• Structural Engineering and Mechanics
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• 제75권3호
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• pp.377-387
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• 2020

Modern long-span floor system typically possesses low damping and low natural frequency, presenting a potential vibration sensitivity problem induced by human activities. Field test and numerical analysis methods are available to study this kind of problems, but would be inconvenient for design engineers. This paper proposes a simplified method to determine the acceleration amplitudes of long-span floor system subjected to walking or running load, which can be carried out manually. To theoretically analyze the acceleration response, the floor system is simplified as an anisotropic rectangular plate and the mode decomposition method is used. To facilitate the calculation of acceleration amplitude a_P, a coefficient α_wmn or α_Rmn is introduced, with the former depending on the geometry and support condition of floor system and the latter on the contact duration t_R and natural frequency. The proposed simplified method is easy for practical use and gives safe structural designs.

• Journal of Advanced Marine Engineering and Technology
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• 제18권1호
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• pp.32-40
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• 1994

The radiative heat transfer analysis in particle layer has an inherent difficulty in treating the governing integro-differential equations, which are derived from the remote effects. Most of the existing analyses are limited to the one dimensional system, taking into account only absorption or isotropic scatting of solid particles. Fortunately, a new Monte Carlo Simulation method is recently developed to analyse multidimensional radiative heat transfer in particles with anisotropically scatting. By this method, the present study analyses the radiative heat transfer in dispersed particles through the numerous droplets in the liquid droplet radiator to develop a technique of liquid droplet radiator. Consequently, knows that the radiative heat flux in particle layer is influenced by exitinction coefficient, optical thickness and surface area of particles in the system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.546-551
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• 1997

In sheet metal forming, since the surface area of workpiece is apparently larger than the volume of it, the surface condition of the sheet metal is much varied. The formability of sheet metal is decided by the forming limit and the macroscopic suface defect as like fracture and wrinkle, and microscopic asponent, The factors affected in forming limit are stain herdening exponent, strain-rate scnsitivity exponent, anisotropic coefficient. The increasing of surface roughness is decresed the forming limit curve. It is known that the greater plastic deformation the more surface roughness by Kienzle, Osadaka. The purpose of this study is to investigate the influences of surface roughness in a uniaxial tension and the traperzoidal-shaped box drawing.

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 1999년도 춘계학술발표대회 논문개요집
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• pp.29-32
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• 1999

The material properties of laser welding zone such as strength coefficient, work-hardening exponent, and plastic anisotropic ratio are analytically obtained from those of base metals based on the tensile tests. . The finite element formulation is developed for predicting strain distributions and weld line movements in the forming processes of laser welded blank. The welding zone(WZ) is modelled with the several, narrow finite elements whose material characteristics are based on the experimental results and the analytical equations. In order to show an application of the developed weld element the stamping process of auto-body door inner panel is simulated. FEM predictions are compared and showed good agreements with experimental observations.

• 한국정밀공학회지
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• 제25권11호
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• pp.95-99
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• 2008

Applications of composite materials in various engineering fields have been extended significantly. For being useful composite materials, we could modify the rigidity and strength characteristics of composite material according to structures and material direction. In this study, CFRP, which has been widely used in space leisure and general structural applications due to the weight, elasticity coefficient, high fatigue strength and lower thermal transformation ect, was selected. As the CFRP is an anisotropic material whose mechanical properties change with its stacking sequence or angle, special attention was given to the effects of the fiber orientation angle on the bending characteristics of CFRP fiat and CFEP square members. It's different on the each result of strength and rigidity of CFRP flat and CFRP square members.

• Progress in Superconductivity
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• 제9권2호
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• pp.127-135
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• 2008

We study the effects of phonon interaction on the superconducting pairing in the high $T_c$ superconductors (HTSC). Using coupled BCS gap equations, we found that phonon interaction can induce a s-wave component to the d-wave gap, mediated by Antiferromagnetic (AFM) spin fluctuations, in the (D+iS) form. However, $T_c$ is not enhanced compared to the pure d-wave pairing without phonon interaction. On the other hand, anisotropic phonon interaction can dramatically enhance the d-wave pairing and $T_c$ itself, together with the AFM spin fluctuation interaction. This ($D_{AFM}+D_{ph}$) type pairing exhibits strongly reduced isotope coefficient despite the large enhancement of $T_c$ by phonon interaction.

• 대한기계학회논문집A
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• 제25권9호
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• pp.1368-1375
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• 2001

This paper examines that it is possible to apply RWCIM for determining eigenvector coefficients associated with eigenvalues for V-notched cracks in anisotropic dissimilar materials using the complex stress function. To verify the RWCIM algorithm, two tests will be shown. First, it is performed to ascertain whether predicted coefficients associated with eigenvectors are obtained exactly. Second, it makes an examination of the state of stresses for FEM and RWCIM according to a number of eigenvectors at a location far away from the v-notched crack tip.

• 한국지반공학회논문집
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• 제17권4호
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• pp.161-171
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• 2001

점성토의 압밀거동은 투수성뿐만 아니라 변형 특성에 따라 크게 영향을 받으며, 변형 특성은 재하 방법에 따른 변형조건과 흙의 특성, 특히 이방성에 따라 다르게 나타난다. 이 논문에서는 점성토의 이방적 변형 특성이 압밀거동에 미치는 영향을 분석하기 위하여 다양한 변형 조건에 대한 압밀방정식과 압밀계수를 직교 이방성 탄성이론을 이용하여 유도하였다. 다양한 변형 조건에서 등방과 이방적 변형 특성하의 압밀계수를 평가하였으며, 그 결과 탄성계수의 이방성이 압밀계수에 미치는 영향이 매우 크고, 특히 수평방향의 변위가 허용되고, 수직방향의 변위가 구속될수록 크게 나타났다. 따라서 점성토 지반에 대한 하중 재하시 압밀소요시간의 정확한 예측을 위해서는 발생 가능한 변형 조건과 이방적 변형 특성에 대한 적절한 고려가 매우 중요함을 알 수 있었다.

• 소성∙가공
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• 제13권7호
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• pp.629-634
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• 2004

Based on plastic instability, analytical prediction of bursting failure on tube hydroforming processes under combined infernal pressure and independent axial feeding is carried out. Bursting is irrecoverable phenomenon due to local instability under excessive tensile stresses. In order to predict the bursting failure, three different classical necking criteria such as diffuse necking criterion for sheet and tube, local necking criterion for sheet are introduced. The incremental theory of plasticity for anisotropic material is adopted and then the hydroforming limit and bursting failure diagram with respect to axial feeding and hydraulic pressure are presented. In addition, the influences of the material properties such as anisotropy Parameter, strain hardening exponent and strength coefficient on bursting Pressure are investigated. As results of the above approach, the hydroforming limit in view of bursting failure is verified with experimental results.

• 터널과지하공간
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• 제16권4호
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• pp.313-325
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• 2006

본 연구에서는 이방성 암반의 방향성 및 측압조건이 터널 변형거동에 미치는 영향을 조사하기 위하여 서로 다른 15가지 이방성 터널 모형에 대해 축소모형실험을 실시하였다. 이를 위해 모래 석고 물의 중량비를 달리한 모형재료에 대한 물성 실험을 통하여 모형재료의 특성을 연구하였다. 대부분의 이방성 터널 모형은 응력이 집중되는 곳에서 전단파괴 현상을 보였으며 절리면을 따라 미끄러짐이 발생하여 절리면의 경사 방향이 터널 변형거동에 큰 영향을 미친 것으로 나타났다. 절리 경사가 $30^{\circ}$보다 작은 모형에서는 반팽창현상이 두드러지게 나타났으며 절리경사가 $50^{\circ}$인 모형은 측압조건에 관계없이 수직 및 수평 내공변위가 가장 작게 나타나 실험된 모형중에서 가장 안정적인 모형으로 판단된다. 또한 모형터널의 파괴 및 변형양상은 측압계수 조건에 따라 매우 상이하게 나타났다.