• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.8
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• pp.693-698
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• 2007

A numerical method for accurate simulations of rotor aerodynamics is proposed. The numerical diffusion in the typically coarse grids away from the rotor blades is improved by implying a fourth-order of interpolation of local characteristic variables of the flow in the reconstruction stage of MUSCL approach in the framework of a finite volume formulation. In addition, different slope limiters are applied to the different characteristic fields, such as compressive limiters to linear characteristic fields to reduce the numerical dissipation whereas, diffusive limiters to nonlinear characteristic fields to increase numerical stability. Various exemplary problems related to the rotor aerodynamics applications are tested and the numerical results show a significant improvement in wake capturing capability. However, rotor aeroacoustic calculations show no meaningful difference over traditional MUSCL approach.

• Journal of The Korean Association For Science Education
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• v.20 no.1
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• pp.77-87
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• 2000

The purpose of the study is to understand the change process of middle school students' physics conceptions by the presented types of conflict situations. 274 middle school students were selected from one school in Pusan, however 257 students were participated in all the procedure of the study. After we classified students' physics conceptions into scientific and unscientific conceptions, presented three types of conflict situations. In this study three different cognitive conflict strategies were adopted; the first one is logical arguments(LCS: logical conflict situation), the second is actual demonstration(DCS: demonstrational conflict situation), and the third is two strategies together(DLCS). In this study, first, we investigated the change process of students' physics conceptions by three types of conflict situations. Second, we compared the effect of three conflict situations presentation, which includes positive effect by conceptual change from misconception to scientific conception and negative effect by conceptual change from scientific conception to misconception. Third, we studied characteristics of conceptual change by characteristics of conflict situations. In result, DLCS group and DCS group were more positive effect than LCS group in mechanics, DLCS group and LCS group were more positive effect than DCS group in electricity. It seems that mechanics are closely related to physical experiences, while electricity are more abstract.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.129-140
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• 2000

최근들어 핵폐기물 지하처분장을 중심으로 터널굴착에 의한 주변 암반의 손상상태와 암반특성의 변화를 정량적으로 평가하기 위한 시도가 이루어지고 있다. 이는 암반의 지지력을 적극적으로 이용하는 NATM개념에 의해 터널을 시공할 셩우 안정성 해석과 최적 보강설계를 위해 필수적인 사항으로 고려된다. 그러나 현재까지 암반 손상영역을 평가하기 위해 제시된 여러 방법들은 아직까지 그 적용성과 타당성이 충분히 검증되지 못한 실정이다. 이 연구에서는 코어시추, 실험실시험, 발파진동측정, 보어홀 카메라 등의 여러 방법에 의해 손상영역을 정량적으로 평가하고자 하였으며 가 방법의 적용성을 검토하였다. 암반상태 및 발파조건을 달리하여 시험발파를 수행하였으며 발파 후에 터널벽면에 수직하게 시추를 하여 암석코어를 채취한 뒤 손상정도에 따른 암석의 물리적, 역학적 특성들？ 변화를 정량적으로 나타내고자 하였다. 코어 채취후 시축공에 보어홀 카메라를 사용하여 손상영역을 시각적으로 판별하고자 하였으며 발파진동 측정결과로부터 손상영역을 예측하고 채취한 암석시표에 대한 실험실시험 결과와 비교하여 적용성을 검토하였다.

• Journal of the Mineralogical Society of Korea
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• v.25 no.4
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• pp.211-220
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• 2012

The numerical modeling and simulation have been used increasingly as tools for examining and interpreting the bulk structure and properties of materials. The use of molecular dynamics (MD) simulations to model the structure of materials is now both widespread and reasonably well understood. In this research, we introduced the numerical method to calculate the physico-chemical properties such as a diffusion coefficient and a viscosity of clay mineral. In this research, a series of MD calculations were performed for clay mineral and clay-water systems, appropriate to a saturated deep geological setting. Then, by using homogenization analysis (HA), the diffusion coefficients are calculated for conditions of the spatial distribution of the water viscosity associated with some configuration of clay minerals. This result of numerical analysis is quite similar to the previous experimental results. It means that the introduced numerical method is very useful to calculate the physico-chemical properties of clay minerals under various environmental conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.219-220
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• 2009

The PillPose of this study, powder containing the recycled fine aggregate is appropriate for developing high strength and liquidity, the characteristic of the SCC and it was increased the ratio of mixing the recycled fine aggregates resulted from waste concrete and the natural fine aggregates by 25%, making differential in total 5 levels and applied to SCC. After all, this study was reviewed the physical properties of the fresh concrete, mechanics and durability of the hardened concrete and tried to ensure the possibility of utilizing the recycled fine aggregates as a material for SCC.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.173-176
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• 2002

This study is performed to examine the dry Hwangtoh mortar. The unit weight is in the range of $1,891kg/m^3{\sim}2,037kg/m^3$, it tend to decrease with increase using the Hwangtoh. The compressive and bending strength are in the range of $105kgf/cm^2{\sim}353kgf/cm^2,\;18kgf/cm^2{\sim}66kgf/cm^2$, respectively. The mortar of using Hwangtoh 20% is showed the highest strength ratio.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.181-184
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• 2001

This study is performed to examine the development of the plantable concrete using excellent soil compound, crushed stone, stone dust and superplasticizer. The following conclusions are drawn ; The void ratio is in the range of $25.10{\sim}31.40%$ and the compressive strength is in the range of $69{\sim}113kgf/cm^{2}$ at the curing age 28days, respectively. The plant length was showed higher block by 10% stone dust than 20%.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2003.10a
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• pp.220-224
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• 2003

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.290-295
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• 2000

Mechanical and physical properties of wood fiber for the reinforcement of thin-sheet cement products were investigated. The slurry-dewatering method followed by pressing was used to manufacture the products. Mechanical and physical properties of wood fiber reinforced cement composites were assessed with flexural strength, density, and water absorption. The results obtained in this study were analyzed statistically using the analysis of variance in order to derive statistically reliable conclusions.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.915-920
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• 2000

The effectiveness of bottom ash on the slump flow, compressive strength of flowable fill is investigated in this study. This study was undertaken on the use of bottom ash as a fine aggregate in flowable fill. Bottom ash is combined with portland cement, fly ash, and water to flowable fill with slump flow(20~30cm). Four different level of bottom ash with fly ash contents, 25%, 50%, 75%, 100% are investigated. Laboratory test results conclude that the inclusion of bottom ash increases the demand for mixing water n obtaining the require slump flow.