• The Korean Journal of Applied Statistics
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• v.22 no.6
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• pp.1265-1275
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• 2009

In this paper, we investigated the composite covariance structure models for repeated measures data with multiple repeat factors. When the number of repeat factors is more than three, it is infeasible to fit the composite covariance models using the existing statistical packages. In order to fit the composite covariance structure models to real data, we proposed two approaches: the dimension reduction approach for repeat factors and the random effect model approximation approach. Our proposed approaches were illustrated by using the blood pressure data with three repeat factors obtained from 883 subjects.

• Steel and Composite Structures
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• v.39 no.1
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• pp.21-33
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• 2021

This paper aims to improve the current state-of-the-art in long-term deflection prediction in steel-concrete composite beams. The efficiency of a time-dependent finite element model based on linear creep theory is verified with available experimental data. A parametric numerical study is then carried out, which focuses on the effects of concrete creep and/or shrinkage, ultimate shrinkage strain and reinforcing bars in the slab. The study shows that the long-term deformations in composite beams are dominated by concrete shrinkage and that a higher area of reinforcing bars leads to lower long-term deformations and steel stresses. The AISC model appears to overestimate the shrinkage-induced deflection. A modified ACI equation is proposed to quantify time-dependent deflections in composite beams. In particular, a modified reduction factor reflecting the influence of reinforcing bars and a coefficient reflecting the influence of ultimate shrinkage are introduced in the proposed equation. The long-term deflections predicted by this equation and the results of extensive numerical analyses are found to be in good agreement.

• KIEAE Journal
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• v.15 no.5
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• pp.47-57
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• 2015

Purpose: The purpose of this study is to set the type of 'the New-hanok type Public Buildings' through a case study for the hanok public buildings completed after 2000 years, and to analyze planned properties of the type. This is significant Establishing legal status of 'the New-hanok type Public Buildings' and seeing review of application possibilities of the type for providing a systematic government support measures of 'the New-hanok type public buildings' when models developing future. Method: Method of research is the first to examine the current laws and established the definition and legal status of 'the New-hanok type Public Buildings'. Followed by Setting the type classification criteria as to classify the type of 'the New-hanok type public buildings' and research architectural overview of selected cases by Literature, Internet searches, etc. After systematizing of the types classification of analysis cases, Characteristics of the type of the building structure looks catch classify in spatial structure, function, beauty. Finally, review application possibilities of the type for systematic government support measures establish when models developing of 'the New-hanok type Public Buildings' through a comprehensive analysis. Result: Selected cases were categorized as 3 types according by structural standard based on the core concept of 'the New-hanok type Public Buildings' set in this study. This can be divided into 'Wooden Structure type' and 'Composite structure - Convergence type' and 'Composite structure - juxtaposed type', 'Wooden Structure type' was re-classified by divided into '(1)Traditional Korean Wooden Structure' and '(2)Laminated Wood Wooden Structure'.

• Composites Research
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• v.32 no.1
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• pp.13-20
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• 2019

In this study, in order to improve the quality issue and component characteristics of the battery module, which is one of the major parts of the electric vehicle. The structure is reinforced by using the composite material and the mechanism structure optimization of Hybrid concept which can overcome the disadvantages of single material was performed and the performance was compared. For this purpose, figure out the main design variables of composite materials according to Classical Laminated Plate Theory (CLPT) and the algorithm for predicting composite material properties have been studied. Based on the mechanical properties of the designed composite materials, finite element analysis (FEM) and the performance of the battery module was verified. Consequently, according to the verification result, Hybrid Battery Module reinforced with Selective Composite Patch can reduce the weight by 30% and reduce the product thickness by 32.5% compared with the existing Al battery module and proved the merit of Hybrid structure such as maintaining impact performance.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.223-226
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• 2002

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. However, the productivity of mold manufacturing has not increased significantly because CNC milling machines have massive slides, which do not allow rapid acceleration and deceleration during the frequent starts/stops encountered in machining molds and dies. This paper presents the use of composites for these slides to overcome this limitation. The vertical and horizontal slides of a large CNC machine were constructed by bonding high-modulus carbon-fiber epoxy composite sandwiches to welded steel structures using adhesives. These composite structures reduced the weight of the vertical and horizontal slides by 34% and 26%, respectively, and increased damping by 1.5 to 5.7 times without sacrificing the stiffness. Without much tuning, this machine had a positional accuracy of $\pm5\mu\textrm{m}$ per 300 m of the slide displacement.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.105-108
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• 2002

Materials, matrices mixed with various kinds of conductive or magnetic powder, such as ferrite, have been used as the electromagnetic wave absorbing ones, so called RAM(radar absorbing material). The structure that does not only have electromagnetic waves absorbing property like RAM but also supports loads is called RAS(radar absorbing structure). One of the existing manufacturing process of RAS is to compound with conductive powders the glass fiber-reinforced composite with good permeability and the ability to support loads. The process, however, causes a number of problems, such as the degradation in the mechanical properties of the composite, especially, interlamina shear strength. In this study, mechanical properties of glass fabric/epoxy composite containing 7wt% carbon black powders were measured and compared with pure glass fabric/epoxy composites.

• Steel and Composite Structures
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• v.35 no.6
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• pp.753-763
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• 2020

In this article, the influence of fuzzified uncertain composite elastic properties on non-linear deformation behaviour of the composite structure is investigated under external mechanical loadings (uniform and sinusoidal distributed loading) including the different end boundaries. In this regard, the composite model has been derived considering the fuzzified elastic properties (through a triangular fuzzy function, α cut) and the large geometrical distortion (Green-Lagrange strain) in the framework of the higher-order mid-plane kinematics. The results are obtained using the fuzzified nonlinear finite element model via in-house developed computer code (MATLAB). Initially, the model accuracy has been established and explored later to show the dominating elastic parameter affect the deflection due to the inclusion of fuzzified properties by solving a set of new numerical examples.

• Journal of Aerospace System Engineering
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• v.5 no.1
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• pp.17-23
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• 2011

Since the time, cost and lack of regulatory information and guidance, one of the largest regulatory obstacles for an airframe manufacturer of polymer based advanced composite materials in certified aircraft applications, is to generate design allowables that will satisfy Airworthiness Regulations. In the past two decades, the design allowables used in military aircraft had been generated and applied in Korea, however the qualification of composite materials used in certifying airframe structure was not accomplished for design and demonstration of compliance to applicable airworthiness regulation. It is the intend of this paper that provide the basis of composite material qualification for small aircraft certification to the airworthiness regulation.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.47-50
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• 2004

Weight reduction of the carbody is of great concern in developing high speed tilting train. Currently the composite materials are widely applied to the carbody structure due to their excellent material properties such as high specific strength and stiffness characteristics. In this paper, finite element analysis was conducted to design sandwich structures of composite carbody of the Korean Tilting Train eXpress(TTX). Several load tests on the carbody according to JIS E 7105, such as static vertical, compressive and torsional load tests was performed by finite element analysis, and the structural safety of composite carbody structure was verified.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.75-78
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• 2004

Traditionally aluminum alloy have been used in manufacturing of aircraft structures, and semi-monocoque structural concept have been mainly applied in structural design of fuselage and wing. However, recently monocoque structural concept is applied in many small-size aircraft structures manufactured with composite materials. In such case appling monocoque structural concept, in initial conceptual design stage on wing, it is not easy to analyze shear flow using classical shear flow analytical method because composite skin structure can support span-wise tension/compression stress as well as sectional shear stress. In this study, an extended shear-flow analytical method to apply to composite monocoque structural concept was developed through extending the classical shear-flow analytical method.