bluuebunny/crossref_metadata_2025 huggingface dataset:
One hundred years of dynamic minimum wage regulation: Lessons from Australia, the United Kingdom and the United States
Authors: HAMILTON Reg , NICHOL Matt
Published: November 2022

Since the first minimum wage legislation was introduced in Australia, the United Kingdom and the United States in the early 1900s, minimum wage regulation has attracted controversy. Opponents of minimum wages use market theory to defend their position, while supporters justify state intervention based on principles of equity and social good. This article examines how these two ideological positions have influenced the fixing of wages, and the ensuing results. As little comparative research exists on the origins, evolution and current systems of minimum wage regulation in the three countries, this article aims to address the gap in the literature.
Complex cycles of divergence and migration shape lineage structure in the common kingsnake species complex
Authors: Harrington Sean , Burbrink Frank T.
Published: November 2022

Aim

The Nearctic is a complex patchwork of habitats and geologic features that form barriers to gene flow resulting in phylogeographic structure and speciation in many lineages. Habitats are rarely stable over geologic time, and the Nearctic has undergone major climatic changes in the past few million years. We use the common kingsnake species complex to study how climate, geography, and history influence lineage formation over a large, complex landscape.

Location

Nearctic/North America.

Taxon

Common kingsnake, Lampropeltis getula, species complex.

Methods

We analysed genome‐wide sequence data from 51 snakes spanning the majority of the species complex's range. We used population clustering, generalized dissimilarity modelling and coalescent methods to identify the number of genetic clusters within the L. getula complex, infer the environmental correlates of genetic differentiation, and estimate models of divergence and gene flow among lineages.

Results

We identified three major lineages within the L. getula complex and further continuous spatial structure within lineages. The most important ecological correlates of genetic distance in the complex are related to aridity and precipitation, consistent with lineage breaks at the Great Plains/Desert ecotone and the Cochise filter barrier. Lineages are estimated to have undergone multiple rounds of isolation and secondary contact, with highly asymmetric migration occurring at present.

Main conclusions

Changing climates combined with a large and geologically complex landscape have resulted in a mosaic of discrete and spatially continuous genetic structure. Multiple rounds of isolation and secondary contact as climate fluctuated over the past ~4.4 My have likely driven the evolution of discrete lineages that maintain high levels of gene flow. Continuous structure is strongly shaped by aridity and precipitation, suggesting roles for major precipitation gradients in helping to maintain lineage identity in the face of gene flow when lineages are in geographic contact.
An examination of the effectiveness of problem‐based learning method supported by augmented reality in science education
Authors: Arici Faruk , Yilmaz Mehmet
Published: November 2022

Background

Augmented reality (AR) is a widely used technology in science education today. Problem‐based learning (PBL) is one of the teaching methods employed in science education for a long time. Studies where AR and PBL are used together are new and rare. PBL and AR technology are used together in the study because it is believed that integrating AR technology with PBL increases the effectiveness of PBL.

Objectives

In the present study, the effect of PBL supported by AR on academic achievement, reflective thinking skills towards problem‐solving, decision‐making abilities, and the permanence levels of the 7th‐grade students were researched.

Methods

The embedded design from mixed methods was used in the study, which had two experimental groups and one control group. For the Experiment‐1, Experiment‐2, and Control Groups, respectively, PBL supported by AR, PBL alone, and the current teaching method were used. The sample consists of 92 students from the seventh grade.

Results and Conclusions

In terms of academic achievement, reflective thinking skills towards problem‐solving, and decision‐making abilities, the Experiment‐1 Group outperformed the Experiment‐2 and Control Groups, and the Experiment‐2 Group outperformed the Control Group. It has been discovered that PBL supported by AR is more effective than solely PBL and the currently used teaching method in terms of improving reflective thinking skills towards problem‐solving and decision‐making abilities, as well as the persistence of academic achievement in a science course.
Glucose and lipopolysaccharide differentially regulate fibroblast growth factor 21 in healthy male human volunteers – A prospective cross‐over trial
Authors: Pohlhammer Johannes , Heinzl Matthias Wolfgang , Klammer Carmen , Feldbauer Roland , Rosenberger Klemens , Resl Michael , Wagner Thomas , Obendorf Florian , Egger‐Salmhofer Margot , Dieplinger Benjamin , Clodi Martin
Published: November 2022

Fibroblast growth factor 21 (FGF21) affects the regulation of metabolism. Additionally, anti‐inflammatory properties are attributed to FGF21, and studies in animals and humans show conflicting results. This study aimed to investigate how FGF21 is affected by glucose and lipopolysaccharide (LPS) in humans. Therefore, FGF21 was measured eight times at different time points within 48 h in this prospective cross‐over trial after glucose and LPS on two different study days. The study included ten healthy, non‐smoking male subjects aged 18–40. Repeated measures analysis of variance and paired t‐test as post hoc analysis were applied. The administration of glucose and LPS resulted in a significant difference in regulating FGF21 (p < 0.001). After glucose administration, FGF21 declined sharply at 360 min, with a subsequent steep increase that exceeded baseline levels. LPS induced a drop in FGF21 after 180 min, while the baseline concentrations were not reached. After 180 min and 24 h, a statistically significant difference was demonstrated after adjusting the Bonferroni–Holm method. So, our results support the hypothesis that glucose and LPS differentially affect the human expression of FGF21 over 48 h.
Measuring community flood resilience and associated factors in rural Malawi
Authors: Dewa Ozius , Makoka Donald , Ayo‐Yusuf Olalekan A.
Published: November 2022

With global estimates showing an increasing trend in flooding and its adverse effects on communities and population health, resilience is presented as a concept with potential to help integrate disaster risk management, sustainable development, and climate change adaptation concerns. Resilience research and practice have conceptual and empirical challenges of how to understand, characterize and measure resilience, particularly at community level. Using a multidimensional framework, this paper takes a systems approach to understanding, characterizing, and measuring community flood resilience. Through cluster analysis, bivariate methods and multivariable‐adjusted binary logistic regression modeling, we developed a context and hazard specific construct of community flood resilience and investigated its predictor variables. The factors defining the community flood resilience construct captured the community needs to withstand disasters through purpose‐built infrastructure, early warning systems for preparedness and utilization of local human capacity for adaptation. These results strengthen the previous arguments for utilizing a comprehensive multidimensional framework for resilience analysis. Access to services for improved health and psychosocial well‐being was significantly associated with the three‐item measure of being more flood resilient. Additionally, a strong sense of place and resistance to relocation were presented as key elements of resilience, maintaining community system function, and preserving livelihoods. The study further found that these key factors would not be adequate to guarantee community flood resilience outside the transformative capacity of a well‐resourced village civil protection committee that can prepare and mobilize stakeholders in response to flood emergencies. Our results suggest that, in the context where policymakers seek to strengthen resilience of communities without relocating them, a focus on public health and on strengthening and utilizing local capacities as adaptation, are key in disaster risk management policymaking and implementation. For the international research community, this study demonstrated the importance of utilizing context and hazard specific measures for defining, characterizing, and measuring resilience to inform policy.
A novel approach for vital visualization and studying of neurons containing Ca2+‐permeable AMPA receptors
Authors: Gaidin Sergei G. , Maiorov Sergei A. , Laryushkin Denis P. , Zinchenko Valery P. , Kosenkov Artem M.
Published: November 2022

Calcium‐permeable AMPA receptors (CP‐AMPARs) play a pivotal role in brain functioning in health and disease. They are involved in synaptic plasticity, synaptogenesis, and neuronal circuits development. However, the functions of neurons expressing CP‐AMPARs and their role in the modulation of network activity remain elusive since reliable and accurate visualization methods are absent. Here we developed an approach allowing the vital identification of neurons containing CP‐AMPARs. The proposed method relies on evaluating Ca2+ influx in neurons during activation of AMPARs in the presence of NMDAR and KAR antagonists, and blockers of voltage‐gated Ca2+ channels. Using this method, we studied the properties of CP‐AMPARs‐containing neurons. We showed that the overwhelming majority of neurons containing CP‐AMPARs are GABAergic, and they are distinguished by higher amplitudes of the calcium responses to applications of the agonists. Furthermore, about 30% of CP‐AMPARs‐containing neurons demonstrate the presence of GluK1‐containing KARs. Although CP‐AMPARs‐containing neurons are characterized by more significant Ca2+ influx during the activation of AMPARs than other neurons, AMPAR‐mediated Na+ influx is similar in these two groups. We revealed that neurons containing CP‐AMPARs demonstrate weak GABA(A)R‐mediated inhibition because of the low percentage of GABAergic synapses on the soma of these cells. However, our data show that weak GABA(A)R‐mediated inhibition is inherent to all GABAergic neurons in the culture and cannot be considered a unique feature of CP‐AMPARs‐containing neurons. We believe that the suggested approach will help to understand the role of CP‐AMPARs in the mammalian nervous system in more detail.

image
The concurrent and longitudinal impact of sleep on mind wandering in early adolescents
Authors: Lin Yue , Su Yanjie
Published: November 2022

Mind wandering refers to task‐unrelated thoughts that can interfere with ongoing tasks and could be sleep‐driven across childhood. The present study investigated the mechanisms of the association between early adolescents' sleep and mind wandering with emotional symptoms and executive function as potential mediators. A total of 257 early adolescents (baseline aged 9–13 years old; 131 boys) completed the questionnaires consisting of the Pittsburgh Sleep Quality Index, mind wandering, depression and anxiety symptoms, and executive function. Cross‐sectional and longitudinal data revealed a sequential mediation pathway of emotional symptoms and executive function in the association between sleep and mind wandering. The mediating effect of emotional symptoms in the link between sleep quality and mind wandering was significant among boys but not girls.
Arginine methylation sites on SepIVA help balance elongation and septation in Mycobacterium smegmatis
Authors: Freeman Angela H. , Tembiwa Karen , Brenner James R. , Chase Michael R. , Fortune Sarah M. , Morita Yasu S. , Boutte Cara C.
Published: November 2022

The growth of mycobacterial cells requires successful coordination between elongation and septation. However, it is not clear which factors mediate this coordination. Here, we studied the function and post‐translational modification of an essential division factor, SepIVA, in Mycobacterium smegmatis. We find that SepIVA is arginine methylated, and that alteration of its methylation sites affects both septation and polar elongation of Msmeg. Furthermore, we show that SepIVA regulates the localization of MurG and that this regulation may impact polar elongation. Finally, we map SepIVA's two regulatory functions to different ends of the protein: the N‐terminus regulates elongation while the C‐terminus regulates division. These results establish SepIVA as a regulator of both elongation and division and characterize a physiological role for protein arginine methylation sites for the first time in mycobacteria.
What drives support for separatism? Exposure to conflict and relative ethnic size in Biafra, Nigeria
Authors: Lewis Jacob S
Published: November 2022

What determines support for separatist movements in Africa? The past two decades have seen a rise in separatism across Africa, including renewed Nigeria's Igbo Biafran nationalism. While a large body of work has focused on the behaviour of African separatist movements themselves, less work has examined the correlates of popular support for their claims and goals. This study does so, focusing on two important factors. First, it examines whether exposure to conflict events involving neo‐Biafran movements increases or decreases support for the claims made by the Indigenous Peoples of Biafra (IPOB). The study uses geo‐coded data from the Afrobarometer and ACLED datasets to measure proximate exposure and finds that more exposure correlates positively with support for secession. Second, it argues that the highest levels of support should be associated with members of ethnic groups that would dominate the proposed state. Drawing again from Afrobarometer, the study finds support for this.
Prevalence of food addiction among patients undergoing metabolic/bariatric surgery: A systematic review and meta‐analysis
Authors: Praxedes Dafiny R. , Silva‐Júnior André E. , Macena Mateus L. , Gearhardt Ashley N. , Bueno Nassib B.
Published: November 2022

Candidates for metabolic/bariatric surgery show a high prevalence of food addiction (FA). However, few studies have investigated FA prevalence after bariatric surgery, especially using longitudinal studies. This systematic review with a meta‐analysis aimed to determine pre‐ and postoperative prevalence of FA among patients undergoing metabolic/bariatric surgery. It included both cross‐sectional and longitudinal studies that used the Yale Food Addiction Scale (YFAS). The following databases were searched: MEDLINE, ScienceDirect, LILACS, PsycArticles, CENTRAL, greylit.org, and opengrey.eu. Studies that used the YFAS to evaluate FA in pre‐ or postoperative patients were included. A random‐effects meta‐analysis was performed with cross‐sectional studies to calculate the weighted prevalence of FA at the pre‐ and postoperative moments. For longitudinal studies, which measured FA at both time points for the same individuals, absolute prevalence reduction (APR) was calculated. Of the 6626 records, 40 studies were included in the meta‐analysis. The preoperative weighted prevalence of FA was 32% (95% CI: 27–37%; 33 groups), whereas the postoperative prevalence was 15% (95% CI: 12–18%; 14 groups). Seven longitudinal studies showed a weighted APR of 26 p.p. (95% CI: 10–41 p.p.). Observational data suggest a reduction in the prevalence of FA among patients that undergo bariatric surgery. Interventional studies are needed to confirm these findings.
Differences in gastrointestinal hormones and appetite ratings between individuals with and without obesity—A systematic review and meta‐analysis
Authors: Aukan Marthe Isaksen , Coutinho Silvia , Pedersen Sindre Andre , Simpson Melanie Rae , Martins Catia
Published: November 2022

Determining if gastrointestinal (GI) hormone response to food intake differs between individuals with, and without, obesity may improve our understanding of obesity pathophysiology. A systematic review and meta‐analysis of studies assessing the concentrations of GI hormones, as well as appetite ratings, following a test meal, in individuals with and without obesity was undertaken. Systematic searches were conducted in the databases MEDLINE, Embase, Cochrane Library, PsycINFO, Web of Science, and ClinicalTrials.gov. A total of 7514 unique articles were retrieved, 115 included in the systematic review, and 70 in the meta‐analysis. The meta‐analysis compared estimated standardized mean difference in GI hormones' concentration, as well as appetite ratings, between individuals with and without obesity. Basal and postprandial total ghrelin concentrations were lower in individuals with obesity compared with controls, and this was reflected by lower postprandial hunger ratings in the former. Individuals with obesity had a lower postprandial concentration of total peptide YY compared with controls, but no significant differences were found for glucagon‐like peptide 1, cholecystokinin, or other appetite ratings. A large methodological and statistical heterogeneity among studies was found. More comprehensive studies are needed to understand if the differences observed are a cause or a consequence of obesity.
Thermal stress exposure of pupal oriental fruit fly has strong and trait‐specific consequences in adult flies
Authors: Mutamiswa Reyard , Tarusikirwa Vimbai Lisa , Nyamukondiwa Casper , Cuthbert Ross N. , Chidawanyika Frank
Published: November 2022

Global climate change is projected to increase the incidence of heat waves, their magnitude and duration resulting in insects experiencing increasing environmental stress in both natural and managed ecosystems. While studies on insect thermal tolerance are rapidly increasing, variation across developmental or juvenile stress cross‐stage effects within and across generations remain largely unexplored. Yet in holometabolous insects, heat stress at an early developmental stage may influence performance and survival during later stages. Here, we investigated the effects of pupal mild heat stress on the performance of laboratory‐reared adult Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) measured as longevity, critical thermal maximum (CTmax), critical thermal minima (CTmin), heat knockdown time (HKDT) and chill coma recovery time (CCRT). Pupal heat stress significantly influenced performance of B. dorsalis adults resulting in impaired longevity and heat tolerance (CTmax and HKDT) in both sexes with improved and compromised cold tolerance (CTmin and CCRT) in females and males, respectively. These findings highlight the role of juvenile stages in mediating stress responses at adult stages. For B. dorsalis, pupal heat stress largely compromised thermal tolerance implying that the species has limited potential to shift its geographic range in heat prone areas. Significant benefits in cold tolerance in females following heat stress may help in improving survival in the cold in the short‐term despite restricted activity to the same traits in males. This study suggests that basal heat tolerance and not short‐term compensatory thermal plasticity following heat stress may have aided the recent invasion of B. dorsalis in African landscapes.
Poor prognostic impact of delirium: especially on mortality and institutionalisation
Authors: Tachibana Masako , Inada Toshiya
Published: November 2022

The course of delirium is associated with increased hospital costs, healthcare complications, increased mortality, and long‐term poor outcomes. Despite delirium being long recognised as one of the most important prognostic components of patients with illnesses, delirium remains poorly understood, effective management options are limited, and no effective treatment has yet been established. This review evaluated the effects of delirium on mortality, institutionalisation, and dementia in various situations to clarify its prognostic seriousness to elucidate important areas for clinical practice and future research. The effect of delirium on mortality in COVID‐19 patients was similar to that in other diseases. The effect of delirium on mortality in patients with delirium between the ages of 18 and 65 may be higher than in those with delirium aged over 65, but studies are scarce. Promoting recognition of delirium at all ages is needed. With careful attention to the specific factors in younger patients that contribute to delirium, healthcare providers may be able to decrease the poor impact of delirium on clinical outcomes. Evaluation of the association between interventions for delirium such as sedation in present clinical practice and the prognosis of delirium is lacking, and further clinical studies are essential.
Pattern, frequency and causes of tooth extraction among adult Syrian refugees
Authors: Salim Nesreen A. , Sawair Faleh A. , Abusidu Ziad , Sharaireh Aseel M. , Satterthwaite Julian D. , Hassona Yazan
Published: November 2022

Aims or Objectives

The Syrian crisis has resulted in a significant impact on refugee oral health status, but the scientific literature lacks information characterizing the pattern of tooth extraction in refugees.

Materials and Methods

The current study analyzed the pattern of tooth extraction and the associated sociodemographic factors among 626 (53.4% females, 46.6% males) Syrian refugees who were treated in dental clinics in the Zaatari camp. All adult Syrian refugees attending the dental unit at Zaatari camp were eligible to participate. Clinical and sociodemographic data were collected from the study sample using a validated semi‐structured survey over a period of 4 months. Descriptive statistics were generated and Chi‐square test, independent samplet‐test, ANOVA test and Bonferroni Post Hoc test were used to examine associations between the different variables.

Results

More than one third of the attendees (33.9%) were young adults (18–29 years), and nearly two thirds (69.8%) had no or very basic education. The mean number of teeth that needed extraction was (1.46 ± 0.84) and was significantly higher in males, smokers, older patients, and those with no or basic education. The most common cause for tooth extraction was dental caries (54.8%), followed by tooth fracture/un‐restorability (38.5%), and periodontitis (3.4%); while the least common reason was tooth extraction for orthodontic treatment (0.20%).

Conclusions

Dental caries and its sequelae were the leading cause of tooth extraction in this refugee population. Molar teeth were found to be the most frequently extracted and lower anteriors were the least. Older age, smoking, patients with lower educational level, poor oral hygiene and male gender all predispose to a higher incidence of tooth extractions.
Point‐of‐care ultrasound needs assessment in a paediatric acute care setting in Malawi
Authors: Moher Justin M. , Morales‐Pérez Liliana , Chiume Msandeni , Crouse Heather L. , Mgusha Yamikani , Betchani Fanuel , D'Amico Beth M. ,   the Pediatric Alliance for Child Health Improvement in Malawi at Kamuzu Central Hospital and Environs (PACHIMAKE) Consortium
Published: November 2022

Objective

To describe the use of point‐of‐care ultrasound (POCUS) in an acute‐care paediatric setting in Malawi, including clinical indications, types of examinations and frequency of positive findings.

Methods

Retrospective, cross‐sectional study of a convenience sample of POCUS examinations performed in one tertiary referral hospital in Lilongwe, Malawi over 1 year. POCUS examinations were performed by Paediatric Emergency Medicine physician consultants as part of routine clinical practice and at the request of local clinicians. Images were saved along with the clinical indication and physician interpretation for quality review. Ultrasounds performed by the radiology department and those examinations that were technically faulty, missing clinical application or interpretation were excluded.

Results

In total, 225 ultrasounds of 142 patients were analysed. The most common clinical indications for which examinations were completed were respiratory distress (23%), oedema (11.7%) and shock/arrest (6.2%). The most common examinations performed were cardiac (41.8%) and lung (15.1%), focused assessment with sonography in trauma (FAST; 12.9%) and ultrasound‐guided procedural examinations (9.8%). Pathology was identified in 68% of non‐procedural examinations. Cardiac examinations demonstrated significant pathology, including reduced cardiac function (12.8%), gross cardiac structural abnormality (11.8%) and pericardial effusion (10.3%).

Conclusions

POCUS was used for both clinical decision‐making and procedural guidance, and a significant number of POCUS examinations yielded positive findings. Thus, we propose that cardiopulmonary, FAST and procedural examinations should be considered in future for the POCUS curriculum in this setting.
A Modified Dissipation Equation for Reynolds Stress Turbulent Mixing Models
Authors: Griffond Jérôme , Soulard Olivier , Gréa Benoît-Joseph
Published: November 2022

A simple modification of the dissipation equation is proposed for augmented Reynolds stress models (RSM) devoted to the prediction of buoyancy-driven turbulent mixing at interfaces. It is based on the partition of the kinetic energy into a “directed” large-scale part related to the turbulence mass flux and a “nondirected” small-scale part internal to the interpenetrating fluid structures. Such a partition is a cornerstone of some two-fluid models but does not appear naturally in the RSM framework. Conditional averaging on the concentration is used as a simple way to provide an equivalent decomposition with the variables available in the augmented RSM. Defining a dissipation equation mimicking the “nondirected” energy rather than the full kinetic energy does not introduce any new coefficient, preserves the properties of the original RSM, and improves its transient behavior in response to a sudden acceleration of the flow. Connections can finally be drawn between the resulting model and two-scale models.
An Experimental and Numerical Investigation to Improve the Efficiency of Combustion Systems for Heavy-Duty Applications
Authors: Yadav Jaykumar , Pischinger Stefan , Schönfeld Sascha , Deppenkemper Kai
Published: November 2022

The European Union made new CO2 limits for heavy-duty vehicles mandatory in 2019, aiming to reduce the average tailpipe CO2 emissions by 15% in 2025 and by 30% in 2030, relative to the 2019 baseline. To meet these challenges, new technologies are needed to further reduce the fuel consumption of new heavy-duty trucks (“tank to wheel”) by using more efficient engines. The present study shows the pathways to improve thermal efficiency through better mixture formation and air utilization. This is achieved by designing a new piston bowl shape that has been numerically optimized iteratively to improve the air/fuel mixing by carefully considering the interaction between the fuel spray plume and the piston bowl. The CFD model was calibrated using data from experimental studies with a heavy-duty single-cylinder diesel engine in best efficiency and rated power operation. Heat transfer and turbulence models are studied to determine their influence on the combustion process and NOx emissions. Indicated thermal efficiency and air utilization were used to evaluate the performance of the piston bowl shape. For three different bowl shapes, the fuel spray interaction with the piston bowl was investigated and compared with the base bowl shape with a compression ratio CR = 18.3. Moreover, the effect of a higher CR of 21 on performance and mixture formation was analyzed for the optimized bowl shape. The higher CR of 21 was attained by geometrically similar reduction of the optimized piston bowl. The results of the numerical and experimental investigations show that a CR of 21 leads to an increase in the indicated thermal efficiency of ∼ 3% in absolute values.
Impact of Discharge Current Profiling on Ignition Characteristics of Hydrogen/Methane Blends
Authors: Jin Long , Leblanc Simon , Zhang Xiaoxi , Bastable Alex , Tjong Jimi , Zheng Ming
Published: November 2022

For future SI engines, the ignition processes of an air-fuel mixture are often subjected to a fuel-lean mixture of considerably higher density, high intake boost, and high compression ratio to further improve engine efficiency. The ignition systems for future gasoline engines should effectively ignite the mixture and secure the flame kernel until it develops into self-sustainable propagation. In this paper, the impact of discharge current profile on flame kernel formation and development processes of methane-hydrogen/air mixtures under engine-like conditions are experimentally investigated in a rapid compression machine.

The discharge current during the glow phase is modulated to change the energy discharge profiles. A Field-programmable gate array based multi-task control system is established to effectively control and stabilize the discharge current amplitude and duration for different ignition strategies. The ignition and combustion process are characterized via simultaneous high-speed direct imaging and in-cylinder pressure measurement. The ignition delay is analyzed with respect to the in-cylinder pressure under various boundary conditions such as fuel blending ratio and spark discharge parameters, with a focus on the efficacy of ignition strategies under various hydrogen/methane blending ratios.
Control-Oriented Reduced-Order Modelling of Conversion Efficiency in Dual-Layer Washcoat Catalysts With Accumulation and Oxidation Functions
Authors: Piqueras Pedro , Pla Benjamín , Sanchis Enrique José , García Elena
Published: November 2022

This work proposes a model for predicting conversion efficiency in multi-functional flow-through catalysts with dual-layer washcoat. The mass transfer is more relevant in these devices than in single-layer washcoats due to the additional transport steps between the catalytic layers. In addition, the different reaction mechanisms between layers make the concentration of the chemical species differ in each layer. To deal with this boundary while consiD+dering the need for real-time computation, a reduced-order explicit solver for the convective diffusive reaction transport of chemical species is presented for the case of dual-layer washcoats. Assuming one-dimensional quasi-steady flow, the solution procedure consisted of substituting the interfacial fluxes defining the diffusive source terms in the bulk gas and washcoat conservation equations by expressions that depend explicitly on the average concentration in the gas phase. The solution was then applied to model the performance of dual-layer oxidation catalysts with reductant accumulation in one washcoat layer, such as diesel oxidation catalyst (DOC) and ammonia slip catalyst (ASC) systems, during driving cycles. Firstly, the response of these catalysts was analyzed by comparing against experimental data and considering additional parameters provided by the model. Next, the importance of the mass transfer limitations was discussed to complete the analysis. The proposed model was compared with a simplified solver where the mass transfer steps were omitted, thus deteriorating the prediction capabilities in some driving cycle phases. Finally, a sensitivity study was performed to assess the impact of the mesh size on the prediction capabilities and computational requirements.
Cycle-Resolved Emissions Analysis of Polyfuel Reciprocating Engines via In-Situ Laser Absorption Spectroscopy
Authors: Schwarm Kevin K. , Minesi Nicolas Q. , Jeevaretanam Barathan , Enayati Sarah , Tsao Tsu-Chin , Spearrin R. Mitchell
Published: November 2022

A high-speed in-situ laser absorption sensor has been developed for cycle-resolved emissions analysis in the exhaust manifold of production-scale internal combustion engines. An inline sensor module, using optical fiber-coupling of interband and quantum cascade lasers, targets the fundamental rovibrational absorption lines of carbon monoxide and nitric oxide near 5 μm in wavelength. The sensor module was integrated into a commercial EPA-certified natural gas spark-ignition generator operated at 3,300 rpm for measurements of exhaust pulse temperature, CO, and NO concentrations at a rate of 10 kHz. Novel high-temperature optomechanical design enabled in-stream sensor coupling near the exhaust valve with local gas temperatures up to ∼1200 K and valve to sensor gas transit times on the order of milliseconds. Measurement results reveal high degrees of intra-cycle and cycle-to-cycle variations which are otherwise undetectable with standard emission gas analyzers. Sensor response to variations in fuel composition was evaluated by introduction of 1–10% NH3 or H2 into the natural gas fuel system. The effects of fuel blending on exhaust emissions of CO and NO were well-distinguished even at 1% volume fraction, and the sensor captured both intra-cycle and cycle-averaged emissions differences between the three fuel types. Measured concentrations of CO and NO ranged from 0.1–2.8% and 30–3500 ppm with detection limits of 0.07% and 26 ppm, respectively. The exhaust sensor presented here has potential for integration with real-time control systems to enable adaptive optimization of polyfuel internal combustion engines to meet the need for flexible, low-carbon, on-demand energy conversion.
Hydrogen Enriched Ammonia Engines: Assessment of Hydrogen Concentration in the Fuel Feed from the Laminar Flame Speed Viewpoint
Authors: Yan Yuchao , Liu Zhentao , Liu Jinlong
Published: November 2022

The global trend toward decarbonization is inspiring researchers to search for low or even zero carbon fuels for internal combustion engines. Ammonia (NH3) is considered a potential alternative fuel to conventional gasoline and diesel without carbon emissions. Although it is not an ideal fuel for use in engines due to its poor combustion properties, the use of hydrogen (H2), which has low ignition energy and can be decomposed from ammonia, as a combustion promoter can enhance its suitability for engine applications. A careful literature review indicates that the relatively few existing studies on NH3/H2 engines and the uncertainty of the NH3/H2 chemistry under typical high-temperature and high-pressure engine environments limit the determination of the ammonia-to-hydrogen ratio. However, this question is important when converting an existing engine to ammonia operation because it is related to compression ratio determination, aftertreatment design, ECU mapping, and on-board hydrogen production rate requirements. In other words, this outstanding question would affect the simultaneous design of other accessory systems and the development of ammonia engines. To increase the knowledge of the hydrogen concentration in the fuel feed of ammonia fueled engines in the engine community, this study discusses this question from the perspective of laminar flame speed (LFS), because it is closely related to reactivity, diffusivity, and exothermicity, which is a macroscopic parameter of premixed combustion and directly affects the efficiency and emissions of spark ignition engines. Specifically, the required proportion of hydrogen blended with ammonia is determined by comparing the NH3/H2 reaction time scale with the millisecond combustion time scale in typical engines. The results show that high temperature enhances the LFS of ammonia, hydrogen and their mixtures, while pressure has an inhibitory effect. In addition, increasing the compression ratio and avoiding fuel-lean operation are effective ways to improve the performance of ammonia combustion with less hydrogen. Considering the high required hydrogen consumption rate and the full load conditions that guarantee high combustion efficiency, off-road application may be a suitable scenario for ammonia-hydrogen engines. Before applying ammonia to automobiles, the technology for on-board hydrogen production should be effectively developed.
Method to Reach High Substitution of an Ammonia Fueled Engine Using Dual Fuel RCCI and Active Combustion Control
Authors: Chiera Domenico , Wood James , Jones Andrew , Buehner Michael , Polley Nolan , Hampson Gregory J.
Published: November 2022

The International Marine Organization (IMO) has a goal of reaching 40% reduction of GHG emissions by 2030 and target of a full 50% reduction in marine fleet wide GHG emissions by 2050, while other organizations and governments desire to develop a path to Net-Zero GHG emissions by no later than 2050. To accomplish this, engines with near zero GHG emissions must be developed now. In addition to new ships, there is a large existing fleet of diesel fueled engines in the market today which are candidates for retrofit. Ammonia fueling of a diesel engine using dual-fuel combustion represents a viable zero-carbon fuel and combustion strategy suitable for long-haul / heavy-duty transportation due to its favorable storage properties of liquid at low tank pressure.

The challenge, however, is ammonia is hard to ignite, slow to burn, and cool when it does burn which creates a significant challenge from a combustion point of view. Conventional dual fuel (CDF) will not be able to burn more than 50% NH3-Diesel ratios efficiently with acceptable combustion quality, thus, combustion enhancement is required to get ammonia to ignite and burn at higher substitution rates.

Woodward has developed a fueling and combustion control strategy using diesel pilot injection as the ignition source and combustion accelerant. And using RCCI combustion (Reactivity Controlled Compression Ignition) controlled by Active Combustion Control (ACC) high ammonia-diesel substitution ratios (GSR) is demonstrated to burn as fast or faster than the baseline diesel. With the proportional reduction of carbon in the fuel and an appropriate ammonia slip catalytic technology, it is demonstrated that ammonia can be used as a GHG reduction fuel in dual-fuel diesel engines which can contribute to reduction in GHG emissions proportional to the NH3 substitution ratio. This is a technology which can be deployed today on both retrofit of existing engines as well as on new engines to meet the marine fleet average GHG emissions goals.
Analysis of Combustion Characteristics and Tailpipe Emissions of Spark-Ignition Engines During the Three-Way Catalyst Warm-Up Phase
Authors: Piqueras Pedro , de la Morena Joaquín , Sanchis Enrique José , Pitarch Rafael
Published: November 2022

Emissions management in hybrid-electric vehicles can be particularly critical. This is due to the drop of exhaust temperature during the shut-off phases of the thermal engine, which can lead the aftertreatment system to fall below its activation temperature. Traditionally, spark-ignition engines have induced this activation by using late spark timings so that the end of combustion occurs close to the exhaust valve opening. However, this has a negative impact on engine thermal and combustion efficiencies (and therefore carbon dioxide emissions). In this paper, the impact of warm-up calibration on combustion and emissions management is analyzed. For this purpose, a fully instrumented 1.3-liter gasoline direct injection engine was tested for different spark calibration and ambient temperature conditions. The speed and load were controlled to represent similar conditions to those achieved in the first stages of a certification cycle. Emissions measurements were performed before and after the three-way catalyst to evaluate its activation. The results show that moderate spark timings are preferable at standard room temperature (25°C), while at cold ambient conditions the best results are found with more aggressive spark timings.
Using Machine Learning to Predict Derived Cetane Number and Fuel Similarity
Authors: Cowart Jim , Dickerson Terrence , McDaniel Andy , Luning Prak Dianne
Published: November 2022

Nearly four hundred different samples of jet and diesel fuels were used to train and test Machine Learning (ML) models for Derived Cetane Number (DCN – ASTM D6890) prediction using eight of the fuels’ physical properties as model inputs. Linear Regression (LR), Artificial Neural Networks (ANNs) and Gaussian based models all showed good performance predicting DCN with nominal prediction errors of 1 to 1.7 cetane numbers (CN). Shallow ANNs showed comparable prediction results as compared to LR, with the Gaussian Exponential Model yielding the best results overall. The DCN prediction models were exercised to observe the most critical-sensitive properties in the DCN prediction. Fuel density and T50 were seen to be the most important for both jet and diesel fuels. This result supports the usage of these two properties in cetane number prediction via the Cetane Index (CI) calculation (ASTM D976). Flash point and Tend of the distillation curve were of secondary importance. Additionally, jet fuel chemical composition data from 8 chemical fuel classes were applied to predict DCN. Adding the chemical composition data to the physical property data did not provide for improved DCN prediction. This result supports the coupling and connection between a fuel’s physical and chemical properties. An analysis of the most important (to DCN) fuel classes shows alkanes (high cetane) and alkyl-benzene (low cetane) components to be the most influential. Finally, fuel similarity was characterized using Self Organizing Maps (SOMs). The SOM map was trained for both jet and diesel fuels using physical properties alone. Different fuels (e.g. alternative Alcohol-to-Jet) were then applied to the SOM to test similarity. SOM Position and Quantization Error are shown to accurately characterize these fuels as significantly different than the conventional jet and diesel fuels used to establish the SOM.
Inducing Viscosity Effects Into Simple Spray Modeling for Flexible-Fuel Injection System of Diesel Engine
Authors: Liu Long , Mei Qihao
Published: November 2022

Diesel engine has contributed a lot to human’s life but also induced serious pollutant emission problems. Developing flexible-fuel diesel engine becomes an inexorable choice to cope with the increasingly stringent emission regulations. But various engine fuels have completely different viscosities, which have a great importance to the spray mixing characteristics. So understanding the effect of fuel viscosity on spray propagation process is significant to assess the influence of various fuels on combustion process and further adjust combustion strategy to maximize the efficiency of flexible-fuel diesel engine. However, the fuel viscosity effect was seldom considered in past simple spray modeling. Therefore, this study aims to optimize the simple spray modeling for the flexible-fuel injection system of diesel engine by inducing the fuel viscosity effects. Firstly, the Gaussian distribution characteristics of various engine fuels’ concentration are modified with the turbulent Schmidt number (Sc). Secondly, the influence of fuel viscosity on the fuel concentration distribution over the spray cross-sectional area is obtained. Finally, the newly-built spray model involving the fuel viscosity effects is validated experimentally. Results show that Sc decreases with the increasing fuel viscosity, and the higher fuel viscosity leads to the smoother fuel concentration distribution profile over spray cross-sectional area.
Parametric Studies of Deflagration-to-Detonation Transition in a Pre-Chamber/Main-Chamber System
Authors: Zhu Rui Xuan , Tang Shizhi , Lai Shuyue , Fang Xiaohang , Davy Martin , Xu Chao
Published: November 2022

Numerical simulations are performed to study the process of flame propagation through a small orifice and transition to detonation in a confined pre-chamber/main-chamber system. The numerical model solves the fully compressible Navier-Stokes equations by a high-order numerical algorithm on a dynamically adapting mesh, coupled with a single-step chemical-diffusive model for a stoichiometric ethylene-oxygen mixture. Four successive stages, namely laminar flame propagation, jet flame formation, flame distortion by shock waves, and transition to detonation, are observed. Parametric studies with varying nozzle diameters and initial temperatures are tested to investigate the effect of nozzle size and the stochasticity of deflagration-to-detonation transition (DDT). The results suggest that the case with a smaller nozzle size, d = 1.5 mm, requires a longer time for the flame to evolve and transition into a detonation. A small change in the initial temperature results in clear fluctuations of flame surface length in the turbulent flame regime. In addition, the case with the smaller orifice size is shown to be more sensitive to the initial temperature. Due to the stochastic nature of DDT, the time and location for detonation initiation vary in all cases. Nevertheless, the detonation mechanism remains the same and is independent of the small variations in the initial temperature or the orifice size.
Combustion and Flame Characteristics of Cl-ODH Byproduct Fuel Mixture With High CO2 Dilution
Authors: Nonavinakere Vinod Kaushik , Gore Matt , Fang Tiegang
Published: November 2022

This study investigates combustion performance of a CO2 rich fuel mixture containing ethane and methane as active species using a constant volume combustion chamber. This fuel is obtained as a byproduct of a chemical looping based oxidative dehydrogenation (Cl-ODH) process ethylene production. The byproduct gas mixture has a CO2 concentration of 40.79%, 39.49% ethane, and 4.88% methane by weight with other minor compounds. Using the fuel for energy extraction would improve the process efficiency of the ethane to ethylene conversion. After initial combustion modelling, the gas fuel mixture was reduced to just the major species: CO2, ethane, and methane. The mixture was then tested for flammability limits and combustion performance under spark-ignition conditions. Effects of ambient conditions like temperatures between 300 to 400 K with initial pressures from 1 to 10 bar were tested. The effects of stoichiometry were tested to understand flame velocities and heat release. The fuel mixture showed an overall reduced flame velocity compared to gasoline. Instability in combustion was believed to be caused by the dissociation of ethane under elevated conditions. At higher pressures, the flame produces lower cumulative heat release. Data from this study was used to modify a small-scale spark-ignition engine to use this fuel and produce usable energy.