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A distributed turn-off delay compensator scheme for voltage balancing of series-connected IGBTs
, Article IEEE Journal of Emerging and Selected Topics in Power Electronics ; Volume 12, Issue 3 , 2024 , Pages 2545-2557 ; 21686777 (ISSN) ; Iannuzzo, F ; Blaabjerg, F ; Kaboli, S ; Sharif University of Technology
2024
Abstract
This article presents a voltage balancing scheme for series-connected insulated gate bipolar transistors (IGBTs) (SCIs) using a turn-off delay compensator. In SCIs, inherent synchronization challenges and parasitic capacitances lead to uneven voltage distribution and potential overvoltage conditions. Traditional time delay adjustment methods adjusting both turn-on and turn-off delays involve complex circuitry, difficult for numerous SCIs. This article examines factors affecting voltage imbalances during turn-on and turn-off transitions, revealing that turn-off imbalances are more critical. Therefore, a straightforward approach is introduced for turn-off delay compensation, eliminating the...
Voltage balancing of series IGBTs in short-circuit conditions
, Article IEEE Transactions on Power Electronics ; Volume 37, Issue 5 , 2022 , Pages 5675-5686 ; 08858993 (ISSN) ; Peyghami, S ; Iannuzzo, F ; Blaabjerg, F ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
This article proposes a scheme for balancing the voltage of series-connected insulated gate bipolar transistors (IGBTs), which is also very effective under short-circuit conditions. An optimized clamp-mode snubber is proposed, including an active-driver to balance the currents of the IGBTs during short-circuit, which in turn allows for a considerable reduction of the snubber capacitance. The approach is proven to be effective under short-circuit conditions by a maximum of 55 V voltage increment and a negligible difference in the current values. The effectiveness of the proposed approach is demonstrated through simulations in PSPICE software and experimental tests performed at 2 kV. ©...
Joint approximate diagonalization of eigenmatrices as a high-throughput approach for analysis of hyphenated and comprehensive two-dimensional gas chromatographic data
, Article Journal of Chromatography A ; Volume 1524 , 2017 , Pages 188-201 ; 00219673 (ISSN) ; Parastar, H ; Sharif University of Technology
2017
Abstract
The objective of the present work is development of joint approximate diagonalization of eigenmatrices (JADE) as a member of independent component analysis (ICA) family, for the analysis of gas chromatography-mass spectrometry (GC–MS) and comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS) data to address incomplete separation problem occurred during the analysis of complex sample matrices. In this regard, simulated GC–MS and GC × GC–MS data sets with different number of components, different degree of overlap and noise were evaluated. In the case of simultaneous analysis of multiple samples, column-wise augmentation for GC–MS and column-wise super-augmentation...
Effect of Cathode Voltage Waveform on the Output Power of Magnetrons
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
In industial applications such as linear accelerators, pulsed lasers, nuclear fusion, radar systems, medical applications and etc. that need great ratio of instantanuse to the average power, pulsed power supplies are used. These power supplies store energy in an energy storage element and discharge this energy to load in a short period of time. The most important characterisitics of them are output pulse quality, reliability and longevity of the resource, efficiency and cost. One of the devices that produce high instantaneous RF power is magnetron tube. In some applications such as radar systems, quality of the output RF is very important and the most important factor that affect the quality...
Improving the Direct Switching Method for High Voltage Applications to Improve the Load Voltage Waveform
, Ph.D. Dissertation Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Pulsed power supplies are used in linear accelerators, pulsed lasers, nuclear welding, radar, some medical applications, etc. which require much more instantaneous power than average power. These sources store energy in an energy storage element for a relatively long period of time and then release this energy in a short period of time. Among the most important goals pursued in these power supplies are the quality of the output pulse, the reliability and lifetime, efficiency, and cost, which depending on their application, some of these features are more important. One of the important applications of pulsed wave power supplies is their use to power microwave lamps. In some applications of...
A fast and series-stacked IGBT switch with balanced voltage sharing for pulsed power applications
, Article IEEE Transactions on Plasma Science ; Volume 44, Issue 10 , 2016 , Pages 2013-2021 ; 00933813 (ISSN) ; Mohsenzade, S ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
The series configuration of fast semiconductor switches seems to be the key component in the high-voltage and fast rising time pulse generation. In this approach, two important issues must be considered. The first is to provide a safe operating condition for the switches in transient intervals. The second is to design a gate drive system with the capability of driving a large number of discrete devices simultaneously. The aim of this paper is to obviate these two requirements. First, different factors affecting the unbalanced voltage sharing between the series switches are discussed. In this investigation, the switch-to-ground parasitic capacitance effect has been recognized as the major...
A series stacked IGBT switch based on a concentrated clamp mode snubber for pulsed power applications
, Article IEEE Transactions on Power Electronics ; Volume 34, Issue 10 , 2019 , Pages 9573-9584 ; 08858993 (ISSN) ; Mohsenzade, S ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Clamp mode snubbers are very well suited for the series structure of the insulated-gate bipolar transistors (IGBTs) in pulsed power applications. They properly meet the necessities expected from them such as the fast operating of the series IGBTs since they have no effect on the gate side. In addition, they can provide safe voltage condition for the IGBTs in short circuit faults, which are very probable in pulsed applications. The clamp mode snubber can perform its voltage balancing task whenever the power capacity of the snubber can support the injected powers due to the voltage unbalancing factors. This paper initially introduces the main factors injecting power to the snubbers. Then, it...
Development and Application of Independent Component Analysis Method for Evaluation of Complex Chromatographic Data
, M.Sc. Thesis Sharif University of Technology ; Parastar Shahri, Hadi (Supervisor)
Abstract
In recent years, chromatographic technique as one of the most important analytical techniques have been developed for the analysis of complex samples. Hyphenated chromatographic techniques such as liquid or gas chromatography combine separation and spectroscopic detection technique to exploit the advantages of both and they have attracted attention of chemists to analyze complex mixtures. However, inadequate separation challenges still exist especially in the analysis of complex samples. Therefore, two-dimensional chromatographic systems such as comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) have been proposed for the analysis of complex samples due to their...
An Extremely low ripple high voltage power supply for pulsed current applications
, Article IEEE Transactions on Power Electronics ; Volume 35, Issue 8 , 2020 , Pages 7991-8001 ; Mohsenzade, S ; Hadizade, A ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This article describes the development of an 18 kV, 30 kW power supply for a pulsed current load with the maximum current of 20 A and a di/dt equal to 100 A/μs. The achieved output ripple is less than 0.01%. In such a high level of precision, the most important issues are considerable difference between the instantaneous and average output powers, as well as insufficient reaction speed of the converter to the fast load change. Very low level of the voltage feedback and its sensitivity to the noise. The first issue necessitates a notable overdesign of the converter switches if the output voltage precision is dedicated to the converter. The second issue raises the problems relevant to...
Hot compressive deformation behavior of Ti-8Al-1Mo-1 V titanium alloy at elevated temperatures: Focus on flow behavior, constitutive modeling, and processing maps
, Article Materials Today Communications ; Volume 37 , 2023 ; 23524928 (ISSN) ; Ebrahimi, G. R ; Taheri, J ; Ezatpour, H. R ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
The deformation behavior of the near-α Ti-8Al-1Mo-1 V titanium (Ti-811) alloy was studied by isothermal compression tests in the temperature range of 950–1075 °C and strain rates of 0.001–1 s−1. According to the physical properties of titanium alloys, the effects of adiabatic heat and friction during hot deformation process were modified on the stress-strain curves, especially at low temperatures and high strain rates. The results showed that the flow stress increases with increasing the strain rate and decreases with an increase in process temperature. Hyperbolic sine (sinh) and Cingara equations were used to model the flow behavior of Ti-811 alloy at elevated temperatures. Results showed a...
Effect of heating profile on desorption curve in temperature programmed desorption analysis: Case study of acid sites distribution of SAPO-34
, Article Journal of Porous Materials ; Volume 16, Issue 5 , 2009 , Pages 599-603 ; 13802224 (ISSN) ; Farhadi, F ; Khorasheh, F ; Yan, Z. F ; Sharif University of Technology
2009
Abstract
Comparison of the traditional linear heating method of TPD with an original stepwise heating scheme was reported for the first time. Stepwise heating TPD was carried out by keeping the temperature constant as soon as ammonia desorption signal rises until the signal returns to the baseline. More ammonia desorption peaks on a SAPO-34 catalyst were identified using TPD with stepwise heating. The effect of temperature ramp on desorption peak broadening in TPD curve was also addressed. The more distinct ammonia desorption peaks in stepwise TPD indicates that ammonia adsorbs in about five or six different ways on SAPO-34, and attribution of different adsorptions may be explained considering some...
Theoretical and experimental study of cascade solar stills
, Article Solar Energy ; Volume 90 , April , 2013 , Pages 205-211 ; 0038092X (ISSN) ; Sharak, A. Z ; Moghadam, H ; Tabrizi, F. F ; Sharif University of Technology
2013
Abstract
Most part of Iran is dominated by arid and semi-arid areas due to low annual rainfall. The need for production of fresh water from brackish water is considerably high, especially in dry regions. In this study 1 month daily-based experimental data from a solar still site has been reported. The technical and operational problems of this site which finally contributed to the total cease of the site are described. Then a detailed analysis is investigated on progress of a prototype which constructed in order to solve the site's problems. The results of 1 month of experimental data of the final design showed that the last prototype could be used to solve the current problems of the site. The...
Application of a continuous kinetic model for the hydrocracking of vacuum gas oil
, Article Petroleum Science and Technology ; Vol. 32, Issue. 18 , 2014 , Pages 2245-2252 ; ISSN: 10916466 ; Khorasheh, F ; Farhadi, F ; Sharif University of Technology
2014
Abstract
Hydrocracking is one of the most versatile petroleum refining processes for production of valuable products including gasoline, gas oil, and jet fuel. In this paper, a five-parameter continuous lumping model was used for kinetic modeling of hydrocracking of vacuum gas oil (VGO). The model parameters were estimated from industrial data obtained from a fixed bed reactor operating at an average temperature of 400°C and residence time of 0.3 h. Product distributions were obtained in terms of the weight fraction of various boiling point cuts. The model parameters were estimated using the Nelder-Mead optimization procedure and were correlated with temperature. Comparison of experimental and...
An improved methodology for design of custom-made hip prostheses to be fabricated using additive manufacturing technologies
, Article Rapid Prototyping Journal ; Volume 18, Issue 5 , 2012 , Pages 389-400 ; 13552546 (ISSN) ; Abbaszadeh, F ; Farahmand, F ; Sharif University of Technology
Emerald
2012
Abstract
Purpose - The purpose of this paper is to present an improved methodology for design of custom-made hip prostheses, through integration of advanced image processing, computer aided design (CAD) and additive manufacturing (AM) technologies. Design/methodology/approach - The proposed methodology for design of custom-made hip prostheses is based on an independent design criterion for each of the intra-medullary and extra-medullary portions of the prosthesis. The intra-medullar part of the prosthesis is designed using a more accurate and detailed description of the 3D geometry of the femoral intra-medullary cavity, including the septum calcar ridge, so that an improved fill and fit performance...
Evaluation and enhancing of operational performance and training objective in accordance with Line Operations Safety Audit (LOSA)
, Article International Air Safety Seminar Proceedings, 1 November 2011 through 3 November 2011 ; November , 2011 , Pages 78-99 ; 02705176 (ISSN) ; 9781618393975 (ISBN) ; Goodarzi, F ; Sharafbafi, F ; Sharif University of Technology
2011
Real-time impulse noise suppression from images using an efficient weighted-average filtering
, Article IEEE Signal Processing Letters ; Volume 22, Issue 8 , 2015 , Pages 1050-1054 ; 10709908 (ISSN) ; Hessar, F ; Marvasti, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this letter, we propose a method for real-time high density impulse noise suppression from images. In our method, we first apply an impulse detector to identify the corrupted pixels and then employ an innovative weighted-average filter to restore them. The filter takes the nearest neighboring interpolated image as the initial image and computes the weights according to the relative positions of the corrupted and uncorrupted pixels. Experimental results show that the proposed method outperforms the best existing methods in both PSNR measure and visual quality and is quite suitable for real-time applications
Kinetic modeling of pyrolysis of scrap tires
, Article Journal of Analytical and Applied Pyrolysis ; Volume 84, Issue 2 , 2009 , Pages 157-164 ; 01652370 (ISSN) ; Farhadi, F ; Khorasheh, F ; Sharif University of Technology
2009
Abstract
The disposal of used tires is a major environmental problem. With increasing interest on recovery of wastes, pyrolysis is considered as an alternative process for recovering some of the value in scrap tires. An accurate kinetic model is required to predict product yields during thermal or catalytic pyrolysis of scrap tires. Pyrolysis products contain a variety of hydrocarbons over a wide boiling range. A common approach for kinetic modeling of such complex systems is lumping where each lump is defined by a boiling point range. Available experimental data for thermal and catalytic pyrolysis of scrap tires from the literature were used to evaluate two types of lumping models; discrete and...
Determine oil content in petroleum waxes
, Article Hydrocarbon Processing ; Volume 85, Issue 6 , 2006 , Pages 95-97 ; 00188190 (ISSN) ; Yazdani, F ; Farhadi, F ; Sharif University of Technology
2006
Analytical modeling of variable-reluctance tubular resolver based on magnetic equivalent circuit and conformal mapping
, Article IEEE Transactions on Instrumentation and Measurement ; Volume 70 , 2021 ; 00189456 (ISSN) ; Zare, F ; Tootoonchian, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Compared with flat linear structures, tubular linear machines do not face edge effects, making their performance better than their flat counterparts. In this article, a novel linear variable-reluctance resolver with tubular configuration is proposed. To optimize the design of an electromagnetic structure, modeling methods are used. Thus, in this article, an analytical model for the proposed resolver is presented. This model is based on the magnetic equivalent circuit (MEC) method and is considerably less time-consuming than finite element analysis (FEA), yet provides accurate results. A conformal mapping is employed to compute the permeance of the air-gap. The proposed model is then utilized...
Information and the Brukner-Zeilinger interpretation of quantum mechanics: A critical investigation
, Article Foundations of Physics Letters ; Volume 19, Issue 1 , 2006 , Pages 1-20 ; 08949875 (ISSN) ; Safinejad, F ; Naqsh, F ; Sharif University of Technology
2006
Abstract
In Brukner and Zeilinger's interpretation of quantum mechanics, information is introduced as the most fundamental notion and the finiteness of information is considered as an essential feature of quantum systems. They also define a new measure of information which is inherently different from the Shannon information and try to show that the latter is not useful in defining the information content in a quantum object. Here, we show that there are serious problems in their approach which make their efforts unsatisfactory. The finiteness of information does not explain how objective results appear in experiments and what an instantaneous change in the so-called information vector (or catalog of...