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    Molecular dynamics simulation of melting, solidification and remelting processes of aluminum [electronic resource]

    , Article Iranian Journal of Science and Technology ( IJST): Transactions of Mechanical Engineering ; 2012, Vol.36, No. M1, P.13-23 Solhjoo, S ; Simchi, A. (Abdolreza) ; Aashuri, H ; Sharif University of Technology
    A molecular dynamics simulation study has been performed to investigate the solidification and remelting of aluminum using Sutton - Chen many body potential. Different numbers of atoms from 108 to 2048 atoms were considered to find an adequate size for the system. Three different cooling and heating rates, i.e. 1 0 12 K/s, 10 13 K/s and 10 14 K/s, were used. The structure of the system was examined using radial distribution function. The melting and crystallization temperatures of aluminum were evaluated by calculating the variation of heat capacity during the phase t ransformation. Additionally, Wendt – Abraham parameters were calculated to determine the glass transition temperature. It is... 

    Effect of particle size on the in vitro bioactivity, hydrophilicity and mechanical properties of bioactive glass-reinforced polycaprolactone composites [electronic resource]

    , Article Journal of Materials Science and Engineering: C ; 10 October 2011, Volume 31, Issue 7, Pages 1526–1533 Tamjid, E ; Bagheri, R ; Vossoughi, M ; Simchi, A. (Abdolreza) ; Sharif University of Technology
    Polycaprolactone (PCL) composite films containing 5 wt.% bioactive glass (BG) particles of different sizes (6 μm, 250 nm, < 100 nm) were prepared by solvent casting methods. The ultra-fine BG particles were prepared by high-energy mechanical milling of commercial 45S5 Bioglass® particles. The characteristics of bioactive glass particles were studied by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD) methods. In vitro bioactivity of the PCL/BG composite films was evaluated through immersion in the simulated body fluid (SBF). The films were analyzed by FE-SEM, energy dispersive... 

    Monitoring the effect of discontinuous shales on the surfactant flooding performance in heavy oil reservoirs using 2D glass micromodels

    , Article Petroleum Science and Technology ; Vol. 32, issue. 12 , Apr , 2014 , p. 1404-1417 ; ISSN: 10916466 Mohammadi, S ; Kharrat, R ; Masihi, M ; Ghazanfari, M. H ; Saidian, M ; Sharif University of Technology
    Although most heavy oil reservoirs contain discontinuous shaly structures, there is a lack of fundamental understanding how the shaly structures affect the oil recovery efficiency, especially during surfactant flooding to heavy oils. Here, an experimental study was conducted to examine the effect of discontinuous shales on performance of surfactant flooding by introducing heterogeneities to represent streaks of shale in five-spot glass micromodels. Results show that oil recovery in presence of shale streak is lower than in its absence. Based on the authors' observations, the presence of flow barriers causes premature breakthrough of injected fluids and also an unstable displacement front. As... 

    Monitoring wettability alteration by silica nanoparticles during water flooding to heavy oils in five-spot systems: A pore-level investigation

    , Article Experimental Thermal and Fluid Science ; Vol. 40, issue , July , 2012 , p. 168-176 ; ISSN: 08941777 Maghzi, A ; Mohammadi, S ; Ghazanfari, M. H ; Kharrat, R ; Masihi, M ; Sharif University of Technology
    It is well known that the displacement efficiency of EOR processes is mainly affected by wettability of porous medium; however, the role of nanoparticles on wettability alteration of pores surfaces remains a topic of debate in the literature. Furthermore, a little is known about how the dispersed silica nanoparticles affect the microscopic/macroscopic recovery efficiency of heavy oils during common immiscible EOR processes such as water flooding. In this study, a series of injection experiments was performed on five-spot glass micromodel which is initially saturated with the heavy oil. Distilled water and dispersed silica nanoparticles in water (DSNW) at different values of weight percent... 

    Experimental study of miscible displacement with hydrocarbon solvent in shaly heavy oil reservoirs using five-spot micromodels: The role of shale geometrical characteristics

    , Article Journal of Porous Media ; Vol. 15, issue. 5 , 2012 , p. 415-427 ; ISSN: 1091028X Mohammadi, S ; Ghazanfari, M. H ; Masihi, M ; Kharrat, R ; Sharif University of Technology
    Most of the heavy oil reservoirs contain discontinuous shale which affects fluid flow through porous media as well as recovery efficiency during enhanced oil recovery processes. However, the role of shale geometrical characteristics (including orientation, length, discontinuity, and spacing of the shale) on oil recovery remains a topic of debate in the literature, especially during miscible injection of heavy oils and five-spot systems. Here, a series of hydrocarbon solvent injection tests have been performed on various five-spot glass micromodels containing barriers which are initially saturated with heavy oil under fixed flow rate conditions. Oil recoveries as a function of pore volumes of... 

    Improvement in CO2/H2 separation by fabrication of poly(ether-b-amide6)/glycerol triacetate gel membranes

    , Article Journal of Membrane Science ; Vol. 469, issue , 2014 , pp. 43-58 ; ISSN: 03767388 Rabiee, H ; Soltanieh, M ; Mousavi, S. A ; Ghadimi, A ; Sharif University of Technology
    The purpose of this study is to investigate separation performance of poly(ether-b-amide6) (Pebax1657)/glycerol triacetate (GTA) gel membranes for CO2 removal from H2, N2 and CH4. GTA as a low molecular weight and highly CO2-phill compound was added to membrane structure at various weight fractions, 20%, 40%, 60% and 80% of Pebax, to fabricate a new high solubility selective membrane with improved performance. Permeation of pure gases was studied at different temperatures from 25 to 65°C and pressures from 4 to 24bar and ideal selectivities were calculated. Results indicated enhancement in permeation for all tested gases. For example, at a pressure of 4bar and a temperature of 25°C, membrane... 

    Preparation and characterization of nanostructured TiO2thin film codoped with nitrogen and vanadium on glass surface by sol–gel dip-coating method

    , Article Research on Chemical Intermediates ; 2014 ; ISSN: 09226168 Khatibnezhad, H ; Sani, M. A. F ; Sharif University of Technology
    To enhance hydrophilicity and photocatalytic activity, N-doped and N–V-codoped TiO2films were coated on glass substrates by the sol–gel dip-coating method. The substrates were previously coated with SiO2using the same method. The coated samples, after annealing at 450 °C for 30 min in air, were analyzed by an X-ray diffractometer, scanning electron microscope, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, and UV–visible spectroscope. The SiO2/N–V-codoped TiO2photocatalyst showed a narrower band gap (2.93 eV) compared to the SiO2/N-doped. Degradation tests, methyl orange under UV light and stearic acid under visible light, were performed in order to evaluate... 

    Investigation of the microscopic displacement mechanisms and macroscopic behavior of alkaline flooding at different wettability conditions in shaly glass micromodels

    , Article Journal of Petroleum Science and Engineering ; Vol. 122, issue , August , 2014 , pp. 595-615 ; ISSN: 09204105 Mehranfar, A ; Ghazanfari, M. H ; Sharif University of Technology
    Among various chemical methods, alkaline flooding has a great potential for enhancing heavy oil recovery, especially for reservoirs which contain acidic crude oil. However, fundamental understanding about microscopic displacement mechanisms and macroscopic behavior during alkaline floods at different wettabilities is not well understood, especially in five-spot shaly models. In this work several alkaline floods are performed on a glass micromodel containing randomly distributed shale streaks at different wettability conditions. Various mechanisms responsible for enhancing heavy oil recovery during alkaline flooding are investigated at different wettability conditions. These mechanisms... 

    Investigation of Pb/PbS a positive Schottky junction formed on conductive glass in contact with alkaline solution

    , Article Journal of Applied Physics ; Vol. 116, issue. 3 , July , 2014 ; ISSN: 00218979 Heidaripour, A ; Jafarian, M ; Gobal, F ; Mahjani, M. G ; Miandari, S ; Sharif University of Technology
    PbS on Pb thin film (Pb/PbS) was deposited on conductive glass (CG) substrate (CG/Pb/PbS) using electrochemical techniques to investigate the Schottky junction in solution. The CG/Pb/PbS electrode was investigated by different techniques based on thermionic emission theory. Electrochemical cell consisted of the CG/Pb/PbS as a working electrode in an alkaline solution showed character of the Schottky junction. Reduction and oxidation of H2O on the CG/Pb/PbS electrode were enhanced under illumination. Water photo splitting is the main process. Study of linear sweep voltammetry at around open circuit potential (OCP) allowed proposing a model based on the Schottky junction which is charged at... 

    Effect of gamma ray on poly(lactic acid)/poly(vinyl acetate-co-vinyl alcohol) blends as biodegradable food packaging films

    , Article Radiation Physics and Chemistry ; Vol. 96 , 2014 , pp. 12-18 ; ISSN: 0969806X Razavi, S. M ; Dadbin, S ; Frounchi, M ; Sharif University of Technology
    Poly(lactic acid) (PLA)/poly(vinyl acetate-. co-vinyl alcohol) [P(VAc-. co-VA)] blends as new transparent film packaging materials were prepared at various blend compositions and different vinyl alcohol contents. The blends and pure PLA were irradiated by gamma rays to investigate the extent of changes in the packaging material during gamma ray sterilization process. The miscibility of the blends was dependent on the blend composition and vinyl alcohol content; gamma irradiation had little effect on the extent of miscibility. The glass transition temperature of pure PLA and PLA/P(VAc-. co-VA) miscible blends reduced after irradiation. On the other hand in PLA/P(VAc-. co-VA) immiscible... 

    Construction of Pt nanoparticle-decorated graphene nanosheets and carbon nanospheres nanocomposite-modified electrodes: Application to ultrasensitive electrochemical determination of cefepime

    , Article RSC Advances ; Volume 4, Issue 15 , 2014 , Pages 7786-7794 ; ISSN: 20462069 Shahrokhian, S ; Hosseini Nassab, N ; Ghalkhani, M ; Sharif University of Technology
    A novel ultrasensitive modified electrode was fabricated with a graphene nanosheets and carbon nanospheres (GNS-CNS)-based nanocomposite film as a powerful platform. Pt nanoparticles (PtNPs) were simply electrodeposited onto the GNS-CNS-coated glassy carbon electrode creating a PtNPs/GNS-CNS hybrid nanocomposite modified electrode. Scanning electron microscopy, energy dispersive X-ray spectroscopy and linear sweep voltammetry (LSV) techniques were used for the characterization of the prepared modified electrode. The results of investigation of electrochemical response characteristics of cefepime (CP) revealed a considerable improvement in the oxidation peak current of CP on PtNPs/GNS-CNS/GCE... 

    Cyclometalated heteronuclear Pt/Ag and Pt/Tl complexes: A structural and photophysical study

    , Article Dalton Transactions ; Vol. 43, issue. 3 , 2014 , pp. 1105-1116 ; ISSN: 14779226 Jamali, S ; Ghazfar, R ; Lalinde, E ; Jamshidi, Z ; Samouei, H ; Shahsavari, H. R ; Moreno, M. T ; Escudero-Adan, E ; Benet-Buchholz, J ; Milic, D ; Sharif University of Technology
    To investigate the factors influencing the luminescent properties of polymetallic cycloplatinated complexes a detailed study of the photophysical and structural properties of the heteronuclear complexes [Pt2Me 2(bhq)2(μ-dppy)2Ag2(μ-acetone) ](BF4)2, 2, [PtMe(bhq)(dppy)Tl]PF6, 3, and [Pt2Me2(bhq)2(dppy)2Tl]PF 6, 4, [bhq = benzo[h]quinoline, dppy = 2-(diphenylphosphino)pyridine] was conducted. Complexes 3 and 4 synthesized by the reaction of [PtMe(bhq)(dppy)], 1, with TlPF6 (1 or 1/2 equiv.) and stabilized by unsupported Pt-Tl bonds as revealed by multinuclear NMR spectroscopy and confirmed by X-ray crystallography for 3. DFT calculations for the previously reported butterfly Pt2Ag2 cluster 2... 

    Enhancing glass ionomer cement features by using the HA/YSZ nanocomposite: A feed forward neural network modelling

    , Article Journal of the Mechanical Behavior of Biomedical Materials ; Vol. 29 , January , 2014 , pp. 317-327 ; ISSN: 17516161 Rajabzadeh, G ; Salehi, S ; Nemati, A ; Tavakoli, R ; Solati Hashjin, M ; Sharif University of Technology
    Despite brilliant properties of glass ionomer cement (GIC), its weak mechanical property poses an obstacle for its use in medical applications. The present research aims to formulate hydroxyapatite/yttria-stabilized zirconia (HA/YSZ) in the composition of GIC to enhance mechanical properties and to improve fluoride release of GIC. HA/YSZ was synthesized via a sol-gel method and characterized by applying X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photo-emission spectroscopy (XPS) and simultaneous thermal analysis (STA) along with transmission electron microscopy (TEM) methods. The synthesized nanocomposite was mixed with GIC at a fixed composition of 5.... 

    In-situ electro-polymerization of graphene nanoribbon/polyaniline composite film: Application to sensitive electrochemical detection of dobutamine

    , Article Sensors and Actuators, B: Chemical ; Vol. 196 , June , 2014 , pp. 582-588 ; ISSN: 09254005 Asadian, E ; Shahrokhian, S ; Zad, A. I ; Jokar, E ; Sharif University of Technology
    The present paper demonstrates the capability of narrow graphene nanoribbons (GNRs) in constructing new sensing platforms. Graphene nanoribbons have been synthesized via a simple solvothermal route through unzipping of carbon nanotubes, which was confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy analysis. These narrow carbon sheets were used to form a composite film by in-situ electro-polymerization with aniline. The produced graphene nanoribbon/polyaniline (GNR/PANI) composite film showed impressive performance in electrochemical determination of dobutamine (DBT). Under optimal conditions, in comparison to... 

    Synthesis and characterization of co-doped TiO2 thin films on glass-ceramic

    , Article Materials Science in Semiconductor Processing ; Vol. 26, Issue 1 , October , 2014 , pp. 41-48 ; ISSN: 13698001 Ahmadi, N ; Nemati, A ; Solati-Hashjin, M ; Sharif University of Technology
    In this research, an attempt was made to improve TiO2 photo-catalyst properties, thus pure, N-Ce co-doped TiO2 thin films were prepared on glass-ceramic substrate using a sol-gel dip-coating technique. The samples were calcinated in air at 475 °C, 550°C, and 650°C for 2 h. The result of simultaneous thermal analysis (STA) and X-ray diffraction (XRD) showed that the presence of Ce in TiO2 could inhibit the phase transformation from anatase to rutile and enhance the thermal stability, and anatase was the dominant phase in N-Ce co-doped TiO2 samples. Also based on the results, the doping results in decreasing the size of TiO 2 crystallite. The results of ultra violet-visible light diffuse... 

    Mixed mode I/II delamination analysis of rubber-modified glass-reinforced epoxy composites

    , Article Journal of Reinforced Plastics and Composites ; Vol. 33, Issue 17 , September , 2014 , pp. 1634-1643 ; ISSN: 07316844 Ghadami, F ; Dadfar, M. R ; Zeraati, A. S ; Sharif University of Technology
    In this study, the effect of carboxyl-terminated butadiene-acrylonitrile liquid rubber on fracture toughness of glass-reinforced epoxy composites has been investigated. Fracture toughness tests were conducted in modes I, II and different mixed mode ratios. The data obtained from these tests have been analyzed by using different methods. Results indicated that interlaminar fracture toughness of composite specimens improved considerably through addition of carboxyl-terminated butadiene-acrylonitrile in modes I, II and mixed mode. Interlaminar fracture surfaces of the specimens were also characterized by field emission scanning electron microscope  

    Electrical behaviour of glass/ carbon- phenolic conductive hybrid composite woven used in electrostatics precipitator filter

    , Article International Journal of Electrochemical Science ; Vol. 9, issue. 11 , 2014 , p. 6416-6430 Neyestanak, A. A. L ; Nazari, S. A ; Sadeghbeigi, N ; Karimzadeh, A ; Sharif University of Technology
    Electrical behavior of hybrid conductive composites made of phenolic resin, graphite woven, glass woven and graphite nano powder has been studied for the first time in the present research to apply as collecting plates in electro static precipitators. To this purpose, two types of four-layer composites smeared with phenolic resin by different amounts of graphite nano powder then produced at 120°C and 200 bars with proper curing cycle. Finally, electrical resistivity of all the plates undergoing impact loading after different rapping cycles was measured by means of a repetitive rapping tester system particularly manufactured for this task. This study performs changes in mechanical behavior of... 

    Investigation of wettability alteration through relative permeability measurement during MEOR process: A micromodel study

    , Article Journal of Petroleum Science and Engineering ; Vol. 120, issue , 2014 , p. 10-17 Khajepour, H ; Mahmoodi, M ; Biria, D ; Ayatollahi, S ; Sharif University of Technology
    Microbial Enhanced Oil Recovery (MEOR) as a tertiary process employs microorganisms and their metabolites to reduce the residual oil saturation of the reservoir mainly through interfacial tension (IFT) reduction and wettability alteration. In spite of its great potential and the mentioned advantages, application of MEOR has been limited because of the lack of practical convincing experimental results. In this study, the effects of MEOR process on wettability changes and the reduction of residual oil saturation have been examined by providing microscopic visualization of two phase flow in transparent glass micromodels. Biosurfactant producing bacterial strain (Enterobacter cloacae) was... 

    Pd-Au nanoparticle decorated carbon nanotube as a sensing layer on the surface of glassy carbon electrode for electrochemical determination of ceftazidime

    , Article Materials Science and Engineering C ; Vol. 34, issue. 1 , 2014 , pp. 318-325 ; ISSN: 09284931 Shahrokhian, S ; Salimian, R ; Rastgar, S ; Sharif University of Technology
    A simple electrodeposition method is employed to construct a thin film modifier of palladium-gold nanoparticles (Pd-AuNPs) decorated multi-walled carbon nanotube (MWCNT) on the surface of glassy carbon electrode (GCE). Morphology and property of Pd-AuNPs-MWCNT have been examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Electrochemical performance of Pd-AuNPs-MWCNT/GCE for detection of ceftazidime (CFZ) has been investigated by cyclic voltammetry (CV). This nanostructured film modified electrode effectively exhibited enhanced properties for detection of ceftazidime (CFZ). The effects of various experimental variables such as, the amount of casted MWCNT,... 

    Nickel hydroxide nanoparticles-reduced graphene oxide nanosheets film: Layer-by-layer electrochemical preparation, characterization and rifampicin sensory application

    , Article Talanta ; Vol. 119 , 2014 , pp. 156-163 ; ISSN: 00399140 Rastgar, S ; Shahrokhian, S ; Sharif University of Technology
    Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of nickel hydroxide nanoparticle-reduced graphene oxide nanosheets (Ni(OH)2-RGO) on a graphene oxide (GO) film pre-cast on a glassy carbon electrode surface. The surface morphology and nature of the nano-hybrid film (Ni(OH)2-RGO) was thoroughly characterized by scanning electron and atomic force microscopy, spectroscopy and electrochemical techniques. The modified electrode appeared as an effective electro-catalytic model for analysis of rifampicin (RIF) by using linear sweep voltammetry (LSV). The prepared modified electrode exhibited a distinctly higher activity...