bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Autonomous Uncertainty Quantification Method for the Digital Age: Transonic Flow Simulations Using Multivariate Padé Approximations
Authors: Ahlfeld Richard , Carnevale Mauro , Salvadori Simone , Montomoli Francesco 
Published: August 2017

There is a need to automate stochastic uncertainty quantification codes in the digital age. Problems in turbomachinery Computational Fluid Dynamics (CFD) are characterised by non-linear and discontinuous responses and long run times. Ensuring the reliability of Uncertainty Quantification (UQ) codes in such conditions, in an autonomous way, is a challenging problem. Human involvement has always been required. In this work, we therefore suggest a new approach that combines three state-of-the-art methods: multivariate Padé approximations, Optimal Quadrature Subsampling and Statistical Learning.
Its main component is the generalised least squares multivariate Padé-Legendre (PL) approximation. PL approximations are globally fitted rational functions that can accurately describe discontinuous non-linear behaviour. They need fewer model evaluations than local or adaptive methods and do not cause the Gibbs phenomenon, like continuous Polynomial Chaos methods.
We describe a series of modifications of the Padé algorithm that allow us to apply it to arbitrary input points instead of optimal quadrature locations. This property is particularly useful for industrial applications, where a database of CFD runs is already available, but not in optimal parameter locations. One drawback of the PL approximation is that it is non-trivial to ensure reliability for multiple input parameters. We therefore suggest a new method to improve stability in this work: Optimal Quadrature Subsampling. Our argument is that least squares errors, caused by an ill-conditioned design matrix, are the main source of error. Finally, we use statistical learning techniques to automatically guarantee smoothness and convergence.
The resulting method is shown to efficiently and correctly fit thousands of partly discontinuous response surfaces for an industrial film cooling and shock interaction problem automatically and using only 9 CFD simulations. It can be applied to any other UQ problem that is characterised by a limited amount of data and the presence of discontinuities.
Experimental and Modeling Study of C1 to C3 Hydrocarbon Ignition in the Presence of Nitric Oxide
Authors: Gokulakrishnan Ponnuthurai , Fuller Casey C. , Klassen Michael S. 
Published: August 2017

Nitric oxide produced during combustion will be present in vitiated air used in many devices with exhaust gas recirculation. An experimental and modeling investigation of the effect of nitric oxide on the ignition of C1 to C3 hydrocarbon fuels, namely, CH4, C2H4, C2H6 and C3H6, is presented. These molecules are important intermediate species generated during the decomposition of long-chain hydrocarbon fuel components typically present in jet fuels. Moreover, CH4 and C2H6 are major components of natural gas fuels. Although the interaction between NOx and CH4 has been studied extensively, limited experimental work is reported on C2H4, C2H6 and C3H6. NOx, even in very low concentrations, has previously been shown to effectively enhance the ignition of CH4. As a continuation of previous work with C3H8, ignition delay time measurements were obtained using a flow reactor facility with the alkanes (CH4 and C2H6) and olefins (C2H4 and C3H6) at 900 K and 950 K temperatures with 15 mole% and 21 mole% O2. Based on the experimental data, the overall effectiveness of NO in promoting ignition is found to be: CH4 > C3H6 > C3H8 > C2H6 > C2H4.
CSE’s detailed kinetic mechanism, developed for natural gas fuel components, is used for model predictions as well as for sensitivity and species flux analyses. As expected, the reaction between HO2 and NO plays a critical role in promoting the ignition by generating the OH radical while converting NO into NO2. In addition, various important fuel-dependent reaction pathways that promote the ignition of these fuels are identified. H-atom abstraction by NO2 has significant contribution to the ignition of C2H4, and C2H6 whereas the reaction between NO2 and allyl radical (aC3H5) is an important route for the ignition of C3H6.
Active Control of Fuel Cell Degradation in an SOFC/GT Hybrid System
Authors: Zaccaria Valentina , Tucker David , Traverso Alberto , Pezzini Paolo , Bryden Kenneth M. 
Published: August 2017

A control strategy to mitigate fuel cell degradation effects in a solid oxide fuel cell (SOFC) gas turbine (GT) hybrid system was implemented on the Hybrid Performance facility at the National Energy Technology Laboratory. In this experiment, a cyber-physical approach was employed to emulate the SOFC component and to couple it to a physical recuperated gas turbine. An empirical degradation model simulated fuel cell performance decay over time depending on operating parameters. A combination of virtual and physical actuators was manipulated with the goal of ensuring safe fuel cell performance over time, maintaining constant voltage and minimizing thermal stresses as fuel cell power degraded. Three single-input single-output controllers were used for this purpose. In particular, a gain scheduling approach was used for voltage control to account for different degraded conditions of operation because stability could not be maintained with the initial controller gains. In addition, a bypass valve control was designed to maintain constant temperature difference across the cell, and turbine load was manipulated to keep constant speed.
This work presents the control design and implementation on the Hybrid Performance facility and illustrates the impact of fuel cell degradation on the entire system long-term performance. Controllers design was based on empirical transfer functions and stability analysis. Issues related to coupling phenomena between controlled variables are discussed. The results show the potential for an adequate control of the system to extend fuel cell operating lifetime.
Connecting Computed-Tomography-Assisted Discontinuity Detection in Ni-Base Superalloys to Engineering Simulation
Authors: Loghin Adrian , Cerrone Al , Singhal Anjali , Zhou Ying 
Published: August 2017

The impact of non-metallic inclusions on fatigue life of various materials (steel alloys, Ni-base) has been studied extensively for more than fifty years. Specimen test procedures at various conditions (temperature, air or vacuum, LCF, HCF, VHCF) have been used to quantify the impact of inherent manufacturing induced discontinuities (ceramic inclusions, pores, carbides) on the fatigue capability of the material. Frequently, the fatigue data shows large scatter, leading to a large set of test specimens that has to be considered to quantify the lower tail of the fatigue life distribution. To understand the specimen recorded fatigue lives, assessment of the discontinuity population is usually conducted post-mortem by fractography wherein the origin of crack nucleation, size of the eventual inclusion on fracture surface, and distance from the free surface are identified.
3D characterization techniques can be leveraged to extract previously unobtainable information out of the testing specimens non-destructively. In this study, samples of different Powder Metallurgy (PM) Ni-base superalloys with different inclusion content and size were scanned to identify the Computed Tomography (CT) test setup that would provide adequate contrast to discriminate between matrix and eventual discontinuities (inclusions, pores). To further validate the capability to identify discontinuities within the matrix (Ni base alloy) using the CT technique, a set of LCF specimens were scanned prior to the test procedure. Post-failure fractography analysis showed that one of the CT indications is correlated with the failure-inducing inclusion.
Volume reconstruction and finite element meshing conclude this study to: a) further provide a size distribution of inclusions in the scanned volume as well as location of these inclusions relative to the surface of the specimen and b) connect direct measurement with engineering simulation.
An Experimental Investigation on the Impact of Inlet Slugging on Wet Gas Compressor Performance
Authors: Bakken Martin , Bjørge Tor 
Published: August 2017

The continuous demand for oil and gas forces the petroleum industry to develop new and cost-efficient technologies in order to increase recovery and exploit existing fields. Subsea wet gas compression of the unprocessed well stream is a powerful tool in increasing production capacity and utilizing remote regions.
Wet gas compressors are particularly useful for handling gas-dominated multiphase flows. Although a limited amount of research has been done on the field, previous studies have revealed that the liquid phase has considerable impact on the compressor performance, from both a fluid mechanical and a thermodynamic perspective.
Being able to ensure stable and predictable compressor behavior in subsea installations is challenging. As the reservoir pressure drops during production, the compressor enters a region where it is far more susceptible to inlet slugging. Inlet slugging may lead to internal compressor damage, including damage to seals, bearings and compressor blades. It needs to be stressed that a slug in this context does not entail 100% liquid holdup upfront of the compressor, but a substantial increase of liquid content in a gas dominated multiphase flow.
An experimental investigation has been carried out on an advanced wet gas test rig, consisting of a shrouded centrifugal impeller, a vaneless diffuser and a circular volute. The paper explores the possibilities of creating realistic inlet slugging scenarios and documents its impact on the compressor system. Slugging was introduced either by collection of liquid in a negatively sloped inlet pipe (i.e. terrain slug simulation) or by sudden opening of an inlet liquid valve upstream of a symmetrical injection manifold, so to create a more “homogenous” slug. The compressor ability to handle such slugs is analyzed. Furthermore, the drive capability to respond to sudden changes in torque requirement is documented. The experimental results form a basis for future dynamic simulation.
A Probabilistic Simulation of Grain Size Effect on Small Crack Growth in a Nickel Based Superalloy
Authors: Hu Dianyin , Mao Jianxing , Wang Rongqiao , Song Jun , Wang Xiyuan 
Published: August 2017

Considerable efforts have been conducted on the modeling of fatigue crack growth (FCG), aiming at an accurate prediction of fatigue life. However, due to the influence of microstructure, it is still challenging to describe FCG behavior, especially for small cracks.
The FCG exhibits obvious variation at small crack growth procedure. In this regard, a probabilistic model by integrating N-R model is proposed to simulate the FCG process at stage I. The concerned material is nickel based superalloy GH4169.
The proposed model involves both macroscopic and microscopic material parameters for the extension of dislocation with the impediment from grain boundary. Random grain size is represented by the fluctuation of FCG rate. Model validation is performed by comparing the simulation results and experimental data. It is revealed that the dependence tends to be less prominent on longer crack length, smaller grain size and higher applied stress.
On the Reliability of RANS Turbulence Models for Endwall Cooling Prediction
Authors: Li Xueying , Ren Jing , Jiang Hongde 
Published: August 2017

The large scale coherent structures in the flow field of film cooling makes it difficult for the modeling of film cooling flow and heat transfer. The interaction between the complex secondary flows near the endwall and the film cooling jets makes it even worse.
A typical flat vane endwall with/without film cooling is investigated experimentally and numerically. The aerodynamic and heat transfer of the endwall is measured. Adiabatic film cooling effectiveness is measured using PSP technique and conjugate overall cooling effectiveness is measured by TSP technique for different conditions. The coolant to mainstream massflow ratio (MFR) is varied from 0.5% to 1.5% in the experiment. Several RANS turbulence models are tested in the prediction of endwall aerodynamics, heat transfer, film cooling and conjugate heat transfer. Detailed analyses of the computational results are performed. The algebraic anisotropic turbulence model proposed previously aiming at a more accurate modeling of the Reynolds stress and turbulent scalar flux is employed in the study.
The SST with transition model shows advantage in the prediction of endwall flow field and film cooling with high blowing ratios which is detached from the surface. The Realizable k-epsilon model is more suitable for predicting attached film cooling and conjugate heat transfer of the endwall. The algebraic anisotropic models show better agreement with the experimental data qualitatively and quantitatively for both adiabatic and conjugate situations.
Zinc Salts Block Hepatitis E Virus Replication by Inhibiting the Activity of Viral RNA-Dependent RNA Polymerase
Authors: Kaushik Nidhi , Subramani Chandru , Anang Saumya , Muthumohan Rajagopalan , Shalimar  , Nayak Baibaswata , Ranjith-Kumar C. T. , Surjit Milan 
Published: August 2017

ABSTRACTHepatitis E virus (HEV) causes an acute, self-limiting hepatitis in healthy individuals and leads to chronic disease in immunocompromised individuals. HEV infection in pregnant women results in a more severe outcome, with the mortality rate going up to 30%. Though the virus usually causes sporadic infection, epidemics have been reported in developing and resource-starved countries. No specific antiviral exists against HEV. A combination of interferon and ribavirin therapy has been used to control the disease with some success. Zinc is an essential micronutrient that plays crucial roles in multiple cellular processes. Zinc salts are known to be effective in reducing infections caused by few viruses. Here, we investigated the effect of zinc salts on HEV replication. In a human hepatoma cell (Huh7) culture model, zinc salts inhibited the replication of genotype 1 (g-1) and g-3 HEV replicons and g-1 HEV infectious genomic RNA in a dose-dependent manner. Analysis of a replication-defective mutant of g-1 HEV genomic RNA under similar conditions ruled out the possibility of zinc salts acting on replication-independent processes. An ORF4-Huh7 cell line-based infection model of g-1 HEV further confirmed the above observations. Zinc salts did not show any effect on the entry of g-1 HEV into the host cell. Furthermore, our data reveal that zinc salts directly inhibit the activity of viral RNA-dependent RNA polymerase (RdRp), leading to inhibition of viral replication. Taken together, these studies unravel the ability of zinc salts in inhibiting HEV replication, suggesting their possible therapeutic value in controlling HEV infection.IMPORTANCEHepatitis E virus (HEV) is a public health concern in resource-starved countries due to frequent outbreaks. It is also emerging as a health concern in developed countries owing to its ability to cause acute and chronic infection in organ transplant and immunocompromised individuals. Although antivirals such as ribavirin have been used to treat HEV cases, there are known side effects and limitations of such therapy. Our discovery of the ability of zinc salts to block HEV replication by virtue of their ability to inhibit the activity of viral RdRp is important because these findings pave the way to test the efficacy of zinc supplementation therapy in HEV-infected patients. Since zinc supplementation therapy is known to be safe in healthy individuals and since high-dose zinc is used in the treatment of Wilson's disease, it may be possible to control HEV-associated health problems following a similar treatment regimen.
Extracellular Matrix Proteins Mediate HIV-1 gp120 Interactions with α4β7
Authors: Plotnik David , Guo Wenjin , Cleveland Brad , von Haller Priska , Eng Jimmy K. , Guttman Miklos , Lee Kelly K. , Arthos James , Hu Shiu-Lok 
Published: August 2017

ABSTRACTGut-homing α4β7highCD4+T lymphocytes have been shown to be preferentially targeted by human immunodeficiency virus type 1 (HIV-1) and are implicated in HIV-1 pathogenesis. Previous studies demonstrated that HIV-1 envelope protein gp120 binds and signals through α4β7and that this likely contributes to the infection of α4β7highT cells and promotes cell-to-cell virus transmission. Structures within the second variable loop (V2) of gp120, including the tripeptide motif LDV/I, are thought to mediate gp120-α4β7binding. However, lack of α4β7binding has been reported in gp120 proteins containing LDV/I, and the precise determinants of gp120-α4β7binding are not fully defined. In this work, we report the novel finding that fibronectins mediate indirect gp120-α4β7interactions. We show that Chinese hamster ovary (CHO) cells used to express recombinant gp120 produced fibronectins and other extracellular matrix proteins that copurified with gp120. CHO cell fibronectins were able to mediate the binding of a diverse panel of gp120 proteins to α4β7in anin vitrocell binding assay. The V2 loop was not required for fibronectin-mediated binding of gp120 to α4β7, nor did V2-specific antibodies block this interaction. Removal of fibronectin through anion-exchange chromatography abrogated V2-independent gp120-α4β7binding. Additionally, we showed a recombinant human fibronectin fragment mediated gp120-α4β7interactions similarly to CHO cell fibronectin. These findings provide an explanation for the apparently contradictory observations regarding the gp120-α4β7interaction and offer new insights into the potential role of fibronectin and other extracellular matrix proteins in HIV-1 biology.IMPORTANCEImmune tissues within the gut are severely damaged by HIV-1, and this plays an important role in the development of AIDS. Integrin α4β7plays a major role in the trafficking of lymphocytes, including CD4+T cells, into gut lymphoid tissues. Previous reports indicate that some HIV-1 gp120 envelope proteins bind to and signal through α4β7, which may help explain the preferential infection of gut CD4+T cells. In this study, we demonstrate that extracellular matrix proteins can mediate interactions between gp120 and α4β7. This suggests that the extracellular matrix may be an important mediator of HIV-1 interaction with α4β7-expressing cells. These findings provide new insight into the nature of HIV-1–α4β7interactions and how these interactions may represent targets for therapeutic intervention.
BA71ΔCD2: a New Recombinant Live Attenuated African Swine Fever Virus with Cross-Protective Capabilities
Authors: Monteagudo Paula L. , Lacasta Anna , López Elisabeth , Bosch Laia , Collado Javier , Pina-Pedrero Sonia , Correa-Fiz Florencia , Accensi Francesc , Navas María Jesús , Vidal Enric , Bustos María J. , Rodríguez Javier M. , Gallei Andreas , Nikolin Veljko , Salas María L. , Rodríguez Fernando 
Published: August 2017

ABSTRACT

African swine fever is a highly contagious viral disease of mandatory declaration to the World Organization for Animal Health (OIE). The lack of available vaccines makes its control difficult; thus, African swine fever virus (ASFV) represents a major threat to the swine industry. Inactivated vaccines do not confer solid protection against ASFV. Conversely, live attenuated viruses (LAV), either naturally isolated or obtained by genetic manipulation, have demonstrated reliable protection against homologous ASFV strains, although little or no protection has been demonstrated against heterologous viruses. Safety concerns are a major issue for the use of ASFV attenuated vaccine candidates and have hampered their implementation in the field so far. While trying to develop safer and efficient ASFV vaccines, we found that the deletion of the viral CD2v (EP402R) gene highly attenuated the virulent BA71 strain
in vivo
. Inoculation of pigs with the deletion mutant virus BA71ΔCD2 conferred protection not only against lethal challenge with the parental BA71 but also against the heterologous E75 (both genotype I strains). The protection induced was dose dependent, and the cross-protection observed
in vivo
correlated with the ability of BA71ΔCD2 to induce specific CD8
+
T cells capable of recognizing both BA71 and E75 viruses
in vitro
. Interestingly, 100% of the pigs immunized with BA71ΔCD2 also survived lethal challenge with Georgia 2007/1, the genotype II strain of ASFV currently circulating in continental Europe. These results open new avenues to design ASFV cross-protective vaccines, essential to fight ASFV in areas where the virus is endemic and where multiple viruses are circulating.

IMPORTANCE
African swine fever virus (ASFV) remains enzootic in most countries of Sub-Saharan Africa, today representing a major threat for the development of their swine industry. The uncontrolled presence of ASFV has favored its periodic exportation to other countries, the last event being in Georgia in 2007. Since then, ASFV has spread toward neighboring countries, reaching the European Union's east border in 2014. The lack of available vaccines against ASFV makes its control difficult; so far, only live attenuated viruses have demonstrated solid protection against homologous experimental challenges, but they have failed at inducing solid cross-protective immunity against heterologous viruses. Here we describe a new LAV candidate with unique cross-protective abilities: BA71ΔCD2. Inoculation of BA71ΔCD2 protected pigs not only against experimental challenge with BA71, the virulent parental strain, but also against heterologous viruses, including Georgia 2007/1, the genotype II strain of ASFV currently circulating in Eastern Europe.