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3D numerical analysis of joule heating effect on electroosmotic flow in microchannels
, Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 A , 2006 , Pages 203-208 ; 0791847608 (ISBN); 9780791847602 (ISBN) ; Yazdi, S ; Salehi, M. A ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
In this paper, a three-dimensional numerical model is developed to analyze the influence of the Joule heating on flow characteristics of an electroosmotic flow through square cross section micro-channels. The governing system of equations consists of three sets of equations: electric potential distribution, flow-field and energy equations. The solution procedure involves three steps. The net charge distribution on the cross section of the micro-channel is computed by solving two-dimensional Poisson-Boltzmann equation using the finite element method. Then, using the computed fluid's charge distribution, the magnitude of the resulting body force due to interaction of an external electric field...
A genetic based method for optimal reactive power compensation of transmission network
, Article Australian Journal of Electrical and Electronics Engineering ; Volume 3, Issue 1 , 2006 , Pages 47-55 ; 1448837X (ISSN) ; Vakilian, M ; Sharif University of Technology
Institution of Engineers (Australia)
2006
Abstract
Reactive power compensation is known as an effective tool to overcome the violations of voltage limits in electric power systems. It is also deployed to be an efficient method to minimise transmission losses. In order to maximize the effectiveness of reactive power compensation, VAr sources of proper sizes should be placed at some network buses. In this paper, a new VAr expansion tool has been developed to improve the voltage profile and reduce MW losses in a bulk power network. Keeping the minimum expansion cost and minimum switching of capacitor banks during change of load level of the system are emphasized in the proposed method. This method is based on application of genetic algorithm in...
GA-based optimization of total harmonic current distortion and suppression of chosen harmonics in induction motors
, Article International Symposium on Power Electronics, Electrical Drives, Automation and Motion, 2006. SPEEDAM 2006, Taormina, 23 May 2006 through 26 May 2006 ; Volume 2006 , 2006 , Pages 1361-1366 ; 1424401941 (ISBN); 9781424401949 (ISBN) ; Aflaki, M ; Rezazade, A. R ; Sharif University of Technology
2006
Abstract
In this study, a genetic algorithm optimization technique is applied, to minimize the total harmonic current distortion (THCD) in induction motors fed by high power inverters, based on an approximate model. That is, having defined a desired fundamental output voltage, optimal pulse patterns (switching angles) are determined to produce the fundamental output voltage while minimizing the THCD. The complete results for two cases of 3 and 5 switching instants in the first quarter period of PWM waveform are presented. In the sequel, considering that the torque pulsation is mainly affected by the presence of low-order harmonics, the fifth, seventh, 11th, and 13th order harmonics (in the case of 5...
Optimization of THD and suppressing certain order harmonics in PWM inverters using genetic algorithms
, Article Joint 2006 IEEE Conference on Control Applications (CCA), Computer-Aided Control Systems Design Symposium (CACSD) and International Symposium on Intelligent Control (ISIC), Munich, 4 October 2006 through 6 October 2006 ; 2006 , Pages 874-879 ; 0780397983 (ISBN); 9780780397989 (ISBN) ; Aflaki, M ; Rezazade, A. R ; Sharif University of Technology
2006
Abstract
In this paper the aim is to minimize the total harmonic distortion (THD) in PWM inverters while suppressing chosen harmonics concurrently and maintaining the fundamental component of the output voltage at a required level. This is reformed as an optimization task and the optimal pulse patterns are accomplished using genetic algorithm (GA) optimization technique to minimize a predefined fitness function. The complete solutions that suppress the 5 th and 7 th harmonics and optimize the THD are given. A practical limitation on the determination of sequential switching angles has been considered as a set of constraints in derivation of the results. © 2006 IEEE
A numerical procedure for obtaining the static and pull-in deflection and voltage of capacitive microcantilever beams
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Alasty, A ; Sharif University of Technology
2006
Abstract
A numerical procedure is proposed for obtaining the static deflection, pull-in (PI) deflection and PI voltage of electrostatically excited capacitive microcantilever beams. The method is not time and memory consuming as Finite Element Analysis (FEA). Nonlinear ordinary differential equation of the static deflection of the beam is derived, w/wo considering the fringing field effects. The nondimensional parameters upon which PI voltage is dependent are then found. Thereafter, using the parameters and the numerical method, three closed form equations for pull-in voltage are developed. The results are in good agreement with others in literature. Copyright © 2006 by ASME
Assessment study of shunt FACTS devices for improving dynamic behavior of induction motors
, Article Sixth International Conference on Power Electronics and Drive Systems, PEDS 2005, Kualu Lumpur, 28 November 2005 through 1 December 2005 ; Volume 2 , 2005 , Pages 1352-1355 ; 0780392965 (ISBN); 9780780392960 (ISBN) ; Oraee, H ; Sharif University of Technology
2005
Abstract
An assessment study of two different shunt FACTS devices for compensating disturbances due to voltage variation in power systems is presented in this paper. Namely, Static Compensator (STATCOM) and Static Var Compensator (SVC) are Considered in this study. Eigen Value analysis and nonlinear time domain simulations for starting motor, motor in load varying state and short circuit on motor terminals show that STATCOM DC Voltage regulation has a better performance Compared to that of SVC. The result that will be presented in the paper will prove the superiorly of STATCOM over SVC in increasing motor speeding up and improving system voltage profile particularly at starting. © 2005 IEEE
A 1.5V 150MS/s current-mode sample-and-hold circuit
, Article 2005 European Conference on Circuit Theory and Design, Cork, 28 August 2005 through 2 September 2005 ; Volume 2 , 2005 , Pages 91-94 ; 0780390660 (ISBN); 9780780390669 (ISBN) ; Rajaee, O ; Jahanian, A ; Bakhtiar, M. S ; Sharif University of Technology
2005
Abstract
A high-speed current-mode sample-and-hold circuit is presented. This circuit allows for high sampling speed together with high linearity and precision. The sample-and-hold circuit has been designed and simulated in standard 0.18μm CMOS technology with 1.5V supply voltage. It is capable of operation with sampling frequency of 150MHz (300MHz using double sampling technique) for 12-bit accuracy using 3.7mW power
High energy efficiency in syngas and hydrocarbon production from dissociation of CH4-CO2 mixture in a non-equilibrium pulsed plasma
, Article Journal of Physics D: Applied Physics ; Volume 38, Issue 20 , 2005 , Pages 3804-3811 ; 00223727 (ISSN) ; Norouzi, S ; Mohammadi, T ; Sharif University of Technology
2005
Abstract
The efficient production of syngas from a CH4+CO2 mixture in an atmospheric pulsed glow discharge, sustained by corona pre-ionization, has been investigated. The products were mainly syngas (CO, H2) and hydrocarbons up to C4, with acetylene having the highest selectivity. The energy efficiency was within 15-40% for different experimental conditions, which demonstrates a comprehensive improvement relative to the achievements of other types of non-equilibrium plasma. These values are, however, comparable with the efficiencies obtained by gliding arc plasmas but this plasma operates at near room temperature. Furthermore, it has been shown that the energy efficiency is increased by decreasing...
Duty-cycle controller for low-jitter frequency-doubling DLL
, Article IEE Proceedings: Circuits, Devices and Systems ; Volume 152, Issue 5 , 2005 , Pages 411-416 ; 13502409 (ISSN) ; Atarodi, M ; Bazargan, H ; Sharif University of Technology
2005
Abstract
This article introduces a novel duty-cycle control circuit (DCC) preceding a delay-locked loop (DLL)-based clock frequency multiplier preventing the output duty-cycle over process, supply voltage and temperature (PVT) variations. However, the proposed DCC eliminates the effect of input duty-cycle variation and, hence, decreases the sensitivity to the input jitter and distortion. The circuit realisation in 0.5-μm CMOS technology shows that the duty-cycle variation at the output clock is less than 2.7%, while driving the digital section of a CODEC chip and also test pads. The analysis, confirmed by measurements, shows a stable and accurate response for the proposed clock generation unit (CGU)....
Analytical results on coherent conductance in a general periodic quantum dot: Transfer matrix method
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 28, Issue 2 , 2005 , Pages 150-161 ; 13869477 (ISSN) ; Shokri, A. A ; Esfarjani, K ; Sharif University of Technology
2005
Abstract
In this work, we study the conductance of a general periodic quantum dot (QD) attached to ideal semi-infinite uniform metallic leads (nanocrystals), fully analytically. We propose a new general formula which relates conductance to transfer matrix (TM) for an isolated cell in the periodic dot. The equation describes exactly the dependence of the transmission coefficient (TC) on Fermi energy, dot-size, dot-lead coupling, and gate voltage for an arbitrary periodic dot. Then, we derive a nonlinear equation which gives the resonance, bound, and surface state energies. Finally, the TC has been calculated for gapless, single, and double gap models exactly. Moreover, we have also calculated the...
Electrodeposition of Ni-Fe-Co alloy nanowire in modified AAO template
, Article Materials Chemistry and Physics ; Volume 91, Issue 2-3 , 2005 , Pages 417-423 ; 02540584 (ISSN) ; Ghorbani, M ; Sharif University of Technology
2005
Abstract
Anodic aluminum oxide (AAO) was used as a template to prepare highly ordered Ni-Fe-Co alloy nanowire arrays. This membrane was fabricated with two-step anodizing method. It is found that there is an optimum barrier thickness to obtain a successful electrodeposition in pores of AAO. The thickness of barrier layer can be modified by additional electrochemical process after completing the anodizing step. Barrier layer thinning can create a rooted structure at the bottom side of the AAO pores and the electrodeposited nanowire arrays. The triple Ni-Fe-Co alloy was deposited in AAO membrane by ac voltage in a simple sulfate bath. The composition of nanowires shows anomalous deposition features...
A low voltage 14-bit self-calibrated CMOS DAC with enhanced dynamic linearity
, Article Analog Integrated Circuits and Signal Processing ; Volume 43, Issue 2 , 2005 , Pages 137-145 ; 09251030 (ISSN) ; Mehrmanesh, S ; Atarodi, M ; Sharif University of Technology
2005
Abstract
A 1-V CMOS current steering digital to analog converter with enhanced static and dynamic linearity is presented. The 14-bit static linearity is achieved by a background analog self calibration technique which is suitable for low voltage applications and does not require error measurement and correction circuits. To improve dynamic linearity at high frequencies a track/attenuate output stage is used at the DAC output. Integral and differential nonlinearities of the proposed DAC corresponding to 14-bit specification are less than 0.35 and 0.25 LSB respectively. The DAC is functional up to 400MS/s with SFDR better than 71 dB in the Nyquist band. The circuit has been designed and simulated in a...
A low-power, multichannel gated oscillator-based CDR for short-haul applications
, Article 2005 International Symposium on Low Power Electronics and Design, San Diego, CA, 8 August 2005 through 10 August 2005 ; 2005 , Pages 107-110 ; 15334678 (ISSN) ; Muller, P ; Atarodi, M ; Leblebici, Y ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2005
Abstract
A gated current-controlled oscillator (GCCO) based topology is used to implement a low-power multi-channel clock and data recovery (CDR) system in a 0.18um digital CMOS technology. A systematic approach is presented to design a reliable and low-power system based on the required specifications. Behavioral simulations are also used to estimate the achievable bit error rate (BER), jitter tolerance (JTOL), and frequency offset tolerance (FTOL) of the proposed CDR. Using a single 1.8V supply voltage, the proposed 20Gbps 8-channel CDR consumes only 70.2mW or 3.51mW/Channel/Gbps while occupies 0.045mm2 silicon area. Copyright 2005 ACM
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...
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...
Simulation and optimization of HEMTs
, Article 3rd International Conference on Advances in Computational Tools for Engineering Applications, 13 July 2016 through 15 July 2016 ; 2016 , Pages 1-6 ; 9781467385237 (ISBN) ; Ashrafi, R ; Khorasani, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
We have developed a simulation system for nanoscale high-electron mobility transistors, in which the self-consistent solution of Poisson and Schrödinger equations is obtained with the finite element method. We solve the exact set of nonlinear differential equations to obtain electron wave function, electric potential distribution, electron density, Fermi surface energy and current density distribution in the whole body of the device. For more precision, local dependence of carrier mobility on the electric field distribution is considered. We furthermore compare the simulation to a recent experimental measurement and observe perfect agreement. We also propose a novel graded channel design,...
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...
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...
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