Institutional repository of university M'Hamed Bougara Boumerdes
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Numerical analysis reveals cold expansion's influence on rivet hole stress and j-integral values
No full textIn the aeronautical construction several rivet holes are drilled, these holes constitute stress concentration zones which can be affects the fatigue life through cracks initiation at the edge of rivet holes. To remedy this problem and minimize stress level in these zones, the cold expansion technique is used to enhancing the fatigue life of rivet holes. The present work aims to investigate through finite element analysis the effect of three degree cold expansion (2%, 4.5% and 6%) on the reduction of stress level on the edge of rivet hole. The hole-crack interaction effect was thus analyzed. This effect is quantified by the values of J-Integral at the two tip of crack. The obtained results show that negative values of J- Integral was found which can be explained by the beneficial effect of residual compressive stresses induced by cold expansion on the crack closing
Évaluation économique d’un projet d’exploration-production
No full text96 p. : ill. ; 30 cmNotre mémoire a pour objectif principal de discuter et d'analyser les différentes méthodes pour attirer des partenaires stratégiques dans le secteur des hydrocarbures en Algérie. Nous allons examiner deux formules de partage spécifiques qui pourraient faciliter ces partenariats et optimiser la répartition des bénéfices et des risques
Renovation d'un melangeur industriel par l'installation d'un nouvel indicateur de pesage
No full text76 p. : ill. ; 30 cmCe projet de fin d’étude a eu lieu chez SARL UNIVER COSMETIQUE encore appelée SWALIS, une entreprise spécialisée dans le développement, la production et la commercialisation des produits cosmétiques. Ma mission était d’effectuer la rénovation d’un mélangeur industriel SME-B4000L par l’installation d’un nouvel indicateur de pesage W100-W100ANA fabriqué par l’entreprise Wimesure. Le précédent indicateur de pesage ne permettant pas l’étalonnage des cellules de pesage à cause de son interface peu ergonomique, l’amélioration de la qualité des produits a dû passer par l’installation d’un indicateur de pesage plus efficace. Répondre à cette problématique m’a permis premièrement de me familiariser avec l’environnement industriel, de faire une étude générale de la chaine de pesage et ensuite effectuer l’installation de l’indicateur de pesage
دراسة تحليلية لأثر سياسة سعر الصرف على التجارة الخارجية خلال الفترة 1989-2019 : دراسة حالة بعض الدول المصدرة للبترول
No full text208 ص. ، 30 سميهدف موضوع الأطروحة إلى دراسة أثر سياسة سعر الصرف على التجارة الخارجية بشكل عام، مع إسقاط ذلك على مجموعة من الدول المصدرة للبترول بشكل خاص، وهذا من خلال التطرق إلى مختلف الأدبيات النظرية والتجريبية فيما يخص سعر الصرف من خلال الفصل الأول، والتجارة الخارجية في الفصل الثاني، ثم محاولة الربط بينهما من الجانب النظري.
ولتحقيق هذا الغرض من الجانب التطبيقي، تم الاعتماد على أسلوب إحصائي قياسي متمثل في بيانات السلاسل الزمنية المقطعية لمعالجة بيانات الدول محل الدراسة وصياغة نموذج قياسي يعبر عن العلاقة السببية الإرتباطية بين متغيرات الدراسة خلال الفترة (1989- 2019).
وقد توصلت الدراسة إلى مجموعة من النتائج تصب في مجملها إلى وجود علاقة عكسية بين سعر الصرف الحقيقي و الميزان التجاري لدول العينة، أي أن تحسن الميزان التجاري غير راجع لسياسة سعر الصرف المتبناة من قبل هذه الدول، كما توصلت الدراسة إلى أن دول العينة التي تتبع نظام صرف ثابت كان لها أفضل أثر من تلك الدول التي تتبع نظام صرف مرن، وهذا راجع إلى التقلب الضعيف في أسعار الصر
مطبوعة بيداغوجية مقدمة لطلبة السنة الثالثة ليسانس تخصص : لسانيات عامة : دروس في المدارس النحوية
No full textMedium-term wind power forecasting using reduced principal component analysis based random forest model
No full textDue to its dependence on weather conditions, wind power (WP) forecasting has become a challenge for grid operators. Indeed, the dispatcher needs to predict the WP generation to apply the appropriate energy management strategies. To achieve an accurate WP forecasting, it is important to choose the appropriate input data (weather data). To this end, a medium-term wind power forecasting using reduced principal component analysis (RKPCA) based Random Forest Model is proposed in this paper. Two-stage WP forecasting model is developed. In the first stage, a Kernel Principal Component Analysis (KPCA) and reduced KPCA (RKPCA)-based data pre-processing techniques are applied to select and extract the important input data features (wind speed, wind direction, temperature, pressure, and relative humidity). The main idea behind the RKPCA technique is to use Euclidean distance for reducing the number of observations in the training data set to overcome the problem of computation time and storage costs of the conventional KPCA in the feature extraction phase. In the second stage, a Random Forest (RF) algorithm is proposed to predict the WP for medium-term. To evaluate the performance of the proposed RKPCA-RF technique it has been applied to data extracted from NOAA’S Surface Radiation (SURFRAD) network at Bondville station, located in USA. The presented results show that the proposed RKPCA-RF technique achieved more accurate results than the state-of-the-art methodologies in terms of RMSE (0.09), MAE (0.23), and R2 (0.85). In addition, the proposed technique achieved the lowest overall computation time (CPU)
Intelligent multi-fault identification and classification of defective bearings in gearbox
No full textBearing faults in gearbox systems pose critical challenges to industrial operations, needing advanced diagnostic techniques for timely and accurate identification. In this paper, we propose a new hybrid method for automated classification and identification of defective bearings in gearbox systems with identical rotating frequencies. The method successfully segmented the signals and captured specific frequency components for deeper analysis employing three distinct signal processing approaches, ensemble empirical mode decomposition EEMD, wavelet packet transform WPT, empirical wavelet transform EWT. By decomposing vibration signals into discrete frequency bands using WPT, relevant features were extracted from each sub-band in the time domain, enabling the capturing of distinct fault characteristics across various frequency ranges. This extensive set of features is then served as inputs for machine learning algorithm in order to identify and classify the defective bearing in the gearbox system. Random forest RF, decision tree DT, ensemble tree ET classifiers showcased a notable accuracy in classifying different fault types and their localizations. The new approach shows the high performance of the diagnostic gearbox with a minimum of accuracy (Min = 99.95 %) and higher stability (standard deviation = 0.1)
Reliability assessment of carbon/epoxy micro-fiber subject to compressive stress
No full textPurpose: This study addresses the reliability of a composite fiber (carbon fibers/epoxy matrix) at microscopic level, with a specific focus on its behavior under compressive stresses. The primary goal is to investigate the factors that influence the reliability of the composite, specifically considering the effects of initial fiber deformation and fiber volume fraction. Design/methodology/approach: The analysis involves a multi-step approach. Initially, micromechanics theory is employed to derive limit state equations that define the stress levels at which the fiber remains within an acceptable range of deformation. To assess the composite's structural reliability, a dedicated code is developed using the Monte Carlo method, incorporating random variables. Findings: Results highlight the significance of initial fiber deformation and volume fraction on the composite's reliability. They indicate that the level of initial deformation of the fibers plays a crucial role in determining the composite reliability. A fiber with 0.5% initial deformation exhibits the ability to endure up to 28% additional stress compared to a fiber with 1% initial deformation. Conversely, a higher fiber volume fraction contributes positively to the composite's reliability. A composite with 60% fiber content and 0.5% initial deformation can support up to 40% additional stress compared to a composite containing 40% fibers with the same deformation. Originality/value: The study's originality lies in its comprehensive exploration of the factors affecting the reliability of carbon fiber-epoxy matrix composites under compressive stresses. The integration of micromechanics theory and the Monte Carlo method for structural reliability analysis contributes to a thorough understanding of the composite's behavior. The findings shed light on the critical roles played by initial fiber deformation and fiber volume fraction in determining the overall reliability of the composite. Additionally, the study underscores the importance of careful fiber placement during the manufacturing process and emphasizes the role of volume fraction in ensuring the final product's reliability
Fuel-air ratio effect on hydrogen-methane flames in a high pressure burner for gas turbines
No full textThis numerical simulation studied the effect of H2-CH4 flame equivalence ratio on turbulent premixed combustion at 50%-50% concentration (by volume). The equivalence ratio was varied from 0.45 to 1.0 in 0.5 increments for 126 kW operating power, matching a 3.3 bar inlet reactant pressure. Tests utilized a gas turbine combustor. The thermal field, flow field, and pollutant emissions (NOx and CO) underwent rigorous analysis. The modelling framework applied steady Reynolds-Averaged Navier-Stokes (RANS) equations coupled to a probability density function (PDF) approach for turbulence-chemistry interactions and a NOx formation model. Results showed increasing equivalence ratio from 0.45 to 1.0 elevated temperature approximately 900 K, significantly promoting NOx up to 1600 ppm and CO beyond 1900 ppm. However, equivalence ratio changes minimally impacted the overall flow field, maintaining stabilized flames. These findings provide new insight on thermochemical effects and flame stability in gas turbine (G.T) combustors across a range of equivalence ratios relevant for clean, high-pressure H2-CH4 combustion. The combined RANS-PDF methodology enables predictive simulation of turbulence, kinetics, emissions, and flame stability to guide optimal fuel-air ratio selection and low-emission combustor design
Optimisation des paramètres opératoires de l'unité de déshydratation «Zotti GCR» et le changement de la philosophie "Timer" par un système hygromètre
No full text146 p. : ill. ; 30 cmCe Mémoire présente une étude sur l'optimisation des paramètres opératoires de l'unité de déshydratation Zotti du complexe de traitement d’huile El-Gassi, en mettant l'accent sur la recherche de la température optimale de fonctionnement des sécheurs pendant les périodes estivales. Des améliorations techniques telles que l'introduction d'un échangeur de chaleur et l'implémentation d'un nouveau système de gestion de l'humidité ont été proposées. Les résultats montrent des avantages significatifs, notamment une meilleure efficacité du processus de séchage, une prolongation de la durée de vie des équipements, des économies financières et une réduction des émissions de CO2