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Wettability of silicon carbide ceramic by Al_2o_3/Dy_2o_3 and Al_2o_3/Yb_2o_3 systems

Journal of Rare Earths 2013年第6期31卷 634-638页

作者： J.A.da silva B.m.moreschi G.C.R.Garcia s.Ribeiro Department of materials Engineering (DEmAR) Engineering School of Lorena (EEL)Pólo Urbo IndustrialGleba AI6CP 11612608-970LorenaSPBrazil

Wettability is an important phenomenon in the liquid phase sintering of silicon carbide （siC） ceramics. This work involved a study of the wetting of siC ceramics by two oxide systems, Al2o3 /Dy2o3 and Al2o3 /Yb2o3, which have so far not been studied for application in the sintering of siC ceramics. Five mixtures of each system were prepared, with different compositions close to their respective eutectic ones. samples of the mixtures were pressed into cylindrical specimens, which were placed on a siC plate and subjected to temperatures above their melting points using a graphite resistance furnace. The behavior of the melted mixtures on the siC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle, the parameter that measures the degree of wettability. The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading. All the samples of the two systems presented final contact angles of 40o to 10o indicating their good wetting on siC in the argon atmosphere. The melted/solidified area and interface between siC and melted/solidified phase were evaluated by scanning electron microscopy （sEm） and their crystalline phases were identified by X-ray diffraction （DRX）. The DRX analysis showed that Al2o3 and RE2o3 reacted and formed the Dy3Al5o12 （DyAg） and Yb3Al5o12 （YbAg） phases. The results indicated that the two systems had a promising potential as additives for the sintering of siC ceramics.

关键词： liquid-phase sintering silicon carbide rare earth oxide wettability contact angle

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Transport mechanism in chemically reactive hybrid nanofluid flow containing gyrotactic micro-organisms over a curved oscillatory surface

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Applied mathematics and mechanics(English Edition) 2025年第1期46卷 177-192页

作者： m.NAVEED m.ImRAN T.AsGHAR Z.ABBAs Department of mathematics Division of Science and TechnologyUniversity of Education Department of mathematics The Islamia University of Bahawalpur

This paper examines the transport analysis, including both heat transfer and mass transfer, in hybrid nanofluid flow containing gyrotactic microorganisms towards a curved oscillatory surface. The influence of magnetic fields is also inspected in terms of their physical characteristics. To depict the phenomena of transport, modified versions of both Fick's and Fourier's laws are used. Additionally, the characteristics of both heterogeneous and homogeneous chemical reactions are also incorporated. Utilizing a curvilinear coordinate system, the flow problem is formulated as partial differential equations(PDEs)for momentum, concentration, microorganism field, and energy. An analytical solution to the obtained flow equations is achieved utilizing the homotopy analysis method(HAm).The effects of significant flow parameters on the pressure and microorganism fields, velocity, oscillation velocity, concentration, and temperature distributions are shown via graphs. Furthermore, the variations in skin friction, mass transfer rate, heat transfer rate, and local motile number due to different involved parameters are presented in tables and are analyzed in detail. Graphical results indicate that the curves of velocity and temperature fields are enhanced as the values of the solid volume fraction variables *** is also verified that the concentration rate field decreases as the values of the homogeneous reaction strength parameter and the radius of curvature parameter increase, and it increases with the schmidt number and the heterogeneous reaction strength *** outcomes show a favorable response of the motile number to advanced values of the Peclet number, the schmidt number, the microorganism difference parameter, and the bio-convective Lewis number.

关键词： Peclet number

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Environmental impacts concerning flexible power generation in a biogas production

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Carbon Resources Conversion 2019年第2期2卷 117-125页

作者： o.Hijazi s.Tappen m.Effenberger Agricultural systems Engineering Technical University of MunichCenter of Life and Food Sciences85354 FreisingGermany Bavarian state Research Center for Agriculture Institute for Agricultural Engineering and Animal HusbandryFreisingGermany

Combined heat-and-power units(CHPUs)of biogas plants can be operated at partial load or in intervals to respond to market conditions or interventions by the grid *** this study,we present calculations for the specific greenhouse gas(GHG)emissions of electricity from biogas driven CHPUs in dependence of engine *** the methodology of life cycle assessment and using measured data from five real-world biogas plants in Bavaria,we investigated the following scenarios for the operation of the CHPU:(1)full load,(2)80%load response and(3)60%load *** system boundary included the whole biogas production chain,starting from the production/supply of the input materials and ending at the supply of electricity(functional unit:1 kWh of electrical energy fed into the grid).As electrical efficiency and engine load are positively correlated,partial-load operation results in higher specific GHG emissions of electricity from *** impact of decreasing efficiency of the CHPU under partial load on overall specific GHG emissions turned out to be higher than the influence of methane slip from the ***,the increase of further efficiencies such as higher yields,efficient use of synthetic and organic fertilizers,as well as minimization of fuel consumption and the use of regenerative fuels also lead to further decrease of GHG emissions.

关键词： Life cycle assessment Biogas plant CHP unit Flexibility Electricity Load response Interval GHG emissions

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Correlations for estimating solar radiation using sunshine hours and temperature measurement in osogbo, osun state, Nigeria

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Frontiers in Energy 2013年第2期7卷 214-222页

作者： o. s. oHUNAKIN m. s. AdaRAmoLA o. m. oYEWoLA R. o. FAGBENLE mechanical Engineering Department Covenant University Ota 11001Ogun State Nigeria Department of Energy and Process Engineering Norwegian Universityof Science and Technology Trondheim N-7491 Norway Department of mechanical Engineering University of Ibadan lbadan200284 Nigeria Department of mechanical Engineering Obafemi Awolowo UniversityIle-Ife 220005 Osun State Nigeria

In this study, the global solar radiation on horizontal surface in osogbo, osun state, Nigeria was analyzed using ll-year data （1997-2007）. Correlations using linear and quadratic expressions were developed to relate the global solar radiation on horizontal surface based on relative sunshine hours and temperature measurements for evaluating the monthly average daily global solar radiation. The calculated monthly clearness index values indicate that the prevailing weather condition in osogbo is heavily overcast. All the developed quadratic correlations gave better correlation coefficients （0.834, 0.872 and 0.823 respectively） than the linear models. However, the Hargreaves and samani related based quadratic model gave the best among the three developed quadratic expressions and is therefore suggested for estimating the monthly global radiation in this site and its surroundings.

关键词： global solar radiation Hargreaves model sunshine hour ambient temperatures osogbo

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Hydrodynamics of marine and offshore structures

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Journal of Hydrodynamics 2014年第6期26卷 835-847页

作者： FALTINsEN o.m. Centre for Autonomous marine operations and systems (Amos) Department of Marine Technology

An overview of hydrodynamic problems related to the broad variety of ships and sea structures involved in transportation, oil and gas exploration and production, marine operations, recovery of oil-spill, renewable energy, infrastructure and aquaculture is given. An approximate hydroelastic model for wave and current induced response of a floating fish farm with circular plastic collar and net cage is discussed. Weakly nonlinear potential-flow problems such as slow-drift motions and stationkeeping, springing of ships and ringing are given special attention. Body-fixed coordinate system is recommended in weakly nonlinear potential-flow analysis of bodies with sharp corners. Dynamic ship instabilities, mathieu-type instabilities, chaos and two-phase flow involving interface instabilities are discussed. It is advocated that slamming must be coupled with structural mechanics in order to find important time scales of the many physical effects associated with slamming and that both water entry and exit matter in describing the global wetdeck slamming effects. Further, sloshing-induced slamming in prismatic LNG tanks is perhaps the most complicated slamming problem because many fluid mechanic and thermodynamic parameters as well as hydroelasticity may matter.

关键词： hydroelastic model slow-drift motion instability slamming

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Investigation into the effect of silica nanoparticles on the rheological characteristics of water-in-heavy oil emulsions

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Petroleum science 2019年第6期16卷 1374-1386页

作者： o.s.Alade D.A.Al shehri m.mahmoud Department of Petroleum Engineering College of Petroleum and GeosciencesKing Fahd University of Minerals and PetroleumDhahranSaudi Arabia

The effect of silica nanoparticles on the rheological characteristics of water-in-heavy oil emulsions has been *** oil recovery methods for heavy oil production(most especially,thermal fluid injection)usually result in the formation of water-in-oil(W/o)*** reality,the emulsion produced also contains some fine solid mineral particles such as silica,which,depending on its quantity,may alter the viscosity and/or rheological properties of the fluid.A series of binary-component emulsions were separately prepared by dispersing silica nanoparticles[phase fraction,βs,=0.5%–5.75%(wt/v)]in heavy oil(s/o suspension)and by dispersing water[water cut,θw=10%–53%(v/v)]in heavy oil(W/o emulsion).Ternary-component emulsions comprising heavy oil,water droplets and suspended silica nanoparticles(s/W/o)were also prepared with similar ranges ofθw andβ*** viscosity was measured at different shear rates(5.1–1021.4 s-1)and temperatures(30–70°C).Both binary-component and ternary-component emulsion systems were observed to exhibit nonNewtonian shear thinning *** viscosity of the heavy oil and W/o emulsions increased in the presence of silica *** effect was,however,less signifi cant belowβs=2%(wt/v).moreover,a generalized correlation has been proposed to predict the viscosity of both binary-component and ternary-component emulsions.

关键词： Heavy oil emulsions Heavy oil–silica nanoparticle suspension Viscosity functions Rheological model Complex fluid

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Influence of environmental predispositions on temperate mountain forest damage at different spatial scales during alternating drought and flood periods:case study in Hruby Jeseník mts.(Czech Republic)

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Journal of mountain science 2022年第7期19卷 1931-1944页

作者： Pavel sAmEC Romana KUDELKoVA Petr LUKEs ales KUCERA Pavel CUDLIN Global Change Research Institute CAs Bělidla 986/4aBrnoCZ-60300Czech Republic Department of Geology and soil science Faculty of Forestry and Wood TechnologyMendel University in BrnoZemědělská3BRNOCZ-61300Czech Republic Department of Geoinformatics Faculty of SciencePalacky University Olomouc17.listopadu 50OlomoucCZ-77900Czech Republic

mountain forests are more prone to environmental predispositions(EPs)than submountain *** remote sensing of mountain forests enables instantaneous damage mapping,the investigation of the causes requires field ***,a local field or regionally modeled environmental characteristics influence remote data evaluation *** study focused on the evaluation of EPs effects damaging mountain forests between various spatial resolutions during environmental *** evaluation was divided into managed and natural forests in the Hruby Jeseník mts.(Czech Republic;240-1491 m a.s.l.;50.082°N,17.231°E).damage was assessed through the discrimination analysis of the normalised difference vegetation index(NDVI)by moDIs VI during alternating drought and flood periods *** local environmental influence was assessed using the discrimination function(DF)separability of forest damage in the training *** regional influence was assessed through map algebra estimated via the DF and a forest decline spatial model based on EPs from differences between risk growth conditions and biomass fuzzy ***,EPs and soil influenced forest NDVI at different *** management afflicted the NDVI more than the *** EPs afflicted the NDVI more than the soil *** winters and droughts had a greater influence on the NDVI than the flood events,with the winter of 2005/2006 inverting the DF direction,and the 2003 drought increasing differences in managed forest biomass and decreasing differences in natural forest *** than 50% of declining managed forests in the training sets occurred on Leptosols,Podzols and *** a regional scale,the soil influence was eliminated by multiple *** EPs influenced 96% of natural forest and 65% of managed forest,though managed forest damage was more *** mountain forest NDVI decline was dependent on both management and risk predispositions.

关键词： mountain environment Forest damage types Canopy density soil group Norway spruce(Picea abies)

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An innovative technique to solve a fractal damping Duffing-jerk oscillator

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Communications in Theoretical Physics 2023年第5期75卷 3-11页

作者： Yusry o El-Dib Nasser s Elgazery Youmna m Khattab Haifa A Alyousef Department of mathematics Faculty of EducationAin Shams UniversityRoxyCairoEgypt Department of Physics College of SciencePrincess Nourah bint Abdulrahman UniversityPO Box 84428Riyadh 11671Saudi Arabia

The idea of the present article is to look into the nonlinear dynamics and vibration of a damping Duffing-jerk oscillator in fractal space exhibiting the non-perturbative *** a new analytical technique,namely,the modification of a He’s fractal derivative that converts the fractal derivative to the traditional derivative in continuous space,this study provides an effective and easy-to-apply procedure that is dependent on the He’s fractal derivative *** analytic approximate solution has a significant match with the results of the numerical simulation as the fractal parameter is very closer to unity,which proves the reliability of the *** behavior is discussed and illustrated *** new powerful analytical tools are developed in an attempt to obtain effective analytical tools,valid for any fractal nonlinear problems.

关键词： modification of He’s fractal derivative fractal duffing-jerk vibration stability analysis non-perturbative approach damping nonlinear fractal system

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Influence of oxygen non-stoichiometry on physical properties of Ndsr_2mn_2o_(7±δ)

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Journal of Rare Earths 2015年第3期33卷 282-288页

作者： A.m.Yankin A.V.Fetisov o.m.Fedorova s.A.Uporov V.Ya.mitrofanov Laboratory of static and Kinetics of Processes Institute of Metallurgy of Ural Branсh of Russian Academy of Science Amundsen St. 101 Ekaterinburg 620016 Russia

Nd sr2mn2o7＋δ compounds were synthesized by ceramic method under three different cooling conditions. The Nd sr2mn2o7＋δ samples were characterized by powder X-ray diffraction（XRD）. oxygen non-stoichiometry data for the studied powders were determined by using gravimetric and X-ray photoelectron spectroscopy（XPs） methods. The correlation of cooling method and oxygen as non-stoichiometry was established. The electroconductivity in samples was studied by using four-point probe method, and the strong correlation with non-stoichiometry was found out. magnetization measurements were carried out. It was found that the magnetic and transport properties of the samples were also influenced by oxygen non-stoichiometry. The evolution of the magnetic properties could be explained by the formation of magnetic clusters in the vicinity of oxygen vacancies（oV） and strong competition between the superexchange and double exchange interactions.

关键词： oxygen stoichiometry gravimetric analysis electroconductivity magnetic properties rare earths

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Evaluating physical changes of iron oxide nanoparticles due to surface modification with oleic acid

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Chinese Physics B 2020年第10期29卷 186-194页

作者： s Rosales N Casillas A Topete o Cervantes G González J A Paz m E Cano Centro Universitario de Ciencias Exactas e Ingenienas Universidad de GuadalajaraBlvd.Marcelino Garcia Burragan 1421C.P.44430GuadalajaraJaliscoMexico Centro Universitario de la Cienegu Universidad de GuadalajaraAv.Universidad 1115C.P.47820OcotlanJaliscoMexico Centro Universitario de Ciencias de In salud Universidad de Guadalajara.Sierra Mojada 950C.P.44340GuadalajaraJaliscoMexico

The physical characterization of a colloidal system of superficially modified magnetic nanoparticles (mNPs) is presented. The system consists of oleic acid-coated iron oxide nanoparticles (oAmNP) suspended in water. A structural analysis is carried out by using standard physical techniques to determine the diameter and shape of the mNPs and also the width of the coating shell. The colloidal stability and the polydispersity index of this ferrofluid are determined by using Zeta potential measurements. Additionally, the magnetic characterization is conducted by obtaining the DC magnetization loops, and the blocking temperatures are determined according to the ZFC–FC protocol. Finally, the values of power absorption density P of the ferrofluid are estimated by using a magneto-calorimetric procedure in a wide range of magnetic field amplitude H and frequency f. The experimental results exhibit spherical-like shape of oAmNP with (20 ± 4) nm in diameter. Due to the use of coating process, the parameters of the magnetization loops and the blocking temperatures are significantly modified. Hence, while the uncoated mNPs show a blocking state of the magnetization, the oAmNP are superparamagnetic above room temperature (300 K). Furthermore, the reached dependence P versus f and P versus H of the ferrofluid with coated mNPs are clearly fitted to linear and quadratic correlations, respectively, showing their accordance with the linear response theory.

关键词： nanoparticles ferrofluid magnetic hyperthermia functionalization

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