• 한국농공학회지
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• 제41권2호
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• pp.104-110
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• 1999

This study was performed to evaluate the properties of permeable polymer concrete with fly ash and CaCO3. The following conclusions are drawn. The static modulusof elasticity is in the range of 1.19 $\times$105 ~1.49$\times$105 kgf/$\textrm{cm}^2$, which is approximately 53 ~56% of that of the normal cement concrete. The oission's number of permeable polymer concrete is in the range of 3.95 ~6.53, which is less than that of the normal cement concrete. The dynamic modulus of elasticity is in the range of 1.29$\times$105 ~1.59$\times$105 kgf/$\textrm{cm}^2$, which is approximately less compared to that of the normal cement of the static modulus . Fly ash 50% and CaCO3 50% filled permeable polymer concrete has showed higher dynamic modulus. The water permeability is in therange of 3.971 ~4.393$\ell$ /$\textrm{cm}^2$/h, and it is largely dependent upon the mix design. These concrete can be used to the structures which need water permeability.

• Geomechanics and Engineering
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• 제11권5호
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• pp.671-690
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• 2016

This work presents a static flexure analysis of laminated composite plates by utilizing a higher order shear deformation theory in which the stretching effect is incorporated. The axial displacement field utilizes sinusoidal function in terms of thickness coordinate to consider the transverse shear deformation influence. The cosine function in thickness coordinate is employed in transverse displacement to introduce the influence of transverse normal strain. The highlight of the present method is that, in addition to incorporating the thickness stretching effect (${\varepsilon}_z{\neq}0$), the displacement field is constructed with only 5 unknowns, as against 6 or more in other higher order shear and normal deformation theory. Governing equations of the present theory are determined by employing the principle of virtual work. The closed-form solutions of simply supported cross-ply and angle-ply laminated composite plates have been obtained using Navier solution. The numerical results of present method are compared with those of the classical plate theory (CPT), first order shear deformation theory (FSDT), higher order shear deformation theory (HSDT) of Reddy, higher order shear and normal deformation theory (HSNDT) and exact three dimensional elasticity theory wherever applicable. The results predicted by present theory are in good agreement with those of higher order shear deformation theory and the elasticity theory. It can be concluded that the proposed method is accurate and simple in solving the static bending response of laminated composite plates.

• Structural Engineering and Mechanics
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• 제51권5호
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• pp.867-891
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• 2014

An equivalent single layer trigonometric shear deformation theory taking into account transverse shear deformation effect as well as transverse normal strain effect is presented for static flexure of cross-ply laminated composite and sandwich plates. The inplane displacement field uses sinusoidal function in terms of thickness coordinate to include the transverse shear deformation effect. The cosine function in thickness coordinate is used in transverse displacement to include the effect of transverse normal strain. The kinematics of the present theory is much richer than those of the other higher order shear deformation theories, because if the trigonometric term (involving thickness coordinate z) is expanded in power series, the kinematics of higher order theories (which are usually obtained by power series in thickness coordinate z) are implicitly taken into account to good deal of extent. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. The closed-form solutions of simply supported cross-ply laminated composite and sandwich plates have been obtained. The results of present theory are compared with those of the classical plate theory (CPT), first order shear deformation theory (FSDT), higher order shear deformation theory (HSDT) of Reddy and exact three dimensional elasticity theory wherever applicable. The results predicted by present theory are in good agreement with those of higher order shear deformation theory and the elasticity theory.

• Structural Engineering and Mechanics
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• 제7권2호
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• pp.181-202
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• 1999

Dynamic response of axisymmetric arbitrary laminated composite cylindrical shell of finite length, using three-dimensional elasticity equations are studied. The shell is simply supported at both ends. The highly coupled partial differential equations are reduced to ordinary differential equations (ODE) with variable coefficients by means of trigonometric function expansion in axial direction. For cylindrical shell under dynamic load, the resulting differential equations are solved by Galerkin finite element method, In this solution, the continuity conditions between any two layer is satisfied. It is found that the difference between elasticity solution (ES) and higher order shear deformation theory (HSD) become higher for a symmetric laminations than their unsymmetric counterpart. That is due to the effect of bending-streching coupling. It is also found that due to the discontinuity of inplane stresses at the interface of the laminate, the slope of transverse normal and shear stresses aren't continuous across the interface. For free vibration analysis, through dividing each layer into thin laminas, the variable coefficients in ODE become constants and the resulting equations can be solved exactly. It is shown that the natural frequency of symmetric angle-ply are generally higher than their antisymmetric counterpart. Also the results are in good agreement with similar results found in literatures.

• 한국기계가공학회지
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• 제16권2호
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• pp.102-107
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• 2017

This study focuses on the effect of the elasticity modulus of jig material on blade edge shape in the grinding process of a sapphire medical knife. The ELID grinding process was applied as the edge-grinding method for sapphire material. Carbon steel and copper have been selected as the hard and soft jig materials, respectively. The blade edge created by ELID grinding was measured by a surface roughness tester and optical microscope. The shape of the ground edge and surface roughness were compared using the measurement results. As a result, it was found that chipping in the blade edge of the sapphire knife occurred more than in the case of jig material with a high-elasticity modulus because of the high normal force in the grinding process. Moreover, the maximum height surface roughness, $R_{max}$,of the ground surface was higher in the case of the jig material with a high-elasticity modulus due to the difference in elasticelongation. It was considered to lead to chipping from the notch effect.

• Advances in materials Research
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• 제5권4호
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• pp.245-261
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• 2016

Thermo-mechanical buckling problem of functionally graded (FG) nanoplates supported by Pasternak elastic foundation subjected to linearly/non-linearly varying loadings is analyzed via the nonlocal elasticity theory. Two opposite edges of the nanoplate are subjected to the linear and nonlinear varying normal stresses. Elastic properties of nanoplate change in spatial coordinate based on a power-law form. Eringen's nonlocal elasticity theory is exploited to describe the size dependency of nanoplate. The equations of motion for an embedded FG nanoplate are derived by using Hamilton principle and Eringen's nonlocal elasticity theory. Navier's method is presented to explore the influences of elastic foundation parameters, various thermal environments, small scale parameter, material composition and the plate geometrical parameters on buckling characteristics of the FG nanoplate. According to the numerical results, it is revealed that the proposed modeling can provide accurate results of the FG nanoplates as compared some cases in the literature. Numerical examples show that the buckling characteristics of the FG nanoplate are related to the material composition, temperature distribution, elastic foundation parameters, nonlocality effects and the different loading conditions.

• 비파괴검사학회지
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• 제29권4호
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• pp.368-373
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• 2009

초음파 의료용 탄성 영상 시스템의 성능을 평가하기 위한 인체 조직 모사 팬텀을 제작하였다. 인체에서 종양이나 암 조직은 주위의 정상조직보다 단단한 특성을 가진다. 이러한 조직의 단단함을 영상화하는 기법이 탄성 영상 기법이다. 인체의 병변 조직의 기계적인 특성을 모사하기 위하여 플라스틱 경화제와 연화제를 이용하여 탄성도가 다른 균일 탄성 팬텀을 제작하였다. 제작된 균일 탄성 팬텀은 시료의 비율에 따라 $11.1{\sim}79.6$ kPa 범위의 탄성계수 값을 얻었다. 이를 바탕으로 외부 매질과 내부 매질의 탄성계수 차이가 5배와 7배 정도인 초음파 병변 모사 팬텀을 제작하여 탄성 영상을 획득하였다. 본 논문에서는 제작된 플라스틱 기반의 탄성 팬텀이 인체의 탄성 특성을 모사하는 탄성 팬텀으로서 유용함을 확인하였다.

• International journal of advanced smart convergence
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• 제8권1호
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• pp.113-125
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• 2019

The radish skin and radish greens are an edible part of the radish. But they are removed before eating the radish and used as a byproduct or an animal feed material because of their tough and rough texture. This study was conducted to investigate the effect of supercritical heat-treated radish-extract on UV-induced HRM-2 wrinkled mouse animal model on anti-aging wrinkles. Supercritical heat-treated radish-extract was applied on the back of seven-weeks old HRM-2 mice. The effect of HRE on skin thickness, elasticity and wrinkle formation of the mice was observed by using UVB lamp to induce melanogenesis and wrinkle formation. As the result, increased depth of wrinkles was observed in the negative control group in comparison to the normal group. In contrast, decreased depth of wrinkles was observed in the radish-extract-free group compared to the negative control group. In the study of the effect of radish-extract on wrinkle-formation related gene expression and protein what protein expression, MMP-2 and MMP-9 gene expression significantly increased in the negative control group compared to the normal group. The gene expression reduced in dependence to the mass of radish-extract treated. Similar to quantitative results of mRNA expression, the expression of MMP-2 protein increased as a result of UVB-irradiation. The MMP-2 expression was inhibited in dependence to the mass of radish-extract treated. In conclusion, the supercritical heat-treated radish-extract has an effect on improving skin wrinkles not only when it is applied to the skin but also when orally ingested. Thus, it can be effectively used as a composition to health functional products. Therefore we can also conclude that radish a food that does not show any side-effects even upon long-term intake can reduce wrinkle formation as well as improve skin elasticity when taken regularly for a long period.

• 한국기계가공학회지
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• 제17권2호
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• pp.137-144
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• 2018

This study describes the 3D design and analysis of a composite insulation boom of an aerial work platform for electric work. Structural analysis of the composite insulation boom was performed using ANSYS and the total deformation, equivalent stress, and normal elasticity were investigated at 150 mm, 500 mm, 1,000 mm, and 1,500 mm using a mounted strain gauge. The results of the analysis and test were similar in a linearly increasing slope and the difference in the strain value was about 10%. This difference depends on the compressive force in the manufacturing process.

• 경영과정보연구
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• 제37권3호
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• pp.65-81
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• 2018

본 연구는 ARDL 모형을 이용하여 한국의 원유수요의 장기와 단기 자체가격, 교차가격 및 소득탄력성을 추정하였다. 첫째, ARDL-UECM의 한계검정결과에서 장기공적분관계가 종속변수인 원유수요와 독립변수인 자체가격과 교차가격 및 소득변수간에 존재하였다. 둘째, ARDL 모형(장기정태모형)을 통해 장기 모수들이 추정되었다. 셋째, 일부의 잔차의 자기상관이 존재하였으나, 반면에 설정오류가 발견되지 않았고 잔차항이 정규분포를 나타내었으며 이분산이 존재하지 않았고 CUSUM & CUSUMSQ 결과에서는 계수가 안정적이었다. 넷째, 추정된 원유수요에 대한 절대값으로 측정된 장기자체가격과 교차가격탄력성 및 소득탄력성은 모두 유의하며 1보다 크고 탄력적으로 민감하였으나, 반면에 단기자체가격과 교차가격탄력성 및 소득탄력성은 모두 유의하며 1보다 적고 비탄력적으로 민감하지 않았을지라도, 장기와 단기의 모든 탄력성들이 실제부호와 기대부호가 일치하였다. 다섯째, 국내의 일부 연구를 제외하고 대부분의 국외의 이전연구에서 단기자체가격과 교차가격 및 소득탄력성은 본 연구의 장기자체가격과 교차가격 및 소득탄력성보다 모두 더 낮다는 것을 확인하였다. 따라서 외국원유에 너무 의존하는 한국은 원유가격의 충격에 취약하게 되므로 유가 상승은 확실히 한국의 무역수지에 부정적인 영향을 미칠 수 있으므로 장기적 원유가격의 탄력성을 이용하여 한국의 원유수요를 효율적으로 통제하고 관리하는데 도움을 줄 수 있다고 사료된다. 시사점으로 원유와 관련한 국가별 정책변화 및 시장동향 모니터링의 강화, 국가별 정책 및 시장현황 맞춤형 진출전략의 수립, 신시장 개척 및 진출분야 다양화를 통한 적극적인 시장선점 노력의 강화 등이 필요하다.