• 한국재료학회지
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• 제22권11호
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• pp.604-608
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• 2012

Recently, inorganic-organic hybrid materials have attracted much attention not only for their excellent thermal conductivity but also for their flame retardant properties. In this study, the properties of organic-inorganic hybrid insulating materials using inorganic fillers and polyurethane foam with different foaming conditions have been investigated. The addition of 1.5 wt% water to polyurethane as foaming agent shows the best foaming properties. The pore size was decreased in the foaming body with increasing of the $CaCO_3$ addition. The apparent density and thermal conductivity were increased by increasing the $CaCO_3$ addition. With an increasing amount of $CaCO_3$ powder, the flame retardant property is improved, but the properties of thermal conductivity and apparent density tend to decrease. When the addition of fine particles of $CaCO_3$, the apparent density and thermal conductivity were increased and, also, with the addition of coarse particles over $45{\mu}m$ in size, the apparent density and thermal conductivity were increased as well. In this study, the adding of $CaCO_3$ with average particle size of $27{\mu}m$ led to the lowest thermal conductivity and apparent density. After evaluation with different inorganic fillers, $Mg(OH)_2$ showed the highest thermal conductivity; on the other hand, $CaCO_3$ showed the lowest thermal conductivity.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.45-46
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• 2023

CLC is used as a filling material for many buildings, and according to energy saving design standards, CLC also requires insulation performance. However, it shows lower insulation performance compared to organic insulation, so additional research is needed. Therefore, in this study, the insulation properties of CLC were analyzed by incorporating EPS beads with high insulation performance into CLC. In this experiment, EPS beads and blast furnace slag were replaced, and W/B was fixed at 33%. The EPS Bead mixing ratio was divided into 5 levels: 0, 0.5, 1.0, 1.5, 2.0 (%), and the experimental items were measured for apparent density and thermal conductivity. As a result of the experiment, the apparent density and thermal conductivity tended to decrease as the mixing ratio of EPS beads increased. It is judged that the density decreased due to the low density and the micropores inside, and the thermal conductivity also decreased.

• 한국세라믹학회지
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• 제49권6호
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• pp.654-658
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• 2012

In this work, the properties of an organic-inorganic hybrid insulating material using an inorganic filler and polyurethane foam with different foaming conditions were investigated. At weight ratios of polyol and isocyanate of 1 to 1.2 good foaming properties were noted. In addition, an addition of 0.4 g of water, 0.1 g of surfactant, and 0.1 g of catalyst with respect to the composites of polyol at 5 g and isocyanate at 6 g showed the lowest apparent density and thermal conductivity. The pore size was smaller in the organic-inorganic hybrid foaming body with an increase in the $CaCO_3$ addition amount. Moreover, the apparent density and thermal conductivity were increased when the added amount of $CaCO_3$ increased. Increasing the amount of $CaCO_3$ powder is expected to improve the flame retardant capabilities; however, doing this tends to increase the apparent density and thermal conductivity.

• Advances in nano research
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• 제1권3호
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• pp.171-182
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• 2013

The alternating current (AC) conductivity in semiconductor crystals with an open-core screw dislocation is studied in the current work. The screw dislocation in crystalline media results in an effective potential field which affects the electronic transport properties of the system. Therefore, from a technological view point, it is interesting to investigate properties of AC conductivity at frequencies of a few terahertz. To quantify the screw-induced potential effect, we calculated the AC conductivity of dislocated crystals using the Kubo formula. The conductivity showed peaks within the terahertz frequency region, where the amplitude of the AC conductivity was large enough to be measured in experiments. The measurable conductivity peaks did not arise in dislocation-free crystals threaded by a magnetic flux tube. These results imply different conductivity mechanisms in crystals with a screw dislocation than those threaded by a magnetic flux tube, despite the apparent similarity in their electronic eigenstates.

• 지질공학
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• 제12권1호
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• pp.63-73
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• 2002

누수 보강 저수지의 그라우팅 개선 구간 평가를 목적으로 물-시멘트 배합비별로 제조된 그라우트에 대하여 재령 변화에 따른 전기비저항과 압축강도 변화를 측정하였다. 동일 조건 하에서 그라우트의 농노가 증가할수록 전도도는 높아지고, 대상 매질에 그라우트가 주입되는 경우 주입 이전에 비해 비저항이 상대적으로 낮아지는 효과가 나타나므로 이를 이용한 주입 구간의 판정이 가능함을 확인하였다. 대상 매질이 서로 다른 세 지구에 대한 그라우팅 이후 전기비저항 수직탐사 결과 겉보기 비저항은 수십∼수백 ohm-m 이하로 낮아졌으며, 주입 이후 수 일이 지난 후부터는 점차 증가된 상태로 일정하게 유지되는 것으로 나타나는데, 이는 그라우트가 주입된 이후 대상 지층 내에서 굳어짐에 따른 강도 증가의 결과로 밝혀졌다.

• 한국세라믹학회지
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• 제56권5호
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• pp.489-496
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• 2019

Cement-based thermal insulation material was manufactured using OPC, lime, anhydrite, and CSA cement in this study. The morphology and physical properties of the material were analyzed using XRD. All samples had ettringite, Ca(OH)₂, and CaCO₃ crystals. The XRD peak intensity of the ettringite and Ca(OH)₂ slightly increased with an increase in curing time from 3 to 7 days. The compressive strength values at 28 days of specimens 1-8 were in the range of 0.25-0.32 MPa, and the compressive strength values of specimens 3-8 were > 0.3 MPa. The coefficients of correlation between compressive strength and apparent gravity at 7 days and those between compressive strength and ettringite/Ca(OH)₂ XRD peak intensity at 28 days were above 0.8. That is, the compressive strength exhibited an influence on apparent gravity at 7 days and on hydrate at 28 days. The thermal conductivity of all specimens was 0.041-0.045 W/mK, and the highest value of thermal conductivity was shown by specimen 5. The coefficient of correlation between apparent gravity and thermal conductivity was 0.84. It was concluded that control of raw materials and hydrates must be considered for manufacturing of insulation materials. The cement-based thermal insulation material in this study could be used in construction fields.

• 한국산학기술학회논문지
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• 제9권5호
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• pp.1368-1373
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• 2008

본 연구는 내분비계 장애물질로써 페놀 및 비스페놀A이 포함된 용액에 대해 전기분해 실험을 수행하였다. 불용성 DSA 양극을 사용하여 오염물질의 전기산화 변화를 확인하였으며 이때 운전인자는 전류밀도, 전도도, 극간거리 등을 변수로 하여 행하였다. 페놀 및 비스페놀A 제거율인 경우 전류밀도가 증가에 비례하여 오염물 제거가 향상되었으며 전도도가 높을수록 비스페놀A 처리율이 증가하였다. 반면 극간거리 변화에 따른 오염물질 제거에는 큰 영향을 보이지 않았다.

• 지구물리와물리탐사
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• 제13권4호
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• pp.370-377
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• 2010

이 연구에서는 지하 이상체와 배경매질의 전기전도도 대비가 큰 경우 측정 겉보기비저항이 일정한 값에 수렴하는 전류포화현상에 대하여 이론적 고찰을 수행하였다. 이를 위하여 몇 가지 간단한 지하구조 모형에 대한 이론해를 통하여 표면전하의 거동을 살펴보았으며, 이들 표면전하가 전류포화를 일으키는 원인 및 겉보기비저항에 미치는 영향을 고찰 하였다. 결과적으로 전기비저항 탐사에서 측정하는 겉보기비저항 이상의 크기는 포화현상에 따라 일정값에 수렴하게 됨을 확인하였으며, 실제 겉보기비저항 이상의 크기는 이상체가 완전도체 혹은 부도체일 경우보다 작다는 것을 입증하였다. 또한 대개 전기전도도 대비가 100배 이상이 될 경우, 전류포화현상이 발생하는 것으로 해석된다.

• 지구물리
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• 제1권1호
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• pp.51-58
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• 1998

단극배열을 사용하는 시추공-시추공 전기비저항 탐사법의 문제점을 파악하기 위하여 원통형 2차원 이상체에 대한 이론해로부터 겉보기 비저항 및 2차전위 분포양상을 계산하고 이를 분석하였다. 분석결과 시추공-시추공 전기비저항 탐사에서 2차원 이상체가 전도체일 경우는 물론이고 부도체일 경우에도 모두 모암의 비저항보다 낮은 겉보기 비저항을 나타낸다. 따라서 단극배열을 사용하여 획득한 시추공-시추공 전기비저항 탐사자료만으로 시추공 사이에 존재하는 이상체의 전도도에 관한 해석이 거의 불가능하다. 이러한 문제점의 해결을 위해서는 3차원 자료획득 및 해석이 필요하며, 이의 실현이 불가능할 경우에는 적어도 동일 시추공 자료를 이용해야만 이상체의 전도도에 관한 해석이 가능해 진다.

• 한국초전도ㆍ저온공학회논문지
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• 제13권2호
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• pp.29-32
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• 2011

The thermal properties of insulation material are essential to develop a high-temperature superconducting (HTS) power cable to be operated at around liquid nitrogen temperature. Unlike metallic materials, nonmetallic materials have a high thermal resistance; therefore special attention needs to be paid to estimate heat flow correctly. Thus, we have developed a precise instrument for measuring the thermal conductivity of insulating materials over a temperature range from 40 K to near room temperature using a cryocooler. Firstly, the measurement of thermal conductivity for Teflon is carried out for accuracy confirmation. For a supplied heat flux, the temperature difference between warm and cold side is measured in steady state, from which the thermal conductivity of Teflon is calculated and compared with published result of NIST. In addition, the apparent thermal conductivity of Polypropylene laminated paper (PPLP) is presented and its temperature dependency is discussed.