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Periodic characteristic ratio (PCR) method: An alternative method to determine the characteristic polynomial
, Article Mathematics and Computers in Simulation ; Volume 80, Issue 9 , May , 2010 , Pages 1841-1853 ; 03784754 (ISSN) ; Haeri, M ; Sharif University of Technology
2010
Abstract
This paper proposes an alternative method to determine the characteristic polynomial based on closed loop desired transient response. To develop the method, we have found optimal characteristic rations in simple arrangement of these parameters via performance map method. Despite its simplicity, the resulted system exhibits better transient response in comparison with the systems obtained from existing methods of determining the characteristics polynomials. Numerical simulations are used to illustrate the specifications of the proposed method
A Study of Ascorbic Acid Electro-Oxidation Process on Silver and Silver Selenide Electrodes
, Ph.D. Dissertation Sharif University of Technology ; Gobal, Fereydoon (Supervisor)
Abstract
Electrocatalytic oxidation of L-ascorbic acid (L-AA) on silver electrode in alkaline solutions was studied employing cyclic voltammetry, chronoamperometry and impedance spectroscopy techniques. In comparison to Pt, the onset potential for L-AA electro-oxidation process on Ag, in a solution containg 0.02 M L-AA and 0.5 M NaOH, was 0.1 V more negative. Also, L-AA oxidation current increased more than 900% at -0.26 V/SCE. According to voltammety and impedance spectropy findings, although hydroxide anion presence was vital for L-AA oxidation to occur, at potentials more positive than -0.2 V/SCE, hydroxide ion tends to inhibit the oxidation process. Studies on the L-AA oxidation process on Ag in...
Design, Manufacture and Study of a Desalination System with Heat Pipe and PTC
, M.Sc. Thesis Sharif University of Technology ; Behshad Shafii, Mohammad (Supervisor)
Abstract
According to studies on solar stills, there has been designed an industrial solar still with a linear parabolic through collector (PTC) having higher efficiency than similar systems. Linear PTC coupled with heat pipe is very effective for increasing the efficiency of solar still. This system includes a parabolic trough collector functions by focusing the sunlight on a heat pipe and absorption of heat by a heat pipe. To minimize heat loss, heat pipe is embedded in an evacuated tube collector. By absorbing the heat, the working fluid of the heat pipe (ethanol) will be evaporated and due to its reduced density, it moves upwards and attains to the condenser. The external part of the condenser is...
CRA based control of fractional order systems subject to control signal constraint
, Article International Conference on Control, Automation and Systems ; 2011 , Pages 268-272 ; 15987833 (ISSN) ; 9781457708350 (ISBN) ; Haeri, M ; Sharif University of Technology
Abstract
An approach is proposed to control transient response of fractional order systems with maximum permissible control signal. This goal is achieved using a newly suggested characteristic ratio assignment method. Based on the proposed method, the generalized time constant τ and the characteristic ratios including their pattern, an adjustable parameter β, and the product of two successive characteristic ratios ρ are determined such that predefined level of overshoot and time specification of closed loop step response are obtained while the control signal is confined to a pre assigned maximum magnitude. The raised issue is solved by defining an optimization problem in which the design parameters...
Effect of substrate thickness on responsivity of free-membrane bolometric detectors
, Article IEEE Sensors Journal ; Volume 11, Issue 12 , October , 2011 , Pages 3283-3287 ; 1530437X (ISSN) ; Kokabi, A ; Moftakharzadeh, A ; Vesaghi, M. A ; Fardmanesh, M ; Sharif University of Technology
2011
Abstract
The effect of substrate thickness and its Debye temperature on the bolometric response of the freestanding-membrane type of superconductor transition-edge detectors is investigated. The investigation is based on the calculation of the variation of the specific heat per unit volume and the heat conductivity using the finite-size scaling method for different Debye temperatures and micron size thickness of substrate. We also calculated the heat capacity and time constant for various materials with Debye temperatures in the range of 600-1400 K. The calculated results are compared with previously reported response values obtained theoretically and experimentally for the thermal-based infrared...
On time-constant robust tuning of fractional order U+005B proportional derivative U+005D controllers
, Article IEEE/CAA Journal of Automatica Sinica ; 2017 ; 23299266 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
Abstract
This paper deals with analyzing a newly introduced method for tuning of fractional order U+005B proportional derivative U+005D U+0028 FO U+005B PD U+005D U+0029 controllers to be used in motion control. By using this tuning method, not only the phase margin and gain crossover frequency are adjustable, but also robustness to variations in the plant time-constant is guaranteed. Conditions on the values of control specifications U+0028 desired phase margin and gain crossover frequency U+0029 for solution existence in this tuning method are found. Also, the number of solutions is analytically determined in this study. Moreover, experimental verifications are presented to indicate the...
On time-constant robust tuning of fractional order proportional derivative controllers
, Article IEEE/CAA Journal of Automatica Sinica ; Volume 6, Issue 5 , 2019 , Pages 1179-1186 ; 23299266 (ISSN) ; Tavazoei, M. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
This paper deals with analyzing a newly introduced method for tuning of fractional order [proportional derivative] (FO[PD]) controllers to be used in motion control. By using this tuning method, not only the phase margin and gain crossover frequency are adjustable, but also robustness to variations in the plant time-constant is guaranteed. Conditions on the values of control specifications (desired phase margin and gain crossover frequency) for solution existence in this tuning method are found. Also, the number of solutions is analytically determined in this study. Moreover, experimental verifications are presented to indicate the applicability of the obtained results. © 2014 Chinese...
UV photodetection of laterally connected ZnO rods grown on porous silicon substrate
, Article Sensors and Actuators, A: Physical ; Volume 180 , 2012 , Pages 11-14 ; 09244247 (ISSN) ; Dariani, R. S ; Iraji Zad, A ; Sharif University of Technology
2012
Abstract
Here, the UV photodetection of ZnO rods grown on porous silicon substrates are reported. Laterally interconnected ZnO rods have been synthesized by chemical vapor transport and condensation method on porous silicon substrates. As characterized by current-voltage measurements the I-V characteristics have linear behavior, indicating space charge effect. The device exhibits photocurrent response of 0.027 A/W for 325 nm UV light under -5 V bias. The rise and decay time constants under these conditions are 19 and 62 s, respectively
Polysulfide poisoning of Ag electrocatalyst during L-ascorbate ion electro-oxidation in alkaline solution
, Article Cuihua Xuebao/Chinese Journal of Catalysis ; Volume 33, Issue 2 , 2012 , Pages 267-274 ; 02539837 (ISSN) ; Majari Kasmaee, L ; Sharif University of Technology
Abstract
L-Ascorbate anion electro-oxidation on a silver electrode in hydroxide solution in the absence and presence of sodium polysulfide of concentrations from 1 × 10 -5 to 4.5 × 10 -4 mol/L was studied using cyclic voltammetry and electrochemical impedance spectroscopy. Both hydroxide and polysulfide ions inhibited L-ascorbate ion oxidation, with the poisoning effect of polysulfide ion being more pronounced in the potential range of -0.3 to -0.2 V/SCE. The time constants for L-ascorbate ion oxidation in the absence and presence of polysulfide were, 10 -3 to 1 × 10 -2 s and 1 × 10 -4 to 1 × 10 -2 s, respectively depending on the potential used for the impedance analysis. Based on the cyclic...
Characteristic ratio assignment in fractional order systems
, Article ISA Transactions ; Volume 49, Issue 4 , October , 2010 , Pages 470-478 ; 00190578 (ISSN) ; Haeri, M ; Sharif University of Technology
2010
Abstract
In this paper the characteristic ratios and generalized time constant are defined for all-pole commensurate fractional order systems. The sufficient condition for stability of these systems in terms of their characteristic ratios is obtained. Also an analytical approach for characteristic ratio assignment (CRA) to have a non-overshooting fast closed loop step response is introduced. The proposed CRA method is then employed to design a fractional order controller. Computer simulation results are presented to illustrate the performance of the CRA based designed fractional order controllers
Kinetic interpretation of a negative time constant impedance of glucose electrooxidation
, Article Journal of Physical Chemistry B ; Volume 112, Issue 49 , 2008 , Pages 15933-15940 ; 15206106 (ISSN) ; Jafarian, M ; Forouzandeh, F ; Gobal, F ; Mahjani, M. G ; Sharif University of Technology
American Chemical Society
2008
Abstract
Nickel - copper alloy modified glassy carbon electrodes (GC/NiCu) prepared by galvanostatic deposition were used for the electrocatalytic oxidation of glucose in alkaline solutions. The electro-oxidation of glucose in a 1 M NaOH solution at different concentration of glucose was studied by the method of ac-impedance spectroscopy. The impedance behavior show different patterns, capacitive, and inductive loops and negative resistances, at different applied anodic potential. The influence of the electrode potential on the impedance pattern is studied and a quantitative explanation for the impedance behavior of glucose oxidation is put forward by a proposed mathematical model. At potentials...
A novel probabilistic method for under frequency load shedding setting considering wind turbine response
, Article IEEE Transactions on Power Delivery ; Volume 37, Issue 4 , 2022 , Pages 2640-2649 ; 08858977 (ISSN) ; Sheikhi, A ; Sun, W ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
The Under Frequency Load Shedding (UFLS) is the last automated action to restore power system frequency stability when a severe contingency causes a significant drop in the frequency of interconnection or islanded areas. In this paper, a novel probabilistic algorithm that considers the wind turbine frequency response is proposed to design and optimize the UFLS scheme. The uncertainties of power systems such as wind speed, hourly load, inertia time constant, and generation losses are taken into account. The Monte-Carlo Simulation (MCS) method is used to model the power system uncertainties. Additionally, a novel method is developed to calculate the power system frequency response and...