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 mAP_0.5 by 1%, mAP_0.75 by 5.7%, and mAP_0.5:0.95 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.

This paper investigates the melting process of phase change material in a rectangular cavity at different inclination angles. Paraffin is used as a phase change material in this study. One side of the cavity is heated while the other sides are considered to be adiabatic. The investigated angles of inclination include 0° (bottom horizontal heating), 30°, 60°, 90° (vertical heating), 120°, 150° and 180° (top horizontal heating). Shapes of the solid liquid interface and temperature variations during the melting process were discussed for all the inclination angles. The results reveal that the inclination angles have a significant impact on the melting behavior of paraffin. As the angle increases from 0° to 180°, the complete melting time increases non-linearly.

The thermophysical properties of phase change material include thermal conductivity, heat of absorption, and phase change temperature range. This paper investigates the measurement methods of thermophysical properties for phase change material inside a full-scale container. The influence of contact thermal resistance is considered in a thermal conductivity test, and the formula for calculating the thermal conductivity of a phase change material inside the full-scale container is derived. In addition, the heat of absorption is measured based on the calibration results of the correction coefficient for heat flux sensors. In order to verify the reliability of the measurement method, the thermophysical properties of docosane and erythritol inside a full-scale specimen are measured, and the results are compared with HotDisk analyzer results and published data. The comparison results reveal that the method proposed in this paper can accurately measure the thermophysical properties of phase change material inside a full-scale specimen.