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전용태(Yongtae Jun),박광현(Kwanghyun Park),노형민(Hyung-Min Rho),최영(Young Choi) Korean Society for Precision Engineering 2004 한국정밀공학회지 Vol.21 No.4
In reverse engineering, the whole surfaces of the three-dimensional product are measured using 3D positional scanners. The raw triangle meshes constructed from a scanned point set are not well fitted for direct use in the downstream engineering or graphic activities. No object can be fully described by a single scan. Although multiple scans are usually taken and aligned to achieve a complete model, a set of scanned points does not entirely wrap the whole object. This is because some surfaces may be inaccessible to the scanner, so some portion of the scanned surface may be missing. This paper discusses the algorithms of a hole-filling that are crucial to refine the triangle meshes. In this paper, the holes are filled with flat triangles first by subdivision operation and then smoothed with neighboring triangles. This process continues until it converges to a certain user-defined iteration number. Examples are given and discussed to validate the system.
전용태(Yongtae Jun) (사)한국CDE학회 2012 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2012 No.2
The major technical challenge of this study is to analysis the 3?dimensional (3D) morphological characteristics of the human spine. We proposed a framework which analysis 3D geometrical parameters of the human spine to determine an appropriate corresponding spinal implant. The parameters include axial parameters and geometrical parameters. Some of them are semi-automatically recognized and extracted, but others need be determined with the surgeon’s intervention.
전용태(Yongtae Jun) (사)한국CDE학회 2011 한국CDE학회 논문집 Vol.16 No.5
The goal of total knee replacement (TKR) surgery is to replace patient’s knee joint with artificial implants in order to restore normal knee joint functions. Since mismatched knee implants often cause a critical balancing problem and short durability, designing a well-fitted implant to a patient’s knee joint is essential to improve surgical outcomes. We developed a software system that three-dimensionally (3D) simulates TKR surgery based upon 3D knee models reconstructed from computed tomography (CT) imaging. The main task of the system was to extract precise 3D anatomical parameters of a patient’s knee that were directly used to determine a custom fit implant and to virtually perform TKR surgery. The virtual surgery was simulated by amputating a 3D knee model and positioning the determined implant components on the amputated knee. The test result shows that it is applicable to derive surgical parameters, determine individualized implant components, rehearse the whole surgical procedure, and train medical staff or students for actual TKR surgery. The feasibility and verification of the proposed system is described with examples.
전용태(Yongtae Jun),임은하(Eun-Ha Lim) (사)한국CDE학회 2015 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2015 No.하계
This paper presents a method to implement a motion detection system using a tri-axial accelerometer of smart phone. The data acquired from a smart phone are processed into information that shows the motional states of the target person using heuristic data. In this system fall motion is the target behavior to be recognized among various activities of daily living (ADL). The pilot tests show that falls could be detected from ADL, so that fall recognition is a feasible technology for elderly people.
전용태(Yongtae Jun),이민형(Minhyung Lee) (사)한국CDE학회 2015 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2015 No.하계
To analyze a hypervelocity impact phenomenon, it is crucial to model physical state regarding explosion or shock. This paper describes the process of integration of various FEM systems that consist of (1) continuum mechanics based analysis, (2) particle-based analysis, (3) plasma-based analysis tool. It is easy and effective for SW engineers to carry out a SW system, if the various modules are processed in single integrated software environment. In this paper, we show the whole process of integration the FEM modules into single system. In addition a case study of hypervelocity impact phenomenon is given and discussed to assess the effectiveness of the proposed system.
전용태(Yongtae Jun),이민형(Minhyung Lee) (사)한국CDE학회 2013 한국CDE학회 논문집 Vol.18 No.6
Computer simulation with FEM is very useful to analyze hypervelocity impact phenomena that are tremendously expensive or otherwise too impractical to analyze experimentally. Shock physics can be efficiently handled by mesh adaptation which allows finite element mesh to be locally optimized to resolve moving shock wave in explosion. In this paper, an adaptive meshing technique based upon quadtree data structure was applied to resolve ballistic impact phenomena. The technique can adaptively refine a mesh in the neighborhood of a shock and coarsen the mesh for the smooth flow behind the shock according to a criterion. The criterion for refinement and coarsening is based upon the standard deviation of the gradient of shock pressure on the associated field. Shock simulation starts with the rough mesh of the pressure field and mesh density is increased locally under the criterion at each time step. The results show that the mesh adaptation enables to minimize the global computation error of FEM and to increase storage and computational saving compared to the fixed resolution of the conventional static mesh approach.