Contribution à la formulation d’une pâte autoplaçante à base de matériaux locaux

Ce travail a pour but la formulation d’une pâte autoplaçante de ciment à base de matériaux locaux algériens (ciment binaire à base d’une pouzzolane naturelle algérienne et fillers calcaires de carrière). Plusieurs pâtes ont été confectionnées à partir du ciment, des fillers calcaires (substituant un taux croissant du ciment), du superplastifiant et de l’eau. L'ouvrabilité et la fluidité des pâtes formées sont déduites des essais del’étalement au mini-cône et du temps d’écoulement au cône de Marsh respectivement. A partir de ces essais considérés comme préliminaires, un domaine expérimental est déduit, a l'intérieur duquel les mesures sont possibles. Par utilisation de la méthode des plans de mélanges, le nombre d'expériences sera considérablement réduit, le problème a été mis en équations (sous forme de contraintes implicites) puis résolu numériquement. Des critères d'optimalisation sont vérifiés en plus des interactivités entre constituants pris deux à deux grâce à des essais faisant intervenir les multiples combinaisons en dosages de ces matériaux. En passant par des courbes des diagrammes ternaires, reliant les réponses étalements et temps d’écoulement des pâtes en fonction des dosages en constituants et en étudiant les fonctions de désirabilités sur chaque réponse: une composition de pâte autoplaçante est déduite.Mots-clés : Formulation, propriétés rhéologiques, plans de mélanges,  iagrammes ternaires, pâte de ciment autoplaçante

Influence des paramètres de composition sur le comportement du béton autoplaçant à l’état frais

La présente étude s’inscrit dans le cadre des travaux de recherche menés au département de génie civil de l'université de Mostaganem, en Algérie. Elle concerne l’étude de l’influence des paramètres de composition sur le comportement du béton autoplaçant à l'état frais. Elle a pour objectif de comprendre les rôles joués par les différents constituants susceptibles d’entrer dans la formulation d'un BAP à base de matériaux locaux notamment le sable de mer et le sable de carrière (considéré comme déchet naturel) et de mettre en évidence les éventuelles interactions entre constituants. Les résultats obtenus offrent de belles perspectives pour optimiser les BAP. Nos essais ont permis de développer une variété de formulations de béton autoplaçant répondant aux critères rhéologiques (bonne déformabilité, moins de ressuage, absence de ségrégation).Mots-clés : Béton autoplaçant, superplastifiant, fines calcaires, matériaux locaux, béton frais

Sustainable biocomposites for food packaging applications

Biocomposites produced from renewable biomass were investigated for suitability in food packaging applications. Poly(lactic acid) was compounded with 10 – 30 wt. % hemp hurd through extrusion and injection moulding to produce rigid plastic biocomposites. In addition to their cost-effectiveness and equivalent mechanical properties, the biocomposites were particularly effective as antimicrobial materials with the inclusion of silver nanoparticles. A 16% cost margin was achieved in the biocomposites with additional antimicrobial capabilities. Through further research, development, and supply chain management, economic and environmental sustainability can be achieved in production

Laser-induced transient currents in CdZnTe quasi-hemispherical radiation detector

Laser-induced transient currents were measured after applying pulsed or direct-current bias to a CdZnTe quasi-hemispherical radiation detector with gold contacts. The temporal evolution of current transients was analyzed to evaluate the dynamics of the space charge formation and its spatial distribution. The observed effects were explained by a model involving hole injection from positively biased contacts. Experimental results were complemented by numerical simulations, which supported the model. This paper discusses how the detected phenomena affect the detector performance and proposes an improved detector design

Theory of periodic swarming of bacteria: application to Proteus mirabilis

The periodic swarming of bacteria is one of the simplest examples for pattern formation produced by the self-organized collective behavior of a large number of organisms. In the spectacular colonies of Proteus mirabilis (the most common species exhibiting this type of growth) a series of concentric rings are developed as the bacteria multiply and swarm following a scenario periodically repeating itself. We have developed a theoretical description for this process in order to get a deeper insight into some of the typical processes governing the phenomena in systems of many interacting living units. All of our theoretical results are in excellent quantitative agreement with the complete set of available observations.Comment: 11 pages, 8 figure

Adaptive forecasting and financial risk estimation

The study is directed towards development of an adaptive decision support system for modeling and forecasting nonlinear nonstationary processes in economy, finances and other areas of human activities. The structure and parameter adaptation procedures for the regression and probabilistic models are proposed as well as the respective information system architecture and functional layout are developed. The system development is based on the system analysis principles such as adaptive model structure estimation, optimization of model parameter estimation procedures, identification and taking into consideration of possible uncertainties met in the process of data processing and mathematical model development. The uncertainties are inherent to data collecting, model constructing and forecasting procedures and play a role of negative influence factors to the information system computational procedures. Reduction of their influence is favourable for enhancing the quality of intermediate and final results of computations. The illustrative examples of practical application of the system developed proving the system functionality are provided

Influence of quorum sensing signal molecules on biofilm formation in Proteus mirabilis O18

The influence of basis of quorum sensing molecules on Proteus strains is much less known as compared to Pseudomonas or Escherichia. We have previously shown that a series of acylated homoserine lactones (acyl-HSL) does not influence the ureolytic, proteolytic, or hemolytic abilities, and that the swarming motility of Proteus mirabilis rods is strain specific. The aim of the presented study was to find out if the presence of a series of acyl-HSL influences biofilm formation of P. mirabilis laboratory strain belonging to O18 serogroup. This serogroup is characterized by the presence of a unique non-carbohydrate component, namely phosphocholine. Escherichia coli and P. mirabilis O18 strains used in this work contains cloned plasmids encoding fluorescent protein genes with constitutive gene expression. In mixed biofilms in stationary and continuous flow conditions, P. mirabilis O18 overgrow whole culture. P. mirabilis O18 strain has genetically proved a presence of AI–2 quorum sensing system. Differences in biofilm structure were observed depending on the biofilm type and culture methods. From tested acylated homoserine lactones (BHL, HHL, OHL, DHL, dDHL, tDHL), a significant influence had BHL on thickness, structure, and the amount of exopolysaccharides produced by biofilms formed by P. mirabilis O18 pDsRed2