• Journal of the Korean Institute of Intelligent Systems
• /
• v.18 no.1
• /
• pp.122-126
• /
• 2008

Integrating a 3D solid modeler with a general purpose FEM code, an automatic stress intensity factor analysis system of the 3D crack problems has been developed. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated and quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. Finally, the complete finite element(FE) model generated, and a stress analysis is performed. This paper describes the methodologies to realize such functions, and demonstrates the validity of the present system.

• Journal of Biomedical Engineering Research
• /
• v.25 no.6
• /
• pp.537-543
• /
• 2004

In order to create three-dimensional model for human body, a method that reconstructs geometric models from contour lines on cross-section images is commonly used. We can get a set of contour lines by acquiring CT or MR images and segmenting anatomical structures. Previously proposed method divides entire contour line into simply matched regions and clefts. Since long processing time is required for reconstructing cleft regions, its performance might be degraded when manipulating complex data such as cross-sections for human body. In this paper, we propose a fast reconstruction method. It generates a triangle strip with single tiling operation for simple region that does not contain branch structures. If there exist branches in contour lines, it partitions the contour line into several sub-contours by considering the number of vertices and their spatial distribution. We implemented an automatic surface reconstruction system by using our method which reconstructs three-dimensional models for anatomical structures.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.46 no.6
• /
• pp.43-57
• /
• 2009

Integrating 3D data acquired in multiple views is one of the most important techniques in 3D modeling. However, the existing integration methods are sensitive to registration errors and surface scanning noise. In this paper, we propose a integration algorithm using the local surface topology. We first find all boundary vertex pairs satisfying a prescribed geometric condition in the areas between neighboring surfaces, and then separates areas to several regions by using boundary vertex pairs. We next compute best fitting planes suitable to each regions through PCA(Principal Component Analysis). They are used to produce triangles that be inserted into empty areas between neighboring surfaces. Since each regions between neighboring surfaces can be integrated by using local surface topology, a proposed method is robust to registration errors and surface scanning noise. We also propose a method integrating of textures by using parameterization technique. We first transforms integrated surface into initial viewpoints of each surfaces. We then project each textures to transformed integrated surface. They will be then assigned into parameter domain for integrated surface and be integrated according to the seaming lines for surfaces. Experimental results show that the proposed method is efficient to face modeling.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.20 no.1
• /
• pp.152-161
• /
• 2017

Making precise 3D maps using Mobile Mapping System (MMS) sensors are essential for the development of self-driving cars. This paper conducts research on the extraction of 3D objects around the roads using the point cloud acquired by the MMS Light Detection and Ranging (LiDAR) sensor through the following steps. First, the digital surface model (DSM) is generated using MMS LiDAR data, and then the slope map is generated from the DSM. Next, the 3D objects around the roads are identified using the slope information. Finally, 97% of the 3D objects around the roads are extracted using the morphological filtering technique. This research contributes a plan for the application of automated driving technology by extracting the 3D objects around the roads using spatial information data acquired by the MMS sensor.

• Journal of the Korean Institute of Gas
• /
• v.4 no.4 s.12
• /
• pp.25-33
• /
• 2000

In recent years, the subject of remaining life assessment has drawn considerable attention in power plants, where various structural components typically operate at high temperature and pressure. Thus a life prediction methodology accounting for high temperature creep fracture is increasingly needed for the components. Critical defects in such structures are generally found in the form of semi-elliptical surface crack, and the analysis of which is consequently an important problem in engineering fracture mechanics. On this background, we first develop an auto mesh generation program for detailed 3-D finite element analyses of axial and circumferential semi-elliptical surface cracks in a piping system. A high temperature creep fracture parameter $C^{\ast}$-integral is obtained from the finite element analyses of generated 3-D models. Post crack growth module is further appended here to calculate the amount of crack growth. Finally the remaining lives of surface cracked pipes for various analytical parameters are assessed using the developed life assessment program.

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.04a
• /
• pp.221-222
• /
• 2003

고분자 용액의 전기방사(electrospinning)는 수 nm ~ 수천 nm 크기 초극세 섬유의 제조가 가능하고 섬유의 생성과 동시에 3차원의 망상구조로 적층된 형태로 제조가 가능하다. 이는 섬유가 가늘어질수록 부피대비 표면적이 넓어질 뿐만 아니라 고분자 사슬이 갖고 있는 기능성 작용기의 상당수가 표면에 노출된다. 이는 작용기의 함량이 크게 증가하는 것을 의미하며, 직경이 굵은 섬유에서 찾아볼 수 없는 새로운 특성이 예측된다. 나노섬유 소재기술은 기존 범용 섬유소재의 성능 한계성을 극복하는 신기술 및 신소재 창출에 크게 기여할 것으로 기대되고 있다. (중략)

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.26 no.3
• /
• pp.311-320
• /
• 2008

A LIDAR can rapidly generate 3D points by densely sampling the surfaces of targets using laser pulses, which has been efficiently utilized to reconstruct 3D models of the targets automatically. Due to this advantage, LIDARs are increasingly applied to the fields of Defense and Security, for examples, being employed to intelligently guided missiles and manned/unmanned reconnaissance planes. For the prior verification of the LIDAR applicability, this study aims at generating simulated LIDAR data. Here, we derived the sensor equation by modelling the geometric relationships between the LIDAR sub-modules, such as GPS, IMU, LS and the systematic errors associated with them. Based on this equation, we developed a program to generate simulated data with the system parameters, the systematic errors, the flight trajectories and attitudes, and the reference terrain model given. This program had been applied to generating simulated LIDAR data for urban areas. By analyzing these simulated data, we verified the accuracy and usefulness of the simulation. The simulator developed in this study will provide economically various test data required for the development of application algorithms and contribute to the optimal establishment of the flight and system parameters.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.35 no.3
• /
• pp.155-166
• /
• 2017

As the utilization of aerial images increases, a variety of software using unmanned aerial photogrammetric procedures as well as traditional aerial photogrammetric procedures are being provided. Previously, software that used the unmanned aerial photogrammetric procedure was used for images captured in small areas. Recently, however, software that uses unmanned aerial photogrammetric procedures for large-scale images taken by using aerial photogrammetric cameras has appeared. Therefore, this study generated ortho-images using aerial photogrammetry and unmanned aerial photogrammetry for large aerial images, and compared the features of both procedures through qualitative and quantitative comparisons. Experiments in the study area show that using the 3D mesh effectively removes the relief displacement of the building rather than using the digital surface model to generate ortho-images.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.8
• /
• pp.3295-3300
• /
• 2012

Three Dimensional finite element method (FEM) was used to obtain the stress intensity factor for subsurface cracks and surface cracks existing in inhomogeneous materials. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model. Nodes are generated by the bubble packing, and ten-noded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. To examine accuracy and efficiency of the present system, the stress intensity factor for a semi-elliptical surface crack in a plate subjected to uniform tension is calculated, and compared with Raju-Newman's solutions. Then the system is applied to analyze interaction effects of two dissimilar semi-elliptical cracks in a plate subjected to uniform tension.

• Journal of Korea Water Resources Association
• /
• v.55 no.1
• /
• pp.33-42
• /
• 2022

In this study, flow patterns in the ice-harbor fishway were analyzed according to fluctuations of the upstream water level, an increase of weir interval, and the presence or absence of orifices using a three-dimensional commercial numerical model, Flow-3D. In order to prove the suitability of the numerical simulation results, the flow velocity and flow rate at the exit of the fishway were observed using a 3D ultrasonic velocimetry on an actual ice-harbor fishway installed downstream of the Daegok bridge in Gyeongan-Cheon. Four types of turbulence modules can be selected for the Flow-3D model. As a result of verification with observation data, the RNG model best described the flow characteristics in the ice-harbor fishway. The velocity structure in the fishway according to fluctuations of the upstream water level was simulated. The results showed that the plunging flow and the streaming flow were mixed at the lowest water level. When the water level increased about 10 cm or more from the lowest water level, the plunging flow disappeared in all pools and only the streaming flow occurred. Contrary to expectations, even when the water level is rose a little, the flow simply occurred mainly on the streaming flow. If the interval between the weirs is increased, both the plunging flow and the streaming flow are showed continued even if the water level rises. In addition, compared to the case where there are no orifices at the bottom of the weirs, the plunging flow tends to be generated in several pools. It is necessary to prevent blocking orifices through active management so that various flow patterns in the fishway can be generated in multiple pools.