• Structural Engineering and Mechanics
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• 제85권2호
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• pp.147-161
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• 2023

Based on the ideas of variational differential quadrature (VDQ) and finite element method (FEM), a numerical approach named as VDQFEM is applied herein to study the large deformations of plate-type structures under static loading with arbitrary shape hole made of functionally graded graphene platelet-reinforced composite (FG-GPLRC) in the context of higher-order shear deformation theory (HSDT). The material properties of composite are approximated based upon the modified Halpin-Tsai model and rule of mixture. Furthermore, various FG distribution patterns are considered along the thickness direction of plate for GPLs. Using novel vector/matrix relations, the governing equations are derived through a variational approach. The matricized formulation can be efficiently employed in the coding process of numerical methods. In VDQFEM, the space domain of structure is first transformed into a number of finite elements. Then, the VDQ discretization technique is implemented within each element. As the last step, the assemblage procedure is performed to derive the set of governing equations which is solved via the pseudo arc-length continuation algorithm. Also, since HSDT is used herein, the mixed formulation approach is proposed to accommodate the continuity of first-order derivatives on the common boundaries of elements. Rectangular and circular plates under various boundary conditions with circular/rectangular/elliptical cutout are selected to generate the numerical results. In the numerical examples, the effects of geometrical properties and reinforcement with GPL on the nonlinear maximum deflection-transverse load amplitude curve are studied.

• Advances in materials Research
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• 제12권2호
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• pp.161-177
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• 2023

This paper proposes an analytical method to investigate the free vibration behaviour of new functionally graded (FG) carbon nanotubes reinforced composite beams based on a higher-order shear deformation theory. Cosine functions represent the material gradation and material properties via the thickness. The kinematic relations of the beam are proposed according to trigonometric functions. The equilibrium equations are obtained using the virtual work principle and solved using Navier's method. A comparative evaluation of results against predictions from literature demonstrates the accuracy of the proposed analytical model. Moreover, a detailed parametric analysis checks for the sensitivity of the vibration response of FG nanobeams to nonlocal length scale, strain gradient microstructure-scale, material distribution and geometry.

• Structural Engineering and Mechanics
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• 제82권4호
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• pp.477-490
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• 2022

This article investigates the nonlinear behavior of two-directional functionally graded materials (TDFGM) doubly curved panels with porosities for the first time. An improved and effectual approach is established based on the improved first-order shear deformation shell theory (IFSDST) and von Karman's type nonlinearity. The IFSDST considers the effects of shear deformation without the need for a shear correction factor. The composition of TDFGM constitutes four different materials, and the modified power-law function is employed to vary the material properties continuously in both thickness and longitudinal directions. A nonlinear finite element method in conjunction with Hamilton's principle is used to obtain the governing equations. Then, the direct iterative method is incorporated to accomplish the numerical results using the frequency-amplitude, nonlinear central deflection relations. Finally, the influence of volume fraction grading indices, porosity distributions, porosity volume, curvature ratio, thickness ratio, and aspect ratio provides a thorough insight into the linear and nonlinear responses of the porous curved panels. Meanwhile, this study emphasizes the influence of the volume fraction gradation profiles in conjunction with the various material and geometrical parameters on the linear frequency, nonlinear frequency, and deflection of the TDFGM porous shells. The numerical analysis reveals that the frequencies and nonlinear deformations can be significantly regulated by changing the volume fraction gradation profiles in a specified direction with an appropriate combination of materials. Hence, TDFGM panels can overcome the drawbacks of the functionally graded materials with a gradation of properties in a single direction.

• Structural Engineering and Mechanics
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• 제86권6호
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• pp.731-738
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• 2023

This article presents an analytical approach to explore the bending behaviour of of two-dimensional (2D) functionally graded (FG) nanobeams based on a two-variable higher-order shear deformation theory and nonlocal strain gradient theory. The kinematic relations are proposed according to novel trigonometric functions. The material gradation and material properties are varied along the longitudinal and the transversal directions. The equilibrium equations are obtained by using the virtual work principle and solved by applying Navier's technique. A comparative evaluation of results against predictions from literature demonstrates the accuracy of the proposed analytical model. Moreover, a detailed parametric analysis checks for the sensitivity of the bending and stresses response of (2D) FG nanobeams to nonlocal length scale, strain gradient microstructure scale, material distribution and geometry.

• Computers and Concrete
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• 제32권2호
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• pp.207-215
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• 2023

This paper investigates wave propagation in functionally graded carbon nano-reinforced composite (FG-CNTRC) plates under the influence of temperature based on Reddy' plate model. The material properties of Carbon Nanotubes (CNTs) are size-dependent, and the volume fraction of CNTs varies only along the thickness direction of the plate for different CNTs reinforcement modes. In addition, the material properties of CNTs can vary for different temperature parameters. By solving the eigenvalue problem, analytical dispersion relations can be derived for CNTRC plates. The partial differential equations for the system are derived from Lagrange's principle and higher order shear deformation theory is used to obtain the wave equations for the CNTRC plate. Numerical analyses show that the wave propagation properties in the CNTRC plate are related to the volume fraction parameters of the CNTRC plate and the distribution pattern of the CNTs in the polymer matrix. The effects of different volume fractions of CNTs and the distribution pattern of carbon nanotubes along the cross section (UD-O-X plate) are discussed in detail.

• 한국식품영양학회지
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• 제24권4호
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• pp.481-488
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• 2011

The purpose of this study was to investigate the relations of breakfast skipping and dietary habits according to breakfast intake frequency. Subjects were 5th and 6th graders of elementary school(n=423) in Gyeonggi area. As a result of analyzing the breakfast intake frequency, 'Having everyday' showed the highest 63.4%, followed by '4~6 times' 16.5%, '2~3 times' 13.5% and '0~1 times' 6.6%. As a result of analyzing the relations between mother and child in the breakfast intake frequency, it showed that the more mothers skipped breakfast, the more their children skipped it. For the reason of skipping breakfast, 'To be in time for school' showed the highest percentage. As a result of analyzing the perception of awareness for the importance of nutrition and dietary habit according to the breakfast intake frequency, there was a statistically significant difference in breakfast intake, dietary habits, selection and intake of proper food, disease and health problem according to the breakfast intake frequency. As a result of study, it is necessary that nutrition education should not be limited to children but expanded to their parents in order to increase the efficiency and effectiveness of nutrition education between school and home.

• 한국의류산업학회지
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• 제14권5호
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• pp.739-748
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• 2012

Modern people gratify their self-satisfaction to express their distinctive image and symbolic significance through various and sensible direction. The image that is formed by each factor of coordination and harmony of aesthetic characteristic has emphasized its importance in modern society. And also, the item which is conflated by the wearer's feeling figures the image and it takes a role that lifts the degree of fashion's completion. For the rapid change of fashion trend in modern society, the role of Jewelry has been emphasized. Even though the shape of Jewelry is tiny, but it has risen as one of the fashion items which could be used for various application. Especially, the Brooches are mainly put on her's top where they hold someone's eyes, so it could be regard as Artwork which assists for wearer's distinctive style and lingering impression. Overviews of Researches Trend in Brooch, they have been concerned about Brooch Design, Internal state of the Accessory in clothes and Accessory Design which is expressed in Fashion. But, the study on the relations between Clothes and Brooch is insufficient. So, in this paper, first of all we arrange the terms according to characteristic of Brooch, and then study empirically for the relations between Clothes and Shape of Brooch, Colors of Brooch, Materials of Brooch in Fashion Collection in order to study for the new physical beauty that is expressed by interaction between Clothes and Brooch.

• 한국게임학회 논문지
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• 제12권3호
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• pp.77-86
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• 2012

최근 트위터와 미투데이 등의 마이크로블로그 서비스가 소셜 네트워킹에서 차지하는 비중이 점점 증가하고 있다. 하지만 이러한 마이크로블로그 서비스는 사용자와 지인들 사이의 메시지를 단순히 시간 순으로 나열하여 보여주기 때문에 사용자와 특정 지인과의 관계를 구체적으로 파악하기는 어렵다. 본 논문에서는 마이크로블로그 서비스를 이용하는 사용자와 지인들이 주고 받은 메시지를 정량적, 정성적, 시간적으로 분석하여 사용자와 지인들과의 관계를 직관적으로 파악할 수 있게 하는 소셜 네트워킹 패턴 분석 및 가시화 시스템을 제안한다. 또한 관계의 변화 패턴을 분류하여 마이크로블로그 서비스 사용자의 인간관계를 관리하고 증진시킬 수 있는 도구도 제공한다. 제안 기법은 스마트폰 어플리케이션에 성공적으로 적용되어 마이크로블로그 서비스 사용자의 인간관계의 분석 및 증진을 위한 도구로서 사용될 수 있다.

• 디지털융복합연구
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• 제10권9호
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• pp.345-350
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• 2012

본 연구에서는 사용자의 경험적인 요소를 바탕으로 직관적이고 쉬운 UX를 인맥관리 GUI에 적용시켜 사용자의 감성적 제스처를 이해하고 활용하는 것에 관점을 두었다. 개체와 개체의 관계를 노드 구조로 형상화 하여 보다 직관적으로 개체를 관리 할 수 있도록 하였다. 손쉬운 그룹핑과 관계의 확장성은 어려웠던 인맥 관리의 불필요한 정보의 과밀성을 최소화 하고 쉬운 구조로 표현하였으며 수정과 삭제의 관리 시간을 줄여주었다. 그러나 이러한 인터페이스의 환경은 많은 기술적 문화적 제약을 가지고 있으며, 이러한 제약적인 요소를 해소하기에는 다소 한계성을 가지고 있다. 본 연구에서는 본 연구에서 제시하는 새로운 인터렉션 경험이 감성의 표현 연구에 적극적으로 활용되어 보다 인간의 언어에 가까운 UX 표현연구에 활용되길 기대한다.

• 한국지진공학회논문집
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• 제5권4호
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• pp.17-26
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• 2001

한반도 남부에서 발생 가능한 강지진동의 최대 지반운동과 주파수에 따른 특성을 추계학적 모사법을 이용하여 간접적으로 추정하였다. 또한 추계학적 모사법에 적용할 진원과 지진파 감쇠에 관한 입력자료를 계산하였다. 응력강하($\Delta$$\sigma$)는 한반도 남부와 미국 동부 및 중국의 연구결과를 종합하여 100-bar로 추정하였다. 감쇠상수는 x는 1996년 9월부터 1997년 12월까지 발생한 지진 중 비교적 기록상태가 양호한 57개의 관측자료를 이용하여 계산하였으며 진원거리(R)에 대하여 0.00112+0.000224 R로 추정되었다. 이와 같은 응력강하($\Delta$$\sigma$)와 감쇠상수 x등의 입력자료를 추계학적 모사법에 적용한 결과를 바탕으로 진원거리에 따른 강진동 감쇠공식을 유도하였다.한 결과를 바탕으로 진원거리에 따른 강진동 감쇠공식을 유도하였다.