2760 research outputs found
Sort by
An adaptive threshold estimation scheme for abrupt changes detection algorithm in a cement rotary kiln
No full textContribution à l'observation par modes glissants pour une commande robuste de la machine à induction (Approche sans capteur mécanique)
No full text88 p. : ill. ; 30 cmLa proposition de ce travail de thèse a pour objectif d’apporter une contribution aux méthodes d’observation des états des machines asynchrones destinées à l’entrainement électrique. Dans ce contexte, plusieurs algorithmes ont été proposés et implémentés. Après une présentation rapide de la commande directe de couple (DTC) classique, une nouvelle approche basée sur la modulation vectorielle est proposée. Une deuxième partie est consacrée à l’observation et à l’estimation des états de la machine, basée sur la technique des modes glissants dans différentes orientations du modèle de la machine. Une comparaison a été faite entre le fonctionnement de ces différentes variantes avec la commande DTC sans capteur mécanique pour une large plage de variation de vitesse. L’analyse des résultats pratiques a grandes et a basses vitesses nous a conduit à proposer une méthode originale pour réduire les fluctuations du courant observé due au phénomène de broutement (chattering). Le problème de robustesse vis-à-vis de la variation des paramètres du modèle de la machine a été traité pour chaque variante par des algorithmes d’adaptation basée sur le calcul des puissances actives d’une part et la fonction de Lyapunov d’une autre part. Enfin, nous avons proposé un algorithme d’estimation et de compensation de l’effet non-linéaire de l’onduleur de tension afin d’améliorer les performances a basses vitesses et de minimiser les pertes dans l’ensemble Onduleur-Machin
Multimodal biometric fusion using evolutionary techniques
No full text75 p. : ill. ; 30 cmThe work of this research focuses on fusing multiple biometric modalities at the score level using different combination rules. The research puts an emphasis on employing optimization techniques in order to achieve optimum accuracies. Due to the limitations that unimodal systems suffer from, such as noisy data, non-universality, and susceptibility to spoof attacks, multibiometric systems have gained much interest in the research community on the grounds that they alleviate most of these limitations and are capable of producing better accuracies and performances. A multibiometric system combines two or more biometric sources in order to overcome their unimodal system counterparts and achieve higher accuracies. One of the important steps to reach this purpose is the choice of the fusion techniques utilized. A thorough study is performed to investigate the different fusion rules and schemes. In this work, a modeling step based on a hybrid algorithm that includes social rules derived from the swarm intelligence, Particle Swarm Optimization, and the concepts of natural selection and evolution, Genetic Algorithm, is used to combine the two modalities at the score level. This optimization algorithm is employed to select the optimum weights associated to the modalities being fused. The performance of the hybrid GA-PSO is compared to those of classical combination rules. For that purpose, the proposed schemes are experimentally evaluated on publicly available score databases (XM2VTS, NIST and BANCA) which come in clean and degraded conditions. An analysis of the results is carried out on the basis of comparing the techniques' resulting EER accuracies and ROC curves. Furthermore, the execution speed of the hybrid approach is compared to that of the single optimization algorithms GA and PS
Dye adsorption behavior of polyvinyl Alcohol/Glutaraldehyde/β-Cyclodextrin polymer membranes
No full textThe self-ignition of fiberglass lines
Get PDFThe fiberglass pipes were used for transportation of water in order to maintain the pressure in the oil field of Zarzaïtine
(Region of in Amenas located in the south of Algeria). During the maintenance work in summer, a season well known for
its extensive heat, the deposits contained in the pipe, and after its contact with the atmosphere, have caused a smoke and it
was followed by a fire that ignited a portion of the pipe. To give an answer to the causes of this phenomenon, we have first
incriminated the role of specific bacterial species and therefore we have made a microbiological analysis of the deposits
collected from the site of the incident. The obtained results revealed the presence of a heterogeneous microbial population
with a high concentration level of sulfate-reducing bacteria (SRB), methanogenic bacteria (MB), yeasts and fungi. The
interaction between the different species of bacteria and the organic matter contained in the deposits has generated the
formation of methane which under the influence of the great heat burnt and the fire caused the ignition of the fiberglass lin
Bond graph to digraph conversion : a sensor placement optimization for fault detection and isolation by a structural approach
Get PDFIn this paper, we consider the optimal sensors placement problem for
faults detection and isolation using a novel structural and qualitative approach. This
approach is based on the conversion of Bond Graph to Digraph representation of
a structural system. When the fault detection and isolation of an existing system’s
sensors are impossible or uncertain, a reconfiguration sensor placement of this system
should be reconsidered. This paper proposes how this reconfiguration takes place
by recovering all missing or redundant parts of the system. This novel approach is
illustrated over a thermo-fluid applicatio
الحوكمة الإلكترونية : رؤيا شاملة
No full textص. 394-415تهدف الحوكمة الإلكتلرونية الى تحسين فعالية ومساءلة الحكومات وتسمح بأن تكون أكثر شفافية، أكثر التزاما، أكثر حيادا، وأكثر مشاركة واستجابة لتلبية احتياجات المواطنين والشركات فهي تسعى الى تقريب الإدارة العامة من مستخدميها وفتح المجال للمواطنين من أجل المشاركة في تحسين الخدمات المقدمة له
حوكمة تكنولوجيا المعلومات ألية لترشيد الخدمة العمومية وانجاح مشروع الحوكمة الإلكترونية في الجزائر
No full textص. 413-430تتناول هذه الورقة البحثية جانبا هاما من جوانب نجاح مشاريع الحوكومة الإلكترونية، والمتعلق بحوكمة تكنولوجيا المعلومات والإتصال كألية لتحسين الإداء الإداري وترشيد الخدمة العمومية في الجزائر. كما تهدف الورقة البحثية الى إبراز دور وانعكاسات تطبيق حوكمة تكنولوجيا المعلومات والإتصال في انجاح مشروع الحوكمة الإلكترونية في الجزائ
ANTIBACTERIAL AND ANTIFUNGUL EFFECTS OF FLAVONOIDS ISOLATED FROM CRATEAGUS OXYACANTHA (L.) FRUITS IN THE NORTH ALGERIAN REGIONS (BOUMERDES AND BAINEM)
No full textThe extracts of plants are currently the subject of many scientific researches aiming to exploit their properties antimicrobial appreciated so much in the therapeutic, nutritional, cosmetic, and pharmaceutical fields. In this work, we have study the antimicrobial activity of the extracts namely flavonoids resulting from the Crateagus oxyacatha fruits in two bioclimatic stages (Dellys and Bainem). The determination of the antimicrobial effects on stocks bacterial of Gram(-); Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae and Gram(+) (Bacillus subtilis and Staphylococcus aureus). We have also tested two yeasts; Candida albicans and Saccharomycec cereviciae.
As regards the extract of C. oxyacantha of the area of Bainem, one announces that E. Coli is slightly sensitive to the extract of C. Oxyacantha. However S. aureus and B. subtilis have a strong sensitivity to this extract. Whereas the other bacteria are fairly sensitive.
With regard to yeasts, one notices that S. cerevisiae is slightly resistant to the extract.
This solution has an inhibiting effect on C. albicans.
Concerning the extract of C. oxyacantha of the area of Dellys, one notes that E. Coli is slightly sensitive to the extract of C. Oxyacantha. However S. aureus and B. subtilis have a strong sensitivity to this extract. Whereas the other bacteria are fairly sensitive.
With regard to yeasts, one notices that S. cerevisiae is slightly resistant to the extract.
This extract has a strong inhibiting effect on C. albicans.
Through this study, one notices clearly the sensitivity of bacteria Gram-plus compared to the bacteria Gram-for the two areas
ANTIMICROBIAL ACTIVITY OF OIL EXTRACTED FROM THE ALMONDS OF THE FRUITS OF ARGANIA SPINOSA IN THE WEST OF ALGERIA (MOSTAGANEM)
No full textThis work examines the study of the antimicrobrial effect of oil extracted from the almonds of Argania spinosa L. (Sapotaceae) in the area of Stida (Mostaganem). This natural substance is extracted by using the Soxhlet. The antimicrobial activity of this oil is evaluated on several microorganisms. It has been tested on five bacterial strains; Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Bacillus subtilis and Staphylococcus aureus. The extract has been studied by using Candida albicans. It should be noted that these agents are characterized by a high frequency of contamination and pathogenicity