• Korean Journal of Crystallography
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• v.6 no.2
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• pp.111-117
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• 1995

TiO2 thin films were prepared on a (100)silicon wafer using a chemical vapor deposition(CVD) method. The deposition experiments were performed using the TTIP in the deposition temperature ransing from 200 content. The deposition rate of TiO2 was increased with the substrate temperature and the oxygen content. The thickness of the deposited thin film and the compositional analysis of this thin films with theoxygen content were measured using Ellipsometry, SEM and ESCA, respectively. The deposited thin film was composed of a bilayer, external TiO2 and internal Ti. Carbon as a residual impurity was found to remain when zero sccm O2 was purged into a reaction chamber and the composition of the deposited thin film was found to change Ti into TiO in a deeper layer. However, when 600sccm O2 was supplied to a reaction chamber, it has been found to reside less carbon content than without O2. Finally, in the condition of 1200sccm O2, no impurity level of carbon was observed and a deeper layer consisted of the Ti composite, even though the deposited surface was composed of TiO2.

• The korean journal of orthodontics
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• v.27 no.3 s.62
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• pp.503-513
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• 1997

This study was undertaken to investigate the effect of oxygen tension on the activity and function of the cells derived from human periodontal ligament by measuring cell activity, total protein synthesis, collagen synthesis, $IL-1{\beta},\;IL-6,\;TNF-{\alpha}$ Human periodontal ligament fibroblasts were collected from premolars extracted for orthodontic treatment and incubated in the environment of $37^{\circ}C,\;5\%\;CO_2,\100\%$ humidity. After the fifth to sixth passage they were used for the experiment. Gaspack system to which $0.2{\mu}m$ Millipore filter was attached was connected to mixed-gas tanks. The mixed gases were composed of $10\%\;O_2,\;5\%\;CO_2,\;85\%\;N_2$ in hyoxic group or $90\%\;O_2,\;5\%\;CO_2,\;5\%\;N_2$ in hyperoxic group and $5\%\;CO_2,\;95\%$ air for control. After incubation in $37^{\circ}C$ for 2, 4, 6 days, cell activity was determined by tetrazolium(MTT) assay and total protein synthesis was assayed using sulforhodamine B(SRB). And measurement of 4-hydroxyproline was performed to assess collagen synthesis md $IL-1{\beta},\;IL-6,\;and\;TNF-{\alpha}$ were measured by enzymeimmunoassay. The results were as follows. 1. The cell activity and total protein synthesis in hypoxic group were a little higher than or almost the same with those in control group. 2. In hyperoxic group, the cell activity was lower than that in control group and total protein synthesis was decreased. 3. Collagen synthesis was significantly decreased initially in both hypoxic and hyperoxic group and increased nearly to the level of control group as the duration of cell incubation was longer 4. As a result of enzymeimmunoassay, the amount of cytokines was $IL-6,\;TNF-{\alpha}\;and\;IL-1{\beta}$ in order. 5. $IL-6,\;TNF-{\alpha}\;and\;IL-1{\beta}$ were increased more rapidly in both hypoxic and hyperoxic group than in control group as the duration of cell incubation was longer. 6. There were more $IL-6\;and\;TNF-{\alpha}$ in hyperoxic group than in control group after 6 days, and there were more $IL-6\;and\;TNF-{\alpha}$ after 6 days than after 2 or 4 days in hyperoxic group. These results suggested that oxygen tension might modulate the production of extracellular matrix and cytokines in the cells derived from human periodontal ligament.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.5
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• pp.288-302
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• 2017

Accurate measurement of benthic nutrient fluxes (BNF) is a prerequisite for evaluating the effect of sediments on nutrient cycle in the surface water. The intact sediment cores were collected in July 2015 at the midstream of Nakdong River. We identified pre-incubation time (6, 12, 24 hr), dissolved oxygen concentration (90, 70, 50% saturation), diffusive boundary layer thickness (0, 0.6-0.8, 1.2-1.4 mm), and incubation temperature (10, 17, 20, $25^{\circ}C$) as the most important control factors, and measured the BNF fluctuation with the variation of these factors using the laboratory sediment core incubation method. Since the chemical composition, redox condition, hydrodynamic regimes and microbial activities at the sediment-water interface were changed as a result of the alteration of control factors, sediment core incubation should be conducted under as close to the natural conditions of study site as possible, in order to produce the results similar to actual values. Relative percentage differences between two replicates were below 20% in most control factors, which showed satisfactory precision for strict compliance with the experimental conditions and procedures. In the further studies, we will compare the results of core incubation with those of in situ measurements to confirm the accuracy of the sediment core incubation method.

• Journal of the Korean Chemical Society
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• v.28 no.4
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• pp.231-237
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• 1984

The x-values in the nonstoichiometric chemical formulas $YO_{1.5+x}\;and\;HoO_{1.5+x}$, have been measured in the temperature range from 700$^{\circ}$C to 1000$^{\circ}$C under oxygen pressures from $2{\times}l0^{-1}\;to\;1{\times}10^{-6}$ atm by gravimetric method. The observed x-values increase with increasing temperature and oxygen pressure. The enthalpies of formation of excess oxygen in yttrium oxide and holmium oxide decrease with decreasing oxygen pressure and are all positive values representing an endothermic process. The 1/n values calculated from the slopes of the plots of log x vs. log $P_{O2}$ increase with temperature and are positive values which means the higher oxygen pressure dependence at higher temperature. We have examined the nonstoichiometric defect and conduction mechanism from x-values and thermodynamic data.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.194.2-194.2
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• 2016

저주파 (수십 kHz)와 고주파 (13.56 MHz)로 구동되는 대기압 플라즈마 젯을 발생시키고, 인가전압 (혹은 인가전력)과 기체 유량에 따른 대기압 플라즈마의 특성을 비교하였다. 고주파에서 발생된 플라즈마는 저주파의 경우보다 안정적이었으며, 인가전압 (혹은 인가전력)이 증가함에 따라 플라즈마 기체온도는 상승하였고, 고주파 젯의 기체온도는 저주파 젯 보다 높았으나 330 K이하인 것을 확인하였다. Optical Emission Spectroscopy (OES)를 이용하여 저주파와 고주파의 광 방출 특성을 측정하였다. 저주파에서는 $N_2{^+}$ (391.4 nm)의 intensity 증가가 두드러지게 나타났지만 고주파 젯에서는 $N_2$, $N_2{^+}$의 intensity는 감소하였으며, OH, NO, $H_{\alpha}$, O와 같은 활성 산소 종 (Reactive Oxygen Species)이 저주파 젯 보다 높게 측정되었다. Boltzmann plot method를 이용한 분석을 통해 저주파와 고주파 영역에서의 플라즈마 전자 여기 온도를 측정하였다. 또한 자외선 흡수분광법을 이용하여 플라즈마-액체 계면에서의 OH이 입자밀도를 측정하여 OES방법으로 측정한 OH 밀도와 비교하였다. 그리고 화학적 측정법 (terephtalic acid solution)을 이용하여 액체 내의 OH의 농도를 측정하였다.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1369-1377
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• 1994

• Korean Journal of Materials Research
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• v.7 no.11
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• pp.981-985
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• 1997

열증착법에 의해서 온도 85$^{\circ}C$인 glass기판 위에 CdS 박막을 제작하였다. 두께가 200nm정도로 측정된 CdS박막은 공기 중에서 온도 25$0^{\circ}C$-55$0^{\circ}C$범위에서 각각 30분간 열처리 되었으며 이들 시료에 대하여 4-point probe, XRD, SEM, UV-Spectrophotometer 및 광발광 측정으로 전기적 광학적 특성을 조사하였다. 이들의 일련의 실험값은 열처리 온도 37$0^{\circ}C$ 근처에서 구조의 변화를 보여주었는데, 열처리 온도에 대한 비저항아니 XRD, SEM 의 측정은 cubic로부터 hexagonal구조로의 변환을 나타내었다. 특히 상온에서 측정한 광발광에서 green edge emission(GEE)피이크가 2.42eV를 나타내었는데 이 때의 발광 중심은 열처리할 때 생긴 S-vacancy에 보상된 산소로 이루어진 'CdO'의 악셉터준위에 기인하는 것으로 해석되며 그 이온화 에너지는 약 0.16eV이었다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.202-203
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• 2003

여러 가지 원소의 동위원소 성분 분석은 생물학, 화학, 환경학, 연대학, 기후학 연구에 있어서 중요한 정보를 제공하는 유용한 수단이다. 동위원소 성분비를 측정하는 방법으로는 가스 동위원소 질량분석기를 이용한 방법이 사용되어 왔지만, 최근 다이오드 레이저의 발달과 함께 다이오드레이저 흡수분광법(TDLAS)이 개발되어 사용되고 있다. TDLAS 방법의 경우 질량분석기를 이용하는 방법에서는 측정이 불가능한 동일질량 분자의 동위원소 성분비를 측정할 수 있다. (중략)

• Journal of the Korean Vacuum Society
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• v.4 no.4
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• pp.373-379
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• 1995

200keV의 에너지로 산소 이온들을 주입한 후 열처리하여 만든 SIMOX의 층구조를 분광 타원해석법을 이용하여 비파괴적으로 분석하여, 약 $300AA$의 계면층과 $800\AA$의 매몰산화층이 $3360\AA$ 정도의 결정성 실리콘층 아래에 존재하는 것을 알 수 있었다. 이러한 매몰산화층의 분포와 TRIM 전산시늉 결과의 비교로부터 매몰산화층의 형성은 산소 이온들이 열처리에 따라 이온 주입시 실리콘의 비정질화가 최대인 곳 주변으로 이동하여 이루어짐을 알 수 있었다. 또한 측정 위치에 따른 분광 타원해석 상수들의 변화로부터 이온주입시의 이온빔의 형태와 주사 방향의 영향으로 생긴 SIMOX층구조의 비균일성을 알 수 있었다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.164-164
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• 2003

UV 발광소자 재료로서 유망한 ZnO film을 ALE법으로 증착하고 photoluminescence특성을 조사하였다. Zn소스로서 DEZn(Diethylzinc)를, 산소 소스로서 DI water를 사용하였고 $N_2$ gas로서 챔버내에 주입된 소스물질을 purge하였다. ALE 공정온도 범위인 17$0^{\circ}C$와 CVD 반응온도 범위인 40$0^{\circ}C$로 ZnO 박막을 증착하고 이 시편을 산소 분위기에서 600-100$0^{\circ}C$의 온도로 1시간 동안 열처리하였다. 그리고 He-Cd laser를 사용하여 photoluminescence를 측정하였다. 17$0^{\circ}C$와 40$0^{\circ}C$ 에서 증착된 시편 모두 as-grown 상태에서는 거의 발광특성을 나타내지 못하였으나 후열처리를 거치면서 발광특성을 나타내었고 열처리 온도가 높을수록 발광강도가 증가하였다. 40$0^{\circ}C$에서의 증착된 시편의 경우는CVD반응이 발생하여 Zn-Zn결합이 많이 생성되어 열처리 온도가 증가하여도 발광강도가 약하였고 가시광 영역의 발광 또한 크게 증가하였으며 17$0^{\circ}C$에서 증착된 시편의 경우는 열처리 온도가 증가할수록 UV영역의 발광강도만이 크게 증가하였으며 가시광 영역의 발광은 거의 증가하지 않았다.