Spontaneous combustion in coal goaf area is one of major disasters in coal mines. Detection technology based on signature Gas and Temperature is the primary means of spontaneous combustion forecasting of coal goaf area. A real-time remote fire detection system is proposed based on tunable diode laser absorption spectroscopy technology and FBG temperature sensing technology, to achieve valid detect of gas concentration and temperature. The System include fiber mathen concentration sensor and fiber temperature sensor based FBG. The system achieved remote on-line monitoring of gas concentration and temperature in mine goaf, meet the fire forecast need for Coal goaf area. There are obvious advantages Compared with the existing beam tube monitoring system in coal mine.

Based on the bead on plate test and the effects of heat input on weld penetration, the equivalence between 2 kW CW (Continuous Wave) Nd:YAG laser power and pulsed GMA(Gas Metal Arc) power and the effect of welding speed on their equivalent ratios in welding carbon steel and Al alloy were studied. The studied results show that 9.8 kW pulsed GMA power is needed to reach the same weld penetration depth with 2 kW CW Nd:YAG laser power for welding of low carbon steel at v=1.2 m/min; for Al alloy, it is 3.92 kW pulsed GMA power. The equivalent ratios of 2 kW Nd:YAG laser power and pulsed GMA power are 4.9~6.4 and 1.85~2.1 times at different welding speed for low carbon steel and Al alloy, respectively. But their equivalent ratios have different variations with welding speed; at which the equivalent ratio of low carbon steel increases with welding speed and that of Al alloy decreases. The studied results offer the experimental boundary of heat input for analyzing the effect of Nd:YAG laser power and pulsed GMA power on laser+pulsed GMA hybrid welding process.

Based on the coupling of laser beam and double arcs, a novel process was investigated. This research set up the laser-double wire pulsed MIG hybrid welding system. Meanwhile the current and voltage sensors were used to detect welding current and arc voltage wave-form and high-speed videography system was used to observe the metal transfer process and arc behavior. The three signals were acquired synchronously. The results showed that the synergic action of the three different heat sources leads to a change in metal transfer mode. It was revealed that the metal transfer mode was two droplets per pulse in laser-double wire hybrid welding process while one droplet per pulse in double wire welding process with the same certain experiment parameters. And we also discovered that the arcs were attracted strongly by the laser beam.