Esmaeili F.,Islamic Azad University at Tabriz |
Rahmani A.,Islamic Azad University at Ajabshir |
Barzegar S.,University of Tabriz |
Afkar A.,Standard Automotive
Materials and Design | Year: 2015
In this paper, the effects of weld arrangement on the fatigue behavior of the multi-spot welded joints have been investigated via experimental and multiaxial fatigue analysis. To do so, three sets of the spot welded specimens with different arrangements were prepared and fatigue tests were conducted under the various cyclic loads. Experimental tests revealed that the spot welded arrangement effect has a considerable role in fatigue strength of multi-spot welded joints. A nonlinear finite element code was used to obtain the stress and strain distributions near the roots of the nuggets for the three kinds of the specimens. Fatigue lives of the specimens were predicted by means of six different multiaxial fatigue criteria using the local stress and strain values obtained from the finite element simulations. It was found that the SWT and Crossland criteria have the best accuracy for all types of the specimens among the applied criteria. © 2015 Elsevier Ltd.
Safaei B.,Islamic Azad University at Tehran |
Naseradinmousavi P.,San Diego State University |
Rahmani A.,Islamic Azad University at Ajabshir
Journal of Molecular Graphics and Modelling | Year: 2016
In the present paper, an analytical solution based on a molecular mechanics model is developed to evaluate the elastic critical axial buckling strain of chiral multi-walled carbon nanotubes (MWCNTs). To this end, the total potential energy of the system is calculated with the consideration of the both bond stretching and bond angular variations. Density functional theory (DFT) in the form of generalized gradient approximation (GGA) is implemented to evaluate force constants used in the molecular mechanics model. After that, based on the principle of molecular mechanics, explicit expressions are proposed to obtain elastic surface Young's modulus and Poisson's ratio of the single-walled carbon nanotubes corresponding to different types of chirality. Selected numerical results are presented to indicate the influence of the type of chirality, tube diameter, and number of tube walls in detailed. An excellent agreement is found between the present numerical results and those found in the literature which confirms the validity as well as the accuracy of the present closed-form solution. It is found that the value of critical axial buckling strain exhibit significant dependency on the type of chirality and number of tube walls. © 2016 Published by Elsevier Inc.
PubMed | San Diego State University, Islamic Azad University at Ajabshir and Islamic Azad University at Tehran
Type: | Journal: Journal of molecular graphics & modelling | Year: 2016
In the present paper, an analytical solution based on a molecular mechanics model is developed to evaluate the elastic critical axial buckling strain of chiral multi-walled carbon nanotubes (MWCNTs). To this end, the total potential energy of the system is calculated with the consideration of the both bond stretching and bond angular variations. Density functional theory (DFT) in the form of generalized gradient approximation (GGA) is implemented to evaluate force constants used in the molecular mechanics model. After that, based on the principle of molecular mechanics, explicit expressions are proposed to obtain elastic surface Youngs modulus and Poissons ratio of the single-walled carbon nanotubes corresponding to different types of chirality. Selected numerical results are presented to indicate the influence of the type of chirality, tube diameter, and number of tube walls in detailed. An excellent agreement is found between the present numerical results and those found in the literature which confirms the validity as well as the accuracy of the present closed-form solution. It is found that the value of critical axial buckling strain exhibit significant dependency on the type of chirality and number of tube walls.
Kisi O.,Erciyes University |
Shiri J.,University of Tabriz |
Nikoofar B.,Islamic Azad University at Ajabshir
Computers and Geosciences | Year: 2012
Accurate prediction of lake-level variations is important for planning, design, construction, and operation of lakeshore structures and also in the management of freshwater lakes for water supply purposes. In the present paper, three artificial intelligence approaches, namely artificial neural networks (ANNs), adaptive-neuro-fuzzy inference system (ANFIS), and gene expression programming (GEP), were applied to forecast daily lake-level variations up to 3-day ahead time intervals. The measurements at the Lake Iznik in Western Turkey, for the period of January 1961-December 1982, were used for training, testing, and validating the employed models. The results obtained by the GEP approach indicated that it performs better than ANFIS and ANNs in predicting lake-level variations. A comparison was also made between these artificial intelligence approaches and convenient autoregressive moving average (ARMA) models, which demonstrated the superiority of GEP, ANFIS, and ANN models over ARMA models. © 2011 Elsevier Ltd.
Khoshravan M.R.,University of Tabriz |
Khalili A.,Islamic Azad University at Ajabshir |
Razavi M.J.,Tabriz Engineering Research Center
Key Engineering Materials | Year: 2011
The aim of this work was to investigate Stress Concentration Factor (SCF) variations induced by adding of holes in a perforated base plate subjected to uniaxial tension load, using Finite Element Method (FEM). Analyses were applied in 2D for different diameters, orientation angels and distances of added holes from the base hole. A parametric model in ANSYS finite element software was used to calculate the SCFs and the differences between SCFs have been shown in various graphs. To investigate the variation of SCF in perforated base plate, two holes with the same diameter were located symmetrically to the longitudinal axis with different angles and distances from the base hole. The results showed that by adding holes with a proper diameter, orientation angles and distances from the base hole, the SCFs can be reduced. Using the obtained graphs and corresponding to the base hole diameter the most adequate diameter and its position was determined. Obtained results for special statuses had a good agreement with the graphs of Peterson's stress concentration factors.
Eftekhari-Sis B.,Islamic Azad University at Maragheh |
Akbari A.,Islamic Azad University at Maragheh |
Amirabedi M.,Islamic Azad University at Ajabshir
Chemistry of Heterocyclic Compounds | Year: 2011
New N-alkyl(aryl)-2,4-diaryl-1H-pyrrol-3-ol derivatives have been synthesized in moderate to good yields in a novel and efficient process by aldol reaction of 1-(4-methoxyphenyl)propan-2-ones with phenylglyoxal in the presence of DABCO in water, followed by Paal-Knorr reaction with amines in the presence of a catalytic amount of p-TSA in toluene at reflux. © 2011 Springer Science+Business Media, Inc.
Kalantari N.N.P.,Islamic Azad University at Tabriz |
Singeri M.,Islamic Azad University at Tabriz |
Jourshari S.R.,Islamic Azad University at Ajabshir
Procedia Engineering | Year: 2015
This research studies the reaction of traditional houses to solar energy according to the function of Iwan as well as the climate in Tabriz city. It aims to investigate the climatic role of Iwan in the rate of energy consumption of these houses. Statistical population of this study contains four traditional buildings registered in Cultural Heritage Organization of the East Azarbayjan province. Solar conveyor system, content analysis, and survey methods with tools including the images, tables and maps have been used for investigating the cases in order to achieve this objective. Obtained results indicates that Iwan was applied only as the symbolic element in the architecture of traditional structures in Tabriz city and its climatic function was rarely considered in designing these structures. © 2015 The Authors. Published by Elsevier Ltd.
Zyaei M.,Islamic Azad University at Ajabshir |
Rostami A.,University of Tabriz |
Haji Khanmohamadi H.,Islamic Azad University at Ajabshir |
Rasooli Saghai H.,University of Tabriz
Progress In Electromagnetics Research B | Year: 2011
A novel kind of room temperature terahertz photodetector based on Electromagnetically Induced Transparency (EIT) is pre-sented. The main idea for room temperature and THz range opera-tion is reduction of dark current which is done by converting of the incoming terahertz signal (long-wavelength Infrared signal) to short-wavelength field through EIT phenomena. For realization of this idea, we examine EIT phenomena in multi levels atomic system and quantum wells cascade structures. In the proposed structure the quantum interference between long wavelength and short-wavelength radiation modifies the absorption characteristic of short-wavelength probe field. By this means, the terahertz signal does not interact directly with ground state electrons, but affects on the absorption characteristics of the short-wavelength or visible probe optical field which directly interact with ground state electrons. Therefore, the important thermionic dark current in terahertz detection, can be strongly reduced. So, the proposed idea is appropriate for terahertz and room temperature applications.
Zyaei M.,Islamic Azad University at Ajabshir |
Usefinia M.,University of Tabriz
Optik | Year: 2013
In this article an asymmetric intersubband quantum well structure as a high temperature terahertz (THz) optical switch is proposed. In our proposed structure the incoming low power energy photon (THz control signal) causes an optical switching. In this structure we introduce an optical terahertz switch based on coherent population trapping (CPT) phenomena. In the presence of electromagnetic THz field, quantum interference between the terahertz control field and short-wavelength probe field under appropriate condition, the medium becomes transparent (zero absorption) for the probe field. So the absorption and refraction characteristic of optical probe field can be modified with THz radiation. Therefore this idea is suitable for all - optical terahertz switching. © 2013 Elsevier GmbH.
Beigbabaei B.,Islamic Azad University at Ajabshir
Advances in Environmental Biology | Year: 2014
Background: Extensive need of human to energy resources and his endeavor to access unending energy resources were always regarded as one of the most essential problems of human life and his inveterate willing. Human consistently look for applying of energy in industries. He used wind power to move sailboats and windmills. At present, it seems necessary to deal with wind power considering the above-mentioned cases and its economical justifiability in comparison with other modern energies. Objective: The purpose of this study was evaluating climate and climatic factors (wind) at residential areas (Rasht). Results: Natural ventilation is one of the best and most inexpensive ventilation methods realized through creating indoor natural air. In traditional architecture, natural ventilation was regarded as one of the most important parts of buildings design. Nowadays, optimal use of wind power is extremely underestimated due to density of adjacent buildings. Rasht is located in a humid climate. Since its humidity is about 100% almost all over the year, creating draught between buildings and their inside is of special importance. Considering importance of the subject, the present study deals with wind flow status of some residential blocks located at Golsar district of Rasht in order to offer approaches to optimally use airflow through evaluating indoor and outdoor draught. External and internal properties and campus effect are of important factors in evaluating these residential buildings. Conclusion: The research uses field and documentary studies and provides some results about better productivity of the energy. © 2013 AENSI Publisher All rights reserved.