Adversarial Convex Bandit

, M.Sc. Thesis Sharif University of Technology Ohadi, Amir Mohammad (Author) ; 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...

Generative Models and their Role in Development of Generality in AI

, M.Sc. Thesis Sharif University of Technology Ekhlasi, Amir Hossein (Author) ; Alishahi, Kasra (Supervisor)

Abstract

In this thesis Generative Models in Deep Learning are discussed, especially Generative Models which are based on latent variables. Deep Generative Models have key role in developing Artificial Intelligence, particularly in developments of general cognition and perception in AI. In this thesis, this role for Generative Models and their applications in cognition development, and also the mathematical foundation of generative models are discussed

An Investigation Into Microstructural Changes and Mechanical Properties During Friction Atir Welding of a Hardenable AA2017

, M.Sc. Thesis Sharif University of Technology Mirjalili, Abolfazl (Author) ; Kokabi, Amir hosein (Co-Advisor) ; Serajzadeh, Siamak (Co-Advisor)

Abstract

Friction stir welding (FSW) is considered a significant manufacturing process for joining of different metals and alloys and usage of this process has been developed in different industries. Accordingly, extensive works have been done on FSW of different engineering materials. However many ambiguous problems related to thermo-mechanical behavior of this process have not been solved yet. This research investigates FSW behavior of a hardenable aluminum alloy, AA2017. Firstly, thermo-mechanical response of the material has been predicted using a three-dimensional finite element analysis performed in ABAQUS software. Then, microstructural events such as grain size, distribution of second phase...

Dynamic Modeling of a Bubble Column Bioreactor Using Hybrid Neural Networks

, M.Sc. Thesis Sharif University of Technology Alishahi, Amir Hosein (Author) ; Pishvaie, Mahmoud Reza (Supervisor) ; Vafa, Ehsan (Supervisor)

Abstract

With the daily increasing demand for energy, we are facing many crises, such as environmental pollution and global warming, etc. Geopolitical issues can also lead to problems for some countries in reaching the energy demand considered in their development plan of them. For this purpose, a part of the global research is focused on removing these obstacles. One of the methods that can be used to produce cleaner fuel, or more precisely "biofuel", is the gaseous fermentation of synthesis gas by microorganisms and algae. A rod-shaped, anaerobic microorganism called Clostridium ljungdahlii uses synthesis gas for its reproduction. In other words, this bacterium can ferment carbon monoxide, carbon...

Study of Effective Parameters on Helium Liquefaction Cycle using Exergy Analysis

, M.Sc. Thesis Sharif University of Technology Eslami, Mahdi (Author) ; Afshin, Hosein (Supervisor)

Abstract

Liquefaction of gases is one of the applications of cryogenic science. Among the gases, Helium has the lowest boiling point, which at a pressure of 1atm is approximately 4.2K. Liquid helium can be used to cool superconductors in transportation equipment, military radars, and medical imaging equipment. For helium liquefaction, various cycles are used; these cycles have different parameters in their structure such as of input mass fraction to expanders, heat exchanger effectiveness, expander arrangement and ... which their analysis for improving the performance of the cycle is important. In this research, the aim is to study 2, 3 and 4 expander cycle with various parameters and structure. For...

Study of Microstructure and Wear behavior of In-Situ Al/Al3Ti Composite Coating on Commercial Pure Al Produced by Aluminum Cored Wires and TIG Process

, M.Sc. Thesis Sharif University of Technology Ansari Jarm Afshari, Afsaneh (Author) ; Kokabi, Amir Hosein (Supervisor) ; Madaah Hoseini, Hamid Reza (Supervisor)

Abstract

Recently, Aluminum alloys have been the materials of choice for both military aircraft and automotive industries due to their high strength-to-weight ratio, high electrical and thermal conductivities and excellent corrosive resistance. However, their applications have been limited due to the low yield stress and wear resistance. In order to improve the surface wear resistance, structural and chemical surface modifications such as producing composite coatings could be applied. Gas Tungsten Arc welding (GTAW) process can be used to produce alloy and composite surface layers on different substrates. In this research, GTAW process and aluminum cored wires were used for coating of Al/Al3Ti...

Know-how-first anti-intellectualism: Williamson against Williamson

, Article Synthese ; Volume 200, Issue 4 , 2022 ; 00397857 (ISSN) Hosein, M ; Khalaj, M. A ; Sharif University of Technology

Springer Science and Business Media B.V 2022

Abstract

Inspired by Williamson’s knowledge-first epistemology, I propose a position on practical knowledge that can be called the ‘know-how-first view’; yet whereas Williamson is one of the pioneers of the new intellectualism about know-how, I employ the know-how-first view to argue against intellectualism and instead develop a know-how-first version of anti-intellectualism. Williamson argues that propositional knowledge is a sui generis unanalyzable mental state that comes first in the epistemic realm; in parallel, I propose that know-how is a sui generis unanalyzable power that comes first in the practical realm. To motivate this suggestion, I put forward two arguments: (1) drawing on...

An Investigation of a Fuzzy Transformation of Variables on the Robustness of Choice Models

, M.Sc. Thesis Sharif University of Technology Sherafatipour, Saeid (Author) ; Pourzahedi, Hosein (Supervisor)

Abstract

Estimation of demand, for example, for transportation is an important issue for the planning and programming of various systems. Thus, enhancing the predictability power of such models is of high value. Demand stems from choices of individuals, and choice is subject to uncertainty and fuzziness. Uncertainty comes from many factors including incomplete information of decision-maker, and fuzziness comes from many other factors including personal perception regarding the value of the variables affecting choice. This study tries to introduce a new approach in building choice models, in which variables are transformed into another variable by the help of a global wisdom. This wisdom shows the...

Study of the Interaction of Non-level Crossing Tunnels, Case Study of Crossing of Tunnels of Line 1 and Line 7 of Tehran Metro

, M.Sc. Thesis Sharif University of Technology Pourjavadi, Sobhan (Author) ; Sadaghiani, Mohammad Hosein (Supervisor)

Abstract

As the crowded cities require public transportation and because of lack of space on the ground, Subway and boring underground tunnels encountered. In this thesis the interaction of boring the line 7 of Tehran metro with the existing station of line 1 of Tehran metro (Molavi station) is studied. By changing the soil specification, The surface settlement is significant so the soil specification is one of the important parameters of the interaction. For comparinf the effect of these parameters, the soil settlement and bending moments is investigated in different parts of station while the lower tunnel is passing beneath it. The 3D Abaqus software is used for modeling this interaction. In...

Text to Phoneme Transcription Capable to Detect Ezafe and Homographs for Persian Speech Synthesis

, M.Sc. Thesis Sharif University of Technology Oskouipour, Navid (Author) ; Sameti, Hosein (Supervisor)

Abstract

In Persian language, there are some special uncertainties and complexities regarding the extraction of phonemes due to its flexible structure. In this work, we try to solve two problems caused by this issue, homographs disambiguation and Ezafe recognition in Persian text to speech systems.
In this work, two methods are presented for solving the two problems. The first one is a pattern recognition method based on Aho-Corasick algorithm that has the best performance according to the execution time. The second method is a hidden Markov model tagger based on Viterbi algorithm that uses bigram and trigram statistics. These methods are run on 10 million word corpus and the results are compared...

Predictive and Nonlinear Control of Aircraft in Presence of Microburst Wind Shear

, M.Sc. Thesis Sharif University of Technology Jafari, Navid (Author) ; Pourtakdoust, Hosein (Supervisor)

Abstract

Airplanes usually experience minor position change and height loss during cruise flight, but under normal circumstances the aircraft total energy is adequately acceptable to maintain the trajectory and the desired performance without severe oscillations. On the other hand, if the airplane encounters a wind-shear or microburst during take-off or landing phases, it would be a dangerous situation, as the aircraft kinetic and potential energy levels are not as high.
In this research, a model predictive controller is designed and investigated to allow a transport category aircraft to either escape or penetrate the microburst. In this regard, initially a DMC controller is designed for 6-DoF...

Study of Loading Orientation Effect on Shear Strength of Rock Mass Discontinuities with Infilling Based on Laboratory Methods

, M.Sc. Thesis Sharif University of Technology Malaksiar, Hosein (Author) ; Sadaghiani, Mohammad Hosein (Supervisor)

Abstract

Recently, Needs for construction of rock structures and underground ones such as tunnels, dam foundations, power plants and caverns built to keep oil, gas and nuclear waste has increased dramatically. In order to design, construct and excavate these underground structures safely and economically, full understanding of rock mass properties, suitable tools and practical techniques of drilling are necessary. Because of existing this discontinuities, including joints and layered rock masses and their effects on mechanical behavior of rock mass, it is necessary for the geomechanical profile, shear strength and failure mechanism of rock mass to be accurately indentified. Shear strength criterions...

The spherical ensemble and uniform distribution of points on the sphere

, Article Electronic Journal of Probability ; Volume 20 , 2015 , 23, 27 pp ; 10836489 (ISSN) Alishahi, K ; Zamani, M ; Sharif University of Technology

University of Washington 2015

Abstract

The spherical ensemble is a well-studied determinantal process with a fixed number of points on $2. The points of this process correspond to the generalized eigenvalues of two appropriately chosen random matrices, mapped to the surface of the sphere by stereographic projection. This model can be considered as a spherical analogue for other random matrix models on the unit circle and complex plane such as the circular unitary ensemble or the Ginibre ensemble, and is one of the most natural constructions of a (statistically) rotation invariant point process with repelling property on the sphere. In this paper we study the spherical ensemble and its local repelling property by investigating the...

Generalized differential transfer matrix for fast and efficient analysis of arbitrary-shaped nonlinear distributed feedback structures

, Article IEEE Journal of Quantum Electronics ; Volume 45, Issue 2 , 2009 , Pages 125-131 ; 00189197 (ISSN) Alishahi, F ; Mehrany, K ; Sharif University of Technology

2009

Abstract

A new, fast, and efficient approach based on the differential transfer matrix idea, is proposed for analysis of nonuniform nonlinear distributed feedback structures. The a priori knowledge of the most-likely electromagnetic field distribution within the distributed feedback region is exploited to speculate and factor out the rapidly varying portion of the electromagnetic fields. In this fashion, the transverse electromagnetic fields are transformed into a new set of envelope functions, whereupon the numerical difficulty of solving the nonlinear coupled differential equations is partly imparted to the analytical factorization of the fields. This process renders a new set of well-behaved...

Volume degeneracy of the typical cell and the chord length distribution for Poisson-Voronoi tessellations in high dimensions

, Article Advances in Applied Probability ; Volume 40, Issue 4 , July , 2008 , Pages 919-938 ; 00018678 (ISSN) Alishahi, K ; Sharifitabar, M ; Sharif University of Technology

2008

Abstract

This paper is devoted to the study of some asymptotic behaviors of Poisson-Voronoi tessellation in the Euclidean space as the space dimension tends to ∞. We consider a family of homogeneous Poisson-Voronoi tessellations with constant intensity λ in Euclidean spaces of dimensions n = 1, 2, 3,... First we use the Blaschke-Pètkantschin formula to prove that the variance of the volume of the typical cell tends to 0 exponentially in dimension. It is also shown that the volume of intersection of the typical cell with the co-centered ball of volume u converges in distribution to the constant λ-1 (1-e-λu). Next we consider the linear contact distribution function of the Poisson-Voronoi tessellation...

Using Data Mining in Production Information Systems

, M.Sc. Thesis Sharif University of Technology Alishahi, Mohammad (Author) ; Hooshmand, Mahmoud (Supervisor)

Abstract

Nowadays, because of high volume and growth of data in industrial organizations and productive factories, registration and storing of data have forgotten manual and tradition styles for which using automation and mechanized machinery and systems has been a necessary task. In order to reach to this revolution, need to some tools, facilities and methods which can fulfill this requirement is felt strongly. Therefore, high volume of data is considered as an advantage because based on precise analysis it is possible to make logical management decisions with less risk. During last years, statistical and numerical methods and simulation were used to discover knowledge and information when one of...

Random Polytopes

, M.Sc. Thesis Sharif University of Technology Rajaee, Mohaddeseh (Author) ; Alishahi, Kasra (Supervisor)

Abstract

Random Polytopes, the first occurrence of which dates back to the famous Sylvester’s four points problem in the 1860s, is a branch of geometric probability, typically concerning the convex hull of some random points chosen from a convex subset of Rd. In this thesis we have studied some special kind of random polytopes; the one that is the convex hull of some independent random points chosen from a convex body (a convex, compact set with interior point) according to the uniform distribution. It was a new approach from A. Rényi and R. Sulanke in 1963 to consider this type when the number of random points tends to infinity.This thesis consists of three main parts: The first part is devoted to...

Generating Random Points in a Convex Body in High Dimensions

, M.Sc. Thesis Sharif University of Technology Khezeli, Ali (Author) ; Alishahi, Kasra (Supervisor)

Abstract

“How can we generate a random point with uniform distribution over a convex body ?” According to it’s applications, it’s important for a solution to this problem to be applicable in high dimensions. Here, we are interested in algorithms with polynomial order with respect to the dimension. All existing methods for dealing with this problem are based on the Markov chain Monte Carlo method, i.e. a random walk is constructed in such that its stationary distribution is the uniform distribution over. Then, after simulating “enough” steps of this random walk, the distribution of the resulting point is “approximately” uniform. The real problem in Monte Carlo method is analyzing its “mixing time”,...

Simultaneous Hypothesis Testing and False Discovery Rate

, M.Sc. Thesis Sharif University of Technology Shahbazi, Mohammad (Author) ; Alishahi, Kasra (Supervisor)

Abstract

The purpose of this thesis is to introduce and review a recent methods in simultaneous hypothesis testing. False discovery rates, Benjamini and Hochberg’s FDR Control Algorithm, is the great success story of the new methodology. Much of what follows is an attempt to explain that success in empirical Bayes terms.The later chapters are at pains to show the limitations of current largescale statistical practice: Which cases should be combined in a single analysis? How do we account for notions of relevance between cases? What is the correct null hypothesis? How do we handle correlations? Some helpful theory is provided in answer, but much of the argumentation is by example, with graphs and...

Determinantal Processes

, M.Sc. Thesis Sharif University of Technology Barzegar, Milad (Author) ; Alishahi, Kasra (Supervisor)

Abstract

Determinantal processes are a special family of stochastic processes that arise in physics (fermions), random matrices (eigenvalues), and in combinatorics (random spanning trees and non-intersecting paths). These processes have repelling property (points close to each other are chosen with low probability). Because of this repelling property, determinantal processes are approporiat for modeling some physical quantities (e.g. the position of electrons). Their probabilistic structure is described by operators on complex vector spaces and their eigenvalues. Determinantal processes have interesting properties, e.g. number of points in a region is a sum of independent Bernoulli random variables....