Institutional repository of university M'Hamed Bougara Boumerdes
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Commercial thyme essential oil as natural beverage preservative and molecular docking study on its mode of action against Saccharomyces cerevisiae
No full textThe present investigation explored the possible use of Thymus vulgaris essential oil (TVEO) as a beverage antifungal preservative instead of chemical ones. The chemical profile of TVEO exposed carvacrol (60.47%) as the predominant compound. The antifungal properties of TVEO were assessed on various food spoilage yeast and mould species using two tests. TVEO showed a powerful antimicrobial effect against all the fungal strains at the three volumes of essential oil (EO) used (i.e. 10, 20, and 30 µL). The minimum inhibition concentration (MIC) of TVEO was also evaluated and ranged from 0.0625% to 0.015% (v/v). Furthermore, the potency of TVEO as a beverage antimicrobial preservative was tested at four distinct concentrations (0.6, 1.25, 4, and 6 μL·mL–1) against Saccharomyces cerevisiae alone and combined with medium heating (70 °C for 2 min) in a real food matrix (Orangina® drink) for eight storage days. TVEO exhibited a significantly higher preservative effect than chemical preservatives (sodium benzoate and potassium sorbate). Lastly, a molecular docking examined the mechanism of action of carvacrol against two crucial enzymes in S. cerevisiae viability [ERG2 (sterol C8-isomerase) and ERG3 (sterol C5-desaturase)] compared to a chemical preservative (potassium sorbate). The two ligands highly interacted with the two target enzymes. However, carvacrol achieved a better score than potassium sorbate against ERG2 and ERG3, with binding energy of –10.19 kcal·mol–1 and –11.73 kcal·mol–1, respectively. Our results open up the perspective of using TVEO as a natural food preservative
Evaluation of Viscoelastic Performance and Molecular Structures of Natural Rubber/NBR Blends Reinforced by Carbon Black and Nano-Silica
No full textThis study focuses on the evaluation of the dynamic mechanical properties, molecular structure, density, hardness, swelling behavior of natural rubber blends (NR) and nitrile rubber (NBR) reinforced with carbon black and/or nano-silica. An experimental work has been conducted to study of the effects of increasing NR content and incorporating nano-silica on the mechanical properties and molecular structure were studied using dynamic mechanical analysis (DMA) and Fourier transform infrared (FTIR) spectroscopy. The results show that increasing the NR content and/or incorporating nano-silica into the elastomer leads to a higher storage modulus with no significant change in the glass transition temperature. FTIR analysis indicates the compatibility of the polyblends and the presence of oxidation of the main polymer chain generated during the grinding of the rubber. Additionally, the results of the swelling study demonstrate that stronger molecular interactions occur on the surface of the nano-silica between the nitrile radicals in the NBR and the silanol (Si-OH) radicals. These findings suggest that blending NR and NBR with carbon black and/or nano-silica can improve the mechanical properties and compatibility of the resulting polyblends, with potential applications in the development of advanced elastomeric materials
La formation initiale des journalistes de L’audiovisuel à la faculté de L’information et de la communication d’alger vue par les enseignants
No full textNous nous intéressons dans cet article à la formation initiale des futurs journalistes inscrits en audiovisuel au niveau de la faculté de l’information et de la communication d’Alger. Il est question de voir comment les enseignants de ladite faculté voient la formation conçue pour les futurs journalistes. Nous nous sommes donc rapprochée d’eux pour effectuer des entretiens semi directifs, moyen d’investigation pour lequel nous avons opté. Nous avons procédé, par la suite, à l’analyse et au commentaire de ces entretiens. Dans la synthèse générale que nous avons élaborée, nous avons essayé de tirer au clair les résultats auxquels nous avons aboutis tout en les mettant en lien avec la didactique professionnelle, notre champ de recherche
Biodegradability assessment of HDPE-based biocomposites: Influence of starch and fiber composition
No full textThis research aims to analyze the biodegradation dynamics of a tertiary composite blend, including High-Density Polyethylene (HDPE), starch and linen fiber, and their combined effect on decay processes in authentic environmental settings. It investigates the relationship between fiber content and decomposition rates, details the biodegradation mechanisms, and evaluates the reactive profiles of the involved constituents. Decay kinetics and the biodegradation mechanism of three formulations: HDPE60S40, HDPE60S20F20, and HDPE60S30F10, representing composites with 60 % HDPE, complemented by 40 %, 20 % starch and 20 %, 10 % linen fiber, respectively, are examined. HDPE60S30F10 is noted for its superior biodegradation rates, showing a 1.2 % weight loss in soil and 9.89 % in marine conditions and an increased resistance to shearing forces, whereas HDPE60S40 recorded a weight loss of 0,63 % in soil and 2.59 % in seawater against 1,7 % and 6.64 % in soil and seawtaer, respectively recorded with HDPE60S20F20. Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations complement these findings, presenting HDPE60S40 as the most rigid, HDPE60S20F20 as the most ductile with a bulk modulus of 13.34 GPa, and HDPE60S30F10 exhibiting the best shear resistance with a shear modulus of 12.48 GPa. Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR) analyses confirm microbial involvement and significant surface erosion, particularly indicating particularly starch degradation. The results suggest that integrating linen fiber into the composites enhances biodegradation
Automatisation et supervision de l'ensemble de la section de peinture intérieure et du système de convoyage
No full text75 p. : ill. ; 30 cmNotre Travail consiste à faire l`automatisation et la supervision de l’ensemble unité de peinture intérieur et système de convoyage au sein de l`usine ALTUMET. En première étape, nous allons comprendre le fonctionnement de l'unité. Ensuite, nous utiliserons l'outil GRAFCET pour la modélisation. Enfin, nous avons choisi un automate programmable industriel pour l’automatisation du processus. Pour le développement du programme et la création de l’interface HMI, nous avons utilisé l’automate programmable industriel SIEMENS S7-1200. La simulation et la vérification du programme a été faite par les logiciels TIA Portal, PLCSIM et Win CC
Commande des onduleurs multicellulaires séries associes aux systèmes «PV»
No full text94 p. : ill. ; 30 cmCe Mémoire de master examine les performances des onduleurs multiniveaux de type multicellulaire séries alimentés par des systèmes photovoltaïques. Elle présente les aspects fondamentaux des cellules photovoltaïques ainsi que l’optimisation via la méthode MPPT. L’étude présente les différentes stratégies de commande utilisées pour améliorer l’efficacité et la stabilité de la conversion de puissance avec les onduleurs multicellulaire séries. Plusieurs simulations sont réalisées pour évaluer les performances des onduleurs dans différentes conditions de fonctionnement. La mémoire présente également l’application de la méthode de contrôle par mode glissant aux onduleurs multicellulaires à 4 et 6 niveaux
Calcul thermique analytique et vérification par simulation « HYSYS » de l’échangeur de chaleur « 12X20400 » au niveau du centre « GS 1» de Gassi El Agreb
No full text53 p. : ill. ; 30 cmCe mémoire se concentre spécifiquement sur les aspects liés aux calculs thermiques dans le domaine des échangeurs de chaleur. L'objectif principal est d'explorer en profondeur les différentes méthodes et techniques utilisées pour analyser et améliorer l'efficacité thermique de l’échangeur 12X20400, à travers une étude approfondie et une modélisation précise, nous chercherons à comprendre les principaux paramètres qui influent sur les performances thermiques des échangeurs de chaleur, ainsi que les stratégies permettant d'optimiser leur conception et leur fonctionnement
Impact Behavior Analysis of Luffa/Epoxy Composites Under Low-Velocity Loading
No full textLuffa cylindrical (LC) has an exceptionally multipartite architecture, a hierarchical and light structure, and a low density. Such a structure is potentially suitable to replace conventional porous-type composites for low-energy absorption and material reinforcement applications. This paper presents an experimental study of the impact behavior of four different luffa/epoxy composites, named (A), (B), (C), and (D) subjected to low-velocity impact (LVI) at energies ranging from barely visible impact damage (BVID) to perforation (5,15, and 20J). Acoustic emission (AE), scanning electron microscopy (SEM), and digital image correlation (DIC) were introduced to the indentation test to offer additional information on damage mechanisms and on strain and displacement fields since the LVI test has a short duration and real-time damage monitoring is not always achievable. The results showed that the values of the peak force of laminates (A), (B), and (D) are relatively lower compared to laminates (C). In the case of perforation impact energy (20J), the Coefficients of Restitution (CoR) of composites (A), (B), and (D) are equal to 0, which indicates that the nature of the impact is completely plastic, except for composite (C) had a value of 0.11, and a lower degree of damage at all impact energies. Composites (C) exhibit the highest impact resistance, followed by composites (A), while composites (D) display the highest energy absorption, followed by composites (B). Multivariable statistical analysis of the AE signals identified four classes of damage: matrix cracking, fiber-matrix debonding, delamination, and fiber breakage. The damage modes found by AE are well presented and proven by SEM analysis. The luffa fiber-reinforced composite has better impact properties than other natural fiber-reinforced composites
Direct Drive Permanent Magnet Synchronous Generator: Design, Modeling, and Control for Wind Energy Applications
No full textThe prominent trend in wind turbine technology centers on the adoption of direct-drive permanent magnet synchronous generators
(DD-PMSG), a choice driven by their capacity to deliver superior efficiency through the elimination of gearboxes.This paper presents
a comprehensive exploration of the design, modeling, and control aspects of a DD-PMSG intended for harnessing wind energy
conversion. Initially, the geometrical design of the generator is meticulously carried out, adhering to predefined technical specifications
and constraints. Subsequently, an in-depth internal modeling, focusing on the electromagnetic behavior of the designed generator, is
executed using finite element analysis (FEA) through the Ansys Maxwell RMXpert software. Finally, the external modeling and control
system integration of the designed generator, connected to the grid through power electronic converters, are simulated using the
Matlab/Simulink software suite. The resulting findings underscore the efficacy and viability of the proposed generator for wind turbine
applications, affirming its potential to enhance wind energy conversion system
Wideband Hybrid Dielectric Resonator Antenna Array for 5G mmWave Mobile Applications
No full textIn this paper, a wideband hybrid dielectric resonator antenna (HDRA) array design is presented for fifth-generation (5G) millimeter wave (mmWave) applications. The hybrid antenna integrates three resonant radiators of feeding slot, ring patch, and DRA to generate four resonances around 28 and 38 GHz frequency bands. The antenna element within an overall size of 0.46λL × 0.46λL× 0.1λL(λLis the free-space wavelength at 28 GHz) can achieve wide impedance bandwidth, covering n257, n259, n260 and n261, simultaneously. The 1 × 4 HDRA array is designed and simulated based on the antenna element which can achieve high realized gain varies between 10.3 to 12.5 dBi and wide beam scanning angles of ±55° and ±40° at 28 and 38 GHz frequency bands, respectively