• 설비공학논문집
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• 제16권6호
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• pp.546-555
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• 2004

With circular tube heated directly or indirectly placed in a cross flow, heat flows circumferentially by conduction due to the asymmetric nature of the fluid flow around the perimeter of the circular tube. The circumferential heat flow affects the wall temperature distribution to such an extent that in some cases. The effects of circumferential wall heat conduction on local convective heat transfer is investigated. The wall heat conduction parameter which can be deduced from the governing energy equation should be used to express the effect of circumferential heat conduction. Two-dimensional temperature distribution is presented through the numerical analysis. The comparison of one-dimensional and two-dimensional solutions is demonstrated on graph of local Nusselt numbers.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
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• pp.36-41
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• 1994

프리캐스트 프리스트레스트 콘크리트 상자형 교량의 정착부에 프리스트레스 힘이 도입되면, 과다한 국부집중 하중으로 인하여 균열이 발행할 수 있으며, 최근 이러한 교량의 건설시 텐던을 따라가며 심각한 균열이 발생한 경우가 있다. 본 논문은 프리캐스트 프리스트레스트 콘크리트 상자형 교량의 정착부에 발생하는 국부집중 응력의 분포 특성을 규명하고, 이를 토대로 파괴기구 고찰함에 목적이 있다. 이를 위하여 정착부 파괴에 직접적인 영향을 미치는 단면의 형상, 텐던의 배치상태, 국부보강 철근의 형태 및 구조보강 철근량 등을 변수로 하는 역학적 거동 실험 및 해석 연구가 수행되었다. 위의 실험 및 해석연구결과 정착부 파괴양상이 규명되었으며, 프리스트레스 정착부의 새로운 파괴기구 개념이 제시되어, 정착부 파괴과정을 적절히 설명하고 있다.

• 대한기계학회논문집B
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• 제27권2호
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• pp.155-162
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• 2003

Design optimization of a transonic compressor rotor (NASA rotor 37) using response surface method and three-dimensional Navier-Stokes analysis has been carried out in this work. Baldwin-Lomax turbulence model was used in the flow analysis. Three design variables were selected to optimize the stacking line of the blade. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, adiabatic efficiency was successfully improved. It is also found that the design process provides reliable design of a turbomachinery blade with reasonable computing time.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.275-280
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• 2004

Shape optimization was performed to obtain the precise shape of cutouts including the internal shape of cutouts in laminated composite plates by three dimensional modeling using solid element. The volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. The volume control of the growth-strain method makes Tsai-Hill failure index at each element uniform in laminated composites under the initial volume. Then shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study. (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsal-Hill failure index was reduced up to 67% when shape optimization was peformed under the initial volume by volume control of growth-strain method.

• 대한기계학회논문집A
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• 제27권5호
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• pp.833-839
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• 2003

The effects of stiffeners on the modal characteristics of rectangular plates are investigated. A modeling method for the modal analysis of rectangular plates with stiffeners is presented. A mass density Dirac's delta function is used to idealize the stiffeners mathematically. The equations of motion for the plates are derived and transformed into a dimensionless form. To confirm the accuracy of the method presented in this study, numerical result are obtained and compared to those of a commercial program. The mode shape variations due to some parameter variations are also exhibited.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.572-575
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• 2008

Flow-field design has much influence over the performance of proton exchange membrane fuel cell (PEMFC) because it affects the pressure magnitude and distribution of the reactant gases. To obtain the pressure magnitude and distribution of reactant gases in four kinds of flow-field designs without additional measurement equipment, computational fluid dynamics (CFD) analysis was performed. After the CFD analysis, the performance values of PEMFC according to the flow-field configurations were measured via a single cell test. As expected, the pressure differences due to different flow-field configurations were related to the PEMFC performance because the actual performance results showed the same tendency as the results of the CFD analysis. A large pressure drop resulted in high PEMFC performance. So, the single serpentine configuration gave the highest performance. On the other hand, the parallel flow-field configuration gave the lowest performance because the pressure difference between inlet and outlet was the lowest.

• 소음진동
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• 제10권2호
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• pp.312-318
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• 2000

A modeling method for the vibration analysis of rotating cantilever plastes with stiffeners is presented. The equations of motion for the plates aer derived and trnasformed into a dimensionless form. A mass density Dirac's delta function is used to idealize the stiffener mathematically. The effects of stiffeners on the model characteristics of the plate are investigated, and mode shape variations due to some parameter variation are exhibited. It is found that veering phenomena occur between some loci and associated mode shapes change significantly during the veering phenomena.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.195-198
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• 2002

Demand for high precision measurement of large area is increasing in many industrial fields. White-light Scanning Interferometer(WSI) is a well-known method for 3D profile measurement. However WSI has some limitations in a measurement range because of the sensing mechanism. Therefore, in this paper we use a heterodyne laser interferometer to get over the limitations of a short measurement range in WSI, We suggest a new WSI system combined with heterodyne laser interferometer. This system is aimed at eliminating Abbe error with measuring the focus point directly. With the use of triggering functionality of WSI, we can use this system as a probe of a precision stage such as a probe of CMM. The suggested system gives a repeatability of 87 nm in the absolute distance measurement test under the laboratory environment.

• 한국정밀공학회지
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• 제17권4호
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• pp.203-208
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• 2000

2진 로봇 머니퓰레이터는 기하학적 형상이 가변트러스 구조로 되어 있으며 조인트의 구동원으로 사용되는 엑츄에이터는 2가지의 변위, 즉 최대 및 최소 변위만으로 동작한다. 따라서 작업영역은 연속적으로 주어지는 일반 로봇 머니퓰레이터와는 달리 유한 개의 위치 벡터의 집합 형태로 나타난다. 기존의 역기구학적 해석방법을 적용하기 어려운 2진 로봇 머니퓰레이터의 불연속적인 특성에 대해 새로운 작업영역과 역기구학 문제를 정의하였다. 유전 알고리즘을 사용하여 새로이 정의된 문제의 역기구학적 해석을 수행하였으며 유전 알고리즘이 2진 로봇 머니퓰레이터의 역기구학적 해석에 있어서 효과적이고 강건한 방법임을 보여주었다.

• Tribology and Lubricants
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• 제12권4호
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• pp.13-17
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• 1996

립실의 중요 설계 변수인 접촉력의 측정에는 스플릿트축장치가 흔히 사용된다. 축과 립실의 간섭량은 두 개 스플릿트축의 간격으로서 조절된다. 두 축을 초기 위치로부터 측정하고자 하는 임의 위치로 이동시킬 때 정확한 원을 이루지 못해 측정되는 접촉력은 오차를 포함되게 된다. 본 연구에서는 작은 간섭량 범위 내에서 접촉력을 이론적으로 예측할 수 있는 수식을 유도하고 측정 오차 값을 예측하였다. 측정된 립실의 접촉력은 측정 간섭량이 초기간섭량과 일치하는 경우 외에는 항상 오차를 포함하고 있음을 밝혔다. 이 오차는 작은 간섭량 범위 내에서 립실의 재료 특성이나 형상에 무관하며, 10% 이내의 측정 오차 유지를 위해서는 측정 간섭량이 초기 간섭량의 68%에서 187% 범위 내에 들어야 함을 확인하였다.