• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1672-1677
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• 2003

Carbon dioxide($CO_2$, R-744) has become a very popular issue in application to refrigeration and air conditioning systems as a natural refrigerant. An experimental study has been carried out to investigate the vapor pressure and miscibility of refrigerant R-744 in the presence of lubricant oil. This is of particular interest in the selection of the lubricant oil for the compressor of a refrigeration system or an air conditioning system using the refrigerant R-744. This apparatus consists of the test section, measuring devices, the vacuum pump, the constant temperature bath and relevant connecting pipes made of stainless steel. Two lubricant oils, such as mineral oil(Naphthenic) and polyol ester(POE) oil, are considered in the present study. For this purpose, test runs were conducted with the oil concentration range from 5 to 50 wt%, and the temperature range from -10 to $10^{\circ}C$ with $2^{\circ}C$ intervals. The results are correlated with the vapor pressure. and showed with the miscibility as visualization for the individual text components.

• 대한조선학회 특별논문집
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• 대한조선학회 2013년도 특별논문집
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• pp.66-72
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• 2013

The demand for an ice class ship is rising expected to rise according to the increase of energy consumption and the opening of arctic sea routes. Ice class ship should be designed to cope with the severe environmental conditions of arctic sea such as a high mechanical impact and abrasion damage, caused by pack ice, ice bergs and low temperature. The ice class ship hulls are coated with an anti-abrasion and low friction coating such as a solvent free epoxy or high solid-volume epoxy. These coatings require two-component heating pump and a high grade surface preparation. In this study, the coating performances for the arctic vessels, such as puncture absorbed energy, abrasive wear loss, friction coefficients and impact absorbed energy were evaluated. Based on this study, a proper coating performance specification for the arctic vessels was proposed and coating selection guideline in terms of coating performance and workability was also established.

• 한국소음진동공학회논문집
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• 제22권5호
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• pp.474-479
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• 2012

A comprehensive vibration assessment program for the advanced power reactor 1400(APR1400) reactor vessel internals is established in accordance with the united states nuclear regulatory commission regulatory guide 1.20 revision 3. This paper is related to instruments and measurement locations based on the vibration and stress response analysis results of the inner barrel assembly top plate in APR1400. The analysis results of the inner barrel assembly top plate in the reactor show that the deterministic stress and deformation due to the reactor coolant pump induced pressure pulsations are larger than the random stress and deformation induced by the flow turbulence. The selection of the instruments and measurement locations at inner barrel assembly top plate in the reactor is essential requirements and very important study process for the vibration and stress measurement program in comprehensive vibration assessment program for APR1400 reactor vessel internals.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.248-251
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• 2008

The objective of this study is to select fuel/air feeders for reliable operation of BOP(Balance of Plant) system for a DMFC (direct methanol fuel cell). A 42-cell 50W DMFC stack is considered for performance comparison of selected fuel pumps and air blowers. The present stack has two serpentine anode channels with depth of 1.2 mm and rib of 1 mm and one serpentine cathode channel with depth of 1.5 mm and rib of 1 mm. The pressure drop through the stack is estimated in advance by utilizing the pre-existing loss coefficients data for various flow configurations. Then the operating points of feeders are determined at the balance point of the flow impedance curves for the channels in the DMFC stack and the selected pump and blower performance curves. After estimating the operating flow rates in the anode and cathode channels, the flow measurement with the selected feeders is performed for the comparison with the estimated flow rates. The measured results show that the discrepancy between the estimation and the measurement for the cathode is about 26%, about 3% for the anode

• 수산해양기술연구
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• 제33권3호
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• pp.202-208
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• 1997

The component materials threatened by cavitation include ship propellers as well as turbine runners, pump impellers, pipe lines and radiators. Today it is known that cavitation damage takes place on many other components including on the coding water side of the cylinder liners of diesel engines. Cavitation erosion - corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. To suppress cavitation erosion as well as cavitation erosion - corrosion to hydraulic equipment, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. In this study, we investigated that the cavitation erosion - corrosion damage under vibratory cavitation can be reduced by adding of side now velocity to the cavitation bubble group in order to eliminate bubbles formed in sea water environment.

• 설비공학논문집
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• 제16권2호
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• pp.150-157
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• 2004

Carbon dioxide ($CO_2$, R-744) has become a very popular issue in application to refrigeration and air conditioning systems as a natural refrigerant. An experimental study has been carried out to investigate miscibility and the vapor pressure of refrigerant R-744 in the presence of lubricant oil. This is of particular interest in the selection of the lubricant oil for the compressor of a refrigeration system or an air conditioning system using the refrigerant R-744. The experimental set-up consists of the equilibrium cell, measuring devices, the vacuum pump, the constant temperature bath and relevant connecting pipes made of stainless steel. Five lubricant oils, such as mineral oil (Naphthenic), AB (Alkyl Benzene) oil, PAO (Poly Alpha Olefin) oil, PAG (Poly Alkylene Glycol) oil and POE (Polyol Ester) oil are considered in the present study. Test runs were conducted with the oil concentration range from 5 to 50 wt％, and the temperature range from -10 to 1$0^{\circ}C$ with 2$^{\circ}C$ intervals. The miscibility results are visualized and correlated with the vapor pressure for the individual test components.

• 설비공학논문집
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• 제5권3호
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• pp.157-168
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• 1993

Pipe network of hot water heat supply system in an apartment house was analyzed. Flowrate and supply heat capacity of each household in which constant flowrate balancing valve is installed in a single zone system were calculated and the results were investigated. In the existing piping system, the non-uniformity of heat supply with floors due to the static pressure and temperature difference between supply main and return main can not be avoided and this tendency get intense with the increase of the height of building. The non-uniformity of heat supply can be prevented by the installation of balancing valve at each household, however if the performance of supply pump is not sufficient to overcome the energy loss due to the installation of balancing valve for constant flow rate or if the selection of the valve capacity is not adequate, the valves will may lose their controllability.

• ETRI Journal
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• 제33권5호
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• pp.752-758
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• 2011

This paper presents a clock and data recovery circuit that supports dual data rates of 5.4 Gbps and 3.24 Gbps for DisplayPort v1.2 sink device. A quarter-rate linear phase detector (PD) is used in order to mitigate high speed circuit design effort. The proposed linear PD results in better jitter performance by increasing up and down pulse widths of the PD and removes dead-zone problem of charge pump circuit. A voltage-controlled oscillator is designed with a 'Mode' switching control for frequency selection. The measured RMS jitter of recovered clock signal is 2.92 ps, and the peak-to-peak jitter is 24.89 ps under $2^{31}-1$ bit-long pseudo-random bit sequence at the bitrate of 5.4 Gbps. The chip area is 1.0 mm${\times}$1.3 mm, and the power consumption is 117 mW from a 1.8 V supply using 0.18 ${\mu}m$ CMOS process.

• 한국전자파학회논문지
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• 제14권8호
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• pp.845-854
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• 2003

광섬유의 색 분산과 비선형 효과에 의해 왜곡된 채널 신호를 보상하기 위한 방법으로 고비선형 분산 천이 광섬유의 광 위상 공액기를 이용한 경로 평균 강도 근사 MSSI(Mid-Span Spectral Inversion)를 채택한 채널 전송률 40 Gbps의 5-채널 WDM시스템의 시뮬레이션을 통하여 채널 각각의 MSSI 보상 특성을 다양한 광섬유 분산 계수에 따라 분석해 보았다. 채널별 보상 특성의 분석은 1 dB 기준 눈 열림 패널티, 수신단에서의 비트 에러율 특성, $10^{-9}$ BER에서의 채널 간 파워 패널티 등을 이용했다. 시스템 전송 길이, 광섬유의 분산 계수, 광 위상 공액기 펌프 광 파장, 광 위상 공액기에서의 WDM신호 파장에 따른 공액파 변환 효율 등에 관계하여 광 위상 공액기를 중심으로 한 첫 번째 전송 링크에서의 신호 평균 전력과 두 번째 전송 링크에서의 공액파 평균 전력을 동일하게 만드는 펌프 광 전력을 적절히 선택하면 고비선형 분산 천이 광섬유가 MSSI 보상을 통한 광대역 WDM 시스템을 위한 광 위상 공액기에서의 비선형 매질로 매우 적합하다는 것을 확인할 수 있었다.

• 터널과지하공간
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• 제13권3호
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• pp.196-206
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• 2003

본 연구에서는 Raise Boring Machine(RBM의 가동율, 관입율, 굴진율과 같은 굴착능력을 조사하기 위하여 직경 3.05 m와 총 연장 98 m의 수직구를 RBM을 이용하여 시험시공 하였다. 이와 함께 국내 양수발전소, 도로터널, 석탄광업소 등에서 RBM으로 시공되었던 4개의 수직구 시공현장으로부터 시공자료를 수집하여 분석을 수행하였다. 연구결과, 주간 평균 굴진장은 약 19.3 m로 분석되었고, 평균 가동율은 약 54.3%011서 75.1 %사이에 분포하는 것으로 나타나, 이는 TBM 시공실적과 비교하여 볼 때 매우 높은 가동율을 보이고 있다. Bit force와 RPM은 (+)의 직선적인 상관관계로 나타났으며 이는 굴착효율에 따라 작업자의 판단에 기인한 결과로 추정된다. 순관입율과의 관계에서는 RBM작업의 bit force와 RPM 및 수직구 심도가 증가함에 따라 순관입율이 저하되는(-)의 상관관계를 나타내었다. 본 연구결과는 수직구 설계 및 RBM장비 선정에 필요한 정보를 줄 수 있을 것으로 사료된다.