• Proceedings of the KSME Conference
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• 2005.11a
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• pp.61.2-61.2
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• 2005

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.611-612
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.715-716
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• 2009

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.621-625
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• 2007

Oscillating wave amplitude in a bottom-mounted owe chamber designed for wave energy converter is investigated by applying characteristic wave conditions in Korean coastal water. The effects of shape parameters of OWC chamber in a view of wave energy absorbing capability are analyzed. Both experimental and numerical approaches are adopted and their results are compared to optimize the shape parameters which can result in a maximum power production under given wave distribution. The experiment was carried out in a wave flume under 2-D assumption of OWC chamber. In numerical scheme, the potential problem inside the chamber is solved by use of the Green integral equation associated with the Rankine Green function, while outer problem with the Kelvin Green function taking account of fluctuating air pressure in the chamber. Air duct diameter, chamber width, and submerged depths of front skirt and back wall of chamber changes the magnitude and peak frequency of wave absorption significantly.

• Journal of Ocean Engineering and Technology
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• v.22 no.1
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• pp.22-29
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• 2008

A numerical investigation is made on the effects of the location and shape of the front wall of an OWC(Oscillating Water Column) chamber on the hydroelastic response of a VLFS. Most of the studies on the effects of an OWC chamber on the response of a VLFS have assumed the location of the OWC chamber to be at the front of the VLFS. In the present study, an OWC-chamber is introduced at an arbitrary position in relation to a VLFS to determine the influence of the location and shape of the OWC chamber on the hydroelastic response of the VLFS. A finite element method is adopted as a numerical scheme for the fluid domain. or the finite element method, combined with a mode superposition method, is applied in order to consider the change of mass and stiffness The OWC chamber in a piecewise constant manner. or the facilitated anefficient analysis of The hydroelastic response of the VLFS, as well as the easy modeling of different shape and material properties for the structure. Reduction of hydroelastic response of the VLFS is investigated for various locations and front wall shapes of the owe chamber.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.318-328
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• 1991

The present paper describes the experimental study on the fixed-type wave-energy conversion system, consisting of the OWC-type wave-energy absorbing chamber and the duct for the air turbine. For simplicity, a screen of wire mesh was employed in place of an air turbine in order to simulate its effects on OWC chamber. Experiments were performed at the towing tank in regular waves with the frequency range of 0.22-0.75Hz. Comparison wish the numerical prediction using a potential flow-based method [4] was made to validate the capability of numerical code. It was shown that the agreements between measured and calculated results are quite good, giving a confidence in prediction method. Simulation of air turbine using a wire-mesh screen was successful, at least in a qualitative sense, to investigate the inter action between the OWC chamber and an air turbine. Results also showed that the effects of a wire-mesh screen on chamber efficiency are negligible, and the present model can be effectively utilized for the practical use in ocean waves with the frequency range under 0.3Hz.

• Analytical Science and Technology
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• v.25 no.5
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• pp.307-312
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• 2012

To perform inhalation toxicity test by using experiment animals, we set up an analytical method to monitor didecyldimethylammonium chloride (DDAC) in aerosol nebulized into inhalation chambers by ion chromatography. DDAC was adsorbed by XAD-2 resin and analyzed with conductivity detector. Recovery of DDAC desorbed by acetonitrile from XAD adsorbent was 87.8%. The method detection limit (MDL) and the limit of quantitation (LOQ) were 2.97 ${\mu}g/m^3$ and 8.92 ${\mu}g/m^3$, respectively. Repeatability was calculated as RSD 7.8% in the range of 0~20 ${\mu}g/mL$. Time needed to analyze a sample was less than 5 minutes. Therefore, the analysis of DDAC by ion chromatography was practically useful in monitoring DDAC in inhalation chambers with rapidity and sensitivity manner to perform inhalation toxicity test using experimental animals.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.11
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• pp.893-900
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• 2021

In this study, air density in a narrow test section is measured using a laser absorption spectroscopy system that detects oxygen absorption lines. An absorption line pair at 13156.28 and 13156.62 cm^-1 are detected. A gas chamber with a height of 40 mm is used as a narrow test section. A triangular spiral-shaped laser path is applied in the gas chamber to amplify absorption strength by extending laser beam path length. A well-known logarithm amplifier and a secondary amplifier are used to electrically amplify absorption signal. An AC-coupling is applied after the logarithm amplifier for signal saturation prevention and noise suppression. Procedure of calculating spectral absorbance from output signal is introduced considering the logarithm amplifier circuit configuration. Air density is determined by fitting the theoretically calculated spectral absorbance to the measured spectral absorbance. Test conditions with room temperature and a pressure range of 10~100 kPa are made in a gas chamber using a Bourdon pressure gauge. It is confirmed that air density in a narrow test section can be measured within a 16 % error through absorption signal amplification using a triangular spiral-shaped beam path and a logarithm amplifier.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.112-115
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• 2017

We analyzed the rocket engine flow to check whether the possibility of the ground test and the equipment safety problems in the high altitude engine test facility. The test condition is that the vacuum chamber is open and the coolant water is injected into the supersonic diffuser. The analysis uses two-dimensional axisymmetry with a mixture of plume, air, and cooling water. As a result, the ground test was possible up to the cooling water flow rate of 200 kg/sec. However, due to the back flow of the initial plume, the vacuum chamber is exposed to high temperature, and at the same time, the inside of the vacuum chamber is contaminated due to the reverse flow of the cooling water. Therefore, sufficient insulation measures and work for pollution avoidance should be preceded.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.11a
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• pp.255-258
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• 2007

본 연구는 현재 전력설비에 사용되고 있는 $SF_6$가스의 대체 절연가스로 건조공기(Dry-Air)의 절연파괴특성 연구를 위하여 모의 GIS 챔버와 AC 300[kV], DC(-) 150[kV] 전원장치로 교류 및 직류고전압을 인가하여 연구를 수행하였다. 평등전계인 구전극 대 구전극을 이용하여 $SF_6$ 가스와 건조공기(Dry-Air)의 절연내력을 비교하기 위해서 20, 30 및 40[N/$cm^2$ ]까지 가스의 압력변화를 주었고 각 압력별 전극간거리(d)에 따른 절연파괴전압($V_B$)을 연구하였다.