Kharmouche A.,Ferhat Abbas University Setif
Journal of Magnetism and Magnetic Materials | Year: 2013
Series of CoxCr1-x thin films have been evaporated under vacuum onto Si (100) and glass substrates. An alternating gradient field magnetometer is used to characterize the static magnetic properties of the samples and Brillouin light scattering is used to study their dynamic magnetic properties. The in-plane easy magnetization axis is found for all samples. Using these results, we computed the first, second and uniaxial magnetic anisotropy factors by several methods. Values of the computed effective magnetic anisotropy factors higher than 106 erg cm-3 have been found. The results are discussed and correlated. © 2012 Elsevier B.V.
Achache M.,Ferhat Abbas University Setif
RAIRO - Operations Research | Year: 2016
In this paper, a weighted-path-following interior point algorithm for P∗(κ)-linear complementarity problems (P∗(κ)-LCP) is presented. The algorithm uses at each weighted interior point iteration only feasible full-Newton steps and the strategy of the central-path for getting a solution for P∗(κ)-LCP. We prove that the proposed algorithm has quadratically convergent with polynomial time. The complexity bound, namely, O((1+κ)√n log n/ε) of the algorithm is obtained. Few numerical tests are reported to show the efficiency of the algorithm. © EDP Sciences, ROADEF, SMAI 2016.
Sayah S.,Ferhat Abbas University Setif |
Hamouda A.,Ferhat Abbas University Setif
Applied Soft Computing Journal | Year: 2013
This paper presents the design and application of an efficient hybrid heuristic search method to solve the practical economic dispatch problem considering many nonlinear characteristics of power generators, and their operational constraints, such as transmission losses, valve-point effects, multi-fuel options, prohibited operating zones, ramp rate limits and spinning reserve. These practical operation constraints which can usually be found at the same time in realistic power system operations make the economic load dispatch problem a nonsmooth optimization problem having complex and nonconvex features with heavy equality and inequality constraints. The proposed approach combines in the most effective way the properties of two of the most popular evolutionary optimization techniques now in use for power system optimization, the Differential Evolution (DE) and Particle Swarm Optimization (PSO) algorithms. To improve the global optimization property of DE, the PSO procedure is integrated as additional mutation operator. The effectiveness of the proposed algorithm (termed DEPSO) is demonstrated by solving four kinds of ELD problems with nonsmooth and nonconvex solution spaces. The comparative results with some of the most recently published methods confirm the effectiveness of the proposed strategy to find accurate and feasible optimal solutions for practical ELD problems. © 2012 Elsevier B.V.
Khebbache H.,Ferhat Abbas University Setif
International Journal of Control and Automation | Year: 2012
The work proposed in this paper aims to design a robust control algorithm for the attitude tracking of a quadrotor UAV system in presence of actuator faults. The attitude dynamic modeling of quadrotor while taking into account various physical phenomena, which can influence the dynamics of a flying structure is presented. Subsequently, a control algorithm which based on robust integral backstepping taking into account the actuator faults is developed. Lyapunov based stability analysis shows that the proposed control algorithm keep the stability of the closed loop dynamics of quadrotor UAV even after the presence of actuator faults. Numerical simulation results are provided to show the good tracking performance of proposed control laws.
Berri S.,Ferhat Abbas University Setif
Journal of Magnetism and Magnetic Materials | Year: 2015
A first-principles approach is used to study the structural, electronic and magnetic properties of Sr2GdReO6, using full-potential linearized augmented plane wave (FP-LAPW) method within the spin density functional theory. At the equilibrium lattice constant, our calculations predict that Sr2GdReO6 is half-metallic (HM) with a magnetic moment of 9 μB/fu and HM flip gap of 1.82 eV. In addition, the ferromagnetic phase is found to be energetically more favorable than paramagnetic phase. Therefore, the Sr2GdReO6 compound is a promising material for future spintronic application. ©2015 Elsevier B.V. All rights reserved.
Layadi A.,Ferhat Abbas University Setif
AIP Advances | Year: 2015
The ferromagnetic resonance intrinsic field linewidth ΔH is investigated for a multilayer system such as a coupled trilayer and a spin valve structure. The magnetic coupling between two ferromagnetic layers separated by a nonmagnetic interlayer will be described by the bilinear J1 and biquadratic J2 coupling parameters. The interaction at the interface of the first ferromagnetic layer with the antiferromagnetic one is account for by the exchange anisotropy field, HE. A general formula is derived for the intrinsic linewidth ΔH. The explicit dependence of ΔH with HE, J1 and J2 will be highlighted. Analytical expressions for each mode field linewidth are found in special cases. Equivalent damping constants will be discussed. © 2015 Author(s).
Bouchama Z.,Ferhat Abbas University Setif |
Harmas M.N.,Ferhat Abbas University Setif
Electric Power Systems Research | Year: 2012
A new particle swarm optimized robust indirect adaptive power system stabilizer is developed based on recently developed synergetic control methodology. Fuzzy systems are used in an adaptive scheme to approximate the system using a nonlinear model while synergetic control guarantees robustness and the use of a chatter free continuous control law which makes the controller easy to implement. In addition the controller parameters are optimized using PSO approach. Simulation of severe operating conditions of a power system is conducted to validate the effectiveness of the proposed approach while stability is guaranteed via Lyapunov synthesis. © 2011 Elsevier B.V. All rights reserved.
Hamouda A.,Ferhat Abbas University Setif |
Sayah S.,Ferhat Abbas University Setif
International Journal of Electrical Power and Energy Systems | Year: 2013
A novel approach to size and locate capacitors in distribution feeders is presented in this paper. The proposed heuristic approach is formulated as a maximisation of a single objective function. This objective function includes both power loss reduction and capacitors investment costs. In this method where the capacitor optimal sizes and locations are decoupled, node stability indices are used to suitably select the capacitor probable locations. The capacitor initial sizes are determined while deriving the objective function subject to some constraints. The usually used voltage constraint has been substituted by a new one made on the reactive branch currents for which positive values (over-compensation) are allowed to improve voltage profile as well as the cost and power loss reductions. The developed algorithm has been implemented on several test systems and the obtained results have been compared with those of authors having used fuzzy logic and other heuristic search methods. © 2012 Elsevier Ltd. All rights reserved.
Saoudi K.,Ferhat Abbas University Setif |
Harmas M.N.,Ferhat Abbas University Setif
International Journal of Electrical Power and Energy Systems | Year: 2014
This paper presents an enhanced indirect adaptive fuzzy sliding mode based power system stabilizer for damping local and inter-area modes of oscillations for multi-machine power systems. The proposed controller design is based on an adaptive fuzzy control combining a proportional integral controller with a sliding mode controller. Generator speed deviation and its derivative are selected as input signals to a fuzzy logic system that approximates unknown power system functions and a proportional integral regulator is used to eliminate the undesirable sliding mode chattering. Using Lyapunov synthesis, adaptation laws are developed in an enhanced indirect adaptive fuzzy scheme which closely tracks changes in power system operating conditions. Performance of the proposed stabilizer is evaluated for a two-area four-machine power system subjected to different types of disturbances. Simulation results are compared to those obtained with a conventional PSS, with a fuzzy logic based stabilizer and with an adaptive fuzzy PSS clearly showing the effectiveness and robustness of the proposed approach. © 2013 Elsevier Ltd. All rights reserved.
Maamache M.,Ferhat Abbas University Setif
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015
It is well known that Hermitian operators have real eigenvalues while non-Hermitian ones may have complex eigenvalues. Recently, numerical and analytical results indicated that the spectra of many non-Hermitians Hamiltonians H are indeed real if they are invariant under the combined action of self-adjoint parity P and time reversal T. The concept of a pseudo-Hermitian operator showed that the remarkable spectral properties of the PT-symmetric Hamiltonians follow from their pseudo-Hermiticity. It is possible to explain these observations by the concept of pseudo-Hermitian operators and to formulate completeness and orthonormality relations. Most of the effort has been devoted to study time-independent non-Hermitian systems. In this paper, we study the exactly solvable time-dependent periodic pseudo-Hermitian Hamiltonians. The method introduced, to make the reality of eigenvalues and phases, is based on a Floquet decomposition of the evolution operator UH(t)=ZH(t)exp(iMHt) associated with the periodic pseudo-hermitian Hamiltonian H(t)=H(t+T). One of the results found in this paper concerns a calculation of Berry's phase for periodic, but not necessarily adiabatic, pseudo-Hermitian Hamiltonians. A two-level pseudo-Hermitian system is discussed as an illustrative example. © 2015 American Physical Society.