• The Journal of the Acoustical Society of Korea
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• 제19권1E호
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• pp.3-12
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• 2000

In this paper, two major theories of effective medium for composite materials are studied, which provide the average dynamic mechanical properties of particulate composites carrying elastic waves on the basis of the concept of self-consistent scattering of waves. These two theories are also compared in detail with each other to delineate the difference in the underlying ideas and their limitation of applicability. Furthermore, prospective directions for potential improvement of the theories are found. Numerical results for three particulate composites are given and discussed.

• Steel and Composite Structures
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• 제23권6호
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• pp.691-714
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• 2017

Rotating fluid induced vibration and instability of embedded piezoelectric nano-composite separators subjected to magnetic and electric fields is the main contribution of present work. The separator is modeled with cylindrical shell element and the structural damping effects are considered by Kelvin-Voigt model. Single-walled carbon nanotubes (SWCNTs) are used as reinforcement and effective material properties are obtained by mixture rule. The perturbation velocity potential in conjunction with the linearized Bernoulli formula is used for describing the rotating fluid motion. The orthotropic surrounding elastic medium is considered by spring, damper and shear constants. The governing equations are derived on the bases of classical shell theory (CST), first order shear deformation theory (FSDT) and sinusoidal shear deformation theory (SSDT). The nonlinear frequency and critical angular fluid velocity are calculated by differential quadrature method (DQM). The detailed parametric study is conducted, focusing on the combined effects of the external voltage, magnetic field, visco-Pasternak foundation, structural damping and volume percent of SWCNTs on the stability of structure. The numerical results are validated with other published works as well as comparing results obtained by three theories. Numerical results indicate that with increasing volume fraction of SWCNTs, the frequency and critical angular fluid velocity are increased.

• Interaction and multiscale mechanics
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• 제1권4호
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• pp.397-409
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• 2008

The interfacial thermal resistance of pristine and defective carbon nanotubes (CNTs) embedded in low-density polyethylene matrix is studied in this paper. Interface thermal resistance in nanosystems is one of the most important factors that lead to the large variation in thermal conductivities in literature and the novelty of this paper lies in the estimation of the interfacial thermal resistance for defective nanotubes-systems. Thermal properties of CNT nanostructures are estimated using molecular dynamics (MD) simulations and the simulations were carried out for various temperatures by rescaling the velocities of carbon atoms in the nanotube. This paper also deals with the mesoscale thermal conductivities of composite systems, using effective medium theories by considering the size effect in the form of interfacial thermal resistance and also using the conventional micromechanical methods like Hashin-Shtrikman bounds and Wakashima-Tsukamoto estimates.

• Advances in aircraft and spacecraft science
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• 제5권6호
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• pp.691-729
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• 2018

In this paper the hygro-thermo-mechanical vibration and buckling behavior of embedded FG nano-plates are investigated. The Eringen's and Gurtin-Murdoch theories are applied to study the small scale and surface effects on frequencies and critical buckling loads. The effective material properties are modeled using Mori-Tanaka homogenization scheme. On the base of RPT and HSDPT plate theories, the Hamilton's principle is employed to derive governing equations. Using iterative and GDQ methods the governing equations are solved and the influence of different parameters on natural frequencies and critical buckling loads are studied.

• 무역상무연구
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• 제13권
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• pp.767-804
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• 2000

International network strategy is intended to examine the validity of existing network-centered theories in order to ascertain why small-and medium-sized enterprises are useful as a strategic correspondence to the internationalization trend. Small-and medium-sized enterprises can be estimated as being vital majorities in terms of their flexibility to meet changable conditions in international marketing compared with the conglomerates Therefore, their dependency on a few conglomerates for the international economy can be diverged. Generally, the successful internationalization of industries can be derived from the creation of suitable strategies for its competence and quality with the effective correction and completion of its strategy and tactics through mistakes. The internationalization strategy of small-and medium-sized enterprises should not be the reckless pursuit of internationalization that depends only on the increase of investment or the simple induction of the other conglomerates strategic models, but it should be accomplished through the evolution and practice of the concrete strategies that will be more proper for the enterprise's property and efficiency. The results of analyses with proof can be summarized with two effects in large in the process of internationalization of domestic small-and medium-sized enterprises. First, the capacity for internationalization of firms results from a long-term training procedure and continuous development of managing activities. Then in time this becomes an important element for the small-and medium-sized firms in terms with its position targeted international trading. However, the domestic enterprises are showing their abilities in the international competition in quantity, and trying to establish relationships between the enterprises through international networks. Second, statistics might not be meaningful in part because of the lack of data for analysis. It seems that more useful results will be derived from obtaining and utilizing sufficient information and from establishing an inter-relationship between the small-and medium-sized enterprises which are investing in foreign companies.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.195-195
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• 2010

In recent years, Anodic aluminum oxide(AAO) has become popular and attractive materials. It can be easily fabricated and self-organized pore structures. It has been widely used as a biosensor membrane, photonic crystal for optical circuit and template for nanotube growth etc. In previous papers, the theory was developed that AAO shows anisotropic optical properties, since it has anisotropic structure with numerous cylindrical pores. It gives rise to the anisotropy of the refractive index called as birefringence. It can be used as conventional polarizing elements with high efficiency and low cost. Therefore, we would like to compare the theory and experimental results in this study. One method which can measure effective refractive index of thin film is the prism coupling technique. It can give accurate results fast and simply. Furthermore, we can also measure separately the refractive index with different polarization using polarization of the laser (TE mode and TM mode). We calculated the effective refractive index with effective medium approximations (EMAs) by pore size in the SEM image. EMAs are physical models that describe the macroscopic system as the homogeneous and typical method of all mean field theories.

• 한국병원경영학회지
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• 제22권3호
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• pp.144-156
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• 2017

Purpose: Crisis is inevitable to every organization and therefore, successful crisis management is critical to the organizations' survival and prosperity. With the understanding, this study aims to draw propositions for successful crisis management of hospitals when facing infectious disease outbreak. For the purpose, a case of a small and medium sized hospital's experience of crisis management during 2015 Middle East Respiratory Syndrome outbreak was analyzed. Methodology/Approach: The detailed internal circumstances and experiences of the hospital during the MERS outbreak were identified by in-depth interview as well as the extensive material review, and analyzed under the view of the theories of accident, error, and crisis in relation of organization management Findings: Overall, nine propositions are drawn by the phase of crisis. In pre-crisis phase, for example, 'the hospital preparedness has positive influence on the effective responding to the crisis'. In detection phase, 'the mindfulness of the hospital organizations' as well as the individuals' has positive influence on detecting the crisis signals'. In crisis phase, for example, 'improvising naturally occurs in crisis by the unknown disease, therefore, a component site supervisor coordinating such improvision is important'. Lastly, in post-crisis phase, 'successful crisis responding experience facilitates the positive hospital culture'. Practical implication: From the experience of a small and medium size hospital, it is suggested that proactive system approach oriented by safety is beneficial for effective crisis management.

• Coupled systems mechanics
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• 제8권4호
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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.

• Steel and Composite Structures
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• 제25권2호
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• pp.141-155
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• 2017

This paper presents an investigation into the magneto-thermo-mechanical vibration and damping of a viscoelastic functionally graded-carbon nanotubes (FG-CNTs)-reinforced curved microbeam based on Timoshenko beam and strain gradient theories. The structure is surrounded by a viscoelastic medium which is simulated with spring, damper and shear elements. The effective temperature-dependent material properties of the CNTs-reinforced composite beam are obtained using the extended rule of mixture. The structure is assumed to be subjected to a longitudinal magnetic field. The governing equations of motion are derived using Hamilton's principle and solved by employing differential quadrature method (DQM). The effect of various parameter like volume percent and distribution type of CNTs, temperature change, magnetic field, boundary conditions, material length scale parameter, central angle, viscoelastic medium and structural damping on the vibration and damping behaviors of the nanocomposite curved microbeam is examined. The results show that with increasing volume percent of CNTs and considering magnetic field, material length scale parameter and viscoelastic medium, the frequency of the system increases and critically damped situation occurs at higher values of damper constant. In addition, the structure with FGX distribution type of CNTs has the highest stiffness. It is also observed that increasing temperature, structural damping and central angle of curved microbeam decreases the frequency of the system.

• 디자인학연구
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• 제19권3호
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• pp.59-70
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• 2006

Narratologists have long raised the question of how narrative theories could be applied to other disciplines that involve stories and storytelling. Focusing on recently revitalized concepts of space, sequence, and story, this article attempts to illustrate narrative constructions in various fields of arts and humanities and examine them particularly in typographical works. Through the concept of narrativity, this article highlights the prevalent uses of narrative in typography and scrutinizes the ways in which a sense of storyness is forming and emerging in some typographical works. Particularly emphasized are the importance of and interplay between the formal and cultural attributes of narrative that transform the spatial world of visual images to the temporal world of stories. Narrative is arguably the most familiar, interesting, and effective medium of communication regardless of age, race, and culture, and can be critically rethought to apply to typography and design.