• 한국기계가공학회지
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• 제19권3호
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• pp.42-50
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• 2020

This study explores the effects of repair width on the deposition characteristics and mechanical properties of stainless steel samples repaired using direct energy deposition (DED). In the DED repair process, defects such as pores and cracks can occur at the interface between the substrate and deposited material. In this study, we changed the width of the pre-machined zone for repair in order to prevent cracks from occurring at the inclined surface. As a result of the experiment, cracks of 10-40 ㎛ in length were formed along the inclined slope regardless of the repair width. Yield and tensile strength decreased slightly as the repair width increased, but the total and uniform elongation increased. This is due to the orientation of the crack. For specimens with a repair width of 20 mm, yield and tensile strength were 883 MPa and 1135 MPa, respectively. Total and uniform elongations were 14.3% and 8.2%, respectively. During observation of the fracture specimens, we noted that the fracture of the specimen with an 8 mm repair width occurred along the slope, whereas specimens with 14 mm and 20 mm repair depths fractured at the middle of the repaired region. In conclusion, we found that tensile properties were dependent upon the repair width and the inclination of the crack occurred at the interface.

• 대한금속재료학회지
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• 제50권11호
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• pp.847-854
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• 2012

Al-doped ZnO (AZO) thin films were grown on quartz substrates by the sol-gel method. The effects of the Al mole fraction on the structural and optical properties of the AZO thin films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-VIS spectroscopy. The particle size of the AZO thin films decreased with an increase in Al concentrations. The optical parameters, the optical band gap, absorption coefficient, refractive index, dispersion parameter, and optical conductivity, were studied in order to investigate the effects of Al concentration on the optical properties of AZO thin films. The dispersion energy, single-oscillator energy, average oscillator wavelength, average oscillator strength, and refractive index at an infinite wavelength of the AZO thin films were affected by the Al incorporation. The optical conductivity of the AZO thin films also increased with increasing photon energy.

• 한국분말재료학회지
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• 제29권5호
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• pp.390-398
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• 2022

Recently, considerable attention has been given to nickel-based superalloys used in additive manufacturing. However, additive manufacturing is limited by a slow build rate in obtaining optimal densities. In this study, optimal volumetric energy density (VED) was calculated using optimal process parameters of IN718 provided by additive manufacturing of laser powder-bed fusion. The laser power and scan speed were controlled using the same ratio to maintain the optimal VED and achieve a fast build rate. Cube samples were manufactured using seven process parameters, including an optimal process parameter. Analysis was conducted based on changes in density and melt-pool morphology. At a low laser power and scan speed, the energy applied to the powder bed was proportional to ${\frac{P}{\sqrt{V}}}$ and not ${\frac{P}{V}}$. At a high laser power and scan speed, a curved track was formed due to Plateau-Rayleigh instability. However, a wide melt-pool shape and continuous track were formed, which did not significantly affect the density. We were able to verify the validity of the VED formula and succeeded in achieving a 75% higher build rate than that of the optimal parameter, with a slight decrease in density and hardness.

• 한국수소및신에너지학회논문집
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• 제35권3호
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• pp.345-351
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• 2024

The unitized regenerative fuel cell (URFC) is a method that can reduce costs and increase system simplification by unitizing a fuel cell system and a water electrolysis system. The spray method is suitable as the membrane electrode assembly (MEA) manufacturing method for URFC because it is easy to control the amount of catalyst, the size of the system is small, and economical manufacturing is possible. In this study, a numerical analysis of the effect of solution concentration on the spray method was performed to use it as basic data for the spray method to be used in MEA manufacturing. As result, as the Nafion solution concentration decreases it was found that the spray speed and the mass flow rate and the discrete phase model concentration increases and the spray range widens.

• 한국건설관리학회논문집
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• 제17권3호
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• pp.52-60
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• 2016

본 연구에서는 LCA 모델을 이용하여 8개 초등학교 건축물의 생애주기 에너지사용량 및 이산화탄소 배출량을 평가 분석하였다. 이를 위하여, 자재생산, 자재운송, 시공, 운영, 해체 폐기단계를 포함하는 건축물 생애주기에서의 에너지사용량 및 이산화탄소 배출량을 평가할 수 있는 LCA 기반의 평가모델을 정의하고, 모델을 이용하여 사례 건축물을 평가하였다. 40년의 운영기간을 가정하여 평가한 결과, 내재에너지(즉, 자재생산, 자재운송, 시공단계 에너지사용량의 합), 운영에너지, 해체 폐기에너지는 평균적으로 2,279, 11,182, 228 Mcal/m2로 산출되었다. 각 단계별 평균 이산화탄소 배출량은 604, 2,708, 60 kg-CO2/m2로 산출되었다. 평가결과는 생애주기 에너지사용량 및 이산화탄소 배출량의 약 17%가 자재생산, 자재운송, 시공단계에서 발생한다는 사실을 보여준다. 따라서 건축물의 에너지사용량 및 이산화탄소 배출량 감축 목표를 달성하기 위해서는 내재에너지 및 이산화탄소 배출량이 반드시 고려되어야 할 것이다. 게다가, 운영에너지는 지역에 따라 확연하게 구분되는 반면, 내재에너지는 지역에 따른 차이가 없는 것으로 나타났다. 따라서 운영단계의 에너지 사용량 편차를 줄이기 위해서는 지역에 따라 보다 상세하게 구분된 단열 기준이 제시되어야 할 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.71-73
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• 2003

The paper discussed for energy saving technology of electric arc furnace (EAF) in steel making industry. The energy of EAF in steel making process is nearly 10% of total manufacturing cost. This paper is shown new trand of energy saving technology and future study analysis of technological evolution of the EAF by 2010 issued IISI.

• Journal of Pharmaceutical Investigation
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• 제33권2호
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• pp.145-149
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• 2003

Manufacturing facilities of the pharmaceuticals must meet certain level of the cleanness required so that foreign substances such as dust, moisture, heat, microorganism, or virus do not contaminate the product. In case of radiopharmaceuticals for medical treatment and diagnosis, not only should the operators and environment be protected from radiation but also need to be isolated from the foreign contaminant. Therefore, manufacturing facilities for radiopharmaceuticals must satisfy the design standards of both hot cell and clean room which are specified by GMP. However, standards of maintaining negative pressure for preventing spread of radioactive contaminant in isolated facilities conflict with the standards of maintaining positive pressure for keeping cleanness. To solve this problem, air pressure of hot cell was designed lower than in the adjacent area to meet standards of the radiation safety. To keep higher cleanness in certain part of the hot cell for filling, minimal relative positive pressure allows. In order to effectively maintain the cleanness that is required for production of Tc-99m generator, which takes 70% of whole demand of radiopharmaceuticals, the rooms placed in each side of production room are used as a buffer area and three lead hot cells are installed in production room. In this research, we established the appropriate engineered design concept for Tc-99m generator manufacturing facility, which satisfies both GMP cleanness standard for preventing particles, bacteria, other contaminants and the regulations of radiation safety for supervising and controlling the amount of radiation exposure and exhausted radioactivity. And the concept of multi-barrier buffer zones is introduced to apply negative air pressure for hot cell with first priority and to continue relative positive air pressure for clean room.

• 자원ㆍ환경경제연구
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• 제20권3호
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• pp.489-529
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• 2011

온실가스 저감정책이 시행되면 에너지 다소비 제조업은 비용 상승으로 인해 많은 영향을 받을 것이다. 그러나 가격설정력이 있는 산업이라면, 비용 상승을 제품 가격의 상승을 통해 소비자에게 전가시킬 것이므로 온실가스 저감정책으로 인한 피해가 적을 것이다. 따라서 본 연구는 에너지 다소비 제조업의 가격설정력을 분석함으로써, 각 산업이 온실가스 저감정책에 얼마나 취약한지 살펴보았다. 본 연구에서 사용한 가격설정력모형은 오차수정모형을 통하여 분석하였으며, 수입재의 가격과 인건비를 주요한 설명변수로 사용하였다. 수입재의 가격에 반응을 한다면 경쟁자의 가격에 따라 가격을 설정하는 가격 순응자로 볼 수 있으며, 이러한 산업은 온실가스 저감정책에 취약할 것이다. 반면에, 국내 비용을 의미하는 인건비에 영향을 받는다면, 가격설정력이 있다고 볼 수 있으며, 온실가스 저감정책에 덜 취약할 것이다. 또한, 에너지 가격의 변동은 우리나라 뿐만 아니라 해외에도 영향을 미치므로 수입재의 가격에 반영이 되어 있을 것이다. 따라서 수입재의 가격의 순영향을 보기 위해 에너지 가격을 통제변수로 사용하였다. 추정 결과, 석유제품, 화학제품, 비금속 광물제품, 섬유제품, 자동차 제조업은 가격설정력이 있는 것으로 분석되었으므로, 이들 산업은 온실가스 저감정책에 대해 경쟁력을 가지고 있다고 볼 수 있다.

• 한국기계가공학회지
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• 제13권4호
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• pp.7-12
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• 2014

A transparent poly methyl methacrylate (PMMA) optical micro-pyramid array-pattern is designed and fabricated using an injection modeling technique. The device's optical characteristics are tested and analyzed theoretically. In the optical pattern generated using the fabricated PMMA pattern, the components, due to not only refraction but also diffraction, are observed simultaneously. Wave optic modeling and analysis reveals that the energy ratio between the diffraction and refraction in the optical pattern are dependent on the critical dimension of the optical pattern such that the refraction and diffraction tend to be directly and inversely proportional to the pattern dimension, respectively.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.672-673
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• 2004