Perylene and pyrromethene doped xerogels for solid state pulsed laser

International audienceHydrophobic photostable dye molecules such as perylenes or pyrromethenes were trapped in xerogel matrices. Using these new materials as solid-state dye lasers, we have demonstrated efficient laser operation. Slope efficiencies of up to 30% were obtained in the millijoule output-energy range. Tunabilities of up to 60 nm were observed, and more than 150,000 pulses were emitted by the same spot of a given sample when the laser was pumped at millijoule energy level

Adaptive wireless sensor networks for aircraft

International audienceWireless Sensor Networks (WSNs) have been largely adopted in various application domains: environmental applications, reasonable use of fertilizers and pesticides in precision agriculture, fire detection, pollutant detection in industrial worksites, exploration of natural resources, to name a few. Are WSNs able to meet the requirements for Aircraft and Launchers? Generally speaking, the benefits of WSNs in Aircraft and Launchers would be a reduction of the complexity and mass of wiring, the facilitation of the addition or removal of sensors, the possibility of installing sensors in locations inaccessible due to wiring constraints and easier increases of the number of sensors. In this paper, we unify the requirements of non-critical and health monitoring applications in Aircraft and Launchers. We present different challenges faced by wireless sensor networks to meet these requirements. We also propose a solution that provides an adaptive multichannel collision-free protocol for data gathering

Multichannel Wireless Sensor Networks for Structural Health Monitoring of Aircraft and Launchers

International audienceStructural health monitoring has recently been applied to Aircraft and Launchers, in which the number of interconnected devices is constantly increasing. Up to now, wired networks have been used, but their high mass leads to increased fuel consumption and high carbon emissions. Wireless sensor networks would certainly reduce the mass and complexity of wiring, yet the essential question is: are they able to meet the requirements of non-critical and health monitoring applications in the specific environment of Aircraft and Launchers? First, we unify the requirements of non-critical and health monitoring applications in Aircraft and Launchers, and we show that such requirements impose the choice of multichannel mesh wireless networks. Multichannel networks bring many advantages in terms of latency, throughput and robustness. However, they do raise a number of challenges, some of which are general, while others are specific to supporting data gathering applications.Different solutions from the state-of-the art are given. These solutions, whether designed to take into account the specificities of data gathering or not, range from medium access control to multihop routing. The best performances are obtained when both problems are tackled together. We establish bounds on the minimum number of time slots needed by a raw data convergecast, taking into account the number of availablechannels, the number of children of the sink in the routing tree, as well as the number of radio interfaces in the sink. We propose SAHARA, a solution that provides an adaptive multichannel collision-free protocol for data gathering and we present many performance results obtained by simulatio