• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.2 no.4
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• pp.62-69
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• 1988

선형 시스템에 대한 Lyapunov 함수의 구성법은 잘 알려져 있으나, 비선형 시스템의 Lyapunov 함수 구성법은 아직 체계화되어 있지 못하다. 따라서, 본 논문에서는, 비선형 시스템의 안전도 해석을 위하여, 종래의 정상상태 부근에서 Taylor 전개에 의한 선형화 기법에 의존하지 않고, 비선형 시스템을 나타내는 상태공간의 활동성 모델로부터, 비선형성을 나타내는 항을 분리하여, 특수행렬변환시킴으로서, 선형 시스템의 Lyapunov 함수 구성법을 살린, 행렬다항식형 Lyapunov 함수를 구성하고, 이를 유도전동기의 안전도 해석에 적용시켰다. 그 결과, 구해진 안정영역은, 선형화에 의한 것보다는 훨씬 넓은 초공간으로 표현되는 유도전동기의 점근안정영역이 되었다.

• The Journal of the Acoustical Society of Korea
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• v.11 no.6
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• pp.15-22
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• 1992

i.i.d 신호의고차 모멘트와 스펙트럼의 성질에 대하여 4차까지 고찰하였으며 이의 결과를 이용하 여 2차 Volterra 급수로 표시되고, i.i.d. 입력 신호를 갖는 시불변 비선형 시스테므이 파라메타들을 추정 하는 알고리즘을 시간 영역과 주파수 영역에서 각각 제안하였다. 비록 2차 Volterra 급수가 i.i.d. 입력 신호에 대하여 orthogonal 모델이 아닐지라도 입력 신호의 각종 시간지연에 대한 모멘트나 역행렬의 계 산등이 요구되지 않으며 선형 전달함수와 2차 전달함수를 추정할 수 있는 알고리즘이 존재하는 것을 보 았다.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.163-165
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• 2008

본 논문에서는 유도전동기를 순시 토크제어하기 위한 방법으로 간접벡터제어를 사용하였고, 간접벡터제어를 통해 계산된 전압추종벡터를 NPC형 3-레벨 인버터의 SVPWM기법을 적용하여 구현하였다. SVPWM방식은 기존의 2레벨 인버터의 알고리즘을 응용하여 선형영역에서 과변조영역까지 선형적으로 전이 하도록 하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.45-51
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• 2002

The characteristics of nonlinear seismic behavior and failure mechanism of RC space frame in railroad viaducts have been studied by the numerical analysis in time domain. The structure concerned is modeled in 3 dimensional extent and the RC frame elements consisting of fibers are employed for the columns. The fibers are characterized as RC zone and PC one to distinguish the different energy release after cracking resulted from the bond characteristic between concrete and re-bar. Due to the deviation of the mass center and the stiffness center of the entire structure the complex behavior is shown under seismic actions. The excessive shear force is concentrated on the column beside flexible one relatively, which leads to the failure of bridge concerned.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.6
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• pp.472-480
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• 2009

This paper describes the overmodulative SVPWM technique and harmonics analyses of three phase NPC type three-level inverter to the modulation index. Three phase NPC type three-level inverter adopted SVPWM to extend the linear region to 0.907, moreover, the following voltage compensation using Fourier series was adopted in the region of overmodulation to make it work to six-step level. PD type of multi carrier method is used with the double Fourier series for the analysis of output power harmonics characteristic. Simulation was performed by PSIM, and the harmonics characteristics of 3-level inverter in each region are analyzed. The side band harmonics of carrier frequency are dominant in the linear region, but these harmonic components are decreased as the inveter goes to overmodulation region, and the harmonics due to the fundamental frequency is increased gradually at the same time. The harmonic analyses are verified through the simulation and experimental results under the same condition.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.11a
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• pp.562-564
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• 1998

보통 음향 신호를 분석을 할 때에 시간영역의 신호를 주파수영역의 신호로 FFT 변환을 해서 분석을 한다. 이렇게 단순히 FFT를 해서 주파수영역의 신호에서 어떤 특징적인 점을 찾기가 매우 어렵다. 그래서 원 신호를 FFT를 하지 않고 선형 예측 분석이라는 방법을 적용하여 신호에 특징적인 피크 점들을 구하면 쉬운 방법이 된다. 본 논문에서는 이러한 음향의 신호를 분석을 할 때에 선형 예측 분석법을 이용하면 신호에서 특징적인 피크들을 구하기가 용이함을 보이고 신호의 특징 피크 점들을 통계적으로 처리하여 분석을 해보았다.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.1-7
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• 2003

This paper presents a novel hybrid time-frequency-domain method for nonlinear soil-structure interaction(SSI) analysis. It employs, in a practical manner, a computer code for equivalent linear SSI analysis and a general-purpose nonlinear finite element program. The proposed method first (calculates dynamic responses on a truncated finite element boundary utilizing an equivalent linear SSI program in the frequency domain. Then, a general purpose nonlinear finite element program is employed to analyze the nonlinear SSI problem in the time domain, in which boundary conditions at the truncated boundary are imposed with the responses calculated in the previous frequency domain SSI analysis, In order to validate the proposed method, seismic response analyses are carried out for a 2-D underground subway station in a multi-layered half-space, For the analyses, a equivalent linear SSI code KIESSI-2D is coupled to ANSYS program. The numerical results indicate that the proposed methodology can be a viable solution for nonlinear SSI problems.

• The KIPS Transactions:PartA
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• v.11A no.3
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• pp.173-180
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• 2004

Quadtree, which 11 a hierarchical data structure, is a very important data structure to represent images. The linear quadtree representation as a way to store a quadtree is efficient to save space compared with other representations. Therefore, it has been widely studied to develop efficient algorithms to execute operations related to quadtrees. The region expansion is an operation to expand images by a given distance and the scaling If an operation to scale images by a given scale factor. In this paper, we present algorithms to perform the region expansion and scaling of images represented by quadtrees, using three-dimensional n${\times}$n${\times}$n processors on RMESH(Reconfigurable MESH). These algorithms have constant time complexities by using efficient basic operations to route the locational codes of quadtree on the hierarchical structure of n${\times}$n${\times}$n RMESH.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.1-12
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• 2010

This study presents a finite element analysis method that can accurately evaluate the nonlinear behaviour of structures affected by shallow soft subsoils and the soil-structure interaction. A two-dimensional finite element model that consists of a structure and shallow soft subsoil was used. The finite element model was used for a nonlinear time domain analysis of the OpenSees program. A parametric study was performed to investigate the effects of soil shear velocities, earthquake input motions, soft soil depth, and soil-structure interaction. The result of the proposed nonlinear finite element analysis method was compared with the result of an existing frequency domain analysis method, which is frequently used for addressing nonlinear soil behavior. The result showed that the frequency domain analysis, which uses equivalent secant soil stiffness and does not address the soil-structure interaction, significantly overestimated the response of the structures with short dynamic periods. The effect of the soil-structure interaction on the response spectrum did not significantly vary with the foundation dimensions and structure mass.

• 한국정보통신설비학회:학술대회논문집
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• 2004.08a
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• pp.50-53
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• 2004

진행파형 광 검출기의 흡수영역에 입사되는 광전력은 흡수계수의 비로써 흡수되어 광전류를 생성한다. 흡수계수는 입사되는 작은 광전력에 독립적이지만, 충분히 큰 광전력에 대해서는 비선형적 함수가 된다. 본 논문에서는 입사되는 광전력의 크기에 따라 흡수계수가 비선형적으로 변화하는 식을 광포화 현상을 포함하여 모델링 하였고, 모델링 한 식을 사용하여 흡수영역에서 생성된 광전류를 계산하였다. 포화흡수로 인해 생성된 광전류가 비선형 특성이 나타남을 모의실험으로 계산하였다. 위의 결과를 입력 광전력에 독립적인 흡수계수를 이용하여 계산한 광전류와 비교하였다. 그리고 입사되는 광전력에 따라 생성된 비선형적 광전류의 특성을 투-톤 실험을 통해 고조파 성분으로 계산하였다.