• 한국세라믹학회지
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• 제56권5호
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• pp.506-512
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• 2019

Although graphene has been successfully grown in large scale via chemical vapor deposition (CVD), it is still questionable whether the mechanical properties of CVD graphene are equivalent to those of exfoliated graphene. In addition, there has been an issue regarding how the tilt angle of the grain boundary (GB) affects the strength of graphene. We investigate the mechanical properties of CVD graphene with nanoindentation from atomic force microscopy and transmission electron microscopy. Surprisingly, the samples with GB angles of 10° and 26° yielded similar fracture stresses of ~ 80 and ~ 79 GPa, respectively. Even for samples with GB exhibiting a wider range, from 0° to 30°, only a slightly wider fracture stress range (~ 50 to ~ 90 GPa) was measured, regardless of tilt angle. The results are contrary to previous studies that have reported that GBs with a larger tilt angle yield stronger graphene film. Such a lack of angle dependence of GB can be attributed to irregular and well-stitched GB structures.

• Asia pacific journal of information systems
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• 제29권4호
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• pp.547-570
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• 2019

With the advances of information technologies, the interest in SmartWork including extended version of telework and flexible work are increasing, and various types of SmartWork attempted to make working time and place flexible with the goal of work and life balance. Despite its emphasis on work and life balance, SmartWork is expected to make the boundaries between work and nonwork blur and role conflicts occur more than before, and thus the goal of work and life balance becomes more distant. A number of SmartWork users are significantly increasing in Korea, but little is known concerning the antecedents and mechanisms to explain psychological work and interferences in the SmartWork environment. In this paper, using boundary theory, we empirically investigate factors affecting the interferences at both work and nonwork domains. The results, based on data collected from SmartWork users in one of the biggest telecommunication companies in Korea where SmartWork is adopted and extensively used, suggest the factors may be affecting differently interferences at the work and nonwork domains.

• Computers and Concrete
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• 제2권2호
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• pp.111-123
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• 2005

The ductility of reinforced concrete bearing walls subjected to high axial loading and moment can be enhanced by improving the deformability of the compression zone or by reducing the neutral axis depth. The current state-of-the-art procedure evaluating the confinement effect prompts a consideration of the spaces between the transverse and longitudinal reinforcing bars, and a provision of tie bars. At the same time, consideration must also be given to the thickness of the walls. However, such considerations indicate that the confinement effect cannot be expected with the current practice of detailing wall ends in Korea. As an alternative, a comprehensive method for dimensioning boundary elements is proposed so that the entire section of a boundary element can stay within the compression zone when the full flexural strength of the wall is developed. In this comprehensive method, the once predominant code approach for determining the compression zone has been advanced by considering the rectangular stress block parameters varying with the extreme compression fiber strain. Moreover, the size of boundary elements can also be determined in relation to the architectural requirement.

• 콘크리트학회논문집
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• 제12권5호
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• pp.47-57
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• 2000

Experimental and numerical studies were done to investigate seismic performance of slender shear walls with no boundary confinement that are principal structural members of high0rise bearing wall buildings. 1/3 scale specimens that model the plastic region of long slender shear walls subjected to combined axial load and bending moment were tested to investigate strength, ductility, capacity of energy dissipation, and strain distribution, The experimental results show that the slender shear walls fail due to early crushing in the compressive boundary, and then have very low ductility. The measured maximum compressive strain is 0.0021, much less than 0.004 being commonly used for estimation of ductility. This result indicates that the maximum compressive strain is not a fixed value but is affected by moment gradient along the shear wall height and distance from the neutral axis to the extreme compressive fiber.

• Geosystem Engineering
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• 제21권6호
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• pp.309-317
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• 2018

We employ a three-dimensional indirect boundary element method (BEM) to simulate temperature change around an underground liquefied natural gas storage cavern. The indirect BEM (IBEM) uses fictitious heat source strength on boundary elements as basic variables which are solved from equations of boundary conditions and then used to compute the temperature change at other points in the considered problem domain. The IBEM requires evaluation of singular integration for temperature change due to heat conduction from a constant heat source on a planar (triangular) region. The singularity can be eliminated by a semi-analytical integration scheme. However, it is found that the semi-analytical integration scheme yields sharp temperature gradient for points close to vertices of triangle. This affects the accuracy of heat flux, if they are evaluated by finite difference method at these points. This difficulty can be overcome by a combination of using a direct numerical integration for these points and the semi-analytical scheme for other points distance away from the vertices. The IBEM and the hybrid integration scheme have been verified with an analytic solution and then used to the application of the underground storage.

• Earthquakes and Structures
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• 제16권2호
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• pp.129-139
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• 2019

This paper develops a new method for estimating the elastic-plastic buckling strength of the truss structures under the static and seismic loads. Firstly, a new method for estimating the buckling strength of the truss structures was derived based on the buckling strength of the representative member considering the parameters, such as the structure configurations, boundary conditions, etc. Secondly, the new method was verified through the buckling strength estimation and the finite element method (FEM) analysis of the single member models, portal frame models and simple truss models. Finally, the method was applied to evaluate the buckling strength of a simple truss structure under seismic load, and the failure loads between the proposed method and the FEM were analyzed reasonably. The results show that the new method is feasible and reliable for structure engineers to estimate the buckling strengths of the truss structures under the static loads and seismic loads.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1664-1666
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• 2004

This paper describes the use of Armaid papers and varnishes in electric motors. We compare with boundary element method(BEM) and finite element method(FEM) by calculated electric field strength. Several computer software package to perform such calculations based on electrostatic field and applicable DC are available.

• 대한기계학회논문집A
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• 제21권8호
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• pp.1322-1331
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• 1997

A method of strength evaluation applying fracture mechanics in the adhesively bonded joints of Al/Steel dissimilar materials was investigated in this paper. Various shapes of adhesively bonded Al/Steel scarf joints focussing on fracture criterion of mixed mode crack were prepared for the static tests. Also, stress intensity factors of the interface cracks in adhesively bonded joints of Al/Steel dissimilar materials were analyzed with 2-dimensional elastic program of boundary element method(BEM), and the experiment of fracture toughness were carried out under various mixed mode conditions. From the results, the fracture criterion and method of strength evaluation by the fracture toughness in adhesively bonded joints of Al/Steel dissimilar materials were proposed.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.156-163
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• 1997

Recently, attempts have been made to be join ceramics to metals in order to make up for the brittleness of ceramics. The difference in the coefficients of linear expansion of the two materials joined at high temperature will cause residual stress, which has a strong influence on the strength of the bonded joints. In this paper, the residual stress distribution and stress intensity factors of the ceramic/metal bonded joints were analyzed by 2-dimensional elastic boundary element method. Fracture toughness tests of ceramic/metal bonded joints with an interface crack were carried out. So the advanced method of quantitative strength evaluation for ceramic/metal bonded joints is to be suggested. Fracture surface and crack propagation path were observed using scanning electron microscope.

• 대한토목학회논문집
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• 제10권4호
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• pp.11-24
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• 1990

본 연구는 RC 뼈대구조물의 실제적인 단부경계조건을 고려한 RC 기둥에 대한 인접부재의 강성을 비선형 거동과 부합시켜 해석하였으며, 인접부재의 단부구속 효과를 고려한 편심축하중을 받는 장주의 극한강도와 거동을 해석하기 위한 해석모델을 정립하여 반복법을 이용한 수치적분법에 의하여 1차로 이론 해석을 하였다. 그리고, 계속 RC 기둥의 극한강도와 거동에 영향을 주는 매개변수를 해석모델을 이용 연구하고져 한다.