• Structural Engineering and Mechanics
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• 제15권2호
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• pp.199-223
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• 2003

The formulation of a non-linear shear deformable shell element is presented for the solution of stability problems of stiffened plates and shells. The formulation of the geometrical stiffness presented here is exactly defined on the midsurface and is efficient for analyzing stability problems of thick plates and shells by incorporating bending moment and transverse shear resultant force. As a result of the explicit integration of the tangent stiffness matrix, this formulation is computationally very efficient in incremental nonlinear analysis. The element is free of both membrane and shear locking behaviour by using the assumed strain method such that the element performs very well in the thin shells. By using six degrees of freedom per node, the present element can model stiffened plate and shell structures. The formulation includes large displacement effects and elasto-plastic material behaviour. The material is assumed to be isotropic and elasto-plastic obeying Von Mises's yield condition and its associated flow rules. The results showed good agreement with references and computational efficiency.

• Structural Engineering and Mechanics
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• 제83권3호
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• pp.283-292
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• 2022

A nonlinear vibrational analysis of sandwich curved panels having multi-scale face sheets has been performed in this article based on differential quadrature method (DQM). All mechanical properties of multi-scale skins have been established in the context of three-dimensional Mori-Tanaka scheme for which the influences of glass fibers and random carbon nanotubes (CNTs) have been taken into account. The governing equations for sandwich the panel have been developed based upon thin shell formulation in which geometry nonlinearities have been taken into account. Next, DQ approach has been applied to solve the governing equations for determining the relationships of frequencies with deflections for curved panels. It will be demonstrated that the relationships of frequencies with deflections are dependent on the changing of CNT weight fractions, fibers alignment, fibers volume, panel radius and skin thickness.

• Structural Engineering and Mechanics
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• 제82권6호
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• pp.691-699
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• 2022

This paper is devoted to the presentation of a numerical study on vibration behavior of composite panels reinforced by glass fibres and carbon nanotubes (CNTs) subjected to thermal environments. The effect of temperature variation has been included as thermal load acting on in-plane direction of the panel. To model the composite material, a micromechanical model which contains random dispersion of nanotubes and single-direction fibers has been selected. The geometry of the panel has been considered to have a single curveture along its width. Based on the above assumptions, the governing equations have been derived by using thin shell theory capturing the panel curveture and also nonlinear deflections. Finally, the panel dependence on various factors such as the curveture, nanotube amount, fiber volume, fiber direction and temperature variation has been researched.

• Structural Engineering and Mechanics
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• 제31권2호
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• pp.137-152
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• 2009

Mechanic behavior of Y-shape thin-walled box girder bridge structure is complex, so one can not exactly hold the mechanical behavior of the Y-shape thin-walled box girder bridge structure through general calculation theory and analytical method. To hold the mechanical behavior better, based on elementary beam theory, by increasing the degree of freedom analytical method, taking account of restrained torsiondistortion angledistortion warp and shearing lag effect at the same time, authors obtain a thin-walled box beam analytical element of 10 degrees of freedom of every node, derive stiffness matrix of the element, and code a finite element procedure. In addition, authors combine the obtained procedure with spatial grillage analytical method, meanwhile, they build a new analytical method that is the spatial thin-walled box girder element grillage analysis method. In order to validate the precision of the obtained analysis method, authors analyze a type Y-shape thin-walled box girder bridge structure according to the elementary beam theory analytical method, the shell theory analytical method and the spatial thin-walled box girder element grillage analysis method respectively. At last, authors test a type Y-shape thin-walled box girder bridge structure. Comparisons of the results of theory analysis with the experimental text show that the spatial thin-walled box girder element grillage analysis method is simple and exact. The research results are helpful for the knowledge of the mechanics property of these Y-shape thin-walled box girder bridge structures.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3593-3599
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• 2010

In an original effort, this lab attempted to employ polystyrene nanoparticles as a template for the synthesis of ordered and highly porous macroporous $SiO_2$ thin films, utilizing their high combustion temperature and narrow size distribution. However, polystyrene nanoparticle thin films were not obtained due to the low interaction between individual particles and between the particle and silicon substrate. However, polystyrene-polyacrylic acid (PS-AA) colloidal particles of a core-shell structure were synthesized by a one-pot miniemulsion polymerization approach, with hydrophilic polyacrylic acid tails on the particle surface that improved interaction between individual particles and between the particle and silicon substrate. The PS-AA thin films were spin-coated in the thickness ranges from monolayer to approximately $1.0\;{\mu}m$. Using the PS-AA thin films as sacrificial templates, macroporous $SiO_2$ thin films were successfully synthesized by vapor deposition or conventional solution sol-gel infiltration methods. Inspection with field emission scanning electron microscopy (FE-SEM) showed that the macroporous $SiO_2$ thin films consist of interconnected air balls (~100 nm). Typical macroporous $SiO_2$ thin films showed ultralow refractive indices ranging from 1.098 to 1.138 at 633 nm, according to the infiltration conditions, which were confirmed by spectroscopy ellipsometry (SE) measurements. This research shows how the synthetic control of the macromolecule such as hydrophilic polystyrene nanopaticles and silicate sol precursors innovates the optical properties and processabilities for actual applications.

• 한국식품영양과학회지
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• 제12권4호
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• pp.407-419
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• 1983

서식환경(棲息環境)이 다른 해산(海産) 참굴, 소라 그리고 담수산(淡水産) 후루미재첩의 3종(種) 패류(貝類)를 시료(試料)로 총지질(總脂質)을 추출(抽出)하여 thin layer chromatography와 TLC-scanner를 이용(利用)하여 총지질(總脂質)을 구성(構成)하는 지질성분(脂質成分)을 정량(定量)하였다. 그리고 gas liquid chromatography로 총지질(總脂質)의 지방산(脂肪酸) 및 sterol 조성(組成)을 정량(定量)하였으며, 총지질(總脂質)을 다시 column chromatography로 중성지질(中性脂質), 당지질(糖脂質) 및 인지질(燐脂質)로 분획(分劃)하여 패류지질(貝類脂質)의 특징(特徵)을 비교(比較) 검토(檢討)하여 다음과 같은 결론(結論)을 얻었다. 1) 시료(試料) 패류(貝類)의 총지질(總脂質) 함량(含量)은 굴이 1.8%, 소라가 0.4% 그리고 후루미재첩이 4.0%였다. 그리고 총지질(總脂質)의 전지방산(全脂肪酸)의 함량(含量)은 굴이 80.7%, 소라가 71.2%, 후루미재첩이 73.2%였고 불감화물은 굴이 15.4%, 소라가 18.1%, 후루미재첩이 23.1%였다. 2) 총지질(總脂質)을 구성(構成)하는 지질성분(脂質成分)으로는 triglyceride, 극성지질일색소(極性脂質一色素) 혼합층(混合層) 그리고 sterol성분(成分)이 가장 많았고 hydrocarbon-esterified sterol 혼합층(混合層)의 순(順)으로 나타났다. 3) 총지질(總脂質)을 구성(構成)하는 지방산(脂肪酸)은 참굴에서는 palmitic(37.0%), eicosapentaenoic(13.5%) 및 linoleic acid(11.2%)가 주성분(主成分)을 이루고 있고 소라에서는 octadecatetraenoic(15.8%), palmitic(11.2%), oleic(8.6%) 및 linoleic acid(8.1%)가 주성분(主成分)을 이루고 있으나, 후루미재첩에서는 palmitic(34.0%), Iinoleic(12.3%) 및 palmitoleic acid(9.8%)가 주성분(主成分)을 이루고 있었다. 특(特)히 참굴과 소라에서는 eicosapentaenoic acid의 함량(含量)이 후루미재첩보다 훨씬 많았다. 4) 3종(種) 패류(貝類)의 sterol성분(成分)은 주(主)로 cholesterol(42.7~64.0%), brassicasterol(15.6~24.7%) 및 24-methylenecholesterol(4.7~21.4%)였다. 그러나 참굴에서는 sitosterol(5.3%)이 소라에는 22-dehydrocholesterol(12.9%)이 검출(檢出)되었다. 5) 총지질(總脂質)에서 분획(分劃)한 비극성지질(非極性脂質)과 극성지질(極性脂質)의 함량(含量)은 시료(試料)에서 공통적(共通的)으로 비극성지질(非極性脂質)이 극성지질(極性脂質)보다 높았다. 그리고 극성지질중(極性脂質中)에서는 당지질(糖脂質)과 인지질(燐脂質)의 함량비(含量比)가 비슷하였다. 6) 중성지질(中性脂質)을 구성(構成)하는 지질성분(脂質成分)은 triglycerides(33.0~36.7%), free sterol(25.7~32.2), esterified sterol(12.4~23.7%) 그리고 free fatty acids(5.1~11.7%)로 구성(構成)되어 있었다. 중성지질(中性脂質)을 구성(構成)하는 지방산(脂肪酸)으로는 참굴과 후루미재첩에서는 palmitic(28.4~26.4%), eicosapentaenoic(18.6~21.9%) 및 linolenic acid(9.0~5.4%)가 주성분(主成分)이었고 소라에서는 octadecatetraenoic(14.5%), eicosapentaenoic(13.5%) 및 palmitic acid(12.3%)가 주성분(主成分)이었다. 7) 당지질(糖脂質)을 구성(構成)하는 지방산(脂肪酸)으로는 참굴에서는 eicosenoic(14.3%), palmitic(12.1%) 및 linolenic acid(10.2%)가 주성분(主成分)이었고, 소라에서는 eicosenoic(26.0%), octadecatetraenoic(14.6%) 및 eicosadienoic acid(12.9%)가 주성분(主成分)이었으며 후루미재첩에서는 eicosadienoic(21.4%), stearic(14.6%), octadecatetraenoic(8.5%) 및 eicosenoic acid(8.5%)가 주성분(主成分)이었다. 8) 인지질(燐脂質)을 구성(構成)하는 지방산(脂肪酸)으로는 참굴에서는 myristic(16.0%), stearic(10.6%), eicosenoic(10.5%) 및 palmitic acid(10.3%)가 주성분(主成分)이었고, 소라에서는 oleic(22.2%), stearic(20.7%) 및 linolenic acid(11.8%)가 주성분(主成分)이었으며, 후루미재첩에서는 eicosapentaenoic(25.1%), myristic(8.7%) 및 arachidonic acid(8.3%)가 주성분(主成分)이었다.

• 한국전산구조공학회논문집
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• 제13권3호
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• pp.321-328
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• 2000

본 연구는 유한한 회전의 2차항을 고려한 변위장에 기초하여 변곡률을 가지는 비대칭 박벽곡선보의 해석이론을 제시한다. Vlasov의 가정에 의한 연속체의 선형화된 가상일의 원리로부터 총 포텐셜 에너지를 유도하고, 모든 변위 파라미터와 ？ 함수는 도심에서 정의된다. 절점당 8개의 자유도를 가지는 박벽곡선보 요소의 개발 과정에서 3차 Hermitian 다항식이 형상함수로 이용된다. 본 연구의 타당성과 정확도를 입증하기 위하여, 일축대칭 단면을 갖는 포물선과 타원형상의 곡선보를 선택하여 3차원 자유진동해석과 안정성 해석을 수행한다. 그리고 이 결과를 ABAQUS의 쉘 요소에 의한 것과 비교한다.

• 한국강구조학회 논문집
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• 제14권3호
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• pp.423-432
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• 2002

비대칭 박벽단면을 갖는 곡선보의 자유진동해석을 수행할 수 있는 엄밀해 및 유한요소 이론을 제시한다. 단순지지된 일축대칭 박벽단면을 갖는 곡선보의 면내 자유진동 모드에 대응하는 엄밀해를 산정하였으며, 곡섬보를 유한요소로 분할하여 요소의 변위장을 요소의 변위벡터의 대하여 축방향 신장조건에서는 3차 그리고 비신장조건에서는 5차의 Hermitian 다항식으로 나타내고, 이를 운동방정식에 대입함으로써 탄성강성행렬과 질량행렬을 유도한다. 또한 본 연구에서 얻어진 엄밀해와 곡선보요소를 이용한 유한요소 해석결과를 ABAQUS 쉘요소를 이용하여 얻어진 결과와 비교 검토함으로써 본 연구의 타당성을 입증한다. 특히 곡선보의 축방향 비신장조건과 두께-곡률효과가 동적거동에 미치는 영향을 조사한다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.1033-1039
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• 2006

To overcome the drawback of currently available curved beam theories having non-symmetric thin-walled cross sections, a curved beam theory based on centroid-shear center formulation is presented for the spatially coupled free vibration and elastic analyses. For this, the elastic strain and kinetic energies considering the thickness-curvature effect and the rotary inertia of curved beam are derived by degenerating the energies of the elastic continuum to those of curved beam. And then the equilibrium equations and the boundary conditions are consistently derived for curved beams having non-symmetric thin-walled cross section. It is emphasized that for curved beams with L- or T-shaped sections, this thin-walled curved beam theory can be easily reduced to tl1e solid beam theory by simply putting the sectional properties associated with warping to zero. In order to illustrate the validity and the accuracy of this study, FE solutions using the Hermitian curved beam elements are presented and compared with the results by previous research and ABAQUS's shell elements.

• 한국의류학회지
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• 제22권7호
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• pp.807-815
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• 1998

Functions of interlinings to the shell fabric are to improve the garment formability for a beautiful silhouette and elastic potential to the deformed fabric during wearing, and also are to enhance appearance and wearing properties of garment. The objective of this study is to analyse the thermal properties of nonwoven fusible interlining to the thin worsted fabric with various fabric structural parameters. For the purpose fo this study, eight specimens with various weft yarn twists and weft densities of thin worsted fabrics are prepared. Three nonwoven fusible interlinings with different structure which were made by Nylon/Polyester were used for adhering to the thin worsted fabrics. Thermal properties of these 24 adhesive fabrics fused with 3 nonwoven interlinings are measured by KES-F7 System for analysing the thermal suitability of nonwoven fusible interlinings to the thin worsted fabrics with various fabric structural parameters. And air permeability, which was measured by KES-F8-API, of 24 nonwoven adhesive interlining fabrics was also analysed and discussed with the various kinds of nonwoven interlinings and fabric structural parameters.