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Traditional visible light target detection is usually applied in scenes with good visibility, while the advantage of infrared target detection is that it can detect targets at nighttime and in harsh weather, thus being able to be applied to ship detection in complex sea conditions all day long. However, in coastal areas where the density of ships is high and there is a significant difference in target scale, this can lead to missed detection of some dense and small targets. To address this issue, this paper proposes an improved detection model based on YOLOv5s. Firstly, this article designs a feature fusion module based on a fusion attention mechanism to enhance the feature fusion of the network and introduces SPD-Conv to improve the detection accuracy of small targets and low-resolution images. Secondly, by introducing Soft-NMS, the detection accuracy is improved while also addressing the issue of missed detections in dense occlusion situations. Finally, the improved algorithm in this article increased mAP0.5 by 1%, mAP0.75 by 5.7%, and mAP0.5:0.95 by 5% on the infrared ship dataset. A large number of comparative experiments have shown that the improved algorithm in this article is effective at improving detection capabilities. [ABSTRACT FROM AUTHOR]

Meteorological conditions play an important role in aerosol pollution. In this study, the relationships between wind, temperature, relative humidity, and aerosol concentrations (PM2.5 and PM10) in Zhengzhou from January 2016 to December 2017 were analysed. Backward trajectory model was also used to investigate the relationship between meteorological parameters and regional transport of pollutants. Significant seasonal variations can be observed in the time series of pollutants and wind, temperature and relative humidity. The simulation of backward trajectories indicated that pollutants from southeast is critical to the air quality in Zhengzhou, in addition to local emissions of pollutants. To improve the air quality in Zhengzhou, joint efforts to reduce emissions in both Zhengzhou and its southeast adjacent regions should be considered.