• Journal of Broadcast Engineering
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• v.13 no.2
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• pp.214-221
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• 2008

In this paper, we proposed a new mesh editing algorithm based on the motion between two sample meshes. First, the motion vectors are defined as the derivation vector of the corresponding vertices on the sample meshes. Then, the motion feature vectors are extracted between the motion vectors. The motion feature vectors represent the similarity of the vertex motion in a local mesh surface. When a mesh structure is forced by an external motion of anchor vertices, the deformed mesh geometry is obtained by minimizing the cost function with preserving the motion feature vectors. Simulation results demonstrated that the proposed algorithm yields visually pleasing editing results.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.6 s.46
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• pp.67-73
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• 2005

Precise analysis of soil-structure interaction requires a proper description of soil profile. However, such approach becomes generally nearly unpractical for soil exhibiting material discontinuity and complex geometry since meshes should match that material discontinuity line. To overcome these difficulties, a different numerical integration method is adopted in this paper, which enables to integrate easily over an element with material discontinuity without regenerating mesh fellowing the discontinuity line. As a result the mesh is highly structured, loading to very regular silliness matrix. The influence of the shape of soil profile on the response is examined and it is seen that the proposed soil-structure analysis method can be easily used on soil-structure interaction problems with complicated soil profile and produce reliable results regardless of material discontinuities.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.403-413
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• 2017

Residual axial capacity from numerical analysis was widely used as a critical indicator for damage assessment of reinforced concrete (RC) columns subjected to blast loads. However, the convergence of the numerical result was generally based on the displacement response, which might not necessarily generate the correct post-blast results in case that the strain softening behavior of concrete was considered. In this paper, two widely used concrete models are adopted for post-blast analysis of a RC column under blast loading, while the calculated results show a pathological mesh size dependence even though the displacement response is converged. As a consequence, a nonlocal integral formulation is implemented in a concrete damage model to ensure mesh size independent objectivity of the local and global responses. Two numerical examples, one to a RC column with strain softening response and the other one to a RC column with post-blast response, are conducted by the nonlocal damage model, and the results indicate that both the two cases obtain objective response in the post-peak stage.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.04a
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• pp.70-77
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• 1996

Recently many efforts have been made to improve the efficiency of design and production of the structures using the automation system. But, this work has been progressed as independent or partial system. And, the study on the integrated system is not sufficient in application for practical problems yet. This paper deals with the fundamental concept of modeling system and application method on structural modeling. At first, the core of the integrated system is a shape modeling system that can represent the geometric and topological information. This system must be designed as an open system to be combined with each independent automation system. The appropriate concept to realize this system on structural modeling is object oriented modeling and this enables to integrate each automation system successfully, This concept was applied to automatic mesh generation. For shape modeling system, half-edge data structure that is being used in solid modeling was modified to handle the plate structure in the plane. And, to generate the triangular meshes, direct node connection method was used. And, as a result, the integrated system that generate the meshes of two dimensional structure automatically was realized. And, programmed by C++, these systems can be combined with other systems easily and have good reusability.

• Structural Engineering and Mechanics
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• v.68 no.1
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• pp.17-38
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• 2018

In this paper, we compare and assess the performance of the standard 3- and 6-node MITC shell elements (Lee and Bathe 2004) with the recently developed MITC triangular elements (Lee et al. 2014, Jeon et al. 2014, Jun et al. 2018) which were based on the partitions of unity approximation, bubble node, or both. The convergence behavior of the shell elements are measured in well-known benchmark tests; four plane stress tests (mesh distortion test, cantilever beam, Cook's skew beam, and MacNeal beam), two plate tests (Morley's skew plate and circular plate), and six shell tests (curved beam, twisted beam, pinched cylinder, hemispherical shells with or without hole, and Scordelis-Lo roof). To precisely compare and evaluate the solution accuracy of the shell elements, different triangular mesh patterns and distorted element mesh are adopted in the benchmark problems. All shell finite elements considered pass the basic tests; namely, the isotropy, the patch, and the zero energy mode tests.

• The KIPS Transactions:PartC
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• v.8C no.4
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• pp.469-478
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• 2001

본 논문에서는 애드 혹 망을 위한 메쉬 기반 멀티캐스트 라우팅 프로토콜 중 하나인 CAMP(Core-Assisted Mesh Protocol)를 보완한 CATMP(Core-Assisted Thick Mesh Protocol)룰 제안한다. CAMP는 트리 구조를 사용하지 않으면서 데이터나 제어 패킷의 플러딩없이 라우팅 구조를 생성하는 유일한 프로토콜이다. 따라서 제어 패킷의 발생이 제한적이고 네트워크의 크기가 확장되어도 잘 적응할 수 있다. 그러나 CAMP는 메쉬의 중심부보다 가장자리가 연결성이 떨어지기 때문에 그룹 멤버의 수가 적은 경우나 멀리 떨어진 위치에 존재하는 그룹 멤버가 있는 경우 데이터 전달율이 저하된다. CATMP에서는 이를 보완하기 위해 메쉬의 연결 정도가 낮은 지역에서도 이웃의 참여를 유도하여 연결 정도를 높여줌으로써 결과적으로 전체 메쉬가 좀 더 균일하게 형성되도록 한다. 시뮬레이션을 통해 CAMP와 CATMP의 성능을 비교한 결과 CAMP의 성능이 저하되는 상황에서 CATMP가 성능을 향상시킬 수 있음을 볼 수 있었다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.168-175
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• 1996

This paper deals with the variable-node element for fluid flow and the adaptive h-version mesh refinement algorithm. The transient element has been formulated by the Galerkin approach in which the pressure term is replaced with the penalty function. The present element having variable mid-side node and is suitable for constructing a locally refined mesh avoiding the use of the highly distorted elements. A modified Gauss quadrature is needed to integrate the element matrices to solve the trouble associated with the discontinuity of derivatives of shape functions. Several numerical examples show that the proposed element can be effectively used in the h-version adapt ive mesh refinement

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.267-271
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• 2000

The local heat transfer rate of an axisymmetric submerged air jet impinging on normal to a heated flat plate was investigated experimentally with varying solidity of mesh screen. The mean velocity and turbulent Intensity profiles of streamwise velocity component were measured using a hot-wire anemometry. The temperature distribution on the heated flat surface was measured with thermocouples. The screen installed in front of the nozzle exit(behind of 35mm) modify the jet flow structure and local heat transfer characteristics. For higher solidity screen, turbulence intensity at core lesion is high and increases the local heat transfer rate at nozzle-to-plate spacings(L/D<6). For larger nozzle-to-plate spacings(L/D>6), however, the turbulent Intensities of all screens tested in this study approach to an asymptotic curve, but the small mean velocity at the core region reduces the local heat transfer rate for high solidity screens.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.1207-1210
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• 2022

2D 이미지로부터 카메라의 위치 정보를 추정할 수 있는 Structure-from-Motion (SfM) 기술과 dense depth map 을 추정하는 Multi-view Stereo (MVS) 기술을 이용하여 2D 이미지에서 point cloud 와 같은 3D data 를 얻을 수 있다. 3D data 는 VR, AR, 메타버스와 같은 컨텐츠에 사용되기 위한 핵심 요소이다. Point cloud 는 보통 VR, AR, 메타버스와 같은 많은 분야에 이용되기 위해 mesh 형태로 변환된 후 texture 를 입히는 Texturing 과정이 필요하다. 기존의 Texturing 방법에서는 mesh의 face에 사용될 image의 outlier를 제거하기 위해 color 정보만을 이용했다. Color 정보를 이용하는 방법은 mesh 의 face 에 대응되는 image 의 수가 충분히 많고 움직이는 물체에 대한 outlier 에는 효과적이지만 image 의 수가 부족한 경우와 부정확한 카메라 파라미터에 대한 outlier 에는 부족한 성능을 보인다. 본 논문에서는 Texturing 과정의 view selection 에서 depth 정보를 추가로 이용하여 기존 방법의 단점을 보완할 수 있는 방법을 제안한다.

• Journal of Institute of Convergence Technology
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• v.10 no.1
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• pp.7-12
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• 2020

We describe a efficient surface reconstruction method that reconstructs a 3D manifold polygonal mesh approximately passing through a set of 3D oriented points. Our algorithm includes 3D convex hull, octree data structure, signed distance function (SDF), and marching cubes. The 3D convex hull provides us with a fast computation of SDF, octree structure allows us to compute a minimal distance for SDF, and marching cubes lead to iso-surface generation with SDF. Our approach gives us flexibility in the choice of the resolution of the reconstructed surface, and it also enables to use on low-level PCs with minimal peak memory usage. Experimenting with publicly available scan data shows that we can reconstruct a polygonal mesh from point cloud of sizes varying from 10,000 ~ 1,000,000 in about 1~60 seconds.