Conception du système de transmission OFDM codé pour les applications à haut débit

On observe de nos jours un intérêt considérable pour de nouvelles technologies sans fil capables de réaliser des hauts débits, comme l'OFDM qui offre une forte protection pour les canaux à trajets multiples. Les perturbations qui interviennent sur ce type de canaux induisent des erreurs de transmission que le codage de système s'efforce de combattre pour assurer un taux d'erreur minimal. Dans ce travail, on propose un système OFDM qui est capable d'offrir une protection améliorée aux trajets multiples, grâce à l'insertion d'un intervalle de garde et une robustesse développée grâce à l'entrelacement temporel des données transmis et un codage de correction d'erreurs. Nous présentons les résultats obtenus en utilisant des codes convolutionnels et des codes Reed Solomon. Le système a été implanté sous Simulink de Mathworks. On a évalué l'effet du choix du code et de l'entrelacement sur la performance du système OFDM. L'analyse des performances du système avec le codage Reed-Solomon montre une amélioration dans l'environnement à trajets multiples. Les performances en terme de taux d'erreurs sont présentées pour différents paramètres de transmission, afin de définir les méthodes et les valeurs optimales du système de transmission OFD

Modeling and Optimization of Cutting Parameters during Machining of Austenitic Stainless Steel AISI304 Using RSM and Desirability Approach

In the current paper, cutting parameters during turning of AISI 304 Austenitic Stainless Steel are studied and optimized using Response Surface Methodology (RSM) and the desirability approach. The cutting tool inserts used in this work were the CVD coated carbide. The cutting speed (vc), the feed rate (f) and the depth of cut (ap) were the main machining parameters considered in this study. The effects of these parameters on the surface roughness (Ra), cutting force (Fc), the specific cutting force (Kc), cutting power (Pc) and the Material Removal Rate (MRR) were analyzed by ANOVA analysis.The results showed that f is the most important parameter that influences Ra with a contribution of 89.69 %, while ap was identified as the most significant parameter (46.46%) influence the Fc followed by f (39.04%). Kc is more influenced by f (38.47%) followed by ap (16.43%) and Vc (7.89%). However, Pc is more influenced by Vc (39.32%) followed by ap (27.50%) and f (23.18%).The Quadratic mathematical models, obtained by the RSM, presenting the evolution of Ra, Fc, Kc and Pc based on (vc, f, and ap) were presented. A comparison between experimental and predicted values presents good agreements with the models found.Optimization of the machining parameters to achieve the maximum MRR and better Ra was carried out by a desirability function. The results showed that the optimal parameters for maximal MRR and best Ra were found as (vc = 350 m/min, f = 0.088 mm/rev, and ap = 0.9 mm)

Linear sliding wear behavior of aluminium matrix composites reinforced by particulates

Linear sliding wear behavior studied for metal composites. Different types of composites were tested and three different fabrication techniques: two foundry techniques with different volume fraction and particulates size and thermal projection. The results show that the lubrication has a strong effect on the wear rate. The composites did not wear when tested under oil lubrication conditions, while the cable wore rapidly. The opposite phenomena occurred when dry tests were performed: the cable was protected while the specimen wore quickly. The critical volume fraction, i.e. the minimum volume fraction of particulates for protecting the composites, is on the order of 10%, whatever the size of the reinforcement. This minimum volume fraction does not seem to significantly depend on the size of the particulates. Finally, it was observed that the wear rate of the composite is the lowest for composites reinforced by a low percentage of particulates. A mechanical model describes the behavior of both partners (cable and MMC)

Propagation of acoustic waves in two waveguides couples by perforations. I. Theory.

International audienceThe problem of propagation in two guides coupled by perforations, important for a perforated tube muffler, is discussed. At low frequencies, if the distance between perforations is sufficiently large, a discrete model can be used. An exact equivalent circuit for a perforation is obtained by using a modal theory and a matrix formalism. A series inductance due to the existence of antisymmetric field in the perforation is proven to exist, completing the perforation shunt impedance concept. This model is directly exploitable for lattice analysis. For homogeneous lattices (i.e. with identical propagation in the two guides), either regular or irregular, two modes exist: a planar mode and a "flute" mode, either propagating or evanescent. Cutoff frequencies of periodic lattices are found to depend on either the shunt inductance or the series inductance (the first cutoff depending on the shunt one). In homogeneous lattices, a new type of evanescent waves can exist, with non-zero energy flux, equal and opposite in sign in each guide. Finally, the effect of mean flow in such a lattice is discussed

Discovery, affinity maturation and multimerization of small molecule ligands against human tyrosinase and tyrosinase-related protein 1

Human tyrosinase (hTYR) and tyrosinase-related protein 1 (hTYRP1) are closely-related enzymes involved in the synthesis of melanin, which are selectively expressed in melanocytes and, in a pathological context, in melanoma lesions. We used a previously described tyrosinase inhibitor (ThiamidolTM) and DNA-encoded library technology for the discovery of novel hTYR and hTYRP1 ligands, that could be used as vehicles for melanoma targeting. Performingde novoselections with DNA-encoded libraries, we discovered novel ligands capable of binding to both hTYR and hTYRP1. More potent ligands were obtained by multimerizing ThiamidolTM moieties, leading to homotetrameric structures that avidly bound to melanoma cells, as revealed by flow cytometry. These findings suggest that melanoma lesions may, in the future, be targeted not only by monoclonal antibody reagents but also by small organic ligands

Computational methods to analyze and predict the binding mode of inhibitors targeting both human and mushroom tyrosinase

Tyrosinase, a copper-containing enzyme critical in melanin biosynthesis, is a key drug target for hyperpigmentation and melanoma in humans. Testing the inhibitory effects of compounds using tyrosinase from Agaricus bisporus (AbTYR) has been a common practice to identify potential therapeutics from synthetic and natural sources. However, structural diversity among human tyrosinase (hTYR) and AbTYR presents a challenge in developing drugs that are therapeutically effective. In this study, we combined retrospective and computational analyses with experimental data to provide insights into the development of new inhibitors targeting both hTYR and AbTYR. We observed contrasting effects of Thiamidol™ and our 4-(4-hydroxyphenyl)piperazin-1-yl-derivative (6) on both enzymes; based on this finding, we aimed to investigate their binding modes in hTYR and AbTYR to identify residues that significantly improve affinity. All the information led to the discovery of compound [4-(4-hydroxyphenyl)piperazin-1-yl](2-methoxyphenyl)methanone (MehT-3, 7), which showed comparable activity on AbTYR (IC50 = 3.52 μM) and hTYR (IC50 = 5.4 μM). Based on these achievements we propose the exploitation of our computational results to provide relevant structural information for the development of newer dual-targeting molecules, which could be preliminarily tested on AbTYR as a rapid and inexpensive screening procedure before being tested on hTYR

Activité antifongique in vitro du phoséthyl-Al sur quelques souches de Verticillium albo-atrum Reinke & Berthold

La fongitoxicité du phosphonate, métabolite actif du phoséthyl-Al est modulée par la composition des milieux de culture. Sur le Cristomalt (milieu naturel) la toxicité du phosphonate vis-à-vis du Verticillium albo-atrum Reinke & Berthold. fonne à microsclérotes. est beaucoup plus grande que sur le Ribeiro (milieu synthétique). L'addition du phosphate au milieu de culture abaisse l'efficacité du phosphonate. Ce sont toujours les souches de Verticillium pathogènes sur la tomate, qui sont les plus sensibles au phoséthyl-Al.In vitro antifungal activity of fosetyl-Al on several strains of Verticillium albo-alrum Reinloe & BertholdToxicity of phosphonate, the active breakdown product of the fosethyl-Al, is modulated by culture media composition. On the Cristomalt ( natural medium), phosphonate toxicity against Verticillium albo-atrum Reinke & Berthold,-microsclerotial fonn, is higher than in synthetic media (Ribeiro). Phosphate is the main constituent of culture medium which modifies phosphonate fungitoxicity. Strains ofVerticillium, pathogenicon tomato, are al ways more sensitive" to fosethyl-Al

Workplace industrial relations in Algeria A case study of oil and chemical industries

SIGLEAvailable from British Library Document Supply Centre- DSC:DX171004 / BLDSC - British Library Document Supply CentreGBUnited Kingdo