• 생물환경조절학회지
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• 제30권4호
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• pp.419-428
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• 2021

모바일 기반 온실에너지 계산프로그램을 제작하기 위해 먼저 주요 단일 피복재 10종 및 보온재 16종에 대한 열관류율 측정하였다. 또한 피복 및 보온재를 이중 및 삼중으로 다층 설치할 때 열관류율 추정을 위하여 이중 설치시 24조합, 삼중설치 시 59조합에 대한 열관류율을 핫박스를 이용하여 측정하였다. 단일 피복재에서는 PE필름(0.08mm) 대비 PO필름(0.15mm)이 가장 열관류율이 가장 작고 열절감율이 가장 큰 것으로 나타났다. 단일 보온재에서는 열관류율에서는 외피가 있는 5겹의 다겹보온커튼이 가장 보온력이 좋은 것으로 나타났다. 또한 단일자재에 대한 열관류율 값과 열저항값을 이용한 피복 및 보온재의 다층설치시의 총 열관류율 값을 산정하였고 실측 값과의 오차를 보정하는 선형회귀식을 도출하였다. 단일재료의 열관류율값에 의한 피복 및 보온재의 다층설치시 열관류율 추정 모형을 개발한 결과 모형평가지수가 0.90(0.5 이상일 때 양호)으로 나타나 추정치가 실측치를 매우 잘 재현 하고 있는 것으로 나타났다. 또한 시험온실을 통한 실증시험결과 예측된 열절감율이 실측치보다 상대오차 2%로 작게 나타나는 것으로 평가되었다. 이러한 연구결과를 기반으로 모바일 기반의 온실 에너지계산 프로그램을 개발하였다. 이 프로그램은 HTML5 표준 웹 기반 모바일 웹 애플리케이션으로 구현하였으며 N-Screen 지원을 통해 다양한 모바일 장치 및 PC 브라우저에서 동작이 가능하게 제작되었다. 또한 온실 피복(12종) 및 보온재(16종)의 조합별 열관류율 및 난방부하계수를 제공하여 농민이 모바일로 온실 위치, 형태 및 피복·보온재 등을 반영한 최대 주야간 냉난방부하 및 기간 난방부하를 산정할 수 있다. 대상 온실의 에너지 소비량에 대한 평가가 가능하며 온실의 지역 및 형태에 따라 피복 및 보온재의 최적 선택으로 에너지 절감형 온실 설계가 가능할 것으로 판단되었다.

• 한국소음진동공학회논문집
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• 제24권7호
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• pp.562-568
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• 2014

This study aimed to identify changes in the physical properties of artificial mineral-fiber materials used as building insulation that had been installed in the outer walls of buildings for a long time. To achieve this goal, glass fiber and rock wool were collected from outer walls in actual buildings and their acoustic and thermal performances were measured. These were compared with measurements from similar products manufactured recently. The results showed that old, used samples had a lower sound absorption coefficient compared to recently manufactured materials. The old samples also displayed increased compressibility compared to new materials. For example, the compressibility difference for glass wool was 7.32 mm. Old samples had a dynamic stiffness $1.28MN/m^3$ higher than new material samples. The thermal conductivity of both old and new samples increased within creasing temperature. They showed similar results at temperatures between 0 and $20^{\circ}C$.

• Applied Science and Convergence Technology
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• 제26권6호
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• pp.208-213
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• 2017

Flexible opto-electronic devices are developed on the insulating layer deposited stainless steel (STS) substrates. The silicon dioxide ($SiO_2$) material as the diffusion barrier of Fe and Cr atoms in addition to the electrical insulation between the electronic device and STS is processed using the plasma enhanced chemical vapor deposition method. Noble silver (Ag) films of approximately 100 nm thickness have been formed on $SiO_2$ deposited STS substrates by E-beam evaporation technique. The films then were annealed at $650^{\circ}C$ for 20 min using the rapid thermal annealing (RTA) technique. It was investigated the variation of the surface morphology due to the interaction between Ag films and $SiO_2$ layers after the RTA treatment. The results showed the movement of Si atoms in silver film from $SiO_2$. In addition, the structural investigation of Ag annealed at $650^{\circ}C$ indicated that the Ag film has the material property of p-type semiconductor and the bandgap of approximately 1 eV. Also, the films annealed at $650^{\circ}C$ showed reflection with sinusoidal oscillations due to optical interference of multiple reflections originated from films and substrate surfaces. Such changes can be attributed to both formation of $SiO_2$ on Ag film surface and agglomeration of silver film between particles due to annealing.

• Journal of Electrical Engineering and Technology
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• 제4권1호
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• pp.123-130
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• 2009

The partial discharge (PD) measurement is a very effective method to assess the winding insulation condition of high-voltage machines, since most of the insulation failure processes are directly or indirectly caused by PD. On-line PD measurements, which can detect insulation defects of winding in the early stages on rotating machines in operation, have been accepted as the most important technique. The epoxy mica capacitive coupler is currently and extensively used for on-line detection of PD pulses of high-voltage rotating machines. To evaluate the feasibility of developing a capacitive coupler that is easier to manufacture at a lower cost compared to epoxy mica couplers, a 100pF capacitive coupler made of ceramic material is designed, fabricated and tested for on-line PD measurements of 23 kV electrical machines. A series of electrical tests and accelerated aging tests are performed on the ceramic coupler to evaluate the performance requirements, long-term reliability and thermal stability for in field application. The test results show that the newly developed ceramic coupler provides equal and improved performance at a lower cost compared to epoxy mica couplers, and estimated voltage life is anticipated to surpass 100 years.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.491-495
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• 2004

The industries use polymer materials for many purposes for they have many merits. The costs of these materials take up too great a proportion of the overall cost of products that use these materials as their major material. It is advantage for polymer industries to reduce these costs. The microcellular foaming process was developed in the early 1980s to solve this problem and proved to be quite successful. Microcellular foaming process uses inert gases such as $CO_2$, $N_2$. As these gases solve into polymer matrices, many properties are changed. The microcellular foaming process makes the glass transition temperature of polymers to low, and diminish the residual stress of polymer matrices. Besides, the microcellular foaming process has several merits, impact strength elevation, thermal insulation, noise insulation, and raw material saving etc. This characteristic of microcellular foaming process has influenced by cell morphology. The cell morphology means cell size and cell density. The cell morphology has influenced by many factors. The examples of factor are pressure drop rate, foaming temperature, foaming time, saturation pressure, saturation time etc. Among their factors, pressure drop rate is the most important factor for cell morphology in microcellular foaming injection molding process. This paper describes about the cell morphology change in accordance with the pressure drop rate of microcellular foaming injection molding process.

• 한국산학기술학회논문지
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• 제14권6호
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• pp.3089-3095
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• 2013

흡음재로 널리 사용되는 헤드라이너는 발포성 폴리우레탄(PU foam)과 유리섬유(Glass Fiber,GF) 로 구성된 복합재료로, 제품의 생산 공정을 거치는 동안 부산물 형태의 폐기물이 발생한다. 헤드라이너 폐기물에 대한 효과적인 재활용을 위해 헤드라이너 구성성분에 대한 분리공정이 중요한 문제점이다. 헤드라이너에 대한 열분석결과에 의하면 중량의 감량 비율은 $400^{\circ}C$까지의 온도범위에서는 발포성 폴리우레탄 > 비발포성 폴리우레탄 > 부직포 > 1st layer > 유리섬유의 순으로 감량이 증가하는 결과를 보이고 있다. HDPE, LLDPE, PP 그리고 Master Batch 에 첨가제 형태로 폐 스크랩 첨가하여 sheet를 제작한 후 DSC 특성을 분석한 결과 PP를 제외한 다른 물질들에서는 결정화에 따른 발열전이가 나타나지 않는 것을 확인 하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.2141-2145
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• 2004

As part of study on thermal hydraulic behavior in the reactor cavity under external vessel cooling in the APR (Advanced Power Reactor) 1400, one dimensional two phase flow of steady state in the reactor cavity have been analyzed to investigate a coolant circulation mass flow rate in the annulus region between the reactor vessel and the insulation material using the RELAP5/MOD3 computer code. The RELAP5/MOD3 results have shown that a two phase natural circulation flow of 300 - 600 kg/s is generated in the annulus region between the reactor vessel and the insulation material when the external vessel cooling has been applied in the APR 1400. An increase in the heat flux of the inner vessel leads to an increase of the coolant mass flow rate. An increase in the coolant outlet area leads to an increase in the coolant circulation mass flow rate, but the coolant inlet area does not effective on the coolant circulation mass flow rate. The change of the lower coolant outlet to a lower position affects the coolant circulation mass flow rate, but the variation trend is not consistent.

• 한국전기전자재료학회논문지
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• 제25권10호
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• pp.779-785
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• 2012

The epoxy/micro-and nano-mixed silica composites(EMNC) systems were prepared and the AC insulation breakdown strength was evaluated. Glass transition temperature (Tg) and crosslink density were also measured by dynamic mechanical analyzer(DMA) in order to correlate them with the electrical and mechanical properties, and the effect of silane coupling agent on the electrical properties was also studied. Electrical properties and crosslink density of epoxy/micro-silica composite were noticeably improved by addition of nano-silica and silane coupling agent, and the highest breakdown strength was obtained by addition of 0.5~5 phr of nano-silica and 2.5 phr of silane coupling agent, and the highest tensile and flexural strength were obtained by addition of 2.5 phr of nano-silica.

• 한국전기전자재료학회논문지
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• 제36권6호
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• pp.570-575
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• 2023

Demand and necessity for eco-friendly offshore wind farms have been increasing. Research on submarine cables is constantly being considered for a reliable and stable power transmission. This study aimed to evaluate the thermal aging characteristic of submarine cables inside the J-tube of offshore wind farms. In this study, a submarine cable was set in three sections: The first is the part exposed to the air above the sea level at high temperature. The second is the section exposed to repeated temperature fluctuation as the sea level rises and falls. The third is the part submerged at low temperature below the sea level. Aged samples were tested by using the method of electrical evaluation to obtain insulation characteristics. The experimental results show that the dielectric breakdown of the sample with temperature fluctuation was 7% lower than the sample with a constant temperature; thereby, demonstrating that the section where the temperature fluctuation occurred in the submarine cables was weaker than the other. The sections of submarine cable with temperature fluctuations are believed as a weak point during operation; therefore, this part should be monitored preferentially.

• 한국건축시공학회지
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• 제18권2호
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• pp.117-123
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• 2018

건물의 건설 및 운영에 있어서 에너지 효율성을 증가시키는 것은 현재 매우 중요한 이슈이다. 에너지 효율은 기본적으로 열전도율이 낮은 재료를 이용할 때 이루어질 수 있으며, 이를 위한 가장 좋은 방법은 재료 내부의 공극률을 상승시키는 것이다. 일반적으로 시멘트 복합체에 공극률을 상승시키기 위한 방법에는 발포제, 기포제 및 알루미늄 가루와 같은 반응성 분말을 활용하는 것인데 본 연구에서는 이들에 대한 대안으로 과산화수소를 이용하고자 하였다. 과산화수소 혼입 시멘트 모르타르를 제작하고 이의 부피 팽창, 단위용적중량, 압축강도 및 열전도율을 측정하였다. 실험 결과에 따르면 과산화수소의 혼입률이 증가할수록 공극률은 증가하고 이로 인해 압축강도 및 열전도율이 감소하는 것으로 나타났다. 따라서 과산화수소를 이용하여 경량기포 모르타르의 제작이 충분히 가능한 것으로 파악되었다.