Link Quality Metrics in Large Scale Indoor Wireless Sensor Networks

International audiencePouvoir estimer la qualité d'un lien sur la base d'un minimum de paquets est essentiel pour un réseau de capteur sans fil multisaut en environnement "indoor" compte tenu du coût énergétique de cette estimation et de ses conséquences sur la stabilité des routes construites sur ces liens. Notre étude s'appuie ainsi sur des expérimentations intensives menées sur une plateforme Senslab (\cite{www_senslab}) qui nous ont permis de trouver des lois de distribution suivies par les métriques physiques (RSSI, LQI) pour 3 catégories de liens (bons, mauvais, intermédiaires) regroupés par plage de PRR (Packet Reception Ratio). Sur la base de ces distributions, nous observons comment elles peuvent nous aider à discriminer les différents liens et ainsi les utiliser dans de futures expérimentations pour améliorer l'efficacité de protocoles de routage de réseaux de capteurs dans le choix des liens

PLANTWIDE CONTROL AND DYNAMICS BEHAVIOR OF AN INTEGRATED PLANT COUPLING NITROBENZENE HYDROGENATION AND METHYL-CYCLOHEXANE DEHYDROGENATION

Coupling of exothermic and endothermic processes is an application of process intensification where two or more processes can be combined in single unit for better utilization of material and energy. Nitrobenzene hydrogenation and dehydrogenation of Methyl cyclohexane in a single adiabatic reactor was investigated and found efficient, stable and economical in the previous study. The scope of this research is to implement plantwide control structure to analyze the dynamics behavior of an integrated system using Aspen Dynamics. Integrated plants where un-reacted reactants are recycled have high sensitivity towards disturbances. The complexity of the plant is reduced by fixing flow rates of reactants at reactor inlet using feedback control strategy. On introduction of individual and combined disturbances in flow rates of reactants ±10%, the system showed robust behavior and achieved stable operation. The system allows production rate changes keeping high purity of products

Integrated Production of γ-butyrolactone through Coupling of Maleic Anhydride Hydrogenation and 1,4-butanediol Dehydrogenation

Design and plantwide control of an integrated plant for the hydrogenation of maleic anhydride and the dehydrogenation of 1,4-butanediol has been studied for the synthesis of γ-butyrolactone in an adiabatic reactor, under different conditions of reaction temperatures and hydrogen to feed ratio, realizing optimal hydrogen utilization and better energy efficiency. Compared to stand-alone processes, the integrated process has several advantages, e.g., easy temperature control, improved γ-butyrolactone yield, good energy efficiency and optimal hydrogen utilization. The stability and robustness of the process is checked by rigorous dynamic simulation in AspenDynamics

Advanced Characterization of Silica–Encapsulated Aluminum Pigments

For environmental reasons, the paints industry shifts from solvent-borne towards water-borne formulations. This change is challenging the business of aluminum pigments, as the hydrogen released by the reaction of aluminum with water degrades the optical properties, besides being a safety concern. In this work, industrial-grade aluminum pigments are encapsulated, by a well-known method, in a silica matrix by sol-gel process using isopropanol - a more suitable solvent for the industry. The effectiveness of the encapsulation process is proven by advanced physical methods (Scanning Electron Microscopy, Energy Dispersive X-Ray Analysis, Selected Area Electron Diffraction, Fourier Transformed InfraRed Spectroscopy, Thermo-Gravimetric Analysis) and by industry-relevant tests (stability in water, hiding power, flop and granulometry). Moreover, advanced surface-applied physical methods (High Resolution Transmission Electron Microscopy combined with Selected Area Electron Diffraction and Scanning Transmission Electron Microscopy, and FT-IR microscopy) clearly show the homogeneity of the resulting pigments, a quality which is highly desirable for practical applications. The results demonstrate that stability comparable to that of pigments passivized by chromium-based inhibitors is easily achieved, for a variety of operating conditions. However, accomplishing a homogeneous silica layer of the right thickness is the determining factor for good optical properties