• Journal of the Korean Geotechnical Society
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• v.33 no.1
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• pp.5-15
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• 2017

Skin friction may be one of the most critical factors in designing the prebored and precast pile. Special attention was given to the interface behavior of cement milk-surrounding soil during the installation of prebored and precast pile. Small-scale field model pile test was conducted for the case of single pile. The size and geometry of the small-scale field model piles were designed with pile length 1.3m, boring diameter 0.067 m. Quick maintain-load test was conducted for the cases of boring diameter 150, 125, 90, 86, 74 mm and water-cement ratio 90, 70, 60%. It was shown that the bearing capacity of the pile increased as the cement-water ratio and cement milk thickness increased. Considering the scale effect between the small-scale model test and the actual construction site, it was found that cement milk thickness of 0.1~0.4D (50~200 mm) was reasonable for the stability of the structure. Also, the proper cement paste water / cement ratio was about 70% when considering the results of this study and quality control.

• Journal of Broadcast Engineering
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• v.21 no.1
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• pp.24-35
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• 2016

By estimating environment light distribution, we can generate realistic shadow images in AR(augmented reality). When we estimate light distribution without sensing equipment, environment light model, geometry of virtual object, and surface reflection property are needed. Previous study using 3D marker builds surrounding light environment with a geodesic dome model and analyzes shadow images. Because this method employs candidate shadow maps in initial scene setup, however, it is difficult to estimate precise light information. This paper presents a novel light estimation method based on hierarchical light distribution model subdivision. By using an overlapping area ratio of the segmented shadow and candidate shadow map, we can make hierarchical subdivision of light geodesic dome.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.50-55
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• 2015

This study examined the relationship between the shape of the inside of the PRV and the cavitation of the water supply system of an apartment house. In this paper, nine types of PRV with different gaps and shapes were analyzed numerically using a 3D model embedded in the commercial code, ANSYS-CFX. The lowest pressure and the maximum velocity occurred at the narrow gap, which is located at the between the stem and the disk. When the gap size was increased, the vapor volume fraction was always greater than 0, but the vapor volume fraction of the type of expansion pipe approached 0. These results indicate that the cavitation of PRV can be reduced by a shape change to the type of expansion pipe.

• Structural Engineering and Mechanics
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• v.47 no.3
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• pp.383-399
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• 2013

High-strength strands are widely used as a key structural element in cable-stayed bridges and prestressed concrete structures. Conventional strands for stay cable and tendons in prestressed concrete structures are ${\phi}$15.7mm coated seven-wire strands and ${\phi}15.2mm$ uncoated seven-wire strands, respectively, but the ultimate strengths of both strands are 1860MPa. The objective of this paper is to investigate the tensile behavior of a newly developed ${\phi}15.7mm$ 2,200 MPa coated strand and a ${\phi}15.2mm$ 2,400 MPa uncoated strand according to various types of mono anchorages and to propose appropriate anchorages for both strands. Finite element analyses were initially performed to find how the geometry of the anchor head affects the interaction among the anchor head, the wedge and the strand and to find how it affects the stress distributions in both parts. Tensile tests for the new strands were carried out with seven different types of mono anchorages. The test results were compared to each other and to the results obtained from the tensile tests with a grip condition. From the analysis and the test results, desirable mono anchorages for the new strands are suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6922-6931
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• 2014

The development of modern science and technology and computer engineering breakthroughs in the field of information and communication have brought about many changes in lifestyle. The government announced the goal of educational policy in 2030 to educate people in future society on a future-oriented perspective. Changes in the curriculum along with changes in educational facilities are essential. Therefore, the operation of a classroom should be associated with classroom spatial information. The BIM design based on 3D geometry information was designed. The BIM design can link the design information and non-geometric information of spatial information. This study examined the operation of school facilities based on classroom spatial information with BIM. This study suggests standardization of classroom spatial information based on BIM. The scenarios of BIM ordering and design for departmentalized classrooms management is proposed.

• The Journal of the Acoustical Society of Korea
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• v.22 no.8
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• pp.637-644
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• 2003

In this study, with the FEM we analyzed the variation of the resonance frequency, bandwidth, and sound pressure of the Tonpilz transducer in relation to its design variables. Through statistical multiple regression analysis of the results, we derived functional forms of the resonance frequency, bandwidth, and sound pressure in terms of the design variables. By applying the constrained optimization technique, SQP-PD, to the derived function, we determined the optimal structure of the transducer that could provide the highest sound pressure level at the resonance frequency of 30,000 Hz and having the -3 dB bandwidth more than 10%, The validity of the optimized results was confirmed through comparison of the optimal performance with that of the FEA. The optimal design method proposed could reflect all the cross-coupled effects of multiple structural variables, and could determine the detailed geometry of the transducer with great efficiency and rapidity.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.6
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• pp.11-20
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• 2019

A Radome protects the radar from the external environment, and as a part of the stealth technology, a frequency-selective surface (FSS) was applied to the radome. Our study investigates the changes in the electrical transmission characteristics of the missile's FSS radome due to aerodynamic heating in various flight scenarios. Accordingly, we designed a FSS radome with a Jerusalem-cross(JSC) geometry and referred the missile flight scenario in the precedent research. Subsequently, electrical transmission characteristics affected by aerodynamic heating were numerically analyzed over time according to the position of radome. As a result, we found that the average transmission value maximally varies -14.3 dB compared to the initial bandwidth owing to changes in electrical transmission characteristics in flight scenarios.

• Journal of the Korea Computer Graphics Society
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• v.7 no.4
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• pp.1-8
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• 2001

3D mesh metamorphosis (morphing) deals with two input polyhedral objects and generates an animation in which the source mesh gradually changes to the target through in-between meshes. The basic and common idea of previous mesh morphing techniques can be summarized as the construction and interpolation of a metamesh. However, an approach based on a metamesh has fundamental limitations of complicated in-between meshes and no topology (connectivity) changes in a metamorphosis. This paper presents a novel approach for 3D mesh morphing, which is not based on a metamesh and overcomes the limitations of previous work. The approach simultaneously interpolates the topology and geometry of input meshes. With the approach, an in-between mesh contains only the vertices from the source and target meshes. Since no additional vertices are introduced, the in-between meshes are much simpler than those generated by previous techniques.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.11
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• pp.983-989
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• 2007

The bird strike simulation is a problem characterized by a high degree of uncertainty. It deals with nonlinear dynamics, complicated models of bird materials and geometry, as well as a plenty of possible boundary and initial conditions. In this complex field, uncertainty management plays an important role. This paper aims to assess the effect of input uncertainty of bird strike analysis on the impact behavior of the leading edge of the WIG(Wing in Ground Effect) craft obtained with finite element analysis using LS-DYNA 3D. The uncertainties of the bird strike simulation arise due to imprecision or lack of information, due to variability or scatter, or as a consequence of model simplification. These uncertain parameters are represented by fuzzy numbers with their membership functions quantifying an initial guess for the actual value of the model parameter. Using the transformation method as a special implementation of fuzzy arithmetic, the model can be analyzed with the intention of determining the influence of each uncertain parameter on the overall bird strike behavior.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.2
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• pp.191-195
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• 2020

In this work, tensile tests, one of the most common test method to assess the condition of a corroded pipe, were conducted. According to ASTM E8 method, the use of flat or curved uni-axial tension test is allowed under the recommendation with the usage of grips corresponding to a curvature of the pipe. However, this method is not for corroded specimen. Furthermore, in the case of performing the multiple tensile tests with various curvatures, it is desirable not to produce zigs that fit each curvatures, if merely processing the specimen grip with curvature into the flat grip can show almost identical tensile behavior. Therefore, various tension simulations were conducted first to check if there exist any differences. Also, experiments on corroded tensile specimen were conducted and compared with the FEM simulation that reflects the actual geometry acquired from the 3D scanner.