• 한국해양공학회지
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• 제22권2호
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• pp.7-12
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• 2008

A far field solution of the slowly varying force on an offshore structure by gravity ocean waves was shown as a function of the reflection and transmission of the body disturbed waves. The solution was obtained from the conservation of the momentum flux, which simply describes various wave forces, while making it unnecessary to compute complicated integration over a control surface. The solution was based on the assumption that the frequency difference of the bichromatic incident waves is small and its second order term is negligible. The final solution is expressed in term of the reflection and transmission waves, i.e. their amplitudes and phase angles. Consequently, it shows that not only the amplitudes but also the phase differences make critical contributions to the slowly varying force. In a limiting case, the slowly varying force solution gives the one of the mean drift force, which is only dependent on the reflection wave amplitude. An approximation is also suggested in a case where only the mean drift force information is available.

• Fisheries and Aquatic Sciences
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• 제1권1호
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• pp.7-18
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• 1998

In order to understand the generation of the Sogcho Eddy due to the strong offshore winds, we first investigated the characteristics of winds at Sogcho, Kangnung and Samchuk, and then carried out a series of numerical experiments using the nonlinear 1 1/2-layer model. The models were forced by wind stress fields, similar in structure to the prevailing winds that a field in the east coast of Korea during the winter season. The winds were composed of the background winds $(-1\;dyne/cm^2)$ for 90 days and the local winds $(-4\;dyne/cm^2)$ for 30 days. The analysis of wind data at three stations (Sogcho, Kangnung, and Samchuk) showed that the wind was stronger in winter than in other seasons and the offshore component was much dominant. According to our numerical solutions, the Sogcho Eddy of about 200 km in diameter was generated due to the strong offshore winds prevailing in the Kangnung - Sogcho regions. The eastward propagation of the Rossby waves reflected at the western boundary resulted in the eastward meandering motion from the eastern side of the eddy.

• Geomechanics and Engineering
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• 제18권6호
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• pp.627-638
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• 2019

Estimation of representative elementary volume (REV) of jointed rock masses is critical to predict the mechanical behavior of field-scale rock masses. The REV of jointed rock masses at site is strongly influenced by stress state. The paper proposed a method to systematically studied the influence of confining stress on the REV of jointed rock masses with various strengths (weak, medium and strong), which were sourced from the water inlet slope of Xiaowan Hydropower Station, China. A finite element method considering material heterogeneity was employed, a series of two-dimensional (2D) models was established based on the Monte-Carlo method and a lot of biaxial compressive tests were conducted. Numerical results showed that the REV of jointed rock masses presented a step-like reduction as the normalized confining stress increased. Confining stress weakened the size effect of jointed rock masses, indicating that the REV determined under uniaxial compression test can be reasonably taken as the REV of jointed rock masses under complexed in-situ stress environment.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.260-265
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• 2003

Recently there are operating the Floating Vessel with the positioning control unit in ocean. This technology is not open to industrial society as exclusive one. In order to improve technical competition for its domestic product. It is required to develope the relevant product like above subject. This system consist of DGPS System, Unique Analysis, System Network, and Mooring System and so on. Accordingly Model/Field test were carried out to verify its Function / Performance for application of practical product. In this development, we have prepared the successful result to operate the speedy / accurate / stable unit as shown on this subject 'Development of Positioning Control System for Ship and Offshore using the DGPS'. And also it is expected to install this product for ship and offshore unit.

• 대한조선학회논문집
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• 제33권4호
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• pp.150-161
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• 1996

본논문에서는 파중에서의 다수의 3차원 임의형상 부체에 의해 지지된 초대형 해양구조물에 작용하는 정상표류력 해석법을 제시한다. 3차원 특이점 분포법, 파의 상호간섭이론, 운동량 이론에 의한 Far field법과 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.

• Geomechanics and Engineering
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• 제31권5호
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• pp.489-503
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• 2022

A 1257-m-long irregular deep foundation pit located in the central of Nanjing, China was constructed using the combined full-width and half-width top-down method. Based on the long-term field monitoring data, this study analyzed the evolution characteristics of the vertical movement of the columns, internal force of the struts, and axial force of the structural beam and slab. The relevance of the three mentioned above and their relationship with the excavation process, structural system, and geological conditions were also investigated. The results showed that the column uplift was within the range of 0.08% to 0.22% of the excavation depth, and the embedded depth ratio of the diaphragm wall and the bottom heave affected significantly on the column uplift. The differential settlement between the column and diaphragm wall remained unchanged after the base slab was cast. The final settlement of the diaphragm wall was twice the column uplift. The internal force of the struts did not varied monotonically but was related to numerous factors such as the excavation depth, number of struts, and environmental conditions. Additionally, the dynamic force and deformation of the columns, beams, and slabs were analyzed to investigate the inherent relationship and variation patterns of the responses of different parts of the structure.

• 수산해양기술연구
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• 제57권4호
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• pp.302-315
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• 2021

In this study, factors such as improvement of a fishing process and safety, reduction of the labor force and headcount and development of the automation technology for offshore (eel and crab) pot fishing vessels were analyzed. A questionnaire survey was conducted to analyze and select the key factors using independent/paired sample t-test and correlation analysis, and a living lab was operated with ship owners, skippers and experts to discuss practical needs of the site. From the result of questionnaire survey and field requirements, it was possible to understand the level of awareness of ship safety, general safety equipment, fishing work process and fishing safety equipment from the point of view of the field. In addition, there were differences in the measurement results of each items because the working environment and experience were different according to the position of the ship owner and the skipper. The results of the questionnaire survey and various perceptions of field stakeholders were reflected when analyzing the fishing system and fishing process to choose the development equipment applicable to the field. From the analysis results, the selected development equipment based on the fishing equipment and process currently in operation are pot washing device, catch separation and fish hold injection device, length limit regulations and bait ejection device after use, automatic main line winding device, bait crusher, automatic (crab) pot hauling separator and so on.

• 한국항해항만학회지
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• 제39권4호
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• pp.353-360
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• 2015

해양 석유 생산은 '해양'이라는 특성에 기인하는 여러 가지 변수를 동반하면서 막대한 비용과 시간을 필요로 한다. 모든 관련된 프로세스는 인명, 환경 그리고 재산의 손실을 줄이기 위한 치밀한 일련의 계획에 의하여 통제된다. 이 논문은 해양 석유 생산 및 수송의 최적화 문제를 다룬다. 문제 영역의 범위를 정의하기 위해 해양 석유 생산 및 수송 네트워크를 제시하고 그 문제를 해결하기 위한 혼합정수계획모형을 구축하였다. 제안된 최적화 모형의 타당성을 확인하기 위해 가상의 해양 유전과 수요 시장을 바탕으로 MS Office Excel의 해찾기를 이용하여 계산실험들을 수행하였다. 해양 석유 생산 및 수송 네트워크 하위 흐름은 해양 유전에서 생산된 원유를 수요 시장으로 배분하는 해사수송문제가 된다. 이 해사수송문제를 해결하기 위해 집합 패킹 모형을 이용하여 구축된 MoDiSS(Model-based DSS in Ship Scheduling)를 사용하였다. 이러한 연구결과들은 실제적인 해양 석유 생산 및 수송 최적화 문제에 의미 있게 적용될 수 있으리라 사료된다.

• 한국해양공학회지
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• 제20권2호
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• pp.1-7
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• 2006

This paper, presents a comparison between numerical analysis and field test on a real offshore platform in Bohai Bay, China. This platform is a steel jacket offshore platform with vertical piles. The field testing under wave-induced force and wind force etc. was conducted, in order to obtain the dynamic parameters of the structure, including the frequencies of the jacket platform, as well as the corresponding damping ratios and mode shapes. The natural excitation technology (NexT) combined with eigensystem realization algorithm (ERA) and the peak picking (PP) method in frequency domain are carried out for modal parameter indentification under operational conditions. The three-dimeansional finite element model (FEM) is constructed by ANSYS and analytical modal analysis is performed to generate modal parameters. The analytical results were compared with experimental results. A good agreement was achieved between the finite element and analysis and field test results. It is further demonstrated that the numerical and experimental modal analysis provide a comprehensive study on the dynamic properties of the jacket platform. According to the analysis results, the modal parameters identification under ambient excitation can calibrate finite element model of the jacket platform structures, or can be used for the structural health monitoring system.

• 방사선산업학회지
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• 제6권1호
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• pp.41-47
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• 2012

A field tracer experiment using a radioisotope was conducted to analyze the transport and dispersion characteristics of pollutants in the coastal area near a Wolsung. A rod float including GPS was released to track the paths of radioisotope. NaI detector was installed to measure the released radioisotope from the boat, and measurements were performed with the real time. The measured tracer data by a field experiment can be used as the basic data for understanding the transport characteristics of pollutants and verifying numerical models near the offshore.