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Power quality survey in a distribution system, standard procedures and limitations
, Article Renewable Energy and Power Quality Journal ; Volume 1, Issue 5 , 2007 , Pages 460-464 ; 2172038X (ISSN) ; Hasani, S ; Masoudi, M ; Sharif University of Technology
European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ)
2007
Abstract
This paper presents the results of a power quality survey in a distribution system. More than fifty nodes are selected and monitored. Power quality indices are extracted based on IEEE and IEC Standards. The evaluation includes field data collection, extraction of statistical power quality indices and comparing the results against standard limits. Experimental data as well as clarifying tables and graphs are presented. The results are then discussed to evaluate the strength and weaknesses of applying standard limits when real observations are to be performed. Some proposals are also made in order to make standard procedures and limits more effective based on practical observations. © 2007,...
Topological spin liquids in the ruby lattice with anisotropic Kitaev interactions
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 94, Issue 12 , 2016 ; 10980121 (ISSN) ; Kargarian, M ; Masoudi, S. F ; Langari, A ; Sharif University of Technology
American Physical Society
2016
Abstract
The ruby lattice is a four-valent lattice interpolating between honeycomb and triangular lattices. In this work we investigate the topological spin-liquid phases of a spin Hamiltonian with Kitaev interactions on the ruby lattice using exact diagonalization and perturbative methods. The latter interactions combined with the structure of the lattice yield a model with Z2×Z2 gauge symmetry. We mapped out the phase diagram of the model and found gapped and gapless spin-liquid phases. While the low-energy sector of the gapped phase corresponds to the well-known topological color code model on a honeycomb lattice, the low-energy sector of the gapless phases is described by an effective spin model...
Using three-dimensional finite element analysis for simulation of residual stresses in railway wheels
, Article Engineering Failure Analysis ; Vol. 45, issue , October , 2014 , p. 449-455 ; Sharif University of Technology
2014
Abstract
One of the most important issues in railway wheels is residual stresses. It is desirable to produce less residual stresses when possible and to decrease the remaining residual stresses in the wheels. The objective of this paper is to provide an estimation of the residual stresses in the rail wheel caused by the stress field from heat treatment process of a railway wheel. A three-dimensional nonlinear stress analysis model has been applied to estimate stress fields of the railway mono-block wheel in heat treatment process. After forging or casting, railway wheels are heat-treated to induce the desirable circumferential compressive residual stress in the upper rim. Finite element analysis...
Exact analysis of level-crossing statistics for (d+1)-dimensional fluctuating surfaces
, Article Journal of Statistical Physics ; Volume 124, Issue 6 , 2006 , Pages 1471-1490 ; 00224715 (ISSN) ; Movahed, M. S ; Nasiri, S. D ; Masoudi, A. A ; Sahimi, M ; Sharif University of Technology
2006
Abstract
We carry out an exact analysis of the average frequency ν+ αxi in the direction x i of positiveslope crossing of a given level α such that, h(x, t) h = α, of growing surfaces in spatial dimension d. Here, h(x, t) is the surface height at time t, and h is its mean value. We analyze the problem when the surface growth dynamics is governed by the Kardar-Parisi-Zhang (KPZ) equation without surface tension, in the time regime prior to appearance of cusp singularities (sharp valleys), as well as in the random deposition (RD) model. The total number N + of such level-crossings with positive slope in all the directions is then shown to scale with time as t d/2 for both the KPZ equation and the RD...
Level crossing analysis of the stock markets
, Article Journal of Statistical Mechanics: Theory and Experiment ; Issue 6 , 2006 ; 17425468 (ISSN) ; Movahed, M. S ; Fazeli, S. M ; Rahimi Tabar, M. R ; Masoudi, S. F ; Sharif University of Technology
2006
Abstract
We investigate the average frequency of positive slope ν α+ crossing for the returns of market prices. The method is based on stochastic processes in which no scaling feature is explicitly required. Using this method we define a new quantity to quantify the stage of development and activity of stock exchanges. We compare the Tehran and western stock markets and show that some, such as the Tehran (TEPIX) and New Zealand (NZX) stock exchanges, are emerging, and also that TEPIX is a non-active market and is financially motivated to absorb capital. © 2006 IOP Publishing Ltd. and SISSA
Intermittency of height fluctuations in stationary state of the Kardar-Parisi-Zhang equation with infinitesimal surface tension in 1+1 dimensions
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 70, Issue 3 1 , 2004 , Pages 031101-1-0311011-3 ; 15393755 (ISSN) ; Bahraminasab, A ; Masoudi, A. A ; Mousavi, S. S ; Tabar, M. R. R ; Sharif University of Technology
2004
Abstract
Intermittency of height fluctuations in stationary state of the Kardar-Parisi-Zhang (KPZ) equation with infinitesimal surface tension in 1+1 dimensions was discussed. Stochastic differential equations were used for the study. It was found that the probability density function [in 1+1] is independent of the coefficient of the linear term. When the random force with smooth spatial correlation was considered, the problem changed to a more complicated one
Intermittency of height fluctuations in stationary state of the Kardar-Parisi-Zhang equationwith infinitesimal surface tension in [Formula presented] dimensions
, Article Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics ; Volume 70, Issue 3 , 2004 , Pages 13- ; 1063651X (ISSN) ; Bahraminasab, A ; Masoudi, A. A ; Mousavi, S. S ; Reza Rahimi Tabar, M ; Sharif University of Technology
2004
Abstract
The Kardar-Parisi-Zhang (KPZ) equation with infinitesimal surface tension, dynamically develops sharply connected valley structures within which the height derivative is not continuous. We discuss the intermittency issue in the problem of stationary state forced KPZ equation in [Formula presented] dimensions. It is proved that the moments of height increments [Formula presented] behave as [Formula presented] with [Formula presented] for length scales [Formula presented]. The length scale [Formula presented] is the characteristic length of the forcing term. We have checked the analytical results by direct numerical simulation. © 2004 The American Physical Society
Large deformation finite element modeling of rubble mound breakwater built on soft seabed using coupled eulerian–lagrangian method
, Article Indian Geotechnical Journal ; Volume 51, Issue 2 , 2021 , Pages 315-328 ; 09719555 (ISSN) ; Shahir, H ; Pak, A ; Sharif University of Technology
Springer
2021
Abstract
For the design of rubble mound breakwaters on soft soil, it is essential to predict the behavior of soft soil and large deformations phenomena occurring in the course of construction of the rubble mound breakwater. Large deformations in various problems can be well simulated using the coupled Eulerian–Lagrangian (CEL) method. In this study, the CEL method has been used to simulate the rubble mounds construction on soft soil and predict the resulting settlements. To validate the numerical model, the results of three experiments conducted in the physical modeling laboratory at Kharazmi University were used. Also, two case studies of real rubble mound breakwaters constructed on soft seabeds...
Rolling Contact Fatigue under Influence of Residual Stresses
, M.Sc. Thesis Sharif University of Technology ; Farahi, Gholamhossin (Supervisor)
Abstract
Rolling contact fatigue (RCF) phenomena is important in reducing the fatigue life and increasing the cost of maintenance. Accurate prediction of crack growth on wheels and the influence of residual stresses by FEM modeling can affect the maintenance planning. Therefore, investigation of rolling contact fatigue and its effect on rolling members life seem necessary. The first step to solve a rolling contact fatigue problem is the residual stress determination. In this research, wheel/rail contact is assumed. A bandage wheel with accurate geometry using finite element method is studied. For this purpose, a 3D elastic-plastic finite element model in ANSYS is conducted using model. The...
The Impact of Temperature on Surface Activity and Stability of Surface Modified Nano Particles
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor)
Abstract
Surface modification is an important property of nano particles. In this project surface of silica nano particles modified with hydrophobic and hydrophilic groups to imrprove surface activity of nano particles. Purpose of this project is to study surface activity of surface modified silica nano particles in different temperatures from 20 to 70 degree centigrade. Also effect of salt and time on the surface activity is studied. At first nano particles modified just with haydrophobic groups and then just with hydrophilic groups (hydrophobic and hydrophilic nano particles) and after that, the surface modification done with both hyadrophilic and hydrophobic groups (amphiphilic nanoparticles)....
Exploring cognitive activation writing strategies among iranian english language teachers
, Article Language Related Research ; Volume 12, Issue 5 , 2021 , Pages 433-462 ; 23223081 (ISSN) ; Hassanzadeh, M ; Masoudi, M ; Sharif University of Technology
Tarbiat Modares University
2021
Abstract
In order to engage students in higher-level thinking, cognitive activation (CA) strategies have been advanced and utilized in mathematics. CA develops when learners are challenged, confronted with conflicts, asked to think and explain clearly on their learning, and realize connections between new and previous content. Extending the theme to English language teaching (ELT), this study investigated Iranian English language teachers‟ knowledge and practice of cognitive activation writing strategies (CAWS). In so doing, a model was proposed based on a questionnaire that was developed and validated in the present study. Through this scale, knowledge and practice of CAWS by 213 English as a...
Exploring cognitive activation writing strategies among iranian english language teachers
, Article Language Related Research ; Volume 12, Issue 5 , 2021 , Pages 433-462 ; 23223081 (ISSN) ; Hassanzadeh, M ; Masoudi, M ; Sharif University of Technology
Tarbiat Modares University
2021
Abstract
In order to engage students in higher-level thinking, cognitive activation (CA) strategies have been advanced and utilized in mathematics. CA develops when learners are challenged, confronted with conflicts, asked to think and explain clearly on their learning, and realize connections between new and previous content. Extending the theme to English language teaching (ELT), this study investigated Iranian English language teachers‟ knowledge and practice of cognitive activation writing strategies (CAWS). In so doing, a model was proposed based on a questionnaire that was developed and validated in the present study. Through this scale, knowledge and practice of CAWS by 213 English as a...
, M.Sc. Thesis Sharif University of Technology ; Shamsollahi, Mohammad Bagher (Supervisor)
Abstract
Apnea-bradycardia is a medical term for prolonged respiratory pause accompanied with a heart rate reduction which is a common event among preterm infants. Repetition of apnea-bradycardia episodescompromises oxygenation and tissue perfusion and may lead to neurological impairment or even short-term morbi-mortality. Main solution to this breathing-related disorder is continues monitoring of infants in neonatal intensive care units in order to detect apnea-bradycardia event, generate an alarm and warn available nurse or physician to initiate quick nursing actions. Various studies have been done in this area and different methods are proposed which mainly focus on cardiac signal processing. This...
Nonlinear Buckling Optimization in Laminated Composite Plate Using Genetic Algorithm
, M.Sc. Thesis Sharif University of Technology ; Kouchakzadeh, Mohammad Ali (Supervisor)
Abstract
Designing structures made from composite materials is challenging due to the need to select the thickness, number of layers, and fiber orientations. By carefully choosing the lamination sequence, the desired properties can be optimized. Buckling is one of the most critical phenomena in the stability analysis of a structure, as it can lead to failure before the structure reaches its yield point. This thesis investigates the layer configuration of laminated composite plates using a genetic algorithm to maximize the nonlinear buckling critical load. In this approach, the nonlinear behavior of the structure is analyzed up to the critical point, and a genetic algorithm is used to find the global...
Zero tension Kardar-Parisi-Zhang equation in (d + 1)-dimensions
, Article Journal of Statistical Physics ; Volume 116, Issue 5-6 , 2004 , Pages 1521-1544 ; 00224715 (ISSN) ; Tabei, S. M. A ; Masoudi, A. A ; Shahbazi, F ; Rahimi Tabar, M. R ; Sharif University of Technology
2004
Abstract
The joint probability distribution function (PDF) of the height and its gradients is derived for a zero tension d + 1-dimensional Kardar-Parisi-Zliang (KPZ) equation. It is proved that the height's PDF of zero tension KPZ equation shows lack of positivity after a finite time tc. The properties of zero tension KPZ equation and its differences with the case that it possess an infinitesimal surface tension is discussed. Also potential relation between the time scale tc and the singularity time scale tc,v→0 of the KPZ equation with an infinitesimal surface tension is investigated. © 2004 Springer Science+Business Media, Inc
Avrami behavior of magnetite nanoparticles formation in co-precipitation process
, Article Journal of Mining and Metallurgy, Section B: Metallurgy ; Volume 47, Issue 2 , 2011 , Pages 211-218 ; 14505339 (ISSN) ; Hosseini, H. M. R ; Masoudi, A ; Sharif University of Technology
2011
Abstract
In this work, magnetite nanoparticles (mean particle size about 20 nm) were synthesized via coprecipitation method. In order to investigate the kinetics of nanoparticle formation, variation in the amount of reactants within the process was measured using pH-meter and atomic absorption spectroscopy (AAS) instruments. Results show that nanoparticle formation behavior can be described by Avrami equations. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were performed to study the chemical and morphological characterization of nanoparticles. Some simplifying assumptions were employed for estimating the nucleation and growth rate of magnetite nanoparticles
A new approach for touching cells segmentation
, Article BioMedical Engineering and Informatics: New Development and the Future - 1st International Conference on BioMedical Engineering and Informatics, BMEI 2008, Sanya, Hainan, 27 May 2008 through 30 May 2008 ; Volume 1 , 2008 , Pages 816-820 ; 9780769531182 (ISBN) ; Mirsafian, A ; Masoudi Nejad, A ; Sharif University of Technology
2008
Abstract
Automatic cell segmentation has various applications in different parts of science. The development of automated methods for cell segmentation, remains challenging in situations where there are touching cells. In this paper we propose a new method for separating touching cells. As the first step, we use a combination of graph segmentation algorithm and thresholding for segmenting foreground objects and producing a binary image. Next, boundary points of separation zone are selected by using a corner detection algorithm. Finally, the marker controller watershed transform is applied to separate touching cells at selected points. © 2008 IEEE
Power quality standards and their application to a granite factory
, Article 2006 International Conference on Power Electronics, Drives and Energy Systems, PEDES '06, New Delhi, 12 December 2006 through 15 December 2006 ; 2006 ; 078039772X (ISBN); 9780780397729 (ISBN) ; Donyavi, F ; Masoudi, M ; Mokhtari, H ; Sharif University of Technology
2006
Abstract
This paper presents the results of a thorough analysis of applying power quality standards to a granite factory. It explains the procedure of determining power quality indices in a power system. The paper presents the field data and provides the results of statistical analysis in order to extract power quality indices. A comparison against standard limits is also given. The case study gives an overview of power quality in such customers and brings up some practical limitations when applying power quality standards. ©2006 IEEE
Kierkegaardian Faith: On The Subject of Faith and Her Hope
, M.Sc. Thesis Sharif University of Technology ; Sefidkhoh, Meisam (Supervisor) ; Azadegan, Ebrahim (Supervisor)
Abstract
In this treatise, it will be shown that the subject of faith is the subject who loves God and in showing her love to God, she sacrifices her dearest things in the world. By doing that, she would free herself from everything that mind herself. She doesn’t do this action to be given a better reward by God. Her motivation for performing this action is nothing but love. Meanwhile, the subject of faith hopes God to respond to her love and engage in an I-Thou relationship with her. Now, her hope would be justified when God plays an active role in the world and admires her action, i.e., when eros can be attributed to God
Long-term investigation on the phase stability, magnetic behavior, toxicity, and MRI characteristics of superparamagnetic Fe/Fe-oxide core/shell nanoparticles
, Article International Journal of Pharmaceutics ; Volume 439, Issue 1-2 , 2012 , Pages 28-40 ; 03785173 (ISSN) ; Madaah Hosseini, H. R ; Seyed Reyhani, S. M ; Shokrgozar, M. A ; Oghabian, M. A ; Ahmadi, R ; Sharif University of Technology
2012
Abstract
To efficiently enhance the contrast obtaining from magnetic resonance imaging (MRI), pharmaceutical grade colloidal dispersions of PEG coated iron-based nanoparticles were prepared and compared to conventional pure iron oxide contrast agent. In this study, we synthesized ∼14 nm iron nanoparticles via NaBH4 reduction of iron(III) chloride in an aqueous medium. The resulting nanoparticles were further oxidized by two different methods via (CH3)3NO oxygen transferring agent and exposure to oxygen flow. XRD and electron microscopy analyses confirmed the formation of a second layer on the surface of α-Fe core. As magnetic measurements and Mössbauer spectra of 4-months post prepared nanoparticles...