• 에너지공학
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• 제14권1호
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• pp.30-36
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• 2005

본 논문에서는 실린더 후류 영역의 열전달 특성에 대한 실험결과를 보고하였다. 정체점(θ=0°)로부터 실린더 뒷면(θ=180°)까지 국소 열전달을 측정하였으며, 축 방향에 대한 누셀트 수의 변화도 조사하였다. 덕트 중앙에 비하여 덕트 벽면근처의 후류영역 열전달계수는 58% 정도 높게 측정되었으며, 종횡비와 열전달 경계조건의 영향도 조사하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2838-2843
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• 2011

Recently, the floating slab track that can effectively mitigate the vibration and structure-borne noise is being discussed to be adopted. The floating slab track which is a track system isolated from the sub-structure by vibration isolators. Unsimilarly to conventional track and the slab deflection is large. Therefore, the running safety and ride comfort should be investigated. Especially at slab joint since the load cannot be transferred, the possibility that the dynamic behavior of track and train became unstable is high. Thus, in general dowel bar are often installed at slab joints. To determine the appropriate dowel ratio the load transfer characteristics should be investigated. In this study, dowel bar joint is modeled by equivalent shear spring and this model is verified by comparison with experimental results. Using the proven model, the load transfer efficiency and deflection at slab joint according to dowel ratio, and stiffness and spacing of vibration isolator were examined.

• 한국분무공학회지
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• 제21권4호
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• pp.177-183
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• 2016

In this study, the evaporation characteristics of water or nanofluid droplets on a heated surface was investigated by visualization of the evaporation process and evaluation of the heat transfer coefficient using the droplet temperature measured. The evaporation characteristics was compared between water and nanofluid droplets and the effects of the mass ratio of nanofluid and the inclination of heated surface were analyzed. The heat transfer rate of nanofluid droplet was higher than that of water droplet. The heat transfer coefficient was increased with the increase of the mass ratio of nanofluid. The effect of the inclination of heated surface was much higher than that of fluid type used, which indicates that the inclination of heated surface should be considered as one of influential parameters in the spray cooling process.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.418-422
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• 2001

To achieve a high performance in direct vector control of induction motor, it is essential to correct estimation of rotor flux. The accuracy of flux observers for induction machines inherently depends on parameter sensitivity. This paper presents an analysis method for conventional flux observers using Parameter Sensitivity. The Parameter sensitivity is defined as the ratio of the percentage change in the system transfer function to the percentage change of the parameter variation. We define the ratio between real flux and estimated flux as the transfer function, and analyzed a parameter sensitivity of this transfer function by simulation.

• 대한기계학회논문집
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• 제14권1호
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• pp.225-229
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• 1990

본 연구에서는 외부조건과 입력이 일정하게 주어져 있는 냉동 사이클에 대하 여 열교환기의 용량을 설계변수로 하여 출력과 효율이 최대가 되는 조건, 즉 최적 설 계조건을 살펴 보고자 한다. 아울러 이 조건과 엔트로피 생성 최소조건과의 관계와 비가역 사이클인 경우도 살펴보았다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 추계학술대회 논문집
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• pp.7-10
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• 2001

To obtain a high performance in a direct vector controlled induction machine, it is essential to correct estimation of rotor flux. The accuracy of flux observers for induction machines inherently depends on parameter sensitivity. This paper presents an analysis method for conventional flux observers using Parameter Sensitivity. The Parameter sensitivity is defined as the ratio of the percentage change in the system transfer function to the percentage change of the parameter variation. We define the ratio between real flux and estimated flux as the transfer function, and analyzed a parameter sensitivity of this transfer function.

• Journal of Advanced Marine Engineering and Technology
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• 제22권3호
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• pp.294-302
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• 1998

The charateristics of the convective mass transfer in horizontal rectangular enclosure with horizontal concentration gradients are analyzed. The effect of Grashof number(Gr) and aspect ratio(L/H) is investigated numerically using the control-volume method. Numerical results are obtained for Grashof numbers between $10^4$ and $10^6$ aspect ratios from 1 to 100 and results are compared with existing andlytical results. It is found that there exists a well defined aspect ratio for which the mean Sherwood number is maximum and the core flow changes from parallel to non-parallel at $Gr^2{Sc^2}(A^{-3}}{\geq}{10^5}$ and in the Ralongrightarrow0 regime the numerical results agreed very well with correlation derived from analytical results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1176-1178
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• 2001

To obtain a high performance in a direct vector controlled induction machine, it is essential to correct estimation of rotor flux. The accuracy of flux observers for induction machines inherently depends on parameter sensitivity. This paper presents an analysis method for conventional flux observers using parameter Sensitivity. The Parameter sensitivity is defined as the ratio of the percentage change in the system transfer function to the percentage change of the parameter variation. We define the ratio between real flux and estimated flux as the transfer function, and analyzed a parameter sensitivity of this transfer function.

• 설비공학논문집
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• 제24권8호
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• pp.621-626
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• 2012

A new baffle configuration, an annular baffles, are considered in the present study as an alternative to reduce the excessive pressure drop associated with the conventional segmental ones in typical operating conditions. The heat transfer and pressure drops are numerically simulated for a single tube shell-and-tube model and compared against the conventional-baffle cases. Baffle blockage ratio and number of baffles are considered as the major variables for the present study specifying a fixed baffle spacing. It is found that the heat transfer increases 1.4~2.2 times without significant pressure loss compared to the bare tube cases and the goodness factor increases 1.35 times compared to the conventional-baffle model.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.353-356
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• 2006

본 논문에서는 초음속 유동장내에 분사된 이차제트 주변에서의 열전달 현상을 고찰 하였다 초음속 유동장내에 등열유속조건이 적용된 표면을 설치하고, jet to freestream momentum ratio의 변화에 따른 2차분사를 하여, 2차분사 노즐 주변의 표면온도변화를 적외선카메라를 통하여 측정하였으며, 이를 바탕으로 대류열전달계수를 계산하였다.