• Advances in materials Research
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• 제6권1호
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• pp.45-63
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• 2017

In this article, static deflection and buckling of functionally graded (FG) nanoscale beams made of porous material are carried out based on the nonlocal Timoshenko beam model which captures the small scale influences. The exact position of neutral axis is fixed, to eliminate the stretching and bending coupling due to the unsymmetrical material change along the FG nanobeams thickness. The material properties of FG beam are graded through the thickness on the basis of the power-law form, which is modified to approximate the material properties with two models of porosity phases. By employing Hamilton's principle, the nonlocal governing equations of FG nanobeams are obtained and solved analytically for simply-supported boundary conditions via the Navier-type procedure. Numerical results for deflection and buckling of FG nanoscale beams are presented and validated with those existing in the literature. The influences of small scale parameter, power law index, porosity distribution and slenderness ratio on the static and stability responses of the FG nanobeams are all explored.

• 아동학회지
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• 제12권1호
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• pp.38-51
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• 1991

This study investigated (1) the relation of aggressiveness to the outcome of conflict, intentional attribution, predicted response, and (2) friendship as a variable affecting intentional attribution and predicted response. The subjects are 78 fifth grade boys selected from a public elementary school located in Seoul. The children were individually tested by the researcher who read the items to the child. Dodge and Somberg's aggression questionnaire and Dodge and Frame's conflict outcome of ambiguosly intended stories were modified for use in this study. The instigator of aggression in the stories was classified as friend or non-friend and aggressive non-friend or nonaggressive non-friend. Two-way analyses of variance involving one between-subjects factor (aggression of subject) and one within-subjects factor (instigator combination) were performed on children's responses to three of the scales (hostile, neutral, positive). The results show that (1) there were differences in intentional attribution to the children's aggressiveness, regardless of the friendship status of the instigator, and (2) the predicted response to aggressiveness varied with type of instigator.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.151-154
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• 2001

Shape memory alloy (SMA) has demonstrated its potentials for various smart structure applications. SMA wires undergo a reversible phase transformation from martensite to austenite as temperature increases. This transformation leads to shape recovery and associated recovery strains. If SMA actuators are embedded off the neutral surface and are oriented in arbitrary angles with respect to a beam axis, then the beam bends and twists due to the coupling effects of recovery strains activated. In this study, the bending and twisting of a SMA/Composite beam were controlled by both electric resistive heating and passive elastic tailoring. 3-dimensional finite element formulations were derived and validated to analyze the responses of the SMA/Composite beam. Numerical results show that the shape of the SMA/Composite beam can be controlled by judicious choices of control temperatures, SMA angles, and elastic tailoring.

• Journal of the Optical Society of Korea
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• 제14권2호
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• pp.152-162
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• 2010

This study examined the effects of surround luminance on the shape of the spatial luminance contrast sensitivity function (CSF). The reduction in brightness of uniform neutral patches shown on a computer controlled display screen is also assessed to explain the change of CSF shape. Consequently, a large amount of reduction in contrast sensitivity at middle spatial frequencies can be observed; however, the reduction is relatively small for low spatial frequencies. In general, the effect of surround luminance on the CSF appears similar to that of mean luminance. Reduced CSF responses result in less power of the filtered image; therefore, the stimulus should appear dimmer with a higher surround luminance.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.148.2-148
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• 2001

The most important difference of an airship from conventional vehicle is that it has the apparent mass and inertia provided from the existence of Helium gas inside the airship. To acquire To acquire the exact response of the airship, the longitudinal responses of airship with respect to the vertical gust, which is the non-linear system, have been studied. An Airship has neutral buoyancy in equilibrium state. When it moves, its motion shows much difference comparing with conventional aircraft. Here, we compare two cases, the one has the apparent mass and the other hasn´t. With the apparent mass, the magnitude of the former response is smaller than the latter, while the frequency is higher. However, the apparent mass delay ...

• 패션비즈니스
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• 제9권4호
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• pp.44-58
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• 2005

In a global market environment with information technology, the textile and apparel industry tries to survive by having competitive power embedded in Supply Chain Management to improve the interrelation among different stages of industries such as fiber, textile, apparel manufacturing, and retailing. The purpose of this empirical study was to investigate performance on Supply Chain Management of textile firms such as 4 textile export firms and 10 collaborate firms which were adopted SCM system. For research methodology, we developed questionnaires based upon interview and literature review. The results of this study were as follows: There were neutral responses or somewhat dissatisfactions on SCM application from CEOs, CMOs, site workers, and collaborators, but over half of respondents indicated 21-40% improvement of affairs. Standard documents and information sharing of SCM system were salient effects. SCM system with standard documents improved receipts/payments and inventory management most.

• 한국의류학회지
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• 제29권12호
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• pp.1527-1534
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• 2005

본 연구는 아동의 체온조절반응의 특징에 성장환경이 어떠한 영향을 미치는가를 명확히 하기 위해, 한국아동(K group)과 일본아동(J group)의 체온조절반응을 검토하였다. 팬츠 착용의 피험자는 중립환경 $(28.5^{\circ}C)$에서 1시간, 추운환경$(22^{\circ}C)$ 또는 더운환경$(37^{\circ}C)$으로 옮겨져 1시간 동안의 체온조절반응이 검토되었다. 그 결과, 직장온은 환경온이 높아짐에 따라 약간 높아졌으며, K group의 직장온이 J group보다 약간 높았다. 추운환경에서의 손과 발의 피부온은 현저히 저하되었으며, J group보다 K group에서 더 현저히 나타났다. 그리고, 두 group의 절대 국소 증발량은 환경온 $22^{\circ}C$와 $28.5^{\circ}C$에서 비슷한 분포를 나타내는 반면, 환경온 $37^{\circ}C$에서는 J group은 몸 전체에서 발한을 나타냈으나 K group은 사지보다 몸통부위의 발한량이 많았다. 맥박은 환경온의 상승에 따라 높아졌으며, J group의 맥박이 K group보다 더 높았다.

• 인지과학
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• 제23권2호
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• pp.165-184
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• 2012

주의를 기울이지 않은 배경자극의 정서가가 표적자극의 지각처리에 미치는 영향을 알아보기 위해 정서적 그림자극(IAPS) 위에 6개 글자들을 함께 제시하고서 실험참가자들에게 특정 글자를 탐지하도록 요구하였다. 글자탐지의 난이도를 달리하여 지각부담을 조작하였는데, 정확율과 반응시간 모두에서 저부담조건이 고부담조건보다 빠르고 정확하였다. ERP 분석 결과, 정서자극 없이 글자탐지만 수행한 통제조건의 경우 후측 시각영역에서 P1과 N1 성분에서 지각부담효과가 관찰되었다. 실험조건에서는 정서가와 지각부담의 상호작용이 후측 시각영역의 N1에서 관찰되었는데, 특히 중립정서보다 부정정서에서 고부담조건과 저부담조건간 진폭 차이가 더 크게 나타났다. 배경자극이 부정적인 경우 중립적인 경우보다 주의용량을 더 소모함으로써 지각부담효과가 더 컸던 것으로 판단되는데, 이는 주의집중 받지 않은 정서자극이 자동적으로 처리되어 표적자극의 초기 지각처리에 영향을 미친다는 것을 시사한다.

• 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.

• Wind and Structures
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• 제27권6호
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• pp.381-397
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• 2018

Nonlinear behavior in fluid-structure interaction (FSI) of bridge decks becomes increasingly significant for modern bridges with increasing spans, larger flexibility and new aerodynamic deck configurations. Better understanding of the nonlinear aeroelasticity of bridge decks and further development of reduced-order nonlinear models for the aeroelastic forces become necessary. In this paper, the amplitude-dependent and neutral angle dependent nonlinearities of the motion-induced loads are further highlighted by series of computational fluid dynamics (CFD) simulations. An effort has been made to investigate a semi-analytical time-domain model of the nonlinear motion induced loads on the deck, which enables nonlinear time domain simulations of the aeroelastic responses of the bridge deck. First, the computational schemes used here are validated through theoretically well-known cases. Then, static aerodynamic coefficients of the Great Belt East Bridge (GBEB) cross section are evaluated at various angles of attack, leading to the so-called nonlinear backbone curves. Flutter derivatives of the bridge are identified by CFD simulations using forced harmonic motion of the cross-section with various frequencies. By varying the amplitude of the forced motion, it is observed that the identified flutter derivatives are amplitude-dependent, especially for $A^*_2$ and $H^*_2$ parameters. Another nonlinear feature is observed from the change of hysteresis loop (between angle of attack and lift/moment) when the neutral angles of the cross-section are changed. Based on the CFD results, a semi-analytical time-domain model for describing the nonlinear motion-induced loads is proposed and calibrated. This model is based on accounting for the delay effect with respect to the nonlinear backbone curve and is established in the state-space form. Reasonable agreement between the results from the semi-analytical model and CFD demonstrates the potential application of the proposed model for nonlinear aeroelastic analysis of bridge decks.