Strain and Stress Measurement by Image Processing Technique

, M.Sc. Thesis Sharif University of Technology Lak, Mehdi (Author) ; Assempour, Ahmad (Supervisor)

Abstract

This study presents an image processing technique for automatic strain and stress measurement in sheet metals. In order to measure the strain automatically, the sheet blank is electrochemically etched to create circular and rectangular grids. After press forming of the sheet, circular grids are deformed into elliptical grids and rectangular grids are deformed into quadrilateral grids. Different photos are captured for using in image processing technique. These photos are taken in different positions. Finally strain can be measured by processing these photos and the stress is obtained by using Levy-Mises flow rule. In this study, three methods of image processing technique are simultaneously...

Photocatalytic activity of TiO2-capped ZnO nanoparticles [electronic resource]

, Article Journal of Materials Science: Materials in Electronics ; 2011 , Vol. 23, Issue 2, P.361-369 Lak, A. (Aidin) ; Simchi, A. (Abdolreza) ; Nemati, Ziarat Ali ; Sharif University of Technology

Abstract

Using a combined hydrothermal and sol–gel route, TiO2-capped ZnO nanoparticles with an average size of 60 nm were prepared. The titania shell was amorphous with a thickness of ~10 nm. Formation of Zn2TiO4 phase at higher calcination temperature was noticed. Effects of Ti/Zn molar ratio and coating time on the thickness of TiO2 shell and the photoactivity of the particles for decolorization of Methylene Blue (MB) under UV lamp irradiation (3 mW/cm2) were investigated. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, fourier-transform infrared spectrometry (FTIR), diffuse reflectance spectroscopy (DLS), and atomic absorption spectroscopy. Analysis of...

Photocatalytic activity of TiO 2-capped ZnO nanoparticles

, Article Journal of Materials Science: Materials in Electronics ; Volume 23, Issue 2 , 2012 , Pages 361-369 ; 09574522 (ISSN) Lak, A ; Simchi, A ; Nemati, Z. A ; Sharif University of Technology

2012

Abstract

Using a combined hydrothermal and sol-gel route, TiO 2 -capped ZnO nanoparticles with an average size of 60 nm were prepared. The titania shell was amorphous with a thickness of ∼10 nm. Formation of Zn 2TiO 4 phase at higher calcination temperature was noticed. Effects of Ti/Zn molar ratio and coating time on the thickness of TiO 2 shell and the photoactivity of the particles for decolorization of Methylene Blue (MB) under UV lamp irradiation (3 mW/cm 2) were investigated. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, fourier-transform infrared spectrometry (FTIR), diffuse reflectance spectroscopy (DLS), and atomic absorption spectroscopy....

Numerical Simulation of Secondary Sedimentation Tanks to Increase the Efficiency

, M.Sc. Thesis Sharif University of Technology Lak, Behzad (Author) ; Firoozabadi, Bahar (Supervisor) ; Afshin, Hossein (Supervisor)

Abstract

Sedimentation tanks are one of the important and costly stages of water treatment process in which remained particles from previous stages settle down due to gravity force. In this research, the hydrodynamics of secondary settling tanks without and in the presence of particles is numerically investigated using VOF method in order to simulate the interphase using RNG k-ε for turbulence modelling. The simulations are performed by means of open-source code OpenFoam, and the code is developed to model particles in the flow. The calculated velocity profiles using VOF method show a reasonable agreement with the experimental data. Comparing the concentration profiles with experiments shows the...

A Machine Learning Approach for Memory Resource Management in GPUs

, M.Sc. Thesis Sharif University of Technology Mohammadi Lak, Masoud (Author) ; Sarbazi Azad, Hamid (Supervisor)

Abstract

Nowadays, GPUs are used in applications such as graph computations and deep learning that require large data processing. These applications necessitate transferring a considerable amount of data between memory and computational units, which increases the average memory access latency. On the other hand, the poor performance of the L1 cache causes many reservation fails, resulting in increased energy consumption and reduced performance. In this thesis, we propose Smart Cache, a new smart cache management in GPUs. This approach models the cache replacement problem as a sequence labeling problem. Then, a machine learning model that combines support vector machine with one-hot encoding and...

Fruits and Vegetables Supply Chain Management (Case Study: Kerman Province)

, M.Sc. Thesis Sharif University of Technology Rajaei Lak, Razieh (Author) ; Akbari Jokar, Mohammad Reza (Supervisor)

Abstract

One of the challenges of today's economy, is improving economic structures and reduce its dependence on oil revenues. Agricultural industry as an important part of the economy, is not dependent on oil revenues and improving its structure can have a significant impact on increasing revenues. Kerman province with a high proportion of horticultural products in the country, plays a significant role in Agricultural industry .However, the problem of water shortages in the country, highlighted the efficient use of water in economic purpose and crop-planning. By the problems with the current structure, lack of management of planting crops, lack of proper supply chain, redesign of agricultural supply...

Rapid formation of hydroxyapatite nanostrips via microwave irradiation

, Article Journal of Alloys and Compounds ; Volume 469, Issue 1-2 , 2009 , Pages 391-394 ; 09258388 (ISSN) Arami, H ; Mohajerani, M ; Mazloumi, M ; Khalifehzadeh, R ; Lak, A ; Sadrnezhaad, S. K ; Sharif University of Technology

2009

Abstract

Hydroxyapatite (HAp) nanostrips were rapidly obtained during a mild microwave heating method. Applying microwave irradiation to Ca(NO3)2·4H2O/CTAB/Na2HPO4 precursor solution, the HAp precipitation process was occurred directly and without common crystallographic transformations including dissolution and slow recrystallization. The cationic surfactant CTAB was used as a soft template to modify nucleation and growth process. TEM investigations showed that the fabricated nanostrips had a width and length of about 10 and 55 nm, respectively. The X-ray diffraction pattern revealed that the fabricated well-crystallized and high purity hydroxyapatite nanostrips had a pattern similar to the bone...

3D bundles of self-assembled lanthanum hydroxide nanorods via a rapid microwave-assisted route

, Article Journal of Alloys and Compounds ; Volume 473, Issue 1-2 , 2009 , Pages 283-287 ; 09258388 (ISSN) Mazloumi, M ; Shahcheraghi, N ; Kajbafvala, A ; Zanganeh, S ; Lak, A ; Mohajerani, M. S ; Sadrnezhaad, K ; Sharif University of Technology

2009

Abstract

Three-dimensional (3D) bundles of self-assembled lanthanum hydroxide nanorods with average crystallite size of about 20 nm were fabricated via a facile and rapid microwave-assisted chemical route. The obtained material was characterized with X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) investigations. The obtained nanorods have average diameter of about 115 nm and average length of about 730 nm. Self-assembly of primary La(OH)3 nanoparticles and their subsequent anisotropic growth along 〈2 0 0〉 direction, was proposed to be the mechanism for the formation of 3D bundles of nanorods, using TEM images. The thermal behavior of the...

Self-assembly of dandelion-like hydroxyapatite nanostructures via hydrothermal method

, Article Journal of the American Ceramic Society ; Volume 91, Issue 10 , 2008 , Pages 3292-3297 ; 00027820 (ISSN) Lak, A ; Mazloumi, M ; Mohajerani, M ; Kajbafvala, A ; Zanganeh, S ; Arami, H ; Sadrnezhaad, S. K ; Sharif University of Technology

2008

Abstract

Self-assembled dandelion-like hydroxyapatite (HAp) nanostructures were successfully synthesized via a mild template-free hydrothermal process, using ethylenediaminetetraacetic acid (EDTA) as the surfactant. The obtained dandelion-like HAp nanostructures were between 5 and 8 μm in diameter and were composed of radially oriented nanorods with an average diameter of about 200 nm. The X-ray diffraction analysis and Fourier transform infrared spectroscopy were used to characterize the crystalline phase and purity of the synthesized nanostructures. The Brunauer-Emmett-Teller surface area of the dandelion-like nanostructures was measured to be about 39 m2/g. The results of thermal analysis revealed...

Design and Fabrication of Inductive High Temperature Superconducting Fault Current Limiter

, Ph.D. Dissertation Sharif University of Technology Hekmati, Arsalan (Author) ; Vakilian, Mehdi (Supervisor) ; Fardmanesh, Mehdi (Supervisor)

Abstract

The continuous rise in electricity demand and the ever growing power generation in different power networks over the world have caused the short circuit level in the power systems to exceed the operational rating of the installed power devices (including cables, circuit breakers and buses). Replacing these devices with new higher rating devices is an expensive solution. From this point of view, utilizing fault current limiters is an economical solution. Superconducting fault current limiters form an efficient category of current limiters. This type is expected to be studied and used widely in future due to their advantages. In this thesis, the first chapter reviews the superconductivity...

, M.Sc. Thesis Sharif University of Technology Mardiha, Milad (Author) ; Vakilian, Mehdi (Supervisor) ; Fardmanesh, Mehdi (Supervisor)

Boehmite nanopetals self assembled to form rosette-like nanostructures

, Article Materials Letters ; Volume 62, Issue 26 , 2008 , Pages 4184-4186 ; 0167577X (ISSN) Mazloumi, M ; Attarchi, M ; Lak, A ; Mohajerani, M. S ; Kajbafvala, A ; Zanganeh, S ; Sadrnezhaad, S. K ; Sharif University of Technology

2008

Abstract

Rosette-like boehmite nanostructures were prepared successfully via a simple hydrothermal process. The obtained material was characterized with X-ray powder diffractometry (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Using Scherrer formula, the average crystallite size of the obtained boehmite rosettes was measured to be about 8 nm. It was shown that boehmite nanopetals with average width of about 41 nm determined by TEM, were formed during the hydrothermal process and then self assembled due to weak hydrogen bonds to fabricate boehmite rosettes. The specific surface area of the obtained rosette-like nanostructures was calculated through BET...

Enhancement of THz Radiation from Josephson Junctions in Superconductors Using Electromagnetic Resonators

, M.Sc. Thesis Sharif University of Technology Iranmehr, Masoud (Author) ; Ahmadi Boroujeni, Mehdi (Supervisor) ; Fardmanesh, Mehdi (Supervisor)

Abstract

Terahertz waves which includes frequencies between 100 GHz to 10 THz of electromagnetic spectrum have found many applications in science, medical treatments and industry. One of the recent methods to produce these waves is using nonlinear properties of superconductors based on Josephson junctions which inherently appear in some superconductors called BSCCO. Stack of intrinsic junctions of these superconducting materials can radiate terahertz waves by only applying a DC voltage across them. This Thesis investigates some of these structures based on Josephson junctions to produce coherent radiation of terahertz waves. For the optimization of the radiation power, this study also investigates...

On the Spectrum of Modified Theories of Gravity

, M.Sc. Thesis Sharif University of Technology Seraj, Ali (Author) ; Golshani, Mehdi (Supervisor) ; Sheikh Jabbari, Mohammad Mehdi (Supervisor)

Abstract

There are different approaches in modifications of General Relativity as the theory of gravity. The modified theories of gravity are important cases in this context, which mostly start by modifying the Einstein-Hilbert action, while keeping the general covariance. Within the modified theories of gravity, we consider two cases. The first is the f(R) theories of gravity, and the second is curvature squared theories of gravity with an action like S = ∫d4x pg( 116GR + (R)2 + R2 +(R)2). Curvature squared theories of gravity have interesting feautures, most important of which is renormalizability, in contrast with General Relativity. But this advantage, as noted by K.S. Stelle in 1977 comes at...

On Thermodynamics and Phase Space of Near Horizon Extremal Geometries

, Ph.D. Dissertation Sharif University of Technology Hajian, Kamal (Author) ; Sheikh-Jabbari, Mohammad Mehdi (Supervisor) ; Golshani, Mehdi (Co-Advisor)

Abstract

Near Horizon Extremal Geometries (NHEG), are geometries which may appear in the near horizon region of the extremal black holes. These geometries have SL(2;R)U(1)n isometry, and constitute a family of solutions to the theory under consideration. In the first part of this report,their thermodynamic properties are reviewed, and their three universal laws are derived. In addition, at the end of the first part, the role of these laws in black hole thermodynamics is presented. In the second part of this thesis, we review building their classical phase space in the Einstein-Hilbert theory. The elements in the NHEG phase space manifold are built by appropriately chosen coordinate transformations of...

Critique and Survey of Various Formulation of Multiverse Theory

, Ph.D. Dissertation Sharif University of Technology Masoumi, Saeed (Author) ; Golshani, Mehdi (Supervisor) ; Sheikh Jabbari, Mohammad Mehdi (Supervisor)

Abstract

Multiverse scenario has been recently addressed by physicists and they have found it useful in many areas of physics. In this dissertation, I have treated some issues about multiverse such as the kinds of multiverses, the arguments for or against multiverse, areas in which multiverse is introduced, etc. This dissertation has six chapters and an appendix. In the chapter one, some classifications of multiverse is introduced, and also some definitions of the concept of a world is presented. Then, my classification and definition of a multiverse and a world is introduced. In the chapter two, the concept of possible worlds in philosophy and its relationship with multiverse hypothesis is examined....

Optimal Multicriteria Design of HTS Transformer and Construction of a Laboratory Scale Sample

, Ph.D. Dissertation Sharif University of Technology Moradnouri, Ahmad (Author) ; Vakilian, Mehdi (Supervisor) ; Fardmanesh, Mehdi (Co-Supervisor) ; Hekmati, Arsalan (Co-Supervisor)

Abstract

Employing high-temperature superconducting (HTS) tapes, instead of copper or aluminum wires for winding in a superconducting transformer, results in a series of significant advantages; such as: smaller volume, lighter weight, higher efficieny, greatly extended overload capability, better voltage regulation, lower life cycle cost, fault current limiting capability, lower environmental pollution and lower risk potential against fire hazards.In this thesis, optimal design of flux diverter using genetic algorithm for axial short circuit force reduction in HTS transformers has been performed. Then, multilayered flux diverters have been proposed for reduction of weight and losses. The impact of...

A Multi-Objective Robust Optimization Model for Logistics Planning in the Earthquake Response Phase [electronic resource]

, Article Transportation Research Part E: Logistics and Transportation Review, Elsevier ; Volume 49, Issue 1, January 2013, , Pages 217–249 Najafi, M. (Mehdi) ; Eshghi, Kourosh ; Dullaert, Wout ; Sharif University of Technology

Abstract

Usually, resources are short in supply when earthquakes occur. In such emergency situations, disaster relief organizations must use these scarce resources efficiently to achieve the best possible emergency relief. This paper therefore proposes a multi-objective, multi-mode, multi-commodity, and multi-period stochastic model to manage the logistics of both commodities and injured people in the earthquake response. Also, a robust approach is developed and used to make sure that the distribution plan performs well under the various situations that can follow an earthquake. Afterwards, it proposes a solution methodology according to hierarchical objective functions and uses it to illustrate the...

Monitoring of Valve Leakage in Internal Combustion Engine Using Acoustic Emission Method

, Ph.D. Dissertation Sharif University of Technology Jafari, Mohammad (Author) ; Behzad, Mehdi (Supervisor) ; Mehdigholi, Hamid (Supervisor) ; Ahmadi, Mohammad Mehdi (Co-Advisor)

Abstract

Valve leak detection is very important due to bad direct effects on parts life and engine power. Acoustic emission (AE) has a good known ability on leak detection between fault detection methods. The aim of this thesis is presenting the ability of AE method for valve leak detection in internal combustion engines. The research method in a general framework based on the idea that firstly some evaluations were done in static tests for leakage due to three faults including clearance, quasi-crack and notch. Then, the evaluations were continued with dynamic analysis of rotational speeds and different loads on the engine. Finally, the neural network approach was used to automatically detect all...

Evaluation of Electromagnetic Forces on three-phase Core-Type Power Transformer Windings during Inrush Current by FEM

, M.Sc. Thesis Sharif University of Technology Eslami, Ali (Author) ; Vakilian, Mehdi (Supervisor)

Abstract

Inrush Current is a form of over-current that occurs during energization of a transformer. For power transformers, the magnitude of the first peak of inrush current is initially several times the rated load current but slowly decreases until it finally reaches the normal exciting current value. This process typically takes several minutes. Time-variant axial and radial electromagnetic forces under inrush current and short-circuit current are calculated (by finite element method; FEM), and compared. An analytic method is presented for computation of inrush current in transformer. The simulation results obtained by this proposed method are compared with the measured values. A compact...