State Key Laboratory of Gas Disaster Detecting, Preventing and Emergency Controlling

Aiming at the demand of mine ventilation monitoring system for high precision and anti-harsh environment wind speed sensor, this paper designs a mine optical fiber hot wire wind speed sensor based on the hot wire wind measurement and the hot wire sensing principle of fiber Bragg grating (FBG). Through the photothermal effect of cobalt-doped fiber, the change of wind speed is converted into FBG wavelength drift, and the quantitative relationship between wind speed and wavelength drift is established by combining the heat transfer model. In the temperature characteristic experiment of the sensor, the center wavelength drift of FBG shows a good linear growth trend with temperature, and the temperature sensitivity can reach 21.5pm/°C, which has higher temperature sensitivity compared to sensors of the same type. The wind tunnel test results show that the sensor has a sensitivity of 1634 pm/(m·s^-1) at 0.35 m/s, and has high sensitivity in the low wind speed range. This provides an effective detection method for the needs of air leakage detection in coal mine goaf.

ABSTRACT To examine hydrogen explosion characteristics and propagation in confined spaces, providing a theoretical basis for prevention and mitigation, experiments were conducted in a 20‐L spherical vessel at various hydrogen concentrations. Computational fluid dynamics simulations analyzed explosions under different initial conditions (concentration, ignition source temperature, initial temperature, and initial pressure). Results show that higher hydrogen concentration reduces the induction period, increasing pressure rise rate and peak values of pressure and temperature. Greater ignition source temperature and pressure also boost the pressure rise rate, slightly raise peak pressure, and increase maximum temperature. Elevated initial temperatures speed up the pressure rise but decrease peak pressure. Qualitative and quantitative analyses of explosion parameters like explosion impulse, explosive energy, and detonation index were performed to explain hydrogen explosion mechanisms.

Frequency dispersion is critical in designing metasurfaces, which enables advanced functionalities such as enhanced light-matter interaction and tailored wave propagation. In this paper, we demonstrated a deep learning approach for on-demand engineering of hyperbolic dispersion in metasurfaces. A deep neural network was trained to establish a direct mapping between pixelated metasurface structures and their electric and magnetic susceptibilities across a range of frequencies and polarizations. Utilizing this trained network, we performed inverse design to create a hyperbolic metasurface exhibiting a unique capability, exciting electric or magnetic hyperbolic polaritons according to source polarization. This work provides an innovative methodology for achieving precise control over hyperbolic dispersion and holds potential as a reusable, versatile inverse design tool, paving the way for novel wave manipulation strategies and advanced metamaterial devices.

To address issues of traditional coalbed methane (CBM) fracturing fluids (high displacement, weak sand-carrying, poor stability, severe coal seam damage), this study synthesized CO2-responsive erucamide propyl dimethylamine surfactant (C22ZEA, yield 99%), with molecular structure verified by 1H NMR (400 MHz, CDCl3) matching the target. Molecular simulation showed CO2 protonates C22ZEA into EA+: 1 wt% forms a simple micelle network, while 3 wt% enhances entanglement into a dense 3D network. Experiments indicated: 3 wt% solution reaches 160 mPa·s viscosity in 200 s under CO2 (0.2 L·min−1); 1.5–4.5 wt% solutions are pseudoplastic (n = 0.14–0.18), with G′ > G″ when concentration > 2 wt%; viscosity recovery rate > 95% after alternating shear (170 s−1/10 s−1); viscosity remains > 160 mPa·s after 1 h shear (170 s−1) at 70 °C; gel breaks to 0.01–0.02 Pa·s in 15 min with N2 at 45 °C; 1.0–3.0 wt% solutions meet non-toxic standards via EC50/96 h LC50. This study supports high-efficiency low-damage smart fracturing fluids, boosting CBM extraction efficiency.

We present a fiber-optic directional curvature sensor utilizing an asymmetric microbubble Fabry-Perot interferometer (AMFPI). The device features a monolithically integrated sealed cavity embedded in a tapered optical fiber, with a waist diameter of 52 µm. Directional sensitivity originates from the asymmetrical displacement of reflection points on the internal spherical cavity surface, induced by asymmetric light incidence during bending. This displacement effectively modulates the optical path difference (OPD), resulting in distinct spectral shifts (redshift or blueshift) corresponding to a bending direction. Further enhancing directional sensitivity, radial wall thickness asymmetry in the microbubble waist is precisely engineered. The fabricated sensor, with an ultra-compact cavity length under 50 µm, achieves a high directional curvature sensitivity of 1.06 nm/m-1 over a curvature range of 0-4.35 m-1. Notably, the sensor exhibits negligible sensitivity to ambient refractive index variations and an exceptionally low thermal sensitivity of 1.09 pm/°C. These attributes render the sensor highly suitable for precise directional curvature detection under challenging environmental conditions, such as biological fluids and temperature fluctuations.

In order to solve the problem of network communication of underground multi-drilling site and multiautomatic operation equipment, this paper proposes a construction scheme of underground intelligent drilling site ad hoc network based on 5 G wireless network, which uses the wireless network communication platform to build automatic drilling rigs, feng shui linkage devices, slag water treatment devices and other equipment in multiple intelligent drilling sites, combines efficient digital interaction and distributed linkage control to realize the centralized automatic control of the whole process of drilling, and adopts TCP/IP communication protocol on site. The 5.8 G wireless ad hoc network in AP mode is adopted between the drilling sites, which reduces the laying of on-site communication cables, and the communication performance is stable and reliable, supports standard protocols such as Modbus TCP, supports direct access to the core controller by the mining management software, and the communication delay is $\leqslant 1 \mathrm{~s}$.