• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.595-597
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• 2002

This paper presents an optimum design, which is able to determine optimal geometric and electric parameters of Switched Reluctance Motor so as to fit respective operating conditions specified in various industrial fields. Those works describe an approach to maximize the average torque while keeping the torque ripple within 10${\sim}$100(%) of respective limited values. This optimum design is obtained by uniting an optimization algorithm of PQRSM to a time stepping finite element method.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.269-276
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• 2009

The local preconditioning method has both robust convergence and accurate solutions by using local flow properties for parameters in the preconditioning matrix. Preconditioning methods have been very effective to low speed inviscid flows. In the viscous and turbulent flows, deterioration of convergence should be overcame on the high aspect ratio grids to get better convergence and accuracy. In the present study, the local time stepping and min-CFL/max-VNN definitions are applied to compare the results and we propose the method that switches between two methods. The min-CFL definition is applied for inviscid flow problems and the min-CFL/max-VNN definition is implemented to viscous and turbulent flow problems.

• 한국전산유체공학회:학술대회논문집
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• 2001.05a
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• pp.78-84
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• 2001

A dual-time stepping algorithm combined with a parallelized multigrid DADI method is presented to predict the dynamic damping coefficients. The Basic Finner model is chosen to validate the prediction capability of the present unsteady Euler method. The linearity of the pitch- and roll-damping coefficients is shown in the low angular rates and the interesting large drop and stiff increment in transonic region for roll-damping coefficients are explained in detail. Through the analysis for the pressure distributions at Mach number 1.0 to 1.2, the sudden drop results from the normal shock and the stiff increment of roll-damping reflects the transition of the normal shock to the oblique shock. The results also show that the Euler equations can give the damping coefficients with a comparable accuracy.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.1
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• pp.1-5
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• 2004

This paper deals with the design and analysis of a 2-phase Switched Reluctance Motor (SRM) used for the cooling fan motor of a refrigerator. To reduce the dead zone and improve the efficiency, the snail-earn type rotor pole and the asymmetric stator pole are investigated. For the optimal shape design, the performances of each model are obtained from numerical calculation results by 2D time-stepping finite element method (FEM) coupled with circuit equations. The accuracy of analysis is verified by comparing the analysis results with experimental data. According to the investigation results, improved shapes of stator and rotor poles are proposed.

• Journal of applied mathematics & informatics
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• v.4 no.1
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• pp.17-30
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• 1997

In this work we approximate the solution of initialboun-dary value problem using a Galerkin-finite element method for the spatial discretization and Implicit Runge-Kutta method for the spatial discretization and implicit Runge-Kutta methods for the time stepping. To deal with the nonlinear term f(x, t, u), we introduce the well-known extrapolation sheme which was used widely to prove the convergence in $L_2$-norm. We present computational results showing that the optimal order of convergence arising under $L_2$-norm will be preserved in $L_{\infty}$-norm.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.828-829
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• 2008

This paper proposes a new pole shaped magnetizing fixture with a non uniform air gap for sinusoidal magnetizing a ring type permanent magnet (PM) to reduce the cogging torque. To obtain more sinusoidal distributed magnetic flux density, the magnetizing fixture's pole shape is optimized by using the sequential response surface method (RSM). And the effects of each design parameter were investigated using the magnetic analysis combined a time stepping finite element method (FEM) with Preisach model. It has been shown, through numerical analysis the optimized modelgives near sinusoidal distributed air gap flux density and drastically reduced cogging torque.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.118-120
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• 2002

In this paper, a multi-object optimization based on a progressive quadratic response surface method (PQRSM) and a time stepping finite element method (FEM) is proposed. The new PQRSM and FEM are able to decide optimal geometric and electric variables of the switched reluctance motor (SRM) with two objective functions: torque ripple minimization and average torque maximization. The result of the optimum design for SRM show an improved performance of motor and a relationship between torque ripple and average torque.

• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.4
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• pp.1-6
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• 1988

In this paper two-dimensional breaking waves of plunger type are numerically simulated both on an even bottom and on a sinusoidally-varying bottom within the framework of potential theory. Based on the boundary integral method derived by Vinje and Brevig, fluid particles on the free surface are treated exactly by using semi-Lagrangian time-stepping. Numerical instability, in particular when the wave front becomes vertical, is discussed and the regriding method of nodal points has been found promising. Numerical accuracy is examined in terms of the wave energy and mass conservations. It is also found that the bottom topography affects significantly and the hydrostatic pressure contributes considerably to the nonoscillating force acting on the bottom, when waves are breaking.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.27-37
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• 1991

In this paper the nonlinear free surface flows for an axisymmetric submerged body oscillating beneath the free surface are solved and the forces acting on the body are calculated. A boundary integral method is applied to solve the axisymmetric boundary value problem and the Runge-Kutta 4-th order method is used for the time stepping of the free surface location. The nonlinear forces acting on the axisymmetric body are computed and compared with published results.

• Journal of Labour Economics
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• v.41 no.3
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• pp.95-128
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• 2018

This study tries to measure the change in the state dependence of the three labor supply choices (part-time, full-time, and the state of unemployed) in Korean married women's labor market by estimating the dynamic multinomial logit model based on MSL (maximum simulated likelihood) method. A component representing individual's unobserved characteristics has been introduced, because it is crucial to control for unobserved heterogeneity in assessing the state dependence. Estimation results show that the state dependences of the three alternatives have strengthened recently. Therefore, part-time job has become more likely to be functioning as an extra option to participate in labor market rather than a bridge(stepping stone) or shelter between unemployment and full-time job.