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Optimum and suboptimum memoryless nonlinearities for the detection of ultrashort light pulses in gaussian noise [electronic resource]
, Article IEEE Transactions on Communications ; 2009 Volume 57, Issue 12, December 2009, Article number 5351650, Pages 3561-3565 ; Salehi, J. A ; Sharif University of Technology
Abstract
Detection of ultrashort light pulses with conventional bandlimited photodetectors can lead to substantial performance degradation in digital lightwave communication systems. All-optical nonlinear processing of the received field prior to the optical to electrical conversion can greatly overcome this problem. In this letter, through a decision-theoretic framework and using a basic invariance property of the photodetector, we obtain the optimal zero-memory nonlinear element and evaluate its performance. Possible suboptimum nonlinearities are also investigated and their performance is examined. The results in this letter strongly justify the intuitive use of power-law devices, such as those...
On the performance of spectrally-encoded spread-time ultrawideband CDMA communication systems [electronic resource]
, Article IEEE Transactions on Wireless Communications ; 2008 Vol. 7, No. 11 ; Salehi, J. A ; Sharif University Of Technology
Abstract
In this paper we study the performance of spectrally-encoded spread-time (SE/ST) technique when applied to ultrawideband (UWB) signals in the context of wireless code-division multiple-access (CDMA) communication. In this technique UWB pulses are spectrally encoded with pseudorandom codes that are assigned uniquely to each user. We shall show that the SE/ST ultrawideband system provides an appropriate multi-user capacity in realistic UWB channels, along with the ability of narrowband interference (NBI) suppression. To this end, after obtaining a suitable statistical model for spectrally encoded spread-time signals, we investigate the performance of the system in the presence of...
Optimum receiver design for transmitted-reference signaling [electronic resource]
, Article IEEE Transactions on Communications ; May 2010, Volume 58, Issue 5, P.1589-1598 ; Salehi, J. A ; Sharif University of Technology
Abstract
Autocorrelation receiver (AcR) is usually used as the general receiver for transmitted reference (TR) communication systems on a quite intuitive basis. In this paper, we apply the principle of statistical invariance to obtain the optimum TR receiver on a decision-theoretic basis, and it is shown that the autocorrelation receiver is optimal only in a special case. Performance of the optimum receiver and the suboptimum AcR for some important modulation schemes is also evaluated. The results imply that allocating a part of the transmitted energy and bandwidth to reference pulses would not help improve the performance of the system and the optimal performance might be achieved via much simpler...
Erratum: Optimum receiver design for transmitted-reference signaling (IEEE Transactions on Communications (2010) 58:5 (1589-1598))
, Article IEEE Transactions on Communications ; Volume 59, Issue 3 , 2011 , Pages 911- ; 00906778 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2011
Optimum and suboptimum memoryless nonlinearities for the detection of ultrashort light pulses in Gaussian noise
, Article IEEE Transactions on Communications ; Volume 57, Issue 12 , 2009 , Pages 3561-3565 ; 00906778 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2009
Abstract
Detection of ultrashort light pulses with conventional bandlimited photodetectors can lead to substantial performance degradation in digital lightwave communication systems. All-optical nonlinear processing of the received field prior to the optical to electrical conversion can greatly overcome this problem. In this letter, through a decision-theoretic framework and using a basic invariance property of the photodetector, we obtain the optimal zero-memory nonlinear element and evaluate its performance. Possible suboptimum nonlinearities are also investigated and their performance is examined. The results in this letter strongly justify the intuitive use of power-law devices, such as those...
On the performance of spectrally-encoded spread-time ultrawideband CDMA communication systems
, Article IEEE Transactions on Wireless Communications ; Volume 7, Issue 11 , 2008 , Pages 4608-4616 ; 15361276 (ISSN) ; Salehi, J. A ; Sharif University of Technology
2008
Abstract
In this paper we study the performance of Spectrally-Encoded Spread-Time (SE/ST) technique when applied to ultrawideband (UWB) signals in the context of wireless code-division multiple-access (CDMA) communication. In this technique UWB pulses are spectrally encoded with pseudorandom codes that are assigned uniquely to each user. We shall show that the SE/ST ultrawideband system provides an appropriate multi-user capacity in realistic UWB channels, along with the ability of narrowband interference (NBI) suppression. To this end, after obtaining a suitable statistical model for spectrallyencoded spread-time signals, we investigate the performance of the system in the presence of...
Spread-time/time-hopping UWB CDMA communication
, Article IEEE International Symposium on Communications and Information Technologies: Smart Info-Media Systems, ISCIT 2004, Sapporo, 26 October 2004 through 29 October 2004 ; Volume 2 , 2004 , Pages 1047-1050 ; 0780385934 (ISBN) ; Salehi, J. A ; Sharif University of Technology
2004
Abstract
The use of Spread-Time CDMA for ultrawideband (UWB) wireless communication is proposed and its capability for supporting many high data rate users is investigated. Furthermore we will study a hybrid technique, namely, Spread-Time/Time-Hopping to increase the capacity of the above mentioned technique and simultaneously minimizing the effect of near-far in a typical CDMA system
Values and identities in Iranian primary school social studies textbooks: a discursive approach
, Article Journal of Beliefs and Values ; Volume 43, Issue 4 , 2022 , Pages 396-413 ; 13617672 (ISSN) ; Abe, S ; Farhang, A ; Sharif University of Technology
Routledge
2022
Abstract
Textbooks provide the most serious source of knowledge construction and transmission for children at schools. This paper used a discursive and qualitative content analysis approach to extract the dominant values, ideologies and identities in four social studies textbooks taught nationwide to children in primary schools in Iran. Textual and visual analysis were applied on these textbooks and the results showed the saliency of four dominant discourses and values including pre-Islamic ethos and Iranian-Islamic identity, war and peace, social and traditional values in Iranian culture, and respect for diversity. Each of these discourses are discussed and some recommendations are made at the end...
Values and identities in Iranian primary school social studies textbooks: a discursive approach
, Article Journal of Beliefs and Values ; 2021 ; 13617672 (ISSN) ; Abe, S ; Farhang, A ; Sharif University of Technology
Routledge
2021
Abstract
Textbooks provide the most serious source of knowledge construction and transmission for children at schools. This paper used a discursive and qualitative content analysis approach to extract the dominant values, ideologies and identities in four social studies textbooks taught nationwide to children in primary schools in Iran. Textual and visual analysis were applied on these textbooks and the results showed the saliency of four dominant discourses and values including pre-Islamic ethos and Iranian-Islamic identity, war and peace, social and traditional values in Iranian culture, and respect for diversity. Each of these discourses are discussed and some recommendations are made at the end...
A sensitivity analysis of thermal lattices kinetic parameters with respect to the spectral weighting function using ultrafine BN method
, Article Progress in Nuclear Energy ; Volume 88 , 2016 , Pages 310-320 ; 01491970 (ISSN) ; Salehi, A. A ; Vosoughi, N ; Ayyoubzadeh, S. M ; Sharif University of Technology
2016
Abstract
Accurate calculation of kinetic parameters is of utmost importance in the safety analysis of a nuclear reactor. In the current paper, two approaches are investigated to evaluate these parameters in energy phase space. In the first approach, these parameters are derived from an energy-continuous form of the forward and adjoint transport equations and then integrals with respect to the energy variable are replaced by weighted summations over the energy groups, while in the second approach these parameters are extracted from the multi-group forward equation and its associate adjoint equation in which their multigroup constants are weighted by forward spectrum. The difference of weighting...
Ultrashort Pulse Receiver Design Via Statistical Invariance Principle
, Ph.D. Dissertation Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
With the emergence and development of ultra broadband communication systems incorporating ultrashort pulses, the design of suitable receiver structures became one the most significant problems in such systems; since due the limited bandwidth and speed of current electronic devices, most of the existing receiver structures cannot be used properly. In the field of radio communications, the design of simple and low power consumption receivers for ultrawideband (UWB) and millimeter wave band communication systems, which do not rely on complex channel estimation mechanisms, is of much interest. In ultrashort light pulse optical communication systems –and specially coherent optical CDMA systems–...
Optimum receiver design for transmitted-reference signaling
, Article IEEE Transactions on Communications ; Volume 58, Issue 5 , May , 2010 , Pages 1589-1598 ; 00906778 (ISSN) ; Salehi, J ; Sharif University of Technology
2010
Abstract
Autocorrelation receiver (AcR) is usually used as the general receiver for transmitted reference (TR) communication systems on a quite intuitive basis. In this paper, we apply the principle of statistical invariance to obtain the optimum TR receiver on a decision-theoretic basis, and it is shown that the autocorrelation receiver is optimal only in a special case. Performance of the optimum receiver and the suboptimum AcR for some important modulation schemes is also evaluated. The results imply that allocating a part of the transmitted energy and bandwidth to reference pulses would not help improve the performance of the system and the optimal performance might be achieved via much simpler...
On the Adequacy of the Experimental Approach to Construct Validation:
The Case of Advertising Literacy
,
M.Sc. Thesis
Sharif University of Technology
;
Salehi, Mohammad
(Supervisor)
Abstract
Given the significance of providing any logical and empirical pieces of evidence to “support the assentation that a test measures the construct as defined and nothing else” (Ary et al., 2013, p. 248), numerous studies have been conducted to investigate construct validity, adopting various approaches. However, there are few studies employing the experimental approach to validation. The current study is aimed at obtaining statistically persuading evidence to answer the question regarding the adequacy of the experimental approach to construct validation, drawing upon the concept of advertising literacy as the construct of the researcher’s concern. To meet this end, the researcher, having...
Probing the local bubble with diffuse interstellar bands
, Article Proceedings of the International Astronomical Union ; Vol. 9, issue. S297 , February , 2014 , pp. 84-88 ; ISSN: 17439213 ; Khosroshahi, H. G ; Javadi, A ; Van Loon, J ; Sharif University of Technology
2014
Abstract
The Sun is located inside an enormous local cavity filled with a million degree, ionized hydrogen gas and surrounded by a wall of dense and cold gas, this cavity is known as the Local Bubble (LB). Since the tempreture of Local Bubble is high, the typical singly-ionized atoms or molecules can not survive at this high tempreture. To overcome this problem we should probe the Local Bubble using species which survive under this condition so we have done a whole sky survey in north hemisphere by observing absorptions in the Diffuse Interstellar Bands (DIBs) for sight-lines with distance >300 pc. We have done 30 nights observation and have observed 473 bright stars. We found that the correlations...
Throughput Analysis of Routing Algorithms in 802.11s-Based Wireless Mesh Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Wireless Mesh Networks (WMNs) can be considered as the result of cooperation among two ad hoc networks, one composed of Mesh Points (MPs) and another one composed of Mesh Clients (MCs) as well as corresponding Access (Mesh) Points. Each one has its own functions and properties. This cooperation results in a flexible network that to fully demonstrate its potentials, requires special routing algorithms and access schemes.Here, we study and analyze three routing algorithms in IEEE 802.11s-based WMNs from throughput point of view. To this end, each node in the network is modeled by a queue during Contention-Free Periods (CFPs). During Contention-Based Period, however, to simplify modeling, we...
Probing the local bubble with diffuse interstellar bands. III. The northern hemisphere data and catalog
, Article Astrophysical Journal, Supplement Series ; Volume 216, Issue 2 , February , 2015 ; 00670049 (ISSN) ; Khosroshahi, H. G ; Javadi, A ; Van Loon, J. T ; Sharif University of Technology
Institute of Physics Publishing
2015
Abstract
We present new high signal-to-noise ratio (S/N) observations of the diffuse interstellar bands (DIBs) in the Local Bubble and its surroundings. We observed 432 sightlines and obtain the equivalent widths of the λ5780 and λ5797 Å DIBs up to a distance of ∼200 pc. All of the observations were carried out using the Intermediate Dispersion Spectrograph on the 2.5 m Isaac Newton Telescope, during three years, to reach a minimum S/N of ∼2000. All of the λ5780 and λ5797 absorptions are presented in this paper and we tabulate the observed values of the interstellar parameters, λ5780, λ5797, Na ID1, and Na ID2, including the uncertainties
Calculation of the Scaling Factor for WWER-1000 Reactor (Boushehr)
,
M.Sc. Thesis
Sharif University of Technology
;
Vossoughi, Nasser
(Supervisor)
Fault-tolerant Control of Formation Flying Satellites Using Machine Learning
, M.Sc. Thesis Sharif University of Technology ; Assadian, Nima (Supervisor)
Abstract
In this thesis, a fault-tolerant method for controlling the relative position and attitude between two satellites in a leader and follower formation is proposed. The follower satellite is equipped with twelve thrusters which are installed on the satellite in a particular pattern. These thrusters are assumed to be afflicted by faults. The satellites are subject to external disturbances – such as the ellipsoidal gravity of Earth (J2), drag force, solar radiation pressure, and the third body, and a controller is designed to attain the desired formation under these disturbances.For this purpose, six separated neural networks are trained, one for each of the position or attitude channels. Since...
Design and implementation of spectrally-encoded spread-time CDMA transceiver
, Article IEEE Communications Letters ; Vol. 18, issue. 5 , 2014 , pp. 741-744 ; ISSN: 10897798 ; Hosseinianfar, H ; Akhoundi F ; Yazdian, E ; Farhang, M ; Salehi, J. A ; Sharif University of Technology
2014
Abstract
In this paper, we present and discuss the physical implementation and testing of a Spectrally-Encoded Spread-Time Code Devision Multiple Access (SE/ST-CDMA) transceiver. The proposed design is suitable for multiple-access and anti jamming wireless communication systems. The design and implementation takes into account the ability to automatically detect and mitigate tone jammers by altering the corresponding Gold sequence codes assigned uniquely to each user and setting the corresponding code's chip to zero. A simple real-time anti jamming mechanism capable of dealing with frequency hopping jammers is also proposed. The simulation results are provided in terms of Bit Error Rate (BER) versus...
Experimental Evaluation of Light Frame Steel Shear Wall with K-Braced and Suitable Sheathing under Cyclic Loading
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor) ; Farahbod, Farhang (Supervisor)
Abstract
Nowadays because of imbalance in supply and demand in the house industry, industrialization of building construction is one of the best ways to solve this problem. Currently, there is a strong tendency to develop guidelines for the design of Cold-Formed Steel (CFS) with different sheathing boards as seismic resistant shear walls. Also, the behavior of this systems is not very well known yet and more research is needed. In this work three K-braced frames with and without sheathing boards under lateral cyclic loading investigated experimentally. The first specimen as a control specimen is without sheathing board, second specimen was sheathed with Fibre-Cement board in one side and gypsum board...