• Journal of the Korean Geotechnical Society
• /
• v.19 no.6
• /
• pp.363-369
• /
• 2003

The purpose of this study is to understand the dissipation pattern of excess pore pressure after liquefaction and to estimate the variation in permeability during shaking load, which should be known for settlement predictions of the ground undergoing liquefaction. In this study, 1-g shaking table tests were carried out for 5 different kinds of sands, all of which had high liquefaction potentials. During the tests excess pore pressure at various depths, and surface settlements were measured. The measured dissipation curve of the excess pore pressure after liquefaction was linearly simulated using the solidification theory, and from the analysis of the slopes of linearly simulated curves, the correlation between dissipation velocity and the gradation characteristics was obtained. By substituting this correlation and the measured settlement to the dissipation velocity equation recommended in solidification theory, the permeability during dissipation was calculated, which was used for estimating the permeability variation during shaking load. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size divided by the coefficient of uniformity. The permeability during dissipation and liquefaction increased by 1.1∼2.8 times and 1.4∼5 times compared to the initial permeability of the original ground, respectively. And the amount of increase became greater as the effective grain size of the test sand increased and the coefficient of uniformity decreased.

• Journal of the Korea Concrete Institute
• /
• v.15 no.4
• /
• pp.594-605
• /
• 2003

Pinching is an important property of reinforced concrete member which characterizes its cyclic behavior. In the present study, numerical studies were performed to investigate the characteristics of pinching behavior and the energy dissipation capacity of flexure-dominated reinforced concrete members. By investigating existing experiments and numerical results, it was found that flexural pinching which has no relation with shear action appears in RC members subject to axial compression force. However, members with specific arrangement and amount of re-bars, have the same energy dissipation capacity regardless of the magnitude of the axial force applied even though the shape of the cyclic curve varies due to the effect of the axial force. This indicates that concrete as a brittle material does not significantly contribute to the energy dissipation capacity though its effect on the behavior increases as the axial force increases, and that energy dissipation occurs primarily by re-bars. Therefore, the energy dissipation capacity of flexure-dominated member can be calculated by the analysis on the cross-section subject to pure bending, regardless of the actual compressive force applied. Based on the findings, a practical method and the related design equations for estimating energy dissipation capacity and damping modification factor was developed, and their validity was verified by the comparisons with existing experiments. The proposed method can be conveniently used in design practice because it accurately estimates energy dissipation capacity with general design parameters.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.10
• /
• pp.73-84
• /
• 2007

For standard piezocones with shoulder filter elements immediately behind the cone tip, general dissipation curves show monotonically decreasing pore pressure from the initial value. However, dilatory dissipation behavior, showing a temporary increase in pore pressure followed by a decrease in the hydrostatic pressure, has been observed in lightly overconsolidated cohesive soils $(1. This unusual dissipation behavior was reported mostly in heavily overconsolidated ground and previous researches were limited to such cases. In this study, the mechanism of dilatory dissipation in lightly overconsolidated cohesive soils was investigated. The relativities of the ground properties evaluated from the CPTu data to the dilatory dissipation were analyzed. And, finite difference analyses on dissipation after cone penetration were performed. It was found that dilatory dissipation occurs in lightly overconsolidated soils since the higher excess pore pressure at the cone face propagates upward to the shoulder filter. Also, it was shown that the ratio of initial excess pore pressure at the cone face to that of the shoulder filter $({\Delta}u_{1i}/{\Delta}u_{2i})$, which is related to overconsolidation ratio (OCR) and hydrostatic pressure $(u_0)$, affects the dilatory dissipation.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.3
• /
• pp.77-86
• /
• 2002

위성은 일단 한 번 발사하고 나면 운용궤도상에서 수리 및 회수가 거의 불가능하기 때문에 위성에 들어가는 모든 개발 부품들은 완벽한 설계, 충분한 해석, 고 작업도의 제작, 그리고 다양한 시험이 반드시 수반되어야 한다. 위성시스템에서 전자 소자의 신뢰성에 영향을 주는 인자는 다양하다. 과도한 열은 전자소자의 실패를 유발해서 결과적으로는 전체 위성의 실패를 유도할 수 있다. 이 논문에서는 다목적 실용위성 2호의 고전력 소산 전장품의 열부하 완화를 위한 방안을 경우별로 연구 비교하였다. 고전력 소산 전장품의 열부하를 완화하기 위해서는 하우징 두께의 증가가 필요하며, 전력조절기의 다이오드나 트랜지스터처럼 전력소산이 큰 소자에 대해서는 장착위치를 변경하거나 장착 부분의 열전도율을 증가시키는 방법이 필요하다. 또한 전력조절기처럼 장착면이 좁은 경우에는 복사의 영향이 크며, 이러한 전장품의 열부하를 완화하기 위해서는 주위 벽면의 온도를 낮추거나 하우징 표면 방사율을 증가시키는 방법이 효과적임이 알 수 있다.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.19 no.4
• /
• pp.303-312
• /
• 2007

There is still a controversy going on about how to model energy dissipation due to breaking over frequency domain. In this study, we unveil the exact structure of energy dissipation using stochastic wave breaking model. It turns out that contrary to our present understanding, energy dissipation is cubically distributed over frequency domain. The verification of proposed model is conducted using the acquired data during SUPERTANK Laboratory Data Collection Project (Krauss et al., 1992). For further verification, we numerically simulate the nonlinear shoaling process of Conoidal wave over a beach of uniform slope, and obtain very promising results from the viewpoint of a skewness and asymmetry of wave field, usually regarded as the most fastidious parameter to satisfy.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.02a
• /
• pp.98-99
• /
• 2000

코어 가까이 측면 연마한 광섬유를 이용하여 광 여파기, 편광기, 감쇠기등의 광통신 소자로 응용하고자 하는 연구가 많이 진행되고 있다.$^{[1]}$ 이 소자는 광섬유를 절단하지 않은 상태에서 코어 가까이 측면 연마하여 광학적 기능을 가진 소자를 제작함으로서 공정이 간단하고 삽입손실이 작은 특성을 가지며 기계적 신뢰성이 우수하다. 측면 연마된 광섬유를 이용한 광 증폭의 경우 광섬유의 소산장(evanescent field)과 펌핑광에 의해서 여기되는 활성 물질과의 상호작용에 의해서 광 이득을 얻는다. 소산장 결합에 의한 평면도파로에서의 광 증폭$^{[2]}$ 과 다중 모드 광섬유에서의 펄스 레이저 증폭, 단일 모드 광섬유에서 632.8nm He-Ne 레이저의 연속광원 증폭$^{[3]}$ 은 이미 보고되었다. 본 논문에서는 측면 연마된 다중 모드 광섬유의 연마된 부위에 색소가 첨가된 용액을 떨어뜨림으로서 발생하는 소산장 결합에 의해서 광섬유내를 진행하는 연속적인 He-Ne 레이저 광을 증폭시키는 방법을 제안하고자 한다. (중략)

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.03a
• /
• pp.153-160
• /
• 2001

피에조콘관입시험(PCPT)의 소산시험은 in-situ 상태의 압밀계수(c/sub v/)를 추정하는 방법으로 널리 이용되어왔다. 본 연구에서는 spherical cavity expansion theory 및 axisymmetric uncoupled linear consolidation equation(Gupta & Davidson, 1986)을 이용하여 과압밀점토에서의 초기과잉간극수압의 분포 및 과잉간극수압의 시간에 대한 소산현상을 해석하는 수치해석방법을 제안하여 현장시험결과 및 실내시험결과와 비교 분석하였다. ADIS (alternating direction implicit scheme)를 이용한 FDM 해석을 실시한 결과와 현장시험의 소산곡선은 잘 부합되는 것으로 나타났으며 압밀계수도 실내실험 또는 피에조콘관입 시험에 대한 추정방법으로 산출된 값과 비교적 일치하는 것으로 나타났다.

• Proceedings of the Korean System Dynamics Society
• /
• 2005.04a
• /
• pp.63-74
• /
• 2005

본 논문에서는 인과지도의 작성자와 독자 간의 심리적 격차에 관하여 분석하고자 한다. 먼저 기존에 연구되어 왔던 소산효과(dissipation effects)와 희석효과(dilution effects)는 인과지도를 작성하는 사람이 아니라 인과지도를 이해하는 사람에게 적용되는 심리적 경향이라는 점을 이 논문에서 지적한다. 소산 효과란 인과고리의 길이가 길어질수록 인과관계의 강도를 낮게 인식하는 심리적 경향을 의미한다. 희석효과는 여러 개의 인과관게가 존재할수록 특정 인과관계의 강도를 낮게 인식하는 심리적 경향을 의미한다. 이들 심리적 경향과는 달리 집중 효과(concentration effect)가 인과지도 작성자의 심리적 경향을 보다 잘 설명하는 것으로 실험 결과 분석되었다. 집중 효과란 주의를 집중하는 영역에 대하여 많은 인과관계를 생각하고, 인과관계의 강도 역시 강하게 생각하는 심리적 경향을 의미한다. 인과지도의 작성자 즉 시스템 컨설팅을 담당하는 사람들에게는 소산효과나 희석효과 보다 집중효과가 더 강하게 작용한다는 것이다. 이러한 심리적 비대칭성이 시스템 다이내믹스 연구자와 그의 고객 간의 의사소통 문제를 야기 시킨다는 점을 본 논문에서 지적한다.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.131.2-131.2
• /
• 2005

• Geotechnical Engineering
• /
• v.13 no.6
• /
• pp.25-36
• /
• 1997

A degree of consolidation at any time can be evaluated by using cone penetration test after soil improvement. In this case, after stopping the penetration of a piezocone, pore pressure dissipation(PPD) best is carried out until the pore pressure remains constant. Since the hydraulic conductivity of soft ground is very small, it takes very long time to finish the PPD test. This research is performed to develop a method overcoming this problem of the PPD test and reducing the test time. The analyses are carried out in the following ways : an equilibrium pore pressure can be determined by using pore pressure measured in the middle of the test, which is predicted by hyperbolic, Asaoka and Hoshino methods. And this equilibrium pore pressure is compared with the one measured in a test of long duration. As a result of the study, it is found that Hoshino method is the best way to predict the equilibrium pore pressure in a teat of short duration. And it is proposed as a methodology to fond a minimal time in which we can get an equilibrium pore pressure.