The culture history of Madagascar

Madagascar's culture is a unique fusion of elements drawn from the western, northern, and eastern shores of the Indian Ocean, and its past has fascinated many scholars, yet systematic archaeological research is relatively recent on the island. The oldest traces of visitors are from the first century AD. Coastal settlements, with clear evidence of ties to the western Indian Ocean trading network, were established in several places over the next millennium. Important environmental changes of both plant and animal communities are documented over this period, including the extinctions of almost all large animal species. Urban life in Madagascar began with the establishment of the entrepôt of Mahilaka on the northwest coast of the island in the twelfth century. At about the same time, communities with ties to the trade network were established around the island's coasts. From the fourteenth to the sixteenth century, social hierarchies developed in several regions of the island. During the succeeding two centuries, Madagascar saw the development of state polities.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45256/1/10963_2004_Article_BF00997802.pd

Système d'alimentation multi-sources basé sur des batteries PV et un générateur diesel pour les applications micro-réseau

International audienceThis article deals with the three level space vector pulse width modulation (SVPWM) technique to control the Neutral Point Clamped (NPC) inverter for energy management in a multi-source system based on a variable speed diesel generator, a PV generator, and a pack of the lithium-batteries for the micro grid applications. The contribution of the paper is focused on the multi-source system energy management using the frequency components distribution method between the linked sources according to the dynamic response capability of the each source.Cet article traite de la technique de modulation de largeur d'impulsion vectorielle spatiale à trois niveaux (SVPWM) pour contrôler l'onduleur Neutral Point Clamped (NPC) pour la gestion de l'énergie dans un système multi-source basé sur un générateur diesel à vitesse variable, un générateur PV et un pack des batteries au lithium pour les applications micro-réseau. La contribution de l'article se concentre sur la gestion de l'énergie du système multi-sources en utilisant la méthode de distribution des composantes de fréquence entre les sources liées en fonction de la capacité de réponse dynamique de chaque source

Stratégie de contrôle d'onduleur à point neutre à trois niveaux utilisant SVPWM pour les applications de système multi-sources

International audienceThis paper highlights the three level space vector pulse width modulation (SVPWM) technique to control the Neutral Point Clamped (NPC) inverter for energy management in a multi-source system based on a diesel generator, a wind turbine, a PV generator, and a pack of the lithium-batteries for micro grid applications. The contribution of the paper is focused on the multi-source system energy management using the frequency components distribution method between the linked sources according to the dynamic response capability of the each source.Cet article met en évidence la technique de modulation de largeur d'impulsion vectorielle spatiale à trois niveaux (SVPWM) pour contrôler l'onduleur Neutral Point Clamped (NPC) pour la gestion de l'énergie dans un système multi-source basé sur un générateur diesel, une éolienne, un générateur PV et un pack de batteries au lithium pour applications micro-réseau. La contribution de l'article se concentre sur la gestion de l'énergie du système multi-sources en utilisant la méthode de distribution des composantes de fréquence entre les sources liées en fonction de la capacité de réponse dynamique de chaque source

Wind turbine and Batteries with Variable Speed Diesel Generator for Micro-grid Applications

International audienceThis paper highlights the three level space vector pulse width modulation (SVPWM) technique to control the Neutral Point Clamped (NPC) inverter for energy management in a multi-source system based on a variable speed diesel generator, a wind turbine, and a pack of the lithium-batteries for the micro grid applications. The contribution of the paper is focused on the multi-source system energy management using the frequency components distribution method between the linked sources according to the dynamic response capability of the each source

Power control for decentralized energy production system based on the renewable energies — using battery to compensate the wind/load/PV power fluctuations

International audience10kW-diesel generator associated to renewable energy sources including a 10kW wind turbine, 12kW photovoltaic, and 53Ah lithium-battery. These energy production sources are interfaced to micro-grid through three-level power electronics converters where the phase-to-phase RMS voltage is 600V. The variable speed diesel generator is considered as the main energy source which is used to control the DC-bus voltage. The wind turbine and PV system are controlled using the Maximum Power Point Tracking (MPPT) technique with bipolar DC-bus voltage equilibration approach. The battery pack is used to compensate the intermittent power fluctuations from the wind turbine and PV system. The hybrid system control is ensured by the three-level converters (AC/DC, DC/DC, and DC/AC) using energy management based on frequency components allocation approach

Indoor and outdoor in-flight odometry based solely on optic flows with oscillatory trajectories

International audienceEstimating distance traveled is a frequently arising problem in robotic applications designed for use in environments where GPS is only intermittently or not at all available. In UAVs, the presence of weight and computational power constraints makes it necessary to develop odometric strategies based on minimilastic equipment. In this study, a hexarotor was made to perform up-and-down oscillatory movements while flying forward in order to test a self-scaled optic flow based odometer. The resulting self-oscillatory trajectory generated series of contractions and expansions in the optic flow vector field, from which the flight height of the hexarotor could be estimated using an Extended Kalman Filter. For the odometry, the downward translational optic flow was scaled by this current visually estimated flight height before being mathematically integrated to obtain the distance traveled. Here we present three strategies based on sensor fusion requiring no, precise or rough prior knowledge of the optic flow variations generated by the sinusoidal trajectory. The “rough prior knowledge” strategy is based on the shape and timing of the variations in the optic flow. Tests were performed first in a flight arena, where the hexarotor followed a circular trajectory while oscillating up and down over a distance of about [Formula: see text] m under illuminances of [Formula: see text] lux and [Formula: see text] lux. Preliminary field tests were then performed, in which the hexarotor followed a longitudinal bouncing [Formula: see text]-long trajectory over an irregular pattern of grass

Modeling the Capillary Pressure for the Migration of the Liquid Phase in Granular Solid-Liquid-Vapor Systems: Application to the Control of the Composition Profile in W-Cu FGM Materials

International audienceA model is developed to compute the capillary pressure for the migration of the liquid phase out or into a uniform solid-liquid-vapor system. The capillary pressure is defined as the reduction of the overall interface energy per volume increment of the transferred fluid phase. The model takes into account the particle size of the solid particle aggregate, the packing configuration (coordination number, porosity), the volume fractions of the different phases, and the values of the interface energies in the system. The model is used for analyzing the stability of the composition profile during processing of W-Cu functionally graded materials combining a composition gradient with a particle size gradient. The migration pressure is computed with the model in two stages: (1) just after the melting of copper, i.e., when sintering and shape accommodation of the W particle aggregate can still be neglected and (2) at high temperature, when the system is close to full density with equilibrium particle shape. The model predicts well the different stages of liquid-phase migration observed experimentally