MIMO radar beamforming using orthogonal decomposition of correlation matrix

, Article Circuits, Systems, and Signal Processing ; Volume 32, Issue 4 , 2013 , Pages 1791-1809 ; 0278081X (ISSN) Shadi, K ; Behnia, F ; Sharif University of Technology

2013

Abstract

MIMO radar is the next generation radar which transmits arbitrary waveforms at each one of its apertures. It has been shown that the design of waveforms for MIMO radars in order to synthesize a desired spatial beampattern is mapped into a waveform correlation matrix R design in the narrowband case. As of now, given a desired beampattern or estimated locations information of targets, calculating R has been modeled as an optimization problem like semi-definite programming. Also, in some special cases like rectangular beampattern, closed-form solutions for R has been proposed. In this paper, we introduce a fast algorithm which is capable of designing R in order to achieve more arbitrary...

Transmit beampattern synthesis using eigenvalue decomposition in MIMO radar

, Article ICICS 2011 - 8th International Conference on Information, Communications and Signal Processing, 13 December 2011 through 16 December 2011 ; December , 2011 , Page(s): 1 - 5 ; 9781457700309 (ISBN) Shadi, K ; Behnia, F ; Sharif University of Technology

2011

Abstract

MIMO radar is the next generation radar which transmits arbitrary waveforms at each one of its apertures. It has been shown that design of waveforms for MIMO radars in order to synthesize a desired spatial beampattern is mapped into a waveform correlation matrix (R) design in the narrowband case. Searching for desired R has been modeled as a convex optimization problem which demands considerable processing power. There are also some close form solutions for special cases like rectangular beampatterns. Here we deal with the problem from a matrix eigenvalue theory perspective and show how close form solutions can be found for more general cases relaxing high computational power demand. Our...

MIMO Radars Waveform Design

, M.Sc. Thesis Sharif University of Technology Shadi, Kamal (Author) ; Behnia, F (Supervisor)

Abstract

MIMO radar is a next generation radar which transmits arbitrary waveforms at each one of its apertures. It has been shown that design of waveforms for MIMO radars in order to synthesize a desired spatial beampattern, is mapped into a waveform correlation matrix (R) design in the narrowband case. Therefore, waveform design in MIMO radar for beamforming could be broken into two steps, namely correlation matrix design and waveform synthesis for achieving given R. As of now, given a desired beampattern or estimated location information of targets, calculating R has been modeled as an optimization problem like SDP. Also, in some special cases like rectangular beampattern, close form solutions for...

Fixed-Mix Rules in an Evolutionary Market Using a Factor Model for Dividends

, M.Sc. Thesis Sharif University of Technology Shadi Givi, Maryam (Author) ; Zamani, Shiva (Supervisor)

Abstract

In this thesis, we simulate the competition between some investment strategies based on dividends with each other and with mean-variance strategy (Markowitz) in an evolutionary finance framework. We perform simulations by two different approaches. In the first one, we use real dividend data and, in the second one we use dividends that are generated according to a dividend factor model. The dividend factor model which relates the dividends to the macro-economic factors is estimated from data using principal component analysis. Our simulations show that in this competition, the evolutionary portfolio rule will eventually hold the total market wealth. According to this simple rule the portfolio...

Extract Non-Line-of-Sight state of base stations and error mitigation technique for wireless localization in micro-cell networks

, Article Computer Communications ; Volume 35, Issue 7 , 2012 , Pages 885-893 ; 01403664 (ISSN) Dehghani, H. L ; Golmohammadi, S ; Shadi, K ; Sharif University of Technology

2012

Abstract

Non Line of Sight (NLOS) propagation is a challenging issue which the performance of network based wireless localization is limited by errors primarily caused by NLOS corruption. NLOS is inherently a dominant source of errors in metropolitan area wireless networks, like cellular one, so in this paper we discuss our proposed algorithm within cellular network terminology. This paper contributes two novel algorithms. The first one is to extract the NLOS state of base station (BS) and the second one is a correction algorithm to enhance the measurements accuracy. Our proposed algorithm discuses a novel localization technique to estimate true mobile terminal (MT) location from a set of possibly...

Well-conditioned sensor placement for range-only localization

, Article 2011 4th IFIP International Conference on New Technologies, Mobility and Security, NTMS 2011 - Proceedings, 7 February 2011 through 10 February 2011 ; February , 2011 , Page(s): 1 - 5 ; ISSN : 21574952 ; 9781424487042 (ISBN) Shadi, K ; Dehghani, H. L ; Gholampour, I ; Sharif University of Technology

2011

Abstract

This paper addresses the optimality of Network topology for localization purposes when measurements are range-only. Localization procedures based on TOA and TDOA range measurements are considered in this paper. As of now, the optimal placement of fixed terminals to locate mobile terminals has been studied based on Cramer-Rao Lower Bound (CRLB). CRLB is a universal bound on the variance of a general unbiased estimator and therefore is not dependent to the estimator and methods of localization. Here we introduce another algorithm dependent criterion, based on perturbation theory of linear equations. Different optimal topologies are presented using the new criterion. These optimal topologies,...

Inverse design of compact power divider with arbitrary outputs for 5G applications

, Article Scientific Reports ; Volume 12, Issue 1 , 2022 ; 20452322 (ISSN) Shadi, M ; Tavakol, M. R ; Atlasbaf, Z ; Sharif University of Technology

Nature Research 2022

Abstract

Since the recent on-demand applications need more sophisticated circuits and subsystems, components with configurable capabilities attract attention more than before in commercial systems, specifically the fifth generation (5G). Power dividers play a crucial role in 5G phased array systems, and their role becomes more significant if the output powers ratio is adjustable. Here, we suggest a design methodology by which planar power splitters with arbitrary output power levels can be designed in light of very simple perturbations, i.e., vias. Through our design procedure, we find an optimized pattern for hybrid vias-some of them are made of PEC, and others are dielectric, e.g., air,...

Studying the Effect of Applying Different Refrigerants in Ground Source Heat Exchangers

, M.Sc. Thesis Sharif University of Technology Shadi Diznab, Mohammad Amin (Author) ; Hakkaki-Fard, Ali (Supervisor)

Abstract

Economical strategy of developed countries imposes to improve energy efficiency and a rational renewable energies usage in the buildings. Ground source heat pumps are one of the most important tools in the way moving toward this goal. This study focuses on studying the effect of applying different refrigerants in the direct expansion ground source heat exchangers. In order to compare the performance of the ground source heat pumps using different refrigerants, a specific methodology is presented and implemented. First on this study, the thermal performance of a geothermal borehole filled with both CO2 and a zeotropic mixture of CO2 and R32 (20/80) is studied and the quality, temperature, and...

Correlations in a multisubband quasi-one-dimensional electron gas

, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 62, Issue 23 , 2000 , Pages 16001-16017 ; 01631829 (ISSN) Nafari, N ; Nafari, N ; Asgari, R ; Asgari, R ; Sharif University of Technology

2000

Abstract

This paper is an extension of an earlier work on electron correlations in semiconducting GaAs-based quasi-one-dimensional quantum wires. The extension was twofold. First, we developed the Singwi, Tosi, Land, and Sölander (STLS) scheme for multisubband structures. Secondly, we developed the multisubband ladder approximation diagrammatic technique. By using the results obtained for the spin symmetric and spin antisymmetric interpolarization and intrapolarization potentials, we calculate the corresponding electron-electron effective potentials. Our results for a two-subband model show that these effective potentials have an attractive part implying the occurrence of s-wave and p-wave pairings,...

Age-hardening behavior and phase identification in solution-treated AEREX 350 superalloy

, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 37, Issue 7 , 2006 , Pages 2051-2057 ; 10735623 (ISSN) Asgari, S ; Sharif University of Technology

2006

Abstract

This article presents results of an investigation on age-hardening behavior of superalloy AEREX 350. Microhardness testing was employed to evaluate the age-hardening response of the alloy while optical, scanning, and transmission electron microscopy techniques were used to characterize the major phases formed during the aging process. No significant hardening was found in solution-treated samples aged at temperatures up to about 680 °C. Aging at 700 °C up to 950 °C, however, caused a characteristic hardening response. This hardening was concurrent with the formation of γ', an ordered phase with L12 structure, as fine precipitate distributed throughout the fcc matrix. In the temperature range...

Anomalous plastic behavior of fine-grained MP35N alloy during room temperature tensile testing

, Article Journal of Materials Processing Technology ; Volume 155-156, Issue 1-3 , 2004 , Pages 1905-1911 ; 09240136 (ISSN) Asgari, S ; Sharif University of Technology

2004

Abstract

In this paper, results of an investigation on the strain hardening responses of superalloy MP35N with two average grain sizes of 38 and 1 μm, during room temperature tensile testing are reported. The microstructural evolution of the deformed samples was studied using optical and transmission electron microscopy (TEM) techniques. The strain hardening behavior of the 38 μm material was rather similar to that previously reported for low stacking fault energy (SFE) fee alloys. The plastic behavior of the fine grain material, however, was unexpected. In the strain range of 0.1-0.4, the work hardening rate of the fine grain size sample was evidently lower than that of the large grain size...

Degradation of benzene, toluene, and xylene (BTX) from aqueous solution by isolated bacteria from contaminated sites

, Article Research on Chemical Intermediates ; Volume 41, Issue 1 , January , 2015 , Pages 265-275 ; 09226168 (ISSN) Mesgari Shadi, A ; Yaghmaei, S ; Vafaei, F ; Khataee, A. R ; Hejazi, M. S ; Sharif University of Technology

Kluwer Academic Publishers 2015

Abstract

The present study was carried out to evaluate the degradation efficiency of benzene, toluene, and xylene (BTX) by isolated bacteria from various petroleum-hydrocarbons contaminated sites. Five isolated bacteria were selected for testing BTX biodegradation from liquid culture media. Each of these bacteria was able to degrade BTX but with different efficiencies. Maximum biodegradation efficiency for benzene (more than 70 %) was obtained by Gram-positive coccobacillus, Gram-positive coccus and Gram-negative bacillus bacteria, for toluene (60 %) and xylene (70 %) by Gram-positive coccobacillus and Gram-negative coccobacillus. It was found that the presence of xylene in the substrate mixture...

Interaction of 3D dewetting nanodroplets on homogeneous and chemically heterogeneous substrates

, Article Journal of Physics Condensed Matter ; Vol. 26, Issue. 22 , 2014 ; ISSN: 09538984 Asgari, M ; Moosavi, A ; Sharif University of Technology

2014

Abstract

Long-time interaction of dewetting nanodroplets is investigated using a long-wave approximation method. Although three-dimensional (3D) droplets evolution dynamics exhibits qualitative behavior analogous to two-dimensional (2D) dynamics, there is an extensive quantitative difference between them. 3D dynamics is substantially faster than 2D dynamics. This can be related to the larger curvature and, as a consequence, the larger Laplace pressure difference between the droplets in 3D systems. The influence of various chemical heterogeneities on the behavior of droplets has also been studied. In the case of gradient surfaces, it is shown how the gradient direction could change the dynamics. For a...

Late-stage evolution of thin liquid coating films over step topographies

, Article Advanced Materials Research ; Volume 569 , 2012 , Pages 560-563 ; 10226680 (ISSN) ; 9783037854808 (ISBN) Asgari, M ; Moosavi, A ; Sharif University of Technology

2012

Abstract

Mesoscopic hydrodynamic equations are solved to investigate late-stage evolution of thin liquid films over step topographies. Different geometrical parameters including step height and initial position and configuration of resultant masses of dewetting (droplets) are probed to find their effects on the mass evolution of the system. Our results indicate that increasing the step height and locating the droplets close to the step enhance the dynamics and accelerate smaller droplet collapse

Reduced master equation for modeling of ferromagnetic single-electron transistor

, Article Applied Mechanics and Materials, 29 July 2011 through 31 July 2011, Bangkok ; Volume 110-116 , July , 2012 , Pages 3103-3110 ; 16609336 (ISSN) ; 9783037852620 (ISBN) Asgari, S ; Faez, R ; Sharif University of Technology

2012

Abstract

In this paper, the reduced master equation which is a fast simulation method of spin dependent transport in ferromagnetic single electron transistors is presented, for first time. This simulation method follows steady state master equation in which all charge states of the system are considered, whereas charge states are decreased in reduced master equation. This method is based on two degrees of electron freedom which are charge and spin. This is applied in the condition that orthodox tunneling theory is applicable to calculate the tunneling rate of electrons through barriers. The comparison between the I-V characteristics of a ferromagnetic single-electron transistor by following the...

Coarsening dynamics of nanodroplets on topographically structured substrates

, Article Journal of Physics Condensed Matter ; Volume 25, Issue 4 , 2013 ; 09538984 (ISSN) Asgari, M ; Moosavi, A ; Sharif University of Technology

2013

Abstract

Employing a biharmonic boundary integral method with linear elements, coarsening dynamics of nanodroplets on topographical step heterogeneity is investigated. It is shown that the step height and droplet configuration have an influential effect on the dynamics. Increasing the step height slows down the process while locating the droplets close to the step boosts the coarsening rate. Considering a slip boundary condition enhances the dynamics and reveals a transition in the droplet migration direction. Our results reveal that increasing the surface wettability weakens the dynamics. Various types of the disjoining pressure over the step are also considered and their effects on the coarsening...

Characterization of LiCoO2 nanopowders produced by sol-gel processing

, Article Journal of Nanomaterials ; Volume 2010 , 2010 ; 16874110 (ISSN) Asgari, S ; Soltanmohammad, S ; Sharif University of Technology

2010

Abstract

LiCoO2 nanopowders, one of the most important cathode materials for lithium-ion batteries, were synthesized via a modified sol-gel process assisted with triethanolamine (TEA) as a complexing agent. The influence of three different chelating agents including acrylic acid, citric acid, and oxalic acid on the size and morphology of particles was investigated. Structure and morphology of the synthesized powders were characterized by thermogravimetric/ differential thermal analyses (TG/DTA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Results indicate that the powder processed with TEA and calcinated at 800 °C had an excellent hexagonal ordering of α-NaFeO2 -type (space...

Approximate method of determining the optimum cross section of microhannel heat sink

, Article Journal of Mechanical Science and Technology ; Volume 23, Issue 12 , 2010 , Pages 3448-3458 ; 1738494X (ISSN) Asgari, O ; Saidi, M.H ; Sharif University of Technology

2010

Abstract

Microchannels are at the forefront of today's cooling technologies. They are widely being considered for cooling of electronic devices and in micro heat exchanger systems due to their ease of manufacture. One issue which arises in the use of microchannels is related to the small length scale of the channel or channel cross-section. In this work, the maximum heat transfer and the optimum geometry for a given pressure loss have been calculated for forced convective heat transfer in microchannels of various cross-section having finite volume for laminar flow conditions. Solutions are presented for 10 different channel cross sections: parallel plate channel, circular duct, rectangular channel,...

Comment on ‘Free vibration and buckling analyses of cylindrical sandwich panel with magneto rheological fluid layer’ (Journal of Sandwich Structures and Materials, doi: 10.1177/1099636215603034)

, Article Journal of Sandwich Structures and Materials ; Volume 21, Issue 7 , 2019 , Pages 2411-2412 ; 10996362 (ISSN) Asgari, M ; Haddadpour, H ; Sharif University of Technology

SAGE Publications Ltd 2019

Tunable circular conversion dichroism and asymmetric transmission of terahertz graphene metasurface composed of split rings

, Article Optics Communications ; Volume 456 , 2020 Asgari, S ; Rahmanzadeh, M ; Sharif University of Technology

Elsevier B.V 2020

Abstract

The asymmetric transmission (AT) has attracted wide attention due to its novel applications. In this paper, we propose and investigate a tunable polarization-dependent intrinsically chiral graphene metasurface composed of split ring arrays in terahertz (THz) region. The resonance frequency of the structure is sensitive to the graphene chemical potential. Circular conversion dichroism (CCD) of the proposed structure is tunable and is reached to 0.36. Our work paths a new approach to propose some other compact and on-chip polarization-dependent structures in THz region. Furthermore, our proposed structure could be a useful segment in polarization-dependent systems. © 2019 Elsevier B.V