• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.1074-1077
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• 2002

Biomechanical behavior of the human femur is very important in various clinical situations. In this study, the data of FE models based on DICOM file exported from Computed tomography(CT). We generated FE models(voxel model, tetra model) of human femur using CT slide image. We compared them with Yon Mises stress results derived from finite element analysis(FEA). Comparing the two models, we found a correlation of them. As a result, the tetra model based proposed marching cube algorithm is a valid and accurate method to predict parameters of the complex biomechanical behavior of human femur.

• 동력기계공학회지
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• 제18권3호
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• pp.59-65
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• 2014

The computational fluid dynamics was carried out to evaluate turbulent models on the swirling flow of a gun-type gas burner(GTGB) according to the mesh size. The commercial SC/Tetra software was used for a steady-state, incompressible and three-dimensional numerical analysis. In consequence, the velocity magnitude from the exit of a GTGB and the flowrate predicted by the turbulent models of MP k-${\varepsilon}$, Realizable k-${\varepsilon}$ and RNG k-${\varepsilon}$ agree with the results measured by an experiment very well. Moreover, the turbulent kinetic energy predicted by the turbulent model of standard k-${\varepsilon}$ with mesh type C only agrees with the experimental result very well along the radial distance. On the other hand, the detailed prediction of the information of swirling flow field near the exit of a GTGB at least needs a CFD analysis using a fairly large-sized mesh such as a mesh type C.

• 한국재료학회지
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• 제28권12호
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• pp.714-718
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• 2018

Anti-reflection thin films are fabricated on glass substrates using the screen printing method. Tetra ethyl silicate(TEOS) and methyl tri methoxy silane(MTMS) are used as starting materials and buthyl carbitol acetate(BCA) and buthyl cellusolve(BC) are mixed to improve the viscosity of the solution. Anti-reflection thin films are fabricated according to the number of the screen mesh and the characteristics improve as the mesh size increases. The transmittance and reflectance of the coated thin film using 325 mesh are about 94 % and 0.43 % in the visible wavelength. The thickness and refractive index of the AR thin film are 107 nm and n = 1.26, respectively.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.177-180
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• 2008

The objective of this study is to get simulation data about pulsatile flow of a non-Newtonian fluid through a bifurcated tube. All the process was based on CFD method, with a commercial FVM code, SC/Tetra ver. 6.0 for solving, and with CATIA R16 for generating geometries. To define a non-Newtonian fluid, the following viscous models are used; the Powell-Eyring model, the modified Powell-Eyring model, the Cross model, the modified Cross model, the Carreau model, the Carreau-Yasuda model and the modified Power Law model. The flow calculation data using each model were compared with the other data of a existing paper. Finally, the Carreau model was recognized to give the best result with the SC/Tetra code, and the succeeding simulations are made with the model. For the pulsating flow condition, the sine wave type velocity profile is given as the inlet boundary condition. To investigate the effect of geometries and mesh, the pre-test is carried out with various curvature conditions of the bifurcated corner, and then with various mesh conditions. The final process is to calculate flow variables such as the wall shear stress (WSS) and the wall shear stress gradient (WSSG). To validate all the result, the simulation is compared with the existing data of the other papers. Generally speaking, there is a noticeable difference in the maximum and minimum value of WSS. It is not sure that the values in each data are on the exactly same location. However, the overall trend is similar. The next study needs to investigate the same situation by experimental method. Furthermore, if the flow is simulated with more pulsatile conditions, more data of flow field through a bifurcated tube could be achieved.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.177-180
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• 2008

The objective of this study is to get simulation data about pulsatile flow of a non-Newtonian fluid through a bifurcated tube. All the process was based on CFD method, with a commercial FVM code, SC/Tetra ver. 6.0 for solving, and with CATIA R16 for generating geometries. To define a non-Newtonian fluid, the following viscous models are used; the Powell-Eyring model, the modified Powell-Eyring model, the Cross model, the modified Cross model, the Carreau model, the Carreau-Yasuda model and the modified Power Law model. The flow calculation data using each model were compared with the other data of a existing paper. Finally, the Carreau model was recognized to give the best result with the SC/Tetra code, and the succeeding simulations are made with the model. For the pulsating flow condition, the sine wave type velocity profile is given as the inlet boundary condition. To investigate the effect of geometries and mesh, the pre-test is carried out with various curvature conditions of the bifurcated corner, and then with various mesh conditions. The final process is to calculate flow variables such as the wall shear stress (WSS) and the wall shear stress gradient (WSSG). To validate all the result, the simulation is compared with the existing data of the other papers. Generally speaking, there is a noticeable difference in the maximum and minimum value of WSS. It is not sure that the values in each data are on the exactly same location. However, the overall trend is similar. The next study needs to investigate the same situation by experimental method. Furthermore, if the flow is simulated with more pulsatile conditions, more data of flow field through a bifurcated tube could be achieved.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.82-87
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• 2007

A cleaner has trouble with too much noise and power consumption. To solve these problems, the investigation for motors, which are the main component of vacuum cleaner, is required. However, it is difficult to analyze the flow by the experimental means because of the high speed of the fan rotation ranging from 30,000 rpm to 50,000 rpm. Moreover it takes much time to perform the numerical simulation for the flow. In this research, it is aimed to analyse the flow through the centrifugal fan which is believed to be a main noise source, by the computational method. The efficiency of the centrifugal fan is affected by friction loss, shock loss and so on. Those losses depend on factors like the velocity of impeller, blade shape and etc. Accordingly, the influence of the shape of impeller on the flow is investigated in this study. The computational analysis was done by changing impeller shapes. The flow around the centrifugal fan is simulated by applying the moving mesh. To verify the validity of the computation results, the air flow rate and the pressure field to the cleaner is compared with the experimental data. All simulations are performed by using commercial code SC/Tetra. The calculated results show good agreement with the experimental ones qualitatively and it is believed to be promising to use computational simulation in the improvement of the vacuum cleaner performance.

• Nuclear Engineering and Technology
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• 제51권8호
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• pp.1905-1915
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• 2019

This paper investigated the influence of simple support girds on flow, irrespective of having mixing vanes, in a 1 × 3 array rod bundle by using CFD methodology and the most accurate turbulence model which could reflect the actual physics of the flow was determined. In this context, a CFD model was created simulating the experimental studies on a single-phase flow [1] and the results were compared with the experimental data. In the first part of the study, influence of mesh was examined. Tetra, hybrid and poly type meshes were analyzed and convergence study was carried out on each in order to determine the most appropriate type and density. k - ε Standard and RSM LPS turbulence models were used in this section. In the second part of the study, the most appropriate turbulence model that could reflect the physics of the actual flow was investigated. RANS based turbulence models were examined using the mesh that was determined in the first part. Velocity and turbulence intensity results obtained on the upstream and downstream of the spacer grid at -3d_h, +3d_h and +40d_h locations were compared with the experimental data. In the last section of the study, the behavior of flow through the spacer grid was examined and its prominent aspects were highlighted on the most appropriate turbulence model determined in the second part. Results of the study revealed the importance of mesh type. Hybrid mesh having the largest number of structured elements performed remarkably better than the other two on results. While comparisons of numerical and experimental results showed an overall agreement within all turbulence models, RSM LPS presented better results than the others. Lastly, physical appearance of the flow through spacer grids revealed that springs has more influence on flow than dimples and induces transient flow behaviors. As a result, flow through a simple support grid was examined and the most appropriate turbulence model reflecting the actual physics of the flow was determined.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1533-1540
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• 2007

The most critical function of the Communication Based Train Control system is wayside and on-board Radio communication. Radio communication must be safely made without errors. The standards for CBTC has not been established yet, and research on Radio communication systems for use in Train control systems adopting CBTC system such as the magnetic levitation train must continue. This paper will discuss the characteristics of Radio communication technology currently used domestically such as GSM-R, IEEE 802.11, TETRA, MESH, and WiMAX/WiBro, and will investigate the potential possibility of applying them to Train control systems.

• 디지털융복합연구
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• 제13권10호
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• pp.327-335
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• 2015

재난통신망은 TETRA(TErrestrial Trunked RAdio)에서 대용량 데이터 통신이 가능한 광대역 이동통신 기술인 Public Safety-LTE(Long Term Evolution) 자가망을 활용하는 방향으로 발전하고 있다. 국내에서는 재난재해 대응기관 간의 일원화된 통신체계 유지를 위해 재난안전통신망 구축사업을 추진하고 있으나, 재난재해 현장에 위치한 피해당사자와의 통신을 고려하지 않고 재난재해 대응기관 간 지휘통제를 중심으로 통신망을 구축하고 있다. 본 연구에서는 국내 재난통신망 구축동향과 해외 선진사례를 해석하여 전 범위 재난통신망 구축을 위한 쟁점을 도출하고 통신주체와 목적에 따라 재난통신 영역을 새롭게 정의하여 재난통신 영역을 통제통신, 대응통신, 현장통신, 당사자통신, 경보통신으로 세분화하였다. 본 연구를 통하여 재정의 된 재난통신 영역의 특성을 분석하고 이에 따른 핵심 품질요건을 재설계하여 영역별 음영지역 없는 전 범위 재난통신 체계 구축방안을 수립하였다.

• 한국전산유체공학회지
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• 제13권4호
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• pp.72-79
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• 2008

This study is to investigate the air flow around a sirocco fan which is used in a range hood. The main object of the study is to improve the flow rate of the fan by analysis of unsteady 3-dimensional incompressible flow. Overall analysis is carried out using CFD method. For this, we used a commercial code, SC/Tetra, and used a sliding mesh method to give the same condition as an actual state. First, verification of the CFD results is done by comparing the experimental data with the numerical data for the suction flow rate. It is confirmed that two results are well consistent. Then for the improvent of flow rate, the effect of shape factors such as diameter ratio of fan, geometry of case, cut-off aperture and guide angle of case exit on the suction flow rate was considered. Especially, for a new design of housing, the principle of Archimedes spiral was used. The overall analysis was applied to a new design of housing, and the result showed an increase of flow rate by 10.7%.