• 동력기계공학회지
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• 제21권2호
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• pp.64-69
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• 2017

The purpose of this study is to investigate the performance characteristics of seawater cooling system for a fishing vessel. The circulation amount of refrigerant, condensation capacity, evaporation capacity, compression work and coefficient of performance(COP) were analyzed as the heat source temperature changed. The experimental setup consisted of an open-type compressor, a shell&tube type condenser, an evaporator and an expansion valve. The heat source was controlled by a constant temperature chamber. The main results of this study are summarized as follows. The condensation capacity increased with increasing heat source temperature, and it was confirmed that the effect of circulating amount of refrigerant was dominant. The amount of heat for vaporization was almost constant even though the temperature of the heat source increased. On the other hand, the compression power was increased. This is because the compression ratio increases as the condensation pressure, the enthalpy difference between inlet and outlet, the amount of circulating refrigerant increases. The performance coefficient of this system showed a tendency decreasing with increasing heat source temperature. Therefore, the basic data of the seawater cooling system for the maintenance of the catch line of the shore fishing boats was acquired through this study, and it is considered that it will be sufficient for the actual design.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.43-46
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• 2010

As the nuclear power plant has been constructed continuously for several decades in Korea, the welding technology for components manufacturing and installation has been improved largely. Standardization for weld test and qualification was also established systematically according to the concerned code. The welding for the main components requires the high reliability to keep the constant quality level, which means the repeatability of weld quality. Therefore the weld process qualified by thorough test and evaluation is able to be applied for manufacturing. Narrow gap SAW and GTAW process are usually applied for girth seam welding of pressure vessel like Reactor vessel, steam generator, and etc. For the surface cladding with stainless steel and Inconel material, strip welding process is mainly used. Inside cladding of nozzles is additionally applied with Hot wire GTAW and semi-auto welding process. Especially the weld joint having elliptical weld line on curved surface needs a specialized weld system which is automatically rotating with adjusting position of the head torch. The small sized pipe, tube, and internal parts of reactor vessel requests precise weld processes like an automatic GTAW and electron beam welding. Welding of dissimilar materials including Inconel690 material has high possibility of weld defects like a lack of fusion, various types of crack. To avoid these kinds of problem, optimum weld parameters and sequence should be set up through the many tests. As the life extension of nuclear power plant is general trend, weld technologies having higher reliability is required gradually. More development of specialized welding systems, weld part analysis and evaluation, and life prediction for main components should be taken into a consideration extensively.

• 한국세라믹학회지
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• 제41권3호
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• pp.229-234
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• 2004

수계슬러리의 동결건조 공정을 이용하여 배향성 기공을 갖는 NiO-YSZ 지지체를 제조하였다. 슬러리의 동결과정에서 형성된 얼음 결정은 진공건조 과정을 거치면서 승화되어 그 자리에 기공을 형성하였으며. 열전달 방향과 속도를 조절함으로써 얼음결정의 성장을 제어할 수 있음을 알 수 있었다. 제조된 NiO-YSZ 지지체는 배향성을 가진 거대(macro) 기공과 함께 표면에는 미세기공이 존재하는 독특한 기공구조를 형성하였다. 이것은 동결과정에 있어서 성형체의 위치에 따라 얼음의 성장속도가 다르기 때문에 발생하는 현상으로 생각된다. 얻어진 다공체 표면에 YSZ 슬러리를 dip 코팅하여 막을 형성한 후 140$0^{\circ}C$에서 동시소성(co-firing)하여 다공성 NiO-YSZ 지지체의 표면에 치밀한 YSZ 막이 코팅된 bilayer 제조에 성공하였다.

• 한국항공우주학회지
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• 제35권1호
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• pp.27-32
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• 2007

본 논문에서는 초음속 제트로부터 유발되는 소음의 특성을 실험적으로 분석하고, 기존의 소음예측식을 사용하여 비교해 봄으로서 예측식의 적용가능 범위를 살펴보았다. 실험을 위하여 제작된 초음속제트 발생장치의 출구마하수를 측정하기 위하여 정체실의 온도, 압력과 함께 피토 튜브를 이용하였고, 결과를 쉐도우 그래프 가시화 방법을 사용하여 얻은 결과와 비교하였다. 제트소음의 스펙트럼을 관찰한 결과, 불완전 팽창의 제트 유동에서 발생하는 충격파 관련 소음인 광대역 소음과 스크리치 톤 소음의 경향이 나타는 것을 확인 할 수 있었다. 아음속 조건에서는 큰 난류 구조에 의해 발생되는 난류 혼합 소음에 의하여 흐름방향으로 강한 방향성을 나타내었고, 초음속 조건에서는 충격파 관련 소음이 흐름의 상류 방향으로도 강하게 전파됨을 확인 하였다. 그리고 제트 엔진의 소음 예측 프로그램인 ARP876D 코드를 이용하여 실험에서 측정한 스펙트럼과 비교해 본 결과 아음속 영역에서보다는 초음속 영역에서 더 좋은 결과를 보였다.

• Journal of Biosystems Engineering
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• 제32권6호
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• pp.448-454
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• 2007

This study was conducted to develop a 100 kPa soil tensiometer mainly consisted of a porous ceramic cup, water-holding tube, and a digital vacuum gauge, through theoretical design analysis and experimental performance evaluation. Major findings were as follows. 1. Theoretical analysis showed that air entry value of a porous media decreased as the maximum effective size of the pore increased, and the maximum diameter of the pores was $2.9\;{\mu}m$ for measuring up a 100 kPa of soil-water tension. 2. Property analysis of tensiometer porous cups supplied in Korean domestic market indicated that main components were $SiO_2$ and $Al_2O_3$ with a porosity range of $33.8{\sim}49.3%$. 3. The porous cup selected through sample fabrication and air-permeability tests showed weight ratios of 87% and 11% for $Al_2O_3$ and $SiO_2$. The analysis of SEM (scanning electron microscope) images showed that the sample was sintered at temperatures of about $1150^{\circ}C$, which consisted of pores with sizes of up to 25% of those for commercial porous cups. 4. The prototype soil tensiometer was fabricated using the developed porous cup and a digital vacuum gauge that could measure water tension with a pressure of 85 kPa in air tests. 5. In-soil tests of the prototype conducted during a period of 25-day drying showed that soil-water tension values measured with the prototype and commercial units were not significantly different, and soil-water characteristic curves could be established for different soils, confirming accuracy and stability of the prototype.

• 한국항공우주학회지
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• 제30권5호
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• pp.24-31
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• 2002

축 대칭 원형노즐 출구에 삼각형 형태의 작은 탭이나 얇은 테이프가 부착되었을 때 나타나는 초음속 제트유동장의 변화에 관한 연구가 쉴리렌 영상과 피토압력 측정을 통하여 수행되었다. 노즐 출구면적의 1 %에 해당하는 작은 탭에서 나타나는 유동방향 와류에 의한 제트유동 변화는 유동이 과소팽창 될 때 완전팽창과 과대팽창의 경우에 비하여 더 크게 나타나며 이로 인한 유동유입이 더 크게 나타남을 알 수 있었다. 탭의 설치각도 변화에 의한 영향도 평가되었으며, 유동이 과대팽창 될 때 노즐 안으로 구부러진 탭의 설치가 충격파의 간섭강도를 약화시키고 이로 인한 마하디스크의 소멸현상을 관찰할 수 있었다. 아울러 노즐내부 낮은 높이의 돌출부가 후방 유동장의 원주방향으로 압력변화를 나타내고, 이러한 압력변화는 유동의 팽창 정도에 영향을 받음을 알 수 있었다.

• 에너지공학
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• 제24권2호
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• pp.91-102
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• 2015

관류식 직관형 증기발생기의 열수력 설계와 성능분석을 위한 해석코드를 개발하였다. 개발한 물리적 모델과 수치 해석 코드를 검증하기 위해 설계 제원이 공개되어 사용되고 있는 관류식 직관형 증기발생기를 개발된 코드를 이용해 해석하고 설계 자료와 비교하였다. 또한 동일한 증기발생기를 최적 열수력 안전해석코드인 MARS를 이용하여 해석한 뒤 비교분석하였다. 열전달면적, 압력 및 온도분포 등의 계산 결과는 설계 자료 및 MARS 코드의 계산 결과와 대부분 일치하게 나타났다. 최종적으로 개발된 코드가 직관형 증기발생기의 열적 설계 최적화 및 민감도 분석을 목적으로 폭넓게 사용될 수 있음을 확인하였다.

• 센서학회지
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• 제18권4호
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• pp.294-300
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• 2009

Cardiopulmonary resuscitation(CPR) is performed by artificial ventilation and thoracic compression for the patient under emergent situation to maintain at least the minimum level of respiration and blood circulation for life survival. Quality of the pre-hospital CPR not only significantly affects the patient's survival rate but also minimizes side effects caused by CPR. Good quality CPR requires monitoring respiration, however, traditional respiratory air flow transducers cannot be used because the transducer elements are located on the flow axis. The present study developed a new technique with no physical object on the flow stream but enabling the air flow measurement and easily incorporated with the CPR devices. A turbulence chamber was formed in the middle of the respiratory tube by locally enlarging the cross-sectional area where the flow related turbulence was generated inducing energy loss which was in turn converted into pressure difference. The turbulence chamber was simply an empty enlarged air space, thus no physical object was placed on the flow stream, but still the flow rate could be evaluated. Both inspiratory and expiratory flows were obtained with symmetric measurement characteristics. Quadratic curve fitting provided excellent calibration formula with a correlation coefficient>0.999 (P<0.0001) and the mean relative error<1 %. The present results can be usefully applied to accurately monitor the air flow rate during CPR.

• Journal of Chest Surgery
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• 제39권1호
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• pp.68-71
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• 2006

종격동 섬유화로 인한 상대정맥증후군을 가진 41세의 남자 환자를 정맥 우회단락을 사용하여 상대정맥 재건술을 시행하였다. 환자는 수술 전 상당히 높은 중심 정맥압을 보였으며, 수술 시 측행혈관이 차단될 수밖에 없어, 수술에 따른 신경학적 합병증의 위험성이 높았다. 수술은 막힌 상대정맥과 무명정맥을 제거한 후에 자가 심낭을 튜브 모양으로 만들어 재건술을 시행하였으며, 수술 중에 정맥 우회 단락을 이용하여 두경부 및 상지의 정맥환류를 유지하였다. 우회단락의 사용은 상대정맥증후군의 수술 시 정맥압을 즉시 감소시키고, 수술시간에 따른 부담이 없었으며, 수술 후 합병증 발생을 예방하는데 효과적이었다.

• 대한기계학회논문집A
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• 제32권11호
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• pp.951-956
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• 2008

The high temperature creep properties of the generating plant's high temperature tube, pipe and header and such are very significant in accordance with long-time exposure to the high temperature and pressure environment. Not only this, but as the welding procedure is compulsory for the cohesion of components, the creep properties regarding the local microstructures of steel weldment are very important. In order to understand the creep properties regarding the local microstructures of steel weldment, the SP-Creep test which is easy to get sample from the field component was conducted. The local microstructure of steel weldment, that is, W.M. and B.M.'s microstructures were observed using the SEM. The rupture time of W.M. was longer as 110 % averagely in a same condition, which is the consequence of the difference of the microstructure. Each lethargy coefficient of B.M. and W.M. is evaluated by the relation among the temperature, load and the rupture time from SP-Creep Test. The life estimation equation can be induced by the transformation of Power-law. B.M. and W.M. for each $550\;^{\circ}C$ and $575\;^{\circ}C$, the very similar to normal temperature of the domestic thermal power generation in working, are estimated.