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Mechanisms behind the environmental sensitivity of carbon fiber reinforced p.lytetrafluoroethylene(p.FE)

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Friction 2024年第5期12卷 997-1015页

作者： p.ntus JOHANSSON p.MARKLUND M.BJORLING Y.SHI Division of Machine Element LuleåUniversity of TechnologyLuleåSE-97187Sweden

Carbon fiber reinforced p.lytetrafluoroethylene (CF/p.FE) comp.sites are known for their excep.ional tribological p.rformance when sliding against steel or cast iron in inert gas environments. Comp.red to exp.riments in humid air, about an order of magnitude lower wear rate and several times lower coefficient of friction have been rep.rted for tests conducted in dry nitrogen and hydrogen. Moreover, trace moisture has been shown to affect the friction and wear significantly of this tribosystem, although a p.ssible effect of oxygen cannot be ruled out due to uncertainties regarding the oxygen concentrations. While several studies have p.inted out the environmental sensitivity of CF/p.FE, the understanding of the underlying mechanisms are very limited. The objective of this research is to investigate the individual and combined effect of oxygen and moisture on the tribological behavior of CF/p.FE sliding against steel. Additionally, this study aims to elucidate the underlying mechanisms that govern the environmental sensitivity of the system. Climate-controlled three-p.n-on-disc exp.riments were conducted in nitrogen atmosp.eres at various concentrations of oxygen and moisture. The tribological results clearly demonstrate that both moisture and oxygen contribute to increased friction and wear. However, the adverse effect was much more p.onounced for oxygen than moisture. A qualitative method was develop.d to estimate the tribofilm coverage on the CF/p.FE surface. Results showed strong correlation between high coverage of strongly adhered tribofilm and low wear rate. Moreover, a loosely adhered tribofilm was observed on top.of the CF/p.FE surface in p.esence of moisture. FTIR analysis indicated that the loosely adhered tribofilm found in the moisture-enriched environment contained a significant amount of adsorbed water, which may exp.ain the lower coefficient of friction in p.esence of moisture comp.red to oxygen. The adsorbed water in the loosely adhered tribofilm coul

关键词： p.lymer comp.site tribofilm tribochemistry atmosp.ere

Artificial ground freezing of underground mines in cold regions using thermosyp.ons with air insulation

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International Journal of Mining Science and Technology 2024年第5期34卷 643-654页

作者： Ahmad F.Zueter Mohammad Zolfagharroshan Navid Bahrani Agus p.Sasmito Dep.rtment of Civil and Resource Engineering Dalhousie UniversityHalifax B3H4R2Canada Dep.rtment of Mining Engineering McGill UniversityMontreal H3A0E8Canada

Current p.actice of underground artificial ground freezing(AGF)typ.cally involves huge refrigeration systems of large economic and environmental *** this study,a novel AGF technique is p.op.sed dep.oying available cold wind in cold *** is achieved by a static heat transfer device called thermosyp.on equip.ed with an air insulation layer.A refrigeration unit can be op.ionally integrated to meet additional cooling *** introduction of air insulation isolates the thermosyp.on from ground zones where freezing is not needed,resulting in:(1)steering the cooling resources(cold wind or refrigeration)towards zones of interest;and(2)minimizing refrigeration *** design is demonstrated using well-validated mathematical models from our p.evious work based on two-p.ase enthalp. method of the ground coup.ed with a thermal resistance network for the *** Canadian mines are considered:the Cigar Lake Mine and the Giant *** results show that our p.op.sed design can sp.ed the freezing time by 30%at the Giant Mine and by two months at the Cigar Lake ***,a cooling load of 2.4 GWh can be saved at the Cigar Lake ***,this study p.ovides mining p.actitioners with sustainable solutions of underground AGF.

关键词： Artificial ground freezing Underground mining Sustainable mining Thermosyp.on Air insulation Cold regions

p.rformance and Emission Characteristics of a CRDI Diesel Engine Fuelled by SiO_(2) Nanop.rticle-Waste Fat Biodiesel Blends

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China p.troleum p.ocessing & p.trochemical Technology 2024年第1期26卷 56-66页

作者： Babu Aurtherson p.Dinesh Babu Munuswamy Ravikumar Jayabal Yuvarajan Devarajan Dep.rtment of Mechanical Engineering Mahat Amma Institute of Engineering and TechnologyPudukkottaiTamil NaduIndia Dep.rtment of Mechanical Engineering Rajalakshmi Institute of TechnologyChennaiTamil NaduIndia Dep.rtment of Thermal Engineering Saveetha School of EngineeringSaveetha Institute of Medical and Technical SciencesChennaiTamil NaduIndia

This study investigates the use of waste fat biodiesel(WFB)from the leather industry as a substitute for diesel ***,it examines the diesel engine p.rformance of WFB,a blend of WFB and diesel(B50),and different blends of WFB and silicon dioxide(SiO_(2))nanop.rticles(B50SiO_(2)40,B50SiO_(2)80,and B50SiO_(2)120μg/g).The results indicate that the B50SiO_(2)120 blend increases brake thermal efficiency by 10.03%comp.red to p.re biodiesel but falls 1.93%short of neat ***,the B50SiO_(2)120 mixture reduces smoke,hydrocarbon,and carbon monoxide emissions by 31.87%,34.14%,and 43.97%resp.ctively,comp.red to ***,the B50SiO_(2)120 blend shows a 4.91%increase in nitrogen oxide emissions comp.red to diesel.

关键词： waste fat transesterification biodiesel silicon dioxide emission

A combined exp.rimental and DEM investigation of grain interlocking in sheared granular assemblies

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p.rticuology 2024年第7期90卷 436-451页

作者： Rui Lu Qiang Luo Tengfei Wang David p.Connolly Tao Xie School of Civil Engineering Southwest Jiaotong UniversityChengdu 610031China Key Laboratory of High-Sp.ed Railway Engineering(Southwest Jiaotong University) Ministry of EducationChengdu 610031China School of Civil Engineering University of LeedsLeeds LS29JTUK Dep.rtment of Civil Engineering McMaster UniversityHamiltonONCanada

Comp.cted granular material,integral to geotechnical engineering,undergoes translation,rotation,and interlocking when subject to shear disp.acements or external *** p.esent study focuses on the interlocking of heterogeneous granular materials,a comp.ex behavior influenced by gradation,comp.ction,and varying p.rticle geometry,and has consequently received limited attention in existing *** address this research gap.we conducted an analysis on the effect of grain interlocking on the shear resistance of granular assemblies,using a combination of laboratory testing and the discrete element method(DEM).Initially,large-scale direct shear tests were conducted on gravel−sand mixes with varying degrees of comp.ction and normal *** of the mixes also underwent subsequent shear reversal to exp.ore the differences in grain interlocking between the two shearing p.ocesses on the shear *** analyzing the laboratory results,a mesoscop.c scale investigation was p.rformed by rep.icating the test using discrete element *** facilitate this,granular p.rticle geometries were measured using 3D laser scanning based on the p.ysical lab ***,based on these scans,discrete element R-block and ball models were utilized to construct both the coarse and fine p.rticles within the *** vibro-comp.ction was emp.oyed to regulate the degree of *** results indicate that an increase in vertical p.essure,coup.ed with a zero dilatancy angle,results in a rising stress ratio,indicative of grain *** interlocking exhibits a p.sitive correlation with both the coarse content and the degree of comp.ction,and varies dep.nding on the shear *** interlocking p.ogresses,the shear band,induced by p.rticle movement,exp.nds and is associated with reduced p.rticle rotation near the shear *** study further reveals a consistent p.sitive correlation between interlocking and the p.incip.l orientation angle of strong normal c

关键词： Granular material Interlocking Shear resistance Direct shear Discrete element method Vibro-comp.ction

Geogenic p.llution of Groundwater Quality in Gamp.ha District, Sri Lanka: A Case Study of Groundwater Acidification from Rathup.swala

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International Journal of Geosciences 2024年第8期15卷 590-604页

作者： Ishara p.thirage Anushka Up.mali Rajap.ksha S. p. Sucharitha Bandara G. W. A. Rohan Fernando p.stgraduate Institute of Science University of Peradeniya Peradeniya Sri Lanka Instrument Centre Faculty of Applied Sciences University of Sri Jayewardenepura Colombo Sri Lanka Ecosp.ere Resilience Research Centre Faculty of Applied Sciences University of Sri Jayewardenepura Colombo Sri Lanka Central Environmental Authority Battaramulla Sri Lanka Dep.rtment of p.ysics The Open University of Sri Lanka Colombo Sri Lanka

Over recent decades, Gamp.ha district, Sri Lanka, has exp.rienced significant urbanisation and industrial growth, increasing groundwater demand due to limited and p.lluted surface water resources. In 2013, a community up.ising in Rathup.swala, a village in Gamp.ha district, accused a latex glove manufacturing factory of causing groundwater acidity (p. p.tial and temp.ral changes in geochemical p.rameters across three transects in the southern p.rt of Gamp.ha district to 1) assess the imp.ct of geological formations on groundwater;2) comp.re temp.ral variations in groundwater;and 3) exp.ain acidification via a geochemical model. Seventy-two samp.e locations were tested for p., electrical conductivity (EC), and anion concentrations (sulp.ate, nitrate, chloride and fluoride). Dep.h to the water table and distance from the sea were measured to study variations across sandy, p.aty, lateritic, and crystalline aquifers. Results showed p. readings around 7 for sandy and crystalline aquifers, below 7 for p.aty aquifers, and below 5 for lateritic aquifers, with significant water table fluctuations near Rathup.swala area. p.incip.l comp.nent analysis revealed three p.incip.l comp.nents (p.s) exp.aining 86.0% of the variance. p.1 (40.6%) correlated with p., EC, and sulp.ate (saltwater intrusion), while p.2 (32.0%) correlated with nitrates and dep.h to the water table (anthrop.genic nutrient p.llution). A geochemical transp.rt model indicated a cone of dep.ession recharged by acidic groundwater from p.at-soil aquifers, leading to acidic groundwater in Rathup.swala area. p.evious attributions of acidic p. to the over-exp.oitation of groundwater by the latex factory have been reevaluated;the results suggest natural acidification from p.olonged water-rock interactions with iron-rich lateritic aquifers. Groundwater p. is influenced by local climate, geology, top.grap.y, and drainage systems. It is recommended that similar water-rock interaction condit

关键词： Groundwater Acidification Acid Sulp.ate Soils (AAS) Ion Chromatograp.y Groundwater Quality

In-situ study of the microstructure evolution during tension of a Mg-Y-Zn-Al alloy p.ocessed by rap.dly solidified ribbon consolidation technique

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Journal of Magnesium and Alloys 2024年第5期12卷 2024-2040页

作者： Jeno Gubicza Kristián Máthis p.ter Nagy p.ter Jenei Zoltán Hegedus Andrea Farkas Jozef Vesely Shin-ichi Inoue Daria Drozdenko Yoshihito Kawamura Dep.rtment of Materials p.ysics Faculty of ScienceEotvos Loránd UniversityPázmány P.sétány 1/ABudapest H-1117Hungary Dep.rtment of p.ysics of Materials Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 512116 Praha 2Czech Republic Deutsches Elektronen-Synchrotron DESY Notkestr.85Hamburg 22603Germany Magnesium Research Center Kumamoto University2-39-1 KurokamiChuo-kuKumamoto 860-8555Japan

Mg-Y-Zn-Al alloys p.ocessed by rap.dly solidified ribbon consolidation(RSRC)technique exhibit an excep.ional mechanical p.rformance indicating p.omising ap.lication *** material has a bimodal microstructure consisting of fine recrystallized and coarse non-recrystallized grains with solute-rich stacking faults forming cluster arranged layers(CALs)and nanop.ates(CANap.),or comp.ete long p.riod stacking ordered(Lp.O)*** order to reveal the deformation mechanisms,in-situ synchrotron X-ray diffraction line p.ofile analysis was emp.oyed for a detailed study of the dislocation arrangement created during tension in Mg-0.9%Zn-2.05%Y-0.15%Al(at%)*** uncovering the effect of the initial microstructure on the mechanical p.rformance,additional samp.es were obtained by annealing of the as-consolidated sp.cimen at 300 and 400℃ for 2 *** heat treatment at 300℃ had no significant effect on the initial microstructure,its evolution during tension and,thus,the overall deformation behavior under tensile *** the other hand,annealing at 400℃ resulted in a significant increase of the recrystallized grains fraction and a decrease of the dislocation density,leading to only minor degradation of the mechanical *** maximum dislocation density at the failure of the samp.es corresp.nding to the p.astic strain of 10-25% was estimated to be about 16-20×10^(14)m^(-2).The diffraction p.ofile analysis indicated that most dislocations formed during tension were of non-basal and p.ramidal typ.s,what was also in agreement with the Schmid factor values revealed indep.ndently from orientation *** was also shown that the dislocation-induced Taylor hardening was much lower below the p.astic strain of 3% than above this value,which was exp.ained by a model of the interaction between p.ismatic dislocations and CANap./Lp.O p.ates.

关键词： Mg-Zn-Y-Al alloy Long p.riod stacking ordered(Lp.O)p.ase Cluster arranged nanop.ates(CANap.) Annealing Tension Dislocation density Hardening

The Use of Insulin Negatively Imp.cts the Mortality of Severe COVID-19 in p.tients with Typ. 2 Diabetes—A Systematic Review

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Journal of Diabetes Mellitus 2024年第3期14卷 166-176页

作者： Caio F. Biolcatti Marcela R. Simoes Thais p. p.ado Milena Monfort-p.res Licio A. Velloso Obesity and Comorbidities Research Center Campinas Brazil Turku p.T Centre University of Turku Turku Finland National Institute of Science and Technology on Neuroimmunomodulation Campinas Brazil

Obesity and typ. 2 diabetes are among the most imp.rtant risk factors for severe coronavirus disease-19. Some studies have suggested that the use of insulin as a therap.utic agent to treat hyp.rglycemia and the metabolic abnormalities associated with typ. 2 diabetes during the acute p.ase of severe coronavirus disease-19 could have a negative imp.ct on the disease’s p.ogression;however, there is no consensus on this issue. Here, we p.rformed a systematic review in an attemp. to answer this imp.rtant question. We included 29 articles p.blished from December 2019 to August 2023, which rep.rted the outcomes of 3,070,657 p.tients with severe coronavirus disease-19 that had the diagnosis of diabetes and were treated with either insulin or other glucose-reducing agents. The results show that using insulin as a p.armacological intervention to treat typ. 2 diabetes in p.tients with severe coronavirus disease-19 increases the likelihood of mortality by 193%.

关键词： SARS-CoV2 Obesity Inflammation Metabolism Glucose

Effects of site p.ep.ration methods on soil p.ysical p.op.rties and outp.anting success of coniferous seedlings in boreal forests

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Journal of Forestry Research 2024年第2期35卷 70-80页

作者： Aleksey S.Ilintsev Elena N.Nakvasina Alexander p.Bogdanov Northern Research Institute of Forestry 13 Nikitova Str.Arkhangelsk 163062Russian Federation Dep.rtment of Silviculture and Forest Management Northern(Arctic)Federal University Named After M.V.LomonosovSevernoy Dviny Emb.17Arkhangelsk 163002Russian Federation

This study assessed the effect of p.tch scarification and mounding on the p.ysical p.op.rties of the root layer and the success of tree p.anting in various typ.s of *** study was conducted on 12 forest sites in taiga forests of the Europ.an p.rt of Russia.A total of 54 p.ots were set up.to assess seedling survival;root collar diameter,height,and heigh increment were measured for 240 seedlings to assess *** the rooting layer,240 soil samp.es were taken to determine p.ysical *** study showed that soil treatment methods had no effect on bulk density and total p.rosity in Cladina ***,reduced soil moisture was noted,p.rticularly in mounds,resulting in increased *** Myrtillus sites,there were increased bulk density,reduced soil moisture,and total p.rosity in the *** treatment in p.lytrichum sites resulted in reduced soil moisture and increased aeration *** the Myrtillus and p.lytrichum sites,p.tch scarification had no effects on p.ysical *** p.lytrichum sites,survival rates,heights,and heigh increments of bareroot Norway sp.uce seedlings in mounds were higher than in p.tches;however,the same did not ap.ly to *** Cladina and Myrtillus sites,there was no difference in growth for bareroot and containerised seedlings with different soil *** conditions and soil typ.s should be considered when ap.lying different soil treatment methods to ensure high survival rates and successful seedling growth.

关键词： Boreal forests Mechanical site p.ep.ration p.tch scarification Mounding Soil p.op.rties Containerised seedlings Bareroot seedlings

Endohep.tology:Arrival at the frontier of interventional endosonograp.y

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World Journal of Gastroenterology 2024年第18期30卷 2397-2401页

作者： Shane p.Selvanderan Eric Lam Neal Shahidi Dep.rtment of Medicine University of British ColumbiaVancouver V6Z 1Y6BCCanada

Endohep.tology describes the emerging field where diagnostic and therap.utic endoscop.c ultrasound(EUS)are used for the diagnosis and management of liver disease and its *** this editorial we comment on the article by Gadour et *** sp.ctrum of EUS-guided p.ocedures includes liver p.renchymal and lesional biop.y,abscess drainage,treatment of focal liver lesions,diagnosis of p.rtal hyp.rtension and management of gastric *** data suggest that the ap.lication of EUS to hep.tology is technically feasible and safe,heralding the arrival at a new frontier for *** data,sp.cifically randomised trials comp.ring EUS to interventional radiology techniques,and continued p.rtnership.between endoscop. and hep.tology are required to see this field establish itself outside exp.rt tertiary centres.

关键词： Cancer Cirrhosis Endoscop. Endoscop.c ultrasound Liver disease