• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.55-60
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• 2004

In this study, the configuration and tension of a towing cable for side-scan sonar are predicted in an ambient flow and at an unsteady towing condition. The governing equation of three-dimensional dynamic analysis for a flexible cable is solved using a finite difference method. We successfully predict the configuration and tension of a side-scan sonar and designed the towing system. It is found in static analyses that the side-scan sonar must be towed to keep a its stable depth at a reasonable speed. The study also reveals in the transient analyses that the dominant component affecting the top tension is the tangential drag force for the larger towing speed than the critical speed, and the self weight of a towed instrument for the smaller towing speed than. It should be maneuvered for a towing vessel with good consideration for the impact effect in a cable due to tension peak when a towing speed is suddenly increase. The developed program can be applicable for three-dimensional dynamic analysis of a towing system for various marine survey instruments.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.249-256
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• 2004

KRISO/KORDI is currently developing a deep-sea unmanned underwater vehicle (UUV) system which is composed of a launcher, an ROV, and an AUV. Two USBL acoustic positioning systems will be used for UUV's navigation. One is for the deep sea positioning of all three vehicles and the other is for AUV's guidance to the docking device on the launcher. In order to increase the position accuracy MFSK(Multiple Frequency Shift Keying) broadband signal will be used. As the first step to the implementation of a USBL system, this paper studies USBL positioning algorithm using MFSK signals. Firstly, the characteristics of MFSK signal is described with various MFSK parameters: number of frequencies, frequency step, center frequency, and pulse length. Time and phase delays between two received signals are estimated by using cross-correlation and cross-spectrum methods. Finally an USBL positioning algorithm is derived by converting the delays to difference of distances and applying trigonometry. The simulation results show that the position accuracy is improved highly when both cross-correlation and cross-spectrum of MFSK signals are used simultaneously.

• Ocean and Polar Research
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• 제32권4호
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• pp.361-367
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• 2010

The principal objective of this paper was to evaluate the steering characteristics of a tandem tracked vehicle, each side of which features two tandem tracks, when crawling on extremely cohesive soft soil. The tandem tracked vehicle is assumed to be a rigid-body with 6-dof. The dynamic analysis program of the tandem tracked vehicle was developed via Newmark's method and the incremental-iterative method. A terra-mechanics model of extremely cohesive soft soil was implemented according to the relationships of normal pressure to sinkage, of shear resistance to shear displacement, and of dynamic sinkage to shear displacement. In order to simplify the characteristics of contact interaction between track segments and cohesive soft soil, the characteristics of soil are equated to the properties of intact soil. In an effort to evaluate the steering characteristics of a tandem tracked vehicle crawling on extremely cohesive soft soil, a series of dynamic simulations were conducted for a tandem tracked vehicle model with respect to the front and rear steering angle, the steering ratio, and the initial velocity.

• Ocean and Polar Research
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• 제29권4호
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• pp.327-337
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• 2007

Plankton communities have close relationships with environmental changes in water columns. Thus, the use of plankton as a biological tool for assessing the marine ecosystem health may be effective. Major issue regarding coastal pollution has been usually recognized as phytoplankton blooms or red tides caused by the eutrophication, an increase in concentration of inorganic nutrients such as nitrogen and phosphorus. However, in order to understand the effects of the overall pollution on marine ecosystem, the organic pollutants as well as the inorganic nutrients should be also considered. For understanding the effects of the organic pollution, among the planktonic organisms, heterotrophic bacteria, heterotrophic flagellates and ciliates should be investigated. Generally, there are three approaches for assessing the marine ecosystem health using the plankton taxa or plankton communities. The first one is a community-based approach such as diversity index and chlorophyll a concentration which are common in analysis of the plankton communities. The second is an indiviual-based approach which is to monitor the pollution indicative species. This approach needs one's ability to identify the plankton to species level. The last approach is a bioassay of toxicity, which can be applied to the plankton. A pilot study in Masan Bay was conducted to assess the effects of the inorganic and organic pollution. In this article, a new approach using plankton communities was tentatively presented as a biological tool for assessing the ecosystem health of Masan Bay.

• Ocean and Polar Research
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• 제34권1호
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• pp.85-91
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• 2012

Physical properties such as sound speed contrast (h) and density contrast (g) of the interested target are key parameters to understand acoustic characteristics by using theoretical scattering models. The density and sound speed of moon jellyfish (common jellyfish, Aurelia aurita s.l.) were measured. Sound speed contrast (h) was measured from travel time difference (time-of-flight method) of an acoustic signal in a water tank for APOP studies (Acoustic Properties Of zooplankton). Density contrast (g) was measured by the displacement volume and wet weight (dual-density method). The sound speed remained almost constant as the moon jellyfish increased in bell length. The mean values${\pm}$standard deviation of h and g were $1.0005{\pm}0.0012$ and $0.9808{\pm}0.0195$), respectively. These results will provide important input for use in theoretical scattering models for estimating the acoustic target strength of jellyfish.

• Animal cells and systems
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• 제13권4호
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• pp.453-460
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• 2009

Morphological and molecular classifications were attempted in an effort to establish species-specific classifications of three species of the genus Pholis in Korea; these species were subjected to morphological and molecular methodologies using body measurements, RFLP, RAPD, and phylogenetic trees using the nucleotide sequences of mitochondrial 16S and 12S ribosomal DNAs, cytochrome c oxidase I, and cytochrome b. The data demonstrated that the three species of genus Pholis are distinct from each other, both morphologically and genetically.

• 한국해양환경ㆍ에너지학회지
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• 제8권1호
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• pp.31-38
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• 2005

본 연구에서는 PMV기반-공조시스템 설계를 위한 기초자료 조사를 목적으로 6가지 물리적/주관적 온열요소의 특성을 평가하였다. 물리적 온열요소의 평가에서는 25톤 함정의 조타실과 통신실, 100톤 함정의 기관실에서 열적 불만족이 발생할 수 있었다. 착의상태 및 활동상태 항목은 육상 실내건축의 내용을 선상 근무에 맞게 수정하여 이용하였다. 주관적 온열요소 중 의닦의 열 저항치는 모든 함정의 선실에서 승조원 사이의 편차가 커서 신진대사량에 비해 온열평가에 미치는 영향이 더 민감한 것으로 나타났다. 주관적 온열요소의 분포는 대체로 표준 정규분포보다 오른쪽으로 꼬리가 긴 비대칭분포를 보였다.

• Ocean and Polar Research
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• 제25권4호
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• pp.545-555
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• 2003

It is widely known that compare to many other countries, the U.S.A. has a strong framework for efficient implementation of mitigation policy to protect wetlands. As indicated in many strong mitigation initiatives, mitigation policy primary requires avoidance rule for wetland damage and if a developer inevitability damages wetlands, the development should be minimize, and as a last resort, the policy impose legal duty that a developer should compensate wetland corresponding to the damaged wetlands. However, the legal system fur Korea's mitigation system does not provide any legal duty for the compensatory mitigation, although the possibility of creation of tidal flat is casually expressed in several Korean legal systems. Therefore, without any strong and enforceable legal system, Korean mitigation system cannot efficiently protect Korea's vast and productive wetlands. To introduce mitigation policy similar to the U.S.A. in Korea, we suggest that there (a) should be a strongly policy which regulate legal duty for the compensatory mitigation, (b) should be an improve management system for actively corresponding to special knowledge relating to environment, and lastly, (c) should be a system which consider a class action introduced in environmental regime for a long term protection of tidal wetlands for future generation.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.187-191
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• 2003

The motion and time-mean drift force of a 2-D floating BBDB in waves are studied with and without taking account of fluctuating air pressure in the air chamber. It has been found numerically that the drift for a of the BBDB is in the reverse direction of propagation of the incident waves over specific frequency ranges as found by McCormick through his experiment work. The drift force is calculated by Pinkster's near-field method. Since Maruo's formula method for the drift force is always positive, Maruo's formula is only approximate and should be replaced by the correct near-field method.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 추계학술대회
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• pp.33-39
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• 2004

파랑중을 운항하는 선박은 항상 파도의 영향을 받아 운동을 하게 된다. 여러방향의 운동형태 중에서 횡동요가 화물의 안전 및 선원의 피로도에 가장 큰 영향을 미친다. 따라서 횡동요가 문제가 되는 선박에는 횡동요 저감 장치의 장착이 늘어나고 있는 추세이다. 본 연구에서는 핀 스태빌라이저(Fin stabilizer)와 이동질량 감요장치(Moving weight stabilizer)의 성능시험을 위하여 자유항주 모형선을 개발하였다. 또한 자세제어장비 성능시험 절차를 정립하고, 개발한 자유항주 모형선올 통하여 성능시험을 수행하였다.