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Nabeul, Tunisia

Maiz F.,University of Cartage | Maiz F.,King Khalid University
Physica B: Condensed Matter | Year: 2015

A novel method to calculate the quantum transmission, resonance and eigenvalue energies forming the sub-bands structure of non-symmetrical, non-periodical semiconducting heterostructure potential has been proposed in this paper. The method can be applied on a multilayer system with varying thickness of the layer and effective mass of electrons and holes. Assuming an approximated effective mass and using Bastard's boundary conditions, Schrödinger equation at each media is solved and then using a confirmed recurrence method, the transmission and reflection coefficients and the energy quantification condition are expressed. They are simple combination of coupled equations. Schrödinger's equation solutions are Airy functions or plane waves, depending on the electrical potential energy slope. To illustrate the feasibility of the proposed method, the N barriers - (N-1) wells structure for N=3, 5, 8, 9, 17 and 35 are studied. All results show very good agreements with previously published results obtained from applying different methods on similar systems. © 2015 Elsevier B.V. All rights reserved.

Bellich B.,University of Trieste | Elisei E.,University of Trieste | Heyd R.,University of Orleans | Heyd R.,University of Cartage | And 4 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2015

The isothermal dehydration process was investigated by calorimetric experiments on water samples, pointing out a substantial correspondence with gravimetric results, even though the heat flow measurement is characterized by a higher resolution on approaching the end of the evaporation. The role of the geometry of the sample on water evaporation rate is analyzed with reference to two model geometries, resembling the spherical and the planar surface. Specific attention was given to the planar surface for the description of the water evaporation from thin film. The development of a theoretical model, which provides information regarding the water activity, was supported by investigating the effect of the several parameters involved in the isothermal dehydration, such as sample mass and temperature. The data collected revealed some limits in the valuable use of the theoretical model when the experimental conditions are outside the range of quasi-equilibrium thermodynamic condition, e.g., at temperature higher that 50 °C. Attention has also been given to control the initial thermal unbalance in order to improve the measurements. © 2015 Akadémiai Kiadó, Budapest, Hungary.

Abdelhedi M.,National Engineering School of Tunis | Hamdi O.,University of Cartage | Bouallegue A.,National Engineering School of Tunis
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

In 1989, N.Sourlas used the parallel that exists between the information theory and the statistical physics to bring out that low density parity check (LDPC) codes correspond to spins glass models. Such a correspondence is contributing nowadays to the similarity between the statistical physics and the error correcting codes. Hence, the statistical physics methods have been applied to study the properties of these codes. Among these methods the Thouless-Anderson-Palmer (TAP) is an approach which is proved to be similar to the Belief Propagation (BP) algorithm. Unfortunately, there are no studies made for the other decoding algorithms. The main purpose of this paper is to provide a statistical physics analysis of LDPC codes performance. First, we investigate the Log-Likelihood Ratios-Belief Propagation (LLR-BP) algorithm as well as its simplified versions the BP-Based algorithm and the λ-min algorithm with the TAP approach. Second, we evaluate the performances of these codes in terms of a statistical physics parameter called the magnetization on the Additive White Gaussian Noise (AWGN) channel. Simulation results obtained in terms of the magnetization show that the λ-min algorithm reduces the complexity of decoding and gets close to LLR-BP performance. Finally, we compare our LLR-BP results with those of the replica method. © Springer International Publishing Switzerland 2015.

Maiz F.,University of Cartage | Maiz F.,King Khalid University
Physica B: Condensed Matter | Year: 2014

Assuming an approximated effective mass and using Bastard's boundary conditions, a simple method is used to calculate the subband structure for periodic semiconducting heterostructures. Our method consists to derive and solve the energy quantification condition (EQC), this is a simple real equation, composed of trigonometric and hyperbolic functions, and does not need any programming effort or sophistic machine to solve it. For less than ten wells heterostructures, we have derived and simplified the energy quantification conditions. The subband is build point by point; each point presents an energy level. Our simple energy quantification condition is used to calculate the subband structure of the GaAs/Ga0.5Al0.5As heterostructures, and build its subband point by point for 4 and 20 wells. Our finding shows a good agreement with previously published results. © 2014 Elsevier B.V.

Maiz F.,King Khalid University | Maiz F.,University of Cartage | Alfaify S.,King Khalid University
Physica B: Condensed Matter | Year: 2014

New and simple numerical method is being reported to solve anharmonic oscillator problems. The method is setup to approach the real potential V(x) of the anharmonic oscillator system as a piecewise linear potential u(x) and to solve the Schrödinger equation of the system using the Airy function. Then, solutions continuity conditions lead to the energy quantification condition, and consequently, the energy eigenvalues. For testing purpose, the method was applied on the sextic and octic oscillators systems. The proposed method is found to be realistic, computationally simple, and having high degrees of accuracy. In addition, it can be applied to any form of potential. The results obtained by the proposed method were seen closely agreeing with results reached by other complicated methods. © 2014 Elsevier B.V.

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