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Boundary layer flow of maxwell fluid due to torsional motion of cylinder: modeling and simulation

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Applied mathematics and mechanics(English Edition) 2020年第4期41卷 667-680页

作者： m.KHAN A.AHmED j.AHmED Department of mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

This paper investigates the boundary layer flow of the maxwell fluid around a stretchable horizontal rotating cylinder under the influence of a transverse magnetic *** constitutive flow equations for the current physical problem are modeled and analyzed for the first time in the *** torsional motion of the cylinder is considered with the constant azimuthal velocity *** partial differential equations(PDEs)governing the torsional motion of the maxwell fluid together with energy transport are simplified with the boundary layer *** current analysis is valid only for a certain range of the positive Reynolds ***,for very large Reynolds numbers,the flow becomes ***,the governing similarity equations are simplified through suitable transformations for the analysis of the large Reynolds *** numerical simulations for the flow,heat,and mass transport phenomena are carried out in view of the bvp4c scheme in *** outcomes reveal that the velocity decays exponentially faster and reduces for higher values of the Reynolds numbers and the flow penetrates shallower into the free stream *** is also noted that the phenomenon of stress relaxation,described by the Deborah number,causes to decline the flow fields and enhance the thermal and solutal energy transport during the fluid *** penetration depth decreases for the transport of heat and mass in the fluid with the higher Reynolds *** excellent validation of the numerical results is assured through tabular data with the existing literature.

关键词： torsional motion maxwell fluid magnetic field stretchable rotating cylinder bvp4c scheme

Homogeneous Plastic Flow of Fully Amorphous and Partially Crystallized Zr_(41.2)Ti_(13.8)Cu_(12.5)Ni_(10)Be_(22.5) Bulk metallic Glass

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journal of materials Science & Technology 2003年第6期19卷 557-560页

作者： Q.WANG j.j.Blandin m.Suery B.Van de moortele j.m.Pelletier GPm2 ENSPG D.U. B.P.46 38042 Grenoble France Institute of Materials Shanghai University Shanghai 200072 ChinaGPM2 ENSPG D.U. B.P.46 38042 Grenoble FranceGPM2 ENSPG D.U. B.P.46 38042 Grenoble FranceGEMPPM Bat. B. PascalINSA 69621 Villeurbanne Cedex FranceGEMPPM Bat. B. PascalINSA 69621 Villeurbanne Cedex France

The homogeneous plastic flow of fully amorphous and partially crystallized Zr(41.2)Ti(13.8)Cu(12.5)Ni(10)Be(22.5) bulk metallic glass (Vitl) has been investigated by compression tests at high temperatures in supercooled liquid region. Experimental results show that at sufficiently low strain rates, the supercooled liquid of the fully amorphous alloy reveals Newtonian flow with a linear relationship between the flow stress and strain rate. As the strain rate is increased, a transition from linear Newtonian to nonlinear flow is detected, which can be explained by the transition state theory. Over the entire strain rate interval investigated, however, only nonlinear flow is present in the partially crystallized alloy, and the flow stress for each strain rate is much higher. It is found that the strain rate-stress relationship for the partially crystaltized alloy at the given temperature of 646 K also obeys the sinh law derived from the transition state theory, similar to that of the initial homogeneous amorphous alloy. Thus, it is proposed that the flow behavior of the nanocrystalline/amorphous composite at 646 K is mainly controlled by the viscous flow of the remaining supercooled liquid.

关键词： Homogeneous plastic flow Zr41.2Ti13.8Cu12.5Ni10Be22.5 amorphous alloy,Partially crystallized amorphous alloy

Effect of Oxide Inclusions on Electrochemical Properties of Aluminium Sacrificial Anodes

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journal of materials Science & Technology 2009年第1期25卷 95-101页

作者： m. Emamy A. Keyvani m. mahta j. Campbell School of metallurgy and materials University of Tehran Tehran Iran Department of metallurgy and materials University of Birmingham B15 2TT UK

Oxide films are incorporated into melts by an entrainment process, and are expected to be present in most metals, but particularly cast Al alloys. The oxides are necessarily present as folded-over double films （bifilms） that are effectively cracks. Their effect on the electrochemical behaviour of cast Al-SZn-0.021n sacrificial anodes was studied in 3 wt pct sodium chloride solution using the NACE efficiency evaluation. Three methods were employed to entrain progressive amounts of oxide in the alloy, including the addition of Al-Zn-ln maching chips to the charge, increasing the pouring height, and agitating the melt. The introduction of oxide bifilms in the cast alloy resulted in the deterioration of the electrochemical properties of the sacrificial anodes, such as current capacity and anode efficiency, and introduced increasing variability in these properties. The results suggest that corrosion behaviour is strongly related to the presence of bifilms suspended in the liquid alloy because bifilms provide crack paths allowing the corrodant to penetrate deeply into the metal matrix, and simultaneously provide localized galvanic cells because of the precipitation of Fe rich intermetallic compounds on their outer surfaces.

关键词： Aluminium Sacrificial anode Efficiency Entrainment Bifilm

Synthesis of ZnO Nanoparticles onto Sepiolite Needles and Determination of Their Sensitivity toward Humidity, NO_2 and H_2

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journal of materials Science & Technology 2016年第6期32卷 573-582页

作者： m.Hassan Ahmed S.Afify j.m.Tulliani Department of Applied Science and Technology Politecnico di Torino

This work investigated the sensitivity toward humidity, NO2 and H2 of ZnO modified sepiolite （Si12mg8O30（OH）4.（H2O）4.8H2O）. To this aim, sepiolite powder was first modified by leaching magnesium ions in HCI then by precipitating nano-sized Zn-based compounds under basic conditions. A subse- quent thermal treatment at 550 ℃ for 1 h was performed. The powders were characterized by X-ray diffraction （XRD）, specific surface area measurements, thermogravimetric and differential thermal anal- ysis and field emission scanning electron microscopy, as well as high resolution transmission electron microscopy. The XRD patterns showed that all leached heat treated samples were made of anhydrous sepiolite and of ZnO. Sensors were then obtained by screen printing these materials onto commercial alumina substrates with Pt electrodes. All the investigated compositions were capable of detecting NO2 down to ppm level and 20 ppm H2, at an optimal working temperature of 300°C. These detection limits are in line with the current best results reported in literature.

关键词： Clay minerals Gas sensor Sensitivity Hydrogen sensor Nitrogen Oxide

Strong emissions of blue-yellow-red regions of La and Ti modified KNaNbO_(3) ferroelectric ceramics

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journal of Advanced Ceramics 2015年第3期4卷 183-189页

作者： m.D.DURRUTHY-RODRIGUEZ m.HERNANDEZ-GARCIA j.PORTELLES j.FUENTES m.A.HERNANDEZ-LANDAVERDE m.RAmIREZ CARDONA j.m.YANEZ-LImON Departamento de Fisica Aplicada Instituto de CiberneticaMatematica y FisicaCITMA15#551VedadoLa HabanaCP 10400Cuba Facultad de Fisica Universidad de La HabanaSan Lazaro y LVedadoLa HabanaCP 10400Cuba CINVESTAV-Unidad Queretaro IPNLibramiento Norponiente 2000Fracc.Real de JuriquillaCP 76230QueretaroMexico Centro de Investigaciones en Ciencias de la Tierra y materiales Universidad Autonoma del Estado de HidalgoMexico

In this work,the results of the study on the optical properties of the perovskite structure ABO3 with La^(3+) substitution for ions K^(+) and Na^(+) in the A site and Ti^(4+) substitution for ion Nb^(5+) in the B site are *** ceramics were sintered at 1100℃ and 1190℃ and formed at 10 mPa and 80 *** ceramics were obtained with 94% of the theoretical *** piezoresponse force microscopy(PFm)showed needle-shaped grains with a size of 30 nm for the samples formed at 10 mPa at both sintering ***,the high temperature and high pressure used in formation reduced the energy of the band gap(Eg)from 3.36 to 3.09 *** emissions to 2.19,1.86,2.5,and 2.31 eV were obtained by exciting the samples at 325,373,457,and 500 nm,respectively;these emissions corresponded to blue-yellow-red regions of the visible spectrum.

关键词： emission spectra condense matter ferroelectric materials band structure X-ray diffraction(XRD)

Assessment of mercury(II) bioavailability using a bioluminescent bacterial biosensor: Practical and theoretical challenges

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journal of Environmental Sciences 2010年第8期22卷 1137-1143页

作者： Paulo R G Barrocas William m Landing Robert j m Hudson Department of Sanitation and Environmental Health National School of Public Health Oswaldo Cruz Foundation Department of Oceanography Florida State University. Tallahassee Department of Natural Resources and Environmental Sciences University of Illinois

Critical methodological challenges in the microbial biosensor approach to assessing Hg（II） bioavailability were evaluated from the perspective of analytical chemists. The main challenge stems from the fact that the chemical speciation of Hg（II） in natural waters exerts a major control on its bioavailability, yet its natural complexation equilibria are extensively altered during conventional bioassays. New data, obtained using a bioluminescent Hg（II）-biosensor, that illustrate these challenges are presented and potential solutions proposed.

关键词： mercury bioavailability biosensor chemical speciation bioluminescent

Asymptotic dynamics of the alternate degrees of freedom for a two-mode system:An analytically solvable model

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Chinese Physics B 2013年第2期22卷 71-75页

作者： m.Arsenijevi j.jekni-Dugi m.Dugi Department of Physics Faculty of ScienceKragujevacSerbia Department of Physics Faculty of Science and MathematicsNiSerbia

The composite systems can be non-uniquely decomposed into parts（subsystems）.Not all decompositions（structures） of a composite system are equally physically *** this paper we answer on theoretical ground why it may be *** consider a pair of mutually un-coupled modes in the phase space representation that are subjected to the independent quantum amplitude damping *** investigating asymptotic dynamics of the degrees of freedom,we find that the environment is responsible for the structures *** one structure is distinguished by both locality of the environmental influence on its subsystems and a classical-like description.

关键词： amplitude dissipative channel two-mode state Kraus representation alternate degrees of freedom

State of the Art on micromilling of materials,a Review

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journal of materials Science & Technology 2012年第8期28卷 673-685页

作者： m.A.Cmara j.C. Campos Rubio A.m. Abro j.P. Davim Department of mechanical Engineering Universidade Federal de Minas GeraisAv.Ant onio Carlos6627-Pampulha Belo Horizonte MGCEP:31.270-901Brazil Department of mechanical Engineering University of AveiroCampus Universitrio de Santiago3810-193AveiroPortugal

The trend towards miniaturization has increased dramatically over the last decade, especially within the fields concerned with bioengineering, microelectronics, and aerospace. micromillin8 is among the principal manu- facturing processes which have allowed the development of components possessing micrometric dimensions, being used to the manufacture of both forming tools and the final product. The aim of this work is to present the principal aspects related to this technology, with emphasis on the work material requirements, tool ma- terials and geometry, cutting forces and temperature, quality of the finished product, process modelling and monitoring and machine tool requirements. It can be noticed that size effect possesses a relevant role with regard to the selection of both work material （grain size） and tooling （edge radius）. Low forces and temper- ature are recorded during micromillin8, however, the specific cutting force may reach high values because of the ploughing effect observed as the uncut chip thickness is reduced. Finally, burr formation is the principal concern with regard to the quality of the finished part.

关键词： micro-milling micromachining Size effect miniaturization

DISSOLUTION KINETICS OF PHOSPHATE ORE IN ACIDIC SOLUTIONS

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Chinese journal of Chemical Engineering 1994年第2期2卷 13-22页

作者：马三剑 E.T.m.j.martynowicz G.j.Witkamp G.m.vanRosmalen Faculty of Chemical Technology and material Science Delft University of TechnologyLeeghwaterstraat 442628RZ DelftThe Netherlands

The dissolution kinetics of Florida and jordan phosphate ore was studied in diluted nitric acid (0.2, 0.5, 1.0 mol ·L-1), and in phosphoric acid (55 wt% H3PO4) aqueous solutions. It was found that the hydrogen ions concentration is a controlling factor, but the calcium ions concentration can not affect the dissolution rate in the range of 0.0 and 2.0 wt% Ca2+. The effects of temperature, stirring intensity and the size of ore particles were also investigated. The transfer of hydrogen ion depends on the diffusion, while the calcium ions transfer is assumed to be depended on mechanically stripping. The shrinking core model with hydrogen ions diffusion control match the experimental results.

关键词： dissolution kinetics phosphate ore diffusion mechanically stripping hydrogen calcium ions concentration shrinking core model