• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.679-686
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• 2005

The corrosion of reinforcement induced by chloride ingress is the main deterioration cause of coastal reinforced concrete structures. In this paper, an experimental study was executed to investigate the effect of the kinds and replacement ratios of mineral admixtures (fly-ash, ground granulated blast-furnace slag silica fume and meta-kaolin), W/B and curing time on chloride diffusion of concrete by long-time immersion test in chloride solution. According to the result, the use of mineral admixtures was effective in improving the resistant to chloride ingress. The chloride penetration depth and diffusion coefficient were decreased as replacement ratios of mineral admixture were increased. The kind and replacement ratio of the mineral admixture are more important than the W/B in reducing the chloride diffusion of concrete. Chloride binding capacity of mineral admixture, which was sequenced in the order of MK

• Journal of the Korean Vacuum Society
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• v.13 no.3
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• pp.109-113
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• 2004

Zn diffusions in InP have been studied by electrochemical capacitance voltage. The InP layer was grown by metal organic chemical vapor deposition, and $Zn_3P_2$ thin film was deposited on the epitaxial substrates. The samples annealed in a rapid thermal annealing. It is demonstrated that surface hole concentration as high as $1\times10^{19}\textrm{cm}^{-3}$ can be achieved. When the Zn diffusion was carried at $550^{\circ}C$ and 5-20 min., the diffusion depth of hole concentration moves from 1.51$\mu\textrm{m}$ to 3.23 $\mu\textrm{m}$, and the diffusion coeffcient of Zn is $5.4\times10^{-11}\textrm{cm}^2$/sec. After activation, the concentration is two orders higher than that of untreated sample at 0.30 $\mu\textrm{m}$ depth. As the annealing time is increase, the hole concentration remains almost constant, except deep depth. It means that excess Zn interstitials exist in the doped region is rapidly diffusion into the undoped region and convert into substitutional When the thickness of $SiO_2$ thin film is above 1,000$\AA$, the hole concentration becomes stable distribution.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.136-136
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• 2018

듀얼 페이즈(DP) 강철과 같은 고강도강(HSS), TRIP강, TWIP강은 무게를 줄이고 자동차의 안전을 향상시키기 위해서 자동차 산업에서 광범위하게 쓰이고 있다. HSS강의 내부식성을 향상시키기 위해서, 향상된 박막 재료와 기존의 아연도금 공정을 대체하는 공정 방법이 필요하다. Zn-Mg 박막은 강의 부식 방지에 대한 강력한 후보이며, 물리적 기상 증착 공정(PVD)은 강의 Zn-Mg 박막의 증착을 위한 유망한 공정이다. 그러나 이전 연구에서 보고 된 바와 같이 Zn-Mg 박막은 Zn-Mg 박막의 높은 취성으로 인하여 Zn 박막에 비하여 접착력이 매우 불충분하였다. 따라서 본 연구에서는 Zn-Mg 박막의 첩착력을 향상시키기 위해 TRIP강 기판 위에 증발 증착법을 활용하여 Zn-Mg/Zn 이중층 박막을 합성하고 진공에서 열처리를 실시하여 박막의 깊이에 따른 Mg의 함량 변화를 유도하였다. Zn-Mg/Zn 박막 합성 시 EMH-PVD를 활용하여 증착하였으며, Zn 중간층을 모재와 Zn-Mg 층 사이에 증착하고 진공중에서 열처리를 실시하여 박막 내에서 Mg 함량의 기울기 변화가 박막의 밀착력에 주는 영향을 평가하였다. 증착된 박막은 FE-SEM을 통하여 미세조직과 박막의 두께를 분석하였고 line-EDS를 통하여 깊이에 따른 Zn와 Mg의 변화를 분석하였으며 XRD를 사용하여 합금상을 분석하였다. Lap shear test를 활용하여 박막의 밀착력을 정략적으로 분석하였다. FE-SEM 및 EDS 분석 결과 Zn-Mg/Zn 박막을 진공에서 열처리를 실시한 후 FE-SEM으로 분석한 결과 미세조직의 큰 차이는 보이지 않았으나, line-EDS 결과 Mg이 확산되는 것을 확인 할 수 있었다. XRD 분석 결과 확산한 Mg에 의해서 Zn상은 감소하고 $Mg_2Zn_{11}$, $MgZn_2$와 같은 합금상은 증가하는 것을 확인하였다. Lap shear test 결과 $200^{\circ}C$에서 열처리한 Zn-15wt.%Mg/Zn 박막의 경우 밀착력이 19 MPa로 열처리를 하지 않았을 경우(11 MPa)보다 향상되는 것을 확인하였다. 이러한 결과는 통하여 Zn-Mg 박막의 두께의 Mg의 함량 변화에 의해서 박막의 밀착력이 변화되는 것을 알 수 있다.

• Korean Journal of Environmental Agriculture
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• v.16 no.2
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• pp.130-135
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• 1997

Tomatoes are flooded differently 0, 5, 10 and 15cm, according to the developing stages such as flowering stage under the condition of greenhouse. Along with this, they are treated according to the time condition such as 6, 12, 24, 48 and 120 hours. The results obtained are summarized as follows. Plant height decreased in the depth of $0{\sim}10cm$ for over 48 hours, in the depth of 15cm for over 24 hours. Number of leaves was the same as in control, and it decreased over. Number of flowers and fruit setting of individuals decreased conspicuously according as the depth and the hours got greater and longer. Adventitious root occurred remarkably in the depth of $0{\sim}10cm$, for over 24 hours and in the depth of 15cm, 12 hours. Epinastic curvature increased greatly as the depth and the hours got greater and longer. Diffusion resistance of stomata cell increased as the depth and the hours got greater and longer. Diseases occurred conspicuously as the hours of flooding got longer rather than as the depth greater. The preventing of diseases caused by insecticide was observed, but it was not greater than in the seedling and transplanting stage. Fertilization was effective in the case of increasing the weight of shoot. Number of fruits per plant did not decrease in the depth of 0cm up to 24 hours, but decreased on the deeper level of flooding and increased as the hours got longer. Moreover with the exception of 120 hours per respective depth of the treatment, average weight of a fruit got greater as the depth and the hours got greater and longer. In the case of epinastic curvature and diffusion resistance, there was negative correlation between all the other investigated characters and positive correlation between weight of a fruits and average weight of a fruit.

• Korean Journal of Materials Research
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• v.10 no.11
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• pp.749-764
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• 2000

Amorphous TaSiN thin films of about 90 nm thick were deposited onto poly-Si and $SiO_2/Si$ substrates by rf magnetron sputtering method. TaSiN films exhibited amorphous phase with no crystllization up to $900^{\circ}C$ in oxygen ambient. The penetration depth of oxygen diffusion increased with increasing annealing temperature in oxygen ambient and reached 20 nm deep in a $Ta_{23}Si_{29}N_{48}$ layer at $600^{\circ}C$ for 30min. The resistivity of as-deposited $Ta_{23}Si_{29}N_{48}$ thin films was about $1,300{\mu}{\Omega}-cm$, however those of annealed films markedly increased above $700^{\circ}C$ in oxygen ambient as the annealing temperature increased.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.133-133
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• 2010

3-5족 화합물 반도체를 이용한 집광형 삼중 접합 태양전지는 35% 이상의 광변환 효율로 주목을 받고 있다. 일반적으로 삼중 접합 태양전지는 넓은 영역대의 파장을 흡수하기 위해 밴드갭이 다른 InGaP, GaAs, Ge이 사용된다. 그 중 하부셀은 기계적 강도가 높고 장파장을 흡수할 수 있는 Ge이 사용되는데, p-type Ge 기판위에 III-V 결정막 성장 시 5족 원소가 확산되어 pn접합을 형성하게 된다. 이러한 구조를 가진 Ge 하부셀이 효율적으로 홀-전자 쌍을 형성하기 위해서는 두꺼운 베이스와 얇은 에미터 접합이 필요하다. InGaP의 phosphorus는 낮은 확산계수로 인해 GaAs의 arsenic에 비해 얇은 접합이 형성 가능하며, Ge표면 에칭효과가 더 적다는 장점이 있다. 이를 고려해 우리 연구그룹에서는 metalorganic chemical vapor depostion(MOCVD)을 이용하여 Ge기판위에 성장한 InGaP layer의 특성을 관찰해 보았다. <111>로 $6^{\circ}$ 기울어진 p-type Ge(100) 기판위에 MOCVD를 통해 InGaP layer를 형성하였고, 성장된 layer를 atomic force microscope(AFM)와 high-resolution x-ray diffraction(HRXRD)을 이용하여 표면형상, 조성, 응력상태 등을 각각 관찰하였다. 또한 phosphorus 확산에 의해 형성되는 도핑농도는 electrochemical capacitance-voltage(ECV)을 이용하여 관찰하였다. 성장된 Ge기판위의 InGaP layer의 경우 특징적으로 높이 50 nm, 밑변 길이 $1\;{\mu}m$의 경사진 표면을 관찰할 수 있었으며, 이러한 구조는 TMIn과 TMGa의 비율이 증가 할수록 감소하였다. 따라서 이러한 경사진 형태의 구조는 격자 불일치 때문인 것으로 판단된다. 추가적으로 V/III ratio의 최적화를 통해 1.3 nm의 표면 거칠기를 갖는 InGaP layer를 얻을 수 있었다. ECV를 통해 Ge 하부셀의 pn접합 형성을 관찰한 결과 약 160 nm에서 접합이 형성되는 것을 관찰할 수 있었다. 또한, 같은 성장 조건의 샘플을 1000 초 열처리 후에 접합깊이의 변화를 관찰한 결과 180 nm에서 접합이 관찰되었지만, GaAs의 arsenic에 의한 pn접합은 열처리 후에 그 깊이가 170 nm에서 300 nm로 증가 하였다. 따라서 삼중접합 태양전지의 제작 공정을 고려할 경우 phosphorus에 의한 접합 형성이 Ge 하부셀의 동작 특성에 유리할 것으로 판단된다.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.261-268
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• 2004

Corrosion of reinforcement is the main cause of damage and early failure of reinforced concrete structures. The corrosion is mainly progressed by the chloride ingress. In this paper, an experimental study is executed to investigate the effect of concrete properties and testing methods on the coefficients of chloride diffusion. Also, it is surveyed the relationship between total chloride and free chloride in concrete. According to this experiment results, W/C ratio and testing method affect chloride diffusion coefficient of concrete. As W/C ratio is increased, diffusion coefficient in concrete is also increased. Diffusion coefficient obtained by each testing method show the different values, respectively. The model equation of diffusion coefficient with W/C ratio is proposed.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.1
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• pp.15-20
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• 2009

Marine concrete structure is exposed to salt injury and deteriorated by steel corrosion due to chloride ions diffusion. It, therefore, is very important to estimate the chloride diffusivity in concrete. In this paper the compressive strength and permeable pore volume of concrete are measured and the diffusion coefficient and penetration depth of chloride ions in concrete were investigated to estimate the chloride diffusivity efficiently. To correlate these results each other, regression analysis was done. The results showed a good linear relation between chloride diffusivity and the fundamental properties of concrete and the chloride diffusivity of concrete with water-cement ratios of $40%{\sim}60%$ were about $2.5{\sim}6.6{\times}10^{-12}m^2/s$.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.7-13
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• 2011

Simulation study were performed for ventilation capability effect on the smoke spread in the deeply-underground subway station(DUSS). Singeumho station(The line # 5, Depth: 46m) was modeled and were analyzed for smoke-spread speed difference between the originally-designed-ventilation-capacity and the measured-ventilation-capacity. Field test data for actual fan in DUSS was applied as a boundary condition of a simulation. The whole station was covered in this analysis and total of 4 million grids were generated for this simulation. The fire-driven flow was analyzed case by case to compare the smoke-spread effects. In order to enhance the efficiency of calculation, parallel processing by MPI was employed and large eddy simulation method in FDS code was adopted.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2885-2890
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• 2011

Simulation study were performed for fire location effect on the smoke spread in the deeply-underground subway station(DUSS). In this research, Shingumho station (The line # 5, Depth: 46m) has been selected as case-study for the analysis of smoke-spread effect with the different fire location. Field test data measured for actual fan in DUSS was applied as a condition of a simulation. The whole station was covered in this analysis and 4 million grids were generated for this simulation. The fire driven flow was analyzed case by case to compare the smoke-spread effect according to the fire location. In order to enhance the efficiency of calculation, parallel processing by MPI was employed and LES(large eddy simulation) method in FDS code was adopted.