• Annual Conference of KIPS
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• 2005.11a
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• pp.713-716
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• 2005

차세대 원자로로 부각되고 있는 고온가스냉각 원자로에서는 고온 안정성 및 핵분열생성물 차단 성능이 우수한 TRISO(Tri-Isotropic) 핵연료를 사용하고 있다. TRISO 핵연료 입자는 직경이 약 1mm인 구 형태로 입자의 중심에는 직경 $0.35^{\sim}0.6\;{\mu}m$의 핵연료 입자가 포함되며 입자 외곽을 코팅 층이 에워 싸고 있다. 이 코팅층은 완충(buffer) PyC 층, 내부 PyC 층, 외부 PyC 층으로 구성되어 있다. 각 코팅 층의 두께를 수십$^{\sim}$백 ${\mu}m$ 범위이며 사양으로 정해져 있어 핵연료 입자 제조 후 사양을 만족하는지를 검사해야 한다. 본 연구에서는 TRISO 핵연료 입자 정보를 컴퓨터로 생성하고 가상의 X-선 래디오그래피 방법을 이용하여 투시 영상을 구성한 후 Filtered Backprojection 기법을 이용하여 단면 영상을 재구성하고 이 단면 영상을 이용하여 코팅 층의 두께를 정밀하게 측정하기 위한 모의 실험을 수행하였다. 경계선이 불명확한 투시영상이 아닌 경계선이 명확한 재구성 단면 영상을 이용하여 코팅 층의 두께를 약 2.3% 이내의 오차율로 정밀하게 측정하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.2
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• pp.125-132
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• 2003

This study introduces a simulation model of radar responses from subsurface voids in concrete for their frequency variations. In this model, resolution and attenuation characteristics due to frequency variations are analyzed at each material interface which has different electromagnetic property. This model aims at the selection of best frequency of radar which can analyze the thickness of voids in concrete from radar responses. It can also be applied to estimate the limitation of propagation depth of radar on subsurface voids in concrete. The computed results show the radar images obtained by using a radar signal processing technique using convolution.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.507-514
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• 2012

This paper proposed the analysis method of the cavity resonance characteristics for a metallic enclosure with a PCB trace source. In order to calculation the electromagnetic fields inside the cavity, coupled integral equations for a current distribution on the PCB trace and an aperture electric field distribution on the boundary of the PCB dielectric are derived and solved by applying Galerkin's method of moments. The result show that the resonant characteristics of the metallic enclosure are fairly good agreement with the simulation(HFSS) and the measured results. The resonant frequencies of the metallic enclosure with the PCB trace are changed by the PCB trace location inside of the cavity. In order to check the validity of the theoretical analysis, the calculated return losses are compared with the measured results.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.87-93
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• 1993

The motion response of a ship moored in a rectangular harbor excited by long waves has been studied theoretically and experimentally. Experiments are performed in a shallow basin. A ship model is set moored by soft springs at various positions in a model harbor subjected to regular waves with period ranging from 2 to 3 seconds. Wave and ship responses are measured and compared with theory. It is found that theoretical results agree qualitatively with experimental results. The main source of quantitative discrepancies is presumably due to real fluid effects such as separation at the harbor entrance and friction on harbor boundaries.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.22-28
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• 1999

Small amplitude in-phase oscillations of multi-cylinders are considered both numerically and experimentally. Flow field is separated into inner and outer regions. The basic unsteady solution is obtained analytically and the secondary flow, termed as steady streaming flow, can be obtained numerically by using Finite Volume Code with Panel Method. The Particle Induced Velocimetry, one of whole field measurements, is introduced for comparison with numerical flow visualization quantitatively. Among the algorithms for PIV, the Three Step Vector Searching Technique is applied to reduce CPU time. Small but non-zero damping coefficient, that is important in lightly damped system can be obtained with varying number of bodies and distances.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.66-74
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• 1992

A panel method in the spirit of Hess & Smith(1962), and also of Dawson(1977) was developed to compute the wave resistance of a submerged, or a surface piercing, body moving in the water of finite depth. As a boundary condition on the free surface what is called the Poisson equation is used, while Yasukawa(1989) chose the Dawson equation for which the double-body flow is regarded as the basic one. In order to satisfy the boundary condition on the bottom surface automatically, the sum of a Rankine source and its image with respect to the bottom surface is chosen as the Green function, and hence the singularity is distributed only on the body and on the free surface thereby decreasing the required number of panels dramatically, compared to that of Yasukawa, without the consequential loss of accuracy. Calculations were done for a submerged sphere and for the Wigley hull, and the results are compared with other existing analytical and numerical data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.113-117
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• 1996

구조물의 진동에 의해 소음이 방사되는 현상은 기계에서 소음의 발생원으로 볼 수 있기 때문에 기게류의 소음을 예측하거나 저감방안을 제시하기 위해서는 구조물의 동특성과 방사특성을 이해하고 있어야 한다. 특히, 엔진블럭, 펀치프레스, 배의 갑판구조물등과 같은 대다수의 소음 발생기계는 평판의 형상을 가진 구조물로서 기계적인 충격 등에 의해 그 표면에서 소음이 발생되므로 강성을 증가시키고, 소음저감을 목적으로 빔과 같은 보강재를 통해 보강되어 있다. 그런데, 해석적인 방법으로는 평판이나 원판 또는 구와 같은 단순한 형태의 특정구조물에 대해서만 그 결과를 얻을 수 있으므로 이와 같은 불연속 평판구조물의 진동 및 방사특성은 평판에 대한 순수 이론으로는 해석이 곤란하여 따라서 본 연구에서는 수치해석적인 방법을 통해 이를 해결하고자 하였다. 수치해석적인 방법으로는 유한요소법(FEM)과 경계요소법(BEM), 및 통계적 에너지 해석기법(SEA)등이 있으며 구조물의 진동-소음연성문제의 경우에 있어서는, 진동해석을 FEM과 SEA으로, 공기 중에서의 방사현상은 BEM으로 예측하고 있다. 본 연구에서는 재질이 균일한 얇은 2차원 평판구조와 보강평판에 대해서 진동특성은 유한요소해석 프로그램을 사용하여 해석하였으며 이때의 진동특성값을 입력데이터로 사용하여 경계요소해석 프로그램으로 방사효율 등을 예측하였다. 또한 이 과정에서 2차원 평판구조의 모우드 밀도와 가진점 모빌리티의 실수값이 가지는 평균치의 물리적 특성을 분석하였으며, 추후 실험을 통해 이를 검증코자 한다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.427-435
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• 2009

This study deals with the analytical solution for soil-lining interaction in a deep and circular tunnel. Simple closed-form analytical solutions for thrust and moment in the circular tunnel lining due to static and seismic loadings are developed by considering the relations between displacement and interaction forces at the soil-lining interface. The interaction effect at the soil-lining interface is considered with new ratios (the normal and shear stiffness ratios). The effects of the ratios on the normalized thrust and the normalized moment are investigated.

• The Journal of the Acoustical Society of Korea
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• v.26 no.5
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• pp.199-206
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• 2007

In this paper we propose a new clustering algorithm that performs clustering the feature vectors for the speaker identification. Unlike typical clustering approaches, the proposed method performs the clustering without the initial guesses of locations of the cluster centers and a priori information about the number of clusters. Cluster centers are obtained incrementally by adding one cluster center at a time through the boundary subtractive clustering algorithm. The number of clusters is obtained from investigating the mutual relationship between clusters. The experimental results for artificial datum and TIMIT DB show the effectiveness of the proposed algorithm as compared with the conventional methods.

• The Journal of the Acoustical Society of Korea
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• v.24 no.2
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• pp.117-126
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• 2005

This study investigates the prosodic characteristics of Korean through the analysis of a large database. One female and one male speakers each read 650 sentences and they were segmentally and prosodically labeled. Statistical analyses were done on these utterances regarding the tonal pattern and the size of prosodic units, correlation between the size of higher level prosodic units and the number of lower level prosodic units. and the slope and F0 of the falling and rising contours of an accentual phrase. The results showed that the duration and the number of words and syllables of a prosodic unit were significantly different not only between speakers but also between its positions within a higher level prosodic nit. The munber of a prosodic unit showed a high correlation with the duration and the number of syllables of its higher level units. The slope of the falling contour within an accentual phrase was inversely Proportional to the number of its syllables. The slope was different depending on the first tone type of an accentual phrase, which could be explained with the F0 rising and the different amount of rising between tones when an accentual phrase starts with an H tone. The slope of the falling contour across an accentual phrase boundary showed a constant and larger value compared to one within an accentual phrase. The rising contours in the beginning and end of an accentual Phrase were similar in their slopes but they differ in the amount of F0 change : the former showed a larger amount of change. The slope of the rising contour which forms an accentual Phrase on its own was inversely Proportional to the number of its syllables.