bluuebunny/crossref_metadata_2025 huggingface dataset:
The linearized classical Boussinesq system on the half‐line
Authors: Johnston C. M. , Gartman Clarence T. , Mantzavinos Dionyssios
Published: January 2021

The linearization of the classical Boussinesq system is solved explicitly in the case of nonzero boundary conditions on the half‐line. The analysis relies on the unified transform method of Fokas and is performed in two different frameworks: (i) by exploiting the recently introduced extension of Fokas's method to systems of equations and (ii) by expressing the linearized classical Boussinesq system as a single, higher order equation, which is then solved via the usual version of the unified transform. The resulting formula provides a novel representation for the solution of the linearized classical Boussinesq system on the half‐line. Moreover, thanks to the uniform convergence at the boundary, the novel formula is shown to satisfy the linearized classical Boussinesq system as well as the prescribed initial and boundary data via a direct calculation.
Convergence rates of vanishing diffusion limit on conservative form of Hsieh's equation
Authors: Fan Long , Toureche Trouba Nafissa
Published: January 2021

The aim of this paper is to study the global unique solvability on Sobolev solution perturbated around diffusion waves to the Cauchy problem of conservative form of Hsieh's equations. Furthermore, convergence rates are also obtained as one of the diffusion parameters goes to zero. The difficulty is created due to conservative nonlinearity to enclose the uniform (in diffusion parameter) higher order energy estimates. However this kind of difficulty will not occur for both the nonconservative nonlinearity and fixed diffusion parameter. The more subtle mathematical analysis needs to be introduced to overcome the difficulties.
Development and validation of the good and evil character traits (GECT) scale
Authors: Jiao Liying , Yang Ying , Guo Zhen , Xu Yan , Zhang Heyun , Jiang Jiang
Published: January 2021

The present study describes the development and validation of the good and evil character traits (GECT) scale. A set of 3,614 good and evil moral character descriptors (i.e., moral and immoral character traits) was selected from a dictionary of contemporary Chinese language and daily life expressions and ultimately condensed into 55 items. Then, exploratory factor analysis (EFA) and parallel analysis (PA) were conducted to explore the structure and final items of the GECT with sample 1 (n = 350), resulting in 21 good items and 32 evil items. After that, in confirmatory factor analysis (CFA) with sample 2 (n = 350), the resulting factor structure was confirmed for the 53‐item scale (Study 1). Additionally, evidence of validity based on correlations with Honesty‐Humility and Dirty Dozen was demonstrated (Study 2). The implications of our findings for the assessment of good and evil characters and further theoretical exploration are discussed.
Time‐series analyses of firearm‐related Google searches and U.S. suicide rates 2004–2016
Authors: Capron Daniel W. , Andel Rita , Voracek Martin , Till Benedikt , Niederkrotenthaler Thomas , Bauer Brian W. , Anestis Michael D. , Tran Ulrich S.
Published: January 2021

Objective

The U.S. suicide rate has increased 35% since 1999. The role of the Internet has not been thoroughly investigated despite Internet use more than doubling from 1999 to present. The majority of U.S. suicide deaths are by firearm; however, there is no examination of the association between trends in firearm Internet searches and overall and firearm monthly suicide rates. We hypothesized that search strings related to firearm suicide would be significantly associated with monthly suicide rates (both all methods and firearm).

Methods

Google Trends provides data on request frequencies of searches. Twenty‐four search strings were examined representing possible searches by individuals considering firearm suicide and compared to U.S. suicide rates with time‐series modeling.

Results

In the time series with higher search volumes, consistent associations were found of negative cross‐correlation at lag +1.

Conclusions

Several searches appeared at least sensitive enough to consistently show associations with overall and firearm suicide rates in the following month. This novel finding should be followed up as the potential exists to predict suicide trends.
Active commuting to school among 36,781 Spanish children and adolescents: A temporal trend study
Authors: Gálvez‐Fernández Patricia , Herrador‐Colmenero Manuel , Esteban‐Cornejo Irene , Castro‐Piñero José , Molina‐García Javier , Queralt Ana , Aznar Susana , Abarca‐Sos Alberto , González‐Cutre David , Vidal‐Conti Josep , Fernández‐Muñoz Santiago , Vida Jerónimo , Ruiz‐Ariza Alberto , Rodríguez‐Rodríguez Fernando , Moliner‐Urdiales Diego , Villa‐González Emilio , Barranco‐Ruiz Yaira , Huertas‐Delgado Francisco Javier , Mandic Sandra , Chillón Palma
Published: January 2021

This study examines trends in the rates of active commuting to school (ACS) in Spanish children (n = 18 343; 8.93 ± 1.68) and adolescents (n = 18 438; 14.11 ± 1.58) aged 6‐18 years from 2010 to 2017. Given the study period included the economic crisis in Spain (2008‐2013), the second aim of this study was to compare ACS rates during and after the economic crisis. Data were obtained from 28 studies conducted across Spain. The overall trends in ACS were evaluated using multilevel logistic regression analysis. Among Spanish children and adolescents, the rates of ACS to school ranged around 60% between 2010 and 2017. The rates of ACS in Spanish youth did not change significantly during the 2010‐2017 period, except a sporadic increase in the rate of ACS in adolescents in 2012‐2013. No significant association between the ACS and the economic crisis time period in youth was found. As conclusion, the ACS remains stable in Spain during the last decade, which is a promising result regarding the evidenced decreasing trend in many countries. Further educational and policy strategies are important to continue promoting this behavior in children and adolescents in the long term.
The impact of integrated STEM modeling on elementary preservice teachers’ self‐efficacy for integrated STEM instruction: A co‐teaching approach
Authors: Johnson Todd M. , Byrd Kelly O. , Allison Elizabeth R.
Published: January 2021

The purpose of the current study was to evaluate the impact of co‐taught integrated STEM methods instruction on preservice elementary teachers’ self‐efficacy for teaching science and mathematics within an integrated STEM framework. Two instructional methods courses (Elementary Mathematics Methods and Elementary Science Methods) were redesigned to include STEM integration components, including STEM model lessons co‐taught by a mathematics and science educator, as well as a special education colleague. Quantitative data were gathered at three time points in the semester (beginning, middle, and end) from 55 preservice teachers examining teacher self‐efficacy for integrated STEM teaching. Qualitative data were gathered from a purposeful sample of seven preservice teachers to further understand preservice teachers’ perceptions on delivering integrated STEM instruction in an elementary setting. Quantitative results showed a significant increase in teacher self‐efficacy across all three time points. Item‐level analysis revealed that self‐efficacy for tasks involving engineering and assessment (both formative and summative) were low across time points, while self‐efficacy for tasks involving technology and flexibility were consistently high. Qualitative results revealed that the preservice teachers did not feel adequately prepared by university‐level science and mathematics courses, in terms of content knowledge and integration of science and mathematics for elementary students.
The Effect of Health Insurance Coverage on Homeownership and Housing Prices: Evidence from the Medicaid Expansion
Authors: Kuroki Masanori , Liu Xiangbo
Published: January 2021

Objective

Homeownership as a way of wealth accumulation is important for low‐income people and the U.S. government has implemented policy to encourage homeownership among low‐income people. This article investigates the effects of health insurance coverage among low‐income people on homeownership and house prices.

Methods

To estimate the causal effects of health insurance coverage, we exploit the Medicaid expansion provisions of the Affordable Care Act as a source of exogenous variation in health insurance coverage and use it as an instrumental variable.

Results

Using county‐level data from 2010 to 2018, this study finds that an increase in health insurance coverage among low‐income people results in an increase in homeownership rates and housing prices for bottom‐tier houses, and the results are robust.

Conclusion

Our study provides new evidence in supporting that higher shares of population with health insurance could increase both homeownership and house prices.
Does Disgust Drive Religious Freedom Attitudes? Experimental Results About the Context of Service Refusal Opinion
Authors: Djupe Paul A. , Lewis Andrew R. , Sokhey Anand E. , Burge Ryan P.
Published: January 2021

Objective

What factors shape public support for service refusals carried out in the name of the free exercise of religion? Existing analyses treat the businesses refusing to serve LGBT citizens as fungible. We hypothesize that the religious context does not matter and that reactions are consistent with the role of socialized disgust.

Methods

We engage the same experimental design in two 2019 samples, one of 800 Colorado adult residents and one of 1,010 Protestants. The 1 × 2 × 2 design enables a contrast between a control, conditions that vary the business between a florist and photographer, and conditions that vary the religious nature of the event.

Results

The results suggest that the religious nature of the context is immaterial and that reactions generally conform with the role of disgust, especially for those socialized to feel it—high attending evangelicals.

Conclusion

We affirm the importance of the context of service delivery for religious freedom attitudes and discuss the role of religion.
A phylogeny of the subfamilyThiotrichinae(Lepidoptera:Gelechiidae) with a revision of the generic classification based on molecular and morphological analyses
Authors: Lee Ga‐Eun , Han Taeman , Park Haechul , Qi Mujie , Li Houhun
Published: January 2021

Thiotrichinae are a subfamily of Gelechiidae with approximately 180 described species in five genera:CalliproraMeyrick,MacrenchesMeyrick,PalumbinaRondani,PolyhymnoChambers andThiotrichaMeyrick. The subfamily was established based on two species in a recent molecular phylogenetic study of Gelechiidae, but the monophyly of each genus and the phylogenetic relationships among the genera have not been tested. To address these questions, we performed the first phylogenetic analyses based on seven molecular markers (COI, EF‐1α, GAPDH, RpS5, CAD, Wg and MDH) and 95 morphological characters for 47 ingroup and 3 outgroup taxa. Each dataset was analysed separately and together using maximum likelihood, Bayesian inference and maximum parsimony methods. The maximum likelihood and Bayesian analyses produced nearly identical tree topologies for ingroup relationships, but the parsimony analysis yielded different results for some lineages. In all our analyses, Thiotrichinae formed a strongly supported monophyletic group with two other gelechiid genera,CnaphostolaMeyrick (Gelechiinae) andSemnostomaMeyrick (Apatetrinae). The genusMacrencheswas recognized as the sister‐group to all other species in this clade.Polyhymno + Calliprorawere found to be sister to all remaining ingroup taxa. The species‐rich groupThiotrichawas non‐monophyletic, and it clustered withPalumbina,CnaphostolaandSemnostoma. The type species ofThiotrichawas included in a monophyletic clade with a majority of congeneric species in the parsimony analyses, but the clade was divided into two groups in the model‐based results. The generic placement of two speciesThiotricha dissobolaMeyrick andT. pyrphoraMeyrick was not confirmed in this study and they were placed asincertae sedis. The monophyly ofPalumbinawas strongly supported by both molecular data and morphological evidence. Based on genetic and morphological affinities and examination of the type specimens, four genera are synonymized withThiotricha:BlastovalvaJansesyn.n.,Cnaphostolasyn.n.,HierangelaMeyricksyn.n.andSemnostomasyn.n.We propose two new genera for newly recognized two sub‐clades:Pulchralagen.n.andTenupalpagen.n., and 15 new combinations are made:Thiotricha adamantina(Meyrick)comb.n.,T. exalbida(Omelko & Omelko)comb.n.,Tenupalpa angustella(Omelko)comb.n.,T. biformis(Omelko)comb.n.,T. flavitermina(Kyaw, Yagi & Hirowatari)comb.n.,T. glenias(Meyrick)comb.n.,T. nephodesma(Meyrick)comb.n.,T. venustalis(Omelko)comb.n.,Pulchrala clidias(Meyrick)comb.n.,P. chujaensis(Park)comb.n.,P. elaeocarpiella(Kyaw, Yagi & Hirowatari)comb.n.,P. epiclista(Meyrick)comb.n.,P. melanacma(Bradley)comb.n.,P. panglycera(Turner)comb.n., andP. saulotis(Meyrick)comb.n.Revised generic concepts are provided in the study.

This published work has been registered on ZooBank,http://zoobank.org/urn:lsid:zoobank.org:pub:0E3C0EB5‐503C‐4ADC‐BE87‐A203230DE6CB.
Risk factors and clinical outcomes of tuberculosis among kidney transplant recipients in high endemic country
Authors: Thitisuriyarax Saranya , Vanichanan Jakapat , Udomkarnjananun Suwasin , Townamchai Natavudh , Jutivorakool Kamonwan
Published: January 2021

Background

Tuberculosis (TB) is considered as a challenge issue in solid organ transplant recipients because of high morbidity and mortality. Active TB after transplant mostly occurs from reactivation of latent infection. Understanding risk factors and clinical information of TB may provide an appropriate prevention and treatment strategies in this specific patient population, however data from high endemic area is scarce.

Methods

A matched single‐center, case‐control study was conducted in our institute. Cases were defined as newly diagnosed confirmed or clinical active TB in patients who underwent kidney transplant (KT) between April 1992 and October 2018. For each case, 5 controls were matched by age and sex. Risk factor associated with TB was determined using univariate and multivariate conditional logistic regression.

Results

Between study period, KT was performed in 787 patients. Twenty‐seven patients (3.43%) were diagnosed with active TB including 20 confirmed and 7 clinical diagnosed cases. The global incidence of TB in our population was 315 cases per 100 000 patients per year. Among 27 cases, pulmonary involvement was the most common (48.1%) followed by disseminated (18.5%), extrapulmonary (14.8%), pleura (11.1%) and pleuropulmonary (7.4%) TB. Allograft rejection was significantly associated with active TB (P < .001). The median onset duration of infection was 17 months (IQR, 4‐59 months) after KT. Twenty‐four (88.9%) patients received rifampicin containing regimen for treatment with median duration of 10 months (IQR, 6‐12 months). All patients were cured after complete treatment, however those with TB remained having unfavorable outcomes including higher all‐cause mortality and graft loss.

Conclusions

Incidence rate of TB in KT recipients is higher than normal population. Allograft rejection was identified as a significant risk factor. Increase unfavorable outcomes including graft loss and mortality were also observed among patients with TB.
Flourishing in water: the early evolution and diversification of plant receptor‐like kinases
Authors: Gong Zhen , Han Guan‐Zhu
Published: January 2021

Receptor‐like kinases (RLKs) play significant roles in mediating innate immunity and development of plants. The evolution of plant RLKs has been characterized by extensive variation in copy numbers and domain configurations. However, much remains unknown about the origin, evolution, and early diversification of plant RLKs. Here, we perform phylogenomic analyses of RLKs across plants (Archaeplastida), including embryophytes, charophytes, chlorophytes, prasinodermophytes, glaucophytes, and rhodophytes. We identify the presence of RLKs in all the streptophytes (land plants and charophytes), nine out of 18 chlorophytes, one prasinodermophyte, and one glaucophyte, but not in rhodophytes. Interestingly, the copy number of RLKs increased drastically in streptophytes after the split of the clade of Mesostigmatophyceae and Chlorokybophyceae and other streptophytes. Moreover, phylogenetic analyses suggest RLKs from charophytes form diverse distinct clusters, and are dispersed along the diversity of land plant RLKs, indicating that RLKs have extensively diversified in charophytes and charophyte RLKs seeded the major diversity of land plant RLKs. We identify at least 81 and 76 different kinase‐associated domains for charophyte and land plant RLKs, 23 of which are shared, suggesting that RLKs might have evolved in a modular fashion through frequent domain gains or losses. We also detect signatures of positive selection for many charophyte RLK groups, indicating potential functions in host–microbe interaction. Taken together, our findings provide significant insights into the early evolution and diversification of plant RLKs and the ancient evolution of plant–microbe symbiosis.
A prospective observational study of the incidence, natural history, and risk factors for intravenous immunoglobulin‐mediated hemolysis
Authors: Pendergrast Jacob , Armali Chantal , Callum Jeannie , Cserti‐Gazdewich Christine , Jiwajee Aziz , Lieberman Lani , Lau Wendy , Lin Yulia , Parmar Nagina , Pavenski Katerina , Riden Lorna Sampson , Shehata Nadine , Willie‐Ramharack Kezia , Tomlinson George , Tong Tik Nga , Binnington Beth , Branch Donald R. ,   The QUEST Research Program
Published: January 2021

Background

Intravenous Immune Globulin (IVIG) is used to treat numerous immune‐mediated and inflammatory conditions. There is growing awareness of hemolysis, occasionally severe, as a side‐effect of this therapy. While most cases are associated with anti‐A and/or anti‐B isoagglutinins, the frequency and mechanism of hemolysis remain poorly characterized.

Study Design and Methods

A prospective observational study was conducted to determine incidence, natural history and risk factors for IVIG‐mediated hemolysis. A total of 99 infusions of high‐dose IVIG (2 g/kg or higher) administered to 78 non‐group O patients were monitored and graded according to Canadian IVIG Hemolysis Pharmacovigilance Group. Serum ferritin and C3/C4 levels were monitored as indicators of macrophage activation and complement consumption, respectively. Supplementary investigations included assessment for ABO zygosity, Secretor status, FcR polymorphisms, eluate IgG subclass, monocyte monolayer assay, and a panel of cytokines.

Results

Hemolysis was observed in 32 of 99 (32%) of infusions, with 19 of 99 (19%) grade 2 or higher. Hemolysis was only apparent 5‐10 days after a completed IVIG infusion in 84% of cases and was associated with increases in serum ferritin without complement‐consumption. In univariate analysis, increased risk was observed in group AB patients, first‐time IVIG recipients, those not taking immuosuppressive medications, or patients treated with a specific IVIG brand; however, in multivariate analysis, product association was no longer observed. No other patient‐ or practice‐related risk factors were identified.

Conclusion

IVIG‐mediated hemolysis is common and frequently severe. Monitoring for 5‐10 days following an infusion should be considered in non‐O patients receiving high‐dose IVIG with known risk factors.
Veterinary Cooperative Oncology Group—Common Terminology Criteria for Adverse Events (VCOG‐CTCAE v2) following investigational therapy in dogs and cats
Authors: LeBlanc Amy K. , Atherton Matthew , Bentley R. Timothy , Boudreau C. Elizabeth , Burton Jenna H. , Curran Kaitlin M. , Dow Steven , Giuffrida Michelle A. , Kellihan Heidi B. , Mason Nicola J. , Oblak Michelle , Selmic Laura E. , Selting Kimberly A. , Singh Ameet , Tjostheim Sonja , Vail David M. , Weishaar Kristen M. , Berger Erika P. , Rossmeisl John H. , Mazcko Christina
Published: January 2021

The updated VCOG‐CTCAE v2 guidelines contain several important updates and additions since the last update (v1.1) was released in 2011 and published within Veterinary and Comparative Oncology in 2016. As the Veterinary Cooperative Oncology Group (VCOG) is no longer an active entity, the original authors and contributors to the VCOG‐CTCAE v1.0 and v1.1 were consulted for input, and additional co‐authors sought for expansion and refinement of the adverse event (AE) categories. VCOG‐CTCAE v2 includes expanded neurology, cardiac and immunologic AE sections, and the addition of procedural‐specific AEs. It is our intent that, through inclusion of additional authors from ACVIM subspecialties and the American College of Veterinary Surgery, that we can more comprehensively capture AEs that are observed during clinical studies conducted across a variety of disease states, clinical scenarios, and body systems. It is also our intent that these updated veterinary CTCAE guidelines will offer improved application and ease of use within veterinary practice in general, as well as within clinical trials that assess new therapeutic strategies for animals with a variety of diseases. Throughout the revision process, we strived to ensure the grading structure for each AE category was reflective of the decision‐making process applied to determination of dose‐limiting events. As phase I trial decisions are based on these criteria and ultimately determine the maximally tolerated dose, there is impact on standard dosing recommendations for any new drug registration or application. This document should be updated regularly to reflect ongoing application to clinical studies carried out in veterinary patients.
Risk of seropositivity to Coxiella burnetii in humans living in areas with endemically infected cattle: No way for specific prevention
Authors: Beaudeau Francois , Pouquet Marie , Guatteo Raphaël , Bareille Nathalie , Moret Leïla
Published: January 2021

Q fever, a zoonotic disease caused by Coxiella burnetii, is endemic among cattle in Western France. However, studies assessing the risk of human infection in such areas are lacking to date, while they may provide information about key specific preventive actions which could be advised to the human populations living with or close to cattle. Therefore, we conducted a cross‐sectional study in two departments of Western France during the 2017/18 winter in order to explore possible risk factors for seropositivity among two distinct populations, i) an occupational risk group, that is, the cattle farmers, and ii) the general adult population (approached by blood donors). Sera were collected in 176 cattle farmers and 347 blood donors respectively, and tested for phase I and II antibodies using an indirect immunofluorescence antibody assay. Each participant was asked to fill in a questionnaire containing socio‐demographic characteristics, occupational and non‐occupational risk exposure. Identified risk factors were: in the general population, working in contact with ruminants, comparatively to any other activity (OR = 4.41; 95% CI: [1.59–6.55]); among farmers, managing an itself infected cattle herd (OR = 3.20; 95% CI: [1.59–6.55]). No other controllable risk factor (lifestyle, outdoor activities, proximity to pets and livestock animals, occupational practices) was here evidenced. In areas with endemically infected cattle, human exposure to Coxiella burnetii is to some extent unavoidable. This strengthens the need for physicians' awareness of the symptoms of Q fever and the appropriateness of general biosecurity measures, especially among at‐risk groups living there.
Phylogeography and systematics ofAlgyroides(Sauria: Lacertidae) of the Balkan Peninsula
Authors: Strachinis Ilias , Poulakakis Nikos , Karaiskou Nikoleta , Patronidis Politis , Patramanis Ioannis , Poursanidis Dimitris , Jablonski Daniel , Triantafyllidis Alexandros
Published: January 2021

The area of the south‐western Balkans hosts a remarkably high species richness and has been considered a biodiversity hotspot. The significance of the Balkan Peninsula as a biodiversity refugium during the Quaternary climatic fluctuations has been repeatedly pointed out in literature, yet the area remains quite understudied in terms of phylogeography. Contributing to the biogeography and phylogeography of the Balkan area, we herein present the phylogeographic relationships within the lizards of the genusAlgyroides, focusing on the two species that occur in the Balkans (namely,A. nigropunctatusandA. moreoticus), including representatives ofDinarolacertaandLacertalizards as outgroups. We combined phylogenetic, phylogeographic and species distribution modelling analyses, using both mitochondrial and nuclear DNA data, in order to uncover the phylogeographic history of the genus and evaluate the validity of the extant taxonomy. Our results reveal three major clades withinAlgyroidesin southern Balkans; one corresponds toA. moreoticus, having sister group relationships with the genusDinarolacerta, and the other two toA. nigropunctatus, each corresponding to one of the morphological subspecies, which seem to be monophyletic, allopatric and reproductively isolated. These results expose an unprecedented phylogeographic pattern in the area of western Greece where the two major clades ofA. nigropunctatusmeet, and can contribute to a taxonomic re‐evaluation of the species. Moreover, questions are raised on the validity ofDinarolacertaas a genus due to it clustering within the genusAlgyroides.
Wolfgang Amadeus Mozart
Authors: Goddard Lalina
Published: January 2021

In dit tweede deel van de reeks Operatheek verkent musicologe Lalina Goddard Così fan tutte, de beroemde komische opera van Wolfgang Amadeus Mozart en librettist Lorenzo Da Ponte. Al sinds het begin verhit Così de gemoederen omdat Da Ponte’s immorele en zelfs misogyne tekst niet te rijmen zou vallen met Mozarts verheven muziek. Achtereenvolgens duikt dit boekje in de literaire rijkdom van het libretto en de speelse ironie van de compositie die onder het oppervlak schuilgaan. Lalina Goddard zoekt hierbij antwoorden op de prangende vragen rond gender en vrouwonvriendelijkheid in deze opera. Met deze handige luistergids neemt ze de nieuwsgierige lezer en luisteraar mee langs de vernuftigste muzikale vondsten en literaire knipogen.
Fabrication of Optical Fiber Sensors Based on Femtosecond Laser Micro Machining
Authors: Zhou Fengfeng , Jo Seunghwan , Fu Xingyu , Tsai Jung-Ting , Jun Martin Byung-Guk
Published: January 2021

In this research, we proposed fabrication process of optical fiber sensors using femtosecond laser and their applications. A beam of femtosecond laser was focused by an objective lens in the optical fiber. By testing different conditions, a group of machining parameters was found that achieve a minimum machining resolution of 3.2 μm. To ablate the core of the optical fiber, which is buried deep inside the cladding, precisely, part of the cladding was removed to expose the core as close as possible to the air. By making a complex pattern to modify the optical path of the laser inside an optical fiber, a sensitivity of 942.8–1015.6 nm per refractive index unit (nm/RIU) was obtained for liquid refractive index sensing. For another sensor, a sensitivity of 1.38 × 105 nm/RIU was obtained, which is high enough to detect small amount of refractive index change of air. It is known to be the first time that we fabricated a complex microstructure in an optical fiber to modify the propagation of the light using femtosecond laser. This research shows the possibility of a complex modification of light in an optical fiber using laser machining.
A Comprehensive Study on Burst Pressure Performance of Aluminum Liner for Hydrogen Storage Vessels
Authors: Kangal Serkan , Harun Sayı A. , Ayakdaş Ozan , Kartav Osman , Aydın Levent , Seçil Artem H. , Aktaş Engin , Yücetürk Kutay , Tanoğlu Metin , Kandemir Sinan , Beylergil Bertan
Published: January 2021

This paper presents a comparative study on the burst pressure performance of aluminum (Al) liner for type-III composite overwrapped pressure vessels (COPVs). In the analysis, the vessels were loaded with increasing internal pressure up to the burst pressure level. In the analytical part of the study, the burst pressure of the cylindrical part was predicted based on the modified von Mises, Tresca, and average shear stress criterion (ASSC). In the numerical analysis, a finite element (FE) model was established in order to predict the behavior of the vessel as a function of increasing internal pressure and determine the final burst. The Al pressure vessels made of Al-6061-T6 alloy with a capacity of 5 L were designed. The manufacturing of the metallic vessels was purchased from a metal forming company. The experimental study was conducted by pressurizing the Al vessels until the burst failure occurred. The radial and axial strain behaviors were monitored at various locations on the vessels during loading. The results obtained through analytical, numerical, and experimental work were compared. The average experimental burst pressure of the vessels was found to be 279 bar. The experimental strain data were compared with the results of the FE analysis. The results indicated that the FE analysis and ASSC-based elastoplastic analytical approaches yielded the best predictions which are within 2.2% of the experimental burst failure values. It was also found that the elastic analysis underestimated the burst failure results; however, it was effective for determining the critical regions over the vessel structure. The strain behavior of the vessels obtained through experimental investigations was well correlated with those predicted through FE analysis.
Bistability in Cylindrical Developable Mechanisms Through the Principle of Reflection
Authors: Butler Jared , Greenwood Jacob , Howell Larry L. , Magleby Spencer
Published: January 2021

We present a resource for designing bistable developable mechanisms (BDMs) that reach their second stable positions while exterior or interior to a cylindrical surface. Analysis of the necessary conditions to create extramobile and intramobile cylindrical BDMs is conducted through a series of three tests. These tests contain elements of both existing and new mechanism design tools, including a novel graphical method for identifying stable positions of linkages using a single dominant torsional spring, called the principle of reflection. These tests are applied to all possible mechanism cases and configurations to identify why certain configurations will always, sometimes, or never be a BDM. Two tables summarize these results as a guide when designing extramobile and intramobile BDMs. The results are compared and demonstrated with a numerical simulation of 30,000+ mechanisms, including several example mechanisms that illustrate the concepts discussed in the work. Discussion is then provided on the implication of these results.
Two-Dimensional Numerical Analysis of Non-Darcy Flow Using the Lattice Boltzmann Method: Pore-Scale Heterogeneous Effects
Authors: Takeuchi Yuto , Takeuchi Junichiro , Izumi Tomoki , Fujihara Masayuki
Published: January 2021

This study simulates pore-scale two-dimensional flows through porous media composed of circular grains with varied pore-scale heterogeneity to analyze non-Darcy flow effects on different types of porous media using the lattice Boltzmann method. The magnitude of non-Darcy coefficients and the critical Reynolds number of non-Darcy flow were computed from the simulation results using the Forchheimer equation. Although the simulated porous materials have similar porosity and representative grain diameters, larger non-Darcy coefficients and an earlier onset of non-Darcy flow were observed for more heterogeneous porous media. The simulation results were compared with existing correlations to predict non-Darcy coefficients, and the large sensitivity of non-Darcy coefficients to pore-scale heterogeneity was identified. The pore-scale heterogeneity and resulting flow fields were evaluated using the participation number. From the computed participation numbers and visualized flow fields, a significant channeling effect for heterogeneous media in the Darcy flow regime was confirmed compared with that for homogeneous media. However, when non-Darcy flow occurs, this channeling effect was alleviated. This study characterizes non-Darcy effect with alleviation of the channeling effect quantified with an increase in participation number. Our findings indicate a strong sensitivity of magnitude and onset of non-Darcy effect to pore-scale heterogeneity and imply the possibility of evaluating non-Darcy effect through numerical analysis of the channeling effect.
The Current-Carrying Tribological Properties of Cu/Graphene Composites
Authors: Zhao Jing , Peng Yitian , Zhou Qianguang , Zou Kun
Published: January 2021

Excellent current-carrying tribological properties including the low-friction, high anti-wear, high current-carrying efficiency, and stability are important for the current-carrying application in transmitting electrical signals and power. Here, the Cu/graphene composites with graphene uniformly distributed in Cu matrix were successfully prepared by combining the electroless plating process and powder metallurgy process. The current-carrying tribological properties including friction, wear, and electrical stability of the Cu/graphene composites with brass pairs were investigated by varying normal applied load and sliding speed under multiple applied voltages. The friction reduction and anti-wear properties of Cu/graphene composites were enhanced by the introduction of graphene. The friction coefficient of the Cu/graphene composites keeps stable under current-carrying and non-current-carrying conditions due to the benefit of the graphene enhancement to Cu. The graphene on wear surface reduces friction force and wear. The current-carrying efficiency and stability increased with the increase of applied load but decreased with increasing sliding speed. The contact stability increased with applied load, while high sliding speed caused the drastic vibration of sliding contact. The studies can provide a beneficial guideline for the current-carrying applications of Cu/graphene composites to reduce the friction and wear.
A Novel Structural Configuration of Modular Floating Wind Farms With Self-Adaptive Property
Authors: Zhang Yuming , Liu Haixiao
Published: January 2021

The present work proposes a novel structural configuration for floating wind farms after an investigation into the structural configurations of current floating wind farms. The uniqueness of the structural configuration lies in the ability to adjust its heading to wind inflow directions, i.e., the self-adaptive property. To verify the existence of the self-adaptive property, a structural design is performed, and a quasi-static framework to analyze the responses is established. To simplify the loads on wind turbines under yawed inflow conditions, empirical expressions for wind loads are proposed, based on which the quasi-static analysis is performed under the yawed inflow direction of 90 deg from the structural heading. The analytical result indicates that under yawed inflow conditions, the structural heading will eventually turn to align with the wind inflow direction on account of the structural configuration and the wind turbine control. Then, the effects of inflow wind velocity, initial offset, number of wind turbines, complex environmental conditions, and hydroelastic properties on the responses of the structure are investigated.
Numerical Study of a Solar-Powered Stirling Engine With a Transparent Top Cover
Authors: Sanmiguel-Rojas E. , Gutierrez-Castillo P. , Auñón-Hidalgo J. A.
Published: January 2021

The present work is focused on the numerical study of a solar-powered Stirling engine, with the particularity that the solar radiation is injected through a transparent top cover. Thus, the working fluid absorbs the heat across a porous layer of a steel woven wire screen placed alongside the inner side of the transparent wall. The engine output net power and efficiency are studied as a function of the porosity, engine speed, temperature of the expansion chamber, and wire diameter of the screen. It is found that the engine efficiency remains practically constant for porosity values over 0.7, but there is a relevant increase of the engine output net power compared to the same working conditions without the absorbing layer. For a given porosity value, the most significant increase of net power due to introducing the porous layer was reached when doubling the engine speed resulting in an increment close to 40%.
A New Approach to Modeling Slip and Work Input for Centrifugal Compressors
Authors: Harrison Herbert M. , Key Nicole L.
Published: January 2021

A new method of modeling slip factor and work input for centrifugal compressor impellers is presented. Rather than using geometry to predict the behavior of the flow at the impeller exit, the new method leverages governing relationships to predict the work input delivered by the impeller with dimensionless design parameters. The approach incorporates both impeller geometry and flow conditions and, therefore, is inherently able to predict the slip factor both at design and off-design conditions. Five impeller cases are used to demonstrate the efficacy of the method, four of which are well documented in the open literature. Multiple implementations of the model are introduced to enable users to customize the model to specific applications. Significant improvement in the accuracy of the prediction of slip factor and work input is obtained at both design and off-design conditions relative to Wiesner’s slip model. While Wiesner’s model predicts the slip factor of 52% of the data within ±0.05 absolute error, the most accurate implementation of the new model predicts 99% of the data within the same error band. The effects of external losses on the model are considered, and the new model is fairly insensitive to the effects of external losses. Finally, detailed procedures to incorporate the new model into a meanline analysis tool are provided in the appendices.
Experimental Investigation of the Effects of Squeeze Film Damper Design on Highspeed Rotor System
Authors: Iacobellis Vincent , Behdinan Kamran , Chan Dennis , Beamish Dave
Published: January 2021

Squeeze film dampers (SFDs) are used in highspeed rotordynamics systems to mitigate vibrations while traversing critical speeds. SFDs are critical in dissipating large amplitude motions and dynamic loading transferred from the rotor to the bearing supports during highspeed operation. Little testing on the effect of SFDs on rotor shafts under highspeed operating conditions is available in the literature. Thus, a SFD-rotor test rig has been designed and built to study the effect of SFD oil supply pressure, oil temperature, oil inlet feed number/orientation, unbalance, and seals on the response of a Jeffcott rotor. In this paper, the test rig is introduced along with its calibration through static and dynamic testing. It was found that the rotor displacement results were improved through the addition of trial masses to provide a runout correction and that using rubber supports for the support structure generated more symmetric results in the vertical and horizontal planes compared to steel supports. Initial results for the test rig are also presented for different unbalances with and without oil supply and with and without SFD end seals. In these cases, increased unbalance produced higher amplitude motion with a corresponding increase in critical speed and decrease in damping.
An Analysis of the Secondary Flow Around a Tandem Blade Under the Presence of a Tip Gap in a High-Speed Linear Compressor Cascade
Authors: Konrath Liesbeth , Peitsch Dieter , Heinrich Alexander
Published: January 2021

Tandem blades have often been under investigation, experimentally as well as numerically, but most studies have been about tandem blade stators without tip gap. This work analyzes the influence of a tip gap on the flow field of a tandem blade for engine core compressors. Experiments have been conducted in a high-speed linear compressor cascade on a tandem and a reference geometry. The flow is analyzed using five-hole probe measurements in the wake of the blades and oil flow visualization to show the near surface stream lines. First, the results for design conditions (tandem and conventional blade) are compared to measurements on corresponding blades without tip gap. Similarities and differences in the flow topology due to the tip clearance are analyzed, showing that the introduction of the tip clearance has a similar influence on the loss and turning development for the tandem and the conventional blade. The tandem blade features two tip clearance vortices with a complex flow interaction and the possible formation of a third counter-rotating vortex between them. An incidence variation from 0° to 5° for both blades indicate at first a similar behavior. After a separation of the flow field into gap and non-gap half it becomes apparent that the tandem blade shows higher losses on the gap side, while featuring a close-to-constant behavior on the non-gap side. Further investigation of the flow on the gap side shows indicators of the front blade exhibiting tip clearance vortex break down, while the rear blade seems unaffected.
Design Guidelines for Axial Turbines Operating With Non-Ideal Compressible Flows
Authors: Giuffre’ Andrea , Pini Matteo
Published: January 2021

The impact of non-ideal compressible flows on the fluid-dynamic design of axial turbine stages is examined. First, the classical similarity equation is revised and extended to account for the effect of flow non-ideality and compressibility. Then, the influence of the most relevant design parameters is investigated through the application of a dimensionless turbine stage model embedding a first-principles loss model. The results show that the selection of optimal duty coefficients is scarcely affected by the molecular complexity of the working fluid, whereas compressibility effects produce an offset in the efficiency trends and in the optimal flow coefficient. Furthermore, flow non-ideality can lead to either an increase or a decrease of stage efficiency of the order of 2–3% relative to turbines designed to operate in dilute gas state. This effect can be predicted at preliminary design phase through the evaluation of the isentropic pressure-volume exponent. 3D RANS simulations of selected test cases corroborate the trends predicted with the reduced-order turbine stage model.
Large Eddy Simulation of Laminar and Turbulent Shock/Boundary Layer Interactions in a Transonic Passage
Authors: Priebe Stephan , Wilkin Daniel , Breeze-Stringfellow Andy , Jothiprasad Giridhar , Cheung Lawrence C.
Published: January 2021

Shock/boundary layer interactions (SBLI) are a fundamental fluid mechanics problem relevant in a wide range of applications including transonic rotors in turbomachinery. This paper uses wall-resolved large eddy simulation (LES) to examine the interaction of normal shocks with laminar and turbulent inflow boundary layers in transonic flow. The calculations were performed using GENESIS, a high-order, unstructured LES solver. The geometry created for this study is a transonic passage with a convergent-divergent nozzle that expands the flow to the desired Mach number upstream of the shock and then introduces constant radius curvature to simulate local airfoil camber. The Mach numbers in the divergent section of the transonic passage simulate single stage commercial fan blades. The results predicted with the LES calculations show significant differences between laminar and turbulent SBLI in terms of shock structure, boundary layer separation and transition, and aerodynamic losses. For laminar flow into the shock, significant flow separation and low-frequency unsteadiness occur, while for turbulent flow into the shock, both the boundary layer loss and the low-frequency unsteadiness are reduced.
Effect of Backward Sweep on Aerodynamic Performance of a 1.5-Stage Highly Loaded Axial Compressor
Authors: Huang Song , Zhou Chuangxin , Yang Chengwu , Zhao Shengfeng , Wang Mingyang , Lu Xingen
Published: January 2021

As a degree of freedom in the three-dimensional blade design of axial compressors, the sweep technique significantly affects the aerodynamic performance of axial compressors. In this paper, the effects of backward sweep rotor configurations on the aerodynamic performance of a 1.5-stage highly loaded axial compressor at different rotational design speeds are studied by numerical simulation. The aim of this work is to improve understanding of the flow mechanism of backward sweep on the aerodynamic performance of a highly loaded axial compressor. A commercial CFD package is employed for flow simulations and analysis. The study found that at the design rotational speed, compared with baseline, backward sweep rotor configurations reduce the blade loading near the leading edge but slightly increases the blade loading near the trailing edge in the hub region. As the degree of backward sweep increases, the stall margin of the 1.5-stage axial compressor increase first and then decrease. Among different backward sweep rotor configurations, the 10% backward sweep rotor configuration has the highest stall margin, which is about 2.5% higher than that of baseline. This is due to the change of downstream stator incidence, which improves flow capacity near the hub region. At 80% rotational design speed, backward sweep rotor configurations improve stall margin and total pressure ratio of the compressor. It’s mainly due to the decreases of the rotor incidence near the middle span, which results in the decreases of separation on the suction surface. At 60% rotational design speed, detached shock disappears. Backward sweep rotor configurations deteriorate stall margin of the compressor, but increase total pressure ratio and adiabatic efficiency when the flow rate is lower than that at peak efficiency condition. Therefore, it’s necessary to consider the flow field structure of axial compressors at whole operating conditions in the design process and use the design freedom of sweep to improve the aerodynamic performance.
Nonlinear Modal Analysis of Frictional Ring Damper for Compressor Blisk
Authors: Sun Yekai , Yuan Jie , Denimal Enora , Salles Loïc
Published: January 2021

The use of integrally blisk is becoming popular because of the advantages in aerodynamic efficiency and mass reduction. However, in an integrally blisk, the lack of the contact interface leads to a low structural damping compared to an assembled bladed-disk. One emerging damping technique for the integrally blisk is based on the use of friction ring damper which exploits the contact interfaces at the underneath of the disk. In this paper, three different geometries of the ring dampers are investigated for damping enhancement of a blisk. A full-scale compressor blisk is considered as a case study where a node to node contact model is used to compute the contact forces. The dynamic behaviour of the blisk with the ring damper is investigated by using nonlinear modal analysis which allows a direct estimation of the damping generated by the friction interface. The damping performance for the different ring dampers are evaluated and compared. It appears that the damping efficiency as well as the shift in the resonant frequency for the different geometries are highly related to the nodal diameter and contact pressure/gap distributed within contact interface. The geometry of the ring damper has significant impact on the damping performance.