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    Four suggested plans of underwater Robo-snake

    , Article World Academy of Science, Engineering and Technology ; Volume 38 , 2009 , Pages 1094-1099 ; 2010376X (ISSN) Babaee, S ; Sharifazadeh, H ; Sharif University of Technology
    Throughout this paper four locomotion mechanisms have been presented for underwater robo-sankes. In this respect; initially, two methods of locomotion including traveling and standing wave have been examined. Next, applications of these methods are described. Ultimately, assessing and comparison of those mechanisms have been studied and the best plan is determined. © 2009 WASET.ORG  

    Preparation of flexible and free-standing graphene-based current collector via a new and facile self-assembly approach: leading to a high performance porous graphene/polyaniline supercapacitor

    , Article Energy ; Volume 152 , 2018 , Pages 178-189 ; 03605442 (ISSN) Pourjavadi, A ; Doroudian, M ; Ahadpour, A ; Pourbadiei, B ; Sharif University of Technology
    Elsevier Ltd  2018
    Flexible all-solid-state supercapacitors are promising electronic devices have been developed in the past decade. Recent efforts to develop such systems are as to construction of free standing electrodes with high specific capacitance. Among these developments, construction of carbon-based current collectors, with high surface areas and good mechanical properties via a facile and economic way, has been taken a great deal of attention. In this study, porous graphene were used as current collector for placement of the carbon fibers functionalized with polyaniline, to prepare a free-standing supercapacitor electrode through a new and facile method. This method begins through blending of the... 

    Dynamic analysis of transmission line connection in restoration of interconnected power systems

    , Article Canadian Conference on Electrical and Computer Engineering; Technology Driving Innovation, 2004, Niagara Falls, 2 May 2004 through 5 May 2004 ; Volume 3 , 2004 , Pages 1621-1624 ; 08407789 (ISSN) Kheradmandi, M ; Ehsan, M ; Sharif University of Technology
    Electrical power system is subjefcted to disturbances. A large disturbance may bring the system to the complete blackout or partial outage. Restoration of power system to normal state constitutes several stages including transmission line connection. In closing network loops, power system operators sometimes encounter an excessive Standing Phase Angle (SPA) across a line. SPA should be within allowable limits before any attempt is made to close breaker. In this paper, the effect of reduction of SPA in improving transient stability and impact on adjacent generators is discussed. Also, the effect of closing of breakers at two ends of the line is studied. At the end, the effect of loading... 

    A computationally efficient Li-ion electrochemical battery model for long-term analysis of stand-alone renewable energy systems

    , Article Journal of Energy Storage ; Volume 17 , 2018 , Pages 93-101 ; 2352152X (ISSN) Astaneh, M ; Dufo Lopez, R ; Roshandel, R ; Golzar, F ; Bernal Agustin, J. L ; Sharif University of Technology
    Elsevier Ltd  2018
    In this paper we introduce a Simplified Single Particle Model (SSPM), which is obtained from the general mathematical formulation of Li-ion batteries. The model is validated by using different commercial graphite/LiFePO4 cells, and results show agreement with more complicated models and experimental data for low operating currents of less than 1C. A maximum relative error of less than 2% can be observed to estimate cell voltage in the plateau region of the charge/discharge curves. Therefore, the proposed model is suitable in the case of stand-alone renewable energy systems, where battery current is typically lower than C/10. By increasing the current, the SSPM deviates from more accurate... 

    BEM modeling of viscous motion of surface water waves

    , Article 23rd International Conference on Offshore Mechanics and Arctic Engineering, Vancouver, BC, 20 June 2004 through 25 June 2004 ; Volume 3 , 2004 , Pages 557-561 Jamali, M ; Sharif University of Technology
    This study is concerned with numerical modeling of viscous surface wave motion using boundary element method (BEM). The equations of motion for thin boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the surface wave motion characteristics including the decay rate. The technique is presented for a standing surface wave motion. The extension to other free surface problems is discussed  

    Standing phase angle reduction based on a wide area monitoring system using genetic algorithm

    , Article International Journal of Emerging Electric Power Systems ; Volume 11, Issue 3 , Jul , 2010 ; 1553779X (ISSN) Nourizadeh, S ; Ranjbar, A. M ; Pishvaie, M. R ; Sadeghi, M ; Sharif University of Technology
    During power system restoration, it is necessary to check the phase angle between two buses before closing circuit breakers to connect a line between them. A novel approach for reducing large standing phase angle (SPA) based on Genetic Algorithm (GA) is presented in this paper. The proposed approach starts with a state estimation on Wide Area Monitoring System (WAMS) data measurements and considering power system operation and angular stability constraints, seeks an optimal control action scenario for reducing SPA. Since these constraints are evaluated based on WAMS data, the presented approach is considerably high speed and accurate. As an optimization problem, objective function of the... 

    Improving sit-to-stand transition by the saddle-assistive device in the spinal cord injury: A case study

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 235, Issue 7 , 2021 , Pages 735-742 ; 09544119 (ISSN) Hojjati Najafabadi, A ; Amini, S ; Farahmand, F ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Physical problems caused by fractures, aging, stroke, and accidents can reduce foot power; these, in the long term, can dwindle the muscles of the waist, thighs, and legs. These conditions provide the basis for the invalidism of the harmed people. In this study, a saddle-walker was designed and evaluated to help people suffering from spinal cord injury and patients with lower limb weakness. This S-AD works based on body weight support against the previously report designs. This saddle-walker consisted of a non-powered four-wheel walker helping to walk and a powered mechanism for the sit-to-stand (STS) transfer. A set of experiments were done on the STS in the use of the standard walker and... 

    , M.Sc. Thesis Sharif University of Technology Ahmadi, Somayeh (Author) ; Roshandel, Ramin (Supervisor)
    Inappropriate effects of fossil fuels and conventional power generation systems on the environment have necessitated a sustainable energy system for the next decade by growing interests in renewable energy systems. The world’s most fast-growing renewable energy resource is the wind energy. The main problem of wind power is the power fluctuations at the load side caused by the variable nature of wind speed, and the main issue in case of remote locations is the long-term storage of power generated by wind turbines. Batteries can be used to store a limited amount of energy for a short time. Although new advances in this field have been achieved, most common type of batteries is hardly able to... 

    Operation Analysis of an Open Cycle Thermoacoustic Refrigerator with Mean Flow

    , M.Sc. Thesis Sharif University of Technology Sadri, Maryam (Author) ; Ghorbanian, Kaveh (Supervisor)
    In this thesis, flow-through (or open cycle), standing wave thermoacoustic refrigerator is investigated. The system has the characteristics that the working fluid travels through the system in an oscillatory mode with a mean flow. This type of thermoacoustic refrigerator enables the working fluid to reach the desired cold temperature without passing through the usually required cold heat exchanger. Consequently, the cold heat exchanger subsystem becomes redundant and the entire system becomes less complex and lower in fabrication costs. In this research, while the hot and cold temperatures are fixed, a parametric study is performed to determine the alteration in performance due to the... 

    Controlling the Polarization of Terahertz Waves by the Meta-Surface for the Imaging Applications

    , M.Sc. Thesis Sharif University of Technology Hajitabar Marznaki, Shiva (Author) ; Ahmadi Boroujeni, Mehdi (Supervisor)
    The purpose of this thesis is the analysis, design and fabrication of polarization converters in the millimeter-wave and terahertz regions using metasurfaces in order to generate different polarizations in the transmitter of terahertz stand-off imaging systems. In this project, the design and fabrication of two linear cross-polarizers and a circular polarization converter have been done at the frequency of 100 GHz. These polarizers are easy to fabricate by printed circuit board (PCB) technology and are capable of converting the polarization of a linear incident wave to the cross-polarized transmission wave and circular polarization, respectively. Linear polarizers are double-layer and... 

    A bio-inspired modular hierarchical structure to plan the sit-to-stand transfer under varying environmental conditions

    , Article Neurocomputing ; Volume 118 , 2013 , Pages 311-321 ; 09252312 (ISSN) Sadeghi, M ; Emadi Andani, M ; Parnianpour, M ; Fattah, A ; Sharif University of Technology
    Human motion planning studies are of considerable importance in producing human-like trajectories for various industrial or clinical applications (e.g. assistive robots). In this case, the capability of Central Nervous System (CNS) in generating a large repertoire of actions can be inspirational to develop more efficient motion planning approaches. Here, inspired by structural and functional modularity in the CNS, a novel modular and hierarchical model is developed to plan the sit-to-stand (STS) transfer under varying environmental conditions. In this model, the planning process is distributed among several functionally simple modules. The cooperation of modules enables the model to plan the... 

    Numerical modeling of turbulent surface wave motion using a coupled boundary element-finite difference technique

    , Article 2008 ASME Fluids Engineering Division Summer Conference, FEDSM 2008, Jacksonville, FL, 10 August 2008 through 14 August 2008 ; Volume 1, Issue PART B , 2009 , Pages 1025-1029 ; 9780791848418 (ISBN) Jamali, M ; Fluids Engineering Division, ASME ; Sharif University of Technology
    In this paper an effective numerical technique is presented to model turbulent motion of a standing surface wave in a tank. The equations of motion for turbulent boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the wave and boundary layer characteristics. A mixing-length theory is used for turbulence modeling. The results are compared with previous experimental data. Although the technique is presented for a standing surface wave, it can be easily applied to other free surface problems. Copyright © 2008 by ASME  

    The Existence and Stability of Classical Solutions in the Neural Fields Equations

    , M.Sc. Thesis Sharif University of Technology Shafiee, Ahmad (Author) ; Fotouhi Firouzabadi, Morteza (Supervisor)
    In this thesis, first, the modeling method of neural fields is precisely presented. Then, Existence and Stability of different solutions of one dimensional neural fields like Standing Pulses, Traveling Waves and ... are investigated in three different models of neural fields. In order for proving Existence and Stability of the solutions the mathematical tools like Fourier transform and Evans function are applied. All the models which analysed in this thesis have the following Integro-Differential Equation form:
    ∂u(x, t)
    = −u(x, t) +
    ∫ +∞
    w(x, y)f[u(y, t)]dy + I(x, t) + s(x, t)
    and also in some models the parameters might be changed  

    Design and Implementation of a Fixed Distance to Object Imaging System using a 3-DOF. Table, with Integrated Software System for Acquisition, Processing and Display of Signals

    , M.Sc. Thesis Sharif University of Technology Karimi, Fateme (Author) ; Ravanbod, Hossein (Supervisor)
    Deriving the shape, area, volume, and orientation of a defect from the ultrasonic nondestructive testing images of the oil pipelines, paves the way for the estimation of its severity. This paper describes the design and implementation of an automatic structure which can move an ultrasonic probe over the surface of a test sample, while preserving the distance, i.e. stand-off, between them, whatever the shape of the surface might be. The fixed stand-off is implemented, closing a feedback loop with a distance meter sensor. Also an integrated software environment is developed for the control of the table, data acquisition, data processing and displaying the results. After acquiring the... 

    Improving the Quality of Standoff Millimeter-Wave Imaging by Using Polarimetry

    , M.Sc. Thesis Sharif University of Technology Shojaeian, Zahra (Author) ; Ahmadi Boroujeni, Mehdi (Supervisor)
    In recent years, the growing importance of imaging in the fields of medicine, security, food quality control, etc. has led to many investigations to find the most efficient imaging methods. In this thesis, the improvement of high frame-rate millimeter-wave stand-off imaging is investigated using the polarimetry method. The main objective of this study was to use Cx-pol scattered waves from rough surfaces, especially the edges of a Perfect Electric Conductor (PEC), to detect the edges of this object from the human body surface. Since the surface of the human body at the desired operating frequency (100 GHz) is almost flat, the background effect can be eliminated by analyzing the Cx-pol... 

    Design and Optimization of a Lens for Beam Shaping in a Terahertz Standoff Imaging System

    , M.Sc. Thesis Sharif University of Technology Abbaszadeh, Afshin (Author) ; Ahmadi Boroujeni, Mehdi (Supervisor)
    Terahertz waves have three important features that make them suitable for security imaging. 1. THz waves can penetrate or can be absorbed from many of non-metallic and non-polar materials and are perfectly reflected from most of the metals, 2. Drugs and explosives have terahertz spectra that can be detected by THz imaging, 3. THz waves do not have an ionizing effect and are harmless to the human body. Lenses can be considered as a major component of the terahertz imaging systems. Because of the relatively large terahertz wavelengths compared with wavelengths, compression, and decreasing the dimensions of the lenses in these systems matters a lot. In addition, reducing the wave reflection... 

    Aero-Hydro-Elastic Analysis of a Floating Beam in a Water Channel Subjected to Cross Wind

    , M.Sc. Thesis Sharif University of Technology Tavanbakhsh, Sadeq (Author) ; Dehghani Firouzabadi, Rouhollah (Supervisor)
    In static floating structures such as floating bridges and offshore runways that are in contact with the water surface from the floor and with the open air from the top, three types of interactions occur: the interaction of the structure with air, the interaction of the structure with water and Interaction of air with water. Due to the long length of such structures and approaching their natural frequencies to the standing wave frequencies (seiche frequencies), the analysis of the elastic behavior of the structure alone is not enough, but the structure-air-water interaction must be evaluated simultaneously in a system. Leading research addresses this issue and examines the behavior of an... 

    Design and Analysis of Microwave Frequency-Reconfigurable Antennas Based on Handedness Preserving Metasurfaces

    , M.Sc. Thesis Sharif University of Technology Motalebi, Amir Hossein (Author) ; Memarian, Mohammad (Supervisor)
    In the last two decades, reconfigurable antennas have attracted significant research attention. Utilization of such antennas can lead to decrease in cost and power consumption in modern communication systems. The main focus of efforts is on frequency reconfigurability using different mechanisms while maintaining desirable antenna characteristics over the tuning range. In this thesis, our goal is to design, analyze and fabricate a reconfigurable antenna based on the concept of polarization standing wave (PSW) in the X band using only a simple physical tuning mechanism. Two anisotropic handedness preserving mirrors (AHPM) are placed at both ends of a cylindrical cavity resonator, thus... 

    Design and Analysis of a Reflector System for Millimeter Wave Active Standoff Imaging

    , M.Sc. Thesis Sharif University of Technology Koohi Ghamsari, Mohammad Hossein (Author) ; Ahmadi Boroujeni, Mehdi (Supervisor)
    In this dissertation, to improve the specifications of the available standoff imaging system in the THz and far-infrared Lab. of the electrical engineering department, we designed and analyzed some examples of reflective optical configurations as an optics of active millimeter-wave imaging systems. The superiority of reflective optics versus refractive optics due to the specifications such as loss reduction, broadband frequency response, proper aberration control, beam scanning capability, and easier transmitter and receiver positioning justifies the utilization of reflective configurations for designing millimeter-wave imaging optics. The defined design goals of this dissertation are as... 

    Beam Shaping by Meta-surfaces in Millimeter-Wave Active Standoff Imaging

    , M.Sc. Thesis Sharif University of Technology Imanbeigi, Ehsan (Author) ; Ahmadi Boroujeni, Mehdi (Supervisor)
    Beam shaping, the transformation of radiated Gaussian beam from the millimeter wave source (conical horn antenna) into a flat-top beam at a certain distance, in the Millimeter wave active stand-off imaging system can be done in different ways, among them, beam shaping with a concave-convex lens (double-sided lens) in transmission mode (previous research done) can be mentioned. This lens consists of a convex-plane and a plane-concave lenses. when the electromagnetic wave passes through the convex-plane part, the wave front of the incident electric field changes from spherical to plane so that the divergent incident rays become parallel, and then the phase profile of the electric field changes...