• Journal of Environmental Science International
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• v.11 no.7
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• pp.637-650
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• 2002

This study presents an investigation of the changes of the currents in Kwangyang Bay due to the construction of harbor, reclamation and coastal developments. Currents were simulated by the numerical experiments with a diagnostic multi-level model and using the seasonal oceanographic data of temperature, salinity and ocean current. The values of kinetic and potential energies for the currents were calculated in cases of three topographical changes; before coastal developments, the existing state and after completion of the development project in Kwangyang Bay. The changes of currents due to the coastal developments are as follow; Kinetic energies of tide induced residual currents and wind driven currents decreased by 35~40 percent and 5 percent respectively, however those of density currents increased by 10 percent since the decrease of the coastal areas. Kinetic energy of residual currents including tide induced residual currents, density currents and wind driven currents reduced by 10 percent compared with before the coastal developments. Decrease of current velocity was greatest in summer. Therefore, in summer it was assumed that the Kwangyang Bay is more easily polluted by stratification and decrease of residual current than before the coastal developments carried out.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.744-746
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• 2002

In this paper the method to limit inrush currents for unloaded transformers is proposed by controlling the opening instant in order to predetermine the residual flux. For the purpose of verifying the performance of the proposed method the test circuit with a single phase transformer is established and the effect of the controlled method is studied. With the basis of the obtained results the controlled method for three phase transformers with a wye-delta winding is also proposed. The analysis studies using EMTP(Electro-Magnetic Transient Program) are carried out in order to reveal its effectiveness.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.2
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• pp.121-129
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• 1992

A two-dimensional numerical tidal model is formulated to reproduce tides in the northeastern Yellow-Sea, Seohan Bay. The model was formulated on spherical grid system with mesh resolution of 1' latitude by 4/3' longitude. As a first step, tidal distribution of four major tidal constituents are computed and compared with coastal observation. Independent tidal charts for the M$_2$, S$_2$, $K_1$, and $O_1$ tides were presented. Residual tidal currents and tidal energy flux were also computed.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.38-40
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• 2008

This paper presents the torque ripple and vibration characteristic of interior type permanent magnet (IPM) motor according to rotor design. In the design methods, the optimal notchs are put on the rotor pole face, which have an effect on variation of permanent magnet (PM) shape or residual flux density of PM. Through the space harmonics field analysis, the positions of notch are found and the optimal shapes of notch are decided by using Finite Element Method (FEM). The validity of the proposed method is confirmed with experiments. Therefore, the vibration, starting current and efficiency of IPM is measured by experiment.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.168-170
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• 2000

This paper presents a protective relaying algorithm for transformers using the ratio of induced voltages. The ratio primary and secondary induced voltages calculated calculates from currents and voltages of primary and secondary windings is used. In case of the steady state and magnetic inrush, it is equal to the turn ratio while it is different from the turn ratio in case of internal winding faults. The proposed algorithm operates satisfactorily even large residual flux.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.213-216
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• 2003

This paper put forward the controlled spin intensity method for the tangentially-fired furnaces to solve the problems existed in the counter-tangential operation. The numerical simulation was used in this paper to discuss some basic principles.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.121-125
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• 2004

The preprocessor - solver - postprocessor software for 2D/Axisymmetric CSCM Upwind Flux Difference Splitting Navier-Stokes code has been developed for undergraduate educational purpose. This computational fluid dynamics (CFD) software allows students to setup, solve, visualize and control dynamically server for their own fluid problems via Internet. The preprocessor Is capable of generating geometry and grid, initial solution data and required solver control parameters. The postprocessor shows vector plot and contour plot with different options while residual plot shows root-mean-square (RMS) error history graphically and retrieves the data from solver interactively. Special feature of the preprocessor is grid generation part which is based on MFC/Visual C++ application and FORTRAN single block grid generator process. Many users can access solver via Internet from client computers and solve desired problems using locally installed pre- and postprocessor and remote powerful solver part.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.141-151
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• 1997

This paper deals with a numerical study of flow-guider applied to controlling current in a bay. Two dimensional numerical model for tidal currents based on the depth averaged equation is developed and standard k-.epsilon. model is adopted to determine the turbulence diffusion. Equations are described in a generalized coordinate system to be implemented by non-staggered grid system and discretized by using finite volume method. Unsteady flow is simulated by fully implicit scheme. Hybrid scheme and central differencing are used to compute the convective terms and source terms, respectively. The tidal current in a rectangular bay is simulated and it gives satisfactory results. The realistic and distinct models of a large structure placed in bay are also exemplified with or without flow-guiders. The simulation results show that the flow-guider gives the residual tidal current in the bay by the different flux with respect to the direction of tidal current.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.47-49
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• 2008

This paper presents the vibration characteristic of interior type permanent magnet (IPM) motor according to rotor design. In the design methods, the optimal notchs are put on the rotor pole face, which have an effect on variation of permanent magnet (PM) shape or residual flux density of PM. Through the space harmonics field analysis, the positions of notch are found and the optimal shapes of notch are decided by using Finite Element Method (FEM). The validity of the proposed method is confirmed with experiments. Therefore, the vibration, starting current and efficiency of IPM is measured by experiment.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.17-22
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• 1999

Convergence characteristics and efficiency of three implicit approximate factorization schemes(ADI, DDADI and MAF) are examined using 2-Dimensional compressible upwind Navier-Stokes code. Second-order CSCM(Conservative Supra Characteristic Method) upwind flux difference splitting method with Fromm scheme is used for the right-hand side residual evaluation, while generally first-order upwind differencing is used for the implicit operator on the left-hand side. Convergence studies are performed using an example of the flow past a NACA0012 airfoil at steady transonic flow condition, i. e. Mach number 0.8 at $1.25^{\circ}$ angle of attack. The results were compared with other computational results in order to validate the current numerical analysis. The results from the implicit AF algorithms were compared well in low surface with the other computational results; however, not well in upper surface. It might be due to lack of the grid around the shock position. Because the algorithm minimizes the errors of the approximate decomposition, the improved convergence rate with MAF were observed.