COMPUTER SIMULATION OF MAGNETIZATION FOR 3D ELLIPSOIDAL TORUS-SHAPED InAs/GaAs QUANTUM RINGS

2003 ◽  
Vol 14 (04) ◽  
pp. 501-507 ◽  
Author(s):  
YIMING LI
Keyword(s):  
Effective Mass ◽  
Three Dimensional ◽  
Structure Study ◽  
Quasi Particle ◽  
Mass Approximation ◽  
Negative Function ◽  
Magnetic Filed ◽  
Energy Dependent ◽  
Nonlinear Iterative Method ◽  
3D Problem

In this paper we computationally investigate the magnetization for three-dimensional (3D) InAs/GaAs nanorings with different radii in an external magnetic field. Our simulation model includes: (i) the effective mass Hamiltonian in nonparabolic approximation, (ii) the position- and energy-dependent quasi-particle effective mass approximation, (iii) the finite hard wall confinement potential, and (iv) the Ben Daniel–Duke boundary conditions. The nonlinear iterative method is applied to solve the 3D problem. With the developed computer simulator, we find the magnetization for the 3D InAs/GaAs ring is a negative function and oscillates nonperiodically. The oscillation saturates when the applied magnetic filed is increased. This result provides an alternative for the nanoring energy shell structure study and is useful for spintronics applications.

EFFECTIVE-MASS APPROXIMATION IN GRADED CRYSTALS

1990 ◽  
Vol 04 (15n16) ◽  
pp. 2357-2369 ◽  
Author(s):  
Y. FU ◽  
K. A. CHAO
Keyword(s):  
Kinetic Energy ◽  
Exact Solutions ◽  
Effective Mass ◽  
Three Dimensional ◽  
Energy Operator ◽  
Effective Mass Approximation ◽  
Kinetic Energy Operator ◽  
Energy Dispersion ◽  
One Dimensional ◽  
Mass Approximation

The effective mass approximation (EMA), when applied to graded crystals, needs a modified form [Formula: see text] for the kinetic energy operator, where 2α + β = −1 and m(z) is the position-dependent effective mass. We have analyzed the energy dispersion of the EMA Hamiltonian, and performed a one-dimensional and a three-dimensional exact calculation to determine the proper value of β. Our conclusion is that when β = −1 the EMA provides better agreement with the exact solutions.

Effects of moving lid direction on mixed convection and entropy generation in a cubical cavity with longitudinal triangular fin insertion

2017 ◽  
Vol 27 (4) ◽  
pp. 839-860 ◽  
Author(s):  
Lioua Kolsi ◽  
Hakan F. Öztop ◽  
Nidal Abu-Hamdeh ◽  
Borjini Mohamad Naceur ◽  
Habib Ben Assia
Keyword(s):  
Mixed Convection ◽  
Entropy Generation ◽  
Three Dimensional ◽  
Thermal Conductivity Ratio ◽  
Governing Equations ◽  
Content Type ◽  
Driven Cavity ◽  
Triangular Fin ◽  
Cubical Cavity ◽  
3D Problem

Purpose The main purpose of this work is to arrive at a three-dimensional (3D) numerical solution on mixed convection in a cubic cavity with a longitudinally located triangular fin in different sides. Design/methodology/approach The 3D governing equations are solved via finite volume technique by writing a code in FORTRAN platform. The governing parameters are chosen as Richardson number, 0.01 ≤ Ri ≤ 10 and thermal conductivity ratio 0.01 ≤ Rc ≤ 100 for fixed parameters of Pr = 0.7 and Re = 100. Two cases are considered for a lid-driven wall from left to right (V+) and right to left (V−). Findings It is observed that entropy generation due to heat transfer becomes dominant onto entropy generation because of fluid friction. The most important parameter is the direction of the moving lid, and lower values are obtained when the lid moves from right to left. Originality The main originality of this work is to arrive at a solution of a 3D problem of mixed convection and entropy generation for lid-driven cavity with conductive triangular fin attachments.

scholarly journals Numerical study of the reconnection process between magnetic cloud and heliospheric current sheet

2018 ◽  
Vol 619 ◽  
pp. A82
Author(s):  
Man Zhang ◽  
Yu Fen Zhou ◽  
Xue Shang Feng ◽  
Bo Li ◽  
Ming Xiong
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Dynamic Process ◽  
Large Scale ◽  
Magnetic Cloud ◽  
Numerical Study ◽  
Three Dimensional ◽  
Heliospheric Current Sheet ◽  
Reconnection Process ◽  
Magnetic Filed

In this paper, we have used a three-dimensional numerical magnetohydrodynamics model to study the reconnection process between magnetic cloud and heliospheric current sheet. Within a steady-state heliospheric model that gives a reasonable large-scale structure of the solar wind near solar minimum, we injected a spherical plasmoid to mimic a magnetic cloud. When the magnetic cloud moves to the heliospheric current sheet, the dynamic process causes the current sheet to become gradually thinner and the magnetic reconnection begin. The numerical simulation can reproduce the basic characteristics of the magnetic reconnection, such as the correlated/anticorrelated signatures in V and B passing a reconnection exhaust. Depending on the initial magnetic helicity of the cloud, magnetic reconnection occurs at points along the boundary of the two systems where antiparallel field lines are forced together. We find the magnetic filed and velocity in the MC have a effect on the reconnection rate, and the magnitude of velocity can also effect the beginning time of reconnection. These results are helpful in understanding and identifying the dynamic process occurring between the magnetic cloud and the heliospheric current sheet.

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