• 한국도로학회논문집
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• 제19권2호
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• pp.127-135
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• 2017

PURPOSES: The objective of this study is to evaluate the effect of anti-stripping on asphalt mixtures constituting anti-stripping agents. METHODS : Based on the literature review, asphalt mixture added with anti-stripping agents was prepared, and these asphalt mixtures were evaluated for anti-stripping properties for each anti-stripping agent through various lab tests, namely, tensile strength ratio (TSR), dynamic immersion test, uniaxial compression test, and indirect tensile strength test (IDT). The liquid anti-stripping agents used in the lab test were premixed with each asphalt binder (PG 64-22, PG 76-22) before being mixed with the aggregate. RESULTS :The result of the TSR test revealed that the effect of anti-stripping was highest when hydrated lime and liquid anti-stripping agent W were added. The correlation coefficient $R^2$ between the TSR result and cohesion ratio is 0.99, which indicates that the sensitivity of the TSR to moisture damage is reliable from the mechanical point of view. The covering ratio of the asphalt binder to the liquid anti-stripping agent W was determined to be higher than that to the other liquid anti-stripping agents. CONCLUSIONS :It is considered that the improved moisture resistance of asphalt mixture as a result of the use of anti-stripping agents can reduce the incidence of various pavement damages such as portholes caused by stripping, and the performance life of the asphalt road pavement can be prolonged.

• Corrosion Science and Technology
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• 제19권3호
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• pp.109-114
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• 2020

The photo-reflectance of aluminum and AISI 304 stainless steel during cyclic immersion test in 3 wt% NaCl solution was examined in this study. Overall, corrosion was not recognized by a visual inspection or weight measurement up to 310 h. When evaluated, it was noted that the roughness of the specimens did not change significantly. However, localized corrosion, which is located at the vicinity of intermetallic precipitation of aluminum or at the grain boundary of stainless steel, was confirmed by the use of an optical microscope and scanning electron microscopy after tens of hours of utilizing the corrosion test. In this respect, an increase of the peak intensity for metallic Al after 90 h of test, and for metallic Fe after 153 h was detected from the X-ray photoelectron spectra. In this context, it was shown that from the photo-reflectance spectra, the reflection of the visible light from the tested samples was changed noticeably over the test duration. As a result, the intensity of reflected light was decreased up to 90 h ~ 153 h, and thereafter was shown to increase higher than the initial intensity before the corrosion test.

• 한국콘텐츠학회논문지
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• 제21권2호
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• pp.707-717
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• 2021

본 연구는 디지털기기에서 앱을 활용한 그림검사가 가능한지를 탐색해보고자 게임 중독군을 대상으로 '나무에서 사과 따는 사람 그리기(Person Picking an Apple from a Tree: 이하 PPAT)' 그림 검사를 바탕으로 진단을 확인하여 미술치료에서의 그림검사 앱을 활용할 수 있는 근거를 마련할 수 있는지를 살펴보는데 목적이 있다. PPAT 그림검사는 사람이 사과를 어떤 식으로 따는지 문제해결력을 검증하는데 유용하고 이에 대한 신뢰도, 타당도가 높은 검사이다. 본 연구를 통해 살펴본 결과, 디지털 기기에서 앱을 활용한 PPAT 그림검사의 형식척도(Formal Elements Art Therapy Scale:이하 FEATS) 항목 14개 중 '문제해결력' 항목에서 인터넷 과몰입군이 일반사용자군 보다 낮은 점수를 받았는데, 과몰입군의 경우 사과를 향해 손을 뻗지 않고 있거나, 사과가 떨어지는 그림, 합리적인지지 기반 없이 사과를 따는 방법으로 사과를 따른 모습을 표현했다. 본 연구에서 발견한 내용은 디지털 기기에서 앱을 사용한 PPAT 그림 검사가 본래의 목적인 '문제해결력'을 유의미하게 드러내었다는 점은 앞으로 디지털 기기를 활용하여 인터넷 과몰입 대상자들을 위한 심리치료적 개입뿐만 아니라 디지털 기기를 익숙하게 활용하는 사용자들에게는 PPAT 그림검사 앱을 활용할 수 있다는 점에서 연구의 의의가 있다.

• 한국발생생물학회지:발생과생식
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• 제15권4호
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• pp.301-308
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• 2011

결빙억제제(CPA)의 종류, 농도 및 침지시간이 참전복 Haliotis discus hannai 발생배의 생존활성에 미치는 영향을 조사하였다. 4세포, 담륜자 및 피면자를 dimethyl sulfoxide, ethylene glycol, propylene glycol 농도별로 10분, 20분 및 30분간 침지하였다. CPA 침지 후 각 발생배의 발생진행률은 각 CPA 농도가 낮을수록, CPA 침지시간이 짧을수록 높았다. 또한, 피면자에서 비틀림전까지의 발생진행률은 4세포에서 담륜자까지의 것보다 높았다. CPA 침지 후 발생진행률 및 유생활성지수는 ethylene glycol에서 가장 높았다. 참전복 발생배의 냉동보존 효과를 높일 수 있는 CPA 및 농도는 ethylene glycol 2.0 M, 평형시간은 30분인 것으로 추정된다.

• Human Ecology Research
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• 제58권4호
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• pp.585-599
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• 2020

This study investigated children's interests in learning English, affected by educational activities in and out of institutes, and mothers' perceptions regarding early childhood English education. We recruited, 253 mothers of 3- to 5-year-old children in either general kindergartens or English immersion institutes. They answered questions on socioeconomic status, perceived interest in English by their children, their perceptions regarding early childhood English education, and English education outside institutes. In addition, 42 English teachers provided information within institutes such as class time per week, teacher-pupil rate, and language use policy during class. The collected data were analyzed through SPSS 22 for frequency analysis, descriptive statistics, independent t-test, and hierarchical multiple regression analysis. The major findings are as follows. First, the two groups were in distinct learning environment. Second, mothers' perceptions and outside-institute activities were significantly different between the two groups. Third, the English interests of children at both institutes were influenced by mothers' worries and at-home English interactions. Fourth, education within institutes did not affect both group's English interests. Fifth, private education and socioeconomic status did not affect both group's English interests. Lastly, only the children's interests in English immersion institutes were affected by gender and mother's perceived necessities. Focusing children's interests, this study helps in understanding young children's affective aspects regarding learning English. The findings are expected to be a guideline for each home and institute to increase children's interest in learning English.

• 비파괴검사학회지
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• 제24권4호
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• pp.348-353
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• 2004

이 연구는 터빈베어링의 신뢰성을 평가하기 위하여 초음파 C-Scan 방법을 적용한 기술이다. 수침법에 관한 연구는 실험실과 현장검사 적용에 광범위하게 사용되는 기술이다. 여기에서는 C-Scan 방법을 이용하여 베어링의 모재와 Babbitt 금속간 경계부의 상태를 평가하였다. 수침법 C-Scan 방법에 의한 초음파 영상은 베어링 경계부의 상태를 확인하는데 효과적인 방법으로 사용될 수 있었다. 초음파 영상의 분해능을 높이기 위하여 집속형 탐촉자를 사용하고, Babbitt 금속과 베어링 모재간의 접합경계면에서 발생하는 초음파 음압 반사율을 측정하여 결함의 검출과 면적을 추정할 수 있었다. 초음파 수침법은 베어링 접합부의 박리위치와 박리면적의 경계면을 결정하여 크기를 계산하는데 아주 유용하게 사용될 수 있는 기술이며, 이 연구에서 개발된 기술은 화력발전소에서 사용되고 있는 터빈베어링의 건전성을 확보하는데 적용되었다.

• 대한금속재료학회지
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• 제50권9호
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• pp.697-702
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• 2012

In this study, unidirectional and plain woven carbon fiber reinforced magnesium matrix composite laminates were fabricated by the liquid pressing infiltration process, and evolutions of the microstructure and compressive strength of the composite laminates under corrosion were investigated by static immersion tests. In the case of the unidirectional composite laminate, the main microstructural damage during immersion appeared as a form of corrosion induced cracks, which were formed at both CF/Mg interfaces and the interfaces between layers. On the otherhand, wrap/fill interface cracks were mainly formed in the plain woven composite laminate, without any cracks at the CF/Mg interface. The formation of these cracks was considered to be associated with internal thermal residual stress, which was generated during cooling after the fabrication process of these materials. As a consequence of the corrosion induced cracks, the thickness of both laminates increased in directions vertical to the fibers with increasing immersion time. With increasing immersion time, the compressive strengths of both composite laminates also decreased continuously. It was found that the plain woven composite laminates have superior corrosion resistance and stability under a corrosive condition than unidirectional laminates.

• 한국콘텐츠학회논문지
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• 제22권6호
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• pp.307-318
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• 2022

가상현실을 이용한 체험교육은 몰입을 통한 학습 효과성을 검증하며 의료분야에서 적극적으로 활용되고 있으나 가상현실 내에서 학습 몰입에 영향을 미치는 요인에 관한 연구는 부족한 실정이다. 이에 본 연구는 문헌 연구를 통해 인터페이스의 사용성 및 인지적 어포던스 평가 요소를 추출하고 가상현실 의료 콘텐츠 4종을 선정하여 전문가 대상 사용성 평가를 실시하였다. 이를 종합하여 가상현실 의료 술기 콘텐츠에 따른 인터페이스 설계 방안을 제안하였다. 내용을 요약하면, 정보를 제공하는 인터페이스는 가시성, 체험자의 시선과의 거리, 색감의 조화, 통일감 있는 시각화, 피드백, 반응 속도, 조작에 따른 예상된 변화로 인해 몰입에 영향을 끼치며 인터페이스를 통해 제공하는 정보의 의미와 용어가 명확해야 몰입을 해치지 않음을 알 수 있었다. 본 연구는 제한된 콘텐츠를 이용하여 일반화에는 한계가 있어, 이후 지속적인 연구를 통해 체험자가 학습의 맥락을 익히고 파악하기 위한 인터페이스 설계에 표준화된 가이드 개발 및 사용자 관점의 인터페이스 설계 연구에 대한 정밀화가 논의되기를 기대한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.995-996
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• 2005

• 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.