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Due to the dramatic effect of scattering caused by underwater medium, blur commonly occurs in underwater images. Moreover, colors are frequently attenuated in underwater situations, in response to the effect that water selectively absorbs light of different wavelengths. Thus, this color loss becomes one of the key features of underwater images. Most present blur/sharpness evaluation algorithms, which...
Phytoplankton are photosynthesizing microscopic organisms that inhabit the upper sunlit layer of almost all oceans and bodies of fresh water. Its abundance and taxonomic composition have impact on marine ecosystem dynamic and global environment change. Therefore, many researchers pay attention to effectively monitoring phytoplankton quantity and species composition. In order to realize this purpose,...
In this paper, research was carried out to analyze the channel environment in the real sea using data measured in the shallow water of West sea of South Korea. By diversifying the distance between transmitter and receiver, we estimated RMS delay spread and maximum excess delay spread in various channel environments to draw coherence bandwidth and then estimated Doppler spread of received signal to...
This paper focuses on structure optimization of wedge-ring joint of underwater robot based on response surface method (RSM). Experiments for the combination of the 4 parameters of Unmanned Underwater Vehicle's (UUV) wedgering joint are designed in combination with central composite experimental method (CCD). FEA software ANSYS is used to get the respond data of structure stress and mass of wedge-ring...
Gliders are the state-of-the-art autonomous underwater vehicles (AUV) that can operate unattended for roughly a month-long period in the ocean. Given a forward horizontal speed of 0.25 ms−1, gliders can cover ∼ 25 km per day. They trace sawtooth profiles in the ocean by changing buoyancy, observing subsurface temperature, conductivity, and other water properties versus depth, and at the surface, fix...
Due to environment disturbance, interference between the normal modes, and the ambient noise, the spatial correlation between received signals is attenuated. In this paper, we consider the problem of detection performance degradation caused by spatial correlation attenuation, and a broadband correlation detection method based on the normal mode extraction is proposed accordingly. The method extracts...
A formula is developed in this paper to calculate array gain when the plane-wave assumption is not applied. The formula is developped based on the assumption that the noise in the deep water is Gassian white and isotropic. The performance of a vertical linear is analyzed in the range-independent ocean, and also in a weak range-dependent ocean perturbed by random internal waves. Simulation results...
Scouring is the major component of levee failures causing floods thus make the scour monitoring very important. There exist some on field mechanisms to monitor the health of the levees but there is still need for a remote, low cost and real time monitoring system. This paper proposes a real time structural monitoring system by presenting a sensor node with embedded electronics which can be deployed...
Underwater communication and networks are very useful for many applications such as oceanography, environmental monitoring, and underwater surveillance. In this paper, one kind high-speed underwater optical communication and networks are designed for those applications. The system is a half-duplex communication system which combines the transmitter module and the receiver module together. The transmitter...
Multicarrier code division multiple access (MC-CDMA) can be applied in underwater acoustic communication networks to combat the narrow bandwidth of the underwater acoustic channel and multipath fading. Power control is one of the key technologies for the MC-CDMA communication networks. In this paper, we propose a multi-objective power control scheme based on improved particle swarm optimization (PSO)...
The majority of port facilities are decreasing in durability such as corrosion due to salt damage of concrete structures. Therefore, the importance of compressive strength management and diagnostic technology of underwater structures is increasing day by day. While the development of high-precision test equipment on land has been quite established, on the other hand the test equipment for underwater...
Underwater object detection has been always issued problems. Acoustic methods are mainly used, however, detection using acoustic methods in shallow sea is difficult problem. Therefore, we carry out preliminary study adopting direct-current (DC) resistivity method, which use constant current as an active source. For the verification of our method, numerical and water tank experiments are conducted...
This paper designs a plankton particle diameter measurement instrument based on laser projection, which uses laser light source to irradiate the photodiode array, and then collects plankton shape data with the shielding effect. The system reconstructs the morphological characteristics of plankton by using the time axis scanning, to complete the collection and analysis of marine plankton particle size...
This paper focuses on coverage sampling over a given region by a fleet of underwater gliders. The coverage performance is evaluated by the observing uncertainty performed by Objective Analysis (OA). Deployed gliders are commonly restricted to move through transects along which the data collected are convenient for data assimilation. We optimize the initial location and the initial heading of each...
With long industry chain and high-tech, the marine energy industry covers various professional areas, it is a strategic emerging industry. The industry chain of marine energy is composed of upstream, midstream and downstream. By reviewing the literature, defining concepts and sorting the basic theories, this paper made a qualitative analysis of the advantages in developing China's marine energy, and...
Processes and strengths of the ocean's biological carbon pump are significant to the study of ocean carbon cycle. However, the development and the utilization of the ocean's biological carbon pump are greatly limited because of human's limited knowledge of the ocean. Remote sensing methods have played important roles in understanding and exploring the ocean, and the lidar is one of the most outstanding...
In recent years, ultraviolet-visible spectroscopy has been widely used for measurements of water quality in seawater, because full spectrum contains large amounts of information. NO3 can be detected in 220–230 nm, and chemical oxygen demand (COD) and total organic carbon (TOC) can be detected in 280–290 nm. In visible spectrum, water color, turbidity and total suspended solids (TSS) can be measured...
With recent advances and interests in underwater wireless optical communications (UWOC), a proper understanding of optical propagation in underwater environment is more essential. In this paper, we study the channel model taking absorption, scattering and turbulence into account. Then we consider average (ergodic) channel capacity of UWOC links under weak turbulence. The fading coefficient of weak...
Submicron particles play an important role in marine and freshwater ecology and, hence, a measurement system to accurately size them is highly desirable. This paper will propose such a method based on the oblique illumination and high numerical aperture lenses. A setup is suggested to measure the forward and backward scattering patterns. And then a ratio is calculated using these patterns. Simulations...
In this study, performance verification of Resource spread FMT-OFDM system and FMT-OFDM system is carried out through a simulation in the underwater channel environment. The measurement was performed in the shallow water of Geojedo located in Namhae-gun, for the real sea channel modeling. We also analyzed the channel delay profile in different underwater channel environments by distance between transmitter...
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