• Toxicological Research
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• 제31권4호
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• pp.347-354
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• 2015

Excess manganese (Mn) is neurotoxic. Increased manganese stores in the brain are associated with a number of behavioral problems, including motor dysfunction, memory loss and psychiatric disorders. We previously showed that the transport and neurotoxicity of manganese after intranasal instillation of the metal are altered in Hfe-deficient mice, a mouse model of the iron overload disorder hereditary hemochromatosis (HH). However, it is not fully understood whether loss of Hfe function modifies Mn neurotoxicity after ingestion. To investigate the role of Hfe in oral Mn toxicity, we exposed Hfe-knockout ($Hfe^{-/-}$) and their control wild-type ($Hfe^{+/+}$) mice to $MnCl_2$ in drinking water (5 mg/mL) for 5 weeks. Motor coordination and spatial memory capacity were determined by the rotarod test and the Barnes maze test, respectively. Brain and liver metal levels were analyzed by inductively coupled plasma mass spectrometry. Compared with the water-drinking group, mice drinking Mn significantly increased Mn concentrations in the liver and brain of both genotypes. Mn exposure decreased iron levels in the liver, but not in the brain. Neither Mn nor Hfe deficiency altered tissue concentrations of copper or zinc. The rotarod test showed that Mn exposure decreased motor skills in $Hfe^{+/+}$ mice, but not in $Hfe^{-/-}$ mice (p = 0.023). In the Barns maze test, latency to find the target hole was not altered in Mn-exposed $Hfe^{+/+}$ compared with water-drinking $Hfe^{+/+}$ mice. However, Mn-exposed $Hfe^{-/-}$ mice spent more time to find the target hole than Mn-drinking $Hfe^{+/+}$ mice (p = 0.028). These data indicate that loss of Hfe function impairs spatial memory upon Mn exposure in drinking water. Our results suggest that individuals with hemochromatosis could be more vulnerable to memory deficits induced by Mn ingestion from our environment. The pathophysiological role of HFE in manganese neurotoxicity should be carefully examined in patients with HFE-associated hemochromatosis and other iron overload disorders.

• Ocean and Polar Research
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• 제37권1호
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• pp.23-35
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• 2015

A 450 m-long sediment section was recovered from Hole U1359D located at the eastern levee of the Jussieau submarine channel on the Wilkes Land continental rise (East Antarctica) during IODP Expedition 318. The age model for Hole U1359D was established by paleomagnetic stratigraphy and biostratigraphy, and the ages of core-top and core-bottom were estimated to be about 5 Ma and 13 Ma, respectively. Biogenic opal content during this period varied between 3% and 60%. In the Southern Ocean, high biogenic opal content generally represents warm climate characterized by the increased light availability due to the decrease of sea-ice distribution. The surface water productivity change in terms of biogenic opal content at about 10.2 Ma in the Wilkes Land continental rise was related to the development of Northern Component Water. After about 10.2 Ma, more production of Northern Component Water in the North Atlantic caused to increase heat transport to the Southern Ocean, resulting in the enhanced diatom production. Miocene isotope events (Mi4~Mi7), which are intermittent cooling intervals during the Miocene, appeared to be correlated to the low biogenic opal contents, but further refinement was required for precise correlation. Biogenic opal content decreased abruptly during 6 Ma to 5.5 Ma, which most likely corresponds to the Messinian salinity crisis. Short-term variation of biogenic opal content was related to the extent of sea-ice distribution associated with the location of Antarctic Polar Front that was controlled by glacial-interglacial paleoclimate change, although more precise dating and correlation will be necessary. Diatom production in the Wilkes Land continental rise increased during the interglacial periods because of the reduced sea-ice distribution and the southward movement of Antarctic Polar Front.

• 한국환경농학회지
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• 제31권3호
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• pp.229-234
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• 2012

BACKGROUND: The fruit quality and flowering characteristics of Kiwifruit (A. deliciosa cv. Hayward) in the following year is known to be affected by the extent and timing of defoliation of the current year. In korea, the production of kiwi, which is a perennial, straggling deciduous warm-temperate fruit, is often restricted by wind damage due to typhoons resulting to defoliation at the middle season of its growing period. In this paper, we report the effect of the different timing of defoliation and severities at the current season to the kiwifruit quality. METHODS AND RESULTS: Twenty seven-year-old 'Hayward' trees grown under polyethylene film rain-shelter were defoliated in different days from August to September at seven day-intervals. In each day, 0, 25, 50, 75 and 100% of leaves were removed from the trees. Fruits from each treatment were classified into four floating types (L: lying in bottom, S: standing on bottom, F: floating and SF: floating at the surface of water) by submerging them into tap water. Defoliation of kiwifruit trees in August and September caused air holes in locules of inner pericarp. Increased number of air hole in locules of a fruit was observed in floating types F and SF, and most of the air holes were located in stem end. The defoliation of trees in August significantly reduced the ratio of L-floating type fruits, which have the least number of locule air holes. The extent of defoliation also affected the distribution of the four types, the more leaves removed, the less L-floating type fruits harvested. The weight of fruits from trees defoliated in August was lower than that of fruits from September. Soluble solids content decreased as the number of locule air holes increased. Negative correlations were observed between the extent of defoliation and the weight and soluble solids content of fruits. CONCLUSION: Early defoliation effect on kiwifruit locule air hole occurrence and fruit quality were more severe in August than in September. And also if the defoliation severity is over 25%, severe fruit quality reduction expected to happen due to increase of fruit locule air hole in the inner pericarp.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.71-71
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• 2018

해상 교통량 증가에 따라 선박 사고로 인한 대형 해양 오염사고가 많이 발생하고 있다. 유조선 충돌에 따른 선체 파공은 원유의 바다 유출을 야기하여 심각한 해양오염을 유발하므로 이러한 사고에 대해서 신속한 방재 대응력이 요구된다. 작은 파공은 목제 플러그를 인위적으로 삽입하여 봉쇄하는 것이 일반적이지만, 대형 파공의 경우 사람이 직접 봉쇄하기에는 어려워 기계적 봉쇄장치 개발이 요구된다. 파공봉쇄 장치 개발을 위해서는 유체의 유출유속을 정확하게 아는 것이 중요하다. 이 연구에서는 2007년 태안 기름유출 사고에서 관측된 초기수심 7.5 m, 직경 30 cm의 파공에 대해서 고해상도 CFD 모델링을 수행하여 수심별 기름 유출 유속의 분포를 계산하였다. 비중 0.85이며, 원유의 온도 $20^{\circ}C-100^{\circ}C$ 조건에 따른 점성계수 $4-12cP(mPa{\cdot}s)$ 조건에서 파공을 통한 원유 유출을 고해상도 모델링한다. 모델링 결과를 분석하여 원유유출에 대한 마찰손실계수와 유량계수의 범위를 레이놀즈수의 함수로 제시한다.

• 헤리티지:역사와 과학
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• 제52권4호
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• pp.124-141
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• 2019

연구는 월지(안압지)의 수질 관리 문제를 유지용수의 순환 체계와 연관지어 접근하였다. 이를 위해 연못의 순환체계와 관련 깊은 입·출수 체계를 검토하였으며, 기존의 입·출수시설 외에 선행 연구에서 제기되었던 추정 입·출수시설을 분석하였다. 입수시설을 검토한 결과, 현재 입수구인 월지 동남측 호안 입수시설은 남북 담장을 사이에 두고 동편의 정원시설(경석, 곡수로, 저수시설)과 수로로 연결된 것으로 파악되었다. 월지 동편 조사에서 별도의 시설군이 있었던 것으로 보이며 1920년대 실측 도면에 경석군이 확인된 것이 이를 뒷받침한다. 추정 입수구인 남서측 호안 입수시설은 월지 서편 건물지 임해전(臨海殿) 터에 남아 있는 화강암 수로와 연관성이 있어 보인다. 월지 남서측 호안을 향해 경사가 낮아지고, 거름망을 꽂았던 홈, 1920년대 실측 도면과 1975년 측량 도면의 입수구에 경석이 배석되어 있는 것으로 보아 깨끗한 물을 입수시키기 위한 것으로 판단된다. 출수시설과 관련하여 북측 호안 출수시설은 총 5단계로 구성되어 있는데, 이 중 목제 수로와 장대석군 집수시설의 기능은 월지의 물을 배수하기 위한 시설만으로는 보이지 않는다. 목제 수로에 나무 물마개가 있는 점과 마지막 단계에 집수시설이 있는 점으로 미루어보아 상황에 따라 발천의 물이 역으로 입수될 수 있다고 판단된다. 즉 북측 호안 출수시설은 양방향으로 물이 드나들었으며 장대석군 집수시설을 통해 개폐 가능한 목제 수로로 입수되기도 한 것으로 판단된다. 추정 출수구인 서측 호안 출수시설은 북측 호안의 출수시설과 매우 유사함을 볼 때 신라시대에 존재하였거나 후대의 어느 시점에 북측 호안 출수시설을 모방하여 만들었을 것이라는 추정 외에는 어려운 실정이다. 다만 조선시대 어느 시점까지는 농업용수 공급을 위한 출수시설로 기능하였을 것으로 보인다. 이상과 같이 월지는 신라 왕경 중심부인 동궁의 시설과 유기적으로 얽혀 있는 체계화된 배수망에 의해서 입·출수가 이루어졌다. 이를 통해 월지를 비롯한 각 시설군에 물이 입수되었으며 왕경 중심부의 중요한 인공 하천인 발천(撥川)을 통해 남천(南川)으로 연결되는 배수 체계를 가지고 있었다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 요약집 춘계학술발표대회
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• pp.89-89
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• 2004

• 한국수자원학회논문집
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• 제34권6호
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• pp.641-649
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• 2001

본 연구에서는 군말뚝 교각 주위에서의 세굴특성을 실험을 통하여 파악하였다. 실험은 4개, 9개, 15개, 35개의 파일로 구성된 군말뚝에 대해 수행하여 파일수, 유속, 접근각에 따른 세굴형상, 최대세굴심의 깊이 및 위치의 변화를 살펴보았다. 실험결과에 의하면, 4개 및 9개로 구성된 군말뚝의 경우 유속비와 상관없이 단일교각의 최대세굴심과 흡사하였고, 15개와 35개로 구성된 군말뚝의 경우 유속비가 증가함에 따라 최대세굴심도 급격히 증가하여 단일교각 세굴심 의 약 2.2배 증가함을 알 수 있었다. 또한 세굴형태는 말뚝간격이 조밀해질수록 원형의 세굴공이 중첩되어 전체적으로 직사각형의 형태를 띠는 것으로 나타났다. 75개의 파일로 구성된 군말뚝에 대한 접근각의 영향을 살펴본 결과 세굴심은 접근각이 35$^{\circ}$에서 최대가 되었으며 이때의 세굴공은 대각선 방향으로 형성됨을 알 수 있었다.

• Structural Monitoring and Maintenance
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• 제1권2호
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• pp.183-195
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• 2014

Scour is one of the leading causes of overwater bridge failures worldwide. While monitoring systems have already been implemented or are still being developed, they suffer from limitations such as high costs, inaccuracies, and low reliability, among others. Also, most sensors only measure scour depth at one location and near the pier. Thus, the objective is to design a simple, low cost, scour hole topography monitoring system that could better characterize the entire depth, shape, and size of bridge scour holes. The design is based on burying a robust, waterproofed, piezoelectric sensor strip in the streambed. When scour erodes sediments to expose the sensor, flowing water excites it to cause the generation of time-varying voltage signals. An algorithm then takes the time-domain data and maps it to the frequency-domain for identifying the sensor's resonant frequency, which is used for calculating the exposed sensor length or scour depth. Here, three different sets of tests were conducted to validate this new technique. First, a single sensor was tested in ambient air, and its exposed length was varied. Upon verifying the sensing concept, a waterproofed prototype was buried in soil and tested in a tank filled with water. Sensor performance was characterized as soil was manually eroded away, which simulated various scour depths. The results confirmed that sensor resonant frequencies decreased with increasing scour depths. Finally, a network of 11 sensors was configured to form a distributed monitoring system in the lab. Their exposed lengths were adjusted to simulate scour hole formation and evolution. Results showed promise that the proposed sensing system could be scaled up and used for bridge scour topography monitoring.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.269-274
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• 2011

A CFD analysis was performed to examine the inner channel blockage of dual-cooled fuel which has being developed for the power uprate of a pressurized water reactor (PWR). The dual-cooled fuel consists of an annular fuel pellet($UO_2$) and dual claddings as well as internal and external cooling channels. The dual-cooled annular fuel is different from a conventional solid 려el by employing an internal cooling channel for each fuel pellet as well as an external cooling channel. One of the key issues is the hypothetical event of inner channel blockage because the inner channel is an isolated flow channel without the coolant mixing between the neighboring flow channels. The inner channel blockage could cause the Departure from Nucleate Boiling (DNB) in the inner channel that eventually causes a fuel failure. This paper presents the CFD simulation of the flow through the side holes of the bottom end plug for the complete entrance blockage of the inner channel. Since the amount of coolant supply to the inner channel depends on largely the pressure loss at the side hole, the pressure loss coefficient of the side hole was estimated by the CFD analysis. The CFD prediction of the loss coefficient showed a reasonable agreement with an experimental data for the complete blockage of both the inner channel entrance and the outer channel. The CFD predictions also showed the decrease of the loss coefficient as the outer channel blockage increases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2747-2752
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• 2007

A numerical study has been performed on the flow past a two-staged orifice in a rectangular duct. The flow field including the recirculation region behind the orifice was investigated and the pressure drop was calculated. Water was used as a working fluid and the flow was treated as the turbulent flow, of which the Raynolds number was 6000. The main parameters for the pressure drop and the recirculation region were the orifice's inclined angle against the duct, the interval between two orifices, the shape of the orifice's hole having the same area, and the change of the hole position at the same interval. The variation of the flow field was investigated with each parameter. Consequently, it was found that the most dominant parameter influencing the drop of the pressure was the change of the hole position at the same interval between orifices. Especially when the interval between orifices was narrow and the relative position the holes was changed, its effect to the flow field was shown most drastically as a result of this study. The SIMPLER algorithm with FLUENT code was employed to analyze the flow field.