• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.745-749
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• 2001

The rigid body properties of a structure may be estimated easily if the mass-line of the structure could be taken exactly. However, the exact mass-line cannot be obtained experimentally. In the past years, the modal analysis for which the structure is mounted on the flexible supporter is frequently used to acquire the mass-line. Unfortunately, it is difficult not only to mount the structure but also to decouple the coupled 6 dof mode. If the structure is pended by very long and flexible rope to act free, the rigid-body modes influenced by the rope will be eliminated and the improved mass-line will be obtained. In this paper, the method using the mass-line of F.R.F. for rigid body in free-condition is suggested. The robustness of the suggested method was tested and verified numerically. The experimental results also showed a good agreement with the true value.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.259-266
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• 2003

Non-rigid registration between different modality images with shape deformation can be used to diagnosis and study for inter-patient image registration, longitudinal intra-patient registration, and registration between a patient image and an atlas image. This paper proposes a hierarchical registration method using bodily tissue based segmentation for registration between color images and CT images of the Visible Human leg areas. The cross-sectional color images and the axial CT images are segmented into three distinctive bodily tissue regions, respectively: fat, muscle, and bone. Each region is separately registered hierarchically. Bounding boxes containing bodily tissue regions in different modalities are initially registered. Then, boundaries of the regions are globally registered within range of searching space. Local boundary segments of the regions are further registered for non-rigid registration of the sampled boundary points. Non-rigid registration parameters for the un-sampled points are interpolated linearly. Such hierarchical approach enables the method to register images efficiently. Moreover, registration of visibly distinct bodily tissue regions provides accurate and robust result in region boundaries and inside the regions.

• Journal of Institute of Convergence Technology
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• v.10 no.1
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• pp.41-45
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• 2020

This paper presents the effects of a virtual mass on the stability boundary of a virtual spring in the haptic system with first-order-hold. The virtual rigid body is modeled as a virtual spring and a virtual mass. When first-order-hold is applied, we analyze the stability boundary of the virtual spring through the simulation according to the virtual mass and the sampling time. As the virtual mass increases, the stability boundary of the virtual spring gradually increases and then decreases after reaching the maximum value. The results are compared with the stability boundary in the haptic system with zero-order-hold. When a virtual mass is small, the stability boundary of a virtual spring in the system with first-order-hold is larger than that in the system with zero-order-hold.

• Communications of the Korean Mathematical Society
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• v.15 no.1
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• pp.173-181
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• 2000

The objective of this paper is to study two dimensional steady gravitational waves on the interface between two immiscible, inviscid and incompressible fluids bounded above by a horizontal rigid boundary and below by a rigid step. A KdV equation for the first order perturbation in an asymptotic expansion can appear. However the coefficient of the KdV theory fails in that case. By a unified asymptotic method, we overcome this difficulty and derive a modified KdV equation with forcing. We find homogeneous steady solutions and present numerical solutions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1092-1103
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• 1989

본 논문에서는 기존의 금속성형의 유한요소해석에서 사용한 바 있는 기하적경 계조건을 직접 유한요소방정식에 대입하는 방법들을 비교검토하고 3차원박판성형에 적용하기 위하여 개선된 방법을 개발하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.1
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• pp.17-31
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• 2002

The new MPEG-4 video coding standard enables content-based functionalities. Image segmentation is an indispensable process for it. This paper addresses an effective segmentation of non-rigid objects. Non-rigid objects are deformable objects with fuzzy, blurred and indefinite boundaries. So it is difficult to segment deformable objects precisely. In order to solve this problem, we propose an effective segmentation of non-rigid objects using watershed algorithms in still pictures. And we propose an automatic segmentation through intra-frame and inter-frame segmentation process in video sequences. Automatic segmentation preforms boundary-based and region-based segmentation to extract precise object boundaries.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.926-927
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• 2005

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.135-143
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• 1990

Based on the mechanism of flat jack used to measure stresses in rocks, a prerssure gauge was developed to measure vertical stresses acting on the rigid boundary in a soil mass. This paper describes the mechanism of the newly built pressure gauge, the process of calibrating the response of this gauge, and its use to centrifugal model tests. By installing this gauge in centrifugal model experiments of reinforced earth retaining walls, vertical stress distribution at the rigid boundary of model wall was obtained and compared with theoretical prediction of trapezoidal vertical stress distribution.

• Computational Structural Engineering
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• v.10 no.2
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• pp.131-138
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• 1997

This paper concerns the stress singularity at the interface corner of the viscoelastic adhesive layer bonded between rigid adherends, subjected to a uniform transverse tensile strain. The characteristic equation is derived in the Laplace transformed space, following Williams, and the transformed characteristic equation is inverted analytically into real time space for the viscoelastic model considered here. The order of the singularity is obtained numerically. The time-domain boundary element method is employed to investigate the nature of stresses along the interface. Numerical results show that the order of the singularity increases with time while the free-edge stress intensity factors are relaxed with time.

• Transactions of Materials Processing
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• v.11 no.5
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• pp.439-446
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• 2002

This study presents a new computational model to analyze the grain deformation in a polycrystalline aggregate in a discrete manner and based directly in the underlying physical micro-mechanisms. When scaling down a metal forming process, the dimensions of the workpiece decrease but the microstructure of the workpiece remains the similar. Since the dimensions of the workpiece are very small, the microstructure especially the grain size will play an important role in micro forming, which is called size effects. As a result, specific characteristics have to be considered for the numerical analysis. The grains and grain boundary elements are introduced to model individual grains and grain boundary facets, respectively, to consider the size effects in the micro forming. The constitutive description of the grain elements accounts for the rigid-plastic and the grain boundary elements for visco-elastic relationships. The capability of the proposed approach is demonstrated through application of grain element and grain boundary element in the micro forming.