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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) ; 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...
MIMO Radars Waveform Design
, M.Sc. Thesis Sharif University of Technology ; 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...
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) ; 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) ; 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...
Fixed-Mix Rules in an Evolutionary Market Using a Factor Model for Dividends
, M.Sc. Thesis Sharif University of Technology ; 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...
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) ; 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) ; 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 ; 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...
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) ; 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...
Recent advances in ageing of 7xxx series aluminum alloys: A physical metallurgy perspective
, Article Journal of Alloys and Compounds ; Volume 781 , 2019 , Pages 945-983 ; 09258388 (ISSN) ; Taheri, A. K ; Taheri, K. K ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Al-Zn-Mg-Cu alloys (7xxx series Al alloys) are extensively used for their superior mechanical and corrosion performance. These properties are microstructure-sensitive and highly dependent on the formation, growth and coarsening of precipitates. To date, a wide variety of ageing procedures have been developed to tailor the evolved microstructures so as to yield a good combination of mechanical capacity and corrosion resistance of 7xxx series Al alloys. Among these methods, isothermal ageing, multi-stage ageing, non-isothermal ageing, retrogression and re-ageing (RRA), and stress ageing (i.e. creep ageing) are the most significant. In the present review, all of these approaches are...
Stiffness and strength estimation of damaged unreinforced masonry walls using crack pattern
, Article Journal of Earthquake Engineering ; Volume 26, Issue 2 , 2022 , Pages 837-856 ; 13632469 (ISSN) ; Beyer, K ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
After an earthquake, the residual stiffness and strength of structural elements are typically estimated based on a qualitative visual inspection of cracks that is prone to error. In this paper a new approach is proposed to automatically estimate the updated stiffness and strength of damaged unreinforced masonry walls by characterization of crack patterns by a mathematical index. It is shown that structural and textural fractal dimensions of a crack pattern reflect the extent of cracking and the type of cracking or crushing, i.e., whether the cracks pass through joints or whether bricks have been damaged and crushed. Using results of six quasi-static cyclic tests on unreinforced brick masonry...
Influence of heat treatment and aging on microstructure and mechanical properties of Mg-1.8Zn-0.7Si-0.4Ca alloy
, Article Materialwissenschaft und Werkstofftechnik ; Volume 50, Issue 2 , 2019 , Pages 187-196 ; 09335137 (ISSN) ; Taheri, K. K ; Taheri, A. K ; Shaeri, M. H ; Sharif University of Technology
Wiley-VCH Verlag
2019
Abstract
In order to optimize the aging treatment of Mg-1.8Zn-0.7Si-0.4Ca alloy, different times and temperatures of solid solution and age hardening were applied to the alloy specimens. Microstructures and mechanical properties of the specimens were investigated using the optical microscopy, field emission scanning electron microscopy equipped with an energy dispersive x-ray spectrometer, x-ray diffraction, hardness, and shear punch tests. The lowest hardness and strength were achieved by solution treating of the alloy at 500 °C for 8 h, presenting the optimal condition for solution treatment of the alloy. The microstructural examinations revealed three different precipitates consisting of CaMgSi,...
The nonlinear diffusion bandwidth: A simple tool for optimizing dispersion maps
, Article Optical Transmission, Switching, and Subsystems IV, Gwangju, 5 September 2006 through 7 September 2006 ; Volume 6353 I , 2006 ; 0277786X (ISSN) ; 0819464481 (ISBN); 9780819464484 (ISBN) ; Fischer, J. K ; Louchet, H ; Jamshidi, K ; Petermann, K ; Sharif University of Technology
2006
Abstract
The concept of a nonlinear transfer function of a fibre-optic communication link is reviewed. Also an approximation of the nonlinear transfer function is introduced, which allows to define an equivalent single-span model of a dispersion-managed multi-span system. In this paper we will show its limits of validity and try to extent these limits by enhancing the theoretical model. In this respect we will discuss the impact of dispersion precompensation and show the influence of residual dispersion per span, number of spans and local dispersion on transmission systems with on-off keying and differential phase-shift keying modulation formats. This approach allows fast assessment of the...
Nickel-based nanosheets array as a binder free and highly efficient catalyst for electrochemical hydrogen evolution reaction
, Article International Journal of Hydrogen Energy ; Volume 47, Issue 82 , 2022 , Pages 34887-34897 ; 03603199 (ISSN) ; Hemmati, K ; Mirabbaszadeh, K ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Hydrogen technology through water electrolyzer systems has attracted a great attention to overcome the energy crisis. So, rationally designed non-noble metal based-electrocatalysts with high activity and durability can lead to high performance water electrolyzer systems and high purity hydrogen generation. Herein, a facile two-step method: hydrothermal and electrodeposition, respectively, are developed to decorate highly porous three-dimensional binder-free structure NiFeO/NiO nanosheets array on Ni foam (NiFeO/NiO/NF) with robust adhesion as a high-performance electrode for Hydrogen Evolution Reaction (HER). The electrodeposition process applied after the initial hydrothermal process...
New operational transconductance amplifiers using current boosting
, Article Midwest Symposium on Circuits and Systems ; 2012 , Pages 109-112 ; 15483746 (ISSN) ; 9781467325264 (ISBN) ; Lazarjan, V. K ; HajSadeghi, K ; Sharif University of Technology
2012
Abstract
New techniques for Class-AB Operational Transconductance Amplifiers (OTAs) are presented. These new techniques are two topologies based on current boosting in class-AB stage which achieve considerable improvement of Slew Rate and Gain-Bandwidth while maintaining the same power consumption as the conventional design. Circuit level analysis and simulation results of proposed circuits in 0.18μm CMOS technology for gain, GBW, slew rate, and settling time are presented to prove the effectiveness of the proposed design method
Ranking of technology transfer barriers in developing countries; case study of Iran's biotechnology industry
, Article IEEE International Conference on Industrial Engineering and Engineering Management, 6 December 2011 through 9 December 2011, Singapore ; 2011 , Pages 1602-1606 ; 21573611 (ISSN) ; 9781457707391 (ISBN) ; Rashvanlouei, K. Y ; Ismail, K ; Sharif University of Technology
2011
Abstract
In this paper, first we shall define a list of technology transfer barriers in the biotechnology field through interviews and literature reviews. Next, we shall categorize them into four major categories of technology, and at last introduce all of the hypotheses on the existence of relationship between each part of technology and failure in the technology transfer process. Questionnaires consisting of two parts were created and handed out to all of the specialists and biotechnology idea-holders in the Iranian National Research center of Biotechnology, Lidco Co, Iran Pastor Institute, Biotechnology Department of University of Tehran, etc. Going on, we've evaluated the factors' validity...
A coupled adjoint formulation for non-cooled and internally cooled turbine blade optimization
, Article Applied Thermal Engineering ; Volume 105 , 2016 , Pages 327-335 ; 13594311 (ISSN) ; Mazaheri, K ; Chaharlang Kiani, K ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Most researches on the application of the adjoint method in turbine blade design are concentrated on the aerodynamic shape optimization without considering the heat transfer to/from the blade material. In this study, the adjoint method is extended to the conjugate heat transfer problems in which the viscous flow field is coupled to heat transfer in the solid region. Introducing a new adjoint variable in the solid domain, a heat adjoint equation is derived which is coupled with the energy adjoint equation in the fluid zone at the fluid/solid interface. The detailed mathematical description associated with the derivation of the heat adjoint equation with corresponding boundary conditions are...
A self-organizing multi-model ensemble for identification of nonlinear time-varying dynamics of aerial vehicles
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; Volume 235, Issue 7 , 2021 , Pages 1164-1178 ; 09596518 (ISSN) ; Ahmadi, K. K. A ; Sharif University of Technology
SAGE Publications Ltd
2021
Abstract
This article presents a novel identification approach which can deal with nonlinear and time-varying characteristics of complex dynamic systems, especially an aerial vehicle in the entire flight envelope. A set of local sub-models are first developed at different operating points of the system, and subsequently a self-organizing multi-model ensemble is introduced to aggregate the outputs of the local models as a single model. The number of employed local models in the proposed multi-model ensemble is optimized using a novel self-organizing approach. Also, wavelet neural networks, which combine both the universal approximation property of neural networks and the wavelet decomposition...
Simple SPR-based colorimetric sensor to differentiate Mg2+ and Ca2+ in aqueous solutions
, Article Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy ; Volume 268 , 2022 ; 13861425 (ISSN) ; Salehi, K ; Sadrnezhaad, S. K ; Sharif University of Technology
Elsevier B.V
2022
Abstract
L-tryptophan functionalized AgNPs were successfully fabricated using a one-pot synthesis method and assessed as a colorimetric probe for rapid and accurate determination of Mg2+ ions. The developed sensor showed a selective response towards Mg2+ with no interference from Ca2+ in the wide concentration range of 1–200 µM. The sensor's response was optimized in the pH range of 9–10, which can be attributed to the protonation of amine groups and their interaction with Mg2+ ions. The stability and selectivity of the sensor were examined in different salt (NaCl) and other metal ions, respectively. The L-tryptophan-AgNPs sensor detected Mg2+ with the limit of detection of 3 µM, which is way lower...
Micro-optoelectromechanical systems accelerometer based on intensity modulation using a one-dimensional photonic crystal
, Article Applied Optics ; Volume 55, Issue 32 , 2016 , Pages 8993-8999 ; 1559128X (ISSN) ; Abedi, K ; Jafari, K ; Gholamzadeh, R ; Sharif University of Technology
OSA - The Optical Society
2016
Abstract
In this paper, we propose what we believe is a novel sensitive micro-optoelectromechanical systems (MOEMS) accelerometer based on intensity modulation by using a one-dimensional photonic crystal. The optical sensing system of the proposed structure includes an air-dielectric multilayer photonic bandgap material, a laser diode (LD) light source, a typical photodiode (1550 nm) and a set of integrated optical waveguides. The proposed sensor provides several advantages, such as a relatively wide measurement range, good linearity in the whole measurement range, integration capability, negligible cross-axis sensitivity, high reliability, and low air-damping coefficient, which results in a wider...