• Tribology and Lubricants
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• v.36 no.5
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• pp.253-261
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• 2020

In this paper, we present an experimental investigation of the frequency characteristics and a visual inspection of an oxidizer pump with a modified rear-floating ring seal for a 7-tonf turbopump. An oxidizer pump typically operates at high rotational speeds and under cryogenic conditions. Despite its low hydraulic efficiency, the floating ring seal is frequently employed as a leakage control solution for turbomachinery because it effectively reduces abrasion by friction. When the oxidizer pump starts up, the floating ring moves excursively but locks up stably against the pump casing when the contact pressure increases. The compressive force on the floating ring depends on the hydrodynamic forces induced by the flow through the floating ring. This force is controlled by the nose position of the floating ring. Based on a validation test for a 7-tonf turbopump with two types of floating rings, we concluded that the floating ring with a small diameter nose can move easily with a low contact pressure in the cooling path. This leads to instability of the pressure fluctuation around the floating ring. In contrast, a floating ring with a large diameter nose has a high contact pressure and attaches strongly to the casing, which causes wear and frictional oxidation between the contact surfaces of the impeller and the floating ring.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.357-364
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• 2013

In previous study, the hybrid floating structure composed of a pontoon and a semi-submersible was suggested to reduce the motions of floating structure. It was reported that the suggested hybrid floating structure could reduce the motions. However, the hybrid floating structure could not support enough buoyancy. In this study, the combination floating structure is newly suggested to resolve the problem. In order to adopt the shape of floating structures reducing the motions, the hydrodynamic analysis of various floating structures such as the pontoon, the hybrid and the combination of floating structure is carried out through hydrodynamic analysis program ANSYS AQWA. It is found that the combination floating structure is remarkably effective to reduce the motions compared to the other cases. Thus, the suggested combination floating structure may be a useful offshore structure for constructing a very large floating structure.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.1
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• pp.1-7
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• 2002

The effects of floating islands on the changes in phytoplankton community structure were investigated in a small artificial pond. The floating islands planted with various emergent macrophytes covered 35% of total water surface area of the pond. Total 17 genera and 25 species of phytoplankton were found in the pond, of which Dinophyceae was 1 genera and 1 species, Cyanophyceae 1 genera and 1 species, Bacillariophyceae 6 genera and 8 species, and Chlorophyceae 9 genera and 15 species. Dominant phytoplanktons under floating islands were changed from Aphanizomenon sp. as a Cyanophyceae to Golenkinia radiata, Kirchneriella contorta and Micractinium pusillum as a Chlorophyceae for 56 days after the construction of floating islands on July 24, 2001. The changes of dominant phytoplanktons of the control without floating islands were similar to those under floating islands in July and August, but Aphanizomenon sp. was rapidly increased in the control sites in September. About 99% of the cell number of Aphanizomenon sp. was disappeared for a month after construction of floating islands. Species diversity of phytoplankton under the floating islands of Iris pseudoacorus was higher than those of other macrophytes as well as the control without floating islands. The cell numbers of Cyanophyceae and Chlorophyceae were fewer under the floating islands of I. pseudoacorus than those of other macrophytes. Our results showed that the floating islands could be a useful eco-technique for the control of water bloom by Cyanophyceae and Chlorophyceae in a pond ecosystem.

• Journal of the Korean Society of Visualization
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• v.19 no.1
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• pp.18-27
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• 2021

As the photo-voltaic (PV) industry grows, the floating PV has been suggested to resolve current environmental destruction and a lack of installation area. Currently, various floating PV systems have been developed, but there is a lack of studies on how the shape of the floating body and other compositions are affecting structural behavior. In this study, the behavior of the floating PV was investigated at the various length of mooring lines, stiffness of connecting hinges, and size of floating bodies. The shortest mooring lines with the distributed type floating PV showed the least force on the floating body and corresponding motion. A frictionless hinge is safer at the regular and low-height wave, while a stiff hinge is safer at irregular and high-height wave. In addition, due to the bi-axial distribution of the connecting hinge, 45° direction wave was found to be the most dangerous.

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.29-36
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• 2004

Floating breakwaters have been recently studied to reduce the transmission ratio of wave energy. The numerical study shows how wave pressure and stress act on the rectangular floating breakwater under various regular wave conditions. In order to evaluate hydrodynamic pressure on the floating breakwater, the infinite element is applied to the linear wave diffraction and radiation problems. SAP2000, a structural analysis program, is used to evaluate stress on the floating breakwater.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.49-53
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• 2003

본, 연구는 새로운 기체방전 AND gate를 AC 3전극 면방전 PDP에 적용하기 위한 AC-DC floating 방전을 사용한 어드레스 구동특성을 해석한 것이다. 실험결과 floating 방전을 이용하여 어드레스 방전을 개시시킬 수 있었으며 표시방전까지 용이하게 동작시킬 수가 있었다. 또한 floating 방전과 타이밍을 동기시켜 보조전극에 프라이밍 방전을 일으켜 줌으로써 floating 방전 공간에 공간전하를 충분히 공급해 줌으로써 데이터 전압을 100V 정도까지 낮출 수 있었으며 어드레스 동작 마진도 100V 정도까지 얻을 수가 있었다.

• Journal of Industrial Technology
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• v.13
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• pp.59-69
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• 1993

Using two current conveyors with the grounded capacitors and resistors, this paper proposed equivalent circuits which can realize the floating L and the floating FDNR. To find out their characteristics, we experiment with these circuits instead of the floating L of the low-pass filter and the floating FDNR of the high-pass filter respectively. Comparing theoretical values with experimental ones, values of the proposed floating L represent the error of 5 percents in the frequency range from 5 KHz to 25 KHz, and values of the floating FDNR represent the error of 5 percents in the range from 8 KHz to 25 KHz. So the proposed floating L and the FDNR circuits are expected to be implemented with current conveyors of an IC.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.161-165
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• 2013

In this paper, possibility of controlling motion of a floating structure using a tuned liquid damper (TLD) is numerically investigated. A TLD is a tank partially filled with liquid. Sloshing phenomena of liquid inside a tank can suppress movement of the tank subject to external excitations at specific frequency. The effects of sloshing phenomena inside a rectangular floating body on its sway motion are investigated by varying excitation frequency. First, a grid-refinement study is carried out to ensure validity of grid independent numerical solutions using present numerical techniques. Then, sway motion of the floating body subjected to wave with five different frequencies are simulated. The normalized amplitudes of sway motion of the target floating body are compared over the frequency, for cases with and without water inside the floating body. It is shown that the motion of the floating body can be minimized by matching the sloshing natural frequency to excitation frequency.

• Korean Journal of Computational Design and Engineering
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• v.15 no.1
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• pp.70-83
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• 2010

Recently, floating cranes are mainly used to erect heavy blocks or cargos for constructing ships in many shipyards. It is important to estimate the dynamic motion of the heavy cargo suspended by a floating crane and the tension of the wire ropes between the floating crane and the heavy cargo. In this paper, the coupled dynamic equations of motion are set up for considering the 6 degree-of-freedom floating crane and the 6-degrees-of-freedom heavy cargo based on multibody system dynamics. Depending on the cargo weight, the motion of the floating crane would be changed to nonlinear state. The nonlinear terms in the equation of motion are considered. In addition, the nonlinear hydrostatic force, the linear hydrodynamic force, wire rope force, mooring force and gravity force are considered as the external forces. As the result of this paper, we analyze the engineering effect for erecting the heavy cargo by using the floating crane.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.5
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• pp.805-811
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• 2015

Floating photovoltaic systems have been developed by the construction process such as design, construction, operation and management. Therefore, the power of floating photovoltaic systems has been calculated by using simple formulas and the optimal tracking interval is set by operation experience. But, flow characteristics have a decisive effect on it unlike land based PV systems. In this paper, a tracking floating photovoltaic system is modeled by using Matlab/simulink. The modeling for the floating photovoltaic system is verified through applying the flow characteristics based on actual operating data of 100㎾ class tracking floating photovoltaic.