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Application of Feedforward Neural Network for Induction Machine Rotor Faults Diagnostics using Stator Current
T. Aroui,Y. Koubaa,A. Toumi
Journal of Electrical Systems , 2007,
Abstract: Faults and failures of induction machines can lead to excessive downtimes and generate large losses in terms of maintenance and lost revenues. This motivates motor monitoring, incipient fault detection and diagnosis. Non-invasive, inexpensive, and reliable fault detection techniques are often preferred by many engineers. In this paper, a feedforward neural network based fault detection system is developed for performing induction motors rotor faults detection and severity evaluation using stator current. From the motor current spectrum analysis and the broken rotor bar specific frequency components knowledge, the rotor fault signature is extracted and monitored by neural network for fault detection and classification. The proposed methodology has been experimentally tested on a 5.5Kw/3000rpm induction motor. The obtained results provide a satisfactory level of accuracy.
Magnetic Coupled Circuits Modeling of Induction Machines Oriented to Diagnostics
Tarek AROUI,Yassine KOUBAA,Ahmed TOUMI
Leonardo Journal of Sciences , 2008,
Abstract: In this paper, a transient model of the faulty machine is developed. The model is referred to a three phase stator winding, while the rotor has been represented by all the meshes allowing for the representation of various faults. The model is based on coupled magnetic circuit theory by considering that the current in each bar is an independent variable. The model incorporates non-sinusoidal air-gap magneto motive force (MMF) produced by both stator and rotor, therefore it will include all the space harmonics in the machine. Simulations and experimental results were then used to study rotor faults cause-effect relationships in the stator current and the frequency signature.
Clustering of the Self-Organizing Map based Approach in Induction Machine Rotor Faults Diagnostics
Tarek AROUI,Yassine KOUBAA,Ahmed TOUMI
Leonardo Journal of Sciences , 2009,
Abstract: Self-Organizing Maps (SOM) is an excellent method of analyzingmultidimensional data. The SOM based classification is attractive, due to itsunsupervised learning and topology preserving properties. In this paper, theperformance of the self-organizing methods is investigated in induction motorrotor fault detection and severity evaluation. The SOM is based on motor currentsignature analysis (MCSA). The agglomerative hierarchical algorithms using theWard’s method is applied to automatically dividing the map into interestinginterpretable groups of map units that correspond to clusters in the input data. Theresults obtained with this approach make it possible to detect a rotor bar fault justdirectly from the visualization results. The system is also able to estimate theextent of rotor faults.
Rotor speed estimation for indirect stator flux oriented induction motor drive based on MRAS scheme
Youssef Agrebi,Moncef Triki,Yassine Koubaa,Mohamed Boussak
Journal of Electrical Systems , 2007,
Abstract: In this paper, a conventional indirect stator flux oriented controlled (ISFOC) induction motor drive is presented. In order to eliminate the speed sensor, an adaptation algorithm for tuning the rotor speed is proposed. Based on the model reference adaptive system (MRAS) scheme, the rotor speed is tuned to obtain an exact ISFOC induction motor drive. The reference and adjustable models, developed in stationary stator reference frame, are used in the MRAS scheme to estimate induction rotor peed from measured terminal voltages and currents. The IP gains speed controller and PI gains current controller are calculated and tuned at each sampling time according to the new estimated rotor speed. The proposed algorithm has been tested by numerical simulation, showing the capability of driving active load; and stability is preserved. Experimental results obtained with a general-purpose 1-kW induction machine are presented showing the effectiveness of the proposed approach in terms of dynamic performance.
Rubella associated with hemophagocytic syndrome. First report in a male and review of the literature
Makram Koubaa,Chakib Marrakchi,Imed Maaloul,Saloua Makni
Mediterranean Journal of Hematology and Infectious Diseases , 2012, DOI: 10.4084/mjhid.2012.
Abstract: A 22-year-old man was admitted to our hospital because of fever, skin rash and epistaxis. Physical examination revealed fever (39.5°C), generalized purpura, lymphadenopathy and splenomegaly. Blood tests showed pancytopenia. Bone marrow aspiration and biopsy showed hemophagocytosis with no evidence of malignant cells. Anti rubella IgM antibody were positif and the IgG titers increased from 16 to 50 UI/mL in 3 days. Therefore, he was diagnosed to have rubella-associated hemophagocytic syndrome. We report herein the first case in a man and the sixth case of rubella-associated hemophagocytic syndrome in the literature by search in Pub Med till March 2012.
DENSIFICATION OF WOOD VENEERS COMBINED WITH OIL-HEAT TREATMENT. PART I: DIMENSIONAL STABILITY
Chang-Hua Fang,Alain Cloutier,Pierre Blanchet,Ahmed Koubaa
BioResources , 2011,
Abstract: Although wood densification by compression improves wood mechanical strength, dimensional stability is often a problem due to compression recovery. Alternatively, oil-heat treatment (OHT) improves wood dimensional stability and enhances resistance to biological attack. This study examined combined wood densification and OHT. Large wood veneer 700 × 700 mm specimens prepared with aspen (Populus tremuloides) were densified using heat, steam, and pressure at 160oC, 180oC, and 200°C, respectively. OHT at 180oC, 200oC, and 220oC for 1, 2, and 3h was then applied to the densified veneers. Results show that OHT efficiently improved dimensional stability and reduced compression set recovery. OHT temperature and duration markedly influenced the reduction of compression set recovery: the higher the OHT temperature and duration, the lower the recovery. Less than 5% recovery was obtained under various OHT conditions, and almost 0% recovery under some OHT conditions. Radial and tangential swellings of densified veneers were reduced dramatically. Compared to OHT duration, OHT temperature had a pronounced higher impact on radial and tangential swelling. Irreversible swelling (IS) in the compression direction of densified veneers decreased after OHT, particularly with high temperature and long duration, and anti-swelling efficiency (ASE) in the compression direction improved significantly.
Prevalence of diabetes mellitus among non institutionalized elderly in Monastir City
Hammami Sonia,Mehri Sounira,Hajem Said,Koubaa Nadia
BMC Endocrine Disorders , 2012, DOI: 10.1186/1472-6823-12-15
Abstract: Background Diabetes is a major public health problem worldwide. This problem is particularly relevant to the elderly. The prevalence of each condition increase with age. The present study aimed to determine the prevalence of Diabetes Mellitus (DM) among elderly; we also examined socio-economic factors and life style that are likely to be associated with DM. Methods A cross-sectional study was conducted in 2008–2009, and used a multistage cluster sampling method to select a representative sample among non institutionalized elderly in Monastir City. A total of 598 elderly aged 65 to 95 years were included. Results The prevalence of DM was 27.4% (29.2% in males’ vs 26.5% in females). Elderly with DM showed higher prevalence of hypertension, obesity and abdominal obesity. DM prevalence decreased with advancing ages in both men and women. Urban residents had a higher prevalence than did their rural counterparts. In multivariate analysis, DM was associated with abdominal obesity (OR [95% CI], 2.6 [1.1-6]; p <0.01), co-existing diseases (3.8 [2.4-6]; p <0.01), and hypertension (2.7 [1.6-4.5] ; p <0.01). Conclusion The study highlights the DM problem in Tunisia. An ageing population together with social, economic and lifestyle changes have led to a dramatic increase in DM. These data emphasize the urgent need for a comprehensive integrated population-based intervention program to ameliorate the growing problem of DM.
Unsupervised Domain Adaptation Using Generative Adversarial Networks for Semantic Segmentation of Aerial Images
Anis Koubaa,Bilel Benjdira,Kais Ouni,Yakoub Bazi
Remote Sensing | An Open Access Journal from MDPI , 2019, DOI: https://doi.org/10.3390/rs11111369
Abstract: Segmenting aerial images is of great potential in surveillance and scene understanding of urban areas. It provides a mean for automatic reporting of the different events that happen in inhabited areas. This remarkably promotes public safety and traffic management applications. After the wide adoption of convolutional neural networks methods, the accuracy of semantic segmentation algorithms could easily surpass 80% if a robust dataset is provided. Despite this success, the deployment of a pretrained segmentation model to survey a new city that is not included in the training set significantly decreases accuracy. This is due to the domain shift between the source dataset on which the model is trained and the new target domain of the new city images. In this paper, we address this issue and consider the challenge of domain adaptation in semantic segmentation of aerial images. We designed an algorithm that reduces the domain shift impact using generative adversarial networks (GANs). In the experiments, we tested the proposed methodology on the International Society for Photogrammetry and Remote Sensing (ISPRS) semantic segmentation dataset and found that our method improves overall accuracy from 35% to 52% when passing from the Potsdam domain (considered as source domain) to the Vaihingen domain (considered as target domain). In addition, the method allows efficiently recovering the inverted classes due to sensor variation. In particular, it improves the average segmentation accuracy of the inverted classes due to sensor variation from 14% to 61%. View Full-Tex
Carcinome adenoide kystique sous-glottique
E Gassab, N Krifa, K Harrathi, A Moussa, J Koubaa, A Gassab
Journal Tunisien d'ORL et de Chirurgie Cervico-Faciale , 2009,
Abstract: Introduction: Laryngeal adenoid cystic carcinoma (ACC) is unusual. It accounts for 0.25% of all malignant tumors in the larynx, and only about 120 cases have been reported in the literature until now. Purpose: We report a case of subglottic ACC and examine the clinical, diagnostic, histological and therapeutic features and the outcome of this tumor in this location. Case report: A 75-year-old man, presented with a laryngeal dyspnea. The computed tomography of the larynx showed a posterior subglottic tumor. The panendoscopy revealed a large nonulcerated submucosal tumor in the posterior wall of the subglottic area. Biopsies made the diagnosis of laryngeal ACC. The patient had total laryngectomy with total thyroidectomy and bilateral lateral neck dissection. Histological examination didn't find neck metastases. The surgery was followed by a postoperative radiotherapy. There were no local recurrence or distant metastases during one year and half of follow-up. Conclusions: ACC shows a very slow growth pattern. Its diagnosis is often delayed and its treatment is based on surgery and postoperative radiotherapy. This tumor is characterized by the occurrence of local recurrence and distant metastases often several years after treatment of the primary tumor.
Litiase paratidienne
J Koubaa, K Harrathi, E Gassab, A Elkorbi, I Stambouli, A Gassab
Journal Tunisien d'ORL et de Chirurgie Cervico-Faciale , 2009,
Abstract: Objectives: Parotid lithiasis is uncommon. Revelled usually by an acute relapsing sialoadenitis. Purpose: analyze of the different clinical and radiological presentation and specify the surgical indication. Patients and methods: five cases of parotid lithiasis were carried over 10 years, between 2000 and 2009. Results: there were 2 males and 3 females, aged between 32 and 73 years. All patients had presented with unilateral acute relapsing sialoadenitis. Sonography had led to diagnosis in 2 cases. Scannography was performed in 4 cases. Treatment was medical and surgical. No recurrence has occurred after a follow-up of 4 years (6 months – 9 years). Conclusion: Actually mini-invasive methods are considered as an alternative to surgical procedures in management of parotid lithiasis.
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