• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.78-90
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• 2005

The spatial and temporal distribution of soil moisture was characterized from soil moisture data through the intensive monitoring using Time Domain Reflectometry (TDR). The recession of soil moisture after a rainfall event was characterized and the empirical equation was used in the recession curve analysis. Recession analysis provides features of soil moisture variation such as recharge and stability depending upon locations of monitoring. The wetness index was useful for explaining spatial and temporal distributions of soil moisture and recession characteristics at hillslope scale.

• Journal of the Korean Magnetics Society
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• v.20 no.3
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• pp.94-99
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• 2010

Minor B-H loop measurement for a rectangular high tensile steel was obtained by using Labview. A ferrite cores of high permeance with primary and secondary windings on the steel plate were used to form a closed loop of magnetic flux. To compensate errors due to an extremely small gap between a pair of ferrite core, and between the ferrite core and the rectangular high tensile steel, quadratic function of least square method was used. Also a 3D FEM magnetic analysis tool was used to measure H and B of the steel. B-H loop of the high tensile steel plate can be measured up to 520 A/m of a magnetic field and 0.15 T of a magnetic flux density.

• Journal of the Korean Geotechnical Society
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• v.37 no.10
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• pp.41-54
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• 2021

In this study, probabilistic steady seepage behavior of soil foundation beneath water retaining structures according to the location of cutoffs was studied. A Monte Carlo Simulation based on the random finite element method that considers the uncertainty and spatial variability of soil permeability was performed to evaluate the probabilistic seepage behavior. Fragility curves were developed by calculating the failure probability conditional on the occurrence of a given water level from the probability distribution obtained from Monte Carlo simulations. The fragility curve was prepared for the flow quantities such as flow rate through foundation soil, uplift force on the base of structure, and exit gradient in downstream to examine the reliability of the water retaining structure and the foundation soil. From the fragility curves, the effect of the location of cutoff wall on the reliability of water retaining structure and foundation soil according to the rise in water level was studied.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.439-448
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• 2001

A two-dimensional finite difference numerical model was developed in order to simulate two-phase fluid flow in a single fracture. In the model, variation of viscosity with pressure and that of relative permeability with water saturation can be treated. For the numerical solution, IMPES method was used, from which the pressure and the saturation of water and gas were computed one by one. Seven cases of model test using parallel plates for a single fracture were performed in order to obtain the characteristic equation of relative permeability which would be used in the numerical model. it was difficult to match the characteristic curves of relative permeability from the model tests with the existing emperical equations, consequently a logistic equation was proposed. As the equation is composed of the parameters involving aperture size, it can be applied to any fracture.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.389-389
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• 2013

HfOx (Hafnium oxide)는 ~25의 고유전상수, 5.25 eV의 비교적 높은 Band-gap을 갖는 물질로 MOSFET (metal-oxide semiconductor field-effect-transistor) 구조의 Oxide 박막을 대체 가능한 물질로 연구가 지속되고 있다. 현재까지 진행된 대다수의 연구는 증착 조건에 따른 박막의 결정학적 및 전기적 특성에 대한 주제로 진행되었고 다양한 연구 결과가 보고된바 있다. 하지만 기존의 연구 기법은 박막의 nanomechanics 특성에 대한 연구가 부족하여 이를 보완하기 위한 연구가 절실하다. 따라서 본 연구에서는 HfOx 박막 내 포함된 산소가 고온 열처리 과정에서 빠져나감으로 인한 박막의 nanomechanics 특성을 확인하고자 하였다. 시료는 rf magnetron sputter를 이용하여Si (silicon) 기판위에 Hafnium target으로 산소유량(5, 10, 15 sccm)을 달리하여 증착하였고, 이후 furnace에서 $400^{\circ}C$에서 $1,000^{\circ}C$까지 질소분위기에서 20분간 열처리를 실시하였다. 실험결과 시료의 전기적 특성을 I-V 곡선을 측정하여 확인하였고, 증착 시 산소 유량이 5 sccm에서 15 sccm으로 증가함에 따라서 누설전류 특성은 급격히 향상되었고, 열처리 온도가 증가함에 따라 감소하는 특성을 나타내었다. 또한 시료의 nanomechanics 특성을 확인하기 위하여 nano-indenter를 이용하여 시료의 표면강도(surface hardness)와 탄성계수(elastic modulus)를 확인하였다. 측정결과 5 sccm 시료의 표면강도와 탄성계수는 상온에서 열처리 온도가 증가함에 따라 각각 7.75 GPa에서 9.19 GPa로, 그리고 133.83 GPa에서 126.64 GPa로 10, 15 sccm의 박막의 비하여 상대적으로 균일한 특성을 나타내었다. 이는 증착 시 박막 내 과포화된 산소가 열처리 과정에서 빠져나감으로 인한 것이며, 또한 과포화된 정도에 따라 더 적은 열처리 에너지에 의하여 박막을 빠져나감으로 인한 것으로 판단된다. 또한 열처리 과정에서 산소가 빠져나가는 상대적인 flux의 영향으로 인하여 박막의 mechanical한 균일도의 변화가 나타났다.

• Journal of the Korean Applied Science and Technology
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• v.24 no.1
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• pp.54-60
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• 2007

이 논문에서는 게이트 절연막 위에 vapor deposition polymerization(VDP)방법을 사용하여 성막한 유기 점착층을 진공 열증착하여 유기 박막 트랜지스터(OTFTs)소자를 제작할 수 있음을 증명하였다. 우리가 제작한 Staggered-inverted top-contact 구조를 사용한 유기 박막 트랜지스터는 전기적 output 특성이 포화 영역안에서는 포화곡선을, triode 영역에서는 비선형적인 subthreshold를 확실히 볼 수 있음을 발견했다. $0.2{\mu}m$ 두께를 가진 게이트 절연막위에 유기 점착층을 사용한 OTFTs의 장 효과 정공의 이동도와 문턱전압, 그리고 절멸비는 각각, 약 0.4cm2/Vs, -0.8V, 106 이 측정되었다. 게이트 절연막의 점착층으로써 폴리이미드의 성막을 위해, 스핀코팅 방법 대신 VDP 방법을 도입하였다. 폴리이미드 고분자막은 2,2bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA)와 4,4'-oxydianiline(ODA)을 고진공에서 동시에 열 증착 시킨 후, 그리고 $150^{\circ}C$에서 1시간, 다시 $200^{\circ}C$에서 1시간 열처리하여 고분자화된 막을 형성하였다. 그리고 점착층이 OTFTs의 전기적 특성에 주는 영향을 설명하기 위해 비교 연구하였다.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.181-194
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• 1999

Both the chemical components and the physical and mechanical properties of the compacted and undisturbed weathered granite soils were estimated to investigate the influences of the degree of weathering and saturation on the shear strength. The weathered granite soils used in this study were taken from six different sites in Korea. The results showed that the shear strength of weathered granite soil decreased with increasing the degree of weathering and saturation. Under the normal stresses less that 40kPa, the shape of Mohr-Coulomb failure envelope followed curved or hyperbolic relationship and a half of cohesion value obtained by the common shear test was observed. Using the Sueoka's method, the values of CWI were ranged from 21.5 to 31.26 which can be characterized as a completely weathered granite soil. Large decrease in shear strength and remarkable variation in dilatancy were observed in saturated granite soil compared to unsaturated soil. It was also found that the shear strength of undisturbed weathered granite soil of Pungam site can be expressed approximately by the equation of ${(\tau)_{sat}= 1.0(\tau)_{unsat}-12.48}$ and this equation can be extended to the other sites considered in this study.

• Journal of the Korean GEO-environmental Society
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• v.24 no.10
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• pp.15-23
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• 2023

In this study, the infiltration behavior of slopes composed of mixed soils with clay contents of 0%, 5%, and 10% in weathered Gneiss soil, which is a representative weathered soil in Korea, was investigated, and the stability of unsaturated slopes due to rainfall infiltration was examined. For this, in this study, the soil water characteristic curve was obtained through the water retention test, and the strength constant was obtained through the triaxial compression test. Based on the obtained results, the influence of clay content and antecedent rainfall effect (i.e., initial suction) on the formation of saturated zone (i.e., wetting band) and slope stability due to rainfall infiltration was examined through infiltration and stability analyses. As a result, it was found that the hig her the initial suction, the slower the formation of the saturated zone on the slope. In addition, it was found that as the clay content increases, the shear strength of the ground increases and the resistance to rainfall infiltration increases, and eventually the slope stability is greatly improved.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.27-35
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• 2008

At low normal stress levels tensile strength of sand varies with either saturation or suction of soil in an up-and-down manner with a peak tensile strength that can occur at any degree of saturation. A theory that accurately predicts tensile strength of wet sand is presented. A closed form expression for tensile strength unifies tensile strength characteristics in all three water retention regimes: pendular, funicular, and capillary. Three parameters are employed in the theory; namely, the Internal friction angle (at low normal stress) ${\phi}_t$, the inverse value of the air-entry pressure ${\alpha}$, and the pore size spectrum parameter n. It is shown that the magnitude of peak tensile strength is dominantly controlled by the ${\alpha}$ parameter. The saturation at which peak tensile strength occurs only depends on the pore size spectrum parameter n.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.4
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• pp.251-258
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• 2004

Soil testing for silicon (Si) in the upland soils has not been sufficiently investigated. The objective of this study was to identify a suitable Si extraction method for upland soils of oriental melon (Cucumis melo L.). Thirty-eight surface soil samples and matured leaf samples were collected from plastic film houses in Sungju, Gyeongbuk province. In the laboratory, six different methods were used for extracting Si from the soils. The methods included 0.5 N HCl extraction, 1 N sodium acetate buffer (PH 4.0) extraction, citric acid 1% extraction, water extraction, Tiis buffer pH 7.0 extraction, and extraction after incubation with water for 1 week. The concentration of dissolved Si in soil extracts from all methods was determined colorimetrically. With 1 N sodium acetate buffer extraction, as the available soil Si increased, the concentration ofSi in oriental melon leaf increased until around $14g\;SiO_2\;kg^{-1}$ was reached in the form of a saturation curve. Also, among the methods studied, extraction with 1 N sodium acetate buffer was the only method provided a significant linear correlation with oriental melon leaf Si content in the range of extractable soil Si lower than the level which inducing Si saturation in oriental melon leaf. These results indicate that 1 N sodium acetate buffer extraction procedure is the best soil Si test method for upland soils of oriental melon. This sodium acetate buffer extraction procedure is rapid and quite well acquainted with scientists and farmers, since the method has been used for routine paddy soil testing.