• Structural Engineering and Mechanics
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• v.68 no.1
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• pp.103-119
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• 2018

In the present research, an attempt is made to obtain a semi analytical solution for both nonlinear natural frequency and forced vibration of embedded functionally graded double layered nanoplates with all edges simply supported based on nonlocal strain gradient elasticity theory. The interaction of van der Waals forces between adjacent layers is included. For modeling surrounding elastic medium, the nonlinear Winkler-Pasternak foundation model is employed. The governing partial differential equations have been derived based on the Mindlin plate theory utilizing the von Karman strain-displacement relations. Subsequently, using the Galerkin method, the governing equations sets are reduced to nonlinear ordinary differential equations. The semi analytical solution of the nonlinear natural frequencies using the homotopy analysis method and the exact solution of the nonlinear forced vibration through the Harmonic Balance method are then established. The results show that the length scale parameters give nonlinearity of the hardening type in frequency response curve and the increase in material length scale parameter causes to increase in maximum response amplitude, whereas the increase in nonlocal parameter causes to decrease in maximum response amplitude. Increasing the material length scale parameter increases the width of unstable region in the frequency response curve.

• The Journal of the Korea Contents Association
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• v.11 no.8
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• pp.448-458
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• 2011

The availability of many smartphone applications and ubiquitous Wi-Fi technology has greatly spread the uses of smartphones. Particularly smartphones with the locative media services in tourism are booming because location-based technology such as GPS is well suit with tourism and tourists' needs. Smartphones also overcome the technological limit of traditional information media such as printed book, newspaper, etc. Based on the Niche Theory, the study examines the competitive relationships among information media that are used in tourism including smartphones, traditional paper publications, and computers. The paper also examines the niche of each medium based on the theory and finds which medium is more effective and preferred by people who utilize the services before and during their travel.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.231-238
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• 2005

On the basis of flow resistance theory the conceptual model and related mathematical descriptions is proposed for resistance modeling of groundwater flow in CPM(continuum Porous medium), DFN(discrete fracture network) and fractured-porous medium. The proposed model is developed on the basis of finite volume method assuming steady-state, constant density groundwater flow. The basic approach of the method is to evaluate inter-block flow resistance values for a staggered grid arrangement, i.e. fluxes are stored at cell walls and scalars at cell centers. The balance of forces, i.e. the Darcy law, is utilized for each control volume centered around the point where the velocity component is stored. The transmissivity (or permeability) at the interface is assumed to be the harmonic average of neighboring blocks. Flow resistance theory was utilized to relate the fluxes between the grid blocks with residual pressures. The flow within porous medium is described by three dimensional equations and that within an individual fracture is described by a two dimensional equivalent of the flow equations for a porous medium. Newly proposed models would contribute to develop flow simulation techniques with various matrix characteristics.

• Coupled systems mechanics
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• v.8 no.4
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• pp.299-313
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• 2019

The paper represents computer modeling of the deformed state of physically nonlinear transversally isotropic bodies with hole. In order to describe the anisotropy of the mechanical properties of transversally-isotropic materials a structurally phenomenological model has been used. This model allows representing the initial material in the form of the coupled isotropic materials: the basic material (binder) considered from the positions of continuum mechanics and the fiber material oriented along the anisotropy direction of the original material. It is assumed that the fibers perceive only the axial tensile-compression forces and are deformed together with the base material. To solve the problems of the theory of plasticity, simplified theories of small elastoplastic deformation have been used for a transversely-isotropic body, developed by B.E. Pobedrya. A simplified theory allows applying the theory of small elastoplastic deformations to solve specific applied problems, since in this case the fibrous medium is replaced by an equivalent transversely isotropic medium with effective mechanical parameters. The essence of simplification is that with simple stretching of composite in direction of the transversal isotropy axis and in direction perpendicular to it, plastic deformations do not arise. As a result, the intensity of stresses and deformations both along the principal axis of the transversal isotropy and along the perpendicular plane of isotropy is determined separately. The representation of the fibrous composite in the form of a homogeneous anisotropic material with effective mechanical parameters allows for a sufficiently accurate calculation of stresses and strains. The calculation is carried out under different loading conditions, keeping in mind that both sizes characterizing the fibrous material fiber thickness and the gap between the fibers-are several orders smaller than the radius of the hole. Based on the simplified theory and the finite element method, a computer model of nonlinear deformation of fibrous composites is constructed. For carrying out computational experiments, a specialized software package was developed. The effect of hole configuration on the distribution of deformation and stress fields in the vicinity of concentrators was investigated.

• Asia pacific journal of information systems
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• v.8 no.3
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• pp.119-134
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• 1998

Among several theories to explain how different communication media affect task performance, media richness theory(MRT) is one of the most frequently cited. Recent studies related to the use of communication media, however, have raised the question of the effectiveness of the MRT as a predictor of media choices or of individual effectiveness. The objective of this research is to examine the assumptions of the MRT. MRT proposes that the properties of media are objective in other words, they are inherent and physical attributes recognizable by users. This study experiments on the effects of task characteristics and medium experience on the perceived media richness and social presence. The results of this study did not support the assumptions of the MRT. There was an interaction effects of task characteristics and medium experience on both the perceived media richness and social presence. While the inexperienced computer-mediated communication(CMC) group perceives their medium richer for the unequivocal task, the experienced CMC group perceives their medium equally for the equivocal and the unequivocal task.

• Advances in nano research
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• v.6 no.4
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• pp.339-356
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• 2018

In this article, the critical buckling of a single-walled carbon nanotube (SWCNT) embedded in Kerr's medium is studied. Based on the nonlocal continuum theory and the Euler-Bernoulli beam model. The governing equilibrium equations are acquired and solved for CNTs subjected to mechanical loads and embedded in Kerr's medium. Kerr-type model is employed to simulate the interaction of the (SWNT) with a surrounding elastic medium. A first time, a comparison with the available results is made, and another comparison between various models Winkler-type, Pasternak-type and Kerr-type is studied. Effects of nonlocal parameter and aspect ratio of length to diameter of nanobeam, as well as the foundation parameters on buckling of CNT are investigated. These results are important in the mechanical design considerations of nanocomposites based on carbon nanotubes.

• Journal of Digital Convergence
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• v.15 no.11
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• pp.107-112
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• 2017

This paper performed an experimental study to test the validity of the prospect theory proposed by Tversky and Kahneman as an alternative to the expected utility theory. 115 college students attended the hypothetical games to choose one of two lotteries, one is safe option while the other one is risky. The risky options were set up to have low, medium or high probability of payoffs or losses. The amount of payoffs and losses of the lotteries was either large or small. Maximum likelihood estimation of the hypothetical games have shown that in case of high probability of positive payoffs the respondents were risk averse and when the probability of positive payoffs were small the respondents were risk loving. when the possibility of loss is high they were risk loving, while the probability is of loss is low the respondents were found to be risk averse. When the probability of risky options were medium the results were significant statistically in case of only losses. The amount of positive payoff or losses does not affect the results. Overall the results of this experiments support the prospect theory more than those of Laury & Holts (2008).

• Korean Institute of Interior Design Journal
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• v.26 no.3
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• pp.34-44
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• 2017

Korean-Japanese architect Itami Jun that proceeded with primeval architecture based on analogue ideas in the digital era realizing nomad architecture is delivering a totally different meaning in the modern time. Not like the Japanese architectural community equipped with rich technologies showed state-of-the-art architecture after 1980s, Itami Jun' formative consciousness intending to assimilate nature from the original position of things is thought to have started from the relationship with Korean-Japanese painters leading MONO-HA desiring to look at the world as it is and approach the source of existence. The purpose of this study is to analyze the spatial characteristics from the viewpoint of 'Theory of Meeting' which is the essence of the work theory of Lee UFan that made the theoretical foundation of MONO-HA to understand Itami Jun's architectural space in the ideological aspect. Although the characteristics of marginal men appearing in Itami Jun's architectural space as others located on the boundary between Korea and Japan, art and architecture, and functions are valuable research objects, they have not been studied in the aspect of source, so it is needed to research his works and the source of the spatial ideas that led his works. Based on Theory of Meeting claiming that the world becomes the place of experience by the medium of objet which is the structure of meeting, and that human beings can meet the truly opened world by self-awareness through body, the expressive characteristics of Itami Jun's interior space was analyzed. As a result of the analysis, it turned out that Itami Jun's interior space actively expressed Theory of Meeting on the unity of structure and space, and on the trans-boundary by the medium of objet. Conclusively, this study suggests that, in the reality of the modern interior design full of technology-intensive designs, analogue approach moving in the opposite way from technologies could be a better expressive method of design delivering the fundamental human emotions.

• Journal of Electrical Engineering and Technology
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• v.6 no.6
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• pp.750-759
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• 2011

This paper focuses on the control of bidirectional power flow in the electric shipboard power systems, especially in the Medium-Voltage Direct Current (MVDC) shipboard power system. Bidirectional power control between the main MVDC bus and the local zones can improve the energy efficiency and control flexibility of electric ship systems. However, since the MVDC system contains various nonlinear loads such as pulsed power load and radar in various subsystems, the voltage of the MVDC and the local zones varies significantly. This voltage variation affects the control performance of the bidirectional DC-DC converters as exogenous disturbances. To improve the control performance regardless of uncertainties and disturbances, this paper proposes a novel controller design method of the bidirectional DC-DC converters using $L_1$ control theory and intelligent optimization algorithm. The performance of the proposed method is verified via large-scale real-time digital simulation of a notional shipboard MVDC power system.

• Steel and Composite Structures
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• v.37 no.1
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• pp.99-115
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• 2020

This article deals with the dynamic analysis in pad concrete foundation containing Silica nanoparticles (SiO₂) subject to seismic load. In order to control the foundation smartly, a piezoelectric layer covered the foundation. The weight of the building by a column on the foundation is assumed with an external force in the middle of the structure. The foundation is located in soil medium which is modeled by spring elements. The Mori-Tanaka law is utilized for calculating the equivalent mechanical characteristics of the concrete foundation. The Kevin-Voigt model is adopted to take into account the structural damping. The concrete structure is modeled by a thick plate and the governing equations are deduced using Hamilton's principle under the assumption of higher-order shear deformation theory (HSDT). The differential quadrature method (DQM) and the Newmark method are applied to obtain the seismic response. The effects of the applied voltage to the smart layer, agglomeration and volume percent of SiO₂ nanoparticles, damping of the structure, geometrical parameters and soil medium of the structure are assessed on the dynamic response. It has been demonstrated by the numerical results that by applying a negative voltage, the dynamic deflection is reduced significantly. Moreover, silica nanoparticles reduce the dynamic deflection of the concrete foundation.