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    A Multi-Output high voltage dc power supply with fast regenerative rectifier

    , Article 26th Iranian Conference on Electrical Engineering, ICEE 2018, 8 May 2018 through 10 May 2018 ; 2018 , Pages 1264-1268 ; 9781538649169 (ISBN) Naghibi Nasab, J ; Kaboli, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    A major problem in a multiple output converter structure is the different power flow via its various outputs. This problem leads to unwanted input DC-link voltage. This paper studies full bridge based DC-DC converters with multiple outputs. The effect of power flow variation is studied and a regenerative converter topology which controls the DC-link voltage by space voltage vector modulation technique is proposed. The proposed converter has a fast response to control the DC-link voltage in an acceptable band. Simulation and experimental results are presented to verify the analytical studies. © 2018 IEEE  

    Analysis of Marx Pulsed Power Generator for Improving the Output Voltage Waveform Characteristics

    , M.Sc. Thesis Sharif University of Technology Naghibi Nasab, Javad (Author) ; Kaboli, Shahriyar (Supervisor)
    Abstract
    In this thesis, marx pulsed power generators are investigated. Due to very large magnitude of its output voltage and very fast rise time, Marx generator is the first choice in lots of pulsed power applications. A significant barrier in the implementation of this generators are the switches with witch the structure is made. The short magnitude nominal voltage and current of the solid state switches lead to use of Spark Gaps in which the determinative parameter of the switch to turn on, is its breakdown voltage. These switches have some limitations in repetition rate and turn off ability. However due to very high range of nominal voltage and currents, they are an appropriate choice for marx... 

    An investigation on the quality of output voltage waveform in a nanosecond pulse generator using reverse recovery diodes

    , Article 9th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2018 ; Volume 2018-January , 19 April , 2018 , Pages 516-521 ; 9781538646977 (ISBN) Naghibi Nasab, J ; Kaboli, S ; Eskandary, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    Nanosecond pulsed-power generators have many applications in industries. As the rise time and fall time of conventional semiconductor switches are usually more than a few nanoseconds, it is necessary to employ special switches or new pulse generating methods to achieve nanosecond pulses. A common method for producing narrow pulse voltage waveforms is using the reverse recovery process of diodes. In this method, a super fast recovery diode is used as an opening switch in an inductor current path. A drift step recovery diode can form a rapid cut-off current front; Hence this method can be an effective solution to generate narrow pulses. This paper describes an investigation about the effect of... 

    A Marx-based generator with adjustable FWHM using a controllable magnetic switch

    , Article IEEE Transactions on Dielectrics and Electrical Insulation ; Volume 26, Issue 2 , 2019 , Pages 324-331 ; 10709878 (ISSN) Naghibi Nasab, J ; Hadizade, A ; Mohsenzade, S ; Zarghany, M ; Kaboli, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    The lack of turn-off ability makes the spark gap-based Marx generator uncontrollable in terminating the output pulse. In addition, there are some limitations for rise time and voltage gain improvements in the conventional critically-damped Marx design. In this paper, an efficient over-damped design of Marx circuit is proposed, which leads to a shorter rise time as well as a larger voltage gain. A chopping magnetic switch is employed to achieve the desired values of the fall time and full width at half maximum (FWHM). Moreover, adding a DC bias circuit to the magnetic switch provides the ability to adjust the pulse FWHM parameter. Therefore, an output pulse with a shorter rise time, larger... 

    MIMO radar waveform design in the presence of clutter

    , Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 47, Issue 2 , 2011 , Pages 770-781 ; 00189251 (ISSN) Naghibi, T ; Behnia, F ; Sharif University of Technology
    2011
    Abstract
    Waveform design for target identification and classification in multiple-input multiple-output (MIMO) radar systems has been studied in several recent works. In previous works, optimal signals for an estimation algorithm are found assuming that only signal- independent noise exists. This work extends previous research by studying the case where clutter is also present. We develop a procedure to design the optimal waveform which minimizes estimation error at the output of the minimum mean squared error (MMSE) estimators in two scenarios. In the first one different transmit antennas see uncorrelated aspects of the target, and we consider the correlated target aspects in the second one.... 

    Convex Optimization and MIMO RADAR waveform design in the presence of clutter

    , Article 2008 2nd International Conference on Signals, Circuits and Systems, SCS 2008, Nabeul, 7 November 2008 through 9 November 2008 ; January , 2008 ; 9781424426287 (ISBN) Naghibi, T ; Behnia, F ; Sharif University of Technology
    2008
    Abstract
    Waveform design for Target identification and classification in MIMO radar systems has been studied in several recent works. While the previous works considered signal independent noise and found optimal signals for an e stimation algorithm, here we extend the results to the case where clutter is also present and then we will find the optimum waveform for several estimators differing in the assumptions on the given statistics. Several different approaches to the optimal waveform design are proposed, including minimizing the error of MMSE estimator, minimizing the maximum error of the covariance shaping least square (CSLS) estimator and minimizing the MSE error of scaled least square (SLS)... 

    Optimal signals for MIMO RADAR in the presence of clutter

    , Article 2008 2nd International Conference on Signals, Circuits and Systems, SCS 2008, Nabeul, 7 November 2008 through 9 November 2008 ; January , 2008 ; 9781424426287 (ISBN) Naghibi, T ; Behnia, F ; Sharif University of Technology
    2008
    Abstract
    Waveform design for Target identification and classification in MIMO radar systems has been studied in several recent works. While the previous works considered signal independent noise and found optimal signals, here we extend the results to the case where clutter is also present and then we will find the optimum waveform for MMSE estimator. Choosing optimal waveform for MMSE estimator leads to the Semidefinite programming (SDP) problem, a convex optimization problem which can be efficiently solved through numerical methods. Explicit solution is developed for this SDP problem in two cases .In the first case, target and clutter covariance matrices are jointly diagonalizable and in the second... 

    Investigations on equivalent circuit models of high frequency transformers

    , Article Proceedings of 2018 IEEE International Conference on Power Electronics, Drives and Energy Systems, PEDES 2018 ; Volume 2018-January , April , 2018 , Pages 475-480 ; 9781538646977 (ISBN) Hadizade, A ; Naghibi Nasab, J ; Aghaei, M ; Kaboli, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    High frequency transformer is an important component in lots of modern power electronic circuits. In order to analyze the behavior of these transformers, equivalent circuit models containing parasitic elements have been proposed. But most of them are complicated and not appropriate to use in processes in which high speed analysis is crucial. In this paper, a second-order simplified model for high frequency transformers is obtained. Besides, the frequency ranges in which the proposed model has enough precision, are calculated and examined. To validate the simplified circuit model, some simulations are carried out. During the simulation, the effects of transformer equivalent circuit parameters... 

    A hybrid three layer architecture for fire agent management in rescue simulation environment

    , Article International Journal of Advanced Robotic Systems ; Volume 2, Issue 2 , 2005 , Pages 111-116 ; 17298806 (ISSN) Geramifard, A ; Nayeri, P ; Zamani Nasab, R ; Habibi, J ; Sharif University of Technology
    2005
    Abstract
    This paper presents a new architecture called FAIS for impie- menting intelligent agents cooperating in a special Multi Agent environ- ment, namely the RoboCup Rescue Simulation System. This is a layered architecture which is customized for solving fire extinguishing problem. Structural decision making algorithms are combined with heuristic ones in this model, so its a hybrid architecture  

    PostRank: A new algorithm for incremental finding of persian blog representative words

    , Article ACM International Conference Proceeding Series ; 2012 ; 9781450309158 (ISBN) Sayyadiharikandeh, M ; Ghodsi, M ; Naghibi, M ; Sharif University of Technology
    2012
    Abstract
    Dimension reduction techniques for text documents can be used for in the preprocessing phrase of blog mining, but these techniques can be more effective if they deal with the nature of the blogs properly. In this paper we propose a novel algorithm called PostRank using shallow approach to identify theme of the blog or blog representative words in order to reduce the dimensions of blogs. PostRank uses a graph-based syntactic representation of the weblog by taking into account some structural features of weblog. At the first step it models the blog as a complete graph and assumes the theme of the blog as a query applied to a search engine like Google and each post as a search result. It tries... 

    Optimal and robust waveform design for MIMO radars in the presence of clutter

    , Article Signal Processing ; Volume 90, Issue 4 , April , 2010 , Pages 1103-1117 ; 01651684 (ISSN) Naghibi, T ; Namvar, M ; Behnia, F ; Sharif University of Technology
    2010
    Abstract
    Waveform design for target identification and classification in MIMO radar systems has been studied in several recent works. While the previous works assumed that the noise was independent of the transmission signals, here we extend the results to the signal dependent noise (clutter). We consider two scenarios. In the first scenario it is assumed that different transmit antennas see uncorrelated aspects of the target. In the second scenario, we consider the correlated target. As clutter is dependent to signal, target estimation error cannot vanish only by increasing the transmission power. It can be shown that in the second scenario, MIMO radar receiver can nullify the clutter subspace.... 

    On the performance of high voltage electrospray echnique for producing nanoparticles

    , Article 26th Iranian Conference on Electrical Engineering, ICEE 2018, 8 May 2018 through 10 May 2018 ; 2018 , Pages 283-288 ; 9781538649169 (ISBN) Kaboli, S ; Naghibi Nasab, J ; Elyasi, M ; Zarrabi, R ; Vosoghi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    Electrospray technique is one of the commonly used methods for generating nanoparticles. In this method, the chemical solution which consists of a polymer and its solvent are injected into an electric field via a nozzle. At the end of this nozzle, due to electric forces, a certain part of this liquid is separated. Then, the separated part is divided into smaller particles and the solvent is evaporated and hence, the nanoparticles are acquired. Produced nanoparticales are collected in deionized water placed under the certain distant from nozzle. However, construction of this method is generally based on practical results. In this paper, modeling and performance evaluation of high voltage... 

    Coronavirus diagnosis using cough sounds: Artificial intelligence approaches

    , Article Frontiers in Artificial Intelligence ; Volume 6 , 2023 ; 26248212 (ISSN) Askari Nasab, K ; Mirzaei, J ; Zali, A ; Gholizadeh, S ; Akhlaghdoust, M ; Sharif University of Technology
    Frontiers Media S.A  2023
    Abstract
    Introduction: The Coronavirus disease 2019 (COVID-19) pandemic has caused irreparable damage to the world. In order to prevent the spread of pathogenicity, it is necessary to identify infected people for quarantine and treatment. The use of artificial intelligence and data mining approaches can lead to prevention and reduction of treatment costs. The purpose of this study is to create data mining models in order to diagnose people with the disease of COVID-19 through the sound of coughing. Method: In this research, Supervised Learning classification algorithms have been used, which include Support Vector Machine (SVM), random forest, and Artificial Neural Networks, that based on the standard... 

    Optimal MIMO Radars Waveform Design

    , M.Sc. Thesis Sharif University of Technology Naghibi Mohammadpour, Tofigh (Author) ; Behnia, Fereidoon (Supervisor)
    Abstract
    Waveform design for Target identification and classification in MIMO radar systems has been studied in several recent works. While the previous works considered signal independent noise and found optimal signals for an estimation algorithm, here we extend the results to the case where clutter is also present and then we will find the optimum waveform for several estimators differing in the assumptions on the given statistics. Several different approaches to the optimal waveform design are proposed, including minimizing the error of MMSE estimator, minimizing the maximum error of the covariance shaping least square (CSLS) estimator and minimizing the MSE error of scaled least square (SLS)... 

    Interaction of Large-scale Oceanic Currents and the Earth’s Wobble

    , Ph.D. Dissertation Sharif University of Technology Naghibi, Elnaz (Author) ; Jalali, Abbas (Supervisor) ; Behzad, Mehdi (Co-Advisor)
    Abstract
    In this thesis, we investigate interactions of a double-gyre in the North Atlantic and the earth’s Chandler wobble using a single-layer ocean model based on depth-averaged Navier-Stokes equations and multiple-scale spectral solutions to it. The overall transfers of energy and angular momentum from the double-gyre to the Chandler wobble are used to calibrate the turbulence parameters of the idealized ocean model and Smagorinsky eddy viscosity is used to estimate turbulent diffusion terms. Our model is tested against a multilayer quasi-geostrophic ocean model in turbulent regime, and base states used in parameter identification are obtained from mesoscale eddy resolving numerical simulations.... 

    Lot sizing and job shop scheduling with compressible process times: A cut and branch approach

    , Article Computers and Industrial Engineering ; Volume 85 , 2015 , Pages 196-205 ; 03608352 (ISSN) Karimi Nasab, M ; Modarres, M ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract
    This paper studies simultaneous lot sizing and scheduling problem in a job shop environment over a finite number of periods. The machines are flexible such that the production manager is able to change their working speeds. Also, the production schedule of the items over machines should be in consistence with technological precedence relationships. The problem is formulated as an integer linear program. Then, a number of valid inequalities are developed based on the problem structures. The proposed valid inequalities are added to the problem formulation in a "cut and branch" manner to accelerate the search process by common solvers. Finally, performance of the valid inequalities is... 

    Thermal stresses and kinetics of phase transformation on the run-out table after hot strip rolling of low-carbon steels

    , Article International Journal of Advanced Manufacturing Technology ; Volume 83, Issue 9-12 , 2016 , Pages 1725-1736 ; 02683768 (ISSN) Hasan Nasab, M ; Serajzadeh, S ; Sharif University of Technology
    2016
    Abstract
    A thermo-elastic analysis coupled with a phase change model is employed to evaluate thermal stresses as well as progress of austenite decomposition after hot strip rolling operations. The thermo-mechanical finite element analysis is utilized to assess the distributions of temperature and thermal stresses during cooling while at the same time, a model based on the additivity rule is used to determine the rate of austenite to ferrite decomposition. The proposed model is applicable to multi-pass rolling schedules while the effects of different process parameters including the rolling speed and cooling configuration of the run-out table can be taken into account. In order to verify the... 

    Estimation of origin–destination matrices using link counts and partial path data

    , Article Transportation ; Volume 47, Issue 6 , 2020 , Pages 2923-2950 Rostami Nasab, M ; Shafahi, Y ; Sharif University of Technology
    Springer  2020
    Abstract
    After several decades of work by several talented researchers, estimation of the origin–destination matrix using traffic data has remained very challenging. This paper presents a set of innovative methods for estimation of the origin–destination matrix of large-scale networks, using vehicle counts on links, partial path data obtained from an automated vehicle identification system, and combinations of both data. These innovative methods are used to solve three origin–destination matrix estimation models. The first model is an extension of Spiess’s model which uses vehicle count data while the second model is an extension of Jamali’s model and it uses partial path data. The third model is a... 

    New half-pixel accuracy motion estimation algorithms for low bitrate video communications

    , Article Scientia Iranica ; Volume 15, Issue 6 , 2008 , Pages 507-516 ; 10263098 (ISSN) Mahdavi Nasab, H ; Kasaei, S ; Sharif University of Technology
    Sharif University of Technology  2008
    Abstract
    Fractional-pixel accuracy Motion Estimation (ME) has been shown to result in higher quality reconstructed image sequences in hybrid video coding systems. However, the higher quality is achieved by notably increased Motion Field (MF) bitrate and more complex computations. In this paper, new half-pixel block matching ME algorithms are proposed to improve the rate-distortion characteristics of low bitrate video communications. The proposed methods tend to decrease the required video bandwidth, while improving the motion compensation quality. The key idea is to put a deeper focus on the search origin of the ME process, based on center-bias characteristics of low bitrate video MFs. To employ the... 

    Half-pixel accuracy block matching motion estimation algorithms for low bitrate video communications

    , Article First IEEE and IFIP International Conference in Central Asia on Internet, 2005, Bishkek, 26 September 2005 through 28 September 2005 ; Volume 2005 , 2005 ; 0780391799 (ISBN); 9780780391796 (ISBN) Mahdavi Nasab, H ; Kasaei, S ; Sharif University of Technology
    2005
    Abstract
    Motion estimation at fractional-pixel accuracy results in higher quality video sequences. However, the higher quality is achieved by more computations and increased required motion field bitrates. In this paper, new half-pixel accuracy block matching-based motion estimation algorithms are proposed to improve the rate-distortion characteristics of low-bitrate video communications. The proposed methods especially tend to decrease the required video bandwidth, with no degradation in quality of reconstructed image sequences. The key idea is to put a deeper focus on the origin (zero motion) based on the center-bias characteristics of low bitrate video motion fields. The experimental results show...