Wireless Sensor Networks are based on the ZigBee standard. ZigBee uses the IEEE 802.15.4 physical and MAC (medium access control) layers to provide standards-based reliable wireless data transfer. Also, ZigBee provides low-power wireless connectivity features. The features allow ZigBee-based products to be installed easily and cost-effectively. Thus, this technology has been attracting extensive research and development efforts to replace the traditional wired solutions for Building Automation Systems. However, wireless communications in indoor building environments are prone to be influenced by multiple concurrent factors, such as multi-path fading, channel contention, other radio interference, human activity and limited battery energy. Also, sensor detection is not fully reliable. Thus, system robustness is very concerning in these applications. In this paper, we propose a reliable wireless sensor network and an accurate occupancy detection mechanism. We implemented this system in an indoor building for the lighting control of public areas, including corridors, a coffee room and a washroom. The system framework was shown to be effective in terms of network communication reliability and sensor detection accuracy.

Functional nanocrystalline metallic iron powder is produced by the method of electro-discharge in the low oxygen environment of water. In order to obtain superparamagnetic iron oxide Fe 3 O 4, the manufacturing Fe particles were oxidized in the oxygen-rich water to continue oxidation process. Besides, the nanocrystalline Fe particle will be oxidized at temperatures of 200° C , 250° C , 300° C , 350° C , 400° C , 500° C and 600° C for 1 h in air to produce iron oxide α- Fe 2 O 3. The X-ray diffraction, SEM and transmission electron microscope (TEM) were used to analyze the crystal structure and the powder morphologies. The results showed that pure Fe and FeO with a pretty narrow particle size distribution ranges from 1 nm to 10 nm were obtained by the method of electro-discharge. After oxygen-rich oxidation treatment the γ- Fe 2 O 3 and Fe 3 O 4 were obtained at room temperature in 10 days. Thereafter, no more transformation was found in water environment. This result proves that Fe 3 O 4 can be a stable superparamagnetic iron oxide. However, for the Fe particles heat-treated at temperatures of 200 to 600° C , α- Fe 2O3 was formed at temperatures above 300° C for 1 h treating time. Further application studies of this material will be presented in our future research works.

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Wireless sensor networks have the advantages of low cost installation and flexibility, which make them an excellent mechanism for capturing environmental data and interacting with the physical environment for the application of building automation. However, radio propagation suffers from multi-path, shadowing and other radio interference problems in building environments. Therefore, deployment of sensor nodes in a dynamic in-building environment is a complex operation that requires expert knowledge and experience. In this paper, we present a deployment planning tool that can provide a set of useful tools for deploying a wireless sensor network in the building environment. The proposed deployment planning tool provides design tools that can assist users to develop a network infrastructure in order to support reliable communication. In addition, a network evaluation tool is provided to measure the index of network quality in order to ensure a reliable network quality. In order to evaluate the effectiveness of this tool, we designed a sensor network and simulated the network quality using this tool. The simulation results matched the experimental results of realistic deployment very well.