• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.17 no.2
• /
• pp.181-186
• /
• 1992

The scattering property of TMz illuminated perfectly conducting and dielectric cylinders of arbitrary cross section are analyzed by the boundary element techniques. The boundary element equations are formulated via Maxwell’s equations, weighted residual or Green’s theorem, and the boundary conditions. The unknown surface fields on the boundaries are then calculated by the boundary element integral equations. Once the surface fields are found, the scattered fields in from a perfectly conducting circular and elliptic cylinders, a dielectric circular and elliptic cylinders are numerically analyzed. A general computer program has been developed using the quadratic elements(higher order boundary elements) and the Gaussian quadrature.

• Korean Journal of Optics and Photonics
• /
• v.16 no.5
• /
• pp.423-427
• /
• 2005

In this paper, we propose easily tooling method for Seidel third order aberration, which are not well utilized in actual design process due to the complication of mathematical operation and the difficulty of understanding Seidel third order aberration theory, even though most insightful and systematic means in pre-designing for the initial data of optimization. First, using paraxial ray tracing and Seidel third order aberration theory, spherical aberration coefficient is derived for a two-mirror system with a finite object distance. The coefficient, which is expressed as a higher-order nonlinear equation, consists of design parameters(object distance, two curvatures, and inter-mirror distance) and effective focal length(EFL). Then, the expressed analytical equation is solved by using a computer with numerical analysis method. From the obtained numerical solutions satisfying the nearly zero coefficient condition($<10^{-6}$), linear fitting process offers a linear relationship called the curvature linear equation between two mirrors. Consequently, this linear equation has two worthy meanings: the equation gives a possibility to obtain initial design data for optimization easily. And the equation shows linear relationship to a two-mirror system with a finite object distance under the condition of corrected third order spherical aberration.

• Journal of Digital Convergence
• /
• v.11 no.3
• /
• pp.101-113
• /
• 2013

Although the methodological literature is replete with advice regarding the development and validation of multi-item scales based on reflective measures, the issue of index construction using formative measures has received little attention. The aim of this paper is to enhance researchers' understanding of formative measures of high-order factor and assist them in their index construction efforts. This article is also to provide some insights into the nature of formative indicators for researchers to reach an informed choice as to the appropriate high order formative measurement model for their needs. We first provide a brief background on formative indicators, drawing from the limited and fragmented literature on the topic. Next we give an example of constructing an index based on actual survey data and highlight the procedures used to assess its quality. We conclude the article with some thoughts about the use of indexes in empirical studies.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.17 no.3
• /
• pp.257-264
• /
• 1999

The lens distortions were corrected directly using the high-order polynomial which was offered in camera calibration data for the forward transformation and the root of Newton-Raphson's $2\times{2}$ nonlinear system for the backward transformation. The 0.04~0.08 pixels increase in accuracy was indicated through the use of direct correction of lens distortions instead of least square methods of commercial software. The least square adjustment method of high-order polynomial requires many control points which has a same weight. But this suggested method which is unnecessary to determine control points was developed and applied. The algorithm showed improved efficacy.

• Journal for History of Mathematics
• /
• v.18 no.4
• /
• pp.1-16
• /
• 2005

Chosun dynasty mathematician Park Yul (1621 - ?) wrote San Hak Won Bon(算學原本) which was posthumously published in 1700 by his son Park Du Se (朴斗世). It is the first mathematics book whose publishing date is known, although we have Muk Sa Jib San Bub (默思集算法) by Gyung Sun Jing (慶善徵, 1616-?). San Hak Won Bon is the first Chosun book which deals with tian yuan shu (天元術) and was quoted by many Chosun authors. We do find it in the library in Korea University. In this paper, we investigate its contents together with its historical significance and influences to the development of Chosun dynasty Mathematics and conclude that Park Yul is one of the most prominent Chosun dynasty mathematicians.

• Geophysics and Geophysical Exploration
• /
• v.14 no.3
• /
• pp.191-202
• /
• 2011

Reserve-time migration (RTM) using a two-way wave equation is one of the most accurate migration techniques. RTM has been conducted by assuming that subsurface media are isotropic. However, anisotropic media are commonly encountered in reality. Conventional isotropic RTM may yield inaccurate results for anisotropic media. In this paper, we develop RTM algorithms for vertical transversely isotropic media (VTI) and tilted transversely isotropic media (TTI). For this, the pseudo-acoustic wave equations are used. The modeling algorithms are based on the high-order finite-difference method (FDM). The RTM algorithms are composed using the cross-correlation imaging condition or the imaging condition using virtual sources. By applying the developed RTM algorithms to the Hess VTI and BP TTI models, we could obtain better images than those obtained by the conventional isotropic RTM.

• Korean Journal of Optics and Photonics
• /
• v.18 no.1
• /
• pp.19-23
• /
• 2007

We derived analytically the generalized curvature linear equation useful in the initial optical design of a two-mirror system with finite object distance, including an infinite object distance from paraxial ray tracing and Seidel third order aberration theory for coma coefficient. These aberration coefficients for finite object distance were described by the curvature, the inter-mirror distance, and the effective focal length. The analytical equations were solved by using a computer with a numerical analysis method. Two useful linear relationships, determined by the generalized curvature linear equations relating the curvatures of the two mirrors, for the cancellation of each aberration were shown in the numerical solutions satisfying the nearly zero condition ($<10^{-10}$) for each aberration coefficient. These equations can be utilized easily and efficiently at the step of initial optical design of a two-mirror system with finite object distance.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.4
• /
• pp.319-327
• /
• 2017

In this study, characteristics of seismic behaviors of offshore wind turbine systems using concrete-suction-type supporting structures are investigated. Applying hydrodynamic pressure from the surrounding sea water and interaction forces from the underlying soil to the structural system which is composed of RNA, the tower, and the supporting structure, a governing equation of the system is derived and its earthquake responses are obtained. It can be observed from the analysis results that the responses are significantly influenced by soil-structure interaction because dynamic responses for higher natural vibration modes are increased due to the flexibility of soil. Therefore, the soil-structure interaction must be taken into consideration for accurate assessment of dynamic behaviors of offshore wind turbine systems using concrete-suction-type supporting structures.

• Journal of the Korea Computer Graphics Society
• /
• v.15 no.1
• /
• pp.1-6
• /
• 2009

This paper presents a new CIP method for unstructured mesh to reduce the numerical dissipation. To reflect precise physical characteristics, CIP method updates both the physical quantity and the derivative information. The proposed method uses the Finite Volume Method(FVM) to solve the non-advection term of CIP equation. And we performed several experiments to improve the accuracy of third-order interpolation. Our result shows that our algorithm has less numerical dissipation than that of linear advection solver.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.11a
• /
• pp.274-278
• /
• 2011

We present an innovative method of multi-physics application involving energetic materials. We use an Eulerian methodology to address these problems. We have devised a new level set based tracking framework that can elegantly handle large gradients typically found in energetic response of high explosive and metals. Proper constitutive relations are employed to model the transient phases of gas, lliquid, and solid in the high strain rate regime. We use the confined and unconfined rate stick results to validate against the experimental data.