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Evolution of the electronic structure and structural properties of BaFe2 As2 at the tetragonal-collapsed tetragonal phase transition
,
Article
Physica C: Superconductivity and its Applications
;
Volume 516
,
2015
,
Pages 36-43
;
09214534 (ISSN)
; 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 BaFe2 As2 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...
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) ; 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) ; 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...
Experimental investigation of the roles of blood volume and density in finger photoplethysmography
, Article IEEE Sensors Journal ; Volume 13, Issue 5 , 2013 , Pages 1397-1398 ; 1530437X (ISSN) ; Zahedi, E ; Attar, H. M ; Aghajani, H ; Sharif University of Technology
2013
Abstract
Using simultaneous photoplethysmogram (PPG) and pulse transducer signals from the same finger, a high correlation (Mean: 98.6, STD: 1) is obtained between the AC part of the PPG and estimated volume changes (after normalization). These results point to the fact that in the resting fingertip, PPG signal variations are only due to volume changes and that blood density does not change thus has no contribution
Experimental study of asphaltene precipitation behavior during miscible carbon dioxide injection
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Vol. 36, issue. 14 , July , 2014 , pp. 1523-1530 ; ISSN: 15567036 ; Nakhli, H ; Kharrat, R ; Ghazanfari, M. H ; Aghajani, M ; Sharif University of Technology
2014
Abstract
Many reservoir and production engineers face asphaltene precipitation as a major problem during miscible carbon dioxide flooding projects. Experimental studies regarding asphaltene precipitation are therefore employed to assist in selecting appropriate facilities and proper operation schemes. During this study, a series of high pressure, high temperature experiments are designed and performed to analyze asphaltene precipitation behavior of an Iranian light reservoir crude at reservoir conditions due to natural production and miscible CO2 gas injection. For both sets of experiments, two different temperature levels (including reservoir temperature) are selected to investigate the role of...
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) ; 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
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) ; 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) ; 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...
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) ; 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) ; 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...
A comparative study of cognitive science of religion and reformed epistemology
, Article Journal of Philosophical Theological Research ; Volume 24, Issue 1 , 2022 , Pages 5-20 ; 17359791 (ISSN) ; Sharif University of Technology
University of Qom
2022
Abstract
Reformed epistemology, based on the reliability of the functions of cognitive faculties, holds that one can believe in God directly without argument or evidence. Alvin Plantinga, one of the proponents of this view, replaces justification with warrant in the classical definition of knowledge and considers true belief, which has a warrant as knowledge. On this basis, he considers it reasonable to believe in the existence of God because it has a warrant and arises from our healthy cognitive faculties without the need for an independent argument. Some defenders of the cognitive science of religion also seek to provide evidence from cognitive science to explain religious beliefs in such a way as...
Muslims’ lifeworld during the pandemic and humanistic interpretation of religions
, Article Contemporary Islam ; 2023 ; 18720218 (ISSN) ; Sharif University of Technology
Springer Science and Business Media B.V
2023
Abstract
Some proponents of new atheism, including Dawkins, claim that religion, especially Islam, is the cause of the war because it encourages divisiveness and labeling. In this article, in the first step, I will show that Islam is not the cause of war, but rather it is a misconception of Islam that is the cause of divisiveness and eventually war. Then, I will demonstrate that the COVID-19 pandemic and its impact on societies and religious behaviors somehow could, and still can, modify this misconception and blur divisions. This effect occurs in two ways: firstly, a pandemic creates common human problems for all people worldwide, making people more aware of their common points that Islam refers to...
Resilient cities, a key solution to safeguard the environment
, Article Scientia Iranica ; Volume 23, Issue 5 , 2016 , Pages 2067-2076 ; 10263098 (ISSN) ; 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...
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) ; 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) ; 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...
Oscillation of solutions of second-order nonlinear differential equations of Euler type
, Article Journal of Mathematical Analysis and Applications ; Volume 326, Issue 2 , 2007 , Pages 1076-1089 ; 0022247X (ISSN) ; Moradifam, A ; Sharif University of Technology
2007
Abstract
We consider the nonlinear Euler differential equation t2 x″ + g (x) = 0. Here g (x) satisfies x g (x) > 0 for x ≠ 0, but is not assumed to be sublinear or superlinear. We present implicit necessary and sufficient condition for all nontrivial solutions of this system to be oscillatory or nonoscillatory. Also we prove that solutions of this system are all oscillatory or all nonoscillatory and cannot be both. We derive explicit conditions and improve the results presented in the previous literature. We extend our results to the extended equation t2 x″ + a (t) g (x) = 0. © 2006 Elsevier Inc. All rights reserved
On the structure of detonation waves in magnetohydrodynamics
, Article Applied Mathematics Research eXpress ; Volume 2006 , 2006 ; 16871200 (ISSN) ; Hesaaraki, M ; Sharif University of Technology
2006
Some sufficient conditions for the intersection with the vertical isocline in the Liénard plane
, Article Applied Mathematics Letters ; Volume 19, Issue 5 , 2006 , Pages 491-497 ; 08939659 (ISSN) ; Moradifam, A ; Sharif University of Technology
2006
Abstract
In this work we study the problem of whether all trajectories of the system ẋ=y-F(x) and ẏ=-g(x) cross the vertical isocline, which is very important for the existence of periodic solutions and oscillation theory. Sufficient conditions are given for all trajectories to cross the vertical isocline. © 2005 Elsevier Ltd. All rights reserved
Nonexistence of limit cycles in two classes of predator-prey systems
, Article Applied Mathematics and Computation ; Volume 175, Issue 1 , 2006 , Pages 356-365 ; 00963003 (ISSN) ; Moradifam, A ; Sharif University of Technology
2006
Abstract
This paper deals with the question of nonexistence of limit cycles in two famous classes of predator-prey systems. We present some sufficient conditions for the nonexistence of limit cycles in these systems. Our results extend and improve the results presented by Moghadas. © 2005 Elsevier Inc. All rights reserved
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) ; 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