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friction 2024年第9期12卷 2126-2138页

作者： Ainhoa GUiNEA Andrea AGiNAGALdE Wilson TATO iñigo LLAVORi Pablo GARCiA Leire ARRAiAGO Alaitz ZABALA Mechanical and industrial Production department Mondragon UnibertsitateaMondragon 20500Spain Orona EiC Orona IdeoHernani 20120Spain

The coefficient of friction(cof)between the deflection pulley and rope in a lift strongly affects the life span of the *** surface roughness is a key factor affecting the metallic pulley–rope cof.its effect on polymeric pulleys is *** present study analyses the effect of roughness and working conditions on cast polyamide 6(PA6G)deflection pulley–thermoplastic polyurethane(TPU)-coated rope *** statistical analysis revealed that the effect of surface roughness on the cof for low-load tests was *** present study contributes significantly to parameter selection in deflection pulley machining to minimise friction between the pulley and rope.

关键词： polymer-on-polymer friction roughness dry sliding

The effect of electrical current on lubricant film thickness in boundary and mixed lubrication contacts measured with ultrasound

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friction 2024年第8期12卷 1882-1896页

作者： Julio A.CAO-ROMERO-GALLEGOS Saeid TAGHiZAdEH Oscar A.AGUiLAR-ROSAS R.S.dWYER-JOYCE Leonardo i.fARfAN-CABRERA Tecnologico de Monterrey Escuela de Ingeniería y CienciasAve.Eugenio Garza Sada 2501MonterreyN.L.64849México department of Mechanical Engineering Leonardo Centre for TribologyUniversity of SheffieldSheffield S13JDUK

This work explores experimentally the effects of dC electrical currents on lubricant film thickness alteration in lubricated sliding steel contacts in the boundary and mixed regime as measured by *** experiments were performed in a two-electrode cell-based pin-on-disk tester instrumented with ultrasonic *** and electrified tribological tests were conducted on steel flat-on-flat contacts under various speeds and loads using both a mineral base oil and a gear *** thickness,coefficient of friction(cof),and electrical contact resistance(ECR)were measured during short experiments(30 s)in unelectrified and electrified(1.5 and 3 A)*** results suggest that film thickness,cof,and all ECR are altered by passing dC currents through the *** particular,film thickness increased and decreased,respectively,by applying electricity at the different speeds and loads *** alterations were majorly ascribed to oil viscosity decrease by local heat and surface oxidation caused by electrical discharge and break down at the interface.

关键词： electrified sliding ultrasonic measurement electric vehicles pin-on-disk

Grazing effects on vegetation dynamics in the savannah ecosystems of the Sahel

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Ecological Processes 2023年第1期12卷 752-763页

作者： Haftay Hailu Gebremedhn Ousmane Ndiaye Sylvanus Mensah cofélas fassinou Simon Taugourdeau Torbern Tagesson Paulo Salgado African Center of Excellence for Climate-Smart Agriculture and Biodiversity Conservation Haramaya UniversityP.O.Box 138Dire DawaEthiopia dispositif en Partenariat«Pôle Pastoralisme Et Zones Sèches» Route du Front de Terre BP 2057Pôle de Recherche de HannISRADakarSenegal Centre de Recherches Zootechniques de dahra Institut Sénégalais de Recherches AgricolesDakarSenegal Laboratoire de Biomathématiques et d’Estimations forestières Facultédes Sciences AgronomiquesUniversitéd’Abomey-CalaviCotonouBenin Chair of forest Growth and dendroecology Albert-Ludwigs-Universität FreiburgFreiburg Im BreisgauGermany facultédes Sciences et Techniques Département BVUniversitéCheikh-Anta-DiopDakarSenegal UMR SELMET CIRADINRAEInstitut Agro Univ MontpellierMontpellierFrance department of Physical Geography and Ecosystem Science Lund UniversitySölvegatan 1222362 LundSweden department of Geosciences and Natural Resource Management University of CopenhagenØster Voldgade 101350 CopenhagenDenmark

Background The savannah ecosystems of Sahel have experienced continuous and heavy grazing of livestock for centuries but still,their vegetation response to grazing pressure remains poorly *** this study,we analysed the herbaceous plant dynamics,measured by species diversity,composition,cover,and biomass in response to grazing pressure in the savannah ecosystems of *** Senegal,we selected four savannah sites represented with high,moderate,light and no grazing intensity *** survey methods were used for sampling the vegetation data within each of the *** richness and composition were analysed using species accumulation curve and multivariate ***,we used General Linear Models and a piecewise Structural Equation Model(pSEM)to examine the relationships between grazing intensity,vegetation cover,diversity and *** The herbaceous species diversity and composition varied significantly among the different grazing intensity levels(pies composition shifted from the dominance of grass cover to the dominance of forb cover with increasing grazing ***,the attributes of species diversity,herbaceous biomass,and ground cover were higher on sites with low grazing than sites with high and moderate grazing *** all sites,species diversity was positively related to total *** pSEM explained 37%of the variance in total biomass and revealed that grazing intensity negatively influenced total biomass both directly and indirectly through its negative influence on species *** Managing grazing intensity may lead to higher plant production and higher mixed forage establishment in the dryland savannah *** information can be used to support land management strategies and promote sustainable grazing practices that balance the needs of livestock with the conservation of ecosystem health and biodiversity.

关键词： Biomass Biodiversity diodella sarmentosa forb Grazing intensity invasive species Pastoral ecosystem Senegal West Africa

Modelling dynamic pantograph loads with combined numerical analysis

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Railway Engineering Science 2024年第1期32卷 81-94页

作者： f.f.Jackson R.Mishra J.M.Rebelo J.Santos P.Antunes J.Pombo H.Magalhaes L.Wills M.Askill School of Computing and Engineering University of HuddersfieldHuddersfieldUK School of Computing and Engineering Institute of Railway ResearchUniversity of HuddersfieldHuddersfieldUK idMEC Instituto Superior TecnicoUniversidade de LisboaLisbonPortugal iSEL Instituto Politecnico de LisboaLisbonPortugal Hitachi Rail Newton AycliffeUK Wabtec/Brecknell Willis ChardUK

Appropriate interaction between pantograph and catenary is imperative for smooth operation of electric *** heights of overhead lines to accommodate level crossings,overbridges,and tunnels pose significant challenges in maintaining consistent current collection performance as the pantograph aerodynamic profile,and thus aerodynamic load changes significantly with operational *** research aims to analyse the global flow characteristics and aerodynamic forces acting on individual components of an HSX pantograph operating in different configurations and orientations,such that the results can be combined with multibody simulations to obtain accurate dynamic insight into contact ***,computational fluid dynamics simulations are used to investigate the pantograph component loads in a representative setting,such as that of the recessed cavity on a Class 800 *** an aerodynamic perspective,this study indicates that the total drag force acting on non-fixed components of the pantograph is larger for the knuckle-leading orientation rather than the knuckle-trailing,although the difference between the two is found to reduce with increasing pantograph *** the aerodynamic loads acting on individual components with multibody tools allows for realistic dynamic insight into the pantograph *** results obtained show how considering aerodynamic forces enhance the realism of the models,leading to behaviour of the pantograph-catenary contact forces closely matching that seen in experimental tests.

关键词： Pantograph-catenary interaction Pantograph aerodynamics Computational fluid dynamics Pantograph loads Current collection performance

Covalent organic framework/carbon black/molecularly imprinted polydopamine composites for the selective recognition and electrochemical detection of ciprofloxacin

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food Science and Human Wellness 2024年

作者： Yufeng Sun Yongfeng Chen Xiaomin Pang Geoffrey i.N.Waterhouse Xuguang Qiao Zhixiang Xu Key Laboratory of food Processing Technology and Quality Control in Shandong Province， College of food Science and Engineering， Shandong Agricultural University School of Chemical Sciences， The University of Auckland

in this work， a novel electrochemical sensor based on covalent organic framework@carbon black@molecularly imprinted polydopamine （cof@CB@MPdA） was developed for selective recognition and determination of ciprofloxacin （Cf）. cof@CB@MPdA possessed good water dispersibility and was synthesized by the self-polymerization of dopamine under alkaline conditions in the presence of the cof， CB and Cf. The high surface area cof enhanced the adsorption of Cf， whilst CB gave the composites high electrical conductivity to improve the sensitivity of the proposed cof@CB@MPdA/GCE sensor. The specific recognition of Cf by cof@CB@MPdA involved hydrogen bonding and van der Waals interactions. Under optimized conditions， the sensor showed a good linear relationship with Cf concentration over the range 5.0 × 10-7mol/L and 1.0 × 10-4mol/L， with a limit of detection （LOd） of 9.53 × 10-8mol/L. further， the developed sensor exhibited high selectivity， repeatability and stability for Cf detection in milk and milk powders. The method used to fabricate the cof@CB@MPdA/GCE sensor could be easily adapted for the selective recognition and detection of other antibacterial agents and organic pollutants in the environment.

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facile synthesis of magnetic covalent organic framework nanocomposites for the enrichment and quantification of trace organophosphorus pesticides in fruit juice

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food Science and Human Wellness 2024年

作者： Quanbin fu Xin Sun Lu Liu Hailong Jiang Geoffrey i.N.Waterhouse Shiyun Ai Rusong Zhao School of Chemical Sciences， The University of Auckland College of Chemistry and Material Science， Shandong Agricultural University Qilu University of Technology (Shandong Academy of Sciences)， Shandong Analysis and Test Center， Key Laboratory for Applied Technology of Sophisticated Analytical instruments of Shandong Province College of food Science and Engineering， Shandong Agricultural University

Organophosphorus pesticides (OPPs) in foods pose a serious threat to human health， motivating the development of novel analytical methods for their rapid detection and quantification. A magnetic covalent organic framework (M-cof) adsorbent for the magnetic solid-phase extraction (MSPE) of OPPs from foods was reported. M-cof was synthesized by the Schiff base condensation reaction of 1，3，5-tris (4-aminophenyl)benzene and 4，4-biphenyldicarboxaldehyde on the surface of amino-functionalized magnetic nanoparticles. density–functional theory (dfT) calculations showed that adsorption of OPPs onto the surface of M-cof.involved hydrophobic effects， Van der Waals interactions， π–π interactions， halogen-N bonding， and hydrogen bonding. Combined with gas chromatography–mass spectrometry (GC–MS) technology， the MSPE method features low limits of detection for OPPs (0.002–0.015 μg/L)， good reproducibility (1.45%–6.14%)， wide linear detection range (0.01–1 μg/L， R≥ 0.9935)， and satisfactory recoveries (87.3%–110.4%). The method was successfully applied for the trace analysis of OPPs in spiked fruit juices.

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Electro-tribological properties of diamond like carbon coatings

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friction 2020年第2期8卷 451-461页

作者： iñigo BRACERAS iñigo iBÁNEZ Santiago dOMiNGUEZ-MEiSTER Xabier VELASCO Marta BRiZUELA iñaki GARMENdiA Tecnalia Research&innovation Mikeletegi Pasealekua 2Donostia-San Sebastian 20009Spain Mechanical Engineering department University of the Basque Country UPV/EHUPlaza de Europa1Donostia-San Sebastian 20018Spain

diamond like carbon(dLC)coatings typically present good self-lubricating tribological properties that could be of interest in sliding dielectric contacts in multiple electrical *** this work electro-tribological studies have been performed on several dLC coatings against aluminum in different humidity conditions,in which the coefficients of friction(cofs)and electrical contact resistance(ECR)were continuously *** show that cof and ECR data can be linked to the properties of the coatings(thickness,finishing,microstructure,residual stresses,and wettability)and the degradation modes of their tribological and electrical ***,electro-tribological data can provide valuable information about the performance of dielectric coatings,the reasons behind it,and assist in the development of the *** also shows potential for on-line monitoring of coated parts in operation.

关键词： dLC electro-tribology ECR-electrical contact resistance coefficient of friction

核桃膳食对老年人诊室和24h动态血压的影响

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中华高血压杂志 2019年第5期27卷 499-499页

作者： domènech M Serra-Mir M Roth i freitas-Simoes T VallsPedret C cofán M López A Sala-Vila A Calvo C Rajaram S SabatéJ Ros E 刘青叶鹏不详

食用坚果可降低血液中的胆固醇,并与心血管病的减少相关,但对血压的影响则不一致。研究者评估了在参加核桃和健康老龄化研究的独立生活的老年人中,2年核桃膳食与对照膳食对诊室血压和24h动态血压的影响,这是一项评估占能量摄入≈15%的... 详细信息

食用坚果可降低血液中的胆固醇,并与心血管病的减少相关,但对血压的影响则不一致。研究者评估了在参加核桃和健康老龄化研究的独立生活的老年人中,2年核桃膳食与对照膳食对诊室血压和24h动态血压的影响,这是一项评估占能量摄入≈15%的核桃对年龄相关疾病影响的随机试验。在预先设定的分析中,研究者招募了305名参与者,其中236名(75%)完成了研究(65%为女性,年龄为69岁,60%为轻度高血压)。参与者对核桃膳食耐受性良好,依从率>98%。平均基线诊室血压为128/79mmHg(lmmHg=0.133kPa)。

关键词： 24h动态血压老年人核桃膳食诊室健康老龄化轻度高血压心血管病

Pyrenetetraone-based covalent organic framework as an effective electrocatalyst for oxygen reduction reaction

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Nano Research 2022年第5期15卷 3907-3912页

作者： Paloma Garcia-Arroyo Emiliano Martinez-Perinan Jorge J.Cabrera-Trujillo Elena Salagre Enrique G.Michel Jose i.Martinez Encarnacion Lorenzo Jose L.Segura departamento de Quimica Organica i Facultad de CC.QuimicasUniversidad Complutense de Madrid28040 MadridSpain departamento de Quimica Analitica y Analisis instrumental Facultad de CienciasUniversidad Autónoma de Madrid28049 MadridSpain departamento de fisica de la Materia Condensada Universidad Autónoma de Madrid28049 MadridSpain Condensed Matter Physics Center(ifiMAC) Universidad Autónoma de Madrid28049 MadridSpain departamento de Nanoestructuras SuperficiesRecubrimientos y Astrofisica MolecularInstituto de Ciencia de Materiales de Madrid(ICMMCSIC)28049 MadridSpain instituto Madrileno de Estudios Avanzados en Nanociencia(iMdEA-Nanociencia) 28049 MadridSpain institute for Advanced Research in Chemical Sciences(iAdChem) Universidad Autonoma de Madrid28049 MadridSpain

A novel porous and crystalline two-dimensional(2d)electrochemically active covalent organic framework(cof)based on ortho-quinone units has been prepared as an innovative approach towards the development of organic cathode materials with multiple redox sites as an efficient electrocatalyst for the oxygen reduction reaction(ORR).in contrast with most of the previously reported cofs as electrocatalysts for the ORR,the electrocatalytic application of this material towards ORR has been investigated without adding any metal or conductive supporting material and avoiding any additional carbonization ***,the electrochemical properties of the cof material have been compared with two analogue amorphous frameworks with similar chemical composition,which points out the important role of the enhanced crystallinity and porosity of the cof network in its superior performance as an electrocatalyst towards ORR.

关键词： electrocatalysis oxygen reduction reaction metal free pyrenetetraone covalent organic framework

Tribological behavior of friction stir processed SiP/ZA40 in-situ composites

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Transactions of Nonferrous Metals Society of China 2020年第11期30卷 3043-3057页

作者： f.RAJABi R.TAGHiABAdi M.H.SHAERi department of Materials Science and Metallurgy Imam Khomeini International University(IKIU)QazvinIran

The effect of friction stir processing(fSP)at different rotation speeds(400,630,800,and 1000 r/min)and traverse speeds(25 and 50 mm/min)on the tribological properties of a Si particle reinforced Zn−40Al−2Cu-based in-situ composite was *** preliminary optimization,800 r/min and 25 mm/min were selected as optimum fSP *** to the results,multi-pass fSP improved the tribological *** instance,at an applied pressure of 0.75 MPa,the wear rate and average coefficient of friction(cof)of four-pass fSPed composite were lower than those of base composite by 53%and 50%,*** examinations of worn surfaces,wear debris,and worn subsurfaces revealed that the intensive refinement and uniform distribution of microstructural phases,especially the coarse Si particles,reduced Si particles interspacing,and elimination of casting defects were the most important factors enhancing the substrate resistance against sliding-induced *** led to the formation of stable tribolayers that improved the tribological properties.

关键词： Zn−40Al−2Cu alloy silicon composite tribology friction stir processing