A ppb-Level Ammonia Detection System Based on TD-FD(HHT)–CNN-TL Deep Learning Model - Zhou, W.; Qi, R.; He, Z.; Jiang, L.; Li, Y.; Zhang, P.; Ren, L.; Qin, Z.; Chen, D.; Wang, T.; Wang, X.; Li, L.; et al. (IEEE Sensors Journal, Sensors Journal, IEEE, IEEE Sensors J., 2025)