• Korean Journal of Computational Design and Engineering
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• v.22 no.1
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• pp.89-99
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• 2017

In order to make a virtual endoscopy system effective for exploring the interior of the 3D model of a human organ, it is necessary to generate an accurate navigation path located inside the 3D model and to obtain consistent camera position and pose estimation along the path. In this paper, we propose an approach to virtual navigation of blood vessels, which makes proper use of orthogonal contours and skeleton curves. The approach generates the orthogonal contours and the skeleton curves from the 3D mesh model and its voxel model, all of which represent the blood vessels. For a navigation zone specified by two nodes on the skeleton curves, it computes the shortest path between the two nodes, estimates the positions and poses of a virtual camera at the nodes in the navigation zone, and interpolates the positions and poses to make the camera move smoothly along the path. In addition to keyboard and mouse input, intuitive hand gestures determined by the Leap Motion SDK are used as user interface for virtual navigation of the blood vessels. The proposed approach provides easy and accurate means for the user to examine the interior of 3D blood vessels without any collisions between the camera and their surface. With a simple user study, we present illustrative examples of applying the approach to 3D mesh models of various blood vessels in order to show its quality and usefulness.

• The Journal of the Korea Contents Association
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• v.9 no.4
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• pp.34-44
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• 2009

Integrating 3D data acquired in multiple views is one of the most important techniques in 3D modeling. However, due to the presence of surface scanning noise and the modification of vertices consisting of surface, the existing integration methods are inadequate to some applications. In this paper, we propose a method of integrating surfaces by using the local surface topology. We first find all boundary vertex pairs satisfying a prescribed geometric condition on adjacent surfaces and then compute 2D planes suitable to each vertex pairs. Using each vertex pair and neighbouring boundary vertices projected to their 2d plane, we produce polygons and divide them to the triangles which will be inserted to empty space between the adjacent surfaces. A proposed method use local surface topology and not modify the vertices consisting of surface to integrate several of surfaces to one surface, so that it is robust and simple. We also integrate the transformed textures to a 2D image plane computed by using a cylindrical projection to composite 3D textured model. The textures will be integrated according to the partition lines which considering attribute of face object. Experimental results on real object data show that the suggested method is simple and robust.

• Journal of the Korean Geotechnical Society
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• v.35 no.5
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• pp.21-30
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• 2019

While the study of the shallow tunnel has been mainly on the longitudinal load transfer and horizontal surface conditions, the study of the ground behavior of shallow tunnel under the slope is not sufficient. Therefore, in this study on the ground behavior around a tunnel due to the sidewall deformation of shallow tunnel under the slope that is excavated in longitudinal direction, a scale-down model test has been performed. The model tunnel has the dimension of 320 mm wide, 210 mm high and 55 mm long with enough material strength in aluminum and the model ground has the uniform ground conditions by 3 types of carbon rods. The model test has been performed with the variables of slopes and the cover depths by controlling the tunnel sidewall deformation, and the change of sidewall-load, load transfer, ground subsidence was monitored and analyzed. According to the increase of the slope, the maximum ground subsidence increased by 20~39% compared to the horizontal surface. The load ratio increased by maximum 20% in the tunnel crown and decreased in sidewall according to the surface slope. The load transfer shows maximum 128% of increase at the cover depth of 1.0D, while at the 1.5D cover depth it shows non-critical difference from horizontal surface. The slope has major effects on load transfer at the cover depth of 1.0D.

• Geophysics and Geophysical Exploration
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• v.5 no.3
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• pp.206-216
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• 2002

The finite element method (FEM), a powerful numerical modeling tool for solving various engineering problems, is frequently applied to three-dimensional (3-D) modeling thanks to its capability of discretizing and simulating the shape of model with finite number of elements. Considering the accuracy of the solution and computing time in modeling of engineering problems, it is preferable to construct physical continuity and simplify mesh system. Although there exist systematic mesh generation systems for arbitrary shaped model, it is hard to model a simple cylinder in terms of 3-D coordinate system especially in the vicinity of the central axis. In this study I adopt cylindrical coordinate system for modeling the 3-D model space and define the origin of the coordinates with mathematically clear coordinate transformation. Since we can simulate the whole space with hexahedral elements, the cylindrical coordinate system is effective in handling the 3-D model structure. The 3-D do resistivity modeling scheme developed in this study provides basie principle for borehole-to-surface resistivity survey, which can be a useful tool for the application to environmental problem.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.23-28
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• 2011

In this paper, a new generation method for ship induced waves is proposed using the fully non-linear 3-D numerical model with non-reflected wave generation system (LES-WASS-3D). A ship induced wave generated by the newly proposed method is examined in comparison with that obtained by an empirical formula. It is then shown that there is a good agreement in free surface the elevation between them. As a result, it is revealed that a ship induced wave in a 3-D numerical wave field can be simulated well using LES-WASS-3D.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 1999.12a
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• pp.66-71
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• 1999

For given 3D geographic data which is usually of DEM(Data Elevation Model) format, we have to represent and manipulate the data in various ways. For example, we have to draw a part of them in drawing canvas. To do this we give users a way of selecting area they want to visualize. And we have to give a base tool for users to select the local area which can be chosen for some geographic operation. In this paper, we propose a 3D data processing method for representation and manipulation. The method utilizes the major properties of DEM and TIN(Triangular Irregular Network), respectively. Furthermore, by approximating DEM with a TIN of an appropriate resolution, we can support a fast and realistic surface modeling. We implement the structure with the following 4 level stages. The first is an optimal resolution of DEM which represent all of wide range of geographic data. The second is the full resolution DEM which is a subarea of original data generated by user's selection in our implemeatation. The third is the TIN approximation of this data with a proper resolution determined by the relative position with the camera. And the last step is multi-resolution TIN data whose resolution is dynamically decided by considering which direction user take notice currently. Specialty, the TIN of the last step is designed for realtime camera navigation. By using the structure we implemented realtime surface clipping, efficient approximation of height field and the locally detailed surface LOD(Level of Detail). We used the initial 10-meter sampling DEM data of Seoul, KOREA and implement the structure to the 3D Virtual GIS based on the Internet.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.287-292
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• 2004

This paper presents the effect of scratches on an optical connector interface surface on the insertion loss of optical connectors. We propose a model for calculating the insertion loss of optical connectors. The model is expressed in terms of geometrical parameters of scratches assuming that the transmission coefficient of a light wave on the scratch surfaces is linearly varied as a function of scratch depth. Geometrical parameters of scratches such as location, width, and depth of scratches are measured using 3D optical interferometry surface profiler. We obtain the equation of the transmission coefficient in terms of scratch depth comparing the experimental insertion loss data to the insertion loss data using the model presented in this paper. Using the model and the equation of the transmission coefficient presented in this paper, we present the results of the insertion loss of optical connectors for various geometrical parameters of scratches. Scratches which are located at longer than two times the core radius from the center of the core show negligible effect on the insertion loss of optical connectors.

• Journal of Radiation Protection and Research
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• v.33 no.4
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• pp.167-172
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• 2008

Recently a high-quality voxel model of a Korean adult male was constructed at Hanyang University by using very high resolution serially-sectioned anatomical images of a cadaver, which was provided by the Korean Institute of Science and Technology Information (KISTI). Most existing voxel phantoms are developed based on an individual in the supine posture. This study converted the HDRK-Man voxel model into surface model and adjusted the flattened back of the HDRK-Man to a normal shape in the upright posture using 3D graphic softwares such as $3D-DOCTOR^{TM}$, $Rapidform^{(R)}$2006, $Rhinoceros^{(R)}$4.0, $MAYA^{(R)}$8.5. The effective doses of adjusted model were compared with those of unadjusted model for some standard irradiation geometries (i.e., AP, PA, LLAT, RLAT). In general, the differences were not very large and, among those, the largest difference was found for the PA radiation geometry, as expected. These methodologies can be used for the development of various deformed posture models of HDRK-Man in the later stage of this project.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.343-350
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• 2021

Unmanned aerial vehicles(UAV) photogrammetry provides a cost-effective option for collecting high-resolution 3D point clouds compared with UAV LiDAR and aerial photogrammetry. The main objectives of this study were to (1) validate the accuracy of 3D site model generated, and (2) determine the differences between Digital Elevation Model(DEM) and Digital Surface Model(DSM). In this study, DEM and DSM were shown to have varying degree of accuracy from observed data. The results indicated that the model predictions were considered tend to over- and under-estimated. The range of RMSE of DSM predicted was from 8.2 and 21.3 when compared with the observation. In addition, RMSE values were ranged from 10.2 and 25.8 to compare between DEM predicted and field data. The predict values resulting from the DSM were in agreement with the observed data compared to DEM calculation. In other words, it was determined that the DSM was a better suitable model than DEM. There is potential for enabling automated topography evaluation of the prior-harvest areas by using UAV technology.

• Transactions of Materials Processing
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• v.29 no.3
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• pp.144-150
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• 2020

In this paper, we propose the generation of a double enveloping worm thread profile with a non-developable ruled surface. Thread surface machining cuts all the way from the tip to the tooth root at one time, like full-face contact machining, rather than cutting several times like point machining. This cutting can reduce the cutting duration and achieve the smooth surface that does not require a grinding process for the threaded surface. The mathematical model of the cutting process was developed from theoretical equations, and the tooth surface was generated using two parameters and modeled in the CATIA using the generated Excel data. Additionally, the machining process of the worm was simulated in a numerical control simulation system. To verify the validity of the proposed method, the deviation between the modeling and the workpiece was measured using a 3D measuring machine.