Real-Time Φ-OTDR Vibration Event Recognition Based on Image Target Detection.

Accurate and fast identification of vibration signals detected based on the phase-sensitive optical time-domain reflectometer (Φ-OTDR) is crucial in reducing the false-alarm rate of the long-distance distributed vibration warning system. This study proposes a computer vision-based Φ-OTDR multi-vibration events detection method in real-time, which can effectively detect perimeter intrusion events and reduce personnel patrol costs. Pulse accumulation, pulse cancellers, median filter, and pseudo-color processing are employed for vibration signal feature enhancement to generate vibration spatio-temporal images and form a customized dataset. This dataset is used to train and evaluate an improved YOLO-A30 based on the YOLO target detection meta-architecture to improve system performance. Experiments show that using this method to process 8069 vibration data images generated from 5 abnormal vibration activities for two types of fiber optic laying scenarios, buried underground or hung on razor barbed wire at the perimeter of high-speed rail, the system mAP@.5 is 99.5%, 555 frames per second (FPS), and can detect a theoretical maximum distance of 135.1 km per second. It can quickly and effectively identify abnormal vibration activities, reduce the false-alarm rate of the system for long-distance multi-vibration along high-speed rail lines, and significantly reduce the computational cost while maintaining accuracy.

Improved Cycle Stability of LiSn Alloy Anode for Different Electrolyte Systems in Lithium Battery.

Lithium metal anode still confronts a series of problems at the way to commercialization though it has advantages in high energy density. The formation of Li dendrite is the major limitation need to be conquered. Here, a facile and simple LiSn alloy anode prepared by a direct metallurgy method is fabricated and evaluated in both liquid electrolyte and solid electrolyte. Structural analysis and electrochemical measurements reveal the promoted ionic transference of interface and enhanced cycling stability in different electrolyte systems, without dendrite formation. Furthermore, the application of this simple and sustainable LiSn alloy can be extended to more alloy anode and might unlock the next-generation anode in the future.