• 한국해양공학회지
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• 제23권6호
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• pp.124-130
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• 2009

This study presents a finite element simulation of elastic waves for detecting anti-symmetric damages in an adhesively-bonded single lap joint. Plane strain elements were used for modeling adherents (aluminum) and adhesives (epoxy). Three types of damage were introduced: thickness reduction, elasticity deterioration, and voids in the adhesive layers, and two excitation and reception arrangements (ER1 and ER2) were used to investigate the detectability of the damage. The simulation showed that symmetrically located damage, such as a thickness reduction, can be detected by one excitation and one reception arrangement (ER1) and anti-symmetric damages, such as elasticity deterioration and voids, can be detected by modified two-point elastic wave excitation (ER2). Compared with the ER1 arrangement, the ER2 arrangement does not require a baseline signal for damage detection; hence, an efficient method of anti-symmetric damage detection in an adhesively-bonded single lap joint is proposed.

• Earthquakes and Structures
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• 제24권5호
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• pp.333-343
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• 2023

Various seismic isolation and reduction devices have been applied to suppress the longitudinal vibration of continuous girder bridges. As representative devices, lead rubber bearing (LRB) and fluid viscous damper (FVD) might suffer from deterioration during the long-term service. This study aims to evaluate the impact of device deterioration on the seismic responses of continuous girder bridges and investigate the seismic behavior of deteriorated LRBs and FVDs. Seismic performance of a simplified bridge model was investigated, and the influence of device deterioration was evaluated by the coefficient of variation method. The contribution of LRB and FVD was assessed by the Sobol global sensitivity analysis method. Finally, the seismic behaviors of deteriorated LRBs and FVDs were discussed. The result shows that (i) the girder-pier relative displacement is the most sensitive to the changes in the deterioration level, (ii) the deterioration of FVD has a greater effect on the structural responses than that of LRB, (iii) FVD plays a major role in energy dissipation with a low degradation level while LRB is more essential in dissipating energy when suffering from high degradation level, (iv) the deteriorated devices are more likely to reach the ultimate state and thus be damaged.

• 한국가구학회지
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• 제24권3호
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• pp.257-262
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• 2013

This study was carried out to investigate the susceptibility of wood-based composite panels exposed to mould and sap-stain fungi. Five wood deterioration fungi (three mould fungi, two sap stain fungi) were inoculated into two types of commercial wood-based composite panels (medium density fiberboard and particleboard), which have three class of formaldehyde emission. All wood-based composite panels were more or less susceptible to mould and sap stain fungi. The attacking mode of the fungi was highly dependent on formaldehyde emission. This study indicates that all wood-based composite panels, specially low formaldehyde emission class panels should be considered to prevent fungal deterioration when they are used for exterior and humid interior applications.

• 사상체질의학회지
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• 제22권1호
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• pp.49-58
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• 2010

1. Objectives: The purpose of this study is to find out the Anti-Oxidative effects of Soyangin Hyeongbangpaedok-san(HBP) in kidney and spleen cells of aged rats. 2. Methods: Aged rats used in this experiment were 6, 52, 68 weeks old. Each age group was divided into three groups again. One group was given no treatment, another group was dosed normal saline and the other group was dosed HBP decoction. The antioxidant effects of HBP decoction were measured by the levels of SOD, GSH, MDA and NO. 3. Results: and Conclusions: 1) The activity of SOD was significantly increased in kidney cells of 68w-HBP group. Deterioration of the activity of SOD in kidney cells was significantly suppressed according to increasing in age of the week. 2) The level of NO was significantly decreased in kidney cells of 68w-HBP group. Deterioration of The level of NO in kidney cells was significantly suppressed according to increasing in age of the week. 3) The activity of SOD was increased in spleen cells of 52w and 68w-HBP group. 4) The level of GSH was significantly increased in spleen cells of 68w-HBP group.

• Journal of the Korean Wood Science and Technology
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• 제49권5호
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• pp.471-481
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• 2021

This study investigated the hygroscopicity and UV deterioration characteristics of 3 domestic and 4 imported woods using natural oil, stain, and varnish paints. In terms of hygroscopicity, it was found that the hygroscopicity of the painted wood was lower than that of the unpainted wood, and that as the number of coatings increased, the hygroscopicity decreased. In terms of anti-absorption, oil-based chemical paints showed higher resistance than water-based paints, and natural oils showed results comparable to oil-based paints. As for the UV deterioration, the amount of color change of the painted wood was lower than that of the unpainted wood, and there was no significant difference according to the number of times of painting. The amount of color change was found to be low in oil-based paints and hardwoods. Through this study, we confirmed effective moisture blocking and small color changes during painting using paints, and it is believed that wood can be protected from internal and external defects through selective and efficient painting based on data for excellent painting performance.

• 조명전기설비학회논문지
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• 제25권10호
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• pp.76-86
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• 2011

This paper proposes novel algorithm for anti-islanding of grid-connected photovoltaic(PV) inverter. The islanding of PV systems can cause a variety of problems such as deterioration in power quality and electric shock. To prevent islanding, many anti-islanding methods are researched. Typical methods of anti-islanding are active frequency drift(AFD) and active frequency drift positive feedback(AFDPF). However, the AFD has problem that widely exists non diction zone(NDZ). The AFDPF is a method that improves the AFD method and is detected islanding by changing the chopping fraction(cf). However, The AFDPF does not detect when cf is very small and does not satisfy the IEEE Std. 929-2000 when cf is very big. Therefore, this paper proposes novel anti-islanding method that is simple to implement using virtual resister. The anti-islanding method proposed in this paper is compared with conventional method. The validity of this paper is proved using this result.

• 한국구조물진단유지관리공학회 논문집
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• 제18권3호
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• pp.167-177
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• 2014

최근 수질오염의 악화로 고도정수처리시설에 대한 수요가 커지고 있으며, 오존처리와 같은 밀폐형 고도정수처리시설의 설치가 늘고 있는 실정이다. 그러나 오존의 강력한 산화작용으로 인해 콘크리트 구조물의 침식이 우려됨에 따라 오존에 대응 가능한 에폭시 방수방식재가 콘크리트 표층부 보호 코팅재로 적용되고 있다. 그러나 이러한 에폭시가 오존에 대한 성능수준 및 장기적 내구성을 명확히 측정할 방법과 기준이 없어 정확한 품질관리가 이루어지지 않고 있는 실정이며, 이로 인해 수처리용 콘크리트 구조물의 장기내구성 확보에 대한 우려가 제기되고 있다. 이 연구에서는 AFM과 나노인덴테이션 기법이 기존에 사용하던 평가방법인 육안관찰, 중량변화, 표면관찰, 색차분석 등의 간접적 평가방법과 함께 에폭시 방수방식재 평가방법으로써의 적합한지를 판단하고자 하였으며, 이를 위해 오존용으로 개발된 6종의 다른 성분으로 구성된 에폭시계 방수방식재를 대상으로 열화특성을 분석하였다. 연구결과 AFM과 나노인덴테이션을 활용할 경우 기존 평가방법보다 직접적이고 정량적인 평가가 가능함을 확인하였으며, 일부 에폭시 코팅재료의 경우 오존에 대한 성능 한계치 (임계치)를 명확히 확인할 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.409-414
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• 2002

This study is intended to develop the self water proof admixture for durability concrete by anti-corrosion inhibitor. Chloride induced corrosion of reinforcement is one of the main factor which cause the deterioration of concrete structure. When the substitute anti-corrosion agents for a part of self waterproofing agent, the corrosion-proof increases for the increased water proofing capacity. And proper self waterproofing agent by cement weight in concrete was generally positive effect to concrete compressive strength, slump, freezing and thawing resistance. Also, permeability and absorption show a straight decrease when self waterproofing agent is added.

• 펄프종이기술
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• 제36권5호
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• pp.36-43
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• 2004

The behaviors of deterioration in the mechanical and optical properties of paper during sunlight exposure are mainly attributed to UV irradiation. The effect of different additives (anti-UV agents) on paper properties during exposure was studied. The results showed negligible changes in the mechanical properties of samples prepared with two different ways, whereas the shielding ability was increased when the additives were applied to the surface of hand sheets. Also, the paper which is treated with anti UV agents can keep freshness more effectively of agricultural products from UV irradiation.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2011년도 정기 학술발표대회
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• pp.91-91
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• 2011

The quality of the surface layer in concrete structures plays an important role in the durability of the concrete. The concrete factory products are made as they improve the appearance of the surface and compressive strength in need. A common criterion to judge the quality of concrete products frequently seen in our daily life appears to be "beauty" in terms of consistent shaping. However, as for most concrete curb in such areas where a large amount of anti-freezing agents(NaCl) and ice and snow melting agents(CaCl2) are spread over roads to ensure road safety during the winter season, since deterioration advances from the surface, scaling is seen on the surface concrete due to deterioration which combined freezing damage and salt damage. Especially, In cold northern districts, the spreading amount of deicing salts increases by regulation of studded tire use, and the scaling of the concrete products, the various parts of concrete structures for roads is increasing in recent years. In this study, L-shape concrete curb were targeted, the permeable form method with the commercial permeable sheet was applied to it and the improvements of the quality were examined. By the permeable form method, surface layers got strengthened, which prevented permeation of the deterioration factor from the outside, and the scaling resistance of the upper surface where the permeable sheet was applied improved exceedingly. It will be expected by applying the permeable form method to various concrete products that frost resistance improves and scaling damage decreases.