bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computation of Intrinsic Instability and Sound Generation From Auto-Ignition Fronts
Authors: Gopalakrishnan Harish S. , Gruber Andrea , Moeck Jonas 
Published: September 2022

Abstract
Burning carbon-free fuels such as hydrogen in gas turbines promise power generation with minimal emissions of greenhouse gases. A two-stage sequential combustor architecture with a propagation-stabilized flame in the first stage and an auto-ignition-stabilized flame in the second stage allows for efficient combustion of hydrogen fuels. However, interactions between the auto-ignition-stabilized flame and the acoustic modes of the combustor may result in self-sustained thermoacoustic oscillations, which severely affect the stable operation of the combustor. In this paper, we study an “intrinsic” thermoacoustic feedback mechanism in which acoustic waves generated by unsteady heat release rate oscillations of the auto-ignition front propagate upstream and induce flow perturbations in the incoming reactant mixture, which, in turn, act as a disturbance source for the ignition front. We first perform detailed reactive Navier–Stokes (direct numerical simulation (DNS)) and Euler computations of an auto-ignition front in a one-dimensional setting to demonstrate the occurrence of intrinsic instability. Self-excited ignition front oscillations are observed at a characteristic frequency and tend to become more unstable as the acoustic reflection from the boundaries is increased. The Euler computations yield identical unsteady ignition front behavior as the DNS computations, suggesting that diffusive mechanisms have a minor effect on the instability. In the second part of this work, we present a simplified framework based on the linearized Euler equations (LEE) to compute the sound field generated by an unsteady auto-ignition front. Unsteady auto-ignition fronts create sources of sound due to local fluctuations in gas properties, in addition to heat release oscillations, which must be accounted for. The LEE predictions of the fluctuating pressure field in the combustor agree well with the DNS data. The findings of this work are essential for understanding and modeling thermoacoustic instabilities in reheat combustors with auto-ignition-stabilized flames.
Block–Wheel–Rail Temperature Assessments Via Longitudinal Train Dynamics Simulations
Authors: Wu Qing , Spiryagin Maksym , Cole Colin 
Published: September 2022

Abstract
Two research gaps were identified in block–wheel–rail temperature assessment. First, current studies are not combined with train dynamics, which are better descriptions of the block–wheel–rail working environment. Second, current studies cannot simulate long rail sections. This paper developed a block–wheel–rail temperature assessment model by following the finite element idea. Models were validated by comparing with ansys Finite Element models and measured data. Case studies were carried out by combining the temperature model with a Longitudinal Train Dynamics model. A full-service and an emergency brake simulation were carried out for a 150-wagon heavy haul train on a 5680 m long rail section. The results show that, due to brake force differences at different wagon positions, the maximum block and wheel temperature differences among individual wagons in the full-service brake simulation were 117.01 °C and 117.91 °C, respectively. This highlighted the contribution of introducing train dynamics into block–wheel–rail temperature assessment. Rail temperature increases caused by wheel–rail temperature differences and frictional heating were about 10.60 °C and 2.65 °C, respectively.
Numerical Simulation of the Natural Convective Heat Transfer of Nanofluids in a Square Cavity Based on Different Predictive Models for Single-Phase and Multiphase Flow Mixtures
Authors: Dong Jingtao , Zheng Qun , Yuan Ze , Xiong Chunhua , Chen Jinmao 
Published: September 2022

Abstract
The flow and heat transfer characteristics of nanofluids in a square cavity were simulated using single-phase and mixed-phase flow models, and the simulation results were compared with the corresponding experimental values. The effects of different prediction models for the thermal properties of nanofluids, Grashof number, and volume fraction on the Nusselt number were analyzed. The velocity and temperature distributions of the nanofluid and de-ionized water in the square cavity were compared, and the effects of the temperature and flow fields on the enhanced heat transfer were analyzed according to the field synergy theory. The results show that for the numerical simulation of convective heat transfer in water, both the single-phase flow models and multiphase flow mixing models had high prediction accuracy. For nanofluids, single-phase flow did not reflect the heat transfer characteristics well, and the simulation results of the single-phase flow model relied more strongly on a highly accurate prediction model for the physical parameters. The multiphase flow mixing model could better reflect the natural convective heat transfer properties of the nanofluids in a square cavity. The nanofluid could significantly improve the flow state in the square cavity, thereby facilitating enhanced convective heat transfer. When the concentration is 2% (Grashof number is 1 × 106), the average Nusselt number of the nanofluid is increased by 19.7% compared with the base fluid.
Designing Cladded Components for High Temperature Nuclear Service: Part I—Analysis Methods
Authors: Messner M. C. , Barua B. , Jetter R. I. , Sham T.-L. 
Published: September 2022

AbstractUse of corrosion-resistant cladding can greatly extend the design life of structural components in many advanced reactor systems. However, there are currently no ASME design rules for cladded components to guard against creep-fatigue failure and ratcheting strain accumulation in elevated temperature nuclear service. This paper, presented in two parts, addresses this gap by proposing a design strategy for cladded components that do not require long-term testing of clad materials. The proposed approach relies on approximate design analysis methods for two types of clad materials—a soft clad that creeps much faster than and has lower yield stress than the class A base material and a hard clad that creeps much slower than and has higher yield stress than the class A base material. Part I discusses the approximate analysis strategies for the clad materials—treat a soft clad as perfectly compliant and a hard clad as linear elastic—and Part II develops a complete set of design rules for each of the two types of cladded components. Finite element analyses of representative high temperature reactor components show that the proposed design analysis methods can bound the design quantities in soft cladded components and approximate the design quantities in hard cladded components.
Robustness Analysis on Aerothermal Performance of the Winglet Squealer Tip—Part II: Heat Transfer Performance
Authors: Huang Ming , Li Zhigang , Li Jun 
Published: September 2022

Abstract
This article is the second part of a robustness analysis of the aerothermal performance of the winglet structure. A challenging analytical test function and an engineering test are considered to further investigate the response performance of the efficient uncertainty quantification framework proposed in Part 1. Then, a series of original visualizing uncertainty quantities are proposed in this article and applied to the study of uncertainty quantification of the winglet structure. Finally, this efficient framework is applied to the uncertainty quantification of the effect of the conventional squealer tip and three different winglet squealer tips on the heat transfer performance of the GE-E3 rotor blade. According to the results of the uncertainty quantification calculation, in actual operation, the setting of the winglet structures will diminish rather than increase the heat transfer performance of the blade tip. This conclusion is completely opposite to the prediction of the deterministic calculation. The heat flux increase and standard deviation of squealer tip with pressure-side winglet are the highest among the four tip structures, which means that the robustness of heat transfer performance of squealer tip with pressure-side winglet is the worst. The parameter that has the greatest influence on the uncertainty of the heat transfer performance of the four tip structures is the tip clearance. But the influence of the inlet total temperature fluctuation must also be taken into account. So a satisfactory control system should be designed for the actual operation of the gas turbine so that the fluctuation of inlet total temperature can be attenuated rapidly. A positive correlation between the heat flux of the blade tip mean value and the standard deviation is revealed by the uncertainty quantification, which implies that reducing the heat flux of the blade tip mean value in the robust design of the blade tip tends to reduce the heat flux fluctuation as well. Therefore, the objective of the robust design of the blade tip can be either one of reducing the mean value of heat flux of the blade tip mean value or reducing the heat flux of the blade tip standard deviation without multi-objective optimization. It is worth noting that, like the aerodynamic performance uncertainty, there is an antagonistic relationship between the pressure-side cavity and suction-side cavity on the heat transfer performance uncertainty of the blade tip. Therefore, a reasonable ratio of pressure-side cavity to suction-side cavity in the turbine design can also lead to a blade tip with strong heat transfer performance robustness.
Optical and Numerical Investigation of Flame Propagation in a Heavy Duty Spark Ignited Natural Gas Engine With a Bowl-in-Piston Chamber
Authors: Liu Jinlong , Ulishney Christopher J. , Dumitrescu Cosmin Emil 
Published: September 2022

Abstract
Increasing the natural gas (NG) use in heavy-duty engines is beneficial for reducing greenhouse-gas emissions from power generation and transportation. However, converting compression ignition (CI) engines to NG spark ignition operation can increase methane emissions without expensive aftertreatment, thereby defeating the purpose of utilizing a low carbon fuel. The widely accepted explanation for the low combustion efficiency in such retrofitted engines is the lower laminar flame speed of natural gas. In addition, diesel engine's larger bowl size compared to the traditional gasoline engines increases the flame travel length inside the chamber and extends the combustion duration. Optical measurements in this study suggested a fast-propagating flame developed even at extremely lean operation. A three-dimensional numerical simulation showed that the squish region of the bowl-in-piston chamber generated a high turbulence intensity inside the bowl. However, the flame propagation speed reduced by 55% when transiting from the bowl to the squish region, due to the large decrease in turbulence intensity inside the squish region. Moreover, the squish volume trapped an important fuel fraction, which experienced a slow and inefficient burning process during the expansion stroke. This resulted in increased methane emissions and reduced combustion efficiency. Overall, it was the specifics of the combustion inside a bowl-in-piston chamber not the methane's slow laminar flame speed that contributed to the low methane combustion efficiency for the retrofitted engine. The results suggest that optimizing the chamber shape is paramount to boost engine efficiency and decrease its emissions.
Experimental and Numerical Investigation of Electromigration Behavior of Printed Silver Wire Under High Current Density
Authors: Zhang Haibin , Sun Quan , Sun Zhidan , Lu Yebo 
Published: September 2022

Abstract
The electromigration (EM) damage is becoming a severe problem in the printed flexible electronics as the printed circuits are fabricated thinner and thinner due to the development of printing technology. In this work, the EM behavior of printed silver wires was investigated by EM experiments and numerical simulations. The EM tests showed that voids are generated in the cathode area and hillocks are formed in the anode area for a wire with a small length. However, with the increase of wire length, hillocks tend to occur on the two sides of the silver wire middle part. The results of numerical simulations based on the atomic flux divergence (AFD) method revealed that the formation of the hillocks on the printed wire is caused by not only the mechanism of electron wind but also the strong temperature gradient along the wire length and width direction. Also, it can be concluded that the temperature gradient induced by Joule heating plays a more important role than electron wind in the atomic migration of the printed silver wire subjected to a high current density. The influence of the printed silver wire size on the EM behavior was also analyzed by numerical simulation, and the results demonstrated that the printed silver wires with a larger length and a smaller width-to-thickness ratio are more likely to develop hillocks on the two sides of silver wire middle part while subjected to a high current density.
In vivo assessment of associations between photoreceptors structure and macular perfusion in type 1 diabetes
Authors: Viggiano Pasquale , Costanzo Eliana , Giannini Daniela , Fragiotta Serena , De Geronimo Daniele , Giorno Paola , Picconi Fabiana , Frontoni Simona , Varano Monica , Parravano Mariacristina 
Published: September 2022

PurposeTo explore the potential relationships between macular vascular network and different adaptive optics (AO) metrics in patients with type 1 diabetes mellitus (DM1) with no signs (NoDR) or mild non-proliferative diabetic retinopathy (NPDR).DesignObservational cross-sectional study.MethodsForty eyes of consecutive patients with DM1 (12 NoDR and 28 NPDR) and 10 healthy age-matched control subjects were included. All patients and controls were imaged using AO retinal camera and PLEX Elite 9000 optical coherence tomography (OCT) angiography (OCTA). The AO outcome measures to evaluate the cone photoreceptor mosaic characteristics were as follows: (1) Cone density (CD); (2) Linear Dispersion Index (LDi) and (3) Heterogeneity Packing Index (HPi). The OCTA outcome measures included: (1) superficial capillary plexus (SCP) perfusion density (PD); (2) deep capillary plexus (DCP) PD and (3) the choriocapillaris (CC) flow deficit percentage (FD%).ResultsNPDR group exhibited a close relationship between cone metrics and CC FD. Notably, CC FD% increase along with LDi (p=0.035), while the increasing CC FD% were associated with reducing CD (p=0.042) and the HPi (p=0.017). Furthermore, the OCTA parameters, including PD SCP and DCP, showed a significant negative correlation with CD.ConclusionsOur results demonstrated the relationship between macular perfusion at both retinal and choroidal levels and the cone mosaic in patients with DM1 interpolating swept-source-OCTA and AO metrics. In NPDR eyes, the photoreceptor damage was accompanied by CC insufficiency since the early stages of the disease.
Efficacy and safety of tai chi for hyperlipidaemia: a protocol for systematic review and meta-analysis
Authors: Dong Weitao , Zhang Feng , Lian Daoshi , Chen Xingliang , Zhou Hongchi , Gong Tingting , Wang Chao 
Published: September 2022

IntroductionThe prevalence of hyperlipidaemia is increasing, and patients with hyperlipidaemia are at increased risk of cardiovascular disease and atherosclerosis. In recent years, there has been a growing number of studies on tai chi for hyperlipidaemia. However, a systematic review on its efficacy and safety is not available. Therefore, this study aims to evaluate the efficacy and safety of tai chi for hyperlipidaemia.Methods and analysisFour English databases and four Chinese databases will be searched from their inception to May 2021: PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure, Chinese Biomedical Literature Database, VIP Database and Wanfang Database. Chinese and English randomised controlled trials related to tai chi for hyperlipidaemia will be included. Two reviewers should independently carry out study selection, data extraction and risk assessment of bias. The risk of bias in the study will be assessed by the Cochrane risk of bias tool. RevMan (V.5.4) statistical software will be applied for meta-analysis. The Grading of Recommendations Assessment, Development and Evaluation system approach will be employed to assess the quality of evidence.Ethics and disseminationEthical approval is not required because this protocol will not involve patients’ individual information and jeopardise the rights of patients. The meta-analysis result will be reported in peer-reviewed journals or disseminated at related conferences.OSF registration numberDOI 10.17605/OSF.IO/79D2S.
Economic impact of the first pass effect in mechanical thrombectomy for acute ischaemic stroke treatment in Spain: a cost-effectiveness analysis from the national health system perspective
Authors: González Diaz Eva , Rodríguez-Paz Carlos , Fernandez-Prieto Andres , Martínez-Galdámez Mario , Martínez-Moreno Rosa , Ortega Quintanilla Joaquín , Tomasello Alejandro , Zamarro Joaquín , Liebeskind David , Zaidat Osama O , Mueller-Kronast Nils H 
Published: September 2022

ObjectiveThe mechanical thrombectomy (MT) benefit is related to the degree of reperfusion achieved. First pass effect (FPE) is defined as complete/near revascularisation of the large-vessel occlusion (modified Thrombolysis in Cerebral Infarction (mTICI) 2c-3) after a single device pass. This study assessed the health benefit and economic impact of achieving FPE for acute ischaemic stroke (AIS) patients from the Spanish National Health System (NHS) perspective.DesignA lifetime Markov model was used to estimate incremental costs and health outcomes (measured in quality-adjusted life-years (QALYs)) of patients that achieve FPE. A subanalysis of the Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischaemic Stroke (STRATIS) registry was performed to obtain clinical outcomes. The base case included all patients that achieved at least a final mTICI ≥2 b, while the alternative scenario included all patients regardless of their final mTICI (0–3). Treatment costs were updated to reflect current practice based on expert panel consensus, while other acute and long-term costs were obtained from a previous cost-effectiveness analysis of MT performed in Spain. Sensitivity analyses were performed to assess the model’s robustness.SettingSpanish healthcare perspective.ParticipantsAIS patients in Spain.InterventionsFPE following MT.Outcome measuresThe model estimated QALYs, lifetime costs and net monetary benefit for the FPE and non-FPE group, depending on the inclusion of reperfusion groups and formal care costs.ResultsSTRATIS subanalysis estimated significantly better clinical outcomes at 90 days for the FPE group in all scenarios. In the base case, the model estimated lifetime cost saving per patient of €16 583 and an incremental QALY gain of 1.2 years of perfect health for the FPE group. Cost savings and QALY gains were greater in the alternative scenario (-€44 289; 1.75). In all scenarios, cost savings were driven by the long-term cost reduction.ConclusionAchieving FPE after MT can lead to better health outcomes per AIS patient and important cost savings for the Spanish NHS.
Bidirectional relationship between cognitive function and loss hierarchy of activities of daily living among older adults with disabilities in urban China: a cross-lagged analysis
Authors: Sun Qian , Jiang Nan , Lu Nan , Lou Vivian W Q 
Published: September 2022

ObjectivesThe present study aimed to determine the bidirectional relationship between cognitive function and the loss hierarchy of activities of daily living (ADL) among older adults in China.DesignData were derived from the Longitudinal Study on Family Caregivers for Frail Older Adults Aged 75 or Above in Shanghai (2010–2013).SettingCommunity-dwelling older adults and their primary caregivers were invited to participate in this research.ParticipantsThe inclusion criteria for the older adults were as follows: (a) have a Shanghai urban household registration status, (b) be 75 years old or older, (c) have no fewer than two limitations in ADLs or equivalent, and (d) have one primary caregiver aged 18 years or older. 469 older adults cared by their spouses or children were included in the final analytical sample of this research.Primary and secondary outcome measuresCognitive function was assessed using the Chinese version of the Short Portable Mental Status Questionnaire and ADLs were measured by self-reports of having difficulty or needing help with basic daily activities.ResultsCognitive function in 2010 was a significant predictor of intermediate loss of ADLs in 2013 (β=−0.13, p<0.05) and late loss of ADLs in 2013 (β=−0.17, p<0.01). The loss hierarchy of ADLs among older adults was not shown to be significant as a risk factor of cognitive function in 2013.ConclusionsPractitioners are encouraged to adopt the ADL loss hierarchy as a supplementary needs assessment tool to make the social service delivery process more effective, economical and tailored. Cognitive function change monitoring programmes and services providing education on nutrition and encouraging social participation of older individuals were also helpful in promoting the quality of life of the older adults.
Microbiome Characteristics in Early Threatened Miscarriage Study (MCETMS): a study protocol for a prospective cohort investigation in China
Authors: Chen Xiaofeng , Guo Yinan , Zhang Yingxuan , Si Chen , Zhang Huimin , Huang Xuge , Luo Songping , Deng Gaopi , Gao Jie 
Published: September 2022

IntroductionStudies have suggested that the vaginal microbiome and gut microbiome are involved in pregnancy-related diseases, but little exploration of the link with early miscarriage or threatened miscarriage (TM) has been done. Whether the characteristics of the vaginal microbiome and gut microbiome in early pregnancy are related to TM and early pregnancy outcomes remains unclear.Methods and analysisThe Microbiome Characteristics in Early Threatened Miscarriage Study (MCETMS) is a prospective investigation that will recruit 326 pregnant women with early TM. Pregnant women will be enrolled at 4–8 weeks of gestation, and their vaginal secretions, faecal samples, clinical data and sociodemographic characteristics will be collected prospectively. Pregnant women with TM will be followed up to 12 weeks of gestation to determine the early pregnancy outcomes (ongoing pregnancy or pregnancy loss). DNA will be extracted from the collected samples and will be analysed by 16S rRNA gene sequencing.Ethics and disseminationThe MCETMS study protocol has been approved by the Ethics Committee of the First Affiliated Hospital of Guangzhou Traditional Chinese Medical University (ZYYECK[2020]051). Dissemination of study findings will occur through peer-reviewed journals, conferences and presentations.Trial registration numberChiCTR2000041172.