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ebrahimi--shahriar
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Reducing the Flow Rate of Short Circuit Fault Current at the Output of the High Voltage Power Supply
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriar (Supervisor)
Abstract
In this research, we have presented a method to delay the propagation of fault current in high voltage power supplies. Common protection methods usually protect the load and do not protect the power supply itself well. In this research, our goal was to propose a method to prevent the short circuit fault current from reaching the power supply elements. At first, the available methods to limit the fault current and protect the high voltage power sources were studied and investigated. Then, using the transmission line theory, a ladder filter was designed as an alternative to the normal filter at the output of the power supply. In the next step, using software simulation, the performance of the...
Analysis of a Ultra Narrow Pulse Width High Voltage Generator
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriar (Supervisor)
Abstract
A Tesla charged PFL Bipolar pulsed power generator has been successfully designed and simulated. The compact Tesla transformer that it employs has successfully charged capacitive loads to peak voltages up to 0.6 MV . The Tesla–driven PFL generator is capable of producing a voltage impulse approaching .3 MV with generating a peak electrical power of up to 1.8 GW for 5 ns when connected to a matched resistive load. Potentially for medical application, a bipolar former has been designed and successfully simulated as an extension to the system and to enable the generation of a sinusoid-like voltage impulse with a peak-to-peak value reaching 600 kV and having a frequency bandwidth beyond 1 GHz....
Bayesian Filtering Approach to Improve Gene Regulatory Networks Inference Using Gene Expression Time Series
, M.Sc. Thesis Sharif University of Technology ; Fatemizadeh, Emadoddin (Supervisor) ; Arab, Shahriar (Co-Advisor)
Abstract
Gene regulatory modeling in different species is one of the main aims of Bioinformatics. Regarding the limitations of the data available and the perspectives which should be taken into account for modeling such networks, proposed methods up to now have not yet been successful in yielding a comprehensive model. In one of the recent researches, the Gene regulation process is considered as a nonlinear dynamic stochastic process and described by state space equations. Afterwards, in order for the unknown parameters to be estimated, Extended Kalman Filtering is used. In this thesis, first of all, Gene complexes are taken into consideration instead of genes and afterwards, Extended Kalman...
Numerical and Experimental Analysis of Biomechanical Behavior in Persian Fixation Method for Distal Humerus Fractures
, M.Sc. Thesis Sharif University of Technology ; Nourani, Amir (Supervisor) ; Shahriar Kamrani, Reza (Supervisor)
Abstract
Distal humerus fractures commonly take place in adults with low bone mineral density causing major technical challenges upon orthopedic surgeons. Persian fixation method was introduced as a novel technique to stabilize small fragments in comminuted distal humerus fractures using a set of K-wires and reconstruction plate. The objective of the present study is to measure the stiffness and stability of this technique and analyze the effect of influential parameters with numerical simulation and biomechanical testing on a cadaveric specimen. Furthermore, we were able to propose new method to model plastic deformation of implants in surgery.Validation of the finite element (FE) model was...
Protein Function Prediction Using Protein Structure and Computational Methods
, M.Sc. Thesis Sharif University of Technology ; Fatemizadeh, Emad (Supervisor) ; Arab, Shahriar ($item.subfieldsMap.e)
Abstract
Predicting the Amino Acids that have a catalytic effect in the enzymes, is a big step in appointing the activity of the enzymes and classifying them. This is a very challenging job, because an Amino Acid can appear in a variety of active sites.The biological activity of a protein usually depends on the existence of a small number of Amino Acids. Detecting these Amino Acids from the sequence of Amino Acids has many applications. Usually, the Amino Acids that are preserved are known as the Amino Acids that build up the active site, but the algorithms for finding the preserved Amino Acids are much more complex. There are a lot of algorithms for predicting the active sites of Amino Acids, but...
A ZVS-resonant bifilar drive circuit for SRM with a reduction in stress voltage of switches
, Article International Aegean Conference on Electrical Machines and Power Electronics, ACEMP 2011 and Electromotion 2011 Joint Conference, Istanbul ; 2013 , Pages 125-128 ; 9781467350037 (ISBN) ; Najmi, V ; Ebrahimi, S ; Oraee, H ; Sharif University of Technology
2013
Abstract
Switched Reluctance Motors (SRMs) are widely used in high-speed and low voltage applications because of their attractive features such as robustness and simplicity. No winding on the rotor of this type of motors allows reaching high speed which is desired for many applications. Drive circuits of SRMs also play an important role in their performance and operation. In this paper, a new bifilar drive circuit for this type of motors has been proposed. This novel configuration has been tested and investigated by PSIM software. Results show that the new bifilar drive circuit highly reduces the voltage stresses on semiconductor switches, and also considerably reduces the switching losses which are...
Energy management of smart home considering residences' satisfaction and PHEV
, Article 2018 International Conference on Smart Energy Systems and Technologies, SEST 2018, 10 September 2018 through 12 September 2018 ; 2018 ; 9781538653265 (ISBN) ; Shokri Gazafroudi, A ; Corchado, J. M ; Ebrahimi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Regarding the increasing number of electrical devices in the smart homes that leads to increase in total electricity consumption and cost, it is essential to use energy management methods to reduce the electricity cost. However, this can cause resident's dissatisfaction. Hence, it is important to define a method in which cost and dissatisfaction be optimized simultaneously. Among different services, an electric vehicle is the one that can be used as an energy storage system, so it can reduce the daily cost despite of increasing the total energy consumption. In this paper, we study the effect of the EV on the cost and dissatisfaction in our proposed method. © 2018 IEEE
Measured impact of different back-off points and cooling methods on pulse-to-pulse stability and sidelobe level of a high-power solid-state amplifier
, Article IET Radar, Sonar and Navigation ; Volume 14, Issue 2 , 2020 , Pages 335-340 ; Khodarahmi, E ; Ebrahimi, E ; Ahmadi, B ; Jalali, M ; Sharif University of Technology
Institution of Engineering and Technology
2020
Abstract
Using solid-state power amplifiers for next generation of weather radars becomes feasible by pulse compression techniques. In this study a 1.5 kW solid-state power amplifier (transmitter) for C-band weather radars is designed and fabricated by GaN high electron mobility transistor (HEMT) technology. An experimental setup based on heterodyne receiver with 16-bit digitiser is developed to investigate the behavior of the power amplifier under different cooling methods and back-off points. Several measurements with shaped LFM pulse show an approximately identical pulse to pulse (P2P) stability for 3 dB compression, P1dB and 2 dB back-off points while the best sidelobe level (SLL) is achieved for...
Probabilistic safety assessment of a UF 6 production process
, Article Advances in Safety, Reliability and Risk Management - Proceedings of the European Safety and Reliability Conference, ESREL 2011 ; 2012 , Pages 1384-1389 ; 9780415683791 (ISBN) ; Sharif University of Technology
2012
Abstract
Application of Probabilistic Safety Assessment (PSA) to a Uranium hexafluoride (UF 6) production process is presented in this paper. The process is constituted from three main units: UF 4 conversion to UF 6, condensation of produced UF 6 gas and tail gas treatment. Radioactive gas is present in all parts of the process and occurrence of high pressure or high temperature in the process equipments may lead to radioactive release to workplace and environment. The work is mainly based on PSA experience in nuclear power plants. Accordingly for the process, eight group of Initiating Events (IE) that lead to UF 6 gas release have been identified using HAZOP study. For each IE, based on related...
On the temperature control in self-controlling hyperthermia therapy
, Article Journal of Magnetism and Magnetic Materials ; Volume 416 , 2016 , Pages 134-140 ; 03048853 (ISSN) ; Sharif University of Technology
Elsevier
2016
Abstract
In self-controlling hyperthermia therapy, once the desired temperature is reached, the heat generation ceases and overheating is prevented. In order to design a system that generates sufficient heat without thermal ablation of surrounding healthy tissue, a good understanding of temperature distribution and its change with time is imperative. This study is conducted to extend our understanding about the heat generation and transfer, temperature distribution and temperature rise pattern in the tumor and surrounding tissue during self-controlling magnetic hyperthermia. A model consisting of two concentric spheres that represents the tumor and its surrounding tissue is considered and temperature...
Atmospheric icing effects of S816 airfoil on a 600 kW wind turbine's performance
, Article Scientia Iranica ; Volume 25, Issue 5B , 2018 , Pages 2693-2705 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2018
Abstract
This study investigates the aerodynamic loads and energy losses of a typical 600 kW wind turbine with S816 airfoil blade under two different icing conditions. Three sections at different radial positions were considered to estimate the icing effect along the blade. Ice accretion simulations in wet and dry regimes were carried out using the NASA LEWICE 3.2 computer program. The airflow simulations were performed with CFD method and SST k -ω turbulence model. The results of these simulations, including streamlines, surface pressure, skin friction, lift, and drag coefficients, were inspected for both clean and iced airfoils. In the case of wet iced airfoil, a separation bubble was created in...
Investigation on the Effects of the Polyacrylamide Copolymers and Their Blends with Sulfonated Lignin on the Soil Stabilization
, M.Sc. Thesis Sharif University of Technology ; Ramazani Saadatabadi, Ahmad (Supervisor) ; Ebrahimi, Hossein (Co-Supervisor)
Abstract
In recent years, dust pollution has become a worldwide issue due to the creation of serious environmental problems and the effects it has on human health. In this research, an environmentally friendly soil stabilizer has been synthesized, and its performance has been investigated. Acrylamide monomers were grafted onto sodium lignosulfonate chains, utilizing solution polymerization. The soil of the Ahvaz deserts was used in the analyses. Using EDX and DLS analyses, the components of this soil and the particle size distribution of the used soil were obtained. Characterization of the functional groups and the structure of the graft copolymer were done by FTIR and H-NMR analysis, respectively,...
On the Domination Polynomial of Graphs
, M.Sc. Thesis Sharif University of Technology ; Akbari, Saeed (Supervisor)Design and Evaluation of a Master/Checker Method for an Embedded Processor
, M.Sc. Thesis Sharif University of Technology ; Miremadi, Ghasem (Supervisor)
Abstract
Ever increasing applications of embedded systems have motivated the designers to pay special attention to the design requirements of such systems. Among embedded applications, safety-critical systems have high reliability requirements as failures in such systems may endanger human life or result in catastrophic consequences. Embedded processors as the computation cores of embedded systems are very crucial from reliability point of view. This is because; a failure in the processor most probably leads to a system failure. One effective way to protect embedded processors against environmental faults is to use system level fault-tolerant techniques such as Master/Checker (M/C) or Triple Modular...
Determining Factors of Foreign Direct Investment Using Gravity Model
, M.Sc. Thesis Sharif University of Technology ; Abedini, Javad (Supervisor)
Abstract
Foreign direct investment (FDI) has considerably increased in recent years and achieved two percent of the world GDP in 2009. The positive impact of FDI on many national economic variables such as export and employment has been a great motivation for countries to seek it. In spite of many promoting factors in Iran, the Iranian FDI inflow still remains small. Using a huge panel dataset including 2604 real observations, this study aims to recognize and evaluate the impact of main factors influencing FDI inwards across the world. Based on a theoretical approach, we develop an empirical gravity model which includes not only the traditional mass variables but also some specific factors to FDI...
Aerodynamic Investigation of an Aeroelastic Flapping Wing and Optimum Design Method
, Ph.D. Dissertation Sharif University of Technology ; Mazaheri, Karim (Supervisor)
Abstract
Flapping wing vehicles produce aerodynamic lift and thrust through the flapping motion of their wings. The dynamic performance of a flexible membrane flapping wing is experimentally investigated here. To investigate aeroelastic effects of flexible wings (specifically, wing’s twisting stiffness) on hovering and cruising aerodynamic performance, a flapping-wing system and an experimental setup were designed and built. This system measures the unsteady aerodynamic and inertial forces, power usage and angular speed of the flapping wing motion for different flapping frequencies, angles of attack, various wind tunnel velocities up to 12 m/s and for various wings with different chordwise...
Introducing a Set of Material Strain Measures in Non-Linear Kinematics of Micropolar Continuum Mechanics and Determining their Time Rates
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
The concept of generalized strains is a well-established subject in the classical continuum mechanics. The characteristics and various applications of the generalized strains have been the point of interest of many researchers in the classical continuum mechanics. The aim of this thesis is the introduction of generalized strains in the micropolar theory, as a non-classical continuum theory. A set of generalized strains is suggested for the deformation of macro-elements. Moreover, a set of generalized strains is proposed for the micro-structures. Since the rate of strains possesses a significant importance in the constitutive equations of nonlinear analysis of solids, expressions for the rate...
Electrochemical Determination of Tyrosine and Tryptophan at the Surface of Pyrolytic Graphite Electrode Modified with Multi-Walled Carbon Nanotubes, New Coccine and Nitrazine
, M.Sc. Thesis Sharif University of Technology ; Shahrokhian, Saeed (Supervisor)
Abstract
At the first part of this thesis, a pyrolitic graphite electrode (PGE) modified with new coccine/multi-walled carbon nanotubes film (NC/MWCNT) was applied as a sensitive electrochemical sensor for determination and study of electrochemical behavior of tyrosine (Tyr) in aqueous solutions. The results showed that NC/MWCNT caused a remarkable increase in the peak current so the NC/MWCNT/PGE electrode surface was far more sensitive to the concentration of Tyr than the PGE surface. The determination of Tyr was investigated by linear sweep voltammetry (LSV). Experimental parameters, such as scan rate, pH and amount of the modifier used on the PGE surface were optimized by monitoring the LSV...
Using Multivariate Tukey distribution in Multivariare Process Capability Indices
, M.Sc. Thesis Sharif University of Technology ; Mahlooji, Hashem (Supervisor)
Abstract
In this thesis we will provide a comprehensive study of process capability indices, and we use multivariate g-and-h Tukey distribution for calculating process capability indices of multivariate non-normal processes. Univariate process capability indices have been used commonly in literature for measuring the capability of a process. However, there are several processes with more than one quality characteristic. When these characteristics are independent, we can use univariate process capability indices, but when the characteristics are dependent we should use multivariate methods for measuring process capability. There have been several studies about multivariate process capability indices,...
Parametric Investigation of Behavior of Moment Connections to CFST Columns
, M.Sc. Thesis Sharif University of Technology ; Khalu, Alireza (Supervisor)
Abstract
In recent years use of concrete filled steel tube column structures has been increased due to their several advantages. In these columns the steel tube provides confinement for the concrete core of the column, so it increases axial strength and flexibility of the concrete core, and prevents spalling of the concrete. On the other hand the concrete core delays the local buckling steel tube and increases its bearing capacity. In addition, these columns have higher stiffness and strength than typical concrete columns due to placement of steel in farthest point of column cross section. The steel tube besides its structural role acts as framework for the concrete core and reduces time and cost of...