• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.575-589
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• 2008

In the present work, we investigate the hydrodynamic behavior of a turbulent bore, such as tsunami bore and tidal bore, generated by the removal of a gate with water impounded on one side. The bore generation system is similar to that used in a general dam-break problem. In order to the numerical simulation of the formation and propagation of a bore, we consider the incompressible flows of two immiscible fluids, liquid and gas, governed by the Navier-Stokes equations. The interface tracking between two fluids is achieved by the volume-of-fluid (VOF) technique and the M-type cubic interpolated propagation (MCIP) scheme is used to solve the Navier-Stokes equations. The MCIP method is a low diffusive and stable scheme and is generally extended the original one-dimensional CIP to higher dimensions, using a fractional step technique. Further, large eddy simulation (LES) closure scheme, a cost-effective approach to turbulence simulation, is used to predict the evolution of quantities associated with turbulence. In order to verify the applicability of the developed numerical model to the bore simulation, laboratory experiments are performed in a wave tank. Comparisons are made between the numerical results by the present model and the experimental data and good agreement is achieved.

• Geotechnical Engineering
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• v.12 no.4
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• pp.157-178
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• 1996

Current design methods for reinforced earth structures take no account of the magnitude of the strains induced in the tensile members as these are invariably manufactured from high modulus materials, such as steel, where straits are unlikely to be significant. With fabrics, however, large strains may frequently be induced and it is important to determine these to enable the stability of the structure to be assessed. In the present paper internal design method of analysis relating to the use of fabric reinforcements in reinforced earth structures for both stress and strain considerations is presented. For the internal stability analysis against rupture and pullout of the fabric reinforcements, a strain compatibility analysis procedure that considers the effects of reinforcement stiffness, relative movement between the soil and reinforcements, and compaction-induced stresses as studied by Ehrlich 8l Mitchell is used. I Bowever, the soil-reinforcement interaction is modeled by relating nonlinear elastic soil behavior to nonlinear response of the reinforcement. The soil constitutive model used is a modified vertsion of the hyperbolic soil model and compaction stress model proposed by Duncan et at., and iterative step-loading approach is used to take nonlinear soil behavior into consideration. The effects of seepage pressures are also dealt with in the proposed method of analy For purposes of assessing the strain behavior oi the fabric reinforcements, nonlinear model of hyperbolic form describing the load-extension relation of fabrics is employed. A procedure for specifying the strength characteristics of paraweb polyester fibre multicord, needle punched non-woven geotHxtile and knitted polyester geogrid is also described which may provide a more convenient procedure for incorporating the fablic properties into the prediction of fabric deformations. An attempt to define improvement in bond-linkage at the interconnecting nodes of the fabric reinforced earth stracture due to the confining stress is further made. The proposed method of analysis has been applied to estimate the maximum tensions, deformations and strains of the fabric reinforcements. The results are then compared with those of finite element analysis and experimental tests, and show in general good agreements indicating the effectiveness of the proposed method of analysis. Analytical parametric studies are also carried out to investigate the effects of relative soil-fabric reinforcement stiffness, locked-in stresses, compaction load and seepage pressures on the magnitude and variation of the fabric deformations.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1430-1434
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• 2005

금강 유역과 같이 복잡한 하천유역 시스템의 관리를 위해서는 시스템 요소들을 통합적으로 분석할 수 있는 효과적인 의사결정지원 도구가 필요하다. K-MODSIM 모형은 단기 물관리, 장기 운영계획, 가뭄 대비계획 및 물관련 분쟁 해결을 위해 보다 개선된 유역관리 전략을 수립하기 위한 컴퓨터 기반 도구로 개발되었으며, 본 연구에서는 K-MODSIM 모형에 저수지 운영률을 반영하여 유역의 용수배분을 평가하였다. 유역 저수지군 운영 환경 및 제약조건을 반영한 네트워크를 구성한 후, 두 단계의 모형 검정을 수행하였다. 먼저 물리적 검정을 통해서 전체 대상 수계의 상하류 물수지를 검토하고, 다음 단계인 운영 측면의 검정에서 물리적으로 나타나는 상황이 댐 운영이나 제약 조건 등에 부합하는지의 여부를 검토하였다. 대청댐과 용담댐의 통합 운영을 위한 최적 운영률의 개발은 동적계획법 소프트웨어인 CSUDP를 이용하여 수행하였으며, 여기서 사유한 접근법은 음해 추계학적 동적계획법이다. 이 접근방법은 유입량 시계열을 추계학적으로 모의발생시키고, CSUDP 모형은 모의발생시킨 유입량 시계열에 대한 최적운영률을 찾기 위해 사용하며, CSUDP의 최적화 결과에 대한 통계적인 분석을 통해 월단위 운영률을 도출하였다. K-MODSIM 모형에 저수지 운영률을 반영하여 유역의 용수배분을 평가하였다. 유역 저수지군 운영 환경 및 제약조건을 반영한 네트워크를 구성하고, 대청댐과 용담댐의 통합 운영을 위한 최적연계 운영를을 개발하여 다음과 같은 운영 시나리오들을 개발하고 평가하였다. $\cdot$ 금강수계에 대한 용당댐의 영향 평가 $\cdot$ 댐 연계운영시 수요량 변화에 따른 영향 평가 $\cdot$ 하도추적을 고려한 일별모형의 검증 개발된 운영률과 하도추적방법을 K-MODSIM 모형에서 검증하기 위해서 vb.net 스크립트 파일을 개발하여 적용하였다.L이하로 이를 유등천 상류부에 공급할 경우 유등천의 수질은 BOD 6.7mg/L, TN 9.80mg/L, TP 0.90mg/L를 나타낼 것으로 예측된다. 고도처리시설의 도입 후 금강 합류점에서 갑천의 예측 BOD는 7.4mg/L로 현재 9.0mg/L에 비하여 개선되지만 이는 금강수계 오염총량 관리계획의 시$\cdot$도 경계지점 목표수질인 5.9mg/L를 만족시키지 못하므로, 이를 만족시키기 위해서는 방류수 BOD 7.2mg/L이하로 처리해야 할 것으로 판단된다.which support only concepts or image features.방하는 것이 선계기준에 적합한 것으로 나타났다. 밸브 개폐에 따른 수압 변화를 모의한 결과 밸브 개폐도를 적절히 유지하여 필요수량의 확보 및 누수방지대책에 활용할 수 있을 것으로 판단된다.8R(mm)(r^2=0.84)$로 지수적으로 증가하는 경향을 나타내었다. 유거수량은 토성별로 양토를 1.0으로 기준할 때 사양토가 0.86으로 가장 작았고, 식양토 1.09, 식토 1.15로 평가되어 침투수에 비해 토성별 차이가 크게 나타났다. 이는 토성이 세립질일 수록 유거수의 저항이 작기 때문으로 생각된다. 경사에 따라서는 경사도가 증가할수록 증가하였으며 $10\% 경사일 때를 기준으로 $Ro(mm)=Ro_{10}{\times}0.797{\times}e^{-0.021s(\%)}$로 나타났다.천성 승모판 폐쇄 부전등을 초래하는 심각한 선천성 심질환이다. 그러나 진단 즉시 직접 좌관상동맥-대동맥 이식술로 수술적 교정을 해줌으로써 좋은 성적을 기대할 수 있음을 보여주었다.특히 교사들이 중요하게 인식하는 해방적 행동에 대한 목표를 강조하여 적용할 필요가 있음을 시사하고 있다.교하여 유의한 차이가 관찰되지 않았다. 또한 HSP 환자군에서도 $IL1RN^{*}2$ allele 빈도와

• The Journal of Engineering Geology
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• v.10 no.1
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• pp.1-12
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• 2000

Heaving of road and subsidence of slope took place at the Wiri region of the local highway 999 in Gyeongsangbukdo, Korea after heavy rain in the next year of construction. Although the state government had performed remedial treatments by reducing the angle and the height of the slope, deformation had never stopped. Therefore, we have preformed the analysis of deformation and stabilityof the slope. Study area consists of the Cretaceous shale, siltstone and sandstone and two faults are found. The major deformation occurred by sliding of rock mass along faults after heavy rain because not only thepore pressure at the fault plane and the unit weight of sliding mass increased, but did the shearstrength of saturated fault clay become very low. The decrease in shear strength of saturated fault clayis the major factor among the reasons for deformation. Numerical simulations using limit equilibriummodel, finite difference model and finite element model were performed for eight cross sections.Although safety factors are above 1.7 during the dry season, they become below 1.0 when groundwaterlevel raises to surface. The maximum displacement is about 15-3Ocm. However, safety factors increasedto above 2.4 and the maximum displacement is below 2.08cm after remedial treatment, Indicating thatthe slope becomes stable.

• Journal of the Korean GEO-environmental Society
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• v.8 no.5
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• pp.57-65
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• 2007

Slope collapse occurs mostly at the rainy season or thawing season in Korea. From a engineer point of view, the design criterion in recent of soil slopes during the rainfall have a conservative tendency because a slope stability is evaluated in the condition that ground water level is located in the surface. However, for the rational design of soil slopes during rainfall, the raining conditions and the unsaturated soil characteristics of soil slopes have to be considered. For the unsaturated soil characteristics of soil slopes, the laboratory tests for unsaturated soils and the seepage analyses for the raining conditions have to be performed. Due to these difficulties, a conservative design of soil slopes in the current design criterion has been carried out. In this paper, therefore, a simple design method is proposed. The method is considered to the unsaturated soil characteristics and the results of seepage analysis without numerical analysis. To verify the suggested design method, it is compared with both analysis results by current design criterion and analysis results based on the seepage analysis. Through the comparative study, it was found that the current design criterion has been excessively conservative. Hence, simple design method in this study was evaluated as the rational design for the soil slopes during rainfall.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.60-68
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• 1991

The updated Lagrangian Finite Element Method is introduced to analyse rigid body-fluid impact problem which is characterized by incompressible Navier-Stokes equations and impact-contact conditions between free surface and rigid body. For the convenience of numerical computation, velocity fields are splinted into vicous and pressure parts, and then the governing equations and boundary conditions are decomposed in accordance with the decomposition. However, Viscous stresses acting an the solid boundaries are neglected on the assumption that very small velocity gradients may occur during extremely small time interval of the impact. Four coded quadrilateral elements are used to discretize the space domain and the fully explicit time-marching algorithm is employed with a reasonably small time step. At the beginning of each time step, contact velocity of the rigid body is computed from the momentum balance between the body and the fluid. The velocity field is then computed to satisfy the discretized equations of motions and incompressibility and contact constraints as well as an exact free surface boundary condition. At the end of each time step, the fluid domain is updated from the velocity field. In the present time stepping numerical analysis, behaviour of the free surface near the body can be observed without any difficulty which is very important in the water impact problem. The applicability of the algorithm is illustrated by a wedge type falling body problem. The numerical solutions for time-varying pressure distributions and impact loadings acting ion the surface are obtained.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.71-78
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• 2014

There is a big risk of bullet impact because military rotorcraft is run in the battle environment. Due to the bullet impact, the rapid increase of the internal pressure can cause the internal explosion or fire of fuel cell. It can be a deadly damage on the survivability of crews. Then, fuel cell of military rotorcraft should be designed taking into account the extreme situation. As the design factor of fuel cell, the internal fluid pressure, structural stress and bullet kinetic energy can be considered. The verification test by real object is the best way to obtain these design data. But, it is a big burden due to huge cost and long-term preparation efforts and the failure of verification test can result in serious delay of a entire development plan. Thus, at the early design stage, the various numerical simulations test is needed to reduce the risk of trial-and-error together with prediction of the design data. In the present study, the bullet impact numerical simulation based on SPH(smoothed particle hydrodynamic) is conducted with the commercial package, LS-DYNA. Then, the resulting equivalent stress, internal pressure and bullet's kinetic energy are evaluated in detail to examine the possibility to obtain the configuration design data of the fuel cell.

• The Journal of the Convergence on Culture Technology
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• v.6 no.1
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• pp.433-439
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• 2020

This study compared and analyzed the change of air consumption according to water depth with human characteristics and theoretical values. The experimental results are as follows. First, subjects A and B showed similar rise rates depending on the water depth. Second, subject C had a significantly higher rate of increase in air consumption at 25m underwater because the body responded sensitively to deep water pressure, which increased air consumption because breathing was faster than other participants. Third, the subjects D and E showed significantly lower overall air consumption. D and E were 37 and 35 years of age, respectively, the youngest, strongest and most experienced in deep sea diving at the time of military service. Fourth, the average air consumption per minute of the test subjects increased from 5m in water to 1.45 times, 10m in water to 1.85 times, and 20m in water to 2.8 times. This seems to be a result of different experiences, physical fitness, the degree of adaptation of the body to underwater, and different breathing techniques. Lastly, the difference between the experimental average value and the theoretical value appears to be the result of using more or less air than the theoretical value depending on the experiences and physical strength of each of the 5 rescuers, the degree of adaptation of the body underwater, and the method of underwater breathing.

• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.133-140
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• 2005

In order to accelerate the rate of consolidation settlement and gain a required shear strength for a given soft clay deposit, vertical drain method combined with a preloading technique has been widely applied. In this paper, a theory of axisymmetric nonlinear consolidation fer drainage-installed deposit, which considers secondary compression (or creep) during primary consolidation, as well as the variations of compressibility and permeability during the consolidation process, has been developed. A computer program named AXICON based on Hypothesis B fur the analysis of axisymmetric nonlinear consolidation was developed by adopting finite difference method. The results of AS(ICON were compared with Hansbo's solution based on Hypothesis A, as well as in-situ settlements and pore pressures measured in test embankment of Ska-Edeby. The results indicated that Hypothesis A usually underestimated the in-situ settlement and Hypothesis B was considered to be logically correct. It was also shown that one may able to appropriately predict the real in-situ behaviors using the proposed program.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.161-173
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• 1999

Settlement analysis based on oedometer test results with or without Skempton-Bjerrum's modification method ( widely used for practical purposes when estimating consolidation settlements of soft clay deposits) has shortcomings that it cannot simulate real stress states and deformation behaviors of soils in case that in-situ loading and deformation conditions are not 1-dimensional. In this study, the stress path method, reflecting various probable stress paths, was employed to normally - consolidated kaolinite samples by using automated triaxial testing device which can control stress paths automatically. From this experimental study, elastic, consolidation, secondary compression and pore pressure development - dissipation behaviors under various stress paths were analyzed and deformation characteristics of soft clays, which can be the basis of rational estimation of settlements, were studied. Also by comparing results of stress path tests with those of 1-dimensional consolidation tests, limitations and problems of conventional methods were clarified.