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165 results on '"Akbarzadeh, H."'

4. Superconductivity in heavily vacant diamond

Author

Alaei, M., Jafari, S. Akbar, and Akbarzadeh, H.

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Materials Science
Abstract

Using first principle electronic structure calculations we investigated the role of substitutional doping of B,N,P,Al and vacancies (${\cal V}$) in diamond (X$_{\alpha}$C$_{1-\alpha}$). In the heavy doping regime, at about $\sim 1-6%$ doping an impurity band appears in the mid gap. Increasing further the concentration of the impurity substitution fills in the gap of the diamond host. Our first principle calculation indicates that in the case of vacancies, a clear single-band picture can be employed to write down an effective {\em one band} microscopic Hamiltonian, which can be used to further study various many-body and disorder effects in impurity band (super)conductors.

Published
2008
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5. Density functional approach to study structural properties and Electric Field Gradients in rare earth materials

Author

Asadabadi, S. Jalali and Akbarzadeh, H.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

We investigated the effect of spin polarization on the structural properties and gradient of electric field (EFG) on Sn, In, and Cd impurity in RSn$_3$ (R=Sm, Eu, Gd) and RIn$_3$ (R=Tm, Yb, Lu) compounds. The calculations were performed self-consistently using the scalar-relativistic full potential linearized augmented plane wave method. The local density approximations (LDA) and generalized gradient approximation without spin polarization (GGA) and with spin polarization (GGA+SP) to density functional theory were applied. In addition to that we performed some calculations within open core treatment (GGA+open core). It is clearly seen that GGA+SP is successful in predicting the larger lattice parameter and the dramatic drop of EFG for R=(Eu, Yb) relative to other rare earth compounds. This is an indication that spin splitting generated by spin polarization without any modification, is capable of treating properly the highly correlated f electrons in these systems., Comment: 14 Pages, 3 Figures, 5 Tables

Published
2007
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6. Valency of rare earths in RIn3 and RSn3: Ab initio analysis of electric-field gradients

Author

Asadabadi, S. Jalali, Cottenier, S., Akbarzadeh, H., Saki, R., and Rots, M.

Subjects
Condensed Matter
Abstract

In RIn3 and RSn3 the rare earth (R) is trivalent, except for Eu and Yb, which are divalent. This was experimentally determined in 1977 by perturbed angular correlation measurements of the electric-field gradient on a 111Cd impurity. At that time, the data were interpreted using a point charge model, which is now known to be unphysical and unreliable. This makes the valency determination potentially questionable. We revisit these data, and analyze them using ab initio calculations of the electric-field gradient. From these calculations, the physical mechanism that is responsible for the influence of the valency on the electric-field gradient is derived. A generally applicable scheme to interpret electric-field gradients is used, which in a transparent way correlates the size of the field gradient with chemical properties of the system., Comment: 10 pages

Published
2002
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9. Singularity Analysis Of An Interface Crack Between Piezoelectric And Orthotropic Half-Spaces

Author

Hu, K.Q., Chen, Z.T., and Akbarzadeh, H.

Abstract

In this paper, an interface crack between piezoelectric and orthotropic half-spaces has been studied in detail. By using integral transformation techniques, the present mixed boundary value problem was reduced to the solution of singular integral equations, which can be further reduced to solving a Riemann-Hilbert problem with a closed form solution. The crack-tip singularities of the interface crack have been investigated for possible combinations of the piezoelectric and orthotropic materials; a criterion based on the g-parameter of the Riemann-Hilbert problem is introduced to study the possible singularity behavior of the interface crack. It is shown that there can be either oscillatory or non- oscillatory singularity for the interface crack depending on the particular combinations of the bi-materials. A closed form solution for stresses, electric field and electric displacement in the cracked bi-materials is given, and of particular interests, the analytical expression of the stresses and electric displacements along the interface has been obtained. Part of Proceedings of the Canadian Society for Mechanical Engineering International Congress 2022.

Published
2022
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10. EFFECTS OF WATER TEMPERATURE ON FILTRATION RATE OF MICRO-ALGAE ISOCHRYSIS AFFINES GALBANA BY BLACK LIP PEARL OYSTER SPAT (PINCTADA MARGARITIFERA)

Author

I. Abdolalian; M. Sajadi; M. Yahyavi; Gh. Akbarzadeh; H. Rameshi

Subjects
PINCTADA MARGARITFERA, microalgae, ISOCHRYSIS AFFINES GALBANA, temperature, Agriculture, Aquaculture. Fisheries. Angling, SH1-691
Abstract

This study was conducted to compare the effects of varying water temperatures on filtration rate of micro-algae Isochrysis affines galbana by Pinctada margaritfera spat on microalgae. To determine the optimum temperature and maximum filtration rate, 10 pearl oyster Pinctada margaritfera spats with mean total and total hinge length 32.67±2.76 and 31.57±2.90 respectively were stocked in 70 liter rectangular glass tanks supplied with filtered seawater. The spats were exposed to seven treatments of temperature including 18.5±0.21oC, 20.5±0.21oC, 23±0.1 oC, 24.5±O.31oC, 26.5±0.21 oC, 27.5±0.15oC and 28.5±0.21 oC with 3 replicates. The results of filtration on Isochiysis affines galbana showed that the maximum filtration of spats on microalgae cells and water volume were 181,324,595 cells and 3626ml per hour and 635,031,212 cells and 12700ml per two hours in 27.5±0.15oC, respectively. The minimum filtration of microalgae cells and water volume were 5,224,028 and 104ml per hour and 65,874,413 cells and 13l7ml per two hours in 18.50±021oC, respectively. The results of this study demonstrated that the optimum tem perature for maximum feeding of spats on Isochrysis affines galbana is 27.5±0.15oC.

Published
2008

20. Deep feature learnt by conventional deep neural network

Author

Niu, H, Xu, W, Akbarzadeh, H, Parvin, H, Beheshti, A, Alinejad-Rokny, H, Niu, H, Xu, W, Akbarzadeh, H, Parvin, H, Beheshti, A, and Alinejad-Rokny, H

Abstract

In this paper, we introduce an approach to discriminate unconventional images and their intelligent filtering. As the target data to this issue are huge and consequently, a handling approach might potentially be a very time consuming one, one of the major challenges to be solved by this introduced approach is its ability for dealing with large-scale datasets. A deep neural network might be a good option to resolve this challenge. It can provide a good accuracy while dealing with huge databases. In the proposed approach, the new architecture is introduced using a combination of AlexNet and LeNet architectures. It uses convolutional, polling and fully-connected layers. The results are tested on two large-scale datasets. These tests show that the introduced architecture is more accurate than the other recently developed methods in identifying unconventional images. The proposed approach may be used in different applications such as intelligent filtering of unconventional images or medical images analysis.

Published
2020

26. First-principles study of Berry curvature and intrinsic anomalous Hall conductivity in ferromagnetic materials using Maximally localized Wannier function

Author

Jebeli, H., S. Javad Hashemifar, Akbarzadeh, H., and Torbatian, Z.

Subjects
Co, Condensed Matter::Materials Science, Berry curvature, Maximally localized Wannier function, Fe-Co alloy, Fe, intrinsic anomalous Hall conductivity, lcsh:Physics, lcsh:QC1-999
Abstract

Electronic properties for bcc Fe and hcp Co in bulk state and also Fe-Co alloy were calculated by quantum calculation based on density functional theory and pseudopotential method. Combination of Wannier function and Berry phase theory was used for calculation of anomalous Hall conductivity in above structures. It was seen that split of band by the spin orbit interaction, lying on the Fermi level, has a major role in Berry curvature. Acquired results agree with experimental ones and thus it seems that conductivity in bulk state is intrinsic.

Published
2013

27. Topological description of mechanical behavior of Cu, Ag and Au: A first-principle study

Author

Saghayezhian, M., S. Javad Hashemifar, Akbarzadeh, H., and Zarbakhsh, J.

Subjects
Condensed Matter::Materials Science, Quantitative Biology::Neurons and Cognition, topology of charge density, stress-strain curve, mechanical properties, quantum stress, lcsh:Physics, lcsh:QC1-999
Abstract

Mechanical properties and stress-strain curves of Cu, Ag and Au single crystals are calculated using ab initio methods. Elastic and Plastic regions are scrutinized. Yield stress and slope of these curves can shed light on brittlenesss and ductility of these metals that prove Cu, despite its high ultimate tensile strength, is less ductile than Au and Ag. Analysis of topology of charge density along with stress-strain curves shows that the elastic-plastic transition accompanies topological transition and for these metals, both transitions occur in the same strain. Some charactristics of critical point, especially bond points, are inspected.

Published
2011

29. Molecular dynamics simulation of molten silica at high pressure.

Author

Vessal, B., Amini, M., and Akbarzadeh, H.

Subjects
MOLECULAR dynamics, SILICON, OXYGEN, INTEGRATED circuits
Abstract

Molecular dynamics simulation of molten silica has been undertaken for an extensive range of pressures using a recently derived potential model. Linear behavior is observed, in plotting (Z-1)V2 vs density square, which is consistent with experimental results on compressed fluids. An increase in the medium range order and the number of higher coordinated silicons and oxygens is observed under pressure. [ABSTRACT FROM AUTHOR]

Published
1994
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33. Free response of a continuous vibrational system with attachments and/or discontinuities using segmented operational Tau method.

Author

Akbarzadeh, H., Sadeghi, Morteza H., Talati, F., and Shahmorad, S.

Subjects
*FREE vibration, *EULER-Bernoulli beam theory, *ANALYTICAL solutions, *BOUNDARY value problems, *PROBLEM solving
Abstract

It has been widely known that for complicated beam-like structures with various types of attachments and/or discontinuities analytical techniques are not always applicable. In this paper, a very efficient numerical method based on the Tau method is proposed to tackle the mentioned problem. A general form of the linear vibrational eigen-equation, based on the Euler–Bernoulli bending theory, together with its boundary conditions and continuity equations is considered. The problem is then formulated using a segmented form of the operational Tau method which is called the segmented operational Tau method. To investigate the reliability and accuracy of the proposed method some vibrational problems are solved and compared with the analytical solutions providing the exact frequencies and mode shapes. For a complicated case of a non-uniform beam with various types of attachments, since there was no analytical solution, results are validated with the finite element method. This paper has provided a platform for solving free vibrational problems of many complicated constrained systems through a very simple, highly accurate technique. [ABSTRACT FROM AUTHOR]

Published
2018
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34. CO/Pt(111): GGA density functional study of site preference for adsorption

Author

Alaei, M., Akbarzadeh, H., Gholizadeh, H., and de Gironcoli, Stefano Maria

Subjects
CO ADSORPTION, LEED, PT(111), METAL-SURFACES, GENERALIZED GRADIENT APPROXIMATION, CO ADSORPTION, METAL-SURFACES, PT(111), EXCHANGE, LEED, EXCHANGE, GENERALIZED GRADIENT APPROXIMATION, Settore FIS/03 - Fisica della Materia
Abstract

Based on density functional formalism, we investigate the site preference for the adsorption of CO on Cu, Rh, Ag, Pt, and Au(111) surfaces. The exchange-correlation term was approximated by BLYP, a functional within the generalized gradient approximation (GGA) family that combines Becke's exchange functional with the Lee-Yang-Parr correlation functional. Our study shows that BLYP, although not a hybrid functional, can correctly predict the adsorption site for CO. This invalidate the general belief that only hybrid functionals are able to predict the correct site preference. We analyze our results by repeating all calculations using another well-known GGA functional, Perdew-Burke-Ernzerhof, which could trace back the origin of the success of BLYP to the different behavior of the two GGA functionals at large values of the reduced density gradients, s proportional to parallel to del n parallel to/n(3/4). This is a region where different functionals in the GGA family may legitimately behave very differently as it is poorly constrained on physical ground. Our present observation points to the possibility of further improving the accuracy of exchange-correlation functionals in the GGA family by properly constraining the remaining flexibility in the exchange-correlation kernel in this underdetermined region so as to reproduce known results in simple but critically important systems like the one studied here.

Published
2008

40. Comparison of prospective and retrospective memory in addicted men, have left addicts, and healthy individuals.

Author

Ghanbari S., Akbarzadeh D., Akbarzadeh H., and Esmailpour K.

Subjects
RETROSPECTIVE studies, DRUG addiction, MEN'S health, SUBSTANCE abuse, BRAIN injuries, PATIENTS, DISEASE duration
Abstract

Background and aims: Addiction is a physical, mental, social and spiritual illness and one of the serious damages following substance abuse is brain injury. The main aim of the present study was to compare of prospective and retrospective memory in addicted males, have left addicts, and healthy. Methods: The study was a descriptive study. 35 addicted, 32 have left addicts, 35 healthy selected by purposive sampling. Prospective and retrospective memory questionnaire (PRMQ) was used for data collecting. Data were analyzed using of multivariate (MANOVA) and Turkey test. Results: There were significant differences in prospective memory performance between addicts, have left addicts, and healthy (P<0.05), but there was no significant difference in retrospective memory performance. Turkey test results also showed that prospective memory score mean more than in addicts and have left addicts, and healthy(P<0.05). Conclusion: The increase duration of addiction causes prospective memory destruction and therefore makes it more difficult to quit addiction. [ABSTRACT FROM AUTHOR]

Published
2015

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