• 한국물환경학회지
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• 제25권4호
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• pp.589-596
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• 2009

The spectroscopic characteristics and chemical oxygen demand (COD) oxidation efficiencies were investigated for dissolved organic matters (DOM) from diverse sources, which may indirectly affect the concentrations and the quality of DOM found in watersheds. The DOM investigated for this study showed a wide range of the percent distributions of refractory organic matter (R-OM) from 8 to 100%. Relatively high R-OM distributions were observed for the DOM with the source of head water, sediments, paddy soils, field soils, and treated sewage whereas the DOM from livestock waste, reed, weeds, algae, and attached algae exhibited lower R-OM percent distributions. The percent distribution of R-OM had positive correlations with specific UV absorbance (SUVA) and humidification indices (HIX) of DOM. The investigated DOM was classified into four different source groups (i.e., biota, vegetables, soils, sediments) by comparing the synchronous fluorescence spectra. The DOM group from biota source was characterized by a prominent presence of protein-like fluorescence (PLF) whereas fulvic-like fluorescence (FLF) was additionally observed for vegetable-source DOM. FLF became significant for the DOM from both soils and sediments although no PLF was found for soil-derived DOM. A range of COD oxidation efficiency was observed for the various DOM, ranging from 36 to 94% and from 65 to 125% for $COD_{Mn}$ and $COD_{Cr}$, respectively. The results indicate that $COD_{Cr}$ reflects the higher OM concentration than $COD_{Mn}$. However, 95% confidence intervals of the COD oxidation efficiencies were similar for the two types of COD, suggesting that $COD_{Cr}$ may not be the superior OM index to $COD_{Mn}$ in terms of the variability of the oxidation efficiency. No significant correlations were obtained between COD oxidation efficiencies and the spectroscopic characteristics of DOM for this study.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.988-991
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• 2004

In the present investigation, we tried AR coating simulation by using the "Essential Macleod optical coating design and analysis" program. After various run of the program we selected appropriate materials which have specific refractive indices and for that thickness was optimized to get the low reflectance. By comparing the simulated results for the different materials,we found that $SiO_2$ and TiN are the appropriate materials for this Flat panel device (FPD) application. Thin films of these materials were deposited using RF magnetron sputtering and Inductively Coupled Plasma Chemical Vapour Deposition (ICPCVD) methods on Polyethyleneterephthalate (PET) substrates. Spectroscopic ellipsometer (SE MF-1000) and UV-Vis spectrophotometer (SCINCO) were used for the optical characterization. The obtained experimental results are in good agreement with the simulation results.

• 천문학회보
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• 제38권2호
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• pp.59.1-59.1
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• 2013

Type Ia supernovae (SNe) are providing the most conclusive evidence for accelerating universe with dark energy in observational cosmology. In these investigations, look-back time evolution of SNe luminosity is regarded as negligible on the basic assumption. However, several recent works present some systematic differences among hosts which have different characteristics of stellar population. For more direct investigation, we are proceeding with our YONSEI (YOnsei Nearby Supernovae Evolution Investigation) project. Only early-type hosts in our catalogue were chosen in order to estimate the luminosity-weighted mean age and metallicity directly using Single Stellar Population (SSP) models and ignore the effect from the dust extinction. Observations using low-resolution spectrographs are still in progress at Las Campanas Observatory with 2.5m telescope and at McDonald Observatory with 2.7m telescope. We have thus far obtained spectra for 30 early-type hosts. After weak emission line correction, Lick/IDS absorption-line indices are measured and YEPS spectroscopic evolution model was applied to determine mean population ages and metallicities. Our preliminary results show that SNe Ia hosted in older galaxies seem to be brighter at 1.4 - 3 sigma levels, however, more observations and analyses are still needed to confirm this correlation.

• 천문학회보
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• 제41권1호
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• pp.46.2-46.2
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• 2016

We explore the similarity and difference of the quasi-periodic pulsations (QPPs) observed during the solar and stellar X-ray flares. For this, we identified 59 solar QPPs in the X-ray observed by the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) and 52 stellar QPPs from X-ray Multi Mirror Newton observatory (XMM-Newton). The Empirical Mode Decomposition (EMD) method and least-square-fit with the damped sine function are applied to obtain the periods and damping times of the QPPs. We found that (1) the periods and damping times of the stellar QPPs are 7.80 and 13.80 min, which are comparable with those of the solar QPPs 0.55 and 0.97 min. (2) The ratio of the damping times to the periods observed in the stellar QPPs are found to be statistically identical to the solar QPPs, (3) The damping times are well describe by the power law. The power indices of the solar and stellar QPPs are $0.891{\pm}0.172$ and $0.953{\pm}0.198$, which are consistent with the previous results. Thus, we conclude that the underlying mechanism responsible for the stellar QPPs are the natural oscillations of the flaring or adjacent coronal loops as in the Sun.

• 한국광학회지
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• 제8권6호
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• pp.445-449
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• 1997

비정질상과 결정상으로 가역변화하는 특성을 이용하여, 기존의 읽기전용 기록매체인 Compact Disk(CD)를 대체할 차세대 광기록매체로 주목받고 있는 Ge$_{2}$Sb$_{2}$Te$_{5}$(GST)의 상태변화에 따른 굴절율과 소광계수, 박막의 두께와 밀도 등 박막상수들을 구하였다. DC 스퍼터링방법으로 제작한 두꺼운 GST의 복소굴절율을 양자역학적 분산식을 이용한 모델링방법으로 구하고, 한편으로는 표면미시거칠기를 AFM(Atomic Force Microscopy)으로 결정한 다음, 타원해석 스펙트럼들을 수치해석적 역방계산하여 구한 복소굴절율과 비교하였다. 결정상과 비정질상일 때의 GST의 복소굴절율을 각각 구하고 이로부터 계산된 반사율을 측정된 반사율과 비교함으로써 수치해석적인 방법이 실제 GST의 복소굴절율과 더 일치하는 값ㅇㄹ 가지게 됨을 확인하였다. 이렇게 구한 GST의 복소굴절율을 기준데이터로 사용하여 실제 설계두께를 가지는 GST박막의 두께 및 표면거칠기층을 정량적으로 구하였다.다.

• Restorative Dentistry and Endodontics
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• 제36권3호
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• pp.219-230
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• 2011

연구목적: 복합레진의 광중합 전후에 일어나는 색과 투명도 변화를 측정하고, CQ의 함량을 정량하였으며, 광중합 전후 복합 레진의 굴절률을 측정해 이들의 상관 관계를 알아보고자 하였다. 연구 재료 및 방법: Esthet-X, Filtek supreme, Gradia Direct, Clearfil Majesty, Beautifil II에 대하여 Colorimeter NF999를 이용하여 광중합 전후의 색과 투명도를 각각 측정하고, GC-MS를 이용해 각 복합레진의 CQ 함량을 측정하였으며, spectroscopic ellipsometer를 이용해 광중합 전후의 굴절률을 측정하였다. 결과: 투명도는 광중합 후에 증가하였고, body shade에서 opaque shade보다 투명도 차이가 크게 나타났다. 모든 레진에서 body shade의 CQ 함량이 opaque shade의 CQ 함량보다 높았다. 굴절률은 광중합 후에 모든 레진에서 증가하였으며, body shade와 opaque shade간에 굴절률의 변화는 유의한 차이가 있었다. 결론: 광중합 후에는 복합레진의 색과 투명도가 상당한 차이를 나타낸다. 따라서 임상에서 direct shade matching을 시행할 때는 중합된 레진을 사용하여야 한다.

• 한국광학회지
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• 제13권3호
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• pp.215-222
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• 2002

광기록매체용 Ge-Sb-Te다층박막 성장과정을 in-situ 타원계를 사용하여 실시간으로 모니터하여 각 층의 두께를 제어하고 성장된 Ge-Sb-Te 다층박막을 ex-site 분광타원법으로 확인하였다. 보호층인 ZnS-SiO$_2$와 기록층인 Ge$_2$Sb$_2$Te$_{5}$을 단결정실리콘 기층 위에 스퍼터링 방법으로 각각 성장시키면서 구한 타원상수 성장곡선을 분석하여 성장에 따르는 보호층의 균일성 및 기록 층의 밀도변화를 파악하고 이를 기초로 하여 Ge-Sb-Te광기록 다층박막의 두께를 정밀하게 제어하였다. Ge$_2$Sb$_2$Te$_{5}$ 단층박막 시료의 복소굴절율은 eX-Situ 분광타원분석을 통하여 구하였다. 제작된 다층구조는 설정된 다층구조인 ZnS-SiO$_2$(1400$\AA$)$\mid$ GST(200 $\AA$)$\mid$ZnS-SiO$_2$(200$\AA$)와 각 층의 두께 및 전체 두께에서 1.5% 이내에서 일치하는 정확도를 보여주었다.주었다.

• 한국안광학회지
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• 제13권1호
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• pp.59-63
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• 2008

목적: 소형 magnetron sputtering 장치를 이용하여 CR-39 안경렌즈와 glass위에 코팅한 썬글라스 렌즈용 Ti박막의 광학적 특성에 관한 연구이다. 방법: SEM 단면 사진으로 Ti 코팅 박막의 두께를 측정하였고, spectrophotometer를 이용하여 Ti 박막의 투과율과 반사율을 측정하였다. Variable angle spectroscopic ellipsometry (VASE)를 이용하여 파장에 따라 Ti 박막의 굴절률과 소멸계수를 구하였다. 결과: 두께가 60 nm, 120 nm, 140 nm인 시료에 대한 투과율은 가시광선 영역인 파장 400 nm에서 750 nm까지 변화가 크지 않았으며 모두 silver tone에 가까운 color를 보였다. 가까운 파장 400 nm 근처에서 약간 올라가는 경향을 보였고, He d선 (587.6 nm)을 기준으로 할 때 Ti 박막의 두께가 60 nm에서 투과율이 33%, 두께가 120 nm에서 투과율이 25%, 두께가 140 nm에서 투과율이 20%를 보였다. 결론: Ti 박막의 경우 60~140 nm의 모든 두께에서 선글라스용으로 적합한 것을 알 수 있었다. Ti박막에 대한 굴절률이 작게 나오는 것은 Ti박막의 두께가 얇기 때문이라고 여겨진다.

• Journal of the Optical Society of Korea
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• 제18권4호
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• pp.359-364
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• 2014

We report parameters that allow the dielectric functions ${\varepsilon}={\varepsilon}_1+i{\varepsilon}_2$ of $AlAs_xSb_{1-x}$ alloys to be calculated analytically over the entire composition range $0{\leq}x{\leq}1$ in the spectral energy range from 0.74 to 6.0 eV by using the dielectric function parametric model (DFPM). The ${\varepsilon}$ spectra were obtained previously by spectroscopic ellipsometry for x = 0, 0.119, 0.288, 0.681, 0.829, and 1. The ${\varepsilon}$ data are successfully reconstructed and parameterized by six polynomials in excellent agreement with the data. We can determine ${\varepsilon}$ as a continuous function of As composition and energy over the ranges given above, and ${\varepsilon}$ can be converted to complex refractive indices using a simple relationship. We expect these results to be useful for the design of optoelectronic devices and also for in situ monitoring of AlAsSb film growth.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.148-155
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• 2018

To get a better understanding of the effect of physicochemical properties and microstructure on $SO_2$ absorption behavior of DESs with different molar ratios of EmimCl and EG (from 2:1 to 1:2), densities (${\rho}$), viscosities (${\eta}$), speeds of sound (u), refractive indices ($n_D$), and thermal decomposition temperatures ($T_d$) of EmimCl-EG DESs were measured and used to obtain the other derived properties, such as thermal expansion coefficient (${\alpha}_p$) and activation energy for viscous flow ($E_{\eta}$). Moreover, FT-IR spectra and in situ variable-temperature NMR spectroscopy were employed to study the microstructures of DESs. Based on physicochemical and spectroscopic properties, the influence of the concentrations of EmimCl on the interactions in DESs was explored to be associated with their $SO_2$ absorption behavior. The results show that the interactions between $Emim^+$ and $Cl^-$ of EmimCl is gradually weakening with increasing the concentration of EG in DESs by forming of hydrogen bond interaction of $O-H{\cdots}Cl^-$, resulting in a decrease of ${\rho}$, ${\eta}$, u, $n_D$, and $T_d$ of DESs, and hindering the charge-transfer interaction of $SO_2$ with $Cl^-$ and deceasing $SO_2$ capture capacity. Moreover, the $SO_2$ absorption capacity of DESs is proportional to their ${\rho}$ and $E_{\eta}$, respectively.