• Journal of Radiation Protection and Research
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• 제9권2호
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• pp.112-117
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• 1984

A lot of radioisotopes are applied to medical fields. It's very important to measure the activities on airborne radioiodine discharged in air from $Na^{131}I$ solutions and from patients treated with radioiodine. Also surface decontamination is another one important problem to be completly solved in the isotope laboratory where there is always the possibility of radiation contamination. The Authors measured the activities on airborne radioiodine with RI collector and scintillation counter. 1. The mean accumulative activity of airborne radioiodine discharged into air from $Na^{131}I$ solution was measured as $1.3{\times}10^{-3}/hr$ rate, and the maximum value was $1.8{\times}10^{-3}/hr$. 2. Radioactivity rate per hour of airborne iodine discharged into air from patients treated with $Na^{131}I$ was measured as $6.2{\times}10^{-5}/hr$ at 8 hour after administration of radioiodine and decreased into $2{\times}10^{-6}/hr$ after 24 hour. 3. Metalic surfaces such as stainless steel or aluminum are decontaminated 5 to 6 times more rapidly than wood and concrete surfaces. 4. Decontamination with wet wiping with detergent was 9 to 10 times more rapidly than dry wiping method, but dry wiping was useful for the first step to prevent spreading and flowing from liquid radioactive materials.

• 공학교육연구
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• 제22권5호
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• pp.49-55
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• 2019

Folded structure is widely applied in various engineering fields. Many of the Japanese folding fans in the Edo era (1603-1868) have been successfully blended with the processing technology of "natural materials" that is the origin of Japan's "Monodzukuri" (craftsmanship) and its application "artistic originality". The charm of a fan lies in the diversity of stereoscopic expression not born in plane representation. For example, the effects of folds, the expression of the front and back sides flowing from the front to the back by double-sided description, and the two-layer effect of raising the backside from the surface using the permeability of Japanese paper, the calculated depiction are also seen. Moreover, by handling the fan, it also produced an illusion effect which skillfully calculated the change due to movement of the viewpoint. Students experience the natural materials such as Japanese paper, bamboo and starch paste, which are the materials of paint and fan at the time, and processing method, and know the difference with the current one. This study is to verify the effectiveness of engineering education which gains experience by making concrete fans and to understand deeply this traditional technology with the artistry of a Japanese fan at the same time. And we can learn from the characteristics of the fan to Japan's history and culture.

• Corrosion Science and Technology
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• 제14권2호
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• pp.99-105
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• 2015

The structures of reinforced concrete have been extensively increased with rapid development of industrial society. Futhermore, these reinforced concretes are easy to expose to severe corrosive environments such as seawater, contaminated water, acid rain and seashore etc.. Thus, corrosion problem of steel bar embedded in concrete is very important in terms of safety and economical point of view. In this study, specimens having six different coating thickness (W/C:0.5) were prepared and immersed in flowing seawater for five years to evaluate the effect of coating thickness and immersion time on corrosion property. The polarization characteristics of these embedded steel bars were investigated using electrochemical methods such as corrosion potential, anodic polarization curve, and impedance. At the 20-day immersion, the corrosion potentials exhibited increasingly nobler values with coating thickness. However, after 5-yr. immersion their values were shifted in the negative direction, and the relationship between corrosion potential and coating thickness was not shown. Although 5-yr. immersion lowered corrosion potential, 5-yr. immersion did not increase corrosion rate. In addition, after 5-yr. immersion, the thinner cover thickness, corrosion current density was decreased with thinning coating thickness. It is due to the fact that ease incorporation of water, dissolved oxygen and chloride ion into a steel surface caused corrosion and hence, leaded to the formation of corrosion product. The corrosion product plays the role as a corrosion barrier and increases polarization resistance. The corrosion probability evaluated depending on corrosion potential may not be a good method for predicting corrosion probability. Hence, the parameters including cover thickness and passed aged years as well as corrosion potential is suggested to be considered for better assessment of corrosion probability of reinforced steel exposed to partially or fully in marine environment for long years.

• 한국해양공학회지
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• 제30권4호
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• pp.327-333
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• 2016

Reinforced concrete structures have found wide usage in land and maritime applications. However, the corrosion of reinforced concrete has been recognized as a serious problem from economic and safety standpoints. In previous studies, the corrosion behavior of the inner steel bar embedded in mortar (W/C: 0.4, 0.5) was investigated using electrochemical methods. In this study, multiple mortar test specimens (W/C: 0.6) with six different cover thicknesses were prepared and immersed in flowing seawater for five years. Subsequently, equations related to the cover thickness, period of immersion, and corrosion characteristics of the embedded steel bar were evaluated using electrochemical methods. Prior to immersion, the corrosion potentials indicated an increase with increasing cover thickness, and after five years, all corrosion potentials demonstrated a trend in the positive direction irrespective of the cover thickness. However, the relationships between the corrosion potential and cover thickness were not in complete agreement. Furthermore, after five years, all of the corrosion potentials indicated values that were nobler compared to those obtained prior to immersion, and their corrosion current densities also decreased compared to their values obtained prior to immersion. It was considered that the embedded steel bar was easily corroded because of the aggression of water, dissolved oxygen, and chloride ions; a higher W/C ratio also assisted the corrosion process. The corrosive products deposited on the surface of the steel bar for five years cast a resistance polarizing effect shifting the corrosion potential in the nobler direction. Consequently, it was considered that the W/C ratio of 0.6 showed nearly same results as those of W/C of 0.4 and 0.5. Therefore, the corrosion potential as well as various parameters such as the cover thickness, period of immersion, and W/C ratio must be considered at once for a more accurate evaluation of the corrosion property of reinforced steel exposed to marine environment for a long period.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.23-32
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• 2022

PSCB 거더교는 고속도로에서 공용중인 교량의 4%로 많은 비중을 차지하고 있지는 않지만, PSCB 거더교의 약 98%가 1·2종 교량이며 전체 교량 연장의 약 16%(192km)를 차지하는 만큼 유지관리가 매우 중요한 교량 형식 중 하나이다. PSCB 거더교의 손상유형을 분석하기 위해 고속도로 공용중 교량의 가설공법, 제설환경 노출등급 비율을 고려한 62개소(477경간) 정밀안전진단 보고서를 선정하여 상세 분석을 수행함과 동시에 실제 열화·손상이 발생한 교량의 현장조사를 수행하였으며, 그 결과 대부분의 열화·손상 원인은 교면포장으로 유입된 우수(염수)가 상부플랜지와 계면 사이에 체수되어 콘크리트가 열화되고, 이후 교면포장의 균열 및 파손, 철근의 부식·팽창으로 인한 콘크리트 박락 등으로 진전되어 나타난 것으로 조사되었다. 또한, 상부플랜지 하면에 발생한 교축방향 균열 원인은 수화열, 건조수축 등으로 인한 균열로 판단된다. 결론적으로 PSCB 거더교의 특성을 고려한 합리적인 유지관리를 위해서는 시공초기 발생되는 상부플랜지 하면 교축방향 균열 제어를 위한 설계측면의 개선 방안이 제시되어야 할 것이며, 공용중 발생되는 열화는 상부플랜지 열화 이전 교면포장의 유지관리를 통한 선제적 대응과 제설환경 노출등급에 따른 차별화된 유지관리 방안이 제시되어야 할 것으로 판단된다.

• 대순사상논총
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• 제27집
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• pp.135-169
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• 2016

증산의 천지공사에 내포된 종교사상을 살펴보면 어느 종교에서도 찾아볼 수 없는 독특한 사상이 다양하게 나타난다. 그중에서도 대표적인 사상이 바로 '인존(人尊)'사상이고, 타종교와 차별되는 대순진리회의 고유사상이기도 하다. 그래서 '인존은 언제부터 구체적으로 구현되었는가? 인존은 신명계와 인간계 사이에서 어떠한 유기적 관계를 가지고 있는가? 인존시대를 맞이하여 신명계와 인간계 사이에서 모사재천(謀事在天)하고 성사재인(成事在人)하는 구체적인 모습과 그 형태의 흐름이 어떻게 되는가?'에 연구 초점을 맞추었다. 그래서 논지를 전개하기 전에 기존의 선행된 담론 및 논문 등 43편을 검색하고, 43편의 연구에서 상관관계를 보기 위하여 자료를 시간 순으로 나열 정리하고, 인존에 관한 시작시기와 인존에 대한 논지를 요약 정리하였다. 논지에서 '인존'만이 가지고 있는 고유성, 독특성, 차별성을 어떻게 설명하는지를 살펴봄으로써 선행 연구에서 발견되는 몇 가지 문제점은 다음과 같다. ①인존에 함의되어 있는 개념을 잘 이끌어 낸 것은 발견되지 않았다. ②인존을 음양합덕·신인조화·해원상생과 관련시켜 검토한 논문도 발견되지 않는다. ③대다수 논문은 인존의 구현 시기를 후천오만년이 시작되는 시점으로 볼 뿐 만아니라 논자들 사이에서도 선천과 후천을 구분하는 시점이 다르다는 것도 발견되었다. ④인존이 구현되는 대상에 대한 심도 있는 논문도 찾기가 쉽지 않았다. ⑤인존에 대한 연구 간의 연계성도 잘 발견되지 않았고, 연구 간에 발전이 있었다고 판단하기도 쉽지가 않았다. 그러므로 이 논문을 통하여 선행 연구에서 발견되는 문제에 대한 답을 제시하고, 논지를 다음과 같이 전개하였다. ①『전경』을 중심으로 선천과 후천에 대한 시대적 구분을 구체적이고 정밀하게 조사하여 인존을 이해하는 데 도움이 되는 '선천(1901)→해원시대→후천(미래의 그 날)'이라는 시대분류 안을 제시하고, ②인존시대는 신축(1901)년부터 인간계의 해원시대를 열어가는 전제 조건이 되며 인존은 해원시대를 열어나가는 우주의 구조적인 운행법칙을 함의하는 시스템적 법칙으로 규정하였고, ③인존시대가 구현되어 가는 변화의 양상을 종합적으로 고찰해 볼 때, 그 고찰 기간은 신축(1901)년부터 후천이 시작되는 시기까지이고, 대상은 인존의 첫 주자인 증산으로부터 시작하여 후천에 살아가는 도통군자와 창생군자들로 귀일되는 흐름으로 규정하였다. 그리고 인존시대에서 인존의 구현 변화과정을 연구하는 것은 해원상생을 연구하는 것과 마찬가지로 대순사상을 깊이 이해하는 데 필요한 공부 방법이지만 이 논문에서는 깊이 논하지 않고 개론적으로만 논의하였다.