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Cementite Characterization with Chromium and Vanadium Contents Using Indentation Technique

Journal of Iron and Steel Research International 2015年第4期22卷 366-370页

作者： john jairo coronado Sara Aida RODRGUEZ Research Group of Fatigue and Surfaces School of Mechanical EngineeringUniversity of Valle

Cast irons with some kinds of cementite with different chromium and vanadium contents were character- ized. Fracture toughness was determined by using an indentation technique, along with microhardness and elastic modulus. The results show that at the load of 1 N, microhardness of the cementite with 5.1% Cr is 10.53 GPa, the microhardness for cementite with 9.2% Cr increased to 11.25 GPa and for cementite with 4.5% V the microhard- ness is 9.18 GPa. The cementite with 9.2% Cr presented the highest elastic modulus of 230.4 GPa and the cement- ire with 4% V presented the lowest value of 201.32 GPa. Cementite with 5.1% Cr presented higher fracture tough- ness than cementite with 9.2% Cr; however, cementite with 4.5% V presented the highest fracture toughness of 2.74 MPa ·m1/2 and the lowest brittleness index of 3.35 μm-1/2.

关键词： cementite microhardness elastic modulus fracture toughness indentation technique

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A New SPME Thermal Desorption Interface for HPLC

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Journal of Analytical Sciences, Methods and Instrumentation 2013年第4期3卷 219-266页

作者： john jairo Ríos Acevedo Mohamed Nour Kayali Sayadi Luis María Polo Díez Department of Analytical Chemistry Faculty of Chemistry Complutense University of Madrid Madrid Spain Mass Spectrometry Unit Faculty of Chemistry Complutense University of Madrid Madrid Spain.

A new SPME/HPLC interface is developed. It is based on thermal desorption from the SPME fiber and organic solvent collection of the desorbed analytes by sweeping them with an argon flow into a small organic solvent volume which is further injected into the HPLC chromatograph. Extraction and desorption parameters were investigated using five PAHs of different volatilities (naphthalene, acenaphthalene, fluorene, phenanthrene and anthracene) as test compounds and fluorimetric detection. Regression coefficients closed to 0.99 with RDS = 3) and detection limits in the range 0.07 - 0.99 μg.L-1 were found. A method was applied to determine the above PAHs in water samples. The results were compared with those supplied by the 550.1 EPA method showing the agreement of both methods at the 0.05 significance level.

关键词： SPME-HPLC-FLD SPME-HPLC Interface Polynuclear Aromatic Hydrocarbons

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Nanowrinkled Carbon Aerogels Embedded with FeN_(x) Sites as Effective Oxygen Electrodes for Rechargeable Zinc-Air Battery

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Research 2019年第1期2019卷 1-13页

作者： Ting He Bingzhang Lu Yang Chen Yong Wang Yaqiang Zhang john L.Davenport Alan P.Chen Chih-Wen Pao Min Liu Zhifang Sun Alexander Stram Alexander Mordaunt jairo Velasco Jr Yuan Ping Yi Zhang Shaowei Chen State Key Laboratory for Powder Metallurgy College of Chemistry and Chemical EngineeringCentral South UniversityChangsha 410083China Department of Chemistry and Biochemistry University of California1156 High StreetSanta CruzCalifornia 95064USA Department of Chemical and Materials Engineering University of AlbertaEdmontonAlbertaCanada T6G 1H9 Department of Physics University of California1156 High StreetSanta CruzCalifornia 95064USA X-Ray Absorption Group National Synchrotron Radiation Research CenterHsinchu 30076Taiwan Institute of Super-Microstructure and Ultrafast Process in Advanced Materials School of Physics and ElectronicsCentral South UniversityChangsha 410083China Key Laboratory of Materials Processing and Mold(Zhengzhou University) Ministry of EducationZhengzhou 450002China

Rational design of single-metal atom sites in carbon substrates by a flexible strategy is highly desired for the preparation of high-performance catalysts for metal-air *** this study,biomass hydrogel reactors are utilized as structural templates to prepare carbon aerogels embedded with single iron atoms by controlled *** tortuous and interlaced hydrogel chains lead to the formation of abundant nanowrinkles in the porous carbon aerogels,and single iron atoms are dispersed and stabilized within the defective carbon skeletons.X-ray absorption spectroscopy measurements indicate that the iron centers are mostly involved in the coordination structure of FeN_(4),with a minor fraction(ca.1/5)in the form of FeN_(3)***-principles calculations show that the FeN_(x) sites in the Stone-Wales configurations induced by the nanowrinkles of the hierarchically porous carbon aerogels show a much lower free energy than the normal *** resulting iron and nitrogen-codoped carbon aerogels exhibit excellent and reversible oxygen electrocatalytic activity,and can be used as bifunctional cathode catalysts in rechargeable Zn-air batteries,with a performance even better than that based on commercial Pt/C and RuO_(2) *** from this study highlight the significance of structural distortions of the metal sites in carbon matrices in the design and engineering of highly active single-atom catalysts.

关键词： Oxygen charge skeleton

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Event-based hydrology and sedimentation in paired watersheds under commercial eucalyptus and grasslands in the Brazilian Pampa biome

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International Soil and Water Conservation Research 2021年第2期9卷 180-194页

作者： Ederson Diniz Ebling Jose Miguel Reichert Jhon jairo Zuluaga Pelaez Miriam Fernanda Rodrigues Mirian Lago Valente Rosane Barbosa Lopes Cavalcante Paolo Reggiani Raghavan Srinivasan Soils Department Universidade Federal de Santa MariaAvenida Roraima1000 Bairro CamobiSanta MariaRS97105-900Brazil Corporacion Colombiana de Investigacion Agropecuaria(AGROSAVIA) Centro de Investigacion NataimaEspinalColombia CMPC Celulose Riograndense Rua Sao Geraldo1680GuaibaRS92500-000Brazil Department of Civil Engineering University of SiegenPaul Bonatz Strasse 9-11Siegen D57068Germany Department of Ecology and Conservation Biology Texas A&M University(TAMU)534 John Kimbrough Blvd.Room 305College StationTX77843-2120USA Current address:Instituto Tecnologico Vale.Rua Boaventura da Silva 955UmarizalBelemPABrazil.

Ecological and hydrological impacts are expected when watersheds are under commercial *** this study we evaluated event-based hydrology and sedimentation in paired watersheds under commercial eucalyptus and grasslands ***,suspended sediment concentration,and sediment production were measured and simulated with the Limburg Soil Erosion Model(LISEM)in paired hydrographic watersheds located in southern Brazil;one occupied with 7-years old Eucalyptus saligna plantation(forest watershed-FW;0.83 km^(2))and another Pampa biome with native and exotic grasses used for beef cattle production(grassland watershed-GW;1.10 km^(2)).The effect of rainfall on hydrological and sedimentological variables was more evident in GW compared with *** shape of the hydrograph was steepest in GW,with rapid,marked increase and decrease in flow during *** parameters changed for model calibration in FW and GW were soil saturated hydraulic conductivity,initial soil moisture,and Manning roughness coefficient,whereby the statistical performance was classified as good(NSE>0.75).Fourteen events different from those used in the calibration process were validated for FW and GW,with NSE index classified as“good”and“very good”for *** study shows limitations of LISEM in calibrating and validating the sediment yield for individual events due to the spatial variability of factors controlling soil *** validated modeling results of this study may be applied in simulating soil and crop scenarios in watersheds cultivated with commercial forest and grassland for grazing.

关键词： Southern grasslands Paired watersheds Runoff Erosion LISEM

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How much has the Sun influenced Northern Hemisphere temperature trends?An ongoing debate

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Research in Astronomy and Astrophysics 2021年第6期21卷 131-198页

作者： Ronan Connolly Willie Soon Michael Connolly Sallie Baliunas Johan Berglund C.john Butler Rodolfo Gustavo Cionco Ana G.Elias Valery M.Fedorov Hermann Harde Gregory W.Henry Douglas V.Hoyt Ole Humlum David R.Legates Sebastian Liming Nicola Scafetta Jan-Erik Solheim Laszlo Szarka Harry van Loon Victor M.Velasco Herrera Richard C.Willson Hong Yan Weijia Zhang Center for Environmental Research and Earth Science(CERES) SalemMA 01970USA Independent scientists DublinIreland Retired formerly Harvard-Smithsonian Center for AstrophysicsCambridgeMA 02138USA Independent researcher MalmoSweden Retired formerly Armagh ObservatoryCollege HillArmagh BT619DGNorthern IrelandUK Comision de Investigaciones Cientlficas de la Provincia de Buenos Aires Argentina Grupo de Estudios Ambientales Universidad Tecnologica NationalColpn 332San Nicolas(2900)Buenos AiresArgentina Laboratorio de Fisica de la Atmosfera Facultad de Ciencias Exactas y TecnologlaUniversidad National de TucumanAv.Independencia 18004000 TucumanArgentina Instituto de Fisica del Noroeste Argentino(Consejo Nacional de Investigaciones Cientficas y Tecnicas-Universidad Nacional de Tucuman) 4000 TucumanArgentina Faculty of Geography LomonosovMoscow State UniversityLeninskie Gory St.1Moscow 119991Russia Helmut-Schmidt-University HamburgGermany Center of Excellence in Information Systems Tennessee State UniversityNashvilleTN 37209 USA Independent scientist Berkeley SpringsWVUSA Emeritus Professor in Physical Geography Department of GeosciencesUniversity of OsloNorway College of Earth Oceanand the EnvironmentUniversity of DelawareNewark DE 19716-2541USA Institute for Hydrography Geoecology and Climate SciencesHauptstra/3e 476315 AgeriSwitzerland Department of Earth Sciences Environment and GeoresourcesUniversity of Naples Federico nComplesso Universitario di Monte S.Angelovia Cinthia2180126 NaplesItaly Retired formerly Department of Physics and TechnologyUiT The Arctic University of Norway9037 TromspNorway ELKH Institute of Earth Physics and Space Science 9400 SopronCsatkai utca 6-8Hungary Retired formerly National Center for Atmospheric ResearchBoulderColoradoUSA Instituto de Geofisica Universidad Nacional Autonoma de MexicoCiudad UniversitariaCoyoacan04510Mexico D.F.Mexico Active Cavity Radiometer Irradiance Monitor(ACRIM) CoronadoCA 92118USA State Key Laboratory of Loe

In order to evaluate how much Total Solar Irradiance(TSI)has influenced Northern Hemisphere surface air temperature trends,it is important to have reliable estimates of both *** different estimates of the changes in TSI since at least the 19th century were compiled from the *** of these estimates are"low variability"and half are"high variability".Meanwhile,five largely-independent methods for estimating Northern Hemisphere temperature trends were evaluated using:1)only rural weather stations;2)all available stations whether urban or rural(the standard approach);3)only sea surface temperatures;4)tree-ring widths as temperature proxies;5)glacier length records as temperature *** standard estimates which use urban as well as rural stations were somewhat anomalous as they implied a much greater warming in recent decades than the other estimates,suggesting that urbanization bias might still be a problem in current global temperature datasets-despite the conclusions of some earlier ***,all five estimates confirm that it is currently warmer than the late 19th century,i.e.,there has been some"global warming"since the 19th *** each of the five estimates of Northern Hemisphere temperatures,the contribution from direct solar forcing for all sixteen estimates of TSI was evaluated using simple linear least-squares *** role of human activity on recent warming was then calculated by fitting the residuals to the UN IPCC’s recommended"anthropogenic forcings"time *** all five Northern Hemisphere temperature series,different TSI estimates suggest everything from no role for the Sun in recent decades(implying that recent global warming is mostly human-caused)to most of the recent global warming being due to changes in solar activity(that is,that recent global warming is mostly natural).It appears that previous studies(including the most recent IPCC reports)which had prematurely concluded the former,had done so be

关键词： Sun:activity (Sun:)solar terrestrial relations (Sun:)sunspots Sun:faculae,plages

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