WAVELETS AND PRINCIPAL COMPONENT ANALYSIS METHOD FOR VIBRATION MONITORING OF ROTATING MACHINERY

Fault diagnosis is playing today a crucial role in industrial systems. To improve reliability, safety and efficiency advanced monitoring methods have become increasingly important for many systems. The vibration analysis method is essential in improving condition monitoring and fault diagnosis of rotating machinery. Effective utilization of vibration signals depends upon effectiveness of applied signal processing techniques. In this paper, fault diagnosis is performed using a combination between Wavelet Transform (WT) and Principal Component Analysis (PCA). The WT is employed to decompose the vibration signal of measurements data in different frequency bands. The obtained decomposition levels are used as the input to the PCA method for fault identification using, respectively, the Q-statistic, also called Squared Prediction Error (SPE) and the Q-contribution. Clearly, useful information about the fault can be contained in some levels of wavelet decomposition. For this purpose, the Q-contribution is used as an evaluation criterion to select the optimal level, which contains the maximum information.Associated to spectral analysis and envelope analysis, it allows clear visualization of fault frequencies. The objective of this method is to obtain the information contained in the measured data. The monitoring results using real sensor measurements from a pilot scale are presented and discussed

Corrosion of a carbon steel covered by treated bentonites in aqueous solution

In the present work we realised an electrochemical system for steel/clay/aqueous solutions study. Two Algerian bentonites have been considered. The obtained results show that both clays are corrosive even in the absence of chloride ions. We show that this corrosiveness is related to the cationic exchange capacity (CEC). The chemical treatment of clays by tungstate reduces significantly their CEC and corrosiveness. Electrochemical impedance spectroscopy results prove that tungstate reduces iron and chlorides ions transport through the clay. This deduction is supported also by microscopic observations.Keywords: Corrosion inhibitor, Carbon steel, Electrochemical Impedances Spectroscopy; Algerian bentonites; Tungstat

Antifungal activity of different extracts of the bark of Cinnamomum cassia used in traditional medicine

The incidence of invasive fungal infections due to Candida albicans has dramatically increased since 25 years. The amphotericin B remains the best treatment despite its severe toxicity. Our work is inscribed in the frame of finding of new natural antifungals agents from a condiment widely used in our diet: the Chinese cinnamon (Cinnamomum cassia). This study is focused in first time, to the qualitative determination of different families of secondary metabolites from the bark of Cinnamon. On the other time, assessing the antifungal activity of some extracts of Cinnamon. The plant material was extracted by exhaustion using increased polarity solvents (hexane, diethyl ether, methanol/water and water). We have made five exhaustions for each solvent, each one was tested separately. The phytochemical study revealed the presence of terpenes, alkaloids and polyphenols represented mainly by flavonoids. Evaluation of antimicrobial activity of the various extracts was carried out against references yeasts strains Candida albicans ATCC10231 and Candida albicans 444IP. Results showed that in the exception of aqueous extracts, all other extracts have an interesting activity, with inhibition zone diameters between 10 mm and 58 mm for the diethyl ether extract. Similar results were obtained for the hexane extracts. Indeed, extracts obtained from low or medium polarity solvents are the most active. In addition, the minimum inhibitory concentration and minimal fungicidal concentration of the first fraction of the hexane extract were respectively 1,9 µg/ml and 3,9 µg/ml against C. albicans ATCC10231 and C. albicans 444IP. They remain comparable than those of amphotericin B against the same strains.L'incidence des infections fongiques invasives due à Candida albicans a considérablement augmenté depuis 25 ans. L’amphotéricine B reste le meilleur traitement en dépit de sa toxicité sévère. Notre travail s'inscrit dans le cadre de la découverte de nouveaux agents antifongiques naturels à partir d'un condiment très utilisé dans notre alimentation: la cannelle de Chine (Cinnamomum cassia). Cette étude s’intéresse dans un premier temps, à la détermination qualitative des différentes familles de métabolites secondaires de l'écorce de cannelle. D'autre part, à évaluer l'activité  antifongique de certains extraits de ce condiment. Le matériel végétal a été extrait par épuisement en utilisant des solvants de polarité croissante (hexane, éther diéthylique, méthanol/eau et eau). Nous avons réalisé cinq extractions pour chaque solvant. Chaque fraction a été testée séparément. L'étude phytochimique a révélé la présence des terpènes, des alcaloïdes et des polyphénols essentiellement représentés par des flavonoïdes. L'évaluation de l'activité antifongique des différents extraits a été réalisée vis-à-vis des souches de références Candida albicans ATCC 10231 et Candida albicans 444IP. L'amphotéricine B qui est un médicament antifongique standard a été utilisé comme témoin positif au cours de notre étude. Les résultats de l'activité antifongique ont montré qu’à l'exception de l’extrait aqueux, tous les autres extraits possèdent une activité antifongique, avec des diamètres des zones d’inhibition allant de 10 à 58 mm pour l’extrait d’éther diéthylique. Des résultats similaires ont été obtenus pour l’extrait hexanique. En effet, les extraits obtenus à partir des solvants de faible ou moyenne polarité sont les plus actifs. En outre, les concentrations minimales inhibitrices  et les concentrations minimales fongicides de la première fraction de l'extrait hexanique étaient respectivement de 1,9 µg/ml et 3,9 µg/ml vis-à-vis de C. albicans ATCC 10231 et and C. albicans 444IP. Ces dernières restent comparables à celles de l'amphotéricine B vis-à-vis des mêmes souches

OPTIMIZATION OF THE FORMULATION PARAMETERS OF A PARAPHARMACEUTICAL 100% BIO CREAM

The extraction of the aromatic fraction (hydrolat, essential oil) fresh aerial part of Lavandula vera was accomplished by steam distillation. The average yield of essential oil is 1-2%. The anti-inflammatory cream BIO obtained has interesting dermal properties. This cream is endowed with remarkable healing properties and anti-infectious. It leads to dermatological applications and opens the way eventually fruitful research. During this work we have formulated an anti-inflammatory cream 100% BIO whose active ingredient is the essential oil of lavender with these attractive properties. Optimization of formulation parameters made it possible to have a stable cream. Physicochemical analysis, sensory (with diagram properties evaluation) and comparative study with a reference cream (conventional) was able to show the qualities of our BIO cream

Hybrid sliding mode control of DFIG with MPPT using three multicellular converters

International audienceThis paper deals with hybrid sliding mode control of Doubly Fed Induction Generator DFIG with Maximum Power Point Tracking MPPT connected by rotor side to three bridges of Multicellular Converters MCCs. The hybrid aspect of the converters is taken into consideration which includes the continuous and discrete states of the converters. The vector control is used to command the DFIG speed and reactive stator power. The currents in Park d-q reference are controlled using hybrid sliding mode. The sliding surfaces are developed using Lyapunov stability method. The developed controller allows decoupled control of the stator active and reactive power. The final results are illustrated at the end of this paper to present the advantages of the control method developed in this paper

Polyphenols Content and Antimicrobial, Antioxidant and Hemolytic Activities of Essential Oils from Four Selected Medicinal Plants Growing in Algeria

The Saharan and steppe spontaneous plants are very characteristic because of their particular adaptation to the desert and extreme environment. Some species have pharmacological properties that give them a medicinal interest. The aim of the present work was to determine the polyphenol contents of essential oils obtained from four endemic plants growing in Algeria (Pituranthos scoparius, Myrtus nivellei, Rosmarinus officinalis and Mentha piperita), and study its biological activity, including antimicrobial, antioxidant, and hemolytic. The antimicrobial activity was evaluated by the microdilution method against twelve strains. The antioxidant activity was carried out by two methods (DPPH radical scavenging and reducing power). However, the hemolytic effect has been evaluated against the red blood cells. P. scoparius and M. piperita showed yields of essential oils higher than 1%. All the strains showed sensitivity against the essential oils tested with the exception of the C. albicans treated by R. officinalis essential oils. The most sensitive strain was C. albicans treated by P. scoparius essential oils by MIC of 0.0781 mg/mL, it was the same plant that shows the highest polyphenol content (14.78 ± 0.72 g GAE/g DS). The antioxidant activity by the DPPH method was greater for all essential oils tested by IC50 ranging from 0.69 ± 0.07 (R. officinalis) to 30.67 ± 2.12 mg/mL (M. nivellei). The R. officinalis essential oils reported more antioxidant power than the positive control (ascorbic acid). In reducing iron, it was the R. officinalis essential oils which were found to be the most active with an EC50 concentration of 9.67 ± 1.36 mg/mL. After 120 min incubation, minimal haemolysis (10%) was obtained with essential oils of R. officinalis at a concentration of 0.39 mg/mL. We conclude that P. scoparius essential oils showed the high content of polyphenols and R. officinalis essential oils reported more antioxidant power than the positive control (ascorbic acid)

Ordonnancement de projets internationaux avec contraintes de matériel et de ressources

RÉSUMÉ L’évolution des processus d’affaires, rendue nécessaire par une globalisation des marchés toujours plus importante, a encouragé les firmes internationales à se tourner vers le fonctionnement par projet, qui s’est peu à peu généralisé. Mais la gestion de projets demeure une discipline complexe, impliquant de nombreux acteurs, sous-traitants et parties prenantes, et nécessitant le transport, l’approvisionnement et la livraison d’équipement et de matériel. Dans ce contexte, des délais d’approvisionnement et des contraintes de capacité de stockage peuvent amener des retards dans l’avancement des projets et des dépassements de budget. En effet, en dépit des tous les efforts accomplis en recherche pour développer des outils efficaces, la prise en compte des contraintes de livraison et d’approvisionnement lors de la phase de planification de projets demeure pour l’essentiel gérée manuellement par le gestionnaire de projets, selon son intuition et son expérience. Ainsi, les méthodes et algorithmes développés ne sont utilisés en pratique que pour la gestion dite « traditionnelle » de projet, ne considérant qu’un unique projet de faible portée, sans contraintes logistiques. Reconnaissant cette nouvelle réalité et les besoins qui en découlent, ce mémoire envisage une approche de résolution plus intégrée où l’on considère le problème de planification de projets avec des contraintes liées au stockage et à la livraison de matériel. Pour cela, un générateur aléatoire de contraintes logistiques a été développé, permettant de définir les données du problème relatives aux contraintes logistiques, tout en jouant sur leur poids relatif. La résolution du problème ainsi formulé est effectuée par le biais d’un algorithme génétique optimisé afin de déterminer un échéancier de projet réalisable. L’algorithme, par des opérations de sélection, croisement et mutation sur une population de solutions admissibles, améliore globalement la qualité de celle-ci au fil des itérations et converge peu à peu vers un optimum.---------- ABSTRACT With globalization of markets, new business models have emerged and international companies started using project management technics. However, the management of international projects remains complex as it involves several sub-contractors and requires the transportation of lots of construction equipment and materials. In that context, long material delivery times and storage capacity constraints may lead to project delays and budget overruns. Indeed, in spite of all research efforts accomplished to develop strong project management tools, project plans taking into account space and equipment availability for the execution of tasks are mostly manually developed on the basis of planner’s intuition and experience. Unfortunately, this task is nearly infeasible to perform in the case of large projects, due to the combinational nature of the resource allocation problem. Methods and algorithms are only used for project management in a “traditional” way, with a single small project and without any logistic constraint. The proposed model addresses this issue by formulating this problem as a scheduling problem with limited resources - resources can be either employees or storage areas - and by defining material delivery constraints. To that purpose, a random logistic constraints generator was developed, in order to create the problem data and to choose its relative weight. The resolution of the formulated problem is performed by a genetic algorithm, which determines a feasible project plan. This algorithm applies many operators on a population of solutions, such as selection crossover and mutation, to improve the population global quality and make the solutions converge towards a local optimum