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ohadi--amir-mohammad
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Adversarial Convex Bandit
, M.Sc. Thesis Sharif University of Technology ; Alishahi, Kasra (Supervisor)
Abstract
Multi armed bandit is a simple framework for modeling sequential decision making problems. A learner should choose between some arms at every time step and gains the reward of corresponding chosen arm. The environment is unknown to the learner, so he should make a balance between staying with the option that gave highest payoffs in the past and exploring new options that might give higher payoffs in the future known as exploration vs exploitation dilemma. The goal is finding a policy that minimizes the regret, which is a performance measure of the learner policy. We can make assumptions on how the rewards are generated, like stationary stochastic model, but we abandon almost all of them and...
Theoretical and Experimental Analysis of Vibration Transfer Paths and Path Ranking of a Vehicle Due to Powertrain Excitations
, Ph.D. Dissertation Sharif University of Technology ; Durali, Mohammad (Supervisor) ; Ohadi Hamedani, Abdolreza (Co-Advisor)
Abstract
By new advancements in vehicle manufacturing; vehicle quality evaluation and assurance has become a more critical issue. Today noise and vibration generated inside and outside a vehicle are more important factors than before. In present work, the vibration transfer path analysis and vibration path ranking of a car interior has been performed. The method is similar to classical multilevel TPA methods but has distinct differences. The method is named VIVS which stands for Vehicle Interior Vibration Simulation. Performance of some tests like chassis dyno test, virtual mass function test and body transfer function test are required in this approach. The accelerations on both sides of the engine...
Investigation of breakdown voltage in InAIAs/InGaAs/InP HEMTs with different structures
, Article IEICE Electronics Express ; Volume 7, Issue 19 , 2010 , Pages 1447-1452 ; 13492543 (ISSN) ; Faez, R ; Hoseini, H. R ; Sharif University of Technology
2010
Abstract
InAlAs/InGaAs/InP high electron mobility transistors have higher mobility comparing to structures without indium. But existence of indium causes smaller Eg and as a result smaller breakdown voltage. However, increasing percentage of indium results in higher mobility and as a result higher current and transconductance. Therefore decreasing percentage of indium causes higher breakdown voltage at the sometime lower transconductance. One of the most important parameters that limit maximum output power of transistor is breakdown voltage. In this paper, InAIAs/InGaAs/InP HEMTs with different structures are simulated and a structure with a good transconductance and breakdown voltage is introduced
Hybrid active noise control of a one-dimensional acoustic duct
, Article Journal of Vibration and Acoustics, Transactions of the ASME ; Volume 124, Issue 1 , 2002 , Pages 10-18 ; 10489002 (ISSN) ; Alasty, A ; Ohadi, A. R ; Sharif University of Technology
2002
Abstract
Based on the closed-form solution of a one-dimensional wave equation, the primary, secondary and acoustic feedback paths for the active control of sound in an acoustic duct have been investigated. Accurate models for the condenser microphone and loudspeaker, which include both the electro-mechanical and mechano-acoustical couplings as well as acoustical damping, have been considered. A generalized form of the filtered-x least mean square (FXLMS) algorithm that uses a more general recursive adaptive weight update equation to improve the performance of the FXLMS algorithm has been developed. Computer simulations were carried out to investigate the performance of acoustical feedback and...
Active noise cancellation using feedforward and hybrid controls
, Article 2001 ASME International Mechanical Engineering Congress and Exposition, New York, NY, 11 November 2001 through 16 November 2001 ; Volume 2 , 2001 , Pages 1405-1412 ; Esmailzadeh, E ; Alasty, A ; Sharif University of Technology
2001
Abstract
The exact closed-form solution of a one-dimensional wave equation including the viscous damping effect has been obtained from the Green's function. Accurate models for the error sensor and secondary loudspeaker, which includes the electro-mechanical and mechano-acoustical couplings, have been used and the transfer function of the primary, secondary and acoustic feedback paths of the active noise control system have been obtained. The generalized form of the classical FXLMS algorithm, referred to G-FXLMS algorithm, has been developed. In contrast to the FXLMS algorithm, G-FXLMS algorithm does not neglect the time shift of the filter coefficients and employs a more general recursive adaptive...
Adaptive feedforward active noise control in an acoustic duct
, Article 18th Biennial Conference on Mechanical Vibration and Noise, Pittsburgh, PA, 9 September 2001 through 12 September 2001 ; Volume 6 B , 2001 , Pages 1541-1548 ; Esmailzadeh, E ; Alasty, A ; Sharif University of Technology
2001
Abstract
The single-reference/multi-output active noise control (ANC) of an accurate physical model of an acoustic duct system has been investigated. Computer model of a multi-channel ANC system with tonal and sweep sine input signals, and an adaptive feedforward algorithm that minimizes the generic cost function are developed. Results obtained for various single-input/single-output (SISO) configurations of ANC systems were compared. The dynamic response of a single-reference/multi-output ANC system, using Minimax and MEFXLMS algorithms, is studied and the effect of acoustical feedback neutralization in a multi-channel ANC system is studied. Simulation results demonstrate that the multi-channel...
Feedforward multiple-input active noise control systems
, Article 2003 ASME International Mechanical Engineering Congress, Washington, DC., 15 November 2003 through 21 November 2003 ; Volume 72, Issue 1 , 2003 , Pages 143-150 ; Mehdigholl, H ; Esmailzadeh, E ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2003
Abstract
The use of adaptive feedforward controllers has proven to be a very successful strategy for controlling noise and vibration in a variety of applications. One reason is that the feedforward controller is an open loop controller, which can be designed to cancel the undesired noise in one position with any accuracy. However, the feedforward controller requires an input signal, called a reference signal, correlated to the noise source. As a consequence, a single reference controller can only reduce noise radiated from a single noise source. In many applications, there is a need to attenuate noise produced by several noise sources. In this paper, three different structures, single, modulating and...
Vibration and frequency analysis of non-uniform Timoshenko beams subjected to axial forces
, Article 2003 ASME International Mechanical Engineering Congress, Washington, DC, 15 November 2003 through 21 November 2003 ; Volume 116, Issue 2 , 2003 , Pages 1057-1064 ; 15214613 (ISSN) ; Mehdigholi, H ; Esmailzadeh, E ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2003
Abstract
Dynamic and stability analysis of non-uniform Timoshenko beam under axial loads is carried out. In the first case of study, the axial force is assumed to be perpendicular to the shear force, while for the second case the axial force is tangent to the axis of the beam column. For each case, a pair of differential equations coupled in terms of the flexural displacement and the angle of rotation due to bending was obtained. The parameters of the frequency equation were determined for various boundary conditions. Several illustrative examples of uniform and non-uniform beams with different boundary conditions such as clamped supported, elastically supported, and free end mass have been...
Driving Behavior Estimation with Smartphone Data
, M.Sc. Thesis Sharif University of Technology ; Samimi, Amir (Supervisor)
Abstract
Identifying driving behaviors and building an efficient and accurate driving behavior recognition model is of paramount importance for improving driving safety. Nowadays, with the ubiquity of smartphone sensors, many researchers are using smartphone sensory data to create models which forecast driving behaviors. This research introduces a logit model that predicts nine types of driving events using accelerometer and gyroscope sensors with an accuracy of 76 percent
Thermal Simulation of Sponge Iron Production by Höganäs Method
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
Sponge Iron production is conducted in various methods that one of them is using coal as a reduction agent. Hoganas process is a different coal-based method that has not been investigated in details. Therefore, the heat transfer method in the system is one of the basic steps to a better recognition of this process (with special Hoganas charging). The present paper investigates the temperature distribution method in the Hoganas cylinder through a numerical model using finite elements. The effects of different parameters, namely preheating and porosity were studied on ceramic crucible made from silicon carbide and it was observed that the consumption energy decreases with the increase of...
Consequence Modelling and Probabilistic Risk Assessment of Oil Spills in the Marine Waters
, Ph.D. Dissertation Sharif University of Technology ; Raie, Mohammad (Supervisor)
Abstract
Different causes in the exploration, production and transport of oil in the marine environment result in oil spill events. Since elimination of the probability of occurrence of spills is not possible, it is important to have a plan to control the risk of oil spills by optimal response. In this research, a general stucture is presented for the DSS required for oil spill response planning. This system can be used for evaluation of the effectiveness of response drills, and risk-based ranking of receptor areas and spill sources. Ranking based on risk is realized through probabilistic or stochastic risk assessment. The applicability of the proposed system is examined in differnet case studies in...
Investigating Effects of Urban Freight Companies' Scale on their Transport Efficiency and Developing a Tool for Integration of Freight Companies
, M.Sc. Thesis Sharif University of Technology ; Samimi, Amir (Supervisor) ; Kermanshah, Amir Hassan (Supervisor)
Abstract
In this research, a dashboard has been developed to support decision-making in the integration of freight companies. Freight companies usually consist of a limited number of vehicles due to the high cost of vehicles, while the fixed costs of a freight company constitute a significant part of that company's total cost. Therefore, if these companies are merged, their total cost will be substantially decreased. Moreover, under particular demand levels, the integration of freight companies reduces the mileage, travel time, and the number of required cars. Therefore, the integration of freight companies not only reduces fixed costs but also reduces other costs including greenhouse gas costs by...
Climatic Map of Atmospheric Corrosion of Iran
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
Atmospheric corrosion as one of the most principal factors of destruction is not Climatic map of atmospheric corrosion is closely related to air and atmospheric factors among which we can point out to different types of atmospheric pollutions such as NOX, SOX gases and pendant materials as well as the rate of humidity and rain and even the rate of sun radiation. The effects of these factors beside each other cause the speed of corrosion from a climate to another climate to be changed, which is presentable in form of a map. There is a 2 method to provide this map. First build up a station to measure the corrosion data and collect them in a long period of time. This method are time consuming...
Reconfigurable Architecture For Cryptanalysis Applications
, M.Sc. Thesis Sharif University of Technology ; Jahangir, Amir Hossein (Supervisor)
Abstract
Nowadays, the significance of securing data and information is undeniable. Cryptography is being used to provide data security. In addition, cryptanalysis is required to evaluate the effectiveness of cryptography methods, and hence, it is an essential concept for securing data. In general, the cryptography functions shall be designed in a way to impose a high load of time-intensive operations to prevent an adversary from accessing the main data from the encrypted data. As a result, cryptography and cryptanalysis algorithms need high performance computations. So far, a number of methods have been proposed to support the required performance. These methods include: distributed computing and...
Regularization from the Machine Learning Point of View
, M.Sc. Thesis Sharif University of Technology ; Daneshgar, Amir (Supervisor)
Abstract
In traditional machine learning approaches to classification, one uses only a labeled set to train the classifier. Labeled instances however are often difficult, expensive, or time consuming to obtain, as they require the efforts of experienced human annotators. Meanwhile unlabeled data may be relatively easy to collect, but there has been few ways to use them. Semi-supervised learning addresses this problem by using large amount of unlabeled data, together with the labeled data, to build better classifiers. Because semi-supervised learning requires less human effort and gives higher accuracy.Formally, this intuition corresponds to estimating a label function f on the graph so that it...
On the Density Matrix of Graphs
, M.Sc. Thesis Sharif University of Technology ; Daneshgar, Amir (Supervisor)
Abstract
Density matrix of graphs as defined -for the first time- in [S. Braunstein and et al. The laplacian of a graph as a density matrix, Annals of Combinatorics, (2006)], is obtained through dividing the Laplacian matrix by the degree sum. This matrix is also semi-positive and trace one. Therefore one may talk about the Von Neumann entropy of this matrix. In [F. Passerini, S. Severini. Quantifying complexity in networks: The Von Neumann entropy. IJATS, (2009)], authors have claimed that this quantity can be consisered as a measure of regularity. Here, using a geometric interpretation of Von Neumann entropy, expresed in [G. Mitchison, R. Jozsa, Towards a geometrical interpretation of quantum...
Data-Oriented Verification of Programs
, M.Sc. Thesis Sharif University of Technology ; Ardeshir, Mohammad (Supervisor)
Abstract
The verification of programs is one of the most important subjects in Computer Science. In this thesis, after reviewing preliminary subjects, While-Programming computational model is presented and its semantics is discussed. Next, the axiomatic method of Hoare is presented, which is a deduction system for verification of programs. With the help of Hoare method, the idea of Data-Oriented verification of programs is developed
Numerical Study of Ignition Transient in Solid Fuel Ramjets
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
Solid fuel ignition transient in dump combustor geometry is numerically studied. The objective of this work is to gain insight into the ignition of the fuel and its controlling parameters in back-step turbulent flow. The system of governing equations is solved with a finite volume approach using a structured grid in which the AUSM+ scheme is used to calculate the gas phase convective fluxes. The Spalart-Allmaras turbulence model is used in these simulations. First, the auto-ignition of solid fuel subject to an inlet oxidizer flow at elevated temperatures is considered and distinct intervals in ignition delay time are studied. We have demonstrated that for inlet oxidizer streams with high...
Investigation of EDC Turbulent Combustion Model for Flameless Combustion Regime in a Certain Combustion Chamber
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
Reducing carbon emissions emanated from combustion of fossil fuels is a challenging problem and consumes huge amount of money that is put into research every year. Nitrogen oxides are among the most important pollutants which have been at the center of attention of industries and international environment protection organizations, especially due to their increased production by commercial aircrafts at higher altitudes of the atmosphere. Flameless is a combustion regime that has been independently discovered by different research teams while working on reducing nitrogen oxides from burning fossil fuels in the early 1990s, and afterwards has been studied for its exclusive characteristics in...
Design and Analysis of Microwave Frequency-Reconfigurable Antennas Based on Handedness Preserving Metasurfaces
, M.Sc. Thesis Sharif University of Technology ; Memarian, Mohammad (Supervisor)
Abstract
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...