David Razafimahefa T.,University of Antsiranana |
Sambatra E.J.R.,Institute Superieur Of Technology Dantsiranana |
Heraud N.,French National Center for Scientific Research
Proceedings of the 2016 International Conference and Exposition on Electrical and Power Engineering, EPE 2016 | Year: 2016
An inter turns short circuit fault is an evolving fault, the beginning of this is the degradation of the insulation of the winding of the induction machine. This degradation can be modeled with a resistance called the resistance of contact. This resistance limits the fault current flowing through the turns short-circuited. This fault current is the responsible of the defect in the electrical machine subjected to inter turns short circuit fault. From the apparition of the fault, this resistance decreases progressively until having a zero value; in this case we have a direct short-circuit. The fault severity is therefore inversely proportional to the value of this resistance. In this paper, we propose a theoretical and experimental study of the evolution of inter turns short circuit fault in induction machine. Several values of the resistance of contact are studied theoretically and experimentally for analyzing the effect of this. Simulation and experimental study are performed on a 0.25kW induction machine with 2.5% of turns short circuited in the one phase of the stator winding. © 2016 IEEE.
Bemarisika P.,University of Antsiranana |
Bemarisika P.,University of Reunion Island |
Totohasina A.,University of Antsiranana
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2017
The negative association rules are less explored compared to the positive rules. The existing models are limited to the structure of binary data requiring of the repetitive accesses to the context, and the traditional couple support-confiance which is not effective in the presence of the dense data. For that, we propose a new model of optimization by using a new structure of data, noted MatriceSupport, and a new more selective couple, support-MGK. © 2017, Springer International Publishing AG.
Andriniriniaimalaza P.F.,Digital Systems |
Andrianantenaina T.P.,University of Antsiranana |
Razafinjaka N.J.,University of Antsiranana
2017 10th International Symposium on Advanced Topics in Electrical Engineering, ATEE 2017 | Year: 2017
Currently, variable gain PI (VGPI) controllers are used in several applications. Its structure is built around PI controller tuning and usually an entire number is chosen for the order or degree. This paper deals with a study of a VGPI with fractional order (VGPIFO). For the PI controller tuning, a method called general method (MG) is adopted. Then, the VGPI one is established. The proposed controller is applied on a doubly fed induction generator (DFIG) inserted in a chain of wind power conversion. Simulation results show that this new controller leads to good performances as test tracking, disturbance rejection and robustness with respect to system operation variation and parameters variation. © 2017 IEEE.
Macron C.,University of Burgundy |
Richard Y.,University of Burgundy |
Garot T.,French National Center for Scientific Research |
Bessafi M.,University of Reunion Island |
And 3 more authors.
Monthly Weather Review | Year: 2016
Using daily rain gauge records for Madagascar and nearby islands, this paper investigates rainfall intraseasonal variability at local and regional scales during the austral summer season (November-February), as well as the respective influences of recurrent convective regimes over the southwest Indian Ocean (SWIO) and the Madden-Julian oscillation (MJO). The results show a general consistency between local-scale rainfall variability in Madagascar and regional-scale features of climate variability. The influence of tropical temperate troughs in their mature phase and/or their easternmost locations is first underlined. The development of such systems over southern Africa and the Mozambique Channel can be considered as precursors for Malagasy wet spells, especially over the southern part of the island. Regional and local effects of the MJO are weaker on average, and only concern the northwest of the island and the north of the Mozambique Channel. MJO and convective regimes are finally shown to explain distinct fractions of regional rainfall variability. © 2016 American Meteorological Society.
Fenoradosoa T.A.,University Blaise Pascal |
Fenoradosoa T.A.,University of Antsiranana |
Ali G.,University Blaise Pascal |
Delattre C.,University Blaise Pascal |
And 4 more authors.
Journal of Applied Phycology | Year: 2010
Matrix polysaccharide from the brown algae Sargassum turbinarioides collected in the coastal waters of Nosy Be (Madagascar) in the Indian Ocean was isolated and its structure was studied by 1H-NMR spectroscopy, FT-IR, SEC-MALLS and HPAEC. An alginate with a molecular weight of 5.528 × 105 g mol-1 was identified as sole polysaccharide. Values of the M/G ratio, FGG, FMM and FGM (or FGM) blocks were measured at respectively 0.94, 0.39, 0.36 and 0.25 and compared with those of alginates from other Sargassum species. This sodium alginate appeared similar to some of the other Sargassum alginates with M/G > 1, high values of homopolymeric blocks (η > 1) and significant polyguluronic block content. © 2009 Springer Science+Business Media B.V.
Jaomiary A.,University of Antsiranana |
Mze S.,University of Antsiranana |
Saandy T.A.,University of Antsiranana
IEEE AFRICON Conference | Year: 2015
This paper proposes a mathematical predictive model of power energy consumption per household in the district of Antsiranana. Based on the national statistical institute INSTAT, the power consumption depends on the demographic population category. Based on the general daily life equipment per household, the ordinary, medium and rich categories are defined in this investigation. Indeed, the trend from the last two decades yearly survey illustrates how the energy consumption in the district of Antsiranana varies. Based on the time dependent fitting approach, the mathematical model of the energy needs as established. The reliability of the proposed model was assessed with the correlation coefficient R2. Based on the data from the last decade, the relevance of the model was investigated. Then, prediction of the energy needs up to 2023 was proposed with 5% relative inaccuracy. Thanks to its simplicity, the method can be useful for the sustainable development. However, further improvement is still needed in order to forecast the energy consumption for tens future decades. © 2015 IEEE.
David Razafimahefa T.,French National Center for Scientific Research |
David Razafimahefa T.,University of Antsiranana |
Heraud N.,Institute Superieur Of Technology |
Sambatra E.J.R.,French National Center for Scientific Research
Proceedings of the 18th Mediterranean Electrotechnical Conference: Intelligent and Efficient Technologies and Services for the Citizen, MELECON 2016 | Year: 2016
Most cases of electrical machines are connected directly to the low voltage power system without inverter, which can be subjected to a harmonic pollution at any time. The presence of these harmonics can compromise the reliability of the fault detection. In this paper, we present the winding fault diagnosis of induction machine connected to a harmonically polluted low voltage power system. The detection method is based on the Hilbert transform. This proposed approach allows the suppression of the harmonics from the network while keeping all possible clues to the presence of winding fault in the induction machine. The proposed approach is tested experimentally to an induction machine subjected to a 2.5% of inter-turns short circuit fault. © 2016 IEEE.
Razafinjaka J.N.,University of Antsiranana |
Andrianantenaina T.P.,University of Antsiranana
IJCCI 2015 - Proceedings of the 7th International Joint Conference on Computational Intelligence | Year: 2015
This paper deals with a study of hybridization based on fuzzy logic controller and a polynomial RST one. This new controller is applied on a Doubly-Fed Induction Generator (DFIG) dedicated in a chain of wind power conversion. These two types or controller have completely different structures: the RST controller uses directly the input and the output to form the command law and the fuzzy logic one needs the error and its variation as inputs. The new proposal consists first to make leave the a priori command from the RST structure and then to form the error and the difference of two consecutive error values for the fuzzy logic controller. The results of simulation show that this technique is realizable and leads to good performances on tracking test, disturbance rejection and robustneb with respect of operating variation and parametric variation. © Copyright 2015 by SCITEPRESS - Science and Technology Publications, Lda.
PubMed | University of Medicine and Pharmacy, Cluj-Napoca, e State Veterinary Laboratory for Animal Health and Safety, University of Antananarivo and University of Antsiranana
Type: Journal Article | Journal: Natural product research | Year: 2015
The purpose of this work was to evaluate chemical constituents, antioxidant and antimicrobial activities of Artabotrys hildebrandtii, an endemic medicinal plant from Madagascar. Ethanol extracts from the leaves and stem bark were tested to evaluate DPPH free radical scavenging, using butylated hydroxytoluene and quercetin as standard antioxidants. An high-performance liquid chromatography/mass spectrometry method was developed to investigate the presence of phenolic compounds in the studied samples; gentisic acid, chlorogenic acid, hyperoside, isoquercitrin, rutin, quercitrin, quercetol, apigenin and luteolin were identified. Total polyphenolic content was determined by a spectrophotometric method using Folin-Cioclteu reagent. Results showed the efficiency of A. hildebrandtii leaves extract against strains of Staphylococcus aureus and Listeria monocytogenes, as the inhibitory activity is more powerful compared to Gentamicin, used as the standard drug. The leaves of A. hildebrandtii can be considered an important source of polyphenols, especially of rutin, with good antioxidant and antimicrobial activities.
PubMed | University of Toamasina, University of Antananarivo and University of Antsiranana
Type: | Journal: The Pan African medical journal | Year: 2016
Transcranial Doppler is an effective diagnostic tool to detect sickle cell children at risk for stroke.We conducted a cross-sectional descriptive study of Malagasy children aged between 24 months and 15 years (group 1: 57 sickle cell diseases, group 2: 43 controls) to assess the cerebral artery velocimetry in the patient population. Transcranial doppler ultrasound with analysis of cerebral blood flow was performed in children of both groups.In subjects with sickle cell disease, the mean velocity (MV) in the middle cerebral artery was 100.9 26.8 cm/s, pulsatility index (PI) was 0.73 0.20, the difference between the right and left middle cerebral artery (MCA) was 19.8 21.5 cm/s, anterior cerebral artery/middle cerebral artery flow velocity ratio (ACA / MCA) was 0.7 0.2. In children without sickle cell disease, MV: 80.6 19.3 cm/s, IP: 0.79 0.14, ACMr: 17 20.1 cm/s, ACA/ACM: 0,8 0,2. The velocity in children with sickle cell disease was higher than in the control group. Velocities were correlated with hemoglobin and age but not with sex and mean corpuscular volume.Cerebral Circulation Speeds are higher in children with sickle cell disease and are influenced by hemoglobin levels and age.