• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2021.06a
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• pp.204-207
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• 2021

LiDAR 장비 및 SfM 과 MVS 방법을 이용하여 생성된 point cloud 와 mesh 에는 항상 노이즈가 포함되어 있다. 이러한 노이즈를 제거하기 위해선 노이즈와 edge 를 효과적으로 구분해낼 수 있어야 한다. 노이즈를 제거하기 위해 mesh 로부터 edge 를 먼저 구분해낸 후 edge 에 해당하는 영역과 평면에 해당하는 영역에 서로 다른 필터를 사용하는 많은 연구들이 있지만 강한 노이즈가 포함된 mesh 에서는 edge를 잘 구분해내지 못하는 문제가 존재한다. 이러한 방법들은 mesh 로부터 edge 를 구분해내는 알고리즘의 성능이 노이즈를 제거하는 전체 알고리즘의 성능에 큰 영향을 주기 때문에 강한 노이즈에서도 edge 를 잘 구분해낼 수 있는 알고리즘이 필요하다. 본 논문에서는 PCA 와 graph-cut 을 이용하여 강한 노이즈가 포함된 mesh 에서 edge 영역을 추출하는 알고리즘을 제안한다.

• Journal of KIISE:Software and Applications
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• v.32 no.3
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• pp.173-180
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• 2005

This paper proposes an effective algorithm that combines both the stereo matching and the marching cube algorithm. By applying the stereo matching technique to an image obtained from various angles, 3D geometry data are acquired, and using the camera extrinsic parameter, the images are combined. After reconstructing the combined data into mesh using the image index, the normal vector equivalent to each point is obtained and the mesh smoothing is processed. This paper describes the successive processes and techniques on the 3D mesh reconstruction, and by proposing the intermediate iso- surface algorithm. Therefore it improves the 3D data instability problem caused when using the conventional marching cube algorithm.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.149-156
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• 2012

This paper suggests the data transmission technology for applying to the actual railway line based on the technological trends and theories for the wireless Mesh techniques. This paper presents a technical basis that is applicable to the economic and efficient use of frequency and to the development of a Communication Based Train Control System by demonstrating its Applicability, Availability, Reliability and Safety for the train control system of the radio frequency of the bandwidth of 5.7 GHz at the experiments.

• Journal of Computational Design and Engineering
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• v.1 no.2
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• pp.96-102
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• 2014

In the field of design and manufacturing, there are many problems with managing dynamic states of three-dimensional (3D) objects. In order to solve these problems, the four-dimensional (4D) mesh model and its modeling system have been proposed. The 4D mesh model is defined as a 4D object model that is bounded by tetrahedral cells, and can represent spatio-temporal changes of a 3D object continuously. The 4D mesh model helps to solve dynamic problems of 3D models as geometric problems. However, the construction of the 4D mesh model is limited on the time-series 3D voxel data based method. This method is memory-hogging and requires much computing time. In this research, we propose a new method of constructing the 4D mesh model that derives from the 3D mesh model with continuous rigid body movement. This method is realized by making a swept shape of a 3D mesh model in the fourth dimension and its tetrahedralization. Here, the rigid body movement is a screwed movement, which is a combination of translational and rotational movement.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.6
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• pp.916-922
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• 1997

This paper attempted to estimate mesh selectivity of gill nets for neon flying squid in the north Pacific Ocean. The 11 linear regressions, (P<0.05) were obtained using the data on catch ratios derived from mesh size combinations between two slightly different mesh sizes of 12 kinds of research gillnet (namely 33, 37, 42, 48, 55, 63, 72. 76, 86, 96, 105 and 115 mm in stretched mesh size). There was an increase in the optimum length with the increase in mesh size but standard deviation showed somewhat increase with the increase in the mesh size. The selectivity curves were well fitted to the length frequency distributions obtained from samples for the mesh sizes from 48 mm through 86 mm. For the mesh sizes of 33, 37 and 42 mm the DML (Dorsal Mantle Length) compositions were distributed towards the right hand-limb of the curves. The DML distributions from the 96 mm and larger meshes showed a trend towards the left hand-limb of the curves. The selectivity curves for different mesh sizes indicate that large mesh sizes catch a greater size range of squid, and the gill net fishery in the north Pacific Ocean captures effectively neon flying squid within the range of $9\~43cm$ DML.

• Korean Journal of Computational Design and Engineering
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• v.18 no.6
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• pp.461-469
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• 2013

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.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.95-105
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• 2009

The flow fields around the HARTII rotor were numerically investigated using a viscous flow solver on adaptive unstructured meshes. An overset mesh and a deforming mesh technique were used to handle the blade motion including blade deflection, which was obtain from the HARTII experimental data. A solution-adaptive mesh refinement technique was also used to capture the rotor wake effectively. Comparison of the sectional normal force and pitching moment at 87% radial station between the two cases, with and without the blade deflection, showed that the blade loading is significantly affected by blade torsion. It was found that as the mesh was refined, the strength of tip vortex is better preserved, and the magnitude of high frequency blade loading, caused by blade-vortex interaction (BVI), is further magnified. It was also found that a proper time step size, which corresponds to the cell size, should be used to predict unsteady solutions accurately. In general, the numerical results in terms of the unsteady blade loading and the rotor wake show good agreement with the experimental data.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.403-409
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• 2003

The finite element method is one of the most widely used method of structural analysis that has wide applications in diverse fields of engineering and science. The method has been proven effective and reliable in many practical problems. One of the reasons for the methods' popularity is its ease of use, but still the user has to input the finite element mesh which affects the accuracy of the results. The knowledge required to form an effective mesh for a given problem is somewhat complex and for sometime there has been research effort to automate the generation of the mesh and this is called the adaptive mesh generation scheme. A good adaptive mesh scheme seemed to require an accurate assessment of error and generally this requires some additional computation. This paper looks into the possibility of generating adaptive meshes based on representative strain values in each finite element method. The proposed adaptive scheme does not require additional computations other that looking up the data values already computed as finite element analysis results and simple manipulations of these data. Two plane stress problems, a plate with a hole and a deep beam with a concentrated load at the end are considered to show the progress of the improved generation of adaptive meshes using the scheme.

• Journal of Computing Science and Engineering
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• v.4 no.3
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• pp.207-224
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• 2010

This paper presents a compression scheme for mesh geometry, which is suitable for mobile graphics. The main focus is to enable real-time decoding of compressed vertex positions while providing reasonable compression ratios. Our scheme is based on local quantization of vertex positions with mesh partitioning. To prevent visual seams along the partitioning boundaries, we constrain the locally quantized cells of all mesh partitions to have the same size and aligned local axes. We propose a mesh partitioning algorithm to minimize the size of locally quantized cells, which relates to the distortion of a restored mesh. Vertex coordinates are stored in main memory and transmitted to graphics hardware for rendering in the quantized form, saving memory space and system bus bandwidth. Decoding operation is combined with model geometry transformation, and the only overhead to restore vertex positions is one matrix multiplication for each mesh partition. In our experiments, a 32-bit floating point vertex coordinate is quantized into an 8-bit integer, which is the smallest data size supported in a mobile graphics library. With this setting, the distortions of the restored meshes are comparable to 11-bit global quantization of vertex coordinates. We also apply the proposed approach to compression of vertex attributes, such as vertex normals and texture coordinates, and show that gains similar to vertex geometry can be obtained through local quantization with mesh partitioning.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.325-326
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• 2009