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Volume 3, article 1

 

bogoliubov transformation for
distinguishable particles

M. Holzmann and F. Laloë

The Bogoliubov transformation is generally derived in the context of identical bosons with the use of "second quantized" a and a operators (or, equivalently, in field theory). Here, we show that the transformation, together with its characteristic energy spectrum, can also be derived within the Hilbert space of distinguishable particles, obeying Boltzmann statistics; in this derivation, ordinary dyadic operators play the rote usually played by the a and a operators; therefore, breaking the symmetry of particles conservation is not necessary.

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Laboratoire de Physique de l'ENS,. LKB and LPS, 24 rue Lhomond, F-75005 Paris, France

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Volume 3, article 2

High Efficiency CIGSS Thin Film based
Solar Cells and Mini-modules

 Ahmed Ennaoui

 The highest efficiency for Cu(Ga,In)Se2 (CIGS) thin-film-based solar cells has been achieved with CdS buffer layers prepared by a solution growth method known as the chemical bath deposition (CBD). With the aim of developing Cd-free chalcopyrite-based-thin-film solar cells, we describe the basic concepts involved in the CBD technique. The recipes developed in our laboratory for the heterogeneous deposition for good-quality thin films of ZnO, ZnSe, ZnS are presented. In view of device optimization, the initial formation of chemical-bath-deposited ZnSe thin films on Cu(Ga,In)(S,Se)2 (CIGSS) and the subsequent development of the CIGSS/ZnSe heterojunction were investigated by X-ray photoelectron spectroscopy (XPS). The good surface coverage was controlled by measuring changes in the valence-band electronic structure as well as change in the In4d , Zn3d core lines. From these measurements, the growth rate was found to be around 3.6 nm/min. The valence band and the conduction band-offsets EV and EC between the layers were determined to be 0.60 and 1.27 eV, respectively for the CIGSS/ZnSe interface. The energy band diagram is discussed in connection with the band-offsets determined from XPS data. Small and large area CIGSS based solar cells with a CIGSS/Zn(Se,OH)/ZnO structure are produced. A ZnSe thickness below 10 nm has been found to be optimum for achieving a homogeneous and compact buffer layer on CIGSS with an active area efficiency of 15.7%. Using Siemens Solar technology this structure is adapted to fabricate Cd-free CIGSS monolithic mini-modules with efficiencies up to 11.7%.

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University Mohammed V, Physics Department, Faculty of Sciences, BP 1014 Rabat-Morocco

 

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Volume 3, article 3

The transverse mixed spin Ising model in a longitudinal random field

 N. Benayad, L. Khaya and A. Fathi

The transverse mixed spin Ising system consisting of spin-1/2 and spin-1 with a longitudinal random field is studied within the finite cluster approximation based on single-site cluster theory. The equations are derived using a probability distribution method based on the use of Van der Waerden identities. In the absence of the transverse field, the complete phase diagram in the case of simple cubic lattice is investigated and exhibits interesting behaviours, where the longitudinal field is bimodally and trimodally distributed. The influence of the transverse field on these behaviours are also examined.

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Groupe de Mécanique Statistique, Laboratoire de Physique Théorique, Faculté des Sciences Aïn Chock, B.P. 5366 Maarif, Casablanca, Morocco.

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Volume 3, article 4

 Wetting and layering transitions
of a spin-1/2 Ising model in a random
transverse field method

L. Bahmad1, A. Benyoussef1, A. El Kenz1, and H. Ez-Zahraouy1,2

The effect of a random transverse field (RTF) on the wetting and layering transitions of a spin-1/2 Ising model, in the presence of bulk and surface fields, is studied within an effective field theory by using the differential operator technique. Indeed, the dependencies of the wetting temperature and wetting transverse field on the probability of the presence of a transverse field are established. For specific values of the surface field we show the existence of a critical probability pc above which wetting and layering transitions disappear.

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1 Laboratoire de Magnétisme et de Physique des Hautes Energies Université Mohammed V, Faculté des Sciences
    Avenue Ibn Batouta, B.P. 1014, Rabat, Morocco.
2 Abdus Salam International Centre For Theoretical Physics, P.O. Box 586, 34100 Trieste Italy.

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Volume 3, article 5

Anisotropy of the gap energy in
high Tc Copper Oxides

M. Bouayad1, M.Laghrissi2, M . Fliyou3, H.Loumrhari2 and M.Chaouch4

Within the frame work of BCS phonon-mediated pairing with a logarithmic (2D) Van Hove Singularity in the density of states, we study the anisotropy of superconductors gap taking into account the anisotropy of attractive coupling and the coulomb repulsion .The results show that gap is more disperse and can explain some observed experimental data.

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PACS numbers : 74. 25. J b; 74. 20. Fg. 74. 72. Bk

1 Faculté Des Sciences et technique -Fes-Saiss. Route d Immouzar, Fes-Morocco
2 Faculté Des Sciences de Meknes-Morocco
3 Equipe de physique du solide .ENS. BP 5206 Bensouda-Fes-Morocco
4 Faculté Des Sciences Dhar el Mahrez, Fes Atlas-Morocco

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Volume 3, article 6

Internal friction and its thermal evolution
on 304 L stainless steel films

M. Idiri1, B. Boubeker1, Ph. Goudeau2 , V. Pelosin3

  Internal friction has been measured between 300 and 760K on 304 L stainless steel (SS) using a vibrating reed device. The 0.6 µm thick samples were deposited with ion beam sputtering technique on (100) silicon substrate. It has been shown that the damping level is considerably reduced by annealing between 500 and 760K. The calculated activation energy and the reaction order, using the Johnson-Mehl-Avrami (J-M-H) kinetic enable us to assume that the observed mechanism is closely related to microstructural rearrangements located at grain boundaries.

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Key words :  304 L Stainless Steel, Ion Beam Sputtering, Internal Friction.

1 UFR : Physique des Milieux Denses et Matériaux, Faculté des Sciences Ben M’Sik Casablanca Morocco
2 Laboratoire de Métallurgie Physique, U.M.R. 6630 C.N.R.S. Université de Poitiers Bât. S.P.2MI. Bd 3-Téléport 2,
    BP 179-86960 Futuroscope cedex - France
3 Laboratoire de Mécanique et Physique des Matériaux, UMR 6617 C.N.R.S.Ecole Nationale Supérieure de Mécanique et d’Aérodynamique,
   
BP 109 - 86960 Futuroscope cedex - France.


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Volume 3, article 7

 The effect of confined Longitudinal Optical
Phonons on the Binding Energy
of an impurity in CdSe Quantum Dot

B. El Amrani 1 , N. Essbai 2 , M. Fliyou 1 , H.Chikhaoui 1 and M. Chaouch 3

  Using a variational approach, the effect of the confined LO-phonon on the binding energy in CdSe Quantum Dot has been calculated. The charge-carrier-phonon coupling is treated within the adiabatic approximation. Our results show that the effect of the confined LO-phonon on the binding energy decreases with the dot size. However the correction of the confined LO-phonon to bound state energy increases with dot size.

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PACS  number : 03

1 Equipe de Physique du Solide E.N.S BP 5206 Bensouda Fès Morocco.
2 Faculté des Sciences & Techniques, Rte d’Imouzzer , BP 2202 Fès Atlas Morocco.
3 Faculté Des Sciences Dhar el Mahrez ,Fes Atlas-Morocco

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Volume 3, article 8

 Magnetization studies in
amorphous Co80-x Gdx B20

A. Hassini and A. Bouhdada

We have studied amorphous Co80-x Gdx B20 alloys prepared by melt spinning technique. The Gd moment at 4.2 K is found to be 7 µB which agrees with the theoretical value indicating a collinear spin structure. The magnetic compensation at 4.2 K occurs for x close to 10.3. The mean-field theory has been used to explain the temperature dependence of the magnetization. The exchange interactions between Co-Co and Co-Gd atom pairs have also been evaluated.

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Laboratoire de Physique des Matériaux et de Micro-électronique, Université Hassan II, Faculté des Sciences Ain Chock,
B.P. 5366, Route d’El Jadida, km-8, Casablanca, Morocco.

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Volume 3, article 9

  Exact and approximate modeling of
electrical properties of
metal /insulator/semiconductor structures

 Y. Khlifi1, 2, K. Kassmi1, L. Roubi2, R. Maimouni1

 In this paper, we present the results of simulation concerning electrical properties of metal/insulator/semiconductor structures both in the absence and presence of charge in the insulator. After establishing different basic equations in integral forms, we have given these equations analytically by using the Maxwell-Boltzmann approximation. Then, we have analyzed the potentials and electrical fields in the insulator and at the insulator-semiconductor interface in terms of the voltage applied to the structure and the charge density. This has yielded to the analysis of the relative errors made on these electrical parameters as a function of respectively the field in the insulator, the semiconductor doping and the charge density. The obtained results show a validation of the Maxwell-Boltzmann approximation; in particular for the electrical field determination in the structure (error is lower than 1.8%). The errors made by using this approximation are interpreted in term of semiconductor interface degeneracy.

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PACS numbers :  70., 73.40.Qv

1 Laboratoire d’Electronique Appliquée et d’Automatique (LEAA), Université Mohamed Ier, Faculté des Sciences, Dépt de Physique, Oujda, Morocco.
2 Laboratoire de Physique du Solide (LPS), Université Mohamed I er , Faculté des Sciences, Dépt de Physique, Oujda, Morocco.

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Volume 3, article 10

Modeling of Fowler-Nordheim current
of metal/ ultra-thin
oxide/ semiconductor structures

Y. Khlifi1, 2, K. Kassmi1, L. Roubi2, R. Maimouni1

 In this paper we present results of a modeling of the current-voltage characteristics of metal/ultra-thin oxide/semiconductor structures with negatively biased metal gate (V<0), when the oxide thickness varies from 45Å to 80Å. We analyze the theoretical influence of the temperature and Schottky effect on the Fowler-Nordheim (FN) conduction. The results obtained show that these influences depend on the electric field in the oxide and on the potential barrier at the metal/oxide interface. At the ambient temperature, the influence on this potential barrier is lower than 1.5%. However, it can reach 45% on the pre-exponential coefficient of the FN current. It is therefore necessary to consider in the FN classical conduction expression a correction term that takes account the temperature and Schottky effects. These results are validated experimentally by modeling the current-voltage characteristics of the realized structures at high field.

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PACS :    70., 73.40.Qv

1 Laboratoire d’Electronique Appliquée et d’Automatique (LEAA), Université Mohamed Ier, Faculté des Sciences, Dépt de Physique, Oujda, Morocco.
2 Laboratoire de Physique du Solide (LPS), Université Mohamed I er ,Faculté des Sciences, Dépt de Physique, Oujda, Morocco.

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Volume 3, article 11

 

 Van der Waals induced polarization
of molecules adsorbed on small metallic
spheres : anisotropy and nonlocality effects

A. Semlali, B. Labani* and A. Ayadi

 The calculation of Van der Waals induced polarization of molecules interacting with small metallic spheres is based on the spherical-tensor theory by using the response field susceptibility of the sphere. The first Euler angle appearing in the expression giving this polarization exhibits the anisotropy of the molecule. In order to illustrate the non locality and anisotropy effects as well as the importance of the metallic sphere curvature on the induced polarization magnitudes, we present numerical results for typical systems (HF, HCl) on (Ag, Al and Cu).

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L.P.M.C , Département de Physique, Faculté des Sciences, B.P 20, El jadida, Morocco.
* Département de Physique, Faculté des Sciences Semlalia, B.P S15, Marrakech, Morocco.

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Volume 3, article 12

 

Effect of heat treatment with CdCl2 on the electrodeposited
CdT
e/CdS heterojunction

M. Rami, E. Benamar, M. Fahoume, F. Chraibi, and A. Ennaoui

CdS/CdTe heterojunction was subjected to chemical treatment commonly used in photovoltaic device fabrication to determine the resulting microscopic effect on the morphology and structure. CdS and CdTe thin films were electrodeposited successively onto indium tin oxide (ITO) from aqueous solution. Containing CdCl2 and Na2S2O3 for the deposition of thin film windows, the ITO/CdS resulting substrates was then used for the deposition of CdTe thin film absorber using aqueous solution of CdSO4 and TeO2. Next CdCl2 dip followed by 400°C heat treatment was used to modify the CdTe/CdS surface and interface. Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) were used to evaluate the resulting surface morphology. X-ray diffraction analysis reveals that the heat treatment enhances the recrystallisation and shifts the CdTe peaks towards a smaller lattice parameter.

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Laboratoire de physique des matériaux, Département de Physique, Faculté des Sciences de Rabat,
B. P. 1014 Rabat-Morocco.

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Volume 3, article 13

Physical properties of CdSexTe1-x
thin films prepared by electrodeposition

E. Benamar, M. Rami, M. Fahoume, F. Chraibi and A. Ennaoui

The cadmium chalcogenides CdSexTe1-x (0≤x ≤1 ) thin films have been electrodeposited onto ITO coated glass substrates from an acid sulphate solution at 90 °C. The structure, the composition and the morphology have been studied as a function of the x coefficient by XRD, EDAX, optical absorbance and AFM techniques. All deposits have a cubic structure with a preferred orientation along the (111) direction. The composition in the films is found to vary linearly with the composition in the solution. The increase of the amount of tellurium in the CdSexTe1-x films decreases the band gap down to 1.35 eV and increases the lattice constant. The photoelectrochemical studies in a polysulfide electrolyte show that CdSexTe1-x thin films behave as n-type semiconductors.

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Université M ed V Agdal, Faculté des Sciences, Département de Physique, Laboratoire de Physique des matériaux.
B.P. 1014 Rabat -Morocco.

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Volume 3, article 14

MOCVD growth of Bi2Te3-Sb2Te3 layers :
Effect of growth parameters on the electrical
and thermoelectrical properties

B. Aboulfarah1, D. Sayah1, A. Mzerd1, A. Giani2, A. Boyer2

  The growth of (Bi1-xSbx)2Te3 thin films by metal-organic chemical vapour deposition (MOCVD) using trimethylbismuth, triethylantimony and diethyltellurium as bismuth, antimony and tellurium sources respectively is investigated on pyrex substrates. The electrical and thermoelectrical properties of this material are also measured over the growth temperature range 360-470°C. The studies are also made on the effect of VI/V ratio on these properties in the variation range 2-9. Polycrystalline structure is confirmed by X-ray diffraction, and it is observed that the intensity of the preferred orientation is higher at 450°C. The measurement of Seebeck coefficient shows that all samples have p-type conduction. The best value of this parameter is obtained for high growth temperature (240µV/K). The good result obtained for (Bi1-xSbx)2Te3 thin films revealed the great potential of MOCVD method which is an industrial technique to produce good materials for device applications (sensors and thermopiles).

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1 Université M ed V Agdal, Faculté des Sciences, Département de Physique, Laboratoire de Physique des Matériaux, Rabat, Morocco.
2 Centre d'Electronique et de Micro-Optoélectronique de Montpellier (CEM2), UM II, UMR 5507 CNRS, Place E. Bataillon,
    34095 Montpellier cédex 05, France.

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Volume 3, article 15

Electron impact ionization of Ar10+

A . Riahi , K . Laghdas, S . Rachafi

Total and single differential cross sections have been calculated for electron impact ionization of Ar10+(1s22s22p4)3Pe using a method that combines the distorted-wave Born approximation and R-matrix theory. In this method, the incident/scattered electron is described by the distorted-wave Born approximation, while both the initial bound state and the final continuum states are expanded in terms of an R-matrix basis. Eight states of the final Ar11+ ion are considered, namely 1s22s22p3 4So 2Do 2Po and 1s2 2s2p4 4Pe 2De 2Se 2Pe 2Po .

Up to the 24- pole components of the interaction with ionizing electron were included, giving ten distinct Ar10+ continuum symmetries. We calculated single differential cross sections summed over final ionic states, as a function of the energy loss. These cross sections exhibit considerable structure due to autoionizing resonances. Total cross sections for production of Ar11+ in each of the eight states are presented for impact energies from threshold energy at 19.8 au to 200 au. Our theoretical values for the total cross section are in good agreement with recent experimental results.

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 Département de Physique, Faculté des Sciences, Université Chouaib Doukkali, B.P. 20, 2400 ElJadida, Morocco

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Volume 3, article 16

Dependence of magnetoresistive properties in
[C
o98Zr2 (25Å)/Cu/Co (25Å)] magnetic
sandwiches on the C
u deposition pressure:
Correlation of the “CoZrC
u” disordered
phase concentration and the interfacial
mixed zone thickness with the Cu pressure

M. Faris1,*, M. EL Harfaoui1, A. Qachaou1, J. Ben Youssef2,
H. Le Gall2, and D. Meziane. Mtalsi1

 The magnetoresistance (MR) and the saturation resistivity (ρs) are studied versus the Cu deposition pressure (PCu) at room temperature, in [Co98Zr2 (25Å)/Cu (tCu) /Co (25Å)] magnetic sandwiches prepared by RF diode sputtering. Results of low angle X-Ray Diffraction patterns have been proved the importante interfacial degradation observed in (CoZr/Cu) multilayers, compared to the usual (Co/Cu) structures. The highest value of transverse MR is obtained along the easy axis, and the MR curve saturates in a small magnetic field of 100 Oe at room temperature. Which leads to an interesting increase in MR sensitivity about 2%/Oe. The main features of the magnetoresistive properties evolution with Cu deposition pressure are: The maximum of MR increases and moves towards larger Cu thicknesses (tCu) for increasing PCu. The saturation resistivity ρs decreases with increasing tCu while it increases versus PCu. The satisfactory agreement between our experimental results and calculated ones in the framework of the Johnson-Camley semi-classical model, allows us to interpret the MR and ρs behavior as a result of a reinforcement of the disordered phase ″CoZrCu″ inside the mixed zone whose thickness tmx increases with PCu .

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1 Laboratoire de Physique de la Matière Condensée (LPMC) B.P:133-14000 Kénitra-Morocco
2 CNRS, LPS, Groupe de Magnétisme, 92 195 Meudon, France

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Volume 3, article 17

Giant magnetoresistance
in (Ni 80 Fe 20 /Cu) multilayers

D. Meziane Mtalsi1, M. EL Harfaoui1, A. Qachaou1, M. Faris1
J. Ben Youssef2 and H. Le Gall2

The dependence of the magnetoresistance (MR) ratio on the thicknesses of the magnetic (m) and non magnetic (nm) layers is studied for Ni80Fe20 /Cu soft magnetic multilayers with a fixed number of bilayers (12). The highest value of the MR is 17,3% at Cu layer thickness of 7 Å. Very high sensitivity, around 132%/kOe has been observed. We present a discussion of the MR results using the Johnson-Camley semiclassical model based on the Boltzmann transport equation.

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1 Laboratoire de Physique de la Matière Condensée(LPMC) B.P:133-1400 Kénitra-Morocco
2 CNRS, LPS, Groupe de Magnétisme, 92 195 Meudon, France

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Volume 3, article 18

Magnetic properties of LaFe1-xCrxO3 and
Fe2-2xCr2xO3 mixed oxides

E. Loudghiri1 , A. Belayachi1,* , M. Nogues2 , M. Taibi3 ,
A. Dahmani
1,3 , M. EL Yamani1 and J. Aride3

Mixed oxides with formula LaFe1-xCrxO3 and Fe2-2xCr2xO3, where 0≤x≤1, are studied. The samples have been prepared using solid state reaction technique in air. The X-ray diffraction spectra indicated that the samples crystallize in a corundum phase with space group ( R3c ) for Fe2-2xCr2xO3 and in the perovskite structure for
LaFe1-xCrxO3. Many techniques have been used to explore the magnetic properties of the systems. High field, ZFC and FC magnetization vs. temperature, d.c. susceptibility and Mössbauer spectroscopy were carried out. High temperature magnetic susceptibility measurements and high field magnetic magnetization (H ≤ 20 T) show that the behavior of the susceptibility and the magnetization are complex. Mössbauer spectra of the solid solutions have been measured at 4.2 K and in the temperature range 77 K to 300 K. The shapes of spectra are unusual, showing strong relaxation phenomena in a wide temperature range as recently observed for many frustrated systems. The results are discussed by establishing the existence of various magnetic structures, inducing intermediate magnetic phases between the antiferromagnetic and the paramagnetic states. Preliminary magnetic phase diagrams of the systems have been established.

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1 Laboratoire de Physique des Matériaux, Faculté des Sciences Université Mohammed V,
    B.P. 1014 Rabat, Morocco.
2 Laboratoire de Magnétisme et d’Optique de l’Université de Versailles (URA 1531), Batiment Fermat, 45 Avenue des Etats Unis, 78035 Versailles Cedex, France.
3 Laboratoire de Physico-Chimie des Matériaux associé à l’AUF (LAF 502), Ecole Normale Supérieure Takadoum
    B.P. 5118 Rabat Morocco.

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Volume 3, article 19

Magnetisation studies in Co-Tb / Pt multilayers

H. Hamoudaa , M. Abidb and D. Saifaouia and R.Krishnanc

We have studied the magnetization in Co86Tb14/Pt multilayers under fields up to 1.8 T and as at room temperature. As the do-Tb layer thickness (tCoTb ) decreases below 200 Å the saturation magnetization magnetization (M) increases, the rectangularity of the M-H loops and the coercivity (Hc ) decrease. The effective anisotropy Keff of the multilayers was determined by a torque magnetometer. The product Keff×tCoTb shows a linear dependence with tCoTb as normally found for the superlatices yielding the bulk and surface anisotropies of 106 erg/cm3 and –0.2 erg/cm2 , respectively. These results are explained in terms of an interfacial Co-Pt layer. Keff and Hc are related by the equation Hc = α Keffn/M with the fitting parameters α and n.

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a Laboratoire de Physique Théorique, Université Hassan II, Faculté des Sciences, B.P. 5366 Maârif, Ain Chock,
    Route d’El Jadida km-8, Casablanca, Morocco.
b Laboratoire de Physique des Matériaux et de Microélectronique, Université Hassan II, Faculté des Sciences,
    B.P. 5366 Maârif, Ain Chock, Route d’El Jadida km-8, Casablanca, Morocco.
c Laboratoire de Magnétisme et d’Optique de l’Université de Versailles, CNRS, URA 1531, 45, Avenue des Etats-Unis,
    78035 Versailles cedex, France.

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Volume 3, article 20

Ballistic heat transport in semiconductors within
the extended irreversible
thermodynamics theory

A.Bourhaleb1,2 , A.Salhoumi1 , Y.Boughaleb1,* and M.Fliyou2

The transport in miniaturised electronic devices requires to go beyond simple hydrodynamic descriptions. So, carrier transports in nano-length devices is no longer dominated by collisions among the particles but the ballistic transport governs at this level. This type of transport occurs when the perturbation characteristic time is of the order of the relaxation time and the mean free path is of the order of the device's dimension. The aim of the present work is to calculate the ballistic velocity of heat transport by using a continued-fraction technique in the framework of extended irreversible thermodynamics. This ballistic speed must be less or equal to the maximum value c0 corresponding to phonon speed. Note that the classical Fourier equation is only able to describe the diffusion regime and the Maxwell-Cattaneo equation predicts a second sound propagation at speed c0/Ö3 but it is silent about the ballistic behaviour .

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1 Laboratoire de Physique de la Matière Condensée, Faculté des sciences Ben M'Sik, BP 7955 Ben M'Sik Casablanca, Morocco.
2 Equipe de l’énergie solaire E.N.S Marrakech, Morocco.

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Volume 3, article 21

Magnetic study in amorphous Gd0.7Zr0.3 alloys

H. Hamouda1 , D. Saifaoui1 and H. Lassri2

We report here our magnetic study on amorphous Gd0.7Zr0.3 alloy. The magnetic saturation is difficult to obtain even for fields up to 50 kOe. This led us to the conclusion that ferromagnetic and antiferromagnetic clusters are present in this alloy. However, the presence of a well defined Tc indicate that the ferromagnetic clusters are dominant and he presence of the coherent anisotropy field can transform this type of magnetic ordering into a ferromagnetic domain structure. The thermomagnetization curve is found to obey the Bloch law, spin wave stiffness constant and the distance between nearest magnetic atoms were calculated from the experimental results.

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1 Laboratoire de Physique Théorique. Université Hassan II, Faculté des Sciences Ain Chock, B.P. 5366, Route d’El Jadida, km-8, Casablanca, Morocco.
2 Laboratoire de Physique des Matériaux et de Micro-électronique. Université Hassan II, Faculté des Sciences Ain Chock,
    B.P. 5366, Route d’El Jadida, km-8, Casablanca, Morocco.

 

 

Copyright © The Moroccan Statistical Physical Society. [mjcm@fsr.ac.ma]. Last modification : July 2010.

ISSN : 1114-2073