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

• Journal of the Korean Institute of Gas
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• v.14 no.3
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• pp.46-52
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• 2010

Flame propagation velocity is the one of the main mechanism of the stabilization of triple flame. To quantity the triple flame propagation velocity, Bilger presents the triple flame propagation velocity, depending on the mixture fraction gradient, based on the laminar jet flow theory. However, in spite of these many analyses, there has not been any attempt to quantify the triple flame propagation velocity with the flame radius of curvature and scalar dissipation rate. In the present research, there was discussion about the radius of flame curvature and scalar dissipation rate, through the numerical study. As a result, we have known that the flame propagation velocity was linear with the nozzle exit velocity and scalar dissipation rate decreases nonlinearly with the flame propagation velocity and radius of curvature of flame increases linearly. Also radius of curvature of flame decreases non-linearly with the scalar dissipation rate. Therefore, we ascertained that there was corelation among the scalar dissipation rate, radius of flame curvature and flame propagation velocity.

• Journal of the Mineralogical Society of Korea
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• v.25 no.3
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• pp.123-130
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• 2012

Leaching experiments of gold and silver from roasted concentrate were carried out using a chlorine-hypochlorite solution. The leaching rate of gold was 75% at 1.5:1 ratio of chlorine and hypochlorite and increased to 81% with adding 1 M NaCl. However, at 1% pulp density and at $65^{\circ}C$, the leaching rates of Au were close to 100%. XRD analysis identified quartz in the solid residues after digestion of roasted concentrate with aqua regia or chlorine-hypochloride leaching solution. This suggests that the gold may not be leached out of the quartz in aqua regia or chlorine-hypochlorite solution. In order to leach the gold from the quartz, the concentrate will have to be pre-treated through ultra-fine grinding or treated with stronger oxidative agents.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.566-577
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• 2002

As advanced earthquake analysis/design methods such as the nonlinear static analysis are developed, it is required to estimate precisely the cyclic behavior of reinforced concrete members that is characterized by strength, deformability, and capacity of energy dissipation. However, currently, estimation of energy dissipation depends on empirical equations that are not sufficiently accurate, or experiment and sophisticated numerical analysis which are difficult to use in practice.0 the present study, nonlinear finite element analysis was performed to investigate the behavioral characteristics of flexure-dominant RC members under cyclic load. The effects of axial force, arrangement of reinforcing bars, and reinforcement ratio on the cyclic behavior were studied. Based on the investigation, a simplified method to estimate the capacity of energy dissipation was proposed, and it was verified by the comparison with the finite element analyses and experiments. The proposed method can estimate the energy dissipation of RC members more precisely than currently used empirical equations, and it is easily applicable in practice.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.409-417
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• 2003

Cure monitoring can be used to improve the quality and productivity of thermosetting resin matrix composite products during their manufacturing process. In this work, the sensitivity of dielectrometry was improved by adequate separation the efforts of sensor and externals on the measured signal. A new algorithm to obtain the degree of cure during dielectric cure monitoring of glass/polyester and glass/epoxy composites was developed by employing a function of both temperature and dissipation factor, in which five cure monitoring parameters were used to calculate the degree of cure. The decreasing pattern of dissipation factor was compared with the relationships between the degree of cure and the resin viscosity. The developed algorithm might be employed for the in situ cure monitoring of thermosetting resin composites.

• Composites Research
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• v.16 no.4
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• pp.51-58
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• 2003

Since the reliability of adhesively bonded joints is much dependent on the curing status of thermosetting adhesive, the on-line cure monitoring during the cure of adhesively joints could improve the quality of adhesively bonded joints. In this work, the dielectric method which measures the dissipation factor of the adhesive during the cure of joints and converts it into the degree of cure of the adhesive was devised. The relation between the dissipation factor and the degree of cure of adhesive was investigated, which could eliminate the temperature effect on the dissipation factor that is a strong function of the degree of cure and temperature of adhesive. From the investigation, it was found that the dissipation factor showed a trend similar to the cure rate of the adhesive.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1323-1327
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• 2006

일반적으로 화력발전소는 원활한 원료 및 냉각수의 공급과 환경적인 요인으로 인해 내륙보다는 해안에 위치하고 있다. 발전소의 안정성을 확보하기 위해서는 고열의 발전기를 냉각하는 냉각설비들이 반드시 필요하며 이를 위해 취수로를 통한 냉각수의 원활한 공급이 이루어져야 한다. 이러한 냉각수 공급은 대용량 펌프에 의해 이루어지며, 취수로 구조물의 형상 및 냉각수의 흐름조건에 따라 성능과 수명이 좌우된다. 특히 해안에 위치하는 지리적 여건상 직접취수가 많으며 이러한 경우 유사가 취수로에 유입되어 펌프 흡입 시 균열과 임펠러 마모 등을 유발시켜 펌프의 안전에 악영향을 미치게 된다. 따라서 취수로에 유사의 퇴적을 유도하는 침사지를 설계하게 되며 Hydraulic Institute Standards(1998)에서는 허용설계유속을 0.2 m/s 이하로 정하고 있다. B 발전소는 직경 3 m의 대형 취수관로 3개를 통해 매우 빠른 유속으로 취수로에 유입되는 냉각수 계통 구조물을 가지고 있어 침사지 내 유속이 허용기준을 초과하였다. 본 연구에서는 침사지내 유속을 만족시키기 위해 다양한 에너지 소산 구조물 설계방안을 제시하였다. 각 설계방안에 따른 흐름 특성 및 유속 분포를 파악하고 common bay 내에서의 난류특성을 분석하여 비교.검토하였다. 수리모형실험 결과를 통해 각각의 설계방안에 따른 침사지의 효율을 평가하였으며 최적의 에너지 소산 구조물에 대한 설계방안을 제안하였다.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.137-146
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• 2002

Field piezocone dissipation tests are performed, and the results are compared to the Rowe cell consolidation tests results to investigate the consolidation characteristics of soft marine deposit at the same location in Korea. From these results, statistical formula fur the relation between the coefficients of horizontal consolidation$(c_r)$ from Rowe cell consolidation tests and $t_{50}$ from pore pressure dissipation tests by Piezocone is suggested through the regression analysis. The results are also compared to the existing theoretical formula. It is also shown that suggested formula is similar to Torstensson's(1977) formula based on cylindrical cavity expansion theory and Houlsby and Teh's(1988) formula based on strain path method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.602-605
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• 2011

본 논문에서는 마찰감쇠기가 설치된 건물이 붕괴하중을 받을 때의 에너지소산능력을 고려하여 등가감쇠비를 유도하였다. 마찰감쇠기는 주로 지진과 같은 수평하중에 대한 에너지를 소산하기위해 설치된다. 마찰감쇠기를 대각 가새형으로 설치하면 수평하중에 대한 저항력뿐 만아니라 수직하중에 대한 저항성능도 발휘된다. 건물에 설치된 마찰감쇠기는 외력의 크기에 따라 정지와 운동의 상태를 반복하여 외부 입력에너지를 소산시키기 때문에 외력과 응답관계가 비선형이다. 건물은 고유의 점성감쇠를 가지므로 마찰감쇠기가 설치된 건물은 마찰과 점성감쇠를 동시에 고려해야하므로 해석적인 정해를 구하기가 어렵다. 에너지 평형을 이용하여 등가감쇠비를 구하고 운동방정식을 등가선형화하면 쉽게 저항 성능을 파악할 수 있다. 우선 건물에 영향을 미치는 것은 감쇠이므로 감쇠의 영향력을 마찰력비, ${\gamma}_c$로 나타내었다. 둘째, 정해를 마찰력비로 표현하여 유도하고 응답특성을 파악하였다. 셋째, 에너지 균형식을 통해 등가감쇠비를 산정하였다. 마지막으로 등가감쇠비를 검증하기 위하여 등가감쇠비를 이용하여 등가선형화한 응답과 실제 마찰감쇠기를 설치하여 비선형 수치해석한 결과와 비교, 검증하였다.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.299-300
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• 2022

구조물의 내진보강방법 중에서 가장 널리 이용되는 방법인 강재 이력형 감쇠장치는 수평하중에 대한 응력-변위 곡선을 이용하여 지진 에너지를 소산시키는 방법인데, 이 경우 편심하중 등에 의해서 부재가 면 외 방향으로 거동하여 응력-변위곡선이 불규칙하여 그 결과의 신뢰성이 떨어지는 경우가 있다. 이러한 형상을 방지하기 위해서는 별도의 채널(Channel)을 시공하는 불편함을 감수해야 하며, 또한 수평력이 반복적으로 작용할 때 그 효과를 장담할 수 없는 문제점이 있다. 본 연구에서는 강재 스트립과 스프링을 결합한 댐퍼를 고안하여 스프링은 탄성변형을, 강재 스트립은 소성변형을 받게 하는 혼합형 댐퍼를 개발하고자한다. 여기서, 스프링은 복원력으로 작용하여 반복하중에 대한 저항성을 키우고 강재 스트립의 하중변위 곡선을 규칙적으로 하는 역할을 수행하게 되며 에너지 소산량을 계산할 때 편리함과 정확도를 높이고자 한다. 강재 스트립의 폭과 길이는 일정하지만 두께를 변화시켜서 5종류를 선택하였으며, 댐퍼 1개당 3개의 스트립을 정삼각형 형태로 배치하고 그 중심에 상당한 강성을 갖는 스프링을 갖는 형태로 제작하였다. 댐퍼 시험체는 5개를 제작한 후, 이 댐퍼를 구조물에 배치하였을 때의 지진에 대한 에너지 소산량과 부재력을 검토하여 댐퍼의 안전성(Safety)를 검증하고자 한다.