bluuebunny/crossref_metadata_2025 huggingface dataset:
The Constitutional Legacy of George W. Bush
Authors: Pfiffner James P.
Published: October 2015

This article examines the assertions of constitutional power by President George W. Bush and argues that he established significant precedents that have enlarged the range of future presidential discretion. Bush broke new constitutional ground in authorizing coercive interrogations, denying suspected terrorists the privilege of habeas corpus, warrantless surveillance of Americans, and the excessive use of signing statements. Senator Barack Obama often criticized Bush on constitutional and policy grounds. When he became president, he curbed some of President Bush's excesses, but he adopted similar policies and extended executive power in other areas. That a president so different from President Bush on partisan affiliation, policy priorities, and temperament would accept and continue important aspects of his constitutional legacy attests to the foresight of the framers of the Constitution that executives continue to seek power.
Qualitative Analyses of Protein Phosphorylation in Bovine Pluripotent Stem Cells Generated from Embryonic Fibroblasts
Authors: Nong W , Xie TS , Li LY , Lu AG , Mo J , Gou YF , Lan G , Jiang H , Len J , Li MM , Jiang QY , Huang B
Published: October 2015

Contents

Pluripotent stem cells (PSCs) generated from somatic cells via ectopic expression of specific transcription factors provide an unlimited cell resource for regenerative medicine and transgenic breeding. Here, we describe the successful generation of bovine induced PSCs (biPSCs) from foetal fibroblasts by lentivirus‐mediated delivery of bovine pluripotency reprogramming factors (PRFs) OCT3/4, SOX2, KLF4, c‐MYC, NANOG and LIN28. The generated biPSCs resembled embryonic stem cells (ESCs) in their gene expression profiles, self‐renewal capabilities and proliferation, as well as maintenance of a normal karyotype and differentiation into diverse cell types of all three germ layers both in vitro and in vivo. Qualitative phosphoproteomics of biPSCs revealed a large number of phosphorylated proteins, which might be related to the control of biPSCs status. The successful generation of biPSCs and the analysis of their phosphoproteome would further our understanding of the epigenetic mechanisms underlying iPSC pluripotency, thus promoting their application in bovine transgenic breeding and marking avenues for future research.
Coenzyme Q10 and α‐Tocopherol Prevent the Lipid Peroxidation of Cooled Equine Semen
Authors: Nogueira BG , Sampaio BFB , Souza MIL , Costa e Silva EV , Zúccari CESN
Published: October 2015

Contents

Biotechnology applied for equine semen increases the levels of reactive oxygen species and reduces the natural antioxidant defence, by both dilution and removal of seminal plasma. Therefore, the aims of this study were to evaluate the effect of adding coenzyme Q10 (CoQ10) and α‐tocopherol (α‐TOH) to the cooling extender, singly or in combination, on sperm parameters, and their effectiveness in preventing lipid peroxidation (LPO) of equine semen during cooling at 5°C for 72 h. Ten adult stallions of proven fertility were used, using two ejaculates each, subjecting them to the treatments with the following concentrations: α‐TOH: 2 mm; CoQ10: 40 μg/ml; and CoQ10 + α‐TOH: 40 μg/ml + 2 mm for control (C) without the addition of antioxidants and for vehicle control (EtOH) with 100 μl ethanol. The CoQ10 group had a higher percentage of total motility (69.1 ± 16.2%) compared to control (62.1 ± 16.2%) and EtOH (58.1 ± 18.6%). CoQ10 + α‐TOH and α‐TOH groups were most effective in preventing LPO compared to controls (1765.9 ± 695.9, 1890.8 ± 749.5, 2506.2 ± 769.4 ng malondialdehyde/108 sptz, respectively). In conclusion, CoQ10 and α‐TOH were effective during the cooling process of equine semen at 5°C for 72 h, providing increased levels of total motility, as well as lower LPO.
Teachers’ Effortful Control and Student Functioning: Mediating and Moderating Processes
Authors: Swanson Jodi , Valiente Carlos , Bradley Robert H. , Lemery‐Chalfant Kathryn , Abry Tashia
Published: October 2015

Evidence is emerging that teachers’ dispositional characteristics are related to students’ classroom functioning, but processes are not well understood. We examined associations between second‐grade teachers’ effortful control (EC), student‐teacher closeness or conflict, students’ EC, and changes in students’ externalizing behaviors and reading and math achievement. Teachers’ EC was directly related to their students’ externalizing behaviors, but not achievement. Conflict, but not closeness, mediated associations between teachers’ EC and students’ externalizing behaviors. In moderated mediation tests, conflict was positively associated with externalizing behaviors most strongly for students low or moderate in EC. Closeness was positively associated with reading achievement, and negatively associated with math achievement, only for low‐EC students.
Attention and Executive Functions as Mediators of Attachment and Behavior Problems
Authors: Low Justin A. , Webster Linda
Published: October 2015

The purpose of this study was to provide a more comprehensive understanding of the relation between early parent‐child interactions and subsequent behavior problems and how certain cognitive processes mediate this relation. Specifically, this study investigated whether attention, inhibition, and planning skills mediate the relation between attachment security and behavior problems. Data were collected as part of the National Institute of Child Health and Development‐Study of Early Child Care and Youth Development when children (N = 1004) were between 36 months and the third grade. Results from structural equation models indicated that sustained attention mediated the relation between disorganized attachment and social problems. Planning mediated the relation between disorganized attachment and subsequent thought problems, attention problems, and delinquent behavior. Avoidant, ambivalent, and disorganized attachment directly predicted several behavior problems. Implications for theory and future research are discussed.
Rill morphology and deposition characteristics on row sideslopes under seepage conditions
Authors: Liu L. , Liu Q. J. , An J. , Yu J. S.
Published: October 2015

Concentrated flow can induce rill and ephemeral gully erosion in contour ridging systems. To better understand the morphological features of rills, deposition characteristics in contour ridging systems and their influencing factors, rainfall simulation experiments were conducted considering four factors: field slope, row grade, ridge height and seepage discharge. The results showed that a simplified power equation that considered the maximum rill depth and length predicts the erosion volume better than an equation that only accounts for rill length, with prediction accuracies of R2 = 0.96 and R2 = 0.61, respectively. The ridge height could promote seepage and extend the maximum rill width and depth. The relationships between seepage and rill width, and seepage and soil loss could be fitted with quadratic equations. Seepage exerted a positive effect when the rill width and total soil loss were <14.3 cm and 0.7 kg, respectively, and presented a negative effect when the rill width and total soil loss were greater. Seepage had a positive effect on the maximum rill depth. Sediment deposition was divided into two types: (i) deposition downstream of the rill and (ii) no deposition on the row sideslope. Greater row grades could result in deposition up to the ridge. The simple rill volume prediction equation could help predicting the soil loss induced by rill erosion in contour ridging systems. The effect of field slope, row grade, ridge height and seepage discharge on soil loss could provide guidance for choosing appropriate ridge morphology on slopeland to reduce rill erosion.
Polymorphisms of RAD50, IL33 and IL1RL1 are associated with atopic asthma in Chinese population
Authors: Chen J. , Zhang J. , Hu H. , Jin Y. , Xue M.
Published: October 2015

Genetic architecture of asthma remains obscure. This study aimed to investigate whether the genetic polymorphisms of CDHR3 (rs6967330), GSDMB (rs2305480), IL33 rs928413, RAD50 (rs6871536) and IL1RL1 (rs1558641) are associated with the development of atopic asthma in Chinese population. Genotype and allele frequencies were compared between 516 patients and 552 controls by Chi‐square test. Patients were found to have significantly higher allele G of rs928413 and allele C of rs6871536 (9.5% vs 6.2%, P = 0.004 for rs928413; 26.1% vs 19.9%, P < 0.001 for rs6871536). Besides, patients were found to have significantly lower frequency of allele A of rs1558641 (17.2% vs 21.7%, P = 0.007). This is the first study validating that IL33, IL1R1, and RAD50 genes are associated with the risk of asthma in Chinese population.
The RNA helicase, eIF4A‐1, is required for ovule development and cell size homeostasis in Arabidopsis
Authors: Bush Maxwell S. , Crowe Natalie , Zheng Tao , Doonan John H.
Published: October 2015

eIF4A is a highly conserved RNA‐stimulated ATPase and helicase involved in the initiation of mRNA translation. The Arabidopsis genome encodes two isoforms, one of which (eIF4A‐1) is required for the coordination between cell cycle progression and cell size. A T‐DNA mutant eif4a1 line, with reduced eIF4A protein levels, displays slow growth, reduced lateral root formation, delayed flowering and abnormal ovule development. Loss of eIF4A‐1 reduces the proportion of mitotic cells in the root meristem and perturbs the relationship between cell size and cell cycle progression. Several cell cycle reporter proteins, particularly those expressed at G2/M, have reduced expression in eif4a1 mutant meristems. Single eif4a1 mutants are semisterile and show aberrant ovule growth, whereas double eif4a1 eif4a2 homozygous mutants could not be recovered, indicating that eIF4A function is essential for plant growth and development.
A pig‐to‐mouse coronary artery transplantation model for investigating the pathogenicity of anti‐pig antibody
Authors: Lin Yi , Miyagi Naoto , Byrne Guerard W. , Du Zeji , Kogelberg Heide , Gazi Mozammel H. , Tazelaar Henry D. , Wang Chunsheng , McGregor Christopher G. A.
Published: October 2015

Background

Rejection of Gal‐free (GTKO) donor pig cardiac xenografts is strongly associated with vascular non‐Gal antibody binding, endothelial cell (EC) injury, and activation and microvascular thrombosis. We adopted a pig‐to‐SCID/beige small animal transplant model to compare the pathogenicity of baboon and human anti‐pig antibody.

Methods

Wild‐type (GT+) or GTKO porcine coronary arteries (PCAs) were transplanted into the infrarenal aorta of SCID/beige mice. Three days after transplant, recipients were infused with anti‐pig antibody (anti‐SLA class I, an isotype control, naive or sensitized baboon serum, or naive human serum). PCAs were recovered 24 h after antibody infusion and examined using histology, immunohistochemistry, and in situ hybridization.

Results

Dose‐dependent intragraft thrombosis occurred after infusion of anti‐SLA I antibody (but not isotype control) in GT+ and GTKO PCA recipients. Naive baboon serum induced thrombosis in GT+ grafts. Thrombosis was significantly reduced by pre‐treating naive baboon serum with Gal polymer and not observed when this serum was infused to GTKO PCA recipients. Naive human serum caused dose‐dependent intragraft thrombosis of GTKO PCAs. In all cases, thrombosis involved graft‐specific vascular antibody and complement deposition, macrophage adherence, EC delamination, and subendothelial thrombus formation.

Conclusions

This study provides the first direct in vivo comparison of the pathogenicity of naive human and baboon serum. The results suggest that human preformed non‐Gal antibody may have increased pathogenicity compared to baboon. This model, which showed a rejected graft histopathology similar to antibody‐mediated rejection in cardiac xenotransplantation, may be useful to assess the pathogenicity of individual protein or carbohydrate specific non‐Gal reactive antibodies.
Engraftment and reversal of diabetes after intramuscular transplantation of neonatal porcine islet‐like clusters
Authors: Wolf‐van Buerck Lelia , Schuster Marion , Baehr Andrea , Mayr Tanja , Guethoff Sonja , Abicht Jan , Reichart Bruno , Nam‐Apostolopoulos Yun‐Chung , Klymiuk Nikolai , Wolf Eckhard , Seissler Jochen
Published: October 2015

Background

Intraportal infusion is currently the method of choice for clinical islet cell transplantation but suffers from poor efficacy. As the liver may not represent an optimal transplantation site for Langerhans islets, we examined the potential of neonatal porcine islet‐like clusters (NPICCs) to engraft in skeletal muscle as an alternative transplantation site.

Methods

Neonatal porcine islet‐like clusters were isolated from 2‐ to 5‐day‐old piglets and either transplanted under the kidney capsule (s.k.) or injected into the lower hindlimb muscle (i.m.) of streptozotocin‐diabetic NOD‐SCID IL2rγ−/− (NSG) mice. Survival, vascularization, maturation, and functional activity were analyzed by intraperitoneal glucose tolerance testing and immunohistochemical analyses.

Results

Intramuscular transplantation of NPICCs resulted in development of normoglycemia and restored glucose homeostasis. Time to reversal of diabetes and glucose tolerance (AUC glucose and AUC insulin) did not significantly differ as compared to s.k. transplantation. Intramuscular grafts exhibited rapid neovascularization and graft composition with cytokeratin‐positive ductal cells and beta cells at post‐transplant weeks 2 and 8 and after establishment of normoglycemia was comparable in both groups.

Conclusions

Intramuscular injection represents a minimally invasive but efficient alternative for transplantation of NPICCs and, thus, offers an attractive alternative site for xenotransplantation approaches. These findings may have important implications for improving the outcome and the monitoring of pig islet xenotransplantation.
The pro--Iwahori Hecke algebra of a reductive -adic group I
Authors: Vigneras Marie-France
Published: October 2015

Let$R$be a commutative ring, let$F$be a locally compact non-archimedean field of finite residual field$k$of characteristic$p$, and let$\mathbf{G}$be a connected reductive$F$-group. We show that the pro-$p$-Iwahori Hecke$R$-algebra of$G=\mathbf{G}(F)$admits a presentation similar to the Iwahori–Matsumoto presentation of the Iwahori Hecke algebra of a Chevalley group, and alcove walk bases satisfying Bernstein relations. This was previously known only for a$F$-split group$\mathbf{G}$.
The fetal brain sparing response to hypoxia: physiological mechanisms
Authors: Giussani Dino A.
Published: October 2015

How the fetus withstands an environment of reduced oxygenation during life in the womb has been a vibrant area of research since this field was introduced by Joseph Barcroft, a century ago. Studies spanning five decades have since used the chronically instrumented fetal sheep preparation to investigate the fetal compensatory responses to hypoxia. This defence is contingent on the fetal cardiovascular system, which in late gestation adopts strategies to decrease oxygen consumption and redistribute the cardiac output away from peripheral vascular beds and towards essential circulations, such as those perfusing the brain. The introduction of simultaneous measurement of blood flow in the fetal carotid and femoral circulations by ultrasonic transducers has permitted investigation of the dynamics of the fetal brain sparing response for the first time. Now we know that major components of fetal brain sparing during acute hypoxia are triggered exclusively by a carotid chemoreflex and that they are modified by endocrine agents and the recently discovered vascular oxidant tone. The latter is determined by the interaction between nitric oxide and reactive oxygen species. The fetal brain sparing response matures as the fetus approaches term, in association with the prepartum increase in fetal plasma cortisol, and treatment of the preterm fetus with clinically relevant doses of synthetic steroids mimics this maturation. Despite intense interest into how the fetal brain sparing response may be affected by adverse intrauterine conditions, this area of research has been comparatively scant, but it is likely to take centre stage in the near future.

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Surface Treatments of Stainless Steel by Electroless Silver Coatings as a Bipolar Plate for Proton Exchange Membrane Fuel Cells
Authors: Huang Ing-Bang , Hwang Ching Chiang
Published: October 2015

The objective of this study is to examine the effect of heat treatment at various temperatures on the corrosion behavior of electroless silver-coated SS 304 in a simulated proton exchange membrane (PEM) fuel cell environment. The corrosion properties of this material were studied using a potentiodynamic polarization technique. X-ray diffraction (XRD) patterns, polarization curves, and scanning electron microscopy (SEM) of coated and heat-treated specimens obtained in various heating temperatures were also utilized. It was found that the corrosion potential of the coated and heat-treated specimens shift toward a noble potential, and a significant decrease in corrosion current density was also observed. The corrosion current density decreased by a factor of about 1/500 for the heat-treated sample of 600 °C compared to the substrate. The heat-treated specimens displayed greater corrosion resistance than unheated and bare ones. According to the polarization studies and SEM images, the heat-treated specimen at 600 °C shows excellent corrosion resistance with a homogeneous dense surface morphology. These results demonstrated the coatings were suited for fuel cell applications in the proton exchange membrane fuel cell (PEMFC) environment.
Design and Experimental Validation of a Supersonic Concentric Micro Gas Turbine
Authors: Vézina Gabriel , Fortier-Topping Hugo , Bolduc-Teasdale François , Rancourt David , Picard Mathieu , Plante Jean-Sébastien , Brouillette Martin , Fréchette Luc
Published: October 2015

This paper presents the design and experimental results of a new micro gas turbine architecture exploiting counterflow within a single supersonic rotor. This new architecture, called the supersonic rim-rotor gas turbine (SRGT), uses a single rotating assembly incorporating a central hub, a supersonic turbine rotor, a supersonic compressor rotor, and a rim-rotor. This SRGT architecture can potentially increase engine power density while significantly reducing manufacturing costs. The paper presents the preliminary design of a 5 kW SRGT prototype having an external diameter of 72.5 mm and rotational speed of 125,000 rpm. The proposed aerodynamic design comprises a single stage supersonic axial compressor, with a normal shock in the stator, and a supersonic impulse turbine. A pressure ratio of 2.75 with a mass flow rate of 130 g/s is predicted using a 1D aerodynamic model in steady state. The proposed combustion chamber uses an annular reverse-flow configuration, using hydrogen as fuel. The analytical design of the combustion chamber is based on a 0D model with three zones (primary, secondary, and dilution), and computational fluid dynamics (CFD) simulations are used to validate the analytical model. The proposed structural design incorporates a unidirectional carbon-fiber-reinforced polymer rim-rotor, and titanium alloy is used for the other rotating components. An analytical structural model and numerical validation predict structural integrity of the engine at steady-state operation up to 1000 K for the turbine blades. Experimentation has resulted in the overall engine performance evaluation. Experimentation also demonstrated a stable hydrogen flame in the combustion chamber and structural integrity of the engine for at least 30 s of steady-state operation at 1000 K.
Clocking Effects of Inlet Nonuniformities in a Fully Cooled High-Pressure Vane: A Conjugate Heat Transfer Analysis
Authors: Griffini Duccio , Insinna Massimiliano , Salvadori Simone , Martelli Francesco
Published: October 2015

A high-pressure vane (HPV) equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side, while the leading edge (LE) is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-averaged Navier–Stokes simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and HPVs are then investigated, considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first in which hot spot and swirl core are aligned with passage; and the second in which they are aligned with the LE. Comparisons between metal temperature distributions obtained from conjugate heat transfer (CHT) simulations are performed, evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The LE aligned configuration is determined to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage-aligned case. A strong sensitivity to both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.
Desensitization of Axial Compressor Performance and Stability to Tip Clearance Size
Authors: Erler Engin , Vo Huu Duc , Yu Hong
Published: October 2015

This paper presents a computational and analytical study to identify and elucidate fundamental flow features associated with the desensitization of performance and aerodynamic stability of an axial compressor rotor to tip clearance change. Parametric studies of various design changes to a baseline double circular arc airfoil axial rotor led to the identification of two flow features associated with reducing sensitivity to tip clearance, namely, high incoming meridional momentum in the tip region and reduction/elimination of double tip leakage. Numerical experiments were subsequently performed on the baseline rotor geometry to validate these two flow features and explain the associated flow physics by variations in incoming meridional momentum and pitch size. Finally, two designs were proposed, namely, a full forward chordwise sweep (FFCS) rotor and a rotor with gradual stagger angle reduction in the outer span, to exploit these flow features. The results indicated that both designs produce the intended flow effects and exhibit lower sensitivity of performance and aerodynamic stability to tip clearance.
Unstable Forced Convection in a Plane Porous Channel With Variable-Viscosity Dissipation
Authors: Barletta A. , Celli M. , Kuznetsov A. V. , Nield D. A.
Published: October 2015

Fully developed and stationary forced convection in a plane-parallel porous channel is analyzed. The boundary walls are modeled as impermeable and subject to external heat transfer. Different Biot numbers are defined at the two boundary planes. It is shown that the combined effects of temperature-dependent viscosity and viscous heating may induce flow instability. The instability takes place at the lowest parametric singularity of the basic flow solution. The linear stability analysis is carried out analytically for the longitudinal modes and numerically for general oblique modes. It is shown that longitudinal modes with vanishingly small wave number are selected at the onset of instability.
Compressible Air Effects in CFD Simulations of Free Fall Lifeboat Drop
Authors: Tregde Vidar
Published: October 2015

A free fall lifeboat is typically dropped from heights between 30 and 40m, but during full scale testing, drop heights have been exceeding 60 m. During a drop, the free fall lifeboat is going through several phases; sliding on the skid, rotation on skid, free fall, water entry, ventilation, maximum submergence, resurfacing and the sailing phase. During impact and submergence the lifeboat will go through a ventilation phase. In this phase the lifeboat creates an air cavity behind the pilot house and a larger one behind the stern.

The air cavity formed on top of canopy, aft of the pilot house is compressed and then starts to oscillate in time giving rise to large oscillating pressures. Computational Fluid Dynamics (CFD) simulations with compressible air flow model are compared with full scale experimental results. The results compare very well, both in oscillating frequency and amplitude.

Later in the ventilation phase, an air bubble aft of the vessel will be drawn down several meters below the water surface. This bubble collapses in an imploding manner and slams with large pressures on the aft bulkhead of the lifeboat. This is simulated in CFD with compressible air model and compares very well to the full scale experimental results. Using incompressible air flow will not capture these effects, and the calculated pressures on the aft bulkhead are a fraction of the real pressures.

The water surface in the cavity eventually hits the aft bulkhead with a high slamming velocity. The structure of the air pocket does not have any symmetry, and seem to be chaotic in nature. The local pressures can be very high and distributed over a small area. The effects of the air cavity also influence the motion and acceleration of the lifeboat in the ventilation phase; this is shown and compared to full scale experimental results.
Strain Path Analysis of Setup Time Around Piles and Caissons
Authors: Aubeny Charles , Grajales Francisco
Published: October 2015

Installation of driven piles and suction caissons in clayey soils generates excess pore pressures that temporarily reduce load capacity due to side resistance. Time dependent dissipation of these excess pore pressures leads to recovery of side resistance, a process known as ‘setup’. Since many facilities cannot be put into operation until sufficient pile load capacity has been mobilized, realistic predictions of setup time can be important. This study consists on the analysis of setup time following open ended pile and caisson installation. Initial excess pore pressures due to installation disturbance are predicted based on a strain path analysis based on a ring source moving at constant velocity in an incompressible medium. It is assumed that the setup occurs primarily due to dissipation of excess pore pressures generated during the installation process; thixotropic effects are neglected. The analysis employs an elastic perfectly plastic model of soil behavior and an uncoupled analysis of consolidation to simulate conditions on the pile shaft outside of the influence of tip effects. A parametric study shows that wall thickness and soil rigidity index can exert order of magnitude differences on setup time. Strain path solutions show reasonable agreement to laboratory and field measurements of pore pressure dissipation around thin-walled piles typical of suction caissons. Strain path solutions tend to underestimate setup time for driven piles, likely due to partial plugging during pile driving.
Hybrid RANS-LES Formulations for Wake Interference Physics in Tandem Cylinders and Multi-Column Floaters
Authors: Gopalan Harish , Ma Peifeng , Xu Haihua , Choudhary Ankit , Hussain Anis , Jaiman Rajeev K.
Published: October 2015

Accurate prediction of hydrodynamic forces on tandem bluff bodies at high Reynolds numbers is of interest in many fields of offshore engineering. The most commonly used turbulence modeling strategy for studying these flows is unsteady Reynolds-averaged Navier-Stokes methods (URANS) due to its speed. However, the accuracy of URANS results are problem dependent and usually poor for bluff bodies flow separation predictions. To overcome this deficiency, two different modeling methods have been considered: (i) large eddy simulation (LES) and (ii) non-linear URANS. LES are accurate and computationally feasible for low to moderate Reynolds number flows. However, the cost of LES makes it infeasible at high Reynolds numbers. On the other hand, non-linear URANS methods are fast like URANS, and its accuracy is comparable to LES for certain flows. It is usually not known in advance if the simulations using non-linear methods are accurate. Hybrid models have been proposed in the literature as an alternative to existing methods. They employ a URANS model in the near-body region and LES in the near and far wake regions. Simulations performed using hybrid models are computationally cheaper than LES and more accurate than URANS. Most hybrid models developed in the literature employ linear URANS models. The use of non-linear URANS models in the hybrid context has not received significant attention. In this study, we propose the use of a hybrid model based on a non-linear URANS model. Flow past tandem cylinders, with different spacing ratio, at sub-critical Reynolds number regime, is chosen as the test case. Simulations are also performed using URANS and linear hybrid models for comparison. It is shown that the non-linear hybrid models provides the best agreement to measurement data in the literature. Non-linear URANS models will be shown to provide acceptable prediction of hydrodynamic forces. The models are finally used to predict the current load on a generic multi-column floater.
Validation of Sound Source Simulation due to Offshore Pile Driving
Authors: Reimann Katja , Grabe Juergen
Published: October 2015

The influence of wave propagation through the soil on hydro sound immission due to offshore pile driving bears a lot of uncertainties. In acoustic analyses of impact pile driving, the sound source description is essential for wave propagation models. The excited open-ended steel pile and the soil interact with each other. In numerical analyses the choice of the used material law for the soil should be well suited, because of the effect on the pile vibration. Prognoses often use the linear elastic approach for non-cohesive granular materials which does not represent the inelastic material behavior of the soil. On the basis of experimental data, a numerical model to simulate one blow of impact pile driving is validated. A parameter study of the wall friction angle between steel and sand is conducted to investigate the influence on the radiated hydro sound level under drained conditions.
Cost Based Analysis of the Offshore Port System
Authors: Kurt Ismail , Boulougouris Evangelos , Turan Osman
Published: October 2015

The container sector has been growing fast since its dawn, and it has almost reached a climax in terms of handling mega containerships at existing ports. In that respect the offshore port system presented here can offer operational advantages. Furthermore, it can bring improvements to the utilisation of ultra large containerships and the enhanced energy efficiency they introduce. In this framework, this paper presents a cost analysis of the possible offshore port systems including their investment cost. This research is based on data from relevant projects and studies coupled with a number of assumptions to be presented. The results suggest that the offshore container port system can play a remarkable role to reduce energy consumption in the container shipping.
Effects of Waves and Currents on Extreme Loads on a Jacket
Authors: Bruserud Kjersti , Haver Sverre
Published: October 2015

In lack of simultaneous data of metocean parameters such as wind, waves and currents, Norwegian design regulations presently recommend a conservative combination of metocean parameters for estimation of characteristic metocean loads on offshore structures. A simplified parametric load model for a jacket, based on waves and currents, is assumed. Several approaches to load estimation are investigated and the following are considered; different averaging length of extreme currents, the effect of peak-over-threshold approach for estimation of extreme wave and currents compared to all-sea states approach and extreme load estimation directly from a load time series. When compared to the recommended approach, all other approaches yield a reduced estimated characteristic metocean load. The results are intended be illustrative and not suitable for use in design.
Estimation of Fluctuating Propeller Torque of Full-Scale Ship Using Free-Running Model in Waves
Authors: Ueno Michio , Tsukada Yoshiaki
Published: October 2015

The authors propose a method to estimate full-scale propeller torque consisting of low-frequency and high-frequency components in waves using measured data of free-running model ship. The duct fan auxiliary thruster (DFAT) [1] and the rudder-effectiveness and speed correction (RSC) [2,3] ensure similar model ship motion to full-scale in external forces, where RSC controls the model ship propeller rate of revolution and the auxiliary thrust depending on measured model ship speed. Analyzing a fluctuating component of effective inflow velocity to propeller due to waves, the method estimates full-scale fluctuating propeller torque in waves. This method also makes it possible to adopt into free-running model ship tests any engine model simulating interaction between propeller torque and engine torque. Trial application of the method exemplifies the property of full-scale fluctuating propeller torque comparing with that of model ship.
Centrifuge and Numerical Modeling of Monopiles for Offshore Wind Towers Installed in Clay
Authors: Murali Madhuri , Grajales Francisco , Beemer Ryan D. , Biscontin Giovanna , Aubeny Charles
Published: October 2015

Offshore wind power has gained momentum as a means to diversify the world’s energy infrastructure; however, little is still known of the global stiffness behavior of the large diameter low aspect ratio monopiles which have become the foundation of choice for offshore wind towers. Traditionally, offshore foundations have been associated with gravity structures for the oil and gas industry, which in general need to resist large vertical loads with limited lateral and moment loading. However, wind towers are purposely designed to be subjected to large lateral and moment loads from the wind and waves in order to maximize power generation. Geotechnical centrifuge tests were conducted and numerical models are being developed to examine the behavior of low aspect ratio piles in clayey soils. Monopiles with aspect ratio of two are being tested in the the 150g-ton centrifuge at Rensselaer Polytechnic Institute. Initial results include momenttheta and force-displacement for various loading conditions. Numerical studies consist of finite element (FE) simulations in order to predict capacities and permanent deformations. The comparisons are to be performed in terms of the total resistance that is exerted by the soil on the caisson. FE studies allow to model capacity for different displacement fields and also to compute interactions between different loading modes. This paper outlines our progress to date including both numerical and experimental results.
Influence of Mooring Lines and Risers on the Trim, Heel and Displacement on FPUs
Authors: Coelho Cecília , Nabuco Bruna
Published: October 2015

By monitoring the variation of weights of floating production units (FPUs), the sum of total weight computed by load calculators on board very often does not match the actual displacement based on the current drafts. Differences can also be observed in the trim and heel of FPUs, which present values different from zero degree in the calculations, but in fact they are frequently kept near zero by ballast control.

The mooring lines and risers tensions are one of the most uncertain weight items in loading conditions reported by the crew on board, therefore, this paper aims to assess the influence and behavior of these systems to a variety of situations in which FPUs operate.

Analyses were performed for semi-submersibles and FPSOs considering two configurations of mooring system: catenary and taut-leg. The purpose is to evaluate how the magnitude of the resulting force varies — and hence how the trim and heel change — for a range of offsets caused by environmental conditions.

The effect of mooring lines and risers is also discussed regarding the water depth by means of case studies considering a range of water depths. Actual lines properties and seabed bathymetry from mooring system models of platforms located offshore Brazil have been taken as reference.

In short, the mooring lines and risers loads will be calculated for different types of floating production units, mooring system configurations and water depths in order to evaluate their influence on the trim, heel and displacement of FPUs.
Development of FIS for Identification of Potential Failure Locations in Topside Piping Sub-Systems: An Expert System Based Approach
Authors: Seneviratne A. M. N. D. B. , Ratnayake R. M. Chandima
Published: October 2015

The identification of potential failure locations in ageing topside piping equipment of offshore production and process facilities (P&PFs) requires rigorous analyses. The risk based inspection (RBI) analysis methods defined in industrial standards classify the equipment according to the risk levels. The RBI analysis carried out on the plant equipment of P&PFs identifies the systems and sub-systems according to the different risk levels. However, the sub-systems (i.e. corrosion loops) are mainly defined according to the degradation behavior of the equipment. The equipment hierarchy for P&PFs is designed based on the RBI analysis outcome.

The major part of risk level evaluation is based on equipment’s probability of failure, which is related to degradation. The risk level analysis of equipment and thickness measurement locations (TMLs) within a sub-system is based on the expert engineering judgments of field experts. This analysis varies depending on the expertise of the evaluator in identifying and classifying critical TMLs in a sub-system. This manuscript illustrates an expert system using fuzzy inference systems (FISs) to identify the potential failure of TMLs in a sub-system suppressing the variation of analysis results given by different field experts. The method is illustrated by considering two degradation mechanisms (corrosion and erosion) to identify the probability of potential failure and integrating the production and process data to the FIS based expert system to generate a dynamic output.
Turbulence Modeling for Free-Surface Flow Simulations in Offshore Applications
Authors: van der Heiden Henri J. L. , Veldman Arthur E. P. , Luppes Roel , van der Plas Peter , Helder Joop , Bunnik Tim
Published: October 2015

To study extreme hydrodynamic wave impact in offshore and coastal engineering, the VOF-based CFD simulation tool ComFLOW is being developed. Recently, much attention has been paid to turbulence modeling, local grid refinement, wave propagation and absorbing boundary conditions. Here we will focus on the design of the turbulence model, which should be suitable for the coare grids as used in industrial applications. Thereto a blend of a QR-model and a regularization model has been designed, in combination with a dedicated wall model. The QR-model belongs to a class of modern eddy-viscosity models, where the amount of turbulent eddy viscosity is kept minimal. The performance of the model will be demonstrated with several applications relevant to the offshore industry. For validation, experiments have been carried out at MARIN.
Investigation on the Use of a Multiphase Eulerian CFD Solver to Simulate Breaking Waves
Authors: Tomaselli Pietro D. , Christensen Erik Damgaard
Published: October 2015

The main challenge in CFD multiphase simulations of breaking waves is the wide range of interfacial length scales occurring in the flow: from the free surface measurable in meters down to the entrapped air bubbles with size of a fraction of a millimeter. This paper presents a preliminary investigation on a CFD model capable of handling this problem. The model is based on a solver, available in the open-source CFD toolkit OpenFOAM, which combines the Eulerian multi-fluid approach for dispersed flows with a numerical interface sharpening method. The solver, enhanced with additional formulations for mass and momentum transfer among phases, was satisfactorily tested against an experimental bubble column flow. The model was then used to simulate the propagation of a laboratory solitary breaking wave. The motion of the free surface was successfully reproduced up to the breaking point. Further implementations are needed to simulate the air entrainment phenomenon.
Evaluation of Fairing Performance by Three-Dimensional Tests Using a Flexible Riser Model
Authors: Skaugset Kjetil , Baarholm Rolf , Lie Halvor , Braaten Henning
Published: October 2015

Due to its low drag and suppression effectiveness, fairings are considered to be an attractive alternative to helical strakes for mitigation of riser Vortex Induced Vibrations (VIV). The Norwegian Deepwater Programme has conducted a project with the objective to develop and qualify effective low drag fairing concepts with respect to VIV and galloping. Furthermore, emphasis is put on easy handling and installation.

By use of 2D small scale tests in a towing tank and in a large cavitation tunnel, a total of 10 different fairing designs have been evaluated and screened in terms of hydrodynamic performance [1]. Three fairing design candidates were promoted for further development. This paper describe the work and findings when studying the effectiveness of promoted fairings on a 3D flexible riser model with respect to galloping and VIV. Three different fairing profiles have been studied in the present model tests.

The tests were carried out in the sub-critical Reynolds number regime with Rn up to about 53000. Four different fairing coverages were tested for each design: full coverage, 60 % coverage, 40 % coverage and full coverage of the lower half of riser.

Differences in performance have been noticed for the fairing profiles, and the findings have laid the ground for further development of the most promising candidates for real life applications. Further, it is concluded that the combination of 2D and 3D tests, as well as combination of small scale and prototype scale tests, has been an efficient strategy in development of VIV suppression devices.
Numerical Simulation of Oblique Wave in Water Basin
Authors: Chen Yu , Zhang Yali , Gao Mimi , Gullman-Strand Johan , Jaiman Rajeev Kumar , Dao MyHa , Chew Lup Wai
Published: October 2015

Simulation of more realistic ocean conditions in wave basins is becoming important for offshore industry. As spreading wave has become more desirable, the capability of reproducing oblique planar wave train is critical for a wave basin’s performance. In this study, the oblique waves have been simulated in a numerical wave basin based on the volume of fluid (VOF) method and Navier-Stokes solver. Multi-element bottom hinged flap motion using the conventional snake principle has been simulated by moving boundary dynamic mesh in OpenFOAM. Finite length of the entire wave maker and finite width of each paddle caused considerable spatial variations in wave height and wave propagating direction. Beaches with slope have been implemented to minimize the sidewall reflection and improve the uniformity of the oblique wave field. The generated linear oblique waves have been compared with the analytical solutions for validation in terms of uniformity and wave height. The time history of the surface elevation at different locations have been computed to investigate the uniformities of general wave fields. In addition, the free surface along the wave propagating direction has also been investigated to show the quality of the generated wave.
Numerical Investigation of the Installation Process and the Bearing Capacity of Suction Bucket Foundations
Authors: Stapelfeldt Marc , Bubel Julian , Grabe Jürgen
Published: October 2015

This paper was developed in cooperation between the TUHH and Overdick GmbH & Co. KG. The goal of the presented work is gaining further knowledge about the installation and bearing behavior of suction bucket foundations for fixed offshore platforms based on sand.

Buckets are usually made of steel and consist of a cylinder and a lid at the top. They are installed into the sea floor by pumping water out of the buckets to create suction, which drives the bucket into the soil. Suction buckets do not require heavy hammer-equipment for construction like common piles. Thus the installation procedure is much faster and protects the environment significantly by avoiding noise emissions. Therefore, suction buckets are to be considered as a serious foundation alternative compared to steel piles.

For this paper numerical investigations are performed with the finite analyses software ABAQUS. A total of five finite element models — three for the bearing and two for the installation — were created to carry out parametric studies, while using a hypoplastic constitutive model to describe the soil conditions. Therefore, the buckets diameter, embedded depth and the pore-ratio are to be investigated. In addition three different load conditions are applied in the bearing capacity tests: the maximum vertical load, the maximum horizontal load and the minimum vertical load. During the simulation of the installation procedure different pore ratios are tested and it is attempted to simulate an installation by water-extraction.

Based on these numerical investigations it is possible to investigate known and currently more or less unknown phenomena of the bearing and the installation of suction buckets. Thus, a more detailed knowledge about the function of this kind of foundation is to be gained. In addition, the numerical studies are compared to the design-procedure according to API RP-2A-WSD and the DNV CN-30.4.
Numerical Simulation of Current Generation in Deep Water Basin
Authors: Zhang Yali , Chen Yu , Gullman-Strand Johan , Dao Myha , Jaiman Rajeev K. , Zhang Wei
Published: October 2015

With the increased activities in the exploration and production in oil and gas in 1,000–3,000m water depth, the offshore industry enters a challenging phase. Reliable model testing in deep water basins requires the controlled modeling of current and wave in time and space to achieve a well-defined offshore environment. Current generation is considered to be one of the key challenges for the design and construction of a physical deep water test basin. Apart from the physical setup, a virtual numerical wave basin is an integral part of the whole facility. Among others, accurate representation of current generation is an indispensable component of the numerical package in order to achieve an accurate numerical simulation of wave and current. In OpenFOAM, the density is not considered in turbulence formulations for two phase flow (Jacobsen, 2012 and Harrif, 2013) where free surface is considered. Thus excessive diffusion of turbulence takes place over the interface, which results in poor results of velocity profiles and turbulence quantities for current generation. In this paper, standard k–ε, realizable k– and SST k–ω turbulence models have been correctly formulated by taking into account the effect of density according to the references (Jones and Launder, 1972; Shih et al., 1994; Hellsten, 1997) and implemented in OpenFOAM two phase flow solver. The velocity profile and turbulence quantities have been calculated and validated against the data by Klopman (1994) using the modified turbulence models. The validation reveals that correctly formulated k–ε, realizable k–ε and SST k ω turbulence models yield better agreement, as compared to the existing models in OpenFOAM, with experimental data in terms of current profile and turbulence quantities. The numerical model is then applied to simulate the generation of a three-layer current system. The turbulence intensity and shear velocity profile are presented.