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An adaptive iterative thresholding algorithm for distributed mimo radars
, Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 55, Issue 2 , 2019 , Pages 523-533 ; 00189251 (ISSN) ; Azghani, M ; Marvasti, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, a Block Iterative Method with Adaptive Thresholding for Sparse Recovery (BIMATSR) is proposed to recover the received signal in an under-sampled distributed multiple-input multiple-output radar. The BIMATSR scheme induces block sparsity with the aid of a signal-dependent thresholding operator which increases the accuracy of the target parameter estimation task. We have proved that under some sufficient conditions, the suggested scheme converges to a stable solution. Moreover, different simulation scenarios confirm that the BIMATSR algorithm outperforms its counterparts in terms of the target parameter estimation. This superiority is achieved at the expense of slightly more...
An adaptive iterative thresholding algorithm for distributed MIMO radars
, Article IEEE Transactions on Aerospace and Electronic Systems ; 16 July , 2018 , Page(s): 523 - 533 ; 00189251 (ISSN) ; Azghani, M ; Marvasti, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
In this paper, a Block Iterative Method with Adaptive Thresholding for Sparse Recovery (BIMATSR) is proposed to recover the received signal in an under-sampled distributed MIMO radar. The BIMATSR scheme induces block sparsity with the aid of a signal-dependent thresholding operator which increases the accuracy of the target parameter estimation task. We have proved that under some sufficient conditions, the suggested scheme converges to a stable solution. Moreover, different simulation scenarios confirm that the BIMATSR algorithm outperforms its counterparts in terms of the target parameter estimation. This superiority is achieved at the expense of slightly more computational complexity. It...
Comparison of CDMA and TDMA in AWGN channels
, Article Scientia Iranica ; Volume 7, Issue 3-4 , 2000 , Pages 197-204 ; 10263098 (ISSN) ; Valaee, S ; Tabiani, M ; Sharif University of Technology
Sharif University of Technology
2000
Abstract
In this paper, two multiple access methods in time and code domains are compared for Additive White Gaussian Noise (AWGN) channels. Time Division Multiple Access (TDMA) has been used for many years and its features are well-known. Characteristics of Code Division Multiple Access (CDMA) and its advantages over TDMA are studied in this paper. The burstiness nature of voice traffic and unequal bit transmission time in TDMA and CDMA are used to compare the performance of the two techniques. Delay, throughput and packet loss, as performance parameters, are evaluated and computed for data and voice traffics. Capability of CDMA in accommodating sources with different bit rates is also considered....
Analysis and modeling time headway distributions under heavy traffic flow conditions in the urban highways: Case of Isfahan
, Article Transport ; Volume 26, Issue 4 , 2011 , Pages 375-382 ; 16484142 (ISSN) ; Tamannaei, M ; Haghshenash, H ; Sharif University of Technology
2011
Abstract
The time headway of vehicles is an importan microscopic traffic flow parameter which affects the safety and capacity of highway facilities such as freeways and multi-lane highways. The present paper intends to provide a report on the results of a study aimed at investigating the effect of the lane position on time headway distributions within the high levels of traffic flow. The main issue of this study is to assess the driver's behavior at different highway lanes based on a headway distribution analysis. The study was conducted in the city of Isfahan, Iran. Shahid Kharrazi six-lane highway was selected for collecting the field headway data. The under-study lanes consisted of passing and...
Iterative block-sparse recovery method for distributed MIMO radar
, Article 2016 Iran Workshop on Communication and Information Theory, IWCIT 2016, 3 May 2016 through 4 May 2016 ; 2016 ; 9781509019229 (ISBN) ; Azghani, M ; Tayefi, J ; Marvasti, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
In this paper, an iterative method for block-sparse recovery is suggested for target parameters estimation in a distributed MIMO radar system. The random sampling has been used as the sensing scheme in the receivers. The simulation results prove that the proposed method is superior to the other state-of-the-art techniques in the accuracy of the target estimation task. © 2016 IEEE
Synthesis of Colloidal Silver Nanoparticles by Microwave Method and Study of its Antibacterial Activity
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Silver nanoparticles are widely used in different industries because of their antibacterial effects. Many synthesis methods were used to obtain silver nanoparticles. In this study the microwave method is used to synthesize nanosilver. This method is easier and faster in comparison to other methods. The effect of precursors’ concentrations, using different solvents, different remaining time in microwave and microwave power were studied. By increasing the reaction time, microwave power and using different solvents, nanosilver particle size varies from 2 nm up to 300nm. The TEM images, size distribution, XRD patterns and UV-visible spectrum are shown. The obtained nanosilver was used to observe...
Integrated Control and Estimation of Satellite Attitude using Adaptive Nero-Fuzzy Inference System
, M.Sc. Thesis Sharif University of Technology ; Assadian, Nima (Supervisor)
Abstract
This paper presents an integrated attitude control and estimation of satellite by using adaptive neural fuzzy (ANFIS) logic, indeed a system which using ANFIS controller and estimator is considered then an ANFIS simulator that can control and estimate contemporary is supposed. ANFIS system has been trained by using data obtained from an optimal PID controller. Then ANFIS controller performance has been compared with the performance of a PID controller, the analogy has repeated in different situations such as noise and uncertainty. Results show that system with ANFIS controller is more optimal than PID’s in all these situations. After that ANFIS estimator is studied and results indicate the...
Sliding mode control application to amplitude control of comb-actuated resonant microscanners
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 5 , 2010 , Pages 633-638 ; 9780791849194 (ISBN) ; Vossoughi, G ; Sharif University of Technology
2010
Abstract
MOEMS (Micro-Opto-Electro-Mechanical System) are MEMS in which the optical part plays a dominant role. The use of MOEMS as scanners and projectors has been studied lately. For high speed scanning applications, electrostatic comb drive actuation has several advantages. In this paper, we demonstrate the application of sliding mode control scheme for amplitude control of comb-actuated resonant microscanners. This method that leads to a simple and practical control function is simply extendable for microscanners with other type of actuation and even for any kind of oscillators that need amplitude control. The functionality and performance of the presented scheme is verified using numerical
Sparsity-based MIMO radars
, Article Applied and Numerical Harmonic Analysis ; 2021 , Pages 323-342 ; 22965009 (ISSN) ; Marvasti, F ; Sharif University of Technology
Birkhauser
2021
Abstract
With advances in technology, Multiple-Input Multiple-Output (MIMO) radars have attracted a lot of attention in different modern military and civilian applications. As there are multiple receivers in a MIMO radar system, the cost can significantly be reduced if we can reduce the sampling rate and send fewer samples to the common processing center. Sometimes, the problem is not even the cost. It is the technology issues of high sampling rates such as the necessity of high-rate Analog-to-Digital (A/D) converters. The reduction in sampling rate can be achieved using Compressive Sensing (CS) or, in a much simpler form, Random Sampling (RS). In CS, we take a number of linear combinations of sparse...
Sparsity-Based MIMO radars
, Article Applied and Numerical Harmonic Analysis ; 2021 , Pages 323-342 ; 22965009 (ISSN) ; Marvasti, F ; Sharif University of Technology
Birkhauser
2021
Abstract
With advances in technology, Multiple-Input Multiple-Output (MIMO) radars have attracted a lot of attention in different modern military and civilian applications. As there are multiple receivers in a MIMO radar system, the cost can significantly be reduced if we can reduce the sampling rate and send fewer samples to the common processing center. Sometimes, the problem is not even the cost. It is the technology issues of high sampling rates such as the necessity of high-rate Analog-to-Digital (A/D) converters. The reduction in sampling rate can be achieved using Compressive Sensing (CS) or, in a much simpler form, Random Sampling (RS). In CS, we take a number of linear combinations of sparse...
Energy allocation for parameter estimation in block CS-based distributed MIMO systems
, Article 2015 International Conference on Sampling Theory and Applications, SampTA 2015, 25 May 2015 through 29 May 2015 ; May , 2015 , Pages 523-527 ; 9781467373531 (ISBN) ; Modarres Hashemi, M ; Marvasti, F ; Tabataba, F. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Exploiting Compressive Sensing (CS) in MIMO radars, we can remove the need of the high rate A/D converters and send much less samples to the fusion center. In distributed MIMO radars, the received signal can be modeled as a block sparse signal in a basis. Thus, block CS methods can be used instead of classical CS ones to achieve more accurate target parameter estimation. In this paper a new method of energy allocation to the transmitters is proposed to improve the performance of the block CS-based distributed MIMO radars. This method is based on the minimization of an upper bound of the sensing matrix block-coherence. Simulation results show a significant increase in the accuracy of multiple...
Power allocation and measurement matrix design for block CS-based distributed MIMO radars
, Article Aerospace Science and Technology ; Volume 53 , 2016 , Pages 128-135 ; 12709638 (ISSN) ; Modarres Hashemi, M ; Marvasti, F ; Tabataba, F. S ; Sharif University of Technology
Elsevier Masson SAS
2016
Abstract
Multiple-input multiple-output (MIMO) radars offer higher resolution, better target detection, and more accurate target parameter estimation. Due to the sparsity of the targets in space-velocity domain, we can exploit Compressive Sensing (CS) to improve the performance of MIMO radars when the sampling rate is much less than the Nyquist rate. In distributed MIMO radars, block CS methods can be used instead of classical CS ones for more performance improvement, because the received signal in this group of MIMO radars is a block sparse signal in a basis. In this paper, two new methods are proposed to improve the performance of the block CS-based distributed MIMO radars. The first one is a new...
Synthesis and Study of Photocatalytic Properties of g-C3N4/TiO2 Nanocomposite
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhaad, Khatiboleslam (Supervisor)
Abstract
In this research, synthesis and characterization of photocatalytic properties of g-C3N4 / TiO2 nanocomposite was carried out. The target of research was to increase the photocatalytic properties of g-C3N4. So at first, g-C3N4 was synthesized from melamine precursor via thermal pyrolysis. Then, TiO2 nanoparticles were synthesized via sol – gel method. g-C3N4 / TiO2 nanocomposite with heterojunction structure was synthesized in one step by thermal pyrolysis of certain amounts of melamine precursor and TiO2 nanoparticles mixture in 550 ℃. Characterization of synthesized samples was carried out by XRD, FT-IR, UV-Vis, PL, BET, DLS and FE-SEM tests. Characterization results showed that g-C3N4,...
Spread-space holographic CDMA technique: Basic analysis and applications
, Article IEEE Transactions on Wireless Communications ; Volume 1, Issue 2 , 2002 , Pages 311-321 ; 15361276 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2002
Abstract
In this paper, we analyze the basic principles of the spread-space holographic code division multiple access (CDMA) technique. We describe the structure of the encoder and decoder and present a basic mathematical analysis based on spatial harmonic decomposition for the receiver's processing module, which is comprised of a Fourier transform lens and a holographic matched filter. Subsequently, we study two applications of optical holographic CDMA, namely, free-space holographic CDMA photonic switch and free-space (wireless) multiaccess optical (infrared) indoor communications. For both techniques, we describe the two-dimensional imaging techniques, namely user's code transmission, and...
Indoors wireless infrared communications based on spread-space holographic CDMA
, Article 11th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2000), London, 18 September 2000 through 21 September 2000 ; Volume 2 , 2000 , Pages 944-948 ; Salehi, J. A ; Sharif University of Technology
2000
Abstract
In this paper we study an application of optical Holographic CDMA for free-space (wireless) optical (infrared) indoor communications. First, we describe the principles of the spread-space Holographic CDMA indicating the structure of the encoder and decoder and describe mathematically the receiver's processing module which is comprised of a Fourier transform lens and a holographic matched-filter. Then, we study the performance of an indoors infrared communication link using spot-diffused configuration. Free-space optical Holographic CDMA processing gain (PG) can in principle be as high as 106-108 and each user can have different modulating signals (Analog or Digital), or different information...
, M.Sc. Thesis Sharif University of Technology ; Abedini, Javad (Supervisor)
Abstract
In this piece of work, a gravity model is suggested as Iranian non-fuel export model to OIC countries. The most important results out of this model are the acquired coefficients of two variables, namely “ECO membership” and “Economic and Trade Freedom of Importer”. At first, we expected that for importer, being a member of ECO would increase the amount of trade with iran. Surprisingly, this is not what we see in a model. In fact, as ECO has not achieved any tangible success in increasing trade between its members, eastern Asian Muslim countries has become an important trade partner for iranians. This result is compatible with other pieces of researches about ECO. “Economic and Trade Freedom...
Effects of the van der Waals force, squeeze-film damping, and contact bounce on the dynamics of electrostatic microcantilevers before and after pull-in
, Article Nonlinear Dynamics ; Vol. 77, issue. 1-2 , 2014 , p. 87-98 ; Vossoughi, G ; Meghdari, A ; Sharif University of Technology
2014
Abstract
The operational range of microcantilever beams under electrostatic force can be extended beyond pull-in in the presence of an intermediate dielectric layer. In this paper, a systematic method for deriving dynamic equation of microcantilevers under electrostatic force is presented. This model covers the behavior of the microcantilevers before and after the pull-in including the effects of van der Waals force, squeeze-film damping, and contact bounce. First, a polynomial approximate shape function with a time-dependent variable for each configuration is defined. Using Hamilton's principle, dynamic equations of microcantilever in all configurations have been derived. Comparison between modeling...
Dynamics of scratch drive actuators during stepwise motion
, Article Applied Mechanics and Materials ; Vol. 664, issue , 2014 , p. 104-110 ; Vossoughi, G ; Meghdari, A ; Sharif University of Technology
2014
Abstract
In this paper, a comprehensive model is used to describe dynamic behavior of SDA and its components during stepwise motion. In this model, Hamilton’s principle and Newton's method are used to extract dynamic equations of the SDA plate and dynamic equation for the linear motion of SDA. Comparison between the modeling results and available experimental data shows that this model is very effective in predicting some design objectives such as step size and output force for this type of actuators
Full operational range dynamic modeling of microcantilever beams
, Article Journal of Microelectromechanical Systems ; Volume 22, Issue 5 , May , 2013 , Pages 1190-1198 ; 10577157 (ISSN) ; Vossoughi, G ; Meghdari, A ; Sharif University of Technology
2013
Abstract
Microcantilever beams are frequently utilized in microelectromechanical systems. The operational range of microcantilever beams under electrostatic force can be extended beyond pull-in in the presence of an intermediate dielectric layer, which has a significant effect on the behavior of the system. Three possible configurations of the beam over the operational voltage range are floating, pinned, and flat configurations. In this paper, a systematic method for deriving dynamic equation of microcantilevers for all configurations is presented. First, a static study is performed on deflection profile of the microcantilever under electrostatic force. After that, a polynomial approximate shape...
Dynamic modeling of scratch drive actuators
, Article Journal of Microelectromechanical Systems ; Volume 24, Issue 5 , April , 2015 , Pages 1370-1383 ; 10577157 (ISSN) ; Vossoughi, G ; Meghdari, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
There has been much research in developing scratch drive actuators (SDAs), but because of their dynamic complexity, these microelectromechanical system-based actuators have not been dynamically analyzed up to now. In this paper, a comprehensive model is presented to describe the dynamic behavior of SDA and its components during stepwise motion. In this model, Hamilton's principle and Newton's method are used to extract dynamic equations of the SDA plate and dynamic equation for the linear motion of SDA. This model presents a good insight into the operating principles of SDA by predicting the variation of different variables, such as bushing angle, contact length, horizontal position, and...