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    Reversibility of Asphaltene Aggregation in Live Oils: Qualitative and Quantitative Evaluation

    , Article Journal of Chemical and Engineering Data ; Volume 60, Issue 9 , August , 2015 , Pages 2646-2654 ; 00219568 (ISSN) Mohammadi, S ; Rashidi, F ; Mousavi Dehghani, S. A ; Ghazanfari, M. H ; Sharif University of Technology
    American Chemical Society  2015
    Despite the numerous experimental studies concerning asphaltene, the extent of reversibility of asphaltene aggregation at reservoir conditions remains still an elusive and controversial issue in the available literature. In this work, a series of depressurization and repressurization experiments were performed on three different live oils for qualitative and quantitative evaluation of the reversibility of asphaltene aggregation under typical pressure and temperature conditions of oil fields. The obtained results reveal that the kinetics and the extent of reversibility of asphaltene aggregation at elevated pressure and temperature are majorly controlled by the characteristics of the reservoir... 

    Nanocar and nanotruck motion on gold surface

    , Article 1st International Conference on Manipulation, Automation and Robotics at Small Scales, MARSS 2016, 18 July 2016 through 21 July 2016 ; 2016 ; 9781509015108 (ISBN) Nemati, A. R ; Nejat Pishkenari, H ; Meghdari, A ; Shorabpour, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    In this paper we have studied the motion of a nanocar and nanotruck on gold substrate using the classical molecular dynamics method. Analyzing the motion regime of the nanocar at different temperatures is one of the main goals of this paper. In the past years, similar molecules such as Trimmer, Z-car and nanotruck have been simulated by Konyukhov and Akimov. To increase the modeling accuracy in this paper we have used classical molecular dynamics contrary to previous works which used a rigid body molecular dynamics method. The result of our simulations were compared qualitatively to the experimental tests performed by Zhang et al. [12]. There was a good agreement between the results achieved... 

    Nanothickness films, nanostructured films, and nanocrystals of barium titanate obtained directly by a newly developed sol–gel synthesis pathway

    , Article Journal of Materials Science: Materials in Electronics ; Vol. 25, issue. 12 , 2014 , p. 5345-5355 Ashiri, R ; Nemati, A ; Sasani Ghamsari, M ; Dastgahi, M. M ; Sharif University of Technology
    This work aims to develop a chemically modified sol–gel synthesis pathway for obtaining various barium titanate nanostructures. The method is able to prepare different BaTiO3 nanostructures such as highly stable nanoparticle embedded colloids, highly transparent amorphous nanolayers, nanocrystalline BaTiO3 powders and ultrathin BaTiO3 nanostructured films directly from a precursor solution. All the products have been prepared at a lower temperature and in a more cost-effective way in contrast to other established sol–gel methods. The results show that the optical transparency of the thin films has been significantly improved in contrast to the similar researches. The deposited thin film is... 

    Experimental study of the startup performance of ferrofluidic open loop Pulsating Heat Pipes

    , Article ASME 2012 Heat Transfer Summer Conference Collocated with the ASME 2012 Fluids Engineering Div. Summer Meeting and the ASME 2012 10th Int. Conf. on Nanochannels, Microchannels and Minichannels, HT 2012, Rio Grande, 8 July 2012 through 12 July 2012 ; Volume 2 , 2012 , Pages 585-591 ; 9780791844786 (ISBN) Maziar, M ; Mehdi, T ; Siamak, K. H ; Mohammad Hassan, S ; Hossein, A ; Mohammad Behshad, S ; Sharif University of Technology
    Pulsating Heat Pipes (PHPs) are new and promising heat transfer devices. To implement the novel idea to vary the startup performance of a PHP using ferrofluid with and without the application of magnetic field, an experimental investigation is conducted. The effects of several important parameters including working fluid, charging ratio, heat input, ferrofluid concentration, internal pressure, and application of magnetic field on the startup performance of Open Loop Pulsating Heat Pipes (Open Loop PHPs) have been considered and described in detail. Obtained results show that using ferrofluid instead of distilled water can improve the startup performance of PHPs in certain conditions.... 

    Al-Al3Ti nanocomposite produced in situ by two-step hot-press sintering

    , Article IOP Conference Series: Materials Science and Engineering ; Volume 40, Issue 1 , 2012 ; 17578981 (ISSN) Nikfar, B ; Ghiabakloo, H ; Hosseini, H. R. M ; Mohammadi, A. V ; Sharif University of Technology
    Aluminum reinforced with a large amount (up to about 55 vol.%) of Al 3Ti particles can be fabricated from Al-20Ti elemental nanometer-sized powder mixture via in-situ two step hot press sintering (TSS). For production of intermetallic reinforced in-situ composite, TSS can provide elevated temperature to facilitate the formation of intermetallic phase in situ and hot consolidation to form a fully dense solid. The first step sintering was employed at a higher temperature to obtain an initial high density, and the second step was held at a lower temperature by isothermal sintering for more time than the first one to increase bulk density without significant grain growth. The optimum TSS regime... 

    Experimental investigation of triton X-100 solution on pulsating heat pipe thermal performance

    , Article Journal of Thermophysics and Heat Transfer ; Volume 32, Issue 3 , 2018 , Pages 806-812 ; 08878722 (ISSN) Nazari, M. A ; Ghasempour, R ; Shafii, M. B ; Ahmadi, M. H ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2018
    Pulsating heat pipes are cooling devices that are partially filled with working fluid. Working fluid thermophysical properties affect the thermal performance of pulsating heat pipes. In this research, the effect of adding a Triton X-100 surfactant to pure water and using the mixture as a working fluid is investigated experimentally. The results indicate that adding surfactant leads to improvement in the thermal performance of the pulsating heat pipe. In particular, the maximum of the thermal resistance improvement is about 61%, which is attributed to 0.01% surfactant concentration. Higher heat transfer ability is attributed to lower surface tension and the contact angle of the mixture... 

    Enhanced solar still condensation by using a radiative cooling system and phase change material

    , Article Desalination ; Volume 467 , 2019 , Pages 43-50 ; 00119164 (ISSN) Amarloo, A ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2019
    In this study, an experimental investigation of using the radiative cooling potential in a solar still was studied. Instead of using an auxiliary radiative panel, an integrated collector was utilized for both processes of absorption of solar radiations and emission of infrared radiations for radiative cooling. At night-time, the coldness was stored in the PCM inside the PCM-condenser. While during the day, the water was evaporated in an evaporation tank, the produced vapor was directed to the PCM-condenser and the air cooled-condenser. Different condenser configurations were tested to evaluate the effect of radiative cooling on daily yield and solar still efficiency. The lower temperature of... 

    Crystallinity of CoSi2 nanolayer grown by refractory metal interlayer and cap layer methods

    , Article Journal of Physics: Conference Series ; Volume 100, Issue PART 4 , 2008 ; 17426588 (ISSN) Akhavan, O ; Moshfegh, A. Z ; Sharif University of Technology
    Institute of Physics Publishing  2008
    Epitaxial formation of CoSi2 nanolayer by solid state reaction of Co-Si in refractory metal intermediate-layer and cap-layer systems was investigated. Thin films of Ta and W, as the refractory metal intermediate or cap layers of the Co film, were deposited on Si(100) substrate and then heat-treated. The both interlayers resulted in formation of epitaxial CoSi 2 with (100) crystallographic orientation at 900°C. However, in the Ta intermediated system, the grown CoSi2 layer was thermally unstable at 1000°C, unlike the W system with a stable silicide layer. We found that use of W cap-layer cannot yield an epitaxial CoSi2 phase. But, a Ta cap-layer resulted in formation of epitaxial CoSi2(100)... 

    Beneficial Role of oxygen in co and propylene oxidation over a pt-pd-based wiremesh catalyst as a retrofit emission control device for four-stroke gasoline spark-ignited motorcycles

    , Article Energy and Fuels ; Volume 35, Issue 12 , 2021 , Pages 10122-10133 ; 08870624 (ISSN) Lotfollahzade Moghaddam, A ; Hamzehlouyan, T ; Hosseini, V ; Mayer, A ; Sharif University of Technology
    American Chemical Society  2021
    Over 200 million motorcycles in use worldwide account for a substantial portion of global mobile source total hydrocarbons (THC) and carbon monoxide (CO) emissions. In Tehran, capital of Iran, ultrarich inefficient combustion in gasoline-fueled motorcycles results in significantly high CO and THC emissions. Motorcycle catalysts can reduce CO and C3H6(as a representative hydrocarbon) emission factors by 60-80%. In the present work, CO and propylene oxidation over a commercial Pt-Pd-based wiremesh catalyst is studied in a flow reactor setup under simulated conditions relevant to 125 cc four-stroke gasoline carburetor motorcycles. Steady-state individual and co-oxidation tests for CO and... 

    Thermal Hall and Nernst responses in ultrathin magnetic films of pyrochlore lattice

    , Article Journal of Physics Condensed Matter ; Volume 33, Issue 26 , 2021 ; 09538984 (ISSN) Sheikhi, B ; Kargarian, M ; Langari, A ; Sharif University of Technology
    IOP Publishing Ltd  2021
    The ultrathin films of pyrochlore lattice along [111] direction provide a fertile ground for exploring topological states in oxide materials, where the electron correlations are strong and magnetically ordered states are favored. As a result of strong interactions, most of states are magnetic insulators with strong Dzyaloshinskii–Moriya and anisotropic spin interactions. We considered three types of heterostructures, a bilayer of triangular-kagome (TK), and two trilayers of triangular-kagome-triangular (TKT) and kagome-triangular-kagome (KTK) thin films. The ground states are magnetically ordered with the low-energy excitations, the magnons, characterized by nontrivial topology. While for TK... 

    Facile one-pot synthesis of polytypic (wurtzite–chalcopyrite) CuGaS2

    , Article Applied Physics A: Materials Science and Processing ; Volume 122, Issue 3 , 2016 , Pages 1-10 ; 09478396 (ISSN) Vahidshad, Y ; Mirkazemi, S. M ; Tahir, M. N ; Iraji Zad, A ; Ghasemzadeh, R ; Tremel, W ; Sharif University of Technology
    Springer Verlag  2016
    Abstract: In this investigation, monodisperse CuGaS2 nanoparticles intended for use as visible-light-absorbing materials were synthesized using a facile one-step heating method that involved dissolving the precursors copper chloride, gallium acetylacetonate, and thiourea in a solvent consisting of either oleylamine alone or a combination of oleylamine, oleic acid, and 1-octadecene. The shapes of the resulting nanoparticles were either elongated, polygonal, or a mixture of both, depending on whether the crystal structure of the nanoparticles was predominantly wurtzite, predominantly chalcopyrite, or a more balanced mixture of both wurtzite and chalcopyrite (i.e., the nanoparticles were... 

    An investigation on tensile properties of coiled carbon nanotubes using molecular dynamics simulation

    , Article Diamond and Related Materials ; Volume 74 , 2017 , Pages 154-163 ; 09259635 (ISSN) Shahini, E ; Karimi Taheri, K ; Karimi Taheri, A ; Sharif University of Technology
    Elsevier Ltd  2017
    A coiled carbon nanotube (CCNT) can be formed from the distortion of parent toroidal carbon nanotube with a uniform pitch length and a uniform spring rise angle. In this research molecular dynamics simulation was carried out to assess the tensile properties of three CCNT having indexes of (3,3), (4,4), and (5,5). The results indicated that Stone-Wales defects are necessary for thermodynamic stability of the CCNTs. The stress-strain curves showed that the yield stress, yield strain, and failure strain are decreased with increase in temperature. The force-displacement curves revealed that the spring constant of these materials is highly depended on the tube diameter and rising angle, while it... 

    Supercritical water in top-down formation of tunable-sized graphene quantum dots applicable in effective photothermal treatments of tissues

    , Article Carbon ; Volume 130 , April , 2018 , Pages 267-272 ; 00086223 (ISSN) Tayyebi, A ; Akhavan, O ; Lee, B. K ; Outokesh, M ; Sharif University of Technology
    Elsevier Ltd  2018
    Supercritical water was used for simultaneous fragmentation and reduction of graphene oxide (GO) sheets into water-dispersible graphene quantum dots (GQDs) with tunable sizes. Transmission electron microscopy (TEM) demonstrated that by increasing the temperature above the critical point of water, the average size and thickness of the GQDs were decreased and the size uniformity and production yield were increased. The results of thermal conductivity measurement of GQD nanofluids with different weight fractions indicated that the GQDs prepared at supercritical condition could enhance the thermal conductivity of water by 65% as compared to 35% for the GQDs synthesized at sub-critical... 

    Novel hot milling approach for the synthesis of fine PbZr0.95Ti0.05O3 powders

    , Article Ceramics International ; Volume 45, Issue 18 , 2019 , Pages 24176-24181 ; 02728842 (ISSN) Sayyadi Shahraki, A ; Hojaji Najafabadi, A. R ; Safaei, S ; Sadrnezhaad, Kh ; Sharif University of Technology
    Elsevier Ltd  2019
    A new and effective hot milling system was designed and applied to the synthesis of PbZr0.95Ti0.05O3 (PZT) powder. PbO, ZrO2 and TiO2 powders were used as starting materials and hot milled at various temperatures ranging from 10 ̊°C to 800 ̊°C. The obtained powders were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Results indicated that pure, crystalline, and fine PZT powders with the average particle size of 170 nm can be successfully synthesized directly after a relatively short synthesis time of 12 h at lower temperature of 800 ̊°C by the hot milling technique. In contrast to this method, this study demonstrates that conventional solid-state... 

    Experimental examination of a natural vacuum desalination system integrated with evacuated tube collectors

    , Article Desalination ; Volume 467 , 2019 , Pages 79-85 ; 00119164 (ISSN) Abbaspour, M. J ; Faegh, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2019
    A solar natural vacuum desalination system was experimentally investigated. Using a barometric water column and creating an equilibrium with atmospheric pressure and gravity, vacuum conditions were maintained inside the evaporation chamber throughout the day, which led to the beginning of evaporation at lower temperatures and as a result, lower energy consumption compared to conventional methods. Solar evacuated tubes were used to more efficiently absorb solar radiation and raise the temperature of saline water. In addition, at the system startup, a vacuum pump was utilized to fill the water column and create vacuum conditions. Then, the existing vacuum in the system was maintained naturally... 

    Non-isothermal pyrolysis of used lubricating oil and the catalytic effect of carbon-based nanomaterials on the process performance

    , Article Journal of Thermal Analysis and Calorimetry ; Volume 139, Issue 2 , 2020 , Pages 1025-1036 Alavi, E ; Abdoli, M. A ; Khorasheh, F ; Bayandori Moghaddam, A ; Sharif University of Technology
    Springer Netherlands  2020
    Pyrolysis is a commonly used method for the recovery of used lubricating oil (ULO), which should be kinetically improved by a catalyst, due to its high level of energy consumption. In this research, the catalytic effects of carbon nanotube (CNT) and graphene nanoplatelets on the pyrolysis of ULO were studied through thermogravimetric analysis. First, the kinetic parameters of ULO pyrolysis including activation energy were calculated to be 170.12 and 167.01 kJ mol−1 by FWO and KAS methods, respectively. Then, the catalytic effects of CNT and graphene nanoplatelets on pyrolysis kinetics were studied. While CNT had a negligible effect on the pyrolysis process, graphene nanoplatelets... 

    New insight into reaction mechanisms of TiCl4 for the synthesis of TiO2 nanoparticles in H2O-assisted atmospheric-pressure CVS process

    , Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 264 , 2021 ; 09215107 (ISSN) Rahiminezhad Soltani, M ; Saberyan, K ; Simchi, A ; Sharif University of Technology
    Elsevier Ltd  2021
    Crystalline anatase TiO2 nanoparticles were synthesized in the gas phase using an H2O-assisted atmospheric-pressure CVS process. Simultaneous oxidation/hydrolysis of TiCl4 in the H2O-assisted APCVS process demonstrates the feasibility of facile fabrication and the designed synthesis of TiO2 nanoparticles in atmospheric pressure. Kinetics and thermodynamics studies of TiCl4 reactions in the gas phase illustrated oxidation or hydrolysis domination theoretically and were confirmed by experimental runs. Effects of H2O/O2 ratio on the reactions mechanisms, phase formation, size characteristics, morphology, and purity of TiO2 nanoparticles were experimentally studied using various analytical... 

    Co-combustion studies of low-rank coal and refuse-derived fuel: performance and reaction kinetics

    , Article Energies ; Volume 14, Issue 13 , 2021 ; 19961073 (ISSN) Azam, M ; Ashraf, A ; Setoodeh Jahromy, S ; Miran, S ; Raza, N ; Wesenauer, F ; Jordan, C ; Harasek, M ; Winter, F ; Sharif University of Technology
    MDPI AG  2021
    In connection to present energy demand and waste management crisis in Pakistan, refuse-derived fuel (RDF) is gaining importance as a potential co-fuel for existing coal fired power plants. This research focuses on the co-combustion of low-quality local coal with RDF as a mean to reduce environmental issues in terms of waste management strategy. The combustion characteristics and kinetics of coal, RDF, and their blends were experimentally investigated in a micro-thermal gravi-metric analyzer at four heating rates of 10, 20, 30, and 40 °C/min to ramp the temperature from 25 to 1000 °C. The mass percentages of RDF in the coal blends were 10%, 20%, 30%, and 40%, respec-tively. The results show... 

    Effect of slow biodegradable substrate addition on biofilm structure and reactor performance in two MBBRs filled with different support media

    , Article Environmental Technology (United Kingdom) ; Volume 41, Issue 21 , 2020 , Pages 2750-2759 Ashrafi, E ; Allahyari, E ; Torresi, E ; Andersen, H. R ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    In this study, two moving-bed biofilm reactors (MBBR1 and MBBR2) filled with different size of carrier media (Kaldnes K1 and Kaldnes K1 micro, respectively) were subjected to soluble (sugar and sodium acetate (Ac)) substrate and mixture of soluble and particulate (particulate potato starch (PS)) substrate in a very high organic loading rate (12 kgCOD/m3·d) at different temperatures (26 and 15°C, in MBBR1 and MBBR2, respectively). The effects of carrier type and substrate on biofilm structure and reactor performance have been studied. Starch was removed by adsorption at the biofilm surface and hydrolyzed which caused substrate gradient in MBBR1, however, hydrolyzed uniformly within biofilm in...