• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.583-586
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• 2000

This work ethibits how susceptive the shear ultrasonic waves are to a little misoriented plies according to the angle variation of shear ultrasoic waves $0^\circ$ , $45^\circ$ and $90^\circ$. Also, it is shown that shear waves, particularly the transmission mode with the transmitter and receiver perpendicular to each other, have high sensitivity for detecting anomalies in fiber orientation and ply layup sequence that may occur in the manufacturing of composite laminates. Experimental results are agreed with modeling solutions which were based on decomposition of shear wave polarization vector as it propagates through the composite laminates. This wave appeared considerably to be sensitive to CFRP composites to the thickness direction along in-plane fibers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.577-584
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• 2003

A crack with growth in ferroelectric ceramics under purely electric loading is analyzed. The crack tip stress intensity factor for the growing crack under small-scale conditions is evaluated by employing the model of nonlinear domain switching. The crack tip stress intensity factor increases or decreases with crack growth, depending on the electrical nonlinear behavior and the direction of an applied electric field. It is shown that the ferroelectric material can be either toughened or weakened as the crack grows. The steady state crack growth in ferroelectric ceramics is also discussed.

• Journal of ILASS-Korea
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• v.2 no.2
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• pp.16-23
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• 1997

In this research a novel two-reference-beam double pulse holographic technique for the measurments of particle sizes and velocities was developed. This holographic method features the capability of separation of the first and second particle images by using two reference beams instead of one and the change of the polarization direction of laser light. The developed holographic system was tested through the measurements of droplet sizes and velocities in the spray created by two high speed impinging jets. The overall spray pattern clearly revealed the inherent wave nature. Smaller and faster droplets were generated with larger impingement angle, higher jet velocity. and smaller orifice diameter.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.279-284
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• 2007

The cultural noise sources in magnetotellurics were localized using the source localization method. Conventional beamforming techniques are not applicable for electromagnetic source localization. In this study, the matched field processing and genetic algorithm are used to localize an electromagnetic source and estimate the polarization direction. The source localization using MT field data shows the characteristics of estimated source distribution related to the strength of cultural noise.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.623-624
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• 2009

Here we report a photo polymerization-induced hybrid alignment of a nematic liquid crystal cell which can be applied for a roll to roll fabrication process. Predominant polymerization in the vicinity of UV incident front induced a diffusion of monomers toward front slide and anisotropic polymer network was formed parallel to the polarization direction of the UV light. This induced planar alignment of liquid crystals at the front slide. Simultaneously, homeotropic alignment was induced at the bottom slide as the polymers are phase-separated from a bottom slide.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.664-667
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• 2009

We would like to show a measuring technique of azimuthal anchoring energy of the nematic liquid crystals. The electro-optical setup of liquid crystal cell, crossed polarizers and magnetic field was assumed. The planar or hybrid alignment cells were prepared. The director in the light entering substrate and the polarization of light was adjusted into parallel to the magnetic field. The director orientation of exit substrate and analyser maintained perpendicular to the magnetic field. As the magnetic field strength is increased, the director deviates from the easy axis and rotates to the field direction. We obtained an equation calculating the change of transmission with the field and measured experimentally the transmission. By comparing the calculating and experimental data, we obtained the azimuthal anchoring strength.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.198-198
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• 2003

Two microscopic particles irradiated by light field influence each other by the forces coursed by the dipole-dipole interaction. The interaction changes also the resonance frequencies of the particles. We show that the dipole forces between atoms, molecules or dielectric particles irradiated by laser light play an important role at distances between the particles about or less the light wavelength. We discuss the properties of the near-field forces, including their dependence on direction and polarization of the laser light. We conclude that the near-field forces can be responsible for farmation of dimers in dense atomic gases. The near-field forces can be also used for control the motion of dielectric particles on micro and nanometer scale.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.81.2-81.2
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• 2021

Emission features formed through Raman scattering with atomic hydrogen provide unique and crucial information to probe the distribution and kinematics of a thick neutral region illuminated by a strong far-ultraviolet radiation source. We introduce a new 3-dimensional Monte-Carlo code to describe the radiative transfer of line photons subject to Raman and Rayleigh scattering with atomic hydrogen. In our Sejong Radiative Transfer through Raman and Rayleigh Scattering (STaRS) code, the position, direction, wavelength, and polarization of each photon is traced until escape. The thick neutral scattering region is divided into multiple cells. Each cell is characterized by its velocity and density, which ensures flexibility of the code in analyzing Raman-scattered features formed in a neutral region with complicated kinematics and density distribution. We are continuously developing STaRS to adopt the absorption and scattering effect by dust. This presentation introduces STaRS and its current state and study.

• Corrosion Science and Technology
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• v.22 no.6
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• pp.429-434
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• 2023

This study investigated the localized corrosion behavior of a UNS G41400 steel surface treated with manganese phosphate. The phosphate coating, primarily composed of oxygen (O), phosphorus (P), and manganese (Mn) elements, had an approximate thickness of 6 ㎛. The particles comprising the coating varied in size by several micrometers; smaller particles were mainly composed of O, P, Mn, and iron (Fe) elements, indicating incomplete formation of the manganese phosphate film. Potentiodynamic polarization curves revealed a decrease in anodic current after surface treatment and a shift in corrosion potential toward the noble direction after treatment. After immersion in a 3.5 wt% NaCl solution for 96 hours, localized corrosion was observed, with some regions retaining residual phosphate film. Even though localized corrosion occurred on the treated surface, it was less severe than that on the untreated UNS G41400 steel surface. These findings suggest that manganese phosphate coating improved resistance to localized corrosion.

• Polymer(Korea)
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• v.31 no.5
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• pp.393-398
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• 2007

We studied the mechanism of liquid crystal alignment on polyvinylfluorocinnamate (PVCN-F) films which were irradiated by UV using polarized fourier transform infrared (FT-IR) spectroscopy and ultraviolet/visible (UV/Vis) spectroscopy. UV irradiation of PVCN-F films caused decrease of vinylene -C=C- stretching peak area at $1638cm^{-1}$ and shift of conjugated C:0 stretching vibration at $1712cm^{-1}\;to\;1734cm^{-1}$ which is caused by nonconjugated C=O stretching nitration. To study the orientation direction of 5CB liquid crystal (LC) molecules in the liquid crystal cell with PUV irradiation, rubbing treatment or without any treatment on the PVCN-F alignment layer, we used polarized FT-IR dichroism technique. We successfully measured 5CB LC alignment directions, which are perpendicular to the irradiated PUV polarization direction and parallel to the rubbing direction in the liquid crystal cell without using dichroic dyes.