• Advances in Computational Design
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• 제1권2호
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• pp.175-194
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• 2016

Nature has provided inspiration for most of the man-made technologies. Scientists believe that dolphins are the second to humans in smartness and intelligence. Echolocation is the biological sonar used by dolphins for navigation and hunting in various environments. This ability of dolphins is mimicked in this paper to develop a new optimization method. Dolphin Echolocation Optimization (DEO) is an optimization method based on dolphin's approach for hunting food and exploration of environment. DEO has already been developed for discrete optimization search space and here it is extended to continuous search space. DEO has simple rules and is adjustable for predetermined computational cost. DEO provides the optimum results and leads to alternative optimality curves suitable for the problem. This algorithm has a few parameters and it is applicable to a wide range of problems like other metaheuristic algorithms. In the present work, the efficiency of this approach is demonstrated using standard benchmark problems.

• 한국해양공학회지
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• 제14권4호
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• pp.1-8
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• 2000

The time simulation of motion responses of dolphin-moored BMP in waves is presented. The equation of motion based on Cummin's theory of impulse responses are employed, and solved in time domain by using the Newmark $\beta$ method. The hydrodynamic coefficient and first order wave exciting forces involved in the equations are obtained from a three-dimensional panel method in the frequency domain. The second order wave drift forces and mooring for dolphin system are taken into account. As for numerical example, time domain analysis are carried out for a BMP in irregular wave condition.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.137-139
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• 2003

As a part of numerical and experimental research works for the prediction and improvement of ship's maneuvering performance, a study on the performance analysis of two different rudders has been carried out. While the planform shape and the aspect ratio of the rudders have been fixed, section shape has been changed. Conventional type of HMRI NP section and special type of dolphin-tail section have been employed. Performances of the rudders have been investigated by using CFD and compared with experimental data obtained in a wind tunnel. A commercial CFD program has been used to solve the RANS equations. Two-equation k-ro model has been applied to close the governing equations. Block-structured grids are used in the numerical calculation. Based upon the calculation results, the rudder with dolphin-tail section has shown a possibility of significantly improving rudder performance if utilized as the section of ship rudders.

• 한국지반환경공학회 논문집
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• 제12권1호
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• pp.61-70
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• 2011

충돌보호공은 해저지반에 깊게 근입되어 있으며 돌핀을 의미하는 상부는 단단한 콘트리트 뚜껑으로 막혀지고 쇄석으로 채워진 원형의 속채움 시트파일의 배열로 구성된다. 본 연구에서는 돌핀의 거동을 규명하기 위해 총 7회의 준정적실험과 11회의 동적 원심모형실험을 수행하였다. 주요한 실험적 결과는 다음과 같다. 우선, 준정적실험의 실험적인 힘-변위 결과는 채움재 강성과 관련된 채움 밀도의 변화로부터 구조물의 초기 강성에 대한 영향을 보여준다. 그리고 동일한 변위에서의 에너지 소산을 비교해보면 더 조밀한 채움에서 직경 20m 돌핀은 16%, 직경 30m 돌핀은 23% 정도 소산율이 증가하는 것으로 나타났다. 30m 직경의 돌핀이 더 큰 민감도를 갖는 것은 채움재의 변형률이 에너지소산에 대해 보다 크게 기여하기 때문이다. 동 정적 충돌실험결과, 일반적으로 동적 응답이 준정적 응답보다 26~58%까지 크고 더 작은 변위에서 에너지 소산이 발생되고 있음을 알 수 있다. 따라서 돌핀 구조물의 거동예측 시 준정적 응답특성을 사용하는 것이 보수적이라는 것을 알 수 있으며, 하부충돌 시 돌핀 저항력은 상부충돌 시와 동일하거나 더 우세한 것으로 나타났다.

• Ocean Science Journal
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• 제43권4호
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• pp.175-182
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• 2008

Bottlenose dolphins are the only cetaceans regularly observed in the northern Adriatic Sea, but they survive at low densities and are exposed to significant threats. This study investigates some of the factors that influence habitat use by the animals in a largely homogeneous environment by combining dolphin data with hydrological and physiographical variables sampled from oceanographic ships. Surveys were conducted year-round between 2003 and 2006, totalling 3,397 km of effort. Habitat modelling based on a binary stepwise logistic regression analysis predicted between 81% and 93% of the cells where animals were present. Seven environmental covariates were important predictors: oxygen saturation, water temperature, density anomaly, gradient of density anomaly, turbidity, distance from the nearest coast and bottom depth. The model selected consistent predictors in spring and summer. However, the relationship (inverse or direct) between each predictor and dolphin presence varied among seasons, and different predictors were selected in fall. This suggests that dolphin distribution changed depending on seasonal forcing. As the study area is relatively uniform in terms of bottom topography, habitat use by the animals seems to depend on complex interactions among hydrological variables, caused primarily by seasonal change and likely to determine shifts in prey distribution.

• Journal of Advanced Research in Ocean Engineering
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• 제3권1호
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• pp.15-24
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• 2017

This paper explores a series of numerical simulations of dynamic responses of multi-piles (dolphin) type substructures for 2.5MW class offshore wind turbine. Firstly computational fluid dynamics (CFD) simulation was performed to evaluate wave loads on the dolphin type substructures with the design wave condition for the west-south region of Korea. Numerical wave tank (NWT) based on CFD was adopted to generate numerically a progressive regular wave using a virtual piston type wave maker. It was found that the water-piercing area of piles of the substructure is a key parameter determining the wave load exerted in horizontal direction. In the next the dynamic structural responses of substructure members under the wave load were calculated using finite element analysis (FEA). In the FEA approach, the dynamic structural responses were able to be calculated including a deformable body effect of substructure members when wave load on each member was determined by Morison's formula. The paper numerically identifies dynamic response characteristics of dolphin type substructures for 2.5MW class offshore wind turbine.

• 대한조선학회논문집
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• 제42권1호
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• pp.43-49
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• 2005

in this paper a dolphin-fender moored pontoon-type floating structure in shallow water depth is studied focusing on mooring force. The pontoon-type floating structure is 500m long, 300m wide. The structure has partially non-uniform drafts of 2.0m and 3.0m. The employed mooring system is a guyed frame type dolphin-fender system. The 1/125 scale model fender system is made of rubber tube to have hi-linear load deflection characteristics. A series of model tests has been conducted focusing on motion and fender force responses in regular and irregular waves at KRISO's ocean engineering basin Non-linear numerical simulation of fender reaction force has been carried out and the results are compared with those of model tests. The simulated rigid body motion and mooring forces also have been compared with the test results.

• 한국해양공학회지
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• 제12권3호통권29호
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• pp.19-30
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• 1998

In this paper, the dynamic analysis of a dolphin system for mooring a floating structure such as barge mounted plant is studied. The characteristics of the soil-pile system are simplified by a set of equivalent spring elements at the mudline. To evaluate the equivalent spring constants, the finite difference method is used. Since the characteristics of the soil-pile system are nonlinear in case of soft foundation, the nonlinear dynamic analysis technique is needed. The Newmark $beta$ method incorporating the modified Newton-Raphson method(initial stiffness method) is used. A numerical analysis is performed on two mooring dolphin systems on soft foundation and rock foundation. In case of the rock foundation, the characteristics are found to be nearly linear, so the linear dynamic analysis may be sufficient to consider the foundation effect. But in case of soft foundation, the non-linearity of the foundation appears to be very signigicant, so the nonlinear dynamic analysis si needed.

• Animal cells and systems
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• 제14권3호
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• pp.213-219
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• 2010

Bottlenose dolphins (Tursiops sp.) commonly inhabit Korean waters, including the coastal waters of Jeju Island. However, their taxonomic position was unclear because of the validity of this genus. The genus Tursiops has recently been determined to comprise two species: the common bottlenose dolphin (Tursiops truncatus) and the Indo-Pacific bottlenose dolphin (Tursiops aduncus). To confirm the taxonomic position of bottlenose dolphins frequenting the coastal waters of Jeju Island, the external morphology and osteology of specimens from Jeju Island were examined. Photographs of free-swimming individuals were also used for determining external morphological characters. The cranial and meristic measurements fell within the ranges of T. aduncus. Osteological ratios were also consistent with those of T. aduncus. The presence of a prominent ventral spot was observed among some individuals. As a result, the dolphins mainly distributed in the coastal waters of Jeju Island were identified as Indo-Pacific bottlenose dolphins (T. aduncus) in terms of their cranial characters and ventral spotting. We propose a new Korean name, 'Nambang-keun-dol-go-rae'.

• 한국음향학회지
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• 제38권5호
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• pp.580-586
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• 2019

본 논문에서는 은밀하게 통신 신호를 전송하기 위해 돌고래 휘슬음을 모방한 통신 기법을 제안하였다. 기존의 CSS(Chirp Spread Spectrum) 변조 기법은 돌고래 휘슬음을 정해진 시간 단위에 따라 여러 슬롯으로 나누고 각 슬롯에 상향 및 하향 처프 신호를 통해 변조하는 기법이다. 이에 따라 본래의 돌고래 휘슬음과의 시간-주파수 특성 차이가 발생하게 되어 모방 성능이 저하된다. 본 논문에서는 이러한 왜곡을 제거하기 위해 지연 시간을 기반으로 하는 변조 기법을 제안하였다. 전산 모의실험 결과 기존의 CSS 변조 기법에 비해 제안 방법의 비트오류율 성능이 약 3.5 dB ~ 8 dB 우수하였으며 시간-주파수 영역에서의 상호 상관도를 통한 모방 성능 평가에서도 CSS 변조 기법에 비해 우수한 것을 보였다.