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In general, a single scalar hydrophone cannot determine the orientation of an underwater acoustic target. However, through a study of sea trial experimental data, the authors found that the sound field interference structures of inbound and outbound ships differ owing to changes in the topography of the shallow continental shelf. Based on this difference, four different convolutional neural networks (CNNs), AlexNet, visual geometry group, residual network (ResNet), and dense convolutional network (DenseNet), are trained to classify inbound and outbound ships using only a single scalar hydrophone. Two datasets, a simulation and a sea trial, are used in the CNNs. Each dataset is divided into a training set and a test set according to the proportion of 40% to 60%. The simulation dataset is generated using underwater acoustic propagation software, with surface ships of different parameters (tonnage, speed, draft) modeled as various acoustic sources. The experimental dataset is obtained using submersible buoys placed near Qingdao Port, including 321 target ships. The ships in the dataset are labeled inbound or outbound using ship automatic identification system data. The results showed that the accuracy of the four CNNs based on the sea trial dataset in judging vessels' inbound and outbound situations is above 90%, among which the accuracy of DenseNet is as high as 99.2%. This study also explains the physical principle of classifying inbound and outbound ships by analyzing the low-frequency analysis and recording diagram of the broadband noise radiated by the ships. This method can monitor ships entering and leaving ports illegally and with abnormal courses in specific sea areas.

Saudi Arabia blockades Yemeni ports as expats try to flee.

Saudi Arabia blockades Yemeni ports as expats try to flee.

Building a "Maritime Community with a Shared Future" (MCSF) is a maritime development concept with Chinese characteristics proposed by Chinese President Xi Jinping in 2019. It is based on the rich cultural tradition and unique historical value of China's maritime civilization. It aims to solve real ocean problems and has outlined the future direction of human ocean development from the perspective of China. The essence of the MCSF is an issue of both ocean cultural and development concepts. It is a conceptual issue that transcends specific national boundaries and regions and is based on how all of humankind, with common interests and common values, can develop in harmony with the oceans. It is not a covert discourse strategy adopted by China in order to realize its "maritime power" ambition, as occasionally described by some Western countries. Starting with an analysis of the essential nature and implications of maritime culture by Chinese researchers, this article clarifies and summarizes the interaction, exchange, and integration of Chinese maritime culture in East Asia from a historical perspective, and extracts the unique characteristics and values of Chinese maritime culture. From the perspective of human-sea interactions, the three historical stages, as well as the existing problems of transforming and upgrading human-ocean culture, are analyzed. The article also contrasts Chinese and Western maritime cultures and proposes to absorb the outstanding achievements of both Chinese and Western maritime civilizations into a common framework in order to fundamentally reverse the antagonistic human-sea relationship that has existed historically. Finally, we propose giving full play to the fundamental role of marine cultural exchange and integration and, through international cooperation on specific issues in the field of global ocean international relations, propose specific and feasible practical pathways to promoting the realization of the MCSF.