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Structural characterization of AA 2024-MoSi_2 nanocomposite powders produced by mechanical milling

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International Journal of Minerals,Metallurgy and Materials 2013年第3期20卷 298-306页

作者： Mahmood Sameezadeh Hassan Farhangi massoud Emamy Center of Excellence for High Performance Materials School of Metallurgy and Materials College of Engineering University of Tehran

Nano-sized MoSi2 powder was produced successfully from commercially available MoSi2 by a mechanical milling process carried out for 100 h, and mechanical alloying was employed to synthesize AA 2024-MoSi2 nanocomposites, The effects of MoSi2 reinforcement and mechanical milling on the structure, morphology, and iron contamination of the produced materials were investigated using X-ray diffraction, scanning electron microscopy, and atomic absorption spectrometry. It is revealed that the morphology of the aluminum alloy changes continuously during milling from spherical to plate-like, irregular, and finally equiaxed. The presence of MoSi2 reinforcement accelerates the milling process and results in a smaller average particle size. The Williamson-Hall method determined that the crystallite size of the aluminum alloy in the composite powder is smaller than that of the unreinforced alloy at the same milling time and this size reaches 45 nm after 16 h milling time. The Fe contamination content is higher for the nanocomposite in comparison with the unreinforced alloy because of the wearing role of MoSi2 hard particles.

关键词： nanocomposites aluminum alloys mechanical milling microstructure

Investigation of secondary phases and tensile strength of nitrogen-containing Alloy 718 weldment

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International Journal of Minerals,Metallurgy and Materials 2020年第9期27卷 1259-1268页

作者： Behrooz Nabavi massoud Goodarzi Abdul Khaliq Khan School of Metallurgy and Materials Engineering Iran University of Science and TechnologyTehran ***Iran Department of Mechanical Engineering Manitoba Institute for MaterialsUniversity of ManitobaWinnipeg R3T 2N2Canada

The influence of nitrogen content on the precipitation of secondary phases and the tensile strength of Alloy 718 during gas tungstenarc welding was investigated. Various types of precipitates were characterized using scanning electron microscopy and transmission electronmicroscopy. The results showed that in the fusion zone, the volume fraction of Nb-rich phases such as Laves, (Nb,Ti)C, and δ phases, as wellas Ti-rich phases such as (Ti,Nb)CN and (Ti,Nb)N, increased with increase in the nitrogen content due to the microsegregation of Nb and Tiwithin interdendritic areas. Nitrogen was also found to decrease the size of γ′′ particles within γ dendrites. For precipitates in the partiallymelted zone, constitutional liquation was observed for both (Nb,Ti)C and (Ti,Nb)N particles. Based on the results of tensile tests, the weld containing0.015wt% nitrogen exhibited the highest ultimate tensile strength (UTS), whereas more addition of nitrogen led to a decrease in both theUTS and yield strength due to the increased content of brittle Laves phases and decreased size of γ′′.

关键词： nitrogen secondary phases gas tungsten arc welding tensile strength Alloy 718

Authenticated Key Agreement Protocol

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China Communications 2010年第5期7卷 1-8页

作者： massoud Hadian Dehkordi Reza Alimoradi Department of Mathematical Sciences Iran University of Science and Technology Narmak Tehran Iran Research Center of Intelligent Signal Processing Tehran Iran

Key agreement and identification protocols are much applicable among current protocols in cryptography. These protocols are used for a secure communication through an insecure channel in a network like Internet. Challenge-response identification protocol is an important identification method. In this paper, by making some slight changes in the public-key-based challenge-response identification protocol, we have introduced a new scheme in which the users in addition to authenticating each other can also agree on multiple keys. Then, this protocol＇s security from both aspects regarding the identification and key agreement will be analyzed. At the end, we will prove our scheme has a high security and efficiency in comparison with some famous and similar protocols.

关键词： identification multiple key agreement pairing challenge-response strong security

Effects of Zr additions on structure and tensile properties of an Al-4.5Cu-0.3Mg-0.05Ti(wt.%) alloy

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China Foundry 2022年第1期19卷 9-16页

作者： Hamed Kamali Erfan Kamali massoud Emamy School of Metallurgy and Materials Engineering College of EngineeringUniversity of TehranP.O.Box 11155-4563TehranIran Faculty of Materials Engineering Sahand University of TechnologyP.O.Box 51335-1996TabrizIran

The effects of different Zr additions(0.05wt.%-0.5wt.%)on the structure and tensile properties of an Al-4.5Cu-0.3Mg-0.05Ti(wt.%)alloy solidified under a high cooling rate(18℃·s^(-1)),in as-cast and T6 heat-treated conditions were *** as-cast structure of the alloy consists of equiaxed grains ofα-Al with an average size of 64μm which is unaffected by the Zr additions,indicating the ineffectiveness of Zr in the grain refinement of the *** electron microscopy,along with X-ray diffraction analysis revealed the presence of elongatedθ-Al2Cu at the grain boundaries;in addition,coarse Al3Zr particles exist in the intergranular regions of the 0.5wt.%Zr-containing *** the T6 heat treatment,the elongatedθparticles were fragmented;however,the coarse Al3Zr particles remained unchanged in the ***,the formation of fineβ’-Al3Zr andθ’’-Al3Cu/θ’-Al2Cu phases during T6 heat treatment was revealed by transmission electron *** results of the tensile tests showed that the Zr additions increase the strength of the alloy in both as-cast and T6 heat-treated conditions,but reduce its elongation,especially with 0.5wt.%Zr *** 0.3wt.%Zr-added alloy in the T6 heat-treated condition has the highest quality index value(249 MPa).Fractography of the fracture surfaces of the alloys revealed ductile fracture mode including dimples and cracked intermetallic phases in both conditions.

关键词： Al-Cu-Mg alloys casting T6 heat treatment structure precipitation hardening tensile properties fractography

A novel and efficient multiparty quantum secret sharing scheme using entangled states

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Science China(Physics,Mechanics & Astronomy) 2012年第10期55卷 1828-1831页

作者： massoud Hadian Dehkordi ELHAM Fattahi School of Mathematics Iran University of Science and TechnologyTehran ***Iran

We proposed a novel and efficient multiparty quantum secret sharing scheme using entangled state which in that the number of parties can be arbitrary *** state which we used,has special properties that make our scheme simple and *** operations which are needed to recover secret message,are only exclusive-or addition and complement *** it is shown that this scheme is secure against *** this scheme provides the best quantum bit efficiency compared with some famous quantum secret sharing schemes.

关键词： quantum secret sharing entangled state multiparty quantum cryptography

Influence of shielding gas on the mechanical and metallurgical properties of DP-GMA-welded 5083-H321 aluminum alloy

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International Journal of Minerals,Metallurgy and Materials 2016年第12期23卷 1416-1426页

作者： Amin Reza Koushki massoud Goodarzi Moslem Paidar Department of Metallurgy and Materials Engineering Iran University of Science and technology Department of Materials Engineering South Tehran Branch Islamic Azad University

In the present research, 6-mm-thick 5083-H321 aluminum alloy was joined by the double-pulsed gas metal arc welding （DP-GMAW） process. The objective was to investigate the influence of the shielding gas composition on the microstructure and properties of GMA welds. A macrostructural study indicated that the addition of nitrogen and oxygen to the argon shielding gas resulted in better weld penetration. Furthermore, the tensile strength and bending strength of the welds were improved when oxygen and nitrogen （at concentrations as high as approximately 0. 1vol%） were added to the shielding gas; however, these properties were adversely affected when the oxygen and nitrogen contents were increased further. This behavior was attributed to the formation of excessive brown and black oxide films on the bead surface, the formation of intermetallic compounds in the weld metal, and the formation of thicker oxide layers on the bead surface with increasing nitrogen and oxygen contents in the argon-based shielding gas. Analysis by energy-dispersive X-ray spectroscopy revealed that most of these compounds are nitrides or oxides.

关键词： aluminum alloys gas metal arc welding shielding gas mechanical properties metallurgical properties

CHAIN CONDITIONS FOR C＊-ALGEBRAS COMING FROM HILBERT C＊-MODULES

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Acta Mathematica Scientia 2018年第4期38卷 1163-1173页

作者： Mahmood POURGHOLAMHOSSEIN Mohammad ROUZBEHANI massoud AMINI Department of Mathematics Faculty of Sciences University of Qom Qom Iran Department of Mathematics Faculty of Mathematical Sciences Tarbiat Modares University 14115-134 Tehran Iran

In this paper we define and study chain conditions for Hilbert C＊-modules through their C＊-algebras of compact operators and discuss their perseverance under Morita equivalence and tensor products. We show that these chain conditions are passed from the C＊-algebra to its Hilbert module under certain conditions. We also study chain conditions for Hilbert modules coming from inclusion of C＊-algebra with a faithful conditional expectation.

关键词： Hilbert C*-module Noetherian and Artinian C*-algebras purely infinite C*-algebras Morita equivalence

Effect of pipe characteristics in umbrella arch method on controlling tunneling-induced settlements in soft grounds

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第5期12卷 984-1000页

作者： Ali Morovatdar massoud Palassi Reza S.Ashtiani Department of Civil Engineering The University of Texas at El PasoEl PasoTX79968USA College of Engineering Faculty of Civil EngineeringUniversity of TehranTehran14155-6619Iran

Recent developments in tunneling have stimulated design practitioners to more effectively utilize the underground ***,tunneling at shallow depth in soft grounds gives rise to concerns associated with tunnel *** arch method(UAM),as a pre-reinforcement approach of tunnels in complex geological conditions,is widely used to maintain the tunnel *** assessment of the impacts of the entire approach and forepoling pipe features on tunnel stability remains challenging due to the complex nature of the UAM *** study aimed to assess the effect of pipe design parameters on reinforcing the tunnels excavated in soft *** practical investigation considered the actual field conditions attributed to the tunneling procedure and UAM ***,the tunneling process was modeled and the tunnel excavation-induced settlements were *** post-processed results confirmed that deploying the UAM substantially reduced the tunnel crown and ground surface settlements by 76%and 42%,*** of various design parameters of pipes underscored the significance of incorporating the optimum value for each individual parameter into design schemes to more effectively control the ***,contrasting the settlement reduction rates(SRRs)for pipe design variables showed that the tunnel stability is more sensitive to the changes in the values of diameter and length,compared to values of the installation angle and center-tocenter distance of the pipes.

关键词： Tunnel reinforcement Umbrella arch method(UAM) Urban tunneling Forepoling pipes Finite element analysis Numerical simulation

Inverse Generalized Minimum Cost Flow Problem Under the Hamming Distances

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Journal of the Operations Research Society of China 2019年第2期7卷 355-364页

作者： Mobarakeh Karimi massoud Aman Ardeshir Dolati Faculty of Mathematics and Statistics University of BirjandBirjandIran Department of Computer Science Shahed UniversityTehranIran

Given a generalized minimum cost flow problem,the corresponding inverse problem is to find a minimal adjustment of the cost function so that the given generalized flow becomes optimal to the *** this paper,we consider both types of the weighted Hamming distances for measuring the *** the sum-type case,it is shown that the inverse problem is *** the bottleneck-type case,we present a polynomial time algorithm.

关键词： Generalized minimum cost flow Inverse problem Hamming distance Binary search