• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.109.1-109.1
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• 2010

파랑의 거동을 해석하기 위해 몇 십 년 동안 많은 연구들이 진행되었다. 그 중에서 해석적인 방법으로 축대칭 지형과 같은 간단한 지형을 지나는 파랑의 변형을 예측하는 것은 실험에 의한 방법에 비해 시간적, 비용적인 측면에서 유리하다. 또한 수치기법에 의한 오차를 발생하지 않기 때문에 보다 정확한 해를 구할 수 있다는 장점이 있다. 그러나 단일주기, 단일방향에 대한 가정을 거치기 때문에 실제 해역에서의 복잡한 파랑 변형을 예측하는데 한계가 있다. 고유함수전개법을 축 대칭 지형에 적용시키는 연구는 Bender and Dean(2005)에 의해 제시되었으며, 본 연구에서는 이것을 발전시켜 다방향 불규칙파에 대한 파랑 변형을 모의하였다. 그리고 결과를 단일주기에 의한 규칙파와 비교하여 그 특성을 알아보았다.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.671-674
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• 2013

단순전력분석(Simple Power Analysis, SPA)은 적은 수의 평문으로 암호 알고리즘에 대한 패턴 뿐만 아니라 비밀키의 정보를 찾는 전력 분석(Power Analysis)의 방법 중 하나이다. SPA의 장점은 차분전력분석(Differential Power Analysis, DPA) 또는 상관전력분석(Correlation Power Analysis, CPA)보다 적은 계산량으로 비밀키 분석을 할 수 있고, DPA 또는 CPA 분석을 하기 위해 필요한 분석위치 탐지에 효율적으로 활용이 되어 진다는 것이다. 하지만 최근 SPA 분석 성능을 저하시키기 위해 클락 노이즈, 전력 노이즈, 딜레이 노이즈 등 다양한 방법들이 제안되어지고 있다. 본 논문에서는 다양한 노이즈가 있는 환경에서 아날로그 수신기를 활용하여 특정 주파수 영역을 필터링한 후 노이즈를 제거하는 방법을 소개한다. 실험을 통해, 아날로그 수신기를 사용하였을 경우에 사용하지 않았을 경우보다 뚜렷한 대칭키 암호의 라운드 함수가 구분되어지며, 라운드 내 함수 구분도 가능함을 보인다. 이는 DPA 또는 CPA를 이용하여 분석을 수행하고자 할 때 분석 위치를 결정하데 아주 유용하게 활용되어지며, 분석 성능향상에도 기여할 것으로 기대되어진다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.8
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• pp.61-67
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• 2010

A characterization procedure for analyzing symmetric coupled MIS(Metal-Insulator-Semiconductor) transmission line is used the same procedure as a general single layer symmetric coupled line with perfect dielectric substrate from the extraction of the characteristic impedance and propagation constant for even- and odd-mode. In this paper, an analysis for a new substrate shielding symmetric coupled MIS structure consisting of grounded crossbar at the interface between Si and SiO2 layer using the Finite-Difference Time-Domain (FDTD) method is presented. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded crossbar lines over time-domain signal has been examined. Symmetric coupled MIS transmission line parameters for even- and odd-mode are investigated as the functions of frequency, and the extracted distributed frequency-dependent transmission line parameters and corresponding equivalent circuit parameters as well as quality factor for the new MIS crossbar embedded structure are also presented. It is shown that the quality factor of the symmetric coupled transmission line can be improved without significant change in the characteristic impedance and effective dielectric constant.

• Journal of the Korea Computer Graphics Society
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• v.2 no.1
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• pp.31-38
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• 1996

Many efforts for finding smooth curves and surfaces satisfying given constraints have been made, and interpolation and approximation theories with the help of computers have played an important role in this endeavour. Most research in curve and surface modeling has been largely dominated by the theory of parametric representations. While they have been successfully used in representing physical objects, parametric surfaces are confronted with some problems when objects are represented and manipulated in geometric modeling systems. In recent year, increasing attention has been paid to implicit algebraic surfaces since they are often more effective than parametric surfaces are. In this paper, we summarize the geometric properties and computational processes of objects represented using implicit algebraic functions and explain of the implementation of design tools which can design curves and surfaces of revolution. These surfaces of revolution are played an importance role in effective areas such as CAD and CAM.

• Journal of Navigation and Port Research
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• v.28 no.3
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• pp.227-232
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• 2004

Vehicle dynamics control systems are complex and non-linear, so they have difficulties in developing a controller for the anti-lock braking systems and the auto-traction systems. Currently the fuzzy-logic technique to estimate the absolute vehicle speed supplies good results in normal conditions. But the estimation error in severe braking is discontented In this paper, we estimate the absolute vehicle speed of UCT(Unmanned Container Transporter) by using the wheel speed data from standard anti-lock braking system wheel speed sensors. Radial symmetric basis function of the neural network model is proposed to implement and estimate the absolute vehicle speed, and principal component analysis on input data is used 10 algorithms are verified experimentally to estimate the absolute vehicle speed and one of them is perfectly shown to estimate the vehicle speed within 4％ error during a braking maneuver.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.5
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• pp.411-420
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• 2009

This study presents an extended finite difference method based on moving least squares(MLS) method for solving potential problems with interfacial boundary. The approximation constructed from the MLS Taylor polynomial is modified by inserting of wedge functions for the interface modeling. Governing equations are node-wisely discretized without involving element or grid; immersion of interfacial condition into the approximation circumvents numerical difficulties owing to geometrical modeling of interface. Interface modeling introduces no additional unknowns in the system of equations but makes the system overdetermined. So, the numbers of unknowns and equations are equalized by the symmetrization of the stiffness matrix. Increase in computational effort is the trade-off for ease of interface modeling. Numerical results clearly show that the developed numerical scheme sharply describes the wedge behavior as well as jumps and efficiently and accurately solves potential problems with interface.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.119-122
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• 2004

G.723.1은 저 전송률 환경에서 고 음질을 제공하여 주고 있으나 CELP형 부호화기가 갖는 합성에 의한 분석(Analysis by Synthesis)방식의 구조로 인해 많은 처리 시간과 계산량을 요구하게 된다. 본 논문에서는 G.723.1에 대해 NAMDF함수를 적용하여 델타 피치 검색과정의 계산량을 줄여 부호화기의 전체 계산량을 감소시키는 방법을 제안하였다. 기존의 피치 검출 알고리즘에서 피치 검출을 위해 사용하고 있는 자기상관함수는 곱셈 연산에서 발생하는 bit의 dynamic range가 커서 나눗셈 연산에서도 과도한 연산량을 필요로 한다. 따라서, 이러한 계산량의 감소를 위해 기존의 자기상관함수 대신 계산량을 감소하기 위하여 NAMDF 방법을 적용하였고 추가된 skipping 기법을 사용하였다. 계산량 감소율 측면에서는 약 $64\%$의 감소율을 보였고 기존의 방법과 제안한 방법간의 피치 pitch contour은 원음성의 피치 contour와 유사하였고, 음질 평가에서도 기존의 G.723.1 부호화기 합성음과 유사한 길과를 얻을 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.31-39
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• 1985

Using the tensor elastic Green functions an exact integral equation is formulated for two anisotropic precipitates embedded in an infinite anisotropic matrix; the matrix is subjected to an applied strain field or the precipitates undergo a stress-free transformation strain. This equation is reduced to an infinite system of algebraic equations by expanding the strains in Taylor series about the two points within each precipitate, and an approximation of the strain distributions within the two spherical precipitates is obtained by truncating the higher order terms. Since the present method requires no symmetry conditio between the two shperical precipitates, it is possible to obtain the strain distribution within the precipitates when the elastic constants and/or the sizes of the precipitates are different each other. The strains are expanded about arbitrary points, giving more accurate distributions of the strains than those presented elsewhere. The present method can be directly estended to the case of more than two spherical precipitates.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.6
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• pp.3-13
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• 2004

Kvarnstrom et al. ${in}^{[10]}$ proposed a rule protection scheme by using one-way hash function to protect rules in security systems over ubiquitous environment. Son et at. ${in}^{[5-6]}$ also prooposed a rule protection scheme for Snort, which is one of the most common IDS. These schemes provide security only for the header information but not for its contents. To solve this problem, this paper presents a scheme based on the symmetric cryptosystem over Snort not only for the header information but also contents. This paper uses the key management based on PCMCIA security module proposed ${by}^{[12]}$ for the symmetric cryptosystem. Our scheme could be adjusted to other security systems, which use the rule based detection.

• Journal of the Korean Chemical Society
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• v.28 no.1
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• pp.34-40
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• 1984

The reorientational motion of $C_6F_6$ in neat liquid is investigated in the temperature range 293∼333K by analyzing ${\nu}_2$ and ${\nu}_16$ bands of its Raman spectrum. Diffusion constants for the tumbling ($D_{\bo}$) and spinning ($D_{\parallel}$) motions are determined. The reorientation of the molecule seems to be distinctly anisotropic. Based on the hydrodynamic model, the tumbling motion of the figure axis of $C_6F_6$ is largely diffusional. On the other hand, the spinning motion of the same axis looks mostly inertial.