• 한국정밀공학회지
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• 제30권7호
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• pp.667-672
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• 2013

This paper presents the development of a condition monitoring system that monitors the operating conditions of a reduction unit, such as the bearing temperature, gearbox vibration, and gear oil deterioration, and notifies the operator of potential problems or abnormal conditions. A series of field tests on high-speed rail and conventional lines was performed to identify the characteristics of temperature rise and vibration levels on the reduction unit during operation. The monitoring system was designed based on the proper sensor selection, measurement method, and signal analysis to optimize the interface with the operating system of high-speed trains. Application of this monitoring system to high-speed trains will play an important role in their proper maintenance and safe operation.

• 생물환경조절학회지
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• 제12권3호
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• pp.127-131
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• 2003

본 연구에서는 양봉사 내부환경을 보다 효율적으로 조절할 수 있는 환기팬 작동방식을 구명하기 위하여 시뮬레이션을 통해 얻어진 환기팬 작동방식에 대한 연 구결과를 양봉사에 직접 적용하여 실험을 실시하였으며, 양봉사 내부의 온도 및 습도변화에 대한 시율레이션과 실험결과를 비교 ${\cdot}$ 분석하여 양봉사 설계시 양봉사 열환경 해석 프로그램의 적용성을 검토하고, 실험결과를 이용하여 환기팬 작동방식별 양봉사 내부환경의 조절 성능을 분석하였다. 기 개발된 양봉사 열환경 해석 프로그램은 앞으로 양봉사 설계에 적절하게 이용할 수 있을 것으로 판단되었다. 외부기온이 비슷한 조건에서는 환기팬 작동방식 B의 경우가 A의 경우보다 양봉사의 내부온도가 대체로 더 낮았으며, 평균적으로 벌통 내부는 2.8$^{\circ}C$, 양봉사 내부는 2.1$^{\circ}C$ 더 낮았다. 이것은 Lee 등(1998b)이 제시한 환기팬 작동방식에 따라 양봉사 내부의 승온억제를 최고 2.8$^{\circ}C$까지 할 수 있다는 내용을 뒷받침하는 실험결과이다. 환기팬 작동방식 A와 B 모두 꿀벌이 월동하기에 적합한 상대습도 범위 (50~75%) 였으나, 방식 B가 A 보다 양봉사 내부 습도의 최고 및 최저편차가 약 2%, 평균습도가 약 5% 적게 나타나 습도환경조절에 있어 좀 더 안정적인 것으로 판단되었다. 따라서 환기팬 작동방식 B는 A 에 비하여 양봉사 내부환경조절 성능이 더욱 우수하고 효율적인 것으로 판단되었다.

• 한국정밀공학회지
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• 제23권1호
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• pp.193-200
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• 2006

To perform the finish grinding process of ferrules which are widely used as fiber optic connectors, a high-precision centerless grinding machine is necessary. The high-precision centerless grinding machine is consisted of the hydrostatic GW and RW spindle systems, hydrostatic RW feeding mechanism, RW swivel mechanism, on-machine GW and RW dressers, and concrete-filled steel bed. In this study, the thermal characteristics of the high-precision centerless grinding machine such as the temperature distribution, temperature rise and thermal deformation, are estimated based on the virtual prototype of the grinding machine and the heat generation rates of heat sources related to the machine operation conditions. The reliability of the predicted results is demonstrated by the temperature characteristics measured from the physical prototype. Especially, the predicted and measured results show the fact that the high-precision centerless grinding machine has very stable thermal characteristics.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.202-202
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• 2006

With a modern size exclusion chromatography (SEC) column, molecular weight analysis of a polymer sample takes about 10 min. However, it is desirable to reduce the analysis time further, in particular, for high throughput measurements required in combinatorial analyses or 2D-HPLC analyses. We implemented the high temperature SEC for the purpose. By inserting a narrow bore tubing between the column and the detector, a sufficient backpressure can be maintained to prevent the mobile phase from boiling and the effluent is cooled down enough when it reaches the detector. Therefore, a normal SEC detector can be used without any modification. The SEC resolution is greatly improved at the elevated temperature at high flow rate which allows high speed operation.

• Journal of Welding and Joining
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• 제26권5호
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• pp.60-65
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• 2008

Ferritic stainless steels of the 400 series have been available for automotive exhaust system, heat exchanger, radiater etc. in various industrial because heat resistance, corrosion resistance and strength are excellent. Especially, automotive exhaust system is required good heat resistance because typical temperature of exhaust system exposed during operation of engine is reach up to $800^{\circ}C$. However, research for effect of high temperature in ferritic stainless steels is not enough. In this study, high temperature tensile properties of lap weld of ferritic stainless steels(STS 429) were investigated. In accordance with heat input, lap welds had been produced and were evaluated at high temperature($800^{\circ}C$) to compare high temperature tensile properties. In addition, room temperature tensile tests were carried out for non-aging and aging specimens. As a result of R.T tensile test, non-aging specimens were fractured in base metal except for low heat input specimen and aging specimens were fractured in weld metal. Also high temperature tensile test were carried out by aging specimen. After high temperature tensile test, fracture of aged specimen was occurred in base metal except for low heat input specimen. Fracture surface of low heat input specimen in weld metal was confirmed as brittle fracture with observation using scanning electron microscope(SEM). Significant decrease in ultimate tensile strength (between 82 and 85%) was observed for aged ferritic stainless steels(STS 429) when tested at high temperature.

• 한국압력기기공학회 논문집
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• 제16권1호
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• pp.65-73
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• 2020

Integrity evaluations on a platen superheater were conducted as per ASME Section VIII Division 2(hereafter 'ASME VIII(2)') which was originally used for design with implicit consideration of creep effects. A platen superheater subjected to severe loading conditions of high pressure and high temperature at creep regime in a supercritical thermal plant in Korea was chosen for present study. Additional evaluations were conducted as per nuclear-grade high-temperature design rule of RCC-MRx that takes creep effects into account explicitly. Comparisons of the two results from ASME VIII(2) and RCC-MRx were conducted to quantify the conservatism of ASME VIII(2). From present analyses, it was shown that the design evaluation results exceeded allowable limits of RCC-MRx for the plant design conditions although limits of ASME VIII(2) were satisfied regardless of operation time, which means that design as per ASME VIII(2) might be potentially non-conservative in case of operation in creep range. A high-temperature design evaluation program as per RCC-MRx, called 'HITEP_RCC-MRx' has been used and it was shown that pressure boundary components can be designed reliably with the program especially for the loading conditions of long-term creep conditions.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.3672-3679
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• 2015

열차 운행에 따른 전장품들의 발열을 예측하기 위해 동력차 내 벽면온도 및 외부 유출 온도 및 풍속, 외부로부터 유입되는 유입 공기의 유입 온도 및 속도를 측정하였다. 이를 위하여 적외선카메라를 이용하여 고속열차 내부의 전장품 및 벽 표면의 온도를 측정하였다. 또한 전장품에서 발생하는 열은 고속열차 천장에 설치된 덕트를 통하여 외부로 배출된다. 배출되는 공기의 온도 및 속도를 측정하였고, 외부에서 동력차 내부로 들어오는 유입공기의 온도 및 속도도 측정하였다. 또한 부착형 온도센서를 이용하여 동력차 내부의 벽 및 전장품 표면에서의 온도를 측정하였다. 측정된 결과를 이용하여 열차 주행에 따른 전장품의 발열 특성을 분석하였다.

• 전기전자학회논문지
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• 제26권1호
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• pp.111-118
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• 2022

본 논문에서는 고전압 SiC Power 소자와 집적이 가능한 4H-SiC CMOS에 대해 연구하였다. SiC CMOS 소자 연구를 통해 고출력 SiC Power 소자와 함께 제작을 가능하게 함으로써 SiC 전력소자를 이용하는 고출력 시스템의 효율 및 비용면에서 우수한 성능을 기대할 수 있다. 따라서 4H-SiC 기판에서 CMOS를 설계한 후 TCAD 시뮬레이션을 통해 전기적 특성 및 고온 동작 신뢰성을 비교하였다. 특히 높은 온도에서 신뢰성 있는 동작을 위해 gate dielectric으로 HfO₂를 변경함으로써 SiO₂보다 열적 특성이 개선됨을 확인하였다.

• 한국기계가공학회지
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• 제17권5호
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• pp.97-102
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• 2018

Combat vehicles require high levels of maneuverability, firepower, armor, and operability. A high-performance power system is required for optimal maneuverability. The fuel pump which supplies fuel stably is very important to achieve this. The fuel pump consists of a pump part, a motor part, and a control part. It is equipped with a BLDC motor. Numerous failures of the fuel pump occurred during vehicle operation when exposed to vibration, shock, and high temperature. The cause of failure was confirmed to be stator slip of the BLDC motor. Stator slip is a consequence of the interference loss between the stator and the housing of the motor part in an high temperature environment. The failure of the fuel pump was solved through size control of the motor housing and the stator. We performed vibration testing at high temperature for verification. This study contributes to improving the reliability of combat vehicles.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.628-631
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• 2001

Current lead is one of the first proposed devices for the application of High Temperature-Superconductor(HTSC). The current lead provides high current for electrical machine using superconductor from room temperature. Its characteristics that is zero resistance and low heat transfer rate under critical temperature lead to research for the replacement of existing current lead with HTSC. In this paper, we investigated the temperature distributions of stacking type and rod type current lead with each cross-section area and length using Nastran program and compared each temperature distribution. It is obtained from this paper that stacking type current lead has flat temperature gradient and than rod type one and more stable operation as current lead is closely related with its cross-section area and length.