• 한국전산유체공학회지
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• 제14권4호
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• pp.78-85
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• 2009

Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work has focused on the simulation of cavitating flow past cylinders with strong side flows. The governing equation is the Navier-Stokes equation based on the homogeneous mixture model. The momentum and energy equation is in the mixture phase while the continuity equation is solved liquid and vapor phase, separately. An implicit dual time and preconditioning method are employed for computational analysis. For the code validation, the results from the present solver have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained. After the code validation, the strong side flow was applied to include the wake flow effects of the submarine or ocean tide.

• 한국유체기계학회 논문집
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• 제11권3호
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• pp.7-13
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• 2008

The cavitating flow simulation is of practical importance for many engineering systems, such as pump, turbine, nozzle, Infector, etc. In the present work, a solver for two-phase flows has been developed and applied to simulate the cavitating flows past hydrofoils. The governing equation is the two-phase Navier-Stokes equation, comprised of the continuity equation of liquid and vapor phase. The momentum and energy equation is in the mixture phase. The solver employs an implicit, dual time, preconditioned algorithm using finite difference scheme in curvilinear coordinates. An experimental data and other numerical data were compared with the present results to validate the present solver. It is concluded that the present numerical code has successfully accounted for two-phase Navier-Stokes model of cavitation flow.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제26권4호
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• pp.333-342
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• 2022

In this paper, we perform a direct comparison study of real experimental data for domain rearrangement and the Cahn-Hilliard (CH) equation on the dynamics of morphological evolution. To validate a mathematical model for physical phenomena, we take initial conditions from experimental images by using an image segmentation technique. The image segmentation algorithm is based on the Mumford-Shah functional and the Allen-Cahn (AC) equation. The segmented phase-field profile is similar to the solution of the CH equation, that is, it has hyperbolic tangent profile across interfacial transition region. We use unconditionally stable schemes to solve the governing equations. As a test problem, we take domain rearrangement of lipid bilayers. Numerical results demonstrate that comparison of the evolutions with experimental data is a good benchmark test for validating a mathematical model.

• 한국산학기술학회논문지
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• 제11권5호
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• pp.1747-1753
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• 2010

본 연구에서는 최대 공비점 압력을 가지는 에탄올과 벤젠 이성분계 혼합물의 기액 상평형 추산을 위하여 상태방정식 모델식과 액체활동도계수 모델식 사이의 비교 연구를 수행하였다. 상태방정식 모델식으로는 Peng-Robinson (PR) 상태방정식을 이용하였으며, Panagiotopoulos 혼합규칙(PRP)을 적용하였다. 한편, 액체 활동도계수 모델식으로는 Renon이 제안한 NRTL 액체 활동도계수 모델식을 이용하였다. PRP 모델식은 2개의 매개변수를 가짐에도 불구하고 3개의 매개변수를 가지는 NRTL 모델식에 비하여 에탄올-벤젠 이성분계에 대해서 저압 영역에서는 유사한 정확성을 고압 영역에서는 좀 더 정확성이 우수함을 확인하였다.

• 농업과학연구
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• 제49권4호
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• pp.949-961
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• 2022

The purpose of this study is to build an oyster outlook model. In particular, by limiting oyster items, it was designed as a partial equilibrium model based on a panel analysis of a fixed effect model on aquaculture facilities. The model was built with a dynamic ecological equation (DEEM) system that considers aquaculture and harvesting processes. As a result of the estimation of the initial aquaculture facilities based on the panel analysis, the elasticity of the remaining facility volume in the previous month was estimated to be 0.63. According to Nerlove's model, the adjustment coefficient was interpreted as 0.31 and the adjustment speed was analyzed to be very slow. Also, the relative income coefficient was estimated to be 2.41. In terms of elasticity, it was estimated as 0.08% in Gyeongnam, 0.32% in Jeonnam, and 1.98% in other regions. It was analyzed that the elasticity of relative income was accordingly higher in non-main production area. In case of the estimation of the monthly harvest facility volume, the elasticity of the remaining facility volume in the previous month was estimated as 0.53, and the elasticity of the farm-gate price was estimated as 0.23. Both fresh and chilled and frozen oysters' exports were estimated to be sensitive to fluctuations in domestic prices and exchange rates, while Japanese wholesale prices were estimated to be relatively low in sensitivity, especially to the exchange rate with Japan. In estimating the farm-gate price, the price elasticity coefficient of monthly production was estimated to be inelastic at 0.25.

• Korea-Australia Rheology Journal
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• 제19권4호
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• pp.221-225
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• 2007

Electrorheological characteristics of a dispersed system of phosphorylated potato starch particles in silicone oil investigated via a rotational rheometer equipped with a high voltage generator is being reanalysized. Flow curves of these ER fluids both under several applied electric field strengths and with different degrees of phosphate substitution were mainly examined via three different rheological constitutive equations of Bingham model, De Kee-Turcotte model and our previously proposed CCJ model. Among these, the CCJ equation was found to fit the data of phosphorylated potato starch well.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.709-710
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• 2002

Cancer angiogenesis is simulated using a two dimensional model. Governing equation of angiogenesis is a TAE (Tumor angiogenesis factor) conservation equation in time and space. A stochastic process model is utilized to simulate vessel formation, proliferation, and migration to a cancer pellet. Numerical results are presented especially in case of growing cancer.

• 대한수학회논문집
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• 제22권4호
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• pp.623-640
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• 2007

The Lotka-McKendrick model which describes the evolution of a single population is developed from the well known Malthus model. In this paper, we introduce the Lotka-McKendrick model. We approximate the solution to the model using hp-discontinuous Galerkin finite element method. The numerical results show that the presented hp-discontinuous Galerkin method is very efficient in case that the solution has a sharp decay.

• Kyungpook Mathematical Journal
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• 제62권3호
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• pp.557-581
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• 2022

The anisotropic-diffusion convection equation with exponentially variable coefficients is discussed in this paper. Numerical solutions are found using a combined Laplace transform and boundary element method. The variable coefficients equation is usually used to model problems of functionally graded media. First the variable coefficients equation is transformed to a constant coefficients equation. The constant coefficients equation is then Laplace-transformed so that the time variable vanishes. The Laplace-transformed equation is consequently written as a boundary integral equation which involves a time-free fundamental solution. The boundary integral equation is therefore employed to find numerical solutions using a standard boundary element method. Finally the results obtained are inversely transformed numerically using the Stehfest formula to get solutions in the time variable. The combined Laplace transform and boundary element method are easy to implement and accurate for solving unsteady problems of anisotropic exponentially graded media governed by the diffusion convection equation.

• Korean Journal of Mathematics
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• 제20권1호
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• pp.47-60
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• 2012

We deal some analytic calculations for European option pricing by using the theory of elementary solution of generalized diffusion equation mainly.