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...

A new method for detection of rolling bearing faults based on the Local Curve Roughness approach

, Article Polish Maritime Research ; Volume 18, Issue 2 , July , 2011 , Pages 44-50 ; 12332585 (ISSN) Behzad, M ; Bastami, A ; Sharif University of Technology

2011

Abstract

Detection of rolling bearing faults by vibration analysis is an important part of condition monitoring programs. In this paper a new method for detection of bearing defects based on a new concept of local surface roughness, is proposed. When a defect in the bearing grows then roughness of the defective surface increases and measurement of the roughness can be a good indicator of the bearing defect. In this paper a method of indirectly measuring surface roughness by using vibration signal is introduced. Several attached examples including both numerically simulated signals and actual experimental data show the effectiveness of the new, easy-to-implement method

Numerical and experimental investigation of the vibration of rotors with loose discs

, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 224, Issue 1 , 2010 , Pages 85-94 ; 09544062 (ISSN) Behzad, M ; Asayesh, M ; Sharif University of Technology

2010

Abstract

In this study, the energy method has been used to develop a finite-element code for studying the effects of loose rotating discs on the rotor-bearing systems' response. A mathematical model of the loose disc has resulted in terms similar to unbalance and gyroscopic effects in the equation of motion of the system. Results of this study show that rotor response and beating phenomena are a function of measurement location, loose disc mass and inertia, ratio of rotating speed to the speed of loose disc, and clearance between the loose disc and shaft considering constant speed for loose disc and shaft. The developed finite-element model can numerically give the response of rotors with any number...

Friction-induced backward rub of rotors in non-annular clearances: Experimental observations and numerical analysis

, Article Tribology International ; Volume 152 , 2020 Behzad, M ; Alvandi, M ; Sharif University of Technology

Elsevier Ltd 2020

Abstract

During backward rub in a turbomachine, rotor is compelled by frictional forces into a severe precessional sliding motion inside stationary parts such as seals or journal bearings in opposite direction of rotor's rotation. Backward rub occurs with high frequency and high amplitude of vibration and can deteriorates rubbing surfaces just for few moments. This paper presents and investigates the idea of clearance profile alteration from annular form to non-annular 3-lobed form in order to affect the reverse rub's characteristics. For this purpose, a test setup consisting of a lightly damped rotor-stator system is designed and built in SUT's condition-monitoring laboratory for testing the...

Unbalance-induced rub between rotor and compliant-segmented stator

, Article Journal of Sound and Vibration ; Volume 429 , 2018 , Pages 96-129 ; 0022460X (ISSN) Behzad, M ; Alvandi, M ; Sharif University of Technology

Academic Press 2018

Abstract

Today, turbomachinery designers are trying to attain zero clearances for optimizing performance and efficiency of machine by designing advanced compliant-segmented seals. This trend involves secondary issues such as rotor-to-stator contact interaction which is to be treated with more technical knowledge in rotordynamic design and condition monitoring programs. The aim of this paper is to gain insight into dynamic interaction between a flexible rotor and a set of compliant arc-shaped segments as stator system. Specifically, the unbalanced-induced forward rubbing response is investigated in tight clearance condition during resonance-passing situations. A Jeffcott rotor modeling is used for...

Experimental investigation on response and efficiency of moored pontoon type floating breakwaters

, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 31, Issue 1 , 2007 , Pages 95-99 ; 03601307 (ISSN) Behzad, M ; Akbari, M ; Sharif University of Technology

2007

Abstract

This paper presents the experimental results of an investigation on the response and efficiency of floating pontoon type breakwaters. Random waves modeled by the Pierson Moskowits wave spectrum are used for various configurations of floating breakwaters. The experimental results are presented in graphs for the transmission coefficient as a function of incident wave length and height for breakwaters used in this study. The obtained results for the breakwaters of this study show that by increasing the wave period and length, the transmission coefficient increases, while increase in the mass and draft of the floating breakwater causes the transmission coefficient to reduce. © Shiraz University

Fault Detection of Rotary System with Signal Processing and Intelligent Systems

, M.Sc. Thesis Sharif University of Technology Tebyanian, Afshin (Author) ; Behzad, Mehdi (Supervisor)

Abstract

Condition monitoring and fault detection is an important way to provide economy in both time and costs. Many methods are developed for this purpose. Vibration analysis is one of the most important ways in this field. In this thesis, fault detection of mechanical rotary systems with nonlinear and non-stationary nature has been developed by use of empirical mode decomposition (EMD) and Hilbert transform. Firstly the measured signal is transformed into some intrinsic mode functions (IMF’s) by EMD, and then the Hilbert transform is implemented on each IMF. With Hilbert transform, the instantaneous frequency of system and then the mean frequency are obtained. Mean frequency is a key definition...

Investigation of Magnetodielectric Resonator Antenna Including Gyroteropic Properties of Material

, M.Sc. Thesis Sharif University of Technology Naghdi, Behnam (Author) ; Rejaei, Behzad (Supervisor)

Abstract

So far, investigations have shown that open dielectric resonator antennas (DRAs) offer several advantages at microwave and millimeter wave frequencies. These advantages include small size, large impedance bandwidth, high radiation efficiency, ease of manufacturing and simple feed-coupling mechanisms (such as probe coupling, aperture coupling or proximity coupling to micro-strip lines). Most microwave ferrites have dielectric constants in the desirable range and they can be used in place of dielectric materials. Such ferrite resonator antennas (FRAs) offer a potential advantage in that their permeability tensor can be controlled by applying an external magnetic field. Up to now and by the...

A Locality Aware P2P Overlay Architecture for Video Streaming

, M.Sc. Thesis Sharif University of Technology Bayat, Navid (Author) ; Akbari, Behzad (Supervisor)

Abstract

Internet video networks have already attracted millions of Internet users, and Internet video is one of the fast growing Internet services. The peer-to-peer (P2P) network is an efficient solution to supporting large scale video streaming on the Internet. P2P networks can deliver live multimedia content to millions of users with low cost at any time, and at anywhere they want. In this thesis, we investigate solutions to enhancing the performance of the unstructured mesh-based. Locality awareness or network proximity is one of the essential characteristics of P2P networks. In live P2P video streaming we face to some challenges like bandwidth heterogeneity of peers, and peer churn. In the P2P...

Condition Monitoring and Fault Diagnosis of Rolling Element Bearing in Phase Space

, M.Sc. Thesis Sharif University of Technology Karimi, Majid (Author) ; Behzad, Mehdi (Supervisor)

Abstract

The failure in rolling element bearings as an important part of rotary machine can lead to machine breakdown.Consequently, bearings can reduce reliability of these components and therefore a maintenance strategy is essential to keep reliability in a desired level. The first and primitive strategy is called breakdown or unplanned maintenance. The next is preventive or planned maintenance. In this scheme, maintenance is done after a specified time period irrespective of machine health status. Out of place maintenance is the disadvantage of preventive maintenance. The most effective generation of maintenance strategy is condition based maintenance (CBM) which suggests maintenance decision based...

Analytical and Finite Element Modeling of Rubbing Phenomena in Rotors

, M.Sc. Thesis Sharif University of Technology Alvandi, Mahdi (Author) ; Behzad, Mahdi (Supervisor)

Abstract

Rotor contact with a stationary element of a rotating machine and the subsequent rubbing at the contact area is a serious malfunction that may lead to the machine’s catastrophic failure. In the past decades, many studies have been done on the rubbing phenomena, its different regimes and its various consequences on the machine performance and safety. However, most of them have used a simple model to investigate the rubbing interaction between the rotor and the stator. This simple model consists of the Jeffcott rotor, as a model for the real rotors, and a rigid annular block surrounding the rotor, as a model for the real stators. The objective of this thesis is to build an algorithm to...

Vibration Isolation of One Degree of Freedom Systems by Magnetorheological (MR) Damper Under Random Excitation

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

Abstract

The effect of Vibration on the human body is considered as one of the limitations in design and use of HSCs at high speeds. One way to reduce the effect of vibration on the human body is to isolate deck vibrations from the crew by means of seat suspension system. This thesis has studied the effect of using an MR damper on the performance of seat suspension in vibration reduction. In fact, employing MR dampers in seat suspension systems enables us to change their damping. Using an MR damper makes it possible to control seat suspension by semi active control strategies. In this work, a number of proposed mathematical models of an MR damper were studied for numerical analysis and the most...