• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.73-76
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• 2007

The present paper describes the results of performance analysis for UH-60A rotor blade in hover. For the numerical simulations, commercial CFD software, FLUENT was used with Spalart-Allmaras turbulence model. The flow solver was based on node based scheme and second order spatial accuracy options was used for simulations. For the enhancement of wake capturing capability, high resolution grid was used around tip vortex region. Granting that somewhat over prediction of thrust was observed near blade tip region, performance was well correlated with experimental data within 3% accuracy in the operating region. Finally it was shown that the present flow solver can be used for preliminary performance analysis tool for hovering helicopter rotor blades.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2195-2199
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• 2007

We demonstrate that high-resolution (~60 nm) near-field fluorescence images of fluorescent nanospheres can be obtained by utilizing the tip-induced fluorescence quenching process. A time-stamped photon counting (TSPC) technique employed enables us to efficiently measure the degree of fluorescence quenching caused by the dielectric or metallic atomic force microscopy tip. We find that the degree of quenching is not only determined by the tip-material but also by the local morphology of the tip. The fringe patterns around individual nanospheres observed are explained in terms of the interference between the excitation field that is directly induced by the laser source, and the scattered excitation field from the tip.

• 광산업정보
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• 통권15호
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• pp.60-65
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• 2003

• Plant Resources
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• 제7권3호
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• pp.200-205
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• 2004

Sweet potato infected with a viral disease (SPFMV) showed irregular chlorotic patterns, so called feathering associated with faint or distinct ring spots that have purple-pigmented borders. SPFMV was eliminated from sweet potato plants using meristem tip culture. MS medium supplemented with BAP (2mg/L) and NAA (0.05 mg/L) was used for shoot proliferation and 1/2 MS medium for rooting of the plants. Highest percentage of regenerated plants (60%) was obtained from the optimum size (0.3-0.5mm) meristem tips. Of these, 60% plants were found negative for SPFMV by RT-PCR. Virus detection by RT-PCR was found to be a reliable method. Meristem-tip culture to produce SPFMV-free quality sweet potato and virus detection by RT-PCR is an efficient, time saving and reliable method for production of SPFMV-free tissue culture raised plants.

• International Journal of Aeronautical and Space Sciences
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• 제10권2호
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• pp.106-116
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• 2009

In order to investigate change of vortex structures and its evolving proceses, two dimensional LDV system was used for measurement of velocity vectors of tip vortex, and PIV system was also used for visualizations of tip vortex array for two bladed rotor, respectively. Experiments provided vortex locations, tangential and axial velocity components of tip vortex at six wake ages of 9.5, 10.5, 60.5, 99.5, 129.5, 169.5 and corresponded six wake ages shifted with 180 degrees per each. It was resulted that tip vortices generated by the first blade satisfy Landgrebe's model for their vortex locations even after they were accelerated by the second blade in downstream. Tangential velocity components of tip vortices follow Vatistas' n=2 model on both inside and outside regions of rotor slipstream without loss of vortex circulation. Axial velocity profiles revealed that there were small but significant perturbations just outside the primary vortex core which implies the second blade affects the wake substantially. It was also found that tip paths of each blade were not willing to be coincided intrinsically.

• 한국추진공학회지
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• 제14권6호
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• pp.60-68
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• 2010

본 연구에서는 팁 형상이 가스터빈 블레이드의 팁 열전달에 미치는 영향을 알아보기 위하여 선형 캐스케이드의 블레이드에 설치된 평면 팁, 스퀼러 팁, Groove 팁들에 대하여 열전달 계수가 측정되었다. 블레이드 팁에서의 열전달 계수는 색상검출방식에 기반을 둔 천이액정법을 이용하여 측정되었으며 각각의 팁 형상에 대하여 팁 간극은 블레이드 스팬의 1.5%와 2.3% 두 조건에서 실험을 수행하였다. 캐스케이드 출구 속도와 블레이드 코드길이에 기초를 둔 Reynolds 수는 $2.48{\times}10^5$ 이다. Groove 팁 표면에서의 열전달 계수는 평면 팁보다 낮게 측정되었으며, 특히 흡입면을 따라 경사진 홈이 파인 팁에서는 스퀼러 팁보다 낮은 열전달 계수가 측정되었다.

• 한국전산유체공학회지
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• 제13권4호
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• pp.45-49
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• 2008

The present paper describes the results of performance analysis for UH-60A rotor blade in hover. For the numerical simulations, commercial CFD software, FLUENT was used with Spalart-Allmaras turbulence model. The flow solver was based on node based scheme and second order spatial accuracy options was used for simulations. For the enhancement of wake capturing capability, high resolution grid was used around tip vortex region. Granting that somewhat over-prediction of thrust was observed near blade tip region, performance was well correlated with experimental data within 3% accuracy in the operating region. Finally it was shown that the present flow solver can be used as a preliminary performance analysis tool for hovering helicopter rotor blades.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.353-353
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• 2007

탄소나노튜브(CNT)의 tip 부분에 존재하는 금속 촉매 입자들은 불순물로써 나노전자소자에 응용하는데 좋지 않은 영향을 미칠 수 있다. 또한, 바이오센서에서 target 바이오 물질과 반응하는 물질을 CNT에 고정시키기 위해서는 CNT-tip을 개방시키는 것이 중요하다. 본 연구에서는 성장된 CNT의 tip부분에 존재하는 금속 촉매 입자의 제거와 CNT-tip을 개방하기 위해 $HNO_3$의 농도 (20, 40, 60)와 etching 시간 (5, 10, 15, 20, 25 min)에 따라 최적의 조건을 찾는 실험을 하였다.

• Journal of Welding and Joining
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• 제22권1호
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• pp.43-49
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• 2004

Contact tip is located so near to welding arc that it is heated to high temperature during long time welding. In such a situation, tip changes in its microstructure and in turn its mechanical properties. This study was intended to investigate those changes by using simulated heat treatment. As a result of this study, it was confirmed that tip of Cu-P alloy hardened with severe cold deformation lose its initial hardness to a large extent within 60 min due to the occurrence of rapid recrystallization while that of Cu-Cr composition hardened by proper aging treatment can preserve its intial hardness for about 1,000 min or longer. Based on these results, suggested was a guideline that can classify contact tips into two different grades: deformation-hardened type and precipitation-hardened type. Following a guideline, a tip with Cu-Cr composition can be classified into the deformation-hardened type if it is in the over-aged condition. Such a guideline is well described.

• 자원리싸이클링
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• 제13권6호
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• pp.16-25
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• 2004

인듐 성분을 포함하는 원료용액을 분무열분해 시켜서 평균 입자크기 100 nm 이하의 인듐 산화물 나노 분말을 제조하였으며, 용액의 농도, nozzle tip 크기 및 공기의 유입속도 변화에 따른 생성된 분말들의 특성 변화를 파악하였다. 본 연구는 폐 ITO로부터 나노 크기의 ITO 분말을 제조하기 위한 전 단계 연구로 수행되었다. 원료용액 내의 인듐 성분의 농도가 40 g/l로부터 350 g/l로 증가됨에 따라 생성된 분말의 평균 입자크기는 20~30 nm로부터 50~60 nm로 점점 증가하는 반면 입도분포는 더욱 불균일하게 나타나고 있었으며, XRD peak의 강도는 점점 증가하고 비표면적은 감소되었다. Nozzle tip의 크기가 1 mm로부터 5 mm로 증가함에 따라 분말들의 평균 입자크기는 40 nm 정도로부터 100 nm 정도까지 점점 증가하고 입도분포는 더욱 불균일하게 나타나고 있었으며, XRD peak 강도는 증가하는 반면 비표면적은 감소되었다. 반응로 내로 유입되는 공기의 압력이 0.1 kg/cm$^2$로부터 0.5 kg/cm$^2$로 증가되는 경우, 분말의 평균 입자크기는 90~100 nm로 현저한 변화를 나타내지 않았다. 반면 공기압력이 1 kg/cm$^2$ 및 3 kg/cm$^2$로 증가하는 경우에는 평균 입자크기가 50~60 nm 정도까지 감소하였으며, XRD peak 강도는 감소하고 비표면적은 증가되었다.