Resonance frequency drift caused by a change in temperature greatly limits the application of high- Q resonators with high temperature sensitivity in photoacoustic (PA) gas detection systems. In this work, a chirp-wavelength combined modulation method was designed by incorporating a real-time frequency scanning in wavelength-modulated PA spectroscopy to reduce the influence of temperature changes on measurement. Theoretical analysis shows that the chirp rate depends on the precision requirements and the cutoff frequency of the cascaded low-pass filter. Trace acetylene measurement experiment at varying temperature verified that the proposed method can significantly reduce the temperature sensitivity within a preset temperature range. Thus, this method can effectively reduce the temperature sensitivity of a high- Q resonator for improving the measurement accuracy and detection limit in trace gas detection.

As the coal mine gets deeper and the stopes’ structures become more complex, gas and coal spontaneously burned composite disaster seriously threatens the efficient operation of coal mines. To study the interaction process and disaster-causing mechanism of gas and coal spontaneous combustion (GCSC), this paper establishes a numerical model to study the influence of drilling location/pressure and N2 injection on the evolution of gas and coal spontaneously burned composite disaster in the goaf. The simulation shows that in the central part of the goaf, a combined area of gas and coal combustion poses a possibility of spontaneous combustion calamity, and the length of the compound disaster area is about 20 m. The methane (CH4) explosion zone and the dioxygen(O2) temperature rise zone do not overlap in the air entrance roadway and return air roadway, indicating that there is no risk of compound disasters. The optimal nitrogen (N2) injection rate for this working face is 2000 m3/h, and the N2 port should be located 25 m profound into the goaf, which can effectively drive the diffusion of N2 and narrow the O2 zone’s breadth. The findings have considerable engineering applications for revealing the evolution process, risk assessment and control for GCSC compound disasters in coal mines.

The Diamond-like Carbon (DLC) modified alumina microparticle is expected to be an ideal filler which can greatly improve the thermal conductivity of the epoxy-alumina composites with high fill factor, meanwhile the composites can still maintain high dielectric properties. Plasma Enhanced Chemical Vapor Deposition (PECVD) has been mostly used to prepare DLC film on bulk material and the ion energy in the plasma shows crucial influence on the properties of the DLC, while properties of the DLC on solid microparticle prepared through PECVD method as well as the effect of the ion energy are still unclear. In this paper, DLC on alumina microparticle has been prepared through a high-efficient method of repeated pulsed hollow cathode discharge in methane gas and characteristics of the DLC on alumina particle has been studied and analyzed. The morphology and bond composition of DLC on particles has been studied through electron microscopy, Raman spectrometer and X-ray photoelectron spectroscopy. The ion energy distribution in the discharge plasma has been diagnosed and used to analyzed its effect on the hybrid bond content of the DLC through correlation analysis. Correlation of the ion energies and the hybrid bonds content of the DLC shows hydrocarbon ions in the discharge plasma with energy of 100~200 eV present most benefit to the formation of the sp3 hybrid bond content of DLC film on alumina microparticle and hydrogen ions with energy of 700~1000 eV are also beneficial to improve sp3 hybrid bond content of the DLC film.

The high density and controllability of radio frequency (RF)-biased inductively coupled plasma offer significant potential for diamond-like carbon (DLC) deposition on alumina. However, the effects of power and atmospheric parameters on DLC deposition have been understudied due to multiple constraints, such as discharge conditions and carbon source requirements. In this study, considering the dual requirements of ion flux and ion kinetic energy for deposition, an RF-biased inductively coupled plasma-enhanced DLC deposition method was proposed. A total of 273 deposition experiments designed by response surface methodology were performed over wide parameter ranges to explore the influence of atmospheric parameters, such as gas pressure and Ar/H2 auxiliary gas fractions, on feasible power. The results showed that there was a power threshold for DLC deposition on alumina, which increased with gas pressure and slightly decreased with auxiliary gas addition. The effect of auxiliary gas on DLC deposition exhibited duality due to changes in the dominance of ion etching and methane dissociation. The feasible power region for DLC deposition in multicomponent atmosphere was jointly constrained by the power threshold and etching action. This research contributed to the DLC modification of alumina substrate in batches.

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