A characteristic-based numerical simulation of water-titanium dioxide nano-fluid in closed domains

, Article International Journal of Engineering, Transactions A: Basics ; Volume 33, Issue 1 , 2020 , Pages 158-163 Adibi, T ; Razavi, S. E ; Adibi, O ; Sharif University of Technology

Materials and Energy Research Center 2020

Abstract

A new characteristic-based method is developed and used for solving the mixed and forced convection problems. The nano-fluid flow with heat transfer is simulated with a novel characteristic-based scheme in closed domains with different aspect ratios. For this purpose, a FORTRAN code has been written and developed. Water as a pure fluid and water-titanium dioxide as a nano-fluid were considered. The governing equations are solved by the finite volume utilizing a characteristic-based scheme for the convective fluxes. The simulation is done at Grashof numbers from 100 to 104, Reynolds numbers from 100 to 1000, and volume fractions of nano-particles from 0% to 10%. Streamlines, isotherms,...

Coupled plasmonic quantum bits

, Article Proceedings of SPIE - The International Society for Optical Engineering, 24 January 2010 through 28 January 2010 ; Volume 7608 , January , 2010 ; 0277786X (ISSN) ; 9780819480040 (ISBN) Eftekharian, A ; Sodagar, M ; Khoshnegar, M ; Khorasani, S ; Adibi, A ; Sharif University of Technology

2010

Abstract

In this paper we introduce a coupled system of two quantum bits residing at the interface of a heterostructure device. The structure encompasses a reference quantum bit, a photonic/plasmonic crystal waveguide and an obedient quantum bit. Each quantum bit is an electronic device which is designed based on an anti-dot lattice of two-dimensional electron gas in heterostructures. By applying a potential gate in the aforementioned structure it is possible to control electronic tunneling rate and hence quantum bits' swapping frequency. Coupling through the plasmonic waveguide may be employed to entangle quantum bits. The waveguide has been designed by exploiting conducting islands of...

Revised guided mode expansion on dispersive photonic media

, Article Photonic and Phononic Crystal Materials and Devices IX, San Jose, CA, 27 January 2009 through 29 January 2009 ; Volume 7223 , 2009 ; 0277786X (ISSN) Eftekharian, A ; Sodagar, M ; Khoshnegar, M ; Khorasani, S ; Chamanzar, M. R ; Adibi, A ; Sharif University of Technology

2009

Abstract

A novel plane-wave-based approach for analytical treatment of dispersive relation is developed and applied to analyze the behavior of electromagnetic waves in plasmonic-photonic-crystal slabs. Here Drude model is used for describing frequency dependent permittivity of plasma rods in host dielectric medium. In the present work, dispersion relation below and above the light line is calculated approximately by means of Maxwell-Garnett effective medium and Revised Plane Wave Method (RPWM). The eigen-functions are then used in Revised Guided Mode Expansion (RGME) as the set of orthonormal bases. Following this procedure, the accurate band structure is obtained. In these kind of methods there are...

Simulation of New Methods in Ventilation of Underground Station Sand Tunnels

, M.Sc. Thesis Sharif University of Technology Adibi, Omid (Author) ; Farhanieh, bijan (Supervisor)

Abstract

Due to growth of the number of passengers in subway transportation systemsthe capacity of the metro stations are on the rise.The generated heat loads in subway line shall be increased by thegrowth of the its capacity. As a result, current subway ventilation systems cannot provide comfort conditions for passengers. Nowadays, modern ventilation systems are designedto improve ventilation performance and to create suitable thermal conditions. Among of these, the under platform andover track exhaust systems and use of platform screen doors can be Cited. The aim of this study is three-dimensional simulation of air flow in modern ventilation systems of subway stations. Numerical simulations are in...

Mott Transition in Ordered and Disordered Honeycomb Lattice Using Strong-coupling Perturbation Theory

, Ph.D. Dissertation Sharif University of Technology Adibi, Elaheh (Author) ; Jafari, Akbar (Supervisor)

Abstract

The ability to determine the nature of the low temperature state of the interacting quantum system is one of the main goals of condensed matter theory. Nevertheless, despite ongoing efforts, no single method has proved to work perfectly for interacting systems. In this thesis, we employ the strong-coupling perturbation theory which corresponds to an expansion in powers of the hopping t around the atomic limit. So, first the strong-coupling perturbation theory is introduced. Next we apply this approach to the half-filled Hubbard model on honeycomb lattice. Within this approach, we are able to obtain an analytical form for single-particle gap, extracted from density of state, as a function of...

Laminar forced convection simulation at different boundary conditions with averaging scheme (numerical and theoretical research)

, Article Mathematical Modelling of Engineering Problems ; Volume 6, Issue 4 , 2019 , Pages 519-526 ; 23690739 (ISSN) Adibi, T ; Adibi, O ; Sharif University of Technology

International Information and Engineering Technology Association 2019

Abstract

In this paper, cavity flow is simulated numerically. Forced convection in different Reynolds numbers between 100 and 5000 is simulated. Different and complex thermal boundary conditions are applied and various parameters are calculated numerically. Up and down walls are in constant temperature and left and right walls are thermal insulation in the first thermal boundary condition. The Left and the down walls are in constant temperature and the temperature of the up and the right walls changes linearly in the second thermal boundary condition. For the third thermal boundary condition, the left and the down walls are in constant temperature and the temperature of the up and the right walls...

Laminar forced convection simulation at different boundary conditions with averaging scheme (numerical and theoretical research)

, Article Mathematical Modelling of Engineering Problems ; Volume 6, Issue 4 , 2019 , Pages 519-526 ; 23690739 (ISSN) Adibi, T ; Adibi, O ; Sharif University of Technology

International Information and Engineering Technology Association 2019

Abstract

In this paper, cavity flow is simulated numerically. Forced convection in different Reynolds numbers between 100 and 5000 is simulated. Different and complex thermal boundary conditions are applied and various parameters are calculated numerically. Up and down walls are in constant temperature and left and right walls are thermal insulation in the first thermal boundary condition. The Left and the down walls are in constant temperature and the temperature of the up and the right walls changes linearly in the second thermal boundary condition. For the third thermal boundary condition, the left and the down walls are in constant temperature and the temperature of the up and the right walls...

Quantum well design and diffraction efficiency of quantum well light emitting diode

, Article Photonic and Phononic Crystal Materials and Devices IX, San Jose, CA, 27 January 2009 through 29 January 2009 ; Volume 7223 , 2009 ; 0277786X (ISSN) Khoshnegar, M ; Eftekharian, A ; Sodagar, M ; Khorasani, S ; Adibi, A ; Sharif University of Technology

2009

Abstract

In this work, a GaN-based quantum well LED is theoretically analyzed in a multi-layer structure composed of a quantum well embedded in a waveguide core surrounded by photonic crystal slab and a sapphire substrate. The electromagnetic eigenmodes are obtained throughout above structure via revised plane wave-scattering matrix method. The omnidirectional transmission and reflection are investigated for both TE and TM polarizations from diffraction channels in Ewald construction. Then, we introduced angular power density and calculated radiative modes extraction efficiency. All structural parameters, such as lattice geometry, lattice constant, photonic crystal thickness and filling factor, are...

Strong-coupling approach to mott transition of massless and massive Dirac fermions on honeycomb lattice

, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 93, Issue 7 , 2016 ; 10980121 (ISSN) Adibi, E ; Jafari, S. A ; Sharif University of Technology

American Physical Society 2016

Abstract

Phase transitions in the Hubbard model and ionic Hubbard model at half-filling on the honeycomb lattice are investigated in the strong-coupling perturbation theory which corresponds to an expansion in powers of the hopping t around the atomic limit. Within this formulation we find analytic expressions for the single-particle spectrum, whereby the calculation of the insulating gap is reduced to a simple root finding problem. This enables high-precision determination of the insulating gap that does not require any extrapolation procedure. The critical value of Mott transition on the honeycomb lattice is obtained to be Uc≈2.38t. Studying the ionic Hubbard model at the lowest order, we find two...

, M.Sc. Thesis Sharif University of Technology Adibi, Behnam (Author) ; Karimi Taheri, Ali (Supervisor)

Abstract

This study was conducted in order to investigate the effect of difference in electrical resistivity between low carbon steel and austenitic stainless steel on the physical and mechanical properties and fracture mode of dissimilar resistance spot welds of these alloys. For this purpose, plastic deformation using constrained groove pressing combined with rolling applied to low carbon steel in three levels of 40%, 156% and 272%. Microstructural characterization, micro-hardness measurements and shear-tension test were performed. It was shown that by increasing the pre-strain in low carbon steel its electrical resistivity increases from 13.08 μΩ.cm to 19.5 μΩ.cm and because of reduction of...

Predictive models for permeability and diffusivity of CH4 through imidazolium-based supported ionic liquid membranes

, Article Journal of Membrane Science ; Volume 371, Issue 1-2 , 2011 , Pages 127-133 ; 03767388 (ISSN) Adibi, M ; Barghi, S.H ; Rashtchian, D ; Sharif University of Technology

2011

Abstract

Experimental permeability and diffusivity values for CO2 and CH4 through imidazolium-based ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf2N]) were determined in the temperature range of 300-320K using temperature correction factor defined in our previous study. According to literature, experimental values of permeability and diffusivity obtained in this study for CO2 in [hmim][Tf2N], showed good agreement with predictive models reported by other researchers. In addition, experimental values of permeability and diffusivity for CH4 in [hmim][Tf2N] as a function of pressure have been reported in this study. Considering the results of present study and...

Numerical study of heat and mass transfer in underexpanded sonic free jet

, Article International Journal of Heat and Technology ; Volume 35, Issue 4 , 2017 , Pages 959-968 ; 03928764 (ISSN) Adibi, O ; Farhanieh, B ; Afshin, H ; Sharif University of Technology

2017

Abstract

In case of unexpected ruptures in high pressure tanks, choking phenomenon occurs in the cracked area which fluid velocity gets sonic and its pressure exceeds atmospheric pressure. Afterward, pressure of discharged gas quickly changes by crossing through compression and expansion shock waves. The main aim of this study was numerical simulation and investigation of this flow in a 3-step process: (a) Detailed analysis of numerical method, (b) Qualitative and quantitative analysis of velocity, pressure, temperature and turbulence intensity, in order to propose safety strategies and (c) parametric studies on the effects of tank pressure and nozzle geometry on flow structure. In numerical...

Observations on failure in blogs

, Article 2007 International Conference on Weblogs and Social Media, ICWSM 2007, Boulder, CO, 26 March 2007 through 28 March 2007 ; 2007 Qazvinian, V ; Rassoulian, A ; Adibi, J ; Sharif University of Technology

2007

Abstract

The capability of placing "comments" on the posts makes the blogspaces rather a complex environment. One of the interesting phenomena in blogspace is "blogger failure" when a blogger stops writing after a certain amount of time and will not return to blogspace for a long time, or when a blogger does not get any comment from her audience. In this paper we illustrate our observation on bloggers failure in a unique blogspace. First, we introduce PersianBlog blogspace briefly along with our observations of behaviors of bloggers on placing comments. Next, we will provide our definition of failure, and give a broad future research path to model failure in blogspace

Photonic band structure of isotropic and anisotropic Abrikosov lattices in superconductors

, Article Physica C: Superconductivity and its Applications ; Volume 467, Issue 1-2 , December , 2007 , Pages 51-58 ; 09214534 (ISSN) Zandi, H ; Kokabi, A ; Jafarpour, A ; Khorasani, S ; Fardmanesh, M ; Adibi, A ; Sharif University of Technology

2007

Abstract

We have performed a numerical solution for band structure of an Abrikosov vortex lattice in type-II superconductors forming a periodic array in two dimensions for applications of incorporating the photonic crystals concept into superconducting materials with possibilities for optical electronics. The implemented numerical method is based on the extensive numerical solution of the Ginzburg-Landau equation for calculating the parameters of the two-fluid model and obtaining the band structure from the permittivity for both orthogonal polarizations, which depends on the above parameters and the frequency. This is while the characteristics of such crystals highly vary with an externally applied...

Design and fabrication of photonic crystal nano-beam resonator: transmission line model

, Article Journal of Lightwave Technology ; Volume 32, Issue 1 , 14 November 2013 , Pages 91-98 Miri, M ; Sodagar, M ; Mehrany, K ; Eftekhar, A. A ; Adibi, A ; Rashidian, B ; Sharif University of Technology

14 November 2013

Abstract

We present a new method for modeling and design of photonic crystal nano-beam resonators (PCNBRs) based on cascaded transmission lines. The proposed model provides an accurate estimate of the PCNBRs properties such as resonance wavelength and quality factor (Q) with much smaller computation cost as compared to the brute-force numerical methods. Furthermore, we have developed a straightforward technique for the design of high-Q PCNBRs based on resonance modes with Gaussian electromagnetic field profiles. The results obtained by using the proposed transmission line model are compared against numerical and experimental results and the accuracy of the model is verified. The proposed model...

Wideband tunable photonic crystal cavity with electrostatic actuation

, Article 2012 IEEE Photonics Conference, IPC 2012, 23 September 2012 through 27 September 2012 ; September , 2012 , Pages 266-267 ; 9781457707315 (ISBN) Miri, M ; Sodagar, M ; Eftekhar, A. A ; Mehrany, K ; Rashidian, B ; Adibi, A ; Sharif University of Technology

2012

Abstract

We present a wideband tunable optical cavity based on electrostatic actuation. Over 60nm shift in wavelength is achieved by applying less than 1 Volt corresponds to a mechanical displacement of 30nm

On the power-bandwidth trade-off in bistable photonic switches

, Article Photonic and Phononic Crystal Materials and Devices IX, San Jose, CA, 27 January 2009 through 29 January 2009 ; Volume 7223 , 2009 ; 0277786X (ISSN) Naqavi, A ; Abediasl, H ; Mehrany, K ; Khorasani, S ; Chamanzar, M. R ; Adibi, A ; Sharif University of Technology

2009

Abstract

Low power operation and high speed have always been desirable in applications such as data processing and telecommunications. While achieving these two goals simultaneously, however, one encounters the well-known powerbandwidth trade-off. This is here discussed in a typical bistable switch based on a two-dimensional photonic crystal with Kerr type nonlinearity. The discussion is supported by the nonlinear finite difference time domain (FDTD) simulation of a direct coupled structure with a home-developed code. Two cases of working near resonant and off- resonant are simulated to compare the power and the speed of the device in the two cases. It is shown that working nearresonance reduces the...

Photonic band structure of abrikosov lattices in superconductors

, Article Photonic Crystal Materials and Devices VI, San Jose, CA, 22 January 2007 through 25 January 2007 ; Volume 6480 , 2007 ; 0277786X (ISSN) Zandi, H ; Kokabi, A ; Jafarpour, A. A ; Khorasani, S ; Fardmanesh, M ; Adibi, A ; Sharif University of Technology

2007

Abstract

We have performed a numerical solution for band structure of an Abrikosov vortex lattice in type-11 superconductors forming a periodic array in two dimensions for applications of incorporating the photonic crystals concept into superconducting materials with possibilities for optical electronics. The implemented numerical method is based on the extensive numerical solution of the Ginzburg-Landau equation for calculating the parameters of the two-fluid model and obtaining the band structure from the permittivity, which depends on the above parameters and the frequency. This is while the characteristics of such crystals highly vary with an externally applied static normal magnetic field,...

Effects of perforated anchors on heat transfer intensification of turbulence nanofluid flow in a pipe

, Article Journal of Thermal Analysis and Calorimetry ; Volume 141, Issue 5 , 2020 , Pages 2047-2059 Adibi, O ; Rashidi, S ; Abolfazli Esfahani, J ; Sharif University of Technology

Springer Netherlands 2020

Abstract

In this paper, a study is conducted to determine the influences of perforated anchors on heat transfer intensification of turbulence nanofluid flow in a pipe. Six different turbulence models are used, and the results obtained by these models are benchmarked with the existing theoretical data to select the best turbulence model. The outputs showed that the k–ε–RNG–scalable wall function model has higher accuracy and so it is selected to simulate this problem. The influences of various parameters including the addition of perforation on the anchors, the perforation diameter (in the range of 1–5 mm), the Re number (in the range of 5000–25,000), and the volumetric concentration of nanoparticles...

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) Adibi, E ; 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...