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

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.

Design and Implementation of a Virtual Calculation Centre (VCC) for Engineering Students

MOKRI A. — 2010-01-31T23:00:00Z

Abstract / Résumé : The majority of academic institutions today provide their attendees with databases where courses and other materials could be uploaded, downloaded and checked by the faculty and students. Those materials are mostly PDF files, MS Word files, MS power point presentations or downloadable computer programs. This paper represents a new approach to providing engineering students with the data and the calculation programs. Engineering students need thermo-physical properties of substances, charts, diagrams, conversion factors and so forth. In addition, many students find it cumbersome downloading and installing superfluous computer programs which they do not need often in their studies. As an attempt to satisfy the academic community needs in the faculty of Engineering in Abou Bekr Belkaid University (Tlemcen, Algeria), we devised Web technologies and techniques to design an interactive virtual space wherein many engineering-related Web applications are accessible on-line. Students and professors can access on-line the properties of many substances, convert physical quantities from and into a variety of units, exploit computer programs on-line without installing them, generate tables and charts, and can use diagrams on-line by means of the mouse. The set of those applications is called a Virtual Calculation Center. This paper presents the different services that could be implemented in a Virtual Calculation Center, and describes the techniques and technologies used to build those applications.

Keywords / Mots clefs : Virtual Calculation Centre ; on-line calculation ; Web application ; electronic chart ; e-learning.

Journal title / Revue : International Journal on Online Engineering, IAOE, Volume 6, Issue 1, February 2010,pp 18-23.

Structural and thermodynamic properties of SbAsGa2 and SbPGa2 chalcopyrites

AMRANI B., KHENATA R., LUANA V., OTERO-DE-LA-ROZA A., OUAHRANI T. — 2009-12-31T23:00:00Z

Abstract / Résumé : The structural and elastic behaviour of the chalcopyrite SbPGa2 and SbAsGa2 crystals has been determined by means of first principles calculations using the full-potential augmented plane wave (FPLAPW) method. Ground state properties such as the lattice parameters (a, c and u), bulk modulus B, its pressure derivative B0 , have been directly calculated and compared to previous experimental and theoretical results when available. We have determined the elastic parameters (C11, C12, C33, C44 and C66), which have not been calculated and measured yet. Thermal properties, including the linear and cubic expansion coefficients and the heat capacity, have been estimated using a quasi-harmonic Debye model. To our knowledge this is the first quantitative theoretical prediction of elastic and thermal properties for these compounds and still awaits experimental confirmations.

Keywords / Mots clefs : FPLAPW, Structural properties, Elastic constants, Quasi-harmonic Debye model.

Journal title / Revue : Computational Materials Science 47 (2010) 655–659

Ab-initio study of the structural, linear and nonlinear optical properties of CdAl2Se4 defect-chalcopyrite

2009-12-31T23:00:00Z

Abstract / Résumé : The complex density functional theory (DFT) calculations of structural, electronic, linear and nonlinear optical properties for the defect chalcopyrite CdAl2Se4 compound have been reported using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code.

We employed the Wu and Cohen generalized gradient approximation (GGA-WC), which is based on exchange–correlation energy optimization to calculate the total energy. Also we have used the Engel–Vosko GGA formalism, which optimizes the corresponding potential for band structure, density of states and the spectral features of the linear and nonlinear optical properties. This compound has a wide direct energy band gap of about 2.927 eV with both the valence band maximum and conduction band minimum located at the center of the Brillouin zone. The ground state quantities such as lattice parameters (a, c, x, y and z), bulk modulus B and its pressure derivative B0 are evaluated. We have calculated the frequency-dependent complex eðoÞ, its zero-frequency limit e1ð0Þ, refractive index nðoÞ, birefringence DnðoÞ, the reflectivity RðoÞ and electron energy loss function LðoÞ. Calculations are reported for the frequency-dependent complex second-order nonlinear optical susceptibilities. We find opposite signs of the contributions of the 2o and 1o inter/intra-band to the imaginary part for the dominant component through the wide optical frequency range.

Keywords / Mots clefs : FP-LAPW, GGA-WC, Electronic properties, Linear and nonlinear optical properties.

Journal title / Revue : Journal of Solid State Chemistry 183 (2010) 46–51.

Selection of alternative routings in real time : DMM and modified DMM rules

HASSAM A., SARI Z. — 2009-11-30T23:00:00Z

Abstract / Résumé : The objective of this study is to test the effectiveness of the modified Dissimilarity Maximisation Method (modified DMM) for real-time Flexible Manufacturing Systems (FMSs) scheduling. The modified DMM is an improvement over the DMM. It is a plan selection method for an alternative process that was developed for routing selection in real-time FMS scheduling. A computer simulation model, which mimics a physical system, is used to evaluate the effect of DMM and modified DMM rules on the system performance. The results show that the modified DMM outperforms DMM on system throughput in a saturation case and increases the utilisation rate of machines and the material-handling system.

Keywords / Mots clefs : flexible manufacturing systems ; alternative routings ; real-time FMS control ; dispatching rules ; dissimilarity maximisation method ; modified DMM rules ; plan selection ; computer simulation ; system performance ; saturation cases ; utilisation rates ; materials handling ; production management ; advanced production systems.

Joournal title / Revue : International Journal of Product Development, Vol 10, N°1/2/3, 2010, pp 241-258 (Editeur : Indersciences Enterprises Ltd) DOI : 10.1504/IJPD.2010.029995.

valorisation de certains bois feuillus algérien chçene vert, peuplier blanc et peuplier noir. Isolement des fibres, cinétique de délignification et caractéristiques des pâtes.

BOUKLI HACENE M.K.M. — 2009-11-30T23:00:00Z

Abstract / Résumé : Non encore disponible.

Keywords / Mots clefs : Non encore disponibles.

Journal title / Revue : Physical & chemical News. Ref F140209/13 à paraître vol n°51 janvier 2010.

Choice of the wavelet analyzing in the phonocardiogram signal analysis using the discrete and the packet wavelet transform

BEREKSI REGUIG F., CHERIF L., DEBBAL M. — 2009-11-30T23:00:00Z

Abstract / Résumé : Non encore disponible.

Keywords / Mots clefs : Non encore disponibles.

Journal title / Revue :EXPERT SYSTEMS WITH APPLICATIONS, Volum 37 N°2, pages 913-918, Année 2010, ISSN 0957-4174, DI 10.1016/j.eswa.2009.09.036

Decay solution for the renewal equation with diffusion

ABDELLAOUI B., TOUAOULA T.M. — 2009-11-30T23:00:00Z

Abstract / Résumé : Non encore disponible.

Keywords / Mots clefs : Non encore disponibles.

Journal title / Revue : Nonlinear Differ. Equ. Appl. c_2010 Birkh¨auser Verlag Basel/Switzerland DOI 10.1007/s00030-009-0053-6