HIGH PRESSURE STUDIES OF SmSe AT 77 K

Nous avons mesuré des spèctres EXAFS de SmSe à haute pression (jusqu'à 57 kbar) et à basse température (77 K) avec une résolution spatiale elevée. Les spèctres au seuil K de Se montrent que les fluctuations dans la distance Sm-Se s'accroît par environ 0.05 Å lorsque le composé passe à travers sa phase de valence intermédiaire. La transition de valence, qui est isostructurale et continue, commence à 25 kbar. Pour réaliser ces mesures nous avons construit un dispositif pour usage à haute pression et basse température. La cellule de haute pression est monté dans l'orientation axiale.EXAFS studies with high spatial resolution have been performed at the Se K-edge edge of SmSe at 77 K and up to 57 kbar. An increase in the fluctuation of the Sm-Se bond length of ~ 0.05 Å is observed upon going through the isostructural mixed valent transition which is continuous and begins at 25 kbar. For these measurements a pressure cell was constructed for use at low temperature. It is used in the axial geometry

A Robot Architecture for Outdoor Competitions

Autonomous navigation in unstructured environments is a common topic of research, being motivated by robotic competitions and involving several sets of skills. We present a modular architecture to integrate different components for path planning and navigation of an autonomous mobile robot. This architecture was developed in order to participate in the RoboMagellan competition hosted by RoboGames. It is divided in the organizational, functional and executive levels in order to secure that the developed system has programmability, autonomy, adaptability and extensibility. Global and local localization strategies use unscented and extended Kalman filters (UKF and EKF) to fuse data from a Global Positioning System (GPS) receiver, inertial measurement unit (IMU), odometry and camera. Movement is controlled by a model reference adaptive controller (MRAC) and a proportional controller. To avoid obstacles a deformable virtual zone (DVZ) approach is used. The architecture was tested in simulated environments and with a real robot, providing a very flexible approach to testing different configurations