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Structural and Mechanical Properties of Al/B_4C Composites Fabricated by Wet Attrition Milling and Hot Extrusion

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Journal of Materials Science & Technology 2013年第8期29卷 725-730页

作者： Morteza Alizadeh mostafa Alizadeh Rasool Amini Department of Materials Science and Engineering Shiraz University of TechnologyModarres Blvd.71555-313 ShirazIran Department of Metals Institute of Materials Science and EngineeringGraduate University of Advanced TechnologyP.O.Box 76315-115KermanIran

In this study, Al matrix composites reinforced by 7.5 and 15 vol.% B4C particles and also monolithic Al （Al without the B4C particles） were produced by wet attrition milling and subsequent hot forward extrusion processes. The microstructure of the composites, evaluated by scanning electron microscopy （SEM）, showed that the B4C particles were properly distributed in the Al matrix. Mechanical properties of the Al/B4C composites and monolithic Al were investigated by tensile, wear and hardness tests, The results revealed that with increasing content of B4C particles, the tensile strength and microhardness of composites increased but the elongation decreased. In addition, the tensile strength and microhardness of composite samples were higher than those of monolithic Al. The density measurements revealed that the density of composites decreased with increasing content of the B4C particles.

关键词： Composites Mechanical properties Attrition milling Hot extrusion

Synthesis and surface modification of nanophosphorous-based flame retardant agent by continuous flow hydrothermal synthesis

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Particuology 2015年第5期13卷 82-88页

作者： Sherif Elbasuney Hosam E.mostafa School of Chemical Engineering Military Technical College

Nanoparticles can provide flame retardance to hosting polymers and act as nano fire extinguishers. Hydroxyapatite （Ca5（OH）（PO4）3）（HA） is not hygroscopic, and is thermally stable up to 800℃, with 18.5 wt% phosphorous content. It is this high phosphorous content that can provide HA with flame retardant properties. In this paper, we report on the continuous synthesis of ultrafine HA using a hydrothermal synthesis technique. The HA surface properties were changed from hydrophilic to hydrophobic by post-synthesis surface modification. The ratio of the HA nanoparticles and an intumescent agent known as Exolit AP750 was investigated to yield a self-extinguishing multi-component epoxy nanocomposite for extended application under extreme fire conditions. The HA/AP750/epoxy nanocomposite was able to resist a flame at 1700 oc and self-extinguish after the flame had been removed. The nanocomposite showed an enhanced flammability performance in standard cone calorimetry testing and formed a compact and cohesive protective char layer with a 50% decrease in peak heat released compared with virgin epoxy. Our aim was to establish the use of HA as an effective nanofiller with phosphorous-based flame retardant properties. The surface of this nano fire extinguisher was modified effectively with different surfactants for enhanced compatibility with different polymeric matrices.

关键词： Flame retardancy Phosphorous-based agent Nanocomposites Hydrothermal synthesis Hydroxyapatite

Fluidized bed coating efficiency and morphology of coatings for producing Al-based nanocomposite hollow spheres

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International Journal of Minerals,Metallurgy and Materials 2014年第11期21卷 1146-1151页

作者： mostafa Amirjan Hamid Khorsand Manouchehr Khorasani Faculty of Materials Science and Engineering K. N. Toosi University of TechnologyP.O. Box 15875-4416 Tehran Iran Color and Polymer Research Center (CPRC) Amirkabir University of TechnologyP.O. Box 15875-4413 Tehran Iran

Abstract： We performed fluidized bed coating ofAl-based nanoeomposite powder-binder suspensions onto polymer substrates. The effects of the type and amount of the binder and nanoparticle additive on the coating process efficiency and coating characteristics were investigated. The efficiency decreased from 52% to 49% as the processing time increased from 15 to 20 min. However, the amount and thickness of the coating also increased as the processing time and amount of the binder were increased. The addition of nanoparticles to the system decreased the thickness of the coating from 222 to 207 μm when polyvinyl alcohol （PVA） was used as a binder. The suspension containing 3wt% R-4410 binder exhibited the greatest efficiency of 60%.

关键词： fluidized bed coating aluminum nanocomposites efficiency nanoparticles hollow spheres binders

Multiscale Mechanics and Optimization of Gastropod Shells

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Journal of Bionic Engineering 2011年第4期8卷 357-368页

作者： mostafa Yourdkhani Damiano Pasini Francois Barthelat Department of Mechanical Engineering McGill University 817 Sherbrooke Street West Montreal QC H3A 2K6 Canada

A vast majority of mollusks grow a hard shell for protection. The structure of these shells comprises several levels of hierarchy that increase their strength and their resistance to natural threats. This article focuses on nacreous shells, which are composed of two distinct layers. The outer layer is made of calcite, which is a hard but brittle material, and the inner layer is made of nacre, a tough and ductile material. The inner and outer layers are therefore made of materials with distinct structures and properties. In this article, we demonstrate that this system is optimum to defeat attacks from predators. A two-scale mod- eling and optimization approach was used. At the macroscale, a two-layer finite element model of a seashell was developed to capture shell geometry. At the microscale, a representative volume element of the microstructure of nacre was used to model the elastic modulus of nacre as well as a multiaxial failure criterion, both expressed as function of microstructural parameters. Experiments were also performed on actual shells of red abalone to validate the results obtained from simulations and gain insight into the way the shell fails under sharp perforation. Both optimization and experimental results revealed that the shell displays optimum performance when two modes of failure coincide within the structure. Finally, guidelines for designing two-layer shells were proposed to improve the performance of engineered protective systems undergoing similar structural and loading conditions.

关键词： seashell multiscale modeling representative volume element failure criterion nacre multiscale optimization

Introducing a proper hydrogen liquefaction concept for using wasted heat of thermal power plants-case study: Parand gas power plant

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Chinese Journal of Chemical Engineering 2021年第12期34卷 187-196页

作者： Hamed Rezaie Azizabadi Masoud Ziabasharhagh mostafa Mafi Faculty of Mechanical Engineering K.N.Toosi University of TechnologyTehranIran Department of Mechanical Engineering Imam Khomeini International UniversityQazvinIran

A hydrogen liquefaction concept with an innovative configuration and a capacity of 4 kg·s^(-1)(345.6 t·d^(-1))is *** concept involves an ammonia absorption refrigeration system for the pre-cooling of hydrogen and MR streams from 25℃ to-30℃.The ammonia absorption refrigeration system is fed by exhaust gases of the Pa rand gas power plant that are normally dissipated to the environment with a temperature of 546℃.The simulation is performed by Aspen HYSYS V9.0,using two separate equations of state for simulating hydrogen and MR streams to gain more accurate results especially for ortho-para *** show that conversion enthalpy estimated by Aspen HYSYS,fits very well to the experimental *** the important independent variables and composition of MRs are done using trial and error procedure,a functional and straightforward method for complicated *** minimum temperature limit in the cooling section is lowered,and an ortho-para converter is implemented in this *** proposed concept performs well from energy aspects and leads to COP and SEC equal to 0.271 and 4.54 kW·h·kg^(-1),*** main advantage of this study is in the low SEC,eliminating the losses of the distribution network,and improving the ability of the hydrogen liquefaction for energy storage in off-peak times.

关键词： Hydrogen Liquefaction Absorption refrigeration Waste treatment Mixed-refrigerant Ortho-para conversion

Coupled hydroelastic vibrations of an elliptical cylindrical tank with an elastic bottom

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Journal of Hydrodynamics 2014年第2期26卷 264-276页

作者： HASHEMINEJAD Seyyed M. TAFANI mostafa Acoustics Research Laboratory Center of Excellence in Experimental Solid Mechanics and Dynamics School of Mechanical Engineering Iran University of Science and Technology

An exact three-dimensional analysis based on the linear potential theory and the elaborated method of eigenfunction expansion in elliptic coordinates are presented to study the free coupled elasto-hyrodynamic characteristics of an upright non-deformable cylindrical container of elliptical planform with a flexible bottom plate, filled to an arbitrary depth with an inviscid incompressible liquid. Extensive numerical data are presented in an orderly fashion for the first few symmetric/anti-symmetric coupled hydroelastic natural frequencies as a function of fluid depth parameter for two plate aspect ratios. Also, selected hydrodynamic and structural deformation modes shapes are presented in graphical form. The effects of liquid level, bottom plate elasticity, and cross sectional aspect ratio on the sloshing frequencies and hydrodynamic pressure modes are examined. The validity of the results is examined through computations using a commercial finite element package as well as by comparison with the data available in literature.

关键词： exact solution fluid-structure interaction free surface oscillations vertical elliptical vessel Mathieu functions

Enhanced Sentiment Analysis Algorithms for Multi-Weight Polarity Selection on Twitter Dataset

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Intelligent Automation & Soft Computing 2023年第1期35卷 1015-1034页

作者： Ayman Mohamed mostafa College of Computer and Information Sciences Jouf UniversitySakaka72314Saudi Arabia

Sentiment analysis is based on the orientation of user attitudes and satisfaction towards services and *** methods and techniques have been introduced to analyze sentiments for obtaining high *** sentiment analysis accuracy depends mainly on supervised and unsupervised *** mechanisms are based on machine learning algorithms that achieve moderate or high accuracy but the manual annotation of data is considered a time-consuming *** unsupervised mechanisms,a lexicon is constructed for storing polarity *** accuracy of analyzing data is considered moderate or low if the lexicon contains small *** addition,most research methodologies analyze datasets using only 3-weight polarity that can mainly affect the performance of the analysis *** both methods for obtaining high accuracy and efficiency with low user intervention during the analysis process is considered a challenging *** paper provides a comprehensive evaluation of polarity weights and mechanisms for recent sentiment analysis research.A semi-supervised framework is applied for processing data using both lexicon and machine learning *** interactive sentiment analysis algorithm is proposed for distributing multi-weight polarities on Arabic lexicons that contain high morphological and linguistic *** enhanced scaling algorithm is embedded in the multi-weight algorithm to assign recommended weight polarities *** experimental results are conducted on two datasets to measure the over-all accuracy of proposed algorithms that achieved high results when compared to machine learning algorithms.

关键词： Sentiment analysis semi-supervised framework multi-weight polarity algorithm Arabic lexicons and automated scaling algorithm

Second-Order Finite Difference/Spectral Element Formulation for Solving the Fractional Advection-Diffusion Equation

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Communications on Applied Mathematics and Computation 2020年第4期2卷 653-669页

作者： mostafa Abbaszadeh Hanieh Amjadian Department of Applied Mathematics Faculty of Mathematics and Computer SciencesAmirkabir University of TechnologyNo.424Hafez Ave.Tehran 15914Iran

The main aim of this paper is to analyze the numerical method based upon the spectral element technique for the numerical solution of the fractional advection-diffusion *** time variable has been discretized by a second-order finite difference *** stability and the convergence of the semi-discrete formula have been ***,the spatial variable of the main PDEs is approximated by the spectral element *** convergence order of the fully discrete scheme is *** basis functions of the spectral element method are based upon a class of Legendre *** numerical experiments confirm the theoretical results.

关键词： Spectral method Finite diference method Fractional advection-difusion equation Galerkin weak form Unconditional stability

Droplets diameter distribution using maximum entropy formulation combined with a new energy-based sub-model

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Chinese Journal of Chemical Engineering 2016年第11期24卷 1625-1630页

作者： Seyed mostafa Hosseinalipour Hadiseh Karimaei Ehsan Movahednejad Energy and Environmental Lab Dpt Mech. Eng. Iran University of Science and Technology 16846-13114 Narmak Tehran lran University of California Berkeley USA

The maximum entropy principle(MEP) is one of the first methods which have been used to predict droplet size and velocity distributions of liquid sprays. This method needs a mean droplets diameter as an input to predict the droplet size distribution. This paper presents a new sub-model based on the deterministic aspects of liquid atomization process independent of the experimental data to provide the mean droplets diameter for using in the maximum entropy formulation(MEF). For this purpose, a theoretical model based on the approach of energy conservation law entitled energy-based model(EBM) is presented. Based on this approach, atomization occurs due to the kinetic energy loss. Prediction of the combined model(MEF/EBM) is in good agreement with the available experimental data. The energy-based model can be used as a fast and reliable enough model to obtain a good estimation of the mean droplets diameter of a spray and the combined model(MEF/EBM) can be used to well predict the droplet size distribution at the primary breakup.

关键词： Mean droplets diameter Energy conservation Maximum entropy formulation (MEF) Size distribution Statistical thermodynamics Mathematical modeling