• 한국건축시공학회지
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• 제17권1호
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• pp.39-46
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• 2017

최근 건축물의 기초는 구조체의 안정성과 연관하여 두꺼운 매스콘크리트 형태가 설계되어지고 있다. 그런데, 이와 같은 매트 매스콘크리트는 800mm 이상의 두꺼운 부재로 설계되는 경우가 많아짐에 따라 수화열에 의한 균열이 문제점으로 제기 되고 있다. 이에, 본 연구에서는 상 하부를 구분하여 타설하는 실무조건을 고려하여, 컴퓨터 프로그램상으로 하부와 상부의 최적치를 도출한 다음, 실구조체에 적용 해석치와 실측치간을 비교하므로서 효율적인 수화열균열 저감방안을 제안하고자 하였다. 그 결과, 상 하부 타설 콘크리트간의 저발열 배합정도를 고려한 수화발열량차 적용은 침하균열 방지 및 수화열 균열제어에 효과적인 것으로 밝혀졌다.

• 한국철도학회논문집
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• 제12권6호
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• pp.1024-1029
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• 2009

콘크리트 구조물의 대형화에 따라 시공 중 수화열에 의한 온도 균열 발생 사례가 증가하고 있다. 지하철 콘크리트 BOX 구조물의 경우, 부재 두께가 1m 이상 되는 경우가 대부분이며, 특히 벽체는 외부구속에 의한 관통균열 발생으로 누수 및 조직 열화가 발생하여 내구성에 나쁜 영향을 주고 있다. 지하철은 일반적으로 도로를 따라 건설되므 로 교통체증을 줄이기 위한 공사기간 단축 시도가 종종 발생하게 된다. 본 연구에서는 공사시간 단축 방안으로서 한 지간씩 건너띠면서 콘크리트를 타설하는 시공방법을 제안하였으며, 이에 대한 온도균열제어에 미치는 영향을 검토하였다. 또한 벽체 높이, 타설온도, 대기온도 등을 현장조건에 따라 변화시켜 온도균열에 대한 민감도 분석을 실시하였다.

• 전기학회논문지
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• 제57권1호
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• pp.82-87
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• 2008

It is impossible to database(DB) the patterns of power cable events and cause analysis of faulted cable because the product liability(PL) law have been enforced in Korea, since 2002. In additions, simulation and pattern of power cable events are needed for DB system under accelerated deterioration. In this paper, we tested for resistance to cracking of cable below the 22.9kV class due to thermal stresses. This method of exam is following IEC 60811-3-1(Common test methods for insulating and sheathing materials of electric cables). From the results, The 22.9kV calss A power cable was discolored on the surface and significantly reduced in the longitudinal direction. As the thermal weight properties of A power cable was definitely varied, we are able to guess the problem of manufacture. If the cable was defect by the manufacture, the victims would be able to claim for damage in the PL system.

• Computers and Concrete
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• 제11권4호
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• pp.271-289
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• 2013

In this research, a developed microstructural model of cement particles was presented to describe the cement hydration procedure. To simplify the hydration process, the whole hydration was analyzed in a series of sub-steps. In each step, the hydration degree, as well as the microstructural size of the hydration cell, was calculated as a function of the radius of the unreacted cement particles. With the consideration of the water consumption and the reduction of the interfacial area between water and hydration products, the micro-level expressions of the cement hydration kinetics were established. Then the heat released and temperature history of the concrete was carried out with the hydration degree obtained from each sub-steps. The equivalent age method based on the Arrhenius law was introduced in this research. Based on the equivalent age method, a maturity model was applied to describe the evolution of the mechanical properties of the material during the hydration process. The finite element program ANSYS was used to analyze the temperature field in concrete structures. Then thermal stress field was calculated using the elasticity modulus obtained from code formulate. And the risk of thermal cracking was estimated by the comparison of thermal stress and concrete tensile strength.

• 자원리싸이클링
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• 제28권1호
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• pp.15-22
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• 2019

습식법으로 고순도 알루미나를 제조할 수 있는 알콕사이드 가수분해법, 암모늄 명반의 열분해법, 암모늄 알루미늄탄산염(AACH) 열분해법을 소개하였다. 상기 세 공정으로 알루미나 제조시 용액의 pH, 온도와 불순물이 알루미나의 상전이와 고순도에 미치는 영향을 조사했다. 알콕사이드와 암모늄 명반의 열분해법으로는 ${\alpha}$와 ${\gamma}$알루미나의 제조가 가능하다. 그러나 AACH 열분해법으로는 ${\gamma}$알루미나 제조는 어렵다.

• 한국전산유체공학회지
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• 제21권3호
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• pp.110-117
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• 2016

It is a essential to minimize production of by-products for economically effective petrochemical process. In order to find key factor to achieve the effective process, 2-dimensional computational fluid dynamics considering a variety of physics such as convective and radiative heat transfer and thermal cracking of ethane are carried out. The reactor is modeled as an isothermal tube, whose length is 1.2 m and radius is 0.01 m, respectively. At first, the axial distribution of representative by-products in ethane thermal cracking are investigated in each inner wall temperature conditions. Then the comparison between concentration of propene($C_3H_6$) and ethane conversion is discussed with respect to inner wall temperature conditions too. Finally, both reaction rate and turbulent kinetic energy are used to identify the production mechanism of $C_3H_6$ under the intersection point in the plot for $C_3H_6$ molar concentration and ethane conversion.

• 한국응용과학기술학회지
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• 제28권3호
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• pp.345-350
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• 2011

Antioxidant agent, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane were prepared and investigated the antioxidant activity on recycled rubber mat manufactured with waste tire powder. Mechanical properties of rubber mat are influenced by many factor such as compounding ingredients and state of cure, process of rubber, and fillers. Our study aim is to investigate influence of antioxidant activities on ozone cracking and the thermal aging time. In this work, the degradation of recycled rubber mat was studied and suggested mechanism to involve two-type of degradation, thermal aging and cracking both of which can be contained antioxidant or non-antioxidant agent.

• 한국도로학회논문집
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• 제2권1호
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• pp.123-133
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• 2000

폐타이어를 분쇄한 고무분말로써 습식방법에 의해 제조된 CRM아스팔트 혼합물은 일반 아스팔트 혼합물에 비해 온도균열. 피로균열 및 소성변형에 대한 저항성이 증진되는 것으로 알려져 있다. 본 연구에서는 국내에서 생성된 폐타이어 고무분말과 아스팔트(AP-3, AP-5)를 사용하여 제조된 CRM 아스팔트 바인더의 물리적 특성 및 CRM아스팔트 혼합물의 역학적 특성을 비교하였다. 시험결과, CRM 아스팔트 바인더는 일반 아스팔트보다 물리적 특성이 증진되었다. DSR을 사용한 아스팔트 바인더의 고온 특성시험결과, CRM아스팔트는 고온에서 내유동성이 증가되는 것으로 기대되며 노화가 감소되는 것으로 나타났고, 저온 역학적 특성시험결과에서는 CRM아스팔트는 저온균열에 대한 저항성이 증가될 것으로 기대된다.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.106-114
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• 1996

Extensive experiments were conducted to investigate the emission of DI diesel engine by using DMC(dimethyl carbonate) as an oxygenated fuel additives. The results indicate that smoke reduces almost linearly with fuel oxygen contents. Reductions of HC and CO were attained noticeably, while a small increase in NOx was encountered concurrently. The effective reduction in smoke with DMC was maintained with the presence of CO2, which suggested a low NOx and smoke operation could be obtained in combination of using oxygenated fuel and EGR. Further experiment was conducted a thermal cracking set-up for mechanism studies.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 12th KACG Technical Meeting and the 4th Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.125-129
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• 1997

The effects of the moisture and thermal annealing on CLBO crystal have been investigated. CLBO has hydrated at high humidity condition, resulting in 5B$_2$O$_3$$.$Cs$_2$O$.$8H$_2$O. The surface hydration seems to induce the cracking and the refractive index change in CLBO. The thermal annealing is effective to restore the changed index.