• 한국전기전자재료학회논문지
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• 제24권3호
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• pp.256-260
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• 2011

ZnO nanostructures with tetrapod, needle and multipod shapes were synthesized without catalysts through a simple thermal oxidation of metallic Zn powder in alumina crucible under air atmosphere. X-ray diffraction data revealed that the ZnO nanostructures had wurtzite structure of hexagonal phase. Energy dispersive X-ray (EDX) spectra showed that the ZnO was of high purity. After the oxidation of Zn powder, white colored product was mainly observed and yellow colored product was observed only a very little on the surface of the oxidized source materials. The white product consisted of tetrapods, while yellow product was composed of needles and multipods. Cathodoluminescece spectra showed that the crystalline quality of tetrapods was better that those of needles and multipods.

• 한국전기전자재료학회논문지
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• 제24권11호
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• pp.920-924
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• 2011

ZnO crystals with belt and comb shapes were synthesized without any catalysts through a simple thermal oxidation of ZnS powder in alumina crucible under air atmosphere. X-ray diffraction (XRD) pattern revealed that the ZnO crystals had wurtzite structure of hexagonal phase. Energy dispersive x-ray (EDX) spectra showed that the ZnO was of high purity. In the cathodoluminescece spectra obtained for the ZnO crystals with belt and comb shapes, a strong ultraviolet emission centered at 380nm was observed, which indicates the ZnO crystal has high crystalline quality.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.162-165
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• 2006

AZO (ZnO:Al) were fabricated by RF magnetron sputtering In $H_2/Ar(5%\;H_2)$ atmosphere, and structural, electrical and optical properties were investigated. The substrate temperatures were varied at RT, $100^{\circ}C,\;150^{\circ}C$ and$200^{\circ}C$. The resistivity of the films grown in $H_2/Ar(5%\;H_2)$ were reduced from $7.67{\times}10^{-4}{\Omega}\;cm$ to $5.95{\times}10^{-4}{\Omega}\;cm$ comparing that Ar (100%) and the transmittance of the ZnO:Al films in the visible range was 85%.

• Progress in Superconductivity
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• 제9권1호
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• pp.115-118
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• 2007

This study investigated the effects of different kinds of seed crystals with miscut angles and pretreatment on the characteristics of a RE-123 superconductor processed by a top-seeded melt-growth (TSMG) method. When the seed crystal was heat-treated in an oxygen atmosphere, the surface structure was cleaned removing hydroxide. When the seed crystal had a miscut angle, in addition, the surface structure showed a well defined hill-and-valley structure after heat-treatment. A better microstructure, with a well-distributed small RE-123 phase, was obtained using a high miscut angle after heat-treatment in an oxygen atmosphere. As a result of the microstructure improvement, the magnetic characteristics also improved. The experimental result can be explained by reduction of nucleation activation energy.

• 한국전기전자재료학회논문지
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• 제25권2호
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• pp.110-113
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• 2012

ZnO crystals with a baseball bat shape were synthesized without any catalysts through a simple thermal oxidation of ZnS powder in alumina crucible under air atmosphere. SEM images demonstrated that the bat structure was composed of two pieces of ZnO crystals, i.e hexagonal-shaped rod and inverted cone-shaped rod. X-ray diffraction (XRD) pattern revealed that the ZnO crystals had wurtzite hexagonal structure. Energy dispersive X-ray (EDX) spectrum showed that the ZnO was of high purity. A strong green emission peak at 510 nm was observed in cathodoluminescece spectrum.

• 한국재료학회지
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• 제16권1호
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• pp.58-62
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• 2006

Effects of doping concentration and annealing atmosphere on the luminescent properties of $Er^{3+}$ doped ZnO phosphor powders were investigated. Photoluminescence (PL) spectra of ZnO:Er exhibit an orange emission band at around 575 nm, while those of pure ZnO show a green emission at 520 nm. Emission difference between ZnO:Er and pure ZnO is attributed to the energy transfer of Er ions in ZnO. The highest PL intensity is obtained by doping 1 mol% Er to ZnO. Luminescent properties of ZnO:Er phosphors annealed at $N_2$+vacuum atmosphere are superior to those annealed at $N_2$ atmosphere.

• 공업화학
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• 제8권2호
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• pp.179-190
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• 1997

준역청탄, 유연탄, 무연탄 및 국내 무연탄을 포함하는 54종의 석탄회분을 대상으로 화학조성 및 광물분석 그리고 용융온도를 측정하여 화학조성이 용융온도에 미치는 영향을 고찰하였다. 석탄회의 구성 산화물중 CaO와 MgO, 그리고 $Fe_2O_3$가 용융온도를 낮추는 산화물임을 알 수 있었다. $Fe_2O_3$에 의한 용융온도 감소 효과는 환원성분위기에서 증가되었다. 산-염기도에서 염기성분의 함량이 증가할수록 용융온도는 감소하였다. 그러나 산-염기도와 용융온도와의 상관관계는 $Fe_2O_3$/CaO비가 증가함에 따라 낮아졌다. 산화성분위기보다는 환원성분위기에서 용융온도가 낮았으며 이때 분위기 변화에 따른 용융온도차는 $Fe_2O_3$의 함량보다는 $SiO_2/Al_2O_3$비와 밀접한 상관성을 보여주었다. 석탄회의 용융온도(연화)를 예측하기 위한 다중회귀분석결과 산화성분위기에서는 Base/Acid, $Fe_2O_3$/CaO, $SiO_2/Al_2O_3$, $(SiO_2/Al_2O_3){\cdot}(Base/Acid)$ 그리고 환원성분위기에서는 Base/Acid, $Fe_2O_3$/CaO, $SiO_2$, $TiO_2$등을 독립변수로 사용함으로써 비교적 상관성이 높은 관계식을 얻을 수 있었다.

• 대한토목학회논문집
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• 제31권3B호
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• pp.285-291
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• 2011

물과 에너지의 순환에 대한 정확한 해석은 수문학, 기후학, 생태학적인 과정을 이해하는데 있어 매우 중요하다. 수문 순환 환경변화의 정확한 예측을 위해 사용되고 있는 모형들 중 Common Land Model(CLM)은 물과 에너지수지 방정식을 기반으로 한 최신 Soil-Vegetation-Atmosphere Transfer(SVAT) 모형 중 하나로써, 비교적 간단한 매개변수를 이용하여 현실적이고 신뢰할 만한 결과를 산출해낼 수 있다. CLM 모형은 전 세계적으로 널리 이용되고 있으나, 국내에서는 정보의 부재와 입력자료의 미흡으로 인하여 실제적인 적용사례가 부족한 실정이다. 본 연구에서는 CLM의 국내 적용성 검증을 위하여 해남 Korea Flux Network(KoFlux)의 자료와 Korea Land Data Assimilation System(KLDAS)의 자료를 이용하여 수문순환 환경인자들의 모형 결과를 산출하였다. 모형의 결과와 관측자료의 비교에서 KoFlux와 KLDAS의 두 입력 자료를 사용한 결과 모두 회귀분석에서의 결정계수 값이 0.73~1.00의 신뢰할 만한 수준으로 나타났다. 본 연구에서 CLM의 국내 적용 가능성을 확인하였고 지점자료가 존재하지 않는 지역에 대한 KLDAS의 이용가능성을 또한 확인하였다.

• 한국가스학회지
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• 제9권1호
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• pp.9-15
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• 2005

수소는 온실효과 가스배출을 저감하기 위한 다양한 연소장치에 이용되는 에너지 전달체로 가장 중요한 물질로 인식되고 있다. 그러나 에너지 전달체로 이용되기 위해서는 수소를 이용하는 장치와 관련된 안전의 문제점이 충분히 조사하고 이해되어야 한다. 따라서 누출된 수소가스와 공기의 혼합 가스운의 확산거동과 점화 가능성에 대한 연구가 필요하다. 본 연구에서는 대기 조건에 따라 대기 중에서 수소가스의 확산거동을 부력을 고려하여 살펴보았다. 풍하방향으로 위험범위는 대기안정도 및 풍속이 증가할수록 증가하게 되고, 지면에서 가스농도는 수소가스의 부력 때문에 거의 제로이다. 그러므로 누출된 수소가스 운의 점화 가능성은 낮고, 화재$\cdot$폭발 위험성은 타 연료가스 즉 부탄 및 프로판에 비하여 낮은 것으로 사료된다.

• 한국태양에너지학회 논문집
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• 제31권3호
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• pp.133-144
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• 2011

The objective of this study is to analyze the characteristic of radiation environment in the urban and rural through the field observation in the summer. The radiation balance was compared through the measurement of the shortwave radiation and long-wave radiation in the urban, sub-urban, and rural. The following conclusion could be obtained from this research. (1)In the results of observation including the rain-day, it was found that the short wave radiance in the urban is lower about 10% than the rural. (2)The upper part of atmosphere layers in the urban are aabsorb much short wave radiation energies compared with the rural relatively. It can increase the temperature of the upper part of atmosphere layers and the emittance of long wave radiation. (3)The ratio of the downward short wave radiation to the downward long wave radiation was 1.24 for the urban, 1.28 for sub-urban and 1.35 for rural. It can be estimated that the atmosphere condition of the rural is better than that of other areas. (4)The net radiation of the rural was lower that of the urban. It was found that the energy in and outflow of the rural is easier than that of the urban. (5)The temperature variation for the long-wave radiation change of the rural showed more sensitive than that of the urban. It was came from the radiation characteristics of the surrounding environment and can be used as the important index to evaluate the thermal environment characteristic of urban.