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![Figure 3. Working principle of sub-bottom profiler detection [21].](publication/356679991/figure/fig1/AS:1098194033360897@1638841269020/Working-principle-of-sub-bottom-profiler-detection-21_Q320.jpg)
![Figure 10. Mid-infrared absorption spectra of some gases [92].](publication/356679991/figure/fig4/AS:1098194033360901@1638841269895/Mid-infrared-absorption-spectra-of-some-gases-92_Q320.jpg)
As the ocean development process speeds up, the technical means of ocean exploration are being upgraded. Due to the characteristics of seawater and the complex underwater environment, conventional measurement and sensing methods used for land are difficult to apply in the underwater environment directly. Especially for the seabed topography, it is...
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Due to the complex underwater environment, conventional measurement and sensing methods used for land are difficult to apply directly in the underwater environment. Especially for seabed topography, it is impossible to perform long-distance and accurate detection by electromagnetic waves. Therefore, various types of acoustic and even optical sensin...
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Nowadays, military threats are very close to us and cover terrestrial, aerial, and maritime attacks. This research defines a submarine defence system capable of monitoring and controlling a certain perimeter, based on submersible drones known as Unmanned Underwater Vehicles (UUV) and a grid of stations fixed to the seabed, which provides positionin...
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... In another mode of operation, a CTD instrument may be pulled through the water to identify horizontal variations (spatial variations). CTD instruments can also be fixed at a particular location and depth, allowing researchers to monitor water properties over time (temporal variations) [1]. CTD sensors are exposed directly to seawater. ...
... As depicted in Figure 21, measured conductivity is a linear function of NaCl concentration in the measured range from 0.05 to 0.8 M (NaCl), with a coefficient of determination R sq = 0.995. The conductivity cell constant (k C ) is a geometrical parameter of electrodes related to the measured transimpedance as described in (1). By measuring the transimpedance Z at a known conductivity of the sample, k C can be determined. ...
... As depicted in Figure 21, measured conductivity is a linear function of NaCl concentration in the measured range from 0.05 to 0.8 M (NaCl), with a coefficient of determination Rsq = 0.995. The conductivity cell constant (kC) is a geometrical parameter of electrodes related to the measured transimpedance as described in (1). By measuring the transimpedance Z at a known conductivity of the sample, kC can be determined. ...
The design, fabrication and characterization of a cost-efficient oceanographic instrument with microfabricated sensors for measuring conductivity, temperature and depth of seawater are presented. Conductivity and temperature sensors were fabricated using MEMS technology, which allows for customized small footprints and low production costs. Dedicated electronics for reading, processing and storing acquired sensor data are described. The developed instrument enables the measurement of seawater conductivity in a range from 4 mS/cm to 70 mS/cm. The conductivity measurement is temperature-compensated in the range from 2 °C to 40 °C, with an accuracy of ±0.1 mS/cm. The temperature sensor’s stability is 0.025 °C. The depth/pressure measurement range is up to 2000 m/200 bar, with a resolution of 0.1 bar. Temperature and conductivity sensor performance was assessed using laboratory equipment and designed electronics. The conductivity sensor was temperature-compensated to 0.01 mS/cm. The conductivity sensor electrode corrosion effect is presented below and was eliminated through adaptation of a signal acquisition circuit. Custom software was developed for monitoring critical conductivity sensor parameters (currents, voltages). A variation of 0.4% between cell conductance currents and voltages was established as a criterion for stable conductivity sensor operation.
... A S THE depth of seawater is one of the most basic and important physical quantities in the marine environment, hydraulic pressure (HP) sensors play a significant role in underwater environmental monitoring [1]. When the underwater robot dives to a certain location, it needs to measure the HP at the location and the surrounding underwater disturbances. ...
Enhancing marine sensory capabilities is a crucial pathway to advance human understanding of the oceans. Triboelectric Nanogenerators (TENG), known for their high-quality self-powered sensing properties, present a novel solution for underwater sensing. In this paper, we introduce a new hydraulic pressure TENG (HP-TENG) structure designed specifically for hydraulic pressure measurements. When the external hydraulic pressure changes, the slider slides along the cylinder shell and the contact area between the fluorinated ethylene propylene (FEP) film and the aluminum electrodes changes, thus generating the electrical signal. The electromechanical performance characteristics of the HP-TENG are experimentally measured. Through underwater experiments, we validate the ability of HP-TENG to measure water pressure and demonstrate its ability to perceive the magnitude of pressure and the speed of pressure change with a linear correlation coefficient greater than 0.995. Furthermore, we provide insights into its applications in real-time control and underwater disturbance detection to demonstrate its utility. The sensor has the advantages of low production cost, self-powered, environmentally friendly, high sensitivity to environmental disturbances (0.954V/N), good mechanical reliability and electrical stability. The experimental results indicate that the proposed sensor exhibits promising potential for environmental monitoring, emphasizing its utility in enhancing ocean perception for underwater robots.
... With advancements in marine science, autonomous underwater vehicles (AUVs) have been increasingly applied in both military and civilian fields. Underwater acoustic (UWA) communication plays an important role, and numerous studies on this topic have been conducted [1][2][3][4][5]. Wu et al. proposed a robust and lowcomplexity synchronization technique in the time and Doppler domains, which is capable of handling adverse channel conditions [6]. ...
Spread spectrum technology has been widely employed for positioning and communicating with autonomous underwater vehicles (AUVs), but conventional spread spectrum sequences lack confidentiality and reliability in UWA channel. Considering the limitations of conventional sequences and the characteristics of underwater acoustic (UWA) channel, a composite chaotic orthogonal sequence (CCOS) based on the UWA channel is proposed. The confidentiality of the CCOS is superior to that of the m‐sequence, while the autocorrelation performance of the CCOS is superior to that of the orthogonal sequence. Moreover, the CCOS can compensate for the imbalance of logistic chaotic sequence when assigned certain initial values. Acquisition is a crucial component of accessing the spread spectrum signal; therefore, the acquisition performance indicates the applicability of the CCOS. The source–target model is established to simulate communication with an underwater moving target. To simulate the acquisition process, a parallel algorithm based on fast Fourier transform is adopted, and the entire simulation process is completed based on the BELLHOP ray acoustic model. Through data processing, the Doppler shift error is less than half of the frequency‐search element. Furthermore, the acquisition probabilities of the CCOS with different numbers of bits are over 90%, which demonstrates the reliability of the CCOS.
... The underwater navigation system is critical in order for underwater vehicles to perform activities that require long-duration and accurate positioning [1,2]. Given the absence of Global Navigation Satellite System (GNSS) signals underwater, the principal navigation systems predominantly rely on the Inertial Navigation System (INS), complemented by Doppler Velocity Log (DVL), underwater acoustic transponders, and geophysical field data [3,4]. ...
... Let z i indicate the bathymetric value of the point x i = b i,x , b i,y . The fitted function between x i and z i can be expressed as Equation (2). ...
Accurate positioning is the necessary basis for autonomous underwater vehicles (AUV) to perform safe navigation in underwater tasks, such as port environment monitoring, target search, and seabed exploration. The position estimates of underwater navigation systems usually suffer from an error accumulation problem, which makes the AUVs difficult use to perform long-term and accurate underwater tasks. Underwater simultaneous localization and mapping (SLAM) approaches based on multibeam-bathymetric data have attracted much attention for being able to obtain error-bounded position estimates. Two problems limit the use of multibeam bathymetric SLAM in many scenarios. The first is that the loop closures only occur in the AUV path intersection areas. The second is that the data association is prone to failure in areas with gentle topographic changes. To overcome these problems, a joint graph-based underwater SLAM approach that fuses bathymetric and magnetic-beacon measurements is proposed in this paper. In the front-end, a robust dual-stage bathymetric data-association method is used to first detect loop closures on the multibeam bathymetric data. Then, a magnetic-beacon-detection method using Euler-deconvolution and optimization algorithms is designed to localize the magnetic beacons using a magnetic measurement sequence on the path. The loop closures obtained from both bathymetric and magnetic-beacon observations are fused to build a joint-factor graph. In the back-end, a diagnosis method is introduced to identify the potential false factors in the graph, thus improving the robustness of the joint SLAM system to outliers in the measurement data. Experiments based on field bathymetric datasets are performed to test the performance of the proposed approach. Compared with classic bathymetric SLAM algorithms, the proposed algorithm can improve the data-association accuracy by 50%, and the average positioning error after optimization converges to less than 10 m.
... In order to address these challenges, there is a new approach based on machine learning for monitoring the contaminating elements in the marine water. For instance, Goncalves et al. [59,60] suggested a polluted site mapping system using radio frequency and a remotely operated autonomous aerial vehicle capable of continuously monitoring plastic waste on the coast. The development of devices to control plant blooms that can cause serious contamination has been a very important area of research. ...
Actually, water is an important resource in different domains namely farming, healthcare and tourism, as well as in industry. Every living being is depending on adequate amounts of good quality water for its survival and development. The global water system is driven by both evaporation and transpiration, as well as condensation, rainfall and runoff, and typically reaches the ocean. Predicting water quality based on different parameters is essential for the design, decision making and management of this resource. Over the past two decades, water quality modeling has enjoyed considerable growth through the implementation of machine learning techniques. This review examines the various supervised, unsupervised, semi-supervised, and ensemble machine learning models implemented for the prediction of groundwater quality parameters. Furthermore, this study listed some water domains where machine learning is used to predict and monitor water quality.
... While they are exceptional over ultra-long range underwater communications [5,6], they are also highly insecure, omni-directional and suffer from very low data rates, especially over these distances [7,8]. For many underwater communication needs such as exploration, research, short range submersibles or military operations [9][10][11], the separation between the sender and receiver is often a far shorter distance than required for the use of acoustic waves. In these instances communication using standard, transversal electromagnetic waves would be far more beneficial for their increased data transmission rates and high level of security [12,13]. ...
Quantum communication has been at the forefront of modern research for decades, however it is severely hampered in underwater applications, where the properties of water absorb nearly all useful optical wavelengths and prevent them from propagating more than, in most cases, a few metres. This research reports on-demand quantum light sources, suitable for underwater optical communication. The single photon emitters, which can be engineered using an electron beam, are based on impurities in hexagonal boron nitride. They have a zero phonon line at ∼436 nm, near the minimum value of water absorption and are shown to suffer negligible transmission and purity loss when travelling through water channels. These emitters are also shown to possess exceptional underwater transmission properties compared to emitters at other optical wavelengths and are utilised in a completely secure quantum key distribution experiment with rates of kbits s⁻¹.
... Recent advancements in underwater acoustics highlight the critical role of ultrasonic transducers in enhancing the versatility and efficiency of marine applications [1]. Broadband underwater ultrasonic transducers have become essential for significant breakthroughs in fields of sonar detection [2], underwater communication [3], active noise cancellation systems [4], etc. ...
Recent advancements in marine technology have highlighted the urgent need for enhanced underwater acoustic applications, from sonar detection to communication and noise cancellation, driving the pursuit of innovative transducer technologies. In this paper, a new underwater thermoacoustic (TA) transducer made from carbon nanotube (CNT) sponge is designed to achieve wide bandwidth, high energy conversion efficiency, simple structure, good transient response, and stable sound response, utilizing the TA effect through electro-thermal modulation. The transducer has potential application in underwater acoustic communication. An electro-thermal-acoustic coupled simulation for the open model, sandwich model, and encapsulated model is presented to analyze the transient behaviors of CNT sponge TA transducers in liquid environments. The effects of key design parameters on the acoustic performances of both systems are revealed. The results demonstrate that a short pulse excitation with a low duty cycle could greatly improve the heat dissipation of the encapsulated transducer, especially when the thermoacoustic response time becomes comparable to thermal relaxation time.
... Swimming, a phenomenon deeply ingrained in the evolutionary tapestry of nature, continues to captivate the scientific and engineering communities [7,8]. Fish swimming, in particular, has been a subject of keen interest, offering profound insights into the optimization of underwater vehicles and biomimetic robots. ...
... This unique methodology aims to provide insights into and support the design of the streamlined shape for robotic fish. Swimming, a phenomenon deeply ingrained in the evolutionary tapestry of nature, continues to captivate the scientific and engineering communities [7,8]. Fish swimming, in particular, has been a subject of keen interest, offering profound insights into the optimization of underwater vehicles and biomimetic robots. ...
This paper conducts a comprehensive analysis of undulating and oscillatory movements in fish, utilizing numerical simulations to explore correlations among fin thrust and swimming speed. The study distinguishes itself through a unique approach by employing kinematic equations of motion control, specifically in oscillation and undulation, for computational fluid dynamics. Despite increasing energy loss with undulation, the study reveals a reduction in power demand with oscillation, underscoring its effectiveness in achieving desired speeds. The dynamics of undulating fins in aquatic and aerial locomotion remain insufficiently understood. The trade-off between more energy-consuming but highly propulsive movements or simpler and faster movements requires sophisticated design techniques to reduce volume. The geometry, developed using Rhino 6 software, incorporates precise fluid resistance calculations conducted with Ansys Fluent 19. Spanning flow velocities from 1 to 4 m/s were used for the simulation condition. Critical factors such as flexibility, viscosity, and shape change were meticulously examined for their impact on efficiency enhancement.
... Mobile Mapping Systems (MMS) combine sensors like LiDAR, cameras, and GPS, mounted on vehicles, capturing detailed geospatial data along road networks and urban areas for infrastructure planning, navigation, and asset management [59,60]. Underwater Remote Sensing employs sonar and acoustic sensors for mapping and monitoring underwater environments, benefiting marine resource management, habitat monitoring, and underwater archaeology [61]. Geophysical Remote Sensing techniques like ground-penetrating radar (GPR), electromagnetic induction (EMI), and magnetometry study subsurface features, archaeological sites, and soil properties, enhancing our understanding of the Earth's surface and subsurface and supporting informed decision-making in various fields [60,62]. ...
Remote sensing and GIS serve as indispensable tools in the ongoing battle against air pollution and in the quest to improve air quality. These technologies, including satellite imagery and aerial mapping, provide a wealth of data pertaining to atmospheric conditions and the presence of pollutants. Through the integration of this data within Geographic Information Systems (GIS) software, researchers and policymakers gain valuable insights into the distribution and concentration of pollutants such as sulphur dioxide, nitrogen oxides, and particulate matter, all of which have significant implications for human health and the environment. The utilization of remote sensing allows for the monitoring of pollutant movement over large geographical areas, enabling the identification of pollution sources and the assessment of their impact on surrounding regions. GIS, on the other hand, facilitates the visualization of this data through the creation of maps and spatial analyses, offering a comprehensive understanding of air pollution patterns and their correlations with demographic characteristics and land use practices. By leveraging these technologies, decision-makers can pinpoint areas with heightened pollution levels, such as urban centers or regions with extensive industrial activity. Armed with this information, targeted mitigation strategies can be devised and implemented to alleviate pollution burdens and safeguard public health. Furthermore, the integrated approach provided by remote sensing and GIS enables the monitoring of the effectiveness of these strategies over time, allowing for adjustments and refinements as needed. In the context of Chhattisgarh, India, where air pollution poses a significant challenge, the application of remote sensing and GIS holds particular promise. By highlighting the advancements and innovations in these fields within the state, we aim to underscore the potential for informed decision-making and proactive measures to combat air pollution and enhance air quality for the benefit of all residents. In this review paper we aim to highlight the advancements in this field that has occurred in controlling air pollution in the state of Chhattisgarh, India.
... Deploying these mission payloads predominantly relies on manned vessels, considerably increasing the human and material costs. A promising alternative is to employ large AUVs to deliver unmanned systems, such as seabed support stations and underwater resource detection instruments [5]. Nonetheless, the intricate marine environment introduces obstacles in deploying mission payloads. ...
This study verifies the effects of deployment parameters on the safe separation of Autonomous Underwater Vehicles (AUVs) and mission payloads. The initial separation phase is meticulously modeled based on computational fluid dynamics (CFD) simulations employing the cubic constitutive Shear Stress Transport (SST) k-ω turbulence model and overset grid technologies. This phase is characterized by a 6-degree-of-freedom (6-DOF) framework incorporating Dynamic Fluid-Body Interaction (DFBI), supported by empirical validation. The SST k-ω turbulence model demonstrates superior performance in managing flows characterized by adverse pressure gradients and separation. DFBI entails computationally modeling fluid–solid interactions during motion or deformation. The utilization of overset grids presents several advantages, including enhanced computational efficiency by concentrating computational resources solely on regions of interest, simplified handling of intricate geometries and moving bodies, and adaptability in adjusting grids to accommodate changing simulation conditions. This research analyzes mission payloads’ trajectories and attitude adjustments after release from AUVs under various cruising speeds and initial release dynamics, such as descent and angular velocities. Additionally, this study evaluates the effects of varying ocean currents at different depths on separation safety. Results indicate that the interaction between AUVs and mission payloads during separation increases under higher navigational speeds, reducing the separation speed and degrading the stability. As the initial drop velocities increase, fast transition through the AUV’s immediate flow field promotes separation. The core of this process is the initial pitch angle management upon deployment. Optimizing initial pitching angular velocity prolongs the time for mission payloads to reach their maximum pitch angle, thus decreasing horizontal displacement and improving separation safety. Deploying AUVs at greater depths alleviates the influence of ocean currents, thereby reducing disturbances during payload separation.
