Loading...
Search for: mokhtari--negin
0.185 seconds

    Refining of Nanostructure of Polypropylene/Nanoclay Composite Via Optimization of Compatibilizer and Masterbatch

    , M.Sc. Thesis Sharif University of Technology Jalili, Negin Sadat (Author) ; Bagheri, Reza (Supervisor)
    Abstract
    Polypropylene (PP) is a fast growing polymer, particularly in automotive industry, where PP compounds have replaced many different parts made of conventional materials. In the first step, PP-g-MA, as compatibilizer, was synthesized. Two kinds of polypropylenes including a homo- and a block co-polymer were incorporated for this goal. Characterizations via titration and FTIR tests revealed higher degree of grafting reaction when homo-polymer was used for synthesizing PP-g-MA. In the next step, nanocomposites containing 3 wt% nanoclay with three different PP-g-MA/nanoclay ratios of 1:1, 2:1 and 3:1were made using a co-rotating twin screw extruder. Tensile, impact and XRD tests were performed to... 

    Oxidative coupling of methane on BaTiO3 perovskites partially substituted with germanium

    , Article 2008 AIChE Spring National Meeting, Conference, New Orleans, LA, 6 April 2008 through 10 April 2008 ; 2008 ; 9780816910236 (ISBN) Mohammadi Boghaee, D ; Hamidzadeh, M ; Negin, S ; Sharif University of Technology
    2008
    Abstract
    The perovskite oxide BaTiO3, doped with Ge oxides oxidized methane to C2 coupled hydrocarbons. The ultraviolet-visible spectra of pure barium titanate and Ge doped BaTi(1-x) GexO3 (x=0.05 ,0.1) were compared. The pure barium titanate exhibited an ultraviolet absorption effect. The addition of GeO2 resulted in an increase in absorption of wavelength. Therefore, small amount of Ge decreased band gap energy. Oxygen is inserted by nucleophilic attack which may be considered as an acid-base process. For promoted BaTiO3 catalysts with stable cation valance, electron donation ability of lattice oxygen is parallels to its ability of adsorb and active oxygen, and decrease the chance of deep oxidation... 

    Oxidative coupling of methane on BaTiO3 perovskites partially substituted with germanium

    , Article 2008 AIChE Spring National Meeting, Conference, New Orleans, LA, 6 April 2008 through 10 April 2008 ; 2008 ; 9780816910236 (ISBN); 9780816910236 (ISBN) Boghaee, D. M ; Hamidzadeh, M ; Negin, S ; Sharif University of Technology
    2008
    Abstract
    The perovskite oxide BaTiO3, doped with Ge oxides oxidized methane to C2 coupled hydrocarbons. The pure barium titanate exhibited an ultraviolet absorption effect. The addition of GeO2 resulted in an increase in absorption of wavelength. Small amount of Ge decreased band gap energy. For promoted BaTiO3 catalysts with stable cation valance, electron donation ability of lattice oxygen was parallel to its ability of adsorb and active oxygen, and decreased the chance of deep oxidation of methyl radicals and C2 hydrocarbons and thus will result in an increase of C2 yield. This is an abstract of a paper presented at the 42nd Loss Prevention Symposium (New Orleans, LA 4/6-10/2008)  

    Oxidative coupling of methane on BaTiO3 perovskites partially substituted with germanium

    , Article Catalysis and Reaction Engineering Division Conference, Presentations at the 2008 AIChE Spring National Meeting, 6 April 2008 through 10 April 2008 ; 2008 , Pages 89-94 ; 9781605602233 (ISBN) Boghaee, D. M ; Hamidzadeh, M ; Negin, S ; Sharif University of Technology
    AIChE  2008
    Abstract
    The perovskite oxide BaTiO3, doped with Ge oxides oxidized methane to C2 coupled hydrocarbons. The ultraviolet-visible spectra of pure barium titanate and Ge doped BaTi(1-x)GexO3(x=0.05,0.1) were compared. The pure barium titanate exhibited an ultraviolet absorption effect. The addition of GeO2 resulted in an increase in absorption of wavelength. Therefore, small amount of Ge decreased band gap energy. Oxygen is inserted by nucleophilic attack which may be considered as an acid-base process. For promoted BaTiO3catalysts with stable cation valance, electron donation ability of lattice oxygen is parallels to its ability of adsorb and active oxygen, and decrease the chance of deep oxidation of... 

    Facilitating Data Exchange Between Streaming Processors in GPUs

    , Ph.D. Dissertation Sharif University of Technology Nematollahizadeh Mahani, Negin Sadat (Author) ; Sadrbazi Azad, Hamid (Supervisor)
    Abstract
    GPUs are used today to accelerate a wide range of general-purpose applications (e.g., regular stencil applications and irregular graph processing applications). Due to the significant growth of the Thread Level Parallelism (TLP) in GPGPU applications, the need for data sharing between different threads has become more apparent. There are a variety of solutions for reusing data in the GPU (e.g., on-chip caches and shuffle instructions), each with its own drawbacks and reduced comprehensiveness (e.g., limiting shared memory to a thread block and shuffle instructions to a warp). Among the standard general-purpose applications, L1 data cache is a major GPU solution for reusing data among... 

    Performance evaluation of thyristor-based static transfer switch with respect to cross current

    , Article IEEE/PES Transmission and Distribution Conference and Exhibition 2002 : Asia Pacific, Yokahama, 6 October 2002 through 10 October 2002 ; Volume 2, Issue ASIA PACIFIC , 2002 , Pages 1326-1331 Mokhtari, H ; Sharif University of Technology
    2002
    Abstract
    Providing clean, continuous and reliable power to many industrial customers has become a necessity. Where possible, sensitive customers are supplied by two medium-voltage utility feeders one of which is used as back up. Thyristor-based Static Transfer Switches (STSs) are able to provide the loads with a fast transfer to the back up feeder when the main one fails. In addition to being fast, the transfer must be performed with no source paralleling which creates a cross current flowing between the main feeder and the back up one. Due to practical limitations, however, in some cases, cross current cannot be avoided. This paper investigates the performance of thyristor-based STSs with respect to... 

    The group delay ripple effects on the performance of phase-modulator based microwave-photonic filter

    , Article 2011 18th International Conference on Telecommunications, ICT 2011, 8 May 2011 through 11 May 2011, Ayia Napa ; 2011 , Pages 162-166 ; 9781457700248 (ISBN) Mokhtari, A ; Akbari, M ; Sharif University of Technology
    2011
    Abstract
    We have developed an analytic approach to investigate the effect of group delay ripple on the performance of phase-modulated microwave photonic filter. Two cases with and without ripple are analyzed to clarify the ripple's effects on the performance of microwave-photonic filter. Comparison of our proposed analytical approach with simulated OptiSystem® results shows a good agreement  

    Two building blocks of microwave photonics filters in the presence of group delay ripple: A comparative survey

    , Article Optical and Quantum Electronics ; Volume 44, Issue 8-9 , 2012 , Pages 403-414 ; 03068919 (ISSN) Mokhtari, A ; Akbari, M ; Sharif University of Technology
    Springer  2012
    Abstract
    We have developed an analytic approach to investigate the effect of group delay ripple of the dispersive devices on the performance of two major building blocks of microwave- photonic filters. Firstly, performance of PM-based block in the presence of an arbitrary group delay ripple (GDR) is analyzed and compared with the ripple-free case to reveal the destructive effects of added group delay ripple. In the next step, we repeat the proposed approach for the AM-based one; again, the performance is compared with the ripple-free case. Two distortion metrics are also introduced to quantify this distortion. Comparison of the performance of two building blocks in the presence of group delay ripple... 

    Performance of phase-modulated microwave photonics in the presence of group delay and reflection amplitude ripples of the dispersive device

    , Article Conference Proceedings - 11th International Conference on Laser and Fiber-Optical Networks Modeling, LFNM 2011, 4 September 2011 through 8 September 2011, Kharkov ; 2011 ; 9781612848136 (ISBN) Mokhtari, A ; Akbari, M ; Sharif University of Technology
    2011
    Abstract
    We develop an analytic approach to investigate the effect of reflection amplitude and group delay ripples of the dispersive device on the performance of phase-modulated microwave-photonic filters. Experimental results conform to our proposed analytical approach  

    The reflection profile engineering approach to optimize VIPA demultiplexer for UWB-Over-Fiber systems

    , Article Proceedings - 10th International Conference on Laser and Fiber-Optical Networks Modeling, LFNM 2010, 12 September 2010 through 14 September 2010 ; September , 2010 , Pages 90-92 ; 9781424469970 (ISBN) Mokhtari, A ; Akbari, M ; Sharif University of Technology
    2010
    Abstract
    We analyze the VIPA demultiplexer for different reflection profiles, i.e., uniform, graded, and Gaussian. It is shown that VIPA demultiplexer characteristics can be improved dramatically by innovative reflection profile engineering. These improvements enhance the performance of demultiplexers in UWB-Over-Fiber systems  

    Effect of a phasor group delay ripple on the performance of phase-modulator based microwavephotonic filter

    , Article 2010 5th International Symposium on Telecommunications, IST 2010, 4 December 2010 through 6 December 2010 ; 2010 , Pages 143-146 ; 9781424481835 (ISBN) Mokhtari, A ; Akbari, M ; Sharif University of Technology
    2010
    Abstract
    We have developed an analytic approach to investigate the effect of a sinusoid group delay ripple on the performance of phase-modulated microwave photonic filter. Frequency of fabricated sinusoid ripple determines the pole's frequency of the resulted transfer function. Comparison of our proposed analytical approach with simulated OptiSystem results shows a good agreement  

    Dissociation of polar oil components in low salinity water and its impact on crude oil–brine interfacial interactions and physical properties

    , Article Petroleum Science ; 2018 ; 16725107 (ISSN) Mokhtari, R ; Ayatollahi, S ; Sharif University of Technology
    China University of Petroleum Beijing  2018
    Abstract
    Despite many efforts into the study of fluids interaction in low salinity water flooding, they are not probing the basics of transport phenomena between the involved phases. This work is aimed to bring new understanding of fluid–fluid interaction during low salinity water flooding through a series of organized experiments in which a crude oil sample with known properties was kept in contact with different brine solutions of various ionic strengths. Measuring brine pH, conductivity and crude oil viscosity and density for a period of 45 days illustrates the strong effect of the contact time and ionic strength on the dissociation of polar components and physical properties of the crude oil and... 

    Dissociation of polar oil components in low salinity water and its impact on crude oil–brine interfacial interactions and physical properties

    , Article Petroleum Science ; Volume 16, Issue 2 , 2019 , Pages 328-343 ; 16725107 (ISSN) Mokhtari, R ; Ayatollahi, S ; Sharif University of Technology
    China University of Petroleum Beijing  2019
    Abstract
    Despite many efforts into the study of fluids interaction in low salinity water flooding, they are not probing the basics of transport phenomena between the involved phases. This work is aimed to bring new understanding of fluid–fluid interaction during low salinity water flooding through a series of organized experiments in which a crude oil sample with known properties was kept in contact with different brine solutions of various ionic strengths. Measuring brine pH, conductivity and crude oil viscosity and density for a period of 45 days illustrates the strong effect of the contact time and ionic strength on the dissociation of polar components and physical properties of the crude oil and... 

    Intensification of heat transfer rate in a rectangular channel equipped with pins, using non-uniform magnetic field

    , Article Journal of Nanofluids ; Volume 8, Issue 5 , 2019 , Pages 1041-1050 ; 2169432X (ISSN) Mokhtari, M ; Hariri, S ; Sharif University of Technology
    American Scientific Publishers  2019
    Abstract
    In the present study, numerical simulation is used to evaluate the influence of the non-uniform magnetic field on the heat transfer of magnetic nanofluids inside a pinned channel. This article focused on the flow pattern and heat transfer of water-based nanofluids in the presence of a wire in a three-dimensional geometry. In this work, the fluid flow is laminar and constant heat flux is applied on the wall of the channel. A wire in various orientations, in comparison with the axis of the channel, generates the magnetic field. The base fluid is water and Nano-particles (Fe3O4 and Fe) add to base fluid with different volume concentrations (0, 0.5, 1%). The computational fluids dynamic is used... 

    Structural aspects and the conduction mechanism of Ln(Ba 2-xPrx)Cu3O7+δ (Ln = Tm, Lu)

    , Article Physica Status Solidi (B) Basic Research ; Volume 244, Issue 9 , 2007 , Pages 3211-3222 ; 03701972 (ISSN) Mokhtari, Z ; Akhavan, M ; Sharif University of Technology
    2007
    Abstract
    TmBa2_xPrxCu3O7+δ and LuBa2_xPrxCu3O7+δ samples with 0.0 < x ≤ 1.0 have been prepared by a solid-state reaction technique. The occurrence of the orthorhombic to tetragonal phase transition, increasing of oxygen content with the increase of Pr doping, and the existence of solubility limit in both systems confirm the correct substitution of Pr at Ba sites. The solubility limit for Pr in the Lu-based samples is less than 0.7, which is less than x = 0.90 for the Tm-based samples. The Tc depression versus doping content in both systems shows that depression of superconductivity by Pr at Ba sites is mostly due to the hole-filling/localization effects. Also, in the Tm-based system, the... 

    Simultaneous Due date assignment and lot sizing with uncertain flow times

    , Article International Journal of Engineering, Transactions A: Basics ; Volume 20, Issue 3 , 2007 , Pages 263-280 ; 17281431 (ISSN) Mokhtari, G ; Kianfar, F ; Sharif University of Technology
    Materials and Energy Research Center  2007
    Abstract
    Due date assignment for customer orders has been studied in various production environments using different modeling approaches. In this paper the researchers consider a production system in which the orders of several customers are produced in a single batch because of the economy of scale. If a batch is completed before receiving customer orders, inventory carrying cost is incurred but if it is completed after receiving customer orders, shortage cost is incurred and finally if the order is delivered after its due date, tardiness cost is charged. The problem is to decide on batch size, due date of batch (imposed on supply process) and lead time (to be quoted to the next coming customers) so... 

    Efficiency map of a switched reluctance motor using finite element method in vehicular applications

    , Article 7th Internatonal Conference on Power Electronics, ICPE'07, Daegu, 22 October 2007 through 26 October 2007 ; 2007 , Pages 644-649 ; 9781424418725 (ISBN) Mokhtari, H ; Tara, E ; Sharif University of Technology
    IEEE Computer Society  2007
    Abstract
    Switched Reluctance Motors (SRMs), which are simple and reliable motors, have attracted interest for electric vehicle propulsion systems. It is shown that an SRM offers a good performance at high acceleration and low speed driving conditions. Efficiency map of an electric motor is a very important characteristic specially when the motor is to be used in a wide range of speed and load variations, which is the case in electric propulsion systems. In this research, the efficiency map of an SRM is derived using a combination of the Finite Element Method (FEM) and a mathematical model. This efficiency map has been used for different driving cycles to test the SRM performance as a vehicle... 

    Flux dynamics in-Ln(Ba2-xPrx)Cu3O 7+δ (Ln = Tm, Lu)

    , Article Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers ; Volume 45, Issue 2 A , 2006 , Pages 742-751 ; 00214922 (ISSN) Mokhtari, Z ; Akhavan, M ; Sharif University of Technology
    2006
    Abstract
    Single-phase Tm(Ba2-xPrx)Cu3O 7+δ and Lu(Ba2-xPrx)Cu3O 7+δ compounds with Pr content 0.0 ≤ x ≤ 1.0 have been prepared by solid-state reaction technique. The oxygen content of our samples is more than 7. X-ray diffraction (XRD) patterns demonstrate an orthorhombic to tetragonal transition with an increase in Pr content in both systems. For each system, a solubility limit exists for substitution of Pr at the Ba site. The intergrain region investigated by the thermally activated flux creep (TAFC) and Ambegaokar-Halperin (AH) models, show that the pinning energy decreases with increasing Pr content; it also decreases in each sample with increasing magnetic field as a power-law relation. The... 

    A new three phase time-domain model for electric arc furnaces using MATLAB

    , Article IEEE/PES Transmission and Distribution Conference and Exhibition 2002 : Asia Pacific, Yokahama, 6 October 2002 through 10 October 2002 ; Volume 3, Issue ASIA PACIFIC , 2002 , Pages 2078-2083 Mokhtari, H ; Hejri, M ; Sharif University of Technology
    2002
    Abstract
    This paper presents a new time domain model for electric arc furnaces using MATLAB, The model can simulate both nonlinear and time varying nature of such loads, which create flicker, harmonics, and voltage/current unbalance. In this model, Cassie and Mayr equations are used in three-phase mode and the effects of arc furnace transformer tap changer and flexible cables mutual inductances are considered. The proposed model takes into account the system inter-relation of parameters and arcing conditions as well  

    A new scheme for a mechanical load position control driven by a permanent magnet DC motor and a nonzero backlash gearbox

    , Article International Symposium on Industrial Electronics 2006, ISIE 2006, Montreal, QC, 9 July 2006 through 13 July 2006 ; Volume 3 , 2006 , Pages 2052-2057 ; 1424404975 (ISBN); 9781424404971 (ISBN) Mokhtari, H ; Barati, F ; Sharif University of Technology
    2006
    Abstract
    In this paper, a new scheme for position control of a mechanical load driven by a permanent magnet DC motor and a gearbox is presented. The gearbox is assumed to have some amount of backlash. The paper derives a model for the backlash nonlinear behavior. It then proposes a new control structure composed of feedback and feed forward control systems. The feedback control system is designed based on zero backlash. The feed forward part is employed to minimize the backlash effects. The new method is evaluated via simulations in MATLAB/SEVIULINK environment. Simulations results are provided to show the response of the proposed technique to various input references. © 2006 IEEE