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Reduced complexity 1-bit high-order digital delta-sigma modulator for low-voltage fractional-N frequency synthesis applications
, Article IEE Proceedings: Circuits, Devices and Systems ; Volume 152, Issue 5 , 2005 , Pages 471-477 ; 13502409 (ISSN) ; Afzali Kusha, A ; Dehghani, R ; Mehrara, M ; Atarodi, S. M ; Nourani, M ; Sharif University of Technology
2005
Abstract
A reduced complexity third-order digital delta-sigma modulator for fractional-N frequency synthesis is presented. The high-performance modulator, which consists of two subblocks, has a single-bit output making it best for this sort of application. A good shaping of quantisation noise is achieved using a new architecture for a digital third-order delta-sigma modulator. The hardware required for this modulator is considerably less than that in previously reported leading to lower power and area consumption and a higher operating frequency. The field programmable gate array (FPGA) implementation of the whole system shows an SNR of at least 94 dB and an operating input range of 0.7 of the full...
Simulation of partial discharge propagation and location in Abetti winding based on structural data
, Article 7th International Power Engineering Conference, IPEC2005, Singapore, 29 November 2005 through 2 December 2005 ; Volume 2005 , 2005 ; 9810544693 (ISBN); 9789810544690 (ISBN) ; Vakilian, M ; Blackburn, T. R ; Phung, B. T ; Hio, N. O ; Naderi, M. S ; Ghaemmaghami, R ; Sharif University of Technology
IEEE Computer Society
2005
Abstract
Power transformer monitoring as a reliable tool for maintaining purposes of this valuable asset of power systems has always comprised partial discharge offline measurements and online monitoring. The reason lies in non-destructive feature of PD monitoring. Partial discharge monitoring helps to detect incipient insulation faults and prevent insulation failure of power transformers. This paper introduces a software package developed based on structural data of power transformer and discusses the results of the simulation on Abetti winding, which might be considered as a basic layer winding. A hybrid model is used to model the transformer winding, which has been developed by first author....
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...
Dynamics of electrostatic interaction and electrodiffusion in a charged thin film with nanoscale physicochemical heterogeneity: Implications for low-salinity waterflooding
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 650 , 2022 ; 09277757 (ISSN) ; Mahani, H ; Niasar, V ; Sharif University of Technology
Elsevier B.V
2022
Abstract
The slow kinetics of wettability alteration toward a more water-wetting state by low-salinity waterflooding (LSWF) in oil-brine-rock (OBR) systems is conjectured to be pertinent to the electrokinetic phenomena in the thin brine film. We hypothesize that the nanoscale physicochemical heterogeneities such as surface roughness and surface charge heterogeneity at the rock/brine interface control further the dynamics of electrodiffusion and electrostatic disjoining pressure (Πel), thus the time-scale and the magnitude of the low salinity effect (LSE). In this regard, film-scale computational fluid dynamics (CFD) simulations were performed. The coupled Poisson-Nernst-Planck (PNP) equations were...
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...
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...
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...
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,...
Viscous dissipation effects on thermal transport characteristics of combined pressure and electroosmotically driven flow in microchannels
, Article International Journal of Heat and Mass Transfer ; Volume 53, Issue 19-20 , 2010 , Pages 3782-3791 ; 00179310 (ISSN) ; Saidi, M. H ; Sharif University of Technology
Abstract
This study investigates the influence of viscous dissipation on thermal transport characteristics of the fully developed combined pressure and electroosmotically driven flow in parallel plate microchannels subject to uniform wall heat flux. Closed form expressions are obtained for the transverse distributions of electrical potential, velocity and temperature and also for Nusselt number. From the results it is realized that the Brinkman number has a significant effect on Nusselt number. Generally speaking, to increase Brinkman number is to decrease Nusselt number. Although the magnitude of Joule heating can affect Brinkman number dependency of Nusselt number, however the general trend remains...
Efficient control scheme of wind turbines with doubly fed induction generators for low-voltage ride-through capability enhancement
, Article IET Renewable Power Generation ; Volume 4, Issue 3 , May , 2010 , Pages 242-252 ; 17521416 (ISSN) ; Parniani, M ; Sharif University of Technology
2010
Abstract
As the penetration of wind power in electrical power systems increases, it is required that wind turbines remain connected to the grid and actively contribute to the system stability during and after grid faults. This study proposes an efficient control strategy to improve the low-voltage ride-through (LVRT) capability in doubly fed induction generators (DFIGs). The proposed scheme consists of passive and active LVRT compensators. The passive compensator is based on a new crowbar arrangement located in series with stator windings. It considerably reduces the rotor inrush current at the instants of occurring and clearing the fault. The active LVRT compensator is realised through rotor voltage...
A multistage model for distribution expansion planning with distributed generation in a deregulated electricity market
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 34, Issue 3 , 2010 , Pages 275-287 ; 10286284 (ISSN) ; Abbaspour Tehrani Fard, A ; Poure, P ; Saadate, S ; Sharif University of Technology
2010
Abstract
Distribution systems management is becoming an increasingly complicated issue due to the introduction of new technologies, new energy trading strategies and a new deregulated environment. In the new deregulated energy market and considering the incentives coming from the technical and economic fields, it is reasonable to consider Distributed Generation (DG) as a viable option for systems reinforcement in competition with voltage regulator devices, to solve the lacking electric power supply problem and meet the load growth requirements with a reasonable price as well as the system power quality problems. The problem of optimal placement and size is formulated in two stages; minimization of...
Effects of structural configuration on vibration control of smart laminated beams under random excitations
, Article Journal of Mechanical Science and Technology ; Volume 24, Issue 5 , 2010 , Pages 1119-1125 ; 1738494X (ISSN) ; Sharif University of Technology
Abstract
The influence of structural configuration on vibration responses of smart laminated beams under random loading is studied. The effect of laminate configurations and locations of sensors/actuators in the smart system is also investigated. The layer-wise approximation for displacement and electric potential is utilized to construct the finite element model. The closed-loop control response is determined through an optimal control algorithm based on the Linear Quadratic Regulator (LQR). The correlation coefficient between the input random force and the applied actuating voltage for various configurations is also computed. It is revealed that for softer configurations, the correlation...
CFD aided procedure for optimizing electrical mobility spectrometer
, Article Defect and Diffusion Forum ; Volume 366 , 2016 , Pages 73-87 ; 10120386 (ISSN) ; Shaygani, A ; Sani, M ; Saidi, M. S ; Sharif University of Technology
Trans Tech Publications Ltd
Abstract
Aerosol measurement is used in a variety of fields such as nanotechnology, materials science, pollution monitoring, air quality measurements, combustion and engine exhaust analysis, inhalation toxicology, and medical studies. One of the most prevalent methods for aerosol measurement is to use electrical mobility. An electrical mobility spectrometer (EMS) is used to measure aerosol particles size distribution ranging from 10-1000 nanometers, under the influence of an electric field. The accuracy of this distribution is influenced by flow conditions, the geometry of the EMS, the electric field, and the number of electrode rings. In this work, a multi-channel EMS is studied using computational...
A new nonlinear controller for active power filters
, Article 2009 International Conference on Electric Power and Energy Conversion Systems, EPECS 2009, 10 November 2009 through 12 November 2009 ; 2009 ; 9789948427155 (ISBN) ; Mokhtari, H ; Sharif University of Technology
Abstract
Linear controllers have been widely used for controlling Active Power Filters (APFs). However, due to their limitations, a tradeoff between the bandwidth of the current control loop (CCL) and the voltage control loop (VCL) need to be made to remain stable in all conditions. This tradeoff leads to imperfect usage of the APF's capacity. Nonlinear controllers can eliminate such limitations and simultaneously remain stable in all conditions. In this paper, a new nonlinear controller for controlling the output current and the DC voltage (Vdc) of an APF is proposed. Feedback linearization method is applied on the CCL and the VCL is controlled via indirect method. In this method, an auxiliary...
Reduction of production rate in y-shaped microreactors in the presence of viscoelasticity
, Article Analytica Chimica Acta ; Volume 990 , 2017 , Pages 121-134 ; 00032670 (ISSN) ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
Abstract
The viscoelasticity effects on the reaction-diffusion rates in a Y-shaped microreactor are studied utilizing the PTT rheological model. The flow is assumed to be fully developed and considered to be created under a combined action of electroosmotic and pressure forces. In general, finite-volume-based numerical simulations are conducted to handle the problem; however, analytical solutions based on the depthwise averaging approach are also obtained for the case for which there is no reaction between the inlet components. The analytical solutions are found to predict accurate results when the width to height ratio is at least 10 and acceptable results for lower aspect ratios. An investigation...
Improving the performance of a numerical model to simulate the EHD interaction effect induced by dielectric barrier discharge
, Article International Journal of Heat and Fluid Flow ; Volume 67 , 2017 , Pages 79-94 ; 0142727X (ISSN) ; Mazaheri, K ; Sharif University of Technology
Abstract
Over the past decade, there has been a growing interest in dielectric-barrier-discharge (DBD) plasma actuators. The lack of a general model to accurately simulate the related phenomena is one of the primary limitations in studying such type of actuators. One of the most frequently used models of this type was proposed by Suzen and Huang (S-H). Despite the numerous efforts made to improve this model, including a recent work of the authors, some deficiencies still exist. In this study, new modifications have been introduced to improve the performance and accuracy of the S-H phenomenological model. Here, a relation between the electrical-potential and charge-density equations has been made in...
A continuous flow microfluidic device based on contactless dielectrophoresis for bioparticles enrichment
, Article Electrophoresis ; Volume 39, Issue 3 , 2018 , Pages 445-455 ; 01730835 (ISSN) ; Mohammadi, A. A ; Kalhor, H. R ; Sharif University of Technology
Wiley-VCH Verlag
2018
Abstract
In recent years, applications of dielectrophoresis-based platforms have been recognized as effective and dependable approach to separate cells and bioparticles, suspended in different carrier fluids, based on particle size and electrical properties. In this study, a microfluidic device was fabricated by an unprecedented electrode pattern, and several experiments were performed to enrich samples including either of yeast, Escherichia coli, or latex particles. A chemical deposition-based method was employed for fabrication of microelectrodes, inducing nonuniform electric field required for dielectrophoresis-based separation. One major advantage of our employed method is low fabrication cost,...
Reliability improvement of distribution systems using SSVR
, Article ISA Transactions ; Volume 48, Issue 1 , 2009 , Pages 98-106 ; 00190578 (ISSN) ; Shayanfar, H. A ; Fotuhi Firuzabad, M ; Sharif University of Technology
2009
Abstract
This paper presents a reliability assessment algorithm for distribution systems using a Static Series Voltage Regulator (SSVR). Furthermore, this algorithm considers the effects of Distributed Generation (DG) units, alternative sources, system reconfiguration, load shedding and load adding on distribution system reliability indices. In this algorithm, load points are classified into 8 types and separated restoration times are considered for each class. Comparative studies are conducted to investigate the impacts of DG and alternative source unavailability on the distribution system reliability. For reliability assessment, the customer-oriented reliability indices such as SAIFI, SAIDI, CAIDI...
Effect of geometric nonlinearity on dynamic pull-in behavior of coupled-domain microstructures based on classical and shear deformation plate theories
, Article European Journal of Mechanics, A/Solids ; Volume 28, Issue 5 , 2009 , Pages 916-925 ; 09977538 (ISSN) ; Moghimi Zand, M ; Ahmadian, M. T ; Sharif University of Technology
2009
Abstract
This paper investigates the dynamic pull-in behavior of microplates actuated by a suddenly applied electrostatic force. Electrostatic, elastic and fluid domains are involved in modeling. First-order shear deformation plate theory and classical plate theory are used to model the geometrically nonlinear microplates. The equations of motion are descritized by the finite element method. The effects of nonlinearity, fluid pressure, initial stress and different geometric parameters on dynamic behavior are examined. In addition, the influences of initial stress and actuation voltage on oscillatory behavior of microplates are evaluated. © 2009 Elsevier Masson SAS. All rights reserved
Free vibration analysis of functionally graded coupled circular plate with piezoelectric layers
, Article Journal of Mechanical Science and Technology ; Volume 23, Issue 8 , 2009 , Pages 2008-2021 ; 1738494X (ISSN) ; Kargarnovin, M. H ; Najafizadeh, M. M ; Sharif University of Technology
2009
Abstract
Based on classical plate theory (CLPT), free vibration analysis of a circular plate composed of functionally graded material (FGM) with its upper and lower surfaces bounded by two piezoelectric layers was performed. Assuming that the material properties vary in a power law manner within the thickness of the plate the governing differential equations are derived. The distribution of electric potential along the thickness direction in piezoelectric layers is considered to vary quadratically such that the Maxwell static electricity equation is satisfied. Then these equations are solved analytically for two different boundary conditions, namely clamped and simply supported edges. The validity of...