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Investigation of Asphaltene Electro-deposition Under Dynamic Flow Conditions
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Ayatollahi, Shahabodin (Supervisor)
Abstract
Asphaltene, known as the heaviest and the most polar component of the crude oil, can precipitate because of the changes in the fluid condition such as pressure, temperature and composition. Asphaltene deposition causes major problems during oil production, in the form of fluid viscosity changes, wellbore damage and fouling in pipelines. The remediation of these problems is very expensive and needs to halt down the crude oil production. The use of electric field has been proposed recently as clean and cheap technique that could also be applied during the production period. In this work, the effect of electric potential on asphaltene precipitation in both static and dynamic modes has been...
Investigation of Asphaltene Electro-deposition In Presence of Addetives
, M.Sc. Thesis Sharif University of Technology ; Ayatollahi, Shahabodin (Supervisor) ; Dehghani, Farzaneh ($item.subfieldsMap.e)
Abstract
Given the decreasing trend of light petroleum reserves and the necessity to produce heavy and extra-heavy oil resources, the challenge of dealing with existing asphaltene related problems, which is the heaviest and the most complex component of crude oil, has become increasingly tangible. Asphaltene precipitates and deposits due to pressure, temperature or composition alterations which leads to obstruction of porous media and production facilities. Set the costly methods aside, one of the available approaches to prevent asphaltene precipitation, is to apply an electric field upon the suspected zone, which is cheap and uncomplicated. Besides, utilizing nano-particles while applying electric...
Numerical Simulation of Micro channel for Cells Counting Based on the Impedance Measurement of Cell Lysate
, M.Sc. Thesis Sharif University of Technology ; Saidi, Mohammad Said (Supervisor) ; Sani, Mahdi ($item.subfieldsMap.e)
Abstract
Nowadays cell-based microfluidic devices have many applications. One of the applications is disease diagnosis according to number of cells. Cell counting has different methods, such as optical cell counting, flow cytometry, hemocytometry, coulter counters,and so on. One of the methods of cells counting is based on measurement of changes in impedance or conductivity of surrounding medium because ions are released from surface-immobilized cells inside a micr of luidic channel.The method of cell lysate impedance spectroscopy is sensitive enough and it was offered for detecting and enumerating CD4+ cells in HIV patients. In this study,...
Pressure effects on electroosmotic flow of power-law fluids in rectangular microchannels
, Article Theoretical and Computational Fluid Dynamics ; Vol. 28, issue. 4 , 2014 , pp. 409-426 ; ISSN: 09354964 ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
Abstract
In this paper, the fully developed electroosmotic flow of power-law fluids in rectangular microchannels in the presence of pressure gradient is analyzed. The electrical potential and momentum equations are numerically solved through a finite difference procedure for a non-uniform grid. A complete parametric study reveals that the pressure effects are more pronounced at higher values of the channel aspect ratio and smaller values of the flow behavior index. The Poiseuille number is found to be an increasing function of the channel aspect ratio for pressure assisted flow and a decreasing function of this parameter for pressure opposed flow. It is also observed that the Poiseuille number is...
An analytical solution for dynamic behavior of thick doubly curved functionally graded smart panels
, Article Composite Structures ; Vol. 107, issue , January , 2014 , p. 88-102 ; Askari Farsangi, M. A ; Sharif University of Technology
Abstract
In this paper, an analytical solution is presented for free vibration and dynamic behavior of doubly curved laminated shell consisting of a functionally graded core layer and surface attached functionally graded piezoelectric layers. Shell through-thickness kinematics is based on higher order shear deformation theory of shells, whereas a quadratic variation is assumed for electric potential. Using Hamilton's principle and Maxwell's equation, the governing equations of motion under mechanical loads are derived as seven highly coupled partial differential equations. Implementing Laplace transformation, doing few mathematical operations and using Laplace inverse method, time dependencies of...
Variational formulation on Joule heating in combined electroosmotic and pressure driven microflows
, Article International Journal of Heat and Mass Transfer ; Volume 61, Issue 1 , June , 2013 , Pages 254-265 ; 00179310 (ISSN) ; Saidi, M. H ; Waezi, Z ; Chakraborty, S ; Sharif University of Technology
2013
Abstract
The present study attempts to analyze the extended Graetz problem in combined electroosmotic and pressure driven flows in rectangular microchannels, by employing a variational formulation. Both the Joule heating and axial conduction effects are taken into consideration. Since assuming a uniform inlet temperature profile is not consistent with the existence of these effects, a step change in wall temperature is considered to represent physically conceivable thermal entrance conditions. The method of analysis considered here is primarily analytical, in which series solutions are presented for the electrical potential, velocity, and temperature. For general treatment of the eigenvalue problem...
Biodegradation of heavy fuel oil by newly isolated strain enterobacter cloacae BBRC10061: Study of unstructured kinetic models and innovative equation
, Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1929-1938 ; 10263098 (ISSN) ; Mashreghi, M ; Yaghmaei, S ; Sharif University of Technology
Sharif University of Technology
2013
Abstract
Modeling process is very important and valuable to predict process outcome, especially bioprocesses which are intricate. Because of complex hydrocarbon compounds and oscillations happened in the medium of process, biodegradation of mazut has not already been investigated by mathematical models. In this study, an indigenous bacterium was isolated from oil contaminated soil to investigate biodegradation of mazut at different experimental conditions. Data resulted from mazut degradation, pH, and electrical potential in the medium were recorded. Some reported kinetic models and combinations were investigated to practically model the process. In addition, a new equation that can predict various...
Electrokinetically driven fluidic transport of power-law fluids in rectangular microchannels
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 414 , 2012 , Pages 440-456 ; 09277757 (ISSN) ; Sadeghi, A ; Saidi, M. H ; Mozafari, A. A ; Sharif University of Technology
2012
Abstract
Electroosmosis is the predominant mechanism for flow generation in lab-on-chip devices. Since most biofluids encountered in these devices are considered to be non-Newtonian, it is vital to study the flow characteristics of common non-Newtonian models under electroosmotic body force. In this paper, the hydrodynamically fully developed electroosmotic flow of power-law fluids in rectangular microchannels is analyzed. The electrical potential and momentum equations are numerically solved through a finite difference procedure for a non-uniform grid. A thoroughgoing parametric study reveals that the Poiseuille number is an increasing function of the channel aspect ratio, the zeta potential, the...
Axisymmetric thermo-electro-elastic analysis of a piezoelectric half space
, Article Mathematics and Mechanics of Solids ; Volume 17, Issue 5 , September , 2012 , Pages 500-515 ; 10812865 (ISSN) ; Hashemi, R ; Hashemi, M ; Sadeghi, H ; Sharif University of Technology
2012
Abstract
In this study, an analytical solution is presented for thermo-electro- elastic analysis of piezoelectric semi-infinite bodies. For this purpose, governing equations are derived for a transversely isotropic piezoelectric material under an axisymmetric thermo-electro-mechanical loading condition. A general closed-form analytical solution is presented for the complementary and particular parts of the components of the displacement vector and also for the electric potential function. Then, boundary conditions are imposed and in that case an explicit solution is obtained for piezoelectric semi-infinite bodies. Results show that when a piezoelectric half space is subjected to constant/ramp surface...
Novel polyamide-based nanofibers prepared by electrospinning technique for headspace solid-phase microextraction of phenol and chlorophenols from environmental samples
, Article Analytica Chimica Acta ; Volume 716 , 2012 , Pages 34-39 ; 00032670 (ISSN) ; Aghakhani, A ; Baghernejad, M ; Akbarinejad, A ; Sharif University of Technology
2012
Abstract
A novel solid phase microextraction (SPME) fiber was fabricated by electrospinning method in which a polymeric solution was converted to nanofibers using high voltages. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three dimensional structure. Polyamide (nylon 6), due to its suitable characteristics was used to prepare the unbreakable SPME nanofiber. The scanning electron microscopy (SEM) images of this new coating showed a diameter range of 100-200nm for polyamide nanofibers with a homogeneous and porous surface...
Welding current and arc voltage control in a GMAW process using ARMarkov based MPC
, Article Control Engineering Practice ; Volume 19, Issue 12 , December , 2011 , Pages 1408-1422 ; 09670661 (ISSN) ; Haeri, M ; Sharif University of Technology
Abstract
A predictive functional controller based on ARMarkov model structure has been designed to control welding current and arc voltage in a GMAW process. The closed loop system performance is investigated through computer simulations and is compared by those achieved from implementing two commonly used controllers i.e. PI and feedback linearization based PID. The local stability of the closed loop system is analyzed in the presence of uncertainties in the linearized model of the process as well as the control parameters. Finally it is shown that the proposed controller performs like a PI controller along with a pre-filter compensator
Double stage switch mode AC voltage regulator
, Article 2011 2nd Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2011, 16 February 2011 through 17 February 2011 ; February , 2011 , Pages 187-192 ; 9781612844213 (ISBN) ; Yazdian, A ; Mokhtari, H ; Sharif University of Technology
2011
Abstract
Development of high frequency power electronic devices leads to high performance and flexible switch mode AC voltage stabilizers instead of traditional electromechanical types. This paper introduces a novel double stage topology for switch mode AC voltage regulators. The system produces a continuous adjustable isolated AC voltage providing a constant output voltage for sensitive loads. In order to simplify the control strategy, a symmetrical PWM is used. In contrast with conventional AC choppers, the proposed circuit does not need any snubber circuits or voltage and current sensors which leads to a simpler and more reliable circuit. Detailed analysis and simulation results show the...
Distribution system planning considering integration of distributed generation and load curtailment options in a competitive electricity market
, Article Electrical Engineering ; Volume 93, Issue 1 , 2011 , Pages 23-32 ; 09487921 (ISSN) ; Abbaspour Tehrani Fard, A ; Poure, P ; Saadate, S ; Sharif University of Technology
Abstract
Distribution systems management is becoming an increasingly complicated issue due to the introduction of new technologies, new energy trading strategies and new deregulated environment. In the new deregulated energy market and considering the incentives coming from the technical and economical fields, it is reasonable to consider distributed generation (DG) as a viable option to solve the lacking electric power supply problem. This paper presents a mathematical distribution system planning model considering three planning options to system expansion and to meet the load growth requirements with a reasonable price as well as the system power quality problems. DG is introduced as an attractive...
Steric effects on electrokinetic flow of non-linear biofluids
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 484 , 2015 , Pages 394-401 ; 09277757 (ISSN) ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
Elsevier
2015
Abstract
Some of electrokinetic-based biomicrofluidic devices work at zeta potentials that are sufficiently high for ionic size (steric) effects to show up. In the present effort, consideration is given to the steric effects on the hydrodynamics of electroosmotic flow in a rectangular microchannel. The distinction between this research and the previous ones is that we account for non-linear rheology of the fluids encountered in biomicrofluidic systems by means of the power-law viscosity model. The method of analysis consists of a finite-difference-based numerical procedure for a non-uniform distribution of grid points, which is applied to the dimensionless form of the governing equations including...
Electrokinetic mixing at high zeta potentials: Ionic size effects on cross stream diffusion
, Article Journal of Colloid and Interface Science ; Volume 442 , 2015 , Pages 8-14 ; 00219797 (ISSN) ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
Academic Press Inc
2015
Abstract
The electrokinetic phenomena at high zeta potentials may show several unique features which are not normally observed. One of these features is the ionic size (steric) effect associated with the solutions of high ionic concentration. In the present work, attention is given to the influences of finite ionic size on the cross stream diffusion process in an electrokinetically actuated Y-shaped micromixer. The method consists of a finite difference based numerical approach for non-uniform grid which is applied to the dimensionless form of the governing equations, including the modified Poisson-Boltzmann equation. The results reveal that, neglecting the ionic size at high zeta potentials gives...
Transport in droplet-hydrogel composites: response to external stimuli
, Article Colloid and Polymer Science ; Volume 293, Issue 3 , March , 2015 , Pages 941-962 ; 0303402X (ISSN) ; Sharif University of Technology
Springer Verlag
2015
Abstract
Determination of effective transport properties of droplet-hydrogel composites is essential for various applications. The transport of ions through a droplet-hydrogel composite subjected to an electric field is theoretically studied as an initial step toward quantifying the effective transport properties of droplet-hydrogel composites. A three-phase electrokinetic model is used to derive the microscale characteristics of the polyelectrolyte hydrogel, and the droplet is considered an incompressible Newtonian fluid. The droplet-hydrogel interface is modeled as a surface, which encloses the interior fluid. The surface has the thickness of zero and the electrostatic potential ζ. Standard...
Neural implant stimulation based on TiO2 nanostructured arrays; A multiphysics modeling verification
, Article IECBES 2014, Conference Proceedings - 2014 IEEE Conference on Biomedical Engineering and Sciences: "Miri, Where Engineering in Medicine and Biology and Humanity Meet", 8 December 2014 through 10 December 2014 ; December , 2015 , Pages 677-680 ; 9781479940844 (ISBN) ; Mohammadpour, R ; Amiri, K ; Silterra; University of Malaya ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Exploiting of the nanostructure arrays as a promising candidate for excitation of neural cells has been analyzed. Based on the importance of the coupling effect between electrode and neuron, a multiphyscis modeling approach has been proposed. The model incorporates theoretically both structural effects (size, geometry) and electrophysiological effects. The system of equations for proposed model has been solved numerically using Finite Element Method for Poisson equation and Finite Difference Method for Cable equation. In this regards we have combined the system of equations in COMSOL platform with Matlab interface accordingly. We have analyzed the effect of excitation of neuron with an extra...
Voltammetric behavior and determination of trace amounts of omeprazole using an edge-plane pyrolytic graphite electrode
, Article Iranian Journal of Pharmaceutical Research ; Volume 14, Issue 2 , Spring , 2015 , Pages 465-471 ; 17350328 (ISSN) ; Ghalkhani, M ; Bayat, M ; Ghorbani Bidkorbeh, F ; Sharif University of Technology
Iranian Journal of Pharmaceutical Research
2015
Abstract
The voltammetric performance of edge-plane pyrolytic graphite (EPG) electrode via adsorptive stripping voltammetry was investigated for study of the electrochemical behavior of omeprazole (OMZ) in aqueous solution. The results revealed that the oxidation of OMZ is an irreversible pH-dependent process that proceeds with the transfer of one electron and one proton in an adsorption-controlled mechanism. The determination conditions, such as the pH values of the supporting electrolyte, accumulation time and scan rate were optimized. Simplicity, high reproducibility and low detection limit (3 nM) of the electrode response as well as wide linear range (0.01 to 4.0 µM) can be stated as significant...
Hydrodynamic and electrochemical modeling of vanadium redox flow battery
, Article Mechanics and Industry ; Volume 16, Issue 2 , 2015 ; 22577777 (ISSN) ; Elyasi, S ; Mollazadeh, M ; Sharif University of Technology
EDP Sciences
2015
Abstract
Two and three dimensional modeling of a single cell of vanadium redox flow battery has been done thoroughly according to electrochemical and fluid mechanic equations in this study. The modeling has been done in stationary state and its results have been presented in three chemical, electrical and mechanical sub models. The parametric analysis on some of important factors in cell operation demonstrated that increase in electrode and membrane conductivity and electrode porosity contributes to electric potential increase in cells. Also operational temperature increase leads to decrease in cells' voltage. Better fluid distribution on the electrode surface area results in better cell operation,...
Optimum nonlinear model predictive controller design for flyback PFC rectifiers
, Article ISIEA 2010 - 2010 IEEE Symposium on Industrial Electronics and Applications, 3 October 2010 through 5 October 2010 ; October , 2010 , Pages 70-75 ; 9781424476473 (ISBN) ; Abedi, M. R ; Rezaei, K ; IEEE Malaysia Section; IEEE Malaysia Power Electron. (PEL)/; Ind. Electron.(IE)/ Ind. Appl. (IA) Jt. Chapter ; Sharif University of Technology
2010
Abstract
Single-phase ac-dc Power Factor Correction (PFC) rectifiers have attracted considerable attention in recent years due to the adoption of increasingly stringent power quality regulations. In this paper a nonlinear model predictive controller design for a single-phase Flyback PFC rectifier is presented. After approximation of the tracking error in the receding horizon by its Taylor-series expansion to a specified order, an analytic solution to the model predictive control (MPC) is developed and a closed-loop nonlinear predictive controller is introduced. The main advantage of this digital control method is that unity power factor can be achieved over wide input voltage, load current range and...