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    Reactive Crystallization in an Impinging Jets Reactor

    , M.Sc. Thesis Sharif University of Technology Raoufi, Farzan (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    Abstract
    Reactive crystallization or precipitation is an important industrial process. Many chemicals and biochemicals such as catalysts and pigments are produced by precipitation. Because of the advantages of impinging jets in chemical engineering processes, the main aim of this research was to investigate the application of this method in precipitation and to study the effects of different operating and design parameters on the product’s quality and properties. Two chemical models of barium sulfate and copper oxalate were used as main products. Each of these chemicals was produced by a liquid-liquid reaction of two aqueous solutions, which were fed to an impinging-jets reactor. Effects of... 

    Numerical and Analytical Study of Mixing in Y-shaped Micromixers: Electroosmotic and Poiseuille Flow of PTT Fluids

    , M.Sc. Thesis Sharif University of Technology Reshadi, Milad (Author) ; Saeedi, Mohammad Hassan (Supervisor) ; Mozaffari, Ali Asghar (Supervisor)
    Abstract
    Dissemination of an analyte under the laminar flows plays a major role in measuring and assessment of biological fluids such as sample preparation in the context of microfluidic systems. Due to the development of manufacturing technology in the Lab-on-a-chip devices, the production of rectangular microchannels with finite aspect ratios and micron and submicron sizes has been provided by which the effect of electrokinetic phenomena on concentration distribution will be magnified in these systems. On the other hand, these biofluids are viscoelastic and show extraordinary flow behaviors, not existing in Newtonian fluids and adopting appropriate constitutive equations these exotic flow behaviors... 

    Effect of Submerged Flexible Vegetation on Vertical Mixing Coefficient

    , M.Sc. Thesis Sharif University of Technology Taheri Paqale, Ahmad (Author) ; Jamali, Mir Mosadegh (Supervisor)
    Abstract
    Environmental flows are seldom independent of plants impact. Aquatic canopies are mostly submerged and flexible; this causes a significant impact on Hydrodynamics of flow and mixing structure. Experimental and analytical investigation of vertical mixing in vegetation canopies with flexible submerged vegetation is the aim of this study. Most of the previous studies on flexible submerged vegetation were conducted to study the transverse and longitudinal mixing. In this study, flexible submerged vegetation in the density range of 2.8% to 4.2% was used to study the vertical mixing.The concentration profiles at four separate stations were obtained by image processing. The results for the... 

    Pore-Scale Investigation of the Roles of Oil Types and Pore Structure in Low Salinity Waterfloogin Using Glass Micromodel

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Saheb (Author) ; Ayatollahi, Shahabodin (Supervisor) ; Mahani, Hassan (Supervisor)
    Abstract
    Oil composition plays an undeniable role on the low salinity water flooding (LSWF) efficiency. This property directly affects the kinetics of wettability alteration through electrostatic interactions and interfacial tension (IFT). For instance, mixing in stagnant zones through a thin water film is considered as one of the most important diffusion controlled phenomenon which is goverened by Non-Fickian solute transport model. The major two potentials controlling the solute transport in thin film are salinity gradient and electrostatic potentials, which can be affected by oil composition and surface charges. This study aims to investigate the effect of oil composition on low salinity... 

    Theoretical and Experimental Study of Gas-Solid Fluidized Beds Dpm Approach

    , M.Sc. Thesis Sharif University of Technology Banaei, Mohammad (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    Abstract
    Because of the importance of gas-solid fluidized beds in industrial plants, many efforts have been done for predicting their behavior up to now. Generally, there are two major attitudes for describing and simulating the hydrodynamics of fluidized beds, Eulerian-Eulerian methods and Eulerian-Lagrangian metods. Both of these approaches have their own advantages and disadvantages and a lot of studies have been done to understand the nature of gas-solid fluidized beds with aid of these models. Due to fewer presumptions in the basic structure of Eulerian-Lagrangian methods such as DEM in comparison with Eulerian-Eulerian methods like TFM, these models can predict the hydrodynamics of fluidized... 

    Detail Design of a Supercritical Injection Tester, Based on Numerical Simulation of the Spray Structures under Supercritical Conditions

    , M.Sc. Thesis Sharif University of Technology Pourmahmoud, Ataollah (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Based on the results of a cryogenic swirl flow numerical simulation under supercritical conditions, a global injection tester has been designed. For numerical simulation of the injection process by using ANSYS FLUENT as the CFD solver, the full 3D flowfield has been meshed by a fully structure manner. k-ω(SST) has been used as the turbulence model which has been captured many of the swirl cryogenic flow structures in the both steady and unsteady conditions. Also, the modified Soave-Redlich-Kwong EOS has been accommodated in a broad range of supercritical pressures for estimating state functions, thermodynamic properties and transport properties. The results show that increasing ambient... 

    An investigation on the structural characteristics and reinforcement of melt processed polyamide 66/multiwalled carbon nanotube composites

    , Article Polymers for Advanced Technologies ; Vol. 25, issue. 4 , 2014 , pp. 406-417 ; ISSN: 10427147 Shojaei, A ; Nourbakhsh, P ; Faghihi, M ; Sharif University of Technology
    Abstract
    Properties of melt processed polyamide 66 (PA66)/multiwalled carbon nanotube composite were first characterized experimentally. The experimental results exhibited the formation of crystalline layer around the nanotubes and a considerable enhancement in mechanical properties by incorporation of multiwalled carbon nanotube up to 1 wt%. Mechanical properties were analyzed in terms of structural parameters using micromechanical models proposed in this study. It was suggested that the mechanical properties were greatly dominated by crystalline layer and nanotube length. It was also deduced that the melt mixing process caused a significant nanotube breakage restricting further enhancement of... 

    Using the direct simulation Monte Carlo method to study the effect of wall temperature variation on gas mixing evolution through micro T-mixers

    , Article 11th International Energy Conversion Engineering Conference ; 2013 Darbandi, M ; Sabouri, M ; Lekzian, E ; Schneider, G. E ; Sharif University of Technology
    2013
    Abstract
    In this work, we study the gas mixing behavior in a micro T-mixer using the direct simulation Monte Carlo (DSMC) method. The gas mixing process is monitored through a T-mixer, which is fed by two different CO and N2 gases; flowing into the T-mixer through the upper and lower inlets. We investigate the effects of axial and lateral wall temperature gradients on the mixing evolution at different rarefaction levels. The achieved results show that any temperature difference between the channel walls would result in an increase in mixing length for the chosen wall temperature gradient ranges and the studies pressure cases. Our observations show that a positive temperature gradient toward the... 

    Mixing enhancement of two gases in a microchannel using DSMC

    , Article Applied Mechanics and Materials, Dubai ; Volume 307 , 2013 , Pages 166-169 ; 16609336 (ISSN) ; 9783037856598 (ISBN) Darbandi, M ; Lakzian, E ; Sharif University of Technology
    2013
    Abstract
    In high Knudsen number flow regimes microgas flow analysis may not be performed accurately using the classical CFD methods. Alternatively, the gas flow through micro-geometries can be investigated reliably using the direct simulation Monte Carlo (DSMC) method. Our concern in this paper is to use DSMC to study the mixing of two gases in entering simultaneously into a microchannel. The mixing process is assumed to be complete when the mass composition of each species deviates by no more than ±1% from its equilibrium composition. To enhance the mixing process, we focus on the effects of inlet-outlet pressure difference and the pressure ratios of the two incoming CO and N2 streams on the mixing... 

    Down-conversion self-oscillating mixer by using CMOS technology

    , Article Proceedings - 2012 IEEE 8th International Colloquium on Signal Processing and Its Applications, CSPA 2012 ; 2012 , Pages 33-36 ; 9781467309615 (ISBN) Kouchaki, M ; Zahedi, A ; Sabaghi, M ; Ameri, S. R. H ; Niyakan, M ; Sharif University of Technology
    2012
    Abstract
    In this paper a self-oscillating mixer is presented fundamental signal generated by the oscillator subcircuit in the mixing process. The oscillator core consumes 3mA of current from a 1.8 V DC supply and results in an output power of -0.867 dBm per oscillator, and a measured phase noise of -91, -102 and -108 dBc/Hz at 100 KHz, 600 KHz and 1 MHz from the carrier, respectively. In the mixing process the proposed mixer achieved IIP3 of 0 dBm with conversation gain of 1.93 dB. The circuit was designed and simulated in 0.18-μm CMOS technology by ADS2010  

    Investigating the effect of reagent parameters on the efficiency of cell lysis within droplets

    , Article Physics of Fluids ; Volume 32, Issue 6 , 2020 Shamloo, A ; Hassani Gangaraj, M ; Sharif University of Technology
    American Institute of Physics Inc  2020
    Abstract
    Cell lysis is an essential primary step in cell assays. In the process of cell lysis, the cell membrane is destroyed and the substances inside the cell are extracted. By utilizing a droplet-based microfluidic platform for cell lysis, the mixer unit that is required for mixing lysis reagents with the cells can be excluded, and thus, the complexity of the fabrication process is reduced. In addition, lysing the cells within the droplets will prevent the cells from exposure to the channel walls, and as a result, cleanliness of the samples and the device is maintained. In this study, cell lysis within the droplets and the parameters affecting the efficiency of this process are investigated using... 

    Design, Simulation and Fabrication of a Centrifugal Microfluidic Platform for Separation and Studying of Circulating Tumor Cells

    , M.Sc. Thesis Sharif University of Technology Akbari, Ali (Author) ; Shamloo, Amir (Supervisor) ; Firoozbakhsh, Keikhosrow (Supervisor)
    Abstract
    In this project a centrifugal, microfluidic platform to the end of separation and studying circulating tumor cells is designed, modelled and analyzed. Circulating tumor cells (CTCs) are specific types of cancer cells which leave the original tumor and enter the blood stream. For the separation of CTCs, a novel anti-body separation technic has been used which targets the specific MCF7 CTCs using their corresponding Ep-CAM antibody. First the Ep-CAM antibody is coated on magnetic nanoparticles through a chemical bonding process. Afterwards the CTCs are exposed to their antibodies, through which they will bind together and form CTCs with magnetic characteristics. Finally through exerting an... 

    Numerical Study of Combustion of H2-O2 Cryogenic Propellant under Supercritical Condition

    , M.Sc. Thesis Sharif University of Technology Barani, Ehsan (Author) ; Mardani, Amir (Supervisor)
    Abstract
    In order to improve performance and optimize design of high pressure combustion devices such as liquid rocket engine, gas turbine engine, and diesel engine there is a need for comprehensive understanding of injection, mixing and combustion in supercritical condition. Under this condition chamber pressure is higher than critical pressure of fuel and oxidizer. The characteristic of supercritical condition, include changing thermophysical properties such as density, CP, and compressibility factor. Therefore under this condition ideal state equation cannot correctly predict the mentioned properties. These characteristics make supercritical combustion different from other combustion regimes.... 

    Numerical Simulations of the Coaxial Shear and Swirl Injectors’ Cryogenic Flowfields under Trans- and Supercritical Conditions

    , Ph.D. Dissertation Sharif University of Technology Poormahmood, Ata’allah (Author) ; Farshchi, Mohammad (Supervisor)
    Abstract
    Characterizing the dynamics dictating injection and mixing of the coaxial shear and swirl injectors is of central importance in the context of space rockets, diesel and direct injection reciprocating engines, and modern turbine gases. Sophisticated with precise thermo-physical models along with high-fidelity turbulence approaches, a computational platform –based on OpenFOAM open source code– is developed to simulate the practical injectors flow-fields under trans- and supercritical conditions. Aiming at providing a deep insight on the underlying physics, the investigations are conducted in a hierarchical manner; the flow complexities are added step-by-step to eventually construct the... 

    Performance analysis of AND gates based on four-wave-mixing for application in optical-code division multiple access systems

    , Article IET Optoelectronics ; Volume 6, Issue 1 , 2012 , Pages 13-25 ; 17518768 (ISSN) Noshad, M ; Noshad, M ; AlaviRad, S. M ; Sallent, S ; Sharif University of Technology
    Abstract
    In this paper, we study the performance of all optical AND gates based on the four-wave-mixing (FWM) process, for application in the receivers of the spectral phase encoded optical code division multiple access (SPE-OCDMA) systems. For the performance analysis, the spectral domain auto-correlation function of the multiple access interference signal at the output of the optical AND gate is derived and then mean and variance of the photo-detector current are calculated. For solving the Fourier transform of FWM non-linear Schrodinger equations, spectral domain Volterra series are used and the solution of these coupled equations is approximated with the first three terms of the Volterra... 

    Use of the freely-swimming, Serratia marcescens bacteria to enhance mixing in microfluidic systems

    , Article ASME 2009 International Mechanical Engineering Congress and Exposition, 13 November 2009 through 19 November 2009 ; Volume 12, Issue PART A , 2010 , Pages 463-467 ; 9780791843857 (ISBN) Peysepar, M ; Shafii, M. B ; Rasoulian, R ; Jamalifar, H ; Fazeli, M. R ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME) 
    Abstract
    Mixing has become a challenge in micro-fluidic systems because of the low Reynolds number in micro-channels. The method which is implemented in this paper is to use freely-swimming bacteria to enhance the mixing process. Accordingly, the Serratia marcescens bacteria were used for this matter. The mixing performance of the system is quantified by measuring the diffusion rate of Rhodamine B in a particular section of a channel connected to a chamber with varying Rhodamine B concentration. The concentration of Rhodamine B was measured using the Laser Induced Fluorescence (LIF) technique. The channel is in the form of a pipe and is closed on the extending side. In this paper, it is demonstrated... 

    Theoretical investigation of imidazolium based ionic liquid/alcohol mixture: A molecular dynamic simulation

    , Article Molecular Physics ; Volume 106, Issue 8 , 2008 , Pages 1015-1023 ; 00268976 (ISSN) Jahangiri, S ; Taghikhani, M ; Behnejad, H ; Ahmadi, S. J ; Sharif University of Technology
    2008
    Abstract
    In this work, molecular dynamic simulation of the mixture of imidazolium based ionic liquids with alcohols is implemented in order to investigate mixing excess properties and some structural and physical properties of the mixture. Excess volumes and enthalpies are evaluated for 11 different mole fractions of ionic liquids at each 0.1, in the range of 0 to 1. Radial distribution function, cohesive energy density, potential of mean force, solvation energy, and diffusion coefficient are reported and analysed. The effects of the cationic alkyl chain length, in comparison with changes of the anions, on these properties are reported. Results reveal that the methanol molecule participates with its...