• Corrosion Science and Technology
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• 제19권3호
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• pp.122-130
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• 2020

In this study, a corrosion failure analysis of a heat transport pipe was conducted, as the result of a pinhole leak. Interestingly, the corrosion damage occurred externally in the pipeline, resulting in severe thickness reduction near the seam line. Also, while a stable magnetite protective film formed on the inner surface, the manganese oxide formation occurred only on the outer surface. The interior and exterior of the pipe were composed of ferrite and pearlite. The large manganese sulfide and alumina inclusions were found near the seam line. In addition, the manganese sulfide inclusions resulted in grooving corrosion, which progressed in the seam line leading to the reduction in the thickness, followed by the exposure of the alumina in the matrix to the outer surface. To note, the corrosion was accelerated by pits generated from the boundaries separating the inclusions from the matrix, which resulted in pinhole leaks and water loss.

• Nuclear Engineering and Technology
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• 제43권6호
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• pp.557-566
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• 2011

A cold spray coating (CSC) of copper was studied for its application to a high-level radioactive waste (HLW) disposal canister. Several copper coatings of 10 mm thick were fabricated using two kinds of copper powders with different oxygen contents, and SS 304 and nodular cast iron were used as their base metal substrates. The fabricated CSC coppers showed a high tensile strength but were brittle in comparison with conventional non-coating copper, hereinafter defined to as "commercial copper". The corrosion behavior of CSC coppers was evaluated by comparison with commercial coppers, such as extruded and forged coppers. The polarization test results showed that the corrosion potential of the CSC coppers was closely related to its purity; low-purity (i.e., high oxygen content) copper exhibited a lower corrosion potential, and high-purity copper exhibited a relatively high corrosion potential. The corrosion rate converted from the measured corrosion current was not, however, dependent on its purity: CSC copper showed a little higher rate than that of commercial copper. Immersion tests in aqueous HCl solution showed that CSC coppers were more susceptible to corrosion, i.e., they had a higher corrosion rate. However, the difference was not significant between commercial copper and high-purity CSC copper. The decrease of corrosion was observed in a humid air test presumably due to the formation of a protective passive film. In conclusion, the results of this study indicate that CSC application of copper could be a useful option for fabricating a copper HLW disposal canister.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.480-480
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• 2010

In the present work, we studied effect of the deposition parameters on the structure and properties of ZnO films deposited by DC arc plasmatron. The varied parameters were gas flow rates, precursor composition, substrate temperature and post-deposition annealing temperature. Vapor of Zinc acetylacetone was used as source materials, oxygen was used as working gas and argon was used as the cathode protective gas and a transport gas for the vapor. The plasmatron power was varied in the range of 700-1,500 watts. Flow rate of the gases and substrate temperature rate were varied in the wide range to optimize the properties of the deposited coatings. After deposition films were annealed in the hydrogen atmosphere in the wide range of temperatures. Structure of coatings was investigated using XRD and SEM. Chemical composition was analyzed using x-ray photo-electron spectroscopy. Sheet conductivity was measured by 4-point probe method. Optical properties of the transparent ZnO-based coatings were studied by the spectroscopy. It was shown that deposition by a DC Arc plasmatron can be used for low-cost production of zinc oxide films with good optical and electrical properties. Sheet resistance of 4 Ohms cm was achieved after the deposition and 30 min annealing in the hydrogen at $350^{\circ}C$. Elevation of the substrate temperature during the deposition process up to $350^{\circ}C$ leads to decreasing of the film's resistance due to rearrangement of the crystalline structure.

• Journal of Radiation Protection and Research
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• 제44권3호
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• pp.110-117
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• 2019

Background: This study aimed to estimate occupational doses and patient peak skin doses (PSDs) during interventional radiology procedures. Materials and Methods: We examined data from brain embolization (n = 30), hepatic chemoembolization (n = 50), and uterine embolization (n = 12). The PSDs were measured using radiochromic film around the patient's head (group 1) or abdominal/pelvic region (group 2). Acquisition technical data and kerma-area products (KAP) were also recorded. Occupational doses were measured using $Instadose^{TM}$ dosimeters near the left eye region (LER), chest, and left ankle. Results and Discussion: The third quartile (median) KAP values were $408.1(235.3)Gy{\cdot}cm^2$ for group 1 and $584.4(449.4)Gy{\cdot}cm^2$ for group 2. The average PSDs were greatest during vascular procedures, reaching 1,004.4 (786.4) mGy, and the highest PSD was 2,352.6 mGy (during hepatic chemoembolization). The third quartile (median) occupational doses were 0.35 (0.21) mSv at the LER, 0.25 (0.15) mSv at the chest, and 1.47 (0.64) mSv at the left ankle. Occupational doses at the LER were higher than at the chest, which highlights the importance of protective glasses and suspended shields. The occupational doses at the ankle region were also high, which highlights the importance of using a lead-lined curtain attached to the table. Conclusion: The results indicate that physicians can reach, for eye region, the weekly occupational dose limit after around 15 procedures, even when using proper protection. The average PSD values were below the threshold for tissue reactions, although the complexity of these procedures emphasises the importance of considering related risks.

• 한국재료학회지
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• 제29권1호
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• pp.11-15
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• 2019

Severe wall thinning is found on the tube of a low-pressure evaporator(LPEVA) module that is used for a heat recovery steam generator(HRSG) of a district heating system. Since wall thinning can lead to sudden failure or accidents that lead to shutdown of the operation, it is very important to investigate the main mechanism of the wall thinning. In this study, corrosion analysis associated with a typical flow-accelerated corrosion(FAC) is performed using the corroded tube connected to an upper header of the LPEVA. To investigate factors triggering the FAC, the morphology, composition, and phase of the corroded product of the tube are examined using optical microscopy, scanning electron microscopy combined with energy dispersive spectroscopy, and x-ray diffraction. The results show that the thinnest part of the tube is in the region where gas directly contacts, revealing the typical orange peel type of morphology frequently found in the FAC. The discovery of oxide scales containing phosphate indicates that phosphate corrosion is the main mechanism that weakens the stability of the protective magnetite film and the FAC accelerates the corrosion by generating the orange peel type of morphology.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.213-226
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• 2022

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl^- and OH^-) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.237-253
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• 2022

The methyl 2-(1,3-dithietan -2- ylidene)-3-oxobutanoate (MDYO) and 2-(1,3-dithietan-2-ylidene) cyclohexane -1,3-dione (DYCD) were synthesized and tested at various concentrations as corrosion inhibitors for 316L stainless steel in 1 M HCl using weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), surface analysis techniques (SEM / EDX and Raman spectroscopy) and Functional Density Theory (DFT) was also used to calculate quantum parameters. The obtained results indicated that the inhibition efficiency of MDYO and DYCD increases with their concentration, and the highest value of corrosion inhibition efficiency was determined in the range of concentrations investigated (0.01 × 10^-3 - 10^-3 M). Polarization curves (Tafel extrapolation) showed that both compounds act as mixed-type inhibitors in 1M HCl solutions. Electrochemical impedance spectra (Nyquist plots) are characterized by a capacitive loop observed at high frequencies, and another small inductive loop near low frequencies. The thermodynamic data of adsorption of the two compounds on the stainless steel surface and the activation energies were determined and then discussed. Analysis of experimental results shows that MDYO and DYCD inhibitors adsorb to the metal surface according to the Langmuir model and the mechanism of adsorption of both inhibitors involves physisorption. SEM-EDX results confirm the existence of an inhibitor protective film on the stainless steel surface. The results derived from theoretical calculations supported the experimental observation.

• Computers and Concrete
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• 제32권2호
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• pp.119-138
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• 2023

Concrete carbonation is a prevalent phenomenon that leads to steel reinforcement corrosion in reinforced concrete (RC) structures, thereby decreasing their service life as well as durability. The process of carbonation results in a lower pH level of concrete, resulting in an acidic environment with a pH value below 12. This acidic environment initiates and accelerates the corrosion of steel reinforcement in concrete, rendering it more susceptible to damage and ultimately weakening the overall structural integrity of the RC system. Lower pH values might cause damage to the protective coating of steel, also known as the passive film, thus speeding up the process of corrosion. It is essential to estimate the carbonation factor to reduce the deterioration in concrete structures. A lot of work has gone into developing a carbonation model that is precise and efficient that takes both internal and external factors into account. This study presents an ML-based adaptive-neuro fuzzy inference system (ANFIS) approach to predict the carbonation depth of fly ash (FA)-based concrete structures. Cement content, FA, water-cement ratio, relative humidity, duration, and CO2 level have been used as input parameters to develop the ANFIS model. Six performance indices have been used for finding the accuracy of the developed model and two analytical models. The outcome of the ANFIS model has also been compared with the other models used in this study. The prediction results show that the ANFIS model outperforms analytical models with R-value, MAE, RMSE, and Nash-Sutcliffe efficiency index values of 0.9951, 0.7255 mm, 1.2346 mm, and 0.9957, respectively. Surface plots and sensitivity analysis have also been performed to identify the repercussion of individual features on the carbonation depth of FA-based concrete structures. The developed ANFIS-based model is simple, easy to use, and cost-effective with good accuracy as compared to existing models.

• 치위생과학회지
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• 제5권2호
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• pp.83-88
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• 2005

구강진료기관에서 이용되는 방사선은 노출량이 극히 미량이라고 알려져 있지만, 장기간 방사선을 취급하는 경우에는 위해 작용이 나타날 수 있으므로 이에 대한 방사선 종사자의 인식 변화가 필요하다고 볼 수 있다. 따라서, 본 연구에서는 치과위생사를 대상으로 치과방사선 촬영실의 방사선 안전관리 실태 및 촬영업무 실태를 조사하여 치과위생사 뿐만 아니라 일반 이용자들의 방사선에 의한 건강장해를 예방하기 위한 방어계획 수립과 치과위생사의 방사선 안전에 대한 보건교육 프로그램을 설계함에 도움이 되는 시사점을 도출하고자 각 지역의 치과병원 및 치과의원에 근무하는 치과위생사를 대상으로 2003년 12월부터 2004년 3월까지 약 4개월 동안 조사하여 다음과 같은 결과를 얻었다. 1. 구내 방사선 촬영 실태를 살펴본 결과, 표준필름의 촬영은 1일 기준으로 1~5장이 47.5%로 가장 많았고, 디지털 촬영은 촬영하지 않는 경우가 69.8%로 가장 많았으며, 교익필름의 촬영은 1주일 기준으로 촬영하지 않는 경우가 67.7%로 가장 많았고, 교합필름의 촬영은 촬영하지 않는 경우가 95.0%로 대부분을 차지하였으며, 소아필름의 촬영은 1장이 47.1%로 가장 많았다. 2. 구외 방사선 촬영 실태를 살펴본 결과, panorama 촬영은 1~5장이 63.7%로 절반 이상을 차지하였고, 촬영을 하지 않는 경우도 20.9%로 나타났다. cephalo 촬영은 촬영하지 않는 경우가 72.3%로 가장 많았고, 다음으로 1~5장이 20.1%로 나타났다. 3. 방사선 안전관리에 대한 교육 실태를 살펴본 결과, 총 278명 중 안전관리 교육을 받은 경우는 18.7%에 불과했고, 또한 교육을 받았을 경우 방사선 안전교육 횟수는 1회가 94.2%로 대부분을 차지하였으며, 안전관리 교육형태로는 보수교육이 63.5%로 가장 많았다. 일반적 특성에 따른 방사선 안전관리에 대한 교육 경험을 살펴보면 연령에 따라(p<0.01), 근무경력에 따라(p<0.001), 결혼 여부에 따라(p<0.01) 통계적으로도 유의한 차이를 보였다. 4. 방사선 피폭에 대한 방어시설의 인식 수준은 보통이라고 인식한 경우가 40.6%로 가장 많았으며, 배치된 방어용구로는 납 에이프런이 71.1%로 가장 많았다.

• 생명과학회지
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• 제24권6호
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• pp.595-602
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• 2014

미더덕껍질(Styela clava tunic, SCT)은 항염증 복합체, 창상필름, 골재생 유도 등을 포함한 다양한 의학적인 치료영역에 이용 되고 있다. 본 연구에서는 미더덕껍질 열수추출물(aqueous extract of Styela clava tunic, AE-SCT)의 $H_2O_2$에 의해 유발된 세포사멸의 보호 효과를 알아보기 위하여 세포 활성도의 변화에 관련된 요인을 측정하였다. 그 결과, AE-SCT는 3.3 mg/g의 플라보노이드와 32.3 mg/g의 페놀화합물을 포함하고 있었으며, HepG2 세포주에 독성을 유발하지 않았다. 또한, $H_2O_2$ 처리 후 AE-SCT를 처리하는 실험에서 AE-SCT는 $H_2O_2$에 의해 유발된 세포사멸을 개선하는 효과를 나타내지 않았다. 그러나, $H_2O_2$ 처리전에 AE-SCT를 사전 처리하는 예방효과 실험에서, 세포생존율은 $H_2O_2$만 처리한 그룹에 비하여 AE-SCT를 처리한 그룹에서 유의적으로 증가하였으며, 특히 AE-SCT를 $50{\mu}g/ml$ 처리한 농도에서 가장 높았다. 또한, FACS분석과 DAPI 염색에서도 사멸 세포의 수는 $H_2O_2$만 처리한 그룹에 비하여 AE-SCT를 처리한 그룹에서 유의적으로 감소하였다. 더불어, $H_2O_2$의 처리에 의해 유도된 Bax/Bcl-2 발현비율은 AE-SCT처리에 의해 농도의존적으로 감소되었다. 이러한 연구 결과는 AE-SCT가 $H_2O_2$에 의해 유발된 세포사멸을 예방하는 우수한 효과를 가지고 있음을 제시하고 있어 향후 다양한 항산화 제품 개발을 위한 기초자료로 사용될 수 있을 것으로 사료된다.