• Journal of Radiation Protection and Research
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• v.22 no.4
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• pp.289-298
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• 1997

Time-consuming experiments have been required in the development of neutron moisture gauge to induce a relation between the water content in soil and the neutron counts. Applying a monte carlo computer code to simulate the experiments of neutron moisture gauging may contribute to reduce time and efforts for experiments and produce a calibration equation which is more applicable to soil in general. In this study MCNP4A, a monte carlo computer code, was employed to simulate soil experiments and the simulated results were compared with experimental ones. The comparative study showed that MCNP4A is applicable to simulate the experiments and calibration equation can be obtained through simulations. Effects of dry density changes were also studied.

• Journal of Radiation Protection and Research
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• v.29 no.4
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• pp.269-273
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• 2004

The hybrid dead time model adopting paralyzable (or extendable) and non-paralyzable (or non-extendable) dead times has been introduced to extend the usable range of G-M counters in high counting rate environment and the relationship between true and observed counting rates is more accurately expressed in the hybrid model. GMSIM, dead time effects simulator, has been developed to analyze the counting statistics of G-M counters using Monte Carlo simulations. GMSIM accurately described the counting statistics of the paralyzable and non-paralyzable models. For G-M counters that follow the hybrid model, the counting statistics behaved in between two idealized models. In the future, GMSIM may be used in predicting counting statistics of three G-M dead time models, which are paralyzable, non-paralyzable and hybrid models.

• KSBB Journal
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• v.15 no.1
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• pp.60-65
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• 2000

In order to predict the chromatogram for organic acid in ion chromatography, Langmuir isotherm parameters were obtained by Retention Time Method (RTM) and moment method. Ion chromatography analysis for formic acid was performed and compared with theoretically predicted profiles under isocratic condition. Band profiles were estimated with the equilibrium-dispersive model of chromatography using a PDEsolver Macsyma . The relationship between the characteristics of chromatogram and the variable operating condition in chromatography such as the flow rate, ionic strength and injection volume was studied. Satisfactory agreement was observed between the experimental and the estimated chromatograms with parameters obtained form the moment method.

• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.371-375
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• 2010

In order to decide the strength requirement of the window glass for the high-speed train, the pressure change during the passage of the EMU type high-speed train has been numerically simulated. Based on the calculation results, the pressure difference between the inner and outer pressure of the cabin has been calculated to yield the amount of load acting on the window glass of the cabin. To simulate the pressure field generated by the high-speed train passing through the tunnel, computational fluid dynamics based on the axi-symmetric Navier-Stokes equation has been employed. The pressure change inside a train has been calculated using first order difference approximation based on a linear equation between the pressure change ratio inside a train and the pressure difference of inside and outside of the train.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.211-222
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• 2000

The design values of rock socketed pile related with properties of rock mass are not clearly established. However, the drilled shafts socketed in rock are widely used as the foundation of large scaled structure. In this study, the characteristics of behavior of rock socketed pile is researched, and the properties of interface between pile and rock considering soil-structure interaction are evaluated for numerical modeling of rock socketed pile based on the previous researches. Based on the properties of interface and rock mass, the behaviors of rock socketed piles are numerically modeled and compared with field measurement. To verify the numerical analysis, a micro pile socketed in rock is modeled and the results of numerical analysis are compared with field measurement. The numerical results show a good agreement with field measured data, especially in terms of load transfer characteristics.

• Tunnel and Underground Space
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• v.10 no.3
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• pp.457-468
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• 2000

The design values of rock socketed pile related with properties of rock mass are not clearly established. However, the drilled shafts socketed in rock are widely used as the foundation of large scaled structure. In this study, the characteristics of behavior of rock socketed pile is researched, and the properties of interface between pile and rock considering soil-structure interaction are evaluated for numerical modeling of rock socketed pile based on the previous researches. Based on the properties of interface and rock mass, the behaviors of rock socketed piles are numerically modeled and compared with field measurement. To verify the numerical analysis, a micro pile socketed in rock is modeled and the results of numerical analysis are compared with field measurement. The numerical results show a good agreement with field measured data, especially in terms of load transfer characteristics.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.85-91
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• 2005

This paper investigates P-S (load-settlement) relationship for the end-bearing Pile in granular material using the CRISP FE Program with the laboratory 2D model pile load test. In order to simulate the effect of end-bearing pile problem in the FEA, the author adopts several forms of slip element around the pile length and the pile tip. Through this study it was found that e degree of non-associated Plastic flow rule incoporated into the Mohr-Coulomb model for the end-bearing pile with the slip elements was a dominant factor in terms of numerical solution convergence. In contrast, the roller boundary used along the pile shaft showed a smooth convergence with respect to the degree of non-associated plastic flow rule.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.312-315
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• 2005

Visual MODFLOW 프로그램 내 MT3D 패키지를 이용하여 다공 추적자 시험 해석 모델을 제시하였으며, 개념모델을 설정하여 추적자 해석 모델 모사 시 입력상수인 수리전도도(K), 비산출률$(S_y)$, 유효공극률$(n_e)$, 종분산지수$({\alpha}_L)$ 및 횡분산지수$({\alpha}_T)$ 등에 따른 민감도를 분석하였다. 또한, 이를 이용하여 부산과 이천지역의 현장 추적자 시험 자료를 해석하였다. 민감도 분석 결과, 유효공극률과 종분산지수의 민감도가 가장 크게 나타났으며, 비산출률의 민감도가 가장 작게 나타났다. 유효공극률은 관측정에서 측정되는 추적자의 최고농도를 결정하는 인자이며, 종분산지수는 추적자 최고농도가 되는 경과시간과 관계가 깊은 것으로 나타났다. 재순환 추적자 시험 해석 모델을 적용한 부산지역의 경우 유효공극률은 0.15, 종분산지수는 5m인 것으로 모사되었으며, 수렴 흐름 추적자 시험 해석 모델을 적용한 이천지역의 경우 유효공극률은 0.01, 종분산지수는 13m로 산정되었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.383-390
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• 2008

This paper presents the formulation and numerical implementation of a spectral scheme specially developed to simulate dynamic fracture events in unidirectional and cross-ply fiber-reinforced composites. The formulation is based on the spectral representation of the transversely isotropic elastodynamic relations between the traction stresses along the fracture plane and the resulting displacements. Example problem of dynamically propagating cracks in fiber-reinforced composites is investigated and compared with reference solutions available in the literature and/or experimental observations. This scheme can be directly applicable to the interfacial fracture analysis in the FRP reinforced concrete structures.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.162-163
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• 2017

해양 HNS(Hazardous and Noxious Substances)의 유출 사고 시, 막대한 인명 피해와 환경 훼손을 피하기 위해 유출 사고 조기 예측과 정확한 확산 경로를 예측하는 것이 필수적이다. 본 연구의 최종목적은 전산유체역학을 이용하여 HNS사고가 발생하였을 때 위험구역을 적절히 예측할 수 있는 수치해석기법을 개발하고, 다양한 해양사고조건과 환경영향을 고려하여 근접역에서의 2차원 확산 특성을 고찰하고 확산 현상을 예측하기 위한 모델을 개발하는 것이다. 본 연구에서는 상용코드인 ANSYS FLUENT(V. 17.2)을 사용하여 근접역에서의 2차원 확산특성을 모사하고 분석하였다. 특히, 누출된 HNS의 위치별 농도를 예측하기 위해 종수송방정식(Species Transport Equation)을 이용하였으며 RANS(Reynolds-Averaged Navier-Stokes) 방정식과 표준 $k-{\varepsilon}$ 모델을 이용하여 난류유동을 모사하였다. 해석된 결과는 문헌에서 얻어진 실험데이터와 상호비교하였으며 해수의 유속, HNS의 밀도에 따른 유층 두께, 해수면 HNS 평균 농도 그리고 HNS 전파 속도를 분석하였다. 유층 두께는 해류 유속에 따라 변화하며 변화 경향에 따라 두 구간으로 나눌 수 있다. 해류 전파 속도는 대체로 해류 유속과 선형적 비례관계를 갖는 것으로 나타났다. 해수면 평균 HNS 농도는 해류 유속에 선형적으로 비례하여 감소하며, HNS 밀도가 큰 경우 해수면 평균 HNS 체적 농도는 더 빠르게 감소하게 된다. 이러한 결과는 HNS 확산 특성을 분석하고 관련된 예측모델을 개발하는 데에 기여할 수 있다.