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Nouredine Ouarab,Messaoud Boumaour 한국물리학회 2017 Current Applied Physics Vol.17 No.9
Electronic properties of Fe1xZnxS2 and Zn1xMgxO alloys are performed by using full potential linearized augmented plane wave method (FP-LAPW). Band gap energies have been calculated by using concomitantly LDA with Tran Blaha modified Becke-Johnson (TB-mBJ) potentials. The corrected positions related to valence band maximum (VBM) and conduction band minimum (CBM) have been evaluated by manybody perturbation theory in GW approximation. The electron affinities of these alloys are determined by knowledge the exact position of CBM from the fit of total density of states (TDOS). In the case of 0 at % of (Zn, Mg) alloyed elements, pyrite FeS2 and wurtzite ZnO, respectively, exhibit positive electron affinities of 3.34 eV and 4.34 eV, which are in close with experimental measurements. As for optical properties, the absorption coefficient spectra and refraction index variations are performed from momentum matrix elements and interpreted via the projected density of states. The studied alloys show significant responses in visible range and a blue shift in connection with increasing the alloyed elements.
Temperature Dependent Poly Crystalline Zinc Oxide Thin Film Transistor Characteristics
Naceur Soufyane,Nouredine Sengouga,Mohammed Labed,Afak Meftah 한국전기전자재료학회 2021 Transactions on Electrical and Electronic Material Vol.22 No.5
The temperature dependence of the electrical characteristics and parameters of a thin fi lm transistor based on polycrystalline zinc oxide (pc-ZnO TFT) is numerically clarifi ed. The drain current as a function the gate voltage (transfer characteristics), of the pc-ZnO TFT is simulated for temperatures ranging from 300 to 400 K. The transfer characteristics, the drain current versus gate voltage, were fi rst computed. The threshold voltage and the electric field mobility were then extracted from these transfer characteristics. The drain current shows Arrhenius-type dependence with temperature. The activation energy varies almost linearly from 0.57 eV at V GS = 2 V to 0.019 eV at V GS = 26 V then goes up to 0.071 eV at V GS = 40 V. This means that this dependence is very strong in the sub-threshold regime while it is inactivated beyond threshold voltage. The threshold voltage and the electric fi eld mobility were also found to be thermally activated. This temperature dependence may be attributed to the contribution of the density of states to the channel electrons in the sub-threshold region or to speed accumulation of electrons at the pc ZnO/SiO 2 interface. However, the contribution of this density of states beyond threshold voltage is negligible. Furthermore, the threshold voltage was found to be proportional to the electric field mobility.
Hiba Meddah,Nouredine Bourahla,Hakim Bechtoula,Hassan Aknouche,Ali Nour 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.4
This paper presents an experimental program carried out to investigate the behavior up to failure of composite wood-coldformed steel studs under monotonic and cyclic axial loading. The composite stud is made of a wood core incorporated inside a CFS C-channel. The main objective of the experiments is to quantify the ultimate strength, the energy dissipation capacity, and the failure mode of full-scale CFS-wood composite elements. For this purpose, eight fi xed-ended columns of 2320 mm in length were tested. The composite CFS C-studs with wood core were subjected to compression and tension monotonic tests in addition to two cyclic tests with diff erent loading rates. For comparison purposes, similar tests were conducted on bare CFS C-studs. The cyclic loading protocol was in accordance with FEMA 461 recommendations, with initial displacement obtained from the monotonic tests. The results revealed that a signifi cant gain of more than 80% in the average ultimate compression strength is achieved by the CFS-wood composite studs, and more importantly, the composite action enhances signifi cantly the energy dissipation capacity characterized by more stable hysteresis loops with less stiff ness and strength degradation. Finally, a detailed FE model using advanced interface modeling techniques, capable of predicting the ultimate strengths and the modes of failure, is elaborated and validated against the experimental results. The numerical model will be used eventually in future research work to optimize and improve the composite action.
Enhancing GaN/AlGaN MQW Micro LED Optical and Electrical Performance with a Non-uniform LQB
Hassani Mohamed,Nouredine Sengouga,Afak Meftah 한국전기전자재료학회 2023 Transactions on Electrical and Electronic Material Vol.24 No.5
In this work, physical device modeling of ultraviolet micro light-emitting diodes (UV-μLEDs) based on GaN/AlGaN multiple quantum wells (MQWs) is presented. We numerically investigated the optical and electrical properties of UV-LEDs with a graded last quantum barrier (LQB). The constant content Aluminium (Al) of the LQB is replaced by a graded Al profile to improve the internal quantum efficiency (IQE) in the active MQWs region. The results show that the internal quantum efficiency (IQE) and radiative recombination rate of UV μLEDs with the last linearly increased Al composition LQB are higher than other samples under 90 A/cm 2 current. This composition also contributes to enhanced hole injection efficiency, effective electron confinement, and uniform distribution of carriers in the MQWs caused by the low electrostatic field. As a result, the optical output power is increased 1.94 times, and the spontaneous emission intensity 2.37 times. The simulated results indicate that the LQB AlGaN layer with different compositions of Al modification can mitigate the effect of the effective electron confinement, Auger recombination rate and hole injection, increasing the overlap between electron ditribution profiles.
Samir Khamel,Nouredine Ouelaa,Khaider Bouacha 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.11
The main of the present study is to investigate the effects of process parameters (cutting speed, feed rate and depth of cut) on performance characteristics (tool life, surface roughness and cutting forces) in finish hard turning of AISI 52100 bearing steel with CBN tool. The cutting forces and surface roughness are measured at the end of useful tool life. The combined effects of the process parameters on performance characteristics are investigated using ANOVA. The composite desirability optimization technique associated with the RSM quadratic models is used as multi-objective optimization approach. The results show that feed rate and cutting speed strongly influence surface roughness and tool life. However, the depth of cut exhibits maximum influence on cutting forces. The proposed experimental and statistical approaches bring reliable methodologies to model, to optimize and to improve the hard turning process. They can be extended efficiently to study other machining processes.
Abdelkader Nour,Samir Lecheb,Nouredine Chikh,M. Ouali Si-Chaïb 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.7
This work concerns the characterization of the thermodynamic behavior of the superalloy Airsist 215 (PN 3601669-7) containing cobalt. Such superalloys are used in aeronautical construction, in the hot parts of the turbine. They are frequently used for the production of the paddles. The parts in service are subjected to dynamic solicitations and thermal fluctuations over the course of time. They are responsible for modification and degradation of material properties. This can lead to the appearance of cracks and, in the long term, to the rupture of these parts. In this paper, a preliminary physical study is made on the appearance of the cracks, followed by experiments using shocks at ambient temperature and under a heating situation which simulates combustion. It is found that these dynamic loads have a significant impact on the development of the cracks that appear on the segments of the turbine nozzle. The study is devoted to the elastic shock of Hertz-Boussinesq extended to viscoelastic bodies by direct convolution of Riemann-Stielges. The interest resides in the local convolution and the distribution of stresses in the contact zone. The shock excitation method includes a deduced force in the load and disload phases. This force is an impulse which approaches a Dirac function. The sample can be modeled approximately by a system of one degree of freedom for natural frequency, damping and transfer function. The spectral response of the specified shock allows calculation of the damping. Every point of this spectrum gives the response for the linear system of the transfer function. Then, viscoelastic shock parameters are deduced.
Effect of a Back-Surface Field and Passivation Layer on a Silicon Schottky Solar Cell
Djemaa Attafi,Rami Boumaraf,Amjad Meftah,Nouredine Sengouga 한국전기전자재료학회 2021 Transactions on Electrical and Electronic Material Vol.22 No.3
In this work, a numerical simulation of a silicon based solar cell (SC) is carried out using Silvaco-Atlas software. The back contact and the back surface field (BSF) combined with a passivation layer (PL) realized by using SiO2 tunneling layer, is addressed in this paper. It is demonstrated that a proper choice of the BSF and PL can enhance a Schottky back contact based solar cell compared to its ohmic counterpart. BSF has to be properly doped to reduce the barrier of the Schottky contact. The tunnel oxide is a vital part in this solar cell. It is required to achieve excellent interface passivation and has to have an optimum thickness and below this thickness, the SC performance is enhanced by a tunneling eff ect, while it is deteriorated by the fi ll factor reduction above this optimum thickness.