Publication Scientifique

Elastic properties and bonding of the AgGaSe2 chalcopyrite

2010-08-31T22:00:00Z

Abstract / Résumé : Full-potential linearized augmented plane waves (FPLAPW) calculations have been used to determine the equilibrium properties and elastic constants of the chalcopyrite phase of AgGaSe2. The topological analysis of the electron density shows a clear polar bonding, with the integrated basin charges revealing a clear dominance of the covalent over the ionic character. The bonding analysis also provides a partition of the bulk modulus and compressibility into atomic contributions. Se is seen to dominate the global behavior (B¼51.2 GPa), with a local bulk modulus intermediate between the values of the other two atoms : 44.8 (Ga), 51.1 (Se), and 56.6 GPa (Ag).

Keywords / Mots clefs : FPLAPW calculations, Elastic properties, Quantum theory of atoms in molecules, Chemical bonding in semiconductors.

Journal title / Revue : Physica B 405 (2010) 3658–3664

A constrained finite strip method for open and closed cross-section members

DJAFOUR M., DJAFOUR N., KERDAL D.E, MEGNOUNIF A. — 2010-08-03T22:00:00Z

Abstract / Résumé :

In this paper, the constrained finite strip method (cFSM) is improved by simplifying the derivation of the constraint matrix which defines the combined buckling mode space formed by global and distortional modes. In the context of the FSM, only two assumptions are made to define this particular and complex subspace : (i) cylindrical plate bending (if any) and (ii) negligible in-plane transverse strains and shear strains. The constraint matrix is derived by means of procedures commonly used in numerical methods, such as FEM or FSM. This led to a simple and systematic formulation which allowed the cFSM to compute pure buckling modes for members with open and closed thin-walled cross-sections.

Keywords / Mots clefs : Stability ; Thin-walled ; Modal decomposition ; Constrained finite strip method

Journal title / Revue : Thin-Walled Structures, 4-AUG-2010

Equilibria of an anareobic wastewater treatment process and their stability

Benyahia B., Harmand J., Sari T., Cherki B. — 2010-07-06T22:00:00Z

Abstract / Résumé : Non encore disponible. Keywords / Mots clefs : Non encore disponibles.

Journal title / Revue :

submitted in BAB10, Symposium on Computer Applications in Biotechnology, July 7-9, 2010, Leuven, Belgium

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2010-06-22T08:56:23Z

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Ab initio study of the stability of X (X=Cr, Nb, Ag) ultra-thin layers on Cu(001)

AOURAG H., CODDET C., GROSDIDIER T., KELLOU A., Tadjer .A — 2010-05-03T08:59:19Z

Ab initio study of the stability of X (X=Cr, Nb, Ag) ultra-thin layers on Cu(001)

Abstract

Full potential Linearized Plane Waves method within the framework of the generalized gradient approximation is applied to study X/Cu(001) (X=Cr, Nb, Ag) layered structures. Self-consistent total energy calculations are carried out to determine the energetics and growth modes of different X/Cu(001) systems : interdiffusion, monolayer, bilayer, trilayer, and island formations. Ideal works of separation and the resulting interfacial energies are estimated for the Cr/Cu, Nb/Cu and Ag/Cu layered structures. The obtained results, which are compared with previously published experimental and theoretical data, show that Ag and Nb elements have quite different behavior than Cr.

Keywords

Metals ; Ab initio calculation ; Interdiffusion ; Density functional theory

Thin Solid Films, Volume 489, Issues 1-2

X-ray Absorption Near-Edge Structure and Valence State of Mn in (Ga,Mn)N

2010-04-30T22:00:00Z

X-ray absorption near-edge structure and valence state of Mn in (Ga,Mn)N

Abstract The band structure of the diluted magnetic semiconductor (Ga,Mn)N, and the x-ray absorption near-edge structure (XANES) at the K edge of Mn, were calculated using the linearized augmented plane wave method. The calculated K-edge spectra fit well with experimental data obtained on samples of Ga1-x Mnx N with a wide range of Mn content, from x=0.3% to 5.7%. These samples were grown by molecular beam epitaxy. X-ray diffraction measurements and extended x-ray absorption fine structure studies were used to confirm the wurtzite structure of the samples, the absence of any secondary phase, and the substitutional position of Mn in the gallium sublattice of GaN. The shape of the measured XANES spectra does not depend on the Mn content, implying the same valence state and local atomic structure around the Mn atom in all samples. The comparison between the measured spectra and the results of the ab initio calculation offers a clear interpretation of the preedge structure : It is mainly due to dipolar transitions, with a single peak in the case of Mn2+ and an additional peak for Mn3+ . Such a behavior of the XANES preedge of Mn2+ was confirmed experimentally on (Ga,Mn)As and (Zn,Mn)Te. We conclude that the valence state of Mn in wurtzite (Ga,Mn)N is 3+ , a conclusion which is also supported by infrared optical transmission and magnetization data obtained on the same samples.

Physical Review B

Analyse de composés phénoliques impliqués dans la défense de l'olivier à la verticilliose par HPLC

Gaouar N. , Bensalah F., HABI M., Klouch N., Lorquin J. — 2010-03-11T12:57:55Z

Abstract / Résumé : Non encore disponible. Keywords / Mots clefs : Non encore disponibles.

Journal title / Revue :

Journée international de produit naturel. 20 Mai 2009. Tlemcen. Algérie

Investigation of fractal flow fields in water-type flat plate solar absorbers

BENZENINE H., MOKRI A., SAIM R. — 2010-03-07T23:00:00Z

Abstract / Résumé : Non-uniform flow distribution through flat plate solar absorbers leads to a poor thermal efficiency. As an attempt to achieve a uniform flow distribution, a computer algorithm called FracTherm was developed by researchers at the Fraunhofer Institute for Solar Energy Systems ISE (Freiburg, Germany) to provide a given flat area with a multi-branched network. These architectures are inspired from natural hydraulic designs and they are called “fractals”. This paper presents the results of a two dimensional numerical study conducted on a fractal water-type flat-plate solar absorber designed by using FracTherm. The fractal absorber was modeled under steady and laminar flow conditions to analyze the flow distribution through the absorber. The effect of Reynolds number on local pressure losses at bifurcations is also discussed. The results bolster the past explanations of flow distribution mechanisms through parallel solar absorbers, and they demonstrate that the fractal architecture enables a better flow distribution and hence a higher thermal efficiency.

Keywords / Mots clefs : FracTherm, solar thermal energy, solar absorber, fractals, CFD.

Journal title / Revue : International Conference on Renewable Energy : Generation and Applications (ICREGA'10), 8-10 March 2010, Al-Ain, UAE.

Numerical simulation of the zinc's solidifi cation in the cylindrical structure

KORTI A.N., GHELLAI L. , KHADRAOUI Y. — 2010-02-24T08:33:43Z

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Journal title / Revue :

05&06-12- 2009 Séminaire International Sur Les Technologies Mécaniques SITEM2009, TLEMCEN .

Nitric oxide decomposition induced by DC corona discharge

Lemerini M., MEDJAHDI I.S., Moreno H., Castellanos A. , Pontiga F. — 2010-02-18T08:10:11Z

Abstract / Résumé : Non encore disponible.

Keywords / Mots clefs : Non encore disponibles.

Journal title / Revue :

International Symposium on Plasma Chemistry 27.-31. July 2009 Bochum, Germany