• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.1015-1023
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• 2010

While various PCPT-based methods for the analysis of consolidation were developed, additional laboratory test is needed to estimate the coefficient of consolidation. In this paper, hyperbolic method using PCPT dissipation curve for the estimation of coefficient of consolidation was proposed. To verify proposed method, field settlement test data and PCPT dissipation test data at same site were collected and analyzed. It is observed that proposed method shows good agreement with measured field settlement data.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1328-1339
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• 2008

For a commonly used piezocone with a shoulder filter element, dilatory dissipation behavior, which shows an initial temporary increase in pore pressure, has been observed in overconsolidated cohesive soils. However, there is no appropriate way to estimate a consolidation parameter from a dilatory dissipation curve because currently available interpretation methods were developed based on the monotonic decrease of the excess pore pressure. In this study, the interpretation method for evaluation of coefficient of consolidation from a dilatory dissipation result of piezocone test was developed by performing the finite difference analysis on the dissipation after cone penetration. The distribution of the initial excess pore pressure induced by cone penetration, which is the core of the analysis, was estimated from the empirical modification of a solution proposed by cavity expansion theory and critical state concept. And the proposed interpretation method was applied to the field piezocone data and the results were compared to those obtained from laboratory tests. Its reliability was confirmed by the insignificant difference between the values of coefficient of consolidation from piezocone tests and laboratory consolidation tests.

• 한국산학기술학회논문지
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• 제9권2호
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• pp.470-474
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• 2008

본 연구에서는 실제 현장에서 수행한 피에조콘관입 및 소산시험결과와 변형률 속도를 고려한 구성모델의 이론적 해석을 비교하였다. 이를 위하여 변형률 속도 의존적 구성모델의 수학적 유도과정을 전개하였다. 해석 결과 변형률속도를 무시한 구성모델보다 변형률속도-의존 구성모델을 활용한 지반의 거동 해석이 비의존적 구성모델인 경우의 해석 보다 현장의 시험결과와 잘 일치하므로 변형률속도-의존 구성모델의 적용이 바람직하다.

• 한국지반공학회논문집
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• 제18권2호
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• pp.137-146
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• 2002

본 연구에서는 국내 해성퇴적 연약지반의 압밀특성을 실험적으로 규명하기 위하여 현장에서의 픽에조콘을 이용한 간극수압소산시험을 수행하고 동일한 위치와 심도에서 채취한 비교란시료를 이용하여 실내에서 Howe cell 압밀시험을 포함한 역학시험과 물성시험을 수행하였다. 이를 근거로 howe cell 압밀시험으로부터 구한 수평압밀계수$(c_r)$와 피에조콘 소산시험으로부터 구한 압밀도 50%에 해당하는 소산시간$(t_{50})$의 관계를 회귀분석을 통하여 실험식을 제안하였으며 이 실험식과 기존의 여러 학자들에 의해 제안된 이론해와의 관계를 비교하였다. 이에 의하면 실린더형 공동팽창이론에 근거한 Torstensson(1977)의 이론해와 변형률경로법에 근거한 Houlsby와 Teh(1988)의 이론해에 비교적 유사한 경향을 보이는 것으로 나타났다

• 한국지반공학회지:지반
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• 제14권4호
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• pp.141-150
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• 1998

본 논문은 콘 선단부에서 간극수압을 관측하는 피에존 콘의 소산시험으로부터 현장 압밀계수 결정시 최적화 기법의 적용에 관한 기존의 연구를 바탕으로 현재 우리나라에서 사용되고 있는 피에조 콘 관입기 콘 선단부 뒤에서의 간극수압 관측의 경우에 대하여 최적화를 사용한 압밀계수 결정방법을 적용한 연구를 수행하였다. 수치 검증예제와 국,내외의 실제예제를 통하여 적용된 최적화 기법의 안정성과 초기 입력 값에 영향을 받지 않는 수렴성을 확인하였으며 제안된 방법이 계측된 소선곡선과 프로그램으로 예측된 소산곡선의 차이를 최소화하는 수평 압밀계수를 산정함으로써 실제 현장의 압밀거동을 모사하기에 매우 효과적 이라 사료된다.

• Geomechanics and Engineering
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• 제6권6호
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• pp.577-592
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• 2014

The methods for estimating in-situ hydraulic conductivity ($k_{hp}$) and coefficient of consolidation ($c_{hp}$) in the horizontal direction from piezocone penetration and dissipation test results have been investigated using test results at two sites in Saga, Japan. At the two sites the laboratory values of hydraulic conductivity ($k_v$) and coefficient of consolidation ($c_v$) in the vertical direction are also available. Comparing $k_{hp}$ with $k_v$ and $c_{hp}$ with $k_v$ values, suitable methods for estimating $k_{hp}$ and $c_{hp}$ values are recommended. For the two sites, where $k_{hp}{\approx}k_v$ and $c_{hp}{\approx}2c_v$. It is suggested that the estimated values of $k_{hp}$ and $c_{hp}$ can be used in engineering design.

• 한국전기전자재료학회논문지
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• 제25권10호
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• pp.786-790
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• 2012

A variety of diagnostic tests are widely applied in the field in industry to evaluate the condition of high voltage (HV) motor stator insulation. In this paper, the influence of temperature on the stator insulation diagnostic tests such as the insulation resistance, AC current, dissipation factor, and partial discharge measurements are studied and reported. The tests are performed with the HV motor stator winding temperature set between $40^{\circ}C$ to $80^{\circ}C$ in $10^{\circ}C$ intervals. It is shown that the AC current, dissipation factor, and partial discharge magnitude steadily increase with temperature, which suggests that temperature must be taken into account in the interpretation of the test results.

• Journal of Mechanical Science and Technology
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• 제19권3호
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• pp.913-923
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• 2005

The dynamic mixed model (DMM) combined with a box filter of Zang et. al. (1993) has been generalized for passive scalar transport and applied to large eddy simulation of turbulent channel flows with Prandtl number up to 10. Results from a priori test showed that DMM is capable of predicting both subgrid-scale (SGS) scalar flux and dissipation rather accurately for the Prandtl numbers considered. This would suggest that the favorable feature of DMM, originally developed for the velocity field, works equally well for scalar transport problem. The validity of the DMM has also been tested a posteriori. The results of the large eddy simulation showed that DMM is superior to the dynamic Smagorinsky model in the prediction of scalar field and the model performance of DMM depends to a lesser degree on the ratio of test to grid filter widths, unlike in the a priori test.

• 한국지반공학회논문집
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• 제15권4호
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• pp.85-97
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• 1999

낙동강 하구의 삼각주 점토에 대하여 현장계측, 실내 및 현장토질시험결과를 이용한 산정법들에 의하여 OCR이 분석되었다. 그 결과, 표준압밀시험결과에 의한 OCR이 0.4~0.7인데 반하여, 현장계측값의 분석으로 얻어진 OCR은 0.95~l.20으로 얻어졌다. 소산시험에 의하여 과잉간극수압의 존재를 거의 확인할 수 없었으므로 미압밀점토의 존재는 찾기 어려웠다. 그리고 피에조콘시험을 이용한 Mayne(1991) 및 Cao 등(1996)의 산정법과 콘관입시험을 이용한 Mayne ＆ Kemper(1988)의 산정법에 의한 결과가 현장계측값의 분석법에 의한 결과와 잘 일치하였다.

• 소성∙가공
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• 제10권4호
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• pp.347-354
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• 2001

Compression tests were carried out to investigate the hot-deformation behavior of Ti-6Al-4V alloy in the temperature range of $915^{\circ}C$ to $1015^{\circ}C$ and the strain rate range of $10^{-3}s^{-i}$ to $10s^{-1}$. Under the given test conditions, the hot-deformation of Ti-6Al-4V alloy was mainly led by dynamic recovery rather than by dynamic recrystallization. The activation energy for the plastic deformation in $\alpha+\beta$ field was about 894 kJ/mol and $\beta$ field was 332kJ/mo1. Processing map for hot working are developed on the basis of the variations of efficiency of power dissipation($\eta$=2m/m＋1) and flow instability criterion using the dynamic material model. The optimum process condition in the ($\alpha＋\beta$) field was obtained at the temperature ranges of $930^{\circ}C$ to $955^{\circ}C$$^{\circ}C$ and a strain rate of $10^{-3}s{-1}$.