• 터널과지하공간
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• 제21권2호
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• pp.117-127
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• 2011

균열암반의 역학적 및 수리적 성질에 암반 초기응력이 미치는 영향을 고찰하였다. 지질 데이터는 스웨덴 원전원료 및 방사성 폐기물 관리회사(SKB)에 의해 수행된 포쉬마크지역의 부지조사로부터 획득되었으며 암반균열망-개별요소법 수치실험(Discrete Fracture Network - Discrete Element Method) 을 통하여 암반의 등가역학적 및 등가수리적 물성을 결정하였다. 수치실험결과 균열 강성의 응력의존성, 균열 방향에 따른 상이한 변형거동, 균열거동에 따른 수리유동 경로의 변화 등의 원인에 의하여 등가역학적 및 등가수리적 물성은 응력의존성이 큰 것을 확인하였다. 본 연구의 결과는 암반 초기응력의 정확한 예측이 특정 부지에서의 경계조건으로서뿐만 아니라 균열암반의 역학적 및 수리적 물성을 이해하는 데도 중요한 역할을 한다는 것을 보여준다.

• 한국재료학회지
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• 제30권3호
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• pp.123-130
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• 2020

In this study, two types of thick steel plates are prepared by controlling carbon equivalent and nickel content, and their microstructures are analyzed. Tensile tests, Vickers hardness tests, and Charpy impact tests are conducted to investigate the correlation between microstructure and mechanical properties of the steels. The H steel, which has high carbon equivalent and nickel content, has lower volume fraction of granular bainite (GB) and smaller GB packet size than those of L steel, which has low carbon equivalent and nickel content. However, the volume fraction of secondary phases is higher in the H steel than in the L steel. As a result, the strength of the L steel is higher than that of the H steel, while the Charpy absorbed energy at -40 ℃ is higher than that of the L steel. The heat affected zone (HAZ) simulated H-H specimen has higher volume fraction of acicular ferrite (AF) and lower volume fraction of GB than the HAZ simulated L-H specimen. In addition, the grain size of AF and the packet sizes of GB and BF are smaller in the H-H specimen than in the L-H specimen. For this reason, the Charpy absorbed energy at -20 ℃ is higher for the H-H specimen than for the L-H specimen.

• Journal of applied mathematics & informatics
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• 제16권1_2호
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• pp.497-507
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• 2004

In this paper, we first seek the equivalent statements with averaging properties in terms of the regular summability method, secondly define some new averaging properties and study their implications. Finally, we investigate the question of what property is dual to the Banach-Saks property suggested by C. Seifert.

• 한국전산구조공학회논문집
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• 제19권3호
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• pp.247-258
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• 2006

물에 잠긴 다공 원통형 쉘의 경우 물에 잠긴 상태로 유한요소해석을 하기에는 거의 불가능하므로 등가물성치를 사용하여야 한다. 다공 평판의 경우 이에 대한 등가물성치를 ASME 코드에서 제시하고 있지만, 다공 원통형 쉘의 등가물성치에 대한 연구는 아직까지 수행된 적이 없다. 따라서 본 연구에서는 유한요소해석을 이용하여 다공 원통형 쉘의 동적 해석에 이용할 수 있는 등가물성치를 제안하였고 그 타당성을 검증하였다.

• 한국건축시공학회지
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• 제8권1호
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• pp.43-48
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• 2008

Fifteen concrete specimens were mixed and tested to explore the significance and limitation of appling the polyvinyl alcohol (PVA) fiber and steel fiber with end hook to concrete. Main parameters investigated were volume fraction and length of the fibers. The measured mechanical properties of fiber reinforced concrete are analyzed according to the equivalent fiber amount index explaining the adding amount and length of fibers. Test results showed that compressive strength of fiber reinforced concrete was higher than that of concrete with no fiber by $10{\sim}20%$. The normalized splitting tensile strength and flexural strength of PVA fiber reinforced concrete were similar to those of concrete with no fiber, whereas those of steel fiber reinforced concrete increased with the increase of the equivalent fiber amount index. In particular, much higher ductile behavior was observed in steel fiber reinforced concrete than in PVA reinforced concrete, indicating that the slope of descending branch of load-displacement relationship of steel fiber reinforced concrete decreased with the increase of the volume fraction and length of the fiber.

• 한국산학기술학회논문지
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• 제7권3호
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• pp.291-297
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• 2006

매우 작은 브릿지 형상을 무수히 지닌 용융탄산염 연료전지용 쉴드슬롯판이 생산 과정 중 일정한 곡률을 가지게 되는데, 자중으로 인해 본래의 곡률을 알 수 없게 되어 교정 작업에 지장을 초래한다. 본 연구에서는 이러한 쉴드슬롯판의 유효 물성치를 실험을 통하여 구하고, 이를 바탕으로 수치해석을 통해 쉴드슬롯판의 원래 곡률을 추정하였다. 구한 유효 물성치를 검증하기 위하여 정방향 및 역방향으로 놓인 쉴드슬롯판의 자중 처짐 형상을 계산을 통해 구하여 실험 결과와 비교하였다. 비교 결과 추정된 유효 물성치는 매우 타당하였고 이로부터 쉴드슬롯판의 원래 곡률을 추정할 수 있었다. 본 연구에서 추정된 유효 물성치는 추후 쉴드슬롯판의 편평도 향상에 대한 연구에서 유용한 자료로 활용될 수 있다.

• 한국소음진동공학회논문집
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• 제24권5호
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• pp.414-420
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• 2014

In this paper, the vibration characteristics of the trapezoidal corrugated plate with axial stiffeners and lumped masses are investigated by the analytical method. The corrugated plate can be treated as an equivalent orthotropic plate as this plate has different flexure properties in two perpendicular directions; flexible in the corrugation direction and stiff in the transverse direction. The effective extensional and flexural stiffness of the equivalent plate are considered to obtain the precise solution in the analysis. The plate is stiffened by concentric stiffeners horizontally to the corrugation direction. The discrete stiffener theory is adopted to consider the position of stiffener. To demonstrate the validity of the proposed approach, the comparison is made with the results of 3D ANSYS finite element solutions. Some numerical results are presented to check the effect of the geometric properties.

• Water Engineering Research
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• 제6권2호
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• pp.91-99
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• 2005

One of the most important factors for estimating a flood runoff from streams is the lag time. It is well known that the lag time is affected by the morphometric properties of basin which can be expressed by catchment shape descriptors. In this paper, the notion of the geometric characteristics of an equivalent ellipse proposed by Moussa(2003) was applied for calculating the lag time of geomorphologic instantaneous unit hydrograph(GIUH) at a basin outlet. The lag time was obtained from the observed data of rainfall and runoff by using the method of moments and the procedure based on geomorphology was used for GIUH. The relationships between the basin morphometric properties and the hydrological response were discussed based on application to 3 catchments in Korea. Additionally, the shapes of equivalent ellipse were examined how they are transformed from upstream area to downstream one. As a result, the relationship between the lag time and descriptors was shown to be close, and the shape of ellipse was presented to approach a circle along the river downwards. These results may be expanded to the estimation of hydrological response of ungauged catchment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.119-120
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• 2006

The impedance spectroscopy is one of the effective ways to understand the electrical properties of organic light emitting diodes. The frequency-dependant properties of small molecule based OLEDs have been studied. The equivalent circuit of single-layer device is composed of contact resistance ($R_c$), bulk resistance ($R_p$) and bulk capacitance ($C_p$). The equivalent circuit of double layer device is composed of two parallel circuits connected in series, each of which is a parallel resistor and a capacitor. We have fabricated a double layer device indium-rio-oxide (ITO, anode), N,NV -diphenyl- N,NV -bis(3-methylphenyI)-1,1V -diphenyl-4,4V-diamine (TPD, hole-transporting layer), tris-(8-hydroxyquinoline) aluminum (Alq3, emitting layer), and aluminum (AI, cathode) and two single layer devices ([TO/ Alq3/ AI, ITO/TPD/AI).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.320-324
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• 2013

A crack identification method using an equivalent bending stiffness for cracked beam and committee of neural networks is presented. The equivalent bending stiffness is constructed based on an energy method for a straight thin-walled pipe, which has a through-the-thickness crack, subjected to bending. Several numerical analysis for a steel cantilever pipe using the equivalent bending stiffness are carried out to extract the natural frequencies and mode shapes of the cracked beam. The extracted modal properties are used in constructing a training patterns of a neural network. The input to the neural network consists of the modal properties and the output is composed of the crack location and size. Multiple neural networks are constructed and each individual network is trained independently with different initial synaptic weights. Then, the estimated crack locations and sizes from different neural networks are averaged. Experimental crack detection is carried out for 3 damage cases using the proposed method, and the identified crack locations and sizes agree reasonably well with the exact values.