• Geomechanics and Engineering
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• 제36권3호
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• pp.295-301
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• 2024

Understanding the post-liquefaction shear behavior is crucial for predicting and assessing the damage, such as lateral flow, caused by liquefaction. Most studies have focused on the behavior until liquefaction occurs. In this study, we performed undrained multi-stage tests on clean sand, sand-silt mixtures, and silty soils to investigate post-liquefaction shear strain based on soil compressibility. The results confirmed that it is necessary to consider the soil compressibility and the shape of soil particles to understand the post-liquefaction shear strain characteristics. Based on this, an index reflecting soil compressibility and particle shape was derived, and the results showed a high correlation with post-liquefaction small resistance characteristic regardless of soil type and fine particle content.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.516-523
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• 2009

The artificial compressibility (AC) method for the incompressible Navier-Stokes equations in the generalized curvilinear coordinates using the primitive form is implemented. The main advantage of the AC approach is that the resulting system of equations resembles the system of compressible N-S equations and can thus be integrated in time using standard, well-established time-marching methods. The errors, which are the odd-even oscillation, for pressure field in using the artificial compressibility can be eliminated by using the $4^{th}$ order artificial dissipation term which is explicitly included. Even though this paper focuses exclusively on 2D laminar flows to validate and assess the performance of this solver, this numerical method is general enough so that it can be readily extended to carry out 3D URANS simulation of engineering flows. This algorithm yields practically identical velocity profiles and primary vortex and secondary vortices that are in excellent overall agreement with the results of the vorticity-stream function formulation (Ghia et al., 1982). However, the grid resolution have to be required to be large enough to express the various vortices.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.389-396
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• 2010

In this paper, a new computational code was developed using Chorin's artificial compressibility method to solve the two-dimensional incompressible Navier-Stokes equations. In spatial derivatives, Roe's flux difference splitting was used for the inviscid flux, while central differencing was used for the viscous flux. Furthermore, AF-ADI with dual time stepping method was implemented for accurate unsteady computations. Two-equation turbulence models, Menter's $k-{\omega}$ SST model and Coakley's $q-{\omega}$ model, hae been adopted to solve high-Reynolds number flows. A number of numerical simulations were carried out for steady laminar and turbulent flow problems as well as unsteady flow problem. The code was verified and validated by comparing the results with other computational results and experimental results. The results of numerical simulations showed that the present developed code with the artificial compressibility method can be applied to slve steady and unsteady incompressible flows.

• 대한기계학회논문집A
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• 제21권5호
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• pp.735-745
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• 1997

In this study, the compressibility of resin was considered in filling analysis to account for the possible packing type flow. A numerical simulation program employing a hybrid finite element/finite difference scheme was developed to solve Hele-Shaw flow of the compressible viscous fluid at non-isothermal conditions. To advance the melt front, a control volume approach was adopted. Thin complex 3-D shapes of cavities, runners, and sprues were discretized by employing triangular, cylindrical and/or rectangular strip elements. Mass conservation was applied to each control volume to solve for the pressure distribution. Directly applying a constant mass flow rate at the inlet removes calculation of the apparent pressure boundary conditions, resulting in better simulation condition. The Cross model was used to model viscosity and the Tait equation was employed to represent density as a function of temperature and pressure. The validity of the developed program was verified through comparisons with available data in the literature and the effect of compressibility on the pressure distribution was discussed. To reduce computation time, 1-D and 2-D elements were used instead of applying triangular elements and the numerical results were compared to each other.

• 한국전산유체공학회지
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• 제18권4호
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• pp.9-16
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• 2013

Cavitation on an axi-symmetric hemispherical head-form body was studied using an Reynolds-averaged Navier-Stokes equations solver based on a cell-centered finite volume method. To consider compressibility effects on the vapor phase and cavity interface, a pressure-based compressible flow CFD code was developed. To validate the developed CFD code, cavitating flow around the hemispherical head-form body was simulated using pressure-based incompressible and compressible CFD codes and validated against existing experimental data in the three-way comparison. The cavity shedding behavior, length of re-entrant jet, drag history, and Strouhal number of the hemispherical head-form body were compared between two CFD codes. The results, in this paper, suggested that the computations of cavitating flow with compressibility effects improve the description of cavity dynamics.

• 한국지반환경공학회 논문집
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• 제9권5호
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• pp.15-20
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• 2008

연약지반의 압밀 침하는 침하속도를 예측하거나 수치 해석적 기법에 대한 것에 집중되어 있으며 실내시험으로부터 추정된 압축특성에 대해 계측결과 등을 이용하여 재평가하려는 시도는 매우 적다. 영산강 하구지역에서 분포하는 해성점토에 대하여 실내 표준 압밀시험, 현장에서 약 3년 동안 축적된 층별침하계, 간극수압계, 지하수위계의 계측결과를 바탕으로 한 현장계측 압밀곡선, 그리고 침하해석 프로그램인 PLAXIS를 이용한 연직 배수재가 설치된 지반의 성토이력에 따른 역 해석으로 압축성을 비교 하였다. 여러 제약조건에도 불구하고 현장계측결과에 의해 평가된 현장계측 압밀곡선은 표준압밀시험 결과와 비교적 잘 일치하였다.

• 펄프종이기술
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• 제40권1호
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• pp.15-22
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• 2008

For the improvement of letterpress printing paper quality, special fibers obtained from the sea were used by mixing with wood fibers. The sizes of the special fibers, which were from red algae in the sea, were 0.5-1 mm in length, and 3-7 ${\mu}m$ in width, respectively, and the fibers were supplied by Pegasus Research Inc. for the study. From the study, it was found that 10% addition of algae fibers greatly improved paper surface strength and internal bonding strength. The compressibility was estimated by utilizing 'Print-surf method' at high clamping pressure and with hard backing. Again, 10% addition of algae fibers greatly improved the compressibility of the paper. These results were expected that algae and wood fibers were distributed evenly through the sheet, and integrated one another to leave no empty space inside the paper.

• 한국정밀공학회지
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• 제18권12호
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• pp.60-65
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• 2001

To simulate the real molding conditions, the effects of phase change and compressibility of the resin were considered in the present investigation. A modified Cross model with either an Arrhenius-type or WLF-type functional form was used for modeling viscosity of the resin. A double-domain Tait equation of state was employed to describe the compressibility of the resin during molding. The energy balance equation including latent-heat dissipation fur semi-crystalline materials was solved in order to predict the solidified layer and temperature profile. Injection molding experiments were carried out using polypropylene(PP) in the present study. Based on the comparison between experiments and simulations, it was found out the predicted pressure distributions and melt front propagations were accurate. Thus it was concluded that the program developed in this study was proved to be useful in simulations of injection molding process.

• 한국분말재료학회지
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• 제26권3호
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• pp.225-230
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• 2019

To develop Taraxacum platycarpum extract (TP)-loaded particles for tablet dosage form, various TP-loaded particles composed of TP, dextrin, microcrystalline cellulose (MCC), silicon dioxide, ethanol, and water are prepared using a spray-drying method and fluid-bed-drying method. Their physical properties are evaluated using angle of repose, Hausner ratio, Carr's index, hardness, disintegrant time, and scanning electron microscopy. Optimal TP-loaded particles improve flowability and compressibility. Furthermore, 2% silicon dioxide gives increased flowability and compressibility. The formula of TP-loaded fluid-bed-drying particles at a TP/MCC/silicon-dioxide amount of 5/5/0.2 improves the angle of repose, Hausner ratio, Carr's index, hardness, and disintegrant time as compared with the TP-loaded spray-drying particles. The TP-loaded fluid-bed-drying particles considerably improve flowability and compressibility ($35.10^{\circ}$ vs. $40.3^{\circ}$, 0.97 vs. 1.17, and 18.97% vs. 28.97% for the angle of repose, Hausner ratio, and Carr's index, respectively), hardness (11.34 vs. 4.7 KP), and disintegrant time (7.4 vs. 10.4 min) as compared with the TP-loaded spray-drying particles. Thus, the results suggest that these fluid-bed-drying particles with MCC and silicon dioxide can be used as powerful particles to improve the flowability and compressibility of the TP.

• 한국지반공학회논문집
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• 제27권9호
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• pp.47-53
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• 2011

항로유지 준설과 해안건설 현장에서 채취된 해양준설토는 일반적으로 점토 성분 내에 다량의 염분을 함유하고 있다. 본 논문은 염분이 포함된 고화준설토(S-SDS)와 염분이 포함되지 않은 고화준설토(N-SDS)의 역학적 특성에 대한 염분의 영향을 분석하였다. 이를 위해 염분이 포함된 준설토와 염분이 포함되지 않은 준설토에 각각 동일한 양의 시멘트를 혼합하여 여러 개의 시편을 제작하였다. 7일 혹은 28일 양생된 N-SDS와 S-SDS 시편에 대하여 전자현미경 분석, 일축압축시험 및 구속압축시험을 수행함으로써 고화준설토의 미세 흙구조, 강도 및 압축 특성을 비교 및 분석하였다. 실험결과 점토에 포함된 염분은 고화준설토의 미세 흙구조 형성 뿐만 아니라 고화토의 강도발현에 영향을 주는 것으로 나타났다. 또한 S-SDS의 압축지수와 팽창지수는 N-SDS 보다 크게 나왔다. 이것으로부터 염분은 고화토의 압축성을 증가시킨다는 것을 알 수 있다. 염분은 고결화된 준설토의 강도발현 및 압축성에 악영향을 주었다.