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1
Content available remote

New Numerical Matrix Methods of Solving the Quasi-One-Dimensional Effective-Mass Equation

100%
Salejda W., Tyc M., Andrzejewski J., Kubisa M., Misiewicz J., Just M., Ryczko K.
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vol. 95
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issue 6
881-896
EN
New efficient numerical methods of computing eigenvalues and eigenvectors of quasi-one-dimensional effective-mass Hamiltonian with arbitrary coordinate dependence of charge carrier mass are presented. Within the proposed approach the effective-mass equation is replaced by a nonsymmetric or symmetric matrix eigenproblem which can be analysed numerically with the help of existing computer routines. The presented methods are verified in special semiconductor heterostructure cases that are solvable within other approaches. A generalization of the presented methods for nonparabolic materials is also discussed.
2
Content available remote

Optimal Design of Light Commercial Vehicle Headlamp for Pedestrian Protection

100%
Yazıcı M., Güçlü H., Karen İ., Kandirmiş İ., Malkoç S., Buyukluoğlu Ö.
Acta Physica Polonica A
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2016
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vol. 130
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issue 1
262-265
EN
In this study, the headlamp of a light commercial vehicle was optimized in the way of pedestrian safety. This work aims to prevent harms to pedestrians in the urban crashes. Finite element analysis models of current headlamp and impactors representing pedestrian body forms were created. Static, modal and dynamic/explicit analyses were carried out by using existing and optimized headlamp models. Both models were in the simulations under the same boundary conditions. The results of two conditions were compared with each other. The results showed that connection regions of the headlamp have a major effect on pedestrian safety in pedestrian-vehicle collisions.
3
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Content available

Ferromagnetic Layered Composites. Transfer Matrix Approach

80%
Puszkarski H., Krawczyk M., Lévy J., Mercier D.
Acta Physica Polonica A
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2001
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vol. 100
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issue Supplement
195-214
EN
A theoretical analysis of spin-wave excitations in a ferromagnetic layered composite (ABAB... ABA; A and B are different homogeneous ferromagnetic materials) is performed by means of the transfer matrix approach. We focus our attention on two features not yet well studied in the present literature, namely, the existence of forbidden energy gaps in the spin-wave mode spectrum, as well as the properties of multilayer spin-wave mode profiles. These features are discussed in relation to several multilayer characteristics, such as the filling fraction, and the exchange or magnetization contrast; surface pinning conditions and dipolar interactions are also taken into account. The existence of forbidden gaps as well as properties of mode profiles are successfully explained by having recourse to an approximate model of indepe ndent constituent sublayers. Finally, as a byproduct of our investigation, we ascertain that the conventional test for computational convergence within the finite difference method demands to be completed by symmetry mode profile verification, in addition to standard verification of the frequency convergence alone.
4
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Simulation of Dislocation Annihilation by Cross-Slip

80%
Pauš P., Beneš M., Kratochvíl J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
509-511
EN
This contribution deals with the numerical simulation of dislocation dynamics, their interaction, merging and changes in the dislocation topology. The glide dislocations are represented by parametrically described curves moving in slip planes. The simulation model is based on the numerical solution of the dislocation motion law belonging to the class of curvature driven curve dynamics. We focus on the simulation of the cross-slip of two dislocation curves where each curve evolves in a different slip plane. The dislocations evolve, under their mutual interaction and under some external force, towards each other and at a certain time their evolution continues outside slip planes. During this evolution the dislocations merge by the cross-slip occurs. As a result, there will be two dislocations evolving in three planes, two planes, and one plane where cross-slip occurred. The goal of our work is to simulate the motion of the dislocations and to determine the conditions under which the cross-slip occurs. The simulation of the dislocation evolution and merging is performed by improved parametric approach and numerical stability is enhanced by the tangential redistribution of the discretization points.
5
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Numerical Simulations of Shock Wave Propagating by a Hybrid Approximation Based on High-Order Finite Difference Schemes

80%
Zeytinoglu A., Sari M., Allahverdiev B.
Acta Physica Polonica A
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2018
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vol. 133
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issue 1
140-151
EN
In this paper, we attempt to display effective numerical simulations of shock wave propagating represented by the Burgers equations known as a significant mathematical model for turbulence. A high order hybrid approximation based on seventh order weighted essentially non-oscillatory finite difference together with the sixth order finite difference scheme implemented for spatial discretization is presented and applied without any transformation or linearization to the Burgers equation and its modified form. Then, the produced system of first order ordinary differential equations is solved by the MacCormack method. The efficiency, accuracy and applicability of the proposed technique are analyzed by considering three test problems for several values of viscosity that can be caused by the steep shock behavior. The performance of the method is measured by some error norms. The results are in good agreement with the results reported previously, and moreover, the suggested approximation relatively comes to the forefront in terms of its low cost and easy implementation.
6
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Growth Analysis and Numerical Simulation of Cu_3BiS_3 Absorbing Layer Solar Cell through the wxAMPS and Finite Element Method

80%
Mesa F., Ballesteros V., Dussan A.
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vol. 125
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issue 2
385-387
EN
The properties and the efficiency of a semiconductor thin film depend on the state of stress and defects in the film structure. When the film is growing layer by layer, the elastic energy due to deformation stress between the substrate and the film is released partly due to the formation of dislocations in the critical thickness deformation. In this paper, we present a finite element analysis of the stress state in a thin film of Cu_3BiS_3 as a function of thickness and elastic energy release by nucleation of dislocations. Initially, we analyze the stress contours associated with the epitaxial growth and dislocation nucleation and then combine these two in order to study the effective potential energy state of the system. Finally, the tool wxAMPS is today an important application for simulation of solar cells with high reliability and an improved design over its analysis of microelectronic and photonic structures predecessor, incorporating physical principles concerning photovoltaic phenomena and uses a new method for solving algorithms, combining Newton and Gummel approaches, which provides greater stability and speed of computation.
7
Content available remote

Numerical Simulation of Dislocation Cross-Slip with Annihilation in Non-Symmetric Configuration

80%
Pauš P., Beneš M., Kratochvíl J.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
737-739
EN
The interpretation of the experimentally determined critical distance of the screw dislocation annihilation in persistent slip bands is still an open question. We attempt to analyze this problem using the discrete dislocation dynamics simulations. Dislocations are represented by parametrically described curves. The model is based on the numerical solution of the dislocation motion law belonging to the class of curvature driven curve dynamics. We focus on the simulation of the cross-slip of one edge dislocation curve bowing out of the wall of a persistent slip band channel and one screw dislocation gliding through the channel. The dislocations move under their mutual interaction, the line tension and the applied stress. A cross-slip leads to annihilation of the dipolar parts. In the changed topology each dislocation evolves in two slip planes and the plane where cross-slip occurred. The goal of our work is to develop and test suitable mathematical and physical model of the situation. The results are subject to comparison with symmetric configuration of two screw dislocations studied in papers by Pauš et al. The simulation of the dislocation evolution and merging is performed by the improved parametric approach. Numerical stability is enhanced by the tangential redistribution of the discretization points.
8
Content available remote

Numerical Study on Gas Flow through a Micro-Nano Porous Media

80%
Abbasbandy S.
Acta Physica Polonica A
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2012
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vol. 121
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issue 3
581-585
EN
The present research examines the unsteady isothermal flow of a gas through a semi-infinite micro-nano porous medium, a nonlinear boundary value problem on semi-infinite interval. This problem is solved by two different methods and compare their results with solution of other methods is compared. Also through the convergence of these methods, the accurate initial slope y(x) with good capturing the essential behavior of y(x) is obtained.
9
Content available remote

Defect Sensitivity of Magnetic Dot Arrays Influenced by Thermal Activation and Intradot Anisotropy

80%
Baláž P., Horváth D., Gmitra M.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
583-586
EN
The influence of non-magnetic central node defect on magnetic hysteresis of regular square-shaped segment of magnetic dot array with perpendicular uniaxial anisotropy under the thermal activation was investigated via computer simulations based on stochastic Landau-Lifshitz-Gilbert equation. The aim of this study is to point out the simultaneous effect of anisotropy and thermal activation to the dynamical properties of magnetic dot arrays.
10
Content available remote

Numerical Simulations of Glide Dislocations in Persistent Slip Band

80%
Kolář M., Beneš M., Kratochvíl J., Pauš P.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
506-509
EN
For the purpose of estimation of possible inaccuracy in standard discrete dislocation dynamics simulations, we study the motion of interacting dislocations in two regimes: the standard stress control and the total strain control. For demonstration of the difference, we consider two dislocations of opposite signs, gliding in parallel slip planes in a channel of a persistent slip band. Exposed to the applied stress, the dislocations move, bow out, and form a dipole. We investigate the passing stress needed for the dislocations to escape each from other, considering the stress controlled regime and the total strain controlled regime. The motion is described by the mean curvature flow and treated by means of the direct (parametric) method. The results of numerical experiments indicate that the stress control and the total strain control provide upper and lower estimate of the passing stress, respectively, and that these two estimates differ by approximately 10%.
11
Content available remote

Non-Polynomial Spline Method for a Time-Dependent Heat-Like Lane- Emden Equation

70%
Caglar S., Ucar M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
262-264
EN
In this study, a time-dependent heat-like Lane-Emden equation is solved by using a non-polynomial spline method. An example is solved to assess the accuracy of the method. The numerical results are obtained for different values (n) of equation. The results indicate that non-polynomial spline method is effectively implemented. It is seen that results are compatible with exact solutions and consistent with other existing numerical methods.
12
Content available remote

The Influence of Sub-Wavelength Effective Refractive Index Layer on the Transmittance of LYSO Scintillator

61%
Modrzyński P., Olejniczak A., Zięba A., Kunicki P., Tomanik M., Wielebski M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 6
1565-1569
EN
From various types of scintillating materials lutetium-yttrium oxyorthosilicate (LYSO) has the highest luminosity and the greatest potential of application in high-energy radiation detectors. Due to the small critical angle of total internal reflection the enhancement of the extraction of light outside a scintillator is a challenge. We study numerically the influence of the effective refractive index layer on the transmittance of LYSO crystal. It is possible to realize such layer by sub-wavelength patterning of crystal surface using for example focused ion beam. The enhancement of transmittance of LYSO crystal up to 100% as well as the possibility to tune the positions of transmittance maxima have been shown.
13
Content available remote

Full-Vectorial Description of the Light Guidance in Anisotropic Photonic Liquid Crystal Fibers

61%
Rutkowska K., Wei L.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
880-890
EN
In this paper we present our theoretical approach for the description of the light guidance in photonic liquid crystal fibers. In particular, we focus on the numerical methods allowing for a full implementation of the liquid crystals properties (i.e., including their optical anisotropy and molecular orientation), with a final target in characterizing photonic liquid crystal fibers with accessible computational effort. For this purpose suitable analytical formulae required for a full-vectorial description of the optical modes in photonic liquid crystal fibers have been derived. In addition, computational schemes allowing for numerical implementation of theoretical formulations (with the use of the finite-difference scheme) have been developed, validated and optimized. Their numerical convergence has been checked for different structures, as well as for different input parameters (e.g., grid-size). Obtained results have been compared to those analytically calculated, known from literature and/or got with use of commercial software. Moreover, the implemented schemes have been examined in accordance with experimental tests performed on the photonic liquid crystal fiber of interest.
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