Signal characteristics of coal and rock dynamics with micro-seismic monitoring technique

In this study, differences of signal characteristics between mine shocks and coal and gas outbursts in coal mines were examined with the micro-seismic monitoring technique and time-frequency analysis. The duration of the mine shock is short while the coal and gas outburst lasts longer. The outburst consists of three stages： the pre-shock, secondary shock and main shock stage, respectively. The velocity amplitude of the mine shock is between 10 s and 10-3 m/s, which is higher than that of the outburst with the same energy level. In addition, in both cases, the correlation between the velocity amplitude and energy is positive while the correlation between the signal frequency band distribution and energy is negative. The signal frequency band of the high energy mine shock is distributed between 0 and 50 Hz, and the low energy mine shock is between 50 and 100 Hz. The fractal characteristics of mine shocks were studied based on a fractal theory. The box dimensions of high energy mine shocks are lower than the low energy ones, however, the box dimensions of outbursts are higher than that of mine shocks with the same energy level. The higher box dimensions indicate more dangerous dynamic events.

Preparation of self-sustained film by sol-gel method

Large size self-sustained film with considerable thickness ranging from 30 to 500 μm was prepared with sol-gel method by using dimethyldiethoxysilane/tetraethoxysilane composite alkoxide as precursor. The film exhibits good plasticity as well. Various factors that may influence the film properties were investigated. IR and AFM techniques were adopted to study the film structure and surface morphology. Gas chromatogram/mass spectrum technique was also adopted to characterize the network structure of the material through identification of different polymers formed during hydrolysis and condensation course.

Chemical composition and antimicrobial activity of the essential oil of Cacalia tangutica (Maxim.) Hand.-Mazz

Essential oil of the subterranean part of Cacalia tangutica(Maxim.)Hand.-Mazz was analyzed by gas chromatography(GC)-mass spectrum(MS)technique in two different capillary columns of different polarities.Thirty-one components were identified in the oil and the main compounds were a-zingiberene(13.49%),germacrene D(10.76%),α-pinene(8.54%),caryophyllene(Z-)(6.36%),linalool(6.16%),β-myrcene(4.89%),β-ocimene(Z-)(4.40%)and ocimenone(Z-)(3.58%).The antimicrobial activity of the oil was evaluated against 2 fungi and 12 bacteria including 6 clinically isolated strains using the agar disc diffusion and broth microdilution methods.The results show that the oil presented a broad antimicrobial spectrum and had better antimicrobial activity against yeast and gram-positive bacteria.The minimum inhibitory concentration values were 0.16–5.00 g/L and minimum bactericidal concentration values were 0.16–5.00 g/L.