• The Journal of Engineering Geology
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• v.28 no.4
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• pp.605-618
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• 2018

Korea follows the slope design criteria during construction. It was enacted by the Ministry of Land, Transport and Maritime Affairs. There are cases where the Soil-nail is designed as a measure to secure slope stability. The arrangement of the soil-nail may be arranged at equal intervals or may be arranged differently depending on the soil failure model. The optimum design of the countermeasure method is determined by securing stability of the slope through optimization of dimensions and shape. However, when uniform nails are placed at low elevations in slopes, the standard safety factor is exceeded, which may hinder economic design. It is preferable to arrange the reinforcement of the nails over the entire slope. When the horizontal spacing of the nails was topology optimized according to the slope height, it was possible to minimize the amount of reinforcement while satisfying the standard safety factor. Since the active load is reduced in the section where the slope height is lowered, the safety factor after reinforcement may be excessively increased. Therefore, the phase optimization method is proposed as an economical optimal design method using the reinforcing shape density. In addition, a relational expression was designed to optimize the horizontal spacing by slope height.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.27-39
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• 2005

A finite difference program with 3-D governing equation expanded from 1-D self-weight consolidation is developed to analyze the consolidation behavior of surface dredged soil with horizontal drains. Various boundary conditions with horizontal drains and seepage pressure of pore water infiltrated to the drains are considered in the program. A laboratory soil chamber experiment for the consolidation of dredged soil is performed to validate the program and the measured settlement-time result is compared with the one predicted by the program. The influence of design conditions of horizontal drains such as horizontal installation spacing, installation depth and number of drain layers, on the consolidation is analyzed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.1
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• pp.1-9
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• 2004

In this study, several new types of floating breakwater are proposed according to the geometry of the vertical barrier and the existence of horizontal plate, and are compared to the steel floating breakwater adopted in Won-Jun fishing port and the performance of wave control is numerically investigated by using Green function method. From the numerical results, model attached the horizontal barrier under the vertical barrier is more efficient for reflection and transmission coefficient than the steel floating breakwater in Won-Jun fishing port. It is confirmed that the transmitted waves can be controlled efficiently by optimizing the length and distance of a vertical and horizontal barriers.

• Journal of Energy Engineering
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• v.10 no.1
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• pp.24-32
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• 2001

본 축열탱크 열전달에 관한 실험적 연구는 국내에서 개발하고 있는 태양열 온수기용으로 현재 널리 이용되고 있는 탱크-코일 방식의 문제점을 해결하면서 열전달 효율이 높은 2중 축열탱크를 개발하기 위한 것이다. 2중 축열탱크의 용량은 100리터로서 수평 및 수직형으로 설치하여 실험이 가능하도록 설계.제작하였고 탱크내부의 온도는 길이방향 및 반지름 방향으로 각각 등간격으로 설치하여 측정하였고 집열매체의 입.출구온도를 동시에 측정하였다. 실험결과는 (1) 축열탱크의 형태에 관계없이 축열탱크와 열교환을 하는 열매체의 유량이 증가할수록 열전달량은 증가한다. (2) 축열탱크의 형태에 따른 탱크내부 물의 온도 상승속도는 수직형(b)인 경우가 가장 크고, 그 다음 수직형(a), 수평형의 순으로 나타났다. 따라서 이중탱크형의 축열탱크는 수평형 보다 수직형이 동일한 용량의 축열매체 온도를 신속히 상승시킬 수 있다. 아울러 열성층화에 의하여 고온의 축열매체를 이용할 경우 수직형 축열탱크가 더욱 우수한 결과를 나타낸다. (3) 축열탱크 열전달계수(UA) 값은 ( $T_{in}$ - $T_{out}$)/$\Delta$ $T_{m}$ 의 크기에 좌우되며, 열전달계수를 설치방법에 따라 비교하면 수직형(b)>수직형(a)>수평형의 순서로 나타났다.다.

• Journal of the Korean Geophysical Society
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• v.8 no.2
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• pp.81-87
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• 2005

Acquisition and processing of vector seismic waves were conducted through simultaneous generation of P, SH, and SV waves and receiving those waves using three-component geophones. Test data were received by 24 8-Hz geophones at an interval of 2 m along a 94-m profile. The data were recorded for 512 ms with sampling intervals of 0.2 ms. Raw data indicate that both reflected and refracted P waves are strongly recorded on the vertical component while SH waves are significant on the transverse horizontal component. On the inline horizontal component, both direct P and converted PS waves are recorded. First arrivals of P and SH waves were detected simultaneously on the vertical and transverse horizontal axes, respectively. The recorded vector data were separately inverted using traveltime tomography to yield P- and SH-wave sections. Using those two velocity sections, Poisson's ratios were able to be obtained effectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.237-244
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• 2011

An experimental study was carried out to investigate the effect of the inclination angle on the nucleate pool boiling of saturated water at atmospheric pressure. We considered an annulus with a gap of 5 mm and a bottom opening. The inner tube of the annulus was heated, and the outer diameter and the length of the tube were 25.4 mm and 500 mm, respectively. The inclination angle was varied from horizontal to vertical. The results were compared to those for an annulus with a larger gap and a single tube. In the small-gap annulus, the effect of the inclination angle on the heat transfer was not significant. However, an early onset of the critical heat flux was observed at 80 kW/$m^2$ when the annulus was horizontal. Liquid agitation and bubble coalescence were considered to be the major heat-transfer mechanisms.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.388-396
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• 2009

Rock bolt is one of the most important supports for tunnelling to prevent excessive ground relaxation at the primary tunnel excavation stage. It forms a ground arch band by confining the ground around a tunnel. Rock bolt has various effects, such as support or hanging effect, internal pressure effect, arching effect, ground improvement effect etc. Most studies on rock bolt focused on the concept of support, but only a few researches on the ground reinforcing effect by pre-tensioning a rock bolts. In this study, large scale model tests are performed to investigate the ground reinforcing effect of rock bolts for regularly jointed rocks. Simple beam model was built to find out the reinforcing effect of jointed rocks, which was reinforced by pre-tensioned rock bolts. Settlement of model beam was analyzed through measuring its sagging for various installation intervals.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.377-380
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• 2000

도플러 로그용 센서를 이용하여 선박의 속도를 측정하면, 선박의 수평방향 이외의 움직임, 즉 핏칭이나 롤링 등에 의한 측정 속도의 부정확성이 문제가 된다. 본 연구에서는 이러한 핏칭과, 수중이라는 환경요인에 기인하여 다른 속도 측정용 센서들이 가지는 문제점을 극복할 수 있도록 진동판을 수평축에서 일정한 각을 가지도록 두 개 또는 네 개를 등 간격으로 배열한 야누스형 초음파 트랜스듀서를 개발하였다. 트랜스듀서 개발을 위하여 그 작동 구조를 해석하고 그에 따라 시제품을 제작한 후, 실험적인 성능 평가를 수행하였다. 시제작된 초음파 트랜스듀서는 지향성 및 감도가 우수하고, 대역폭이 넓은 성능을 가지고 있어, 실제 선박에 장착되어 도플러 로그용 초음파 트랜스듀서로 사용될 수 있는 가능성이 확인되었다.

• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.86-91
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• 2001

In lateral ground flow, slope stability, and land slide problems, H-piles have been often used for a horizontally deforming ground to prevent the failure of mass of soil in a downward and outward movement of a slope. Here, Theoretical equations are derived to estimate the lateral force, assuming that the Mohr-coulomb's Plastic states occures in the ground just around H-piles. In this study, the mechanism of lateral force acting on passive pile that is in a row, situated in the ground undergoing plastic deformation was discussed, and its theoretical analysis was carried out considering the interval between H-piles. The solution of the theoretical equation derived from here showed resonable characteristic for constants of soil as well as for the interval, widths, and heights of H-pile.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.44-48
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• 2002

In lateral ground flow, slope stability, and land slide problems, H-piles have often been used, on a horizontally deforming ground, to prevent the failure of mass of soil in a downward and outward movement of a slope. Here, theoretical equations are derived to estimate the lateral force, assuming that the Mohr-Coulomb's plastic states occur in the ground, just around H-piles. In this study, some model experiments were performed to check the lateral forces determined from theoretical equations, using several pile widths, heights and various interval ratios between H-piles for sand specimens. The solution of the theoretical equation, derived from previous studies, showed reasonable characteristics for constants of soil, as well as for the interval, widths, and heights of H-Pile.