• Journal of Energy Engineering
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• v.23 no.3
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• pp.174-180
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• 2014

Experimental study of liquid nitrogen pool spread is carried out when it is continuously released. The liquid nitrogen spreads over a cement mortar plate with continuous release. Evaporation rate per unit area of the liquid nitrogen is measured using a digital balance, and a spreading distance of the liquid pool is measured by thermocouples. It is discovered that the evaporation rate per unit area of liquid nitrogen tends to decrease as the liquid pool spreads.

• Nuclear Engineering and Technology
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• v.29 no.6
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• pp.17-28
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• 1997

콘크리트를 통한 핵종의 확산계수는 처분장으로 부터의 핵종 유출을 평가하는데 중요한입력 인자이다. 본 연구에서는 콘크리트에서의 핵종확산 연구 현황 및 핵종화산에 미치는 주요 인자들의 영향 등이 조사되었고, 주요 핵종의 확산계수가 직접 측정되었다. 내부확산법으로 측정된 확산계수값은 시료의 물과 시멘트 비 (W/C)가 증가할수록 증가하였으나 거의 같은 승수내에 있었으며, 공극확산이 핵종이동을 지배하였다. Cs 과 I 의 겉보기 확산계수는 순수 시멘트에서 각각 $1.0{\times}10^{-12}~1.0{\times}10^{-11}m^2/s$ 및 $3.0{\times}10^{-14}~1.0{\times}10^{-13}m^2/s$, 몰타르에서는 각각 $3.0{\times}10^{-12}~9.0{\times}10^{-11}m^2/s$ 및 $3.0{\times}10^{-11}m^2/s$의 범위에 있었다. 이와 병행하여 시멘트, 몰타르 및 콘크리트에서의 주요 방사성핵종의 확산계수 값을 문헌으로부터 수집, 정리하였다. 대상 핵종은 Cs, I, Sr, C, Co, H, Am, PU, Ni, Mn, Fe, Nb 및 Tc로서 수집된 핵종확산계수 값은 시료의 조건 (공극률 밀도, W/C 비, 온도 등) 에 따라 큰 편차를 보여주고 있다.

• KCID journal
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• v.5 no.2
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• pp.41-51
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• 1998

Spatial distributional patterns of temperature in the sediments and the concentration of nutrients in interstitial water were particular interests on the ecological research of tidal flats. It was the aim of this paper to grasp inhabiting environment of t

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.215-217
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• 2007

반도체 집적화 기술의 발달로 반도체 공정에서 디바이스의 선폭은 줄어들고, 박막의 다층화가 필수적인 과정이 되었다. 이에 따라 반도체에서 Si 기판과 금속 배선과의 열적 안정성에 대한 신뢰성이 더욱 중요시 되어가고 있다. 이를 방지하기 위하여 우리는 3개의 화합물로 구성된 Tungsten-Carbon-Nitrogen (W-C-N) 확산방지막을 사용하였다. 실험은 Si 기판위에 W-C-N박막을 물리적 기상 증착법(PVD)으로 질소비율을 변화하며 확산방지막을 증착하여 Si 기판과 W-C-N확산방지막의 특성을 여러 온도 열처리 조건에서 확인하였다. 특성을 분석을 위하여 ${\alpha}-step$과 ${\beta}-ray$를 이용하여 증착률을 확인한 후 4-point probe를 이용하여 비저항을 측정하였고, X-ray Diffraction 분석을 통하여 결정 내부의 변화를 확인하였다. 이를 통하여 W-C-N 확산방지막의 열적인 안정성을 질소변화에 따라 조사하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.54-61
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• 2023

In this paper, the compressive strength, pore characteristics, and chloride diffusion coefficient were measured at 28 days of age in order to examine the influence of curing conditions for the chloride diffusion and pores in concrete cured under extreme condition. According to the test results, the compressive strength was improved as the relative humidity increased. Additionally, higher compressive strength was observed when the specimens were cured at 35℃. However, the compressive strength of specimens cured at 45℃ was decreased. Meanwhile, the chloride diffusion coefficient decreased with an increase in curing temperature and relative humidity, indicating a difference compared to the trend observed for compressive strength. On the other hand, the excellent correlation showed between compressive strength and chloride diffusion coefficient, porosity and chloride diffusion coefficient when the concrete cured under water. However, when the concrete cured under extreme condition, this correlation was significantly reduced compared to the water curing case. In contrast, it has been determined that there is no significant correlation between the average pore size and chloride diffusion coefficient, regardless of the curing conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.53-59
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• 2010

Recently, NDTs (Non-Destructive Techniques) using infrared camera are widely studied for detection of damage and void in RC (reinforced concrete) structures and they are also considered as an effective techniques for maintenance of infrastructures. The temperature on concrete surface depends on material and thermal properties such as specific heat, thermal conductivity, and thermal diffusion coefficient. Different porosity on cement mortar due to different mixture proportions can show different heat behavior in cooling stage. The porosity can affect physical and durability properties like strength and chloride diffusion coefficient as well. In this paper, active thermography which uses flash for heat induction is utilized and thermal characteristics on surface are evaluated. Samples of cement mortar with W/C (water to cement ratio) of 0.55 and 0.65 are prepared and physical properties like porosity, compressive strength, and chloride diffusion coefficient are evaluated. Then infrared thermography technique is carried out in a constant room condition (temperature $20{\sim}22^{\circ}C$ and relative humidity 55-60%). The mortar samples with higher porosity shows higher residual temperature at the cooling stage and also shows reduced critical time which shows constant temperature due to back wall effect. Furthermore, simple equation for critical time of back wall effect is suggested with porosity and experimental constants. These characteristics indicate the applicability of infrared thermography as an NDT for quality assessment of cement based composite like concrete. Physical properties and thermal behavior in cement mortar with different porosity are analyzed in discussed in this paper.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.128-138
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• 2015

Carbonation is one of the most critical deterioration phenomena to concrete structures exposed to high $CO_2$ concentration, sheltered from rain. Lots of researches have been performed on evaluation of carbonation depth and changes in hydrate compositions, however carbonation modeling is limitedly carried out due to complicated carbonic reaction and diffusion coefficient. This study presents a simplified carbonation model considering diffusion coefficient, solubility of $Ca(OH)_2$, porosity reduction, and carbonic reaction rate for low concentration. For verification, accelerated carbonation test with varying temperature and MIP (Mercury Intrusion Porosimetry) test are carried out, and carbonation depths are compared with those from the previous and the proposed model. Field data with low $CO_2$ concentration is compared with those from the proposed model. The proposed model shows very reasonable results like carbonation depth and consuming $Ca(OH)_2$ through reduced diffusion coefficient and porosity compared with the previous model.

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.86-91
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• 1998

Multimode planar waveguides have been fabricated by an electric-field assisted ion exchange in soda-lime glass substrates. Measurements of the mode indices have been made and the index profiles modeled on modified Fermi function are explained by a comparative analysis with the concentration profiles obtained using an electron probe X-ray micro analyzer. The analytical measurements showed that no more than 95% of sodium ions were replaced by the cesium ions. We established formulas for guide depth, mobility, and refractive index change, given the applied electric field, the diffusion temperature, and the time. We have verified the linear relations in the formulas not only between guide and root of diffusion time but also between guide depth and the applied electric filed experimentally.

• Magazine of the Korea Concrete Institute
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• v.10 no.3
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• pp.153-164
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• 1998

본 연구는 양생온도의 영향에 따른 콘크리트의 장기강도 예측식을 개발하고, 기존에 보고된 데이터를 이용하여 제안식의 신뢰성을 검증하기 위한 것이다. 제안식은 반응률상수 모델을 이용하였으며, 콘크리트의 장기강도에 영향을 미치는 인자로 양생온도에 따른 확산장벽의 효과를 고려하였다. 제안식을 검증하기위하여 각각의 데이터를 28일 상대강도의비로바꾸어 -0.6~59.7$^{\circ}C$ 범위의 8개의 평균 양생온도에 대해서 회귀분석하였다. 회귀분석을통해 제안식의 온도 영향계수인 반응율상수, 한계강도, 반응지수를 양생온도에 따른 함수식으로 표현하였다. 제안식은 기존의모델식에 비해 신뢰성이 높았으며, 초기재령에서는 기존의 모델식등과 큰 차이를나타내지 않았으나 장기재령으로 갈수록 제안식의 정확도가 크게 높아짐을 알 수 있었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.474-474
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• 2014

Boron-rich Layer (BRL) 는 결정질 실리콘 태양전지를 제작하는 과정 중 보론 확산 공정 시 형성된다. 본 연구에서는, n-type 실리콘 태양전지에서 BRL의 구조적, 광학적, 전기적 특성을 조사하였다. 보론 에미터는 튜브 형식의 열처리 로에서 $950^{\circ}C$의 온도 하에서 BBr3 액상 소스를 이용하여 형성하였다. BRL은 비정질 상을 보였고, $1023atoms/cm^3$이 넘는 보론 농도를 나타내었다. BRL은 보론, 실리콘, 산소로 구성되었고, 산소는 비정질 상 형성의 원인으로 추정되고 있다. BRL은 1.5~2.0의 굴절률을 나타내었고, $0.8m{\Omega}{\cdot}cm^2$의 접촉 저항을 보였다.