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Equal Channel Angular Pressing of Tubular samples

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Acta metallurgica sinica(English Letters) 2013年第5期26卷 574-580页

作者： F.Djavanroodi A.A.Zolfaghari m.Ebrahimi K.m.Nikbin Department of mechanical Engineering Imperial College Department of mechanical Engineering Gassim University Department of mechanical Engineering Iran University of Science and Technology

A new technique to equal channel angular pressing of tubular samples has been proposed and investigated through experiments and simulations. Deformation behavior of copper tube sample was numerically analyzed during the first pass of tubular ECAP process. The investigation included the efect of various tube wall thicknesses on the efective strain magnitude and strain distribution uniformity. It is shown that tube wall thickness of 3.5 mm gives the optimum value for strain behavior. In addition, copper tube specimens with 3.5 mm wall thickness have been successfully ECAPed up to four passes with the die channel angle of 90 using flexible polyurethane rubber pad. micro-hardness measurements on both annealed and ECAPed tubes show that 33% and 57% increases in hardness value and also, 50% and 70% reductions in the grain size were achieved after the first and fourth passes respectively. Furthermore, tube wall thickness measurements show that the process does not change the dimension of deformed specimens.

关键词： ECAP Tube FEm strain behavior Hardness distribution

The effect of ozone and drought on the photosynthetic performance of canola

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Journal of Integrative Agriculture 2018年第5期17卷 1137-1144页

作者： Bheki G maliba Prabhu m Inbaraj Jacques m Berner Unit for Environmental sciences and management North-West University Eskom Research Testing and Development Department of Chemistry School of ScienceRK University

Canola plants were fumigated in open-top chambers with ozone（O3）（120 ppb）under well-watered（WW）and water-stressed（Ws）conditions for 4 ***-fumigated plants were also studied to facilitate comparison between treatments for the same week and over ***,the treatments were：WW,WW-O3,Ws and *** fast chlorophyll a fluorescence transients OJIP for the four treatments emitted upon illumination of dark-adapted leaves were measured after week 1,2,3,4 and analysed by the JIP-test to evaluate the resulting changes in photosynthetic *** fumigation led to a decline of total performance index（PI（total））in well-watered *** effect of O3 was minor under drought conditions,as revealed by a decrease of PI（total） by 3%.The PI（total） decreased as the treatment was prolonged,due to leaf ageing for all cases and the decline was more pronounced under *** the average of all weeks,WW had the highest PI（total)and the lowest WW-O3（decrease by 27%）,while in Ws and Ws-O3,it was lower than WW（14 and 17%,respectively）.We found that the absorption（ABs）/reaction centre（RC）increases,while the maximum quantum yield of primary photochemistry（φ（Po））undergoes slight changes,and trapping（TR0）/RC closely followed the increase in ABs/*** indicates that O3and drought caused an increase in the functional antenna *** maximum quantum yield of primary photochemistry showed slight differences for all treatments and over time,suggesting that this parameter is less sensitive to drought and O3 ***,the more sensitive components of the photosynthetic electron transport chain appeared to be the probability that an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PsI acceptor side（δ（Ro））and the RC density on a chlorophyll basis（RC/ABs）.

关键词： canola Chl a fluorescence JIP-test open-top chamber ozone

saxicolous lichen communities in three basins associated with mining activity in northwestern Argentina

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Journal of Arid Land 2023年第8期15卷 989-1005页

作者： Juan m HERNÁNDEZ Renato A GARCÍA Edith R FILIPPINI Cecilia EsTRABOU martha s CAÑAs Juan m RODRÍGUEZ Faculty of Technology and Applied sciences Regional Centre of Energy and Environment for Sustainable DevelopmentNational University of CatamarcaCatamarca 4700Argentina Laboratory of Biodiversity and Environmental Genetics National University of AvellanedaAvellaneda 1870Argentina Institute of Biological and Technological Research Centre for Ecology and Renewable Natural ResourcesFaculty of ExactPhysical and Natural SciencesNational University of CordobaCordoba 5000Argentina

mining activity affects the vegetation and soils of the ***,the effects of mining activity on saxicolous lichen communities are less ***,the aim of this study was to characterize saxicolous lichen communities in three basins(Vis-Vis River basin,Poteros River basin,and Capillitas River basin)surrounding metalliferous mining projects of different types of operation and at different stages of exploitation.A large-scale mine(Bajo de la Alumbrera)with more than 25 a of open-pit mining located in the Vis-Vis River basin(CRV).A pre-exploitation mine(Agua Rica)located in the Poteros River basin(CRP),and a small-scale mine(minas Capillitas)with more than 160 a of underground mining located in the Capillitas River basin(CAC).In each basin,species richness,cover,and frequency of lichen communities were measured on 40 rock ***,explanatory variables were recorded,i.e.,altitude,slope,aspect,vegetation cover,rock,and soil cover around the rocky area *** and total cover of lichen communities were analysed using linear models,and species composition was explored using multivariate ordination *** showed that a total of 118 lichen species were *** species richness differed among basins and the lichen composition present in areas close to mining sites responded mainly to basins,altitude,and microsite *** lichen cover showed no difference among basins,but it changed under different rock and vegetation *** was not possible to quantify the effects of mining activity on species richness and ***,the low richness values found in the downstream of minera Alumbrera could be associated with the negative impact of open-pit ***,the effects of large-scale mining activity on lichen communities needs more investigation.

关键词： lichen community altitude microsite metalliferous mining vegetation

synthesis and electrochemical properties of environmental free Lglutathione grafted graphene oxide/ZnO nanocomposite for highly selective piroxicam sensing

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Journal of Pharmaceutical Analysis 2021年第1期11卷 48-56页

作者： N.Dhanalakshmi T.Priya s.Thennarasu s.sivanesan N.Thinakaran Environmental Research Lab PG and Research Department of ChemistryAlagappa Government Arts CollegeKaraikudi630003Tamil NaduIndia school of Chemistry Bharathidasan UniversityThiruchirapalli620024Tamil NaduIndia Department of Applied science and Technology AC TechAnna UniversityChennai25India

A simple and reliable strategy was proposed to engineer the glutathione grafted graphene oxide/ZnO nanocomposite(glutathione-GO/ZnO)as electrode material for the high-performance piroxicam *** prepared glutathione-GO/ZnO nanocomposite was well characterized by X-ray diffraction(XRD),Fourier transform infrared spectrum(FTIR),X-ray photoelectron spectroscopy(XPs),field emission scanning electron microscopy(FE-sEm),cyclic voltammetry(CV),electrochemical impedance spectroscopy(EIs)and differential pulse voltammetry(DPV).The novel nanocomposite modified electrode showed the highest electrocatalytic activity towards piroxicam(oxidation potential is 0.52 V).Under controlled experimental parameters,the proposed sensor exhibited good linear responses to piroxicam concentrations ranging from 0.1 to 500 μ*** detection limit and sensitivity were calculated as 1.8 μm and 0.2 μA/μm·cm^(2),***,it offered excellent selectivity,reproducibility,and long-term stability and can effectively ignore the interfering candidates commonly existing in the pharmaceutical tablets and human fluids even at a higher ***,the reported sensor was successfully employed to the direct determination of piroxicam in practical samples.

关键词： Reduced graphene oxide Glutathione ZnO Piroxicam Electrochemical sensing

Non-isothermal nano-crystallization kinetics in amorphous Ni_(55)Nb_(35)si_(10) alloy

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Transactions of Nonferrous metals society of China 2019年第2期29卷 358-364页

作者： H.mINOUEI G.H.AKBARI m.H.ENAYATI s.I.HONG Department of metallurgy and materials science Shahid Bahonar University Department of material Engineering Nanotechnology and Advanced Material InstituteIsfahan University of Technology (IUT) Department of Nanomaterials Engineering Chungnam National University

The non-isothermal crystallization kinetics of Ni55Nb35si10 amorphous alloy,prepared by mechanical alloying,was studied using differential scanning *** amorphous alloy showed one-stage crystallization on heating,which led to the formation of nano-intermetallic crystals in amorphous *** apparent activation energy for the crystallization of the alloy,determined by the Kissinger equation,was relatively high(468 kJ/mol),indicating that this amorphous alloy has high thermal *** in the activation energy during the crystallization process,were also evaluated by iso-conversional *** results showed that it decreases slowly from the beginning to crystallized fractionα=0.35 and it remains almost constant to the end of the *** nano-crystallization mechanism for the non-isothermal crystallization of the amorphous alloy was explained by determining Avrami *** electron microscopy studies revealed the microstructural modification of amorphous alloy via nanocrystallization during *** results suggest that the nucleation rate decreases with increasing time and the crystallization mechanism is governed dominantly by a three-dimensional diffusion-controlled growth.A predictive equation was obtained based on the sestak-Berggren autocatalytic model to describe quantitatively the non-isothermal crystallization kinetics.

关键词： amorphous alloy kinetics nano-crystallization DsC activation energy

A Note on Tropical Triangles in the Plane

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Acta mathematica sinica,English series 2009年第11期25卷 1775-1786页

作者： m.ANsOLA m.J.de la PUENTE Departamento de Algebra Facultad de matemáticas Universidad Complutense

We define transversal tropical triangles （affine and projective） and characterize them via six inequalities to be satisfied by the coordinates of the vertices. We prove that the vertices of a transversal tropical triangle are tropically independent and they tropically span a classical hexagon whose sides have slopes ∞, 0, 1. Using this classical hexagon, we determine a parameter space for transversal tropical triangles. The coordinates of the vertices of a transversal tropical triangle determine a tropically regular matrix. Triangulations of the tropical plane are obtained.

关键词： tropical triangles tropical triangulation linear inequalities convexity tropical semi-field

Development and testing of a detailed kinetic mechanism of natural gas combustion in internal combustion engine

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Journal of Natural Gas Chemistry 2010年第2期19卷 97-106页

作者： m.mansha A.R.saleemi Badar m.Ghauri Naveed Ramzan Department of Chemical Engineering University of Engineering & TechnologyLahore 5457Pakistan Institute of space Technology Islamabad 44000Pakistan

A detailed chemical mechanism to describe the combustion of natural gas in internal combustion （IC） engine has been developed,which is consisting of 233 reversible reactions and 79 *** mechanism accounts for the oxidation of methane,ethane,propane and *** has been tested using IC engine model of CHEmKIN 4.1.1 and experimental *** performance of the proposed mechanism was evaluated at various equivalence ratios （φ=0.6 to φ=1.3）,initial reactor conditions （Tini=500 to 3500 ℃; Pini=1.0 to 10 atm） and engine speed （2000-7000 rpm）.The proposed kinetic mechanism shows good concordances with GRI3.0 mechanism especially in the prediction of temperature,pressure and major product species （H2O,CO2） profiles at stoichiometric conditions （φ=1.0）.The experimental results of measured cylinder pressure,species fractions were also in agreement with simulation results derived from the proposed kinetic *** proposed mechanism successfully predicts the formation of gaseous pollutants （CO,NO,NO2,NH3） in the engine *** there are some discrepancies among each simulation profile,the proposed detailed mechanism is good to represent the combustion of natural gas in IC engine.

关键词： natural gas detailed mechanism equivalence ratio pollutants emission combustion

Effect of partition coefficient on microsegregation during solidification of aluminium alloys

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International Journal of minerals,metallurgy and materials 2014年第10期21卷 980-989页

作者： m.H.Avazkonandeh-Gharavol m.Haddad-sabzevar H.Fredriksson Department of metallurgy and materials Engineering Faculty of Engineering Ferdowsi University of Mashhad Department of materials science and Engineering School of Industrial Engineering and Management Royal Institute of Technology

In the modeling of microsegregation, the partition coefficient is usually calculated using data from the equilibrium phase diagrams. The aim of this study was to experimentally and theoretically analyze the partition coefficient in binary aluminum--copper alloys. The sam- ples were analyzed by differential thermal analysis （DTA）, which were melted and quenched from different temperatures during solidifica- tion. The mass fraction and composition of phases were measured by image processing and scanning electron microscopy （sEm） equipped with an energy-dispersive X-ray spectroscopy （EDs） unit. These data were used to calculate as the experimental partition coefficients with four different methods. The experimental and equilibrium partition coefficients were used to model the concentration profile in the primary phase. The modeling results show that the profiles calculated by the experimental partition coefficients are more consistent with the experi- mental profiles, compared to those calculated using the equilibrium partition coefficients.

关键词： aluminum copper alloys solidification partition coefficient microsegregation numerical modeling differential thermal analysis

Events and reaction mechanisms during the synthesis of an AI2O3-TiB2 nanocomposite via high energy ball milling

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Frontiers of Chemical science and Engineering 2013年第2期7卷 123-129页

作者： m. ABDELLAHI m. ZAKERI H. BAHmANPOUR materials Engineering Department Islamic Azad University Saveh Branch Saveh Iran Ceramic Department Materials and Energy Research Center Tehran 31787/316 Iran Chemical engineering and materials science Department University of California Davis CA 95616 USA

An AI2O3-TiB2 nanocomposite was success- fully synthesized by the high energy ball milling of A1, B2O3 and TiO2. The structures of the powdered particles formed at different milling times were evaluated by X-ray diffraction （XRD）, scanning electron microscopy （sEm） and transmission electron microscopy （TEm）. Thermo- dynamic calculations showed that the composite formed in two steps via highly exothermic mechanically induced self-sustaining reactions （msRs）. The composite started to form at milling times of 9-10 h but the reaction was not complete. The remaining starting materials were consumed by increasing the milling time to 15 h. The XRD patterns of the annealed powders showed that aluminum borate is one of the intermediate products and that it is consumed at higher temperatures. Heat treatment of the 6-h milled sample at l l00℃ led to a complete formation of the composite. Increasing the milling time to 15 h led to a refining of the crystallite sizes. A nanocomposite powder with a mean crystallite size of 35-40 nm was obtained after milling for 15 h.

关键词： ball milling nanocomposite AI2O3 TiB2