• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.746-751
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• 2014

In this paper, ship performance prediction solver was developed using open source computational fluid dynamics (CFD) libraries. The mass- and momentum-conservation equations and turbulent model with a wall function for the turbulent closer were considered. The volume fraction transport equation with a high-resolution interface capturing scheme were selected for free-surface simulation. The predicted wave pattern around KRISO container ship (KCS) using developed program showed good agreement against existing experimental data. For the revolution of a propeller in the propulsive test, general grid interface (GGI) library was used. The predicted propulsive performance showed 7 % difference against experimental data. Two-phase mixture model was developed to simulate a cavitation and applied to a propeller. The sheet cavitation on the propeller was predicted well. From results, the potential of the numerical tank developed by open source libraries was verified by applying it to KCS.

• Management & Information Systems Review
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• v.32 no.3
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• pp.107-125
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• 2013

This study deals with a strategic decision making in two level supply chain network design. This study presents more realistic mathematical model than the previous studies by considering simultaneous location of plants and distribution centers, determination of capacity level for both plants and distribution centers, and upper limit condition for numbers of locating plants and distribution centers. This paper tries to help the strategic decision making for two level supply chain network design. For this purpose, three different sized numerical examples are generated and optimal solutions are obtained by applying Excel Solver program. And sensitivity analysis is performed for the biggest sized example problem, which has 10 potential plants, 20 potential distribution centers, and 200 customer zones. After the plants being located are fixed, optimal minimum costs are obtained and compared for each of 7 different numbers of distribution centers to be located. As the number of distribution centers increases, changes in inbound transportation cost and outbound transportation cost can be derived. In case of considering cost as well as customer satisfaction level for two level supply chain network design, the analysis of this changes may help more sophisticated decision making.

• Geophysics and Geophysical Exploration
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• v.16 no.3
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• pp.119-130
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• 2013

We developed a method for inverting magnetic data to recover the 3D susceptibility models. The major difficulty in the inversion of the potential data is the non-uniqueness and the vast computing time. The insufficient number of data compared with that of inversion blocks intensifies the non-uniqueness problem. Furthermore, there is poor depth resolution inherent in magnetic data. To overcome this non-uniqueness problem, we propose a resolution model constraint that imposes large penalty on the model parameter with good resolution; on the other hand, small penalty on the model parameter with poor resolution. Using this model constraint, the model parameter with a poor resolution can be effectively resolved. Moreover, the wavelet transform and parallel solving were introduced to save the computing time. Through the wavelet transform, a large system matrix was transformed to a sparse matrix and solved by a parallel linear equation solver. This procedure is able to enormously save the computing time for the 3D inversion of magnetic data. The developed inversion algorithm is applied to the inversion of the synthetic data for typical models of magnetic anomalies and real airborne data obtained at the Geumsan area of Korea.

• Membrane Journal
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• v.20 no.1
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• pp.29-39
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• 2010

This study focuses on the modeling of DMFC to predict the characteristics and to improve its performance. This modeling requires deep understanding of the design and operating parameters that influence on the cell potential. Furthermore, the knowledge with reference to electrochemistry, transport phenomena and fluid dynamics should be employed for the duration of mathematical description of the given process. Considering the fact that MEA is the nucleus of DMFC, special attention was made to the development of mathematical model of MEA. Multiscale modeling is comprised of process modeling as well as a computational fluid dynamics (CFD) modeling. The CFD packages and process simulation tools are used in simulating the steady-state process. The process simulation tool calculates theelectrochemical kinetics as well as the change of fractions, and at the same time, CFD calculates various balance equations. The integrated simulation with multiscal modeling explains experimental observations of transparent DMFC.

• Korean Journal of Soil Science and Fertilizer
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• v.14 no.1
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• pp.8-16
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• 1981

A mathematical model based on the water flow equation was developed with the Ohm's analogy and the partial differential equations. Simulation of water uptake was performed by numerically solving the equations with the aid of a differential equation solver, DGEAR in IMSL package, in FORTRAN version. The input data necessary were climatological parameters (temperature, solar radiation, humidity and wind speed). plant parametors (leaf water potential, leaf area, root conductivity and root length density) and soil parameters (hydraulic conductivity and The graphical comparison of the simulated and measured water contents as the functions of time showed good agreement, but there still was some disparity due to possible inacouracy of the field measured parameters. The simulated soil evaporation showed about 2 mm/day early in the growing period and dropped to about 0.4 mm/day as the full canopy developed and the soil water depleted. During the dry period, soil evaporation was as low as 0.1 mm/day. The transpiration was as high as 5mm/day. Deep percolation calculated from the flux between the 180-cm layer was about 0.2mm/day and became smaller with time. After the soil water of upper layers depleted, the flux reversed showing capillary rise. The rate of the capillary rise reached about 0.07mm/day, which was too low to satisfy water uptake of the root system. Therefore, to increase use of water in deep soil, expansion of the root system is necessary.