• 전기학회논문지
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• 제66권10호
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• pp.1532-1539
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• 2017

The floating photovoltaic system is a new concept in the renewable energy technology. That is similar to land based photovoltaic technology except floating system. So the system needs buoyant objects, mooring, ect, besides modules and supports, and that is able to withstand in water level changes and wind strength. Therefore the floating photovoltaic system is much different from land photovoltaic system. K-water (Korea Water Resources Corporation) has been operating two floating photovoltaic system that's capacity is 100 kW and 500 kW respectively since in summer 2011 for commercial generation, and have construction project for 2,000 kW in Boryeong multipurpose Dam and other areas. Furthermore K-water was developing a tracking-type floating photovoltaic system at Daecheong multipurpose Dam and developed and installed an ocean floating photovoltaic demonstration plant at Sihwa Lake in October 2013 for R&D. In this paper, we introduce that structure of floating photovoltaic system include buoyant structure, mooring system and auxiliary device. Especially the rope which is in part of mooring should be always maintain tension under any water level. Also we explain about structure design concept to wind load in an every loading condition and a kind of structure materials and PV structure types used in water environment. Especially ocean floating PV system is affected by tidal current and typhoon. So there are considering the elements in design. Finally we compare with floating and land photovoltaic on power amount. As a result of that we verified the floating photovoltaic system is more about 6.6~14.2 % efficiency than a general land photovoltaic system.

• 전기전자학회논문지
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• 제17권3호
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• pp.346-351
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• 2013

모바일 시스템에서는 비용 및 전력 효율이 중요하기 때문에 부동소수점 연산기 개발 시 32-비트 데이터 형식대신 24-비트 데이터 형식을 사용하는 것이 좋다. 하지만 24-비트 데이터 형식을 사용할 경우 32-비트 데이터 형식에 비해 연산기의 정확도가 낮아질 수 있다. 3D 그래픽과 같이 연속적인 부동소수점 연산 처리가 많이 요구될 경우 연산기의 정확도에 대한 논의와 검증이 중요하다. 나눗셈은 3D 그래픽에 사용되는 연산 중 OpenGL에서 규정한 정확도를 만족하기 가장 어려운 연산 중 하나이다. 현재까지 OpenGL에서 규정한 정확도를 만족하는 것이 대수적으로 검증된 24-비트 부동소수점 제산기는 알려진 바가 없다. 본 논문에서는 24-비트 부동소수점 제산기를 분석하고, OpenGL ES 3.0에서 규정한 $10^{-5}$의 정확도를 만족함을 대수적으로 검증한다.

• 전기전자학회논문지
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• 제24권4호
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• pp.1156-1161
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• 2020

본 논문에서는 기존 단방향 SCR의 구조적인 변경을 통해 향상된 전기적 특성을 갖는 새로운 ESD 보호회로를 제안한다. 제안된 ESD 보호회로는 삽입 된 N+ Floating 및 P+ Floating 영역으로 인해 높은 Holding Voltage 특성을 가져 Latch-up 면역특성이 향상되었다. 또한 구조적인 변경으로 모든 4가지 유형(PD, PS, ND, NS)의 Zapping Mode에서 ESD 방전이 가능하므로 단방향 SCR보다 우수한 면적효율을 가진다. 그리고 기생 바이폴라 트랜지스터의 베이스 길이에 해당하는 P+ floating, N+ floating 길이와 P+ floating과 N+ floating 사이의 거리를 설계변수로 지정하였으며, 높은 Holding Voltage를 갖는 것을 Synopsys 사의 TCAD Simulator를 통해 검증하였다.

• Tribology and Lubricants
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• 제24권3호
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• pp.140-146
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• 2008

The floating ring seal which is used in the high pressure turbo pump is frequently used in the oxidizer pump and the fuel pump of the turbo pump of the liquid propulsion rocket, because it is able to minimize clearance to decrease the leakage flow rate. But, the floating ring seal has a tendency to increase instability in decreasing eccentricity ratio. To complement this weakness, it is devised bump floating ring seal which is inserted bump in the outer surface. It has various experiment results. But the theoretical study of the bump floating ring seal didn't investigated yet. In this paper, we analyse about static characteristics of bump floating ring seal, compared previous experimental results. To analyze the characteristic of bump floating ring seal, we coupled perturbation method of floating ring seal and FEM of bump foil.

• Structural Engineering and Mechanics
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• 제74권4호
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• pp.521-532
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• 2020

A floating dry dock is an advanced structure that can provide a solution for dry dock space shortages. The critical point in floating dock operation is compensating the deflection caused by a heavy payload by adjusting the water level in the ballast system. An appropriate ballasting plan warrants safe and precise construction on a floating dock. Particularly, in the case of a 2D floating dock, ballasting plan evaluation is crucial due to complex deformation modes. In this paper, we developed a method to calculate the optimal ballasting plan for accurate and precise construction on a 2D floating dock. The finite element method was used for considering the flexibility of the floating dock as well as the construction blocks. Through a gradient-based optimization algorithm, the optimal ballasting plan for the given load condition was calculated in semi-real time (5 min). The present method was successfully used for the actual construction of an offshore structure on the 2D floating dock.

• 한국주거학회논문집
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• 제26권5호
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• pp.97-104
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• 2015

This paper aims to discuss the concept of resilience in floating housing, to investigate the resilient features of floating houses & to review the possibility of floating housing as a new form of resilient living, and to suggest some reference ideas for the planning and design of floating housing projects. Resilient features of the floating house can be summarized as the buoyant characteristics for natural disasters, the easy employment & potential use of renewable and nearly self-sufficient energy systems in locations subject to limited energy sources, the movability, mobility, long life, water recycle system, prefabrication and modular construction with the potential for reduced environmental impact. Additional benefits include the potential for a peaceful and comfortable atmosphere due to direct connections with nature, good relationship with neighbors, a solid social spirit of unity, and sense of security. Considering the resilient features of floating house at a time of serious climate change requires a new paradigm, and floating/amphibious/floatable housing has great possibility as a new form of resilient living.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.407-413
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• 2013

This paper deals with the analysis of dynamic characteristics of mooring system of floating-type offshore wind turbine. A spar-type floating structure which consists of a nacelle, a tower and the platform excepting blades, is used to model the floating wind turbine and connect three catenary cables to substructure. The motion of floating structure is simulated when the mooring system is attached using irregular wave Pierson-Moskowitz model. The mooring system is analyzed by changing cable position of floating structure. The dynamic behavior characteristics of mooring system are investigated comparing with cable tension and 6-dof motion of floating structure. These characteristics are much useful to initial design of floating-type structure. From the simulation results, the optimized design parameter that is cable position of connect point of mooring cable can be obtained.

• Journal of Positioning, Navigation, and Timing
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• 제3권3호
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• pp.117-122
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• 2014

In CDGPS, ambiguity resolution is determined by the performance of a floating solution, and thus, the performance needs to be improved. In the case of precise positioning at a stationary position, the batch method using multiple measurements is used for the accuracy improvement of a position. The position accuracy performance of a floating solution is outstanding, but it has a problem of high computation cost because all measurements are used. In this study, to improve the floating solution performance of the initial static user in CDGPS, a floating solution method using a recursive filter was implemented. A recursive filter estimates the position solution of the current epoch using the position solution of up to the previous epoch and the pseudorange measurement of the current epoch. The computation cost of the floating solution method using a recursive filter was found to be similar to that of the epoch-by-epoch method. Also, based on actual GPS signals, the floating solution performance was found to be similar to that of the batch method. The floating solution using a recursive filter could significantly improve the performance of the prompt initial position and ambiguity resolution of the initial static user.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2017년도 학술발표회
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• pp.514-514
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• 2017

Floating breakwaters were treated as solid bodies without any perforation in previous studies. In this study, however, a floating breakwater is perforated to allow the partial absorption of the energy produced by incident waves and an air chamber is placed in the upper part to control the breakwater draft. A series of laboratory experiments for a floating breakwater installed with a mooring system are carried out. In general, a mooring system can be classified by the number of mooring points, the shape of the mooring lines, and the degree of line tension. In this study, a four-point mooring is employed since it is relatively easier to analyze the measured results. Furthermore, both the tension-leg and the catenary mooring systems have been adopted to compare the performance of the system. In laboratory experiments, the hydraulic characteristics of a floating breakwater were obtained and analyzed in detail. Also, a hydraulic model test was carried out on variable changes by changing the mooring angle and thickness of perforated wall. A hydraulic model was designed to produce wave energy by generating a vortex with the existing reflection method. Analysis on wave changes was conducted and the flow field around the floating breakwater and draft area, which have elastic behavior, was collected using the PIV system. From the test results the strong vortex was identified in the draft area of the perforated both-sides-type floating breakwater. Also, the wave control performance of the floating breakwater was improved due to the vortex produced as the tension in the mooring line decreased.

• 한국항해항만학회지
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• 제33권6호
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• pp.375-380
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• 2009

1년 전까지만 해도 조선시황은 한없는 호항을 누릴 것으로 보였다. 그러나 2008년 후반에 찾아든 글로벌 경제의 불황은 바로 해운시장을 뒤흔들었고 그 여파는 바로 조선 사장에도 한없는 추락을 가져오고 있다. 저자들은 이러한 사태를 예견하여 이미 드라이 도크의 건조에 신중을 기할 것을 주장한 바 있다. 여기에 비하여 Floating Dock는 건조 비용도 덜 들고, 건조 기간도 짧고, 이동성마저 갖추고 있기 때문에 훨씬 더 유연한 도크 건설 방법이 될 수 있다. 그러나 Floating Dock는 대형의 블록을 탑재할 때 갑작스런 중량의 이동으로 인한 중심의 큰 변화로 안정성이 크게 위협 받게 된다. 따라서 안전하게 블록을 탑재하기 위하여서는 아주 고도의 정밀한 발라스트 작업이 수행되어야 한다. 본 연구에서는 육상에서 만들어진 거대 블록을 플로팅도크에 밀어 넣는 Skid Launching System을 위한 플로팅도크 제어 시스템을 완성하여 안정적인 SLS를 구현하고자 한다. 이를 위하여 저자들은 우선 가상의 진수 절차를 만들어 모의 조정하는 시뮬레이터를 개발(Kim et al. 2008)한 바 있다. 본 논문에서는 이시뮬레이션을 바탕으로 실시간 모니터링하면서 실시간 제어하는 시스템을 만들고 실제 진수에 적용하고자 한다.