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Functional neuroimaging for addiction medicine: From mechanisms to practical considerations
, Article Progress in Brain Research ; Volume 224 , 2016 , Pages 129-153 ; 00796123 (ISSN) ; 9780444637161 (ISBN) ; Faghiri, A ; Oghabian, M. A ; Paulus, M. P ; Ekhtiari H. E ; Paulus M. P ; Sharif University of Technology
Elsevier
2016
Abstract
During last 20 years, neuroimaging with functional magnetic resonance imaging (fMRI) in people with drug addictions has introduced a wide range of quantitative biomarkers from brain's regional or network level activities during different cognitive functions. These quantitative biomarkers could be potentially used for assessment, planning, prediction, and monitoring for "addiction medicine" during screening, acute intoxication, admission to a program, completion of an acute program, admission to a long-term program, and postgraduation follow-up. In this chapter, we have briefly reviewed main neurocognitive targets for fMRI studies associated with addictive behaviors, main study types using...
Nonuniform line generator for high-power RF applications
, Article IEEE Transactions on Plasma Science ; Volume 46, Issue 1 , 2018 , Pages 64-71 ; 00933813 (ISSN) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Line generators were attractive structures for high-power radio frequency (RF) pulse generation for two decades. Due to some disadvantages, there has been little attention to this type of generator for a relatively long time. In this paper, a nonuniform line generator is used which resolves some of the main shortcomings of conventional line generators. The considered generator can generate RF pulses at higher frequencies with considerably higher repetition rates. Furthermore, the implementation of nonuniform line generators is significantly easier than that of their conventional counterparts. Measurement results for three nonuniform line generators are presented. The possibility of...
Inferring the Directionality of Coupling forTwo Time Series
, M.Sc. Thesis Sharif University of Technology ; Rahimi Tabar, Mohammad Reza (Supervisor)
Abstract
The synchronization phenomena are abundant is science, nature, engineering, and social life. Systems as diverse as clocks, singing crickets, cardiac pacemakers, firing neurons, and applauding audiences exhibit a tendency to operate in synchrony. These phenomena are universal and can be understood within a common framework based on modern nonlinear dynamics. First chapter of this thesis describes the basic ideas of the synchronization in an intuitive way. The main physical concepts are presented with experimental examples.
One of the main effects of synchronization is the ability to infer the directionality of coupling for two time series. Uncovering the directionality of coupling is a...
One of the main effects of synchronization is the ability to infer the directionality of coupling for two time series. Uncovering the directionality of coupling is a...
A disambiguation technique for passive localization using trajectory analysis
, Article IEEE Transactions on Aerospace and Electronic Systems ; 2018 ; 00189251 (ISSN) ; Behnia, F ; Sharif University of Technology
2018
Abstract
In some well-known passive localization methods, when the number of equations equals the number of unknown object coordinates, there arise finite number of possible solutions. A localization disambiguation technique is required to identify the correct solution in these cases. As an example, the exact solution of time-difference-of-arrival (TDOA) based equations for four receiver sites, leads to a couple of solutions with only one of them being the true target position. This ambiguity, conventionally is resolved by using angle-of-arrival (AOA) measurements or using an additional receiver site which increase the cost and complexity of the system. In this paper a localization disambiguation...
Single-site source localisation using scattering data
, Article IET Radar, Sonar and Navigation ; Volume 12, Issue 2 , February , 2018 , Pages 250-259 ; 17518784 (ISSN) ; Behnia, F ; Sharif University of Technology
Institution of Engineering and Technology
2018
Abstract
Passive localisation of non-cooperative targets through their electromagnetic emissions is an attractive issue. This localisation task can be carried out using multitude of receiver sites being linked together. This multiplicity, however, brings about difficulties in organising and coordinating the sites. One can even claim that the method is no longer passive considering the necessary communication links between the sites. On the other hand, single-site localisation methods basically overcome these difficulties eliminating the need for inter-site communications. In this study, a single-site localisation method is presented and analysed. This method is applicable to scenarios with a large...
A Disambiguation technique for passive localization using trajectory analysis
, Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 55, Issue 2 , 2019 , Pages 820-829 ; 00189251 (ISSN) ; Behnia, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In some well-known passive localization methods, when the number of equations equals the number of unknown object coordinates, there arise finite number of possible solutions. A localization disambiguation technique is required to identify the correct solution in these cases. As an example, the exact solution of time-difference-of-arrival (TDOA) based equations for four receiver sites, leads to a couple of solutions with only one of them being the true target position. This ambiguity conventionally is resolved by using angle-of-arrival measurements or using an additional receiver site, which increase the cost and complexity of the system. In this paper, a localization disambiguation...
A compact MW-Class short pulse generator
, Article IEEE Transactions on Plasma Science ; Volume 46, Issue 6 , 2018 , Pages 2059-2063 ; 00933813 (ISSN) ; Hashemi, M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
A megawatt-range short pulse generator based on the diode step recovery phenomenon and the Marx generator idea is presented. This generator utilizes both opening and closing switches in one circuit. The proposed circuit is compact, light, and low cost and is driven by a low-power source. By using a three-stage Marx generator, the output peak power of 0.6 MW was obtained. The dimensions of the generator are 8 cm $ imes8$ cm. Experimental measurements of the output pulse characteristics showed a rise time of 100 ns for a 16- $Omega $ load. The input peak power was 4 W which showed more than 105 times increase in the pulse peak power. © 1973-2012 IEEE
The Simultaneous Berth and Quay Crane Scheduling
, M.Sc. Thesis Sharif University of Technology ; Salmasi, Naser (Supervisor)
Abstract
This study addresses the simultaneous berth and quay crane (QC) scheduling problem in a container terminal. The berths are considered as a continuous area and the vessels arrive dynamically. QCs are allowed to move to other vessels before completing the process on an assigned vessel.The objective function is determined based on the practical applications of the problem. It deals with minimization of sum of the completion time of vessels. In this research, a mathematical model has been developed for the research problem. According to NP-hardness of the research problem, two meta heuristic algorithms based on Tabu Search are proposed. To solve the problem, these methods have two layers with...
Developing the MIDA Method for Mid-Rise Structures with Non-symmetrical Plan
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masood (Supervisor)
Abstract
Performance based design becomes an effective method for estimating seismic demands of buildings. Incremental dynamic analysis (IDA) based on a nonlinear response time history analysis (NL-RHA) is considered to be the most accurate method in seismic demand calculations. However, modal incremental dynamic analysis (MIDA), based on the equivalent single degree-of-freedom (SDF) oscillator, is also often used in studying structural engineering performances. The MIDA procedure for estimating seismic demands is extended to unsymmetric-plan buildings. In the MIDA procedure, the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by...
Model Based Analysis of tDCS Effects on Brain Networks in Methamphetamine Addicts
, M.Sc. Thesis Sharif University of Technology ; Fatemizadeh, Emadodin (Supervisor) ; Ekhtiari, Hamed (Co-Advisor)
Abstract
Despite intensive scientific investigations, drug addiction treatment outcomes have not significantly improved in more than 30 years. The addicted human brain can be conceptualized as a set of networks that spatially and temporally interact with each other in an abnormal way. Over the past several decades, neuroimaging techniques have contributed important novel insights into the neuroplastic alterations that result from drug dependence. Also functional connectivity magnetic resonance imaging (fcMRI) has emerged as a powerful tool for mapping large-scale networks in the human brain. On the other hand, transcranial direct current stimulation (tDCS) has been reintroduced as a noninvasive brain...
Functional Mapping of Regions Involved In Addiction Using Magnetic Resonance Imaging and Proposing a New Measure for Multivariate Methods
, M.Sc. Thesis Sharif University of Technology ; Vosughi Vahdat, Bijan (Supervisor) ; Ekhtiari, Hamed (Co-Advisor)
Abstract
Methamphetamine (meth) abuse and addiction (MA), with its serious medical, psychiatric and social complications, is a growing national disaster in Iran. Response control deficit during exposure to drug related cues is one of the main neurocognitive cores in MA and results in continued drug use and treatment failure. There have been many studies focused on cue exposure, but most of their paradigms required subjects to passively view the cues; this aspect of these paradigms cause a wide gap between reality and experimental studies. Developing a functional and structural neuroimaging protocol to map realistic brain circuits that are involved in craving among meth users is of importance....
Endurance wave analysis (EWA) and its application for assessment of offshore structures under extreme waves
, Article Applied Ocean Research ; Volume 37 , 2012 , Pages 98-110 ; 01411187 (ISSN) ; Matin Nikoo, H ; Estekanchi, H ; Sharif University of Technology
2012
Abstract
The aim of this paper is to introduce a novel approach, called Endurance Wave Analysis (EWA), for non-linear dynamic analysis and assessment of offshore structures subjected to irregular wave forces. This is, in fact, an extension of the Endurance Time Analysis (ETA) already presented by previous researchers for the seismic assessment of onshore structures. With the EWA method, the offshore structure is simulated under a predefined Intensifying Wave Train Function (IWTF), corresponding to a gradually deteriorating sea state at a specific site. The function is designed so that the roughness of the sea state represented by them increases over the time and even goes well beyond the design sea...
High-power nanosecond pulse generator with high-voltage srd and gdt switch
, Article IEEE Transactions on Plasma Science ; Volume 43, Issue 9 , April , 2015 , Pages 3268-3276 ; 00933813 (ISSN) ; Hashemi, S. M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
A high-power short-pulse generator based on the dual action of two coupled diodes, a high-voltage step recovery diode and a high-current diode, is presented. This is made possible using a gas discharge tube. Both analysis and SPICE simulation show about 20-dB peak power increment. This gives a high output power level of 5.7 MW with 1-ns pulsewidth and 450-kHz repetition rate obtained from an input average power of 7.1 kW. An efficiency of about 73% is obtained with more than 30 dB increase in the average power delivered to a 50-Ω load
A compact all-solid-state self-compressing low-to-high power converting rF pulse generator
, Article IEEE Transactions on Plasma Science ; Volume PP, Issue 99 , 2016 ; 00933813 (ISSN) ; Hashemi, S. M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
In this paper, a novel method for high-repetition-rate high-power radio frequency (RF) pulse generation, which involves only passive solid-state devices and is capable of being used for generating high power microwaves using a low-to-high power converting scheme based on nonlinear self-compression is proposed. The method is also expected to be of low jitter. In the proposed circuit, two high voltage diodes with proper reverse recovery characteristics are used. The simulation results show that the proposed circuit generates RF pulses, with central frequencies up to gigahertz range. By applying a sub-kilowatt power supply, the maximum output power was well over 10 kW. This power can be...
New soliton solution of a varactor-loaded nonlinear transmission line
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 65, Issue 11 , 2017 , Pages 4084-4092 ; 00189480 (ISSN) ; Ali Hashemi, S. M ; Sharif University of Technology
2017
Abstract
The nonlinearity of a nonlinear transmission line (NLTL) may have a variety of forms. The Korteweg-de Vries (KdV) equation is the governing equation of a highly specific category of NLTLs having a C - V characteristic as C(V) = C0 (1-bV), but works as an approximate model in a general NLTL having any other kinds of nonlinearities. Here, the soliton response of a varactor-loaded NLTL is studied analytically. The presented analysis gives the exact nonlinear partial differential equation (PDE) governing these networks. It is shown that the obtained PDE, being different from the KdV equation, has soliton solutions showing the well-known properties of the KdV solitons. These obtained solitons...
Analysis of the power transfer to a nonlinear transmission line
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 65, Issue 11 , 2017 , Pages 4073-4083 ; 00189480 (ISSN) ; Hashemi, S. M. A ; Sharif University of Technology
2017
Abstract
The input current of a nonlinear transmission line (NLTL), driven by a step voltage pulse, was analyzed theoretically. As specific results of the analysis, two basic parameters of NLTLs were formulated for the first time: the energy injected to NLTLs and their characteristic impedance. The energy delivered to an NLTL by a square voltage source, with a series resistance of RS, is given by a closed-form formula, which depends on the NLTL parameters and the input pulse characteristics. Considering the importance of the problem of the determining the injected energy content in a wide variety of the different applications of NLTLs, the obtained result will be of great importance, facilitating the...
Geometrical optimization of half toroidal continuously variable transmission using particle swarm optimization
, Article Scientia Iranica ; Volume 18, Issue 5 , 2011 , Pages 1126-1132 ; 10263098 (ISSN) ; Saadat Foumani, M ; Boroushaki, M ; Ekhtiari, M ; Dehghani, M ; Sharif University of Technology
2011
Abstract
The objective of this research is geometrical optimization of half toroidal Continuously Variable Transmission (CVT) in order to achieve high power transmission efficiency. The dynamic analysis of CVT is implemented and contact between the disk and the roller is modeled viaelastohydrodynamic (EHL) lubrication principles. Computer model is created using geometrical, thermal and kinetic parameters to determine the efficiency of CVT. Results are compared by other models to confirm the model validity. Geometrical parameters are obtained by means of Particle Swarm Optimization (PSO) algorithm, while the optimization objective is to maximize the power transmission efficiency. Optimization was...
Dynamic and Static Instability of Conical Shells Made of FGM and Conveying Hot Flow
, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan (Supervisor) ; Dehghani Firoozabadi, Rouhollah (Supervisor)
Abstract
Static and dynamic instability of truncated conical shells made up of functionally graded materials (FGMs) conveying hot fluid is presented in this paper. Temperature-dependent material properties are considered and Material properties of the truncated FGM conical shells are functionally graded in the thickness direction according to a volume fraction power-law distribution. Governing equation of FGM conical shells is written based on First-Order Shear Deformation Theory (FSDT). The treatment is developed within the theory of linear elasticity, when materials are assumed to be isotropic and inhomogeneous through the thickness direction. The two-constituent functionally graded shell consists...
DSRD-based HVdc power supply
, Article IEEE Transactions on Plasma Science ; Volume 46, Issue 6 , 2018 , Pages 2108-2113 ; 00933813 (ISSN) ; Hashemi, M. A ; Vakilian, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
A novel high-voltage direct current (HVdc) power supply which has no transformer or voltage multiplier circuit is presented and analyzed in this paper. This is made possible upon the diodes storage delay phenomenon. This proposed power supply is compact, lightweight, and low cost. Its basic structure includes a diode with a proper reverse recovery specification that plays the role of a step-up transformer in the conventional HVdc supplies and a high-voltage capacitor which stabilizes the output voltage. This structure has remarkable advantages over the conventional transformer-based HVdc supplies, such as compactness, a low ripple output, and a low-cost power supply. Performance of the...
Theory of terminated nonlinear transmission lines
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 66, Issue 1 , 2018 , Pages 91-99 ; 00189480 (ISSN) ; Hashemi, M. A ; Farzaneh, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Properly terminating a transmission line, in order to transfer the maximum available power to the load, is an important issue. The problem, fully analyzed in linear lines, is still considered as a persisting problem in the area of nonlinear transmission lines (NLTLs). In this paper, an accurate analysis is presented which gives a closed-form formula for the matching efficiency of the NLTLs. Using this analysis, optimal resistive terminating load for the NLTLs was extracted. These results will considerably ease the design of all kinds of the NLTL-based systems, such as high-frequency oscillators and ultrashort pulse generators. This consistent analysis also gives the reflection coefficient...