Loading...
Search for: aghajani--m
0.154 seconds

    Influence of In situ thermal processing strategies on the weldability of martensitic stainless steel resistance spot welds: effect of second pulse current on the weld microstructure and mechanical properties

    , Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 50, Issue 11 , 2019 , Pages 5191-5209 ; 10735623 (ISSN) Aghajani, H ; Pouranvari, M ; Sharif University of Technology
    Springer Boston  2019
    Abstract
    Martensitic stainless steel (MSS) welds are notorious for their susceptibility to low-energy failure due to the formation of brittle martensitic structure in the fusion zone. The unique approach to enhance the mechanical properties of MSS resistance spot welds during both the tensile-shear and the cross-tension loading is to improve the fracture toughness of the fusion zone. In the present study, the effect of double-pulse welding on the microstructure-mechanical properties relationship of the AISI420 MSS resistance spot welds is investigated. Depending on the second pulse current level, various metallurgical phenomena was observed including (i) rapid tempering of martensite in the fusion... 

    A pathway to produce strong and tough martensitic stainless steels resistance spot welds

    , Article Science and Technology of Welding and Joining ; Volume 24, Issue 3 , 2019 , Pages 185-192 ; 13621718 (ISSN) Aghajani, H ; Pouranvari, M ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    Martensitic stainless steel (MSS) resistance spot welds are prone to quasi-cleavage interfacial failure with very low energy absorption capability due to formation of hard and brittle carbon and chromium rich martensite in the fusion zone (FZ). In this work, a new pathway is proposed to enhance strength/toughness of the MSS resistance spot welds based on modification of the FZ composition/microstructure via introducing a nickel interlayer. This altered the FZ microstructure from dual phase microstructure of martensite and δ-ferrite to austenitic microstructure with finely dispersed ultra-fine chromium rich carbides. Formation of a tough predominately austenitic microstructure in the FZ... 

    On the structure of detonation waves in magnetohydrodynamics

    , Article Applied Mathematics Research eXpress ; Volume 2006 , 2006 ; 16871200 (ISSN) Aghajani, A ; Hesaaraki, M ; Sharif University of Technology
    2006

    On the structure of ionizing shock waves in magnetofluiddynamics

    , Article International Journal of Mathematics and Mathematical Sciences ; Volume 29, Issue 7 , 2002 , Pages 395-415 ; 01611712 (ISSN) Aghajani, A ; Hesaaraki, M ; Sharif University of Technology
    2002
    Abstract
    Ionizing shock waves in magnetofluiddynamics occur when the coefficient of electrical conductivity is very small ahead of the shock and very large behind it. For planner motion of plasma, the structure of such shock waves are stated in terms of a system of four-dimensional equations. In this paper, we show that for the above electrical conductivity as well as for limiting cases, that is, when this coefficient is zero ahead of the shock and/or is infinity behind it, ionizing fast, slow, switch-on and switch-off shocks admit structure. This means that physically these shocks occur. © 2002 Hindawi Publishing Corporation. All rights reserved  

    Resilient cities, a key solution to safeguard the environment

    , Article Scientia Iranica ; Volume 23, Issue 5 , 2016 , Pages 2067-2076 ; 10263098 (ISSN) Aghajani, Y ; Abbaspour, M ; Mohammadi, A ; Reza Soltani, S ; Aghajani, D ; Ahmadi, A ; Sharif University of Technology
    Sharif University of Technology  2016
    Abstract
    In the 21st century, the world population is growing at a spiraling pace. Much of this growth is occurring in developing countries, where access to food, sanitary water, education, and health is severely limited. The ever-increasing urbanization highlighted the need for sustainable development based on human-environment interaction. The excessive and unplanned expansion of cities has resulted in numerous environmental predicaments due to clearly emphasized economic issues at the expense of social and environmental concerns. The most significant features of megacities are indicated in this paper and the environmental, social, physical, and economic criteria are addressed in order to attain... 

    Structural image representation for image registration

    , Article 2015 International Symposium on Artificial Intelligence and Signal Processing, AISP 2015, 3 March 2015 through 5 March 2015 ; March , 2015 , Pages 95-100 ; 9781479988174 (ISBN) Aghajani, K ; Shirpour, M ; Manzuri, M. T ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Image registration is an important task in medical image processing. Assuming spatially stationary intensity relation among images, conventional area based algorithms such as CC (Correlation Coefficients) and MI (Mutual Information), show weaker results alongside spatially varying intensity distortion. In this research, a structural representation of images is introduced. It allows us to use simpler similarity metrics in multimodal images which are also robust against the mentioned distortion field. The efficiency of this presentation in non-rigid image registration in the presence of spatial varying distortion field is examined. Experimental results on synthetic and real-world data sets... 

    Evolution of the electronic structure and structural properties of BaFe2As2 at the tetragonal-collapsed tetragonal phase transition

    , Article Physica C: Superconductivity and its Applications ; Volume 516 , 2015 , Pages 36-43 ; 09214534 (ISSN) Aghajani, M ; Khosroabadi, H ; Akhavan, M ; Sharif University of Technology
    Elsevier  2015
    Abstract
    Density functional theory generalized gradient approximation has been used to calculate the electronic and structural properties of BaFe2As2 compound up to 56 GPa by using Quantum Espresso code. Structural properties like bulk modulus, Fe-As bond length, and As-Fe-As bond angles have been investigated by pressure especially near the tetragonal to collapsed tetragonal (T-cT) structural phase transition. This study shows considerable changes of these parameters in the cT phase, which happens near our calculated critical pressure, Pc = 24 ± 2 GPa. Electronic band structure and its orbital-resolved, total and partial density of states and Fermi surfaces have been... 

    On the existence of fast strong and fast weak ionizing detonation waves in magnetohydrodynamics

    , Article Chaos, Solitons and Fractals ; Volume 40, Issue 1 , 2009 , Pages 298-308 ; 09600779 (ISSN) Aghajani, A ; Farjami, Y ; Hesaaraki, M ; Sharif University of Technology
    2009
    Abstract
    The existence of structure for ionizing fast-strong and fast-weak detonation waves in magnetohydrodynamics are proved. The reactions are assumed to be one step exothermic reactions with a natural discontinuous reaction rate function. The problem is studied for a general gas, considering some general thermodynamics rules which described by a fairly mild set of hypotheses. The uniqueness and nonuniqueness of structure are also considered. © 2007 Elsevier Ltd. All rights reserved  

    Pressure dependence of effective Coulomb interaction parameters in BaFe2As2 by first-principle calculation

    , Article Physica C: Superconductivity and its Applications ; Volume 548 , 15 May , 2018 , Pages 61-64 ; 09214534 (ISSN) Aghajani, M ; Hadipour, H ; Akhavan, M ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    Pressure dependence of the onsite Coulomb interactions of the BaFe2As2 has been studied by employing the constrained random phase approximation within first-principle calculations. Analyzing total and projected density of states, a pseudogap is found for dxy band at the energy roughly 0.25 eV higher than the Fermi level. Also, by applying pressure the spectral weight of the dxy orbital vanishes while other orbitals remain metallic. The different screening channels, as discussed in four different models, affect significantly on the Hubbard U while the Hund J remains almost unchanged. The average onsite bare and partially and fully screened Coulomb interactions increase with different rates... 

    Mechanical and chemical pressure effects on the AeFe 2 As 2 (Ae = Ba, Sr, Ca) compounds: Density functional theory

    , Article Computational Materials Science ; Volume 160 , 2019 , Pages 233-244 ; 09270256 (ISSN) Aghajani, M ; Hadipour, H ; Akhavan, M ; Sharif University of Technology
    Elsevier B.V  2019
    Abstract
    We have studied the pressure-induced structural, magnetic and electronic properties of AeFe 2 As 2 (Ae = Ba, Sr, Ca) compounds in the framework of density functional theory within the GGA-PBE method. The effects of chemical pressure generated by Sr and Ca substitutions in BaFe 2 As 2 have been investigated. We have found a magnetic transition at the same primitive unit cell volume, around 81 Å 3 for the (Ba⧹Ca)Fe 2 As 2 compounds, which predicts a magnetic transition pressure of 12 GPa for SrFe 2 As 2 . The structural parameters of FeAs 4 tetrahedra are obtained after ionic relaxation and compared with the existing experimental results. The change of these internal parameters is ascribed to... 

    Life prediction of wind turbine blades using multi-scale damage model

    , Article Journal of Reinforced Plastics and Composites ; Volume 40, Issue 17-18 , 2021 , Pages 644-653 ; 07316844 (ISSN) Aghajani, S ; Hemati, M ; Torabnia, S ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Abstract
    Wind turbine blade life prediction is the most important parameter to estimate the power generation cost. Due to the price and importance of wind blade, many experimental and theoretical methods were developed to estimate damages and blade life. A novel multiaxial fatigue damage model is suggested for the life prediction of a wind turbine blade. Fatigue reduction of fiber and interfiber characteristics are separately treated and simulated in this research. Damage behavior is considered in lamina level and then extended to laminate; hence, this model can be used for multidirectional laminated composites. The procedure of fatigue-induced degradation is implemented in an ABAQUS user material... 

    Life prediction of wind turbine blades using multi-scale damage model

    , Article Journal of Reinforced Plastics and Composites ; Volume 40, Issue 17-18 , 2021 , Pages 644-653 ; 07316844 (ISSN) Aghajani, S ; Hemati, M ; Torabnia, S ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Abstract
    Wind turbine blade life prediction is the most important parameter to estimate the power generation cost. Due to the price and importance of wind blade, many experimental and theoretical methods were developed to estimate damages and blade life. A novel multiaxial fatigue damage model is suggested for the life prediction of a wind turbine blade. Fatigue reduction of fiber and interfiber characteristics are separately treated and simulated in this research. Damage behavior is considered in lamina level and then extended to laminate; hence, this model can be used for multidirectional laminated composites. The procedure of fatigue-induced degradation is implemented in an ABAQUS user material... 

    Intensity based image registration by minimizing the complexity of weighted subtraction under illumination changes

    , Article Biomedical Signal Processing and Control ; Volume 25 , 2016 , Pages 35-45 ; 17468094 (ISSN) Aghajani, K ; Yousefpour, R ; Shirpour, M ; Manzuri, M. T ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    One crucial part of an image registration algorithm is utilization of an appropriate similarity metric. For common similarity metrics such as CC or MI, it is assumed that the intensities of image pixels are independent from each other and stationary. Accepting these assumptions, one will have difficulty doing image registration in the presence of spatially varying intensity distortion. In Myronenko et al. [5] a solution based on minimization of residual complexity is introduced to solve this problem. In this work, the weakness of RC method is investigated for more complex spatially varying intensity distortions and a modification of this method is presented to improve its performance in such... 

    A robust voice activity detection based on wavelet transform

    , Article 2nd International Conference on Electrical Engineering, ICEE, Lahore, 25 March 2008 through 26 March 2008 ; 2008 ; 9781424422937 (ISBN) Aghajani, K ; Manzuri, M. T ; Karami, M ; Tayebi, H ; Sharif University of Technology
    2008
    Abstract
    Voice activity detection is an important step in some speech processing systems, such as speech recognition, speech enhancement, noise estimation, speech compression ... etc. In this paper a new voice activity detection algorithm based on wavelet transform is proposed. In this algorithm we use the energy in each sub band, and by two methods we extract feature vector from these values. Experimental results demonstrate advantage over different VAD methods. ©2008 IEEE  

    Power allocation and performance analysis for incremental-selective decode-and-forward cooperative communications over Nakagami-m fading channels

    , Article IEICE Transactions on Communications ; Volume E96-B, Issue 6 , 2013 , Pages 1531-1539 ; 09168516 (ISSN) Aghajani, R ; Saadat, R ; Aref, M. R ; Sharif University of Technology
    2013
    Abstract
    The focus of this study is the performance of the relaying network with incremental selective decode-and-forward (ISDF) protocol in non-selective slow Nakagami-m fading channels. To enhance bandwidth efficiency, when the direct transmission is not successful the relay is used to retransmit a clean copy of the source signal. The proposed protocol achieves a significant reduction in the power consumption and an improvement in performance compared to the fixed decode-and-forward (DF). The exact symbol error rate (SER) of M-PSK modulation for the ISDF protocol over general fading channels is derived. However, as the exact SER analysis is very complicated, we provide an approximated SER... 

    A robust image registration method based on total variation regularization under complex illumination changes

    , Article Computer Methods and Programs in Biomedicine ; Volume 134 , 2016 , Pages 89-107 ; 01692607 (ISSN) Aghajani, K ; Manzuri, M. T ; Yousefpour, R ; Sharif University of Technology
    Elsevier Ireland Ltd  2016
    Abstract
    Background and objective Image registration is one of the fundamental and essential tasks for medical imaging and remote sensing applications. One of the most common challenges in this area is the presence of complex spatially varying intensity distortion in the images. The widely used similarity metrics, such as MI (Mutual Information), CC (Correlation Coefficient), SSD (Sum of Square Difference), SAD (Sum of Absolute Difference) and CR (Correlation Ratio), are not robust against this kind of distortion because stationarity assumption and the pixel-wise independence cannot be obeyed and captured by these metrics. Methods In this paper, we propose a new intensity-based method for... 

    Using Web-GIS technology as a smart tool for resiliency management to monitor wind farms performances (Ganjeh site, Iran)

    , Article International Journal of Environmental Science and Technology ; Volume 16, Issue 9 , 2019 , Pages 5011-5022 ; 17351472 (ISSN) Aghajani, D ; Abbaspour, M ; Radfar, R ; Mohammadi, A ; Sharif University of Technology
    Center for Environmental and Energy Research and Studies  2019
    Abstract
    Considering the wide spread locations of wind farms in Iran, it is important to develop a suitable decision support system (DSS) to fulfill proper management of wind farms. Extensive literature survey indicates that there are no integrated forms of DSS to manage a set of wind farms. The existing wind farms are performing independently, and there is no practical method for exchanging the online data. DSS can contribute to optimal operation of wind farms, operation and maintenance scheduling, pricing policy, etc. In this study, a geographic information system and RETSCREEN software were linked to the designed DSS to achieve a more suitable result. Also, a huge number of data are constantly... 

    Using Web-GIS technology as a smart tool for resiliency management to monitor wind farms performances (Ganjeh site, Iran)

    , Article International Journal of Environmental Science and Technology ; 2018 ; 17351472 (ISSN) Aghajani, D ; Abbaspour, M ; Radfar, R ; Mohammadi, A ; Sharif University of Technology
    Center for Environmental and Energy Research and Studies  2018
    Abstract
    Considering the wide spread locations of wind farms in Iran, it is important to develop a suitable decision support system (DSS) to fulfill proper management of wind farms. Extensive literature survey indicates that there are no integrated forms of DSS to manage a set of wind farms. The existing wind farms are performing independently, and there is no practical method for exchanging the online data. DSS can contribute to optimal operation of wind farms, operation and maintenance scheduling, pricing policy, etc. In this study, a geographic information system and RETSCREEN software were linked to the designed DSS to achieve a more suitable result. Also, a huge number of data are constantly... 

    Assessing the explanatory power of naturalism in addressing ultimate questions

    , Article Vestnik Sankt-Peterburgskogo Universiteta, Filosofiia i Konfliktologiia ; Volume 37, Issue 2 , 2021 , Pages 217-228 ; 25422278 (ISSN) Aghajani, J. D ; Sharif University of Technology
    Saint Petersburg State University  2021
    Abstract
    A typical scientist has no responsibility other than to explain how a natural event occurred. However, when a philosopher asks about the conditions under which a scientist’s explanation is true, he is, in fact, raising an ultimate question, the concept which Karl Popper used for the first time. Answering this question requires that no elements are neglected in the explanation, and no significant factors in the explanation are overlooked. In other words, in explaining a phenomenon, at any level of its explanation, there should be no remainder. These requirements can be achieved through the full explanation. In the present article, by drawing on concepts such as theory-ladenness of... 

    Metaphysical necessity in the neo-sadraian school and assessment of necessitarian theories of the laws of nature

    , Article Teorie Vedy / Theory of Science ; Volume 43, Issue 1 , 2021 , Pages 33-57 ; 12100250 (ISSN) Aghajani, J. D ; Sharif University of Technology
    Czech Academy of Sciences  2021
    Abstract
    To differentiate between the laws of nature and accidental generalizations, we must adopt a view of necessity that is capable of being realized in relationships existing among natural objects. In neo-Sadraian Islamic philosophy, metaphysical necessity is accepted as part of the cause-effect relationship. This paper compares the neo-Sadraian interpretation of necessity and necessitarian theories about the laws of nature, particularly essentialism and universal theory. By resorting to specific forms al-shûrat al-naw’iyyah, the origin of the essential properties of natural objects, I argue that neo-Sadraians have proposed a perspective on metaphysical necessity that is epistemologically a...