Rock disasters caused by rock fractures seriously threaten the safe and sustainable mining of deep coal resources. The infrared thermal imaging of rock fractures has a non-uniform distribution. This is important information for the monitoring and early warning of rock mass instability. In this paper, the multi-fractal theory was introduced to analyze the infrared thermal image obtained from the uniaxial loading of sandstone, which is expected to provide quantitative indicators for the infrared monitoring of rock failure. The results show that the multi-fractal parameters Δα (non-uniformity of temperature) and Δf (frequency diversity of minimum and maximum temperature) can be used to describe the distribution of the thermal field; they are sensitive to the rock macro fracture. Both Δα and Δf are constant during the initial loading stage. When the samples yield and there is a failure in the later stage of loading, the Δα and Δf change abruptly. The sudden change in Δα and Δf can be regarded as the precursor to rock failure. The research results preliminarily show the feasibility and potential of multi-fractal analysis in rock mass disaster monitoring and early warning.

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The 6MF-30 pneumatic extinguisher is a widely utilized and efficient tool for combating wildland fires. However, using incorrect extinguishing angles can diminish its effectiveness. This study aimed to determine the optimal extinguishing angle for the 6MF-30 pneumatic extinguisher by conducting computational fluid dynamics simulations and experimental verification. The findings revealed that ground roughness did not significantly affect the optimal extinguishing angle or the attenuation of jet velocity near the fan outlet region. The study determined that an optimal extinguishing angle of 37° applies to lossless ground, natural grassland, grassland with artificial disturbance, and enclosed grassland. Furthermore, among the selected angles, the highest rate of jet velocity reduction was observed at 45°, whereas the slowest reduction occurred at 20° and 25°. These findings offer valuable insights and recommendations for enhancing the efficacy of wildland fire-fighting when employing the 6MF-30 pneumatic extinguisher.

With the increase of fire in high-rise buildings in recent years, the demand for high-performance Water Tower Fire Truck (WTFT) is increasing day by day. In order to improve the injection capacity of ultrafine dry powder of the WTFT, this article adopts the way of adding blow-assisted pipe to realize nitrogen-assisted blowing, and the internal flow field of existing blow-assisted pipe was analyzed and optimized by CFD simulation. The influence law of size parameters on the mass flow rate and velocity of ultrafine dry powder and nitrogen was analyzed and summarized under different inlet pressure conditions. The optimization result is that the diameter of the nitrogen-assisted blowing pipe is increased between 10 mm and 20 mm, the diameter of the outlet pipe is 32 mm, and the diameter of the inlet of the mixing pipe is 90 mm.

<p>For the calibration of space plasma analyzers, in particular low-energy ion mass spectrometers, a low energy ion beam system was developed. The positive ion beam is produced by a hot-cathode penning source and modified by a series of electrostatic lenses. And a 75 mm diameter 2-D imaging system and a Faraday cup mounted on movable arms are used for ion beam diagnostics. With protons as primary species, the system provides an ion beam in the energy range of 1 eV - 1000 eV with a large area ( ~ 50 cm<sup>2</sup>), highly parallel ( ± 0.5°), and spatially uniform ( ± 5%).</p>