• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.41-44
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• 2007

A large eddy simulation method with unstructured mesh is presented. Two explicit filtering procedures are adopted for reducing the aliasing error of the nonlinear convective term and measuring the level of subgrid scale velocity fluctuation, respectively. The developed subgrid scale model is basically an eddy viscosity model which depends on both local velocity fluctuation level and local grid scale. As a validation problem, the flows around a sphere of several Reynolds numbers are simulated and some characteristic quantities are compared to experimental data and numerical results in the literature.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1013-1018
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• 2010

This paper presents a numerical evaluation of the launch dynamics and thermo-fluid phenomena for gas generator launch eject system. The existing gas dynamic model for launching eject body used ideal gas and adiabatic assumption with empirical energy loss model. In present study, a turbulent Navier-Stokes solver with CHIMERA mesh is employed to predict the detail unsteady thermo-fluid dynamics for the launched body. The calculation results show that proper grid number is necessary for good agreement with experimental data. The important effects for accurate prediction are a gap distance and thermal boundary condition on the wall. The computational results show good agreement with experiment data.

• Journal of Computational Design and Engineering
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• v.1 no.1
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• pp.1-12
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• 2014

In this paper, we propose a new method of reconstructing the hand models for individuals, which include the link structure models, the homologous skin surface models and the homologous tetrahedral mesh models in a reference posture. As for the link structure model, the local coordinate system related to each link consists of the joint rotation center and the axes of joint rotation, which can be estimated based on the trajectories of optimal markers on the relative skin surface region of the subject obtained from the motion capture system. The skin surface model is defined as a three-dimensional triangular mesh, obtained by deforming a template mesh so as to fit the landmark vertices to the relative marker positions obtained motion capture system. In this process, anatomical dimensions for the subject, manually measured by a caliper, are also used as the deformation constraints.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9A
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• pp.916-922
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• 2007

Wireless networks (WNs) are developed and applied widely in a lot of areas. Now, a new generation of wireless networks is coming, and that is Wireless Mesh Network (WMN). At present, there are not so many researches which deal on this area. Most researches are derived from Mobile Ad hoc Networks (MANET) and WNs. In WMNs, there are some applications that require real-time delivery. To guarantee this, rate control and congestion control are needed. This problem leads to optimization issue in transport layer. In this paper, we propose a mathematical model which is applied in rate and congestion control in WNMs. From this model, we optimize rate and congestion control in WMNs by maximizing network utility. The proposed algorithm is implemented in distributed way both in links and sources.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.27 no.4
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• pp.77-82
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• 2004

Being in an internet era, the rapid transmission of 3D mesh models is getting more important and efforts toward the compression of various aspects of mesh models have been provided. Even though a mesh model usually consists of coordinates of vertices and properties such as colors and normals, topology plays the most important part in the compression of other information in the models. Despite the extensive studies on Edgebreaker, the most frequently used and rigorously evaluated topology compressor, the probability distribution of its five op-codes, C, R, E, S, and L, has never been rigorously analyzed yet. In this paper, we present probability distribution of the op-codes which is useful for both the optimization of the compression performance and a priori estimation of compressed file size.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.1
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• pp.10-19
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• 2012

The mesh selectivity of a drift net for yellow croaker (Larimichthys polyactis) was examined in field experiments with six different net mesh size (40, 45, 50, 55, 60 and 65mm) from April to December, 2008 in the coastal areas of Jeollanam-do in Korea. The total catch of 6,748 consisted of yellow croaker (n=6,310; 89.1% of total catch), common mackerel (n=158; 5.6%) and other species (n=280; 9.6%). The selectivity curve for yellow croaker was fit by the models of selectivity curve in SELECT method. The optimal mesh size for 50% retention for minimum landing size (191mm) of yellow croaker was estimated as 49.6mm-51mm by selectivity curves. And the bi-normal model for the selectivity curve was found to fit the data best.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.685-690
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• 2011

This paper describes a seismic analysis of chemical pump using automated mesh generation system. The use of an automated analysis system, involving FE codes together with CAD systems and FE pre- and post-processors, has provided an important step towards shortening the design process and structural optimization. The FE model, which is a FE mesh accompanied with the analysis condition, is automatically converted from the analysis model. The FE models are then automatically analyzed using the FE analysis code. This integrated FE simulation system is applied to an analysis of three-dimensional complex solid structures such as a chemical pump.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.8
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• pp.488-490
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• 2014

This paper deals with distributed time and frequency synchronization algorithms using the flocking technique for OFDMA-based wireless mesh networks. We propose a time and frequency synchronization model taking into account channel propagation delays existing in wireless mesh networks, and analyze the convergence condition of the proposed synchronization algorithm. Convergence performance of the proposed synchronization algorithm is analyzed via computer simulation in terms of synchronization parameters in the time and frequency synchronization model.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1441-1446
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• 2009

Numerical analysis is a powerful method in evaluating the soil-pile-structure interaction under the dynamic loading, and this approach has been applied to the practical area due to the development of computer technology. Finite Difference Method, one of the most popular numerical methods, is sensitive to the shape and the number of mesh. However, the trial and error approach is conducted to obtain the accurate results and the reasonable simulation time because of the lack of researches about mesh size and the number. In this study, FLAC 3D v3.1 program(FDM) is used to simulate the dynamic pile model tests, and the numerical results are compared with the 1G shaking table tests results. With the different size and shape of mesh, the responses of pile behavior and the simulation time are estimated, and the optimum mesh sizes in dynamic analysis of single pile is studied.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.204-209
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• 2001

The finite element model for automotive muffler analysis is improved by modifying the boundary condition of outlet and the mesh of finite element model. The model minimizes the difference between transmission loss from analysis and that from experiment. Four different boundary conditions and the four types of finite element model are tested to find out the best one of those. From the case study it is verified that the bevel of transmission loss can be changed by the variation of radiation impedance value. Also the resonance or anti-resonance frequencies of transmission loss can be shifted by the variation of finite element mesh. An improved finite element model of muffler is proposed in consideration with the accuracy and the computing time of analysis.