• 한국결정성장학회지
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• 제15권2호
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• pp.57-60
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• 2005

[ $SiO_2$ ]로 산화된 웨이퍼 위에 상압화학기상증착 기술로 반도체 탄소나노튜브를 성장했으며, 이 나노튜브의 전기적 특성을 조사하였다. 전기적 특성은 반도체 탄소나노튜뷰를 $300^{\circ}C$, 대기 중에서 산화 열처리 시간을 변화시키면서 상온대기에서 측정하였다. 반도체 탄소나노튜브는 $300^{\circ}C$에서 산화 열처리 시간을 증가할수록 점차적으로 금속 탄소나노튜브로 변형되는 것을 보았다. 탄소나노튜브는 $300^{\circ}C$, 대기에서 6시간 동안 산화 열처리 후 표면의 일부가 없어지는 현상을 투과 전자현미경으로 확인하였다.

• 대기
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• 제29권2호
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• pp.219-226
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• 2019

Generally, the weather forecast system has been run using prescribed ocean condition. As it is widely known that coupling between atmosphere and ocean process produces consistent initial condition at all-time scales to improve forecast skill, there are many trials on the application of data assimilation of coupled model. In this study, we implemented a weakly coupled data assimilation (short for WCDA) system in global NWP model with low horizontal resolution for coupled forecast with uncoupled initialization, following WCDA system at the Met Office. The experiment is carried out for a typhoon evolution forecast in 2017. Air-sea exchange process provides SST cooling and gives a substantial impact on tendency of central pressure changes in the decaying phase of the typhoon, except the underestimated central pressure. Coupled data assimilation is a challenging new area, requiring further work, but it would offer the potential for improving air-sea feedback process on NWP timescales and finally contributing forecast accuracy.

• 대기
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• 제28권4호
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• pp.383-392
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• 2018

This study investigates synoptic characteristics of cold surges over South Korea during winter season (December-February). A total of 63 cold events are selected by quantile regression analysis using daily mean temperature observations from 11 KMA stations for 38 years (1979/80-2016/17). Large-scale pressure pattern during the cold surges is well characterized by high over Siberia and low over Aleutian regions, which elucidates cold advection over the Korean peninsula. However, the large-scale pattern cannot successfully explain the observed sudden decrease of temperature during the cold surges. Composite analyses reveal that a synoptic-scale cyclone developing over the northern Japan is a key feature that significantly contribute to the enhancement of cold advection by increasing pressure gradient over the Korean peninsula. Enhanced sensible and latent heat fluxes are observed over the southern ocean of Korea and Japan during the cold surges due to temperature and humidity differences between the near surface and the lower atmosphere over the ocean. The evaporated water vapor transported toward the center of the surface cyclone and condenses in the lower-to-middle troposphere. The released energy likely promotes the development of the surface cyclone by inducing positive PV near the surface of the heating region.

• 한국세라믹학회지
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• 제39권7호
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• pp.635-641
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• 2002

고온 프로톤전도체인 $Y_2O_3$가 도핑된 $SrZrO_3$에 대하여 전기전도도의 가스 분위기 및 온도 의존도를 impedance spectroscopy로 측정하였다. 수소의 용해는 산소가 공존할 때 더 큰 열역학적 추진력을 갖게 되어 결과적으로 수증기 형태로 결정 속으로 유입되며, 프로톤전도도는 ${P_w}^{1/2}$ (수증기분압)에 의존하여 증가하였다. 순수 수소 분위기에서의 수소의 용해반응 $H_2(g)=2H_{i}$ +2e'은 전자가 산소이온공공에 trapping됨에 따른 열역학적 활동도의 감소에 의해 반응의 추진력이 커지며 그 결과 저온에서는 아르곤 분위기에서 보다 높은 전기전도도를 나타내었다. 전기전도도의 활성화에너지는 $600~900^{\circ}C$ 온도범위의 아르곤분위기에서 50kJ/mo1로 문헌에 나타난 프로톤전도도의 그것과 비슷한 크기를 나타냈다. 프로톤전도도의 입계저항은 10% 도핑한 경우 $700^{\circ}C$ 이하의 저온에서 현저하게 나타났다.

• 한국세라믹학회지
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• 제33권11호
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• pp.1260-1266
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• 1996

The effects of SiO2 MnO2 and sintering atmospheres (O2, N2) on the piezoelectric properties and densification behaviors of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 were investigated. The addition of SiO2 to the system enhanced the rate of densification but supressed the rate of grain growth. On the other hand the addition of MnO2 to the system did not nearly affect the rate of densification but increased slightly the rate of grain growth The densification of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 containing of SiO2 or MnO2 was promoted with increasing the partial pressure of O2. The relative dielectric constant ($\varepsilon$r) and piezoelectric constant (d33) of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 containing of SiO2 or MnO2 sintered under O2 atmosphere were higher than under N2 atmosphere. Whereas the mechanical quality factor (Qm) of specimens sintered under O2 atmosphere were lower than under N2 atmosphere. Thus the sintering atmosphere of O2 and N2 in Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 containing of SiO2 or MnO2 acted as donor and acceptor respectively. As the amount of SiO2 increased the relative dielectric constant ($\varepsilon$r) and piezoelectric constant (d33) of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 but the mechanical quality factor (Qm) did not nearly change, In the case of the addition of MnO2 to the system the relative dielectric constant ($\varepsilon$r) and piezoelectric constant (d33) of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 sintered under O2 atmosphere decreased rapidly with increasing the amount of MnO2 but they were unchanged with increasing the amount of MnO2 under N2 sintering atmosphere. Therefore the differences of the relative dielect-ric constant ($\varepsilon$r) and piezoelectric constant (d33) due to sintering atmosphere were diminished as the amount of MnO2 increased.

• 한국안전학회지
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• 제31권3호
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• pp.42-46
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• 2016

In LCD Display or semiconductor manufacturing processes, the anti-static technology of glass substrates and wafers becomes one of the most difficult issues which influence the yield of the semiconductor manufacturing. In order to overcome the problems of wafer surface contamination various issues such as ionization in decompressed vacuum and inactive gas(i.e. $N_2$ gas, Ar gas, etc.) environment should be considered. Soft X ray radiation is adequate in air and $O_2$ gas at atmospheric pressure while UV radiation is effective in $N_2$ gas Ar gas and at reduced pressure. At this point of view, the "vacuum ultraviolet ray ionization" is one of the most suitable methods for static elimination. The vacuum ultraviolet can be categorized according to a short wavelength whose value is from 100nm to 200nm. this is also called as an Extreme Ultraviolet. Most of these vacuum ultraviolet is absorbed in various substances including the air in the atmosphere. It is absorbed substances become to transit or expose the electrons, then the ionization is initially activated. In this study, static eliminator based on the vacuum ultraviolet ray under the above mentioned environment was tested and the results show how the ionization performance based on vacuum ultraviolet ray can be optimized. These vacuum ultraviolet ray performs better in extreme atmosphere than an ordinary atmospheric environment. Neutralization capability, therefore, shows its maximum value at $10^{-1}{\sim}10^{-3}$ Torr pressure level, and than starts degrading as pressure is gradually reduced. Neutralization capability at this peak point is higher than that at reduced pressure about $10^4$ times on the atmospheric pressure and by about $10^3$ times on the inactive gas. The introductions of these technology make it possible to perfectly overcome problems caused by static electricity and to manufacture ULSI devices and LCD with high reliability.

• 한국분말재료학회지
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• 제18권2호
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• pp.141-148
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• 2011

Carbon material shows relatively high strength at high temperature in vacuum atmosphere and can be easily removed as CO or $CO_2$ gas in oxidation atmosphere. Using these characteristics, we have investigated the applicability of carbon mold for precision casting of high melting point metal such as nickel. Disc shape carbon mold with cylindrical pores was prepared and Ni-base super alloy (CM247LC) was used as casting material. The effects of electroless Nickel plating on wettability and cast parameters such as temperature and pressure on castability were investigated. Furthermore, the proper condition for removal of carbon mold by evaporation in oxidation atmosphere was also examined. The SEM observation of the interface between carbon mold and casting materials (CM247LC), which was infiltrated at temperature up to $1600^{\circ}C$, revealed that there was no particular product at the interface. Carbon mold was effectively eliminated by exposure in oxygen rich atmosphere at $705^{\circ}C$ for 3 hours and oxidation of casting materials was restrained during raising and lowering the temperature by using inert gas. It means that the carbon can be applicable to precision casting as mold material.

• 환경위생공학
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• 제19권4호
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• pp.1-8
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• 2004

This study has been investigated to analyze the thermal stability of cesium reacted with fly ash with changing mole ratio of Cs/Al in hydrogen atmosphere. When the $CsNO_3$ and fly ash were reacted at $1000^{\circ}C$ in hydrogen atmosphere, cesium $nepheline(CsAlSiO_4)$ Phase began to emerge in addition to $pollucite(CsAlSi_2O_6)$ phase when the cesium loading quantity was greater than $0.32(g-Cs_2O/g-fly\; ash)$. Cesium $nepheline(CsAlSiO_4)$ Phase increased with increasing cesium loading quantity. When cesium trapped on a fly ash was exposed to $1200^{\circ}C$ in hydrogen atmosphere, no weight loss due to the volatilization was shown until the cesium loading quantity was reached at $0.32(g-Cs_2O/g-fly\; ash)$. In the case of the cesium loading quantity of $0.48-0.74(g-Cs_2O/g-fly\;ash)$ in hydrogen atmosphere, the weight loss increased with increasing the cesium loading quantity. This is considered to be due to the cesium $nepheline(CsAlSiO_4)$ whose vapor pressure is higher than that of $pollucite(CsAlSi_2O_6)$.

• 한국분말재료학회지
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• 제23권4호
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• pp.303-306
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• 2016

An optimum route to synthesize Ti-Mo system powders is investigated by analyzing the effect of the heat treatment atmosphere on the formation of the reaction phase by dehydrogenation and hydrogen reduction of ball-milled $TiH_2-MoO_3$ powder mixtures. Homogeneous powder mixtures with refined particles are prepared by ball milling for 24 h. XRD analysis of the heat-treated powder in a hydrogen atmosphere shows $TiH_2$ and $MoO_3$ peaks in the initial powders as well as the peaks corresponding to the reaction phase species, such as $TiH_{0.7}$, TiO, $MoO_2$, Mo. In contrast, powder mixtures heated in an argon atmosphere are composed of Ti, TiO, Mo and $MoO_3$ phases. The formation of reaction phases dependent on the atmosphere is explained by the partial pressure of $H_2$ and the reaction temperature, based on thermodynamic considerations for the dehydrogenation reaction of $TiH_2$ and the reduction behavior of $MoO_3$.

• 한국화재소방학회논문지
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• 제20권1호
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• pp.77-82
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• 2006

본 연구에서는 온도가 보상된 압력을 제연구역의 기준압력으로 설정하기 위한 공학적인 메커니즘과 보상방법을 정립하였고, 통합 제연시스템의 컨트롤러의 개발을 위한 프로세스, 알고리즘 확립과 엔지니어링 데이터의 구축으로 신뢰성이 확보된 통합 제연시스템의 컨트롤러를 개발하였다. 컨트롤러를 개발함으로서 비제연구역의 압력측정을 위해서 별도로 설치되는 압력측정관을 생략할 수 있어 제작단가와 설치비용 및 작업공수를 줄일 수 있고, 층별 제연구역의 차압측정을 위한 비제연구역의 압력측정포트를 시스템에 일체화함으로서 차압의 정밀도를 향상시킬 수 있다. 기존의 개별제어 방식에서 통합 제연시스템의 컨트롤러로부터 중앙집중식 통합관리를 함으로서 보다 정확하고 신뢰성 있는 차압을 얻을 수 있으며, 제연시스템에 유연성을 부과시킬 수 있을 것으로 본다. 또한 통합 제연시스템의 기틀을 마련하고 제연의 유연성을 주며 방재성능을 향상시킬 것으로 본다.