• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.523-524
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• 2008

• 한국인터넷방송통신학회논문지
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• 제12권2호
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• pp.145-151
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• 2012

심혈관계 질환의 발병 위험요인 분석이 가능한 맥진기는 한방 의료기기에서 대표적인 연구 분야 가운데 하나이다. 그러나 기존의 대부분의 센서 기반의 맥진기는 측정시의 맥박 박동처와 센서부의 접촉상태에 따른 편위, 검출된 파형의 부정확성 및 파형분석의 어려움 등에 있어서 문제점이 발생한다. 따라서 본 논문에는 특성 센서를 사용하지 않고 단지 맥동에 의해서 유발되는 모세관 시험액의 상태 변화를 촬영한 맥동영상을 분석하여 환자의 맥파의 측정이 가능한 맥진기를 제안한다. 제안한 방법에서는 맥동영상 분석을 위한 시약영역 추출, 이진화, 수정된 열림연산, 변위측정 등의 영상처리 방법들이 적용된다. 제안한 맥진기의 성능 평가를 위해서는 추출된 압맥파로부터 맥파분석에 필수적인 5가지 주요 특징점에 대한 추출률을 측정한 결과 성공적인 결과를 보였다.

• 대한의용생체공학회:의공학회지
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• 제41권1호
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• pp.8-13
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• 2020

To develop cardiovascular simulator capable of implementing pulse waves similar to the human body, accurate information about reflection wave is required. However, the conclusion is still not clear and various discussions are underway. In this study, the pulse wave velocity of the tube used in the experiment was first determined by measuring the pressure waves at two points in a single tube system with the experimental device to implement the pulse wave transmission of blood vessels, and the superposition time and characteristics of the reflection wave were confirmed. After that, an air chamber was set at the reflection site, and the effect of the change of air volume on the reflection wave was investigated. Finally, the effect of the number of branches connected to a single tube on the reflection wave was investigated. The superposition time of the reflection wave can be controlled by the air volume of the air chamber, and the magnitude of the reflection wave is influenced by the number of reflection sites that generate the reflection wave. The results of this study may be of practical assistance to simulator researchers who want to implement pulse wave similar to clinical data. It is expected that the more results similar to clinical are provided, the greater the scope of the simulator's contribution to clinical cardiovascular research.

• 한국음향학회지
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• 제34권3호
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• pp.192-199
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• 2015

펄스 튜브를 이용하여 시편의 전달 손실 성능을 측정할 경우, 시편 설치를 위해 필연적으로 시편과 펄스 튜브 내벽 사이에 간극이 존재한다. 본 논문에서는 이와 같은 간극이 전달 손실 측정 결과에 미치는 영향에 대해 평가했다. 평면파에 대해 일정 폭 및 길이를 갖는 간극 전과 후 음압의 비를 구하여 전달 계수를 유도하고 측정 대상 시편의 전달 계수와 조합하여 간극이 포함된 시편의 전달 손실을 구했다. 이와 같은 해석 모델을 이론해가 존재하는 10 mm 두께의 스테인리스 스틸 시편에 적용하여 시험 결과와 비교함으로서 해석 모델의 적절성을 보였다. 마지막으로 해석 모델을 통하여 간극크기 및 시편 전달 손실 성능에 따라 전달 손실 측정에 미치는 영향을 분석했다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권5호
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• pp.190-197
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• 2005

A reliable and compact pulse power supply using a thyratron and a magnetic pulse compression (MPC) circuit was developed for a metal vapor laser. The life time of the pulse power supply is expected to be much longer than that of a conventional thyratron-discharge type pulse power supply. A thyratron generated a long pulse of its conduction pulse width 500 ns and then it was compressed to less than 80 ns of its output voltage rise time by a three stage MPC circuit. This pulse power supply was applied to a laser plasma tube of 30 mm inner diameter and 1.5 m discharge length. It was operated several hundreds hours without any troubles.

• 한국전산유체공학회지
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• 제19권3호
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• pp.14-19
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• 2014

The flow characteristics of inertance pulse tube cryocooler(IPTC) was investigated with a computational thermal fluid dynamics for the reciprocating flow in IPTC including the piston movement of linear compressor. Two dimensional axisymmetric modeling was applied for the flow in an IPTC with a clearance between the piston and cylinder wall of linear compressor. The pressure, velocity, and temperature distribution were examined for the steady state. These were compared with previous results to confirm the validity in the modeling and computational results. The leakage between piston and cylinder wall affect the cooling capacity seriously. The dependence on mesh numbers were also examined to obtain a proper mesh numbers to improve the accuracy of calculation, which showed significant effect on the results. The user-defined function was used for the process of compression and expansion of piston.

• 한국진공학회지
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• 제22권2호
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• pp.45-54
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• 2013

맥동관형 크라이오펌프 개발 사업 2단계를 맞아 우성진공(유)을 중심으로 상용화 시제품 개발이 성공적으로 끝나가고 있다. 최종 크라이오펌프 개발품은 흡기구 직경(내경) 16.5 (14) 인치에 질소 배기속도 3,600 L/s 이상을 목표로 하고 있다. 개발품의 성능확인을 위해 우선 몬테카를로 계산을 통해 배기속도를 예측하고 구조설계를 최적화했으며 이를 바탕으로 가공 조립된 크라이오펌프 시제품의 성능을 표준화된 장치에서 표준화된 절차를 통해 평가하여 설계 목표값과 비교했다. 시제품의 질소 배기속도는 4,600 L/s로 측정되어 설계값과 잘 일치하였으며 개발목표를 훨씬 상회하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제20권3호
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• pp.21-27
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• 2018

It is difficult to fabricate and maintain moving parts of expander at cryogenic temperature. This paper describes numerical analysis and experimental investigation on a cryogenic reciprocating expander without moving piston. An intake valve which takes high-pressure gas, and an exhaust valve which discharges low-pressure gas, are connected to a tube. The inside pressure of the tube is pulsated for work production. This geometric configuration is similar to that of pulse tube refrigerator but without regenerator. An orifice valve and a reservoir are installed to control the phase of the mass flow and the pressure. At the warm end, a heat exchanger rejects the heat which is converted from the produced work of the expanded gas. For the numerical analysis, mass conservation, energy conservation, and local mass function for valves are used as the governing equations. Before performing cryogenic experiments, we carried out the expander test at room temperature and compared the performance results with the numerical results. For cryogenic experiments, the gas is pre-cooled by liquid nitrogen, and then it enters the pulse tube expander. The experiments are controlled by the opening of the orifice valve. Numerical analysis also found the expander conditions that optimize the expander performance by changing the intake pressure and valve timing as well as the opening of the orifice valve. This paper discusses the experimental data and the numerical analysis results to understand the fundamental behavior of such a newly developed non-mechanical expander and elucidate its potential feature for cryogenic application.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.624-628
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• 2011

펄스데토네이션 엔진의 개발을 위해서는 데토네이션 현상의 이해와 그 발생 및 분석 기법에 대한 고찰이 필요하다. 본 연구에서는 산소($O_2$)-아세틸렌($C_2H_2$) 추진제 조합을 사용하는 DDT 튜브를 제작하였으며, 추진제 당량비 및 Schelkin spiral 유무에 따른 데토네이션파 생성특성에 관한 실험적 연구를 수행, 데이터를 수집, 분석하였다.

• 태양에너지
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• 제9권3호
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• pp.64-72
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• 1989

In this study, the computer simulation for the heat transfer in pulse combustion water heater is performed. The attention is focused to the effects of the installation of corebuster in the flue tube on heat transfer. The energy equations are established for both wall and gas side in the combustion chamber, flue way, exhaust chamber and muffler, and the numerical calculation is executed. Zone method takes longer computer calculation time compared with semi-zone method. Semi-zone method is chosen for numerical calculation. As a result of this study, it is found that the installation of the core buster in flue tube increases total heat transfer. It is also found that the total heat transfer is increased with the increasing of the ratio of the cross section area of corebuster to that of the flue tube. However, the heat transfer effect is negligible for the area ratio above 0.5.