FireSonic: Design and Implementation of an Ultrasound Sensing-Based Fire Type Identification System.

Accurate and prompt determination of fire types is essential for effective firefighting and reducing damage. However, traditional methods such as smoke detection, visual analysis, and wireless signals are not able to identify fire types. This paper introduces FireSonic, an acoustic sensing system that leverages commercial speakers and microphones to actively probe the fire using acoustic signals, effectively identifying fire types. By incorporating beamforming technology, FireSonic first enhances signal clarity and reliability, thus mitigating signal attenuation and distortion. To establish a reliable correlation between fire type and sound propagation, FireSonic quantifies the heat release rate (HRR) of flames by analyzing the relationship between fire-heated areas and sound wave propagation delays. Furthermore, the system extracts spatiotemporal features related to fire from channel measurements. The experimental results demonstrate that FireSonic attains an average fire type classification accuracy of 95.5% and a detection latency of less than 400 ms, satisfying the requirements for real-time monitoring. This system significantly enhances the formulation of targeted firefighting strategies, boosting fire response effectiveness and public safety.

Insight into the effect of fracture surfaces in graphdiyne on the anode performance for lithium ion batteries.

Two-dimensional (2D) materials are promising anode materials for the next generation of lithium ion batteries. While the Li storage and kinetics at the surface and intercalation sites of 2D materials are widely explored, the effects of the fracture surfaces (FSs) are rarely considered despite the fact that there are numerous FSs in real 2D materials. Herein, we investigate how the FSs in graphdiyne (GDY) affect the anode performance based on first-principles calculations. Results show that both the internal and external FSs have much lower binding energies to Li atoms than perfect GDY, meaning FSs are more active in storing Li atoms. Then, the diffusion barriers of Li atoms on the internal and external FSs are only 0.42 and 0.47 eV, respectively, close to the 0.315 eV of surface sites and lower than the 0.638 eV of intercalation sites, indicating a good kinetics of Li atoms. In addition, due to the new electronic states from the C atoms with dangling bonds, the FSs convert the semiconductor characteristics of perfect GDY to metallic ones, which is helpful to the electronic conductivity. Our work demonstrates that the FSs in 2D materials are beneficial to the anode performance, which may enlighten the design of anode materials.