• Tribology and Lubricants
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• 제40권3호
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• pp.97-102
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• 2024

The next-generation Molten Salt Reactor is known for its high safety because it uses nuclear fuel dissolved in high-temperature molten salt, unlike traditional solid atomic fuel methods. However, the high-temperature molten salt causes severe corrosion in internal structural materials, threatening the reactor's safety. Therefore, it is crucial to investigate the high-temperature corrosion resistance and wear performance of materials used in reactors to ensure safety. In this study, the high-temperature corrosion resistances and wear performances of corrosion samples in a NaCl-MgCl2-KCl (20-40-40 [wt%]) molten salt are investigated to evaluate the applicability of economically viable stainless steels, 316SS and 304SS. Hastelloy C276 and a new alloy containing a small amount of Nb are used as reference samples for comparative analysis. The mass loss, mass loss rate per unit volume, and surface roughness of each sample are measured to understand the corrosion mechanisms. Scanning electron microscopy and energy-dispersive spectroscopy analyses are employed to analyze the corrosion mechanisms. Wear tests on the corroded samples are also conducted to assess the extent of corrosion. Based on the experimental results, we predict the lifespans of the materials and evaluate their suitability as candidate materials for molten salt reactors. The data obtained from the experiments provide a valuable database for structural materials that can enhance the stability of molten salt reactors and recommend high-temperature corrosion-resistant materials suitable for next-generation reactors.

• 한국임상수의학회지
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• 제10권2호
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• pp.227-235
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• 1993

The effectiveness of sodium carboxymethylcellulose(SCMC) and dextran 70 in the prevention of adhesion formation in abdominal cavity of rabbits following artificial injuries was elucidated and the effects -of these medicines on blood pictures were also examined. After abrasion treatment on jejunum in gonadotropins primed rabbits, 1, 2 and 3% of SCMC solutions, 6 and 10% dextran 70 solutions and a synthetic solution of 1% SCMC and loft dextran 70 in 0.9% saline solution were infused into the abdominal cavity. Four weeks later the abdominal cavities were reopened under general anesthesia. The synthetic solution showed the highest adhesion reduction rate(100%), while 1% SCMC, 6 and loft dextran solutions showed no significantly evident effect of adhesion prevention. The SCMC solutions showed better adhesion reduction effect than dextran 70 solutions. After infusion of these adhesion preventive medicines, the changes of total leucocytes, erythrocytes, lymphocytes, PCV, plasma fibrinogen and protein contents were examined. No remarkable difference in blood pictures was shown between the synthetic solution and the other medicines. Therefore, it can be suggested that the synthetic solution of 1% SCMC and 10% dextran 70 in 0.9% saline solution at dose of 5$m\ell$/kg of body weight is prominently effective in the prevention of postoperative adhesion formation and wolf be safe in animals and human.

• Tribology and Lubricants
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• 제32권2호
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• pp.50-55
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• 2016

Recently, a double-side machining process has been adopted in fabricating a sapphire glass to enhance the manufacturability. Double-side lap grinding (DLG) is one of the emerging processes that can reduce process steps in the fabrication of sapphire glasses. The DLG process uses two-body abrasion with fixed abrasives including pallet. This process is designed to have a low pressure and high rotational speed in order to obtain the required material removal rate. Thus, the temperature is distributed on the DLG platen during the process. This distribution affects the shape of the substrate after the DLG process. The coolant that is supplied into the cooling channel carved in the base platen can help to control the temperature distribution of the DLG platen. This paper presents the results of computational fluid dynamics with regard to the heat transfer in a DLG platen, which can be used for fabricating a sapphire glass. The simulation conditions were 200 rpm of rotational speed, 50℃ of frictional temperature on the pallet, and 20℃ of coolant temperature. The five cases of the coolant flow rate (20~36 l/min) were simulated with a tetrahedral mesh and prism mesh. The simulation results show that the capacity of the generated cooling system can be used for newly developed DLG machines. Moreover, the simulation results may provide a process parameter influencing the uniformity of the sapphire glass in the DLG process.

• Tribology and Lubricants
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• 제31권2호
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• pp.50-55
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• 2015

This study investigates the effects of a pattern of 200 μm dimples in a hexagonal array on tribological characteristics. A textured surface might reduce the friction coefficient and wear caused by third-body abrasion and thus improve the tribological performance. There are three friction conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction conditions. In this experiment, we investigate the friction characteristics by carrying out the friction tests at sliding speeds ranging from 0.06 to 0.34 m/s and normal load ranging from 10 to 100 N. We create dimple surfaces for texturing by using the photolithography method. There are three kinds of specimens with different dimple densities ranging from 10% to 30%. The dimple density on the surface area is the one of the important factors affecting friction characteristics. Friction coefficient generally decreases with an increase in the velocity and load, indicating that the lubrication regime changes depending on the load and velocity. The fluid friction regime is fully developed, as indicated by the duty number graph. Fluid friction occurs at a velocity of 0.14-0.26 m/s. The best performance is seen at 10% dimple density and 200 μm dimple circle in the hexagonal array.

• 한국문화재보존과학회:학술대회논문집
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• 한국문화재보존과학회 2004년도 제20회 발표논문집
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• pp.92-100
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• 2004

The host rocks of brick-shaped stone pagoda in the Bunhwangsa temple are lots of kinds andesitic rocks, which has gone through mechanical and chemical weathering. As the overall observation, the pagoda is serious damages by air pollutants, and the northeast parts show the much advanced state of turning white, while the southeast parts are heavily cracked in the materials. The rocks of brick-shaped pagoda body are in a relatively stable condition of weathering and damage except for the abrasion and cracks of the corners. The rocks of the pagoda roof suffer from more symptoms including multiple peel-offs, exfoliation, cracks forming round lines, and falling off stone pieces. The pagoda roof rocks are dominated by the thriving leafy lichens and mosses, especially, there are higher plants (selaginella involvens, dandelions) taking root actively between the brick stones and content mortar. There are even light gray precipitates like stalactites between the rocks of the body, In particular, the 1st and 2nd floor in the east side and the body parts in the north side are the most serious. Their major minerals are calcite, gypsum and clay minerals. The rocks of the stylobate and the tabernacle in all the four directions are composed mainly of granitic rocks. The materials consisting of the tabernacles show the severe splits and distortion, which causes the structural instability. The stylobate rocks are heavily contaminated by some weeds with the often marks of inorganic contamination by secondary hydroxides. The central part of the east stylobate has been sinking, while that of the 1st floor west stylobate is protruded nesting a line of cracks. Accordingly, the inside of the tabernacle is always humid with the constant introduction of rainwater. The stone lion standing in the southeast and northeast side are alkali granite, while that in the southwest and northwest lithic tuff. Each of the stone lion also coated with various colored lichens, mosses, algae, bacteria and bryophyte. The external materials of the pagoda have deteriorated the functions of the rocks and made the loss, falling off, and biological contamination even worse due to the surface weathering. Thus it's urgent to come up with scientific restoration and conservation measures through clinical tests.

• 자원환경지질
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• 제35권4호
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• pp.347-353
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• 2002

현재 우리 나라에서 조리용구로 많이 사용되고 있는 석재에는 휘석암과 각력암, 흑운모섬록암 등이 있으며, 이중 유색광물이 상대적으로 많은 휘석암과 흑운모섬록암은 비중이 3.0으로 각력암(2.5)보다 약간 더 무거운 특징을 보였고, 흡수율은 각력암이 2.9%로 가장 높았으며, pH는 모두 9.7-9.9의 범위로 약알칼리성을 나타내었다. 또한 조리용구용 석재중 흑운모섬록암이 각력암이나 휘석암보다 마모에 대한 내구성과 강도가 가장 우수하석 다른 특별한 요인이 없는 한 가장 오랫동안 사용할 수 있음을 나타내었다. 용출시험 결과, Cu, Pb, Co, Cr Ni 등의 유독성 중금속 원소들은 연구대상 암석에서 모두 반응시간 및 용액의 초기 pH에 관계없이 모두 측정 한계값인 0.1 ppm 이하로 낮았으나, 철(Fe)은 암석의 종류 및 용출 조건에 따라 다소간의 용출량 차이를 보였는데, 대체로 중성보다는 산성용액을 첨가하였을 경우에 약 1.8-31배 정도 더 높은 용출량을 나타내었고, 반응용액이 중성인 조건에서는 각력암에서, 산성인 경우에는 흑운모섬록암에서 가장 높은 철(Fe)의 용출량을 보여 주었다. 석재를 인체에 해가 없는 고기능성 조리용구로 이용하기 위해서는 인체에 영향을 미칠 수 있는 중금속 및 다량 무기질 원소들에 대한 용출함량 기준이 먼저 마련되어야 하며, 또한 보다 많은 종류의 조리용구용 석재와 화학원소들을 대상으로 좀 더 체계적인 무기화학적 특성에 하한 연구가 필요할 것으로 생각한다.

• 접착 및 계면
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• 제24권4호
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• pp.124-130
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• 2023

외부 온도 변화에 따른 특성변화가 적어야 하는 자동차 부품용 코팅제는 외부 환경 변화에 의한 노이즈 특성 변화가 매우 중요하다. 이에 내한성, 내후성, 내마모성이 우수한 연질의 폴리우레탄과 하이드록시 말단 혹은 곁사슬이 아민으로 변성된 폴리실록산 등이 널리 사용되고 있다. 본 연구에서는 각각의 폴리머 성분들이 노이즈에 미치는 영향을 확인하기 위하여 수분산 폴리우레탄을 합성하였고, 폴리실록산, ultra high molecular polypropylene (UHMWPP) 분말, 카본블랙, 소광제를 첨가하여 코팅제를 제조하였다. 수분산 폴리우레탄의 hard/soft 세그먼트의 함량을 27.1%/72.9%, 아민으로 변성된 폴리실록산과 하이드록시 말단 폴리실록산이 2:7의 비율에서 노이즈의 발생이 가장 적었으며, 마찰자가 고속에서 움직일 때 마찰계수의 차이가 컸다. 또한 SiO₂를 UHMWPP 분말로 대체함으로써, 노이즈가 감소하였으며 광택도 또한 감소하였다.

• 지역사회간호학회지
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• 제12권3호
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• pp.815-827
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• 2001

Accidents involving students are an important cause of death and disability. They also have enormous financial implications. In order to prevent childhood accidents. research and education for safety should be strengthened. The purpose of this study was to determine how often lower grade elementary students have accidents and what factors affect the accident rate. The study population consisted of 676 students who were in the 2nd, 3rd and 4th grades of twelve elementary schools located in Kun Wi Gun. The questionnaires were distributed to all of the 2nd to 4th grade student in the Kun Wi Gun to be completed by their parents about all the accidents which happened last one year and collected during the period of March 19, to March 30, 2001. The data were analyzed by using SPSS WIN 10.0 statistical package. The results of the study are as follow: 1. Among 676 students. 270 students had 540 accidental injuries during the study period. 2. The month, the day and the time with the highest accident rate were April. Monday. and between 1 and 4 p. m. each. 3. In the analysis of the location where the injury took place, the most frequent place was on school, around their homes and. then inside the home. 4. Most of accidents were caused by carelessness on the part of the students and the most frequent type of injury was an abrasion. 5. Students most injured part of the body was their legs. 6. They were treated at home most often and usually emergency treatment was performed by family members with disinfectant as first aid measure. Cost of the treatment of the accident ranged from 10.000 to 30,000 won in most cases. 7. Students' personality. type of family composition. mother's age and parents' education level were statistically significant. As a conclusion. 1st to 3rd grade rural elementary students need their assessment for accident involving condition. This study gave a very useful and important data to prepare accident prevention teaching program and to prepare accident prevention strategies.

• Journal of Trauma and Injury
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• 제24권2호
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• pp.61-67
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• 2011

Purpose: Lawn trimmers are widely used to cut the weeds around graves in South Korea, but they can cause ocular injury. We investigate at the emergency room the incidence and the clinical features of ocular trauma induced by lawn trimmers. Methods:The authors analyzed 106 patients who visited Konyang University Hospital's emergency room from March 1, 2007, to October 31, 2011, because of ocular trauma caused by a lawn trimmer. Patients were sorted into two groups, severe ocular injury and mild ocular injury. Results: Over a 5-year period, 106 patients with ocular trauma caused by a lawn trimmer underwent clinical study. Most of the patient (103 patients) were males, and the average age of the patients was $51.75{\pm}11.66$ years. The incidence of ocular trauma peaked in the sixth decade of life. Most injuries occurred between July and September. Severe ocular injury developed in 46.2% of all patients. As age increased, so did the severity of the ocular injury. The impacting object was a small stone in 43.4% of all patients. Nobody wore protective gear. The most common diagnosis were corneal abrasion, followed by intraocular foreign body, corneal laceration, and sclera laceration. Fifty-four patients were followed up, and thirty-six patients of them had severe injury. The most common complication was a traumatic cataract. Conclusion: Ocular trauma induced by a lawn trimmer is more severe than general ocular trauma. We suggest that everyone using a lawn trimmer should wear protective gear and follow safety guidelines.