs or manure samples inoculated
in vitro
with
E. coli
M63 with or without probiotics was studied. The results showed that
E. coli
M63 and ED1a were good gut colonizers. The reduction in the level of fecal excretion of CTX-RE in
E. coli
ED1a-treated pigs compared to that in nontreated pigs was usually less than 1 log
10
CFU and was mainly observed during the probiotic administration period. The results obtained with
E. coli
Nissle 1917 did not differ significantly from those obtained with
E. coli
ED1a. CTX-RE survival did not differ significantly in manure samples with or without probiotic treatment. In conclusion, under our experimental conditions,
E. coli
ED1a and
E. coli
Nissle 1917 could not durably prevent CTX-RE colonization of the pig gut.
Pharmacokinetic/Pharmacodynamic Modeling and Simulation of Cefiderocol, a Parenteral Siderophore Cephalosporin, for Dose Adjustment Based on Renal Function
Authors: Katsube Takayuki , Wajima Toshihiro , Ishibashi Toru , Arjona Ferreira Juan Camilo , Echols Roger
Published: October 2016

Cefiderocol, a novel parenteral siderophore cephalosporin, exhibits potent efficacy against most Gram-negative bacteria, including carbapenem-resistant strains. Since cefiderocol is excreted primarily via the kidneys, this study was conducted to develop a population pharmacokinetics (PK) model to determine dose adjustment based on renal function. Population PK models were developed based on data for cefiderocol concentrations in plasma, urine, and dialysate with a nonlinear mixed-effects model approach. Monte-Carlo simulations were conducted to calculate the probability of target attainment (PTA) of fraction of time during the dosing interval where the free drug concentration in plasma exceeds the MIC (

T
f

>MIC
) for an MIC range of 0.25 to 16 μg/ml. For the simulations, dose regimens were selected to compare cefiderocol exposure among groups with different levels of renal function. The developed models well described the PK of cefiderocol for each renal function group. A dose of 2 g every 8 h with 3-h infusions provided >90% PTA for 75%

T
f

>MIC
for an MIC of ≤4 μg/ml for patients with normal renal function, while a more frequent dose (every 6 h) could be used for patients with augmented renal function. A reduced dose and/or extended dosing interval was selected for patients with impaired renal function. A supplemental dose immediately after intermittent hemodialysis was proposed for patients requiring intermittent hemodialysis. The PK of cefiderocol could be adequately modeled, and the modeling-and-simulation approach suggested dose regimens based on renal function, ensuring drug exposure with adequate bactericidal effect.
Evaluating Polymyxin B-Based Combinations against Carbapenem-Resistant Escherichia coli in Time-Kill Studies and in a Hollow-Fiber Infection Model
Authors: Cai Yiying , Lim Tze-Peng , Teo Jocelyn Qi-Min , Sasikala Suranthran , Chan Eric Chun Yong , Hong Yan Jun , Lee Winnie , Tan Thean Yen , Tan Thuan Tong , Koh Tse Hsien , Hsu Li Yang , Kwa Andrea L.
Published: October 2016

Polymyxin B-based combinations have emerged as a mainstay treatment against carbapenem-resistant
Escherichia coli
(CREC). We investigated the activity of polymyxin B-based two-antibiotic combinations against CREC using time-kill studies (TKS) and validated the findings in a hollow-fiber infection model (HFIM). TKS were conducted using 5 clinical CREC strains at 5 log
10
CFU/ml against 10 polymyxin B-based two-antibiotic combinations at maximum clinically achievable concentrations. HFIMs simulating dosing regimens with polymyxin B (30,000U/kg/day) and tigecycline (100 mg every 12 h) alone and in combination were conducted against two CREC strains at 5 log
10
CFU/ml over 120 h. Emergence of resistance was quantified using antibiotic-containing media. Phenotypic characterization (growth rate and stability of resistant phenotypes) of the resistant isolates was performed. All five CREC strains harbored carbapenemases. Polymyxin B and tigecycline MICs ranged from 0.5 mg/liter to 2 mg/liter and from 0.25 mg/liter to 8 mg/liter, respectively. All antibiotics alone did not have bactericidal activity at 24 h in the TKS, except for polymyxin B against two strains. In combination TKS, only polymyxin B plus tigecycline demonstrated both bactericidal activity and synergy in two out of five strains. In the HFIM, polymyxin B alone was bactericidal against both CREC strains before regrowth was observed at 8 h. Phenotypically stable polymyxin B-resistant mutants were observed for both strains, with a reduced growth rate observed in one strain. Tigecycline alone resulted in a slow reduction in bacterial counts. Polymyxin B plus tigecycline resulted in rapid and sustained bactericidal killing up to 120 h. Polymyxin B plus tigecycline is a promising combination against CREC. The clinical relevance of our results warrants further investigations.
Complete Genome Sequence of the First H5N1 Avian Influenza Virus Isolated from Chickens in Lebanon in 2016
Authors: Ibrahim Elias , Sirawan Abeer , El-Bazzal Bassel , El Hage Jeanne , Abi Said Mounir , Zaraket Hassan , Kandeil Ahmed , Ali Mohamed A. , Kayali Ghazi
Published: October 2016

We generated the full genome of a highly pathogenic H5N1 avian influenza virus that caused an outbreak on a chicken farm in Lebnaon in April 2016. Analysis revealed that the virus belonged to clade 2.3.2.1c that recently caused outbreaks in West Africa and the United Arab Emirates.
Myeloperoxidase Attenuates Pathogen Clearance during Plasmodium yoelii Nonlethal Infection
Authors: Theeß Wiebke , Sellau Julie , Steeg Christiane , Klinke Anna , Baldus Stephan , Cramer Jakob P. , Jacobs Thomas
Published: October 2016

Myeloperoxidase (MPO), a leukocyte-derived enzyme mainly secreted by activated neutrophils, is known to be involved in the immune response during bacterial and fungal infection and inflammatory diseases. Nevertheless, the role of MPO in a parasitic disease like malaria is unknown. We hypothesized that MPO contributes to parasite clearance. To address this hypothesis, we used
Plasmodium yoelii
nonlethal infection in wild-type and MPO-deficient mice as a murine malaria model. We detected high MPO plasma levels in wild-type mice with
Plasmodium yoelii
infection. Unexpectedly, infected MPO-deficient mice did not show increased parasite loads but were able to clear the infection more rapidly than wild-type mice. Additionally, the presence of neutrophils at the onset of infection seemed not to be essential for the control of the parasitemia. The effect of decreased parasite levels in MPO-deficient mice was absent from animals lacking mature T and B cells, indicating that this effect is most likely dependent on adaptive immune response mechanisms. Indeed, we observed increased gamma interferon and tumor necrosis factor alpha production by T cells in infected MPO-deficient mice. Together, these results suggest that MPO modulates the adaptive immune response during malaria infection, leading to an attenuated parasite clearance.