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Analysis of edge defects in an elastic plate using SH-waves
Brahim Mohammedi,Nahil A Sobh,Diab Abueidda,Belgacem-Bouzida Aissa 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1
The interaction of guided SH-waves with the beveled free end of a semi-infinite plate is analytically and numerically investigated. The material of the plate is assumed to be elastic, homogenous, and isotropic. The plate is modeled as a combination of a semi-infinite region and bounded wedged region separated by a common boundary. The analytical solution of the vertical free end case for the two regions is derived and used in verifying the numerical implementation. In this study, the SH 0 and the SH 1 first two incident modes are individually applied to analyze the corresponding reflected modes from the free end. Specifically, the elastic energy carried by the reflected modes is reported for a wide range of beveled angles and incident frequencies.
Magnetic Anisotropy of Pd/Co/Pd Ultrathin Film: Interface Vacancy Defect and O Diffusion Effect
Brahim Marfoua,Jisang Hong 한국자기학회 2021 Journal of Magnetics Vol.26 No.3
Using first principles calculation, we investigated the magnetic anisotropy of Pd/Co/Pd ultrathin film. Here, we explored the magnetic anisotropy of pristine Pd/Co/Pd ultrathin film and also interface vacancy defect (Pd or Co) and the oxygen diffusion as well. No substantial change in the magnetic moment is found in the vacancy defect and also in the O diffusion structure relative to the pristine system. We found that the pristine Pd/Co/Pd system has a perpendicular magnetic anisotropy of 1.37 meV/cell. This perpendicular magnetic anisotropy decreased to 0.46 meV/cell in Pd vacancy defect and it became 0.56 meV/cell in Co vacancy defect. We also obtained similar magnetic anisotropy energy of 0.52 meV/cell in the O impurity system. Although the vacancy defect and O impurity system exhibited a similar magnetic anisotropy, we found that this feature originated from different spin-orbit coupling effect which is sensitive to the sample preparation condition.
Brahim Es-Sabbar,Mourad Essalhi,Abdelhafid Essalhi,Hicham Si Mhamdi 대한자원환경지질학회 2020 자원환경지질 Vol.53 No.4
The study area is located in the southern part of the M’aider Paleozoic basin in the Moroccan Eastern Anti-Atlas. It is an arid region, characterized by minimal vegetation cover, which can provide an ideal environment to apply remote sensing. In this study, remote sensing and field investigations were integrated for lithological and structural lineaments mapping. The Landsat 8 OLI data were processed in order to understand the role of lithology and geological structures in the distribution of mineral deposits in the study area. To achieve this purpose, the Color Composite (CC), the Principal Component Analysis (PCA) and Band Rationing transformation (BR) tests were performed. The results of remote sensing techniques coupled with field investigations have shown that the zones of high lineaments densities are highly correlated with the occurrences of barite mineralization. These findings depict a spatial relationship between structural lineaments and the mineralization distribution zones. Therefore, the barite and Iron oxides mineralization veins, which occur mainly in the Ras Kammouna district, seem to have a structural control. The methodological approach used in this study examining lithological mapping and lineament extractions can be used to explore mineral deposits in arid regions to a high degree of efficiency.
Optical Properties of a Two-Dimensional GeTe Layer
Brahim Marfoua,홍지상 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.3
Using the first principles calculations, we explored the optical properties of the two-dimensional -GeTe structure. The 2D monolayer -GeTe had an indirect band gap of 1.79 eV, and that indirect band gap was still observed in the bilayer although the band gap had decreased to 0.61 eV. We found that the optical band gap was much larger than the electrical band gap, which was due to the indirect band gap feature of the 2D -GeTe system. In both systems, we found a very large refractive index in the visible range. Particularly, the bilayer system had a refractive index larger than 2.5 for blue light. Furthermore, the bilayer structure was found to have a larger reflectivity at ultraviolet frequencies. Consequently, we propose that the bilayer -GeTe film can be utilized for potential optical device applications.
Brahim Gaies,Mahmoud-Sami Nabi 세종대학교 경제통합연구소 2019 Journal of Economic Integration Vol.34 No.3
This study examines how external financing (EF) affects growth in developing countries by distinguishing between two forms of external financing: debt and foreign direct investment (FDI). We show that both types favor growth by boosting investment through the credit channel. However, excessive external debt increases vulnerability to financial crises. Contrariwise, FDI plays an amortizing role by reducing a crisis’ effects. The empirical evidence confirms these results and demonstrates that, despite the more secure nature of FDI, mixed financing (debt and FDI) remains more profitable for developing countries because of the inverted U-shaped growth effect of the FDI-to-debt ratio. Moreover, exchange rate stability decreases vulnerability to financial crises, whereas higher stability turns into exchange rate rigidity and thus increases crisis occurrence.
Brahim Brahmi,Ibrahim El Bojairami,Maarouf Saad,Mark Driscoll,Samir Zemam,Mohamed Hamza Laraki 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.1
This paper presents the design and validation of a new adaptive variable gain reaching law, integrated with sliding mode control (SMC), to control perturbed and unperturbed nonlinear systems. The novelty behind this law stems from its capability to overcome the main limitations involved with SMC. In contrast to existing reaching laws, system’s performance can be substantially enhanced via this law, with signifi cant reduction in the chattering phenomenon, along ensuring rapid convergence time of system’s trajectories towards equilibrium. The designed law not only integrates the features of both the exponential reaching law (ERL) and the power rate reaching law (PRL), but also overcomes their limitations. Simulation and comparison studies against ERL and PRL were carried out to validate the eff ectiveness and advantages of the proposed reaching law scheme (Proposed-RL). Furthermore, controlled experimental investigations were conducted using an exoskeleton robot (ETS-MARSE) to validate the scheme in real-time.