• Journal of the Society of Naval Architects of Korea
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• v.38 no.2
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• pp.26-32
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• 2001

In this paper, elastic responses of a floating structure in waves with a breakwater are presented. The method of source-dipole distribution is used to analyze the velocity potentials for the fluid region. The deflections of structure are expanded approximately in terms of natural mode functions of free-free beam. The model for present calculation is a floating plate with an length of 1000m and the hydroelastic responses for a floating structure with a straight breakwater are shown. The effects of distance between breakwater and structure, bending rigidity and relative length of regular waves are examined.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.458-465
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• 2003

In this paper, we analyze the transient electromagnetic response from three-dimensional(3-D) dielectric bodies using a time-domain electric field integral equation formulation. The solution method in this paper is based on the Galerkin＇s method that involves separate spatial and temporal testing procedures. Triangular patch basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D dielectric structures. The time-domain unknown coefficients of the equivalent electric and magnetic currents are approximated as an orthonormal basis function set that is derived from the Laguerre functions. These basis functions are also used as the temporal testing. Numerical results involving equivalent currents and far fields computed by the proposed method are presented.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.169-174
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• 2005

In this paper, we proposed a new algorithm of the inverse scattering for the reconstruction of unknown dielectric scatterers using the finite-difference time-domain method and the design sensitivity analysis. We introduced the design sensitivity analysis based on the gradient for the fast convergence of the reconstruction. By introducing the adjoint variable method for the efficient calculation, we derived the adjoint variable equation. As an optimal algorithm we used the steepest descent method and reconstructed the dielectric targets using the iterative estimation. To verify our algorithm we will show the numerical examples for the two-dimensional $TM^2$ cases.

• Progress in Medical Physics
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• v.15 no.3
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• pp.140-148
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• 2004

The absorbed dose for proton beam in water was calculated using the PTRAN code system. The proton interactions with water and the description on absorbed dose calculations are discussed, and the file structure and an execution example of the PTRAN codes are described. For 60, 100, 150, 200, and 250 MeV proton beams it is demonstrated that the absorbed dose is determined from the sum of Coulomb interactions and nuclear reactions, and that the Bragg peak feature depends On the energy straggling and multiple scattering. The PTRAN code was useful for studying the fundamental mechanism of the absorbed dose to water for clinical proton beams.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.3
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• pp.246-253
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• 1996

In this paper, a problem that occurred in the telegraphist equation established by mode conversion method is solved as analysis tapered transmission line is applied to a waveguide taper. After comparing and analyzing the taper function with variant properties, we select on of taper functions not only that is easily designed but also that have good properties. And then we propose the applicant method to design the waveguide taper and deal with the design of mode transducer between rectangular waveguide and circular waveguide. The measured results of scattering coefficients for the mode transducer fabricated with designed data are agreed well with the theoretical results and the validity of the proposed design and analysis method has been confirmed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1096-1103
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• 2003

In this paper, we analyze the transient electromagnetic response from three-dimensional(3-D) dielectric bodies using a time-domain PMCHW(Poggio, Miller, Chang, Harrington, Wu) formulation. The solution method in this paper is based on the Galerkin's method that involves separate spatial and temporal testing procedures. Triangular patch basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D dielectric structures. The time-domain unknown coefficients of the equivalent currents are approximated by a set of orthonormal basis functions that are derived from the Laguerre polynomials. These basis functions are also used as the temporal testing. Numerical results involving equivalent currents and far fields computed by the proposed method are presented.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.920-932
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• 1994

The combustion phenomena of a reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. This paper describes cycle resolved LDV measurement of turbulent flow inside the cylinder of a 4-valve engine under motoring(non-firing) conditions, and studies the effect of intake port configurations on the turbulence characteristics using following parameters ; Eulerian temporal autocorrelation coefficient, turbulence energy spectral density function, Taylor micro time scale, integral time scale, and integral length scale.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.791-799
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• 2008

In this paper, the electromagnetic modeling and network analysis are proposed for design of GTEM cell operating from DC to 18 GHz. 3D electromagnetic numerical analysis models composed of the coaxial mode-converter for the feeder of GTEM cell, 5 m expanded rectangular coaxial transmission line, and the resistive termination load for current and field transmitted from the feeder are developed. Equivalent network model of feeder, transmission line, and termination load in the GTEM cell is also proposed, so the return loss of GTEM cell is calculated using S-parameters using the electromagnetic numerical analysis. To verify the proposed design method, the GTEM cell is designed, constructed and tested, with its size of $5{\times}2.5{\times}1.7\;m$ and operating frequency of $DC{\sim}18\;GHz$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.561-567
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• 2011

The inverse radiation analysis of a two-dimensional irregular configuration using unstructured triangular meshes is presented. In this study, an enclosure filled with an absorbing, emitting and scattering medium with diffusely emitting and reflecting opaque boundaries is considered. The finite volume method is applied to solve the radiative transfer equation in order to simulate the measured incident radiation values which are used as input data for the inverse analysis. The conjugate gradient method is adopted for the estimation of wall emissivities by minimizing the objective function at each iteration step. To verify the performance of the unstructured grid system, we compare the results with those using a structured grid system for the two-dimensional lopsided shape. The effect of measurement errors on the estimation accuracy is also investigated.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.11-18
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• 2002

In this paper, the method calculating hydroelastic responses of very large floating structure close to a breakwater in waves is presented. The source-dipole distribution method is used to calculate the generalized radiation problem considering breakwater effects and the diffraction problem is analyzed by using the source-dipole distribution andvelocity potential continuation method. The response of a VLFS is approximated by anexpansion in terms of a free-free beam. Calculated model is a VLFS with 1000m in length in a sea with a straight breakwater. The vertical displacements and bonding moments around a VLFS are calculated by variations for distance between a VLFS and a breakwater and incident wave angle to know the effect of a breakwater.