• 대한전자공학회논문지TC
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• 제39권10호
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• pp.38-45
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• 2002

본 논문에서는 기존의 Compact 2D FDTD(Finite-Difference Time-Domain)에 대한 고속 알고리즘으로써 시간간격 △t가 안정조건(Stability Condition)에 의해 제한받지 않는 Compact 2D ADI(Alternating Direction Implicit)-FDTD 차분식을 제안하였다. 또한 구현된 알고리즘의 정확성 및 효율성을 검증하기 위하여 내부가 공기로 채워져 있는 구형(Rectangular) 도파관과 차폐된 전송선로를 해석하였다. 본 논문의 결과는 기존의 Compact 2D FDTD의 결과 및 해석적인 해와 매우 잘 일치하며, 계산 소요시간도 기존의 Compact 2D FDTD에 비해 상당히 절약되었음을 확인하였다. 제안된 알고리즘은 도파관 구조의 분산 특성 연구에 있어 효율적인 고속화 기술로서 의미가 있다고 할 수 있다.

• 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.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.749-755
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• 2023

A new approximation method was proposed for treating the non-resonant spatial self-shielding effects of double heterogeneous region such as the double heterogeneous effect of VHTR fuel compact in the thermal energy range and that of BP compact with BISO. The method was developed based on the effective homogenization method and a spherical unit cell model with explicit coated layers and a matrix layer. The self-shielding factor was derived from the relation between the collision probabilities for a double heterogeneous compact and the effective cross section for the homogenized compact. First, the collision probabilities and transmission probabilities for all layers of the spherical model were calculated using conventional collision probability solver. Then, the effective cross section for the homogenized sphere cell representing the homogenized compact was obtained from the transmission probability calculated using the probability density function of a chord length. The verification calculations revealed that the proposed method can predict the self-shielding factor with a maximum error of 2.3% and the double heterogeneous effect with a maximum error of 200 pcm in the typical VHTR problems with various packing fractions and BP compact sizes.

• 한국통신학회논문지
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• 제31권7C호
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• pp.706-712
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• 2006

본 논문에서는 OFDM(Orthogonal Frequency Division Multiplexing) 시스템의 반송파 주파수 동기화부 구현을 위하여 Compact CORDIC 처리기를 제안한다. Compact CORDIC 처리기는 반송파 주파수 옵셋 추정 및 보상시에 요구되는 OFDM 시스템의 독특한 특성을 이용하여 제안되었으며, Compact CORDIC 전처리부와 Compact CORDIC 처리부로 구성된다. Compact CORDIC 전처리부에서는 신호의 정규화를 효율적으로 수행하며, Compact CORDIC 처리부에서는 Vector 모드 CORDIC 과 Rotation 모드 CORDIC 연산을 효율적으로 결합하여 동시에 처리하여 반송파 주파수 동기화를 수행한다. FPGA 구현을 통하여 제안된 Compact CORDIC 처리기가 기존 CORDIC 방법보다 성능이 우수하며 구현 복잡도가 크게 감소함을 확인한다.

• 대한수학회보
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• 제54권2호
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• pp.679-686
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• 2017

The present paper is devoted to self-adjoint cyclically compact operators on Hilbert-Kaplansky module over a ring of bounded measurable functions. The spectral theorem for such a class of operators is given. We use more simple and constructive method, which allowed to apply this result to compact operators relative to von Neumann algebras. Namely, a general form of compact operators relative to a type I von Neumann algebra is given.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.27-30
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• 2002

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. In this study, 3-dimensional unsteady incompressible Wavier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade' scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• 한국수자원학회논문집
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• 제45권5호
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• pp.473-480
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• 2012

고정확도를 보장할 수 있는 Compact Finite Volume Method를 이용하여 수심적분형 흐름 모형과 수심평균된 이송확산 방정식을 해석하는 수치모형 개발과정을 기술하였다. 이차원의 흐름과 파랑의 상호작용에 대한 실험결과와 제시된 수치모형을 이용한 계산결과는 양호하게 일치하였다. 일차원과 이차원공간에서의 흐름에 의한 스칼라의 이송에 관한 수치모의에서도 수차확산이 거의 발견되지 않았고, 매우 정확히 일치하였다. 개수로에서의 난류혼합에 관한 수치모의 결과에서도 합리적인 스칼라의 혼합양상이 관찰되었다.

• Structural Engineering and Mechanics
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• 제10권4호
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• pp.371-392
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• 2000

Application of "advanced analysis" methods suitable for non-linear analysis and design of steel frame structures permits direct and accurate determination of ultimate system strengths, without resort to simplified elastic methods of analysis and semi-empirical specification equations. However, the application of advanced analysis methods has previously been restricted to steel frames comprising only compact sections that are not influenced by the effects of local buckling. A concentrated plasticity method suitable for practical advanced analysis of steel frame structures comprising non-compact sections is presented in this paper. The pseudo plastic zone method implicitly accounts for the effects of gradual cross-sectional yielding, longitudinal spread of plasticity, initial geometric imperfections, residual stresses, and local buckling. The accuracy and precision of the method for the analysis of steel frames comprising non-compact sections is established by comparison with a comprehensive range of analytical benchmark frame solutions. The pseudo plastic zone method is shown to be more accurate and precise than the conventional individual member design methods based on elastic analysis and specification equations.

• 한국분말재료학회지
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• 제12권1호
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• pp.30-35
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• 2005

An aluminum powder compact consolidated by a powder-in sheath rolling (PSR) method was severely deformed by accumulative roll-bonding (ARB) process. The ARB process was performed up to 8 cycles at ambient temperature without lubrication. Optical microscope and transmission electron microscope observations revealed that microstructure of the ARB-processed Al powder compact is inhomogeneous in the thickness direction. The ultra-fine subgrains often reported in the ARB-processed bulky materials were also developed near surface of the Al powder compacts in this study. Tensile strength of the ARB-processed Al powder compact increased at the 1st cycle, but from the 2nd cycle it rather decreased slightly.

• 대한기계학회논문집A
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• 제29권8호
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• pp.1118-1122
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• 2005

The direct current potential drop (DCPD) method and the unloading compliance (UC) method with a crack opening displacement gauge were applied simultaneously to the Zr-2.5Nb curved compact tension (CCT) specimens to determine which of the two methods can precisely determine the crack initiation point and hence the crack length for evaluation of their fracture toughness. The DCPD method detected the crack initiation at a smaller load-line displacement compared to the UC method. As a verification, a direct observation of the fracture surfaces on the curved compact tension specimens was made on the CCT specimens experiencing either 0.8 to 1.0 mm load line displacement or various loads from $50\%\;to\;80\%$ of the maximum peak load, or $P_{max}$. The DCPD method is concluded to be more precise in determining the crack initiation and fracture toughness, J in Zr-2.5Nb CCT specimens than the UC method.