• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.4
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• pp.85-92
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• 1996

This paper describes thermal-mechanical performance and ultimate mechanical-strength test for the purpose of aging analysis of suspension insulator. The temperature of insulator surface according to the aging of suspension insulator was rised about 2[$^{\circ}C$] to 7~8[$^{\circ}C$] difference comparing with the atmospheric temperature. The autoclave expansion of portland cement at the specimen that had much puncture insulator(autoclave measuring value : 0.37[%]) was higher than those of a little puncture insulator (autoclave measuring value : 0.1[ %] ). Quality standard and mechanical-strength of used suspension insulator deteriorate more remarkably than those of new suspension insulator. It is required that thermal-mechanical performance test standard be revised in the future.

• Proceedings of the Korean Fiber Society Conference
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• 1998.04a
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• pp.266-269
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• 1998

세 번수 단사로 제직된 모직물은 그 사용도가 높아지고 있으나 의복의 형태안정성이 문제되고 있다. 형태안정성 중에서 특히 공기중 수분의 흡수, 발산에 따른 수분율의 차이로 발생하는 습윤팽창은 시임 퍼커링, 의복의 뒤틀림, 의복 사이즈의 불량, 접착심지의 이탈등의 다양한 의복 외관상의 문제점을 야기시킬수 있다$^{1-4)}$ . 이러한 모직물의 습윤팽창은 직물의 길이와 두께를 변화시켜서 기공도에 영향을 미치고 나아가 의복의 쾌적감에도 영향을 미치게 된다.(중략)

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.547-552
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• 2022

In this study, we secured a technology for manufacturing expanded glass of uniform quality by using general tempered glass, that is, window glass, among automotive glass that is scrapped, and verified whether the manufactured expanded glass can be used for lithium battery fire suppression. The process of manufacturing expanded glass using waste glass is generally divided into Crushing → Milling → Granulation → Expansion → Cooling. With several trials a nd errors. It is obtained a yield of 0.5 ø mm to 2 ø mm spherical particles of 80 % or more. By comparing the surface analysis and physical properties, a more suitable sample was selected as a fire extinguishing agent for lithium batteries, and it was confirmed that the result of the adaptability test for lithium battery fire was satisfactory.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2010.04a
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• pp.340-345
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• 2010

국내의 건축물은 강한 내력을 갖기 위해 사용되는 HSC빈도가 점진적 증가하고 있으며, HSC로 시공되어진 건축구조물에서의 화재 발생시 폭렬현상의 문제점이 대두되고 있다. 이에 국내외에서 폭렬현상에 대한 연구들이 진행되었고, 이를 통해 폭렬현상에 원인을 알게 되어 이를 토대로 폭렬 방지 방안을 세웠다. 이에 따라 폭렬현상의 원인 중 합수율이 있으며, 이는 콘크리트가 함유하고 있는 수분으로 고온시에 팽창하여 폭렬현상의 매커니즘이 형성된다. 또한 이러한 함수율이 폭렬 발생에 미치는 영향을 크게 하는 요인으로 탄산화와 양생방법이 있다. 우선 탄산화는 반응을 일으킬 경우, 생성물이 공극을 채워 고온시 팽창된 수분이 외부로 나가는 것을 방해하여 수증기압을 축적시키고, 양생방법에 따라 함수율이 달라지게 되어 고온시 팽창될 수분의 양을 결정하게 된다. 특히, 함수율에 의해 발생되는 폭렬을 방지하기 위해 고강도 콘크리트 내부의 수분을 제거하는 강제건조를 하거나 팽창된 수분이 빠져나갈 곳을 만들기 위해 고온에서 녹는 PP섬유를 사용해 공극을 만들어주는 방법이 있다. 따라서 본 연구는 HSC의 폭렬현상방지 대책을 위한 기초자료를 제시하고자 한다.

• Korean Journal of Agricultural Science
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• v.18 no.2
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• pp.140-147
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• 1991

This paper was performed to obtain the data applied to use of synthetic lightweight aggregate concrete affected by alkali silica reaction. The results obtained were summarized as follows : 1. The expansion of each type concrete was increased with increase of curing age, respectively. Also, at the curing age 90 days, the rate of expansion of type A, B, C and D concrete was increased 0.173%, 0.575%, 0.230% and 0.680%, respectively. Specially, the rate of expansion of type D concrete was shown 3.93 times higher than the type A concrete. The cracks width were increased with increase of expansion and at the 0.680% expansion, the maximum width was shown 0.5 mm. 2. The dynamic modulus of elasticity of each type concrete was increased with increase of curing age, respectively. At the curing age 30 days, the highest dynamic modulus of elasticity was showed at each type concrete, respectively. But, it was gradually decreased with increase of curing age at those concrete, respectively. Also, at the curing age A, B, C and D concrete was increased 24.3%, 33.7%, 28.1% and 37.0%, respectively. The rate of loss in type D concrete was shown 1.52 times higher than the type A concrete. 3. The ultrasonic pulse velocity of each type concrete was increased with increase of curing age, respectively. At the curing age 30 days, the highest ultrasonic pulse velocity was showed at each type concrete, respectively. But, it was gradually decreased with increase of curing age at those concrete, respectively. Also, at the curing age 90 days, the percentage loss of ultrasonic pulse velocity of type A, B, C and D concrete was increased 6.4%, 8.7%, 8.5% and 14.2%, respectively. The rate of loss in type D concrete was shown 2.21 times higher than the type A concrete. 4. The relation between dynamic modulus of elasticity and ultrasonic pulse velocity was highly significant. The dynamic modulus of elasticity was increased with increase and decreased with decrease of ultrasonic pulse velocity. Also, the decreasing rate of the dynamic modulus of elasticity was shown 2-7 times higher than the ultrasonic pulse velocity at each age, respectively. 5. The dynamic modulus of elasticity and ultrasonic pulse velocity were decreased with increase of expansion, and the decreasing rates were increased with increase of curing age. The increasing rate of expansion was shown higher than the decreasing rate of dynamic modulus and ultrasonic pulse velocity.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.24-33
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• 2012

The present work has suggested the design methods of the bolt body for making the anti-releasing bolts and provided the changed properties of the bolt body after explosion. To prove this work, two models of the anti-releasing bolts, M10 and M20, are produced and the expansion properties of each model are experimentally obtained. This study verify that the expansion of the bolt body is reproducible and the expansion rate could be controlled by the combination of the design factors and the anti-releasing characteristics could be quantified. It also could provide the data that would be needed to make the bolts with the anti-releasing effect.

• Composites Research
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• v.28 no.6
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• pp.340-347
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• 2015

As resin impregnates through the fiber preform in vacuum assisted resin transfer molding process, the volume of fibers is changed by expansion of fiber mat according to filling time. It causes not only the change in dimension but also the decrease of mechanical properties of the composite product. Moreover, it results in the economic loss by increase of the used amount of resin especially in the large product such as wind turbine blade. In this study, the ways to control fiber volume fraction were investigated by both the experimental and theoretical analyses on the expansion of fiber preform as the preform was impregnated by resin in the VARTM process. Two kinds of swelling stage were observed as flow front progressed, which was analyzed by comparing the experimental and simulation results. The process parameters are expected to be optimized by investigating the swelling behavior of fiber preform in the manufacturing process of the composite product.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.11b
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• pp.18-30
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• 2002

이암 및 셰일은 점토를 함유하고 있어 풍화작용을 받을 경우 공학적 성질이 급격히 변화하여 강도 저하, 내구성저하현상 및 토사와 유사한 거동을 보이는 등 토목공사에 위험한 요소가 되고 있다. 풍화된 시료엔 대한 실험용 시료 가공이 어렵고 적용 가능한 실험법이 적어 공학적 특성이나 거동을 정량적으로 파악하는 기법이 다른 암종에 비해 극히 제한된다. 현재까지 강도측정과 같은 일반적인 물성의 단순측정보다는 내구성을 분석하는 슬레이킹 내구성 시험 (Slake durability test), Modified Jar test, 팽창율 측정시험 (Swelling test) 등의 정량화 시험법이 주로 사용되고 있으며 국내 현장에서도 적용을 권장할 수 있다. 이러한 실험치의 해석에서 단일 실험치 (예: 팽창율)만으로 지질공학적 특성을 파악하는 경우 잘못된 판단을 할 수도 있으므로, X선 회절분석시험 (XRD: X-Ray Diffraction Test), TG-DTA분석, 주사전자현미경 (SEM: Scanning Electron Microscope) 이미지 분석, 투수계수 측정실험 등도 함께 수행하여 실험결과를 종합적으로 해석하는 것이 바람직하다.

• Journal of the Korean Wood Science and Technology
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• v.27 no.2
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• pp.38-45
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• 1999

This study was to figure out proper Formaldehyde/Urea molar ratio of UF resin with satisfactory bonding strength of plywood and properties of particleboard. The six kinds of UF resins were manufactured with F/U molar ratio 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0. The boards were made of three kinds of raw materials : Veneer, Sliver-Particle and Strand-Particle. Manufacturing condition of plywood : amount of mixing resin was 150g/$m^2$. The fourty secs/mm simple-pressing schedule in the pressure 10kgf/$m^2$ was applied for 480mm${\times}$700mm board at the temperature of $110^{\circ}C$ in a hot press. Manufacturing condition of particleboard : Target density was 0.65g/$cm^2$. The stepwise 9 minutes- multi-pressing schedule in the maximum pressure 40kgf/$cm^2$, the minimum pressure 15kgf/$cm^2$ was applied for $480mm{\times}634mm{\times}12mm$ board at the temperature of $150^{\circ}C$ in a hot press. The results are as follows : I. In bonding strength, plywood which was made by F/U molar ratio 1.2 showed the highest value. Other molar ratio resin also gave the satisfied value of KS standard, 7.5kgf/$cm^2$. 2. In internal bond strength of particleboard, Sliver-Particleboard(SLPB) and Strand-Particleboard(STPB) varied respectively from 5.9kgf/$cm^2$ to 4.8kgf/$cm^2$, from 6.7kgf/$cm^2$ to 5.4kgf/$cm^2$. SLPB with F/U=1.2 and STPB with F/U=1.6 had higher IB value. Also, both SLPB and STPB showed lower IB value in F/U molar ratio 2.0 and 1.0. 3. SLPB and STPB with six kinds of UF resin respectively satisfied bending strength of KS standard 150 Type(130kgf/$cm^2$) and 200 Type(180kgf/$cm^2$). Bending strength data for both of SLPB and STPB showed little or no loss from F/U=1.8 to F/U=1.2. Also, STPB was approximately two times higher than that of SLPB. Therefore, the raw material's shape had more effect on bending strength than the FlU molar ratio. 4. F/U=1.6 and 1.4 showed the lower thickness swelling in SLPB and STPB. All of STPBs satisfied thickness swelling of KS standard, under 12%.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.727-732
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• 2022

Applying the calculated cross-sectional reduction due to the corroded rebar investigated in the field to the numerical analysis model, the damage pattern and delamination of concrete in the field showed a tendency relatively similar to the numerical analysis results. It was analyzed that when the expansion pressure due to corrosion of the reinforcing bar is greater than the tensile stress of the concrete, cracks are generated and the concrete cover can be fracture. As a result of this study, the correlation between the corrosion rate of reinforcing bars and the crack occurrence of the concrete cover of the subway box structure was verified based on the numerical analysis and field test results. To prevent rebar corrosion, the corrosion rate can be reduced by applying rust prevention to the reinforcing bar and changing the material. In the case of exposed to a corrosive environment, the tensile strength of the concrete is improved by adjusting the concrete compressive strength to secure durability against the expansion pressure caused by the corroded rebar.