• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2354-2359
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• 2007

Influence of changing combustor pressure on flame stabilization and emission index in the swirl-stabilized flame was investigated. The combustor pressure was controlled by suction fan at combustor exit. Pressure index ($P^{\ast}$=Pabs/Patm), where Pabs and Patm indicated the absolute pressure and atmosphere pressure, respectively, was controlled in the range of 0.7${\sim}$1.3 for each equivalence ratio conditions. The flammable limits of swirl flames were largely influenced by changing combustor pressure and they showed similar tendency with laminar flames. NOx emission index decreased with decreasing pressure index for overall equivalence ratio conditions. R.m.s. of pressure fluctuations is increased with decreasing combustor pressure. This flame fluctuation caused incomplete combustion, hence CO emission index increased. These oscillating flames were measured by simultaneous $CH^{\ast}$ chemiluminescence time-series visualization and pressure fluctuation measurement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.571-576
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• 2000

This paper summarized deformation properties of hydroelectric power concrete dam through the comparison between measured and analysed data. This is a part of the process to evaluate concrete dam safety, which has become a critical concern in the country. We analysed strain and angle deformation data by considering only the effect of atmosphere temperature to evaluate deformation properties of Gaisan hydroelectric power concrete dam. Analysis results are almost identical with measured data, and behavior of Gusian dam can be cleared up more reliably in case of acting the external loads (seismic, wind water pressure, etc.) except the influence of temperature.

• 한국대기환경학회지
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• 제13권1호
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• pp.1-7
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• 1997

Anion concentrations and distributions of airborne fine particles less than 2 $\mu$m in urban atmosphere were determined from Feb. 5 to 16, 1996. The sampling was carried out using 8 stages Hering's low pressure impactor (LPI, aerodynamic cutoff diameters are 0.05, 0.075, 0.11, 0.26, 0.50, 1.0, 2.0, and 4.0$\mu$m) on the top of a five-story building located at Kon-Kuk university in Seoul. Average concentrations if C $l^{[-10]}$ , N $O_3$$^{[-10]}$ and S $O_4$$^{2-}$ were 9.4, 8.4, and 14.5 $\mu\textrm{g}$/㎥, respectively. The distributions of these anion concentrations were bimodal types which showed two peaks in the range of 0.075~0.12 ${\mu}{\textrm}{m}$ and 0.5~1 ${\mu}{\textrm}{m}$ in aerodynamic diameter. These results were 2.5~4.7 times higher than anion concentrations collected by Anderson low volume air sampler.

• 한국세라믹학회지
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• 제33권3호
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• pp.259-268
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• 1996

In the present study the effect of the addition of Fe on the pressureless and hot press sintering behavior was studied under Ar atmosphere. Pressureless sintering was performed 1900~220$0^{\circ}C$ under. Ar atmosphere. The addition of 1 wt% Fe was increased effectively of the sintered density. However it was impossible to obtain high density higher than 90%,. Zr-Fe-B compound in liquid phase was observed from the EDS and WDS analysis. It was considered that sinterability was enhanced due to the mass transfer through Fe based liquid phase formed at the sintering temperature. Hot pressing was performed at 1600~1$700^{\circ}C$ under Ar atmos-phere for 1 hr. It was possible obtain 95% relative density of ZrB2 specimen which is higher density at pressure-less sintering. It could be thought that ZrB2 particles was rearranged through liquid phase by applied pressure during initial stage of sintering.

• Advances in Energy Research
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• 제8권4호
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• pp.265-273
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• 2022

In this study, a product gas yield and carbon conversion were measured during the coal pyrolysis. The pyrolysis process occurred under two different atmospheres such as subcritical (45 bar, 10℃) and supercritical CO₂ condition (80 bar, 35℃). Under the same pressure (80 bar), the atmosphere temperature increased from 35℃ to 45℃ to further examine temperature effect on the pyrolysis at supercritical CO₂ condition. For all three cases, a power input supplied to heating wire placed below coal bed was controlled to make coal bed temperature constant. The phase change of CO₂ atmosphere and subsequent pyrolysis behaviors of coal bed were observed using high-resolution camcorder. The pressure and temperature in the reactor were controlled by a CO₂ pump and heater. Then, the coal bed was heated by wire heater to proceed the pyrolysis under supercritical CO₂ condition.

• 한국전자파학회논문지
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• 제19권6호
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• pp.698-705
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• 2008

전자파가 대기를 통과할 때 대기를 형성하고 있는 다양한 요인들에 의해 그 특성이 변동하게 된다. 전파 특성에 영향을 미치는 대기의 주요 요인으로는 수증기, 안개, 산소와 같은 대기 입자, 강우, 강설 및 그 외 여러 종류의 에어로졸을 들 수 있으며, 이러한 것들은 지형 및 지역적 특성에 따라 다르게 분포한다. 따라서 대기 환경에서의 전파 특성을 예측하기 위해서는 주어진 환경에 대한 기온, 습도, 기압, 풍속, 에어로졸 및 강우율 등의 통계적 분석이 중요하다. 본 논문에서는 국내 대기 환경에 대한 통계적 분석을 수행하였으며, 이를 바탕으로 국내 대기 환경에서의 전파 특성을 분석하였다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1991년도 추계연구발표회 논문개요집
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• pp.72-73
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• 1991

• 한국자동차공학회논문집
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• 제13권6호
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• pp.7-12
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• 2005

In order to analyze the microscopic spray characteristics of free spray in ultra high pressure region, the droplets size and velocity of free spray injected under atmosphere condition were measured by PDPA. As injection pressure became ultra high pressure, the droplets size was decreased continuously due to the increase of mutual reaction between droplets and air. But the decreasing rate became moderate. The velocity was increased until 250 MPa, and then decreased over that of injection pressure. It was seemed that the droplet size was similar in range of $280\~350\;MPa$, but increased in 414 MPa, even though injection pressure was increased. The microscopic spray characteristics of free spray got worse in 414 MPa.

• 전기전자학회논문지
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• 제23권3호
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• pp.865-872
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• 2019

대기압에서의 Ar 직류 글로우방전 현상을 1차원 유체모델을 통하여 시뮬레이션을 수행하였다. Ar 기체방전의 여기입자들로부터 방출되는 광원으로서 4가지(${\lambda}_{128nm}$, ${\lambda}_{727nm}$, ${\lambda}_{912nm}$ 그리고 ${\lambda}_{966nm}$) 파장의 빛을 검토하였다. 그 결과, 사인형태의 전원 전압을 인가하였을 경우, ${\lambda}_{128nm}$와 ${\lambda}_{727nm}$의 광원이 직류 전압파형을 인가하였을 때보다 거의 2배에 가까운 빛을 방출하는 것을 확인하였다. 또한, 전원전압의 스위칭 시간이 짧을수록, ${\lambda}_{128nm}$와 ${\lambda}_{727nm}$의 방출이 더 많아지는 것을 알 수 있었다. 본 연구에서는 하전입자에 의한 줄 열과 소모 전력에 관해서도 논의하였다.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1465-1468
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• 2014

In this study, an intermediate temperature ionic conductor, $Ce_{0.95}Eu_{0.05}P_2O_7$, was prepared by solid state reaction. The variation of conductivities with the pressure $pH_2O$ or time were studied. The highest conductivity of $Ce_{0.95}Eu_{0.05}P_2O_7$ sample was observed in dry air atmosphere at $300^{\circ}C$ to be $1.1{\times}10^{-4}S{\cdot}cm^{-1}$ and in wet air atmosphere ($pH_2O=7.4{\times}10^3Pa$) at $100^{\circ}C$ to be $1.4{\times}10^{-3}S{\cdot}cm^{-1}$, respectively. The log ${\sigma}$ ~ log ($pO_2$) plot result indicated that $Ce_{0.95}Eu_{0.05}P_2O_7$ was almost a pure ionic conductor under high oxygen partial pressure and a mixed conductor of ion and electron under low oxygen partial pressure.