• Solar Energy
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• v.11 no.1
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• pp.78-86
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• 1991

Heat transfer characteristics of a rotating heat pipe have been studied numerically and experimentally with using water-ethanol mixture as working fluid. And triangular fins are attached inside the rotating heat pipe. Experimental results generally agreed with numerical results. According to increasing rpm and vapour pressure of the rotating heat pipe, the heat transfer rate increased. And also according to decreasing the concentration of ethanol, the heat transfer rate increased. In the case of using the pure ethanol as working fluid, the heat transfer rate was about 80% of using distilled water. The heat transfer rate and operating temperature difference of the rotating heat pipe was much influenced by ethanol concentration, and the optimum ethanol concentration was 0.2.

• Proceedings of the Korea Information Processing Society Conference
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• 2022.11a
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• pp.303-304
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• 2022

근골격계 질환 재활환자들의 신체 능력을 평가하기 위한 주요 측정 도구로 관절 가동 범위(ROM: Range of Motion)가 사용된다. 본 논문에서는 근골격계 환자들의 재활운동을 통한 관절 가동 범위 정보를 시각적 이해하기 용이하도록 서비스하기 위하여 3차원 아바타를 이용한 관절 가동 범위 시각화 시스템을 제안한다. 제안하는 3차원 아바타를 이용한 관절 가동 범위 시각화 시스템은 근골격계 질환 재활환자들의 관절 가동 범위 데이터를 3차원 아바타의 대응하는 관절 작동 범위로 사상하고 다양한 시점으로 시각화하거나 애니메이션으로 재현함으로써 재활 수준의 변화를 직관적으로 제공할 수 있다.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.61-70
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• 2017

In this paper, an Ethernet equalizer that compensates for automotive temperature variations within a broad range is presented. Communications in automotive systems have become increasingly important because of the many electronics in vehicles. Ethernet protocols are a good candidate for automotive communications. However, they should satisfy the AEC-Q100 requirements that stipulate an operational temperature range from -40 to $150^{\circ}C$. This paper proposes an Ethernet equalizer that can recover data up until 100 m length of CAT-5 cable adaptively within a temperature range of -40 to $150^{\circ}C$. To support the wide temperature range, a feedback system is used. The proposed equalizer has a bandwidth of 31.25 MHz with a fully-differential structure and is implemented in a Hynix $0.13{\mu}m$ BCDMOS technology.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.3
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• pp.20-28
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• 2007

The easiest way to see the phenomena of compressor surge is to show the static and dynamic operation characteristic on the map. Its operation zone will be restricted by the surge limit and, static and transient process must have some margin for it. Effect of rotor moment of inertia, air/gas volumes and heat transfer are factors to cause the transition from the static line. In case a large volume such as heat exchanger exists in the system it will exert a substantial influence to dynamic characteristics. In the present paper, influence of air volume bled from the compressor exit on transient process is investigated with an example of an auxiliary power unit micro-turbine engine. Turbine mass, pressure ratio, rotation speed, power and moment are calculated based on mass and work conservation. Result from the present study can give guidance to design the control system. A computer program is developed to calculate the dynamic process using the MathCAD commercial software.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.202-209
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• 2005

This study concerns the performance of boiling heat transfer in inclined thermosyphons with internal grooves. A study was carried out with the performance of the heat transfer of the inclined thermosyphon having 60 internal grooves in which boiling and condensation occur. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphon is also tested for comparison. Distilled water, methanol and ethanol have been used as the working fluid. The inclination angle, three working fluids, heat flux and the boiling heat transfer coefficient at the evaporator zone are estimated from the experimental results. The experimental results have been assessed and compared with existing correlations. Imura's and Kusuda's correlation for boiling showed in good agreement with experimental results within ${\pm}20%$ in plain thermosyphon. The high heat transfer coefficient was found between $25^{\circ}$ and $30^{\circ}$ of inclination angle for water and between $20^{\circ}$ and $25^{\circ}$ for methanol and ethanol. The relatively high rates of heat transfer have been achieved in the thermosyphon with internal micro grooves.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.10a
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• pp.327-332
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• 1995

가압중수형 원자로의 원자로건물내 주중기관 파단사고는 냉각재 상실사고와는 달리 핵연료 건전성이 유지됨에도 불구하고 파단 부위를 통한 과도한 중기 방출에 따른 일차측 급냉 및 감압에 의하여 경수를 수원으로 사용하는 비상노심냉각 계통(Emergency Core Cooling System:ECCS)의 작동으로 인하여 일차측 중수의 규정농도가 규정치 98% 이하로 저하되어 교체 또는 승급을 요하는 막대한 경제적 손실을 초래 할 수 있다. 원자로건물내 주중기관 파단사고시 비상노심냉각계통의 작동을 방지 또는 지연시키기 위한 운전기법으로 이차측 급수의 차단을 고려하였다. 주증기관 파단크기 50% 이하 범위에서는 원자로 정지후 급수 차단을 통해 비상노심냉각계통 작동을 막을 수 있음이 평가되었다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.11a
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• pp.229-229
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• 2013

본 연구에서는 미세 물분무 노즐의 소화성능을 분석하기 위해 유량계수, 방사거리, 방사각도, 그리고 작동압력에 따라 분사되는 물입자 크기를 측정하였다. 이를 위해서 이중 구조의 미세 물분무 노즐 LPN-61과 LPN-63을 제작하였으며, 미분무 소화설비를 구성하여 이중구조 노즐의 형상에 따라서 유동특성을 정량화하였다. 그 결과 LPN-61은 유량계수 5.116, 방사각 $120^{\circ}{\sim}125^{\circ}$로 작동압력이 $4kgf/cm^2$에서 $10kgf/cm^2$까지 증가함에 따라서 SMD는 $127{\mu}m$정도에서 $88{\mu}m$까지 입자 크기가 감소하였으며, LPN-63은 유량계수 5.121, 방사각도 $120^{\circ}{\sim}125^{\circ}$로 동일한 작동압력 범위에서 SMD는 $108{\mu}m$에서 $80{\mu}m$까지 감소하는 것을 확인하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.226-230
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• 2005

This paper presents the actuation performance of a conducting shape memory polyurethane (CSMPU) actuator. We introduced a concept of shape memory polyurethane activated by electric power while conventional shape memory polyurethanes are activated by external heat source. A conducting shape memory polyurethane actuator was manufactured by adding cabon nano-tube to conventional shape memory polyurethane. The main problem of the previous CSMPU was bad dispersion of carbon nano-tubes in polyurethane. In this paper, we have tried to find manufacturing method to solve the dispersion problem. With a lot of elaborative works, we have developed conducting shape memory polyurethane actuator with good electrical performance. The actuation performance of the developed conducting shape memory polyurethane actuator was measured and assessed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.11
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• pp.899-905
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• 2014

This paper describes preliminary research conducted for developing a high-efficiency clean large cauldron using the liquid-vapor phase change heat transfer. To improve the isothermal environment of the cauldron, naphthalene and FC-40 were selected as the working fluids to operate well in the temperature range of $100-200^{\circ}C$ and used in experimental investigations of the heat transfer characteristics. A two-phase closed thermosyphon was designed and built to demonstrate the functionality of the working fluids. Startup, boiling, and condensation tests were performed, and the test results were used to examine the possibility of complementary effects of the startup and heat transfer characteristics of the two-phase closed thermosyphon using a mixture of naphthalene and FC-40.

• Journal of the KSME
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• v.32 no.5
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• pp.410-419
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• 1992

이 글에서는 길이의 정밀 측정에 널리 사용되고 있는 여러 종류의 레이저 간섭계에 대하여 그 작동 원리 및 응용 예를 간략하게 살펴보았다. 아울러, 나노 영역에서의 길이 및 각도를 높은 정확도로 측정할 수 있는 X-선 간섭계의 원리 및 응용에 대하여도 간략히 기술하였는데, 이러한 X-선 간섭계를 이용한 정밀 측정기술은 앞으로도 개발의 여지가 많은 새로운 분야이며, 따라서 그 응용 범위도 점차 널리 확대되리라 예상된다.