• International Journal of Concrete Structures and Materials
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• 제10권2호
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• pp.149-161
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• 2016

This paper presents an experimental work to study the flexural strength of reinforced concrete (RC) beams strengthened by partially de-bonded near surface-mounted (NSM) fiber reinforced polymer (FRP) strip with various de-bonded length. Especially, considering high anchorage capacity at end of a FRP strip, the effect of de-bonded region at a central part was investigated. In order to check the improvement of strength or deformation capacity when the bonded surface area only increased without changing the FRP area, single and triple lines of FRP were planned. In addition, the flexural strength of the RC member strengthened by a partially de-bonded NSM FRP strip was evaluated by using the existing researchers' strength equation to predict the flexural strength after retrofit. From the study, it was found that where de-bonded region exists in the central part of a flexural member, the deformation capacity of the member is expected to be improved, because FRP strain is not to be concentrated on the center but to be extended uniformly in the de-bonded region. Where NSM FRP strips are distributed in triple lines, a relatively high strength can be exerted due to the increase of bond strength in the anchorage.

• 한국분말재료학회지
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• 제23권1호
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• pp.54-60
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• 2016

This study focuses on fabricating silver flake powder by a mechanical milling process and investigating the formation of flake-shaped particles during milling. The silver flake powder is fabricated by varying the mechanical milling parameters such as the amount of powder, ball size, impeller rotation speed, and milling time of the attrition ballmill. The particle size of the silver flake powder decreases with increasing amount of powder; however, it increases with increasing impeller rotation speed. The change in the particle size of the silver flake powder is analyzed based on elastic collision between the balls, taking energy loss of the balls due to the powder into consideration. The change in the particle size of the silver flake powder with mechanical milling parameters is consistent with the change in the diameter of the elastic deformation contact area of the ball, due to the collision between the balls, with milling parameters. The flake-shaped silver particles are formed at the elastic deformation contact area of the ball due to the collision.

• Structural Engineering and Mechanics
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• 제51권3호
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• pp.413-431
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• 2014

By carrying out the experiment of eight pieces of brick masonry walls with pilaster strengthened by Glass fiber reinforced polymer (GFRP) and one piece of normal masonry wall with pilaster under low reversed cyclic loading, the failure characteristic of every wall is explained; Seismic performances such as hysteresis, stiffness and its degeneration, deformation, energy consumption and influence of some measures including strengthening means, reinforcement area proportion between GFRP and wall surface, "through-wall" anchor on reinforcement effects are studied. The test results showed that strengthening modes have little influence on stiffness, stiffness degeneration and deformation of the wall, but it is another thing for energy consumption of the wall; The ultimate load, deformation and energy consumption of the walls reinforced by glass fiber sheets was increased remarkably, rigidity and its degeneration was slower; Seismic performance of the wall which considers strengthening means, reinforcement area proportion between GFRP and wall surface, "through-wall" anchor at the same time is better than under the other conditions.

• Tribology and Lubricants
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• 제30권2호
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• pp.116-123
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• 2014

The objective of this study is to model and simulate the nonlinear lubrication performance of the sliding part between the piston and cylinder wall in a hydrostatic swash-plate-type axial piston pump. A numerical algorithm is developed that facilitates simultaneous calculation of the rotating body motion and fluid film pressure to observe the fluid film geometry and power loss. It is assumed that solid asperity contact, so-called mixed lubrication in this study, invariably occurs in the swash-plate-type axial piston pump, which produces a higher lateral moment on the pistons than other types of hydrostatic machines. Two comparative mixed lubrication models, rigid and elastic, are used to determine the reaction force and sliding friction. The rigid model does not allow any elastic deformation in the partial lubrication area. The patch shapes, reactive forces, and virtual local elastic deformation in the partial lubrication area are obtained in the elastic contact model using a simple Hertz contact theory. The calculation results show that a higher reaction force and friction loss are obtained in the rigid model, indicating that solid deformation is a significant factor on the lubrication characteristics of the reciprocating piston part.

• 대한조선학회논문집
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• 제52권2호
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• pp.161-169
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• 2015

According to SOLAS Regulation XII/6.5.3 and IMO GBS functional requirement(IMO, 2010), the structural redundancy of multi-bay stiffened panel in cargo area of bulk carrier should be provided enough in order to endure the initial design load though one bay of the stiffened panel is damaged due to plastic deformation or fatigue crack. To satisfy structural redundancy, Harmonized Common Structural Rules (hereinafter CSR-H, IACS, 2014) proposed to use 1.15 instead of 1.0 for buckling usage factor of stiffened panel in cargo area. This paper shows that buckling usage factor in CSR-H for structural redundancy is somewhat conservative considering the ultimate strength calculated by using nonlinear FEA for the damaged condition which is only one bay's plastic deformation due to colliding by weigh object like a bucket. Also, this paper presents that increasing of plate thickness only is more effective to get enough structural redundancy.

• 한국주조공학회지
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• 제4권1호
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• pp.5-11
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• 1984

Green compressive strength, permeability, deformation, flowability, compactability and green hardness values at room temperature are dependable on the grain distribution and grain shape. The results obtained under constant moisture (4% for sand) and bentonite (8% for sand) were as follows; 1. With decreasing grain size, surface area of sand grain was increased. 2. With decreasing grain size, coefficient of angularity was increased. 3. As surface area increased from $8926.43cm^2$ to $21211.16cm^2$ , green compressive strength was increased from $210.93\;g/cm^2$ to $449.98\;g/cm^2$, hardness was increased from 76.7 to 82.3, but permeability was decreased from $411.7\;{\frac{\;cc\;{\cdot}\;cm\;}{atm\;{\cdot}\;cm^2\;{\cdot}\;min.}}$ to $113.7\;{\frac{\;cc\;{\cdot}\;mm\;}{atm\;{\cdot}\;cm^2\;{\cdot}\;min.}}$ 4. As surface area increased from $8926.43\;cm^2$ to $21211.16\;cm^2$, flowability was decreased from 82.3% to 80.8%, deformation was decreased from $67.1\;cm\;{\times}\;10^{-3}$ to $54.6\;cm\;{\times}\;10^{-3}$, but compactability was increased from 44.8% to 54.3%. 5. Room temperature properties of molding sand were affected by variation of surface area.

• 암석학회지
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• 제7권3호
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• pp.190-206
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• 1998

북부 소백산육괴의 중남부에 위치한 장군봉지역의 고생대 변성퇴적암류(조선누층군과 평안층군)에 대한 미구조와 변형작용과 변성광물들 성장(변성작용) 사이의 상대적인 시간관계를 연구하였다. 첫 번째 변성작용은 스태크상 클로리토이드 및 조립 흑운모와 안구상 홍주석 광물들의 결정화작용과 관련된 저압형 변성작용으로 인지된다. 이러한 변성작용은 동-서향의 등사 향사습곡(장군봉 습곡)과 그 축면엽리에 해당하는 S1 엽리면 형성과 관련된 D1 변형 이전의 비변형조건하에서 발생하는 고생대 변성퇴적암류에 광역적인 동-서향의 광물분대를 형성시켰다. 두 번째 변성작용은 직선 내지 곡선 형태의 내부엽리 Si를 갖는 십자석과 석류석 반상변정들의 성장과 관련된 중압형 변성작용이다. 이러한 변성작용은 장군봉 습곡 구성지층들의 부분적인 결손을 초래하는 동-서향 드러스트들의 발달과 관련된 D1 변형 이후의 비변형조건하에서 발생하였고, 동-서향의 예천전단대 형성과 관련된 D2 변형 동안에 계속 발생하여 고생대 변성퇴적암류에 역시 광역적인 동-서향의 광물분대를 형성시켰다. 세 번째 변성 작용은 팻치상 홍주석과 주상 내지 섬유상 규선석 그리고 조립 석류석 광물들의 성장과 관련된 쥬라기 춘양화강암에 의한 접촉변성작용이다. 이러한 접촉변성작용은 S3 파랑엽리면 형성과 관련된 D3 변형 이전의 비변형조건하에서 발생하였고, D3 변형의 전기단계 동안에 계속 발생하여 춘양화강암체의 근접부에 제한된 남-북향의 광물분대를 형성시켰다.

• 한국해양공학회지
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• 제33권6호
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• pp.581-589
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• 2019

In order to understand the characteristics of beach deformation, in this study, numerical simulations were conducted using a 3-D hydro-morphodynamic model (HYMO-WASS-3D) to analyze the characteristics of beach deformation due to the coastal groundwater levels. HYMO-WASS-3D directly analyzed the nonlinear interaction between the hydrodynamic and morphodynamic processes in the coastal area. The simulation results of HYMO-WASS-3D showed good agreement with the experimental results on the changes in the profile of the beach in the surf and swash zones. Then, numerical simulations were conducted to examine the characteristics of beach deformation due to the variation of the level of the coastal groundwater. As a result, the beach profiles were examined in relation to the wave breaking in the surf zone and the wave uprush and backwash in the swash zone due to the differences in the water levels. This paper also discussed the temporal and spatial distributions of the velocities, vorticities, and suspended sediments in the surf and swash zones with various levels of the coastal groundwater.

• 물과 미래
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• 제26권2호
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• pp.39-48
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• 1993

해안에서 발생하는 재해의 큰 원인은 파랑작용에 기인되기 때문에 해양 기술자는 정확한 파랑변형을 예측하는 것이 매우 중요하다. 파랑변형의 주요인은 간수효과, 반사, 회석, 굴석, 산란, 방사등을 들 수 있다. 최근, 파랑변형에 대하여 수치모델이 이용되고 있다. 본 연구는 굴석과 회석을 동시에 고려할 수 있는 완경사방정식을 이용하여 유한요소법으로 수치모델을 수립했다. 이 방법은 복잡한 경계조건을 갖는 해안에 정확한 파랑예측을 할 수 있는 장점이 있지만 몇 가지의 개선해야할 문제점도 있는 것으로 나타났다. 본 계산결과를 검정하기 위해 모형실험을 실시했다. 완경사 방정식을 유한요소법으로 계산한 계산값과 Lee의 방법(Helmholtz 방정식을 유한차분법으로 수치계산한 방법)으로 계산한 값, 그리고 실험값과 비교한 결과 타당성있는 일치를 얻었다.

• Journal of Computing Science and Engineering
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• 제6권3호
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• pp.219-226
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• 2012

Recently, shape analysis of human organs has achieved much attention, owing to its potential to localize structural abnormalities. For a group-wise shape analysis, it is important to accurately restore the shape of a target structure in each subject and to build the inter-subject shape correspondences. To accomplish this, we propose a shape modeling method based on the Laplacian deformation framework. We deform a template model of a target structure in the segmented images while restoring subject-specific shape features by using Laplacian surface representation. In order to build the inter-subject shape correspondences, we implemented the progressive weighting scheme for adaptively controlling the rigidity parameter of the deformable model. This weighting scheme helps to preserve the relative distance between each point in the template model as much as possible during model deformation. This area-preserving deformation allows each point of the template model to be located at an anatomically consistent position in the target structure. Another advantage of our method is its application to human organs of non-spherical topology. We present the experiments for evaluating the robustness of shape modeling against large variations in shape and size with the synthetic sets of the second cervical vertebrae (C2), which has a complex shape with holes.