• 한국세라믹학회지
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• 제32권12호
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• pp.1349-1356
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• 1995

The change of permeation mechanism from Knudsen diffusion to micropore diffusion was observed after CVD modification of an alumina-sol coated alumina support which was prepared by slip coating process. Permselectivities of He/N2, H2/N2, and CO2/N2 were 5.67, 5.02, and 1.44, respectively. These values were higher than those under Knudsen diffusion controlled region.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1451-1453
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• 2003

Shrink fitting is often used to replace conventional mechanical fasteners and fastening methods. Localized heating of the mating surface provides temporary expansion and allows slip fit assembly. The resulting interference fit exhibits exceptional strength without surface deformation at ambient temperatures. We studied an analysing method to find out a deformation of motor axis with shrink fitting of thermal expansion.

• 터널과지하공간
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• 제15권4호
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• pp.288-295
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• 2005

암반은 여러 가지 지질학적 요인에 기인한 역학적 결함을 많이 포함하고 있기 때문에 이방성 거동을 보이는 경우가 대부분이다. 그러므로 안정한 암반구조물이나 암반기초의 설계를 위해서는 이방성 암반에서 응력분포의 특성을 이해하는 것이 매우 중요하다. 이 연구에서는 반무한 평면이방성 지반의 표면에 선하중이 작용할 때 지반에 야기되는 탄성응력 분포의 특성을 고찰하였다. 절리의 강성과 절리의 간격, 경사각이 응력분포 형태에 미치는 영향이 검토되었다. 절리면의 미끄러짐 조건으로 Mohr-Coulomb 식을 가정할 경우, 절리면을 통한 미끄러짐이 발생할 수 있는 영역에 대한 고찰도 수행되었다.

• 한국안전학회지
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• 제28권5호
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• pp.54-60
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• 2013

In this study, a finite element model based on the SU/PG scheme was developed to solve shallow-water equations and the influences of parameters and internal boundary conditions on depth-averaged flow behavior were investigated. To analyze the effect of roughness coefficient and eddy viscosity on flow characteristics, the developed model was applied to rectangular meandering channel with two bends, and transverse velocities and water depth distributions were examined. As the roughness coefficient adjacent to wall increased, the velocities near the wall decreased, and the reduced velocities were compensated by the expanding mid-channel velocities. In addition, the flow characteristics around a circular cylinder were analyzed by varying the internal boundary conditions as free slip and no slip. The assignment of slip condition changed the velocity distribution on the cylinder surface and reduced the magnitude of the shear stress up to one third.

• Tribology and Lubricants
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• 제23권1호
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• pp.9-13
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• 2007

Despite numerous researches on atomic-scale friction have been carried out for understanding the origin of friction, lots of questions about sliding friction still remain. It is known that friction at atomic-scale always shows unique phenomena called 'stick-slips' which reflect atomic lattice of a scanned surface. In this work, experimental study on the effects of system stiffnesses and load on the atomic-scale stick-slip friction of graphite was performed by using an Atomic Force Microscope and various cantilevers/tips. The objective of this research is to figure out the dependency of atomic-scale friction on the nanomechanical properties in sliding contact such as load, stiffness and contact materials systematically. From this work, the experimental observation of transitions in atomic-scale friction from smooth sliding to multiple stick-slips in air was first made, according to the lateral cantilever stiffness and applied normal load. The superlubricity of graphite could be verified from friction vs. load experiments. Based on the results, the relationship between the stickslip behaviors and contact stiffness was carefully discussed in this work. The results or this work indicate that the atomic-scale stick-slip behaviors can be controlled by adjusting the system stiffnesses and contact materials.

• 한국구조물진단유지관리공학회 논문집
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• 제12권1호
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• pp.65-72
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• 2008

최근에 상용 FRP 판(plank)을 콘크리트 구조물의 영구 거푸집 및 보강재로 이용하기 위한 연구가 진행되고 있다. FRP 판과 타설 콘크리트가 합성효과를 발휘하기 위해서는 두 재료간의 부착이 중요한 요인 중의 하나이다. 이러한 부착을 확보하기 위하여 FRP 판에 모래를 일반적으로 건설현장에서 많이 사용하는 에폭시를 이용하여 부착하였다. FRP 판과 콘크리트 합성구조의 구조적 거동을 이해하기 위해서는 FRP판과 타설 콘크리트 사이의 정량적인 국부 부착모델이 필요하다. 본 연구에서는 이와 같은 합성구조 시스템에 간단히 적용할 수 있는 단순 부착모델을 제안한다.

• 열처리공학회지
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• 제11권4호
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• pp.274-282
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• 1998

The effect of Al addition on the fatigue properties of austenitic Fe-25Mn-Al-0.5C steels was studied. When Al was not added to the Fe-25Mn 0.5C steel, the strain induced ${\varepsilon}$ martensites, deformation twins and slip bands were formed during fatigue deformation. When 2wt% of Al was added to the steel, the deformation twins and slip bands were formed during fatigue deformation. When 5wt% of Al was added, only slip bands were formed. In low cycle fatigue test, the alloys containing 0wt% and 2wt%Al showed the cyclic hardening due to ${\varepsilon}$ martensites and deformation twins, resulting in shorter fatigue lives than the alloy containing 5wt%Al. In fatigue crack propagation test, the alloy without Al showed the highest crack propagation rate. The fracture surface of the alloy without Al was flat, whereas that of the alloy with 2% or 5%Al was rough. The ${\Delta}K_{th}$, values of the alloys with 0%, 2% and 5%Al were 16, 17.5, and $20.5MPam^{1/2}$, respectively.

• 대한산업공학회지
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• 제22권3호
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• pp.337-349
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• 1996

A study was conducted to find the possible relationship between slip distance and dynamic coefficient of friction (DCOF) through the biomechanical study of slips and falls using a broader variety of floors and levels of slipperiness than those used before. Four different floor surfaces covering the full range of floor slipperiness (with and without on oil contaminant) were prepared for ten subjects with each walking at a fixed velocity. The results showed that slip distance and heel velocity had a decreasing trend while stride length had a increasing trend as DCOF increased. The contaminant effect overpowered floor slipperiness effect because a higher DCOF surface with oil contaminant created longer slip distance than the lower DCOF with dry floor. Normal gait pattern and suggested heel velocity (10 to 20 cm/sec) were seen on dry floors but abnormally longer stride length and 5 to 10 times faster heel velocity were found an oily floors. In other words, faster heel velocity (greater than 10 to 20 cm/sec) is recommended to measure DCOF on oily floors because the assumption of normal gait was no longer valid.

• Earthquakes and Structures
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• 제13권1호
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• pp.67-77
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• 2017

Oil storage tanks are vital life-line structures, suffered significant damages during past earthquakes. In this study, a numerical model for an unanchored vertical vaulted-type tank was established by ANSYS software, including the tank-liquid coupling, nonlinear uplift and slip effect between the tank bottom and foundation. Four actual earthquakes recorded at different soil sites were selected as input to study the dynamic characteristics of the tank by nonlinear time-history dynamic analysis, including the elephant-foot buckling, the liquid sloshing, the uplift and slip at the bottom. The results demonstrate that, obvious elephant-foot deformation and buckling failure occurred near the bottom of the tank wall under the seismic input of Class-I and Class-IV sites. The local buckling failure appeared at the location close to the elephant-foot because the axial compressive stress exceeded the allowable critical stress. Under the seismic input of Class-IV site, significant nonlinear uplift and slip occurred at the tank bottom. Large amplitude vertical sloshing with a long period occurred on the free surface of the liquid under the seismic wave record at Class-III site. The seismic properties of the storage tank were affected by site class and should be considered in the seismic design of large tanks. Effective measures should be taken to reduce the seismic response of storage tanks, and ensure the safety of tanks.

• 한국지반공학회논문집
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• 제24권12호
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• pp.65-73
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• 2008

현재 일본에서는 사면 안정 문제에 있어서 파괴면상의 전단강도는 일반적으로 점착력의 경험적 예측에 기초를 두고 있으며, 그 점착력은 표토상부에서 가정한 활동 면까지 흙두께에 비례한다고 가정한다. 이 예측법은 안정해석 결과가 설계자에 의한 영향을 받지 않는다는 점이 이점이나, 이론적인 배경이 부족하고, 파괴면 상의 흙두께가 매우 두꺼운 경우에는 점착력이 과다평가되어 역으로 때때로 그로 인한 전단저항각이 과소평가되지기도 한다. 본 연구에서는 2007년 효고현의 자연사면 파괴사례를 대상으로 파괴면상의 현장전단응력의 효과를 고려한 일련의 직접전단시험을 실시하여 주의 깊게 조사하였다. 그 결과, 초기전단음력을 고려한 시험으로부터 구한 전단강도가 사면파괴의 역해석에 적용되었을 때의 안전률이 현장상황과 부합하고 있음을 알 수 있었다.