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    Model Test to Evaluate Behavior of Tension Leg Platform in Waves

    , M.Sc. Thesis Sharif University of Technology Razaghian, Amir Hosein (Author) ; Seif, Mohammad Saeid (Supervisor) ; Tabeshpour, Mohammad Reza (Co-Advisor)
    Abstract
    A Tension Leg Platform (TLP) can be difined as a vertically moored, buoyant and compliant platform, where the excess buoyancy of the platform maintains tension in the mooring system (tethers). This platform type is usually used for drilling in deep water and includes the following sections, foundation, tendons, risers, hull and deck which is the most important section in terms of hydrodynamic forces and weight. Enough initial tension can be used to inhibit vertical movement of the structure. one of The main properties of this oil platform is extraction at large oil fields. Body of TLP is consist of vertical column, horizontal circular or rectangular cross section Pantoons and circular... 

    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... 

    Study of Mechanical Response of Wind Turbine Blades Made of Thermosetting and Thermoplastic Resins

    , M.Sc. Thesis Sharif University of Technology Razaghian, Pardis (Author) ; Abedian, Ali (Supervisor)
    Abstract
    This project has been carried out to investigate the feasibility of using thermoplastic materials in constructing large wind turbine blades made of composite materials. By proving the similarity of the mechanical behavior of blades made of thermoplastic and thermosetting composite materials, the possibility of using these materials with better recycling capabilities has been studied. By studying different thermosetting and thermoplastic resins and checking the Processing methods and mechanical properties of thermoplastic resins, the materials for blades have been selected. The suitable manufacturing method for producing large blades with dimensions above 30 meters is the vacuum-assisted... 

    A novel decision-making methodology for materials selection under uncertainty: modified fuzzy logic method

    , Article Soft Computing ; Volume 26, Issue 22 , 2022 , Pages 12093-12114 ; 14327643 (ISSN) Sharifan, M ; Abedian, A ; Razaghian, P ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2022
    Abstract
    In this research work, a modified fuzzy approach referred to as modified fuzzy logic method (MFLM) is proposed to more conveniently solve intricate decision-making problems under uncertainty and data deficiency. The method resolves major drawbacks like inaccuracy, complexity, and a high volume of computational efforts with the existing approaches for the mentioned problems. Here, MFLM is applied to materials selection for a cryogenic storage tank and a gas turbine blade, which are standard engineering problems used for verification by researchers, and the ranking results are compared with the state-of-the-art techniques in the literature, such as the conventional fuzzy logic method.... 

    A hybrid reasoning-based tool for analog circuit synthesis

    , Article Scientia Iranica ; Volume 9, Issue 4 , 2002 , Pages 419-424 ; 10263098 (ISSN) Razaghian, F ; Sadughi, S ; Badie, K ; Sharif University of Technology
    Sharif University of Technology  2002
    Abstract
    In this paper, an intelligent CAD tool for the design of analog circuits is presented. First, the system uses fuzzy rule based reasoning to select alternative architectures for the circuits at each level of hierarchy and, then, deduces the device size using case-based reasoning, whose objective is to determine the plausible building blocks subspecifications on the basis of past design experience. In cases where some of the specifications have not been met, a qualitative reasoning-based approach is used to make final corrections. The above approach is demonstrated through the example of a CMOS Op-Amp  

    Low-power high-speed phase frequency detector based on carbon nano-tube field effect transistors

    , Article Analog Integrated Circuits and Signal Processing ; 2021 ; 09251030 (ISSN) Soltani Mohammadi, M ; Sadughi, S ; Razaghian, F ; Sharif University of Technology
    Springer  2021
    Abstract
    A phase frequency detector (PFD) with a very low dead zone is proposed which is based on a configuration adaptable to both CMOS or carbon nano-tube transistors (CNTFETs). In the first step the proposed configuration is designed using CMOS transistors, and then CNTFETs are substituted to improve the speed and reduce the propagation delay. The proposed PFD in addition to very low dead zone, has low power consumption and high frequency range of operation, which are achieved as a result of the elimination of the reset path. The simulation results based on 32 nm technology for CNTFET and 180 nm technology for CMOS, illustrate that CNTFET-based proposed circuit dissipates 2 µW and has frequency of... 

    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... 

    Verifying the Empirical Validity of the Trilemma using U.S. Monetary Shocks

    , M.Sc. Thesis Sharif University of Technology Karimi, Mahtab (Author) ; Barakchian, Mahdi (Supervisor) ; Joshaghani, Hosein (Co-Supervisor)
    Abstract
    According to the impossible trinity, countries can only enjoy from two of the following choices simultaneously: fixed exchange rate, free capital flow and independent monetary policy. A part of the economics literature has tried to verify the theory empirically. Some of the researches like Klein and Shambugh(2015) has concluded that the trilemma is valid on the occasion of transferring the effect of base countries interest rate changes to other countries. On the other side, a few papers like Ray(2013) has shown that an independent monetary policy can just be obtained by a closed capital flow and a float exchange rate system can not necessarily give central banks the autonomy of monetary... 

    Design and Implementation a Controller for a XY Nano-Positioning System using Piezo Stack with Strain Gauge Fitted

    , M.Sc. Thesis Sharif University of Technology Bayat, Saeed (Author) ; Nejat, Hosein (Supervisor) ; Salarieh, Hassan (Supervisor)
    Abstract
    Nanopositioning is the technology to control position of the objects with precision of the scale of nanometers. Nowdays, This technology emerged as one of the components of research and production in the micro and nanometer dimensions, helping researches and producers to carry out many state of the art projects. A nanopositioning device, consists of a support to path guidance, an actuator to apply force and motion, a driving circuit for communication with the actuator, a sensor for measuring displacement, a circuit for reading sensor’s data, a controlling algorithm to reach the desired precision, a controlling hardware to enforce controlling logic, a power supply and a graphical user... 

    Investigating the effect of geometric parameters on hydrodynamic and hydro-acoustic performances of submerged propellers

    , Article Applied Ocean Research ; Volume 114 , 2021 ; 01411187 (ISSN) Razaghian, A. H ; Ebrahimi, A ; Zahedi, F ; Javanmardi, M. R ; Seif, M. S ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    The hydro-acoustic analysis of submerged propellers is an important issue in marine industries, which is examined to reduce the vibrations and noise level of vessels alongside reducing fuel consumption and improving hydrodynamic efficiency. B-series propellers are common propellers whose hydrodynamic and acoustic investigation through applying suitable rake, and skew angle can offer proper results to designers for enhancing the hydrodynamic performance and reducing noise. In this study, a model of the five-bladed B-series propeller with the normal skew angle is chosen. The effects of geometric parameters, including the rake angle, skew angle, geometric pitch ratio, and the number of blades... 

    Real-Time IDS using reinforcement learning

    , Article 2008 2nd International Symposium on Intelligent Information Technology Application, IITA 2008, Shanghai, 21 December 2008 through 22 December 2008 ; Volume 2 , January , 2008 , Pages 593-597 ; 9780769534978 (ISBN) Sagha, H ; Bagheri Shouraki, S ; Hosein, K ; Mahdi, D ; Sharif University of Technology
    2008
    Abstract
    In this paper we proposed a new real-time learning method. The engine of this method is a fuzzy-modeling technique which is called ink drop spread (IDS). IDS method has good convergence and is very simple and away from complex formula. The proposed method uses a reinforcement learning approach by an actor-critic system similar to Generalized Approximate Reasoning based Intelligent Control (GARIC) structure to adapt the IDS by delayed reinforcement signals. Our system uses Temporal Difference (TD) learning to model the behavior of useful actions of a control system. It is shown that the system can adapt itself, commencing with random actions. © 2008 IEEE  

    To Investigae How and Why Iran Economy Experienced Jobless Growth between 2005 to 2011

    , M.Sc. Thesis Sharif University of Technology Sartipnia, Abouzar (Author) ; Nili, Masoud (Supervisor) ; Joshaghani, Hosein (Supervisor)
    Abstract
    In this research, it has been tried to answer jobless growth in Iran’s economy between 2005 to 2011. At first, the added value and employment of various major sectors will be investigated. It will be observed that two major sectors, agriculture and industry, have been experienced jobless growth. After having been investigated more, it will be shown that the major part loss of the job in the agriculture is relating to unwaged family workers. In the industry about all the loss of the job has been happened in the textile sub-sector. In these two sectors, the most of the separated people has been inactive. Getting inactive and not being allocated of the separated people have been led to... 

    Study of Tangential Coefficient of Restitution in Nano-particles Collision

    , M.Sc. Thesis Sharif University of Technology Shahbakhti, Abbas (Author) ; Sayyadi, Hasan (Supervisor) ; Nejat, Hosein (Co-Supervisor)
    Abstract
    In this thesis, the collisions of two fluorine-C60 nanoparticles have been studied using molecular dynamics simulation. The main purpose of this thesis is to present a completely new method based on the definition of the vertical and tangential coefficient of restitution, although by using the combination of the simulation and theory results, we can obtain the approximate parameters of physical properties of nanoparticles, such as hardness coefficient, surface tension, friction coefficient, etc.At first, two fluorine C60 under different conditions, including collision velocity, collision angle, initial temperature, initial rotational angle of the molecule, and various potential applications...