bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the Dynamic-Response-Based Intact Stability Criterion for Floating Wind Turbines
Authors: Masciola Marco , Chen Xiaohong , Yu Qing 
Published: October 2015

As an alternative to the conventional intact stability criterion for floating offshore structures, known as the area-ratio-based criterion, the dynamic-response-based intact stability criteria was initially developed in the 1980s for column-stabilized drilling units and later extended to the design of floating production installations (FPIs). Both the area-ratio-based and dynamic-response-based intact stability criteria have recently been adopted for floating offshore wind turbines (FOWTs).
In the traditional area-ratio-based criterion, the stability calculation is quasi-static in nature, with the contribution from external forces other than steady wind loads and FOWT dynamic responses captured through a safety factor. Furthermore, the peak wind overturning moment of FOWTs may not coincide with the extreme storm wind speed normally prescribed in the area-ratio-based criterion, but rather at the much smaller rated wind speed in the power production mode. With these two factors considered, the dynamic-response-based intact stability criterion is desirable for FOWTs to account for their unique dynamic responses and the impact of various operating conditions.
This paper demonstrates the implementation of a FOWT intact stability assessment using the dynamic-response-based criterion. Performance-based criteria require observed behavior or quantifiable metrics as input for the method to be applied. This is demonstrated by defining the governing load cases for two conceptual FOWT semisubmersible designs at two sites. This work introduces benchmarks comparing the area-ratio-based and dynamic-response-based criteria, gaps with current methodologies, and frontier areas related to the wind overturning moment definition.
Some Issues in Ice Mechanics
Authors: Jordaan Ian 
Published: October 2015

Ice mechanical behavior is time-dependent, as has been known for many decades. But in many references, the attempt is made to use time-independent plasticity theory. The relevant analytical approach that accounts for time is viscoelastic theory. The need for this approach is made quite essential by study of microstructural changes that occur in ice under high stresses. In no case does there appear to be a clear yield condition, with flow occurring after a certain threshold value. Furthermore, the microstructural changes occurring under stress result in a highly significant enhancement of the creep rates. This results in a spatially varying viscoelastic response that is a function of prior stress history. The ice response is then a function of position resulting in a microstucturally modified layer in the region where compressive stress is applied. This can be deep or highly localized, depending on the loading rate. The most promising approach is that based on damage mechanics combined with viscoelasticity, using the thermodynamics of irreversible processes.
Ice is also prone to fracture, especially at high loading rates and under high stresses. This is basic to the notion of scale effect. Fracture processes are also time-dependent in viscoelastic materials, a phenomenon that needs to be explored further. Furthermore, failure often will take place in a random fashion, depending on the distribution of flaws in ice. This indicates strongly that a theory based on “weakest-link” hypotheses and probability theory is appropriate.
Finally, some aspects relevant to practical data analysis are discussed. These include measurement uncertainties of Molikpaq data, and geometric approximations of ice features, e.g. ridges as uniform beams.
Coupled Dynamic Analysis for Multi-Unit Floating Offshore Wind Turbine in Maximum Operational and Survival Conditions
Authors: Jang H. K. , Kim H. C. , Kim M. H. , Kim K. H. 
Published: October 2015

Numerical tools for a single floating offshore wind turbine (FOWT) have been developed by a number of researchers, while the investigation of multi-unit floating offshore wind turbines (MUFOWT) has rarely been performed. Recently, a numerical simulator was developed by TAMU to analyze the coupled dynamics of MUFOWT including multi-rotor-floater-mooring coupled effects.
In the present study, the behavior of MUFOWT in time domain is described through the comparison of two load cases in maximum operational and survival conditions. A semi-submersible floater with four 2MW wind turbines, moored by eight mooring lines is selected as an example. The combination of irregular random waves, steady currents and dynamic turbulent winds are applied as environmental loads. As a result, the global motion and kinetic responses of the system are assessed in time domain. Kane’s dynamic theory is employed to formulate the global coupled dynamic equation of the whole system. The coupling terms are carefully considered to address the interactions among multiple turbines. This newly developed tool will be helpful in the future to evaluate the performance of MUFOWT under diverse environmental scenarios.
In the present study, the aerodynamic interactions among multiple turbines including wake/array effect are not considered due to the complexity and uncertainty.
Investigation of Compaction and Sand Migration Effect on Permeability and Non-Darcy Coefficient With Pore-Scale Simulations
Authors: Anbar Sultan , Tyagi Mayank , Thompson Karsten 
Published: October 2015

Compaction and sand migration are some of the main problems for the loosely consolidated and unconsolidated high rate gas reservoirs. A reliable estimation of the well productivity depends on accurate modeling of permeability and inertial effects. Therefore, the key objective of this paper is to quantify the flow parameters change in the case of compaction and sand migration, and the development of permeability and the non-Darcy coefficient correlations that can be used in reservoir simulations. The compaction effects are simulated by increasing grains diameters with the same ratio. Permeability and the non-Darcy coefficients are calculated from lattice Boltzmann method (LBM). Results indicate that permeability decrease is not directional and the change in permeability can be estimated from porosity change with a Kozeny-Carman type relation with an exponent of 3.2. A Kozeny-Carman type relation between the non-Darcy coefficient and permeability is also found with an exponent −1.303. For high compressibility reservoirs, estimation of the inertial effects from the correlations developed as a function of permeability and porosity may also lead to underestimation of the inertial effects.
Sand migration causes pore-throat plugging that leads to significant reduction in permeability. Permeability impairment due to sand or fines migration is usually estimated from Kozeny-Carman type relation based on porosity. There is no study in the literature on how the inertial effects are changed with permeability impairment due to sand or fines migration. Sand particle plugging locations are found from the network simulations for different pore volume reduction, and corresponding permeability and the non-Darcy coefficient are calculated from LBM. It is found that permeability change with sand plugging is direction dependent: permeability reduction in the flow direction is twice compared to other directions. Porosity reduction does not depend on only pore-throat plugging, porosity can be decrease due to compaction and pore-surface deposition. Therefore, a correlation is developed to estimate permeability from pore-throat sand concentration. Even though permeability change is directional, the trend between permeability and the non-Darcy coefficient is similar and the magnitude of exponent in Kozeny-Carman type relation is larger, −1.803, compared to that of compaction.
Analysis and Design of an Oscillating Water Column Wave Energy Converter With Dielectric Elastomer Power Take-Off
Authors: Moretti Giacomo , Rosati Gastone Pietro Papini , Alves Marco , Grases Manuel , Vertechy Rocco , Fontana Marco 
Published: October 2015

In this paper, we present a concept of near/off-shore Oscillating Water Column (OWC) Wave Energy Converter (WEC) that is equipped with a Power Take Off (PTO) unit based on Dielectric Elastomer Generators (DEGs). DEGs are soft/deformable generators with variable capacitance able to directly convert the mechanical energy that is employed for their deformation into electrostatic energy.
The proposed WEC is based on an existing tubular collector chamber of an OWC system designed by the company Sendekia, that is combined with an Inflatable Circular Diaphragm (ICD) DEG. This simplified design presents a very reduced number of moving parts showing potentially high efficiency, reliability and noise-free operation.
A multi-physics dynamic model of the system is built using time domain linear hydrodynamics coupled with an analytical non-linear electro-hyperelastic model for the DEG-based PTO. The power matrix of the system is calculated for both regular and irregular waves. Some design issues are introduced showing that the electro-elastic response of the DEG provides the system with an additional stiffness that adds up to the hydrostatic stiffness and affects the resonance of the WEC. As a consequence, the geometric shape/dimensions of the OWC chamber and the layout of the DEG diaphragm should be chosen using an integrated procedure aimed at tuning the overall response of the WEC to the spectra a reference wave climate.
An Integrated Numerical Approach to Design Offshore Pipelines Susceptible to Lateral Buckling
Authors: Van den Abeele F. , Boël F. , Hayes D. , Scales D. 
Published: October 2015

Lateral buckling is a global response to excessive compressive axial force due to thermal and internal pressure loads which when combined, exceeds the initiating Euler Buckling force and overcomes the lateral friction force reacting against a pipeline laid on the seabed.
According to DNV-RP-F110, the integrity of a pipeline susceptible to buckling can be assured by either restraining the pipeline, thus sustaining large axial compressive forces, or releasing them through a combination of pipeline displacements; lateral buckles. Buckling may be rogue in nature or engineered at predetermined locations, either of which must demonstrate compliance to DNV OS F101. Engineered lateral buckles are a cost effective way to manage for example HP/HT pipelines as opposed to the construction of restraint designs. However, uncertainty in the initial buckle formation process and buckle behaviour may reduce design reliability; resulting in an increased level of redundancy in a buckle management system.
This paper presents the vision of an engineering tool aimed at providing an integrated single model environment which enables straightforward engineering analysis, with application to all phases of design, and providing support to operations. Verification of buckling forces and post-buckling configurations is undertaken through comparison with Hobbs and Kerr analytical models and validated against ABAQUS.
Economic Effects of Multiple Disasters in the Gulf of Mexico
Authors: Dahi-Taleghani Negar , Tyagi Mayank 
Published: October 2015

With the recent exploration/discovery of deep-water reservoirs andcontinued developments of drilling and production, it remains very important to have a comprehensive and quantitative risk assessment ofthe drilling/production processes including effective response to deal with such disasters. What measures must be taken to recover from the disaster scenario of a hurricane impacting the same region in the aftermath of an oil spill? The Deepwater Horizon oil spill, the largest marine oil spill in history, was caused by an explosion on a semi-submersible drilling rig about 50 miles southeast of the Mississippi River delta on April 20, 2010. Catastrophic events such as oil spills have enormous impact for the local economy of the area and even for the local labor markets. Another regional disaster, Hurricane Katrina impacted Louisiana, Mississippi, and Alabama, as it ripped over the core of the Gulf of Mexico (GoM) producing zone, one of the important oil and gas production areas of the worldin 2005. Also, if acatastrophic disaster occurs and the emergency response supply chain is not adequately prepared, then the economic consequences of sucheventcan be huge. Whenever a disaster happens, another reaction to this event that should be considered is resiliency. It is the ability to reduce or remove potential losses due to disaster events.
The impact of different shocks on various aspects of a state’s economic performance is estimated using a Vector Autoregressive model (VAR). In this study, the dynamic response of a variety of industrial sectors in Louisiana to each of these disasters is considered. The responses of different impulses in this model are shown to demonstrate the interdependence of various time series data.
A Control Strategy for PTO Systems in a U-OWC Device
Authors: Strati Federica Maria , Malara Giovanni , Laface Valentina , Romolo Alessandra , Arena Felice 
Published: October 2015

This paper deals with the implementation of a control algorithm for a turbine equipped into a U-Oscillating water column (U-OWC) plant. The open literature has largely ignored the problem of coupling the U-OWC behaviour to the turbine behaviour with the objective of maximizing the energy harvesting. Therefore, this paper has the objective of assessing the reliability of a Maximum Power Point Tracking (MPPT) algorithm.
The paper uses a numerical algorithm for estimating the energy produced by a U-OWC in real seas. In this regard, the computations rely on long time domain analyses that allow testing a variety of environmental conditions.
The MPPT is proved adequate for controlling the turbine behavior in conjunction with U-OWCs. In this context, it is shown that a reference parameter, used for determining the reference rotational speed, can be the significant wave height.
Post Well Vibration Analysis in the North Sea: A Tool to Understand Drilling Performance
Authors: Al Dushaishi M. F. , Nygaard R. , Hoel E. , Hellvik S. , Andersen M. 
Published: October 2015

Severe drill stem vibrations could leads to excessive damage to the bottom hole assembly causing an increase in nonproductive time. Different drill stem vibrations models are used to predict and avoid resonance regions by optimizing the selection of bottom hole assembly components and operating parameters such as weight on bit, and surface RPM. In addition to avoid the resonance regions, specialized tools have been developed to reduce vibrations. However a complete understanding on how to mitigate vibration and its effect on drilling performance is still lacking. This study investigates the cause of drill stem vibrations, its effect on drilling performance, and the effect of including vibration reductions tools in the bottom hole assembly design in several recent drilled wells in the North Sea.
Vibration damping tools used in this study were able to reduce both lateral and torsional drill stem vibration compared to a well with no vibration damping tool. Torsional drill stem vibrations tend to increase through rich sand zones causing an increase in lateral vibrations. The impact drill stem vibrations have on drilling performance was identified through rate of penetration. As lateral vibration intensity increases, instantaneous rate of penetration decreases.
New Benchmark Data for Manoeuvring in Shallow Water Based on Free Running Manoeuvring Tests Including Uncertainty of the Results
Authors: Tonelli Roberto , Quadvlieg Frans 
Published: October 2015

This paper gives the results of free running model tests for the KVLCC2 in shallow water. The paper describes how free running model tests in shallow water are carried out, and gives the results of free running model tests at two shallow water depths, corresponding to a water depth to draught ratio h/T of 1.2 and 1.5. Free running (partly) turning circle tests and zigzag tests are carried out in shallow water in a dedicated shallow water basin where the water depth is lowered to sail above a concrete floor, while measuring the level of flatness of the concrete floor.
The ITTC issued a brand new approach to perform uncertainty analysis for free running manoeuvring tests. For a proper comparison of simulations to model tests, it is of prime importance to not just know the results of a free running manoeuvre, but also to know the uncertainty of the results. This paper addresses also the uncertainty of the results. The combination of the results of the model tests and the uncertainty analysis allows the use of this data as benchmark data.
Long-Term Wave Measurement by an Onboard Radar Wave Meter and Prediction of Ship Motions Based on the Onboard Wave Measurements
Authors: Yoshida Hisafumi , Orihara Hideo , Yamasaki Keiichi 
Published: October 2015

Continuous measurement of waves, ship motions (roll and pitch), and so on has been carried out for about five years by onboard monitoring system installed ocean-going vessel. Measured wave data, including wave height, wave period and wave direction, are thoroughly evaluated with corresponding onboard weather observation data by comparing directly in terms of time series and statistical values.
Then, short term prediction of ship motions (roll and pitch) based on the measured wave data are compared with onboard motion data measured by vertical gyro.
From the results described, good accuracy and effectiveness of wave measurements by an onboard radar wave meter for safe navigation are demonstrated.
Molecular Epidemiology of Streptococcus uberis Clinical Mastitis in Dairy Herds: Strain Heterogeneity and Transmission
Authors: Davies P. L. , Leigh J. A. , Bradley A. J. , Archer S. C. , Emes R. D. , Green M. J. 
Published: October 2015

ABSTRACT

Multilocus sequence typing was successfully completed on 494 isolates of
Streptococcus uberis
from clinical mastitis cases in a study of 52 commercial dairy herds over a 12-month period. In total, 195 sequence types (STs) were identified.
S. uberis
mastitis cases that occurred in different cows within the same herd and were attributed to a common ST were classified as potential transmission events (PTEs). Clinical cases attributed to 35 of the 195 STs identified in this study were classified PTE. PTEs were identified in 63% of the herds. PTE-associated cases, which include the first recorded occurrence of that ST in that herd (index case) and all persistent infections with that PTE ST, represented 40% of all the clinical mastitis cases and occurred in 63% of the herds. PTE-associated cases accounted for >50% of all
S. uberis
clinical mastitis cases in 33% of the herds. Nine STs (ST-5, -6, -20, -22, -24, -35, -233, -361, and -512), eight of which were grouped within a clonal complex (sharing at least four alleles), were statistically overrepresented (OVR STs). The findings indicate that 38% of all clinical mastitis cases and 63% of the PTEs attributed to
S. uberis
in dairy herds may be caused by the nine most prevalent strains. The findings suggest that a small subset of STs is disproportionally important in the epidemiology of
S. uberis
mastitis in the United Kingdom, with cow-to-cow transmission of
S. uberis
potentially occurring in the majority of herds in the United Kingdom, and may be the most important route of infection in many herds.
Accuracy of Conventional PCR Targeting the 16S rRNA Gene with the Ot-16sRF1 and Ot-16sRR1 Primers for Diagnosis of Scrub Typhus: a Case-Control Study
Authors: Kim Choon-Mee , Cho Min Keun , Kim Dong-Min , Yun Na-Ra , Kim Seok Won , Jang Sook Jin , Ahn Young-Joon , Lim Donghoon 
Published: October 2015

ABSTRACT

We retrospectively evaluated the accuracy of conventional PCR targeting the 16S rRNA gene (16S C-PCR) using the Ot-16sRF1/Ot-16sRR1 primers for diagnosing scrub typhus. The diagnosis of
Orientia tsutsugamushi
infection by 16S C-PCR presented an increased sensitivity of 87.0% and specificity of 100% compared with those obtained with other targets and is thus a simple and clinically useful method with good diagnostic accuracy.
Molecular Identification of Zoonotic Tissue-Invasive Tapeworm Larvae Other than Taenia solium in Suspected Human Cysticercosis Cases
Authors: Tappe Dennis , Berkholz Jörg , Mahlke Uwe , Lobeck Hartmut , Nagel Thomas , Haeupler Alexandra , Muntau Birgit , Racz Paul , Poppert Sven 
Published: October 2015

ABSTRACT

Rarely, zoonotic
Taenia
species other than
Taenia solium
cause human cysticercosis. The larval stages are morphologically often indistinguishable. We therefore investigated 12 samples of suspected human cysticercosis cases at the molecular level and surprisingly identified one
Taenia crassiceps
and one
Taenia serialis
(coenurosis) infection, which were caused by tapeworm larvae normally infecting rodents and sheep via eggs released from foxes and dogs.
First Detection of TR34 L98H and TR46 Y121F T289A Cyp51 Mutations in Aspergillus fumigatus Isolates in the United States
Authors: Wiederhold Nathan P. , Gil Veronica Garcia , Gutierrez Felipe , Lindner Jonathan R. , Albataineh Mohammad T. , McCarthy Dora I. , Sanders Carmita , Fan Hongxin , Fothergill Annette W. , Sutton Deanna A. 
Published: October 2015

ABSTRACT

Azole resistance in
Aspergillus fumigatus
is an increasing problem. The TR34 L98H and TR46 Y121F T289A mutations that can occur in patients without previous azole exposure have been reported in Europe, Asia, the Middle East, Africa, and Australia. Here, we report the detection of both the TR34 L98H and TR46 Y121F T289A mutations in confirmed
A. fumigatus
isolates collected in institutions in the United States. These mutations, other mutations known to cause azole resistance, and azole MICs are reported here.