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New structural approach for bond graph to digraph conversion : a sensor placement optimisation for fault detection and isolation
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Synthèse des matrices thermodurcissables chargées : Résine époxyde,charges minérales, rhéologie, comportement mécanique, propriétés physico-chimiques, microstructure
No full textLe présent travail consiste à faire une synthèse des matériaux composites avec des nouvelles formulations des matrices thermodurcissables de type époxyde, par l’incorporation de fortes proportions des charges minérales locales. Ces dernières confèrent à la matrice des propriétés qu’elle ne possède pas seule, d’une part, à réduire le prix de revient des matériaux composites, et d’autre part, à améliorer la mise en œuvre par l’augmentation de la viscosité et la diminution du retrait à sa valeur minimale. Elles ont aussi la faculté d’augmenter les propriétés diélectriques des matériaux, mais aussi d’améliorer la rigidité mécanique et touchent les propriétés physico-chimiques en permettant au matériau d’avoir une meilleure tenue aux agents chimique, ce qui permet à la nouvelle matrice de très large domaines d’utilisation tel que l’industrie automobile, l’industrie de fabrication des composants diélectriques, des équipements de sport et de loisirs et dans le revêtement des sols
Numerical simulations of laminar burning velocities of a major volatile organic compound involved in accelerating forest fires
No full textThis paper is dedicated to a first approach for the study of the so called eruptive fires or accelerating forest fires. It is a preliminary work to test the hypothesis of Volatile Organic Compounds (VOCs) accumulation as the cause of this phenomenon. In this work we explore the ability of the numerical code Fire Dynamics Simulator (FDS-v5.5) to simulate premixed flame spread. In a first part the burning velocities of propane/air and n-decane/air mixtures are calculated for different initial temperatures and equivalence ratio (0.7-1.3) at atmospheric pressure using a cylindrical combustion chamber. The preheat temperatures range for propane and n-decane fuels are respectively 300-423 K and 360-470 K. In a second part, the laminar burning speeds of the α-pinene, which is the main VOC emitted by Mediterranean vegetal species, is simulated for the same equivalence ratio and initial temperatures 373-453 K. The obtained results of these three fuels are compared to the experimental and computed results of the literature. These comparisons demonstrate the ability of FDS-v5.5 to deliver reliable predictions on laminar burning velocities of premixed flame
دور المعايير المحاسبية ومعايير الإبلاغ المالي الدولبة في تفعيل التحليل المالي في المؤسسة : دراسة حالة المؤسسة المدنية والبناء(GCB)
No full textص. 139 : إيض. ; 30 سميعتبر التحليل المالي من أهم ما هو مستخدم ضمن آليات التخطيط و الرقابة و الحصول على معلومات تساهم بشكل أو بآخر في ترشيد قرارات المؤسسة اعتمادا على دراسة البيانات الظاهرة بالقوائم المالية ، حيث يتم إعداد هذه الأخيرة وفق ما تمليھ متطلبات المعايير المحاسبية و معايير الإبلاغ المالي الدولية التي تسهل من تطبيق تقنيات التحليل المالي في المؤسسة ؛ وفي هذا السياق تناولنا موضوع التحليل المالي من خلال معالجة إشكالية يدور مضمونها حول مدى مساهمة المعايير المحاسبية و معايير الإبلاغ المالي الدولية في تفعيل التحليل المالي في المؤسسات ، ومن أجل ذلك قمنا بمعالجة الموضوع من خلال الجمع بين الدراسة النظرية و الدراسة الميدانية حيث تناول الجانب النظري الإطار النظري للمعايير المحاسبية الدولية ومن ثم انعكاساتها و إسهاماتها في تفعيل التحليل المالي ثم تم إسقاط ذلك في الدراسة الميدانية على المؤسسة الوطنية للهندسة المدنية و البناء ليتم في النهاية التوصل إلى مجموع نتائج مفاد جلها أنه فعلا لمعايير المحاسبة الدولية دور تفعيلي في التحليل المالي بالمؤسسا
Probabilistic model to forecast earthquakes in the Zemmouri (Algeria) seismoactive area on the basis of moment magnitude scale distribution functions
Get PDFBased on the moment magnitude scale, a probabilistic model was developed to predict the occurrences of strong earthquakes in the seismoactive area of Zemmouri, Algeria. Firstly, the distributions of earthquake magnitudes M i were described using the distribution function F 0(m), which adjusts the magnitudes considered as independent random variables. Secondly, the obtained result, i.e., the distribution function F 0(m) of the variables M i was used to deduce the distribution functions G(x) and H(y) of the variables Y i = Log M 0,i and Z i = M 0,i , where (Y i)i and (Z i)i are independent. Thirdly, some forecast for moments of the future earthquakes in the studied area is give
Methods of the rational choice of a labyrinth seal design for gas pumping units
Get PDFThis present paper describes a method of improving the labyrinth seal design by the development of three-dimensional parametric computer of its model and an anal-ysis of its work for gas pumping units (GPU) using the finite-element method. The authors have improved design labyrinth seal of the GPU according to the criterion of minimum pressure in the last gap by Gauss-Seidel method of optimization, which will increase GPU operational efficiency by reducing flowing medium at various operating modes of GPU. It is shown that change of geometrical sizes and form of creating more compact part of labyrinth seal with inclination them toward greater pressure for an angle of 80° decrease leakages of gas, that in same time considerably influences on the expense of working environment on the output of labyrinth sea
Numerical study of natural melt convection in cylindrical cavity with hot walls and cold bottom sink
Get PDFNumerical study of natural convection heat transfer and fluid flow in cylindrical cavity with hot walls and cold sink is conducted. Calculations are performed in terms of the cavity aspect ratio, the heat exchanger length, and the thermo physical properties expressed via the Prandtl and the Rayleigh numbers. Results are presented in the form of isotherms, streamlines, average Nusselt number, and average bulk temperature for a range of Rayleigh number up to 106. It is observed that Rayleigh number and heat exchanger length influences fluid flow and heat transfer, whereas the cavity aspect ratio has no significant effect
Thermal behaviour of five different date palm residues of algeria by thermogravimetric analysis
Get PDFRenewable energy has become more important globally especially with the current fuel and economic crisis. Date palm biomasses are highly potential materials for energy resources. The fact that they are renewable and abundantly available are amongst the attractive reasons of employing them as the major source for renewable energy. The purpose of this research was to investigate the thermal behavior of date palm biomass in order to evaluate their usefulness for energy production. In microparticular scale, the thermogravimetric analysis (TGA) is one of the techniques used to determine the thermal properties of five different date palm residues that were studied: (date palm rachis (DPR), date palm trunk (DPT), leaf base (Petiole) (LB), fruitstalk prunings (FP) and liff (LP)). The TGA technique consists to record the lost weight during the increase in temperature from 20°C until 600°C with a 10°C/min heating rate. The thermograms presented a departure phase of free water (from room temperature to 110°C) before the degradation process of the lignocellulosic constituents. The lignin and hemicellulose play an important role on the degradation of lignocellulosic materials at the temperature under 250°C. The degradation of cellulose begins at 250°C and overlaps to that of lignin until 450°
Valorisation of loads petroleum load via thermal process
No full textThis study was performed to allow the study of the chemical composition influence of the coking process load on the efficiency and the quality of coke. For this reason, the coking of the following loads was realized: Atmospheric residue, vacuum residue and catalytic residue of cracking. As the oil residues are rich for their strongly polar composition, such as the asphaltene resins and complex structures units, which has a role in the formation of coke and as the dispersion of these latter improves the quality of coke, a study on the stability of aggregation was carried out by the addition of one stabilizer (oil extract) in the coking process load. The compounding (extracted from/the residue of cracking oil) has been drived to the best efficiency of cok