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Three-qubits ground state and thermal entanglement of anisotropic Heisenberg (XXZ) and Ising models with Dzyaloshinskii-Moriya interaction
, Article International Journal of Quantum Information ; Volume 9, Issue 4 , 2011 , Pages 1057-1079 ; 02197499 (ISSN) ; Langari, A ; Sharif University of Technology
2011
Abstract
We have studied the symmetric and non-symmetric pairwise ground state and thermal entanglement in three-qubits system. We have considered the anisotropic Heisenberg (XXZ) model in the presence of DzyaloshinskiiMoriya (DM) interaction in addition to the Ising model in a magnetic field with DM interaction. We have found that the increment of DM interaction and magnetic field can enhance and reduce the entanglement of the system. We have shown that the non-symmetric pairwise state has higher value concurrence and critical temperature (above which the entanglement vanishes) than the symmetric pairwise one. For the negative anisotropy, the non-symmetric entanglement is a monotonic function of DM...
Phase diagram of the one-dimensional S= 1 2 XXZ model with ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor interactions
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 76, Issue 1 , 2007 ; 10980121 (ISSN) ; Langari, A ; Sharif University of Technology
2007
Abstract
We have studied the phase diagram of the one-dimensional S= 1 2 XXZ model with ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor interactions. We have applied the quantum renormalization group (QRG) approach to obtain stable fixed points and the scaling of coupling constants. The QRG prescription has to be implemented to the second order of interblock interactions to obtain a self-similar Hamiltonian after each step of the QRG. This model shows a rich phase diagram which includes quantum spin-fluid and dimer phases in addition to the classical Néel and ferromagnetic ones. We have found the border between different phases by tracing the scaling of coupling constants....
CFD study of droplet formation in a cross-Junction microfluidic device: investigating the impact of outflow channel design and viscosity ratio
, Article Engineering Applications of Computational Fluid Mechanics ; Volume 17, Issue 1 , 2023 ; 19942060 (ISSN) ; Shamloo, A ; Sharif University of Technology
Taylor and Francis Ltd
2023
Abstract
This study employed computational fluid dynamics (CFD) to investigate various regimes of droplet formation in a square microfluidic cross-junction device. The first part of the study focused on investigating the impact of viscosity ratios ranging from 0.1 to 5 on droplet characteristics under different flow rate ratios. The transition regime between the dripping and jetting exhibited particularly interesting behavior, with droplet volume being proportional to viscosity ratio. However, when conditions were far from the transition regime, the volume of droplets did not vary significantly with respect to viscosity ratios greater than one. The results of the study indicate the feasibility of...
Phase transitions in the binary-alloy Hubbard model: Insights from strong-coupling perturbation theory
, Article Physical Review B ; Volume 99, Issue 1 , 2019 ; 24699950 (ISSN) ; Habibi, A ; Jafari, S. A ; Sharif University of Technology
American Physical Society
2019
Abstract
In the binary alloy with composition AxB1-x of two atoms with ionic energy scales ±Δ, an apparent Anderson insulator (AI) is obtained as a result of randomness in the position of atoms. Using our recently developed technique that combines the local self-energy from strong-coupling perturbation theory with the transfer matrix method, we are able to address the problem of adding a Hubbard U to the binary-alloy problem for millions of lattice sites on the honeycomb lattice. By adding the Hubbard interaction U, the resulting AI phase will become metallic, which in our formulation can be manifestly attributed to the screening of disorder by Hubbard U. Upon further increase in U, again the AI...
Electron currents from gradual heating in tilted dirac cone materials
, Article SciPost Physics Core ; Volume 6, Issue 1 , 2023 ; 26669366 (ISSN) ; Torabian, M ; Jafari, A ; Sharif University of Technology
SciPost Foundation
2023
Abstract
Materials hosting tilted Dirac/Weyl fermions provide an emergent spacetime structure for the solid state physics. They admit a geometric description in terms of an effective spacetime metric. Using this metric that is rooted in the long-distance behavior of the underlying lattice, we formulate the hydrodynamic theory for tilted Dirac/Weyl materials in 2 + 1 spacetime dimensions. We find that the mingling of space and time through the off-diagonal components of the metric gives rise to: (i) heat and electric currents proportional to the temporal gradient of temperature, ∂t T and (ii) a non-zero Hall-like conductance σi j ∝ζiζj where ζj parameterize the tilt in j'th space direction. The...
An optimal analytical solution for maximizing expected battery lifetime using the calculus of variations
, Article Integration ; Volume 71 , March , 2020 , Pages 86-94 ; Ejlali, A ; Sharif University of Technology
Elsevier B.V
2020
Abstract
The exponential growth in the semiconductor industry and hence the increase in chip complexity, has led to more power usage and power density in modern processors. On the other hand, most of today's embedded systems are battery-powered, so the power consumption is one of the most critical criteria in these systems. Dynamic Voltage and Frequency Scaling (DVFS) is known as one of the most effective energy-saving methods. In this paper, we propose the optimal DVFS profile to minimize the energy consumption of a battery-based system with uncertain task execution time under deadline constraints using the Calculus of Variations (CoV). The contribution of this work is to analytically calculate the...
A new basis for the U-invariants of binary forms
, Article Communications in Algebra ; Volume 51, Issue 1 , 2023 , Pages 248-253 ; 00927872 (ISSN) ; Najafi Amin, A ; Sharif University of Technology
Taylor and Francis Ltd
2023
Abstract
Let K be a field of characteristic zero. The K-vector space Vn of all binary forms (Formula presented.) of degree n with coefficients in K carries a natural action of the group (Formula presented.) via substitutions of variables x and y. The invariant polynomials (Formula presented.) under the action of certain subgroups of (Formula presented.) were studied intensively in the 19th century. If U is the subgroup of the upper triangular unipotent matrices, with the aid of heavy computer calculations, we know the algebra of U-invariant polynomials in (Formula presented.) only for (Formula presented.) It appears to be a hopeless task to get much further along these lines. However, it is known...
Adsorption and solar light activity of transition-metal doped TiO 2 nanoparticles as semiconductor photocatalyst
, Article Journal of Materials Science: Materials in Electronics ; Volume 23, Issue 3 , 2012 , Pages 659-667 ; 09574522 (ISSN) ; Simchi, A ; Jafari, T ; Sharif University of Technology
2012
Abstract
There is an eminent interest to improve the photoactivity of TiO 2 nanostructures via doping with midband gap donors or acceptors to achieve a high solar absorption. In the present work, Cr- and V-doped TiO 2 nanoparticles were prepared via a facile chemical vapor synthesis method. The effect of the transition metals (TM) on the solar light activity of the semiconductor nanoparticles as photocatalyst was examined by degradation of methylene blue and acid red 27. Induced coupled plasma and X-ray photoelectron spectroscopy analyses indicated high efficiency of the doping process in the hot wall reactor without surface covering of the TiO 2 nanoparticles by the dopants. Diffuse reflectance...
Synthesis and cytotoxicity assessment of superparamagnetic iron-gold core-shell nanoparticles coated with polyglycerol
, Article Journal of Colloid and Interface Science ; Volume 345, Issue 1 , 2010 , Pages 64-71 ; 00219797 (ISSN) ; Simchi, A ; Khakpash, N ; Sharif University of Technology
2010
Abstract
Core-shell iron-gold (Fe@Au) nanoparticles were synthesized by a facile reverse micelle procedure and the effect of water to surfactant molar ratio (w) on the size, size distribution and magnetic properties of the nanoparticles was studied. MTT assay was utilized to evaluate the cell toxicity of the nanoparticles. To functionalize the particles for MRI imaging and targeted drug delivery, the particles were coated by polyglycerol through capping with thiol followed by polymerization of glycidol. The characteristics of the particles were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometere (VSM), UV-visible spectroscopy, and Fourier...
An improved constant-factor approximation algorithm for planar visibility counting problem
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 2 August 2016 through 4 August 2016 ; Volume 9797 , 2016 , Pages 209-221 ; 03029743 (ISSN) ; 9783319426334 (ISBN) ; Ghodsi, M ; Jafari, A ; Sharif University of Technology
Springer Verlag
2016
Abstract
Given a set S of n disjoint line segments in ℝ2, the visibility counting problem (VCP) is to preprocess S such that the number of segments in S visible from any query point p can be computed quickly. This problem can trivially be solved in logarithmic query time using O(n4) preprocessing time and space. Gudmundsson and Morin proposed a 2-approximation algorithm for this problem with a tradeoff between the space and the query time. They answer any query in Oε(n1−α) with Oε(n2+2α) of preprocessing time and space, where α is a constant 0 ≤ α ≤ 1, ε > 0 is another constant that can be made arbitrarily small, and Oε(f(n)) = O(f(n)nε). In this paper, we propose a randomized approximation algorithm...
The experimental investigation concerning the heat transfer enhancement via a four-point star swirl generator in the presence of water–ethylene glycol mixtures
, Article Journal of Thermal Analysis and Calorimetry ; Volume 144 , February , 2020 , 167–178 ; Farajollahi, A ; Gazori, H ; Sharif University of Technology
Springer Netherlands
2020
Abstract
In the present study, a new swirling flow generator is studied which aims to enhance the convective heat transfer rate in a heat exchanger tube. This device has a four-point star cross section. The study mainly investigates the effect of swirl generator on heat transfer rate and pressure drop along the test tube which is under a constant and uniform heat flux. The working fluid in the experiments is the water–ethylene glycol mixtures with Prandtl numbers ranging from 5 to 150 at different Reynolds numbers from 12,000 to 27,000. The results clarify the potential of the applied swirl generator to make a significant enhancement in the heat transfer rate with a satisfactory rise in the pressure...
Path integral optimization for T T deformation path integral optimization for T T ... Ghadir Jafari, Ali Naseh, and Hamed Zolfi
, Article Physical Review D ; Volume 101, Issue 2 , January , 2020 ; Naseh, A ; Zolfi, H ; Sharif University of Technology
American Physical Society
2020
Abstract
We use the path integral optimization approach of Caputa, Kundu, Miyaji, Takayanagi, and Watanabe to find the time slice of geometries dual to vacuum, primary, and thermal states in the TT-deformed two-dimensional conformal field theories (CFTs). The obtained optimized geometries actually capture the entire bulk, which fits well with the integrability and expected UV completeness of TT-deformed CFTs. When the deformation parameter is positive, these optimized solutions can be reinterpreted as geometries at finite bulk radius, in agreement with a previous proposal by McGough, Mezei, and Verlinde. We also calculate the holographic entanglement entropy and quantum state complexity for these...
Randomized approximation algorithms for planar visibility counting problem
, Article Theoretical Computer Science ; Volume 707 , 2018 , Pages 46-55 ; 03043975 (ISSN) ; Ghodsi, M ; Jafari, A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Given a set S of n disjoint line segments in R2, the visibility counting problem (VCP) is to preprocess S such that the number of segments in S visible from any query point p can be computed quickly. This problem can be solved trivially in O(logn) query time using O(n4logn) preprocessing time and O(n4) space. Gudmundsson and Morin (2010) [10] proposed a 2-approximation algorithm for this problem with a tradeoff between the space and the query time. For any constant 0≤α≤1, their algorithm answers any query in Oϵ(m(1−α)/2) time with Oϵ(m1+α) of preprocessing time and space, where ϵ>0 is a constant that can be made arbitrarily small and Oϵ(f(n))=O(f(n)nϵ) and m=O(n2) is a number that depends...
The effects of trochlear groove geometry on patellofemoral joint stability - A computer model study
, Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 222, Issue 1 , 2008 , Pages 75-88 ; 09544119 (ISSN) ; Farahmand, F ; Meghdari, A ; Sharif University of Technology
2008
Abstract
The effect of the variation in the femoral groove geometry on patellofemoral joint stability was studied using a two dimensional transverse plane model with deformable articular surfaces. The femoral and patellar bony structures were modelled as rigid bodies with their profiles expressed by splines. The articular cartilage was discretized into compression springs, distributed along the femoral and patellar profiles, based on the rigid-body spring model. The medial and lateral retinacula were modelled as linear tensile springs, and the quadriceps muscles and patellar tendon as strings with known tension. The anatomical data were obtained from the transverse plane magnetic resonance images of...
A rigid body spring model to investigate the lateral shift-Restraining force behavior of the patellar
, Article 29th Annual International Conference of IEEE-EMBS, Engineering in Medicine and Biology Society, EMBC'07, Lyon, 23 August 2007 through 26 August 2007 ; 2007 , Pages 4679-4682 ; 05891019 (ISSN) ; 1424407885 (ISBN); 9781424407880 (ISBN) ; Farahmand, F ; Meghdari, A ; Sharif University of Technology
2007
Abstract
Patellar lateral stability was studied using a 2D transverse plane model with deformable articular surfaces. Quadriceps muscles and patellar tendon were considered as strings with predefined forces and lateral and medial retinaculum as tensile springs. Deformation behavior of articular cartilage was modeled by a set of compression springs perpendicular to articular surfaces, based on rigid body spring model method (RBSM). Patellar lateral stability was investigated using restraining force method (the external force required to cause up to 10 mm lateral displacement on patella). The results were in good agreement with experimental reports for normal joint, vastus lateralis and vastus medialis...
The experimental investigation concerning the heat transfer enhancement via a four-point star swirl generator in the presence of water–ethylene glycol mixtures
, Article Journal of Thermal Analysis and Calorimetry ; Volume 144, Issue 1 , 2021 , Pages 167-178 ; 13886150 (ISSN) ; Farajollahi, A ; Gazori, H ; Sharif University of Technology
Springer Science and Business Media B.V
2021
Abstract
In the present study, a new swirling flow generator is studied which aims to enhance the convective heat transfer rate in a heat exchanger tube. This device has a four-point star cross section. The study mainly investigates the effect of swirl generator on heat transfer rate and pressure drop along the test tube which is under a constant and uniform heat flux. The working fluid in the experiments is the water–ethylene glycol mixtures with Prandtl numbers ranging from 5 to 150 at different Reynolds numbers from 12,000 to 27,000. The results clarify the potential of the applied swirl generator to make a significant enhancement in the heat transfer rate with a satisfactory rise in the pressure...
Surface modeling of complicated geometries with incomplete erroneous data points- An extension to B-spline approach
, Article 2005 27th Annual International Conference of the Engineering in Medicine and Biology Society, IEEE-EMBS 2005, Shanghai, 1 September 2005 through 4 September 2005 ; Volume 7 VOLS , 2005 , Pages 1634-1637 ; 05891019 (ISSN); 0780387406 (ISBN); 9780780387409 (ISBN) ; Farahmand, F ; Meghdari, A ; Sharif University of Technology
2005
Abstract
Based on the analogy between the B-spline curve modeling and the force-deflection behavior of a beam subjected to lateral point loads, an extension to the B-spline surface modeling method was introduced. The proposed method has strong extrapolating capability and can develop accurate surface models over an incomplete net of data points without affecting the original data. Extrapolation of the incomplete part of the data net Is conducted simultaneously with interpolation of the existing part, with no need to recalculation. Approximation or data smoothing is a natural extension of the method, however, the smoothing intensity can be controlled continuously without reducing the number of spline...
Discrete-modulation measurement-device-independent continuous-variable quantum key distribution with a quantum scissor: exact non-Gaussian calculation
, Article Optics Express ; Volume 30, Issue 7 , 2022 , Pages 11400-11423 ; 10944087 (ISSN) ; Golshani, M ; Bahrampour, A ; Sharif University of Technology
Optica Publishing Group (formerly OSA)
2022
Abstract
In this paper, we study non-Gaussian discrete-modulated measurement-deviceindependent continuous-variable quantum key distribution protocol equipped with a proposed quantum scissor at the receiver side. Our suggested scissor truncates all multiphoton number states with four or more photons and amplifies remaining photon number states in a probabilistic way. Using exact non-Gaussian calculation, we find that quantum scissor meliorates the fidelity and entanglement between two legitimate parties Alice and Bob, at long distances. Therefore, quantum scissor enhances the continuous-variable quantum key distribution protocol range. Examination of the system for different values of the excess noise...
Tunning the tilt of the Dirac cone by atomic manipulations in 8Pmmn borophene
, Article Communications Physics ; Volume 6, Issue 1 , 2023 ; 23993650 (ISSN) ; Hadipour, H ; Jafari, A ; Sharif University of Technology
Nature Research
2023
Abstract
Two dimensional quantum materials possessing Dirac cones in their spectrum are fascinating due to their emergent low-energy Dirac fermions. In 8Pmmn borophene the Dirac cone is furthermore tilted, which is a proxy for spacetime geometry, since the future light-cone depends on the underlying metric. Therefore it is important to understand the microscopic origin of the tilt. Here, based on ab-initio calculations, we decipher the atomistic mechanism of the formation of tilt. First, nearest-neighbor hopping on a buckled honeycomb lattice forms an upright Dirac cone. Then, the difference in the renormalized anisotropic second-neighbor hopping, formed by virtual hoppings on one-dimensional chains...
High-fidelity continuous-variable quantum key distribution via the proper combination of zero-photon catalysis and quantum scissors
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 40, Issue 3 , 2023 , Pages 661-666 ; 07403224 (ISSN) ; Golshani, M ; Bahrampour, A ; Sharif University of Technology
Optica Publishing Group (formerly OSA)
2023
Abstract
In this paper, we examine how the combination of zero-photon catalysis (ZPC) and a quantum scissors (QS) intensifies the range and the fidelity of a continuous-variable quantum key distribution CV-QKD protocol. Using a non-Gaussian calculation, we realized that the QS significantly boosts the range of the protocol and enhances its fidelity at long distances. At negligible values of excess noise, ZPC operation leads to incredibly high fidelity values, even at large distances. In this case, an optimal strength of the ZPC operation exists that maximizes the secure distance of the protocol. Finally, our study of a system with a nonzero value of excess noise reveals that the fidelity generally...