• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.61-67
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• 2011

The confocal laser scanning microscopy and two-photon microscopy was implemented based on a single laser source and an objective lens. We imaged and compared the morphology of identical sites of ex vivo human skin using both microscopes. The back-scattering emission from the sample provided the contrast for the confocal microscopy. The intrinsic autofluorescence and the second harmonic generation were used as the luminescence source for the two-photon microscopy. The wavelength of the Ti:Sapphire laser was tuned at 710 nm, which corresponds to the excitation peak of NADH and FAD in skin tissue. The various cell layers in the epidermis and the papillary dermis were clearly distinguished by both imaging modalities. The two-photon microscopy more clearly visualized the intercellular region and the nucleus of the cell compared to the confocal microscopy. The fibrous structures in the dermis were more clearly resolved by the confocal microscopy. Numerous cells in papillary dermal layer, as deep as $100\;{\mu}m$, were observed in both CLSM and two-photon microscopy. While most previous studies focused on fibrous structure imaging (collagen and elastin fiber) in the dermis, we demonstrated that the combined imaging with the CLSM and two-photon microscopy can be applied for the non-invasive study of the population, distribution and metabolism of papillary dermal cells in skin.

• Nuclear Engineering and Technology
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• v.54 no.12
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• pp.4431-4440
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• 2022

An advanced nuclear reactor based on molten salts including a molten salt reactor and pyroprocessing needs a sensitive monitoring system suitable for operation in harsh environments with limited access. Multi-element detection is challenging with the conventional technologies that are compatible with the in-situ operation; hence laser-induced breakdown spectroscopy (LIBS) has been investigated as a potential alternative. However, limited precision is a chronic problem with LIBS. We increased the precision of LIBS under high temperature by protecting optics using a gas protective layer and correcting for shotto-shot variance and lens-to-sample distance using a laser-induced acoustic signal. This study investigates cerium as a surrogate for uranium and corrosion products for simulating corrosive environments in LiCl-KCl. While the un-corrected limit of detection (LOD) range is 425-513 ppm, the acoustic-corrected LOD range is 360-397 ppm. The typical cerium concentrations in pyroprocessing are about two orders of magnitude higher than the LOD found in this study. A LIBS monitoring system that adopts these methods could have a significant impact on the ability to monitor and provide early detection of the transient behavior of salt composition in advanced molten salt-based nuclear reactors.

• Ceramist
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• v.10 no.3
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• pp.55-66
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• 2007

Infrared Scanning Near-field Optical Microscopy (IR-SNOM) is an extremely powerful analytical instrument since it combines IR spectroscopy's high chemical specificity with SNOM's high spatial resolution. In order to do this in the infrared, specialty chalcogenide glass fibers were fabricated and their ends tapered to generate SNOM probes. The fiber tips were installed in a modified near field microscope and both inorganic and biological samples illuminated with the tunable output from a free-electron laser located at Vanderbilt University. Both topographical and IR spectral images were simultaneously recorded with a resolution of ${\sim}50\;nm$ and ${\sim}100\;nm$, respectively. Unique spectroscopic features were identified in all samples, with spectral images exhibiting resolutions of up to ${\lambda}/60$, or at least 30 times better than the diffraction limited lens-based microscopes. We believe that IR-SNOM can provide a very powerful insight into some of the most important bio-medical research topics.

• ETRI Journal
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• v.36 no.2
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• pp.232-241
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• 2014

A holographic display system with a 22-inch LCD panel is developed to provide a wide viewing angle and large holographic 3D image. It is realized by steering a narrow viewing window resulting from a very large pixel pitch compared to the wave length of the laser light. Point light sources and a lens array make it possible to arbitrarily control the position of the viewing window for a moving observer. The holographic display provides both eyes of the observer with a holographic 3D image using two vertically placed LCD panels and a beam splitter to support the holographic stereogram.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1000-1003
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• 2002

For high density optical storage, there should be a high NA objective lens and a shorter wavelength laser diode. To secure the disc tilt margin related to the coma aberration, moreover, it's difficult to apply the tilt compensation mechanism into the portable PC. In this paper, we proposed the 3-axis asymmetry pickup actuator with high efficiency symmetric magnetic circuit, which consisted of the top cover type inner yoke for high magnetic flux density, the coil stack unit for the 3-axis independent operation and vertically polarized magnets. This newly suggested actuator features DVD-RAM recording, we achieved the high focus & track AC sensitivity and the greatly stabilized system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.1
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• pp.1-10
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• 1994

The flow and heat transfer characteristics behind a backward facing step located in a vertical channel has been studied. In this study, the numerical prediction has been performed by solving the Navier-Stokes equation and energy equation simultaneously with the SIMPLE algorithm embedied in TEACH code. Local heat flux was measured by using Schlieren Interferometer. The flow visualization was performed using the cylindrical lens and the laser beam that is scattered by the supplied glycerine particles. The velocity and temperature distributions, recirculation region, reattachment length, and local heat flux are obtained under the various parameters to investigate the buoyancy effect on the flow and heat transfer characteristics behind the step.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.629-632
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• 1989

The scattered light intensity from a spherical particle passing through the cross-over region of two coherent laser beams, varies periodically. Photodetection of this light beams produces a periodic signal of varying amplitude. The phase of the signal varies with the particle size and refractive index, the beam crossing angle and wavelength, and the position and size of the scattered ligth collecting aperture. In this paper the phase variation with respect to the particle absorptive index of retraction, collecting lens size and beam crossing angle is calculated using both Mie scattering theory and reflection theory. The two theories show good agreement in phase predictions, especially for large absorptive indices and for small collection lenses. Both theories predict phase to be inversely proportional to the beam crossing angle.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1561-1563
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• 2001

In this paper, an novel optical measuring system based on the electro-optic effect has been proposed and realized using Pockels cell with a view to detecting partial discharge taking place at the needle plane electrode. This system has the following advantages ; nonmetallic probe sensor, immune to external EMI noise and broad band response of the Pockels cell from DC to GHz. And also it is constructed by He-Ne laser, optical fiber, $LiNbO_3$ Pockels cell, photo detector, grin lens, oscilloscope and PC. The characteristics of the developed prototype sensor are investigated under AC and corona discharges.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.101.3-101
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• 2001

By setting a refractor with a certain angle against the optical axis of the CCD camera lens, the image of a measuring point recorded on the image plane is displaced by the corresponding amounts related to the distance between the camera and the measuring point. When the refractor that keeps the angle against the optical axis is rotated physically at high speed during the exposure of the camera, the image of a measuring point draws an annular streak. Since the size of the annular streak is inversely proportional to the distance between the camera and the measuring point, the 3D position of the measuring point can be obtained by processing the streak. In this paper, for one of the applications of our system, the measurement of a moving surface is introduced. In order to measure the moving surface, multi laser spots are projected on the surface of object. Each position of ...

• Journal of Power System Engineering
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• v.3 no.2
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• pp.13-19
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• 1999

The purpose of the present experimental study is to apply multi-point simultaneous measurement by PIV(Particle Image Velocimetry) to high-speed flow region within a domestic boiler circulation pump. Two different kinds of flow rate($27{\ell}/min,\;19{\ell}/min$)are selected as experimental condition. A volute casing and Impeller made of transparent Polycarbonate were made for the easy access of the illumination laser via fiber optical line and cylinder lens assembly to the measuring region. A CCD camera is syncronized with AOM to acquire clear original particle images. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. The instantaneous and time-mean velocity distribution, velocity profile and kinetic energy are represented quantitatively at the full-scale region for the deeper understanding of the unsteady flow characteristics in a commercial circulation pump.