• Journal of Energy Engineering
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• v.16 no.1 s.49
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• pp.46-52
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• 2007

The piecewise constant angular approximation is developed to replace the conventional angular quadrature sets in the solution of the second-order, multi-dimensional $S_{N}$ neutron transport equations. The newly generated quadrature sets by this method substantially mitigate ray effects and can be used in the same manner as the conventional quadrature sets are used. The discrete-ordinates and the piecewise-constant approximations are applied to both the first-order Boltzmann and the second-order form of neutron transport equations in treating angular variables. The result is that the mitigation of ray effects is only achieved by the piecewise-constant method, in which new angular quadratures are generated by integrating angle variables over the specified region. In other sense, the newly generated angular quadratures turn out to decrease the contribution of mixed-derivative terms in the even-parity equation that is one of the second-order neutron transport equation. This result can be interpreted as the entire elimination or substantial mitigation of ray effect are possible in the simplified even-parity equation which has no mixed-derivative terms.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.5
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• pp.228-233
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• 2002

A computational method for analysis of the 3 dimensional electro-magnetic induction problems has been developed. The developed method is capable of modeling the induced current and analyzing its characteristics using only scalar Potential at each node. A benchmark model of asymmetrical conductor with a hole is analyzed to verify the application of the developed method. The calculated value of magnetic flux density are compared with the measured value, and the results indicate that the developed method is valid. Also, Comparing with 3-D finite element method (FEM) results, we conformed effectiveness of the developed method for the accuracy and computation times.

• Journal of the Korean Mathematical Society
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• v.51 no.3
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• pp.545-565
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• 2014

In this paper we derive a priori $L^{\infty}(L^2)$ error estimates for expanded mixed finite element formulations of semilinear Sobolev equations. This formulation expands the standard mixed formulation in the sense that three variables, the scalar unknown, the gradient and the flux are explicitly treated. Based on this method we construct finite element semidiscrete approximations and fully discrete approximations of the semilinear Sobolev equations. We prove the existence of semidiscrete approximations of u, $-{\nabla}u$ and $-{\nabla}u-{\nabla}u_t$ and obtain the optimal order error estimates in the $L^{\infty}(L^2)$ norm. And also we construct the fully discrete approximations and analyze the optimal convergence of the approximations in ${\ell}^{\infty}(L^2)$ norm. Finally we also provide the computational results.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.693-695
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• 2001

A computational method for the 3 dimensional electro-magnetic induction problems has been developed. The proposed method is capable of modeling the eddy current and analyzing its characteristics using only scalar potential. A benchmark model of asymmetrical conductor with a hole is analyzed to verify the application of the developed method. The calculated value of magnetic flux density are compared with the measured value, and the results indicate that the developed method is valid.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.9
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• pp.465-471
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• 2006

In this paper, a synchronous permanent magnet planar motor (SPMPM) with Halbach array is proposed. First, we give the equations of the magnetic scalar potential and a series of boundary conditions. The magnetization and flux density distribution of Halbach array are obtained by analytical method; then, the characteristics of this SPMPM such as inductance, back-EMF, and thrust are evaluated. At last, the experiment results are used to verify the analysis property of this SPMPM. By comparison, it can be concluded that the analysis of SPMPM with Halbach magnet array is credible and feasible.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.138-144
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• 1998

The BGK equation, which is the kinetic model equation of Boltzmann equation, is solved using FDDO(finite difference with the discrete-ordinate method) to compute the rarefied flow of monatomic gas. Using reduced velocity distribution and discrete ordinate method, the scalar equation is transformed into a system of hyperbolic equations. High resolution ENO(Essentially Non-Oscillatory) scheme based on Harten-Yee's MFA(Modified Flux Approach) method with Strang-type explicit time integration is applied to solve the system equations. The calculated results are well compared with the experimental density field of NACA0012 airfoil, validating the developed computer code. Next. the computed results of circular cylinder flow for various Knudsen numbers are compared with the DSMC(Direct Simulation Monte Carlo) results by Vogenitz et al. The present scheme is found to be useful and efficient far the analysis of two-dimensional rarefied gas flows, especially in the transitional flow regime, when compared with the DSMC method.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.841-842
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• 2006

In this paper, a synchronous permanent magnet planar motor (SPMPM) with Halbach array is proposed for its performance improvement. The magnetization and flux density distribution are obtained by magnet scalar potential; the characteristics such as back-EMF and thrust are evaluated. It can be concluded that the analysis of SPMPM with Halbach magnet array is credible and feasible.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.21-23
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• 1997

The analysis of the permanent type synchronous motor is performed by using the finite element method (FEM). The optimal design of the permanent magnet is presented for minimizing cogging torque in this paper. The cogging torque is expressed in terms of scalar potential computed by the virtual work formula. The minimization of cogging torque is achieved by using the ( ${\mu}$ + ${\lambda}$ ) Evolution Strategy (ES) and the selected flux densities are used to a constraint.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.6
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• pp.11-19
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• 1997

For the circuit modeling of th ecoplanar waveguide (CPW) discontinuities, th eequivalent inductance is analyzed via the 3-dimensional boundary element method. The proposed method utilizes the magnetic scalar potential to obtain the magnetic flux passing sthrough the air-dielectric interfaces of the coplanar waveguide. The boundary integral is simplified by use fo the symmetry when the substrate is composed of the nonmagnetic material. In the numerical analysis, linear basis function and the collocationscheme are employed. The short-end and the step discontinuities are cahracterized through the calculations of the equivalent inductance andd the capacitance. The present method avoids the usual vector formulation and is quite advantageous in the quasi-staic characterization of the CPW disconditnuities.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1007-1009
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• 1993

In this paper, The hybrid method in order to reduce the unknown varible for 3D eddy current calculation is proposed. we adopt the current vector potential(T) and the magnetic scalar potential($\Omega$) as field variable, and adopt image charge method for symetric boundary condition in BEM. We apply the hybrid method to electromagnet for levitation system and analyze the charateristics of eddy current airgap flux distribution, attractive and magnetic drag force according to velocity.