Decorrelating closely spaced antennas by pattern design in uniform scattering environments

, Article IET Microwaves, Antennas and Propagation ; Volume 4, Issue 11 , November , 2010 , Pages 1903-1909 ; 17518725 (ISSN) Shariatpanahi, S. P ; Khalaj, B. H ; Shishegar, A. A ; Saligheh Rad, H ; Sharif University of Technology

2010

Abstract

The authors propose a novel solution for decorrelating closely spaced antennas with identical radiation patterns. By proper steering of the directional elements' patterns, the decorrelation distance is reduced to 0.25λ in comparison with the well-established 0.4λ result based on the Bessel-shaped correlation expression. In addition, by proposing the definition of Decorrelation Factor of an antenna pattern, a framework for comparison of correlation behaviour of different antennas is provided. Subsequently, a performance metric characterised by the Jensen upper bound for the capacity of closely spaced antennas is proposed. Finally, we apply our results to two practical directional antennas,...

Decorrelating closely-placed antennas by pattern design in uniform scattering environments

, Article 2008 10th International Conference on Advanced Communication Technology, Phoenix Park, 17 February 2008 through 20 February 2008 ; Volume 3 , 2008 , Pages 2092-2095 ; 17389445 (ISSN); 9788955191356 (ISBN) Shariatpanahi, P ; Hossein Khalaj, B ; Shishegar, A. A ; Saligheh Rad, H ; Sharif University of Technology

2008

Abstract

MIMO system's performance depends greatly on the correlation of employed antennas. The more the correlation is, the worse the performance will be. We propose a solution to the problem of decorrelating closely spaced antennas assuming the antennas have identical radiation patterns with the same steering angles. In fact, we will show that by proper steering of the antenna patterns, the decorrelation distance is reduced to 0.25λ which is a great improvement comparing with the well-established 0.4λ result coming from the Bessel-shaped correlation expression. Also, we analyze this result in the regime of very closely placed antennas and by proposing the definition of Decorrelation Factor of an...

Non-fixed scatterers and their effects on MIMO multicarrier fading communication channels

, Article 50th Annual IEEE Global Telecommunications Conference, GLOBECOM 2007, Washington, DC, 26 November 2007 through 30 November 2007 ; December , 2007 , Pages 3765-3769 ; 1424410436 (ISBN); 9781424410439 (ISBN) Saligheh Rad, H ; Gazor, S ; Shariatpanahi, P ; Sharif University of Technology

2007

Abstract

There are two types of scatterers in a multipath propagation environment: fixed and non-fixed scatterers. Fixed scatterers like buildings, mountains and tree stems do not move, while non-fixed (moving) scatterers like cars, people and tree leaves move from their initial positions. In addition to different movements of the mobile station (MS) that cause different kinds of Doppler fading, movements of non-fixed scatterers are also anticipated to generate other kinds of fading/correlation. This fading changes depend on the type of the propagation environment and the type of movements of local surrounding scatterers. In this paper we characterize these effects in terms of temporal correlations....

Low SNR regime capacity analysis of MIMO systems using directional antennas

, Article 2008 International Symposium on Telecommunications, IST 2008, Tehran, 27 August 2008 through 28 August 2008 ; 2008 , Pages 393-398 ; 9781424427512 (ISBN) Shariatpanahi, P ; Shishegar, A. A ; Khalaj, B. H ; Salavati, A. H ; Saligheh Rad, H. R ; Sharif University of Technology

2008

Abstract

In this paper, we evaluate the capacity of Multiple-Input Multiple-Output (MIMO) systems using directional antennas in non-isotropic scattering environments. Our analytical analysis approach results in closed-form approximate formulas in low Signal to Noise Ratio (SNR) regime (in contrast to previous research works which have investigated the same problem by employing experimental or simulation frameworks). We propose an upper bound for the introduced approximate error. Our results show that MIMO systems equipped with directional antennas may have much higher capacity in nonisotropic scattering environments compared to MIMO systems equipped with omni-directional antennas. We also evaluate...

Magnetite/dextran-functionalized graphene oxide nanosheets for in vivo positive contrast magnetic resonance imaging

, Article RSC Advances ; Volume 5, Issue 59 , May , 2015 , Pages 47529-47537 ; 20462069 (ISSN) Moradi, S ; Akhavan, O ; Tayyebi, A ; Rahighi, R ; Mohammadzadeh, M ; Saligheh Rad, H. R ; Sharif University of Technology

Royal Society of Chemistry 2015

Abstract

Superparamagnetic iron oxide (SPIO) nanomaterials are widely used as magnetic resonance imaging (MRI) contrast agents (CAs). These CAs significantly shorten transverse relaxation time (T2) and so decrease the intensity of the T2-weighted MRI (negative contrast imaging). However, the partial-volume effect is known to be one of the problems in negative contrast MRI. In this work, SPIO nanoparticles were modified by dextran and graphene oxide (GO) nanosheets to achieve a positive contrast MRI with high intensity. This modification resulted in shortening the longitudinal relaxation time (T1) of the SPIO nanoparticles (in addition to the T2 shortening)....

The feasibility Study on Magnetic Resonance Spectroscopy (MRS) Thermometry in the Presence of Magnetic Field Inhomogeneity

, M.Sc. Thesis Sharif University of Technology Taghavi, Marziyeh (Author) ; Samadfam, Mohammad (Supervisor) ; Saligheh Rad, Hamid Reza (Supervisor)

Abstract

1H-MRS thermometry as one of MRI thermometry methods, provides useful information about the distribution of the absolute temperature of tissue that can be used in diagnostic and therapeutic applications. It seems that the magnetic field inhomogeneity and the reduction of spectra resolution also affects the accuracy of MRS thermometry. To our knowledge, effects of magnetic field inhomogeneity on MRS thermometry has never been reported. In this study, we evaluated the effect of susceptibility inhomogeneity on MRS thermometry. In the first stage, MRS thermometry equation was derived in the presence of field inhomogeneity. Then simulation used for estimate the effect of filed inhomogeneity based...

Study on the Efficiency of Graphene and Graphene Oxide-coated Iron Oxide Nanoparticles in the Treatment of Cancer Cells to Hyperthermia

, M.Sc. Thesis Sharif University of Technology Azizi Darsara, Fatemeh (Author) ; Otukesh, Mohammad (Supervisor) ; Saligheh Rad, Hamid Reza (Co-Advisor)

Abstract

The main methods have been used clinically for cancer treatment are included: surgery, chemotherapy, radiation therapy and hyperthermia. Hyperthermia (heat therapy) treatment method in which by raising the temperature of the tumor it removed. Magnetic hyperthermia is known as a kind of hyperthermia that have been represent appropriate results. In this study, using iron oxide nanoparticle coated with graphene for cancer treatment under a magnetic field of the laser. In the first stage, graphene oxide nanosheets and nanoparticles Magntayt are synthesized by chemical oxidation and co-precipitation, respectively. At the end, the nanoparticles on the substrate of graphene layer is obtained...

Quantitative assessment of resting-state functional connectivity MRI to differentiate amnestic mild cognitive impairment, late-onset Alzheimer's disease from normal subjects

, Article Journal of Magnetic Resonance Imaging ; Volume 57, Issue 6 , 2023 , Pages 1702-1712 ; 10531807 (ISSN) Mohammadian, F ; Zare Sadeghi, A ; Noroozian, M ; Malekian, V ; Abbasi Sisara, M ; Hashemi, H ; Mobarak Salari, H ; Valizadeh, G ; Samadi, F ; Sodaei, F ; Saligheh Rad, H ; Sharif University of Technology

John Wiley and Sons Inc 2023

Abstract

Background: Alzheimer disease (AD) is a neurological disorder with brain network dysfunction. Investigation of the brain network functional connectivity (FC) alterations using resting-state functional MRI (rs-fMRI) can provide valuable information about the brain network pattern in early AD diagnosis. Purpose: To quantitatively assess FC patterns of resting-state brain networks and graph theory metrics (GTMs) to identify potential features for differentiation of amnestic mild cognitive impairment (aMCI) and late-onset AD from normal. Study Type: Prospective. Subjects: A total of 14 normal, 16 aMCI, and 13 late-onset AD. Field Strength/Sequence: A 3.0 T; rs-fMRI: single-shot 2D-EPI and...

Numerical Evaluation of the Influence of Hydro-Mechanical Factors on the Conventional Methods of Hydraulic Fracture Analysis in Oil Reservoirs

, M.Sc. Thesis Sharif University of Technology Saligheh Doust, Mostafa (Author) ; Pak, Ali (Supervisor)

Abstract

The exploitation of oil and gas has been changed dramatically since the advent of hydraulic fracturing. Hydraulic fracture is one of the enhanced oil recovery methods in which high-pressure injecting fluid is pumped into the well to overcome the lowest in-situ stress and rock resistance to create cracks in the deep-rock formations. It is estimated that the benefits of the mentioned method lead to a net economic profit of $48 billion per year in the world’s oil and gas industry.While there are various analytical models for predicting hydraulic fracture characteristics, KGD and PKN are amongst the most popular Models. The conditions of plane strain in two-dimensional space are taken into...

A new algorithm for optimal measurement placement, observability analysis and harmonic state estimation in power systems

, Article PEDSTC 2013 - 4th Annual International Power Electronics, Drive Systems and Technologies Conference ; 2013 , Pages 518-523 ; 9781467344845 (ISBN) Rad, M. S ; Mokhtari, H ; Karimi, H ; Sharif University of Technology

2013

Abstract

Harmonic State Estimation (HSE) is a technique for identifying harmonic distributions in power systems with limited measurements. The main problem in HSE is the optimal placement of measurement meters such that the estimation error is minimized, while making the system fully observable. The second issue is the HSE method. This method must be accurate and fast enough in order to have an accurate HSE. This paper presents a new algorithm that uses minimum variance criterion (MVC) and a sequential method for optimal meters placement, SVD method for observability analysis and finally WLS method for harmonic estimation. The proposed method minimizes the number of measurement devices and the error...

An optimal measurement placement method for power system harmonic state estimation

, Article EPE 2012 - Proceedings of the 2012 International Conference and Exposition on Electrical and Power Engineering ; 2012 , Pages 271-275 ; 9781467350013 (ISBN) Rad, M. S ; Mokhtari, H ; Karimi, H ; Sharif University of Technology

2012

Abstract

Harmonic state estimation (HSE) method has been used to locate harmonic sources and estimate harmonic distribution in power systems with limited number of harmonic meters. This paper focuses on a new technique for optimal placement of measurement devices and observability analysis for power systems harmonic state estimation. The proposed method optimizes the number of measurements and minimizes the error of estimation at the same time. The method is tested on the IEEE 14-bus power system to show its precision

Frictional viscoelastic based model for spherical particles collision

, Article Granular Matter ; Volume 20, Issue 4 , 2018 ; 14345021 (ISSN) Kaviani Rad, H ; Nejat Pishkenari, H ; Sharif University of Technology

Springer New York LLC 2018

Abstract

In this paper, collision of two balls in three dimensions with regard to energy loss and friction is studied. This investigation intends to propose the procedure which can determine the condition of pure sliding, sliding with rolling or sticking, and rolling or sticking at the beginning of contact. Furthermore, the other aim of this research is to suggest the closed-form relation for post-collision angular and linear velocities in which the possibility of three regimes of impact, pure sliding, sliding with rolling, and pure rolling, are considered. In this investigation, viscous Hertz contact force describes the normal interaction force. Moreover, stick regime is not taken into account and...

Adaptive model predictive TCP delay-based congestion control

, Article Computer Communications ; Volume 29, Issue 11 , 2006 , Pages 1963-1978 ; 01403664 (ISSN) Haeri, M ; Mohsenian Rad, A. H ; Sharif University of Technology

2006

Abstract

Adaptive Model Predictive Transmission Control Protocol (AMP-TCP) as a new TCP delay-based congestion control algorithm is introduced. Both aspects of design and implementation of the algorithm are described using simulations on the ns-2 network simulator. The design stage is composed of two steps. First, a recursive system identification approach is proposed to capture the network delay dynamics from TCP source view. Second, the proposed modeling is employed to develop an adaptive model predictive TCP congestion control strategy in the absence of any explicit congestion notification. The characteristics and performance of AMP-TCP are investigated using several network simulations. Finally a...

TCP retransmission timer adjustment mechanism using model-based RTT predictor

, Article 2004 5th Asian Control Conference, Melbourne, 20 July 2004 through 23 July 2004 ; Volume 1 , 2004 , Pages 686-693 ; 0780388739 (ISBN) Haeri, M ; Mohsenian Rad, A. H ; Sharif University of Technology

2004

Abstract

Transmission Control Protocol (TCP) uses multiple timers to do its work. The most important of these is the retransmission timer. In this paper, the TCP retransmission timer adjustment mechanism is approached from a system point of view and a new mechanism is proposed. A simple recursive system identification algorithm is used to capture both time variant and time invariant Internet behavior. Also a dynamic model-based Round-Trip Time (RTT) predictor was provided. Based on network simulation and real Internet data collection, it was observed that when the retransmission timer is adjusted by the proposed predictor instead of the traditional RTT estimator, performance increased significantly

Transformation of sliding motion to rolling during spheres collision

, Article Granular Matter ; Volume 19, Issue 4 , 2017 ; 14345021 (ISSN) Nejat Pishkenari, H ; Kaviani Rad, H ; Jafari Shad, H ; Sharif University of Technology

2017

Abstract

In this research, we have investigated the three-dimensional elastic collision of two balls, based on friction in the tangential plane. Our aim is to offer analytical closed form relations for post collision parameters such as linear and angular velocities, collision time and tangential and normal impulse in three dimensions. To simplify the problem, stick regime is not considered. In other words, balls have a low tangential coefficient of restitution. Sliding, sliding then rolling, and rolling at the beginning of contact are three cases that can occur during impact which have been considered in our research. The normal interaction force is described by the Hertz contact force and...

Inverse design of supersonic diffuser with flexible walls using a Genetic Algorithm

, Article Journal of Fluids and Structures ; Volume 22, Issue 4 , 2006 , Pages 529-540 ; 08899746 (ISSN) Ziaei-Rad, S ; Ziaei-Rad, M ; Sharif University of Technology

2006

Abstract

An efficient algorithm for the design optimization of the compressible fluid flow problem through a flexible structure is presented. The methodology has three essential parts: first the behavior of compressible flow in a supersonic diffuser was studied numerically in quasi-one-dimensional form using a flux splitting method. Second, a fully coupled sequential iterative procedure was used to solve the steady state aeroelastic problem of a flexible wall diffuser. Finally, a robust Genetic Algorithm was implemented and used to calculate the optimum shape of the flexible wall diffuser for a prescribed pressure distribution. © 2006 Elsevier Ltd. All rights reserved

A macro analytic success model for Entrepreneurial university

, Article World Applied Sciences Journal ; Volume 27, Issue 8 , 2013 , Pages 1049-1056 ; 18184952 (ISSN) Fateh rad, M ; Mansourian, F ; Lotfi, H ; Sharif University of Technology

2013

Abstract

One of the new forming world discipline feature is knowledge based innovation. World new discipline, vitality condition is to establish new science and technology and suitable utility from that. Therefore, the new era witness those grand variations in university systems and for more utilization process in national, regional and international economical development. In this context, traditional university variation and conversion to Entrepreneurial University and holding and creating idea and supporting it to transform in final product or service is concerned, which means knowledge-based entrepreneurship. Thus, this university can develop knowledge-based staff and has nontraditional processes...

Heat transfer enhancement in shell-and-tube heat exchangers using porous media

, Article Heat Transfer Engineering ; Volume 36, Issue 3 , 2015 , Pages 262-277 ; 01457632 (ISSN) Esmaeili Rad, S ; Afshin, H ; Farhanieh, B ; Sharif University of Technology

Taylor and Francis Ltd 2015

Abstract

A numerical simulation has been carried out to investigate the heat transfer enhancement in a shell-and-tube heat exchanger using a porous medium inside its shell and tubes, separately. A three-dimensional geometry with k-ε turbulent model is used to predict the heat transfer and pressure drop characteristics of the flow. The effects of porosity and dimensions of these media on the heat exchanger's thermal performance and pressure drop are analyzed. Inside the shell, the entire tube bundle is wrapped by the porous medium, whereas inside the tubes the porous media are located in two different ways: (1) at the center of the tubes, and (2) attached to the inner wall of the tubes. The results...

Multiuser precoding and power allocation in downlink of cooperative CDMA networks

, Article ATC 2009 - Proceedings of the 2009 International Conference on Advanced Technologies for Communications, 12 October 2009 through 14 October 2009, Hai Phong ; 2009 , Pages 279-283 ; 9781424451395 (ISBN) Abdizadeh, M ; Jafarnia, A ; Jamali Rad, H ; Sharif University of Technology

2009

Abstract

In this paper, we study the downlink of cooperative Direct-Sequence Code Division Multiple Access (DS-CDMA) systems, where a set of Mobile Terminals (MT) cooperate with the purpose of improving their downlink communications reliability with Base Station (BS). For combating Multiple-Access Interference (MAI) as well as transferring complexity and spatial processing from the mobile terminals to the transmitter of BS, multiuser transmitter precoding is considered. In addition to multiuser precoding based on Minimum Mean-Square Error (MMSE) criterion for mitigating MAI, the proper transmission power control strategy under a fixed total power constraint is proposed and analyzed. Compared with...

Pseudo DVL reconstruction by an evolutionary TS-fuzzy algorithm for ocean vehicles

, Article Measurement: Journal of the International Measurement Confederation ; Volume 147 , 2019 ; 02632241 (ISSN) Ansari-Rad, S ; Hashemi, M ; Salarieh, H ; Sharif University of Technology

Elsevier B.V 2019

Abstract

By development of ocean exploration, autonomous vehicles are employed to perform on-water and underwater tasks. Using an extended Kalman filter, Inertial Navigation System/Doppler Velocity Log (INS/DVL) integrated systems are trying to navigate in oceans and underwater environments when Global Positioning System (GPS) signals are not accessible. The dependency of DVL signals on acoustic environments may cause any DVL malfunction due to sea creatures or strong wave-absorbing material. In this paper, an improved version of evolutionary TS-fuzzy (eTS) is proposed in order to predict DVL sensor outputs at DVL malfunction moment, by utilizing an artificial intelligent (AI) aided integrated...