A yellow-emitting phosphor, ${\mathrm{La}}_{1-x}{\mathrm{Ce}}_x^{3+}{\mathrm{Sr}}_2\mathrm{Al}{\mathrm{O}}_5$ , is reported that displays a peak in the excitation at $450\mathrm{nm}$ and a peak in the emission at $556\mathrm{nm}$ . When this phosphor is pumped by a blue InGaN light-emitting diode $({\lambda }_{\max }=450\mathrm{nm})$ we obtain white light with color rendering index $\left(R_a\right)$ between 81 and 85 and color temperatures between 4200 and $5500\mathrm{K}$ , suggesting that this material is competitive as a blue-pumped yellow phosphors.

Environment monitoring is important for the safety of underground coal mine production, and it is also an important application of Wireless Sensor Networks (WSNs). We put forward an integrated environment monitoring system for underground coal mine, which uses the existing Cable Monitoring System (CMS) as the main body and the WSN with multi-parameter monitoring as the supplementary technique. As CMS techniques are mature, this paper mainly focuses on the WSN and the interconnection between the WSN and the CMS. In order to implement the WSN for underground coal mines, two work modes are designed: periodic inspection and interrupt service; the relevant supporting technologies, such as routing mechanism, collision avoidance, data aggregation, interconnection with the CMS, etc., are proposed and analyzed. As WSN nodes are limited in energy supply, calculation and processing power, an integrated network management scheme is designed in four aspects, i.e., topology management, location management, energy management and fault management. Experiments were carried out both in a laboratory and in a real underground coal mine. The test results indicate that the proposed integrated environment monitoring system for underground coal mines is feasible and all designs performed well as expected.