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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...
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...
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....
Transcranial DC stimulation modifies functional connectivity of large-scale brain networks in abstinent methamphetamine users
, Article Brain and Behavior ; Volume 8, Issue 3 , 2018 ; 21623279 (ISSN) ; Ebrahimpoor, M ; Hariri, A ; Nitsche, M. A ; Hatami, J ; Fatemizadeh, E ; Oghabian, M. A ; Ekhtiari, H ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
Background: Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation tool suited to alter cortical excitability and activity via the application of weak direct electrical currents. An increasing number of studies in the addiction literature suggests that tDCS modulates subjective self-reported craving through stimulation of dorsolateral prefrontal cortex (DLPFC). The major goal of this study was to explore effects of bilateral DLPFC stimulation on resting state networks (RSNs) in association with drug craving modulation. We targeted three large-scale RSNs; the default mode network (DMN), the executive control network (ECN), and the salience network (SN). Methods:...
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...
Temporal dynamics of neural response to drug cues in abstinent methamphetamine users
, Article Basic and Clinical Neuroscience ; Volume 15, Issue 3 , 2024 , Pages 317-332 ; 22287442 (ISSN) ; Sangchooli, A ; Ebrahimpoor, M ; Najafi, M. A ; Vahdat, B. V ; Shahbabaie, A ; Oghabian, M.A ; Ekhtiari, H ; Sharif University of Technology
2024
Abstract
Introduction: Cue-induced craving is central to addictive disorders. Most cue-reactivity functional magnetic resonance imaging studies are analyzed statically and report averaged signals, disregarding the dynamic nature of craving and task fatigue. Accordingly, this study investigates temporal dynamics of the neural response to drug cues as a functional magnetic resonance imaging study among methamphetamine users. Methods: A total of 32 early abstinent methamphetamine users underwent functional magnetic resonance imaging while viewing visual methamphetamine cues. A craving > neutral contrast was obtained in regions of interest. To explore the changes over time, the pre-processed signal was...
Nonlinear interstory drift contours for idealized forward directivity pulses using "modified fish-bone" models
, Article Advances in Structural Engineering ; Volume 18, Issue 5 , May , 2015 , Pages 603-627 ; 13694332 (ISSN) ; Khosravi, H ; Jamnani, H. H ; Sharif University of Technology
Multi-Science Publishing Co. Ltd
2015
Abstract
Four 5-, 10-, 20- and 30-story moment frames, representing low-, mid-, and two high-rise structures, were subjected to a great number of idealized directivity pulses. The amplitudes and periods of pulses vary from 0.02 g to 1.0 g and 0.5 to 12 sec, respectively. Over 1400 nonlinear dynamic analyses of low- to high-rise moment frames were performed which were feasible through using modified fish-bone model. The distribution of interstory drift along the height was studied and two applied contours were proposed: (i) the maximum interstory drift contour, and (ii) the critical story contour. These contours were demonstrated versus the ratio of natural period of the structure to the pulse period...
Analysis of singularities of a 3DOF parallel manipulator based on a novel geometrical method
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Sadeghian, H ; Roozbehani, H ; Zohoor, H ; Sharif University of Technology
2006
Abstract
In this article singular points of a parallel manipulator are obtained based on a novel geometrical method. Here we introduce the constrained plain method (CPM) and some of its application in parallel mechanism. Given the definition of constraint plane (CP) and infinite constraint plane (ICP) the dependency conditions of constraints is achieved with the use of a new theorem based on the Ceva geometrical theorem. The direction of angular velocity of a body is achieved by having three ICPs with the use of another theorem. Finally, with the use of the above two novel theorems singularities of the 3UPF_PU mechanism are obtained. It should be emphasized that this method is completely geometrical,...
Melting enthalpy and entropy of freestanding metallic nanoparticles based on cohesive energy and average coordination number
, Article Journal of Physical Chemistry C ; Volume 115, Issue 35 , August , 2011 , Pages 17310-17313 ; 19327447 (ISSN) ; Delavari H., H ; Madaah Hosseini, H. R ; Sharif University of Technology
2011
Abstract
An analytical model is proposed to study the effect of particle size on melting enthalpy and entropy of metallic nanoparticles (NPs). The Mott's and Regel's equations for melting entropy in the combination of core average coordination number (CAC) and surface average coordination number (SAC) of freestanding NPs are considered. Clusters of icosahedral (IC), body centered cubic (BCC), and body centered tetragonal (BCT) structure without any vacancies and defects are modeled. Using the variable coordination number made this model to be in good agreement with experimental and molecular dynamic (MD) results of different crystal structures. The model predicts melting entropy and enthalpy of...
On the temperature and residual stress field during grinding
, Article WCE 2010 - World Congress on Engineering 2010, 30 June 2010 through 2 July 2010 ; Volume 2 , 2010 , Pages 1196-1200 ; 9789881821072 (ISBN) ; Farrahi, G. H ; Ghadbeigi, H ; Sharif University of Technology
2010
Abstract
Grinding is widely used for manufacturing of components that require fine surface finish and good dimensional accuracy. In this study a thermo-mechanical finite element analysis is conducted to find out how grinding parameters can affect temperature and residual stress distribution in the workpiece. Results of parametric study presented in this work indicate, by carefully selecting the grinding parameters, minimum thermal and mechanical damage can be achieved. Higher workpiece velocities produce higher surface residual stress. By increasing depths of cut, depth of tensile residual stresses increases. Convection heat coefficient does not have any considerable effect on surface residual stress...
A new lattic LP-based post filter for adaptive noise cancellers in mobile and vehicular applications
, Article Proceedings of the 8th IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2008, 16 December 2008 through 19 December 2008, Sarajevo ; 2008 , Pages 407-412 ; 9781424435555 (ISBN) ; Sameti, H ; Veisi, H ; Abutalebi, H. R ; Sharif University of Technology
2008
Abstract
Adaptive Noise Cancellation (ANC) is a well-known technique for background noise reduction in automobile and vehicular environments. The noise fields in automobile and other vehicle interior obey the diffuse noise field model closely. On the other hand, the ANC does not provide sufficient noise reduction in the diffuse noise fields. In this paper, a new multistage post-filter is designed for ANC as a solution to diffuse noise conditions. The designed post-filter is a single channel Linear Prediction (LP) based speech enhancement system. The LP is performed by an adaptive lattice filter and attempts to extract speech components by using intermediate ANC signals. The post-filter has no...
Advancing Compressive Strength Prediction in Self-Compacting Concrete via Soft Computing: A Robust Modeling Approach
, Article Journal of Soft Computing in Civil Engineering ; Volume 8, Issue 1 , 2024 , Pages 126-140 ; 25882872 (ISSN) ; Maleki, H ; Naderpour, H ; Khatami, M. H ; Sharif University of Technology
2024
Abstract
Self-Compacting Concrete (SCC) is a unique type of concrete that can flow and fill spaces without the need for vibrating compaction, resulting in a dense and uniform material. This article focuses on estimating the compressive strength of SCC utilizing Artificial Neural Networks. Specifically, the study employs multilayer perceptrons with back-propagation learning algorithms, which are commonly used in various problem-solving scenarios. The study covers essential components such as structure, algorithm, data preprocessing, over-fitting prevention, and sensitivity analysis in MLPs. The input variables considered in the research include water, fine aggregate, super-plasticizer, fly ash, coarse...
Cost estimation models for seismic retrofit of masonry school buildings
, Article International Journal of Construction Management ; Volume 24, Issue 8 , 2024 , Pages 843-853 ; 15623599 (ISSN) ; Amiri Hanzaei, H ; Khaleghi, H ; Kashani, H ; Sharif University of Technology
2024
Abstract
Seismic retrofits can significantly reduce the vulnerability of masonry buildings. Multiple seismic retrofit alternatives are often available for a given building. Estimating the cost of each candidate action is essential to selecting and implementing the appropriate seismic retrofit initiatives. This research harnesses the capabilities of various regression models for cost estimation. A dataset from 167 retrofit projects for masonry school buildings was used to develop models. Three main retrofit actions were taken into consideration: shotcrete, steel belt and fiber-reinforced polymer. Various regression methods, including multiple linear regression, ridge regression, lasso regression, and...
Finite element analysis of shot-peening effect on fretting fatigue parameters
, Article Tribology International ; Volume 44, Issue 11 , 2011 , Pages 1583-1588 ; 0301679X (ISSN) ; Alvandi Tabrizi, Y ; Farrahi, G. H ; Majzoobi, G. H ; Ghadbeigi, H ; Sharif University of Technology
2011
Abstract
Shot peening is widely used to improve the fretting fatigue strength of critical surfaces. Fretting fatigue occurs in contacting parts that are subjected to fluctuating loads and sliding movements at the same time. This paper presents a sequential finite element simulation to investigate the shot peening effects on normal stress, shear stress, bulk stress and slip amplitude, which are considered to be the controlling parameters of fretting damage. The results demonstrated that among the modifications related to shot peening, compressive residual stress has a dominant effect on the fretting parameters
Mechanically activated synthesis of single crystalline MgO nanostructures
, Article Journal of Alloys and Compounds ; Volume 506, Issue 2 , September , 2010 , Pages 715-720 ; 09258388 (ISSN) ; Yoozbashizadeh, H ; Askari, M ; Kobatake, H ; Fukuyama, H ; Sharif University of Technology
2010
Abstract
One-dimensional (1D) MgO structures were successfully synthesized via carbothermic reduction of mechanically activated mixture of MgO and graphite. Mechanical activation of source materials before carbothermic reduction can substantially enhance the formation of MgO products at a temperature (1000 °C) relatively lower than that required in previous approaches (≥1200 °C). However, the morphology of MgO formed is dependent on the degree of mechanical activation and the condition of the subsequent carbothermic reduction. Two distinctive morphologies were found for MgO products synthesized using our method: single crystalline nanorods with rectangular cross-sections whose diameters range from 50...
Boundary control design for vibration suppression and attitude control of flexible satellites with multi-section appendages
, Article Acta Astronautica ; Volume 173 , 2020 , Pages 22-30 ; Salarieh, H ; Nejat Pishkenari, H ; Jalili, H ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Attitude and vibration control of a general form of flexible satellites is addressed in this paper. Partial differential dynamic equations are derived considering new details such as multi sectioned solar panels and elastic connections between main hub and solar panels. Boundary control approach is adopted to eliminate simplification errors of discrete models, using just one actuator in the hub. Asymptotic stability of attitude dynamics is proved for a group of boundary controllers and necessary conditions for asymptotic stability of vibrations are discussed. Being independent of modeling accuracy and using easily measurable feedbacks are among advantages of the proposed class of...
Characterization and calcination behavior of a low-grade manganese ore
, Article Materials Today Communications ; Volume 25 , 2020 ; Becker, H ; Eftekhari, H ; Yoozbashizadeh, H ; Safarian, J ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Characterization and calcination behavior of a low-grade manganese ore, as a part of Mn ferroalloys production, was studied by XRF, ex-situ XRD, in-situ XRD, and SEM-EDS techniques. Calcination experiments were carried out at and up to 900 °C (1173 K) in air and argon atmospheres. The samples were in particles and powder forms. The results indicated that both quartz and calcite phases in the ore exhibit a bimodal spatial distribution; as relatively large regions and finely distributed in the Mn- and Fe-containing phases. By Rietveld analysis of the in-situ XRD data, the reactions occurring upon heating during the calcination process were deduced. Thermal decomposition and reactive diffusion...
Minimizing the error of time difference of arrival method in mobile networks
, Article 2005 International Conference on Wirelessand Optical Communications Networks, Dubai, 6 March 2005 through 8 March 2005 ; 2005 , Pages 328-332 ; 0780390199 (ISBN); 9780780390195 (ISBN) ; Aghababa, H ; Radfar, M. H ; Khalaj, B. H ; Sharif University of Technology
2005
Abstract
Estimating the position of a mobile set is of great importance in new mobile services. However, in most cases, the accuracy should be less than 100 meters. This accuracy is hard to reach especially in urban areas. The main problem is that there are a lot of obstacles like buildings between the BTS and the mobile set. Thus the time measured between BTS and the mobile set is somehow greater than the time it takes the wave to travel directly between two points. This paper introduces an optimized solution for TDOA as one of the most efficient ways for finding the location of a mobile phone. Considering the standards and limitations of both GSM and UMTS, the Authors present a solution for...