bluuebunny/crossref_metadata_2025_split huggingface dataset:
Volute Flow Influence on Wet Gas Compressor Performance
Authors: Bakken Martin , Bjørge Tor 
Published: February 2018

The world’s energy demand is increasing, asking for new and cost-efficient ways to extract oil and gas. With traditional technologies, oil and gas production relies on a sufficiently high well head pressure for transportation to nearby process facilities. Utilization of subsea wet gas compression systems enables production at significantly lower pressures and is a favourable solution concerning production in remote regions.
Wet gas compressors are particularly useful when handling multiphase mixtures consisting of 95%–100% gas, on a volumetric basis. The remaining content is water and liquid condensate, which introduces flow mechanisms such as droplet deposition, liquid film formation and momentum transfer, which influence the fundamental flow behavior through the compressor. Previous tests have documented the occurrence of compressor hysteresis at low compressor flow rates. Recent findings have revealed the flow interaction between the diffuser and the volute is a governing factor concerning the documented hysteresis. This kind of behaviour induces challenges with regard to compressor performance prediction and securing stable operation.
An experimental test campaign has been performed at the Norwegian University of Science and Technology (NTNU). The test facility is an open loop configuration consisting of a shrouded centrifugal impeller, a vaneless diffuser and a circular volute. The test was performed by establishing the compressor characteristics while monitoring the diffuser/volute flow regime. Emphasis was put on the volute flow characteristics and the correlation with the compressor performance.
The investigation reveals that the volute flow characteristics and the interaction with the diffuser has a distinct impact on the compressor performance, particularly at lower gas mass fractions. Furthermore, the test reveals that the diffuser design is a key factor concerning the performance impact.
An Experimental Study of the Slip Factor in a Wet Gas Centrifugal Compressor With IGV
Authors: Vigdal Levi André B. , Bakken Lars E. 
Published: February 2018

The introduction of wet gas compression provides the opportunity for future cost-effective production of oil and gas. A wet gas compressor consists of a robust unit able to increase the pressure of untreated natural gas. This permits longer transport of hydrocarbons without topside facilities if installed at the well head. Obvious benefits include prolonging the life of existing wells and the possibility of exploiting smaller hydrocarbon sources otherwise considered non-commercial.
Successful development of robust wet gas compressors requires further understanding of the phenomena which occur when liquid is present in the gas stream. Understanding the way the presence of liquid affects the velocity triangle and slip factor is essential for the design of wet gas compressors and for comprehending their response to varying levels of liquid content in the inlet stream.
An experimental study has been performed with various levels of liquid fractions and inlet swirl angles. Impeller-exit velocity components and shift in slip factors are presented within the experimental test boundary.
A shift in velocity components and slip factor is experienced with increasing liquid content and inlet guide vane (IGV) setting angle. Consequently, existing slip factor correlations not utilizing inlet flow characteristics are not valid for wet gas flow or with impeller inlet swirl.
Computational Studies on High Pressure Turbine Rim Seal Cavities
Authors: Chengappa Manjunath B. , Srinivasan Karthik , Chouhan Rohit , Bather Simon , Blidmark Eric 
Published: February 2018

The efficiency of a turbine stage is impacted by a number of factors such as the component design philosophy, operating environment, leakage flow and its interaction with the main gas flow path. When looking at improving a turbine stage performance, there is a natural tendency amidst the designers to look into the factors listed above. Every engine manufacture has a unique style of component design philosophy and hence there are fewer opportunities to radically change the design. On the other hand, the operating environment or operating conditions are usually becoming more challenging. Hence, component designers typically look for opportunities to reduce the leakage or to reduce the losses due to interactive effect of the leakage with the gas path. The rim seal flow and its interaction with the gas path has been of interest for the past few decades and many studies have been carried out to understand the impact of cavity geometry, leakage flows and the ingestion of the hot gas into the rim seal cavities.
The rim seal cavities functionally act as a buffer cavity to dilute and dampen the effect of the hot gas ingested into the secondary air flow path and to prevent the discs from being exposed to ingested hot gas. The successful function of the rim seal cavity depends on multiple factors like rotor-stator axial clearance, cavity volume, cavity shape, cavity approach to the gas path and its interface, in addition to the leakage flow into the main flow path.
The present paper aims at providing a review of a typical rim seal cavity used in the High Pressure Turbine based on systematic CFD studies of the rim seal cavities. While the paper does not present validation data for the approach, the authors attempt to provide references to specific design aspects that are already available in the literature, which are usually less noticed.
Computational Analysis on Primary Breakup and Deformation of Kerosene Jet in Subsonic Cross Flow Using VOF Method
Authors: Govindaraj Muthuselvan , Halebidu Suryanarayanarao Muralidhara , Kotegar Prateekkumar , Gupta Sonali , Shankar Sanjay , Deekshith Manoja , Mourya Suhruth , Kumar Akshaya 
Published: February 2018

The main objective of this computational analysis is to investigate the effect of increase in Weber number at constant momentum flux ratio on the primary breakup process and deformation of kerosene jet in cross stream air flow. Unsteady computational analysis with VOF approach is carried out to simulate the two phase flow at three different cross flow Weber number conditions (150, 350 and 400) at constant momentum flux ratio of 17. Since the results of VOF technique is highly sensitive to the size and distribution of grid, grid optimization process is carried out, with both structured and unstructured forms of the grid. Since the structured grid with number of elements 17,96,181 displayed better matching with experimental results of upper trajectory of kerosene jet; this grid is used to investigate the effect of turbulence model and Weber number on the windward trajectory of kerosene jet in cross flow air stream. Initially to evaluate the results of computational analysis; simulations are carried out with larger computational domain (with number of elements 17,96,181). Windward trajectory of computational analysis is compared with experimental results of upper trajectory predicted using image processing technique and reasonable overall matching is observed.
To investigate the primary breakup process and deformation of liquid jet at three different increasing Weber number conditions, simulations are carried out with smaller computational domain with higher mesh density with number of elements 33,96,146. The computational technique used in the present analysis exactly captures the modes of breakup observed from experimental results at different Weber number operating conditions. To characterize the deformation of liquid jet at different Weber number conditions; near-field trajectory, cross stream dimension and wave length of liquid jet are quantified at different instants of time. With increase in Weber number, decrease in penetration of liquid jet along transverse direction and more bending of liquid jet along flow direction is observed. From the velocity profile along transverse direction of three different conditions, stronger shearing of liquid film is observed in higher Weber number conditions.
Natural Frequencies of Pre-Twisted Airfoil Blades
Authors: Chakshu Neeraj Kavan , Sinha Sunil K. 
Published: February 2018

In this paper, the natural frequencies of pre-twisted cantilever blades of various angles of twist having different airfoil cross sections in the NACA 6 series have been determined. The main objectives of this paper are to replicate the results previously published for the similar types of blades but with the assumption of a uniform rectangular cross-section and to compare it with the results obtained for blades with more refined airfoil cross-sections. Cantilevered type clamped-free boundary conditions have been used in this paper for all blades.
The comparison of the natural frequencies among different airfoils of the same NACA series has also been described in the paper in order to find out if any parameter of the airfoil such as camber, maximum thickness etc have any significant role in changing the frequencies of the beam. Commonly used commercial codes for finite element analysis have been used to determine these results.
A Study of Multiple Techniques to Simulate Blade Out Event
Authors: Ramanadham Koti Satish , Kasina Lakshman , Bommisetty Kondaiah , Raghavan Kotur Srinivasan 
Published: February 2018

Successful demonstration of safety of aircraft engines during extreme events such as Foreign Object Damage and Containment are mandatory for FAA (Federal Aviation Administration) certification. According to FAA every engine has to undergo fan blade out tests and engine has to contain this event without leading to major hazard to aircraft and loss of life. The fan blade out containment test involves the intentional release of a fan blade when the engine is running at full power. The released blade must not pierce or fracture the engine cases during the impact and which in turn can cause damage to the aircraft.
The current trend in the industry is to minimize tests through analytical simulations and demonstrate compliance to regulations and flight-safety requirements. Accurate simulations of such events save significant effort, time and cost. This paper presents the various simulation techniques to demonstrate fan case containment when subjected to fan blade out event. The modeling is carried out with simplifications and assumptions to minimize problem size and maximizing the accuracy in simulation. Various simulation techniques analyzed in this study are used to assess the modeling approach and parameters influence on the event simulation. The effect of rotor imbalance on blade failure and blade kinetic energy are also studied in this paper. LS-DYNA has the capability to perform implicit and explicit methods which is used to analyze the blade out event in this study.
CFD Analyses of Combustor-Diffuser System of Marine Gas Turbine Engine
Authors: Karuppannan Srinivasan , Sondur Vaibhav Murlidhar , Sivaramakrishna Gullapalli , Navindgi Raju D. , Muthuveerappan N. 
Published: February 2018

Reverse flow can annular combustor configuration becomes the inevitable option for industrial and marine gas turbine engine, due to its advantages over other configurations. The complexity associated with can annular configuration is optimum design of annular diffuser, as its flow field is dominated by downstream blockage created by transition duct geometry.
In the present study, flow behavior in the annular diffuser has been analyzed by simulating realistic downstream combustor liner and transition duct geometry. Flow analysis has been carried out using ANSYS Fluent and turbulence has been modeled using Realizable k-ε model. The diffuser is designed based on G* method, for optimum pressure recovery. Six diffuser configurations have been analyzed by varying the inner wall profile. The effect of parameters on flow field within diffuser and dump region has been studied. Also, the static pressure recovery and total pressure loss coefficient of diffuser is calculated and compared. The results show that the profile of the inner wall and the dump region needs to be tailored to get optimum performance from diffuser.
Pharmacokinetics and Safety of Intravenous Murepavadin Infusion in Healthy Adult Subjects Administered Single and Multiple Ascending Doses
Authors: Wach Achim , Dembowsky Klaus , Dale Glenn E. 
Published: February 2018

ABSTRACT

Murepavadin is the first in class of the outer membrane protein-targeting antibiotics (OMPTA) and a pathogen-specific peptidomimetic antibacterial with a novel, nonlytic mechanism of action targeting
Pseudomonas aeruginosa
. Murepavadin is being developed for the treatment of hospital-acquired bacterial pneumonia (HABP) and ventilator-associated bacterial pneumonia (VABP). The pharmacokinetics (PK) and safety of single and multiple doses of murepavadin were investigated in healthy male subjects. Part A of the study was a double-blind, randomized, placebo-controlled, single-ascending-dose investigation in 10 sequential cohorts where each cohort comprised 6 healthy male subjects; 4 subjects were randomized to murepavadin, and 2 subjects were randomized to placebo. Part B was a double-blind, randomized, placebo-controlled, multiple-ascending-dose investigation in 3 sequential cohorts. After a single dose of murepavadin, the geometric mean half-life (2.52 to 5.30 h), the total clearance (80.1 to 114 ml/h/kg), and the volume of distribution (415 to 724 ml/kg) were consistent across dose levels. The pharmacokinetics of the dosing regimens evaluated were dose proportional and linear. Murepavadin was well tolerated, adverse events were transient and generally mild, and no dose-limiting toxicity was identified.
Depression and anxiety symptoms in 17 teams of female football players including 10 German first league teams
Authors: Junge Astrid , Prinz Birgit 
Published: February 2018

BackgroundInformation on the prevalence of mental health problems of elite athletes is inconclusive, most probably due to methodological limitations, such as low response rates, heterogeneous samples.AimsTo evaluate the prevalence and risk factors of depression and anxiety symptoms in high-level female football players.MethodsFemale football players of 10 German first league (Bundesliga) and 7 lower league teams were asked to answer a questionnaire on players’ characteristics, the Center of Epidemiologic Studies Depression Scale (CES-D) and the Generalised Anxiety Disorder (GAD-7) scale.ResultsA total of 290 players (184 first and 106 lower league players) took part in the study. The CES-D score indicated mild to moderate symptoms of depression in 48 (16.6%) and severe symptoms in 41 (14.1%) players. The GAD-7 score indicated an at least moderate generalised anxiety disorder in 24 (8.3%) players. The prevalence of depression symptoms and generalised anxiety disorders was similar to the female general population of similar age. However, significantly more second league players reported symptoms of depression than first league players, and thus the prevalence of depression symptoms in second league players was higher than in the general population. Only a third of the 45 (15.7%) players who stated that they currently wanted or needed psychotherapeutic support received it.ConclusionThe prevalence of depression and generalised anxiety symptoms in elite football players is influenced by personal and sport-specific variables. It is important to raise awareness of athletes’ mental health problems in coaches and team physicians, to reduce stigma and to provide low-threshold treatment.
Azithromycin and metronidazole versus metronidazole-based therapy for the induction of remission in mild to moderate paediatric Crohn’s disease : a randomised controlled trial
Authors: Levine Arie , Kori Michal , Kierkus Jarek , Sigall Boneh Rotem , Sladek Malgorzata , Escher Johanna C , Wine Eytan , Yerushalmi Baruch , Amil Dias Jorge , Shaoul Ron , Veereman Wauters Gigi , Boaz Mona , Abitbol Guila , Bousvaros Athos , Turner Dan 
Published: February 2018

ObjectiveCrohn’s disease (CD) pathogenesis associated with dysbiosis and presence of pathobionts in the lumen, intracellular compartments and epithelial biofilms. Azithromycin is active in all three compartments. Our goal was to evaluate if azithromycin-based therapy can improve response and induce remission compared with metronidazole alone in paediatric CD.DesignThis blinded randomised controlled trial allocated children 5–18 years with 10<Pediatric Crohn’s Disease Activity Index (PCDAI)≤40 to azithromycin 7.5 mg/kg, 5 days/week for 4 weeks and 3 days/week for another 4 weeks with metronidazole 20 mg/kg/day (group 1) or metronidazole alone (group 2), daily for 8 weeks. Failures from group 2 were offered azithromycin as open label. The primary end point was response defined by a decrease in PCDAI>12.5 or remission using intention to treat analysis.Results73 patients (mean age 13.8±3.1 years) were enrolled, 35 to group 1 and 38 to group 2. Response and remission rates at week 8 were identical 23/35 (66%) in group 1 and 17/38 (45%) and 15/38 (39%) in group 2 (P=0.07 and P=0.025, respectively). The needed to treat for remission was 3.7. Faecal calprotectin declined significantly in group 1 (P=0.003) but not in group 2 (p=0.33), and was lower at week 8 (P=0.052). Additional therapy was required in 6/35(17%) from group 1 versus 16/38(42%) in group 2 (P=0.027) by week 8. Among 12 failures in group 2, open-label azithromycin led to remission in 10/12 (83%).ConclusionsThe combination of azithromycin and metronidazole failed to improve response but was superior for induction of remission and reduction in calprotectin.Trial registration numberNCT01596894.
Association of different antiplatelet therapies with mortality after primary percutaneous coronary intervention
Authors: Olier Ivan , Sirker Alex , Hildick-Smith David J R , Kinnaird Tim , Ludman Peter , de Belder Mark A , Baumbach Andreas , Byrne Jonathan , Rashid Muhammad , Curzen Nick , Mamas Mamas A 
Published: February 2018

ObjectivesPrasugrel and ticagrelor both reduce ischaemic endpoints in high-risk acute coronary syndromes, compared with clopidogrel. However, comparative outcomes of these two newer drugs in the context of primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI) remains unclear. We sought to examine this question using the British Cardiovascular Interventional Society national database in patients undergoing primary PCI for STEMI.MethodsData from January 2007 to December 2014 were used to compare use of P2Y12 antiplatelet drugs in primary PCI in >89 000 patients. Statistical modelling, involving propensity matching, multivariate logistic regression (MLR) and proportional hazards modelling, was used to study the association of different antiplatelet drug use with all-cause mortality.ResultsIn our main MLR analysis, prasugrel was associated with significantly lower mortality than clopidogrel at both 30 days (OR 0.87, 95% CI 0.78 to 0.97, P=0.014) and 1 year (OR 0.89, 95% CI 0.82 to 0.97, P=0.011) post PCI. Ticagrelor was not associated with any significant differences in mortality compared with clopidogrel at either 30 days (OR 1.07, 95% CI 0.95 to 1.21, P=0.237) or 1 year (OR 1.058, 95% CI 0.96 to 1.16, P=0.247). Finally, ticagrelor was associated with significantly higher mortality than prasugrel at both time points (30 days OR 1.22, 95% CI 1.03 to 1.44, P=0.020; 1 year OR 1.19 95% CI 1.04 to 1.35, P=0.01).ConclusionsIn a cohort of over 89 000 patients undergoing primary PCI for STEMI in the UK, prasugrel is associated with a lower 30-day and 1-year mortality than clopidogrel and ticagrelor. Given that an adequately powered comparative randomised trial is unlikely to be performed, these data may have implications for routine care.
How to use sequence analysis for life course epidemiology? An example on HIV-positive Sub-Saharan migrants in France
Authors: Gosselin Anne , Desgrées du Loû Annabel , Lelièvre Eva 
Published: February 2018

BackgroundLife course epidemiology is now an established field in social epidemiology; in sociodemography, the quantitative analysis of biographies recently experienced significant trend from event history analysis to sequence analysis. The purpose of this article is to introduce and adapt this methodology to a social epidemiology question, taking the example of the impact of HIV diagnosis on Sub-Saharan migrants’ residential trajectories in the Paris region.MethodsThe sample consists of 640 migrants born in Sub-Saharan Africa receiving HIV care. They were interviewed in healthcare facilities in the Paris region within the PARCOURS project, conducted from 2012 to 2013, using life event history calendars, which recorded year by year their health, family and residential histories. We introduce a two-step methodological approach consisting of (1) sequence analysis by optimal matching to build a typology of migrants’ residential pathways before and after diagnosis, and (2) a Cox model of the probability to experience changes in the residential situation.ResultsThe seven-clusters typology shows that for a majority, the HIV diagnosis did not entail changes in residential situation. However 30% of the migrants experienced a change in their residential situation at time of diagnosis. The Cox model analysis reveals that this residential change was in fact moving in with one’s partner (HR 2.99, P<0.000) rather than network rejection.ConclusionThis original combination of sequence analysis and Cox models is a powerful process that could be applied to other themes and constitutes a new approach in the life course epidemiology toolbox.Trial registration numberNCT02566148.
The effect of d and f states of ytterbium on the electronic and magnetic properties of Al1−xYbxN: DFT+U study
Authors: Belhachi S. 
Published: February 2018

Using density functional theory combined LSDA+U method, the structural, electronic and magnetic behaviors of ytterbium implanted in wurtzite AlN were investigated. Low formation energy shows that Yb atom favors to substitute for Al site and to confirm this stability, the adsorption energy has been calculated. It is found that Al[Formula: see text]Yb[Formula: see text]N possesses a semiconductor behavior. The magnetic moment 0.9891 [Formula: see text] per molecule principally comes from Yb ion with small contribution from the Al and N atoms. We predict that Yb ions order ferromagnetically in AlN. The hybridization between the f orbital of the Yb atom and the p orbital of the N atom is also observed. We see that AlN:Yb will be among the good candidates for spintronic applications.
Effect of electric field, dielectric screening and conduction band nonparabolicity of donor in a quantum dot
Authors: Rejo Jeice A. , Jayam Sr. Gerardin , Joseph Wilson K. S. 
Published: February 2018

The effect of electric field, dielectric screening, conduction band nonparabolicity and effective mass mismatch of a hydrogenic donor in a GaAs/Ga[Formula: see text]Al[Formula: see text]As spherical quantum dot is investigated by assuming parabolic confinement using variational method. In the present work we obtain the increase of binding energy by decreasing the dot size for certain dot radii (50 Å) and the screening function gives uniformly larger values for smaller dot size. The effect of electric field and temperature decrease the donor binding energy whereas the conduction band nonparabolicity leads to increased binding energy.