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Simulated multi-crystalline silicon solar cells with aluminum back surface field
No full textIn photovoltaic solar cells manufacturing, we are confronted to the perpetual challenge for conversion efficiency enhancing. We propose in this work to quantify the back surface field aluminium (Al-BSF) rear contact effect deposited by screen printing metallization. Al-BSF numerical simulation has been performed by the use of softwares dedicated to photovoltaic like PC1D, SCAPS 2.7 and AFORS-HET. In this work, a SiNx/Si(n+)/ Si(p)/Si(p+) structure is studied. This means that we have a classical junction np passivated at the front face with SiNx anti-reflective coating (ARC) and at the rear face a screen printed Aluminum contact. The back Al-BSF, must to be thick (no least 10µm) and highly p-doped (holes concentration between 1018 and 1019 cm-3) in order to reduce effective rear recombination velocity, yielding to an enhancement of the Al layer performance. Were inserted in the software parameters data: the lifetime measured for the inner bulk (Tn=30 µs and Tp=90 µs) with Al diffusion (10.8 µm deep). For emitter doping equals to 1.5*1020 cm-3, front surface recombination velocity Sf=8600 cm/s and the effective minority diffusion length Leff=227 µm. After simulation of the input parameters, an efficiency of 18.0% is obtained by PC1D, in good accordance with the results presented in the literature. While the obtained efficiencies results with AFORS-HET and SCAPS 2.7 are 17.15% and 18.73% respectively. A rapprochement occurs between PC1D and SCAPS quantum efficiency curves with begin values ~ 70% QE while AFORS-HET is so far with ~ 34% Q
Simulation and modeling the deferred behavior induced by the creep of a reinforced concrete section
Get PDFIn the reinforced concrete structures, the differed deformations due to creep increase with time. They become dominating compared to the instantaneous strains, corresponding to a given loading. In order to ensure itself of the good behavior of an element or a concrete structure reinforced in service and with the absolute limit, it is necessary to correctly evaluate the instantaneous and differed deformations and displacements. Within the framework of this study one is interested in modeling and simulation of the behaviors instantaneous and differed from a zone bent out of reinforced concrete. For the simulation of the instantaneous behavior, in composed inflection, an existing program is used and of the complements of validations is realized. For the modeling of the differed behavior, a formulation based on the method of the adjusted effective module is presented. Another data-processing program is developed. It makes it possible to simulate the deformations of a zone bent under loading supported in time. The differed effects are taken into account by using the coefficient of creep recommended by the CEB 90. The simulations carried out on experimental tests allow the validation of the approach used. The results show that the best functioning of the approach used by the program and the comparison test-calculation is satisfactor
Conception of hydrofiber wound dressing from cellulose of esparto
No full textThe first synthesis of a cellulose derivative goes back to a little more than a century with the development of industrial production of nitrocellulose, which has promoted the development of ethers and esters of cellulose. The carboxymethylcellulose is a derivative occupies an important place in the industry processing and enjoys a wide field of food and pharmaceutical usage; The hydrophilic character of its fibers and their adsorption capacity fact that either at the base of drug composition and design of a wide range of tissue dressings. These dressings are used to treat the wounds of several natures; they are constituted of supports to which has been added to the fibrous layer carboxymethylcellulose whose role is to suck the molecules produced by the bacteria and wound exudate. In this sense we set the target to conceive a wound dressing using the cellulose contained in stems of the esparto, annual vegetal, widely used in Algeria; To do this, two types of extraction were carried out: one, by alkaline delignification in the presence of temperature, followed by a bleaching with hypochlorite and alkaline purification; the other by direct extraction with organic solvent (acetone) using the Kurchner. Method; The cellulose extracted is subsequently quenched in a solution of 30% sodium hydroxide dried to obtain an akali-cellulose and treated it in an excess of mono chloro acetic acid (MCA), thereby to prepare for the CMC, main component of our wound dressing hydrofibre. The different characterization results (identification, humidity, purity tests, degree of substitution, etc.) showed that the CMC obtained is comparable to that which are commercially available and could then meet our goa
Metakaolin-slag-clinker blends.the role of Na+ or K+ as alkaline activators of theses ternary blends
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Etude des charges aéroélastiques d'une pale en composite
No full text171 p. : ill. ; 30 cmLe but de ce travail est d'étudier le système des articulations de la pale des amortisseurs hydrauliques et en élastomère pour réduire le niveau vibratoire dans les rotors d'hélicoptères. Ces amortisseurs comprennent des moyens de rappel élastique à raideur et amortissement déterminés, pour éviter les phénomènes de résonance, en particulier de résonance de trainée et aussi de résonance de battement qui peuvent apparaître notamment sur les pales d'hélicoptères. En premier lieu une étude du comportement dynamique du système rotor avec les différents modes de vibrations et évaluation des contraintes des pales est établie. En deuxième lieu un modèle non linéaire identifiant les contraintes aéroélastiques en fonction de la rigidité du fuselage est simulé. Une modélisation en trois D par éléments finis de la structure en fonction des caractéristiques mécaniques du matériau et des charges aéroélastiques est présentée. Les calculs numériques sur le modèle développes tenant compte de l'interaction aéroélastique prouve que les amortisseurs en élastomère de type viscoélastique donne des meilleurs résultats par rapport aux autres hydrauliques. Une simulation numérique de la fissure sous les charges aérodynamiques sur la pale est présentée. Ce qui a permis de mettre en évidence un indicateur pour la surveillance et la prédiction de l'endommagement dans les pales d'hélicoptère. Enfin expérimentalement le choc dynamique d'impacts, a montré clairement la variation des propriétés mécaniques (la fréquence propre, la rigidité et le facteur d'amortissement) sous l'influence de la propagation de la fissur