• Corrosion Science and Technology
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• 제12권5호
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• pp.239-244
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• 2013

Marine equipment exposed to harsh environments requires not only excellent corrosion resistance but also improvement of physical characteristics against natural material degradation. With growing interests in ocean energy resources, the higher reliability for marine equipment has become more important in terms of material characteristics. ALBC3 alloy represents excellent corrosion resistance and is widely used in corrosive environments. However, cavitation damage occurs frequently due to its poor durability in high flow rate of marine environment. In this research, shot peening technology was employed as a surface modification with shot peening stand-off distance to mitigate cavitation damage. The effects of shot peening on extent of cavitation damage and weight loss were evaluated for both shot peened and non-peened specimens. The results revealed that the application of shot peeing decreased cavitation damage for all experimental conditions in comparison with the non-peened specimens. The optimum stand-off distance was determined to be 10 cm, since more than 35 % of cavitation damage reduction was observed.

• 한국표면공학회지
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• 제51권2호
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• pp.87-94
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• 2018

Various sealing techniques were applied to the anodized 5083 aluminum alloy for marine environment to reduce corrosion and cavitation erosion damage. Electrochemical experiments and cavitation erosion tests were conducted to evaluate the corrosion resistance and cavitation resistance of the anodic oxide film treated with sealing in natural seawater solution. Then, damaged surface morphology was analyzed by scanning electron microscope(SEM) and 3D microscope. As the results of the electrochemical experiments, it was observed that the surface damage of all the experimental conditions in the anodic polarization experiment was locally grown by the combination of crack and corrosion damage. In the Tafel analysis, the corrosion resistance of all sealing treatment conditions was improved compared to the anodizing. On the other hand, cavitation erosion tests showed that the anodizing and all the sealing treatment conditions generated local pit damage by cavitation erosion attack and grew to crater damage in the observation of damaged surface by SEM. Also, the weight loss and the surface damage depth measured with the experiment time presented that most of the sealing treatment conditions showed better cavitation erosion resistance than the anodizing, and they had an incubation period at the beginning of the experiment.

• 비파괴검사학회지
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• 제29권4호
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• pp.323-330
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• 2009

본 연구의 목적은 전기 저항 측정을 통한 탄소 섬유 강화 복합재의 파손 감지를 위한 효과적인 방법을 개발하는 것이다. 이를 위하여 복합재 적층판에 특정 파손을 인위적으로 모사하고 전기 저항의 변화와 모사된 파손과의 관계를 정립하려 하였다. 많은 량의 측정치를 효과적으로 처리하기 위하여 자동화된 측정 시스템을 개발하였다. 전기 저항 측정을 위하여 시편 표면에 전극을 제작하는 방법을 개발하였다. 쿠폰과 평판형태의 탄소 섬유 강화 복합재 적층 시편에 인위적인 파손을 부과하고 전기 저항을 측정하고 그 결과를 후처리하는 과정으로 파손을 검출하였다. 쿠폰 형태의 시편은 제작시에 다양한 크기의 테플론 필름을 삽입하여 층간 분리를 모사하였다. 전기 저항 측정 결과 층간 분리 크기가 증가함에 따라 전기 저항도 증가하는 경향을 보였으며, 이를 통해 층간 분리의 존재와 그 크기를 검출할 수 있음을 보였다. 평판 시편은 초기에는 인위적인 파손 없이 제작하여 전기저항을 측정하고, 이후 특정 위치에 원공을 뚫고 원공의 직경을 증가시켜 가며 전기저항의 변화를 관찰하였다. 실험에 사용한 평판은 각 변에 6개의 전극을 설치하여 총 24개의 전극을 갖도록 하였으며 수직, 수평, 대각선 방향의 전극간의 전기 저항을 측정하였다. 측정 결과는 탄소 섬유 강화 복합재 구조물의 파손 검출을 위하여 전기 저항 측정법의 가능성을 보였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.242-242
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• 2010

Si(100) 표면에 이온을 일정한 에너지로 dose량을 동일하게 유지하고, dose rate만을 변화시켜가며 주입한 후에 depth profile과 damage, 그리고 sheet resistance를 조사하였다. 일정한 에너지로 이온을 주입하여도 dose rate의 변화에 따라서 depth profile에 변화를 보이는 것을 확인할 수 있었고 sheet resistance역시 dose rate변화에 비례하여 변화하는 것을 확인할 수 있었다. 본 연구는 Crystal-TRIM program으로 computer simulation 하여 damage profile의 결과를 통해 dose rate가 클수록 시료 표면 근처에 잔류 damage의 양이 높게 나타나는 것을 알 수 있었고 그 잔류 damage의 표면근방 분포가 sheet resistance에 직접적인 영향을 미친다는 것을 확인할 수 있었다.

• 미생물학회지
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• 제26권2호
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• pp.113-121
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• 1988

Ozone, an atmospheric pollutant, can damage similar UV and X-rays DNA and its components. It is possible then that the KNA damage produced by this gas are similar, to some extent, to those of radiations and that they could be repaired by the same DNA repair mechanisms. It has been observed in Escherichia coli that radiosensitive strains such as lex A, rec A and pol A, all deficient to some extent for DNA repair, are more sensitive to ozone than a wild type strain. We have thendetermined the ozone resistance and host-cell reactivation of ozone-damaged T3 phages for the E. coli double mutants pol A, lex A, uvr B, lex A, uvr A, rec A and rec A lox A. According to the results, the DNA polymerase 1 plays a key role in ozone resistance and Type 11 mechanism and/or shory patch excision repair are the most important for it. The interactions between the different DNA repair mechanisms are secondary. There is a strong correlation between ozone resistance and the capacity to reactivate T3 phages damaged by ozone.

• Smart Structures and Systems
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• 제14권3호
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• pp.469-477
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• 2014

As a kind of intelligent materials, conductive asphalt concrete has a broad application prospect including melting ice and snow on the pavement, closing cracks in asphalt concrete, sensing pavement damage, and so on. Conductive pavement will be suffered from fatigue failure as conventional pavement in the process of service, and this fatigue damage of internal structure can be induced by electrical signal output. The characteristics of electrical signal variation of conductive asphalt concrete in the process of fatigue cracking were researched in this paper. The whole process was clearly divided into three stages according to resistance changes, and the development of fatigue damage wasn't obvious in stage I and stage II, while in stage III, the synchronicity between the resistance and damage began to appear. Thus, fatigue damage variable D and initial damage value $D_0$ represented by the functions of resistance were introduced in stage III. After calculating the initial damage value $D_0$ under different stress levels, it was concluded that the initial damage value $D_0$ had no noticeable change, just ranged between 0.24 and 0.25. This value represented a critical point which could be used to inform the repair time of early fatigue damage in the conductive asphalt pavement.

• Asian Pacific Journal of Cancer Prevention
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• 제13권10호
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• pp.4879-4881
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• 2012

Epidermal growth factor receptor (EGFR) overexpression is associated with resistance to chemotherapy and radiotherapy. The EGFR modulates DNA repair after radiation-induced damage through an association with the catalytic subunit of DNA protein kinase. DNA double-strand breaks (DSBs) are the most lethal type of DNA damage induced by ionizing radiation, and non-homologous end joining is the predominant pathway for repair of radiation-induced DSBs. Some cell signaling pathways that respond to normal growth factors are abnormally activated in human cancer. These pathways also invoke the cell survival mechanisms that lead to resistance to radiation. The molecular connection between the EGFR and its control over DNA repair capacity appears to be mediated by one or more signaling pathways downstream of this receptor. The purpose of this mini-review was not only to highlight the relation of the EGFR signal as a regulatory mechanism to DNA repair and radiation resistance, but also to provide clues to improving existing radiation resistance through novel therapies based on the above-mentioned mechanism.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.233-236
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• 2003

This study is intended to investigate the resistance of frost damage of concrete for planting, which recycled aggregate is used, by freezing in air and thawing in water. According to the results, if AE agent of 0.005% is mixed in making concrete for planting, it is thought that the resistance of frost damage is guaranteed in winter because concrete for planting is not under severe freezing and thawing function, but under natural weather action.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.293-302
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• 2010

2 types of geogrids and geotextiles was used to evaluate shear behaviors after installation damage test. Shear behaviors were compared after installation damage test and coefficient of resistance to direct sliding($f_{ds}$) was estimated by theoretical shear analysis. Shear strength of damaged geogrid decreased under high normal stress of 150kPa and shear strength of geotextile decreased with increasing normal stress. It is seen that $f_{ds}$ values after installation damage decreased than before installation damage through comparison calculated $f_{ds}$ by direct theoretical shear analysis. $f_{ds}$ values to be calculated by theoretical shear analysis were changed with before and after installation damage.

• 한국표면공학회지
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• 제31권5호
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• pp.297-303
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• 1998

The influences of vanadium addition on the cavitation erosion resistance pf Fe-Cr-Ni-Si-C hardfacing alloy were investigated using a vibratory apparatus up to 30 hrs. It was shown that 1wt.%V additioned alloy improved the resistance to cavitation damage. However, further increase in V content up to 2wt.% reduced the cavitation erosion resistance. It was considered that the addition of V developed the cavitation erosion resistance by reducing the stacking fault energy of Fe-Cr-Ni-Si-C alloy. However, the further increase in V content seemed to reduce the cavitation erosion resistance by increasing the matrix/carbide interfacial area, which was the preferential sites of the cavitation damage.