• 복합신소재구조학회 논문집
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• 제1권3호
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• pp.1-9
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• 2010

본 연구에서는 Lagrangian 및 Hermite 보간함수를 혼합정식화한 유한요소법과 다양한 전단변형함수로 등방성, 대칭 적층 및 샌드위치판 모델을 제시하였다. 제시된 전단변형이론은 판의 상하면에서 전단응력이 0이 되는 다항식, 삼각함수, 쌍곡삼각함수 및 지수함수로 구성되어 있다. 모든 전단변형함수는 해석해, 정해 및 기발표된 유한요소 결과치와 비교하였으며, 합리적인 정확도를 갖는 것으로 예측되었다. 특히, 지수형태의 전단변형함수(Karama et al. 2003; Aydogu 2009)가 적층 및 샌드위치판 해석에 있어서 상대적으로 가장 우수한 결과를 보였다.

• Structural Engineering and Mechanics
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• 제3권1호
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• pp.91-103
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• 1995

An analysis to determine shear centers for anisotropic elastic thin-walled composite beams, cantilevered and loaded transversely at the free end is presented. The shear center is formulated based on familiar strength of material procedures analogous to those for isotropic beams. These procedures call for a balancing of torsional moments on the cross sectional surface and lead to a condition of zero resultant torsional couple. As a consequence, due the presence of anisotropic coupling, certain non-classical effects are manifested and are illustrated in two example problems. The most distinguishing result is that twisting may occur for composite beams even if shear forces are applied at the shear center. The derived shear center locations do not depend on any specific anisotropic bending theories per se, but only on the values of bending and shear stresses which such theories produce.

• Coupled systems mechanics
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• 제8권3호
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• pp.199-218
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• 2019

This paper studies the forced vibration of the hydro-elastic system consisting of the anisotropic (orthotropic) plate, compressible viscous fluid and rigid wall within the scope of the exact equations and relations of elastodynamics for anisotropic bodies for describing of the plate motion, and with utilizing the linearized exact Navier-Stokes equations for describing of the fluid flow. For solution of the corresponding boundary value problem it is employed time-harmonic presentation of the sought values with respect to time and the Fourier transform with respect to the space coordinate on the coordinate axis directed along the plate length. Numerical results on the pressure acting on the interface plane between the plate and fluid are presented and discussed. The main aim in this discussion is focused on the study of the influence of the plate material anisotropy on the frequency response of the mentioned pressure. In particular, it is established that under fixed values of the shear modulus of the plate material a decrease in the values of the modulus of elasticity of the plate material in the direction of plate length causes to increase of the absolute values of the interface pressure. The numerical results are presented not only for the viscous fluid case but also for the inviscid fluid case.

• Geomechanics and Engineering
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• 제24권3호
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• pp.267-280
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• 2021

The research presented in this paper deals with dynamic stability analysis of the graphene nanoplatelets (GPLs) reinforced composite spinning disk. The presented small-scaled structure is simulated as a disk covered by viscoelastic substrate which is two-parametric. The centrifugal and Coriolis impacts due to the spinning are taken into account. The stresses and strains would be obtained using the first-order-shear-deformable-theory (FSDT). For Poisson ratio, as well as various amounts of mass densities, the mixture rule is employed, while a modified Halpin-Tsai model is inserted for achieving the elasticity module. The structure's boundary conditions (BCs) are obtained employing GPLs reinforced composite (GPLRC) spinning disk's governing equations applying principle of Hamilton which is based on minimum energy and ultimately have been solved employing numerical approach called generalized-differential quadrature-method (GDQM). Spinning disk's dynamic properties with different boundary conditions (BCs) are explained due to the curves drawn by Matlab software. Also, the simply-supported boundary conditions is applied to edges 𝜃=𝜋/2, and 𝜃=3𝜋/2, while, cantilever, respectively, is analyzed in R=R_i, and R₀. The final results reveal that the GPLs' weight fraction, viscoelastic substrate, various GPLs' pattern, and rotational velocity have a dramatic influence on the amplitude, and vibration behavior of a GPLRC rotating cantilevered disk. As an applicable result in related industries, the spinning velocity impact on the frequency is more effective in the higher radius ratio's amounts.

• 대한화장품학회지
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• 제31권3호
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• pp.227-235
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• 2005

피부노화는 피부의 이상현상이나 질환은 아니며 나이가 들어감에 따라 시간의 진행에 따라 일어나는 퇴행성 변화로 외적형태의 변화로는 피부 건조 및 주름 등이 있다. 주름을 생성하는 원인에는 자외선, 건조 및 물리적, 화학적 자극 등 환경요인에 기인하는 피부 스트레스와 각질층의 수분량 저하, 비후화, 진피의 교원섬유, 탄력섬유의 양적, 질적 변화 등이 유발하는 피부의 탄력성이나 신축성의 저하를 들 수 있다. 본 연구에서는 Angelim dahurica root에서 얻어진 3종의 주름개선 유효성분의 구조분석 및 피부 노화에 대한 효과를 살펴보았다.

• 한국수산과학회지
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• 제57권2호
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• pp.109-115
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• 2024

This study investigated the effects of various naked barley starch contents (0, 0.67, 1.34, 2.0, and 2.67 wt%) in surimi mixtures for 3D printing. Adding starch to surimi altered its texture, potentially reducing production costs. Unheated surimi became less firm with higher starch content. After heating, there was an increase in hardness, adhesiveness, springiness, cohesiveness, gumminess, chewiness, and resilience, peaking at 1.34 wt% starch. Compared to the negative control, starch-added heated surimi had a tougher texture. The color values (L^*, a^*, and b^*) decreased after heating, with no significant change in shearing force with increasing starch content. Sensory evaluation indicated improved smell, texture, hardness, elasticity, and preference over the negative control. Higher starch content increased hardness for 3D printing suitability with no significant difference above 1.34 wt% starch indicating this is the most appropriate content. Naked barley starch enhanced surimi strength without affecting smell and preference, suggesting it as a potential surimi additive.

• 폴리머
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• 제36권6호
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• pp.705-711
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• 2012

본 연구에서는 일반 리포좀의 단점을 보완하기 위하여 인지질(PC)과 계면활성제($Tego^{(R)}$ care 450)로 구성된 탄성 리포좀을 제조하였다. 탄성 리포좀의 유효성분으로 천연 항산화제로 알려진 쿼세틴을 담지하였고, 탄성 리포좀의 입자크기 및 가변형성과 쿼세틴의 포집 효율, 안정성, in vitro 피부투과를 평가하였다. 쿼세틴을 담지한 탄성 리포좀의 평균 입자크기는 208.2~303.4 nm이였고, 포집효율은 64.1~87.5%로 측정되었다. 0.1% 쿼세틴을 담지한 탄성리포좀 중에서 인지질과 계면활성제 비율이 90 : 10인 경우가 가장 높은 포집효율(87.5%)과 가변형성 지수(28.3)를 나타내었다. 이 제형을 대상으로 피부 투과 실험을 진행하였다. 그 결과 대조군으로 사용된 일반 리포좀($114.8{\mu}g/cm^2$)과 1,3-butylene glycol($75.1{\mu}g/cm^2$) 용액보다 탄성 리포좀의 피부 투과능($164.6{\mu}g/cm^2$)이 훨씬 더 크게 나타났다. 이러한 결과들로 미루어 보아 $Tego^{(R)}$ care 450을 이용한 탄성 리포좀이 피부를 통한 유효성분 전달에 유용하게 이용될 수 있음을 확인하였다.

• Preventive Nutrition and Food Science
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• 제17권4호
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• pp.245-253
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• 2012

Collagen tripeptide (CTP) is a functional food material with several biological effects such as improving dry skin and wound and bone fracture healing. This study focused on the anti-photoaging effects of CTP on a hairless mouse model. To evaluate the effects of CTP on UVB-induced skin wrinkle formation in vivo, the hairless mice were exposed to UVB radiation with oral administration of CTP for 14 weeks. Compared with the untreated UVB control group, mice treated with CTP showed significantly reduced wrinkle formation, skin thickening, and transepidermal water loss (TEWL). Skin hydration and hydroxyproline were increased in the CTP-treated group. Moreover, oral administration of CTP prevented UVB-induced MMP-3 and -13 activities as well as MMP-2 and -9 expressions. Oral administration of CTP increased skin elasticity and decreased abnormal elastic fiber formation. Erythema was also decreased in the CTP-treated group. Taken together, these results strongly suggest that CTP has potential as an anti-photoaging agent.

• 한국전산구조공학회논문집
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• 제19권4호
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• pp.407-418
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• 2006

본 논문에서는 일차전단변형이론(FSDT)을 이용한 복합재료 적층평판의 고정밀 해석기법을 소개한다. 전단수정계수가 자동적으로 포함되도록 횡방향 전단 변형에너지를 혼합변분이론(mixed variational theorem)을 이용하여 개선하였다. 혼합변분이론에서는 변분을 횡방향 응력들에 대해서만 취하였다. 가정된 횡방향 전단응력은 효율적인 고차이론(Cho and Parmerter, 1993)으로부터 구하였다 횡방향 수직응력은 3차 다항식으로 가정하였고, 무전단 응력조건과 평판의 윗면과 아랫면에서의 응력을 만족하는 조건을 부과함으로써 얻었다. 한편, 변위들에 대해서는 일차전단변형이론의 변위장을 사용하였다. 이렇게 해서 얻어진 변형 에너지를 본 논문에서는 EFSDTM3D이라고 명명 하였다. 본 논문에서 개발된 EFSDTM3D는 변위와 응력의 계산에서 고전적인 FSDT와 같은 정도의 계산 효율을 가지면서, 동시에 변위와 응력의 두께방향의 정확도를 면내 방향 응력들에 대한 최소오차자승법에 기초하여 응력 회복 과정을 적용함으로써 개선하였다. 계산된 결과는 고전적인 FSDT, 3차원 탄성해, 그리고 참고문헌 중에서 이용 가능한 결과들과 비교하여 검증하였다.

• Smart Structures and Systems
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• 제19권2호
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• pp.115-126
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• 2017

In this paper, size dependent bending and free flexural vibration behaviors of functionally graded (FG) nanobeams are investigated using a nonlocal quasi-3D theory in which both shear deformation and thickness stretching effects are introduced. The nonlocal elastic behavior is described by the differential constitutive model of Eringen, which enables the present model to become effective in the analysis and design of nanostructures. The present theory incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect, and furthermore accounts for both shear deformation and thickness stretching effects by virtue of a hyperbolic variation of all displacements through the thickness without using shear correction factor. The material properties of FG nanobeams are assumed to vary through the thickness according to a power law. The neutral surface position for such FG nanobeams is determined and the present theory based on exact neutral surface position is employed here. The governing equations are derived using the principal of minimum total potential energy. The effects of nonlocal parameter, aspect ratio and various material compositions on the static and dynamic responses of the FG nanobeam are discussed in detail. A detailed numerical study is carried out to examine the effect of material gradient index, the nonlocal parameter, the beam aspect ratio on the global response of the FG nanobeam. These findings are important in mechanical design considerations of devices that use carbon nanotubes.