• 한국추진공학회지
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• 제24권4호
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• pp.41-47
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• 2020

본 연구에서는 염소가스 등 유해가스의 발생을 줄이고 질소가스 방출을 증가시키는 친환경 추진제 조성개발을 목표로 한다. 이에 고체 추진제에 일반적으로 사용되는 AP(Ammonium Perchlorate)와 Al(Aluminium)를 대신하여 저탄소 고질소 물질인 GUDN(N-Guanylurea dinitramide)과 BTATz(3,6-bis(1H-1,2,3,4-tetrazol-5-ylamino)-1,2,4,5-tetrazine)를 사용하였다. 제조된 추진제는 기계적 및 연소 특성, 성능 그리고 AGARD 연기등급을 분석하였다. AP/Al 추진제에 비해 GUDN/BTATz추진제는 기계적 성질과 연소 속도가 감소하는 경향을 나타내었다. 또한, 4인치표준모타 제작 후 지상연소 시험 결과 GUDN/BTATz추진제 연소 시 성능은 감소하였으나, 염소가스 등의 유해 가스를 줄여 2차 연기 등급도 개선됨을 확인할 수 있었다.

• 방사성폐기물학회지
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• 제20권4호
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• pp.489-500
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• 2022

The decommissioning of nuclear facilities produces various types of radiologically contaminated waste. In addition, dismantlement activities, including cutting, packing, and clean-up at the facility site, result in secondary radioactive waste such as filters, resin, plastic, and clothing. Determining of the radionuclide content of this waste is an important step for the determination of a suitable management strategy including classification and disposal. In this work, we radiochemically characterized the radionuclide activities of filters used during the decommissioning of Korea Research Reactors (KRRs) 1 and 2. The results indicate that the filter samples contained mainly ³H (500-3,600 Bq·g^-1), ¹⁴C (7.5-29 Bq·g^-1), ⁵⁵Fe (1.1- 7.1 Bq·g^-1), ⁵⁹Ni (0.60-1.0 Bq·g^-1), ⁶⁰Co (0.74-70 Bq·g^-1), ⁶³Ni (0.60-94 Bq·g^-1), ⁹⁰Sr (0.25-5.0 Bq·g^-1), ¹³⁷Cs (0.64-8.7 Bq·g^-1), and ¹⁵²Eu (0.19-2.9) Bq·g^-1. In addition, the gross alpha radioactivity of the samples was measured to be between 0.32-1.1 Bq·g^-1. The radionuclide concentrations were below the concentration limit stated in the low- and intermediatelevel waste acceptance criteria of the Nuclear Safety and Security Commission, and used for the disposal of the KRRs waste drums to a repository site.

• 한국산업융합학회 논문집
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• 제26권2_2호
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• pp.333-340
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• 2023

Environmental regulations are being strengthened worldwide to solve global warming. For this reason, interest in eco-friendly gas fuels such as LNG and hydrogen is continuously increasing. However, when adopting eco-friendly gas fuel, liquefying at a cryogenic temperature is essential to ensure economic feasibility in storage and transportation. Although austenitic stainless steel is typically applied to store cryogenic liquefied gas, structural steel can experience sudden heat shrinkage in the case of leakage in the loading and unloading process of LNG. In severe cases, the phase of the steel may change, so care is required. This study conducted Charpy impact tests on steel material in nine different temperature ranges, from room to cryogenic temperatures, to analyze the effects of cryogenic liquefied gas leaks. As a result of the study, it was not easy to find variations in ductile to brittle transition temperature (DBTT) due to the leakage of cryogenic liquefied gas. Still, the overall impact toughness tended to decrease, and these results were verified through fracture surface analysis. In summary, brittle fracture of the steel plate may occur when a secondary load is applied to steel for hull structural use exposed to a cryogenic environment of -40 ℃ or lower. Therefore, it needs to be considered in the ship design and operating conditions.

• 반도체디스플레이기술학회지
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• 제22권4호
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• pp.32-37
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• 2023

For the potential applications in large-area OLED lightings, hydrogen fuel cells, and secondary batteries, we have performed an intermittent coating of high-viscosity polydimethylsiloxane using roll-to-roll slot die coater. During intermittent coating, dead zones inevitably appear where the thickness of PDMS patch films becomes non-uniform, especially at the leading/trailing edge. To reduce it, we have coated the PDMS patches by varying the process parameters such as the installation angle of the slot die head, coating speed, and patch interval. It is observed that the PDMS solution flows down and thus the thickness profile is non-uniform for horizonal intermittent coating, whereas the PDMS solution remaining on the head lip causes an increase in the PDMS thickness at the leading/trailing edges for vertical intermittent coating when the coating velocity is low. As the coating speed increases, however, the dead zone is shown to be reduced. It is addressed that the overall dead zone (the dead zone at the leading edge + the dead zone at the trailing edge) is smaller with horizontal intermittent coating than with vertical intermittent coating.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.252.2-252.2
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• 2010

Biomass is considered to be a major potential fuel and renewable resource for the future. In fact, there is high potential to produce the large amount of energy from biomass around the world. In this study, to obtain basic data for practical application of wood pellet and wood pellet boiler system as heating system in agriculture, agricultural biomass resources were surveyed, pellet was made of agricultural by-product such as stem of rape, oat and rice, ricehusk and sawdust and wood pellet boiler system with capacity of 116 kW was manufactured and installed in greenhouse of $38.5m{\times}32m$. High heating value, bulk density and ash content of pellet made of agricultural by-product and efficiency and heating performance of this system was estimated. Rice straw was the largest agricultural biomass in 2005 and the total amount of rice straw converted into energy of $131.71{\times}10^{11}$ kJ. And in 2005, total amount of forest' by-product converted into energy of $29,277.05{\times}10^{11}$ kJ. High heating values of pellets made of agricultural by-products of stem and seed of rape, stem of oat, rice straw and rice husk were 16,034, 16,026, 16,089, 15,650, 15,044 kJ/kg respectively. High heating values of pellets made of agricultural by-products were 83.6% compared to that of wood pellet. Average bulk density of pellets made of agricultural by-products of stem and seed of rape, stem of oat, rice straw and rice husk was 1,400 $kg/m^3$. Ash contents of the pellets were 6.6, 7.0, 6.2, 5.5, 33% respectively. Ash content of rice husk pellet was the largest compared to other kind of pellets. To increase efficiency of agricultural pellet boiler, the boiler adopted secondary heat exchanger. The agricultural pellet boiler designed and manufactured in this study had high efficiency of 84.2% compared to the conventional agricultural pellet boiler, when water flow rate, exhaust gas temperature and average combustion furnace temperature were 39L/min, $180^{\circ}C$, $680^{\circ}C$ respectively. And pellet supplying and pausing time were 13, 43 seconds respectively. In March of 2010, prices of wood pellet, agricultural tax free diesel, diesel, kerosene were 350 won/kg, 811 won/L, 1,422 won/L, 976 Won/L respectively. Also in terms of energy, prices per same heating value were 77.8, 90.1, 158, 108.4 Won/Mcal. Energy saving rate of wood pellet was 16, 50, 39% compared to agricultural tax free diesel, diesel and kerosene respectively.

• 방사성폐기물학회지
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• 제13권3호
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• pp.171-180
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• 2015

본 연구는 고방사성해수폐액에 함유되어 있는 주요 고방사성 핵종인 Cs을 제거하기 위하여 IE911 (crystalline silicotitanate)에 의한 흡착 제거를 수행하였다. Cs의 효율적 흡착제거 및 2차 고체폐기물의 발생량을 최소화하기 위하여 IE911-Cs 흡착은 m/V (흡착제 질량/용액 부피) 비=2.5 g/L, 흡착시간은 1 시간 정도가 효과적이었다. 이때 Cs은 약 99%, Sr은 5% 이하가 각각 흡착되었다. 또한 IE911-Cs 흡착은 Langmuir 등온식 및 유사 (pseudo) 2차 속도 식으로 표현할 수 있으며, 흡착속도상수(k₂)는 Cs의 초기농도 및 입자크기 증가에 따라 감소하는데 반하여, m/V 비, 온도 및 교반속도 증가에 따라서는 증가하고 있다. IE911-Cs 흡착의 활성화에너지는 약 79.9 kJ/mol 로, IE911-Cs 흡착이 보다 강력한 결합 형태를 이룬 화학적 흡착임을 보여주고 있다. 그리고 음수 값의 Gibbs 자유에너지 및 엔탈피는 IE911-Cs의 흡착반응이 정반응의 발열반응이고, 저온에서 반응이 상대적으로 활발함을 의미하며, 음수 값의 엔트로피는 흡착된 Cs이 IE911에 균일하게 정렬되어 있음을 나타낸다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.663-666
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• 2005

Gas hydrates are ice-like compounds that form at the low temperature and high pressure conditions common in shallow marine sediments at water depths greater than 300-500 m when concentrations of methane and other hydrocarbon gases exceed saturation. Estimates of the total mass of methane carbon that resides in this reservoir vary widely. While there is general agreement that gas hydrate is a significant component of the global near-surface carbon budget, there is considerable controversy about whether it has the potential to be a major source of fossil fuel in the future and whether periods of global climate change in the past can be attributed to destabilization of this reservoir. Also essentially unknown is the interaction between gas hydrate and the subsurface biosphere. ODP Leg 204 was designed to address these questions by determining the distribution, amount and rate of formation of gas hydrate within an accretionary ridge and adjacent basin and the sources of gas for forming hydrate. Additional objectives included identification of geologic proxies for past gas hydrate occurrence and calibration of remote sensing techniques to quantify the in situ amount of gas hydrate that can be used to improve estimates where no boreholes exist. Leg 204 also provided an opportunity to test several new techniques for sampling, preserving and measuring gas hydrates. During ODP Leg 204, nine sites were drilled and cored on southern Hydrate Ridge, a topographic high in the accretionary complex of the Cascadia subduction zone, located approximately 80km west of Newport, Oregon. Previous studies of southern Hydrate Ridge had documented the presence of seafloor gas vents, outcrops of massive gas hydrate, and a pinnacle' of authigenic carbonate near the summit. Deep-towed sidescan data show an approximately $300\times500m$ area of relatively high acoustic backscatter that indicates the extent of seafloor venting. Elsewhere on southern Hydrate Ridge, the seafloor is covered with low reflectivity sediment, but the presence of a regional bottom-simulating seismic reflection (BSR) suggests that gas hydrate is widespread. The sites that were drilled and cored during ODP Leg 204 can be grouped into three end-member environments basedon the seismic data. Sites 1244 through 1247 characterize the flanks of southern Hydrate Ridge. Sites 1248-1250 characterize the summit in the region of active seafloor venting. Sites 1251 and 1252 characterize the slope basin east of Hydrate Ridge, which is a region of rapid sedimentation, in contrast to the erosional environment of Hydrate Ridge. Site 1252 was located on the flank of a secondary anticline and is the only site where no BSR is observed.

• 한국산학기술학회논문지
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• 제19권3호
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• pp.52-60
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• 2018

최근 자동차 산업에서는 연비향상 및 안전규제 강화에 따라 차량 경량화가 필수적으로 요구됨에 따라 DP강(Dual Phase steel), CP강(Complex Phase steel), MS강(Martensitic Steel), TRIP강(Transformation Induced Plasticity steel), TWIP강(Twinning Induced Plasticity steel) 등과 같은 인장강도 700MPa 이상인 초고장력강(Ultra High Strength Steel)의 적용이 증가하고 있다. 초고장력강을 차체에 적용하기 위해서는 용접공정이 필수적이며, 원가 측면에서 유리한 전기저항점용접(Resistance Spot Welding, RSW)이 차체 용접에서 80%이상으로 가장 많이 적용되고 있다. 초고장력강은 강도향상을 위해 합금원소 함량을 늘이기 때문에 일반적으로 용접성이 열악한 것으로 알려져 있다. 이러한 초고장력강의 저항점용접의 경우 적정 용접조건 영역이 축소되고 용접부에서 계면파단 및 부분계면파단이 발생하는 것으로 보고되어 있어 결함 및 품질을 실시간으로 예측할 수 있는 용접품질 판정 연구가 활발히 진행되고 있다. 이에 따라 본 연구에서는 저항 점 용접을 수행할 때 검출되는 2차 회로 공정 변수를 이용하여 용접부의 동저항을 모니터링하고, 이 동저항 패턴에서 용접 품질 판단에 필요한 인자들을 추출하였다. 추출한 인자들을 상관분석하여 용접 품질과의 상관성을 파악하였으며, 상관성이 높은 인자들을 이용하여 회귀분석을 실시하였다. 이를 근거로 현장 적용이 가능한 회귀 모델을 제시하였다.

• 방사성폐기물학회지
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• 제11권1호
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• pp.1-9
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• 2013

파이로그린공정의 염폐기물처리과정에서 발생되는 주요 산화물 형태의 폐기물에는 희토류폐기물이 있으며 주요 구성 핵종은 Y, La, Ce, Pr, Nd, Sm, Eu, Gd 등 8종이다. 최종적인 희토류폐기물의 형태는 산화물 형태로 발생된다. 본 연구에서는 붕규산 유리계 내에서 희토류 산화물의 유리화 타당성을 평가 하기 위하여 6종의 유리조성을 개발하였다. 희토류 8핵종 혼합에 대한 solubility는 $1,200^{\circ}C$에서 25wt% 미만, $1,300^{\circ}C$에서 30wt% 미만 waste loading으로 온도 상승에 따라 증가하는 것으로 나타났으며 liquidus temperature는 균질한 유리가 형성된 20wt% waste loading에서 $950^{\circ}C$ 이하로 평가되었다. 희토류 산화물의 유리매질 내 solubility 이상에서는 희토류-oxide-silicate 결정이 생성된 유리세라믹을 이차상으로 형성하였으며 20~25wt% waste loading의 표면균질성이 양호한 유리는 용융온도 $1,200{\sim}1,300^{\circ}C$ 범위에서 점도 100 poise 이하, 전기전도도 1 S/cm 이상으로 유도가열식 저온용융로설비에서의 운전 용이성이 매우 양호한 것으로 평가되었다. 개발된 유리조성에 대한 기타 물리 화학적 특성 평가를 위한 실험들이 향후 수행될 예정이다.

• 자원리싸이클링
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• 제23권2호
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• pp.3-16
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• 2014

탄산가스 삭감과 자동차 연비를 향상시키기 위한 자동차의 경량화는 현시대적 큰 과제이다. 경량화를 위하여 Hybrid Electrical Vehicle(HEV), Electrical Vehicle(EV)의 고성능 모터용 Nd 자석, Li이온 2차전지 및 배기가스 정화용 PGM촉매의 성능개발이 활성화 되고 있다. 우리나라는 자동차 경량화와 기능 향상을 위하여 사용하는 희소금속을 자원이 편재되어 있는 중국 등에서 수입하기 때문에 수출국의 공급 조절, 가격 폭등 등으로 수급이 불안정한 경우가 있다. 이를 대비하여 차세대 자동차에서 배출되는 폐 희소자원을 리싸이클링 할 필요가 있다. 본고는 리싸이클링 기술과 현상에 대하여 조사 분석한 정보를 기술자나 연구자에게 전해주어 국가 자동차 산업 발전에 기여하는데 목적이 있다. 조사 결과, 폐 자동차에서 배출되는 고성능 모터, 배기가스 정화용 백금족금속(PGM) 폐촉매, Li이온 배터리 등의 리싸이클링기술은 전처리 기술과 후처리 기술로 분류하는데, 전처리 기술인 기계적 분리 선별 기술은 연구 개발 중이며, 후처리기술인 습, 건식 제련 기술은 확립되어 있다. 리싸이클링 경제성 측면에서 폐 부품의 기계적 선별 기술에 대하여 집중적으로 연구할 필요가 있다.