To overcome the shortcomings of the traditional manual detection of underwater targets in side-scan sonar (SSS) images, a real-time automatic target recognition (ATR) method is proposed in this paper. This method consists of image preprocessing, sampling, ATR by integration of the transformer module and YOLOv5s (that is, TR–YOLOv5s), and target localization. By considering the target-sparse and feature-barren characteristics of SSS images, a novel TR–YOLOv5s network and a down-sampling principle are put forward, and the attention mechanism is introduced in the method to meet the requirements of accuracy and efficiency for underwater target recognition. Experiments verified the proposed method achieved 85.6% mean average precision (mAP) and 87.8% macro-F2 score, and brought 12.5% and 10.6% gains compared with the YOLOv5s network trained from scratch, and had the real-time recognition speed of about 0.068 s per image.

Electrochemical oxidation technology is an effective technique to treat high-concentration wastewater, which can directly oxidize refractory pollutants into simple inorganic compounds such as H2O and CO2. In this work, two-dimensionally stable anodes, Ti/RuO2-IrO2-SnO2, have been developed in order to degrade organic pollutants from pharmaceutical wastewater. Characterization by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) showed that the oxide coating was successfully fabricated on the Ti plate surface. Electrocatalytic oxidation conditions of high concentration pharmaceutical wastewater was discussed and optimized, and the best results showed that the COD removal rate was 95.92% with the energy consumption was 58.09 kW·h/kgCOD under the electrode distance of 3 cm, current density of 8 mA/cm2, initial pH of 2, and air flow of 18 L/min.

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The idea of constructing the “GNSS-like” seafloor geodetic network for underwater positioning, navigation, and timing (PNT) has been proposed by many countries. Based on this idea, this paper introduces the principle of the seafloor PNT network and provides a combined measurement method, including the absolute positioning and the relative positioning. Experimental results show that the positioning difference between the proposed method and circle-sailing positioning is approximately 10 cm, and the observation efficiency is higher than the existing measurement in the seafloor PNT network. In addition, a model is derived to determine the optimal configuration of the unit network (the basic component of the seafloor PNT network), considering the ranging capability of acoustic beacons, which is helpful to balance the side length of the unit network and the number of observation sessions in the relative positioning. Finally, a chain coordinate transfer strategy in the whole seafloor PNT network is proposed, and the positions where the absolute positioning should be carried out in the whole network are derived based on the conditional adjustment model. Based on this strategy, the design schemes of a seafloor PNT network with centimeter, decimeter, and meter positioning accuracy when the acoustic velocity measuring accuracy is 0.02 m/s and the time measuring accuracy is 10−5 s, are given in the experimental section.

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