• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.3
• /
• pp.1-10
• /
• 1988

A higher order plate bending finite element using cubic in-plane displacement profiles is proposed for geometrically nonlinear analysis of thin and thick plates. The higher order plate bending element has been derived from the three dimensional plate-like continuum by discretization of the equations of motion by Galerkin weighted residual method, together with enforcing higher order plate assumptions. Total Lagrangian formulation has been used for geometrically nonlinear analysis of plates and consistent linearization by Newton-Raphson method has been performed to solve the nonlinear equations. The element characteristics have been computed by, selective reduced integration technique using Gauss quadrature to avoid shear locking phenomenon in case of extremely thin plates. Several numerical examples were solved with FEAP macro program to demonstrate versatility and accuracy of the present higher order plate bending element.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.3 no.1
• /
• pp.41-54
• /
• 1999

For free vibration of non-symmetric thin-walled circular arches including restrained warping effect, the elastic strain and kinetic energy is derived by introducing displacement fields of circular arches in which all displacement parameters are defined at the centroid axis. The cubic Hermitian polynomials are utilized as shape functions for development of the curved thin-walled beam element having eight degrees of freedom. Analytical solution for in-plane free vibration behaviors of simply supported thin-walled curved beams with monosymmetric cross-sections is newly derived. Also, a finite element formulation using two noded curved beams element is presented by evaluating elastic stiffness and mass matrices. In order to illustrate the accuracy and practical usefulness of this study, analytical and numerical solutions for free vibration of circular arches are presented and compared with solutions analyzed by the straight beam element and the ABAQUS's shell element.

• Journal of Navigation and Port Research
• /
• v.29 no.5 s.101
• /
• pp.403-408
• /
• 2005

The techniques of estimating angle of arrival(AOA) have played a key role for enhancement of wireless communications using array antennas. Among those techniques, the superresolution algorithms, such as MUSIC and ESPRIT, calculate the covariance matrix of the array output vectors which are observed at the array antennas, and then by using eigen-decomposition of the covariance matrix, they estimate AOAs of the received signals with high accuracy. However, superresolution algorithms based eigenvalue decomposition fails to estimate AOAs under multipath environments. Under multipath environments, it is difficult to estimate AOAs of the received signals due to coherency and high-correlation. To resolve coherent signals, the covariance matrix is calculated by using the conventional spatial smoothing technique, and then the techniques based on eigen-descomposition is applied. The result of the conventional spatial smoothing technique, however, is obtained at the cost of losing effective spatial aperture. Moreover, the conventional technique ignores any information in the cross-correlations of the array outputs the subarrays. As the result, the performance for AOA estimation is degraded. In this paper, we propose a new spatial smoothing technique, which consider the cross-correlation for subarrays. By computer simulation, the AOA estimation performance of the proposed method is compared with the conventional method and evaluated.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.3 s.36
• /
• pp.509-523
• /
• 1998

A consistent finite element formulation and analytic solutions are presented for stability of thin-walled circular arch. The total potential energy is derived by applying the principle of linearized virtual work and including second order terms of finite semitangential rotations. As a result, the energy functional corresponding to the semitangential moment is newly derived. Analytic solutions for the out-of-plane buckling of symmetric thin-walled curved beam subjected to pure bending or uniform compression with simply supported boundary conditions are obtained. For finite element analysis, the cubic Hermitian polynomials are utilized as shape functions and $16{\times}16$ stiffness matrix for curved beam elements and $14{\times}14$ stiffness matrix for straight beam elements are evaluated, respectively. In order to illustrate the accuracy of this study, analytical and numerical results for lateral buckling problems of circular arch are presented and compared with available analytical solutions.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.12 no.3
• /
• pp.495-508
• /
• 1999

변형된 라이저의 단위 접선벡터상의 운동학적 제약조건을 적용하여 심해저 라이저의 비선형 동적해석을 행한다. 이 조건의 적용으로 자유도수를 감소시킬 수 있으며 심한 비선형성으로 인한 해의 발산 가능성을 제거할 수 있다. 라이저의 거대변형으로 인한 기하학적 비선형성과 비선형 경계조건이 고려된다. 또한, 비선형성이 포함되는 수동학적 하중이 조류와 파랑에 의해 발생하여 내부에 정상류가 흐르는 라이저관의 외벽에 작용하게 된다. 이 외에도라이저 자체의 축방향 변형조건을 고려한다. Galerkin의 유한요소 근사화와 시간증분자를 적용하여 유한요소에 대한 평형 메트릭스 방정식을 유도하고, 수치해석을 위한 알고리즘을 제안하며 API 보고서의 결과와 비교함으로써 제안된 모델이 검증된다. 또한, 기하학적 비선형성으로 인한 영향을 조사하였다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2003.04c
• /
• pp.322-324
• /
• 2003

생체인식 기술은 현재까지 많은 발전을 거듭하고 있으며 국내에서도 연구는 물론 표준화작업 및 데이터 베이스 구축이 활발히 진행되고 있다. 생체인식은 신체의 여러 부분을 이용하는 방법과 습관에서 비롯된 특징을 이용하는 방법이 있는데, 본 연구에서는 이 중에서 개인의 필기습관 정보를 이용하여 인식하였다. 본 연구에서는 필기습관에 주목하여 서명하는 사람의 습관이 잘 드러나는 펜의 기울임과 눌림, 펜의 방위각도 둥의 성분이 표현되어지는 동적인 생채정보를 감지하고 특성을 추출할 수 있는 타블렛과 펜을 사용하여 서명정보를 추출한다. 이렇게 생성된 서명정보의 특징을 추출하기 위하여 패턴인식분야에 널리 활용하고 있는 주성분요소분석(PCA, Principal Component Analysis), 독립성분요소분석(ICA, Independent Component Analysis)기법에 적용하였다. 생성된 두 특징벡터 사이의 거리를 Euclidean Distance를 이용하여 구하고 Nearest Neighbor를 비교하여 인식률을 알아보고 교차인식(Cross Validation) 기법 중 하나인 Leave-One-Out 방법을 이용한 분류성능 측정을 통하여 데이터의 신뢰수준을 알아보았다.

• Annual Conference on Human and Language Technology
• /
• 2012.10a
• /
• pp.157-159
• /
• 2012

화자의 의도를 결정하는 문제는 대화 시스템에서 핵심적인 부분이다. 기존의 연구에서는 모델의 간소화를 위해 화자의 의도를 화행과 개념이라는 두 요소로 분리하여 분석하였다. 하지만 두 요소는 서로 밀접하게 관련되어 있기 때문에 모델의 간소화는 의도 분석 성능 저하의 원인이 되었다. 이런 문제점을 해결하기 위해 본 논문에서는 화자 의도 분류를 위한 재학습 방법을 제안한다. 제안된 방법은 화자의 의도를 분석하기 위해 화행 분류 모델과 개념열 분석 모델로 분리하여 분석한다. 학습 단계에서 화행 분류 모델은 개념열 분류 결과를 입력으로 사용하고 개념열 역시 마찬가지로 적용하였다. 목적 지항 대화를 대상으로 한 실험에서 제안된 시스템은 화자 의도 분류에서 최대엔트로피 모델과 지지 벡터 기계의 성능을 효과적으로 향상시켰다.

• Journal of the Korean Magnetics Society
• /
• v.7 no.3
• /
• pp.159-165
• /
• 1997

Recently, many researchers are interested in the analysis of the magnetic fields considering the vector relation between the magnetic flux density and the magnetic field intensity. In this paper, Finite Element Method with two dimensional tensor permeability is adopted to calculate the magnetic field quantities in the system having the rotational magnetic field. In addition, the method of analyzing the magnetic field considering the harmonic components is introduced. The validity of the proposed method is proved compared with the experimental results.

• 한국전산유체공학회:학술대회논문집
• /
• 2007.10a
• /
• pp.220-225
• /
• 2007

This paper is a continuation of the recent development on the hermite-based divergence free basis function and deals with a non-isothermal fluid flow thru the buoyancy driven flow in a square cavity with temperature difference across the two sides. The basis functions for the velocities consist of the hermite function and its curl. However, the basis for the temperature are the hermite function and its gradienst. Hence, the number of degrees of freedom at a node becomes 6, which are the stream function, two velocities, the temperature and its x- and y-derivatives. Numerical results for the streamlines, the temperatures, the x-velocities and the y-velocities show good agreements with those of De vahl Davis[7].

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.10 no.1
• /
• pp.16-22
• /
• 2001

In this study for reduction degree of freedom of dynamic model, a mixed method to combined finite element method and transfer matrix method is presented. This offers the advantages of an automatic reduction in the size of the eigenvalues problem and of a straightforward means of dynamic substructuring. The analytical procedure in this method for dynamic analysis of 3-dimensional cantilevered box beam are described. the result of numerical example is shown to demonstate the efficiency and accuracy of this method. The result form this example agree well those obtained by ANSYS, By using this technique, the number of nodes required in the regular finite element method is reduced and therefore a smaller com-puter can be used.