• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.3
• /
• pp.305-319
• /
• 2000

Numerical solution lot frictional contact problems of nonlinearly deformable bodies having large deformation is presented. The contact conditions on the possible contact points are expressed by using the contact error vector, and the iterative scheme is used to reduce the contact error vector monotonically toward zero. At each iteration the solution consists of two steps : The first step is to revise the contact force by using the contact error vector given by the previous geometry, and the second step is to compute the displacement and the contact error vector by solving the equilibrium equation with the contact force given at the first step. Convergence of the iterative scheme to the correct solution is analyzed, and the numerical simulations we performed with a rigid-plastic membrane and a nonlinear elastic beam.

• Journal of Power System Engineering
• /
• v.7 no.4
• /
• pp.49-54
• /
• 2003

스프링은 가장 널리 이용되어지고 있는 기계요소이다. 본 논문에서는 원추형 코일스프링의 강성을 구하기 위하여, 빔요소를 이용한 유한요소법을 사용하였다. 가상일의 법칙을 이용하였고, 코일스프링의 하중벡터를 압축 분포하중으로 대체하였다. 하중의 증가에 의한 절점에서의 변위는 유한요소법를 이용하여 계산하였다. 단계법으로 결점의 변위를 중첩하여 전체 강성행렬을 구하였다. 유한요소법에 의한 해석치는 실험치와 잘 일치하였다. 본 논문에서 제시한 프로그램을 사용하여, 스프링 강성과 응력을 예측할 수 있을 것으로 사료된다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.19 no.3
• /
• pp.237-244
• /
• 2001

On this study, a 50-years-old earth dam was measured by the static method of GPS for deformation monitoring. The reference network was measured by the vector between points in twice times and the monitored points were observed in four times at test field, i.e. an embankment which was restored by mortar, In addition, gross errors in the measurement were estimated and eliminated by data snooping method and random errors were adjusted by least square method. Finally, the amount of displacement was estimated from variance-covariance matrix. Also, precision of points were showed by the confidence ellipse(95%), and the amount of displacement was figured.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2010.04a
• /
• pp.192-195
• /
• 2010

본 논문에서는 해상 크레인과 중량물의 동적 거동을 시뮬레이션하기 위해, 유한 요소 정식화(finite element formulation)를 이용하여 해상 크레인의 붐(boom)을 탄성체로 모델링 하였다. 붐은 3차원 탄성 빔(beam) 요소로 가정하고, 각 요소의 변형에 의한 변위는 형상 함수(shape function)과 절점 좌표(nodal coordinate)를 이용하여 정의하였다. 변형 변위를 이용하여 탄성 붐의 강성 행렬(stiffnes matrix)을 유도하고, 탄성 변위를 포함하는 위치 벡터를 이용하여 질량 행렬을 유도한다. 해상 크레인과 중량물로 이루어진 운동 방정식에 탄성 붐을 포함하여 유연 다물체계(flexible multibody system) 운동 방정식을 구성한다. 외력으로는 선박 유체정역학적 힘, 유체동역학적 힘, wire rope의 장력, 중력 그리고 계류력(mooring force)이 고려되었다. 먼저 요소의 개수를 변경하며 탄성 붐의 동적 거동을 시뮬레이션 하여, 유한 요소 정식화를 이용한 모델링의 타당성을 검증하였다. 그리고 해상 크레인과 중량물의 동적 거동 시뮬레이션에 탄성 붐 모델을 적용하였다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2006.11a
• /
• pp.295-298
• /
• 2006

본 논문에서는 극 좌표계에서의 벡터 표현 방식을 이용한 per-pixel displacement mapping 방법을 제시한다. per-pixel displacement mapping은 triangle mesh의 처리 방식에 상관없이 변위매핑을 수행할 수 있도록 한 것으로, 2차원 screen space로 projection 된 triangle의 각 pixel의 위치를 객체 표면 정보에 따라 displacement 해주는 방법이다. 이는 기 검증된 범프매칭 하드웨어에 약간의 하드웨어를 추가함으로써 변위매핑을 수행할 수 있도록 한 효과적인 구조이다. 제안 방식에 의해 생성된 영상과 기존 방식에 의해 생성된 영상을 비교해본 결과, 시각적으로 거의 차이가 없음을 알 수 있다.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2011.10a
• /
• pp.45-47
• /
• 2011

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.6
• /
• pp.71-80
• /
• 2003

Though a nonlinear time history analysis may be provided to estimate more exactly the seismic performance of building structure, approximation methods are still needed in the aspect of practicality and simplicity, In converting a multi-story structure to an equivalent SDOF system, the mode vectors of the multi-story structure are assumed as the mode shape in elastic state regardless of elastic or elastic-plastic state. However, the characteristics of displacement mode are also changed after the yielding made in the structural elements, because the structure becomes inelastic in each incremental load step. In this research, a method of converting MDOF system to ESDOF system is presented by using nonlinear displacement mode considering the mode change of structures after the yielding. Also, the accuracy and efficiency of the method of the nonlinear displacement mode method of the estimate of seismic response of Mixed Building Structures were examined by comparing the displacements of the roof level of the multi-story building structures estimated from this converted displacement response of ESDOF with the displacement of the roof level through the nonlinear dynamic analysis of the multi-story building structures subjected to an actual earthquake excitation.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.12
• /
• pp.2287-2297
• /
• 1992

The Formulation of a new Hermite straight beam element to eliminate the shear locking is presented. All the kinematic variables in Timoshenko beam are reinterpreted by the consideration of equilibrium equations together. It shows that when the modified transverse displacement field is used the Timoshenko beam looks apparently the same as the Euler beam. The element is formulated for the modified transverse displacement field to have the same interpolation scheme as that in the Hermite element. Transformation Matrix which relates a modified nodal vector with nonmodified one is also introduced to deal with general boundary conditions. Several examples are demonstrated and discussed for the purpose of verification of the concepts employed. The solutions obtained reveal that the element describes of the beam quite correctly, showing no locking and that it is also applicable to the analysis of both thin and thick beams.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.1C
• /
• pp.47-55
• /
• 2003

This paper proposes a composition method of mosaic image from the compressed MPEG-2 video stream, in which the displacement between successive frames according to the camera operation is estimated directly from the information involved in the stream. In the proposed method. the approximated optical flow is constructed from motion vectors of macro blocks, and it is used to determine the parameters of the displacements according to the camera operation associated with pan and tilt. The extracted parameters are used to determine the geometric transform of successive video frames in order to construct a mosaic image. The construction of mosaic uses several blending techniques including the one proposed by Nichols in which an analytic weight is used to determine pixel values. Through the experiment, the blending technique based on analytic weights was superior to the others such as averaging and median-based techniques. It provided more smooth changes in background and made use of instantaneous frame information to construct a mosaic. The mosaic in the paper puts the emphasis on the reduction of computation because it is constructed from the motion vectors included in the compressed video without decoding and recalculating exact optical flows. The constructed mosaic can be used in the retrieval of the compressed video as the representative frame of a shot.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.27 no.4
• /
• pp.303-312
• /
• 1991

This paper describes the general formulation for the in-plane flexural free vibration analysis of two layered structure by the transfer influence coefficient method. The structure is regared as a distributed mass system with lumped mass and inertia moments, massless linear and rotational springs, and joints elements of releases and rolls at which the displacements are discontinuous in each layer. The results of the simple numerical examples on a personal computer demonstrate the validity of the present method, that is, the numerical high accuracy, the high speed, the flexibility for programming of the present algorithm, compared with the transfer matrix method.