• 대한기계학회논문집B
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• 제24권4호
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• pp.504-511
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• 2000

PIV(Particle Image Velocimetry) is a recently developed technique for visualizing the fluid velocity fields. Because it has several advantages over the LDV(Laser Doppler Velocimetry), it became one of the most popular diagnostic tools in spite of its short history. However, its application to combustion is restricted by some problems such as flame illumination, scattered light refraction, particle density variation due to heat release, the combined effect of abrupt change in particle density and fluid velocity on flame contour, and thermophoresis which is particle lagging due to temperature gradient. These problems are expected to be originated from the non-continuous characteristics of flames and the limitations of particle dynamics. In the present study, these problems were considered for the visualization of the instantaneous coaxial hydrogen diffusion flame. And the instantaneous flame contour was detected using particle density difference. The visualized diffusion flame velocity field shows its turbulent and meandering nature. It was also observed that the flame is located inside the outer shear layer and flame geometry is largely influenced by the vorticity.

• 한국초전도ㆍ저온공학회논문지
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• 제26권1호
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• pp.10-13
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• 2024

We performed angle-resolved Raman spectroscopy experiments on lead-doped and undoped Bi₂Sr₂CaCu₂O_8+δ(Bi2212) samples using a 660 nm laser and analyzed the Raman tensor of the phonon modes. The phonon mode was clearly observed at the 60, 103, and 630 cm^-1 Raman shifts. The 60, 630 cm^-1 peaks were only clearly observed when the incident and scattered light polarizations were configured to be parallel. The polarization angle dependence of the amplitude of the 60, 630 cm^-1 peak on the parallel configuration shows a twofold symmetry; therefore, both peaks originate from Ag phonons and the crystal structure of Bi2212 should be considered orthorhombic. On the other hand, the 103 cm^-1 peak is clearly observed in both parallel and perpendicular configurations. Remarkably, the off-diagonal component of the Raman tensor of the 103 cm^-1 peak showed an anti-symmetry that could not be realized within the known crystal structure of Bi2212. The implications of our findings are discussed.

• Journal of the Optical Society of Korea
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• 제14권1호
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• pp.42-48
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• 2010

We used video-rate Confocal Laser Scanning Microscopy (CLSM) to observe the motion of blood cells in a micro-channel. Video-rate CLSM allowed us to acquire images at the rate of 30 frames per second. The acquired images were used to perform Particle Image Velocimetry (PIV), thus providing the velocity profile of the blood in a micro-channel. While previous confocal microscopy-assisted PIV required exogenous micro/nano particles as the tracing particles, we employed blood cells as tracing particles for the CLSM in the reflection mode, which uses light back-scattered from the sample. The blood flow at various depths of the micro-channel was observed by adjusting the image plane of the microscope. The velocity profile at different depths of the channel was measured. The confocal micro-PIV technique used in the study was able to measure blood velocity up to a few hundreds ${\mu}m/sec$, equivalent to the blood velocity in the capillaries of a live animal. It is expected that the technique presented can be applied for in vivo blood flow measurement in the capillaries of live animals.

• 대한화장품학회지
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• 제44권1호
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• pp.81-87
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• 2018

본 연구에서는 각질층의 산란에 대한 새로운 분석 방법을 제공하고 광학에 사용되는 광산란 감소 물질들의 피부 각질층에서의 영향을 확인하였다. 각질층과 피부 구성 성분에 의해 산란되어지는 빛의 변화를 측정하기 위해 각질 테이프로 분리한 각질세포의 다크 필드 이미지 분석을 통해 다양한 광산란 감소 물질들의 각질층에서의 광산란 효과를 측정하고 분석하였다. 광산란 감소 물질의 처리 후 각질층의 물리적 특성(수분 함량, 케라틴 구조 및 두께) 변화는 FT-IR, 3D 레이저 현미경으로 관찰하였는데 화장품에서 보습제로 사용되는 단당류, 당 알코올, 환원당, 히알루론산 등은 광산란을 감소시킬 수 있었다. 그러나 광학에서의 탈수 현상과 달리 낮은 농도조건의 광산란 감소 물질은 각질층 케라틴 구조의 내부로 물의 침투를 향상시켜 각질층의 부피를 증가시키고 강성을 감소시키는 효과를 나타내었다. 이러한 광산란 감소 물질에 의한 각질층 각질세포의 수화 현상은 각질층의 광산란을 감소시켜 피부를 보다 투명하게 보이게 해 줄뿐만 아니라 지속적인 보습효과를 제공할 수 있는 각질층 타겟의 새로운 피부 개선 연구의 가능성을 확인할 수 있었다.