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.

To meet the demand of in situ accurate monitoring of seawater dissolved oxygen using a domestic sensor, an optical seawater dissolved oxygen sensor was developed using modulation-demodulation digital quadrature lock-in amplification detection technology. The developed sensor achieved accurate detection of weak fluorescence lifetime. The dissolved oxygen sensor temperature coefficient was calibrated through polynomial regression analysis. A polynomial quantitative algorithm model of the fluorescence phase, dissolved oxygen concentration, and temperature was established to achieve the accurate detection of dissolved oxygen. Under a random temperature and dissolved oxygen concentration within the calibration test temperature range, the temperature measurement accuracy of the sensor is ±0.1 ℃ and the accuracy of dissolved oxygen measurement is ±0.1 mg/L after calibration.

Considering the poor safety and controllability of a lithium iron phosphate battery in marine exploration robots, a charge/discharge management system based on an STM32 single-chip microcomputer is proposed. The hardware and related circuits of the main control module, single-battery voltage monitoring module, and equalization module are designed. The control mode adopts a master-slave topology. Through hardware tuning and optimization, the work area of the circuit board is considerably reduced, and the cooling performance of the system is improved. Test results show that the voltage, current, and temperature data are correctly displayed; the maximum detection deviation of single-battery voltage is 0.96%; and the maximum single-battery voltage exceeds the average voltage of a battery pack by 6 mV. Thus, the balancing effect is good.

In this study, a design is proposed based on the cross-platform Modbus library Libmodbus’ navigational sea surface temperature monitoring system to address the current situation in which the sea surface water temperature observations are mainly conducted via manual processes. In this design, the sensors located under the waterline toward the side of the ship are used to obtain the surface water temperature. The RS485/Modbus protocol is adopted to implement a multistation multipoint network to obtain a distributed system for automatically obtaining the sea surface temperature. The host computer is based on the Modbus-RTU protocol and involves cyclic redundancy check to ensure remote control of the water temperature sensor and the reliability as well as safety of the surface water temperature collection function. The designed system is not only stable, simple, and easy to operate but also portable and scalable. The experimental results show that the designed system can monitor the sea surface temperature in a stable and reliable manner and realize online measurement of the surface water temperature with respect to a ship.

In this study, theoretical and statistical analysis of relevant influencing factors, including the signal coherent accumulation time, connection between the vessel navigation state and sea clutter area and the joint domain study of measured data, are conducted to facilitate the detection of target vessels from the sea clutter of a compact high frequency surface wave radar. The obtained results provide a range of signal coherent integration time. The results show that the potential dwell time of long-distance non-maneuvering target in sea clutter is over the signal coherent integration time. Furthermore, the Doppler variation induced by the non-maneuvering targets in sea clutter is limited. However, the sea clutter and non-maneuvering targets exhibit major differences in the space-time and polarization domains, which can be considered as an important criteria for target detection from sea clutter.

Herein, an external-drive rotary pressure exchanger with tilted rotor channel was proposed to improve the performance of the exchanger. Energy recovery efficiency and volume mixing ratio were used as performance indexes. We used commercial CFD software Fluent to simulate the model and compared it with the simulation data of a DC out-of-channel-drive rotary pressure energy exchanger. Results showed that when the processing volume was equal, both the energy recovery efficiency and volume mixing ratio decreased with rotor speed increasing. Under the same rotor speed, with the rotor incline angle changed, the energy recovery efficiency changed to no more than 0.04%. The rotor incline angle had a significant impact on the volume mixing ratio. The results can be a guidance for improving the performance of external-drive rotary pressure exchanger.

To pre-estimate the full-scale fishing ship resistance, this paper takes a 11.75 m fishing ship as the research object,and a complete set of methods is developed to convert the numerical simulation result of the ship model to a full-scale ship based on the CFD method. The results denote that this method can effectively estimate the hull resistance of the fishing ships and reduce the design cost. Based on the vertical hydrodynamic of the ship, the reasons for the peak point and valley point on the curve of the resistance are analyzed explaining the manner in which the resistance increases initially and subsequently decreases with increasing speed of the ship.

In order to study the wave making technology of active striking box in a wide glass water tank（10 m×0.5 m）, this paper designed a wave making system based on a PLC motion controller, servo motor and driver, industrial computer and wave height acquisition instrument. The system implements an active wave making algorithm in the PLC motion control program according to the hydrodynamic parameters. It not only uses the AC servo driver and the motor of the same size to complete the wave making undulations of the wedge plate, but also controls the overall state of the wave making machine system through the man-machine interface on the industrial computer. To improve the control accuracy, the closed-loop control of wave height and frequency based on a PID algorithm is added to the external closed-loop control of the servo driver. A practical application shows that the system can ensure the accuracy and stability of control by real-time feedback of the waveform, and achieve the purpose of active wave making.

In this study, a monitoring alarm and technical remote support system, featuring a monitoring alarm, maintenance and fault diagnosis material sharing, operational work software sharing, and online support, has been designed and developed based on the B/S structure and Java server pages (JSP) as a development tool with respect to the mesoscale automatic weather stations. The developed system provides technical and software support for realtime and effective fault monitoring, maintenance, and fault diagnosis at automatic weather stations. The operation results denote that the proposed design improves the time efficiency and accuracy of the equipment support with respect to the automatic weather stations as well as the professional competence of its personnel.

A marine ecological-environment monitoring system based on ZigBee technology and an embedded platform was designed in this study to solve the problem that communication cables are easily corroded and damaged and have complicated wiring requirements. A small wireless sensor network was constructed for ocean stations or buoys using a wireless sensor network to realize wireless data transmission between the master controller and sensors. The experimental results showed that the data transmission of the wireless sensors network was stable and reliable. This study has certain practical significance and provides great convenience for marine ecological environment monitoring.

In this study, we investigated the weak signal detection technology of seawater nutrient salt based on the principle of photoelectric detection and phase-locked amplification technology. In hardware, the weak voltage signal of the photoelectric diode was preamplified to filter the noise using the analog phase-locked amplifier circuit. Based on the STM32F401 hardware platform, the improvement of the variable step size least mean square adaptive filtering algorithm was used in software to filter the noise. Then, the weak voltage signal of the seawater nutrients was accurately detected. Long-term simulation and experimental data denote that the weak signal detection scheme of the seawater nutrients proposed in this study is considerable significance to improve the data accuracy of the nutrient sensor.

According to the data management requirements of seafloor observatory network, the function model of data management system was established, and the related implementation algorithms of key technologies such as data communication, equipment management, fault diagnosis and data quality control were designed. The data management system for seafloor observatory network was developed based on Socket network programming, MySQL database technologies and modular design idea. The sea trial results show that the data management system has realized the functions of real-time data acquisition, state monitoring, data classified storage and data sharing, and it has the advantages of stable and reliable operation and strong expandability.

The abnormal methane concentration in cold seep water is not only an important indicator of natural gas hydrate occurrence in the seabed, but also of great significance to the study of the marine environment and global climate change. Based on the analysis and study of the characteristics of the existing cold seeps, a inversion method for quantitatively obtaining methane concentration distribution in cold seep water based on single beam sounding data was established. Taking the cold seep area in the northwest slope of the Kurile Basin in the Okhotsk Sea as an example, the concentration of dissolved methane in cold seep water of the study area was calculated by using the 12 kHz and 20 kHz acoustic echo sounding data obtained from the sea trial. Compared with the chromatographic analysis results of the cold seep water samples, the calculation results of this inversion method were in good agreement with the field measured data. And due to the advantages of beam angle and bubble resonance effect, the inversion results corresponding to 12 kHz sounding data were closer to the measured data. At the same time, relevant calculation results showed that the dissolved methane in the water of the survey region mainly came from the free methane gas released from cold seeps. In addition, the field observation results showed that the hydrated crust on the surface of the cold seep bubble in hydrate stability zone could significantly prolong the floating time and distance of the bubbles.

This paper presented a design scheme of communication function of ship meteorological instrument based on Ethernet technology. Combining S3C2440A and DM9000AE chips, the communication board of ship meteorological instrument was designed. The test results show that the design realizes the Ethernet communication between the ship meteorological instrument and other shipborne equipment, fully meeting the requirements of the ship meteorological instrument for Ethernet communication.

When light is transmitted in water, it is severely attenuated by water absorption and scattering of suspended particles, resulting in low contrast and color distortion of underwater optical image. In this paper, a method of underwater image enhancement based on transmittance optimization and color calibration was proposed. According to the underwater optical imaging model, the transmittance was estimated based on the principle of minimum information loss, and the estimated accuracy of transmittance was improved by combining with guidance filtering. The clear underwater image was obtained by inverse solution of the underwater imaging model. The histogram equalization was utilized to further improve image contrast, and white balance method was used to calibrate color. Experimental results show that this method can effectively remove the blur caused by backscattering, improve the contrast and clarity of the image, and correct the color imbalance.

An experimental comparison device for dissolved oxygen determination has been built in the laboratory to explore the difference between optical method and classical Winkler titration under different temperature and dissolved oxygen concentration conditions. The results show that the correlation between optical sensors and classical Winkler titration is good with correlation coefficient higher than 0.998 at different temperatures. Dissolved oxygen measured by optical sensors is slightly lower than that of classical Winkler titration in the concentration of dissolved oxygen lower than 4 mg·L^-1. The difference values between optical sensors and classical Winkler titration are mainly concentrated in -0.25~0.25 mg·L^-1 when the concentration of dissolved oxygen is higher than 4 mg·L^-1. The results measured by two kinds of optical sensors are close, and the difference is less than 0.10 mg·L^-1. This result proves that optical sensor is a reliable method for detecting dissolved oxygen, which can be applied to marine survey and conventional on-line monitoring in aquaculture areas.

According to the measurement principle of the ocean current signal sensor, the technical scheme of the acquisition amplifier circuit was proposed. Aiming at the characteristics of large noise of the collected signal, the weak signal of the ocean current electric field was filtered and extracted, realizing the compensation amplification of the in-phase component of the signal. To a certain extent, it overcame the strong interference of the induced electric field caused by the sensor when it sank, and improved the accuracy of circuit measurement. At the same time, the principle of multi-stage amplification was adopted to amplify the weak signal to the observable range of the instrument. It is verified by Multisim simulation software that the acquisition amplifier circuit meets the design requirements and amplifies the signal to 105~106 times while ensuring the quality of the signal.

In this paper, the ocean-atmosphere-wave coupled model, COAWST, was used to conduct two sets of 72hour simulation tests centered over the East China Sea. The impacts of dynamic wave processes on shortterm weather simulation were analyzed by comparing the two tests, one of which considered the dynamic wave processes and the other not. The results revealed that the simulation of sensible and latent heat flux would be enhanced if considering the wave processes. Consequently, wetter and warmer air at the sea surface was detected, leading to lower sea level pressure (SLP) and acceleration on convective activity. The changes of circulation would strengthen the local wetter and warmer difference, which made for the generation of positive feedbacks. The wettest and warmest difference was detected over the northwestern area of the South China Sea along with the Philippine waters. In addition, the difference would decrease with the height, and finally disappear near the 500 hPa height.

Since the existing ocean buoys lack effective monitoring and management of the power supply, a method based on LabVIEW and SQL server programming, combining with C8051F021 microcontroller hardware, was put forward. The shore station terminal server monitoring software and the hardware circuit installed on the buoy were designed. By means of realtime communication such as network or Beidou communication, the realtime monitoring and management of the power supply on buoy was realized, and the ability of utilizing and managing the power supply on buoy was improved.

By focusing on the bottleneck of network transmission performance in the distributed sharing of ocean spatio-temporal monitoring data, the representation and transmission mode in distributed cloud computing environment was proposed to establish an efficient service-oriented sharing framework for ocean spatiotemporal data. While adopting GML, KML and GeoJSON to encode ocean observing data, a data transmission mode based on real-time compression was proposed. The applicability of compression algorithms to ocean monitoring data enhanced the efficiency of data real-time transmission. Finally, based on the Ali cloud computing platform, a distributed GIS system for marine applications was designed and deployed as the testbed, and systematic experiments were conducted. The experimental results reveal that using the combination of GeoJSON and Deflate-6 / GZIP to establish the ocean observing spatiotemporal data representation and transmission mode shows better applicability and more outstanding performance advantages in distributed sharing and integration system.

According to the problems of the handheld launching method of expendable bathythermograph (XBT) , such as measurement disturbances from operators, an automatic drawing mechanism for the probe plug in the sea trials was proposed in this work. The lever was adopted here to magnify the tensile force in order to draw out the plug in limited stroke, which would make sure the full-automatic launching of expendable probes. The effectiveness and reliability of this mechanism has been verified by the corresponding laboratory tests. The success rate of probes deployment is over 95% and the mean time of the operation time is shortened more than 50%. The mechanism can also be used into various automatic launchers of expendable probes through a little configuration adjustment, which has a wide field of applications.

In order to effectively improve the accuracy of extreme value detection of weak photoelectric signal, through the analysis of the change rules of signals measured, a filtering algorithm for the extremum detection of the target signals with high precision was proposed, and the solutions to the signal detection under ideal conditions and strong interference conditions were also discussed. Firstly, in this algorithm, an improved dynamic threshold method was used to obtain the initial extremum data. Then the acquisition value was filtered by the combination of two kinds of filtering method, which were the median absolute deviation based moving filtering and the weighted average filtering. Finally, the extreme value of the signal was obtained. The test results show that the measurement results of the algorithm are consistent with the actual value, the minimum average relative error is controlled at about 0.1%, which meets the accuracy requirement. The accuracy and stability of this algorithm are higher than those of the traditional method. The research provides a certain reference for the high accurate measurement of peak and trough values of weak signals with different waveform.

In order to monitor the overall fuel consumption of ocean vessel in real time, a fuel consumption monitoring system was designed, which was based on flow collection, RTU remote transmission terminal and GPRS DTU technology. Firstly, the system was installed in the fuel filler to carry out measurement and monitoring, and ZigBee wireless communication technology was used to complete the wireless short distance transmission of data in realtime. Then RTU terminal was applied to collect and process data, and to control the output. Finally GPRS DTU module was employed to convey small amount of data to the shorebased platform in realtime. The practical application indicates that the system not only ensures the accuracy and realtime of fuel consumption information, but also can reduce the cost.