The feedwater heaters are critical components in a nuclear power plant. As the operation years of heaters go by, the maintenance costs required for continuous operation increase. Integral drains cooler is the separate heat exchanger combined in the heater shell. The integral drains cooler must be isolated from the other zones. The integral drains cooler must be free from leakage and the entrance into the zone be sealed against the entrance of steam from the condensing zone. Cause of tubes leakage since tubes replacement is the same as the cause before tubes replacement. Therefore, feedwater refurbishment method was selected by heater internal structure condition.

Phaya-Thon-Zu temple has a unique architectural style connected by the three temples, and cultural values are highly as murals remain on some of the walls. However, various damages in internal walls and vaults have occurred due to earthquake and environmental influences. In order to analyze these damages, accurate structural analysis is required, but structural modeling is difficult, because Phaya-Thon-Zu temple is the complex masonry structure which is stacked with small bricks. Therefore, this study intends to analyze the causes of damages by examining collapse mechanism for cross section and longitudinal section of vaults in the entrance hall and shrine by using thrust line analysis, which is a geometric method, and to compare it with the actual damage situation.

The suspension system of special tracked vehicle is using hydraulic piston pump to adjust track tension and control vehicle position change. During operation of vehicle on rough field, failure of suspension control was occurred due to the piston pump failure. In this study, investigation was performed to analyze the cause of hydraulic piston pump failure. Main reason of piston pump failure is strong peak pressure and insufficient structural safety of shoe. The static stress analysis considering peak pressure was performed to find the weak point of the shoe. From the result, it is confirmed that pass hole of lubrication is the weakest point. Improved piston shoe shows 27% decrease in maximum stress and satisfies the design target which is less than 40% of stress margin.

There are many reasons of damage in Namhansanseong Yeojang. Lots of damage types are observed in each Yeojang. There are many types of damage factors but major damage factor is breakage by freezing and thawing. So Conduct non-destructive evaluation about damage factors in Namhansanseong Yeojang to analysis weathering factors in Yeojang by measuring directional microclimate. The study will pave the way for conservation management in Namhansanseong by suggesting the conservation calendar about weather condition and damage factors.

최근 들어 겨울철 날씨가 추운 강원도, 경기도, 충청도 지역의 콘크리트 구조물에 동결손상에 의한 파손이 빈번히 일어나고 있다. 특히 택지개발공사 구간의 도로 소구조물에 다량의 표면박리파손이 조기에 발생하고 있어, 사회적인 문제로 대두되고 있다. 본 연구에서는 도로 소구조물 중 하나인 L형 측구에 발생된 표면박리 파손의 원인을 분석하기 위해, 일부 택지개발공사 구간을 대상으로 건전, 불건전 구간을 구분하여 코어채취를 실시하였으며, 이 코어시료를 이용하여 압축강도실험과 화상분석실험을 수행하였다. 압축강도실험결과, 설계기준강도를 만족하지 못하는 곳이 16개소 중 6개소로 나타났다. 일반적으로 강도는 내부에 발생되는 응력에 저항하기 위한 능력을 나타내는 지표 중 하나이고, 이에 강도가 큰 구간이 파손정도가 작고, 파손시점도 지연될 수 있는 가능성이 있는 것은 분명하다. 그러나 전체적으로 압축강도크기와 상관없이 건전구간과 불건전구간이 무작위로 존재하는 특성을 나타내었다. 화상분석실험결과, 적정 공기량, 간격계수를 확보한 구간이 단 몇 개소 정도밖에 되지 않으며, 전반적으로 콘크리트의 공기량 부족, 공극구조 불량으로 나타났다. 이와 같은 결과가 실제 현장에서 다량의 표면박리파손을 유도한 주요한 요인일 수 있는 것으로 판단된다. 본 연구결과, 건전구간과 불건전구간에 공극구조가 분명한 차이를 나타내고 있어, 본 구간의 적정 공기량을 확보하지 못한 것이 주요한 파손의 원인이라고 판단된다. 또한 해당 구간의 물-결합재비가 약 60%정도를 나타내고 있어, 높은 물-결합재비가 이와 같은 손상에 일부 영향을 미쳤을 것으로 판단된다.

As the aging of the facility increases, the safety, durability, and serviceability that were originally possessed by the natural aging deteriorate. Accordingly, periodic safety inspections, repair and strengthening are the basic procedures for th maintenances of facilities. However, except for some facilities that are prescribed in the law, the safety and maintenance of facilities are still insufficient. Especially, social welfare facilities, which occupy the majority of small-scale vulnerable facilities, have a high proportion of old facilities with many years of age, leading to major damages that affect the durability and safety of facilities. The purpose of this paper is to identify the main damage and its causes according to the change of the years of social welfare facilities, and to use it as a basic data to suggest reasonable maintenance methods.

This paper introduces and summarizes damage cases of cable for cable supported bridges. The damage cases of similar bridge types may become an important database in the maintenance and management of cable supported bridges in the future. It will also be used as a base material for improving and developing the technology of inspection and maintenance of cable supported bridges.

This paper introduces and summarizes damage cases of cable for cable supported bridges. The damage cases of similar bridge types may become an important database in the maintenance and management of cable supported bridges in the future. It will also be used as a base material for improving and developing the technology of inspection and maintenance of cable supported bridges.

Reinforced earth retaining wall is being applied in many construction sites such as slopes, roads, retaining walls with the development of geosynthetic. The case caused a problem with the stability of the reinforced earth retaining walls often occurs because the construction is being conducted, ignoring the basic assumptions of the economical design. In this study, reinforced earth retaining wall damage cases were analyzed in order to derive the causes. The results of this study will be useful for future maintenance of reinforced earth retaining wall.

Lateral movement of bridge abutment is frequently causing damages to the expansion joints, bearings, bridge backwall and settlement of approach slabs. In this study, about 1,000 bridges which was lateral movement occur were investigated. The investigation shows that the lateral movement of abutment occurred not only in soft ground, but also in abutment on embankment of the normal soil conditions. The causes of lateral movement included settlement and deformation of high embankment, lateral spread of soft ground, expansion of con'c pavement by alkali-aggregate reaction.

Vibration measurement analysis and In-depth inspection were carried out to understand the cause of defects occurred on joint of bridge. A cause of defects, such as metallic sounds, water leak&corrosion and rubber seal rupture turn out to be due to deterioration and vibrating impact by period so that the bridge is in need of repair and effective maintenance.

본 연구는 돌연변이원(mutagen)의 하나인 메틸수은(methylmercuric chloride, MMC)의 세포독성을 알아보기 위하여 배양 NIH3T3 섬유모세포를 재료로 메틸수은의 독성을 산화적 손상측 면에서 조사하였으며, 또한 메틸수은의 세포독성에 대한 꿀풀 (Prunella vulgaris L. var lilacina Nakai) 추출물의 영향을 세포 생존율을 비롯한 SOD-유사 활성(SOD-like activity) 및 지질과산 화(lipid peroxidation, LP) 저해능과 같은 항산화 측면에서 분석 하였다. 본 실험에서 배양 NIH3T3 섬유모세포에 15∼35uM의 메 틸수은을 처리한 결과 처리농도에 비례하여 세포생존율이 대조군 에 비하여 유의하게 감소하였으며, 또한 XTT50값이 34.2uM에서 나타나 고독성(highly-toxic)인 것으로 나타났다. 한편, 항산화제 인 vitamin E는 메틸수은에 의하여 감소된 세포생존율을 유의하게 증가시켰다. 메틸수은의 세포독성에 대한 꿀풀 추출물의 영향에 있 어서, 꿀풀 추출물은 메틸수은에 의하여 감소된 세포생존율을 유의 하게 증가시킴으로서 메틸수은의 세포독성을 방어하였으며, 동시 에, SOD-유사 활성 및 지질과산화 저해능을 보임으로서 항산화능 을 나타냈다. 위의 결과로 부터 메틸수은의 세포독성에 산화적 손 상이 관여하고 있으며, 동시에 꿀풀 추출물은 항산화능에 의하여 메틸수은의 산화적 손상을 효과적으로 방어하였다. 따라서, 꿀풀 추출물과 같은 천연물질은 메틸수은과 같이 산화적 손상과 관련된 중금속의 독성을 방어 내지는 치료하는데 있어 항산화 소재로서의 유효한 기능이 있음을 제시하고 있다.

This study suggested an improvement of expansion joint and asphalt pavement construction to prevent pavement and bridges damage due to alkali silica reaction. First, for the case study of alkali silica reaction, we conducted a field survey of expressway 15 Mokpo - Muan. As a result, those following damages were investigated such as abutment tensile cracks, pavement crazing and rising, joint contractions and localized damage etc. To prevent this, we applied those following improvements to Muan2 bridge and Samjeong bridge of expressway 15 and confirmed improvement effectiveness by monitoring. 1) Installing an expansion joint on a bridge near pavement slabs(3 points), 2) constructing asphalt pavement after removing concrete pavement(6m). In conclusion, through such improvements suggested above, we expect that we will be able to effectively prevent bridges damage due to Alkali Silica Reaction. Consequentially, it will also contribute improving the safety of vehicles in the expressway.

마디풀과(Polygonaceae)에 속하는 소리쟁이(Rumex crispus L.) 추출물이 환경오염원인 염화카드뮴(CdCl2)에 미치는 영향을 조사하기 위하여 배양 NIH3T3 섬유모세포(NIH3T3 fibroblast)를 재료로, 이의 항산화(antioxidation) 및 멜라닌화(melanogenesis)에 대한 영향을 조사하였다. 본 연구에서 CdCl2는 배양 NIH3T3 섬유모세포에 처리한 농도에 비례하여 세포생존율을 유의하게 감소시켰으며(p<0.001), 이 과정에서 XTT50값은 45.7μM로 측정되었다. 또한, 이 값은 Borenfreund and Puerner에 의한 독성판정기준에 따라 고독성인 것으로 나타났다. 한편, 항산화제인 vitamin E는 CdCl2에 의하여 감소된 세포생존율을 유의하게 증가시킴으로서 CdCl2의 세포독성을 방어하였다. CdCl2의 세포독성에 대한 소리쟁이 추출물의 영향에 있어서는, 소리쟁이 추출물은 CdCl2만의 처리에 비하여 세포생존율을 유의하게 증가시켰으며(p<0.001), 또한 DPPH-라디칼 소거능(DPPH-radical scavenging activity)에 의한 항산화능을 나타냈다. 멜라닌화에 있어서, 소리쟁이 추출물은 CdCl2에 의하여 증가된 티로시나제(tyrosinase) 활성과 총멜라닌양을 모두 유의하게 감소시켰다(p<0.001). 이상의 결과로부터 CdCl2의 세포독성에 산화적 손상이 관여하고 있으며, 소리쟁이 추출물은 항산화능에 의하여 CdCl2의 세포독성을 효과적으로 방어하였다. 또한 소리쟁이 추출물은 티로시나제 활성과 총멜라닌양을 유의하게 감소시킴으로서 멜라닌화를 방어하는데 효과적인 것으로 나타났다. 따라서 소리쟁이와 같은 천연물을 대상으로 CdCl2 처럼 산화적 손상과 관련된 중금속계 환경오염원의 독성으로부터 보호할 수 있는 물질에 대한 탐색 및 개발은 이의 활용적 가치가 크다고 생각된다.