• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1549-1554
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• 2008

In this paper, The evaluation of durability of the PC Panel lining for tunnel structure was examined through the rapid test by carbonation and freezing and thawing. Also for the purpose of improvement of durability. Namely, the durable characteristics of PC Panel lining by carbonation and freezing and thawing, was evaluated by rapid test and long-term field exposure test and main influence factors were derived. As a result of test, Correlation of accelerating test in deterioration chamber and long-term field exposure test, it will be expected that the proposed correlation well to the prediction of life expectancy of structure and is contributed greatly in the future.

• 한국철도학회논문집
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• 제9권4호
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• pp.349-356
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• 2006

At present, the selecting system and analytic estimation criterion on repair materials and methods of the deteriorated RC structures have not yet been set up in domestic. Under these circumstances, deterioration such as shrinkage crack, corrosion of rebar has been often occurred after repair, and this finally results in too frequent repairs. In this study, three types of repair methods were experimentally investigated by the accelerating test in a combined deterioration chamber and long-term field exposure test. Three types of repair methods applied in this study belong to a group of polymer cement mortar, which is commonly used in repair works. According to the results of this study, durability of repair mortar layers and corrosion properties of recovered rebar could be investigated in short period by the accelerating test in a combined deterioration chamber, which can simulate the condition of repeated high-and-low temperature and repeated dry-and-wet environment, spraying chloride solution and emitting $CO_2$ gas. After 36 month long-term filed exposure test in the coastal area, harmful macro-cracks are observed in the polymer cement mortar layer of some repair methods. These crack are considered to result from drying shrinkage of polymer cement mortar. Also, after 36 month exposure, amount of corrosion area and weight loss of rebar are found to be different according to the types of repair methods.

• Composites Research
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• 제19권1호
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• pp.43-48
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• 2006

High performance fiber reinforced cement composites have better performances than traditional cement based materials, therefore, have been expected as new construction applications such as the materials for construction & bridge structure, repair and rehabilitation applications, anti-collapse applications, anti-noise applications etc. However, they have lots of the problems such as material design, fabrication method and structural analysis. Also, the most serious problems of High performance fiber reinforced cement composites have been expensive initial cost, lack of long-term exposure data. As a result, it is needed that the efforts for lowering the initial cost and accumulation of long-term exposure. There has been hardly assessment results of life cycle cost for HPFRCC in construction field, but some papers showed that total life cycle cost could be profitable if the initial cost could be reduced.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 춘계학술대회 논문집
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• pp.86-89
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• 2004

Recently polymer arresters are being used widely but we don't have appropriate long term characteristics test methods. Therefore we need to develop special test facility to evaluate long term reliability of polymer arresters. It's polymeric housing can be degraded by environmental stress and the interface between housing and inner module can be affected by moisture absorption. This moisture absorption can cause leakage current and tracking in the interface. We developed multi stress accelerated ageing test facility to simulate field conditions including UV, temperature, humidity, voltage, salt fog and rain. In addition, we carried out field exposure test at the outdoor test yard and characteristics analysis of field operated specimens to evaluate accelerating factor of this accelerated aging test.

• 한국잡초학회지
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• 제17권1호
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• pp.73-79
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• 1997

Governments and industry have a growing interest in the harmonization of environmental test methods and risk assessment procedures. OECD are currently producing a set of harmonised test guidelines for studying the environmental fate and ecological effects of pesticides. FAO has published an environmental risk assessment procedure. This procedure, which is similar to those used in US and Europe, is based on calculating the ratio of the toxicity of a pesticide to indicator organisms to their level of exposure to the pesticide. The exposure depends on both the concentration of the pesticide and its bioavailability. Ratios which indicate a pesticide will not produce a harmful effect have been established using ecological field studies. Examples are presented for assessing the risk to aquatic ecosystems, earthworms and honeybees. Long-term field studies(up to 20 years) have also shown that pesticides can be used indefinitely without harming soil fertility. Herbicides can be used to avoid the ecologically damaging effects of using soil cultivations excessively for weed control.

• Journal of electromagnetic engineering and science
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• 제15권3호
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• pp.151-157
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• 2015

The increasing use of mobile phones has raised public concern about the possible biological effects of radiofrequency electromagnetic field (RF-EMF) exposure on the human brain. To investigate the potential effect of RF-EMF exposure on the brain, we examined the behaviors and hippocampal morphology of C57BL/6 mice after sub-chronic exposure to RF-EMFs with a relatively high SAR level (5.0 W/kg). We applied a 2-hour daily exposure of WCDMA 1,950 MHz using a reverberation chamber that was designed for whole-body exposure for 60 days. In the behavioral tests, RF-EMF did not alter the physical activity or long-term memory of mice. Moreover, no alteration was found in the neuronal and glial cells in the hippocampus by RF-EMFs. In this study, we showed that sub-chronic whole body RF exposure did not produce memory impairment and hippocampal morphological alteration in C57BL/6 mice.

• Biomolecules & Therapeutics
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• 제22권6호
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• pp.570-576
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• 2014

Studies have demonstrated that electromagnetic waves, as the one of the most important physical factors, may alter cognitive and non-cognitive behaviors, depending on the frequency and energy. Moreover, non-ionizing radiation of low energy waves e.g. very low frequency waves could alter this phenomenon via alterations in neurotransmitters and neurohormones. In this study, short, medium, and long-term exposure to the extremely low frequency electromagnetic field (ELF-EMF) (1 and 5 Hz radiation) on behavioral, hormonal, and metabolic changes in male Wistar rats (250 g) were studied. In addition, changes in plasma concentrations for two main stress hormones, noradrenaline and adrenocorticotropic hormone (ACTH) were evaluated. ELF-EMF exposure did not alter body weight, and food and water intake. Plasma glucose level was increased and decreased in the groups which exposed to the 5 and 1Hz wave, respectively. Plasma ACTH concentration increased in both using frequencies, whereas noradrenaline concentration showed overall reduction. At last, numbers of rearing, sniffing, locomotor activity was increased in group receiving 5 Hz wave over the time. In conclusions, these data showed that the effects of 1 and 5 Hz on the hormonal, metabolic and stress-like behaviors may be different. Moreover, the influence of waves on stress system is depending on time of exposure.

• 한국지반신소재학회논문집
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• 제9권4호
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• pp.75-84
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• 2010

본 연구에서는 띠형 섬유보강재의 인장특성, 크리프 변형, 내시공성 및 내구성을 평가하기 위한 일련의 장기성능 평가시험을 수행하였다. 또한 시험결과를 바탕으로 장기설계인장강도 산정을 위한 강도감소계수를 평가하였다. 먼저, 크리프 변형 특성을 평가하기 위해 단계 등온법과 시간-온도 중첩법을 이용하였으며, 크리프 감소계수는 1.6을 적용하는 것이 바람직한 것으로 평가되었다. 다음으로 입도 조정된 화강풍화토를 성토재로 사용하여 수행한 내시공성 시험 결과, 보강재의 강도특성에 영향을 미치는 원사의 손상이 거의 없는 것으로 확인되어, 장기설계인장강도에 큰 영향을 미치지 않을 것으로 분석되었다. 마지막으로 내구성 평가 결과, 내화학성, 내미생물 및 내후성을 고려한 강도감소계수는 1.1을 적용하는 것이 합리적인 것으로 평가되었다.

• 한국가축번식학회지
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• 제26권1호
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• pp.53-59
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• 2002

웅성 생쥐에 자기장을 15일 동안 1일 5시간씩 60G의 강도로 노출시킨 결과, 정자농도는 대조구와 자기장 15일 처리구가 각각 25.1$\pm$6.5$\times$$10^{6}$$m\ell$와 15.7$\pm$5.3$\times$$10^{6}$$m\ell$로서 처리구가 대조구에 비하여 유의적으로 낮게 나타났다(P＜0.05). 생존율은 대조구와 자기장 15일 처리구가 각각 34.4%와 29.3%로서 처리구가 대조구에 비하여 낮게 나타났지만 유의적인 차이는 인정되지 않았다(P〉0.05). 기형율은 대조구와 자기장 15일 처리구가 각각 11.7%와 18.0%로서 처리구가 대조구에 비하여 유의적으로 높은 성적을 나타냈다(P〉0.05). 체중과 번식기관 무게는 대조구와 자기장 처리구간에 차이가 인정되지 않았다. 장기무게중 간, 신장은 대조구와 자기장 처리구간에 차이가 인정되지 않았으나, 비장은 대조구와 자기장 15일 처 리구가 각각 0.116g과 0.227g으로서 처리구가 대조구에 비하여 유의적으로 높게 나타났다(P＜0.05).

• 한국강구조학회 논문집
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• 제21권3호
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• pp.301-310
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• 2009

가시설 구조물의 재료로 강재가 널리 사용되고 있으나, 방식처리가 실시되지 않아 부식손상으로 인한 내하력 저하가 우려된다. 그러나 환경조건과 사용기간에 따른 가시설 강재의 부식감소량이 제시되어 있지 않아, 가시설 강재의 설계시 부식손상을 고려한 정량적인 내하력 및 장기 안전성 평가가 곤란한 실정이다. 본 연구에서는 가혹한 대기부식환경인 지하철 공사현장을 대상으로 가시설 강재의 장기 안전성 평가에 필요한 부식 두께감소량 예측식을 제안하기 위하여, 실내부식실험과 현장노출실험을 실시하였다. 실내부식실험에서는 상대습도와 염화칼슘이 강재의 부식손상에 미치는 영향을 검토하였으며, 현장노출실험에서는 실제 지하철 공사현장 환경하에 놓인 가시설 강재의 부식두께감소량을 측정하였다. 그 결과 11개월간의 현장노출실험을 통하여 환경조건과 사용기간에 따른 가시설 강재의 부식두께감소량 예측식을 제안하였다. 그리고 6개월간의 실내 부식실험을 통하여 부식영향인자인 상대습도와 염화칼슘에 따른 부식두께감소량 예측식을 제안하였다.