Real-time, accurate and reliable monitoring of marine environmental information plays a crucial role in marine disaster warning and prediction, disaster prevention and reduction, marine resource development, and ensuring marine safety. In recent years, with the continuous development and upgrading of global navigation satellite systems (GNSS), the detection of atmospheric and marine environmental information based on GNSS navigation signals has become a new method and a hot research topic in the marine environmental monitoring technology. This method has been widely applied to domains such as marine meteorological monitoring and numerical forecasting. This article systematically reviews the current research status of the GNSS technology in marine environmental monitoring, including effective wave height, wind speed, rainfall intensity, water vapor and tide level monitoring. Furthermore, this paper systematically summarizes new technologies and methods and looks forward to provide reference for the future research in related fields.

Underwater biological object detection is crucial for aquaculture, endangered species protection,and ecological environment monitoring. This study comprehensively analyzes the applications of various deep learning methods in underwater biological object detection. The commonly used underwater biological object detection datasets are introduced. The state-of-the-art underwater biological object detection methods are classified, analyzed, and summarized by two stages and one stage. The actual applications of various detection methods are thoroughly described, and the advantages and disadvantages of their optimization strategies are analyzed and summarized. Future works in the field of underwater biological object detection based on deep learning are presented. This study provides a reference basis for researchers in the field of underwater biological object detection.

Water dynamics analysis was conducted on a compact and portable autonomous underwater vehicle(AUV) with side-scan sonar and amodified AUV with streamlined side-scan sonar. The analysis focused on examining the drag forces experienced by both AUVs at different speeds. The results demonstrated that the streamlined side-scan sonar effectively reduced pressure and viscous drag forces, resulting in an overall drag reduction of 15.4% at a normal speed of 3 knots, with a 9% reduction in viscous drag and an 18% reduction in pressure drag.At a high speed of 6 knots, the overall drag was reduced by 10.1%, with a 4.2% reduction in viscous drag and a 12% reduction in pressure drag. These findings demonstrate that optimizing the streamlined design of the AUV with side-scan sonar can effectively enhance the dynamic performance of the AUV, reduce its drag force, and improve its efficiency and performance.

This study proposes an efficient wave sensor fault diagnosis method based on wavelet packet decomposition, dimension reduction, and k-nearest neighbor algorithm(KNN) classification network to address the difficulty of wave sensor fault diagnosis, unidentifiable fault types, and time-consuming diagnosis. First, the standard deviation of the original signal is normalized. The normalized data is then subjected to a three-layer wavelet packet decomposition. The extracted feature vectors represent normalized data from the eight bands on layer 3. The second step involves using the t-distributed stochastic neighbor embedding (t-SNE) algorithm to reduce the dimension of the feature data. Finally, the dimension-reduced feature data is input into the KNN classification network for fault classification and detection. Experimental results show that the proposed method can improve the accuracy and diagnosis speed of the wave sensor fault diagnosis, with a diagnosis accuracy of up to 93.55% for normal and six faulty conditions.

Based on the actual marine hydrological data obtained from apredetermined sea area, a submerged buoy system is established herein for performing electromagnetic measurements using the lumped mass method. Further, the balance stance of the submerged buoy system and the tension distribution of the cable are simulated and analyzed. The results show that the design of the system has maintained a good linear correlation between the measurement nodes; the linear correlation coefficient is maintained above 0.995.The counterweight buffer cable can achieve good antiwave buffer effect. The analysis of field trial data at the sea shows that the submerged buoy system with a static buoyancy of 600 N, a buffer cable length of 150 m, and a counterweight of 40 m and 1 N/m can form a U shaped buffer belt with a buffer depth of 21 m when the surface current velocity is 0.5 m/s, which is consistent with the results of simulation analysis.

As the acoustic detection of seabed cold springs requires accurate information of bubble characteristics, this paper develops a simulated observation system for the gas leakage of seabed cold springs with high control accuracy and full functions based on the bubble distribution characteristics of real seabed cold springs.The gas flow is precisely controlled viathe fuzzy PID control algorithm. Compared with the conventional control method, the flow error rate can be reduced by up to 1.5% and the cold spring bubbles in the real environment can be simulated accurately and controllably. The dual cameras are driven viaan Ethernet synchronous trigger, and thesynchronized shooting reduces the shooting synchronization error range by 1.1 ms.The system accurately realizes the orthogonal synchronous observation of the bubble shape in the initial overflow stage and provides data support for the detection of seabed cold springs.

To investigate the operating performance of breakwater integrated with an oscillating water column wave-energy converter, a model experimental study was performed in the wave flume. An air turbine and an electric generator were used for converting pneumatic power to electricity. Performances of the device under different incident wave conditions were examined. The results show that the wave period has a considerable effect on the performance of breakwater integrated with an oscillating water column and the device shows better performance under long wave period conditions. The device represents low energy conversion efficiency when the incident wave height is small.

In the field of shipbuilding and ocean engineering, there exists a variety of cavity flows, wherein the flow process is more complex with an obvious turbulence structure. This study explores the influence of different aspect ratios on the cavity flow. Three cavity models with different height-width ratios were taken as the research objects, the mesh independence was analyzed, and the appropriate mesh was selected for numerical calculation. Large eddy simulation was used to analyze the flow field information of cavity flow with different aspect ratios. Furthermore, the velocity distribution, pressure distribution, and vorticity distribution were analyzed. The flow in the cavity with a small aspect ratio was more complex, and the vorticity nonlinearity was obvious, whereas the velocity and vorticity distribution in the cavity with a high aspect ratio were concentrated in the cavity opening region. The results of this study lay a theoretical foundation for the application of cavity flow in the field of ship engineering.

Using Fluent, the difference in the stirring effect of a biological stirred tank with and without baffle was calculated and compared. Based on the finite volume method, the RANS（Reynolds-averaged Navier-Stokes） model was used to simulate the flow field in the biological stirred tank, and the velocity distribution, pressure distribution and turbulent kinetic energy in the stirring process were obtained. The structural morphology of the flow field was analyzed. The results show that the larger the baffle width, the greater the velocity fluctuation, the greater the velocity vector change, and the greater the turbulent kinetic energy, which is helpful in improving the stirring effect of the biological stirred tank. According to the pressure distribution analysis, with or without a baffle, the minimum pressure in the biological stirred tank is 0.12 m away from the bottom of the tank. The minimum pressure with a baffle is lower than that without a baffle, The velocity vector in the flow field of the stirred tank with baffle exhibits a stronger cyclone effect, which could result in more intense chemical reaction occurring during the stirring process.

Slope is a commonly coastal and reservoir protection engineering structure that is used to provides defense against the invasion of land from waves and currents. Based on the computational fluid dynamics software Fluent, a two-dimensional wave numerical flume was established. Under the condition of regular waves, the wave overtopping process of smooth slopes and slopes with fences was simulated. Results show that the fence panel exhibits a mitigation effect on the surging water body and can effectively improve the wave absorbing ability of the slope. Comparing the over-the-top wave volume of slopes with different gradients and different panel spaceings, the results show that the slope designed herein has a significant wave-eliminating ability under the conditions of small gradient and small spacing.

To improve the detection performance of an NaI (Tl) spectrometer for in situ marine radioactivity monitoring, Monte Carlo simulation and statistical calculation methods were used to study and analyze the effect of mechanical design of spectrometer package, material, and size on detection performance. Considering the requirements of gamma ray attenuation, sealing, pressure resistance, and corrosion resistance, the mechanical optimization design of the spectrometer and on-site detection experiments were conducted. The minimum detectable activity of the optimized spectrometer was approximately 0.30 Bq/L for 40K, and the relative error of measurement was 0.45%. This study has important guiding significance for the performance optimization design and field application of gamma spectrometers for in situ marine radioactivity monitoring.

The wave inversion technology plays an important role in sensor development. In this study, a SVS-603 sensor was installed in DWR-MKIII buoy, and wave parameters and wave spectra measured by the SVS-603 were compared with the data measured by DWR-MKIII. Based on the results, the wave inversion technology of the SVS-603 sensor was studied in detail, and the difference and reliability comparison between the wave spectra smoothened on time domain and frequency domain were made. Results showed that the wave spectra smoothened on time domain were more close to those of the DWR-MKIII, whereas, the wave spectra smoothened on frequency domain were employed, spectra on low frequencies were unfiltered, and wave peak periods were oscillated.This research can provide more accurate wave algorithms for the development of acceleration principle wave equipment.

In view of the present mechanical current meter big power consumption, lower attitude measuring precision, large volume, complex maintenance, velocity of flow measurement data of the single, we design a controller based on local area network (controller area network,CAN) bus STM32F103RCT6 as the control core of current meter measurement and control module, low power machinery and gives the overall structure, hardware interface circuit of measurement and control module system, communication protocol, software design and main technical index. The results of marine experiments show that this module not only realizes the signal acquisition and control of current velocity and flow direction, but also realizes the measurement of different current velocity and flow direction through the expansibility of CAN bus, which increases the range of marine hydrological survey and improves its flexibility.