• Journal of the Korean Geotechnical Society
• /
• v.21 no.5
• /
• pp.93-101
• /
• 2005

The formation of slopes is unavoidable under the special circumstance of Korea where $7%$ of the whole area are composed of mountains and civil engineering projects such as road and site developments are increasing with industrial development and horizontal expansions of urban area. Stability of slopes is one of quite important issues under special meteorological characteristics that over two-thirds of annual average rainfall is concentrated in summer season and the localized torrential downpour is getting more frequent recently. As a result of these circumstances, partial slope failures by debris flow of the high water content soils occur frequently in cut soil slopes. In this case of debris flow slope failure, slope declination method is selected fur the stable recovery because it is impossible to recover entirely by existing recovery methods. Seeding or special grass planting methods are followed separately without exception. The method by which entire recover with bigger stability ratio would be possible and grass planting work would be done simultaneously is developed. For debris flow failure slopes, this study secured the safety of slopes by preventing the inflow of rainwater and scour using geosynthetics-reinforced embankment, and created nature-friendly slopes by planting trees on the slopes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.03b
• /
• pp.33-33
• /
• 2010

최근 개발된 식물성 절연유는 광유에 비해 약 3배 정도 점도가 높아 변압기 냉각에 상당한 영향을 주게 된다. 뿐만 아니라 식물유의 유동점은 $-20^{\circ}C$이하로 광유에 비해 높은 것이 단점이다. 온도가 낮을수록 점도가 급격히 높아질 뿐만 아니라 유동점에 도달할수록 응고되어 가기 때문에 겨울철에 변압기 부하가 낮거나, 교체 운전 초기에 냉각 특성 및 전기적 특성의 변화를 가져올 수 있다. 이에 따라 식물성 절연유를 유동점에 가까운 온도로 냉각한 후 절연파괴전압을 측정하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1993.10a
• /
• pp.35-41
• /
• 1993

산업사회가 발전함에 따라 거대한 플랜트(plant)를 포함하여, 원자력 발전소 와 로켓트 등과 같이 구조적 안전성과 정확한 성능의 확보가 극히 중요시되 는 설비들이 많이 등장하고 있다. 이들 설비를 구성하고 있는 파이프계 (piping system)는 강성 또는 연성재료 및 각종 valve등으로 구성되어 있기 때문에, 고온 고압 고속의 유체가 파이프 내부를 흐를 때 일으키는 진동현상 및 플랜트의 과도운전 상황에서의 일어나는 수격현상(water hammer 또는 steam hammer)과 이로 기인한 제반 진동문제는 안전성확보 측면에서 많은 관심이 고조되고 있다. 이와 관련되어 유체유발진동에 관한 많은 연구들이 수행되었으며, 파이프계에 장착된 밸브에 대한 연구는 Weaver등에 의하여 실험적, 이론적으로 수행되었다. 그들은 유동방정식에서 비정상 베르누이 방 정식을 사용하여 내부유동방정식을 간략하게 유도하였으나, jet flow에 의한 유체의 운동량변화를 고려하지 않고 해석되어 그 결과에 의문이 제기된다. 그러므로 본 연구에서는 체크밸브(check valve)가 부착된 파이프계에서 일어 나는 유체유발진동 및 안정성에 관한 이론적 연구를 수행하여, 파이프계의 설계에 필요한 파라미터의 영향을 파악하고자 한다. 원자력 발전소와 같이 구조적 안정성이 요구되는 플랜트를 국내 기술로 설계 시공하려는 국내 실 정에서 이로 인한 파이프계에 발생할 수 있는 유체유발진동과 안정성을 예 측할 수 있는 해석이론은 파이프계의 설계 및 운전조건의 선정에 있어서 그 의의가 크다고 할 수 있겠다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2005.11a
• /
• pp.117-120
• /
• 2005

The present study describes unsteady flow phenomena generated in a supersonic flow passing over a rectangular cavity and suggests a way of control of pressure oscillation, doing harm to overall performance and stable operation of aerodynamic and industrial applications. The three-dimensional, unsteady, compressible Navier-stokes equations are numerically solved based on a fully implicit finite volume scheme and large eddy simulation. The cavity flow are simulated with and without control methods, including a triangular bump and blowing jet installed near the leading edge of the cavity. The results show that the pressure oscillation is attenuated by both control techniques, especially near the trailing edge of cavity.

• Korean Journal of Construction Engineering and Management
• /
• v.14 no.1
• /
• pp.43-51
• /
• 2013

The changes in business structure of domestic construction companies suggest that there is a close relationship between the volume of overseas project and a company's financial condition. Based on this assumption, this study conducts an empirical analysis on a relationship between overseas project and financial stability of a construction company. The ratio of liquidity and liability was used as liquidity index and stability index respectively. The analysis was based on quarterly time-series data between 2000 and 2010. Two models were constructed for the analysis: Model 1 was based on the liquidity ratio and the amount of domestic and overseas construction project; Model 2 was based on the debt ratio and the amount of domestic and overseas construction project. The analysis results showed that the increasing amount of overseas project facilitated short-term financing with greater liquidity, and yet it was not very effective in lowering the debt ratio. This suggests that the dramatic increase in overseas construction project, which is observed recently, is not entirely an optimistic sign.

• Computational Structural Engineering
• /
• v.11 no.1
• /
• pp.90-95
• /
• 1998

본 고에서는 비압축성 점성유체의 유한요소해석 기법을 소개하였다. 대류항의 상류화 기법으로 안정된 해를 도출할 수 있으며 Penalty 방법에 기반하여 압력항을 지배방정식으로부터 소거함으로써 해석시간과 요구저장공간을 감소시켰다. 실린더 주변의 유동장을 해석하여 와의 방출을 성공적으로 묘사하였으며 항력계수를 17%정도의 오차로 계산하였다. 적응적 요소세분화 기법에 대한 연구를 통해 적절한 오차평가 기법 및 최적의 체눈을 형성하는 기법을 제시하였다. 또한 동적 해석에 적합한 요소재결합 알고리즘에 대한 연구가 진행중이다. 본 고의 결과는 직접적으로 풍공학분야에 사용하기에는 아직 계산 시간의 효율성이나 해의 정확도 및 안정성면에서 무리가 있으나 추가적인 연구를 통하여 해석기법의 개선을 도모하고 컴퓨터 등 계산장비의 급속한 발전으로 장래에 경쟁력을 획득할 수 있을 것으로 기대된다.

• Journal of computational fluids engineering
• /
• v.6 no.4
• /
• pp.43-53
• /
• 2001

본 논문은 충격파 불안정성이 나타나지 않는 충격파 안정적인 수치기법의 개발을 목표로 하고 있다. Roe의 수치기법은 유동의 수치계산에 있어 높은 정확도를 보장하지만 carbuncle 현상과 같은 충격파 불안정성이 나타나는 것으로 알려져 있다. Roe의 수치기법과 HLLE 수치기법의 수치점성을 비교하여 충격파 불안정성의 원인을 살펴보았으며, Roe의 수치기법에 나타나는 반감쇠항에 마하수의 함수인 조절함수 f와 g를 도입하여 충격파 안정성을 획득하였다. 본 논문에서 제안된 수치기법을 다양한 유동문제에 적용하여 수치기법의 충격파 안정성과 정확성을 검증하였다

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.20 no.1
• /
• pp.52-63
• /
• 1994

It was investigated that the effects of surfactant to cosurfactant ratio on the stability and rheological properties of o/w microemulsion. The stability of microemulsion was good in the surfactant to cosurfactant ratio 20/40 - 30/30. In the point of rheological properties, a yield stress meande the inner structure formation was detected and the area of hysteresis loop was increased with increasing of surfactant content of the ratio. The microemulsion prepared by the Microfluidizer was characterized by rheopetic.

• Journal of Convergence Society for SMB
• /
• v.3 no.2
• /
• pp.1-8
• /
• 2013

This study examine the relation between small and medium firm's stability and tax avoidance. We use some financial data of small and medium IT firms in KOSDAQ during 2001 to 2009. Following previous research(Desai and Dhamapala 2006), we estimate corporate tax avoidance. And we use quick ratio and current ratio as a short-term stability and equity ratio as a long-term stability. Empirical results follows as. First, It was not significant statistically between short-term stability and corporate tax avoidance. Second, it was significant statistically between the long-term stability and corporate. As corporate tax avoidance increases, the long-term stability(equity ratio) was low. Our analysis provides the empirical evidence between long-term stability and tax avoidance. It offers implications of corporate tax avoidance to small and medium IT firms in KOSDAQ. But this results is difficult generalization because of sample limits.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.4
• /
• pp.349-357
• /
• 2019

Controlled low strength material(CLSM) has been developed using variety of material such as excavated soil, industrial by-product and industrial waste. But theses research limited at laboratory test and failed at commercialization. So in this paper evaluates CLSM used excavated soil characteristics such as flowability, bleeding rate, early strength for following process and 28day strength for re-excavatability. Also, various mix proportion of CLSM by water-binder ratio and soil-binder ratio were evaluated in laboratory. And derive the optimized CLSM mix proportion for using at field application test by movable batch plant. After applying CLSM at trench, evaluate core sample strength and excavatability by shovel, pickax and excavator for verify re-excavation. Furthermore, measure the level change after casting CLSM to inspect subsidence stability. As results of these assessments, not only confirmed the characteristics of CLSM at field but the fillability around pipe and subsidence stability.