http://depot.umc.edu.dz/handle/123456789/9223 2026-06-01T14:50:22Z 2026-06-01T14:50:22Z Moulla, Fatima Boukheit, Nahemen http://depot.umc.edu.dz/handle/123456789/14805 2026-01-19T08:46:58Z 2023-06-18T00:00:00Z

Etude et caractérisation des spinelles CuAl2O4 et MgAl2O4 synthétisés par différentes techniques. Moulla, Fatima; Boukheit, Nahemen The work of this thesis is part of recent research concerning the development and characterization of nanometric oxides by different techniques. In view of the comparison with the many works already carried out of this important and still current subject, we were interested in the synthesis and the characterization of the two spinels CuAl2O4 and MgAl2O4 despite the complexity of the mechanisms involved in the Sol-Gel process. The first part was devoted to the structural characterization of CuAl2O4 and MgAl2O4 spinels but also to that of the mixed oxide CuAlO2. The characteristics of each of these bodies are explained according to the different synthesis conditions and the experimental means available. This work clearly establishes the nanoscale size of the three bodies. On the other hand, the presence of intermediate reaction phases has been demonstrated in the two spinels CuAl2O4, MgAl2O4. In the second part, we aimed to high light the role of pressure on pellets prepared from CuAl2O4 and MgAl2O4 powders calcined at 900°C for 4 hours. Following fine characterization techniques, this work has made it possible to observe structural modifications in the case of CuAl2O4 pellets. In the last part, we give a more technological application of the two spinels by studying the degradation of methylene blue by the two spinels.

2023-06-18T00:00:00Z Medjenah, Samia Benamira, Farid http://depot.umc.edu.dz/handle/123456789/14746 2025-12-16T14:28:09Z 2023-06-21T00:00:00Z

Supersymétrie en mécanique quantique relativiste et non relativiste et applications à des problèmes avec masse dépendante de la position par l’approche supersymétrique. Medjenah, Samia; Benamira, Farid This work concerns the application of the approach of supersymmetry in quantum mechanics (SUSYQM) to solve the one-dimensional Schrödinger, Klein-Gordon and Dirac equations for a particle of position-dependent mass subject to known potentials. Within the framework of the Schrödinger equation, we present the resolution of a model with a mass distribution that we can qualify as a Hulthén-type function and subject to a one-dimensional Morse-type potential. We solved it exactly by the generalized SUSYQM approach and obtained the spectrum of bound states and the corresponding eigenfunctions in an elegant algebraic way. In the second work, we solved an interesting model of Klein-Gordon equation with constant mass and mixing proportional scalar and vector potentials. The resolution was made using the approach of standard SUSYQM. But since the Klein-Gordon equation is not an eigenvalues equation and the effective potential explicitly depends on the energy, we used an interesting anzatz to successfully use standard SUSYQM unambiguously. Then, the energy levels are obtained in compact form with constraints on the problem parameters that must be satisfied for the physical solutions. Concerning the Dirac equation, we considered a particle whose mass depends on the position and placed in a vector potential. For a vector potential equal or opposite to the mass term, we reduced the upper component equation of the two-dimensional spinor to a position-dependent mass Schrödinger-type equation with an energy-dependent effective potential. By choosing the potential as a hyperbolic function and using generalized SUSYQM, combining with the previous ansatz, the spectrum and the eigenfunctions are explicitly obtained in a compact form.

2023-06-21T00:00:00Z Allouche, Bilel Djezzar, Mahfoud Taybi, Tahar http://depot.umc.edu.dz/handle/123456789/14739 2025-12-16T10:04:02Z 2023-06-19T00:00:00Z

Approche numérique de la convection naturelle dans des espaces annulaires excentrés remplis de nanofluides hybrides. Allouche, Bilel; Djezzar, Mahfoud; Taybi, Tahar In this work, we have numerically analyzed the problem of heat transfer by laminar and permanent natural convection in an eccentric annular space filled with a hybrid nanofluid. The two internal and external cylindrical walls are maintained respectively at the temperature Th and Tc. The fluid is considered Newtonian and the flow is incompressible. The governing equations formulated in bipolar coordinates are written in terms of dimensionless equations. The resulting algebraic equations are discretized by the finite volume method and solved by a FORTRAN language. Numerical simulation is performed for Rayleigh numbers: Ra=103, 104, 105, different radiation numbers: Nr=0, 0.5, 1, 10, 25, 50, different volume fractions: 0-4 % and the geometry parameters (the angle of inclination α= 90°, the radius ratio r = 2.4 and the relative eccentricity e = 0.6. The results obtained show that increasing the volume fraction improves the transfer rate of heat for the considered values of the Rayleigh number. They also show that the average Nusselt number increases considerably with the increase in the radiation number and that the stability of the flow is improved by the presence of the radiation.

2023-06-19T00:00:00Z Saad Azzem, Lokmane Bellel, Nadir http://depot.umc.edu.dz/handle/123456789/14735 2025-12-15T14:39:22Z 2023-05-25T00:00:00Z

Elaboration, caractérisation physique et hygrothermique de composite Bio-sourcés dédiés à des applications d’enveloppe des bâtiments. Saad Azzem, Lokmane; Bellel, Nadir This thesis work focuses on the thermal performance of biosourced materials of plant origin with the aim of using them as thermal insulation in buildings. We have studied their use, particularly in subtropical climates. The research was conducted on wheat straw fibers. Where Wheat straw fibers were used in bulk, that is to say without chemical binder. The objective is to provide a simpler application with little processing of raw products in order to make insulation accessible to people with extremely low incomes who live in makeshift or basic housing. The plant resource used in our work is considered waste, and the recovery of this renewable material is free in Algeria. We were able to see the physico-chemical and morphological characteristics of the fibers thanks to the characterization procedures used in the experiments we carried out. In this research work, the high cellulose content of wheat straw gives it a high absorption capacity. Where Chemical analysis using the FTIR method revealed that cellulose, hemicellulose and lignin make up the fiber of wheat straw. The amorphous nature of hemicellulose and lignin was discovered by X-ray diffraction. According to observations made with a scanning electron microscope (SEM), the fibers are cylindrical and have an irregular shape with a few threads, cells and pores which allow them to adhere well to the plaster. Composites constructed from wheat straw fibers cannot be processed at temperatures above 220°C. Thermal conductivity is one of the most important characteristics of materials used in building walls. There is a decrease in thermal conductivity as the wheat straw content increases. It decreases rapidly as the proportion of wheat straw increases, until it reaches 0.324 W/m.K for 15% wheat straw, and the percentage decrease is 20.6%. in general, cause a reduction in density and the formation of porosity in the samples. The time difference of a wall with various configurations is influenced by the thermophysical parameters of the material, the thickness and the orientation of the wall. There is an inverse relationship between time lag and that of thermal energy and thermal diffusion. Increasing the proportion of wheat straw in the plaster samples resulted in an increase in thermal resistance as well as an increased time lag. Plaster containing 15% wheat straw has good thermal performance and better performance in terms of energy saving. The compound of plaster and wheat straw has low thermal conductivity and energy savings of 20.6% compared to pure plaster. This is due to the proportion of natural fibers incorporated into the compound. Although the results are important and the model obtained from the envelopment of new materials in this research, further research still needs to be done for more specific characteristics based on this research. Here are the recommendations for future work : In terms of perspective, we want to encourage the production of vegetable fiber panels because they are more environmentally friendly than conventional insulating materials. This will help reduce or even completely eliminate the use of synthetic items. In order to apply plant fiber panels directly on the walls of buildings, we will have to envelop a process for their manufacture that does not require chemical binders. 1. Develop a research program with the same experimental test that can be carried out and wrapped using different natural fibers 2. To develop an investigation on the effect of fiber on the thermal response, the cyclic loading of composite materials. General Conclusion and perspectives 3. Study simulation models to predict mechanical properties and cracks with the finite element method. 4. Apply the results of research conducted on building materials products.

2023-05-25T00:00:00Z