• 한국전자파학회논문지
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• 제12권7호
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• pp.1131-1138
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• 2001

본 논문에서는 기존의 Compact 2D FDTD(Finite-Difference Time-Domain)에 대한 고속화 알고리즘으로써 Haar 웨이블릿 기반 Compact 2D MRTD(MultiResolution Time-Domain) 차분식을 제안하였다. 구현된 알고리즘을 이용하여 내부가 공기로 태워져 있는 구형 도과관과 포과관 내부치 일부가 유전체로 채워져 있는 구형 도파관을 해석하였다. 본 논문의 결과는 기존의 Compact 2D FDTD치 결과 및 해석적인 해와 매우 잘 일치한다. 또한 계산 소요시간이 기존의 Compact 2D FDTD에 비해 절반 가까이 절약되었음을 확인하였다. 제안된 알고리즘은 도파관 구조의 분산 특성 연구에 있어 효율적인 고속화 기술로서 의미가 있다고 할 수 있다.

• 한국기계연구소 소보
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• 통권9호
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• pp.169-181
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• 1982

This paper presents three methods for ship hull form improvement on the basis of wave pattern analysis. These methods are primarily based on the assumption that a linear relation exists between the small difference of hull sections and the difference of the wave amplitude functions. The improved hull form of ship is made by superposing a thin hull form on that of a parent model. The first method use the simplification of framelines and Michell's Theory to the formula of wave resistance for superposed thin ship. The second method use tent functions and Michell's Theory to that. And the third is experimental method.

• Journal of Welding and Joining
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• 제15권3호
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• pp.47-55
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• 1997

Dynamic characteristics of the short circuit mode are investigated using the Volume of Fluid (VOF) method. When the initial molten drop volume, contact area and wire feed rate are given, rate change of the molten bridge profiles, pressure and velocity distributions are predicted. The electromagnetic force with proper boundary conditions are included in the formulation to consider the effects of welding current. It is found that the molten metal is transferred to the weld pool mainly due to the pressure difference caused by the curvatures in the initial stage, and electromagnetic force becomes dominant factor in the final stage of short circuit transfer. Necking occurs at the contact position between the molten drop and weld pool, and the initial molten drop volume and welding current have significant effects on break-up time.

• Tribology and Lubricants
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• 제22권2호
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• pp.93-98
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• 2006

The numerical analysis of the negative pressure porous gas bearings is presented. The pressure distribution is calculated using the finite difference method. The Reynolds equation and Darcy's equation are solved simultaneously. The air bearing stiffness and damping are evaluated using the perturbation method. Rectangular uniform grid is employed to model the bearing. The vacuum preloading is considered. The pressure in the vacuum pocket is assumed to be a constant negative pressure. The total load, stiffness, damping and flow rate are calculated fur several geometrical configurations and several values of negative pressure. It is found that too large vacuum pocket can result in negative total force.

• 한국생활과학회지
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• 제7권2호
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• pp.63-73
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• 1998

To get well-fitted ready-made clothings with beautiful silhouettes, it's better to classify body forms into several forms and to assign sizing within each form than to grade just based on body size regardless of body styles. This study illucidated the importance of drop value in the results of surveying the current values of sizing and grading. Therefore, it's meaningful to get the classification of body form with appropriate distribution of drop values of the body, and the distribution of drop value and the frequency of each form is very helpful to name the combined sizing or coverage of ready-made clothes. This study aimed at classifying body forms with various drop values using multivariate analysis for sizing and grading. Factor analysis and cluster analysis were done using measured values from 346 unmarried women. The results are as follows: 1. The factor which explains body forms was obtained by factor analysis, and the representative major 18 items which have important roles in classifying body forms were selected among the measured values with high factor loading and communality. 2. The body forms were classified into 8 groups based on the charateristics, frequencies and distributions of them obtained from cluster analysis. 3. Each classified body form showed conspicuous difference in drop value and the difference of body form mainly resulted from the difference between waist and hip rather than the difference between bust circumference and waist in Korean unmarried women.

• 패션비즈니스
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• 제5권3호
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• pp.73-84
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• 2001

The purpose of this study is to apply fundamental data of impression formation research by analysing and observing the various facial image that can be effected from hair style as well as be helpful for choosing suitable hair style for T.P.O in modern society. This study targeted 305 college women in Daegu and Gyung-book area. Hair Style Image Scale(HSIS)was used the scale of seven point modified the S-D(Semantic Differential) method. The analysis of impression formation effect of hair style using SPSS WIN package have completed from the principal component analysis by Varimax perpendicular rotation method and ANOVA was used to recognize the difference in impression formation according to hair style change. In the case of statistical difference was appeared, LSD post-verification was applied for that. The conclusions of this study is as followed ; 1. The factors of impression formation effected by hair style were classified as goodwill factor, refinement factor, elegance factor and individuality factor. 2. In terms of goodwill factor, long hair style showed highest level and short cut hair, bobbed hair in an order. In refinement factor, there was no difference between short cut hair and bobbed hair and both of them was higher than long hair. In elegance factor, long hair was highest and bobbed hair was lowest. In individuality factor, short cut hair and bobbed hair higher than long hair and no difference between short cut hair and bobbed hair.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.2-7
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• 2008

A highly efficient moving least squares finite difference method (MLS FDM) for heat transfer analysis of composite material with interface. In the MLS FDM, governing differential equations are directly discretized at each node. No grid structure is required in the solution procedure. The discretization of governing equations are done by Taylor expansion based on moving least squares method. A wedge function is designed for the modeling of the derivative jump across the interface. Numerical examples showed that the numerical scheme shows very good computational efficiency together with high aocuracy so that the scheme for heat transfer problem with different heat conductivities was successfully verified.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.660-664
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• 2004

The indirect rotor position detection method using terminal voltage of brushless DC motor (BLDCM) requires simple control circuit, and has wide speed range of sensorless operation. However, because the substantial phase difference exists between real back emf and terminal voltage, the existing indirect detection method using analog filter which is affected by frequency, speed, and load sensitively cannot be synchronized with current, in the end, it advances or delays. This paper presents new analog filter circuit design for rotor position estimation in order to solve the problem, and proposes novel sensorless operation method which is stable even in high speed range and not influenced by parameters with analysis on phase difference by load and speed. Moreover, the appropriateness of the proposed sensorless drive in this paper is verified and analyzed by experimentation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.192-198
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• 1997

In the concurrent engineering, the CAD-based design model is necessary for multidisciplinary analysis and for computer-aided manufacturing (CAM). A shape and configuration design velocity field computation of structure has been developed using a computer-aided design (CAD) tool, Pro/ENGINEER. The design Parameterization with CAD tool is to characterize the change in dimensions and movements of geometric control points that govern the shape/orientation of the structural boundary. The boundary velocity is obtained by using a CAD-based finite difference method and the domain velocity field is obtained from finite element analysis (FEA) using the boundary displacement method. In this paper, the continuum configuration DSA for NVH problem, which requires the shape velocity field and the orientation velocity field at the same time, is developed using linear shape functions. For validation of continuum design sensitivity coefficients, design sensitivity coefficients are compared with the coefficients computed using by the finite difference method.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1993년도 제18회 학술대회 초록집
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• pp.63-69
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• 1993

In this paper the characteristics of Hydrostatic Bearing of piston of cylinder are investigated . The dynamic characteristic equations of piston considering both parallel and rotational motion and time dependent modified Reynolds Equation are analyzed and the dynamic pressure distribution of oil film is numerically calculated by perturbation method and finite difference method. and the atatic analysis is carried out. so, the influence of design parameter of piston on the characteristic of bearing is analyzed.