• Ocean Systems Engineering
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• 제8권2호
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• pp.167-182
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• 2018

RTI (Rayleigh-Taylor instability) is investigated by a multi-liquid MPS (Moving Particle Semi-implicit) method for both viscous and inviscid flows for various density differences, initial-disturbance amplitudes, viscosities, and surface tensions. The MPS simulation can be continued up to the late stage of high nonlinearity with complicated patterns and its initial developments agree well with the linear theoretical results. According to the relevant linear theory, the difference between inviscid and viscous fluids is the rising velocity at which upward-mushroom-like RTI flow with vortex formation is generated. However, with the developed MPS program, significant differences in both growing patters and developing speeds are observed. Also, more dispersion can be observed in the inviscid case. With larger Atwood (AT) number, stronger RTI flows are developed earlier, as expected, with higher potential-energy differences. With larger initial disturbances, quite different patterns of RTI-development are observed compared to the small-initial-disturbance case. If AT number is small, the surface tension tends to delay and suppress the RTI development when it is sufficiently large. Interestingly, at high AT number, the RTI-suppressions by increased surface tension become less effective.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.162-176
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• 2022

In Lead-based reactor (LBR) severe accident, the meltdown and migration inside the reactor core will lead to fuel fragment concentration, which may further cause re-criticality and even core disintegration. Accurately predicting the migration and solidification behavior of melt in LBR severe accidents is of prime importance for safety analysis of LBR. In this study, the Moving Particle Semi-implicit (MPS) method is validated and used to simulate the migration and solidification behavior. Two main surface tension models are validated and compared. Meanwhile, the MPS method is validated by the L-plate solidification test. Based on the improved MPS method, the migration and solidification behavior of melt in LBR severe accident was studied furthermore. In the Pb-Bi coolant, the melt flows upward due to density difference. The migration and solidification behavior are greatly affected by the surface tension and viscous resistance varying with enthalpy. The whole movement process can be divided into three stages depending on the change in velocity. The heat transfer of core melt is determined jointly by two heat transfer modes: flow heat transfer and solid conductivity. Generally, the research results indicate that the MPS method has unique advantage in studying the migration and solidification behavior in LBR severe accident.

• 한국화재소방학회논문지
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• 제29권2호
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• pp.33-38
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• 2015

고압과 정량 흡상을 목적으로 클리어런스가 없는 초고압 회전용적형 헬리컬기어 펌프의 개발을 진행하였다. 펌프의 내부 압력과 토출 유속을 검증하기 위해 CFD 해석을 수행하였다. 이에 따라 FVM 기법으로 유동해석을 수행하였는데 클리어런스가 없는 완전히 밀폐된 형태의 FVM 유동해석은 격자가 연속하게 구성되지 않아 유체영역이 분리되어 정상적인 결과를 얻어낼 수 없었다. 이러한 문제로 격자 구성이 필요치 않은 MPS 기법으로 유동해석을 수행하였고, MPS 유동해석을 통해 펌프의 내부 압력과 토출 유속을 확인할 수 있었다. 로터의 회전속도 1,000 rpm에서 펌프 내부의 압력은 최소일 때 19.5 bar, 최대일 때 44.6 bar이고, 평균 압력은 33.9 bar로 확인되었다. 토출 유속은 최소일 때 64.5 m/s, 최대일 때 84.8 m/s이고, 평균 유속은 76.1 m/s로 확인되었다. 본 연구를 통해 클리어런스가 없는 해석 모델의 유동해석은 FVM 기법보다는 MPS 기법이 더 적합하였음을 확인할 수 있었다. 또한 초고압 회전 용적형 헬리컬기어 펌프의 압력의 변화에 따른 유속과의 관계를 본 연구를 통해 규명할 수 있었다.

• 한국해양공학회지
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• 제27권2호
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• pp.53-58
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• 2013

Recently, some fluid-structure interaction (FSI) problems involving the fluid impact loads interacting with structures, such as sloshing, slamming, green-water, etc., have been considered, especially in the ocean engineering field. The governing equations for both an elastic solid model and flow model were originally derived from similar continuum mechanics principles. In this study, an elastic model based on a particle method, the MPS method, was developed for simulating the FSI problems. The developed model was first applied to a simple cantilever deflection problem for verification. Then, the model was coupled with the fluid flow model, the PNU (Pusan National University modified)-MPS method, and applied to the numerical investigation of the coupling effects between a cantilever and a mass of water, which has variable density, free-falling to the end of the cantilever.

• Journal of mucopolysaccharidosis and rare diseases
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• 제2권1호
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• pp.17-18
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• 2016

Enzyme replacement therapy (ERT) is a well-established means of treating lysosomal storage disease (LSD). However, classical IV infusion based ERT method produces less than ideal results, especially, CNS defects and quality of life in patients. To improve these main problems of parental IV formulation for LSDs, we investigate modified ERT method and evaluated the efficacy in animal model.

• Elastomers and Composites
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• 제36권4호
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• pp.237-245
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• 2001

고무의 충전제로 사용되는 실리카의 보강효과를 높이기 위해 실란 커플링제인 bistriethox ysilyipropyltetrasulfide(Si 69)와 ${\gamma}$-mercaptopropyltrimethoxy silane(MPS)를 사용하여 실리카의 화학처리를 건식법과 습식법으로 행하였으며, 실란 커플링제를 직접 실리카와 혼합하는 건식법보다 혼합하기 전에 화학적으로 처리하는 건식법이 분산성, 젖음성, 동적특성 및 안정성에서 더욱 우수하였다. 화학처리된 실리카를 SBR 배합에 니더와 믹싱롤을 사용하여 균일하게 혼련하였고 측정한 물성으로부터 비교, 검토하였으며, 실란 커플링제를 사용하지 않을 때보다 물성이 현저히 증가하였으며, 실험으로부터 건식법의 경우 Si 69와 MPS의 최적 사용량은 2 w/w%이지만. 습식법의 경우 EA 및 TGA 분석으로부터 4 w/w% 이였다.

• 한국해양공학회지
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• 제31권6호
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• pp.388-396
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• 2017

A Lagrangian approach based computational fluid dynamics (CFD) was used to simulate large and/or sharp deformations and fragmentations of interfaces, including free surfaces, through tracing each particle with physical quantities. According to the concept of the particle-based CFD method, it is possible to apply it to both fluid particles and solid particles such as sand, gravel, and rock. However, the presence of more than two different phases in the same domain can make it complicated to calculate the interaction between different phases. In order to solve multiphase problems, particle interaction models for multiphase problems, including surface tension, buoyancy-correction, and interface boundary condition models, were newly adopted into the moving particle semi-implicit (MPS) method. The newly developed MPS method was used to simulate a typical validation problem involving dam breaking. Because the soil and other particles, excluding the water, may have different viscosities, various viscosity coefficients were applied in the simulations for validation. The newly developed and validated MPS method was used to simulate the mobile beds induced by broken dam flows. The effects of the viscosity on soil particles were also investigated.

• 한국해양공학회지
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• 제24권5호
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• pp.31-38
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• 2010

The Floating storage and re-gasification unit (FSRU), which has large cargo storage tanks, is a floating liquefied natural gas (LNG) import terminal. The sloshing motion in tanks that are partially filled with LNG can cause impact pressure on the containment system and affect the global motion of the FSRU. Therefore, the accurate prediction of sloshing motion has been a significant issue in the offshore gas production industry. In this paper, a particle method based on the moving particle semi-implicit (MPS) method proposed by Koshizuka and Oka (1996) has been modified to predict sloshing motion accurately in a rectangular tank with the filling ratio of water. The simulation results, including the violent sloshing of the fluid, were validated by comparison with the original MPS method.

• 대한조선학회논문집
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• 제45권1호
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• pp.1-9
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• 2008

The free-surface motions interacting with structures are investigated numerically using the Moving Particle Semi-implicit (MPS) method proposed by Koshizuka et al. (1996) for solving incompressible flow. In the method, Lagrangian moving particles are used instead of Eulerian approach using grid system. Therefore the terms of time derivatives in Navier-Stokes equation can be directly calculated without any numerical diffusion or instabilities due to the fully Lagrangian treatment of fluid particles and topological failure never occur. The MPS method is applied to the numerical study on the fluid impact loads for wet-drop tests in a LNG tank, and the results are compared with experimental ones.

• Clinical and Experimental Pediatrics
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• 제55권11호
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• pp.430-437
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• 2012

Purpose: Mucopolysaccharidosis IVA (MPS IVA; Morquio A syndrome) is rare lysosomal storage disorder caused by N-acetylgalactosamine-6-sulfatase (GALNS) deficiency. Only a few MPS IVA cases have been reported in the Korean literature; there is a paucity of research about clinical or radiologic findings for this disorder. Therefore, we studied clinical findings, radiological features, and genetic data of Korean MPS IVA patients for determining factors that may allow early diagnosis and that may thus improve the patients' quality of life. Method: MPS IVA was confirmed via assay for enzymatic activity of leukocytes in 10 patients. The GALNS gene was analyzed. Patients' charts were retrospectively reviewed for obtaining clinical features and evaluated for radiological skeletal surveys, echocardiography, pulmonary function test, and ophthalmologic test results. Result: Nine patients had severe clinical phenotype, and 1 had an intermediate phenotype, on the basis of clinical phenotype criteria. Radiologic findings indicated skeletal abnormalities in all patients, especially in the hips and extremities. Eight patients had an odontoid hypoplasia, and 1 showed mild atlantoaxial subluxation and cord myelopathy. Genetic analysis indicated 10 different GALNS mutations. Two mutations, c.451C>A and c.1000C>T, account for 37.5% (6/16) and 25% (4/16) of all mutations in this samples, respectively. Conclusion: An understanding of the clinical and radiological features involved in MPS IVA may allow early diagnosis of MPS IVA. Adequate evaluations and therapy in the early stages may improve the quality of life of patients suffering from skeletal abnormalities and may reduce life-threatening effects of atlantoaxial subluxation.