• Steel and Composite Structures
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• 제32권2호
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• pp.281-292
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• 2019

Nonlocal elasticity and Reddy plant theory are used to study the vibration response of functionally graded (FG) nanoplates resting on two parameters elastic medium called Pasternak foundation. Nonlocal higher order theory accounts for the effects of both scale and the effect of transverse shear deformation, which becomes significant where stocky and short nanoplates are concerned. It is assumed that the properties of FG nanoplate follow a power law through the thickness. In addition, Poisson's ratio is assumed to be constant in this model. Both Winkler-type and Pasternak-type foundation models are employed to simulate the interaction of nanoplate with surrounding elastic medium. Using Hamilton's principle, size-dependent governing differential equations of motion and corresponding boundary conditions are derived. A differential quadrature approach is being utilized to discretize the model and obtain numerical solutions for various boundary conditions. The model is validated by comparing the results with other published results.

• 대한화학회지
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• 제63권1호
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• pp.24-28
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• 2019

In this work, we discuss where the failure of Kohn-Sham Density Functional Theory (DFT) occurs in weak interactions. We have adopted density-corrected density functional calculations and dispersion correction separately to find out whether the failure is due to density-driven error or functional error. The results of Benzene Ar complex, one of the most common examples of van der Waals interactions, show that DFT calculations of van der Waals interaction suffer from functional error, rather than density-driven error. In addition, errors in DFT calculations of the S22 dataset, which contains small to relatively large (30 atoms) complexes with non-covalent interactions, are governed by functional errors.

• Advances in aircraft and spacecraft science
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• 제6권1호
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• pp.1-18
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• 2019

This present article represents the study of the forced vibration of nanobeam of a single-walled carbon nanotube (SWCNTs) surrounded by a polymer matrix. The modeling was done according to the Euler-Bernoulli beam model and with the application of the non-local continuum or elasticity theory. Particulars cases of the local elasticity theory have also been studied for comparison. This model takes into account the different effects of the interaction of the Winkler's type elastic medium with the nanobeam of carbon nanotubes. Then, a study of the influence of the amplitude distribution and the frequency was made by variation of some parameters such as (scale effect ($e_0{^a}$), the dimensional ratio or aspect ratio (L/d), also, bound to the mode number (N) and the effect of the stiffness of elastic medium ($K_w$). The results obtained indicate the dependence of the variation of the amplitude and the frequency with the different parameters of the model, besides they prove the local effect of the stresses.

• Coupled systems mechanics
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• 제9권6호
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• pp.575-597
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• 2020

Equilibrium equations of a porous FG plate resting on Winkler-Pasternak foundations with various boundary conditions are derived using a new refined shear deformation theory. Different types of porosity distribution rate are considered. Governing equations are obtained including the plate-foundation interaction. This new model meets the nullity of the transverse shear stress at the upper and lower surfaces of the plate. The novel rule of mixture is proposed to describe and approximate material properties of the FG plates with different distribution case of porosity. The validity of this theory is studied by comparing some of the present results with other higher-order theories reported in the literature. Effects of variation of porosity distribution rate, boundary conditions, foundation parameter, power law index, plate aspect ratio, side-to-thickness ratio on the deflections and stresses are all discussed.

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.325-331
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• 1992

By using the general theoretical framework proposed recently for treating the fluorescence quenching kinetics, we investigate the effect of light pulse intensity on the decay of fluorescence which follows excitation of fluorophors by the light pulse of very short but finite duration. It is seen that conventional theory breaks down when the exciting light pulse has a pulse width comparable to the fluorescent lifetime and its intensity is very high. We also find that even when the light intensity is not too high, conventional theory may fail in either of the following cases: (i) when the quencher concentration is high, (ii) when there is an attractive potential of mean force between the fluorophor and quencher, or (iii) when the energy transfer from the fluorophor to the quencher may also occur at a distance, e.g., via dipole-dipole interaction. The validity of the predictions of the present theory may thus be tested by fluorescence quenching experiments performed under such situations.

• 한국멀티미디어학회논문지
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• 제24권6호
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• pp.815-824
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• 2021

Based on the theory of space perception, this paper concludes that the mixed reality application under the theory of space perception has a three-level definition of visual hierarchy and then analyzes the component elements of interface design and the classification mode of interface windows. Next, carry out case practice research through this theoretical definition, and finally conduct the survey and analysis of questionnaire data, verifying that the mixed reality interface design based on spatial perception theory meets the user experience elements of Usability, Availability, and Attraction. The conclusion is that the constituent elements of interface design and the window classification mode can provide specific and practical design specifications for mixed reality interface design, reduce the interaction cost of completing tasks, reduce users' cognitive load, and make it easier for users to receive interface information

• 논리연구
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• 제18권1호
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• pp.83-133
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• 2015

이 글에서는 상반된 이중 원인 효과를 해명하는 데 히치콕(Hitchcock 2001a)이 제시한 두 가지 원인 효과를 비판적으로 평가하고 그 비판을 상쇄할 대안을 제시한다. 이를 위해 다섯 가지를 논의한다. 첫째, 상반된 이중 원인 효과에 관한 사례를 소개하고 이에 대한 오테(Otte 1985)와 엘스(Eells 1987)의 논쟁을 검토한다. 이 검토는 이중 원인 효과에 대한 이해와 그와 관련해 논의할 히치콕, 카트라이트(Cartwright 1979, 1989, 1995), 엘스(Eells 1991, 1995)의 이론들을 비교, 평가하는 준비가 된다. 둘째, 구조 방정식 모형에서 두 원인 효과에 착안하여, 히치콕이 제시한 원인 효과의 두 개념, 망 효과와 요소 효과를 소개한다. 셋째, 이중 원인 효과를 해명하는 데 카트라이트와 엘스의 논쟁을 논의하면서, 동질적 부분 집단의 역할, 인과 상호 작용의 중요성에 주목한다. 넷째, 이중 원인 효과를 해명하는 데 히치콕이 적용한 두 원인 효과 개념을 비판적으로 검토하고, 엘스의 이론에 대한 히치콕의 비판을 다시 비판한다. 다섯째, 구조 방정식 모형의 조절 효과 개념을 인과에 대한 확률 이론에 응용하여, 이중 원인 효과에서 초래된 인과 상호 작용을 선언(disjunctive) 관계와 반 사실적 요인으로 형식화하여 보여준다. 조절 효과에 대한 논의는 최근에 많은 주목을 받은 구조 방정식 모형에 토대한 인과 모형 이론들이 인과의 문제들을 해결하는 데 기여할 수 있다. 다른 한편으로, 선언 관계, 반 사실적 조건을 이용한 인과 상호 작용에 대한 논의는 통계적 방법론으로서 구조 방정식 모형을 제고하는 데 도움을 줄 수 있다.

• Structural Engineering and Mechanics
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• 제25권5호
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• pp.501-518
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• 2007

In this work, a new approach is developed for dynamic analysis of a composite beam with an interply crack, based on finite element solution of partial differential equations with the use of the COMSOL Multiphysics package, allowing for fast and simple change of geometric characteristics of the delaminated area. The use of COMSOL Multiphysics package facilitates automatic mesh generation, which is needed if the problem has to be solved many times with different crack lengths. In the model, a physically impossible interpenetration of the crack faces is prevented by imposing a special constraint, leading to taking account of a force of contact interaction of the crack faces and to nonlinearity of the formulated boundary value problem. The model is based on the first order shear deformation theory, i.e., the longitudinal displacement is assumed to vary linearly through the beam's thickness. The shear deformation and rotary inertia terms are included into the formulation, to achieve better accuracy. Nonlinear partial differential equations of motion with boundary conditions are developed and written in the format acceptable by the COMSOL Multiphysics package. An example problem of a clamped-free beam with a piezoelectric actuator is considered, and its finite element solution is obtained. A noticeable difference of forced vibrations of the delaminated and undelaminated beams due to the contact interaction of the crack's faces is predicted by the developed model.

• Steel and Composite Structures
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• 제21권5호
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• pp.1045-1067
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• 2016

Concrete bridges with corrugated steel webs and prestressed by both internal and external tendons have emerged as one of the promising bridge forms. In view of the different behaviour of components and the large shear deformation of webs with negligible flexural stiffness, the assumption that plane sections remain plane may no longer be valid, and therefore the classical Euler-Bernoulli and Timoshenko beam models may not be applicable. In the design of this type of bridges, both the ultimate load and ductility should be examined, which requires the estimation of full-range behaviour. An analytical sandwich beam model and its corresponding beam finite element model for geometric and material nonlinear analysis are developed for this type of bridges considering the diaphragm effects. Different rotations are assigned to the flanges and corrugated steel webs to describe the displacements. The model accounts for the interaction between the axial and flexural deformations of the beam, and uses the actual stress-strain curves of materials considering their stress path-dependence. With a nonlinear kinematical theory, complete description of the nonlinear interaction between the external tendons and the beam is obtained. The numerical model proposed is verified by experiments.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 제17회 워크샵 및 추계학술대회
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• pp.634-637
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• 2005

Hydrogen adsorption mechanism onto the porous metal-organic frameworks (MOFs) has been studied by density functional theory calculation. The selected functionals for the predict ion of interact ion energies between hydrogen and potential adsorption sites of MOF was utilized after the evaluation with the various functionals for interaction energy of $H_2C_6H_6$ model system the adsorption energy of hydrogen molecule into MOF was investigated with the consideration of the favorable adsorption sites and the orientations. We also calculated the second favorable adsorption sites by geometry optimization using every combination of two first absorbed hydrogen molecules. Based on the calculation of first and second adsorption sites and energies, the hydrogen adsorption into MOF follows a cooperative mechanism in which the initial metal sites initiate the propagation of the hydrogen adsorption on the whole frameworks. In addition, it was found that the interaction strength between the simple benzene ring with hydrogen is significantly reinforced when the benzene ring has been incorporated into the framework of MOFs.