• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.151.2-151.2
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• 2011

IGRINS (Immersion GRating INfrared Spectrometer) will provide the spectra with high-resolution and an instantaneous spectral coverage of H and K band in NIR region. Therefore, it is expected that the wide coverage of wavelength would make a production of an extensive NIR high-resolution spectra of standard stars as a prior program of IGRINS. As a counter part of these NIR spectra, we have planned to obtain the high-resolution spectra of those standard stars in optical band. These optical high-resolution spectra would give us an opportunity to produce the library of high-resolution stellar spectra covering from optical to NIR band, and to confirm the method to determine the stellar parameters and chemical abundances from the NIR high-resolution spectra. Before using the NIR high-resolution spectra, we have tested the method to determine the stellar parameters by comparing between the observed spectra and the synthetic spectra in optical band. In order to make the synthetic spectra, we have used the Kurucz ATLAS9 model grids and the SYNTH code described by Fiorella Castelli (http://wwwuser.oat.ts.astro.it/castelli/). For the cross-check against the parameters that would be derived from the NIR spectra, the stellar parameters such as effective temperature and surface gravity were determined using the optical spectra of the solar-like stars, as preliminary results.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.153.1-153.1
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• 2011

For the stars cooler than the Sun, it is difficult to determine the stellar parameters and chemical abundances because of the strong molecular lines in the optical region. Therefore the NIR high-resolution spectra, such as those obtained by IGRINS would be a solution to determine the stellar parameters for late-type stars, such as M dwarfs. As using the NIR high-resolution spectra, we are expecting that it would be more reliable to compare observed spectra with synthetic spectra for the stellar parameters. In order to confirm the method by using high-resolution spectra in NIR band, it should be cross-checked against the stellar parameters from optical high-resolution spectra. We have derived the stellar parameters of M dwarfs using the synthetic spectra in the long wavelength region of the optical spectra (over 8000 $\bar{A}$), which is relatively less contaminated by molecular lines as well as telluric lines.

• Carbon letters
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• v.8 no.4
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• pp.307-312
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• 2007

A method for evaluating bulk sensitive structural characteristics of unpurified, as-purified, and acid treated single walled carbon nanotubes (SWNTs) was described in the present study. The optical spectra of SWNT solutions were well resolved after prolonged sonication and they were correlated to the diameter and the distribution of nanotubes. The acid-treated SWNTs were similar to as-purified SWNTs in terms of catalyst residue, radial breathing mode (RBM) in the Raman spectra, and the first band gap energy of semiconducting tubes in the optical spectra. The solution phase optical spectra were more sensitive to changes in the small diameter and metallic tubes after the acid treatment than were the RBM spectra.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.558-563
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• 2014

Sum-frequency generation spectra of a Langmuir monolayer on water surface at varying surface areas were studied with two-dimensional correlation analysis. Upon enlarging the area/molecule of the Langmuir monolayer, the sum-frequency spectra changed reflecting the conformation change of the alkyl chains of the molecules in the monolayer. These changes stood out more clearly by employing two-dimensional correlation analysis of the above sum-frequency spectra. Features not very pronounced in the original spectra such as closely-spaced spectral bands can also be easily distinguished in the two-dimensional correlation spectra.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.102-105
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• 2012

The structural, electrical, and optical properties of layer-by-layer ZnO nanoparticles deposited using sol-gel spin coating technique were studied and now presented. Thicknesses of the thin films were varied by increasing the number of deposited layers. As part of our characterization process, XRD and FE-SEM were used to characterize the structural properties, current-voltage measurements for the electrical properties, and UV-Vis spectra and photoluminescence spectra for the optical properties of the ZnO thin films. ZnO thin films with thicknesses ranging from 14.2 nm to 62.7 nm were used in this work. Film with thickness of 42.7 nm gave the lowest resistivity among all, $1.39{\times}10^{-2}{\Omega}{\cdot}cm$. Photoluminescence spectra showed two peaks which were in the UV emission centered at 380 nm, and visible emission centered at 590 nm. Optical transmittance spectra of the samples indicated that all films were transparent (>88%) in the visible-NIR range. The optical band gap energy was estimated to be 3.21~3.26 eV, with band gap increased with the thin film thickness.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.242-243
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• 2015

Fault detection using optical emission spectra with modified K-means cluster analysis and principal component anal ysis are demonstrated for inductive coupl ed pl asma cl eaning processes. The optical emission spectra from optical emission spectroscopy (OES) are used for measurement. Furthermore, Principal component analysis and K-means cluster analysis algorithm is modified and applied to real-time detection and sensitivity enhancement for fluorocarbon cleaning processes. The proposed techniques show clear improvement of sensitivity and significant noise reduction when they are compared with single wavelength signals measured by OES. These techniques are expected to be applied to various plasma monitoring applications including fault detections as well as chamber cleaning endpoint detection.

• Progress in Superconductivity and Cryogenics
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• v.21 no.3
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• pp.6-12
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• 2019

Extended Drude model has been used to obtain information of correlations from measured optical spectra of strongly correlated electron systems. The optical self-energy can be defined by the extended Drude model formalism. One can extract the optical self-energy and the electron-boson spectral density function from measured reflectance spectra using a well-developed usual process, which is consistent with several steps including the extended Drude model and generalized Allen's formulas. Here we used a reverse process of the usual process to investigate the extended Drude analysis when an additional low-energy interband transition is included. We considered two typical electron-boson spectral density model functions for two different (normal and d-wave superconducting) material states. Our results show that the low-energy interband transition might give significant effects on the electron-boson spectral density function obtained using the usual process. However, we expect that the low-energy interband transition can be removed from measured spectra in a proper way if the transition is well-defined or well-known.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.14-18
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• 2013

We introduce a generic method to analyze optical 17reflectance spectra of strongly correlated electron systems including high-temperature superconductors by using an extended Drude model and Allen's approach. We explain the process step by step from reflectance through the optical conductivity and the scattering rate to the bosonic spectral function. Through the process we are able to get important information on the interactions between charge carriers from measured optical conductivity of the strongly correlated electron systems including copper oxide and iron pnitide high temperature superconductors.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.52.2-52.2
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• 2011

The correlation between black hole mass and galaxy stellar velocity dispersion gives an important clue on the black hole growth and galaxy evolution. In the case of AGN, however, it is extremely difficult to measure stellar velocity dispersions in the optical spectra since AGN continuum dilutes stellar absorption features. In contrast, stellar velocity dispersions of active galaxies can be measured in the near-IR, where AGN-to-star flux ratio is much smaller, particularly with the laser-guide-star adaptive optics. However, it is crucial to test whether the stellar velocity dispersion measured from the near-IR spectra is consistent with that measured from the optical spectra. Using the TripleSpec at the Palomar 5-m Telescope, we obtained high quality spectra ranging from 1 to 2.4 micron for a sample of 35 nearby galaxies, for which dynamical black hole masses and optical stellar velocity dispersion measurements are available, in order to calibrate the stellar velocity dispersion in the near-IR. In this poster, we present the initial results based on 10 galaxies, with the stellar velocity dispersion measured in the H-band.

• Journal of the Optical Society of Korea
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• v.5 no.4
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• pp.123-130
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• 2001

In this paper, we report measurement of absorption coefficient for various InGaAs MQW QCSE device structures. The absorption spectra over a range of QCSE were obtained from measured photocurrent spectra. The refractive index changes with applied electric field were calculated from the absorption spectra.