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mehrafrooz--behzad
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Mechanical differences between ATP and ADP actin states: A molecular dynamics study
, Article Journal of Theoretical Biology ; Volume 448 , 2018 , Pages 94-103 ; 00225193 (ISSN) ; Shamloo, A ; Sharif University of Technology
Academic Press
2018
Abstract
This paper aims to give a comprehensive atomistic modeling of the nanomechanical behavior of actin monomer. Actin is a ubiquitous and essential component of cytoskeleton which forms many different cellular structures. Despite for several years great effort has been devoted to the investigation of mechanical properties of the actin filament, studies on the nanomechanical behavior of actin monomer are still lacking. These scales are, however, important for a complete understanding of the role of actin as an important component in the cytoskeleton structure. Based on the accuracy of atomistic modeling methods such as molecular dynamics simulations, steered molecular dynamics method is performed...
Dynamic analysis of an n-revolute planar serial manipulator and sensitivity analysis based on Sobol's method
, Article International Conference on Robotics and Mechatronics, ICROM 2015, 7 October 2015 through 9 October 2015 ; 2015 , Pages 569-574 ; 9781467372343 (ISBN) ; Mohammadi, M ; Masouleh, M. T ; Sharif University of Technology
2015
Abstract
In this paper, dynamic modeling and dynamic sensitivity analysis of an n-revolute planar serial robot are investigated. First, a dynamic modeling algorithm is proposed which is based on the concept of the so-called Natural Orthogonal Complement. The main goal of this algorithm consists in deriving the corresponding dynamic equations of a planar serial manipulator systematically. As a comparison study, 3-DOF a planar serial manipulator is modeled and the results of the proposed algorithm is compared with other methods, i.e., Newton-Euler, Lagrange-Euler, Adams software and an Open Dynamics Engine, the so-called MatODE. Then, in order to develop a dynamic sensitivity analysis scheme, Sobol's...
Molecular Dynamics Simulation of Actin: An Investigation into the Mechanical Properties
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor) ; Firoozbakhsh, Keikhosrow (Supervisor)
Abstract
Actin is the most abundant protein in most eukaryotic cells. It is highly conserved and participates in more protein-protein interactions than any known protein. Actin plays a crucial role in cell motility, adhesion, morphology and intracellular transport. Its biologically active form is the filament (F-actin), which is assembled from monomeric G-actin. In this thesis, the mechanical properties and characteristics of both G- and F-actin are studied using molecular dynamics simulations. In general, this thesis can be categorized into two individual parts: First, steered molecular dynamics simulation was performed to assess tension of monomeric G-actin molecule, and stress-strain curves were...
Workload-Aware Task Assignment in Real-time Fog-based Systems
, M.Sc. Thesis Sharif University of Technology ; Ejlali, Alireza (Supervisor) ; Ansari, Mohsen (Co-Supervisor)
Abstract
Cloud computing has provided a suitable platform for processing and storing Internet of Things data over the last few decades by establishing data centers with high processing power. Today, with the rise of real-time processing applications in the Internet of Things, such as voice assistants, smart health controls, and self-driving cars, the number of real-time tasks has increased rapidly; this is despite the fact that cloud servers cannot meet the deadline constraint due to physical distance delays. To address this challenge, Fog computing has been introduced. By moving computational and storage resources closer to the edge of the network, fog computing enables executing real-time tasks...
Vibration Analysis of Edge Cracked Timoshenko Beam with Continuous Crack Model
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
Structural defects such as cracks may be produced in structures and machineries under fatigue load operating conditions. The presence of crack can lead to catastrophic failures in certain conditions. The occurrence of cracks affects the dynamic and vibration behavior of the structure considerably. These vibrations can be used for identifying the cracks and appropriate actions can be taken to prevent more damage to the system. Therefore, in this thesis vibration analysis of a Timoshenko beam with a vertical and horizontal crack has been considered. A continuous model for vibration analysis of a beam with an open edge crack including the effects of shear deformation and rotary inertia has been...
Setar Production Modification With Vibration Analysis
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
Setar is a traditional Persian musical instrument. Nowadays, Setar is one of the most common musical instruments in Persian music. A systematic method for Setar production modification has not been introduced yet. This work is the first scientific work about analysis of this instrument. The aim of this study is to undertake early steps for Setar quality improvement. In this thesis, after analysis of the wood using in Setar construction, numerical and experimental methods have been utilized to analyze this instrument. After that, some works has been performed to extract an objective function which can judge about Setar quality. The results show good agreement between experimental and...
Fault Detection of Rotary System with Signal Processing and Intelligent Systems
, M.Sc. Thesis Sharif University of Technology ; 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...
Analytical and Finite Element Modeling of Rubbing Phenomena in Rotors
, M.Sc. Thesis Sharif University of Technology ; 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...
A Locality Aware P2P Overlay Architecture for Video Streaming
, M.Sc. Thesis Sharif University of Technology ; 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...
Traffic Engineering In Cloud Infrastructure By Software Defined Networks
, M.Sc. Thesis Sharif University of Technology ; Akbari, Behzad (Supervisor)
Abstract
In the recent years, cloud data center issues have been the center of attention. Also for them topologies with multi paths between end hosts are offered. For use of multi path traffic engineering is essential. Researches show congestion occurred in the cloud data center networks, because the mean of link utilization is down. This means, some of links are congested while there are some other with much available bandwidth. Currently, the most common method is Equal Cost Multipath (ECMP) algorithm for routing flows in the data center network. ECMP decides on routing without any attention to network congestion condition. There, may be two big flows placed in the one path and it causes creation...
Development of a Three Layer Model for Simulating Transient Behavior Cutting Transport in Extended-reach Well
, Ph.D. Dissertation Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
A major concern in directional well drilling is the transport mechanism of cuttings by drilling fluid. This thesis describes the effect of angular velocity and postbuckled vibrations of drillstring on cuttings transport in a directional well drilling. The analysis proceeds in two stages. First, a finite element model is used to predict the dynamic behavior of postbuckled drillstring inside a directional well. Second, a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach to simulate the cuttings transport considering the dynamic collision process. In the combined computational fluid dynamics and discrete element method (CFD-DEM), the fluid phase is treated...
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) ; 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
Experimental and Numerical Investigation on the Hydrodynamic Properties of Heave Plates in Translational and Rotational Oscillations
, Ph.D. Dissertation Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
Many offshore platforms as TLP, Semi-submersible and Spar are used for oil extraction and energy harvesting. One of the challenges of these structures is related to vibrations due to the environmental sea waves and wind loads. The optimal way for the response reduction of an offshore structure in heave direction is the installing of thin heave plate. The heave plate induces vortex shedding and pressure drop on fluid flow downstream. Diameter difference of heave plates in an array can improve the obtained damping and added mass for a given small spacing between plates, which has not been studied up to now. Hence, in the present thesis it was observed that converting of the uniform to...
Application of SPM for Fault Detection and RUL Estimation; Comparison with Vibration Analysis
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
Rolling element bearings (REBs) are one of the most critical components in rotating ma-chines. Failure of these components may lead to fatal and costly breakdowns in rotating machinery. Therefore, it is significant to detect faults at early stage accurately. The pur-pose of this study is to compare vibration analysis and shock pulse method (SPM) in early detection of fault and remaining useful life prediction of REBs. To the aim, a set of ac-celerated life tests on REBs was planned. Vibration and shock pulse values accelerated life tests of the REBs were simultaneously measured from the moment of start to the end of the failure by two vibration and shock pulse sensors and their changes were...
Modeling and Predicting the Residual Life of Roller Bearings under Variable-Velocity Radial Loading Using Vibration Analysis and Neural Network
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
The main objective of this research is to predict the life of a bearing that works in variable speed working condition. In this project, two series of experiments were conducted to investigate the vibration of the bearings. In the first series of experiments, multiple imperfections have been created on parts of the bearing that are susceptible including the inner ring, the outer ring and the balls. The results of this test have been used to study the importance of speed compared to other parameters in increasing the vibration levels of the bearing. In addition, the results of this experiment have been used as inputs to a neural network. This neural network is trained to classify bearing...
Friction-induced backward rub of rotors in non-annular clearances: Experimental observations and numerical analysis
, Article Tribology International ; Volume 152 , 2020 ; 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...
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) ; 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...
Identification of Vibrational Characteristic of System under Colored Excitation base on the Transmissibility Functions
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
Operational modal analysis (OMA) techniques are proper methods to identify the modal parameters of the structures such as natural frequencies, damping ratios and mode shapes based on the system responses. First research in this area are stared from civil engineering. Difference between civil structure and industrial machines are in the type of excitation.in most industries such as aerospace or mechanical, colored or harmonic forces due to rotary machines, excited the system. Under this condition, traditional methods in OMA are not capable any more. Many works has been done to modify traditional methods. Most of these work limited to situations that forces are harmonic and harmonic...
Condition Monitoring of CNG Electrocompressors
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mahdi (Supervisor)
Abstract
In order to increase the service life and prevent the breakdown of apparatuses, instalations and equipments, we are in a position to maintain them. In this regard, there are three methods for maintenance of machineries, which are called reaction maintenance, preventive maintenance and predictive maintenance. By carrying out a predictive method or monitoring the situation, it is possible to know the health of the machine and take the necessary measures before the damages occurs. Vibration analysis, temperature analysis, oil analysis and flow analysis can be used for monitoring the situation. Reciprocating compressors are one of the most costly repair equipment that needs to be monitored...
Unbalance-induced rub between rotor and compliant-segmented stator
, Article Journal of Sound and Vibration ; Volume 429 , 2018 , Pages 96-129 ; 0022460X (ISSN) ; 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...