A Low-Cost AI Buoy System for Monitoring Water Quality at Offshore Aquaculture Cages.

The ocean resources have been rapidly depleted in the recent decade, and the complementary role of aquaculture to food security has become more critical than ever before. Water quality is one of the key factors in determining the success of aquaculture and real-time water quality monitoring is an important process for aquaculture. This paper proposes a low-cost and easy-to-build artificial intelligence (AI) buoy system that autonomously measures the related water quality data and instantly forwards them via wireless channels to the shore server. Furthermore, the data provide aquaculture staff with real-time water quality information and also assists server-side AI programs in implementing machine learning techniques to further provide short-term water quality predictions. In particular, we aim to provide a low-cost design by combining simple electronic devices and server-side AI programs for the proposed buoy system to measure water velocity. As a result, the cost for the practical implementation is approximately USD 2015 only to facilitate the proposed AI buoy system to measure the real-time data of dissolved oxygen, salinity, water temperature, and velocity. In addition, the AI buoy system also offers short-term estimations of water temperature and velocity, with mean square errors of 0.021 °C and 0.92 cm/s, respectively. Furthermore, we replaced the use of expensive current meters with a flow sensor tube of only USD 100 to measure water velocity.

Properties of Transmission and Leaky Modes in a Plasmonic Waveguide Constructed by Periodic Subwavelength Metallic Hollow Blocks.

Based on the concept of low-frequency spoof surface plasmon polaritons (spoof SPPs), a kind of leaky mode is proposed in a waveguide made of a subwavelength metal-block array with open slots. Numerical results reveal that a new transmission mode is found in the periodic subwavelength metal open blocks. This modal field is located inside the interior of a hollow block compared with that in a solid metal block array. The dispersion curve shows that such a new SPPs mode has a negative slope, crossing the light line, and then going into a zone of leaky mode at higher frequencies. The leaky mode has a wider frequency bandwidth, and this can lead to a radiation scanning angle of 53° together with high radiation efficiency. Based on the individual characteristics exhibited by a frequency-dependent radiation pattern for the present leaky mode, the waveguide structure can have potential applications such as frequency dividers and demultiplexers. Experimental verification of such a leaky mode at microwave has been performed, and the experimental results are found to be consistent with the theoretical analysis.