• Journal of Ocean Engineering and Technology
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• v.23 no.6
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• pp.44-52
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• 2009

In this study, the behavior of a breasting dolphin with various dolphin heights and formations in the coastal area of Incheon was investigated. The dynamic deflection, shear stress, and moment of the pile were analyzed using the coefficient of the horizontal subgrade reaction that resulted from loading tests of different DWT (Dead Weight Tonnage). In the case of a vertical pile type dolphin, the deflection, shear stress, and moment increased as the dolphin height increased. In the case of the battered pile type dolphin, small values of shear stress and moment were shown at a low dolphin height, and the characteristics of the dynamic behavior of the dolphin showed that the deflection, shear stress, and moment increased as the pile slope of the dolphin decreased or the DWT increased.

• Journal of Fisheries and Marine Sciences Education
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• v.20 no.1
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• pp.121-126
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• 2008

This study presents the results of basic sighting surveys conducted for dolphin watching from 2004 to 2006 in the northeastern waters of Jeju. The sighting probability of dolphins (bottlenose dolphin, Tursiops truncatus) was 71.9% (82 sightings out of 114 surveys). The dolphin's attractive behaviors observed included leaping, tail or peduncle slapping and surfing. The findings of this study provide useful baseline data for dolphin watching in the northeastern waters of Jeju.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.143-150
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• 2005

In this study, to evaluate the collision behaviors of the navigating vessel and the dolphin protective system protecting the substructures of bridges, the numerical simulation was performed. The analysis model of vessel bow that the plastic deformations are concentrated was composed by shell elements, and the main body of vessel was modeled by beam elements to represent the mass distribution and the change of potential energy. The material model reflecting the confining condition was used for the modeling of the filling soil of dolphin system. The surrounding soil of the dolphin system was modeled as nonlinear springs. As results, it is verified that the dolphin system can adequately dissipate the kinematic energy of the collision vessel. The surrounding soil of the dolphin system is able to resist the collision force of the vessel. And the major energy dissipation mechanism of collision energy is the plastic deformation of the vessel bow and the dolphin system.

• Journal of Ocean Engineering and Technology
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• v.13 no.3 s.33
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• pp.3-11
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• 1999

Optimum design of mooring dolphin is numerically investigated. Design optimization problem of moring dolphin is first formulated. Geometry and cross sections of piles are used as design variables. Design objective is the total weight of steel piles of mooring dolphin, and the constraints of stress, penetration depth, lower and upper bounds on design variables are imposed. Based on the design variable linking and fixing, several class of design variations are sought. For the numerical optimization, both PLBA(Pshenichny - Lim - Belegundu - Arora) program and DNCONF subroutine code in IMSL library are used. For a dolphin structure with 20 steel piles, vertical and inclined, optimum designs for different cases are successfully obtained, which can be applied for the mooring of a very large floating structure.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.6
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• pp.704-713
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• 2018

Globally, the survival of many marine mammals is threatened by entanglement in fishing gear and there is also a high bycatch in Korea. This study analyzed the bycatch data of most cetacean species for Korean waters from 2011 to 2017, including the narrow-ridged finless porpoise Neophocaena asiaeorientalis, common dolphin Delphinus delphis, common minke whale Balaenoptera acutorostrata, and Pacific white-sided dolphin Lagenorhynchus obliquidens. A total of 12,262 cetaceans were captured as bycatch. In the Yellow and South Seas, the main species affected was the narrow-ridged finless porpoise, with 82.9% caught in stow nets and 11.5% captured in trawls. In the East Sea, the common minke whale, common dolphin, and Pacific white-sided dolphin were reported. The main common minke whale bycatch (43.5%) was in set nets, while common dolphins (49.0%) and Pacific white-sided dolphins (91.4%) were mainly caught in gill nets. The narrow-ridged finless porpoise, common dolphin, and common minke whale were most commonly reported in March, April, and May, while the Pacific white-sided dolphin was most frequently captured as bycatch in January and December. Each of these factors (season and gear responsible for bycatch) depended on the characteristics of the cetacean species. To conserve cetaceans, it is necessary to reduce the bycatch.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.237-244
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• 1998

Optimum design of mooring dolphin is numerically investigated. Design optimization problem of mooring dolphin is first formulated. Geometry and cross sections of piles are used as design variables. Design objective is the total weight of steel piles of mooring dolphin and the constraints of stress, penetration depth, lower and upper bounds on design variables are imposed. Based on the design variable linking and fixing, several class of design variations are sought. For the numerical optimization, both PLBA( Pshenichny-Lim-Belegundu-Arora) program and DNCONF subroutine code in IMSL library are used. For a dolphin with 20 steel piles, vertical and inclined, optimum designs for different cases are successfully obtained, which can be applied for the mooring of a large floating structure.

• Smart Structures and Systems
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• v.21 no.3
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• pp.321-333
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• 2018

Simplified Dolphin Echolocation (SDE) algorithm is a recently developed meta-heuristic algorithm. This algorithm is an improved and simplified version of the Dolphin Echolocation Optimization (DEO) method, based on the baiting behavior of the dolphins. The main advantage of the SDE algorithm is that it needs no empirical parameter. In this paper, the SDE algorithm is applied for optimization of three well-studied frame structures. The designs are then compared with those of other meta-heuristic methods from the literature. Numerical results show the efficiency of the SDE algorithm and its competitive ability with other well-established meta-heuristics methods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3B
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• pp.281-287
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• 2009

In this study, the behavior of breasting dolphin caused by the maximum wave height in the coastal area of Incheon has been investigated. The dynamic deflection, shear stress and moment of pile are analyzed using the coefficient of horizontal subgrade reaction resulted from loading tests for different DWT (Dead Weight Tonnage). The dynamic characteristics of pile in accumulated and dredged soils show almost the same pattern. It is shown that the resistance of dolphin to external load increases as the diameter of pile increases. The bettered pile dolphin is more than 10 times stable than the vertical pile type based on the study of dynamic characteristics of dolphin.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.103-110
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• 2020

Bio-inspired underwater robots have been studied to improve the dynamic performance of fins, such as swimming speed and efficiency, which is the most basic performance. Among them, bio-inspired soft robots with a compliant tail fin can have high degrees of freedom. On the other hand, to improve the driving efficiency of the compliant fins, the stiffness of the tail fin should be changed with the driving frequency. Therefore, a new type of variable stiffness mechanism has been developed and verified. This study, which was inspired by the anatomy of a real dolphin, assessed a process of designing and manufacturing a robotic dolphin with a variable stiffness mechanism. By mimicking the vertebrae of a dolphin, the variable stiffness driving part was manufactured using subtractive and additive manufacturing. A driving tendon was placed considering the location of the tendon in the actual dolphin, and the additional tendon was installed to change its stiffness. A robotic dolphin was designed and manufactured in a streamlined shape, and the swimming speed was measured by varying the stiffness. When the stiffness of the tail fin was varied at the same driving frequency, the swimming speed and thrust changed by approximately 1.24 and 1.5 times, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.6
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• pp.940-946
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• 2015

The Indo-Pacific bottlenose dolphin Tursiops aduncus commonly inhabits the coastal waters of Jeju Island, Korea. An investigation was conducted using data from vessel sightings and point sightings from land. During 40 days of vessel sighting surveys between 2007 and 2010, a total of 18 dolphin groups were encountered. The overall sighting rate was 0.01 group/n.m. Most Indo-Pacific bottlenose dolphins were sighted within 500 m of the northern coast of Jeju Island during surveys. Also, dolphin groups were observed 47 times during 109 days of shore-based surveys conducted between 2011 and 2015. The results of a dolphin distribution survey conducted in 2011 were generally similar to the results of previous surveys. However, there were no dolphin sightings from 2012 in Hanllim-eup, in the north-western part of the island, where dolphins were sighted frequently until 2011, whereas dolphin observations increased in the southern part of the island. The mean group size was 35.4 (SD=18.08) individuals. The most frequently sighted group size was 36-40 individuals. To conserve resident dolphins off Jeju Island, long term sighting surveys and environmental assessment are required to monitor their distribution patterns.