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          • 다수의 부체로 지지된 초대형 해양구조물에 작용하는 정상표류력 (Ⅱ)

            이창호,홍사영,구자삼,조효제,김경태 韓國海洋大學校 附設 海洋科學技術硏究所 1997 硏究論文集 Vol.5 No.-

            본 논문에서는 파중에서의 다수의 3차원 임의형상 부체에 의해 지지된 초대형 해양구조물에 작용하는 정상표류력 해석법을 제시한다. 3차원 특이점 분포법, 파의 상호간섭이론, 운동량 이론에 의한 Far field 법과 3차원 골조구조를 다루기 위한 유한요소법을 결합하여 이론을 정식화하였으며, 수치계산 결과를 Kagemoto [6]에 의한 33(3행11렬)개의 footing형 축대칭 부체에 의해 지지된 해양구조물에 작용하는 정상표류력의 실험치 및 계산치와 서로 비교 검토함으로써 본 해석법의 타당성을 검정하였다. A numerical procedure is described for predicting steady drift forces on very large offshore structures supported by a large number of the floating bodies of arbitrary shape in waves. The developed numerical approach is based on a combination of the three-dimensional source distribution method, the wave interaction theory, the far-field method of using momentum theory and the finite element method for structurally treating the space frame elements. Numerical results are compared with the experimental or numerical ones, which are obtained in the literature, of steady drift forces on a offshore structure supported by the 33 (3 by 11) floating composite vertical cylinders in waves. The results of comparison confirmed the validity of the proposed approach.

          • 海洋景觀을 考慮한 海洋建築計劃에 關한 硏究

            李漢錫 韓國海洋大學校 附設 海洋科學技術硏究所 1998 硏究論文集 Vol.7 No.-

            There are numerous structures linked with the sea. They are standing on the water's edge in the waterfront area or ocean space. The most important one of them is oceanic architecture. Oceanic architecture is architectural space created by directly or indirectly using the features of the waterfront or ocean in the design. Therefore the quality of seascape(or oceanscape) can be greatly influenced by the oceanic architecture. In this paper the characteristics and planning of seascape are examined. Especially recommendations for planning of seascape are dealted with each category of seascape, and then on the basis of them architectural design guidelines are suggested for creating good quality of seascape.

          • 거리의존 해양환경에서 수동소나체계의 표적탐지거리예측

            김태학,김재수 韓國海洋大學校 附設 海洋科學技術硏究所 1997 硏究論文集 Vol.6 No.-

            원거리에서 수동소나에 의한 탐지거리를 예측하기 위해서는 소나방정식이 이용된다. 본 연구에서는 거리와 깊이함수의 신호이득 및 탐지확률을 구한 후 이를 거리로 적분하여 거리의존 해양환경에서 탐지거리를 계산하는 탐지거리 예측모델을 개발하였다. 개발된 모델은 기존에 발표된 거리독립 해양환경에서의 결과와 비교하여 검증하였고, 이를 바탕으로 거리의존 해양환경에서 수동소나에 의한 표적탐지에 큰 영향을 주는 나수성 소용돌이 해양환경에 확장 적용하여 표적의 탐지거리를 예측하였으며, 그 결과에 대하여 소개한다. The prediction of detection range of a passive sonar system is essential to estimate the performance and to optimize the operation of a developed sonar system. In this paper, a model for the prediction of detection range in a range-dependent ocean environment based on the sonar equation is developed and tested. The prediction model calculates the transmission loss using PE propagation model, signal excess, and the detection probability at each target depth and range. The detection probability is integrated to give the estimated detection range. In order to validate the developed model, two cases are considered. One is the case when the target depth is known. The other is the case when the target depth is unknown. The environment. Also, the developed model is applied to the range-dependent ocean environment where the warm eddy exists. The computational results are shown and discussed. The developed model can be used to find the optimal frequency of detection, as well as the optimal search depth for the given range-dependent ocean environment.

          • 다방향 불규칙파중의 초대형 해양구조물의 동적응답해석

            구자삼,조효제,김경태 韓國海洋大學校 附設 海洋科學技術硏究所 1997 硏究論文集 Vol.6 No.-

            본 논문에서는 3차원 특이점분포법, 파의 상호간섭이론 및 유한요소법을 결합한 Goo등[29]이 개발한 초대형 해양구조물의 동적응답 해석법과 스펙트럴 해석법을 이용하여 다수의 임의형상 지지부체간의 유체역학적 상호간섭을 고려한 다방향 불규칙파중의 초대형 해양구조물의 운동응답 및 구조응답의 유의치를 동시에 계산할 수 있는 동적응답 해석법을 개발하였으며, 반잠수식 Ring 형상의 초대형 해양구조물을 수치계산 모델로 하여 구조물의 동적응답에 미치는 상호간섭과 다방향파의 영향을 평가하였다. A numerical procedure is described for predicting the motion and structural responses of the very large floating offshore structures supported by multiple 3-D floating bodies of arbitrary shape in multi-directional irregular waves. The developed numerical approach taking into account of the hydrodynamic interactions among the multiple floating bodies is based on a combination of the 3-D source distribution method, the wave interaction theory, the finite element method and the spectral analysis method to get the significant values of the dynamic responses in the multi-directional irregular waves. The effects of wave interactions and directionality on the dynamic responses of a very large offshore structure, which is semisubmersible ring type, are numerically examined.

          • The Effect of Exogenous Hormone Treatment on Spermiation in Rhynchocypris oxycephalus : Sauvage and Dabry

            PARK, I.-S.,CHOI, G. C.,NAM, Y. K.,KIM, D. S. 韓國海洋大學校 附設 海洋科學技術硏究所 2002 硏究論文集 Vol.11 No.2

            For the evaluation of hormonal control of spermiation in fish, a method to quanify the spermiation response of mature Rhynchocypris oxycephalus (Sauvage and Dabry) to hormonal therapy is described. Spermatocrit was determined after 7 min centrifugation at 18,000×g and sperm density was estimated by a standard hemocytomer method. Sperm density can be predicted from spermatocrit since their relationship is linear as described by the regression equation. Y=3.68X - 27.18 (R^2=0.82, N=50), where Y is spermatocrit and X is sperm density. Milt production by mature R. oxycephalus was highest at 24 h after injection of 1,000 IU human chorionic gonadotropin(HCG) and 50㎍ luteinizing hormone-releasing hormone analogue (LHRHa) per kg body weight. Increased milt production coincided with low spermatocrit and sperm density levels. These results demonstrate that spermiation in mature R. oxycephalus can be reliably evaluated by a spermatocrit method and that HCG and LHRHa are effective in stimulation of spermiation in this species.

          • An Electrochemical Study on the Microbiological Influenced Corrosion of Steels Sulfate-Reducing Bacteria

            Moon, Kyung-Man,Lee, Myung-Hoon,Kim, Ki-Joon,Park, Guen-Hyun,Koh, Sung-Cheol 韓國海洋大學校 附設 海洋科學技術硏究所 2002 硏究論文集 Vol.11 No.1

            We have investigated the differences between the general corrosion and microbiological influenced corrosion (MIC) of a steel in terms of electrochemical behavior and surface phenomena. Corrosion potential of a steel in medium solution without SRB (Sulphate Reducing Bacteria) shifted to a low direction continuously as a function of submerging time. The potential caused by MIC with SRB shifted to a noble direction after 20days' incubation, indication the growth of SRB biofilm and the test metal specimens and a formation of corrosion product. In addition, the color of medium inoculated with SRB changed from grey to black., the color change was observed in the medium without SRB inoculation. Moreover, corrosion rated of a steel in MIC were higher than those is the absence of SRB. This is probably because SRB caused be associated with the increasing corrosion rates through increasing cathodic reaction which caused the reducing sulfate to sulphide as well as formation of an oxygen concentration cell. The pitting corrosion was also observed in the of SRB inoculated medium.

          • A three-dimensional mixed finite-difference Galerkin function model for the oceanic circulation in the Yellow Sea and the East China Sea in the presence of M_2 tide

            Lee, Ho Jin,Jung, Kyung Tae,So, Jae Kwi,Chung, Jong Yul 韓國海洋大學校 附設 海洋科學技術硏究所 2002 硏究論文集 Vol.11 No.1

            This paper, as a sequel to Lee et al. (Continental Shelf Research 20(2000) 863) describes the simulation of the oceanic current in the Yellow Sea (YS) and the East China Sea (ECS) with forcings of M_2 tide as well as oceanic flows prescribed at the open boundary. The model is three dimensional and barotropic, and uses a finite-difference approximation in the horizontal plane and function expansions in the vertical direction. The bottom stress is represented by the conventional quadratic friction law and the vertical eddy viscosity takes a flow-related form. A radiation condition is employed along the open boundaries to handle the M_2 tide and oceanic flows simultaneously. From a series of numerical calculations with M_2 tide forcing only, the bottom friction coefficient, 0.0035, has been found as an optimum value with which RMS errors (amplitude, phase lag) are calculated as 16.4cm, 19.5°. Calculations have also been carried out to investigate the effects of using an empirical function expansion for the current profiles below the main stream of Kuroshio. Despite the bias of the tidal propagation and the associated flux, the tidal chart has been calculated with tolerable accuracy. The model calculation confirms the results of Exp. 4 Lee et al. (Continental Shelf Research 20 (2000) 863), in that the tide-enhanced bottom friction effectively blocks the penetration of northwestward flow into the YS known as the Yellow Sea Warm Current (YSWC). The presence of small gyres, however, complicates the circulation near the southern YS and west of Cheju Island and tidal residual currents omnipresent at the shallow sea region off the Chinese coast between 32°N and 34.5°N also contribute to the suppression of the formation of the YSWC. The distribution of the sea surface elevation averaged over the M_2 tidal period is qualitatively in good agreement with that of Yanagi et al. (Continental Shelf Research 17 (1997 655), calculated from the TOPEX altimetric data. Calculation with an inflow of 25.1 Sv through open boundaries on both sides of Taiwan shows that 1.15 Sv goes through Korea/Tsushima Strait, 0.36 Sv through the north of Tokara Strait (between Kyushu and Yakushima Island), 20.95 Sv through Tokara Strait and 2.77 Sv through open boundaries along the Ryukyu Islands. Calculations with fortnightly variation in M_2 open boundary forcings show that the oceanic circulation as well as tidal residuals vary significantly in the southern Yellow Sea; penetration of oceanic flows into the Yellow Sea occurs deeper at the neap tide than at the spring tide. The seasonal variation in the volume transport of the oceanic inflows/outflows without baroclinic effects has little effect to the exchange between the YS and the ECS. ⓒ 2002 elsevier Science Ltd. All rights reserved.

          • 해양탐사장비 예인케이블의 3차원 동적해석에 관한 연구

            정동호,박한일 韓國海洋大學校 附設 海洋科學技術硏究所 2002 硏究論文集 Vol.11 No.2

            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 sound that the side-scan must be towed to keep a its stable depth at a reasonable speed. The developed program can be applicable for three-dimensional dynamic analysis of a towing system for various marine survey instruments.

          • A Simulator Study on Yaw-checking and Coursekeeping Ability in IMO's Ship Manoeuvrability Standards

            Sohn, Kyoung-Ho,Yang, Seung-Yeul,Lee, Dong-Sub 韓國海洋大學校 附設 海洋科學技術硏究所 2002 硏究論文集 Vol.11 No.2

            Yaw-checking and course-keeping ability in IMO's ship manoeuvrability standards is reviewed from the viewpoint of safe navigation. Three kinds of virtual series-ships, which have different course instability, are taken as test models. The numerical simulation on Z-test is carried out in order to examine the correlation between known manoeuvrability in spiral characteristics and various kinds of over shoot angle. Then simulator experiments are executed with series-ships in a curved, narrow waterway by five pilots in order to examine the correlation between known manoeuvrability and degree of manoeuvring difficulty. IMO criteria for yaw-checking and course-keeping ability are discussed and new criteria are proposed.

          • Crystal Orientation and Morphology on the Tribological and Corrosive Properties of Silver Thin Films

            Lee, Myeong-Hoon,Moon, Kyung-Man,Jang, Ji-Yon,Yun, Yong-Sup,Lee, Kyung-Hwang 韓國海洋大學校 附設 海洋科學技術硏究所 2002 硏究論文集 Vol.11 No.1

            Silver is known to possess method such characteristics as low shear strength, good transfer-film forming tendency and good corrosion resistance. Silver thin films were prepared by e-beam ion plating. They are deposited on various deposition conditions such as argon gas pressures and bias voltages etc. After the silver films were prepared, the properties in them were examined by gas pressure and bias voltage of substrate. The structure of deposited film was analyzed by X-ray diffraction technique. The morphology of the top surface of films was observed by scanning electron microscope(SEM). Silver films were investigated by not only the tribological properties but also corrosion properties as a function of deposition condition by friction coefficient tester at vacuum ambient and potentio-stat in 0.5M Na_2S solution respectively. After anodic polarization being carried out, the morphology of corroded film was observed by SEM. Tribological and corrosion properties of silver thin films prepared by e-beam ion plating are discussed and compared in this paper.

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