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Numerical investigation of gas bubble behavior in tapered fluidized beds

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Particuology 2018年第3期16卷 152-164页

作者： Ramin Khodabandehlou Hossein Askaripour Asghar molaei Dehkordi Department of Chemical and Petroleum Engineering Sharif University of Technology P.O. Box 11155-9465 Tehran Iran

In this article, the behavior of gas bubbles in tapered fluidized beds is investigated with the use of a two- fluid model incorporating kinetic theory of granular flow. The effects of various parameters such as apex angle, particle size, and particle density on the size distribution and the rise velocity of gas bubbles were examined. In addition, the simulation results for the bubble fraction and axial velocity of gas bubbles were compared with experimental data reported in the literature and good agreement was observed. As the apex angle was increased, the fraction of gas bubbles with large sizes increased and the fraction of bubbles with small sizes decreased. As the particle size increased, the fraction of gas bubbles with large diameters decreased; however, the fraction of bubbles with medium diameters increased. The obtained results clearly indicate that an increased solid density increased the bubble rise velocity up to a specified height and reduced the velocity at larger heights, in tapered fluidized beds.

关键词： Tapered fluidized beds Apex angle Particle size and density Bubble size distribution Rise velocity of bubbles

Improving the wear resistance of plasma electrolytic oxidation(PEO)coatings applied on Mg and its alloys under the addition of nano-and micro-sized additives into the electrolytes:A review

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Journal of Magnesium and Alloys 2021年第4期9卷 1167-1189页

作者： Maryam molaei Kazem Babaei Arash Fattah-alhosseini Department of Materials Engineering Bu-Ali Sina UniversityHamedan 65178-38695Iran

As an efficient surface modification approach,the plasma electrolytic oxidation(PEO)technique can boost the capability of wear protection in Mg and its alloys by applying a hard and thick ceramic *** this procedure,more efficient protection can be acquired via adding additives(in the form of particle,powder,sheet,etc.)into solutions and producing composite *** additives result in more efficient protection against wear via getting stuck in the cracks and pores of coatings and rising the thickness,hardness,and diminishing the porosity size and *** efficiency of each additive can be changed owing to its intrinsic properties like melting point,size,participation type(reactive,partly reactive,or inert)and potential of *** this review,the effects of distinct additives in nano-and micro-scale size on wear behavior of PEO coatings on Mg and its alloys is going to be reviewed.

关键词： Plasma electrolytic oxidation(PEO) Mg alloys Wear behavior Nano-sized additives Micro-sized additives

CFD-DEM modelling of mixing and segregation of binary mixtures of ellipsoidal particles in liquid fluidizations

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Journal of Hydrodynamics 2019年第6期31卷 1190-1203页

作者： Esmaeil Abbaszadeh molaei Aibing Yu Zongyan Zhou Laboratory for Simulation and Modelling of Particulate Systems Department of Chemical EngineeringMonash UniversityClaytonVic 3800Australia

Solid-liquid fluidized beds of binary mixtures are widely used in many *** segregation may occur as particles can differ in size,density,or *** studies have been conducted in the past to understand the effects of particlesize and density on the mixing and segregation,but the effect of particle shape has not been well ***,in the present work,CFD-DEM approach is employed to perform a numerical analysis of the effect of particle shape on the particle mixing and segregation phenomenon in liquid fluidization *** particle shapes from oblate to prolate are produced by varying aspect ratio of ellipsoids from 0.25 to 3,and eight binary mixtures of spheres and ellipsoids are *** results show that when oblate or prolate particles are added to spheres,the segregation takes *** segregation degree increases with particle aspect ratio diverging from 1.0 and also liquid superficial *** relationship of mixing index with aspect ratio under different liquid velocities is established,and a detailed explanation is *** is revealed that increasing the projected area and hence the drag force results in the separation of ellipsoidal particles from spheres.

关键词： Mixing segregation binary mixture ellipsoids liquid fluidization CFD-DEM

Simply synthesized TiO_2 nanorods as an effective scattering layer for quantum dot sensitized solar cells

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Chinese Physics B 2014年第4期23卷 531-538页

作者： Mahmoud Samadpour Azam Iraji zad Mehdi molaei Department of Physics Faculty of Science K. N. Toosi University of Technology Institute for Nanoscience and Nanotechnology Sharif University of Technology Department of Physics Sharif University of Technology Department of Physics Faculty of ScienceVali-e-Asr University

TiO2 nanorod layers are synthesized by simple chemical oxidation of Ti substrates. Diffuse reflectance spectroscopy measurements show effective light scattering properties originating from nanorods with length scales on the order of one micron. The films are sensitized with CdSe quantum dots （QDs） by successive ionic layer adsorption and reaction （SILAR） and integrated as a photoanode in quantum dot sensitized solar cells （QDSCs）. Incorporating nanorods in photoanode structures provided 4- to 8-fold enhancement in light scattering, which leads to a high power conversion efficiency, 3.03% （Voc = 497 mV, Jsc = 11.32 mA/cm2, FF = 0.54）, in optimized structures. High efficiency can he obtained just by tuning the photoanode structure without further treatments, which will make this system a promising nanostructure for efficient quantum dot sensitized solar cells.

关键词： solar cell nanorod quantum dot scattering

Practical copper-catalyzed N-arylation of amines with 20% aqueous solution of n-Bu_4NOH

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Chinese Chemical Letters 2012年第3期23卷 301-304页

作者： Hamidreza molaei Mohammad Mehdi Ghanbari Department of Chemistry Sarvestan BranchIslamic Azad UniversitySarvestanIran

N-Arylation of a wide variety of amines with phenylboronic acid catalyzed by copper acetate under 20%aqueous solution of n-Bu_4NOH was accomplished in good to excellent yields（up to 92%） and substrate conversions（u... 详细信息

关键词： Copper-catalyzed N-Arylation Phenylboronic acid Amines

REPELLERS FOR MULTIFUNCTIONS OF SEMI-BORNOLOGICAL SPACES

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Acta Mathematica Scientia 2008年第3期28卷 545-550页

作者： M.R. molaei T. Waezizadeh Department of Mathematics University of Kerman

In this article the notion of repeller for multifunctions from the viewpoints of semi-bornologicul spaces is considered. The concept of lower semi-continuous multifunctions is extended by the use of semi-bornological spaces. Semi-bornological vector spaces are studied. The notion of conjugacy for semi-bornological multifunctions is considered. The persistence of repeller under conjugate relation is proved.

关键词： Semi-bornology repeller multifunction conjugacy

Antibacterial activity of bioceramic coatings on Mg and its alloys created by plasma electrolytic oxidation(PEO): A review

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Journal of Magnesium and Alloys 2022年第1期10卷 88-106页

作者： Arash Fattah-alhosseini Maryam molaei Meisam Nouri Kazem Babaei Department of Materials Engineering Bu-Ali Sina UniversityHamedan 65178-38695Iran

Mg and its alloys are suitable choices for implant materials due to their biodegradability and biocompatibility features. However, the high electrochemical activity of this family of biomaterials results in their fast degradation and severe corrosion in the physiological environment,producing hydrogen(H;) gas, and therefore increasing the p H of the environment. To meet the clinical requirements, the degradation rate of Mg biomaterials needs to be reduced. Nevertheless, higher corrosion resistance of Mg results in a low alkaline p H, weakening the antibacterial activity. Therefore, while the rapid degradation problem of Mg-based biomaterials needs to be addressed, good antibacterial properties are also necessary. By using the plasma electrolytic oxidation(PEO) surface modification technique, the antibacterial activity of Mg and its alloys can be enhanced while maintaining their corrosion protection properties at a high level. Throughout the PEO process, introducing antibacterial agents into solutions results in a major increase in antibacterial activity of the coatings. Moreover, post-or pre-processing on PEO coatings can provide better protection against bacteria. In this review, the antibacterial activity of PEO coatings applied on Mg and also its alloys will be discussed in more detail.

关键词： Antibacterial activity Magnesium Plasma electrolytic oxidation(PEO) Gram-positive bacteria Gram-negative bacteria

Steel rings as seismic fuses for enhancing ductility of cross braced frames

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Earthquake Engineering and Engineering Vibration 2022年第4期21卷 1103-1117页

作者： Farhad Behnamfar Saeid arman Hassan Zibasokhan Department of Civil Engineering Isfahan University of TechnologyIsfahan ***Iran Department of Civil Engineering Kermanshah University of TechnologyKermanshah ***Iran

A new remedy is proposed in this study to increase the ductility of cross-braced frames to a level comparable with ductile moment *** suggested system consists of one or two concentric steel rings installed in the cross-braced bay *** steel rings are designed such that they fail in bending sooner than failure of the braces in *** the rings act as seismic fuses with multiple bending plastic *** nonlinear static analysis,it is shown that the proposed system can be designed to behave like cross-braced frames with regard to stiffness and strength,and like special moment frames with regard to *** design factors for the proposed system are recommended based on nonlinear pushover and cyclic analysis studies.

关键词： cross brace special moment frame steel ring seismic fuse ductility

Usability of Waste Steel Grits in Concrete Pavement

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Journal of Wuhan University of Technology(Materials Science) 2022年第2期37卷 248-255页

作者： Abdulrezzak Bakis Sumeyra K arman Department of Civil Engineering Batman UniversityBatman 72100Turkey Department of Civil Engineering Bitlis Eren UniversityBitlis 13100Turkey

The usability of waste steel grits and limestone sand in the construction of concrete pavement was *** different types of pavement concretes were produced,including coarse limestone concrete not containing waste steel grit,coarse limestone concrete containing waste steel grit,limestone sand concrete not containing waste steel grit,and limestone sand concrete containing waste steel *** this study,water/binder ratio in concrete production was taken as *** the production of limestone sand concrete containing waste steel grit,limestone sand with a grain diameter of 0.1-1.0 mm was used as *** steel grits with a grain diameter of 0.2-0.7 mm were added to the concrete *** water curing and combined curing were applied to concrete *** standard water curing and combined curing,compression and bending tests of the same types of cube and beam concrete samples were carried *** a result of the study,the maximum compressive and bending strengths were found to be 50.21 MPa and 5.07 MPa for limestone sand concrete containing waste steel *** study results show that waste steel grits increase the compressive and bending strength of concrete pavement.

关键词： infrastructures for sustainable transport sustainable cement-based materials concrete pavement concrete curing waste steel grits