Doctorat (Physique)
http://hdl.handle.net/123456789/133124
2018-08-16T07:53:56Z.الدراسة الديناميكية لنموذج الطاقة المظلمة اللزجة في الكوسمولوجيا الكلاسيكية و الجاذبية الكوانتية الحلقية
http://hdl.handle.net/123456789/136373
.الدراسة الديناميكية لنموذج الطاقة المظلمة اللزجة في الكوسمولوجيا الكلاسيكية و الجاذبية الكوانتية الحلقية
بن الشيخ, سارة; مباركي, نور الدين
In this thesis we have suggested two cosmological models.in the first one we
have studied the dynamical behaviors and stability properties of a flat space
FRW universe filled with pressureless dark matter and viscous dark energy in
the context of standard classical and loop quantum cosmology. Assuming that
the dark energy has a constant bulk viscosity, it is found that the bulk viscosity
effects influence only the quintessence model case leading to the existence of
a viscous late time attractor solution of de-Sitter type, whereas, the quantum
geometry effects influence the phantom model case where the big rip
singularity is removed. Moreover, compared with the more recent data, our
results of the Hubble parameter as a function of the redshift are in a good
agreement. However, in the second model we have studied the dynamical
behaviors and stability properties of a flat space FRW universe filled with
pressureless dark matter and viscous dark energy in the context of loop
quantum cosmology. Assuming that the dark energy has bulk viscosity in the
general form, we have found there exists under some appropriate parameters
a stable late time viscous dark energy dominated solution of de Sitter type. the
problem of future singularity (big rip) will never occur in this scenario.
2018-02-04T00:00:00ZContrôle de la couche limite laminaire d’un écoulement stationnaire, visqueux, compressible et subsonique autour d’un profil bidimensionnel
http://hdl.handle.net/123456789/136343
Contrôle de la couche limite laminaire d’un écoulement stationnaire, visqueux, compressible et subsonique autour d’un profil bidimensionnel
Nahoui, Azzedine; Bahi, Lakhdar
A numerical study of a laminar boundary layer of a stationary, viscous, compressible and subsonic flow around a two-dimensional NACA profile was conducted without and with control.
The flow domain has been divided into two zones, one near-wall, the boundary layer, which is responsible for friction phenomena, and the other, an external zone where flow is considered potential.
The potential flow is studied by the panel method for the determination of the external velocity distribution necessary for the treatment of the boundary layer.
The boundary layer was studied using the PRANDTL model and the KELLER method by reducing the order of the first-order differential equations, the writing of the algebraic equations, and the linearization by the Newton method via an iterative calculation process and finally the resolution by the method of elimination by blocks.
The distributions of the pressure and lift coefficients were determined and examined for different Mach numbers and different angles of attack with varying relative thickness.
Thermal control by wall heating or wall cooling was studied and the results demonstrated only the effectiveness of the wall cooling control on the recoil of the separation point around 10% of the chord of the profile.
The dynamic control by suction or blowing has demonstrated its effectiveness on the decline of the separation point; the decline has reached 10% of the chord of the profile.
The superimposition of the thermal and dynamic control procedures demonstrated once again more efficiency on the retreat of the boundary layer separation point with a gain of 15% of the chord of the profile.
2018-02-18T00:00:00ZEffet d’une interaction non locale et separable sur le processus de creation de paires de particules
http://hdl.handle.net/123456789/136337
Effet d’une interaction non locale et separable sur le processus de creation de paires de particules
Hafdallah, Abdelhakim; Chetouani, Lyazid
The probability of pair creation of the Dirac equation by a separable and
non-local potential of the matrix type is calculated as follows the Schwinger
approach. It was found that this probability was zero. In a particular case, the
potential δ is considered separable. Also, the Duffin-Kemmer-Petiau (DKP)
equation describing the spin-0 particles is solved for the same interaction via
the determination of the free Green function. Thus, it has been shown that the
spectrum of energies is obtained from the calculation of the determinant and as
illustration we have chosen a simple form for the matrix M relative to the
interaction.
2018-05-13T00:00:00ZTirage et caractérisation des fibres monocristallines scintillatrices de composition grenat
http://hdl.handle.net/123456789/136332
Tirage et caractérisation des fibres monocristallines scintillatrices de composition grenat
Djebli, Abdelghani; Boudjada, Fahima; Lebbou, Kheirreddine
The work of thesis was realized in collaboration with Our laboratory of Crystallography -
University frères Mentouri, Constantine1- Algeria, institut lumière - matière ( ILM ) Lyon1-
france, the European Center for Nuclear Research (CERN) in Geneva-Switzerland, and the
Institute for Scintillation Materials NAS, Kharkov-Ukraine (ISMA), we developed and
characterized crystal fibers doped with cerium and praseodymium by micro-pulling down
technique.
Studies of the scintillation properties of cerium and praseodymium doped garnets, were
performed on crystal fibers elaborated by the micro-pulling down growing technique.
Aluminates of A3Al5O12 (A = Y or Lu) doped with Ce3+ or Pr3+ ions were synthesized as
mono-crystals fibers.
The studies carried out by DRX, absorption and emission spectroscopy demonstrate that the
YAG and LuAG phases are obtained alone without any other parasitic phases. Measurements
of attenuation along the fibers and distribution of the rare earth activator (Ce3+ or Pr3+) gave
spatial mapping of the distribution of dopants in the fibers, which made it possible to evaluate
the luminous in-homogeneities within the fiber Material as a function of the different growing
parameters, which made it possible to evaluate the efficiency of each of the two materials in
detecting the gamma rays.
The whole of this work clearly shows the potential applications of these two materials.
2017-07-02T00:00:00Z