• Journal of Convergence for Information Technology
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• v.10 no.5
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• pp.216-223
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• 2020

We investigated the morphology of the scalp hair shaft from the base to the distal end of the newborn hair and the ratio of the longitudinal axis diameter of the scale exposed to the surface of the hair to the diameter of the hair by scanning electron microscopy(SEM). Neonatal hair was observed to taper from the area adjacent to the scalp toward the end of the hair. In this study, as the thickness of the hair increases, the ratio of the long axis diameter of the exposed scale becomes relatively small, but the long axis diameter of the exposed scale on the surface of the hair is similar in length regardless of the thickness of the hair. In conclusion, it was confirmed that the major axis diameter of the scales exposed to the surface of fine or thick hair does not change significantly.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.39-51
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• 2014

This paper deals with design of a direct-coupled, small-scaled permanent magnet generator (PMG) for wind power application. First, this paper determines rated power and speed of the PMG from measured characteristics of wind turbines. Second, we derive analytical solutions for the open-circuit field in order to determine optimum magnet thickness and pole pitch/arc ratio. Third, on the basis of open circuit field solutions, stator magnetic circuit including slot opening, teeth width and yoke thickness is designed. And then, a diameter of stator coil which agree with a required current density is calculated, and its turns are determined from the area of slot considering winding packing factor. Finally, finite element (FE) method is employed in analyzing the details of the designed PMG and, test results such as back-emf measurements are given to confirm the design.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.223-230
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• 2009

In this study we deal with bending behaviors of a concrete filled tubular(CFT) with various diameter-thickness ratios and concrete strengths. In finite element analysis using a commercial package(LUSAS), the bonding effect between concrete and steel in CFT structures is modeled by applying a joint element for the bonding surface. In order to consider the nonlinearity of concrete and steel tubes, stress-strain curves of the concrete and steel are used for the increased stresses in a plastic domain. The numerical results obtained from the proposed method show good agreement with the experimental data from load-displacement curves of a steel tube under distributed loads. Several parametric studies are focused on structural characteristics of CFT under bending effects for different diameter-thickness ratios and concrete strengths.

• Journal of Biomedical Engineering Research
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• v.24 no.2
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• pp.113-119
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• 2003

In this paper we introduced optimized deformed shape to prevent the blood vessel disease caused by the discord of deformed shape in the end-to-end anastomosis. This study considered the preliminary deformed shape induced by suture in the anastomosis of artery and PTFE, artificial blood vessel, with different diameters. Then we analyzed the final deformed shape of the anastomotic part under the systolic blood pressure. 120mmHg(16.0kPa). The final deformed shape of the anstomotic part was analyzed with respect to the change of initial diameter ratio(R$_{I}$) and the PTFE thickness. Equivalent and circumferential stresses induced by the systolic blood pressure in the anastomosis were also analyzed with respect to the initial diameter ratio(R$_{I}$). The results obtained were as follows : 1. Considering the preliminary deformed shape induced by suture and the systolic pressure in the anastomosis, not intimal hyperplasia, the optimal initial diameter ratio(R$_{I}$) was 1.073. 2. As the initial diameter ratio(R$_{I}$) became larger, higher equivalent and circumferential stresses were induced. And all the maximum stresses occurred on the side of PTFE 0.4mm apart from the anastomosis.

• Journal of computational fluids engineering
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• v.15 no.3
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• pp.16-23
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• 2010

Shape optimization of an upper plenum of a PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of height of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.187-194
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• 2010

Shape optimization of an upper plenum of PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of eight of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1649-1654
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• 2004

The near field structures of an under-expanded, dual, coaxial, jets issuing from the coaxial nozzles with four different geometries are visualized by using a shadowgraph optical method. Experiments are conducted to investigate the effects of the nozzle-lip thickness, secondary stream thickness, the nozzle pressure ratio and the secondary swirl stream on the characteristics of under-expanded jets. The results show that the presence of secondary annular swirling stream causes the Mach disk to move further downstream and increases its diameter, which decreases with a decrease in the nozzle-lip thickness. The secondary stream thickness has an influence on the location of an annular shock wave.

• Transactions of Materials Processing
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• v.23 no.1
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• pp.23-28
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• 2014

The aspect ratio of a hole is defined as the ratio of the thickness to the diameter of the sheet metal. Most holes in the sheet metal industry are made by piercing. However, for thick sheets, which have an aspect ratio greater than 2, a machining process like drilling instead of piercing is usually used to make holes. In the current study, piercing, which is a shearing process, is evaluated to punch a hole with a high aspect ratio by using a newly designed die set-up. The piercing die was manufactured to prevent the punch from buckling and also to improve the alignment between the die components. An aluminum alloy sheet was selected for the experiments. The influence of several process parameters such as sheet thickness, clearance and stripping force were investigated. Experimentally, a hole with an aspect ratio of 5 was pierced. The resulting hole had a clean surface and the dimensional accuracy of pierced hole was considerably improved with decreasing clearance between punch and die. It is also shown that the larger penetration depth of the effective sheared surface can be achieved for high aspect ratio piercing relative to conventional piercing with a low aspect ratio.

• Steel and Composite Structures
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• v.17 no.4
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• pp.517-533
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• 2014

Experimental results of 39 specimens including concrete columns, RC columns, hollow steel tube columns, concrete filled steel tubular (CFT) columns, and reinforced concrete filled steel tubular (RCFT) columns are presented. Based on the experimental results, the load-carrying capacity, confined effect, ductility, and failure mode of test columns are investigated. The effects of the main factors such as width-thickness ratio (the ratio of external diameter and wall thickness for steel tubes), concrete strength, steel tube with or without rib, and arrangement of reinforcing bars on the mechanical characteristics of columns are discussed as well. The differences between CFT and RCFT are compared. As a result, it is thought that strength, rigidity and ductility of RCFT are improved; especially strength and ductility are improved after the peak of load-displacement curve.

• Journal of the Korean Wood Science and Technology
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• v.43 no.2
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• pp.145-155
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• 2015

Fiber morphology and basic characteristics of Legi bamboos (Gigantochloa atter) growing on Yogyakarta were studied considering their age and height positions in the culms. Culms of 4, 16, and 40 months were harvested, and their total lengths were measured. The length, diameter, and wall thickness of each internode were measured. All the sample culms were divided into three different parts along the height, and their fiber dimension and physical properties were observed. The data obtained were analyzed by analysis of variance. The results showed that the culms had a diameter of 5.8 to 10.8 cm. The lowest internodes always showed the shortest length and the thickest wall. The culms had an average fiber length of 2.41 mm and Runkel ratio of 0.61. Fiber length was affected by the height, while fiber diameter, lumen diameter, and fiber wall thickness were affected significantly by the age of the culms. The culms had high green moisture content (GMC) of 157.89%, and basic density (BD) of $456.67kg.m^{-3}$, a total longitudinal shrinkage of 0.35%, and relatively low R/T shrinkage ratio. The interactions between age and height were affected GMC and BD.