• 반도체디스플레이기술학회지
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• 제18권3호
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• pp.12-18
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• 2019

The protective double layer polymer coatings on silica optical fibers are realized by wet-on-wet liquid coating process and they play an important role in final quality of mass produced optical fibers. This numerical study aims to analyze the effects of secondary coating die design parameters by employing two dimensional axisymmetric model of coating cup and coating die geometry and computational fluid dynamics simulations which include temperature dependent viscosity of polymer coating liquids and viscous dissipation heating. Under high speed fiber drawing conditions and pressurized coating liquid supply, the effects of converging die angle are investigated in order to appreciate the change of coating liquid flow patterns such as flow recirculation zone near coating die as well as primary and secondary coating layer thicknesses. The auxiliary coating die to converging coating die is also tested and the results find that this concept is advantageous in achieving stable double layer coatings on silica glass fiber.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.97-104
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• 2005

Vision-based lane sensing systems require accurate and robust sensing performance in lane detection. Besides, there exists trade-off between the computational burden and processor cost, which should be considered for implementing the systems in passenger cars. In this paper, a stereo vision-based lane detection system is developed with considering sensor configuration aspects. An inverse perspective mapping method is formulated based on the relative correspondence between the left and right cameras so that the 3-dimensional road geometry can be reconstructed in a robust manner. A new monitoring model for estimating the road geometry parameters is constructed to reduce the number of the measured signals. The selection of the sensor configuration and specifications is investigated by utilizing the characteristics of standard highways. Based on the sensor configurations, it is shown that appropriate sensing region on the camera image coordinate can be determined. The proposed system is implemented on a passenger car and verified experimentally.

• 한국태양에너지학회 논문집
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• 제35권1호
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• pp.69-80
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• 2015

A series of numerical analyses was conducted to predict the thermal performance of a solar air heater depending on the hole configuration and geometry in the absorber plate. The planar dimensions of the prototype were 1 m (W) by 1.6 m (H), and the maximum air flow considered was $187m^3/h$. It was considered that protruding holes with a triangular opening in the absorber plate would invoke turbulence in the air flow to enhance the convection heat transfer. Six different hole configurations were investigated and compared with each other, while the hole opening height was considered as a design variable. Three-dimensional transient analyses were performed with a commercial software package on the airflow and heat transfer in the model. The numerical results were analyzed and compared from the view point of the outlet air temperature and its time response to derive the optimal hole pattern and hole opening height.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.665-675
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• 2019

The wire-wrapped fuel bundle is an assembly design in a sodium-cooled fast reactor. A wire spacer is used to maintain a constant gap between rods and to enhance the mixing of coolants. The wire makes the flow complicated by creating a sweeping flow and vortex flow. The vortex affects the flow field and heat transfer inside the subchannels. However, studies on vortices in this geometry are limited. The purpose of this research is to investigate the vortex flow created in the wire-wrapped fuel bundle. For analysis, a RANS-based numerical analysis was conducted for a 37-pin geometry. The sensitivity study shows that simulation with the shear stress transport model is appropriate. For the case of Re of 37,100, the mechanisms of onset, periodicity, and rotational direction were analyzed. The vortex structures were reconstructed in a three-dimensional space. Vortices were periodically created in the interior subchannel three times for one wire rotation. In the edge subchannel, the largest vortex occurred. This large vortex structure blocked the swirl flow in the peripheral region. The small vortex formed in the corner subchannel was negligible. The results can help in understanding the flow field inside subchannels with sweeping flow and vortex structures.

• The Journal of Advanced Prosthodontics
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• 제16권2호
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• pp.91-104
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• 2024

PURPOSE. The objectives of the current study were to estimate the influence of self-reinforced hollow structures with a graded density on the dimensional accuracy, weight, and mechanical properties of Co-Cr objects printed with the direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS. Sixty-five dog-bone samples were manufactured to evaluate the dimensional accuracy of printing, weight, and tensile properties of DMLS printed Co-Cr. They were divided into Group 1 (control) (n = 5), Group 2, 3, and 4 with incorporated hollow structures based on (spherical, elliptical, and diamond) shapes; they were subdivided into subgroups (n = 5) according to the volumetric reduction (10%, 15%, 20% and 25%). Radiographic imaging and microscopic analysis of the fractographs were conducted to validate the created geometries; the dimensional accuracy, weight, yield tensile strength, and modulus of elasticity were calculated. The data were estimated by one-way ANOVA and Duncan's tests at P < .05. RESULTS. The accuracy test showed an insignificant difference in the x, y, z directions in all printed groups. The weight was significantly reduced proportionally to the reduced volume fraction. The yield strength and elastic modulus of the control group and Group 2 at 10% volume reduction were comparable and significantly higher than the other subgroups. CONCLUSION. The printing accuracy was not affected by the presence or type of the hollow geometry. The weight of Group 2 at 10% reduction was significantly lower than that of the control group. The yield strength and elastic modulus of the Group 2 at a 10% reduction showed means equivalent to the compact objects and were significantly higher than other subgroups.

• 천문학회보
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• 제38권2호
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• pp.56.2-56.2
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• 2013

We study the three-dimensional genus topology of large-scale structure using the CMASS Data Release 11 sample of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). The CMASS sample yields a genus curve that is characteristic of one produced by Gaussian random-phase initial conditions. The data thus supports the standard model of inflation where random quantum fluctuations in the early universe produced Gaussian random-phase initial conditions. Modest deviations in the observed genus from random phase are as expected from the nonlinear evolution of structure. We construct mock SDSS CMASS surveys along the past light cone from the Horizon Run 3 (HR3) N-body simulations, where gravitationally bound dark matter subhalos are identified as the sites of galaxy formation. We study the genus topology of the HR3 mock surveys with the same geometry and sampling density as the observational sample, and the observed genus topology to be consistent with LCDM as simulated by the HR3 mock samples.

• IEIE Transactions on Smart Processing and Computing
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• 제3권2호
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• pp.59-64
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• 2014

This paper presents a method for estimating the bounding volume for image-based 3D object reconstruction. The bounding volume of an object is a three-dimensional space where the object is expected to exist, and the size of the bounding volume strongly affects the resolution of the reconstructed geometry. Therefore, the size of a bounding volume should be as small as possible while it encloses an actual object. To this end, the proposed method uses a set of silhouettes of an object and generates a point cloud using a point filter. A bounding volume is then determined as the minimum sphere that encloses the point cloud. The experimental results show that the proposed method generates a bounding volume that encloses an actual object as small as possible.

• 한국전산구조공학회논문집
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• 제23권6호
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• pp.607-613
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• 2010

FRANC3D is a program for simulating arbitrary three-dimensional crack growth. Recently, a completely new version of the program, FRANC3D/NG, has been created. Unlike previous versions, which relied largely on boundary element analysis, the new version of the program works with finite element analysis exclusively and is designed to work with general-purpose commercial finite element packages. This paper presents the theoretical underpinnings of the procedures to adaptively modify the geometry and mesh of a model to simulate crack growth.

• Nuclear Engineering and Technology
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• 제38권7호
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• pp.665-674
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• 2006

Three-dimensional neutron flux and fluence of Kori Unit 3 were evaluated using the synthesis technique described in Regulatory Guide 1.190 for all reactor geometry. For this purpose DORT neutron transport calculations from Cycle 1 to Cycle 15 were performed using BUGLE-96 cross-section library. The calculated flux and fluence were validated by comparing the calculated reaction rates to the measurement data from the dosimetry sensor set of the $5^{th}$ surveillance capsule withdrawn at the end of cycle 15 of Kori Unit 3. And then the best estimation of the neutron exposures for the reactor vessel beltline region was performed using the least square evaluation. These results can be used in the assessment of the state of embrittlement of Kori Unit 3 pressure vessel.

• Bulletin of the Korean Chemical Society
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• 제20권4호
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• pp.417-421
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• 1999

The complex, K3[La(TTHA)]5H,O, was prepared and its crystal structure was analyzed by single crystal X-ray diffraction method. In the complex, the La(Ⅲ) ion adopts a ten-coordinate geometry with four nitrogen atoms and six carboxyl oxygen atoms from the same TTHA ligand molecule. Its coordination polyhedron can be described as a distorted bicapped square antiprism. Each [La(TTHA)]3- anion is linked by K+ cations via carboxyl groups of TTHA ligand to form a three dimensional crystal structure. The thermal properties were investigated by TG and DTA techniques in argon atmosphere. The materials resulting from thermal treatment were La(OH)3 and K2O which were identified by powder X-ray diffraction technique.