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    Effect of rolling speed on the occurrence of strain aging during and after warm rolling of a low-carbon steel

    , Article Journal of Materials Science ; Volume 45, Issue 13 , July , 2010 , Pages 3405-3412 ; 00222461 (ISSN) Koohbor, B ; Ohadi, D ; Serajzadeh, S ; Akhgar, J. M ; Sharif University of Technology
    2010
    Abstract
    In this study, effect of rolling speed on strain aging phenomena in warm rolling of a carbon steel has been investigated. For this purpose, by using a mathematical model and predicting temperature and strain rate fields, the possibility of occurrence of dynamic strain aging during the warm rolling was first evaluated. In the next stage, warm-rolled samples were aged up to 11 months at room temperature for studying the kinetics of static strain aging, while mechanical tests as well as microstructural evolutions have been performed to determine the effect of strain aging on material behavior. The results indicate that dynamic strain aging may not occur for the employed rolling program;... 

    Molecular dynamics simulation of pull-in phenomena in carbon nanotubes with Stone-Wales defects

    , Article Solid State Communications ; Volume 157 , March , 2013 , Pages 38-44 ; 00381098 (ISSN) Fakhrabadi, M. M. S ; Khorasani, P. K ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    2013
    Abstract
    This paper deals with investigation of deformations and pull-in charges of the cantilever and doubly clamped carbon nanotubes (CNTs) with different geometries using molecular dynamics simulation technique. The well-known AIREBO potential for the covalent bonds between carbon atoms, Lennar-Jones potential for the vdW interaction and the Coulomb potential for electrostatic actuation are employed to model the nano electromechanical system. The results reveal that longer CNTs with smaller diameters have smaller pull-in charges in comparison with shorter CNTs possessing larger diameters. Furthermore, the pull-in charges of the doubly clamped CNTs are higher than the pull-in charges of the... 

    First principles study of oxygen adsorption on nickel-doped graphite

    , Article Molecular Physics ; Volume 110, Issue 13 , Feb , 2012 , Pages 1437-1445 ; 00268976 (ISSN) Nahali, M ; Gobal, F ; Sharif University of Technology
    2012
    Abstract
    Density functional theory is used in a spin-polarized plane wave pseudopotential implementation to investigate molecular oxygen adsorption and dissociation on graphite and nickel-doped graphite surfaces. Molecular oxygen physisorbs on graphite surface retaining its magnetic property. The calculated adsorption energy is consistent with the experimental value of 0.1eV. It is found that substituting a carbon atom of the graphite surface by a single doping nickel atom (2.8% content) makes the surface active for oxygen chemisorption. It is found that the molecular oxygen never adsorbs on doping nickel atom while it adsorbs and dissociates spontaneously into atomic oxygens on the carbon atoms... 

    Van der Waals energy surface of a carbon nanotube sheet

    , Article Solid State Communications ; Volume 152, Issue 3 , February , 2012 , Pages 225-230 ; 00381098 (ISSN) Motahari, S ; Shayeganfar, F ; Neek Amal, M ; Sharif University of Technology
    Abstract
    The van der Walls interaction between a carbon nanotube sheet (CNTS) and a rare gas atom, is studied using both atomistic and continuum approaches. We present analytical expressions for the van der Waals energy of continuous nanotubes interacting with a rare gas atom. It is found that the continuum approach does not properly treat the effect of atomistic configurations on the energy surfaces. The energy barriers are small as compared to the thermal energy, which implies the free motion above the CNTS in heights about one nanometer. In contrast to the energy surface of a graphene sheet, the honeycomb lattice structure in the energy surface of a CNTS is imperceivable. Defects alter the energy... 

    Catalytic activity of TiO 2 nanotubes modified with carbon and Pt nanoparticles for detection of dopamine

    , Article ECS Transactions ; Volume 35, Issue 35 , 2011 , Pages 53-62 ; 19385862 (ISSN) ; 9781607682950 (ISBN) Mahshid, S ; Mahshid, S. S ; Ghahremaninezhad, A ; Askari, M ; Dolati, A ; Yang, L ; Luo, Sh ; Cai, Q ; Sensor; Organic and Biological Electrochemistry ; Sharif University of Technology
    2011
    Abstract
    Catalytic activity of carbon/Pt nanoparticles modified TiO 2 nanotubes electrode was studied by using dopamine contained solutions. The TiO 2 nanotubes electrode was prepared using anodizing method in aqueous solution. The electrochemical pulse method was then applied for electrodeposition of Pt nanoparticles onto the TiO 2 nanotubes. Further modification was achieved by decomposition of polyethylene glycol in a tube furnace to have a carbon/Pt nanoparticles modified TiO 2 nanotubes electrode. The final modified electrode could successfully detect the electro-oxidation of dopamine in a ImM contained solution using cyclic voltametry method. Also, a high sensitivity towards the oxidation of... 

    Selective voltammetric determination of d-penicillamine in the presence of tryptophan at a modified carbon paste electrode incorporating TiO2 nanoparticles and quinizarine

    , Article Journal of Electroanalytical Chemistry ; Volume 644, Issue 1 , Jan , 2010 , Pages 1-6 ; 15726657 (ISSN) Mazloum Ardakani, M ; Beitollahi, H ; Taleat, Z ; Naeimi, H ; Taghavinia, N ; Sharif University of Technology
    2010
    Abstract
    A carbon paste electrode (CPE) chemically modified with TiO2 nanoparticles and quinizarine (QZ) was used as a selective electrochemical sensor for the simultaneous determination of minor amounts of d-penicillamine (D-PA) and tryptophan (Trp). This modified electrode showed very efficient electrocatalytic activity for anodic oxidation of both d-PA and Trp. Substantial decreases of anodic overpotentials for both compounds made this analysis possible. Results of square wave voltammetry (SWV) using this modified electrode showed two well-resolved anodic waves for the oxidation of d-PA and Trp, which makes the simultaneous determination of both compounds possible. The peak potential for the... 

    Novel nanostructure electrochemical sensor for electrocatalytic determination of norepinephrine in the presence of high concentrations of acetaminophene and folic acid

    , Article Applied Catalysis A: General ; Volume 378, Issue 2 , 2010 , Pages 195-201 ; 0926860X (ISSN) Mazloum Ardakani, M ; Beitollahi, H ; Sheikh Mohseni, M. A ; Naeimi, H ; Taghavinia, N ; Sharif University of Technology
    2010
    Abstract
    In the present paper, the use of a carbon paste electrode modified by 2,2′-[1,2 buthanediylbis (nitriloethylidyne)]-bis-hydroquinone (BH) and TiO2 nanoparticles prepared by a simple and rapid method was described. The modified electrode showed an excellent character for electrocatalytic oxidization of norepinephrine (NE), acetaminophene (AC) and folic acid (FA). Using differential pulse voltammetry (DPV), a highly selective and simultaneous determination of NE, AC and FA has been explored at the modified electrode. Differential pulse voltammetry (DPV) peak currents of NE, AC and FA increased linearly with their concentration at the ranges of 4.0-1100.0 μM, 12.5-500.0 μM and 200.0-3200.0 μM,... 

    Fabrication of modified TiO 2 nanoparticle carbon paste electrode for simultaneous determination of dopamine, uric acid, and l-cysteine

    , Article Journal of Solid State Electrochemistry ; Volume 13, Issue 9 , 2009 , Pages 1433-1440 ; 14328488 (ISSN) Mazloum Ardakani, M ; Talebi, A ; Naeimi, H ; Nejati Barzoky, M ; Taghavinia, N ; Sharif University of Technology
    2009
    Abstract
    A carbon paste electrode, modified with 2, 2″-[1,7- hepthandiylbis(nitriloethylidyne)]-bis-hydroquinone and TiO 2 nanoparticles, was used for the simultaneous determination of dopamine (DA), uric acid (UA), and l-cysteine. The study was carried out by using cyclic voltammetry, chronoamperometry, and square wave voltammetry (SWV) techniques. Some kinetic parameters such as the electron transfer coefficient (α) and heterogeneous rate constant (k s) were also determined for the DA oxidation. A dynamic range of 8.0-1400 μM, with the detection limit of 8.4∈×∈10 -7 M for DA, was obtained using SWV (pH∈=∈7.0). The prepared electrode was successfully applied for the determination of DA, UA, and... 

    Electrochemical determinations of 6-mercaptopurine on the surface of a carbon nanotube-paste electrode modified with a cobalt salophen complex

    , Article Journal of Solid State Electrochemistry ; Volume 16, Issue 4 , April , 2012 , Pages 1643-1650 ; 14328488 (ISSN) Shahrokhian, S ; Ghorbani Bidkorbeh, F ; Mohammadi, A ; Dinarvand, R ; Sharif University of Technology
    2012
    Abstract
    A mixture of multi-walled carbon nanotube/graphite paste electrode modified with a salophen complex of cobalt was prepared and was applied for the study of the electrochemical behavior of 6-mercaptopurine (MP) using cyclic and differential pulse voltammetry (DPV). An excellent electrocatalytic activity toward the oxidation of MP was achieved, which led to a considerable lowering in the anodic overpotential and remarkable increase in the response sensitivity in comparison with unmodified electrode. Utilizing DPV method, a linear dynamic range of 1-100 μM with detection limit of 0.1 μM was obtained in phosphate buffer of pH 3.0. The electrochemical detection system was very stable, and the... 

    Investigation of the interphase effects on the mechanical behavior of carbon nanotube polymer composites by multiscale modeling

    , Article Journal of Applied Polymer Science ; Volume 117, Issue 1 , March , 2010 , Pages 361-367 ; 00218995 (ISSN) Montazeri, A ; Naghdabadi, R ; Sharif University of Technology
    2010
    Abstract
    In this article, a multiscale modeling procedure is implemented to study the effect of interphase on the Young's modulus of CNT/polymer composites. For this purpose, a three-phase RVE is introduced which consists of three components, i.e., a carbon nanotube, an interphase layer, and an outer polymer matrix. The nanotube is modeled at the atomistic scale using molecular structural mechanics. Moreover, three-dimensional elements are employed to model the interphase layer and polymer matrix. The nanotube and polymer matrix are assumed to be bonded by van der Waals interactions based on the Lennard-Jones potential at the interface. Using this Molecular Structural Mechanics/Finite Element... 

    Simultaneous voltammetric determination of ascorbic acid, acetaminophen and isoniazid using thionine immobilized multi-walled carbon nanotube modified carbon paste electrode

    , Article Electrochimica Acta ; Volume 55, Issue 3 , 2010 , Pages 666-672 ; 00134686 (ISSN) Shahrokhian, S ; Asadian, E ; Sharif University of Technology
    2010
    Abstract
    A carbon paste electrode (CPE) modified with thionine immobilized on multi-walled carbon nanotube (MWCNT), was prepared for simultaneous determination of ascorbic acid (AA) and acetaminophen (AC) in the presence of isoniazid (INZ). The electrochemical response characteristics of the modified electrode toward AA, AC and INZ were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results showed an efficient catalytic role for the electro-oxidation of AA and AC, leading to a remarkable peak resolution (∼303 mV) for two compounds. On the other hand, the presence of INZ, which is considered as important drug interference for AC, does not affect the voltammetric responses... 

    Application of carbon-paste electrode modified with iron phthalocyanine for voltammetric determination of epinephrine in the presence of ascorbic acid and uric acid

    , Article Sensors and Actuators, B: Chemical ; Volume 137, Issue 2 , 2009 , Pages 669-675 ; 09254005 (ISSN) Shahrokhian, S ; Ghalkhani, M ; Amini, M. K ; Sharif University of Technology
    2009
    Abstract
    A carbon-paste electrode (CPE) modified with iron(II) phthalocyanine was used for the sensitive voltammetric determination of epinephrine (EN). The electrochemical response characteristics of the modified electrode toward EN, ascorbic acid (AA) and uric acid (UA) were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results show an efficient catalytic activity of the electrode for the electro-oxidation of EN, which leads to improvement of reversibility of the electrode response and lowering its overpotential by more than 100 mV. The effect of pH and potential sweep rate on the mechanism of the electrode process was investigated. The modified electrode exhibits an...