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Power consumption is a critical issue in Wireless Sensor Networks(WSN) applications and typically the energy consumed by the wireless communication dominates. Reducing the WSN node activity and the communication energy can extend the lifetime of the node considerably. This work presents a direct application approach to extend the lifetime of a wireless senor node using a MEMS piezoelectric energy harvesting device in combination with a nano-Watt wake-up radio receiver, in order to build an efficient power device. The design of the power device will be connected to each node as a normal battery bringing the wake-up radio capabilities. Two scenarios were implemented to use the power unit as a wireless switch with harvesters, or to use the power management wake up polices while the MEMS piezoelectric harvester was designed as a power supply directly to the wake up radio receiver. The experimental results and characterization of the muW-MEMS harvester are presented. Finally, measurements on a generic node present the benefits of this approach bringing the power consumption in low power mode down to nano-Watt level (zero power) when the node is not needed in the application.

This paper presents the design, implementation and characterization of an energy–efficient smart power unit for a wireless sensor network with a versatile nano-Watt wake up radio receiver. A novel Smart Power Unit has been developed featuring multi-source energy harvesting, multi-storage adaptive recharging, electrochemical fuel cell integration, radio wake-up capability and embedded intelligence. An ultra low power on board microcontroller performs maximum power point tracking (MPPT) and optimized charging of supercapacitor or Li-Ion battery at the maximum efficiency. The power unit can communicate with the supplied node via serial interface (I2C or SPI) to provide status of resources or dynamically adapt its operational parameters. The architecture is very flexible: it can host different types of harvesters (solar, wind, vibration, etc.). Also, it can be configured and controlled by using the wake-up radio to enable the design of very efficient power management techniques on the power unit or on the supplied node. Experimental results on the developed prototype demonstrate ultra-low power consumption of the power unit using the wake-up radio. In addition, the power transfer efficiency of the multi-harvester and fuel cell matches the state-of-the-art for Wireless Sensor Networks.

Yttrium gadolinium aluminate ((Y1-xGdx)(3) Al5O12:Ce) doped cerium phosphors with the different yttrium and gadolinium concentration were prepared by a wet-chemical route via the reagent simultaneous addition technique (WCS-SimAdd). The phosphors were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL), radioluminescence (RL) of cerium doped yttrium gadolinium aluminate phosphors. With increasing Gd dopant concentration, the PL intensity was shifted to the red region. Preliminary RI measurements were performed to further evaluate these newly prepared materials. Intense RL was observed that is typical of Ce3+ doped structure. (C) 2012 Elsevier B.V. All rights reserved.

In this study we report the synthesis of a series of composite nanostructures comprising LDH and TiO2 phases. The materials characterization showed that the LDH crystallites are encapsulated inside the TiO2 matrix after the anatase seeds are deposited on Mgx Al-LDHs. The structure in which LDH phase is embedded into anatase matrix is unique bringing important advantages to the photocatalytic performances of the nanocomposites. The photocatalytic activity of the prepared nanocomposites was tested on the degradation of the methylene blue (MB) in aqueous solution. The photocatalytic activities of the nanocomposites were compared with commercial TiO2 nanoparticles Degussa P25. The nanocomposites exhibited superior photocatalytic activity in basic environment because the negatively charged surface of TiO2 nanoparticles at high pH attracts the positively charged methylene blue species.